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Most bees are polylectic (generalist) meaning they collect pollen from a range of flowering plants, but some are oligoleges (specialists), in that they only gather pollen from one or a few species or genera of closely related plants. In Melittidae and Apidae we also find a few genera that are highly specialized for col... | Bee | Wikipedia | 480 | 4654 | https://en.wikipedia.org/wiki/Bee | Biology and health sciences | Hymenoptera | null |
Brood parasites occur in several bee families including the apid subfamily Nomadinae. Females of these species lack pollen collecting structures (the scopa) and do not construct their own nests. They typically enter the nests of pollen collecting species, and lay their eggs in cells provisioned by the host bee. When th... | Bee | Wikipedia | 456 | 4654 | https://en.wikipedia.org/wiki/Bee | Biology and health sciences | Hymenoptera | null |
Vertebrate predators of bees include bee-eaters, shrikes and flycatchers, which make short sallies to catch insects in flight. Swifts and swallows fly almost continually, catching insects as they go. The honey buzzard attacks bees' nests and eats the larvae. The greater honeyguide interacts with humans by guiding them ... | Bee | Wikipedia | 464 | 4654 | https://en.wikipedia.org/wiki/Bee | Biology and health sciences | Hymenoptera | null |
The image of a community of honey bees has been used from ancient to modern times, in Aristotle and Plato; in Virgil and Seneca; in Erasmus and Shakespeare; Tolstoy, and by political and social theorists such as Bernard Mandeville and Karl Marx as a model for human society. In English folklore, bees would be told of im... | Bee | Wikipedia | 410 | 4654 | https://en.wikipedia.org/wiki/Bee | Biology and health sciences | Hymenoptera | null |
Among Classical Era authors, beekeeping with the use of smoke is described in Aristotle's History of Animals Book 9. The account mentions that bees die after stinging; that workers remove corpses from the hive, and guard it; castes including workers and non-working drones, but "kings" rather than queens; predators incl... | Bee | Wikipedia | 481 | 4654 | https://en.wikipedia.org/wiki/Bee | Biology and health sciences | Hymenoptera | null |
Apart from colony collapse disorder, losses outside the US have been attributed to causes including pesticide seed dressings, using neonicotinoids such as clothianidin, imidacloprid and thiamethoxam. From 2013 the European Union restricted some pesticides to stop bee populations from declining further. In 2014 the Inte... | Bee | Wikipedia | 477 | 4654 | https://en.wikipedia.org/wiki/Bee | Biology and health sciences | Hymenoptera | null |
Apitherapy is a branch of alternative medicine that uses honey bee products, including raw honey, royal jelly, pollen, propolis, beeswax and apitoxin (Bee venom). The claim that apitherapy treats cancer, which some proponents of apitherapy make, remains unsupported by evidence-based medicine.
Stings
The painful stin... | Bee | Wikipedia | 161 | 4654 | https://en.wikipedia.org/wiki/Bee | Biology and health sciences | Hymenoptera | null |
Hawaiian honeycreepers are a group of small birds endemic to Hawaii. They are members of the finch family Fringillidae, closely related to the rosefinches (Carpodacus), but many species have evolved features unlike those present in any other finch. Their great morphological diversity is the result of adaptive radiation... | Hawaiian honeycreeper | Wikipedia | 496 | 15975113 | https://en.wikipedia.org/wiki/Hawaiian%20honeycreeper | Biology and health sciences | Passerida | Animals |
A phylogenetic tree of the recent Hawaiian honeycreeper lineages is shown here. Genera or clades with question marks (?) are of controversial or uncertain taxonomic placement.
The classification of Paroreomyza and Oreomystis as sister genera and forming the second most basal group is based on genetic and molecular evi... | Hawaiian honeycreeper | Wikipedia | 419 | 15975113 | https://en.wikipedia.org/wiki/Hawaiian%20honeycreeper | Biology and health sciences | Passerida | Animals |
Today, the flowers of the native ōhia (Metrosideros polymorpha) are favored by a number of nectarivorous honeycreepers. The wide range of bill shapes in this group, from thick, finch-like bills to slender, down-curved bills for probing flowers have arisen through adaptive radiation, where an ancestral finch has evolve... | Hawaiian honeycreeper | Wikipedia | 178 | 15975113 | https://en.wikipedia.org/wiki/Hawaiian%20honeycreeper | Biology and health sciences | Passerida | Animals |
Drepanidini
Genus Aidemedia Olson & James, 1991 – straight thin bills, insectivores
Aidemedia chascax Olson & James, 1991 – Oahu icterid-like gaper (prehistoric)
Aidemedia lutetiae Olson & James, 1991 – Maui Nui icterid-like gaper (prehistoric)
Aidemedia zanclops Olson & James, 1991 – sickle-billed gaper (prehistoric)
... | Hawaiian honeycreeper | Wikipedia | 493 | 15975113 | https://en.wikipedia.org/wiki/Hawaiian%20honeycreeper | Biology and health sciences | Passerida | Animals |
Drepanis pacifica Gmelin, 1788 – Hawaiʻi mamo (extinct, 1898)
Drepanis coccinea Forster, 1780 – ʻiʻiwi
Genus Dysmorodrepanis Perkins, 1919 – pincer-like bill, possibly snail specialist
Dysmorodrepanis munroi Perkins, 1919 – Lanaʻi hookbill (extinct, 1918)
Genus Hemignathus Lichtenstein, 1839 – pointed or long and dow... | Hawaiian honeycreeper | Wikipedia | 510 | 15975113 | https://en.wikipedia.org/wiki/Hawaiian%20honeycreeper | Biology and health sciences | Passerida | Animals |
Oreomystis bairdi Stejneger, 1887 – ʻakikiki
Genus Orthiospiza – large weak bill, possibly soft seed or fruit specialist?
