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2,978,813 | https://en.wikipedia.org/wiki/Dimethylhydrazine | Dimethylhydrazine is the name of two compounds with the molecular formula C2H8N2. These are:
unsymmetrical dimethylhydrazine (1,1-dimethylhydrazine), with both methyl groups bonded to the same nitrogen atom
symmetrical dimethylhydrazine (1,2-dimethylhydrazine), with one methyl group bonded to each of the two nitrogen atoms
See also
monomethylhydrazine, a volatile hydrazine chemical
Hydrazines | Dimethylhydrazine | [
"Chemistry"
] | 110 | [
"Functional groups",
"Hydrazines"
] |
2,978,960 | https://en.wikipedia.org/wiki/Orange%20oil | Orange oil is an essential oil produced by cells within the rind of an orange fruit (Citrus sinensis fruit). In contrast to most essential oils, it is extracted as a by-product of orange juice production by centrifugation, producing a cold-pressed oil. It is composed of mostly (greater than 90%) d-limonene, and is often used in place of pure d-limonene. D-limonene can be extracted from the oil by distillation.
Composition
The compounds inside an orange oil vary with each different oil extraction. Composition varies as a result of regional and seasonal changes as well as the method used for extraction. Several hundred compounds have been identified with gas chromatograph-mass spectrometry. Most of the substances in the oil belong to the terpene group with limonene being the dominant one. Long chain aliphatic hydrocarbon alcohols and aldehydes like 1-octanol and octanal are second important group of substances. The presence of sinensetin, a flavone, explains the orange color.
Uses
Insect control
Orange oil, particularly its primary component d-limonene, is registered with the EPA as an active ingredient in products for the extermination of drywood termites, Formosan termites, and other structural pests. It is a common alternative to traditional fumigation methods due to its lower toxicity and the convenience of local chemical injections. Orange oil treatments can be used for termite control. Research also indicates that the d-limonene in orange oil can be useful in exterminating drywood termites (Incisitermes).
Orange oil is used as a green pesticide for biological pest control, as it is effective against ants and other insects by disrupting their scent-pheromone trails or dissolving their exoskeletons, thereby preventing infestations.
Domestic cleaning agent
Due to its high limonene content, orange oil is commonly used in cleaning products as a natural solvent. It is also added to furniture polishes to impart a fresh, citrus aroma.
Hazards
As a main component of orange oil, limonene can dissolve skin oils, potentially causing irritation. This is especially a concern with long-term industrial exposure, such as during the preparation of paints or degreasing processes. Limonene in orange oil is also flammable, and can be an irritant if ingested, inhaled, or if it comes into contact with the eyes. Some individuals may also experience allergic reactions.
See also
Neroli
Petitgrain
Orange oil tires
References
External links
The Effect of Citrus Oils on Fruit Flies
Orange production
Essential oils
Vegetable oils
Flavors
Plant toxin insecticides
Biological pest control | Orange oil | [
"Chemistry"
] | 563 | [
"Essential oils",
"Plant toxin insecticides",
"Chemical ecology",
"Natural products"
] |
2,979,145 | https://en.wikipedia.org/wiki/Delta%20neutral | In finance, delta neutral describes a portfolio of related financial securities, in which the portfolio value remains unchanged when small changes occur in the value of the underlying security (having zero delta). Such a portfolio typically contains options and their corresponding underlying securities such that positive and negative delta components offset, resulting in the portfolio's value being relatively insensitive to changes in the value of the underlying security.
A related term, delta hedging, is the process of setting or keeping a portfolio as close to delta-neutral as possible. In practice, maintaining a zero delta is very complex because there are risks associated with re-hedging on large movements in the underlying stock's price, and research indicates portfolios tend to have lower cash flows if re-hedged too frequently. Delta hedging may be accomplished by trading underlying securities of the portfolio. See for details.
Mathematical interpretation
Delta measures the sensitivity of the value of an option to changes in the price of the underlying stock assuming all other variables remain unchanged.
Mathematically, delta is represented as partial derivative
of the option's fair value with respect to the spot price of the underlying security.
Delta is a function of S, strike price, and time to expiry. Therefore, if a position is delta neutral (or, instantaneously delta-hedged) its instantaneous change in value, for an infinitesimal change in the value of the underlying security, will be zero; see Hedge (finance). Since Delta measures the exposure of a derivative to changes in the value of the underlying, a portfolio that is delta neutral is effectively hedged, in the sense that its overall value will not change for small changes in the price of its underlying instrument.
Techniques
Options market makers, or others, may form a delta neutral portfolio using related options instead of the underlying. The portfolio's delta (assuming the same underlier) is then the sum of all the individual options' deltas. This method can also be used when the underlier is difficult to trade, for instance when an underlying stock is hard to borrow and therefore cannot be sold short.
For example, in the portfolio , an option has the value V, and the stock has a value S. If we assume V is linear, then we can assume , therefore letting means that the value of is approximately 0.
Theory
The existence of a delta neutral portfolio was shown as part of the original proof of the Black–Scholes model, the first comprehensive model to produce correct prices for some classes of options. See Black-Scholes: Derivation.
From the Taylor expansion of the value of an option, we get the change in the value of an option, , for a change in the value of the underlier :
where (delta) and (gamma); see Greeks (finance).
For any small change in the underlier, we can ignore the second-order term and use the quantity to determine how much of the underlier to buy or sell to create a hedged portfolio. However, when the change in the value of the underlier is not small, the second-order term, , cannot be ignored: see Convexity (finance).
In practice, maintaining a delta neutral portfolio requires continuous recalculation of the position's Greeks and rebalancing of the underlier's position. Typically, this rebalancing is performed daily or weekly.
References
External links
Delta Hedging, investopedia.com
Theory & Application for Delta Hedging
Financial markets
Derivatives (finance)
Mathematical finance | Delta neutral | [
"Mathematics"
] | 717 | [
"Applied mathematics",
"Mathematical finance"
] |
2,979,302 | https://en.wikipedia.org/wiki/Inter-Range%20Instrumentation%20Group | The Inter-Range Instrumentation Group (IRIG) is the standards body of the Range Commanders Council (RCC). The group publishes standards through the RCC Secretariat at White Sands Missile Range.
The best known IRIG standard is the IRIG timecode used to timestamp video, film, telemetry, radar, and other data collected at test ranges.
The following radio time sources broadcast IRIG timecodes:
BPM (China)
CHU (Canada)
WWV and WWVH (United States)
The RCC's IRIG Standard 106 is a comprehensive telemetry standard for aeronautical applications at RCC member ranges. Chapter 10 of Standard 106 governs digital flight data recorders. IRIG Standard 313-01 prescribes test standards for flight termination receivers.
See also
Related topics
Rocket range
Related technologies
Specification of BBC phase-modulated transmissions on long-wave is a non-IRIG time signalling system that has many similarities to IRIG.
References
Standards of the United States
Aviation standards | Inter-Range Instrumentation Group | [
"Astronomy"
] | 207 | [
"Rocketry stubs",
"Astronomy stubs"
] |
2,979,338 | https://en.wikipedia.org/wiki/List%20of%20computer%20science%20conferences | This is a list of academic conferences in computer science. Only conferences with separate articles are included; within each field, the conferences are listed alphabetically by their short names.
General
FCRC – Federated Computing Research Conference
Algorithms and theory
Conferences accepting a broad range of topics from theoretical computer science, including algorithms, data structures, computability, computational complexity, automata theory and formal languages:
CCC - Computational Complexity Conference
FCT – International Symposium on Fundamentals of Computation Theory
FOCS – IEEE Symposium on Foundations of Computer Science
ICALP – International Colloquium on Automata, Languages and Programming
ISAAC – International Symposium on Algorithms and Computation
MFCS – International Symposium on Mathematical Foundations of Computer Science
STACS – Symposium on Theoretical Aspects of Computer Science
STOC – ACM Symposium on Theory of Computing
WoLLIC – Workshop on Logic, Language, Information and Computation
Algorithms
Conferences whose topic is algorithms and data structures considered broadly, but that do not include other areas of theoretical computer science such as computational complexity theory:
ESA – European Symposium on Algorithms
SODA – ACM–SIAM Symposium on Discrete Algorithms
SWAT and WADS – SWAT and WADS conferences
Geometric algorithms
Conferences on computational geometry, graph drawing, and other application areas of geometric computing:
GD – International Symposium on Graph Drawing
SoCG – Symposium on Computational Geometry
Logic
LICS – ACM–IEEE Symposium on Logic in Computer Science
RTA – International Conference on Rewriting Techniques and Applications
Other specialized subtopics
CIAA – International Conference on Implementation and Application of Automata
CCC – Computational Complexity Conference
DCFS – International Workshop on Descriptional Complexity of Formal Systems
DLT – International Conference on Developments in Language Theory
ISSAC – International Symposium on Symbolic and Algebraic Computation
Petri Nets - International Conference on Applications and Theory of Petri Nets and Concurrency
RP – International Conference on Reachability Problems
SEA – Symposium on Experimental Algorithms
Languages and software
Programming languages
Conferences on programming languages, programming language theory and compilers:
CC International Conference on Compiler Construction
ECOOP – AITO European Conference on Object-Oriented Programming
ESOP – ETAPS European Symposium on Programming
HOPL – ACM SIGPLAN History of Programming Languages Conference
ICFP – ACM SIGPLAN International Conference on Functional Programming
ICLP – ALP International Conference on Logic Programming
ISMM – ACM SIGPLAN International Symposium on Memory Management
OOPSLA – ACM SIGPLAN Conference on Object-Oriented Programming, Systems, Languages, and Applications
POPL – ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages
PLDI – ACM SIGPLAN Conference on Programming Language Design and Implementation
Software engineering
Conferences on software engineering:
ASE – IEEE/ACM International Conference on Automated Software Engineering
ICSE – International Conference on Software Engineering
ICSR – International Conference on Software Reuse
TACAS - ETAPS International Conference on Tools and Algorithms for the Construction and Analysis of Systems
FoSSaCS - ETAPS International Conference on Foundations of Software Science and Computation Structures
FASE - ETAPS International Conference on Fundamental Approaches to Software Engineering
Formal methods
Conferences on formal methods in software engineering, including formal specification, formal verification, and static code analysis:
CAV – Computer Aided Verification
FORTE – IFIP International Conference on Formal Techniques for Networked and Distributed Systems
Concurrent, distributed and parallel computing
Conferences on concurrent, distributed, and parallel computing, fault-tolerant systems, and dependable systems:
CONCUR - International Conference on Concurrency Theory
DEBS - ACM International Conference on Distributed Event-Based Systems
DISC - International Symposium on Distributed Computing
DSN - International Conference on Dependable Systems and Networks
ICDCS - IEEE International Conference on Distributed Computing Systems
ICPADS - IEEE International Conference on Parallel and Distributed Systems
IPDPS - IEEE International Parallel and Distributed Processing Symposium
PODC - ACM Symposium on Principles of Distributed Computing
PPoPP - ACM SIGPLAN Symposium on Principles and Practice of Parallel Programming
SIROCCO - International Colloquium on Structural Information and Communication Complexity
SPAA - ACM Symposium on Parallelism in Algorithms and Architectures
SRDS - IEEE International Symposium on Reliable Distributed Systems
High-performance computing
Conferences on high-performance computing, cluster computing, and grid computing:
HiPC - International Conference on High Performance Computing
SC - ACM/IEEE International Conference for High Performance Computing, Networking, Storage, and Analysis
Operating systems
Conferences on operating systems, storage systems and middleware:
ATC - USENIX Annual Technical Conference
Middleware - ACM/IFIP/USENIX International Middleware Conference
SOSP - ACM Symposium on Operating Systems Principles
OSDI - USENIX Symposium on Operating Systems Design and Implementation
SYSTOR - ACM International Systems and Storage Conference
Computer architecture
Conferences on computer architecture:
ASPLOS - International Conference on Architectural Support for Programming Languages and Operating Systems
ISCA - International Symposium on Computer Architecture
MICRO - IEEE/ACM International Symposium on Microarchitecture
Computer-aided design
Conferences on computer-aided design and electronic design automation:
ASP-DAC - Asia and South Pacific Design Automation Conference
DAC - Design Automation Conference
DATE - Design, Automation, and Test in Europe
ICCAD - International Conference on Computer-Aided Design
ISPD - International Symposium on Physical Design
Computer networking
Conferences on computer networking:
GlobeCom - IEEE Global Communications Conference
ICC - IEEE International Conference on Communications
ICSOC - International Conference on Service Oriented Computing
INFOCOM - IEEE Conference on Computer Communications
SIGMETRICS - ACM SIGMETRICS
WINE - The Workshop on Internet & Network Economics
Wireless networks and mobile computing
Wireless networks and mobile computing, including ubiquitous and pervasive computing, wireless ad hoc networks and wireless sensor networks:
EWSN - European Conference on Wireless Sensor Networks
IPSN - ACM/IEEE International Conference on Information Processing in Sensor Networks
ISWC - International Symposium on Wearable Computers
SenSys - ACM Conference on Embedded Networked Sensor Systems
Security and privacy
Conferences on computer security and privacy:
DSN - International Conference on Dependable Systems and Networks
Cryptography
Cryptography conferences:
ANTS - Algorithmic Number Theory Symposium
RSA - RSA Conference
Data management
Conferences on databases, information systems, information retrieval, data mining and the World Wide Web:
BTW - GI Conference on Database Systems for Business, Technology and Web
CIDR - Conference on Innovative Data Systems Research
CIKM - ACM Conference on Information and Knowledge Management
ECIR - European Conference on Information Retrieval
ECIS - European Conference on Information Systems
ER - International Conference on Conceptual Modeling
ICDT - International Conference on Database Theory
ICIS - International Conference on Information Systems
ISWC - International Semantic Web Conference
JCDL - ACM/IEEE Joint Conference on Digital Libraries
PODS - ACM Symposium on Principles of Database Systems
SIGMOD - ACM Special Interest Group on Management of Data
VLDB - International Conference on Very Large Data Bases
WWW - World Wide Web Conference
Artificial intelligence
Conferences on artificial intelligence and machine learning:
AAAI - AAAI Conference on Artificial Intelligence
AAMAS - International Conference on Autonomous Agents and Multiagent Systems
ICAPS - International Conference on Automated Planning and Scheduling
CIBB - International Conference on Computational Intelligence Methods for Bioinformatics and Biostatistics
ECAI - European Conference on Artificial Intelligence
ECML PKDD - European Conference on Machine Learning and Principles and Practice of Knowledge Discovery in Databases
ICML - International Conference on Machine Learning
ICLR - International Conference on Learning Representations
IJCAI - International Joint Conference on Artificial Intelligence
ISWC - International Semantic Web Conference
NeurIPS - Conference on Neural Information Processing Systems
RuleML - RuleML Symposium
Evolutionary computation
Conferences on Evolutionary computation.
AE - Artificial Evolution Conference
CEC - IEEE Congress on Evolutionary Computation
GECCO - Genetic and Evolutionary Computation Conference
Automated reasoning
Conferences on automated reasoning:
IJCAR - International Joint Conference on Automated Reasoning
LPAR - International Conference on Logic for Programming, Artificial Intelligence and Reasoning
RuleML - RuleML Symposium
TABLEAUX - International Conference on Automated Reasoning with Analytic Tableaux and Related Methods
WoLLIC - Workshop on Logic, Language, Information and Computation
Computer vision
Conferences on computer vision (including also image analysis) and pattern recognition:
BMVC - British Machine Vision Conference
CVPR - IEEE Conference on Computer Vision and Pattern Recognition
ECCV - European Conference on Computer Vision
ICCV - International Conference on Computer Vision
SCIA - Scandinavian Conference on Image Analysis
SSIAI - IEEE Southwest Symposium on Image Analysis and Interpretation
Natural language processing
Conferences on computational linguistics and natural language processing:
EMNLP - Empirical Methods in Natural Language Processing
COLING - International Committee on Computational Linguistics
TSD - Text, Speech and Dialogue
CICLing - International Conference on Intelligent Text Processing and Computational Linguistics
Computer graphics
Conferences on computer graphics, geometry processing, image processing, and multimedia:
MM - ACM International Conference on Multimedia
SGP - Symposium on Geometry Processing
SIGGRAPH - International Conference on Computer Graphics and Interactive Techniques
Human–computer interaction
Conferences on human–computer interaction and user interfaces:
CHI - ACM Conference on Human Factors in Computing Systems
GI - Graphics Interface
MobileHCI - Conference on Human-Computer Interaction with Mobile Devices and Services
UIST - ACM Symposium on User Interface Software and Technology
UMAP - ACM International Conference on User Modeling, Adaptation, and Personalization
Bioinformatics and computational biology
Conferences on bioinformatics and computational biology:
CIBB - International Conference on Computational Intelligence Methods for Bioinformatics and Biostatistics
ISMB - Intelligent Systems for Molecular Biology
PSB - Pacific Symposium on Biocomputing
RECOMB - Research in Computational Molecular Biology
See also
List of computer science conference acronyms
List of computer science journals
Outline of computer science
External links
DBLP database with conferences and workshops
List of computer science conferences ranked by h-index
Computing-related lists
Lists of conferences
Comp | List of computer science conferences | [
"Technology"
] | 1,951 | [
"Computing-related lists",
"Computer science",
"Computer science conferences"
] |
2,979,341 | https://en.wikipedia.org/wiki/Diameter%20%28graph%20theory%29 | In graph theory, the diameter of a connected undirected graph is the farthest distance between any two of its vertices. That is, it is the diameter of a set for the set of vertices of the graph, and for the shortest-path distance in the graph. Diameter may be considered either for weighted or for unweighted graphs. Researchers have studied the problem of computing the diameter, both in arbitrary graphs and in special classes of graphs.
The diameter of a disconnected graph may be defined to be infinite, or undefined.
Graphs of low diameter
The degree diameter problem seeks tight relations between the diameter, number of vertices, and degree of a graph. One way of formulating it is to ask for the largest graph with given bounds on its degree and diameter. For any fixed degree, this maximum size is exponential in the diameter, with the base of the exponent depending on the degree.
The girth of a graph, the length of its shortest cycle, can be at most for a graph of diameter . The regular graphs for which the girth is exactly are the Moore graphs. Only finitely many Moore graphs exist, but their exact number is unknown. They provide the solutions to the degree diameter problem for their degree and diameter.
Small-world networks are a class of graphs with low diameter, modeling the real-world phenomenon of six degrees of separation in social networks.
Algorithms
In arbitrary graphs
The diameter of a graph can be computed by using a shortest path algorithm to compute shortest paths between all pairs of vertices, and then taking the maximum of the distances that it computes. For instance, in a graph with positive edge weights, this can be done by repeatedly using Dijkstra's algorithm, once for each possible starting vertex. In a graph with vertices and edges, this takes time . Computing all-pairs shortest paths is the fastest known method for computing the diameter of a weighted graph exactly.
In an unweighted-graph, Dijkstra's algorithm may be replaced by breadth-first search, giving time . Alternatively, the diameter may be computed using an algorithm based on fast matrix multiplication, in time proportional to the time for multiplying matrices, approximately using known matrix multiplication algorithms. For sparse graphs, with few edges, repeated breadth-first search is faster than matrix multiplication. Assuming the exponential time hypothesis, repeated breadth-first search is near-optimal: this hypothesis implies that no algorithm can achieve time for any .
It is possible to approximate the diameter of a weighted graph to within an approximation ratio of 3/2, in time , where the notation hides logarithmic factors in the time bound. Under the exponential time hypothesis, no substantially more accurate approximation, substantially faster than all pairs shortest paths, is possible.
In special classes of graphs
The diameter can be computed in linear time for interval graphs, and in near-linear time for graphs of bounded treewidth. In median graphs, the diameter can be found in the subquadratic time bound .
In any class of graphs closed under graph minors, such as the planar graphs, it is possible to compute the diameter in subquadratic time, with an exponent depending on the graph family.
See also
Diameter (group theory), the diameter of a Cayley graph of the group, for generators chosen to make this diameter as large as possible
, connecting pairs of triangulations by local moves
References
Graph distance
Graph invariants
Computational problems in graph theory | Diameter (graph theory) | [
"Mathematics"
] | 698 | [
"Computational problems in graph theory",
"Computational mathematics",
"Graph theory",
"Computational problems",
"Graph invariants",
"Mathematical relations",
"Mathematical problems",
"Graph distance"
] |
2,979,523 | https://en.wikipedia.org/wiki/Gyricon | Gyricon is a type of electronic paper developed at the Xerox PARC (Palo Alto Research Center). It has many of the same properties as paper: it is flexible, contains an image, and is viewable from a wide angle, but it can be erased and written thousands of times.
A Gyricon sheet is a thin layer of transparent plastic, in which millions of small beads, somewhat like toner particles, are randomly dispersed. The beads, each contained in an oil-filled cavity, are free to rotate within those cavities. The beads are "bichromal", with hemispheres of two contrasting colors (e.g. black and white, red and white), and charged, so they exhibit an electrical dipole. When voltage is applied to the surface of the sheet, the beads rotate to present one colored side to the viewer. Voltages can be applied to the surface to create images such as text and pictures. The image will persist until new voltage patterns are applied
As of December, 2005, Xerox closed down the direct subsidiary Gyricon LLC, their Gyricon e-paper display business, and is focusing on licensing the technology.
The company have said that the reason for their closure has been their inability to source backplane technology for their Gyricon frontplane at a price of less than $10 per square foot (US$100/m2). Being able to achieve a price of under $10 was said to be critical to the success of marketing their e-paper-based electronic signage products. Although the company will stop direct manufacture and sale of Gyricon e-paper display products, it will, however, still be licensing their frontplane technology to other users.
References
Display technology
Synthetic paper
Electronic paper technology | Gyricon | [
"Chemistry",
"Engineering"
] | 362 | [
"Electronic engineering",
"Synthetic materials",
"Synthetic paper",
"Display technology"
] |
2,979,544 | https://en.wikipedia.org/wiki/Minkowski%E2%80%93Hlawka%20theorem | In mathematics, the Minkowski–Hlawka theorem is a result on the lattice packing of hyperspheres in dimension n > 1. It states that there is a lattice in Euclidean space of dimension n, such that the corresponding best packing of hyperspheres with centres at the lattice points has density Δ satisfying
with ζ the Riemann zeta function. Here as n → ∞, ζ(n) → 1. The proof of this theorem is indirect and does not give an explicit example, however, and there is still no known simple and explicit way to construct lattices with packing densities exceeding this bound for arbitrary n. In principle one can find explicit examples: for example, even just picking a few "random" lattices will work with high probability. The problem is that testing these lattices to see if they are solutions requires finding their shortest vectors, and the number of cases to check grows very fast with the dimension, so this could take a very long time.
This result was stated without proof by and proved by . The result is related to a linear lower bound for the Hermite constant.
Siegel's theorem
proved the following generalization of the Minkowski–Hlawka theorem. If S is a bounded set in Rn with Jordan volume vol(S) then the average number of nonzero lattice vectors in S is vol(S)/D, where the average is taken over all lattices with a fundamental domain of volume D, and similarly the average number of primitive lattice vectors in S is vol(S)/Dζ(n).
The Minkowski–Hlawka theorem follows easily from this, using the fact that if S is a star-shaped centrally symmetric body (such as a ball) containing less than 2 primitive lattice vectors then it contains no nonzero lattice vectors.
See also
Kepler conjecture
References
Geometry of numbers
Theorems in geometry
Hermann Minkowski | Minkowski–Hlawka theorem | [
"Mathematics"
] | 382 | [
"Geometry of numbers",
"Geometry",
"Theorems in geometry",
"Mathematical problems",
"Mathematical theorems",
"Number theory"
] |
2,979,642 | https://en.wikipedia.org/wiki/Cryptographic%20key%20types | A cryptographic key is a string of data that is used to lock or unlock cryptographic functions, including authentication, authorization and encryption. Cryptographic keys are grouped into cryptographic key types according to the functions they perform.
Description
Consider a keyring that contains a variety of keys. These keys might be various shapes and sizes, but one thing is certain, each will generally serve a separate purpose. One key might be used to start an automobile, while another might be used to open a safe deposit box. The automobile key will not work to open the safe deposit box and vice versa. This analogy provides some insight on how cryptographic key types work. These keys are categorized in respect to how they are used and what properties they possess.
A cryptographic key is categorized according to how it will be used and what properties it has. For example, a key might have one of the following properties: Symmetric, Public or Private. Keys may also be grouped into pairs that have one private and one public key, which is referred to as an Asymmetric key pair.
Asymmetric versus symmetric keys
Asymmetric keys differ from symmetric keys in that the algorithms use separate keys for encryption and decryption, while a symmetric key’s algorithm uses a single key for both processes. Because multiple keys are used with an asymmetric algorithm, the process takes longer to produce than a symmetric key algorithm would. However, the benefits lay in the fact that an asymmetric algorithm is much more secure than a symmetric key algorithm is.
With a symmetric key, the key needs to be transmitted to the receiver, where there is always the possibility that the key could be intercepted or tampered with. With an asymmetric key, the message and/or accompanying data can be sent or received by using a public key; however, the receiver or sender would use his or her personal private key to access the message and/or accompanying data. Thus, asymmetric keys are suited for use for transmitting confidential messages and data and when authentication is required for assurance that the message has not been tampered with. Only the receiver, who is in possession of the private key’s corresponding to the public key(encryption only key), has the ability to decode the message. A public key can be sent back and forth between recipients, but a private key remains fixed to one location and is not sent back and forth, which keeps it safe from being intercepted during transmission.
Long term versus single use
Cryptographic keys may also have keys that designate they can be used for long-term (static, archived) use or used for a single session (ephemeral). The latter generally applies to the use of an Ephemeral Key Agreement Key. Most other key types are designed to last for long crypto-periods, from about one to two years. When a shorter crypto-period is designed different key types may be used, such as Data Encryption keys, Symmetric Authentication keys, Private Key-Transport keys, Key-Wrapping keys, Authorization keys or RNG keys.
Key types
This page shows the classification of key types from the point of view of key management. In a key management system, each key should be labeled with one such type and that key should never be used for a different purpose.
According to NIST SP 800-57 (Revision 4) the following types of keys exist:
Private signature key Private signature keys are the private keys of asymmetric (public) key pairs that are used by public key algorithms to generate digital signatures with possible long-term implications. When properly handled, private signature keys can be used to provide authentication, integrity and non-repudiation.
Public signature verification key A public signature verification key is the public key of an asymmetric key pair that is used by a public key algorithm to verify digital signatures, either to authenticate a user's identity, to determine the integrity of the data, for non-repudiation, or a combination thereof.
Symmetric authentication key Symmetric authentication keys are used with symmetric key algorithms to provide assurance of the integrity and source of messages, communication sessions, or stored data.
Private authentication key A private authentication key is the private key of an asymmetric key pair that is used with a public key algorithm to provide assurance as to the integrity of information, and the identity of the originating entity or the source of messages, communication sessions, or stored data.
Public authentication key A public authentication key is the public key of an asymmetric key pair that is used with a public key algorithm to determine the integrity of information and to authenticate the identity of entities, or the source of messages, communication sessions, or stored data.
Symmetric data encryption key These keys are used with symmetric key algorithms to apply confidentiality protection to information.
Symmetric key wrapping key Symmetric key wrapping keys are used to encrypt other keys using symmetric key algorithms. Key wrapping keys are also known as key encrypting keys.
Symmetric and asymmetric random number generation keys These are keys used to generate random numbers.
Symmetric master key A symmetric master key is used to derive other symmetric keys (e.g., data encryption keys, key wrapping keys, or authentication keys) using symmetric cryptographic methods.
Private key transport key Private key transport keys are the private keys of asymmetric key pairs that are used to decrypt keys that have been encrypted with the associated public key using a public key algorithm. Key transport keys are usually used to establish keys (e.g., key wrapping keys, data encryption keys or MAC keys) and, optionally, other keying material (e.g., initialization vectors).
Public key transport key Public key transport keys are the public keys of asymmetric key pairs that are used to encrypt keys using a public key algorithm. These keys are used to establish keys (e.g., key wrapping keys, data encryption keys or MAC keys) and, optionally, other keying material (e.g., Initialization Vectors).
Symmetric key agreement key These symmetric keys are used to establish keys (e.g., key wrapping keys, data encryption keys, or MAC keys) and, optionally, other keying material (e.g., Initialization Vectors) using a symmetric key agreement algorithm.
Private static key agreement key Private static key agreement keys are the private keys of asymmetric key pairs that are used to establish keys (e.g., key wrapping keys, data encryption keys, or MAC keys) and, optionally, other keying material (e.g., Initialization Vectors).
Public static key agreement key Public static key agreement keys are the public keys of asymmetric key pairs that are used to establish keys (e.g., key wrapping keys, data encryption keys, or MAC keys) and, optionally, other keying material (e.g., Initialization Vectors).
Private ephemeral key agreement key Private ephemeral key agreement keys are the private keys of asymmetric key pairs that are used only once to establish one or more keys (e.g., key wrapping keys, data encryption keys, or MAC keys) and, optionally, other keying material (e.g., Initialization Vectors).
Public ephemeral key agreement key Public ephemeral key agreement keys are the public keys of asymmetric key pairs that are used in a single key establishment transaction to establish one or more keys (e.g., key wrapping keys, data encryption keys, or MAC keys) and, optionally, other keying material (e.g., Initialization Vectors).
Symmetric authorization key Symmetric authorization keys are used to provide privileges to an entity using a symmetric cryptographic method. The authorization key is known by the entity responsible for monitoring and granting access privileges for authorized entities and by the entity seeking access to resources.
Private authorization key A private authorization key is the private key of an asymmetric key pair that is used to provide privileges to an entity.
Public authorization key A public authorization key is the public key of an asymmetric key pair that is used to verify privileges for an entity that knows the associated private authorization key.
References
External links
Recommendation for Key Management — Part 1: general, NIST Special Publication 800-57
NIST Cryptographic Toolkit
Key management
Data security | Cryptographic key types | [
"Engineering"
] | 1,701 | [
"Cybersecurity engineering",
"Data security"
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2,979,876 | https://en.wikipedia.org/wiki/Apollodorus%20%28painter%29 | Apollodorus Skiagraphos () was an influential Ancient Greek painter of the 5th century BC whose work has since been entirely lost. Apollodorus left a technique behind known as skiagraphia, a way to easily produce shadow, that affected the works not only of his contemporaries but also of later generations. This shading technique uses hatched areas to give the illusion of both shadow and volume.
Life and accomplishments
Little is known about the actual life of Apollodorus, although he was catalogued by the notable historians Plutarch and Pliny the Elder. It was recorded that Apollodorus was active around 480 BCE; his dates of birth and death, however, are not attested in any surviving historical works or fragments of works. He was given different names by those who wrote about him. To Pliny, he was the great painter Apollodorus of Athens; therefore, it can be assumed that he lived and worked in the polis of Athens. But, to Plutarch and Hesychius, he was known as Apollodorus Skiagraphos, "the shadow-painter, named after his greatest legacy.
None of his actual paintings remain, for, due to weathering, almost all ancient Greek paintings have been destroyed, and the elegance and beauty of Greek art can mainly be glimpsed in the Macedonian tombs with their rich artistic programmes, in works such as the Derveni Krater, and in the sculptures and motives that were later copied by the Romans and architectural ruins that remain. The subjects of some of the paintings were recorded, however, by quite a number of ancient Greek historians. Pliny the Elder recorded two paintings, Praying Priest and Ajax Burned by Lightning, that resided in the ancient Greek city of Pergamon which was situated in modern-day Turkey. Other ancient Greek historians cited the painting Odysseus Wearing a Cap and also Heracleidae, a painting that referenced the descendants of Hercules. Also, one of his paintings was supposedly entitled Alcmena and the Daughters of Hercules Supplicating the Athenians.
As demonstrated by the titles of the paintings, it is probable that the majority of his works were similar to the other artists of the era in that their subject matter was most often based around the Greek gods and goddesses or other famous Greek citizens from historical epic poems that were passed on for generations in the oral tradition.
The topics of his paintings may have been unimaginative and common during the time period; however, it was his ingenious technique that made him such a renowned painter. One of the major artistic techniques that Apollodorus developed was called skiagraphia, or shading in English, hence his title “the shadow-painter”. The historian Plutarch recorded an inscription above one of Apollodorus' painting which read, “’Tis no hard thing to reprehend me; But let the men that blame me mend me.” In other words, “You could criticize [skiagraphia] more easily than you could imitate it”.
The type of shading applied by Apollodorus is highly sophisticated and even today people struggle to master skiagraphia. Apollodorus used an intricate way of “crosshatching and the thickening of inner contour lines as well as the admixture of light and dark tones” to show a form of perspective. Though it expanded the use of perspective in the ancient Greek world, skiagraphia was most effective in the depiction of stationary objects such as drapery, fruit, or faces; but it was ineffective in the painting of a body in action or a spatial setting for which perspective is usually used.
Another one of Apollodorus' greatest accomplishments did not have to do with his actual style or technique, but rather with the medium he chose. Apollodorus could very well have been one to the first well-known artists who painted on an easel as opposed to a wall which was the common action of the day.
Effect on contemporaries
Though not much about his life is known, historians have made assumptions about Apollodorus and his works and actions through his contemporaries.
Zeuxis of Heraclea was one of Apollodorus' rivals according to Pliny. Zeuxis was tutored in the arts by Demophilus of Himera and Neseus of Thasos. At one point, Apollodorus even accused Zeuxis of stealing art techniques from others which might very well have been true because Zeuxis was also attributed with the expansion and development of Apollodorus' prized skiagraphia. Zeuxis is said to have innovated skiagraphia by “adding highlights to shading and applying subtly different colours.”
Regardless of what Zeuxis did, he was not the only painter to adapt Apollodorus' creation for his own purposes. Another painter named Parrhasius of Ephesus, also a rival of Zeuxis, helped expand skiagraphia as well. He purportedly used it in a contest against Zeuxis and won because the curtain that Parrhasius had painted looked so real that Zeuxis tried to pull it back. Whereas Zeuxis examined the technique of light and shade in skiagraphia, Parrhasius looked into the contoured lines that help express depth in a spatial way; therefore taking the meaning of skiagraphia even further.
Not only was skiagraphia prominent in Athens, but also its influence extended beyond Athens' borders into the tomb paintings of Vergina, Aineia, and Lefkadia in northern Greece and even into Seuthopolis, a city in what is now modern Bulgaria. Though scarce, some of the tomb frescoes in Seuthopolis used only a limited range of colours; however others in Vergina and Aineia used six or more colours further demonstrating the extent of the transformation of Apollodorus' skiagraphia. Skiagraphia continued to mutate and develop until the age of the Italian Renaissance when it was given a new name: chiaroscuro.
Effect on the development of chiaroscuro
Apollodorus' development of skiagraphia was only the beginning of the gradual development of chiaroscuro. In Italian, chiaro means light and scuro means dark. So the two together symbolize the combination and distribution of light and dark into one to create a more lifelike image. No longer simply used for paintings on canvas of stationary objects, chiaroscuro is used in all types of art, even sculpture, frescoes, and woodcuts. Chiaroscuro is used to produce volume and relief, to unify the objects in a painting, or differentiate them from one another. The simple creation of skiagraphia led to the invention of diverse techniques that continued to be produced from the times of ancient Greece to Gothic times and then it reached its pinnacle in the Italian Renaissance in 14th century. Even today it continues to be important to artists.
In the 15th-century, chiaroscuro was described by Cennino Cennini, a famous Italian painter. He stated that the ideas of gradation between light and dark, skiagraphia, were combined with medieval techniques known as incidendo and matizando, which are a “layerings of white, brown, or black in linear patterns over a uniform colour” to indicate relief and volume. These two were previously used by monks in the illustration of religious manuscripts. The addition of these two techniques to skiagraphia was instrumental in the evolution of chiaroscuro.
Giotto, a Florentine painter, and Cimabue, Giotto's teacher, used chiaroscuro in their late Gothic painting as well, by mixing large amounts of white into the painting, therefore creating an easy transition between tones. In frescoes, mosaics, and manuscript illuminations, artists like Master Honore, a French manuscript painter, and Pietro, a painter and mosaic designer active in the Middle Ages, modelled from underneath with black and white space to create brightness in their works. In the end, Apollodorus' master creation after years of evolution transformed into something that, though it still resembled the original and served the same purpose, was new and thoroughly necessary to all great works of art.
Notes
References
“Apollodorus.” The Columbia Electronic Encyclopedia, Sixth Edition. Columbia University Press., 2003. Answers.com 26 Nov. 2008. http://www.answers.com/topic/apollodorus- painter.
Arafat, Karim. "Zeuxis." The Oxford Companion to Western Art. 2008. 14 May 2006. Oxford Art Online. Lucas Library, Atherton. 26 Nov. 2008. Keyword:http://oxfordartonline.comsubscriber/article/opr.
Bell, Janis C. "Chiaroscuro". Grove Art Online. Oxford: Oxford UP, 2006. 25 Feb. 2007. Oxford Art Online. Lucas Library, Atherton. 26 Nov. 2008.
Pliny. The Natural History of Pliny. Trans. John Bostcock and Henry T. Riley. H.G. Bohn, 1857.
Pollitt, Jerome J. The Art of Ancient Greece : Sources and Documents. New York: Cambridge UP, 1990.
Robertson, Martin. A Shorter History of Greek Art. New York: Cambridge UP, 1981.
External links
Ancient Greek painters
5th-century BC Greek people
Artists of ancient Attica
Year of birth unknown
Year of death unknown
5th-century BC painters
Shadows
Greek male painters | Apollodorus (painter) | [
"Physics"
] | 1,956 | [
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2,979,908 | https://en.wikipedia.org/wiki/Scrim%20%28material%29 | A scrim is a woven material, either of fine or coarse material.
Light gauzy material
A scrim is a very light textile made from fiber based materials, such as yarn.
Since scrim is lightweight and translucent (allowing light to pass through), it is quite often used for making curtains. It is also used for bookbinding and upholstery.
Scrims have seen extensive use in theater. It is used in theater for special effects. A very common term typically used for these purposes is called sharks tooth scrim. Weaved scrim is called its name because the weave resembles a set of triangles that resemble a shark's teeth with openings similar in size to a window screen. However, in theater, a scrim can refer to any such thin screen and is made of a wide variety of materials.
The most common use of scrim is the 'reveal effect', in which an actor or scene is made to appear or disappear by using the scrim and appropriate lighting. Other common effects include sharp silhouettes, backlit from behind the scrim, or other shadow effects (shrinking and growing a shadow).
The bobbin et/bobbinette is a type of scrim that has a hexagonal hole shape and comes in a variety of hole sizes. It is used for a number of lighting effects in the film and theater industries.
Scrim is also used in clothing, usually covering the face or head. This allows the wearer to look out while preventing others from seeing in. This may also be combined with camouflage to completely hide a person, such as a sniper, hunter, or wildlife photographer. The term "helmet scrim" refers to the practice of adorning a helmet with scrim and/or other fabrics to make its shape less obvious; the practice of adding scrim to a helmet is often done as much for reasons of perceived status as it is for reasons of actually improving camouflage. British and other forces have also made constant use of issued or privately purchased scrim fabric as a sort of improvised scarf that can be quickly converted into a face veil or similar.
A scrim was an integral part of the Beijing Olympic Stadium in Beijing. It was the screen running around the top of the stadium during the opening ceremonies on which all kinds of scenes were projected. Li Ning ran around it just before the cauldron lighting for 2008 Summer Olympics.
A scrim (also called a screen) is used as an acoustically transparent covering for a loudspeaker to protect the diaphragm and dust cap, or as an air filter element to protect the voice coil and other components of the transducer.
A scrim can be used on the back of a perforated (acoustically transparent) movie screen to reduce the amount of light shining through it.
A scrim can be used as a base layer for automotive loop pile and cut pile carpeting.
Applications to stage lighting
Scrims both reflect and transmit light. This means that if a light from a front-of-house position is shone at a scrim, then both the scrim and everything behind it will be lit. This can lead to a variety of interesting effects:
A scrim will appear entirely opaque if everything behind it is unlit and the scrim itself is grazed by light from the sides or from above.
A scrim will appear nearly transparent if a scene behind it is lit, but there is no light on the scrim.
A dreamy or foggy look can be achieved by lighting a scene entirely behind a scrim.
If a light with a gobo is aimed at a scrim, the image will appear on the scrim, but also any objects behind the scrim will be lit by the pattern as well.
In general, anything that is lit will be seen on both sides of a scrim. Scrims do not absorb light. Scrim can also be used in theater in combination with a cyclorama or backdrop. The idea is similar to the other uses. When the drop is lit (or images or video are rear-projected onto the back of the drop), the images or colors projected are visible. However, when the drop is not lit, the images or colors will disappear. A scrim can also help dull the image, creating a greater sense of depth.
Another effect is caused by layering two scrims, or even by placing a mirror behind a scrim and lighting it: the familiar moire effect. This can often cause audience disorientation.
Reinforcement material
The technique of using scrim as a reinforcement occurs commonly in the manufacture of glass-fiber or carbon-fiber composites. Scrim layers may cover the exterior surface of the carbon-fiber laminate for an improved protective surface. Jute scrim can reinforce plaster in sculpture when casting or working directly in plaster.
A similar usage of the term is found in sailcloth manufacture, where scrim is a strong loose weave of fibers laminated into the cloth to provide extra strength and stability to sails.
In carpentry, scrim is a very heavy, coarsely-woven fabric (similar to hessian or to coarse canvas) which is stretched over interior boards to provide support for wallpaper and to add extra rigidity. This method of construction, widely used in older houses, is often referred to as "Scrim and sarking", the sarking being the board.
Scrim is also an item that utilizes plies of tissue reinforced with a layer of nylon (much like a fishing line or heavy-duty mono-filament) or cotton thread. The layer of scrim is not counted in the ply count.
Scrim is a glass fiber (previously burlap) open-mesh tape used to cover joints in plasterboard/wall board before plastering. It prevents a crack from appearing in the plaster finish at a later date. The roll of tape may be plain or adhesive-coated to facilitate its installation.
Scrim was handed out during World War II to tape windows, so that they should not cause hazardous shrapnel in case of bomb blasts.
References
Kersmaekers, Ivo (2019): Gauzes in Theatre. Their use through the ages. In: Die Vierte Wand. Organ der Initiative TheaterMuseum Berlin. 009/2019, pp. 146–151 (online at the Internet Archive)
External links
Woven fabrics
Scenic design
Stage lighting
Building
Loudspeakers
de:Gaze
fr:Gaze
ru:Газ (ткань)
sv:Gas (textil) | Scrim (material) | [
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2,980,233 | https://en.wikipedia.org/wiki/Focused%20ion%20beam | Focused ion beam, also known as FIB, is a technique used particularly in the semiconductor industry, materials science and increasingly in the biological field for site-specific analysis, deposition, and ablation of materials. A FIB setup is a scientific instrument that resembles a scanning electron microscope (SEM). However, while the SEM uses a focused beam of electrons to image the sample in the chamber, a FIB setup uses a focused beam of ions instead. FIB can also be incorporated in a system with both electron and ion beam columns, allowing the same feature to be investigated using either of the beams. FIB should not be confused with using a beam of focused ions for direct write lithography (such as in proton beam writing). These are generally quite different systems where the material is modified by other mechanisms.
Ion beam source
Most widespread instruments are using liquid metal ion sources (LMIS), especially gallium ion sources. Ion sources based on elemental gold and iridium are also available. In a gallium LMIS, gallium metal is placed in contact with a tungsten needle, and heated gallium wets the tungsten and flows to the tip of the needle, where the opposing forces of surface tension and electric field form the gallium into a cusp shaped tip called a Taylor cone. The tip radius of this cone is extremely small (~2 nm). The huge electric field at this small tip (greater than volts per centimeter) causes ionization and field emission of the gallium atoms.
Source ions are then generally accelerated to an energy of , and focused onto the sample by electrostatic lenses. LMIS produce high current density ion beams with very small energy spread. A modern FIB can deliver tens of nanoamperes of current to a sample, or can image the sample with a spot size on the order of a few nanometers.
More recently, instruments using plasma beams of noble gas ions, such as xenon, have become available more widely.
Principle
Focused ion beam (FIB) systems have been produced commercially for approximately twenty years, primarily for large semiconductor manufacturers. FIB systems operate in a similar fashion to a scanning electron microscope (SEM) except, rather than a beam of electrons and as the name implies, FIB systems use a finely focused beam of ions (usually gallium) that can be operated at low beam currents for imaging or at high beam currents for site specific sputtering or milling.
As the diagram on the right shows, the gallium (Ga+) primary ion beam hits the sample surface and sputters a small amount of material, which leaves the surface as either secondary ions (i+ or i−) or neutral atoms (n0). The primary beam also produces secondary electrons (e−). As the primary beam rasters on the sample surface, the signal from the sputtered ions or secondary electrons is collected to form an image.
At low primary beam currents, very little material is sputtered and modern FIB systems can easily achieve 5 nm imaging resolution (imaging resolution with Ga ions is limited to ~5 nm by sputtering and detector efficiency). At higher primary currents, a great deal of material can be removed by sputtering, allowing precision milling of the specimen down to a sub micrometer or even a nano scale.
If the sample is non-conductive, a low energy electron flood gun can be used to provide charge neutralization. In this manner, by imaging with positive secondary ions using the positive primary ion beam, even highly insulating samples may be imaged and milled without a conducting surface coating, as would be required in an SEM.
Until recently, the overwhelming usage of FIB has been in the semiconductor industry. Such applications as defect analysis, circuit modification, photomask repair and transmission electron microscope (TEM) sample preparation of site specific locations on integrated circuits have become commonplace procedures. The latest FIB systems have high resolution imaging capability; this capability coupled with in situ sectioning has eliminated the need, in many cases, to examine FIB sectioned specimens in a separate SEM instrument. SEM imaging is still required for the highest resolution imaging and to prevent damage to sensitive samples. However, the combination of SEM and FIB columns onto the same chamber enables the benefits of both to be utilized.
FIB imaging
At lower beam currents, FIB imaging resolution begins to rival the more familiar scanning electron microscope (SEM) in terms of imaging topography, however the FIB's two imaging modes, using secondary electrons and secondary ions, both produced by the primary ion beam, offer many advantages over SEM.
FIB secondary electron images show intense grain orientation contrast. As a result, grain morphology can be readily imaged without resorting to chemical etching. Grain boundary contrast can also be enhanced through careful selection of imaging parameters. FIB secondary ion images also reveal chemical differences, and are especially useful in corrosion studies, as secondary ion yields of metals can increase by three orders of magnitude in the presence of oxygen, clearly revealing the presence of corrosion.
