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68,776,341 | https://en.wikipedia.org/wiki/Trino%20%28SQL%20query%20engine%29 | Trino is an open-source distributed SQL query engine designed to query large data sets distributed over one or more heterogeneous data sources. Trino can query data lakes that contain a variety of file formats such as simple row-oriented CSV and JSON data files to more performant open column-oriented data file formats like ORC or Parquet residing on different storage systems like HDFS, AWS S3, Google Cloud Storage, or Azure Blob Storage using the Hive and Iceberg table formats. Trino also has the ability to run federated queries that query tables in different data sources such as MySQL, PostgreSQL, Cassandra, Kafka, MongoDB and Elasticsearch. Trino is released under the Apache License.
History
In January 2019, the original creators of Presto, Martin Traverso, Dain Sundstrom, and David Phillips, created a fork of the Presto project. They initially kept the name Presto and used the PrestoSQL web handle to distinguish it from the original PrestoDB project. Simultaneously, they announced the Presto Software Foundation. The foundation is a not-for-profit organization dedicated to the advancement of the Presto open source distributed SQL query engine.
In December 2020, PrestoSQL was rebranded as Trino. The Trino Software Foundation, code base, and all other PrestoSQL assets were renamed as part of the rebrand.
Presto and Trino were originally designed and developed by Martin, Dain, David, and Eric Hwang at Facebook to allow data analysts to run interactive queries on its large data warehouse in Apache Hadoop. Trino shares the first six years of development with the Presto project. To learn more about the earlier history of Trino, you can reference the Presto history section.
Trino is used in many data platforms and products from cloud providers and other vendors. Customization of these products varies from pure Trino usage to heavily customized systems to run a data platform or integration in specialized data platforms for usage with specific data. Examples include Amazon Athena, Starburst Galaxy, Dune, and many others.
Architecture
Trino is written in Java. It runs on a cluster of servers that contains two types of nodes, a coordinator and a worker.
The coordinator is responsible for parsing, analyzing, optimizing, planning, and scheduling a query submitted by a client. The coordinator interacts with the service provider interface (SPI) to obtain the available tables, table statistics, and other information needed to carry out its tasks.
The workers are responsible for executing the tasks and operators fed to them by the scheduler. These tasks process rows from the data sources which produce results that are returned to the coordinator and ultimately back to the client.
Trino adheres to the ANSI SQL standard and includes various parts of the following ANSI specifications: SQL-92, SQL:1999, SQL:2003, SQL:2008, SQL:2011, SQL:2016, SQL:2023.
Trino supports the separation of compute and storage and may be deployed both on-premises and in the cloud.
Trino has a Distributed computing MPP architecture. Trino first distributes work over multiple workers by running ad-hoc partitioning operations or relying on existing partitions in the data of the underlying data store. Once this data has reached the worker, the data is processed over pipelined operators carried out on multiple threads.
See also
Presto (SQL query engine)
Big data
Data Intensive Computing
Apache Drill
Computer cluster
References
External links
Trino Software Foundation (formerly Presto Software Foundation)
SQL
Free system software
Hadoop
Cloud platforms
Java platform | Trino (SQL query engine) | Technology | 750 |
9,421,673 | https://en.wikipedia.org/wiki/Parts%20cleaning | Parts cleaning is a step in various industrial processes, either as preparation for surface finishing or to safeguard delicate components. One such process, electroplating, is particularly sensitive to part cleanliness, as even thin layers of oil can hinder coating adhesion.
Cleaning methods encompass solvent cleaning, hot alkaline detergent cleaning, electro-cleaning, and acid etch. In industrial settings, the water-break test is a common practice to assess machinery cleanliness. This test involves thoroughly rinsing and vertically holding the surface. Hydrophobic contaminants, like oils, cause water to bead and break, leading to rapid drainage. In contrast, perfectly clean metal surfaces are hydrophilic and retain an unbroken sheet of water without beading or draining off. It is important to note that this test may not detect hydrophilic contaminants, but they can be displaced during the water-based electroplating process. Surfactants like soap can reduce the test's sensitivity and should be thoroughly rinsed off.
Definitions and classifications
For the activities described here, the following terms are often found: metal cleaning, metal surface cleaning, component cleaning, degreasing, parts washing, and parts cleaning. These are well established in technical language usage, but they have their shortcomings. Metal cleaning can easily be mixed up with the refinement of un-purified metals. Metal surface cleaning and metal cleaning do not consider the increasing usage of plastics and composite materials in this sector. The term component cleaning leaves out the cleaning of steel sections and sheets, and finally, degreasing only describes a part of the topic, as in most cases, chips, fines, particles, salts, etc. also have to be removed.
The terms "commercial and industrial parts cleaning", "parts cleaning in craft and industry", or "commercial parts cleaning" probably best describe this field of activity. There are some specialists who prefer the term "industrial parts cleaning", because they want to exclude maintenance of buildings, rooms, areas, windows, floors, tanks, machinery, hygiene, hands washing, showers, and other non-commercial objects.
Elements and their interactions
Cleaning activities in this sector can only be characterized sufficiently by a description of several factors. These are outlined in the first image above.
Parts and materials to be cleaned
First, consider the parts to be cleaned. They may comprise non-processed or hardly processed sections, sheets and wires, but also machined parts or assembled components needing cleaning. Therefore, they may be composed of different metals or different combinations of metals. Plastics and composite materials can frequently be found and indeed are on the increase because, e.g. the automobile industry, as well as others, are using more and lighter materials.
Mass can be very important for the selection of cleaning methods. For example, big shafts for ships are usually cleaned manually, whereas tiny shafts for electrical appliances are often cleaned in bulk in highly automated plants.
Similarly important is the geometry of the parts. Long, thin, branching, threaded holes, which could contain jammed chips, feature among the greatest challenges in this technical field. High pressure and the power wash process are one way to remove these chips, as well as robots, which are programmed to exactly flush the drilled holes under high pressure.
Contaminations
The parts are usually covered by unwanted substances, contaminants, or soiling. The definition used is quite different. In certain cases, these coverings may be desired: e.g. one may not wish to remove a paint layer but only the material on top. In another cases, where crack proofing is necessary, one has to remove the paint layer, as it is regarded as an unwanted substance.
The classification of soiling follows the layer structure, starting from the base material:
Deformed boundary layer, > 1 μm
Reaction layer, 1–10 nm
Sorption layer, 1–10 nm
Contamination layer, > 1 μm
See illustration 2: Structure of a metallic surface
The closer a layer is to the substrate surface, the more energy is needed to remove it. Correspondingly, the cleaning itself can be structured according to the type of energy input:
Mechanical – abrasive: blasting, grinding
Mechanical – non-abrasive: stirring, mixing, ultrasound, spraying
Thermal – reactive: heat treatment much above 100 °C in reactive gases
Thermal – non-reactive: temperature below 100 °C, increased bath temperature, vapor degreasing
Chemical – abrasive/reactive: pickling in liquids, plasma-assisted, sputter-cleaning, electropolishing
Chemical – non-reactive: organic solvents, aqueous solutions, supercritical CO2
The contamination layer may then be further classified according to:
Origin
Composition: e.g. cooling lubricants may be composed differently. Single components may account for big problems, especially for job shop cleaners, who have no control over prior processes and thus don't know the contaminants. For example, silicates may obstruct nitriding.
State of aggregation
Chemical and physical properties
The American Society for Testing and Materials (ASTM) presents six groups of contaminations in their manual "Choosing a cleaning process" and relates them to the most common cleaning methods, the suitability of cleaning methods for the removal of a given contaminate is discussed. In addition, they list exemplary cleaning processes for different typical applications. Since one has to consider very many different aspects when choosing a process, this can only serve as a first orientation. The groups of contaminants are stated:
Pigmented drawing compounds
Unpigmented oil and grease
Chips and cutting fluids
Polishing and buffing compounds
Rust and scale
Others
Charging
In order to select suitable equipment and media, it should be known also which amount and which throughput have to be handled. In larger factories, little amounts are virtually ever cleaned economically . Additionally, the pricing method needs to be determined. Sensitive parts sometimes need to be fixed in boxes. When dealing with large amounts, bulk charging can be used, but it's difficult to achieve a sufficient level of cleanliness with flat pieces clinging together. Drying can also be difficult in these cases.
Place of cleaning
Another consideration is the place of cleaning. Cleaning in a workshop calls for different methods as compared to cleaning that is to be done on site, which can be the case with maintenance and repair work.
Usually, the cleaning takes place in a workshop. Several common methods include solvent degreasing, vapor degreasing, and the use of an aqueous parts washer. Companies often want the charging, loading and unloading to be integrated into the production line, which is much more demanding as regards size and throughout the ability of the cleaning system.
Such cleaning systems often exactly match the requirements regarding parts, contaminants and charging methods (special production). Central cleaning equipment, often built as multi task systems, is commonly used. These systems can suit different cleaning requirements. Typical examples are the wash stands or the small cleaning machines, which are found in many industrial plants.
Cleaning equipment and procedure
First, one can differentiate among the following techniques (ordered from most to least technologically advanced):
Manual
Mechanical
Automatic
Robot supported
The process may be performed in one step, which is especially true for the manual cleaning, but typically it requires several steps. Therefore, it is not uncommon to find 10 to 20 steps in large plants, e.g., for the medical and optical industry. This can be especially complex because non-cleaning steps may be integrated in such plants like application of corrosion protection layers or phosphating. Cleaning can also be simple: the cleaning processes are integrated into other processes, as it is the case with electroplating or galvanising, where it usually serves as a pre-treatment step.
The following procedure is quite common:
Pre-cleaning
Main cleaning
Rinsing
Rinsing with deionised water
Rinsing with corrosion protection
Drying
Each of these steps may take place in its own bath, chamber, or, in case of spray cleaning, in its own zone (line or multi-chamber equipment). But often these steps may have a single chamber into which the respective media are pumped in (single chamber plant).
Cleaning media plays an important role as it removes the contaminants from the substrate.
For liquid media, the following cleaners can be used: aqueous agents, semi-aqueous agents (an emulsion of solvents and water), hydrocarbon-based solvents, and halogenated solvents. Usually, the latter are referred to as chlorinated agents, but brominated and fluorinated substances can be used. The traditionally used chlorinated agents, TCE and PCE, which are hazardous, are now only applied in airtight plants and the modern volume shift systems limit any emissions. In the group of hydrocarbon-based solvents, there are some newly developed agents like fatty acid esters made of natural fats and oils, modified alcohols and dibasic esters.
Aqueous cleaners are mostly a combination of various substances like alkaline builders, surfactants, and sequestering agents. With ferrous metal cleaning, rust inhibitors are added into the aqueous cleaner to prevent flash rusting after washing. Their use is on the rise as their results have proven to be most times as good or better than hydrocarbon cleaners. The waste generated is less hazardous, which reduces disposal costs.
Aqueous cleaners have advantages as regards to particle and polar contaminants and only require higher inputs of mechanical and thermal energy to be effective, whereas solvents more easily remove oils and greases but have health and environmental risks. In addition, most solvents are flammable, creates fire and explosion hazards. Nowadays, with proper industrial parts washer equipment, it is accepted that aqueous cleaners remove oil and grease as easily as solvents.
Another approach is with solid cleaning media (blasting) which comprises the CO2 dry ice process: For tougher requirements, pellets are used while for more sensitive materials or components CO2 in form of snow is applied. One drawback is the high energy consumption required to make dry ice.
Last but not least, there are processes with no media like vibration, laser, brushing and blow/exhaust systems.
All cleaning steps are characterized by media and applied temperatures and their individual agitation/application (mechanical impact). There is a wide range of different methods and combinations of these methods:
Blasting
Boiling under pressure
Carbon dioxide cleaning
Circulation of bath
Flooding
Gas or air injection into bath
Hydroson
Injection flooding
Megasonic, see megasonic cleaning
Movement of parts (turning, oscillating, pivoting)
Power wash process
Pressure flooding
Spraying
Sprinkling
Ultrasonic, see ultrasonic cleaning
Finally, every cleaning step is described by the time which the parts to be cleaned spends in the respective zone, bath, or chamber, and thus medium, temperature, and agitation can affect the contamination.
Every item of cleaning equipment needs a so-called periphery. This term describes measures and equipment on the one hand side to maintain and control baths and side to protect human beings and the environment.
In most plants, the cleaning agents are circulated until their cleaning power has eventually decreased and reached the maximum tolerable contaminant level. In order to delay the bath exchange as much as possible, there are sophisticated treatment attachments in use, removing contaminants and the used up agents from the system. Fresh cleaning agents or parts thereof have to be supplemented, which requires a bath control. The latter is more and more facilitated online and thus allows a computer aided change of the bath. With the help of oil separators, demulsifying agents and evaporators, aqueous processes can be conducted 'wastewater free'. Complete exchange of baths becomes only necessary every 3 to 12 months.
When using organic solvents, the preferred method to achieve a long operating bath life is distillation, an especially effective method to separate contaminants and agents.
The periphery also includes measures to protect the workers like encapsulation, automatic shutoff of power supply, automatic refill and sharpening of media (e.g., gas shuttle technique), explosion prevention measures, exhaust ventilation etc., and also measures to protect the environment, e.g. capturing of volatile solvents, impounding basins, extraction, treatment and disposal of resulting wastes. Solvents based cleaning processes have the advantage that the dirt and the cleaning agent can be more easily separated, whereas in aqueous processes is more complex.
In processes without cleaning media, like laser ablation and vibration cleaning, only the removed dirt has to be disposed of as there is no cleaning agent. Quite little waste is generated in processes like CO2 blasting and automatic brush cleaning at the expense of higher energy costs.
Quality requirements
A standardization of the quality requirements for cleaned surfaces regarding the following process (e.g. coating, heat treatment) or from the point of view of technical functionality is difficult. However, it is possible to use general classifications. In Germany, it was attempted to define cleaning as a subcategory of metal treatment (DIN 8592: Cleaning as sub category of cutting processes), but this does not cope with all the complexities of cleaning.
The rather general rules include the classification in intermediate cleaning, final cleaning, precision cleaning and critical cleaning (s. table), in practice seen only as a general guideline.
(1) Related to the total dirt; (2) Only related to carbon
Thus, the rule of thumb is still followed, stating that the quality requirements are met if the subsequent process (see below) does not cause any problems. For example, a paint coating does not flake off before the guarantee period ends.
Where this is not sufficient, especially in case of external orders, because of missing standards, there are often specific customer requirements regarding remaining contamination, corrosion protection, spots and gloss level, etc.
Measuring methods to ensure quality therefore do not play a bigger role in the workshops, although there are a broad scale of different methods, from visual control over simple testing methods (water break test, wipe test, measurement of contact angle, test inks, tape test, among others) to complex analysis methods (gravimetric test, particle counting, infrared spectroscopy, glow discharge spectroscopy, energy dispersive X-ray analysis, scanning electron microscopy and electrochemical methods, among others). There are only a few methods, which can be applied directly in the line and which offer reproducible and comparable results. It was not until recently that bigger advancements in this area have been made
The general situation has changed, meanwhile, because of dramatically rising cleanliness requirements for certain components in the automotive industry. For example, brake systems and fuel-injection systems need to be fitted with increasingly smaller diameters and they have to withstand increasingly higher pressures. Therefore, a very minor particle contamination may lead to big problems. Because of the rising innovation speed, the industry cannot afford to identify possible failures at a relatively late stage. Therefore, the standard VDA 19/ISO 16232 'Road Vehicles – Cleanliness of Components of Fluid Circuits' was developed which describes methods that can control the compliance with the cleanliness requirements.
Subsequent process
When choosing cleaning techniques, cleaning agents and cleaning processes, the subsequent processes, i.e. the further processing of the cleaned parts, is of special interest.
The classification follows basically the metal work theory:
Machining
Cutting
Joining
Coating
Heat treatment
Assembling
Measuring, testing
Repairing, maintenance
In time, empirical values were established, how efficient the cleaning has to be, to assure the processes for the particular guarantee period and beyond. Choosing the cleaning method often starts from here.
Challenges and trends
The details above illustrate how extremely complex this specific field is. Small variations in requirements can cause completely different processes. It becomes more and more important to receive the required cleanliness as cost-effective as possible and with continuously minimized health and environmental risks, because cleaning has become of central importance for the supply chain in manufacturing. Applying companies usually rely on their suppliers, who—because of a big experience base—suggest adequate equipment and processes, which are then adapted to the detailed requirements in tests stations at the supplier's premises. However, they are limited to their scope of technology. To put practitioners in a position to consider all relevant possibilities meeting their requirements, some institutes have developed different tools:
SAGE:
Unfortunately, no longer in operation, the comprehensive expert system for parts cleaning and degreasing provided a graded list with relatively general processes of solvent and process alternatives. Developed by the Surface Cleaning Program at the Research Triangle Institute, Raleigh, North Carolina, USA, in cooperation with the U.S. EPA (used to be available under: http://clean.rti.org/).
Cleantool:
A 'Best Practice' database in seven languages with comprehensive and specific processes, directly recorded in companies. It contains furthermore an integrated evaluation tool, which covers the areas of technology, quality, health and safety at work, environmental protection and costs. Also included is a comprehensive glossary (seven languages, link see below).
Bauteilreinigung:
A selection system for component cleaning developed by the University of Dortmund, assisting the users to analyze their cleaning tasks regarding the suitable cleaning processes and cleaning agents (German only, link see below).
TURI, Toxic Use Reduction Institute:
A department of the University of Lowell, Massachusetts (USA). TURI's laboratory has been conducting evaluations on alternative cleaning products since 1993. A majority of these products were designed for metal surface cleaning. The results are available on-line through the Institute's laboratory database.
See also
Acoustic cleaning
Brake cleaner
Parts washer
Solvent degreasing
Sonication
Ultrasonic cleaning
Vapor degreasing
References
Further reading
John B. Durkee: "Management of Industrial Cleaning Technology and Processes," 2006, Elsevier, Oxford, United Kingdom, .
Carole A. LeBlanc: The search for safer and greener chemical solvents in surface cleaning : a proposed tool to support environmental decision-making. 2001, Erasmus University Centre for Environmental Studies, Rotterdam, the Netherlands.
David S. Peterson: Practical guide to industrial metal cleaning. 1997, Hanser Gardner Publications, Cincinnati, Ohio, USA.
Barbara Kanegsberg ed.: Handbook for critical cleaning. 2001, CRC Press, Boca Raton, Florida, USA.
Malcolm C. McLaughlin et al.: The aqueous cleaning handbook : a guide to critical-cleaning procedures, techniques, and validation. 2000, The Morris-Lee Publishing Group, Rosemont, New Jersey, USA.
Karen Thomas, John Laplante, Alan Buckley: Guidebook of part cleaning alternatives : making cleaning greener in Massachusetts. 1997, Toxics Use Reduction Institute, University of Massachusetts, Lowell, Massachusetts, USA
ASM International: Choosing a cleaning process. 1996, ASM International, Materials Park, Ohio, USA.
ASM International: Guide to acid, alkaline, emulsion, and ultrasonic cleaning. 1997, ASM International, Materials Park, Ohio, USA.
ASM International: Guide to vapour degreasing and solvent cold cleaning. 1996, ASM International, Materials Park, Ohio, USA.
ASM International: Guide to mechanical cleaning systems. 1996, ASM International, Materials Park, Ohio, USA.
ASM International: Guide to pickling and descaling, and molten salt bath cleaning. 1996, ASM International, Materials Park, Ohio, USA.
Klaus-Peter Müller: Praktische Oberflächentechnik. Edition 2003.XII, vieweg, Braunschweig/Wiesbaden,
Thomas W. Jelinek: Reinigen und Entfetten in der Metallindustrie. 1. Edition 1999, Leuze Verlag, Saulgau,
Brigitte Haase: Wie sauber muß eine Oberfläche sein? in: Journal Oberflächentechnik. Nr. 4, 1997
Brigitte Haase: Reinigen oder Vorbehandeln? Oberflächenzustand und Nitrierergebnis, Bauteilreinigung, Prozesskontrolle und –analytik. Hochschule Bremerhaven
Bernd Künne: Online Fachbuch für industrielle Reinigung. in: bauteilreinigung.de. Universität Dortmund, Fachgebiet Maschinenelemente
Reiner Grün: Reinigen und Vorbehandeln - Stand und Perspektiven. in: Galvanotechnik. 90, 1999, Nr. 7, S. 1836-1844
Günter Kreisel et al.: Ganzheitliche Bilanzierung/Bewertung von Reinigungs-/Vorbehandlungstechnologien in der Oberflächenbehandlung. 1998, Jena, Institut für Technische Chemie der FSU
Cleaning
Industrial processes
Metalworking | Parts cleaning | Chemistry | 4,303 |
46,417,331 | https://en.wikipedia.org/wiki/89P/Russell | 89P/Russell is a periodic comet in the Solar System with a current orbital period of 7.28 years.
It was discovered on a photographic plate by Kenneth Russell of Siding Spring Observatory in New South Wales, Australia on 28 September 1980. Brightness was estimated at a magnitude of 17. The elliptical orbit calculated by Brian G. Marsden gave a perihelion date of 19 May 1980 and an orbital period of 7.12 years.
It has been observed on each subsequent apparition, most recently in 2009. The next perihelion is computed as 14 December 2016.
See also
List of numbered comets
References
External links
Periodic comets
0089
089P
090P
089P
19800928 | 89P/Russell | Astronomy | 145 |
23,666,373 | https://en.wikipedia.org/wiki/Krammer | The Krammer is a body of fresh water located in the western part of Volkerak in the Netherlands.
It is part of the Rhine–Meuse–Scheldt delta, and is situated between the islands Goeree-Overflakkee and Sint Philipsland. To the west, it continues into the Grevelingen, from which it is separated by the Grevelingendam.
Before 1967, it was a tidal river, but it was closed off as part of the Delta Works.
References
Goeree-Overflakkee
Tholen
Delta Works
Landforms of South Holland
Landforms of Zeeland | Krammer | Physics | 130 |
61,245,573 | https://en.wikipedia.org/wiki/ASME%20QME-1 | ASME QME-1 is a standard maintained by the American Society of Mechanical Engineers that provides the requirements and guidelines for the qualification of active mechanical equipment (QME) whose function is required to ensure the safe operation or safe shutdown of a nuclear facility.
Organization of QME-1
The 2017 edition of QME-1 is organized by the following major sections:
Section QR: General Requirements
Section QDR: Qualification of Dynamic Restraints
Section QP: Qualification of Active Pump Assemblies
Section QV: Qualification Requirements for Active Valve Assemblies for Nuclear Facilities
Standards Committee on Qualification of Mechanical Equipment Used in Nuclear Facilities (QME)
ASME QME-1 is maintained and revised by QME and its associated sub-tier groups using the ASME standards development process. Work activities are delegated to specific subcommittees, as per their established charters.
QME Subcommittee on General Requirements
QME Subcommittee on Qualification of Active Dynamic Restraints
QME Subcommittee on Qualification of Pump Assemblies
QME Subcommittee on Qualification of Valve Assemblies
References
External links
QME Subcommittee on General Requirements
QME Subcommittee on Qualification of Active Dynamic Restraints
QME Subcommittee on Qualification of Pump Assemblies
QME Subcommittee on Qualification of Valve Assemblies
Mechanical standards
ASME standards | ASME QME-1 | Engineering | 241 |
1,504,236 | https://en.wikipedia.org/wiki/Creed%20%26%20Company | Creed & Company was a British telecommunications company founded by Frederick George Creed which was an important pioneer in the field of teleprinter machines. It was merged into the International Telephone and Telegraph Corporation (ITT) in 1928.
History
The company was founded by Frederick George Creed and Danish telegraph engineer Harald Bille, and was first incorporated in 1912 as "Creed, Bille & Company Limited". After Bille's death in a railway accident in 1916, his name was dropped from the company's title and it became simply Creed & Company.
The Company spent most of World War I producing high-quality instruments, manufacturing facilities for which were very limited at that time in the UK. Among the items produced were amplifiers, spark-gap transmitters, aircraft compasses, high-voltage generators, bomb release apparatus, and fuses for artillery shells and bombs.
In 1924 Creed entered the teleprinter field with their Model 1P, which was soon superseded by the improved Model 2P. In 1925 Creed acquired the patents for Donald Murray's Murray code, a rationalised Baudot code, and it was used for their new Model 3 Tape Teleprinter of 1927. This machine printed received messages directly onto gummed paper tape at a rate of 65 words per minute and was the first combined start-stop transmitter-receiver teleprinter from Creed to enter mass production.
Some of the key models were:
Creed model 6S (punched paper tape reader)
Creed model 7 (page printing teleprinter introduced in 1931)
Creed model 7B (50 baud page printing teleprinter)
Creed model 7E (page printing teleprinter with overlap cam and range finder)
Creed model 7/TR (non-printing teleprinter reperforator)
Creed model 54 (page printing teleprinter introduced in 1954)
Creed model 75 (page printing teleprinter introduced in 1958)
Creed model 85 (printing reperforator introduced in 1948)
Creed model 86 (printing reperforator using 7/8" wide tape)
Creed model 444 (page printing teleprinter introduced in 1966 - GPO type 15)
In July 1928, Creed & Company were merged into ITT.
During World War II Creed Company manufactured some of the British Typex machines, cipher devices similar to the German Enigma machine.
References
External links
Creed and Company Limited. The First 50 years
History of Nova Scotia Creed and Company Limited
Defunct telecommunications companies of the United Kingdom
Telecommunications companies established in 1912
Rotor machines
Cryptographic hardware
1912 establishments in England
Technology companies disestablished in 1928
1928 disestablishments in England
British companies disestablished in 1928
British companies established in 1912 | Creed & Company | Physics,Technology | 548 |
78,612,468 | https://en.wikipedia.org/wiki/Sipavibart | Sipavibart is an experimental medication under investigation for the prevention of COVID-19 in people who are immunocompromised. Sipavibart is a recombinant human IgG1 monoclonal antibody that provides passive immunization against SARS-CoV-2 by binding its spike protein receptor binding domain.
Society and culture
Legal status
In December 2024, the Committee for Medicinal Products for Human Use of the European Medicines Agency adopted a positive opinion, recommending the granting of a marketing authorization for the medicinal product Kavigale, intended for the prevention of COVID-19 in immunocompromised people aged twelve years of age and older. Kavigale was reviewed under the EMA's accelerated assessment program. The applicant for this medicinal product is AstraZeneca AB.
Names
Sipavibart is the international nonproprietary name.
References
Further reading
Anti–RNA virus drugs
Antiviral drugs
COVID-19 drug development
Experimental antiviral drugs
Monoclonal antibodies | Sipavibart | Chemistry,Biology | 213 |
433,739 | https://en.wikipedia.org/wiki/Spitball | A spitball is a now-illegal baseball pitch in which the ball has been altered by the application of a foreign substance such as saliva or petroleum jelly. This technique alters the wind resistance and weight on one side of the ball, causing it to move in an atypical manner. It may also cause the ball to "slip" out of the pitcher's fingers without the usual spin that accompanies a pitch. In this sense, a spitball can be thought of as a fastball with knuckleball action. Alternative names for the spitball are spitter, mud ball, shine ball, supersinker, or vaseline ball (because originally, Vaseline was used to give the ball a little more break). A spitball technically differs from an emery ball, in which the surface of the ball is cut or abraded. Saliva or Vaseline smooths the baseball, while the emery paper roughens it. The general term for altering the ball in any way is doctoring.
History
The invention of the spitball has been popularly credited to a number of individuals, among them Elmer Stricklett and Frank Corridon. Numerous accounts, however, refer to different players experimenting with versions of the spitball throughout the latter half of the 19th century, and it remains unlikely that any one individual "invented" the spitball.
Ed Walsh, however, is certainly responsible for popularizing it. Walsh dominated the American League from 1906 to 1912, primarily on the strength of his spitball, and pitchers around the league soon copied his spitball or invented their own trick pitch.
The dramatic increase in the popularity of "freak deliveries" led to a great deal of controversy throughout the 1910s regarding the abolition of the spitball and related pitches. In his autobiography, Ty Cobb wrote that such "freak pitches [...] were outlawed when the owners greedily sold out to home runs."
In addition, there were serious issues with the spitball, including some that affected safety. A variation on the standard spitball called for the pitcher to smear the entire surface of the normally white ball with a mixture of tobacco spittle and dirt or mud in order to stain it the same deep brown color as the infield which made it nearly impossible for batters to see (and sometimes avoid) in low-light conditions. In August 1920, Ray Chapman was killed when he was struck in the temple by a pitch thrown by known spitball pitcher Carl Mays during a poorly lit game.
Ban
In Major League Baseball (MLB), the spitball was banned in two stages. In the winter of 1919–1920, managers voted to partially ban the spitball. Each team was allowed to designate up to two pitchers who would be permitted to throw spitballs. After the 1920 season, the use of the spitball was banned with the exception of a group of 17 existing spitballers, who became legacy spitballers who were allowed to throw the pitch legally until they retired.
Of the exempted group, Burleigh Grimes lasted the longest, retiring in 1934. The complete list of exempted spitballers is: Ray Fisher (played through 1920); Doc Ayers (1921); Ray Caldwell (1921); Phil Douglas (1922); Dana Fillingim (1925); Marv Goodwin (1925); Dutch Leonard (1925); Allen Russell (1925); Allen Sothoron (1926); Dick Rudolph (1927); Stan Coveleski (1928); Urban Shocker (1928); Bill Doak (1929); Clarence Mitchell (1932); Red Faber (1933); Jack Quinn (1933); and Grimes.
In March 1955, MLB Commissioner Ford Frick advocated for the return of the spitball, telling a sportswriter, "If I had my way, I'd legalize the old spitter. It was a great pitch and one of the easiest to throw. There was nothing dangerous about it." Despite the Commissioner's enthusiasm, the pitch remained illegal.
Methodology
The spitball is now banned in Major League baseball. It is a pitching violation in NCAA Baseball. However, it is still sometimes thrown in violation of the rules. In 1942, Leo Durocher, then-manager of the Brooklyn Dodgers, fined Bobo Newsom for throwing a spitball and "lying to me about it." Typically, a lubricant is hidden behind the pitcher's knee or under the peak of his cap. Others will place the ball in their mitt and then cough on or lick it. Another tactic pitchers use is to soak their hair in water before going out to the mound, and then rub their hair before a pitch.
Preacher Roe, who played for the Brooklyn Dodgers in the 1950s, was renowned both for his ability to control the spitball and to throw it without getting caught and described his methodology in a 1955 article in Sports Illustrated. "The Outlawed Spitball Was My Money Pitch" was published a year after he retired. Another famous user of the pitch was Gaylord Perry, who went so far as to title his autobiography Me and the Spitter and chronicled the clever ways in which he avoided detection. For example, Perry would put Vaseline on his zipper because umpires would never check a player's groin. Don Drysdale also used the pitch regularly, as did Lew Burdette. Drysdale would apply oil to the back of his hair to put on the ball to make it sink. Mike Fiers has been accused of doctoring the baseball during both his no-hitters.
Legal spits
The name dry spitter is sometimes used to describe a pitch that moves like a spitball without saliva, such as the forkball or split-finger fastball. It is sometimes used simply as slang for the knuckleball.
There is also the remote term of God-given spitter, which is when the ball is naturally dampened by moist air or light rainfall, which allows pitchers to be able to throw pitches with sharper breaks, much like a spitball.
See also
2021 pitch doctoring controversy
Ball tampering in cricket
Cheating in baseball
Live-ball era and dead-ball era
References
Baseball pitches
Banned sports tactics
Cheating in baseball
Major League Baseball controversies | Spitball | Biology | 1,267 |
2,104,649 | https://en.wikipedia.org/wiki/Super%20soldier | A super soldier (or supersoldier) is a concept soldier capable of operating beyond normal human abilities through technological augmentation or (in fictional depictions) genetic modification or cybernetic augmentation. Soldiers that obtain greater-than-normal physical abilities by wearing powered armor or a technological exoskeleton (such as the Mobile Infantry in Robert A. Heinlein´s Starship Troopers novella) are a distinct, but related concept and the two often overlap, as is the case for Halo and Warhammer 40,000 universes, for example.
Fiction
Super soldiers are common in military science fiction literature, films, and video games. Well-known examples include the novel The Forever War by Joe Haldeman and the Halo franchise. Super soldiers are also prevalent in the science fiction universe of Warhammer 40,000 and its prequel The Horus Heresy. Critic Mike Ryder has argued that the super soldiers depicted in these worlds serve as a mirror to present-day issues around sovereignty, military ethics and the law. Marvel Comics, and by extension the Marvel Cinematic Universe, feature a wide array of heroes and villains whose powers are obtained through various competing attempts to create a super soldier, including Captain America, Hulk, the German Red Skull, and the Russian Red Guardian.
Fictional super soldiers are usually heavily augmented, possibly through surgical means, eugenics, genetic engineering, drugs, brainwashing, traumatic events, an extreme training regimen or other scientific and pseudoscientific means, or a combination of some of these methods. Some depictions can be categorized as cyborgs or cybernetic organisms due to their augmentations taking the form of technology integrated into a living organism. A few stories also use paranormal methods or technology, and science of extraterrestrial origin. The fictional masterminds of such programs are depicted often as mad scientists or stern military personnel depending on the needs of the plot, in stories that typically explore the ethical boundaries of the pursuit of science and victory.
China
In 2022, the People's Liberation Army Academy of Military Sciences reported that a team of military scientists inserted a gene from the tardigrade into human embryonic stem cells in an experiment with the stated possibility of creating soldiers resistant to acute radiation syndrome who could survive nuclear fallout.
U.S. Army
In the book The Men Who Stare at Goats (2004), Welsh journalist Jon Ronson documented how the U.S. military repeatedly tried and failed to train soldiers in the use of parascientific and pseudoscientific combat techniques during the Cold War, experimenting with New Age methods and psychic phenomena such as remote viewing, astral projection, "death touch" and mind reading against various Soviet targets. The book also inspired a war comedy of the same name (2009) directed by Grant Heslov, starring George Clooney.
Fictional examples
The following are examples of fictional super soldiers in various media:
Bloodshot from Valiant Comics
Bane, Captain Atom, Deathstroke, KGBeast, Major Force, and Ravager from DC Comics
Captain America, Deadpool, Deathlok, Nuke, Sabretooth, U.S. Agent, Winter Soldier, Abomination and Wolverine from Marvel Comics
The Clone troopers and the Stormtroopers from the Star Wars franchise
Duke Nukem
Genetic infantry (G. I.) soldiers from Rogue Trooper comic strip by Gerry Finley-Day and Dave Gibbons, featured in the comics anthology 2000 AD.
Hannah from the 2011 live-action film of the same name and the 2019 TV series of the same name
Jill Valentine from Resident Evil
Lars Alexandersson from the Tekken franchise
Kull warriors from the Stargate television series.
Master Chief and other SPARTAN soldiers from Halo
The Doomguy (Protagonist in the Doom Franchise)
The protagonist of the 2006 First-person shooter game ÜberSoldier.
Universal Soldier franchise.
Solid Snake and Big Boss from Metal Gear. Also unit FOXHOUND and Genome solders appearing in Metal Gear Solid 1, Cobra unit soldiers appearing in Metal Gear Solid 3: Snake Eater, Beauty and the Beast Corps soldiers appearing in Metal Gear Solid 4: Guns of the Patriots, and the characters of Quiet and the Parasite unit, "Skulls" soldiers appearing in Metal Gear Solid V: The Phantom Pain.
The Space Marines from the Warhammer 40,000 universe.
Coloninal Defense Forces soldiers from the Old Man's War military science fiction novel series by John Scalzi.
The Terminator
Soldier: 76 and Reaper from the Overwatch franchise.
See also
First Earth Battalion
Future Soldier 2030 Initiative
Human enhancement
List of psychoactive drugs used by militaries
Superhuman
Übermensch
Space marine
Superhero
Other
Hysterical strength
References
Military projects
Research projects
Fiction about eugenics
Military science fiction
Fictional soldiers
Stock characters
Science fiction weapons
Superhero fiction themes
Fiction about cyborgs | Super soldier | Engineering,Biology | 964 |
34,474,694 | https://en.wikipedia.org/wiki/CT%20Value | CT Values are an important part of calculating disinfectant dosage for the chlorination of drinking water. A CT value is the product of the concentration of a disinfectant (e.g. free chlorine) and the contact time with the water being disinfected. It is typically expressed in units of mg-min/L.
The goal of disinfection is the inactivation of microorganisms. This depends on: the microorganism, the disinfectant being used, the concentration of the disinfectant, the contact time, and the temperature and pH of the water.
Kinetics
The disinfection kinetics are conventionally calculated via the Chick-Watson model, named for the work of Harriette Chick and H. E. Watson. This model is expressed by the following equation:
Where:
is the survival ratio for the microorganisms being killed
is the Chick-Watson coefficient of specific lethality
is the concentration of the disinfectant (typically in mg/L)
is the coefficient of dilution, frequently assumed to be 1
is the contact time (typically in minutes or seconds)
The survival ratio is commonly expressed as an inactivation ratio (in %) or as the number of reductions in the order of magnitude of the microorganism concentration. For example, a situation where N0=107 CFU/L and N=104 CFU/L would be reported as a 99.9% inactivation or "3-log10" removal.
In water treatment practice, tables of the product C×t are used to calculate disinfection dosages. The calculated CT value is the product of the disinfectant residual (in mg/L) and the detention time (in minutes), through the section at peak hourly flow. These tables express the required CT values to achieve a desired removal of microorganisms of interest in drinking water (e.g. Giardia lamblia cysts) for a given disinfectant under constant temperature and pH conditions. A portion of such a table is reproduced below.
Example CT Table
CT Values for the Inactivation of Giardia Cysts by Free Chlorine at 5 °C and pH ≈ 7.0:
Full tables are much larger than this example and should be obtained from the regulatory agency for a particular jurisdiction.
See also
Chlorination
Disinfectant
References
External links
Water treatment
Chlorine | CT Value | Chemistry,Engineering,Environmental_science | 507 |
23,617 | https://en.wikipedia.org/wiki/Pump | A pump is a device that moves fluids (liquids or gases), or sometimes slurries, by mechanical action, typically converted from electrical energy into hydraulic or pneumatic energy.
Mechanical pumps serve in a wide range of applications such as pumping water from wells, aquarium filtering, pond filtering and aeration, in the car industry for water-cooling and fuel injection, in the energy industry for pumping oil and natural gas or for operating cooling towers and other components of heating, ventilation and air conditioning systems. In the medical industry, pumps are used for biochemical processes in developing and manufacturing medicine, and as artificial replacements for body parts, in particular the artificial heart and penile prosthesis.
When a pump contains two or more pump mechanisms with fluid being directed to flow through them in series, it is called a multi-stage pump. Terms such as two-stage or double-stage may be used to specifically describe the number of stages. A pump that does not fit this description is simply a single-stage pump in contrast.
In biology, many different types of chemical and biomechanical pumps have evolved; biomimicry is sometimes used in developing new types of mechanical pumps.
Types
Mechanical pumps may be submerged in the fluid they are pumping or be placed external to the fluid.
Pumps can be classified by their method of displacement into electromagnetic pumps, positive-displacement pumps, impulse pumps, velocity pumps, gravity pumps, steam pumps and valveless pumps. There are three basic types of pumps: positive-displacement, centrifugal and axial-flow pumps. In centrifugal pumps the direction of flow of the fluid changes by ninety degrees as it flows over an impeller, while in axial flow pumps the direction of flow is unchanged.
Electromagnetic pump
Positive-displacement pumps
A positive-displacement pump makes a fluid move by trapping a fixed amount and forcing (displacing) that trapped volume into the discharge pipe.
Some positive-displacement pumps use an expanding cavity on the suction side and a decreasing cavity on the discharge side. Liquid flows into the pump as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses. The volume is constant through each cycle of operation.
Positive-displacement pump behavior and safety
Positive-displacement pumps, unlike centrifugal, can theoretically produce the same flow at a given rotational speed no matter what the discharge pressure. Thus, positive-displacement pumps are constant flow machines. However, a slight increase in internal leakage as the pressure increases prevents a truly constant flow rate.
A positive-displacement pump must not operate against a closed valve on the discharge side of the pump, because it has no shutoff head like centrifugal pumps. A positive-displacement pump operating against a closed discharge valve continues to produce flow and the pressure in the discharge line increases until the line bursts, the pump is severely damaged, or both.
A relief or safety valve on the discharge side of the positive-displacement pump is therefore necessary. The relief valve can be internal or external. The pump manufacturer normally has the option to supply internal relief or safety valves. The internal valve is usually used only as a safety precaution. An external relief valve in the discharge line, with a return line back to the suction line or supply tank, provides increased safety.
Positive-displacement types
A positive-displacement pump can be further classified according to the mechanism used to move the fluid:
Rotary-type positive displacement: internal and external gear pump, screw pump, lobe pump, shuttle block, flexible vane and sliding vane, circumferential piston, flexible impeller, helical twisted roots (e.g. the Wendelkolben pump) and liquid-ring pumps
Reciprocating-type positive displacement: piston pumps, plunger pumps and diaphragm pumps
Linear-type positive displacement: rope pumps and chain pumps
Rotary positive-displacement pumps
These pumps move fluid using a rotating mechanism that creates a vacuum that captures and draws in the liquid.
Advantages: Rotary pumps are very efficient because they can handle highly viscous fluids with higher flow rates as viscosity increases.
Drawbacks: The nature of the pump requires very close clearances between the rotating pump and the outer edge, making it rotate at a slow, steady speed. If rotary pumps are operated at high speeds, the fluids cause erosion, which eventually causes enlarged clearances that liquid can pass through, which reduces efficiency.
Rotary positive-displacement pumps fall into five main types:
Gear pumps – a simple type of rotary pump where the liquid is pushed around a pair of gears.
Screw pumps – the shape of the internals of this pump is usually two screws turning against each other to pump the liquid
Rotary vane pumps
Hollow disc pumps (also known as eccentric disc pumps or hollow rotary disc pumps), similar to scroll compressors, these have an eccentric cylindrical rotor encased in a circular housing. As the rotor orbits, it traps fluid between the rotor and the casing, drawing the fluid through the pump. It is used for highly viscous fluids like petroleum-derived products, and it can also support high pressures of up to 290 psi.
Peristaltic pumps have rollers which pinch a section of flexible tubing, forcing the liquid ahead as the rollers advance. Because they are very easy to keep clean, these are popular for dispensing food, medicine, and concrete.
Reciprocating positive-displacement pumps
Reciprocating pumps move the fluid using one or more oscillating pistons, plungers, or membranes (diaphragms), while valves restrict fluid motion to the desired direction. In order for suction to take place, the pump must first pull the plunger in an outward motion to decrease pressure in the chamber. Once the plunger pushes back, it will increase the chamber pressure and the inward pressure of the plunger will then open the discharge valve and release the fluid into the delivery pipe at constant flow rate and increased pressure.
Pumps in this category range from simplex, with one cylinder, to in some cases quad (four) cylinders, or more. Many reciprocating-type pumps are duplex (two) or triplex (three) cylinder. They can be either single-acting with suction during one direction of piston motion and discharge on the other, or double-acting with suction and discharge in both directions. The pumps can be powered manually, by air or steam, or by a belt driven by an engine. This type of pump was used extensively in the 19th century—in the early days of steam propulsion—as boiler feed water pumps. Now reciprocating pumps typically pump highly viscous fluids like concrete and heavy oils, and serve in special applications that demand low flow rates against high resistance. Reciprocating hand pumps were widely used to pump water from wells. Common bicycle pumps and foot pumps for inflation use reciprocating action.
These positive-displacement pumps have an expanding cavity on the suction side and a decreasing cavity on the discharge side. Liquid flows into the pumps as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses. The volume is constant given each cycle of operation and the pump's volumetric efficiency can be achieved through routine maintenance and inspection of its valves.
Typical reciprocating pumps are:
Plunger pump – a reciprocating plunger pushes the fluid through one or two open valves, closed by suction on the way back.
Diaphragm pump – similar to plunger pumps, where the plunger pressurizes hydraulic oil which is used to flex a diaphragm in the pumping cylinder. Diaphragm valves are used to pump hazardous and toxic fluids.
Piston pump displacement pumps – usually simple devices for pumping small amounts of liquid or gel manually. The common hand soap dispenser is such a pump.
Radial piston pumpa form of hydraulic pump where pistons extend in a radial direction.
Vibratory pump or vibration pumpa particularly low-cost form of plunger pump, popular in low-cost espresso machines. The only moving part is a spring-loaded piston, the armature of a solenoid. Driven by half-wave rectified alternating current, the piston is forced forward while energized, and is retracted by the spring during the other half cycle. Due to their inefficiency, vibratory pumps typically cannot be operated for more than one minute without overheating, so are limited to intermittent duty.
Various positive-displacement pumps
The positive-displacement principle applies in these pumps:
Rotary lobe pump
Progressing cavity pump
Rotary gear pump
Piston pump
Diaphragm pump
Screw pump
Gear pump
Hydraulic pump
Rotary vane pump
Peristaltic pump
Rope pump
Flexible impeller pump
Gear pump
This is the simplest form of rotary positive-displacement pumps. It consists of two meshed gears that rotate in a closely fitted casing. The tooth spaces trap fluid and force it around the outer periphery. The fluid does not travel back on the meshed part, because the teeth mesh closely in the center. Gear pumps see wide use in car engine oil pumps and in various hydraulic power packs.
Screw pump
A screw pump is a more complicated type of rotary pump that uses two or three screws with opposing thread — e.g., one screw turns clockwise and the other counterclockwise. The screws are mounted on parallel shafts that often have gears that mesh so the shafts turn together and everything stays in place. In some cases the driven screw drives the secondary screw, without gears, often using the fluid to limit abrasion. The screws turn on the shafts and drive fluid through the pump. As with other forms of rotary pumps, the clearance between moving parts and the pump's casing is minimal.
Progressing cavity pump
Widely used for pumping difficult materials, such as sewage sludge contaminated with large particles, a progressing cavity pump consists of a helical rotor, about ten times as long as its width. This can be visualized as a central core of diameter x with, typically, a curved spiral wound around of thickness half x, though in reality it is manufactured in a single casting. This shaft fits inside a heavy-duty rubber sleeve, of wall thickness also typically x. As the shaft rotates, the rotor gradually forces fluid up the rubber sleeve. Such pumps can develop very high pressure at low volumes.
Roots-type pump
Named after the Roots brothers who invented it, this lobe pump displaces the fluid trapped between two long helical rotors, each fitted into the other when perpendicular at 90°, rotating inside a triangular shaped sealing line configuration, both at the point of suction and at the point of discharge. This design produces a continuous flow with equal volume and no vortex. It can work at low pulsation rates, and offers gentle performance that some applications require.
Applications include:
High capacity industrial air compressors.
Roots superchargers on internal combustion engines.
A brand of civil defense siren, the Federal Signal Corporation's Thunderbolt.
Peristaltic pump
A peristaltic pump is a type of positive-displacement pump. It contains fluid within a flexible tube fitted inside a circular pump casing (though linear peristaltic pumps have been made). A number of rollers, shoes, or wipers attached to a rotor compress the flexible tube. As the rotor turns, the part of the tube under compression closes (or occludes), forcing the fluid through the tube. Additionally, when the tube opens to its natural state after the passing of the cam it draws (restitution) fluid into the pump. This process is called peristalsis and is used in many biological systems such as the gastrointestinal tract.
Plunger pumpsPlunger pumps are reciprocating positive-displacement pumps.
These consist of a cylinder with a reciprocating plunger. The suction and discharge valves are mounted in the head of the cylinder. In the suction stroke, the plunger retracts and the suction valves open causing suction of fluid into the cylinder. In the forward stroke, the plunger pushes the liquid out of the discharge valve.
Efficiency and common problems: With only one cylinder in plunger pumps, the fluid flow varies between maximum flow when the plunger moves through the middle positions, and zero flow when the plunger is at the end positions. A lot of energy is wasted when the fluid is accelerated in the piping system. Vibration and water hammer may be a serious problem. In general, the problems are compensated for by using two or more cylinders not working in phase with each other. Centrifugal pumps are also susceptible to water hammer. Surge analysis, a specialized study, helps evaluate this risk in such systems.
Triplex-style plunger pump
Triplex plunger pumps use three plungers, which reduces the pulsation relative to single reciprocating plunger pumps. Adding a pulsation dampener on the pump outlet can further smooth the pump ripple, or ripple graph of a pump transducer. The dynamic relationship of the high-pressure fluid and plunger generally requires high-quality plunger seals. Plunger pumps with a larger number of plungers have the benefit of increased flow, or smoother flow without a pulsation damper. The increase in moving parts and crankshaft load is one drawback.
Car washes often use these triplex-style plunger pumps (perhaps without pulsation dampers). In 1968, William Bruggeman reduced the size of the triplex pump and increased the lifespan so that car washes could use equipment with smaller footprints. Durable high-pressure seals, low-pressure seals and oil seals, hardened crankshafts, hardened connecting rods, thick ceramic plungers and heavier duty ball and roller bearings improve reliability in triplex pumps. Triplex pumps now are in a myriad of markets across the world.
Triplex pumps with shorter lifetimes are commonplace to the home user. A person who uses a home pressure washer for 10 hours a year may be satisfied with a pump that lasts 100 hours between rebuilds. Industrial-grade or continuous duty triplex pumps on the other end of the quality spectrum may run for as much as 2,080 hours a year.
The oil and gas drilling industry uses massive semi-trailer-transported triplex pumps called mud pumps to pump drilling mud, which cools the drill bit and carries the cuttings back to the surface.
Drillers use triplex or even quintuplex pumps to inject water and solvents deep into shale in the extraction process called fracking.
Diaphragm pump
Typically run on electricity compressed air, diaphragm pumps are relatively inexpensive and can perform a wide variety of duties, from pumping air into an aquarium, to liquids through a filter press. Double-diaphragm pumps can handle viscous fluids and abrasive materials with a gentle pumping process ideal for transporting shear-sensitive media.
Rope pump
Devised in China as chain pumps over 1000 years ago, these pumps can be made from very simple materials: A rope, a wheel and a pipe are sufficient to make a simple rope pump. Rope pump efficiency has been studied by grassroots organizations and the techniques for making and running them have been continuously improved.
Impulse pump
Impulse pumps use pressure created by gas (usually air). In some impulse pumps the gas trapped in the liquid (usually water), is released and accumulated somewhere in the pump, creating a pressure that can push part of the liquid upwards.
Conventional impulse pumps include:
Hydraulic ram pumps – kinetic energy of a low-head water supply is stored temporarily in an air-bubble hydraulic accumulator, then used to drive water to a higher head.
Pulser pumps – run with natural resources, by kinetic energy only.
Airlift pumps – run on air inserted into pipe, which pushes the water up when bubbles move upward
Instead of a gas accumulation and releasing cycle, the pressure can be created by burning of hydrocarbons. Such combustion driven pumps directly transmit the impulse from a combustion event through the actuation membrane to the pump fluid. In order to allow this direct transmission, the pump needs to be almost entirely made of an elastomer (e.g. silicone rubber). Hence, the combustion causes the membrane to expand and thereby pumps the fluid out of the adjacent pumping chamber. The first combustion-driven soft pump was developed by ETH Zurich.
Hydraulic ram pump
A hydraulic ram is a water pump powered by hydropower.
It takes in water at relatively low pressure and high flow-rate and outputs water at a higher hydraulic-head and lower flow-rate. The device uses the water hammer effect to develop pressure that lifts a portion of the input water that powers the pump to a point higher than where the water started.
The hydraulic ram is sometimes used in remote areas, where there is both a source of low-head hydropower, and a need for pumping water to a destination higher in elevation than the source. In this situation, the ram is often useful, since it requires no outside source of power other than the kinetic energy of flowing water.
Velocity pumps
Rotodynamic pumps (or dynamic pumps) are a type of velocity pump in which kinetic energy is added to the fluid by increasing the flow velocity. This increase in energy is converted to a gain in potential energy (pressure) when the velocity is reduced prior to or as the flow exits the pump into the discharge pipe. This conversion of kinetic energy to pressure is explained by the First law of thermodynamics, or more specifically by Bernoulli's principle.
Dynamic pumps can be further subdivided according to the means in which the velocity gain is achieved.
These types of pumps have a number of characteristics:
Continuous energy
Conversion of added energy to increase in kinetic energy (increase in velocity)
Conversion of increased velocity (kinetic energy) to an increase in pressure head
A practical difference between dynamic and positive-displacement pumps is how they operate under closed valve conditions. Positive-displacement pumps physically displace fluid, so closing a valve downstream of a positive-displacement pump produces a continual pressure build up that can cause mechanical failure of pipeline or pump. Dynamic pumps differ in that they can be safely operated under closed valve conditions (for short periods of time).
Radial-flow pump
Such a pump is also referred to as a centrifugal pump. The fluid enters along the axis or center, is accelerated by the impeller and exits at right angles to the shaft (radially); an example is the centrifugal fan, which is commonly used to implement a vacuum cleaner. Another type of radial-flow pump is a vortex pump. The liquid in them moves in tangential direction around the working wheel. The conversion from the mechanical energy of motor into the potential energy of flow comes by means of multiple whirls, which are excited by the impeller in the working channel of the pump. Generally, a radial-flow pump operates at higher pressures and lower flow rates than an axial- or a mixed-flow pump.
Axial-flow pump
These are also referred to as all-fluid pumps. The fluid is pushed outward or inward to move fluid axially. They operate at much lower pressures and higher flow rates than radial-flow (centrifugal) pumps. Axial-flow pumps cannot be run up to speed without special precaution. If at a low flow rate, the total head rise and high torque associated with this pipe would mean that the starting torque would have to become a function of acceleration for the whole mass of liquid in the pipe system.
