source stringlengths 31 227 | text stringlengths 9 2k |
|---|---|
https://en.wikipedia.org/wiki/Damper%20%28flow%29 | A damper is a valve or plate that stops or regulates the flow of air inside a duct, chimney, VAV box, air handler, or other air-handling equipment. A damper may be used to cut off central air conditioning (heating or cooling) to an unused room, or to regulate it for room-by-room temperature and climate control -- for example in the case of Volume Control Dampers. Its operation can be manual or automatic. Manual dampers are turned by a handle on the outside of a duct. Automatic dampers are used to regulate airflow constantly and are operated by electric or pneumatic motors, in turn controlled by a thermostat or building automation system. Automatic or motorized dampers may also be controlled by a solenoid, and the degree of air-flow calibrated, perhaps according to signals from the thermostat going to the actuator of the damper in order to modulate the flow of air-conditioned air in order to effect climate control.
In a chimney flue, a damper closes off the flue to keep the weather (and birds and other animals) out and warm or cool air in. This is usually done in the summer, but also sometimes in the winter between uses. In some cases, the damper may also be partly closed to help control the rate of combustion. The damper may be accessible only by reaching up into the fireplace by hand or with a woodpoker, or sometimes by a lever or knob that sticks down or out. On a wood-burning stove or similar device, it is usually a handle on the vent duct as in an air conditioning system. Forgetting to open a damper before beginning a fire can cause serious smoke damage to the interior of a home, if not a house fire.
Automated zone dampers
A zone damper (also known as a Volume Control Damper or VCD) is a specific type of damper used to control the flow of air in an HVAC heating or cooling system. In order to improve efficiency and occupant comfort, HVAC systems are commonly divided up into multiple zones. For example, in a house, the main floor may be served by one he |
https://en.wikipedia.org/wiki/Intermediate%20disturbance%20hypothesis | The intermediate disturbance hypothesis (IDH) suggests that local species diversity is maximized when ecological disturbance is neither too rare nor too frequent. At low levels of disturbance, more competitive organisms will push subordinate species to extinction and dominate the ecosystem. At high levels of disturbance, due to frequent forest fires or human impacts like deforestation, all species are at risk of going extinct. According to IDH theory, at intermediate levels of disturbance, diversity is thus maximized because species that thrive at both early and late successional stages can coexist. IDH is a nonequilibrium model used to describe the relationship between disturbance and species diversity. IDH is based on the following premises: First, ecological disturbances have major effects on species richness within the area of disturbance. Second, interspecific competition results in one species driving a competitor to extinction and becoming dominant in the ecosystem. Third, moderate ecological scale disturbances prevent interspecific competition.
The hypothesis is ambiguous with its definitions of the terms "intermediate" and "disturbance". Whether a given disturbance can be defined as "intermediate" inherently depends on the previous history of disturbances within a given system, as well as the component of disturbance that is evaluated (i.e. the frequency, extent, intensity, or duration of the disturbances).
Disturbances act to disrupt stable ecosystems and clear species' habitat. As a result, disturbances lead to species movement into the newly cleared area. Once an area is cleared there is a progressive increase in species richness and competition takes place again. Once disturbance is removed, species richness decreases as competitive exclusion increases. "Gause's Law", also known as competitive exclusion, explains how species that compete for the same resources cannot coexist in the same niche. Each species handles change from a disturbance different |
https://en.wikipedia.org/wiki/Vinclozolin | Vinclozolin (trade names Ronilan, Curalan, Vorlan, Touche) is a common dicarboximide fungicide used to control diseases, such as blights, rots and molds in vineyards, and on fruits and vegetables such as raspberries, lettuce, kiwi, snap beans, and onions. It is also used on turf on golf courses. Two common fungi that vinclozolin is used to protect crops against are Botrytis cinerea and Sclerotinia sclerotiorum. First registered in 1981, vinclozolin is widely used but its overall application has declined. As a pesticide, vinclozolin is regulated by the United States Environmental Protection Agency (U.S. EPA). In addition to these restrictions within the United States, as of 2006 the use of this pesticide was banned in several countries, including Denmark, Finland, Norway, and Sweden.
It has gone through a series of tests and regulations in order to evaluate the risks and hazards to the environment and animals. Among the research, a main finding is that vinclozolin has been shown to be an endocrine disruptor with antiandrogenic effects.
Use in the United States
Vinclozolin is manufactured by the chemical company BASF and has been registered for use in the United States since 1981. The following is a compilation of data indicating the national use of vinclozolin per crop (lbs AI/yr) in 1987: apricots, 124; cherries, 3,301; green beans, 13,437; lettuce, 24,779; nectarines, 1,449; onions, 829; peaches, 15,203; plums, 163; raspberries, 3,247; and strawberries, 41,006. In 1997, two applications totaling 285 pounds each, were applied to kiwifruit in California to prevent the gray mold and soft rot caused by Botrytis cinerea. In general, the United States has seen an overall decline in the national use of vinclozolin. In 1992, a total of approximately 135,000 pounds were used. However, in 1997 this number dropped to 122,000 and in 2002 it was down to 55,000 pounds.
Preparation and application
The following chemical reactions are used to make vinclozolin: One method combin |
https://en.wikipedia.org/wiki/Turbomachinery | Turbomachinery, in mechanical engineering, describes machines that transfer energy between a rotor and a fluid, including both turbines and compressors. While a turbine transfers energy from a fluid to a rotor, a compressor transfers energy from a rotor to a fluid.
These two types of machines are governed by the same basic relationships including Newton's second Law of Motion and Euler's pump and turbine equation for compressible fluids. Centrifugal pumps are also turbomachines that transfer energy from a rotor to a fluid, usually a liquid, while turbines and compressors usually work with a gas.
History
The first turbomachines could be identified as water wheels, which appeared between the 3rd and 1st centuries BCE in the Mediterranean region. These were used throughout the medieval period and began the first Industrial Revolution. When steam power started to be used, as the first power source driven by the combustion of a fuel rather than renewable natural power sources, this was as reciprocating engines. Primitive turbines and conceptual designs for them, such as the smoke jack, appeared intermittently but the temperatures and pressures required for a practically efficient turbine exceeded the manufacturing technology of the time. The first patent for gas turbines were filed in 1791 by John Barber. Practical hydroelectric water turbines and steam turbines did not appear until the 1880s. Gas turbines appeared in the 1930s.
The first impulse type turbine was created by Carl Gustaf de Laval in 1883. This was closely followed by the first practical reaction type turbine in 1884, built by Charles Parsons. Parsons’ first design was a multi-stage axial-flow unit, which George Westinghouse acquired and began manufacturing in 1895, while General Electric acquired de Laval's designs in 1897. Since then, development has skyrocketed from Parsons’ early design, producing 0.746 kW, to modern nuclear steam turbines producing upwards of 1500 MW. Furthermore, steam turbines ac |
https://en.wikipedia.org/wiki/Simplesse | Simplesse is a multi-functional dairy ingredient made from whey protein concentrate used as a fat substitute in low-calorie foods. Originally brought to market in 1988, the manufacturer, CP Kelco (a former NutraSweet subsidiary), sells Simplesse to food processors as a "microparticulated whey protein concentrate" in dry powder form, and recommends that it be labelled as dairy protein on food labels. Older versions of the product also contain egg whites.
The protein is partially coagulated by heat, creating a micro dispersion, in a process known as microparticulation. It is due to the small particle size of the protein that the dispersion is perceivable as a fluid with similar creaminess and richness of fat.
History
Simplesse began in 1979 as "a substance that gelled like egg white but crumbled like Styrofoam." At that time, Shoji Yamamoto, an associate of Norman S. Singer at Canadian beer company John Labatt Ltd. in London, Ontario, brought Singer the whey protein substance. After sensing that it gave the taste texture of cream cheese, another scientist put a sample under a powerful microscope and saw "tiny spheres of protein rolling over each other" about a tenth the size of particles of powdered sugar. It was this particle rolling action that gave a smooth creaminess sensation. Another associate of Singer, scientist Nina Davis, worked for three years with Simplesse (then called microcurd) to adapt it to and incorporate it into many different food products. After Singer's boss observed that the product tasted like cheesecake, Singer filed for and received a United States patent for his efforts with the product. Labatt licensed the product to NutraSweet, a subsidiary of Creve Coeur, Missouri, United States chemical conglomerate Monsanto, in 1984. The product was given the trademark "Simplesse" in January 1988. An initial version of the product, approved for use in frozen desserts like low-fat ice cream substitutes by the U.S. Food and Drug Administration (FDA), w |
https://en.wikipedia.org/wiki/Seed%20ball | Seed balls, also known as earth balls or , consist of seeds rolled within a ball of clay and other matter to assist germination. They are then thrown into vacant lots and over fences as a form of 'guerilla gardening'. Matter such as humus and compost are often placed around the seeds to provide microbial inoculants. Cotton-fibres or liquefied paper are sometimes added to further protect the clay ball in particularly harsh habitats. An ancient technique, it was re-discovered by Japanese natural farming pioneer Masanobu Fukuoka.
Development of technique
The technique for creating seed balls was rediscovered by Japanese natural farming pioneer Masanobu Fukuoka. The technique was also used, for instance, in ancient Egypt to repair farms after the annual spring flooding of the Nile. Masanobu Fukuoka developed his technique during the period of the Second World War, while working in a Japanese government lab as a plant scientist on the mountainous island of Shikoku. He wanted to find a technique that would increase food production without taking away from the land already allocated for traditional rice production which thrived in the volcanic rich soils of Japan.
Construction
To make a seed ball, generally about five measures of red clay by volume are combined with one measure of seeds. The balls are formed between 10 mm and 80 mm (about " to 3") in diameter. After the seed balls have been formed, they must dry for 24–48 hours before use.
Seed bombing
Seed bombing is the practice of introducing vegetation to land by throwing or dropping seed balls. It is used in modern aerial seeding as a way to deter seed predation. It has also been popularized by green movements such as guerrilla gardening as a way to introduce new plants to an environment.
Guerrilla gardening
The term "seed green-aide" was first used by Liz Christy in 1973 when she started the Green Guerillas. The first seed green-aides were made from condoms filled with tomato seeds, and fertilizer. They were t |
https://en.wikipedia.org/wiki/Subtended%20angle | In geometry, an angle is subtended by an arc, line segment or any other section of a curve when its two rays pass through the endpoints of that arc, line segment or curve section. Conversely, the arc, line segment or curve section confined within the rays of an angle is regarded as the corresponding subtension of that angle. It is also sometimes said that an arc is intercepted or enclosed by that angle.
The precise meaning varies with context. For example, one may speak of the angle subtended by an arc of a circle when the angle's vertex is the centre of the circle.
See also
Central angle
Inscribed angle
External links
Definition of subtended angle, mathisfun.com, with interactive applet
How an object subtends an angle, Math Open Reference, with interactive applet
Angle definition pages, Math Open Reference, with interactive applets that are also useful in a classroom setting.
Angle |
https://en.wikipedia.org/wiki/Index%20of%20meteorology%20articles | This is a list of meteorology topics. The terms relate to meteorology, the interdisciplinary scientific study of the atmosphere that focuses on weather processes and forecasting. (see also: List of meteorological phenomena)
A
advection
aeroacoustics
aerobiology
aerography (meteorology)
aerology
air parcel (in meteorology)
air quality index (AQI)
airshed (in meteorology)
American Geophysical Union (AGU)
American Meteorological Society (AMS)
anabatic wind
anemometer
annular hurricane
anticyclone (in meteorology)
apparent wind
Atlantic Oceanographic and Meteorological Laboratory (AOML)
Atlantic hurricane season
atmometer
atmosphere
Atmospheric Model Intercomparison Project (AMIP)
Atmospheric Radiation Measurement (ARM)
(atmospheric boundary layer [ABL]) planetary boundary layer (PBL)
atmospheric chemistry
atmospheric circulation
atmospheric convection
atmospheric dispersion modeling
atmospheric electricity
atmospheric icing
atmospheric physics
atmospheric pressure
atmospheric sciences
atmospheric stratification
atmospheric thermodynamics
atmospheric window (see under Threats)
B
ball lightning
balloon (aircraft)
baroclinity
barotropity
barometer ("to measure atmospheric pressure")
berg wind
biometeorology
blizzard
bomb (meteorology)
buoyancy
Bureau of Meteorology (in Australia)
C
Canada Weather Extremes
Canadian Hurricane Centre (CHC)
Cape Verde-type hurricane
capping inversion (in meteorology) (see "severe thunderstorms" in paragraph 5)
carbon cycle
carbon fixation
carbon flux
carbon monoxide (see under Atmospheric presence)
ceiling balloon ("to determine the height of the base of clouds above ground level")
ceilometer ("to determine the height of a cloud base")
celestial coordinate system
celestial equator
celestial horizon (rational horizon)
celestial navigation (astronavigation)
celestial pole
Celsius
Center for Analysis and Prediction of Storms (CAPS) (in Oklahoma in the US)
Center for the Study o |
https://en.wikipedia.org/wiki/Dimethylsulfoniopropionate | Dimethylsulfoniopropionate (DMSP), is an organosulfur compound with the formula (CH3)2S+CH2CH2COO−. This zwitterionic metabolite can be found in marine phytoplankton, seaweeds, and some species of terrestrial and aquatic vascular plants. It functions as an osmolyte as well as several other physiological and environmental roles have also been identified. DMSP was first identified in the marine red alga Polysiphonia fastigiata.
Biosynthesis
In higher plants, DMSP is biosynthesized from S-methylmethionine. Two intermediates in this conversion are dimethylsulfoniumpropylamine and dimethylsulfoniumpropionaldehyde. In algae, however, the biosynthesis starts with the replacement of the amino group in methionine by hydroxide.
Degradation
DMSP is broken down by marine microbes to form two major volatile sulfur products, each with distinct effects on the environment. One of its breakdown products is methanethiol (CH3SH), which is assimilated by bacteria into protein sulfur. Another volatile breakdown product is dimethyl sulfide (CH3SCH3; DMS). There is evidence that DMS in seawater can be produced by cleavage of dissolved (extracellular) DMSP by the enzyme DMSP-lyase, although many non-marine species of bacteria convert methanethiol to DMS.
DMS is also taken up by marine bacteria, but not as rapidly as methanethiol. Although DMS usually consists of less than 25% of the volatile breakdown products of DMSP, the high reactivity of methanethiol makes the steady-state DMS concentrations in seawater approximately 10 times those of methanethiol (~3 nM vs. ~0.3 nM). Curiously, there have never been any published correlations between the concentrations of DMS and methanethiol. This is probably due to the non-linear abiotic and microbial uptake of methanethiol in seawater, and the comparatively low reactivity of DMS. However, a significant portion of DMS in seawater is oxidized to dimethyl sulfoxide (DMSO).
Relevant to global climate, DMS is thought to play a role in the Earth's |
https://en.wikipedia.org/wiki/Online%20identity | Internet identity (IID), also online identity, online personality or internet persona, is a social identity that an Internet user establishes in online communities and websites. It may also be an actively constructed presentation of oneself. Although some people choose to use their real names online, some Internet users prefer to be anonymous, identifying themselves by means of pseudonyms, which reveal varying amounts of personally identifiable information. An online identity may even be determined by a user's relationship to a certain social group they are a part of online. Some can be deceptive about their identity.
In some online contexts, including Internet forums, online chats, and massively multiplayer online role-playing games (MMORPGs), users can represent themselves visually by choosing an avatar, an icon-sized graphic image. Avatars are one way users express their online identity. Through interaction with other users, an established online identity acquires a reputation, which enables other users to decide whether the identity is worthy of trust. Online identities are associated with users through authentication, which typically requires registration and logging in. Some websites also use the user's IP address or tracking cookies to identify users.
The concept of the self, and how this is influenced by emerging technologies, are a subject of research in fields such as education, psychology, and sociology. The online disinhibition effect is a notable example, referring to a concept of unwise and uninhibited behavior on the Internet, arising as a result of anonymity and audience gratification.
Online personal identity
Triangular relationships of personal online identity
There are three key interaction conditions in the identity processes: Fluid Nature of Online and Offline, overlapping social networks, and expectations of accuracy. Social actors accomplish the ideal-authentic balance through self-triangulation, presenting a coherent image in multiple ar |
https://en.wikipedia.org/wiki/Null%20allele | A null allele is a nonfunctional allele (a variant of a gene) caused by a genetic mutation. Such mutations can cause a complete lack of production of the associated gene product or a product that does not function properly; in either case, the allele may be considered nonfunctional. A null allele cannot be distinguished from deletion of the entire locus solely from phenotypic observation.
A mutant allele that produces no RNA transcript is called an RNA null (shown by Northern blotting or by DNA sequencing of a deletion allele), and one that produces no protein is called a protein null (shown by Western blotting). A genetic null or amorphic allele has the same phenotype when homozygous as when heterozygous with a deficiency that disrupts the locus in question. A genetic null allele may be both a protein null and an RNA null, but may also express normal levels of a gene product that is nonfunctional due to mutation.
Null alleles can have lethal effects depending on the importance of the mutated gene. For example, mice homozygous for a null allele for insulin die 48 to 72 hours after birth. Null alleles can also have beneficial effects, such as the elevated harvest index of semi-dwarf rice of the green revolution caused by null alleles in GA20ox-2.
Evidence
Polymerase chain reaction (PCR)
A microsatellite null allele is an allele at a microsatellite locus that does not amplify to detectable levels in a polymerase chain reaction test. Microsatellite regions are usually characterized by short, repeated sequences of nucleotides. Primers that are specific to a particular locus are used in PCR amplification to bind to these nucleotide sequence repeats and are used as genetic markers. The primers anneal to either end of the locus and are derived from source organisms in a genomic library. Divergence from the reference sequences (from genetic mutations) results in poor annealing of the primers so that the marker cannot be used, representative of a null allele.
Parentage |
https://en.wikipedia.org/wiki/Reconstruction%20from%20zero%20crossings | The problem of reconstruction from zero crossings can be stated as: given the zero crossings of a continuous signal, is it possible to reconstruct the signal (to within a constant factor)? Worded differently, what are the conditions under which a signal can be reconstructed from its zero crossings?
This problem has two parts. Firstly, proving that there is a unique reconstruction of the signal from the zero crossings, and secondly, how to actually go about reconstructing the signal. Though there have been quite a few attempts, no conclusive solution has yet been found. Ben Logan from Bell Labs wrote an article in 1977 in the Bell System Technical Journal giving some criteria under which unique reconstruction is possible. Though this has been a major step towards the solution, many people are dissatisfied with the type of condition that results from his article.
