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There is a kind of continuum with three semi-distinct categories dealing with anthropogenic hybridization: hybridization without introgression, hybridization with widespread introgression (backcrossing with one of the parent species), and hybrid swarms (highly variable populations with much interbreeding as well as bac... | Hybrid (biology) | Wikipedia | 405 | 41244 | https://en.wikipedia.org/wiki/Hybrid%20%28biology%29 | Biology and health sciences | Genetics and taxonomy | null | vital_articles |
In agriculture and animal husbandry, the Green Revolution's use of conventional hybridization increased yields by breeding high-yielding varieties. The replacement of locally indigenous breeds, compounded with unintentional cross-pollination and crossbreeding (genetic mixing), has reduced the gene pools of various wild... | Hybrid (biology) | Wikipedia | 474 | 41244 | https://en.wikipedia.org/wiki/Hybrid%20%28biology%29 | Biology and health sciences | Genetics and taxonomy | null | vital_articles |
One of the most common interspecific hybrids in geese occurs between Greylag and Canada geese (Anser anser x Branta canadensis). One potential mechanism for the occurrence of hybrids in these geese is interspecific nest parasitism, where an egg is laid in the nest of another species to be raised by non-biological paren... | Hybrid (biology) | Wikipedia | 384 | 41244 | https://en.wikipedia.org/wiki/Hybrid%20%28biology%29 | Biology and health sciences | Genetics and taxonomy | null | vital_articles |
The two closely related harvester ant species Pogonomyrmex barbatus and Pogonomyrmex rugosus have evolved to depend on hybridization. When a queen fertilizes her eggs with sperm from males of her own species, the offspring is always new queens. And when she fertilizes the eggs with sperm from males of the other species... | Hybrid (biology) | Wikipedia | 416 | 41244 | https://en.wikipedia.org/wiki/Hybrid%20%28biology%29 | Biology and health sciences | Genetics and taxonomy | null | vital_articles |
Some crop plants are hybrids from different genera (intergeneric hybrids), such as Triticale, × Triticosecale, a wheat–rye hybrid. Most modern and ancient wheat breeds are themselves hybrids; bread wheat, Triticum aestivum, is a hexaploid hybrid of three wild grasses. Several commercial fruits including loganberry (Rub... | Hybrid (biology) | Wikipedia | 396 | 41244 | https://en.wikipedia.org/wiki/Hybrid%20%28biology%29 | Biology and health sciences | Genetics and taxonomy | null | vital_articles |
There is evidence of hybridization between modern humans and other species of the genus Homo. In 2010, the Neanderthal genome project showed that 1–4% of DNA from all people living today, apart from most Sub-Saharan Africans, is of Neanderthal heritage. Analyzing the genomes of 600 Europeans and East Asians found that ... | Hybrid (biology) | Wikipedia | 405 | 41244 | https://en.wikipedia.org/wiki/Hybrid%20%28biology%29 | Biology and health sciences | Genetics and taxonomy | null | vital_articles |
In electrodynamics, linear polarization or plane polarization of electromagnetic radiation is a confinement of the electric field vector or magnetic field vector to a given plane along the direction of propagation. The term linear polarization (French: polarisation rectiligne) was coined by Augustin-Jean Fresnel in 182... | Linear polarization | Wikipedia | 290 | 41316 | https://en.wikipedia.org/wiki/Linear%20polarization | Physical sciences | Optics | Physics | vital_articles |
In telecommunications and computer networking, multiplexing (sometimes contracted to muxing) is a method by which multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share a scarce resource a physical transmission medium. For example, in telecommunications, several telep... | Multiplexing | Wikipedia | 446 | 41389 | https://en.wikipedia.org/wiki/Multiplexing | Technology | Signal processing | null | vital_articles |
In wired communication, space-division multiplexing, also known as space-division multiple access (SDMA) is the use of separate point-to-point electrical conductors for each transmitted channel. Examples include an analog stereo audio cable, with one pair of wires for the left channel and another for the right channel,... | Multiplexing | Wikipedia | 417 | 41389 | https://en.wikipedia.org/wiki/Multiplexing | Technology | Signal processing | null | vital_articles |
Time-division multiplexing (TDM) is a digital (or in rare cases, analog) technology that uses time, instead of space or frequency, to separate the different data streams. TDM involves sequencing groups of a few bits or bytes from each individual input stream, one after the other, and in such a way that they can be asso... | Multiplexing | Wikipedia | 462 | 41389 | https://en.wikipedia.org/wiki/Multiplexing | Technology | Signal processing | null | vital_articles |
Orbital angular momentum multiplexing is a relatively new and experimental technique for multiplexing multiple channels of signals carried using electromagnetic radiation over a single path. It can potentially be used in addition to other physical multiplexing methods to greatly expand the transmission capacity of such... | Multiplexing | Wikipedia | 506 | 41389 | https://en.wikipedia.org/wiki/Multiplexing | Technology | Signal processing | null | vital_articles |
Code-division multiplexing (CDM) is a technique in which each channel transmits its bits as a coded channel-specific sequence of pulses. This coded transmission is typically accomplished by transmitting a unique time-dependent series of short pulses, which are placed within chip times within the larger bit time. All ch... | Multiplexing | Wikipedia | 500 | 41389 | https://en.wikipedia.org/wiki/Multiplexing | Technology | Signal processing | null | vital_articles |
In video editing and processing systems, multiplexing refers to the process of interleaving audio and video into one coherent data stream.