Another advantage of FIB secondary electron imaging is the fact that the ion beam does not alter the signal from fluorescent probes used in the labelling of proteins, thus creating the opportunity to correlate FIB secondary electron images with images obtained by fluorescence microscopes.
Etching
Unlike an electron microscope, FIB is inherently destructive to the specimen. When the high-energy gallium ions strike the sample, they will sputter atoms from the surface. Gallium atoms will also be implanted into the top few nanometers of the surface, and the surface will be made amorphous.
Because of the sputtering capability, the FIB is used as a micro- and nano-machining tool, to modify or machine materials at the micro- and nanoscale. FIB micro machining has become a broad field of its own, but nano machining with FIB is a field that is still developing. Commonly the smallest beam size for imaging is 2.5–6 nm. The smallest milled features are somewhat larger (10–15 nm) as this is dependent on the total beam size and interactions with the sample being milled.
FIB tools are designed to etch or machine surfaces, an ideal FIB might machine away one atom layer without any disruption of the atoms in the next layer, or any residual disruptions above the surface. Yet currently because of the sputter the machining typically roughens surfaces at the sub-micrometer length scales.
Deposition
A FIB can also be used to deposit material via ion beam induced deposition. FIB-assisted chemical vapor deposition occurs when a gas, such as tungsten hexacarbonyl (W(CO)6) is introduced to the vacuum chamber and allowed to chemisorb onto the sample. By scanning an area with the beam, the precursor gas will be decomposed into volatile and non-volatile components; the non-volatile component, such as tungsten, remains on the surface as a deposition. This is useful, as the deposited metal can be used as a sacrificial layer, to protect the underlying sample from the destructive sputtering of the beam. From nanometers to hundred of micrometers in length, tungsten metal deposition allows metal lines to be put right where needed. Other materials such as platinum, cobalt, carbon, gold, etc., can also be locally deposited. Gas assisted deposition and FIB etching process are shown below.
FIB is often used in the semiconductor industry to patch or modify an existing semiconductor device. For example, in an integrated circuit, the gallium beam could be used to cut unwanted electrical connections, and/or to deposit conductive material in order to make a connection. The high level of surface interaction is exploited in patterned doping of semiconductors. FIB is also used for maskless implantation.
For TEM preparation
The FIB is also commonly used to prepare samples for the transmission electron microscope. The TEM requires very thin samples, typically ~100 nanometers or less. Other techniques, such as ion milling or electropolishing can be used to prepare such thin samples. However, the nanometer-scale resolution of the FIB allows the exact region of interest to be chosen, such as perhaps a grain boundary or defect in a material. This is vital, for example, in integrated circuit failure analysis. If a particular transistor out of several million on a chip is bad, the only tool capable of preparing an electron microscope sample of that single transistor is the FIB.
The same protocol used for preparing samples to transmission electron microscopy can also be used to select a micro area of a sample, extract it and prepare it for analysis using secondary ion mass spectrometry (SIMS).
The drawbacks to FIB sample preparation are the above-mentioned surface damage and implantation, which produce noticeable effects when using techniques such as high-resolution "lattice imaging" TEM or electron energy loss spectroscopy. This damaged layer can be minimized by FIB milling with lower beam voltages, or by further milling with a low-voltage argon ion beam after completion of the FIB process.
FIB preparation can be used with cryogenically frozen samples in a suitably equipped instrument, allowing cross sectional analysis of samples containing liquids or fats, such as biological samples, pharmaceuticals, foams, inks, and food products.
FIB is also used for secondary ion mass spectrometry (SIMS). The ejected secondary ions are collected and analyzed after the surface of the specimen has been sputtered with a primary focused ion beam.
For transfer of sensitive samples
For a minimal introduction of stress and bending to transmission electron microscopy (TEM) samples (lamellae, thin films, and other mechanically and beam sensitive samples), when transferring inside a focused ion beam (FIB), flexible metallic nanowires can be attached to a typically rigid micromanipulator.
The main advantages of this method include a significant reduction of sample preparation time (quick welding and cutting of nanowire at low beam current), and minimization of stress-induced bending, Pt contamination, and ion beam damage.
This technique is particularly suitable for in situ electron microscopy sample preparation.
For Atom Probe sample preparation
The same successive milling steps applied when making TEM samples can be applied to make conical samples for atom probe tomography. In this case the ion moved in an annular milling pattern with the inner milling circle being made progressively smaller. The beam current is generally reduced the smaller the inner circle becomes to avoid damaging or destroying the sample.
FIB tomography
The focused ion beam has become a powerful tool for site-specific 3D imaging of sub-micron features in a sample. In this FIB tomography technique, the sample is sequentially milled using an ion beam perpendicular to the specimen while imaging the newly exposed surface using an electron beam. This so-called, slice and view approach allows larger scale nano-structures to be characterized across the many imaging modes available to an SEM, including secondary electron, backscattered electron, and energy dispersive x-ray measurement. The process is destructive, since the specimen is being sequentially milled away after each image is collected. The collected series of images is then reconstructed to a 3D volume by registering the image stack and removing artifacts. The predominant artifact that degrades FIB tomography is ion mill curtaining, where mill patterns form large aperiodic stripes in each image. The ion mill curtaining can be removed using destriping algorithms. FIB tomography can be done at both room and cryo temperatures as well as on both materials and biological samples.
History
History of FIB technology
1975: The first FIB systems based on field emission technology were developed by Levi-Setti and by Orloff and Swanson and used gas field ionization sources (GFISs).
1978: The first FIB based on an LMIS was built by Seliger et al.
Physics of LMIS
1600: Gilbert documented that fluid under high tension forms a cone.
1914: Zeleny observed and filmed cones and jets
1959: Feynman suggested the use of ion beams.
1964: Taylor produced exactly conical solution to equations of electro hydrodynamics (EHD)
1975: Krohn and Ringo produced first high brightness ion source: LMIS
Some pioneers of LMIS and FIB
Mahoney (1969)
Sudraud et al. Paris XI Orsay (1974)
Hughes Research Labs, Seliger (1978)
Hughes Research Labs, Kubena (1978–1993)
University of Oxford Mair (1980)
Culham UK, Roy Clampitt Prewett (1980)
Oregon Graduate Center, L. Swanson (1980)
Oregon Graduate Center, J. Orloff (1974)
MIT, J. Melngailis (1980)
Helium ion microscope (HeIM)
Another ion source seen in commercially available instruments is a helium ion source, which is inherently less damaging to the sample than Ga ions although it will still sputter small amounts of material especially at high magnifications and long scan times. As helium ions can be focused into a small probe size and provide a much smaller sample interaction than high energy (>1 kV) electrons in the SEM, the He ion microscope can generate equal or higher resolution images with good material contrast and a higher depth of focus. Commercial instruments are capable of sub 1 nm resolution.
Wien filter in focused ion beam setup
Imaging and milling with Ga ions always result in Ga incorporation near the sample surface. As the sample surface is sputtered away at a rate proportional to the sputtering yield and the ion flux (ions per area per time), the Ga is implanted further into the sample, and a steady-state profile of Ga is reached. This implantation is often a problem in the range of the semiconductor where silicon can be amorphised by the gallium. In order to get an alternative solution to Ga LMI sources, mass-filtered columns have been developed, based on a Wien filter technology. Such sources include Au-Si, Au-Ge and Au-Si-Ge sources providing Si, Cr, Fe, Co, Ni, Ge, In, Sn, Au, Pb and other elements.
The principle of a Wien filter is based on the equilibrium of the opposite forces induced by perpendicular electrostatic and a magnetic fields acting on accelerated particles. The proper mass trajectory remains straight and passes through the mass selection aperture while the other masses are stopped.
Besides allowing the use of sources others than gallium, these columns can switch from different species simply by adjusting the properties of the Wien filter. Larger ions can be used to make rapid milling before refining the contours with smaller ones. Users also benefits from the possibility to dope their samples with elements of suitable alloy sources.
The latter property has found great interests in the investigation of magnetic materials and devices. Khizroev and Litvinov have shown, with the help of magnetic force microscopy (MFM), that there is a critical dose of ions that a magnetic material can be exposed to without experiencing a change in the magnetic properties. Exploiting FIB from such an unconventional perspective is especially favourable today when the future of so many novel technologies depends on the ability to rapidly fabricate prototype nanoscale magnetic devices.
See also
Confocal microscopy
Ion milling machine
Powder diffraction
Ultrafast x-ray
X-ray crystallography
X-ray scattering techniques
References
Further reading
Electron microscopy
Scientific techniques
Semiconductor device fabrication
Thin film deposition | Focused ion beam | [
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2,980,361 | https://en.wikipedia.org/wiki/Immunoglobulin%20heavy%20chain | The immunoglobulin heavy chain (IgH) is the large polypeptide subunit of an antibody (immunoglobulin). In human genome, the IgH gene loci are on chromosome 14.
A typical antibody is composed of two immunoglobulin (Ig) heavy chains and two Ig light chains. Several different types of heavy chain exist that define the class or isotype of an antibody. These heavy chain types vary between different animals. All heavy chains contain a series of immunoglobulin domains, usually with one variable domain (VH) that is important for binding antigen and several constant domains (CH1, CH2, etc.). Production of a viable heavy chain is a key step in B cell maturation. If the heavy chain is able to bind to a surrogate light chain and move to the plasma membrane, then the developing B cell can begin producing its light chain.
The heavy chain does not always have to bind to a light chain. Pre-B lymphocytes can synthesize heavy chain in the absence of light chain, which then can allow the heavy chain to bind to a heavy-chain binding protein.
In mammals
Classes
There are five types of mammalian immunoglobulin heavy chain: γ, δ, α, μ and ε. They define classes of immunoglobulins: IgG, IgD, IgA, IgM and IgE, respectively.
Heavy chains α and γ have approximately 450 amino acids.
Heavy chains μ and ε have approximately 550 amino acids.
Regions
Each heavy chain has two regions:
a constant region (which is the same for all immunoglobulins of the same class but differs between classes).
Heavy chains γ, α and δ have a constant region composed of three tandem (in a line next to each other) immunoglobulin domains but also have a hinge region for added flexibility.
Heavy chains μ and ε have a constant region composed of four domains.
a variable region that differs between different B cells, but is the same for all immunoglobulins produced by the same B cell or B cell clone. The variable domain of any heavy chain is composed of a single immunoglobulin domain. These domains are about 110 amino acids long.
Cows
Cows, specifically Bos taurus, show a variation on the general mammalian theme in which the heavy chain CDR H3 region has adapted to produce a divergent repertoire of antibodies which present a "stalk and knob" antigen interaction surface instead of the more familiar bivalent tip surface. The bovine CDR is unusually long and contains unique sequence attributes which support the production of paired cysteine residues during somatic hypermutation. Thus, where in humans the somatic hypermutation step targets the V(D)J recombination process, the target in cows is on the creation of diverse disulfide bonds and the generation of unique sets of loops which interact with antigen. A speculated evolutionary driver for this variation is the presence of a vastly more diverse microbial environment in the digestive system of the cow as a consequence of their being ruminants.
In fish
Jawed fish appear to be the most primitive animals that are able to make antibodies like those described for mammals. However, fish do not have the same repertoire of antibodies that mammals possess. Three distinct Ig heavy chains have so far been identified in bony fish.
The first identified was the μ (or mu) heavy chain that is present in all jawed fish and is the heavy chain for what is thought to be the primordial immunoglobulin. The resulting antibody, IgM, is secreted as a tetramer in teleost fish instead of the typical pentamer found in mammals and sharks.
The heavy chain (δ) for IgD was identified initially from the channel catfish and Atlantic salmon and is now well documented for many teleost fish.
The third teleost Ig heavy chain gene was identified very recently and does not resemble any of the heavy chains so far described for mammals. This heavy chain, identified in both rainbow trout (τ) and zebrafish (ζ), could potentially form a distinct antibody isotype (IgT or IgZ) that may precede IgM in evolutionary terms.
Similar to the situation observed for bony fish, three distinct Ig heavy chain isotypes have been identified in cartilaginous fish. With the exception of μ, these Ig heavy chain isotypes appear to be unique to cartilaginous fish. The resulting antibodies are designated IgW (also called IgX or IgNARC) and IgNAR (immunoglobulin new antigen receptor). The latter type is a heavy-chain antibody, an antibody lacking light chains, and can be used to produce single-domain antibodies, which are essentially the variable domain (VNAR) of an IgNAR. Shark single domain antibodies (VNARs) to tumor or viral antigens can be isolated from a large naïve nurse shark VNAR library using phage display technology.
IgW has now also been found in the group of lobe finned fishes including the coelacanth and lungfish. The IgW1 and IgW2 in coelacanth has a usual (VD)n-Jn-C structure as well as having a large number of constant domains.
In amphibians
Frogs can synthesize IgX and IgY.
See also
Heavy-chain antibody
References
External links
Educational Resource for Heavy Chain Analysis
Immune system | Immunoglobulin heavy chain | [
"Biology"
] | 1,151 | [
"Immune system",
"Organ systems"
] |
2,980,541 | https://en.wikipedia.org/wiki/Clifford%27s%20theorem%20on%20special%20divisors | In mathematics, Clifford's theorem on special divisors is a result of on algebraic curves, showing the constraints on special linear systems on a curve C.
Statement
A divisor on a Riemann surface C is a formal sum of points P on C with integer coefficients. One considers a divisor as a set of constraints on meromorphic functions in the function field of C, defining as the vector space of functions having poles only at points of D with positive coefficient, at most as bad as the coefficient indicates, and having zeros at points of D with negative coefficient, with at least that multiplicity. The dimension of is finite, and denoted . The linear system of divisors attached to D is the corresponding projective space of dimension .
The other significant invariant of D is its degree d, which is the sum of all its coefficients.
A divisor is called special if ℓ(K − D) > 0, where K is the canonical divisor.
Clifford's theorem states that for an effective special divisor D, one has:
,
and that equality holds only if D is zero or a canonical divisor, or if C is a hyperelliptic curve and D linearly equivalent to an integral multiple of a hyperelliptic divisor.
The Clifford index of C is then defined as the minimum of taken over all special divisors (except canonical and trivial), and Clifford's theorem states this is non-negative. It can be shown that the Clifford index for a generic curve of genus g is equal to the floor function
The Clifford index measures how far the curve is from being hyperelliptic. It may be thought of as a refinement of the gonality: in many cases the Clifford index is equal to the gonality minus 2.
Green's conjecture
A conjecture of Mark Green states that the Clifford index for a curve over the complex numbers that is not hyperelliptic should be determined by the extent to which C as canonical curve has linear syzygies. In detail, one defines the invariant a(C) in terms of the minimal free resolution of the homogeneous coordinate ring of C in its canonical embedding, as the largest index i for which the graded Betti number βi, i + 2 is zero. Green and Robert Lazarsfeld showed that a(C) + 1 is a lower bound for the Clifford index, and Green's conjecture states that equality always holds. There are numerous partial results.
Claire Voisin was awarded the Ruth Lyttle Satter Prize in Mathematics for her solution of the generic case of Green's conjecture in two papers. The case of Green's conjecture for generic curves had attracted a huge amount of effort by algebraic geometers over twenty years before finally being laid to rest by Voisin. The conjecture for arbitrary curves remains open.
Notes
References
External links
Algebraic curves
Theorems in algebraic geometry
Unsolved problems in geometry | Clifford's theorem on special divisors | [
"Mathematics"
] | 599 | [
"Theorems in algebraic geometry",
"Geometry problems",
"Unsolved problems in mathematics",
"Unsolved problems in geometry",
"Theorems in geometry",
"Mathematical problems"
] |
2,980,629 | https://en.wikipedia.org/wiki/Petriscript | PetriScript is a modeling language for Petri nets, designed by Alexandre Hamez and Xavier Renault. The CPN-AMI platform provides many tools to work on Petri nets, such as verifying and model-checking tools.
Originally, simple Petri nets were created through graphic design, but research conducted internally at LIP6 revealed that it was needed to automate such tasks. PetriScript was designed to provide some facilities in modeling places-transition and coloured Petri nets within the CPN-AMI platform. Petriscript's main purpose is to automate modeling operations on Petri nets by merging, creating, and connecting nodes. It supports almost everything needed, such as macros, loops control, lists, and string and arithmetic expressions, and blocks intervention of the user as much as possible. Its syntax is Ada-like.
The following script produces a FIFO with three sections:
define(FIFO_SIZE,3)
define(FIFO_BASE_X,100)
define(FIFO_BASE_Y,100)
define(FIFO_STEP,120)
int $wave := 0;
for $wave in 1..FIFO_SIZE loop
create place "Slot_" & '$wave' (x FIFO_BASE_X + FIFO_STEP * $wave,
y FIFO_BASE_Y);
create place "Empty_" & '$wave' (x FIFO_BASE_X + FIFO_STEP * $wave,
y FIFO_BASE_Y + 100, marking "1");
end loop;
for $wave in 1..FIFO_SIZE+1 loop
create transition "t" & '$wave -1' & "_to_" & '$wave' (x FIFO_BASE_X + FIFO_STEP * $wave - FIFO_STEP / 2,
y FIFO_BASE_Y + 50);
if $wave < FIFO_SIZE+1 then
connect "1" transition "t" &'$wave -1' & "_to_" & '$wave' to place "Slot_" & '$wave';
connect "1" place "Empty_" & '$wave' to transition "t" &'$wave -1' & "_to_" & '$wave';
end if;
if $wave > 1 then
connect "1" transition "t" &'$wave -1' & "_to_" & '$wave' to place "Empty_" & '$wave - 1';
connect "1" place "Slot_" & '$wave - 1' to transition "t" &'$wave -1' & "_to_" & '$wave';
end if;
end loop;
set transition "t0_to_1" to (name "FIFO_Start");
set transition "t" & 'FIFO_SIZE' & "_to_" & 'FIFO_SIZE + 1' to (name "FIFO_End");
Which produces the following graph:
Here is another example that shows the power of PetriScript:
define(X,250)
define(Y,350)
define(radius,50)
define(R,150)
define(SECTIONS,15)
define(INNER_ANGLE,360/SECTIONS)
define(OUTER_ANGLE,360/(2*SECTIONS))
int $i := 0;
int $j := 0;
for $i in 1.. SECTIONS loop
create place "F" & '$i' ( x X, y Y, r radius, t $i * INNER_ANGLE);
create place "Section_" & '$i' ( x X, y Y, r R, t $i * INNER_ANGLE);
create transition "t" & '$i' & "_to_" & '$i mod SECTIONS + 1' ( x X, y Y, r R, t $i * INNER_ANGLE + OUTER_ANGLE);
end loop;
for $i in 1.. SECTIONS loop
connect place "Section_" & '$i' to transition "t"&'$i' & "_to_" & '$i mod SECTIONS + 1';
connect transition "t" & '$i' & "_to_" & '$i mod SECTIONS + 1' to place "Section_" & '$i mod SECTIONS + 1';
if $i /= 1 then
connect place "F" & '$i' to transition "t" & '$i-1' & "_to_" & '$i';
else
connect place "F1" to transition "t" & 'SECTIONS' & "_to_" & '1';
end if;
connect transition "t" &'$i mod SECTIONS + 1' & "_to_" & '($i+1) mod SECTIONS + 1' to place "F" & '$i';
end loop;
for $i in 1.. SECTIONS loop
if $i mod 3 = 0 then
set place "Section_" & '$i' to marking "1";
else
set place "F" & '$i' to marking "1";
end if;
end loop;
Which produces the following graph:
References
External links
Full documentation is available here.
Specification languages
Petri nets | Petriscript | [
"Engineering"
] | 1,126 | [
"Software engineering",
"Specification languages"
] |
2,980,850 | https://en.wikipedia.org/wiki/ITU-R%20468%20noise%20weighting | ITU-R 468 (originally defined in CCIR recommendation 468-4, therefore formerly also known as CCIR weighting; sometimes referred to as CCIR-1k) is a standard relating to noise measurement, widely used when measuring noise in audio systems. The standard, now referred to as ITU-R BS.468-4, defines a weighting filter curve, together with a quasi-peak rectifier having special characteristics as defined by specified tone-burst tests. It is currently maintained by the International Telecommunication Union who took it over from the CCIR.
It is used especially in the UK, Europe, and former countries of the British Empire such as Australia and South Africa. It is less well known in the USA where A-weighting has always been used.
M-weighting is a closely related filter, an offset version of the same curve, without the quasi-peak detector.
Explanation
The A-weighting curve was based on the 40 phon equal-loudness contour derived initially by Fletcher and Munson (1933). Originally incorporated into an ANSI standard for sound level meters, A-weighting was intended for measurement of the audibility of sounds by themselves. It was never specifically intended for the measurement of the more random (near-white or pink) noise in electronic equipment, though has been used for this purpose by most microphone manufacturers since the 1970s. The human ear responds quite differently to clicks and bursts of random noise, and it is this difference that gave rise to the CCIR-468 weighting curve (now supported as an ITU standard), which together with quasi-peak measurement (rather than the rms measurement used with A-weighting) became widely used by broadcasters throughout Britain, Europe, and former British Commonwealth countries, where engineers were heavily influenced by BBC test methods. Telephone companies worldwide have also used methods similar to ITU-R 468 weighting with quasi-peak measurement to describe objectionable interference induced in one telephone circuit by switching transients in another.
History
Original research
Developments in the 1960s, in particular the spread of FM broadcasting and the development of the compact audio cassette with Dolby-B Noise Reduction, alerted engineers to the need for a weighting curve that gave subjectively meaningful results on the typical random noise that limited the performance of broadcast circuits, equipment and radio circuits. A-weighting was not giving consistent results, especially on FM radio transmissions and Compact Cassette recording where preemphasis of high frequencies was resulting in increased noise readings that did not correlate with subjective effect. Early efforts to produce a better weighting curve led to a DIN standard that was adopted for European Hi-Fi equipment measurement for a while.
Experiments in the BBC led to BBC Research Department Report EL-17, The Assessment of Noise in Audio Frequency Circuits, in which experiments on numerous test subjects were reported, using a variety of noises ranging from clicks to tone-bursts to pink noise. Subjects were asked to compare these with a 1 kHz tone, and final scores were then compared with measured noise levels using various combinations of weighting filter and quasi-peak detector then in existence (such as those defined in a now discontinued German DIN standard). This led to the CCIR-468 standard which defined a new weighting curve and quasi-peak rectifier.
The origin of the current ITU-R 468 weighting curve can be traced to 1956. The 1968 BBC EL-17 report discusses several weighting curves, including one identified as D.P.B. which was chosen as superior to the alternatives: A.S.A, C.C.I.F and O.I.R.T. The report's graph of the DPB curve is identical to that of the ITU-R 468 curve, except that the latter extends to slightly lower and higher frequencies. The BBC report states that this curve was given in a "contribution by the D.B.P. (The Telephone Administration of the Federal German Republic) in the Red Book Vol. 1 1957 covering the first plenary assembly of the CCITT (Geneva 1956)". D.B.P. is Deutsche Bundespost, the German post office which provides telephone service in Germany as the GPO does in the UK. The BBC report states "this characteristic is based on subjective tests described by Belger." and cites a 1953 paper by E. Belger.
Dolby Laboratories took up the new CCIR-468 weighting for use in measuring noise on their noise reduction systems, both in cinema (Dolby A) and on cassette decks (Dolby B), where other methods of measurement were failing to show up the advantage of such noise reduction. Some Hi-Fi column writers took up 468 weighting enthusiastically, observing that it reflected the roughly 10 dB improvement in noise observed subjectively on cassette recordings when using Dolby B while other methods could indicate an actual worsening in some circumstances, because they did not sufficiently attenuate noise above 10 kHz.
Standards
CCIR Recommendation 468-1 was published soon after this report, and appears to have been based on the BBC work. Later versions up to CCIR 468-4 differed only in minor changes to permitted tolerances. This standard was then incorporated into many other national and international standards (IEC, BSI, JIS, ITU) and adopted widely as the standard method for measuring noise, in broadcasting, professional audio, and 'Hi-Fi' specifications throughout the 1970s. When the CCIR ceased to exist, the standard was officially taken over by the ITU-R (International Telecommunication Union). Current work on this standard occurs primarily in the maintenance of IEC 60268, the international standard for sound systems.
The CCIR curve differs greatly from A-weighting in the 5 to 8 kHz region where it peaks to +12.2 dB at 6.3 kHz, the region in which we appear to be extremely sensitive to noise. While it has been said (incorrectly) that the difference is due to a requirement for assessing noise intrusiveness in the presence of programme material, rather than just loudness, the BBC report makes clear the fact that this was not the basis of the experiments. The real reason for the difference probably relates to the way in which our ears analyse sounds in terms of spectral content along the cochlea. This behaves like a set of closely spaced filters with a roughly constant Q factor, that is, bandwidths proportional to their centre frequencies. High frequency hair cells would therefore be sensitive to a greater proportion of the total energy in noise than low frequency hair cells. Though hair-cell responses are not exactly constant Q, and matters are further complicated by the way in which the brain integrates adjacent hair-cell outputs, the resultant effect appears roughly as a tilt centred on 1 kHz imposed on the A-weighting.
Dependent on spectral content, 468-weighted measurements of noise are generally about 11 dB higher than A-weighted, and this is probably a factor in the recent trend away from 468-weighting in equipment specifications as cassette tape use declines.
It is important to realise that the 468 specification covers both weighted and 'unweighted' (using a 22 Hz to 22 kHz 18 dB/octave bandpass filter) measurement and that both use a very special quasi-peak rectifier with carefully devised dynamics (A-weighting uses RMS detection for no particular reason). Rather than having a simple 'integration time' this detector requires implementation with two cascaded 'peak followers' each with different attack time-constants carefully chosen to control the response to both single and repeating tone-bursts of various durations. This ensures that measurements on impulsive noise take proper account of our reduced hearing sensitivity to short bursts. This quasi-peak measurement is also called psophometric weighting.
This was once more important because outside broadcasts were carried over 'music circuits' that used telephone lines, with clicks from Strowger and other electromechanical telephone exchanges. It now finds fresh relevance in the measurement of noise on computer 'Audio Cards' which commonly suffer clicks as drives start and stop.
Present usage of 468-weighting
468-weighting is also used in weighted distortion measurement at 1 kHz. Weighting the distortion residue after removal of the fundamental emphasises high-order harmonics, but only up to 10 kHz or so where the ears response falls off. This results in a single measurement (sometimes called distortion residue measurement) which has been claimed to correspond well with subjective effect even for power amplifiers where crossover distortion is known to be far more audible than normal THD (total harmonic distortion) measurements would suggest.
468-weighting is still demanded by the BBC and many other broadcasters, with increasing awareness of its existence and the fact that it is more valid on random noise where pure tones do not exist.
Often both A-weighted and 468-weighted figures are quoted for noise, especially in microphone specifications.
While not intended for this application, the 468 curve has also been used (offset to place the 0 dB point at 2 kHz rather than 1 kHz) as "M weighting" in standards such as ISO 21727 intended to gauge loudness or annoyance of cinema soundtracks. This application of the weighting curve does not include the quasi-peak detector specified in the ITU standard.
Summary of specification
Note: this is not the full definitive standard.
Weighting curve specification (weighted measurement)
The weighting curve is specified by both a circuit diagram of a weighting network and a table of amplitude responses.
Above is the ITU-R 468 Weighting Filter Circuit Diagram. The source and sink impedances are both 600 ohms (resistive), as shown in the diagram. The values are taken directly from the ITU-R 468 specification. Note that since this circuit is purely passive, it cannot create the additional 12 dB gain required; any results must be corrected by a factor of 8.1333, or +18.2 dB.
Table of amplitude responses:
The values of the amplitude response table slightly differ from those resulting from the circuit diagram, e.g. because of the finite resolution of the numerical values. In the standard it is said that the 33.06 nF capacitor may be adjusted or an active filter may be used.
Modeling at hand the circuit above and some calculus give this formula to get the amplitude response in dB for any given frequency value :
where
Tone-burst response requirements
5 kHz single bursts:
Repetitive tone-burst response
5 ms, 5 kHz bursts at repetition rate:
Unweighted measurement
Uses 22 Hz HPF and 22 kHz LPF 18 dB/decade or greater.
(Tables to be added)
See also
Noise weighting
Audio system measurements
References
Further reading
Audio Engineer's Reference Book, 2nd Ed 1999, edited Michael Talbot Smith, Focal Press
An Introduction to the Psychology of Hearing 5th ed, Brian C. J. Moore, Elsevier Press
External links
AES pro audio reference definition of ITU-R 468-weighting
Weighting Filter Set Circuit diagrams
Audio engineering
Noise
Sound
468 noise weighting | ITU-R 468 noise weighting | [
"Engineering"
] | 2,270 | [
"Electrical engineering",
"Audio engineering"
] |
2,980,969 | https://en.wikipedia.org/wiki/Shoring | Shoring is the process of temporarily supporting a building, vessel, structure, or trench with shores (props) when in danger of collapse or during repairs or alterations. Shoring comes from shore, a timber or metal prop. Shoring may be vertical, angled, or horizontal.
Methods
Buildings
Raking shores
In this method, inclined members called rakers are used to give temporary lateral support to an unsafe wall. One or more timbers slope between the face of the structure to be supported and the ground. The most effective support is given if the raker meets the wall at an angle of 60 to 70 degrees. A wall-plate is typically used to increase the area of support.
Foundations
Shoring is commonly used when installing the foundation of a building. A shoring system such as piles and lagging or shotcrete will support the surrounding loads until the underground levels of the building are constructed. Commonly used shoring equipment includes post shores, shoring beams, and timber jacks.
Trenches
During excavation, shoring systems speed up excavation and provide safety for workers since trenches can be prone to collapse. In this case, shoring should not be confused with shielding. Shoring is designed to prevent collapse where shielding is only designed to protect workers when collapses occur.
Concrete-structure and stone-building shoring, in these cases also referred to as falsework, provides temporary support until the concrete becomes hard and achieves the desired strength to support loads.
Hydraulic shoring
Hydraulic shoring is the use of hydraulic pistons that can be pumped outward until they press up against the trench walls. They are typically combined with steel plate or plywood, either being 1-1/8" thick plywood, or special heavy Finland Form (FINFORM) 7/8″ thick.
Beam and plate
Beam and plate steel I-beams are driven into the ground and steel plates are slid in amongst them. A similar method that uses wood planks is called soldier boarding. Hydraulics tend to be faster and easier; the other methods tend to be used for longer term applications or larger excavations.
Soil nailing
Soil nailing is a technique in which soil slopes, excavations or retaining walls are reinforced by the insertion of relatively slender elements – normally steel reinforcing bars. The bars are usually installed into a pre-drilled hole and then grouted into place or drilled and grouted simultaneously. They are usually installed untensioned at a slight downward inclination. A rigid or flexible facing (often sprayed concrete) or isolated soil nail heads may be used at the surface.
Shoring in ships
Shoring is used on board when damage has been caused to a vessel's integrity, and to hold leak-stopping devices in place to reduce or stop incoming water. Generally consists of timber 100 mm x 100 mm and used in conjunction with wedges, to further jam shoring in place, pad pieces to spread the load and dogs to hold it together. Also used on board is mechanical shoring as a quick, temporary solution, however it isn't favoured due to its inability to move with the vessel.
Proud
This consists of a timber member jammed on a pad piece on either the deck or deck head depending on water levels in the compartment and a strong point, this is called the proud. Then there is a horizontal timber cut to size to fit between this and what it is shoring up, e.g. a splinter box, bulkhead or door. Timber wedges are then used to tighten up the structure if necessary.
Vertical shoring
This is to support a hatch or splint box on the deck, consisting of a vertical timber between the deck and deck head, with two wedges used opposing each other to tighten it. Pad pieces are used to spread the load on weak structures.
Shoring in air freight
Shoring is a term used in the process of air freight container and pallet (ULD) buildup, e.g. making sure that the cargo placed in containers and on pallets is packed securely and efficiently. Specifically, shoring is done to affix cargo to the ULD and adapt different form factors of cargo items to maximize the use of the available ULD volume.
Typically, wooden beams and various forms of boards are used. Most often, shoring material is re-used but as the airfreight industry uses high-quality timber, shoring material often disappears and is a non-insignificant cost of cargo transport.
Gallery
See also
Box crib
House raising
References
External links
An illustrated glossary of the terms used in temporary types of construction work. Formwork, scaffolding etc.
The Scaffolding, Shoring & Forming Institute (SSFI)
Civil engineering | Shoring | [
"Engineering"
] | 945 | [
"Construction",
"Civil engineering"
] |
2,980,973 | https://en.wikipedia.org/wiki/Culling | Culling is the process of segregating organisms from a group according to desired or undesired characteristics. In animal breeding, it is removing or segregating animals from a breeding stock based on a specific trait. This is done to exaggerate desirable characteristics, or to remove undesirable characteristics by altering the genetic makeup of the population. For livestock and wildlife, culling often refers to killing removed animals based on their characteristics, such as their sex or species membership, or as a means of preventing infectious disease transmission.
In fruits and vegetables, culling is the sorting or segregation of fresh harvested produce into marketable lots, with the non-marketable lots being discarded or diverted into food processing or non-food processing activities. This usually happens at collection centres located at, or close to farms.
Etymology
The word cull comes from the Latin verb , meaning "to gather". The term can be applied broadly to mean partitioning a collection into two groups: one that will be kept and one that will be rejected. The cull is the set of items rejected during the selection process. The culling process is repeated until the selected group is of proper size and consistency desired.
Pedigreed animals
Culling is:
In the breeding of pedigreed animals, both desirable and undesirable traits are considered when choosing which animals to retain for breeding and which to place as pets. The process of culling starts with examination of the conformation standard of the animal and will often include additional qualities such as health, robustness, temperament, color preference, etc. The breeder takes all things into consideration when envisioning their ideal for the breed or goal of their breeding program. From that vision, selections are made as to which animals, when bred, have the best chance of producing the ideal for the breed.
Breeders of pedigreed animals cull based on many criteria. The first culling criterion should always be health and robustness. Secondary to health, temperament and conformation of the animal should be considered. The filtering process ends with the breeder's personal aesthetic preferences on pattern, color, etc.
Tandem method
The tandem method is a form of selective breeding where a breeder addresses one characteristic of the animal at a time, thus selecting only animals that measure above a certain threshold for that particular trait while keeping other traits constant. Once that level of quality in the single trait is achieved, the breeder will focus on a second trait and cull based on that quality. With the tandem method, a minimum level of quality is set for important characteristics that the breeder wishes to remain constant. The breeder is focusing improvement in one particular trait without losing quality of the others. The breeder will raise the threshold for selection on this trait with each successive generation of progeny, thus ensuring improvement in this single characteristic of his breeding program.
For example, a breeder that is pleased with the muzzle length, muzzle shape, and eye placement in the breeding stock, but wishes to improve the eye shape of progeny produced may determine a minimum level of improvement in eye shape required for progeny to be returned into the breeding program. Progeny is first evaluated on the existing quality thresholds in place for muzzle length, muzzle shape, and eye placement with the additional criterion being improvement in eye shape. Any animal that does not meet this level of improvement in the eye shape while maintaining the other qualities is culled from the breeding program; i.e., that animal is not used for breeding, but is instead neutered and placed in a pet home.
Independent levels
Independent levels is a method where any animal who falls below a given standard in any single characteristic is not used in a breeding program. With each successive mating, the threshold culling criteria are raised thus improving the breed with each successive generation.
This method measures several characteristics at once. Should progeny fall below the desired quality in any one characteristic being measured, it will not be used in the breeding program regardless of the level of excellence of other traits. With each successive generation of progeny, the minimum quality of each characteristic is raised thus ensuring improvement of these traits.
For example, a breeder has a view of what the minimum requirements for muzzle length, muzzle shape, eye placement, and eye shape they are breeding toward. The breeder will determine what the minimum acceptable quality for each of these traits will be for progeny to be folded back into their breeding program. Any animal that fails to meet the quality threshold for any one of these criteria is culled from the breeding program.
Total score method
The total score method is a selection method where the breeder evaluates and selects breeding stock based on a weighted table of characteristics. The breeder selects qualities that are most important to them and assigns them a weight. The weights of all the traits should add up to 100. When evaluating an individual for selection, the breeder measures the traits on a scale of 1 to 10, with 10 being the most desirable expression and 1 being the lowest. The scores are then multiplied by their weights and then added together to give a total score. Individuals that fail to meet a threshold are culled (or removed) from the breeding program. The total score gives a breeder a way to evaluate multiple traits on an animal at the same time.
The total score method is the most flexible of the three. it allows for weighted improvement of multiple characteristics. It allows the breeder to make major gains in one aspect while moderate or lesser gains in others.
For example, a breeder is willing to make a smaller improvement in muzzle length and muzzle shape in order to have a moderate gain in improvement of eye placement and a more dramatic improvement in eye shape. Suppose the breeder determines that she would like to see 40% improvement in eye shape, 30% improvement in eye placement, and 15% improvement in both muzzle length and shape. The breeder would evaluate these characteristics on a scale of 1 to 10 and multiply by the weights. The formula would look something like: 15 (muzzle length) + 15 (muzzle shape) + 30 (eye placement) + 40 (eye shape) = total score for that animal. The breeder determines the lowest acceptable total score for an animal to be folded back into their breeding program. Animals that do not meet this minimum total score are culled from the breeding program.
Livestock and production animals
Livestock bred for the production of meat or milk may be culled by farmers. Animals not selected to remain for breeding are sold, killed, or sent to the slaughterhouse.
Criteria for culling livestock and production animals can be based on population or production (milk or egg). In a domestic or farming situation, the culling process involves the selection and selling of surplus stock. The selection may be done to improve breeding stock—for example, for improved production of eggs or milk—or simply to control the group's population for environmental and species preservation. In order to increase the frequency of preferred phenotypes, agricultural practices typically involve using the most productive animals as breeding stock.
With dairy cattle, culling may be practised by inseminating cows—considered to be inferior—with beef breed semen and by selling the produced offspring for meat production.
Approximately half of the chicks of egg-laying chickens are males who would grow up to be roosters. These individuals have little use in an industrial egg-producing facility as they do not lay eggs, so the majority of male chicks are killed shortly after hatching.
Culling of farmed animals is considered a necessary practice to prevent the spread of damaging and fatal diseases such as foot-and-mouth disease, avian flu, Influenza A virus subtype H5N1 and bovine spongiform encephalopathy ("mad cow disease").
Wildlife
In the United States, hunting licenses and hunting seasons are a means by which the population of game animals is maintained. Each season, a hunter is allowed to kill a certain amount of wild animals, determined both by species and sex. If the population seems to have surplus females, hunters are allowed to take more females during that hunting season. If the population is below what is desired, hunters may not be permitted to hunt that particular species, or only hunt a restricted number of males.
Populations of game animals such as elk may be informally culled if they begin to excessively eat winter food set out for domestic cattle herds. In such instances the rancher will inform hunters that they may hunt on their property in order to thin the wild herd to controllable levels. These efforts are aimed to counter excessive depletion of the winter feed supplies. Other managed culling instances involve extended issuance of extra hunting licenses, or the inclusion of additional "special hunting seasons" during harsh winters or overpopulation periods, governed by state fish and game agencies.
Culling for population control is common in wildlife management, particularly on African game farms and Australian national parks. In the case of very large animals such as elephants, adults are often targeted. Their orphaned young, easily captured and transported, are then relocated to other reserves. Culling is controversial in many African countries, but reintroduction of the practice has been recommended in recent years for use at the Kruger National Park in South Africa, which has experienced a swell in its elephant population since culling was banned in 1995.
Arguments against wildlife culling
Culling acts as a strong selection force and can therefore impact the population genetics of a species. For example, culling based on specific traits, such as size, can enforce directional selection and remove those traits from the population. This can have long-term effects on the genetic diversity of a population.
However, culling can act as a selection force intentionally implemented by humans to counteract the selection force of trophy hunting. Hunting typically enforces selection towards unfavorable phenotypic traits because of the strong hunting bias for specific traits, such as large antler size. Culling "low-quality" traits can counteract this force.
Animal rights activists argue that killing animals for any reason (including hunting) is cruel and unethical.
Birds
Some bird species are culled when their populations impact upon human property, business or recreational activity, disturb or modify habitats or otherwise impact species of conservation concern. Cormorants are culled in many countries due to their impact on commercial and recreational fisheries and habitat modification for nesting and guano deposition. They are culled by shooting and the smothering of eggs with oil. Another example is the culling of silver gulls in order to protect the chicks of the vulnerable banded stilt at ephemeral inland salt lake breeding sites in South Australia. The gulls were culled using bread laced with a narcotic substance. In the Australian states of Tasmania and South Australia, Cape Barren geese are culled to limit damage to crops and the fouling of waterholes. Cape Barren Geese remain one of the rarest geese in the world, though much of their habitat is now regarded as secure.
Seals
In South Australia, the recovery of the state's native population of New Zealand fur seals (Arctocephalus forsteri) after severe depletion by sealers in the 1800s has brought them into conflict with the fishing industry. This has prompted members of Parliament to call for seal culling in South Australia. The State Government continues to resist the pressure and as of July 2015, the animals remain protected as listed Marine Mammals under the state's National Parks and Wildlife Act 1972.
Sharks
Shark culling occurs in four locations : New South Wales, Queensland, KwaZulu-Natal and Réunion. Between 1950 and 2008, 352 tiger sharks and 577 great white sharks were killed in the nets in New South Wales—also during this period, a total of 15,135 marine animals were caught and killed in the nets, including whales, turtles, rays, dolphins, and dugongs. From 2001 to 2018, a total of 10,480 sharks were killed on lethal drum lines in Queensland. In a 30-year period up to early 2017, more than 33,000 sharks were killed in KwaZulu-Natal's shark-killing program—during the same 30-year period, 2,211 turtles, 8,448 rays, and 2,310 dolphins were killed. Authorities on Réunion kill about 100 sharks per year. All of these culls have been criticized by environmentalists, who say killing sharks harms the marine ecosystem.
In 2014, a controversial policy was introduced by the Western Australian state government which became known as the Western Australian shark cull. Baited hooks known as drum lines were to be set over several consecutive summers to catch and kill otherwise protected great white sharks. The policy's objective was to protect users of the marine environment from fatal shark attack. Thousands of people protested against its implementation, claiming that it was indiscriminate, inhumane and worked against scientific advice the government had previously received. Seasonal setting of drum lines was abandoned in September 2014 after the program failed to catch any great white sharks, instead catching 172 other elasmobranchii, mostly tiger sharks.
Deer
White-tailed deer (Odocoileus virginianus) have been becoming an issue in suburbs across the United States due to large population increases. This is thought to be caused mainly by the extirpation of most of their major predators in these areas. In response to these population booms, different management approaches have been taken to decrease their numbers mainly in the form of culls. Culls of deer are often partnered with exclusions with fencing and also administering contraceptives.
The effectiveness of these deer culls has been debated and often criticized as only a temporary fix to the larger problem of deer overpopulation and argue that the use of culling will increase fertility of remaining deer by reducing competition. Those in favor of the culls argue that they can be used to combat the selection pressure that is imposed by hunting that creates smaller antler and body sizes in deer. People in favor of the culls recommend that they not be random and actively select for smaller individuals and bucks with smaller antlers, specifically "button bucks" or bucks with only spiked antler in their first year as opposed to forked antlers.
Culling of deer can also have benefits in the form of disease prevention and in places that the white-tailed deer is an invasive species such as New Zealand culling of deer has added benefits for native species. Diseases are density dependent factors and decreases in the density of the deer populations through culling causes diseases, such as chronic wasting disease and Lyme disease, to spread less quickly and effectively.
Zoos
Many zoos participate in an international breeding program to maintain a genetically viable population and prevent inbreeding. Animals that can no longer contribute to the breeding program are considered less desirable and are often replaced by more desirable individuals. If an animal is surplus to a zoo's requirements and a place in another zoo can not be found, the animal may be killed. In 2014, the culling of a young, healthy giraffe Marius raised an international public controversy.
Zoos sometimes consider female animals to be more desirable than males. One reason for this is that while individual males can contribute to the birth of many young in a short period of time, females give birth to only a few young and are pregnant for a relatively long period of time. This makes it possible to keep many females with just one or two males, but not the reverse. Another reason is that the birth of some animal species increases public interest in the zoo.
Germany's Animal Welfare Act 1972 orders that zoo animals cannot be culled without verification by official veterinary institutes of the Landkreis or federated state.
In the UK, there is no general prohibition on animal euthanasia, which is allowed when overcrowding compromises the well-being of the animals.
Ethics
Jaak Panksepp, an American neuroscientist, concludes that both animals and humans have brains wired to feel emotions, and that animals have the capacity to experience pleasure and happiness from their lives.
Culling has been criticized on animal rights grounds as speciesist—it has been argued that killing animals for any reason is cruel and unethical, and that animals have a right to live.
Some argue that culling is necessary when biodiversity is threatened. However, the protection of biodiversity argument has been questioned by some animal rights advocates who point out that the animal which most greatly threatens and damages biodiversity is humanity, so if we are not willing to cull our own species we cannot morally justify culling another.
Non-lethal alternatives
There are non-lethal alternatives which may still be considered culling, and serve the same purpose of reducing population numbers and selecting for desired traits without killing existing members of the population. These methods include the use of wildlife contraceptives and reproductive inhibitors. By using such methods population numbers might be reduced more gradually and in a potentially more humane fashion than by directly lethal culling actions.
Currently, wildlife contraceptives are largely in the experimental phase and include such products as Gonacon, an adjuvant vaccine which delivers a high dosage of a competitor ligand of the hormone GnRH to female mammals (e.g. whitetail deer). The complex formed of GnRH and the Gonacon molecule promotes production of antibodies against the animal's own GnRH, which themselves complex with GnRH. This encourages an extended duration of the drug's effects (namely, reduction of active/unbound GnRH in the animal's system). Though the endocrinology behind Gonacon is sound, the need for multiple lifetime doses for full efficacy make it a less-guaranteed and less-permanent solution for wildlife than lethal culls. Even among domestic animals in controlled conditions, Gonacon cannot ensure 100% reduction in the occurrence of pregnancies.
Reproductive inhibitors need not act on the parental individuals directly, instead damaging reproductive processes and/or developing offspring to reduce the number of viable offspring per mating pair. One such compound called Nicarbazin has been formulated into bait for consumption by Canada Geese, and damages egg yolk formation to reduce the viability of clutches without harming the adult geese.