Orthiospiza howarthi James & Olson, 1991 - highland finch (prehistoric)
Genus Palmeria Rothschild, 1893 – thin-billed, nectarivorous, favors Metrosideros polymorpha
Palmeria dolei Wilson, 1891 – ʻak... | Hawaiian honeycreeper | Wikipedia | 509 | 15975113 | https://en.wikipedia.org/wiki/Hawaiian%20honeycreeper | Biology and health sciences | Passerida | Animals |
Vangulifer neophasis – thin-billed finch (prehistoric)
Genus Viridonia
Viridonia sagittirostris Rothschild, 1892 – greater ʻamakihi (extinct, 1901)
Genus Xestospiza James & Oslon, 1991 – cone-shaped bills, possibly insectivorous
Xestospiza conica James & Olson, 1991 – cone-billed finch (prehistoric)
Xestospiza fastig... | Hawaiian honeycreeper | Wikipedia | 105 | 15975113 | https://en.wikipedia.org/wiki/Hawaiian%20honeycreeper | Biology and health sciences | Passerida | Animals |
Hawaiian honeycreepers were formerly classified into three tribes – Hemignathini, Psittirostrini, and Drepanidini – but they are not currently classified as such.
Conservation | Hawaiian honeycreeper | Wikipedia | 39 | 15975113 | https://en.wikipedia.org/wiki/Hawaiian%20honeycreeper | Biology and health sciences | Passerida | Animals |
Winchester measure is a set of legal standards of volume instituted in the late 15th century (1495) by King Henry VII of England and in use, with some modifications, until the present day. It consists of the Winchester bushel and its dependent quantities, the peck, (dry) gallon and (dry) quart. They would later become ... | Winchester measure | Wikipedia | 492 | 15982783 | https://en.wikipedia.org/wiki/Winchester%20measure | Physical sciences | Measurement systems | Basics and measurement |
Prior to the Norman Conquest, the following units of capacity measure were used: sester, amber, mitta, coomb, and seam. A statute of 1196 (9 Ric. 1. c. 27) decreed: It is established that all measures of the whole of England be of the same amount, as well of corn as of vegetables and of like things, to wit, one good ho... | Winchester measure | Wikipedia | 392 | 15982783 | https://en.wikipedia.org/wiki/Winchester%20measure | Physical sciences | Measurement systems | Basics and measurement |
In 1496, An Act for Weights and Measures (12 Hen. 7. c. 5) stated That the Measure of a Bushel contain Gallons of Wheat, and that every Gallon contain of Wheat of Troy Weight, and every Pound contain Ounces of Troy Weight, and every Ounce contain Sterlings, and every Sterling be of the Weight of Corns of Wheat th... | Winchester measure | Wikipedia | 459 | 15982783 | https://en.wikipedia.org/wiki/Winchester%20measure | Physical sciences | Measurement systems | Basics and measurement |
In 1824 a new Act was passed in which the gallon was defined as the volume of ten pounds of pure water at with the other units of volume changing accordingly. The "Winchester bushel", which was some 3% smaller than the new bushel (eight new gallons), was retained in the English grain trade until formally abolished in ... | Winchester measure | Wikipedia | 241 | 15982783 | https://en.wikipedia.org/wiki/Winchester%20measure | Physical sciences | Measurement systems | Basics and measurement |
Data sharing is the practice of making data used for scholarly research available to other investigators. Many funding agencies, institutions, and publication venues have policies regarding data sharing because transparency and openness are considered by many to be part of the scientific method.
A number of funding ag... | Data sharing | Wikipedia | 444 | 10806718 | https://en.wikipedia.org/wiki/Data%20sharing | Physical sciences | Science basics | Basics and measurement |
Federal law
On August 9, 2007, President Bush signed the America COMPETES Act (or the "America Creating Opportunities to Meaningfully Promote Excellence in Technology, Education, and Science Act") requiring civilian federal agencies to provide guidelines, policies and procedures, to facilitate and optimize the open exc... | Data sharing | Wikipedia | 428 | 10806718 | https://en.wikipedia.org/wiki/Data%20sharing | Physical sciences | Science basics | Basics and measurement |
The Alliance for Taxpayer Access is a group of organizations that support open access to government sponsored research. The group has expressed a "Statement of Principles" explaining why they believe open access is important. They also list a number of international public access policies. This is no more so than in t... | Data sharing | Wikipedia | 483 | 10806718 | https://en.wikipedia.org/wiki/Data%20sharing | Physical sciences | Science basics | Basics and measurement |
Scientists in training
A study of scientists in training indicated many had already experienced data withholding. This study has given rise to the fear the future generation of scientists will not abide by the established practices.