According to Logan, a signal is uniquely reconstructible from its zero crossings if:
The signal x(t) and its Hilbert transform xt have no zeros in common with each other.
The frequency-domain representation of the signal is at most 1 octave long, in other words, it is bandpass-limited between some frequencies B and 2B.
Further reading
External links
Signal processing |
https://en.wikipedia.org/wiki/Gauge%20fixing | In the physics of gauge theories, gauge fixing (also called choosing a gauge) denotes a mathematical procedure for coping with redundant degrees of freedom in field variables. By definition, a gauge theory represents each physically distinct configuration of the system as an equivalence class of detailed local field configurations. Any two detailed configurations in the same equivalence class are related by a gauge transformation, equivalent to a shear along unphysical axes in configuration space. Most of the quantitative physical predictions of a gauge theory can only be obtained under a coherent prescription for suppressing or ignoring these unphysical degrees of freedom.
Although the unphysical axes in the space of detailed configurations are a fundamental property of the physical model, there is no special set of directions "perpendicular" to them. Hence there is an enormous amount of freedom involved in taking a "cross section" representing each physical configuration by a particular detailed configuration (or even a weighted distribution of them). Judicious gauge fixing can simplify calculations immensely, but becomes progressively harder as the physical model becomes more realistic; its application to quantum field theory is fraught with complications related to renormalization, especially when the computation is continued to higher orders. Historically, the search for logically consistent and computationally tractable gauge fixing procedures, and efforts to demonstrate their equivalence in the face of a bewildering variety of technical difficulties, has been a major driver of mathematical physics from the late nineteenth century to the present.
Gauge freedom
The archetypical gauge theory is the Heaviside–Gibbs formulation of continuum electrodynamics in terms of an electromagnetic four-potential, which is presented here in space/time asymmetric Heaviside notation. The electric field E and magnetic field B of Maxwell's equations contain only "physical |
https://en.wikipedia.org/wiki/Gribov%20ambiguity | In gauge theory, especially in non-abelian gauge theories, global problems at gauge fixing are often encountered. Gauge fixing means choosing a representative from each gauge orbit, that is, choosing a section of a fiber bundle. The space of representatives is a submanifold (of the bundle as a whole) and represents the gauge fixing condition. Ideally, every gauge orbit will intersect this submanifold once and only once. Unfortunately, this is often impossible globally for non-abelian gauge theories because of topological obstructions and the best that can be done is make this condition true locally. A gauge fixing submanifold may not intersect a gauge orbit at all or it may intersect it more than once. The difficulty arises because the gauge fixing condition is usually specified as a differential equation of some sort, e.g. that a divergence vanish (as in the Landau or Lorenz gauge). The solutions to this equation may end up specifying multiple sections, or perhaps none at all. This is called a Gribov ambiguity (named after Vladimir Gribov).
Gribov ambiguities lead to a nonperturbative failure of the BRST symmetry, among other things.
A way to resolve the problem of Gribov ambiguity is to restrict the relevant functional integrals to a single Gribov region whose boundary is called a Gribov horizon.
Still one can show that this problem is not resolved even when reducing the region to the first Gribov region. The only region for which this ambiguity is resolved is the fundamental modular region (FMR).
Background
When doing computations in gauge theories, one usually needs to choose a gauge. Gauge degrees of freedom do not have any direct physical meaning, but they are an artifact of the mathematical description we use to handle the theory in question. In order to obtain physical results, these redundant degrees of freedom need to be discarded in a suitable way
In Abelian gauge theory (i.e. in QED) it suffices to simply choose a gauge. A popular one is the Lorenz |
https://en.wikipedia.org/wiki/Simple%20precedence%20grammar | A simple precedence grammar is a context-free formal grammar that can be parsed with a simple precedence parser. The concept was first created in 1964 by Claude Pair, and was later rediscovered, from ideas due to Robert Floyd, by Niklaus Wirth and Helmut Weber who published a paper, entitled EULER: a generalization of ALGOL, and its formal definition, published in 1966 in the Communications of the ACM.
Formal definition
G = (N, Σ, P, S) is a simple precedence grammar if all the production rules in P comply with the following constraints:
There are no erasing rules (ε-productions)
There are no useless rules (unreachable symbols or unproductive rules)
For each pair of symbols X, Y (X, Y (N ∪ Σ)) there is only one Wirth–Weber precedence relation.
G is uniquely inversible
Examples
precedence table
Notes |
https://en.wikipedia.org/wiki/Cytochrome%20f | Cytochrome f is the largest subunit of cytochrome b6f complex (plastoquinol—plastocyanin reductase; ). In its structure and functions, the cytochrome b6f complex bears extensive analogy to the cytochrome bc1 complex of mitochondria and photosynthetic purple bacteria. Cytochrome f (cyt f) plays a role analogous to that of cytochrome c1, in spite of their different structures.
The 3D structure of Brassica rapa (Turnip) cyt f has been determined. The lumen-side segment of cyt f includes two structural domains: a small one above a larger one that, in turn, is on top of the attachment to the membrane domain. The large domain consists of an anti-parallel beta-sandwich and a short haem-binding peptide, which form a three-layer structure. The small domain is inserted between beta-strands F and G of the large domain and is an all-beta domain. The haem nestles between two short helices at the N terminus of cyt f. Within the second helix is the sequence motif for the c-type cytochromes, CxxCH (residues 21–25), which is covalently attached to the haem through thioether bonds to Cys-21 and Cys-24. His-25 is the fifth haem iron ligand. The sixth haem iron ligand is the alpha-amino group of Tyr-1 in the first helix. Cyt f has an internal network of water molecules that may function as a proton wire. The water chain appears to be a conserved feature of cyt f. |
https://en.wikipedia.org/wiki/Solutions%20of%20the%20Einstein%20field%20equations | Solutions of the Einstein field equations are metrics of spacetimes that result from solving the Einstein field equations (EFE) of general relativity. Solving the field equations gives a Lorentz manifold. Solutions are broadly classed as exact or non-exact.
The Einstein field equations are
where is the Einstein tensor, is the cosmological constant (sometimes taken to be zero for simplicity), is the metric tensor, is a constant, and is the stress–energy tensor.
The Einstein field equations relate the Einstein tensor to the stress–energy tensor, which represents the distribution of energy, momentum and stress in the spacetime manifold. The Einstein tensor is built up from the metric tensor and its partial derivatives; thus, given the stress–energy tensor, the Einstein field equations are a system of ten partial differential equations in which the metric tensor can be solved for.
Where appropriate, this article will use the abstract index notation.
Solving the equations
It is important to realize that the Einstein field equations alone are not enough to determine the evolution of a gravitational system in many cases. They depend on the stress–energy tensor, which depends on the dynamics of matter and energy (such as trajectories of moving particles), which in turn depends on the gravitational field. If one is only interested in the weak field limit of the theory, the dynamics of matter can be computed using special relativity methods and/or Newtonian laws of gravity and then the resulting stress–energy tensor can be plugged into the Einstein field equations. But if the exact solution is required or a solution describing strong fields, the evolution of the metric and the stress–energy tensor must be solved for together.
To obtain solutions, the relevant equations are the above quoted EFE (in either form) plus the continuity equation (to determine evolution of the stress–energy tensor):
This is clearly not enough, as there are only 14 equations (10 from the fi |
https://en.wikipedia.org/wiki/Mac%20OS%20X%20Leopard | Mac OS X Leopard (version 10.5) is the sixth major release of macOS, Apple's desktop and server operating system for Macintosh computers. Leopard was released on October 26, 2007 as the successor of Mac OS X Tiger, and is available in two editions: a desktop version suitable for personal computers, and a server version, Mac OS X Server. It retailed for $129 for the desktop version and $499 for Server. Leopard was superseded by Mac OS X Snow Leopard (version 10.6) in 2009. Mac OS X Leopard is the last version of macOS that supports the PowerPC architecture as its successor, Mac OS X Snow Leopard, functions solely on Intel based Macs.
According to Apple, Leopard contains over 300 changes and enhancements compared to its predecessor, Mac OS X Tiger, covering core operating system components as well as included applications and developer tools. Leopard introduces a significantly revised desktop, with a redesigned Dock, Stacks, a semitransparent menu bar, and an updated Finder that incorporates the Cover Flow visual navigation interface first seen in iTunes. Other notable features include support for writing 64-bit graphical user interface applications, an automated backup utility called Time Machine, support for Spotlight searches across multiple machines, and the inclusion of Front Row and Photo Booth, which were previously included with only some Mac models.
Apple missed Leopard's release time frame as originally announced by Apple's CEO Steve Jobs. When first discussed in June 2005, Jobs had stated that Apple intended to release Leopard at the end of 2006 or early 2007. A year later, this was amended to Spring 2007; however, on April 12, 2007, Apple issued a statement that its release would be delayed until October 2007 because of the development of the iPhone.
Mac OS X Leopard is the first version of Mac OS X to run on the MacBook Air.
New and changed features
End-user features
Apple advertised that Mac OS X Leopard has 300+ new features, including:
A new and |
https://en.wikipedia.org/wiki/Hotspot%20gateway | A hotspot gateway is a device that provides authentication, authorization and accounting for a wireless network. This can keep malicious users off of a private network even in the event that they are able to break the encryption.
A wireless hotspot gateway helps solve guest user connectivity problems by offering instant Internet access without the need for configuration changes to the client computer or any resident client-side software. This means that even if client configuration such as network IP address (including Gateway IP, DNS) or HTTP Proxy settings are different from that of the provided network, the client can still get access to the network instantly with their existing network configuration.
Some of the prominent hotspot gateway brands are - WiJungle, Nomadix, Wavertech etc.
See also
Hotspot (Wi-Fi) |
https://en.wikipedia.org/wiki/Electric-field%20integral%20equation | The electric-field integral equation is a relationship that allows the calculation of an electric field () generated by an electric current distribution ().
Derivation
When all quantities in the frequency domain are considered, a time-dependency that is suppressed throughout is assumed.
Beginning with the Maxwell equations relating the electric and magnetic field, and assuming a linear, homogeneous media with permeability and permittivity :
Following the third equation involving the divergence of
by vector calculus we can write any divergenceless vector as the curl of another vector, hence
where A is called the magnetic vector potential. Substituting this into the above we get
and any curl-free vector can be written as the gradient of a scalar, hence
where is the electric scalar potential. These relationships now allow us to write
where , which can be rewritten by vector identity as
As we have only specified the curl of , we are free to define the divergence, and choose the following:
which is called the Lorenz gauge condition. The previous expression for now reduces to
which is the vector Helmholtz equation. The solution of this equation for is
where is the three-dimensional homogeneous Green's function given by
We can now write what is called the electric field integral equation (EFIE), relating the electric field to the vector potential A
We can further represent the EFIE in the dyadic form as
where here is the dyadic homogeneous Green's Function given by
Interpretation
The EFIE describes a radiated field given a set of sources , and as such it is the fundamental equation used in antenna analysis and design. It is a very general relationship that can be used to compute the radiated field of any sort of antenna once the current distribution on it is known. The most important aspect of the EFIE is that it allows us to solve the radiation/scattering problem in an unbounded region, or one whose boundary is located at infinity. For closed s |
https://en.wikipedia.org/wiki/Computer-aided%20production%20engineering | Computer-aided production engineering (CAPE) is a relatively new and significant branch of engineering. Global manufacturing has changed the environment in which goods are produced. Meanwhile, the rapid development of electronics and communication technologies has required design and manufacturing to keep pace.
Description of CAPE
CAPE is seen as a new type of computer-aided engineering environment which will improve the productivity of manufacturing/industrial engineers. This environment would be used by engineers to design and implement future manufacturing systems and subsystems. Work is currently underway at the United States National Institute of Standards and Technology (NIST) on CAPE systems. The NIST project is aimed at advancing the development of software environments and tools for the design and engineering of manufacturing systems.
CAPE and the Future of Manufacturing
The future of manufacturing will be determined by the efficiency with which it can incorporate new technologies. The current process in engineering manufacturing systems is often ad hoc, with computerized tools being used on a limited basis. Given the costs and resources involved in the construction and operation of manufacturing systems, the engineering process must be made more efficient. New computing environments for engineering manufacturing systems could help achieve that objective.
Why is CAPE important? In much the same way that product designers need computer-aided design systems, manufacturing and industrial engineers need sophisticated computing capabilities to solve complex problems and manage the vast data associated with the design of a manufacturing system.
In order to solve these complex problems and manage design data, computerized tools must be used in the application of scientific and engineering methods to the problem of the
design and implementation of manufacturing systems. Engineers must address the entire factory as a system and the interactions of that sy |
https://en.wikipedia.org/wiki/Solid-state%20nuclear%20magnetic%20resonance | Solid-state NMR (ssNMR) spectroscopy is a technique for characterizing atomic level structure in solid materials e.g. powders, single crystals and amorphous samples and tissues using nuclear magnetic resonance (NMR) spectroscopy. The anisotropic part of many spin interactions are present in solid-state NMR, unlike in solution-state NMR where rapid tumbling motion averages out many of the spin interactions. As a result, solid-state NMR spectra are characterised by larger linewidths than in solution state NMR, which can be utilized to give quantitative information on the molecular structure, conformation and dynamics of the material. Solid-state NMR is often combined with magic angle spinning to remove anisotropic interactions and improve the resolution as well as the sensitivity of the technique.
Nuclear spin interactions
The resonance frequency of a nuclear spin depends on the strength of the magnetic field at the nucleus, which can be modified by isotropic (e.g. chemical shift, isotropic J-coupling) and anisotropic interactions (e.g. chemical shift anisotropy, dipolar interactions). In a classical liquid-state NMR experiment, molecular tumbling coming from Brownian motion averages anisotropic interactions to zero and they are therefore not reflected in the NMR spectrum. However, in media with no or little mobility (e.g. crystalline powders, glasses, large membrane vesicles, molecular aggregates), anisotropic local fields or interactions have substantial influence on the behaviour of nuclear spins, which results in the line broadening of the NMR spectra.
Chemical shielding
Chemical shielding is a local property of each nuclear site in a molecule or compound, and is proportional to the applied external magnetic field. The external magnetic field induces currents of the electrons in molecular orbitals. These induced currents create local magnetic fields that lead to characteristic changes in resonance frequency. These changes can be predicted from molecular structu |
https://en.wikipedia.org/wiki/Vital%20capacity | Vital capacity (VC) is the maximum amount of air a person can expel from the lungs after a maximum inhalation. It is equal to the sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume. It is approximately equal to Forced Vital Capacity (FVC).
A person's vital capacity can be measured by a wet or regular spirometer. In combination with other physiological measurements, the vital capacity can help make a diagnosis of underlying lung disease. Furthermore, the vital capacity is used to determine the severity of respiratory muscle involvement in neuromuscular disease, and can guide treatment decisions in Guillain–Barré syndrome and myasthenic crisis.
A normal adult has a vital capacity between 3 and 5 litres. A human's vital capacity depends on age, sex, height, mass, and possibly ethnicity. However, the dependence on ethnicity is poorly understood or defined, as it was first established by studying black slaves in the 19th century and may be the result of conflation with environmental factors.
Lung volumes and lung capacities refer to the volume of air associated with different phases of the respiratory cycle. Lung volumes are directly measured, whereas lung capacities are inferred from volumes.
Role in diagnosis
The vital capacity can be used to help differentiate causes of lung disease. In restrictive lung disease the vital capacity is decreased. In obstructive lung disease it is usually normal or only slightly decreased.
Estimated vital capacities
Formulas
Vital capacity increases with height and decreases with age. Formulas to estimate vital capacity are:
where is approximate vital capacity in cm3, is age in years, and is height in cm. |
https://en.wikipedia.org/wiki/QuickTransit | QuickTransit was a cross-platform virtualization program developed by Transitive Corporation. It allowed software compiled for one specific processor and operating system combination to be executed on a different processor and/or operating system architecture without source code or binary changes.
QuickTransit was an extension of the Dynamite technology developed by the University of Manchester Parallel Architectures and Languages research group, which now forms part of the university's Advanced Processor Technologies research group.
Silicon Graphics announced QuickTransit's first availability in October 2004 on its Prism visualization systems. These systems, based on Itanium 2 processors and the Linux operating system, used QuickTransit to transparently run application binaries compiled for previous SGI systems based on the MIPS processor and IRIX operating system.
This technology was also licensed by Apple Computer in its transition from PowerPC to Intel (x86) CPUs, starting in 2006. Apple marketed this technology as "Rosetta".
In August 2006, IBM announced a partnership with Transitive to run Linux/x86 binaries on its Power ISA-based Power Systems servers. IBM named this software System p AVE during its beta phase, but it was renamed to PowerVM Lx86 upon release.
In November 2006, Transitive launched QuickTransit for Solaris/SPARC-to-Linux/x86-64, which enabled unmodified Solaris applications compiled for SPARC systems to run on 64-bit x86-based systems running Linux. This was followed in October 2007 by QuickTransit for Solaris/SPARC-to-Linux/Itanium, which enabled Solaris/SPARC applications to run on Itanium systems running Linux. A third product, QuickTransit for Solaris/SPARC-to-Solaris/x86-64, was released in December 2007, enabling Solaris/SPARC applications to run on 64-bit x86 systems running Solaris.
IBM acquired Transitive in June 2009 and merged the company into its Power Systems division. IBM announced in September 2011 it would discontinue mar |
https://en.wikipedia.org/wiki/I%20Palindrome%20I | "I Palindrome I" is a song by American alternative rock duo They Might Be Giants. It was the second single from Apollo 18, released in 1992 by Elektra Records.
They Might Be Giants performed the song on Late Night with David Letterman in 1992. Michael McKean recites the lyrics of the song in the documentary Gigantic: A Tale of Two Johns.
Composition
The title of "I Palindrome I" came from a demo written by John Flansburgh for They Might Be Giants's telephone service, Dial-A-Song. John Linnell adapted the lyric after attending a reading by the American poet Hal Sirowitz. The song's opening line, "Someday mother will die and I'll get the money", is a reference to Sirowitz's portrayal of mother-child relationships.
The song contains several palindromes and references to the concept of recursion. For example, the lyrics contain the straightforward palindromes "Egad, a base tone denotes a bad age" and "Man o nam". The middle 8 consists of what critic Stewart Mason calls a "sentence palindrome", in which the words (rather than the letters) are the units in a sequence which reads the same backwards and forwards: Son I am able,' she said, 'Though you scare me.' 'Watch,' said I. 'Beloved,' I said, 'Watch me scare you though.' Said she, 'Able am I, son. The lyrics also reference "a snake head eating the head on the opposite side" (an ouroboros), which reviewer Ira Robbins interprets as "a grim life mask [carved] from the conceptual clay of reversible phrases".