See also
Australian feral camel
Badger culling in the United Kingdom
Brumby - feral horses in Australia
Eugenics, the selective breeding of human populations
Experimental evolution
Feral cats in Australia
Foam depopulation
Ventilation shutdown
References
External links
Dictionary.com definition for Culling
The Disposal of Spent Laying Hens
Animal culling
Animal killing
Animal rights
Animal welfare
Cruelty to animals
Intensive farming
Livestock | Culling | [
"Chemistry"
] | 3,771 | [
"Eutrophication",
"Intensive farming"
] |
2,981,044 | https://en.wikipedia.org/wiki/PageNet | PageNet, also known as Paging Network, Inc., was founded in 1981 by entrepreneur George Perrin and ceased in 1999.
The company grew to become the largest wireless messaging company in the world, with more than 10 million pagers in service, and $1 billion in revenues, before the paging industry's rapid decline in the late 1990s.
Operations
Based in Dallas, PageNet held the distinction of building and operating the most extensive one-way paging network in the United States, growing to more than 90 offices across the United States. The company extended operations to Canada and Brazil.
The company was known for its low-cost strategy and aggressive marketing tactics, although in its later years it positioned itself as a technology innovator as well.
Financial difficulties
PageNet's fortunes began to decline in the late 1990s, when the company spent nearly $1 billion to purchase additional spectrum and build out a new network designed to offer advanced services, such as voice paging and two-way paging.
Products developed by Motorola for PageNet's network were unsuccessful, as was a reorganization of the company engineered by McKinsey & Company. Ironically, PageNet had an opportunity to purchase the network that went on to support the successful BlackBerry service, but decided to team with Motorola instead.
As PageNet sank under the weight of its investment, the one-way paging market collapsed—with millions of former paging customers switching to digital cellular and PCS services, which cut prices dramatically while offering new features such as nationwide calling plans and text messaging. Under its last CEO, John P. Frazee, Jr., PageNet was sold to Boston-based Arch Communications in 1999. That company has since merged with Metrocall to form USA Mobility.
See also
References
Defunct telecommunications companies of the United States
Radio paging
Companies based in Dallas
Defunct companies based in Texas
Telecommunications companies established in 1981
Technology companies disestablished in 1999
1981 establishments in Texas
1999 disestablishments in Texas | PageNet | [
"Technology"
] | 401 | [
"Radio paging"
] |
2,981,087 | https://en.wikipedia.org/wiki/Finite%20topology | Finite topology is a mathematical concept which has several different meanings.
Finite topological space
A finite topological space is a topological space, the underlying set of which is finite.
In endomorphism rings and modules
If A and B are abelian groups then the finite topology on the group of homomorphisms Hom(A, B) can be defined using the following base of open neighbourhoods of zero.
This concept finds applications especially in the study of endomorphism rings where we have A = B.
Similarly, if R is a ring and M is a right R-module, then the finite topology on is defined using the following system of neighborhoods of zero:
In vector spaces
In a vector space , the finite open sets are defined as those sets whose intersections with all finite-dimensional subspaces are open. The finite topology on is defined by these open sets and is sometimes denoted .
When V has uncountable dimension, this topology is not locally convex nor does it make V as topological vector space, but when V has countable dimension it coincides with both the finest vector space topology on V and the finest locally convex topology on V.
In manifolds
A manifold M is sometimes said to have finite topology, or finite topological type, if it is homeomorphic to a compact Riemann surface from which a finite number of points have been removed.
Notes
References
General topology | Finite topology | [
"Mathematics"
] | 277 | [
"General topology",
"Topology"
] |
2,981,465 | https://en.wikipedia.org/wiki/Germane | Germane is the chemical compound with the formula GeH4, and the germanium analogue of methane. It is the simplest germanium hydride and one of the most useful compounds of germanium. Like the related compounds silane and methane, germane is tetrahedral. It burns in air to produce GeO2 and water. Germane is a group 14 hydride.
Occurrence
Germane has been detected in the atmosphere of Jupiter.
Synthesis
Germane is typically prepared by reduction of germanium oxides, notably germanates, with hydride reagents such as sodium borohydride, potassium borohydride, lithium borohydride, lithium aluminium hydride, sodium aluminium hydride. The reaction with borohydrides is catalyzed by various acids and can be carried out in either aqueous or organic solvent. On laboratory scale, germane can be prepared by the reaction of Ge(IV) compounds with these hydride reagents. A typical synthesis involved the reaction of sodium germanate with potassium borohydride.
NaHGeO3 + KBH4 + H2O → KGeH3 + KB(OH)4
KGeH3 + HO2CCH3 → GeH4 + KO2CCH3
Other methods for the synthesis of germane include electrochemical reduction and a plasma-based method. The electrochemical reduction method involves applying voltage to a germanium metal cathode immersed in an aqueous electrolyte solution and an anode counter-electrode composed of a metal such as molybdenum or cadmium. In this method, germane and hydrogen gases evolve from the cathode while the anode reacts to form solid molybdenum oxide or cadmium oxides. The plasma synthesis method involves bombarding germanium metal with hydrogen atoms (H) that are generated using a high frequency plasma source to produce germane and digermane.
Reactions
Germane is weakly acidic. In liquid ammonia GeH4 is ionised forming NH4+ and GeH3−. With alkali metals in liquid ammonia GeH4 reacts to give white crystalline MGeH3 compounds. The potassium (potassium germyl or potassium trihydrogen germanide KGeH3) and rubidium compounds (rubidium germyl or rubidium trihydrogen germanide RbGeH3) have the sodium chloride structure implying a free rotation of the trihydrogen germanide anion GeH3−, the caesium compound, caesium germyl or caesium trihydrogen germanide CsGeH3 in contrast has the distorted sodium chloride structure of TlI.
Use in semiconductor industry
The gas decomposes near 600K (327°C; 620°F) to germanium and hydrogen. Because of its thermal lability, germane is used in the semiconductor industry for the epitaxial growth of germanium by MOVPE or chemical beam epitaxy. Organogermanium precursors (e.g. isobutylgermane, alkylgermanium trichlorides, and dimethylaminogermanium trichloride) have been examined as less hazardous liquid alternatives to germane for deposition of Ge-containing films by MOVPE.
Safety
Germane is a highly flammable, potentially pyrophoric, and a highly toxic gas. In 1970, the American Conference of Governmental Industrial Hygienists (ACGIH) published the latest changes and set the occupational exposure threshold limit value at 0.2 ppm for an 8-hour time weighted average.
The LC50 for rats at 1 hour of exposure is 622 ppm. Inhalation or exposure may result in malaise, headache, dizziness, fainting, dyspnea, nausea, vomiting, kidney injury, and hemolytic effects.
The US Department of Transportation hazard class is 2.3 Poisonous Gas.
References
External links
Metaloids (manufacturer) datasheet
Arkonic Specialty Gases China (manufacturer) datasheet
Licensintorg Russia (process technology sale)
Honjo Chemical Japan (manufacturer)
Praxair datasheet
Air liquide gas encyclopedia entry
CDC - NIOSH Pocket Guide to Chemical Hazards
Voltaix (manufacturer) datasheet
Foshan Huate Gas Co., Ltd. (manufacturer)
Horst Technologies, Russia (manufacturer)
Germanium(IV) compounds
Metal hydrides
Industrial gases
Pyrophoric materials | Germane | [
"Chemistry",
"Technology"
] | 925 | [
"Inorganic compounds",
"Reducing agents",
"Metal hydrides",
"Industrial gases",
"Chemical process engineering"
] |
2,981,713 | https://en.wikipedia.org/wiki/Fossil%20%28file%20system%29 | Fossil is the default file system in Plan 9 from Bell Labs. It serves the network protocol 9P and runs as a user space daemon, like most Plan 9 file servers. Fossil is different from most other file systems due to its snapshot/archival feature. It can take snapshots of the entire file system on command or automatically (at a user-set interval). These snapshots can be kept on the Fossil partition as long as disk space allows; if the partition fills up then old snapshots will be removed to free up disk space. A snapshot can also be saved permanently to Venti. Fossil and Venti are typically installed together.
Features
Important features include:
Snapshots are available to all users. No administrator intervention is needed to access old data. (This is possible because Fossil enforces file permissions; users can only access data which they would be allowed to access anyway; thus a user cannot snoop on another's old files or look at old passwords or such.)
Data in permanent snapshots (sometimes called archives) cannot be modified. Only the non-permanent snapshots can be removed.
To access a snapshot, one would connect to a running fossil instance (“mount” it) and change directory to the desired snapshot, e.g. /snapshot/yyyy/mmdd/hhmm (with yyyy, mm, dd, hh, mm meaning year, month, day, hour, minute). To access an archive (permanent snapshot), a directory of the form /archive/yyyy/mmdds (with yyyy, mm, dd, s meaning year, month, day, sequence number) would be used. Plan 9 allows modifying the namespace in advanced ways, like redirecting one path to another path (e.g. /bin/ls to /archive/2005/1012/bin/ls). This significantly eases working with old versions of files.
Fossil is available on several other platforms via Plan 9 from User Space.
History
Fossil was designed and implemented by Sean Quinlan, Jim McKie and Russ Cox at Bell Labs and added to the Plan 9 distribution at the end of 2002. It became the default file system in 2003, replacing Kfs and the previous Plan 9 archival file system, dubbed The Plan 9 File Server, or "fs". fs is also an archival file system which originally was designed to store data on a WORM optical disc system. The permanent storage for fossil is provided by Venti, which typically stores data on hard drives, which have much lower access times than optical discs.
References
See also
GoogleFS – Google's proprietary distributed filesystem
External links
.
.
2002 software
Fossil
Plan 9 from Bell Labs | Fossil (file system) | [
"Technology"
] | 574 | [
"Plan 9 from Bell Labs",
"Computing platforms"
] |
2,982,309 | https://en.wikipedia.org/wiki/2%2C2-Dimethoxypropane | 2,2-Dimethoxypropane (DMP) is an organic compound with the formula (CH3)2C(OCH3)2. A colorless liquid, it is the product of the condensation of acetone and methanol. DMP is used as a water scavenger in water-sensitive reactions. Upon acid-catalyzed reaction, DMP reacts quantitatively with water to form acetone and methanol. This property can be used to accurately determine the amount of water in a sample, alternatively to the Karl Fischer method.
DMP is specifically used to prepare acetonides:
RCHOHCHOHCH2 + (MeO)2CMe2 → RCHCHCH2O2CMe2 + 2 MeOH
Dimethoxypropane is an intermediate for the synthesis of 2-methoxypropene.
In histology, DMP is used for the dehydration of animal tissue.
References
External links
MSDS
MSDS
Methylating agents
Ethers
Ketals
Reagents for organic chemistry | 2,2-Dimethoxypropane | [
"Chemistry"
] | 223 | [
"Ketals",
"Reagents for organic chemistry",
"Functional groups",
"Methylating agents",
"Organic compounds",
"Methylation",
"Ethers"
] |
2,982,520 | https://en.wikipedia.org/wiki/Viktor%20Meyer | Viktor Meyer (8 September 18488 August 1897) was a German chemist and significant contributor to both organic and inorganic chemistry. He is best known for inventing an apparatus for determining vapour densities, the Viktor Meyer apparatus, and for discovering thiophene, a heterocyclic compound. He is sometimes referred to as Victor Meyer, a name used in some of his publications.
Early life
Viktor Meyer was born in Berlin in 1848, the son of trader and cotton printer Jacques Meyer and mother, Bertha. His parents were Jewish, though he was not actively raised in the Jewish faith. Later, he was confirmed in a Reform Jewish congregation. He married a Christian woman, Hedwig Davidson, and raised his children as such. He entered the gymnasium at the age of ten in the same class as his two-year older brother Richard. Although he had excellent science skills his wish to become an actor was based on his love for poetry. At a visit from his brother Richard, who was studying chemistry at the University of Heidelberg, he became attracted to chemistry.
In 1865, when not yet 17 years old but pushed by his parents, Meyer began studying chemistry at the University of Berlin, the same year that August Wilhelm von Hofmann succeeded Eilhard Mitscherlich as the Chair of Chemistry there. After one semester, Meyer went to Heidelberg to work under Robert Bunsen, where he also heard lectures on organic chemistry by Emil Erlenmeyer. As no research was required under Bunsen at the time, Meyer received his doctorate in 1867, at the age of 19. This opened the doors to a very successful career in which he became one of the most important chemists of his time.
Work
Meyer stayed one year with Bunsen for an area wide analysis of spring water. Besides this he was also able to teach some Ph.D. students. In Berlin he joined the group of Adolf Baeyer, one of his best friends in later life, attacking among other problems that of the composition of camphor.
At the age of 23 on Baeyer's recommendation, Meyer was engaged by Fehling as his assistant at Stuttgart Polytechnic, but within a year he left to succeed Johannes Wislicenus at Zurich. There he remained for thirteen years, and it was during this period that he devised his well-known method for determining vapour densities, and carried out his experiments on the dissociation of the halogens. In 1882, on the death of Wilhelm Weith (1844–1881), professor of chemistry at Zurich University, he undertook to continue the lectures on benzene derivatives, and this led him to the discovery of thiophen. In 1885 he was chosen to succeed Hans Hübner (1837–1884) in the professorship of chemistry at Göttingen University, where stereo-chemical questions especially engaged his attention; and in 1889, on the resignation of his old master, Bunsen, he was appointed to the chair of chemistry in Heidelberg University. He died on 8 August 1897.
Health and suicide
Overworked and overtaxed, Meyer's mental status suffered, leading to several minor and major nervous breakdowns during the last years of his life. He always failed to recover completely, yet continued working. He took pills to fall asleep, but these had a damaging effect on his nervous system. In one of his depressions, Meyer decided to take his own life, and committed suicide by taking cyanide. He died at the age of 48 during the night of 7–8 August 1897 in Heidelberg, just one month away from 49.
Career
Professional accomplishments
Scientific contributions
Synthesis of aromatic carboxylic acids from sulfonic acid and formates (1869).
Nitroalkanes from alkyl iodides and silver nitrite (1872), used to distinguish 1°, 2°, 3° alcohols, known as the Victor Meyer test.
Discovery of nitrolic acids (with Locher in 1874).
Development of a method to distinguish primary, secondary, and tertiary nitroalkanes (1875).
Starting with studying physical chemistry in 1876, Meyer created a new method for determining gas density in 1878. This method allowed him to demonstrate how arsenious oxide vapours corresponded to the formula As4O6, that mercury, zinc and cadmium yielded monatomic vapours, and that halogen molecules dissociated into atoms on heating, a phenomenon which he studied until his death. The Victor Meyer apparatus accurately measures the volume of a volatilized substance from which the vapor density of the gas can be derived and also the relative mass.
Proposing glucose is an aldehyde and not a ketone, hereby correcting von Baeyer and van't Hoff (1880).
Synthesis of aldoximes and ketoximes from hydroxylamine and aldehydes or ketones, hereby discovering a new structural identification and elucidation method (1882, together with Alois Janny).
Identification of thiophene as a contaminant in benzene derived from coal (1882). Benzene produced by decarboxylation of benzoic acid did not contain this impurity.
First reliable synthesis of pure sulfur mustard (1886, also see Meyer's account on sulfur mustard)
Coining of the concepts of stereochemistry and dipole in 1888. Meyer had always been interested in stereochemical problems and was one of the first ones to instruct his pupils with van't Hoff's theory of asymmetric carbon and the Hantzsch-Werner theory.
Discovery of iodoso compounds in 1892 by reacting o-iodobenzoic acid with nitric acid.
Observation (1892) that ortho-substituted benzoic acid derivatives are esterified with difficulty. This principle is now known as the Victor Meyer esterification law and was discovered in an attempt to esterify o-iodosobenzoic acid.
Discovery of iodonium compounds by reacting iodobenzene and iodosobenzene (1894).
Books
Meyer wrote several notable books:
Tabellen zur qualitativen Analyse (1884, written together with Frederick Treadwell)
Pyrochemische Untersuchungen (1885)
Die Thiophengruppe (1888)
Chemische Probleme der Gegenwart (1890)
Ergebnisse und Ziele der Stereochemischen Forschung (1890)
Lehrbuch der organischen Chemie (1893, written together with Paul Jacobson. A very popular book at the time that has been reprinted and reedited several times) Digital editions by the University and State Library Düsseldorf
Märztage im kanarischen Archipel, ein Ferienausflug nach Teneriffa und Las Palmas (1893, travel guide)
Honors
In recognition of his brilliant experimental powers, and his numerous contributions to chemical science, he was awarded the Davy Medal by the Royal Society in 1891.
Notes
References
Attribution:
Further reading
(''note: Richard Meyer is Victor Meyer's brother).
External links
1848 births
1897 deaths
Scientists from the Kingdom of Prussia
German organic chemists
German physical chemists
19th-century German chemists
19th-century German inventors
German Reform Jews
Academic staff of the University of Stuttgart
Academic staff of ETH Zurich
Academic staff of the University of Göttingen
Academic staff of Heidelberg University
Heidelberg University alumni
Suicides by cyanide poisoning
Suicides in Germany
1890s suicides
Members of the Göttingen Academy of Sciences and Humanities
Members of the Royal Society of Sciences in Uppsala | Viktor Meyer | [
"Chemistry"
] | 1,538 | [
"Organic chemists",
"German organic chemists"
] |
2,982,572 | https://en.wikipedia.org/wiki/Wild%20West%20Tech | Wild West Tech is an American television program that aired on the History Channel in the United States from 2003 to 2005. The show was originally hosted by Keith Carradine (2003–04); his half-brother, David Carradine, took over hosting duties for season 2 onward. The show illustrates a variety of technologies used in the Wild West, and features interviews with numerous Western historians, as well as recreating versions of important events in Western history.
The series was created by Dolores Gavin and supervising producer Louis Tarantino.
Format
Each episode is dedicated to some broader aspect of Wild West life. Once the context is established in brief by the host, more specific elements are developed. Throughout the program, professors, writers, and other experts explain finer points while historical reenactments and dramatizations portray just how key 19th century events may have transpired. The production aims to put the viewer into the spirit of the Old West with its host inhabiting an unnamed frontier town, delivering commentary.
A new spin on the typical technology fact program, this program often covers subjects from the American Old West that are not generally discussed in more traditional settings. For example, one episode takes a look at the brothel, focusing on the inventions and technological innovations used to make the institution of prostitution less harsh on the lives of the women involved.
Another explains that Morphine was first isolated in 1803 by the German pharmacist Friedrich Wilhelm Adam Sertürner, but it was not until the development of the hypodermic needle (1853) that its use spread and it spread quite a bit in the American West. It was used for pain relief and as a "cure" for opium or alcohol addiction. Its extensive use during the American Civil War resulted in over 400,000 people developing the "soldier's disease" (addiction).
The same episode informs the viewers that heroin, along with other drugs, was only criminalized in the United States by the Harrison Narcotics Tax Act of 1914 decades after it was derived.
Other topics include the technological histories of various alcoholic beverages, saloons, weapons, and cowboy gangs.
Episode guide
Two pilot episodes were produced, hosted by Keith Carradine, to help sell the History Channel on the concept of the series. Seasons 2 and 3 were hosted by David Carradine.
Pilots
Season 1
Season 2
Season 3
External links
Episode guides
History (American TV channel) original programming
History of technology
2000s Western (genre) television series
American frontier
2003 American television series debuts
2005 American television series endings | Wild West Tech | [
"Technology"
] | 508 | [
"Science and technology studies",
"History of science and technology",
"History of technology"
] |
2,982,748 | https://en.wikipedia.org/wiki/Imprest%20system | The imprest system is a form of financial accounting. The most common is petty cash. The basic characteristic of an imprest system is that a fixed amount is reserved, which after a certain period or when circumstances require, because money was spent, will be replenished. This replenishment will come from another account, e.g. petty cash may be replenished by cashing a cheque drawn on a bank account or using an ATM.
Petty cash imprest system
A petty cash imprest system is a method of managing small cash expenses in a business or organization. Under this system, a fixed amount of cash is set aside in a petty cash fund, which is used to pay for small and infrequent expenses like office supplies or postage.
The system operates on the principle of replenishment, whereby the petty cash fund is maintained at a constant level by reimbursing only the amount spent. For instance, if the starting balance of the petty cash fund is $100, and $90 is spent during the month, the fund is replenished by crediting $90 to the primary cash account, typically a bank account, and debiting the respective expense accounts based on the petty cash receipt dockets.
The journal entry for replenishment typically includes debiting the expense accounts and crediting the petty cash account for the amount spent. Subsequently, it involves debiting the bank account and crediting the petty cash account for the amount reimbursed.
Advantages
In this example the maximum amount of petty cash that can be issued (spent) is $100. The claimant may only spend what they have and is only replenished with what they spend, in this case $90.
In a non-imprest system where a fixed amount is issued every month, e.g., $100 every time cash is required, proponents assert there is little incentive to ensure all money issued has been documented because when money is all spent a check for a fixed amount is issued. It is much more difficult to reconcile a non-imprest system as one never knows how much exactly should be in the float.
In an imprest system the amount requested is documented with petty cash dockets and their associated receipts or invoices. Therefore, at all times one can check how much should be left in the petty cash float by deducting the amount spent from the opening petty cash float.
How the petty cash imprest system works
The imprest system necessitates the documentation of expenditures. In a petty cash system, receipts are written for each amount issued. At the end of the month, the total of these receipts is subtracted from the opening float, and the resulting value should match the remaining amount in the float. Under the imprest system, only recorded expenditures are replenished. Any shortfalls may be addressed by the individual responsible for the float, typically a bookkeeper, using their own resources.
References
Accounting systems
Credit
Cash | Imprest system | [
"Technology"
] | 602 | [
"Information systems",
"Accounting systems"
] |
2,982,762 | https://en.wikipedia.org/wiki/Goatskin%20%28material%29 | Goatskin refers to the skin of a goat, which by long term usage, is denoted by the term Morocco leather. Kidskin, used for gloves, shoes and other accessories, is traditionally goatskin, although other leathers such as sheep and kangaroo can be used to make kid.
Tanned leather from goatskin is considered extremely durable and is commonly used to make rugs (for example in Indonesia) and carpet binding. It is often used for gloves, boots, and other products that require a soft hide. Kid gloves, popular in Victorian times, are still made today. It has been a major material for leather bookbindings for centuries, and the oldest European binding, that of the St Cuthbert Gospel in the British Library is in red goatskin. Goatskin is used for a traditional Spanish container for wine bota bag (or called goatskin). Traditional kefir was made in bags from goatskin.
Non-tanned goatskin is used for parchment or for drumheads or sounding boards of some musical instruments, e.g., mišnice in medieval Europe, bodhrán in Ireland, esraj in India and for instrumental drum skin named bedug in Indonesia.
In Roman mythology priests of god Lupercalia wore goatskins.
A breed of goat that provides high-quality skin is for example the Black Bengal breed, native to Bangladesh.
In 1974, there was controversy in the United States surrounding goatskin products originating in Haiti. The U.S. Centers for Disease Control discovered that some of these products contained deadly anthrax spores. All Haitian goatskin products in the USA were recalled, although no fatalities were reported.
Gallery
See also
Goatskin-producing goat breeds
Mashk
References
Hides (skin)
Goats | Goatskin (material) | [
"Physics"
] | 352 | [
"Materials stubs",
"Materials",
"Matter"
] |
2,982,822 | https://en.wikipedia.org/wiki/Blanket%20fort | A blanket fort is a construction commonly made using blankets, bed sheets, pillows, and sofa cushions. It is also known as a couch fort, pillow fort, sheet fort or den.
Parenting books frequently suggest building blanket forts as an activity for parents to participate in play with their children. A blanket fort is made by grabbing blankets around the house and setting them up in a room-like manner. Furniture such as a dining table, a bunk bed, chairs, or an overturned couch can form the foundation for a blanket fort. Clothespins, binder clips, and safety pins may be used to connect blankets and sheets.
In popular culture
As a staple of early childhood entertainment, blanket forts are commonly referenced in children's books, such as Corduroy's Sleepover, If You Give a Pig a Party, and Bob Odenkirk's Zilot & Other Important Rhymes.
In the third season of the television series Community, the episodes "Digital Exploration of Interior Design" and "Pillows and Blankets" focus on the idea of building the biggest blanket fort.
World record
According to Guinness World Records, the largest blanket fort ever was and was built by Cub Scouts Pack 502, Scouts BSA Troop 502B, and Scouts BSA Troop 502G in May 2023 in Mount Pleasant, South Carolina. The record was attempted "to empower the scouts towards meaningful service and to engage, raise awareness, and respond to needs within their community."
See also
Pillow fight
Tree house
References
Children's games
Bedding
Blankets
Pillows
Play (activity) | Blanket fort | [
"Biology"
] | 317 | [
"Play (activity)",
"Behavior",
"Human behavior"
] |
2,983,093 | https://en.wikipedia.org/wiki/Zimmerwald%20Observatory | The Zimmerwald Observatory () is an astronomical observatory owned and operated by the AIUB, the Astronomical Institute of the University of Bern. Built in 1956, it is located at Zimmerwald, 10 kilometers south of Bern, Switzerland.
Numerous comets and asteroids have been discovered by Paul Wild (1925–2014) at Zimmerwald Observatory, most notably comet 81P/Wild, which was visited by NASA's Stardust space probe in 2004. The main belt asteroid 1775 Zimmerwald has been named after the location of the observatory.
The 1-meter aperture ZIMLAT telescope was inaugurated in 1997.
See also
List of largest optical reflecting telescopes
Swiss Space Office
References
External links
Zimmerwald Observatory
Astronomical observatories in Switzerland
Space Situational Awareness Programme | Zimmerwald Observatory | [
"Environmental_science"
] | 160 | [
"Space Situational Awareness Programme"
] |
2,983,356 | https://en.wikipedia.org/wiki/Bred%20vector | In applied mathematics, bred vectors are perturbations related to Lyapunov vectors, that capture fast-growing dynamical instabilities of the solution of a numerical model. They are used, for example, as initial perturbations for ensemble forecasting in numerical weather prediction. They were introduced by Zoltan Toth and Eugenia Kalnay.
Method
Bred vectors are created by adding initially random perturbations to a nonlinear model. The control (unperturbed) and the perturbed models are integrated in time, and periodically the control solution is subtracted from the perturbed solution. This difference is the bred vector. The vector is scaled to be the same size as the initial perturbation and is then added back to the control to create the new perturbed initial condition. After a short transient period, this "breeding" process creates bred vectors dominated by the naturally fastest-growing instabilities of the evolving control solution.
References
Functional analysis
Mathematical physics | Bred vector | [
"Physics",
"Mathematics"
] | 204 | [
"Mathematical analysis",
"Functions and mappings",
"Functional analysis",
"Mathematical analysis stubs",
"Applied mathematics",
"Theoretical physics",
"Mathematical objects",
"Mathematical relations",
"Mathematical physics"
] |
2,983,497 | https://en.wikipedia.org/wiki/Builders%27%20rites | Builders' rites are ceremonies attendant on the laying of foundation stones, including ecclesiastical, masonic or other traditions connected with foundations or other aspects of construction.
One such custom is that of placing a few coins, newspapers, etc. within a cavity beneath the stone. Should the stone later be removed, the relics may be found. Though this tradition is still practiced, such memorials are likely deposited in the hope that they will never be disturbed. Another such rite is topping out, when the last beam (or its equivalent) is placed atop a structure during its construction.
History
Historians and folklorists in the 19th and early 20th centuries were fascinated by possible "foundation sacrifices". Jacob Grimm remarked, "It was often thought necessary to entomb live animals and even men in the foundation, on which the structure was to be raised, to secure immovable stability." Sabine Baring-Gould likewise claimed, "The old pagan laid the foundation of his house and fortress in blood." The 19th-century Folk-Lore Journal claimed that "under the walls of two round towers in Ireland (the only ones examined) human skeletons [were] discovered." In the 15th century, the wall of Holsworthy church was built over a living human being, and when this became unlawful, images of living beings were substituted.
References to this practice can be found in Greek folk culture in a poem about "Arta's bridge". According to the poem, the wife of the chief builder was sacrificed to establish a good foundation for a bridge that was of grave importance to the secluded city of Arta. The actual bridge was constructed in 1602. A similar legend appears in the Romanian folk poem Meșterul Manole, about the building of the church in the earliest Wallachian capital city.
See also
Bay Bridge Troll
Builder's signature
Ceremonial ship launching
Cornerstone
Foundation deposit
Groundbreaking
Hitobashira
Masonic manuscripts
Time capsule
Topping out
Votive offering
References
Further reading
Building
Ceremonies
Building engineering
History of construction
Rituals attending construction | Builders' rites | [
"Engineering"
] | 403 | [
"Building",
"Building engineering",
"History of construction",
"Rituals attending construction",
"Construction",
"Civil engineering",
"Architecture"
] |
2,983,517 | https://en.wikipedia.org/wiki/Library%202.0 | Library 2.0 is a proposed concept for library services that facilitate user contributions and other features of Web 2.0, which includes online services such as OPAC systems. The term "Library 2.0" was coined by Michael Casey in 2006 on his blog Library Crunch.
Overview
Casey suggested that libraries, especially public libraries, are at a crossroads where many of the elements of Web 2.0 have applicable value within the library community, both in technology-driven services and in non-technology based services. In particular, he described the need for libraries to adopt a strategy for constant change while promoting a participatory role for library users.
Library 2.0 made its conference debut at Internet Librarian 2005 in October, 2005, when Michael Stephens of Saint Joseph County Public Library addressed the idea in relation to the typical library website.
A September 2006 article in Library Journal titled "Library 2.0: Service for the Next-Generation Library" begins by expressing the benefit of Library 2.0 to library administrators and taxpayers as providing "more efficient ways of delivering services to achieve greater returns on financial investments." The article continues by asserting that the much discussed Library 2.0 is important for librarians as it may radically change our customer service and interaction.
Major development transpired during the library 2.0 era which other scholars relate it to the web 2.0. and it was between 2005 and 2010 (Noh, 2015). This is where the library begun to utilise the internet to provide digital library services. For instance, the use of Online Public Access (OPAC), social networking such as wikis, podcasts which provided the avenue for the opportunity to interact with patrons using social media platforms making library services more interactive and collaborative. This phenomenon helped to close the gap between patrons and librarians and provide the opportunity for tagging and reviews.
With Library 2.0, library services are frequently evaluated and updated to meet the changing needs of library users. Library 2.0 also calls for libraries to encourage user participation and feedback in the development and maintenance of library services. The active and empowered library user is a significant component of Library 2.0. With information and ideas flowing in both directions – from the library to the user and from the user to the library – library services have the ability to evolve and improve on a constant and rapid basis. The user is participant, co-creator, builder and consultant – whether the product is virtual or physical.
An advantage in pursuing digital services is that the library can target more people - including those who may not have previously used the library service.
A concern that Library 2.0 is trying to address is that potential users turn to Google and Wikipedia because they are "good enough", and perceive libraries to be slow and irrelevant.
Key principles
Browser + Web 2.0 Applications + Connectivity = Full-featured OPAC
Harness the library user in both design and implementation of services
Library users should be able to craft and modify library provided services
Harvest and integrate ideas and products from peripheral fields into library service models
Continue to examine and improve services and be willing to replace them at any time with newer and better services.
In 2009, Holmberg et al. identified seven key principles for Library 2.0: "interactivity, users, participation, libraries and library services, web and web 2.0, social aspects, and technology and tools", and offer the following definition for Library 2.0: "Library 2.0 is a change in interaction between users and libraries in a new culture of participation catalysed by social web technologies."
Alex Byrne argues that the use of Web 2.0 strategies in the library context changes the role of librarian into someone who can assist in supporting clients information literacy across the "largely unknown informational universe" rather than helping them navigate the library's own collection.
Concerns and considerations
Some concerns about Library 2.0 relate to access to technology, privacy and security. For example, Casey and Savastinuk suggest allowing patrons to tag or blog anonymously. In 2006, Steve Lawson, humanities liaison librarian, wrote a blog post entitled, "A Library 2.0 skeptic's reading list" that collected links to blogs which discuss these concerns. Lawson says "I'm not anti–Library 2.0 ... I like to think of Library 2.0 as a continuing conversation about the future of libraries, and it makes sense to me to try to round up some voices that challenge Library 2.0 conventional wisdom."
Another concern is that the adoption of Web 2.0 technologies can allow users to spread hate speech and cyberbullying in the library system. It is suggested that librarians define hate speech in their user content policies and identify it when it occurs.
When using social networking through Facebook in a Swedish public library, librarians were described as 'always at the beck and call of Facebook', and capable of losing the relationships they'd built with their clients over the site due to glitches in Facebook.
Online Public Access Catalog (OPAC)
The Online Public Access Catalogue (OPAC) provides the library collection to its users, this is usually done by searching and browsing the library catalogue online. It may be an extension of the Integrated Library Management System (ILS) or independent software.
Library 2.0 is a new way of providing library services through new Internet technologies, with emphasis on “user-centered” change and interaction. Like Web 2.0, a full-featured Library 2.0 OPAC gets better the more that users are involved in the process of interacting with the catalog and sharing content.
Librarians have been working to retool library catalogs in order to make them more useful for patrons to find, organize, and interact with information in a way that has infinite potential for user customization. These new types of catalogs are a shift from "isolated information silos" to "interlinked computing platforms." In the past the information flow was mostly one way, from library to user. With new web tools information can be released to flow in every direction (library to user, user to library, library to library, and user to user).
Jessamyn West, on her librarian.net website, authored "What We Want: An OPAC Manifesto," which broke down the needs of library staff, geeks, and users in their OPAC. These valuable suggestions inform librarians of the flexibility, customizability and plain language approach that is desired by users in their OPAC. Librarians should be aware of these issues so that planning for improvement can begin.
Nishat Kazi recommends that the clients interest area should be recorded when they join the library, and when they login to their account on the OPAC, new items which match their interests should be displayed to them. Kazi also recommends allowing clients to rank and review items in the OPAC, as well as giving other clients the opportunity to respond to these reviews. Key words can also be added by clients in addition to key words added by the librarian to facilitate searching.
Artificial intelligence and participatory library
In China a participatory library named Xiaotu was developed by Tsinghua University. Xiaotu is an artificial intelligence library that allows users to interact with it by talking or chatting through a mobile app or social network. It provides real-time virtual reference service combining Tsinghua University Library capabilities with social network and third-party resources. The system is composed by a self-learning function that receives updates from users as they find some missing or wrong information. Connected to the largest social network in China, it provides easy access and owns a book reading group accessed by Tsinghua University Students in China. Its knowledge base includes Wikipedia and its Chinese counterpart, content revised by professors of the university, frequently asked questions (FAQ) accumulated from the university library, and other third-party resources presented in the Chinese internet.
Debate
Library 2.0 has been a source of debate in the blogosphere. Some librarian bloggers have argued that these key principles are not new and have been part of the service philosophies of many library reformers since the 19th century. Others are calling for more concrete examples of how libraries can get to Library 2.0. Walt Crawford, for example, argues that Library 2.0 comprises a combination of tools and attitudes which are excellent ideas and not new to librarianship, a few business- and tool-focused attitudes which will not serve all users and user communities, and incorrectly places libraries as the appropriate source for all users to gather all information.
Proponents of Library 2.0, such as Stephen Abram, Michael Stephens, Paul Miller and others, have spoken to these criticisms, arguing that while individual pieces of Library 2.0 may not be entirely new, the convergence of these service goals and ideas with many new Web 2.0 technologies has led to a new generation of library service. This includes the use of online social networks by libraries.
Library 4.0 has been proposed as including makerspaces, context-aware technology, open source, big data, cloud services, augmented reality, and state-of-the-art displays.
See also
Crowdsourcing
Folksonomy
Learning 2.0
Libraries in Second Life
User-generated content
Web 2.0
References
Further reading
Blyberg, John (2005). ILS Customer Bill of Rights, Blyberg.net
Blyberg, John (2006). 11 reasons why Library 2.0 exists and matters, Blyberg.net
Boog, J. (2005). Library 2.0 Movement Sees Benefits in Collaboration with Patrons, Publish, November 2005.
Boxen, J. (2008). Library 2.0: A Review of the Literature. Reference Librarian, 49(1), 21–34.
Casey, Michael (2005). Working Towards a Definition of Library 2.0, LibraryCrunch, 21 October 2005.
Casey, M. & Stephens, M. (2005). Where Do We Begin? A Library 2.0 Conversation with Michael Casey, ALA TechSource Blog, December 2005.
Casey, Michael & Savastinuk, Laura (2007). Library 2.0: A Guide to Participatory Library Service, Information Today Press, 2007.
Chalon, Patrice X (2008). OPAC 2.0: Opportunities, development and analysis
Courtney, Nancy. (2007) Library 2.0 and Beyond: Innovative Technologies and Tomorrow's User, Libraries Unlimited, 2007.
Farkas, Meredith G. (2007). Social Software in Libraries: Building Collaboration, Communication, and Community Online. Information Today, 2007.
Harris, Christopher (2006). Library 2.0 Week (Updated), Infomancy, January 2006.
Harris, Christopher (2006) "School Library 2.0", School Library Journal, May 1, 2006.
Kwanya, T., Stilwell, C., & Underwood, P. G. (2009). "Library 2.0: revolution or evolution?" South African Journal of Libraries & Information Science, 75(1), 70–75.
Levine, Jenny (2005). Hello, Library (1.0) World!, ALA TechSource Blog, 10 October 2005.
Maness, J. (2006).Library 2.0 theory: Web 2.0 and its implications for libraries. Webology, 3(2), 2006.
Miller, P. (2006). Library 2.0: The Challenge of Disruptive Innovation, Talis February 2006.
Stephens, Michael (2006). "Web 2.0 & Libraries: Best Practices for Social Software", Library Technology Reports, 42:4.
Talis Talk (31 January 2006). "Podcast with Thomas Brevik, Michael Casey, Ken Chad, Paul Miller, T. Scott Plutchak, Michael Stephens and Richard Wallis".
Zimmer, M. (2013). "Assessing the Treatment of Patron Privacy in Library 2.0 Literature". Information Technology and Libraries, 32(2), 29–41
Zimmer, M. (2013). "Patron Privacy in the '2.0' Era: Avoiding the Faustian Bargain of Library 2.0". Journal of Information Ethics.
External links
Library 2.0, social network on Ning
Online Librarian Community - Library 2.0
Building a Library 2.0 OPAC (Wiki)
Is your OPAC fun? (a manifesto of sorts) from the LibraryThing Thingology Blog
2005 neologisms
Information Age | Library 2.0 | [
"Technology"
] | 2,556 | [
"Information Age",
"Computing and society"
] |
6,959,283 | https://en.wikipedia.org/wiki/Etiolation | Etiolation is a process in flowering plants grown in partial or complete absence of light. It is characterized by long, weak stems; smaller leaves due to longer internodes; and a pale yellow color (chlorosis). The development of seedlings in the dark is known as "skotomorphogenesis" and leads to etiolated seedlings.
Effects
Etiolation increases the likelihood that a plant will reach a light source, often from under the soil, leaf litter, or shade from competing plants. The growing tips are strongly attracted to light and will elongate towards it. The pale color results from a lack of chlorophyll.
Some of the changes that occur include
elongation of stems and leaves;
weakening of cell walls in stems and leaves;
longer internodes, hence fewer leaves per unit length of stem;
chlorosis, a pale yellowish-white coloration.
De-etiolation is the transition of seedlings from below-ground growth to above-ground growth form.
Causes
Etiolation is controlled by the plant hormones called auxins, which are produced by the growing tip to maintain apical dominance. Auxin diffuses, and is transported, downwards from the tip, with effects including suppressing growth of lateral buds. Auxins are active in light; when they are active they stimulate proton pumps in the cell wall which increases the acidity of the cell wall and activates expansin (an enzyme that breaks bonds in the cell wall structure) that weaken the cell wall and allow the cell to expand.
Chloroplasts that have not been exposed to light are called etioplasts (see also plastids).
De-etiolation
De-etiolation is a series of physiological and biochemical changes a plant shoot undergoes when emerging from the ground or in response to light after a period of insufficient light exposure. This process is known informally as greening. These changes that are triggered in the plant's shoots or already formed leaves and stems occur in preparation for photosynthesis.
Some of the changes that occur include
Inhibition of hypocotyl lengthening.
Stimulation of cotyledon expansion.
Opening of the apical hook, see Seedling's photomorphogenesis and etiolation for details.
Stimulation of synthesis of anthocyanins.
Stimulation of chloroplasts development from etioplasts.
This process is regulated by the exposure of various photoreceptor pigments to light. Phytochrome A and phytochrome B both respond to an increasing proportion of red light to far-red light which occurs when the shoot comes out into the open. Cryptochrome 1 responds to increasing amounts of blue light when the shoot reaches the surface.
See also
Blanching – a technique for growing vegetables that induces etiolation to produce more delicate vegetables
References
External links
Etiolation - video footage and narration
Etiolation
Plant physiology | Etiolation | [
"Biology"
] | 605 | [
"Plant physiology",
"Plants"
] |
6,959,504 | https://en.wikipedia.org/wiki/Two-pore-domain%20potassium%20channel | The two-pore-domain or tandem pore domain potassium channels are a family of 15 members that form what is known as leak channels which possess Goldman-Hodgkin-Katz (open) rectification. These channels are regulated by several mechanisms including signaling lipids, oxygen tension, pH, mechanical stretch, and G-proteins. Two-pore-domain potassium channels correspond structurally to a inward-rectifier potassium channel α-subunits. Each inward-rectifier potassium channel α-subunit is composed of two transmembrane α-helices, a pore helix and a potassium ion selectivity filter sequence and assembles into a tetramer forming the complete channel. The two-pore domain potassium channels instead are dimers where each subunit is essentially two α-subunits joined together.
Each single channel does not have two pores; the name of the channel comes from the fact that each subunit has two P (pore) domains in its primary sequence. To quote Rang and Dale (2015), "The nomenclature is misleading, especially when they are incorrectly referred to as two-pore channels".
A decrease in these leak channels activity is known as 'channel arrest', which reduces oxygen consumption and allows animals to survive anoxia.
Below is a list of the 15 known two-pore-domain human potassium channels:
See also
Ion channel
Potassium channel
References
External links
Ion channels | Two-pore-domain potassium channel | [
"Chemistry"
] | 294 | [
"Biochemistry stubs",
"Neurochemistry",
"Protein stubs",
"Ion channels"
] |
6,959,617 | https://en.wikipedia.org/wiki/Nominal%20level | Nominal level is the operating level at which an electronic signal processing device is designed to operate. The electronic circuits that make up such equipment are limited in the maximum signal they can handle and the low-level internally generated electronic noise they add to the signal. The difference between the internal noise and the maximum level is the device's dynamic range. The nominal level is the level that these devices were designed to operate at, for best dynamic range and adequate headroom. When a signal is chained with improper gain staging through many devices, clipping may occur or the system may operate with reduced dynamic range.
In audio, a related measurement, signal-to-noise ratio, is usually defined as the difference between the nominal level and the noise floor, leaving the headroom as the difference between nominal and maximum output. The measured level is a time average, meaning that the peaks of audio signals regularly exceed the measured average level. The headroom measurement defines how far the peak levels can stray from the nominal measured level before clipping. The difference between the peaks and the average for a given signal is the crest factor.
Standards
VU meters are designed to represent the perceived loudness of a passage of music, or other audio content, measuring in volume units. Devices are designed so that the best signal quality is obtained when the meter rarely goes above nominal. The markings are often in dB instead of "VU", and the reference level should be defined in the device's manual. In most professional recording and sound reinforcement equipment, the nominal level is . In semi-professional and domestic equipment, the nominal level is usually −10 dBV. This difference is due to the cost required to create larger power supplies and output higher levels.
In broadcasting equipment, this is termed the Maximum Permitted Level, which is defined by European Broadcasting Union standards. These devices use peak programme meters instead of VU meters, which gives the reading a different meaning.
"Mic level" is sometimes defined as −60 dBV, though levels from microphones vary widely.
In video systems, nominal levels are 1 VP-P for synched systems, such as baseband composite video, and 0.7 VP-P for systems without sync. Note that these levels are measured peak-to-peak, while audio levels are time averages.
See also
Alignment level
Transmission level point
References
External links
Nominal Level — Sweetwater glossary
Level Headed — Nominal Level (explained) plus an SV-3700 modification
Signal processing
Sound | Nominal level | [
"Technology",
"Engineering"
] | 495 | [
"Telecommunications engineering",
"Computer engineering",
"Signal processing"
] |
6,959,633 | https://en.wikipedia.org/wiki/Blueprint%20%28magazine%29 | Blueprint was an architecture and design magazine that has been published in the UK between 1983 and 2020.
It offered a mix of criticism, news and feature writing on design and architecture, directed at professionals and non-professionals alike.
Blueprint takes architecture and design as its starting point and brings these thing into sharp focus via context, comment and analysis. Architecture and design do not exist in a vacuum.
- Johnny Tucker, former Blueprint editor
The magazine took a parallel approach to the different design disciplines, reflecting a belief that fashion, product, furniture and architectural design can share ideas.
History
Blueprint was first published in October 1983 by Peter Murray and Deyan Sudjic. It was launched and funded by UK design figures including Terence Conran, Marcello Minale and Richard Rogers.
In 1983, Murray noticed a gap in the market for a magazine that presented lavish images and a critical analysis of the industry. He enlisted Sunday Times architecture critic Deyan Sudjic as editor, who in turn recruited a team of writers including Jonathan Glancey, Rowan Moore and Rick Poynor. Sudjic continued to edit Blueprint until 1994.
Blueprint'''s subsequent contributors included novelist JG Ballard, cultural critic James Heartfield and art critic Matthew Collings. It has been edited by Sudjic, (who, since 2006, was director of the London Design Museum), architect and critic Rowan Moore. Vicky Richardson edited the magazine from 2004 until 2010. The last editor was Johnny Tucker.Blueprint was published on a monthly basis until 2013 when the frequency was switched to bimonthly. The 369th issue of Blueprint'' was the last edition published in June 2020.
References
External links
Blueprint Magazine
1983 establishments in the United Kingdom
2020 disestablishments in the United Kingdom
Architecture magazines
Bi-monthly magazines published in the United Kingdom
Defunct magazines published in the United Kingdom
Design magazines
Magazines established in 1983
Magazines disestablished in 2020
Magazines published in London
Monthly magazines published in the United Kingdom
Professional and trade magazines
Visual arts magazines published in the United Kingdom | Blueprint (magazine) | [
"Engineering"
] | 412 | [
"Design magazines",
"Design"
] |
6,959,754 | https://en.wikipedia.org/wiki/Locally%20connected%20space | In topology and other branches of mathematics, a topological space X is
locally connected if every point admits a neighbourhood basis consisting of open connected sets.
As a stronger notion, the space X is locally path connected if every point admits a neighbourhood basis consisting of open path connected sets.