Differing approaches in different fields
Requirements for data sharing are more common... | Data sharing | Wikipedia | 261 | 10806718 | https://en.wikipedia.org/wiki/Data%20sharing | Physical sciences | Science basics | Basics and measurement |
The Port of Ningbo-Zhoushan is the busiest port in the world in terms of cargo tonnage. It handled 888.96 million tons of cargo in 2015. The port is located in Ningbo and Zhoushan, on the coast of the East China Sea, in Zhejiang province on the southeast end of Hangzhou Bay, across which it faces the municipality of Sh... | Port of Ningbo-Zhoushan | Wikipedia | 464 | 10809525 | https://en.wikipedia.org/wiki/Port%20of%20Ningbo-Zhoushan | Technology | Specific piers and ports | null |
Economic trade
The Port of Ningbo-Zhoushan is involved in economic trade with cargo shipment, raw materials and manufactured goods from as far as North and South America and Oceania. It has economic trade with over 560 ports from more than 90 countries and regions in the world. It is one of a growing number of ports ... | Port of Ningbo-Zhoushan | Wikipedia | 321 | 10809525 | https://en.wikipedia.org/wiki/Port%20of%20Ningbo-Zhoushan | Technology | Specific piers and ports | null |
A drug is any chemical substance other than a nutrient or an essential dietary ingredient, which, when administered to a living organism, produces a biological effect. Consumption of drugs can be via inhalation, injection, smoking, ingestion, absorption via a patch on the skin, suppository, or dissolution under the to... | Drug | Wikipedia | 487 | 9311172 | https://en.wikipedia.org/wiki/Drug | Biology and health sciences | Drugs and medication | null |
Etymology
In English, the noun "drug" is thought to originate from Old French "", possibly deriving from " ()" from Middle Dutch meaning "dry (barrels)", referring to medicinal plants preserved as dry matter in barrels.
In the 1990s however, Spanish lexicographer Federico Corriente Córdoba documented the possible orig... | Drug | Wikipedia | 487 | 9311172 | https://en.wikipedia.org/wiki/Drug | Biology and health sciences | Drugs and medication | null |
In the United Kingdom, behind-the-counter medicines are called pharmacy medicines which can only be sold in registered pharmacies, by or under the supervision of a pharmacist. These medications are designated by the letter P on the label. The range of medicines available without a prescription varies from country to co... | Drug | Wikipedia | 440 | 9311172 | https://en.wikipedia.org/wiki/Drug | Biology and health sciences | Drugs and medication | null |
Silene undulata is regarded by the Xhosa people as a sacred plant and used as an entheogen. Its roots are traditionally used to induce vivid (and according to the Xhosa, prophetic) lucid dreams during the initiation process of shamans, classifying it a naturally occurring oneirogen similar to the more well-known dream ... | Drug | Wikipedia | 394 | 9311172 | https://en.wikipedia.org/wiki/Drug | Biology and health sciences | Drugs and medication | null |
Other drugs known as designer drugs are produced. An early example of what today would be labelled a 'designer drug' was LSD, which was synthesised from ergot. Other examples include analogs of performance-enhancing drugs such as designer steroids taken to improve physical capabilities; these are sometimes used (legall... | Drug | Wikipedia | 498 | 9311172 | https://en.wikipedia.org/wiki/Drug | Biology and health sciences | Drugs and medication | null |
A bolus is the administration of a medication, drug or other compound that is given to raise its concentration in blood rapdily to an effective level, regardless of the route of administration
Control of drugs
Numerous governmental offices in many countries deal with the control and supervision of drug manufacture an... | Drug | Wikipedia | 298 | 9311172 | https://en.wikipedia.org/wiki/Drug | Biology and health sciences | Drugs and medication | null |
Cyclohexane conformations are any of several three-dimensional shapes adopted by cyclohexane. Because many compounds feature structurally similar six-membered rings, the structure and dynamics of cyclohexane are important prototypes of a wide range of compounds.
The internal angles of a regular, flat hexagon are 120°,... | Cyclohexane conformation | Wikipedia | 149 | 1524030 | https://en.wikipedia.org/wiki/Cyclohexane%20conformation | Physical sciences | Stereochemistry | Chemistry |
Consider the carbon atoms numbered from 1 to 6 around the ring. If we hold carbon atoms 1, 2, and 3 stationary, with the correct bond lengths and the tetrahedral angle between the two bonds, and then continue by adding carbon atoms 4, 5, and 6 with the correct bond length and the tetrahedral angle, we can vary the thre... | Cyclohexane conformation | Wikipedia | 506 | 1524030 | https://en.wikipedia.org/wiki/Cyclohexane%20conformation | Physical sciences | Stereochemistry | Chemistry |
The boat and twist-boat conformations, as said, lie along a continuum of zero angle strain. If there are substituents that allow the different carbon atoms to be distinguished, then this continuum is like a circle with six boat conformations and six twist-boat conformations between them, three "right-handed" and three ... | Cyclohexane conformation | Wikipedia | 455 | 1524030 | https://en.wikipedia.org/wiki/Cyclohexane%20conformation | Physical sciences | Stereochemistry | Chemistry |
The C–C ring of the chair conformation has the same shape as the 6-membered rings in the diamond cubic lattice. This can be modeled as follows. Consider a carbon atom to be a point with four half-bonds sticking out towards the vertices of a tetrahedron. Place it on a flat surface with one half-bond pointing straight up... | Cyclohexane conformation | Wikipedia | 412 | 1524030 | https://en.wikipedia.org/wiki/Cyclohexane%20conformation | Physical sciences | Stereochemistry | Chemistry |