Mixed-flow pumps function as a compromise between radial and axial-flow pumps. The fluid experiences both radial acceleration and lift and exits the impeller somewhere between 0 and 90 degrees from the axial direction. As a consequence mixed-flow pumps operate at higher pressures than axial-flow pumps while delivering higher discharges than radial-flow pumps. The exit angle of the flow dictates the pressure head-discharge characteristic in relation to radial and mixed-flow.
Regenerative turbine pump
Also known as drag, friction, liquid-ring pump, peripheral, traction, turbulence, or vortex pumps, regenerative turbine pumps are a class of rotodynamic pump that operates at high head pressures, typically .
The pump has an impeller with a number of vanes or paddles which spins in a cavity. The suction port and pressure ports are located at the perimeter of the cavity and are isolated by a barrier called a stripper, which allows only the tip channel (fluid between the blades) to recirculate, and forces any fluid in the side channel (fluid in the cavity outside of the blades) through the pressure port. In a regenerative turbine pump, as fluid spirals repeatedly from a vane into the side channel and back to the next vane, kinetic energy is imparted to the periphery, thus pressure builds with each spiral, in a manner similar to a regenerative blower.
As regenerative turbine pumps cannot become vapor locked, they are commonly applied to volatile, hot, or cryogenic fluid transport. However, as tolerances are typically tight, they are vulnerable to solids or particles causing jamming or rapid wear. Efficiency is typically low, and pressure and power consumption typically decrease with flow. Additionally, pumping direction can be reversed by reversing direction of spin.
Side-channel pump
A side-channel pump has a suction disk, an impeller, and a discharge disk.
Eductor-jet pump
This uses a jet, often of steam, to create a low pressure. This low pressure sucks in fluid and propels it into a higher-pressure region.
Gravity pumps
Gravity pumps include the syphon and Heron's fountain. The hydraulic ram is also sometimes called a gravity pump. In a gravity pump the fluid is lifted by gravitational force.
Steam pump
Steam pumps have been for a long time mainly of historical interest. They include any type of pump powered by a steam engine and also pistonless pumps such as Thomas Savery's or the Pulsometer steam pump.
Recently there has been a resurgence of interest in low-power solar steam pumps for use in smallholder irrigation in developing countries. Previously small steam engines have not been viable because of escalating inefficiencies as vapour engines decrease in size. However the use of modern engineering materials coupled with alternative engine configurations has meant that these types of system are now a cost-effective opportunity.
Valveless pumps
Valveless pumping assists in fluid transport in various biomedical and engineering systems. In a valveless pumping system, no valves (or physical occlusions) are present to regulate the flow direction. The fluid pumping efficiency of a valveless system, however, is not necessarily lower than that having valves. In fact, many fluid-dynamical systems in nature and engineering more or less rely upon valveless pumping to transport the working fluids therein. For instance, blood circulation in the cardiovascular system is maintained to some extent even when the heart's valves fail. Meanwhile, the embryonic vertebrate heart begins pumping blood long before the development of discernible chambers and valves. Similar to blood circulation in one direction, bird respiratory systems pump air in one direction in rigid lungs, but without any physiological valve. In microfluidics, valveless impedance pumps have been fabricated, and are expected to be particularly suitable for handling sensitive biofluids. Ink jet printers operating on the piezoelectric transducer principle also use valveless pumping. The pump chamber is emptied through the printing jet due to reduced flow impedance in that direction and refilled by capillary action.
Pump repairs
Examining pump repair records and mean time between failures (MTBF) is of great importance to responsible and conscientious pump users. In view of that fact, the preface to the 2006 Pump User's Handbook alludes to "pump failure" statistics. For the sake of convenience, these failure statistics often are translated into MTBF (in this case, installed life before failure).
In early 2005, Gordon Buck, John Crane Inc.'s chief engineer for field operations in Baton Rouge, Louisiana, examined the repair records for a number of refinery and chemical plants to obtain meaningful reliability data for centrifugal pumps. A total of 15 operating plants having nearly 15,000 pumps were included in the survey. The smallest of these plants had about 100 pumps; several plants had over 2000. All facilities were located in the United States. In addition, considered as "new", others as "renewed" and still others as "established". Many of these plants—but not all—had an alliance arrangement with John Crane. In some cases, the alliance contract included having a John Crane Inc. technician or engineer on-site to coordinate various aspects of the program.
Not all plants are refineries, however, and different results occur elsewhere. In chemical plants, pumps have historically been "throw-away" items as chemical attack limits life. Things have improved in recent years, but the somewhat restricted space available in "old" DIN and ASME-standardized stuffing boxes places limits on the type of seal that fits. Unless the pump user upgrades the seal chamber, the pump only accommodates more compact and simple versions. Without this upgrading, lifetimes in chemical installations are generally around 50 to 60 percent of the refinery values.
Unscheduled maintenance is often one of the most significant costs of ownership, and failures of mechanical seals and bearings are among the major causes. Keep in mind the potential value of selecting pumps that cost more initially, but last much longer between repairs. The MTBF of a better pump may be one to four years longer than that of its non-upgraded counterpart. Consider that published average values of avoided pump failures range from US$2600 to US$12,000. This does not include lost opportunity costs. One pump fire occurs per 1000 failures. Having fewer pump failures means having fewer destructive pump fires.
As has been noted, a typical pump failure, based on actual year 2002 reports, costs US$5,000 on average. This includes costs for material, parts, labor and overhead. Extending a pump's MTBF from 12 to 18 months would save US$1,667 per year — which might be greater than the cost to upgrade the centrifugal pump's reliability.Submersible slurry pumps in high demand. Engineeringnews.co.za. Retrieved on 2011-05-25.
Applications
Pumps are used throughout society for a variety of purposes. Early applications includes the use of the windmill or watermill to pump water. Today, the pump is used for irrigation, water supply, gasoline supply, air conditioning systems, refrigeration (usually called a compressor), chemical movement, sewage movement, flood control, marine services, etc.
Because of the wide variety of applications, pumps have a plethora of shapes and sizes: from very large to very small, from handling gas to handling liquid, from high pressure to low pressure, and from high volume to low volume.
Priming a pump
Typically, a liquid pump cannot simply draw air. The feed line of the pump and the internal body surrounding the pumping mechanism must first be filled with the liquid that requires pumping: An operator must introduce liquid into the system to initiate the pumping, known as priming the pump. Loss of prime is usually due to ingestion of air into the pump, or evaporation of the working fluid if the pump is used infrequently. Clearances and displacement ratios in pumps for liquids are insufficient for pumping compressible gas, so air or other gasses in the pump can not be evacuated by the pump's action alone. This is the case with most velocity (rotodynamic) pumps — for example, centrifugal pumps. For such pumps, the position of the pump and intake tubing should be lower than the suction point so it is primed by gravity; otherwise the pump should be manually filled with liquid or a secondary pump should be used until all air is removed from the suction line and the pump casing. Liquid ring pumps have a dedicated intake for the priming liquid separate from the intake of the fluid being pumped, as the fluid being pumped may be a gas or mix of gas, liquid, and solids. For these pumps the priming liquid intake must be supplied continuously (either by gravity or pressure), however the intake for the fluid being pumped is capable of drawing a vacuum equivalent to the boiling point of the priming liquid.
Positive–displacement pumps, however, tend to have sufficiently tight sealing between the moving parts and the casing or housing of the pump that they can be described as self-priming. Such pumps can also serve as priming pumps, so-called when they are used to fulfill that need for other pumps in lieu of action taken by a human operator.
Pumps as public water supplies
One sort of pump once common worldwide was a hand-powered water pump, or 'pitcher pump'. It was commonly installed over community water wells in the days before piped water supplies.
In parts of the British Isles, it was often called the parish pump. Though such community pumps are no longer common, people still used the expression parish pump to describe a place or forum where matters of local interest are discussed.
Because water from pitcher pumps is drawn directly from the soil, it is more prone to contamination. If such water is not filtered and purified, consumption of it might lead to gastrointestinal or other water-borne diseases. A notorious case is the 1854 Broad Street cholera outbreak. At the time it was not known how cholera was transmitted, but physician John Snow suspected contaminated water and had the handle of the public pump he suspected removed; the outbreak then subsided.
Modern hand-operated community pumps are considered the most sustainable low-cost option for safe water supply in resource-poor settings, often in rural areas in developing countries. A hand pump opens access to deeper groundwater that is often not polluted and also improves the safety of a well by protecting the water source from contaminated buckets. Pumps such as the Afridev pump are designed to be cheap to build and install, and easy to maintain with simple parts. However, scarcity of spare parts for these type of pumps in some regions of Africa has diminished their utility for these areas.
Sealing multiphase pumping applications
Multiphase pumping applications, also referred to as tri-phase, have grown due to increased oil drilling activity. In addition, the economics of multiphase production is attractive to upstream operations as it leads to simpler, smaller in-field installations, reduced equipment costs and improved production rates. In essence, the multiphase pump can accommodate all fluid stream properties with one piece of equipment, which has a smaller footprint. Often, two smaller multiphase pumps are installed in series rather than having just one massive pump.
Types and features of multiphase pumps
Helico-axial (centrifugal)
A rotodynamic pump with one single shaft that requires two mechanical seals, this pump uses an open-type axial impeller. It is often called a Poseidon pump, and can be described as a cross between an axial compressor and a centrifugal pump.
Twin-screw (positive-displacement)
The twin-screw pump is constructed of two inter-meshing screws that move the pumped fluid. Twin screw pumps are often used when pumping conditions contain high gas volume fractions and fluctuating inlet conditions. Four mechanical seals are required to seal the two shafts.
Progressive cavity (positive-displacement)
When the pumping application is not suited to a centrifugal pump, a progressive cavity pump is used instead. Progressive cavity pumps are single-screw types typically used in shallow wells or at the surface. This pump is mainly used on surface applications where the pumped fluid may contain a considerable amount of solids such as sand and dirt. The volumetric efficiency and mechanical efficiency of a progressive cavity pump increases as the viscosity of the liquid does.
Electric submersible (centrifugal)
These pumps are basically multistage centrifugal pumps and are widely used in oil well applications as a method for artificial lift. These pumps are usually specified when the pumped fluid is mainly liquid.Buffer tankA buffer tank is often installed upstream of the pump suction nozzle in case of a slug flow. The buffer tank breaks the energy of the liquid slug, smooths any fluctuations in the incoming flow and acts as a sand trap.
As the name indicates, multiphase pumps and their mechanical seals can encounter a large variation in service conditions such as changing process fluid composition, temperature variations, high and low operating pressures and exposure to abrasive/erosive media. The challenge is selecting the appropriate mechanical seal arrangement and support system to ensure maximized seal life and its overall effectiveness.John Crane Seal Sentinel – John Crane Increases Production Capabilities with Machine that Streamlines Four Machining Functions into One . Sealsentinel.com. Retrieved on 2011-05-25.
Specifications
Pumps are commonly rated by horsepower, volumetric flow rate, outlet pressure in metres (or feet) of head, inlet suction in suction feet (or metres) of head.
The head can be simplified as the number of feet or metres the pump can raise or lower a column of water at atmospheric pressure.
From an initial design point of view, engineers often use a quantity termed the specific speed to identify the most suitable pump type for a particular combination of flow rate and head.
Net Positive Suction Head (NPSH) is crucial for pump performance. It has two key aspects:
1) NPSHr (Required): The Head required for the pump to operate without cavitation issues.
2) NPSHa (Available): The actual pressure provided by the system (e.g., from an overhead tank).
For optimal pump operation, NPSHa must always exceed NPSHr. This ensures the pump has enough pressure to prevent cavitation, a damaging condition.
Pumping power
The power imparted into a fluid increases the energy of the fluid per unit volume. Thus the power relationship is between the conversion of the mechanical energy of the pump mechanism and the fluid elements within the pump. In general, this is governed by a series of simultaneous differential equations, known as the Navier–Stokes equations. However a more simple equation relating only the different energies in the fluid, known as Bernoulli's equation can be used. Hence the power, P, required by the pump:
where Δp is the change in total pressure between the inlet and outlet (in Pa), and Q, the volume flow-rate of the fluid is given in m3/s. The total pressure may have gravitational, static pressure and kinetic energy components; i.e. energy is distributed between change in the fluid's gravitational potential energy (going up or down hill), change in velocity, or change in static pressure. η is the pump efficiency, and may be given by the manufacturer's information, such as in the form of a pump curve, and is typically derived from either fluid dynamics simulation (i.e. solutions to the Navier–Stokes for the particular pump geometry), or by testing. The efficiency of the pump depends upon the pump's configuration and operating conditions (such as rotational speed, fluid density and viscosity etc.)
For a typical "pumping" configuration, the work is imparted on the fluid, and is thus positive. For the fluid imparting the work on the pump (i.e. a turbine), the work is negative. Power required to drive the pump is determined by dividing the output power by the pump efficiency. Furthermore, this definition encompasses pumps with no moving parts, such as a siphon.
Efficiency
Pump efficiency is defined as the ratio of the power imparted on the fluid by the pump in relation to the power supplied to drive the pump. Its value is not fixed for a given pump, efficiency is a function of the discharge and therefore also operating head. For centrifugal pumps, the efficiency tends to increase with flow rate up to a point midway through the operating range (peak efficiency or Best Efficiency Point (BEP) ) and then declines as flow rates rise further. Pump performance data such as this is usually supplied by the manufacturer before pump selection. Pump efficiencies tend to decline over time due to wear (e.g. increasing clearances as impellers reduce in size).
When a system includes a centrifugal pump, an important design issue is matching the head loss-flow characteristic with the pump so that it operates at or close to the point of its maximum efficiency.
Pump efficiency is an important aspect and pumps should be regularly tested. Thermodynamic pump testing is one method.
Minimum flow protection
Most large pumps have a minimum flow requirement below which the pump may be damaged by overheating, impeller wear, vibration, seal failure, drive shaft damage or poor performance. A minimum flow protection system ensures that the pump is not operated below the minimum flow rate. The system protects the pump even if it is shut-in or dead-headed, that is, if the discharge line is completely closed.
The simplest minimum flow system is a pipe running from the pump discharge line back to the suction line. This line is fitted with an orifice plate sized to allow the pump minimum flow to pass. The arrangement ensures that the minimum flow is maintained, although it is wasteful as it recycles fluid even when the flow through the pump exceeds the minimum flow.
A more sophisticated, but more costly, system (see diagram) comprises a flow measuring device (FE) in the pump discharge which provides a signal into a flow controller (FIC) which actuates a flow control valve (FCV) in the recycle line. If the measured flow exceeds the minimum flow then the FCV is closed. If the measured flow falls below the minimum flow the FCV opens to maintain the minimum flowrate.
As the fluids are recycled the kinetic energy of the pump increases the temperature of the fluid. For many pumps this added heat energy is dissipated through the pipework. However, for large industrial pumps, such as oil pipeline pumps, a recycle cooler is provided in the recycle line to cool the fluids to the normal suction temperature. Alternatively the recycled fluids may be returned to upstream of the export cooler in an oil refinery, oil terminal, or offshore installation.
References
Further reading
Australian Pump Manufacturers' Association. Australian Pump Technical Handbook, 3rd edition. Canberra: Australian Pump Manufacturers' Association, 1987. .
Hicks, Tyler G. and Theodore W. Edwards. Pump Application Engineering. McGraw-Hill Book Company.1971.
Robbins, L. B. "Homemade Water Pressure Systems". Popular Science'', February 1919, pages 83–84. Article about how a homeowner can easily build a pressurized home water system that does not use electricity.
Ancient inventions | Pump | Physics,Chemistry | 7,966 |
60,154,910 | https://en.wikipedia.org/wiki/Paul%20Cremer | Paul S. Cremer (born 1967) is an American chemist in physical and analytical chemistry at biological interfaces.
Education and academic career
Cremer graduated from University of Wisconsin-Madison with a BA in 1990, completed his PhD at University of California, Berkeley in 1996, and completed postdoctoral work at Stanford University (1996-1998).
Cremer joined the faculty in the chemistry department, Texas A&M University in 1998.
He is known for his work in Hofmeister series and supported lipid bilayers. He is also interested in nanofabrication, sum-frequency generation and biosensing.
Cremer joined the faculty in the chemistry department, Penn State University, in 2013. He continues his research in the lipid bilayer and protein folding.
References
External links
Cremer lab website
Google Scholar Profile
American chemists
Analytical chemistry
University of Wisconsin–Madison alumni
Living people
University of California, Berkeley alumni
Stanford University alumni
Pennsylvania State University faculty
1967 births | Paul Cremer | Chemistry | 199 |
4,878,376 | https://en.wikipedia.org/wiki/Merovingian%20art%20and%20architecture | Merovingian art is the art of the Merovingian dynasty of the Franks, which lasted from the 5th century to the 8th century in present-day France, Benelux and a part of Germany.
The advent of the Merovingian dynasty in Gaul in the 5th century led to important changes in the field of arts. Sculptural arts consisted of the ornamentation of sarcophagi, altars and ecclesiastical furniture. Gold work and the new medium of manuscript illumination integrated "barbarian" animal-style decoration, with Late Antique motifs, and other contributions from as far as Syria or Ireland to constitute Merovingian art.
Architecture
The unification of the Frankish kingdom under Clovis I (465–511) and his successors, corresponded with the need for the building of churches, and especially monastery churches, as these were now the power-houses of the Merovingian church. Plans often continued the Roman basilica tradition, but also took influences from as far away as Syria and Armenia. In the East, most structures were in timber, but stone was more common for significant buildings in the West and in the southern areas that later fell under Merovingian rule. Most major churches have been rebuilt, usually more than once, but many Merovingian plans have been reconstructed from archaeology.
The description in Bishop Gregory of Tours' History of the Franks of the basilica of Saint-Martin, built at Tours by Saint Perpetuus (bishop 460–490) at the beginning of the period and at the time on the edge of Frankish territory, gives cause to regret the disappearance of this building, one of the most beautiful Merovingian churches, which he says had 120 marble columns, towers at the East end, and several mosaics: "Saint-Martin displayed the vertical emphasis, and the combination of block-units forming a complex internal space and the correspondingly rich external silhouette, which were to be the hallmarks of the Romanesque". A feature of the basilica of Saint-Martin that became a hallmark of Frankish church architecture was the sarcophagus or reliquary of the saint raised to be visible and sited axially behind the altar, sometimes in the apse. There are no Roman precedents for this Frankish innovation. The Saint Peter's church in Vienne is the only surviving one. A number of other buildings, now lost, including the Merovingian foundations of Saint-Denis, St. Gereon in Cologne, and the Abbey of Saint-Germain-des-Prés in Paris, are described as similarly ornate.
Some small buildings remain, especially baptisteries, which fell out of fashion and were spared rebuilding. In Aix-en-Provence, Riez and Fréjus, three octagonal baptistries, each covered with a cupola on pillars, are testimony to the influence of oriental architecture (the baptistry of Riez, in the Alpes-de-Haute-Provence, recalls that of St. George, Ezra', Syria). Very different from these Provençal baptistries, except for the quatrefoil one of Venasque, that of St. Jean at Poitiers (6th century) has the form of a rectangle flanked by three apses. The original building has probably undergone a number of alterations but preserves in its decoration (marble capitals) a Merovingian character.
Among the very many crypts, numerous due to the importance of the cult of saints at the time, only those of St. Seurin, Bordeaux, St. Laurent, Grenoble, the crypt of the Abbey of Saint Médard in Soissons,and the abbey of Jouarre (7th century) survive.
Other arts
By the 7th century, the abilities of Merovingian craftsmen must have been well regarded, as they were brought to England to re-introduce glass making skills, and Merovingian stonemasons were used to build English churches. Merovingian masons also employed the opus gallicum extensively and are responsible for bringing it to England and bequeathing it to the Normans, who brought it to Italy.
Very few Merovingian illuminated manuscripts survive, of which the most richly decorated is the 8th century Gelasian Sacramentary in the Vatican Library, which has geometric and animal decoration, less complex than that of the Insular art of the British Isles, but like it derived from metalwork motifs, with some influence from Late Antiquity and the Near-East. The principal centres were the Abbey of Luxeuil, an Irish foundation, and later its daughter house at Corbie Abbey.
A large Merovingian art collection in Berlin was taken by Soviet troops to Russia, where it remains to this day.
Gallery
See also
Migration Period art
List of Merovingian monasteries
Merovingian script
Notes
References
European Commission: Raphaël Programme. The Normans, a European people: The Norman heritage, 10th – 12th century. Architectural Heritage: Italy — the Molise §8 Fortifications and castles: Fortifications — The opus gallicum in the fortifications. 2004.
Gilbert, Edward. "Brixworth and the English Basilica." The Art Bulletin, Vol. 47, No. 1. (Mar., 1965), pp 1–20.
Bede. Lives of the Holy Abbots of Wearmouth and Jarrow.
External links
Age of spirituality : late antique and early Christian art, third to seventh century from The Metropolitan Museum of Art
A large collection of Merovingian art was taken from Berlin by the Soviet military forces in 1945.
Architectural history
Architectural styles
Merovingian art | Merovingian art and architecture | Engineering | 1,143 |
32,150,292 | https://en.wikipedia.org/wiki/Uroguanylin | Uroguanylin is a 16 amino acid peptide that is secreted by enterochromaffin cells in the duodenum and proximal small intestine. Guanylin acts as an agonist of the guanylyl cyclase receptor guanylate cyclase 2C (GC-C), and regulates electrolyte and water transport in intestinal and renal epithelia. By agonizing this guanylyl cyclase receptor, uroguanylin and guanylin cause intestinal secretion of chloride and bicarbonate to dramatically increase; this process is helped by the second messenger cGMP. Its sequence is H-Asn-Asp-Asp-Cys(1)-Glu-Leu-Cys(2)-Val-Asn-Val-Ala-Cys(1)-Thr-Gly-Cys(2)-Leu-OH.
In humans, the uroguanylin peptide is encoded by the GUCA2B gene. Uroguanylin may be involved in appetite and perceptions of 'fullness' after eating meals, as suggested by a study into mice.
See also
Natriuretic peptide
Plecanatide – a medication structurally related to uroguanylin
References
External links
Peptides
Digestive system | Uroguanylin | Chemistry,Biology | 281 |
32,237,275 | https://en.wikipedia.org/wiki/Advanced%20Comprehensive%20Operating%20System | Advanced Comprehensive Operating System (ACOS) is a family of mainframe computer operating systems developed by NEC for the Japanese market. It consists of three systems, based on the General Comprehensive Operating System family developed by General Electric, Honeywell, and Bull. Two of these systems, ACOS-2 (based on GCOS 4) and ACOS-4 (based on GCOS 7) are still sold, although only ACOS-4 is under active development. ACOS-6 (based on GCOS 8) is an obsolete high-end mainframe platform, which ceased active development in the early 2000s.
The first two models in NEC's SX series of supercomputers, the SX-1 and the SX-2 (released in 1985), ran an operating system derived from ACOS-4, which was variously called either SX-OS or SXCP (SX System Control Program). However, subsequent SX supercomputers, starting with the SX-3 (released in 1990), instead ran a derivative of Unix.
In late September 2012, NEC announced a return from IA-64 to the previous NOAH line of proprietary mainframe processors for ACOS-4, now produced in a quad-core variant on 40 nm, called NOAH-6.
ACOS-2 runs on Intel Xeon servers.
In June 2022, i-PX AKATSUKI server equipped with NEC's original processor (NOAH-7) was released.
See also
Timeline of operating systems
References
External links
ACOS Club home page
A history of GE/Honeywell/NEC/Bull operating systems
Proprietary operating systems
Computing platforms
NEC software
Mainframe computers
Mainframe computer software | Advanced Comprehensive Operating System | Technology | 347 |
36,834,542 | https://en.wikipedia.org/wiki/GAMA202627 | GAMA202627 (also known as G202627 or PGC 165514) is a barred spiral galaxy similar to our own Milky Way, located 700 million light-years from Earth
in the Hydra constellation.
The galaxy was described in a 2012 paper
by astronomer Dr Aaron Robotham, jointly from the University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR) and the University of St Andrews in Scotland, when he searched for groups of galaxies similar to ours in the most detailed map of the local Universe yet, the Galaxy And Mass Assembly survey (GAMA). The Galaxy and Mass Assembly (GAMA) survey is an international collaboration led from ICRAR and the Australian Astronomical Observatory to map our local Universe in closer detail. The galaxy has a redshift measured at z = 0.051219 +/- 0.000123, which corresponds to a distance of 705 Mly, or 216 Mpc.
Dr Robotham noted, "We found about 3% of galaxies similar to the Milky Way have companion galaxies like the Magellanic Clouds, which is very rare indeed. In total we found 14 galaxy systems that are similar to ours, with two of those being an almost exact match."
The Milky Way is surrounded by its close companions, the Large and Small Magellanic Clouds, which are visible in the southern sky. Many galaxies have smaller galaxies in orbit around them, but few have two that are as large as the Magellanic Clouds. That is why GAMA202627 is so unique as it has two massive satellite galaxies in close proximity.
References
Barred spiral galaxies
165514
Hydra (constellation) | GAMA202627 | Astronomy | 337 |
10,821,683 | https://en.wikipedia.org/wiki/Bryan%20Simonaire | Bryan Warner Simonaire (born September 6, 1963) is an American politician who serves as a Maryland state senator representing District 31, which encompasses much of northern Anne Arundel County's Baltimore suburbs. A member of the Republican Party, he served as the minority leader of the Maryland Senate from 2020 to 2023.
Background
Simonaire was born in Baltimore. He graduated from Bob Jones University in 1985, receiving a Bachelor of Science degree in computer science, and from Loyola College, where he earned a Master of Science degree in engineering in 2005. He is a member of Upsilon Pi Epsilon.
After graduating from Bob Jones, Simonaire has worked as a computer systems engineer for Westinghouse Electronic Systems (now Northrop Grumman since its acquisition in 1995). In 2002, he founded Heroes-at-Home, a web-based program that helps the needy.
Simonaire became involved in politics in 2005, when he joined the North Count Republican Club's board of directors. He entered the race for state Senate in District 31 later that year, seeking to succeed retiring Democratic state senator Philip C. Jimeno and running on a "common sense, conservative" platform that included opposition to same-sex marriage. The district was targeted by the Maryland Republican Party, which saw the election as an opportunity to make legislative gains. Simonaire won the Republican primary in September 2006, and later won the general election on November 7, 2006, defeating Democratic state delegate Walter J. Shandrowsky by 659 votes, or a margin of 1.72 percent. It was the closest election in the 2006 Maryland Senate elections.
In the legislature
Simonaire was sworn into the Maryland Senate on January 10, 2007. He was initially a member of the Judicial Proceedings Committee from 2007 to 2010, afterwards serving on the Health and Environmental Affairs Committee until 2022. Since 2023, he has served on the Education, Energy, and the Environment Committee.
Simonaire endorsed Mitt Romney in the 2012 Republican Party presidential primaries and later served a Romney delegate to the 2012 Republican National Convention.
In 2014, Simonaire proposed a constitutional amendment to remove legislative leaders' ability to remove voting powers from any member of the Maryland General Assembly. The amendment was introduced after state Delegate Don H. Dwyer Jr. was stripped of his voting powers and committee assignments after being sentenced to 30 weekends in jail for driving under the influence. In 2016, Simonaire introduced the "Dwyer amendment", which would have prevented Senate president Thomas V. Miller Jr. from removing a member's voting powers. The proposed rule change was rejected in a 11-31 vote.
In October 2020, Simonaire was elected as the minority leader of the Maryland Senate, which was seen by the media as the Senate Republican caucus becoming more conservative as to push back on the perceived leftward shift of the Maryland Democratic Party following the election of Bill Ferguson as Senate president. In this capacity, Simonaire sought to allow his party to make their own committee assignments and oversaw the party's state Senate campaign in 2022, in which the party lost two seats in the Maryland Senate. Following the 2022 elections, Senate Republicans opted to elect Stephen S. Hershey Jr. as minority leader.
Simonaire endorsed Maryland Secretary of Commerce Kelly M. Schulz in the 2022 Maryland gubernatorial election. After she was defeated by far-right state delegate Dan Cox in the Republican primary, he declined to endorse or campaign with Cox, instead focusing on competitive Senate elections.
Political positions
Crime and justice
In 2009, Simonaire said he would vote to repeal the death penalty if legislators passed a constitutional amendment to ban same-sex marriage in Maryland. He later voted for an amendment to the death penalty repeal bill to limit the death penalty's use rather than fully repeal it, which passed 25-21. During the 2013 legislative session, Simonaire voted against repealing the death penalty.
During the 2022 legislative session, Simonaire implored legislators to pass a tough-on-crime bill introduced by Governor Larry Hogan. He also expressed willingness to work with Democrats to pass a bipartisan judicial transparency bill.
Education
Simonaire opposes the Blueprint for Maryland's Future, calling for its repeal during the 2021 legislative session and comparing them to the Bridge of Excellence education reforms in 2002. He supports legislation requiring the Maryland State Board of Education to prepare a problem gambling curriculum in schools.
During the 2011 legislative session, Simonaire said he opposed Maryland's Dream Act, a bill that extended in-state tuition for undocumented immigrants.
During the 2022 legislative session, Simonaire introduced a bill that would force the county Board of Education to vote on certain curriculum items if a petition got the signatures of at least three percent of parents.
Electoral reform
During the 2015 legislative session, Simonaire testified against a bill to restore voting rights for ex-felons.
In May 2020, Simonaire asked Governor Larry Hogan to call a special session to pass election integrity bills, expressing concern that the use of mail-in ballots in the 2020 elections would lead to voter fraud.
During the 2021 legislative session, Simonaire introduced a package of election reform bills, including voter ID laws and signature verification on mail-in ballots, citing what he called "major deficiencies" in the 2020 United States presidential election. The package failed to move out of committee, and many bills from the package were reintroduced in 2022. He also supported a bill to shift control of local election boards to whichever party had a majority of registered voters in each jurisdiction, and sought to amend a bill to expand early voting centers to require local boards of elections to consider "geographical distance" in deciding where to locate early voting centers.
Simonaire opposed the congressional maps drawn by the Legislative Redistricting Advisory Committee (LRAC), of which he was a member, instead supporting maps drawn by Governor Larry Hogan's Maryland Citizens Redistricting Commission. During the LRAC's map drawing process, he pressed for a bipartisan map drawing process and hoped legislators would produce a single map, but predicted that Democrats on the commission would pass their own map. He criticized the commission's final congressional and legislative maps as "seriously gerrymandered". After Judge Lynne A. Battaglia struck down the state's congressional maps in March 2022, Simonaire criticized Democrats for not including Republicans in the process of drafting a new map.
Environment
Simonaire is an environmentalist and has expressed willingness to work with legislators to pass a bipartisan climate bill. He voted in favor of bills to ban fracking and foam containers in Maryland.
Simonaire was critical of Maryland's "Rain Tax" and introduced legislation in 2013 to offset the fee in Anne Arundel County. In 2015, he voted in favor of a bill to make the rain tax optional for Maryland's largest jurisdictions.
During the 2021 legislative session, Simonaire expressed concern with the Climate Solutions Now Act, which he said would force jurisdictions to choose between planting more trees and protecting local sewage projects. After it was reintroduced in 2022, he objected to provisions that would require large buildings to become carbon neutral by 2040 and expressed that legislators should instead focus on climate solutions "starting at the regional level".
Gun policy
During the 2013 legislative session, Simonaire voted against the Firearms Safety Act, a bill that placed restrictions on firearm purchases and magazine capacity in semi-automatic rifles.
Social issues
Simonaire is a social conservative, opposing abortion rights and same-sex marriage, citing religious beliefs.
Simonaire opposed the Civil Marriage Protection Act, reading King & King on the Senate floor to protest the bill and warning that "young, impressionable students" would be taught the "homosexual worldview" if the bill passed. He also unsuccessfully sought to amend the bill to allow religious adoption agencies to refuse services to same-sex couples. In 2015, he voted against a bill that would allow same-sex couples to use donor sperm for in vitro fertilization.
In 2014, Simonaire said he opposed a bill to prohibit discrimination against transgender people. In 2021, he was the lone vote against a bill to allow transgender people to change their names without advertising it in newspapers.
In 2015, Simonaire introduced a "right to try" bill that would allow terminally ill patients to try experimental drugs not approved by the Food and Drug Administration. In 2019, he spoke against the End-of-Life Option Act, which would have provided palliative care to terminally ill adults.
During the 2016 legislative session, Simonaire introduced legislation to revise a translation of the state's motto to "Strong deeds, gentle words", saying that he believed that the current meaning of the motto ("Manly deeds, womanly words") was sexist.
In 2022, Simonaire downplayed the impact of the U.S. Supreme Court's decision in Dobbs v. Jackson Women's Health Organization, which overturned Roe v. Wade, calling it a "Democratic ploy" to energize voters. In 2023, during debate on a bill creating a ballot referendum to codify abortion access rights into the Constitution of Maryland, Simonaire compared abortion to the death penalty and sought to amend the bill to prohibit abortions after fetal viability, which failed by a vote of 13-33.
Taxes
In 2013, Simonaire said he opposed a bill to provide $450,000 in tax breaks to Lockheed Martin.
In 2021, Simonaire spoke against legislation to extend the state's earned income tax credit to undocumented immigrants. He also opposed legislation to allow counties to implement progressive income taxes and to impose a tax on digital advertising, and unsuccessfully attempted to amend the tax bill to prevent large companies from increasing prices for consumers or small businesses to pay for the tax.
During the 2022 legislative session, Simonaire supported a bill to cut taxes on centenarians and implored legislators to pass additional tax cuts.
Transportation
In March 2024, following the Francis Scott Key Bridge collapse, Simonaire and state senator Johnny Ray Salling introduced a bill that would allow the governor to declare a year-long state of emergency after damage to critical infrastructure, though it would eliminate the authority to seize private property for government use, as now allowed under a state of emergency. The bill was withdrawn following discussions with the Moore administration.
Personal life
Simonaire is married and has seven children. He lives in Pasadena, Maryland, and attends nondenominational Christian churches.
During the 2018 legislative session, Simonaire spoke against a bill to ban conversion therapy on minors, arguing that it would dissuade teens from seeking counseling. His daughter, Meagan, a member of the Maryland House of Delegates, spoke in support of the bill and accused her father of seeking conversion therapy for her after she came out as bisexual in 2015. Simonaire disputed his daughter's story in interviews with the media, saying that he had recommended her Christian counseling after she approached him for advice with her depression and anxiety, but added that he disagreed with her "lifestyle".
Electoral history
References
External links
1963 births
Bob Jones University alumni
Christians from Maryland
Computer systems engineers
Living people
Loyola University Maryland alumni
People from Pasadena, Maryland
Politicians from Baltimore
Republican Party Maryland state senators
21st-century members of the Maryland General Assembly | Bryan Simonaire | Technology | 2,270 |
39,352,361 | https://en.wikipedia.org/wiki/Epimedium%20%C3%97%20rubrum | Epimedium × rubrum, known as red barrenwort, is a species of perennial flowering plant in the family Berberidaceae, cultivated in gardens. It is considered to be a hybrid between E. alpinum and E. grandiflorum (hence the symbol ×). The Royal Horticultural Society has given it the Award of Garden Merit (AGM).
Description
Epimedium × rubrum is a deciduous perennial, spreading by rhizomes. It is about tall. When the young leaves emerge in spring, they are tinged with red. The leaves also turn red in the autumn. The flowers appear with the young leaves in spring, and are borne on a loose raceme. Individual flowers are about across, with red sepals and yellow petals.
Cultivation
Epimedium × rubrum is recommended for cultivation in shade or part-shade in moist soil, although it tolerates drier conditions when well-established. Old foliage should be cut back before the new leaves and flowers appear in spring. It was given the Award of Garden Merit by the Royal Horticultural Society in 1993, with a hardiness rating of H7, meaning that it is very hardy, withstanding temperatures below .
References
rubrum
Garden plants
Hybrid plants | Epimedium × rubrum | Biology | 251 |
39,541,688 | https://en.wikipedia.org/wiki/BL%20Herculis%20variable | BL Herculis variables are a subclass of type II Cepheids with low luminosity and mass, that have a period of less than eight days. They are pulsating stars with light curves that frequently show a bump on the descending side for stars of the shortest periods and on the ascending side for longer period stars. Like other type II Cepheids, they are very old population II stars found in the galaxy’s halo and globular clusters. Also, compared to other type II Cepheids, BL Herculis variables have shorter periods and are fainter than W Virginis variables. Pulsating stars vary in spectral class as they vary in brightness and BL Herculis variables are normally class A at their brightest and class F when most dim. When plotted on the Hertzsprung–Russell diagram they fall in-between W Virginis and RR Lyrae variables.
The prototype star, BL Herculis, varies between magnitude 9.7 and 10.6 in a period of 1.3 days. The brightest BL Herculis variables, with their maximum magnitudes, are:
VY Pyxidis, 7.7
V553 Centauri, 8.2
SW Tauri, 9.3
RT Trianguli Australis, 9.4
V351 Cephei, 9.5
BL Herculis. 9.7
BD Cassiopeiae, 10.8
UY Eridani, 10.9
The BL Herculis stars show a wide variety of light curves, temperatures, and luminosity, and three subdivisions of the class have been defined, with the acronym AHB referring to above horizontal branch:
XX Virginis stars (AHB1), with very fast rises to maximum and low metallicity
CW stars (AHB2), W Virginis variables, longer periods, the bump on the ascending leg
BL Herculis stars (AHB3), shorter periods, the bump on the descending leg
References
External links
OGLE Atlas of Variable Star Light Curves - BL Herculis stars
Astrometry
Standard candles
Variable stars
BL Herculis variables | BL Herculis variable | Physics,Astronomy | 450 |
35,830,503 | https://en.wikipedia.org/wiki/Nu%20Orionis | Nu Orionis (ν Orionis) is a binary star system in the northeastern part of the constellation Orion. It should not be confused with the variable star NU Orionis. Nu Orionis has an apparent visual magnitude of 4.42, which is bright enough to be seen with the naked eye. Based upon an annual parallax shift of 0.00632 arcseconds, the distance to this system is roughly 520 light years.
This is a single-lined spectroscopic binary system, which means that only the absorption line features of one of the components can be distinguished. The components orbit each other with a period of 131.2 days and an eccentricity of 0.64. Depending on the source, the primary is either a B-type main sequence star with a stellar classification of B3 V, or a more evolved B-type subgiant star of class B3 IV. It has an angular diameter of 0.251 mas, which, at the estimated distance of this system, yields a physical size of about 4.3 times the radius of the Sun. The mass is 6.7 times that of the Sun and it shines with 1,965 times the solar luminosity from its outer atmosphere at an effective temperature of 17,880 K.
References
B-type main-sequence stars
Spectroscopic binaries
Orion (constellation)
Orionis, Nu
Orionis, 67
041753
029038
02159
Durchmusterung objects | Nu Orionis | Astronomy | 302 |
21,006,532 | https://en.wikipedia.org/wiki/Sysload%20Software | Sysload Software, was a computer software company specializing in systems measurement, performance and capacity management solutions for servers and data centers, based in Créteil, France. It has been acquired in September 2009 by ORSYP, a computer software company specialist in workload scheduling and IT Operations Management, based in La Défense, France.
History
Sysload was created in 1999 as a result of the split of Groupe Loan System into two distinct entities: Loan Solutions, a developer of financial software and Sysload Software, a developer of performance management and monitoring software.
As of March 31, 2022, all Sysload products are in end of life.
Products
The following products are developed by Sysload:
SP Analyst
Is a performance and diagnostic solution for physical and virtual servers. It is a productivity tool destined to IT teams to diagnose performance problems and manage server resource capacity.
SP Monitor
A monitoring solution for incident management and IT service availability. It aims at providing real-time management of IT infrastructure events while correlating them to business processes. SP Monitor receives and stores event data, makes correlations and groups them within customizable views which can be accessed via an ordinary web browser.
SP Portal
A capacity and performance reporting solution for servers and data centers to allow IT managers analyze server resource allocation within information systems.
Sysload products are based on a 3-tiered (user interfaces, management modules and collection and analysis modules) architecture metric collection technology that provides detailed information on large and complex environments. Sysload software products are available for various virtualized and physical platforms including: VMware, Windows, AIX, HP-UX, Solaris, Linux, IBM i, PowerVM, etc.
References
External links
System administration
Computer systems
Software companies established in 1999
French companies established in 1999
Software companies of France | Sysload Software | Technology,Engineering | 377 |
54,071,558 | https://en.wikipedia.org/wiki/Dacryobolus%20gracilis | Dacryobolus gracilis is a species of crust fungus in the family Fomitopsidaceae. This brown rot fungus was described as new to science in 2016 by Hai-Sheng Yuan. It has a fragile, waxy fruit body with small, slender spines. The fungus has been found in Chongqing and Guangxi, in southwestern China.
References
Fomitopsidaceae
Fungi described in 2016
Fungi of China
Fungus species | Dacryobolus gracilis | Biology | 90 |
61,334 | https://en.wikipedia.org/wiki/Pygmy%20hippopotamus | The pygmy hippopotamus or pygmy hippo (Choeropsis liberiensis) is a small hippopotamid which is native to the forests and swamps of West Africa, primarily in Liberia, with small populations in Sierra Leone, Guinea, and Ivory Coast. It has been extirpated from Nigeria.
The pygmy hippo is reclusive and nocturnal. It is one of only two extant species in the family Hippopotamidae, the other being its much larger relative, the common hippopotamus (Hippopotamus amphibius) or Nile hippopotamus. The pygmy hippopotamus displays many terrestrial adaptations, but like the common hippo, it is semiaquatic and relies on water to keep its skin moist and its body temperature cool. Behaviors such as mating and giving birth may occur in water or on land. The pygmy hippo is herbivorous, feeding on ferns, broad-leaved plants, grasses, and fruits it finds in the forests.
A rare nocturnal forest creature, the pygmy hippopotamus is a difficult animal to study in the wild.
Pygmy hippos were unknown outside West Africa until the 19th century. Introduced to zoos in the early 20th century, they breed well in captivity and the vast majority of research is derived from zoo specimens. The survival of the species in captivity is more assured than in the wild; in a 2015 assessment, the International Union for Conservation of Nature estimated that fewer than 2,500 pygmy hippos remain in the wild.
Pygmy hippos are primarily threatened by loss of habitat, as forests are logged and converted to farm land, and are also vulnerable to poaching, hunting for bushmeat, natural predators, and war. Pygmy hippos are among the species illegally hunted for food in Liberia.
Taxonomy and origins
Nomenclature of the pygmy hippopotamus reflects that of the hippopotamus; the plural form is pygmy hippopotamuses or pygmy hippopotami. A male pygmy hippopotamus is known as a bull, a female as a cow, and a baby as a calf. A group of hippopotami is known as a herd or a bloat.
The pygmy hippopotamus is a member of the family Hippopotamidae where it is classified as a member of the genus Choeropsis ("resembling a hog"). Members of Hippopotamidae are sometimes known as hippopotamids. Sometimes the sub-family Hippopotaminae is used. Further, some taxonomists group hippopotami and anthracotheres in the superfamily Anthracotheroidea or Hippopotamoidea.
The taxonomy of the genus of the pygmy hippopotamus has changed as understanding of the animal has developed. Samuel G. Morton initially classified the animal as Hippopotamus minor, but later determined it was distinct enough to warrant its own genus, and labeled it Choeropsis. In 1977, Shirley C. Coryndon proposed that the pygmy hippopotamus was closely related to Hexaprotodon, a genus that consisted of prehistoric hippos mostly native to Asia.
This assertion was widely accepted, until Boisserie asserted in 2005 that the pygmy hippopotamus was not a member of Hexaprotodon, after a thorough examination of the phylogeny of Hippopotamidae. He suggested instead that the pygmy hippopotamus was a distinct genus, and returned the animal to Choeropsis. ITIS verifies Hexaprotodon liberiensis as the valid scientific name. All agree that the modern pygmy hippopotamus, be it H. liberiensis or C. liberiensis, is the only extant member of its genus. The American Society of Mammalogists moved it back to Choeropsis in 2021, a move supported by the IUCN.
Nigerian subspecies
A distinct subspecies of pygmy hippopotamus existed in Nigeria until at least the 20th century, though the validity of this has been questioned. The existence of the subspecies, makes Choeropsis liberiensis liberiensis (or Hexaprotodon liberiensis liberiensis under the old classification) the full trinomial nomenclature for the Liberian pygmy hippopotamus. The Nigerian pygmy hippopotamus was never studied in the wild and never captured. All research and all zoo specimens are the Liberian subspecies. The Nigerian subspecies is classified as C. liberiensis heslopi.
The Nigerian pygmy hippopotamus ranged in the Niger River Delta, especially near Port Harcourt, but no reliable reports exist after the collection of the museum specimens secured by Ian Heslop, a British colonial officer, in the early 1940s. It is probably extinct. The subspecies is separated by over and the Dahomey Gap, a region of savanna that divides the forest regions of West Africa. The subspecies is named after Heslop, who shot three members of it in 1935 and 1943. He estimated that perhaps no more than 30 pygmy hippos remained in the region.
Heslop sent four pygmy hippopotamus skulls he collected to the British Museum of Natural History in London. These specimens were not subjected to taxonomic evaluation, however, until 1969 when classified the skulls as belonging to a separate subspecies based on consistent variations in the proportions of the skulls. The Nigerian pygmy hippos were seen or shot in Rivers State, Imo State and Bayelsa State, Nigeria. While some local humans are aware that the species once existed, its history in the region is poorly documented.
Evolution
The evolution of the pygmy hippopotamus is most often studied in the context of its larger cousin. Both species were long believed to be most closely related to the family Suidae (pigs and hogs) or Tayassuidae (peccaries), but research within the last 10 years has determined that pygmy hippos and hippos are most closely related to cetaceans (whales and dolphins). Hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around .
This hypothesized ancestor likely split into two branches about six million years later. One branch would evolve into cetaceans, the other branch became the anthracotheres, a large family of four-legged beasts, whose earliest member, from the Late Eocene, would have resembled narrow hippopotami with comparatively small and thin heads.
Hippopotamids are deeply nested within the family Anthracotheriidae. The oldest known hippopotamid is the genus Kenyapotamus, which lived in Africa from . Kenyapotamus is known only through fragmentary fossils, but was similar in size to C. liberiensis. The Hippopotamidae are believed to have evolved in Africa, and while at one point the species spread across Asia and Europe, no hippopotami have ever been discovered in the Americas. Starting the Archaeopotamus, likely ancestors to the genus Hippopotamus and Hexaprotodon, lived in Africa and the Middle East.
While the fossil record of hippos is still poorly understood, the lineages of the two modern genera, Hippopotamus and Choeropsis, may have diverged as far back as . The ancestral form of the pygmy hippopotamus may be the genus Saotherium. Saotherium and Choeropsis are significantly more basal than Hippopotamus and Hexaprotodon, and thus more closely resemble the ancestral species of hippos.
Extinct pygmy and dwarf hippos
Several species of small hippopotamids have also become extinct in the Mediterranean in the late Pleistocene or early Holocene. Though these species are sometimes known as "pygmy hippopotami" they are not believed to be closely related to C. liberiensis. These include the Cretan dwarf hippopotamus (Hippopotamus creutzburgi), the Sicilian hippopotamus (Hippopotamus pentlandi), the Maltese hippopotamus (Hippopotamus melitensis) and the Cyprus dwarf hippopotamus (Hippopotamus minor).
These species, though comparable in size to the pygmy hippopotamus, are considered dwarf hippopotamuses, rather than pygmies. They are likely descended from a full-sized species of European hippopotamus, and reached their small size through the evolutionary process of insular dwarfism which is common on islands; the ancestors of pygmy hippopotami were also small and thus there was never a dwarfing process. There were also several species of pygmy hippo on the island of Madagascar (see Malagasy hippopotamus).
Description
Pygmy hippos share the same general form as a hippopotamus. They have a graviportal skeleton, with four stubby legs and four toes on each foot, supporting a portly frame. Yet, the pygmy is only half as tall as the hippopotamus and weighs less than 1/4 as much as its larger cousin. Adult pygmy hippos stand about high at the shoulder, are in length and weigh . Their lifespan in captivity ranges from 30 to 55 years, though it is unlikely that they live this long in the wild.
The skin is greenish-black or brown, shading to a creamy gray on the lower body. Their skin is very similar to the common hippo's, with a thin epidermis over a dermis that is several centimeters thick. Pygmy hippos have the same unusual secretion as common hippos, that gives a pinkish tinge to their bodies, and is sometimes described as "blood sweat" though the secretion is neither sweat nor blood. This substance, hipposudoric acid, is believed to have antiseptic and sunscreening properties. The skin of hippos dries out quickly and cracks, which is why both species spend so much time in water.
The skeleton of C. liberiensis is more gracile than that of the common hippopotamus, meaning their bones are proportionally thinner. The common hippo's spine is parallel with the ground; the pygmy hippo's back slopes forward, a likely adaptation to pass more easily through dense forest vegetation. Proportionally, the pygmy hippo's legs and neck are longer and its head smaller.
The orbits and nostrils of a pygmy hippo are much less pronounced, an adaptation from spending less time in deep water (where pronounced orbits and nostrils help the common hippo breathe and see). The feet of pygmy hippos are narrower, but the toes are more spread out and have less webbing, to assist in walking on the forest floor.
Despite adaptations to a more terrestrial life than the common hippopotamus, pygmy hippos are still more aquatic than all other terrestrial even-toed ungulates. The ears and nostrils of pygmy hippos have strong muscular valves to aid submerging underwater, and the skin physiology is dependent on the availability of water.
Behavior
The behavior of the pygmy hippo differs from the common hippo in many ways. Much of its behavior is more similar to that of a tapir, though this is an effect of convergent evolution. While the common hippopotamus is gregarious, pygmy hippos live either alone or in small groups, typically a mated pair or a mother and calf. Pygmy hippos tend to ignore each other rather than fight when they meet. Field studies have estimated that male pygmy hippos range over , while the range of a female is .Pygmy hippos spend most of the day hidden in rivers. They will rest in the same spot for several days in a row, before moving to a new spot. At least some pygmy hippos make use of dens or burrows that form in river banks. It is unknown if the pygmy hippos help create these dens, or how common it is to use them. Though a pygmy hippo has never been observed burrowing, other artiodactyls, such as warthogs, are burrowers.
Diet
Like the common hippopotamus, the pygmy hippo emerges from the water at dusk to feed. It relies on game trails to travel through dense forest vegetation. It marks trails by vigorously waving its tail while defecating to further spread its feces. The pygmy hippo spends about six hours a day foraging for food.
Pygmy hippos are herbivorous. They do not eat aquatic vegetation to a significant extent and rarely eat grass because it is uncommon in the thick forests they inhabit. The bulk of a pygmy hippo's diet consists of herbs, ferns, broad-leaved plants, herbaceous shoots, forbs, sedges and fruits that have fallen to the forest floor. The wide variety of plants pygmy hippos have been observed eating suggests that they will eat any plants available. This diet is of higher quality than that of the common hippopotamus.
Reproduction
A study of breeding behavior in the wild has never been conducted; the artificial conditions of captivity may cause the observed behavior of pygmy hippos in zoos to differ from natural conditions. Sexual maturity for the pygmy hippopotamus occurs between three and five years of age. The youngest reported age for giving birth is a pygmy hippo in the Zoo Basel, Switzerland which bore a calf at three years and three months. The oestrus cycle of a female pygmy hippo lasts an average of 35.5 days, with the oestrus itself lasting between 24 and 48 hours.
Pygmy hippos consort for mating, but the duration of the relationship is unknown. In zoos they breed as monogamous pairs. Copulation can take place on land or in the water, and a pair will mate one to four times during an oestrus period. In captivity, pygmy hippos have been conceived and born in all months of the year. The gestation period ranges from 190 to 210 days, and usually a single young is born, though twins are known to occur.The common hippopotamus gives birth and mates only in the water, but pygmy hippos mate and give birth on both land and water. Young pygmy hippos can swim almost immediately. At birth, pygmy hippos weigh 4.5–6.2 kg (9.9–13.7 lb) with males weighing about 0.25 kg (0.55 lb) more than females. Pygmy hippos are fully weaned between six and eight months of age; before weaning they do not accompany their mother when she leaves the water to forage, but instead hide in the water by themselves. The mother returns to the hiding spot about three times a day and calls out for the calf to suckle. Suckling occurs with the mother lying on her side.
Temperament
Although not considered dangerous to humans and generally docile, pygmy hippos can be highly aggressive at times. Although there have been no human deaths associated with pygmy hippos, there have been several attacks - while most of these were provoked by human behaviour, several have had no apparent cause.
Conservation
The greatest threat to the remaining pygmy hippopotamus population in the wild is loss of habitat. The forests in which pygmy hippos live have been subject to logging, settling and conversion to agriculture, with little efforts made to make logging sustainable. As forests shrink, the populations become more fragmented, leading to less genetic diversity in the potential mating pool.
Pygmy hippos are among the species illegally hunted for food in Liberia. Their meat is said to be of excellent quality, like that of a wild boar; unlike those of the common hippo, the pygmy hippo's teeth have no value. The effects of West Africa's civil strife on the pygmy hippopotamus are unknown, but unlikely to be positive. The pygmy hippopotamus can be killed by leopards, pythons and crocodiles. How often this occurs is unknown.
C. liberiensis was identified as one of the top 10 "focal species" in 2007 by the Evolutionarily Distinct and Globally Endangered (EDGE) project. Some populations inhabit protected areas, such as the Gola Forest Reserve in Sierra Leone.