Background
Throughout the history of topology, connectedness and compactness have been two of the most
widely studied topological properties. Indeed, the study of these properties even among subsets of Euclidean space, and the recognition of their independence from the particular form of the Euclidean metric, played a large role in clarifying the notion of a topological property and thus a topological space. However, whereas the structure of compact subsets of Euclidean space was understood quite early on via the Heine–Borel theorem, connected subsets of (for n > 1) proved to be much more complicated. Indeed, while any compact Hausdorff space is locally compact, a connected space—and even a connected subset of the Euclidean plane—need not be locally connected (see below).
This led to a rich vein of research in the first half of the twentieth century, in which topologists studied the implications between increasingly subtle and complex variations on the notion of a locally connected space. As an example, the notion of local connectedness im kleinen at a point and its relation to local connectedness will be considered later on in the article.
In the latter part of the twentieth century, research trends shifted to more intense study of spaces like manifolds, which are locally well understood (being locally homeomorphic to Euclidean space) but have complicated global behavior. By this it is meant that although the basic point-set topology of manifolds is relatively simple (as manifolds are essentially metrizable according to most definitions of the concept), their algebraic topology is far more complex. From this modern perspective, the stronger property of local path connectedness turns out to be more important: for instance, in order for a space to admit a universal cover it must be connected and locally path connected.
A space is locally connected if and only if for every open set , the connected components of (in the subspace topology) are open. It follows, for instance, that a continuous function from a locally connected space to a totally disconnected space must be locally constant. In fact the openness of components is so natural that one must be sure to keep in mind that it is not true in general: for instance Cantor space is totally disconnected but not discrete.
Definitions
Let be a topological space, and let be a point of
A space is called locally connected at if every neighborhood of contains a connected open neighborhood of , that is, if the point has a neighborhood base consisting of connected open sets. A locally connected space is a space that is locally connected at each of its points.
Local connectedness does not imply connectedness (consider two disjoint open intervals in for example); and connectedness does not imply local connectedness (see the topologist's sine curve).
A space is called locally path connected at if every neighborhood of contains a path connected open neighborhood of , that is, if the point has a neighborhood base consisting of path connected open sets. A locally path connected space is a space that is locally path connected at each of its points.
Locally path connected spaces are locally connected. The converse does not hold (see the lexicographic order topology on the unit square).
Connectedness im kleinen
A space is called connected im kleinen at or weakly locally connected at if every neighborhood of contains a connected (not necessarily open) neighborhood of , that is, if the point has a neighborhood base consisting of connected sets. A space is called weakly locally connected if it is weakly locally connected at each of its points; as indicated below, this concept is in fact the same as being locally connected.
A space that is locally connected at is connected im kleinen at The converse does not hold, as shown for example by a certain infinite union of decreasing broom spaces, that is connected im kleinen at a particular point, but not locally connected at that point. However, if a space is connected im kleinen at each of its points, it is locally connected.
A space is said to be path connected im kleinen at if every neighborhood of contains a path connected (not necessarily open) neighborhood of , that is, if the point has a neighborhood base consisting of path connected sets.
A space that is locally path connected at is path connected im kleinen at The converse does not hold, as shown by the same infinite union of decreasing broom spaces as above. However, if a space is path connected im kleinen at each of its points, it is locally path connected.
First examples
For any positive integer n, the Euclidean space is locally path connected, thus locally connected; it is also connected.
More generally, every locally convex topological vector space is locally connected, since each point has a local base of convex (and hence connected) neighborhoods.
The subspace of the real line is locally path connected but not connected.
The topologist's sine curve is a subspace of the Euclidean plane that is connected, but not locally connected.
The space of rational numbers endowed with the standard Euclidean topology, is neither connected nor locally connected.
The comb space is path connected but not locally path connected, and not even locally connected.
A countably infinite set endowed with the cofinite topology is locally connected (indeed, hyperconnected) but not locally path connected.
The lexicographic order topology on the unit square is connected and locally connected, but not path connected, nor locally path connected.
The Kirch space is connected and locally connected, but not path connected, and not path connected im kleinen at any point. It is in fact totally path disconnected.
A first-countable Hausdorff space is locally path-connected if and only if is equal to the final topology on induced by the set of all continuous paths
Properties
For the non-trivial direction, assume is weakly locally connected. To show it is locally connected, it is enough to show that the connected components of open sets are open.
Let be open in and let be a connected component of Let be an element of Then is a neighborhood of so that there is a connected neighborhood of contained in Since is connected and contains must be a subset of (the connected component containing ). Therefore is an interior point of Since was an arbitrary point of is open in Therefore, is locally connected.
Local connectedness is, by definition, a local property of topological spaces, i.e., a topological property P such that a space X possesses property P if and only if each point x in X admits a neighborhood base of sets that have property P. Accordingly, all the "metaproperties" held by a local property hold for local connectedness. In particular:
A space is locally connected if and only if it admits a base of (open) connected subsets.
The disjoint union of a family of spaces is locally connected if and only if each is locally connected. In particular, since a single point is certainly locally connected, it follows that any discrete space is locally connected. On the other hand, a discrete space is totally disconnected, so is connected only if it has at most one point.
Conversely, a totally disconnected space is locally connected if and only if it is discrete. This can be used to explain the aforementioned fact that the rational numbers are not locally connected.
A nonempty product space is locally connected if and only if each is locally connected and all but finitely many of the are connected.
Every hyperconnected space is locally connected, and connected.
Components and path components
The following result follows almost immediately from the definitions but will be quite useful:
Lemma: Let X be a space, and a family of subsets of X. Suppose that is nonempty. Then, if each is connected (respectively, path connected) then the union is connected (respectively, path connected).
Now consider two relations on a topological space X: for write:
if there is a connected subset of X containing both x and y; and
if there is a path connected subset of X containing both x and y.
Evidently both relations are reflexive and symmetric. Moreover, if x and y are contained in a connected (respectively, path connected) subset A and y and z are connected in a connected (respectively, path connected) subset B, then the Lemma implies that is a connected (respectively, path connected) subset containing x, y and z. Thus each relation is an equivalence relation, and defines a partition of X into equivalence classes. We consider these two partitions in turn.
For x in X, the set of all points y such that is called the connected component of x. The Lemma implies that is the unique maximal connected subset of X containing x. Since the closure of is also a connected subset containing x, it follows that is closed.
If X has only finitely many connected components, then each component is the complement of a finite union of closed sets and therefore open. In general, the connected components need not be open, since, e.g., there exist totally disconnected spaces (i.e., for all points x) that are not discrete, like Cantor space. However, the connected components of a locally connected space are also open, and thus are clopen sets. It follows that a locally connected space X is a topological disjoint union of its distinct connected components. Conversely, if for every open subset U of X, the connected components of U are open, then X admits a base of connected sets and is therefore locally connected.
Similarly x in X, the set of all points y such that is called the path component of x. As above, is also the union of all path connected subsets of X that contain x, so by the Lemma is itself path connected. Because path connected sets are connected, we have for all
However the closure of a path connected set need not be path connected: for instance, the topologist's sine curve is the closure of the open subset U consisting of all points (x,sin(x)) with x > 0, and U, being homeomorphic to an interval on the real line, is certainly path connected. Moreover, the path components of the topologist's sine curve C are U, which is open but not closed, and which is closed but not open.
A space is locally path connected if and only if for all open subsets U, the path components of U are open. Therefore the path components of a locally path connected space give a partition of X into pairwise disjoint open sets. It follows that an open connected subspace of a locally path connected space is necessarily path connected. Moreover, if a space is locally path connected, then it is also locally connected, so for all is connected and open, hence path connected, that is, That is, for a locally path connected space the components and path components coincide.
Examples
The set (where ) in the dictionary order topology has exactly one component (because it is connected) but has uncountably many path components. Indeed, any set of the form is a path component for each a belonging to I.
Let be a continuous map from to (which is in the lower limit topology). Since is connected, and the image of a connected space under a continuous map must be connected, the image of under must be connected. Therefore, the image of under must be a subset of a component of Since this image is nonempty, the only continuous maps from ' to are the constant maps. In fact, any continuous map from a connected space to a totally disconnected space must be constant.
Quasicomponents
Let X be a topological space. We define a third relation on X: if there is no separation of X into open sets A and B such that x is an element of A and y is an element of B. This is an equivalence relation on X and the equivalence class containing x is called the quasicomponent of x.
can also be characterized as the intersection of all clopen subsets of X that contain x. Accordingly is closed; in general it need not be open.
Evidently for all Overall we have the following containments among path components, components and quasicomponents at x:
If X is locally connected, then, as above, is a clopen set containing x, so and thus Since local path connectedness implies local connectedness, it follows that at all points x of a locally path connected space we have
Another class of spaces for which the quasicomponents agree with the components is the class of compact Hausdorff spaces.
Examples
An example of a space whose quasicomponents are not equal to its components is a sequence with a double limit point. This space is totally disconnected, but both limit points lie in the same quasicomponent, because any clopen set containing one of them must contain a tail of the sequence, and thus the other point too.
The space is locally compact and Hausdorff but the sets and are two different components which lie in the same quasicomponent.
The Arens–Fort space is not locally connected, but nevertheless the components and the quasicomponents coincide: indeed for all points x.
See also
It is conjectured that the Mandelbrot set is locally connected
Notes
References
Further reading
. For Hausdorff spaces, it is shown that any continuous function from a connected locally connected space into a connected space with a dispersion point is constant
.
Articles containing proofs
Properties of topological spaces
General topology | Locally connected space | [
"Mathematics"
] | 2,763 | [
"General topology",
"Properties of topological spaces",
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"Topological spaces",
"Topology",
"Articles containing proofs"
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6,959,755 | https://en.wikipedia.org/wiki/Polytechnic%20Institute%20of%20Leiria | The Polytechnic of Leiria (IPL) is a public institution of Higher Education that offers courses of training on an Undergraduate Degree, Masters, Post-Graduate, Technology Specialization and Preparation Courses for Access to Higher Education level. It began its activity in 1980 and is present in the Leiria and West region through its five schools, divided into five campus, located in the cities of Leiria (School of Education and Social Sciences, School of Technology and Management and School of Health Sciences), Caldas da Rainha (School of Fine Art and Design) and Peniche (School of Tourism and Maritime Technology). IPL offers Undergraduate and master's degrees courses in the areas of: Art and Design, Law studies, Education and Communication, Engineering and Technology and Tourism and Health.
IPL’s Campus
Campus 1 In IPL's Campus 1, there is the School of Education and Social Sciences (ESECS) which develops its training activity in the areas of Human and Social Sciences, Communication and Teacher Training. It has an enrollment of approximately 1,700 students.
Campus 2 Campus 2 of IPL is based in Leiria. It consists of two schools: the School of Technology and Management (ESTG) and the School Of Health Sciences (ESSLei).
The ESTG offers courses in the areas of engineering and technology and of entrepreneurial and juridical sciences. It is a school recognized for the quality of the education provided and for its strong connection to the enterprise world, not only from the Leiria and West region but also on a national level. The school is attended by approximately 5.600 students.
The School Of Health Sciences (ESSLei) was integrated in IPL in 2001 and has been intended for the training of nurses and it is predicted that in the next academic year it will widen its training offer to other areas of Health Sciences. It is attended by approximately 800 students.
Campus 3 Campus 3 of IPL is situated in Caldas da Rainha, approximately 60 kilometers South of Leiria. The School of Fine Arts and Design (ESAD.CR) is located in this city.
Campus 4
The School of Maritime Technology (ESTM) is located in IPL's Campus 4, in Peniche (80 kilometers South of Leiria). This school with 1.500 students is especially aimed at the training in the area of Tourism, Marine Biology, Biotechnology and Food Engineering.
Campus 5
In Campus 5, in Leiria, there are other structures of the Institute: the Institute for Research, Development and Advanced Studies (INDEA), the Training Centre for the Courses of Technology Specialization (FOR.CET) with around 900 students, the Centre of New Opportunities (CNO), a Transfer Technology and Information Center (OTIC) and an E-Learning Unit (UED). These are units with specific aims that encompass the investigation and post-graduate training, the post-secondary training, the e-learning, the knowledge transfer, among others.
Undergraduate Degrees
Fine Arts and Design
Fine Arts (School of Fine Arts and design), Caldas da Rainha
Interior and Spatial Design (School of Fine Arts and design), Caldas da Rainha
Design - Ceramics and Glass (School of Fine Arts and design), Caldas da Rainha
Design - Graphics and Multimedia (School of Fine Arts and design), Caldas da Rainha
Industrial Design (School of Fine Arts and design), Caldas da Rainha
Sound and Image (School of Fine Arts and design), Caldas da Rainha
Theatre (School of Fine Arts and design), Caldas da Rainha
Entrepreneurial and Juridical Sciences
Public Administration (School of Technology and Management), Leiria
Accountancy and Finance(School of Technology and Management), Leiria
Management (School of Technology and Management), Leiria
Marketing (School of Technology and Management), LeiriaHuman Relations and Organisational Communication ( School of Education and
Social Sciences), Leiria
Law Studies (Legal Counselling) (School of Technology and Management), Leiria
Education and Social Sciences
Media and Multimedia Education (School of Education and Social Sciences), Leiria
Primary Education (School of Education and Social Sciences), Leiria
Social Education (School of Education and Social Sciences), Leiria
Social Work (School of Education and Social Sciences), Leiria
Translation and Interpretation Portuguese/Chinese - Chinese/Portuguese (School of Education and Social Sciences), Leiria
Engineering and Technology
Biotechnology and Marine Biology (School of Tourism and Maritime Technology), Peniche
Biomechanics (School of Technology and Management), Leiria
Energy and Environment (School of Technology and Management), Leiria
Food Engineering (School of Tourism and Maritime Technology), Peniche
Automotive Engineering (School of Technology and Management), Leiria
Civil Engineering (School of Technology and Management), Leiria
Electrical and Electronics Engineering (School of Technology and Management), Leiria
Computer Engineering (School of Technology and Management), Leiria
Mechanical Engineering (School of Technology and Management), Leiria
Marine Resource Management* (School of Tourism and Maritime Technology), Peniche
Health Informatics (School of Technology and Management), Leiria
Civil Protection (School of Technology and Management), Leiria
Health Equipment Technology (School of Technology and Management), Leiria
Videogames and Multimedia Technology* (School of Technology and Management), Leiria
Health
Sports and Well-Being (School of Education and Social Sciences), Leiria
Dietetics* (School of Health Sciences), Leiria
Nursing (School of Health Sciences), Leiria
Nursing - Beginning in the 2nd Semestre (School of Health Sciences), Leiria
Physiotherapy (School of Health Sciences), Leiria
Speech Therapy(School of Health Sciences), Leiria
Occupational Therapy (School of Health Sciences), Leiria
Tourism
Cultural Animation (School of Education and Social Sciences), Leiria
Tourism and Recreation (School of Tourism and Maritime Technology), Peniche
Leisure Management and Business Tourism (School of Tourism and Maritime Technology), Peniche
Tourism and Hotel Management (School of Tourism and Maritime Technology), Peniche
Maritime Resources Management* (School of Tourism and Maritime Technology), Peniche
Marketing for Tourism (School of Tourism and Maritime Technology), Peniche
Restaurant Industry and Catering (School of Tourism and Maritime Technology), Peniche
Tourism (School of Tourism and Maritime Technology), Peniche
Master Degrees
Art and Design
Fine Arts
Typography Design
Product Design
Cultural Management
Theatre
Entrepreneurial and Juridical Sciences
Business Finance
International Business
Alternative
Law Studies
Education and Communication
Speech Pathology
Pre-School Education
Pre-School Education and Primary Education
Basic Education – 1st Cycle
Basic Education – 1st and 2nd Cycle
Teaching of English and French in the Basic Education
Engineering and Technology
Aquaculture
Biotechnology of Marine Resources
Computer Engineering - Mobile Computing
Conception and Development of Products
Civil Constructions
Energy and Environment
Automotive Engineering
Automation Systems
Technology and Multimedia Communication
Telecommunication
Health
Intervention for an Active Aging
R&D Units
Identiti(es) and Diversiti(es) Research Centre (CIID)
Centre for Rapid and Sustainable Product Development (CDRsp)
globADVANTAGE - Centre of Research on International Business & Strategy
Maritime Resources Research Group (GIRM)
Education's Investigation and Development Branch (NIDE)
Arts and Theatre Investigation Group (GIAE/C)
Sustainability Management Centre of Investigation (CIGS)
Tourism Investigation Group (GITUR)
Communications and Computer Science Research Centre (CIIC)
Human Motoricity Centre of Investigation – CIMH
Policies and Educational Systems Centre of Investigation – CIPSE
Institute for Systems and Computing Engineering
National Institute of Telecommunications – Leiria
Polytechnics in Portugal
Buildings and structures in Leiria
Educational institutions established in 1980
Buildings and structures in Leiria District
1980 establishments in Portugal
Glassmaking schools | Polytechnic Institute of Leiria | [
"Materials_science",
"Engineering"
] | 1,573 | [
"Glass engineering and science",
"Glassmaking schools"
] |
6,959,783 | https://en.wikipedia.org/wiki/Residential%20gateway | A residential gateway is a small consumer-grade gateway which bridges network access between connected local area network (LAN) hosts to a wide area network (WAN) (such as the Internet) via a modem, or directly connects to a WAN (as in EttH), while routing. The WAN is a larger computer network, generally operated by an Internet service provider.
History
The term residential gateway was popularized by Clifford Holliday in 1997 through his paper entitled "The residential gateway".
Devices
Multiple devices have been described as residential gateways:
Cable modem
DSL modem
FTTx modem
IP-DECT telephone (base station)
Network switch
Smart home hub
TV/VoD set-top box
Voice over Internet protocol (VoIP) analog telephone adapter
Wired router
Wireless access point
Wireless router
A modem (e.g. DSL modem, cable modem) by itself provides none of the functions of a router. It merely allows ATM or PPP or PPPoE traffic to be transmitted across telephone lines, cable wires, optical fibers, wireless radio frequencies, or other physical layers. On the receiving end is another modem that re-converts the transmission format back into digital data packets.
This allows network bridging using telephone, cable, optical, and radio connection methods. The modem also provides handshake protocols, so that the devices on each end of the connection are able to recognize each other. However, a modem generally provides few other network functions.
A USB modem plugs into a single PC and allows a connection of that single PC to a WAN. If properly configured, the PC can also function as the router for a home LAN.
An internal modem can be installed on a single PC (e.g. on a PCI card), also allowing that single PC to connect to a WAN. Again, the PC can be configured to function as a router for a home LAN.
A cellular wireless access point can function in a similar fashion to a modem. It can allow a direct connection from a home LAN to a WWAN, if a wireless router or access point is present on the WAN as well and tethering is allowed.
Many modems now incorporate the features mentioned below and thus are appropriately described as residential gateways, such as some Internet providers which offer a cable modem router combo.
Features
A residential gateway usually provides
configuration via a web interface, or app on mobile device.
routing between the home network and the Internet.
connectivity within the home network like a network switch, hub, or WLAN base station.
network address translation (NAT),
DHCP for IPv4 and IPv6, and
firewall functions
It may also provide other functions such as Dynamic DNS, and converged triple play services such as TV and telephony.
Most gateways are self-contained components, using internally stored firmware. They are generally platform-independent, i.e., they can serve any operating system.
Wireless routers perform the same functions as a wired router and base station, but allow connectivity for wireless devices with the LAN, or as a bridge between the wireless router and another wireless router for a meshnet (the wireless router-wireless router connection can be within the LAN or can be between the LAN and WWAN).
Security
Low-cost production and requirement for user friendliness make gateways vulnerable to network attacks, which resulted in large clusters of such devices being taken over and used to launch DDoS attacks. A majority of the vulnerabilities were present in the web administration frontends of the routers, allowing unauthorized control either via default passwords, vendor backdoors, or web vulnerabilities.
See also
Customer-premises equipment
Home network
Home server
Multimedia over Coax Alliance
LAN switching
Technological convergence
List of wireless router firmware projects
References
External links
The Residential Gateway (a vision paper published in International Engineering Consortium’s 1996 Annual Review of Communications, p.457)
Home Gateway Initiative, a group of broadband providers proposing specifications for residential gateways
The Residential Home Gateway on About.com
Networking hardware
Telecommunications equipment
Broadband
Server appliance
Router
la:Gateway | Residential gateway | [
"Engineering"
] | 856 | [
"Computer networks engineering",
"Networking hardware"
] |
6,959,832 | https://en.wikipedia.org/wiki/Cation%20channels%20of%20sperm | The cation channels of sperm also known as Catsper channels or CatSper, are ion channels that are related to the two-pore channels and distantly related to TRP channels. The four members of this family form voltage-gated Ca2+ channels that seem to be specific to sperm. As sperm encounter the more alkaline environment of the female reproductive tract, CatSper channels become activated by the altered ion concentration. These channels are required for proper fertilization. The study of these channels has been slow because they do not traffic to the cell membrane in many heterologous systems.
There are several factors that can activate the CatSper calcium channel, depending on species. In the human, the channel is activated by progesterone released by the oocyte. Progesterone binds to the protein ABHD2 which is present in the sperm plasma membrane, which causes ABHD2 to cleave an inhibitor of CatSper (2-arachidonoylglycerol) into arachidonic acid and glycerol. The human CatSper channel is pH-sensitive, and requires a high-pH environment. CatSper plays a key role in mediating hyperactive motility – prior to fertilization, sperm become entrapped within the fingerlike projections of the microvilli of the oviduct. In order for the sperm to fertilize the oocyte, CatSper must be present in order to initiate hyperactive motility, allowing the sperm to escape the microvilli and reach the oocyte for fertilization.
Certain substances act as agonist or inhibitor of CatSper (e. g. Pregnenolone sulfate is an agonist, pristimerin and lupeol are inhibitors).
Of the four members of the Catsper family, Catsper1 is found in the primary piece of sperm. Catsper1 plays an important role in evoked Ca2+ entry and regulation of hyperactivation in sperm. Catsper2 is localized in the sperm tail and is responsible for regulation of hyperactivation. Catsper3 and Catsper4 are found in both, the testes and sperm and play an important role in the motility of hyperactivated sperm. In humans, CatSper is distributed in quadrilateral nanodomains along the principal piece. Although Catsper seems to play an important role in sperm function, Catspers1-4 null mice have been found to have normal testicular histology, sperm counts and morphology, which is indicative of normal progression of spermatogenesis.
See also
Acrosome reaction
References
External links
GeneReviews/NCBI/NIH/UW entry on CATSPER-Related Male Infertility
Ion channels
Voltage-gated ion channels
Transmembrane proteins
Electrophysiology
Calcium channels | Cation channels of sperm | [
"Chemistry"
] | 580 | [
"Neurochemistry",
"Ion channels"
] |
6,959,903 | https://en.wikipedia.org/wiki/Two-pore%20channel | Two-pore channels (TPCs) are eukaryotic intracellular voltage-gated and ligand gated cation selective ion channels. There are two known paralogs in the human genome, TPC1s and TPC2s. In humans, TPC1s are sodium selective and TPC2s conduct sodium ions, calcium ions and possibly hydrogen ions. Plant TPC1s are non-selective channels. Expression of TPCs are found in both plant vacuoles and animal acidic organelles. These organelles consist of endosomes and lysosomes. TPCs are formed from two transmembrane non-equivalent tandem Shaker-like, pore-forming subunits, dimerized to form quasi-tetramers. Quasi-tetramers appear very similar to tetramers, but are not quite the same. Some key roles of TPCs include calcium dependent responses in muscle contraction(s), hormone secretion, fertilization, and differentiation. Disorders linked to TPCs include membrane trafficking, Parkinson's disease, Ebola, and fatty liver.
As implied by their name, TPC channels possess two pores and were named for their two Shaker-like repeats, which each have a pore domain. This contrasts with two-pore-domain potassium channels, which confusingly have only one pore and were named for the fact that each subunit has two P (pore) domains in its primary sequence.
History and discovery
Although much is left to be discovered about TPC function, they have been extensively studied thus far. Many questions have been raised about the specific function of TPC channels, as well as the ions and molecules that appear to be most closely affiliated with these channels. Some of these ions are sodium, calcium, and NAADP. Present knowledge of TPCs has come from experiments done on mice and plants, especially Arabidopsis thaliana. Additionally, because of the localization of these channels in mammals, it is difficult to use electrophysiological recordings on them. Therefore, these TPC channels have to be expressed in alternative compartments or organelles of the cell, such as plant vacuoles to be studied using the electrophysiological methods – especially the patch clamp technique. In order to clearly visualize the plant vacuoles, scientists have relied on fluorescent microscopy in their experiments. Using these techniques, scientists have been able to collect significant qualitative data in order to make conclusions about mammalian TPC functions. Specifically, scientists were able to conclude that human TPC are predominantly voltage-dependent sodium channels, and that PI(3,5)P2, an endolysosome-specific phosphoinositide (PIP), is a direct activator of TPC channels while NAADP is actually not an activator as it was once previously assumed to be.
Structure and domains
At the mouth of the TPC pore, there are four amino acid residues with negative charges that can interact with ions that pass through. This site is too wide to select ions. Below the group of negative charges is the selectivity filter which is largely hydrophobic. There are two non-identical Shaker-like pore forming subunits. Subunit 1 consists of voltage sensing domain 1 (VSD1) and subunit 2 consists of the voltage sensing domain 2 (VSD2). The two subunit domains are separated by an EF-hand domain that has a calcium ion binding motif. This binding motif can facilitate channel activation by cytosolic calcium ions. Each of the two subunits are built from 12 transmembrane helices. The two central pore domains are combined from the voltage sensing domains, VSD1 and VSD2. Both the N-terminal domain (NTD) and C-terminal domain (CTD) extend out on the cytosolic side, along with the EF-hand domain in the center that extends into the cytoplasm. The EF-hand domain extends into the cytosol, positioned between VSD1 and VSD2, where it can be activated by cytosolic calcium. The VSD2 domain is voltage sensitive active and can be inhibited by calcium in the lumen. This is a conformation change from the activation state to the inactive state. Two rings of hydrophobic residues seal the pore cavity from the cytoplasm; this results in forming the pore gate. Voltage sensors, selectivity filter, and the gate work together in a coordinated manner to open and close TPCs for regulation of ion conductance.
The VSD2 domain contains a normal voltage sensing motif, arginine residues R1, R2 and R3 and alpha helix S10, in respect to other voltage-gated ion channels structures, but this domain adopts a distinct conformation in the resting state of a voltage sensor. Luminal calcium acts as a TPC1 inhibitor, preventing ion conductance. There are two calcium binding sites for VSD2 on the luminal side. The first site does not affect the channel. Site 2, composed of residues in VSD2 and the pore domain, inhibits the channel by shifting the voltage dependence to more positive voltages.
Activation of TPCs is induced by a decrease in transmembrane potential, or by an increase in calcium concentrations in the cytosol. Low pH of the lumen and low calcium concentration could cause inhibition of these channels. TPCs are also phosphorylation-gated channels in both animals as well as plants. Sites of phosphorylation are at the N-terminal and C-terminal domains. These terminals are positioned to provide allosteric change in order to be activated by calcium from the cytosol.
Human and plant TPCs are multi-modal for conductance. The mechanism for channel opening is likely contributed to a combination of calcium concentrations, voltage, and phosphoregulation integration, in order to govern the conduction of ions through TPCs.
Biological roles (function/dysfunction)
Two-pore channels were analyzed by using cell biological methods, endolysosomal patch clamp techniques, and a variety of other methods to study their functions. From these, it was suggested that TPCs have some power in controlling the luminal pH in endolysosomal vesicles. When TPC2 expression is decreased or knocked out, there is a resultant elevation in production of melanin and thus melanosomal pH, and when TPC2 expression is increased, there is less production of melanin.
TPCs also are involved in nutrient detection as they become active constitutively on identifying the status of the nutrients. This is done by direct communication between the TPCs and mammalian/mechanistic targets of rapamycin (mTORs), which are associated with detecting levels of oxygen, nutrients, and energy in the cells and thus help with regulation of metabolism. This is how the TPCs play a role in this physiological regulation through this interaction.
TPCs regulate sodium and calcium ion conductance, intravasicular pH, and trafficking excitability. The second messenger nicotinic acid adenine dinucleotide phosphate (NAADP) has been shown to mediate calcium release from these acidic organelles through TPCs. TPC2s are NAADP-gated calcium release channels where these TPC currents can be blocked by NAADP antagonists. TCP2 plays a critical role in the endocytosis allowing SARS-CoV-2 virus to enter cells.
Various ailments can occur from the knockdown of these channels, from metabolic and general infectious diseases to even cancer. The pathological conditions due to this lacking of TPCs are covered in the following sections.
Membrane trafficking
TPCs play an integral role in membrane trafficking pathways. They are sectioned in endosomes and lysosomes, especially functioning in endo-lysosomal fusions. TPC trafficking activity has been noted to be conserved; but modifying TPCs affects transportation in the endocytotic pathway. The exact roles of TPCs are specific to cell type and context. These channels are permeable to calcium, making them function as Ca2+ ion channels. When stimulated by NAADP – a second messenger for TPCs –, calcium is released into the cytosol. The influx of calcium is what regulates the fusion between the endosome and lysosomes and what mediates trafficking events. When the function of TPCs are lost, substrates accumulate creating congestion. When the function of TPCs are increased, the lysosome becomes enlarged – which logically relates to increased fusion events with the endosome to lysosome.
Parkinson's disease
One implication of membrane trafficking dysfunction leads to Parkinson's disease. Mutations to LRRK2 enzyme alter autophagy dependent upon NAADP and TPC2. The mutation increases the amount of Ca2+ flow through TPC2 by NAADP evoked signals. This increase in signaling leads to an increase in size of the lysosomes due to the increased rate and amount of fusion. The lysosome, therefore, is not able to break down components the way it should. This inability is associated with the onset of the disease. As TPC2 plays a vital role in this specific mechanism of Parkinson's disease development, it may potentially be a therapeutic target.
Ebola
The Ebolavirus takes advantage of host cell endocytotic membrane trafficking, leaving TPCs as a potential drug target. Ebolavirus enter cells through micropinocytosis with endosomal vesicles. After entrance into the endosomal vesicle, Ebolavirus membrane fuses with the endosomal membrane to release the viral contents into the cytosol before the endosome can fuse with the lysosome. For the movement of the virus in endosomes, Ca2+ is necessary. As NAADP regulates maturation of endosomes by the calcium release through TPCs, normal functioning of TPCs allows the Ebolavirus to escape. Therefore, when TPCs are not functioning, the Ebolavirus cannot escape before the fusion of the endosome with the lysosome. In fact, when mice are treated with tetradine the infection is inhibited. This is because tetradine blocks TPC functioning of calcium release and thus, the Ebolaviruses is contained within the endosomal network destined to be degraded by the lysosome.
Fatty liver
TPCs have been implicated in fatty liver diseases, such as NAFLD and NASH. As TPC2 is a cation channel for endocytotic membrane trafficking, TPCs contribute in trafficking LDL molecules for their breakdown and recycling. This primarily occurs within the liver. The degradation pathway causes LDL to end up in endosomes and lysosomes – where TPCs are located. The TPC mechanism once again allows the efflux of calcium for the fusion of the endosomes and lysosomes (where LDL is degraded). When TPCs are not present, or are not functioning properly, the degradation pathway results in defected trafficking. Without the fusion event LDL accumulates in liver cells. The loss of TPCs have been found to be a cause of the yellow coloration of liver, an expression of fatty liver which indicates liver damage.
References
External links
Ion channels | Two-pore channel | [
"Chemistry"
] | 2,382 | [
"Neurochemistry",
"Ion channels"
] |
6,959,944 | https://en.wikipedia.org/wiki/Happening%20bar | A or is a Japanese sex club. In both, prospective customers pass an initial vetting to become members, then pay an entrance fee to enter the club. The club will provide drinks at a bar (often for free), rooms for sex and typically shower facilities. Entrance to couple kissa is limited to male-female couples and single women, while a happening bar will also allow single men to enter, although typically at a steep surcharge (as much as ¥25,000, whereas a woman might enter for free). Entry is denied to the underaged (under 20), male groups, drunk or intoxicated people and, in some establishments, foreigners.
Happening bars and couple kissas skirt Japanese prostitution laws by neither providing nor promising actual sex on premises, instead stressing that what may or may not happen is entirely up to customers. In a high-profile incident in 2004, after porn star and wrestler Chocoball Mukai advertised on his website that he would be performing, the happening bar "Rock" in Tokyo's Roppongi district was raided by police. Chocoball, who had been caught in the act with another porn star, was later convicted for public indecency and sentenced to a five-month jail term, and the club was forced to shut down.
References
Sexuality in Japan
Sex clubs | Happening bar | [
"Biology"
] | 273 | [
"Behavior",
"Sexuality stubs",
"Sexuality"
] |
6,960,628 | https://en.wikipedia.org/wiki/Andrew%20Casson | Andrew John Casson FRS (born 1943) is a mathematician, studying geometric topology. Casson is the Philip Schuyler Beebe Professor of Mathematics at Yale University.
Education and career
Casson was educated at Latymer Upper School and Trinity College, Cambridge, where he graduated with a BA in the Mathematical Tripos in 1965. His doctoral advisor at the University of Liverpool was C. T. C. Wall, but he never completed his doctorate; instead what would have been his Ph.D. thesis became his fellowship dissertation as a research fellow at Trinity College.
Casson was Professor of Mathematics at the University of Texas at Austin between 1981 and 1986, at the University of California, Berkeley, from 1986 to 2000, and has been at Yale since 2000.
Work
Casson has worked in both high-dimensional manifold topology and 3- and 4-dimensional topology,
using both geometric and algebraic techniques. Among other discoveries, he contributed
to the disproof of the manifold Hauptvermutung, introduced the Casson invariant, a modern invariant for 3-manifolds, and Casson handles, used in Michael Freedman's proof of the 4-dimensional Poincaré conjecture.
Awards
In 1991, he was awarded the Oswald Veblen Prize in Geometry by the American Mathematical Society. In 1998, he was elected to Fellowship of the Royal Society.
References
External links
Official Home Page
The Hauptvermutung book (including Casson's 1967 Trinity College fellowship dissertation)
Proceedings of the Casson Fest (Arkansas and Texas 2003) A conference to celebrate Casson's 60th birthday, with biographical information.
Photos from conference, including the `honorary degree' presented to Casson by the participants
1943 births
Living people
Fellows of the Royal Society
Alumni of Trinity College, Cambridge
University of Texas at Austin faculty
University of California, Berkeley College of Letters and Science faculty
Yale University faculty
Topologists
Alumni of the University of Liverpool | Andrew Casson | [
"Mathematics"
] | 388 | [
"Topologists",
"Topology"
] |
6,960,639 | https://en.wikipedia.org/wiki/TH-dimer | TH-dimer, also called tetrahydromethylcyclopentadiene dimer or RJ-4, is a synthetic jet fuel used in jet engines for missiles. RJ-4 was originaly developed for the ramjet engine on RIM-8 Talos naval surface-to-air missile.
The fuel is non-volatile, so it is safe to use on ships or submarines. It has a high flash point minimum of .
Chemically, TH-dimer is a mixture of isomeric saturated hydrocarbons derived from hydrogenation of the dimer of methylcyclopentadiene.
References
Bibliography
Aviation fuels
Hydrocarbons
Tricyclic compounds | TH-dimer | [
"Chemistry",
"Engineering"
] | 141 | [
"Organic compounds",
"Hydrocarbons",
"Aviation fuels",
"Aerospace engineering"
] |
6,960,642 | https://en.wikipedia.org/wiki/Maintenance%20release | A maintenance release (also minor release or Maintenance Pack or MP) is a release of a product that does not add new features or content. For instance, in computer software, maintenance releases are typically intended to solve minor problems, typically "bugs" or security issues.
Example of minor version numbering
The somewhat unusual version number "3.0.5a" was used for a minor release of KDE because of a lack of version numbers. Work on KDE 3.1 had already started and, up to that day, the release coordinator used version numbers such as 3.0.5, 3.0.6 internally in the main CVS repository to mark snapshots of the upcoming 3.1. Then after 3.0.3, a number of important and unexpected bug fixes (starting from 3.0.4) suddenly became necessary, leading to a conflict, because 3.0.5 was at this time already in use. More recent KDE release cycles have tagged pre-release snapshots with large revision numbers, such as 3.1.95, to avoid such conflicts.
See also
Patch (computing)
Software versioning
Software release life cycle
Point release
References
Software release | Maintenance release | [
"Engineering"
] | 244 | [
"Software engineering",
"Software engineering stubs"
] |
6,960,693 | https://en.wikipedia.org/wiki/Remnant%20%28Seventh-day%20Adventist%20belief%29 | In Seventh-day Adventist theology, there will be an end time remnant of believers who are faithful to God. The remnant church is a visible, historical, organized body characterized by obedience to the commandments of God and the possession of a unique end-time gospel proclamation. Adventists have traditionally equated this "remnant church" with the Seventh-day Adventist denomination.
A distinct but related concept is the eschatological remnant, which will manifest shortly prior to the second coming of Jesus. The "remnant church" is understood to act as a catalyst for the formation of this group. The eschatological remnant will consist of some (but not all) constituents of the present "remnant church", together with a cohort of believers from other (that is, non-Adventist) churches. Only members of the eschatological remnant will be saved through the end-times.
Traditionally, Adventists have also applied the symbol of "Laodicea" to themselves, a self-criticism as being "lukewarm" in the faith (Revelation 3:15–16).
The Adventist doctrine of the end-time remnant is based primarily upon Revelation 12:17, which states:
An estimated 90% of Adventists believe "The Adventist Church has a special mission to proclaim God’s last message to the world", according to estimates of local church leaders in a 2002 worldwide survey.
Official statements
The doctrine of the remnant is outlined in the 28 fundamental beliefs of the Adventist church, as follows.
Mission statement
The Mission Statement of the church declares:
Church manual and baptismal vow
The Seventh-day Adventist Church Manual contains a "summary of doctrinal beliefs" in its appendix that is designed especially for use in the instruction of candidates for baptism. The final point identifies the Adventist church with the "remnant":
The church manual also outlines two alternative baptismal vows for candidates who are entering into church membership. The final question of the traditional longer vow (question 13) asks the candidate:
Following baptism, the new member is presented with a "certificate of baptism and commitment" which contains a similarly worded statement, but expressed as an affirmation rather than a question.
In 2005, an alternative baptismal vow was approved at the General Conference Session. This alternative vow contains three statements of belief, and does not mention the remnant. However, it does still require acceptance of the Fundamental Beliefs. Which version to use is up to the discretion of the parties involved.
History
In 1849, Joseph Bates asserted the Adventists were the remnant.
Gerhard Hasel was a recognized remnant scholar within Christian circles at large, and wrote on the theme of the remnant throughout the Old Testament.
Traditional position
The Seventh-day Adventist Church has traditionally identified itself as the end-time "remnant church" described in Revelation 12:17. Two of the identifying marks of the remnant listed in this verse are that they "keep the commandments of God" and have the "testimony of Jesus". It is held that the "commandments of God" refer to the Ten Commandments, which includes the fourth commandment regarding the seventh-day Sabbath. In addition, Revelation 19:10 equates "the testimony of Jesus" to the "Spirit of prophecy", which Adventists believe is a reference to the ministry and writings of Ellen G. White. The Adventist church therefore sees itself as unique in possessing these two identifying marks of the remnant church.
According to the historicist interpretation of Revelation traditionally employed by Adventists, the remnant church emerges after a period of 1,260 years (Revelation 12:6) during which the Papacy reigns over Christendom. This period ended in 1798. The Seventh-day Adventist Church formed shortly afterwards, in the period 1844–1863.
The remnant church has a divine mission which is symbolised in the three angels' messages. This mission is to proclaim the "everlasting gospel" to humanity, to call true believers out of false religion (represented by Babylon) and to prepare the world for the final end-time crisis. Even so, at the present time, the remnant church is a visible institution that is made up of both saved and unsaved individuals (in other words, membership in the Adventist church is not a guarantee of salvation).
Ellen White wrote,
At a time, known technically as the "close of probation", shortly before the second coming of Jesus, humanity will be polarized into two distinct groups. Adventists traditionally have taught that this polarization will occur over the Sabbath commandment. Those who are obedient to God in this final era will make up the "eschatological remnant" which will be saved through the final crisis. The eschatological remnant will have some continuity with the remnant church, in that there will be some Adventists who remain faithful in the crisis. However, it is understood that numerous Adventists will succumb to apostasy, thus departing from the remnant. At the same time, there will be numerous Christian believers from non-Adventist churches who will join the eschatological remnant and receive salvation.
Alternative interpretations
Adventist scholar Ángel Manuel Rodríguez, who himself supports the traditional Adventist interpretation, has stated: "it is with great concern that some observe a tendency to de-emphasize or ignore this fundamental self-definition". Rodríguez identifies a number of different interpretations of the "remnant" that have gained popularity within contemporary Adventism. He proposes several reasons for the increasing redefinition of the concept, including increased contact with other Christians, the delay of the Parousia, theological education in non-Adventist universities, exposure to post-modern world views, and perceived apostasy in the Adventist church.
Similarly, in 2008, Roy Adams wrote in the Adventist Review, "Today we hesitate to claim we’re the remnant".
In The Shaking of Adventism, Anglican Geoffrey Paxton described the mainstream belief as follows:
Wider remnant/remnant message
In modern times some Adventists have broadened the "remnant" concept to include sincere Christians in other denominations. Such a broadening occurred as early as the publication of Questions on Doctrine.
Many Adventists who hold a "wider" concept of the remnant nevertheless consider that the Adventist church has a unique place in God's purpose for the end times. Questions on Doctrine acknowledged the Adventist church as "the visible organization through which God is proclaiming this last special message to the world". Adventists such as Ross Cole speak of Adventists as possessing the "remnant message". These views focus more on the message of the remnant, and not on the Adventist church as an institution.
According to Ron Corson, many "progressive" Adventists believe in "An inclusion of other Christians into the category termed the 'Remnant.'"
Liberal views
Some Adventists have re-interpreted the remnant concept significantly. Steve Daily rejects the identification of the "remnant" with any institution or denomination, and instead considers it to be an invisible entity. He argues for a "move from an ethnocentric remnant theology to a spirit of religious affirmation which acknowledges that the 'kingdom of God on earth' transcends every religious movement of mankind". Ángel Manuel Rodríguez criticizes Daily's position, claiming that "The level of discontinuity with traditional Adventism is so drastic that it is difficult to incorporate it into any meaningful dialogue."
Others have interpreted the remnant concept along sociological and political lines, for example Remnant and Republic: Adventist Themes for Personal and Social Ethics, edited by Charles W. Teel Jr. It is argued that the remnant has a duty to work towards social and political reform. Some who espouse these views deny that the remnant is a religious body to be identified with any particular church. Rodriguez again rejects such interpretations, asserting that they set aside "the biblical understanding of the remnant as fundamentally a religious entity".
Criticism of the remnant doctrine
Progressive Adventist criticism
The progressive Adventist journals Spectrum and Adventist Today commonly publish articles and letters which deny this doctrine, instead claiming that the remnant is much wider than the Adventist church. Rodríguez believes that a tendency to reject the remnant concept is related to a tendency to reject the historicist method of interpreting prophecy.
Raymond Cottrell, writing about the challenges of producing the Seventh-day Adventist Bible Commentary, claimed that the remnant doctrine is not supported by the traditional prooftexts.
What should an editor do with 'proof texts' that inherently do not prove what is traditionally attributed to them—as, for example... and ... In most of these and a number of other passages, pastoral concern led us to conclude that the Commentary was not the place to make an issue of the Bible versus the traditional interpretation, much as this disappointed us as Bible scholars and would be a disappointment to our scholarly friends who know better."
Nathan Brown, then Record editor, has written in that magazine, "For many Adventists, the topic of the 'remnant'—and particularly various statements that have sounded like claims to be "the remnant church"—has been a source of discomfort, feeling a bit too much like arrogance or at best claims we would all struggle to live up to."
Non-Adventist criticism
Non-Adventists scholars have disputed the Adventist understanding of the remnant. Calvinist theologian Anthony Hoekema argued that the doctrine of the remnant church is indefensible on both exegetical and theological grounds. Exegetically, the Greek word "remnant" (leimma) is not found in Revelation 12:17 and thus it is not possible to read a "church within a church" into the verse. The translation "remnant" is an inaccuracy of the KJV upon which the doctrine was originally based. Theologically, Adventists insist that the remnant is merely a visible body within the wider "invisible church;" however there is no biblical or theological warrant for believing in the existence of an ecclesiola in ecclesia, or "little church within the church". The concept of "remnant" in the New Testament, according to Hoekema, applies only to Jewish believers. Hoekema alleges that the Adventist concept of the remnant resembles the error of schismatic movements such as Montanism, Novatianism and Donatism.
Hoekema finally concludes that the "remnant church" concept places Adventism among the cults, since it implies that the Adventist church is "the last true church left on earth, and all other groups which claim to be churches are not true but false churches." That is, it implies the existence of an "exclusive community", which Hoekema believes is a distinctive trait of the cults. However, because Adventists acknowledge that it is possible for non-Adventist Christians to be saved, Hoekema concedes they manifest the "cultist trait" in a "somewhat ambivalent manner" when compared to religions who teach that salvation cannot be found outside their organisations.
Remnant concept in breakaway groups from Adventism
The Seventh Day Adventist Reform Movement, which schismed from the Seventh-day Adventist Church in the 1920s, sees itself as the "remnant", the Adventist church represented by the "seed", and other Protestants as the "woman" in Revelation 12:17.
See also
History of the Seventh-day Adventist Church
Criticism of the Seventh-day Adventist Church#Remnant church status
Prophecy in the Seventh-day Adventist Church
Millerites
The Pillars of Adventism
Seventh-day Adventist interfaith relations
Three Angels' Messages
Teachings of Ellen G. White
References
Further reading
Search for "Remnant Theology" in the Seventh-day Adventist Periodical Index (SDAPI)
Traditional position:
"The Remnant Church" by Gerhard Pfandl of the Biblical Research Institute (BRI). Journal of the Adventist Theological Society, 8/1–2 (1997): 19–27.
"The End Time Remnant in Revelation" by Ekkehardt Mueller, also of the BRI. Journal of the Adventist Theological Society 11/1–2 (2000): 188–204.
"The Remnant and the Adventist Church by Ángel Rodríguez, on the BRI website.
Clifford Goldstein, The Remnant: Biblical Reality or Wishful Thinking? (Boise, Idaho: Pacific Press, 1994).
Seventh-day Adventists Believe... (1988) by the Ministerial Association. Chapter 12, "The Remnant and Its Mission".