The chair conformation cannot be deformed without changing bond angles or lengths. It can be represented as two linked chains, C1–C2–C3–C4 and C1–C6–C5–C4, each mirroring the other, with opposite dihedral angles. The C1–C4 distance depends on the absolute value of this dihedral angle, so in a rigid model, changing one ... | Cyclohexane conformation | Wikipedia | 478 | 1524030 | https://en.wikipedia.org/wiki/Cyclohexane%20conformation | Physical sciences | Stereochemistry | Chemistry |
The interconversion of chair conformers is called ring flipping or chair-flipping. Carbon–hydrogen bonds that are axial in one configuration become equatorial in the other, and vice versa. At room temperature the two chair conformations rapidly equilibrate. The proton NMR spectrum of cyclohexane is a singlet at room te... | Cyclohexane conformation | Wikipedia | 472 | 1524030 | https://en.wikipedia.org/wiki/Cyclohexane%20conformation | Physical sciences | Stereochemistry | Chemistry |
Twist-boat to twist-boat
The boat conformation (C, below) is a transition state, allowing the interconversion between two different twist-boat conformations. While the boat conformation is not necessary for interconversion between the two chair conformations of cyclohexane, it is often included in the reaction coordina... | Cyclohexane conformation | Wikipedia | 470 | 1524030 | https://en.wikipedia.org/wiki/Cyclohexane%20conformation | Physical sciences | Stereochemistry | Chemistry |
Disubstituted cyclohexanes
For 1,2- and 1,4-disubstituted cyclohexanes, a cis configuration leads to one axial and one equatorial group. Such species undergo rapid, degenerate chair flipping. For 1,2- and 1,4-disubstituted cyclohexane, a trans configuration, the diaxial conformation is effectively prevented by its hig... | Cyclohexane conformation | Wikipedia | 483 | 1524030 | https://en.wikipedia.org/wiki/Cyclohexane%20conformation | Physical sciences | Stereochemistry | Chemistry |
Gauche interactions occur when a non-hydrogen substituent on a cyclohexane occupies the equatorial position. The equatorial substituent is in a staggered position with the 2-carbons relative to itself (there will be two such carbons and thus two 1,2 gauche interactions). This creates a dihedral angle of ~60°. This stag... | Cyclohexane conformation | Wikipedia | 403 | 1524030 | https://en.wikipedia.org/wiki/Cyclohexane%20conformation | Physical sciences | Stereochemistry | Chemistry |
Effects on conformational equilibrium
Conformational equilibrium is the tendency to favor the conformation where cyclohexane is the most stable. This equilibrium depends on the interactions between the molecules in the compound and the solvent. Polarity and nonpolarity are the main factors in determining how well a so... | Cyclohexane conformation | Wikipedia | 388 | 1524030 | https://en.wikipedia.org/wiki/Cyclohexane%20conformation | Physical sciences | Stereochemistry | Chemistry |
Historical background
In 1890, , a 28-year-old assistant in Berlin, published instructions for folding a piece of paper to represent two forms of cyclohexane he called symmetrical and asymmetrical (what we would now call chair and boat). He clearly understood that these forms had two positions for the hydrogen atoms (... | Cyclohexane conformation | Wikipedia | 402 | 1524030 | https://en.wikipedia.org/wiki/Cyclohexane%20conformation | Physical sciences | Stereochemistry | Chemistry |
The blue spruce (Picea pungens), also commonly known as Colorado spruce or Colorado blue spruce, is a species of spruce tree native to North America in Arizona, Colorado, Idaho, New Mexico, Utah and Wyoming. It is noted for its blue-green colored needles, and has therefore been used as an ornamental tree in many places... | Blue spruce | Wikipedia | 487 | 1526695 | https://en.wikipedia.org/wiki/Blue%20spruce | Biology and health sciences | Pinaceae | Plants |
Chemistry
The phytochemistry of the blue spruce is relatively little studied. The ripe seeds have a 1.17% yield of essential oils while the cones produce only 0.38% when steam distilled for four hours. The main component, over 40%, of the essential oils is limonene with β-Pinene and α-Pinene the next most significant.
... | Blue spruce | Wikipedia | 420 | 1526695 | https://en.wikipedia.org/wiki/Blue%20spruce | Biology and health sciences | Pinaceae | Plants |
Ecology
Blue Spruce occurs at high elevations, in the forests of the South Central Rockies and in the Southern Rocky Mountains. It grows in mesic montane conifer forests, often associating with Douglas-fir, ponderosa pine, or white fir. It has a riparian affinity, preferring moist soils such as those along streams o... | Blue spruce | Wikipedia | 512 | 1526695 | https://en.wikipedia.org/wiki/Blue%20spruce | Biology and health sciences | Pinaceae | Plants |
Rooting habits
Blue spruce seedlings have shallow roots that penetrate approximately into the soil during the first year of growth. Although freezing can't damage much in blue spruce, frost heaving will cause seedling loss. Shadows in late spring and early autumn minimize this frost heaving loss. Despite the shallow ... | Blue spruce | Wikipedia | 508 | 1526695 | https://en.wikipedia.org/wiki/Blue%20spruce | Biology and health sciences | Pinaceae | Plants |
Range
The native range of the blue spruce is largely in the Central and Southern Rocky Mountains and moist mountain valleys and canyons to the west. In New Mexico it only grows naturally in the higher mountain ranges of the state such as the Sandia–Manzano Mountains, Sangre de Cristo Mountains, and San Juan Mountains, ... | Blue spruce | Wikipedia | 454 | 1526695 | https://en.wikipedia.org/wiki/Blue%20spruce | Biology and health sciences | Pinaceae | Plants |
Common cultivars (those marked have gained the Royal Horticultural Society's Award of Garden Merit):
'Baby Blue Eyes', 'Baby Blueeyes', or 'Baby Blue' – This is a semi-dwarf cultivar that grows slowly, but may eventually reach in height. It has a pyramidal shape and holds its color well.
'Fat Albert' – compact perfec... | Blue spruce | Wikipedia | 389 | 1526695 | https://en.wikipedia.org/wiki/Blue%20spruce | Biology and health sciences | Pinaceae | Plants |
Percussion is a technique of clinical examination.
