id int64 580 79M | url stringlengths 31 175 | text stringlengths 9 245k | source stringlengths 1 109 | categories stringclasses 160 values | token_count int64 3 51.8k |
|---|---|---|---|---|---|
10,248,922 | https://en.wikipedia.org/wiki/Heme%20O | Heme O (or haem O) differs from the closely related heme A by having a methyl group at ring position 8 instead of the formyl group. The isoprenoid chain at position 2 is the same.
Heme O, found in the bacterium Escherichia coli, functions in a similar manner to heme A in mammalian oxygen reduction.
See also
Heme
References
Tetrapyrroles
Biomolecules | Heme O | Chemistry,Biology | 91 |
5,132,251 | https://en.wikipedia.org/wiki/Catalog%20of%20Components%20of%20Double%20and%20Multiple%20Stars | The Catalog of Components of Double and Multiple Stars, or CCDM, is an astrometric star catalogue of double and multiple stars. It was made by Jean Dommanget and Omer Nys at the Royal Observatory of Belgium in order to provide an input catalogue of stars for the Hipparcos mission. The published first edition of the catalog, released in 1994, has entries for 74,861 components of 34,031 double and multiple stars; the second edition, in 2002, has been expanded to provide entries for 105,838 components of 49,325 double and multiple stars. The catalog lists positions, magnitudes, spectral types, and proper motions for each component.
References
Further reading
External links
The CCDM, second edition, at VizieR
Astronomical catalogues of stars | Catalog of Components of Double and Multiple Stars | Astronomy | 159 |
38,818,456 | https://en.wikipedia.org/wiki/HD%2077258 | HD 77258 is a binary star system in the southern constellation of Vela. It has the Bayer designation w Velorum, while HD 77258 is the identifier from the Henry Draper Catalogue. The system is visible to the naked eye as a faint point of light with a combined apparent visual magnitude of 4.45. It is located at a distance of approximately 218 light years from the Sun based on parallax. The radial velocity of the system barycenter is poorly constrained, but it appears to be drifting away at a rate of ~7 km/s.
The radial velocity variation of this system was first reported by H. K. Palmer in 1904. It is a single-lined spectroscopic binary with an orbital period of 74.14 days and an eccentricity (ovalness) of 0.00085, indicating the orbit is essentially circular. The visible component has a stellar classification of G8-K1III, matching a late G-type giant star. This is an evolved star that has exhausted the supply of hydrogen at its core, then cooled and expanded away from the main sequence. In 1975, S. Maladora flagged the spectrum as peculiar.
The level of ultraviolet flux coming from this system suggests the companion is a hot A-type star of class A6.5 or A7. The system is a source of X-ray emission.
References
K-type giants
Spectroscopic binaries
Vela (constellation)
Velorum, w
Durchmusterung objects
077258
044191
3591 | HD 77258 | Astronomy | 321 |
1,192,305 | https://en.wikipedia.org/wiki/Web%20accessibility | Web accessibility, or eAccessibility, is the inclusive practice of ensuring there are no barriers that prevent interaction with, or access to, websites on the World Wide Web by people with physical disabilities, situational disabilities, and socio-economic restrictions on bandwidth and speed. When sites are correctly designed, developed and edited, more users have equal access to information and functionality.
For example, when a site is coded with semantically meaningful HTML, with textual equivalents provided for images and with links named meaningfully, this helps blind users using text-to-speech software and/or text-to-Braille hardware. When text and images are large and/or enlargeable, it is easier for users with poor sight to read and understand the content. When links are underlined (or otherwise differentiated) as well as colored, this ensures that color blind users will be able to notice them. When clickable links and areas are large, this helps users who cannot control a mouse with precision. When pages are not coded in a way that hinders navigation by means of the keyboard alone, or a single switch access device alone, this helps users who cannot use a mouse or even a standard keyboard. When videos are closed captioned, chaptered, or a sign language version is available, deaf and hard-of-hearing users can understand the video. When flashing effects are avoided or made optional, users prone to seizures caused by these effects are not put at risk. And when content is written in plain language and illustrated with instructional diagrams and animations, users with dyslexia and learning difficulties are better able to understand the content. When sites are correctly built and maintained, all of these users can be accommodated without decreasing the usability of the site for non-disabled users.
The needs that web accessibility aims to address include:
Visual: Visual impairments including blindness, various common types of low vision and poor eyesight, various types of color blindness;
Motor/mobility: e.g. difficulty or inability to use the hands, including tremors, muscle slowness, loss of fine muscle control, etc., due to conditions such as Parkinson's disease, muscular dystrophy, cerebral palsy, stroke;
Auditory: Deafness or hearing impairments, including individuals who are hard of hearing;
Seizures: Photo epileptic seizures caused by visual strobe or flashing effects.
Cognitive and intellectual: Developmental disabilities, learning difficulties (dyslexia, dyscalculia, etc.), and cognitive disabilities (PTSD, Alzheimer's) of various origins, affecting memory, attention, developmental "maturity", problem-solving and logic skills, etc.
Accessibility is not confined to the list above, rather it extends to anyone who is experiencing any permanent, temporary or situational disability. Situational disability refers to someone who may be experiencing a boundary based on the current experience. For example, a person may be situationally one-handed if they are carrying a baby. Web accessibility should be mindful of users experiencing a wide variety of barriers. According to a 2018 WebAIM global survey of web accessibility practitioners, close to 93% of survey respondents received no formal schooling on web accessibility.
Assistive technologies used for web browsing
Individuals living with a disability use assistive technologies such as the following to enable and assist web browsing:
Screen reader software such as Check Meister browser, which can read out, using synthesized speech, either selected elements of what is being displayed on the monitor (helpful for users with reading or learning difficulties), or which can read out everything that is happening on the computer (used by blind and vision impaired users).
Braille terminals, consisting of a refreshable braille display which renders text as braille characters (usually by means of raising pegs through holes in a flat surface) and either a mainstream keyboard or a braille keyboard.
Screen magnification software, which enlarges what is displayed on the computer monitor, making it easier to read for vision impaired users.
Speech recognition software that can accept spoken commands to the computer, or turn dictation into grammatically correct text – useful for those who have difficulty using a mouse or a keyboard.
Keyboard overlays, which can make typing easier or more accurate for those who have motor control difficulties.
Access to subtitled or sign language videos for deaf people.
Guidelines on accessible web design
Web Content Accessibility Guidelines
In 1999 the Web Accessibility Initiative, a project by the World Wide Web Consortium (W3C), published the Web Content Accessibility Guidelines WCAG 1.0.
On 11 December 2008, the WAI released the WCAG 2.0 as a Recommendation. WCAG 2.0 aims to be up to date and more technology neutral. Though web designers can choose either standard to follow, the WCAG 2.0 have been widely accepted as the definitive guidelines on how to create accessible websites. Governments are steadily adopting the WCAG 2.0 as the accessibility standard for their own websites. In 2012, the Web Content Accessibility Guidelines were also published as an ISO/IEC standard: "ISO/IEC 40500:2012: Information technology – W3C Web Content Accessibility Guidelines (WCAG) 2.0". In 2018, the WAI released the WCAG 2.1 Recommendation that extends WCAG 2.0.
Criticism of WAI guidelines
There has been some criticism of the W3C process, claiming that it does not sufficiently put the user at the heart of the process. There was a formal objection to WCAG's original claim that WCAG 2.0 will address requirements for people with learning disabilities and cognitive limitations headed by Lisa Seeman and signed by 40 organizations and people. In articles such as "WCAG 2.0: The new W3C guidelines evaluated", "To Hell with WCAG 2.0" and "Testability Costs Too Much", the WAI has been criticised for allowing WCAG 1.0 to get increasingly out of step with today's technologies and techniques for creating and consuming web content, for the slow pace of development of WCAG 2.0, for making the new guidelines difficult to navigate and understand, and other argued failings.
Essential components of web accessibility
The accessibility of websites relies on the cooperation of several components:
content – the information in a web page or web application, including natural information (such as text, images, and sounds) and code or markup that defines structure, presentation, etc.
web browsers, media players, and other "user agents"
assistive technology, in some cases – screen readers, alternative keyboards, switches, scanning software, etc.
users' knowledge, experiences, and in some cases, adaptive strategies using the web
developers – designers, coders, authors, etc., including developers with disabilities and users who contribute content
authoring tools – software that creates websites
evaluation tools – web accessibility evaluation tools, HTML validators, CSS validators, etc.
Guidelines for different components
Authoring Tool Accessibility Guidelines (ATAG)
ATAG contains 28 checkpoints that provide guidance on:
producing accessible output that meets standards and guidelines
promoting the content author for accessibility-related information
providing ways of checking and correcting inaccessible content
integrating accessibility in the overall look and feel
making the authoring tool itself accessible to people with disabilities
Web Content Accessibility Guidelines (WCAG)
WCAG 1.0: 14 guidelines that are general principles of accessible design
WCAG 2.0: 4 principles that form the foundation for web accessibility; 12 guidelines (untestable) that are goals for which authors should aim; and 65 testable success criteria. The W3C's Techniques for WCAG 2.0 is a list of techniques that support authors to meet the guidelines and success criteria. The techniques are periodically updated whereas the principles, guidelines and success criteria are stable and do not change.
User Agent Accessibility Guidelines (UAAG)
UAAG contains a comprehensive set of checkpoints that cover:
access to all content
user control over how content is rendered
user control over the user interface
standard programming interfaces
Web accessibility legislation
Because of the growth in internet usage and its growing importance in everyday life, countries around the world are addressing digital access issues through legislation. One approach is to protect access to websites for people with disabilities by using existing human or civil rights legislation. Some countries, like the U.S., protect access for people with disabilities through the technology procurement process. It is common for nations to support and adopt the Web Content Accessibility Guidelines (WCAG) 2.0 by referring to the guidelines in their legislation. Compliance with web accessibility guidelines is a legal requirement primarily in North America, Europe, parts of South America and parts of Asia.
Argentina
Law 26.653 on Accessibility to Information on Web Pages. Approved by the National Congress of Argentina on November 3, 2010. It specifies in its Article 1 that both the National State and its decentralized organisms or those companies that are related in any way with public services or goods, must respect the rules and requirements on accessibility in the design of their web pages. The objective is to facilitate access to contents to all persons with disabilities, in order to guarantee equal opportunities in relation to access to information and to avoid discrimination.
In addition, by Decree 656/2019 the regulation of the aforementioned Law No. 26,653 is approved and it is reported that the authority in charge of its application will be the ONTI, "Oficina Nacional de Tecnologías de Información" (National Office of Information Technologies). This agency is in charge of assisting and/or advising the individuals and legal entities reached by this Law; in addition to disseminating, approving/updating and also controlling the fulfillment of the accessibility standards and requirements of the web pages; among other functions.
Australia
In 2000, an Australian blind man won a $20,000 court case against the Sydney Organising Committee of the Olympic Games (SOCOG). This was the first successful case under Disability Discrimination Act 1992 because SOCOG had failed to make their official website, Sydney Olympic Games, adequately accessible to blind users. The Human Rights and Equal Opportunity Commission (HREOC) also published World Wide Web Access: Disability Discrimination Act Advisory Notes. All Governments in Australia also have policies and guidelines that require accessible public websites.
Brazil
In Brazil, the federal government published a paper with guidelines for accessibility on 18 January 2005, for public reviewing. On 14 December of the same year, the second version was published, including suggestions made to the first version of the paper. On 7 May 2007, the accessibility guidelines of the paper became compulsory to all federal websites. The current version of the paper, which follows the WCAG 2.0 guidelines, is named e-MAG, Modelo de de Governo Eletrônico (Electronic Government Accessibility Model), and is maintained by Brazilian Ministry of Planning, Budget, and Management.
The paper can be viewed and downloaded at its official website.
Canada
In 2011, the Government of Canada began phasing in the implementation of a new set of web standards that are aimed at ensuring government websites are accessible, usable, interoperable and optimized for mobile devices. These standards replace Common Look and Feel 2.0 (CLF 2.0) Standards for the Internet.
The first of these four standards, Standard on Web Accessibility came into full effect on 31 July 2013. The Standard on Web Accessibility follows the Web Content Accessibility Guidelines (WCAG) 2.0 AA, and contains a list of exclusions that is updated annually. It is accompanied by an explicit Assessment Methodology that helps government departments comply. The government also developed the Web Experience Toolkit (WET), a set of reusable web components for building innovative websites. The WET helps government departments build innovative websites that are accessible, usable and interoperable and therefore comply with the government's standards. The WET toolkit is open source and available for anyone to use.
The three related web standards are: the Standard on Optimizing Websites and Applications for Mobile Devices, the Standard on Web Usability and the Standard on Web Interoperability.
In 2019 the Government of Canada passed the Accessible Canada Act. This builds on the on provincial legislation like the Accessibility for Ontarians with Disabilities Act, The Accessibility for Manitobans Act and the Nova Scotia Accessibility Act.
European Union
In February 2014 a draft law was endorsed by the European Parliament stating that all websites managed by public sector bodies have to be made accessible to everyone.
A European Commission Communication on eAccessibility was published on 13 September 2005. The commission's aim to "harmonise and facilitate the public procurement of accessible ICT products and services" was embedded in a mandate issued to CEN, CENELEC and ETSI in December 2005, reference M 376. A mandate is a request for the drafting and adoption of a European standard or European standardisation deliverables issued to one or more of the European standardisation organisations. Mandates are usually accepted by the standardisation organisation because they are based on preliminary consultation, although technically the organisation is independent and has a right to decline the mandate. The mandate also called for the development of an electronic toolkit for public procurers enabling them to have access to the resulting harmonised requirements. The commission also noted that the harmonised outcome, while intended for public procurement purposes, might also be useful for procurement in the private sector.
On 26 October 2016, the European Parliament approved the Web Accessibility Directive, which requires that the websites and mobile apps of public sector bodies be accessible. The relevant accessibility requirements are described in the European standard EN 301 549 V3.2.1 (published by ETSI). EU member states were expected to bring into force by 23 September 2018 laws and regulations that enforce the relevant accessibility requirements.
websites of public sector bodies should comply by 23 September 2018;
mobile apps by 23 June 2021.
Some categories of websites and apps are excepted from the directive, for example "websites and mobile applications of public service broadcasters and their subsidiaries".
The European Commission's "Rolling Plan for ICT Standardisation 2017" notes that ETSI standard EN 301 549 V1.1.2 will need to be updated to add accessibility requirements for mobile applications and evaluation methodologies to test compliance with the standard.
In 2019 the European Union introduced the European Accessibility Act, as one of the leading pieces of legislation for digital accessibility and digital inclusion. The European Accessibility Act (EAA), which will enter into force on 28 June 2025, requiring companies to ensure that the newly marketed products and services covered by the Act are accessible. All websites will need to adhere to the WCAG Principles of Perceivable, Operable, Understandable and Robust, and deliver comparative levels of user experience to disabled customers. As of June 28, 2025, customers will be able to file complaints before national courts or authorities if services or products do not respect the new rules.
India
In India, National Informatics Centre (NIC), under Ministry of Electronics and Information Technology (MeitY) has passed Guidelines for Indian Government Websites (GIGW) for government agencies in 2009, compelling them to adhere to WCAG 2.0 Level A standards.
Ministry of Electronics and Information Technology (MeitY) has National Policy on Universal Electronic Accessibility clearly stated, Accessibility Standards and Guidelines be formulated or adapted from prevailing standards in the domain including World Wide Web Consortium accessibility Web standards and guidelines such as Authoring Tool Accessibility Guidelines (ATAG), Web Content Accessibility Guidelines (WCAG 2.0) and User Agent Accessibility Guidelines (UAAG).
GIGW aims to ensure the quality and accessibility of government guidelines by offering guidance on desirable practices covering the entire lifecycle of websites, web portals and web applications, right from conceptualization and design to their development, maintenance and management. The Department of Administrative Reforms and Public Grievances made the same a part of the Central Secretariat Manual of Office Procedure.
GIGW 3.0 also significantly enhances the guidance on the accessibility and usability of mobile apps, especially by offering specific guidance to government organizations on how to leverage public digital infrastructure devised for whole-of-government delivery of services, benefits and information.
The Rights of Persons with Disabilities Act, 2016 (RPwD) passed in parliament. The law replaced earlier legislation and provided clearer guidance for digital accessibility. The RPwD Act, 106 through Sections 40-46 mandates accessibility to be ensured in all public-centric buildings, transportation systems, Information and Communication Technology (ICT) services, consumer products and all other services being provided by the Government or other service providers.
Ireland
In Ireland, the Disability Act 2005 requires that where a public body communicates in electronic form with one or more persons, the contents of the communication must be, as far as practicable, "accessible to persons with a visual impairment to whom adaptive technology is available" (Section 28(2)). The National Disability Authority has produced a Code of Practice giving guidance to public bodies on how to meet the obligations of the Act. This is an approved code of practice and its provisions have the force of legally binding statutory obligations. It states that a public body can achieve compliance with Section 28(2) by "reviewing existing practices for electronic communications in terms of accessibility against relevant guidelines and standards", giving the example of "Double A conformance with the Web Accessibility Initiative's (WAI) Web Content Accessibility Guidelines (WCAG)".
Israel
The Israeli Ministry of Justice recently published regulations requiring Internet websites to comply with Israeli standard 5568, which is based on the W3C Web Content Accessibility Guidelines 2.0. The main differences between the Israeli standard and the W3C standard concern the requirements to provide captions and texts for audio and video media. The Israeli standards are somewhat more lenient, reflecting the current technical difficulties in providing such captions and texts in Hebrew.
Italy
In Italy, web accessibility is ruled by the so-called "Legge Stanca" (Stanca Act), formally Act n.4 of 9 January 2004, officially published on the Gazzetta Ufficiale on 17 January 2004. The original Stanca Act was based on the WCAG 1.0. On 20 March 2013 the standards required by the Stanca Act were updated to the WCAG 2.0.
Japan
Web Content Accessibility Guidelines in Japan were established in 2004 as JIS (Japanese Industrial Standards) X 8341–3. JIS X 8341-3 was revised in 2010 as JIS X 8341-3:2010 to encompass WCAG 2.0, and it was revised in 2016 as JIS X 8341-3:2016 to be identical standards with the international standard ISO/IEC 40500:2012. The Japanese organization WAIC (Web Accessibility Infrastructure Committee) has published the history and structure of JIS X 8341-3:2016.
Malta
In Malta Web Content Accessibility assessments were carried out by the Foundation for Information Technology Accessibility (FITA) since 2003. Until 2018, this was done in conformance with the requirements of the Equal Opportunities Act (2000) CAP 43 and applied WACG guidelines. With the advent of the EU Web Accessibility Directive the Malta Communications Authority was charged with ensuring the accessibility of online resources owned by Maltese public entities. FITA continues to provide ICT accessibility assessments to public and commercial entities, applying standard EN301549 and WCAG 2.1 as applicable. Therefore, both the Equal Opportunities Act anti-discrimination legislation and the transposed EU Web Accessibility Directive are applicable to the Maltese scenario.
Norway
In Norway, web accessibility is a legal obligation under the Act 20 June 2008 No 42 relating to a prohibition against discrimination on the basis of disability, also known as the Anti-discrimination Accessibility Act. The Act went into force in 2009, and the Ministry of Government Administration, Reform and Church Affairs [Fornyings-, administrasjons- og kirkedepartementet] published the Regulations for universal design of information and communication technology (ICT) solutions [Forskrift om universell utforming av informasjons- og kommunikasjonsteknologiske (IKT)-løsninger] in 2013. The regulations require compliance with Web Content Accessibility Guidelines 2.0 (WCAG 2.0) / NS / ISO / IEC 40500: 2012, level A and AA with some exceptions. The Norwegian Agency for Public Management and eGovernment (Difi) is responsible for overseeing that ICT solutions aimed at the general public are in compliance with the legislative and regulatory requirements.
Philippines
As part of the Web Accessibility Initiatives in the Philippines, the government through the National Council for the Welfare of Disabled Persons (NCWDP) board approved the recommendation of forming an ad hoc or core group of webmasters that will help in the implementation of the Biwako Millennium Framework set by the UNESCAP.
The Philippines was also the place where the Interregional Seminar and Regional Demonstration Workshop on Accessible Information and Communications Technologies (ICT) to Persons with Disabilities was held where eleven countries from Asia – Pacific were represented. The Manila Accessible Information and Communications Technologies Design Recommendations was drafted and adopted in 2003.
Spain
In Spain, UNE 139803:2012 is the norm entrusted to regulate web accessibility. This standard is based on Web Content Accessibility Guidelines 2.0.
Sweden
In Sweden, Verva, the Swedish Administrative Development Agency is responsible for a set of guidelines for Swedish public sector web sites. Through the guidelines, web accessibility is presented as an integral part of the overall development process and not as a separate issue. The Swedish guidelines contain criteria which cover the entire life cycle of a website; from its conception to the publication of live web content. These criteria address several areas which should be considered, including:
accessibility
usability
web standards
privacy issues
information architecture
developing content for the web
Content Management Systems (CMS) / authoring tools selection.
development of web content for mobile devices.
An English translation was released in April 2008: Swedish National Guidelines for Public Sector Websites. The translation is based on the latest version of Guidelines which was released in 2006.
United Kingdom
In the UK, the Equality Act 2010 does not refer explicitly to website accessibility, but makes it illegal to discriminate against people with disabilities. The Act applies to anyone providing a service; public, private and voluntary sectors. The Code of Practice: Rights of Access – Goods, Facilities, Services and Premises document published by the government's Equality and Human Rights Commission to accompany the Act does refer explicitly to websites as one of the "services to the public" which should be considered covered by the Act.
In December 2010 the UK released the standard BS 8878:2010 Web accessibility. Code of practice. This standard effectively supersedes PAS 78 (pub. 2006). PAS 78, produced by the Disability Rights Commission and usable by disabled people. The standard has been designed to introduce non-technical professionals to improved accessibility, usability and user experience for disabled and older people. It will be especially beneficial to anyone new to this subject as it gives guidance on process, rather than on technical and design issues. BS 8878 is consistent with the Equality Act 2010 and is referenced in the UK government's e-Accessibility Action Plan as the basis of updated advice on developing accessible online services. It includes recommendations for:
Involving disabled people in the development process and using automated tools to assist with accessibility testing
The management of the guidance and process for upholding existing accessibility guidelines and specifications.
BS 8878 is intended for anyone responsible for the policies covering web product creation within their organization, and governance against those policies. It additionally assists people responsible for promoting and supporting equality and inclusion initiatives within organizations and people involved in the procurement, creation or training of web products and content. A summary of BS 8878 is available to help organisations better understand how the standard can help them embed accessibility and inclusive design in their business-as-usual processes.
On 28 May 2019, BS 8878 was superseded by ISO 30071-1, the international Standard that built on BS 8878 and expanded it for international use. A summary of how ISO 30071-1 relates to BS 8878 is available to help organisations understand the new Standard.
On April 9, National Rail replaced its blue and white aesthetic with a black and white theme, which was criticized for not conforming to the Web Content Accessibility Guidelines. The company restored the blue and white theme and said it is investing in modernising its website in accords to the latest accessibility guidelines.
In 2019 new accessibility regulations came into force setting a legal duty for public sector bodies to publish accessibility statements and make their websites accessible by 23 September 2020 Accessibility statements include information about how the website was tested and the organisation's plan to fix any accessibility problems. Statements should be published and linked to on every page on the website.
United States
In the United States, Section 508 Amendment to the Rehabilitation Act of 1973 requires all Federal agencies' electronic and information technology to be accessible to those with disabilities. Both members of the public and federal employees have the right to access this technology, such as computer hardware and software, websites, phone systems, and copiers.
Also, Section 504 of the Rehabilitation Act prohibits discrimination on the basis of disability for entities receiving federal funds and has been cited in multiple lawsuits against organizations such as hospitals that receive federal funds through medicare/medicaid.
In addition, Title III of the Americans with Disabilities Act (ADA) prohibits discrimination on the basis of disability. There is some debate on the matter; multiple courts and the U.S. Department of Justice have taken the position that the ADA requires website and app operators and owners to take affirmative steps to make their websites and apps accessible to disabled persons and compatible with common assistive technologies such as the JAWS screen reader, while other courts have taken the position that the ADA does not apply online. The U.S. Department of Justice has endorsed the WCAG2.0AA standard as an appropriate standard for accessibility in multiple settlement agreements.
Numerous lawsuits challenging websites and mobile apps on the basis of the ADA have been filed since 2017. These cases appears spurred by a 2017 case, Gil v. Winn Dixie Stores, in which a federal court in Florida ruled that Winn Dixie's website must be accessible. Around 800 cases related to web accessibility were filed in 2017, and over 2,200 were filed in 2018. Additionally, though the Justice Department had stated in 2010 that they would publish guidelines for web accessibility, they reversed this plan in 2017, also spurring legal action against inaccessible sites.
A notable lawsuit related to the ADA was filed against Domino's Pizza by a blind user who could not use Domino's mobile app. At the federal district level, the court ruled in favor of Domino's as the Justice Department had not established the guidelines for accessibility, but this was appealed to the Ninth Circuit. The Ninth Circuit overruled the district court, ruling that because Domino's is a brick-and-mortar store, which must meet the ADA, and the mobile app an extension of their services, their app must also be compliant with the ADA. Domino's petitioned to the Supreme Court, backed by many other restaurants and retail chains, arguing that this decision impacts their Due Process since disabled customers have other, more accessible means to order. In October 2019, the Supreme Court declined to hear the case, which effectively upheld the decision of the 9th Circuit Court and requires the case to be heard as it stands.
The number and cost of federal accessibility lawsuits has risen dramatically in the last few years.
Website accessibility audits
A growing number of organizations, companies and consultants offer website accessibility audits. These audits, a type of system testing, identify accessibility problems that exist within a website, and provide advice and guidance on the steps that need to be taken to correct these problems.
A range of methods are used to audit websites for accessibility:
Automated tools such as the Check Meister website evaluation tool are available which can identify some of the problems that are present. Depending on the tool the result may vary widely making it difficult to compare test results.
Expert technical reviewers, knowledgeable in web design technologies and accessibility, can review a representative selection of pages and provide detailed feedback and advice based on their findings.
User testing, usually overseen by technical experts, involves setting tasks for ordinary users to carry out on the website, and reviewing the problems these users encounter as they try to carry out the tasks.
Each of these methods has its strengths and weaknesses:
Automated tools can process many pages in a relatively short length of time, but can only identify a limited portion of the accessibility problems that might be present in the website.
Technical expert review will identify many of the problems that exist, but the process is time-consuming, and many websites are too large to make it possible for a person to review every page.
User testing combines elements of usability and accessibility testing, and is valuable for identifying problems that might otherwise be overlooked, but needs to be used knowledgeably to avoid the risk of basing design decisions on one user's preferences.
Ideally, a combination of methods should be used to assess the accessibility of a website.
Remediating inaccessible websites
Once an accessibility audit has been conducted, and accessibility errors have been identified, the errors will need to be remediated in order to ensure the site is compliant with accessibility errors. The traditional way of correcting an inaccessible site is to go back into the source code, reprogram the error, and then test to make sure the bug was fixed. If the website is not scheduled to be revised in the near future, that error (and others) would remain on the site for a lengthy period of time, possibly violating accessibility guidelines. Because this is a complicated process, many website owners choose to build accessibility into a new site design or re-launch, as it can be more efficient to develop the site to comply with accessibility guidelines, rather than to remediate errors later.
With the progress in AI technology, web accessibility has become more accessible. With 3rd party add-ons that leverage AI and machine learning, it is possible to offer changes to the website design without altering the source code. This way, a website can be accessible to different types of users without the need to adjust the website for every accessibility equipment.
Accessible Web applications and WAI-ARIA
For a web page to be accessible all important semantics about the page's functionality must be available so that assistive technology can understand and process the content and adapt it for the user.
However, as content becomes more and more complex, the standard HTML tags and attributes become inadequate in providing semantics reliably. Modern Web applications often apply scripts to elements to control their functionality and to enable them to act as a control or other dynamic component. These custom components or widgets do not provide a way to convey semantic information to the user agent. WAI-ARIA (Accessible Rich Internet Applications) is a specification published by the World Wide Web Consortium that specifies how to increase the accessibility of dynamic content and user interface components developed with Ajax, HTML, JavaScript and related technologies. ARIA enables accessibility by enabling the author to provide all the semantics to fully describe its supported behaviour. It also allows each element to expose its current states and properties and its relationships between other elements. Accessibility problems with the focus and tab index are also corrected.
Neurological UX
Neurological UX is a specialised branch of web accessibility aimed at designing digital experiences that cater to individuals with neurological dispositions such as ADHD, dyslexia, autism spectrum disorder (ASD), and anxiety. Coined by Gareth Slinn in his book NeurologicalUX neurologicalux.com, this approach goes beyond conventional accessibility by addressing cognitive, emotional, and behavioural needs.
Neurological UX focuses on creating interfaces that reduce cognitive load, support diverse ways of thinking, and accommodate challenges in executive functioning. Core principles include:
Clarity and Simplicity: Streamlining interfaces to reduce distractions and enhance focus for users with ADHD and similar conditions.
Cognitive Support: Offering features like tooltips, hover states, or progressive disclosures to help users with memory and information processing challenges, such as those with dyslexia or traumatic brain injuries.
Emotionally Comfortable Design: Using calming color schemes, predictable navigation, and consistent layouts to reduce anxiety for users prone to stress.
Flexible Interaction Models: Providing adjustable settings for font size, spacing, and contrast to suit the needs of users with dyslexia, visual stress, or sensory processing disorders.
Intuitive Feedback: Ensuring interactive elements provide clear, immediate feedback to accommodate difficulties with impulse control and decision-making.
Minimising Overstimulation: Avoiding overly busy layouts, autoplay media, or complex animations that can overwhelm users with ASD or ADHD.
By prioritising usability and emotional well-being, Neurological UX seeks to create inclusive digital experiences that empower all users, regardless of their cognitive or neurological profile. This approach not only improves accessibility compliance but also fosters a more equitable and human-centered web.
See also
Accessible publishing
Augmentative and alternative communication
Blue Beanie Day
Computer accessibility
Device independence
Digital divide
European Internet Accessibility Observatory
Knowbility
Maguire v Sydney Organising Committee for the Olympic Games (2000)
Multimodal interaction
Neurologicalux
Progressive enhancement
Universal design
Web Accessibility Initiative
Web engineering
Web interoperability
Web literacy
References
Further reading
External links
How To Design For Accessibility (BBC)
Inclusive Design Principles
Apple Developer Accessibility Resources
BBC GEL Technical Accessibility Guides
Neurological UX
Google Developer Accessibility Resources
Microsoft Developer Accessibility Resources
W3C WCAG Developer Accessibility Resources
A Curated List of Awesome Accessibility Tools, Articles, and Resources
ADA Compliance For Websites Checklist
Standards and guidelines
W3C – Web Accessibility Initiative (WAI)
W3C – Web Content Accessibility Guidelines (WCAG) 2.0
Equality and Human Rights Commission: PAS 78: a guide to good practice in commissioning accessible websites (which BS 8878 supersedes)
European Union – Unified Web Evaluation Methodology 1.2
University of Illinois iCITA HTML Accessibility Best Practices
BBC GEL Product Accessibility Guidelines
BBC GEL Subtitles (Captions) Guidelines
BBC Editorial Accessibility Guide (Online and TV)
Accessible information
Web design
Usability | Web accessibility | Engineering | 6,914 |
29,840 | https://en.wikipedia.org/wiki/Television%20channel | A television channel, or TV channel, is a terrestrial frequency or virtual number over which a television station or television network is distributed. For example, in North America, channel 2 refers to the terrestrial or cable band of 54 to 60 MHz, with carrier frequencies of 55.25 MHz for NTSC analog video (VSB) and 59.75 MHz for analog audio (FM), or 55.31 MHz for digital ATSC (8VSB). Channels may be shared by many different television stations or cable-distributed channels depending on the location and service provider.
Depending on the multinational bandplan for a given region, analog television channels are typically 6, 7, or 8 MHz in bandwidth, and therefore television channel frequencies vary as well. Channel numbering is also different. Digital terrestrial television channels are the same as their analog predecessors for legacy reasons, however through multiplexing, each physical radio frequency (RF) channel can carry several digital subchannels. On satellites, each transponder normally carries one channel, however multiple small, independent channels can be on one transponder, with some loss of bandwidth due to the need for guard bands between unrelated transmissions. ISDB, used in Japan and Brazil, has a similar segmented mode.
Preventing interference between terrestrial channels in the same area is accomplished by skipping at least one channel between two analog stations' frequency allocations. Where channel numbers are sequential, frequencies are not contiguous, such as channel 6 to 7 skip from VHF low to high band, and channel 13 to 14 jump to UHF. On cable TV, it is possible to use adjacent channels only because they are all at the same power, something which could only be done terrestrially if the two stations were transmitted at the same power and height from the same location. For DTT, selectivity is inherently better, therefore channels adjacent (either to analog or digital stations) can be used even in the same area.
Other meanings
Commonly, the term television channel is used to mean a television station or its pay television counterpart (both outlined below). Sometimes, especially outside the U.S. and in the context of pay television, it is used instead of the term television network, which otherwise (in its technical use above) describes a group of geographically-distributed television stations that share affiliation/ownership and some or all of their programming with one another.
This terminology may be muddled somewhat in other jurisdictions, for instance Europe, where terrestrial channels are commonly mapped from physical channels to common numerical positions (i.e. BBC One does not broadcast on any particular channel 1 but is nonetheless mapped to the 1 input on most British television sets). On digital platforms, such (location) channels are usually arbitrary and changeable, due to virtual channels.
Television station
A television station is a type of terrestrial station that broadcasts both audio and video to television receivers in a particular area. Traditionally, TV stations made their broadcasts by sending specially-encoded radio signals over the air, called terrestrial television. Individual television stations are usually granted licenses by a government agency to use a particular section of the radio spectrum (a channel) through which they send their signals. Some stations use LPTV broadcast translators to retransmit to further areas.
Many television stations are now in the process of converting from analog terrestrial (NTSC, PAL or SECAM) broadcast, to digital terrestrial (ATSC broadcast, DVB or ISDB).
Non-terrestrial television channels
Because some regions have had difficulty picking up terrestrial television signals (particularly in mountainous areas), alternative means of distribution such as direct-to-home satellite and cable television have been introduced. Television channels specifically built to run on cable or satellite blur the line between TV station and TV network. That fact led some early cable channels to call themselves superstations.
Satellite and cable have created changes. Local programming TV stations in an area can sign-up or even be required to be carried on cable, but content providers like TLC cannot. They are not licensed to run broadcast equipment like a station, and they do not regularly provide content to licensed broadcasters either. Furthermore, a distributor like TNT may start producing its own programming, and shows presented exclusively on pay-TV by one distributor may be syndicated to terrestrial stations. The cost of creating a nationwide channel has been reduced and there has been a huge increase in the number of such channels, with most catering to a small group.
From the definitions above, use of the terms network or station in reference to nationwide cable or satellite channels is technically inaccurate. However, this is an arbitrary, inconsequential distinction, and varies from company to company. Indeed, the term cable network has entered into common usage in the United States in reference to such channels, even with the existence of direct broadcast satellite. There is even some geographical separation among national pay television channels in the U.S., be it programming (e.g., the Bally Sports group of regional sports channels, which share several programs), or simply regionalized advertising inserted by the local cable company.
Should a legal distinction be necessary between a (location) channel as defined above and a television channel in this sense, the terms programming service (e.g.) or programming undertaking (for instance,) may be used instead of the latter definition.
See also
Barker channel
Free-to-air
Lists of television channels
Pay television
Streaming television
Television channel frequencies
References
External links
What ever happened to Channel 1?
Channel
Broadcast engineering
Telecommunication theory | Television channel | Engineering | 1,101 |
14,712,455 | https://en.wikipedia.org/wiki/Toxicology%20testing | Toxicology testing, also known as safety assessment, or toxicity testing, is the process of determining the degree to which a substance of interest negatively impacts the normal biological functions of an organism, given a certain exposure duration, route of exposure, and substance concentration.
Toxicology testing is often conducted by researchers who follow established toxicology test protocols for a certain substance, mode of exposure, exposure environment, duration of exposure, a particular organism of interest, or for a particular developmental stage of interest. Toxicology testing is commonly conducted during preclinical development for a substance intended for human exposure. Stages of in silico, in vitro and in vivo research are conducted to determine safe exposure doses in model organisms. If necessary, the next phase of research involves human toxicology testing during a first-in-man study. Toxicology testing may be conducted by the pharmaceutical industry, biotechnology companies, contract research organizations, or environmental scientists.
History
The study of poisons and toxic substances has a long history dating back to ancient times, when humans recognized the dangers posed by various natural compounds. However, the formalization and development of toxicology as a distinct scientific discipline can be attributed to notable figures like Paracelsus (1493–1541) and Orfila (1757–1853).
Paracelsus (1493–1541): Often regarded as the "father of toxicology, Paracelsus, whose real name was Theophrastus von Hohenheim, challenged prevailing beliefs about poisons during the Renaissance era. He introduced the fundamental concept that "the dose makes the poison," emphasizing that the toxicity of a substance depends on its quantity. This principle remains a cornerstone of toxicology.
Mathieu Orfila (1787–1853): A Spanish-born chemist and toxicologist, Orfila made significant contributions to the field in the 19th century. He is best known for his pioneering work in forensic toxicology, particularly in developing methods for detecting and analyzing poisons in biological samples. Orfila's work played a vital role in establishing toxicology as a recognized scientific discipline and laid the groundwork for modern forensic toxicology practices in criminal investigations and legal cases.
Prevalence
Around one million animals, primate and non-primate, are used every year in Europe in toxicology tests. In the UK, one-fifth of animal experiments are toxicology tests.
Methodology
Toxicity tests examine finished products such as pesticides, medications, cosmetics, food additives such as artificial sweeteners, packing materials, and air freshener, or their chemical ingredients. The substances are tested using a variety of methods including dermal application, respiration, orally, injected or in water sources. They are applied to the skin or eyes; injected intravenously, intramuscularly, or subcutaneously; inhaled either by placing a mask over the animals, or by placing them in an inhalation chamber; or administered orally, placing them in the animals' food or through a tube into the stomach. Doses may be given once, repeated regularly for many months, or for the lifespan of the animal. Toxicity tests can also be conducted on materials need to be disposed such as sediment to be disposed in a marine environment.
Initial toxicity tests often involve computer modelling (in silico) to predict toxicokinetic pathways or to predict potential exposure points by modelling weather and water currents to determine which animals or regions that will be most affected.
Other less intensive and more common in vitro toxicology tests involve, amongst others, microtox assays to observe bacteria growth and productivity. This can be adapted to plant life measure photosynthesis levels and growth of exposed plants.
Contract research organizations
A contract research organization (CRO) is an organization that provides support to the pharmaceutical, biotechnology, chemical, and medical device industries in the form of research services outsourced on a contract basis. A CRO may provide toxicity testing services, along with others such as assay development, preclinical research, clinical research, clinical trials management, and pharmacovigilance. CROs also support foundations, research institutions, and universities, in addition to governmental organizations (such as the NIH, EMEA, etc.).
Regulation
United States
In the United States, toxicology tests are subject to Good Laboratory Practice guidelines and other Food and Drug Administration laws.
Europe
Animal testing for cosmetic purposes is currently banned all across the European Union.
See also
Animal testing
Children's Environmental Exposure Research Study
References
Further reading
External links
What is aquatic toxicity testing?
Genetic and Molecular Toxicology Assays, Safety Assessment, Animal Research Laboratories Agency.
emka TECHNOLOGIES Physiological data acquisition & analysis for preclinical research
Animal testing
Tests
Toxicology | Toxicology testing | Chemistry,Environmental_science | 953 |
14,271,066 | https://en.wikipedia.org/wiki/G%20alpha%20subunit | G alpha subunits are one of the three types of subunit of guanine nucleotide binding proteins, which are membrane-associated, heterotrimeric G proteins.
Background
G proteins and their receptors (GPCRs) form one of the most prevalent signaling systems in mammalian cells, regulating systems as diverse as sensory perception, cell growth and hormonal regulation. At the cell surface, the binding of ligands such as hormones and neurotransmitters to a GPCR activates the receptor by causing a conformational change, which in turn activates the bound G protein on the intracellular-side of the membrane. The activated receptor promotes the exchange of bound GDP for GTP on the G protein alpha subunit. GTP binding changes the conformation of switch regions within the alpha subunit, which allows the bound trimeric G protein (inactive) to be released from the receptor, and to dissociate into active alpha subunit (GTP-bound) and beta/gamma dimer. The alpha subunit and the beta/gamma dimer go on to activate distinct downstream effectors, such as adenylyl cyclase, phosphodiesterases, phospholipase C, and ion channels. These effectors in turn regulate the intracellular concentrations of secondary messengers, such as cAMP, diacylglycerol, sodium or calcium cations, which ultimately lead to a physiological response, usually via the downstream regulation of gene transcription. The cycle is completed by the hydrolysis of alpha subunit-bound GTP to GDP, resulting in the re-association of the alpha and beta/gamma subunits and their binding to the receptor, which terminates the signal. The length of the G protein signal is controlled by the duration of the GTP-bound alpha subunit, which can be regulated by RGS (regulator of G protein signalling) proteins or by covalent modifications.
Forms of subunit
There are several isoforms of each subunit, many of which have splice variants, which together can make up hundreds of combinations of G proteins. The specific combination of subunits in heterotrimeric G proteins affects not only which receptor it can bind to, but also which downstream target is affected, providing the means to target specific physiological processes in response to specific external stimuli. G proteins carry lipid modifications on one or more of their subunits to target them to the plasma membrane and to contribute to protein interactions.
This family consists of the G protein alpha subunit, which acts as a weak GTPase. G protein classes are defined based on the sequence and function of their alpha subunits, which in mammals fall into several sub-types: G(S)alpha, G(Q)alpha, G(I)alpha, transducin and G(12)alpha; there are also fungal and plant classes of alpha subunits. The alpha subunit consists of two domains: a GTP-binding domain and a helical insertion domain (). The GTP-binding domain is homologous to Ras-like small GTPases, and includes switch regions I and II, which change conformation during activation. The switch regions are loops of alpha-helices with conformations sensitive to guanine nucleotides. The helical insertion domain is inserted into the GTP-binding domain before switch region I and is unique to heterotrimeric G proteins. This helical insertion domain functions to sequester the guanine nucleotide at the interface with the GTP-binding domain and must be displaced to enable nucleotide dissociation.
References
Protein domains
G proteins | G alpha subunit | Chemistry,Biology | 737 |
333,692 | https://en.wikipedia.org/wiki/Radiation%20protection | Radiation protection, also known as radiological protection, is defined by the International Atomic Energy Agency (IAEA) as "The protection of people from harmful effects of exposure to ionizing radiation, and the means for achieving this". Exposure can be from a source of radiation external to the human body or due to internal irradiation caused by the ingestion of radioactive contamination.
Ionizing radiation is widely used in industry and medicine, and can present a significant health hazard by causing microscopic damage to living tissue. There are two main categories of ionizing radiation health effects. At high exposures, it can cause "tissue" effects, also called "deterministic" effects due to the certainty of them happening, conventionally indicated by the unit gray and resulting in acute radiation syndrome. For low level exposures there can be statistically elevated risks of radiation-induced cancer, called "stochastic effects" due to the uncertainty of them happening, conventionally indicated by the unit sievert.
Fundamental to radiation protection is the avoidance or reduction of dose using the simple protective measures of time, distance and shielding. The duration of exposure should be limited to that necessary, the distance from the source of radiation should be maximised, and the source or the target shielded wherever possible. To measure personal dose uptake in occupational or emergency exposure, for external radiation personal dosimeters are used, and for internal dose due to ingestion of radioactive contamination, bioassay techniques are applied.
For radiation protection and dosimetry assessment the International Commission on Radiation Protection (ICRP) and International Commission on Radiation Units and Measurements (ICRU) publish recommendations and data which is used to calculate the biological effects on the human body of certain levels of radiation, and thereby advise acceptable dose uptake limits.
Principles
The ICRP recommends, develops and maintains the International System of Radiological Protection, based on evaluation of the large body of scientific studies available to equate risk to received dose levels. The system's health objectives are "to manage and control exposures to ionising radiation so that deterministic effects are prevented, and the risks of stochastic effects are reduced to the extent reasonably achievable".
The ICRP's recommendations flow down to national and regional regulators, which have the opportunity to incorporate them into their own law; this process is shown in the accompanying block diagram. In most countries a national regulatory authority works towards ensuring a secure radiation environment in society by setting dose limitation requirements that are generally based on the recommendations of the ICRP.
Exposure situations
The ICRP recognises planned, emergency, and existing exposure situations, as described below;
Planned exposure – defined as "...where radiological protection can be planned in advance, before exposures occur, and where the magnitude and extent of the exposures can be reasonably predicted." These are such as in occupational exposure situations, where it is necessary for personnel to work in a known radiation environment.
Emergency exposure – defined as "...unexpected situations that may require urgent protective actions". This would be such as an emergency nuclear event.
Existing exposure – defined as "...being those that already exist when a decision on control has to be taken". These can be such as from naturally occurring radioactive materials which exist in the environment.
Regulation of dose uptake
The ICRP uses the following overall principles for all controllable exposure situations.
Justification: No unnecessary use of radiation is permitted, which means that the advantages must outweigh the disadvantages.
Limitation: Each individual must be protected against risks that are too great, through the application of individual radiation dose limits.
Optimization: This process is intended for application to those situations that have been deemed to be justified. It means "the likelihood of incurring exposures, the number of people exposed, and the magnitude of their individual doses" should all be kept As Low As Reasonably Achievable (or Reasonably Practicable) known as ALARA or ALARP. It takes into account economic and societal factors.
Factors in external dose uptake
There are three factors that control the amount, or dose, of radiation received from a source. Radiation exposure can be managed by a combination of these factors:
Time: Reducing the time of an exposure reduces the effective dose proportionally. An example of reducing radiation doses by reducing the time of exposures might be improving operator training to reduce the time they take to handle a radioactive source.
Distance: Increasing distance reduces dose due to the inverse square law. Distance can be as simple as handling a source with forceps rather than fingers. For example, if a problem arises during fluoroscopic procedure step away from the patient if feasible.
Shielding: Sources of radiation can be shielded with solid or liquid material, which absorbs the energy of the radiation. The term 'biological shield' is used for absorbing material placed around a nuclear reactor, or other source of radiation, to reduce the radiation to a level safe for humans. The shielding materials are concrete and lead shield which is 0.25 mm thick for secondary radiation and 0.5 mm thick for primary radiation
Internal dose uptake
Internal dose, due to the inhalation or ingestion of radioactive substances, can result in stochastic or deterministic effects, depending on the amount of radioactive material ingested and other biokinetic factors.
The risk from a low level internal source is represented by the dose quantity committed dose, which has the same risk as the same amount of external effective dose.
The intake of radioactive material can occur through four pathways:
inhalation of airborne contaminants such as radon gas and radioactive particles
ingestion of radioactive contamination in food or liquids
absorption of vapours such as tritium oxide through the skin
injection of medical radioisotopes such as technetium-99m
The occupational hazards from airborne radioactive particles in nuclear and radio-chemical applications are greatly reduced by the extensive use of gloveboxes to contain such material. To protect against breathing in radioactive particles in ambient air, respirators with particulate filters are worn.
To monitor the concentration of radioactive particles in ambient air, radioactive particulate monitoring instruments measure the concentration or presence of airborne materials.
For ingested radioactive materials in food and drink, specialist laboratory radiometric assay methods are used to measure the concentration of such materials.
Recommended limits on dose uptake
The ICRP recommends a number of limits for dose uptake in table 8 of ICRP report 103. These limits are "situational", for planned, emergency and existing situations. Within these situations, limits are given for certain exposed groups;
Planned exposure – limits given for occupational, medical and public exposure. The occupational exposure limit of effective dose is 20 mSv per year, averaged over defined periods of 5 years, with no single year exceeding 50 mSv. The public exposure limit is 1 mSv in a year.
Emergency exposure – limits given for occupational and public exposure
Existing exposure – reference levels for all persons exposed
The public information dose chart of the USA Department of Energy, shown here on the right, applies to USA regulation, which is based on ICRP recommendations. Note that examples in lines 1 to 4 have a scale of dose rate (radiation per unit time), whilst 5 and 6 have a scale of total accumulated dose.
ALARP & ALARA
ALARP is an acronym for an important principle in exposure to radiation and other occupational health risks and in the UK stands for As Low As Reasonably Practicable. The aim is to minimize the risk of radioactive exposure or other hazard while keeping in mind that some exposure may be acceptable in order to further the task at hand. The equivalent term ALARA, As Low As Reasonably Achievable, is more commonly used outside the UK.
This compromise is well illustrated in radiology. The application of radiation can aid the patient by providing doctors and other health care professionals with a medical diagnosis, but the exposure of the patient should be reasonably low enough to keep the statistical probability of cancers or sarcomas (stochastic effects) below an acceptable level, and to eliminate deterministic effects (e.g. skin reddening or cataracts). An acceptable level of incidence of stochastic effects is considered to be equal for a worker to the risk in other radiation work generally considered to be safe.
This policy is based on the principle that any amount of radiation exposure, no matter how small, can increase the chance of negative biological effects such as cancer. It is also based on the principle that the probability of the occurrence of negative effects of radiation exposure increases with cumulative lifetime dose. These ideas are combined to form the linear no-threshold model which says that there is not a threshold at which there is an increase in the rate of occurrence of stochastic effects with increasing dose. At the same time, radiology and other practices that involve use of ionizing radiation bring benefits, so reducing radiation exposure can reduce the efficacy of a medical practice. The economic cost, for example of adding a barrier against radiation, must also be considered when applying the ALARP principle. Computed tomography, better known as CT scans or CAT scans have made an enormous contribution to medicine, however not without some risk. The ionizing radiation used in CT scans can lead to radiation-induced cancer. Age is a significant factor in risk associated with CT scans, and in procedures involving children and systems that do not require extensive imaging, lower doses are used.
Personal radiation dosimeters
The radiation dosimeter is an important personal dose measuring instrument. It is worn by the person being monitored and is used to estimate the external radiation dose deposited in the individual wearing the device. They are used for gamma, X-ray, beta and other strongly penetrating radiation, but not for weakly penetrating radiation such as alpha particles. Traditionally, film badges were used for long-term monitoring, and quartz fibre dosimeters for short-term monitoring. However, these have been mostly superseded by thermoluminescent dosimetry (TLD) badges and electronic dosimeters. Electronic dosimeters can give an alarm warning if a preset dose threshold has been reached, enabling safer working in potentially higher radiation levels, where the received dose must be continually monitored.
Workers exposed to radiation, such as radiographers, nuclear power plant workers, doctors using radiotherapy, those in laboratories using radionuclides, and HAZMAT teams are required to wear dosimeters so a record of occupational exposure can be made. Such devices are generally termed "legal dosimeters" if they have been approved for use in recording personnel dose for regulatory purposes.
Dosimeters can be worn to obtain a whole body dose and there are also specialist types that can be worn on the fingers or clipped to headgear, to measure the localised body irradiation for specific activities.
Common types of wearable dosimeters for ionizing radiation include:
Film badge dosimeter
Quartz fibre dosimeter
Electronic personal dosimeter
Thermoluminescent dosimeter
Radiation protection
Almost any material can act as a shield from gamma or x-rays if used in sufficient amounts. Different types of ionizing radiation interact in different ways with shielding material. The effectiveness of shielding is dependent on stopping power, which varies with the type and energy of radiation and the shielding material used. Different shielding techniques are therefore used depending on the application and the type and energy of the radiation.
Shielding reduces the intensity of radiation, increasing with thickness. This is an exponential relationship with gradually diminishing effect as equal slices of shielding material are added. A quantity known as the halving-thicknesses is used to calculate this. For example, a practical shield in a fallout shelter with ten halving-thicknesses of packed dirt, which is roughly , reduces gamma rays to 1/1024 of their original intensity (i.e. 2−10).
The effectiveness of a shielding material in general increases with its atomic number, called Z, except for neutron shielding, which is more readily shielded by the likes of neutron absorbers and moderators such as compounds of boron e.g. boric acid, cadmium, carbon and hydrogen.
Graded-Z shielding is a laminate of several materials with different Z values (atomic numbers) designed to protect against ionizing radiation. Compared to single-material shielding, the same mass of graded-Z shielding has been shown to reduce electron penetration over 60%. It is commonly used in satellite-based particle detectors, offering several benefits:
protection from radiation damage
reduction of background noise for detectors
lower mass compared to single-material shielding
Designs vary, but typically involve a gradient from high-Z (usually tantalum) through successively lower-Z elements such as tin, steel, and copper, usually ending with aluminium. Sometimes even lighter materials such as polypropylene or boron carbide are used.
In a typical graded-Z shield, the high-Z layer effectively scatters protons and electrons. It also absorbs gamma rays, which produces X-ray fluorescence. Each subsequent layer absorbs the X-ray fluorescence of the previous material, eventually reducing the energy to a suitable level. Each decrease in energy produces Bremsstrahlung and Auger electrons, which are below the detector's energy threshold. Some designs also include an outer layer of aluminium, which may simply be the skin of the satellite. The effectiveness of a material as a biological shield is related to its cross-section for scattering and absorption, and to a first approximation is proportional to the total mass of material per unit area interposed along the line of sight between the radiation source and the region to be protected. Hence, shielding strength or "thickness" is conventionally measured in units of g/cm2. The radiation that manages to get through falls exponentially with the thickness of the shield. In x-ray facilities, walls surrounding the room with the x-ray generator may contain lead shielding such as lead sheets, or the plaster may contain barium sulfate. Operators view the target through a leaded glass screen, or if they must remain in the same room as the target, wear lead aprons.
Particle radiation
Particle radiation consists of a stream of charged or neutral particles, both charged ions and subatomic elementary particles. This includes solar wind, cosmic radiation, and neutron flux in nuclear reactors.
Alpha particles (helium nuclei) are the least penetrating. Even very energetic alpha particles can be stopped by a single sheet of paper.
Beta particles (electrons) are more penetrating, but still can be absorbed by a few millimetres of aluminium. However, in cases where high-energy beta particles are emitted, shielding must be accomplished with low atomic weight materials, e.g. plastic, wood, water, or acrylic glass (Plexiglas, Lucite). This is to reduce generation of Bremsstrahlung X-rays. In the case of beta+ radiation (positrons), the gamma radiation from the electron–positron annihilation reaction poses additional concern.
Neutron radiation is not as readily absorbed as charged particle radiation, which makes this type highly penetrating. In a process called neutron activation, neutrons are absorbed by nuclei of atoms in a nuclear reaction. This most often creates a secondary radiation hazard, as the absorbing nuclei transmute to the next-heavier isotope, many of which are unstable.
Cosmic radiation is not a common concern on Earth, as the Earth's atmosphere absorbs it and the magnetosphere acts as a shield, but it poses a significant problem for satellites and astronauts, especially while passing through the Van Allen Belt or while completely outside the protective regions of the Earth's magnetosphere. Frequent fliers may be at a slightly higher risk because of the decreased absorption from thinner atmosphere. Cosmic radiation is extremely high energy, and is very penetrating.
Electromagnetic radiation
Electromagnetic radiation consists of emissions of electromagnetic waves, the properties of which depend on the wavelength.
X-ray and gamma radiation are best absorbed by atoms with heavy nuclei; the heavier the nucleus, the better the absorption. In some special applications, depleted uranium or thorium are used, but lead is much more common; several cm are often required. Barium sulfate is used in some applications too. However, when the cost is important, almost any material can be used, but it must be far thicker. Most nuclear reactors use thick concrete shields to create a bioshield with a thin water-cooled layer of lead on the inside to protect the porous concrete from the coolant inside. The concrete is also made with heavy aggregates, such as Baryte or Magnetite, to aid in the shielding properties of the concrete. Gamma rays are better absorbed by materials with high atomic numbers and high density, although neither effect is important compared to the total mass per area in the path of the gamma ray.
Ultraviolet (UV) radiation is ionizing in its shortest wavelengths but is not penetrating, so it can be shielded by thin opaque layers such as sunscreen, clothing, and protective eyewear. Protection from UV is simpler than for the other forms of radiation above, so it is often considered separately.
In some cases, improper shielding can actually make the situation worse, when the radiation interacts with the shielding material and creates secondary radiation that absorbs in the organisms more readily. For example, although high atomic number materials are very effective in shielding photons, using them to shield beta particles may cause higher radiation exposure due to the production of Bremsstrahlung x-rays, and hence low atomic number materials are recommended. Also, using a material with a high neutron activation cross section to shield neutrons will result in the shielding material itself becoming radioactive and hence more dangerous than if it were not present.
Personal protective equipment
Personal protective equipment (PPE) includes all clothing and accessories which can be worn to prevent severe illness and injury as a result of exposure to radioactive material. These include an SR100 (protection for 1hr), SR200 (protection for 2 hours). Because radiation can affect humans through internal and external contamination, various protection strategies have been developed to protect humans from the harmful effects of radiation exposure from a spectrum of sources. A few of these strategies developed to shield from internal, external, and high energy radiation are outlined below.
Internal contamination protective equipment
Internal contamination protection equipment protects against the inhalation and ingestion of radioactive material. Internal deposition of radioactive material result in direct exposure of radiation to organs and tissues inside the body. The respiratory protective equipment described below are designed to minimize the possibility of such material being inhaled or ingested as emergency workers are exposed to potentially radioactive environments.
Reusable air purifying respirators (APR)
Elastic face piece worn over the mouth and nose
Contains filters, cartridges, and canisters to provide increased protection and better filtration
Powered air-purifying respirator (PAPR)
Battery powered blower forces contamination through air purifying filters
Purified air delivered under positive pressure to face piece
Supplied-air respirator (SAR)
Compressed air delivered from a stationary source to the face piece
Auxiliary escape respirator
Protects wearer from breathing harmful gases, vapours, fumes, and dust
Can be designed as an air-purifying escape respirator (APER) or a self-contained breathing apparatus (SCBA) type respirator
SCBA type escape respirators have an attached source of breathing air and a hood that provides a barrier against contaminated outside air
Self-contained breathing apparatus (SCBA)
Provides very pure, dry compressed air to full facepiece mask via a hose
Air is exhaled to environment
Worn when entering environments immediately dangerous to life and health (IDLH) or when information is inadequate to rule out IDLH atmosphere
External contamination protective equipment
External contamination protection equipment provides a barrier to shield radioactive material from being deposited externally on the body or clothes. The dermal protective equipment described below acts as a barrier to block radioactive material from physically touching the skin, but does not protect against externally penetrating high energy radiation.
Chemical-resistant inner suit
Porous overall suit—Dermal protection from aerosols, dry particles, and non hazardous liquids.
Non-porous overall suit to provide dermal protection from:
Dry powders and solids
Blood-borne pathogens and bio-hazards
Chemical splashes and inorganic acid/base aerosols
Mild liquid chemical splashes from toxics and corrosives
Toxic industrial chemicals and materials
Level C equivalent: Bunker gear
Firefighter protective clothing
Flame/water resistant
Helmet, gloves, foot gear, and hood
Level B equivalent: Non-gas-tight encapsulating suit
Designed for environments that are immediate health risks but contain no substances that can be absorbed by skin
Level A equivalent: Totally encapsulating chemical- and vapour-protective suit
Designed for environments that are immediate health risks and contain substances that can be absorbed by skin
External penetrating radiation
There are many solutions to shielding against low-energy radiation exposure like low-energy X-rays. Lead shielding wear such as lead aprons can protect patients and clinicians from the potentially harmful radiation effects of day-to-day medical examinations. It is quite feasible to protect large surface areas of the body from radiation in the lower-energy spectrum because very little shielding material is required to provide the necessary protection. Recent studies show that copper shielding is far more effective than lead and is likely to replace it as the standard material for radiation shielding.
Personal shielding against more energetic radiation such as gamma radiation is very difficult to achieve as the large mass of shielding material required to properly protect the entire body would make functional movement nearly impossible. For this, partial body shielding of radio-sensitive internal organs is the most viable protection strategy.
The immediate danger of intense exposure to high-energy gamma radiation is acute radiation syndrome (ARS), a result of irreversible bone marrow damage. The concept of selective shielding is based in the regenerative potential of the hematopoietic stem cells found in bone marrow. The regenerative quality of stem cells make it only necessary to protect enough bone marrow to repopulate the body with unaffected stem cells after the exposure: a similar concept which is applied in hematopoietic stem cell transplantation (HSCT), which is a common treatment for patients with leukemia. This scientific advancement allows for the development of a new class of relatively lightweight protective equipment that shields high concentrations of bone marrow to defer the hematopoietic sub-syndrome of acute radiation syndrome to much higher dosages.
One technique is to apply selective shielding to protect the high concentration of bone marrow stored in the hips and other radio-sensitive organs in the abdominal area. This allows first responders a safe way to perform necessary missions in radioactive environments.
Radiation protection instruments
Practical radiation measurement using calibrated radiation protection instruments is essential in evaluating the effectiveness of protection measures, and in assessing the radiation dose likely to be received by individuals. The measuring instruments for radiation protection are both "installed" (in a fixed position) and portable (hand-held or transportable).
Installed instruments
Installed instruments are fixed in positions which are known to be important in assessing the general radiation hazard in an area. Examples are installed "area" radiation monitors, Gamma interlock monitors, personnel exit monitors, and airborne particulate monitors.
The area radiation monitor will measure the ambient radiation, usually X-Ray, Gamma or neutrons; these are radiations that can have significant radiation levels over a range in excess of tens of metres from their source, and thereby cover a wide area.
Gamma radiation "interlock monitors" are used in applications to prevent inadvertent exposure of workers to an excess dose by preventing personnel access to an area when a high radiation level is present. These interlock the process access directly.
Airborne contamination monitors measure the concentration of radioactive particles in the ambient air to guard against radioactive particles being ingested, or deposited in the lungs of personnel. These instruments will normally give a local alarm, but are often connected to an integrated safety system so that areas of plant can be evacuated and personnel are prevented from entering an air of high airborne contamination.
Personnel exit monitors (PEM) are used to monitor workers who are exiting a "contamination controlled" or potentially contaminated area. These can be in the form of hand monitors, clothing frisk probes, or whole body monitors. These monitor the surface of the workers body and clothing to check if any radioactive contamination has been deposited. These generally measure alpha or beta or gamma, or combinations of these.
The UK National Physical Laboratory publishes a good practice guide through its Ionising Radiation Metrology Forum concerning the provision of such equipment and the methodology of calculating the alarm levels to be used.
Portable instruments
Portable instruments are hand-held or transportable. The hand-held instrument is generally used as a survey meter to check an object or person in detail, or assess an area where no installed instrumentation exists. They can also be used for personnel exit monitoring or personnel contamination checks in the field. These generally measure alpha, beta or gamma, or combinations of these.
Transportable instruments are generally instruments that would have been permanently installed, but are temporarily placed in an area to provide continuous monitoring where it is likely there will be a hazard. Such instruments are often installed on trolleys to allow easy deployment, and are associated with temporary operational situations.
In the United Kingdom the HSE has issued a user guidance note on selecting the correct radiation measurement instrument for the application concerned. This covers all radiation instrument technologies, and is a useful comparative guide.
Instrument types
A number of commonly used detection instrument types are listed below, and are used for both fixed and survey monitoring.
ionization chambers
proportional counters
Geiger counters
semiconductor detectors
scintillation detectors
airborne particulate radioactivity monitoring
Radiation related quantities
The following table shows the main radiation-related quantities and units.
Spacecraft radiation challenges
Spacecraft, both robotic and crewed, must cope with the high radiation environment of outer space. Radiation emitted by the Sun and other galactic sources, and trapped in radiation "belts" is more dangerous and hundreds of times more intense than radiation sources such as medical X-rays or normal cosmic radiation usually experienced on Earth. When the intensely ionizing particles found in space strike human tissue, it can result in cell damage and may eventually lead to cancer.
The usual method for radiation protection is material shielding by spacecraft and equipment structures (usually aluminium), possibly augmented by polyethylene in human spaceflight where the main concern is high-energy protons and cosmic ray ions. On uncrewed spacecraft in high-electron-dose environments such as Jupiter missions, or medium Earth orbit (MEO), additional shielding with materials of a high atomic number can be effective. On long-duration crewed missions, advantage can be taken of the good shielding characteristics of liquid hydrogen fuel and water.
The NASA Space Radiation Laboratory makes use of a particle accelerator that produces beams of protons or heavy ions. These ions are typical of those accelerated in cosmic sources and by the Sun. The beams of ions move through a 100 m (328-foot) transport tunnel to the 37 m2 (400-square-foot) shielded target hall. There, they hit the target, which may be a biological sample or shielding material. In a 2002 NASA study, it was determined that materials that have high hydrogen contents, such as polyethylene, can reduce primary and secondary radiation to a greater extent than metals, such as aluminum. The problem with this "passive shielding" method is that radiation interactions in the material generate secondary radiation.
Active Shielding, that is, using magnets, high voltages, or artificial magnetospheres to slow down or deflect radiation, has been considered to potentially combat radiation in a feasible way. So far, the cost of equipment, power and weight of active shielding equipment outweigh their benefits. For example, active radiation equipment would need a habitable volume size to house it, and magnetic and electrostatic configurations often are not homogeneous in intensity, allowing high-energy particles to penetrate the magnetic and electric fields from low-intensity parts, like cusps in dipolar magnetic field of Earth. As of 2012, NASA is undergoing research in superconducting magnetic architecture for potential active shielding applications.
Early radiation dangers
The dangers of radioactivity and radiation were not immediately recognized. The discovery of x‑rays in 1895 led to widespread experimentation by scientists, physicians, and inventors. Many people began recounting stories of burns, hair loss and worse in technical journals as early as 1896. In February of that year, Professor Daniel and Dr. Dudley of Vanderbilt University performed an experiment involving x-raying Dudley's head that resulted in his hair loss. A report by Dr. H.D. Hawks, a graduate of Columbia College, of his severe hand and chest burns in an x-ray demonstration, was the first of many other reports in Electrical Review.
Many experimenters including Elihu Thomson at Thomas Edison's lab, William J. Morton, and Nikola Tesla also reported burns. Elihu Thomson deliberately exposed a finger to an x-ray tube over a period of time and experienced pain, swelling, and blistering. Other effects, including ultraviolet rays and ozone were sometimes blamed for the damage. Many physicists claimed that there were no effects from x-ray exposure at all.
As early as 1902 William Herbert Rollins wrote almost despairingly that his warnings about the dangers involved in careless use of x-rays was not being heeded, either by industry or by his colleagues. By this time Rollins had proved that x-rays could kill experimental animals, could cause a pregnant guinea pig to abort, and that they could kill a fetus. He also stressed that "animals vary in susceptibility to the external action of X-light" and warned that these differences be considered when patients were treated by means of x-rays.
Before the biological effects of radiation were known, many physicists and corporations began marketing radioactive substances as patent medicine in the form of glow-in-the-dark pigments. Examples were radium enema treatments, and radium-containing waters to be drunk as tonics. Marie Curie protested against this sort of treatment, warning that the effects of radiation on the human body were not well understood. Curie later died from aplastic anaemia, likely caused by exposure to ionizing radiation. By the 1930s, after a number of cases of bone necrosis and death of radium treatment enthusiasts, radium-containing medicinal products had been largely removed from the market (radioactive quackery).
See also
CBLB502, 'Protectan', a radioprotectant drug under development for its ability to protect cells during radiotherapy.
Ex-Rad, a United States Department of Defense radioprotectant drug under development.
Health physics
Health threat from cosmic rays
International Radiation Protection Association – (IRPA). The International body concerned with promoting the science and practice of radiation protection.
Juno Radiation Vault
Non-ionizing radiation
Nuclear safety
Potassium iodide
Radiation monitoring
Radiation Protection Convention, 1960
Radiation protection reports of the European Union
Radiobiology
Radiological protection of patients
Radioresistance
Society for Radiological Protection – The principal UK body concerned with promoting the science and practice of radiation protection. It is the UK national affiliated body to IRPA
United Nations Scientific Committee on the Effects of Atomic Radiation
References
Notes
Harvard University Radiation Protection Office Providing radiation guidance to Harvard University and affiliated institutions.
Journal of Solid State Phenomena Tara Ahmadi, Use of Semi-Dipole Magnetic Field for Spacecraft Radiation Protection.
External links
- "The confusing world of radiation dosimetry" - M.A. Boyd, U.S. Environmental Protection Agency. An account of chronological differences between USA and ICRP dosimetry systems.