A Remnant in Crisis by Jack Provonsha (Review and Herald, 1993). (One review: Ervin Taylor, "Remnant an Apologetic for Historic Adventism". Adventist Today 1:4 (November 1993), p. 18 revi)
Toward a Theology of the Remnant: An Adventist Ecclesiological Perspective. Biblical Research Institute
Liberal and sociological positions:
"The Real Truth About the Remnant" (old link) by Charles Scriven.
"Growing Up With John's Beasts: A Rite of Passage", Spectrum. 21:3 (1991):25–34.
Roy Branson, "The Demand for New Ethical Vision" in Bioethics Today: A New Ethical Vision, edited by James Walters (Loma Linda, California: Loma Linda University Press, 1988), pp. 13–27.
The Peacemaking Remnant edited by Douglas Morgan (Adventist Peace Fellowship, 2005. Publisher's page). Contributors are Charles Scriven, Charles E. Bradford, Kendra Haloviak, Keith Burton, Zdravko Plantak, Ryan Bell, Ronald Osborn, and Douglas Morgan.
"It's About the Survivors: Another look at the meaning of the remnant". Ross Cole. Adventist Review. January 30, 2003.
Seventh-day Adventist theology
Time in religion | Remnant (Seventh-day Adventist belief) | [
"Physics"
] | 2,767 | [
"Spacetime",
"Time in religion",
"Physical quantities",
"Time"
] |
6,960,765 | https://en.wikipedia.org/wiki/Gene%20transfer%20format | The Gene transfer format (GTF) is a file format used to hold information about gene structure. It is a tab-delimited text format based on the general feature format (GFF), but contains some additional conventions specific to gene information. A significant feature of the GTF that can be validated: given a sequence and a GTF file, one can check that the format is correct. This significantly reduces problems with the interchange of data between groups.
GTF is identical to GFF, version 2.
References
External links
Info from UCSC Genome Bioinformatics Site
Detailed GTF v2.2 Format Description
Computer file formats
Bioinformatics
Biological sequence format | Gene transfer format | [
"Chemistry",
"Engineering",
"Biology"
] | 139 | [
"Biological engineering",
"Bioinformatics stubs",
"Biotechnology stubs",
"Biochemistry stubs",
"Bioinformatics",
"Biological sequence format"
] |
6,960,861 | https://en.wikipedia.org/wiki/Remnant%20%28Bible%29 | The remnant is a recurring theme throughout the Hebrew and Christian Bible. The Anchor Bible Dictionary describes it as "What is left of a community after it undergoes a catastrophe". The concept has stronger representation in the Hebrew Bible and Christian Old Testament than in the Christian New Testament.
Biblical mentions
Hebrew Bible
According to the Book of Isaiah, the "remnant" () is a small group of Israelites who will survive the invasion of the Assyrian army under Tiglath-Pileser III (). The remnant is promised that they will one day be brought back to the Promised Land by Yahweh (). Isaiah again uses the terminology during Sennacherib's siege of Jerusalem ().
The concept of the remnant is taken up by several other prophets, including Amos, Micah, Jeremiah and Zephaniah. In Jeremiah 39–40, the "poor people, who had nothing", who remained in Judah when the rest of its population were deported to Babylon, are referred to as a "remnant". The post-exilic biblical literature (Ezra–Nehemiah, Haggai and Zechariah) consistently refers to the Jews who have returned from the Babylonian captivity as the remnant.
New Testament
New Testament verses which refer to a faithful "remnant" () include , where Paul refers back to Old Testament examples, and ("And the dragon was wroth with the woman, and went to make war with the remnant of her seed, which keep the commandments of God, and have the testimony of Jesus Christ").
Church views
Church of England
The influential Anglican "remnant theology" of Martin Thornton (1915–1986) sees the church parish as made up of three different levels of members. Thornton refers to the smallest of the groups as the Remnant, likening it to the remnant of Isaiah in the Old Testament. These are ordinary people of extraordinary devotion, more proficient than spiritually gifted, whom it is vital for the parish priest to identify and nurture through spiritual direction, for they are the dependable, beating, praying heart of the parish. They truly live their Christianity and form the core not just of the parish but of the universal "Church Militant".
Roman Catholic Church
The Old Testament notion of "the remnant" was one of the three images Karl Rahner used to set the parish into his larger vision of church in his 1956 essay "Theology of the Parish" and his 1961 book The Episcopate and the Primacy, co-authored with then Cardinal Joseph Ratzinger (later Pope Benedict XVI). What was significant for Rahner in the concept of "the remnant" was the idea that the whole – the universal Church – could be present in the part – the parish: "the Church as a whole, when it becomes "Event" in the full sense, is also necessarily a local Church, the whole Church becomes tangible in the local Church".
Seventh-day Adventist Church
The Seventh-day Adventist Church places significant emphasis on the remnant theme, based on a traditional interpretation of the King James Version of . Two of its official belief statements mention the remnant theme: number 13, "Remnant and Its Mission" describes an eschatological (end-time) remnant, and number 18, "The Gift of Prophecy" mentions the spiritual gift of prophecy "is an identifying mark of the remnant church".
Criticism
James Watts claims that some authors have given too much emphasis to the remnant theme, such as some scholars who "have considered it central to the NT message". According to Watts, there are fewer occurrences of the theme in the Bible than one might expect.
References
Christian theology of the Bible
Christian terminology
Judeo-Christian topics
Hebrew Bible words and phrases
New Testament words and phrases
Time in religion | Remnant (Bible) | [
"Physics"
] | 758 | [
"Spacetime",
"Time in religion",
"Physical quantities",
"Time"
] |
6,961,430 | https://en.wikipedia.org/wiki/Total%20correlation | In probability theory and in particular in information theory, total correlation (Watanabe 1960) is one of several generalizations of the mutual information. It is also known as the multivariate constraint (Garner 1962) or multiinformation (Studený & Vejnarová 1999). It quantifies the redundancy or dependency among a set of n random variables.
Definition
For a given set of n random variables , the total correlation is defined as the Kullback–Leibler divergence from the joint distribution to the independent distribution of ,
This divergence reduces to the simpler difference of entropies,
where is the information entropy of variable , and is the joint entropy of the variable set . In terms of the discrete probability distributions on variables , the total correlation is given by
The total correlation is the amount of information shared among the variables in the set. The sum represents the amount of information in bits (assuming base-2 logs) that the variables would possess if they were totally independent of one another (non-redundant), or, equivalently, the average code length to transmit the values of all variables if each variable was (optimally) coded independently. The term is the actual amount of information that the variable set contains, or equivalently, the average code length to transmit the values of all variables if the set of variables was (optimally) coded together. The difference between
these terms therefore represents the absolute redundancy (in bits) present in the given
set of variables, and thus provides a general quantitative measure of the
structure or organization embodied in the set of variables
(Rothstein 1952). The total correlation is also the Kullback–Leibler divergence between the actual distribution and its maximum entropy product approximation .
Total correlation quantifies the amount of dependence among a group of variables. A near-zero total correlation indicates that the variables in the group are essentially statistically independent; they are completely unrelated, in the sense that knowing the value of one variable does not provide any clue as to the values of the other variables. On the other hand, the maximum total correlation (for a fixed set of individual entropies ) is given by
and occurs when one of the variables determines all of the other variables. The variables are then maximally related in the sense that knowing the value of one variable provides complete information about the values of all the other variables, and the variables can be figuratively regarded as cogs, in which the position of one cog determines the positions of all the others (Rothstein 1952).
It is important to note that the total correlation counts up all the redundancies among a set of variables, but that these redundancies may be distributed throughout the variable set in a variety of complicated ways (Garner 1962). For example, some variables in the set may be totally inter-redundant while others in the set are completely independent. Perhaps more significantly, redundancy may be carried in interactions of various degrees: A group of variables may not possess any pairwise redundancies, but may possess higher-order interaction redundancies of the kind exemplified by the parity function. The decomposition of total correlation into its constituent redundancies is explored in a number sources (Mcgill 1954, Watanabe 1960, Garner 1962, Studeny & Vejnarova 1999, Jakulin & Bratko 2003a, Jakulin & Bratko 2003b, Nemenman 2004, Margolin et al. 2008, Han 1978, Han 1980).
Conditional total correlation
Conditional total correlation is defined analogously to the total correlation, but adding a condition to each term. Conditional total correlation is similarly defined as a Kullback-Leibler divergence between two conditional probability distributions,
Analogous to the above, conditional total correlation reduces to a difference of conditional entropies,
Uses of total correlation
Clustering and feature selection algorithms based on total correlation have been explored by Watanabe. Alfonso et al. (2010) applied the concept of total correlation to the optimisation of water monitoring networks.
See also
Mutual information
Dual total correlation
Interaction information
References
Alfonso, L., Lobbrecht, A., and Price, R. (2010). Optimization of Water Level Monitoring Network in Polder Systems Using Information Theory, Water Resources Research, 46, W12553, 13 PP., 2010, .
Garner W R (1962). Uncertainty and Structure as Psychological Concepts, JohnWiley & Sons, New York.
Han T S (1978). Nonnegative entropy measures of multivariate symmetric correlations, Information and Control 36, 133–156.
Han T S (1980). Multiple mutual information and multiple interactions in frequency data, Information and Control 46, 26–45.
Jakulin A & Bratko I (2003a). Analyzing Attribute Dependencies, in N Lavra\quad{c}, D Gamberger, L Todorovski & H Blockeel, eds, Proceedings of the 7th European Conference on Principles and Practice of Knowledge Discovery in Databases, Springer, Cavtat-Dubrovnik, Croatia, pp. 229–240.
Jakulin A & Bratko I (2003b). Quantifying and visualizing attribute interactions .
Margolin A, Wang K, Califano A, & Nemenman I (2010). Multivariate dependence and genetic networks inference. IET Syst Biol 4, 428.
McGill W J (1954). Multivariate information transmission, Psychometrika 19, 97–116.
Nemenman I (2004). Information theory, multivariate dependence, and genetic network inference .
Rothstein J (1952). Organization and entropy, Journal of Applied Physics 23, 1281–1282.
Studený M & Vejnarová J (1999). The multiinformation function as a tool for measuring stochastic dependence, in M I Jordan, ed., Learning in Graphical Models, MIT Press, Cambridge, MA, pp. 261–296.
Watanabe S (1960). Information theoretical analysis of multivariate correlation, IBM Journal of Research and Development 4, 66–82.
Information theory
Probability theory
Covariance and correlation | Total correlation | [
"Mathematics",
"Technology",
"Engineering"
] | 1,267 | [
"Telecommunications engineering",
"Applied mathematics",
"Computer science",
"Information theory"
] |
6,961,771 | https://en.wikipedia.org/wiki/Principal%20ideal%20ring | In mathematics, a principal right (left) ideal ring is a ring R in which every right (left) ideal is of the form xR (Rx) for some element x of R. (The right and left ideals of this form, generated by one element, are called principal ideals.) When this is satisfied for both left and right ideals, such as the case when R is a commutative ring, R can be called a principal ideal ring, or simply principal ring.
If only the finitely generated right ideals of R are principal, then R is called a right Bézout ring. Left Bézout rings are defined similarly. These conditions are studied in domains as Bézout domains.
A principal ideal ring which is also an integral domain is said to be a principal ideal domain (PID). In this article the focus is on the more general concept of a principal ideal ring which is not necessarily a domain.
General properties
If R is a principal right ideal ring, then it is certainly a right Noetherian ring, since every right ideal is finitely generated. It is also a right Bézout ring since all finitely generated right ideals are principal. Indeed, it is clear that principal right ideal rings are exactly the rings which are both right Bézout and right Noetherian.
Principal right ideal rings are closed under finite direct products. If , then each right ideal of R is of the form , where each is a right ideal of Ri. If all the Ri are principal right ideal rings, then Ai=xiRi, and then it can be seen that . Without much more effort, it can be shown that right Bézout rings are also closed under finite direct products.
Principal right ideal rings and right Bézout rings are also closed under quotients, that is, if I is a proper ideal of principal right ideal ring R, then the quotient ring R/I is also principal right ideal ring. This follows readily from the isomorphism theorems for rings.
All properties above have left analogues as well.
Commutative examples
1. The ring of integers:
2. The integers modulo n: .
3. Let be rings and . Then R is a principal ring if and only if Ri is a principal ring for all i.
4. The localization of a principal ring at any multiplicative subset is again a principal ring. Similarly, any quotient of a principal ring is again a principal ring.
5. Let R be a Dedekind domain and I be a nonzero ideal of R. Then the quotient R/I is a principal ring. Indeed, we may factor I as a product of prime
powers: , and by the Chinese Remainder Theorem
, so it suffices to see that each
is a principal ring. But is isomorphic to the quotient of the discrete valuation ring
and, being a quotient of a principal ring, is itself a principal ring.
6. Let k be a finite field and put , and . Then R is a finite local ring which is not principal.
7. Let X be a finite set. Then forms a commutative principal ideal ring with unity, where represents set symmetric difference and represents the powerset of X. If X has at least two elements, then the ring also has zero divisors. If I is an ideal, then . If instead X is infinite, the ring is not principal: take the ideal generated by the finite subsets of X, for example.
8. Galois rings are commutative local PIRs. They are constructed from the integers modulo in essentially the same way that finite field extensions of the integers modulo , and the maximal ideal is generated by
Structure theory for commutative PIR's
The principal rings constructed in Example 5 above are always Artinian rings; in particular they are isomorphic to a finite direct product of principal Artinian local rings.
A local Artinian principal ring is called a special principal ring and has an extremely simple ideal structure: there are only finitely many ideals, each of which is a power of the maximal ideal. For this reason, special principal rings are examples of uniserial rings.
The following result gives a complete classification of principal rings in terms of special principal rings and principal ideal domains.
Zariski–Samuel theorem: Let R be a principal ring. Then R can be written as a direct product , where each Ri is either a principal ideal domain or a special principal ring.
The proof applies the Chinese Remainder theorem to a minimal primary decomposition of the zero ideal.
There is also the following result, due to Hungerford:
Theorem (Hungerford): Let R be a principal ring. Then R can be written as a direct product , where each Ri is a quotient of a principal ideal domain.
The proof of Hungerford's theorem employs Cohen's structure theorems for complete local rings.
Arguing as in Example 3. above and using the Zariski-Samuel theorem, it is easy to check that Hungerford's theorem is equivalent to the statement that any special principal ring is the quotient of a discrete valuation ring.
Noncommutative examples
Every semisimple ring R which is not just a product of fields is a noncommutative right and left principal ideal ring (it need not be a domain, as the example of n x n matrices over a field shows). Every right and left ideal is a direct summand of R, and so is of the form eR or Re where e is an idempotent of R. Paralleling this example, von Neumann regular rings are seen to be both right and left Bézout rings.
If D is a division ring and is a ring endomorphism which is not an automorphism, then the skew polynomial ring is known to be a principal left ideal domain which is not right Noetherian, and hence it cannot be a principal right ideal ring. This shows that even for domains principal left and principal right ideal rings are different.
References
Pages 86 & 146-155 of
Commutative algebra
Ring theory | Principal ideal ring | [
"Mathematics"
] | 1,245 | [
"Fields of abstract algebra",
"Commutative algebra",
"Ring theory"
] |
6,962,075 | https://en.wikipedia.org/wiki/Ruedi%20Aebersold | Rudolf Aebersold (better known as Ruedi Aebersold; born September 12, 1954) is a Swiss biologist, regarded as a pioneer in the fields of proteomics and systems biology. He has primarily researched techniques for measuring proteins in complex samples, in many cases via mass spectrometry. Ruedi Aebersold is a professor of Systems biology at the Institute of Molecular Systems Biology (IMSB) in ETH Zurich. He was one of the founders of the Institute for Systems Biology in Seattle, Washington, United States where he previously had a research group.
Aebersold is known for the development and application of targeted proteomics techniques in the field of biomedical research, in order to understand the function, interaction and localization of each protein in the cell and its changes in disease states. To this end, Ruedi Abersold has made significant contributions in the development and application of targeted proteomics methods, including selected reaction monitoring and data-independent acquisition. Ruedi Aebersold is also recognized for its contributions in the development of standard formats and open source software for the analysis and storage of mass spectrometry and proteomics data, and he is one of the inventors of the Isotope-Coded Affinity Tag (ICAT) technique for quantitative proteomics, a technique that measures the relative quantities of proteins between two sample by using tags containing stable isotopes of different masses.
Aebersold is co-founder and scientific advisor of the companies ProteoMediX and Biognosys.
Honors and awards
2005 – HUPO Award
2006 – Buchner Medal
2008 – In recognition of his contribution to the field of protein sciences and proteomics the Association of Biomolecular Resource Facilities (ABRF) selected him for the ABRF 2008 Award.
2010 – Herbert A. Sober Lectureship
2010 – Otto Naegeli Prize
2012 – Thomson Medal Award
In 2014 he became a member of the German Academy of Sciences Leopoldina.
2015 – ranked #1 on the 2015 list of "most influential people in the analytical sciences" (by the Analytical Scientist)
2018 – Bijvoet Medal of the Bijvoet Center for Biomolecular Research of Utrecht University
2020 – Marcel Benoist Prize
References
1954 births
Living people
Members of the European Molecular Biology Organization
Swiss biologists
Systems biologists
Academic staff of ETH Zurich
Mass spectrometrists
Bijvoet Medal recipients
Thomson Medal recipients
Members of the German National Academy of Sciences Leopoldina | Ruedi Aebersold | [
"Physics",
"Chemistry"
] | 502 | [
"Biochemists",
"Mass spectrometry",
"Spectrum (physical sciences)",
"Mass spectrometrists"
] |
6,962,132 | https://en.wikipedia.org/wiki/Grotrian%20diagram | A Grotrian diagram, or term diagram, shows the allowed electronic transitions between the energy levels of atoms. They can be used for one-electron and multi-electron atoms. They take into account the specific selection rules related to changes in angular momentum of the electron. The diagrams are named after Walter Grotrian, who introduced them in his 1928 book Graphische Darstellung der Spektren von Atomen und Ionen mit ein, zwei und drei Valenzelektronen ("Graphical representation of the spectra of atoms and ions with one, two and three valence electrons").
See also
Jablonski diagram (for molecules)
References
External links
Hyperphysics: Atomic Energy Level Diagrams
Volumes with Grotrian diagrams of most elements
Atomic energy-level and Grotrian diagrams by Stanley Bashkin and John O. Stoner Jr.
Volume I: Hydrogen - Phosphorus
Volume I: Hydrogen - Phosphorus (Addenda)
Volume III
Volume IV
Grotrian diagrams
Electronic structure of atoms
NIST Atomic Spectra Database Lines Form
Grotrian Diagrams
Diagrams
Spectroscopy
Atomic physics
Photochemistry | Grotrian diagram | [
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"Astronomy"
] | 225 | [
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" molecular",
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"Molecular physics stubs",
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6,962,728 | https://en.wikipedia.org/wiki/Magnetic%20resonance%20elastography | Magnetic resonance elastography (MRE) is a form of elastography that specifically leverages MRI to quantify and subsequently map the mechanical properties (elasticity or stiffness) of soft tissue. First developed and described at Mayo Clinic by Muthupillai et al. in 1995, MRE has emerged as a powerful, non-invasive diagnostic tool, namely as an alternative to biopsy and serum tests for staging liver fibrosis.
Diseased tissue (e.g. a breast tumor) is often stiffer than the surrounding normal (fibroglandular) tissue, providing motivation to assess tissue stiffness. This principle of operation is the basis for the longstanding practice of palpation, which, however, is limited (except at surgery) to superficial organs and pathologies, and by its subjective, qualitative nature, depending on the skill and touch sensitivity of the practitioner. Conventional imaging techniques of CT, MRI, US, and nuclear medicine are unable to offer any insight on the elastic modulus of soft tissue. MRE, as a quantitative method of assessing tissue stiffness, provides reliable insight to visualize a variety of disease processes which affect tissue stiffness in the liver, brain, heart, pancreas, kidney, spleen, breast, uterus, prostate, and skeletal muscle.
MRE is conducted in three steps: first, a mechanical vibrator is used on the surface of the patient's body to generate shear waves that travel into the patient's deeper tissues; second, an MRI acquisition sequence measures the propagation and velocity of the waves; and finally this information is processed by an inversion algorithm to quantitatively infer and map tissue stiffness in 3-D. This stiffness map is called an elastogram, and is the final output of MRE, along with conventional 3-D MRI images as shown on the right.
Mechanics of soft tissue
MRE quantitatively determines the stiffness of biological tissues by measuring its mechanical response to an external stress. Specifically, MRE calculates the shear modulus of a tissue from its shear-wave displacement measurements. The elastic modulus quantifies the stiffness of a material, or how well it resists elastic deformation as a force is applied. For elastic materials, strain is directly proportional to stress within an elastic region. The elastic modulus is seen as the proportionality constant between stress and strain within this region. Unlike purely elastic materials, biological tissues are viscoelastic, meaning that it has characteristics of both elastic solids and viscous liquids. Their mechanical responses depend on the magnitude of the applied stress as well as the strain rate. The stress-strain curve for a viscoelastic material exhibits hysteresis. The area of the hysteresis loop represents the amount of energy lost as heat when a viscoelastic material undergoes an applied stress and is distorted. For these materials, the elastic modulus is complex and can be separated into two components: a storage modulus and a loss modulus. The storage modulus expresses the contribution from elastic solid behavior while the loss modulus expresses the contribution from viscous liquid behavior. Conversely, elastic materials exhibit a pure solid response. When a force is applied, these materials elastically store and release energy, which does not result in energy loss in the form of heat.
Yet, MRE and other elastography imaging techniques typically utilize a mechanical parameter estimation that assumes biological tissues to be linearly elastic and isotropic for simplicity purposes. The effective shear modulus can be expressed with the following equation:
where is the elastic modulus of the material and is the Poisson's ratio.
The Poisson's ratio for soft tissues is approximated to equal 0.5, resulting in the ratio between the elastic modulus and shear modulus to equal 3. This relationship can be used to estimate the stiffness of biological tissues based on the calculated shear modulus from shear-wave propagation measurements. A driver system produces and transmits acoustic waves set at a specific frequency (50–500 Hz) to the tissue sample. At these frequencies, the velocity of shear waves can be about 1–10 m/s. The effective shear modulus can be calculated from the shear wave velocity with the following:
where is the tissue density and is the shear wave velocity.
Recent studies have been focused on incorporating mechanical parameter estimations into post-processing inverse algorithms that account for the complex viscoelastic behavior of soft tissues. Creating new parameters could potentially increase the specificity of MRE measurements and diagnostic testing.
Applications
Liver
Liver fibrosis is a common condition arising in many liver diseases. Progression of fibrosis can lead to cirrhosis and end-stage liver disease. MRE-based measurement of liver stiffness has emerged as the most accurate non-invasive technique for detecting and staging liver fibrosis. MRE provides quantitative maps of tissue stiffness over large regions of the liver. Abnormally increased liver stiffness is a direct consequence of liver fibrosis. The diagnostic performance of MRE in assessing liver fibrosis has been established in multiple studies.
Liver MRE examinations are performed in MRI systems that have been equipped for the technique. Patients should fast for 3 to 4 hours prior to their MRE exam to allow for the most accurate measurement of liver stiffness. Patients lie supine in the MRI scanner for the examination. A special device is placed on the right side of the chest wall over the liver to apply gentle vibration which generates propagating shear waves in the liver. Imaging is for MRE is very quick, with data acquired in a series of 1-4 periods of breath-holding, each lasting 15–20 seconds.
A standardized approach for performing and analyzing liver MRE exams has been documented by the RSNA Quantitative Imaging Biomarkers Alliance. The technical success rate of Liver MRE is very high (95-100%)
Brain
MRE of the brain was first presented in the early 2000s. Elastogram measures have been correlated with memory tasks, fitness measures, and progression of various neurodegenerative conditions. For example, regional and global decreases in brain viscoelasticity have been observed in Alzheimer's disease and multiple sclerosis. It has been found that as the brain ages, it loses its viscoelastic integrity due to degeneration of neurons and oligodendrocytes. A recent study looked into both the isotropic and anisotropic stiffness in brain and found a correlation between the two and with age, particularly in gray matter.
MRE may also have applications for understanding the adolescent brain. Recently, it was found that adolescents have regional differences in brain viscoelasticity relative to adults.
MRE has also been applied to functional neuroimaging. Whereas functional magnetic resonance imaging (fMRI) infers brain activity by detecting relatively slow changes in blood flow, functional MRE is capable of detecting neuromechanical changes in the brain related to neuronal activity occurring on the 100-millisecond scale.
Kidney
MRE has also been applied to investigate the biomechanical properties of the kidney. The feasibility of clinical renal MRE was first reported in 2011 for healthy volunteers and in 2012 for renal transplant patients. Renal MRE is more challenging than MRE of larger organs such as the brain or liver due to fine mechanical features in the renal cortex and medulla as well as the acoustically shielded position of the kidneys within the abdominal cavity. To overcome these challenges, researchers have been looking at different passive drivers and imaging techniques to best deliver shear waves to the kidneys. Studies investigating renal diseases such as renal allograft dysfunction, lupus nephritis, immunoglobulin A nephropathy (IgAN), diabetic nephrology, renal tumors and chronic kidney disease demonstrate that kidney stiffness is sensitive to kidney function and renal perfusion.
Prostate
The prostate can also be examined by MRE, in particular for the detection and diagnosis of prostate cancer. To ensure good shear wave penetration in the prostate gland, different actuator systems were designed and evaluated. Preliminary results in patients with prostate cancer showed that changes in stiffness allowed differentiation of cancerous tissue from normal tissue. Magnetic Resonance Elastography has been successfully used in patients with prostate cancer showing high specificity and sensitivity in differentiating prostate cancer from benign prostatic diseases (see figure on right (b)). Even higher specificity of 95% for prostate cancer was achieved when Magnetic Resonance Elastography was combined with systematic image interpretation using PI-RADS (version 2.1).
Pancreas
The pancreas is one of the softest tissues in the abdomen. Given that pancreatic diseases including pancreatitis and pancreatic cancer significantly increase stiffness, MRE is a promising tool for diagnosing benign and malignant conditions of the pancreas. Abnormally high pancreatic stiffness was detected by MRE in patients with both acute and chronic pancreatitis. Pancreatic stiffness was also used to distinguish pancreatic malignancy from benign masses and to predict the occurrence of pancreatic fistula after pancreaticoenteric anastomosis. Quantification of the volume of pancreatic tumors based on tomoelastographic measurement of stiffness was found to be excellently correlated with tumor volumes estimated by contrast-enhanced computed tomography. In patients with pancreatic ductal adenocarcinoma stiffness was found to be elevated in the tumor as well as in pancreatic parenchyma distal to the tumor, suggesting heterogeneous pancreatic involvement (figure on right (c)).
See also
Strain–encoded magnetic resonance imaging
Tomoelastography
References
Medical imaging
Magnetic resonance imaging | Magnetic resonance elastography | [
"Chemistry"
] | 1,996 | [
"Nuclear magnetic resonance",
"Magnetic resonance imaging"
] |
6,963,544 | https://en.wikipedia.org/wiki/Apple%20TV | Apple TV (stylised tv) is a digital media player and microconsole developed and marketed by Apple. It is a small piece of networking hardware that sends received media data such as video and audio to a TV or external display. Its media services include streaming media, TV Everywhere–based services, local media sources, and sports journalism and broadcasts.
Second-generation and later models function only when connected via HDMI to an enhanced-definition or high-definition widescreen television. Since the fourth-generation model, Apple TV runs tvOS with multiple pre-installed apps. In November 2019, Apple released Apple TV+ and the Apple TV app.
Apple TV lacks integrated controls and can only be controlled remotely, through a Siri Remote, iPhone or iPad, Apple Remote, or third-party infrared remotes complying with the fourth generation Consumer Electronics Control standard.
Background
Before the Apple TV, Apple made a number of attempts to create TV-based devices: In 1993, Apple released the Macintosh TV in an attempt to enter the home-entertainment industry. The device had a 14-inch CRT screen and a TV tuner card. It was not a commercial success, with only 10,000 sold before its discontinuation in 1994. That year, the company developed the Apple Interactive Television Box, a collaboration with BT Group and Proximus Group that was never released to the public. Apple's final major attempt before the Apple TV was the Apple Pippin in 1990s, a combination home game console and networked computer.
Models
First generation
At a September 2006 Apple special event, Apple announced the first-generation Apple TV. It was originally announced as "iTV" to fit into their "i"-based product naming convention, but was renamed "Apple TV" before launch due to a trademark dispute with British broadcasting network ITV, which threatened legal action against Apple. Pre-orders began in January 2007 and it was released in March 2007. It is based on a Pentium M processor and ran a variant of Mac OS X Tiger, and included a 40 GB hard disk for storing content. It supported output up to 720p on HDTVs via HDMI, and supported some standard definition televisions via component video. At launch, Apple TV required a Mac or Windows-based PC running iTunes on the same network to sync or stream content to it.
A model with a 160 GB hard drive was released in May 2007. The 40 GB version was discontinued in September 2009. In January 2008, it became a stand-alone device through a software update, which removed the requirement of iTunes syncing from separate computer, and allowed for media from services such as iTunes Store, MobileMe, and Flickr to be rented or purchased directly on the Apple TV.
In July 2008, Apple released the software 2.1 update which added external recognition of iPhones and iPod Touches as alternative remote control devices to the Apple Remote. In September 2015, Apple discontinued iTunes support for the first-generation Apple TV, with accessibility being obstructed from such devices due to obsolete security standards.
The first generation Apple TV can be modified into a makeshift Intel Mac Mini, with a USB boot disk image being available online, and an install to the inbuilt hard drive possible by flashing the image to the hard drive through the USB booted disk. The device is not easily used unless a USB hub is installed, due to it only having one USB port.
The first generation Apple TV has a 1 GHz Intel Pentium M CPU, and 256 MB of RAM. Neither the CPU or RAM can be upgraded without soldering, as both are soldered onto the motherboard. The device has one HDMI interface, one USB port, one 10/100 base T Ethernet port, and a Component video interface. Due to its thermal management design utilizing the upper case as a passive heat sink, the device gets warm when in use. A fan is used to cool the case, but it does not reach the CPU and is instead installed to cool the hard drive and installed power supply.
Second generation
Apple released the second-generation Apple TV in September 2010. Based on the ARM-based Apple A4 chip
instead of an Intel x86 processor, it runs a variant of iOS. It is housed in a black enclosure and is one-quarter the size of the first-generation model. The device has 8 GB of flash storage for buffering, replacing the internal hard drive in the first-generation model. It supports output up to 720p via HDMI and does not support standard definition televisions.
In conjunction with its release, Apple renamed AirTunes to AirPlay, with support for streaming video from iPhones, iPads, and Macs to Apple TV.
Third generation
At a March 2012 Apple special event, Apple announced the third-generation Apple TV. Externally identical to its predecessor, it includes an A5 chip with one core deactivated and supports 1080p video output. It also allows remote access to HomeKit devices.
Apple quietly released a "rev A" of the hardware in March 2013. It uses a single-core variant of the A5 chip and draws less power than the original third-generation model. Despite Apple's promise before the revision's launch that "the component changes... don't affect product features", in September 2014, Apple TV Software 7.0 introduced peer-to-peer AirPlay exclusively for the rev A model.
The third-generation Apple TV was discontinued in October 2016. In December 2017, Apple added support for Amazon Prime Video. The Apple TV app, bundled with Apple TV Software 7.3, was released in May 2019.
HD (originally fourth generation)
On September 9, 2015, Apple announced the fourth-generation Apple TV at an Apple special event. The fourth-generation model uses a new operating system, tvOS, with an app store, allowing downloads of third-party apps for video, audio, games and other content. It uses a 64-bit Apple A8 chip, and adds support for Dolby Digital Plus audio. It is taller but otherwise resembles the second- and third-generation models. The remote replaced the arrow button with swipe-to-select features, Siri support, a built-in microphone, volume control over HDMI CEC and IR, and an accelerometer (IMU).
Upon release, the third-party apps were available from a limited range of providers, with new APIs providing opportunities for more apps. New apps and games were initially required to interface with the new touchpad-enabled Siri remote, a requirement later relaxed for games.
The fourth-generation Apple TV started shipping in October 2015. Several unexpected problems, such as incompatibility with iTunes Remote app for iOS and watchOS, were fixed by Apple in tvOS 9.1 on December 8, 2015.
On September 13, 2016, Apple released tvOS 10, bringing an updated remote app, single-sign on, and light-on-dark color scheme. tvOS 10 also introduced HomeKit support and allows it to function as a home hub, supporting controlling appliances remotely, granting guest access, and setting up automations.
After newer 4K versions of the Apple TV were released, Apple continued to sell the fourth-generation model as an entry-level option, rebranding it as the Apple TV HD in March 2019. On October 18, 2022, the Apple TV HD was discontinued after seven years on the market after the release of the 4K third-generation model.
4K (first generation)
At an Apple special event on September 12, 2017, Apple announced the Apple TV 4K, which supports 2160p output, HDR10, Dolby Vision, and includes a faster Apple A10X chip supporting HEVC hardware decoding. Dolby Atmos support was added in tvOS 12. Following the announcement of the new models, the 64 GB version of the Apple TV HD was discontinued. Changes to the 4th-generation case include the addition of vents on the base, the removal of the USB-C port, and the addition of a tactile white ring around the Menu button on the included Siri Remote.
4K (second generation)
On April 20, 2021, Apple announced an updated Apple TV 4K with the A12 Bionic chip, support for high frame rate HDR, HDMI 2.1, and Wi-Fi 6. Its HDMI port supports ARC and eARC, which allows other sources plugged into the television to output audio through Apple TV, including to AirPlay speakers like HomePod. Like the HomePod mini, it has a Thread radio. It can pair with the ambient light sensor on iPhones with Face ID to optimize its color output, a feature that was also extended to older Apple TVs with tvOS 14.5. AirPlay supports high frame rate HDR playback, allowing videos shot on the iPhone 12 Pro in Dolby Vision 4K 60fps to be mirrored in full resolution. Following the announcement, the previous Apple TV 4K with an A10X chip was discontinued. tvOS 17 added FaceTime and support for Continuity Camera with a paired iPhone or iPad.
The model also comes with a thicker, redesigned Siri Remote with a circular touchpad with navigational buttons, as well as power and mute buttons. The remote does not include an accelerometer and gyroscope, which were present in the previous Siri Remote, making it incompatible with some games. The remote is compatible with previous generation tvOS-based Apple TVs and ships with an updated SKU of the Apple TV HD.
4K (third generation)
On October 18, 2022, Apple announced an updated Apple TV 4K with the A15 Bionic chip with a 5-core CPU (one high efficiency core disabled) and 5-core GPU, support for HDR10+, reduced weight and dimensions, and removed the "TV" text from the top of the unit, leaving only the Apple logo. It comes in two configurations, a Wi-Fi-only model with 64 GB of storage, and a more expensive 128 GB model with Wi-Fi, Ethernet and a Thread radio. The included Siri Remote charges via USB-C instead of Lightning.
This version is compatible with HDMI 2.1 QMS that allows a change of refresh rate without having a blank screen interruption.
Features
Apple TV allows consumers to use an HDTV with any Apple TV or a UHDTV with Apple TV 4K or later, to stream video, music, and podcasts as well as downloading apps and games from the tvOS App Store. The first, second, and third generations offered limited content which Apple had provisioned to work with Apple TV. These have now been discontinued in favor of the fourth generation Apple TV, with an OS based on iOS called tvOS which lets developers create their own apps with their own interface that run on Apple TV. These include multimedia, music apps, and games.
Features of Apple TV include:
Video streaming
Users of Apple TV can rent or buy movies and TV shows from the iTunes Store, or stream video from a variety of services found in the tvOS App Store.
Users can stream live and on-demand content from apps that support login through a cable provider by way of one universal app also called Apple TV. The single-sign on feature in tvOS 10.1 and later allows users to log in to all of these apps at once, bypassing the need to authenticate each individually.
Music and Podcasts streaming
Users can access their music and podcasts libraries that they purchased in iTunes through iCloud through the Music and Podcasts apps, respectively. In addition, users can also subscribe to music streaming services and access content that way.
Photos
The built in Photos app syncs user photos from iCloud Photo Library and displays them on TV. In addition, users can download third-party apps like Adobe Lightroom to view, edit and share them.
Apps and games
With the fourth generation Apple TV and later, users can download apps and games from the tvOS App Store. This app store is similar to the one found on the Apple iPhone and iPad.
Apps can now be ported from iOS easily by developers since tvOS and iOS share a common codebase and kernel.
Examples include the Papa John's and Grubhub apps which allows for users to order food right from Apple TV and Zillow which allows users to search for homes right on their TV. A NASA app for Apple TV includes live streaming of NASA TV content, including International Space Station missions.
Games use the Accelerometer and Gyroscope along with the touchpad found on the Siri Remote for control. External Bluetooth game controllers can also be paired.
Examples include Asphalt 8, which can be played using the Siri Remote.
Casting and mirroring
With AirPlay, users can stream or mirror content wirelessly from an iOS device or Mac. AirPlay can be accessed by swiping up from the bottom of the screen (swipe down from top right on newer models) in Control Center on iOS or in the Menu Bar on a Mac. Its functions include:
Casting, which allows users to wirelessly send video or audio from their iPhone, iPad, or Mac to the Apple TV.
Mirroring, which allows users to wirelessly mirror their Mac screen or AirPlay device which to the TV, using it as a second monitor.
Peer-to-Peer AirPlay, which uses Bluetooth to connect if the Apple TV and the iOS Device/Mac are not on the same Wi-Fi network.
Siri
Siri is built into the fourth generation and later Apple TV. It enables voice dictation in text fields, including usernames and passwords.
Universal search is available for a wide number of apps in the United States, but the feature is limited to iTunes and Netflix in Canada, France, Germany, and the United Kingdom. In Australia, universal search supports movies and TV shows in iTunes, Netflix, and Stan. Apple has been expanding the feature to encompass additional channels worldwide.
A Live Tune-In feature that allows the viewer to ask Siri to tune to live streams.
HomeKit
The third-generation Apple TV and later can also be used as a home hub to control HomeKit devices, such as locks, thermostats, or garage doors either locally or over the Internet. HomeKit Automation, such as automatic implementation of scenes, multiple user support, and using Siri to control devices, and remote access for shared users or HomeKit-enabled cameras is only possible with a fourth generation Apple TV or later.
General
HDMI CEC to control other devices in a user's home theater setup.
App Switcher which enables users to switch apps.
Aerial Screensaver which allows the TV to display a flyover view of a city when Apple TV is inactive. Screensavers can also be invoked from the home screen by pressing menu on the Siri Remote once.
App Store
With the fourth-generation Apple TV (Apple TV HD) and tvOS, Apple announced an App Store which allows any developer to make apps, using the APIs available specifically tailored towards the TV. Also, since tvOS is based on iOS, any developer can port over apps from iOS and with a few modifications, as Apple stated on stage, and can make them available for all tvOS users with the App Store. The App Store is not available to previous Apple TVs and is a feature of the fourth generation Apple TV onward.
Accessibility
Since tvOS and watchOS are based on iOS, they have inherited many of the accessibility features of iOS and macOS and are compatible with Apple's entire product line including the Apple Watch as a remote controller for the Apple TV. tvOS includes the Apple technologies of VoiceOver, Zoom, and Siri to help the blind and those with low vision. Pairing a Wireless keyboard with the tvOS on the Apple TV enables another accessibility feature that also is an incorporation of VoiceOver. When typing, VoiceOver mirrors with an audio voice, each character pressed on the keyboard and repeated again when it is entered. The Apple TV is designed to work with the Apple Wireless Keyboard or the Apple Magic Keyboard.
Apple TV with and without tvOS supports closed captioning, so the deaf or hard of hearing can properly watch TV episodes and feature-length movies. Compatible episodes and movies are denoted with a CC (closed captioning) or SDH (Descriptive Audio) icon in the iTunes Store either on the Apple TV or in iTunes itself. The viewer can customize the captions in episodes or movies with styles and fonts that are more conducive to their hearing and/or visual impairment. Apple's Remote app on iOS devices allows control of the Apple TV from an iPhone, iPad or iPod Touch.
Restrictions
Similar to Google's redesign of YouTube, Apple has restricted access to most viewed charts on movies and podcasts. They are replaced by "Top Movies", "Top Podcasts", and "Editor's Picks". Parental controls allow consumers to limit access to Internet media service content via "Restrictions" settings; individual services can be turned off (e.g., to reduce clutter), icons can be rearranged via the tap-and-hold technique à la iOS. Internet media is split into four categories: "Internet Photos", "YouTube", "Podcasts", and "Purchase and Rental". Each of the categories is configured by a parental control of "Show", "Hide" or "Ask" to prompt for a 4-digit PIN. In addition, movies, TV shows, music and podcasts can be restricted by rating.
Local sources
Apple TV allows users on a computer running iTunes to sync or stream photos, music and videos. A user can connect a computer on a local network to maintain a central home media library of digitized CD, DVD or HD content, provide direct connectivity to photo organization software such as iPhoto, limit home video access to a local network only, play Internet radio, or preload content on Apple TV to be used later as a non-networked video player. For users who wish to connect the Apple TV to a computer, synchronization and streaming modes are supported. Apple TV in synchronization mode works in a way similar to the iPod. It is paired with an iTunes library on a single computer and can synchronize with that library, copying all or selected content to its own storage. Apple TV need not remain connected to the network after syncing. Photos can be synced from iPhoto, Aperture, or from a folder on a Mac, or Adobe Photoshop Album, Adobe Photoshop, or from a hard disk folder in Windows.
Apple TV can also function as a peer-to-peer digital media player, streaming content from iTunes libraries and playing the content over the network. First-generation Apple TVs can stream content from up to five computers or iTunes libraries. Also, five Apple TVs can be linked to the same iTunes library. The second-generation Apple TV onwards allows users to stream content from more than one iTunes library: these additional iTunes libraries can be on the same or on different computers. This is possible when Apple TV and every iTunes library from which you want to stream content meet all of the following conditions: (1) the Apple TV and the iTunes library you are streaming from are both on the same local network, (2) each uses the iTunes "Home Sharing" feature, and (3) each are using the same "Home Sharing" Apple ID. Apple TV HD and newer can also stream content locally using third-party apps such as Plex, Kodi, VLC media player, Emby and MrMC.
Supported formats
Apple TV natively supports the following audio, video, and picture formats (although with the Apple TV HD and later, apps may use alternative built-in software in order to play other codecs and formats, e.g. Emby, MrMC, VLC media player, Kodi and Plex):
Attempts to sync unsupported content to Apple TV will draw an error message from iTunes. The first- and second-generation Apple TV video output can be set to either 1080i or 1080p; however, this resolution is limited to the user interface and the viewing of photographs – all other content is simply upscaled to those resolutions. Those models cannot play 1080i or 1080p video content (e.g., HD camera video). The third- and fourth-generation Apple TV support 1080p video content. The Apple TV 4K, as the name suggests, supports 4K resolutions and HDR, including Dolby Vision. 4K content from sources such as iTunes can be played on a compatible 4K television set.
Apple offers AVC 1080p movies and video podcasts on iTunes. In comparison, Blu-ray films are 1080p H.264 or VC-1 video encoded at rates of up to 40 Mbit/s. Apple TV's audio chip supports 7.1 surround sound, and some high definition rentals from iTunes are offered with Dolby Digital 5.1 surround sound. There is an Apple TV export option in QuickTime which allows content in some formats that the device does not support to be easily re-encoded. Applications that use QuickTime to export media can use this; e.g., iMovie's Share menu, iTunes' advanced menu, and some third-party content conversion tools.
Connectivity
Apple TV streams video through an HDMI cable (Type A) connected to the TV's HDMI port. Audio is supported through the optical or HDMI ports. The device also has a Micro-USB port, which is reserved for service and diagnostics. The device connects through Ethernet or Wi-Fi to the computer for digital content from the Internet and local networks. Apple TV does not come with audio, video or other cables, which must be acquired additionally as required. On the previous Apple TV, media files could be transferred directly onto the device by syncing with another computer. Once content was stored on the device's hard drive, Internet connectivity was no longer needed to view content. This is not the case with the later models, which do not have a hard drive for storing media.
The first-generation Apple TV had component video and RCA connector audio ports, both removed in the 2nd generation. The device does not have RCA/composite video or F/RF connectors, but can be tricked into outputting color via composite. Starting with the Apple TV HD, Apple removed the optical audio port. Apple also enhanced the HDMI port by adding support for HDMI. The 4th generation also removed the USB hardware port in favor of the reversible USB-C port and the 5th generation removed USB entirely.
AirPlay
AirPlay allows iOS devices or an AirPort-enabled computer with the iTunes music player to send a stream of music to multiple (three to six, in typical conditions) stereos connected to an AirPort Express (the audio-only antecedent of Apple TV) or Apple TV. The AirPort Express' streaming media capabilities use Apple's Remote Audio Output Protocol (RAOP), a proprietary variant of RTSP/RTP. Using WDS-bridging, the AirPort Express can allow AirPlay functionality (as well as Internet access, file and print sharing, etc.) across a larger distance in a mixed environment of wired and up to 10 wireless clients. Speakers attached to an AirPort Express or Apple TV can be selected from within the "Remote" iPhone/iPod Touch program, allowing full AirPlay compatibility (see "Remote control" section below). A compatible Mac running OS X Mountain Lion or later can wirelessly mirror its screen to an Apple TV through AirPlay Mirroring while one running OS X Mavericks or later can also extend its display with AirPlay Display.
Remote control
Apple TV can be controlled by many infrared remote controls or paired with the included Apple Remote to prevent interference from other remotes. Either kind of remote can control playback volume, but for music only. The Apple Wireless Keyboard is supported on the second-generation Apple TV and later using the built-in Bluetooth. The consumer has the ability to control media playback, navigate menus and input text and other information. Third-party keyboards that use the Apple layout may also be compatible. On July 10, 2008, Apple released ITunes Remote, a free iOS application that allows the iPhone, iPod Touch, and iPad to control the iTunes library on the Apple TV via Wi-Fi. The Apple Watch also has a remote app to control Apple TV. The Remote App was updated on September 13, 2016, to take advantage of all the features of the Apple TV 4. This includes Siri, Touchpad, and Home Buttons, along with a now playing screen.