Overview
Percussion is a method of tapping on a surface to determine the underlying structures, and is used in clinical examinations to assess the condition of the thorax or abdomen. It is one of the four methods of clinical examination, together with inspection, pal... | Percussion (medicine) | Wikipedia | 446 | 1527059 | https://en.wikipedia.org/wiki/Percussion%20%28medicine%29 | Biology and health sciences | Diagnostics | Health |
In programming and software design, a binding is an application programming interface (API) that provides glue code specifically made to allow a programming language to use a foreign library or operating system service (one that is not native to that language).
Characteristics
Binding generally refers to a mapping of ... | Language binding | Wikipedia | 478 | 3002110 | https://en.wikipedia.org/wiki/Language%20binding | Technology | Programming languages | null |
Mesosaurus (meaning "middle lizard") is an extinct genus of reptile from the Early Permian of southern Africa and South America. Along with it, the genera Brazilosaurus and Stereosternum, it is a member of the family Mesosauridae and the order Mesosauria. Mesosaurus was long thought to have been one of the first marine... | Mesosaurus | Wikipedia | 468 | 5492915 | https://en.wikipedia.org/wiki/Mesosaurus | Biology and health sciences | Prehistoric marine reptiles | Animals |
Description
Mesosaurus had a long skull that was larger than that of Stereosternum and had longer teeth. The teeth are angled outwards, especially those at the tips of the jaws.The bones of the postcranial skeleton are thick, having undergone pachyostosis. Mesosaurus is unusual among reptiles in that it possesses a cl... | Mesosaurus | Wikipedia | 414 | 5492915 | https://en.wikipedia.org/wiki/Mesosaurus | Biology and health sciences | Prehistoric marine reptiles | Animals |
While many features suggest a wholly aquatic lifestyle, Mesosaurus may have been able to move onto land for short periods of time. Its elbows and ankles were restricted in their movement, making walking appear impossible. It is more likely that if Mesosaurus moved onto land, it would push itself forward in a similar wa... | Mesosaurus | Wikipedia | 453 | 5492915 | https://en.wikipedia.org/wiki/Mesosaurus | Biology and health sciences | Prehistoric marine reptiles | Animals |
Distribution
Mesosaurus was significant in providing evidence for the theory of continental drift, because its remains were found in southern Africa, Whitehill Formation, and eastern South America (Melo Formation, Uruguay and Irati Formation, Brazil), two widely separated regions. As Mesosaurus was a coastal animal, a... | Mesosaurus | Wikipedia | 86 | 5492915 | https://en.wikipedia.org/wiki/Mesosaurus | Biology and health sciences | Prehistoric marine reptiles | Animals |
In mathematics, stability theory addresses the stability of solutions of differential equations and of trajectories of dynamical systems under small perturbations of initial conditions. The heat equation, for example, is a stable partial differential equation because small perturbations of initial data lead to small v... | Stability theory | Wikipedia | 453 | 5493795 | https://en.wikipedia.org/wiki/Stability%20theory | Mathematics | Dynamical systems | null |
Stability means that the trajectories do not change too much under small perturbations. The opposite situation, where a nearby orbit is getting repelled from the given orbit, is also of interest. In general, perturbing the initial state in some directions results in the trajectory asymptotically approaching the given o... | Stability theory | Wikipedia | 424 | 5493795 | https://en.wikipedia.org/wiki/Stability%20theory | Mathematics | Dynamical systems | null |
If the rank is zero, then , and there is no flow.
If the rank is one, then and are both one-dimensional.
If , then let span , and let be a preimage of , then in basis, , and so the flow is a shearing along the direction. In this case, .
If , then let span and let span , then in basis, for some nonzero re... | Stability theory | Wikipedia | 442 | 5493795 | https://en.wikipedia.org/wiki/Stability%20theory | Mathematics | Dynamical systems | null |
If the eigenvalue has a two-dimensional eigenspace (geometric multiplicity 2), then the system is a central node (sometimes called a "star", or "dicritical node") which is either a source (when ) or a sink (when ).
If it has a one-dimensional eigenspace (geometric multiplicity 1), then the system is a degenerate node ... | Stability theory | Wikipedia | 438 | 5493795 | https://en.wikipedia.org/wiki/Stability%20theory | Mathematics | Dynamical systems | null |
There is an analogous criterion for a continuously differentiable map with a fixed point , expressed in terms of its Jacobian matrix at , . If all eigenvalues of are real or complex numbers with absolute value strictly less than 1 then is a stable fixed point; if at least one of them has absolute value strictly grea... | Stability theory | Wikipedia | 489 | 5493795 | https://en.wikipedia.org/wiki/Stability%20theory | Mathematics | Dynamical systems | null |
A general way to establish Lyapunov stability or asymptotic stability of a dynamical system is by means of Lyapunov functions. | Stability theory | Wikipedia | 31 | 5493795 | https://en.wikipedia.org/wiki/Stability%20theory | Mathematics | Dynamical systems | null |
In electromagnetism, current density is the amount of charge per unit time that flows through a unit area of a chosen cross section. The current density vector is defined as a vector whose magnitude is the electric current per cross-sectional area at a given point in space, its direction being that of the motion of the... | Current density | Wikipedia | 442 | 5498706 | https://en.wikipedia.org/wiki/Current%20density | Physical sciences | Electrodynamics | Physics |
where is the dot product of the unit vectors. That is, the component of current density passing through the surface (i.e. normal to it) is , while the component of current density passing tangential to the area is , but there is no current density actually passing through the area in the tangential direction. The only... | Current density | Wikipedia | 476 | 5498706 | https://en.wikipedia.org/wiki/Current%20density | Physical sciences | Electrodynamics | Physics |
where
is the current density vector;
is the particles' average drift velocity (SI unit: m∙s−1);
is the charge density (SI unit: coulombs per cubic metre), in which
is the number of particles per unit volume ("number density") (SI unit: m−3);
is the charge of the individual particles with density (SI unit: coulo... | Current density | Wikipedia | 506 | 5498706 | https://en.wikipedia.org/wiki/Current%20density | Physical sciences | Electrodynamics | Physics |
The total current is simply the sum of the free and bound currents:
Displacement current
There is also a displacement current corresponding to the time-varying electric displacement field :
which is an important term in Ampere's circuital law, one of Maxwell's equations, since absence of this term would not predict e... | Current density | Wikipedia | 476 | 5498706 | https://en.wikipedia.org/wiki/Current%20density | Physical sciences | Electrodynamics | Physics |
In the semiconductors field, the maximum current densities for different elements are given by the manufacturer. Exceeding those limits raises the following problems:
The Joule effect which increases the temperature of the component.