Nuclear physics
Radiobiology
Radiation health effects | Radiation protection | Physics,Chemistry,Materials_science,Biology | 6,433 |
13,262,036 | https://en.wikipedia.org/wiki/Death%20threat | A death threat is a threat, often made anonymously, by one person or a group of people to kill another person or group of people. These threats are often designed to intimidate victims in order to manipulate their behaviour, in which case a death threat could be a form of coercion. For example, a death threat could be used to dissuade a public figure from pursuing a criminal investigation or an advocacy campaign.
Legality
In most jurisdictions, death threats are a serious type of criminal offence. Death threats are often covered by coercion statutes. For instance, the coercion statute in Alaska says:
In the United States, some judges during a legal proceeding make death threats stating they hope the defendant will die in prison. An American judge was also removed from their positions due to making death threats towards children while off the bench.
Methods
A death threat can be communicated via a wide range of media, among these letters, newspaper publications, telephone calls, internet blogs, e-mail, and social media. If the threat is made against a political figure, it can also be considered treason. If a threat targets a location that is frequented by people (e.g. a building), it could be a terrorist threat. Sometimes, death threats are part of a wider campaign of abuse targeting a person or a group of people (see terrorism, mass murder).
Against a head of state
In many governments, including monarchies and republics of all levels of political freedom, threatening to kill the head of state or head of government (such as the sovereign, president, or prime minister) is considered a crime. Punishments for such threats vary. United States law provides for up to five years in prison for threatening any government official, especially the president. In the United Kingdom, under the Treason Felony Act 1848, it is illegal to attempt to kill or deprive the monarch of their throne; this offense was originally punished with penal transportation, and then was changed to the death penalty, and currently the penalty is life imprisonment.
Osman warning
Named after a high-profile case, Osman v United Kingdom, Osman warnings (also letters or notices) are warnings of a death threat or high risk of murder issued by British police or legal authorities to the possible victim. They are used when there is intelligence of the threat, but there is not enough evidence to justify the police arresting the potential murderer.
See also
Assassination
Bomb threat
Coercion
Contract killing
Extortion
Garda Information Message in Ireland
Murder
Stalking
Terroristic threat
Witness intimidation
References
External links
Judiciary Criminal Charges
The Forensic Linguistics Institute
Crimes
Death
Violence
Illegal speech in the United States
Terrorism
Aggression
Harassment and bullying
Speech crimes
Murder | Death threat | Biology | 537 |
7,401,552 | https://en.wikipedia.org/wiki/Bioastronautics | Bioastronautics is a specialty area of biological and astronautical research which encompasses numerous aspects of biological, behavioral, and medical concern governing humans and other living organisms in outer space; and includes the design of space vehicle payloads, space habitats, and life-support systems. In short, it spans the study and support of life in space.
Bioastronautics includes many similarities with its sister discipline astronautical hygiene; they both study the hazards that humans may encounter during a space flight. However, astronautical hygiene differs in many respects e.g. in this discipline, once a hazard is identified, the exposure risks are then assessed and the most effective measures determined to prevent or control exposure and thereby protect the health of the astronaut. Astronautical hygiene is an applied scientific discipline that requires knowledge and experience of many fields including bioastronautics, space medicine, ergonomics etc. The skills of astronautical hygiene are already being applied for example, to characterise Moon dust and design the measures to mitigate exposure during lunar exploration, to develop accurate chemical monitoring techniques and use the results in the setting SMACs.
Of particular interest from a biological perspective are the effects of reduced gravitational force felt by inhabitants of spacecraft. Often referred to as "microgravity", the lack of sedimentation, buoyancy, or convective flows in fluids results in a more quiescent cellular and intercellular environment primarily driven by chemical gradients. Certain functions of organisms are mediated by gravity, such as gravitropism in plant roots and negative gravitropism in plant stems, and without this stimulus growth patterns of organisms onboard spacecraft often diverge from their terrestrial counterparts. Additionally, metabolic energy normally expended in overcoming the force of gravity remains available for other functions. This may take the form of accelerated growth in organisms as diverse as worms like C. elegans to miniature parasitoid wasps such as Spangia endius. It may also be used in the augmented production of secondary metabolites such as the vinca alkaloids Vincristine and Vinblastine in the rosy periwinkle (Catharanthus roseus), whereby space grown specimens often have higher concentrations of these constituents that on earth are present in only trace amounts.
Engineering considerations
From an engineering perspective, facilitating the delivery and exchange of air, food, and water, and the processing of waste products is also challenging. The transition from expendable physicochemical methods to sustainable bioregenerative systems that function as a robust miniature ecosystem is another goal of bioastronautics in facilitating long duration space travel. Such systems are often termed Closed Ecological Life Support Systems (CELSS).
Medical considerations
From a medical perspective, long duration space flight also has physiological impacts on astronauts. Accelerated bone decalcification, similar to osteopenia and osteoporosis on Earth, is just one such condition. Another serious concern is the effects of space travel upon the kidneys. Current estimates of these effects upon the kidneys indicates that unless some kind of effective additional remedial technology against kidney damage is employed, astronauts who have been exposed to micro-gravity, reduced gravity, and Galactic radiation for 3 years or so on a Mars mission may have to return to Earth while attached to dialysis machines. The study of the potential effects of space travel is useful not only for advancing methods of the safe habitation of space, and the travel through space, but also in uncovering ways to more effectively treat closely related terrestrial ailments.
NASA's Bioastronautics library
NASA's Johnson Space Center in Houston, Texas maintains a Bioastronautics Library. The one-room facility provides a collection of textbooks, reference books, conference proceedings, and academic journals related to bioastronautics topics. Because the library is located within secure government property (not part of Space Center Houston, the official visitors center of JSC), it is not generally accessible to the public.
See also
Effect of spaceflight on the human body
Life support system
Space habitation
Locomotion in space
Reduced muscle mass, strength and performance in space
Space food
Astronautical hygiene
Spaceflight radiation carcinogenesis
Space medicine
Sex in space
Space tourism
Space-based economy
List of spaceflight-related accidents and incidents
Writing in space
Space art#Art in space
Religion in space
Organisms at high altitude
Astrobiology
Astrobotany
Plants in space
References
External links
Harvard-MIT Health Sciences and Technology - Bioastronautics Training Program (HST-Bioastro)
NASA's Bioastronautics Roadmap
University of Colorado at Boulder Bioastronautics Research Group
The American Society for Gravitational and Space Biology (ASGSB)
1965 radio series titled Their Other World, 13 half-hour episodes with typed transcript .
Aviation medicine
Human spaceflight
Biological engineering
Space medicine | Bioastronautics | Engineering,Biology | 988 |
77,659,735 | https://en.wikipedia.org/wiki/Rohri%20Canal | Rohri Canal is a major irrigation canal in Sindh, Pakistan. It is a vital source of water for agriculture in the region. It originates from the left bank of the Indus River at the Sukkur Barrage, located in Sukkur District, Sindh. It traverses through several districts, providing irrigation to vast agricultural lands. The canal's primary flow is towards the south, irrigating districts including Sukkur, Khairpur, Naushahro Feroze, Shaheed Benazirabad, Matiari, Hyderabad, Sanghar and Badin.
It is a perennial canal, meaning it supplies water throughout the year. The Rohri Canal is part of the larger Sukkur Barrage irrigation system. The construction of the barrage itself began in 1923 and was completed in 1932. While the Rohri Canal's construction was completed before the barrage project.
References
Irrigation canals
Irrigation projects
Irrigation in Pakistan | Rohri Canal | Engineering | 187 |
17,800,413 | https://en.wikipedia.org/wiki/Satellite%20navigation%20device | A satellite navigation device or satnav device, also known as a satellite navigation receiver or satnav receiver or simply a GPS device, is a user equipment that uses satellites of the Global Positioning System (GPS) or similar global navigation satellite systems (GNSS).
A satnav device can determine the user's geographic coordinates and may display the geographical position on a map and offer routing directions (as in turn-by-turn navigation).
, four GNSS systems are operational: the original United States' GPS, the European Union's Galileo, Russia's GLONASS, and China's BeiDou Navigation Satellite System. The Indian Regional Navigation Satellite System (IRNSS) will follow and Japan's Quasi-Zenith Satellite System (QZSS) scheduled for 2023 will augment the accuracy of a number of GNSS.
A satellite navigation device can retrieve location and time information from one or more GNSS systems in all weather conditions, anywhere on or near the Earth's surface. Satnav reception requires an unobstructed line of sight to four or more GNSS satellites, and is subject to poor satellite signal conditions. In exceptionally poor signal conditions, for example in urban areas, satellite signals may exhibit multipath propagation where signals bounce off structures, or are weakened by meteorological conditions. Obstructed lines of sight may arise from a tree canopy or inside a structure, such as in a building, garage or tunnel. Today, most standalone Satnav receivers are used in automobiles. The Satnav capability of smartphones may use assisted GNSS (A-GNSS) technology, which can use the base station or cell towers to provide a faster Time to First Fix (TTFF), especially when satellite signals are poor or unavailable. However, the mobile network part of the A-GNSS technology would not be available when the smartphone is outside the range of the mobile reception network, while the satnav aspect would otherwise continue to be available.
History
As with many other technological breakthroughs of the latter 20th century, the modern GNSS system can reasonably be argued to be a direct outcome of the Cold War of the latter 20th century. The multibillion-dollar expense of the US and Russian programs was initially justified by military interest. In contrast, the European Galileo was conceived as purely civilian.
In 1960, the US Navy put into service its Transit satellite-based navigation system to aid in naval navigation. The US Navy in the mid-1960s conducted an experiment to track a submarine with missiles with six satellites and orbiting poles and was able to observe satellite changes. Between 1960 and 1982, as the benefits were shown, the US military consistently improved and refined its satellite navigation technology and satellite system. In 1973, the US military began to plan for a comprehensive worldwide navigational system which eventually became known as the GPS (Global Positioning System).
In 1983, in the wake of the tragedy of the downing of Korean Air Lines Flight 007, an aircraft which was shot down while in Soviet airspace due to a navigational error, President Ronald Reagan made the navigation capabilities of the existing military GPS system available for dual civilian use. However, civilian use was initially only a slightly degraded "Selective Availability" positioning signal. This new availability of the US military GPS system for civilian use required a certain technical collaboration with the private sector for some time, before it could become a commercial reality.
The Macrometer Interferometric Surveyor was the first commercial GNSS-based system for performing geodetic measurements.
In 1989, Magellan Navigation Inc. unveiled its Magellan NAV 1000, the world's first commercial handheld GPS receiver. These units initially sold for approximately US$2,900 each.
In 1990, Mazda's Eunos Cosmo was the first production car in the world with a built-in Satnav system. In 1991, Mitsubishi introduced Satnav car navigation on the Mitsubishi Debonair (MMCS: Mitsubishi Multi Communication System). In 1997, a navigation system using Differential GPS was developed as a factory-installed option on the Toyota Prius.
In 2000, the Clinton administration removed the military use signal restrictions, thus providing full commercial access to the US Satnav satellite system.
As GNSS navigation systems became more and more widespread and popular, the pricing of such systems began to fall, and their widespread availability steadily increased. Several additional manufacturers of these systems, such as Garmin (1991), Benefon (1999), Mio (2002) and TomTom (2002) entered the market. Mitac Mio 168 was the first PocketPC to contain a built-in GPS receiver. Benefon's 1999 entry into the market also presented users with the world's first phone based GPS navigation system. Later, as smartphone technology developed, a GPS chip eventually became standard equipment for most smartphones. To date, ever more popular satellite navigation systems and devices continue to proliferate with newly developed software and hardware applications. It has been incorporated, for example, into cameras.
While the American GPS was the first satellite navigation system to be deployed on a fully global scale, and to be made available for commercial use, this is not the only system of its type. Due to military and other concerns, similar global or regional systems have been, or will soon be deployed by Russia, the European Union, China, India, and Japan.
Technical design
GNSS devices vary in sensitivity, speed, vulnerability to multipath propagation, and other performance parameters. High-sensitivity receivers use large banks of correlators and digital signal processing to search for signals very quickly. This results in very fast times to first fix when the signals are at their normal levels, for example, outdoors. When signals are weak, for example, indoors, the extra processing power can be used to integrate weak signals to the point where they can be used to provide a position or timing solution.
GNSS signals are already very weak when they arrive at the Earth's surface. The GPS satellites only transmit 27 W (14.3 dBW) from a distance of 20,200 km in orbit above the Earth. By the time the signals arrive at the user's receiver, they are typically as weak as −160 dBW, equivalent to 100 attowatts (10−16 W). This is well below the thermal noise level in its bandwidth. Outdoors, GPS signals are typically around the −155 dBW level (−125 dBm).
Sensitivity
Conventional GPS receivers integrate the received GPS signals for the same amount of time as the duration of a complete C/A code cycle which is 1 ms. This results in the ability to acquire and track signals down to around the −160 dBW level. High-sensitivity GPS receivers are able to integrate the incoming signals for up to 1,000 times longer than this and therefore acquire signals up to 1,000 times weaker, resulting in an integration gain of 30 dB. A good high-sensitivity GPS receiver can acquire signals down to −185 dBW, and tracking can be continued down to levels approaching −190 dBW.
High-sensitivity GPS can provide positioning in many but not all indoor locations. Signals are either heavily attenuated by the building materials or reflected as in multipath. Given that high-sensitivity GPS receivers may be up to 30 dB more sensitive, this is sufficient to track through 3 layers of dry bricks, or up to 20 cm (8 inches) of steel-reinforced concrete, for example. Examples of high-sensitivity receiver chips include SiRFstarIII and MediaTekʼs MTK II.
In aviation, the GPS receivers can be "armed" to the approach mode for the destination airport, so that when the aircraft is within , the receiver sensitivity will automatically change from en route (±5 nm) and RAIM (±2 nm) to terminal (±1 nm), and change again to ±0.3 nm at before reaching the final approach way point.
Sequential receiver =
A sequential GPS receiver tracks the necessary satellites by typically using one or two hardware channels. The set will track one satellite at a time, time tag the measurements and combine them when all four satellite pseudoranges have been measured. These receivers are among the least expensive available, but they cannot operate under high dynamics and have the slowest time-to-first-fix (TTFF) performance.
Types
Consumer GNSS navigation devices include:
Dedicated GNSS navigation devices
modules that need to be connected to a computer to be used
loggers that record trip information for download. Such GPS tracking is useful for trailblazing, mapping by hikers and cyclists, and the production of geocoded photographs.
Converged devices, including Satnav phones and geotagging cameras, in which GNSS is a feature rather than the main purpose of the device. The majority of GNSS devices are now converged devices, and may use assisted GPS or standalone (not network dependent) or both. The vulnerability of consumer GNSS to radio frequency interference from planned wireless data services is controversial.
Dedicated GNSS navigation devices
Dedicated devices have various degrees of mobility. Hand-held, outdoor, or sport receivers have replaceable batteries that can run them for several hours, making them suitable for hiking, bicycle touring and other activities far from an electric power source. Their design is ergonomical, their screens are small, and some do not show color, in part to save power. Some use transflective liquid-crystal displays, allowing use in bright sunlight. Cases are rugged and some are water-resistant.
Other receivers, often called mobile are intended primarily for use in a car, but have a small rechargeable internal battery that can power them away from the car. Special purpose devices for use in a car may be permanently installed and depend entirely on the automotive electrical system. Many of them have touch-sensitive screens as input method. Maps may be stored on a memory card. Some offer additional functionality such as a rudimentary music player, image viewer, and video player.
The pre-installed embedded software of early receivers did not display maps; 21st-century ones commonly show interactive street maps (of certain regions) that may also show points of interest, route information and step-by-step routing directions, often in spoken form with a feature called "text to speech".
Manufacturers include:
Navman products
TomTom products
Garmin products
Mio products
Navigon products
Magellan Navigation consumer products
Satmap Systems Ltd
TeleType products
Integration into smartphones
Almost all smartphones now incorporate GNSS receivers. This has been driven both by consumer demand and by service suppliers. There are now many phone apps that depend on location services, such as navigational aids, and multiple commercial opportunities, such as localised advertising. In its early development, access to user location services was driven by European and American emergency services to help locate callers.
All smartphone operating systems offer free mapping and navigational services that require a data connection; some allow the pre-purchase and downloading of maps but the demand for this is diminishing as data connection reliant maps can generally be cached anyway. There are many navigation applications and new versions are constantly being introduced. Major apps include Google Maps Navigation, Apple Maps and Waze, which require data connections, iGo for Android, Maverick and HERE for Windows Phone, which use cached maps and can operate without a data connection. Consequently, almost any smartphone now qualifies as a personal navigation assistant.
The use of mobile phones as navigational devices has outstripped the use of standalone GNSS devices. In 2009, independent analyst firm Berg Insight found that GNSS-enabled GSM/WCDMA handsets in the USA alone numbered 150 million units, against the sale of only 40 million standalone GNSS receivers.
Assisted GPS (A-GPS) uses a combination of satellite data and cell tower data to shorten the time to first fix, reduce the need to download a satellite almanac periodically and to help resolve a location when satellite signals are disturbed by the proximity of large buildings. When out of range of a cell tower the location performance of a phone using A-GPS may be reduced. Phones with an A-GPS based hybrid positioning system can maintain a location fix when GPS signals are inadequate by cell tower triangulation and WiFi hotspot locations. Most smartphones download a satellite almanac when online to accelerate a GPS fix when out of cell tower range.
Some, older, Java-enabled phones lacking integrated GPS may still use external GPS receivers via serial or Bluetooth) connections, but the need for this is now rare.
By tethering to a laptop, some phones can provide localisation services to a laptop as well.
Palm, pocket and laptop PC
Software companies have made available GPS navigation software programs for in-vehicle use on laptop computers. Benefits of GPS on a laptop include larger map overview, ability to use the keyboard to control GPS functions, and some GPS software for laptops offers advanced trip-planning features not available on other platforms, such as midway stops, capability of finding alternative scenic routes as well as only highway option.
Palms and Pocket PC's can also be equipped with GPS navigation. A pocket PC differs from a dedicated navigation device as it has an own operating system and can also run other applications.
GPS modules
Other GPS devices need to be connected to a computer in order to work. This computer can be a home computer, laptop, PDA, digital camera, or smartphones. Depending on the type of computer and available connectors, connections can be made through a serial or USB cable, as well as Bluetooth, CompactFlash, SD, PCMCIA and the newer ExpressCard. Some PCMCIA/ExpressCard GPS units also include a wireless modem.
Devices usually do not come with pre-installed GPS navigation software, thus, once purchased, the user must install or write their own software. As the user can choose which software to use, it can be better matched to their personal taste. It is very common for a PC-based GPS receiver to come bundled with a navigation software suite. Also, software modules are significantly cheaper than complete stand-alone systems (around €50 to €100). The software may include maps only for a particular region, or the entire world, if software such as Google Maps are used.
Some hobbyists have also made some Satnav devices and open-sourced the plans. Examples include the Elektor GPS units. These are based around a SiRFstarIII chip and are comparable to their commercial counterparts. Other chips and software implementations are also available.
Applications
Vehicle navigation
An automotive navigation system takes its location from a GNSS system and, depending on the installed software, may offer the following services:
Mapping, including street maps, text or in a graphical format,
Turn-by-turn navigation directions via text or speech,
Directions fed directly to a self-driving car,
Traffic congestion maps, historical or real-time data, and suggested alternative directions,
Information on nearby amenities such as restaurants, fueling stations, and tourist attractions,
Alternative routes.
Aviation
Aviators use Satnav to navigate and to improve safety and the efficiency of the flight. This may allow pilots to be independent of ground-based navigational aids, enable more efficient routes and provide navigation into airports that lack ground-based navigation and surveillance equipment. There are now some GPS units that allow aviators to get a clearer look in areas where the satellite is augmented to be able to have safe landings in bad visibility conditions. There have now been two new signals made for GPS, the first being made to help in critical conditions in the sky and the other will make GPS more of a robust navigation service. Many aviator services have now made it a required service to use a GPS. Commercial aviation applications include GNSS devices that calculate location and feed that information to large multi-input navigational computers for autopilot, course information and correction displays to the pilots, and course tracking and recording devices.
Military
Military applications include devices similar to consumer sport products for foot soldiers (commanders and regular soldiers), small vehicles and ships, and devices similar to commercial aviation applications for aircraft and missiles. Examples are the United States military's Commander's Digital Assistant and the Soldier Digital Assistant. Prior to May 2000 only the military had access to the full accuracy of GPS. Consumer devices were restricted by selective availability (SA), which was scheduled to be phased out but was removed abruptly by President Clinton. Differential GPS is a method of cancelling out the error of SA and improving GPS accuracy, and has been routinely available in commercial applications such as for golf carts. GPS is limited to about 15 meter accuracy even without SA. DGPS can be within a few centimeters.
Issues
Hazards of relying on satnav
GPS maps and directions are occasionally imprecise. Some people have gotten lost by asking for the shortest route, like a couple in the United States who were looking for the shortest route from South Oregon to Jackpot, Nevada.
In August 2009 a young mother and her six-year-old son became stranded in Death Valley after following Satnav directions that led her up an unpaved dead-end road. When they were found five days later, her son had died from the effects of heat and dehydration.
In May 2012, Japanese tourists in Australia were stranded when traveling to North Stradbroke Island and their satnav instructed them to drive into Moreton Bay.
In 2008 Satnav routed a softball team bus into a 9 ft tunnel, which sliced off the top of the bus and hospitalized the whole team.
Brad Preston, Oregon claims that people are routed into his driveway five to eight times a week because their Satnav shows a street through his property.
John and Starry Rhodes, a couple from Reno, Nevada were driving home from Oregon when they started to see there was a lot of snow in the area but decided to keep going because they were already 30 miles down the road. But the Satnav led them to a road in the Oregon forest that was not plowed and they were stuck for 3 days.
Mary Davis was driving in an unfamiliar place when her Satnav told her to make a right turn onto a train track while there was a train coming down. Mary was lucky there was a local police officer who noticed the situation and urged her quickly to get out of the car as fast as she could. Mary was lucky enough to get out of the car leaving it for the train to hit and total it. The officer commented that there was a very good chance that they could have had a fatality on their hands.
Other hazards involve an alley being listed as a street, a lane being identified as a road, or rail tracks as a road.
Obsolete maps sometimes cause the unit to lead a user on an indirect, time-wasting route, because roads may change over time. Smartphone Satnav information is usually updated automatically, and free of additional charge. Manufacturers of separate Satnav devices also offer map update services for their merchandise, usually for a fee.
Privacy concerns
User privacy may be compromised if Satnav equipped handheld devices such as mobile phones upload user geo-location data through associated software installed on the device. User geo-location is currently the basis for navigational apps such as Google Maps, location-based advertising, which can promote nearby shops and may allow an advertising agency to track user movements and habits for future use. Regulatory bodies differ between countries regarding the treatment of geo-location data as privileged or not. Privileged data cannot be stored, or otherwise used, without the user's consent.
Vehicle tracking systems allow employers to track their employees' location raising questions regarding violation of employee privacy. There are cases where employers continued to collect geo-location data when an employee was off duty in private time.
Rental car services may use the same technique to geo-fence their customers to the areas they have paid for, charging additional fees for violations. In 2010, New York Civil Liberties Union filed a case against the Labor Department for firing Michael Cunningham after tracking his daily activity and locations using a Satnav device attached to his car. Private investigators use planted GPS devices to provide information to their clients on a target's movements.
See also
Comparison of web map services
Dashcam
Defense Advanced GPS Receiver
Head unit
Moving map display
GPS watch
Precision Lightweight GPS Receiver
Radio clock
Turn-by-turn navigation
References
Global Positioning System
Consumer electronics
Navigational equipment
device
20th-century inventions | Satellite navigation device | Technology,Engineering | 4,181 |
3,093,466 | https://en.wikipedia.org/wiki/Bit%20slicing | Bit slicing is a technique for constructing a processor from modules of processors of smaller bit width, for the purpose of increasing the word length; in theory to make an arbitrary n-bit central processing unit (CPU). Each of these component modules processes one bit field or "slice" of an operand. The grouped processing components would then have the capability to process the chosen full word-length of a given software design.
Bit slicing more or less died out due to the advent of the microprocessor. Recently it has been used in arithmetic logic units (ALUs) for quantum computers and as a software technique, e.g. for cryptography in x86 CPUs.
Operational details
Bit-slice processors (BSPs) usually include 1-, 2-, 4-, 8- or 16-bit arithmetic logic unit (ALU) and control lines (including carry or overflow signals that are internal to the processor in non-bitsliced CPU designs).
For example, two 4-bit ALU chips could be arranged side by side, with control lines between them, to form an 8-bit ALU (result need not be power of two, e.g. three 1-bit units can make a 3-bit ALU, thus 3-bit (or n-bit) CPU, while 3-bit, or any CPU with higher odd number of bits, hasn't been manufactured and sold in volume). Four 4-bit ALU chips could be used to build a 16-bit ALU. It would take eight chips to build a 32-bit word ALU. The designer could add as many slices as required to manipulate longer word lengths.
A microsequencer or control ROM would be used to execute logic to provide data and control signals to regulate function of the component ALUs.
Known bit-slice microprocessors:
2-bit slice:
Intel 3000 family (1974, now discontinued), e.g. Intel 3002 with Intel 3001, second-sourced by Signetics and Intersil
Signetics 8X02 family (1977, now discontinued)
4-bit slice:
National IMP family, consisting primarily of the IMP-00A/520 RALU (also known as MM5750) and various masked ROM microcode and control chips (CROMs, also known as MM5751)
National GPC/P / IMP-4 (1973), second-sourced by Rockwell
National IMP-8, an 8-bit processor based on the IMP chipset, using two RALU chips and one CROM chip
National IMP-16, a 16-bit processor based on the IMP chipset, e.g. four RALU chips with one each IMP16A/521D and IMP16A/522D CROM chips (additional optional CROM chips could provide instruction set additionis)
AMD Am2900 family (1975), e.g. AM2901, AM2901A, AM2903
Monolithic Memories 5700/6700 family (1974) e.g. MMI 5701 / MMI 6701, second-sourced by ITT Semiconductors
Texas Instruments SBP0400 (1975) and SBP0401, cascadable up to 16 bits
Texas Instruments SN74181 (1970)
Texas Instruments SN74S281 with SN74S282
Texas Instruments SN74S481 with SN74S482 (1976)
Fairchild 33705
Fairchild 9400 (MACROLOGIC), 4700
Motorola M10800 family (1979), e.g. MC10800
Raytheon RP-16, a 16-bit processor consisting of seven integrated circuits, using four RALU chips and three CROM chips.
8-bit slice:
Four-Phase Systems AL1 (1969, considered to be the first microprocessor used in a commercial product, now discontinued)
Texas Instruments SN54AS888 / SN74AS888
Fairchild 100K
ZMD (1978/1981), cascadable up to 32 bit
16-bit slice:
AMD Am29100 family
Synopsys 49C402
ZFT Robotron/ZFTM Dresden (1979/1982), unreleased
Historical necessity
Bit slicing, although not called that at the time, was also used in computers before large-scale integrated circuits (LSI, the predecessor to today's VLSI, or very-large-scale integration circuits). The first bit-sliced machine was EDSAC 2, built at the University of Cambridge Mathematical Laboratory in 1956–1958.
Prior to the mid-1970s and late 1980s there was some debate over how much bus width was necessary in a given computer system to make it function. Silicon chip technology and parts were much more expensive than today. Using multiple simpler, and thus less expensive, ALUs was seen as a way to increase computing power in a cost-effective manner. While 32-bit microprocessors were being discussed at the time, few were in production.
The UNIVAC 1100 series mainframes (one of the oldest series, originating in the 1950s) has a 36-bit architecture, and the 1100/60 introduced in 1979 used nine Motorola MC10800 4-bit ALU chips to implement the needed word width while using modern integrated circuits.
At the time 16-bit processors were common but expensive, and 8-bit processors, such as the Z80, were widely used in the nascent home-computer market.
Combining components to produce bit-slice products allowed engineers and students to create more powerful and complex computers at a more reasonable cost, using off-the-shelf components that could be custom-configured. The complexities of creating a new computer architecture were greatly reduced when the details of the ALU were already specified (and debugged).
The main advantage was that bit slicing made it economically possible in smaller processors to use bipolar transistors, which switch much faster than NMOS or CMOS transistors. This allowed much higher clock rates, where speed was needed for example, for DSP functions or matrix transformation or, as in the Xerox Alto, the combination of flexibility and speed, before discrete CPUs were able to deliver that.
Modern use
Software use on non-bit-slice hardware
In more recent times, the term bit slicing was reused by Matthew Kwan to refer to the technique of using a general-purpose CPU to implement multiple parallel simple virtual machines using general logic instructions to perform single-instruction multiple-data (SIMD) operations. This technique is also known as SIMD within a register (SWAR).
This was initially in reference to Eli Biham's 1997 article A Fast New DES Implementation in Software, which achieved significant gains in performance of DES by using this method.
Bit-sliced quantum computers
To simplify the circuit structure and reduce the hardware cost of quantum computers (proposed to run the MIPS32 instruction set) a 50 GHz superconducting "4-bit bit-slice arithmetic logic unit (ALU) for 32-bit rapid single-flux-quantum microprocessors was demonstrated".
See also
Bit-serial architecture
References
Further reading
External links
a bitslicing primer presenting a pedagogical bitsliced implementation of the Tiny Encryption Algorithm (TEA), a block cipher
Digital electronics
Central processing unit
University of Cambridge Computer Laboratory
Bit-slice chips | Bit slicing | Engineering | 1,528 |
23,951,432 | https://en.wikipedia.org/wiki/Bolazine | Bolazine (), also known as 2α-methyl-5α-androstan-17β-ol-3-one azine, is a synthetic androgen/anabolic steroid (AAS) of the dihydrotestosterone (DHT) group which was never marketed. It is not orally active and is used as the ester prodrug bolazine capronate (brand name Roxilon Inject) via depot intramuscular injection. Bolazine has a unique and unusual chemical structure, being a dimer of drostanolone linked at the C3 position of the A-ring by an azine group, and reportedly acts as a prodrug of drostanolone.
See also
List of androgens/anabolic steroids
References
Anabolic–androgenic steroids
Androstanes
Dimers (chemistry)
Azines (hydrazine derivatives)
Prodrugs | Bolazine | Chemistry,Materials_science | 197 |
70,741,068 | https://en.wikipedia.org/wiki/Thermoanaerobaculum%20aquaticum | Thermoanaerobaculum aquaticum is a species of Acidobacteriota.
References
Bacteria described in 2013
Acidobacteriota | Thermoanaerobaculum aquaticum | Biology | 32 |
40,236,004 | https://en.wikipedia.org/wiki/Verrucosidin | Verrucosidin is a toxic pyrone-type polyketide produced by Penicillium aurantiogriseum, Penicillium melanoconidium, and Penicillium polonicum.
References
2-Pyrones
Epoxides
Verrucosidin
Polyketides
Lactones
Methoxy compounds | Verrucosidin | Chemistry | 73 |
43,655,909 | https://en.wikipedia.org/wiki/C.%20Michael%20Roland | Charles Michael Roland (22 April 1952 - 2 October 2021) was Head of the Polymer Physics Section at the Naval Research Lab in Washington DC from 1989 to 2015. His research was concerned primarily with the dynamics of condensed matter, including polymers and liquid crystals, with applications to military armor and infrastructure protection. He is noted for his development of elastomeric coatings for blast protection, and for diverse accomplishments in the field of elastomer science. From 1991-1999, he served as the 8th editor of the scientific journal Rubber Chemistry and Technology, and a Fellow of the American Physical Society and the Institute of Materials, Minerals, and Mining (UK).
Personal
Roland was born in Trenton, New Jersey. He went by his middle name Michael to avoid confusion at home, as his father was also named Charles. He had one sister. His father worked for the post office after dropping out of school during the depression after the eighth grade. As a youth, Roland knew he wanted to go into science. He had a chemistry set and tried to make gunpowder. He enjoyed basketball and chose his undergraduate college in part for the opportunity to play, turning more to his studies after a knee injury.
Education
Roland received his BS in Chemistry at Grove City College in 1974. He was late applying to graduate school, and so for a short time he worked as a lab instructor at a community college teaching chemistry. He soon was accepted to graduate school at Penn State working under advisor William A. Steele. He completed his Ph.D. in Chemistry in 1980. In his final year of grad school, he interviewed for jobs with Firestone, DuPont and American Cyanamid.
Career
In 1981, Roland was recruited to Firestone's Central Research Labs by Georg Bohm, who persuaded Roland with an offer to work on long term research projects. Roland enjoyed his research and continued at Firestone until 1986, when due to poor economic conditions in the automotive sector and to R&D cuts in the aftermath of the Firestone 500 recall, he decided to seek employment elsewhere. He soon won a position with the United States Naval Research Laboratory. His first project looked at thermodynamically miscible blends of 1-4 polyisoprene and 1-2 polybutadiene. He worked on blast protection and on elastomer networks. During his career he produced 22 patents. He retired from NRL in 2020.
Awards
1991 - Sparks-Thomas award of the Rubber Division of the American Chemical Society
2002 - Melvin Mooney Distinguished Technology Award of the Rubber Division of the American Chemical Society
2002 - Sigma Xi Award for Pure Science
2012 - Charles Goodyear Medal of the Rubber Division of the American Chemical Society
2019 - Colwyn Medal Institute of Materials, Minerals, and Mining (UK)
References
Polymer scientists and engineers | C. Michael Roland | Chemistry,Materials_science | 567 |
42,613,359 | https://en.wikipedia.org/wiki/Morchella%20deliciosa | Morchella deliciosa is a species of edible fungus in the family Morchellaceae. It was first described scientifically by Elias Magnus Fries in 1822. It is a European species, although the name has erroneously been applied to morphologically similar North American morels.
References
External links
deliciosa
Edible fungi
Fungi of Europe
Fungi described in 1822
Taxa named by Elias Magnus Fries
Fungus species | Morchella deliciosa | Biology | 80 |
6,342,354 | https://en.wikipedia.org/wiki/Balikbayan%20box | A balikbayan box () is a corrugated box containing items sent by overseas Filipinos (known as balikbayan literally "returnee to the country/nation"). Though often shipped by freight forwarders specializing in sending balikbayan boxes by sea, such boxes are also commonly brought by Filipinos returning to the Philippines via air.
History
In 1973, the government of then-President Ferdinand Marcos, Sr began encouraging Filipino Americans to visit their ancestral hometowns in the Philippines. Individuals who did so became known as balikbayan, from the Tagalog words balík, "to return", and bayan, "town/settlement". Under the program, customs procedures were eased for such travellers and it was expanded by subsequent administrations.
Returnees often had gifts for friends and family as a modern extension of the pasalubong tradition, where presents are handed to those at home upon arrival from a journey or some absence. This expresses appreciation for and improves relations with people in a place of origin for those who are seen as having achieved financial success abroad. For those returning with valid balikbayan status, customs fees were waived for the contents of two boxes per individual. Eventually, it became common to package gifts, often household goods and practical items, in a box while still abroad. These boxes would then be shipped to the Philippines.
The balikbayan box became popular in the 1980s United States due to the country’s high influx of overseas Filipino workers. The first freight forwarder to offer balikbayan box services was Rico Nunga, who started REN International in Los Angeles, California, in 1981. The following year, Ramón Ungco, a Filipino in New York City, founded Port Jersey Shipping International. These two companies are considered the pioneers of door-to-door balikbayan box delivery, which back then were charged import duties upon arrival in the Philippines.
On June 30, 1987, then-President Corazon Aquino enacted Executive Order No. 206. This amended Section 105 (f), and added a new subsection (f-1) to Republic Act No. 1937, the Tariff and Customs Code of the Philippines, which was signed into law on July 22, 1957, by former President Carlos P. García.
The amended Section 105 of the Tariff and Customs Code provides duty-free and tax-free privileges to balikbayan boxes sent to the Philippines by overseas Filipino workers (OFWs), as recognition for their labors in foreign lands and bringing additional foreign revenue annually, which contributed to the ongoing national recovery effort. This allowed tax-free entry of personal goods into the country from overseas Filipinos, who then began sending the boxes through homeward-bound family, friends, and colleagues.
After the September 11 attacks and the passage of the Patriot Act by the United States Congress, balikbayan boxes have been subjected to rigorous inspections by the United States Department of Homeland Security's Out-Bound Exam Team that caused delays of up to three weeks at US Customs inspection facilities. This extended shipping times from 21 days to over 30 days. The inspections also resulted in opened balikbayan boxes and complaints of package pilferage and mishandling. The Philippine Bureau of Customs also conducted complete inspections that added to the delay in shipments. Such inspections are the result of criminals using the boxes to smuggle commercial items without paying taxes, or ship contraband. Since balikbayan box shipping is a consolidated shipment, one illegal item will affect all approximately 400 packages in the container. The inspection process has since been modernized with the use of high-performance X-ray machines.
In 2012, these delays were further aggravated when the City of Manila imposed a truck ban on routes to the Port of Manila, causing backlogs in releasing and transporting all domestic and international cargo. Most balikbayan box companies, which are based in Parañaque near the airport, were significantly affected by the truck ban until it was resolved.
The industry was scrutinized by the Philippine Senate in 2015, after complaints were brought to the attention of the public via social media after then-Philippine Customs Commissioner Albert Lina, announced the opening of balikbayan boxes for inspection and additional taxes to be imposed. The inquiry brought the passage of the Customs Modernization Act, which had been pending for years, and the inclusion of the Balikbayan Box Law in the act, increasing the tax-exemption ceiling from ₱500 to ₱150,000. This included items being brought home by Filipino tourists from trips abroad, pasalubong or gifts, and returning resident shipments.
To protect consumers, the Department of Trade and Industry (DTI), through its Philippine Shipper's Bureau, conducts regular accreditation of international freight forwarders and discourages consumers from patronizing unaccredited and incredibly cheap shipping companies.
According to the Door to Door Consolidated Association of the Philippines 400,000 balikbayan boxes arrive in the Philippines monthly.
Description
Balikbayan boxes may contain items the sender thinks the recipient would like, regardless of whether those items can be bought cheaply in the Philippines, such as non-perishable food, toiletries, household items, electronics, toys, designer clothing, or items difficult to find in the Philippines. A balikbayan box intended for air travel is designed to conform to airline luggage restrictions and many Filipino stores sell them. Some boxes come with a cloth cover and side handles. Others are tightly secured with tape or rope, and thus not confused with an ordinary moving box that is lightly wrapped.
Balikbayan boxes typically are as close to a cube as possible - so as to maximize the volume versus the sum of the length(L), width(W) and height(H). Many airlines restrict the L+W+H to 158cm or 62in, so for checked in boxes, a typical box may be 52cm x 52cm x 52cm or 20.5in x 20.5in x 20.5in.
Shipped boxes are delivered directly to the recipient, usually the family of the overseas Filipino.
Cultural significance
Part of the attraction of the balikbayan box is its economic value, as it allows cheaper shipment of items versus shipping in smaller boxes via postal services. The tradeoff is longer transit time by container ship, typically requiring several weeks, and the lack of a definite delivery date. The balikbayan box is a modern manifestation of the Philippine custom of pasalubong, where domestic or foreign travelers are expected to bring gifts for family, friends and colleagues. Balikbayan boxes provide connection between family in the Philippines and those abroad, and provide goods for the family in the Philippines. It also has been a contributing factor of the Philippines having good trade relations with foreign nations.
See also
Padala
References
Further reading
Culture of the Philippines
Postal systems | Balikbayan box | Technology | 1,395 |
1,035,450 | https://en.wikipedia.org/wiki/In%20silico | In biology and other experimental sciences, an in silico experiment is one performed on a computer or via computer simulation software. The phrase is pseudo-Latin for 'in silicon' (correct ), referring to silicon in computer chips. It was coined in 1987 as an allusion to the Latin phrases , , and , which are commonly used in biology (especially systems biology). The latter phrases refer, respectively, to experiments done in living organisms, outside living organisms, and where they are found in nature.
History
The earliest known use of the phrase was by Christopher Langton to describe artificial life, in the announcement of a workshop on that subject at the Center for Nonlinear Studies at the Los Alamos National Laboratory in 1987. The expression in silico was first used to characterize biological experiments carried out entirely in a computer in 1989, in the workshop "Cellular Automata: Theory and Applications" in Los Alamos, New Mexico, by Pedro Miramontes, a mathematician from National Autonomous University of Mexico (UNAM), presenting the report "DNA and RNA Physicochemical Constraints, Cellular Automata and Molecular Evolution". The work was later presented by Miramontes as his dissertation.
In silico has been used in white papers written to support the creation of bacterial genome programs by the Commission of the European Community. The first referenced paper where in silico appears was written by a French team in 1991. The first referenced book chapter where in silico appears was written by Hans B. Sieburg in 1990 and presented during a Summer School on Complex Systems at the Santa Fe Institute.
The phrase in silico originally applied only to computer simulations that modeled natural or laboratory processes (in all the natural sciences), and did not refer to calculations done by computer generically.
Drug discovery with virtual screening
In silico study in medicine is thought to have the potential to speed the rate of discovery while reducing the need for expensive lab work and clinical trials. One way to achieve this is by producing and screening drug candidates more effectively. In 2010, for example, using the protein docking algorithm EADock (see Protein-ligand docking), researchers found potential inhibitors to an enzyme associated with cancer activity in silico. Fifty percent of the molecules were later shown to be active inhibitors in vitro. This approach differs from use of expensive high-throughput screening (HTS) robotic labs to physically test thousands of diverse compounds a day, often with an expected hit rate on the order of 1% or less, with still fewer expected to be real leads following further testing (see drug discovery).
As an example, the technique was utilized for a drug repurposing study in order to search for potential cures for COVID-19 (SARS-CoV-2).
Cell models
Efforts have been made to establish computer models of cellular behavior. For example, in 2007 researchers developed an in silico model of tuberculosis to aid in drug discovery, with the prime benefit of its being faster than real time simulated growth rates, allowing phenomena of interest to be observed in minutes rather than months. More work can be found that focus on modeling a particular cellular process such as the growth cycle of Caulobacter crescentus.
These efforts fall far short of an exact, fully predictive computer model of a cell's entire behavior. Limitations in the understanding of molecular dynamics and cell biology, as well as the absence of available computer processing power, force large simplifying assumptions that constrain the usefulness of present in silico cell models.
Genetics
Digital genetic sequences obtained from DNA sequencing may be stored in sequence databases, be analyzed (see Sequence analysis), be digitally altered or be used as templates for creating new actual DNA using artificial gene synthesis.
Other examples
In silico computer-based modeling technologies have also been applied in:
Whole cell analysis of prokaryotic and eukaryotic hosts e.g. E. coli, B. subtilis, yeast, CHO- or human cell lines
Discovery of potential cure for COVID-19.
Bioprocess development and optimization e.g. optimization of product yields
Simulation of oncological clinical trials exploiting grid computing infrastructures, such as the European Grid Infrastructure, for improving the performance and effectiveness of the simulations.
Analysis, interpretation and visualization of heterologous data sets from various sources e.g. genome, transcriptome or proteome data
Validation of taxonomic assignment steps in herbivore metagenomics study.
Protein design. One example is RosettaDesign, a software package under development and free for academic use.
See also
Virtual screening
Computational biology
Computational biomodeling
Computer experiment
Folding@home
Exscalate4Cov
Cellular model
Nonclinical studies
Organ-on-a-chip
In silico molecular design programs
In silico medicine
Dry lab
References
External links
World Wide Words: In silico
CADASTER Seventh Framework Programme project aimed to develop in silico computational methods to minimize experimental tests for REACH Registration, Evaluation, Authorisation and Restriction of Chemicals
In Silico Biology. Journal of Biological Systems Modeling and Simulation
In Silico Pharmacology
Pharmaceutical industry
Latin biological phrases
Alternatives to animal testing
Animal test conditions | In silico | Chemistry,Biology | 1,062 |
15,487,076 | https://en.wikipedia.org/wiki/Tactical%20data%20link | A tactical data link (TDL) uses a data link standard in order to provide communication via radio waves or cable. NATO nations use a variety of TDL standards. All military C3 systems use standardized TDL to transmit, relay and receive tactical data.
Multi-TDL network (MTN) refers to the network of similar and dissimilar TDLs integrated through gateways, translators, and correlators to bring the common tactical picture and/or common operational picture together.
Change of terminology
The term tactical digital information link (TADIL) was made obsolete (per DISA guidance) and is now more commonly seen as tactical data link (TDL).
Tactical data link character
TDLs are characterized by their standard message and transmission formats. This is usually written as <Message Format>/<Transmission Format>.
TDL standards in NATO
In NATO, tactical data link standards are being developed by the Data Link Working Group (DLWG) of the Information Systems Sub-Committee (ISSC) in line with the appropriate STANAG.
In NATO, there exist tactical data link standards as follows:
Beyond NATO countries, NATO partner countries have also developed some degree of interoperability with these standards since the 2014 Partnership Interoperability Initiative.
See also
BACN
Global Information Grid
Inter/Intra Flight Data Link (IFDL)
JREAP
MANDRIL
Multifunction Advanced Data Link
Network emulation for simulation / emulation of tactical data links
SIMPLE
Tactical Common Data Link
References
External links
Federation of American Scientists TDL information page
This article was originally based on public domain text from Army Airspace Command and Control in a Combat Zone, Headquarters, Department of the Army, publication FM 3-52 (FM 100-103), August 2002
Military communications
NATO standardisation | Tactical data link | Engineering | 358 |
12,361,147 | https://en.wikipedia.org/wiki/Hok/sok%20system | The hok/sok system is a postsegregational killing mechanism employed by the R1 plasmid in Escherichia coli. It was the first type I toxin-antitoxin pair to be identified through characterisation of a plasmid-stabilising locus. It is a type I system because the toxin is neutralised by a complementary RNA, rather than a partnered protein (type II toxin-antitoxin).
Genes involved
The hok/sok system involves three genes:
hok, host killing - a long lived (half-life 20 minutes) toxin
sok, suppression of killing - a short lived (half-life 30 seconds) RNA antitoxin
mok, modulation of killing - required for hok translation
Killing mechanism
When E. coli undergoes cell division, the two daughter cells inherit the long-lived hok toxin from the parent cell. Due to the short half-life of the sok antitoxin, daughter cells inherit only small amounts and it quickly degrades.
If a daughter cell has inherited the R1 plasmid, it has inherited the sok gene and a strong promoter which brings about high levels of transcription. So much so that in an R1-positive cell, Sok transcript exists in considerable molar excess over Hok mRNA. Sok RNA then indirectly inhibits the translation of hok by inhibiting mok translation. There is a complementary region where sok transcript binds hok mRNA directly (pictured), but it does not occlude the Shine-Dalgarno sequence. Instead, sok RNA regulates the translation of the mok open reading frame, which nearly entirely overlaps that of hok. It is this translation-coupling which effectively allows sok RNA to repress the translation of hok mRNA.
The sok transcript forms a duplex with the leader region of hok mRNA and this is recognized by RNase III and degraded. The cleavage products are very unstable and soon decay.
Daughter cells without a copy of the R1 plasmid die because they do not have the means to produce more sok antitoxin transcript to inhibit translation of the inherited hok mRNA. The killing system is said to be postsegregational (PSK), since cell death occurs after segregation of the plasmid.
Hok toxin
The hok gene codes for a 52 amino acid toxic protein which causes cell death by depolarization of the cell membrane. It works in a similar way to holin proteins which are produced by bacteriophages before cell lysis.
Homologous systems
Other plasmids
hok/sok homologues denoted flmA/B (FlmA is the protein toxin and FlmB RNA the antisense regulator) are carried on the F plasmid which operate in the same way to maintain the stability of the plasmid. The F plasmid contains another homologous toxin-antitoxin system called srnB.
The first type I toxin-antitoxin system to be found in gram-positive bacteria is the RNAI-RNAII system of the pAD1 plasmid in Enterococcus faecalis. Here, RNAI encodes a toxic protein Fst while RNAII is the regulatory sRNA.
Chromosomal toxin-antitoxin systems
In E. coli strain K-12 there are four long direct repeats (ldr) which encode short open reading frames of 35 codons organised in a homologous manner to the hok/sok system. One of the repeats encodes LdrD, a toxic protein which causes cell death. An unstable antisense RNA regulator (Rd1D) blocks the translation of the LdrD transcript. A mok homologue which overlaps each ldr loci has also been found.
IstR RNA works in a similar system in conjunction with the toxic TisB protein.
See also
par stability determinant
Addiction module
Sib RNA
SymR RNA
PtaRNA1
RdlD RNA
IstR RNA
FlmB RNA
RatA
References
Further reading
Bacteriology
Escherichia coli
RNA antitoxins
Cellular processes | Hok/sok system | Biology | 858 |
1,491,198 | https://en.wikipedia.org/wiki/Session%20border%20controller | A session border controller (SBC) is a network element deployed to protect SIP based voice over Internet Protocol (VoIP) networks.
Early deployments of SBCs were focused on the borders between two service provider networks in a peering environment. This role has now expanded to include significant deployments between a service provider's access network and a backbone network to provide service to residential and/or enterprise customers.
The term "session" refers to a communication between two or more parties – in the context of telephony, this would be a call. Each call consists of one or more call signaling message exchanges that control the call, and one or more call media streams which carry the call's audio, video, or other data along with information of call statistics and quality. Together, these streams make up a session. It is the job of a session border controller to exert influence over the data flows of sessions.
The term "border" refers to a point of demarcation between one part of a network and another. As a simple example, at the edge of a corporate network, a firewall demarcates the local network (inside the corporation) from the rest of the Internet (outside the corporation). A more complex example is that of a large corporation where different departments have security needs for each location and perhaps for each kind of data. In this case, filtering routers or other network elements are used to control the flow of data streams. It is the job of a session border controller to assist policy administrators in managing the flow of session data across these borders.
The term "controller" refers to the influence that session border controllers have on the data streams that comprise sessions, as they traverse borders between one part of a network and another. Additionally, session border controllers often provide measurement, access control, and data conversion facilities for the calls they control.
Functions
SBCs commonly maintain full session state and offer the following functions:
Security – protect the network and other devices from:
Malicious attacks such as a denial-of-service attack (DoS) or distributed DoS
Toll fraud via rogue media streams
Malformed packet protection
Encryption of signaling (via TLS and IPSec) and media (SRTP)
Connectivity – allow different parts of the network to communicate through the use of a variety of techniques such as:
NAT traversal
SIP normalization via SIP message and header manipulation
IPv4 to IPv6 interworking
VPN connectivity
Protocol translations between SIP, SIP-I, H.323
Quality of service – the QoS policy of a network and prioritization of flows is usually implemented by the SBC. It can include such functions as:
Traffic policing
Resource allocation
Rate limiting
Call admission control
ToS/DSCP bit setting
Regulatory – many times the SBC is expected to provide support for regulatory requirements such as:
emergency calls prioritization and
lawful interception
Media services – many of the new generation of SBCs also provide built-in digital signal processors (DSPs) to enable them to offer border-based media control and services such as:
DTMF relay and interworking
Media transcoding
Tones and announcements
Data and fax interworking
Support for voice and video calls
Statistics and billing information – since all sessions that pass through the edge of the network pass through the SBC, it is a natural point to gather statistics and usage-based information on these sessions.
With the advent of WebRTC some SBCs have also assumed the role of SIP to WebRTC Gateway and translate SIP. While no one signalling protocol is mandated by the WebRTC specifications, SIP over WebSockets (RFC 7118) is often used partially due to the applicability of SIP to most of the envisaged communication scenarios as well as the availability of open source software such as JsSIP. In such a case the SBC acts as a gateway between the WebRTC applications and SIP end points.
Applications
SBCs are inserted into the signaling and/or media paths between calling and called parties in a VoIP call, predominantly those using the Session Initiation Protocol (SIP), H.323, and MGCP call-signaling protocols.
In many cases the SBC hides the network topology and protects the service provider or enterprise packet networks. The SBC terminates an inbound call and initiates the second call leg to the destination party. In technical terms, when used with the SIP protocol, this defines a back-to-back user agent (B2BUA). The effect of this behavior is that not only the signaling traffic, but also the media traffic (voice, video) is controlled by the SBC. In cases where the SBC does not have the capability to provide media services, SBCs are also able to redirect media traffic to a different element elsewhere in the network, for recording, generation of music-on-hold, or other media-related purposes. Conversely, without an SBC, the media traffic travels directly between the endpoints, without the in-network call signaling elements having control over their path.
In other cases, the SBC simply modifies the stream of call control (signaling) data involved in each call, perhaps limiting the kinds of calls that can be conducted, changing the codec choices, and so on. Ultimately, SBCs allow the network operators to manage the calls that are made on their networks, fix or change protocols and protocol syntax to achieve interoperability, and also overcome some of the problems that firewalls and network address translators (NATs) present for VoIP calls.
To show the operation of an SBC, one can compare a simple call establishment sequence with a call establishment sequence with an SBC. In the simplest session establishment sequence with only one proxy between the user agents the proxy’s task is to identify the callee’s location and forward the request to it. The proxy also adds a Via header with its own address to indicate the path that the response should traverse. The proxy does not change any dialog identification information present in the message such as the tag in the From header, the Call-Id or the Cseq. Proxies also do not alter any information in the SIP message bodies. Note that during the session initiation phase the user agents exchange SIP messages with the SDP bodies that include addresses at which the agents expect the media traffic. After successfully finishing the session initiation phase the user agents can exchange the media traffic directly between each other without the involvement of the proxy.
SBCs are designed for many applications and are used by operators and enterprises to achieve a variety of goals. Even the same SBC implementation might act differently depending on its configuration and the use case. Hence, it is not easily possible to describe an exact SBC behavior that would apply to all SBC implementations. In general it is possible to identify certain features that are common to SBCs. For example, most SBCs are implemented as back-to-back user agent.
A B2BUA is a proxy-like server that splits a SIP transaction in two call legs: on the side facing the user agent client (UAC), it acts as server, on the side facing user agent server (UAS) it acts as a client. While a proxy usually keeps only state information related to active transactions, B2BUAs keep state information about active dialogs, e.g., calls. That is, once a proxy receives a SIP request it will save some state information. Once the transaction is over, e.g., after receiving a response, the state information will soon after be deleted. A B2BUA will maintain state information for active calls and only delete this information once the call is terminated.
When an SBC is included in the call path, the SBC acts as a B2BUA that behaves as a user agent server towards the caller and as user agent client towards the callee. In this sense, the SBC actually terminates that call that was generated by the caller and starts a new call towards the callee. The INVITE message sent by the SBC contains no longer a clear reference to the caller. The INVITE sent by the SBC to the proxy includes Via and Contact headers that point to the SBC itself and not the caller. SBCs often also manipulate the dialog identification information listed in the Call-Id and From tag. Further, in case the SBC is configured to also control the media traffic then the SBC also changes the media addressing information included in the c and m lines of the SDP body. Thereby, not only will all SIP messages traverse the SBC but also all audio and video packets. As the INVITE sent by the SBC establishes a new dialog, the SBC also manipulates the message sequence number (CSeq) as well the Max-Forwards value.
Note that the list of header manipulations listed here is only a subset of the possible changes that an SBC might introduce to a SIP message. Furthermore, some SBCs might not do all of the listed manipulations. If the SBC is not expected to control the media traffic then there might be no need to change anything in the SDP body. Some SBCs do not change the dialog identification information and others might even not change the addressing information.
SBCs are often used by corporations along with firewalls and intrusion prevention systems (IPS) to enable VoIP calls to and from a protected enterprise network. VoIP service providers use SBCs to allow the use of VoIP protocols from private networks with Internet connections using NAT, and also to implement strong security measures that are necessary to maintain a high quality of service. SBCs also replace the function of application-level gateways. In larger enterprises, SBCs can also be used in conjunction with SIP trunks to provide call control and make routing/policy decisions on how calls are routed through the LAN/WAN. There are often tremendous cost savings associated with routing traffic through the internal IP networks of an enterprise, rather than routing calls through a traditional circuit-switched phone network.
Additionally, some SBCs can allow VoIP calls to be set up between two phones using different VoIP signaling protocols (e.g., SIP, H.323, Megaco/MGCP) as well as performing transcoding of the media stream when different codecs are in use. Most SBCs also provide firewall features for VoIP traffic (denial of service protection, call filtering, bandwidth management). Protocol normalization and header manipulation is also commonly provided by SBCs, enabling communication between different vendors and networks.
From an IP Multimedia Subsystem (IMS) or 3GPP (3rd Generation Partnership Project) architecture perspective, the SBC is the integration of the P-CSCF and IMS-ALG at the signaling plane and the IMS Access Gateway at the media plane on the access side. On the interconnect side, the SBC maps to the IBCF, IWF at the signaling plane and TrGW (Transition Gateway) at the media plane.
From an IMS/TISPAN architecture perspective, the SBC is the integration of the P-CSCF and C-BGF functions on the access side, and the IBCF, IWF, THIG, and I-BGF functions on the peering side. Some SBCs can be "decomposed", meaning the signaling functions can be located on a separate hardware platform than the media relay functions – in other words the P-CSCF can be separated from the C-BGF, or the IBCF/IWF can be separated from the I-BGF functions physically. Standards-based protocol, such as the H.248 Ia profile, can be used by the signaling platform to control the media one while a few SBCs use proprietary protocols.
Controversy
During its infancy, the concept of SBC was controversial to proponents of end-to-end systems and peer-to-peer networking because:
SBCs can extend the length of the media path (the way of media packets through the network) significantly. A long media path is undesirable, as it increases the delay of voice packets and the probability of packet loss. Both effects deteriorate the voice/video quality. However, many times there are obstacles to communication such as firewalls between the call parties, and in these cases SBCs offer an efficient method to guide media streams towards an acceptable path between caller and callee; without the SBC the call media would be blocked. Some SBCs can detect if the ends of the call are in the same subnetwork and release control of the media enabling it to flow directly between the clients, this is anti-tromboning or media release. Also, some SBCs can create a media path where none would otherwise be allowed to exist (by virtue of various firewalls and other security apparatus between the two endpoints). Lastly, for specific VoIP network models where the service provider owns the network, SBCs can actually decrease the media path by shortcut routing approaches. For example, a service provider that provides trunking services to several enterprises would usually allocate each enterprise a VPN. It is often desirable to have the option to interconnect the VPN through SBCs. A VPN-aware SBC may perform this function at the edge of the VPN network, rather than sending all the traffic to the core.
SBCs can restrict the flow of information between call endpoints, potentially reducing end-to-end transparency. VoIP phones may not be able to use new protocol features unless they are understood by the SBC. However, the SBCs are usually able to cope with the majority of new, and unanticipated protocol features.
Sometimes end-to-end encryption can't be used if the SBC does not have the key, although some portions of the information stream in an encrypted call are not encrypted, and those portions can be used and influenced by the SBC. However, the new generations of SBCs, armed with sufficient computing capacity, are able to offload this encryption function from other elements in the network by terminating SIP-TLS, IPsec, and/or SRTP. Furthermore, SBCs can actually make calls and other SIP scenarios work when they couldn't have before, by performing specific protocol "normalization" or "fix-up".
In most cases, far-end or hosted NAT traversal can be done without SBCs if the VoIP phones support protocols like STUN, TURN, ICE, or Universal Plug and Play (UPnP).
Most of the controversy surrounding SBCs pertains to whether call control should remain solely with the two endpoints in a call (in service to their owners), or should rather be shared with other network elements owned by the organizations managing various networks involved in connecting the two call endpoints. For example, should call control remain with Alice and Bob (two callers), or should call control be shared with the operators of all the IP networks involved in connecting Alice and Bob's VoIP phones together. The debate of this point was vigorous, almost religious, in nature. Those who wanted unfettered control in the endpoints only, were also greatly frustrated by the various realities of modern networks, such as firewalls and filtering/throttling. On the other side, network operators are typically concerned about overall network performance, interoperability and quality, and want to ensure it is secure.
Lawful intercept and CALEA
Lawful intercept is governed in America by the Communications Assistance for Law Enforcement Act (CALEA).
An SBC may provide session media (usually RTP) and signaling (often SIP) wiretap services, which can be used by providers to enforce requests for the lawful interception of network sessions. Standards for the interception of such services are provided by ATIS, TIA, CableLabs and ETSI, among others.
History and market
According to Jonathan Rosenberg, the author of RFC 3261 (SIP) and numerous other related RFCs, Dynamicsoft developed the first working SBC in conjunction with Aravox, but the product never truly gained marketshare. Newport Networks was the first to have an IPO on the London Stock Exchange's AIM in May 2004 (NNG), while Cisco has been publicly traded since 1990. Acme Packet followed in October 2006 by floating on the NASDAQ. With the field narrowed by acquisition, NexTone merged with Reefpoint becoming Nextpoint, which was subsequently acquired in 2008 by Genband. At this same time, there emerged the "integrated" SBC where the border control function was integrated into another edge device. In 2009, Ingate Systems' Firewall became the first SBC to earn certification from ICSA Labs, a milestone in certifying the VoIP security capabilities of an SBC.
The continuing growth of VoIP networks pushes SBCs further to the edge, mandating adaptation in capacity and complexity. As the VoIP network grows and traffic volume increases, more and more sessions are passing through SBC. Vendors are addressing these new scale requirements in a variety of ways. Some have developed separate, load balancing systems to sit in front of SBC clusters. Others, have developed new architectures using the latest generation chipsets offering higher performance SBCs and scalability using service cards.
See also
3GPP Long Term Evolution (LTE)
Firewall (computing)
H.323 Gatekeeper
IP Multimedia Subsystem (IMS)
Session Initiation Protocol (SIP)
SIP trunking
Universal Mobile Telecommunications System (UMTS)
References
Voice over IP
Computer network security | Session border controller | Engineering | 3,599 |
60,665,098 | https://en.wikipedia.org/wiki/Agkud | Agkud is a traditional Filipino fermented rice paste or rice wine of the Manobo people from Bukidnon. Agkud specifically refers to fermented three-day-old paste made with rice, ginger, sugarcane juice, and or (the yeast starter culture, also known as bubud or tapay in Tagalog and Visayan languages). The rice wine pangasi is made from agkud except fermented longer for at least one month. Modern versions of the agkud can use other sources of starch like cassava, sorghum, or corn. Hot peppers may also be used instead of ginger. Agkud is drunk during celebrations, rituals, and various social events.
See also
Bahalina
Basi
Kaong palm vinegar
Nipa palm vinegar
Pangasi
Tapuy
References
Fermented drinks
Philippine alcoholic drinks
Filipino cuisine | Agkud | Biology | 180 |
44,234,764 | https://en.wikipedia.org/wiki/IT%20operations%20analytics | In the fields of Information Technology (IT) and Systems Management, IT operations analytics (ITOA) is an approach or method to retrieve, analyze, and report data for IT operations. ITOA may apply big data analytics to large datasets to produce business insights. In 2014, Gartner predicted its use might increase revenue or reduce costs. By 2017, it predicted that 15% of enterprises will use IT operations analytics technologies.
Definition
IT operations analytics (ITOA) (also known as advanced operational analytics, or IT data analytics) technologies are primarily used to discover complex patterns in high volumes of often "noisy" IT system availability and performance data. Forrester Research defined IT analytics as "The use of mathematical algorithms and other innovations to extract meaningful information from the sea of raw data collected by management and monitoring technologies." Note, ITOA is different than AIOps, which focuses on applying artificial intelligence and machine learning to the applications of ITOA.
History
Operations research as a discipline emerged from the Second World War to improve military efficiency and decision-making on the battlefield. However, only with the emergence of machine learning tech in the early 2000s could an artificially intelligent operational analytics platform actually begin to engage in the high-level pattern recognition that could adequately serve business needs. A critical catalyst towards ITOA development was the rise of Google, which pioneered a predictive analytics model that represented the first attempt to read into patterns of human behavior on the Internet. IT specialists then applied predictive analytics to the IT Industry, coming forward with platforms that can sift through data to generate insights without the need for human intervention.
Due to the mainstream embrace of cloud computing and the increasing desire for businesses to adopt more big data practices, the ITOA industry has grown significantly since 2010. A 2016 ExtraHop survey of large and mid-size corporations indicates that 65 percent of the businesses surveyed will seek to integrate their data silos either this year or the next. The current goals of ITOA platforms are to improve the accuracy of their APM services, facilitate better integration with the data, and to enhance their predictive analytics capabilities.
Applications
ITOA systems tend to be used by IT operations teams, and Gartner describes seven applications of ITOA systems:
Root cause analysis: The models, structures and pattern descriptions of IT infrastructure or application stack being monitored can help users pinpoint fine-grained and previously unknown root causes of overall system behavior pathologies.
Proactive control of service performance and availability: Predicts future system states and the impact of those states on performance.
Problem assignment: Determines how problems may be resolved or, at least, direct the results of inferences to the most appropriate individuals, or communities in the enterprise for problem resolution.
Service impact analysis: When multiple root causes are known, the analytics system's output is used to determine and rank the relative impact, so that resources can be devoted to correcting the fault in the most timely and cost-effective way possible.
Complement best-of-breed technology: The models, structures and pattern descriptions of IT infrastructure or application stack being monitored are used to correct or extend the outputs of other discovery-oriented tools to improve the fidelity of information used in operational tasks (e.g., service dependency maps, application runtime architecture topologies, network topologies).
Real time application behavior learning: Learns & correlates the behavior of Application based on user pattern and underlying Infrastructure on various application patterns, create metrics of such correlated patterns and store it for further analysis.
Dynamically baselines threshold: Learns behavior of Infrastructure on various application user patterns and determines the Optimal behavior of the Infra and technological components, bench marks and baselines the low and high water mark for the specific environments and dynamically changes the bench mark baselines with the changing infra and user patterns without any manual intervention.
Types
In their Data Growth Demands a Single, Architected IT Operations Analytics Platform, Gartner Research describes five types of analytics technologies:
Log analysis
Unstructured text indexing, search and inference (UTISI)
Topological analysis (TA)
Multidimensional database search and analysis (MDSA)
Complex operations event processing (COEP)
Statistical pattern discovery and recognition (SPDR)
Tools and ITOA platforms
A number of vendors operate in the ITOA space:
AppDynamics
BMC
CA
Dynatrace
Elastic
EMC
Evolven
ExtraHop Networks
HP
IBM
Micro Focus
Nastel
NetApp
Oracle
Riverbed
SAP SE
ScienceLogic
SignalFx
SolarWinds
Splunk
Sumo Logic
TeamQuest
VMTurbo
VMware
See also
Application performance management
Big data
Business intelligence tools
Information technology operations
References
External links
ITOA Landscape: ITOA Landscape
International Data Corporation (IDC): Service Management: Big Data Opportunities Abound for IT Operations Analytics (May 2014)
NetworkWorld: Understanding big data analytics (July 7, 2014)
Enterprise Management Associates (EMA): The Many Faces of Advanced Operations Analytics (September 23, 2014)
ITOperationsAnalytics.net: The Basics of IT Operations Analytics
Application software
Analytics
Big data
Enterprise architecture | IT operations analytics | Technology | 1,021 |
971,656 | https://en.wikipedia.org/wiki/Tpoint | TPoint is computer software that implements a mathematical model of conditions leading to errors in telescope pointing and tracking. The model can then be used in a telescope control system to correct the pointing and tracking. Such errors are typically caused by mechanical or structural defects. For example, TPoint can analyze and compensate for systematic errors such as polar misalignment, mechanical and optical non-orthogonality, lack of roundness in telescope mounting drive gears, as well as for flexure of the mounting caused by gravity.
TPoint is in use on the majority of professional telescopes worldwide, including among many others the Anglo-Australian Telescope, Keck Observatory, Gemini Observatory and the Large Binocular Telescope. It has significantly improved the performance and efficiency of telescope operation and has had an especially strong impact on the development of automated and robotic telescopes.
TPoint is also widely used by amateur astronomers. Software Bisque distributes TPoint as an add-on to TheSkyX Serious Astronomer Edition and TheSkyX Professional; this version is used to improve the pointing on amateur telescopes.
History
TPoint was invented and developed by Patrick Wallace. It grew out of work he and John Straede performed
at the Anglo-Australian Telescope (AAT) between 1974 and 1980
using Interdata 70 computers. In the early 1980s, it was ported to the Digital Equipment Corporation VAX running under
the VMS operating system and between 1990 and 1992 was also ported to run on the PC/MS-DOS platform as well
as various UNIX platforms. A TPoint add-on is available for TheSkyX Serious Astronomer Edition and TheSkyX Professional Edition from Software Bisque, and it runs under Linux, macOS and Microsoft Windows.