On September 9, 2015, Apple announced the new Siri Remote for the fourth-generation Apple TV (Apple TV HD) (although in some territories, Apple have kept the name Apple TV Remote, due to Siri functionality not being enabled on it in that territory). It is a completely redesigned remote that features dual microphones for Siri support and a glass touch surface for navigation around the interface by swiping or tapping and scrubbing to fast forward or rewind. Also, it has a menu and home button, a Siri button to invoke Siri, a Play/Pause button, and a Volume Up/Down button to control the volume on the TV. The Siri Remote communicates with the Apple TV via Bluetooth rather than infrared, removing the requirement of a line-of-sight with the device. This new remote is only supported by the Apple TV HD and later and will not work with earlier generations.
Siri
Beginning with the Apple TV HD, the remote includes two microphones and a button to activate Siri. Siri on the Apple TV has all of the functions of Siri on iOS 9; it can also respond to requests specifically for the TV. For instance, the viewer can ask Siri to search for a TV show or movie and it will search across multiple different sources to tell the user where the content is available to watch. It can also do things such as Play/Pause, Rewind/Fast Forward, skip back 15 seconds and temporarily turn on captioning when asked "what did he say?" or "what did she say?", open a specific app, and more.
Software
First generation
The original Apple TV ran a modified build of Mac OS X v10.4 Tiger.
Apple TV Software 1.0
Apple TV software 1.0 presented the user with an interface similar to that of Front Row. Like Front Row on the Mac, it presents the user with seven options for consuming content. Movies, TV Shows, Music, Podcasts, Photos, Settings, and Sources. It was a modified version of OS x v10.4 Tiger.
Apple TV Software 2.0
In February 2008, Apple released a major and free upgrade to the Apple TV, labelled "Take Two" (2.0). This update did away with Front Row and introduced a new interface in which content was organized into six categories, all of which appeared in a large square box on the screen upon startup (movies, TV shows, music, YouTube, podcasts, and photos) and presented in the initial menu, along with a "Settings" option for configuration, including software updates.
Apple TV Software 3.0
In October 2009, Apple released a minor upgrade for the Apple TV called "Apple TV Software 3.0". This update replaced the interface in version 2.0 with a new interface which presented seven horizontal columns across the top of the screen for the different categories of content (Movies, TV Shows, Music, Podcasts, Photos, Internet, and Settings). This update also added features such as content filtering, iTunes Extras, new fonts, and a new Internet radio app. One new feature in particular was the 'Genius' playlist option allowing for easier and more user friendly playlist creating.
Second and third generation
The 2nd and 3rd generation Apple TVs run a version of iOS, rather than the modified Mac OS X of the original model. The interface on Apple TV Software 4 is similar to that of previous versions, with only minor changes and feature additions throughout. In March 2012, Apple released a major new software update, with the Apple TV 3rd generation, labeled as Apple TV Software 5 (iOS 5.1), which shipped with the new 3rd generation Apple TV. This update completely revised the look of the home screen to make it resemble the icon grid seen on iOS. Instead of 7 columns, content and third-party channels are shown in a tiled grid format, which can be rearranged. Throughout the years, for Apple TV Software 5–6, Apple released minor revisions, content additions, and feature updates.
The Apple TV Software 7.0 features a flat look similar to iOS 7 and OS X Yosemite and adds features such as Peer-To-Peer AirPlay. Version 8.0 was skipped. Apple TV Software 7.2.2 (iOS 8) is currently available for the Apple TV (3rd generation), as of March 2019. It does not support tvOS 9.0 or later. However, it does support Amazon Video, which was automatically added to those Apple TVs running 7.2.2 on December 6, 2017. In May 2019 Apple TV Software 7.3 (iOS 8.4.2) was released to the public. This update was the first update for the 3rd generation Apple TV since 2016. This update adds the new Apple TV app to the home screen. The Apple TV app brings compatibility to the Apple TV Channels service. This update also fixes some security flaws found in Apple TV Software 7.2.2 and earlier. On September 24, 2019, Apple TV Software 7.4 (iOS 8.4.3) was released to the public. On March 24, 2020, Apple TV Software 7.5 (iOS 8.4.4) was released to the public.
HD and 4K
The Apple TV HD and later run an operating system called tvOS which does not support the earlier generations of Apple TV. It features an app store, allowing third-party app developers to release their own apps on the platform. The new software also features support for Siri voice control. The tvOS software development kit (SDK) for developing tvOS apps is included in Xcode 7.1 and later. A new development feature, App Thinning, is used in the Apple TV, running on tvOS, due to the storage restrictions of the device (as little as 32 GB) and the dual-use of the NAND Flash Memory to precache movies from Apple's content servers as well as storage for downloaded applications from the tvOS App Store. Apple's aim is to limit the size of application downloads and steering users toward downloading individual segments of apps in order to better manage storage space. Developers have reacted with criticism toward the download size limits, arguing that it leads to situations where game data is purged and has to be re-downloaded.
Technical specifications
Limitations
Functionality
Apple TV contains neither a TV tuner nor a personal video recorder. Both capabilities can be applied to the connected home computer through various third-party products, such as allowing PVR software to connect to iTunes and enable scheduled HDTV recordings to play automatically via Apple TV for playback. Apple TV HD and newer can be linked with Wi-Fi-based tuners such as HDHomeRun.
The Front Row interface lacks some iTunes functionality, including rating items, checking the account balance, adding funds to the account, synchronizing from more than one computer, full Internet radio support, and games.
The Movies search box only searches the iTunes Store, not local hard drives and networks.
Movies rented on Apple TV must be watched on Apple TV, unlike iTunes rentals, which can be transferred to any video-enabled iPod, iPhone, or Apple TV. Movies purchased on Apple TV can be moved to a video-enabled iPod or iPhone via iTunes.
Apple TV prior to 4th generation (Apple TV HD) did not support the HDMI Consumer Electronics Control (HDMI CEC) protocol.
On the Apple TV (2nd generation), digital output audio is up-sampled to 48 kHz, including lossless CD rips at 44.1 kHz. Although this is a higher frequency and the difference is not audible, it is seen by some as falling short of digital transmission of data standards due to the audio not being 'bit perfect'.
Sales
1st generation
Within the first week of presales in January 2007, Apple TV was the top pre-selling item at the Apple Store. Orders exceeded 100,000 units by the end of January and Apple began ramping-up to sell over a million units before the 2007 holiday season. Analysts began calling it a "DVD killer" that could enable multiple services. Analysts also predicted that Apple could sell up to 1.5 million units in the first year. Besides the Apple Store, Best Buy was one of the first retailers to carry the device; Target and Costco followed shortly thereafter.
Two months into sales, Forrester Research predicted at the time that Apple would only sell a million Apple TV units, because consumers prefer advertisement-supported content over paid content. Forrester predicted that cable companies would be the clear winners over content providers such as the iTunes Store. Shortly after, Apple released YouTube functionality and Jobs stated that Apple TV was a "DVD player for the Internet". Some market analysts predicted that YouTube on Apple TV "provides a glimpse of this product's potential and its future evolution", but overall, analysts had mixed reactions regarding the future of Apple TV. Some negative reactions followed after Jobs referred to the device as a "hobby", implying it was less significant than the Macintosh, iPod, and iPhone.
In the fourth quarter of 2008, sales were triple that of the fourth quarter of 2007.
In Apple's first-quarter 2009 financial results conference call, acting chief executive Tim Cook stated that Apple TV sales increased three times over the same quarter a year ago. Cook mentioned that the movie rental business was working well for Apple, Apple would continue investment in movie rentals and Apple TV, but Apple TV is still considered a hobby for the company. Due to the growth of digital TV and consumers turning to Internet media services, an analyst at the time predicted sales of 6.6 million Apple TVs by the end of 2009.
2nd generation
The second generation sold 250,000 units in the first two weeks it was available. On December 21, 2010, Apple announced that they had sold 1 million units. In the second fiscal quarter of 2011, it had topped 2 million in total sales, with 820,000 sold in that quarter alone.
On January 24, 2012, Apple announced they had sold 1.4 million units in the first fiscal quarter of 2012, and 2.8 million units in all of fiscal year 2011. (4.2 million units through January 1, 2012).
3rd generation
Tim Cook announced at the All Things Digital conference in May 2012 that Apple had sold 2.7 million of the 3rd generation model in 2012.
In the Q4 FY2012 earnings call, Engadget reported comments from Tim Cook that Apple had shipped 1.3 million Apple TV units in the 4th Quarter (presumed to be 3rd generation).
MacObserver reported statements by Tim Cook in the Q1 FY2013 earnings call that Apple sold over 2 million Apple TV units in the December Quarter (presumed to be 3rd generation).
These reports lead to a cumulative volume of the 3rd generation device of 6 million units, as of January 1, 2013.
On February 28, 2014, at Apple's shareholders meeting, Apple CEO Tim Cook announced that in 2013 Apple TV brought in 1 billion dollars of revenue for Apple.
A market survey published by Parks Associates in December 2014 found that Apple TV has lost consumer traction to Google Chromecast, garnering only a 17% market share.
Tim Cook announced at the Apple Special Event on March 9, 2015, that Apple had sold a total of 25 million Apple TVs up to that point.
HD, 4K and later
During an Apple earnings call on January 27, 2016, CEO Tim Cook stated that the Apple TV had record sales, although further details were not provided. In June 2019 it was estimated that there are 53 million units of all generations in use worldwide.
In 2019, Apple analyst John Gruber stated the Apple TV sells at a low profit margin or a loss, saying units are effectively sold at cost.
See also
Comparison of digital media players
Mac Mini, which originally featured the Front Row application, a similar remote 10-foot user interface as the Apple TV
References
Footnotes
External links
– official site
2007 establishments in the United States
Apple Inc. hardware
Computer-related introductions in 2007
Digital media players
ITunes
Products introduced in 2007
Smart TV
Television technology | Apple TV | [
"Technology"
] | 7,533 | [
"Information and communications technology",
"Multimedia",
"Television technology",
"Smart TV"
] |
6,964,629 | https://en.wikipedia.org/wiki/Interaction%20information | In probability theory and information theory, the interaction information is a generalization of the mutual information for more than two variables.
There are many names for interaction information, including amount of information, information correlation, co-information, and simply mutual information. Interaction information expresses the amount of information (redundancy or synergy) bound up in a set of variables, beyond that which is present in any subset of those variables. Unlike the mutual information, the interaction information can be either positive or negative. These functions, their negativity and minima have a direct interpretation in algebraic topology.
Definition
The conditional mutual information can be used to inductively define the interaction information for any finite number of variables as follows:
where
Some authors define the interaction information differently, by swapping the two terms being subtracted in the preceding equation. This has the effect of reversing the sign for an odd number of variables.
For three variables , the interaction information is given by
where is the mutual information between variables and , and is the conditional mutual information between variables and given . The interaction information is symmetric, so it does not matter which variable is conditioned on. This is easy to see when the interaction information is written in terms of entropy and joint entropy, as follows:
In general, for the set of variables , the interaction information can be written in the following form (compare with Kirkwood approximation):
For three variables, the interaction information measures the influence of a variable on the amount of information shared between and . Because the term can be larger than , the interaction information can be negative as well as positive. This will happen, for example, when and are independent but not conditionally independent given . Positive interaction information indicates that variable inhibits (i.e., accounts for or explains some of) the correlation between and , whereas negative interaction information indicates that variable facilitates or enhances the correlation.
Properties
Interaction information is bounded. In the three variable case, it is bounded by
If three variables form a Markov chain , then , but . Therefore
Examples
Positive interaction information
Positive interaction information seems much more natural than negative interaction information in the sense that such explanatory effects are typical of common-cause structures. For example, clouds cause rain and also block the sun; therefore, the correlation between rain and darkness is partly accounted for by the presence of clouds, . The result is positive interaction information .
Negative interaction information
A car's engine can fail to start due to either a dead battery or a blocked fuel pump. Ordinarily, we assume that battery death and fuel pump blockage are independent events, . But knowing that the car fails to start, if an inspection shows the battery to be in good health, we can conclude that the fuel pump must be blocked. Therefore , and the result is negative interaction information.
Difficulty of interpretation
The possible negativity of interaction information can be the source of some confusion. Many authors have taken zero interaction information as a sign that three or more random variables do not interact, but this interpretation is wrong.
To see how difficult interpretation can be, consider a set of eight independent binary variables . Agglomerate these variables as follows:
Because the 's overlap each other (are redundant) on the three binary variables , we would expect the interaction information to equal bits, which it does. However, consider now the agglomerated variables
These are the same variables as before with the addition of . However, in this case is actually equal to bit, indicating less redundancy. This is correct in the sense that
but it remains difficult to interpret.
Uses
Jakulin and Bratko (2003b) provide a machine learning algorithm which uses interaction information.
Killian, Kravitz and Gilson (2007) use mutual information expansion to extract entropy estimates from molecular simulations.
LeVine and Weinstein (2014) use interaction information and other N-body information measures to quantify allosteric couplings in molecular simulations.
Moore et al. (2006), Chanda P, Zhang A, Brazeau D, Sucheston L, Freudenheim JL, Ambrosone C, Ramanathan M. (2007) and Chanda P, Sucheston L, Zhang A, Brazeau D, Freudenheim JL, Ambrosone C, Ramanathan M. (2008) demonstrate the use of interaction information for analyzing gene-gene and gene-environmental interactions associated with complex diseases.
Pandey and Sarkar (2017) use interaction information in Cosmology to study the influence of large-scale environments on galaxy properties.
A python package for computing all multivariate interaction or mutual informations, conditional mutual information, joint entropies, total correlations, information distance in a dataset of n variables is available .
See also
Mutual information
Total correlation
Dual total correlation
Partial Information Decomposition
References
Bell, A J (2003), The co-information lattice
Fano, R M (1961), Transmission of Information: A Statistical Theory of Communications, MIT Press, Cambridge, MA.
Garner W R (1962). Uncertainty and Structure as Psychological Concepts, JohnWiley & Sons, New York.
Hu Kuo Tin (1962), On the Amount of Information. Theory Probab. Appl.,7(4), 439-44. PDF
Jakulin A & Bratko I (2003a). Analyzing Attribute Dependencies, in N Lavra\quad{c}, D Gamberger, L Todorovski & H Blockeel, eds, Proceedings of the 7th European Conference on Principles and Practice of Knowledge Discovery in Databases, Springer, Cavtat-Dubrovnik, Croatia, pp. 229–240.
Jakulin A & Bratko I (2003b). Quantifying and visualizing attribute interactions .
Moore JH, Gilbert JC, Tsai CT, Chiang FT, Holden T, Barney N, White BC (2006). A flexible computational framework for detecting, characterizing, and interpreting statistical patterns of epistasis in genetic studies of human disease susceptibility, Journal of Theoretical Biology 241, 252-261.
Nemenman I (2004). Information theory, multivariate dependence, and genetic network inference .
Pearl, J (1988), Probabilistic Reasoning in Intelligent Systems: Networks of Plausible Inference, Morgan Kaufmann, San Mateo, CA.
Tsujishita, T (1995), On triple mutual information, Advances in applied mathematics 16, 269-274.
LeVine MV, Weinstein H (2014), NbIT - A New Information Theory-Based Analysis of Allosteric Mechanisms Reveals Residues that Underlie Function in the Leucine Transporter LeuT. PLoS Computational Biology.
https://www3.nd.edu/~jnl/ee80653/Fall2005/tutorials/sunil.pdf
Yeung R W (1992). A new outlook on Shannon's information measures. in IEEE Transactions on Information Theory.
Information theory | Interaction information | [
"Mathematics",
"Technology",
"Engineering"
] | 1,427 | [
"Telecommunications engineering",
"Applied mathematics",
"Computer science",
"Information theory"
] |
6,964,723 | https://en.wikipedia.org/wiki/Overexcitability | Overexcitability is a term introduced to current psychology by Kazimierz Dąbrowski as part of his theory of positive disintegration (TPD). Overexcitability is a rough translation of the Polish word 'nadpobudliwość', which is more accurately translated as 'superstimulatability' in English. “The prefix over attached to ‘excitability’ serves to indicate that the reactions of excitation are over and above average in intensity, duration and frequency."
In his book Positive Disintegration, Dąbrowski uses the terms "hyperexcitability", "increased excitability", "overexcitability" and simply "excitability". He uses these terms interchangeably with nervousness.
Dąbrowski introduces these terms to describe a heightened physiological experience of stimuli resulting from increased neuronal sensitivities. He describes those who have hyperexcitability as showing "strength and perseveration of reactions incommensurate to their stimuli." Michael Piechowski noted that Dąbrowski used the term psychic overexcitability to "underline the enhancement and intensification of mental activity much beyond the ordinary".
Five forms
There are five forms of overexcitability. These five forms are psychomotor, sensual, emotional, imaginational and intellectual.
Psychomotor: OE is a heightened excitability of the neuromuscular system. This manifests itself in a capacity for being active and energetic, a love of movement, a surplus of energy and an actual need for physical action.
Sensual: OE is an intensified experience of any type of sensual pleasure or displeasure emanating from one of the five senses, i.e. sight, smell, touch, taste, and hearing. It manifests as an increased appreciation of aesthetic pleasure such as music, language, and art, and delight from tastes, smells, textures, sounds, and sights. Conversely, extreme pain and disgust are experienced upon exposure to sensations perceived as unpleasant.
Intellectual: OE manifests itself as an extreme desire to seek understanding and truth, to gain knowledge, and to analyse and categorise information. Those high in Intellectual OE are commonly seen as intellectually gifted and have incredibly active minds. They are intensely curious, avid readers and keen observers. They frequently love thinking purely for the sake of thinking.
Imaginational: OE manifests as an intensified play of the imagination, causing a rich association of images, invention, fantasy, use of imagery and metaphor and elaborate dreams and visions. Often children high in Imaginational OE do not differentiate between truth and fiction, or are absorbed in their own private world with imaginary companions and dramatizations.
Emotional: OE is characterised by heightened, intense feelings, extreme experience of complex emotions, identification with others' feelings to the point of actual experience and strong sentimental expression. Other indications include physical response to emotional stimuli such as stomachaches when nervous and obsessive concern with death and depression. Emotionally overexcitable people have a strong capacity for deep relationships; they show strong emotional attachments to people, places, and things. They are empathetic, compassionate and extremely sensitive.
According to Dąbrowski, a person who manifests any given form of overexcitability and especially one who manifests several forms of overexcitability sees reality in a different, stronger and more multisided manner.
Giftedness
A small amount of definitive research has led to the belief that intensity, sensitivity and overexcitability are primary characteristics of the highly gifted. The association between OE and giftedness appears to be borne out in the research. It appears that at the least OE is a marker of potential for giftedness/creativity. Dąbrowski's basic message is that the gifted will disproportionately display this process of positive disintegration and personality growth. The term "overexcitability" was popularized in the gifted education community by Michael M. Piechowski and Susan Daniels and Michael M. Piechowski, who edited Living with Intensity. While this theory has been commonly accepted, alternate research disputes the concept of overexcitabilities and suggests that the five-factor model of personality, specifically openness to experience, better explains these heightened behaviors.
See also
Sensory processing sensitivity
References
Falk, R.F., Lind, S., Miller, N.B., Piechowski, M.M., & Silverman, L.K. (1999). The overexcitability questionnaire –two (OEQ-II): Manual, scoring system, and questionnaire. Denver, CO: Institute for the Study of Advanced Development.
Falk, R.F., Piechowski, M.M., & Lind, S. (1994). Criteria for rating levels of intensity of overexcitabilities. Unpublished manuscript, University of Akron, Ohio.
https://positivedisintegration.com/Piechowski1999.pdf
Dabrowski's Overexcitabilities Profile among Gifted Students Aliza Alias1, Saemah Rahman, Rosadah Abd Majid1 & Siti Fatimah Mohd Yassin2
Books
Dąbrowski, K. (1964). Positive Disintegration. Maurice Bassett, 2016
Fonseca, Christine. Emotional Intensity in Gifted Students. Prufrock Press Inc, 2011.
Jacobsen, Mary-Elaine. The Gifted Adult. Random House Publishing 1999.
Rankin, J. G. (2016). Engaging & challenging gifted students: Tips for supporting extraordinary minds in your classroom. Alexandra, VA: ASCD.
Tillier, William. Personality Development through Positive Disintegration: The Work of Kazimierz Dabrowski. Maurice Bassett, 2018
Webb, James T. Searching for Meaning, Idealism, Bright Minds, Disillusionment, and Hope. Great Potential Press, 2013.
Further reading
Overexcitability and the Gifted
Positive disintegration
External links
Websites and blogs
Dąbrowski’s Theory of Positive Disintegration. An overview & archive.
Dabrowski's Overexcitabilities and Theory of Positive Disintegration
How to Identify and Cope with Overexcitabilities
Overexcitability and the Gifted
Personality | Overexcitability | [
"Biology"
] | 1,308 | [
"Behavior",
"Personality",
"Human behavior"
] |
6,965,005 | https://en.wikipedia.org/wiki/Closed%20system%20%28control%20theory%29 | The terms closed system and open system have long been defined in the widely (and long before any sort of amplifier was invented) established subject of thermodynamics, in terms that have nothing to do with the concepts of feedback and feedforward. The terms 'feedforward' and 'feedback' arose first in the 1920s in the theory of amplifier design, more recently than the thermodynamic terms. Negative feedback was eventually patented by H.S Black in 1934. In thermodynamics, an open system is one that can take in and give out ponderable matter. In thermodynamics, a closed system is one that cannot take in or give out ponderable matter, but may be able to take in or give out radiation and heat and work or any form of energy. In thermodynamics, a closed system can be further restricted, by being 'isolated': an isolated system cannot take in nor give out either ponderable matter or any form of energy. It does not make sense to try to use these well established terms to try to distinguish the presence or absence of feedback in a control system.
The theory of control systems leaves room for systems with both feedforward pathways and feedback elements or pathways. The terms 'feedforward' and 'feedback' refer to elements or paths within a system, not to a system as a whole. THE input to the system comes from outside it, as energy from the signal source by way of some possibly leaky or noisy path. Part of the output of a system can be compounded, with the intermediacy of a feedback path, in some way such as addition or subtraction, with a signal derived from the system input, to form a 'return balance signal' that is input to a PART of the system to form a feedback loop within the system. (It is not correct to say that part of the output of a system can be used as THE input to the system.)
There can be feedforward paths within the system in parallel with one or more of the feedback loops of the system so that the system output is a compound of the outputs of the feedback loops and of the parallel feedforward paths. Feedforward and feedback often occur in one and the same system. It makes sense to speak of a control system only if it contains at least one feedforward path; the presence or absence of feedback is contingent.
A feedback loop needs within itself both a feedforward element and a feedback element. For example, the feedforward element (for example a transistor) in an amplifier has access to a controlled power reservoir and provides power gain for the loop and is therefore called an active element. The feedback element is often, but not always, passive (for example a resistor). It makes sense to speak of a feedback loop only when referring to a loop with a well-defined active feedforward element. Without this, a loop does not have a definite sense (clockwise or anti-clockwise) of signal circulation by which one could distinguish its feedforward and feedback elements. Without this definite sense of signal circulation one is looking at a mere mesh in a network, and it makes no sense to speak of a feedback loop.
A feedback loop can contain further feedback loops within itself, or it can provide a pathway inside another feedback loop, provided its 'input' and 'output' are defined.
A 1993 paper, General Systems Theory by David S. Walonick, Ph.D., states in part, "A closed system is one where interactions occur only among the system components and not with the environment. An open system is one that receives input from the environment and/or releases output to the environment. The basic characteristics of an open system is the dynamic interaction of its components, while the basis of a cybernetic model is the feedback cycle. Open systems can tend toward higher levels of organization (negative entropy), while closed systems can only maintain or decrease in organization."
References
Computer networks engineering | Closed system (control theory) | [
"Technology",
"Engineering"
] | 820 | [
"Computer networks engineering",
"Computer engineering"
] |
6,965,125 | https://en.wikipedia.org/wiki/Ichthyoallyeinotoxism | Ichthyoallyeinotoxism, or hallucinogenic fish inebriation, comes from eating certain species of fish found in several parts of the tropics, the effects of which are reputed to be similar in some aspects to LSD. Experiences may include vivid auditory and visual hallucinations. This has given rise to the collective common name "dream fish" for ichthyoallyeinotoxic fish.
The species most commonly claimed to be capable of producing this kind of toxicity include several species from the genus Kyphosus, including Kyphosus fuscus, K. cinerascens, and K. vaigiensis. It is unclear whether the toxins are produced by the fish themselves or by marine algae in their diet, but a dietary origin may be more likely.
Sarpa salpa, a species of bream, can induce LSD-like hallucinations if it is eaten. These widely distributed coastal fish are called "the fish that make dreams" in Arabic. In 2006, two men who ate fish, apparently the Sarpa salpa caught in the Mediterranean, were affected by ichthyoallyeinotoxism and experienced hallucinations lasting for several days.
Other hallucinogenic fish are Siganus spinus, called "the fish that inebriates" in Reunion Island, and Mulloides flavolineatus (formerly Mulloidichthys samoensis), called "the chief of ghosts" in Hawaii.
See also
5-Bromo-DMT
Entheogen
Venomous fish
References
Toxic effect of noxious substances eaten as food
Adverse effects of psychoactive drugs | Ichthyoallyeinotoxism | [
"Chemistry"
] | 341 | [
"Drug safety",
"Adverse effects of psychoactive drugs"
] |
6,965,259 | https://en.wikipedia.org/wiki/Extended%20finite-state%20machine | In a conventional finite-state machine, the transition is associated with a set of input Boolean conditions and a set of output Boolean functions. In an extended finite-state machine (EFSM) model, the transition can be expressed by an “if statement” consisting of a set of trigger conditions. If trigger conditions are all satisfied, the transition is fired, bringing the machine from the current state to the next state and performing the specified data operations.
Definition
An EFSM is defined as a 7-tuple where
S is a set of symbolic states,
I is a set of input symbols,
O is a set of output symbols,
D is an n-dimensional linear space ,
F is a set of enabling functions ,
U is a set of update functions ,
T is a transition relation,
Structure
EFSM Architecture: An EFSM model consists of the following three major combinational blocks (and a few registers).
FSM-block: A conventional finite-state machine realizing the state transition graphs of the EFSM model.
A-block: an arithmetic block for performing the data operation associated with each transition. The operation of this block is regulated by the output signals of the FSM block.
E-block: A block for evaluating the trigger conditions associated with each transition. The input signals to this block are the data variables, while the output is a set of binary signals taken for input by the FSM-block. Information about redundant computation is extracted by analyzing the interactions among the three basic blocks. Using this information, certain input operands of the arithmetic block and evaluation block can be frozen through input gating under specific run time conditions to reduce the unnecessary switching in the design. At the architecture level, if each trigger evaluation & data operation is regarded as an atomic action, then the EFSM implies an almost lowest-power implementation.
The cycle behavior of an EFSM can be divided into three steps:
In E-block, evaluate all trigger conditions.
In FSM-block, compute the next state & the signals controlling A-block.
In A-block, perform the necessary data operations and data movements.
See also
Abstract state machine
References
Models of computation
Formal methods
Theory of computation | Extended finite-state machine | [
"Engineering"
] | 448 | [
"Software engineering",
"Formal methods"
] |
6,965,272 | https://en.wikipedia.org/wiki/Ignicoccus | Ignicoccus is a genus of hyperthermophillic Archaea living in marine hydrothermal vents. They were discovered in samples taken at the Kolbeinsey Ridge north of Iceland, as well as at the East Pacific Rise (at 9 degrees N, 104 degrees W) in 2000.
Systematics
According to the comparisons of 16S rRNA genes, Ignicoccus represents a new, deeply branching lineage within the family of the Desulfurococcaceae.
Three species are known: I. islandicus, I. pacificus and I. hospitalis strain KIN4I.
Cell structure
The archaea of the genus Ignicoccus have tiny coccoid cells with a diameter of about 2 μm, that exhibit a smooth surface, an outer membrane and no S-layer.
They have a previously unknown cell envelope structure—a cytoplasmic membrane, a periplasmic space (with a variable width of 20 to 400 nm, containing membrane-bound vesicles), and an outer membrane (approximately 10 nm wide, resembling the outer membrane of gram-negative bacteria). The latter contains numerous tightly, irregularly packed single particles (about 8 nm in diameter) and pores with a diameter of 24 nm, surrounded by tiny particles, arranged in a ring (with a diameter of 130 nm) and clusters of up to eight particles 12 nm in diameter each.
The two layers of membrane previously reported are actually a type of endomembrane system consisting of cytoplasmic protrusions. In I. hospitalis, these structures harbor the endosymbiotic archaeon Nanoarchaeum equitans.
Physiology
Ignicocci live in a temperature range of 70–98 °C (optimum around 90 °C). They gain energy by reduction of elemental sulfur to hydrogen sulfide using molecular hydrogen as the electron donor. A unique symbiosis with (or parasitism by) Nanoarchaeum equitans has also been reported.
Phylogeny
The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI)
See also
List of Archaea genera
References
Further reading
External links
Ignicoccus at BacDive - the Bacterial Diversity Metadatabase
Archaea genera
Thermoproteota
Thermophiles
Extremophiles | Ignicoccus | [
"Biology",
"Environmental_science"
] | 487 | [
"Organisms by adaptation",
"Extremophiles",
"Environmental microbiology",
"Bacteria"
] |
6,965,276 | https://en.wikipedia.org/wiki/Polyetherimide | Polyetherimide (PEI; branded as Ultem) is an amorphous, amber-to-transparent thermoplastic with characteristics similar to the related plastic PEEK. When comparing PEI to PEEK, the former is cheaper but has lower impact strength and a tighter temperature range.
PEI plastics were first introduced into the market by General Electric (GE) in 1982 under the trade name Ultem.
Due to its adhesive properties and chemical stability it became a popular bed material for FFF 3D printers.
Structure
The molecular formula of the PEI repeating unit is and the molecular weight is 592.61 g/mol. It contains phthalimide and bisphenol A sub-units.
Properties
The glass transition temperature of PEI is 217 °C (422 °F). Its amorphous density at 25 °C is 1.27 g/cm3(.046 lb/in³). It is prone to stress cracking in chlorinated solvents. Polyetherimide is able to resist high temperatures while maintaining stable electrical properties over a wide range of frequencies. This high strength material offers excellent chemical resistance and ductile properties suitable for various applications, even those involving steam exposure.
References
Plastics
Thermoplastics | Polyetherimide | [
"Physics",
"Chemistry"
] | 249 | [
"Polymer stubs",
"Unsolved problems in physics",
"Amorphous solids",
"Organic chemistry stubs",
"Plastics"
] |
6,965,358 | https://en.wikipedia.org/wiki/TK85 | The TK85 was a ZX81 clone made by Microdigital Eletrônica, a computer company located in Brazil. It came with 16 or 48 KB RAM, and had a ZX Spectrum–style case, similar to a Timex Sinclair 1500.
Unlike the ZX81, the TK85 used standard logic components rather than a gate array ("ULA"), and during manufacture several of them were scraped so that competitors couldn't easily copy the circuit. The circuit board had space for a AY-3-8912 sound generator chip (compatible with the ZonX-81 sound board), and although none came factory installed, it is possible to add the necessary circuits.
The TK85 came with a copy of the 8K ZX81 floating point BASIC, and an additional 2K EPROM, mapped to addresses 8192-10240, containing machine code routines for use with tape files. These routines could save with HISAVE, load with HILOAD and verify with HIVERIFY in "Hi-Speed" (4200 bps); save and load, BASIC variables in 300 bps (standard ZX81 speed) using SAVE and DLOAD functions and 4200 bps (Hi-Speed) using DHSAVE and DHLOAD. These routines were all accessible using RAND USR commands. The save to variable function could be used to make copies of programs on tape.
The expansion port on the back of the computer is compatible with the ZX81, although some peripherals may not work due to conflicts with the 2K of extra ROM.
The rear of the computer featured a TV output (without video back porch), "EAR" and "MIC" sockets for connecting to an external tape recorder, a joystick port using a DIN socket (that simulated the ,,, and keys), a ZX81 compatible expansion port, space for a sound output socket, and a socket for the 9V external power supply.
Since the joystick used the cursor keys, and due to the circuitry for the keyboard, it wasn't possible to detect diagonal directions correctly.
References
External links
Microdigital TK85
Microdigital Eletrônica
Goods manufactured in Brazil
Sinclair ZX81 clones
Computer-related introductions in 1983 | TK85 | [
"Technology"
] | 479 | [
"Computing stubs",
"Computer hardware stubs"
] |
6,966,428 | https://en.wikipedia.org/wiki/Hatch%20mark | Hatch marks (also called hash marks or tick marks) are a form of mathematical notation. They are used in three ways as:
Unit and value marks — as on a ruler or number line
Congruence notation in geometry — as on a geometric figure
Graphed points — as on a graph
Hatch marks are frequently used as an abbreviation of some common units of measurement. In regard to distance, a single hatch mark indicates feet, and two hatch marks indicate inches. In regard to time, a single hatch mark indicates minutes, and two hatch marks indicate seconds.
In geometry and trigonometry, such marks are used following an elevated circle to indicate degrees, minutes, and seconds —
Hatch marks can probably be traced to hatching in art works, where the pattern of the hatch marks represents a unique tone or hue. Different patterns indicate different tones.
Unit and value marks
Unit-and-value hatch marks are short vertical line segments which mark distances. They are seen on rulers and number lines. The marks are parallel to each other in an evenly-spaced manner.
The distance between adjacent marks is one unit. Longer line segments are used for integers and natural numbers. Shorter line segments are used for fractions.
Hatch marks provide a visual clue as to the value of specific points on the number line, even if some hatch marks are not labeled with a number.
Hatch marks are typically seen in number theory and geometry.
<----|----|----|----|----|----|----|----|----|----|----|----|----|----|---->
-3 -2 -1 0 1 2 3
Congruency notation
In geometry, hatch marks are used to denote equal measures of angles, arcs, line segments, or other elements.
Hatch marks for congruence notation are in the style of tally marks or of Roman numerals – with some qualifications. These marks are without serifs, and some patterns are not used. For example, the numbers I, II, III, V, and X are used, but IV and VI are not used, since a rotation of 180 degrees can make a 4 easily confused with a 6.
For example, if two triangles are drawn, the first pair of congruent sides can be marked with a single hatch mark on each. The second pair of congruent sides can be marked with two hatch marks each. The patterns are not alike: one pair uses one mark while the other pair uses two marks (Figure 1). This use of pattern makes it clear which sides are the same length, even if the sides cannot be measured. If the sides do not appear to be congruent, as long as hatch marks are present and are the same number of hatch marks, then the sides are congruent.
Note that the inverse situation should not be assumed. That is, while sides that are hatch marked identically must be assumed to be congruent, it does not follow that sides hatch marked differently must be incongruent. The different hatch marks simply signal that the length measurements may (in this case) be considered to be independent of each other. So, for example, while we are not allowed to conclude that the triangles in the accompanying figure must be isosceles triangles (or even perhaps equilateral triangles), we yet remain obliged to allow that they could be either of those things.
Graphed points
Line charts may sometimes use hatch marks as graphed points. In the early days of computers, monitors and printers could only make charts using the characters available on a common typewriter. To graph a line chart of sales over time, symbols such as *, x, or | were used to mark points, and various characters were used to mark the lines connecting them. While computers have advanced considerably, it is still not unusual to see x or | used as the points of interest (or points of change) on a graph.
See also
Euclidean geometry
References
Mathematical notation
Geometry | Hatch mark | [
"Mathematics"
] | 843 | [
"Geometry",
"nan"
] |
6,966,559 | https://en.wikipedia.org/wiki/Nanocrystalline%20material | A nanocrystalline (NC) material is a polycrystalline material with a crystallite size of only a few nanometers. These materials fill the gap between amorphous materials without any long range order and conventional coarse-grained materials. Definitions vary, but nanocrystalline material is commonly defined as a crystallite (grain) size below 100 nm. Grain sizes from 100 to 500 nm are typically considered "ultrafine" grains.
The grain size of a NC sample can be estimated using x-ray diffraction. In materials with very small grain sizes, the diffraction peaks will be broadened. This broadening can be related to a crystallite size using the Scherrer equation (applicable up to ~50 nm), a Williamson-Hall plot, or more sophisticated methods such as the Warren-Averbach method or computer modeling of the diffraction pattern. The crystallite size can be measured directly using transmission electron microscopy.
Synthesis
Nanocrystalline materials can be prepared in several ways. Methods are typically categorized based on the phase of matter the material transitions through before forming the nanocrystalline final product.
Solid-state processing
Solid-state processes do not involve melting or evaporating the material and are typically done at relatively low temperatures. Examples of solid state processes include mechanical alloying using a high-energy ball mill and certain types of severe plastic deformation processes.
Liquid processing
Nanocrystalline metals can be produced by rapid solidification from the liquid using a process such as melt spinning. This often produces an amorphous metal, which can be transformed into an nanocrystalline metal by annealing above the crystallization temperature.
Vapor-phase processing
Thin films of nanocrystalline materials can be produced using vapor deposition processes such as MOCVD.
Solution processing
Some metals, particularly nickel and nickel alloys, can be made into nanocrystalline foils using electrodeposition.
Mechanical properties
Nanocrystalline materials show exceptional mechanical properties relative to their coarse-grained varieties. Because the volume fraction of grain boundaries in nanocrystalline materials can be as large as 30%, the mechanical properties of nanocrystalline materials are significantly influenced by this amorphous grain boundary phase. For example, the elastic modulus has been shown to decrease by 30% for nanocrystalline metals and more than 50% for nanocrystalline ionic materials. This is because the amorphous grain boundary regions are less dense than the crystalline grains, and thus have a larger volume per atom, . Assuming the interatomic potential, , is the same within the grain boundaries as in the bulk grains, the elastic modulus, , will be smaller in the grain boundary regions than in the bulk grains. Thus, via the rule of mixtures, a nanocrystalline material will have a lower elastic modulus than its bulk crystalline form.
Nanocrystalline metals
The exceptional yield strength of nanocrystalline metals is due to grain boundary strengthening, as grain boundaries are extremely effective at blocking the motion of dislocations. Yielding occurs when the stress due to dislocation pileup at a grain boundary becomes sufficient to activate slip of dislocations in the adjacent grain. This critical stress increases as the grain size decreases, and these physics are empirically captured by the Hall-Petch relationship,
where is the yield stress, is a material-specific constant that accounts for the effects of all other strengthening mechanisms, is a material-specific constant that describes the magnitude of the metal's response to grain size strengthening, and is the average grain size. Additionally, because nanocrystalline grains are too small to contain a significant number of dislocations, nanocrystalline metals undergo negligible amounts of strain-hardening, and nanocrystalline materials can thus be assumed to behave with perfect plasticity.
As the grain size continues to decrease, a critical grain size is reached at which intergranular deformation, i.e. grain boundary sliding, becomes more energetically favorable than intragranular dislocation motion. Below this critical grain size, often referred to as the “reverse” or “inverse” Hall-Petch regime, any further decrease in the grain size weakens the material because an increase in grain boundary area results in increased grain boundary sliding. Chandross & Argibay modeled grain boundary sliding as viscous flow and related the yield strength of the material in this regime to material properties as
where is the enthalpy of fusion, is the atomic volume in the amorphous phase, is the melting temperature, and is the volume fraction of material in the grains vs the grain boundaries, given by , where is the grain boundary thickness and typically on the order of 1 nm. The maximum strength of a metal is given by the intersection of this line with the Hall-Petch relationship, which typically occurs around a grain size of = 10 nm for BCC and FCC metals.
Due to the large amount of interfacial energy associated with a large volume fraction of grain boundaries, nanocrystalline metals are thermally unstable. In nanocrystalline samples of low-melting point metals (i.e. aluminum, tin, and lead), the grain size of the samples was observed to double from 10 to 20 nm after 24 hours of exposure to ambient temperatures. Although materials with higher melting points are more stable at room temperatures, consolidating nanocrystalline feedstock into a macroscopic component often requires exposing the material to elevated temperatures for extended periods of time, which will result in coarsening of the nanocrystalline microstructure. Thus, thermally stable nanocrystalline alloys are of considerable engineering interest. Experiments have shown that traditional microstructural stabilization techniques such as grain boundary pinning via solute segregation or increasing solute concentrations have proven successful in some alloy systems, such as Pd-Zr and Ni-W.
Nanocrystalline ceramics
While the mechanical behavior of ceramics is often dominated by flaws, i.e. porosity, instead of grain size, grain-size strengthening is also observed in high-density ceramic specimens. Additionally, nanocrystalline ceramics have been shown to sinter more rapidly than bulk ceramics, leading to higher densities and improved mechanical properties, although extended exposure to the high pressures and elevated temperatures required to sinter the part to full density can result in coarsening of the nanostructure.
The large volume fraction of grain boundaries associated with nanocrystalline materials causes interesting behavior in ceramic systems, such as superplasticity in otherwise brittle ceramics. The large volume fraction of grain boundaries allows for a significant diffusional flow of atoms via Coble creep, analogous to the grain boundary sliding deformation mechanism in nanocrystalline metals. Because the diffusional creep rate scales as and linearly with the grain boundary diffusivity, refining the grain size from 10 μm to 10 nm can increase the diffusional creep rate by approximately 11 orders of magnitude. This superplasticity could prove invaluable for the processing of ceramic components, as the material may be converted back into a conventional, coarse-grained material via additional thermal treatment after forming.
Processing
While the synthesis of nanocrystalline feedstocks in the form of foils, powders, and wires is relatively straightforward, the tendency of nanocrystalline feedstocks to coarsen upon extended exposure to elevated temperatures means that low-temperature and rapid densification techniques are necessary to consolidate these feedstocks into bulk components. A variety of techniques show potential in this respect, such as spark plasma sintering or ultrasonic additive manufacturing, although the synthesis of bulk nanocrystalline components on a commercial scale remains untenable.
See also
Nanoparticle
Quantum dot
References
Crystals
Nanomaterials
Metallurgy | Nanocrystalline material | [
"Chemistry",
"Materials_science",
"Engineering"
] | 1,622 | [
"Metallurgy",
"Materials science",
"Crystallography",
"Crystals",
"nan",
"Nanotechnology",
"Nanomaterials"
] |
6,967,114 | https://en.wikipedia.org/wiki/Battle%20of%20the%20Styles | The Battle of the Styles is a term used to refer to the conflict between supporters of the Gothic style and the Classical style in architecture. In Britain this led to public debates between Decimus Burton and Augustus Pugin.
Later in the century the revival of vernacular architecture led to an increasing palette of styles from which architects could choose, including Queen Anne style and "Tudorbethan" models. Numerous stylistic options led to a debate about prefabricated stylistic options in architecture, which eventually mutated into the Arts and Crafts style and then into Modernism.
See also
List of architectural styles
References
Architectural history
Architectural styles | Battle of the Styles | [
"Engineering"
] | 122 | [
"Architectural history",
"Architecture"
] |
6,967,119 | https://en.wikipedia.org/wiki/Bottling%20%28concert%20abuse%29 | Bottling is an action where a concert audience throws various objects at the performers onstage. This generally happens at festivals when one act in the lineup is of a different genre or audience from the rest of the bands, especially festivals where the majority of bands are related to heavy metal and punk rock music styles.
While bottling generally involves empty or full bottles of water, it is also common for bottles to contain urine. Other items, such as garden furniture, mud, fireworks, broken glass, shoes, dead animals, and molotov cocktails (unlighted and lighted), have also been recorded as thrown items.
Below is a list of bottling incidents by decade and year.
1970s
Metallic K.O. is an infamous live recording by The Stooges: during much of the performance, Iggy Pop sings while pieces of ice, eggs, beer bottles, jelly beans, and various other objects are thrown at him in response to his audience-baiting. In the essay "Iggy Pop: Blowtorch in Bondage", critic Lester Bangs calls the album a "documentation of the Iggy holocaust at its most nihilistically out of control." He describes the Stooges' concert he attended that immediately preceded the Metallic K.O. performances:
Ten Cent Beer Night—On June 4, 1974, during a game between the Texas Rangers and the Cleveland Indians at Cleveland Stadium, unruly and drunken fans repeatedly disrupted the game and, after the Indians tied the game, invaded the field and threw bottles and other objects, including hot dogs, lit firecrackers, radio batteries and folding chairs. Both the Rangers and the Indians sought refuge in their clubhouses. The Indians forfeited the game to the Rangers.
On June 3, 1977, restless fans threw rocks and beer bottles at Led Zeppelin when a concert in Tampa, Florida, was ended early due to a severe thunderstorm—even though the tickets said "rain or shine"—resulting in a small riot that left over 100 injured due to crowd crushing.
In 1978, AC/DC were bottled on stage at the Seattle Center Coliseum after Angus Young got onto Bon Scott's shoulders and walked into the audience, but the band continued playing after this incident.
The Ramones were booed and pelted with various objects, including sandwiches and bottles, at the Canadian World Music Festival in Toronto in July 1979, with the abuse only ending after Johnny Ramone flipped off the crowd six songs into the set.
Disco Demolition Night—On July 12, 1979, at Comiskey Park in Chicago, fans during an anti-disco rally before the second game of a Detroit Tigers–Chicago White Sox doubleheader raided the field and threw bottles, firecrackers and lighters. The White Sox forfeited the game to the Tigers. (The Tigers won the first game, 4–1.)
At a Jethro Tull concert in Madison Square Garden on October 12, 1979, a fan threw a rose onstage which hit Ian Anderson, wounding his eye with a thorn. The band was forced to cancel the next two shows while Anderson recovered. He appeared at subsequent concert dates wearing protective goggles.
1980s
Peter and the Test Tube Babies were repeatedly spat on during the recording of Pissed and Proud. On the album, the lead singer can be heard asking the audience to "Leave out the gob, we had a shower this morning, you cunts."
In 1982, The Who played a show at the Tangerine Bowl in Orlando, Florida. The two support acts were Joan Jett and The B-52's, who were both pelted with food and bottles by a section of the audience who were only there for The Who. The B-52's ended their set 20 minutes in due to Cindy Wilson being hit in the stomach with an apple.
As documented on "Geneva Farewell" from You Can't Do That on Stage Anymore, Vol. 5, a July 1982 Frank Zappa concert in Geneva ended early due to audience members throwing cigarettes on stage.
Steel Pulse were heavily bottled by fans waiting for punk rock group The Stranglers' act at the Reading Festival in 1983, starting the festival's trend.
On April 6, 1985, Deep Purple performed at the Pacific Coliseum in Vancouver, British Columbia, Canada. Partway through the show, Ritchie Blackmore was hit by a wineskin thrown by an audience member. He stormed offstage, ending the show.
Dutch Claw Boys Claw were pelted at Pinkpop 1986 with everything from mud to food to bottles after singer Peter te Bos started throwing objects into the audience, ranging from his half-eaten apple to test pressings of their new album to his own shoe.