Reception
"I Palindrome I" received generally positive attention from critics. Writing for Allmusic, Stewart Mason concluded that the song was musically appealing enough to overcome its shallow lyrics, which he felt employed wordplay for its own sake rather than "in the service of a particular idea or emotion". In a review of Apollo 18, Karen Schlosberg said that the lyrics of "I Palindrome I" sound like "Edgar Allan Poe and David Lynch meeting the Monkees", creating an "unlikely sing-along hook". In a 2016 Gothami |
https://en.wikipedia.org/wiki/Flavelle%20Medal | The Flavelle Medal is an award of the Royal Society of Canada "for an outstanding contribution to biological science during the preceding ten years or for significant additions to a previous outstanding contribution to biological science". It is named in honour of Joseph Wesley Flavelle and is awarded bi-annually. The award consists of a gold plated silver medal.
Recipients
Source: Royal Society of Canada
2022 - Graham Bell, FRSC
2020 - Marla Sokolowski, FRSC
2018 - Frank Plummer, FRSC
2016 -
2014 - Spencer Barrett, FRSC
2012 - Siegfried Hekimi, FRSC
2010 - Kenneth B. Storey, FRSC
2008 - John Smol, FRSC
2006 - Brett Finlay, FRSC
2004 - Brian D. Sykes, FRSC
2002 - Lewis E. Kay
2000 - David R. Jones, FRSC
1998 - Anthony Pawson, FRSC
1996 - Ian C. P. Smith, FRSC
1994 - Robert J. Cedergren, MSRC
1992 - Michael Smith, FRSC
1990 - Peter W. Hochachka, FRSC
1988 - Robert Haynes, FRSC
1986 - Neil Towers, FRSC
1984 - Robert G.E. Murray, FRSC
1982 - Clayton Oscar Person, FRSC
1980 - Gordon Dixon, FRSC
1978 - Louis Siminovitch, FRSC
1976 - Michael Shaw, FRSC
1974 - Juda Hirsh Quastel, FRSC
1972 - Douglas Harold Copp, FRSC
1970 - William Edwin Ricker, FRSC
1968 - Jacques Genest, MSRC
1966 - Erich Baer, FRSC
1965 - William Stewart Hoar, FRSC
1964 - Gleb Krotkov, FRSC
1963 - Robert James Rossiter, FRSC
1962 - Frederick Ernest Joseph Fry, FRSC
1961 - Charles Philippe Leblond, FRSC
1960 - Edmund Murton Walker, FRSC
1959 - Murray L. Barr, FRSC
1958 - Allan Grant Lochhead, FRSC
1957 - Thomas Wright M. Cameron, FRSC
1956 - George Lyman Duff, FRSC
1955 - Charles Samuel Hanes, FRSC
1954 - David Alymer Scott, FRSC
1953 - Everitt George Dunne Murray, FRSC
1952 - Archibald G. Huntsman, FRSC
1951 - Wilder Penfield, FRSC
1950 - Charles Best, FRSC
1949 - W. P. Thompson, FRSC
1948 - Margaret Newton, FRSC
1947 - Guilford Bevil Reed, FRSC
1946 - William Rowan, FRSC
1945 - Robert Boyd Thomson, FRSC
1944 - Velyien Ewart Henderson, FRSC
1943 - B. |
https://en.wikipedia.org/wiki/CCNA | CCNA (Cisco Certified Network Associate) is an information technology (IT) certification from Cisco Systems. CCNA certification is an associate-level Cisco Career certification.
The Cisco exams have changed several times in response to changing IT trends. In 2020, Cisco announced an update to its certification program that "Consolidated and updated associate-level training and certification." Cisco has consolidated the previous different types of Cisco-certified Network Associate with a general CCNA certification.
The content of the exams is proprietary. Cisco and its learning partners offer a variety of different training methods, including books published by Cisco Press, and online and classroom courses available under the title "Interconnecting Cisco Network Devices".
Exam
To achieve a CCNA certification, candidates must earn a passing score on Cisco exam No. 200-301. After the exam, candidates receive a score report along with a score breakdown by exam section and the passing score for the given exam.
The exam tests a candidate's knowledge and skills required to install, operate, and troubleshoot a small to medium size enterprise branch network. The exam covers a broad range of fundamentals, including network fundamentals, network access, IP connectivity, IP services, security fundamentals, automation, and programmability.
Prerequisites
There are no prerequisites to take the CCNA certification exam. There is also a starting point of networking which is the CCT (Cisco Certified Technician).
Validity
The validity of CCNA Certification is three years. Renewal requires certification holders to register for and pass the same or higher level Cisco re-certification exam(s) every three years.
See also
Cisco Networking Academy
Cisco certifications
DevNet
Cyber Ops
CCNP
CCIE Certification |
https://en.wikipedia.org/wiki/Logical%20security | Logical security consists of software safeguards for an organization's systems, including user identification and password access, authenticating, access rights and authority levels. These measures are to ensure that only authorized users are able to perform actions or access information in a network or a workstation. It is a subset of computer security.
Elements
Elements of logical security are:
User IDs, also known as logins, user names, logons or accounts, are unique personal identifiers for agents of a computer program or network that is accessible by more than one agent. These identifiers are based on short strings of alphanumeric characters, and are either assigned or chosen by the users.
Authentication is the process used by a computer program, computer, or network to attempt to confirm the identity of a user. Blind credentials (anonymous users) have no identity, but are allowed to enter the system. The confirmation of identities is essential to the concept of access control, which gives access to the authorized and excludes the unauthorized.
Biometrics authentication is the measuring of a user’s physiological or behavioral features to attempt to confirm his/her identity. Physiological aspects that are used include fingerprints, eye retinas and irises, voice patterns, facial patterns, and hand measurements. Behavioral aspects that are used include signature recognition, gait recognition, speaker recognition and typing pattern recognition. When a user registers with the system which he/she will attempt to access later, one or more of his/her physiological characteristics are obtained and processed by a numerical algorithm. This number is then entered into a database, and the features of the user attempting to match the stored features must match up to a certain error rate.
Token authentication
Token authentication are small devices that authorized users of computer systems or networks carry to assist in identifying that who is logging into a compu |
https://en.wikipedia.org/wiki/Photovoltaic%20effect | The photovoltaic effect is the generation of voltage and electric current in a material upon exposure to light. It is a physical and chemical phenomenon.
The photovoltaic effect is closely related to the photoelectric effect. For both phenomena, light is absorbed, causing excitation of an electron or other charge carrier to a higher-energy state. The main distinction is that the term photoelectric effect is now usually used when the electron is ejected out of the material (usually into a vacuum) and photovoltaic effect used when the excited charge carrier is still contained within the material. In either case, an electric potential (or voltage) is produced by the separation of charges, and the light has to have a sufficient energy to overcome the potential barrier for excitation. The physical essence of the difference is usually that photoelectric emission separates the charges by ballistic conduction and photovoltaic emission separates them by diffusion, but some "hot carrier" photovoltaic devices concepts blur this distinction.
History
The first demonstration of the photovoltaic effect, by Edmond Becquerel in 1839, used an electrochemical cell. He explained his discovery in Comptes rendus de l'Académie des sciences, "the production of an electric current when two plates of platinum or gold immersed in an acid, neutral, or alkaline solution are exposed in an uneven way to solar radiation."
The first solar cell, consisting of a layer of selenium covered with a thin film of gold, was experimented by Charles Fritts in 1884, but it had a very poor efficiency. However, the most familiar form of the photovoltaic effect uses solid-state devices, mainly in photodiodes. When sunlight or other sufficiently energetic light is incident upon the photodiode, the electrons present in the valence band absorb energy and, being excited, jump to the conduction band and become free. These excited electrons diffuse, and some reach the rectifying junction (usually a diode p–n juncti |
https://en.wikipedia.org/wiki/TinyURL | TinyURL is a URL shortening web service, which provides short aliases for redirection of long URLs. Kevin Gilbertson, a web developer, launched the service in January 2002 as a way to post links in newsgroup postings which frequently had long, cumbersome addresses. TinyURL was the first notable URL shortening service and is one of the oldest still currently operating.
Service
The TinyURL homepage includes a form which is used to submit a long URL for shortening. For each URL entered, the server adds a new alias in its hashed database and returns a short URL. According to the website, the shortened URLs will never expire.
TinyURL offers an API which allows applications to automatically create short URLs.
Short URL aliases are seen as useful because they are easier to write down, remember or distribute. They also fit in text boxes with a limited number of characters allowed. Some examples of limited text boxes are IRC channel topics, email signatures, microblogs (such as Twitter, which notably limits all posts to first 140 and later 280 characters), certain printed newspapers (such as .net magazine or even Nature), and email clients that impose line breaks on messages at a certain length.
Starting in 2008, TinyURL allowed users to create custom, more meaningful aliases. This means that a user can create descriptive URLs rather than a randomly generated address. For example, https://tinyurl.com/wp-tinyurl leads to the Wikipedia article about the website.
Preview short URLs
To preview the full URL from the short TinyURL, the user can visit TinyURL first and enable previews as a default browser cookie setting or copy and paste the short URL into the browser address bar, and prepend the short tinyurl.com/x with preview.tinyurl.com/x. Another preview feature is not well documented at the TinyURL site, but the alternative shortened URL with preview capability is also offered to shortcut creators as an option at the time of the creation of the link.
Impact
Similar s |
https://en.wikipedia.org/wiki/Context-based%20access%20control | Context-based access control (CBAC) is a feature of firewall software, which intelligently filters TCP and UDP packets based on application layer protocol session information. It can be used for intranets, extranets and internets.
CBAC can be configured to permit specified TCP and UDP traffic through a firewall only when the connection is initiated from within the network needing protection. (In other words, CBAC can inspect traffic for sessions that originate from the external network.) However, while this example discusses inspecting traffic for sessions that originate from the external network, CBAC can inspect traffic for sessions that originate from either side of the firewall. This is the basic function of a stateful inspection firewall.
Without CBAC, traffic filtering is limited to access list implementations that examine packets at the network layer, or at most, the transport layer. However, CBAC examines not only network layer and transport layer information but also examines the application-layer protocol information (such as FTP connection information) to learn about the state of the TCP or UDP session. This allows support of protocols that involve multiple channels created as a result of negotiations in the FTP control channel. Most of the multimedia protocols as well as some other protocols (such as FTP, RPC, and SQL*Net) involve multiple control channels.
CBAC inspects traffic that travels through the firewall to discover and manage state information for TCP and UDP sessions. This state information is used to create temporary openings in the firewall's access lists to allow return traffic and additional data connections for permissible sessions (sessions that originated from within the protected internal network).
CBAC works through deep packet inspection and hence Cisco calls it 'IOS firewall' in their Internetwork Operating System (IOS).
CBAC also provides the following benefits:
Denial-of-service prevention and detection
Real-time alerts and |
https://en.wikipedia.org/wiki/Conner%20Peripherals | Conner Peripherals, Inc. (commonly referred to as Conner), was a company that manufactured hard drives for personal computers. Conner Peripherals was founded in 1985 by Seagate Technology co-founder and San Jose State University alumnus Finis Conner (1943– ). In 1986, they merged with CoData, a Colorado start-up founded by MiniScribe founders Terry Johnson and John Squires. CoData was developing a new type of small hard disk that put the capacity of a 5.25-inch drive into the smaller (and now commonplace) 3.5-inch format. The CoData drive was the first Conner Peripherals product. The company was partially financed by Compaq, who was also a major customer for many years.
Hard disks
Design concepts
Conner's drives were notable for eschewing the "tub" type of head-disk assembly, where the disks are inside a large base casting shaped like a square bowl or vault with a flat lid; instead, they preferred the flat base plate approach, which was more resistant to shock and less likely to warp or deform when heated. Their first drives had the base plate carrying the disks, head arm and actuator enclosed inside a long aluminum cartridge, fixed to a bulkhead on the other side with two screws and sealed with a large, square O-ring. Conner's 1/3-height (1-inch thick) drives used a domed, cast aluminum lid with four screws, one on each corner, sealed to the base plate with a rubber gasket. The printed circuit board was bolted to the bottom of the base plate, with the mounting holes for the drive drilled into tabs cast into the sides of the base plate. This design would be Conner's trademark look well into the 1990s.
Logically, Conner's drives had some of the characteristics of the original MiniScribe drives (of which John Squires had also been a designer), with a large amount of intelligence built into the drive's central processing unit (CPU); Conner drives used a single Motorola 68HC11 microcontroller, and ran a proprietary real-time operating system that implemented the tr |
https://en.wikipedia.org/wiki/Plant%20Proteome%20Database | The Plant Proteome Database is a National Science Foundation-funded project to determine the biological function of each protein in plants. It includes data for two plants that are widely studied in molecular biology, Arabidopsis thaliana and maize (Zea mays). Initially the project was limited to plant plastids, under the name of the Plastid PDB, but was expanded and renamed Plant PDB in November 2007.
See also
Proteome |
https://en.wikipedia.org/wiki/Signaling%20protocol | A signaling protocol is a type of communications protocol for encapsulating the signaling between communication endpoints and switching systems to establish or terminate a connection and to identify the state of connection.
The following is a list of signaling protocols:
ALOHA
Digital Subscriber System No. 1 (EDSS1)
Dual-tone multi-frequency signaling
H.248
H.323
H.225.0
Jingle
Media Gateway Control Protocol (MGCP)
Megaco
Regional System R1
NBAP (Node B Application Part)
Signalling System R2
Session Initiation Protocol
Signaling System No. 5
Signaling System No. 6
Signaling System No. 7
Skinny Client Control Protocol (SCCP, Skinny)
Q.931
QSIG
Network protocols
Telephony signals |
https://en.wikipedia.org/wiki/Nuclear%20matrix | In biology, the nuclear matrix is the network of fibres found throughout the inside of a cell nucleus after a specific method of chemical extraction. According to some it is somewhat analogous to the cell cytoskeleton. In contrast to the cytoskeleton, however, the nuclear matrix has been proposed to be a dynamic structure. Along with the nuclear lamina, it supposedly aids in organizing the genetic information within the cell.
The exact function of this structure is still disputed, and its very existence has been called into question. Evidence for such a structure was recognised as long ago as 1948, and consequently many proteins associated with the matrix have been discovered. The presence of intra-cellular proteins is common ground, and it is agreed that proteins such as the Scaffold, or Matrix Associated Proteins (SAR or MAR) have some role in the organisation of chromatin in the living cell. There is evidence that the nuclear matrix is involved in regulation of gene expression in Arabidopsis thaliana.
Whenever a similar structure can actually be found in living cells remains a topic of discussion. According to some sources, most, if not all proteins found in nuclear matrix are the aggregates of proteins of structures that can be found in the nucleus of living cells. Such structures are nuclear lamina, which consist of proteins termed lamins which can be also found in the nuclear matrix.
Validity of nuclear matrix
For a long time the question whether a polymer meshwork, a “nuclear matrix” or “nuclear-scaffold” or "NuMat" is an essential component of the in vivo nuclear architecture has remained a matter of debate. While there are arguments that the relative position of chromosome territories (CTs), the equivalent of condensed metaphase chromosomes at interphase, may be maintained due to steric hindrance or electrostatic repulsion forces between the apparently highly structured CT surfaces, this concept has to be reconciled with observations according to which |
https://en.wikipedia.org/wiki/Redback%20Networks | Redback Networks provided hardware and software used by Internet service providers to manage broadband services. The company's products included the SMS (Subscriber Management System), SmartEdge, and SmartMetro product lines.
In January 2007, the company was acquired by Ericsson.
History
Redback Networks was founded in August 1996 by Gaurav Garg, Asher Waldfogel, and William M. Salkewicz. The company received seed money from Sequoia Capital.
In May 1999, during the dot-com bubble, the company became a public company via an initial public offering. After pricing at $23 each, shares soared 266% on the first day of trading.
In November 1999, the company acquired Siara Systems, which at the time only had products in the prototype stage, for $4.3 billion in stock.
In 2000, its share price peaked at $198 but fell to $0.27 in October 2002, after the burst of the dot-com bubble.
In August 2000, the company acquired Abatis Systems.
In October 2000, the company opened a regional headquarters in Hong Kong.
In January 2007, the company was acquired by Ericsson for $1.9 billion, or $25 per share. |
https://en.wikipedia.org/wiki/FINO | In computer science, FINO is a humorous scheduling algorithm. It is an acronym for first in, never out as opposed to traditional first in, first out (FIFO) and last in, first out (LIFO) algorithms. A similar acronym is "FISH", for first in, still here.
FINO works by withholding all scheduled tasks permanently. No matter how many tasks are scheduled at any time, no task ever actually takes place.
A stateful FINO queue can be used to implement a memory leak.
The first mention of FINO appears in the Signetics 25120 write-only memory joke datasheet.
See also
Bit bucket
Black hole (networking)
Null route
Write-only memory |
https://en.wikipedia.org/wiki/Music%20scheduling%20system | Music scheduling systems are employed to sequence music at radio stations. Although these systems were originally implemented by manual index card methods, since the late 1970s they have exploited the efficiency and speed of digital computers. They are essential tools for broadcasting by music radio stations.
These systems are databases of the songs in active rotation at a radio station, plus an ample set of rules for sequencing them in accordance with specific policies. For example, there may be restrictions on how much time must pass between two songs by the same artist, or whether a song played during noontime today may be heard at noontime tomorrow (or not). There are also rules for what kinds of songs may succeed another according to tempos or other characteristics.
Many people believe that disc jockeys at radio stations are responsible for choosing the music which is heard on their shows. In reality, playlists for each hour of the day have usually been generated in advance by a radio station's program director using a music scheduling system. This ensures that the station programming is optimal and adheres to the policies and objectives of the station's management. These policies and objectives are usually designed to please the greatest number of people inside the radio station's demographic target, and garner the best ratings possible for the radio station. However, there are some radio stations, for example those of BBC, which do allow most (but not all) disc jockeys to choose the music themselves without obligations, as these stations cover an eclectic range of genres. In addition, shows from resident/guest disc jockeys (particularly on mainstream stations) also do not need the program director's opinion for their playlists.
Music scheduling is simply the function of generating a playlist. Other systems are responsible for actually reproducing the music.
The first widely used commercial music scheduler for radio is Selector, originally written by Dr. |
https://en.wikipedia.org/wiki/RC%204000%20multiprogramming%20system | The RC 4000 Multiprogramming System (also termed Monitor or RC 4000 depending on reference) is a discontinued operating system developed for the RC 4000 minicomputer in 1969. For clarity, this article mostly uses the term Monitor.