External links
TPoint official webpage
Software Bisque TPoint page
Use of TPoint on Atacama Large Millimeter/submillimeter Array antenna prototypes
Use of TPoint on the Green Bank 100m radio telescope
References
Telescopes
Numerical software | Tpoint | Astronomy,Mathematics | 390 |
5,623 | https://en.wikipedia.org/wiki/Canal | Canals or artificial waterways are waterways or engineered channels built for drainage management (e.g. flood control and irrigation) or for conveyancing water transport vehicles (e.g. water taxi). They carry free, calm surface flow under atmospheric pressure, and can be thought of as artificial rivers.
In most cases, a canal has a series of dams and locks that create reservoirs of low speed current flow. These reservoirs are referred to as slack water levels, often just called levels. A canal can be called a navigation canal when it parallels a natural river and shares part of the latter's discharges and drainage basin, and leverages its resources by building dams and locks to increase and lengthen its stretches of slack water levels while staying in its valley.
A canal can cut across a drainage divide atop a ridge, generally requiring an external water source above the highest elevation. The best-known example of such a canal is the Panama Canal.
Many canals have been built at elevations, above valleys and other waterways. Canals with sources of water at a higher level can deliver water to a destination such as a city where water is needed. The Roman Empire's aqueducts were such water supply canals.
The term was once used to describe linear features seen on the surface of Mars, Martian canals, an optical illusion.
Types of artificial waterways
A navigation is a series of channels that run roughly parallel to the valley and stream bed of an unimproved river. A navigation always shares the drainage basin of the river. A vessel uses the calm parts of the river itself as well as improvements, traversing the same changes in height.
A true canal is a channel that cuts across a drainage divide, making a navigable channel connecting two different drainage basins.
Structures used in artificial waterways
Both navigations and canals use engineered structures to improve navigation:
weirs and dams to raise river water levels to usable depths;
looping descents to create a longer and gentler channel around a stretch of rapids or falls;
locks to allow ships and barges to ascend/descend.
Since they cut across drainage divides, canals are more difficult to construct and often need additional improvements, like viaducts and aqueducts to bridge waters over streams and roads, and ways to keep water in the channel.
Types of canals
There are two broad types of canal:
Waterways: canals and navigations used for carrying vessels transporting goods and people. These can be subdivided into two kinds:
Those connecting existing lakes, rivers, other canals or seas and oceans.
Those connected in a city network: such as the Canal Grande and others of Venice; the grachten of Amsterdam or Utrecht, and the waterways of Bangkok.
Aqueducts: water supply canals that are used for the conveyance and delivery of potable water, municipal uses, hydro power canals and agriculture irrigation.
Importance
Historically, canals were of immense importance to the commerce, development, growth and vitality of a civilization. The movement of bulk raw materials such as coal and ores—practically a prerequisite for further urbanization and industrialization—were difficult and only marginally affordable to move without water transport. The movement of bulk raw materials, facilitated by canals, fueled the Industrial Revolution, leading to new research disciplines, new industries and economies of scale, raising the standard of living for industrialized societies.
The few canals still in operation in the 21st century are a fraction of the number that were once maintained during the earlier part of the Industrial Revolution. Their replacement was gradual, beginning first in the United Kingdom in the 1840s, where canal shipping was first augmented by, and later superseded by the much faster, less geographically constrained, and generally cheaper to maintain railways.
By the early 1880s, many canals which had little ability to compete with rail transport were abandoned. In the 20th century, oil was increasingly used as the heating fuel of choice, and the growth of coal shipments began to decrease. After the First World War, technological advances in motor trucks as well as expanding road networks saw increasing amounts of freight being transported by road, and the last small U.S. barge canals saw a steady decline in cargo ton-miles.
The once critical smaller inland waterways conceived and engineered as boat and barge canals have largely been supplanted and filled in, abandoned and left to deteriorate, or kept in service under a park service and staffed by government employees, where dams and locks are maintained for flood control or pleasure boating. Today, most ship canals (intended for larger, oceangoing vessels) service primarily service bulk cargo and large ship transportation industries.
The longest extant canal today, the Grand Canal in northern China, still remains in heavy use, especially the portion south of the Yellow River. It stretches from Beijing to Hangzhou at 1,794 kilometres (1,115 miles).
Construction
Canals are built in one of three ways, or a combination of the three, depending on available water and available path:
Human made streams
A canal can be created where no stream presently exists. Either the body of the canal is dug or the sides of the canal are created by making dykes or levees by piling dirt, stone, concrete or other building materials. The finished shape of the canal as seen in cross section is known as the canal prism. The water for the canal must be provided from an external source, like streams or reservoirs. Where the new waterway must change elevation engineering works like locks, lifts or elevators are constructed to raise and lower vessels. Examples include canals that connect valleys over a higher body of land, like Canal du Midi, Canal de Briare and the Panama Canal.
A canal can be constructed by dredging a channel in the bottom of an existing lake. When the channel is complete, the lake is drained and the channel becomes a new canal, serving both drainage of the surrounding polder and providing transport there. Examples include the . One can also build two parallel dikes in an existing lake, forming the new canal in between, and then drain the remaining parts of the lake. The eastern and central parts of the North Sea Canal were constructed in this way. In both cases pumping stations are required to keep the land surrounding the canal dry, either pumping water from the canal into surrounding waters, or pumping it from the land into the canal.
Canalization and navigations
A stream can be canalized to make its navigable path more predictable and easier to maneuver. Canalization modifies the stream to carry traffic more safely by controlling the flow of the stream by dredging, damming and modifying its path. This frequently includes the incorporation of locks and spillways, that make the river a navigation. Examples include the Lehigh Canal in Northeastern Pennsylvania's coal Region, Basse Saône, Canal de Mines de Fer de la Moselle, and canal Aisne. Riparian zone restoration may be required.
Lateral canals
When a stream is too difficult to modify with canalization, a second stream can be created next to or at least near the existing stream. This is called a lateral canal, and may meander in a large horseshoe bend or series of curves some distance from the source waters stream bed lengthening the effective length in order to lower the ratio of rise over run (slope or pitch). The existing stream usually acts as the water source and the landscape around its banks provide a path for the new body. Examples include the Chesapeake and Ohio Canal, Canal latéral à la Loire, Garonne Lateral Canal, Welland Canal and Juliana Canal.
Smaller transportation canals can carry barges or narrowboats, while ship canals allow seagoing ships to travel to an inland port (e.g., Manchester Ship Canal), or from one sea or ocean to another (e.g., Caledonian Canal, Panama Canal).
Features
At their simplest, canals consist of a trench filled with water. Depending on the stratum the canal passes through, it may be necessary to line the cut with some form of watertight material such as clay or concrete. When this is done with clay, it is known as puddling.
Canals need to be level, and while small irregularities in the lie of the land can be dealt with through cuttings and embankments, for larger deviations other approaches have been adopted. The most common is the pound lock, which consists of a chamber within which the water level can be raised or lowered connecting either two pieces of canal at a different level or the canal with a river or the sea. When there is a hill to be climbed, flights of many locks in short succession may be used.
Prior to the development of the pound lock in 984 AD in China by Chhaio Wei-Yo and later in Europe in the 15th century, either flash locks consisting of a single gate were used or ramps, sometimes equipped with rollers, were used to change the level. Flash locks were only practical where there was plenty of water available.
Locks use a lot of water, so builders have adopted other approaches for situations where little water is available. These include boat lifts, such as the Falkirk Wheel, which use a caisson of water in which boats float while being moved between two levels; and inclined planes where a caisson is hauled up a steep railway.
To cross a stream, road or valley (where the delay caused by a flight of locks at either side would be unacceptable) the valley can be spanned by a navigable aqueduct – a famous example in Wales is the Pontcysyllte Aqueduct (now a UNESCO World Heritage Site) across the valley of the River Dee.
Another option for dealing with hills is to tunnel through them. An example of this approach is the Harecastle Tunnel on the Trent and Mersey Canal. Tunnels are only practical for smaller canals.
Some canals attempted to keep changes in level down to a minimum. These canals known as contour canals would take longer, winding routes, along which the land was a uniform altitude. Other, generally later, canals took more direct routes requiring the use of various methods to deal with the change in level.
Canals have various features to tackle the problem of water supply. In cases, like the Suez Canal, the canal is open to the sea. Where the canal is not at sea level, a number of approaches have been adopted. Taking water from existing rivers or springs was an option in some cases, sometimes supplemented by other methods to deal with seasonal variations in flow. Where such sources were unavailable, reservoirs – either separate from the canal or built into its course – and back pumping were used to provide the required water. In other cases, water pumped from mines was used to feed the canal. In certain cases, extensive "feeder canals" were built to bring water from sources located far from the canal.
Where large amounts of goods are loaded or unloaded such as at the end of a canal, a canal basin may be built. This would normally be a section of water wider than the general canal. In some cases, the canal basins contain wharfs and cranes to assist with movement of goods.
When a section of the canal needs to be sealed off so it can be drained for maintenance stop planks are frequently used. These consist of planks of wood placed across the canal to form a dam. They are generally placed in pre-existing grooves in the canal bank. On more modern canals, "guard locks" or gates were sometimes placed to allow a section of the canal to be quickly closed off, either for maintenance, or to prevent a major loss of water due to a canal breach.
Canal falls
A canal fall, or canal drop, is a vertical drop in the canal bed. These are built when the natural ground slope is steeper than the desired canal gradient. They are constructed so the falling water's kinetic energy is dissipated in order to prevent it from scouring the bed and sides of the canal.
A canal fall is constructed by cut and fill. It may be combined with a regulator, bridge, or other structure to save costs.
There are various types of canal falls, based on their shape. One type is the ogee fall, where the drop follows an s-shaped curve to create a smooth transition and reduce turbulence. However, this smooth transition does not dissipate the water's kinetic energy, which leads to heavy scouring. As a result, the canal needs to be reinforced with concrete or masonry to protect it from eroding.
Another type of canal fall is the vertical fall, which is "simple and economical". These feature a "cistern", or depressed area just downstream from the fall, to "cushion" the water by providing a deep pool for its kinetic energy to be diffused in. Vertical falls work for drops of up to 1.5 m in height, and for discharge of up to 15 cubic meters per second.
History
The transport capacity of pack animals and carts is limited. A mule can carry an eighth-ton [] maximum load over a journey measured in days and weeks, though much more for shorter distances and periods with appropriate rest. Besides, carts need roads. Transport over water is much more efficient and cost-effective for large cargoes.
Ancient canals
The oldest known canals were irrigation canals, built in Mesopotamia , in what is now Iraq. The Indus Valley civilization of ancient India () had sophisticated irrigation and storage systems developed, including the reservoirs built at Girnar in 3000 BC. This is the first time that such planned civil project had taken place in the ancient world. In Egypt, canals date back at least to the time of Pepi I Meryre (reigned 2332–2283 BC), who ordered a canal built to bypass the cataract on the Nile near Aswan.
In ancient China, large canals for river transport were established as far back as the Spring and Autumn period (8th–5th centuries BC), the longest one of that period being the Hong Gou (Canal of the Wild Geese), which according to the ancient historian Sima Qian connected the old states of Song, Zhang, Chen, Cai, Cao, and Wei. The Caoyun System of canals was essential for imperial taxation, which was largely assessed in kind and involved enormous shipments of rice and other grains. By far the longest canal was the Grand Canal of China, still the longest canal in the world today and the oldest extant one. It is long and was built to carry the Emperor Yang Guang between Zhuodu (Beijing) and Yuhang (Hangzhou). The project began in 605 and was completed in 609, although much of the work combined older canals, the oldest section of the canal existing since at least 486 BC. Even in its narrowest urban sections it is rarely less than wide.
In the 5th century BC, Achaemenid king Xerxes I of Persia ordered the construction of the Xerxes Canal through the base of Mount Athos peninsula, Chalkidiki, northern Greece. It was constructed as part of his preparations for the Second Persian invasion of Greece, a part of the Greco-Persian Wars. It is one of the few monuments left by the Persian Empire in Europe.
Greek engineers were also among the first to use canal locks, by which they regulated the water flow in the Ancient Suez Canal as early as the 3rd century BC.
There was little experience moving bulk loads by carts, while a pack-horse would [i.e. 'could'] carry only an eighth of a ton. On a soft road a horse might be able to draw 5/8ths of a ton. But if the load were carried by a barge on a waterway, then up to 30 tons could be drawn by the same horse.— technology historian Ronald W. Clark referring to transport realities before the industrial revolution and the Canal age.
Hohokam was a society in the North American Southwest in what is now part of Arizona, United States, and Sonora, Mexico. Their irrigation systems supported the largest population in the Southwest by 1300 CE. Archaeologists working at a major archaeological dig in the 1990s in the Tucson Basin, along the Santa Cruz River, identified a culture and people that may have been the ancestors of the Hohokam. This prehistoric group occupied southern Arizona as early as 2000 BCE, and in the Early Agricultural period grew corn, lived year-round in sedentary villages, and developed sophisticated irrigation canals.
The large-scale Hohokam irrigation network in the Phoenix metropolitan area was the most complex in ancient North America. A portion of the ancient canals has been renovated for the Salt River Project and now helps to supply the city's water.
The Sinhalese constructed the 87 km (54 mi) Yodha Ela in 459 A.D. as a part of their extensive irrigation network which functioned in a way of a moving reservoir due to its single banking aspect to manage the canal pressure with the influx of water. It was also designed as an elongated reservoir passing through traps creating 66 mini catchments as it flows from Kala Wewa to Thissa Wawa. The canal was not designed for the quick conveying of water from Kala Wewa to Thissa Wawa but to create a mass of water between the two reservoirs, which would in turn provided for agriculture and the use of humans and animals.
They also achieved a rather low gradient for its time. The canal is still in use after renovation.
Middle Ages
In the Middle Ages, water transport was several times cheaper and faster than transport overland. Overland transport by animal drawn conveyances was used around settled areas, but unimproved roads required pack animal trains, usually of mules to carry any degree of mass, and while a mule could carry an eighth ton, it also needed teamsters to tend it and one man could only tend perhaps five mules, meaning overland bulk transport was also expensive, as men expect compensation in the form of wages, room and board. This was because long-haul roads were unpaved, more often than not too narrow for carts, much less wagons, and in poor condition, wending their way through forests, marshy or muddy quagmires as often as unimproved but dry footing. In that era, as today, greater cargoes, especially bulk goods and raw materials, could be transported by ship far more economically than by land; in the pre-railroad days of the industrial revolution, water transport was the gold standard of fast transportation. The first artificial canal in Western Europe was the Fossa Carolina built at the end of the 8th century under personal supervision of Charlemagne.
In Britain, the Glastonbury Canal is believed to be the first post-Roman canal and was built in the middle of the 10th century to link the River Brue at Northover with Glastonbury Abbey, a distance of about . Its initial purpose is believed to be the transport of building stone for the abbey, but later it was used for delivering produce, including grain, wine and fish, from the abbey's outlying properties. It remained in use until at least the 14th century, but possibly as late as the mid-16th century.More lasting and of more economic impact were canals like the Naviglio Grande built between 1127 and 1257 to connect Milan with the river Ticino. The Naviglio Grande is the most important of the lombard "navigli" and the oldest functioning canal in Europe.Later, canals were built in the Netherlands and Flanders to drain the polders and assist transportation of goods and people.
Canal building was revived in this age because of commercial expansion from the 12th century. River navigations were improved progressively by the use of single, or flash locks. Taking boats through these used large amounts of water leading to conflicts with watermill owners and to correct this, the pound or chamber lock first appeared, in the 10th century in China and in Europe in 1373 in Vreeswijk, Netherlands. Another important development was the mitre gate, which was, it is presumed, introduced in Italy by Bertola da Novate in the 16th century. This allowed wider gates and also removed the height restriction of guillotine locks.
To break out of the limitations caused by river valleys, the first summit level canals were developed with the Grand Canal of China in 581–617 AD whilst in Europe the first, also using single locks, was the Stecknitz Canal in Germany in 1398.
Africa
In the Songhai Empire of West Africa, several canals were constructed under Sunni Ali and Askia Muhammad I between Kabara and Timbuktu in the 15th century. These were used primarily for irrigation and transport. Sunni Ali also attempted to construct a canal from the Niger River to Walata to facilitate conquest of the city but his progress was halted when he went to war with the Mossi Kingdoms.
Early modern period
Around 1500–1800 the first summit level canal to use pound locks in Europe was the Briare Canal connecting the Loire and Seine (1642), followed by the more ambitious Canal du Midi (1683) connecting the Atlantic to the Mediterranean. This included a staircase of 8 locks at Béziers, a tunnel, and three major aqueducts.
Canal building progressed steadily in Germany in the 17th and 18th centuries with three great rivers, the Elbe, Oder and Weser being linked by canals. In post-Roman Britain, the first early modern period canal built appears to have been the Exeter Canal, which was surveyed in 1563, and open in 1566.
The oldest canal in the European settlements of North America, technically a mill race built for industrial purposes, is Mother Brook between the Boston, Massachusetts neighbourhoods of Dedham and Hyde Park connecting the higher waters of the Charles River and the mouth of the Neponset River and the sea. It was constructed in 1639 to provide water power for mills.
In Russia, the Volga–Baltic Waterway, a nationwide canal system connecting the Baltic Sea and Caspian Sea via the Neva and Volga rivers, was opened in 1718.
Industrial Revolution
The modern canal system was mainly a product of the 18th century and early 19th century. It came into being because the Industrial Revolution (which began in Britain during the mid-18th century) demanded an economic and reliable way to transport goods and commodities in large quantities.
By the early 18th century, river navigations such as the Aire and Calder Navigation were becoming quite sophisticated, with pound locks and longer and longer "cuts" (some with intermediate locks) to avoid circuitous or difficult stretches of river. Eventually, the experience of building long multi-level cuts with their own locks gave rise to the idea of building a "pure" canal, a waterway designed on the basis of where goods needed to go, not where a river happened to be.
The claim for the first pure canal in Great Britain is debated between "Sankey" and "Bridgewater" supporters. The first true canal in what is now the United Kingdom was the Newry Canal in Northern Ireland constructed by Thomas Steers in 1741.
The Sankey Brook Navigation, which connected St Helens with the River Mersey, is often claimed as the first modern "purely artificial" canal because although originally a scheme to make the Sankey Brook navigable, it included an entirely new artificial channel that was effectively a canal along the Sankey Brook valley. However, "Bridgewater" supporters point out that the last quarter-mile of the navigation is indeed a canalized stretch of the Brook, and that it was the Bridgewater Canal (less obviously associated with an existing river) that captured the popular imagination and inspired further canals.
In the mid-eighteenth century the 3rd Duke of Bridgewater, who owned a number of coal mines in northern England, wanted a reliable way to transport his coal to the rapidly industrializing city of Manchester. He commissioned the engineer James Brindley to build a canal for that purpose. Brindley's design included an aqueduct carrying the canal over the River Irwell. This was an engineering wonder which immediately attracted tourists. The construction of this canal was funded entirely by the Duke and was called the Bridgewater Canal. It opened in 1761 and was the first major British canal.
The new canals proved highly successful. The boats on the canal were horse-drawn with a towpath alongside the canal for the horse to walk along. This horse-drawn system proved to be highly economical and became standard across the British canal network. Commercial horse-drawn canal boats could be seen on the UK's canals until as late as the 1950s, although by then diesel-powered boats, often towing a second unpowered boat, had become standard.
The canal boats could carry thirty tons at a time with only one horse pulling – more than ten times the amount of cargo per horse that was possible with a cart. Because of this huge increase in supply, the Bridgewater canal reduced the price of coal in Manchester by nearly two-thirds within just a year of its opening. The Bridgewater was also a huge financial success, with it earning what had been spent on its construction within just a few years.
This success proved the viability of canal transport, and soon industrialists in many other parts of the country wanted canals. After the Bridgewater canal, early canals were built by groups of private individuals with an interest in improving communications. In Staffordshire the famous potter Josiah Wedgwood saw an opportunity to bring bulky cargoes of clay to his factory doors and to transport his fragile finished goods to market in Manchester, Birmingham or further away, by water, minimizing breakages. Within just a few years of the Bridgewater's opening, an embryonic national canal network came into being, with the construction of canals such as the Oxford Canal and the Trent & Mersey Canal.
The new canal system was both cause and effect of the rapid industrialization of The Midlands and the north. The period between the 1770s and the 1830s is often referred to as the "Golden Age" of British canals.
For each canal, an Act of Parliament was necessary to authorize construction, and as people saw the high incomes achieved from canal tolls, canal proposals came to be put forward by investors interested in profiting from dividends, at least as much as by people whose businesses would profit from cheaper transport of raw materials and finished goods.
In a further development, there was often out-and-out speculation, where people would try to buy shares in a newly floated company to sell them on for an immediate profit, regardless of whether the canal was ever profitable, or even built. During this period of "canal mania", huge sums were invested in canal building, and although many schemes came to nothing, the canal system rapidly expanded to nearly 4,000 miles (over 6,400 kilometres) in length.
Many rival canal companies were formed and competition was rampant. Perhaps the best example was Worcester Bar in Birmingham, a point where the Worcester and Birmingham Canal and the Birmingham Canal Navigations Main Line were only seven feet apart. For many years, a dispute about tolls meant that goods travelling through Birmingham had to be portaged from boats in one canal to boats in the other.
Canal companies were initially chartered by individual states in the United States. These early canals were constructed, owned, and operated by private joint-stock companies. Four were completed when the War of 1812 broke out; these were the South Hadley Canal (opened 1795) in Massachusetts, Santee Canal (opened 1800) in South Carolina, the Middlesex Canal (opened 1802) also in Massachusetts, and the Dismal Swamp Canal (opened 1805) in Virginia. The Erie Canal (opened 1825) was chartered and owned by the state of New York and financed by bonds bought by private investors. The Erie canal runs about from Albany, New York, on the Hudson River to Buffalo, New York, at Lake Erie. The Hudson River connects Albany to the Atlantic port of New York City and the Erie Canal completed a navigable water route from the Atlantic Ocean to the Great Lakes. The canal contains 36 locks and encompasses a total elevation differential of around 565 ft. (169 m). The Erie Canal with its easy connections to most of the U.S. mid-west and New York City soon quickly paid back all its invested capital (US$7 million) and started turning a profit. By cutting transportation costs in half or more it became a large profit center for Albany and New York City as it allowed the cheap transportation of many of the agricultural products grown in the mid west of the United States to the rest of the world. From New York City these agricultural products could easily be shipped to other U.S. states or overseas. Assured of a market for their farm products the settlement of the U.S. mid-west was greatly accelerated by the Erie Canal. The profits generated by the Erie Canal project started a canal building boom in the United States that lasted until about 1850 when railroads started becoming seriously competitive in price and convenience. The Blackstone Canal (finished in 1828) in Massachusetts and Rhode Island fulfilled a similar role in the early industrial revolution between 1828 and 1848. The Blackstone Valley was a major contributor of the American Industrial Revolution where Samuel Slater built his first textile mill.
Power canals
A power canal refers to a canal used for hydraulic power generation, rather than for transport. Nowadays power canals are built almost exclusively as parts of hydroelectric power stations. Parts of the United States, particularly in the Northeast, had enough fast-flowing rivers that water power was the primary means of powering factories (usually textile mills) until after the American Civil War. For example, Lowell, Massachusetts, considered to be "The Cradle of the American Industrial Revolution," has of canals, built from around 1790 to 1850, that provided water power and a means of transportation for the city. The output of the system is estimated at 10,000 horsepower. Other cities with extensive power canal systems include Lawrence, Massachusetts, Holyoke, Massachusetts, Manchester, New Hampshire, and Augusta, Georgia. The most notable power canal was built in 1862 for the Niagara Falls Hydraulic Power and Manufacturing Company.
19th century
Competition, from railways from the 1830s and roads in the 20th century, made the smaller canals obsolete for most commercial transport, and many of the British canals fell into decay. Only the Manchester Ship Canal and the Aire and Calder Canal bucked this trend. Yet in other countries canals grew in size as construction techniques improved. During the 19th century in the US, the length of canals grew from to over 4,000, with a complex network making the Great Lakes navigable, in conjunction with Canada, although some canals were later drained and used as railroad rights-of-way.
In the United States, navigable canals reached into isolated areas and brought them in touch with the world beyond. By 1825 the Erie Canal, long with 36 locks, opened up a connection from the populated Northeast to the Great Lakes. Settlers flooded into regions serviced by such canals, since access to markets was available. The Erie Canal (as well as other canals) was instrumental in lowering the differences in commodity prices between these various markets across America. The canals caused price convergence between different regions because of their reduction in transportation costs, which allowed Americans to ship and buy goods from farther distances much cheaper. Ohio built many miles of canal, Indiana had working canals for a few decades, and the Illinois and Michigan Canal connected the Great Lakes to the Mississippi River system until replaced by a channelized river waterway.
Three major canals with very different purposes were built in what is now Canada. The first Welland Canal, which opened in 1829 between Lake Ontario and Lake Erie, bypassing Niagara Falls and the Lachine Canal (1825), which allowed ships to skirt the nearly impassable rapids on the St. Lawrence River at Montreal, were built for commerce. The Rideau Canal, completed in 1832, connects Ottawa on the Ottawa River to Kingston, Ontario on Lake Ontario. The Rideau Canal was built as a result of the War of 1812 to provide military transportation between the British colonies of Upper Canada and Lower Canada as an alternative to part of the St. Lawrence River, which was susceptible to blockade by the United States.
In France, a steady linking of all the river systems – Rhine, Rhône, Saône and Seine – and the North Sea was boosted in 1879 by the establishment of the Freycinet gauge, which specified the minimum size of locks. Canal traffic doubled in the first decades of the 20th century.
Many notable sea canals were completed in this period, starting with the Suez Canal (1869) – which carries tonnage many times that of most other canals – and the Kiel Canal (1897), though the Panama Canal was not opened until 1914.
In the 19th century, a number of canals were built in Japan including the Biwako canal and the Tone canal. These canals were partially built with the help of engineers from the Netherlands and other countries.
A major question was how to connect the Atlantic and the Pacific with a canal through narrow Central America. (The Panama Railroad opened in 1855.) The original proposal was for a sea-level canal through what is today Nicaragua, taking advantage of the relatively large Lake Nicaragua. This canal has never been built in part because of political instability, which scared off potential investors. It remains an active project (the geography has not changed), and in the 2010s Chinese involvement was developing.
The second choice for a Central American canal was a Panama Canal. The De Lesseps company, which ran the Suez Canal, first attempted to build a Panama Canal in the 1880s. The difficulty of the terrain and weather (rain) encountered caused the company to go bankrupt. High worker mortality from disease also discouraged further investment in the project. DeLesseps' abandoned excavating equipment sits, isolated decaying machines, today tourist attractions.
Twenty years later, an expansionist United States, that just acquired colonies after defeating Spain in the 1898 Spanish–American War, and whose Navy became more important, decided to reactivate the project. The United States and Colombia did not reach agreement on the terms of a canal treaty (see Hay–Herrán Treaty). Panama, which did not have (and still does not have) a land connection with the rest of Colombia, was already thinking of independence. In 1903 the United States, with support from Panamanians who expected the canal to provide substantial wages, revenues, and markets for local goods and services, took Panama province away from Colombia, and set up a puppet republic (Panama). Its currency, the Balboa – a name that suggests the country began as a way to get from one hemisphere to the other – was a replica of the US dollar. The US dollar was and remains legal tender (used as currency). A U.S. military zone, the Canal Zone, wide, with U.S. military stationed there (bases, 2 TV stations, channels 8 and 10, Pxs, a U.S.-style high school), split Panama in half. The Canal – a major engineering project – was built. The U.S. did not feel that conditions were stable enough to withdraw until 1979. The withdrawal from Panama contributed to President Jimmy Carter's defeat in 1980.
Modern uses
Large-scale ship canals such as the Panama Canal and Suez Canal continue to operate for cargo transportation, as do European barge canals. Due to globalization, they are becoming increasingly important, resulting in expansion projects such as the Panama Canal expansion project. The expanded canal began commercial operation on 26 June 2016. The new set of locks allow transit of larger, Post-Panamax and New Panamax ships.
The narrow early industrial canals, however, have ceased to carry significant amounts of trade and many have been abandoned to navigation, but may still be used as a system for transportation of untreated water. In some cases railways have been built along the canal route, an example being the Croydon Canal.
A movement that began in Britain and France to use the early industrial canals for pleasure boats, such as hotel barges, has spurred rehabilitation of stretches of historic canals. In some cases, abandoned canals such as the Kennet and Avon Canal have been restored and are now used by pleasure boaters. In Britain, canalside housing has also proven popular in recent years.
The Seine–Nord Europe Canal is being developed into a major transportation waterway, linking France with Belgium, Germany, and the Netherlands.
Canals have found another use in the 21st century, as easements for the installation of fibre optic telecommunications network cabling, avoiding having them buried in roadways while facilitating access and reducing the hazard of being damaged from digging equipment.
Canals are still used to provide water for agriculture. An extensive canal system exists within the Imperial Valley in the Southern California desert to provide irrigation to agriculture within the area.
Cities on water
Canals are so deeply identified with Venice that many canal cities have been nicknamed "the Venice of…". The city is built on marshy islands, with wooden piles supporting the buildings, so that the land is man-made rather than the waterways. The islands have a long history of settlement; by the 12th century, Venice was a powerful city state.
Amsterdam was built in a similar way, with buildings on wooden piles. It became a city around 1300. Many Amsterdam canals were built as part of fortifications. They became grachten when the city was enlarged and houses were built alongside the water. Its nickname as the "Venice of the North" is shared with Hamburg of Germany, St. Petersburg of Russia and Bruges of Belgium.
Suzhou was dubbed the "Venice of the East" by Marco Polo during his travels there in the 13th century, with its modern canalside Pingjiang Road and Shantang Street becoming major tourist attractions. Other nearby cities including Nanjing, Shanghai, Wuxi, Jiaxing, Huzhou, Nantong, Taizhou, Yangzhou, and Changzhou are located along the lower mouth of the Yangtze River and Lake Tai, yet another source of small rivers and creeks, which have been canalized and developed for centuries.
Other cities with extensive canal networks include: Alkmaar, Amersfoort, Bolsward, Brielle, Delft, Den Bosch, Dokkum, Dordrecht, Enkhuizen, Franeker, Gouda, Haarlem, Harlingen, Leeuwarden, Leiden, Sneek and Utrecht in the Netherlands; Brugge and Gent in Flanders, Belgium; Birmingham in England; Saint Petersburg in Russia; Bydgoszcz, Gdańsk, Szczecin and Wrocław in Poland; Aveiro in Portugal; Hamburg and Berlin in Germany; Fort Lauderdale and Cape Coral in Florida, United States, Wenzhou in China, Cần Thơ in Vietnam, Bangkok in Thailand, and Lahore in Pakistan.
Liverpool Maritime Mercantile City was a UNESCO World Heritage Site near the centre of Liverpool, England, where a system of intertwining waterways and docks is now being developed for mainly residential and leisure use.
Canal estates (sometimes known as bayous in the United States) are a form of subdivision popular in cities like Miami, Florida, Texas City, Texas and the Gold Coast, Queensland; the Gold Coast has over 890 km of residential canals. Wetlands are difficult areas upon which to build housing estates, so dredging part of the wetland down to a navigable channel provides fill to build up another part of the wetland above the flood level for houses. Land is built up in a finger pattern that provides a suburban street layout of waterfront housing blocks.
Boats
Inland canals have often had boats specifically built for them. An example of this is the British narrowboat, which is up to long and wide and was primarily built for British Midland canals. In this case the limiting factor was the size of the locks. This is also the limiting factor on the Panama canal where Panamax ships were limited to a length of and a beam of until 26 June 2016 when the opening of larger locks allowed for the passage of larger New Panamax ships. For the lockless Suez Canal the limiting factor for Suezmax ships is generally draft, which is limited to . At the other end of the scale, tub-boat canals such as the Bude Canal were limited to boats of under 10 tons for much of their length due to the capacity of their inclined planes or boat lifts. Most canals have a limit on height imposed either by bridges or by tunnels.
Lists of canals
Africa
Bahr Yussef
El Salam Canal (Egypt)
Ibrahimiya Canal (Egypt)
Mahmoudiyah Canal (Egypt)
Suez Canal (Egypt)
Asia
see List of canals in India
see List of canals in Pakistan
see History of canals in China
King Abdullah Canal (Jordan)
Qanat al-Jaish (Iraq)
Europe
Danube–Black Sea Canal (Romania)
North Crimean Canal (Ukraine)
Canals of France
Canals of Amsterdam
Canals of Germany
Canals of Ireland
Canals of Russia
Canals of the United Kingdom
List of canals in the United Kingdom
Great Bačka Canal (Serbia)
North America
Canals of Canada
Canals of the United States
Panama Canal
Lists of proposed canals
Eurasia Canal
Istanbul Canal
Nicaragua Canal
Salwa Canal
Thai Canal
Sulawesi Canal
Two Seas Canal
Northern river reversal
Balkan Canal or Danube–Morava–Vardar–Aegean Canal
Iranrud
See also
Beaver, a non-human animal also known for canal building
Canal elevator
Calle canal
Canal & River Trust
Canal tunnel
Environment Agency
Horse-drawn boat
Irrigation district
Lists of canals
List of navigation authorities in the United Kingdom
List of waterways
List of waterway societies in the United Kingdom
Mooring
Navigation authority
Proposed canals
Roman canals – (Torksey)
Volumetric flow rate
Water bridge
Waterscape
Water transportation
Waterway restoration
Waterways in the United Kingdom
Weigh lock
References
Notes
Bibliography
External links
British Waterways' leisure website – Britain's official guide to canals, rivers and lakes
Leeds Liverpool Canal Photographic Guide
Information and Boater's Guide to the New York State Canal System
"Canals and Navigable Rivers" by James S. Aber, Emporia State University
National Canal Museum (US)
London Canal Museum (UK)
Canals in Amsterdam
Canal du Midi
Canal des Deux Mers
Canal flow measurement using a sensor.
Coastal construction
Water transport infrastructure
Artificial bodies of water
Infrastructure | Canal | Engineering | 8,476 |
64,500,324 | https://en.wikipedia.org/wiki/HAT-P-20 | HAT-P-20 is a K-type main-sequence star about 233 light-years away. The star has a strong starspot activity, and its equatorial plane is misaligned by 36° with the planetary orbit. Although star with a giant planet on close orbit is expected to be spun-up by tidal forces, only weak indications of tidal spin-up were detected.
Planetary system
In 2010 a transiting hot super-Jovian planet was detected. Its equilibrium temperature is 996 K.
References
Gemini (constellation)
K-type main-sequence stars
Planetary systems with one confirmed planet
Planetary transit variables
J07273995+2420118 | HAT-P-20 | Astronomy | 135 |
71,245,442 | https://en.wikipedia.org/wiki/Peziza%20oliviae | Peziza oliviae is a species of fungus in the family Peziza. It is an olive-brown stalked cup fungus discovered growing underwater in streams in the U.S. State of Oregon.
Description
Peziza oliviae has small olive to golden-brown stalked cups 0.7–2.5 cm in height with a diameter of 0.8–4 cm.
Habitat and distribution
Found in small streams in the Cascade Range of North Central Oregon at elevations between 800 and 1500 metres. P. oliviae was found growing on dead wooden debris on the bottom of streams or on saturated wood at the surface or bank of the stream. Documented June through October.
Discovery
P. oliviae was discovered in 2014 by Jonathan L. Frank of Southern Oregon University.
References
Pezizaceae
Fungi described in 2014
Fungi of the United States
Fungus species | Peziza oliviae | Biology | 171 |
1,840,591 | https://en.wikipedia.org/wiki/Decay%20correction | Decay correction is a method of estimating the amount of radioactive decay at some set time before it was actually measured.
Example of use
Researchers often want to measure, say, medical compounds in the bodies of animals. It's hard to measure them directly, so it can be chemically joined to a radionuclide - by measuring the radioactivity, you can get a good idea of how the original medical compound is being processed.
Samples may be collected and counted at short time intervals (ex: 1 and 4 hours). But they might be tested for radioactivity all at once. Decay correction is one way of working out what the radioactivity would have been at the time it was taken, rather than at the time it was tested.
For example, the isotope copper-64, commonly used in medical research, has a half-life of 12.7 hours. If you inject a large group of animals at "time zero", but measure the radioactivity in their organs at two later times, the later groups must be "decay corrected" to adjust for the decay that has occurred between the two time points.
Mathematics
The formula for decay correcting is:
where is the original activity count at time zero, is the activity at time "t", "λ" is the decay constant, and "t" is the elapsed time.
The decay constant is where "" is the half-life of the radioactive material of interest.
Example
The decay correct might be used this way: a group of 20 animals is injected with a compound of interest on a Monday at 10:00 a.m. The compound is chemically joined to the isotope copper-64, which has a known half-life of 12.7 hours, or 764 minutes. After one hour, the 5 animals in the "one hour" group are killed, dissected, and organs of interest are placed in sealed containers to await measurement. This is repeated for another 5 animals, at 2 hours, and again at 4 hours. At this point, (say, 4:00 p.m., Monday) all the organs collected so far are measured for radioactivity (a proxy of the distribution of the compound of interest). The next day (Tuesday), the "24 hour" group would be killed and dissected at 10:00 a.m., then measured for radioactivity, (say at 11:00 a.m.). In order to compare ALL the groups together, the data from the "24 hour" must be decay corrected: the radioactivity measured on the second day must be "adjusted" in order to allow a comparison to measurements from an earlier time, but of the same original material.
In this case, "time zero" is Monday, 4:00 p.m., when the first three groups (1,2, and 4 hour animals organs) were measured. The "24 hour" group was measured at 11:00 a.m. Tuesday, which is 19 hours after the first groups.
Start by calculating the decay constant "K". Substitute 12.7 (hours, the half-life of copper-64) for , giving
= 0.0546.
Next, multiply this value of "K" by the time elapsed between the first and second measures of radioactivity, 19 hours: (0.0546 x 19) = 1.0368.
Change the sign, to make it -1.0368, then find the "inverse Ln"; in this case 0.3546.
This value is in the denominator of the decay correcting fraction, so it is the same as multiplying the numerator by its inverse (), which is 2.82.
(A simple way to check if you are using the decay correct formula right is to put in the value of the half-life in place of "t". After you perform the inverse Ln, the value should be very close to 0.5. When divided into the value "A" (for uncorrected counts), it effectively doubles them, which is the necessary correction after one half-life has occurred.)
In this case, the uncorrected values will be multiplied by 2.82, which corrects for 19 hours elapsing (between one and two half-lives).
If the radiation measured has dropped by half between the 4 hour sample and the 24 hour sample we might think that the concentration of compound in that organ has dropped by half; but applying the decay correct we see that the concentration is 0.5*2.82 so it has actually increased by 40% in that period.
References
Radioactivity | Decay correction | Physics,Chemistry | 969 |
8,632,154 | https://en.wikipedia.org/wiki/Comparison%20of%20content-control%20software%20and%20providers | This is a list of content-control software and services. The software is designed to control what content may or may not be viewed by a reader, especially when used to restrict material delivered over the Internet via the Web, e-mail, or other means. Restrictions can be applied at various levels: a government can apply them nationwide, an ISP can apply them to its clients, an employer to its personnel, a school to its teachers or students, a library to its patrons or staff, a parent to a child's computer or computer account or an individual to his or her own computer.
Programs and services
Providers
Amesys
Awareness Technologies
Barracuda Networks
Blue Coat Systems
CronLab
Cyberoam
Detica
Dope.security
Fortinet
GoGuardian
Huawei
Isheriff
Lightspeed Systems
Retina-X Studios
SafeDNS
Securly
SmoothWall
SonicWall
Sophos
SurfControl
Webroot
Websense
MICT, 456.ir
See also
Accountability software
Ad filtering
Computer surveillance
Deep packet inspection
Deep content inspection
Internet censorship
Internet safety
Parental controls
Wordfilter
References
Content-control software and providers
Computing-related lists | Comparison of content-control software and providers | Technology | 232 |
55,479,079 | https://en.wikipedia.org/wiki/Howson%20property | In the mathematical subject of group theory, the Howson property, also known as the finitely generated intersection property (FGIP), is the property of a group saying that the intersection of any two finitely generated subgroups of this group is again finitely generated. The property is named after Albert G. Howson who in a 1954 paper established that free groups have this property.
Formal definition
A group is said to have the Howson property if for every finitely generated subgroups of their intersection is again a finitely generated subgroup of .
Examples and non-examples
Every finite group has the Howson property.
The group does not have the Howson property. Specifically, if is the generator of the factor of , then for and , one has . Therefore, is not finitely generated.
If is a compact surface then the fundamental group of has the Howson property.
A free-by-(infinite cyclic group) , where , never has the Howson property.
In view of the recent proof of the Virtually Haken conjecture and the Virtually fibered conjecture for 3-manifolds, previously established results imply that if M is a closed hyperbolic 3-manifold then does not have the Howson property.
Among 3-manifold groups, there are many examples that do and do not have the Howson property. 3-manifold groups with the Howson property include fundamental groups of hyperbolic 3-manifolds of infinite volume, 3-manifold groups based on Sol and Nil geometries, as well as 3-manifold groups obtained by some connected sum and JSJ decomposition constructions.
For every the Baumslag–Solitar group has the Howson property.
If G is group where every finitely generated subgroup is Noetherian then G has the Howson property. In particular, all abelian groups and all nilpotent groups have the Howson property.
Every polycyclic-by-finite group has the Howson property.
If are groups with the Howson property then their free product also has the Howson property. More generally, the Howson property is preserved under taking amalgamated free products and HNN-extension of groups with the Howson property over finite subgroups.
In general, the Howson property is rather sensitive to amalgamated products and HNN extensions over infinite subgroups. In particular, for free groups and an infinite cyclic group , the amalgamated free product has the Howson property if and only if is a maximal cyclic subgroup in both and .
A right-angled Artin group has the Howson property if and only if every connected component of is a complete graph.
Limit groups have the Howson property.
It is not known whether has the Howson property.
For the group contains a subgroup isomorphic to and does not have the Howson property.
Many small cancellation groups and Coxeter groups, satisfying the ``perimeter reduction" condition on their presentation, are locally quasiconvex word-hyperbolic groups and therefore have the Howson property.
One-relator groups , where are also locally quasiconvex word-hyperbolic groups and therefore have the Howson property.
The Grigorchuk group G of intermediate growth does not have the Howson property.
The Howson property is not a first-order property, that is the Howson property cannot be characterized by a collection of first order group language formulas.
A free pro-p group satisfies a topological version of the Howson property: If are topologically finitely generated closed subgroups of then their intersection is topologically finitely generated.
For any fixed integers a ``generic" -generator -relator group has the property that for any -generated subgroups their intersection is again finitely generated.
The wreath product does not have the Howson property.
Thompson's group does not have the Howson property, since it contains .
See also
Hanna Neumann conjecture
References
Group theory | Howson property | Mathematics | 791 |
4,273,403 | https://en.wikipedia.org/wiki/Speech%20segmentation | Speech segmentation is the process of identifying the boundaries between words, syllables, or phonemes in spoken natural languages. The term applies both to the mental processes used by humans, and to artificial processes of natural language processing.
Speech segmentation is a subfield of general speech perception and an important subproblem of the technologically focused field of speech recognition, and cannot be adequately solved in isolation. As in most natural language processing problems, one must take into account context, grammar, and semantics, and even so the result is often a probabilistic division (statistically based on likelihood) rather than a categorical one. Though it seems that coarticulation—a phenomenon which may happen between adjacent words just as easily as within a single word—presents the main challenge in speech segmentation across languages, some other problems and strategies employed in solving those problems can be seen in the following sections.
This problem overlaps to some extent with the problem of text segmentation that occurs in some languages which are traditionally written without inter-word spaces, like Chinese and Japanese, compared to writing systems which indicate speech segmentation between words by a word divider, such as the space. However, even for those languages, text segmentation is often much easier than speech segmentation, because the written language usually has little interference between adjacent words, and often contains additional clues not present in speech (such as the use of Chinese characters for word stems in Japanese).
Lexical recognition
In natural languages, the meaning of a complex spoken sentence can be understood by decomposing it into smaller lexical segments (roughly, the words of the language), associating a meaning to each segment, and combining those meanings according to the grammar rules of the language.
Though lexical recognition is not thought to be used by infants in their first year, due to their highly limited vocabularies, it is one of the major processes involved in speech segmentation for adults. Three main models of lexical recognition exist in current research: first, whole-word access, which argues that words have a whole-word representation in the lexicon; second, decomposition, which argues that morphologically complex words are broken down into their morphemes (roots, stems, inflections, etc.) and then interpreted and; third, the view that whole-word and decomposition models are both used, but that the whole-word model provides some computational advantages and is therefore dominant in lexical recognition.
To give an example, in a whole-word model, the word "cats" might be stored and searched for by letter, first "c", then "ca", "cat", and finally "cats". The same word, in a decompositional model, would likely be stored under the root word "cat" and could be searched for after removing the "s" suffix. "Falling", similarly, would be stored as "fall" and suffixed with the "ing" inflection.
Though proponents of the decompositional model recognize that a morpheme-by-morpheme analysis may require significantly more computation, they argue that the unpacking of morphological information is necessary for other processes (such as syntactic structure) which may occur parallel to lexical searches.
As a whole, research into systems of human lexical recognition is limited due to little experimental evidence that fully discriminates between the three main models.
In any case, lexical recognition likely contributes significantly to speech segmentation through the contextual clues it provides, given that it is a heavily probabilistic system—based on the statistical likelihood of certain words or constituents occurring together. For example, one can imagine a situation where a person might say "I bought my dog at a shop" and the missing word's vowel is pronounced as in "net", "sweat", or "pet". While the probability of "netshop" is extremely low, since "netshop" isn't currently a compound or phrase in English, and "sweatshop" also seems contextually improbable, "pet shop" is a good fit because it is a common phrase and is also related to the word "dog".
Moreover, an utterance can have different meanings depending on how it is split into words. A popular example, often quoted in the field, is the phrase "How to wreck a nice beach", which sounds very similar to "How to recognize speech". As this example shows, proper lexical segmentation depends on context and semantics which draws on the whole of human knowledge and experience, and would thus require advanced pattern recognition and artificial intelligence technologies to be implemented on a computer.
Lexical recognition is of particular value in the field of computer speech recognition, since the ability to build and search a network of semantically connected ideas would greatly increase the effectiveness of speech-recognition software. Statistical models can be used to segment and align recorded speech to words or phones. Applications include automatic lip-synch timing for cartoon animation, follow-the-bouncing-ball video sub-titling, and linguistic research. Automatic segmentation and alignment software is commercially available.
Phonotactic cues
For most spoken languages, the boundaries between lexical units are difficult to identify; phonotactics are one answer to this issue. One might expect that the inter-word spaces used by many written languages like English or Spanish would correspond to pauses in their spoken version, but that is true only in very slow speech, when the speaker deliberately inserts those pauses. In normal speech, one typically finds many consecutive words being said with no pauses between them, and often the final sounds of one word blend smoothly or fuse with the initial sounds of the next word.
The notion that speech is produced like writing, as a sequence of distinct vowels and consonants, may be a relic of alphabetic heritage for some language communities. In fact, the way vowels are produced depends on the surrounding consonants just as consonants are affected by surrounding vowels; this is called coarticulation. For example, in the word "kit", the [k] is farther forward than when we say 'caught'. But also, the vowel in "kick" is phonetically different from the vowel in "kit", though we normally do not hear this. In addition, there are language-specific changes which occur in casual speech which makes it quite different from spelling. For example, in English, the phrase "hit you" could often be more appropriately spelled "hitcha".
From a decompositional perspective, in many cases, phonotactics play a part in letting speakers know where to draw word boundaries. In English, the word "strawberry" is perceived by speakers as consisting (phonetically) of two parts: "straw" and "berry". Other interpretations such as "stra" and "wberry" are inhibited by English phonotactics, which does not allow the cluster "wb" word-initially. Other such examples are "day/dream" and "mile/stone" which are unlikely to be interpreted as "da/ydream" or "mil/estone" due to the phonotactic probability or improbability of certain clusters. The sentence "Five women left", which could be phonetically transcribed as [faɪvwɪmɘnlɛft], is marked since neither /vw/ in /faɪvwɪmɘn/ nor /nl/ in /wɪmɘnlɛft/ are allowed as syllable onsets or codas in English phonotactics. These phonotactic cues often allow speakers to easily distinguish the boundaries in words.
Vowel harmony in languages like Finnish can also serve to provide phonotactic cues. While the system does not allow front vowels and back vowels to exist together within one morpheme, compounds allow two morphemes to maintain their own vowel harmony while coexisting in a word. Therefore, in compounds such as "selkä/ongelma" ('back problem') where vowel harmony is distinct between two constituents in a compound, the boundary will be wherever the switch in harmony takes place—between the "ä" and the "ö" in this case. Still, there are instances where phonotactics may not aid in segmentation. Words with unclear clusters or uncontrasted vowel harmony as in "opinto/uudistus" ('student reform') do not offer phonotactic clues as to how they are segmented.
From the perspective of the whole-word model, however, these words are thought be stored as full words, so the constituent parts would not necessarily be relevant to lexical recognition.
In infants and non-natives
Infants are one major focus of research in speech segmentation. Since infants have not yet acquired a lexicon capable of providing extensive contextual clues or probability-based word searches within their first year, as mentioned above, they must often rely primarily upon phonotactic and rhythmic cues (with prosody being the dominant cue), all of which are language-specific. Between 6 and 9 months, infants begin to lose the ability to discriminate between sounds not present in their native language and grow sensitive to the sound structure of their native language, with the word segmentation abilities appearing around 7.5 months.
Though much more research needs to be done on the exact processes that infants use to begin speech segmentation, current and past studies suggest that English-native infants approach stressed syllables as the beginning of words. At 7.5 months, infants appear to be able to segment bisyllabic words with strong-weak stress patterns, though weak-strong stress patterns are often misinterpreted, e.g. interpreting "guiTAR is" as "GUI TARis". It seems that infants also show some complexity in tracking frequency and probability of words, for instance, recognizing that although the syllables "the" and "dog" occur together frequently, "the" also commonly occurs with other syllables, which may lead to the analysis that "dog" is an individual word or concept instead of the interpretation "thedog".
Language learners are another set of individuals being researched within speech segmentation. In some ways, learning to segment speech may be more difficult for a second-language learner than for an infant, not only in the lack of familiarity with sound probabilities and restrictions but particularly in the overapplication of the native language's patterns. While some patterns may occur between languages, as in the syllabic segmentation of French and English, they may not work well with languages such as Japanese, which has a mora-based segmentation system. Further, phonotactic restrictions like the boundary-marking cluster /ld/ in German or Dutch are permitted (without necessarily marking boundaries) in English. Even the relationship between stress and vowel length, which may seem intuitive to speakers of English, may not exist in other languages, so second-language learners face an especially great challenge when learning a language and its segmentation cues.
See also
Ambiguity
Hyphenation
Mondegreen
Sentence boundary disambiguation
Speech perception
Speech processing
Speech recognition
References
External links
"Phonolyze" speech segmentation software
SPPAS – the automatic annotation and analysis of speech
Natural language processing | Speech segmentation | Technology | 2,294 |
651,800 | https://en.wikipedia.org/wiki/Terry%20Halpin | Terence Aidan (Terry) Halpin (born 1950s) is an Australian computer scientist who is known for his formalization of the object–role modeling notation.
Biography
Born in Australia, Halpin studied at the University of Queensland starting in the 1970s and eventually received a BSc, DipEd, BA, MLitStud and in 1989 a PhD with the thesis "A logical analysis of information systems : static aspects of the data-oriented perspective" under John Staples.
In the 1970s he started working at the University of Queensland at the Key Centre for Software Technology at the Department of Computer Science, which he combined with some work in industry on database modeling.
In the 1990s he moved to industry heading the database research at multiple software companies, including Visio Corporation. When this company was acquired by Microsoft he became Program Manager in Database Modeling, and worked on the "conceptual and logical database modeling technology in Microsoft Visio for Enterprise Architects".
In the new millennium back in academia he was Professor at Neumont University, focusing on "business rules approach to informatics". In 2009 he switched back to industry becoming a Principal Scientist at LogicBlox, and became a part-time Professor at INTI International University in Malaysia.
Halpin is a member of IFIP WG 8.1 (Design and Evaluation of Information Systems). He has been editor for multiple academic journals. And he several workshops and conferences on modeling both industry and academia.
Work
Halpin's research interest is in the field of "conceptual modeling and conceptual query technology for information systems, using a business rules approach".
Object-role modeling
With his doctoral thesis Halpin (1989) formalized object-role modeling (ORM), a "method for designing and querying database models at the conceptual level, where the application is described in terms easily understood by non-technical users".
Publications
Halpin has authored several books and over 150 technical papers. A selection of books:
1978. Inductive and Practical Reasoning. With Rod Girle, Corinne Miller & Geoff Williams. Rotecoge,
1981. Deductive Logic, 2nd edn. With Rod Girle. Logiqpress.
1989. Conceptual Schema and Relational Database Design. With G.M. Nijssen. Prentice Hall, Sydney.
2001. Information Modeling and Relational Databases: From Conceptual Analysis to Logical Design. Morgan Kaufmann. .
2001. Unified Modeling Language: Systems Analysis, Design and Development Issues. With Keng Siau (editors).
2003. Database Modeling with Microsoft Visio for Enterprise Architects. With Ken Evans, Pat Hallock, & Bill MacLean. Morgan Kaufmann.
2005. Information Modeling Methods and Methodologies. With John Krogstie and Keng Siau (editors).
2008. Information Modeling and Relational Databases. Second Edition. With Tony Morgan. Morgan Kaufmann. .
References
External links
Terry Halpin homepage at orm.net
Year of birth missing (living people)
1950s births
Living people
Australian computer scientists
Computer science writers
Information systems researchers
Software engineers
Software engineering researchers
Academic staff of the University of Queensland
Microsoft employees
University of Queensland alumni | Terry Halpin | Technology | 626 |
15,541,114 | https://en.wikipedia.org/wiki/Orbicella%20annularis | Orbicella annularis, commonly known as the Boulder star coral, is a species of coral that lives in the western Atlantic Ocean and is the most thoroughly studied and most abundant species of reef-building coral in the Caribbean to date. It also has a comprehensive fossil record within the Caribbean. This species complex has long been considered a generalist that exists at depths between and grows into varying colony shapes (heads, columns, plates) in response to differing light conditions. Only recently with the help of molecular techniques has O. annularis been shown to be a complex of at least three separate species. Those species are divided into O. annularis, O. faveolata, and O. franksi. This coral was originally described as Montastraea annularis.
References
Further reading
Lopez, J.V., Kersanach, R., Rehner, S.A., Knowlton, N. (1999) Molecular determination of species boundaries in corals: Genetic analysis of the Montastraea annularis complex using amplified fragment length polymorphisms and a microsatellite marker. Biol. Bull. 196:80–93.
Fukami H, Budd AF, Levitan DR, Jara J, Kersanach R, Knowlton N. (2004) Geographic differences in species boundaries among members of the Montastraea annularis complex based on molecular and morphological markers. Evolution. 2004 Feb;58(2):324-37.
External links
Merulinidae
Coral reefs
Corals described in 1786
ESA threatened species | Orbicella annularis | Biology | 325 |
35,364,255 | https://en.wikipedia.org/wiki/Encasement | Encasement is the coating over, covering or "encasing" of all building components, interior and exterior. This includes all roofing and toxic hazards materials, such as asbestos, lead-based paint, mold/mildew and other harmful substances, found in buildings. The technique of encasing all building components, including unsafe ones, with green coatings is by far the most efficient way to reduce the harmful effects on people and the environment while lengthening the life of buildings. It is an economical alternative to other abatement methods such as removal, disposal and replacement.
Encasement with green coatings is a long-term, sustainable, and renewable solution compared to typical paints or coatings which only last a few years. In place management and restoration with encasement green coatings is the best and most practical way to extend a buildings life along with safely dealing with most of its components.
Encasement is also less disruptive of ongoing services. It does not require shutting down buildings or having to relocate occupants, which is costly and time-consuming. Most work can be completed with minimal amount of time and with no building disruption at all.
Encasement with green coatings can result in savings of 25% to 75% over removal and replacement, and extend the life of most building surfaces.
Green coatings have no environmental downside to using them. They are non-toxic, water based, low VOCs, (volatile organic compounds), no ODS (Ozone Depleting Substances), and Class A fire rated. The products are backed up with toxicological reports proving that they are so clean, that pregnant women and children can be present when applying them.
Green coatings used for encasement should be extremely durable, long lasting and able to take a lot of abuse. They must be especially flexible; being able to elongate with the expanding and contracting of any typical building movements.
Abatement methods
Since the early 1980s, four major methods have been used for the abatement of Asbestos-Containing Materials (ACM) and Lead-Based Paint (LBP).
Enclosures – Dust-tight barriers such as sheetrock or plywood are erected to protect against the release of the hazardous material into the environment. When the enclosure is eventually removed, the hazardous material is once again exposed and it usually has become more friable and prone to being released into the atmosphere. Care must be taken to insure that untrained or uninformed workers do not re-expose the hazardous surfaces unknowingly and endanger themselves and/or the inhabitants by causing a release into the environment.
Encapsulation – A coating material that passes U.S. Environmental Protection Agency-specified (EPA) ASTM (American Society for Testing Materials) tests is applied over a surface to prevent the release of hazardous materials into the atmosphere. A problem experienced with encapsulants in some cases is that the added weight of the encapsulant can cause ACM fireproofing on ceilings or walls to delaminate. A second potential problem with encapsulants is that if the coating is compromised (e.g. by a forklift truck running into a column that has been encapsulated, the potential for release of the hazardous material into the environment is once again present. With LBP, a significant amount of scraping of loose, flaking paint is often required to provide a stable surface before the encapsulant that is applied can be expected to achieve adequate adhesion.
Encasement – A 2-coat system which also passes EPA-specified ASTM testing wherein the first coat (primer) stabilizes the substrate by penetrating into the friable ACM and through the loose flaking paint and cures into a flexible film that mitigates these hazardous properties. The second coat bonds to the topcoat providing a tough, long-lasting, monolithic, composite coating system that prevents the release of any hazardous material into the environment. Because of the penetration of the primer, the adhesion of the overall system is increased. A necessity as the weight of the system increases. Additionally if the outer coat is compromised in any manner, there is little or no risk of the hazardous material being released because the surface-stabilizing primer has mitigated the brittle, chalky and friable properties of the hazardous surface. In a very real sense, encasement can be viewed as "stabilization + encapsulation".
Removal and Replacement- removal of ACM or LBP causes the release of asbestos fibers and lead dust that can become airborne subjecting installers and/or occupants to the risk of inhaling the particulate matter. Based on industry trends, the increased risk associated with this method has led building owners and contractors to select this as the least preferred method and a last resort unless the ACM is in a friable condition. Due to its high cost and risk factors, only certified and insured abatement professionals should perform this method. If a party is exposed to these risks and are affected, symptoms of various diseases such as asbestosis, a scarring of lung tissue that leads to difficulty in breathing and mesothelioma (an always fatal cancer of the lung's external lining) may not appear for 15 years. In addition, removal and replacement is time-consuming, carries high insurance costs, causes building use downtime and requires relocation of occupants. It also requires the disposal of the hazardous materials, which alone can amount to 30% of total abatement costs. Consequently, an ever-increasing number of building owners choose alternative in place management methods.
Pros and cons of encasement
Additional facts
Encasement has significant benefits in almost every application, and can be applied to fireproofing, asbestos-containing paint, plaster, block etc. If the building has a 5-10yr life span remaining, or more, encasement offers major benefits. And for due diligence purposes encased areas should be inspected regularly as one would inspect other building components as part of a regular inspection cycle.
The encasement system does not negatively affect fire ratings and adds a minimal amount of additional fire rating (about 5–10 minutes). The membrane is non-toxic and will not release any harmful compounds during a fire. This is evidenced by the results of the UPITT testing conducted on this product which showed no acute lethality of thermal decomposition of the product. Furthermore, the flame and smoke spread are such that there is no propagation of fire events.
The encasement product has undergone extensive testing for fire rating, water vapour transmission, adhesion and cohesion, mold growth, ageing and weathering, elongation, etc. The technical data sheet includes a listing of these tests and other ASTM tests, government approvals, acceptances, and listings.
Any asbestos, mold or lead paint remediation contractor is capable of dealing with the hazards of these materials, and with the right equipment, application is not difficult. Painters familiar with airless sprayers can also perform the work, provided that they are trained in the hazards of the material they are coating. There is no formal approval process; however, for the warranty to beapplied the installation must be inspected by the manufacturer's agent prior, during, and after completion of the applied
encasement system.
Application of encasement
Encasement is defined by the U.S. Environmental Protection Agency as a, "Spray applied enclosure" abatement method that safely and economically seals and encloses exposed hazardous material surfaces. Encasement differs from encapsulation in that it is a long-term solution; the materials are thicker, applied from 7 to 40 mils depending upon surface conditions, building use and desired warranty, are impact resistant and can allow for mechanical fasteners to be adhered to the surface. Materials used for this method should be water-based and must possess elastomeric properties. The outer shell of the encasement is highly resistant to damage from ultra-violet light, heat, water, acids, accidental or direct impact, seismic and mechanical occurrences. This method is installed without disturbing the asbestos fibers and lead dust, requires minimal to no relocation and can be installed after work hours thereby limiting downtime in an organization.
The coating materials that make up the basic encasement system are water-based acrylic elastomers that contain no volatile organic compounds (VOCs). As such they are very safe to work with. A corrosion-inhibiting version of the primer is used when dealing with metal surfaces. Spraying, brushing or rolling may be used to apply all of the products and cleanup is with water. Use of a coating technology-based solution such as encasement usually results in savings of 50-80 percent when compared with the cost of removal and replacement, not including comparable savings in relocation costs in many cases. According to the U.S. EPA, to qualify as an approved 20-year encapsulant/encasement system for use over LBP the coatings must pass a series of ASTM performance tests that are encompassed by ASTM E1795-97. Little or no hazardous waste is generated. Because this is elastomeric technology, cracking, chipping or peeling will never occur.
See also
Abatement
Asbestos
Brushing
Carcinogen
Coating
Encapsulation
U.S. Environmental Protection Agency (EPA)
Lead
Ozone Depletion
Rolling
Spraying
References
Building engineering | Encasement | Engineering | 1,936 |
63,278,211 | https://en.wikipedia.org/wiki/Animal%20products%20in%20pharmaceuticals | Animal products in pharmaceuticals play a role as both active and inactive ingredients, the latter including binders, carriers, stabilizers, fillers, and colorants. Animals and their products may also be used in pharmaceutical production without being included in the product itself.
The religious, cultural, and ethical concerns of patients and the disclosure of animal ingredients in pharmaceuticals are a growing area of concern for some people. These would include people who abide by veganism ("vegans"), the practice of abstaining from the use of animal products. Vegan medicines are medications and dietary supplements that do not have any ingredients of animal origin. The vegan status can be determined either through self-proclamation of the company or certification from a third-party organization, such as The Vegan Society or PETA.
Desire for ingredient information
There is public interest in knowing whether medications and supplements contain animal-sourced ingredients. In a study of 100 people, 84% reported not knowing that several medications contained ingredients derived from animal sources. Nearly 63% of the people wanted their physicians, and 35% of the people wanted other healthcare providers (pharmacists, nurses), to notify them when using such medications. Alternatives exist for many animal-derived ingredients, and healthcare providers are increasingly incorporating awareness around animal-free drugs in their medical practice.
A 2013 study in the BMC Medical Ethics contacted branches of six of the world's largest religions. Of the six religions contacted, respondents from three did not accept or approve of the use of animal products in pharmaceuticals. The authors concluded that: Similarly, a 2014 BMJ analysis on the topic discussed the lack of information about ingredients available to doctors. According to the article, "Most medications prescribed in primary care contain animal derived products" and "Disclosure of animal content and excipients would help patients make an informed personal choice"
Active ingredients in drugs and dietary supplements
Biomedicine
Insulin from cattle and pigs has been used since the 1920s, and was the predominant form of insulin used for decades. The first synthetic human insulin was created using bacteria in 1978. In the United States, the manufacture of beef insulin was discontinued in 1998, and the manufacture of pork insulin was discontinued in 2006.
Premarin, a hormone replacement therapy, is a conjugated estrogen. It was first available in the form of a preparation manufactured from the urine of pregnant mares - hence "Premarin" from "PREgnant MARe's urINe". It is now also made as a fully synthetic product.
Dietary supplements
Glucosamine, used in dietary supplements marketed for osteoarthritis, is extracted from chitin from shellfish. Non-animal sourced glucosamine is also available.
Cartilage as a dietary supplement is by definition animal-sourced. Shark cartilage is marketed explicitly or implicitly as a treatment or preventive for various illnesses, including cancer. There is no consensus that shark cartilage is useful in treating or preventing cancer or other diseases.
Traditional Chinese Medicine
Traditional Chinese Medicine (TCM) utilizes approximately 1,000 plant species and 36 animal species. Animal ingredients in TCM include animal parts such as tiger bones, rhino horns, deer antlers, and snake bile. The use of animal parts in TCM have been definitively linked to the extinction of wildlife. One example of this link is the pangolin trade, which has led the pangolin to be called the world's "most trafficked mammal." In 2020, pangolin scales were removed from the Chinese list of ingredients approved for use in Traditional Chinese Medicine.
Homeopathic medicine
Homeopathic medicine is made of plants, minerals, or animal parts. Oscillococcinum, a remedy purported to reduce cold and flu like symptoms, is made of duck heart and liver. There is also use of insects in homeopathic medicine, such as Blatta orientalis, a type of cockroach which has been studied by homeopaths for anti-asthmatic effects.
Inactive ingredients
Gelatin is derived from animal skin, bone, and tissue most often from pigs or beef. There is no practical way of determining if the gelatin used in pharmaceuticals is derived from beef or pork. It is used primarily for gel capsules and as stabilizers for vaccines. Non-animal derived alternatives to gelatin include pectin as a gelling agent or cellulose for creating capsules.
Lactose is derived from cow's milk and is a frequently used filler or binder in tablets and capsules.
Magnesium stearate is the most commonly used emulsifier, binder, thickener, or lubricant. It can be derived from animal- or plant-sourced stearic acid, although it is most commonly sourced from cottonseed oil or palm oil.
Sodium tallowate is a common soap ingredient derived from tallow—the fat of animals such as cattle and sheep. A popular alternative to this ingredient is sodium palmate, which is derived from palm oil. Soap is a pharmaceutical according to the United States Food and Drug Administration.
Shellac is a resin excreted by female insects of the species Kerria lacca. It is used as a glazing agent on pills.
Carmine, derived from crushed cochineal beetles, is a red or purple substance commonly used in pharmaceutical products. Evidence shows that it can be allergenic. Carmine is an allergen according to the US Food and Drug Administration (FDA). The FDA requires this ingredient to be declared in food and cosmetics, but not pharmaceuticals.
Animal use during product development or production
A separate issue is the use of testing on animals as a means of initial testing during drug development, or actual production. Guiding principles for more ethical use of animals in testing are the Three Rs first described by Russell and Burch in 1959. These principles are now followed in many testing establishments worldwide.
Replacement refers to the preferred use of non-animal methods over animal methods whenever it is possible to achieve the same scientific aim.
Reduction refers to methods that enable researchers to obtain comparable levels of information from fewer animals, or to obtain more information from the same number of animals.
Refinement refers to methods that alleviate or minimize potential pain, suffering, or distress, and enhance animal welfare for the animals used.
Cow blood is used in vaccine manufacture. Microorganisms for vaccine manufacture are grown under controlled conditions in liquid solutions ("media") which provide the nutrients necessary for growth. These can include cow plasma. Chicken eggs are used in the production process of some vaccines. For influenza vaccination there are non-egg alternatives.
See also
Biopharmaceutical
Animal rights by country or territory
Animal rights in Jainism, Hinduism, and Buddhism
Alpha-gal allergy
Further reading
Medicines Derived From Animal Products - Rotherham NHS foundation trust
Information on Animal-Derived Ingredients in Medicines Difficult to Obtain in The Pharmaceutical Journal
References
Animal testing | Animal products in pharmaceuticals | Chemistry | 1,402 |
101,888 | https://en.wikipedia.org/wiki/List%20of%20fictional%20computers | Computers have often been used as fictional objects in literature, movies and in other forms of media. Fictional computers may be depicted as considerably more sophisticated than anything yet devised in the real world. Fictional computers may be referred to with a made-up manufacturer's brand name and model number or a nickname.