The electromigration effect which will erode the interconnection and eventually caus... | Current density | Wikipedia | 373 | 5498706 | https://en.wikipedia.org/wiki/Current%20density | Physical sciences | Electrodynamics | Physics |
Carya laciniosa, the shellbark hickory, in the Juglandaceae or walnut family is also called kingnut, big, bottom, thick, or western shellbark, attesting to some of its characteristics. It is a slow-growing, long-lived tree, hard to transplant because of its long taproot, and subject to insect damage. The nuts, largest ... | Carya laciniosa | Wikipedia | 488 | 11794177 | https://en.wikipedia.org/wiki/Carya%20laciniosa | Biology and health sciences | Fagales | Plants |
On mature trees, the bark peels away from the trunk in long, sometimes broad, strips. This gives the trees a “shaggy” appearance that is easily confused with that of the Shagbark hickory (Carya ovata). That close similarity is the reason Shellbark hickories are frequently misidentified. A closer examination of other... | Carya laciniosa | Wikipedia | 492 | 11794177 | https://en.wikipedia.org/wiki/Carya%20laciniosa | Biology and health sciences | Fagales | Plants |
Distribution and habitat
Shellbark hickory is widely distributed, but is common nowhere. The range extends from western New York through southern Michigan to southeast Iowa, south through eastern Kansas into northern Oklahoma, and eastward through Tennessee into Pennsylvania. This species is most prominent in the lowe... | Carya laciniosa | Wikipedia | 432 | 11794177 | https://en.wikipedia.org/wiki/Carya%20laciniosa | Biology and health sciences | Fagales | Plants |
Associated forest cover
Shellbark hickory may be found in pure groups of several trees but is more frequent singly in association with other hardwoods. The species is a minor component of the forest cover types bur oak (Society of American Foresters type 42), pin oak–sweetgum (type 65), and swamp chestnut oak–cherryba... | Carya laciniosa | Wikipedia | 459 | 11794177 | https://en.wikipedia.org/wiki/Carya%20laciniosa | Biology and health sciences | Fagales | Plants |
Uses
The seeds within shellbark hickory nuts are edible and consumed by ducks, quail, wild turkeys, squirrels, chipmunks, deer, foxes, raccoons, and white-footed mice. A few plantations of shellbark hickory have been established for nut production, but the nuts are difficult to crack, though the kernel is sweet. The w... | Carya laciniosa | Wikipedia | 205 | 11794177 | https://en.wikipedia.org/wiki/Carya%20laciniosa | Biology and health sciences | Fagales | Plants |
Carya tomentosa, commonly known as mockernut hickory, mockernut, white hickory, whiteheart hickory, hognut, bullnut, is a species of tree in the walnut family Juglandaceae. The most abundant of the hickories, and common in the eastern half of the United States, it is long lived, sometimes reaching the age of 500 years.... | Carya tomentosa | Wikipedia | 469 | 11794330 | https://en.wikipedia.org/wiki/Carya%20tomentosa | Biology and health sciences | Fagales | Plants |
Mockernut hickory produces one of the heaviest seeds of the hickory species; cleaned seeds range from 70 to 250 seeds/kg (32 to 113/lb). Seed is disseminated mainly by gravity and wildlife, particularly squirrels. Birds also help disperse seed. Wildlife such as squirrels and chipmunks often bury the seed at some distan... | Carya tomentosa | Wikipedia | 437 | 11794330 | https://en.wikipedia.org/wiki/Carya%20tomentosa | Biology and health sciences | Fagales | Plants |
The current annual growth of mockernut hickory on dry sites is estimated at 1.0 m3/ha (15 ft3/acre). In fully stocked stands on moderately fertile soil2.1 m3 /ha (30 ft3 /acre) is estimated, though annual growth rates of 3.1 m3/ha (44 ft3/acre) were reported in Ohio (26). Greenwood and bark weights for commercial-size ... | Carya tomentosa | Wikipedia | 490 | 11794330 | https://en.wikipedia.org/wiki/Carya%20tomentosa | Biology and health sciences | Fagales | Plants |
The species' name comes from the Latin word tomentum, meaning "stuffing", referring to the underside of the leaves, which are covered with dense, short hairs, which help identify the species. Also called the white hickory due to the light color of the wood, the common name mockernut likely refers to the would-be nut ea... | Carya tomentosa | Wikipedia | 454 | 11794330 | https://en.wikipedia.org/wiki/Carya%20tomentosa | Biology and health sciences | Fagales | Plants |
Mockernut hickory grows primarily on ultisols occurring on an estimated 65% of its range, including much of the southern to northeastern United States. These soils are low in nutrients and usually moist, but during the warm season, they are dry part of the time. Along the mid-Atlantic and in the southern and western ra... | Carya tomentosa | Wikipedia | 463 | 11794330 | https://en.wikipedia.org/wiki/Carya%20tomentosa | Biology and health sciences | Fagales | Plants |
Mockernut hickory nuts are consumed by many species of birds and other animals, including wood duck, red-bellied woodpecker, red fox, squirrels, beaver, eastern cottontail, eastern chipmunk, turkey, white-tailed deer, white-footed mice, and others. Many insect pests eat hickory leaves and bark. Mockernut hickories also... | Carya tomentosa | Wikipedia | 445 | 11794330 | https://en.wikipedia.org/wiki/Carya%20tomentosa | Biology and health sciences | Fagales | Plants |
Damaging agents