Overview
The RC 4000 Multiprogramming System is historically notable for being the first attempt to break down an operating system into a group of interacting programs communicating via a message passing kernel. RC 4000 was not widely used, but was highly influential, sparking the microkernel concept that dominated operating system research through the 1970s and 1980s.
Monitor was created largely by one programmer, Per Brinch Hansen, who worked at Regnecentralen where the RC 4000 was being designed. Leif Svalgaard participated in implementing and testing Monitor. Brinch Hansen found that no existing operating system was suited to the new machine, and was tired of having to adapt existing systems. He felt that a better solution was to build an underlying kernel, which he referred to as the nucleus, that could be used to build up an operating system from interacting programs. Unix, for instance, uses small interacting programs for many tasks, transferring data through a system called pipelines or pipes. However, a large amount of fundamental code is integrated into the kernel, notably things like file systems and program control. Monitor would relocate such code also, making almost the entire system a set of interacting programs, reducing the kernel (nucleus) to a communications and support system only.
Monitor used a pipe-like system of shared memory as the basis of its inter-process communication (IPC). Data to be sent from one process to another was copied into an empty memory data buffer, and when the receiving program was ready, back out again. The buffer was then returned to the pool. Programs had a very simple application programming interface (API) for passing data, using an asynchronous set of four methods. Client applications se |
https://en.wikipedia.org/wiki/Callaloo | Callaloo (many spelling variants, such as kallaloo, calaloo, calalloo, calaloux or callalloo; ) is a plant used in popular dishes in many Caribbean countries, while for other Caribbean countries, a stew made with the plant is called callaloo. Cuisines including the plant Callaloo or dishes called callaloo varies throughout the Caribbean. Countries like Jamaica and Belize refer to an indigenous green leaf vegetable, Caribbean amaranth, as callaloo. In countries such as Trinidad and Tobago or Grenada, the dish itself is called callaloo, and uses taro leaves (known by many local names such as 'dasheen bush', 'callaloo bush', or 'bush') or Xanthosoma leaves (known by many names, including cocoyam and tannia).
Since the leaf vegetable used in some regions differs, some confusion can arise among the vegetables with the dish itself. This, as is the case with many other Caribbean dishes, is a remnant of West African and Taino cuisine.
Etymology of the word callaloo can be traced to Caribbean Patois, with influences from the African word kalúlu.
Cooking variations
Trinbagonians, Grenadians and Dominicans primarily use taro/dasheen bush for callaloo, although Dominicans also use water spinach. Jamaicans, Belizeans, St. Lucians and Guyanese on the other hand use the name callaloo to refer to an indigenous variation of amaranth, and use it in a plethora of dishes and also a drink ("callaloo juice"). The "callaloo" made in Jamaica is different from the "callaloo" made in Trinidad and Tobago, Grenada and rest of the Caribbean in terms of main ingredient (the leaf used) and other ingredients included.
While Jamaicans tend to steam callaloo leaf with garlic, carrots, local powdered seasoning, tomatoes, salt, Scotch bonnet peppers, onions, scallions, thyme, sweet pepper, pimento, with or without salt fish or other meats, and even in rice or their famous patty pastries. Trinidadians and Saint Lucians however, uses dasheen bush, okra, coconut milk, pumpkin, onions, bell peppers |
https://en.wikipedia.org/wiki/Pseudorandom%20binary%20sequence | A pseudorandom binary sequence (PRBS), pseudorandom binary code or pseudorandom bitstream is a binary sequence that, while generated with a deterministic algorithm, is difficult to predict and exhibits statistical behavior similar to a truly random sequence. PRBS generators are used in telecommunication, such as in analog-to-information conversion, but also in encryption, simulation, correlation technique and time-of-flight spectroscopy. The most common example is the maximum length sequence generated by a (maximal) linear feedback shift register (LFSR). Other examples are Gold sequences (used in CDMA and GPS), Kasami sequences and JPL sequences, all based on LFSRs.
In telecommunications, pseudorandom binary sequences are known as pseudorandom noise codes (PN or PRN codes) due to their application as pseudorandom noise.
Details
A binary sequence (BS) is a sequence of bits, i.e.
for .
A BS consists of ones and zeros.
A BS is a pseudorandom binary sequence (PRBS) if its autocorrelation function, given by
has only two values:
where
is called the duty cycle of the PRBS, similar to the duty cycle of a continuous time signal. For a maximum length sequence, where , the duty cycle is 1/2.
A PRBS is 'pseudorandom', because, although it is in fact deterministic, it seems to be random in a sense that the value of an element is independent of the values of any of the other elements, similar to real random sequences.
A PRBS can be stretched to infinity by repeating it after elements, but it will then be cyclical and thus non-random. In contrast, truly random sequence sources, such as sequences generated by radioactive decay or by white noise, are infinite (no pre-determined end or cycle-period). However, as a result of this predictability, PRBS signals can be used as reproducible patterns (for example, signals used in testing telecommunications signal paths).
Practical implementation
Pseudorandom binary sequences can be generated using linear-feedback shif |
https://en.wikipedia.org/wiki/Servbot | The Servbot, known as Kobun (コブン) in Japan, is a type of fictional sentient robot that appears in an assortment of video games and associated media developed and published by Capcom. The Servbot originated in the 1997 title Mega Man Legends, and appears in all media within the sub-series of the same name. Within series fiction, Servbots are a group of childlike robots who follow their creator, the pirate Tron Bonne, as her loyal but incompetent henchmen. The Servbots serve as a source of comic relief for the majority of their appearances.
Considered to be the most enduring aspect of the Legends series by critics, Servbots have made extensive appearances outside of the Mega Man Legends series, where they often presented as mascots or representatives of the series in crossover games. Servbot iconography is also a staple feature in the Dead Rising series. Servbots have appeared in a number of official promotional material and merchandise released by Capcom, and have also been subject to fan labor efforts.
Characteristics
Servbots are a group of diminutive robots with yellow heads and blue bodies, with their overall design resembling Lego minifigures. Created by the pirate Tron Bonne, they are characterized as unquestioningly loyal followers who share a parent-child relationship with her. They are depicted as childlike in nature, lacking the capacity to understand the concept of morality or the illegality of the criminal actions they are tasked with performing. Each Servbot fulfills a designated role, ranging from domestic chores to combat abilities. While small in size, the Servbots are shown to be effective combatants and are important to the exploits of Tron Bonne and her family as pirates. A frequent running gag within the series involve the incompetence or ineptitude of various Servbot units, leading to disastrous outcomes and consequently punishment from Tron. In spite of their inorganic nature, Servbots are depicted in series canon as being capable of consuming |
https://en.wikipedia.org/wiki/Zacharias%20Dase | Johann Martin Zacharias Dase (June 23, 1824, Hamburg – September 11, 1861, Hamburg) was a German mental calculator.
He attended schools in Hamburg from a very early age, but later admitted that his instruction had little influence on him. He used to spend a lot of time playing dominoes, and suggested that this played a significant role in developing his calculating skills. Dase had epilepsy from early childhood throughout his life.
At age 15 he began to travel extensively, giving exhibitions in Germany, Austria and England. Among his most impressive feats, he multiplied 79532853 × 93758479 in 54 seconds. He multiplied two 20-digit numbers in 6 minutes; two 40-digit numbers in 40 minutes; and two 100-digit numbers in 8 hours 45 minutes. The famous mathematician Carl Friedrich Gauss commented that someone skilled in calculation could have done the 100-digit calculation in about half that time with pencil and paper.
These exhibitions however did not earn him enough money, so he tried to find other employments. In 1844 he obtained a position in the Railway Department of Vienna, but this didn't last long since in 1845 he was reported in Mannheim and in 1846 in Berlin.
In 1844, Dase calculated π to 200 decimal places over the course of approximately two months, a record for the time, from the Machin-like formula:
He also calculated a 7-digit logarithm table and extended a table of integer factorizations from 6,000,000 to 9,000,000.
Dase had very little knowledge of mathematical theory. The mathematician Julius Petersen tried to teach him some of Euclid's theorems, but gave up the task once he realized that their comprehension was beyond Dase's capabilities.
Gauss however was very impressed with his calculating skill, and he recommended that the Hamburg Academy of Sciences should allow Dase to do mathematical work on a full-time basis, but Dase died shortly thereafter.
The book "Gödel, Escher, Bach" by Douglas Hofstadter mentions his calculating abilities. "... he |
https://en.wikipedia.org/wiki/Outer%20trench%20swell | The outer trench swell, outer trench high, or outer rise is a subtle ridge on the seafloor near an oceanic trench, where a descending plate begins to flex and fault in preparation for its descent into the mantle at a subduction zone. The lithosphere is bent upwards by plate stresses, and is not in isostatic equilibrium (distinguish from the "outer ridge" of a forearc).
Characteristics
Typically, the gravity field over the outer swell is about 50 mGal (0.5 mm/s²) higher than expected from isostasy, while gravity over the trench is about 200 mGal (2 mm/s²) less than that expected from isostatic considerations.
The bending of the plate is associated with tension in the upper 20 km, and shallow earthquakes, caused by tensional failure induced by the downward bending of the oceanic plate are common; about 20 extensional outer rise earthquakes with magnitude 5 or greater occur annually. Most tension axes are perpendicular to the trench, independent of the direction of relative motion between the two plates, indicating that failure is controlled by bending stresses in the plate. Plate bending also causes deeper (down to 50 km) earthquakes due to compression.
The wavelength and amplitude of this flexure can be used to constrain the state of stress across the plate boundary. The width of the outer rise is directly related to the flexural rigidity of the lithosphere. The thickness of the elastic lithosphere varies between 20 and 30 km for most trench profiles. Faulting related to plate bending and stair-stepping of the descending slab into the trench may allow seawater to infiltrate deep into the crust and perhaps upper mantle. This may lead to large scale formation of serpentinite in the upper mantle of the downgoing plate (Ranero et al., 2003).
Faulting of the downgoing plate results in a horst and graben structure that allows sediment that reaches the trench to be deposited in graben and carried downward. This faulting also breaks up seamounts as they approach the tr |
https://en.wikipedia.org/wiki/BRLESC | The BRLESC I (Ballistic Research Laboratories Electronic Scientific Computer) was one of the last of the first-generation electronic computers. It was built by the United States Army's Ballistic Research Laboratory (BRL) at Aberdeen Proving Ground with assistance from the National Bureau of Standards (now the National Institute of Standards and Technology), and was designed to take over the computational workload of EDVAC and ORDVAC, which themselves were successors of ENIAC. It began operation in 1962. The Ballistic Research Laboratory became a part of the U.S. Army Research Laboratory in 1992.
BRLESC was designed primarily for scientific and military tasks requiring high precision and high computational speed, such as ballistics problems, army logistical problems, and weapons systems evaluations. It contained 1727 vacuum tubes and 853 transistors and had a memory of 4096 72-bit words. BRLESC employed punched cards, magnetic tape, and a magnetic drum as input-output devices, which could be operated simultaneously.
It was capable of five million (bitwise) operations per second. A fixed-point addition took 5 microseconds, a floating-point addition took 5 to 10 microseconds, a multiplication (fixed- or floating-point) took 25 microseconds, and a division (fixed- or floating-point) took 65 microseconds. (These times are including the memory access time, which was 4-5 microseconds.) It was the fastest computer in the world until the CDC 6600 was introduced in 1964.
BRLESC and its predecessor, ORDVAC, used their own unique notation for hexadecimal numbers. Instead of the sequence A B C D E F universally used today, the digits 10 to 15 were represented by the letters K S N J F L, corresponding to the teletypewriter characters on five-track paper tape. The mnemonic phrase "King Size Numbers Just For Laughs" was used to remember the letter sequence.
BRLESC II, using integrated circuits, became operational in November 1967; it was designed to be 200 times faster than |
https://en.wikipedia.org/wiki/Ring%20oscillator | A ring oscillator is a device composed of an odd number of NOT gates in a ring, whose output oscillates between two voltage levels, representing true and false. The NOT gates, or inverters, are attached in a chain and the output of the last inverter is fed back into the first.
Details
Because a single inverter computes the logical NOT of its input, it can be shown that the last output of a chain of an odd number of inverters is the logical NOT of the first input. The final output is asserted a finite amount of time after the first input is asserted and the feedback of the last output to the input causes oscillation.
A circular chain composed of an even number of inverters cannot be used as a ring oscillator. The last output in this case is the same as the input. However, this configuration of inverter feedback can be used as a storage element and it is the basic building block of static random access memory or SRAM.
The stages of the ring oscillator are often differential stages, that are more immune to external disturbances. This renders available also non-inverting stages. A ring oscillator can be made with a mix of inverting and non-inverting stages, provided the total number of inverting stages is odd. The oscillator period is in all cases equal to twice the sum of the individual delays of all stages.
A ring oscillator only requires power to operate. Above a certain voltage, typical well below the threshold voltage of the MOSFETs used, oscillations begin spontaneously. To increase the frequency of oscillation, two methods are commonly used. First, making the ring from a smaller number of inverters results in a higher frequency of oscillation, with about the same power consumption. Second, the supply voltage may be increased. In circuits where this method can be applied, it reduces the propagation delay through the chain of stages, increasing both the frequency of the oscillation and the current consumed.
Operation
To understand the operation of a ring |
https://en.wikipedia.org/wiki/Quark%20model | In particle physics, the quark model is a classification scheme for hadrons in terms of their valence quarks—the quarks and antiquarks that give rise to the quantum numbers of the hadrons. The quark model underlies "flavor SU(3)", or the Eightfold Way, the successful classification scheme organizing the large number of lighter hadrons that were being discovered starting in the 1950s and continuing through the 1960s. It received experimental verification beginning in the late 1960s and is a valid effective classification of them to date. The model was independently proposed by physicists Murray Gell-Mann, who dubbed them "quarks" in a concise paper, and George Zweig, who suggested "aces" in a longer manuscript. André Petermann also touched upon the central ideas from 1963 to 1965, without as much quantitative substantiation. Today, the model has essentially been absorbed as a component of the established quantum field theory of strong and electroweak particle interactions, dubbed the Standard Model.
Hadrons are not really "elementary", and can be regarded as bound states of their "valence quarks" and antiquarks, which give rise to the quantum numbers of the hadrons. These quantum numbers are labels identifying the hadrons, and are of two kinds. One set comes from the Poincaré symmetry—JPC, where J, P and C stand for the total angular momentum, P-symmetry, and C-symmetry, respectively.
The other set is the flavor quantum numbers such as the isospin, strangeness, charm, and so on. The strong interactions binding the quarks together are insensitive to these quantum numbers, so variation of them leads to systematic mass and coupling relationships among the hadrons in the same flavor multiplet.
All quarks are assigned a baryon number of . Up, charm and top quarks have an electric charge of +, while the down, strange, and bottom quarks have an electric charge of −. Antiquarks have the opposite quantum numbers. Quarks are spin- particles, and thus fermions. Each quark |
https://en.wikipedia.org/wiki/Expression%20cassette | An expression cassette is a distinct component of vector DNA consisting of a gene and regulatory sequence to be expressed by a transfected cell. In each successful transformation, the expression cassette directs the cell's machinery to make RNA and protein(s). Some expression cassettes are designed for modular cloning of protein-encoding sequences so that the same cassette can easily be altered to make different proteins.
An expression cassette is composed of one or more genes and the sequences controlling their expression. An expression cassette comprises three components: a promoter sequence, an open reading frame, and a 3' untranslated region that, in eukaryotes, usually contains a polyadenylation site.
Different expression cassettes can be transfected into different organisms including bacteria, yeast, plants, and mammalian cells as long as the correct regulatory sequences are used.
See also
Expression vector
Gene cassette |
https://en.wikipedia.org/wiki/Mensural%20notation | Mensural notation is the musical notation system used for polyphonic European vocal music from the late 13th century until the early 17th century. The term "mensural" refers to the ability of this system to describe precisely measured rhythmic durations in terms of numerical proportions between note values. Its modern name is inspired by the terminology of medieval theorists, who used terms like musica mensurata ("measured music") or cantus mensurabilis ("measurable song") to refer to the rhythmically defined polyphonic music of their age, as opposed to musica plana or musica choralis, i.e., Gregorian plainchant. Mensural notation was employed principally for compositions in the tradition of vocal polyphony, whereas plainchant retained its own, older system of neume notation throughout the period. Besides these, some purely instrumental music could be written in various forms of instrument-specific tablature notation.
Mensural notation grew out of an earlier, more limited method of notating rhythms in terms of fixed repetitive patterns, the so-called rhythmic modes, which were developed in France around 1200. An early form of mensural notation was first described and codified in the treatise Ars cantus mensurabilis ("The art of measured chant") by Franco of Cologne (). A much expanded system allowing for greater rhythmic complexity was introduced in France with the stylistic movement of the Ars nova in the 14th century, while Italian 14th-century music developed its own, somewhat different variant. Around 1400, the French system was adopted across Europe, and became the standard form of notation of the Renaissance music of the 15th and 16th centuries. Over the course of the 17th century, mensural notation gradually evolved into modern measure (or bar) notation.
The decisive innovation of mensural notation was the systematic use of different note shapes to denote rhythmic durations that stood in well-defined, hierarchical numerical relations to each other. While le |
https://en.wikipedia.org/wiki/Ansys | Ansys, Inc. is an American multinational company with its headquarters based in Canonsburg, Pennsylvania. It develops and markets CAE/multiphysics engineering simulation software for product design, testing and operation and offers its products and services to customers worldwide.
Origins
Ansys was founded in 1970 by John Swanson, who sold his interest in the company to venture capitalists in 1993. Ansys went public on NASDAQ in 1996. In the 2000s, the company acquired other engineering design companies, obtaining additional technology for fluid dynamics, electronics design, and physics analysis. Ansys became a component of the NASDAQ-100 index on December 23, 2019.
The idea for Ansys was first conceived by John Swanson while working at the Westinghouse Astronuclear Laboratory in the 1960s. At the time, engineers performed finite element analysis (FEA) by hand. Westinghouse rejected Swanson's idea to automate FEA by developing general purpose engineering software, so Swanson left the company in 1969 to develop the software on his own. He founded Ansys under the name Swanson Analysis Systems Inc. (SASI) the next year, working out of his farmhouse in Pittsburgh.
Swanson developed the initial Ansys software on punch-cards and used a mainframe computer that was rented by the hour. Westinghouse hired Swanson as a consultant, under the condition that any code he developed for Westinghouse could also be included in the Ansys product line. Westinghouse also became the first Ansys user.