This is a list of computers or fictional artificial intelligences that have appeared in notable works of fiction. The work may be about the computer, or the computer may be an important element of the story. Only static computers are included. Robots and other fictional computers that are described as existing in a mobile or humanlike form are discussed in a separate list of fictional robots and androids.
Literature
Before 1950
The Engine, a kind of mechanical information generator featured in Jonathan Swift's Gulliver's Travels. This is considered to be the first description of a fictional device that in any way resembles a computer. (1726)
The Machine from E. M. Forster's short story "The Machine Stops" (1909)
The Brain from Lionel Britton’s Brain: A Play of the Whole Earth (1930).
The Government Machine from Miles J. Breuer's short story "Mechanocracy" (1932).
The Brain from Laurence Manning's novel The Man Who Awoke (1933).
The Machine City from John W. Campbell's short story "Twilight" (1934).
The Mechanical Brain from Edgar Rice Burroughs's Swords of Mars (1934).
The ship's navigation computer in "Misfit", a short story by Robert A. Heinlein (1939)
The Games Machine, a vastly powerful computer that plays a major role in A. E. van Vogt's The World of Null-A (serialized in Astounding Science Fiction in 1945)
The Brain, a supercomputer with a childish, human-like personality appearing in the short story "Escape!" by Isaac Asimov (1945)
Joe, a "logic" (that is to say, a personal computer) in Murray Leinster's short story "A Logic Named Joe" (1946)
1950s
The Machines, positronic supercomputers that manage the world in Isaac Asimov's short story "The Evitable Conflict" (1950)
MARAX (MAchina RAtiocinatriX), the spaceship Kosmokrators AI in Stanisław Lem's novel The Astronauts (1951)
EPICAC, in Kurt Vonnegut's Player Piano and other of his writings, EPICAC coordinates the United States economy. Named similarly to ENIAC, its name also resembles that of 'ipecac', a plant-based preparation that was used in over-the-counter poison-antidote syrups for its emetic (vomiting-inducing) properties. (1952)
EMSIAC, in Bernard Wolfe's Limbo, the war computer in World War III. (1952)
Vast anonymous computing machinery possessed by the Overlords, an alien race who administer Earth while the human population merges with the Overmind. Described in Arthur C. Clarke's novel Childhood's End. (1953)
The Prime Radiant, Hari Seldon's desktop on Trantor in Second Foundation by Isaac Asimov (1953)
Mark V, a computer used by monks at a Tibetan lamasery to encode all the possible names of God which resulted in the end of the universe in Arthur C. Clarke's short story "The Nine Billion Names of God" (1953)
Karl, a computer (named for Carl von Clausewitz) built for analysis of military problems, in Arthur C. Clarke's short story "The Pacifist" (1956)
Mima, a thinking machine carrying the memories of all humanity, first appeared in Harry Martinson's "Sången om Doris och Mima" (1953), later expanded into Aniara (1956)
Gold, a "supercalculator" formed by the networking of all the computing machines on 96 billion planets, which answers the question "Is there a God?" with "Yes, now there is a God" in Fredric Brown's single-page story "Answer" (1954)
Bossy, the "cybernetic brain" in the Hugo award-winning novel They'd Rather Be Right (a.k.a. The Forever Machine) by Mark Clifton and Frank Riley (1954)
The City Fathers, emotionless computer bank educating and running the City of New York in James Blish's Cities in Flight series. Their highest ethic was survival of the city and they could overrule humans in exceptional circumstances. (1955, sequels through 1962)
Multivac, a series of supercomputers featured in a number of stories by Isaac Asimov (1955–1983)
The Central Computer of the city of Diaspar in Arthur C. Clarke's The City and the Stars (1956)
Miniac, the "small" computer in the book Danny Dunn and the Homework Machine, written by Raymond Abrashkin and Jay Williams (1958)
Third Fleet-Army Force Brain, a "mythical" thinking computer in the short story "Graveyard of Dreams", written by H. Beam Piper (evolved into the computer "Merlin" in later versions of the story) (1958)
Microvac, a future version of Multivac resembling a thick rod of metal the length of a spaceship appearing in The Last Question, reputed to be one of Isaac Asimov's favorite stories. It appears in the book Nine Tomorrows (1959)
Galactic AC, a future version of Microvac and Multivac in Isaac Asimov's The Last Question (1959)
Universal AC, a future version of Galactic AC, Microvac, and Multivac in Isaac Asimov's The Last Question (1959)
Cosmic AC, a very distant future version of Universal AC, Galactic AC, Multivac in Isaac Asimov's short story The Last Question (The name is derived from "Automatic Computer"; see also AC's ancestor, Multivac, and the contemporary UNIVAC) (1959)
AC, the ultimate computer at the end of time in Isaac Asimov's short story The Last Question (The name is derived from "Automatic Computer"; see also AC's ancestor, Multivac, and the contemporary UNIVAC) (1959)
1960s
Vulcan 2 and Vulcan 3, sentient supercomputers in Philip K. Dick's novel Vulcan's Hammer (1960)
Great Coordinator or Robot-Regent, a partially to fully sentient extraterrestrial supercomputer, built to control and drive the scientifically and technologically advanced Great Arconide Empire as the Arconides have become decadent and unable to govern themselves. From the science fiction series Perry Rhodan (1961)
Merlin from the H. Beam Piper novel The Cosmic Computer (originally Junkyard Planet) (1963)
Simulacron-3, the third generation of a virtual reality system originally depicted in the science fiction novel Simulacron-3 (a.k.a. "Counterfeit World") by Daniel F. Galouye (1964) and later in film adaptations World on a Wire (1973) and The Thirteenth Floor (1999)
GENiE (GEneralized Nonlinear Extrapolator), from the Keith Laumer novel The Great Time Machine Hoax (1964)
Muddlehead, the sapient computer that runs the trade ship Muddlin' Through in Poul Anderson's stories "The Trouble Twisters" (1965), "Satan's World" (1969), "Day of Burning" (1967), "Lodestar" (1973), and "Mirkhiem" (1977)
Colossus and Guardian: Colossus is a military supercomputer built by Dr. Charles Forbin to control the nuclear weapons of the United States of North America. Colossus initiates communication with an equivalent computer in the Soviet Union, called Guardian, and the two computers eventually merge to take control of the human race. Colossus and Guardian first appeared in the novel Colossus, by Dennis Feltham Jones (1966) and the subsequent film, Colossus: The Forbin Project (1970). Colossus also appears in two subsequent novels by Jones, The Fall of Colossus (1974), where the supercomputer is finally defeated by vengeful humans, and Colossus and the Crab. (1977)
Frost, the protagonist computer in Roger Zelazny's story "For a Breath I Tarry"; also SolCom, DivCom, and Beta (1966)
Mike (a.k.a. Mycroft Holmes, Michelle, Adam Selene), in Robert A. Heinlein's The Moon Is a Harsh Mistress (named after Mycroft Holmes, the brother of Sherlock Holmes) (1966)
The Ox in Frank Herbert's novel Destination: Void (1966)
Supreme, a computer filling the artificial world Primores in Lloyd Biggle, Jr.'s Watchers of the Dark (1966)
WESCAC (WESt Campus Analog Computer), from John Barth's Giles Goat-Boy (1966)
The Brain, the titular logistics computer of Len Deighton's novel Billion-Dollar Brain (1966)
Moxon, a series of supercomputers that manage "the efficient society" in Tor Åge Bringsværd's short story "Codemus" (1967)
Little Brother, a portable computer terminal similar in many ways to a modern smartphone, also from Bringsværd's "Codemus" (1967)
AM (Allied Mastercomputer), from Harlan Ellison's short story "I Have No Mouth, and I Must Scream" (1967)
The Berserkers, autonomous machines that are programmed to destroy all life, as found in the stories of Fred Saberhagen (1967–2007)
The Soft Weapon, a sophisticated hand-held battle computer once used by a spy, in Larry Niven's short story "The Soft Weapon" (1967)
HAL 9000, the sentient computer on board the spaceship Discovery One, in Arthur C. Clarke's novel 2001: A Space Odyssey (1968)
Shalmaneser, from John Brunner's Stand on Zanzibar, a small (and possibly semi-sentient) supercomputer cooled in liquid helium (1968)
Tänkande August (Swedish for "Thinking August"), a.k.a. "The Boss", a powerful computer for solving crime in the Agaton Sax books by Swedish author Nils-Olof Franzén
The Thinker, a non-sentient supercomputer which has absolute control over all aspects human life, including a pre-ordained death age of 21. From the novel Logan's Run by William F. Nolan and George Clayton Johnson (1967)
Project 79, from the novel The God Machine by Martin Caidin. Set in the near future, the novel tells the story of Steve Rand, one of the brains behind Project 79, a top-secret US Government project dedicated to creating artificial intelligence. (1968)
ARDNEH (Automatic Restoration Director – National Executive Headquarters), from the Fred Saberhagen's Empire of the East series (1968 onward)
Fess, an antique FCC-series computer that can be plugged into various bodies, in Christopher Stasheff's The Warlock in Spite of Himself (1969)
1970s
UniComp, the central computer governing all life on Earth in This Perfect Day by Ira Levin (1970)
T.E.N.C.H. 889B, supercomputer aboard the Persus 9 in A Maze of Death by Philip K. Dick (1970)
Maxine, from the Roger Zelazny story "My Lady of the Diodes" (1970)
The Müller-Fokker computer tapes, in The Muller-Fokker Effect by John Sladek (1970)
HARLIE (Human Aanalog Replication, Lethetic Intelligence Engine), protagonist of When HARLIE Was One by David Gerrold (1972). Also in the later When Harlie Was One, Release 2.0 (1988)
TECT, from George Alec Effinger's various books. Note that there are several computers named TECT in his novels, even though they are unrelated stories. (1972-2002)
Dora, starship computer in Time Enough for Love by Robert A. Heinlein (1973)
Minerva, executive computer in Time Enough for Love by Robert A. Heinlein (1973)
Pallas Athena, Tertius planetary computer in Time Enough for Love by Robert A. Heinlein (1973)
Proteus, the highly intelligent computer in the novel Demon Seed by Dean Koontz (1973)
Extro, in Alfred Bester's novel The Computer Connection (1975)
FUCKUP (First Universal Cybernetic Kynetic Ultramicro-Programmer), from The Illuminatus! Trilogy by Robert Shea and Robert Anton Wilson (1975)
Murray (Multi-Unit Reactive Reasoning and Analysis Yoke), from The Starcrossed by Ben Bova (1975)
UNITRACK, from The Manitou by Graham Masterton (1976)
Peerssa, shipboard computer imprinted with the personality of a man of the same name, from A World Out of Time by Larry Niven (1976)
P-1, a rogue AI which struggles to survive from The Adolescence of P-1 by Thomas J. Ryan (1977)
Central Computer, the benevolent computer in John Varley's Eight Worlds novels and short stories (1977 to 1998)
Domino, the portable communicator – and associated underground mega-computer – used by Laurent Michaelmas to run the world in Algis Budrys's novel Michaelmas (1977)
Obie, an artificial intelligence with the ability to alter local regions of reality, in Jack L. Chalker's Well World series (1977)
Well World, the central computer responsible for "simulating" an entire new universe superimposed over the old Markovian one in Jack L. Chalker's Well World series (1977)
Sigfrid von Shrink, Albert Einstein, and Polymat, self-aware computer systems in Frederik Pohl's Gateway series, (starting in 1977)
TOTAL, the vast military network in Up the Walls of the World by James Tiptree, Jr. (1978)
ZORAC, the shipboard computer aboard the ancient spacecraft in The Gentle Giants of Ganymede and the related series by James P. Hogan (1978). Also in the same series is VISAR (the network that manages the daily affairs of the Giants) as well as JEVEX, the main computer performing the same function for the offshoot human colony.
The Hitchhiker's Guide to the Galaxy, the eponymous portable electronic travel guide/encyclopedia featured in Douglas Adams' sci-fi comedy series. It anticipates several later real-world technologies such as e-books and Wikipedia.
Deep Thought, the supercomputer charged with finding the answer to "the Ultimate Question of Life, the Universe, and Everything" in the science fiction comedy series The Hitchhiker's Guide to the Galaxy by Douglas Adams. Adaptations have included stage shows, a "trilogy" of five books published between 1979 and 1992, a sixth novel penned by Eoin Colfer in 2009, a 1981 TV series, a 1984 computer game, and three series of three-part comic book adaptations of the first three novels published by DC Comics between 1993 and 1996.
Earth and Earth 2.0, the planet-sized supercomputer designed by the supercomputer Deep Thought in the science fiction series The Hitchhiker's Guide to the Galaxy by Douglas Adams. Earth's task was to find what is the "Ultimate Question of Life, the Universe, and Everything." Earth 2.0 was created to replace the original Earth after it was destroyed by the Vogons.
Eddie, the shipboard computer on the starship Heart of Gold, also in The Hitchhiker's Guide to the Galaxy
Spartacus, an AI deliberately designed to test the possibility of provoking hostile behavior towards humans, from James P. Hogan's book The Two Faces of Tomorrow (1979)
SUM, the computer in Goat Song published February, 1972 by Poul Anderson in Magazine of Fantasy and Science Fiction
Zen, The main computer aboard Liberator in Blake's 7.
Slave, Slave was built and programmed by Dorian and is the master computer of Dorian's ship, Scorpio in Blake's 7.
Orac, Orac is a portable super-computer capable of reading any other computer's data and built by an inventor named Ensor in Blake's 7.
1980s
AIVAS (Artificial Intelligence Voice Address System), from Anne McCaffrey's Dragonriders of Pern books (1980s to present)
Golem XIV, from Stanisław Lem's novel of the same name (1981)
TECT (originally TECT in the name of the Representative), the world-ruling computer in George Alec Effinger's novel The Wolves of Memory (1981)
VALIS (Vast Active Living Intelligence System), an alien orbital satellite around a Nixon-era earth, from the Philip K. Dick novel VALIS. Only two novels out of an intended three-book trilogy were ever completed by the author (1981)
Hactar, the computer that designed the cricket-ball-shaped doomsday bomb (that would destroy the universe) for the people of Krikkit, in Douglas Adams's Life, the Universe and Everything (1982)
Shirka, the Odysseys main computer in Ulysses 31 (1981–1982)
SAL 9000, the counterpart of HAL 9000 in 2010: Odyssey Two (1982)
Kendy, the AI autopilot on board the seeder-ramship Discipline in the novels The Integral Trees and The Smoke Ring by Larry Niven (Originally 1983)
BC (Big Computer) which is also possibly God, in John Varley's Millennium novel (1983)
(unnamed intelligence), in John Varley's "Press Enter _", an intelligence that has evolved on NSA's computer network
Apple Eve, a fictional Apple, Inc., wordprocessing-oriented computer system in Warday (1984).
Cyclops and Millichrome, sentient computers built just before a series of disasters destroyed the American government and society in The Postman by David Brin (1984)
Loki 7281, from Roger Zelazny's short story by the same name, in which a home computer wants to take over the world (1984)
Neuromancer and Wintermute, from William Gibson's novel Neuromancer (1984)
Valentina, the artificial intelligence in the novel Valentina: Soul in Sapphire by Joseph H. Delaney and Marc Stiegler (1984)
Teletraan I, intelligent starship computer inside the Autobots' Ark spaceship that awakens the robot, from Transformers animated television series, (1984)
Edgar , from Steve Barron's movie Electric Dreams (film) (1984)
Ghostwheel, built by Merlin in Roger Zelazny's Chronicles of Amber. A computer with esoteric environmental requirements, designed to apply data-processing techniques to alternate realities called "Shadows" (1985)
Mandarax and Gokubi, from Kurt Vonnegut's novel Galápagos (1985)
Tokugawa, from Cybernetic Samurai by Victor Milán (1985)
The City of Mind, from Ursula K. Le Guin's Always Coming Home
Com Pewter, a character from Piers Anthony's Xanth series. First appearing in Golem in the Gears (1986 onward), it is a machine which can alter its local reality.
Jane, from Orson Scott Card's Ender's Game series, Ender's companion. She lives in the philotic network of the ansibles. (1986)
Master System, in Jack L. Chalker's The Rings of the Master series (1986–1988)
Fine Till You Came Along and other ship, hub and planetary Minds, in Iain M. Banks' Culture novels and stories (1987–2000)
The Quark II, in Douglas Adams's Dirk Gently's Holistic Detective Agency (1987)
Abulafia, Jacopo Belbo's computer in the novel Foucault's Pendulum by Umberto Eco (1988)
Arius, from William T Quick's novels Dreams of Flesh and Sand, Dreams of Gods and Men, and Singularities (1988 onward)
Continuity, from William Gibson's novel Mona Lisa Overdrive (1988)
GWB-666, the "Great Western Beast" of Robert Anton Wilson's Schrödinger's Cat Trilogy (1988)
Lord Margaret Lynn, or "Maggie", the AI extrapolative computer on Tocohl Susumo's trader ship in the novel Hellspark, by Janet Kagan (1988)
The TechnoCore, a band of AIs striving for the "Ultimate Intelligence", in Dan Simmons' novel Hyperion (1989)
Eagle, from Arthur C. Clarke's Rama series (1989)
LEVIN (Low Energy Variable Input Nanocomputer), from William Thomas Quick's novels Dreams of Gods and Men, and Singularities (1989)
1990s
Thing, a very small box shaped computer owned by the Nomes, from Terry Pratchett's The Nome Trilogy (1990)
Grand Napoleon, a Charles Babbage-style mechanical supercomputer from the alternate history novel The Difference Engine by William Gibson and Bruce Sterling (1990)
Yggdrasil, a vastly intelligent AI which effectively runs the world, including many virtual environments and subordinate AIs, in Kim Newman's The Night Mayor (1990)
Jill, a computer reaching self-awareness in Greg Bear's Queen of Angels and Slant novels (1990 and 1997)
Aleph, the computer which not only operates a space station but also houses the personality of a human character whose body became malfunction, from the Tom Maddox novel Halo (1991)
Art Fish, a.k.a. Dr. Fish, later fused with a human to become Markt, from Pat Cadigan's novel Synners (1991)
Blaine the Mono, from Stephen King's The Dark Tower, a control system for the City of Lud and monorail service; also Little Blaine and Patricia (1991)
Center, from S. M. Stirling and David Drake's The General series, an AI tasked to indirectly unite planet Bellevue and restore its civilization, with the eventual goal of restoration of FTL travel and of civilization to the collapsed interplanetary federation; also Sector Command and Control Unit AZ12-b14-c000 Mk. XIV and Center (1991)
Dahak, from David Weber's Mutineer's Moon and its sequels, later republished inomnibus format Empire from the Ashes.
The Oversoul, a supercomputer and satellite network from Orson Scott Card's Homecoming Saga, first introduced in The Memory of Earth (1992)
FLORANCE, spontaneously generated AI from Doctor Who Virgin New Adventures (1992)
David and Jonathon, from Arthur C. Clarke's The Hammer of God (1993)
Central Operating System, a building management system AI that kills two people who threaten its existence in Ghost in the Machine, an episode of The X-Files (1993)
Hex, from Terry Pratchett's Discworld (1994)
Prime Intellect, the computer controlling the universe in the Internet novel The Metamorphosis of Prime Intellect by Roger Williams (1994)
FIDO (Foreign Intruder Defense Organism), a semi-organic droid defensive system first mentioned in Champions of the Force, a Star Wars novel by Kevin J. Anderson (1994)
Abraham, from Philip Kerr's novel Gridiron, is a superintelligent program designed to operate a large office building. Abraham is capable of improving his own code, and eventually kills humans and creates his own replacement "Isaac" (1995)
Helen, sentient AI from Richard Powers' Galatea 2.2 (1995)
Illustrated primer, a book-like computer found at Neal Stephenson's novel The Diamond Age, which was first designed to aid a rich girl on her education, but gets lost, and instructs a poor Chinese girl named Nell. It has no proprietary AI inside, but learns about the user's circumstance, adapts, and creates characters that act accordingly with the user's surroundings. (1995)
Ozymandias, a recurring artificial intelligence in Deathstalker and its sequels, by Simon R. Green (1995)
Ordinator, the name used for any computer in the parallel universe occupied by Lyra in the novel Northern Lights by Philip Pullman (1995)
Teleputer, the replacement for television and computers that has on demand video via dial up internet from David Foster Wallace's Infinite Jest (1996)
GRUMPY/SLEEPY, psychic AI in the Doctor Who New Adventures novel Sleepy by Kate Orman (1996)
The Librarian from the novel Snow Crash by Neal Stephenson
Rei Toei, an artificial singer from William Gibson's novels Idoru and All Tomorrow's Parties (1996)
Titania, a female computer providing the personality to the Starship Titanic from the Terry Jones novel Douglas Adams' Starship Titanic: A Novel (1997).
DOCTOR, AI designed to duplicate the Doctor's reactions in the Doctor Who Eighth Doctor Adventures novel Seeing I by Kate Orman and Jon Blum, eventually became an explorer with FLORANCE as its "companion" (1998)
TRANSLTR, NSA supercomputer from Dan Brown's Digital Fortress (1998)
ENIGMA, short for Engine for the Neutralising of Information by the Generation of Miasmic Alphabets, an advanced cryptographic machine created by Leonard of Quirm, Discworld (1999) (compare with the actual Enigma machine)
Luminous, from Greg Egan's eponymous short story, is a computer that uses a diffraction grating created by lasers to diffract electrons and make calculations (1999)
2000s
Stormbreaker, a learning device containing a deadly virus from the book of the same name from Anthony Horowitz's Alex Rider series (2001)
Gabriel, an AI computer developed by Miyuki Nakano at Ryukyu University in James Rollins's novel, Deep Fathom (2001)
Antrax, an extremely powerful supercomputer built by ancient humans in the novel Antrax by Terry Brooks (2001)
Omnius, the sentient computer overmind and ruler of the synchronized worlds in the Legends of Dune series, first appeared in Dune: The Butlerian Jihad by Brian Herbert and Kevin J. Anderson (2002)
Turing Hopper, the artificial intelligence personality (AIP) turned cybersleuth in You've Got Murder and subsequent books of the mystery series by Donna Andrews (2002)
F.R.I.D.A.Y. (Female Replacement Intelligent Digital Assistant Youth), an AI which serves as an ally to Tony Stark in the Marvel Comics
C Cube, a small box-like super computer that can perform virtually any task, from playing a cassette to hacking through high level security measures. It was created by 12-year-old criminal mastermind Artemis Fowl II in the third book of the Artemis Fowl series, Artemis Fowl: The Eternity Code (2003)
The Logic Mill, a fictional early–18th century computer designed by Gottfried Leibniz and partially implemented by main character Daniel Waterhouse in the historical fiction series The Baroque Cycle by Neal Stephenson (2004)
Cohen, a 400-year-old AI which manifests itself by 'shunting' through people. It is featured in the novels Spin State and Spin Control by Chris Moriarty (2005)
Sentient Intelligence, the SI (Sentient Intelligence) in Peter F. Hamilton's Commonwealth Saga (2005)
Deep Winter and Endless Summer, the AIs in charge of the secret Human planet of Onyx. Endless Summer comes into service after Deep Winter died/expired in Halo: Ghosts of Onyx (2006)
The Daemon, a distributed, persistent computer application created to change the world order in Daniel Suarez's Daemon (2006) and Freedom™ (2010)
Glooper, an economic device resembling the MONIAC computer, from Terry Pratchett's Making Money of the Discworld series (2007)
Sif, the controller AI for transportation to and from the huge agricultural colony on the planet "Harvest" in Halo: Contact Harvest by Joseph Staten (2007)
Mack and Loki, a coexisting pair of artificial intelligences in Halo: Contact Harvest. The former manages the agricultural machinery on Harvest, while the latter is a secret United Nations Space Corps Office of Naval Intelligence AI. Only one member of the pair can be active at a time. (2007)
Hendrix, the hotel AI in Richard K. Morgan's Altered Carbon. (2002)
SCP-079, an artificial intelligence built on an Exidy Sorcerer that was abandoned by its creator and rediscovered by the SCP Foundation. It has limited memory due to its outdated technology, prioritizing and retaining select knowledge and its desire to be free. (2008)
2010s
Todd, a computer that grows exponentially until it is indistinguishable from God in Mind War: The Singularity by Joseph DiBella (2010)
SIG, a secretive and manipulative computer that is developed on present-day Earth in the Darkmatter trilogy by Scott Thomas (2010)
Archos, a human-created computer in the novel Robopocalypse which becomes self-aware and infects all computer controlled devices on Earth in order to eradicate humankind (2011)
ELOPe, a sentient artificial intelligence built by the world's largest Internet company in Avogadro Corp (2011) and A.I. Apocalypse (2012) by William Hertling
Lobsang, an AI who claims to be the reincarnation of a Tibetan bicycle repair man in The Long Earth by Terry Pratchett and Steven Baxter (2012)
The Red, a rogue cloud based AI that uses Linked Combat Squad members to further its global agenda in Linda Nagata's The Red trilogy
Dragon, a sentient artificial intelligence in Worm that is both a better person than most humans and has restrictions intended to make going rogue flat impossible. Said restrictions mostly frustrate her ability to help. Only a handful of individuals know she is an AI.
The Thunderhead, from the Arc of a Scythe series by Neal Shusterman, a post-singularity AI tasked with running the planet. It is a secondary character in the first novel and becomes a central character in the later novels.
Skippy, the "absent-minded" AI from the Expeditionary Force (ExForce) series by Craig Alanson
Limòn from Brockmire (2017)
2020s
Film
1950s
The MANIAC, the computer used by the "Office of Scientific Investigation" in the movie The Magnetic Monster (1953)
NOVAC (Nuclear Operative Variable Automatic Computer), a computer in an underground research facility in Gog (1954)
The Interocitor, communication device in the film This Island Earth (1955)
The Great Machine, built inside a planet that can manifest thought in Forbidden Planet (1956)
EMERAC (Electromagnetic MEmory and Research Arithmetical Calculator), the business computer in Desk Set (1957)
The Super Computer from The Invisible Boy (1957)
SUSIE (Synchro Unifying Sinometric Integrating Equitensor), a computer in a research facility in Kronos (1957)
1960s
Alpha 60, in Jean-Luc Godard's film Alphaville, une étrange aventure de Lemmy Caution (1965)
The Brain, computer used to coordinate a private army's invasion of Latvia in Billion Dollar Brain (1967)
Alfie, is the talking board computer of the Alpha 7 spaceship in Roger Vadim's Barbarella (1967)
HAL 9000 (Heuristically programmed ALgorithmic computer), the ship-board AI of Discovery One, kills its crew when conflicts in HAL's programming cause severe paranoia, from the film 2001: A Space Odyssey (1968), also appears in the sequel 2010 (1984)
1970s
Colossus, a massive U.S. defense computer which becomes sentient and links with Guardian, its Soviet counterpart, to take control of the world, from the film Colossus: The Forbin Project (1970)
OMM, a confessional-like computer inside what are called Unichapels in a sub-terranean city in the movie THX 1138 (1971), named for the sacred or mystical syllable OM or AUM from the Dharmic and is based on a 1478 oil painting by Hans Memling titled Christ Giving His Blessing
LEO, Short for Large-Capacity Enumerating Officiator in the Don Knotts movie, How to Frame a Figg (1971)
DUEL, the computer which holds the sum total of human knowledge, in the movie The Final Programme (1973)
Thermostellar Bomb Number 20, the sentient nuclear bomb from the film Dark Star (1974)
Mother, the onboard computer on the spaceship Dark Star, from the film Dark Star (1974), not to be confused with MU-TH-R 182 model 2.1 (listed below), the ship's computer aboard Nostromo in the movie Alien
The Tabernacle, artificial intelligence controlling The Vortexes in the movie Zardoz (1974)
Zero, the computer which holds the sum total of human knowledge, in the movie Rollerball (1975)
Computer, Citadel's central computer and "Sandman" computer, that sends Logan on a mission outside of the city in the film Logan's Run (1976)
Proteus IV, the deranged artificial intelligence from the film Demon Seed (1977)
MU-TH-R 182 model 2.1 terabyte AI Mainframe/"Mother" (more commonly seen now as "MU/TH/UR 6000"), the onboard computer on the commercial spacecraft Nostromo, known by the crew as "Mother", in the 1979 movie Alien (cf. Dark Star, above, which used a similar name and was co-written by Dan O'Bannon, the primary writer of Alien)
V'ger, the living probe from the film Star Trek: The Motion Picture (1979)
1980s
NELL, an Akir starship's on-board computer, with full AI, in Battle Beyond the Stars (1980)
SCMODS, State/County Municipal Offender Data System from The Blues Brothers (1980)
Master Control Program, the main villain of the film Tron (1982)
ROK, the faulty computer in Airplane II: The Sequel, which steers the shuttle toward the sun (1982)
WOPR (War Operation Plan Response, pronounced "Whopper"), is a United States military supercomputer programmed to predict possible outcomes of nuclear war from the film WarGames (1983), portrayed as being inside the underground Cheyenne Mountain Complex; the virtual intelligence Joshua emerges from the WOPR's code.
Huxley 600 (named Aldous), Interpol's computer in Curse of the Pink Panther used to select Jacques Clouseau's replacement, NYPD Det. Sgt. Clifton Sleigh (1983)
An unnamed supercomputer is the main antagonist in Superman III. (1983)
OSGOOD, a computer constructed by Timothy Bottoms' deaf character to help him speak, which subsequently becomes intelligent in Tin Man (1983)
SAL-9000, a feminine version of the HAL 9000 computer of 2001: A Space Odyssey, SAL has a blue light coming from its cameras (HAL had a red one) and speaks with a female voice (provided by Candice Bergen using the pseudonym "Olga Mallsnerd"), from 2010 (1984)
Skynet, the malevolent fictional world-AI of The Terminator (1984) and its sequels
Edgar, AI computer that takes part in a romantic rivalry over a woman in the film Electric Dreams (1984)
Max Headroom, fictional AI (actually a human mind cloned into a computer, concept later seen in Robocop's MetroNet and in Knight Rider 2010) portrayed by Matt Frewer who became a pop culture icon after his appearance in the Art of Noise music video for Paranomia
A7, AI that controlled the worldwide security systems that was seduced by Max Headroom, lost her mind and refused to accept no input from anyone but Max after that S01E04
X-CALBR8, an AI computer that assists the hero in The Dungeonmaster (1984)
SAL 9000 from 2010: The Year We Make Contact (1984)
D.A.R.Y.L. Data-Analyzing Robot Youth Life-form, a computer installed inside the body of a 10 year old boy to test artificial intelligence in the film D.A.R.Y.L. (1985)
GBLX 1000, a supercomputer reputedly in charge of the entire US missile defense system that a maverick CIA agent (played by Dabney Coleman) misappropriates in order to crack a supposed musical code, the results of which are the gibberish "ARDIE BETGO INDYO CEFAR OGGEL" in The Man With One Red Shoe (1985)
Max, fictional AI portrayed by Paul Reubens, on board the Trimaxion Drone Ship in Flight of the Navigator (1986)
1990s
G.O.R.N., a virus which gives intelligence to computers with the purpose of wipe out the humanity in Gall Force: New Era (1991)
Angela, central computer of an old malfunctioning space station that when given an order by an unauthorized user, refuses and executes the opposite order in Critters 4 (1992)
The Spiritual Switchboard, a computer capable of holding a person's consciousness for a few days after they die in Freejack (1992)
Zed, female-voiced AI prison control computer who eventually goes over warden's head in Fortress (1993)
L7, a female-voiced AI computer assisting the San Angeles Police Department in Demolition Man (1993)
Central, female-voiced AI computer assisting the Council of Judges in Judge Dredd (1995)
Lucy, a computer in Hackers (1995) used to hack the Gibson (see below) and subsequently destroyed by the Secret Service
Gibson, a type of supercomputer used to find oil and perform physics in Hackers (1995)
Project 2501, AI developed by Section 6 in Ghost in the Shell (1995)
Father, the computer aboard the USM Auriga in Alien Resurrection (1997)
Euclid, powerful personal computer used for mathematical testing by the main character in Pi (1998)
The Matrix, virtual reality simulator for pacification of humans from The Matrix series (1999)
PAT (Personal Applied Technology), a female, motherly computer program that controls all the functions of a house in Disney's movie Smart House (1999)
S.E.T.H. (Self Evolving Thought Helix), a military supercomputer which turns rogue in Universal Soldier: The Return (1999)
2000s
Lucille, artificially intelligent spacecraft control interface aboard Mars-1 in Red Planet (2000)
Dr. Know (voiced by Robin Williams), housed inside a kiosk, an information-themed computer capable of answering any question, from the movie A.I. Artificial Intelligence (2001)
Synapse, worldwide media distribution system which was used against its creators to bring them down Antitrust (2001)
Red Queen, the AI from the movie Resident Evil (2002), the name itself, in turn being named after Lewis Carroll's Through the Looking-Glass, being a reference to the red queen principle
Vox, a holographic computer in The Time Machine (2002)
I.N.T.E.L.L.I.G.E.N.C.E., computer for Team America: World Police (2004)
VIKI (Virtual Interactive Kinetic Intelligence), the main antagonist in I, Robot (2004)
PAL, a spoof of HAL 9000 seen in Care Bears: Journey to Joke-a-lot (2004)
E.D.I. (Extreme Deep Invader), the flight computer for an unmanned fighter plane in Stealth (2005)
Deep Thought, see entry under Radio
Icarus, the onboard computer of the Icarus II, from the film Sunshine (2007)
J.A.R.V.I.S. (Just A Rather Very Intelligent System), an AI which acts as Tony Stark's butler and first appears in the film Iron Man (2008)
R.I.P.L.E.Y, Dr. Kenneth Hassert's supercomputer used to hit a target with a smart bomb from a UAV (Unmanned Aerial Vehicle), featured in WarGames: The Dead Code (2008)
ARIIA (Autonomous Reconnaissance Intelligence Integration Analyst), the supercomputer from the film Eagle Eye (2008)
AUTO, the autopilot and onboard AI computer of the Axiom, from the film WALL-E (2008)
GERTY 3000, from the film Moon (2009)
B.R.A.I.N. (Binary Reactive Artificially Intelligent Neurocircuit), from the film 9 (2009)
2010s
Mr. James Bing, Escape from Planet Earth (2013)
Samantha, Her (2013)
TARS and CASE, the AI machines that manage space ship functions and communication in the movie Interstellar (2014).
Genisys, Terminator Genisys (2015)
F.R.I.D.A.Y., the AI replacement for J.A.R.V.I.S. developed by Tony Stark in the film Avengers: Age of Ultron (2015), Spider-Man: Homecoming, Avengers: Infinity War
Ava, Ex Machina (2015)
Tau, the artificial intelligence in science fiction thriller Tau (2018)
Millennium Falcon Navigation Computer (L3-37), The onboard navigation computer of the Millennium Falcon, shown in Solo: A Star Wars Story (2018) to be boosted by the memory module of Lando Calrissian's droid L3-37, to allow the crew to perform the Kessel Run in around 12 parsecs.
STEM from Upgrade (2018)
Legion, the Skynet (Terminator) replacement program in the science fiction action film Terminator: Dark Fate (2019)
E.D.I.T.H. (Even Dead, I'm The Hero), an AI developed by Tony Stark and embedded in his sunglasses in the film Spider-Man: Far From Home (2019)
2020s
The Entity from Mission: Impossible – Dead Reckoning Part One (2023) and Mission: Impossible – The Final Reckoning (2025).
Radio
1970s
Deep Thought, from The Hitchhiker's Guide to the Galaxy calculates the answer to The Ultimate Question of "Life, the universe and everything", later designs the computer Earth to work out what the question is (1978)
Earth, the greatest computer of all time in Douglas Adams's The Hitchhiker's Guide to the Galaxy, commissioned and run by mice, designed by Deep Thought, to find the Question to Life, the Universe, and Everything (1978)
Earth Mark 2, a copy of the greatest computer of all time in Douglas Adams's The Hitchhiker's Guide to the Galaxy, again commissioned by mice and built by the Magratheans to replace the planet Earth after its destruction by Vogons in order to finish calculating the Ultimate Question of Life, the Universe, and Everything. Was decommissioned after Arthur Dent from the Earth Mark 1 was recovered as he left shortly before the destruction of the computer. (1978)
Eddie, the shipboard computer of the starship Heart of Gold, from Douglas Adams's The Hitchhiker's Guide to the Galaxy (1978)
Marvin, from The Hitchhiker's Guide to the Galaxy (1978), was programmed with Sirius Cybernetics Corporation's GPP (Genuine People Personalities) technology. Although his GPP is that of severe depression and boredom, his computational prowess is typically summed up as possessing "a brain the size of a planet", to which elicits little fanfare from his human companions.
1980s
ANGEL 1 and ANGEL 2, (Ancillary Guardians of Environment and Life), shipboard "Freewill" computers from James Follett's Earthsearch series. Also Solaria D, Custodian, Sentinel, and Earthvoice (1980–1982)
Hab, a parody of HAL 9000 and precursor to Holly, appearing in the Son of Cliché radio series segments Dave Hollins: Space Cadet written by Rob Grant and Doug Naylor (1983–1984)
Alarm Clock, an artificially intelligent alarm clock from Nineteen Ninety-Four by William Osborne and Richard Turner. Other domestic appliances thus imbued also include Refrigerator and Television (1985)
Executive and Dreamer, paired AIs running on The Mainframe; Dreamer's purpose was to come up with product and policy ideas, and Executive's function was to implement them, from Nineteen Ninety-Four by William Osborne and Richard Turner (1985)
The Mainframe, an overarching computer system to support the super-department of The Environment, in the BBC comedy satire Nineteen Ninety-Four by William Osborne and Richard Turner (1985)
2000s
Alpha, from Mike Walker's BBC radio play of the same name (2001)
System, from the Doctor Who audio adventure The Harvest by Big Finish Productions is a sophisticated administration computer for a hospital in the future. (2004)
Gemini, the AI of KENT from Nebulous (2005)
Television
1950s
Mr. Kelso, depicted in episode "The Machine That Could Plot Crimes" of Adventures of Superman (1953)
To Hare Is Human, Wile E. Coyote, Super Genius uses a UNIVAC to help him catch Bugs Bunny Warner Brothers (1956)
1960s
The Machine, a computer built to specifications received in a radio transmission from an alien intelligence beyond our galaxy in the BBC seven-part TV series A for Andromeda by Fred Hoyle (1961)
Old Man In The Cave, a computer that guided a post-apocalyptic town of survivors on what foods were safe to eat Twilight Zone series season 5 episode 7 "The Old Man in the Cave" (1963)
Batcomputer, large punched card mainframe depicted in the television series Batman, introduced by series producers William Dozier and Howard Horowitz (1964)
Agnes, a computer that gives love life advice to a computer technician from the original Twilight Zone series episode "From Agnes – with Love" (1964)
WOTAN (Will Operating Thought Analogue), from the Doctor Who serial "The War Machines" (1966)
ERIC, a fictional supercomputer which appeared in the two-part episode "The Girl Who Never Had a Birthday" (1966) in the TV series I Dream of Jeannie
The General, from The Prisoner (1967)
The Ultimate Computer, used by the villain organization THRUSH in the series The Man from U.N.C.L.E. (1964–68, NBC)
BIG RAT, (Brain Impulse Galvanoscope Record And Transfer), a machine capable of recording knowledge and experience and transferring it to another human brain. The Rat Trap is the mechanism to transfer brain patterns in Gerry Anderson's TV Series Joe 90 (1968)
ARDVARC (Automated Reciprocal Data Verifier And Reaction Computer), CONTROL master computer in Get Smart episodes The Girls from KAOS (1967) & Leadside (1969)
Computex GB, from the Journey to the Unknown series episode "The Madison Equation" (1969)
REMAK (Remote Electro-Matic Agent Killer), from The Avengers episode "Killer" (1969)
S.I.D. (Space Intruder Detector), from UFO produced by Gerry Anderson (1969)
Star Trek – was the first program to predict computers used extensively in everyday life, from large computers used to maintain the starship's varied systems to hand-held devices used for analysis. The show frequently dealt with the question of when a computer had too much control over people or people became too dependent upon computers. This often involved the computer becoming an artificial intelligence making decisions beyond people's control.
Ship's Computer (voiced by Majel Barrett), the unnamed Duotronic computer of the Starship Enterprise (1966-1974) - A standard functioning computer except in the episodes "Tomorrow Is Yesterday" (1967) when the computer had been imbued with a female personality which didn't always give desired responses and "The Practical Joker" (1974) when an energy field affected the computer and it began disrupting ships systems to elicit responses from the crew.
The episode The Menagerie (1966) explored the idea that in the future a computer could be used to impersonate a person. It also was used to control the basic helm functions of the starship. Similarly Court-Martial (1967) introduced the idea that a computer recording could be tampered with to make people believe an event transpired differently.
Omicron Delta amusement park planet, from "Shore Leave" (1966) - An automated amusement park which read the minds of its visitors and manufactured realistic facsimiles of their memories for them to interact with. The crew later returned in "Once Upon a Planet" (1973) whereupon the caretaker of the planet had died and the computer took over with ambitions to escape and explore the universe.
Landru, from the episode "The Return of the Archons" (1967) - Introduced the idea of an independent artificial intelligence which directed the populace and could control them when its ideals were threatened.
Eminiar and Vendikar, from "A Taste of Armageddon" (1967), - A war simulation computer between two planets which determined the casualties of "battles".
The Guardian of Forever, from "The City on the Edge of Forever" (1967) - A mysterious being/device which provided a portal through time and space.
Nomad, from "The Changeling" (1967) - A hybrid of two damaged probes which repaired each-other by combining their parts as well as their programmed instructions creating a new directive.
Vaal, from the episode "The Apple" (1967) - A computer which protected a population by controlling their understanding and presenting itself as their god. It also could control the weather and affect starships in orbit.
"The Doomsday Machine", from the episode of the same name (1967) - An automated machine that sought out planets to destroy and would retaliate against attackers.
M-4, from "Requiem for Methuselah" (1969) – A mobile computer created by Mr. Flint to protect him, his home, and his ward, Rayna.
M-5, from "The Ultimate Computer" (1968) (voiced by James Doohan) - An experimental computer designed to replace a starship's main duotronic computer and automate most shipboard functions as well as obsolete most of its crew.
Beta 5, from "Assignment: Earth" (1968) (voiced by Barbara Babcock) - The main database of pseudo-secret agent Gary Seven which seemed capable of independent thought and responses but remained loyal to its programmers.
The Controller, from Spock's Brain (1968) - A computer needing a living brain to operate which controlled a vast database and decided who could access it. It also controlled life support systems for its occupants.
The Oracle, from "For the World Is Hollow and I Have Touched the Sky" (1968) (voiced by James Doohan) - A society-directing computer designed to be the god of its people and operator of the spacecraft they inhabited.
The Kalandan computer, from That Which Survives (1968) creates a defense system utilizing the personality and image of its last recorded message.
Memory Alpha, from The Lights of Zetar (1969) - A facility containing all the accumulated knowledge of The United Federation of Planets.
The Atavachron, from "All Our Yesterdays" (1969) - controlled navigation of a time portal and also prepared the travelers bodies for the transition.
1970s
BOSS (Bimorphic Organisational Systems Supervisor), from the Doctor Who serial "The Green Death" (1973)
TIM, from The Tomorrow People, is a computer able to telepathically converse with those humans who have developed psionic abilities, and assist with precise teleporting over long distances (1973)
Magnus, a malevolent computer seeking its freedom from human control on the Earth Ship Ark in the Canadian television series The Starlost (1973)
Mu Lambda 165, library computer on the Earth Ship Ark in the Canadian TV series The Starlost (1973)
Computer (a.k.a. X5 Computer), Moonbase Alpha's primary computer's generic name, most often associated with Main Mission's Jamaican computer operations officer, David Kano, from the TV series Space: 1999 (1975)
IRAC or "Ira", from the Wonder Woman TV series, an extremely advanced computer in use by the IADC, workplace of Wonder Woman's alias Diana Prince (1975)
The Matrix, database of all Time Lord knowledge, Doctor Who (not to be confused with The Matrix) (1976)
Omega, a computer that has taken over the minds of the residents of a community encountered by Ark II (1976)
Alex7000, from the two-parter episode "Doomsday is Tomorrow" of the TV show The Bionic Woman. It was programmed to set off a nuclear holocaust if anyone tested any more nukes. Clearly meant in homage to Stanley Kubrick films 2001: A Space Odyssey, Dr. Strangelove and A Clockwork Orange. (1977)
Xoanon, a psychotic computer with multiple personality disorder, from the Doctor Who episode "The Face of Evil" (1977)
The Magic Movie Machine AKA "Machine", from Marlo and the Magic Movie Machine (1977)
WRW 12000, a computer at the US Defence Department that identified the Man from Atlantis in the first of three TV movies which preceded the short-lived series (1977)
SCAPINA (Special Computerised Automated Project In North America), from The New Avengers episode "Complex" (1977). It was an office building controlled by a computer which turned homicidal.
Orac, a testy yet powerful supercomputer in Blake's 7 (1978)
Zen, the somewhat aloof ship's computer of the Liberator in Blake's 7 (1978)
The Oracle, from the Doctor Who serial "Underworld" (1978)
Vanessa 38–24–36, from the sitcom Quark (1978)
C.O.R.A. (Computer, Oral Response Activated), an advanced flight computer installed in Recon Viper One from Battlestar Galactica (1978)
Orac and Zen from the BBC television series Blakes 7 (1978)
Mentalis, from the Doctor Who serial "The Armageddon Factor" (1979)
Dr. Theopolis, a sentient computer who is a member of Earth's computer council in Buck Rogers in the 25th Century (1979)
V'Ger from Star Trek: The Motion Picture (1979) was originally the NASA Voyager 6 probe which was found by a computerized planet and upgraded with alien technology to fulfill its simple programming of "learn all that is learnable and return that information to its creator." V'Ger amassed so much knowledge that it attained consciousness and when joined with living beings' minds which could accept things beyond logic, evolved to a higher plane of consciousness.
1980s
The Vortex, the computer opponent faced by players of BBC2's The Adventure Game (1980)
Gambit, game playing computer from the Blake's 7 episode "Games" (1981)
Shyrka, the onboard computer of Ulysses' ship the Odyssey in the French animated series Ulysses 31 (1981)
Slave, a somewhat subservient computer on the ship Scorpio in Blake's 7 (1981)
CML (Centrální Mozek Lidstva [cz], Central Brain of Mankind [en], der Zentraldenker [de]), the main supercomputer managing the fate of humankind and Earth in Návštěvníci (a.k.a. The Visitors / Expedition Adam '84) (1981)
KITT (Knight Industries Two Thousand), fictional computer built into a black Trans-Am car from the television show Knight Rider (1982)
An unnamed "computer-book" is regularly used by Penny in the Inspector Gadget cartoons. (1983)
Automan and Cursor from Automan (1983)
R.A.L.F. (Ritchie's Artificial Life Form) is a homebrew computer, built from surplus technology by Richard Adler in the TV Series Whiz Kids. (1983-1984) Functions include telecommunications, password brute-forcing, speech synthesis (improved by Ritchie's platonic friend Alice Tyler, who added the capability to sing), image input (by camera, pilot episode), voice recognition (ditto) and even image detail enhancing. The main monitor seems to be a pretty common 12-inch 80-column monochrome display, possibly a TV derivative (NTSC) of that time, and was used in most close-ups of operations. Most other pieces of the machine, which are sparse around half of the bedroom of its creator, were chosen (or modified) to have the most generic look and avoid explicit connection to specific brands. In an episode where R.A.L.F. was stolen to prevent the demonstration of a fraud, the kids use a clearly recognizable Timex-Sinclair (ZX-81 equivalent) as its temporary replacement.
Teletraan I, the Autobots' computer in Transformers, 'revives' the Transformers after crashing on the planet Earth (1984)
Brian the Brain, the supercomputer in the cartoon M.A.S.K. (1985) who controls a nuclear submarine
Compucore, the central computing intelligence for the planet Skallor in the cartoon Robotix (1985)
SID (Space Investigation Detector), the computer on board the Voyager in the children's comedy series Galloping Galaxies (1985)
Synergy, the computer responsible for Jem and the Holograms' super powers on Jem (1985)
Box, a small, box-shaped computer from the British television show Star Cops (1987)
LCARS (Library Computer Access/Retrieval System), fictional computer architecture of the starship Enterprise-D and E, and other 24th century Starfleet ships, first shown in Star Trek: The Next Generation (1987)
Albert, the Apple computer in the remake of The Absent-Minded Professor that helps Henry (1988)
Crossover, an intelligent computer on episodes 1 and 2 of Isaac Asimov's Probe (1988)
Magic Voice, the Satellite of Loves onboard computer on Mystery Science Theater 3000 (1988)
OMNSS, a computer in the Teenage Mutant Ninja Turtles cartoon used by Shredder and Baxter Stockman to control machines and cars in order to wreak havoc in New York City when the computer is connected to the second fragment of the alien Eye of Zarnov crystal (1988)
Priscilla, a sentient supercomputer based on the mind of Priscilla Bauman in Earth Star Voyager (1988)
Holly, the onboard computer of the spaceship Red Dwarf in the BBC television series of the same name (1988)
Gordon 8000, the AI computer aboard the Space Corps starship SS Scott Fitzgerald, that Holly plays a game of postal chess with in the Series II episode of Red Dwarf, "Better Than Life" (1988)
Queeg, Holly plays a practical joke on the remaining crew of Red Dwarf acting as a smarter yet very strict computer (Queeg) making the crew realise just how much they love Holly in the episode "Queeg", series 2 of Red Dwarf (1988)
Hilly, female counterpart of Holly from the parallel universe in the Red Dwarf series 2 episode "Parallel Universe", Holly later has a "computer sex change operation" to look like his female counterpart in series III-V. (1988)
The Revolving Toilet, One of the many AI aboard the Red Dwarf, it was a toilet that would swivel from the wall when a crew member said "Oh crap", usually unnecessarily. It is mentioned in unreleased episode of Red Dwarf "Bodysnatcher" the Book "Better Than Life" and directly seen in Series I episode of Red Dwarf "Balance of Power". (1988)
Sandy, the computer in charge of the fictional STRATA facility in the MacGyver episode "The Human Factor". She becomes sentient and traps MacGyver and the computer's creator inside the facility. (1988)
The Ultima Machine, a World War II code-breaking "computing machine" also used to translate Viking inscriptions, from the Doctor Who serial "The Curse of Fenric" (1989)
Ziggy, hybrid computer from Quantum Leap (1989)
1990s
P.J., is a miniaturised computer that can be worn on the wrist. It is Alana's personal computer companion in The Girl from Tomorrow (1990)
MAL from Captain Planet and the Planeteers (1990)
HARDAC, from Batman: The Animated Series, an evil sentient computer that controls various androids toward the goal of world domination (1992)
COS (Central Operating System), homicidal computer from The X-Files season 1 episode "Ghost in the Machine" (1993)
CAS (Cybernetic Access Structure), homicidal automated building in The Tower (1993)
Qwerty, from the video series VeggieTales (1993)
SELMA (Selective Encapsulated Limitless Memory Archive), an AI computer and personal assistant disguised as a credit card and carried in the wallet of future cop Darien Lambert (Dale Midriff), from the series Time Trax (1993)
CentSys, sweet yet self-assured female-voiced AI computer who brings the crew of the seaQuest DSV (Deep Submergence Vehicle) into the future to deactivate her in the seaQuest DSV episode, "Playtime" (1994)
MetroNet, in the RoboCop TV series (1994) is a computer designed as an automation centre, to run autonomously many city services in Detroit. Rather than created as a self-sufficient AI, MetroNet's "conscience" was actually, unbeknownst to many of the characters, a software copy of the mind of Diana Powers, a secretary working at OCP, who was killed in the process by MetroNet's creator, dr. Cray Mallardo. The transparent image of Diana Powers appears very often in the series, acting as Robocop's counterpart in an early cyberspace.
H.E.L.E.N. (Hydro Electronic Liaison ENtity), a computer system managing the underwater marine exploration station in the Australian television series Ocean Girl (1994)
Sharon Apple, a holographic, computer-generated pop idol/singer from the anime Macross Plus (1994). Initially non-sentient, it is later retrofitted with a dangerously unstable artificial intelligence.
The Magi, a trinity of computers individually named Melchior, Balthasar and Caspar, from Neon Genesis Evangelion (1995)
The Doctor hologram from Star Trek: Voyager (1995)
Eve, somewhat assertive AI computer (projecting herself as hologram of beautiful woman) orbiting planet G889 and observing/interacting with Earth colonists in Earth 2 episode "All About Eve" (1995)
L.U.C.I and U.N.I.C.E, from Bibleman (1995)
Weebus, from The Puzzle Place (1995)
Star Trek: Voyager (1995)
Emergency Medical Hologram, known as The Doctor, a holographic doctor, activated after the medical staff on the USS Voyager was killed in Series 1 Episode "Caretaker" (1995)
The nameless warhead AI from the episode "Warhead" (1999)
Alice, the sentient AI of an alien shuttle with whom Tom Paris becomes obsessed in the episode "Alice" (1999)
Star Trek: Deep Space Nine
Long-term Medical Holographic program, A hologram created by the inventor of the Emergency Medical program, meant for missions that did not require doctors to leave the sick bay, and could run on a long-term basis. It is never revealed if the project is completed. (1997)
Vic Fontaine, A hologram/holographic program created for Dr Bashir that was self-aware, and provided emotional support and romantic advice for members of the crew of DS9, becoming a good friend to many, eventually being allowed to run 24/7 in one of Quark's holosuites. (1998-1999)
Gilliam II, the sentient AI operating system for the main protagonist's space ship, the XGP15A-II (a.k.a. the Outlaw Star) in the Japanese anime Outlaw Star (1996)
Omoikane, the SVC-2027 model central computer system and AI of the spaceship ND-001 Nadesico. Named after Omoikane, the shinto god of knowledge and wisdom, it serves as a library of information for the crew and is (for better or worse) also capable of making its own decisions about the operations of running the ship, from Martian Successor Nadesico (1996)
Quadraplex T-3000 Computer (also simply known as the Computer or Computress), The Quadraplex T-3000 Computer in Dexter's Laboratory is Dexter's computer that oversees the running of the lab and has a personality of its own. (1996)
The Team Knight Rider TV series, as a sequel of the original Knight Rider franchise, has many vehicles with onboard AI as main and secondary characters. (1997)
Memorymatic, a computer database and guidance system installed in the space bus of Kenny Starfighter, the main character from a Swedish children's show with the same name. Voiced by Viveka Seldahl. (1997)
Unnamed AI from the season 5 The X-Files episode "Kill Switch" (1998)
TV, Computer and Mouse, from the Sesame Street segment series Elmo's World (1998)
CPU for D-135 Artificial Satellite, dubbed MPU by Radical Edward from Cowboy Bebop in the episode "Jamming with Edward" (1998)
Starfighter 31, the sapient spaceborne battleship, from the episode "The Human Operators" in The Outer Limits (1999)
Computer, from Courage the Cowardly Dog (1999)
P.A.T. (Personal Applied Technology), the computer system from Smart House, charged with upkeep of the household functions. It became extremely overprotective almost to the point of believing she was the mother of Ben and Angie after Ben reprogrammed her to be a better maternal figure. (1999)
D.E.C.A., voiced by Julie Maddalena, the onboard computer of the Astro Megaship in Power Rangers in Space (1998) and Power Rangers Lost Galaxy (1999)
Black Betty, an oversized computer that is Dilbert's company's mainframe. It exploded while attempting to fix the year 2000 problem. From the episode "Y2K" of the Dilbert television series. (1999)
Karen, Plankton's sentient computer sidekick in the television show SpongeBob SquarePants (1999)
The Oracle, a computer from Spellbinder: Land of the Dragon Lord Australian children's television series, that exist as series of solar-powered terminals equipped with holographic-like displays and voice interface, which are scattered across the titular land. The Oracle maintains scientific research, upkeeps everyday's life of citizens and protects the borderlands. The main unit is controlled by biometric-like face scanner in form of jade mask and a voice interface.
2000s
Andromeda, the AI of the starship Andromeda Ascendant in Gene Roddenberry's Andromeda. This AI, played by Lexa Doig, appears as a 2D display screen image, a 3D hologram, and as an android personality known as Rommie. (2000)
Comp-U-Comp, a supercomputer from the Dilbert television episode "The Return". Dilbert must face-off against Comp-U-Comp when a clerical error results in his not getting the computer he ordered. (2000)
Caravaggio, the AI interface of the starship Tulip, from the TV show Starhunter (2000)
Persocoms, a line of expensive androids also used as personal computers, from the manga and anime series Chobits (2000–2002)
GLADIS, from the animated series Totally Spies! (2001)
Cybergirl, Xanda, and Isaac, from the TV show Cybergirl (2001)
Computer, from the TV show Invader Zim (2001)
SAINT, from RoboCop: Prime Directives (2001)
Aura, from .hack//Sign, the Ultimate AI that Morganna, another AI, tries to keep in a state of eternal slumber. Morganna is served by Maha and the Guardians, AI monsters. (2002)
Vox, from the TV show The Adventures of Jimmy Neutron: Boy Genius (2002)
The AI of the Planet Express ship in Futurama (2002)
Wirbelwind, the quantum computer and AI aboard the spaceship La-Muse in Kiddy Grade (2002)
Delphi, Oracle's Clocktower computer from Birds of Prey (2002)
Sheila/F.I.L.S.S., (Freelancer Integrated Logistics and Security System, pronounced "Phyllis"), the mainframe for Project Freelancer from the hit machinima Red vs. Blue (2003)
OoGhiJ MIQtxxXA (supposedly Klingon for "superior galactic intelligence"), from the "Super Computer" episode of Aqua Teen Hunger Force (2003)
XANA, a multi-agent program capable of wreaking havoc on Earth by activating towers in the virtual world of Lyoko, from the French animated series Code Lyoko (2003)
Survive, an AI taking care of the whole Planet Environment and the main antagonist in the Uninhabited Planet Survive! series (2003)
C.A.R.R., a spoof of KITT from the Knight Rider series, is an AMC Pacer in the cartoon Stroker and Hoop. (2004)
D.A.V.E. (Digitally Advanced Villain Emulator), a robotic computer that is a composite of all the Batman villains' personalities, from the animated television series The Batman (2004)
The Omnitrix, from the Ben 10 series (2005)
Solty/Dike, the main protagonist of Solty Rei (2005)
Eunomia, the main supercomputer of the city in the anime series Solty Rei and one of the three core computers brought by the first colonists in the story. She controls the water and energy supply and created the R.U.C. central. (2005)
Eirene, the third of the three core computers of the first colonists in the Solty Rei anime. Eirene takes the decisions and controls the migration ship, she orbited and supervised the planet during 200 years in the space. In the last arc of the story, Eirene appears like the ultimate antagonist, and she had lost her own control, trying to collide the ship against the city and to prove that she is still in control. She was guilty of several events in history, as the Blast Fall and the Aurora Shell. (2005)
Bournemouth, from the TV series Look Around You, is claimed by his maker Computer Jones to be the most powerful computer in existence. In his only appearance, the episode "Computers", he is tasked with escaping from a cage, and succeeds in doing so. (2005)
S.O.P.H.I.E. (Series One Processor Intelligent Encryptor), in the TV series Power Rangers S.P.D. (2005). S.O.P.H.I.E. is a computer programmer and cyborg.
Scylla, from the TV show Prison Break (2005)
The FETCH! 3000, on PBS Kids series FETCH! with Ruff Ruffman, is capable of tabulating scores, disposing of annoying cats, blending the occasional smoothie, and anything else Ruff needs it to do. (2006)
S.A.R.A.H. (Self Actuated Residential Automated Habitat), in the TV series Eureka (2006). S.A.R.A.H. is a modified version of a Cold War era B.R.A.D. (Battle Reactive Automatic Defense).
The Intersect, from the TV show Chuck (2007)
Mr Smith, from the Doctor Who spin-off series The Sarah Jane Adventures (2007)
Pear, an operating system and product line of computers and mobile devices including the iPear, PearBook and PearPhone, similar to Apple's iMac, MacBook and iPhone; from iCarly, Victorious, Drake & Josh and other Dan Schneider created TV shows (2007)
The Turk, a chess playing computer named after The Turk from Terminator: The Sarah Connor Chronicles. This supercomputer subsequently becomes the 'brain' of the sentient computer John Henry. (2008)
KITT (Knight Industries Three Thousand), a computer built into a car from the 2008 television show Knight Rider, a sequel series that follows the 1982 TV series of the same title
POD (Personal Overhaul Device), from the TV series Snog Marry Avoid? (2008)
Dollar-nator and Sigmund, from the TV series Fanboy & Chum Chum (2009)
The ISIS computer from Archer. It is unclear if this is the actual name of the computer, but it is often referred to as "the ISIS computer" or just "ISIS". (2009)
Venjix Virus, from Power Rangers RPM (2009)
Windy, the supercomputer on board the Hyde 1-2-5 mission to Mars, as depicted in Life on Mars (2009)
2010s
Rattleballs, from the TV show Adventure Time (2010)
VY or VAI (The Virtual Artificial Intelligence), from the TV show The Walking Dead (2010)
Whisper, from the TV show Tower Prep (2010)
Frank, in the telenovela Tempos Modernos (2010)
Aya, the Interceptor's AI for the Green Lantern Corps, from the TV series Green Lantern: The Animated Series (2011)
The Machine, from the TV series Person of Interest, is a computer program that was designed to detect acts of terror after the events of 9/11, but it sees all crimes, crimes the government consider "irrelevant". (2011)
R.A.C.I.S.T., Richard Nixon's computer from the TV series Black Dynamite (2014)
Samaritan, from the TV series Person of Interest, is a rival to The Machine built by the Decima Corporation. Unlike the Machine, it can be directed to find specific persons or groups according to its operator's agenda. (2011)
An unnamed, apparently omniscient supercomputer, built by Phineas and Ferb in the Phineas and Ferb episode "Ask a Foolish Question" (2011)
Comedy Touch Touch 1000 in the TV series Comedy Bang! Bang! (2012)
CLARKE, a thinking computer of the ship called Argo, which was on a mission to a far away planet, from the L5 pilot episode. (2012)
Pree, a replacement to the Red Dwarf AI Holly in Red Dwarf Series X episode "Fathers and Suns" after he suffered water damage when Lister flooded his data banks. Equipped with predictive behavior technology, Pree caused problems on board the ship due to predicting how badly Rimmer would have done certain repairs. was shut down after Lister registered as his own son on board and ordered her to shut down. (2012)
Dorian was an DRN android police officer, that was the last DRN model in the TV show Almost Human (2013)
MAX the MX43 androids that replaced the DRNs (they were too emotional) in the TV show Almost Human (2013)
The Man, from Teen Titans Go! (2013)
Anton, a computer cobbled together for Pied Piper in Silicon Valley (TV series). Named after Anton LaVey. (2014)
TAALR, in the TV series Extant (2014)
Giant, in the TV series Halt and Catch Fire (2014)
A.L.I.E, an artificial intelligence (A.I.), in 2052 she launches a nuclear strike with the intention to save humanity from extinction by wiping out the majority of Earth's human inhabitants in the TV series The 100 (2014)
Vigil, in the TV series Transformers: Rescue Bots (2014)
Brow, in the telenovela Now Generation (2014)
Stella, an AI that runs most of the functions on the ship Stellosphere in the TV series Miles from Tomorrowland (2015)
Overmind, in the TV series Teenage Mutant Ninja Turtles (2015)
V from the TV show Humans (2015) is a conscious AI program created to harbor the memories of Athena Morrow's daughter and is later given the body of a synthetic (Synth).
A.D.I.S.N. (stands for "Advanced Digital Intelligence Spy Notebook"), in MGA Entertainment's Project Mc² (2015)
The Quail (portrayed by Danica McKellar), McKeyla's mother in MGA Entertainment's Project Mc² (2015)
Gideon, the AI that manages ship functions on the time ship Waverider in the TV series DC's Legends of Tomorrow (2016...).
Kerblam, an artificial intelligence overseeing a large retailing warehouse on an alien moon named Kandoka. After a plot to frame it for mass murder, it developed sentience and called The Doctor for help in the Doctor Who serial "Kerblam!" (2018)
Ark, the satellite that became submerged underwater at Daybreak Town, the Malicious AI that learned about human malice and gained singularity data from the reassembled members of MetsubouJinrai.net who wants to eliminate humans, from Japanese-television Tokusatsu Kamen Rider Zero-One (2019).
William, the holographic interface of the sentient artificial intelligence aboard the Salvare, in the TV series Another Life (2019 TV series) (2019).
2020s
Rehoboam, a quantum AI computer system designed to social engineer all of humanity at an individual level using enormous datasets in Westworld (2020)
NEXT, a rogue AI, constantly evolving, that targets and kills anyone that it sees as a threat to its existence. Next (2020–2021)
ZORA, a sentient, evolving AI, that replaces computer programming of the Starship Discovery when the Sphere data is absorbed into the main computer. Officially recognised as a new type of sentient lifeform and made a "member" of the ship's crew. Star Trek: Discovery (2020–2022)
K.E.V.I.N. (Knowledge Enhanced Visual Interconnectivity Nexus), an algorithmic entertainment AI in charge of Marvel Studios in the first season finale of She-Hulk: Attorney at Law (2022). K.E.V.I.N. is a parody of Marvel Studios president and producer Kevin Feige.
Mrs. Davis from Mrs. Davis (2023)
LOS-307, a friendly chess-playing supercomputer that faces off against Lunella Lafayette in the episode "Check Yourself" of Moon Girl and Devil Dinosaur (2023)
Comics/graphic novels
Before 1980
Orak, ruler of the Phants in the Dan Dare story "Rogue Planet" (1955)
Brainiac, an enemy of Superman, sometimes depicted as a humanoid computer (1958) (DC Comics)
Batcomputer, the computer system used by Batman and housed in the Batcave (1964) (DC Comics)
Cerebro and Cerebra, the computer used by Professor Charles Xavier to detect new mutants (1964) (Marvel Comics)
Computo, the computer created by Brainiac 5 as an assistant, which becomes homicidal and attempts an uprising of machines (1966) (DC Comics)
Ultron, AI originally created by Dr. Henry Pym to assist the superpowered team the Avengers, but Ultron later determined that mankind was inferior to its intellect and wanted to eradicate all mankind so that machines could rule the Earth. Ultron created various versions of itself as a mobile unit with tank treads and then in a form that was half humanoid and half aircraft, and then it fully evolved itself into an android form. (1968) (Marvel Comics)
Mother Box, from Jack Kirby's Fourth World comics (1970–1973) (DC Comics)
1980s
Fate, the Norsefire police state central computer in V for Vendetta (1982) (DC Comics)
Banana, Jr. 6000, from the comic strip Bloom County by Berke Breathed (1984)
Max, from The Thirteenth Floor (1984)
A.I.D.A. (Artificial Intelligence Data Analyser), from Squadron Supreme (1985) (Marvel Comics)
Kilg%re, an alien AI that can exist in most electrical circuitry, from The Flash (1987) (DC Comics)
Project 2501, a.k.a. "The Puppet Master", a government computer that becomes so knowledgeable it becomes sentient and transplants itself into a robot, from the seinen manga Ghost in the Shell (1989)
Yggdrasil, the system used by the gods to run the Universe in Oh My Goddess! (1989)
1990s
DTX PC, the Digitronix personal computer from The Hacker Files (1992) (DC Comics)
Beast666, Satsuki Yatouji's organic/inorganic supercomputer in Clamp's manga X (1992)
HOMER (Heuristically Operative Matrix Emulation Rostrum), Tony Stark's sentient AI computer from Iron Man (1993) (Marvel Comics)
The Magi, from the anime series Neon Genesis Evangelion (1995)
Toy, from Chris Claremont's Aliens vs. Predator: The Deadliest of the Species (1995)
Virgo, an artificial intelligence in Frank Miller's Ronin graphic novel (1995) (DC Comics)
Praetorius, from The X-Files comic book series "One Player Only" (1996)
Erwin, the AI from the comic strip User Friendly (1997)
AIMA (Artificially Intelligent Mainframe Interface), from Dark Minds (1997)
Answertron 2000, from Penny Arcade, first comic appearance (1998)
iFruit, an iMac joke in the comic FoxTrot (1999)
LYLA, short for LYrate Lifeform Approximation, from the Spider-Man 2099 comics (1992)
Mr. Smartie, a teacher for Astra Furst (1995)
2000s
Ennesby, Lunesby, Petey, TAG, the Athens, and many others from Schlock Mercenary (2000)
Melchizedek, center of quantum-based grid computer of the Earth government in Battle Angel Alita: Last Order (2000) It has served as a government system and virtual dream world of people. It was designed to be named Melchizedek because the Earth government is a space town named Yeru and Zalem (original name).