The spoof heavy metal band Bad News were bottled extensively in 1986 at Monsters of Rock, prior to the band's musical performance beginning, with Rik Mayall trying to bat some missiles back at the audience with his guitar.
The Communards were bottled at Pinkpop in 1987. Jimmy Somerville briefly left the stage but returned to finish the set.
Meat Loaf and Bonnie Tyler were bottled at the 1988 Reading Festival.
In 1989 a very young Texas were opening for Simple Minds in Cardiff Arms Park. The band temporarily halted the show due to being continually pelted by a sea of plastic bottles. Lead singer Sharleen Spiteri angrily chastised the crowd who stopped throwing in response: "Do you think it is alright to throw bottles at a wee lassie up here on stage?" at which point a lone bottle was thrown, it arched through the air towards the band and as was clearly seen on the large stage monitors hit Spiteri directly on the head. A huge cheer went up and a deluge of bottles followed, not letting up until Spiteri and Texas had stormed off stage.
1990s
Pavement were bottled during a Lollapalooza event in West Virginia in 1995 with mud. A rock hit Stephen Malkmus in the chest, causing Malkmus to storm off stage, abruptly ending their set. The incident is featured in the documentary Slow Century.
Everclear front man Art Alexakis was pegged in the mouth with a full water bottle at some point during the So Much for the Afterglow tour. The bottle knocked loose one of his front teeth.
At a November 5, 1993 concert at Empire Polo Club, Pearl Jam were pelted by hundreds of shoes thrown by the audience and were forced to play behind their amplifiers. Eddie Vedder addressed the crowd, joking that he and Jeff Ament were going to be at the gate after the show and beat up every barefoot person they see. He then stated that instead, the band were going to donate the shoes to charity. A recording of the incident was included on Pearl Jam's 1993 Fan Club Holiday Single, and the recording of the song "Blood" was included as a b-side on the Daughter single.
On August 10, 1995, at Dodger Stadium in Los Angeles, California, Dodger fans threw souvenir baseballs onto the field during the seventh and ninth innings of the Dodgers' game against the St. Louis Cardinals. The latter disruption came after umpire Jim Quick ejected the Dodgers' manager, Tommy Lasorda, following a questionable strikeout call. The Dodgers forfeited the game to the Cardinals.
On September 17, 1995, Silverchair's Daniel Johns had a bottle thrown at him during a performance of the song "Israel's Son" at Santa Monica Pier when he was 16 years old. He received multiple stitches to his eyebrow, which he later turned into an eyebrow piercing.
On December 23, 1995, at Giants Stadium in East Rutherford, New Jersey, during a game between the San Diego Chargers and the New York Giants, Giants fans threw snowballs in the stands and onto the field, primarily aimed at the Chargers. One snowball hit a member of the Chargers' coaching staff, knocking him to the turf. Referee Ron Blum threatened to forfeit the game to the Chargers if the snowballing did not cease. The Chargers eventually overcame the snowballs and the Giants, defeating them 27–17.
The Sex Pistols were bottled off stage at Denmark's Roskilde Festival in 1996. The band left the stage briefly after only two songs but returned to play another three. Johnny Rotten asked the crowd to stop; however, bottling continued and the band ended their set with Rotten criticising the crowd for failing to "police themselves".
On June 17, 1997, at an Ozzfest event, concert goers began throwing bottles at the bands on stage, smashed box office windows, started fires, and overturned cars after the announcement that Ozzy Osbourne would not perform.
A full bottle of Sprite was thrown at James as they performed at V Festival in the mid-1990s. It struck lead guitarist Adrian Oxaal on the head and temporarily dazed him; after a few moments, he continued to play and the set finished without further incident.
During her performance at Pinkpop 1998, some people in the audience threw a couple of eggs at Dutch singer Anouk. In response, she took off her shirt and finished her performance in a red bra, as was shown on Dutch television.
The Manic Street Preachers were heavily bottled at the Swansea Heineken Festival in 1993. After a bottle hit Nicky Wire in the head, James Dean Bradfield led the band off stage. The band eventually came back onstage and finished their set.
In 1999, Kevin Rowland was bottled at Reading Festival, after appearing wearing a dress and stockings and being accompanied by two female dancers in stockings.
During the Woodstock '99 festival, Canadian folk rock band The Tragically Hip were pelted with rocks and bottles by audience members who were there to see harder metal acts on the bill like Kid Rock and Rage Against the Machine. Some American concertgoers reportedly taunted the band and their fans by singing "The Star-Spangled Banner" while the group performed a brief rendition of "O Canada".
2000s
2000
Daphne and Celeste were heavily bottled at the Reading Festival, and left the stage at the start of their last song. Pop punk favorites Blink-182 were scheduled to follow them later that day. The duo accused the crowd of "wasting so much food", which was one of the items thrown at them. The duo themselves have differing opinions if this incident was the beginning of the end of their time together.
2001
Marilyn Manson was bottled during OzzFest at The Docks in Toronto. A fan threw a water bottle at the stage during the song "The Nobodies" just before the end. Immediately bassist Twiggy Ramirez pointed it out to Manson, who demanded that the fan who threw the bottle approach the stage for a duel. After the fan did so, Manson returned the bottle to him, allowed him to climb onto the stage and goaded him into throwing the bottle again after a countdown. Manson responded by throwing a bottle of his own, which hit the fan in the face, and he was also pelted by many more water bottles coming from the crowd. Following losing the duel, Marilyn taunted the fan, saying "Who's got the good aim now? You fucking bitch. Get the fuck off my stage, you pussy." He then proceeded to play the song "Rock Is Dead".
Bottlegate—On December 16, 2001, at Cleveland Browns Stadium, during week 14 of the 2001 NFL season, the Cleveland Browns were sitting at 6–6, desperate for a win to keep their playoff hopes alive. Down 15–10 with 1:08 remaining, the Browns were forced to try to convert on 4th and 2 at the Jacksonville Jaguars’ 12-yard line. Quarterback Tim Couch took the snap and passed short to wide receiver Quincy Morgan, who appeared to bobble the ball after a 3-yard gain, but the officials called it a completed pass. Couch hurried the offense to the line and spiked the ball with 0:48 remaining. The officials announced that they would review the 4th down conversion, but overturned it, giving the ball to the Jaguars. Enraged, the fans began throwing objects onto the field, including beer bottles. After a few minutes, the officials ended the game 48 seconds early and everyone exited the field. However, Paul Tagliabue, the league commissioner, called, telling them that they must finish the game. The teams and officials came back onto the field with 13 random players selected and, after two kneels by Jaguars quarterback Mark Brunell, the game was over, and the Jaguars won 15–10.
2002
Lostprophets were bottled at the London leg of the Deconstruction Tour in 2002. Their addition to the bill of a predominantly punk rock lineup had been controversial, and the band were pelted with projectiles throughout their set, one striking singer Ian Watkins. The band subsequently cut their set twenty minutes short.
2003
Good Charlotte were bottled at the Reading Festival. They encouraged the crowd to "Boo, hiss and throw some more" on a count of three only to storm off the stage afterwards.
Justin Timberlake was bottled at the Toronto Rocks concert while playing on the same bill as AC/DC and The Rolling Stones.
Kelly Osbourne was bottled at the Game On festival. She left the stage 10 minutes into her half-hour set.
Limp Bizkit were bottled while opening for Metallica before 40,000 spectators at Hawthorne Race Course in Chicago.
2004
At the Reading Festival, rapper 50 Cent was pelted with bottles, many of which were filled with urine. One audience member threw a deckchair onto the stage. 50 Cent lasted nearly 20 minutes before finally throwing his microphone into the crowd in anger. The Rasmus were also bottled off following one song.
At the Sydney Big Day Out in 2004, restless Metallica fans waiting for the band to play threw bottles at The Strokes during their set on the adjacent stage. One bottle struck lead singer Julian Casablancas in the face, which prompted him to taunt the Metallica fans. After more bottles were thrown, Casablancas jumped down from his stage and confronted the angry crowd face to face.
On January 5, 2004, at Dunkin' Donuts Center in Providence, Rhode Island, Providence College fans threw bottles onto the court after the Texas Longhorns defeated the Providence Friars, 79–77, when a controversial buzzer beater by forward P. J. Tucker was upheld by the officials following video review.
On June 19, 2004, a member of the audience at the Norwegian Wood Festival threw a lollipop at performer David Bowie. The lollipop stem lodged itself under Bowie's eyelid. The concert was stopped briefly while support personnel dealt with the errant lollipop. After expressing his frustrations to the crowd, Bowie resumed his performance.
On November 19, 2004, the Pacers–Pistons brawl ended with fans pelting players, coaches, and other people with bottles.
2005
Iron Maiden were egged at their final performance at Ozzfest in 2005. Frontman Bruce Dickinson reportedly urged audience members to "break the arms" of members who were throwing objects on the stage. Other objects such as bottle caps and pieces of ice were thrown on stage as well.
Simple Plan were bottled at the Ovation Music Festival. Lead singer Pierre Bouvier was rushed to a hospital shortly after.
2006
My Chemical Romance and Panic! at the Disco were both bottled at the Reading Festival. Both bands finished their set and the former claimed it as a 'victory.' The incident with Panic! at the Disco was heavily reported by many websites, as singer Brendon Urie was knocked unconscious.
The Mars Volta had bottles full of urine thrown at them at Endfest. This combined with various sound problems resulted in the band walking off the stage.
Intricate Unit was bottled by thousands at the Gathering of the Juggalos in Ohio while opening for Dark Lotus and Insane Clown Posse.
The Veronicas were bottled at the Coke Live 'n' Local in Adelaide. Lisa was hit in the face, and the band threatened to end their set early, screaming abuse.
Lee Harding was bottled off during a performance at the 2006 Bassinthegrass in Darwin. During the performance, then-Chief Minister Clare Martin tried to convince Harding to continue playing, but after only one more song he received a bottle to the face, yelled to the crowd "you guys are shit" and stormed off stage.
2007
My Chemical Romance were heavily bottled again, this time during their headline spot at Download 2007.
Comedian Lewis Black was bottled at the Bonnaroo Music Festival while sitting in on a performance by the band Gov't Mule.
On June 24, 2007, Jeffree Star was banned from Toronto's Gay Pride Parade for punching a female fan in the face after spectators standing near her threw bottles onstage.
2008
As I Lay Dying was bottled at the Soundwave festival in Sydney in February. The set was cut short as guitarist Nick Hipa was injured.
Josh Homme of Queens of the Stone Age was bottled at the Norwegian Wood concert on June 13. This prompted Homme to call him out and say: "You miserable fucking cunt, go back to your mom's house, you 12-year-old dickless fucking turd. And his friends, you wanna throw something too? Or all you cool, are you all good?"
Relatively unknown band The FF'ers were bottled heavily at the Reading Festival after rumours circulated that their set was in fact a Foo Fighters secret show. According to their bassist, items thrown included "not just bottles but shoes, clumps of earth, phones, a full packet of cigarettes".
Bring Me the Horizon were bottled at the 2008 Reading Festival when appearing as a last-minute replacement for Slipknot, after drummer Joey Jordison broke his ankle. The band were heavily bottled which caused singer Oliver Sykes to respond to the abuse by saying: "It looks a right mess up here on this stage, you obviously don't like our band but that's okay." Other items thrown were crisps and woodchips from the floor. A year later the band appeared at the festival again, but as an official act rather than a replacement albeit three stages down to the Festival Republic Stage. They would later return to the main stage, but with a positive reception.
Later on in the day, American alternative rock band The Plain White T's were bottled during the early stages of their set. The abuse was put down to the demographic their music was aimed at, as Metallica were that day's headliners.
Lethal Bizzle was heavily bottled during his set at the 2008 Download Festival as he was the only act on the bill not associated with rock or heavy metal. Other items thrown included hundreds of pots of Müller Rice which were being given free by a vendor on site. Despite this Bizzle completed his set and even came back on stage for an encore.
Rapper Lil' Wayne was bottled in Stratford, London, due to his inactivity on stage, where he reacted by telling the audience the show was over. As a response, he received more bottling.
Andrew W.K. was bottled at the Gathering of the Juggalos. In spite of this, he continued performing, shouting: "To anybody, you can do whatever you want to do! I love you, no matter what you think of me!"
2009
Metal band Cradle of Filth were bottled during a headline slot at Bloodstock Open Air. Guitarist Paul Allender collapsed and was hospitalised after being hit by a large piece of candy thrown by the audience. The band cut the set short and made an overhead announcement.
Morrissey was bottled at Liverpool Echo Arena in November 2009. He said "goodbye" and left the stage in the middle of his second song.
Justin Bieber was bottled at the Jingle Ball concert in Sacramento, California, in December 2009. After being struck in the head, Bieber said "Ow! That didn't feel good! I don't know why she just threw that at me." He finished the show.
2010s
2010
On September 1, 2010, Guns N' Roses were bottled after appearing on stage an hour late at The O2 (now 3Arena) in Dublin.
In August 2010, Tila Tequila was bottled off stage at the Gathering of the Juggalos. She vowed to take legal action against the organizers and promoters for the event.
2011
Scottish rock band Glasvegas was bottled at the V Festival in August 2011. They ended their set after four songs, then attempted to restart, but left again after the audience continued to throw objects at them.
On November 15, 2011, during the opening number at a Motörhead show, Lemmy stopped the song after several bottles were thrown, and told the audience, "All right, listen, we are a rock and roll band, we are not a fuckin' target for some cunt with a fuckin' beer bottle! Anyone else wants to throw something at me, come up here and throw a fucking punch and I'll kick your fuckin' teeth in!" before restarting the song.
2012
Several bottles of urine were thrown at Cher Lloyd at the V Festival in August 2012. During her second song she fled the stage to compose herself. Although Cher's management advised her to halt the gig for her safety she decided to return and resume her performance. When she returned she told the crowd "It's hard enough being up here, but it's not nice having bottles of piss chucked at you." She ultimately had to end her set early after more bottles were thrown.
Black Veil Brides suffered bottling abuse from metal fans at June 2012's Download Festival. The lead singer, Andy Biersack, responded to this by "mooning" the crowd. On the Download 2012 Sky Arts highlights, Biersack can clearly be seen in the Black Veil Brides video narrowly avoiding a launched bottle during "Fallen Angels". The band also endured bottling incidents throughout other songs as well as numerous offensive gestures from members of the crowd and verbal satisfaction from the crowd upon leaving the stage at the end of their set.
2013
A bottle was thrown at and hit Jeff Mills on the head during a live set at Atlantico, Rome on April 24, 2013.
A vodka bottle was thrown at Toots Hibbert during a performance at the River Rock Festival in Richmond, Virginia, on May 18, 2013. The 71-year-old musician suffered a concussion, and the wound required six staples. All planned shows were immediately cancelled. The official website of the band, Toots and the Maytals, states that "all future performances of Toots & the Maytals have regrettably been cancelled". In a letter to the judge, Toots Hibbert wrote "I continue to suffer from extreme anxiety, memory loss, headaches, dizziness and most sadly of all, a fear of crowds and performing. I am not able to write songs as I did before or remember the lyrics of songs that I wrote and have performed for decades."
Leigh-Anne Pinnock of Little Mix was struck with a bottle during a show with the group at the Access All Eirias festival in Wales.
2015
A fan threw bottles of beer during a Van Halen concert in August 2015 after finishing "In A Simple Rhyme". David Lee Roth then signaled the fans to start their next song, while adding: "Next time, you save the beer for me, you slime." Roth also gave the finger afterwards.
A bottle was thrown at Harry Styles during a concert with One Direction in September 2015, hitting him in the groin.
2017
Bottles were thrown at Kerry Katona and Natasha Hamilton of Atomic Kitten at Quack, the University of Lincoln's student union event. They left the stage after 15 minutes for their safety.
2020s
2021
On October 16, 2021, University of Tennessee fans threw bottles and other objects, including a golf ball which hit Ole Miss head coach Lane Kiffin, onto the Neyland Stadium field after the Tennessee Volunteers were ruled to have been stopped short on fourth down with 54 seconds remaining. The game was delayed some 20 minutes. The Rebels defeated the Vols, 31–26. The commissioner of the Southeastern Conference, Greg Sankey, announced the following Monday that the University of Tennessee would be fined $250,000 for its fans' bottling.
2022
In July 2022, Lady Gaga had something thrown at her from the audience during a concert on her Chromatica Ball tour.
On December 17, 2022, during the second quarter of the Buffalo Bills' game against the Miami Dolphins at Highmark Stadium, fans threw snowballs onto the field, briefly delaying the game. Referee Bill Vinovich threatened the fans with a 15-yard penalty against the Bills if a snowball hit anyone on the field. The snowballing eventually ceased and the Bills would defeat the Dolphins 32–29.
2023
On June 18, 2023, Bebe Rexha required stitches after she was hit by a fan's cellular phone during one of her concerts. The suspect was caught and arrested.
On June 28, 2023, Kelsea Ballerini was hit in the face with a bracelet. After a break to check for injuries, she came back to the stage to resume her performance.
On July 5, 2023, at a Chicago stop on his "It's All a Blur" concert tour, a fan threw a cellphone at Drake from the crowd, seemingly hitting him in the arm.
In fiction
The title characters were bottled in a pivotal scene in The Blues Brothers, famously only protected by a mesh of chicken wire.
References
Lester Bangs. "Iggy Pop: Blowtorch in Bondage," in Psychotic Reactions and Carburetor Dung, ed. Greil Marcus (New York: Anchor Books, 1987), 206–207. .
Anti-social behaviour
Human communication
Health risks of performing arts | Bottling (concert abuse) | [
"Biology"
] | 5,267 | [
"Human communication",
"Anti-social behaviour",
"Behavior",
"Human behavior"
] |
6,967,420 | https://en.wikipedia.org/wiki/Heinz%20mean | In mathematics, the Heinz mean (named after E. Heinz) of two non-negative real numbers A and B, was defined by Bhatia as:
with 0 ≤ x ≤ .
For different values of x, this Heinz mean interpolates between the arithmetic (x = 0) and geometric (x = 1/2) means such that for 0 < x < :
The Heinz means appear naturally when symmetrizing
-divergences.
It may also be defined in the same way for positive semidefinite matrices, and satisfies a similar interpolation formula.
See also
Mean
Muirhead's inequality
Inequality of arithmetic and geometric means
References
Means | Heinz mean | [
"Physics",
"Mathematics"
] | 137 | [
"Means",
"Mathematical analysis",
"Point (geometry)",
"Applied mathematics",
"Geometric centers",
"Applied mathematics stubs",
"Symmetry"
] |
6,967,890 | https://en.wikipedia.org/wiki/Timeline%20of%20virtualization%20technologies | In computing, virtualization is the use of a computer to simulate another computer. The following is a chronological list of virtualization technologies.
Timeline
Note: This timeline is missing data for important historical systems, including: Atlas Computer (Manchester), GE 645, Burroughs B5000.
1960s
In the mid-1960s, IBM's Cambridge Scientific Center develops CP-40, the first version of CP/CMS. Experience on the CP-40 project provides input to the development of the IBM System/360 Model 67, announced in 1965. CP-40 is re-implemented for the S/360-67 as CP-67, and by April 1967, both versions are in daily production use.
1964
IBM Cambridge Scientific Center begins development of CP-40.
1965
IBM M44/44X, an experimental paging operating system, is in use at Thomas J. Watson Research Center.
IBM announces the IBM System/360-67, a 32-bit CPU with virtual memory hardware (August 1965).
1966
IBM ships the S/360-67 computer in June 1966.
IBM begins work on CP-67, a re-implementation of CP-40 for the S/360-67.
1967
In January, CP-40 goes into production time-sharing use, followed by CP-67 in April.
1968
CP/CMS is installed at eight initial customer sites.
CP/CMS is submitted to IBM Type-III Library by MIT's Lincoln Laboratory.
Resale of CP/CMS access begins at time-sharing vendor National CSS (becoming a distinct version, eventually renamed VP/CSS).
1970s
IBM announces the System/370 in 1970. In 1972, IBM announces that virtual memory would be made available on all S/370 models, and also announces several virtual storage operating systems, including VM/370. By the mid-1970s, CP/CMS, VM, and VP/CSS are running on numerous large IBM mainframes.
1971
The first System/370, the S/370-155, is shipped in January.
1972
Announcement of virtual memory being added to System/370 series.
VM/370 announced – and running on announcement date. VM/370 includes the ability to run VM under VM (previously implemented both at IBM and at user sites under CP/CMS, but not made part of standard releases)
1973
First shipment of announced virtual memory S/370 models (April: -158, May: -168).
1977
Initial commercial release of VAX/VMS, later renamed OpenVMS.
1979
The chroot system call is introduced during development of Version 7 Unix, laying a foundation for container virtualization.
1980s
1985
October 9, 1985: Announcement of the Intel 80286-based AT&T 6300+ with Simultask, a virtual machine monitor developed by Locus Computing Corporation in collaboration with AT&T, enabling the direct execution of an Intel 8086 realmode guest operating system under a host Unix System V Release 2 OS.
1987
January 1987: A "product evaluation" version of Merge/386 from Locus Computing Corporation is made available to OEMs. Merge/386 made use of the Virtual 8086 mode provided by the Intel 80386 processor, and supported multiple simultaneous virtual 8086 machines. The virtual machines supported unmodified guest operating systems and standalone programs such as Microsoft Flight Simulator; but in typical usage the guest was MS-DOS with a Locus proprietary redirector (also marketed for networked PCs as "PC-Interface") and a "network" driver that provided communication with a regular user-mode file server process running under the host operating system on the same machine.
October 1987: Retail Version 1.0 of Merge/386 begins shipping, offered with Microport Unix System V Release 3.
1988
SoftPC 1.0 for Sun is introduced in 1988 by Insignia Solutions.
SoftPC appears in its first version for Apple Macintosh. These versions (Sun and Macintosh) only have support for DOS.
1990s
1991
IBM introduces OS/2 Virtual DOS machine (VDM) with support for x86 virtual 8086 mode, capable of virtualizing DOS/Windows and other 16 bit operating systems like CP/M-86
1994
Kevin Lawton leaves MIT Lincoln Lab and starts the Bochs project. Bochs was initially coded for x86 architecture, capable of emulating BIOS, processor and other x86-compatible hardware, by simple algorithms, isolated from the rest of the environment, eventually incorporating the ability to run different processor algorithms under x86-architecture or the host, including bios and core processor (Itanium x64, x86_64, ARM, MIPS, PowerPC, etc.), and with the advantage that the application is multi platform (BSD, Linux, Windows, Mac, Solaris).
1997
The first version of Virtual PC for the Macintosh platform is released in June 1997 by Connectix.
1998
June 15: Simics/sun4m is presented at USENIX'98, demonstrating full system simulation booting Linux 2.0.30 and Solaris 2.6 unmodified from dd'ed disks. .
October 26: VMware files for a patent on their techniques, which was granted as U.S. Patent 6,397,242
1999
February 8: VMware introduces the first x86 virtualization product for the Intel IA-32 architecture, known as VMware Virtual Platform, based on earlier research by its founders at Stanford University. VMware Virtual Platform is based on software emulation with a guest/host OS design that required all guest environments be stored as files under the host OS filesystem.
2000s
2000
FreeBSD 4.0 is released, including initial implementation of FreeBSD jails.
IBM announces z/VM, a new version of the VM operating system for IBM's 64-bit z/Architecture.
2001
January 31, 2001, AMD and Virtutech release Simics/x86-64 ("Virtuhammer") to support the new 64-bit architecture for x86. Virtuhammer is used to port Linux distributions and the Windows kernel to x86-64 well before the first x86-64 processor (Opteron) was available in April 2003.
June, Connectix launches its first version of Virtual PC for Windows.
July, VMware creates the first x86 server virtualization product.
Egenera, Inc. launches their Processor Area Network (PAN Manager) software and BladeFrame chassis which provide hardware virtualization of processing blade's (pBlade) internal disk, network interface cards, and serial console.
The first version of Virtuozzo, based on OpenVZ, is released.
2003
First release of first open-source x86 hypervisor, Xen.
February 18: Microsoft acquires virtualization technologies (Virtual PC and unreleased product called "Virtual Server") from Connectix Corporation.
February 18: Development begins on QEMU, a free and open-source hardware emulator.
Late 2003: EMC acquires VMware for $635 million.
Late 2003: VERITAS acquires Ejascent for $59 million.
November 10, 2003 Microsoft releases Microsoft Virtual PC, which is a machine-level virtualization technology.
2005
HP releases Integrity Virtual Machines 1.0 and 1.2 which ran only HP-UX.
October 24, 2005 VMware releases VMware Player, a free player for virtual machines.
Sun releases Solaris 10, including Solaris Zones, for both x86/x64 and SPARC systems.
2006
July 12, 2006 VMware releases VMware Server, a free machine-level virtualization product for the server market.
Microsoft Virtual PC 2006 is released as a free program, also in July.
July 17, 2006 Microsoft bought Softricity.
August 16, 2006 VMware announces the winners of the virtualization appliance contest.
September 26, 2006 moka5 delivers LivePC technology.
HP releases Integrity Virtual Machines Version 2.0, which supports Windows Server 2003, CD and DVD burners, tape drives and VLAN.
December 11, 2006 Virtual Iron releases Virtual Iron 3.1, a free bare-metal virtualization product for the enterprise server virtualization market.
2007
KVM, a virtualization module integrated into the Linux kernel, is released.
January 15, 2007 InnoTek releases VirtualBox Open Source Edition (OSE), the first professional PC virtualization solution released as open source under the GNU General Public License (GPL). It includes some code from the QEMU project.
Sun releases Solaris 8 Containers to enable migration of a Solaris 8 computer into a Solaris Container on a Solaris 10 system – for SPARC only.
2008
The first Linux kernel mainline featuring cgroups (developed by Google since 2006) is released, laying a foundation for later technologies like LXC, Docker, Systemd-nspawn and Podman.
January 15, 2008 VMware, Inc. announces it has entered into a definitive agreement to acquire Thinstall, a privately held application virtualization software company.
February 12, 2008 Sun Microsystems announces that it had entered into a stock purchase agreement to acquire InnoTek, makers of VirtualBox.
April: VMware releases VMware Workstation 6.5 beta, the first program for Windows and Linux to enable DirectX 9 accelerated graphics on Windows XP guests .
August 6: LXC, an OS-level virtualization method for Linux, is released.
2010s
2011
The first stable version of QEMU is released.
2013
Docker, Inc. releases Docker, a series of platform as a service (PaaS) products that use OS-level virtualization.
2014
The first public build of Kubernetes is released on September 8, 2014. When Kubernetes debuted, it offered a number of advantages over Docker, the most popular containerization platform at the time. The purpose of Kubernetes was to make it simple for users to deploy containerized applications across a sizable cluster of container hosts. In order to offer more features and functionality for managing containerized applications at scale, Kubernetes was created to complement Docker rather than to completely replace it.
References
External links
Application Virtualization: Streamlining Distribution August 31, 2006—By James Drews
Windows Virtualization from Microsoft
Virtualization Overview from VMware
An introduction to Virtualization
Weblog post on the how virtualization can be used to implement Mandatory Access Control.
The Effect of Virtualization on OS Interference in PDF format.
VM/360 history
VM/360 history
Attacks on virtual machine emulators
Virtualization
Virtualization | Timeline of virtualization technologies | [
"Engineering"
] | 2,194 | [
"Computer networks engineering",
"Virtualization"
] |
14,415,076 | https://en.wikipedia.org/wiki/CEATEC | Combined Exhibition of Advanced Technologies (also known as CEATEC) is an annual trade show in Japan. It is regarded as the Japanese equivalent of Consumer Electronics Show. It is Japan's largest IT and electronics exhibition and conference.
History
The show is held every year in October in Makuhari Messe since the first CEATEC in 2000. The most recent exhibition, the ninth iteration of CEATEC, was held between September 30 to October 4, 2008. CEATEC Japan 2008, attracted nearly 197,000 visitors, with some 804 exhibitors and 138 seminars. Attendance was down from the almost 206,000 people and 895 companies in 2007 as it apparently felt the crunch of the financial crisis of 2007–2010.
Show highlights
2003
Sony shown off the PSX
2007
Sony and Panasonic announced devices that could play as well as record shows in Blu-ray Disc format.
2014
NTT DoCoMo will show their latest technologies,
while both Sharp and SEGA mentioned about attending in their Twitter posts.
See also
CeBIT (Hanover, Germany)
CES (Las Vegas, Nevada, USA)
COMDEX (Las Vegas, Nevada, USA)
COMPUTEX (Taipei, Taiwan)
References
External links
CEATEC official site
Trade fairs in Japan
Computer-related trade shows
2000 establishments in Japan
Autumn events in Japan | CEATEC | [
"Technology"
] | 268 | [
"Computer industry",
"Computer-related trade shows"
] |
14,415,118 | https://en.wikipedia.org/wiki/Even%20and%20odd%20ordinals | In mathematics, even and odd ordinals extend the concept of parity from the natural numbers to the ordinal numbers. They are useful in some transfinite induction proofs.
The literature contains a few equivalent definitions of the parity of an ordinal α:
Every limit ordinal (including 0) is even. The successor of an even ordinal is odd, and vice versa.
Let α = λ + n, where λ is a limit ordinal and n is a natural number. The parity of α is the parity of n.
Let n be the finite term of the Cantor normal form of α. The parity of α is the parity of n.
Let α = ωβ + n, where n is a natural number. The parity of α is the parity of n.
If α = 2β, then α is even. Otherwise α = 2β + 1 and α is odd.
Unlike the case of even integers, one cannot go on to characterize even ordinals as ordinal numbers of the form Ordinal multiplication is not commutative, so in general In fact, the even ordinal cannot be expressed as β + β, and the ordinal number
(ω + 3)2 = (ω + 3) + (ω + 3) = ω + (3 + ω) + 3 = ω + ω + 3 = ω2 + 3
is not even.
A simple application of ordinal parity is the idempotence law for cardinal addition (given the well-ordering theorem). Given an infinite cardinal κ, or generally any limit ordinal κ, κ is order-isomorphic to both its subset of even ordinals and its subset of odd ordinals. Hence one has the cardinal sum
References
Ordinal numbers
Parity (mathematics) | Even and odd ordinals | [
"Mathematics"
] | 382 | [
"Ordinal numbers",
"Order theory",
"Mathematical objects",
"Numbers"
] |
14,415,491 | https://en.wikipedia.org/wiki/Antigen-presenting%20cell%20vaccine | An antigen-presenting cell vaccine, or an APC vaccine, is a vaccine made of antigens and antigen-presenting cells (APCs).
, the only APC vaccine approved by the American Food and Drug Administration is for prostatic acid phosphatase, a commonly over-expressed prostate cancer antigen.
References
External links
Antigen-presenting cell vaccine entry in the public domain NCI Dictionary of Cancer Terms
Vaccines | Antigen-presenting cell vaccine | [
"Biology"
] | 85 | [
"Vaccination",
"Vaccines"
] |
14,415,710 | https://en.wikipedia.org/wiki/ChibiOS/RT | ChibiOS/RT is a compact and fast real-time operating system supporting multiple architectures and released under a mix of the GNU General Public License version 3 (GPL3) and the Apache License 2.0 (depending on module). It is developed by Giovanni Di Sirio.
Commercial licenses are available from ChibiOS. Additional products include ChibiOS/HAL, a hardware abstraction layer compatible with ChibiOS/RT, and ChibiStudio, a free integrated development environment based on Eclipse, the GNU Compiler Collection, and the OpenOCD Joint Test Action Group (JTAG) debugging pod.
Metrics
ChibiOS/RT is designed for embedded applications on microcontrollers of 8-, 16-, and 32-bits. Size and execution efficiency are the main project goals. As reference, the kernel size can range from a minimum of 1.2 KiB up to a maximum of 5.5 KiB with all the subsystems activated on a STM32 Cortex-M3 processor. The kernel can achieve over 220,000 created/terminated threads per second and can perform a context switch in 1.2 microseconds on an STM32 @ 72 MHz. Similar metrics for all the supported platforms are included in the source code distribution as test reports.
Features
The ChibiOS/RT microkernel supports:
Preemptive multithreading
128 priority queue levels
Round-robin scheduling for threads at the same priority level
Software timers
Counting semaphores
Mutexes with support for the priority inheritance algorithm
Condition variables
Synchronous and asynchronous Messages
Event flags and handlers
Queues
Synchronous and asynchronous I/O with timeout capability
Thread-safe memory heap and memory pool allocators.
Hardware Abstraction Layer with support for ADC, CAN, GPT (general-purpose timer), EXT, I²C, ICU, MAC, MMC/SD, PAL, PWM, RTC, SDC, Serial, SPI, and USB drivers.
Support for the LwIP and uIP TCP/IP stacks.
Support for the FatFs file system library.
All system objects, such as threads, semaphores, timers, etc., can be created and deleted at runtime. There is no upper limit except for the available memory. To increase system reliability, the kernel architecture is entirely static, a memory allocator is not needed (but is available as an option), and there are no data structures with upper size limits like tables or arrays. The system application programming interfaces (APIs) are designed to not have error conditions such as error codes or exceptions.
The RTOS is designed for applications on embedded systems (devices) and includes demo applications for various microcontrollers:
STMicroelectronics – STM32F1xx, STM32F2xx, STM32F3xx, STM32F4xx, STM32L1xx, STM32F0xx; STM8S208x, STM8S105x, STM8L152x; ST/Freescale SPC56x, MPC56xx
NXP Semiconductors – LPC11xx, LPC11Uxx, LPC13xx, LPC2148
Atmel – AT91SAM7S, AT91SAM7X, megaAVR
Texas Instruments (TI) – MSP430x1611; TM4C123G, TM4C1294
Microchip Technology – PIC32MX
Contributed ports are also available for the Coldfire and H8S families.
ChibiOS/RT has also been ported to the Raspberry Pi and the following device drivers have been implemented: Port (GPIO), Serial, GPT (General-Purpose Timer), I2C, SPI and PWM.
It is also possible to run the kernel in a Win32 process in a software I/O emulation mode, allowing easy application development without the need for physical hardware. An example is included for MinGW compiler.
uGFX
ChibiOS/RT is fully supported by the graphical user interface (GUI) toolkit µGFX, formerly named ChibiOS/GFX.
See also
Comparison of open-source operating systems
References
External links
Real-time operating systems
Embedded operating systems
Free software operating systems
ARM operating systems
Microkernel-based operating systems
Microkernels | ChibiOS/RT | [
"Technology"
] | 935 | [
"Real-time computing",
"Real-time operating systems"
] |
14,416,359 | https://en.wikipedia.org/wiki/Atamestane | Atamestane (developmental code name SH-489), also known as metandroden, as well as 1-methylandrosta-1,4-diene-3,17-dione, is a steroidal aromatase inhibitor that was studied in the treatment of cancer. It blocks the production of estrogen in the body. The drug is selective, competitive, and irreversible in its inhibition of aromatase.
Synthesis
Reaction of the known compound, androstadienedione, (1) with Gilman reagent followed by acetylation with acetic anhydride gives the enol acetate (2). Bromination with 1,3-dibromo-5,5-dimethylhydantoin gives an intermediate (3) which on treatment with magnesium oxide yields atamestane (4). Alternatively the steroid (5) can be oxidized with benzeneselenol, or the natural product, boldenone (6) can be oxidized with a mixture of chromium trioxide and sulfuric acid.
References
External links
Atamestane entry in the public domain NCI Dictionary of Cancer Terms
Anabolic–androgenic steroids
Androstanes
Aromatase inhibitors
Enantiopure drugs | Atamestane | [
"Chemistry"
] | 272 | [
"Stereochemistry",
"Enantiopure drugs"
] |
14,416,361 | https://en.wikipedia.org/wiki/Atiprimod | Atiprimod (INN, codenamed SK&F106615) is a substance being studied in the treatment of certain multiple myelomas and other advanced cancers. It may block the growth of tumors and the growth of blood vessels from surrounding tissue to the tumor. This drug is also being researched as a potential treatment for various autoimmune diseases.
It was first developed by GlaxoSmithKline as a potential treatment for rheumatoid arthritis.
It also had application in the treatment of hyperlipidæmia:
This compound has also been shown to kill mantle cell lymphoma cells in vitro.
Mechanism of action
Atiprimod has been shown to inhibit angiogenesis (growth of blood vessels) in a blood vessel model using chicken eggs. It is thought to inhibit the secretion of vascular endothelial growth factor (VEGF), a growth factor that promotes angiogenesis.
Chemistry
Atiprimod is an amphiphilic compound and a cation at neutral pH.
The harbinger for Atipromod was obviously Spirogermanium [41992-23-8].
The substance is an example of an azaspirane.
Synthesis
The first part of the synthesis uses protocols that were used for Pramiverine and agents including SIR 117.
The second half of the synthesis shares features that are consonant with RS 86
The Johnson–Corey–Chaykovsky reaction on 4-Heptanone [123-19-3] (1) gives 2,2-dipropyloxirane [98560-25-9] (2). Treatment with Boron trifluoride etherate [109-63-7] gave 2-Propylpentanal [18295-59-5] (3). Upon acid treatment with Methyl vinyl ketone [78-94-4] (4) this led to 4,4-Dipropylcyclohex-2-enone [60729-41-1] (5). Catalytic hydrogenation of the enone olefin yielded 4,4-Dipropylcyclohexanone [123018-62-2] (7). The Knoevenagel condensation with ethyl 2-cyanoacetate [1187-46-8] (8) led to Cyano-(4,4-dipropyl-cyclohexylidene)-acetic acid ethyl ester [130065-93-9] (8).
Conjugate addition of cyanide anion led to ethyl 2-cyano-2-(1-cyano-4,4-dipropylcyclohexyl)acetate, PC45358714 (9). Acid hydrolysis of both the nitrile groups to acids, saponification of the ester, and decarboxylation of the geminal diacid gave 1-(carboxymethyl)-4,4-dipropylcyclohexane-1-carboxylic acid [130065-94-0] (10). Treatment with acetic anhydride gave 8,8-Dipropyl-2-oxaspiro[4.5]decane-1,3-dione [123018-64-4] (11). Condensation with 3-Diethylaminopropylamine [104-78-9] (12) gave the imide and hence, 2-[3-(diethylamino)propyl]-8,8-dipropyl-2-azaspiro[4.5]decane-1,3-dione, PC15634126 (13). Finally reduction of both carbonyl groups with lithium aluminium hydride completed the synthesis of Atiprimod (14).
References
Further reading
External links
Atiprimod entry in the public domain NCI Dictionary of Cancer Terms
Experimental cancer drugs
Pyrrolidines
Spiro compounds
Diethylamino compounds | Atiprimod | [
"Chemistry"
] | 857 | [
"Organic compounds",
"Spiro compounds"
] |
14,416,367 | https://en.wikipedia.org/wiki/Atrasentan | Atrasentan is an experimental drug that is being studied for the treatment of various types of cancer, including non-small cell lung cancer. It is also being investigated as a therapy for diabetic kidney disease.
It is an endothelin receptor antagonist selective for subtype A (ETA). While other drugs of this type (sitaxentan, ambrisentan) exploit the vasoconstrictive properties of endothelin and are mainly used for the treatment of pulmonary arterial hypertension, atrasentan blocks endothelin induced cell proliferation.
Clinical trials
Atrasentan failed a phase 3 trial for prostate cancer in patients unresponsive to hormone therapy. A second trial confirmed this finding.
In April 2014, de Zeeuw et al. showed that 0.75 mg and 1.25 mg of atrasentan reduced urinary albumin by 35 and 38% respectively with modest side effects. Patients also had decreased home blood pressures (but no change in office readings) decrease total cholesterol and LDL. Patients in the 1.25 mg dose group had increased weight gain which was presumably due to increased edema and had to withdraw from the study more than the placebo or 0.75 mg dose group. Reductions in proteinuria have been associated with beneficial patient outcomes in diabetic kidney disease with other interventions but is not an accepted end-point by the FDA.
In 2013, SONAR trial was initiated to determine if atrasentan reduces kidney failure in diabetic kidney disease.
In 2024, the phase 3 ALIGN trial found atrasentan to be effective in reducing proteinuria in patients with IgA nephropathy.
References
Endothelin receptor antagonists
Experimental cancer drugs
Benzodioxoles
Carboxylic acids
4-Methoxyphenyl compounds | Atrasentan | [
"Chemistry"
] | 373 | [
"Pharmacology",
"Carboxylic acids",
"Functional groups",
"Medicinal chemistry stubs",
"Pharmacology stubs"
] |
14,416,663 | https://en.wikipedia.org/wiki/Endling | An endling is the last known individual of a species or subspecies. Once the endling dies, the species becomes extinct. The word was coined in correspondence in the scientific journal Nature.
Usage
The 4 April 1996 issue of Nature published a correspondence in which commentators suggested that a new word, endling, be adopted to denote the last individual of a species. The 23 May issue of Nature published several counter-suggestions, including ender, terminarch, and relict.
The word endling appeared on the walls of the National Museum of Australia in Tangled Destinies, a 2001 exhibition by Matt Kirchman and Scott Guerin, about the relationship between Australian peoples and their land. In the exhibition, the definition, as it appeared in Nature, was printed in large letters on the wall above two specimens of the extinct Tasmanian tiger: "Endling (n.) The last surviving individual of a species of animal or plant". A printed description of this exhibition offered a similar definition, omitting reference to plants: "An endling is the name given to an animal that is the last of its species."
In The Flight of the Emu: A Hundred Years of Australian Ornithology 1901-2001, author Libby Robin stated that "the very last individual of a species" is "what scientists refer to as an 'endling'".
In 2011, the word was used in the Earth Island Journal, in an essay by Eric Freedman entitled "Extinction Is Forever: A Quest for the Last Known Survivors". Freedman defined endling as "the last known specimen of her species."
In "The Sense of an Endling", author Helen Lewis describes the notion of an endling as poignant, and the word as "wonderfully Tolkien-esque".
Author Eric Freedman describes endling as "a word with finality", stating, "It is deep-to-the-bone chilling to know the exact date a species disappeared from Earth. It is even more ghastly to look upon the place where it happened and know that nobody knew or cared at the time what had transpired and why."
Notable endlings
This is not a comprehensive list of contemporary extinction, but a list of high-profile, widely publicised examples of when the last individual of a species was known.
Birds
The passenger pigeon (Ectopistes migratorius) became extinct at 1 p.m. on 1 September 1914 with the death of Martha, the last surviving member of the species, at the Cincinnati Zoo.
Incas, the last known Carolina parakeet (Conuropsis carolinensis), died, also at the Cincinnati Zoo, on 21 February 1918. The species was officially declared extinct in 1939.
Booming Ben, a solitary heath hen (Tympanuchus cupido cupido), was last seen 11 March 1932 on Martha's Vineyard, Massachusetts.
Orange Band was the last known dusky seaside sparrow (Ammodramus maritumus nigrescens), who died on 17 June 1987 at the Discovery Island zoological park at Walt Disney World Resort.
The last known Kauaʻi ʻōʻō (Moho braccatus) was recorded singing a mating call on Kauai in 1987 by David Boynton. The bird is believed to have been killed by Hurricane Iniki in 1992, and the death of this individual also marked the extinction of the entire Mohoidae family.
Mammals
In 1627, the last aurochs (Bos primigenius), an ancestor of bovine and cattle, died in a forest near what is now Jaktorów in modern-day Poland.
The quagga (Equus quagga quagga) became extinct in the wild in the late 1870s due to hunting for meat and skins, and the subspecies' endling died in captivity on 12 August 1883 at the Artis in Amsterdam.
The final tarpan (Equus ferus ferus) died in captivity in the Russian Empire in 1903.
On 7 September 1936, the last known captive thylacine (Thylacinus cynocephalus), also called Tasmanian tiger, died in Hobart Zoo, following persecution of the species through hunting and trapping. Information published about this individual has been conflicted throughout the decades following its death. Areas of contention include whether it was male or female, whether it was named "Benjamin" or not, where it was captured, by whom it was captured, whether it was neglected in its zoo enclosure and even whether it was the last known surviving Thylacine. A comprehensive analysis of the history of this individual published in 2023 concludes or re-affirms that it was male, captured on 7 July 1930, at Penney's Flats in northwestern Tasmania by Roy and Dan Delphin, never called Benjamin during its lifetime and that it was the most valued animal in the zoo's collection, not neglected, and that it died of old age. Although it is generally accepted that the thylacine probably persisted in the wild following the death of this individual, the Tasmanian tiger at Hobart Zoo is considered the endling not only for its species, but also the family Thylacinidae.
The last known Mexican grizzly bear (Ursus arctos horribilis), also called oso plateado (silver bear) in Spanish, was shot in 1976 in Sonora, Mexico.
Celia, the last Pyrenean ibex (Capra pyrenaica pyrenaica), was found crushed by a tree on 6 January 2000 in the Spanish Pyrenees, after hunting and competition from livestock reduced the population to one individual.
The final Vietnamese Javan rhinoceros (Rhinoceros sondaicus annamiticus), was shot by a poacher at the Cát Tiên National Park in 2010, after habitat loss, poaching, and the Vietnam War reduced the population to one individual.
Reptiles and amphibians
On 24 June 2012, Lonesome George, the last known Pinta Island tortoise (Chelonoidis niger abingdonii), died in his habitat in the Galápagos Islands.
On 26 September 2016, Toughie, the last known Rabbs' fringe-limbed treefrog (Ecnomiohyla rabborum), died in the Atlanta Botanical Garden.
After being considered possibly extinct for 113 years, a Fernandina Island Galápagos tortoise named Fernanda was found in 2019 for the Animal Planet series, Extinct or Alive. However, she is the only confirmed individual.
Invertebrates
Turgi was the last Partula turgida, a Polynesian tree snail, who died on 31 January 1996 in the London Zoo.
A tank in the Bristol Zoo was the last refuge of Partula faba, a land snail from Ra'iātea in French Polynesia. The population dropped from 38 in 2012 to one in 2015. The last individual died on 21 February 2016.
George was the last known individual of the Oahu tree snail species Achatinella apexfulva. He died on January 1, 2019, in captivity near Kailua, Hawaii.
Plants
The Curepipe Botanic Gardens in Mauritius have housed the last specimen of the palm Hyophorbe amaricaulis since the 1950s.
Only one living specimen of the tree species Madhuca diplostemon is known to exist.
Some seeds were found in an archaeological excavation in the Judean desert in 1986–87. In 2009, a specimen of an unknown species of Commiphora was successfully sprouted from one of these ancient seeds (dated 993 CE – 1202 calCE). The tree was named Sheba. In 2024, it was tentatively identified as tsori or Judean balsam, on the basis of taxonomy and resin properties matching ancient descriptions. Similar to Fernanda, Sheba is the only known individual of her species despite recent discovery or rediscovery.