Mockernut hickory is extremely sensitive to fire because of the low insulating capacity of the hard, flinty bark. It is not subject to severe loss from disease. The main fungus of hickory is Poria spiculosa, a trunk rot. This fungus kills the bark, which produces a canker, causes heart rot and decay, an... | Carya tomentosa | Wikipedia | 444 | 11794330 | https://en.wikipedia.org/wiki/Carya%20tomentosa | Biology and health sciences | Fagales | Plants |
Two casebearers (Acrobasis caryivorella and A. juglandis) feed on buds and leaves; later, they bore into succulent hickory shoots. Larvae of A. caryivorella may destroy entire nut sets. The living-hickory borer (Goes pulcher) feeds on hickory boles and branches throughout the East. Borers commonly found on dying or dea... | Carya tomentosa | Wikipedia | 465 | 11794330 | https://en.wikipedia.org/wiki/Carya%20tomentosa | Biology and health sciences | Fagales | Plants |
pignut hickory (Carya glabra)
shagbark hickory (C. ovata)
bitternut hickory (C. cordiformis)
black oak (Quercus velutina)
scarlet oak (Q. coccinea)
post oak (Q. stellata)
bur oak (Q. macrocarpa)
blackgum (Nyssa sylvatica)
yellow-poplar (Liriodendron tulipifera)
maples (Acer spp.)
white ash (Fraxinus americana... | Carya tomentosa | Wikipedia | 491 | 11794330 | https://en.wikipedia.org/wiki/Carya%20tomentosa | Biology and health sciences | Fagales | Plants |
In the loblolly pine-hardwood type in the southern forest, mockernut commonly grows in the upland and drier sites with:
white oak (Quercus alba)
post oak
northern red oak (Q. rubra)
southern red oak (Q. falcata)
scarlet oak
shagbark and pignut hickories
blackgum
flowering dogwood
hawthorn
sourwood
greenbrie... | Carya tomentosa | Wikipedia | 456 | 11794330 | https://en.wikipedia.org/wiki/Carya%20tomentosa | Biology and health sciences | Fagales | Plants |
Genetics
Mockernut is a 64-chromosome species, so rarely crosses with 32-chromosome species such as pecan or shellbark hickory. No published information exists concerning population or other genetic studies of this species. Efforts are currently underway to map the genome of pecan in a collaborative effort. The genome ... | Carya tomentosa | Wikipedia | 193 | 11794330 | https://en.wikipedia.org/wiki/Carya%20tomentosa | Biology and health sciences | Fagales | Plants |
Caninae (whose members are known as canines () is the only living subfamily within Canidae, alongside the extinct Borophaginae and Hesperocyoninae. They first appeared in North America, during the Oligocene around 35 million years ago, subsequently spreading to Asia and elsewhere in the Old World at the end of the Mioc... | Caninae | Wikipedia | 428 | 11795855 | https://en.wikipedia.org/wiki/Caninae | Biology and health sciences | Canines | Animals |
DNA analysis shows that the first three form monophyletic clades. The wolf-like canines and the South American canines together form the tribe Canini. Molecular data imply a North American origin of living Canidae some 10 Mya and an African origin of wolf-like canines (Canis, Cuon, and Lycaon), with the jackals being t... | Caninae | Wikipedia | 193 | 11795855 | https://en.wikipedia.org/wiki/Caninae | Biology and health sciences | Canines | Animals |
NGC 6302 (also known as the Bug Nebula, Butterfly Nebula, or Caldwell 69) is a bipolar planetary nebula in the constellation Scorpius. The structure in the nebula is among the most complex ever seen in planetary nebulae. The spectrum of Butterfly Nebula shows that its central star is one of the hottest stars known, wit... | NGC 6302 | Wikipedia | 472 | 4117384 | https://en.wikipedia.org/wiki/NGC%206302 | Physical sciences | Notable nebulae | Astronomy |
Central star
The central star, among the hottest stars known, had escaped detection because of a combination of its high temperature (meaning that it radiates mainly in the ultraviolet), the dusty torus (which absorbs a large fraction of the light from the central regions, especially in the ultraviolet) and the bright ... | NGC 6302 | Wikipedia | 375 | 4117384 | https://en.wikipedia.org/wiki/NGC%206302 | Physical sciences | Notable nebulae | Astronomy |
A computer network is a set of computers sharing resources located on or provided by network nodes. Computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are made up of telecommunication network technologies based on physically wired, optical, ... | Computer network | Wikipedia | 281 | 4122592 | https://en.wikipedia.org/wiki/Computer%20network | Technology | Networks | null |
In the late 1950s, a network of computers was built for the U.S. military Semi-Automatic Ground Environment (SAGE) radar system using the Bell 101 modem. It was the first commercial modem for computers, released by AT&T Corporation in 1958. The modem allowed digital data to be transmitted over regular unconditioned tel... | Computer network | Wikipedia | 506 | 4122592 | https://en.wikipedia.org/wiki/Computer%20network | Technology | Networks | null |
In 1969, the first four nodes of the ARPANET were connected using circuits between the University of California at Los Angeles, the Stanford Research Institute, the University of California at Santa Barbara, and the University of Utah. Designed principally by Bob Kahn, the network's routing, flow control, software des... | Computer network | Wikipedia | 493 | 4122592 | https://en.wikipedia.org/wiki/Computer%20network | Technology | Networks | null |
In 1977, the first long-distance fiber network was deployed by GTE in Long Beach, California.