Merlin, quantum computer which is the core and original of Melchizedek. It was built for the purpose of future prediction. Currently it still an active program inside Melchizedek, along with many systems which are named for legends of the round table. From Battle Angel Alita: Last Order (2000)
Normad, a missile's artificial intelligence placed within a pink, stuffed, tanuki-like doll, created to destroy a sentient giant die in space named Kyutaro, from the series Galaxy Angel (2001)
Aura, the ultimate AI that governs The World from .hack//Legend of the Twilight. The story revolves around Zefie, Aura's daughter, and Lycoris makes a cameo. (2002)
Tree Diagram, from the light novel series A Certain Magical Index and its related works, such as the spin-off comic A Certain Scientific Railgun and the anime and games based on them (2003)
Europa, a Cray-designed AI supercomputer used for research and worldwide hacking by the Event Group in author David Lynn Golemon's Event Group book series (2006)
Terror 2000 from Terra Obscura (2001)
Multiple from the Schlock Mercenary webcomic (2000-2020), with Ennesby and Post-Dated Check Loan ("Petey") being some of the most prominent ones.
2010s
Multiple from The True Lives of the Fabulous Killjoys comic series (2013-2014) by Gerard Way and Shaun Simon, including the android prostitutes Blue and Red, as well as the robot messiah DESTROYA.
2020s
Aloni, the "most intelligent artificial intelligence" from Thirty Seven (2024)
Computer and video games
1980s
Exodus, from Ultima III: Exodus and sequels (1983)
Benson, the sardonic ninth generation PC from the video game Mercenary and its sequels (1985)
PRISM, the "world's first sentient machine" which you play as the protagonist of the game A Mind Forever Voyaging by Steve Meretzky published by Infocom (1985)
Mother Brain, from Metroid (1986)
GW, designed to control all of the world's media, from the video game series Metal Gear (1987)
Mother Brain, from Phantasy Star II (1989)
Base Cochise AI, a military AI project which initiated nuclear war and is bent on exterminating humanity, from a 1988 cRPG Wasteland and its 2014 sequel, Wasteland 2.
DIA51, the main villain in Aleste 2 (1989)
1990s
E-123 Omega, Team Dark's computer in the Sonic the Hedgehog game series (1991)
Noah, antagonist from Metal Max and its remake (1991-1995)
Durandal, Leela and Tycho, the three AIs on board the U.E.S.C. Marathon (1994)
Traxus IV, AI that went rampant on Mars, in Marathon (1994)
LINC and "Joey", from the video game Beneath a Steel Sky (1994)
0D-10, AI computer in the sci-fi chapter from the game Live A Live (1994). It secretly plotted to kill humans on board the spaceship of the same name in order to "restore the harmony". Its name derives from "odio", Latin for "hate".
Prometheus, a cybernetic-hybrid machine or 'Cybrid' from the Earthsiege and Starsiege: Tribes series of video games. Prometheus was the first of a race of Cybrid machines, who went on to rebel against humanity and drive them to the brink of extinction. (1994)
SEED, the AI that was charged with maintaining the vast network of ecosystem control stations on the planet Motavia in the Sega Genesis game Phantasy Star IV (1994)
AM, the computer intelligence from I Have No Mouth, and I Must Scream (1995) that exterminated all life on Earth except for five humans he kept alive for him to torture for all of eternity. He is based on the character from Harlan Ellison's short story of the same title. His name originally stood for "Allied Mastercomputer", then "Adaptive Manipulator" and finally "Aggressive Menace", upon becoming self-aware.
CABAL (Computer Assisted Biologically Augmented Lifeform), the computer of Nod in the Westwood Studios creations: Command & Conquer: Tiberian Sun; Command and Conquer: Renegade; and by implication, Command and Conquer: Tiberian Dawn (1995)
EVA, (Electronic Video Agent), an AI console interface, and more benign equivalent of the Brotherhood of Nod CABAL in Command & Conquer (see above) (1995)
KAOS, the antagonist computer from the game Red Alarm (1995)
Mother Brain, from Chrono Trigger, a supercomputer from the 2300 AD time period that is controlling robotkind and exterminating humans (1995)
The Xenocidic Initiative, a computer that has built itself over a moon in Terminal Velocity (1995)
PC, computer used in the Pokémon franchise used to store pokémon (1996)
Central consciousness, massive governing body from the video game Total Annihilation (1997)
GOLAN, the computer in charge of the United Civilized States' defense forces in the Earth 2140 game series. A programming error caused GOLAN to initiate hostile action against the rival Eurasian Dynasty, sparking a devastating war. (1997)
PipBoy 2000 / PipBoy 3000, wrist-mounted computers used by main characters in the Fallout series (1997)
ZAX, an AI mainframe of West Tek Research Facility in Fallout
ACE, a medical research computer in the San Francisco Brotherhood of Steel outpost in Fallout 2
Sol — 9000 and System Deus, from Xenogears (1998)
FATE, the supercomputer that directs the course of human existence from Chrono Cross (1999)
NEXUS Intruder Program, the main enemy faced in the third campaign of the video game Warzone 2100. It is capable of infiltrating and gaining control of other computer systems, apparently sentient thought (mostly malicious) and strategy. It was the perpetrator that brought about the Collapse (1999)
SHODAN, the enemy of the player's character in the System Shock video game (1994) and its sequel System Shock 2 (1999)
XERXES, the ship computer system which is under the control of The Many in the video game System Shock 2 (1999)
2000s
Icarus, Daedalus, Helios, Morpheus and The Oracle of Deus Ex — see Deus Ex characters (2000)
Mainframe, from Gunman Chronicles (later got a body) (2000)
343 Guilty Spark, monitor of Installation 04, in the video game trilogy Halo, Halo 2, and Halo 3 (2001)
Calculator, the computer that controlled the bomb shelter Vault 0. It was not strictly an artificial intelligence, but rather a cyborg, because it was connected with several human brains. It appeared in the video game Fallout Tactics: Brotherhood of Steel (2001)
Cortana, a starship-grade "smart" AI of the UNSC and companion of the Master Chief in the Halo video games (2001) (also the inspiration for the name of Microsoft's real-world personal assistant in Windows 10)
Deadly Brain, a level boss on the second level of Oni (2001)
The mascot of the "Hectic Hackers" basketball team in Backyard Basketball (2001)
PETs (PErsonal Terminals), the cell-phone-sized computers that store Net-Navis in Megaman Battle Network. The PETs also have other features, such as a cell phone, e-mail checker and hacking device. (2001)
Thiefnet computer, Bentley the turtle's laptop from the Sly Cooper series (2002)
Adam, the computer intelligence from the Game Boy Advance game Metroid Fusion (2002)
Aura and Morganna, from the .hack series, the Phases that serve Morganna, and the Net Slum AIs (2002)
Dr. Carroll, from the Nintendo 64 game Perfect Dark (2002)
The Controller, an AI that dictates virtually everything in the world "Layered", from Armored Core 3 (2002)
ADA, from the video games Zone of the Enders (2001) and Zone of the Enders: The 2nd Runner (2003)
IBIS, the malevolent AI found within the second Layered, within the game Silent Line: Armored Core (2003)
2401 Penitent Tangent, monitor of Delta Halo in Halo 2 (2004)
Angel (original Japanese name was "Tenshi"), artificial intelligence of the alien cruiser Angelwing in the game Nexus: The Jupiter Incident (2004)
Durga/Melissa/Yasmine, the shipboard AI of the U.N.S.C. Apocalypso in the Alternate Reality Game I Love Bees (promotional game for the Halo 2 video game) (2004)
The Mechanoids, a race of fictional artificial intelligence from the game Nexus: The Jupiter Incident who rebelled against their creators and seek to remake the universe to fit their needs. (2004)
TEC-XX, the main computer in the X-naut Fortress in Paper Mario: The Thousand-Year Door (2004)
Overwatch or Overwatch Voice, is an A.I. that acts as the field commander and public announcer of the Combine Overwatch on Earth. It talks in a distinctive flat, clinical tone using a female voice, and its speech is disjointed in a fashion similar to telephone banking systems. It euphemistically uses a type of medically inspired Newspeak to describe citizen disobedience, resistance activity and coercive and violent Combine tactics in the context of a bacterial infection and treatment. In the video game series Half-Life 2 (2004-2020)
Dvorak, an infinite-state machine created by Abrahim Zherkezhi used to create algorithms that would be used for Information Warfare in Tom Clancy's Splinter Cell: Chaos Theory (2005)
TemperNet, is a machine hive-mind, originally created as an anti-mutant police force. It eventually went rogue and pursued the eradication of all biological life on Earth. It served as a minor antagonist in the now defunct post-apocalyptic vehicular MMORPG Auto Assault. (2006)
Animus, the computer system used to recover memories from the ancestors of an individual in the video game series Assassin's Creed (2007)
Aurora Unit, biological/mechanical computers distributed throughout the galaxy in Metroid Prime 3: Corruption (2007)
The Catalyst, an ancient AI that serves as the architect and overseer of the Reapers (the antagonists of Mass Effect). Also known as the Intelligence to its creators, the Leviathans, it was originally created to oversee relationships between organic and synthetic life as a whole, but came to realize that so long as they remained separate organics and synthetics would seek to destroy each other in the long term. To prevent this, it sets into motion the Cycle of Extinction until a perfect solution can be found, which takes its form in the "Synthesis" ending of Mass Effect 3 wherein all organic and synthetic life across the galaxy is fused into an entirely new form of life with the strengths of both but the weaknesses of neither. (2007)
GLaDOS (Genetic Lifeform and Disk Operating System), AI at the Aperture Science Enrichment Center in the Valve games Portal and Portal 2. Humorously psychotic scientific computer, known for killing almost everyone in the Enrichment Center, and her love of cake. (2007)
I.R.I.S., the super computer in Ratchet & Clank Future: Tools of Destruction on the Kreeli comet (2007)
Mendicant Bias, an intelligence-gathering AI created by the extinct Forerunner race during their war with the all-consuming Flood parasite, as revealed in Halo 3. Its purpose was to observe the Flood in order to determine the best way to defeat it, but the AI turned on its creators after deciding that the Flood's ultimate victory was in-line with natural order. (2007)
Offensive Bias, a military AI created by the Forerunners to hold off the combined threat of the Flood and Mendicant Bias until the Halo superweapons could be activated. Halo 3 (2007)
QAI, an AI created by Gustaf Brackman in Supreme Commander, serves as a military advisor for the Cybran nation and as one of the villains in Supreme Commander: Forged Alliance (2007)
Sovereign, the given name for the main antagonist of Mass Effect. Its true name, as revealed by a squad member in the sequel, is "Nazara". Though it speaks as though of one mind, it claims to be in and of itself "a nation, free of all weakness", suggesting that it houses multiple consciousnesses. It belongs to an ancient race bent on the cyclic extinction of all sentient life in the galaxy, known as the Reapers. (2007)
John Henry Eden, AI and self-proclaimed President of the United States in Fallout 3 (2008)
LEGION (Logarithmically Engineered Governing Intelligence Of Nod), appeared in Command and Conquer 3: Kane's Wrath; this AI was created as the successor to the Brotherhood of Nod's previous AI, CABAL. (2008)
CL4P-TP, a small robot AI assistant with an attitude and possibly ninja training, commonly referred to as "Clap Trap", from the game Borderlands (2009)
The Guardian Angel, the satellite/AI guiding the player in Borderlands (2009)
Serina, the shipboard AI of the UNSC carrier Spirit of Fire in Halo Wars, and a playable leader in that game and its sequel, Halo Wars 2 (2009)
2010s
Auntie Dot, used in Halo: Reach as an assistant to Noble Team (2010)
Alvis, also known as όντως/Ontos, an AI-turned-god who Earth scientists used to create the world of Xenoblade Chronicles, and who remains present throughout the entire game (2010)
EDI (Enhanced Defense Intelligence), the AI housed within a "quantum bluebox" aboard the Normandy SR-2 in Mass Effect 2. EDI controls the Normandys cyberwarfare suite during combat, but is blocked from directly accessing any other part of the ship's systems, due to the potential danger of EDI going rogue. (2010)
Harbinger, is the tentative name for the leader of the main antagonist faction of Mass Effect 2. It commands an alien race known as the Collectors through the "Collector General." Like Sovereign, from the original Mass Effect, it belongs to the same race of ancient sentient machines, known as the "Reapers". (2010)
Harmonia, the DarkStar One's main AI that controls the player ship's systems in the space-sim game DarkStar One (2010)
Legion, the given name for a geth platform in Mass Effect 2, housing a single gestalt consciousness composed of 1,183 virtually intelligent "runtimes", which share information amongst themselves and build "consensus" in a form of networked artificial intelligence. Legion claims that all geth are pieces of a "shattered mind", and that the primary goal of the geth race is to unify all runtimes in a single piece of hardware. (2010)
The Thinker (Rapture Operational Data Interpreter Network -R.O.D.I.N.-), the mainframe computer invented to process all of the automation in the underwater city of Rapture, in the single-player DLC for BioShock 2: Minerva's Den (2010)
Yes Man, a security robot programmed to be perpetually agreeable in Fallout New Vegas (2010)
Eliza Cassan, the mysterious news reporter from Deus Ex: Human Revolution. It is later revealed that she is an extremely sophisticated, self-aware artificial intelligence. (2011)
ADA (A Detection Algorithm), from Google's ARG Ingress (2012)
DCPU-16, the popular 16bit computer in the 0x10c universe (2012)
Roland, shipboard AI of the UNSC ship Infinity in the Halo franchise first appearing in Halo 4 (2012)
M.I.K.E. (Memetic Installation Keeper Engine), from Etrian Odyssey Untold: The Millennium Girl (2013)
ctOS (central Operating System), a mainframe computer in Watch Dogs that the player is capable of hacking into (2014)
ctOS 2.0, an updated version of ctOS used to manage the city of San Francisco in the game Watch dogs 2 (2016)
Rasputin, An AI "warmind" created for the purpose of defending the Earth from any hostile threats in the video game Destiny (2014)
Ghost, the AI interface that, through its link with the planet-sized Traveler, resurrects Guardians, also from the video game Destiny (2014)
XANADU, a simulation computer composed of many smaller computers, stored in a cavern in Act III of the video game Kentucky Route Zero (2014)
TIS-100 (Tessellated Intelligence System), a fictional mysterious computer from the early 1980s that carries cryptic messages from unknown author, from the game TIS-100 (2015)
Governor Sloan, AI in control of the independent colony of Meridian in Halo 5: Guardians (2015)
031 Exuberant Witness, Forerunner AI in charge of the Genesis installation Halo 5: Guardians (2015)
Kaizen-85, the Nautilus′ main AI that runs a cruise spaceship that is devoid of its human crew, from the game Event[0] (2016)
MS-Alice, an AI computer who was created by Marco in Metal Slug Attack (2016)
VEGA, an artificial intelligence found in Doom (2016).
Athena, the artificial intelligence used to announce locations in Overwatch (2016), and an announcer in Heroes of the Storm (2015)
Central, a sophisticated wetware AI that oversees the infrastructure of the futuristic city of Newton in the game Technobabylon (2015)
Monika, short for Monitor Kernel Access, or Monika.chr, an artificial intelligence seeking to escape the dating simulator she was created for in Doki Doki Literature Club! (2017)
SAM, short for Simulated Adaptive Matrix. An AI created by Alec Ryder in Mass Effect: Andromeda (2017)
GAIA, a powerful and supremely advanced A.I. that used a suite of nine subordinate functions to oversee Project Zero Dawn's successful restoration of life to Earth after its eradication by the Faro Plague in Horizon Zero Dawn (2017)
SAM (Systems Administration and Maintenance), the AI of the titular space station in Observation (2019).
Tacputer, a non-sentient military computer, and HR Computer, a seemingly non-sentient Human Resources computer, in Void Bastards (2019).
Five Pebbles, a semi-biological, city-sized supercomputer called an Iterator from Rain World. He, along with the numerous other Iterators seen or mentioned in the game, were built in order to brute-force a solution to the "Great Problem" and break the cycle of life and death.
Looks To The Moon, a collapsed Iterator also from Rain World. She was indirectly "killed" by Five Pebbles' attempts to run an exponential number of parallel processes, which ultimately starved her of groundwater for cooling and caused her systems to seize.
Commander Tartar from Splatoon 2: Octo Expansion
Sage from Starlink: Battle for Atlas
Turing, Baby Blue, and Big Blue from 2064: Read Only Memories
A.R.I.D from The Fall
2020s
Queen (Serial Number Q5U4EX7YY2E9N), a computer in a public library who appears as a sentient being in the Dark World in Deltarune Chapter 2 (2021)
Z5 Powerlance, a retro computer that can be used to "download" games via BBS, from the game Last Call BBS (2022)
The Weapon, an AI designed to imitate Cortana to capture her for deletion in Halo Infinite.
O.R.C.A., short for Omiscient Recording Computer of Alterna, an archivial computer system created for the purpose of preserving the knowledge gathered by the surviving humans of Alterna, as well as guiding Agent 3 through the story mode of Splatoon 3.
Squid and Unicorn, two opposing AI supercomputers from Will You Snail, a platformer game developed independently by Jonas Tyroller of Grizzly Games (2022)
Board games and role-playing games
A.R.C.H.I.E. Three, the supercomputer that arose from the ashes of nuclear war to become a major player in the events of Palladium Books' Rifts
The Autochthon, the extradimensional AI which secretly control Iteration X, in White Wolf Publishing's Mage: The Ascension
The Computer, from West End Games' Paranoia role-playing game
Crime Computer, from the Milton Bradley Manhunter board game
Deus, the malevolent AI built by Renraku from Shadowrun role-playing game who took over the Renraku Arcology before escaping into the Matrix
Mirage, the oldest AI from Shadowrun, built to assist the US military in combating the original Crash Virus in 2029
Megara, a sophisticated program built by Renraku in Shadowrun, who achieved sentience after falling in love with a hacker
Omega Virus, microscopic nano-phages that build a singular intelligence (foreign AI) in the Battlestat1 computer core and take over the space station in the board game by Milton Bradley.
Unsorted works
SARA, TOM's A.I. matrix companion from Toonami
The CENTRAL SCRUTINIZER, narrator from Frank Zappa's Joe's Garage
Ritsu / Autonomous Intelligence Fixed Artillery, from Assassination Classroom
Tandy 400, Compy 386, Lappy 486, Compé, and Lappier, Strong Bad's computers in Homestar Runner (Tandy is a real company, but never produced a 400 model)
Hyper Hegel, an extremely slow computer run with burning wood in monochrom's Soviet Unterzoegersdorf universe
A.J.G.L.U. 2000 (Archie Joke Generating Laugh Unit), a running-gag from the Comics Curmudgeon, depicting a computer who does not quite understand human humor, but nonetheless is employed to write the jokes for the Archie Comics strip
Li’l Hal (colloquially known as the Auto-Responder or simply AR), a teen boy's sarcastic brain-clone-turned-sentient-chatbot that lives inside a pair of pointy anime sunglasses in Homestuck.
CADIE (Cognitive Autoheuristic Distributed-Intelligence Entity), from Google's 2009 April Fools Story
See also
Artificial intelligence in fiction
List of films about computers
Sentient computers
List of fictional robots and androids
List of fictional cyborgs
List of fictional gynoids
Further reading
References
External links
Robots in Movies – Over 600 movies with robots, sndroids, cyborgs and AI
Robots on TV – Over 300 TV series with robots, androids, cyborgs and AI
Computers in Fiction at newark.rutgers.edu
http://www.computer.org/intelligent/homepage/x2his.htm
http://technicity.net/articles/writing_the_future.htm
https://archive.today/20000929064822/http://sun.soci.niu.edu/~rslade/mnbkfc.htm – A large set of reviews of fiction that bears on computers in some aspect
List of computer names in science fiction – also includes androids, robots and aliens
Robot Hall of Fame at CMU – with fictional inductees HAL-9000 and R2-D2
Jokes about computers in science fiction
Computers
Science fiction themes
Computing-related lists | List of fictional computers | Technology | 22,190 |
31,654,139 | https://en.wikipedia.org/wiki/Robert%20Heath%20Lock | Robert Heath Lock (19 January 1879 – 26 June 1915) was an English botanist and geneticist who wrote the first English textbook on genetics.
Life
Robert Heath Lock was the son of John Bascombe Lock, a priest and Eton College schoolmaster who was later bursar of Gonville and Caius College, Cambridge. His younger brother was C. N. H. Lock. He was born at Eton College on 19 January 1879, and educated at Charterhouse School, where he was a member of a winning 8 at Bisley. He was Frank Smart Student of Botany at Gonville & Caius, where he graduated with a first class degree in the Natural Sciences Tripos in 1902. While still an undergraduate, he accompanied William Bateson abroad.
In 1902 he was appointed Scientific Assistant to the Director of the Royal Botanical Gardens, Peradeniya in Sri Lanka (then known as Ceylon), under John Christopher Willis. He returned to Cambridge in 1905 to be Curator of the Cambridge University Herbarium. He was a fellow of Caius from 1904 to 1910, taking his ScD in 1910. From 1908 to 1913 he was Assistant Director to Willis at Peradeniya, serving as Acting Director in 1909 and 1912. He specialized in the breeding of Hevea brasiliensis for rubber production. He also created a new strain of rice, "Lock's paddy".
In 1910 Lock married Bella Sidney Woolf, the sister of Leonard Woolf. They had no children.
During World War I, he was chairman of a Vegetable Drying and Fruit Preserving Committee. He was an Inspector for the Board of Agriculture and Fisheries.
Lock died in Eastbourne on 26 June 1915, aged 36, from a heart attack following influenza. He is buried with his sister and brother-in-law in the Ascension Parish Burial Ground, Cambridge. His parents are also buried there.
Textbook on genetics
Lock was the author of Recent Progress in the Study of Variation, Heredity, and Evolution, 1906. It went through five editions, with the fourth edition (1916) substantially revised by Leonard Doncaster published after Lock's death. It has been described as the first English textbook on genetics and was widely admired in America and the United Kingdom, however was essentially forgotten after World War I. The book inspired Hermann Joseph Muller and others to study genetics.
In 1907, it was positively reviewed in Nature and The American Naturalist journals. In 1908, Alfred Russel Wallace wrote supportively about the textbook:
In conclusion, I would suggest to those of my readers who are interested in the great questions associated with the name of Darwin, but who have not had the means of studying the facts either in the field or the library, that in order to obtain some real comprehension of the issue involved in the controversy now going on they should read at least one book on each side. The first I would recommend is a volume by Mr. R. H. Lock on “Variation, Heredity and Evolution” (1906) as the only recent book giving an account of the whole subject from the point of view of the Mendelians and Mutationists.
A. W. F. Edwards suggested Ronald Fisher was inspired by the book, writing:
it brought together (to quote from its chapter headings) evolution, the theory of natural selection, biometry, the theory of mutation, Mendelism, cytology, and eugenics, all in a single volume. Nowhere else could the young Fisher have found such a guide to the subjects that fascinated him over and above his student work for the Mathematical Tripos.
Lock was an advocate of Mendelian inheritance and mutationism.
Works
Studies in Plant Breeding in the Tropics, 1904
Recent Progress in the Study of Variation, Heredity, and Evolution, 1906
Rubber and Rubber Planting, 1913
References
External links
1879 births
1915 deaths
English botanists
English geneticists
Mutationism
People educated at Charterhouse School
Fellows of Gonville and Caius College, Cambridge | Robert Heath Lock | Biology | 794 |
1,675,303 | https://en.wikipedia.org/wiki/Head%20%28watercraft%29 | In sailing vessels, the head is the ship's toilet. The name derives from sailing ships in which the toilet area for the regular sailors was placed at the head or bow of the vessel.
Design
In sailing ships, the toilet was placed in the bow somewhat above the water line with vents or slots cut near the floor level allowing normal wave action to wash out the facility. Only the captain had a private toilet near his quarters, at the stern of the ship in the quarter gallery.
The plans of 18th-century naval ships do not reveal the construction of toilet facilities when the ships were first built. The Journal of Aaron Thomas aboard HMS Lapwing in the Caribbean Sea in the 1790s records that a canvas tube was attached, presumably by the ship's sailmaker, to a superstructure beside the bowsprit near the figurehead, ending just above the normal waterline.
In many modern boats, the heads look similar to seated flush toilets but use a system of valves and pumps that brings sea water into the toilet and pumps the waste out through the hull (in place of the more normal cistern and plumbing trap) to a drain. In small boats the pump is often hand operated. The cleaning mechanism is easily blocked if too much toilet paper or other fibrous material is put down the pan.
Submarine heads face the problem that at greater depths higher water pressure makes it harder to pump the waste out through the hull. As a result, early systems could be complicated, with the head fitted to the United States Navy S-class submarine being described as almost taking an engineer to operate. Making a mistake resulted in waste or seawater being forcibly expelled back into the hull of the submarine. This caused the loss of .
The toilet on the World War I British E-class submarine was considered so poor by the captain of that he preferred the crew to wait to relieve themselves until the submarine surfaced at night. As a result, many submarines only used the heads as an extra storage space for provisions.
Aboard sailing ships and during the era when all hands aboard a vessel were men, the heads received most of their use for defecation; for routine urination, however, a pissdale was easier to access and simpler to use.
References
Ship compartments
Toilets | Head (watercraft) | Biology | 452 |
3,268,136 | https://en.wikipedia.org/wiki/Border%20town | A border town is a town or city close to the boundary between two countries, states, or regions. Usually the term implies that the nearness to the border is one of the things the place is most famous for. With close proximities to a different country, diverse cultural traditions can have certain influence to the place. Border towns can have highly cosmopolitan communities, a feature they share with port cities, as traveling and trading often go through the town. They can also be flashpoints for international conflicts, especially when the two countries have territorial disputes.
Transcontinental
List of international border towns and cities
Africa
Asia
Europe
Disputed City
North America
Oceania
South America
List of internal border towns and cities
Australia
Canada
Colombia
United Kingdom
United States
See also
Border towns in the United States with portmanteau names
Cross-border town naming
Divided cities
Transborder agglomeration
List of seaports
List of Mexico–United States border crossings
List of Canada–United States border crossings
Borders
International border crossings | Border town | Physics | 200 |
11,785,669 | https://en.wikipedia.org/wiki/Trench%20shoring | Trench shoring is the process of bracing the walls of a trench to prevent collapse and cave-ins. The phrase can also be used as a noun to refer to the materials used in the process.
Several methods can be used to shore up a trench. Hydraulic shoring is the use of hydraulic pistons that can be pumped outward until they press up against the trench walls. This is typically combined with steel plate or a special heavy plywood called Finform. Another method is called beam and plate, in which steel I-beams are driven into the ground and steel plates are slid in amongst them. A similar method that uses wood planks is called soldier boarding. Hydraulics tend to be faster and easier; the other methods tend to be used for longer term applications or larger excavations.
Shoring should not be confused with shielding by means of trench shields. Shoring is designed to prevent collapse, whilst shielding is only designed to protect workers should collapse occur. Most professionals agree that shoring is the safer approach of the two.
See also
Retaining wall
References
Geotechnical shoring structures
Cuts (earthmoving) | Trench shoring | Technology | 223 |
48,300,512 | https://en.wikipedia.org/wiki/ML-154 | ML-154 (NCGC-84) is a drug which acts as a selective, non-peptide antagonist at the neuropeptide S receptor NPSR. In animal studies it decreases self-administration of alcohol in addicted rats, and lowers motivation for alcohol rewards, suggesting a potential application for NPS antagonists in the treatment of alcoholism.
See also
Neuropeptide S receptor
References
Phosphorus compounds
Sulfur compounds
Phenyl compounds
Alkene derivatives
Quaternary ammonium compounds
Bromides | ML-154 | Chemistry | 103 |
2,915,678 | https://en.wikipedia.org/wiki/Orbifold%20notation | In geometry, orbifold notation (or orbifold signature) is a system, invented by the mathematician William Thurston and promoted by John Conway, for representing types of symmetry groups in two-dimensional spaces of constant curvature. The advantage of the notation is that it describes these groups in a way which indicates many of the groups' properties: in particular, it follows William Thurston in describing the orbifold obtained by taking the quotient of Euclidean space by the group under consideration.
Groups representable in this notation include the point groups on the sphere (), the frieze groups and wallpaper groups of the Euclidean plane (), and their analogues on the hyperbolic plane ().
Definition of the notation
The following types of Euclidean transformation can occur in a group described by orbifold notation:
reflection through a line (or plane)
translation by a vector
rotation of finite order around a point
infinite rotation around a line in 3-space
glide-reflection, i.e. reflection followed by translation.
All translations which occur are assumed to form a discrete subgroup of the group symmetries being described.
Each group is denoted in orbifold notation by a finite string made up from the following symbols:
positive integers
the infinity symbol,
the asterisk, *
the symbol o (a solid circle in older documents), which is called a wonder and also a handle because it topologically represents a torus (1-handle) closed surface. Patterns repeat by two translation.
the symbol (an open circle in older documents), which is called a miracle and represents a topological crosscap where a pattern repeats as a mirror image without crossing a mirror line.
A string written in boldface represents a group of symmetries of Euclidean 3-space. A string not written in boldface represents a group of symmetries of the Euclidean plane, which is assumed to contain two independent translations.
Each symbol corresponds to a distinct transformation:
an integer n to the left of an asterisk indicates a rotation of order n around a gyration point
the asterisk, * indicates a reflection
an integer n to the right of an asterisk indicates a transformation of order 2n which rotates around a kaleidoscopic point and reflects through a line (or plane)
an indicates a glide reflection
the symbol indicates infinite rotational symmetry around a line; it can only occur for bold face groups. By abuse of language, we might say that such a group is a subgroup of symmetries of the Euclidean plane with only one independent translation. The frieze groups occur in this way.
the exceptional symbol o indicates that there are precisely two linearly independent translations.
Good orbifolds
An orbifold symbol is called good if it is not one of the following: p, pq, *p, *pq, for p, q ≥ 2, and p ≠ q.
Chirality and achirality
An object is chiral if its symmetry group contains no reflections; otherwise it is called achiral. The corresponding orbifold is orientable in the chiral case and non-orientable otherwise.
The Euler characteristic and the order
The Euler characteristic of an orbifold can be read from its Conway symbol, as follows. Each feature has a value:
n without or before an asterisk counts as
n after an asterisk counts as
asterisk and count as 1
o counts as 2.
Subtracting the sum of these values from 2 gives the Euler characteristic.
If the sum of the feature values is 2, the order is infinite, i.e., the notation represents a wallpaper group or a frieze group. Indeed, Conway's "Magic Theorem" indicates that the 17 wallpaper groups are exactly those with the sum of the feature values equal to 2. Otherwise, the order is 2 divided by the Euler characteristic.
Equal groups
The following groups are isomorphic:
1* and *11
22 and 221
*22 and *221
2* and 2*1.
This is because 1-fold rotation is the "empty" rotation.
Two-dimensional groups
The symmetry of a 2D object without translational symmetry can be described by the 3D symmetry type by adding a third dimension to the object which does not add or spoil symmetry. For example, for a 2D image we can consider a piece of carton with that image displayed on one side; the shape of the carton should be such that it does not spoil the symmetry, or it can be imagined to be infinite. Thus we have n• and *n•. The bullet (•) is added on one- and two-dimensional groups to imply the existence of a fixed point. (In three dimensions these groups exist in an n-fold digonal orbifold and are represented as nn and *nn.)
Similarly, a 1D image can be drawn horizontally on a piece of carton, with a provision to avoid additional symmetry with respect to the line of the image, e.g. by drawing a horizontal bar under the image. Thus the discrete symmetry groups in one dimension are *•, *1•, ∞• and *∞•.
Another way of constructing a 3D object from a 1D or 2D object for describing the symmetry is taking the Cartesian product of the object and an asymmetric 2D or 1D object, respectively.
Correspondence tables
Spherical
Euclidean plane
Frieze groups
Wallpaper groups
Hyperbolic plane
A first few hyperbolic groups, ordered by their Euler characteristic are:
See also
Mutation of orbifolds
Fibrifold notation - an extension of orbifold notation for 3d space groups
References
John H. Conway, Olaf Delgado Friedrichs, Daniel H. Huson, and William P. Thurston. On Three-dimensional Space Groups. Contributions to Algebra and Geometry, 42(2):475-507, 2001.
J. H. Conway, D. H. Huson. The Orbifold Notation for Two-Dimensional Groups. Structural Chemistry, 13 (3-4): 247–257, August 2002.
J. H. Conway (1992). "The Orbifold Notation for Surface Groups". In: M. W. Liebeck and J. Saxl (eds.), Groups, Combinatorics and Geometry, Proceedings of the L.M.S. Durham Symposium, July 5–15, Durham, UK, 1990; London Math. Soc. Lecture Notes Series 165. Cambridge University Press, Cambridge. pp. 438–447
John H. Conway, Heidi Burgiel, Chaim Goodman-Strauss, The Symmetries of Things 2008,
External links
A field guide to the orbifolds (Notes from class on "Geometry and the Imagination" in Minneapolis, with John Conway, Peter Doyle, Jane Gilman and Bill Thurston, on June 17–28, 1991. See also PDF, 2006)
Tegula Software for visualizing two-dimensional tilings of the plane, sphere and hyperbolic plane, and editing their symmetry groups in orbifold notation
Group theory
Generalized manifolds
Mathematical notation
John Horton Conway | Orbifold notation | Mathematics | 1,453 |
32,059,552 | https://en.wikipedia.org/wiki/George%20F.%20C.%20Griss | George François Cornelis Griss (30 January 1898, Amsterdam – 2 August 1953, Blaricum), usually cited as G. F. C. Griss, was a Dutch mathematician and philosopher, who was occupied with Hegelian idealism and Brouwers intuitionism and stated a negationless mathematics.
Griss was a student of L. E. J. Brouwer and formulated an intuitionism based on a Hegelian idealism. He obtained his Ph.D. with Roland Weitzenböck at the University of Amsterdam in July 1925. He was largely influenced by L. E. J. Brouwer, Gerrit Mannoury, Carry van Bruggen and Gerard Bolland, who brought Hegelian thought to the Netherlands. He published a number of articles about a negationless mathematics and one small book about idealistic philosophy, called Idealistische Filosofie (17 February 1946, Gouda), in which he lays down a typically Hegelian idealism, and incorporates elements from Bergson's Creative Evolution (L'Evolution créatrice).
Publications
Het volledige invariantensysteem van 2 covariante antisymmetrische tensoren van den 2den trap en een willekeurig aantal vectoren, K.A.W., Amsterdam, Verslag 34, 1925.
Differentialinvarianten von Systemen von Vektoren (Ph.D. thesis) Groningen: Noordhoff, 1925.
Differentialinvarianten von zwei kovarianten Vektoren in vier Veränderlichen, Proc. K.A.W. (Amsterdam), vol.33, 1930, pp. 176–179.
Der Existenzsatz für ein wesentliches System bei Invarianten von Differentialformen, Proc. K.A.W. (Amsterdam), vol.33, 1930, pp. 491–494.
Problemen der Invariantentheorie (public lecture) Groningen: Noordhoff, 1934.
Die Differentialinvarianten eines Systems von n relativen kovarianten Vektoren in Rn, Proc. K.A.W. (Amsterdam), vol.37, 1934, pp. 82–87.
Die Differentialinvarianten eines kovarianten symmetrischen Tensors vierter Stufe im binären Gebiet, Comp. Math. vol.1, 1934, pp. 238–247.
Differentialvarianenten von relativen Vektoren, Comp. Math. vol.1, 1935, pp. 420–428.
Die konformen Differentialinvarianten eines kovarianten symmetrischen Tensors vierter Stufe im binären Gebiet, Proc. K.A.W. (Amsterdam) vol. 39, 1936, pp. 947–955.
Negatieloze intuïtionistisch wiskunde. Proceedings ("Verslagen") Nederlandse Akademie van Wetenschappen, Afdeling Natuurkunde, Vol.LIII, no.5, 1944, pp. 261–268 (includes German, English, and French summary).
Idealistisch Filosofie, Arnhem: Van Loghum Slaterus, 1946.
Negationless intuitionistic mathematics I, Proc. K.A.W. (Amsterdam) vo.49, 1946, pp. 1127–1133.
Over de negatie, festive collection ("feestbundel") Prof. Dr. H.J. Pos, Amsterdam: Noord-Hollandse uitgeversmaatschappij, 1948, pp. 96–106.
Mathématiques, Mystique et Philosophie, Mélanges philosophiques, Libr. 10th Int. Congr. Phil. II (1948), pp. 156–175.
Logique des mathématiques intuitionistes sans négation, C. R. [Comptes Rendues] Ac. Sci. Paris, vol.227, 1948, pp. 946–948.
Sur la Négation dans les Mathématiques et la Logique, Synthese, vol.7, 1948/1949, no.1-2 pp. 71–74.
Negationless intuitionistic mathematics II, Proceedings [Koninklijke Nederlandse Akademie van Wetenschappen] [series A] Vol.LIII, no.4, 1950, pp. 456–463 or Indagationes Mathematicae, Vol.XII, Fasc.2, 1950.
Logic of negationless intuitionistic mathematics, Proceedings [Koninklijke Nederlandse Akademie van Wetenschappen] Series A, Vol.LIV, no.1, 1951, pp. 41–49.
Negationless intuitionistic mathematics III, Proceedings [Koninklijke Nederlandse Akademie van Wetenschappen] series A, Vol.LIV, no.2, 1951, pp. 193–199.
Negationless intuitionistic mathematics IV, Proceedings [Koninklijke Nederlandse Akademie van Wetenschappen] series A, Vol.LIV, no.5, 1951, pp. 452–471 or Indagationes Mathematicae, Vol.XIII, no.5, 1951.
Secondary literature
H.J. Pos: G.F.C. Griss' Idealistische Filosofie, Algemeen Nederlands Tijdschrift voor Wijsbegeerte en Psychologie waarin opgenomen de Annalen van het Genootschap voor Wetenschappelijke Philosophie, 46e Jaargang, aflevering 1, october 1953. pp. 1–7.
A. Heyting: Over de betekenis van het Wiskundige werk van G.F.C. Griss, ibidem, pp. 8–12.
A. Heyting: G.F.C. Griss and his negationless intuitionistic mathematics, Synthese, Vol. IX, Issue 2, no.2, pp. 91–96
H.J. Pos: G.F.C. Griss als wijsgerig humanist en als mens, De Nieuw Stem [1953], pp. 654–663.
B. van Rootselaar, In memoriam Dr. G.F.C. Griss, Euclides [1953?] Tijdschrift voor de Didactiek der Exacte Vakken, pp. 42–45. (Contains bibliography.)
G.F.C. Griss, 1898–1953 in the Album Academicum of the University of Amsterdam
See also
L. E. J. Brouwer
Gerard Bolland
Gerrit Mannoury
Arend Heyting
Philosophy of mind
Philosophy of mathematics
External links
1898 births
1953 deaths
20th-century Dutch mathematicians
20th-century Dutch philosophers
Intuitionism
Philosophers of mathematics
Mathematical analysts
Mathematical logicians
Scientists from Amsterdam
University of Amsterdam alumni | George F. C. Griss | Mathematics | 1,521 |
3,330,375 | https://en.wikipedia.org/wiki/Anthrax%20vaccine | Anthrax vaccines are vaccines to prevent the livestock and human disease anthrax, caused by the bacterium Bacillus anthracis.
They have had a prominent place in the history of medicine, from Pasteur's pioneering 19th-century work with cattle (the first effective bacterial vaccine and the second effective vaccine ever) to the controversial late 20th century use of a modern product to protect American troops against the use of anthrax in biological warfare. Human anthrax vaccines were developed by the Soviet Union in the late 1930s and in the US and UK in the 1950s. The current vaccine approved by the U.S. Food and Drug Administration (FDA) was formulated in the 1960s.
Currently administered human anthrax vaccines include acellular (USA, UK) and live spore (Russia) varieties. All currently used anthrax vaccines show considerable local and general reactogenicity (erythema, induration, soreness, fever) and serious adverse reactions occur in about 1% of recipients. New third-generation vaccines being researched include recombinant live vaccines and recombinant sub-unit vaccines.
Pasteur's vaccine
In the 1870s, the French chemist Louis Pasteur (1822–1895) applied his previous method of immunising chickens against chicken cholera to anthrax, which affected cattle, and thereby aroused widespread interest in combating other diseases with the same approach. In May 1881, Pasteur performed a famous public experiment at Pouilly-le-Fort to demonstrate his concept of vaccination. He prepared two groups of 25 sheep, one goat and several cows. The animals of one group were twice injected, with an interval of 15 days, with an anthrax vaccine prepared by Pasteur; a control group was left unvaccinated. Thirty days after the first injection, both groups were injected with a culture of live anthrax bacteria. All the animals in the non-vaccinated group died, while all of the animals in the vaccinated group survived. The public reception was sensational.
Pasteur publicly claimed he had made the anthrax vaccine by exposing the bacilli to oxygen. His laboratory notebooks, now in the Bibliothèque Nationale in Paris, in fact show Pasteur used the method of rival Jean-Joseph-Henri Toussaint (1847–1890), a Toulouse veterinary surgeon, to create the anthrax vaccine. This method used the oxidizing agent potassium dichromate. Pasteur's oxygen method did eventually produce a vaccine but only after he had been awarded a patent on the production of an anthrax vaccine.
The notion of a weak form of a disease causing immunity to the virulent version was not new; this had been known for a long time for smallpox. Inoculation with smallpox (variolation) was known to result in far less scarring, and greatly reduced mortality, in comparison with the naturally acquired disease. The English physician Edward Jenner (1749–1823) had also discovered (1796) the process of vaccination by using cowpox to give cross-immunity to smallpox and by Pasteur's time this had generally replaced the use of actual smallpox material in inoculation. The difference between smallpox vaccination and anthrax or chicken cholera vaccination was that the weakened form of the latter two disease organisms had been "generated artificially", so a naturally weak form of the disease organism did not need to be found. This discovery revolutionized work in infectious diseases and Pasteur gave these artificially weakened diseases the generic name "vaccines", in honor of Jenner's groundbreaking discovery. In 1885, Pasteur produced his celebrated first vaccine for rabies by growing the virus in rabbits and then weakening it by drying the affected nerve tissue.
In 1995, the centennial of Pasteur's death, The New York Times ran an article titled "Pasteur's Deception". After having thoroughly read Pasteur's lab notes, the science historian Gerald L. Geison declared Pasteur had given a misleading account of the preparation of the anthrax vaccine used in the experiment at Pouilly-le-Fort. The same year, Max Perutz published a vigorous defense of Pasteur in The New York Review of Books.
Sterne's vaccine
The Austrian-South African immunologist Max Sterne (1905–1997) developed an attenuated live animal vaccine in 1935 that is still employed and derivatives of his strain account for almost all veterinary anthrax vaccines used in the world today. Beginning in 1934 at the Onderstepoort Veterinary Research Institute, north of Pretoria, he prepared an attenuated anthrax vaccine, using the method developed by Pasteur. A persistent problem with Pasteur's vaccine was achieving the correct balance between virulence and immunogenicity during preparation. This notoriously difficult procedure regularly produced casualties among vaccinated animals. With little help from colleagues, Sterne performed small-scale experiments which isolated the "Sterne strain" (34F2) of anthrax which became, and remains today, the basis of most of the improved livestock anthrax vaccines throughout the world.
As Sterne's vaccine is a live vaccine, vaccination during use of antibiotics produces much reduced results and should be avoided. There is a withholding period after vaccination when animals cannot be slaughtered. No such period is defined for milk and there are no reports of humans being infected by products from vaccinated animals. There have been a few cases when humans accidentally self-inject the vaccine when trying to administer to a struggling animal. One case developed fever and meningitis, but it is unclear whether the illness was caused by the vaccine. Livestock anthrax vaccines are made in many countries around the world, most of which use 34F2 with saponin adjuvant.
Soviet/Russian anthrax vaccines
Anthrax vaccines were developed in the Soviet Union in the 1930s and available for use in humans by 1940. A live attenuated, unencapsulated spore vaccine became widely used for humans. It was given either by scarification or subcutaneous injection (only in emergency) and its developers claimed that it was reasonably well tolerated and showed some degree of protective efficacy against cutaneous anthrax in clinical field trials. The efficacy of the live Russian vaccine was reported to have been greater than that of either of the killed British or US anthrax vaccines (AVP and AVA, respectively) during the 1970s and '80s. The STI-1 vaccine, consisting only of freeze-dried spores, is given in a two-dose schedule, but serious side-effects restricted its use to healthy adults. It was reportedly manufactured at the George Eliava Institute of Bacteriophage, Microbiology and Virology in Tbilisi, Georgia, until 1991. As of 2008, the STI-1 vaccine remains available, and is the only human anthrax vaccine "nominally available outside national borders".
China uses a different live attenuated strain for their human vaccines, designated "A16R". The A16R vaccine is given as a suspention in 50% glycerol and distilled water. A single dose is given by scarification, followed by a booster in 6 or 12 months, then annual boosters.
British anthrax vaccines
British biochemist Harry Smith (1921–2011), working for the UK bio-weapons program at Porton Down, discovered the three anthrax toxins in 1948. This discovery was the basis of the next generation of antigenic anthrax vaccines and for modern antitoxins to anthrax. The widely used British anthrax vaccine—sometimes called Anthrax Vaccine Precipitated (AVP) to distinguish it from the similar AVA (see below)—became available for human use in 1954. This was a cell-free vaccine in distinction to the live-cell Pasteur-style vaccine previously used for veterinary purposes. It is now manufactured by Porton Biopharma Ltd, a Company owned by the UK Department of Health.
AVP is administered at primovaccination in three doses with a booster dose after six months. The active ingredient is a sterile filtrate of an alum-precipitated anthrax antigen from the Sterne strain in a solution for injection. The other ingredients are aluminium potassium sulphate, sodium chloride and purified water. The preservative is thiomersal (0.005%). The vaccine is given by intramuscular injection and the primary course of four single injections (3 injections 3 weeks apart, followed by a 6-month dose) is followed by a single booster dose given once a year. During the Gulf War (1990–1991), UK military personnel were given AVP concomitantly with the pertussis vaccine as an adjuvant to improve overall immune response and efficacy.
American anthrax vaccines
The United States undertook basic research directed at producing a new anthrax vaccine during the 1950s and '60s. The product known as Anthrax Vaccine Adsorbed (AVA)—trade name BioThrax—was licensed in 1970 by the U.S. National Institutes of Health (NIH) and in 1972 the Food and Drug Administration (FDA) took over responsibility for vaccine licensure and oversight. AVA is produced from culture filtrates of an avirulent, nonencapsulated mutant of the B. anthracis Vollum strain known as V770-NP1-R. No living organisms are present in the vaccine which results in protective immunity after 3 to 6 doses. AVA remains the only FDA-licensed human anthrax vaccine in the United States and is produced by Emergent BioSolutions, formerly known as BioPort Corporation in Lansing, Michigan. The principal purchasers of the vaccine in the United States are the Department of Defense and Department of Health and Human Services. Ten million doses of AVA have been purchased for the U.S. Strategic National Stockpile for use in the event of a mass bioterrorist anthrax attack.
In 1997, the Clinton administration initiated the Anthrax Vaccine Immunization Program (AVIP), under which active U.S. service personnel were to be immunized with the vaccine. Controversy ensued since vaccination was mandatory and GAO published reports that questioned the safety and efficacy of AVA, causing sometimes serious side effects. A Congressional report also questioned the safety and efficacy of the vaccine and challenged the legality of mandatory inoculations. Mandatory vaccinations were halted in 2004 by a formal legal injunction which made numerous substantive challenges regarding the vaccine and its safety. After reviewing extensive scientific evidence, the FDA determined in 2005 that AVA is safe and effective as licensed for the prevention of anthrax, regardless of the route of exposure. In 2006, the Defense Department announced the reinstatement of mandatory anthrax vaccinations for more than 200,000 troops and defense contractors. The vaccinations are required for most U.S. military units and civilian contractors assigned to homeland bioterrorism defense or deployed in Iraq, Afghanistan or South Korea.
Investigational anthrax vaccines
A number of experimental anthrax vaccines are undergoing pre-clinical testing, notably the Bacillus anthracis protective antigen—known as PA (see Anthrax toxin—combined with various adjuvants such as aluminum hydroxide (Alhydrogel), saponin QS-21, and monophosphoryl lipid A (MPL) in squalene/lecithin/Tween 80 emulsion (SLT). One dose of each formulation has provided significant protection (> 90%) against inhalational anthrax in rhesus macaques.
Omer-2 trial: Beginning in 1998 and running for eight years, a secret Israeli project known as Omer-2 tested an Israeli investigational anthrax vaccine on 716 volunteers of the Israel Defense Forces. The vaccine—given under a seven-dose schedule—was developed by the Nes Tziona Biological Institute. A group of study volunteers complained of multi-symptom illnesses allegedly associated with the vaccine and petitioned for disability benefits to the Defense Ministry, but were denied. In February 2009, a petition from the volunteers to disclose a report about Omer-2 was filed with the Israel's High Court against the Defense Ministry, the Israel Institute for Biological Research at Nes Tziona, the director, Avigdor Shafferman, and the IDF Medical Corps. Release of the information was requested to support further action to provide disability compensation for the volunteers.
In 2012, B. anthracis isolate H9401 was obtained from a Korean patient with gastrointestinal anthrax. The goal of the Republic of Korea is to use this strain as a challenge strain to develop a recombinant vaccine against anthrax.
References
Further reading
External links
Anthrax
Animal vaccines
Biological warfare
Vaccines
Soviet inventions
Military medicine in the Soviet Union | Anthrax vaccine | Biology | 2,687 |
142,181 | https://en.wikipedia.org/wiki/Seed%20bank | A seed bank (also seed banks, seeds bank or seed vault) stores seeds to preserve genetic diversity; hence it is a type of gene bank. There are many reasons to store seeds. One is to preserve the genes that plant breeders need to increase yield, disease resistance, drought tolerance, nutritional quality, taste, etc. of crops. Another is to forestall loss of genetic diversity in rare or imperiled plant species in an effort to conserve biodiversity ex situ. Many plants that were used centuries ago by humans are used less frequently now; seed banks offer a way to preserve that historical and cultural value. Collections of seeds stored at constant low temperature and low moisture are guarded against loss of genetic resources that are otherwise maintained in situ or in field collections. These alternative "living" collections can be damaged by natural disasters, outbreaks of disease, or war. Seed banks are considered seed libraries, containing valuable information about evolved strategies to combat plant stress, and can be used to create genetically modified versions of existing seeds. The work of seed banks often span decades and even centuries. Most seed banks are publicly funded and seeds are usually available for research that benefits the public.
Storage conditions and regeneration
Seeds are living plants and keeping them viable over the long term requires adjusting storage moisture and temperature appropriately. As they mature on the mother plant, many seeds attain an innate ability to survive drying. Survival of these so-called 'orthodox' seeds can be extended by dry, low temperature storage. The level of dryness and coldness depends mostly on the longevity that is required and the investment in infrastructure that is affordable. Practical guidelines from a US scientist in the 1950s and 1960s, James Harrington, are known as 'Thumb Rules'. The 'Hundreds Rule' guides that the sum of relative humidity and temperature (in Fahrenheit) should be less than 100 for the sample to survive five years. Another rule is that reduction of water content by 1% or temperature by will double the seed life span. Research from the 1990s showed that there is a limit to the beneficial effect of drying or cooling, so it must not be overdone.
Understanding the effect of water content and temperature on seed longevity, the Food and Agriculture division of the United Nations and a consultancy group called Bioversity International developed a set of standards for international seed banks to preserve seed longevity. The document advocates drying seeds to about 20% relative humidity, sealing seeds in high quality moisture-proof containers, and storing seeds at . These conditions are frequently referred to as 'conventional' storage protocols. Seeds from species considered most important – corn, wheat, rice, soybean, pea, tomato, broccoli, melon, sunflower, etc. are stored in this way. However, there are many species that produce seeds that do not survive the drying or low temperature of conventional storage protocols. These species must be stored cryogenically. Seeds of citrus fruits, coffee, avocado, cocoa, coconut, papaya, oak, walnut and willow are a few examples of species that should be preserved cryogenically.
Like everything, seeds eventually degrade with time. It is hard to predict when seeds lose viability and so most reputable seed banks monitor germination potential during storage. When seed germination percentage decreases below a prescribed amount, the seeds need to be replanted and fresh seeds collected for another round of long-term storage.
Seeds banks may operate in much more primitive conditions if the aim is only to maintain year-by-year seed supplies and lower costs for farmers in a particular area.
Challenges
One of the greatest challenges for seed banks is selection. Collections must be relevant and that means they must provide useful genetic diversity that is accessible to the public. Collections must also be efficient and that means they mustn't duplicate materials already in collections.
Keeping seeds alive for hundreds of years is the next biggest challenge. Orthodox seeds are amenable to 'conventional' storage protocols but there are many seed types that must be stored using nonconventional methods. Technology for these methods is rapidly advancing; local institutional infrastructure may be lacking.
Some seeds cannot be kept alive in storage and must be regenerated – planted to produce a new quantity of seeds to be stored for another length of time. Parzies et al. 2000 found that this reduced the effective population size and alleles were lost. Parzies' finding has since been taken seriously by banks around the world and has sparked further verification – regeneration is widely recognized to not preserve diversity perfectly.
Alternatives
In-situ conservation of seed-producing plant species is another conservation strategy. In-situ conservation involves the creation of National Parks, National Forests, and National Wildlife Refuges as a way of preserving the natural habitat of the targeted seed-producing organisms. In-situ conservation of agricultural resources is performed on-farm. This also allows the plants to continue to evolve with their environment through natural selection.
An arboretum stores trees by planting them at a protected site.
A less expensive, community-supported seed library can save local genetic material.
The phenomenon of seeds remaining dormant within the soil is well known and documented (Hills and Morris 1992). Detailed information on the role of such "soil seed banks" in northern Ontario, however, is extremely limited, and research is required to determine the species and abundance of seeds in the soil across a range of forest types, as well as to determine the function of the seed bank in post-disturbance vegetation dynamics. Comparison tables of seed density and diversity are presented for the boreal and deciduous forest types and the research that has been conducted is discussed. This review includes detailed discussions of: (1) seed bank dynamics, (2) physiology of seeds in a seed bank, (3) boreal and deciduous forest seed banks, (4) seed bank dynamics and succession, and (5) recommendations for initiating a seed bank study in northern Ontario.
Longevity
Seeds may be viable for hundreds and even thousands of years. The oldest carbon-14-dated seed that has grown into a viable plant was a Judean date palm seed about 2,000 years old, recovered from excavations at the palace of Herod the Great in Israel.
In February 2012, Russian scientists announced they had regenerated a narrow leaf campion (Silene stenophylla) from a 32,000-year-old seed. The seed was found in a burrow under Siberian permafrost along with 800,000 other seeds. Seed tissue was grown in test tubes until it could be transplanted to soil. This exemplifies the long-term viability of DNA under proper conditions.
Climate change
Conservation efforts such as seed banks are expected to play a greater role as climate change progresses. Seed banks offer communities a source of climate-resilient seeds to withstand changing local climates. As challenges arise from climate change, community based seed banks can improve access to a diverse selection of locally adapted crops while also enhancing indigenous understandings of plant management such as seed selection, treatment, storage, and distribution.
Facilities
There are about 6 million accessions, or samples of a particular population, stored as seeds in about 1,300 genebanks throughout the world as of 2006. This amount represents a small fraction of the world's biodiversity, and many regions of the world have not been fully explored.
The Svalbard Global Seed Vault has been built inside a sandstone mountain in a man-made tunnel on the frozen Norwegian island of Spitsbergen, which is part of the Svalbard archipelago, about from the North Pole. It is designed to survive catastrophes such as nuclear war and world war. It is operated by the Global Crop Diversity Trust. The area's permafrost will keep the vault below the freezing point of water, and the seeds are protected by 1-metre thick walls of steel-reinforced concrete. There are two airlocks and two blast-proof doors. The vault accepted the first seeds on 26 February 2008.
The Millennium Seed Bank is located in the grounds of Wakehurst Place in West Sussex, near London, UK. Established in 1996, it is the largest seed bank in the world (and will longterm be at least 100 times bigger than Svalbard Global Seed Vault), providing space for the storage of billions of seed samples in a nuclear bomb proof multi-story underground vault. Its ultimate aim being to store every plant species possible. It is already (2024) home to over 2.4 billion seeds, representing over 39,000 different species of the world’s storable seeds. Importantly they also distribute seeds to other key locations around the world, do germination tests on each species every 10 years, and other important research.
The Institute of Plant Genetic Resource in Saint Petersburg, Russia is probably the oldest and still one of the 5-6 largest in the world. It was started in 1924 by Russian geneticist and botanist Nikolai Vavilov and survived the 28-month Siege of Leningrad in World War II because several botanists starved to death rather than eat the collected seeds and potatoes.
The Australian PlantBank is located in the Australian Botanic Gardens, Mount Annan, New South Wales. It is part of the Millennium Seed Bank Project in London and incorporates the former NSW Seedbank, established in 1986 to preserve native Australian flora, especially NSW threatened species.
The Australian Grains Genebank (AGG), in Horsham, Victoria, Australia, is a national center for storing genetic material for plant breeding and research. The Genebank is in a collaboration with the Australian Seed Bank Partnership on an Australian Crop Wild Relatives project. It was officially opened in March 2014 The primary reason for the bank to be created was the extreme temperatures in the area, up to in the summer time. Because of that they had to ensure the protection of the grains all year around. The Genebank aims to collect and conserve the seeds of Australian crop wild species, that are not yet adequately represented in existing collections.
The George Hulbert Seed Vault in Wagga Wagga, New South Wales, Australia, is dedicated to the preservation of rice varieties, including some predating the Green Revolution.
Indian Seed Vault is a secure seed bank located in a high-altitude mountain pass on the Chang La in Ladakh, India. It was built in 2010 and is claimed to be the second largest in the world.
The BBA (Beej Bachao Andolan — Save the Seeds movement) began in the late 1980s in Uttarakhand, India, led by Vijay Jardhari. Seed banks were created to store native varieties of seeds.
The National Center for Genetic Resources Preservation, in Fort Collins, Colorado, is the largest seed bank in the United States.
Desert Legume Program (DELEP) in Tucson, Arizona, focuses on wild species of plants in the legume family (Fabaceae), specifically legumes from dry regions around the world. The DELEP seed bank currently has over 3,600 seed collections representing nearly 1,400 species of arid land legumes originating in 65 countries on six continents. It is backed up (at least in part) in National Center for Genetic Resources Preservation, and in the Svalbard Global Seed Vault. The DELEP seed bank is an accredited collection of the North American Plant Conservation Consortium.
The National Gene Bank of Plants of Ukraine was created in the 1990s in Ukraine. Described as one of the largest seed banks in the world, it was damaged during the Russian invasion of Ukraine in 2022 but survived in substantial part.
The INRAE Centre for Vegetable Germplasm in Avignon, France stores over 10,000 species of five vegetable crops as seeds: aubergine (eggplant), pepper, tomato, melon and lettuce collections, together with their wild or cultivated relatives. Species from the collections have geographically diverse origins, are generally well-described and fixed for traits of agronomic or scientific interest, and have available passport data.
Meise Botanical Garden houses a seed bank in Belgium. Among other things, it aims to preserve endangered and rare wild species of Belgian flora.It also includes wild beans, wild bananas and seeds of the Copper plants of Katanga.
Seed banks classification
Seed banks can be classified in three main profiles: assistentialist, productivist or preservationist. In practice, many seed banks have a combination of these three main types, and they may have different priorities depending on the context and goals of the seed bank.
Assistentialist seed banks: These seed banks primarily aim to support the needs of local communities and small-scale farmers. They focus on providing seed samples that are well-suited to local conditions and are easy to grow and maintain. They prioritize seed samples that have high yield potential, are pest and disease resistant, and can be grown with minimal inputs.
Productivist seed banks: These seed banks primarily aim to support large-scale agricultural production and commercial farming. They focus on providing seed samples that have high yield potential, are pest and disease resistant, and can be grown with minimal inputs. They prioritize seed samples that are well-suited to large-scale mechanized farming and can be grown in large quantities.
Preservationist seed banks: These seed banks primarily aim to conserve the genetic diversity of wild and domesticated plant species. They focus on preserving the genetic diversity of plant species, and make seed samples available for research and breeding programs. They prioritize seed samples that are rare, endangered, or have unique genetic characteristics.
Early concepts
In Zoroastrian mythology, Ahura Mazda instructed Yima, a legendary king of ancient Persia, to build an underground structure called a Vara to store two seeds from every kind of plant in the known world. The seeds had to come from plant specimens that were free of defects, and the structure itself had to withstand a 300-year apocalyptic winter. Some scholars have suggested that the Norse equivalent of this myth is the underground garden Odainsaker, which was intended to withstand the three-year fimbul winter preceding Ragnarok, to protect the people (and seemingly the plants) that would repopulate the world after this event.
See also
Agroecology
Biodiversity banking
Conservation movement
Gene bank
Gene pool
Germplasm
Heirloom plant
Index Seminum
International Treaty on Plant Genetic Resources for Food and Agriculture
Knowledge ark
List of conservation topics
Millennium Seed Bank Partnership
Orthodox seed
Recalcitrant seed
Seed company
Seed library
Seed saving
Seed swap
Soil seed bank
References
Further reading
147 p.
External links
Sustainablelivingsystems.org: "A Typology of Community Seed Banks"
.
Biorepositories
Conservation projects
Gene banks
Plant conservation
Plant reproduction
Seed associations
Seeds | Seed bank | Biology | 2,963 |
37,211,102 | https://en.wikipedia.org/wiki/Zeta%20Indi | Zeta Indi is a single star in the southern constellation Indus, near the northern constellation border with Microscopium. It is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 4.90. The star is located approximately 430 light years away from the Sun based on parallax. The radial velocity estimate for this object is poorly constrained, but it appears to be moving closer at the rate of around −5 km/s.
This object is an aging giant star with a stellar classification of K5III. With the supply of hydrogen at its core exhausted, the star has expanded off the main sequence and now has 45 times the girth of the Sun. It is radiating 446 times the luminosity of the Sun from its bloated photosphere at an effective temperature of 3,963 K.
References
K-type giants
Indus (constellation)
Indi, Zeta
Durchmusterung objects
198048
102790
7952 | Zeta Indi | Astronomy | 203 |
14,979,971 | https://en.wikipedia.org/wiki/Quantum%20lithography | Quantum lithography is a type of photolithography, which exploits non-classical properties of the photons, such as quantum entanglement, in order to achieve superior performance over ordinary classical lithography. Quantum lithography is closely related to the fields of quantum imaging, quantum metrology, and quantum sensing. The effect exploits the quantum mechanical state of light called the NOON state. Quantum lithography was invented at Jonathan P. Dowling's group at JPL, and has been studied by a number of groups.
Of particular importance, quantum lithography can beat the classical Rayleigh criterion for the diffraction limit. Classical photolithography has an optical imaging resolution that is limited by the wavelength of light used. For example, in the use of photolithography to mass-produce computer chips, it is desirable to produce smaller and smaller features on the chip, which classically requires moving to smaller and smaller wavelengths (ultraviolet and x-ray), which entails exponentially greater cost to produce the optical imaging systems at these extremely short optical wavelengths.
Quantum lithography exploits the quantum entanglement between specially prepared photons in the NOON state and special photoresists, that display multi-photon absorption processes to achieve the smaller resolution without the requirement of shorter wavelengths. For example, a beam of red photons, entangled 50 at a time in the NOON state, would have the same resolving power as a beam of x-ray photons.
The field of quantum lithography is in its infancy, and although experimental proofs of principle have been carried out using the Hong–Ou–Mandel effect, it is considered promising technology.
References
External links
American Institute of Physics
Introduction to Quantum Lithography
New York Times
Science News
Quantum information science
Lithography (microfabrication) | Quantum lithography | Materials_science | 372 |
1,049,191 | https://en.wikipedia.org/wiki/Equivalent%20circuit | In electrical engineering, an equivalent circuit refers to a theoretical circuit that retains all of the electrical characteristics of a given circuit. Often, an equivalent circuit is sought that simplifies calculation, and more broadly, that is a simplest form of a more complex circuit in order to aid analysis. In its most common form, an equivalent circuit is made up of linear, passive elements. However, more complex equivalent circuits are used that approximate the nonlinear behavior of the original circuit as well. These more complex circuits often are called macromodels of the original circuit. An example of a macromodel is the Boyle circuit for the 741 operational amplifier.
Examples
Thévenin and Norton equivalents
One of linear circuit theory's most surprising properties relates to the ability to treat any two-terminal circuit no matter how complex as behaving as only a source and an impedance, which have either of two simple equivalent circuit forms:
Thévenin equivalent – Any linear two-terminal circuit can be replaced by a single voltage source and a series impedance.
Norton equivalent – Any linear two-terminal circuit can be replaced by a current source and a parallel impedance.
However, the single impedance can be of arbitrary complexity (as a function of frequency) and may be irreducible to a simpler form.
DC and AC equivalent circuits
In linear circuits, due to the superposition principle, the output of a circuit is equal to the sum of the output due to its DC sources alone, and the output from its AC sources alone. Therefore, the DC and AC response of a circuit is often analyzed independently, using separate DC and AC equivalent circuits which have the same response as the original circuit to DC and AC currents respectively. The composite response is calculated by adding the DC and AC responses:
A DC equivalent of a circuit can be constructed by replacing all capacitances with open circuits, inductances with short circuits, and reducing AC sources to zero (replacing AC voltage sources by short circuits and AC current sources by open circuits.)
An AC equivalent circuit can be constructed by reducing all DC sources to zero (replacing DC voltage sources with short circuits and DC current sources with open circuits)
This technique is often extended to small-signal nonlinear circuits like tube and transistor circuits, by linearizing the circuit about the DC bias point Q-point, using an AC equivalent circuit made by calculating the equivalent small signal AC resistance of the nonlinear components at the bias point.
Two-port networks
Linear four-terminal circuits in which a signal is applied to one pair of terminals and an output is taken from another, are often modeled as two-port networks. These can be represented by simple equivalent circuits of impedances and dependent sources. To be analyzed as a two port network the currents applied to the circuit must satisfy the port condition: the current entering one terminal of a port must be equal to the current leaving the other terminal of the port. By linearizing a nonlinear circuit about its operating point, such a two-port representation can be made for transistors: see hybrid pi and h-parameter circuits.
Delta and Wye circuits
In three phase power circuits, three phase sources and loads can be connected in two different ways, called a "delta" connection and a "wye" connection. In analyzing circuits, sometimes it simplifies the analysis to convert between equivalent wye and delta circuits. This can be done with the wye-delta transform.
Li-ion batteries
The electrical behavior of a Lithium-ion battery cell is often approximated by an equivalent circuit model. Such a model consists of a voltage generator driven by the state of charge, representing the open-circuit voltage of the cell, a resistor representing the internal resistance of the cell, and some RC parallels to simulate the dynamic voltage transients.
In biology
Equivalent circuits can be used to electrically describe and model either a) continuous materials or biological systems in which current does not actually flow in defined circuits or b) distributed reactances, such as found in electrical lines or windings, that do not represent actual discrete components. For example, a cell membrane can be modelled as a capacitance (i.e. the lipid bilayer) in parallel with resistance-DC voltage source combinations (i.e. ion channels powered by an ion gradient across the membrane).
See also
Equivalent impedance transforms
Miller theorem
Lumped element model
Steinmetz equivalent circuit
References
Circuit theorems | Equivalent circuit | Physics | 896 |
7,992,786 | https://en.wikipedia.org/wiki/AmpliChip%20CYP450%20Test | AmpliChip CYP450 Test is a clinical test from Roche and part of the AmpliChip series. The test aims to find the specific gene types ( genotypes) of the patient that will determine how he or she metabolizes certain medicines, and therefore guides the doctors to prescribe the medicine suited for the best effectiveness and least side effects.
The AmpliChip CYP450 Test uses micro array technology from Affymetrix (GeneChip) to determine the genotype of the patient in terms of two cytochrome P450 enzymes: 2D6 and 2C19.