History
By 1991, SASI had 153 employees and $29 million in annual revenue, controlling 10 percent of the market for finite element analysis software. According to The Engineering Design Revolution, the company became "well-respected" among engineering circles, but remained small.
In 1992, SASI acquired Compuflo, which marketed and developed fluid dynamics analysis software.
In 1994, Swanson sold his majority interest in the company to venture capitalist firm TA Associates. Peter Smith |
https://en.wikipedia.org/wiki/Poikilotherm | A poikilotherm () is an animal (Greek poikilos – 'various, spotted', and therme – 'heat) whose internal temperature varies considerably. Poikilotherms have to survive and adapt to environmental stress. One of the most important stressors is temperature change, which can lead to alterations in membrane lipid order and can cause protein unfolding and denaturation at elevated temperatures. It is the opposite of a homeotherm, an animal which maintains thermal homeostasis. While the term in principle can apply to all organisms, it is generally only applied to animals, and mostly to vertebrates. Usually the fluctuations are consequence of variation in the ambient environmental temperature. Many terrestrial ectotherms are poikilothermic. However some ectotherms remain in temperature-constant environments to the point that they are actually able to maintain a constant internal temperature and are considered homeothermic. It is this distinction that often makes the term "poikilotherm" more useful than the vernacular "cold-blooded", which is sometimes used to refer to ectotherms more generally.
Poikilothermic animals include types of vertebrate animals, specifically some fish, amphibians, and reptiles, as well as many invertebrate animals. The naked mole-rat and sloth are some of the rare mammals which are poikilothermic.
Etymology
The term derives from Greek poikilos (), meaning "varied," ultimately from a root meaning "dappled" or “painted,” and thermos (), meaning "heat".
Physiology
Poikilotherm animals must be able to function over a wider range of temperatures than homeotherms. The speed of most chemical reactions vary with temperature, and in order to function poikilotherms may have four to ten enzyme systems that operate at different temperatures for an important chemical reaction. As a result, poikilotherms often have larger, more complex genomes than homeotherms in the same ecological niche. Frogs are a notable example of this effect, though their complex de |
https://en.wikipedia.org/wiki/Tiling%20with%20rectangles | A tiling with rectangles is a tiling which uses rectangles as its parts. The domino tilings are tilings with rectangles of side
ratio. The tilings with straight polyominoes of shapes such as , and
tilings with polyominoes of shapes such as fall also into this category.
Congruent rectangles
Some tiling of rectangles include:
Tilings with non-congruent rectangles
The smallest square that can be cut into (m × n) rectangles, such that all m and n are different integers, is the 11 × 11 square, and the tiling uses five rectangles.
The smallest rectangle that can be cut into (m × n) rectangles, such that all m and n are different integers, is the 9 × 13 rectangle, and the tiling uses five rectangles.
See also
Squaring the square
Tessellation
Tiling puzzle
Notes
Tessellation |
https://en.wikipedia.org/wiki/Unicode%20and%20email | Many email clients now offer some support for Unicode. Some clients will automatically choose between a legacy encoding and Unicode depending on the mail's content, either automatically or when the user requests it.
Technical requirements for sending of messages containing non-ASCII characters by email include
encoding of certain header fields (subject, sender's and recipient's names, sender's organization and reply-to name) and, optionally, body in a content-transfer encoding
encoding of non-ASCII characters in one of the Unicode transforms
negotiating the use of UTF-8 encoding in email addresses and reply codes (SMTPUTF8)
sending the information about the content-transfer encoding and the Unicode transform used so that the message can be correctly displayed by the recipient (see Mojibake).
If the sender's or recipient's email address contains non-ASCII characters, sending of a message requires also encoding of these to a format that can be understood by mail servers.
Unicode support in protocols
provides a mechanism for allowing non-ASCII email addresses encoded as UTF-8 in an SMTP or LMTP protocol
Unicode support in message header
To use Unicode in certain email header fields, e.g. subject lines, sender and recipient names, the Unicode text has to be encoded using a MIME "Encoded-Word" with a Unicode encoding as the charset. To use Unicode in domain part of email addresses, IDNA encoding must traditionally be used. Alternatively, SMTPUTF8 allows the use of UTF-8 encoding in email addresses (both in a local part and in domain name) as well as in a mail header section. Various standards had been created to retrofit the handling of non-ASCII data to the originally ASCII-only email protocol:
provides support for encoding non-ASCII values such as real names and subject lines in email headers
provides support for encoding non-ASCII domain names in the Domain Name System
allows the use of UTF-8 in a mail header section
Unicode support in message bodies
|
https://en.wikipedia.org/wiki/Plan%20%28archaeology%29 | In archaeological excavation, a plan is a drawn record of features and artifacts in the horizontal plane.
Overview
Archaeological plan can either take the form of
a "multi context" plan, which is drawn with many contexts on it to show relationships between these features as part of some phase, or
alternatively a single context plan with a single feature is drawn .
Excavated features are drawn in three dimensions with the help of drawing conventions such as hachures. Single context planning developed by the Museum of London has become the professional norm. The basic advantage of single context planning is context plans draw on "transparent perma-trace paper" can be overlaid for re-interpretation at a later date.
Multi-context Plans as opposed to single context plans can be made of complete sites, trenches or individual features. In the United Kingdom, the scale of the plans is usually 1:20. They are linked to the site recording system by the inclusion of known grid points and height readings, taken with a dumpy level or a total station (see surveying). Excavation of a site by the removal of human made deposits in the reverse order they were created is the preferred method of excavation and is referred to as stratigraphic area excavation "in plan" as opposed to excavation "in section". Plan and section drawings have an interpretive function as well as being part of the recording system, because the draughts-person makes conscious decisions about what should be included or emphasised.
Archaeological plan topics
The grid
It is common and good practice on excavations to lay out a grid of 5m squares so as to facilitate planning. This grid is marked out on-site with grid pegs that form the baselines for tapes and other planning tools to aid the drawing of plans. It is also common practice that planning is done for each context on a separate piece of perma-trace that conforms to these 5m grid squares. This is part of the single context recording system (see |
https://en.wikipedia.org/wiki/Regularization%20%28mathematics%29 | In mathematics, statistics, finance, computer science, particularly in machine learning and inverse problems, regularization is a process that changes the result answer to be "simpler". It is often used to obtain results for ill-posed problems or to prevent overfitting.
Although regularization procedures can be divided in many ways, the following delineation is particularly helpful:
Explicit regularization is regularization whenever one explicitly adds a term to the optimization problem. These terms could be priors, penalties, or constraints. Explicit regularization is commonly employed with ill-posed optimization problems. The regularization term, or penalty, imposes a cost on the optimization function to make the optimal solution unique.
Implicit regularization is all other forms of regularization. This includes, for example, early stopping, using a robust loss function, and discarding outliers. Implicit regularization is essentially ubiquitous in modern machine learning approaches, including stochastic gradient descent for training deep neural networks, and ensemble methods (such as random forests and gradient boosted trees).
In explicit regularization, independent of the problem or model, there is always a data term, that corresponds to a likelihood of the measurement and a regularization term that corresponds to a prior. By combining both using Bayesian statistics, one can compute a posterior, that includes both information sources and therefore stabilizes the estimation process. By trading off both objectives, one chooses to be more addictive to the data or to enforce generalization (to prevent overfitting). There is a whole research branch dealing with all possible regularizations. In practice, one usually tries a specific regularization and then figures out the probability density that corresponds to that regularization to justify the choice. It can also be physically motivated by common sense or intuition.
In machine learning, the data term correspo |
https://en.wikipedia.org/wiki/Regularization%20%28physics%29 | In physics, especially quantum field theory, regularization is a method of modifying observables which have singularities in order to make them finite by the introduction of a suitable parameter called the regulator. The regulator, also known as a "cutoff", models our lack of knowledge about physics at unobserved scales (e.g. scales of small size or large energy levels). It compensates for (and requires) the possibility that "new physics" may be discovered at those scales which the present theory is unable to model, while enabling the current theory to give accurate predictions as an "effective theory" within its intended scale of use.
It is distinct from renormalization, another technique to control infinities without assuming new physics, by adjusting for self-interaction feedback.
Regularization was for many decades controversial even amongst its inventors, as it combines physical and epistemological claims into the same equations. However, it is now well understood and has proven to yield useful, accurate predictions.
Overview
Regularization procedures deal with infinite, divergent, and nonsensical expressions by introducing an auxiliary concept of a regulator (for example, the minimal distance in space which is useful, in case the divergences arise from short-distance physical effects). The correct physical result is obtained in the limit in which the regulator goes away (in our example, ), but the virtue of the regulator is that for its finite value, the result is finite.
However, the result usually includes terms proportional to expressions like which are not well-defined in the limit . Regularization is the first step towards obtaining a completely finite and meaningful result; in quantum field theory it must be usually followed by a related, but independent technique called renormalization. Renormalization is based on the requirement that some physical quantities — expressed by seemingly divergent expressions such as — are equal to the observed |
https://en.wikipedia.org/wiki/Small-angle%20approximation | The small-angle approximations can be used to approximate the values of the main trigonometric functions, provided that the angle in question is small and is measured in radians:
These approximations have a wide range of uses in branches of physics and engineering, including mechanics, electromagnetism, optics, cartography, astronomy, and computer science. One reason for this is that they can greatly simplify differential equations that do not need to be answered with absolute precision.
There are a number of ways to demonstrate the validity of the small-angle approximations. The most direct method is to truncate the Maclaurin series for each of the trigonometric functions. Depending on the order of the approximation, is approximated as either or as .
Justifications
Graphic
The accuracy of the approximations can be seen below in Figure 1 and Figure 2. As the measure of the angle approaches zero, the difference between the approximation and the original function also approaches 0.
Geometric
The red section on the right, , is the difference between the lengths of the hypotenuse, , and the adjacent side, . As is shown, and are almost the same length, meaning is close to 1 and helps trim the red away.
The opposite leg, , is approximately equal to the length of the blue arc, . Gathering facts from geometry, , from trigonometry, and , and from the picture, and leads to:
Simplifying leaves,
Calculus
Using the squeeze theorem, we can prove that
which is a formal restatement of the approximation for small values of θ.
A more careful application of the squeeze theorem proves that from which we conclude that for small values of θ.
Finally, L'Hôpital's rule tells us that which rearranges to for small values of θ. Alternatively, we can use the double angle formula . By letting , we get that .
Algebraic
The Maclaurin expansion (the Taylor expansion about 0) of the relevant trigonometric function is
where is the angle in radians. In clearer terms |
https://en.wikipedia.org/wiki/Sieve%20tube%20element | Sieve elements are specialized cells that are important for the function of phloem, which is a highly organized tissue that transports organic compounds made during photosynthesis. Sieve elements are the major conducting cells in phloem. Conducting cells aid in transport of molecules especially for long-distance signaling. In plant anatomy, there are two main types of sieve elements. Companion cells and sieve cells originate from meristems, which are tissues that actively divide throughout a plant's lifetime. They are similar to the development of xylem, a water conducting tissue in plants whose main function is also transportation in the plant vascular system. Sieve elements' major function includes transporting sugars over long distance through plants by acting as a channel. Sieve elements elongate cells containing sieve areas on their walls. Pores on sieve areas allow for cytoplasmic connections to neighboring cells, which allows for the movement of photosynthetic material and other organic molecules necessary for tissue function. Structurally, they are elongated and parallel to the organ or tissue that they are located in. Sieve elements typically lack a nucleus and contain none to a very small number of ribosomes. The two types of sieve elements, sieve tube members and sieve cells, have different structures. Sieve tube members are shorter and wider with greater area for nutrient transport while sieve cells tend to be longer and narrower with smaller area for nutrient transport. Although the function of both of these kinds of sieve elements is the same, sieve cells are found in gymnosperms, non-flowering vascular plants, while sieve tube members are found in angiosperms, flowering vascular plants.
Discovery
Sieve elements were first discovered by the forest botanist Theodor Hartig in 1837. Since this discovery, the structure and physiology of phloem tissue has been emphasized more as there has been greater focus on its specialized components such as the sieve |
https://en.wikipedia.org/wiki/Geosmin | Geosmin ( ) is an irregular sesquiterpenoid, produced from the universal sesquiterpene precursor farnesyl pyrophosphate (also known as farnesyl diphosphate), in a two-step -dependent reaction. Geosmin, along with the irregular monoterpene 2-methylisoborneol, together account for the majority of biologically-caused taste and odor outbreaks in drinking water worldwide. Geosmin has a distinct earthy or musty odor, which most people can easily smell. The geosmin odor detection threshold in humans is very low, ranging from 0.006 to 0.01 micrograms per liter in water. Geosmin is also responsible for the earthy taste of beetroots and a contributor to the strong scent (petrichor) that occurs in the air when rain falls after a spell of dry weather or when soil is disturbed.
In chemical terms, geosmin is a bicyclic alcohol with formula , a derivative of decalin. Its name is derived from the Ancient Greek words (), meaning "earth", and (), meaning "smell". The word was coined in 1965 by the American biochemist Nancy N. Gerber (1929–1985) and the French-American biologist Hubert A. Lechevalier (1926–2015).
Production
Geosmin is produced by various blue-green algae (cyanobacteria) and filamentous bacteria in the class Actinomyces, and also some other prokaryotes and eukaryotes. The main genera in the cyanobacteria that have been shown to produce geosmin include Anabaena, Phormidium, and Planktothrix, while the main genus in the Actinomyces that produces geosmin is Streptomyces. Communities whose water supplies depend on surface water can periodically experience episodes of unpleasant-tasting water when a sharp drop in the population of these bacteria releases geosmin into the local water supply. Under acidic conditions, geosmin decomposes into odorless substances.
In 2006, geosmin was biosynthesized by a bifunctional Streptomyces coelicolor enzyme. A single enzyme, geosmin synthase, converts farnesyl diphosphate to geosmin in a two-step reaction.
Not all blue-green alga |
https://en.wikipedia.org/wiki/Stackless%20Python | Stackless Python, or Stackless, is a Python programming language interpreter, so named because it avoids depending on the C call stack for its own stack. In practice, Stackless Python uses the C stack, but the stack is cleared between function calls. The most prominent feature of Stackless is microthreads, which avoid much of the overhead associated with usual operating system threads. In addition to Python features, Stackless also adds support for coroutines, communication channels, and task serialization.
Design
With Stackless Python, a running program is split into microthreads that are managed by the language interpreter itself, not the operating system kernel—context switching and task scheduling is done purely in the interpreter (these are thus also regarded as a form of green thread). Microthreads manage the execution of different subtasks in a program on the same CPU core. Thus, they are an alternative to event-based asynchronous programming and also avoid the overhead of using separate threads for single-core programs (because no mode switching between user mode and kernel mode needs to be done, so CPU usage can be reduced).
Although microthreads make it easier to deal with running subtasks on a single core, Stackless Python does not remove CPython's Global Interpreter Lock, nor does it use multiple threads and/or processes. So it allows only cooperative multitasking on a shared CPU and not parallelism (preemption was originally not available but is now in some form). To use multiple CPU cores, one would still need to build an interprocess communication system on top of Stackless Python processes.
Due to the considerable number of changes in the source, Stackless Python cannot be installed on a preexisting Python installation as an extension or library. It is instead a complete Python distribution in itself. The majority of Stackless's features have also been implemented in PyPy, a self-hosting Python interpreter and JIT compiler.
Use
Although the whole |
https://en.wikipedia.org/wiki/Comparison%20of%20open-source%20and%20closed-source%20software | Free/open-source software – the source availability model used by free and open-source software (FOSS) – and closed source are two approaches to the distribution of software.
Background
Under the closed-source model source code is not released to the public. Closed-source software is maintained by a team who produces their product in a compiled-executable state, which is what the market is allowed access to. Microsoft, the owner and developer of Windows and Microsoft Office, along with other major software companies, have long been proponents of this business model, although in August 2010, Microsoft interoperability general manager Jean Paoli said Microsoft "loves open source" and its anti-open-source position was a mistake.
The FOSS model allows for able users to view and modify a product's source code, but most of such code is not in the public domain. Common advantages cited by proponents for having such a structure are expressed in terms of trust, acceptance, teamwork and quality.
A non-free license is used to limit what free software movement advocates consider to be the essential freedoms. A license, whether providing open-source code or not, that does not stipulate the "four software freedoms", are not considered "free" by the free software movement. A closed source license is one that limits only the availability of the source code. By contrast a copyleft license claims to protect the "four software freedoms" by explicitly granting them and then explicitly prohibiting anyone to redistribute the package or reuse the code in it to make derivative works without including the same licensing clauses. Some licenses grant the four software freedoms but allow redistributors to remove them if they wish. Such licenses are sometimes called permissive software licenses. An example of such a license is the FreeBSD License which allows derivative software to be distributed as non-free or closed source, as long as they give credit to the original designers.
A miscon |
https://en.wikipedia.org/wiki/Oxyria%20digyna | Oxyria digyna (mountain sorrel, wood sorrel, Alpine sorrel or Alpine mountain-sorrel) is a species of flowering plant in the buckwheat family (Polygonaceae). It is native to arctic regions and mountainous parts of the Northern Hemisphere.
Description
Mountain sorrel is a perennial plant with a tough taproot; the plant grows to a height of . It grows in dense tufts, with stems that are usually unbranched and hairless. Both flowering stems and leaf stalks are somewhat reddish. The leaves are kidney-shaped, somewhat fleshy, on stalks from the basal part of the stem. Flowers are small, green and later reddish, and are grouped in an open upright cluster. The fruit is a small nut, encircled by a broad wing which finally turns red. Forming dense, red tufts, the plant is easily recognized. Oxyria digyna grows in wet places protected by snow in winter. Oxyria (from Greek) means "sour".
Distribution and habitat
Mountain sorrel is common in the tundra of the Arctic. Further south, it has a circumboreal distribution, growing in high mountainous areas in the Northern Hemisphere such as the Alps, the Sierra Nevada, and the Cascade Range. It typically grows in alpine meadows, scree, snow-bed sites and beside streams.
On the coast of Norway, the pollen of this plant has been found in peat bogs that are 12,600 years old, indicating that it must have been one of the first plants to colonise the area after the retreating ice age glaciers.
Deer and elk favor the plant.