Basel Zoo in Switzerland holds the international studbook and coordinates the entire captive pygmy hippo population that freely breeds in zoos around the world. Between 1970 and 1991 the population of pygmy hippos born in captivity more than doubled. The survival of the species in zoos is more certain than the survival of the species in the wild. In captivity, the pygmy hippo lives from 42 to 55 years, longer than in the wild. Since 1919, only 41 percent of pygmy hippos born in zoos have been male.
History and folklore
While the common hippopotamus has been known to Europeans since classical antiquity, the pygmy hippopotamus was unknown outside its range in West Africa until the 19th century. Due to their nocturnal, forested existence, they were poorly known within their range as well. In Liberia the animal was traditionally known as a water cow.
Early field reports of the animal misidentified it as a wild hog. Several skulls of the species were sent to the American natural scientist Samuel G. Morton, during his residency in Monrovia, Liberia. Morton first described the species in 1843. The first complete specimens were collected as part of a comprehensive investigation of Liberian fauna in the 1870s and 1880s by Dr. Johann Büttikofer. The specimens were taken to the Natural History Museum in Leiden, The Netherlands.
The first pygmy hippo was brought to Europe in 1873 after being captured in Sierra Leone by a member of the British Colonial Service but died shortly after arrival. Pygmy hippos were successfully established in European zoos in 1911. They were first shipped to Germany and then to the Bronx Zoo in New York City where they also thrived.
In 1927, Harvey Firestone of Firestone Tires presented Billy the pygmy hippo to U.S. President Calvin Coolidge. Coolidge donated Billy to the National Zoo in Washington, D.C. According to the zoo, Billy is a common ancestor to most pygmy hippos in U.S. zoos today.
Moo Deng is a pygmy hippo living in Khao Kheow Open Zoo, in Thailand, who gained notability in September 2024 as a popular Internet meme after images of her went viral online. Because of the popularity of the hippo, whose name translates to "bouncy pork", the zoo saw a boosted attendance. It has been reported that some visitors to the zoo threw water and other objects at the baby hippo to get her to react.
Several folktales have been collected about the pygmy hippopotamus. One tale says that pygmy hippos carry a shining diamond in their mouths to help travel through thick forests at night; by day the pygmy hippo has a secret hiding place for the diamond, but if a hunter catches a pygmy hippo at night the diamond can be taken. Villagers sometimes believed that baby pygmy hippos do not nurse but rather lick secretions off the skin of the mother.
References
External links
Videos of Pygmy Hippos at Arkive.org
Pygmy hippo caught on camera in Liberia (video), BBC News 2011-12-19
Rare pygmy hippos caught on film, BBC News 2008-03-10
Camera trap results, Sapo National Park, Liberia, Zoological Society of London (EDGE of Existence Programme). 10 March 2008. First reports showing Pygmy Hippos in wild, surviving Liberian Civil War.
Pygmy hippos survive two civil wars, Zoological Society of London Press Release, 10 March 2008.
EDGE of Existence "(Pygmy hippo)", Saving the World's most Evolutionarily Distinct and Globally Endangered (EDGE) species
pygmy hippopotamus
EDGE species
Mammals of West Africa
Fauna of Rivers State
Endangered fauna of Africa
Semiaquatic mammals
Articles containing video clips
pygmy hippopotamus | Pygmy hippopotamus | Biology | 4,419 |
4,585,250 | https://en.wikipedia.org/wiki/Magnetic%20tension | In physics, magnetic tension is a restoring force with units of force density that acts to straighten bent magnetic field lines. In SI units, the force density exerted perpendicular to a magnetic field can be expressed as
where is the vacuum permeability.
Magnetic tension forces also rely on vector current densities and their interaction with the magnetic field. Plotting magnetic tension along adjacent field lines can give a picture as to their divergence and convergence with respect to each other as well as current densities.
Magnetic tension is analogous to the restoring force of rubber bands.
Mathematical statement
In ideal magnetohydrodynamics (MHD) the magnetic tension force in an electrically conducting fluid with a bulk plasma velocity field , current density , mass density , magnetic field , and plasma pressure can be derived from the Cauchy momentum equation:
where the first term on the right hand side represents the Lorentz force and the second term represents pressure gradient forces. The Lorentz force can be expanded using Ampère's law, , and the vector identity
to give
where the first term on the right hand side is the magnetic tension and the second term is the magnetic pressure force.
The force due to changes in the magnitude of and its direction can be separated by writing with and a unit vector:
where the spatial constancy of the magnitude has been assumed and
has magnitude equal to the curvature, or the reciprocal of the radius of curvature, and is directed from a point on a magnetic field line to the center of curvature. Therefore, as the curvature of the magnetic field line increases, so too does the magnetic tension force resisting this curvature.
Magnetic tension and pressure are both implicitly included in the Maxwell stress tensor. Terms representing these two forces are present along the main diagonal where they act on differential area elements normal to the corresponding axis.
Plasma physics
Magnetic tension is particularly important in plasma physics and MHD, where it controls dynamics of some systems and the shape of magnetic structures. For example, in a homogeneous magnetic field and an absence of gravity, magnetic tension is the sole driver of linear Alfvén waves.
See also
Magnetic pinch
Magnetosonic wave
References
Magnetic circuits
Plasma parameters
Magnetohydrodynamics | Magnetic tension | Chemistry | 435 |
55,334,875 | https://en.wikipedia.org/wiki/NGC%204907 | NGC 4907 is a barred spiral galaxy located about 270 million light-years away in the constellation of Coma Berenices. It is also classified as a LINER galaxy. NGC 4907 was discovered by astronomer Heinrich d'Arrest on May 5, 1864. The galaxy is a member of the Coma Cluster, located equidistant between NGC 4928 and NGC 4829.
See also
List of NGC objects (4001–5000)
NGC 4921 another barred spiral galaxy in the Coma Cluster
References
External links
Barred spiral galaxies
LINER galaxies
Coma Berenices
4907
44819
Astronomical objects discovered in 1864
Coma Cluster | NGC 4907 | Astronomy | 125 |
18,265,121 | https://en.wikipedia.org/wiki/Bepotastine | Bepotastine (Talion, Bepreve) is a 2nd generation antihistamine. It was approved in Japan for use in the treatment of allergic rhinitis and urticaria/pruritus in July 2000, and January 2002, respectively. It is marketed in the United States as an eye drop under the brand name Bepreve, by ISTA Pharmaceuticals, a subsidiary of Bausch + Lomb.
Pharmacology
Bepotastine is available as an ophthalmic solution and oral tablet. It is a direct H1-receptor antagonist that inhibits the release of histamine from mast cells. The ophthalmic formulation has shown minimal systemic absorption, between 1 and 1.5% in healthy adults. Common side effects are eye irritation, headache, unpleasant taste, and nasopharyngitis. The main route of elimination is urinary excretion, 75-90% excreted unchanged.
Marketing history
It is marketed in Japan by Tanabe Seiyaku under the brand name Talion. Talion was co-developed by Tanabe Seiyaku and Ube Industries, the latter of which discovered bepotastine. In 2001, Tanabe Seiyaku granted Senju, now owned by Allergan, exclusive worldwide rights, with the exception of certain Asian countries, to develop, manufacture and market bepotastine for ophthalmic use. Senju, in turn, has granted the United States rights for the ophthalmic preparation to ISTA Pharmaceuticals.
Sales and patents
In 2011, ISTA pharmaceuticals experienced a 2.4% increase in net revenues from 2010, which was driven by the sales of Bepreve. Their net revenue for 2011 was $160.3 million. ISTA Pharmaceuticals was acquired by Bausch & Lomb in March 2012 for $500 million. Bausch & Lomb hold the patent for bepotastine besilate (https://www.accessdata.fda.gov/scripts/cder/ob/docs/temptn.cfm. On November 26, 2014, Bausch & Lomb sued Micro Labs USA for patent infringement. Bausch & Lomb was recently bought out by Valeant Pharmaceuticals in May 2013 for $8.57 billion, Valeant's largest acquisition to date, causing the company's stock to rise 25% when the deal was announced.
Clinical trials
A Phase III clinical trial was carried out in 2010 to evaluate the effectiveness of bepotastine besilate ophthalmic solutions 1.0% and 1.5%. These solutions were compared to a placebo and evaluated for their ability to reduce ocular itchiness. The study was carried out with 130 individuals and evaluated after 15 minutes, 8 hours, or 16 hours. There was a reduction in itchiness at all-time points for both ophthalmic solutions. The study concluded that bepotastine besilate ophthalmic formulations reduced ocular itchiness for at least 8 hours after dosing compared to placebo. Phase I and II trials were carried out in Japan.
Studies have been performed in animals and bepotastine besilate was not found to be teratogenic in rats during fetal development, even at 3,300 times more than typical use in humans. Evidence of infertility was seen in rats at 33,000 times the typical ocular dose in humans. The safety and efficacy has not been established in patients under 2 years of age and has been extrapolated from adults for patients under 10 years of age.
References
4-Chlorophenyl compounds
Ethers
H1 receptor antagonists
Leukotriene antagonists
Mast cell stabilizers
Piperidines
2-Pyridyl compounds
Peripherally selective drugs
Ophthalmology drugs | Bepotastine | Chemistry | 789 |
22,992,249 | https://en.wikipedia.org/wiki/Disjunctive%20population | A disjunctive population, in ecology, is a colony of plants, animals, or other organisms whose geographical locus is severed from the continuous range of the bulk of the species distribution. Although a disjunctive population may sometimes occur on an island, which creates physical separation via water, a large percentage of disjunctive populations are separated from their main range simply by landmass. In some cases a disjunctive population represents a relatively small outlier population from the main range, but in other cases, such as for the painted hunting dog, Lycaon pictus, the entire population is scattered (throughout much of Africa) and is intrinsically disjunctive.
See also
Ecological island
Disjunct distribution
Notes
References
A.W.D. Larkum, Robert Joseph Orth and Carlos M. Duarte. 2006. Seagrasses: biology, ecology, and conservation, Published by Springer, , 9781402029424 691 pages
Ecology | Disjunctive population | Biology | 203 |
35,031,328 | https://en.wikipedia.org/wiki/C47H80O19P3 | The molecular formula C47H80O19P3 may refer to:
Phosphatidylinositol 3,4-bisphosphate
Phosphatidylinositol 3,5-bisphosphate
Phosphatidylinositol 4,5-bisphosphate
Molecular formulas | C47H80O19P3 | Physics,Chemistry | 67 |
3,997,849 | https://en.wikipedia.org/wiki/Uranyl%20sulfate | Uranyl sulfate describes a family of inorganic compounds with the formula UO2SO4(H2O)n. These salts consist of sulfate, the uranyl ion, and water. They are lemon-yellow solids. Uranyl sulfates are intermediates in some extraction methods used for uranium ores. These compounds can also take the form of an anhydrous salt.
Structure
The structure of UO2(SO4)(H2O)3.5 is illustrative of the uranyl sulfates. The trans-UO22+ centers are encased in a pentagonal bipyramidal coordination sphere. In the pentagonal plane are five oxygen ligands derived from sulfate and aquo ligands. The compound is a coordination polymer.
Uses
Aside from the large scale use in mining, uranyl sulfate finds some use as a negative stain in microscopy and tracer in biology. The Aqueous Homogeneous Reactor experiment, constructed in 1951, circulated a fuel composed of 565 grams of U-235 enriched to 14.7% in the form of uranyl sulfate.
The acid process of milling uranium ores involves precipitating uranyl sulfate from the pregnant leaching solution to produce the semi-refined product referred to as yellowcake.
Related compounds
the hydrogensulfate.
potassium uranyl sulfate, K2UO2(SO4)2, is a double salt used by Henri Becquerel in his discovery of radioactivity.
References
Uranyl compounds
Sulfates
Nuclear materials | Uranyl sulfate | Physics,Chemistry | 318 |
96,842 | https://en.wikipedia.org/wiki/Cytochrome%20c%20oxidase | The enzyme cytochrome c oxidase or Complex IV (was , now reclassified as a translocase EC 7.1.1.9) is a large transmembrane protein complex found in bacteria, archaea, and the mitochondria of eukaryotes.
It is the last enzyme in the respiratory electron transport chain of cells located in the membrane. It receives an electron from each of four cytochrome c molecules and transfers them to one oxygen molecule and four protons, producing two molecules of water. In addition to binding the four protons from the inner aqueous phase, it transports another four protons across the membrane, increasing the transmembrane difference of proton electrochemical potential, which the ATP synthase then uses to synthesize ATP.
Structure
The complex
The complex is a large integral membrane protein composed of several metal prosthetic sites and 13 protein subunits in mammals. In mammals, ten subunits are nuclear in origin, and three are synthesized in the mitochondria. The complex contains two hemes, a cytochrome a and cytochrome a, and two copper centers, the Cu and Cu centers. In fact, the cytochrome a and Cu form a binuclear center that is the site of oxygen reduction. Cytochrome c, which is reduced by the preceding component of the respiratory chain (cytochrome bc1 complex, Complex III), docks near the Cu binuclear center and passes an electron to it, being oxidized back to cytochrome c containing Fe. The reduced Cu binuclear center now passes an electron on to cytochrome a, which in turn passes an electron on to the cytochrome a>-Cu binuclear center. The two metal ions in this binuclear center are 4.5 Å apart and coordinate a hydroxide ion in the fully oxidized state.
Crystallographic studies of cytochrome c oxidase show an unusual post-translational modification, linking C6 of Tyr(244) and the ε-N of His(240) (bovine enzyme numbering). It plays a vital role in enabling the cytochrome a- Cu binuclear center to accept four electrons in reducing molecular oxygen and four protons to water. The mechanism of reduction was formerly thought to involve a peroxide intermediate, which was believed to lead to superoxide production. However, the currently accepted mechanism involves a rapid four-electron reduction involving immediate oxygenoxygen bond cleavage, avoiding any intermediate likely to form superoxide.
The conserved subunits
Assembly
COX assembly in yeast are a complex process that is not entirely understood due to the rapid and irreversible aggregation of hydrophobic subunits that form the holoenzyme complex, as well as aggregation of mutant subunits with exposed hydrophobic patches. COX subunits are encoded in both the nuclear and mitochondrial genomes. The three subunits that form the COX catalytic core are encoded in the mitochondrial genome. Over 30 different nuclear-encoded chaperone proteins are required for COX assembly.
Cofactors, including hemes, are inserted into subunits I & II. The two heme molecules reside in subunit I, helping with transport to subunit II where two copper molecules aid with the continued transfer of electrons. Subunits I and IV initiate assembly. Different subunits may associate to form sub-complex intermediates that later bind to other subunits to form the COX complex. In post-assembly modifications, COX will form a homodimer. This is required for activity. Dimers are connected by a cardiolipin molecule, which has been found to play a key role in stabilization of the holoenzyme complex. The dissociation of subunits VIIa and III in conjunction with the removal of cardiolipin results in total loss of enzyme activity. Subunits encoded in the nuclear genome are known to play a role in enzyme dimerization and stability. Mutations to these subunits eliminate COX function.
Assembly is known to occur in at least three distinct rate-determining steps. The products of these steps have been found, though specific subunit compositions have not been determined.
Synthesis and assembly of COX subunits I, II, and III are facilitated by translational activators, which interact with the 5’ untranslated regions of mitochondrial mRNA transcripts. Translational activators are encoded in the nucleus. They can operate through either direct or indirect interaction with other components of translation machinery, but exact molecular mechanisms are unclear due to difficulties associated with synthesizing translation machinery in-vitro. Though the interactions between subunits I, II, and III encoded within the mitochondrial genome make a lesser contribution to enzyme stability than interactions between bigenomic subunits, these subunits are more conserved, indicating potential unexplored roles for enzyme activity.
Biochemistry
The overall reaction is
4 Fe – cytochrome c + 4 H + O → 4 Fe – cytochrome c + 2 HO ΔG' = - 218 kJ/mol, E' = +565 mV
Two electrons are passed from two cytochrome c's, through the Cu and cytochrome a sites to the cytochrome a–Cu binuclear center, reducing the metals to the Fe form and Cu. The hydroxide ligand is protonated and lost as water, creating a void between the metals that is filled by O. The oxygen is rapidly reduced, with two electrons coming from the Fe-cytochrome a, which is converted to the ferryl oxo form (Fe=O). The oxygen atom close to Cu picks up one electron from Cu, and a second electron and a proton from the hydroxyl of Tyr(244), which becomes a tyrosyl radical. The second oxygen is converted to a hydroxide ion by picking up two electrons and a proton. A third electron from another cytochrome c is passed through the first two electron carriers to the cytochrome a–Cu binuclear center, and this electron and two protons convert the tyrosyl radical back to Tyr, and the hydroxide bound to Cu to a water molecule. The fourth electron from another cytochrome c flows through Cu and cytochrome a to the cytochrome a–Cu binuclear center, reducing the Fe=O to Fe, with the oxygen atom picking up a proton simultaneously, regenerating this oxygen as a hydroxide ion coordinated in the middle of the cytochrome a–Cu center as it was at the start of this cycle. Overall, four reduced cytochrome c's are oxidized while O and four protons are reduced to two water molecules.
Inhibition
COX exists in three conformational states: fully oxidized (pulsed), partially reduced, and fully reduced. Each inhibitor has a high affinity to a different state. In the pulsed state, both the heme a and the Cu nuclear centers are oxidized; this is the conformation of the enzyme that has the highest activity. A two-electron reduction initiates a conformational change that allows oxygen to bind at the active site to the partially-reduced enzyme. Four electrons bind to COX to fully reduce the enzyme. Its fully reduced state, which consists of a reduced Fe at the cytochrome a heme group and a reduced Cu binuclear center, is considered the inactive or resting state of the enzyme.
Cyanide, azide, and carbon monoxide all bind to cytochrome c oxidase, inhibiting the protein from functioning and leading to the chemical asphyxiation of cells. Higher concentrations of molecular oxygen are needed to compensate for increasing inhibitor concentrations, leading to an overall decrease in metabolic activity in the cell in the presence of an inhibitor. Other ligands, such as nitric oxide and hydrogen sulfide, can also inhibit COX by binding to regulatory sites on the enzyme, reducing the rate of cellular respiration.
Cyanide is a non-competitive inhibitor for COX, binding with high affinity to the partially-reduced state of the enzyme and hindering further reduction of the enzyme. In the pulsed state, cyanide binds slowly, but with high affinity. The ligand is posited to electrostatically stabilize both metals at once by positioning itself between them. A high nitric oxide concentration, such as one added exogenously to the enzyme, reverses cyanide inhibition of COX.
Nitric oxide can reversibly bind to either metal ion in the binuclear center to be oxidized to nitrite. NO and CN will compete with oxygen to bind at the site, reducing the rate of cellular respiration. Endogenous NO, however, which is produced at lower levels, augments CN inhibition. Higher levels of NO, which correlate with the existence of more enzyme in the reduced state, lead to a greater inhibition of cyanide. At these basal concentrations, NO inhibition of Complex IV is known to have beneficial effects, such as increasing oxygen levels in blood vessel tissues. The inability of the enzyme to reduce oxygen to water results in a buildup of oxygen, which can diffuse deeper into surrounding tissues. NO inhibition of Complex IV has a larger effect at lower oxygen concentrations, increasing its utility as a vasodilator in tissues of need.
Hydrogen sulfide will bind COX in a noncompetitive fashion at a regulatory site on the enzyme, similar to carbon monoxide. Sulfide has the highest affinity to either the pulsed or partially reduced states of the enzyme, and is capable of partially reducing the enzyme at the heme a center. It is unclear whether endogenous HS levels are sufficient to inhibit the enzyme. There is no interaction between hydrogen sulfide and the fully reduced conformation of COX.
Methanol in methylated spirits is converted into formic acid, which also inhibits the same oxidase system. High levels of ATP can allosterically inhibit cytochrome c oxidase, binding from within the mitochondrial matrix.
Extramitochondrial and subcellular localizations
Cytochrome c oxidase has 3 subunits which are encoded by mitochondrial DNA (cytochrome c oxidase subunit I, subunit II, and subunit III). Of these 3 subunits encoded by mitochondrial DNA, two have been identified in extramitochondrial locations. In pancreatic acinar tissue, these subunits were found in zymogen granules. Additionally, in the anterior pituitary, relatively high amounts of these subunits were found in growth hormone secretory granules. The extramitochondrial function of these cytochrome c oxidase subunits has not yet been characterized. Besides cytochrome c oxidase subunits, extramitochondrial localization has also been observed for large numbers of other mitochondrial proteins. This raises the possibility about existence of yet unidentified specific mechanisms for protein translocation from mitochondria to other cellular destinations.
Genetic defects and disorders
Defects involving genetic mutations altering cytochrome c oxidase (COX) functionality or structure can result in severe, often fatal metabolic disorders. Such disorders usually manifest in early childhood and affect predominantly tissues with high energy demands (brain, heart, muscle). Among the many classified mitochondrial diseases, those involving dysfunctional COX assembly are thought to be the most severe.
The vast majority of COX disorders are linked to mutations in nuclear-encoded proteins referred to as assembly factors, or assembly proteins. These assembly factors contribute to COX structure and functionality, and are involved in several essential processes, including transcription and translation of mitochondrion-encoded subunits, processing of preproteins and membrane insertion, and cofactor biosynthesis and incorporation.
Currently, mutations have been identified in seven COX assembly factors: SURF1, SCO1, SCO2, COX10, COX15, COX20, COA5 and LRPPRC. Mutations in these proteins can result in altered functionality of sub-complex assembly, copper transport, or translational regulation. Each gene mutation is associated with the etiology of a specific disease, with some having implications in multiple disorders. Disorders involving dysfunctional COX assembly via gene mutations include Leigh syndrome, cardiomyopathy, leukodystrophy, anemia, and sensorineural deafness.
Histochemistry
The increased reliance of neurons on oxidative phosphorylation for energy facilitates the use of COX histochemistry in mapping regional brain metabolism in animals, since it establishes a direct and positive correlation between enzyme activity and neuronal activity. This can be seen in the correlation between COX enzyme amount and activity, which indicates the regulation of COX at the level of gene expression. COX distribution is inconsistent across different regions of the animal brain, but its pattern of its distribution is consistent across animals. This pattern has been observed in the monkey, mouse, and calf brain. One isozyme of COX has been consistently detected in histochemical analysis of the brain. Such brain mapping has been accomplished in spontaneous mutant mice with cerebellar disease such as reeler and a transgenic model of Alzheimer's disease. This technique has also been used to map learning activity in the animal brain.
Additional images
See also
Cytochrome c oxidase subunit I
Cytochrome c oxidase subunit II
Cytochrome c oxidase subunit III
Heme a
References
External links
The Cytochrome Oxidase home page at Rice University
Interactive Molecular model of cytochrome c oxidase (Requires MDL Chime)
Cellular respiration
EC 1.9.3
Hemoproteins
Integral membrane proteins
Copper enzymes | Cytochrome c oxidase | Chemistry,Biology | 2,790 |
12,991,932 | https://en.wikipedia.org/wiki/Level%20staff | A level staff, also called levelling rod, is a graduated wooden or aluminium rod, used with a levelling instrument to determine the difference in height between points or heights of points above a vertical datum.
When used for stadiametric rangefinding, the level staff is called a stadia rod.
Rod construction and materials
Levelling rods can be one piece, but many are sectional and can be shortened for storage and transport or lengthened for use. Aluminum rods may be shortened by telescoping sections inside each other, while wooden rod sections can be attached to each other with sliding connections or slip joints, or hinged to fold when not in use.
There are many types of rods, with names that identify the form of the graduations and other characteristics. Markings can be in imperial or metric units. Some rods are graduated on one side only while others are marked on both sides. If marked on both sides, the markings can be identical or can have imperial units on one side and metric on the other.
Reading a rod
In the photograph on the right, both a metric (left) and imperial (right) levelling rod are seen. This is a two-sided aluminum rod, coated white with markings in contrasting colours. The imperial side has a bright yellow background.
The metric rod has major numbered graduations in meters and tenths of meters (e.g. 18 is 1.8 m - there is a tiny decimal point between the numbers). Between the major marks are either a pattern of squares and spaces in different colours or an E shape (or its mirror image) with horizontal components and spaces between of equal size. In both parts of the pattern, the squares, lines or spaces are precisely one centimetre high. When viewed through an instrument's telescope, the observer can visually interpolate a 1 cm mark to a tenth of its height, yielding a reading with precision in mm. Usually readings are recorded with millimetre precision. On this side of the rod, the colours of the markings alternate between red and black with each meter of length.
The imperial graduations are in feet (large red numbers), tenths of a foot (small black numbers) and hundredths of a foot (unnumbered marks or spaces between the marks). The tenths of a foot point is indicated by the top of the long mark with the upward sloped end. The point halfway between tenths of a foot marks is indicated by the bottom of a medium length black mark with a downward sloped end. Each mark or space is approximately 3mm, yielding roughly the same accuracy as the metric rod.
Classes of rods
Rods come in two classes:
Self-reading rods (sometimes called speaking rods).
Target rods.
Self-reading rods are rods that are read by the person viewing the rod through the telescope of the instrument. The graduations are sufficiently clear to read with good accuracy. Target rods, on the other hand, are equipped with a target. The target is a round or oval plate marked in quarters in contrasting colours such as red and white in opposite quarters. A hole in the centre allows the instrument user to see the rod's scale. The target is adjusted by the rodman according to the instructions from the instrument man. When the target is set to align with the crosshairs of the instrument, the rodman records the level value. The target may have a vernier to allow fractional increments of the graduation to be read.
Digital levels electronically read a bar-coded scale on the staff. These instruments usually include data recording capability. The automation removes the requirement for the operator to read a scale and write down the value, and so reduces blunders. It may also compute and apply refraction and curvature corrections.
Topographer's rods
Topographer's rods are special purpose rods used in topographical surveys. The rod has the zero mark at mid-height and the graduations increase in both directions away from the mid-height.
In use, the rod is adjusted so that the zero point is level with the instrument (or the surveyor's eye if he is using a hand level for low-resolution work). When placed at any point where the level is to be read, the value seen is the height above or below the viewer's position.
An alternative topographer's rod has the graduations numbered upwards from the base.
See also
Measuring rod
Philadelphia rod
Pole (surveying)
Ranging rod
Retroreflector
Stadia mark
Staff (head) gauge
External links
Levelling rods
References
Raymond Davis, Francis Foote, Joe Kelly, Surveying, Theory and Practice, McGraw-Hill Book Company, 1966 LC 64-66263
Measuring instruments
Surveying instruments | Level staff | Technology,Engineering | 955 |
7,081,715 | https://en.wikipedia.org/wiki/Micropower | Micropower describes the use of very small electric generators and prime movers or devices to convert heat or motion to electricity, for use close to the generator. The generator is typically integrated with microelectronic devices and produces "several watts of power or less." These devices offer the promise of a power source for portable electronic devices which is lighter weight and has a longer operating time than batteries.
Microturbine technology
The components of any turbine engine — the gas compressor, the combustion chamber, and the turbine rotor — are fabricated from etched silicon, much like integrated circuits. The technology holds the promise of ten times the operating time of a battery of the same weight as the micropower unit, and similar efficiency to large utility gas turbines. Researchers at Massachusetts Institute of Technology have thus far succeeded in fabricating the parts for such a micro turbine out of six etched and stacked silicon wafers, and are working toward combining them into a functioning engine about the size of a U.S. quarter coin.
Researchers at Georgia Tech have built a micro generator 10 mm wide, which spins a magnet above an array of coils fabricated on a silicon chip. The device spins at 100,000 revolutions per minute, and produces 1.1 watts of electrical power, sufficient to operate a cell phone. Their goal is to produce 20 to 50 watts, sufficient to power a laptop computer.
Scientists at Lehigh University are developing a hydrogen generator on a silicon chip that can convert methanol, diesel, or gasoline into fuel for a microengine or a miniature fuel cell.
Professor Sanjeev Mukerjee of Northeastern University's chemistry department is developing fuel cells for the military that will burn hydrogen to power portable electronic equipment, such as night vision goggles, computers, and communication equipment. In his system, a cartridge of methanol would be used to produce hydrogen to run a small fuel cell for up to 5,000 hours. It would be lighter than rechargeable batteries needed to provide the same power output, with a longer run time. Similar technology could be improved and expanded in future years to power automobiles.
The National Academies' National Research Council recommended in a 2004 report that the U.S. Army should investigate such micropower sources for powering electronic equipment to be carried by soldiers in the future, since batteries sufficient to power the computers, sensors, and communications devices would add considerable weight to the burden of infantry soldiers.
The Future Warrior Concept of the U.S. Army envisions a 2- to 20-watt micro turbine fueled by a liquid hydrocarbon being used to power communications and wearable heating/cooling equipment for up to six days on 10 ounces of fuel.
Other microgenerator/nanogenerator technologies
Professor Orest Symko of the University of Utah physics department and his students developed Thermal Acoustic Piezo Energy Conversion (TAPEC), devices of a cubic inch (16 cubic centimeters), or so, which convert waste heat into acoustic resonance and then into electricity. It would be used to power microelectromechanical systems, or MEMS. The research was funded by the U.S. Army. Symko was to present a paper at the Acoustical Society of America. June 8, 2007. Researchers at MIT developed the first micro-scale piezoelectric energy harvester using thin film PZT in 2005. Arman Hajati and Sang-Gook Kim invented the Ultra Wide-Bandwidth micro-scale piezoelectric energy harvesting device by exploiting the nonlinear stiffness of a doubly clamped microelectromechanical systems (MEMS) resonator. The stretching strain in a doubly clamped beam shows a nonlinear stiffness, which provides a passive feedback and results in amplitude-stiffened Duffing mode resonance.
Professor Zhong Lin Wang of the Georgia Institute of Technology said his team of investigators had developed a "nanometer-scale generator ... based on arrays of vertically aligned zinc oxide nanowires that move inside a "zigzag" plate electrode." Built into shoes, it could generate electricity from walking to power small electronic devices. It could also be powered by blood flow to power biomedical devices. Per an account of the device which appeared in the journal Science, bending of the zinc oxide nanowire arrays produces an electric field by the piezoelectric properties of the material. The semiconductor properties of the device create a Schottky barrier with rectifying capabilities. The generator is estimated to be 17% to 30% efficient in converting mechanical motion into electricity. This could be used to power biomedical devices that have wireless transmission capabilities for data and control. A later development was to grow hundreds of such nanowires on a substrate that functioned as an electrode. On top of this was placed a silicon electrode covered with a series of platinum ridges. Vibration of the top electrode caused the generation of direct current. A report by Wang was to appear in the August 8, 2007 issue of the journal "Nano Letters," saying that such devices could power implantable biomedical devices. The device would be powered by flowing blood or a beating heart. It could function while immersed in body fluids, and would get its energy from ultrasonic vibrations. Wang expects that an array of the devices could produce 4 watts per cubic centimeter. Goals for further development are to increase the efficiency of the array of nanowires, and to increase the lifetime of the device, which as of April 2007 was only about one hour. By November 2010 Wang and his team were able to produce 3 volts of potential and as much as 300 nanoamperes of current, an output level 100 times greater than was possible a year earlier, from an array measuring about 2 cm by 1.5 cm.
The windbelt is a micropower technology invented by Shawn Frayne. It is essentially an aeolian harp, except that it exploits the motion of the string produced by aeroelastic flutter to create a physical oscillation that can be converted to electricity. It avoids the losses inherent in rotating wind powered generators. Prototypes have produced 40 milliwatts in a 16 km/h wind. Magnets on the vibrating membrane generate currents in stationary coils.
Piezoelectric nanofibers in clothing could generate enough electricity from the wearer's body movements to power small electronic devices, such as iPods or some of the electronic equipment used by soldiers on the battlefield, based on research by University of California, Berkeley Professor Liwei Lin and his team. One million such fibers could power an iPod, and would be altogether as large as a grain of sand. Researchers at Stanford University are developing "eTextiles" — batteries made of fabric — that might serve to store power generated by such technology.
Thermal resonator technology allows generation of power from the daily change of temperature, even when there is no instantaneous temperature difference as needed for thermoelectric generation, and no sunlight as needed for photovoltaic generation. A phase change material such as octadecane is selected which can change from solid to liquid when the ambient temperature changes a few degrees celsius. In a small demonstration device created by chemical engineering professor Michael Strano and seven others at MIT, a 10 degree celsius daily change produced 350 millivolts and 1.3 milliwatts. The power levels envisioned could power sensors and communication devices.
See also
Battery (electricity)
Cell phone
Electrical generator
Electronics
Fuel cell
Gas turbine
Hub dynamo
Integrated circuits
Laptop
Microelectronics
Microelectromechanical systems
Portable fuel cell applications
Windbelt
Nanogenerator
References
External links
MIT Gas Turbine Laboratory
Z.L. Wang's lab at Georgia Institute of Technology
Electrical generators
Microtechnology | Micropower | Physics,Materials_science,Technology,Engineering | 1,568 |
16,883,374 | https://en.wikipedia.org/wiki/Malcolm%20Dole | Malcolm Dole (March 4, 1903 – November 29, 1990) was an American chemist known for the Dole Effect in which he proved that the atomic weight of oxygen in air is greater than that of oxygen in water and for his work on electrospray ionization, polymer chemistry, and electrochemistry.
Dole effect
The Dole effect is the inequality in the ratio of heavy oxygen isotope 18O to the more abundant 16O in the Earth's atmosphere and in seawater.
This effect was reported by Dole in 1935. The effect is due to slightly different reaction rates for the two isotopes in respiration in plants and in animals which tends to retain the lighter 16O, which increases the relative concentration of 18O in the atmosphere. The effect has also been linked to hydrologic processes, such as the enrichment of the lighter 16O as water vapor is transported poleward.
Electrospray
Electrospray is a process in which a high voltage is applied to a liquid to create an aerosol containing highly charged droplets. Dole in 1968 was the first to use electrospray ionization with mass spectrometry.
Books
References
1903 births
1990 deaths
American physical chemists
Baylor University faculty
Harvard University alumni
Mass spectrometrists
Northwestern University faculty
Fellows of the American Physical Society
20th-century American chemists | Malcolm Dole | Physics,Chemistry | 269 |
42,043,354 | https://en.wikipedia.org/wiki/MTS%20945 | The MTS 945 GLONASS was the world's first smartphone that was compatible with GLONASS. The phone was available from Mobile TeleSystems, and was built by Qualcomm and ZTE. The phone was released on March 31, 2011. The phone was discontinued following low sales numbers.
History
On December 28, 2010 the CEO of AFK Sistema Vladimir Yevtushenkov and the Russian Deputy Prime Minister Sergei Ivanov presented Vladimir Putin with the MTS 945 - the first phone equipped with a dual system GLONASS\GPS.
During the meeting, Vladimir Yevtushenko claimed that the phone was equivalent to the iPhone 4, with the addition of GLONASS capabilities.
The MTS 945 was developed jointly by Sitronics, Qualcomm, and ZTE, and went on sale in March 2011 at the price of 10 990 rubles (US$360).
The initial plans for the phone called for 500,000 units shipped in the first batch, however in early 2011 it was reduced to 100,000. This was later reduced again to just 5000 units, which took six months to sell.
In February 2012 ZTE announced that they were ending production of the phone due to poor sales. Before the MTS 945 was released ZTE was planning to create 3-5 phones with support for GLONASS, but the slow launch month put those plans into development hell, and they were eventually cancelled. Huawei, which was also planning to launch a phone with GLONASS around the same time decided to delay the launch of their own GLONASS compatible phones.
Specifications
The phone is capable of receiving signals of two Global Navigation Satellite Systems : GLONASS and GPS.
The phone's SoC is the Qualcomm MSM7230, and it runs Android.
Criticism
Tests found that the MTS 945 performed comparably to or worse than comparable smartphones that also ran Android 2.2 and only received signals from GPS. At the same time, the MTS 945 GLONASS was significantly more expensive than the other devices this level.
Next model
In May 2012, MTS launched a second smartphone with GLONASS, the MTS 962. The new model was launched at half the price of its predecessor, about 5300 rubles.
References
Mobile phones
Android (operating system) devices
Mobile phones introduced in 2011
GLONASS
Qualcomm | MTS 945 | Technology | 499 |
38,411,234 | https://en.wikipedia.org/wiki/Anja%20Cetti%20Andersen | Anja Cetti Andersen (born 25 September 1965) is an astronomer and astrophysicist from Hørsholm, Denmark.
Life
She received her BSc in 1991, MSc in astronomy in 1995, and her PhD in 1999, from the University of Copenhagen. Her thesis was titled "Cosmic Dust and Late-Type Stars". Her postdoctoral research was funded by the Carlsberg Foundation, firstly at the Department of Astronomy & Space Physics, Uppsala University, and then at the Astronomical Observatory at the University of Copenhagen. After this she was funded by her home institution and received a Diploma in Higher Education Teaching and Teaching Practice from the Faculty of Sciences. Her interest in astronomy was kindled when she was in the seventh grade, after a visit to her school from Uffe Grae Jorgensen, a Danish astronomer, and with whom she now works in Copenhagen. She has three children, Julie, Cecilie and Jakob.
Career
Her work concentrates on cosmic dust, and its role "in relation to the formation of complex molecules, stars and planets." She is currently an associate professor at the Niels Bohr Institute, and is part of the management team where she conducts research at the Dark Cosmology Center in Copenhagen. She is a publisher of academic papers, has written several books, and is a lecturer, and also considered one of the best speakers currently using public outreach techniques in order to raise the profile of science in the community. It is characteristic of Anja Andersen's research that she works at the intersection between physics, chemistry, geology and biology. Her early research was involved with presolar grains from meteorites. Working with Susanne Hofner, their research in 2003 showed that "correct micro-physical description of the dust is crucial for predicting the mass loss rates of AGB stars." Her work with Hofner continued, leading to further developments in the understanding of the action of dust-driven wind, and she collaborated with researchers in Uppsala to study "how the optical properties of dust grains change" when they leave a star and move into inter-stellar regions. While she is researching the influence of cosmic dust on early planet formation, she is also working on models of why life on Earth is constructed of left hand twisted amino acids and right hand twisted sugars. There is a hint of the unconventional about Andersen in her interdisciplinary approach to her work, and indeed her method of working. She states that she feels herself to be an "atypical astronomer, because I am in the laboratory much of the times studying the chemical composition of meteorites in order to use that knowledge for theoretical models of how solar systems can be formed".
She is also an author, working with fellow Dane Peter Clausen to produce works about astronomy which are aimed at the general public. Whilst she is recognized as one of the foremost researchers in her fields, she is also a scientist who believes that "it is important to tell the world and young people in particular about exciting new research". She has written books for children, explaining astronomy to a young audience, as well as "Stjernsov og Galakser" (Starduast and Galaxies), and most recently "Livet er et Mirakel" (Life is a Miracle), with theologist Anna Mejlhede. Many of her awards have been for her teaching ability, and "public outreach", her work in raising the profile of science. She is also an advocate of improving the numbers of women currently in respected positions within science academia, stating at the Djof Conference on Gender Equality in 2007 "I'd rather have a top post, because I'm a woman, and show what I can do, than sit outside the door and never get the chance. For me it does not matter whether you use a whip or a carrot, we just get some action." She explains her work about dark energy and dark matter, cosmic dust and many other matters in astronomy in the following educational video: "Interview with Anja Cetti Andersen – Author, Professor, and Researcher – Copenhagen University". In addition, she has a minor planet named after her, 8820 Anjandersen, alternate designation 1985 VG = 1961 CE1 = 1978 YO1 = 1992 SG24 = 1994 CS1
Awards
2016: Awarded the Silver H.C. Ørsted Medal for outstanding dissemination of exact science to broad circles.
2011: Awarded Det Naturvidenskabelige Fakultets Formidlingspris (Dissemination Prize) for extraordinary contributions to the public outreach activities of the Faculty,
2009: Awarded Svend Bergsøes Fonds Formidlingspris for outstanding public outreach.
2009: Awarded Mathilde Prize for contributions towards equality between women and men in academia. The prize is named after Mathilde Fibiger.
2008: Awarded The Danish Association of Masters and PhDs research prize "for her unparalleled ability to combine internationally recognized leading edge research with the ability to communicate her research results and create a broad interest for astronomy."
2007: Elected member of The
2006: Awarded the Danish Radio's Rosenkjær Prize for outstanding public outreach.
2006: Awarded The Kirstine Meyer Award for outstanding research.
2006: Awarded The Outstanding Young Person TOYP 2006 for academic achievement, by JCI – Worldwide Federation of Young Leaders and Entrepreneurs.
2005: Awarded The Descartes Prize for Science Communication (laureate) for outstanding excellence in Science Communication, given by the European Union.
2004: Awarded The Danish Award for Outstanding Public Outreach (Danmarks Forskningskommunikationspris 2004) by the Danish Ministry of Science, Technology and Innovation
2003: Nominated for The Educational Material Prize (Undervisningsministeriets Undervisningsmiddelspris 2003) from the Danish Ministry of Education, for the teaching material Videnskabet, which included the book "Made of Stardust" (Skab af Stjernestøv).
2000: Awarded the Allan Mackintosh Award for public outreach by Jette Mackintosh and the Niels Bohr Institute.
1999: The program Kosmos, on which Andersen was a presenter, won the Prix Magazine at the 16th International Science-television-festival in Paris. Kosmos was the most popular programs on DR2 in 1998.
1997: Awarded Writer of the year (Årets forfatter 1997) by the Danish Astronomical Society (Dansk Astronomisk Selskab).
Memberships
Learned Societies
Since 2007: The Danish Academy of Technical Sciences
Since 2003: The International Astronomical Union
Since 2001: The European Astronomical Society
Since 1999: Foreningen for Kønsforskning i Danmark
Since 1997: The European Physical Society
Since 1996: The Meteoritical Society
Since 1994: The Danish Physical Society, Dansk Fysisk Selskab
Since 1993: The Danish Astronomical Society, Dansk Astronomisk Selskab
In addition she is a Fellow of The Nordic Institute for Theoretical Physics NORDITA, and sits on the Astrophysics and Astrobiology Research Committee.
Network Groups
Since 2009: VLgruppe 77 – København
Since 2007: Albrightgruppen.dk
Since 2005: The Nordic network of women in physics (NORWIP)
Since 2003: Skeptica.dk
Since 1999: Women in Physics in Sweden
Since 1998: Networks of Women Scientists established under the fifth frame work program of EU
Since 1995: Network for Women in Physics in Denmark
References
External links
1965 births
Living people
21st-century Danish astronomers
Danish astrophysicists
University of Copenhagen alumni
People from Hørsholm Municipality
20th-century Danish astronomers
Women astronomers
20th-century Danish women scientists
21st-century Danish women scientists | Anja Cetti Andersen | Astronomy | 1,565 |
15,676,779 | https://en.wikipedia.org/wiki/List%20of%20environmental%20economics%20journals | This is a list of articles about scholarly journals in ecological, resource and environmental economics.
A
Agricultural and Resource Economics Review
American Journal of Agricultural Economics
Annual Review of Resource Economics
Australian Journal of Agricultural and Resource Economics
C
Climate Change Economics
Climate Policy
E
Ecological Economics
Economic and Environmental Geology
Economics of Disasters and Climate Change
Energy Economics
Energy Journal
Energy Policy
Environment and Development Economics
Environmental and Resource Economics
Environmental Economics
Environmental Management
Economics of Energy and Environmental Policy
Environmental Science and Policy
G
Growth and Change
I
International Journal of Ecology & Development
J
Journal of Agricultural and Applied Economics
Journal of Agricultural and Resource Economics
Journal of Development Economics
Journal of Environmental Economics and Management
Journal of Environmental Economics and Policy
Journal of Environmental Management
Journal of Environmental Planning and Management
Journal of the Association of Environmental and Resource Economics
Journal of Transport Economics and Policy
L
Land Economics
M
Marine Resource Economics
N
Natural Resources Journal
Natural Resource Modeling
R
Resource and Energy Economics
Review of Environmental Economics and Policy
W
Water Resources Research
See also
List of economics journals
List of environmental journals
List of environmental social science journals
Environmental
Environmental economics
Environmental economics journals | List of environmental economics journals | Environmental_science | 205 |
1,182,058 | https://en.wikipedia.org/wiki/Double%20switching | Double switching, double cutting, or double breaking is the practice of using a multipole switch to close or open both the positive and negative sides of a DC electrical circuit, or both the hot and neutral sides of an AC circuit. This technique is used to prevent shock hazard in electric devices connected with unpolarised AC power plugs and sockets. Double switching is a crucial safety engineering practice in railway signalling, wherein it is used to ensure that a single false feed of current to a relay is unlikely to cause a wrong-side failure. It is an example of using redundancy to increase safety and reduce the likelihood of failure, analogous to double insulation. Double switching increases the cost and complexity of systems in which it is employed, for example by extra relay contacts and extra relays, so the technique is applied selectively where it can provide a cost-effective safety improvement.
Examples
Landslip and Washaway Detectors
A landslip or washaway detector is buried in the earth embankment, and opens a circuit should a landslide occur. It is not possible to guarantee that the wet earth of the embankment will not complete the circuit which is supposed to break. If the circuit is double cut with positive and negative wires, any wet conductive earth is likely to blow a fuse on the one hand, and short the detecting relay on the other hand, either of which is almost certain to apply the correct warning signal.
Accidents
Clapham
The Clapham Junction rail crash of 1988 was caused in part by the lack of double switching (known as "double cutting" in the British railway industry). The signal relay in question was switched only on the hot side, while the return current came back on an unswitched wire. A loose wire bypassed the contacts by which the train detection relays switched the signal, allowing the signal to show green when in fact there was a stationary train ahead. 35 people were killed in the resultant collision.
United Flight 811
A similar accident on the United Airlines Flight 811 was caused in part by a single-switched safety circuit for the baggage door mechanism. Failure of the wiring insulation in that circuit allowed the baggage door to be unlocked by a false feed, leading to a catastrophic de-pressurisation, and the deaths of nine passengers.
Signalling in NSW
A study of railway electrical signalling in New South Wales from the 1900s, shows an ever increasing proportion of double switching compared to single switching.
Double switching does of course cost more wires, more relay contacts, and testing.
On the other hand double switching is inherently less prone to wrong side failures; it helps overcome short-circuit faults that are hard to test for.
Partial double switching might double switch the lever controls, and the track circuits between one signal and the next, while single switching the track circuits in the less critical overlap beyond the next signal.
Double switching is facilitated by more modern relays that have more contacts in less space:
Pre-1950 Shelf Type Relay - 12 contacts (front (make) and back (break)) - full size
Post-1950 Q-type plug in relay - 16 contacts (front (make) and back (break)) - about half size
See also
Redundancy (engineering)
Double insulation
Single-wire earth return
References
Couplers
Railway signalling
Safety
Fault tolerance | Double switching | Engineering | 657 |
61,762,764 | https://en.wikipedia.org/wiki/K2-18 | K2-18, also known as EPIC 201912552, is a red dwarf star with two planetary companions located from Earth, in the constellation of Leo.
Its name is because it was discovered by the K2 Mission, which extended the mission of the Kepler Space Telescope after failure of two of its reaction wheels.
Planetary system
The star has a transiting exoplanet, called K2-18b, a super-Earth located within the habitable zone of K2-18. It was discovered in 2015 by the Kepler space telescope in its K2 mission. It is the first exoplanet in the habitable zone, albeit a hydrogen-rich sub-Neptune, to have its atmosphere characterized; initially thought to contain water vapor, more recent observations have instead detected methane and carbon dioxide. The presence of these molecules and non-detection of ammonia is consistent with predictions for a hycean planet.
A second, non-transiting planet, K2-18c, was discovered in 2017 by radial velocity with HARPS. This planet was challenged by another team with CARMENES data, but its existence was reaffirmed by the discovery team based on both HARPS and CARMENES data. This planet has also been confirmed by a later independent study. System tidal simulation suggests that K2-18c is a gas-rich, Neptune-like planet, similar to K2-18b.
References
External links
NASA says distant planet could hold life after they spot signs of rare water ocean - MSN News
Leo (constellation)
M-type main-sequence stars
Planetary systems with two confirmed planets
J11301450+0735180 | K2-18 | Astronomy | 336 |
252,461 | https://en.wikipedia.org/wiki/Winning%20Ways%20for%20Your%20Mathematical%20Plays | Winning Ways for Your Mathematical Plays (Academic Press, 1982) by Elwyn R. Berlekamp, John H. Conway, and Richard K. Guy is a compendium of information on mathematical games. It was first published in 1982 in two volumes.
The first volume introduces combinatorial game theory and its foundation in the surreal numbers; partizan and impartial games; Sprague–Grundy theory and misère games. The second volume applies the theorems of the first volume to many games, including nim, sprouts, dots and boxes, Sylver coinage, philosopher's phutball, fox and geese. A final section on puzzles analyzes the Soma cube, Rubik's Cube, peg solitaire, and Conway's Game of Life.
A republication of the work by A K Peters split the content into four volumes.
Editions
1st edition, New York: Academic Press, 2 vols., 1982; vol. 1, hardback: , paperback: ; vol. 2, hardback: , paperback: .
2nd edition, Wellesley, Massachusetts: A. K. Peters Ltd., 4 vols., 2001–2004; vol. 1: ; vol. 2: ; vol. 3: ; vol. 4: .
Games mentioned in the book
This is a partial list of the games mentioned in the book.
Note: Misère games not included
Hackenbush
Blue-Red Hackenbush
Blue-Red-Green Hackenbush (Introduced as Hackenbush Hotchpotch in the book)
Childish Hackenbush
Ski-Jumps
Toads-and-Frogs
Cutcake
Maundy Cake
(2nd Unnamed Cutcake variant by Dean Hickerson)
Hotcake
Coolcakes
Baked Alaska
Eatcake
Turn-and-Eatcake
Col
Snort
Nim (Green Hackenbush)
Prim
Dim
Lasker's Nim
Seating Couples
Northcott's Game (Poker-Nim)
The White Knight
Wyt Queens (Wythoff's Game)
Kayles
Double Kayles
Quadruple Kayles
Dawson's Chess
Dawson's Kayles
Treblecross
Grundy's Game
Mrs. Grundy
Domineering
No Highway
De Bono's L-Game
Snakes-and-Ladders (Adders-and-Ladders)
Jelly Bean Game
Dividing Rulers
Reviews
Games
See also
On Numbers and Games by John H. Conway, one of the three coauthors of Winning Ways
References
1982 non-fiction books
Books about game theory
Combinatorial game theory
John Horton Conway | Winning Ways for Your Mathematical Plays | Mathematics | 518 |
30,562 | https://en.wikipedia.org/wiki/Glossary%20of%20general%20topology | This is a glossary of some terms used in the branch of mathematics known as topology. Although there is no absolute distinction between different areas of topology, the focus here is on general topology. The following definitions are also fundamental to algebraic topology, differential topology and geometric topology. For a list of terms specific to algebraic topology, see Glossary of algebraic topology.
All spaces in this glossary are assumed to be topological spaces unless stated otherwise.
A
Absolutely closed See H-closed
Accessible See .
Accumulation point See limit point.
Alexandrov topology The topology of a space X is an Alexandrov topology (or is finitely generated) if arbitrary intersections of open sets in X are open, or equivalently, if arbitrary unions of closed sets are closed, or, again equivalently, if the open sets are the upper sets of a poset.
Almost discrete A space is almost discrete if every open set is closed (hence clopen). The almost discrete spaces are precisely the finitely generated zero-dimensional spaces.
α-closed, α-open A subset A of a topological space X is α-open if , and the complement of such a set is α-closed.
Approach space An approach space is a generalization of metric space based on point-to-set distances, instead of point-to-point.
B
Baire space This has two distinct common meanings:
A space is a Baire space if the intersection of any countable collection of dense open sets is dense; see Baire space.
Baire space is the set of all functions from the natural numbers to the natural numbers, with the topology of pointwise convergence; see Baire space (set theory).
Base A collection B of open sets is a base (or basis) for a topology if every open set in is a union of sets in . The topology is the smallest topology on containing and is said to be generated by .
Basis See Base.
β-open See Semi-preopen.
b-open, b-closed A subset of a topological space is b-open if . The complement of a b-open set is b-closed.
Borel algebra The Borel algebra on a topological space is the smallest -algebra containing all the open sets. It is obtained by taking intersection of all -algebras on containing .
Borel set A Borel set is an element of a Borel algebra.
Boundary The boundary (or frontier) of a set is the set's closure minus its interior. Equivalently, the boundary of a set is the intersection of its closure with the closure of its complement. Boundary of a set is denoted by or .
Bounded A set in a metric space is bounded if it has finite diameter. Equivalently, a set is bounded if it is contained in some open ball of finite radius. A function taking values in a metric space is bounded if its image is a bounded set.
C
Category of topological spaces The category Top has topological spaces as objects and continuous maps as morphisms.
Cauchy sequence A sequence {xn} in a metric space (M, d) is a Cauchy sequence if, for every positive real number r, there is an integer N such that for all integers m, n > N, we have d(xm, xn) < r.
Clopen set A set is clopen if it is both open and closed.
Closed ball If (M, d) is a metric space, a closed ball is a set of the form D(x; r) := {y in M : d(x, y) ≤ r}, where x is in M and r is a positive real number, the radius of the ball. A closed ball of radius r is a closed r-ball. Every closed ball is a closed set in the topology induced on M by d. Note that the closed ball D(x; r) might not be equal to the closure of the open ball B(x; r).
Closed set A set is closed if its complement is a member of the topology.
Closed function A function from one space to another is closed if the image of every closed set is closed.
Closure The closure of a set is the smallest closed set containing the original set. It is equal to the intersection of all closed sets which contain it. An element of the closure of a set S is a point of closure of S.