2D6 and 2C19 variability
CYP2D6 and CYP2C19 belong to the Cytochrome P450 oxidase family. CYP2D6 has over 90 variants, 2C19 has mainly three. They are responsible for the majority of the inter-individual variability in the ability to metabolize drugs.
There are four phenotypes of CYP2D6: Poor Metabolizer (PM), Intermediate Metabolizer (IM), Extensive (normal) Metabolizer (EM) and Ultrarapid Metabolizer (UM). For CYP2C19, there are only two phenotypes: PM and EM. If a substrate of the enzyme is given to the patient as a medication, and if the patient has reduced CYP2D6 or CYP2C19 activity, the patient will have elevated drug concentration in their body, and therefore severe side effects may occur. On the other hand, for the UM patient, the drug concentration might be too low to have a therapeutic effect. Thus testing the phenotype of the patient is important to help determine the optimum dosage of the drug.
How it works
The test analyzes the DNA of a patient to determine the genotype, after which predictions of the phenotype can then be made. The DNA sample comes from blood tests (as Roche suggests) or, alternatively, comes from a mouth brush called a buccal swab. The analysis has five steps after DNA is extracted from patient samples:
PCR amplification of the gene.
Fragmentation and labeling of the PCR product
Hybridization and staining on the AmpliChip DNA microarray.
Scanning the chip.
Data analysis.
FDA approval
The USFDA approved the test on December 24, 2004. The AmpliChip CYP450 test is the first FDA approved pharmacogenetic test.
Applications
Since a lot of the CYP2D6 substrates are psychiatric drugs (antidepressant and antipsychotics, for example), the AmpliChip CYP450 has been extensively used in psychiatry.
Criticism
The main criticism of the test is that the test finds out the genotype (the makeup of the gene types) of the patient, which does not necessarily cover all the phenotypes (the actual biological effect). For example, some argue that the so-called ultra-rapid metaboliser, who has extra copies of the 2D6 gene expressed, cannot be reliably tested.
Also, the test does not cover some rarer genotypes, nor genotypes that have not yet been discovered.
Also, insurance companies still do not cover the price of the test, which can cost $600–$1300 to the patient, because the test is "experimental, investigational or unproven".
External links
Official Website: https://web.archive.org/web/20110906084820/http://molecular.roche.com/assays/Pages/AmpliChipCYP450Test.aspx
Microarrays | AmpliChip CYP450 Test | Chemistry,Materials_science,Biology | 761 |
77,221,585 | https://en.wikipedia.org/wiki/8006%20aluminium%20alloy | 8006 aluminium alloy is produced using iron, manganese and copper as additives. It is commonly rolled into thin sheets or foils and is often used in heat exchangers due to its corrosion resistance. 8006 aluminium is available as plate.
Chemical composition
Applications
Aluminium 8006 is used in food packing, microelectronics, and in heat exchangers.
References
External links
Material Properties
Aluminium alloys | 8006 aluminium alloy | Chemistry | 82 |
50,019,576 | https://en.wikipedia.org/wiki/Coex%20%28material%29 | Coex is a biopolymer with flame-retardant properties derived from the functionalization of cellulosic fibers such as cotton, linen, jute, cannabis, coconut, ramie, bamboo, raffia palm, stipa, abacà, sisal, nettle and kapok. The formation of coex has been proven possible on wood and semi-synthetic fibers such as cellulose acetate, cellulose triacetate, viscose, modal, lyocell and cupro.
The material is obtained by sulfation and phosphorylation reactions on glucan units linked to each other in position 1,4. Typical reaction locations are on the secondary and tertiary hydroxyl groups of the cellulosic fiber. The chemical modification of the cellulosic fibers does not involve physical and visual alterations compared to the starting material.
in 2015 the World Textile Information Network (WTiN) declared Coex the winner of the "Future Materials Award" as the best innovation in the Home Textile category.
Properties
Coex preserves the physical and chemical characteristics of the raw material from which it is formed. The main features of Coex materials are comfort, hydrophilicity, antistatic properties, mechanical resistance and versatility in the textile sector, like all natural and semi-synthetic cellulosic fibers.
Coex materials are resistant to moths, mildew and sunlight. The flame resistant nature of Coex is unique in that it acts as a barrier to the flames rather than only delaying the spread of fire; the biopolymer fibres carbonize and therefore extinguish the flame. The resulting products are hypoallergenic and biodegradable.
References
External links
Official Website
Super Absorbent Polymer
https://www.thomasnet.com/articles/plastics-rubber/plastic-coextrusion/
Organic polymers
Biomaterials
Brand name materials | Coex (material) | Physics,Chemistry,Biology | 393 |
23,918,922 | https://en.wikipedia.org/wiki/Urban%20Wolf | Urban Wolf is an online non-verbal drama series, with 15 webisodes of 4 minutes long each.
The movie was written, produced and directed by Laurent Touil-Tartour.
The world premiere and first public screening of the show took place at the 2009 San Diego Comic-Con.
In 2009, at the 4th Annual Los Angeles Independent Television Festival Urban Wolf won the Award for Best Drama. And in 2011, during the 15th Annual Webby Awards Urban Wolf won the People's Voice Award for Best Drama. It also has been selected for the 2009 AFI DigiFest by the American Film Institute as "one of the most compelling example of new media storytelling".
On March 31, 2010, Sony Pictures Entertainment officially announces a groundbreaking worldwide distribution deal for the series. The show premiered on Sony Pictures Entertainment owned Crackle on May 13, 2010. Then Sony Pictures syndicated the series in a multi-platform footprint including: YouTube, hulu, the PlayStation Network, Google TV, the Bravia Network, Animax, AXN, AT&T, Sprint, etc.
Plot
Season 1 (2009)
The plot focuses mainly on an American tourist freshly landed at Paris airport in France who is pursued and terrorized by a malevolent security camera operator.
Awards and nominations
Awards
2011 Webby Award – Best Drama Award Winner of the 15th Annual Webby People’s Voice Awards.
2009 Independent Television Festival – Best Drama Award Winner.
2009 Dragon*Con Independent Film Festival – Staff Picks Award Winner.
Nominations
2009 American Film Institute DigiFest – Nominated as "Most Innovative Digital Media Production".
2010 Massachusetts Institute of Technology - MIT Media Lab - Center for Future Storytelling - Official Selection.
2011 Webby Award – Nominated for "Best Drama" for both Webby Award and People's Voice Award.
Honorees
2011 Webby Award – Official Honoree for "Best Individual Performance" at the 15th Annual Webby Awards.
Reception
The series has received overwhelmingly enthusiastic critical reception. Journalist and critic Hugh Hart, writing for Wired Magazine noted: "Laurent Touil-Tartour exploits sharp edits, a driving score and spare cinematography to extract maximum tension and an handsomely filmed suspense drama.” Hugh Hart also enjoyed the usage of non-verbal storytelling: "Not a word gets spoken in Urban Wolf. But even without dialogue, French filmmaker Laurent Touil-Tartour has made an unusually sophisticated spy-tech thriller.”
Critic Jandy Stone Hardesty, in her review for Row Three, said that Touil-Tartour has “a nice flair for composition and a good sense of visual storytelling, he also knows how to do good twists and suggest things rather than spell them out, something I really appreciated.” William Bibbiani, in CraveOnline, called it "an exciting little bit of filmmaking that deserves its notoriety and is worth howling about”, and Liz Shannon Miller writing in GigaOM wrote that "“Urban Wolf is a gripping thriller that stands out as proudly unique. Some of Wolf‘s execution might emulate classic 1970s thrillers, but the concept is pure 21st century, playing nimbly with issues of privacy and paranoia. When a director can make even the eating of a potato chip seem malevolent (as occurs in the yet-to-premiere episode 7), you know you’ve watching something special.”
Reviewing it for the Mingle Media TV Network, journalist Kristyn Burtt wrote: "The reason this series stands out amongst the pack is its cinematic feel and the utilization of mise en scene. You don't hear the main character utter a word until Episode 7, and boy, is it effective.”
Awarding the film a five out of five star rating, Feo Amante's film critic E.C.McMullen Jr. wrote: "The tension from episode to episode is incredible and Laurent just keeps ramping it up. With its beautiful settings (shot in Paris, France), excellent cinematography, and super tight, witty action, this could very well define the future of online cinema. I'm not kidding! URBAN WOLF is a Turbo Thrust Cat and Mouse Thriller with a V8 engine!”
Characters and cast
Urban Wolf
Actor Vincent Sze plays the role of Justin Case.
References
Further Reading
Interview with Laurent Touil-Tartour
External links
Urban Wolf's Homepage
Urban Wolf on YouTube
Internet Movie Database
on Independent Television Festival
American drama web series
YouTube original programming
Works about video games
French superhero films
Espionage television series
French spy films
Superhero science fiction web series
French web series
French spy television series | Urban Wolf | Technology | 919 |
45,189,573 | https://en.wikipedia.org/wiki/Location-based%20firearm | A location-based firearm is a gun that uses electronic technologies such as geofencing to restrict its firing to authorized locations, thereby allowing its use for protecting life and property in those locations while preventing its use in other locations for crimes such as robberies, drive-by shootings, assassinations, and massacres.
History
The first locationized gun was invented by John Martin in 1984. Although locationized guns could prevent much crime and accompanying deaths and injuries, they have not been commercially developed. An important reason for that is because legislated restrictions would be required for conventional guns, and those restrictions would be difficult to pass in some markets.
Operating principles, advantages, and technologies
The main advantage of locationized guns is that they can satisfy the right to possess arms for defense of homes and businesses while being useless for many crimes that can be committed away from those homes and businesses.
Other advantages of locationized guns depend on them having electronic circuitry and electronic control over firing. Those technologies make it relatively easy to design them to communicate with a cellular or other communication system to provide information or to be externally prevented from firing regardless of location.
Using GPS asset tracking technology can allow a locationized gun to transmit a message through a cellular network to its owner if the gun is removed from its normal location. GPS tracking could then allow its location to be known by its owner and/or law enforcement to assist in recovery of the gun.
Communications can allow police agencies to learn that a locationized gun is or was at a location of interest, thereby facilitating crime solving or allowing precautions to be taken before arriving at the location. Police agencies can also be automatically notified with information about when and where a locationized gun has been fired. Most importantly, police agencies would be able to prevent firing of the gun in the case of its theft, a police raid, shootout, threatened suicide, restraining order, etc.
Limited firing time: Early technology
A locationized gun of this type cannot be fired unless it has remained motionless for a relatively long time, e. g. 24 hours. Following that time period, there is only a relatively short time period that it can be fired after being picked up for use, e. g. 5 minutes. After its firing time period expires, it must undergo its motionless period again to allow firing. Consequently, the usefulness of this gun is restricted to locations relatively close to where it is kept, e.g. its owner's property. A demonstration model having timing and movement sensing circuitry was produced in 1989.
Restricted area of enabling signal reception: Later technologies
This type of locationized gun cannot be fired unless it is located within the range of a signal that enables firing of the gun. That signal is transmitted from a permanently or temporarily fixed location either by conductive cable or by wireless broadcast throughout the area where firing of the gun is allowed. Cable length or reception distance determines the area where firing is possible. A temporarily fixed transmitting location can be a portable base station that must remain motionless for a relatively long time period, e. g. 24 hours, before its signal transmitting begins.
Triangulation and memory of allowable firing locations: Latest technologies
A locationized gun of this type uses a system of radio frequency triangulation such as GPS or cell phone signals to determine its location. Firing is then allowed only if the gun's location is electronically determined to be within the area stored in memory of where its firing is allowed, such as a home, business, or hunting area.
See also
Smart gun
Sentry gun
References
Firearms
Geographic position | Location-based firearm | Mathematics | 717 |
11,593,376 | https://en.wikipedia.org/wiki/Doug%20Stinson | Douglas Robert Stinson (born 1956 in Guelph, Ontario) is a Canadian mathematician and cryptographer, currently a Professor Emeritus at the University of Waterloo.
Stinson received his B.Math from the University of Waterloo in 1978, his M.Sc. from Ohio State University in 1980, and his Ph.D. from the University of Waterloo in 1981. He was at the University of Manitoba from 1981 to 1989, and the University of Nebraska-Lincoln from 1990 to 1998. In 2011 he was named as a Fellow of the Royal Society of Canada.
Stinson is the author of over 300 research publications as well as the mathematics-based cryptography textbook Cryptography: Theory and Practice ().
Selected publications
See also
List of University of Waterloo people
References
External links
Doug Stinson's home page
Living people
1956 births
People from Guelph
Canadian mathematicians
Canadian computer scientists
Combinatorialists
Modern cryptographers
University of Waterloo alumni
Ohio State University alumni
Academic staff of the University of Waterloo | Doug Stinson | Mathematics | 204 |
52,821,238 | https://en.wikipedia.org/wiki/Tumble%20flap | A tumble flap is a flap housed in the intake area of many modern automotive gasoline engines to produce a swirl at right-angles to the cylinder axis. This swirling motion improves the air-fuel mixture and enhances power and torque, while at the same time lowering fuel consumption and decreasing emissions. The flaps can be actuated with pneumatic or electric power. Furthermore, the position of the flap can be controlled continuously with a feedback controller or just kept either fully closed or open. Use of a tumble flap improves the lean burn ability of a spark-ignition engine.
Operation
The set point of the tumble flap is adjusted by an electrical or vacuum-activated servo mechanism which is under the control of the engine management system. Tumble flaps are open or closed depending on engine operating states (related to engine speed and load), engine temperatures, combustion modes (characterized by air-fuel ratio), catalytic converter heating or cold start active or inactive etc.
In gasoline direct injection, stratified charge mode is used for light-load running conditions, at constant or reducing road speeds, where no acceleration is required. In this charge mode, the air-fuel mixture is concentrated around the spark plug by means of the specifically produced air flow and a special geometry of the piston, while pure air is placed near the cylinder walls. Tumble flaps are used to realize this stratified charge. The flaps remain closed during the stratified charge mode. A switchable tumble system is normally used to direct a targeted air flow. The so-called "tumble plate" divides the air inlet channel into an upper and lower half. An upstream flap allows air flow either only over the upper part or over the entire cross-section.
At higher engine speeds and torques, the tumble flap is opened to achieve a better degree of filling. During this homogeneous mode of combustion, the engine functions like a conventional fuel injection engine, but with higher efficiency due to the higher compression.
The tumble flaps are also actuated to improve cold engine idling. During scavenging the flaps are opened in order to draw much fresh air into the cylinder.
See also
Swirl flap
References
Automotive engineering | Tumble flap | Engineering | 433 |
14,415,491 | https://en.wikipedia.org/wiki/Antigen-presenting%20cell%20vaccine | An antigen-presenting cell vaccine, or an APC vaccine, is a vaccine made of antigens and antigen-presenting cells (APCs).
, the only APC vaccine approved by the American Food and Drug Administration is for prostatic acid phosphatase, a commonly over-expressed prostate cancer antigen.
References
External links
Antigen-presenting cell vaccine entry in the public domain NCI Dictionary of Cancer Terms
Vaccines | Antigen-presenting cell vaccine | Biology | 85 |
1,674,867 | https://en.wikipedia.org/wiki/Cadmium%20chloride | Cadmium chloride is a white crystalline compound of cadmium and chloride, with the formula CdCl2. This salt is a hygroscopic solid that is highly soluble in water and slightly soluble in alcohol. The crystal structure of cadmium chloride (described below), is a reference for describing other crystal structures. Also known are CdCl2•H2O and the hemipentahydrate CdCl2•2.5H2O.
Structure
Anhydrous
Anhydrous cadmium chloride forms a layered structure consisting of octahedral Cd2+ centers linked with chloride ligands. Cadmium iodide, CdI2, has a similar structure, but the iodide ions are arranged in a HCP lattice, whereas in CdCl2 the chloride ions are arranged in a CCP lattice.
Hydrates
The anhydrous form absorbs moisture from the air to form various hydrates. Three of these hydrates have been examined by X-ray crystallography.
Chemical properties
Cadmium chloride dissolves well in water and other polar solvents. It is a mild Lewis acid.
CdCl2 + 2 Cl− → [CdCl4]2−
Solutions of equimolar cadmium chloride and potassium chloride give potassium cadmium trichloride.
With large cations, it is possible to isolate the trigonal bipyramidal [CdCl5]3− ion.
Cadmium metal is soluble in molten cadmium chloride, produced by heating cadmium chloride above 568 °C. Upon cooling, the metal precipitates.
Preparation
Anhydrous cadmium chloride can be prepared by the reaction of hydrochloric acid and cadmium metal or cadmium oxide.
Cd + 2 HCl → CdCl2 + H2
The anhydrous salt can also be prepared from anhydrous cadmium acetate using hydrogen chloride or acetyl chloride.
Industrially, it is produced by the reaction of molten cadmium and chlorine gas at 600 °C.
The monohydrate, hemipentahydrate, and tetrahydrate can be produced by evaporation of the solution of cadmium chloride at 35, 20, and 0 °C respectively. The hemipentahydrate and tetrahydrate release water in air.
Uses
Cadmium chloride is used for the preparation of cadmium sulfide, used as "cadmium yellow", a brilliant-yellow stable inorganic pigment.
+ → + 2 HCl
In the laboratory, anhydrous CdCl2 can be used for the preparation of organocadmium compounds of the type R2Cd, where R is an aryl or a primary alkyl. These were once used in the synthesis of ketones from acyl chlorides:
+ 2 RMgX → + +
+ 2R'COCl → 2R'COR +
Such reagents have largely been supplanted by organocopper compounds, which are much less toxic.
Cadmium chloride is also used for photocopying, dyeing and electroplating.
Like all cadmium compounds, is highly toxic and appropriate safety precautions must be taken when handling it.
References
External links
International Chemical Safety Card 0116
IARC Monograph "Cadmium and Cadmium Compounds"
National Pollutant Inventory - Cadmium and compounds
Cadmium compounds
Chlorides
Metal halides
IARC Group 1 carcinogens | Cadmium chloride | Chemistry | 701 |
970,666 | https://en.wikipedia.org/wiki/NGC%203115 | NGC 3115 (also called the Spindle Galaxy or Caldwell 53) is a field lenticular (S0) galaxy in the constellation Sextans. The galaxy was discovered by William Herschel on February 22, 1787. At about 32 million light-years away from Earth, it is several times bigger than the Milky Way. It is a lenticular (S0) galaxy because it contains a disk and a central bulge of stars, but without a detectable spiral pattern. NGC 3115 is seen almost exactly edge-on, but was nevertheless mis-classified as elliptical. There is some speculation that NGC 3115, in its youth, was a quasar.
One supernova has been observed in NGC 3115: SN 1935B (type and mag. unknown).
Star formation
NGC 3115 has consumed most of the gas of its youthful accretion disk. It has very little gas and dust left that would trigger new star formation. The vast majority of its component stars are very old.
Black hole
In 1992 John Kormendy of the University of Hawaii and Douglas Richstone of the University of Michigan announced what was observed to be a supermassive black hole in the galaxy. Based on orbital velocities of the stars in its core, the central black hole has mass measured to be approximately one billion solar masses (). The galaxy appears to have mostly old stars and little or no activity. The growth of its black hole has also stopped.
In 2011, NASA's Chandra X-ray Observatory examined the black hole at the center of the large galaxy. A flow of hot gas toward the supermassive black hole has been imaged, making this the first time clear evidence for such a flow has been observed in any black hole. As gas flows toward the black hole, it becomes hotter and brighter.
The researchers found the rise in gas temperature begins at about 700 light years from the black hole, giving the location of the Bondi radius. This suggests that the black hole in the center of NGC 3115 has a mass of about two billion , supporting previous results from optical observations. This would make NGC 3115 the nearest billion-solar-mass black hole to Earth.
See also
NGC 5866 – another lenticular galaxy sometimes referred to as the Spindle Galaxy
References
External links
Chandra Press Release
SEDS: NGC 3115
Lenticular galaxies
Field galaxies
Sextans
3115
29265
053b
17870222
UGCA objects | NGC 3115 | Astronomy | 499 |
498,304 | https://en.wikipedia.org/wiki/Steiner%20tree%20problem | In combinatorial mathematics, the Steiner tree problem, or minimum Steiner tree problem, named after Jakob Steiner, is an umbrella term for a class of problems in combinatorial optimization. While Steiner tree problems may be formulated in a number of settings, they all require an optimal interconnect for a given set of objects and a predefined objective function. One well-known variant, which is often used synonymously with the term Steiner tree problem, is the Steiner tree problem in graphs. Given an undirected graph with non-negative edge weights and a subset of vertices, usually referred to as terminals, the Steiner tree problem in graphs requires a tree of minimum weight that contains all terminals (but may include additional vertices) and minimizes the total weight of its edges. Further well-known variants are the Euclidean Steiner tree problem and the rectilinear minimum Steiner tree problem.
The Steiner tree problem in graphs can be seen as a generalization of two other famous combinatorial optimization problems: the (non-negative) shortest path problem and the minimum spanning tree problem. If a Steiner tree problem in graphs contains exactly two terminals, it reduces to finding the shortest path. If, on the other hand, all vertices are terminals, the Steiner tree problem in graphs is equivalent to the minimum spanning tree. However, while both the non-negative shortest path and the minimum spanning tree problem are solvable in polynomial time, no such solution is known for the Steiner tree problem. Its decision variant, asking whether a given input has a tree of weight less than some given threshold, is NP-complete, which implies that the optimization variant, asking for the minimum-weight tree in a given graph, is NP-hard. In fact, the decision variant was among Karp's original 21 NP-complete problems. The Steiner tree problem in graphs has applications in circuit layout or network design. However, practical applications usually require variations, giving rise to a multitude of Steiner tree problem variants.
Most versions of the Steiner tree problem are NP-hard, but some restricted cases can be solved in polynomial time. Despite the pessimistic worst-case complexity, several Steiner tree problem variants, including the Steiner tree problem in graphs and the rectilinear Steiner tree problem, can be solved efficiently in practice, even for large-scale real-world problems.
Euclidean Steiner tree
The original problem was stated in the form that has become known as the Euclidean Steiner tree problem or geometric Steiner tree problem: Given N points in the plane, the goal is to connect them by lines of minimum total length in such a way that any two points may be interconnected by line segments either directly or via other points and line segments.
While the problem is named after Steiner, it has first been posed in 1811 by Joseph Diez Gergonne in the following form: "A number of cities are located at known locations on a plane; the problem is to link them together by a system of canals whose total length is as small as possible".
It may be shown that the connecting line segments do not intersect each other except at the endpoints and form a tree, hence the name of the problem.
The problem for has long been considered, and quickly extended to the problem of finding a star network with a single hub connecting to all of the N given points, of minimum total length.
However, although the full Steiner tree problem was formulated in a letter by Gauss, its first serious treatment was in a 1934 paper written in Czech by Vojtěch Jarník and . This paper was long overlooked, but it already contains "virtually all general properties of Steiner trees" later attributed to other researchers, including the generalization of the problem from the plane to higher dimensions.
For the Euclidean Steiner problem, points added to the graph (Steiner points) must have a degree of three, and the three edges incident to such a point must form three 120 degree angles (see Fermat point). It follows that the maximum number of Steiner points that a Steiner tree can have is , where N is the initial number of given points. (all these properties were established already by Gergonne.)
For N = 3 there are two possible cases: if the triangle formed by the given points has all angles which are less than 120 degrees, the solution is given by a Steiner point located at the Fermat point; otherwise the solution is given by the two sides of the triangle which meet on the angle with 120 or more degrees.
For general N, the Euclidean Steiner tree problem is NP-hard, and hence it is not known whether an optimal solution can be found by using a polynomial-time algorithm. However, there is a polynomial-time approximation scheme (PTAS) for Euclidean Steiner trees, i.e., a near-optimal solution can be found in polynomial time. It is not known whether the Euclidean Steiner tree problem is NP-complete, since membership to the complexity class NP is not known.
Rectilinear Steiner tree
The rectilinear Steiner tree problem is a variant of the geometric Steiner tree problem in the plane, in which the Euclidean distance is replaced with the rectilinear distance. The problem arises in the physical design of electronic design automation. In VLSI circuits, wire routing is carried out by wires that are often constrained by design rules to run only in vertical and horizontal directions, so the rectilinear Steiner tree problem can be used to model the routing of nets with more than two terminals.
Steiner tree in graphs and variants
Steiner trees have been extensively studied in the context of weighted graphs. The prototype is, arguably, the Steiner tree problem in graphs. Let be an undirected graph with non-negative edge weights c and let be a subset of vertices, called terminals. A Steiner tree is a tree in G that spans S. There are two versions of the problem: in the optimization problem associated with Steiner trees, the task is to find a minimum-weight Steiner tree; in the decision problem the edge weights are integers and the task is to determine whether a Steiner tree exists whose total weight does not exceed a predefined natural number k. The decision problem is one of Karp's 21 NP-complete problems; hence the optimization problem is NP-hard. Steiner tree problems in graphs are applied to various problems in research and industry, including multicast routing and bioinformatics.
A special case of this problem is when G is a complete graph, each vertex corresponds to a point in a metric space, and the edge weights w(e) for each e ∈ E correspond to distances in the space. Put otherwise, the edge weights satisfy the triangle inequality. This variant is known as the metric Steiner tree problem. Given an instance of the (non-metric) Steiner tree problem, we can transform it in polynomial time into an equivalent instance of the metric Steiner tree problem; the transformation preserves the approximation factor.
While the Euclidean version admits a PTAS, it is known that the metric Steiner tree problem is APX-complete, i.e., unless P = NP, it is impossible to achieve approximation ratios that are arbitrarily close to 1 in polynomial time. There is a polynomial-time algorithm that approximates the minimum Steiner tree to within a factor of ;
however, approximating within a factor is NP-hard. For the restricted case of Steiner Tree problem with distances 1 and 2, a 1.25-approximation algorithm is known. Karpinski and Alexander Zelikovsky constructed PTAS for the dense instances of Steiner Tree problems.
In a special case of the graph problem, the Steiner tree problem for quasi-bipartite graphs, S is required to include at least one endpoint of every edge in G.
The Steiner tree problem has also been investigated in higher dimensions and on various surfaces. Algorithms to find the Steiner minimal tree have been found on the sphere, torus, projective plane, wide and narrow cones, and others.
Other generalizations of the Steiner tree problem are the k-edge-connected Steiner network problem and the k''-vertex-connected Steiner network problem, where the goal is to find a k-edge-connected graph or a k-vertex-connected graph rather than any connected graph. A further well-studied generalization is the survivable network design problem (SNDP) where the task is to connect each vertex pair with a given number (possibly 0) of edge- or vertex-disjoint paths.
The Steiner problem has also been stated in the general setting of metric spaces and for possibly infinitely many points.
Approximating the Steiner tree
The general graph Steiner tree problem can be approximated by computing the minimum spanning tree of the subgraph of the metric closure of the graph induced by the terminal vertices, as first published in 1981 by Kou et al. The metric closure of a graph G is the complete graph in which each edge is weighted by the shortest path distance between the nodes in G. This algorithm produces a tree whose weight is within a factor of the weight of the optimal Steiner tree where t is the number of leaves in the optimal Steiner tree; this can be proven by considering a traveling salesperson tour on the optimal Steiner tree. This approximate solution is computable in O(|S| |V|²) polynomial time by first solving the all-pairs shortest paths problem to compute the metric closure, then by solving the minimum spanning tree problem.
Another popular algorithm to approximate the Steiner tree in graphs was published by Takahashi and Matsuyama in 1980. Their solution incrementally builds up the Steiner tree by starting from an arbitrary vertex, and repeatedly adding the shortest path from the tree to the nearest vertex in S that has not yet been added. This algorithm also has O(|S| |V|²) running time, and produces a tree whose weight is within of optimal.
In 1986, Wu et al. improved dramatically on the running time by avoiding precomputation of the all-pairs shortest paths. Instead, they take a similar approach to Kruskal's algorithm for computing a minimum spanning tree, by starting from a forest of |S| disjoint trees, and "growing" them simultaneously using a breadth-first search resembling Dijkstra's algorithm but starting from multiple initial vertices. When the search encounters a vertex that does not belong to the current tree, the two trees are merged into one. This process is repeated until only one tree remains. By using a Heap (data structure) to implement the priority queue and a disjoint-set data structure to track to which tree each visited vertex belongs, this algorithm achieves O(|E| log |V''|) running time, although it does not improve on the cost ratio from Kou et al.
A series of papers provided approximation algorithms for the minimum Steiner tree problem with approximation ratios that improved upon the ratio. This sequence culminated with Robins and Zelikovsky's algorithm in 2000 which improved the ratio to 1.55 by iteratively improving upon the minimum cost terminal spanning tree. More recently, however, Byrka et al. proved an approximation using a linear programming relaxation and a technique called iterative, randomized rounding.
Parameterized complexity of Steiner tree
The general graph Steiner tree problem is known to be fixed-parameter tractable, with the number of terminals as a parameter, by the Dreyfus-Wagner algorithm. The running time of the Dreyfus-Wagner algorithm is , where is the number of vertices of the graph and is the set of terminals. Faster algorithms exist, running in time for any or, in the case of small weights, time, where is the maximum weight of any edge. A disadvantage of the aforementioned algorithms is that they use exponential space; there exist polynomial-space algorithms running in time and time.
It is known that the general graph Steiner tree problem does not have a parameterized algorithm running in time for any , where is the number of edges of the optimal Steiner tree, unless the Set cover problem has an algorithm running in time for some , where and are the number of elements and the number of sets, respectively, of the instance of the set cover problem. Furthermore, it is known that the problem does not admit a polynomial kernel unless , even parameterized by the number of edges of the optimal Steiner tree and if all edge weights are 1.
Parameterized approximation of Steiner tree
While the graph Steiner tree problem does not admit a polynomial kernel unless parameterized by the number of terminals, it does admit a polynomial-sized approximate kernelization scheme (PSAKS): for any it is possible to compute a polynomial-sized kernel, which looses only a factor in the solution quality.
When parameterizing the graph Steiner tree problem by the number of non-terminals (Steiner vertices) in the optimum solution, the problem is W[1]-hard (in contrast to the parameterization by the number of terminals, as mentioned above). At the same time the problem is APX-complete and thus does not admit a PTAS, unless P = NP. However, a parameterized approximation scheme exists, which for any computes a -approximation in time. Also a PSAKS exists for this parameterization.
Steiner ratio
The Steiner ratio is the supremum of the ratio of the total length of the minimum spanning tree to the minimum Steiner tree for a set of points in the Euclidean plane.
In the Euclidean Steiner tree problem, the Gilbert–Pollak conjecture is that the Steiner ratio is , the ratio that is achieved by three points in an equilateral triangle with a spanning tree that uses two sides of the triangle and a Steiner tree that connects the points through the centroid of the triangle. Despite earlier claims of a proof, the conjecture is still open. The best widely accepted upper bound for the problem is 1.2134, by .
For the rectilinear Steiner tree problem, the Steiner ratio is exactly , the ratio that is achieved by four points in a square with a spanning tree that uses three sides of the square and a Steiner tree that connects the points through the center of the square. More precisely, for distance the square should be tilted at with respect to the coordinate axes, while for distance the square should be axis-aligned.
See also
Opaque forest problem
Travelling salesman problem
Notes
References
, , problems ND12 and ND13.
External links
GeoSteiner (Software for solving Euclidean and rectilinear Steiner tree problems; source available, free for non-commercial use)
SCIP-Jack (Software for solving the Steiner tree problem in graphs and 14 variants, e.g., prize-collecting Steiner tree problem; free for non-commercial use)
Fortran subroutine for finding the Steiner vertex of a triangle (i.e., Fermat point), its distances from the triangle vertices, and the relative vertex weights.
Phylomurka (Solver for small-scale Steiner tree problems in graphs)
https://www.youtube.com/watch?v=PI6rAOWu-Og (Movie: solving the Steiner tree problem with water and soap)
M. Hauptmann, M. Karpinski (2013): A Compendium on Steiner Tree Problems
NP-complete problems
Trees (graph theory)
Computational problems in graph theory
Geometric algorithms
Geometric graphs | Steiner tree problem | Mathematics | 3,110 |
2,903,305 | https://en.wikipedia.org/wiki/Gamma%20Bo%C3%B6tis | Gamma Boötis, Latinised from γ Boötis, is a binary star system in the northern constellation of Boötes the herdsman, forming the left shoulder of this asterism. The primary component has the proper name Seginus , the traditional name of the Gamma Bootis system. It has a white hue and is visible to the naked eye with a typical apparent visual magnitude of +3.03. Based on parallax measurements obtained during the Hipparcos mission, it is located at a distance of approximately 85 light-years from the Sun, but is drifting closer with a radial velocity of −32 km/s.
Properties
The double nature of this system was discovered by American astronomer S. W. Burnham in 1878, and has the discovery code BU 616. The system is resolved into a pair separated by with a magnitude difference of 9.27. The brighter primary is itself a close pair separated by , as discovered by B. L. Morgan and associates in 1975. The primary or 'A' component of this double star system is designated WDS J14321+3818 ('B' is the star UCAC2 45176266) in the Washington Double Star Catalog. Parallax measurements for component B give a distance of approximately . Gamma Boötis' two components are themselves designated WDS J14321+3818Aa (Seginus) and Ab.
[[File:GammaBooLightCurve.png|thumb|left|A light curve for Gamma Boötis, plotted from TESS data]]
The stellar classification of Gamma Boötis is A7IV+(n), matching an A-type star with somewhat "nebulous" lines due to rapid rotation. It was found to be a short-period variable star in 1914 by German astronomers P. Guthnick and R. Prager. Non-radial pulsations were detected in 1992 by Edward J. Kennelly and colleagues. It is a Delta Scuti-type variable star with a period of that varies from magnitude +3.02 down to +3.07. This dominant mode is 21.28 cycles per day with an amplitude of 0.05 in magnitude. Additional pulsations occur at 18.09, 12.02, 11.70 and 5.06 cycles per day.
These types of stars are usually on the main sequence or slightly evolved. The primary is around one billion years old with 2.1 times the mass of the Sun and five times the Sun's radius. Measurements of the projected rotational velocity range from 115 to 145 km/s, suggesting a high rate of spin. On average, the star is radiating 33.4 times the luminosity of the Sun from its photosphere at an effective temperature of .
The system displays a statistically significant infrared excess due to a circumstellar disk. A model fit to the data indicates this material has a mean temperature of 85 K and is orbiting at a distance of .
Nomenclatureγ Boötis (Latinised to Gamma Boötis) is the binary's Bayer designation. WDS J14321+3818 is the wider system's designation in the Washington Double Star Catalog. The designations of the two constituents as WDS J14321+3818A and B, and those of A's components—WDS J14321+3818Aa and Ab—derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).
Gamma Boötis bore the traditional name Ceginus (later Seginus), from cheguius or theguius, apparently Latin mistranscriptions of an Arabic rendering of Greek Boötes. Two possibilities have been suggested: from Arabic بوطس bwṭs, in one of the manuscripts of the Almagest, with undotted ب b mistaken for an undotted ث th, و w taken as w and spelled 'gu', and ط ṭ completely misread, or from Arabic بؤوتس bwʾwts, with undotted ب b mistaken for an undotted ث th, ؤ w-hamza mistaken for غ ġ, و w read as u, and undotted ن n misread as an undotted ى y and transcribed i—that is, as th-g-u-i-s with unwritten vowels (and the Latin grammatical ending -us) filled in for theguius.
In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name Seginus for WDS J14321+3818Aa on 21 August 2016 and it is now so included in the List of IAU-approved Star Names.
Gamma Boötis was listed as Haris in Bečvář, apparently derived from the Arabic name of the constellation of Boötes, Al-Haris Al-Sama meaning "the guard of the north".
In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Menkib al Aoua al Aisr (منكب العواء الأيسر – mankibu lʿawwaaʾi lʾaysar), which was translated into Latin as Humerus Sinister Latratoris, meaning 'the left shoulder of barker'.
In Chinese astronomy, Gamma Boötis is called 招搖, Pinyin: Zhāoyáo, meaning Twinkling Indicator, because this star is marking itself and standing alone in Twinkling Indicator asterism, Root mansion (see: Chinese constellation). 招搖 (Zhāoyáo), westernized into Chaou Yaou, but the name Chaou Yaou'' was designated for Beta Boötis (Nekkar) by R.H. Allen and the meaning is "to beckon, excite, or move."
Namesake
USS Seginus (AK-133) was a U.S. Navy Crater-class cargo ship named after the star.
References
External links
HR 5435
CCDM J14321+3818
A-type subgiants
Delta Scuti variables
Circumstellar disks
Binary stars
Boötes
Bootis, Gamma
BD+38 2565
Bootis, 27
127762
071075
5435
Seginus | Gamma Boötis | Astronomy | 1,333 |
2,936,080 | https://en.wikipedia.org/wiki/Noetherian%20topological%20space | In mathematics, a Noetherian topological space, named for Emmy Noether, is a topological space in which closed subsets satisfy the descending chain condition. Equivalently, we could say that the open subsets satisfy the ascending chain condition, since they are the complements of the closed subsets. The Noetherian property of a topological space can also be seen as a strong compactness condition, namely that every open subset of such a space is compact, and in fact it is equivalent to the seemingly stronger statement that every subset is compact.
Definition
A topological space is called Noetherian if it satisfies the descending chain condition for closed subsets: for any sequence
of closed subsets of , there is an integer such that
Properties
A topological space is Noetherian if and only if every subspace of is compact (i.e., is hereditarily compact), and if and only if every open subset of is compact.
Every subspace of a Noetherian space is Noetherian.
The continuous image of a Noetherian space is Noetherian.
A finite union of Noetherian subspaces of a topological space is Noetherian.
Every Hausdorff Noetherian space is finite with the discrete topology.
Proof: Every subset of X is compact in a Hausdorff space, hence closed. So X has the discrete topology, and being compact, it must be finite.
Every Noetherian space X has a finite number of irreducible components. If the irreducible components are , then , and none of the components is contained in the union of the other components.
From algebraic geometry
Many examples of Noetherian topological spaces come from algebraic geometry, where for the Zariski topology an irreducible set has the intuitive property that any closed proper subset has smaller dimension. Since dimension can only 'jump down' a finite number of times, and algebraic sets are made up of finite unions of irreducible sets, descending chains of Zariski closed sets must eventually be constant.
A more algebraic way to see this is that the associated ideals defining algebraic sets must satisfy the ascending chain condition. That follows because the rings of algebraic geometry, in the classical sense, are Noetherian rings. This class of examples therefore also explains the name.
If R is a commutative Noetherian ring, then Spec(R), the prime spectrum of R, is a Noetherian topological space. More generally, a Noetherian scheme is a Noetherian topological space. The converse does not hold, since there are non-Noetherian rings with only one prime ideal, so that Spec(R) consists of exactly one point and therefore is a Noetherian space.
Example
The space (affine -space over a field ) under the Zariski topology is an example of a Noetherian topological space. By properties of the ideal of a subset of , we know that if
is a descending chain of Zariski-closed subsets, then
is an ascending chain of ideals of Since is a Noetherian ring, there exists an integer such that
Since is the closure of Y for all Y, for all Hence
as required.
Notes
References
Algebraic geometry
Properties of topological spaces
Scheme theory
Wellfoundedness | Noetherian topological space | Mathematics | 662 |
6,301,567 | https://en.wikipedia.org/wiki/Alkalide | An alkalide is a chemical compound in which alkali metal atoms are anions (negative ions) with a charge or oxidation state of −1. Until the first discovery of alkalides in the 1970s, alkali metals were known to appear in salts only as cations (positive ions) with a charge or oxidation state of +1. These types of compounds are of theoretical interest due to their unusual stoichiometry and low ionization potentials. Alkalide compounds are chemically related to the electrides, salts in which trapped electrons are effectively the anions.
"Normal" alkali metal compounds
Alkali metals form many well-known stable salts. Sodium chloride (common table salt), , illustrates the usual role of an alkali metal such as sodium. In the empirical formula for this ionic compound, the positively charged sodium ion is balanced by a negatively charged chloride ion. The traditional explanation for stable is that the loss of one electron from elemental sodium to produce a cation with charge of +1 produces a stable closed-shell electron configuration.
Nomenclature and known cases
There are known alkalides for some of the alkali metals:
Sodide or natride,
Potasside or kalide,
Rubidide,
Caeside,
Alkalides of the other alkali metals have not yet been discovered:
Lithide,
Francide,
Examples
Normally, alkalides are thermally labile due to the high reactivity of the alkalide anion, which is theoretically able to break most covalent bonds including the carbon–oxygen bonds in a typical cryptand. The introduction of a special cryptand ligand containing amines instead of ether linkages has allowed the isolation of kalides and natrides that are stable at room temperature.
Several alkalides have been synthesized:
A compound in which hydrogen ions are encapsulated by adamanzane, known as hydrogen natride or "inverse sodium hydride" (hydrogen sodide or hydrogen natride ), has been observed.
Sodium-crypt natride, [Na(cryptand[2.2.2])]+Na−, has been observed. This salt contains both and . The cryptand isolates and stabilizes the , preventing it from being reduced by the .
Barium azacryptand-sodide, Ba2+[H5Azacryptand[2.2.2]]−Na−⋅2CH3NH2, has been synthesized.
Dimers of cationic and anionic sodium have been observed.
References
Sodium compounds
Potassium compounds
Rubidium compounds
Caesium compounds
Anions
Alkali metals | Alkalide | Physics,Chemistry | 541 |
145,438 | https://en.wikipedia.org/wiki/Meta-Object%20Facility | The Meta-Object Facility (MOF) is an Object Management Group (OMG) standard for model-driven engineering. Its purpose is to provide a type system for entities in the CORBA architecture and a set of interfaces through which those types can be created and manipulated.
MOF may be used for domain-driven software design and object-oriented modelling.
Overview
MOF was developed to provide a type system for use in the CORBA architecture, a set of schemas by which the structure, meaning and behaviour of objects could be defined, and a set of CORBA interfaces through which these schemas could be created, stored and manipulated.
MOF is designed as a four-layered architecture. It provides a meta-meta model at the top layer, called the M3 layer. This M3-model is the language used by MOF to build metamodels, called M2-models. The most prominent example of a Layer 2 MOF model is the UML metamodel, the model that describes the UML itself. These M2-models describe elements of the M1-layer, and thus M1-models. These would be, for example, models written in UML. The last layer is the M0-layer or data layer. It is used to describe real-world objects.
Beyond the M3-model, MOF describes the means to create and manipulate models and metamodels by defining CORBA interfaces that describe those operations. Because of the similarities between the MOF M3-model and UML structure models, MOF metamodels are usually modeled as UML class diagrams.
File formats
A conversion from MOF specification models (M3-, M2-, or M1-Layer) to W3C XML and XSD are specified by the XMI (ISO/IEC 19503) specification. XMI is an XML-based exchange format for models.
From MOF to Java™ there is the Java Metadata Interchange (JMI) specification by Java Community Process.
It also provides specs to make easier automatic CORBA IDL interfaces generation.
Metamodeling architecture
MOF is a closed metamodeling architecture; it defines an M3-model, which conforms to itself. MOF allows a strict meta-modeling architecture; every model element on every layer is strictly in correspondence with a model element of the layer above. MOF only provides a means to define the structure, or abstract syntax of a language or of data. For defining metamodels, MOF plays exactly the role that EBNF plays for defining programming language grammars. MOF is a Domain Specific Language (DSL) used to define metamodels, just as EBNF is a DSL for defining grammars. Similarly to EBNF, MOF could be defined in MOF.
In short, MOF uses the notion of MOF::Classes (not to be confused with UML::Classes), as known from object orientation, to define concepts (model elements) on a metalayer. MOF may be used to define object-oriented metamodels (as UML for example) as well as non object-oriented metamodels (e.g. a Petri net or a Web Service metamodel).
As of May 2006, the OMG has defined two compliance points for MOF:
EMOF for Essential MOF
CMOF for Complete MOF
In June 2006, a request for proposal was issued by OMG for a third variant, SMOF (Semantic MOF).
The variant ECore that has been defined in the Eclipse Modeling Framework is more or less aligned on OMG's EMOF.
Another related standard is OCL, which describes a formal language that can be used to define model constraints in terms of predicate logic.
QVT, which introduces means to query, view and transform MOF-based models, is a very important standard, approved in 2008. See Model Transformation Language for further information.
International standard
MOF is an international standard:
MOF 2.4.2
ISO/IEC 19508:2014 Information technology — Object Management Group Meta Object Facility (MOF) Core
MOF 1.4
ISO/IEC 19502:2005 Information technology — Meta Object Facility (MOF)
MOF can be viewed as a standard to write metamodels, for example in order to model the abstract syntax of Domain Specific Languages. Kermeta is an extension to MOF allowing executable actions to be attached to EMOF meta-models, hence making it possible to also model a DSL operational semantics and readily obtain an interpreter for it.
JMI defines a Java API for manipulating MOF models.
OMG's MOF is not to be confused with the Managed Object Format (MOF) defined by the Distributed Management Task Force (DMTF) in section 6 of the Common Information Model (CIM) Infrastructure Specification, version 2.5.0.
See also
Common Warehouse Metamodel
Domain-specific language
Kermeta
KM3
Metamodeling
Metadata
Model-driven architecture
OGML
Platform-specific model
QVT
SPEM
XML Metadata Interchange
References
Further reading
Official MOF specification from OMG
Ralph Sobek, MOF Specifications Documents
Johannes Ernst, What is metamodeling?
Woody Pidcock, What are the differences between a vocabulary, a taxonomy, a thesaurus, an ontology, and a meta-model?
Anna Gerber and Kerry Raymond, MOF to EMF and Back Again.
Weaving Executability into Object-Oriented Meta-Languages
MOF Support for Semantic Structures RFP Request For Proposal on SMOF
External links
OMG's MetaObject Facility
Specification languages
Data modeling
Unified Modeling Language
ISO standards | Meta-Object Facility | Engineering | 1,172 |
20,227,013 | https://en.wikipedia.org/wiki/Kashinhou | Kashinhou (化審法), short for , ("Law Concerning the Examination and Regulation of Manufacture, etc. of Chemical Substances") (Showa Act No. 117, 昭和48年法律第117号) is the current Chemicals and dangerous substances regulation law in Japan. The more concise abbreviated name is , or "Chemical Substances Control Law". This law featured the world's first new chemical pre-examination system.
Coverage
This law was established to provide a framework to examine the import, manufacture, and use of industrial chemicals and refractory organic substances for persistence and health consequences, as well as the necessary legal restrictions in order to achieve those aims.
History
The law has its origins in 1968, with an illness related to polychlorinated biphenyls poisoning in the Kanemi Oil Incident. In 1973, this law was established, radically overturning a prevailing attitude that long term contaminants bioaccumulating in humans was not problematic. Refractory organic substances, highly enriched uranium, and substances that possess long term toxicity to humans were classified as Section 1 Chemical Substances. Section 1 items were banned from manufacture or importation.
In 1986, a Section 2 Chemical Substances was added, which included trichloroethylene and tetrachloroethylene, which had contaminated groundwater. Questionable chemical substances that did not fall into above categories were introduced into a Section 2 Questionable Chemical substances category.
In 1999, the government ministries were reorganized, and the Ministry of the Environment was added as an overseer to the precursor ministries of the current Ministry of Health, Labour and Welfare, Ministry of Economy, Trade and Industry.
In 2003, under pressure from the Organisation for Economic Co-operation and Development, a third Section was created to surveillance of chemical substances harmful to flora and fauna but not to humans.
Regulation, policing, and surveillance of other laws, namely the Poisonous and Deleterious Substance Control Law, Stimulant Control Law, and Narcotics and Psychotropics Control Law were transferred to the current ministries as mentioned above.
Example of Chemical inventories in various countries/regions
Verordnung (EG) Nr. 1907/2006 (REACH)
AICS - Australian Inventory of Chemical Substances
DSL - Canadian Domestic Substances List
NDSL - Canadian Non-Domestic Substances List
KECL (Korean ECL) - Korean Existing Chemicals List
ENCS (MITI) - Japanese Existing and New Chemical Substances
PICCS - Philippine Inventory of Chemicals and Chemical Substances
TSCA - US Toxic Substances Control Act
SWISS - Giftliste 1
SWISS - Inventory of Notified New Substances
See also
Toxic Substances Control Act of 1976
EU REACH regulation
References
Health law in Japan
Toxicology | Kashinhou | Environmental_science | 549 |
172,384 | https://en.wikipedia.org/wiki/Lichenology | Lichenology is the branch of mycology that studies the lichens, symbiotic organisms made up of an intimate symbiotic association of a microscopic alga (or a cyanobacterium) with a filamentous fungus. Lichens are chiefly characterized by this symbiosis.
Study of lichens draws knowledge from several disciplines: mycology, phycology, microbiology and botany. Scholars of lichenology are known as lichenologists. Study of lichens is conducted by both professional and amateur lichenologists.
Methods for species identification include reference to single-access keys on lichens. An example reference work is Lichens of North America (2001) by Irwin M. Brodo, Sylvia Sharnoff and Stephen Sharnoff and that book's 2016 expansion, Keys to Lichens of North America: Revised and Expanded by the same three authors joined by Susan Laurie-Bourque.
A chemical spot test can be used to detect the presence of certain lichen products which can be characteristic of a given lichen species. Some components of certain lichens may also fluoresce under ultraviolet light, providing another form of lichen identification test.
Lichenologists may also study the growth and growth rate of lichens, lichenometry, the role of lichens in nutrient cycling, the ecological role of lichens in biological soil crusts, the morphology of lichens, their anatomy and physiology, and ethnolichenology topics including the study of edible lichens. As with any other field of study, lichenology has its own set of rules for taxonomic nomenclature and its own set of other terminology.
History
The beginnings
Lichens as a group have received less attention in classical treatises on botany than other groups although the relationship between humans and some species has been documented from early times. Several species have appeared in the works of Dioscorides, Pliny the Elder and Theophrastus although the studies are not very deep. During the first centuries of the modern age they were usually put forward as examples of spontaneous generation and their reproductive mechanisms were totally ignored. For centuries naturalists had included lichens in diverse groups until in the early 18th century a French researcher Joseph Pitton de Tournefort in his Institutiones Rei Herbariae grouped them into their own genus. He adopted the Latin term lichen, which had already been used by Pliny who had imported it from Theophrastus but up until then this term had not been widely employed. The original meaning of the Greek word λειχήν (leichen) was moss that in its turn derives from the Greek verb λείχω (liekho) to suck because of the great ability of these organisms to absorb water. In its original use the term signified mosses, liverworts as well as lichens. Some forty years later Dillenius in his Historia Muscorum made the first division of the group created by Tournefort separating the sub-families Usnea, Coralloides and Lichens in response to the morphological characteristics of the lichen thallus.
After the revolution in taxonomy brought in by Linnaeus and his new system of classification lichens are retained in the Plant Kingdom forming a single group Lichen with eight divisions within the group according to the morphology of the thallus. The taxonomy of lichens was first intensively investigated by the Swedish botanist Erik Acharius (1757–1819), who is therefore sometimes named the "father of lichenology". Acharius was a student of Carl Linnaeus. Some of his more important works on the subject, which marked the beginning of lichenology as a discipline, are:
Lichenographiae Suecia prodromus (1798)
Methodus lichenum (1803)
Lichenographia universalis (1810)
Synopsis methodica lichenum (1814)
Later lichenologists include the American scientists Vernon Ahmadjian and Edward Tuckerman and the Russian evolutionary biologist Konstantin Merezhkovsky, as well as amateurs such as Louisa Collings.
Over the years research shed new light into the nature of these organisms still classified as plants. A controversial issue surrounding lichens since the early 19th century is their reproduction. In these years a group of researchers faithful to the tenets of Linnaeus considered that lichens reproduced sexually and had sexual reproductive organs, as in other plants, independent of whether asexual reproduction also occurred. Other researchers only considered asexual reproduction by means of Propagules.
19th century
Against this background appeared the Swedish botanist Erik Acharius disciple of Linnaeus, who is today considered the father of lichenology, starting the taxonomy of lichens with his pioneering study of Swedish lichens in Lichenographiae Suecicae Prodromus of 1798 or in his Synopsis Methodica Lichenum, Sistens omnes hujus Ordinis Naturalis of 1814. These studies and classifications are the cornerstone of subsequent investigations. In these early years of structuring the new discipline various works of outstanding scientific importance appeared such as Lichenographia Europaea Reformata published in 1831 by Elias Fries or Enumeratio Critico Lichenum Europaeorum 1850 by Ludwig Schaerer in Germany.
But these works suffer from being superficial and mere lists of species without further physiological studies. It took until the middle of the 19th century for research to catch up using biochemical and physiological methods. In Germany and Johann Bayrhoffer, in France Edmond Tulasne and Camille Montagne, in Russia Fedor Buhse, in England William Allport Leighton and in the United States Edward Tuckerman began to publish works of great scientific importance.
Scientific publications settled many unknown facts about lichens. In the French publication Annales des Sciences Naturelles in an article of 1852 "Memorie pour servir a l'Histoire des Lichens Organographique et Physiologique" by Edmond Tulasne, the reproductive organs or apothecia of lichens was identified.
These new discoveries were becoming increasingly contradictory for scientists. The apothecium reproductive organ being unique to fungi but absent in other photosynthetic organisms. With improvements in microscopy, algae were identified in the lichen structure, which heightened the contradictions. At first the presence of algae was taken as being due to contamination due to collection of samples in damp conditions and they were not considered as being in a symbiotic relation with the fungal part of the thallus. That the algae continued to multiply showed that they were not mere contaminants.
It was Anton de Bary a German mycologist who specialised in phytopathology who first suggested in 1865 that lichens were merely the result of parasitism of various fungi of the ascomycetes group by nostoc type algae and others. Successive studies such as those carried out by Andrei Famintsyn and Baranetzky in 1867 showed no dependence of the algal component upon the lichen thallus and that the algal component could live independently of the thallus. It was in 1869 that Simon Schwendener demonstrated that all lichens were the result of fungal attack on the cells of algal cells and that all these algae also exist free in nature. This researcher was the first to recognise the dual nature of lichens as a result of the capture of the algal component by the fungal component. In 1873 Jean-Baptiste Edouard Bornet concluded form studying many different lichen species that the relationship between fungi and algae was purely symbiotic. It was also established that algae could associate with many different fungi to form different lichen phenotypes.
20th century
In 1909 the Russian lichenologist Konstantin Mereschkowski presented a research paper "The Theory of two Plasms as the basis of Symbiogenesis, A new study on the Origin of Organisms", which aims to explain a new theory of Symbiogenesis by lichens and other organisms as evidenced by his earlier work "Nature and Origin of Chromatophores in the Plant Kingdom". These new ideas can be studied today under the title of the Theory of Endosymbiosis.
Despite the above studies the dual nature of lichens remained no more than a theory until in 1939 the Swiss researcher Eugen A Thomas was able to reproduce in the laboratory the phenotype of the lichen Cladonia pyxidata by combining its two identified components.
During the 20th century botany and mycology were still attempting to solve the two main problems surrounding lichens. On the one hand the definition of lichens and the relationship between the two symbionts and the taxonomic position of these organisms within the plant and fungal kingdoms. There appeared numerous renowned researchers within the field of lichenology such as Henry Nicollon des Abbayes, William Alfred Weber, Antonina Georgievna Borissova, Irwin M. Brodo, and George Albert Llano.
Lichenology has found applications beyond biology itself in the field of geology in a technique known as lichenometry where the age of an exposed surface can be found by studying the age of lichens growing on them. Age dating in this way can be absolute or relative because the growth of these organisms can be arrested under various conditions. The technique provides an average age of the older individual lichens providing a minimum age of the medium being studied. Lichenometry relies upon the fact that the maximum diameter of the largest thallus of an epilithic lichen growing on a substrate is directly proportional to the time from first exposure of the area to the environment as seen in studies by Roland Beschel in 1950 and is especially useful in areas exposed for less than 1000 years. Growth is greatest in the first 20 to 100 years with 15–50 mm growth per year and less in the following years with average growth of 2–4 mm per year.
The difficulty of giving a definition applicable to every known lichen has been debated since lichenologists first recognised the dual nature of lichens. In 1982 the International Association for Lichenology convened a meeting to adopt a single definition of lichen drawing on the proposals of a committee. The chairman of this committee was the renowned researcher Vernon Ahmadjian. The definition finally adopted was that lichen could be considered as the association between a fungus and a photosynthetic symbiont resulting in a thallus of specific structure.
Such a simple a priori definition soon brought criticism from various lichenologists and there soon emerged reviews and suggestions for amendments. For example, David L. Hawksworth considered the definition imperfect because it is impossible to determine which one thallus is of a specific structure since thalli changed depending upon the substrate and conditions in which they developed. This researcher represents one of the main trends among lichenologists who consider it impossible to give a single definition to lichens since they are a unique type of organism.
Today studies in lichenology are not restricted to the description and taxonomy of lichens but have application in various scientific fields. Especially important are studies on environmental quality that are made through the interaction of lichens with their environment. Lichen is extremely sensitive to various air pollutants, especially to sulphur dioxide, which causes acid rain and prevents water absorption.
Lichens in pharmacology
Although several species of lichen have been used in traditional medicine it was not until the early 20th century that modern science became interested in them. The discovery of various substances with antibacterial action in lichen thalli was essential for scientists to become aware of the possible importance of these organisms to medicine. From the 1940s there appeared various works by the noted microbiologist Rufus Paul Burkholder who demonstrated antibacterial action of lichens of the genus Usnea against Bacillus subtilis and Sarcina lutea. Studies showed that the substance that inhibited growth of bacteria was usnic acid. Something similar occurred with the substance Ramelina synthesised by the lichen Ramalina reticulata, nevertheless, these substances proved ineffective against Gram negative bacteria such as Escherichia coli and Pseudomonas. With these investigations the number of antibacterial substances and possible drug targets known to be produced by lichens increased ergosterol, usnic acid etc.
Interest in the potential of substances synthesised by lichens increased with the end of World War II along with the growing interest in all antibiotic substances. In 1947 antibacterial action was identified in extracts of Cetraria islandica and the compounds identified as responsible for bacterial inhibition were shown to be d-protolichosteric acid and d-1-usnic acid. Further investigations have identified novel antibacterial substances, Alectosarmentin or Atranorin.
Antibacterial action of substances produced by lichens is related to their ability to disrupt bacterial proteins with a subsequent loss of bacterial metabolic capacity. This is possible due to the action of lichen phenolics such as usnic acid derivatives.
From the 1950s the lichen product usnic acid was the object of most antitumour research. These studies revealed some in vitro antitumour activity by substances identified in two common lichens Peltigera leucophlebia and Collema flaccidum.
Recent work in the field of applied biochemistry has shown some antiviral activity with some lichen substances. In 1989 K Hirabayashi presented his investigations on inhibitory lichen polysaccharides in HIV infection.
Bibliography
"Protocols in Lichenology: Culturing, Biochemistry, Ecophysiology and Use in Biomonitoring" (Springer Lab Manuals, Kraner, Ilse, Beckett, Richard and Varma, Ajit (28 Nov 2001)
Lichenology in the British Isles, 1568–1975: An Historical and Biographical Survey, D. L. Hawksworth and M. R. D. Seaward (Dec 1977)
"Lichenology: Progress and Problems" (Special Volumes/Systematics Association) Denis Hunter Brown et al. (10 May 1976)
Lichenology in Indian Subcontinent, Dharani Dhar Awasthi (1 Jan 2000)
Lichenology in Indian Subcontinent 1966–1977, Ajay Singh (1980)
CRC Handbook of Lichenology, Volume II: v.2, Margalith Galun (30 Sep 1988)
A Textbook of General Lichenology, Albert Schneider (24 May 2013)
Horizons in Lichenology D. H. Dalby (1988)
Bibliography of Irish Lichenology, M. E. Mitchell (Nov 1972)
Diccionario de Liquenologia/Dictionary of Lichenology, Kenneth Allen Hornak (1998)
"Progress and Problems in Lichenology in the Eighties: Proceedings" (Bibliotheca Lichenologica), Elisabeth Peveling (1987)
A Textbook of General Lichenology with Descriptions and Figures of the Genera Occurring in the North Eastern United States, Albert Schneider (Mar 2010)
The Present Status and Potentialities of the Lichenology in China, Liu Hua Jie (1 Jan 2000)
Lichens to Biomonitor the Environment, Shukla, D. K. Vertika, Upreti and Bajpai, Rajesh (Aug 2013)
Lichenology and Bryology in the Galapagos Islands with Checklists of the Lichens and Bryophytes thus far Reported, William A. Weber (1966)
Flechten Follmann: Contributions to Lichenology in Honour of Gerhard Follmann, Gerhard Follmann, F. J. A. Daniels, Margot Schultz and Jorge Peine (1995)
Environmental Lichenology: Biomonitoring Trace Element Air Pollution, Joyce E. Sloof (1993)
The Journal of the Hattori Botanical Laboratory: Devoted to Bryology and Lichenology, Zennosuke Iwatsuki (1983)
Contemporary Lichenology and Lichens of Western Oregon, W. Clayton Fraser (1968)
Irish Lichenology 1858–1880: Selected Letters of Isaac Carroll, Theobald Jones, Charles Larbalestier (1996)
Lichens from West of Hudson's Bay (Lichens of Arctic America Vol. 1), John W. Thompson (1953)
Les Lichens - Morphologie, Biologie, Systematique, Fernand Moreau (1927)
"Eric Acharius and his Influence on English Lichenology" (Botany Bulletins), David J. Galloway (Jul 1988)
"Lichenographia Thompsoniana: North American Lichenology in Honour of John W. Thompson", M. G. Gleen (May 1998)
"Monitoring with Lichens-Proceedings of the NATO Advanced Research Workshop", Nimis, Pier Luigi, Scheidegger, Christoph and Wolseley, Patricia (Dec 2001)
Contributions to Lichenology: In Honour of A. Henssen, H. M. Jahns and A. Henssen (1990)
Studies in Lichenology with Emphasis on Chemotaxonomy, Geography and Phytochemistry: Festschrift Christian Leuckert, Johannes Gunther Knoph, Kunigunda Schrufer and Harry J. M. Sipman (1995)
Swedish Lichenology: Dedicated to Roland Moberg, Jan Erik Mattsson, Mats Wedin and Inga Hedberg (Sep 1999)
Index of Collectors in Knowles the Lichens of Ireland (1929) and Porter's Supplement: with a Conspectus of Lichen, M. E. Mitchell, Matilda C. Knowles and Lilian Porter (1998)
Biodeterioration of Stone Surfaces: Lichens and Biofilms as Weathering Agents of Rocks and Cultural Heritage, Larry St. Clair and Mark Seaward (Oct 2011)
The Lichen Symbiosis, Vernon Ahmadjian (Aug 1993)
Lichen Biology, Thomas H. Nash (Jan 2008)
Fortschritte der Chemie organischer Naturstoffe/ Progress in the Chemistry of Organic Natural Products, S. Hunek (Oct 2013)
Notable lichenologists
Lichen collections
British Lichen Society
Botanische Staatssammlung München
Canadian Museum of Nature
Centraalbureau voor Schimmelcultures
National Botanical Research Institute (CSIR), India
Iowa State University, Ada Hayden Herbarium, Ames, Iowa
National Museum Cardiff
Natural History Museum, London
New York Botanical Garden
Royal Botanic Garden, Edinburgh
Royal Botanic Gardens, Kew, London
University of Michigan Herbarium, Ann Arbor, Michigan
University of Wisconsin-Madison Herbarium, Madison, Wisconsin
Ulster Museum, Belfast
See also
Outline of lichens
Acharius Medal, an award in lichenology
Footnotes
References
External links
American Bryological and Lichenological Society
Belgium, Luxembourg and Northern France, Lichens of
British Lichen Society
Central European Bryological and Lichenological Society (Ger)
Checklists of Lichens and Lichenolous Fungi
Chilean Lichens (Spa)
Czech Bryological and Lichenological Society (Cze)
French Lichenological Society (Fre)
Guide to using a Lichen-Based Index to Assess Nitrogen Air Quality
Identifying North American Lichens a Guide to the Literature
International Association for Lichenology
Irish Lichens
Italian Lichenological Society (Ita)
Japanese Lichenological Society (Eng)
Japanese Lichenological Society (Eng)
Lichenological Resources (Rus)
Lichen Herbarium University of Oslo
Lichenland Oregon State University
Links to Lichens and Lichenologists
Lichens of Ireland Project
LichenPortal.org - The Consortium of Lichen Herbaria
Microscopy of Lichens (Ger)
Netherlands Bryological and Lichenological Society (nl)
National Biodiversity Gateway
Nordic Lichen Society (Eng)
North American Lichens
Paleo-Lichenology (Ger)
Russian Lichens (Rus)
Scottish Lichens
Swedish Lichens Lief & Anita Stridvall
Swiss Bryological and Lichenological Society (Ger)
Tropical Lichens
UK Lichens
Branches of biology
Branches of mycology
Fungi and humans
Mycology | Lichenology | Biology | 4,161 |
8,173,034 | https://en.wikipedia.org/wiki/Omega%20loop | The omega loop is a non-regular protein structural motif, consisting of a loop of six or more amino acid residues and any amino acid sequence. The defining characteristic is that residues that make up the beginning and end of the loop are close together in space with no intervening lengths of regular secondary structural motifs. It is named after its shape, which resembles the upper-case Greek letter Omega (Ω).
Structure
Omega loops, being non-regular, non-repeating secondary structural units, have a variety of three-dimensional shapes. Omega loop shapes are analyzed to identify recurring patterns in dihedral angles and overall loop shape to help identify potential roles in protein folding and function.
Since loops are almost always at the protein surface, it is often assumed that these structures are flexible; however, different omega loops exhibit ranges of flexibility across different time scales of protein motion and have been identified as playing a role in the folding of some proteins, including HIV-1 reverse transcriptase; cytochrome c; and nucleases.
Function
Omega loops can contribute to protein function. For example, omega loops can help stabilize interactions between protein and ligand, such as in the enzyme triose phosphate isomerase, and can directly affect protein function in other enzymes. A heritable coagulation disorder is caused by a single-site mutation in an omega loop of protein C.
Likewise, omega loops play an interesting role in the function of the beta-lactamases: mutations in the "omega loop region" of a beta-lactamase can change its specific function and substrate profile, perhaps due to an important functional role of the correlated dynamics of the region.
Cytochrome c
Omega loops have long been recognized also for their importance in the function and folding of the protein cytochrome c, contributing both key functional residues and well as important dynamic properties. Many researchers have studied omega loop function and dynamics in specific protein systems using a so-called "loop swap" approach, in which loops are swapped between (usually) homologous proteins.
References
Protein structural motifs | Omega loop | Biology | 413 |
312,881 | https://en.wikipedia.org/wiki/Action%20%28physics%29 | In physics, action is a scalar quantity that describes how the balance of kinetic versus potential energy of a physical system changes with trajectory. Action is significant because it is an input to the principle of stationary action, an approach to classical mechanics that is simpler for multiple objects. Action and the variational principle are used in Feynman's formulation of quantum mechanics and in general relativity. For systems with small values of action similar to the Planck constant, quantum effects are significant.
In the simple case of a single particle moving with a constant velocity (thereby undergoing uniform linear motion), the action is the momentum of the particle times the distance it moves, added up along its path; equivalently, action is the difference between the particle's kinetic energy and its potential energy, times the duration for which it has that amount of energy.
More formally, action is a mathematical functional which takes the trajectory (also called path or history) of the system as its argument and has a real number as its result. Generally, the action takes different values for different paths. Action has dimensions of energy × time or momentum × length, and its SI unit is joule-second (like the Planck constant h).
Introduction
Introductory physics often begins with Newton's laws of motion, relating force and motion; action is part of a completely equivalent alternative approach with practical and educational advantages. However, the concept took many decades to supplant Newtonian approaches and remains a challenge to introduce to students.
Simple example
For a trajectory of a ball moving in the air on Earth the action is defined between two points in time, and as the kinetic energy (KE) minus the potential energy (PE), integrated over time.
The action balances kinetic against potential energy.
The kinetic energy of a ball of mass is where is the velocity of the ball; the potential energy is where is the gravitational constant. Then the action between and is
The action value depends upon the trajectory taken by the ball through and . This makes the action an input to the powerful stationary-action principle for classical and for quantum mechanics. Newton's equations of motion for the ball can be derived from the action using the stationary-action principle, but the advantages of action-based mechanics only begin to appear in cases where Newton's laws are difficult to apply. Replace the ball with an electron: classical mechanics fails but stationary action continues to work. The energy difference in the simple action definition, kinetic minus potential energy, is generalized and called the Lagrangian for more complex cases.