Uses
The leaves of mountain sorrel have a sour or fresh acidic taste (due to oxalic acid) and are rich in vitamin C, containing about 36 mg/100 g. They can be eaten raw or cooked. They were used by the Inuit to prevent and cure scurvy. Mountain sorrel has also been an important plant in Saami diet. The plant is important for both insects and larger animals that feed on it in arctic and alpine regions where it occurs. |
https://en.wikipedia.org/wiki/Nonverbal%20learning%20disorder | Nonverbal learning disability (NVLD) is proposed category of neurodevelopmental disorder characterized by core deficits in visual-spatial processing and a significant discrepancy between verbal and nonverbal intelligence (where verbal intelligence is higher). A review of papers found that proposed diagnostic criteria were inconsistent. Proposed additional diagnostic criteria include intact verbal intelligence, and deficits in the following: visuoconstruction abilities, speech prosody, fine-motor coordination, mathematical reasoning, visuospatial memory and social skills. NVLD is not recognised by the DSM-5 and is not clinically distinct from learning disorder.
NVLD's symptoms can overlap with symptoms of Autism Spectrum Disorder (ASD), bipolar disorder, and ADHD. For this reason, some claim a diagnosis of NVLD is more appropriate in some subset of these cases.
Signs and symptoms
Considered to be neurologically based, nonverbal learning disorder is characterized by:
impairments in visuospatial processing
discrepancy between average to superior verbal abilities and impaired nonverbal abilities such as:
visuoconstruction
fine motor coordination
mathematical reasoning
visuospatial memory
socioemotional skills
People with NVLD may have trouble understanding charts, reading maps, assembling jigsaw puzzles, and using an analog clock to tell time. "Clumsiness" is not unusual in people with NVLD, especially children, and it may take a child with NVLD longer than usual to learn how to tie shoelaces or to ride a bicycle.
At the beginning of their school careers, children with symptoms of NVLD struggle with tasks that require eye–hand coordination, such as coloring and using scissors, but often excel at memorizing verbal content, spelling, and reading once the shapes of the letters are learned. A child with NVLD's Average or Superior verbal skills can be misattributed to attention deficit hyperactivity disorder, defiant behavior, inattention, or lack of effort. Earl |
https://en.wikipedia.org/wiki/National%20symbols%20of%20the%20United%20States | National symbols of the United States are the symbols used to represent the United States of America.
List of symbols
See also
Lists of United States state symbols |
https://en.wikipedia.org/wiki/Species%20Plantarum | (Latin for "The Species of Plants") is a book by Carl Linnaeus, originally published in 1753, which lists every species of plant known at the time, classified into genera. It is the first work to consistently apply binomial names and was the starting point for the naming of plants.
Publication
was published on 1 May 1753 by Laurentius Salvius in Stockholm, in two volumes. A second edition was published in 1762–1763, and a third edition in 1764, although this "scarcely differed" from the second. Further editions were published after Linnaeus' death in 1778, under the direction of Karl Ludwig Willdenow, the director of the Berlin Botanical Garden; the fifth edition (1800) was published in four volumes.
Importance
was the first botanical work to consistently apply the binomial nomenclature system of naming to any large group of organisms (Linnaeus' tenth edition of would apply the same technique to animals for the first time in 1758). Prior to this work, a plant species would be known by a long polynomial, such as (meaning "plantain with pubescent ovate-lanceolate leaves, a cylindrical spike and a terete scape") or (meaning "Nepeta with flowers in a stalked, interrupted spike"). In , these cumbersome names were replaced with two-part names, consisting of a single-word genus name, and a single-word specific epithet or "trivial name"; the two examples above became Plantago media and Nepeta cataria, respectively. The use of binomial names had originally been developed as a kind of shorthand in a student project about the plants eaten by cattle.
After the specific epithet, Linnaeus gave a short description of each species, and a synonymy. The descriptions were careful and terse, consisting of few words in small genera; in Glycyrrhiza, for instance, the three species (Glycyrrhiza echinata, Glycyrrhiza glabra and "Glycyrrhiza hirsuta", respectively) were described as "", "" and "".
Because it is the first work in which binomial nomenclature was consistently applied |
https://en.wikipedia.org/wiki/Pentane%20interference | Pentane interference or syn-pentane interaction is the steric hindrance that the two terminal methyl groups experience in one of the chemical conformations of n-pentane. The possible conformations are combinations of anti conformations and gauche conformations and are anti-anti, anti-gauche+, gauche+ - gauche+ and gauche+ - gauche− of which the last one is especially energetically unfavorable. In macromolecules such as polyethylene pentane interference occurs between every fifth carbon atom. The 1,3-diaxial interactions of cyclohexane derivatives is a special case of this type of interaction, although there are additional gauche interactions shared between substituents and the ring in that case. A clear example of the syn-pentane interaction is apparent in the diaxial versus diequatorial heats of formation of cis 1,3-dialkyl cyclohexanes. Relative to the diequatorial conformer, the diaxial conformer is 2-3 kcal/mol higher in energy than the value that would be expected based on gauche interactions alone. Pentane interference helps explain molecular geometries in many chemical compounds, product ratios, and purported transition states. One specific type of syn-pentane interaction is known as 1,3 allylic strain or (A1,3 strain).
For instance in certain aldol adducts with 2,6-disubstituted aryl groups the molecular geometry has the vicinal hydrogen atoms in an antiperiplanar configuration both in a crystal lattice (X-ray diffraction) and in solution proton (NMR coupling constants) normally reserved for the most bulky groups i.d. both arenes:
The other contributing factor explaining this conformation is reduction in allylic strain by minimizing the dihedral angle between the arene double bond and the methine proton.
Syn-pentane interactions are responsible for the backbone-conformation dependence of protein side chain rotamer frequencies and their mean dihedral angles, which is evident from statistical analysis of protein side-chain rotamers in the Backbone-depende |
https://en.wikipedia.org/wiki/Sparsely%20totient%20number | In mathematics, a sparsely totient number is a certain kind of natural number. A natural number, n, is sparsely totient if for all m > n,
where is Euler's totient function. The first few sparsely totient numbers are:
2, 6, 12, 18, 30, 42, 60, 66, 90, 120, 126, 150, 210, 240, 270, 330, 420, 462, 510, 630, 660, 690, 840, 870, 1050, 1260, 1320, 1470, 1680, 1890, 2310, 2730, 2940, 3150, 3570, 3990, 4620, 4830, 5460, 5610, 5670, 6090, 6930, 7140, 7350, 8190, 9240, 9660, 9870, ... .
The concept was introduced by David Masser and Peter Man-Kit Shiu in 1986. As they showed, every primorial is sparsely totient.
Properties
If P(n) is the largest prime factor of n, then .
holds for an exponent .
It is conjectured that . |
https://en.wikipedia.org/wiki/Steady%20state%20%28biochemistry%29 | In biochemistry, steady state refers to the maintenance of constant internal concentrations of molecules and ions in the cells and organs of living systems. Living organisms remain at a dynamic steady state where their internal composition at both cellular and gross levels are relatively constant, but different from equilibrium concentrations. A continuous flux of mass and energy results in the constant synthesis and breakdown of molecules via chemical reactions of biochemical pathways. Essentially, steady state can be thought of as homeostasis at a cellular level.
Maintenance of steady state
Metabolic regulation achieves a balance between the rate of input of a substrate and the rate that it is degraded or converted, and thus maintains steady state. The rate of metabolic flow, or flux, is variable and subject to metabolic demands. However, in a metabolic pathway, steady state is maintained by balancing the rate of substrate provided by a previous step and the rate that the substrate is converted into product, keeping substrate concentration relatively constant.
Thermodynamically speaking, living organisms are open systems, meaning that they constantly exchange matter and energy with their surroundings. A constant supply of energy is required for maintaining steady state, as maintaining a constant concentration of a molecule preserves internal order and thus is entropically unfavorable. When a cell dies and no longer utilizes energy, its internal composition will proceed toward equilibrium with its surroundings.
In some occurrences, it is necessary for cells to adjust their internal composition in order to reach a new steady state. Cell differentiation, for example, requires specific protein regulation that allows the differentiating cell to meet new metabolic requirements.
ATP
The concentration of ATP must be kept above equilibrium level so that the rates of ATP-dependent biochemical reactions meet metabolic demands. A decrease in ATP will result in a decre |
https://en.wikipedia.org/wiki/Ground%20expression | In mathematical logic, a ground term of a formal system is a term that does not contain any variables. Similarly, a ground formula is a formula that does not contain any variables.
In first-order logic with identity with constant symbols and , the sentence is a ground formula. A ground expression is a ground term or ground formula.
Examples
Consider the following expressions in first order logic over a signature containing the constant symbols and for the numbers 0 and 1, respectively, a unary function symbol for the successor function and a binary function symbol for addition.
are ground terms;
are ground terms;
are ground terms;
and are terms, but not ground terms;
and are ground formulae.
Formal definitions
What follows is a formal definition for first-order languages. Let a first-order language be given, with the set of constant symbols, the set of functional operators, and the set of predicate symbols.
Ground term
A is a term that contains no variables. Ground terms may be defined by logical recursion (formula-recursion):
Elements of are ground terms;
If is an -ary function symbol and are ground terms, then is a ground term.
Every ground term can be given by a finite application of the above two rules (there are no other ground terms; in particular, predicates cannot be ground terms).
Roughly speaking, the Herbrand universe is the set of all ground terms.
Ground atom
A , or is an atomic formula all of whose argument terms are ground terms.
If is an -ary predicate symbol and are ground terms, then is a ground predicate or ground atom.
Roughly speaking, the Herbrand base is the set of all ground atoms, while a Herbrand interpretation assigns a truth value to each ground atom in the base.
Ground formula
A or is a formula without variables.
Ground formulas may be defined by syntactic recursion as follows:
A ground atom is a ground formula.
If and are ground formulas, then , , and are ground formulas.
Ground f |
https://en.wikipedia.org/wiki/Wirth%E2%80%93Weber%20precedence%20relationship | In computer science, a Wirth–Weber relationship between a pair of symbols is necessary to determine if a formal grammar is a simple precedence grammar. In such a case, the simple precedence parser can be used. The relationship is named after computer scientists Niklaus Wirth and Helmut Weber.
The goal is to identify when the viable prefixes have the pivot and must be reduced. A means that the pivot is found, a means that a potential pivot is starting, and a means that a relationship remains in the same pivot.
Formal definition
Precedence relations computing algorithm
We will define three sets for a symbol:
The pseudocode for computing relations is:
RelationTable := ∅
For each production
For each two adjacent symbols in
add(RelationTable, )
add(RelationTable, )
add(RelationTable, )
add(RelationTable, ) where is the initial non terminal of the grammar, and $ is a limit marker
add(RelationTable, ) where is the initial non terminal of the grammar, and $ is a limit marker
Examples
Head(a) = ∅
Head(S) = {a, c}
Head(b) = ∅
Head(c) = ∅
Tail(a) = ∅
Tail(S) = {b, c}
Tail(b) = ∅
Tail(c) = ∅
Head(a) = a
Head(S) = {a, c}
Head(b) = b
Head(c) = c
a Next to S
S Next to S
S Next to b
there is only one symbol, so no relation is added.
precedence table
Further reading
Formal languages |
https://en.wikipedia.org/wiki/Operator-precedence%20grammar | An operator precedence grammar is a kind of grammar for formal languages.
Technically, an operator precedence grammar is a context-free grammar that has the property (among others)
that no production has either an empty right-hand side or two adjacent nonterminals in its
right-hand side. These properties allow precedence relations to be
defined between the terminals of the grammar. A parser that exploits these relations is considerably simpler than more general-purpose parsers such as LALR parsers. Operator-precedence parsers can be constructed for a large class of context-free grammars.
Precedence relations
Operator precedence grammars rely on the following three precedence relations between the terminals:
These operator precedence relations allow to delimit the handles in the right sentential forms: marks the left end, appears in the interior of the handle, and marks the right end. Contrary to other shift-reduce parsers, all nonterminals are considered equal for the purpose of identifying handles.
The relations do not have the same properties as their un-dotted counterparts;
e. g. does not generally imply , and does not follow
from . Furthermore, does not generally hold, and is possible.
Let us assume that between the terminals and there is always exactly one precedence relation. Suppose that $ is the end of the string.
Then for all terminals we define: and . If we remove all nonterminals and place the correct precedence relation:
, , between the remaining terminals, there remain strings that can be analyzed by an easily developed bottom-up parser.
Example
For example, the following operator precedence relations can
be introduced for simple expressions:
They follow from the following facts:
+ has lower precedence than * (hence and ).
Both + and * are left-associative (hence and ).
The input string
after adding end markers and inserting precedence relations becomes
Operator precedence parsing
Having precedence relations allows to iden |
https://en.wikipedia.org/wiki/Karp%27s%2021%20NP-complete%20problems | In computational complexity theory, Karp's 21 NP-complete problems are a set of computational problems which are NP-complete. In his 1972 paper, "Reducibility Among Combinatorial Problems", Richard Karp used Stephen Cook's 1971 theorem that the boolean satisfiability problem is NP-complete (also called the Cook-Levin theorem) to show that there is a polynomial time many-one reduction from the boolean satisfiability problem to each of 21 combinatorial and graph theoretical computational problems, thereby showing that they are all NP-complete. This was one of the first demonstrations that many natural computational problems occurring throughout computer science are computationally intractable, and it drove interest in the study of NP-completeness and the P versus NP problem.
The problems
Karp's 21 problems are shown below, many with their original names. The nesting indicates the direction of the reductions used. For example, Knapsack was shown to be NP-complete by reducing Exact cover to Knapsack.
Satisfiability: the boolean satisfiability problem for formulas in conjunctive normal form (often referred to as SAT)
0–1 integer programming (A variation in which only the restrictions must be satisfied, with no optimization)
Clique (see also independent set problem)
Set packing
Vertex cover
Set covering
Feedback node set
Feedback arc set
Directed Hamilton circuit (Karp's name, now usually called Directed Hamiltonian cycle)
Undirected Hamilton circuit (Karp's name, now usually called Undirected Hamiltonian cycle)
Satisfiability with at most 3 literals per clause (equivalent to 3-SAT)
Chromatic number (also called the Graph Coloring Problem)
Clique cover
Exact cover
Hitting set
Steiner tree
3-dimensional matching
Knapsack (Karp's definition of Knapsack is closer to Subset sum)
Job sequencing
Partition
Max cut
Approximations
As time went on it was discovered that many of the problems can be solved efficiently if restricted to special cases, or can |
https://en.wikipedia.org/wiki/Password%20synchronization | Password synchronization is a process, usually supported by software such as password managers, through which a user maintains a single password across multiple IT systems.
Provided that all the systems enforce mutually-compatible password standards (e.g. concerning minimum and maximum password length, supported characters, etc.), the user can choose a new password at any time and deploy the same password on his or her own login accounts across multiple, linked systems.
Where different systems have mutually incompatible standards regarding what can be stored in a password field, the user may be forced to choose more than one (but still fewer than the number of systems) passwords. This may happen, for example, where the maximum password length on one system is shorter than the minimum length in another, or where one system requires use of a punctuation mark but another forbids it.
Password synchronization is a function of certain identity management systems and it is considered easier to implement than enterprise single sign-on (SSO), as there is normally no client software deployment or need for active user enrollment.
Uses
Password synchronization makes it easier for IT users to recall passwords and so manage their access to multiple systems, for example on an enterprise network. Since they only have to remember one or at most a few passwords, users are less likely to forget them or write them down, resulting in fewer calls to the IT Help Desk and less opportunity for coworkers, intruders or thieves to gain improper access. Through suitable security awareness, automated policy enforcement and training activities, users can be encouraged or forced to choose stronger passwords as they have fewer to remember.
Security
If the single, synchronized password is compromised (for example, if it is guessed, disclosed, determined by cryptanalysis from one of the systems, intercepted on an insecure communications path, or if the user is socially engineered into reset |
https://en.wikipedia.org/wiki/Load%20cell | A load cell converts a force such as tension, compression, pressure, or torque into a signal (electrical, pneumatic or hydraulic pressure, or mechanical displacement indicator) that can be measured and standardized. It is a force transducer. As the force applied to the load cell increases, the signal changes proportionally. The most common types of load cells are pneumatic, hydraulic, and strain gauge types for industrial applications. Typical non-electronic bathroom scales are a widespread example of a mechanical displacement indicator where the applied weight (force) is indicated by measuring the deflection of springs supporting the load platform, technically a "load cell".
Strain gauge load cell
Strain gauge load cells are the kind most often found in industrial settings. It is ideal as it is highly accurate, versatile, and cost-effective. Structurally, a load cell has a metal body to which strain gauges have been secured. The body is usually made of aluminum, alloy steel, or stainless steel which makes it very sturdy but also minimally elastic. This elasticity gives rise to the term "spring element", referring to the body of the load cell. When force is exerted on the load cell, the spring element is slightly deformed, and unless overloaded, always returns to its original shape. As the spring element deforms, the strain gauges also change shape. The resulting alteration to the resistance in the strain gauges can be measured as voltage. The change in voltage is proportional to the amount of force applied to the cell, thus the amount of force can be calculated from the load cell's output.
Strain Gauges
A strain gauge is constructed of very fine wire, or foil, set up in a grid pattern and attached to a flexible backing. When the shape of the strain gauge is altered, a change in its electrical resistance occurs. The wire or foil in the strain gauge is arranged in a way that, when force is applied in one direction, a linear change in resistance results. Tension |
https://en.wikipedia.org/wiki/Self-service%20password%20reset | Self-service password reset (SSPR) is defined as any process or technology that allows users who have either forgotten their password or triggered an intruder lockout to authenticate with an alternate factor, and repair their own problem, without calling the help desk. It is a common feature in identity management software and often bundled in the same software package as a password synchronization capability.
Typically users who have forgotten their password launch a self-service application from an extension to their workstation login prompt, using their own or another user's web browser, or through a telephone call. Users establish their identity, without using their forgotten or disabled password, by answering a series of personal questions, using a hardware authentication token, responding to a notification e-mail or, less often, by providing a biometric sample such as voice recognition. Users can then either specify a new, unlocked password, or ask that a randomly generated one be provided.
Self-service password reset expedites problem resolution for users "after the fact", and thus reduces help desk call volume. It can also be used to ensure that password problems are only resolved after adequate user authentication, eliminating an important weakness of many help desks: social engineering attacks, where an intruder calls the help desk, pretends to be the intended victim user, claims to have forgotten the account password, and asks for a new password.
Multi-factor authentication
Rather than merely asking users to answer security questions, modern password reset systems may also leverage a sequence of authentication steps:
Ask users to complete a CAPTCHA, to demonstrate that they are human.
Ask users to enter a PIN which is sent to their personal e-mail address or mobile phone.
Require use of another technology, such as a one-time-password token.
Leverage biometrics, such as a voice print.