Closure operator See Kuratowski closure axioms.
Coarser topology If X is a set, and if T1 and T2 are topologies on X, then T1 is coarser (or smaller, weaker) than T2 if T1 is contained in T2. Beware, some authors, especially analysts, use the term stronger.
Comeagre A subset A of a space X is comeagre (comeager) if its complement X\A is meagre. Also called residual.
Compact A space is compact if every open cover has a finite subcover. Every compact space is Lindelöf and paracompact. Therefore, every compact Hausdorff space is normal. See also quasicompact.
Compact-open topology The compact-open topology on the set C(X, Y) of all continuous maps between two spaces X and Y is defined as follows: given a compact subset K of X and an open subset U of Y, let V(K, U) denote the set of all maps f in C(X, Y) such that f(K) is contained in U. Then the collection of all such V(K, U) is a subbase for the compact-open topology.
Complete A metric space is complete if every Cauchy sequence converges.
Completely metrizable/completely metrisable See complete space.
Completely normal A space is completely normal if any two separated sets have disjoint neighbourhoods.
Completely normal Hausdorff A completely normal Hausdorff space (or T5 space) is a completely normal T1 space. (A completely normal space is Hausdorff if and only if it is T1, so the terminology is consistent.) Every completely normal Hausdorff space is normal Hausdorff.
Completely regular A space is completely regular if, whenever C is a closed set and x is a point not in C, then C and {x} are functionally separated.
Completely T3 See Tychonoff.
Component See Connected component/Path-connected component.
Connected A space is connected if it is not the union of a pair of disjoint nonempty open sets. Equivalently, a space is connected if the only clopen sets are the whole space and the empty set.
Connected component A connected component of a space is a maximal nonempty connected subspace. Each connected component is closed, and the set of connected components of a space is a partition of that space.
Continuous A function from one space to another is continuous if the preimage of every open set is open.
Continuum A space is called a continuum if it a compact, connected Hausdorff space.
Contractible A space X is contractible if the identity map on X is homotopic to a constant map. Every contractible space is simply connected.
Coproduct topology If {Xi} is a collection of spaces and X is the (set-theoretic) disjoint union of {Xi}, then the coproduct topology (or disjoint union topology, topological sum of the Xi) on X is the finest topology for which all the injection maps are continuous.
Core-compact space
Cosmic space A continuous image of some separable metric space.
Countable chain condition A space X satisfies the countable chain condition if every family of non-empty, pairswise disjoint open sets is countable.
Countably compact A space is countably compact if every countable open cover has a finite subcover. Every countably compact space is pseudocompact and weakly countably compact.
Countably locally finite A collection of subsets of a space X is countably locally finite (or σ-locally finite) if it is the union of a countable collection of locally finite collections of subsets of X.
Cover A collection of subsets of a space is a cover (or covering) of that space if the union of the collection is the whole space.
Covering See Cover.
Cut point If X is a connected space with more than one point, then a point x of X is a cut point if the subspace X − {x} is disconnected.
D
δ-cluster point, δ-closed, δ-open A point x of a topological space X is a δ-cluster point of a subset A if for every open neighborhood U of x in X. The subset A is δ-closed if it is equal to the set of its δ-cluster points, and δ-open if its complement is δ-closed.
Dense set A set is dense if it has nonempty intersection with every nonempty open set. Equivalently, a set is dense if its closure is the whole space.
Dense-in-itself set A set is dense-in-itself if it has no isolated point.
Density the minimal cardinality of a dense subset of a topological space. A set of density ℵ0 is a separable space.
Derived set If X is a space and S is a subset of X, the derived set of S in X is the set of limit points of S in X.
Developable space A topological space with a development.
Development A countable collection of open covers of a topological space, such that for any closed set C and any point p in its complement there exists a cover in the collection such that every neighbourhood of p in the cover is disjoint from C.
Diameter If (M, d) is a metric space and S is a subset of M, the diameter of S is the supremum of the distances d(x, y), where x and y range over S.
Discrete metric The discrete metric on a set X is the function d : X × X → R such that for all x, y in X, d(x, x) = 0 and d(x, y) = 1 if x ≠ y. The discrete metric induces the discrete topology on X.
Discrete space A space X is discrete if every subset of X is open. We say that X carries the discrete topology.
Discrete topology See discrete space.
Disjoint union topology See Coproduct topology.
Dispersion point If X is a connected space with more than one point, then a point x of X is a dispersion point if the subspace X − {x} is hereditarily disconnected (its only connected components are the one-point sets).
Distance See metric space.
Dowker space
Dunce hat (topology)
E
Entourage See Uniform space.
Exterior The exterior of a set is the interior of its complement.
F
Fσ set An Fσ set is a countable union of closed sets.
Filter See also: Filters in topology. A filter on a space X is a nonempty family F of subsets of X such that the following conditions hold:
The empty set is not in F.
The intersection of any finite number of elements of F is again in F.
If A is in F and if B contains A, then B is in F.
Final topology On a set X with respect to a family of functions into , is the finest topology on X which makes those functions continuous.
Fine topology (potential theory) On Euclidean space , the coarsest topology making all subharmonic functions (equivalently all superharmonic functions) continuous.
Finer topology If X is a set, and if T1 and T2 are topologies on X, then T2 is finer (or larger, stronger) than T1 if T2 contains T1. Beware, some authors, especially analysts, use the term weaker.
Finitely generated See Alexandrov topology.
First category See Meagre.
First-countable A space is first-countable if every point has a countable local base.
Fréchet See T1.
Frontier See Boundary.
Full set A compact subset K of the complex plane is called full if its complement is connected. For example, the closed unit disk is full, while the unit circle is not.
Functionally separated Two sets A and B in a space X are functionally separated if there is a continuous map f: X → [0, 1] such that f(A) = 0 and f(B) = 1.
G
Gδ set A Gδ set or inner limiting set is a countable intersection of open sets.
Gδ space A space in which every closed set is a Gδ set.
Generic point A generic point for a closed set is a point for which the closed set is the closure of the singleton set containing that point.
H
Hausdorff A Hausdorff space (or T2 space) is one in which every two distinct points have disjoint neighbourhoods. Every Hausdorff space is T1.
H-closed A space is H-closed, or Hausdorff closed or absolutely closed, if it is closed in every Hausdorff space containing it.
Hemicompact A space is hemicompact, if there is a sequence of compact subsets so that every compact subset is contained in one of them.
Hereditarily P A space is hereditarily P for some property P if every subspace is also P.
Hereditary A property of spaces is said to be hereditary if whenever a space has that property, then so does every subspace of it. For example, second-countability is a hereditary property.
Homeomorphism If X and Y are spaces, a homeomorphism from X to Y is a bijective function f : X → Y such that f and f−1 are continuous. The spaces X and Y are then said to be homeomorphic. From the standpoint of topology, homeomorphic spaces are identical.
Homogeneous A space X is homogeneous if, for every x and y in X, there is a homeomorphism f : X → X such that f(x) = y. Intuitively, the space looks the same at every point. Every topological group is homogeneous.
Homotopic maps Two continuous maps f, g : X → Y are homotopic (in Y) if there is a continuous map H : X × [0, 1] → Y such that H(x, 0) = f(x) and H(x, 1) = g(x) for all x in X. Here, X × [0, 1] is given the product topology. The function H is called a homotopy (in Y) between f and g.
Homotopy See Homotopic maps.
Hyperconnected A space is hyperconnected if no two non-empty open sets are disjoint Every hyperconnected space is connected.
I
Identification map See Quotient map.
Identification space See Quotient space.
Indiscrete space See Trivial topology.
Infinite-dimensional topology See Hilbert manifold and Q-manifolds, i.e. (generalized) manifolds modelled on the Hilbert space and on the Hilbert cube respectively.
Inner limiting set A Gδ set.
Interior The interior of a set is the largest open set contained in the original set. It is equal to the union of all open sets contained in it. An element of the interior of a set S is an interior point of S.
Interior point See Interior.
Isolated point A point x is an isolated point if the singleton {x} is open. More generally, if S is a subset of a space X, and if x is a point of S, then x is an isolated point of S if {x} is open in the subspace topology on S.
Isometric isomorphism If M1 and M2 are metric spaces, an isometric isomorphism from M1 to M2 is a bijective isometry f : M1 → M2. The metric spaces are then said to be isometrically isomorphic. From the standpoint of metric space theory, isometrically isomorphic spaces are identical.
Isometry If (M1, d1) and (M2, d2) are metric spaces, an isometry from M1 to M2 is a function f : M1 → M2 such that d2(f(x), f(y)) = d1(x, y) for all x, y in M1. Every isometry is injective, although not every isometry is surjective.
K
Kolmogorov axiom See T0.
Kuratowski closure axioms The Kuratowski closure axioms is a set of axioms satisfied by the function which takes each subset of X to its closure:
Isotonicity: Every set is contained in its closure.
Idempotence: The closure of the closure of a set is equal to the closure of that set.
Preservation of binary unions: The closure of the union of two sets is the union of their closures.
Preservation of nullary unions: The closure of the empty set is empty.
If c is a function from the power set of X to itself, then c is a closure operator if it satisfies the Kuratowski closure axioms. The Kuratowski closure axioms can then be used to define a topology on X by declaring the closed sets to be the fixed points of this operator, i.e. a set A is closed if and only if c(A) = A.
Kolmogorov topology
TKol = {R, }∪{(a,∞): a is real number}; the pair (R,TKol) is named Kolmogorov Straight.
L
L-space An L-space is a hereditarily Lindelöf space which is not hereditarily separable. A Suslin line would be an L-space.
Larger topology See Finer topology.
Limit point A point x in a space X is a limit point of a subset S if every open set containing x also contains a point of S other than x itself. This is equivalent to requiring that every neighbourhood of x contains a point of S other than x itself.
Limit point compact See Weakly countably compact.
Lindelöf A space is Lindelöf if every open cover has a countable subcover.
Local base A set B of neighbourhoods of a point x of a space X is a local base (or local basis, neighbourhood base, neighbourhood basis) at x if every neighbourhood of x contains some member of B.
Local basis See Local base.
Locally (P) space There are two definitions for a space to be "locally (P)" where (P) is a topological or set-theoretic property: that each point has a neighbourhood with property (P), or that every point has a neighourbood base for which each member has property (P). The first definition is usually taken for locally compact, countably compact, metrizable, separable, countable; the second for locally connected.
Locally closed subset A subset of a topological space that is the intersection of an open and a closed subset. Equivalently, it is a relatively open subset of its closure.
Locally compact A space is locally compact if every point has a compact neighbourhood: the alternative definition that each point has a local base consisting of compact neighbourhoods is sometimes used: these are equivalent for Hausdorff spaces. Every locally compact Hausdorff space is Tychonoff.
Locally connected A space is locally connected if every point has a local base consisting of connected neighbourhoods.
Locally dense see Preopen.
Locally finite A collection of subsets of a space is locally finite if every point has a neighbourhood which has nonempty intersection with only finitely many of the subsets. See also countably locally finite, point finite.
Locally metrizable/Locally metrisable A space is locally metrizable if every point has a metrizable neighbourhood.
Locally path-connected A space is locally path-connected if every point has a local base consisting of path-connected neighbourhoods. A locally path-connected space is connected if and only if it is path-connected.
Locally simply connected A space is locally simply connected if every point has a local base consisting of simply connected neighbourhoods.
Loop If x is a point in a space X, a loop at x in X (or a loop in X with basepoint x) is a path f in X, such that f(0) = f(1) = x. Equivalently, a loop in X is a continuous map from the unit circle S1 into X.
M
Meagre If X is a space and A is a subset of X, then A is meagre in X (or of first category in X) if it is the countable union of nowhere dense sets. If A is not meagre in X, A is of second category in X.
Metacompact A space is metacompact if every open cover has a point finite open refinement.
Metric See Metric space.
Metric invariant A metric invariant is a property which is preserved under isometric isomorphism.
Metric map If X and Y are metric spaces with metrics dX and dY respectively, then a metric map is a function f from X to Y, such that for any points x and y in X, dY(f(x), f(y)) ≤ dX(x, y). A metric map is strictly metric if the above inequality is strict for all x and y in X.
Metric space A metric space (M, d) is a set M equipped with a function d : M × M → R satisfying the following axioms for all x, y, and z in M:
d(x, y) ≥ 0
d(x, x) = 0
if d(x, y) = 0 then x = y (identity of indiscernibles)
d(x, y) = d(y, x) (symmetry)
d(x, z) ≤ d(x, y) + d(y, z) (triangle inequality)
The function d is a metric on M, and d(x, y) is the distance between x and y. The collection of all open balls of M is a base for a topology on M; this is the topology on M induced by d. Every metric space is Hausdorff and paracompact (and hence normal and Tychonoff). Every metric space is first-countable.
Metrizable/Metrisable A space is metrizable if it is homeomorphic to a metric space. Every metrizable space is Hausdorff and paracompact (and hence normal and Tychonoff). Every metrizable space is first-countable.
Monolith Every non-empty ultra-connected compact space X has a largest proper open subset; this subset is called a monolith.
Moore space A Moore space is a developable regular Hausdorff space.
N
Nearly open see preopen.
Neighbourhood/Neighborhood A neighbourhood of a point x is a set containing an open set which in turn contains the point x. More generally, a neighbourhood of a set S is a set containing an open set which in turn contains the set S. A neighbourhood of a point x is thus a neighbourhood of the singleton set {x}. (Note that under this definition, the neighbourhood itself need not be open. Many authors require that neighbourhoods be open; be careful to note conventions.)
Neighbourhood base/basis See Local base.
Neighbourhood system for a point x A neighbourhood system at a point x in a space is the collection of all neighbourhoods of x.
Net A net in a space X is a map from a directed set A to X. A net from A to X is usually denoted (xα), where α is an index variable ranging over A. Every sequence is a net, taking A to be the directed set of natural numbers with the usual ordering.
Normal A space is normal if any two disjoint closed sets have disjoint neighbourhoods. Every normal space admits a partition of unity.
Normal Hausdorff A normal Hausdorff space (or T4 space) is a normal T1 space. (A normal space is Hausdorff if and only if it is T1, so the terminology is consistent.) Every normal Hausdorff space is Tychonoff.
Nowhere dense A nowhere dense set is a set whose closure has empty interior.
O
Open cover An open cover is a cover consisting of open sets.
Open ball If (M, d) is a metric space, an open ball is a set of the form B(x; r) := {y in M : d(x, y) < r}, where x is in M and r is a positive real number, the radius of the ball. An open ball of radius r is an open r-ball. Every open ball is an open set in the topology on M induced by d.
Open condition See open property.
Open set An open set is a member of the topology.
Open function A function from one space to another is open if the image of every open set is open.
Open property A property of points in a topological space is said to be "open" if those points which possess it form an open set. Such conditions often take a common form, and that form can be said to be an open condition; for example, in metric spaces, one defines an open ball as above, and says that "strict inequality is an open condition".
Orthocompact
A space is orthocompact, if every open cover has an interior-preserving open refinement.
P
Paracompact A space is paracompact if every open cover has a locally finite open refinement. Paracompact implies metacompact. Paracompact Hausdorff spaces are normal.
Partition of unity A partition of unity of a space X is a set of continuous functions from X to [0, 1] such that any point has a neighbourhood where all but a finite number of the functions are identically zero, and the sum of all the functions on the entire space is identically 1.
Path A path in a space X is a continuous map f from the closed unit interval [0, 1] into X. The point f(0) is the initial point of f; the point f(1) is the terminal point of f.
Path-connected A space X is path-connected if, for every two points x, y in X, there is a path f from x to y, i.e., a path with initial point f(0) = x and terminal point f(1) = y. Every path-connected space is connected.
Path-connected component A path-connected component of a space is a maximal nonempty path-connected subspace. The set of path-connected components of a space is a partition of that space, which is finer than the partition into connected components. The set of path-connected components of a space X is denoted π0(X).
Perfectly normal a normal space which is also a Gδ.
π-base A collection B of nonempty open sets is a π-base for a topology τ if every nonempty open set in τ includes a set from B.
Point A point is an element of a topological space. More generally, a point is an element of any set with an underlying topological structure; e.g. an element of a metric space or a topological group is also a "point".
Point of closure See Closure.
Polish A space is Polish if it is separable and completely metrizable, i.e. if it is homeomorphic to a separable and complete metric space.
Polyadic A space is polyadic if it is the continuous image of the power of a one-point compactification of a locally compact, non-compact Hausdorff space.
Polytopological space A polytopological space is a set together with a family of topologies on that is linearly ordered by the inclusion relation where is an arbitrary index set.
P-point A point of a topological space is a P-point if its filter of neighbourhoods is closed under countable intersections.
Pre-compact See Relatively compact.
A subset A of a topological space X is preopen if .
Prodiscrete topology The prodiscrete topology on a product AG is the product topology when each factor A is given the discrete topology.
Product topology If is a collection of spaces and X is the (set-theoretic) Cartesian product of then the product topology on X is the coarsest topology for which all the projection maps are continuous.
Proper function/mapping A continuous function f from a space X to a space Y is proper if is a compact set in X for any compact subspace C of Y.
Proximity space A proximity space (X, d) is a set X equipped with a binary relation d between subsets of X satisfying the following properties:
For all subsets A, B and C of X,
A d B implies B d A
A d B implies A is non-empty
If A and B have non-empty intersection, then A d B
A d (B C) if and only if (A d B or A d C)
If, for all subsets E of X, we have (A d E or B d E), then we must have A d (X − B)
Pseudocompact A space is pseudocompact if every real-valued continuous function on the space is bounded.
Pseudometric See Pseudometric space.
Pseudometric space A pseudometric space (M, d) is a set M equipped with a real-valued function satisfying all the conditions of a metric space, except possibly the identity of indiscernibles. That is, points in a pseudometric space may be "infinitely close" without being identical. The function d is a pseudometric on M. Every metric is a pseudometric.
Punctured neighbourhood/Punctured neighborhood A punctured neighbourhood of a point x is a neighbourhood of x, minus {x}. For instance, the interval (−1, 1) = {y : −1 < y < 1} is a neighbourhood of x = 0 in the real line, so the set is a punctured neighbourhood of 0.
Q
Quasicompact See compact. Some authors define "compact" to include the Hausdorff separation axiom, and they use the term quasicompact to mean what we call in this glossary simply "compact" (without the Hausdorff axiom). This convention is most commonly found in French, and branches of mathematics heavily influenced by the French.
Quotient map If X and Y are spaces, and if f is a surjection from X to Y, then f is a quotient map (or identification map) if, for every subset U of Y, U is open in Y if and only if f 1(U) is open in X. In other words, Y has the f-strong topology. Equivalently, is a quotient map if and only if it is the transfinite composition of maps , where is a subset. Note that this does not imply that f is an open function.
Quotient space If X is a space, Y is a set, and f : X → Y is any surjective function, then the Quotient topology on Y induced by f is the finest topology for which f is continuous. The space X is a quotient space or identification space. By definition, f is a quotient map. The most common example of this is to consider an equivalence relation on X, with Y the set of equivalence classes and f the natural projection map. This construction is dual to the construction of the subspace topology.
R
Refinement A cover K is a refinement of a cover L if every member of K is a subset of some member of L.
Regular A space is regular if, whenever C is a closed set and x is a point not in C, then C and x have disjoint neighbourhoods.
Regular Hausdorff A space is regular Hausdorff (or T3) if it is a regular T0 space. (A regular space is Hausdorff if and only if it is T0, so the terminology is consistent.)
A subset of a space X is regular open if it equals the interior of its closure; dually, a regular closed set is equal to the closure of its interior. An example of a non-regular open set is the set U = ∪ in R with its normal topology, since 1 is in the interior of the closure of U, but not in U. The regular open subsets of a space form a complete Boolean algebra.
Relatively compact A subset Y of a space X is relatively compact in X if the closure of Y in X is compact.
Residual If X is a space and A is a subset of X, then A is residual in X if the complement of A is meagre in X. Also called comeagre or comeager.
Resolvable A topological space is called resolvable if it is expressible as the union of two disjoint dense subsets.
Rim-compact A space is rim-compact if it has a base of open sets whose boundaries are compact.
S
S-space An S-space is a hereditarily separable space which is not hereditarily Lindelöf.
Scattered A space X is scattered if every nonempty subset A of X contains a point isolated in A.
Scott The Scott topology on a poset is that in which the open sets are those Upper sets inaccessible by directed joins.
Second category See Meagre.
Second-countable A space is second-countable or perfectly separable if it has a countable base for its topology. Every second-countable space is first-countable, separable, and Lindelöf.
Semilocally simply connected A space X is semilocally simply connected if, for every point x in X, there is a neighbourhood U of x such that every loop at x in U is homotopic in X to the constant loop x. Every simply connected space and every locally simply connected space is semilocally simply connected. (Compare with locally simply connected; here, the homotopy is allowed to live in X, whereas in the definition of locally simply connected, the homotopy must live in U.)
Semi-open A subset A of a topological space X is called semi-open if .
Semi-preopen A subset A of a topological space X is called semi-preopen if
Semiregular A space is semiregular if the regular open sets form a base.
Separable A space is separable if it has a countable dense subset.
Separated Two sets A and B are separated if each is disjoint from the other's closure.
Sequentially compact A space is sequentially compact if every sequence has a convergent subsequence. Every sequentially compact space is countably compact, and every first-countable, countably compact space is sequentially compact.
Short map See metric map
Simply connected A space is simply connected if it is path-connected and every loop is homotopic to a constant map.
Smaller topology See Coarser topology.
Sober In a sober space, every irreducible closed subset is the closure of exactly one point: that is, has a unique generic point.
Star The star of a point in a given cover of a topological space is the union of all the sets in the cover that contain the point. See star refinement.
-Strong topology Let be a map of topological spaces. We say that has the -strong topology if, for every subset , one has that is open in if and only if is open in
Stronger topology See Finer topology. Beware, some authors, especially analysts, use the term weaker topology.
Subbase A collection of open sets is a subbase (or subbasis) for a topology if every non-empty proper open set in the topology is the union of a finite intersection of sets in the subbase. If is any collection of subsets of a set X, the topology on X generated by is the smallest topology containing this topology consists of the empty set, X and all unions of finite intersections of elements of Thus is a subbase for the topology it generates.
Subbasis See Subbase.
Subcover A cover K is a subcover (or subcovering) of a cover L if every member of K is a member of L.
Subcovering See Subcover.
Submaximal space A topological space is said to be submaximal if every subset of it is locally closed, that is, every subset is the intersection of an open set and a closed set.
Here are some facts about submaximality as a property of topological spaces:
Every door space is submaximal.
Every submaximal space is weakly submaximal viz every finite set is locally closed.
Every submaximal space is irresolvable.
Subspace If T is a topology on a space X, and if A is a subset of X, then the subspace topology on A induced by T consists of all intersections of open sets in T with A. This construction is dual to the construction of the quotient topology.
Suslin line
T
T0 A space is T0 (or Kolmogorov) if for every pair of distinct points x and y in the space, either there is an open set containing x but not y, or there is an open set containing y but not x.
T1 A space is T1 (or Fréchet or accessible) if for every pair of distinct points x and y in the space, there is an open set containing x but not y. (Compare with T0; here, we are allowed to specify which point will be contained in the open set.) Equivalently, a space is T1 if all its singletons are closed. Every T1 space is T0.
T2 See Hausdorff space.
T3 See Regular Hausdorff.
T3½ See Tychonoff space.
T4 See Normal Hausdorff.
T5 See Completely normal Hausdorff.
Top See Category of topological spaces.
θ-cluster point, θ-closed, θ-open A point x of a topological space X is a θ-cluster point of a subset A if for every open neighborhood U of x in X. The subset A is θ-closed if it is equal to the set of its θ-cluster points, and θ-open if its complement is θ-closed.
Topological invariant A topological invariant is a property which is preserved under homeomorphism. For example, compactness and connectedness are topological properties, whereas boundedness and completeness are not. Algebraic topology is the study of topologically invariant abstract algebra constructions on topological spaces.
Topological space A topological space (X, T) is a set X equipped with a collection T of subsets of X satisfying the following axioms:
The empty set and X are in T.
The union of any collection of sets in T is also in T.
The intersection of any pair of sets in T is also in T.
The collection T is a topology on X.
Topological sum See Coproduct topology.
Topologically complete Completely metrizable spaces (i. e. topological spaces homeomorphic to complete metric spaces) are often called topologically complete; sometimes the term is also used for Čech-complete spaces or completely uniformizable spaces.
Topology See Topological space.
Totally bounded A metric space M is totally bounded if, for every r > 0, there exist a finite cover of M by open balls of radius r. A metric space is compact if and only if it is complete and totally bounded.
Totally disconnected A space is totally disconnected if it has no connected subset with more than one point.
Trivial topology The trivial topology (or indiscrete topology) on a set X consists of precisely the empty set and the entire space X.
Tychonoff A Tychonoff space (or completely regular Hausdorff space, completely T3 space, T3.5 space) is a completely regular T0 space. (A completely regular space is Hausdorff if and only if it is T0, so the terminology is consistent.) Every Tychonoff space is regular Hausdorff.
U
Ultra-connected A space is ultra-connected if no two non-empty closed sets are disjoint. Every ultra-connected space is path-connected.
Ultrametric A metric is an ultrametric if it satisfies the following stronger version of the triangle inequality: for all x, y, z in M, d(x, z) ≤ max(d(x, y), d(y, z)).
Uniform isomorphism If X and Y are uniform spaces, a uniform isomorphism from X to Y is a bijective function f : X → Y such that f and f−1 are uniformly continuous. The spaces are then said to be uniformly isomorphic and share the same uniform properties.
Uniformizable/Uniformisable A space is uniformizable if it is homeomorphic to a uniform space.
Uniform space A uniform space is a set X equipped with a nonempty collection Φ of subsets of the Cartesian product X × X satisfying the following axioms:
if U is in Φ, then U contains { (x, x) | x in X }.
if U is in Φ, then { (y, x) | (x, y) in U } is also in Φ
if U is in Φ and V is a subset of X × X which contains U, then V is in Φ
if U and V are in Φ, then U ∩ V is in Φ
if U is in Φ, then there exists V in Φ such that, whenever (x, y) and (y, z) are in V, then (x, z) is in U.
The elements of Φ are called entourages, and Φ itself is called a uniform structure on X. The uniform structure induces a topology on X where the basic neighborhoods of x are sets of the form {y : (x,y)∈U} for U∈Φ.
Uniform structure See Uniform space.
W
Weak topology The weak topology on a set, with respect to a collection of functions from that set into topological spaces, is the coarsest topology on the set which makes all the functions continuous.
Weaker topology See Coarser topology. Beware, some authors, especially analysts, use the term stronger topology.
Weakly countably compact A space is weakly countably compact (or limit point compact) if every infinite subset has a limit point.
Weakly hereditary A property of spaces is said to be weakly hereditary if whenever a space has that property, then so does every closed subspace of it. For example, compactness and the Lindelöf property are both weakly hereditary properties, although neither is hereditary.
Weight The weight of a space X is the smallest cardinal number κ such that X has a base of cardinal κ. (Note that such a cardinal number exists, because the entire topology forms a base, and because the class of cardinal numbers is well-ordered.)
Well-connected See Ultra-connected. (Some authors use this term strictly for ultra-connected compact spaces.)
Z
Zero-dimensional A space is zero-dimensional if it has a base of clopen sets.
See also
Naive set theory, Axiomatic set theory, and Function for definitions concerning sets and functions.
Topology for a brief history and description of the subject area
Topological spaces for basic definitions and examples
List of general topology topics
List of examples in general topology
Topology specific concepts
Compact space
Connected space
Continuity
Metric space
Separated sets
Separation axiom
Topological space
Uniform space
Other glossaries
Glossary of algebraic topology
Glossary of differential geometry and topology
Glossary of areas of mathematics
Glossary of Riemannian and metric geometry
References
Also available as Dover reprint.
External links
A glossary of definitions in topology
Topology
Wikipedia glossaries using description lists | Glossary of general topology | Physics,Mathematics | 9,083 |
58,692,548 | https://en.wikipedia.org/wiki/Aspergillus%20neoniveus | Aspergillus neoniveus is a species of fungus in the genus Aspergillus. It is from the Terrei section. The species was first described in 2011. It has been isolated from forest soil in Thailand and soil in Canada.
Growth and morphology
A. neoniveus has been cultivated on both yeast extract sucrose agar (YES) plates and Malt Extract Agar Oxoid® (MEAOX) plates. The growth morphology of the colonies can be seen in the pictures below.
References
neoniveus
Fungi described in 2011
Fungus species | Aspergillus neoniveus | Biology | 116 |
3,587,634 | https://en.wikipedia.org/wiki/Mercury%20%28cipher%20machine%29 | Mercury was a British cipher machine used by the Air Ministry from 1950 until at least the early 1960s. Mercury was an online rotor machine descended from Typex, but modified to achieve a longer cycle length using a so-called double-drum basket system.
History
Mercury was designed by Wing Commander E. W. Smith and F. Rudd, who were awarded £2,250 and £750 respectively in 1960 for their work in the design of the machine. E. W. Smith, one of the developers of TypeX, had designed the double-drum basket system in 1943, on his own initiative, to fulfil the need for an on-line system.
Mercury prototypes were operational by 1948, and the machine was in use by 1950. Over 200 Mercury machines had been made by 1959 with over £250,000 spent on its production. Mercury links were installed between the UK and various Overseas stations, including in Canada, Australia, Singapore, Cyprus, Germany, France, Middle East, Washington, Nairobi and Colombo. The machine was used for UK diplomatic messaging for more or less a decade, but saw almost no military use.
In 1960, it was anticipated that the machine would remain in use until 1963, when it would be made obsolete by the arrival of BID 610 (Alvis) equipment.
A miniaturised version of Mercury was designed, named Ariel, but this machine appears not to have been adopted for operational use.
Design
In the Mercury system, two series of rotors were used. The first series, dubbed the control maze, had four rotors, and stepped cyclometrically as in Typex. Five outputs from the control maze were used to determine the stepping of five rotors in the second series of rotors, the message maze, the latter used to encrypt and decrypt the plaintext and ciphertext. A sixth rotor in the message maze was controlled independently and stepped in the opposite direction to the others. All ten rotors were interchangeable in any part of either maze. Using rotors to control the stepping of other rotors was a feature of an earlier cipher machine, the US ECM Mark II.
Mercury also used double-wired rotors, consisting of "Inside and Outside Scrambled Wheels", the Outer wheels being settable in a number of positions with respect to the Inner wheels.
Security
It had been mathematically determined that Typex had a sufficiently large cycle to permit only 750 characters to be sent using a single arrangement of its rotors without fear of compromising security. A counter recorded the number of keystrokes and when these reached 750 a predetermined rotor was manually advanced one step, thus permitting TypeX to safely encrypt messages with more than 750 key strokes.
Mercury, with its longer cycle length, was judged to be safe even after 56700 characters had passed on one setting of the rotors. This cycle length was sufficient for the machine to be used as an on-line cipher machine with traffic flow security — the machine would transmit continuously, even if not sending a message.
See also
5-UCO
References
"Awards to civilian personnel in respect of cypher machine development", 1955–1960, PRO AVIA 65/977.
Rotor machines
Cryptographic hardware | Mercury (cipher machine) | Physics,Technology | 658 |
6,356,594 | https://en.wikipedia.org/wiki/Probe%20card | A probe card (commonly referred to as a DUT board) is used in automated integrated circuit testing. It is an interface between an electronic test system and a semiconductor wafer.
Use and manufacture
A probe card or DUT board is a printed circuit board (PCB), and is the interface between the integrated circuit and a test head, which in turn attaches to automatic test equipment (ATE) (or "tester"). Typically, the probe card is mechanically docked to a Wafer testing prober and electrically connected to the ATE . Its purpose is to provide an electrical path between the test system and the circuits on the wafer, thereby permitting the testing and validation of the circuits at the wafer level, usually before they are diced and packaged. It normally comprises a PCB and some form of contact elements, usually metallic.
A semiconductor manufacturer will typically require a new probe card for each new device wafer and for device shrinks (when the manufacturer reduces the size of the device while keeping its functionality) because the probe card is effectively a custom connector that takes the universal pattern of a given tester and translates the signals to connect to electrical pads on the wafer. For testing of Dynamic random-access memory (DRAM) and Flash memory (FLASH) devices, these pads are typically made of aluminum and are 40–90 per side. Other devices may have flat pads, or raised bumps or pillars made of copper, copper alloys or many types of solders such as lead-tin, tin-silver and others.
The probe card must make good electrical contact to these pads or bumps during the testing of the device. When the testing of the device is complete, the prober will index the wafer to the next device to be tested.
Normally a probe card is inserted into a wafer prober, inside which the position of the wafer to be tested will be adjusted to ensure a precise contact between the probe card and wafer. Once the probe card and the wafer are loaded, a camera in the prober will optically locate several tips on the probe card and several marks or pads on the wafer, and using this information it will align the pads on the device under test (DUT) to the probe card contacts.
Design and types
Probe cards are broadly classified into needle type, vertical type, and MEMS (Micro Electro-Mechanical System) type depending on shape and forms of contact elements. MEMS type is the most advanced technology currently available. The most advanced type of probe card currently can test an entire 12" wafer with one touchdown.
Probe cards or DUT boards are designed to meet both the mechanical and electrical requirements of the particular chip and the specific test equipment to be used. One type of DUT board is used for testing the individual die of a silicon wafer before they are cut free and packaged, and another type is used for testing packaged IC's.
Efficiency factors
Probe card efficiency is affected by many factors. Perhaps the most important factor impacting probe card efficiency is the number of DUTs that can be tested in parallel. Many wafers today are still tested one device at a time. If one wafer had 1000 of these devices and the time required to test one device was 10 seconds and the time for the prober to move from one device to another device was 1 second, then to test an entire wafer would take 1000 x 11 seconds = 11,000 seconds or roughly 3 hours. If however, the probe card and the tester could test 16 devices in parallel (with 16 times the electrical connections) then the test time would be reduced by almost exactly 16 times (to about 11 minutes).
Advanced Tester Resource Enhancement (ATRE) is a powerful means of increasing the number of DUTs that can be tested by a probe card in parallel (or in one touchdown during which probe card needles remain in contact with the wafer DUTs). ATRE allows the sharing of tester resources among DUTs using active components, which have the ability to connect and disconnect DUTs from the tester resources. Without ATRE, a single tester resource (power, DC or AC signal) would normally only go directly to one DUT. However by installing ATRE-configured relays (switches) onto the probe card PCB, the tester resource can split or branch out to multiple DUTs. For example in a x4 sharing configuration, 1 power signal is fed into 4 relays whose outputs go to 4 DUTs, respectively. Then by turning each relay ON and OFF sequentially (in the case of a DUT current measurement test), the tester can test each of the 4 DUTs in turn during the same touchdown (without having to move the prober from one device to the other). Therefore a tester that has only 256 power signals will appear to have its resources expanded or enhanced so as to enable it to test 1024 DUTs in one touchdown, thanks to the 1024 onboard relays in the x4 sharing scheme implemented on the probe card. ATRE brings dramatic savings in terms of test time and cost, as it can allow a chip manufacturer or test house to validate more DUTs in one touchdown without the need to purchase a more advanced tester equipped with more resources.
Contamination issues
Another major factor is debris that accumulates on the tips of the probe needles. Normally these are made of tungsten or tungsten/rhenium alloys or advanced palladium based alloys like PdCuAg. Some modern probe cards have contact tips manufactured by MEMS technologies.
Irrespective of the probe tip material, contamination builds up on the tips as a result of successive touchdown events (where the probe tips make physical contact with the bond pads of the die). Accumulation of debris has an adverse effect on the critical measurement of contact resistance. To return a used probe card to a contact resistance that is acceptable, the probe tips must be spotless. Cleaning can be done offline using an NWR style laser to reclaim the tips by selectively removing the contamination. Online cleaning can be used during testing to optimize the testing results within the wafer or within wafer lots.
Notes
References
External links
Additional Slides for Lecture 16: "Testing, Design for Testability", EE271
System-in-Package (SiP) Testing, Jin-Fu Li, National Central University, Taiwan
Probe Card Tutorial, Keithley Instruments
Semiconductor device fabrication
Hardware testing | Probe card | Materials_science | 1,311 |
13,464,520 | https://en.wikipedia.org/wiki/Husky%20VMMD | The Husky VMMD (Vehicle-Mounted Mine Detection) is a configurable counter-IED MRAP (Mine-Resistant Ambush Protected) vehicle, developed by South African-based DCD Protected Mobility and American C-IED company Critical Solutions International. Designed for use in route clearance and de-mining operations, the Husky is equipped with technologies to help detect explosives and minimise blast damage.
The Husky VMMD can help operators detect land mines, and improvised explosive devices (IEDs) using basic sensor equipment, and imaging systems. The Husky is equipped with countermeasures like jamming systems in an attempt to help disrupt the effect of IEDs. The Husky's armour is also able to withstand damage from basic explosives.
Development
The Husky traces its lineage to the Pookie, a Rhodesian mine clearance vehicle.
Originally used as the lead element of a mine removal convoy, the Husky was employed as part of the Chubby mine detection system. The early Chubby system comprised a lead detection vehicle (the Meerkat), a second proofing vehicle (the Husky) towing a mine detonation trailer, and a third vehicle carrying spare parts for expedient blast repair.
The Husky was initially deployed in the 1970s. During the South African Border War, the South African Defense Force used the Husky extensively to clear mines from military convoy routes in Namibia and Angola.
In the mid-1990s, DCD Group and Critical Solutions International planned to bring the technology to the U.S. and underwent a two-year foreign comparative test program with the United States Department of Defense and follow-on modifications and testing. In 1997, CSI was directed to produce and deliver production systems under the U.S. Army Interim Vehicle Mounted Mine Detection Program.
Over the next twenty years, the Husky underwent several iterations and upgrades. U.S. military clearance units currently train on and employ Husky vehicles as detection assets and clearance vehicles.
Design
The Husky is part of a class of MRAP vehicles developed from South African blast protection designs.
The sharp V-hull of the Husky helps reduces blast effect by increasing ground clearance and standoff from the blast, increasing structural hull rigidity, and diverting blast energy and fragmentation away from the platform and its occupants.
The Husky is designed to break apart in a blast event, allowing energy to transfer to the detachable front and rear modules rather than the critical components of the vehicle or the occupants located in the cab. Its three main components (a center cab with front and rear wheel modules) are connected by shear pins.
Critical components are engineered to break apart predictably, to help prevent catastrophic damage, and enabling users to quickly replace modules on site. This approach increases the lifespan of the vehicle and limits the need for recovery teams to evacuate the vehicle to maintenance facilities.
The cabin of the Husky is fitted with bulletproof glass windows. There is an entry hatch on the roof.
The Husky Mk III and 2G are powered by a Mercedes-Benz OM906LA turbo diesel engine coupled with an Allison Transmission 2500 SP 5-speed automatic transmission. It can reach a maximum speed of 72 km/h, and has a range of 350 km.
Variants
Husky Mk I
First Husky production model. Replaced by Husky Mk II.
Husky Mk II
Second Husky model. Replaced by Husky Mk III.
Husky Mk III
Modern single-occupant Husky model. The platform is integrated with pulse induction metal detector panels and overpass tires that enable operators to regulate tire air pressure in order to reduce the risk of initiating land mines without causing detonation. The Mk III, like other Husky models, is engineered in a modular, frangible configuration.
Husky 2G
Project Type
- Mine clearance vehicle
Manufacturer
- DCD Protected Mobility
Crew
- Two
Operating Weight
- 9,200kg
Husky 2G is a two-seat variant of Husky MK III vehicle mounted mine detector (VMMD) designed and manufactured by South African firm DCD Protected Mobility (DCD PM). Equipped with a number of sensors, the vehicle is ideally suited for mine-clearing operations including detection, identification and destruction of improvised explosive devices (IED), landmines and other explosive materials.
Development of the Husky 2G was prompted by the need to conduct longer missions and employ multiple detection systems. The Husky 2G was designed with added high sensitivity detectors, ground-penetrating radar, video optics suites, and remote weapon stations. These additional components required a second operator to manage the additional workload, hence the required two occupants.
Equipment
The Husky is capable of carrying the following equipment and payloads:
Autonomous vehicle upgrades
Rocket-propelled grenade armor and netting
Smoke grenade launchers
Electronic countermeasures
Remote weapon station
Metal detectors
Ground-penetrating radar
Nonlinear junction detectors
Gunfire detectors
Robotic arms
Blowers
Water diggers
Thermal cameras
Optics suite
Mine-clearing line charges
Mine rollers
Rhino Passive Infrared Defeat System
Mine plows
Proofing rollers
Electrostatic discharge
Red Pack repair kit
Operators
Husky Mk III
United States Army
United States Marine Corps
Canadian Army
Australian Army
South African Defense Force
Kenyan Army
Husky 2G
Islamic Republic of Iran Army
Iraqi Army
Turkish Army
Spanish Army
Royal Saudi Land Forces
Egyptian Army
Jordanian Army
Latvian Army
United States Army (limited fielding in support of Operation Enduring Freedom)
Recognitions
The Husky was listed on the U.S. Army’s Top Ten inventions of 2010.
References
External links
Critical Solutions International (CSI)
Soldier Armed magazine article
Military engineering vehicles
Cold War military equipment of South Africa
Mine warfare countermeasures
Military vehicles of the United States
Military vehicles of South Africa
Bomb disposal
Military vehicles introduced in the 1970s | Husky VMMD | Chemistry,Engineering | 1,127 |
15,209,166 | https://en.wikipedia.org/wiki/Ringing%20out | Ringing out is a process in audio engineering technique used to prevent audio feedback between on-stage microphones and loudspeakers, and to maximize gain before feedback. Depending on the acoustics of a venue, certain frequencies may be resonant and thus will be more prone to feedback.
To ring out a room, a sound technician will raise the gain or fader controls on a mixing desk to induce an audio system to feedback. Once feedback occurs, the technician uses an equalizer, usually a graphic equalizer to reduce the gain at the frequency of the feedback. The frequency of the feedback can be identified using a spectrum analyzer. This is repeated until feedback is sufficiently reduced without compromising the quality of the sound.
Ringing out is particularly important for the stage monitor system. While the performer or musician is usually behind the main PA system, the monitors are so they can hear themselves. As such, a microphone is much more likely to feedback through the monitor loudspeakers than the main PA.
Ringing out can become quite complex when working with a large number of microphones and monitors. Indeed, with larger touring acts, one of the major advantages of using in-ear monitors is the minimal ringing out that needs to be done.
Hardware exists that can perform many of the same functions that ringing out provides, such as feedback suppression and room optimization.
Audio engineering | Ringing out | Engineering | 275 |
47,786,981 | https://en.wikipedia.org/wiki/Women%20in%20NASA | The role of women in and affiliated with NASA has varied over time. As early as 1922 women were working as physicists and in other technical positions.[1] Throughout the 1930s to the present, more women joined the NASA teams not only at Langley Memorial, but at the Jet Propulsion Laboratory, the Glenn Research Center, and other numerous NASA sites throughout the United States.[2] As the space program has grown, women have advanced into many roles, including astronauts.
History
1920s
As early as 1922 women like Pearl I. Young were working as physicists and other technical positions. Young was the second female physicist working for the federal government at the National Advisory Committee for Aeronautics (NACA), at Langley Memorial Aeronautical Laboratory building 1202 in Langley, Virginia.
1960s
Women first worked in support as administrators, secretaries, doctors, psychologists, and later engineers. In the 1960s, NASA started recruiting women and minorities for the space program. By the end of the 1960s, NASA had employed thousands of women. Some of the women like Mary Shep Burton, Gloria B. Martinez (the first Spanish woman hired), Cathy Osgood, and Shirley Hunt worked in the computer division while Sue Erwin, Lois Ransdell, and Maureen Bowen worked as secretaries for various members of the Mission and Flight Control teams. Dana Ulery was the first woman engineer to be hired at the Jet Propulsion Laboratory (JPL) of NASA. Although she was only considered as a junior engineer, for more than seven years, no woman engineer got into JPL besides Ulery. Another woman, Donna Shirley, worked in JPL as a mission engineer in the 1960s. Also, Dr. Carolyn Huntoon, a woman, was a pioneer in researching astronaut metabolisms and other body systems. Margaret Hamilton was the guidance computer lead programmer for the Apollo program. Judy Sullivan was the lead biomedical engineer for the Apollo 11 mission.
Although woman had a difficult time establishing themselves within the organization, NASA did have some women who charted unknown territory throughout the time period. For example, Katherine Johnson was one of the most prolific figures in NASA history. Johnson worked through the ranks as a black woman and made it as one of the top and most respected engineers on the Apollo mission. This was seen as a major step for blacks and women throughout NASA and the general public for others to look up to. Along with Katherine Johnson, who ended up playing a pivotal role as a computer for NASA, Dorothy Vaughan and Mary Jackson helped calculate integral equations and mathematical calculations to recheck and assure that the launching of spacecraft was calculated correctly. Overall, these figures stood as pioneers to the growing commonality of women working for NASA.
However, not everyone was accepting of this phenomenon. In 1962, George Low, NASA's Chief of Manned Spaceflight, fought against women by telling the congress that working with women would delay his work. Meanwhile, in the same year, John F. Kennedy signed the President's Commission on the Status of Women to encourage gender equality in the workforce. This eventually led to James Webb, a NASA administrator, creating an agency-wide policy directive stating that NASA provides equal opportunities for all kinds of people willing to work with NASA. Despite this, no women were selected to join the astronaut corps in 1963/65/66/67.
1970s
The 1970s was a stepping stone that lead women a step closer to becoming astronauts. At the same time, the military began accepting women for pilot training that eventually led to women astronauts. In 1977, the recruitment of NASA skyrocketed because of Nichelle Nichols's help. Part of the advantage Nichols had in the recruitment was that her role as Lieutenant Uhura on Star Trek inspired young girls to become astronauts at NASA when they grow up. One of these girls was Dr. Mae Jemison, the first black woman astronaut in 1992. Another important character in the 1970s was Dr. Carolyn Huntoon who turned down being an astronaut to serve on the astronaut selection committee. NASA sent Huntoon around the United States to encourage women to apply as astronauts or to get into the STEM field. In 1979, Kathryn Sullivan flew a NASA WB-57F reconnaissance aircraft to 63,300 feet altitude breaking an unofficial altitude record for American women.
1980s
On June 18, 1983, Sally Ride made history as the first American woman astronaut to go into space. About more than a year later, Judith Resnik took the Space Shuttle Discovery into space and became the second American woman in space. In 1988, Ellen Ochoa joined NASA and became the first Hispanic woman astronaut. Ochoa took on multiple missions that included Space shuttles Discovery, Atlantis, four flights, and almost 1,000 hours in space. In 1985, Shannon Lucid took on her first flight and by the end of her career she had spent 188 days in space. Lucid set an American record, for both men and women, with the most number of days in space until 2002.
1990s
By the 1990s, NASA was doing a lot of research in women's bodies and the effects of space to their bodies. Carolyn Huntoon gave a speech in 1994 at the 2nd Annual Women's Health and Space Luncheon by giving light to the unrecognized work of NASA. On February 3, 1995, history was made when Colonel Eileen Collins became the first woman to pilot an US spacecraft. Meanwhile, Shannon Lucid, a board engineer, took on five missions in space and worked as chief scientist for NASA in Washington, DC.
2000s
Starting year 2000, the number of women in NASA's planetary missions started to increase. Women were most given roles as Co-Investigators and Participating Scientists. From below 10% of women selected until the 1990s, this percentage started to increase in the 2000s up to around 30% of women, particularly, the women being given the role as Co-Investigators. Pamela Melroy, for example, took on several missions to the International Space Station on the shuttles Discovery and Atlantis. Not only was Melroy an astronaut but she was also a veteran military pilot who has more than 5,000 hours of flight time. In 2007, Peggy Whitson became the first woman to command the International Space Station. Aside from commanding, Whitson conducted dozens of tests in space that furthered space technologies that are still being used today.
In the same year, Barbara Morgan became the first teacher in space; however, it was argued that Christa McAuliffe was announced in 1985 as the first teacher in space, and Barbara Morgan was only an alternate or secondary candidate. In 1986, Christa McAuliffe died in Challenger accident and Morgan was unable to go to space until 2007.
2010s
Sunita Williams is known for holding many records for women, including 322 total days in space, spent over 50 hours walking in space and being the second women to command the ISS.
Women in space program
The unofficial program of Mercury 13 was considered as the start of inclusion of women in U.S space programs, wherein the first seven astronauts chosen for this project were all white men. Randy Lovelace and Don Flickinger, who were involved in the selection process, considered including women for this project. Lovelace thought that women can also do major tasks in space just like men. Through this, Lovelace and Flickinger met Jerrie Cobb, a woman, in 1960, who played a major role in recruiting and testing women.
Women in Space Program (December 20, 1959) was the “revived” version of the Women in Space Earliest program that was cancelled in November 1959. Similar to the program for men, this required candidate testings. However, the parameters for these tests were varied to accommodate women. In the screening phase, for example, men were required to be degree-holder jet pilots, went to military test pilot school, and with experience of minimum 1,500 hours of flying time. Since women were deprived from some of these opportunities, screenings shifted to women with commercial pilot licenses, especially that women served as instructors during this time. Cobb, who underwent the testing first, became the leader of the FLATs (Fellow Lady Astronaut Trainees) with 12 other women, which made 13 women in total (hence, the media named it Mercury 13). Even though Cobb was assigned as a NASA consultant and continued doing the testings, women were still not trained to be astronauts.
During the examinations for women, some scientists thought that women showed advantages for being sent to space rather than men. For example, internal organs of women were assumed to be more suitable in radiation and vibrations. Due to the relatively smaller size of women, spacecraft and flights would be less expensive if women were to use spacecraft. However, testing for women were cancelled after it was discovered that NASA did not issue an official request for such action. Lovelace decided to not continue the program and ended up in an uncomfortable situation at NASA. Meanwhile, Jerrie Cobb, who assumed leadership and facilitated the testings for women, was removed from her position at NASA.
Today in NASA
Since the first astronaut, Sally Ride, there have been 43 American women who have gone to space by the year 2012. Outside of the U.S. there have only been 12 other women astronauts that have been in space. As of 2009, about 10 percent of astronauts in NASA are women.
Major events
1959: Brigadier General Don Flickinger, a member of the NASA Special Advisory Committee on Life Sciences, along with Dr. W. Randolph “Randy” Lovelace II, inaugurated the Woman in Space Earliest (WISE) program
1960: Dr. Nancy Grace Roman became the first woman to hold an executive position at NASA
1961: Jerrie Cobb was appointed as a NASA administration consultant
1961: John F. Kennedy stated in the American Girl magazine that both sexes are needed in America's space program
1963: Soviet cosmonaut Valentina Tereshkova became the first woman to be in space
1978: Anna Fisher, Shannon W. Lucid, Judith A. Resnik, Sally K. Ride, Margaret R. Seddon, and Kathryn D. Sullivan chosen to become astronauts
1983 (June 18): Sally Ride became the first US woman to fly to space
1984: Kathryn Dwyer Sullivan became the first US woman to walk in space
1986 (January): Judith A. Resnik and payload specialist, Sharon Christa McAuliffe, died in the Challenger accident.
1992 (September 11): Mae Jemison became first black woman in space
1993: Ellen Ochoa became the first Hispanic woman in space
1994: Carolyn Huntoon became the first woman center director at NASA (at Johnson Space Center)
1996: Shannon Lucid became the first woman to receive the Congressional Space Medal of Honor
1999 (July 20): Eileen Collins became the first US woman to command a spacecraft
2005: Shana Dale became the first woman Deputy Administrator of NASA
2007: Peggy Whitson became the first woman to command the International Space Station
Active Women Astronauts
Serena M. Auñón-Chancellor, MD
Tracy Caldwell Dyson, PhD
Jeanette J. Epps, PhD
Christina Hammock Koch
Nicole Mann, LtCol, U.S. Marine Corps
Megan McArthur, PhD
Anne C. McClain, Lt Col, U.S. Army
Jessica U. Meir, PhD
Kathleen Rubins, PhD
Shannon Walker, PhD
Stephanie D. Wilson
Sunita L. Williams, Captain, U.S. Navy, Ret.
See also
NASA
Women's history
References
External links
"The Women of NASA". National Women's History Museum.
"Women @ NASA" NASA
NASA
Women in science and technology
NASA
People by government agency | Women in NASA | Technology | 2,330 |
1,120,348 | https://en.wikipedia.org/wiki/MKM%20steel | MKM steel, an alloy containing nickel and aluminum, was developed in 1931 by metallurgist Tokushichi Mishima (三島徳七). While conducting research into the properties of nickel, Mishima discovered that a strongly magnetic steel could be created by adding aluminum to non-magnetic nickel steel.
Characteristics
The developers claim MKM steel is tough and durable, inexpensive to produce, maintains strong magnetism when miniaturized and can produce a stable magnetic force in spite of temperature changes or vibration. MKM steel is similar to Alnico.
Acronym
MKM is an acronym for Mishima Kizumi Magnetic, 'Kizumi (喜住)' being the inventor's childhood surname.
References
Steels
Magnetic alloys
Ferromagnetic materials
1931 introductions
Aluminium alloys
Japanese inventions | MKM steel | Physics,Chemistry,Materials_science,Engineering | 160 |
1,076,955 | https://en.wikipedia.org/wiki/Warp%20%28video%20games%29 | A warp, also known as a portal or teleporter, is an element in video game design that allows a player character instant travel between two locations or levels. A specific area that allows such travel is referred to as a warp zone. A warp zone might be a secret passage, accessible only to players capable of finding it, but they are also commonly used as a primary mean of travel in certain games. Warps might be deliberately installed within puzzles, be used to avoid danger in sections of a game that have been previously accomplished, be something a player can abuse for cheating, or be used as a punishment to a player straying from the "correct" path.