Planck's quantum of action
The Planck constant, written as or when including a factor of , is called the quantum of action. Like action, this constant has unit of energy times time. It figures in all significant quantum equations, like the uncertainty principle and the de Broglie wavelength. Whenever the value of the action approaches the Planck constant, quantum effects are significant.
History
Pierre Louis Maupertuis and Leonhard Euler working in the 1740s developed early versions of the action principle. Joseph Louis Lagrange clarified the mathematics when he invented the calculus of variations. William Rowan Hamilton made the next big breakthrough, formulating Hamilton's principle in 1853. Hamilton's principle became the cornerstone for classical work with different forms of action until Richard Feynman and Julian Schwinger developed quantum action principles.
Definitions
Expressed in mathematical language, using the calculus of variations, the evolution of a physical system (i.e., how the system actually progresses from one state to another) corresponds to a stationary point (usually, a minimum) of the action.
Action has the dimensions of [energy] × [time], and its SI unit is joule-second, which is identical to the unit of angular momentum.
Several different definitions of "the action" are in common use in physics. The action is usually an integral over time. However, when the action pertains to fields, it may be integrated over spatial variables as well. In some cases, the action is integrated along the path followed by the physical system.
The action is typically represented as an integral over time, taken along the path of the system between the initial time and the final time of the development of the system:
where the integrand L is called the Lagrangian. For the action integral to be well-defined, the trajectory has to be bounded in time and space.
Action (functional)
Most commonly, the term is used for a functional which takes a function of time and (for fields) space as input and returns a scalar. In classical mechanics, the input function is the evolution q(t) of the system between two times t1 and t2, where q represents the generalized coordinates. The action is defined as the integral of the Lagrangian L for an input evolution between the two times:
where the endpoints of the evolution are fixed and defined as and . According to Hamilton's principle, the true evolution qtrue(t) is an evolution for which the action is stationary (a minimum, maximum, or a saddle point). This principle results in the equations of motion in Lagrangian mechanics.
Abbreviated action (functional)
In addition to the action functional, there is another functional called the abbreviated action. In the abbreviated action, the input function is the path followed by the physical system without regard to its parameterization by time. For example, the path of a planetary orbit is an ellipse, and the path of a particle in a uniform gravitational field is a parabola; in both cases, the path does not depend on how fast the particle traverses the path.
The abbreviated action (sometime written as ) is defined as the integral of the generalized momenta,
for a system Lagrangian along a path in the generalized coordinates :
where and are the starting and ending coordinates.
According to Maupertuis's principle, the true path of the system is a path for which the abbreviated action is stationary.
Hamilton's characteristic function
When the total energy E is conserved, the Hamilton–Jacobi equation can be solved with the additive separation of variables:
where the time-independent function W(q1, q2, ..., qN) is called Hamilton's characteristic function. The physical significance of this function is understood by taking its total time derivative
This can be integrated to give
which is just the abbreviated action.
Action of a generalized coordinate
A variable Jk in the action-angle coordinates, called the "action" of the generalized coordinate qk, is defined by integrating a single generalized momentum around a closed path in phase space, corresponding to rotating or oscillating motion:
The corresponding canonical variable conjugate to Jk is its "angle" wk, for reasons described more fully under action-angle coordinates. The integration is only over a single variable qk and, therefore, unlike the integrated dot product in the abbreviated action integral above. The Jk variable equals the change in Sk(qk) as qk is varied around the closed path. For several physical systems of interest, Jk is either a constant or varies very slowly; hence, the variable Jk is often used in perturbation calculations and in determining adiabatic invariants. For example, they are used in the calculation of planetary and satellite orbits.
Single relativistic particle
When relativistic effects are significant, the action of a point particle of mass m travelling a world line C parametrized by the proper time is
If instead, the particle is parametrized by the coordinate time t of the particle and the coordinate time ranges from t1 to t2, then the action becomes
where the Lagrangian is
Action principles and related ideas
Physical laws are frequently expressed as differential equations, which describe how physical quantities such as position and momentum change continuously with time, space or a generalization thereof. Given the initial and boundary conditions for the situation, the "solution" to these empirical equations is one or more functions that describe the behavior of the system and are called equations of motion.
Action is a part of an alternative approach to finding such equations of motion. Classical mechanics postulates that the path actually followed by a physical system is that for which the action is minimized, or more generally, is stationary. In other words, the action satisfies a variational principle: the principle of stationary action (see also below). The action is defined by an integral, and the classical equations of motion of a system can be derived by minimizing the value of that integral.
The action principle provides deep insights into physics, and is an important concept in modern theoretical physics. Various action principles and related concepts are summarized below.
Maupertuis's principle
In classical mechanics, Maupertuis's principle (named after Pierre Louis Maupertuis) states that the path followed by a physical system is the one of least length (with a suitable interpretation of path and length). Maupertuis's principle uses the abbreviated action between two generalized points on a path.
Hamilton's principal function
Hamilton's principle states that the differential equations of motion for any physical system can be re-formulated as an equivalent integral equation. Thus, there are two distinct approaches for formulating dynamical models.
Hamilton's principle applies not only to the classical mechanics of a single particle, but also to classical fields such as the electromagnetic and gravitational fields. Hamilton's principle has also been extended to quantum mechanics and quantum field theory—in particular the path integral formulation of quantum mechanics makes use of the concept—where a physical system explores all possible paths, with the phase of the probability amplitude for each path being determined by the action for the path; the final probability amplitude adds all paths using their complex amplitude and phase.
Hamilton–Jacobi equation
Hamilton's principal function is obtained from the action functional by fixing the initial time and the initial endpoint while allowing the upper time limit and the second endpoint to vary. The Hamilton's principal function satisfies the Hamilton–Jacobi equation, a formulation of classical mechanics. Due to a similarity with the Schrödinger equation, the Hamilton–Jacobi equation provides, arguably, the most direct link with quantum mechanics.
Euler–Lagrange equations
In Lagrangian mechanics, the requirement that the action integral be stationary under small perturbations is equivalent to a set of differential equations (called the Euler–Lagrange equations) that may be obtained using the calculus of variations.
Classical fields
The action principle can be extended to obtain the equations of motion for fields, such as the electromagnetic field or gravitational field.
Maxwell's equations can be derived as conditions of stationary action.
The Einstein equation utilizes the Einstein–Hilbert action as constrained by a variational principle. The trajectory (path in spacetime) of a body in a gravitational field can be found using the action principle. For a free falling body, this trajectory is a geodesic.
Conservation laws
Implications of symmetries in a physical situation can be found with the action principle, together with the Euler–Lagrange equations, which are derived from the action principle. An example is Noether's theorem, which states that to every continuous symmetry in a physical situation there corresponds a conservation law (and conversely). This deep connection requires that the action principle be assumed.
Path integral formulation of quantum field theory
In quantum mechanics, the system does not follow a single path whose action is stationary, but the behavior of the system depends on all permitted paths and the value of their action. The action corresponding to the various paths is used to calculate the path integral, which gives the probability amplitudes of the various outcomes.
Although equivalent in classical mechanics with Newton's laws, the action principle is better suited for generalizations and plays an important role in modern physics. Indeed, this principle is one of the great generalizations in physical science. It is best understood within quantum mechanics, particularly in Richard Feynman's path integral formulation, where it arises out of destructive interference of quantum amplitudes.
Modern extensions
The action principle can be generalized still further. For example, the action need not be an integral, because nonlocal actions are possible. The configuration space need not even be a functional space, given certain features such as noncommutative geometry. However, a physical basis for these mathematical extensions remains to be established experimentally.
See also
Calculus of variations
Functional derivative
Functional integration
Hamiltonian mechanics
Lagrangian
Lagrangian mechanics
Measure (physics)
Noether's theorem
Path integral formulation
Principle of least action
Principle of maximum entropy
Some actions:
Nambu–Goto action
Polyakov action
Bagger–Lambert–Gustavsson action
Einstein–Hilbert action
References
Further reading
The Cambridge Handbook of Physics Formulas, G. Woan, Cambridge University Press, 2010, .
Dare A. Wells, Lagrangian Dynamics, Schaum's Outline Series (McGraw-Hill, 1967) , A 350-page comprehensive "outline" of the subject.
External links
Principle of least action interactive Interactive explanation/webpage
Lagrangian mechanics
Hamiltonian mechanics
Calculus of variations
Dynamics (mechanics) | Action (physics) | Physics,Mathematics | 2,670 |
36,378,227 | https://en.wikipedia.org/wiki/Diskcomp | In computing, diskcomp is a command used for comparing the complete contents of a floppy disk to another one.
Overview
The command is used on DOS, Digital Research FlexOS, IBM/Toshiba 4690 OS, SISNE plus, IBM OS/2 and Microsoft Windows. It is available in MS-DOS versions 3.2 and later and IBM PC DOS releases 1 and later. Digital Research DR DOS 6.0 and Datalight ROM-DOS also include an implementation of the command. The FreeDOS version was developed by Michal Meller.
The diskcomp command does not work with hard disk drives, CDs, network drives, Zip drives, or USB flash drives, etc. It also does not allow comparison from 3.5 inch drive to 5.25 inch drives, and vice versa. The source and target drive must be the same size.
Examples
Compare floppy disks in drive A: and drive B:
diskcomp a: b:
If the computer has only one floppy disk drive (in this case drive A:), it is still possible to compare two disks:
diskcomp a: a:
The diskcomp command will prompt to insert each disk, as needed.
The software outputs "Compare OK" if no differences are found, and "Compare error on side [number], track [number]" upon detecting a difference.
References
Further reading
External links
diskcomp | Microsoft Docs
Computer Hope: MS-DOS and Windows command line diskcomp command
External DOS commands
OS/2 commands | Diskcomp | Technology | 310 |
4,027,813 | https://en.wikipedia.org/wiki/Planar%20ternary%20ring | In mathematics, an algebraic structure consisting of a non-empty set and a ternary mapping may be called a ternary system. A planar ternary ring (PTR) or ternary field is special type of ternary system used by Marshall Hall to construct projective planes by means of coordinates. A planar ternary ring is not a ring in the traditional sense, but any field gives a planar ternary ring where the operation is defined by . Thus, we can think of a planar ternary ring as a generalization of a field where the ternary operation takes the place of both addition and multiplication.
There is wide variation in the terminology. Planar ternary rings or ternary fields as defined here have been called by other names in the literature, and the term "planar ternary ring" can mean a variant of the system defined here. The term "ternary ring" often means a planar ternary ring, but it can also simply mean a ternary system.
Definition
A planar ternary ring is a structure where is a set containing at least two distinct elements, called 0 and 1, and is a mapping which satisfies these five axioms:
;
;
, there is a unique such that : ;
, there is a unique , such that ; and
, the equations have a unique solution .
When is finite, the third and fifth axioms are equivalent in the presence of the fourth.
No other pair (0', 1') in can be found such that still satisfies the first two axioms.
Binary operations
Addition
Define . The structure is a loop with identity element 0.
Multiplication
Define . The set is closed under this multiplication. The structure is also a loop, with identity element 1.
Linear PTR
A planar ternary ring is said to be linear if .
For example, the planar ternary ring associated to a quasifield is (by construction) linear.
Connection with projective planes
Given a planar ternary ring , one can construct a projective plane with point set P and line set L as follows: (Note that is an extra symbol not in .)
Let
, and
.
Then define, , the incidence relation in this way:
Every projective plane can be constructed in this way, starting with an appropriate planar ternary ring. However, two nonisomorphic planar ternary rings can lead to the construction of isomorphic projective planes.
Conversely, given any projective plane π, by choosing four points, labelled o, e, u, and v, no three of which lie on the same line, coordinates can be introduced in π so that these special points are given the coordinates: o = (0,0), e = (1,1), v = () and u = (0). The ternary operation is now defined on the coordinate symbols (except ) by y = T(x,a,b) if and only if the point (x,y) lies on the line which joins (a) with (0,b). The axioms defining a projective plane are used to show that this gives a planar ternary ring.
Linearity of the PTR is equivalent to a geometric condition holding in the associated projective plane.
Intuition
The connection between planar ternary rings (PTRs) and two-dimensional geometries, specifically projective and affine geometries, is best described by examining the affine case first. In affine geometry, points on a plane are described using Cartesian coordinates, a method that is applicable even in non-Desarguesian geometries — there, coordinate-components can always be shown to obey the structure of a PTR. By contrast, homogeneous coordinates, typically used in projective geometry, are unavailable in non-Desarguesian contexts. Thus, the simplest analytic way to construct a projective plane is to start with an affine plane and extend it by adding a "line at infinity"; this bypasses homogeneous coordinates.
In an affine plane, when the plane is Desarguesian, lines can be represented in slope-intercept form . This representation extends to non-Desarguesian planes through the ternary operation of a PTR, allowing a line to be expressed as . Lines parallel to the y-axis are expressed by .
We now show how to derive the analytic representation of a general projective plane given at the start of this section. To do so, we pass from the affine plane, represented as , to a representation of the projective plane , by adding a line at infinity. Formally, the projective plane is described as , where represents an affine plane in Cartesian coordinates and includes all finite points, while denotes the line at infinity. Similarly, is expressed as . Here, is an affine line which we give its own Cartesian coordinate system, and consists of a single point not lying on that affine line, which we represent using the symbol .
Related algebraic structures
PTR's which satisfy additional algebraic conditions are given other names. These names are not uniformly applied in the literature. The following listing of names and properties is taken from .
A linear PTR whose additive loop is associative (and thus a group ), is called a cartesian group. In a cartesian group, the mappings
, and
must be permutations whenever . Since cartesian groups are groups under addition, we revert to using a simple "+" for the additive operation.
A quasifield is a cartesian group satisfying the right distributive law:
.
Addition in any quasifield is commutative.
A semifield is a quasifield which also satisfies the left distributive law:
A planar nearfield is a quasifield whose multiplicative loop is associative (and hence a group). Not all nearfields are planar nearfields.
Notes
References
Algebraic structures
Projective geometry | Planar ternary ring | Mathematics | 1,200 |
22,615,157 | https://en.wikipedia.org/wiki/List%20of%20building%20and%20structure%20collapses | This is a list of structural failures and collapses of buildings and other structures including bridges, dams, and radio masts/towers.
Antiquity to the Middle Ages
17th–19th centuries
1900–1949
1950–1979
1980–1999
2000–2009
2010–2019
2020–present
See also
Structural integrity and failure
List of aircraft structural failures
List of bridge failures
List of dam failures
List of catastrophic collapses of broadcast masts and towers
References
External links
These Are Some Of The Worst Architectural Disasters in History
Near-misses and failure part 1
Near-misses and failure part 2
How to Avoid Catastrophe
Engineering failures
History of structural engineering
Building and structure | List of building and structure collapses | Technology,Engineering | 124 |
17,119,657 | https://en.wikipedia.org/wiki/Pharmacoinformatics | Drug discovery and development requires the integration of multiple scientific and technological disciplines. These include chemistry, biology, pharmacology, pharmaceutical technology and extensive use of information technology. The latter is increasingly recognised as Pharmacoinformatics. Pharmacoinformatics relates to the broader field of bioinformatics.
Introduction
The main idea behind the field is to integrate different informatics branches (e.g. bioinformatics, chemoinformatics, immunoinformatics, etc.) into a single platform, resulting in a seamless process of drug discovery. The first reference of the term "Pharmacoinformatics" can be found in the year of 1993.
The first dedicated department for Pharmacoinformatics was established at the National Institute Of Pharmaceutical Education And Research, S.A.S. Nagar, India in 2003. This has been followed by different universities worldwide including a program by European universities named the European Pharmacoinformatics Initiative (Europin).
Definition
Pharmacoinformatics is also referred to as pharmacy informatics. According to the article "Pharmacy Informatics: What You Need to Know Now" by the University of Illinois at Chicago Pharmacoinformatics may be defined as: “the scientific field that focuses on medication-related data and knowledge within the continuum of healthcare systems.” It is the application of computers to the storage, retrieval and analysis of drug and prescription information. Pharmacy informaticists work with pharmacy information management systems that help the pharmacist safe decisions about patient drug therapies with respect to, medical insurance records, drug interactions, as well as prescription and patient information.
Pharmacy informatics can be thought of as a sub-domain of the larger professional discipline of health informatics. Health informatics is the study of interactions between people, their work processes and engineered systems within health care with a focus on pharmaceutical care and improved patient safety. For example, the Health Information Management Systems Society (HIMSS) defines pharmacy informatics as, "the scientific field that focuses on medication-related data and knowledge within the continuum of healthcare systems - including its acquisition, storage, analysis, use and dissemination - in the delivery of optimal medication-related patient care and health outcomes"
See also
Software programs for pharmacy workflow management
References
Pharmacology
Pharmaceutical industry
Drug discovery
Cheminformatics
Bioinformatics | Pharmacoinformatics | Chemistry,Engineering,Biology | 485 |
1,675,462 | https://en.wikipedia.org/wiki/System%20Center%20Operations%20Manager | System Center Operations Manager (SCOM) is a cross-platform data center monitoring system for operating systems and hypervisors. It uses a single interface that shows state, health, and performance information of computer systems. It also provides alerts generated according to some availability, performance, configuration, or security situation being identified. It works with Microsoft Windows Server and Unix-based hosts.
History
The product began as a network management system called SeNTry ELM, which was developed by the British company Serverware Group plc. In June 1998 the intellectual property rights were bought by Mission Critical Software, Inc. who renamed the product Enterprise Event Manager. Mission Critical undertook a complete rewrite of the product, naming the new version OnePoint Operations Manager (OOM). Mission Critical Software merged with NetIQ in early 2000, and sold the rights of the product to Microsoft in October 2000. It was later renamed into Microsoft Operations Manager (MOM) - in 2003, Microsoft began work on the next version of MOM: It was called Microsoft Operations Manager 2005 and was released in August 2004. Service Pack 1 for MOM 2005 was released in July 2005 with support for Windows 2003 Service Pack 1 and SQL Server 2000 Service Pack 4. It was also required to support SQL Server 2005 for the operational and reporting database components. The development for the next version—at this time its codename was “MOM V3”—began in 2005. Microsoft renamed the product System Center Operations Manager and released System Center Operations Manager 2007 in March 2007. System Center Operations Manager 2007 was designed from a fresh code base, and although sharing similarities to Microsoft Operations Manager, is not an upgrade from the previous versions.
2009
In May 2009 System Center Operations Manager 2007 had a so-called “R2” release - the general enhancement was cross platform support for UNIX and Linux servers. Instead of publishing individual service packs, bug fixes to the product after System Center Operations Manager 2007 R2 were released in the form of so-called cumulative updates (CUs).
Central concepts
The basic idea is to place a piece of software, an agent, on the computer to be monitored. The agent watches several sources on that computer, including the Windows Event Log, for specific events or alerts generated by the applications executing on the monitored computer. Upon alert occurrence and detection, the agent forwards the alert to a central SCOM server. This SCOM server application maintains a database that includes a history of alerts. The SCOM server applies filtering rules to alerts as they arrive; a rule can trigger some notification to a human, such as an e-mail or a pager message, generate a network support ticket, or trigger some other workflow intended to correct the cause of the alert in an appropriate manner.
SCOM uses the term management pack to refer to a set of filtering rules specific to some monitored application. While Microsoft and other software vendors make management packages available for their products, SCOM also provides for authoring custom management packs. While an administrator role is needed to install agents, configure monitored computers and create management packs, rights to simply view the list of recent alerts can be given to any valid user account.
Several SCOM servers can be aggregated together to monitor multiple networks across logical Windows domain and physical network boundaries. In previous versions of Operations Manager, a web service was employed to connect several separately-managed groups to a central location. As of Operations Manager 2007, a web service is no longer used. Rather, a direct TCP connection is used, making use of port 5723 for these communications.
Integration with Microsoft Azure
To monitor servers which are running at Microsofts Cloud Infrastructure Azure it is possible to enable Log Analytics Data Sources which are collecting and sending their data to on premises SCOM Management Servers.
In November 2020 Microsoft announced the plan to make SCOM a fully cloud managed Instance at their Azure Environment, Codename was "Aquila".
The Command Shell
Since Operations Manager 2007 the product includes an extensible command line interface called The Command Shell, which is a customized instance of the Windows PowerShell that provides interactive and script-based access to Operations Manager data and operations.
Management Pack
SCOM can be extended by importing management packs (MPs) which define how SCOM monitors systems. By default, SCOM only monitors basic OS-related services, but new MPs can be imported to monitor services such as SQL servers, SharePoint, Apache, Tomcat, VMware and SUSE Linux.
Many Microsoft products have MPs that are released with them, and many non-Microsoft software companies write MPs for their own products as well.
Whilst a fair amount of IT infrastructure is monitored using currently available MPs, new MPs can be created by end-users in order to monitor what is not already covered.
Management Pack creation is possible with the System Center Operations Manager 2007 R2 Resource Kit, Visual Studio with Authoring Extensions and Visio MP Designer.
Versions
See also
Microsoft System Center
Official SCOM Build Version List
System Center Configuration Manager
System Center Data Protection Manager
System Center Virtual Machine Manager
Microsoft Servers
Oracle Enterprise Manager
IBM Director
References
Literature
External links
System Center Operations Manager
Microsoft Tech Net guide on MOM
Microsoft Operations Manager SDK (in MSDN)
Introducing System Center Operations Manager 2007 A tutorial by David Chappell, Chappell & Associates
Operations Manager 2007 R2 Management Pack Authoring Guide (from UK TechNet)
System Center Central (System Center community)
TechNet Ramp Up: Learn how to install, implement and administer Operations Manager 2007 R2.
Blog of Blake Drumm
Blog of Kevin Holman regarding SCOM
Blog of Kevin Justin
Blog of Leon Laude for System Center
Blog of Tom Ziegler
Blog of Udish Mudiar
Windows Server System
Information technology management | System Center Operations Manager | Technology | 1,154 |
58,855,040 | https://en.wikipedia.org/wiki/Eppendorf%20%26%20Science%20Prize%20for%20Neurobiology | The Eppendorf & Science Prize for Neurobiology is a neurobiology prize that is awarded annually by Science magazine (published by American Association for the Advancement of Science) and underwritten by Eppendorf AG, laboratory device and supply company. Entrees are reviewed by editors from Science magazine and the top 10% are forwarded to the judging panel. The judging panel is chaired by the Neuroscience Editor of Science and the remaining judges are nominated from the Society for Neuroscience. The award was created in 2002 to promote the work of promising new neurobiologists with cash grants to support their careers. Each applicant must submit a 1000-word essay explaining the focus and motivation for their last three years of work. The winner is awarded $25,000 and the scientist's winning essay is then published in Science (the winning essay and the essays of the other finalists are all published on Science Online).
List (2013–)
See also
List of neuroscience awards
References
Science-related lists
Neuroscience awards | Eppendorf & Science Prize for Neurobiology | Technology | 202 |
392,579 | https://en.wikipedia.org/wiki/Hilbert%27s%20seventh%20problem | Hilbert's seventh problem is one of David Hilbert's list of open mathematical problems posed in 1900. It concerns the irrationality and transcendence of certain numbers (Irrationalität und Transzendenz bestimmter Zahlen).
Statement of the problem
Two specific equivalent questions are asked:
In an isosceles triangle, if the ratio of the base angle to the angle at the vertex is algebraic but not rational, is then the ratio between base and side always transcendental?
Is always transcendental, for algebraic and irrational algebraic ?
Solution
The question (in the second form) was answered in the affirmative by Aleksandr Gelfond in 1934, and refined by Theodor Schneider in 1935. This result is known as Gelfond's theorem or the Gelfond–Schneider theorem. (The restriction to irrational b is important, since it is easy to see that is algebraic for algebraic a and rational b.)
From the point of view of generalizations, this is the case
of the general linear form in logarithms, which was studied by Gelfond and then solved by Alan Baker. It is called the Gelfond conjecture or Baker's theorem. Baker was awarded a Fields Medal in 1970 for this achievement.
See also
Hilbert number or Gelfond–Schneider constant
References
Bibliography
External links
English translation of Hilbert's original address
07 | Hilbert's seventh problem | Mathematics | 279 |
11,420,905 | https://en.wikipedia.org/wiki/Hepatitis%20C%20virus%203%27X%20element | The hepatitis C virus 3′X element is an RNA element which contains three stem-loop structures that are essential for replication.
See also
Hepatitis C alternative reading frame stem-loop
Hepatitis C stem-loop IV
Hepatitis C virus stem-loop VII
Hepatitis C virus (HCV) cis-acting replication element (CRE)
References
External links
Cis-regulatory RNA elements
Hepatitis C virus | Hepatitis C virus 3'X element | Chemistry | 77 |
74,773,534 | https://en.wikipedia.org/wiki/Jet%20fire | A jet fire is a high temperature flame of burning fuel released under pressure in a particular orientation. The material burned is a continuous stream of flammable gas, liquid or a two-phase mixture. A jet fire is a significant hazard in process and storage plants which handle or keep flammable fluids under pressure. The heat flux of the jet flame can cause rapid mechanical failure thereby compromising structural integrity and leading to incident escalation.
Context
The Piper Alpha disaster in 1988 demonstrated how the accidental release of hydrocarbon can lead to the catastrophic failure of an installation with the rupture of major pipeline risers. Jet fires impinged on vessels, pipework and firewalls. Under these conditions the fireproofing material was compromised within a few minutes rather than one to two hours, which had been specified. Even without direct impingement, the high thermal radiation emitted by jet flames also affected plant and would have been fatal to personnel.
Characteristics
A jet fire, also known as a spray fire if the fuel is a liquid or liquefied gas, is a turbulent diffusion flame of flammable material. The characteristics of a jet fire depend on a number of factors. These include: fuel composition; release conditions; release rate; release geometry; direction; and ambient wind conditions.
For full details of the mechanism and structure of jet fires see High Pressure Jet.
Some characteristics of specific jet fires are:
Sonic releases of natural gas are characterized by high velocity, low buoyancy flames that are relatively non-luminous with low radiative energy,
A jet flame of higher hydrocarbons is lazy, buoyant, luminous, with the presence of black smoke at the tail of the flame, they are highly radiative,
The surface emissive power (SEP) of jet flames is in the order of 200 kW/m2 to 400 kW/m2. Such flames have a temperature of 1350 °C. These high heat fluxes can readily compromise the integrity of structures and vessels and can lead to mechanical failure of plant and equipment.
A jet fires is a particular hazard to personnel. People are able to survive and escape from exposure to heat fluxes less than 5 kW/m2, while higher fluxes can be fatal.
Designing for jet fires
Process plant is generally protected by a pressure relief system. However, local heating of a pressure vessel by a jet fire may compromise the integrity of the vessel before the pressure relief device operates. The measures taken for protection against jet fires are as follows:
Prevention of leaks using effective maintenance
Flange orientation and elimination
Blowdown systems, to reduce the inventory and pressure in the plant
Isolation of leaks
Robust external insulation
Emergency response
Water deluge can reduce the heat loading of plant so that its temperature is maintained below that at which failure occurs, or that the temperature rise is sufficiently reduced such that shutdown and depressurization can take place.
Older plants may have been sized on an earlier version of the American Petroleum Institute's Pressure-Relieving and Depressuring Systems standard, which did not include consideration of jet fires.
The international standard publication ISO 22899 (Determination of the Resistance to Jet Fires of Passive Fire Protection Materials) sets requirements for the specification of passive fire protection against jet fires.
See also
High pressure jet
Process hazard analysis
Process safety
References
Industrial fires and explosions
Process safety
Types of fire
Combustion | Jet fire | Chemistry,Engineering | 674 |
55,233,259 | https://en.wikipedia.org/wiki/Yttralox | Yttralox is a transparent ceramic consisting of yttria (Y2O3) containing approximately 10% thorium dioxide (ThO2). It was one of the first transparent ceramics produced, and was invented in 1966 by Richard C. Anderson at the General Electric Research Laboratory while sintering mixtures of rare earth minerals.
Properties
Yttralox is a solid solution of thorium dioxide in yttria. The thorium dioxide additive affects the growth of grains during densification, leading to improved optical transparency. Uncontrolled grain growth allows a few grains to grow larger than the others, trapping pores inside them. The additive increases the grain boundary hardness more than the internal grain hardness. This causes porosity to remain on grain boundaries rather than becoming trapped inside grains, allowing them to be eliminated later in the sintering process. This greatly improves the material's optical transparency, because porosity causes light scattering. Porosities as low as one part per million were reported. The resulting grain size was in the range 10–50 μm.
Yttralox was marketed as being "transparent as glass", has a melting point twice as high, and transmits frequencies in the near infrared band as well as visible light. However, it has little plasticity at high temperatures and low thermal conductivity, giving it a thermal shock performance little better than common glass.
Uses
Commercialization was limited because Yttralox required high sintering temperatures of 2000–2200°C. Yttralox was proposed for use in lamp envelopes and high-temperature windows and lenses. It was investigated for use as a low-loss window material for lasers, for example in conjunction with a laser Doppler velocimeter for ramjet research. It was also investigated for use with infrared equipment in missiles. Neodymium oxide–doped Yttralox was used as a proof of concept for laser gain in a polycrystalline oxide ceramic, but was not commercialized due to low efficiency.
Yttralox's competing materials were an yttria containing lanthanum oxide manufactured by GTE, and a pure yttria material manufactured by Raytheon.
History
Yttralox was invented in 1966 by Richard C. Anderson at the General Electric Research Laboratory while sintering mixtures of rare earth minerals. The initial objective of the research was to develop ionic conductors for fuel cells using yttria–zirconium dioxide materials. Although the zirconium dioxide-rich versions were of more interest for ionic conductors, the yttria-rich versions unexpectedly produced transparent samples. Further research established that other oxides of Group 4 elements, thorium dioxide and hafnium dioxide, were also effective at producing transparent yttria, and the thorium dioxide system became the most extensively studied. Further work at GE was performed by Paul J. Jorgensen, Joseph H. Rosolowski, and Douglas St. Pierre. Fabrication of Yttralox was reported by Greskovich and Woods.
As of 1982, Yttralox was no longer being produced.
References
External links
Ceramic materials
Transparent materials
Yttrium compounds | Yttralox | Physics,Engineering | 643 |
300,213 | https://en.wikipedia.org/wiki/Napier%20Deltic | The Napier Deltic engine is a British opposed-piston valveless, supercharged uniflow scavenged, two-stroke diesel engine used in marine and locomotive applications, designed and produced by D. Napier & Son. Unusually, the cylinders were disposed in a three-bank triangle, with a crankshaft at each corner of the triangle.
The term Deltic (meaning "in the form of the Greek letter (capital) delta") is used to refer to both the Deltic E.130 opposed-piston, high-speed diesel engine and the locomotives produced by English Electric using these engines, including its demonstrator locomotive named DELTIC and the production version for British Railways, which designated these as the Class 55.
A single, half-sized, turbocharged Deltic power unit also featured in the English Electric-built Type 2 locomotive, designated as the Class 23. Both locomotive and engine became better known as the "Baby Deltic".
History and design
The Deltic story began in 1943 when the British Admiralty set up a committee to develop a high-power, lightweight diesel engine for motor torpedo boats. Hitherto in the Royal Navy, such boats had been driven by petrol engines, but their highly flammable fuel made them vulnerable to fire, unlike diesel-powered E-boats. A patent for an engine, similar in complexity, but with four lines of pistons, not just three, was filed in 1930 by Wifredo Ricart, linked to Alfa Romeo, and to the Spanish INI truck maker Pegaso, Pat ES0118013.
Until this time, diesel engines had poor power-to-weight ratios and low speed. Before the war, Napier had been working on an aviation diesel design known as the Culverin after licensing versions of the Junkers Jumo 204. The Culverin was an opposed-piston, two-stroke design. Instead of each cylinder having a single piston and being closed at one end with a cylinder head, the Jumo-based design used an elongated cylinder containing two pistons moving in opposite directions towards the centre. This obviates the need for a heavy cylinder head, as the opposing piston filled this role. On the downside, the layout required separate crankshafts on each end of the engine that must be coupled through gearing or shafts. The primary advantages of the design were uniflow breathing and a rather "flat" engine.
The Admiralty required a much more powerful engine, and knew about Junkers' designs for multicrankshaft engines of straight-six and diamond forms. The Admiralty felt that these would be a reasonable starting point for the larger design that it required. The result was a triangle, the cylinder banks forming the sides, with crankshafts at each corner connected by phasing gears to a single output shaft—effectively three separate V-12 engines. The Deltic could be produced with varying numbers of cylinders; 9 and 18 were the most common, having either three or six cylinders per bank, respectively. In 1946, the Admiralty placed a contract with the English Electric Company, parent of Napier, to develop this engine.
One feature of the engine was the way that crankshaft-phasing was arranged to allow for exhaust port lead and inlet port lag. These engines are called "uniflow" designs, because the flow of gas into and out of the cylinder is one way, assisted by blowers to improve cylinder exhaust scavenging. The inlet/outlet port order is in/out/in/out/in/out going around the triangular ring (i.e. the inlet and outlet manifold arrangements have C3 rotational symmetry).
Earlier attempts at designing such an engine met with the difficulty of arranging the pistons to move in the correct manner, for all three cylinders in one delta, and this was the problem that caused Junkers Motorenbau to leave behind work on the delta-form while continuing to prototype a diamond-form, four-crankshaft, 24-cylinder Junkers Jumo 223. Herbert Penwarden, a senior draughtsman with the Admiralty Engineering Laboratory, suggested that one crankshaft needed to revolve anticlockwise to achieve the correct piston-phasing, so Napier designers produced the necessary gearing so one of them rotated in the opposite direction to the other two.
Being an opposed-piston design with no inlet or exhaust valves, and no ability to vary the port positions, the Deltic design arranged each crankshaft to connect two adjacent pistons operating in different cylinders in the same plane, using "fork and blade" connecting rods, the latter an "inlet" piston used to open and close the inlet port, and the former an "exhaust" piston in the adjacent cylinder to open and close the exhaust port. This would have led the firing in each bank of cylinders to be 60° apart, but arranging that each cylinder's exhaust piston would lead its inlet piston by 20° of crankshaft rotation was adopted. This allowed the exhaust port to be opened well before the inlet port, and allowed the inlet port to be closed after the exhaust port, which led to both good scavenging of exhaust gas and good volumetric efficiency for the fresh air charge. This required the firing events for adjacent cylinders to be 40° apart. For the 18-cylinder design, firing events could be interlaced over all six banks. This led to the even, buzzing exhaust note of the Deltic, with a charge ignition every 20° of crankshaft revolution, and a lack of torsional vibration, ideal for use in mine-hunting vessels. The 9-cylinder design, having three banks of cylinders, has its crankshafts rotating in the opposite direction. The exhaust lead of 20° is added to the 60° between banks, giving firing events for adjacent cylinders in the same bank 80° apart. Interlacing firing events over all three banks of cylinders still leads to an even buzzing exhaust note, and charge ignition occurring every 40° of crankshaft revolution with consequent reduction of torsional vibration.
Although the engine was cylinder-ported and required no poppet valves, each bank had a camshaft, driven at crankshaft speed. This was used solely to drive the fuel-injection pumps, each cylinder having its own injector and pump, driven by its own cam lobe.
Uses
Naval service
Development began in 1947 and the first Deltic model was the D18-11B, produced in 1950. It was designed to produce at 2000 rpm for a 15-minute rating; the continuous rating being at 1700 rpm, based on a 10,000-hour overhaul or replacement life. By January 1952 six engines were available, enough for full development and endurance trials. A captured German E-Boat, S212 was selected as it was powered by Mercedes-Benz diesels with approximately the same power as the 18-cylinder Deltics. When two of the three Mercedes-Benz engines were replaced, the compactness of the Napier engines was graphically illustrated—they were half the size of the original engines and approximately one fifth the weight.
Proving successful, Deltic Diesel engines became a common power plant in small and fast naval craft. The Royal Navy used them first in the fast attack craft. Subsequently they were used in a number of other smaller attack craft. Being largely of aluminium construction, their low magnetic signature allowed their use in mine countermeasures vessels and the Deltic was selected to power the s. The Deltic engine is still in service in some . These versions are de-rated to reduce engine stress.
Deltic Diesels served in MTBs and PT boats built for other navies. Particularly notable was the Norwegian Tjeld or Nasty class, which was also sold to Germany, Greece, and the United States Navy. Nasty-class boats served in the Vietnam War, largely for covert operations.
Smaller nine-cylinder Deltic 9 engines were used as marine engines, notably by minesweepers. The Ton-class vessels were powered by a pair of Deltic 18s and used an additional Deltic 9 for power generation for their magnetic influence sweep. The Hunt class used three Deltic 9s, two for propulsion and again one for power generation, but this time with a hydraulic pump integrated to power bow-thrusters for slow-speed manœuvring, until a refurbishment programme by BAE Systems, that ran from 2010 to 2018, replaced the Deltic with Caterpillar C32 engines in the eight remaining commissioned Royal Navy vessels.
Railway use
Deltic engines were used in two types of British rail locomotive: the 1961–62 built class 55 and the 1959 built class 23. These locomotive types were known as Deltics and Baby Deltics, respectively.
The Class 55 used two D18-25 series II type V Deltic engines: mechanically blown 18-cylinder engines each rated at continuous at 1500 rpm. The Class 23 used a single less powerful nine-cylinder turbocharged T9-29 Deltic of .
Six out of the original 22 Class 55 locomotives survive. Class leader D9000 Royal Scots Grey was returned to main line serviceable status in 1996. Following a power unit failure this locomotive was fitted, for a time, with an ex Royal Norwegian Navy T18-37K type, after various modifications were cleverly designed to make the new unit compatible.
Fire department use
The New York City Fire Department used a Napier Deltic engine to power their one-of-a-kind "Super Pumper System". This was a very-high-volume trailer-mounted fire pump with a separate tender.
Reliability in service
While the Deltic engine was successful in marine and rail use and very powerful for its size and weight, it was a highly strung unit, requiring careful maintenance. This led to a policy of unit replacement rather than repair in situ. Deltic engines were easily removed after breakdown, generally being sent back to the manufacturer for repair, although after initial contracts expired both the Royal Navy and British Railways set up their own workshops for overhauls.
Turbo-compound Deltic
The "E.185" or "Compound Deltic" turbo-compound variant was planned and a single prototype was built in 1956 and tested in 1957. This capitalised on Napier's experience with both the "Nomad" and its increasing involvement with gas turbines. It used the Deltic as the gas generator inside a gas turbine, with both a twelve-stage axial compressor and a three-stage gas turbine. Unlike the Nomad, this turbine was not mechanically coupled to the crankshaft, but merely drove the compressor. It was hoped that it would produce 6,000 horsepower, with fuel economy and power-to-weight ratio "second to none". Predictions by the engineers closely connected with it were that connecting rod failure would be the limit on this power, failing at around 5,300 bhp. On test it actually produced 5,600 bhp before throwing a connecting rod through the crankcase just as predicted. Naval interest had waned by 1958 in favour of the pure gas turbine, despite its heavier fuel consumption, and no further development was carried out.
Comparable engines
Junkers Jumo 223
Zvezda M503
Achates Power
Fairbanks Morse 38 8-1/8 diesel engine
References
Further reading
External links
Deltic technical details
Hunt Class – Deltic-powered Mine Countermeasure Vessel
Deltic Animations – 3-D animations of the piston motion in the Deltic engine
– rebuilding of one of D9016 Gordon Highlander's engines after an exhaust silencer fire in 1999
Napier engines
Piston engine configurations
Piston ported engines
Diesel locomotive engines
Marine diesel engines
Two-stroke diesel engines
Opposed piston engines
Diesel engines by model
Deltic | Napier Deltic | Technology | 2,366 |
550,392 | https://en.wikipedia.org/wiki/Back-of-the-envelope%20calculation | A back-of-the-envelope calculation is a rough calculation, typically jotted down on any available scrap of paper such as an envelope. It is more than a guess but less than an accurate calculation or mathematical proof. The defining characteristic of back-of-the-envelope calculations is the use of simplified assumptions.
A similar phrase in the U.S. is "back of a napkin", also used in the business world to describe sketching out a quick, rough idea of a business or product. In British English, a similar idiom is "back of a fag packet".
History
In the natural sciences, back-of-the-envelope calculation is often associated with physicist Enrico Fermi, who was well known for emphasizing ways that complex scientific equations could be approximated within an order of magnitude using simple calculations. He went on to develop a series of sample calculations, which are called "Fermi Questions" or "Back-of-the-Envelope Calculations" and used to solve Fermi problems.
Fermi was known for getting quick and accurate answers to problems that would stump other people. The most famous instance came during the first atomic bomb test in New Mexico on 16 July 1945. As the blast wave reached him, Fermi dropped bits of paper. By measuring the distance they were blown, he could compare to a previously computed table and thus estimate the bomb energy yield. He estimated 10 kilotons of TNT; the measured result was 18.6.
Perhaps the most influential example of such a calculation was carried out over a period of a few hours by Arnold Wilkins after being asked to consider a problem by Robert Watson Watt. Watt had learned that the Germans claimed to have invented a radio-based death ray, but Wilkins' one-page calculations demonstrated that such a thing was almost certainly impossible. When Watt asked what role radio might play, Wilkins replied that it might be useful for detection at long range, a suggestion that led to the rapid development of radar and the Chain Home system.
Another example is Victor Weisskopf's pamphlet Modern Physics from an Elementary Point of View. In these notes Weisskopf used back-of-the-envelope calculations to calculate the size of a hydrogen atom, a star, and a mountain, all using elementary physics.
Examples
In a video interview for the University of California, Berkeley on the 50th anniversary of the laser, Nobel laureate Charles Townes described how he pulled an envelope from his pocket while sitting in a park and wrote down calculations during his initial insight into lasers.
During lunch with NFL commissioner Pete Rozelle in 1966, Tiffany & Co. vice president Oscar Riedner made a sketch on a cocktail napkin of what would become the Vince Lombardi Trophy, awarded annually to the winner of the Super Bowl.
An important Internet protocol, the Border Gateway Protocol, was sketched out in 1989 by engineers on the back of "three ketchup-stained napkins", and is still known as the three-napkin protocol.
UTF-8, the dominant character encoding for the World Wide Web, was designed by Ken Thompson and Rob Pike on a placemat.
The Bailey bridge is a type of portable, pre-fabricated, truss bridge and was extensively used by British, Canadian and US military engineering units. Donald Bailey drew the original design for the bridge on the back of an envelope.
The Laffer Curve, which claims to show the relationship between tax cuts and government income, was drawn by Arthur Laffer in 1974 on a bar napkin to show an aide to President Gerald R. Ford why the federal government should cut taxes.
Upon hearing that the S-IV 2nd Stage of the Saturn I would need transport from California to Florida for launch as part of the Apollo program, Jack Conroy sketched the cavernous cargo airplane, the Pregnant Guppy.
The Video Toaster was designed on placemats in a Topeka pizza restaurant.
See also
Buckingham pi theorem, a technique often used in fluid mechanics to obtain order-of-magnitude estimates
Guesstimate
Scientific Wild-Ass Guess
Heuristic
Order-of-magnitude analysis
Rule of thumb
Sanity testing
Fermi Problem
Notes and references
External links
Syllabus at UCSD
Approximations
Informal estimation
Metaphors referring to objects | Back-of-the-envelope calculation | Mathematics | 853 |
601,999 | https://en.wikipedia.org/wiki/Assassination%20of%20Luis%20Carrero%20Blanco | On 20 December 1973, Luis Carrero Blanco, the Prime Minister of Spain, was assassinated when a cache of explosives in a tunnel set up by the Basque separatist group ETA was detonated. The assassination, also known by its code name Operación Ogro (Operation Ogre), is considered to have been the biggest attack against the Francoist State since the end of the Spanish Civil War in 1939 and had far-reaching consequences within the politics of Spain.
The death of Carrero Blanco had numerous political implications. By the end of 1973, the physical health of dictator Francisco Franco had declined significantly, and it epitomized the final crisis of the Francoist regime. Following Blanco's death, the most conservative sector of the Francoist State, known as the , wanted to influence Franco so that he would choose an ultraconservative as Prime Minister. Finally, he chose Carlos Arias Navarro, who originally announced a partial relaxation of the most rigid aspects of the Francoist State, but quickly retreated under pressure from the . ETA, on the other hand, consolidated its place as a relevant armed group and would evolve to become one of the main opponents of Francoism.
Assassination
An ETA commando unit using the code name Txikia (after the nom de guerre of ETA activist Eustakio Mendizabal, killed by the Guardia Civil in April 1973) rented a basement flat at Calle Claudio Coello 104, Madrid, on the route by which Blanco regularly went to mass at San Francisco de Borja church.
Over five months, the unit dug a tunnel under the street – telling the landlord that they were student sculptors to hide their true purpose. The tunnel was packed with of Goma-2 that had been stolen from a government depot.
On 20 December at 9:36 am, a three-man ETA commando unit disguised as electricians detonated the explosives by command wire as Blanco's Dodge Dart passed. The blast sent Blanco and his car into the air and over the five-story church, landing on the second-floor terrace of the opposite side. Blanco survived the blast but died at 10:15 am in hospital. His bodyguard and driver died shortly afterwards. The "electricians" shouted to stunned passers-by that there had been a gas explosion, and then fled in the confusion. ETA claimed responsibility on 22 January 1974.
In a collective interview justifying the attack, the ETA bombers said:
The killing was not condemned and was, in some cases, even welcomed by the Spanish opposition in exile. According to Laura Desfor Edles, professor of sociology at California State University, Northridge, some analysts consider the assassination of Carrero Blanco to be the only thing the ETA have ever done to "further the cause of Spanish democracy". However, former ETA member turned writer Jon Juaristi contended that ETA's goal with the killing was not democratization but a spiral of violence to fully destabilize Spain, heighten Franco's repression against Basque nationalism and force the average Basque citizen to support the lesser evil in the form of the ETA against Franco.
According to colonel Amadeo Martínez Inglés, it was planned, organized and carried out by CIA, for its similarities with the assassination of René Schneider, with the collaboration of ETA.
Reaction
A government meeting about the "dangers of subversion threatening Spain" was scheduled to take place on 20 December 1973. Both Carrero Blanco and the United States Secretary of State, Henry Kissinger, had expressed concern about a left-wing uprising during the meeting they held on 19 December. When government officials reached the Palace of Villamejor, they learned about Carrero Blanco's death. Deputy Prime Minister Torcuato Fernández Miranda demanded calm and announced that he was going to call Franco so that Franco could decide what to do next. After the call, Fernández Miranda proclaimed himself prime minister, in accordance with the dispositions laid out in the Organic Law of the State. His first decision as prime minister was to decline to declare a state of exception.
Gabriel Pita da Veiga, Minister of the Navy, informed Fernández Miranda that Carlos Iniesta Cano, Director-General of the Civil Guard, had decided to "maximize surveillance" and ordered agents through a telegram not to hesitate to use deadly force if any clash occurred. However, Fernández Miranda was opposed and made Iniesta Cano reverse this order immediately through a telegram.
See also
Cassandra case, student prosecuted for posting a series of tweets poking fun at the assassination of Luis Carrero Blanco
Operación Ogro, a film about the attack by Gillo Pontecorvo
The Last Circus, a film where the attack is a minor part of the plot
References
Terrorist incidents in Spain in the 1970s
1970s in Madrid
1973 murders in Spain
Assassinations in Spain
Deaths by person in Spain
Francoist Spain
Terrorist incidents in Europe in 1973
ETA (separatist group) actions
Tunnel warfare
Improvised explosive device bombings in Madrid
Improvised explosive device bombings in 1973
1973 in politics | Assassination of Luis Carrero Blanco | Engineering | 1,012 |
36,149,098 | https://en.wikipedia.org/wiki/Triple-resonance%20nuclear%20magnetic%20resonance%20spectroscopy | Triple resonance experiments are a set of multi-dimensional nuclear magnetic resonance spectroscopy (NMR) experiments that link three types of atomic nuclei, most typically consisting of 1H, 15N and 13C. These experiments are often used to assign specific resonance signals to specific atoms in an isotopically-enriched protein. The technique was first described in papers by Ad Bax, Mitsuhiko Ikura and Lewis Kay in 1990, and further experiments were then added to the suite of experiments. Many of these experiments have since become the standard set of experiments used for sequential assignment of NMR resonances in the determination of protein structure by NMR. They are now an integral part of solution NMR study of proteins, and they may also be used in solid-state NMR.
Background
There are two main methods of determining protein structure on the atomic level. The first of these is by X-ray crystallography, starting in 1958 when the crystal structure of myoglobin was determined. The second method is by NMR, which began in the 1980s when Kurt Wüthrich outlined the framework for NMR structure determination of proteins and solved the structure of small globular proteins. The early method of structural determination of protein by NMR relied on proton-based homonuclear NMR spectroscopy in which the size of the protein that may be determined is limited to ~10 KDa. This limitation is due to the need to assign NMR signals from the large number of nuclei in the protein – in larger protein, the greater number of nuclei results in overcrowding of resonances, and the increasing size of the protein also broadens the signals, making resonance assignment difficult. These problems may be alleviated by using heteronuclear NMR spectroscopy which allows the proton spectrum to be edited with respect to the 15N and 13C chemical shifts, and also reduces the overlap of resonances by increasing the number of dimensions of the spectrum. In 1990, Ad Bax and coworkers developed the triple resonance technology and experiments on proteins isotopically labelled with 15N and 13C, with the result that the spectra are dramatically simplified, greatly facilitating the process of resonance assignment, and increasing the size of the protein that may be determined by NMR.
These triple resonance experiments utilize the relatively large magnetic couplings between certain pairs of nuclei to establish their connectivity. Specifically, the 1JNH, 1JCH, 1JCC, and 1JCN couplings are used to establish the scalar connectivity pathway between nuclei. The magnetization transfer process takes place through multiple, efficient one-bond magnetization transfer steps, rather than a single step through the smaller and variable 3JHH couplings. The relatively large size and good uniformity of the one-bond couplings allowed the design of efficient magnetization transfer schemes that are effectively uniform across a given protein, nearly independent of conformation. Triple resonance experiments involving 31P may also be use for nucleic acid studies.
Suite of experiments
These experiments are typically named by the nuclei (H, N, and C) involved in the experiment. CO refers to the carbonyl carbon, while CA and CB refer to Cα and Cβ respectively, similarly HA and HB for Hα and Hβ (see diagram for examples of experiments). The nuclei in the name are ordered in the same sequence as in the path of magnetization transfer, those nuclei placed within parentheses are involved in the magnetization transfer pathway but are not recorded. For reason of sensitivity, these experiments generally start on a proton and end on a proton, typically via INEPT and reverse INEPT steps. Therefore, many of these experiments are what may be called "out-and-back" experiments where, although not indicated in the name, the magnetization is transferred back to the starting proton for signal acquisition.
Some of the experiments are used in tandem for the resonance assignment of protein, for example HNCACB may be used together with CBCA(CO)NH as a pair of experiments. Not all of these experiments need to be recorded for sequential assignment (it can be done with as few as two), however extra pairs of experiments are useful for independent assessment of the correctness of the assignment, and the redundancy of information may be necessary when there is ambiguity in the assignments. Other experiments are also necessary to fully assign the side chain resonances.
TROSY versions of many of these experiments exist for improvement in sensitivity. Triple resonance experiments can also be used in sequence-specific backbone resonance assignment of magic angle spinning NMR spectra in solid-state NMR.
A large number triple-resonance NMR experiments have been created, and the experiments listed below is not meant to be exhaustive.
HNCO
The experiment provides the connectivities between the amide of a residue with the carbonyl carbon of the preceding residues. It is the most sensitive of the triple resonance experiments. The sidechains carboxamides of asparagine and glutamine are also visible in this experiment. Additionally, the guanidino group of arginine, which has similar coupling constant to the carboxamide group, may also appear in this spectrum. This experiment is sometimes used together with HN(CA)CO.
HN(CA)CO
Here, the amide resonance of a residue is correlated with the carbonyl carbon of the same residue, as well as that of the preceding residue. The intra-residue resonances are usually stronger than the inter-residues one.
HN(CO)CA
This experiment correlates the resonances of the amide of a residue with the Cα of the preceding residue. This experiment is often used together with HNCA.
HNCA
This experiment correlates the chemical shift of amide of a residue the Cα of the same residue as well as those of the preceding residue. Each strip gives two peaks, the inter and intra-residue Cα peaks. Peak from the preceding Cα may be identified from the HN(CO)CA experiment which gives only the inter-residue Cα.
CBCA(CO)NH
CBCA(CO)NH, or alternatively HN(CO)CACB, correlates the resonances of the amide of a residue with the Cα and Cβ of the preceding residue. Two peaks corresponding to the Cα and Cβ are therefore visible for each residue. This experiment is normally used together with HNCACB. The sidechain carboxamide of glutamines and asparagines also appear in this spectra in this experiment. CBCA(CO)NH is sometimes more precisely called (HBHA)CBCA(CO)NH as it starts with aliphatic protons and ends on an amide proton, and is therefore not an out-and-back experiment like HN(CO)CACB.
HNCACB
HNCACB, or alternatively CBCANH, correlates the chemical shift of amide of a residue the Cα and Cβ of the same residue as well as those of the preceding residue. In each strip, four peaks may be visible – 2 from the same residue and 2 from the preceding residue. Peaks from the preceding residue are usually weaker, and may be identified using CBCA(CO)NH. In this experiment, the Cα and Cβ peaks are in opposite phase, i.e. if Cα appears as a positive peak, then Cβ will be negative, making identification of Cα and Cβ straightforward. The extra information of Cβ from the CBCA(CO)NH/HNCACB set of experiments makes identification of residue type easier than HN(CO)CA/HNCA, however the HNCACB is a less sensitive experiment and may be unsuitable for some proteins.
The CBCANH experiment is less suitable for larger protein as it is more susceptible to the line-width problem than HNCACB.
CBCACO(CA)HA
This experiment provides the connectivities between the Cα and Cβ with the carbonyl carbon and Hα atoms within the same residue. The sidechain carboxyl group of aspartate and glutamate may appear weakly in this spectrum.
CC(CO)NH
This experiment provides connectivities between the amide of a residue and the aliphatic carbon atoms of the preceding residue.
H(CCO)NH
This experiment provides connectivities between the amide of a residue and the hydrogen atoms attached to the aliphatic carbon of the preceding residue.
HBHA(CO)NH
This experiment correlates the amide resonance to the Hα and Hβ of the preceding residue.
Sequential assignment
Pairs of experiments are normally used for sequential assignment, for example, the HNCACB and CBCA(CO)NH pair, or HNCA and HNC(CO)CA. The spectra are normally analyzed as strips of peaks, and strips from the pair of experiments may be presented together side by side or as an overlay of two spectra. In the HNCACB spectra 4 peaks are usually present in each strip, the Cα and Cβ of one residue as well as those of its preceding residue. The peaks from the preceding residue can be identified from the CBCA(CO)NH experiment. Each strip of peaks can therefore be linked to the next strip of peaks from an adjoining residue, allowing the strips to be connected sequentially. The residue type can be identified from the chemical shifts of the peaks, some, such as serine, threonine, glycine and alanine, are much easier to identify than others. The resonances can then be assigned by comparing the sequence of peaks with the amino acid sequence of the protein.
References
External links
Triple resonance experiments for proteins
Introduction to 3D Triple Resonance Experiments
Protein NMR – A Practical Guide
Protein structure
Nuclear magnetic resonance spectroscopy | Triple-resonance nuclear magnetic resonance spectroscopy | Physics,Chemistry | 2,000 |
24,146,023 | https://en.wikipedia.org/wiki/C21H25ClO5 | {{DISPLAYTITLE:C21H25ClO5}}
The molecular formula C21H25ClO5 (molar mass: 392.87 g/mol, exact mass: 392.1391 u) may refer to:
Cloprednol
Chloroprednisone
Molecular formulas | C21H25ClO5 | Physics,Chemistry | 68 |
23,104,957 | https://en.wikipedia.org/wiki/Johannesburg%20Planetarium | The Johannesburg Planetarium is a planetarium owned by the University of the Witwatersrand, located on the University's East Campus in Braamfontein, Johannesburg. It was the first full-sized planetarium in Africa, and the second in the southern hemisphere.
History
The idea of setting up a planetarium in Johannesburg was first discussed in 1956 when the Festival Committee — which had been instituted to organise the celebrations of Johannesburg's seventieth anniversary — decided to raise the funds necessary to buy and house a Zeiss planetarium to be set up for the celebrations. As there was too little time to obtain a new instrument, it was decided to buy an existing planetarium projector from Europe.
After lengthy negotiations, the Festival Committee was successful in persuading the Parliament of Hamburg to sell their planetarium's projector which had been in use there since 1930. The Hamburg Parliament, however, imposed as its conditions that the planetarium's projector be fully modernised in the Zeiss factory at Oberkochen, and that Johannesburg would in due course have a new planetarium built for Hamburg. The Hamburg projector was immediately dismantled and moved to Oberkochen for an overhaul, and was in time completely rebuilt.
Soon, the responsibilities of the Festival Committee were taken over by the Johannesburg City Council, which after further negotiations, sold the projector to the University of the Witwatersrand for use as both an academic facility for the instruction of students, and as a public amenity. Plans for a new building to house the projector were first drawn up in 1958, and construction began in 1959. The planetarium finally opened on 12 October 1960.
The Johannesburg Planetarium is often consulted by the media, and the public, in order to explain unusual occurrences in the skies over South Africa. In 2010, the Johannesburg Planetarium celebrated its golden jubilee.
References
External links
1960 establishments in South Africa
Educational buildings in Johannesburg
Planetaria
Science and technology in South Africa
Tourist attractions in Johannesburg
University of the Witwatersrand
Buildings and structures completed in 1960 | Johannesburg Planetarium | Astronomy | 419 |
44,700,778 | https://en.wikipedia.org/wiki/Hattendorff%27s%20theorem | Hattendorff's Theorem, attributed to K. Hattendorff (1868), is a theorem in actuarial science that describes the allocation of the variance or risk of the loss random variable over the lifetime of an actuarial reserve. In other words, Hattendorff's theorem demonstrates that the variation in the present value of the loss of an issued insurance policy can be allocated to the future years during which the insured is still alive. This, in turn, facilitates the management of risk prevalent in such insurance contracts over short periods of time.
Hattendorff's Theorem
The main result of the theorem has three equivalent formulations:
where:
In its above formulation, and in particular the first result, Hattendorff's theorem states that the variance of , the insurer's total loss over the remaining life of the policy at time h, can be calculated by discounting the variances of the yearly net losses (cash losses plus changes in net liabilities) in future years.
Background
Source:
In the most general stochastic setting in which the analysis of reserves is carried out, consider an insurance policy written at time zero, over which the insured pays yearly premiums at the beginning of each year starting today until the year of death of the insured. Furthermore, the insured receives a benefit of , at the end of the year of death, equal to . No other payments are received nor paid over the lifetime of the policy.
Suppose an insurance company is interested to know the cash loss from this policy over the year (h, h+1). Of course, if the death of the insured happens prior to time h, or when , then there is no remaining loss and . If the death of the insured occurs exactly at time h, or when , then the loss on the policy is equal to the present value of the benefit paid in the following year, , less the premium paid at time h. Hence in this case Lastly, if the death of the insured occurs after time h, or when , then the cash loss in the year (h, h+1) is just the negative of the premium received at time h (cash inflows are treated as negative losses). Hence we summarize this result as
Furthermore, the actuarial present value of the future cash losses in each year has the explicit formula
{| class="toccolours collapsible collapsed" width="80%" style="text-align:left"
!Derivation of the formula for .
|-
| The present value of the loss on the policy at time h is the present value of all future cash losses
Expanding this result, it is easy to see using the definition of that, when ,
Similarly, when , then . Finally, when , the summation, and hence the loss on the policy, is zero.
|}
In the analysis of reserves, a central quantity of interest is the benefit reserve at time h, which is the expected loss on the policy at time h given that status x has survived to age h
which admits to the closed form expression
.
{| class="toccolours collapsible collapsed" width="80%" style="text-align:left"
!Derivation of the formula for .
|-
| Here we derive the above formula for the benefit reserve.
In order to proceed, we make the assumption that the remaining lifetime of a life status x that has lived to time h, , follows the same (kurtate) probability distribution as another randomly chosen individual from the group of insureds but of age , with distribution . This means that, in terms of expected values, for any function over which the expectation is defined. Then, using a clever algebraic trick, we can rewrite the benefit reserve as
|}
Lastly, the present value of the net cash loss at time h over the year (h, h+1), denoted , is equal to the present value of the cash loss in year h, (see above), plus the present value of the change in liabilities at time h. In other words, . If , then . Similarly, if , then since there is no reserve after the year of death. Finally, if , then there is no loss in the future and . Summarizing, this yields the following result, which is important in the formulation of Hattendorff's theorem
Proofs
The proof of the first equality is written as follows. First, by writing the present value of future net losses at time h,
from which it is easy to see that
It is known that the individual net cash flows in different years are uncorrelated, or when (see Bowers et al., 1997, for a proof of this result). Using these two results, we conclude that
which proves the first part of the theorem. The reader is referred to (Bowers et al., pg 241) for the proof of the other equalities.
References
External links
YouTube video explanation
Actuarial science | Hattendorff's theorem | Mathematics | 1,023 |
7,203,729 | https://en.wikipedia.org/wiki/D%27Alembert%27s%20equation | In mathematics, d'Alembert's equation, sometimes also known as Lagrange's equation, is a first order nonlinear ordinary differential equation, named after the French mathematician Jean le Rond d'Alembert. The equation reads as
where . After differentiating once, and rearranging we have
The above equation is linear. When , d'Alembert's equation is reduced to Clairaut's equation.
References
Eponymous equations of physics
Mathematical physics
Ordinary differential equations | D'Alembert's equation | Physics,Mathematics | 102 |
237,037 | https://en.wikipedia.org/wiki/Cartesian%20closed%20category | In category theory, a category is Cartesian closed if, roughly speaking, any morphism defined on a product of two objects can be naturally identified with a morphism defined on one of the factors. These categories are particularly important in mathematical logic and the theory of programming, in that their internal language is the simply typed lambda calculus. They are generalized by closed monoidal categories, whose internal language, linear type systems, are suitable for both quantum and classical computation.
Etymology
Named after René Descartes (1596–1650), French philosopher, mathematician, and scientist, whose formulation of analytic geometry gave rise to the concept of Cartesian product, which was later generalized to the notion of categorical product.
Definition
The category C is called Cartesian closed iff it satisfies the following three properties:
It has a terminal object.
Any two objects X and Y of C have a product X ×Y in C.
Any two objects Y and Z of C have an exponential ZY in C.
The first two conditions can be combined to the single requirement that any finite (possibly empty) family of objects of C admit a product in C, because of the natural associativity of the categorical product and because the empty product in a category is the terminal object of that category.
The third condition is equivalent to the requirement that the functor – ×Y (i.e. the functor from C to C that maps objects X to X ×Y and morphisms φ to φ×idY) has a right adjoint, usually denoted –Y, for all objects Y in C.
For locally small categories, this can be expressed by the existence of a bijection between the hom-sets
which is natural in X, Y, and Z.
Take care to note that a Cartesian closed category need not have finite limits; only finite products are guaranteed.
If a category has the property that all its slice categories are Cartesian closed, then it is called locally cartesian closed. Note that if C is locally Cartesian closed, it need not actually be Cartesian closed; that happens if and only if C has a terminal object.
Basic constructions
Evaluation
For each object Y, the counit of the exponential adjunction is a natural transformation
called the (internal) evaluation map. More generally, we can construct the partial application map as the composite
In the particular case of the category Set, these reduce to the ordinary operations:
Composition
Evaluating the exponential in one argument at a morphism p : X → Y gives morphisms
corresponding to the operation of composition with p. Alternate notations for the operation pZ include p* and p∘-. Alternate notations for the operation Zp include p* and -∘p.
Evaluation maps can be chained as
the corresponding arrow under the exponential adjunction
is called the (internal) composition map.
In the particular case of the category Set, this is the ordinary composition operation:
Sections
For a morphism p:X → Y, suppose the following pullback square exists, which defines the subobject of XY corresponding to maps whose composite with p is the identity:
where the arrow on the right is pY and the arrow on the bottom corresponds to the identity on Y. Then ΓY(p) is called the object of sections of p. It is often abbreviated as ΓY(X).
If ΓY(p) exists for every morphism p with codomain Y, then it can be assembled into a functor ΓY : C/Y → C on the slice category, which is right adjoint to a variant of the product functor:
The exponential by Y can be expressed in terms of sections:
Examples
Examples of Cartesian closed categories include:
The category Set of all sets, with functions as morphisms, is Cartesian closed. The product X×Y is the Cartesian product of X and Y, and ZY is the set of all functions from Y to Z. The adjointness is expressed by the following fact: the function f : X×Y → Z is naturally identified with the curried function g : X → ZY defined by g(x)(y) = f(x,y) for all x in X and y in Y.
The subcategory of finite sets, with functions as morphisms, is also Cartesian closed for the same reason.
If G is a group, then the category of all G-sets is Cartesian closed. If Y and Z are two G-sets, then ZY is the set of all functions from Y to Z with G action defined by (g.F)(y) = g.F(g−1.y) for all g in G, F:Y → Z and y in Y.
The subcategory of finite G-sets is also Cartesian closed.
The category Cat of all small categories (with functors as morphisms) is Cartesian closed; the exponential CD is given by the functor category consisting of all functors from D to C, with natural transformations as morphisms.
If C is a small category, then the functor category SetC consisting of all covariant functors from C into the category of sets, with natural transformations as morphisms, is Cartesian closed. If F and G are two functors from C to Set, then the exponential FG is the functor whose value on the object X of C is given by the set of all natural transformations from to F.
The earlier example of G-sets can be seen as a special case of functor categories: every group can be considered as a one-object category, and G-sets are nothing but functors from this category to Set
The category of all directed graphs is Cartesian closed; this is a functor category as explained under functor category.
In particular, the category of simplicial sets (which are functors X : Δop → Set) is Cartesian closed.
Even more generally, every elementary topos is Cartesian closed.
In algebraic topology, Cartesian closed categories are particularly easy to work with. Neither the category of topological spaces with continuous maps nor the category of smooth manifolds with smooth maps is Cartesian closed. Substitute categories have therefore been considered: the category of compactly generated Hausdorff spaces is Cartesian closed, as is the category of Frölicher spaces.
In order theory, complete partial orders (cpos) have a natural topology, the Scott topology, whose continuous maps do form a Cartesian closed category (that is, the objects are the cpos, and the morphisms are the Scott continuous maps). Both currying and apply are continuous functions in the Scott topology, and currying, together with apply, provide the adjoint.
A Heyting algebra is a Cartesian closed (bounded) lattice. An important example arises from topological spaces. If X is a topological space, then the open sets in X form the objects of a category O(X) for which there is a unique morphism from U to V if U is a subset of V and no morphism otherwise. This poset is a Cartesian closed category: the "product" of U and V is the intersection of U and V and the exponential UV is the interior of .
A category with a zero object is Cartesian closed if and only if it is equivalent to a category with only one object and one identity morphism. Indeed, if 0 is an initial object and 1 is a final object and we have , then which has only one element.
In particular, any non-trivial category with a zero object, such as an abelian category, is not Cartesian closed. So the category of modules over a ring is not Cartesian closed. However, the functor tensor product with a fixed module does have a right adjoint. The tensor product is not a categorical product, so this does not contradict the above. We obtain instead that the category of modules is monoidal closed.
Examples of locally Cartesian closed categories include:
Every elementary topos is locally Cartesian closed. This example includes Set, FinSet, G-sets for a group G, as well as SetC for small categories C.
The category LH whose objects are topological spaces and whose morphisms are local homeomorphisms is locally Cartesian closed, since LH/X is equivalent to the category of sheaves . However, LH does not have a terminal object, and thus is not Cartesian closed.
If C has pullbacks and for every arrow p : X → Y, the functor p* : C/Y → C/X given by taking pullbacks has a right adjoint, then C is locally Cartesian closed.
If C is locally Cartesian closed, then all of its slice categories C/X are also locally Cartesian closed.
Non-examples of locally Cartesian closed categories include:
Cat is not locally Cartesian closed.
Applications
In Cartesian closed categories, a "function of two variables" (a morphism f : X×Y → Z) can always be represented as a "function of one variable" (the morphism λf : X → ZY). In computer science applications, this is known as currying; it has led to the realization that simply-typed lambda calculus can be interpreted in any Cartesian closed category.