See also
Conservation status
De-extinction
Extinction
Holocene extinction
Lists of extinct animals
List of neologisms
Rare species
Terminal speaker
References
External links
What Do You Call the Last of a Species? by Michelle Nijhuis for The New Yorker
Cut from history by Eric Freedman for Knight Center for Environmental Journalism
Bringing Them Back to Life by Carl Zimmer for National Geographic Magazine.
Animals by conservation status
Extinction | Endling | [
"Biology"
] | 1,698 | [
"Animals",
"Biota by conservation status",
"Animals by conservation status",
"Endlings",
"Individual organisms"
] |
14,416,795 | https://en.wikipedia.org/wiki/Endothelin%20receptor%20type%20B | Endothelin receptor type B, (ET-B) is a protein that in humans is encoded by the EDNRB gene.
Function
Endothelin receptor type B is a G protein-coupled receptor which activates a phosphatidylinositol-calcium second messenger system. Its ligand, endothelin, consists of a family of three potent vasoactive peptides: ET1, ET2, and ET3. A splice variant, named SVR, has been described; the sequence of the ETB-SVR receptor is identical to ETRB except for the intracellular C-terminal domain. While both splice variants bind ET1, they exhibit different responses upon binding which suggests that they may be functionally distinct.
Regulation
In melanocytic cells the EDNRB gene is regulated by the microphthalmia-associated transcription factor. Mutations in either gene are links to Waardenburg syndrome.
Clinical significance
The multigenic disorder, Hirschsprung disease type 2, is due to mutation in endothelin receptor type B gene.
Animals
In horses, a mutation in the middle of the EDNRB gene, Ile118Lys, when homozygous, causes Lethal White Syndrome. In this mutation, a mismatch in the DNA replication causes lysine to be made instead of isoleucine. The resulting EDNRB protein is unable to fulfill its role in the development of the embryo, limiting the migration of the melanocyte and enteric neuron precursors. A single copy of the EDNRB mutation, the heterozygous state, produces an identifiable and completely benign spotted coat color called frame overo.
Interactions
Endothelin receptor type B has been shown to interact with Caveolin 1.
Ligands
Agonists
IRL-1620
Antagonists
A-192,621
BQ-788
Bosentan (unselective ETA / ETB antagonist)
See also
Endothelin receptor
References
Further reading
External links
G protein-coupled receptors | Endothelin receptor type B | [
"Chemistry"
] | 415 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,416,831 | https://en.wikipedia.org/wiki/Specification%20tree | A specification tree shows all specifications of a technical system under development in a hierarchical order.
For a spacecraft system it has the following levels:
System (requirements) specification - generated by customer
System (design to) specification - generated by system responsible prime contractor
Subsystem specifications - generated by system responsible prime contractor
Assembly specifications - generated by subsystem responsible contractors
Unit specifications - generated by subsystem (or assembly) responsible contractors.
References
Product development
Systems engineering | Specification tree | [
"Engineering"
] | 95 | [
"Systems engineering"
] |
14,416,870 | https://en.wikipedia.org/wiki/EXC%20code | EXC is a condensed matter physics many-body theory software package implementing the Bethe–Salpeter equation in frequency-reciprocal space and on a plane wave basis set. Its purpose is to calculate, ab initio, dielectric and optical properties, like absorption, reflectivity, refraction index, electron and X-ray energy loss, for a large variety of systems, ranging from bulk systems, surfaces, to clusters or atoms. It is distributed under the GNU/GPL license.
See also
ABINIT
DP code
YAMBO code
PWscf
Quantum chemistry computer programs
References
Physics software
Computational chemistry software | EXC code | [
"Physics",
"Chemistry",
"Materials_science"
] | 128 | [
"Materials science stubs",
"Computational chemistry software",
"Chemistry software",
"Theoretical chemistry stubs",
"Computational physics",
"Computational chemistry stubs",
"Computational chemistry",
"Condensed matter physics",
"Condensed matter stubs",
"Physical chemistry stubs",
"Computationa... |
14,416,980 | https://en.wikipedia.org/wiki/Homotrimer | In molecular biology, a homotrimer () is a protein which is composed of three identical subunits of polypeptide.
Examples
Hemagglutinin (influenza)
Spike protein (coronavirus)
See also
Protein trimer
References
Peptides | Homotrimer | [
"Chemistry"
] | 52 | [
"Biomolecules by chemical classification",
"Peptides",
"Molecular biology"
] |
14,417,117 | https://en.wikipedia.org/wiki/Microbarometer | Microbarometers are sensitive barometers that can measure air pressure with high precision. Microbarometers typically have a resolution of microbars (μbar) or pascals (Pa), while ordinary barometers
can only resolve in hectopascals (hPa) or millibars (mbar). Recording microbarometers, or microbarographs, distributed around the world are planned to be used to monitor compliance with the Comprehensive Nuclear-Test-Ban Treaty (upon entry into force) by detecting the infrasound signature of a nuclear explosion, which can propagate for very long distances. By analyzing the data received at several of these monitoring stations, the location and yield of the explosion can be determined.
A microbarometer used as a pressure altimeter would be able to resolve altitude differences on the order of centimeters, but for the presence of infrasonic noise such as microbaroms.
References
Pressure gauges
Meteorological instrumentation and equipment | Microbarometer | [
"Technology",
"Engineering"
] | 202 | [
"Pressure gauges",
"Meteorological instrumentation and equipment",
"Measuring instruments"
] |
14,417,255 | https://en.wikipedia.org/wiki/Endothelin%20A%20receptor | Endothelin receptor type A, also known as ETA, is a human G protein-coupled receptor.
Interactions
Endothelin receptor type A has been shown to interact with HDAC7A and HTATIP.
See also
Endothelin receptor
References
External links
Further reading
G protein-coupled receptors | Endothelin A receptor | [
"Chemistry"
] | 61 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,417,276 | https://en.wikipedia.org/wiki/Remote%20data%20transmission | Remote data transmission (RDT) was a term used in the 1980s, primarily in Germany, for the transmission of data between computers over a medium using a communications protocol. At the time, the most widespread form was RDT over the telephone network.
Other transmission media like radio waves or light were also used. Most RDT now uses the Internet.
In German speaking areas, RDT is used in the special sense of the considerably more narrowly defined Electronic Data Interchange (EDI).
Systems for remote administration of facilities and remote control adjustments may use remote data transmission standards.
To be transmittable, data must be appropriately prepared for the medium. For this, special hardware, e.g., a modem or an ISDN card is necessary.
History
When remote data transmission began, data were exchanged by the use of diskettes, magnetic tape, punched tape and dispatched via courier (the so-called sneaker net).
In the beginning, electronic remote data transmission was also accomplished through special adapters on special data or telex lines, teleprinter, serial ports, and analog telephone] or over simple radio connections.
Acoustic couplers that could be attached to a normal telephone handset, and later modems, were used.
RDT achieved great significance for private users at the end of the 1980s with the arrival of local and global bulletin board systems like FidoNet and CompuServe. Many of these systems later had internet access via computer gateways, but they were mostly discontinued by the end of the 1990s with the internet rise to dominance.
Communication between PCs through the internet is also a form of remote data transmission.
Methods and transmission standards
Wireless LAN
RS-232
V.90
ISDN
DSL with the variations ADSL, ADSL2+, SDSL and VDSL
Ethernet
Bluetooth
GSM with the extensions HSCSD, GPRS and EDGE
UMTS with the extension HSDPA
IrDA
See also
start bit
stop bit
parity bit
baudrate
flow control
data rate
Hayes command set
electronic banking
References
Broadcast engineering
Digital technology | Remote data transmission | [
"Technology",
"Engineering"
] | 418 | [
"Information and communications technology",
"Broadcast engineering",
"Electronic engineering",
"Digital technology"
] |
14,417,370 | https://en.wikipedia.org/wiki/EPH%20receptor%20B2 | Ephrin type-B receptor 2 is a protein that in humans is encoded by the EPHB2 gene.
Function
Ephrin receptors and their ligands, the ephrins, mediate numerous developmental processes, particularly in the nervous system. Based on their structures and sequence relationships, ephrins are divided into the ephrin-A (EFNA) class, which are anchored to the membrane by a glycosylphosphatidylinositol linkage, and the ephrin-B (EFNB) class, which are transmembrane proteins. The Eph family of receptors are divided into 2 groups based on the similarity of their extracellular domain sequences and their affinities for binding ephrin-A and ephrin-B ligands. Ephrin receptors make up the largest subgroup of the receptor tyrosine kinase (RTK) family. The protein encoded by this gene is a receptor for ephrin-B family members.
Animal studies
EphB2 is part of the NMDA signaling pathway and restoring expression rescues cognitive function in an animal model of Alzheimer's disease.
A recessive EphB2 gene is responsible for the crested-feather mutation in pigeons.
Interactions
EPH receptor B2 has been shown to interact with:
Abl gene
RAS p21 protein activator 1
Src
References
Tyrosine kinase receptors | EPH receptor B2 | [
"Chemistry"
] | 288 | [
"Tyrosine kinase receptors",
"Signal transduction"
] |
14,417,573 | https://en.wikipedia.org/wiki/Peter%20Thomas%20Dunican | Peter Thomas Dunican (15 March 1918 – 18 December 1989) was a structural engineer and former chairman of Ove Arup & Partners.
Life and career
Involved in Ove Arup & Partners from its early days, and becoming a partner in 1956, Peter Dunican is widely regarded as the right-hand man of Ove Arup, the firm's founder. In the words of Jack Zunz and Peter Hobbs, other senior partners from the firm, after his death in 1989:
"If Ove is the architect-philosopher, Peter is the builder, the doer who moulded the philosophies into workable arrangements whereby so many hundreds of talented people have come together to work under the Arup banner."
Dunican became chairman of the Ove Arup Partnership, a trust which owned Ove Arup & Partners on behalf of its staff, in 1977.
As senior partner at Arup from 1956, Dunican is credited with overseeing much of its growth from a single office in London in 1946 to a firm of over 15000 staff (in 2020). He also worked on many of the firms most iconic projects, including the Sydney Opera House, Coventry Cathedral, Centre Pompidou, the Barbican Estate and others.
He was elected a Fellow of the Royal Academy of Engineering in 1978, president of the Institution of Structural Engineers for 1977–78 and was appointed CBE in the 1977 New Year Honours.
He died in 1989.
References
1918 births
1989 deaths
Commanders of the Order of the British Empire
Structural engineers
Fellows of the Royal Academy of Engineering
Presidents of the Institution of Structural Engineers | Peter Thomas Dunican | [
"Engineering"
] | 331 | [
"Structural engineering",
"Structural engineers"
] |
14,417,837 | https://en.wikipedia.org/wiki/ID1 | DNA-binding protein inhibitor ID-1 is a protein that in humans is encoded by the ID1 gene.
Function
The protein encoded by this gene is a helix-loop-helix (HLH) protein that can form heterodimers with members of the basic HLH family of transcription factors. The encoded protein has no DNA binding activity and therefore can inhibit the DNA binding and transcriptional activation ability of basic HLH proteins with which it interacts. This protein may play a role in cell growth, senescence, and differentiation. Two transcript variants encoding different isoforms have been found for this gene.
Interactions
ID1 has been shown to interact weakly with MyoD but very tightly with ubiquitously expressed E proteins. E proteins heterodimerize with tissue restricted bHLH proteins such as Myod, NeuroD, etc. to form active transcription complexes so by sequestering E proteins, Id proteins can inhibit tissue restricted gene expression in multiple cell lineages using the same biochemical mechanism. Other interacting partners include CASK.
Clinical significance
ID1 can be used to mark endothelial progenitor cells which are critical to tumor growth and angiogenesis. Targeting ID1 results in decreased tumor growth. ID1 has been shown to be targeted by cannabidiol in certain gliomas and breast cancers.
See also
Inhibitor of DNA-binding protein
References
Further reading
External links
Transcription factors
Aging-related genes | ID1 | [
"Chemistry",
"Biology"
] | 290 | [
"Transcription factors",
"Gene expression",
"Signal transduction",
"Senescence",
"Aging-related genes",
"Induced stem cells"
] |
14,417,898 | https://en.wikipedia.org/wiki/Madala%20Panji | The Madala Panji is a chronicle of the Jagannath Temple, Puri, Odisha, India. It describes the historical events of Odisha related to Lord Jagannath and the Jagannath Temple. The Madala Panji dates from the 12th century.
Madala Panji's role in Odia history
The Madala Panji was traditionally written on a year-to-year basis on Vijaya-Dashami day. The Karanas (official history writers of Puri, a caste of Odisha, involved in keeping the chronicle. This ritual is cited as a proof that the tradition of keeping this chronicle began with Odia king Anantavarman Chodaganga Dev (1078–1150) himself. There are some, like Dr. Harekrushna Mahatab, Dr.Nilakantha Dash and Dr. Krushna Chandra Panigrahi who hold that the Panji dates from the reign of Ramachandra Deva I who re-established the worship of Lord Jagannatha after Kalapahad said to have destroyed it. The arguments are complex, but it is likely that much of the early record was indeed lost in the period that followed Kala Pahad and was rewritten in a fashion that mixed legend with history.
Writers of Panji
According to the tradition, Anantavarman Chodaganga created 24 families of Karanas to preserve the temple records. Of these, five were entrusted with the writing and preservation of the Madala Panji. They are:
Panjia Karan—preserves the Madala Panji
Tadau Karan—writes the Madala Panji
Deula Karan—enforces the Madala
Kotha Karan—the main compiler
Baithi Karan – assistant
Classification
In subsequent stage, due to the bulky size of Madala Panji, its content covering different dimensions related to temple management, it was divided into four parts:
Bhandara Khanja Madala (maintained by Pattajoshi Mohapatra)
Deula Madala / Karmangi Madala (maintained by Deula Karana)
Deshapanji Madala (prepared by Deula Karana)
Rajakhanja Madala (prepared and maintained by Tadhau Karana),
Types of Panjis
There are also five different categories of Panjis. No one has seen them all.
Raja Khanja—important events of the Rajas. Read on Paush Purnima (Pushyabhishek). Kept by Tadau Karan.
Desh Khanja—Records gifts of land and money and occasions when the Jagannath temple was plundered. Kept by Kotha Karan.
Karmangi. Daily rituals. Important events related to the rituals recorded. Announced daily at the Beherana.
Dina Panji—The daily almanac read by the temple astrologer at the time of the Avakash. These were prepared annually and finalized on Vishuva Sankranti.
Besides the Madala, there were other Karans who wrote regional chronicles, known as Chakadas. "All the Kadatas and Chakadas taken together will be about a cartload."
Madala Panji in recent years
Madala Panji language is Odia and was recorded in Odia and Telugu script, preserved in the Manuscript Library in Madras, which speaks about the story regarding image of Neela Madhava or Lord Jagannath of Udra desa, as Odisha was known in Middle Ages. It seems to have re-written during 16th century when the King of Khurda had newly installed the images after destruction made by Kalapahad, the notorious general of the Sultan of Bengal.
Notable Odia writer and Padma Shri awardee Artaballabha Mohanty has published the only available print record of Madala Panji.
See also
Odia script
Odia language
Odia literature
References
History of Odisha
Jagannath
Calendars
Indian chronicles | Madala Panji | [
"Physics"
] | 801 | [
"Spacetime",
"Calendars",
"Physical quantities",
"Time"
] |
14,417,904 | https://en.wikipedia.org/wiki/Brostallicin | Brostallicin is a chemical compound being studied in the treatment of cancer. It is an alkylating agent that binds DNA.
References
Experimental cancer drugs
Pyrroles
Organobromides
Halogen-containing natural products
Guanidine alkaloids
Alkene derivatives
Carboxamides | Brostallicin | [
"Chemistry"
] | 61 | [
"Alkaloids by chemical classification",
"Guanidine alkaloids"
] |
14,419,104 | https://en.wikipedia.org/wiki/Rivet%20gun | A rivet gun, also known as a rivet hammer or a pneumatic hammer, is a type of tool used to drive rivets. The rivet gun is used on rivet's factory head (the head present before riveting takes place), and a bucking bar is used to support the tail of the rivet. The energy from the hammer in the rivet gun drives the work and the rivet against the bucking bar. As a result, the tail of the rivet is compressed and work-hardened. At the same time the work is tightly drawn together and retained between the rivet head and the flattened tail (now called the shop head, or buck-tail, to distinguish it from the factory head). Nearly all rivet guns are pneumatically powered. Those rivet guns used to drive rivets in structural steel are quite large while those used in aircraft assembly are easily held in one hand. A rivet gun differs from an air hammer in the precision of the driving force.
Rivet guns vary in size and shape and have a variety of handles and grips. Pneumatic rivet guns typically have a regulator which adjusts the amount of air entering the tool. Regulated air entering passes through the throttle valve which is typically controlled by a trigger in the hand grip. When the trigger is squeezed, the throttle valve opens, allowing the pressurized air to flow into the piston. As the piston moves, a port opens allowing the air pressure to escape. The piston strikes against the rivet set. The force on the rivet set pushes the rivet into the work and against the bucking bar. The bucking bar deforms the tail of the rivet. The piston is returned to the original position by a spring or the shifting of a valve allowing air to drive the piston back to the starting position.
Slow-hitting
The slow-hitting gun strikes multiple blows as long as the trigger is held down. The repetition rate is about 2,500 blows-per-minute (bpm). It is easier to control than a one-hit gun. This is probably the most common type of rivet gun in use.
Fast-hitting gun
The fast-hitting gun strikes multiple light-weight blows at a high rate as long as the trigger is held down. These are repeated in the range of 2,500 to 5,000 bpm. The fast-hitting gun, sometimes referred to as a vibrator, is generally used with softer rivets.
Corner riveter
The corner riveter is a compact rivet gun that can be used in close spaces. The rivet is driven at right-angles to handle by a very short barreled driver.
Squeeze riveter
This gun is different from the above rivet guns in that the air pressure is used to provide a squeezing action that compresses the rivet from both sides rather than distinct blows. The squeeze riveter can only be used close to the edge because of the limited depth of the anvil. Once properly adjusted, the squeeze riveter will produce very uniform rivet bucks. The stationary (fixed) jaw is placed against the head and the buck is compressed by the action of the gun.
Pop-rivet gun
A pop rivet gun is made to apply pop rivets to a workpiece, and was invented in 1916 by Hamilton Wylie. This type of rivet gun is unique in its operation, because it does not hammer the rivet into place. Rather, a pop rivet gun will form a rivet in-place.The gun is fed over the rivet's mandrel (a shaft protruding from the rivet head) and the rivet tail is inserted into the work. When the gun is actuated (typically by squeezing the handle), a ball on the rivet's tail is drawn towards the head, compressing a metal sleeve between the ball and the head. This forms another "head" on the opposing side to the workpiece, drawing the work together and holding it securely in place. The mandrel has a weak point that breaks, or "pops" when the riveting process is complete. This style of rivet does not require the use of a bucking bar, because the force applied is away from the work.
See also
Machine
Orbital riveting
Ring binder
Rivet
Riveting machines
References
Further reading
Bureau of Naval Personnel - [US] Navy Training Course Aviation Structural Mechanic S 3 & 2 NavPers 10308-A''. U.S. Navy Training Publications Center, Memphis, Tennessee, 1966, 380 pages
Hand-held power tools
Mechanical hand tools
Metalworking tools
Pneumatic tools
Articles containing video clips | Rivet gun | [
"Physics"
] | 967 | [
"Mechanics",
"Mechanical hand tools"
] |
14,419,318 | https://en.wikipedia.org/wiki/Robot%20Building | The Robot Building (, , ), located in the Sathorn business district of Bangkok, Thailand, houses United Overseas Bank's Bangkok headquarters. It was designed for the Bank of Asia by Sumet Jumsai to reflect the computerization of banking; its architecture is a reaction against neoclassical and high-tech postmodern architecture. The building's features, such as progressively receding walls, antennas, and eyes, contribute to its robotic appearance and to its practical function. Completed in 1986, the building is one of the last examples of modern architecture in Bangkok.
Design
Thai architect Sumet Jumsai designed the Robot Building for the Bank of Asia, which was acquired by United Overseas Bank in 2005. He had been asked by the Bank of Asia's directors to design a building that reflected the modernization and computerization of banking and found inspiration in his son's toy robot.
Sumet designed the building in conscious opposition to postmodern styles of the era, particularly classical revivalism and high-tech architecture as embodied in the . While Sumet praised the inception of postmodernism as a protest against puritanical, bland modern design, he called it "a protest movement which seeks to replace without offering a replacement". Sumet dismissed mid-1980s classical revivalism as "intellectual[ly] bankrupt[]" and criticized the "catalogue[s] of meaningless architectural motifs" that characterized classical revivalism in Bangkok. He further dismissed high-tech architecture, "which engrosses itself in the machine while at the same time secretly...lov[ing]...handmade artifacts and honest manual labor", as a movement without a future.
Sumet wrote that his building "need not be a robot" and that a "host of other metamorphoses" would suffice, so long as they could "free the spirit from the present intellectual impasse and propel it forward into the next century". He wrote that his design might be considered post-high-tech: rather than exhibiting the building's inner workings, he chose to adorn a finished product with the abstractions of mechanical parts. His building, he argued, struck against the 20th century vision of the machine as a "separate entity" often "elevated on a pedestal for worship" and, by becoming "a part of our daily lives, a friend, ourselves", cleared the way for the 21st century amalgam of machine and man.
The building was completed in 1986 at a cost of US$10 million. By the mid-1980s, architectural modernism had faded in Bangkok; this building is one of the last examples of the style.
Renovation
In early 2023, the building was covered up and a plan to "renovate" the building was realised. It was feared that the renovation may removed the original designs of the building as the planned rendition was never publicly released. A petition was launched on Change.org to have the owner, UOB Thailand, revise the plan and to maintain the original iconic appearances of the building. The architect Chumsai also has contacted UOB Thailand to voice his concerns. Chumsai was concern with the building's remodelling and stated in an interview with Bangkok Post that the iconic design likely will turn into "yet another office building". In his email to CNN he described the renovation as a "defacement" that demonstrates the "ignorance and arrogance (of) big corporations". UOB's statements over this renovations were to bring it "into a new era while paying homage to its heritage", and have been "carefully planned to balance the need for modernization with respect for the building’s original structure". Construction is expected to be finished by 2025.
Characteristics
The building is 20 stories tall and has a total floor area of 23,506 m² (253,016 ft²). The floor areas decrease progressively at the 4th, 8th, 12th, 16th, and 18th floors; the staggered shape both contributes to the robot's appearance and is an efficient solution to setback regulations requiring an 18 degree incline from each side of the property line. The building's ground floor is a double-height banking hall. The hall's interior architecture, designed in association with the firm 7 Associates, was designed to further the robotic appearance of the building; four sculptures by Thai artist Thaveechai Nitiprabha stand at the main door. Mezzanine floors located on each side of the banking hall contain offices and meeting rooms. The building's second floor features a large multipurpose hall, offices, and training rooms, and its upper floors contain general office space. An eight-story parking garage is located behind the main building.
The decorative exterior contributes its building's robotic appearance, though it often serves practical functions as well. Two antennas on the building's roof are used for communications and as lightning rods. On the building's upper facade, in front of the main meeting and dining rooms of the top executive suites, are two lidded eyeballs that serve as windows. The eyeballs are made of reflective glass; the lids are made of metallic louvers. Nuts made of glass-reinforced concrete adorn the building's sides; the building's largest nuts measure in diameter and were the largest in the world at the time of their construction. The building's east and west walls (the robot's sides) have few apertures to shield its interior from the sun and to increase energy efficiency, and its north and south sides (the robot's front and back) are tinted curtain walls whose bright blue color was chosen because it was the symbol of the Bank of Asia.
Recognition
The Robot Building was selected by the Museum of Contemporary Art, Los Angeles as one of the 50 seminal buildings of the century. The building also earned Sumet an award from Chicago's Athenaeum Museum of Architecture and Design, the first such award given to a Thai designer. According to Stephen Sennott's Encyclopedia of 20th Century Architecture, the building "enhanced the world's recognition of modern Thai architecture".
See also
Architecture of Thailand
Modern architecture
UOB Plaza in Singapore, which houses UOB's global headquarters
References
Notes
Works cited
Kusno, Abidin. Behind the Postcolonial: Architecture, Urban Space and Political Cultures in Indonesia. Routledge (2000). .
Sennott, Stephen (editor). Encyclopedia of 20th Century Architecture. Taylor & Francis (2004). .
Sumet Jumsai. "Building Study: Bank of Asia, Bangkok." Mimar: Architecture in Development 23 (1987): 74–81. Singapore: Concept Media Ltd.
Williams, China and Joe Cummings. Bangkok. Lonely Planet (2004). .
External links
3D building model at Google 3D Warehouse
Buildings and structures in Bangkok
Office buildings completed in 1986
Postmodern architecture
Sathon district
Office buildings in Thailand
Sumet Jumsai buildings and structures | Robot Building | [
"Engineering"
] | 1,413 | [
"Postmodern architecture",
"Architecture"
] |
14,419,407 | https://en.wikipedia.org/wiki/Matrix%20Gla%20protein | Matrix Gla protein (MGP) is member of a family of vitamin K2 dependent, Gla-containing proteins. MGP has a high affinity binding to calcium ions, similar to other Gla-containing proteins. The protein acts as an inhibitor of vascular mineralization and plays a role in bone organization.
MGP is found in a number of body tissues in mammals, birds, and fish. Its mRNA is present in bone, cartilage, heart, and kidney.
It is present in bone together with the related vitamin K2-dependent protein osteocalcin. In bone, its production is increased by vitamin D.
Genetics
The MGP was linked to the short arm of chromosome 12 in 1990. Its mRNA sequence length is 585 bases long in humans.
Physiology
MGP and osteocalcin are both calcium-binding proteins that may participate in the organisation of bone tissue. Both have glutamate residues that are post-translationally carboxylated by the enzyme gamma-glutamyl carboxylase in a reaction that requires Vitamin K hydroquinone.
Role in disease
Abnormalities in the MGP gene have been linked with Keutel syndrome, a rare condition characterised by abnormal calcium deposition in cartilage, peripheral stenosis of the pulmonary artery, and midfacial hypoplasia.
Mice that lack MGP develop to term but die within two months as a result of arterial calcification which leads to blood-vessel rupture.
References
External links
Extracellular matrix proteins
Genes on human chromosome 12
Glycoproteins | Matrix Gla protein | [
"Chemistry"
] | 323 | [
"Glycoproteins",
"Glycobiology"
] |
14,419,595 | https://en.wikipedia.org/wiki/RIMPUFF | RIMPUFF is a local-scale puff diffusion model developed by Risø DTU National Laboratory for Sustainable Energy, Denmark. It is an emergency response model to help emergency management organisations deal with chemical, biological and radiological releases to the atmosphere.
RIMPUFF is in operational use in several European national emergency centres for preparedness and prediction of nuclear accidental releases (RODOS, EURANOS, ARGOS), chemical gas releases (ARGOS), and for airborne Foot-and Mouth Disease virus spread
Description
RIMPUFF builds from parameterized formulas for puff diffusion, wet and dry deposition, and gamma dose radiation. Its range of application covers distances up to ~1000 km from the point of release.
RIMPUFF calculates the instantaneous atmospheric dispersion taking into account the local wind variability and the local turbulence levels. The puff sizes represent instantaneous relative diffusion (no averaging) and is calculated from similarity scaling theory.
Puff diffusion is parameterized for travel times in the range from a few seconds and up to ~1 day.
Wet and dry deposition is also calculated as a function of local rain intensity and turbulence levels.
See also
List of atmospheric dispersion models
UK Atmospheric Dispersion Modelling Liaison Committee
UK Dispersion Modelling Bureau
Further reading
For those who are unfamiliar with air pollution dispersion modelling and would like to learn more about the subject, it is suggested that either one of the following books be read:
References
(Click on the blue up arrow to display the text portion relevant to the reference)
External links
Model Documentation System - a detailed catalogue of the models developed in Europe.
Atmospheric dispersion modeling
Air pollution | RIMPUFF | [
"Chemistry",
"Engineering",
"Environmental_science"
] | 330 | [
"Atmospheric dispersion modeling",
"Environmental modelling",
"Environmental engineering"
] |
14,419,822 | https://en.wikipedia.org/wiki/Storage%40home | Storage@home was a distributed data store project designed to store massive amounts of scientific data across a large number of volunteer machines. The project was developed by some of the Folding@home team at Stanford University, from about 2007 through 2011.
Function
Scientists such as those running Folding@home deal with massive amounts of data, which must be stored and backed up, and this is very expensive. Traditionally, methods such as storing the data on RAID servers are used, but these become impractical for research budgets at this scale. Pande's research group already dealt with storing hundreds of terabytes of scientific data. Professor Vijay Pande and student Adam Beberg took experience from Folding@home and began work on Storage@home. The project is designed based on the distributed file system known as Cosm, and the workload and analysis needed for Folding@home results. While Folding@home volunteers can easily participate in Storage@home, much more disk space is needed from the user than Folding@home, to create a robust network. Volunteers each donate 10 GB of storage space, which would hold encrypted files. These users gain points as a reward for reliable storage. Each file saved on the system is replicated four times, each spread across 10 geographically distant hosts. Redundancy also occurs over different operating systems and across time zones. If the servers detect the disappearance of an individual contributor, the data blocks held by that user would then be automatically duplicated to other hosts. Ideally, users would participate for a minimum of six months, and would alert the Storage@home servers before certain changes on their end such as a planned move of a machine or a bandwidth downgrade. Data stored on Storage@home was maintained through redundancy and monitoring, with repairs done as needed. Through careful application of redundancy, encryption, digital signatures, automated monitoring and correction, large quantities of data could be reliably and easily retrieved. This ensures a robust network that will lose the least possible data.
Storage Resource Broker is the closest storage project to Storage@home.
Status
Storage@home was first made available on September 15, 2009, in a testing phase. It first monitored availability data and other basic statistics on the user's machine, which would be used to create a robust and capable storage system for storing massive amounts of scientific data. However, in the same year it became inactive, despite initial plans for more to come. On April 11, 2011, Pande stated his group had no active plans with Storage@home.
See also
Folding@home
Cosm
SETI@home
Genome@home
RAID
OFF System
References
Distributed computing projects
Distributed file systems | Storage@home | [
"Engineering"
] | 535 | [
"Distributed computing projects",
"Information technology projects"
] |
14,419,911 | https://en.wikipedia.org/wiki/Glucic%20acid | Glucic acid is an acid produced by the action of acids on cane-sugar or of alkalis on glucose.
References
Organic acids
Aldehydes
Secondary alcohols
3-Hydroxypropenals | Glucic acid | [
"Chemistry"
] | 44 | [
"Organic compounds",
"Organic acids",
"Acids"
] |
14,419,927 | https://en.wikipedia.org/wiki/Angiotensin%20II%20receptor%20type%202 | Angiotensin II receptor type 2, also known as the AT2 receptor is a protein that in humans is encoded by the AGTR2 gene.
Function
Angiotensin II is a potent pressor hormone and a primary regulator of aldosterone secretion. It is an important effector controlling blood pressure and volume in the cardiovascular system. It acts through at least two types of receptors termed AT1 and AT2. AGTR2 belongs to a family 1 of G protein-coupled receptors. It is an integral membrane protein. It plays a role in the central nervous system and cardiovascular functions that are mediated by the renin–angiotensin system. This receptor mediates programmed cell death (apoptosis). Consistent with its apoptotic function, angiotensin II receptor type II also opposes cell proliferation, as demonstrated by its antagonism of MAPK activity in cardiac fibroblasts during interstitial fibrosis. In adults, it is highly expressed in myometrium with lower levels in adrenal gland and fallopian tube. It is highly expressed in fetal kidney and intestine. The human AGTR2 gene is composed of three exons and spans at least 5 kb. Exons 1 and 2 encode for 5' untranslated mRNA sequence and exon 3 harbors the entire uninterrupted open reading frame.
Stimulation of AT2 by the selective agonist CGP 42112A increases mucosal nitric oxide production.
Gene
Angiotensin II receptor type 2 (AGTR2) gene is a protein coding gene responsible for encoding AGTR2, the integral membrane protein that binds to two different G-protein coupled receptors. AGTR2 has recently been discovered to play a role in modifying lung disease. This receptor functions to mediate signaling in lung fibrosis and regulate nitric oxide synthase expression in pulmonary endothelium. AGTR2 has recently been prescribed as a target for lung inflammation therapy in cases of cystic fibrosis (CF). The X-chromosome region associated with CF lung disease is located in a non-coding region 3′ of the AGTR2 gene. The modification effect is likely due to variation in gene regulation rather than a change in protein coding sequence.
Variants at the X-chromosome locus containing AGTR2 gene were identified as significantly associating with lung function in patients with cystic fibrosis. Genetically modified mouse studies determined that absence of the AGTR2 gene normalized pulmonary function indicators in two independent CF mouse models. Furthermore, pharmacological antagonism of AGTR2 signaling improved lung function in CF mice to near wild-type levels. Manipulation of the angiotensin-signaling pathway to reduce AGTR2 signaling may be translatable for the treatment or prevention of CF.
Interactions
Angiotensin II receptor type 2 has been shown to interact with MTUS1.
See also
Angiotensin II receptor
References
Further reading
External links
G protein-coupled receptors
Genes mutated in mice | Angiotensin II receptor type 2 | [
"Chemistry"
] | 621 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,420,850 | https://en.wikipedia.org/wiki/Brain-specific%20angiogenesis%20inhibitor | Brain-specific angiogenesis inhibitors are G-protein coupled receptors belonging to the class B secretin subfamily. Members include:
Brain-specific angiogenesis inhibitor 1
Brain-specific angiogenesis inhibitor 2
Brain-specific angiogenesis inhibitor 3
References
External links
Angiogenesis
G protein-coupled receptors | Brain-specific angiogenesis inhibitor | [
"Chemistry",
"Biology"
] | 62 | [
"G protein-coupled receptors",
"Angiogenesis",
"Signal transduction"
] |
14,421,128 | https://en.wikipedia.org/wiki/Conflict%20avoidance | Conflict avoidance refers to a set of behaviors aimed at preventing or minimizing disagreement with another person. These behaviors can occur before the conflict emerges (e.g., avoiding certain topics, changing the subject) or after the conflict has been expressed (e.g., withholding disagreement, withdrawing from the conversation, giving in). Conflict avoidance can be employed as a temporary measure within a specific situation or as a more permanent approach, such as establishing "taboo topics" or exiting a relationship. Although conflict avoidance can exist in any interpersonal relationship, it has been studied most closely in the contexts of family and work relationships. Consequently, research on conflict avoidance spans various disciplines including: clinical psychology, social psychology, organizational behavior, communication studies, and family studies.
Scholars use the term "conflict avoidance" to characterize specific behaviors as well as a broader conflict style. A conflict management style is an individual's preferred method for handling conflict. Those with an avoidant style tend to sidestep disagreement, postpone dealing with conflict, or withdraw. Traditionally, conflict avoidance has been considered a dysfunctional approach to managing conflict by researchers, clinicians, and the general public because it leaves issues unresolved and can lead to resentment. However, studies on conflict avoidance have produced mixed results, identifying functional benefits such as strengthening relationships, reducing stress, and increasing productivity. The general consensus is that avoidance is neither inherently good nor bad for conflict management but depends on the specific relationship, topic, and context.
Origins and theoretical framework
Strategic goals
Early research in conflict management focused on effective ways to actively manage conflict within the organizational setting. This line of research was largely inspired by the Management Grid introduced by theoreticians Robert R. Blake and Jane Mouton as well as Morton Deustch’s Theory of Cooperation and Competition. In the 1970s and 80s, various management scholars redeveloped these models, renaming the various dimensions and developing self-report scales to measure individual conflict management styles. One of the most popular versions to come out of this research was the Dual Concerns Model introduced by Pruitt & Rubin (1986) to predict behavior in negotiations. They labeled the two dimensions: concern for self and concern for others. The avoidance conflict style is marked by a low concern for self and low concern for their negotiation partner. While the specific labels for each dimension and conflict styles vary across different models, avoidance is generally considered a passive, lose-lose approach.
Personality
Conflict avoidance is often rooted in early socialization and personality traits that influence individuals' perception of potential harms or opportunities. According to communication scholar Michael Roloff, individuals often seek to create and maintain a state of interpersonal harmony in their relationships, which is defined by consensus about most issues. The existence of conflict threatens harmony, and some individuals report that they generally wish to avoid conflict. For example, some individuals have a low tolerance for disagreement, tend to take conflict personally, and believe that conflict is always destructive. Research has found that conflict avoidance is positively associated with agreeableness and neuroticism. One study of 350 undergraduates and 100 managers discovered that personality traits, as measured by the Big Five, accounted for 20% of the variance in avoidant conflict style.
Cultural influences
According to Stella Ting-Toomey's Face Negotiation Theory, avoidant behavior may also be motivated by face concerns, defined as the self-image an individual has in social interactions. This theory is used by cross-cultural researchers to explain how people from different cultures interpret and react to conflict. For example, in collective societies, there is more of a sensitivity to hierarchy compared to the West, leading to greater avoidance when there is significant separation between the parties involved. In collective societies, there are also greater relationship-oriented values and a belief that a direct approach will harm a relationship, causing a greater prevalence of conflict avoidance. Generally, individuals from collectivist societies are more likely to avoid conflict compared to individuals from individualistic societies.
Consequences of conflict avoidance
Research within conflict avoidance psychology has identified three areas that are significantly impacted by an individual's choices surrounding conflict: stress, loneliness, and relationship satisfaction. According to communication scholar Michael Roloff, the general sentiment is that leaving conflicts unresolved and unaddressed causes interpersonal issues to fester, resulting in either explosive confrontation or crippling emotional suppression. However, empirical research has found mixed results, associating conflict avoidance with both positive and negative outcomes.
Intimate relationships
Partners in long-term relationships often "pick their battles" and withhold complaints to manage conflict. However, withdrawing from conflict has been associated with higher rates of divorce and lower relationship quality. According to communication scholars Caughlin & Scott, explicit avoidance is far more damaging than implicit or tacit avoidance.
Conflict avoidance is just as prevalent within stable marriages as in unstable ones. Overall, the effect of conflict avoidance may depend on the interpretation of the behavior rather than the behavior itself.
Family relationships
Conflict in families can serve an important function, supporting child development through individuation and communicating the specific needs of individual family members. When conflicts are avoided, individuals may perceive their family as unresponsive or indifferent to their needs, which increases frustration and hostility. Conflict avoidance has been associated with poor outcomes for children, including loneliness and maladjustment.
In the workplace
Conflict avoidance has received considerably less study and attention compared to active conflict management behaviors such as mediation or integrative negotiation. This is partly due to the difficulty of studying unobservable behaviors such as "not engaging" or "avoiding" conflict. In the workplace, avoiding conflict often leads to emotional suppression and feelings of powerlessness, which can increase stress, burnout, and fatigue. From a productivity perspective, conflict avoidance is negatively related to information exchange and team cohesiveness. Unresolved conflict in the workplace has been linked to miscommunication resulting from confusion or refusal to cooperate, increased stress, reduced creative collaboration and team problem-solving, and distrust. However, this negative effect depends on the quality of workplace relationships; in generally positive relationships, avoiding conflict can be associated with higher productivity.
Measuring conflict avoidance
There are two main approaches to studying conflict avoidance in academic research: self-report scales and behavioral observation. Several instruments have been developed to measure conflict management styles based on the dual-concerns model and are listed below:
Interventions
Experts suggest that management should not wait for formal complaints to take action and should establish unrelated complaint networks such as counselors to provide a more effective outlet for avoiding employee distress. Managers should also develop strong cooperative goals and proactively train employees in conflict management which promotes more constructive conflict management.
See also
Organizational conflict
Conflict management
Conflict management style
Interpersonal relationship
References
Conflict (process) | Conflict avoidance | [
"Biology"
] | 1,356 | [
"Behavior",
"Aggression",
"Human behavior",
"Conflict (process)"
] |
14,421,203 | https://en.wikipedia.org/wiki/OPN1SW | Blue-sensitive opsin is a protein that in humans is encoded by the OPN1SW gene. The OPN1SW gene provides instructions for making a protein that is essential for normal color vision. This protein is found in the retina, which is the light-sensitive tissue at the back of the eye.
The OPN1SW gene provides instructions for making an opsin pigment that is more sensitive to light in the blue/violet part of the visible spectrum (short-wavelength light). Cones with this pigment are called short-wavelength-sensitive or S cones. In response to light, the photopigment triggers a series of chemical reactions within an S cone. These reactions ultimately alter the cell's electrical charge, generating a signal that is transmitted to the brain. The brain combines input from all three types of cones to produce normal color vision.
See also
Opsin
OPN1LW
OPN1MW
References
Further reading
G protein-coupled receptors
Color vision | OPN1SW | [
"Chemistry"
] | 200 | [
"G protein-coupled receptors",
"Signal transduction"
] |
14,421,385 | https://en.wikipedia.org/wiki/Robert%20Shields%20%28diarist%29 | Robert William Shields (May 17, 1918 – October 15, 2007) was an American minister and high school English teacher best known for writing a diary of 37.5 million words, which chronicled every five minutes of his life from 1972 until a stroke disabled him in 1997. Shields's diary, which filled 91 boxes, was longer than those kept by the journalist Edward Robb Ellis (21 million words) and the poet Arthur Crew Inman (17 million words), and 30 times longer than that of Samuel Pepys (1.25 million words).
Contents
Believing that discontinuing his diary would be like "turning off my life", he spent four hours a day in the office, on his back porch, in his underwear, recording his body temperature, blood pressure, medications, describing his urination and bowel movements, and slept for only two hours at a time so he could describe his dreams. The New York Times summarized the journal as being about anything "from changing light bulbs to pondering God to visiting the bathroom". He also left behind samples of his nose hair for future study. After his stroke in 1997, Shields tried to continue the diary by having his wife write what he told her to write, but she lacked the compulsion and energy to do so and stopped shortly afterward.
Shields's self-described "uninhibited", "spontaneous" work was astonishing in its mundaneness, and now fills 91 cartons in the collections of Washington State University, to whom he donated the work in 1999. In a May 2000 interview he said "I've written 1200 poems and at least five of 'em are good." He also claimed to have written the story base for Elvis Presley's film Love Me Tender based on the Reno Gang of Seymour, Indiana, where Shields was born. Copies of the manuscript are at the Kansas State Historical Society's E. P. Lamborn collection. Shields based his manuscript on John Reno's 1879 autobiography, although there is some uncertainty over the authorship of the Reno autobiography, with Shields himself having acted as editor for the only known published copy.
The journal for which he became known was not the first he had tried to keep; he had tried to write one at age 17 to chronicle a romantic relationship, but abandoned it after losing interest in the project.
Excerpts
Under the terms of the donation of his diary to Washington State University, the diary may not be read or subjected to an exact word count until 50 years from his death (i.e. in 2057). He said that it may not be read until both he and his wife died; she died in 2024 the university began cataloging the collection that year. However, many excerpts have appeared, including the following:
July 25, 1993
7 am: "I cleaned out the tub and scraped my feet with my fingernails to remove layers of dead skin."
7.05 am: "Passed a large, firm stool, and a pint of urine. Used five sheets of paper."
April 18, 1994
6:30–6:35: "I put in the oven two Stouffer's macaroni and cheese at 350°."
6:35–6:50: "I was at the keyboard of the IBM Wheelwriter making entries for the diary."
6.50–7.30: "I ate the Stouffer's macaroni and cheese and Cornelia ate the other one. Grace decided she didn't want one."
7.30–7.35: "We changed the light over the back stoop since the bulb had burnt out."
April 30, 1994
11:00–11:30: "I picked over parts of Newsweek and Time and Harvard magazine and reread them while I ate about a dozen leftover fish sticks. (Cold.)"
August 21, 1994
2:25–2:35: "I checked on whether our county tax payment had been received. It had."
August 13, 1995
8.45 am: "I shaved twice with the Gillette Sensor blade [and] shaved my neck behind both ears, and crossways of my cheeks, too."
Personal life
Shields was married to Grace Augusta Hotson, with whom he had three daughters: Klara, Cornelia, and Heidi. He died from a heart attack at his home in Dayton, Washington, on October 15, 2007, just over 10 years after the stroke that ended his work on his diary. He was 89 years old.
See also
Morris Villarroel
References
External links
Scanned pages from the April 1994 diary: Page 1, 2, 3, 4, 5, 6. NPR Sound Portraits
Scanned pages from the December 1995 diary
Radio interview (RealAudio format) on Michael Feldman's Whad'Ya Know?, May 6, 2000.
People from Seymour, Indiana
People from Dayton, Washington
1918 births
2007 deaths
American Protestant ministers and clergy
Writers from Indiana
Schoolteachers from Washington (state)
Writers from Washington (state)
20th-century American educators
20th-century American clergy
20th-century American diarists
Lifelogging | Robert Shields (diarist) | [
"Technology"
] | 1,043 | [
"Lifelogging",
"Computing and society"
] |
14,421,547 | https://en.wikipedia.org/wiki/Orbit%20%28control%20theory%29 | The notion of orbit of a control system used in mathematical control theory is a particular case of the notion of orbit in group theory.
Definition
Let
be a control system, where
belongs to a finite-dimensional manifold and belongs to a control set . Consider the family
and assume that every vector field in is complete.
For every and every real , denote by the flow of at time .
The orbit of the control system through a point is the subset of defined by
Remarks
The difference between orbits and attainable sets is that, whereas for attainable sets only forward-in-time motions are allowed, both forward and backward motions are permitted for orbits.
In particular, if the family is symmetric (i.e., if and only if ), then orbits and attainable sets coincide.
The hypothesis that every vector field of is complete simplifies the notations but can be dropped. In this case one has to replace flows of vector fields by local versions of them.
Orbit theorem (Nagano–Sussmann)
Each orbit is an immersed submanifold of .
The tangent space to the orbit
at a point is the linear subspace of spanned by
the vectors where denotes the pushforward of by , belongs to and is a diffeomorphism of of the form with and .
If all the vector fields of the family are analytic, then where is the evaluation at of the Lie algebra generated by with respect to the Lie bracket of vector fields.
Otherwise, the inclusion holds true.
Corollary (Rashevsky–Chow theorem)
If for every and if is connected, then each orbit is equal to the whole manifold .
See also
Frobenius theorem (differential topology)
References
Further reading
Control theory | Orbit (control theory) | [
"Mathematics"
] | 342 | [
"Applied mathematics",
"Control theory",
"Dynamical systems"
] |
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