An authenticator, such as Google Authenticator or an SMS code.
|
https://en.wikipedia.org/wiki/Squround | A squround (or scround) is a container whose shape is between a square and a round tub. It resembles an oval but is sometimes closer to a rectangle with rounded corners. These allow the contents to be easily scooped out of the container. The name is a portmanteau for "square round" (cartons), referring to a compromise between a square and a round carton.
As an adjective, squround has been applied to other objects, such as watches or swimming pools.
Ice cream squround containers
The term applies mostly to ice cream packaging design, where the switch to a squround from paperboard bricks, cylindrical half-gallons and other containers is motivated by consumer preference, as well as cost effectiveness. These packages are more rectangular than square, but the side edges are rounded, while top and bottom surfaces are completely flat. Squround packaging affords some of the consumer appeal of traditional cylindrical packaging, while also packing tightly like brick-shaped square cartons.
The container is usually made of paperboard but can have thermoformed or injection molded plastic components. There is usually a separate lid made of paperboard, plastic, or both.
It offers several advantages over other ice cream packages:
it can be easily scooped out
it fits better in home freezers
it packs tightly into secondary packages for shipping
it makes more efficient use of retail shelf space
it has good brand recognition (over the round half-gallon) since the flatter front is a more legible "billboard" for each flavor
the lid can have tamper-evident features.
Although squrounds are available in traditional half-gallon sizes, there exists a trend toward marketing non-traditional 56-ounce, and recently even 48-ounce sized cartons. The downsizing in carton size has not seemed to negatively affect unit sales.
Mayfield Dairy, which announced the switch to squround cartons in January 2003, told Food Engineering in April that they expect to sell the same number of 56 oz. un |
https://en.wikipedia.org/wiki/Klotski | Klotski (from ) is a sliding block puzzle thought to have originated in the early 20th century. The name may refer to a specific layout of ten blocks, or in a more global sense to refer to a whole group of similar sliding-block puzzles where the aim is to move a specific block to some predefined location.
Rules
Like other sliding-block puzzles, several different-sized block pieces are placed inside a box, which is normally 4×5 in size. Among the blocks, there is a special one (usually the largest) which must be moved to a special area designated by the game board. The player is not allowed to remove blocks, and may only slide blocks horizontally and vertically. Common goals are to solve the puzzle with a minimum number of moves or in a minimum amount of time.
Naming
The earliest known reference of the name Klotski originates from the computer version for Windows 3.x by ZH Computing in 1991, which was also included in Microsoft Windows Entertainment Pack. The sliding puzzle had already been trademarked and sold under different names for decades, including Psychoteaze Square Root, Intreeg, and Ego Buster. There was no known widely used name for the category of sliding puzzles described before Klotski appeared.
History
It is still unknown which version of the puzzle is the original. There are many confusing and conflicting claims, and several countries claim to be the ultimate origin of this game. One game—lacking the 5 × 4 design of Pennant, Klotski, and Chinese models but a likely inspiration—is the 19th century 15-puzzle, where fifteen wooden squares had to be rearranged. It is suggested that unless a 19th-century Asian evidence is found, the most reasonably likely path of transmission is from the late 19th century square designs to the early 20th century rectangular, such as Pennant, thence to Klotski and Huarong Road.
United States
The 15-puzzle enjoyed immense popularity in western countries during the late 19th century. Around this time, patents appeared f |
https://en.wikipedia.org/wiki/SPECint | SPECint is a computer benchmark specification for CPU integer processing power. It is maintained by the Standard Performance Evaluation Corporation (SPEC). SPECint is the integer performance testing component of the SPEC test suite. The first SPEC test suite, CPU92, was announced in 1992. It was followed by CPU95, CPU2000, and CPU2006. The latest standard is SPEC CPU 2017 and consists of SPECspeed and SPECrate (aka SPECCPU_2017).
SPECint 2006
CPU2006 is a set of benchmarks designed to test the CPU performance of a modern server computer system. It is split into two components, the first being CINT2006, the other being CFP2006 (SPECfp), for floating point testing.
SPEC defines a base runtime for each of the 12 benchmark programs. For SPECint2006, that number ranges from 1000 to 3000 seconds. The timed test is run on the system, and the time of the test system is compared to the reference time, and a ratio is computed. That ratio becomes the SPECint score for that test. (This differs from the rating in SPECINT2000, which multiplies the ratio by 100.)
As an example for SPECint2006, consider a processor which can run 400.perlbench in 2000 seconds. The time it takes the reference machine to run the benchmark is 9770 seconds. Thus the ratio is 4.885. Each ratio is computed, and then the geometric mean of those ratios is computed to produce an overall value.
Background
For a fee, SPEC distributes source code files to users wanting to test their systems. These files are written in a standard programming language, which is then compiled for each particular CPU architecture and operating system. Thus, the performance measured is that of the CPU, RAM, and compiler, and does not test I/O, networking, or graphics.
Two metrics are reported for a particular benchmark, "base" and "peak". Compiler options account for the difference between the two numbers. As the SPEC benchmarks are distributed as source code, it is up to the party performing the test to compile this |
https://en.wikipedia.org/wiki/Microbiology%20Society | The Microbiology Society (previously the Society for General Microbiology) is a learned society based in the United Kingdom with a worldwide membership based in universities, industry, hospitals, research institutes and schools. It is the largest learned microbiological society in Europe. Interests of its members include basic and applied aspects of viruses, prions, bacteria, rickettsiae, mycoplasma, fungi, algae and protozoa, and all other aspects of microbiology. Its headquarters is at 14–16 Meredith Street, London. The Society's current president is Prof. Gurdyal S. Besra. The Society is a member of the Science Council.
History
The society was founded on 16 February 1945 as the Society for General Microbiology. Its first president was Alexander Fleming. The Society's first academic meeting was in July 1945 and its first journal, the Journal of General Microbiology (later renamed Microbiology), was published in 1947. A symposium series followed in 1949, and a sister journal, the Journal of General Virology, in 1967. The society purchased its own headquarters in Reading in 1971, after initially sharing accommodation with the Biochemical Society in London. In 2014 the Society moved to Charles Darwin House, London, sharing the premises with several other learned societies. In 2015, the Society changed its name to the Microbiology Society, after its members voted in favour of the change. In 2019 the Society moved to its new headquarters at 14–16 Meredith Street, London.
Activities
The Society currently organises a large Annual Conference and a number of smaller Focused Meetings, which cover a specific microbiology discipline. It publishes a magazine, Microbiology Today (formerly SGM Quarterly), and academic journals in virology and microbiology:
Microbiology
International Journal of Systematic and Evolutionary Microbiology
Journal of General Virology
Journal of Medical Microbiology
Microbial Genomics
Access Microbiology
JMM Case Reports (now closed)
Society Prizes |
https://en.wikipedia.org/wiki/Pandanus%20tectorius | Pandanus tectorius is a species of Pandanus (screwpine) that is native to Malesia, Papuasia, eastern Australia, and the Pacific Islands. It grows in the coastal lowlands typically near the edge of the ocean. Common names in English include thatch screwpine, Tahitian screwpine, hala tree ( in Hawaiian) and pandanus. The fruit is edible and sometimes known as hala fruit.
Description
P. tectorius is a small tree that grows upright to reach in height. The single trunk is slender with brown ringed bark. It is spiny, grows to 4.5–11 m (15–35 ft) in width, and forks at a height of . It is supported by aerial roots (prop roots) that firmly anchors the tree to the ground. Roots sometimes grow along the branch, and they grow at wide angles in proportion to the trunk.
Flowers
Pandanus tectorius is dioecious, meaning male and female flowers are borne on separate trees, with very different male and female flowers. Male flowers, known as racemes, are small, fragrant, and short-lived, lasting only a single day. The flowers are grouped in 3 and gathered in large clusters surrounded by big, white bracts. these clusters are about 1 ft in length and are fragrant. Female flowers resemble pineapples.
In Hawaiʻi the male flower is called hīnano and the bracts are used for making very fine mats (moena hīnano''' or ʻahu hīnano).
Fruit
The female P. tectorius trees produce a segmented, large fruit. Although not closely related, the fruit resembles a pineapple. The fruit of P. tectorius is either ovoid, ellipsoid, subglobose or globose with a diameter of and a length of . The fruit is made up of 38–200 wedge-like phalanges, often referred to as keys or carpels, which have an outer fibrous husk and are 8 inches in length. There are roughly 40 to 80 keys in each fruit and the color of the fruit can be yellow, orange, or red with a green top. Phalanges contain two seeds on average, with a maximum of eight reported. The phalanges are buoyant, and the seeds within them can remain viable fo |
https://en.wikipedia.org/wiki/Anaplerotic%20reactions | Anaplerotic reactions, a term coined by Hans Kornberg and originating from the Greek ἀνά= 'up' and πληρόω= 'to fill', are chemical reactions that form intermediates of a metabolic pathway. Examples of such are found in the citric acid cycle (TCA cycle). In normal function of this cycle for respiration, concentrations of TCA intermediates remain constant; however, many biosynthetic reactions also use these molecules as a substrate. Anaplerosis is the act of replenishing TCA cycle intermediates that have been extracted for biosynthesis (in what are called anaplerotic reactions).
The TCA cycle is a hub of metabolism, with central importance in both energy production and biosynthesis. Therefore, it is crucial for the cell to regulate concentrations of TCA cycle metabolites in the mitochondria. Anaplerotic flux must balance cataplerotic flux in order to retain homeostasis of cellular metabolism.
Reactions of anaplerotic metabolism
There are five major reactions classed as anaplerotic, and it is estimated that the production of oxaloacetate from pyruvate has the most physiologic importance.
The malate is created by PEP carboxylase and malate dehydrogenase in the cytosol. Malate, in the mitochondrial matrix, can be used to make pyruvate (catalyzed by malic enzyme) or oxaloacetic acid, both of which can enter the citric acid cycle.
Glutamine can also be used to produce oxaloacetate during anaplerotic reactions in various cell types through "glutaminolysis", which is also seen in many c-Myc transformed cells. Anaplerotic enzymes mediate an alternative pathway to insulin secretion by aiding the production of cytosolic signal molecules. Pancreatic β-cells which regulate blood glucose level by secreting insulin,contain high a mounts of pyruvate carboxylase. A decrease in insulin secretion and anaplerotic activity has been found in β-cells that do not have hypoxia-inducible factor-1 beta
Diseases of anaplerotic metabolism
Pyruvate carboxylase deficiency is an inherited |
https://en.wikipedia.org/wiki/Project%20Genoa | Project Genoa was a software project commissioned by the United States' DARPA which was designed to analyze large amounts of data and metadata to help human analysts counter terrorism.
Program synopsis
Genoa's primary function was intelligence analysis in order to assist human analysts.
The program was designed to support both top-down and bottom-up approaches; a policy maker could hypothesize a possible attack and use Genoa to look for supporting evidence of such a plot, or it would compile pieces of intelligence into a diagram and suggest possible outcomes. Human analysts would then be able to modify the diagram to test various cases.
Companies such as Integral Visuals, Saffron Technology, and Syntek Technologies were involved in Genoa's development. It cost a total of $42 million to complete the program.
History
Genoa was conceived in late 1995 by retired Rear Admiral John Poindexter, a chief player in the Iran-Contra Affair. At the time, Poindexter was working at Syntek, a company often contracted to do work for the Department of Defense. He proposed a computer system that would help humans crunch large amounts of data in order to more effectively predict potential national security threats. Poindexter brought his ideas to former colleagues working with the United States National Security Council.
That year, a team of researchers was assembled for the project and began studying various historical events to which Genoa could be applied. The Tokyo subway sarin attack in March was the primary focus. Instead of analyzing the attack itself, the researchers looked into the history of Aum Shinrikyo, the group that perpetrated the attack, to find evidence that could have suggested their intentions.
In order to pitch their ideas, the researchers set up a mock crisis command center in DARPA's main building, full of monitors staffed by actors. An audience would watch as a fictitious scenario would unfold before them, guided along by an animated video segment. Poindex |
https://en.wikipedia.org/wiki/Darwin%27s%20tubercle | Darwin's tubercle (or auricular tubercle) is a congenital ear condition which often presents as a thickening on the helix at the junction of the upper and middle thirds.
History
This atavistic feature is so called because its description was first published by Charles Darwin in the opening pages of The Descent of Man, and Selection in Relation to Sex, as evidence of a vestigial feature indicating common ancestry among primates which have pointy ears. However, Darwin himself named it the Woolnerian tip, after Thomas Woolner, a British sculptor who had depicted it in one of his sculptures and had first theorised that it was an atavistic feature.
Prevalence
The feature is present in approximately 10.4% of the Spanish adult population, 40% of adults in India, and 58% of Swedish school children. This acuminate nodule represents the point of the mammalian ear. The trait can potentially be bilateral, meaning present on both ears, or unilateral, where it is present on only one ear. There is mixed evidence in regard to whether the bilateral or unilateral expression is related to population, or other factors. Some populations express full bilateral, while others may express either unilateral or bilateral. However, bilateral appears to be more common than unilateral as it pertains to the expression of the trait.
Inheritance
The gene for Darwin's tubercle was once thought to be inherited in an autosomal dominant pattern with incomplete penetrance, meaning that those who possess the allele (version of a gene) will not necessarily present with the phenotype. However, genetic and family studies have demonstrated that the presence of Darwin's tubercle may be more likely to be influenced by one's environment or developmental accidents than it is by genetics alone. There is no clear argument for whether the trait has significance in sexual dimorphism studies or age related studies. In some studies, there is clear data that Darwin's tubercle is not associated with sex. In contr |
https://en.wikipedia.org/wiki/Two-hybrid%20screening | Two-hybrid screening (originally known as yeast two-hybrid system or Y2H) is a molecular biology technique used to discover protein–protein interactions (PPIs) and protein–DNA interactions by testing for physical interactions (such as binding) between two proteins or a single protein and a DNA molecule, respectively.
The premise behind the test is the activation of downstream reporter gene(s) by the binding of a transcription factor onto an upstream activating sequence (UAS). For two-hybrid screening, the transcription factor is split into two separate fragments, called the DNA-binding domain (DBD or often also abbreviated as BD) and activating domain (AD). The BD is the domain responsible for binding to the UAS and the AD is the domain responsible for the activation of transcription. The Y2H is thus a protein-fragment complementation assay.
History
Pioneered by Stanley Fields and Ok-Kyu Song in 1989, the technique was originally designed to detect protein–protein interactions using the Gal4 transcriptional activator of the yeast Saccharomyces cerevisiae. The Gal4 protein activated transcription of a gene involved in galactose utilization, which formed the basis of selection. Since then, the same principle has been adapted to describe many alternative methods, including some that detect protein–DNA interactions or DNA-DNA interactions, as well as methods that use different host organisms such as Escherichia coli or mammalian cells instead of yeast.
Basic premise
The key to the two-hybrid screen is that in most eukaryotic transcription factors, the activating and binding domains are modular and can function in proximity to each other without direct binding. This means that even though the transcription factor is split into two fragments, it can still activate transcription when the two fragments are indirectly connected.
The most common screening approach is the yeast two-hybrid assay. In this approach the researcher knows where each prey is located on the us |
https://en.wikipedia.org/wiki/IBM%20702 | The IBM 702 was an early generation tube-based digital computer produced by IBM in the early to mid-1950s. It was the company's response to Remington Rand's UNIVAC—the first mainframe computer to use magnetic tapes. As these machines were aimed at the business market, they lacked the leading-edge computational power of the IBM 701 and ERA 1103, which were favored for scientific computing, weather forecasting, the aircraft industry, and the military and intelligence communities.
Within IBM, the 702 was notable for adapting the new technology of magnetic-core memory for random-access applications.
The 702 was announced September 25, 1953, and withdrawn October 1, 1954, but the first production model was not installed until July 1955. It was superseded by the IBM 705.
History
Fourteen 702s were built. The first one was used at IBM. Due to problems with the Williams tubes, the decision was made to switch to magnetic-core memory instead. The fourteenth 702 was built using magnetic-core memory, and the others were retrofitted with magnetic-core memory.
The successor to the 702 in the 700/7000 series was the IBM 705, which marked the transition to magnetic-core memory.
Overview
The 702 was designed for business data processing. Therefore, the memory of the computer was oriented toward storing characters. The system used electrostatic storage, consisting of 14, 28, 42, 56, or 70 Williams tubes with a capacity of 1000 bits each for the main memory, giving a memory of 2,000 to 10,000 characters of seven bits each (in increments of 2,000 characters), and 14 Williams tubes with a capacity of 512 bits each for the two 512-character accumulators.
A complete system included the following units:
IBM 702 Central Processing Unit
IBM 712 Card Reader
IBM 756 Card Reader Control Unit
IBM 717 Printer
IBM 757 Printer Control Unit
IBM 722 Card Punch
IBM 758 Card Punch Control Unit
IBM 727 Magnetic Tape Unit
IBM 752 Tape Control Unit
IBM 732 Magnetic Drum Storage Unit
Total weig |
https://en.wikipedia.org/wiki/Swedish%20National%20Food%20Agency | The Swedish National Food Agency (), formerly the National Swedish Food Administration () is a Swedish government agency that answers to the Ministry of Agriculture, Food and Consumer Affairs. The agency is located in Uppsala.
It is the central supervisory authority for matters relating to food and drinking water. It has the task of protecting consumer interest by working for safe food of good quality, fair practices in the food trade, and healthy eating habits.
See also
Food Administration
Government agencies in Sweden |
https://en.wikipedia.org/wiki/Hypoallergenic%20dog%20breed | A hypoallergenic dog breed is a dog breed (or crossbreed) that is purportedly more compatible with allergic people than are other breeds. However, prominent allergen researchers have determined that there is no basis to the claims that certain breeds are hypoallergenic and, while allergen levels vary among individual dogs, the breed is not a significant factor.
Scientific findings
Though some studies suggest the possible existence of hypoallergenic dog breeds, there is too much variability to conclude that such a breed exists. According to researchers, claims about the existence of hypoallergenic dog breeds may have been fueled by unsubstantiated articles on the internet. The significant allergens are proteins found in the dog's saliva and dander.
Some studies have suggested that the production of the allergen, and therefore human allergenic reaction, varies by breed, yet more recent scientific findings indicate that there are no significant differences between breeds in the generation of these allergens. One study found hypoallergenic breeds to have significantly more allergen in their coats than non-hypoallergenic breeds and no differences in the allergen levels in the air or on the floor.