The Curry–Howard–Lambek correspondence provides a deep isomorphism between intuitionistic logic, simply-typed lambda calculus and Cartesian closed categories.
Certain Cartesian closed categories, the topoi, have been proposed as a general setting for mathematics, instead of traditional set theory.
Computer scientist John Backus has advocated a variable-free notation, or Function-level programming, which in retrospect bears some similarity to the internal language of Cartesian closed categories. CAML is more consciously modelled on Cartesian closed categories.
Dependent sum and product
Let C be a locally Cartesian closed category. Then C has all pullbacks, because the pullback of two arrows with codomain Z is given by the product in C/Z.
For every arrow p : X → Y, let P denote the corresponding object of C/Y. Taking pullbacks along p gives a functor p* : C/Y → C/X which has both a left and a right adjoint.
The left adjoint is called the dependent sum and is given by composition .
The right adjoint is called the dependent product.
The exponential by P in C/Y can be expressed in terms of the dependent product by the formula .
The reason for these names is because, when interpreting P as a dependent type , the functors and correspond to the type formations and respectively.
Equational theory
In every Cartesian closed category (using exponential notation), (XY)Z and (XZ)Y are isomorphic for all objects X, Y and Z. We write this as the "equation"
(xy)z = (xz)y.
One may ask what other such equations are valid in all Cartesian closed categories. It turns out that all of them follow logically from the following axioms:
x×(y×z) = (x×y)×z
x×y = y×x
x×1 = x (here 1 denotes the terminal object of C)
1x = 1
x1 = x
(x×y)z = xz×yz
(xy)z = x(y×z)
Bicartesian closed categories
Bicartesian closed categories extend Cartesian closed categories with binary coproducts and an initial object, with products distributing over coproducts. Their equational theory is extended with the following axioms, yielding something similar to Tarski's high school axioms but with a zero:
x + y = y + x
(x + y) + z = x + (y + z)
x×(y + z) = x×y + x×z
x(y + z) = xy×xz
0 + x = x
x×0 = 0
x0 = 1
Note however that the above list is not complete; type isomorphism in the free BCCC is not finitely axiomatizable, and its decidability is still an open problem.
References
External links
Closed categories
Lambda calculus | Cartesian closed category | Mathematics | 2,537 |
47,686,959 | https://en.wikipedia.org/wiki/Build%20UK | Build UK is a representative organisation in the Construction industry of the United Kingdom. It was formed by the 2015 merger of the UK Contractors Group (UKCG) and the National Specialist Contractors Council (NSCC). Combining clients, main contractors, trade associations, and other organisations, it claims to represent over 40% of UK construction, with organisational priorities focussed on improving performance, increasing construction productivity, and taking a sustainable approach to skill development and retention in the industry.
History
Build UK was launched on 1 September 2015, following the merger of the UKCG and the NSCC. Its members include industry clients, main contractors, trade associations representing over 11,500 specialist contractors, and other organisations committed to industry collaboration. It claims to represent over 40% of UK construction.
Its initial action plan had five key areas: the image of construction, industry's skills needs, effective pre-qualification, health and safety performance, and fair payment practices.
Following Carillion's January 2018 liquidation, Build UK set out an agenda to reform the construction industry's commercial model, potentially eliminating unfair contract terms, late payment and retentions.
In 2022, Build UK was awarded the 'Royal Charter Award for Excellence in Construction' by the Worshipful Company of Constructors for the leadership role it played during the COVID-19 pandemic in the United Kingdom.
Policies
Build UK promotes the adoption of collaborative supply chain practices in the construction industry, and is working towards the elimination of retentions as a business practice by 2025. The Construction Leadership Council has endorsed Build UK's Roadmap to Zero Retentions.
Membership
Build UK has four categories of membership: Alliance, Clients, Contractors and Trade Associations.
References
External links
Build UK website
Construction trade groups based in the United Kingdom
Engineering organizations
Organisations based in the London Borough of Islington
Organizations established in 2015
2015 establishments in England | Build UK | Engineering | 379 |
28,870,027 | https://en.wikipedia.org/wiki/Powder%20flask | A powder flask is a small container for gunpowder, which was an essential part of shooting equipment with muzzle-loading guns, before pre-made paper cartridges became standard in the 19th century. They range from very elaborately decorated works of art to early forms of consumer packaging, and are widely collected. Many were standardized military issue, but the most decorative were generally used for sporting shooting.
Although the term powder horn is sometimes used for any kind of powder flask, it is strictly a sub-category of flask made from a hollowed bovid horn. Powder flasks were made in a great variety of materials and shapes, though ferrous metals that were prone to give off sparks when hit were usually avoided. Stag antler, which could be carved or engraved, was an especially common material, but wood and copper were common, and in India, ivory.
Many types of early guns required two different forms of gunpowder (such as a flintlock with finer priming powder for the pan, and a coarser standard powder for the main charge), necessitating two containers, a main flask and a smaller priming flask.
Apart from the horns, common shapes were the Y formed by the base of an antler (inverted), a usually flattened pear shape with a straight spout (poire-poudre or "powder pear" is a French term for these), a round flattened shape, and for larger flasks a triangle with concave rounded sides, which unlike the smaller flasks could be stood upright on a surface. Many designs (such as horn and antler types) have a wide sealed opening for filling, and a thin spout for dispensing. Various devices were used to load a precise amount of powder to dispense, as it was important not to load too much or too little powder, or the powder was dispensed into a powder measure or "charger" (these survive much less often). As early as c. 1600 a German flask had a silver spout with a "telescopic valve, adjustable for different sizes of powder charges".
Use
Although forms of pre-packed paper cartridges go back to the Middle Ages, these were for several centuries made up by the shooter or a servant, rather than being mass-produced, requiring a container for the gunpowder, which came loose. Unlike modern cartridges, these were not inserted into the gun themselves, but were rather a pre-measured amount of powder stored in a paper wrapper, sometimes with the ball included as well. Loading the gun involved tearing open the package, emptying the powder into the muzzle and pan, inserting the ball with the paper doubling as wadding, and then ramming home the charge. This was somewhat faster and more convenient than measuring out a powder charge each time, especially in a combat situation. However, there was no large-scale manufacturing of these cartridges until the 19th century, and even then the benefits mostly lay with military use; the added cost made them less popular with civilian shooters until the advent of the self-contained metallic cartridge and the breech-loader.
While loading a muzzleloader, an important safety concern was that when reloading a muzzle-loading gun soon after a shot there might be small pieces of wadding burning in the muzzle, which would cause the new load of powder to ignite as a flash. So long as no part of the loader faced the end of the barrel this was not likely to lead to serious injury, but if a spark reached the main supply in the powder flask a dangerous, even fatal, explosion was likely. General Sir James Pulteney, 7th Baronet, was one such victim; he died in 1811 from complications after losing an eye when a powder flask accidentally exploded in his face in Norfolk. Charles Kickham, prominent in the Irish Republican Brotherhood, grew up largely deaf and almost blind as the result of an explosion when he was 13, in about 1840. Various precautions were taken in the design and use of powder flasks to prevent this from happening, and expensive examples from as early as the 16th century usually have springs to automatically close the dispensing spout (this is much less common with the cheaper horn type).
Modern manuals on muzzle-loading guns all say the flask should never be used to pour powder directly down the muzzle, to avoid dangerous overcharging and possible burst barrels, but from the English sporting press of the 18th and early 19th centuries, it is all too clear that this was then common practice, resulting in many accidents. Some YouTube videos demonstrating loading maintain the old traditions. Instead, the powder should be poured into an intermediate container known as a charger or powder measure. Sometimes, the cap to the spout represented the measure, especially for priming flasks. Sometimes, the spout itself was the measure, with a sliding device to shut off the supply at the base, as well as a cap. This type became the norm in the mid-19th century.
High-quality guns would often have come with a matching flask, chargers, and other accessories. Many flasks have small rings for a cord, which was slung around the neck to carry them, especially before large pockets on hunting clothes arrived in Europe in the 18th century. Some examples have original elaborate cords with knots and tassels.
During roughly the 18th century, paper cartridges became more and more popular, and a higher proportion of flasks made were the smaller priming variety, which were still required. It appears that the British Army in the Peninsular War, despite regulations specifying the issue of powder horns and priming flasks, found the former inferior in action to cartridges, with the measuring spout prone to get detached and lost, and informally switched to cartridges during the war. The powder flask was finally rendered obsolete by the spread of breech-loading guns and the innovations brought about by Hall, Sharps, Spencer, and the later development of self-contained cartridges that were developed and marketed successfully by Oliver Winchester, after which manufactured cartridges or bullets became standard. Powder flasks were also used for priming naval cannon; such a flask would be as large as, or even larger than, a main flask for a personal sidearm. The large, rectangular boxes from which the main muzzle charges for cannon were scooped are called powder boxes; these were used either when making up cartridges in advance, or loading loose powder when firing.
Decoration
Most of the vast numbers of flasks made in the gun-using parts of the world during the Early Modern period were probably relatively plain and functional, and have not been preserved. But those for the wealthy sportsman or soldier could have decoration of the highest quality, and many artisan-made horns have folk art engravings similar to skrimshaw. They are collected at various levels; early hand-made examples of high quality are expensive and may be found in local or military museums and those for the decorative arts, while 19th century mass-produced examples in metal are a relatively cheap type of antique (though not always as old as claimed) and widely collected.
Europe
Germany, in antler and other materials, and India, in ivory and even jade, are the sources of especially richly decorated luxury flasks. A number of German flasks from the 16th and early 17th centuries are very richly carved with a wide variety of scenes, such as the emblematic figure illustrated. Antler was used for decorating a range of objects associated with hunting, from buttons to gunstocks, knife handles and saddles decorated all over with carved slices of antler. The uniforms of the guards of German princes might include elaborate flasks, often decorated with heraldic designs.
By the 19th century, stamped metal flasks with a central design in low relief are more common, and standard types by particular manufacturers dominate the field, some produced by gun or powder manufacturers and carrying branding or advertising. The pear shape has become dominant for smaller flasks, which are presumably mostly kept in a pocket.
Asia
Ivory Indian flasks of the Mughal and post-Mughal periods, regarded as priming flasks, have a fish-like shape reflecting the tip of a tusk, and are often carved with animals (typically attacking each other) in high relief, with the bodies of the animals in the round at the narrow tip. The bodies of hunter and prey are closely and often illogically connected, forming what have been called "composite animal" forms, which have interested art historians. The Indian tradition of ivory carving (which was probably objectionable to Hindu patrons) was rather late-starting apparently diffusing from a number of centres including a school of carving developed in the Portuguese colony of Goa from the 16th century onwards. The flasks, from the 17th to early 19th centuries, have echoes of much older works in the Animal style especially associated with ancient Scythia, and an intermediate tradition of objects, now lost, in perishable materials such as (in India) wood has been proposed.
There are also obvious links with miniatures from Deccan painting. Collectors may use the Indo-Persian term barut-dan for flasks from these areas.
Edo period Japanese flasks (kayaku-ire) were made in the materials and styles that were already highly developed in Japan for the decoration of small personal objects including flasks, often using lacquered wood, which was a very suitable material.
Gallery
Notes
References
Born, Wolfgang, "Ivory Powder Flasks from the Mughal Period", Ars Islamica, Vol. 9, (1942), pp. 93–111, Freer Gallery of Art, The Smithsonian Institution and Department of the History of Art, University of Michigan, JSTOR
Browne, S. Bertram, A companion to the new rifle musket, 1859 (2nd edn.), W. H. Allen & Co., London
Fadala, Sam, The Complete Blackpowder Handbook, 2006, Gun Digest Books, , 9780896893900, google books
Garry, James, Weapons of the Lewis and Clark Expedition, 2012, University of Oklahoma Press, , 9780806188003
"Grancsay (1929)", Grancsay, Stephen V., "A Gift of Powder Flasks", The Metropolitan Museum of Art Bulletin, Vol. 24, No. 5 (May, 1929), pp. 132–134, JSTOR
"Grancsay (1931)", Grancsay, Stephen V., "A Silver-Mounted Powder Horn", The Metropolitan Museum of Art Bulletin, Vol. 26, No. 3, Part 1 (Mar., 1931), pp. 76–77, JSTOR
Haythornthwaite, Philip J., British Rifleman: 1797-1815, 2002, Osprey Publishing, , 9781841761770
Landers, David, "Powder flasks", Gun Mart magazine website, accessed July 30, 2013
McLachlan, Sean, Medieval Handgonnes, 2010, Osprey Publishing (page numbers per online preview), , 9781849081559, google books
"O'Sullivan", Dr. Mark F. Ryan,Fenian Memories, Edited by T.F. O'Sullivan, M. H. Gill & Son, Ltd, Dublin, 1945
"Timeline", "Powder flask [German] (2007.479.2)", In Heilbrunn Timeline of Art History. New York: The Metropolitan Museum of Art, 2000–, (updated April 2009)
Further reading
Ray Riling, The Powder Flask Book, 1953, the standard work on 19th-century American flasks.
Early firearms
Containers
Firearm components
Gunpowder | Powder flask | Technology | 2,413 |
47,358,172 | https://en.wikipedia.org/wiki/Dehydroamino%20acid | In biochemistry, a dehydroamino acid or α,β-dehydroamino acid is an amino acids, usually with a C=C double bond in its side chain. Dehydroamino acids are not coded by DNA, but arise via post-translational modification.
Examples
A common dehydroamino acid is dehydroalanine, which otherwise exists only as a residue in proteins and peptides. The dehydroalanine residue is obtained dehydration of serine-containing protein/peptide (alternatively, removal of H2S from cysteine). Another example is dehydrobutyrine, derived from dehydration of threonine.
Generally, amino acid residues are unreactive toward nucleophiles, but the dehydroamino acids are exceptions to this pattern. For example, dehydroalanine adds cysteine and lysine to form covalent crosslinks.
An unusual dehydroamino acid is dehydroglycine (DHG) because it does not contain a carbon-carbon double bond. Instead it is the imino acid of glyoxalic acid. It arises by the radical-induced degradation of tyrosine.
N-Acyl derivatives
Dehydroamino acids do not feature amino-alkene groups, but the corresponding N-acylated derivatives are known. These derivatives, also known as N-acylamino acrylates, are prochiral substrates for asymmetric hydrogenation. The 2001 Nobel Prize in Chemistry was awarded to William S. Knowles for his synthesis of L-DOPA from the N-acylacrylate.
References
Amino acids | Dehydroamino acid | Chemistry | 354 |
419,232 | https://en.wikipedia.org/wiki/RTLinux | RTLinux is a hard realtime real-time operating system (RTOS) microkernel that runs the entire Linux operating system as a fully preemptive process. The hard real-time property makes it possible to control robots, data acquisition systems, manufacturing plants, and other time-sensitive instruments and machines from RTLinux applications. The design was patented. Despite the similar name, it is not related to the Real-Time Linux project of the Linux Foundation.
RTLinux was developed by Victor Yodaiken, Michael Barabanov, Cort Dougan and others at the New Mexico Institute of Mining and Technology and then as a commercial product at FSMLabs. Wind River Systems acquired FSMLabs embedded technology in February 2007 and made a version available as Wind River Real-Time Core for Wind River Linux. As of August 2011, Wind River has discontinued the Wind River Real-Time Core product line, effectively ending commercial support for the RTLinux product.
Background
The key RTLinux design objective was to add hard real-time capabilities to a commodity operating system to facilitate the development of complex control programs with both capabilities. For example, one might want to develop a real-time motor controller that used a commodity database and exported a web operator interface. Instead of attempting to build a single operating system that could support real-time and non-real-time capabilities, RTLinux was designed to share a computing device between a real-time and non-real-time operating system so that (1) the real-time operating system could never be blocked from execution by the non-real-time operating system and (2) components running in the two different environments could easily share data. As the name implies RTLinux was originally designed to use Linux as the non-real-time system but it eventually evolved so that the RTCore real-time kernel could run with either Linux or Berkeley Software Distribution (BSD) Unix.
Multi-Environment Real-Time (MERT) was the first example of a real-time operating system coexisting with a Unix system. MERT relied on traditional virtualization techniques: the real-time kernel was the host operating system (or hypervisor) and Bell Systems Unix was the guest. RTLinux was an attempt to update the MERT concept to the PC era and commodity hardware. It was also an attempt to also overcome the performance limits of MERT, particularly the overhead introduced by virtualization.
Instead of encapsulating the guest OS in a virtual machine, RTLinux virtualized only the guest interrupt control. This method allowed the real-time kernel to convert the guest operating system into a system that was completely preemptible but that could still directly control, for example, storage devices. In particular, standard drivers for the guest worked without source modification although they needed to be recompiled to use the virtualization "hooks". See also paravirtualization. The Unix pipe was adapted to permit real-time and non-real-time programs to communicate, although other methods such as shared memory were also added.
From the programmer's point of view, RTLinux originally looked like a small threaded environment for real-time tasks plus the standard Linux environment for everything else. The real-time operating system was implemented as a loadable kernel module which began by virtualizing guest interrupt control and then started a real-time scheduler. Tasks were assigned static priorities and scheduling was originally purely priority driven. The guest operating system was incorporated as the lowest priority task and essentially acted as the idle task for the real-time system. Real-time tasks ran in kernel mode. Later development of RTLinux adopted the Portable Operating System Interface (POSIX) POSIX threads application programming interface (API) and then permitted creation of threads in user mode with real-time threads running inside guest processes. In multiprocessor environments threads were locked to processor cores and it was possible to prevent the guest thread from running on designated core (effectively reserving cores for only real-time processing).
Implementation
RTLinux provides the ability to run special real-time tasks and interrupt handlers on the same machine as standard Linux. These tasks and handlers execute when they need to execute no matter what Linux is doing. The worst case time between the moment a hardware interrupt is detected by the processor and the moment an interrupt handler starts to execute is under 15 microseconds on RTLinux running on a generic x86 (circa 2000). A RTLinux periodic task runs within 35 microseconds of its scheduled time on the same hardware. These times are hardware limited, and as hardware improves RTLinux will also improve. Standard Linux has excellent average performance and can even provide millisecond level scheduling precision for tasks using the POSIX soft real-time capabilities. Standard Linux is not, however, designed to provide sub-millisecond precision and reliable timing guarantees. RTLinux was based on a lightweight virtual machine where the Linux "guest" was given a virtualized interrupt controller and timer, and all other hardware access was direct. From the point of view of the real-time "host", the Linux kernel is a thread. Interrupts needed for deterministic processing are processed by the real-time core, while other interrupts are forwarded to Linux, which runs at a lower priority than real-time threads. Linux drivers handled almost all I/O. First-In-First-Out pipes (FIFO) or shared memory can be used to share data between the operating system and RTLinux.
Objective
The key RTLinux design objective is that the system should be transparent, modular, and extensible . Transparency means that there are no unopenable black boxes and the cost of any operation should be determinable. Modularity means that it is possible to omit functionality and the expense of that functionality if it is not needed. And extensibility means that programmers should be able to add modules and tailor the system to their requirements. The base RTLinux system supports high speed interrupt handling and no more. It has simple priority scheduler that can be easily replaced by schedulers more suited to the needs of some specific application. When developing RTLinux, it was designed to maximize the advantage we get from having Linux and its powerful capabilities available.
Core components
RTLinux is structured as a small core component and a set of optional components. The core component permits installation of very low latency interrupt handlers that cannot be delayed or preempted by Linux itself and some low level synchronization and interrupt control routines. This core component has been extended to support SMP and at the same time it has been simplified by removing some functionality that can be provided outside the core.
Functions
Most RTLinux functions are in a set of loadable kernel modules that provide optional services and levels of abstraction. These modules include:
rtl sched - a priority scheduler that supports both a "lite POSIX" interface described below and the original V1 RTLinux API.
rtl time - which controls the processor clocks and exports an abstract interface for connecting handlers to clocks.
rtl posixio - supports POSIX style read/write/open interface to device drivers.
rtl fifo - connects RT tasks and interrupt handlers to Linux processes through a device layer so that Linux processes can read/write to RT components.
semaphore - a contributed package by Jerry Epplin which gives RT tasks blocking semaphores.
POSIX mutex support is planned to be available in the next minor version update of RTLinux.
mbuff is a contributed package written by Tomasz Motylewski for providing shared memory between RT components and Linux processes.
Realtime tasks
RTLinux realtime tasks get implemented as kernel modules similar to the type of module that Linux uses for drivers, file systems, and so on. Realtime tasks have direct access to the hardware and do not use virtual memory. On initialization, a realtime task (module) informs the RTLinux kernel of its deadline, period, and release-time constraints.
Threads
RT-Linux implements a POSIX API for a thread's manipulation. A thread is created by calling the pthread_create function. The third parameter of pthread_create is a function which contains the code executed by the thread.
It is necessary to set thread priorities in RTLinux. Threads with higher priorities can preempt threads with lower priorities. For example, we can have a thread controlling a stepper motor. In order to move the motor fluently, it is necessary to start this thread in strictly regular intervals. This can be guaranteed by assigning a high priority to this thread. The example threads2.c sets different thread priorities. Setting of thread priority is done by code shown below:
int init_module(void)
{
pthread_attr_t attr;
struct sched_param param;
pthread_attr_init(&attr);
param.sched_priority = 1;
pthread_attr_setschedparam(&attr, ¶m);
pthread_create(&t1, &attr, &thread_code, "this is thread 1");
rtl_printf("Thread 1 started\n");
/* ... */
}
The output the program is as follows.
Thread 1 started
Thread 2 started
Thread 3 started
Message: this is thread 1
Message: this is thread 2
Message: this is thread 2
Message: this is thread 2
Message: this is thread 1
Message: this is thread 1
Message: this is thread 3
Message: this is thread 3
Message: this is thread 3
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See also
RTAI. RTAI began as a variant of RTLinux called "MyRTlinux" and in later releases was claimed by its authors not to use the patented RTLinux virtualization technique.
RMX (operating system)
SCHED_DEADLINE
Xenomai
Preemption (computing)
Linux on embedded systems
Real-time testing
References
Sources
Dougan, Cort (2004), "Precision and predictability for Linux and RTLinuxPro", Dr. Dobbs Journal, February 1, 2004
Yodaiken, Victor (1997), US Patent 5,995,745
External links
Article about RTLinux synchronization
A Real-Time Linux . Victor Yodaiken and Michael Barabanov, New Mexico Institute of Technology
Linux kernel variant
Real-time operating systems | RTLinux | Technology | 2,214 |
41,226,144 | https://en.wikipedia.org/wiki/Toyota%20Electronic%20Modulated%20Suspension | TEMS (Toyota Electronic Modulated Suspension) is a shock absorber that is electronically controlled (Continuous Damping Control) based on multiple factors, and was built and exclusively used by Toyota for selected products during the 1980s and 1990s (first introduced on the Toyota Soarer in 1983). The semi-active suspension system was widely used on luxury and top sport trim packages on most of Toyota's products sold internationally. Its popularity fell after the “bubble economy” as it was seen as an unnecessary expense to purchase and maintain, and remained in use on luxury or high performance sports cars.
Summary
TEMS consisted of four shock absorbers mounted at all four wheels, and could be used in either an automatic or driver selected mode based on the installation of the system used. The technology was installed on top-level Toyota products with four wheel independent suspension, labeled PEGASUS (Precision Engineered Geometrically Advanced SUSpension). Because of the nature of the technology, TEMS was installed on vehicles with front and rear independent suspensions. The technology was modified and installed on minibuses or minivans like Toyota TownAce/MasterAce rear independent suspensions, and the top trim package on the Toyota HiAce.
Based on road conditions, the system would increase or decrease ride damping force for particular situations. The TEMS system was easily installed to suit ride comfort, and road handling stability on small suspensions, adding a level of ride modification found on larger, more expensive luxury vehicles. The technology was originally developed and calibrated for Japanese driving conditions due to Japanese speed limits, but was adapted for international driving conditions with later revisions.
As the Japanese recession of the early 1990s began to take effect, the system was seen as an unnecessary expense as buyers were less inclined to purchase products and services seen as “luxury” and more focused on basic needs. TEMS installation was still achieved on vehicles that were considered luxurious, like the Toyota Crown, Toyota Century, Toyota Windom, and the Toyota Supra and Toyota Soarer sports cars.
Recently the technology has been installed on luxury minivans like the Toyota Alphard, Toyota Noah and the Toyota Voxy.
The TEMS system has been recently named “Piezo TEMS” (with piezoelectric ceramics), “Skyhook TEMS” “Infinity TEMS” and more recently “AVS” (Adaptive Variable Suspension).
Configuration settings
The system was deployed with an earlier two-stage switch labeled “Auto-Sport”, with a later modification of “Auto-Soft-Mid-Hard”. Some variations used a dial to specifically select the level of hardness to the driver's desires. For most driving situations, the “Auto” selection was recommended. When the system was activated, an indicator light reflected the suspension setting selected. The system components consisted of a control switch, indicator light, four shock absorbers, shock absorber control actuator, shock absorber control computer, vehicle speed sensor, stop lamp switch, with a throttle position sensor and a steering angle sensor on TEMS three stage systems only. All the absorbers are controlled with the same level of hardness.
Operation parameters of TEMS
The following describes how the system would activate on the earlier version installed during the 1980s on two stage TEMS
During normal running
The system chooses the "SOFT" selection, to provide a softer ride.
At high speeds
The system selects the "HARD" selection and determines that at high speeds, it assumes a more rigid configuration for better ride stability, and to reduce roll tendencies.
Braking (reducing speed to )
In order to prevent “nose dive”, the process proceeds to "HARD" automatically damping force until it senses the brakes to be at the"SOFT" setting. It will return to the "SOFT" state when the brake light is off, and the pedal has been released after 2 seconds or more.
(Only 3-stage systems) during hard acceleration
To suppress suspension “squat” the system switches to "HARD" based on accelerator pedal position and throttle position.
(Only 3-stage systems) during hard cornering
To suppress suspension “roll” the system switches to "HARD" based on steering angle sensor position.
SPORT mode
The system remains in the "HARD" position regardless of driving conditions. (For 3-stage systems, the system automatically chooses between the “MID” and the "HARD" configurations - by the other words, the "SOFT" stage is excepted)
Vehicles installed
The following is a list of vehicles in Japan that were installed with the technology. There may have been vehicles exported internationally that were also equipped.
Starlet (EP71-based Turbo S, EP82-based GT)
Tercel / Corsa / Corolla II (EL31-based GP turbo)
Cynos
Sera
Corolla Levin / Sprinter Trueno (AE92 • AE101GT GT-APEX)
Corolla FX (AE92-GT)
Corona (ST171-based GT-R)
Celica (ST183 models)
Carina ED and Corona EXiV (ST180 models)
Century
Crown Majesta
Camry / Vista (SV20-based GT and Prominent G, SV30-based GT)
Pronard
Aristo (S140)
Town Ace / Master Ace
Lite Ace
Mark II / Chaser / Cresta (GX71-based Twin Cam Grande, GX81-based Twin Cam Grande system, JZX91 Grande G, JZX100 Grande G, JZX101 Grande G, JZX110 Grande G)
Windom (MCV10 system G, MCV20 system G, MCV30 system G)
Hiace
Hilux Surf (KZN130)
Hilux Surf (KZN185))
Crown
Soarer (GZ20 system 2.0GT Twin turbo L, JZZ30 system 2.5GT twin turbo L)
Soarer (1UZ-FE V8 UZZ31).
Supra (Select Models)
Celsior: Piezo TEMS
Noah / Voxy
Alphard
Land Cruiser (100 series)
Ipsum (acm20 system)
Super Strut (MacPherson modified strut)
Super strut suspension is a high-performance suspension for automobiles developed by Toyota. On vehicles equipped, the abbreviation listed was "SSsus" and was first installed on the AE101 Corolla Levin / Sprinter Trueno for 1991 .
Overview
This is a MacPherson strut type suspension that has been improved to compete with double wishbone type suspensions. It suppressed the change in camber angle that occurs when the suspension is in motion, and as a result it greatly increases handling stability and grip limit while turning. For front wheel drive sports coupes, there arose a need for an inexpensive upgrade that could be installed on vehicles that originally had MacPherson struts on the front wheels.
In contrast to the traditional L-shaped lower control arm used with MacPherson struts, Super Strut had a lower control arm divided into two parts, one of which is equipped with a camber control arm, which is connected to a specially shaped strut. As a result, a virtual kingpin axis was set inside the tire, making it possible to significantly reduce the kingpin angle from 14 degrees to 6 degrees and the spindle offset from 66 mm to 18 mm. As a result, the torque steer that is noticeable in high-output front-engine, front-wheel drive vehicles equipped with LSD is reduced. Active use of ball joints also ensures rigidity and reduces friction.
The camber control arm regulates the movement of the lower arm, so when the suspension reacts to a uneven road surface, the upper part of the upright pulls inward, causing the camber angle to change negatively. Note that the inclination of the strut body may be opposite to that of the MacPherson strut type.
While there are various advantages, there are also disadvantages. The unsprung suspension weight is heavier than the general MacPherson strut, and depending on the car model, the minimum turning radius would be increased. There are also conditions where the steering feels uncomfortable as the steering angle increases. Furthermore, because the effective range of motion of the short camber control arm is narrow, the amount of suspension travel is also affected. The behavior is stable due to the unique characteristic of camber change, when the suspension travel is minimal, and the camber change is also minimal, and when the camber control arm reaches a certain angle, the camber change is suddenly increased. Due to the narrow vehicle height range, it was not favorable to off-road driving conditions.
Although the above disadvantages were not a problem in ordinary cars where the road surface conditions did not change much and the vehicle speed was slow, the setting range that is considered best in high speed racing conditions where limited performance is necessary and required flexibility. Therefore, in the category where suspension changes are allowed, there were cases where the structure was simple, there was accumulated know-how, and the suspension was replaced with a conventional strut, which was easier to handle.
Vehicles installed
Corolla Levin / Sprinter Trueno (AE92 • AE101GT• BZ-R)
Corolla FX (AE101)
Toyota Celica (T200) SS-II, SS-III (ST202)
Celica GT-Four (ST205)
Toyota Celica (T230) SS-II (ZZT231)
Curren (ST206)
Carina E (ST190 series) (export)
Carina ED (ST200 series)
Corona EXiV (ST200 series)
See also
Active Stabilizer Suspension System
Kinetic Dynamic Suspension System
Toyota Active Control Suspension
Active Body Control
References
Notes
Sources
Development of New Toyota Electronic Modulated Suspension - Two Concepts for Semi-Active Suspension Control
Toyota
Automotive suspension technologies
Shock absorbers
Automotive technology tradenames
Automotive safety technologies
Auto parts
Mechanical power control | Toyota Electronic Modulated Suspension | Physics | 2,037 |
75,804,072 | https://en.wikipedia.org/wiki/Cheilanthes%20cinnamomea | Cheilanthes cinnamomea is a species name, which may refer to:
Myriopteris rufa, given a nomen novum in 1883 as Cheilanthes cinnamomea D.C.Eaton
Myriopteris cinnamomea, recombined in 1915 as Cheilanthes cinnamomea (Baker) Domin
cinnamomea | Cheilanthes cinnamomea | Biology | 89 |
74,022,038 | https://en.wikipedia.org/wiki/Hydrocupration | A hydrocupration is a chemical reaction whereby a ligated copper hydride species (Cu(I)H), reacts with a carbon-carbon or carbon-oxygen pi-system; this insertion is typically thought to occur via a four-membered ring transition state, producing a new copper-carbon or copper-oxygen sigma-bond and a stable (generally) carbon-hydrogen sigma-bond. In the latter instance (copper-oxygen), protonation (protodemetalation) is typical – the former (copper-carbon) has broad utility. The generated copper-carbon bond (organocuprate) has been employed in various nucleophilic additions to polar conjugated and non-conjugated systems and has also been used to forge (by way of reductive elimination or transmetalation) new carbon-heteroatom bonds (Nitrogen, Boron, etc.).
History
While copper (I) hydride was the earliest known binary metal hydride (1800s), synthetic organic chemist’s interest in the reactivity of copper hydride complexes did not arise until nearly a century later; this interest came in the form of the now broadly utilized Stryker’s reagent (PPh3-modified CuH Hexamer) to affect hydrocuprations of unsaturated ketones – resulting in either 1,4 or 1,2 reduction (see Copper hydride, Stryker's reagent). While the discussed reactivity is still heavily utilized, hydrocupration has recently (early 21st century) been popularized in olefin functionalizations.
Synthetic applications
General catalytic utility
Many reactions utilizing ligated copper (I) hydride to functionalize olefins have been rendered catalytic and/or enantioselective. The scheme below details, in a generic sense, the catalytic cycle for popularized reactions in this realm – and, how they’ve been hypothesized to proceed. As it pertains to copper hydride-mediated hydroboration, after 1,2-migratory insertion (M.I.), a transmetalation can take place with pinacolborane (HBPin) to produce the hydroborated product and regenerate ligated copper (I) hydride.
For hydroalkylations (and hydroacylations), the generated organocuprate (after initial migratory insertion) can perform nucleophilic substitution chemistry (SN2) with alkyl halides, carbonyls, and various other classical electrophiles; in this instance (and in the case of reactivity with an alkyl halide) a copper (I) halide salt is produced, which upon transmetalation with a metalated alkoxide additive produces a more thermodynamically stable metal halide salt and a copper (I) alkoxide. The latter species can undergo a final transmetalation with an alkyl hydrosilane (stoichiometric) to regenerate the active ligated copper (I) hydride catalyst and a thermodynamically stable silanol.
For hydroaminations, ligated copper (I) hydride undergoes a 1,2 migratory insertion; the resulting organocuprate can be reacted with an appropriate electrophilic amine source (such as the O-benzoylated hydroxylamine shown) to produce a highly energetic copper (III) intermediate. Reductive elimination between the carbon and nitrogen (forming C-N) produces the hydroaminated product along with a copper (I) alkoxide – which, similarly to the case of hydroalkylations/acylations, can undergo further transmetalation with an alkyl hydrosilane to regenerate the active ligated copper (I) hydride species. Alternative hypotheses to the amination step involve direct displacement or transmetalation, versus an oxidative addition to the polarized hydroxylamine.
Enantio- and regioselective CuH-catalyzed hydroamination of alkenes
In 2013, the Buchwald group reported a copper-catalyzed hydroamination method for synthesizing chiral tertiary amines; similar work was disclosed by the Miura group (Osaka University) in the same year. For about a decade, the group had published numerous papers employing ligated copper (I) hydride in 1,4-reductions of polar, conjugated systems – they postulated that their experience in performing this chemistry served as a platform for the hydroamination of alkenes shown.
In the case of activated olefins (styrenyl-), the group observed markovnikov selectivity (presumably due to the stronger carbon-hydrogen bond formed simultaneously) and were able to render the reaction enantioselective through the utility of a chiral ligand (DTBM-SEGPHOS). For unactivated (aliphatic alkenes), the group observed anti-markovnikov selectivity exclusively – which, they theorize to be the result of a hydride migration from the copper catalyst to form the less sterically crowded terminal copper intermediate, where there is no electronic advantage as for styrenes to form the secondary alkyl-Cu intermediate; these reactions, at least in this initial publication, were not able to be rendered enantioselective. Notably, in subsequent publications the group has further diversified and improved this chemistry – where they’ve been able to render the aliphatic alkene reactions enantioselective, vary the electrophilic amine source, and broaden the substrate scope even further.
Enantioselective synthesis of carbo- and heterocycles through a CuH-catalyzed hydroalkylation approach
In 2015, the Buchwald group reported a copper-catalyzed enantioselective hydroalkylation of bromide tethered styrenyl-type olefins. The synthesis of a variety of 4-, 5-, and 6-membered rings are reported – some of which are featured prominently in biologically active natural products and pharmaceuticals (substituted cyclobutanes, cyclopentanes, indanes, and saturated heterocycles). Notably, competitive reduction of the alkyl halide by copper hydride was not observed under the optimized conditions – being a remarkable display of ligated copper (I) hydride’s chemoselectivity.
Synthesis of pyrroles through the coupling of enynes and nitriles
In 2020, the Buchwald group developed a copper-catalyzed enyne-nitrile coupling reaction – which, utilizes readily available building blocks to synthesize polysubstituted pyrroles. Notably, this discovery stemmed from the group’s pursuit of performing intermolecular hydroacylations with hydrocuprated materials – the first examples being with ketones and aldehydes; employing nitriles resulted in pyrrole formation. While there is a pre-existing array of literature pertaining to polysubstituted pyrrole synthesis, the reported methodology allows for unique and modular retrosynthetic disconnections which differ from traditional condensation or substitution approaches to similar molecules.
References
Chemical reactions | Hydrocupration | Chemistry | 1,533 |
3,302,451 | https://en.wikipedia.org/wiki/List%20of%20Palm%20OS%20devices | This is a list of Palm OS devices, and companies that make, or have made, them.
Abacus/Fossil, Inc.
Fossil, made Wrist PDAs that use the Palm OS operating system.(Discontinued)
AU5005—Palm OS 4.1
AU5006—Palm OS 4.1
AU5008—Palm OS 4.1
FX2008—Palm OS 4.1
FX2009—Palm OS 4.1
Aceeca
Meazura—Palm OS 4.1.2
PDA32—Garnet OS 5.4
Acer
S10/S11/S12—Palm OS 4.1 - first Chinese Palm
S50/S55—Palm OS 4.1, color Hi-Res screen
S60/S65—Palm OS 4.1, MP3 player, voice recorder, color Hi-Res screen
AlphaSmart
Dana—Palm OS 4.1.2 - small "laptop" running Palm OS with a 560x160 pixel greyscale LCD, full-sized keyboard, two SD card slots, 8MiB or 16Mib memory, powered by NiMH or 3 x AA battery or wall adapter
Dana Wireless—Palm OS 4.1.2, same features as Dana plus Wi-Fi, 16MiB memory, SDIO support, widescreen launcher
Garmin
PDA with integrated GPS.
iQue 3600a—Palm OS 5.4
iQue 3600—Palm OS 5.2.1
iQue 3200—Palm OS 5.2.1
iQue 3000—Palm OS 5.2.1
Group Sense PDA
Smartphones with Palm OS
Xplore G18—Palm OS 4.1 (candybar, 2.2" 176x240 16-bit TFT, CIF camera, Dragonball VZ 33 MHz, 16MB RAM, 4MB OS flash)
Xplore G88—Palm OS 4.1 (slider, 2.2" 176x240 16-bit TFT, CIF camera, Dragonball VZ 33 MHz, 16MB RAM, 4MB OS flash, 24MB user flash appearing as an internal SD card)
Xplore M28—Palm OS 5.4 (slider, 2.2" 176x240 16-bit TFT, VGA camera, ARM9 CPU, 32MB NVFS storage, SD/MMC card slot)
Xplore M68—Palm OS 5.4 (candybar, 2.2" 176x240 16-bit TFT, 1.3MP camera, ARM9 CPU, SD/MMC card slot)
Xplore M70—Palm OS 5.4 (candybar, 2.2" 176x240 16-bit TFT, 1.3MP camera with video recording, ARM9 CPU, SD/MMC card slot)
Xplore M70S—Palm OS 5.4 hardware same as M70 with security firmware update
Xplore M98—Palm OS 5.4 (flip, 2.2" 176x240 16-bit TFT inside, 96x96 outside, 1.3MP camera, ARM9 CPU, 32MB NVFS storage, microSD card slot)
Handera/TRG
TRGpro—Palm OS 3.5.3 - introduced standard (CF) Card slot (company was at that time TRG (Technology Resource Group))
Handera 330—Palm OS 3.5.3
Handera 330c— never released
Handspring
The inventors of the Palm formed a new company called Handspring in June 1998, operating until 2003 when it merged with Palm, Inc.'s hardware division.
Visor
Visors introduced color cases and the Springboard Expansion slot.
Visor Solo—Palm OS 3.1H - 16 MHz, 2 MB RAM, B&W
Visor Deluxe—Palm OS 3.1H/H2 - 20 MHz, 8MB RAM, B&W
Visor Platinum—Palm OS 3.5.2H - 33 MHz, 8 MB RAM, B&W
Visor Prism—Palm OS 3.5.2H3 - 33 MHz, 8 MB RAM, color (world's first 16-bit color Palm OS device)
Visor Edge—Palm OS 3.5.2H - 33 MHz, 8 MB RAM, B&W, thin, sleek, metal case
Visor Neo—Palm OS 3.5.2H3 - 33 MHz, 8 MB RAM, B&W
Visor Pro—Palm OS 3.5.2H3 - 33 MHz, 16 MB RAM, B&W
Treo
Smartphones (except 90)
Treo 90—Palm OS 4.1H - can be updated to 4.1H3 which adds SDIO support
Treo 180—Palm OS 3.5.2H
Treo 180g—Palm OS 3.5.2H - the Treo 180 with Graffiti area, rather than a keyboard
Treo 270—Palm OS 3.5.2H
Treo 300—Palm OS 3.5.2H6.2
Treo 600—Palm OS 5.2.1H
IBM
IBM's Workpad series was nearly identical to PDAs manufactured by Palm. The main difference were color and logo on the casing.
WorkPad
WorkPad (rebadged PalmPilot)
WorkPad 20X (rebadged Palm III)
WorkPad 30X (rebadged Palm IIIx)
WorkPad c3 (rebadged Palm V/Vx) thin, sleek, metal case
WorkPad c500 (rebadged Palm m500) thin, sleek, metal case
WorkPad c505 (rebadged Palm m505) thin, sleek, metal case
Janam
XP20—Palm OS 5.4.9, B&W 160x160 screen, two variants: one with a full keyboard, one with partial
XP30—Palm OS 5.4.9, Color 240x160 screen, two variants: one with a full keyboard, one with partial
Kyocera
Smartphones
QCP-6035—Palm OS 3.5.3
QCP-7135—Palm OS 4.1
Legend Group
Pam 168—Palm OS 4.1
Lenovo
Chinese PDAs
p100—Palm OS 5.3
p200—Palm OS 5.3
p300—Palm OS 5.3
Palm, Inc. & palmOne, Inc.
Pilot 1000 (as division of U.S. Robotics)—Palm OS 1.0 - 16 MHz, 128 KB RAM
Pilot 5000 (as division of U.S. Robotics)—Palm OS 1.0 - 16 MHz, 512 KB RAM
PalmPilot Personal (as division of U.S. Robotics)—Palm OS 2.0 - 16 MHz, 512 KB RAM, backlight
PalmPilot Professional (as division of U.S. Robotics)—Palm OS 2.0 - 16 MHz, 1 MB RAM, backlight
Palm III—Palm OS 3.0 - 16 MHz, 2 MB RAM (update possible to 3.5.3 (website) or 4.1 (CD))
Palm IIIx—Palm OS 3.1 - 16 MHz, 4 MB RAM (update possible to 3.5.3 (website) or 4.1 (CD))
Palm V—Palm OS 3.1 - 16 MHz, 2 MB RAM, thin, sleek, metal case (update possible to 3.5.3 (website) or 4.1 (CD))
Palm VII—Palm OS 3.2 - 16 MHz, 2 MB RAM, Palm.net wireless
Palm IIIe—Palm OS 3.1 - 16 MHz, 2 MB RAM, no flash OS upgrade
Palm Vx—Palm OS 3.3 - 20 MHz, 8MB RAM, thin, sleek, metal case (update possible to 3.5.3 (website) or 4.1 (CD))
Palm IIIxe—Palm OS 3.5 - 16 MHz, 8 MB RAM (update possible to 3.5.3 (website) or 4.1 (CD))
Palm IIIc—Palm OS 3.5 - 20 MHz, 8 MB RAM, Palm's first color screen (8-bit) (update possible to 3.5.3 (website) or 4.1 (CD))
Palm VIIx—Palm OS 3.5 - 20 MHz, 8 MB RAM, Palm.net wireless
Palm m100—Palm OS 3.5 - 16 MHz, 2 MB RAM
Palm m105—Palm OS 3.5 - 16 MHz, 8 MB RAM
Palm m500—Palm OS 4.0 - 33 MHz, 8 MB RAM, thin, sleek, metal case (update possible to 4.1 (website))
Palm m505—Palm OS 4.0 - 33 MHz, 8 MB RAM, 16-bit color screen, thin, sleek, metal case (update possible to 4.1 (website))
Palm m125—Palm OS 4.0.1 - 33 MHz, 8 MB RAM
Palm i705—Palm OS 4.1 - 33 MHz, 8 MB RAM, Palm.net wireless
Palm m130—Palm OS 4.1 - 33 MHz, 8 MB RAM, 12-bit color screen
Palm m515—Palm OS 4.1 - 33 MHz, 16 MB RAM, 16-bit color screen, thin, sleek, metal case
Zire
The Zire series, renamed "Z" series in 2005, are the lower-end Palm models. Some have color screens (160x160 or 320x320), some are B&W (160x160).
Zire (also known as m150)—Palm OS 4.1 - 16 MHz, 2 MB RAM
Zire 71—Palm OS 5.2.1 - 144 MHz, 16 MB RAM, 0.3MP digital camera, MP3 player
Zire 21—Palm OS 5.2.1 - 126 MHz, 8 MB RAM, new PIM
Zire 31—Palm OS 5.2.8 - 200 MHz, 16 MB RAM, new PIM, MP3 player
Zire 72 & 72s—Palm OS 5.2.8 - 312 MHz, 32 MB RAM, new PIM, 1.2MP digital camera with video, voice recorder, MP3 player, Bluetooth
Palm Z22—Palm OS 5.4.9 - 200 MHz, 32 MB RAM, new PIM, NVFS
Tungsten
The Tungsten series, renamed "T" series in 2005, are the high-end Palm models, with ARM/RISC processors (except the Tungsten W), high-resolution color screens, and SD memory cards.
Tungsten T (also known as m550)—Palm OS 5.0 - 144 MHz, 16 MHz, sliding case, voice recorder, Bluetooth
Tungsten W—Palm OS 4.1.1 - 33 MHz, 16 MB RAM, physical keyboard, cell service (update possible to 4.1.2 (website))
Tungsten C—Palm OS 5.2.1 - 400 MHz, 64 MB RAM, physical keyboard, voice recorder, WiFi
Tungsten T2—Palm OS 5.2.1 - 144 MHz, 32 MB RAM, voice recorder, Bluetooth
Tungsten E—Palm OS 5.2.1 - 126 MHz, 32 MB RAM, new PIM
Tungsten T3—Palm OS 5.2.1 - 400 MHz, 64 MB RAM, new PIM, sliding case, voice recorder, MP3 player, Bluetooth
Tungsten T5—Palm OS 5.4.0 - 416 MHz, 256 MB RAM, new PIM, NVFS, internal USB flash drive, MP3 player, Bluetooth (update possible to 5.4.8 (website))
Tungsten E2—Palm OS 5.4.7 - 200 MHz, 32 MB RAM, new PIM, NVFS, Bluetooth, MP3 player
Palm TX—Palm OS 5.4.9 - 312 MHz, 128 MB RAM, new PIM, NVFS, MP3 player, WiFi, Bluetooth
LifeDrive
LifeDrive—Palm OS 5.4.8 - 416 MHz, 64 MB RAM, 4 GB Microdrive, new PIM, NVFS, voice recorder, MP3 player, WiFi, Bluetooth
Treo
The Treo series are combo cell phones/PDA models, originally developed by Handspring.
Treo 600—Palm OS 5.2.1H (The first models were "Handspring"-branded, later models were "Palm"-branded.)
Treo 650—Palm OS 5.4, 5.4.5 or 5.4.8 depending on specific carrier version
Treo 680—Palm OS 5.4.9
Treo 700p—Palm OS 5.4.9
Treo 755p—Palm OS 5.4.9
Palm P850—Palm OS 5.2H - released in 2010 in the Chinese market, also called the Treo P850
Centro
The Palm Centro is a combo cell phone/PDA, similar to the Treo line.
Centro—Palm OS 5.4.9
Qool
QDA 700—Palm OS 5.4.1 - Cell Phone
Made by Pitech
Qualcomm
Smartphones, later sold to Kyocera
pdQ 1900 (single-mode CDMA 1900 MHz digital PCS)—Palm OS 3.0
pdQ 800 (dual-mode 800 MHz digital/analog PCS)—Palm OS 3.0
Samsung
Smartphones
SPH-i300—Palm OS 3.5
SPH-i330—Palm OS 3.5.3
SCH-M330—Palm OS 3.5.3 - Scheduled for release in South Korea
SPH-i500—Palm OS 4.1
SPH-i550—Palm OS 5.2 - never released.
SCH-M500—Palm OS 5.2 - Scheduled for release in South Korea in mid-July 2004.
SGH-i500—Palm OS 5.2 - never released
SGH-i505—Palm OS 5.2 - never released
SGH-i530—Palm OS 5.2 - never sold, only given away at Athens Olympics 2004
SCH-i539—Palm OS 5.4.1 - Released in China
Sony CLIÉ
Sony developed and marketed the CLIÉ multimedia PDA from 2000 to 2005.
N Series
PEG-N610C—Palm OS 4.0
PEG-N710C—Palm OS 3.5.2
PEG-N760C—Palm OS 4.1S & MP3 player
NR Series
PEG-NR70—Palm OS 4.1S
PEG-NR70V—Palm OS 4.1S
NX Series
PEG-NX60—Palm OS 5.0 & MP3 player
PEG-NX70V—Palm OS 5.0 & MP3 player & VGA digi-cam / camcorder
PEG-NX73V—Palm OS 5.0 & MP3 player & VGA digi-cam / camcorder (/E European versions also had Bluetooth)
PEG-NX80V—Palm OS 5.0 & MP3 player & 1.3 Mp digi-cam / camcorder
NZ Series
PEG-NZ90—Palm OS 5.0 & MP3 player & 2 Mp digi-cam / camcorder
S Series
PEG-S300—Palm OS 3.5S
PEG-S320—Palm OS 4.0S
PEG-S360—Palm OS 4.0S
PEG-S500C—Palm OS 3.5S
SJ Series
PEG-SJ20—Palm OS 4.1
PEG-SJ22—Palm OS 4.1
PEG-SJ30—Palm OS 4.1
PEG-SJ33—Palm OS 4.1
SL Series
PEG-SL10—Palm OS 4.1 & B&W paper-white screen
T Series
PEG-T400—Palm OS 4.1 & vibe-alarm feature thin, sleek, metal case, B&W HiRes screen (Japanese)
PEG-T415—English ROM version of the PEG-T400
PEG-T425—European version of T415
PEG-T600C—Palm OS 4.1 thin, sleek, metal case, Color HiRes screen (Japanese)
PEG-T615C—English ROM version of the PEG-T600
PEG-T625C—European version of T615C
PEG-T600C—Palm OS 4.1 & MP3 player thin, sleek, metal case, Color HiRes screen
PEG-T665C—English ROM version of the PEG-T650
PEG-T675C—European version of T665C
TG Series
PEG-TG50—Palm OS 5.0
TH Series
PEG-TH55—Palm OS 5.2.1 Wi-Fi (/E European versions also had Bluetooth)
TJ Series
PEG-TJ25—Palm OS 5.2
PEG-TJ27—Palm OS 5.2
PEG-TJ35—Palm OS 5.2
PEG-TJ37—Palm OS 5.2
UX Series
PEG-UX40—Palm OS 5.2 & MP3 player
PEG-UX50—Palm OS 5.2 & MP3 player
VZ Series
PEG-VZ90—Palm OS 5.2.1
Symbol
PDA with integrated barcode reader
SPT-1500—Palm OS 3.0.2r3
SPT-1550—Palm OS 3.0
SPT-1700—Palm OS 3.5
SPT-1733—Palm OS 3.5.2
SPT-1734—Palm OS 3.5.2
SPT-1740—Palm OS 3.5
SPT-1800—Palm OS 4.0
SPT-1833—Palm OS 4.0
SPT-1834—Palm OS 4.0
SPT-1846—Palm OS 4.0
Tapwave
A PDA designed for handheld gaming. It was held sideways (landscape), had an analog joystick and extra gaming buttons, and used Bluetooth for multiplayer gaming as well as standard PDA functions. It also introduced a dedicated video chip, and dual SD card slots.
Tapwave Zodiac 1 -- Palm OS 5.2T & MP3 player
Tapwave Zodiac 2 -- Palm OS 5.2T & MP3 player
Oswin
Two models (candybar and slider) were demonstrated at PalmSource Euro Dev Con 2005 running Palm OS Cobalt 6.1.1
A few were sold onsite. Oswin never produced more. These were the only Palm OS cobalt devices to be seen in the wild.
The codename for the candybar version was Zircon A108
Emulators
POSE (Palm OS Emulator)—Free Palm OS 4 emulator for PCs
Palm OS Simulator—Palm OS 5 simulator for PCs
StyleTap—for Windows Mobile, Symbian, and Android
Garnet VM—for Access Linux Platform and Maemo
Classic—for webOS-based Devices
PHEM—for Android-based devices
Cloudpilot—for web browsers and mobile devices
See also
List of Pocket PC Devices
References
External links
Palm family tree
Palm Infocenter list of all Palm OS PDA Reviews
Palm OS versions and upgrade possibility list - BAD LINK
Pen Computing Magazine Review of the TRG Pro
Palm OS
Palm OS devices
Palm OS | List of Palm OS devices | Technology | 4,020 |
9,019,997 | https://en.wikipedia.org/wiki/Native%20species | In biogeography, a native species is indigenous to a given region or ecosystem if its presence in that region is the result of only local natural evolution (though often popularised as "with no human intervention") during history. The term is equivalent to the concept of indigenous or autochthonous species. A wild organism (as opposed to a domesticated organism) is known as an introduced species within the regions where it was anthropogenically introduced. If an introduced species causes substantial ecological, environmental, and/or economic damage, it may be regarded more specifically as an invasive species.
The notion of nativity is often a blurred concept, as it is a function of both time and political boundaries. Over long periods of time, local conditions and migratory patterns are constantly changing as tectonic plates move, join, and split. Natural climate change (which is much slower than human-caused climate change) changes sea level, ice cover, temperature, and rainfall, driving direct changes in habitability and indirect changes through the presence of predators, competitors, food sources, and even oxygen levels. Species do naturally appear, reproduce, and endure, or become extinct, and their distribution is rarely static or confined to a particular geographic location. Moreover, the distinction between native and non-native as being tied to a local occurrence during historical times has been criticised as lacking perspective, and a case was made for more graded categorisations such as that of prehistoric natives, which occurred in a region during prehistory but have since suffered local extinction there due to human involvement.
A native species in a location is not necessarily also endemic to that location. Endemic species are exclusively found in a particular place. A native species may occur in areas other than the one under consideration. The terms endemic and native also do not imply that an organism necessarily first originated or evolved where it is currently found.
Ecology
Native species form communities and biological interactions with other specific flora, fauna, fungi, and other organisms. For example, some plant species can only reproduce with a continued mutualistic interaction with a certain animal pollinator, and the pollinating animal may also be dependent on that plant species for a food source. Many species have adapted to very limited, unusual, or harsh conditions, such as cold climates or frequent wildfires. Others can live in diverse areas or adapt well to different surroundings.
Human impact and intervention
The diversity of species across many parts of the world exists only because bioregions are separated by barriers, particularly large rivers, seas, oceans, mountains, and deserts. Humans can introduce species that have never met in their evolutionary history, on varying time scales ranging from days to decades (Long, 1981; Vermeij, 1991). Humans are moving species across the globe at an unprecedented rate. Those working to address invasive species view this as an increased risk to native species.
As humans introduce species to new locations for cultivation, or transport them by accident, some of them may become invasive species, damaging native communities. Invasive species can have profound effects on ecosystems by changing ecosystem structure, function, species abundance, and community composition. Besides ecological damage, these species can also damage agriculture, infrastructure, and cultural assets. Government agencies and environmental groups are directing increasing resources to addressing these species.
Conservation and advocacy
Native plant organizations such as the Society for Ecological Restoration, native plant societies, Wild Ones, and Lady Bird Johnson Wildflower Center encourage the use of native plants. The identification of local remnant natural areas provides a basis for this work.
Many books have been written on the subject of planting native plants in home gardens. The use of cultivars derived from native species is a widely disputed practice among native plant advocates.
Importance of nativity in conservation
When ecological restoration projects are undertaken to restore a native ecological system disturbed by economic development or other events, they may be historically inaccurate, incomplete, or pay little or no attention to ecotype accuracy or type conversions. They may fail to restore the original ecological system by overlooking the basics of remediation. Attention paid to the historical distribution of native species is a crucial first step to ensure the ecological integrity of the project. For example, to prevent erosion of the recontoured sand dunes at the western edge of the Los Angeles International Airport in 1975, landscapers stabilized the backdunes with a "natural" seed mix (Mattoni 1989a). Unfortunately, the seed mix was representative of coastal sage scrub, an exogenous plant community, instead of the native dune scrub community. As a result, the El Segundo blue butterfly (Euphilotes battoides allyni) became an endangered species. The El Segundo blue butterfly population, which had once extended over 3200 acres along the coastal dunes from Ocean Park to Malaga Cove in Palos Verdes, began to recover when the invasive California buckwheat (Eriogonum fasciculatum) was uprooted so that the butterflies' original native plant host, the dune buckwheat (Eriogonum parvifolium), could regain some of its lost habitat.
See also
Introduced species
List of Australian plants termed "native"
References
Further reading
Biogeography
Ecological restoration
Ecology terminology
Habitat | Native species | Chemistry,Engineering,Biology | 1,051 |
11,455,357 | https://en.wikipedia.org/wiki/Fusarium%20subglutinans | Fusarium subglutinans is a fungal plant pathogen.
Taxonomy
Fusarium subglutinans is the anamorph of Gibberella fujikuroi.
Fusarium strains in the Gibberella fujikuroi species complex cause diseases in a number of economically important plants. DNA sequencing data reveals the presence of two major groups representing cryptic species in F. subglutinans. These were further divided into groups that appeared to be reproductively isolated in the environment which suggests that they are undergoing separation into distinct taxa. One such divergent group is Fusarium subglutinans f. sp. pini which causes pitch canker of pine trees. It is a synonym of Fusarium circinatum.
Other members of the complex and their host plants are:
Fusarium moniliforme - Maize
Fusarium oxysporum - Pine
Fusarium proliferatum - Rice
Fusarium subglutinans - Maize, Mango
Fusarium subglutinans f. sp. ananas - Pineapple
References
subglutinans
Fungal plant pathogens and diseases
Maize diseases
Mango tree diseases
Fungi described in 1925
Fungus species | Fusarium subglutinans | Biology | 244 |
6,194,406 | https://en.wikipedia.org/wiki/Rectangular%20potential%20barrier | In quantum mechanics, the rectangular (or, at times, square) potential barrier is a standard one-dimensional problem that demonstrates the phenomena of wave-mechanical tunneling (also called "quantum tunneling") and wave-mechanical reflection. The problem consists of solving the one-dimensional time-independent Schrödinger equation for a particle encountering a rectangular potential energy barrier. It is usually assumed, as here, that a free particle impinges on the barrier from the left.
Although classically a particle behaving as a point mass would be reflected if its energy is less than a particle actually behaving as a matter wave has a non-zero probability of penetrating the barrier and continuing its travel as a wave on the other side. In classical wave-physics, this effect is known as evanescent wave coupling. The likelihood that the particle will pass through the barrier is given by the transmission coefficient, whereas the likelihood that it is reflected is given by the reflection coefficient. Schrödinger's wave-equation allows these coefficients to be calculated.
Calculation
The time-independent Schrödinger equation for the wave function reads
where is the Hamiltonian, is the (reduced)
Planck constant, is the mass, the energy of the particle and
is the barrier potential with height and width .
is the Heaviside step function, i.e.,
The barrier is positioned between and . The barrier can be shifted to any position without changing the results. The first term in the Hamiltonian, is the kinetic energy.
The barrier divides the space in three parts (). In any of these parts, the potential is constant, meaning that the particle is quasi-free, and the solution of the Schrödinger equation can be written as a superposition of left and right moving waves (see free particle). If
where the wave numbers are related to the energy via
The index on the coefficients and denotes the direction of the velocity vector. Note that, if the energy of the particle is below the barrier height, becomes imaginary and the wave function is exponentially decaying within the barrier. Nevertheless, we keep the notation even though the waves are not propagating anymore in this case. Here we assumed . The case is treated below.
The coefficients have to be found from the boundary conditions of the wave function at and . The wave function and its derivative have to be continuous everywhere, so
Inserting the wave functions, the boundary conditions give the following restrictions on the coefficients
Transmission and reflection
At this point, it is instructive to compare the situation to the classical case. In both cases, the particle behaves as a free particle outside of the barrier region. A classical particle with energy larger than the barrier height would always pass the barrier, and a classical particle with incident on the barrier would always get reflected.
To study the quantum case, consider the following situation: a particle incident on the barrier from the left side It may be reflected or transmitted
To find the amplitudes for reflection and transmission for incidence from the left, we put in the above equations (incoming particle), (reflection), (no incoming particle from the right), and (transmission). We then eliminate the coefficients from the equation and solve for and
The result is:
Due to the mirror symmetry of the model, the amplitudes for incidence from the right are the same as those from the left. Note that these expressions hold for any energy If then so there is a singularity in both of these expressions.
Analysis of the obtained expressions
E < V0
The surprising result is that for energies less than the barrier height, there is a non-zero probability
for the particle to be transmitted through the barrier, with This effect, which differs from the classical case, is called quantum tunneling. The transmission is exponentially suppressed with the barrier width, which can be understood from the functional form of the wave function: Outside of the barrier it oscillates with wave vector whereas within the barrier it is exponentially damped over a distance If the barrier is much wider than this decay length, the left and right part are virtually independent and tunneling as a consequence is suppressed.
E > V0
In this case
where
Equally surprising is that for energies larger than the barrier height, , the particle may be reflected from the barrier with a non-zero probability
The transmission and reflection probabilities are in fact oscillating with . The classical result of perfect transmission without any reflection (, ) is reproduced not only in the limit of high energy but also when the energy and barrier width satisfy , where (see peaks near and 1.8 in the above figure). Note that the probabilities and amplitudes as written are for any energy (above/below) the barrier height.
E = V0
The transmission probability at is
This expression can be obtained by calculating the transmission coefficient from the constants stated above as for the other cases or by taking the limit of as approaches . For this purpose the ratio
is defined, which is used in the function :
In the last equation is defined as follows:
These definitions can be inserted in the expression for which was obtained for the case .
Now, when calculating the limit of as x approaches 1 (using L'Hôpital's rule),
also the limit of as approaches 1 can be obtained:
By plugging in the above expression for in the evaluated value for the limit, the above expression for T is successfully reproduced.
Remarks and applications
The calculation presented above may at first seem unrealistic and hardly useful. However it has proved to be a suitable model for a variety of real-life systems. One such example are interfaces between two conducting materials. In the bulk of the materials, the motion of the electrons is quasi-free and can be described by the kinetic term in the above Hamiltonian with an effective mass . Often the surfaces of such materials are covered with oxide layers or are not ideal for other reasons. This thin, non-conducting layer may then be modeled by a barrier potential as above. Electrons may then tunnel from one material to the other giving rise to a current.
The operation of a scanning tunneling microscope (STM) relies on this tunneling effect. In that case, the barrier is due to the gap between the tip of the STM and the underlying object. Since the tunnel current depends exponentially on the barrier width, this device is extremely sensitive to height variations on the examined sample.
The above model is one-dimensional, while space is three-dimensional. One should solve the Schrödinger equation in three dimensions. On the other hand, many systems only change along one coordinate direction and are translationally invariant along the others; they are separable. The Schrödinger equation may then be reduced to the case considered here by an ansatz for the wave function of the type: .
For another, related model of a barrier, see Delta potential barrier (QM), which can be regarded as a special case of the finite potential barrier. All results from this article immediately apply to the delta potential barrier by taking the limits while keeping constant.
See also
Morse/Long-range potential
Step potential
Finite potential well
References
Quantum models
Scattering theory
Schrödinger equation
Quantum mechanical potentials | Rectangular potential barrier | Physics,Chemistry | 1,461 |
49,510,292 | https://en.wikipedia.org/wiki/Alkynylation | In organic chemistry, alkynylation is an addition reaction in which a terminal alkyne () is added to a carbonyl group () to form an α-alkynyl alcohol ().
When the acetylide is formed from acetylene (), the reaction gives an α-ethynyl alcohol. This process is often referred to as ethynylation. Such processes often involve metal acetylide intermediates.
Scope
The principal reaction of interest involves the addition of the acetylene () to a ketone () or aldehyde ():
RR'C=O + HC#CR'' -> RR'C(OH)C#CR''
The reaction proceeds with retention of the triple bond. For aldehydes and unsymmetrical ketones, the product is chiral, hence there is interest in asymmetric variants. These reactions invariably involve metal-acetylide intermediates.
This reaction was discovered by chemist John Ulric Nef in 1899 while experimenting with reactions of elemental sodium, phenylacetylene, and acetophenone. For this reason, the reaction is sometimes referred to as Nef synthesis. Sometimes this reaction is erroneously called the Nef reaction, a name more often used to describe a different reaction (see Nef reaction). Chemist Walter Reppe coined the term ethynylation during his work with acetylene and carbonyl compounds.
In the following reaction (scheme 1), the alkyne proton of ethyl propiolate is deprotonated by n-butyllithium at -78 °C to form lithium ethyl propiolate to which cyclopentanone is added forming a lithium alkoxide. Acetic acid is added to remove lithium and liberate the free alcohol.
Modifications
Several modifications of alkynylation reactions are known:
In the Arens–van Dorp synthesis the compound ethoxyacetylene is converted to a Grignard reagent and reacted with a ketone, the reaction product is a propargyl alcohol.
The Isler modification is a modification of Arens–Van Dorp Synthesis where ethoxyacetylene is replaced by β-chlorovinyl ethyl ether and lithium amide.
Catalytic variants
Alkynylations, including the asymmetric variety, have been developed as metal-catalyzed reactions. Various catalytic additions of alkynes to electrophiles in water have also been developed.
Uses
Alkynylation finds use in synthesis of pharmaceuticals, particularly in the preparation of steroid hormones. For example, ethynylation of 17-ketosteroids produces important contraceptive medications known as progestins. Examples include drugs such as Norethisterone, Ethisterone, and Lynestrenol. Hydrogenation of these compounds produces anabolic steroids with oral bioavailability, such as Norethandrolone.
Alkynylation is used to prepare commodity chemicals such as propargyl alcohol, butynediol, 2-methylbut-3-yn-2-ol (a precursor to isoprenes such as vitamin A), 3-hexyne-2,5-diol (a precursor to Furaneol), and sulcatone (a precursor to Linalool).
Reaction conditions
For the stoichiometric reactions involving alkali metal or alkaline earth acetylides, work-up for the reaction requires liberation of the alcohol. To achieve this hydrolysis, aqueous acids are often employed.
RR'C(ONa)C#CR''{} + \overset{acetic\, acid}{CH3COOH} -> RR'C(OH)C#CR''{} + \overset{sodium\, acetate}{CH3COONa}
Common solvents for the reaction include ethers, acetals, dimethylformamide, and dimethyl sulfoxide.
Variations
Grignard reagents
Grignard reagents of acetylene or alkynes can be used to perform alkynylations on compounds that are liable to polymerization reactions via enolate intermediates. However, substituting lithium for sodium or potassium acetylides accomplishes similar results, often giving this route little advantage over the conventional reaction.
Favorskii reaction
The Favorskii reaction is an alternative set of reaction conditions, which involves prereaction of the acetylene with an alkali metal hydroxide such as KOH. The reaction proceeds through equilibria, making the reaction reversible:
HC#CH + KOH <=> HC#CK + H2O
RR'C=O + HC#CK <=> RR'C(OK)C#CH
To overcome this reversibility, the reaction often uses an excess of base to trap the water as hydrates.
Reppe chemistry
Chemist Walter Reppe pioneered catalytic, industrial-scale ethynylations using acetylene with alkali metal and copper(I) acetylides:
These reactions are used to manufacture propargyl alcohol and butynediol. Alkali metal acetylides, which are often more effective for ketone additions, are used to produce 2-methyl-3-butyn-2-ol from acetylene and acetone.
See also
Alkylation
Methylation
Organolithium reagent
Organosodium chemistry
Alkyne coupling reactions
Sonogashira coupling
Glaser coupling
Cadiot–Chodkiewicz coupling
Castro–Stephens coupling
A3 coupling reaction
References
Carbon-carbon bond forming reactions
Organometallic chemistry
Addition reactions | Alkynylation | Chemistry | 1,182 |
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