In some games, a player can only use warps to travel to locations they have visited before. Because of this, a player has to make the journey by normal route at least once, but are not required to travel the same paths again if they need to revisit earlier areas in the game. Finding warp zones might become a natural goal of a gaming session, being used as a checkpoint.
History
Though it is unclear which video game first made use of teleportation areas or devices, the element has been traced back to MUDs, where it allowed connected rooms to not be "topologically correct" if necessary. A predecessor appears in the board game Cluedo (1949), where secret passages connect the rooms in the corner of the floorplan to each other. While developing his game Crystal Castles (1983), Franz Lanzinger watched people play Tempest and having to take long periods of time to get to the level of play they wanted to be at. This inspired Lanzinger to include warps in Crystal Castles, to let advanced players get to the more difficult stages early and to keep game time low for more income on a coin-op arcade game.
The element was later popularized by Super Mario Bros., in which secret areas referred to within the game as warp zones allowed players to skip forward through the game.
Advantages and criticism
Author Luke Cuddy states that warps are used to keep the players entertained by "allowing them to jump to the next gameplay goal, straight into the action." However, he has also criticized them for robbing the player of the sensation of "being in" a virtual world, stating that "[b]y emphasizing destination over the places in between, warping encourages a 'quick visit, move-on-to-the-next-place' mentality that frames space as disposable." Warps discourage exploration and may weaken the player's knowledge of spatial relationships.
Ernest Adams critiques possible unexpected behavior by warp zones: "Teleporters can further complicate matters by not always working the same way, teleporting the player to one place the first time they are used, but to somewhere else the second time, and so on. They can also be one-way or two-way, teleporting players somewhere with no way to get back, or allowing them to teleport again."
On the other hand, a 2009 paper by Alison Gazzard from the University of Hertfordshire provides some advantages of warps. Gazzard points that warps can be used to create puzzles and Easter eggs, saying that warps allow the player to "move through spaces in a way not possible in the real world, and discover ‘magical’ ways of traveling through the gamespace." Gazzard points out that warps make "travel from different parts of the game quicker" as well as act as a reward to allow to the player to access certain areas.
Despite the linear simplicity of Super Mario Bros., the game has been described as having a "surprising amount of depth and spatial complexity" in part due to secret warp zones found through the game. Portal is a critically acclaimed game that uses warps as its core gameplay mechanic.
See also
Teleportation
Teleportation in fiction
Wraparound (video games)
Hyperlinks in virtual worlds
References
Video game terminology | Warp (video games) | Technology | 819 |
36,585,368 | https://en.wikipedia.org/wiki/RCW%2088 | RCW 88 is an emission nebula in the southern constellation of Circinus that first appeared in the 1960 astronomical catalogue by Rodgers, Campbell & Whiteoak (RCW) of Hα-emission regions within the southern Milky Way. Earlier observers, like James Wray in 1966, misclassified this as a likely 12.0v magnitude planetary nebula, but later spectroscopic investigations revealed this as a diffuse nebulae. RCW 88 was then to be identified by the infrared satellite IRAS as an HII region.
Deep red images reveal that the inner nebula is divided into two parts by a central dark lane, and there is evidence of a larger halo of fainter nebulosity extending perhaps out to 10 arcmin. The RCW catalogue states the Hα image size is 3'×2.
RCW 88 is located about 3300 parsecs (10,000 light years) from us, though other estimates place this at a closer 1800±300 pc. or 1800±200 pc. Assuming the former distance and the diameter as 5'-6' across, finds by simple trigonometry the true size subtends a minimum of 5±1 parsecs (16±3 light-years.) This small emission nebula shows a mean radial velocity of −18 km.s−1, and is also a faint radio source that was identified by Lloyd Higgs in 1971. Due to the large distance from us, astronomers have made few studies into the nature of RCW 88.
Field Star
There is a 10.8v magnitude star identified as TYC 8702-56-1 positioned at RA : 15h 07m 25.1s Dec. : –57° 48' 32" (2000), place 137 arc seconds southwest of the centre of the bright nebulosity. It is unlikely that this star is associated with the nebulosity being probably a field star.
References
Emission nebulae
Circinus
Star-forming regions | RCW 88 | Astronomy | 402 |
17,639,871 | https://en.wikipedia.org/wiki/VIA%20OpenBook | VIA OpenBook is a laptop reference design from VIA Technologies, announced in 2008. The laptop case design was released as open source.
Specifications
Dimensions
Dimensions: 24.0w x 17.5d x 3.62h cm (at battery), (9.45w x 6.89d x 1.43h in)
Weight: under 1 kg
Processor, memory
Processor: 1.0 GHz VIA Nano ULV
Chipset: VIA VX800 unified
Memory: DDR2 SO-DIMM up to 2 GB
Hard disk: 160 GB or above
Networking, wireless
Networking: 10/100/1000 Mbit/s Broadcom Giga NIC Ethernet
Wireless: 802.11b/g Broadcom or 802.16e GCT
Bluetooth, Wi-Fi, WiMAX, EV-DO /W-CDMA, HSDPA, GPS options.
Peripherals
Screen: LED 8.9" WVGA 1024 x 600
Graphics: VIA Chrome9 HC3 DX9 3D engine with shared system memory up to 256 MB
Card reader: 4-in-1 embedded
USB: 3 x (Ver. 2.0 Type A Port)
Audio: Realtek HD audio codec, 2 speakers
Audio jacks: 1 microphone-in, 1 headphone out
Camera: CCD 2.01 megapixel, dual-headed rotary
Battery
Battery: 4 cell
See also
Open-design movement
External links
VIA Unveils VIA OpenBook Mini-Note Reference Design (Press Release)
References
Subnotebooks
VIA Technologies
Netbooks
Open design
Computer-related introductions in 2008 | VIA OpenBook | Engineering | 324 |
16,592,741 | https://en.wikipedia.org/wiki/Stonewalling | Stonewalling is a refusal to communicate or cooperate. Such behaviour occurs in situations such as marriage counselling, diplomatic negotiations, politics and legal cases. Body language may indicate and reinforce this by avoiding contact and engagement with the other party. People use deflection in a conversation in order to render a conversation pointless and insignificant. Tactics in stonewalling include giving sparse, vague responses; refusing to answer questions; and responding to questions with additional questions. Stonewalling can be used as a stalling tactic rather than an avoidance tactic.
Politics
In politics, stonewalling is used to refuse to answer or comment on certain questions about policy and issues, especially when a committee or politician is under investigation. Stonewalling in politics and business can sometimes create a critical advantage. William Safire wrote that stonewalling was originally used in Australian cricket, but its use during president Richard Nixon's Watergate affair brought it into usage in American politics as a "refusal to comment".
Stonewalling can also be seen as filibustering, or stalling the passage of bills until they become outdated or changed when engaging in parliamentary procedures.
Relationships
When one or both members of a couple refuse to communicate, this can mark the final step in the breakdown of their relationship. John Gottman characterised this stage as the fourth horseman in his Cascade Model of Relational Dissolution. In his studies, "stonewalling" was overwhelmingly done by men, with women overwhelmingly using "criticism". In his studies, men's physiology reached a state of arousal before "stonewalling", while the female partner showed a physiological reaction of increased heart rate after her partner had "stonewalled" her. Gottman goes into detail on The Four Horsemen in his book, "The Seven Principles of Making a Marriage Work".
As stonewalling persists in a relationship and becomes a continuous cycle, the negative effects of stonewalling outweigh the positive effects, it then becomes the greatest predictor of divorce in a marriage. When one or both partners in a relationship stonewall, their ability to hear each other or listen to each other's disagreement, concern, side or argument, reduces their ability to engage and help address the situation. Stonewalling can be detrimental to relationships because there is often no chance for resolution of conflict.
When stonewalling occurs, it has both a physiological and psychological effect on the person who is stonewalling. Physiologically, the person who is stonewalling can completely shut down, particularly when it is used as a self-soothing mechanism. The person doing stonewalling may be aware or unaware that this is taking place, because of an increase in adrenaline due to an increase in stress, where the person can either engage or flee the situation. Because stonewalling is a physiological reaction, the stonewalling can be thought of as a fight or flight response. Psychologically, stonewalling is a defense mechanism for preserving one's self and emotions.
Other signs of stonewalling are silence, mumbling monotone utterances, changing the subject and physically removing oneself from the situation (e.g., leaving the room).
Witnesses
Witnesses in court or other legal actions may refuse to cooperate with a counsel by withholding information and refusing to testify. Prosecutors may try to break their united front by offering incentives such as immunity from prosecution. Another tactic of stonewalling is to provide the jurors with misleading information or withhold possibly self-incriminating information. When witnesses use the stonewalling practice, they are usually in an agreement with other witnesses to do the same in order for the tactic to be effective.
See also
Cold shoulder
Dumb insolence
Filibuster
Obstructionism
Passive aggression
Running out the clock
Send to Coventry
Silent treatment
Social rejection
Spiral of silence
References
Further reading
Human behavior
Social psychology
Shunning
Silence | Stonewalling | Biology | 780 |
11,757,410 | https://en.wikipedia.org/wiki/Phragmidium%20rubi-idaei | Phragmidium rubi-idaei is a plant pathogen infecting caneberries, Rubus spp.
References
Fungal plant pathogens and diseases
Small fruit diseases
Pucciniales
Taxa named by Augustin Pyramus de Candolle
Fungi described in 1815
Fungus species | Phragmidium rubi-idaei | Biology | 57 |
13,595,249 | https://en.wikipedia.org/wiki/Kilokaiser | The Kaiser (K) is a unit of energy. A common form is kiloKaiser (kK). 1 kK = 1000 cm−1. ( cm−1, wavenumber or inverse wavelength.) This unit is most commonly used with respect to energy transitions between electronic states in inorganic complexes.
See also
Wavenumber
Kilokaiser is a common but incorrect spelling of the unit KiloKayser, which equals 1000 wavenumber (cm−1). The unit is named after Heinrich Gustav Johannes Kayser (16 March 1853 – 14 October 1940), a German physicist.
References
Scarlata, Suzanne; Rakesh Gupta; et al. Biochemistry, Vol. 35, No. 47, 1996
Fuguet, Elisabet; Carla Ráfols; et al. Langmuir, Vol. 19, No. 1, 2003
Douglas, Bodie; Darl McDaniel; and John Alexander. Concepts and Models of Inorganic Chemistry. 3rd ed. John Wiley & Sons, Inc. New York. 1994.
Units of energy | Kilokaiser | Mathematics | 214 |
15,664,920 | https://en.wikipedia.org/wiki/Ammonium%20polyphosphate | Ammonium polyphosphate is an inorganic salt of polyphosphoric acid and ammonia containing both chains and possibly branching. Its chemical formula is H(NH4PO3)nOH showing that each monomer consists of an orthophosphate radical of a phosphorus atom with three oxygens and one negative charge neutralized by an ammonium cation leaving two bonds free to polymerize. In the branched cases some monomers are missing the ammonium anion and instead link to three other monomers.
The properties of ammonium polyphosphate depend on the number of monomers in each molecule and to a degree on how often it branches. Shorter chains (n < 100) are more water sensitive and less thermally stable than longer chains (n > 1000), but short polymer chains (e.g. pyro-, tripoly-, and tetrapoly-) are more soluble and show increasing solubility with increasing chain length.
Ammonium polyphosphate can be prepared by reacting concentrated phosphoric acid with ammonia. However, iron and aluminum impurities, soluble in concentrated phosphoric acid, form gelatinous precipitates or "sludges" in ammonium polyphosphate at pH between 5 and 7. Other metal impurities such as copper, chromium, magnesium, and zinc form granular precipitates. However, depending on the degree of polymerization, ammonium polyphosphate can act as a chelating agent to keep certain metal ions dissolved in solution.
Ammonium polyphosphate is used as a food additive, emulsifier, (E number: E545) and as a fertilizer.
Ammonium polyphosphate (APP) is also used as a flame retardant in many applications such as paints and coatings, and in a variety of polymers: the most important ones are polyolefins, and particularly polypropylene, where APP is part of intumescent systems. Compounding with APP-based flame retardants in polypropylene is described in. Further applications are thermosets, where APP is used in unsaturated polyesters and gel coats (APP blends with synergists), epoxies and polyurethane castings (intumescent systems). APP is also applied to flame retard polyurethane foams.
Ammonium polyphosphates used as flame retardants in polymers have long chains and a specific crystallinity (Form II). They start to decompose at 240 °C to form ammonia and phosphoric acid. The phosphoric acid acts as an acid catalyst in the dehydration of carbon-based poly-alcohols, such as cellulose in wood. The phosphoric acid reacts with alcohol groups to form heat-unstable phosphate esters. The esters decompose to release carbon dioxide and regenerate the phosphoric acid catalyst . In the gas phase, the release of non-flammable carbon dioxide helps to dilute the oxygen of the air and flammable decomposition products of the material that is burning. In the condensed phase, the resultant carbonaceous char helps to shield the underlying polymer from attack by oxygen and radiant heat. Use as an intumescent is achieved when combined with starch-based materials such as pentaerythritol and melamine as expanding agents. The mechanisms of intumescence and the mode of action of APP are described in a series of publications.
References
External links
Food additives
Polymers
Ammonium compounds
Inorganic fertilizers
Flame retardants | Ammonium polyphosphate | Chemistry,Materials_science | 760 |
49,957,896 | https://en.wikipedia.org/wiki/Chroma%20feature | In Western music, the term chroma feature or chromagram closely relates to twelve different pitch classes. Chroma-based features, which are also referred to as "pitch class profiles", are a powerful tool for analyzing music whose pitches can be meaningfully categorized (often into twelve categories) and whose tuning approximates to the equal-tempered scale. One main property of chroma features is that they capture harmonic and melodic characteristics of music, while being robust to changes in timbre and instrumentation.
Definition
The underlying observation is that humans perceive two musical pitches as similar in color if they differ by an octave. Based on this observation, a pitch can be separated into two components, which are referred to as tone height and chroma. Assuming the equal-tempered scale, one considers twelve chroma values represented by the set
{C, C, D, D, E, F, F, G, G, A, A, B}
that consists of the twelve pitch spelling attributes as used in Western music notation. Note that in the equal-tempered scale different pitch spellings such
C and D refer to the same chroma. Enumerating the chroma values, one can identify the set of chroma values with the set of integers {1,2,...,12}, where 1 refers to chroma C, 2 to C, and so on. A pitch class is defined as the set of all pitches that share the same chroma. For example, using the scientific pitch notation, the pitch class corresponding to the chroma C is the set
{..., C−2, C−1, C0, C1, C2, C3 ...}
consisting of all pitches separated by an integer number of octaves. Given a music representation (e.g. a musical score or an audio recording), the main idea of chroma features is to aggregate for a given local time window (e.g. specified in beats or in seconds) all information that relates to a given chroma into a single coefficient. Shifting the time window across the music representation results in a sequence of chroma features each expressing how the representation's pitch content within the time window is spread over the twelve chroma bands. The resulting time-chroma representation is also referred to as chromagram. The figure above shows chromagrams for a C-major scale, once obtained from a musical score and once from an audio recording. Because of the close relation between the terms chroma and pitch class, chroma features are also referred to as pitch class profiles.
Applications
Identifying pitches that differ by an octave, chroma features show a high degree of robustness to variations in timbre and closely correlate to the musical aspect of harmony. This is the reason why chroma features are a well-established tool for processing and analyzing music data. For example, basically every chord recognition procedure relies on some kind of chroma representation. Also, chroma features have become the de facto standard for tasks such as music alignment and synchronization as well as audio structure analysis. Finally, chroma features have turned out to be a powerful mid-level feature representation in content-based audio retrieval such as cover song
identification, audio matching or
audio hashing.
Computation of audio chromagrams
There are many ways for converting an audio recording into a chromagram. For example, the conversion of an audio recording into a chroma representation (or chromagram) may be performed either by using short-time Fourier transforms in combination with binning strategies or by employing suitable multirate filter banks.
Furthermore, the properties of chroma features can be significantly changed by
introducing suitable pre- and post-processing steps modifying spectral, temporal,
and dynamical aspects. This leads to a large number of chroma variants, which
may show a quite different behavior in the context of a specific music analysis scenario.
See also
Time-frequency analysis
Time-frequency analysis for music signal
Pitch (music)
Musical theory
References
External links
Chroma Toolbox Free MATLAB implementations of various chroma types of pitch-based and chroma-based audio features
Harmonic Pitch Class Profile plugin
Music information retrieval
Music technology
Musicology
Time–frequency analysis | Chroma feature | Physics | 889 |
36,949,627 | https://en.wikipedia.org/wiki/6%20Ceti | 6 Ceti is a single star in the equatorial constellation of Cetus. It is visible to the naked eye with an apparent magnitude of 4.89. The annual parallax shift as measured from Earth's orbit is 53.34 mas, which yields a distance estimate of 61.1 light years. The star is moving further from the Sun with a constant radial velocity of +16.70 km/s. It is one of the IAU's standard velocity stars.
Gray et al. (2006) assigned this star a stellar classification of , indicating it is an F-type main-sequence star with an underabundance of iron and the CH molecule in its stellar atmosphere. It is about 4.2 billion years old with 1.12 times the mass of the Sun and is spinning with a projected rotational velocity of 4.88 km/s. The star is radiating 3.34 times the Sun's luminosity from its photosphere at an effective temperature of about 6,289 K.
References
F-type main-sequence stars
Cetus
Durchmusterung objects
Ceti, 06
0010
000693
000910
0033
TIC objects | 6 Ceti | Astronomy | 242 |
36,537,922 | https://en.wikipedia.org/wiki/7%20Aquilae | 7 Aquilae is a star in the equatorial constellation of Aquila, located 359 light years away from the Sun. 7 Aquilae is the Flamsteed designation. It is visible to the naked eye as a faint, yellow-white hued star with a baseline apparent visual magnitude of 6.9. The star is moving closer to the Earth with a heliocentric radial velocity of .
Houk and Swift (1999) find a stellar classification of F0IV, matching an F-type subgiant star that has exhausted the hydrogen at its core and is evolving into a giant. Fox Machado et al. (2010) found a class of F0V, suggesting it is still a main sequence star. Ennio Poretti et al. discovered 7 Aquilae is a variable star while searching for targets to be observed by the CoRoT satellite, and published their discovery in 2003. It is a pulsating variable star of the Delta Scuti type. It has double the mass of the Sun and 2.7 times the Sun's radius. The detection of an infrared excess suggests a debris disk with a mean temperature of 140 K is orbiting about away from the host star.
References
F-type main-sequence stars
F-type subgiants
Delta Scuti variables
Circumstellar disks
Aquila (constellation)
Aquilae, V1728
BD-03 4390
Aquilae, 07
174532
092501 | 7 Aquilae | Astronomy | 300 |
28,258,369 | https://en.wikipedia.org/wiki/SMBH%2C%20Inc. | SMBH, Inc. is a full-service structural engineering firm located in Columbus, Ohio. Providing structural engineering services for architects, contractors and building owners, SMBH, Inc. has experience designing educational facilities, medical centers, courthouses and commercial and residential buildings. Since 1972, SMBH, Inc. has served the architectural and construction communities in Ohio and surrounding states. SMBH, Inc. has worked with architectural firms such as Graham Gund's Gund Partnership, Mack Scogin Merrill Elam Architects, Peter Eisenman, and Robert A.M. Stern.
History
SMBH, Inc. located in Columbus, Ohio, was founded in 1972 as a structural engineering firm for the architectural industry. Founded as Lantz and Jones, the firm changed its name to Lantz Jones and Nebraska, Inc. in 1975 to reflect a change in ownership. Lantz Jones and Nebraska had offices in Charleston, West Virginia and Stuart, Florida. SMBH, Inc. still performs work in these areas, but now operates out of the Columbus, Ohio office. During the past two decades, the ownership has transitioned from Bill Lantz, Tom Jones and Jim Nebraska to Stephen J. Metz, Bob Baumann, and Jon Beier. The ownership transition prompted the name change to Shelley Metz Baumann Hawk, Inc. in 2005 and in 2013, the company name was shortened to SMBH, Inc. In March 2013, Bill Shelley stepped down from his role as president of the company. He was replaced by Stephen Metz.
Major Projects
SMBH, Inc. has worked on the following projects: Franklin County Courthouse, located in Columbus, Ohio, the William Oxley Thompson Memorial Library, located on Ohio State University campus, the Polaris Hilton Conference Center, located in Columbus, Ohio, Limited Brands World Headquarters & Distribution Center, located in Columbus, Ohio, Hocking College Residence Hall, located on the Hocking College campus, the Austin Eldon Knowlton School of Architecture, located on The Ohio State University campus, Grange Insurance Headquarters Expansion Office and Parking Garage, located in downtown Columbus, Ohio, Nationwide Children’s Hospital Research Building 3, located in Columbus, Ohio, Broad Street United Methodist Church, located in Columbus, Ohio, Farmer School of Business, located at Miami University, Ohio School for the Deaf/Ohio State School for the Blind, located in Columbus, Ohio, Linden-McKinley High School, Columbus, Ohio Public Schools, the South High Rise residence halls located on the campus of the Ohio State University, and the Morris Hospital, located in Morris, Illinois.
Sustainable Design
SMBH, Inc. has been involved with sustainable and Leadership in Energy and Environmental Design (LEED) certified projects, as well as team members who are LEED Accredited Professionals.
Examples of green building and sustainable design includes work on the following projects: Student Academic Services Office Building; Columbus, Ohio, Franklin County Courthouse, Columbus, Ohio; West Side Family Health Center, Columbus, Ohio; Grange Insurance Audubon Center, Columbus, Ohio; Columbus State Community College – Academic Center E, Delaware, Ohio; Ohio School for the Blind/Ohio State School for the Deaf, Columbus, Ohio; Mid Ohio Food Bank, Columbus, Ohio; Hocking College – Energy Institute, Logan, Ohio; Miami University – Farmer School of Business Building, Oxford, Ohio.
Associations
SMBH, Inc. are members of the following associations: American Council of Engineering Companies (ACEC), American Institute of Architects (AIA) - Columbus, Ohio, American Institute of Architects (AIA)- West Virginia, American Institute of Steel Construction (AISC), American Concrete Institute (ACI), American Society of Civil Engineers (ASCE), International Concrete Repair Institute (ICRI), National Trust for Historic Preservation, Post-Tensioning Institute (PTI), Structural Engineers Association of Ohio (SEAo0), Tilt-Up Concrete Association (TCA).
References
External links
SMBH, Inc.
Structural engineering
Companies based in Ohio
Institution of Structural Engineers
Construction and civil engineering companies of the United States | SMBH, Inc. | Engineering | 821 |
70,735,451 | https://en.wikipedia.org/wiki/Neohygrocybe%20nitrata | Neohygrocybe nitrata is a species of agaric (gilled mushroom) in the family Hygrophoraceae. It has been given the recommended English name of nitrous waxcap, based on its smell. The species has a European distribution, occurring mainly in agriculturally unimproved grassland. Threats to its habitat have resulted in the species being assessed as globally "vulnerable" on the IUCN Red List of Threatened Species.
Taxonomy
The species was first described in 1801 by mycologist Christiaan Hendrik Persoon as Agaricus nitratus. Czech mycologist Josef Herink transferred it to the genus Neohygrocybe in 1958, but this combination was not validly published. It was later validly combined by Alexander Kovalenko in 1989.
Recent molecular research, based on cladistic analysis of DNA sequences, has confirmed that Neohygrocybe nitrata is a distinct species but does not belong in Hygrocybe sensu stricto.
Description
Basidiocarps are agaricoid, up to 60 mm (5 in) tall, the cap convex to flat, up to 70 mm (3 in) across. The cap surface is smooth, dry, sometimes breaking up into scales when old, grey-brown. The lamellae (gills) are waxy, pale grey to buff with whiter margins. The stipe (stem) is smooth, pale grey to buff, lacking a ring. The spore print is white, the spores (under a microscope) smooth, inamyloid, ellipsoid, measuring about 8 to 9 by 4.5 to 5.5 μm. Basidiocarps have a distinctly nitrous smell.
Similar species
Neohygrocybe pseudoingrata, recently described from the Czech Republic and Slovakia, has a similar nitrous smell, but basidiocarps are typically larger and paler with white stipes. The more widespread European Neohygrocybe ingrata has a context that stains reddish.
Distribution and habitat
The Nitrous Waxcap is widespread but generally rare throughout Europe. Like other waxcaps, it occurs in old, agriculturally unimproved, short-sward grassland (pastures and lawns).
Recent research suggests waxcaps are neither mycorrhizal nor saprotrophic but may be associated with mosses.
Conservation
Neohygrocybe nitrata is typical of waxcap grasslands, a declining habitat due to changing agricultural practices. As a result, the species is of global conservation concern and is listed as "vulnerable" on the IUCN Red List of Threatened Species. Neohygrocybe nitrata also appears on the official or provisional national red lists of threatened fungi in several European countries, including Croatia, Czech Republic, Denmark, Germany, and Norway.
See also
List of Hygrocybe species
List of fungi by conservation status
References
Fungi of Europe
Fungi described in 1801
Hygrophoraceae
Taxa named by Christiaan Hendrik Persoon
Fungus species | Neohygrocybe nitrata | Biology | 635 |
22,977,267 | https://en.wikipedia.org/wiki/Streptamer | Strep Tamer is a technology which allows the reversible isolation and staining of antigen-specific T-cells. This technology combines a current T-cell isolation method with the Strep-Tag technology. In principle, the T-cells are separated by establishing a specific interaction between the T-cell of interest and a molecule, that is conjugated to a marker which enables the isolation. The reversibility of this interaction and the low temperatures at which it is performed allow for the isolation and characterization of functional T-cells. Because T-cells remain phenotypically and functionally indistinguishable from untreated cells, this method offers modern strategies in clinical and basic T-cell research.
Classic methods in T cell research
T cells play an important role in the adaptive immune system. They are capable of orchestrating, regulating and coordinating complex immune responses. A wide array of clinically relevant aspects are associated with the function or malfunction of T-cells: Autoimmune diseases, control of viral or bacterial pathogens, development of cancer or graft versus host responses.
Over the past years, various methods (ELISpot Assay, intracellular cytokine staining, secretion assay) have been developed for the identification of T cells, but only major histocompatibility complex (MHC) procedures allow identification and purification of antigen-specific T cells independent of their functional status.
In principle, MHC procedures are using the T cell receptor (TCR) ligand, which is the MHC-peptide complex, as a staining probe. The MHC interacts with the TCR, which in turn is expressed on the T cells. Because TCR-MHC interactions have only a very weak affinity towards each other, monomeric MHC-epitope complexes cannot provide stable binding. This problem can be solved by using multimerized MHC-epitopes, which increases the binding avidity and therefore allows stable binding. Fluorochromes conjugated to the MHC-multimers then can be used for identification of T cells by flow cytometry.
Nowadays, MHC molecules can be produced recombinantly together with the antigenic peptides which are known for a fast-growing number of diseases.
The Streptamer technology
The Streptamer backbone
The Streptamer staining principle combines the classic method of T cell isolation by MHC-multimers with the Strep-tag/Strep-Tactin technology. The Strep-tag is a short peptide sequence that displays moderate binding affinity for the biotin-binding site of a mutated streptavidin molecule, called Strep-Tactin. For the Streptamer technology, the Strep-Tactin molecules are multimerized and form the "backbone", thus creating a platform for binding to strep-tagged proteins. Additionally, the Strep-Tactin backbone has a fluorescent label to allow flow cytometry analysis. Incubation of MHC-Strep-tag fusion proteins with the Strep-Tactin backbone results in the formation of a MHC-multimer, which is capable for antigen-specific staining of T cells.
Reversible staining
Because the molecule d-biotin has a much higher affinity to Strep-Tactin than Strep-tag, it can effectively compete for the binding site. Therefore, a MHC multimer based on the interaction of Strep-tag with Strep-Tactin is easily disrupted in the presence of relatively low concentrations of d-biotin. Without the Strep-Tactin backbone, the single MHC-Strep-tag fusion proteins spontaneously detach from the TCR of the T cell, because of weak binding affinities (monomeric MHC-epitope complexes cannot provide stable binding, see above).
References
Protein methods
Biotechnology
Molecular biology techniques
Biochemistry
Laboratory techniques | Streptamer | Chemistry,Biology | 832 |
40,332,450 | https://en.wikipedia.org/wiki/The%20Rape%20of%20the%20Daughters%20of%20Leucippus | The Rape of the Daughters of Leucippus is a 1618 painting by Peter Paul Rubens and Jan Wildens. It is displayed at the Alte Pinakothek in Munich.
History
The painting was bought in Antwerp in 1716 by Johann Wilhelm, Elector Palatine. Initially sent to Mannheim, by 1805/06 it had reached Munich.
The landscape specialist Jan Wildens painted the landscape.
Description
The painting depicts the mortal Castor and the immortal Pollux abducting Phoebe and Hilaeira, daughters of Leucippus of Messenia. Castor the horse-tamer is recognisable from his armour, whilst Pollux the boxer is shown with a bare and free upper body. They are also distinguished by their horses—Castor's is well-behaved and supported by a putto, whereas Pollux's is rearing. The putto's black wing shows the twins' ultimate fate.
In the painting, Phoebe and Hilaeira do not have distinguishing attributes. From the literature on Greek myths, however, we learn that Phoebe bore a son, Mnesleos, to Pollux, and Hilaeira bore a son, Anogon, to Castor. It would seem therefore, from the directions of the twins' fixed stares, that the daughter in the lower position, with her back to us, is Phoebe, and the daughter in the upper position, displaying a frontal view, is Hilaeira.
Bibliography
Alte Pinakothek-Ausgewählte Werke; [Editor: Bayerischen Staatsgemäldesammlungen, Authors: Marcus Dekiert, Nina Schleif], München; Pinakothek-DuMont, 2005, ,
50 Klassiker: Gemälde, H. Johannsen, Gerstenberg, 2001, .
External links
Raub der Töchter des Leukippos , Bayerische Staatsgemäldesammlungen, Alte Pinakothek München
1618 paintings
Mythological paintings by Peter Paul Rubens
Collection of the Alte Pinakothek
Paintings of Greek myths
Horses in art
Nude art
Castor and Pollux
Putti | The Rape of the Daughters of Leucippus | Astronomy | 442 |
9,801,876 | https://en.wikipedia.org/wiki/Simultaneous%20nitrification%E2%80%93denitrification | Simultaneous nitrification–denitrification (SNdN) is a wastewater treatment process. Microbial simultaneous nitrification-denitrification is the conversion of the ammonium ion to nitrogen gas in a single bioreactor. The process is dependent on floc characteristics, reaction kinetics, mass loading of readily biodegradable chemical oxygen demand {rbCOD}, and the dissolved oxygen {DO} concentration.
Microbiology
The oxidation of the ammonium to nitrogen gas has been achieved with attached growth and suspended growth wastewater treatment processes. The most common bacteria responsible for the two step conversion are the autotrophic organisms, Nitrosomonas and Nitrobacter, and many different heterotrophs. The former obtain energy from the oxidation of ammonia, obtain carbon from CO2, and use oxygen as the electron acceptor. They are termed autotrophic because of their carbon source and termed aerobes because of their aerobic environment. The heterotrophic organisms are responsible for denitrification or the reduction of nitrate, NO3−, to nitrogen gas, N2. They use carbon from complex organic compounds, prefer low to zero dissolved oxygen, and use nitrate as the electron acceptor.
Systems Design
The most common design uses two different basins: one catering to the autotrophic bacteria and the second to the heterotrophic bacteria. However, SNdN accommodates to both in one basin with strict control of DO. This has been done in two common approaches. One is to develop an oxygen gradient by adding oxygen in one location in the basin. Near the O2 injection point, a high DO concentration is maintained allowing for nitrification and oxidation of other organic compounds. Oxygen is the electron acceptor and is depleted. The DO level in localized environments decreases with increasing distance from the injection point. In these low DO locations, the heterotrophic bacteria complete the nitrogen removal. The Orbal process is a technology in practice today using this method. The other method is to produce an oxygen gradient within the bio floc. The DO concentration remains high in the outside rings of the floc where nitrification occurs but low in the inner rings of the floc where denitrification occurs. This method is dependent on the floc size and characteristics; however controlling flocs is not well understood and is an active field of study
Typically, SNdN has slower ammonia and nitrate utilization rates as compared to separate basin designs because only a fraction of the total biomass is participating in either the nitrification or the denitrification steps. The SNdN limitation due to partial active biomass has led to research in novel bacteria and system designs. Huang achieved significant ammonia removal in an attached growth process with ciliated columns packed with granular sulfur where the denitrifying bacteria used the sulfur as the electron donor and nitrate as the electron acceptor. Another well established pathway is via autotrophic denitrifying bacteria in the process termed the Anammox process. It is typically used for high ammonia strength wastewater.
Notes
References
Nitrogen cycle
Water treatment | Simultaneous nitrification–denitrification | Chemistry,Engineering,Environmental_science | 629 |
3,551,139 | https://en.wikipedia.org/wiki/Spiro%20compound | In organic chemistry, spiro compounds are compounds that have at least two molecular rings sharing one common atom. Simple spiro compounds are bicyclic (having just two rings). The presence of only one common atom connecting the two rings distinguishes spiro compounds from other bicyclics. Spiro compounds may be fully carbocyclic (all carbon) or heterocyclic (having one or more non-carbon atom). One common type of spiro compound encountered in educational settings is a heterocyclic one— the acetal formed by reaction of a diol with a cyclic ketone.
The common atom that connects the two (or sometimes three) rings is called the spiro atom. In carbocyclic spiro compounds like spiro[5.5]undecane, the spiro-atom is a quaternary carbon, and as the -ane ending implies, these are the types of molecules to which the name spirane was first applied (though it is now used general of all spiro compounds). The two rings sharing the spiro atom are most often different, although they can be identical [e.g., spiro[5.5]undecane and spiropentadiene, at right].
Carbocyclic spiro compounds
Bicyclic ring structures in organic chemistry that have two fully carbocyclic (all carbon) rings connected through a carbon atom are the usual focus of the topic of spirocycles. Simple parent spirocycles include spiropentane, spirohexane, etc. up to spiroundecane. Several exist as isomers. Lower members of the class are strained. The symmetric isomer of spiroundecane is not.
Some spirocyclic compounds occur as natural products.
Preparation
The spirocyclic core is usually prepared by dialkylation of an activated carbon center. The dialkylating group is often a 1,3-, 1,4-, etc. dihalide. In some cases the dialkylating group is a dilithio reagent, such as 1,5-dilithiopentane. For generating spirocycles containing a cyclopropane ring, cyclopropanation with cyclic carbenoids has been demonstrated.
Spiro compounds are often prepared by diverse rearrangement reactions. For example, the pinacol-pinacolone rearrangement is illustrated below. is employed in the preparation of aspiro[4.5]decane.].
Heterocyclic spiro compounds
Spiro compounds are considered heterocyclic if the spiro atom or any atom in either ring are not carbon atoms. Cases with a spiro heteroatom such as boron, silicon, and nitrogen (but also other Group IVA [14] are often trivial to prepare. Many borate esters derived from glycols illustrate this case. Likewise, a tetravalent neutral silicon and quaternary nitrogen atom (ammonium cation) can be the spiro center. Many such compounds have been described.
Particularly common spiro compounds are ketal (acetal) formed by condensation of cyclic ketones and diols and dithiols. A simple case is the acetal 1,4-dioxaspiro[4.5]decane from cyclohexanone and glycol. Cases of such ketals and dithioketals are common.
Chirality
Spiranes can be chiral, in various ways. First, while nevertheless appearing to be twisted, they yet may have a chiral center making them analogous to any simple chiral compound, and second, while again appearing twisted, the specific location of substituents, as with alkylidenecycloalkanes, may make a spiro compound display central chirality (rather than axial chirality resulting from the twist); third, the substituents of the rings of the spiro compound may be such that the only reason they are chiral arises solely from the twist of their rings, e.g., in the simplest bicyclic case, where two structurally identical rings are attached via their spiro atom, resulting in a twisted presentation of the two rings. Hence, in the third case, the lack of planarity described above gives rise to what is termed axial chirality in otherwise identical isomeric pair of spiro compounds, because they differ only in the right- versus left-handed "twist" of structurally identical rings (as seen in allenes, sterically hindered biaryls, and alkylidenecycloalkanes as well). Assignment of absolute configuration of spiro compounds has been challenging, but a number of each type have been unequivocally assigned.
Some spiro compounds exhibit axial chirality. Spiroatoms can be the origin of chirality even when they lack the required four different substituents normally observed in chirality. When two rings are identical the priority is determined by a slight modification of the CIP system assigning a higher priority to one ring extension and a lower priority to an extension in the other ring. When rings are dissimilar the regular rules apply.
Nomenclature and etymology
Nomenclature for spiro compounds was first discussed by Adolf von Baeyer in 1900.
IUPAC provides advice on naming of spiro compounds.
The prefix spiro denotes two rings with a spiro junction. The main method of systematic nomenclature is to follow with square brackets containing the number of atoms in the smaller ring then the number of atoms in the larger ring, separated by a period, in each case excluding the spiroatom (the atom by which the two rings are bonded) itself. Position-numbering starts with an atom of the smaller ring adjacent to the spiroatom around the atoms of that ring, then the spiroatom itself, then around the atoms of the larger ring. For example, compound A in the image is called 1-bromo-3-chlorospiro[4.5]decan-7-ol, and compound B is called 1-bromo-3-chlorospiro[3.6]decan-7-ol.
A spiro compound, or spirane, from the Latin spīra, meaning a twist or coil, is a chemical compound, typically an organic compound, that presents a twisted structure of two or more rings (a ring system), in which 2 or 3 rings are linked together by one common atom,
Further reading
For a further but less stable source of the same text that provides access to the relevant material, see , same access date.
Examples of spiro natural products and their synthesis:
References
External links | Spiro compound | Chemistry | 1,415 |
725,585 | https://en.wikipedia.org/wiki/10%20Hygiea | 10 Hygiea is a major asteroid located in the main asteroid belt. With a mean diameter of between km and a mass estimated to be 3% of the total mass of the belt, it is the fourth-largest asteroid in the Solar System by both volume and mass, and is the largest of the C-type asteroids (dark asteroids with a carbonaceous surface) in classifications that use G type for 1 Ceres. It is very close to spherical, apparently because it had re-accreted after the disruptive impact that produced the large Hygiean family of asteroids.
Observation
Despite its size, Hygiea appears very dim when observed from Earth. This is due to its dark surface and its position in the outer main belt. For this reason, six smaller asteroids were observed before Annibale de Gasparis discovered Hygiea on 12 April 1849. At most oppositions, Hygiea has a magnitude that is four magnitudes dimmer than Vesta's, and observing it typically requires at least a telescope. However, while at a perihelic opposition, it can be observed just with 10×50 binoculars as Hygiea would have a magnitude of +9.1.
Discovery and name
On 12 April 1849, in Naples, Italy, astronomer Annibale de Gasparis (age 29) discovered Hygiea. It was the first of his nine asteroid discoveries. The director of the Naples observatory, Ernesto Capocci, named the asteroid. He chose to call it Igea Borbonica ("Bourbon Hygieia"), after the Greek goddess of health, daughter of Asclepius, and in honor of the ruling family of the Kingdom of the Two Sicilies where Naples was located.
In 1852, John Russell Hind wrote that "it is universally termed Hygiea, the unnecessary appendage 'Borbonica' being dropped." The English form is an irregular spelling of Greek Hygieia or Hygeia (Latin Hygea or Hygia).
Symbol
The intended astronomical symbol for Hygiea was a zeta-shaped serpent crowned with a star, in the pipeline for Unicode 17.0 as U+1F779 the serpent and serpent drinking from a bowl are traditional symbols of the goddess Hygieia (cf. U+1F54F 🕏). In later years it was substituted with a rod of Asclepius: (a serpent twined around a staff, U+2695 ⚕), confusing Hygieia with her masculine counterpart. These symbols are now both largely obsolete. In this century, 10 Hygiea has seen some minor astrological use, and its symbol was confused once again, with Asclepsius's rod replaced by Mercury's caduceus: , though in a more elaborate form (U+2BDA ⯚) than the symbol of the planet Mercury. The caduceus has long been mistaken for the rod of Asclepius.
Physical characteristics
Observations taken with the Very Large Telescope's SPHERE imager in 2017 and 2018 revealed that Hygiea is nearly spherical and is close to a hydrostatic equilibrium shape.
Based on spectral evidence, Hygiea's surface is thought to consist of primitive carbonaceous materials similar to those found in carbonaceous chondrite meteorites. Aqueous alteration products have been detected on its surface, which could indicate the presence of water ice in the past which was heated sufficiently to melt. The primitive present surface composition indicates that Hygiea had not melted during the early period of Solar System formation. However, observations suggest Hygiea suffered a major collision early in its history that completely disrupted it, with its present spherical shape due to re-accretion of the disrupted material. No deep basins are visible in VLT images, indicating that any large craters that formed after re-accretion must have flat floors, consistent with an icy C-type composition.
In images taken with the VLT in 2017, a bright surface feature is visible, as well as at least two dark craters, which have been informally named Serpens and Calix after the Latin words for 'snake' and 'cup', respectively. Serpens has a diameter of 180 km, Calix of 90 km.
Hygiea is the largest of the class of dark C-type asteroids that are dominant in the outer asteroid belt, beyond the Kirkwood gap at 2.82 AU. Its mean diameter . Hygiea is close to spherical, with an axis ratio of that is consistent with a MacLaurin ellipsoid. Aside from being the smallest of the "big four", Hygiea has a relatively low density of , comparable to Ceres (2.16) and the larger icy satellites of the Solar System (Ganymede 1.94, Callisto 1.83, Titan 1.88, Triton 2.06) rather than to Pallas () or Vesta (3.45).
Although it is the largest body in its region, due to its dark surface and farther-than-average distance from the Sun, Hygiea appears very dim when observed from Earth. In fact, it is the third dimmest of the first twenty-three asteroids discovered, with only 13 Egeria and 17 Thetis having lower mean opposition magnitudes. At most oppositions, Hygiea has a magnitude of around +10.2, which is as much as four orders fainter than Vesta, and observation calls for at least a telescope to resolve. However, at a perihelic opposition, Hygiea can reach +9.1 magnitude and may just be resolvable with 10 × 50 binoculars, unlike the next two largest asteroids in the asteroid belt, 704 Interamnia and 511 Davida, which are always beyond binocular visibility.
A total of 17 stellar occultations by Hygiea have been tracked by Earth-based astronomers, including two (in 2002 and 2014) that were seen by a large number of observers. The observations have been used to constrain Hygiea's size, shape and rotation axis. The Hubble Space Telescope has resolved the asteroid and ruled out the presence of any orbiting companions larger than about in diameter.
Orbit and rotation
Orbiting at an average of 3.14 AU from the Sun, Hygiea is the most distant of the "big four" asteroids. It lies closer to the ecliptic as well, with an orbital inclination of 4°. Its orbit is less circular than those of Ceres or Vesta, with an eccentricity of around 0.12. Its perihelion is at a quite similar longitude to those of Vesta and Ceres, though its ascending and descending nodes are opposite to the corresponding ones for those objects. Although its perihelion is extremely close to the mean distance of Ceres and Pallas, a collision between Hygiea and its larger companions is impossible because at that distance they are always on opposite sides of the ecliptic. In 2056, Hygiea will pass 0.025 AU from Ceres, and then in 2063, Hygiea will pass 0.020 AU from Pallas. At aphelion Hygiea reaches out to the extreme edge of the asteroid belt at the perihelia of the Hilda family, which is in a 3:2 orbital resonance with Jupiter.
As one of the most massive asteroids, Hygiea is used by the Minor Planet Center to calculate perturbations.
Hygiea is in an unstable three-body mean motion resonance with Jupiter and Saturn. The computed Lyapunov time for this asteroid is 30,000 years, indicating that it occupies a chaotic orbit that will change randomly over time because of gravitational perturbations by the planets. It is the lowest numbered asteroid in such a resonance (the next lowest numbered being 70 Panopaea).
Hygiea has a rotation period of 13.83 hours. Its single-peaked light curve has an amplitude of 0.27 mag, which is largely attributed to albedo variations. Hygiea's north pole points towards ecliptic longitude and ecliptic latitude , which gives an axial tilt of 119° with respect to the ecliptic.
Hygiea family
Hygiea is the main member of the Hygiean asteroid family that constitutes about 1% of asteroids in the main belt. The family was formed when an object with a diameter of about 100 km collided with proto-Hygiea about 2 billion years ago. Because the impact craters on Hygiea today are too small to contain the volume of ejected material, it is thought that Hygiea was completely disrupted by the impact and that the majority of the debris recoalesced after the pieces that formed the rest of the family had escaped. Hygiea contains almost all the mass (over 98%) of the family.
See also
List of former planets
Notes
References
External links
A simulation of the orbit of Hygiea
Stellar occultation of 11 August 2013 (video)
(displays Elong from Sun and V mag for 2011)
Hygiea asteroids
Hygiea
Hygiea
Possible dwarf planets
C-type asteroids (Tholen)
C-type asteroids (SMASS)
18490412
18490412 | 10 Hygiea | Physics,Astronomy | 1,950 |
38,700,865 | https://en.wikipedia.org/wiki/HR%204072 | HR 4072 is a binary star system in the northern circumpolar constellation of Ursa Major. It has the variable star designation ET Ursae Majoris, abbreviated ET Uma, while HR 4072 is the system's designation from the Bright Star Catalogue. It has a white hue and is faintly visible to the naked eye with an apparent visual magnitude that fluctuates around 4.94. The system is located at a distance of approximately 339 light years from the Sun based on parallax measurements. The radial velocity measurement is poorly constrained, but it appears to be drifting closer to the Sun at the rate of around −3 km/s.
This is a double-lined spectroscopic binary star system with an orbital period of 11.6 days and an eccentricity of 0.26. The orbit for this star was first determined by R. H. Baker in 1912, then later revised.
The primary, designated component A, is an Ap type chemically-peculiar star with a stellar classification of A1:VpSiSrHg, although it has also been considered to be a mercury-manganese star. The suffix notation indicates abundance anomalies of silicon, strontium, and mercury in the spectrum. It is an α2 Canum Venaticorum variable with an amplitude of 0.05 magnitude in the B (blue) band. The star is rotating slowly with a projected rotational velocity of 4.5 km/s. It is radiating 139 times the luminosity of the Sun from its photosphere at an effective temperature of 10,307 K.
The secondary component has been reported to have characteristics of an Am star.
References
A-type main-sequence stars
Mercury-manganese stars
Alpha2 Canum Venaticorum variables
Spectroscopic binaries
Ursa Major
Durchmusterung objects
9327
089822
050933
4072
Ursae Majoris, ET
Ap stars
Am stars | HR 4072 | Astronomy | 396 |
12,808,284 | https://en.wikipedia.org/wiki/Xylobiose | Xylobiose is a disaccharide of xylose monomers with a beta-1,4-bond between them.
References
Disaccharides | Xylobiose | Chemistry | 38 |
2,026,216 | https://en.wikipedia.org/wiki/Bouveault%20aldehyde%20synthesis | The Bouveault aldehyde synthesis (also known as the Bouveault reaction) is a one-pot substitution reaction that replaces an alkyl or aryl halide with a formyl group using a N,N-disubstituted formamide.
For primary alkyl halides this produces the homologous aldehyde one carbon longer. For aryl halides this produces the corresponding carbaldehyde. The Bouveault aldehyde synthesis is an example of a formylation reaction, and is named for French scientist Louis Bouveault.
Reaction mechanism
The first step of the Bouveault aldehyde synthesis is the formation of the Grignard reagent. Upon addition of a N,N-disubstituted formamide (such as dimethylformamide) a hemiaminal is formed, which can easily be hydrolyzed into the desired aldehyde.
Variations
Variants using organolithium reagents instead of magnesium-based Grignard reagents are also considered Bouveault aldehyde syntheses.
See also
Bodroux-Chichibabin aldehyde synthesis
Bouveault–Blanc reduction
Duff reaction
References
Addition reactions
Carbon-carbon bond forming reactions
Formylation reactions
Name reactions | Bouveault aldehyde synthesis | Chemistry | 262 |
3,146,792 | https://en.wikipedia.org/wiki/Reed%20reaction | The Reed reaction is a chemical reaction that utilizes light to oxidize hydrocarbons to alkylsulfonyl chlorides. This reaction is employed in modifying polyethylene to give chlorosulfonated polyethylene (CSPE), which is noted for its toughness.
Commercial implementations
Polyethylene is treated with a mixture of chlorine and sulfur dioxide under UV-radiation. Vinylsulfonic acid can also be prepared beginning with the sulfochlorination of chloroethane. Dehydrohalogenation of the product gives vinylsulfonyl chloride, which subsequently is hydrolyzed to give vinylsulfonic acid:
=
==
Mechanism
The reaction occurs via a free radical mechanism. UV-light initiates homolysis of chlorine, producing a pair of chlorine atoms:
Chain initiation:
Cl2 ->[h\nu] 2Cl.
Thereafter a chlorine atom attacks the hydrocarbon chain, freeing hydrogen to form hydrogen chloride and an alkyl free radical. The resulting radical then captures SO2. The resulting sulfonyl radical attacks another chlorine molecule to produce the desired sulfonyl chloride and a new chlorine atom, which continues the reaction chain.
Chain propagation steps:
{R-H} + .Cl -> {R.} + HCl
{R.} + {:}SO2 -> R-\dot{S}O2
{R-\dot{S}O2} + Cl2 -> {R-SO2-Cl} + Cl.
See also
Chain reaction
Historical readings
Reed, C. F. ; ; .
References
Substitution reactions
Carbon-heteroatom bond forming reactions
Name reactions | Reed reaction | Chemistry | 359 |
15,417,785 | https://en.wikipedia.org/wiki/KIAA0515 | Protein BAT2-like is a protein that in humans is encoded by the BAT2L gene.
Interactions
KIAA0515 has been shown to interact with EHMT2.
References
Further reading | KIAA0515 | Chemistry | 41 |
22,482,566 | https://en.wikipedia.org/wiki/VV%20Corvi | VV Corvi (abbreviated as VV Crv) is a close spectroscopic binary in the constellation Corvus. It is also an eclipsing binary, varying from magnitude 5.19 to 5.34 over 3.145 days. The two stars orbit each other with a period of 1.46 days and an eccentricity of 0.088. The mass ratio of the two stars is 0.775±0.024. The primary is 1.978 ± 0.010 times as massive as the Sun, 18.253 ± 2.249 its luminosity and has 3.375 ± 0.010 the Sun's radius. The secondary is 1.513 ± 0.008 times as massive as the Sun, 4.745 ± 0.583 its luminosity and has 1.650 ± 0.008 the Sun's radius. Both are yellow-white main sequence stars of spectral type F5V, though the primary has begun expanding and cooling as it nears the end of its time on the main sequence. A tertiary companion was discovered during the Two Micron All-Sky Survey.
The system shares a common proper motion with HR 4822, which is 5"2 away.
References
Corvus (constellation)
Spectroscopic binaries
Corvi, VV
110317
061910
Durchmusterung objects
F-type subgiants
4821 | VV Corvi | Astronomy | 298 |
3,605,843 | https://en.wikipedia.org/wiki/Percy%20John%20Heawood | Percy John Heawood (8 September 1861 – 24 January 1955) was a British mathematician, who concentrated on graph colouring.
Life
He was the son of the Rev. John Richard Heawood of Newport, Shropshire, and his wife Emily Heath, daughter of the Rev. Joseph Heath of Wigmore, Herefordshire; and a first cousin of Oliver Lodge, whose mother Grace was also a daughter of Joseph Heath. He was educated at Queen Elizabeth's School, Ipswich, and matriculated at Exeter College, Oxford in 1880, graduating B.A. in 1883 and M.A. in 1887.
Heawood spent his academic career at Durham University, where he was appointed Lecturer in 1885. He was, successively, Censor of St Cuthbert's Society between 1897 and 1901 succeeding Frank Byron Jevons in the role, Senior Proctor of the university from 1901, Professor in 1910 and Vice-Chancellor between 1926 and 1928. He was awarded an OBE, as Honorary Secretary of the Preservation Fund, for his part in raising £120,000 to prevent Durham Castle from collapsing into the River Wear.
Heawood was fond of country pursuits, and one of his interests was Hebrew. His nickname was "Pussy".
Durham University awards an annual Heawood Prize to a student graduating in Mathematics whose performance is outstanding in the final year.
Works
Heawood devoted himself to the four colour theorem and related questions. In 1890 he exposed a flaw in Alfred Kempe's proof, that had been considered as valid for 11 years. The four colour theorem being an open question again, he established the weaker five colour theorem. The four colour theorem itself was finally established by a computer-based proof in 1976.
Heawood also studied colouring of maps on higher surfaces and established the upper bound on the chromatic number of such a graph in terms of the connectivity (genus, or number of handles) of the surface. This upper bound was proved only in 1968 to be the actual maximum.
Writing in the Journal of the London Mathematical Society, G. A. Dirac wrote:
Family
Heawood married in 1890 Christiana Tristram, daughter of Henry Baker Tristram; they had a son and a daughter.