Breeds that shed less are more likely to be hypoallergenic, since the dog's dander and saliva stick to the hair and are not released into the environment. However, protein expression levels play a major role and amount of shedding alone does not determine degree of allergic reaction. "Even if you get a hairless dog, it's still going to produce the allergen," states Dr. Wanda Phipatanakul, chair of the Indoor Allergen Committee for the American Academy of Allergy, Asthma, and Immunology.
If a person is allergic, they may be best able to tolerate a specific dog, possibly of one of the hypoallergenic breeds. Dr. Thomas A. Platts-Mills, head of the Asthma and Allergic Disease Center at the University of Virginia, explained that there are cases in which a specific dog (not br |
https://en.wikipedia.org/wiki/List%20of%20knot%20theory%20topics | Knot theory is the study of mathematical knots. While inspired by knots which appear in daily life in shoelaces and rope, a mathematician's knot differs in that the ends are joined so that it cannot be undone. In precise mathematical language, a knot is an embedding of a circle in 3-dimensional Euclidean space, R3. Two mathematical knots are equivalent if one can be transformed into the other via a deformation of R3 upon itself (known as an ambient isotopy); these transformations correspond to manipulations of a knotted string that do not involve cutting the string or passing the string through itself.
History
Knots, links, braids
Knot (mathematics) gives a general introduction to the concept of a knot.
Two classes of knots: torus knots and pretzel knots
Cinquefoil knot also known as a (5, 2) torus knot.
Figure-eight knot (mathematics) the only 4-crossing knot
Granny knot (mathematics) and Square knot (mathematics) are a connected sum of two Trefoil knots
Perko pair, two entries in a knot table that were later shown to be identical.
Stevedore knot (mathematics), a prime knot with crossing number 6
Three-twist knot is the twist knot with three-half twists, also known as the 52 knot.
Trefoil knot A knot with crossing number 3
Unknot
Knot complement, a compact 3 manifold obtained by removing an open neighborhood of a proper embedding of a tame knot from the 3-sphere.
Knots and graphs general introduction to knots with mention of Reidemeister moves
Notation used in knot theory:
Conway notation
Dowker–Thistlethwaite notation (DT notation)
Gauss code (see also Gauss diagrams)
continued fraction regular form
General knot types
2-bridge knot
Alternating knot; a knot that can be represented by an alternating diagram (i.e. the crossing alternate over and under as one traverses the knot).
Berge knot a class of knots related to Lens space surgeries and defined in terms of their properties with respect to a genus 2 Heegaard surface.
Cable knot, see Sate |
https://en.wikipedia.org/wiki/Autoantibody | An autoantibody is an antibody (a type of protein) produced by the immune system that is directed against one or more of the individual's own proteins. Many autoimmune diseases (notably lupus erythematosus) are associated with such antibodies.
Production
Antibodies are produced by B cells in two ways: (i) randomly, and (ii) in response to a foreign protein or substance within the body. Initially, one B cell produces one specific kind of antibody. In either case, the B cell is allowed to proliferate or is killed off through a process called clonal deletion. Normally, the immune system is able to recognize and ignore the body's own healthy proteins, cells, and tissues, and to not overreact to non-threatening substances in the environment, such as foods. Sometimes, the immune system ceases to recognize one or more of the body's normal constituents as "self", leading to production of pathological autoantibodies. Autoantibodies may also play a nonpathological role; for instance they may help the body to destroy cancers and to eliminate waste products. The role of autoantibodies in normal immune function is also a subject of scientific research.
Cause
The causes of autoantibody production are varied and not well understood. It is thought that some autoantibody production is due to a genetic predisposition combined with an environmental trigger, such as a viral illness or a prolonged exposure to certain toxic chemicals. There is generally not a direct genetic link however.
While families may be susceptible to autoimmune conditions, individual family members may have different autoimmune disorders, or may never develop an autoimmune condition. Researchers believe that there may also be a hormonal component as many of the autoimmune conditions are much more prevalent in women of childbearing age. While the initial event that leads to the production of autoantibodies is still unknown, there is a body of evidence that autoantibodies may have the capacity to maintain thei |
https://en.wikipedia.org/wiki/Chemoprophylaxis | Chemoprevention or chemoprophylaxis refers to the administration of a medication for the purpose of preventing disease or infection. Antibiotics, for example, may be administered to patients with disorders of immune system function to prevent bacterial infections (particularly opportunistic infection). Antibiotics may also be administered to healthy individuals to limit the spread of an epidemic, or to patients who have repeated infections (such as urinary tract infections) to prevent recurrence. It may also refer to the administration of heparin to prevent deep venous thrombosis in hospitalized patients.
In some cases, chemoprophylaxis is initiated to prevent the spread of an existing infection in an individual to a new organ system, as when intrathecal chemotherapy is administered in patients with malignancy to prevent further infection.
The use of chemoprophylaxis is limited primarily by two factors: risk and financial costs.
All medications have the potential to cause side effects. In general, chemoprophylaxis should be initiated only when the benefits of treatment outweigh the risks.
The cost associated with chemoprophylaxis may be prohibitive, particularly when the cost of treatment is high or the incidence of the target disease is low. Many forms of chemoprophylaxis are therefore not cost-effective.
Specific diseases
Using chemoprophylaxis as a treatment against early signs of tuberculosis has proven to be effective. In familial adenomatous polyposis physicians observed polyps regression with NSAIDs for anti-inflammatory therapy. Chemoprophylaxis is also used to treat several different varieties of meningococcal infections for close contact exposure to Neisseria meningitidis.
The World Health Organization recommends chemoprevention to prevent Malaria in the Sahel region of Sub-Saharan Africa through the use of the drugs sulfadoxine/pyrimethamine and amodiaquine. This technique is called Seasonal Malaria Chemoprevention (SMC). The charity evaluator Give |
https://en.wikipedia.org/wiki/Rieske%20protein | Rieske proteins are iron–sulfur protein (ISP) components of cytochrome bc1 complexes and cytochrome b6f complexes and are responsible for electron transfer in some biological systems. John S. Rieske and co-workers first discovered the protein and in 1964 isolated an acetylated form of the bovine mitochondrial protein. In 1979 Trumpower's lab isolated the "oxidation factor" from bovine mitochondria and showed it was a reconstitutively-active form of the Rieske iron-sulfur protein
It is a unique [2Fe-2S] cluster in that one of the two Fe atoms is coordinated by two histidine residues rather than two cysteine residues. They have since been found in plants, animals, and bacteria with widely ranging electron reduction potentials from -150 to +400 mV.
Biological function
Ubiquinol-cytochrome-c reductase (also known as bc1 complex or complex III) is an enzyme complex of bacterial and mitochondrial oxidative phosphorylation systems. It catalyses the oxidation-reduction reaction of the mobile components ubiquinol and cytochrome c, contributing to an electrochemical potential difference across the mitochondrial inner or bacterial membrane, which is linked to ATP synthesis.
The complex consists of three subunits in most bacteria, and nine in mitochondria: both bacterial and mitochondrial complexes contain cytochrome b and cytochrome c1 subunits, and an iron–sulfur 'Rieske' subunit, which contains a high potential 2Fe-2S cluster. The mitochondrial form also includes six other subunits that do not possess redox centres. Plastoquinone-plastocyanin reductase (b6f complex), present in cyanobacteria and the chloroplasts of plants, catalyses the oxidoreduction of plastoquinol and cytochrome f. This complex, which is functionally similar to ubiquinol-cytochrome c reductase, comprises cytochrome b6, cytochrome f and Rieske subunits.
The Rieske subunit acts by binding either a ubiquinol or plastoquinol anion, transferring an electron to the 2Fe-2S cluster, then releasing the elect |
https://en.wikipedia.org/wiki/National%20CAD%20Standard | The National CAD Standard (NCS) is a collaborative effort in the United States among computer-aided design (CAD) and building information modeling (BIM) users. Its goal is to create a unified approach to the creation of building design data. Development of the NCS is open to all building professionals in a collaborative process led by the buildingSMART Alliance.
The NCS is composed of CAD layer guidelines from the American Institute of Architects, uniform drawing system modules from the Construction Specifications Institute, and BIM implementation and plotting guidelines from the National Institute of Building Sciences. Adoption of the NCS is voluntary, however adopting companies and agencies can require its use by their associates. |
https://en.wikipedia.org/wiki/Grip%20strength | Grip strength is the force applied by the hand to pull on or suspend from objects and is a specific part of hand strength. Optimum-sized objects permit the hand to wrap around a cylindrical shape with a diameter from one to three inches. Stair rails are an example of where shape and diameter are critical for proper grip in case of a fall. Other grip strengths that have been studied are the hammer and other hand tools. In applications of grip strength, the wrist must be in a neutral position to avoid developing cumulative trauma disorders (CTDs).
Grip strength is a general term also used to refer to the physical strength of an animal and, for athletes, to the muscular power and force that can be generated with the hands. In athletics, grip strength is critical for rock climbers and is an important factor in strongman competitions and weight lifting. Grip strength training is also a major feature in martial arts and can be useful in various professions where people must work with their hands.
Types of grip
The human hand can be used to grip objects in several different positions. These different positions require different types of grip strength which are typically quantified based on the way the hand is being used.
The crush grip is what is most commonly thought of as "grip". It involves a handshake-type grip, where the object being gripped rests firmly against the palm and all fingers. A strong crush grip is useful in bone-crushing handshakes, or for breaking objects with pressure.
In a pinch grip, the fingers are on one side of an object, and the thumb is on the other. Typically, an object lifted in a pinch grip does not touch the palm. This is generally considered a weaker grip position. The pinch grip is used when grabbing something like a weight plate or lifting a sheet of plywood by the top edge.
A support grip typically involves holding something, such as the handle of a bucket, for a long time. This type of strength is epitomized by the Farmer's |
https://en.wikipedia.org/wiki/Extended%20System%20Configuration%20Data | The Extended System Configuration Data (ESCD) is a specification for configuring x86 computers of the ISA PNP era. The specification was developed by Compaq, Intel and Phoenix Technologies. It consists of a method for storing configuration information in nonvolatile BIOS memory and three BIOS functions for working with that data.
The ESCD data may at one time have been stored in the latter portion of the 128 byte extended bank of battery-backed CMOS RAM but eventually it became too large and so was moved to BIOS flash.
It contains information about ISA PnP devices is stored. It is used by the BIOS to allocate resources for devices like expansion cards. The ESCD data is stored using the data serialization format used for EISA. Its data starts with the "ACFG" signature in ASCII. PCI configuration can also be stored in ESCD, using virtual slots. Typical storage usage for ESCD data is 2–4 KB
The BIOS also updates the ESCD each time the hardware configuration changes, after deciding how to re-allocate resources like IRQ and memory mapping ranges. After the ESCD has been updated, the decision need not be made again, which thereafter results in faster startup without conflicts until the next hardware configuration change. |
https://en.wikipedia.org/wiki/Code%20Access%20Security | Code Access Security (CAS), in the Microsoft .NET framework, is Microsoft's solution to prevent untrusted code from performing privileged actions. When the CLR loads an assembly it will obtain evidence for the assembly and use this to identify the code group that the assembly belongs to. A code group contains a permission set (one or more permissions). Code that performs a privileged action will perform a code access demand which will cause the CLR to walk up the call stack and examine the permission set granted to the assembly of each method in the call stack.
The code groups and permission sets are determined by the administrator of the machine who defines the security policy.
Microsoft considers CAS as obsolete and discourages its use. It is also not available in .NET Core and .NET.
Evidence
Evidence can be any information associated with an assembly. The default evidences that are used by .NET code access security are:
Application directory: the directory in which an assembly resides.
Publisher: the assembly's publisher's digital signature (requires the assembly to be signed via Authenticode).
URL: the complete URL where the assembly was launched from
Site: the hostname of the URL/Remote Domain/VPN.
Zone: the security zone where the assembly resides
Hash: a cryptographic hash of the assembly, which identifies a specific version.
Strong Name: a combination of the assembly name, version and public key of the signing key used to sign the assembly. The signing key is not an X.509 certificate, but a custom key pair generated by the strong naming tool, SN.EXE or by Visual Studio.
A developer can use custom evidence (so-called assembly evidence) but this requires writing a security assembly and in version 1.1 of .NET this facility does not work.
Evidence based on a hash of the assembly is easily obtained in code. For example, in C#, evidence may be obtained by the following code clause:
this.GetType().Assembly.Evidence
Policy
A policy is a set of expressions t |
https://en.wikipedia.org/wiki/Spidron | This article discusses the geometric figure; for the science-fiction character see Spidron (character).
In geometry, a spidron is a continuous flat geometric figure composed entirely of triangles, where, for every pair of joining triangles, each has a leg of the other as one of its legs, and neither has any point inside the interior of the other. A deformed spidron is a three-dimensional figure sharing the other properties of a specific spidron, as if that spidron were drawn on paper, cut out in a single piece, and folded along a number of legs.
Origin and development
It was first modelled in 1979 by Dániel Erdély, as a homework presented to Ernő Rubik, for Rubik's design class, at the Hungarian University of Arts and Design (now: Moholy-Nagy University of Art and Design). Erdély also gave the name "Spidron" to it, when he discovered it in the early 70s. The name originates from the English names of spider and spiral, because the shape is reminiscent of a spider web. The term ends with the affix "-on" as in polygon.
In his initial work Erdély started with a hexagon. He combined every corner with the after-next one. In his mathematical analysis of spidrons Stefan Stenzhorn demonstrated that it is possible to create a spidron with every regular Polygon greater than four. Furthermore, you can vary the number of points to the next combination. Stenzhorn reasoned that after all the initial hexagon-spidron is just the special case of a general spidron.
In a two-dimensional plane a tessellation with hexagon-spidrons is possible. The form is known from many works by M.C. Escher, who devoted himself to such bodies of high symmetry. Due to their symmetry spidrons are also an interesting object for mathematicians.
The spidrons can appear in a very large number of versions, and the different formations make possible the development of a great variety of plane, spatial and mobile applications. These developments are suitable to perform aesthetic and practical functions th |
https://en.wikipedia.org/wiki/YEPD | YEPD or yeast extract peptone dextrose, also often abbreviated as YPD, is a complete medium for yeast growth. It contains yeast extract, peptone, double-distilled water, and glucose (dextrose). It can be used as solid medium by including agar. The yeast extract will typically contain all the amino acids necessary for growth. By being a complete medium, YEPD cannot be used as a selection medium to test for auxotrophs. Instead, YEPD is used as a growth medium to grow yeast cultures.
YEPD typically contains 1% yeast extract, 2% peptone, and 2% glucose in distilled water. It may be made as a broth, or made into an agar gel by adding 1.5 to 2% agar. |
https://en.wikipedia.org/wiki/Nichols%20plot | The Nichols plot is a plot used in signal processing and control design, named after American engineer Nathaniel B. Nichols.
Use in control design
Given a transfer function,
with the closed-loop transfer function defined as,
the Nichols plots displays versus . Loci of constant and are overlaid to allow the designer to obtain the closed loop transfer function directly from the open loop transfer function. Thus, the frequency is the parameter along the curve. This plot may be compared to the Bode plot in which the two inter-related graphs - versus and versus ) - are plotted.
In feedback control design, the plot is useful for assessing the stability and robustness of a linear system. This application of the Nichols plot is central to the quantitative feedback theory (QFT) of Horowitz and Sidi, which is a well known method for robust control system design.
In most cases, refers to the phase of the system's response. Although similar to a Nyquist plot, a Nichols plot is plotted in a Cartesian coordinate system while a Nyquist plot is plotted in a Polar coordinate system.
See also
Hall circles
Bode plot
Nyquist plot
Transfer function |
https://en.wikipedia.org/wiki/Bitmap%20index | A bitmap index is a special kind of database index that uses bitmaps.
Bitmap indexes have traditionally been considered to work well for low-cardinality columns, which have a modest number of distinct values, either absolutely, or relative to the number of records that contain the data. The extreme case of low cardinality is Boolean data (e.g., does a resident in a city have internet access?), which has two values, True and False. Bitmap indexes use bit arrays (commonly called bitmaps) and answer queries by performing bitwise logical operations on these bitmaps. Bitmap indexes have a significant space and performance advantage over other structures for query of such data. Their drawback is they are less efficient than the traditional B-tree indexes for columns whose data is frequently updated: consequently, they are more often employed in read-only systems that are specialized for fast query - e.g., data warehouses, and generally unsuitable for online transaction processing applications.
Some researchers argue that bitmap indexes are also useful for moderate or even high-cardinality data (e.g., unique-valued data) which is accessed in a read-only manner, and queries access multiple bitmap-indexed columns using the AND, OR or XOR operators extensively.
Bitmap indexes are also useful in data warehousing applications for joining a large fact table to smaller dimension tables such as those arranged in a star schema.
Example
Continuing the internet access example, a bitmap index may be logically viewed as follows:
On the left, Identifier refers to the unique number assigned to each resident, HasInternet is the data to be indexed, the content of the bitmap index is shown as two columns under the heading bitmaps. Each column in the left illustration under the Bitmaps header is a bitmap in the bitmap index. In this case, there are two such bitmaps, one for "has internet" Yes and one for "has internet" No. It is easy to see that each bit in bitmap Y shows whether a part |
https://en.wikipedia.org/wiki/Least%20mean%20squares%20filter | Least mean squares (LMS) algorithms are a class of adaptive filter used to mimic a desired filter by finding the filter coefficients that relate to producing the least mean square of the error signal (difference between the desired and the actual signal). It is a stochastic gradient descent method in that the filter is only adapted based on the error at the current time. It was invented in 1960 by Stanford University professor Bernard Widrow and his first Ph.D. student, Ted Hoff.
Problem formulation
The picture shows the various parts of the filter. is the input signal, which is then transformed by an unknown filter that we wish to match using . The output from the unknown filter is , which is then interfered with a noise signal , producing . Then the error signal is computed, and it is fed back to the adaptive filter, to adjust its parameters in order to minimize the mean square of the error signal .
Relationship to the Wiener filter
The realization of the causal Wiener filter looks a lot like the solution to the least squares estimate, except in the signal processing domain. The least squares solution for input matrix and output vector
is
The FIR least mean squares filter is related to the Wiener filter, but minimizing the error criterion of the former does not rely on cross-correlations or auto-correlations. Its solution converges to the Wiener filter solution.
Most linear adaptive filtering problems can be formulated using the block diagram above. That is, an unknown system is to be identified and the adaptive filter attempts to adapt the filter to make it as close as possible to , while using only observable signals , and ; but , and are not directly observable. Its solution is closely related to the Wiener filter.
Definition of symbols
is the number of the current input sample
is the number of filter taps
(Hermitian transpose or conjugate transpose)
estimated filter; interpret as the estimation of the filter coefficients after s |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.