In 1979, Robert Metcalfe pursued making Ethernet an open standard.
In 1980, Ethernet was upgraded from the original protocol to the 10 Mbit/s protocol, which was developed by Ron Crane, Bob Garner, Roy Ogus, and Yogen Dalal... | Computer network | Wikipedia | 142 | 4122592 | https://en.wikipedia.org/wiki/Computer%20network | Technology | Networks | null |
Use
Computer networks enhance how users communicate with each other by using various electronic methods like email, instant messaging, online chat, voice and video calls, and video conferencing. Networks also enable the sharing of computing resources. For example, a user can print a document on a shared printer or use ... | Computer network | Wikipedia | 467 | 4122592 | https://en.wikipedia.org/wiki/Computer%20network | Technology | Networks | null |
Common topologies are:
Bus network: all nodes are connected to a common medium along this medium. This was the layout used in the original Ethernet, called 10BASE5 and 10BASE2. This is still a common topology on the data link layer, although modern physical layer variants use point-to-point links instead, forming a st... | Computer network | Wikipedia | 495 | 4122592 | https://en.wikipedia.org/wiki/Computer%20network | Technology | Networks | null |
The most striking example of an overlay network is the Internet itself. The Internet itself was initially built as an overlay on the telephone network. Even today, each Internet node can communicate with virtually any other through an underlying mesh of sub-networks of wildly different topologies and technologies. Addr... | Computer network | Wikipedia | 480 | 4122592 | https://en.wikipedia.org/wiki/Computer%20network | Technology | Networks | null |
Coaxial cable is widely used for cable television systems, office buildings, and other work-sites for local area networks. Transmission speed ranges from 200 million bits per second to more than 500 million bits per second.
ITU-T G.hn technology uses existing home wiring (coaxial cable, phone lines and power lines) to ... | Computer network | Wikipedia | 389 | 4122592 | https://en.wikipedia.org/wiki/Computer%20network | Technology | Networks | null |
Network connections can be established wirelessly using radio or other electromagnetic means of communication.
Terrestrial microwave – Terrestrial microwave communication uses Earth-based transmitters and receivers resembling satellite dishes. Terrestrial microwaves are in the low gigahertz range, which limits all com... | Computer network | Wikipedia | 455 | 4122592 | https://en.wikipedia.org/wiki/Computer%20network | Technology | Networks | null |
In Ethernet networks, each NIC has a unique Media Access Control (MAC) address—usually stored in the controller's permanent memory. To avoid address conflicts between network devices, the Institute of Electrical and Electronics Engineers (IEEE) maintains and administers MAC address uniqueness. The size of an Ethernet M... | Computer network | Wikipedia | 413 | 4122592 | https://en.wikipedia.org/wiki/Computer%20network | Technology | Networks | null |
Bridges and switches operate at the data link layer (layer 2) of the OSI model and bridge traffic between two or more network segments to form a single local network. Both are devices that forward frames of data between ports based on the destination MAC address in each frame.
They learn the association of physical por... | Computer network | Wikipedia | 470 | 4122592 | https://en.wikipedia.org/wiki/Computer%20network | Technology | Networks | null |
In a protocol stack, often constructed per the OSI model, communications functions are divided up into protocol layers, where each layer leverages the services of the layer below it until the lowest layer controls the hardware that sends information across the media. The use of protocol layering is ubiquitous across th... | Computer network | Wikipedia | 497 | 4122592 | https://en.wikipedia.org/wiki/Computer%20network | Technology | Networks | null |
SONET/SDH
Synchronous optical networking (SONET) and Synchronous Digital Hierarchy (SDH) are standardized multiplexing protocols that transfer multiple digital bit streams over optical fiber using lasers. They were originally designed to transport circuit mode communications from a variety of different sources, primar... | Computer network | Wikipedia | 414 | 4122592 | https://en.wikipedia.org/wiki/Computer%20network | Technology | Networks | null |
In packet-switched networks, routing protocols direct packet forwarding through intermediate nodes. Intermediate nodes are typically network hardware devices such as routers, bridges, gateways, firewalls, or switches. General-purpose computers can also forward packets and perform routing, though because they lack speci... | Computer network | Wikipedia | 437 | 4122592 | https://en.wikipedia.org/wiki/Computer%20network | Technology | Networks | null |
Local area network
A local area network (LAN) is a network that connects computers and devices in a limited geographical area such as a home, school, office building, or closely positioned group of buildings. Wired LANs are most commonly based on Ethernet technology. Other networking technologies such as ITU-T G.hn als... | Computer network | Wikipedia | 475 | 4122592 | https://en.wikipedia.org/wiki/Computer%20network | Technology | Networks | null |
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