See also
Heawood conjecture
Heawood number
Heawood graph
Four color theorem
Five color theorem
References
External links
MacTutor biography
1861 births
1955 deaths
Newport, Shropshire
19th-century British mathematicians
20th-century British mathematicians
People from Newport, Shropshire
Combinatorialists
Academics of Durham University
Vice-chancellors and wardens of Durham University
Officers of the Order of the British Empire
Place of birth missing | Percy John Heawood | Mathematics | 530 |
5,536,529 | https://en.wikipedia.org/wiki/LED%20circuit | In electronics, an LED circuit or LED driver is an electrical circuit used to power a light-emitting diode (LED). The circuit must provide sufficient current to light the LED at the required brightness, but must limit the current to prevent damaging the LED. The voltage drop across a lit LED is approximately constant over a wide range of operating current; therefore, a small increase in applied voltage greatly increases the current. Datasheets may specify this drop as a "forward voltage" () at a particular operating current. Very simple circuits are used for low-power indicator LEDs. More complex, current source circuits are required when driving high-power LEDs for illumination to achieve correct current regulation.
Basic circuit
The simplest circuit to drive an LED is through a series resistor. It is commonly used for indicators and digital displays in many consumer appliances. However, this circuit is not energy-efficient, because energy is dissipated in the resistor as heat.
The LED's depends on its material. Ohm's law and Kirchhoff's circuit laws are used to calculate the appropriate resistor value, by subtracting the LED's from the supply voltage and dividing by the desired operating current. With a sufficiently high supply voltage, multiple LEDs in series can be powered with one resistor.
If the supply voltage is close or equal to the LED's , then no reasonable value for the resistor can be calculated, so some other method of current limiting is used.
Power source considerations
The voltage versus current characteristics of an LED is similar to any diode. Current is approximately an exponential function of voltage according to the Shockley diode equation, and a small voltage change may result in a large change in current. If the voltage is below or equal to the threshold no current flows and the result is an unlit LED. If the voltage is too high, the current will exceed the maximum rating, overheating and potentially destroying the LED.
LED drivers are designed to handle fluctuation load, providing enough current to achieve the required brightness while not allowing damaging levels of current to flow. Drivers may be constant current (CC) or constant voltage (CV). In CC drivers, the voltage changes while the current stays the same. CC drivers are used when the electrical load of the LED circuit is either unknown or fluctuates, for example, a lighting circuit where a variable number of LED lamp fixtures may be installed.
As an LED heats up, its voltage drop decreases (band gap decrease). This can encourage the current to increase.
MOSFET drivers
An active constant current source is commonly used for high power LEDs, stabilizing light output over a wide range of input voltages which might increase the useful life of batteries. Active constant current is typically regulated using a depletion-mode MOSFET (metal–oxide–semiconductor field-effect transistor), which is the simplest current limiter. Low drop-out (LDO) constant current regulators also allow the total LED voltage to be a higher fraction of the power supply voltage.
Switched-mode power supplies (e.g. buck, boost, and buck-boost converters) are used in LED flashlights and household LED lamps. Power MOSFETs are typically used for switching LED drivers, which is an efficient solution to drive high-brightness LEDs. Power integrated circuit (IC) chips are widely used to drive the MOSFETs directly, without the need for additional circuitry.
Series resistor
Series resistors are a simple way to stabilize the LED current, but energy is wasted in the resistor.
Miniature indicator LEDs are normally driven from low voltage DC via a current-limiting resistor. Currents of 2 mA, 10 mA and 20 mA are common. Sub-mA indicators may be made by driving ultra-bright LEDs at very low current. Efficiency tends to reduce at low currents, but indicators running on 100 μA are still practical.
In coin cell powered keyring-type LED lights, the resistance of the cell itself is usually the only current limiting device.
LEDs with built-in series resistors are available. These may save printed circuit board space, and are especially useful when building prototypes or populating a PCB in a way other than its designers intended. However, the resistor value is set at the time of manufacture, removing one of the key methods of setting the LED's intensity.
The value for the series resistance may be obtained from Ohm's law, considering that the supply voltage is offset by the diode's , which varies little over the range of useful currents:
or
where:
is resistance in ohms, typically rounded up to the next higher resistor value.
is the power supply voltage in volts, e.g. 9-volt battery.
is the LED's forward voltage drop in volts when lit. and the LED's light frequency (which we perceive as color) increase with the band gap of the LED's materials. Consequently, ranges from around 1.7 to 2.0 volts for red LEDs to around 2.8 to 4.0 volts for violet LEDs.
is the voltage drop across the switch in volts: (A) for no switch, use 0 volts, (B) for mechanical switch, use 0 volts, (C) for BJT transistor, use collector-emitter saturation voltage from the transistor datasheet.
is the desired current of the LED in amps. The maximum continuous-on current is shown on LED datasheets, for example 20 mA (0.020 A) is common for most small LEDs. Many circuits operate LEDs at less than the specified maximum current to save power, or to reduce brightness, or to use a common resistor value. For indoor use, tiny surface mount high-efficiency LEDs can easily light up with 1 mA (0.001 A) or more current, which most digital logic outputs can easily source or sink.
Using the algebraic formula (above) and assuming is 0 (to simplify examples), the resistance is calculated as follows:
Example 1 with of 9 V, = 1.8 V, = 5 mA:
= (9 V - 1.8 V) / 5 mA = (9 - 1.8) / 0.005 = 1440 ohms, then round up to a 1.5K ohm resistor (per common resistor values).
Example 2 with of 5 V, = 1.8 V, = 1K ohm:
= (5 V - 1.8 V) / 1K ohm = (5 - 1.8) / 1000 = 0.0032, which is 3.2 mA
LED arrays
Strings of multiple LEDs are normally connected in series. In one configuration, the source voltage must be greater than or equal to the sum of the individual LED voltages; typically the LED voltages add up to around two-thirds of the supply voltage. A single current-limiting resistor may be used for each string.
Parallel operation is also possible but can be more problematic. Parallel LEDs must have closely matched in order to have similar branch currents and, therefore, similar light output. Variations in the manufacturing process can make it difficult to obtain satisfactory operation when connecting some types of LEDs in parallel.
LED display
LEDs are often arranged in ways such that each LED (or each string of LEDs) can be individually turned on and off.
Direct drive is the simplest-to-understand approach—it uses many independent single-LED (or single-string) circuits.
For example, a person could design a digital clock such that when the clock displays "12:34" on a seven-segment display,
the clock would turn on the appropriate segments directly and leave them on until something else needs to be displayed.
However, multiplexed display techniques are more often used than direct drive, because they have lower net hardware costs.
For example, most people who design digital clocks design them such that when the clock displays "12:34" on a seven-segment display, at any one instant the clock turns on the appropriate segments of one of the digits—all the other digits are dark. The clock scans through the digits rapidly enough that it gives the illusion that it is "constantly" displaying "12:34" for an entire minute. However, each "on" segment is actually being rapidly pulsed on and off many times a second.
An extension of this technique is Charlieplexing where the ability of some microcontrollers to tri-state their output pins means larger numbers of LEDs can be driven, without using latches. For N pins, it is possible to drive n2-n LEDs.
The use of integrated circuit technology to drive LEDs dates back to the late 1960s. In 1969, Hewlett-Packard introduced the HP Model 5082-7000 Numeric Indicator, an early LED display and the first LED device to use integrated circuit technology. Its development was led by Howard C. Borden and Gerald P. Pighini at HP Associates and HP Labs, who had engaged in research and development (R&D) on practical LEDs between 1962 and 1968. It was the first intelligent LED display, making it a revolution in digital display technology, replacing the Nixie tube and becoming the basis for later LED displays.
Polarity
Unlike incandescent light bulbs, which illuminate regardless of the electrical polarity, LEDs will only light with the correct electrical polarity. When the voltage across the p-n junction is in the correct direction, a significant current flows and the device is said to be forward-biased. If the voltage is of the wrong polarity, the device is said to be reverse biased, very little current flows, and no light is emitted. LEDs can be operated with alternating current, but they will only light on the half of the AC cycle where the LED is forward-biased. This causes the LED to turn on and off at the frequency of the AC supply.
Most LEDs have relatively low reverse breakdown voltage ratings compared to standard diodes, so it may be easier than expected to enter this mode and cause damage to the LED due to overcurrent. However, the cut-in voltage is always less than the breakdown voltage, so no special reverse protections are necessary when driving an LED directly from an AC supply when properly current-limited for forward-biased operation.
The manufacturer will normally advise how to determine the polarity of the LED in the product datasheet. However, there is no standardization of polarity markings for surface mount devices.
Pulsed operation
Many systems pulse LEDs on and off, by applying power periodically or intermittently. So long as the flicker rate is greater than the human flicker fusion threshold, and the LED is stationary relative to the eye, the LED will appear to be continuously lit. Varying the on/off ratio of the pulses is known as pulse-width modulation (PWM). In some cases, PWM-based drivers are more efficient than constant current or constant voltage drivers.
Most LED data sheets specify a maximum DC current that is safe for continuous operation. Often they specify some higher maximum pulsed current that is safe for brief pulses, as long as the LED controller keeps the pulse short enough and then turns off the power to the LED long enough for the LED to cool off.
LED as a light sensor
In addition to emission, an LED can be used as a photodiode in light detection. This capability may be used in a variety of applications including ambient light detection and bidirectional communications.
As a photodiode, an LED is sensitive to wavelengths equal to or shorter than the predominant wavelength it emits. For example, a green LED is sensitive to blue light and some green light, but not to yellow or red light.
This implementation of LEDs may be added to designs with only minor modifications in circuitry. An LED can be multiplexed in such a circuit, such that it can be used for both light emission and sensing at different times.
See also
Joule thief - powering an LED using 1.5 V battery and voltage booster circuit
Planck–Einstein relation - relation between band gap and photon frequency
Shockley diode equation - relation between forward voltage and current
References
External links
LED Resistor Calculator
Analog circuits
Light-emitting diodes
American inventions | LED circuit | Engineering | 2,531 |
11,834,731 | https://en.wikipedia.org/wiki/Cerberus%20%28protein%29 | Cerberus is a protein that in humans is encoded by the CER1 gene. Cerberus is a signaling molecule which contributes to the formation of the head, heart and left-right asymmetry of internal organs. This gene varies slightly from species to species but its overall functions seem to be similar.
Cerberus is secreted by the anterior visceral endoderm and blocks the action of BMP, Nodal and Wnt, secreted by the primitive node, which allows for the formation of a head region. This is accomplished by inhibiting the formation of mesoderm in this region. Xenopus Cerberus causes a protein to be secreted that is able to induce the formation of an ectopic head. Knockdown experiments have helped to explain Cerberus's role in both the formation of the head and left and right symmetry. These experiments have shown that Cerberus helps to keep Nodal from crossing to the right side of the developing embryo, allowing left and right asymmetry to form. This is why misexpression of Cerberus can cause the heart to fold in the opposite direction during development. When Cerberus is “knocked down” and BMP and Wnt are up regulated the head does not form. Other experiments using mice that this gene has been “knocked out” showed no head defects, which suggest that it is the combination of the up regulation of BMP and Wnt along with the absence of Cerberus that causes this defect. For the heart, Cerberus is one of several factors that inhibits Nodal to initiate cardiomyogenic differentiation
The Cerberus gene family produces many different signal proteins that are antagonistically involved in establishing anterior-posterior patterning and left-right patterning in vertebrate embryos.
Function
Cerberus is an inhibitor in the TGF beta signaling pathway secreted during the gastrulation phase of embryogenesis. Cerberus (Cer) is a gene that encodes a cytokine (a secreted signaling protein) important for induction and formation of the heart and head in vertebrates. The Cerberus gene encodes a polypeptide that is 270 amino acids in length and is expressed in the anterior domain of a gastrula in the endoderm layer. Cerberus also plays a large role as an inhibitory molecule, which is important for proper head induction. Cerberus inhibits the proteins bone morphogenetic protein 4 (BMP4), Xnr1, and Xwnt8.
This gene encodes a cytokine member of the cystine knot superfamily, characterized by nine conserved cysteines and a cysteine knot region. The cerberus-related cytokines, together with Dan and DRM / Gremlin, represent a group of bone morphogenetic protein (BMP) antagonists that can bind directly to BMPs and inhibit their activity.
In human embryonic development, Cerberus and the protein coded by GREM3 inhibit NODAL in the Wnt signaling pathway during the formation of the germ layers. Specifically, Cerberus and GREM3 act as antagonists to Nodal in the anterior region of the developing embryo, blocking its expression and halting the progression of the primitive node. Orthologs of the gene that codes Cerberus (CER1) are conserved in other non-rodent mammals, indicating that Cerberus has similar functions in other vertebrates.
A gene knockdown experiment was conducted in Xenopus, where the amount of Cerberus expressed was decreased by inhibiting translation. The proteins that Cerberus inhibits (BMP4, Xnr1, Xwnt8) concentrations were increased also. It was also shown that just the decrease of Cerberus translation alone was not enough to inhibit the formation of head structures. While the increase of just BMP4, Xnr1, Xwnt8 led to defects in the formation of the head. The increase of BMP4, Xnr1, Xwnt8 and the decrease of Cerberus together blocked the formation of the head. This gene knockdown experiment showed the necessity of Cerberus’ inhibitory functions in the formation of head structures. It quite possibly may be that although Cerberus is necessary for the induction of a head, its inhibitory actions may play a more significant role in ensuring the head is developed properly.
Overexpression or overabundance of Cerberus is associated with the development of ectopic heads. These additional head-like structures may contain varying characteristics of a normal head (eye or eyes, brain, notochord) depending on the ratio of overabundant Cerberus to other proteins associated with anterior development that Cerberus inhibits (Wnt, Nodal, and BMP). If only Nodal is blocked, a single head will still form but with abnormalities such as cyclopia. If both Nodal and BMP or Wnt and BMP are sufficiently inhibited, ectopic, abnormal head-like structures will form. Inhibition of all three proteins by Cerberus is required for the development of complete, ectopic heads.
Location
It is expressed in the anterior endoderm but can vary dorsally and ventrally between species. For example, in amphibians Cerberus is expressed in the anterior dorsal endoderm and in mice it is expressed in the anterior visceral endoderm.
Anterior-posterior patterning
Anterior-posterior patterning by Cerberus is accomplished by acting as an antagonist to nodal, bmp, and wnt signaling molecules in the anterior region of the vertebrate embryo during gastrulation. Knock down experiments in which Cerberus was partially repressed show a decreased formation of the head structures. In experiments where Cerberus was decreased and wnt, bmp and nodal signals were increased, embryos completely lacked head structures and develop only trunk structures. These experiments suggest that a balance of these signaling molecules is required for proper development of the anterior and posterior regions.
Left-right asymmetry
Cerberus is also involved in establishing left-right asymmetry that is critical to the normal physiology of a vertebrate. By blocking nodal in the right side of the embryo, concentrations of nodal remain high only in the left side of the embryo and the nodal cascade cannot be activated in the right side. Because left-right asymmetry is so vital, Cerberus works along with the nodal cilia that push left-determining signal molecules to the left side of the embryo to ensure that the left-right axis is correctly established. Misexpression experiments show that lack of Cerberus expression on the right side can result in situs inversus and cardiovascular malformations.
Heart development
Cerberus plays a vital role in heart development and differentiation of cardiac mesoderm through activation of Nodal signaling molecule. Nodal and Wnt activity is antagonized in the endoderm which results in diffusible signals from Cerberus. More specifically, Nodal inhibits certain cells from joining cardiogenesis while simultaneously activating cells. The cells that respond to Nodal produce Cerberus in the underlying endoderm which causes heart development in adjacent cells. Knockdown experiments of Cerberus reduced endogenous cardiomyogenesis and ectopic heart induction. Block of Nodal leads to induction of cardiogenic genes through chromatin remodeling. The heart is developed asymmetrically using the left-right patterning induced by Cerberus which creates a higher concentration of signaling molecules on the left side. Experiments that inhibited Cerberus led to a loss of left-right polarity of the heart, which was shown by bilateral expression of left side-specific genes.
During mammalian heart induction, a mammalian homologue, Cer1, is associated with the coordinated suppression of the TGFbeta superfamily members Nodal and BMP. This induces Brahma-associated factor 60c (Baf60c), one of three Baf60 variants (a, b, and c) that are mutually exclusively assembled into the SWI/SNF chromatin remodelling complex. Blocking Nodal and BMP also induces lineage-specific transcription factors Gata4 and Tbx5, which interact with Baf60c. Collectively, these proteins redirect SWI/SNF to activate the cardiac program of gene expression. Targeted inactivation of another homologue, Cerberus like-2 (Cerl2), in the mouse leads to left ventricular cardiac hyperplasia and systolic dysfunction.
Evolutionary role and conservation
The Nodal signaling pathway, including Cerberus, is evolutionary conserved. It is theorized that the gut was the first asymmetrical organ to develop, but in modern vertebrates, most internal organs display asymmetry. While the Nodal pathway is found in deuterostomes and protostomes, a proposed common ancestor called Urbilateria has been theorized to be the progenitor of all bilaterally symmetrical animals. The only protostomes to possess Nodal are mollusks (including snails), while the vast majority of deuterostomes possess this signaling pathway. Cerberus is present in the signaling pathway of amphioxus, an early chordate. As a result, it is likely that the majority of vertebrates possess Cerberus or analogous molecules (such as Coco in frogs, Dand5 in mice, and charon in zebrafish). Notably, chickens lack the ciliary dependent mechanisms of Nodal distribution, but Nodal and Cerberus are still an integral part of their asymmetrical L-R development. Pigs also lack this ciliary mechanism, but both species rely on an ion pump to accomplish L-R distribution of Nodal. Cerberus's (and analogous molecules') role in this pathway is to bind to Nodal in an inhibitory manner.
References
Further reading
External links
Cytokines | Cerberus (protein) | Chemistry | 2,091 |
12,150,996 | https://en.wikipedia.org/wiki/TAN-1057%20A | TAN-1057 A and TAN-1057 B are organic compounds found in the Flexibacter sp. PK-74 bacterium. TAN-1057 A and B are closely related structurally as diastereomers. Also related are TAN-1057 C and TAN-1057 D, isolated from the same bacteria. The four compounds have been shown to be an effective antibiotics against methicillin-resistant strains of Staphylococcus aureus which act through the inhibition of protein biosynthesis.
References
Antibiotics
Alkaloids
Guanidines
Carboxamides
Ureas
Pyrimidones | TAN-1057 A | Chemistry,Biology | 128 |
42,976,070 | https://en.wikipedia.org/wiki/Ichthyosaurus%20posthumus | "Ichthyosaurus" posthumus is a species of ichthyosaurs known from the Late Jurassic (early Tithonian age) Solnhofen Formation of Bavaria, Germany. Though several specimens have been referred to this species in the past, its type specimen consists only of isolated teeth that were destroyed during World War II, and it is today considered a nomen dubium. The teeth almost certainly do not belong to Ichthyosaurus itself, which was a wastebin taxon at the time this species was named.
References
Fossil taxa described in 1852
Ichthyosaurs of Europe
Late Jurassic ichthyosaurs
Solnhofen fauna
Nomina dubia | Ichthyosaurus posthumus | Biology | 135 |
58,664 | https://en.wikipedia.org/wiki/Gas%20turbine | A gas turbine or gas turbine engine is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the direction of flow:
a rotating gas compressor
a combustor
a compressor-driving turbine.
Additional components have to be added to the gas generator to suit its application. Common to all is an air inlet but with different configurations to suit the requirements of marine use, land use or flight at speeds varying from stationary to supersonic. A propelling nozzle is added to produce thrust for flight. An extra turbine is added to drive a propeller (turboprop) or ducted fan (turbofan) to reduce fuel consumption (by increasing propulsive efficiency) at subsonic flight speeds. An extra turbine is also required to drive a helicopter rotor or land-vehicle transmission (turboshaft), marine propeller or electrical generator (power turbine). Greater thrust-to-weight ratio for flight is achieved with the addition of an afterburner.
The basic operation of the gas turbine is a Brayton cycle with air as the working fluid: atmospheric air flows through the compressor that brings it to higher pressure; energy is then added by spraying fuel into the air and igniting it so that the combustion generates a high-temperature flow; this high-temperature pressurized gas enters a turbine, producing a shaft work output in the process, used to drive the compressor; the unused energy comes out in the exhaust gases that can be repurposed for external work, such as directly producing thrust in a turbojet engine, or rotating a second, independent turbine (known as a power turbine) that can be connected to a fan, propeller, or electrical generator. The purpose of the gas turbine determines the design so that the most desirable split of energy between the thrust and the shaft work is achieved. The fourth step of the Brayton cycle (cooling of the working fluid) is omitted, as gas turbines are open systems that do not reuse the same air.
Gas turbines are used to power aircraft, trains, ships, electrical generators, pumps, gas compressors, and tanks.
Timeline of development
50: Earliest records of Hero's engine (aeolipile). It most likely served no practical purpose, and was rather more of a curiosity; nonetheless, it demonstrated an important principle of physics that all modern turbine engines rely on.
1000: The "Trotting Horse Lamp" (, zŏumădēng) was used by the Chinese at lantern fairs as early as the Northern Song dynasty. When the lamp is lit, the heated airflow rises and drives an impeller with horse-riding figures attached on it, whose shadows are then projected onto the outer screen of the lantern.
1500: The Smoke jack was drawn by Leonardo da Vinci: Hot air from a fire rises through a single-stage axial turbine rotor mounted in the exhaust duct of the fireplace and turns the roasting spit by gear-chain connection.
1791: A patent was given to John Barber, an Englishman, for the first true gas turbine. His invention had most of the elements present in the modern day gas turbines. The turbine was designed to power a horseless carriage.
1894: Sir Charles Parsons patented the idea of propelling a ship with a steam turbine, and built a demonstration vessel, the Turbinia, easily the fastest vessel afloat at the time.
1899: Charles Gordon Curtis patented the first gas turbine engine in the US.
1900: Sanford Alexander Moss submitted a thesis on gas turbines. In 1903, Moss became an engineer for General Electric's Steam Turbine Department in Lynn, Massachusetts. While there, he applied some of his concepts in the development of the turbocharger.
1903: A Norwegian, Ægidius Elling, built the first gas turbine that was able to produce more power than needed to run its own components, which was considered an achievement in a time when knowledge about aerodynamics was limited. Using rotary compressors and turbines it produced .
1904: A gas turbine engine designed by Franz Stolze, based on his earlier 1873 patent application, is built and tested in Berlin. The Stolze gas turbine was too inefficient to sustain its own operation.
1906: The Armengaud-Lemale gas turbine tested in France. This was a relatively large machine which included a 25-stage centrifugal compressor designed by Auguste Rateau and built by the Brown Boveri Company. The gas turbine could sustain its own air compression but was too inefficient to produce useful work.
1910: The first operational Holzwarth gas turbine (pulse combustion) achieves an output of . Planned output of the machine was and its efficiency is below that of contemporary reciprocating engines.
1920s The practical theory of gas flow through passages was developed into the more formal (and applicable to turbines) theory of gas flow past airfoils by A. A. Griffith resulting in the publishing in 1926 of An Aerodynamic Theory of Turbine Design. Working testbed designs of axial turbines suitable for driving a propeller were developed by the Royal Aeronautical Establishment.
1930: Having found no interest from the RAF for his idea, Frank Whittle patented the design for a centrifugal gas turbine for jet propulsion. The first successful test run of his engine occurred in England in April 1937.
1932: The Brown Boveri Company of Switzerland starts selling axial compressor and turbine turbosets as part of the turbocharged steam generating Velox boiler. Following the gas turbine principle, the steam evaporation tubes are arranged within the gas turbine combustion chamber; the first Velox plant is erected at a French Steel mill in Mondeville, Calvados.
1936: The first constant flow industrial gas turbine is commissioned by the Brown Boveri Company and goes into service at Sun Oil's Marcus Hook refinery in Pennsylvania, US.
1937: Working proof-of-concept prototype turbojet engine runs in UK (Frank Whittle's) and Germany (Hans von Ohain's Heinkel HeS 1). Henry Tizard secures UK government funding for further development of Power Jets engine.
1939: The First 4 MW utility power generation gas turbine is built by the Brown Boveri Company for an emergency power station in Neuchâtel, Switzerland. The turbojet powered Heinkel He 178, the world's first jet aircraft, makes its first flight.
1940: Jendrassik Cs-1, a turboprop engine, made its first bench run. The Cs-1 was designed by Hungarian engineer György Jendrassik, and was intended to power a Hungarian twin-engine heavy fighter, the RMI-1. Work on the Cs-1 stopped in 1941 without the type having powered any aircraft.
1944: The Junkers Jumo 004 engine enters full production, powering the first German military jets such as the Messerschmitt Me 262. This marks the beginning of the reign of gas turbines in the sky.
1946: National Gas Turbine Establishment formed from Power Jets and the RAE turbine division to bring together Whittle and Hayne Constant's work. In Beznau, Switzerland the first commercial reheated/recuperated unit generating 27 MW was commissioned.
1947: A Metropolitan Vickers G1 (Gatric) becomes the first marine gas turbine when it completes sea trials on the Royal Navy's M.G.B 2009 vessel. The Gatric was an aeroderivative gas turbine based on the Metropolitan Vickers F2 jet engine.
1995: Siemens becomes the first manufacturer of large electricity producing gas turbines to incorporate single crystal turbine blade technology into their production models, allowing higher operating temperatures and greater efficiency.
2011 Mitsubishi Heavy Industries tests the first >60% efficiency combined cycle gas turbine (the M501J) at its Takasago, Hyōgo, works.
Theory of operation
In an ideal gas turbine, gases undergo four thermodynamic processes: an isentropic compression, an isobaric (constant pressure) combustion, an isentropic expansion and isobaric heat rejection. Together, these make up the Brayton cycle, also known as the "constant pressure cycle". It is distinguished from the Otto cycle, in that all the processes (compression, ignition combustion, exhaust), occur at the same time, continuously.
In a real gas turbine, mechanical energy is changed irreversibly (due to internal friction and turbulence) into pressure and thermal energy when the gas is compressed (in either a centrifugal or axial compressor). Heat is added in the combustion chamber and the specific volume of the gas increases, accompanied by a slight loss in pressure. During expansion through the stator and rotor passages in the turbine, irreversible energy transformation once again occurs. Fresh air is taken in, in place of the heat rejection.
Air is taken in by a compressor, called a gas generator, with either an axial or centrifugal design, or a combination of the two. This air is then ducted into the combustor section which can be of a annular, can, or can-annular design. In the combustor section, roughly 70% of the air from the compressor is ducted around the combustor itself for cooling purposes. The remaining roughly 30% the air is mixed with fuel and ignited by the already burning air-fuel mixture, which then expands producing power across the turbine. This expansion of the mixture then leaves the combustor section and has its velocity increased across the turbine section to strike the turbine blades, spinning the disc they are attached to, thus creating useful power. Of the power produced, 60-70% is solely used to power the gas generator. The remaining power is used to power what the engine is being used for, typically an aviation application, being thrust in a turbojet, driving the fan of a turbofan, rotor or accessory of a turboshaft, and gear reduction and propeller of a turboprop.
If the engine has a power turbine added to drive an industrial generator or a helicopter rotor, the exit pressure will be as close to the entry pressure as possible with only enough energy left to overcome the pressure losses in the exhaust ducting and expel the exhaust. For a turboprop engine there will be a particular balance between propeller power and jet thrust which gives the most economical operation. In a turbojet engine only enough pressure and energy is extracted from the flow to drive the compressor and other components. The remaining high-pressure gases are accelerated through a nozzle to provide a jet to propel an aircraft.
The smaller the engine, the higher the rotation rate of the shaft must be to attain the required blade tip speed. Blade-tip speed determines the maximum pressure ratios that can be obtained by the turbine and the compressor. This, in turn, limits the maximum power and efficiency that can be obtained by the engine. In order for tip speed to remain constant, if the diameter of a rotor is reduced by half, the rotational speed must double. For example, large jet engines operate around 10,000–25,000 rpm, while micro turbines spin as fast as 500,000 rpm.
Mechanically, gas turbines can be considerably less complex than Reciprocating engines. Simple turbines might have one main moving part, the compressor/shaft/turbine rotor assembly, with other moving parts in the fuel system. This, in turn, can translate into price. For instance, costing for materials, the Jumo 004 proved cheaper than the Junkers 213 piston engine, which was , and needed only 375 hours of lower-skill labor to complete (including manufacture, assembly, and shipping), compared to 1,400 for the BMW 801. This, however, also translated into poor efficiency and reliability. More advanced gas turbines (such as those found in modern jet engines or combined cycle power plants) may have 2 or 3 shafts (spools), hundreds of compressor and turbine blades, movable stator blades, and extensive external tubing for fuel, oil and air systems; they use temperature resistant alloys, and are made with tight specifications requiring precision manufacture. All this often makes the construction of a simple gas turbine more complicated than a piston engine.
Moreover, to reach optimum performance in modern gas turbine power plants the gas needs to be prepared to exact fuel specifications. Fuel gas conditioning systems treat the natural gas to reach the exact fuel specification prior to entering the turbine in terms of pressure, temperature, gas composition, and the related Wobbe index.
The primary advantage of a gas turbine engine is its power to weight ratio.
Since significant useful work can be generated by a relatively lightweight engine, gas turbines are perfectly suited for aircraft propulsion.
Thrust bearings and journal bearings are a critical part of a design. They are hydrodynamic oil bearings or oil-cooled rolling-element bearings. Foil bearings are used in some small machines such as micro turbines and also have strong potential for use in small gas turbines/auxiliary power units
Creep
A major challenge facing turbine design, especially turbine blades, is reducing the creep that is induced by the high temperatures and stresses that are experienced during operation. Higher operating temperatures are continuously sought in order to increase efficiency, but come at the cost of higher creep rates. Several methods have therefore been employed in an attempt to achieve optimal performance while limiting creep, with the most successful ones being high performance coatings and single crystal superalloys. These technologies work by limiting deformation that occurs by mechanisms that can be broadly classified as dislocation glide, dislocation climb and diffusional flow.
Protective coatings provide thermal insulation of the blade and offer oxidation and corrosion resistance. Thermal barrier coatings (TBCs) are often stabilized zirconium dioxide-based ceramics and oxidation/corrosion resistant coatings (bond coats) typically consist of aluminides or MCrAlY (where M is typically Fe and/or Cr) alloys. Using TBCs limits the temperature exposure of the superalloy substrate, thereby decreasing the diffusivity of the active species (typically vacancies) within the alloy and reducing dislocation and vacancy creep. It has been found that a coating of 1–200 μm can decrease blade temperatures by up to .
Bond coats are directly applied onto the surface of the substrate using pack carburization and serve the dual purpose of providing improved adherence for the TBC and oxidation resistance for the substrate. The Al from the bond coats forms Al2O3 on the TBC-bond coat interface which provides the oxidation resistance, but also results in the formation of an undesirable interdiffusion (ID) zone between itself and the substrate. The oxidation resistance outweighs the drawbacks associated with the ID zone as it increases the lifetime of the blade and limits the efficiency losses caused by a buildup on the outside of the blades.
Nickel-based superalloys boast improved strength and creep resistance due to their composition and resultant microstructure. The gamma (γ) FCC nickel is alloyed with aluminum and titanium in order to precipitate a uniform dispersion of the coherent gamma-prime (γ') phases. The finely dispersed γ' precipitates impede dislocation motion and introduce a threshold stress, increasing the stress required for the onset of creep. Furthermore, γ' is an ordered L12 phase that makes it harder for dislocations to shear past it. Further Refractory elements such as rhenium and ruthenium can be added in solid solution to improve creep strength. The addition of these elements reduces the diffusion of the gamma prime phase, thus preserving the fatigue resistance, strength, and creep resistance. The development of single crystal superalloys has led to significant improvements in creep resistance as well. Due to the lack of grain boundaries, single crystals eliminate Coble creep and consequently deform by fewer modes – decreasing the creep rate. Although single crystals have lower creep at high temperatures, they have significantly lower yield stresses at room temperature where strength is determined by the Hall-Petch relationship. Care needs to be taken in order to optimize the design parameters to limit high temperature creep while not decreasing low temperature yield strength.
Types
Jet engines
Airbreathing jet engines are gas turbines optimized to produce thrust from the exhaust gases, or from ducted fans connected to the gas turbines. Jet engines that produce thrust from the direct impulse of exhaust gases are often called turbojets. While still in service with many militaries and civilian operators, turbojets have mostly been phased out in favor of the turbofan engine due to the turbojet's low fuel efficiency, and high noise. Those that generate thrust with the addition of a ducted fan are called turbofans or (rarely) fan-jets. These engines produce nearly 80% of their thrust by the ducted fan, which can be seen from the front of the engine. They come in two types, low-bypass turbofan and high bypass, the difference being the amount of air moved by the fan, called "bypass air". These engines offer the benefit of more thrust without extra fuel consumption.
Gas turbines are also used in many liquid-fuel rockets, where gas turbines are used to power a turbopump to permit the use of lightweight, low-pressure tanks, reducing the empty weight of the rocket.
Turboprop engines
A turboprop engine is a turbine engine that drives an aircraft propeller using a reduction gear to translate high turbine section operating speed (often in the 10s of thousands) into low thousands necessary for efficient propeller operation. The benefit of using the turboprop engine is to take advantage of the turbine engines high power-to-weight ratio to drive a propeller, thus allowing a more powerful, but also smaller engine to be used. Turboprop engines are used on a wide range of business aircraft such as the Pilatus PC-12, commuter aircraft such as the Beechcraft 1900, and small cargo aircraft such as the Cessna 208 Caravan or De Havilland Canada Dash 8, and large aircraft (typically military) such as the Airbus A400M transport, Lockheed AC-130 and the 60-year-old Tupolev Tu-95 strategic bomber. While military turboprop engines can vary, in the civilian market there are two primary engines to be found: the Pratt & Whitney Canada PT6, a free-turbine turboshaft engine, and the Honeywell TPE331, a fixed turbine engine (formerly designated as the Garrett AiResearch 331).
Aeroderivative gas turbines
Aeroderivative gas turbines are generally based on existing aircraft gas turbine engines and are smaller and lighter than industrial gas turbines.
Aeroderivatives are used in electrical power generation due to their ability to be shut down and handle load changes more quickly than industrial machines. They are also used in the marine industry to reduce weight. Common types include the General Electric LM2500, General Electric LM6000, and aeroderivative versions of the Pratt & Whitney PW4000, Pratt & Whitney FT4 and Rolls-Royce RB211.
Amateur gas turbines
Increasing numbers of gas turbines are being used or even constructed by amateurs.
In its most straightforward form, these are commercial turbines acquired through military surplus or scrapyard sales, then operated for display as part of the hobby of engine collecting. In its most extreme form, amateurs have even rebuilt engines beyond professional repair and then used them to compete for the land speed record.
The simplest form of self-constructed gas turbine employs an automotive turbocharger as the core component. A combustion chamber is fabricated and plumbed between the compressor and turbine sections.
More sophisticated turbojets are also built, where their thrust and light weight are sufficient to power large model aircraft. The Schreckling design constructs the entire engine from raw materials, including the fabrication of a centrifugal compressor wheel from plywood, epoxy and wrapped carbon fibre strands.
Several small companies now manufacture small turbines and parts for the amateur. Most turbojet-powered model aircraft are now using these commercial and semi-commercial microturbines, rather than a Schreckling-like home-build.
Auxiliary power units
Small gas turbines are used as auxiliary power units (APUs) to supply auxiliary power to larger, mobile, machines such as an aircraft, and are a turboshaft design. They supply:
compressed air for air cycle machine style air conditioning and ventilation,
compressed air start-up power for larger jet engines,
mechanical (shaft) power to a gearbox to drive shafted accessories, and
electrical, hydraulic and other power-transmission sources to consuming devices remote from the APU.
Industrial gas turbines for power generation
Industrial gas turbines differ from aeronautical designs in that the frames, bearings, and blading are of heavier construction. They are also much more closely integrated with the devices they power—often an electric generator—and the secondary-energy equipment that is used to recover residual energy (largely heat).
They range in size from portable mobile plants to large, complex systems weighing more than a hundred tonnes housed in purpose-built buildings. When the gas turbine is used solely for shaft power, its thermal efficiency is about 30%. However, it may be cheaper to buy electricity than to generate it. Therefore, many engines are used in CHP (Combined Heat and Power) configurations that can be small enough to be integrated into portable container configurations.
Gas turbines can be particularly efficient when waste heat from the turbine is recovered by a heat recovery steam generator (HRSG) to power a conventional steam turbine in a combined cycle configuration. The 605 MW General Electric 9HA achieved a 62.22% efficiency rate with temperatures as high as .
For 2018, GE offers its 826 MW HA at over 64% efficiency in combined cycle due to advances in additive manufacturing and combustion breakthroughs, up from 63.7% in 2017 orders and on track to achieve 65% by the early 2020s.
In March 2018, GE Power achieved a 63.08% gross efficiency for its 7HA turbine.
Aeroderivative gas turbines can also be used in combined cycles, leading to a higher efficiency, but it will not be as high as a specifically designed industrial gas turbine. They can also be run in a cogeneration configuration: the exhaust is used for space or water heating, or drives an absorption chiller for cooling the inlet air and increase the power output, technology known as turbine inlet air cooling.
Another significant advantage is their ability to be turned on and off within minutes, supplying power during peak, or unscheduled, demand. Since single cycle (gas turbine only) power plants are less efficient than combined cycle plants, they are usually used as peaking power plants, which operate anywhere from several hours per day to a few dozen hours per year—depending on the electricity demand and the generating capacity of the region. In areas with a shortage of base-load and load following power plant capacity or with low fuel costs, a gas turbine powerplant may regularly operate most hours of the day. A large single-cycle gas turbine typically produces 100 to 400 megawatts of electric power and has 35–40% thermodynamic efficiency.
Industrial gas turbines for mechanical drive
Industrial gas turbines that are used solely for mechanical drive or used in collaboration with a recovery steam generator differ from power generating sets in that they are often smaller and feature a dual shaft design as opposed to a single shaft. The power range varies from 1 megawatt up to 50 megawatts. These engines are connected directly or via a gearbox to either a pump or compressor assembly. The majority of installations are used within the oil and gas industries. Mechanical drive applications increase efficiency by around 2%.
Oil and gas platforms require these engines to drive compressors to inject gas into the wells to force oil up via another bore, or to compress the gas for transportation. They are also often used to provide power for the platform. These platforms do not need to use the engine in collaboration with a CHP system due to getting the gas at an extremely reduced cost (often free from burn off gas). The same companies use pump sets to drive the fluids to land and across pipelines in various intervals.
Compressed air energy storage
One modern development seeks to improve efficiency in another way, by separating the compressor and the turbine with a compressed air store. In a conventional turbine, up to half the generated power is used driving the compressor. In a compressed air energy storage configuration, power is used to drive the compressor, and the compressed air is released to operate the turbine when required.
Turboshaft engines
Turboshaft engines are used to drive compressors in gas pumping stations and natural gas liquefaction plants. They are also used in aviation to power all but the smallest modern helicopters, and function as an auxiliary power unit in large commercial aircraft. A primary shaft carries the compressor and its turbine which, together with a combustor, is called a Gas Generator. A separately spinning power-turbine is usually used to drive the rotor on helicopters. Allowing the gas generator and power turbine/rotor to spin at their own speeds allows more flexibility in their design.
Radial gas turbines
Scale jet engines
Also known as miniature gas turbines or micro-jets.
With this in mind the pioneer of modern Micro-Jets, Kurt Schreckling, produced one of the world's first Micro-Turbines, the FD3/67. This engine can produce up to 22 newtons of thrust, and can be built by most mechanically minded people with basic engineering tools, such as a metal lathe.
Microturbines
Evolved from piston engine turbochargers, aircraft APUs or small jet engines, microturbines are 25 to 500 kilowatt turbines the size of a refrigerator.
Microturbines have around 15% efficiencies without a recuperator, 20 to 30% with one and they can reach 85% combined thermal-electrical efficiency in cogeneration.
External combustion
Most gas turbines are internal combustion engines but it is also possible to manufacture an external combustion gas turbine which is, effectively, a turbine version of a hot air engine.
Those systems are usually indicated as EFGT (Externally Fired Gas Turbine) or IFGT (Indirectly Fired Gas Turbine).
External combustion has been used for the purpose of using pulverized coal or finely ground biomass (such as sawdust) as a fuel. In the indirect system, a heat exchanger is used and only clean air with no combustion products travels through the power turbine. The thermal efficiency is lower in the indirect type of external combustion; however, the turbine blades are not subjected to combustion products and much lower quality (and therefore cheaper) fuels are able to be used.
When external combustion is used, it is possible to use exhaust air from the turbine as the primary combustion air. This effectively reduces global heat losses, although heat losses associated with the combustion exhaust remain inevitable.
Closed-cycle gas turbines based on helium or supercritical carbon dioxide also hold promise for use with future high temperature solar and nuclear power generation.
In surface vehicles
Gas turbines are often used on ships, locomotives, helicopters, tanks, and to a lesser extent, on cars, buses, and motorcycles.
A key advantage of jets and turboprops for airplane propulsion – their superior performance at high altitude compared to piston engines, particularly naturally aspirated ones – is irrelevant in most automobile applications. Their power-to-weight advantage, though less critical than for aircraft, is still important.
Gas turbines offer a high-powered engine in a very small and light package. However, they are not as responsive and efficient as small piston engines over the wide range of RPMs and powers needed in vehicle applications. In series hybrid vehicles, as the driving electric motors are mechanically detached from the electricity generating engine, the responsiveness, poor performance at low speed and low efficiency at low output problems are much less important. The turbine can be run at optimum speed for its power output, and batteries and ultracapacitors can supply power as needed, with the engine cycled on and off to run it only at high efficiency. The emergence of the continuously variable transmission may also alleviate the responsiveness problem.
Turbines have historically been more expensive to produce than piston engines, though this is partly because piston engines have been mass-produced in huge quantities for decades, while small gas turbine engines are rarities; however, turbines are mass-produced in the closely related form of the turbocharger.
The turbocharger is basically a compact and simple free shaft radial gas turbine which is driven by the piston engine's exhaust gas. The centripetal turbine wheel drives a centrifugal compressor wheel through a common rotating shaft. This wheel supercharges the engine air intake to a degree that can be controlled by means of a wastegate or by dynamically modifying the turbine housing's geometry (as in a variable geometry turbocharger).
It mainly serves as a power recovery device which converts a great deal of otherwise wasted thermal and kinetic energy into engine boost.
Turbo-compound engines (actually employed on some semi-trailer trucks) are fitted with blow down turbines which are similar in design and appearance to a turbocharger except for the turbine shaft being mechanically or hydraulically connected to the engine's crankshaft instead of to a centrifugal compressor, thus providing additional power instead of boost. While the turbocharger is a pressure turbine, a power recovery turbine is a velocity one.
Passenger road vehicles (cars, bikes, and buses)
A number of experiments have been conducted with gas turbine powered automobiles, the largest by Chrysler. More recently, there has been some interest in the use of turbine engines for hybrid electric cars. For instance, a consortium led by micro gas turbine company Bladon Jets has secured investment from the Technology Strategy Board to develop an Ultra Lightweight Range Extender (ULRE) for next-generation electric vehicles. The objective of the consortium, which includes luxury car maker Jaguar Land Rover and leading electrical machine company SR Drives, is to produce the world's first commercially viable – and environmentally friendly – gas turbine generator designed specifically for automotive applications.
The common turbocharger for gasoline or diesel engines is also a turbine derivative.
Concept cars
The first serious investigation of using a gas turbine in cars was in 1946 when two engineers, Robert Kafka and Robert Engerstein of Carney Associates, a New York engineering firm, came up with the concept where a unique compact turbine engine design would provide power for a rear wheel drive car. After an article appeared in Popular Science, there was no further work, beyond the paper stage.
Early concepts (1950s/60s)
In 1950, designer F.R. Bell and Chief Engineer Maurice Wilks from British car manufacturers Rover unveiled the first car powered with a gas turbine engine. The two-seater JET1 had the engine positioned behind the seats, air intake grilles on either side of the car, and exhaust outlets on the top of the tail. During tests, the car reached top speeds of , at a turbine speed of 50,000 rpm. After being shown in the United Kingdom and the United States in 1950, JET1 was further developed, and was subjected to speed trials on the Jabbeke highway in Belgium in June 1952, where it exceeded . The car ran on petrol, paraffin (kerosene) or diesel oil, but fuel consumption problems proved insurmountable for a production car. JET1 is on display at the London Science Museum.
A French turbine-powered car, the SOCEMA-Grégoire, was displayed at the October 1952 Paris Auto Show. It was designed by the French engineer Jean-Albert Grégoire.
The first turbine-powered car built in the US was the GM Firebird I which began evaluations in 1953. While photos of the Firebird I may suggest that the jet turbine's thrust propelled the car like an aircraft, the turbine actually drove the rear wheels. The Firebird I was never meant as a commercial passenger car and was built solely for testing & evaluation as well as public relation purposes. Additional Firebird concept cars, each powered by gas turbines, were developed for the 1953, 1956 and 1959 Motorama auto shows. The GM Research gas turbine engine also was fitted to a series of transit buses, starting with the Turbo-Cruiser I of 1953.
Starting in 1954 with a modified Plymouth, the American car manufacturer Chrysler demonstrated several prototype gas turbine-powered cars from the early 1950s through the early 1980s. Chrysler built fifty Chrysler Turbine Cars in 1963 and conducted the only consumer trial of gas turbine-powered cars. Each of their turbines employed a unique rotating recuperator, referred to as a regenerator that increased efficiency.
In 1954, Fiat unveiled a concept car with a turbine engine, called Fiat Turbina. This vehicle, looking like an aircraft with wheels, used a unique combination of both jet thrust and the engine driving the wheels. Speeds of were claimed.
In the 1960s, Ford and GM also were developing gas turbine semi-trucks. Ford displayed the Big Red at the 1964 World's Fair. With the trailer, it was long, high, and painted crimson red. It contained the Ford-developed gas turbine engine, with output power and torque of and . The cab boasted a highway map of the continental U.S., a mini-kitchen, bathroom, and a TV for the co-driver. The fate of the truck was unknown for several decades, but it was rediscovered in early 2021 in private hands, having been restored to running order. The Chevrolet division of GM built the Turbo Titan series of concept trucks with turbine motors as analogs of the Firebird concepts, including Turbo Titan I (, shares GT-304 engine with Firebird II), Turbo Titan II (, shares GT-305 engine with Firebird III), and Turbo Titan III (1965, GT-309 engine); in addition, the GM Bison gas turbine truck was shown at the 1964 World's Fair.
Emissions and fuel economy (1970s/80s)
As a result of the U.S. Clean Air Act Amendments of 1970, research was funded into developing automotive gas turbine technology. Design concepts and vehicles were conducted by Chrysler, General Motors, Ford (in collaboration with AiResearch), and American Motors (in conjunction with Williams Research). Long-term tests were conducted to evaluate comparable cost efficiency. Several AMC Hornets were powered by a small Williams regenerative gas turbine weighing and producing at 4450 rpm.
In 1982, General Motors used an Oldsmobile Delta 88 powered by a gas turbine using pulverised coal dust. This was considered for the United States and the western world to reduce dependence on middle east oil at the time
Toyota demonstrated several gas turbine powered concept cars, such as the Century gas turbine hybrid in 1975, the Sports 800 Gas Turbine Hybrid in 1979 and the GTV in 1985. No production vehicles were made. The GT24 engine was exhibited in 1977 without a vehicle.
Later development
In the early 1990s, Volvo introduced the Volvo ECC which was a gas turbine powered hybrid electric vehicle.
In 1993, General Motors developed a gas turbine powered EV1 series hybrid—as a prototype of the General Motors EV1. A Williams International 40 kW turbine drove an alternator which powered the battery–electric powertrain. The turbine design included a recuperator. In 2006, GM went into the EcoJet concept car project with Jay Leno.
At the 2010 Paris Motor Show Jaguar demonstrated its Jaguar C-X75 concept car. This electrically powered supercar has a top speed of and can go from in 3.4 seconds. It uses lithium-ion batteries to power four electric motors which combine to produce 780 bhp. It will travel on a single charge of the batteries, and uses a pair of Bladon Micro Gas Turbines to re-charge the batteries extending the range to .
Racing cars
The first race car (in concept only) fitted with a turbine was in 1955 by a US Air Force group as a hobby project with a turbine loaned them by Boeing and a race car owned by Firestone Tire & Rubber company. The first race car fitted with a turbine for the goal of actual racing was by Rover and the BRM Formula One team joined forces to produce the Rover-BRM, a gas turbine powered coupe, which entered the 1963 24 Hours of Le Mans, driven by Graham Hill and Richie Ginther. It averaged and had a top speed of . American Ray Heppenstall joined Howmet Corporation and McKee Engineering together to develop their own gas turbine sports car in 1968, the Howmet TX, which ran several American and European events, including two wins, and also participated in the 1968 24 Hours of Le Mans. The cars used Continental gas turbines, which eventually set six FIA land speed records for turbine-powered cars.
For open wheel racing, 1967's revolutionary STP-Paxton Turbocar fielded by racing and entrepreneurial legend Andy Granatelli and driven by Parnelli Jones nearly won the Indianapolis 500; the Pratt & Whitney ST6B-62 powered turbine car was almost a lap ahead of the second place car when a gearbox bearing failed just three laps from the finish line. The next year the STP Lotus 56 turbine car won the Indianapolis 500 pole position even though new rules restricted the air intake dramatically. In 1971 Team Lotus principal Colin Chapman introduced the Lotus 56B F1 car, powered by a Pratt & Whitney STN 6/76 gas turbine. Chapman had a reputation of building radical championship-winning cars, but had to abandon the project because there were too many problems with turbo lag.
Buses
General Motors fitted the GT-30x series of gas turbines (branded "Whirlfire") to several prototype buses in the 1950s and 1960s, including Turbo-Cruiser I (1953, GT-300); Turbo-Cruiser II (1964, GT-309); Turbo-Cruiser III (1968, GT-309); RTX (1968, GT-309); and RTS 3T (1972).
The arrival of the Capstone Turbine has led to several hybrid bus designs, starting with HEV-1 by AVS of Chattanooga, Tennessee in 1999, and closely followed by Ebus and ISE Research in California, and DesignLine Corporation in New Zealand (and later the United States). AVS turbine hybrids were plagued with reliability and quality control problems, resulting in liquidation of AVS in 2003. The most successful design by Designline is now operated in 5 cities in 6 countries, with over 30 buses in operation worldwide, and order for several hundred being delivered to Baltimore, and New York City.
Brescia Italy is using serial hybrid buses powered by microturbines on routes through the historical sections of the city.
Motorcycles
The MTT Turbine Superbike appeared in 2000 (hence the designation of Y2K Superbike by MTT) and is the first production motorcycle powered by a turbine engine – specifically, a Rolls-Royce Allison model 250 turboshaft engine, producing about 283 kW (380 bhp). Speed-tested to 365 km/h or 227 mph (according to some stories, the testing team ran out of road during the test), it holds the Guinness World Record for most powerful production motorcycle and most expensive production motorcycle, with a price tag of US$185,000.
Trains
Several locomotive classes have been powered by gas turbines, the most recent incarnation being Bombardier's JetTrain.
Tanks
The Third Reich Wehrmacht Heer's development division, the Heereswaffenamt (Army Ordnance Board), studied a number of gas turbine engine designs for use in tanks starting in mid-1944. The first gas turbine engine design intended for use in armored fighting vehicle propulsion, the BMW 003-based GT 101, was meant for installation in the Panther tank. Towards the end of the war, a Jagdtiger was fitted with one of the aforementioned gas turbines.
The second use of a gas turbine in an armored fighting vehicle was in 1954 when a unit, PU2979, specifically developed for tanks by C. A. Parsons and Company, was installed and trialed in a British Conqueror tank. The Stridsvagn 103 was developed in the 1950s and was the first mass-produced main battle tank to use a turbine engine, the Boeing T50. Since then, gas turbine engines have been used as auxiliary power units in some tanks and as main powerplants in Soviet/Russian T-80s and U.S. M1 Abrams tanks, among others. They are lighter and smaller than diesel engines at the same sustained power output but the models installed to date are less fuel efficient than the equivalent diesel, especially at idle, requiring more fuel to achieve the same combat range. Successive models of M1 have addressed this problem with battery packs or secondary generators to power the tank's systems while stationary, saving fuel by reducing the need to idle the main turbine. T-80s can mount three large external fuel drums to extend their range. Russia has stopped production of the T-80 in favor of the diesel-powered T-90 (based on the T-72), while Ukraine has developed the diesel-powered T-80UD and T-84 with nearly the power of the gas-turbine tank. The French Leclerc tank's diesel powerplant features the "Hyperbar" hybrid supercharging system, where the engine's turbocharger is completely replaced with a small gas turbine which also works as an assisted diesel exhaust turbocharger, enabling engine RPM-independent boost level control and a higher peak boost pressure to be reached (than with ordinary turbochargers). This system allows a smaller displacement and lighter engine to be used as the tank's power plant and effectively removes turbo lag. This special gas turbine/turbocharger can also work independently from the main engine as an ordinary APU.
A turbine is theoretically more reliable and easier to maintain than a piston engine since it has a simpler construction with fewer moving parts, but in practice, turbine parts experience a higher wear rate due to their higher working speeds. The turbine blades are highly sensitive to dust and fine sand so that in desert operations air filters have to be fitted and changed several times daily. An improperly fitted filter, or a bullet or shell fragment that punctures the filter, can damage the engine. Piston engines (especially if turbocharged) also need well-maintained filters, but they are more resilient if the filter does fail.
Like most modern diesel engines used in tanks, gas turbines are usually multi-fuel engines.
Marine applications
Naval
Gas turbines are used in many naval vessels, where they are valued for their high power-to-weight ratio and their ships' resulting acceleration and ability to get underway quickly.
The first gas-turbine-powered naval vessel was the Royal Navy's motor gunboat MGB 2009 (formerly MGB 509) converted in 1947. Metropolitan-Vickers fitted their F2/3 jet engine with a power turbine. The Steam Gun Boat Grey Goose was converted to Rolls-Royce gas turbines in 1952 and operated as such from 1953. The Bold class Fast Patrol Boats Bold Pioneer and Bold Pathfinder built in 1953 were the first ships created specifically for gas turbine propulsion.
The first large-scale, partially gas-turbine powered ships were the Royal Navy's Type 81 (Tribal class) frigates with combined steam and gas powerplants. The first, was commissioned in 1961.
The German Navy launched the first in 1961 with 2 Brown, Boveri & Cie gas turbines in the world's first combined diesel and gas propulsion system.
The Soviet Navy commissioned in 1962 the first of 25 with 4 gas turbines in combined gas and gas propulsion system. Those vessels used 4 M8E gas turbines, which generated . Those ships were the first large ships in the world to be powered solely by gas turbines.
The Danish Navy had 6 Søløven-class torpedo boats (the export version of the British Brave class fast patrol boat) in service from 1965 to 1990, which had 3 Bristol Proteus (later RR Proteus) Marine Gas Turbines rated at combined, plus two General Motors Diesel engines, rated at , for better fuel economy at slower speeds. And they also produced 10 Willemoes Class Torpedo / Guided Missile boats (in service from 1974 to 2000) which had 3 Rolls-Royce Marine Proteus Gas Turbines also rated at , same as the Søløven-class boats, and 2 General Motors Diesel Engines, rated at , also for improved fuel economy at slow speeds.
The Swedish Navy produced 6 Spica-class torpedo boats between 1966 and 1967 powered by 3 Bristol Siddeley Proteus 1282 turbines, each delivering . They were later joined by 12 upgraded Norrköping class ships, still with the same engines. With their aft torpedo tubes replaced by antishipping missiles they served as missile boats until the last was retired in 2005.
The Finnish Navy commissioned two corvettes, Turunmaa and Karjala, in 1968. They were equipped with one Rolls-Royce Olympus TM1 gas turbine and three Wärtsilä marine diesels for slower speeds. They were the fastest vessels in the Finnish Navy; they regularly achieved speeds of 35 knots, and 37.3 knots during sea trials. The Turunmaas were decommissioned in 2002. Karjala is today a museum ship in Turku, and Turunmaa serves as a floating machine shop and training ship for Satakunta Polytechnical College.
The next series of major naval vessels were the four Canadian helicopter carrying destroyers first commissioned in 1972. They used 2 ft-4 main propulsion engines, 2 ft-12 cruise engines and 3 Solar Saturn 750 kW generators.
The first U.S. gas-turbine powered ship was the U.S. Coast Guard's , a cutter commissioned in 1961 that was powered by two turbines utilizing controllable-pitch propellers. The larger High Endurance Cutters, was the first class of larger cutters to utilize gas turbines, the first of which () was commissioned in 1967. Since then, they have powered the U.S. Navy's s, and s, and guided missile cruisers. , a modified , is to be the Navy's first amphibious assault ship powered by gas turbines.
The marine gas turbine operates in a more corrosive atmosphere due to the presence of sea salt in air and fuel and use of cheaper fuels.
Civilian maritime
Up to the late 1940s, much of the progress on marine gas turbines all over the world took place in design offices and engine builder's workshops and development work was led by the British Royal Navy and other Navies. While interest in the gas turbine for marine purposes, both naval and mercantile, continued to increase, the lack of availability of the results of operating experience on early gas turbine projects limited the number of new ventures on seagoing commercial vessels being embarked upon.
In 1951, the diesel–electric oil tanker Auris, 12,290 deadweight tonnage (DWT) was used to obtain operating experience with a main propulsion gas turbine under service conditions at sea and so became the first ocean-going merchant ship to be powered by a gas turbine. Built by Hawthorn Leslie at Hebburn-on-Tyne, UK, in accordance with plans and specifications drawn up by the Anglo-Saxon Petroleum Company and launched on the UK's Princess Elizabeth's 21st birthday in 1947, the ship was designed with an engine room layout that would allow for the experimental use of heavy fuel in one of its high-speed engines, as well as the future substitution of one of its diesel engines by a gas turbine. The Auris operated commercially as a tanker for three-and-a-half years with a diesel–electric propulsion unit as originally commissioned, but in 1951 one of its four diesel engines – which were known as "Faith", "Hope", "Charity" and "Prudence" – was replaced by the world's first marine gas turbine engine, a open-cycle gas turbo-alternator built by British Thompson-Houston Company in Rugby. Following successful sea trials off the Northumbrian coast, the Auris set sail from Hebburn-on-Tyne in October 1951 bound for Port Arthur in the US and then Curaçao in the southern Caribbean returning to Avonmouth after 44 days at sea, successfully completing her historic trans-Atlantic crossing. During this time at sea the gas turbine burnt diesel fuel and operated without an involuntary stop or mechanical difficulty of any kind. She subsequently visited Swansea, Hull, Rotterdam, Oslo and Southampton covering a total of 13,211 nautical miles. The Auris then had all of its power plants replaced with a directly coupled gas turbine to become the first civilian ship to operate solely on gas turbine power.
Despite the success of this early experimental voyage the gas turbine did not replace the diesel engine as the propulsion plant for large merchant ships. At constant cruising speeds the diesel engine simply had no peer in the vital area of fuel economy. The gas turbine did have more success in Royal Navy ships and the other naval fleets of the world where sudden and rapid changes of speed are required by warships in action.
The United States Maritime Commission were looking for options to update WWII Liberty ships, and heavy-duty gas turbines were one of those selected. In 1956 the John Sergeant was lengthened and equipped with a General Electric HD gas turbine with exhaust-gas regeneration, reduction gearing and a variable-pitch propeller. It operated for 9,700 hours using residual fuel (Bunker C) for 7,000 hours. Fuel efficiency was on a par with steam propulsion at per hour, and power output was higher than expected at due to the ambient temperature of the North Sea route being lower than the design temperature of the gas turbine. This gave the ship a speed capability of 18 knots, up from 11 knots with the original power plant, and well in excess of the 15 knot targeted. The ship made its first transatlantic crossing with an average speed of 16.8 knots, in spite of some rough weather along the way. Suitable Bunker C fuel was only available at limited ports because the quality of the fuel was of a critical nature. The fuel oil also had to be treated on board to reduce contaminants and this was a labor-intensive process that was not suitable for automation at the time. Ultimately, the variable-pitch propeller, which was of a new and untested design, ended the trial, as three consecutive annual inspections revealed stress-cracking. This did not reflect poorly on the marine-propulsion gas-turbine concept though, and the trial was a success overall. The success of this trial opened the way for more development by GE on the use of HD gas turbines for marine use with heavy fuels. The John Sergeant was scrapped in 1972 at Portsmouth PA.
Boeing launched its first passenger-carrying waterjet-propelled hydrofoil Boeing 929, in April 1974. Those ships were powered by two Allison 501-KF gas turbines.
Between 1971 and 1981, Seatrain Lines operated a scheduled container service between ports on the eastern seaboard of the United States and ports in northwest Europe across the North Atlantic with four container ships of 26,000 tonnes DWT. Those ships were powered by twin Pratt & Whitney gas turbines of the FT 4 series. The four ships in the class were named Euroliner, Eurofreighter, Asialiner and Asiafreighter. Following the dramatic Organization of the Petroleum Exporting Countries (OPEC) price increases of the mid-1970s, operations were constrained by rising fuel costs. Some modification of the engine systems on those ships was undertaken to permit the burning of a lower grade of fuel (i.e., marine diesel). Reduction of fuel costs was successful using a different untested fuel in a marine gas turbine but maintenance costs increased with the fuel change. After 1981 the ships were sold and refitted with, what at the time, was more economical diesel-fueled engines but the increased engine size reduced cargo space.
The first passenger ferry to use a gas turbine was the GTS Finnjet, built in 1977 and powered by two Pratt & Whitney FT 4C-1 DLF turbines, generating and propelling the ship to a speed of 31 knots. However, the Finnjet also illustrated the shortcomings of gas turbine propulsion in commercial craft, as high fuel prices made operating her unprofitable. After four years of service, additional diesel engines were installed on the ship to reduce running costs during the off-season. The Finnjet was also the first ship with a combined diesel–electric and gas propulsion. Another example of commercial use of gas turbines in a passenger ship is Stena Line's HSS class fastcraft ferries. HSS 1500-class Stena Explorer, Stena Voyager and Stena Discovery vessels use combined gas and gas setups of twin GE LM2500 plus GE LM1600 power for a total of . The slightly smaller HSS 900-class Stena Carisma, uses twin ABB–STAL GT35 turbines rated at gross. The Stena Discovery was withdrawn from service in 2007, another victim of too high fuel costs.
In July 2000, the Millennium became the first cruise ship to be powered by both gas and steam turbines. The ship featured two General Electric LM2500 gas turbine generators whose exhaust heat was used to operate a steam turbine generator in a COGES (combined gas electric and steam) configuration. Propulsion was provided by two electrically driven Rolls-Royce Mermaid azimuth pods. The liner uses a combined diesel and gas configuration.
In marine racing applications the 2010 C5000 Mystic catamaran Miss GEICO uses two Lycoming T-55 turbines for its power system.
Advances in technology
Gas turbine technology has steadily advanced since its inception and continues to evolve. Development is actively producing both smaller gas turbines and more powerful and efficient engines. Aiding in these advances are computer-based design (specifically computational fluid dynamics and finite element analysis) and the development of advanced materials: Base materials with superior high-temperature strength (e.g., single-crystal superalloys that exhibit yield strength anomaly) or thermal barrier coatings that protect the structural material from ever-higher temperatures. These advances allow higher compression ratios and turbine inlet temperatures, more efficient combustion and better cooling of engine parts.
Computational fluid dynamics (CFD) has contributed to substantial improvements in the performance and efficiency of gas turbine engine components through enhanced understanding of the complex viscous flow and heat transfer phenomena involved. For this reason, CFD is one of the key computational tools used in design and development of gas turbine engines.
The simple-cycle efficiencies of early gas turbines were practically doubled by incorporating inter-cooling, regeneration (or recuperation), and reheating. These improvements, of course, come at the expense of increased initial and operation costs, and they cannot be justified unless the decrease in fuel costs offsets the increase in other costs. The relatively low fuel prices, the general desire in the industry to minimize installation costs, and the tremendous increase in the simple-cycle efficiency to about 40 percent left little desire for opting for these modifications.
On the emissions side, the challenge is to increase turbine inlet temperatures while at the same time reducing peak flame temperature in order to achieve lower NOx emissions and meet the latest emission regulations. In May 2011, Mitsubishi Heavy Industries achieved a turbine inlet temperature of on a 320 megawatt gas turbine, and 460 MW in gas turbine combined-cycle power generation applications in which gross thermal efficiency exceeds 60%.
Compliant foil bearings were commercially introduced to gas turbines in the 1990s. These can withstand over a hundred thousand start/stop cycles and have eliminated the need for an oil system. The application of microelectronics and power switching technology have enabled the development of commercially viable electricity generation by microturbines for distribution and vehicle propulsion.
In 2013, General Electric started the development of the GE9X with a compression ratio of 61:1.
Advantages and disadvantages
The following are advantages and disadvantages of gas-turbine engines:
Advantages include:
Very high power-to-weight ratio compared to reciprocating engines.
Smaller than most reciprocating engines of the same power rating.
Smooth rotation of the main shaft produces far less vibration than a reciprocating engine.
Fewer moving parts than reciprocating engines results in lower maintenance cost and higher reliability/availability over its service life.
Greater reliability, particularly in applications where sustained high power output is required.
Waste heat is dissipated almost entirely in the exhaust. This results in a high-temperature exhaust stream that is very usable for boiling water in a combined cycle, or for cogeneration.
Lower peak combustion pressures than reciprocating engines in general.
High shaft speeds in smaller "free turbine units", although larger gas turbines employed in power generation operate at synchronous speeds.
Low lubricating oil cost and consumption.
Can run on a wide variety of fuels.
Very low toxic emissions of CO and HC due to excess air, complete combustion and no "quench" of the flame on cold surfaces.
Disadvantages include:
Core engine costs can be high due to the use of exotic materials, especially in applications where high reliability is required (e.g. aircraft propulsion)
Less efficient than reciprocating engines at idle speed.
Longer startup than reciprocating engines.
Less responsive to changes in power demand compared with reciprocating engines.
Characteristic whine can be hard to suppress. The exhaust (particularly on turbojets) can also produce a distinctive roaring sound.
Major manufacturers
Siemens Energy
Ansaldo
Mitsubishi Heavy Industries
Rolls-Royce
GE Aviation
Silmash
ODK
Pratt & Whitney
P&W Canada
Solar Turbines
Alstom
Zorya-Mashproekt
MTU Aero Engines
MAN Turbo
IHI Corporation
Kawasaki Heavy Industries
HAL
BHEL
MAPNA
Techwin
Doosan Heavy
Shanghai Electric
Harbin Electric
AECC
Testing
British, German, other national and international test codes are used to standardize the procedures and definitions used to test gas turbines. Selection of the test code to be used is an agreement between the purchaser and the manufacturer, and has some significance to the design of the turbine and associated systems. In the United States, ASME has produced several performance test codes on gas turbines. This includes ASME PTC 22–2014. These ASME performance test codes have gained international recognition and acceptance for testing gas turbines. The single most important and differentiating characteristic of ASME performance test codes, including PTC 22, is that the test uncertainty of the measurement indicates the quality of the test and is not to be used as a commercial tolerance.
See also
List of aircraft engines
Centrifugal compressor
Gas turbine modular helium reactor
Pneumatic motor
Pulsejet
Steam turbine
Turbine engine failure
Wind turbine
References
Further reading
Stationary Combustion Gas Turbines including Oil & Over-Speed Control System description
"Aircraft Gas Turbine Technology" by Irwin E. Treager, McGraw-Hill, Glencoe Division, 1979, .
"Gas Turbine Theory" by H.I.H. Saravanamuttoo, G.F.C. Rogers and H. Cohen, Pearson Education, 2001, 5th ed., .
R. M. "Fred" Klaass and Christopher DellaCorte, "The Quest for Oil-Free Gas Turbine Engines," SAE Technical Papers, No. 2006-01-3055, available at sae.org
"Model Jet Engines" by Thomas Kamps Traplet Publications
Aircraft Engines and Gas Turbines, Second Edition by Jack L. Kerrebrock, The MIT Press, 1992, .
"Forensic Investigation of a Gas Turbine Event" by John Molloy, M&M Engineering
"Gas Turbine Performance, 2nd Edition" by Philip Walsh and Paul Fletcher, Wiley-Blackwell, 2004
External links
Technology Speed of Civil Jet Engines
MIT Gas Turbine Laboratory
MIT Microturbine research
California Distributed Energy Resource guide – Microturbine generators
Introduction to how a gas turbine works from "how stuff works.com"
Aircraft gas turbine simulator for interactive learning
An online handbook on stationary gas turbine technologies compiled by the US DOE.
Engines
Marine propulsion | Gas turbine | Physics,Technology,Engineering | 12,211 |
41,768,528 | https://en.wikipedia.org/wiki/Smithella%20propionica | Smithella propionica is a species of bacteria, the type species of its genus. It is anaerobic, syntrophic, propionate-oxidizing bacteria, with type strain LYPT (= OCM 661T).
References
Further reading
External links
LPSN
Type strain of Smithella propionica at BacDive - the Bacterial Diversity Metadatabase
Thermodesulfobacteriota | Smithella propionica | Biology | 88 |
17,175,847 | https://en.wikipedia.org/wiki/MOAP | MOAP (Mobile Oriented Applications Platform) is the software platform for NTT DoCoMo's Freedom of Mobile Multimedia Access (FOMA) service for mobile phones.
It has a closed user interface, so third parties cannot develop software for native application software, or install third party applications, unlike S60 and UIQ.
Versions
Two MOAP versions exist:
MOAP(S) – supported by Symbian OS based phones from several manufacturers such as Fujitsu, Sony Ericsson Japan, Mitsubishi, Sharp and others. Unlike other platforms based on Symbian, S60 and UIQ, MOAP(S) was not an open development platform, originally, but was then released as open-source software from Symbian Foundation under the Eclipse Public License (EPL).
MOAP(L) – supported by Linux based phones from Panasonic and NEC. It is not an open development platform.
References
Mobile Linux
Mobile phone standards
Mobile software
Symbian OS
NTT Docomo | MOAP | Technology | 201 |
64,993 | https://en.wikipedia.org/wiki/Skin%20cancer | Skin cancers are cancers that arise from the skin. They are due to the development of abnormal cells that have the ability to invade or spread to other parts of the body. It occurs when skin cells grow uncontrollably, forming malignant tumors. The primary cause of skin cancer is prolonged exposure to ultraviolet (UV) radiation from the sun or tanning devices. Skin cancer is the most commonly diagnosed form of cancer in humans. There are three main types of skin cancers: basal-cell skin cancer (BCC), squamous-cell skin cancer (SCC) and melanoma. The first two, along with a number of less common skin cancers, are known as nonmelanoma skin cancer (NMSC). Basal-cell cancer grows slowly and can damage the tissue around it but is unlikely to spread to distant areas or result in death. It often appears as a painless raised area of skin that may be shiny with small blood vessels running over it or may present as a raised area with an ulcer. Squamous-cell skin cancer is more likely to spread. It usually presents as a hard lump with a scaly top but may also form an ulcer. Melanomas are the most aggressive. Signs include a mole that has changed in size, shape, color, has irregular edges, has more than one color, is itchy or bleeds.
More than 90% of cases are caused by exposure to ultraviolet radiation from the Sun. This exposure increases the risk of all three main types of skin cancer. Exposure has increased, partly due to a thinner ozone layer. Tanning beds are another common source of ultraviolet radiation. For melanomas and basal-cell cancers, exposure during childhood is particularly harmful. For squamous-cell skin cancers, total exposure, irrespective of when it occurs, is more important. Between 20% and 30% of melanomas develop from moles. People with lighter skin are at higher risk as are those with poor immune function such as from medications or HIV/AIDS. Diagnosis is by biopsy.
Decreasing exposure to ultraviolet radiation and the use of sunscreen appear to be effective methods of preventing melanoma and squamous-cell skin cancer. It is not clear if sunscreen affects the risk of basal-cell cancer. Nonmelanoma skin cancer is usually curable. Treatment is generally by surgical removal but may, less commonly, involve radiation therapy or topical medications such as fluorouracil. Treatment of melanoma may involve some combination of surgery, chemotherapy, radiation therapy and targeted therapy. In those people whose disease has spread to other areas of the body, palliative care may be used to improve quality of life. Melanoma has one of the higher survival rates among cancers, with over 86% of people in the UK and more than 90% in the United States surviving more than 5 years.
Skin cancer is the most common form of cancer, globally accounting for at least 40% of cancer cases. The most common type is nonmelanoma skin cancer, which occurs in at least 2–3 million people per year. This is a rough estimate; good statistics are not kept. Of nonmelanoma skin cancers, about 80% are basal-cell cancers and 20% squamous-cell skin cancers. Basal-cell and squamous-cell skin cancers rarely result in death. In the United States, they were the cause of less than 0.1% of all cancer deaths. Globally in 2012, melanoma occurred in 232,000 people and resulted in 55,000 deaths. White people in Australia, New Zealand and South Africa have the highest rates of melanoma in the world. The three main types of skin cancer have become more common in the last 20 to 40 years, especially regions where the population is predominantly White.
Classification
There are three main types of skin cancer: basal-cell skin cancer (basal-cell carcinoma) (BCC), squamous-cell skin cancer (squamous-cell carcinoma) (SCC) and malignant melanoma.
Basal-cell carcinomas are most commonly present on sun-exposed areas of the skin, especially the face. They rarely metastasize and rarely cause death. They are easily treated with surgery or radiation. Squamous-cell skin cancers are also common, but much less common than basal-cell cancers. They metastasize more frequently than BCCs. Even then, the metastasis rate is quite low, with the exception of SCC of the lip or ear, and in people who are immunosuppressed. Melanoma are the least frequent of the three common skin cancers. They frequently metastasize, and can cause death once they spread.
Less common skin cancers include: Merkel cell carcinoma, Paget's disease of the breast, atypical fibroxanthoma, porocarcinoma, spindle cell tumors, sebaceous carcinomas, microcystic adnexal carcinoma, keratoacanthoma, and skin sarcomas, such as angiosarcoma, dermatofibrosarcoma protuberans, Kaposi's sarcoma, leiomyosarcoma.
BCC and SCC often carry a UV-signature mutation indicating that these cancers are caused by UVB radiation via direct DNA damage. However malignant melanoma is predominantly caused by UVA radiation via indirect DNA damage. The indirect DNA damage is caused by free radicals and reactive oxygen species. Research indicates that the absorption of three sunscreen ingredients into the skin, combined with a 60-minute exposure to UV, leads to an increase of free radicals in the skin, if applied in too little quantity and too infrequently. However, the researchers add that newer creams often do not contain these specific compounds, and that the combination of other ingredients tends to retain the compounds on the surface of the skin. They also add that frequent re-application reduces the risk of radical formation.
Signs and symptoms
There are a variety of different skin cancer symptoms. These include changes in the skin that do not heal, ulcering in the skin, discolored skin, and changes in existing moles, such as jagged edges to the mole, enlargement of the mole, changes in color, the way it feels or if it bleeds. Other common signs of skin cancer can be painful lesion that itches or burns and large brownish spot with darker speckles.
Basal-cell skin cancer
Basal-cell skin cancer (BCC) usually presents as a raised, smooth, pearly bump on the sun-exposed skin of the head, neck, torso or shoulders. Sometimes small blood vessels (called telangiectasia) can be seen within the tumor. Crusting and bleeding in the center of the tumor frequently develops. It is often mistaken for a sore that does not heal. This form of skin cancer is the least deadly, and with proper treatment can be eliminated, often without significant scarring.
Squamous-cell skin cancer
Squamous-cell skin cancer (SCC) is commonly a red, scaling, thickened patch on sun-exposed skin. Some are firm hard nodules and dome shaped like keratoacanthomas. Ulceration and bleeding may occur. When SCC is not treated, it may develop into a large mass. Squamous-cell is the second most common skin cancer. It is dangerous, but not nearly as dangerous as a melanoma.
Melanoma
Most melanoma consist of various colours from shades of brown to black. A small number of melanoma are pink, red or fleshy in colour; these are called amelanotic melanoma and tend to be more aggressive. Warning signs of malignant melanoma include change in the size, shape, color or elevation of a mole. Other signs are the appearance of a new mole during adulthood or pain, itching, ulceration, redness around the site, or bleeding at the site. An often-used mnemonic is "ABCDE", where A is for "asymmetrical", B for "borders" (irregular: "Coast of Maine sign"), C for "color" (variegated), D for "diameter" (larger than 6 mm – the size of a pencil eraser) and E for "evolving."
Other
Merkel cell carcinomas are most often rapidly growing, non-tender red, purple or skin colored bumps that are not painful or itchy. They may be mistaken for a cyst or another type of cancer.
Causes
Ultraviolet radiation from sun exposure is the primary environmental cause of skin cancer. This can occur in professions such as farming. Other risk factors that play a role include:
Light skin color
Age
Smoking tobacco
HPV infections increase the risk of squamous-cell skin cancer.
Some genetic syndromes including congenital melanocytic nevi syndrome which is characterized by the presence of nevi (birthmarks or moles) of varying size which are either present at birth, or appear within 6 months of birth. Nevi larger than 20 mm (3/4") in size are at higher risk for becoming cancerous.
Chronic non-healing wounds. These are called Marjolin's ulcers based on their appearance, and can develop into squamous-cell skin cancer.
Ionizing radiation such as X-rays, environmental carcinogens, and artificial UV radiation (e.g. tanning beds). It is believed that tanning beds are the cause of hundreds of thousands of basal and squamous-cell skin cancer. The World Health Organization now places people who use artificial tanning beds in its highest risk category for skin cancer.
Alcohol consumption, specifically excessive drinking increase the risk of sunburns.
The use of many immunosuppressive medications increases the risk of skin cancer. Cyclosporin A, a calcineurin inhibitor for example increases the risk approximately 200 times, and azathioprine about 60 times.
Deliberate exposure of sensitive skin not normally exposed to sunlight during alternative wellness behaviors such as perineum sunning.
UV-induced DNA damage
UV-irradiation of skin cells causes damage to DNA through photochemical reactions. Cyclobutane pyrimidine dimers formed by adjacent thymine bases, or by adjacent cytosine bases, are frequent types of DNA damage induced by UV. Human skin cells are capable of repairing most UV-induced damage by nucleotide excision repair, a process that protects against skin cancer, but may be inadequate at high levels of exposure.
Pathophysiology
A malignant epithelial tumor that primarily originates in the epidermis, in squamous mucosa or in areas of squamous metaplasia is referred to as a squamous-cell carcinoma.
Macroscopically, the tumor is often elevated, fungating, or may be ulcerated with irregular borders. Microscopically, tumor cells destroy the basement membrane and form sheets or compact masses which invade the subjacent connective tissue (dermis). In well differentiated carcinomas, tumor cells are pleomorphic/atypical, but resembling normal keratinocytes from prickle layer (large, polygonal, with abundant eosinophilic (pink) cytoplasm and central nucleus).
Their disposal tends to be similar to that of normal epidermis: immature/basal cells at the periphery, becoming more mature to the centre of the tumor masses. Tumor cells transform into keratinized squamous cells and form round nodules with concentric, laminated layers, called "cell nests" or "epithelial/keratinous pearls". The surrounding stroma is reduced and contains inflammatory infiltrate (lymphocytes). Poorly differentiated squamous carcinomas contain more pleomorphic cells and no keratinization.
A molecular factor involved in the disease process is mutation in gene PTCH1 that plays an important role in the Sonic hedgehog signaling pathway.
Diagnosis
Diagnosis is by biopsy and histopathological examination.
Non-invasive skin cancer detection methods include photography, dermatoscopy, sonography, confocal microscopy, Raman spectroscopy, fluorescence spectroscopy, terahertz spectroscopy, optical coherence tomography, the multispectral imaging technique, thermography, electrical bio-impedance, tape stripping and computer-aided analysis.
Dermatoscopy may be useful in diagnosing basal cell carcinoma in addition to skin inspection.
There is insufficient evidence that optical coherence tomography (OCT) is useful in diagnosing melanoma or squamous cell carcinoma. OCT may have a role in diagnosing basal cell carcinoma but more data is needed to support this.
Computer-assisted diagnosis devices have been developed that analyze images from a dermatoscope or spectroscopy and can be used by a diagnostician to aid in the detection of skin cancer. CAD systems have been found to be highly sensitive in the detection of melanoma, but have a high false-positive rate. There is not yet enough evidence to recommend CAD as compared to traditional diagnostic methods.
High-frequency ultrasound (HFUS) is of unclear usefulness in the diagnosis of skin cancer. There is insufficient evidence for reflectance confocal microscopy to diagnose basal cell or squamous cell carcinoma or any other skin cancers.
Prevention
Sunscreen is effective and thus recommended to prevent melanoma and squamous-cell carcinoma. There is little evidence that it is effective in preventing basal-cell carcinoma. Other advice to reduce rates of skin cancer includes avoiding sunburn, wearing protective clothing, sunglasses and hats, and attempting to avoid sun exposure or periods of peak exposure. The U.S. Preventive Services Task Force recommends that people between 9 and 25 years of age be advised to avoid ultraviolet light.
The risk of developing skin cancer can be reduced through a number of measures including decreasing indoor tanning and mid-day sun exposure, increasing the use of sunscreen, and avoiding the use of tobacco products.
It is important to limit sun exposure and to avoid tanning beds, because they both involve UV light. UV light is known to damage skin cells by mutating their DNA. The mutated DNA can cause tumors and other growths to form on the skin. Further, there are other risk factors beside just UV exposure. Fair skin, prolonged history of sunburns, moles, and family history of skin cancer are just a few.
There is insufficient evidence either for or against screening for skin cancers. Vitamin supplements and antioxidant supplements have not been found to have an effect in prevention. Evidence for reducing melanoma risk from dietary measures is tentative, with some supportive epidemiological evidence, but no clinical trials.
Zinc oxide and titanium oxide are often used in sunscreen to provide broad protection from UVA and UVB ranges.
Eating certain foods may decrease the risk of sunburns but this is much less than the protection provided by sunscreen.
A meta-analysis of skin cancer prevention in high risk individuals found evidence that topical application of T4N5 liposome lotion reduced the rate of appearance of basal cell carcinomas in people with xeroderma pigmentosum, and that acitretin taken by mouth may have a skin protective benefit in people following kidney transplant.
A paper published in January 2022 showed that a vaccine that stimulates the production of a protein critical to the skin's antioxidant network could reinforce people's defenses against skin cancer.
Treatment
Treatment is dependent on the specific type of cancer, location of the cancer, age of the person, and whether the cancer is primary or a recurrence. For a small basal-cell cancer in a young person, the treatment with the best cure rate (Mohs surgery or CCPDMA) might be indicated. In the case of an elderly frail man with multiple complicating medical problems, a difficult to excise basal-cell cancer of the nose might warrant radiation therapy (slightly lower cure rate) or no treatment at all. Topical chemotherapy might be indicated for large superficial basal-cell carcinoma for good cosmetic outcome, whereas it might be inadequate for invasive nodular basal-cell carcinoma or invasive squamous-cell carcinoma. In general, melanoma is poorly responsive to radiation or chemotherapy.
For low-risk disease, radiation therapy (external beam radiotherapy or brachytherapy), topical chemotherapy (imiquimod or 5-fluorouracil) and cryotherapy (freezing the cancer off) can provide adequate control of the disease; all of them, however, may have lower overall cure rates than certain type of surgery. Other modalities of treatment such as photodynamic therapy, epidermal radioisotope therapy, topical chemotherapy, electrodesiccation and curettage can be found in the discussions of basal-cell carcinoma and squamous-cell carcinoma.
Mohs' micrographic surgery (Mohs surgery) is a technique used to remove the cancer with the least amount of surrounding tissue and the edges are checked immediately to see if tumor is found. This provides the opportunity to remove the least amount of tissue and provide the best cosmetically favorable results. This is especially important for areas where excess skin is limited, such as the face. Cure rates are equivalent to wide excision. Special training is required to perform this technique. An alternative method is CCPDMA and can be performed by a pathologist not familiar with Mohs surgery.
In the case of disease that has spread (metastasized), further surgical procedures or chemotherapy may be required.
Treatments for metastatic melanoma include biologic immunotherapy agents ipilimumab, pembrolizumab, nivolumab, cemiplimab; BRAF inhibitors, such as vemurafenib and dabrafenib; and a MEK inhibitor trametinib.
In February 2024, the Food and Drug Administration approved the first cancer treatment that uses tumor-infiltrating lymphocytes, also called TIL therapy, specifically for melanomas that have not improved with other treatments. Additionally, scientists are testing a vaccine designed to match the unique genetic details of a patient's cancer in an advanced clinical trial.
Reconstruction
Currently, surgical excision is the most common form of treatment for skin cancers. The goal of reconstructive surgery is the restoration of normal appearance and function. The choice of technique in reconstruction is dictated by the size and location of the defect. Excision and reconstruction of facial skin cancers are generally more challenging due to the presence of highly visible and functional anatomic structures in the face.
When skin defects are small in size, most can be repaired with simple repair where skin edges are approximated and closed with sutures. This will result in a linear scar. If the repair is made along a natural skin fold or wrinkle line, the scar will be hardly visible. Larger defects may require repair with a skin graft, local skin flap, pedicled skin flap, or a microvascular free flap. Skin grafts and local skin flaps are by far more common than the other listed choices.
Skin grafting is patching of a defect with skin that is removed from another site in the body. The skin graft is sutured to the edges of the defect, and a bolster dressing is placed atop the graft for seven to ten days, to immobilize the graft as it heals in place. There are two forms of skin grafting: split thickness and full thickness. In a split thickness skin graft, a shaver is used to shave a layer of skin from the abdomen or thigh. The donor site regenerates skin and heals over a period of two weeks. In a full thickness skin graft, a segment of skin is totally removed and the donor site needs to be sutured closed.
Split thickness grafts can be used to repair larger defects, but the grafts are inferior in their cosmetic appearance. Full thickness skin grafts are more acceptable cosmetically. However, full thickness grafts can only be used for small or moderate sized defects.
Local skin flaps are a method of closing defects with tissue that closely matches the defect in color and quality. Skin from the periphery of the defect site is mobilized and repositioned to fill the deficit. Various forms of local flaps can be designed to minimize disruption to surrounding tissues and maximize cosmetic outcome of the reconstruction. Pedicled skin flaps are a method of transferring skin with an intact blood supply from a nearby region of the body. An example of such reconstruction is a pedicled forehead flap for the repair of a large nasal skin defect. Once the flap develops a source of blood supply form its new bed, the vascular pedicle can be detached.
Prognosis
The mortality rate of basal-cell and squamous-cell carcinoma is around 0.3%, causing 2000 deaths per year in the US. In comparison, the mortality rate of melanoma is 15–20% and it causes 6500 deaths per year. Even though it is much less common, malignant melanoma is responsible for 75% of all skin cancer-related deaths.
The survival rate for people with melanoma depends upon when they start treatment. The cure rate is very high when melanoma is detected in early stages, when it can easily be removed surgically. The prognosis is less favorable if the melanoma has spread to other parts of the body. As of 2003 the overall five-year cure rate with Mohs' micrographic surgery was around 95 percent for recurrent basal cell carcinoma.
Australia and New Zealand exhibit one of the highest rates of skin cancer incidence in the world, almost four times the rates registered in the United States, the UK and Canada. Around 434,000 people receive treatment for non-melanoma skin cancers and 10,300 are treated for melanoma. Melanoma is the most common type of cancer in people between 15 and 44 years in both countries. The incidence of skin cancer has been increasing. The incidence of melanoma among Auckland residents of European descent in 1995 was 77.7 cases per 100,000 people per year, and was predicted to increase in the 21st century because of "the effect of local stratospheric ozone depletion and the time lag from sun exposure to melanoma development."
Epidemiology
Skin cancers result in 80,000 deaths a year as of 2010, 49,000 of which are due to melanoma and 31,000 of which are due to non-melanoma skin cancers. This is up from 51,000 in 1990.
More than 3.5 million cases of skin cancer are diagnosed annually in the United States, which makes it the most common form of cancer in that country. One in five Americans will develop skin cancer at some point of their lives. The most common form of skin cancer is basal-cell carcinoma, followed by squamous cell carcinoma. Unlike for other cancers, there exists no basal and squamous cell skin cancers registry in the United States.
Melanoma
In the US in 2008, 59,695 people were diagnosed with melanoma, and 8,623 people died from it. In Australia more than 12,500 new cases of melanoma are reported each year, out of which more than 1,500 die from the disease. Australia has the highest per capita incidence of melanoma in the world.
Although the rates of many cancers in the United States is falling, the incidence of melanoma keeps growing, with approximately 68,729 melanomas diagnosed in 2004 according to reports of the National Cancer Institute.
Melanoma is the fifth most common cancer in the UK (around 13,300 people were diagnosed with melanoma in 2011), and the disease accounts for 1% all cancer deaths (around 2,100 people died in 2012).
Non-melanoma
Approximately 2,000 people die from basal or squamous cell skin cancers (non-melanoma skin cancers) in the United States each year. The rate has dropped in recent years. Most of the deaths happen to people who are elderly and might not have seen a doctor until the cancer had spread; and people with immune system disorders.
Veterinary medicine
Risk factors
White people and people with light skin are prone to skin cancer.
References
External links
Skin cancer procedures: text, images and videos
Integumentary neoplasia
Sun tanning
Wikipedia medicine articles ready to translate
Medical mnemonics | Skin cancer | Chemistry | 5,111 |
43,953,213 | https://en.wikipedia.org/wiki/Steady%20flight | Steady flight, unaccelerated flight, or equilibrium flight is a special case in flight dynamics where the aircraft's linear and angular velocity are constant in a body-fixed reference frame. Basic aircraft maneuvers such as level flight, climbs and descents, and coordinated turns can be modeled as steady flight maneuvers. Typical aircraft flight consists of a series of steady flight maneuvers connected by brief, accelerated transitions. Because of this, primary applications of steady flight models include aircraft design, assessment of aircraft performance, flight planning, and using steady flight states as the equilibrium conditions around which flight dynamics equations are expanded.
Reference frames
Steady flight analysis uses three different reference frames to express the forces and moments acting on the aircraft. They are defined as:
Earth frame (assumed inertial)
Origin - arbitrary, fixed relative to the surface of the Earth
xE axis - positive in the direction of north
yE axis - positive in the direction of east
zE axis - positive towards the center of the Earth
Body frame
Origin - airplane center of gravity
xb (longitudinal) axis - positive out the nose of the aircraft in the plane of symmetry of the aircraft
zb (vertical) axis - perpendicular to the xb axis, in the plane of symmetry of the aircraft, positive below the aircraft
yb (lateral) axis - perpendicular to the xb,zb-plane, positive determined by the right-hand rule (generally, positive out the right wing)
Wind frame
Origin - airplane center of gravity
xw axis - positive in the direction of the velocity vector of the aircraft relative to the air
zw axis - perpendicular to the xw axis, in the plane of symmetry of the aircraft, positive below the aircraft
yw axis - perpendicular to the xw,zw-plane, positive determined by the right hand rule (generally, positive to the right)
The Euler angles linking these reference frames are:
Earth frame to body frame: yaw angle ψ, pitch angle θ, and roll angle φ
Earth frame to wind frame: heading angle σ, flight-path angle γ, and bank angle μ
Wind frame to body frame: angle of sideslip β, angle of attack α (in this transformation, the angle analogous to φ and μ is always zero)
Force balance and the steady flight equations
The forces acting on an aircraft in flight are the weight, aerodynamic force, and thrust. The weight is easiest to express in the Earth frame, where it has magnitude W and is in the +zE direction, towards the center of the Earth. The weight is assumed to be constant over time and constant with altitude.
Expressing the aerodynamic force in the wind frame, it has a drag component with magnitude D opposite the velocity vector in the −xw direction, a side force component with magnitude C in the +yw direction, and a lift component with magnitude L in the −zw direction.
In general, the thrust can have components along each body frame axis. For fixed wing aircraft with engines or propellers fixed relative to the fuselage, thrust is usually closely aligned with the +xb direction. Other types of aircraft, such as rockets and airplanes that use thrust vectoring, can have significant components of thrust along the other body frame axes. In this article, aircraft are assumed to have thrust with magnitude T and fixed direction +xb.
Steady flight is defined as flight where the aircraft's linear and angular velocity vectors are constant in a body-fixed reference frame such as the body frame or wind frame. In the Earth frame, the velocity may not be constant since the airplane may be turning, in which case the airplane has a centripetal acceleration in the xE-yE plane, where is the magnitude of the true airspeed and is the turn radius.
This equilibrium can be expressed along a variety of axes in a variety of reference frames. The traditional steady flight equations derive from expressing this force balance along three axes: the xw-axis, the radial direction of the aircraft's turn in the xE-yE plane, and the axis perpendicular to xw in the xw-zE plane,
where g is the standard acceleration due to gravity.
These equations can be simplified with several assumptions that are typical of simple, fixed-wing flight. First, assume that the sideslip β is zero, or coordinated flight. Second, assume the side force C is zero. Third, assume that the angle of attack α is small enough that cos(α)≈1 and sin(α)≈α, which is typical since airplanes stall at high angles of attack. Similarly, assume that the flight-path angle γ is small enough that cos(γ)≈1 and sin(γ)≈γ, or equivalently that climbs and descents are at small angles relative to horizontal. Finally, assume that thrust is much smaller than lift, T≪L. Under these assumptions, the equations above simplify to
These equations show that the thrust must be sufficiently large to cancel drag and the longitudinal component of weight. They also show that the lift must be sufficiently large to support the aircraft weight and accelerate the aircraft through turns.
Dividing the second equation by the third equation and solving for R shows that the turn radius can be written in terms of the true airspeed and the bank angle,
The constant angular velocity in the body frame leads to a balance of moments, as well. Most notably, the pitching moment being zero puts a constraint on the longitudinal motion of the aircraft that can be used to determine the elevator control input.
Force balance in straight and level flight
In steady level longitudinal flight, also known as straight and level flight, the aircraft holds a constant heading, airspeed, and altitude. In this case, the flight-path angle , the bank angle , and the turn radius becomes infinitely large since the airplane is not turning. For steady level longitudinal flight, the steady flight equations simplify to
So, in this particular steady flight maneuver thrust counterbalances drag while lift supports the aircraft's weight. This force balance is pictured in the graphic at the beginning of the article.
Steady flight maneuvers
The most general maneuver described by the steady flight equations above is a steady climbing or descending coordinated turn. The trajectory the aircraft flies during this maneuver is a helix with zE as its axis and a circular projection on the xE-yE plane. Other steady flight maneuvers are special cases of this helical trajectory.
Steady longitudinal climbs or descents (without turning): bank angle μ=0
Steady level turns: flight-path angle γ=0
Steady level longitudinal flight, also known as straight and level flight: bank angle μ=0 and flight-path angle γ=0
Steady gliding descents (turning or longitudinal): thrust T=0
The definition of steady flight also allows for other maneuvers that are steady only instantaneously if the control inputs are held constant. These include the steady roll, where there is a constant and non-zero roll rate, and the steady pull up, where there is a constant but non-zero pitch rate.
See also
Flight dynamics (fixed-wing aircraft)
Notes
References
Aerodynamics | Steady flight | Chemistry,Engineering | 1,424 |
24,093,673 | https://en.wikipedia.org/wiki/Pangu%20utility | The PANGU (Planet and Asteroid Natural scene Generation Utility) is a computer graphics utility of which the development was funded by ESA and performed by University of Dundee. It generates scenes of planets, moons, asteroids, spacecraft and rovers. The main purpose of the tool is to test and validate navigation techniques based on the processing of images coming from on-board sensors, such as a camera or imaging LIDAR on a planetary lander.
References
External links
http://spacetech.dundee.ac.uk/research/planetary-lander-technology/pangu/pangu-planet-and-asteroid-natural-scene-generation-utilit
PANGU User Resources
Graphics software | Pangu utility | Astronomy | 141 |
31,001,884 | https://en.wikipedia.org/wiki/Transcription%20activator-like%20effector%20nuclease | Transcription activator-like effector nucleases (TALEN) are restriction enzymes that can be engineered to cut specific sequences of DNA. They are made by fusing a TAL effector DNA-binding domain to a DNA cleavage domain (a nuclease which cuts DNA strands). Transcription activator-like effectors (TALEs) can be engineered to bind to practically any desired DNA sequence, so when combined with a nuclease, DNA can be cut at specific locations. The restriction enzymes can be introduced into cells, for use in gene editing or for genome editing in situ, a technique known as genome editing with engineered nucleases. Alongside zinc finger nucleases and CRISPR/Cas9, TALEN is a prominent tool in the field of genome editing.
TALE DNA-binding domain
TAL effectors are proteins that are secreted by Xanthomonas bacteria via their type III secretion system when they infect plants. The DNA binding domain contains a repeated highly conserved 33–34 amino acid sequence with divergent 12th and 13th amino acids. These two positions, referred to as the Repeat Variable Diresidue (RVD), are highly variable and show a strong correlation with specific nucleotide recognition. This straightforward relationship between amino acid sequence and DNA recognition has allowed for the engineering of specific DNA-binding domains by selecting a combination of repeat segments containing the appropriate RVDs. Notably, slight changes in the RVD and the incorporation of "nonconventional" RVD sequences can improve targeting specificity.
DNA cleavage domain
The non-specific DNA cleavage domain from the end of the FokI endonuclease can be used to construct hybrid nucleases that are active in a yeast assay. These reagents are also active in plant cells and in animal cells. Initial TALEN studies used the wild-type FokI cleavage domain, but some subsequent TALEN studies also used FokI cleavage domain variants with mutations designed to improve cleavage specificity and cleavage activity. The FokI domain functions as a dimer, requiring two constructs with unique DNA binding domains for sites in the target genome with proper orientation and spacing. Both the number of amino acid residues between the TALE DNA binding domain and the FokI cleavage domain and the number of bases between the two individual TALEN binding sites appear to be important parameters for achieving high levels of activity.
Engineering TALEN constructs
The simple relationship between amino acid sequence and DNA recognition of the TALE binding domain allows for the efficient engineering of proteins. In this case, artificial gene synthesis is problematic because of improper annealing of the repetitive sequence found in the TALE binding domain. One solution to this is to use a publicly available software program (DNAWorks) to calculate oligonucleotides suitable for assembly in a two step PCR oligonucleotide assembly followed by whole gene amplification. A number of modular assembly schemes for generating engineered TALE constructs have also been reported. Both methods offer a systematic approach to engineering DNA binding domains that is conceptually similar to the modular assembly method for generating zinc finger DNA recognition domains.
Transfection
Once the TALEN constructs have been assembled, they are inserted into plasmids; the target cells are then transfected with the plasmids, and the gene products are expressed and enter the nucleus to access the genome. Alternatively, TALEN constructs can be delivered to the cells as mRNAs, which removes the possibility of genomic integration of the TALEN-expressing protein. Using an mRNA vector can also dramatically increase the level of homology directed repair (HDR) and the success of introgression during gene editing.
Genome editing
Mechanisms
TALEN can be used to edit genomes by inducing double-strand breaks (DSB), which cells respond to with repair mechanisms.
Non-homologous end joining (NHEJ) directly ligates DNA from either side of a double-strand break where there is very little or no sequence overlap for annealing. This repair mechanism induces errors in the genome via indels (insertion or deletion), or chromosomal rearrangement; any such errors may render the gene products coded at that location non-functional. Because this activity can vary depending on the species, cell type, target gene, and nuclease used, it should be monitored when designing new systems. A simple heteroduplex cleavage assay can be run which detects any difference between two alleles amplified by PCR. Cleavage products can be visualized on simple agarose gels or slab gel systems.
Alternatively, DNA can be introduced into a genome through NHEJ in the presence of exogenous double-stranded DNA fragments.
Homology directed repair can also introduce foreign DNA at the DSB as the transfected double-stranded sequences are used as templates for the repair enzymes.
Applications
TALEN has been used to efficiently modify plant genomes, creating economically important food crops with favorable nutritional qualities. They have also been harnessed to develop tools for the production of biofuels. In addition, it has been used to engineer stably modified human embryonic stem cell and induced pluripotent stem cell (IPSCs) clones and human erythroid cell lines, to generate knockout C. elegans, knockout rats, knockout mice, and knockout zebrafish. Moreover, the method can be used to generate knockin organisms. Wu et al.obtained a Sp110 knockin cattle using Talen nickases to induce increased resistance of tuberculosis. This approach has also been used to generate knockin rats by TALEN mRNA microinjection in one-cell embryos.
TALEN has also been utilized experimentally to correct the genetic errors that underlie disease. For example, it has been used in vitro to correct the genetic defects that cause disorders such as sickle cell disease, xeroderma pigmentosum, and epidermolysis bullosa. Recently, it was shown that TALEN can be used as tools to harness the immune system to fight cancers; TALEN-mediated targeting can generate T cells that are resistant to chemotherapeutic drugs and show anti-tumor activity.
In theory, the genome-wide specificity of engineered TALEN fusions allows for correction of errors at individual genetic loci via homology-directed repair from a correct exogenous template. In reality, however, the in situ application of TALEN is currently limited by the lack of an efficient delivery mechanism, unknown immunogenic factors, and uncertainty in the specificity of TALEN binding.
Another emerging application of TALEN is its ability to combine with other genome engineering tools, such as meganucleases. The DNA binding region of a TAL effector can be combined with the cleavage domain of a meganuclease to create a hybrid architecture combining the ease of engineering and highly specific DNA binding activity of a TAL effector with the low site frequency and specificity of a meganuclease.
In comparison to other genome editing techniques, TALEN falls in the middle in terms of difficulty and cost. Unlike ZFNs, TALEN recognizes single nucleotides. It's far more straightforward to engineer interactions between TALEN DNA binding domains and their target nucleotides than it is to create interactions with ZFNs and their target nucleotide triplets. On the other hand, CRISPR relies on ribonucleotide complex formation instead of protein/DNA recognition. gRNAs have occasionally limitations regarding feasibility due to lack of PAM sites in the target sequence and even though they can be cheaply produced, the current development lead to a remarkable decrease of cost for TALENs, so that they are in a similar price and time range like CRISPR based genome editing.
TAL effector nuclease precision
The off-target activity of an active nuclease may lead to unwanted double-strand breaks and may consequently yield chromosomal rearrangements and/or cell death. Studies have been carried out to compare the relative nuclease-associated toxicity of available technologies. Based on these studies and the maximal theoretical distance between DNA binding and nuclease activity, TALEN constructs are believed to have the greatest precision of the currently available technologies.
See also
Genome editing with engineered nucleases
Zinc finger nuclease
Meganuclease
CRISPR
References
External links
E-TALEN.org A comprehensive tool for TALEN design
PDB Molecule of the Month An entry in the Protein Database's monthly structural highlight
Biological engineering
DNA
Genetic engineering
Genome editing
History of biotechnology
Molecular biology
Non-coding RNA
Repetitive DNA sequences | Transcription activator-like effector nuclease | Chemistry,Engineering,Biology | 1,751 |
56,071,996 | https://en.wikipedia.org/wiki/List%20of%20investigational%20antipsychotics | This is a list of investigational antipsychotics, or antipsychotics that are currently under development for clinical use but are not yet approved. Chemical/generic names are listed first, with developmental code names, synonyms, and brand names in parentheses.
This list was last comprehensively updated in December 2017. It is likely to become outdated with time.
Receptor modulators
Monoamine receptor modulators
Brilaroxazine (RP5063; oxaripiprazole) – atypical antipsychotic (D2/3/4 and 5-HT1A partial agonist and 5-HT2A/2B/7 antagonist)
FKF-02SC (TGOF-02N) – atypical antipsychotic (D2 and 5-HT2A receptor antagonist, other actions)
Masupirdine (SUVN-502) – 5-HT6 receptor antagonist
N-Methylamisulpride (LB-102) – D2,3, 5-HT7, receptor antagonist (methylated version of amisulpride)
Ralmitaront (RG-7906, RO-6889450) – TAAR1 agonist
Ulotaront (SEP-856, SEP-363856) – 5-HT1A receptor and TAAR1 agonist
Usmarapride (SUVN-D4010) – 5-HT4 receptor partial agonist
Glutamate receptor modulators
Pomaglumetad methionil (DB-103, LY-2140023, LY-2812223) – mGluR2 and mGluR3 agonist
Iclepertin – glycine transporter-1 inhibitor
Acetylcholine receptor modulators
Emraclidine (CVL-231) – M4 muscarinic acetylcholine receptor positive allosteric modulator.
ML-007 – M1 and M4 muscarinic acetylcholine receptor agonist.
NBI-1117568 (HTL 0016878) – M4 muscarinic acetylcholine receptor agonist.
NS-136 – M4 muscarinic acetylcholine receptor positive allosteric modulator
Cannabinoid receptor modulators
Cannabidiol (CBD; GW-42003, GWP-42003, GWP-42003-P, ECP-012A; Arvisol, Epidiolex) – cannabinoid receptor modulator, antioxidant, other actions
Other/mixed receptor modulators
CVN766 – Orexin receptor type 1 antagonist
Deudextromethorphan (d-DM; AVP-786, CTP-786) – σ1 receptor agonist, serotonin–norepinephrine reuptake inhibitor, uncompetitive NMDA receptor antagonist, muscarinic acetylcholine receptor agonist, other actions
Roluperidone (CYR-101, MIN-101, MT-210) – 5-HT2A and σ2 receptor antagonist
TAK-041 (NBI 1065846) – GPR139 receptor agonist
Enzyme inhibitors
Luvadaxistat (NBI 1065844, TAK-831) – D-amino acid oxidase inhibitor. (DAAO is a pathway to NMDAR.)
MK-8189 – phosphodiesterase 10A inhibitor.
Osoresnontrine (BI-409306, SUB-166499) – phosphodiesterase 9A inhibitor
Sodium benzoate (SND-11, SND-12, SND-13, SND-14; Clozaben, NaBen) – D-amino acid oxidase inhibitor
Ion channel modulators
Evenamide (NW-3509; NW-3509A) – Nav1.3, Nav1.7, and Nav1.8 voltage-gated sodium channel blocker
Others
TS-134 (TS-1341) – undefined mechanism of action
Kratom – Has shown antipsychotic-like effects on par with haloperidol in animal testing
See also
List of investigational drugs
References
External links
AdisInsight – Springer
2016 Medicines in Development for Mental Health – PhRMA
Antipsychotics
Antipsychotics, investigational
Dynamic lists
Experimental psychiatric drugs | List of investigational antipsychotics | Chemistry | 956 |
78,826,190 | https://en.wikipedia.org/wiki/Giving%20Machine | A Giving Machine is a specialized vending machine that allows people to donate various items to select nonprofit organizations. The vending machines are put up in public areas throughout the world during the Christmas and holiday season by The Church of Jesus Christ of Latter-day Saints (also known as the LDS or Mormon Church).
Overview
The Church of Jesus Christ of Latter-day Saints partners with both multinational, national, and local charities in various cities throughout the world. These charities select items that will help them fulfill their mission. People using the machines select an item, which is symbolized by a car with a picture, the name of the item, the name of the charity requesting the item, and the price. After purchasing the item, the card drops into a collection bin that allows people to see the items that have been donated. At certain machines, people can take photos with the card to share on social media, with the intention of spreading the word.
Examples of items are a $2.00 box of macaroni and cheese, an $8.00 hygiene kit, a $200 emergency utility bill payment, and various priced livestock. The money from raised from the machines goes to the charity requesting the various items. The charities are expected to use the money for the requested item although occasionally will use it for other similar items or initiatives. The LDS Church does not keep any money from the machines, and pays for their upkeep and space rental from other funds.
Machines are generally staffed by local Latter-day Saints or Church service missionaries.
History
The first Giving Machine was unveiled in 2017 in Salt Lake City, Utah at the Joseph Smith Memorial Building on Temple Square and the number of locations has slowly increased. The machines were not available in 2020 due to the COVID-19 pandemic.
References
The Church of Jesus Christ of Latter-day Saints
Vending machines | Giving Machine | Engineering | 375 |
1,142,259 | https://en.wikipedia.org/wiki/Balance%20shaft | Balance shafts are used in piston engines to reduce vibration by cancelling out unbalanced dynamic forces. The counter balance shafts have eccentric weights and rotate in opposite direction to each other, which generates a net vertical force.
The balance shaft was invented and patented by British engineer Frederick W. Lanchester in 1907. It is most commonly used in inline-four and V6 engines used in automobiles and motorcycles.
Overview
The operating principle of a balance shaft system is that two shafts carrying identical eccentric weights rotate in opposite directions at twice the engine speed. The phasing of the shafts is such that the centrifugal forces produced by the weights cancel the vertical second-order forces (at twice the engine RPM) produced by the engine. The horizontal forces produced by the balance shafts are equal and opposite, and so cancel each other.
The balance shafts do not reduce the vibrations experienced by the crankshaft.
Applications
Two-cylinder engines
Numerous motorcycle engines— particularly parallel-twin engines— have employed balance shaft systems, for example the Yamaha TRX850 and Yamaha TDM850 engines have a 270° crankshaft with a balance shaft. An alternative approach, as used by the BMW GS parallel-twin, is to use a 'dummy' connecting rod which moves a hinged counterweight.
Four-cylinder engines
Balance shafts are often used in inline-four engines, to reduce the second-order vibration (a vertical force oscillating at twice the engine RPM) that is inherent in the design of a typical inline-four engine. This vibration is generated because the movement of the connecting rods in an even-firing inline-four engine is not symmetrical throughout the crankshaft rotation; thus during a given period of crankshaft rotation, the descending and ascending pistons are not always completely opposed in their acceleration, giving rise to a net vertical force twice in each revolution (which increases quadratically with RPM).
The amount of vibration also increases with engine displacement, resulting in balance shafts often being used in inline-four engines with displacements of or more. Both an increased stroke or bore cause an increased secondary vibration; a larger stroke increases the difference in acceleration and a larger bore increases the mass of the pistons.
The Lanchester design of balance shaft systems was refined with the Mitsubishi Astron 80, an inline-four car engine introduced in 1975. This engine was the first to locate one balance shaft higher than the other, to counteract the second order rolling couple (i.e. about the crankshaft axis) due to the torque exerted by the inertia caused by increases and decreases in engine speed.
In a flat-four engine, the forces are cancelled out by the pistons moving in opposite directions. Therefore balance shafts are not needed in flat-four engines.
Five-cylinder engines
Balance shafts are also used in straight-five engines such as GM Vortec 3700.
Six-cylinder engines
In a straight-six engine and flat-six engine, the rocking forces are naturally balanced out, therefore balance shafts are not required.
V6 engines are inherently unbalanced, regardless of the V-angle. Any inline engine with an odd number of cylinders has a primary imbalance, which causes an end-to-end rocking motion. As each cylinder bank in a V6 has three cylinders, each cylinder bank experiences this motion. Balance shaft(s) are used on various V6 engines to reduce this rocking motion.
Eight-cylinder engines
Examples are the Mercedes-Benz OM629 and Volvo B8444S engine.
See also
Balancing machine
Engine balance
References
Engine technology | Balance shaft | Technology | 716 |
53,266,177 | https://en.wikipedia.org/wiki/Targeted%20analysis%20sequencing | Targeted analysis sequencing (sometimes called target amplicon sequencing) (TAS) is a next-generation DNA sequencing technique focusing on amplicons and specific genes. It is useful in population genetics since it can target a large diversity of organisms. The TAS approach incorporates bioinformatics techniques to produce a large amount of data at a fraction of the cost involved in Sanger sequencing. TAS is also useful in DNA studies because it allows for amplification of the needed gene area via PCR, which is followed by next-gen sequencing platforms. Next-gen sequencing use shorter reads 50–400 base pairs which allow for quicker sequencing of multiple specimens. Thus TAS allows for a cheaper sequencing approach for that is easily scalable and offers both reliability and speed.
References
DNA sequencing | Targeted analysis sequencing | Chemistry,Biology | 160 |
2,728,382 | https://en.wikipedia.org/wiki/Beta%20Delphini | Beta Delphini (β Delphini, abbreviated Beta Del, β Del) is a binary star in the constellation of Delphinus. It is the brightest star in Delphinus.
The two components of the system are designated Beta Delphini A (officially named Rotanev , which is historically the name of the system) and B.
Nomenclature
β Delphini (Latinised to Beta Delphini) is the binary's Bayer designation. The designations of the two components as Beta Delphini A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).
Beta Delphini bore an historical name, Rotanev, which arose as follows: Niccolò Cacciatore was the assistant to Giuseppe Piazzi, and later his successor as Director of the Palermo Observatory. The name first appeared in Piazzi's Palermo Star Catalogue. When the Catalogue was published in 1814, the unfamiliar names Sualocin and Rotanev were attached to Alpha and Beta Delphini, respectively. Eventually the Reverend Thomas Webb, a British astronomer, puzzled out the explanation. Cacciatore's name, Nicholas Hunter in English translation, would be Latinized to Nicolaus Venator. Reversing the letters of this construction produces the two names. They have endured, the result of Cacciatore's little practical joke of naming the two after himself. How Webb arrived at this explanation 45 years after the publication of the catalogue is still a mystery.
In 2016, the International Astronomical Union 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 Rotanev for the component Beta Delphini A on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.
In Chinese, (), meaning Good Gourd, refers to an asterism consisting of Beta Delphini, Alpha Delphini, Gamma2 Delphini, Delta Delphini, and Zeta Delphini.
Properties
Beta Delphini was found to be a binary star system in 1873 by the American astronomer S. W. Burnham. The system consists of a pair of F-type stars that orbit each other with a period of 26.66 years and an eccentricity of 0.36. The plane of the orbit is inclined by an angle of 61° to the line of sight from the Earth. The two stars have an angular separation of about 0.44 arcseconds, making them a challenge to resolve with a telescope. The larger member of the pair is a giant star with 1.75 times the mass and 24 times the luminosity of the Sun, while the secondary component is a subgiant star that has 1.47 times the Sun's mass and around 8 times the Sun's luminosity. The system is around 1.8 billion years old.
See also
Sualocin and Rotanev
References
External links
Delphinus
F-type subgiants
F-type giants
Binary stars
Delphini, Beta
Delphini, 06
196524
101769
Rotanev
BD+14 4369
7882 | Beta Delphini | Astronomy | 684 |
58,665,743 | https://en.wikipedia.org/wiki/Latifa%20Elouadrhiri | Latifa Elouadrhiri is a Moroccan experimental physicist and researcher at Thomas Jefferson National Accelerator Facility studying elementary particle physics and nuclear physics.
She has worked significantly with the CLAS collaboration in Jefferson Lab's Hall B, performing 3D imaging of nucleons. Additionally, she is the spokesperson of the Deeply Virtual Compton Scattering (DVCS) experiment, studying Generalized Parton Distributions
.
Elouadrhiri is a fellow of the American Physical Society, and has served as a member of the Department of Energy (DOE) Nuclear Science Advisory Committee (NSAC) and the DOE Nuclear Physics (NP) Committee of Visitors (COV).
Childhood
Latifa Elouadrhiri’s was born in Morocco she was one of eight children. She was born to a mother who had never been to school and couldn't read or write but who supported them and "believed in the power of education." Elouadrhiri became fascinated with physics when she first took a physics class in high school. When she turned 15 she got her first physics book from a flea market.
Education
Elouadrhiri obtained a physics B.Sc. from Mohammed V University in 1984, continuing to complete a M.Sc. in theoretical physics in 1987 entitled Poincare and Lorentz group (Group Theory). She continued to complete a Diplôme des Etudes Approfondies at the University of Blaise Pascal, Clermont-Ferrand in particle physics in 1987 entitled Development of Drift Chamber tracking Program. Following this, she completed her PhD in 1991 in physics, also at the University of Blaise Pascal, Clermont-Ferrand in experimental hadronic physics with electromagnetic probes, producing a thesis entitled Measurement of the Nucleon Axial Form Factor from Low Energy Pion Electroproduction (Saclay nuclear physics experiment)
Career
At an American Physical Society meeting her work got the attention of Nathan Isgur who at the time was the chief scientist and Jefferson Lab. In 1994, Elouadrhiri chose to come to Jefferson Laboratory for a joint appointment with CNU, joining the lab as a staff scientist in 2001 as one of the first female staff scientists in the physics division. Here, she led the measurement of the first observation of electron beam asymmetries in polarized, exclusive Deeply Virtual Compton Scattering. From 2006 to 2015, Elouadrhiri was the Project Manager for the Hall B 12 GeV Upgrade, including all detectors, magnets and infrastructure for the CLAS12 system.
Other
In 2015, Elouadrhiri was interviewed for an article in the Chicago Tribune about the impacts of women in science and engineering.
In 2018, she was personally recognized by the US Embassy in Rabat for her contributions to nuclear physics on both the official embassy Twitter and Facebook pages.
Honors and awards
2010 Inducted a Fellow of the American Physical Society
2021 Received the Jesse W. Beams Award
References
External links
Latifah Elouadrhiri's GWU Bio Page
Interview with Elouadrhiri
Living people
21st-century American physicists
Experimental physicists
20th-century American physicists
Fellows of the American Physical Society
Moroccan women physicists
American women physicists
20th-century American women scientists
21st-century American women scientists
Moroccan physicists
Mohammed V University alumni
Year of birth missing (living people) | Latifa Elouadrhiri | Physics | 673 |
5,579,825 | https://en.wikipedia.org/wiki/JTS%20Topology%20Suite | JTS Topology Suite (Java Topology Suite) is an open-source Java software library that provides an object model for Euclidean planar linear geometry together with a set of fundamental geometric functions. JTS is primarily intended to be used as a core component of vector-based geomatics software such as geographical information systems. It can also be used as a general-purpose library providing algorithms in computational geometry.
JTS implements the geometry model and API defined in the OpenGIS Consortium Simple Features Specification for SQL.
JTS defines a standards-compliant geometry system for building spatial applications; examples include viewers, spatial query processors, and tools for performing data validation, cleaning and integration.
In addition to the Java library, the foundations of JTS and selected functions are maintained in a C++ port, for use in C-style linking on all major operating systems, in the form of the GEOS software library.
Up to JTS 1.14, and the GEOS port, are published under the GNU Lesser General Public License (LGPL).
With the LocationTech adoption future releases will be under the EPL/BSD licenses.
Scope
JTS provides the following functionality:
Geometry model
Geometry classes support modelling points, linestrings, polygons, and collections. Geometries are linear, in the sense that boundaries are implicitly defined by linear interpolation between vertices. Geometries are embedded in the 2-dimensional Euclidean plane. Geometry vertices may also carry a Z value.
User-defined precision models are supported for geometry coordinates. Computation is performed using algorithms which provide robust geometric computation under all precision models.
Geometric functions
Topological validity checking
Area and Distance functions
Spatial Predicates based on the Egenhofer DE-9IM model
Overlay functions (including intersection, difference, union, symmetric difference)
Buffer computation (including different cap and join types)
Convex hull
Geometric simplification including the Douglas–Peucker algorithm
Geometric densification
Linear referencing
Precision reduction
Delaunay triangulation and constrained Delaunay triangulation
Voronoi diagram generation
Smallest enclosing rectangle
Discrete Hausdorff distance
Spatial structures and algorithms
Robust line segment intersection
Efficient line arrangement intersection
Efficient point in polygon
Spatial index structures including quadtree and STR-tree
Planar graph structures and algorithms
I/O capabilities
Reading and writing of WKT, WKB and GML formats
History
Funding for the initial work on JTS was obtained in the Fall 2000 from GeoConnections and the Government of British Columbia, based on a proposal put forward by Mark Sondheim and David Skea. The work was carried out by Martin Davis (software design and lead developer) and Jonathan Aquino (developer), both of Vivid Solutions at the time. Since then JTS has been maintained as an independent software project by Martin Davis.
Since late 2016/early 2017 JTS has been adopted by LocationTech.
Projects using JTS
GeoServer
GeoTools
OpenJUMP and forks
uDig
gvSIG
Batik
Hibernate Spatial
Whitebox Geospatial Analysis Tools
Platforms
JTS is developed under the Java JDK 1.4 platform. It is 100% pure Java. It will run on all more recent JDKs as well.
JTS has been ported to the .NET Framework as the Net Topology Suite.
A JTS subset has been ported to C++, with entry points declared as C interfaces, as the GEOS library.
C/C++ port: GEOS
GEOS is the C/C++ port of a subset of JTS and selected functions. It is a foundation component in a software ecosystem of native, compiled executable binaries on Linux, Mac and Windows platforms. Due to the runtime construction of Java and the Java Virtual Machine (JVM), code libraries that are written in Java are basically not usable as libraries from a standardized cross-linking environment (often built from C). Linux, Microsoft Windows and the BSD family, including Mac OSX, use a linking structure that enables libraries from various languages to be integrated (linked) into a native runtime executable. Java, by design, does not participate in this interoperability without unusual measures (JNI).
Applications using GEOS
GEOS links and ships internally in popular applications listed below; and, by delineating and implementing standards-based geometry classes available to GDAL, which in turn is a widely supported inner-engine in GIS, GEOS becomes a core geometry implementation in even more applications:
GDAL - OGR - raster and vector data munging
QGIS - Desktop cross-platform, open source GIS
PostGIS - spatial types and operations for PostgreSQL
GeoDjango – Django's support for GIS-enabled databases
Google Earth – A virtual globe and world imaging program
GRASS GIS Library and Application
MapServer - an open source development environment for building spatially enabled internet applications
World Wind Java – NASA's open source virtual globe and world imaging technology
Orfeo toolbox – A satellite image processing library
R – Open source statistical software with extensions for spatial data analysis.
SAGA GIS A cross-platform open source GIS software
See also
DE-9IM, a topological model
Geospatial topology
References
External links
Net Topology Suite Home page
GEOS Home page
Geometric algorithms
Application programming interfaces
Free software programmed in Java (programming language)
Geographic data and information software
Geometric topology | JTS Topology Suite | Mathematics | 1,102 |
52,475,512 | https://en.wikipedia.org/wiki/7%CE%B1-Hydroxyepiandrosterone | 7α-Hydroxyepiandrosterone (7α-OH-EPIA), also known as 3β,7α-dihydroxy-5α-androstan-17-one, is an endogenous, naturally occurring metabolite of epiandrosterone and dehydroepiandrosterone (DHEA) that is formed by the enzyme CYP7B1 in tissues such as the liver and brain.
See also
7β-Hydroxyepiandrosterone
7α-Hydroxy-DHEA
7β-Hydroxy-DHEA
7-Oxo-DHEA
References
Androstanes
Diols
Ketones | 7α-Hydroxyepiandrosterone | Chemistry | 141 |
1,312,201 | https://en.wikipedia.org/wiki/Jon%20Huntsman%20Sr. | Jon Meade Huntsman Sr. (June 21, 1937 – February 2, 2018) was an American businessman and philanthropist. He was the founder and executive chairman of Huntsman Corporation, a global manufacturer and marketer of specialty chemicals. Huntsman plastics are used in a wide variety of familiar objects, including (formerly) clamshell containers for McDonald's hamburgers. Huntsman Corporation also manufactures a wide variety of organic and inorganic chemicals that include polyurethanes, textiles, and pigments. Huntsman's philanthropic giving exceeded $1.5 billion, focusing on areas of cancer research, programs at various universities, and aid to Armenia.
Early life and education
Jon Meade Huntsman was born in Blackfoot, Idaho, into a poor family. His mother, Sarah Kathleen (née Robison; 1910–1969), was a homemaker, and his father, Alonzo Blaine Huntsman Sr. (1910–1990), was a teacher. In 1950, the family moved to Palo Alto, California, where Alonzo pursued graduate studies at Stanford University, earning an M.A. and Ed.D. He then became a superintendent of schools in the Los Altos district.
Jon Huntsman attended Palo Alto High School, where he became student body president. He was recruited by Harold Zellerbach, chairman of Crown-Zellerbach Paper Company, to attend the Wharton School of the University of Pennsylvania on a Zellerbach scholarship. He graduated from Wharton in the spring of 1959, a brother of the Sigma Chi fraternity.
Huntsman married Karen Haight, daughter of David B. Haight, in June 1959, just weeks after he graduated. Both were members of the Church of Jesus Christ of Latter-day Saints (LDS Church). In July 1959, Huntsman left to serve for two years in the U.S. Navy as an officer aboard the USS Calvert. He subsequently earned an MBA from the University of Southern California's Marshall School of Business in 1966.
Business career
Dolco Packaging Corporation
In 1961, Huntsman was employed by Olson Brothers, Inc., an egg-producing company in Los Angeles. There, he advanced through the ranks to assume the role of vice president of operations. Recognizing that the company sustained substantial losses due to poor packaging, Huntsman became interested in developing a better alternative. His leadership was key in developing the first plastic egg carton. In 1965, he established contact with the polystyrene operations of the Dow Chemical Company. In 1967, he became president of a joint venture between Olson Brothers, Inc., and Dow Chemical, the Dolco Packaging Corporation.
Huntsman Container Corporation
Seeing an opportunity to create packaging for the emerging fast-food industry, Huntsman left Dolco in 1970 to form the Huntsman Container Corporation with his brother, Alonzo Blaine Jr. (1936–2012), and others in Fullerton, California. Plants were constructed in Fullerton, California, in 1971 and in Troy, Ohio, in 1972. Since cash flow was an issue for the new company, Huntsman mortgaged his house and borrowed heavily from banks. In 1973 the company nearly collapsed when an Arab oil embargo cut off supplies of polystyrene, used to make expandable/expanded polystyrene (or EPS).
In 1974, Huntsman Container Corporation created the "clamshell" container for McDonald's Big Mac. The company also developed other popular products, including the first plastic plates, bowls, and fast-food containers. In 1976, after completion of its first international plant at Skelmersdale, England, a stock deal was arranged to sell Huntsman Container Corporation to Keyes Fiber Company. Huntsman continued to serve as CEO of the container business for four more years and held a directorship of Keyes Fiber Company.
Huntsman Chemical Company – Huntsman Corporation
In 1982, after serving as a mission president for the LDS Church in Washington, DC, for three years, Huntsman continued his plastics and petrochemical pursuits with the formation of a new company, Huntsman Chemical Company, in Salt Lake City, Utah. In his capacity as CEO and Chairman, he grew the business into a multibillion-dollar company, in part by acquiring a number of businesses in the polystyrene, styrene, and polypropylene industry when they were not seen as profitable. Between 1986 and 2000 Huntsman acquired 36 companies, 35 of which turned out to be hugely profitable.
In 1994, the Huntsman Chemical Company was renamed the Huntsman Corporation. In 1996, Peter R. Huntsman became President and COO of Huntsman Corporation. In 2000 he replaced his father as the company's CEO. Jon M. Huntsman continued to be involved in the company as Chairman.
During the 2000s, Huntsman continued its pattern of expansion, both in America and around the world, and reorganization. Huntsman Corporation became publicly traded on the New York Stock Exchange in 2005. As of 2014, Huntsman reported that it operated 80 manufacturing and R&D facilities in 30 countries and employed approximately 12,000 associates.
Huntsman Gay Global Capital
In 2007 Huntsman co-founded an additional new private equity firm, Huntsman Gay Global Capital (now known as HGGC), with two former Bain Capital executives, Robert C. Gay (1989–2004, managing director) and Greg Benson (executive vice president in London), former Sorenson Capital co-founder and managing director Rich Lawson, and Pro Football Hall of Fame quarterback Steve Young to focus on investments in middle market companies.
Scientific awards and honors
Huntsman has been awarded thirteen honorary doctorate degrees at various universities. In 2004 he received the Othmer Gold Medal, awarded by the Chemical Heritage Foundation in recognition of contributions in research, innovation, legislation or philanthropy. In 2013 he received the Leadership Award for Lifetime Achievement from the Chemical Marketing and Economics (CM&E) group.
In 2015, he received the Bower Award from the Franklin Institute.
Personal life and death
Huntsman and his wife, Karen, were married for over 58 years and had nine children: Jon Jr., Peter, Christena, Kathleen ( 2010), David, Paul, James, Jennifer, and Mark. At the time of Huntsman's death, they had 56 grandchildren, two of whom were adopted from China and India, and 19 great-grandchildren.
Huntsman's eldest son, Jon Jr., also served as a Huntsman Corporation executive. He was elected Governor of Utah in 2004 and was a candidate in the Republican Party presidential primaries in 2012. He has also served in other governmental positions, including as Ambassador of the United States to Singapore, China, and (as of 2017) Russia.
Huntsman's second eldest son, Peter, took over as CEO of the Huntsman Corporation in July 2000 and as chairman in January 2018.
On December 8, 1987, Huntsman's son, James, then age 16, was kidnapped and held for $1 million ransom by Nicholas Hans Byrd, a former classmate. FBI agents traced the kidnapper and rescued James unharmed, but agent Al Jacobsen was stabbed in the chest during the arrest.
Huntsman has published a book about his life experience, communicating moral lessons. Titled Winners Never Cheat: Everyday Values We Learned as Children (But May Have Forgotten), it was published by Wharton School Publishing in 2005. A second edition, titled Winners Never Cheat: Even in Difficult Times, made the Wall Street Journals best-sellers list.
Huntsman was a four-time cancer survivor. He died on February 2, 2018, at his home in Salt Lake City.
Religion
As a member of the Latter Day Saints (LDS) Church, Huntsman served as an area seventy from 1996 to 2011. He also served as a regional representative, stake president, and as president of the church's Washington, D.C. Mission from 1980 to 1983.
Politics
In 1977 he was chairman of the Western States Republican Leaders. He was also the Republican Party of Utah national committeeman from 1976 to 1980. He was a friend of conservative radio talk show host Glenn Beck and has been interviewed on his show. He was more socially conservative than his son, Jon Huntsman Jr. He was close friends with both Glenn Beck on the right and Harry Reid on the left, who both helped further the mission of Huntsman Cancer Institute.
Nixon administration
While the Huntsman Container Corporation's first packaging plant was being built in 1970, Huntsman joined the Nixon Administration as Associate Administrator of the Department of Health, Education and Welfare and later served as Special Assistant and Staff Secretary to President Nixon. Upon completion of the second Huntsman Container site in Troy, Ohio, in 1972, Huntsman left the White House staff to become President and CEO of Huntsman Container, while still serving – in a non-paid position – as a consultant to the Office of the President.
Presidential elections
He served as chairman for Utah in Ronald Reagan's presidential campaign in 1984 and George H. W. Bush's campaigns in 1988 and 1992.
1988 Utah gubernatorial election
In March 1988, Huntsman announced he would run against incumbent Utah Governor Norm Bangerter in the Republican primary. Huntsman was leading in public opinion polls, sometimes by a double-digit margin. He reportedly raised almost $300,000 in campaign advertising, returning all funds raised back to the donors. A few weeks later, Huntsman went on a 10-day business trip to Asia with his friend, U.S. Senator Jake Garn, who was chairman of Governor Bangerter's campaign. In mid-April Huntsman dropped out of the gubernatorial race and endorsed the governor, saying that party unity and his business responsibilities were more important than his political career, and asking political independents to support Bangerter. Later that year, Governor Bangerter appointed Huntsman to be the first Ambassador for Economic Development for the State of Utah.
Son's 2012 Republican presidential campaign
Huntsman's son, Jon Huntsman Jr., served in the administrations of five U.S. Presidents, including Barack Obama (as U.S. Ambassador to China) and most recently Donald Trump (as Ambassador to Russia), and was a candidate for the 2012 Republican presidential nomination.
There was considerable speculation that the viability of Jon Huntsman Jr.'s campaign might depend on Jon Huntsman Sr.'s willingness to fund advertising for it, via the Superpac "Our Destiny PAC". Jon Huntsman Jr. reportedly downplayed the possibility of receiving campaign funding from his family before the New Hampshire primary election, telling NPR that "the Huntsman family gives to humanitarian causes and doesn't consider a political campaign to be a humanitarian cause". However, reports filed with the Federal Election Commission later showed that Our Destiny PAC received $2.7 million in contributions, $1.9 million of it from Huntsman Sr. Much of that money was spent on campaign ads, including $914,000 on campaign ads in New Hampshire in the two months before the January primary.
Huntsman Sr. appeared on stage with Jon Huntsman Jr. and his wife and daughters at the third-place finish celebration in Manchester, New Hampshire. Huntsman Jr. announced his intention in Manchester to continue the campaign in South Carolina but dropped out on January 16, in advance of the vote there, throwing his support to Mitt Romney.
Philanthropy
Huntsman was widely recognized for his humanitarian giving which, including contributions to the homeless, the ill and the under-privileged, exceeds $1.5 billion and has assisted thousands, both domestically and internationally. The Chronicle of Philanthropy placed Jon and Karen Huntsman second on their 2007 list of largest American donors. On January 1, 2000, The Salt Lake Tribune included him among "The 10 Utahns Who Most Influenced Our State in the 20th Century" for his donations to education and medical research. In 2001 Jon and Karen Huntsman were presented with the Entrepreneur of the Year Award for Principle-Centered Leadership. In 2003 he received the Humanitarian of the Year Award, presented by Larry King of CNN. In November 2008, the American Cancer Society presented him its Medal of Honor for Cancer Philanthropy, and in 2014 he was awarded the William E. Simon Prize for Philanthropic Leadership. In 2015, he was awarded the Philanthropy Roundtable's Carnegie Medal of Philanthropy Award.
Cancer research
One of Huntsman's most notable causes is the Huntsman Cancer Institute (HCI) at the University of Utah, of which he was the founder and principal benefactor. He and his wife Karen established the Huntsman Cancer Institute in 1993 with a gift of $10 million from the Huntsman family. The Huntsmans gave the institute a further $100 million in 1995, an amount roughly equal to a year's total distribution to researchers from the American Cancer Society. Their goal was to accelerate the work of curing cancer through human genetics. The institute is now one of America's major cancer research centers dedicated to finding a cure for cancer with a state-of-the-art cancer specialty hospital.
The Institute continues to receive substantial gifts from the Huntsman family. Huntsman, a cancer survivor, has stated "Except for my family and faith, there is no cause more important to me than fighting cancer ... I have committed the rest of my life to doing all I can to support clinical and research efforts to eliminate this disease." To date, the Huntsman family and close associates have donated more than $656 million in support of the mission of HCI.
In November 2013, Huntsman donated or raised $120 million to Huntsman Cancer Institute at the University of Utah for the construction of a new research building dedicated to children's cancer. The Primary Children's and Families' Cancer Research Center at Huntsman Cancer Institute was dedicated June 21, 2017, Huntsman's 80th birthday.
Huntsman also promoted support of the institute through the Sigma Chi fraternity. Sigma Chi chose the Huntsman Cancer Foundation as one of its preferred philanthropic partners in December 2012. As of April 12, 2013, Sigma Chi had raised their first one-million dollars for cancer research. By 2017, Sigma Chi's total has reached over five million dollars for cancer research.
Education
Huntsman had supported the University of Utah in Salt Lake City in other ways as well.
The 15,000-seat Jon M. Huntsman Center for special events opened in 1969 and is used for gymnastics, basketball, and volleyball. It has been the site of national championships in both gymnastics and basketball, including NCAA men's basketball. As of 2013, the Huntsmans have supported the building of an additional basketball practice facility, to be named the Jon M. and Karen Huntsman Basketball Center.
Huntsman has also given support to other universities. He has served as Chairman of the Board of Overseers of his alma mater, the Wharton School of the University of Pennsylvania, in Philadelphia, Pennsylvania. One of the school's signature buildings, Jon Huntsman Hall, was named in his honor. Huntsman made an unrestricted gift of more than $50 million to Wharton, which was critical to development of the $140 million project. As of 1994, the Huntsmans also endowed the Huntsman Program in International Studies and Business at the University of Pennsylvania, a four-year undergraduate program that combines business education and liberal arts.
In 1989 Huntsman gave $1 million to Utah State University in Logan, Utah, for the Huntsman Environmental Research Center. At a press conference to announce the gift, Huntsman said the preservation of the environment is the single most important issue in the world. The Huntsmans also donated $500,000 to rebuild the Alumni Center, renamed the David B. Haight Alumni Center in honor of Mrs. Huntsman's father. In December 2007, Utah State University announced that its College of Business would be renamed the Jon M. Huntsman School of Business, in recognition of a gift from Huntsman and his wife of $26 million, a major contributor for the new $40 million school of business building referred to as Huntsman Hall—the largest in the university's history to that time. In 2017, Huntsman and Charles Koch donated another $50 million to the Huntsman School of Business for student scholarships and a new Center for Growth and Opportunity.
The law library at Brigham Young University, built in 1975, was expanded and renamed for Howard W. Hunter in 1995 with financial support from Jon and Karen Huntsman and other donors. A new library building at Southern Utah University, named in honor of retiring SUU President Gerald R. Sherratt, contains the Jon and Karen Huntsman Reading Room. The Huntsmans also contributed to the Karen H. Huntsman Library in Snow College, Utah. Completed in 2010, it is a "green" building, expected to be the first academic library in the state to achieve gold Leadership in Energy and Environmental Design certification.
Aid to Armenia
Huntsman has also contributed to efforts to rebuild in Armenia, which was devastated by an earthquake in 1988. He and other family members have made 46 trips to Armenia over 25 years. He estimates that he has given at least $50 million to relief efforts in Armenia, including money to build schools and hospitals. One of his earliest projects there involved setting up a plant to make pre-stressed concrete, to supply building materials for reconstruction and to employ Armenians. The Huntsmans have built a tile roofing plant in Yerevan, apartment complexes, and a K-12 school in the city of Gyumri. The Huntsmans also provide scholarships to bring Armenian students to America to study at Utah State University. Huntsman has been granted citizenship in the country and awarded two medals of honor by Armenia, one of them the St. Mesrop Mashtots Order.
Huntsman's donations of more than $1.2 billion overall dropped him from the "Forbes 400" list as of 2010. His wealth was not disclosed; however, he was listed as number 937 on the "Forbes World's Richest Persons" for 2010. He was one of only 19 of the world's 1,200 billionaires to have donated more than $1 billion. He has said that he wants to "die broke" by giving his money away to various charities.
Rocky Anderson, Democratic mayor of Salt Lake City, has said of Huntsman:
Awards
1954 – Student body President, Palo Alto High School
1955 – Awarded the Crown Zellerbach Scholarship to The Wharton School, University of Pennsylvania
1959 – University of Pennsylvania Student Alumni Award of Merit (undergrad)
1959 – University of Pennsylvania Spoon Award (most outstanding student graduate)
1959 – International Balfour Award (most outstanding Sigma Chi in US/Canada)
1971 – José Marti Brotherhood Award, from Cuban Americans, Most Respected U.S. Citizen
1991 – Armenian Medal of Honor
1994 – American Academy of Achievement
1994 – Kaveler Award, Most Outstanding CEO, Chemical Industry
1994 - Inducted into the Plastics Hall of Fame
1996 – Great Humanitarian Award, Freedom Foundation
1996 – National Caring Award, Caring Institute
1997 – Horatio Alger National Award
1999 – Armenian Presidential Award
1999 – University of Pennsylvania Alumni Award of Merit
2000 – Named One of Ten Most Influential Utahns in the 20th Century
2001 – Entrepreneur of the Year, Ernst & Young
2003 – Humanitarian of the Year
2004 – Othmer Award, Outstanding Inventions in Plastics, Chemical Heritage Foundation
2005 – Giant in our City Award, Salt Lake Chamber of Commerce
2006 – American Red Cross Excellence in Governance Award
2008 – Medal of Honor, American Cancer Society
2008 – Trustee Emeritus, University of Pennsylvania
2009 – Chairman Emeritus, The Wharton School Board of Overseers (University of Pennsylvania)
2010 – Distinguished Public Service Award, American Assn. for Cancer Research
2010 – Inducted into Idaho's Hall of Fame
2010 – National Award for Charity (Restoring Honor Day, Washington, D.C.)
2011 – Service Above Self Award
2011 – WSJ's Innovator of the Year Award
2013 – Leadership Award for Lifetime Achievement, American Chemical Society
2014 – William E. Simon Award for Philanthropy
2015 – The Franklin Institute of Philadelphia's Business Leadership Award (Bower Award)
2015 – Philanthropy Roundtable's Carnegie Medal of Philanthropy Award
2016 – Insider Magazine listed Huntsman as second largest contributor to charities in America; Fortune Magazine names Huntsman as 2nd most generous man in America.
Controversy
Huntsman contributed to the resignation of the CEO of University of Utah Healthcare (HCI), Vivian Lee, after threatening to withhold $250 million in donations to the Huntsman Cancer Institute and attacking Lee's character in the public sphere. Lee resigned after the public backlash she received, particularly from editorials printed in the Salt Lake Tribune, a newspaper owned by the Huntsman family.
In an editorial, Huntsman described Lee as attempting a "power-grab", while Huntsman was attempting to sever HCI and University of Utah ties. This controversy has raised the question of how much private donors should have a say in publicly funded healthcare.
References
External links
Huntsman Cancer Foundation.
Huntsman biographical sketch
Huntsman Corporation
Philanthropy videos of Jon Huntsman from Salt Lake City to Armenia GoodTube.org
Glenn Beck Show – Audio/Transcript of Interview – January 31, 2008
Video about Huntsman's philanthropy, by CNN
Philanthropy Magazine article about Huntsman
1937 births
2018 deaths
20th-century Mormon missionaries
Area seventies (LDS Church)
American billionaires
American manufacturing businesspeople
American leaders of the Church of Jesus Christ of Latter-day Saints
American Mormon missionaries in the United States
21st-century American philanthropists
Military personnel from Idaho
Mission presidents (LDS Church)
Palo Alto High School alumni
People from Blackfoot, Idaho
People in the chemical industry
Huntsman family
Utah State University people
Wharton School alumni
Writers from Idaho
Writers from Utah
Utah Republicans
Marshall School of Business alumni
White House Staff Secretaries
Latter Day Saints from Idaho
Latter Day Saints from California
Latter Day Saints from Utah
Latter Day Saints from Pennsylvania
Benjamin Franklin Medal (Franklin Institute) laureates | Jon Huntsman Sr. | Chemistry | 4,432 |
3,516,085 | https://en.wikipedia.org/wiki/Kelly%20hose | A kelly hose (also known as a mud hose or rotary hose) is a flexible, steel reinforced, high pressure hose that connects the standpipe to the kelly (or more specifically to the goose-neck on the swivel above the kelly) and allows free vertical movement of the kelly while facilitating the flow of drilling fluid through the system and down the drill string. The Kelly hose has a diameter of 3-5 inches (inside diameter).
References
Petroleum engineering
Drilling technology
Hoses | Kelly hose | Chemistry,Engineering | 99 |
7,661,439 | https://en.wikipedia.org/wiki/Argon%20fluorohydride | Argon fluorohydride (systematically named fluoridohydridoargon) or argon hydrofluoride is an inorganic compound with the chemical formula HArF (also written ArHF). It is a compound of the chemical element argon.
Discovery
The discovery of this argon compound is credited to a group of Finnish scientists, led by Markku Räsänen. On 24 August 2000, in the journal Nature, they announced their discovery of argon fluorohydride. This discovery caused the recognition that argon could form weakly bound compounds, even though it was not the first compound made with noble gases.
Synthesis
This chemical was synthesized by mixing argon and hydrogen fluoride on a caesium iodide surface at 8 K (−265 °C), and exposing the mixture to ultraviolet radiation. This caused the gases to combine.
The infrared spectrum of the resulting gas mixture shows that it definitely contains chemical bonds, albeit very weak ones; thus, it is argon fluorohydride, and not a supermolecule or a mixture of argon and hydrogen fluoride. Its chemical bonds are stable only if the substance is kept at temperatures below 27 K (−246 °C); upon warming, it decomposes into argon and hydrogen fluoride.
References
Further reading
Fluorides
Nonmetal halides
Argon compounds
Hydrogen compounds
Triatomic molecules
Substances discovered in the 2000s | Argon fluorohydride | Physics,Chemistry | 296 |
70,922,711 | https://en.wikipedia.org/wiki/Robert%20S.%20Roth | Robert S. Roth (August 21, 1926 – July 16, 2012) was an American materials scientist known for his comprehensive research into the phase diagrams of ceramic materials and the structures of nonstoichiometric compounds.
Education and career
Roth studied geology at Coe College and University of Illinois Urbana-Champaign, where he obtained his PhD in 1951. He worked at the United States Geological Survey as a field assistant, and after his PhD, he joined the National Bureau of Standards (later NIST), where he remained for most of his career. Since 1981, he was a senior editor of the book series Phase Diagrams for Ceramists, a major set of reference books in the field of ceramic materials.
While visiting CSIRO in Melbourne, Australia in the 1960s, Roth collaborated with the Australian materials scientist Arthur D. Wadsley to understand the structures of transition metal oxides, which led to a series of publications. The ordered phases of transition metal oxides exhibiting shear structures are now referred to as the Wadsley-Roth phases.
Honors and awards
Roth received the United States Department of Commerce Gold Medal in 1986. He received the Sosman Award in 1991, the John Jeppson Award in 1995, the Spriggs Phase Equilibria Award in 2003, all from the American Ceramic Society. He received the Buessem Award from the Center for Dielectric Studies in 2001.
Bibliography
References
1926 births
2012 deaths
Coe College alumni
University of Illinois Urbana-Champaign alumni
National Institute of Standards and Technology people
American materials scientists
Solid state chemists
Materials scientists and engineers | Robert S. Roth | Chemistry,Materials_science,Engineering | 314 |
25,209,987 | https://en.wikipedia.org/wiki/Ipomoea%20%C3%97%20multifida | Ipomea × multifida is a hybridogenic species. Its ancestors are I. coccinea and I. quamoclit (the cypress vine).
Its allotetraploid is Ipomoea sloteri. Both are known as cardinal climber.
References
multifida
Hybrid plants | Ipomoea × multifida | Biology | 63 |
32,108,559 | https://en.wikipedia.org/wiki/Negative%20hyperconjugation | In organic chemistry, negative hyperconjugation is the donation of electron density from a filled π- or p-orbital to a neighboring σ*-orbital. This phenomenon, a type of resonance, can stabilize the molecule or transition state. It also causes an elongation of the σ-bond by adding electron density to its antibonding orbital.
Negative hyperconjugation is seldom observed, though it can be most commonly observed when the σ*-orbital is located on certain C–F or C–O bonds.
In negative hyperconjugation, the electron density flows in the opposite direction (from a π- or p-orbital to an empty σ*-orbital) than it does in the more common hyperconjugation (from a σ-orbital to an empty p-orbital).
See also
Negative hyperconjugation in silicon
Conjugated system
References
Physical organic chemistry | Negative hyperconjugation | Chemistry | 182 |
12,993,409 | https://en.wikipedia.org/wiki/DNS%20rebinding | DNS rebinding is a method of manipulating resolution of domain names that is commonly used as a form of computer attack. In this attack, a malicious web page causes visitors to run a client-side script that attacks machines elsewhere on the network. In theory, the same-origin policy prevents this from happening: client-side scripts are only allowed to access content on the same host that served the script. Comparing domain names is an essential part of enforcing this policy, so DNS rebinding circumvents this protection by abusing the Domain Name System (DNS).
This attack can be used to breach a private network by causing the victim's web browser to access computers at private IP addresses and return the results to the attacker. It can also be employed to use the victim machine for spamming, distributed denial-of-service attacks, or other malicious activities.
How DNS rebinding works
The attacker registers a domain (such as attacker.com) and delegates it to a DNS server that is under the attacker's control. The server is configured to respond with a very short time to live (TTL) record, preventing the DNS response from being cached. When the victim browses to the malicious domain, the attacker's DNS server first responds with the IP address of a server hosting the malicious client-side code. For instance, they could point the victim's browser to a website that contains malicious JavaScript or Flash scripts that are intended to execute on the victim's computer.
The malicious client-side code makes additional accesses to the original domain name (such as attacker.com). These are permitted by the same-origin policy. However, when the victim's browser runs the script it makes a new DNS request for the domain, and the attacker replies with a new IP address. For instance, they could reply with an internal IP address or the IP address of a target somewhere else on the Internet.
Protection
The following techniques attempt to prevent DNS rebinding attacks:
DNS servers in the chain can filter out private IP addresses and loopback IP addresses:
External public DNS servers (e.g. OpenDNS) can implement DNS filtering.
Local system administrators can configure the organization's local nameserver(s) to block the resolution of external names into internal IP addresses. (This has the downside of allowing an attacker to map the internal address ranges in use.)
A firewall (e.g. dnswall), in the gateway or in the local pc, can filter DNS replies that pass through it, discarding local addresses.
Web browsers can resist DNS rebinding:
Web browsers can implement DNS pinning: the IP address is locked to the value received in the first DNS response. This technique may block some legitimate uses of Dynamic DNS, and may not work against all attacks. However, it is important to fail-safe (stop rendering) if the IP address does change, because using an IP address past the TTL expiration can open the opposite vulnerability when the IP address has legitimately changed and the expired IP address may now be controlled by an attacker.
The NoScript extension for Firefox includes ABE, a firewall-like feature inside the browser which in its default configuration prevents attacks on the local network by preventing external webpages from accessing local IP addresses.
Web servers can reject HTTP requests with an unrecognized Host header.
See also
DNS hijacking
DNS spoofing
References
External links
Protecting Browsers from DNS Rebinding Attacks (2007)
DNS hardening update for Adobe Flash Player (2008)
Security Sun Alert 200041 for the Sun JVM (2008-09-04)
DNS Rebinding with Robert RSnake Hansen (2009)
Domain Name System
Internet security
Web security exploits | DNS rebinding | Technology | 796 |
37,487,265 | https://en.wikipedia.org/wiki/Variational%20method%20%28quantum%20mechanics%29 | In quantum mechanics, the variational method is one way of finding approximations to the lowest energy eigenstate or ground state, and some excited states. This allows calculating approximate wavefunctions such as molecular orbitals. The basis for this method is the variational principle.
The method consists of choosing a "trial wavefunction" depending on one or more parameters, and finding the values of these parameters for which the expectation value of the energy is the lowest possible. The wavefunction obtained by fixing the parameters to such values is then an approximation to the ground state wavefunction, and the expectation value of the energy in that state is an upper bound to the ground state energy. The Hartree–Fock method, density matrix renormalization group, and Ritz method apply the variational method.
Description
Suppose we are given a Hilbert space and a Hermitian operator over it called the Hamiltonian . Ignoring complications about continuous spectra, we consider the discrete spectrum of and a basis of eigenvectors (see spectral theorem for Hermitian operators for the mathematical background):
where is the Kronecker delta
and the satisfy the eigenvalue equation
Once again ignoring complications involved with a continuous spectrum of , suppose the spectrum of is bounded from below and that its greatest lower bound is . The expectation value of in a state is then
If we were to vary over all possible states with norm 1 trying to minimize the expectation value of , the lowest value would be and the corresponding state would be the ground state, as well as an eigenstate of . Varying over the entire Hilbert space is usually too complicated for physical calculations, and a subspace of the entire Hilbert space is chosen, parametrized by some (real) differentiable parameters . The choice of the subspace is called the ansatz. Some choices of ansatzes lead to better approximations than others, therefore the choice of ansatz is important.
Let's assume there is some overlap between the ansatz and the ground state (otherwise, it's a bad ansatz). We wish to normalize the ansatz, so we have the constraints
and we wish to minimize
This, in general, is not an easy task, since we are looking for a global minimum and finding the zeroes of the partial derivatives of over all is not sufficient. If is expressed as a linear combination of other functions ( being the coefficients), as in the Ritz method, there is only one minimum and the problem is straightforward. There are other, non-linear methods, however, such as the Hartree–Fock method, that are also not characterized by a multitude of minima and are therefore comfortable in calculations.
There is an additional complication in the calculations described. As tends toward in minimization calculations, there is no guarantee that the corresponding trial wavefunctions will tend to the actual wavefunction. This has been demonstrated by calculations using a modified harmonic oscillator as a model system, in which an exactly solvable system is approached using the variational method. A wavefunction different from the exact one is obtained by use of the method described above.
Although usually limited to calculations of the ground state energy, this method can be applied in certain cases to calculations of excited states as well. If the ground state wavefunction is known, either by the method of variation or by direct calculation, a subset of the Hilbert space can be chosen which is orthogonal to the ground state wavefunction.
The resulting minimum is usually not as accurate as for the ground state, as any difference between the true ground state and results in a lower excited energy. This defect is worsened with each higher excited state.
In another formulation:
This holds for any trial φ since, by definition, the ground state wavefunction has the lowest energy, and any trial wavefunction will have energy greater than or equal to it.
Proof:
can be expanded as a linear combination of the actual eigenfunctions of the Hamiltonian (which we assume to be normalized and orthogonal):
Then, to find the expectation value of the Hamiltonian:
Now, the ground state energy is the lowest energy possible, i.e., . Therefore, if the guessed wave function is normalized:
In general
For a hamiltonian H that describes the studied system and any normalizable function Ψ with arguments appropriate for the unknown wave function of the system, we define the functional
The variational principle states that
, where is the lowest energy eigenstate (ground state) of the hamiltonian
if and only if is exactly equal to the wave function of the ground state of the studied system.
The variational principle formulated above is the basis of the variational method used in quantum mechanics and quantum chemistry to find approximations to the ground state.
Another facet in variational principles in quantum mechanics is that since and can be varied separately (a fact arising due to the complex nature of the wave function), the quantities can be varied in principle just one at a time.
Helium atom ground state
The helium atom consists of two electrons with mass m and electric charge , around an essentially fixed nucleus of mass and charge . The Hamiltonian for it, neglecting the fine structure, is:
where ħ is the reduced Planck constant, is the vacuum permittivity, (for ) is the distance of the -th electron from the nucleus, and is the distance between the two electrons.
If the term , representing the repulsion between the two electrons, were excluded, the Hamiltonian would become the sum of two hydrogen-like atom Hamiltonians with nuclear charge . The ground state energy would then be , where is the Rydberg constant, and its ground state wavefunction would be the product of two wavefunctions for the ground state of hydrogen-like atoms:
where is the Bohr radius and , helium's nuclear charge. The expectation value of the total Hamiltonian H (including the term ) in the state described by will be an upper bound for its ground state energy. is , so is .
A tighter upper bound can be found by using a better trial wavefunction with 'tunable' parameters. Each electron can be thought to see the nuclear charge partially "shielded" by the other electron, so we can use a trial wavefunction equal with an "effective" nuclear charge : The expectation value of in this state is:
This is minimal for implying shielding reduces the effective charge to ~1.69. Substituting this value of into the expression for yields , within 2% of the experimental value, −78.975 eV.
Even closer estimations of this energy have been found using more complicated trial wave functions with more parameters. This is done in physical chemistry via variational Monte Carlo.
References
Quantum chemistry
Theoretical chemistry
Computational chemistry
Computational physics
Approximations
Electronic structure methods | Variational method (quantum mechanics) | Physics,Chemistry,Mathematics | 1,388 |
13,170,237 | https://en.wikipedia.org/wiki/Jure%20uxoris | Jure uxoris (a Latin phrase meaning "by right of (his) wife") describes a title of nobility used by a man because his wife holds the office or title suo jure ("in her own right"). Similarly, the husband of an heiress could become the legal possessor of her lands. For example, married women in England and Wales were legally incapable of owning real estate until the Married Women's Property Act 1882.
Middle Ages
During the feudal era, the husband's control over his wife's real property, including titles, was substantial. On marriage, the husband gained the right to possess his wife's land during the marriage, including any acquired after the marriage. Whilst he did not gain the formal legal title to the lands, he was able to spend the rents and profits of the land and sell his right, even if the wife protested.
The concept of jure uxoris was standard in the Middle Ages even for queens regnant. In the Kingdom of Jerusalem, Fulk V of Anjou, Guy of Lusignan, Conrad of Montferrat, Henry II of Champagne, and Aimery of Lusignan all became kings as a result of marriage. Another famous instance of jure uxoris occurring was in the case of Richard Neville, 16th Earl of Warwick, who gained said title via his marriage to Anne Beauchamp, 16th Countess of Warwick, herself a daughter of Richard Beauchamp, 13th Earl of Warwick.
Sigismund of Luxembourg married Queen Mary of Hungary and obtained the crown through her, retaining it after her death in 1395.
A man who held the title jure uxoris could retain it even after the death or divorce of his wife. When the marriage of Marie I of Boulogne and Matthew of Boulogne was annulled in 1170, Marie ceased to be countess, while Matthew I continued to reign until 1173. Likewise, upon the death of Maria, Queen of Sicily in 1401, her widower Martin I of Sicily continued to reign as King until his death in 1409. In some cases, the kingdom could pass to the husband's heirs, even when they were not an issue of the wife in question (e.g. Jogaila, who became king by marrying Jadwiga and passed on the kingdom to his children with Sophia of Halshany).
Kings jure uxoris in the medieval era include:
Philip I of Navarre, who was married to Joan I of Navarre
Frederick II, Holy Roman Emperor, who was named King of Jerusalem by virtue of his marriage to Isabella II of Jerusalem
Louis I of Naples, whose wife was Joanna I of Naples
Philip III of Navarre, who was married to Joan II of Navarre
John I of Castile, who was a claimant to the throne of Portugal by virtue of his marriage to Beatrice of Portugal
Guy of Lusignan, who ruled as King of Jerusalem by right of marriage to Sibylla of Jerusalem
Władysław II Jagiełło, who ruled as King of Poland by right of his marriage to Jadwiga of Poland
Renaissance
By the time of the Renaissance, laws and customs had changed in some countries: a woman sometimes remained monarch, with only part of her power transferred to her husband. This was usually the case when multiple kingdoms were consolidated, such as when Isabella and Ferdinand shared crowns.
The precedent of jure uxoris complicated the lives of Henry VIII's daughters, both of whom inherited the throne in their own right. The marriage of Mary I to King Philip in 1554 was seen as a political act, as an attempt to bring England and Ireland under the influence of Catholic Spain. Parliament passed the Act for the Marriage of Queen Mary to Philip of Spain specifically to prevent Philip from seizing power on the basis of jure uxoris. As it turned out, the marriage produced no children, and Mary died in 1558, ending Philip's jure uxoris claims in England and Ireland, as envisaged by the Act, and was followed by the accession of Elizabeth I, who never married.
In Navarre, Jeanne d'Albret had married Antoine of Navarre in 1548, and she became queen regnant at her father's death in 1555. Antoine was crowned co-ruler jure uxoris with Jeanne in August.
Partial transference of power
In Great Britain, husbands acted on their wives' behalf in the House of Lords, from which women were once barred. These offices were exercised jure uxoris.
When Lady Priscilla Bertie inherited the title Baroness Willougby de Eresby in 1780, she also held the position of Lord Great Chamberlain. However, her husband Sir Peter Gwydyr acted on her behalf in that office instead.
Conditions
In Portugal, a male consort could not become a king jure uxoris until the queen regnant had a child and royal heir. Although Queen Maria II married her second husband in 1836, Ferdinand of Saxe-Coburg-Gotha did not become King Ferdinand II until 1837, when their first child was born. Queen Maria's first husband, Auguste of Beauharnais, never became monarch, because he died before he could father an heir. The queen's child did not have to be born after her accession. For example, Queen Maria I already had children by her husband when she acceded, so he became King Peter III at the moment of his wife's accession.
although he is not technically entitled to it under the law. For example, Jaime de Marichalar was often referred to as the Duke of Lugo during his marriage to Infanta Elena, Duchess of Lugo. After their divorce, he ceased to use the title. His brother-in-law Iñaki Urdangarin was referred to as the Duke of Palma before corruption allegations prompted the King to take action. Since 12 June 2015, he is no longer referred to as the Duke of Palma de Mallorca, following the removal of that title from his wife, Infanta Cristina.
See also
Jure matris
List of Latin phrases
References
Latin legal terminology
Nobility
Genealogy
Inheritance
Jure uxoris emperors | Jure uxoris | Biology | 1,254 |
73,949,761 | https://en.wikipedia.org/wiki/Chain%20extender | In polymer chemistry, a chain extender is a low molecular weight (MW) reagent that converts polymeric precursors to higher molecular weight derivatives. Often, it is convenient to prepare a polymer at an intermediate MW, which are suitable for solution- or melt-processing. At or near the final stages of production, the material is treated with a chain extender. Typically, chain extenders are bifunctional, i.e., they have two functional groups, which can link together two polymers. Representative classes of chain extenders are diglycidyl ethers, diols, diamines, or dianhydrides. Chain extenders are often applied to polyurethanes.
References
Coatings
Elastomers
Plastics | Chain extender | Physics,Chemistry | 155 |
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