In digital video, such a transport stream is normally a feature of a container format which may include metadata and other information, such as subtitles. The audio and video strea... | Multiplexing | Wikipedia | 385 | 41389 | https://en.wikipedia.org/wiki/Multiplexing | Technology | Signal processing | null | vital_articles |
Analog broadcasting
In FM broadcasting and other analog radio media, multiplexing is a term commonly given to the process of adding subcarriers to the audio signal before it enters the transmitter, where modulation occurs. (In fact, the stereo multiplex signal can be generated using time-division multiplexing, by switc... | Multiplexing | Wikipedia | 411 | 41389 | https://en.wikipedia.org/wiki/Multiplexing | Technology | Signal processing | null | vital_articles |
The neper (symbol: Np) is a logarithmic unit for ratios of measurements of physical field and power quantities, such as gain and loss of electronic signals. The unit's name is derived from the name of John Napier, the inventor of logarithms. As is the case for the decibel and bel, the neper is a unit defined in the int... | Neper | Wikipedia | 462 | 41402 | https://en.wikipedia.org/wiki/Neper | Physical sciences | Ratio | Basics and measurement | vital_articles |
The derived units decineper (1 dNp = 0.1 neper) and centineper (1 cNp = 0.01 neper) are also used. The centineper for root-power quantities corresponds to a log point or log percentage, see . | Neper | Wikipedia | 56 | 41402 | https://en.wikipedia.org/wiki/Neper | Physical sciences | Ratio | Basics and measurement | vital_articles |
Network topology is the arrangement of the elements (links, nodes, etc.) of a communication network. Network topology can be used to define or describe the arrangement of various types of telecommunication networks, including command and control radio networks, industrial fieldbusses and computer networks.
Network top... | Network topology | Wikipedia | 440 | 41413 | https://en.wikipedia.org/wiki/Network%20topology | Technology | Networks | null | vital_articles |
In contrast, logical topology is the way that the signals act on the network media, or the way that the data passes through the network from one device to the next without regard to the physical interconnection of the devices. A network's logical topology is not necessarily the same as its physical topology. For exampl... | Network topology | Wikipedia | 418 | 41413 | https://en.wikipedia.org/wiki/Network%20topology | Technology | Networks | null | vital_articles |
Coaxial cable is widely used for cable television systems, office buildings, and other work-sites for local area networks. The cables consist of copper or aluminum wire surrounded by an insulating layer (typically a flexible material with a high dielectric constant), which itself is surrounded by a conductive layer. Th... | Network topology | Wikipedia | 443 | 41413 | https://en.wikipedia.org/wiki/Network%20topology | Technology | Networks | null | vital_articles |
An optical fiber is a glass fiber. It carries pulses of light that represent data. Some advantages of optical fibers over metal wires are very low transmission loss and immunity from electrical interference. Optical fibers can simultaneously carry multiple wavelengths of light, which greatly increases the rate that dat... | Network topology | Wikipedia | 499 | 41413 | https://en.wikipedia.org/wiki/Network%20topology | Technology | Networks | null | vital_articles |
Both cases have a large round-trip delay time, which gives slow two-way communication, but does not prevent sending large amounts of information.
Nodes
Network nodes are the points of connection of the transmission medium to transmitters and receivers of the electrical, optical, or radio signals carried in the medium... | Network topology | Wikipedia | 449 | 41413 | https://en.wikipedia.org/wiki/Network%20topology | Technology | Networks | null | vital_articles |
Repeaters and hubs
A repeater is an electronic device that receives a network signal, cleans it of unnecessary noise and regenerates it. The signal may be reformed or retransmitted at a higher power level, to the other side of an obstruction possibly using a different transmission medium, so that the signal can cover ... | Network topology | Wikipedia | 452 | 41413 | https://en.wikipedia.org/wiki/Network%20topology | Technology | Networks | null | vital_articles |
Switches
A network switch is a device that forwards and filters OSI layer 2 datagrams (frames) between ports based on the destination MAC address in each frame.
A switch is distinct from a hub in that it only forwards the frames to the physical ports involved in the communication rather than all ports connected. It can... | Network topology | Wikipedia | 488 | 41413 | https://en.wikipedia.org/wiki/Network%20topology | Technology | Networks | null | vital_articles |
The simplest topology with a dedicated link between two endpoints. Easiest to understand, of the variations of point-to-point topology, is a point-to-point communication channel that appears, to the user, to be permanently associated with the two endpoints. A child's tin can telephone is one example of a physical dedic... | Network topology | Wikipedia | 473 | 41413 | https://en.wikipedia.org/wiki/Network%20topology | Technology | Networks | null | vital_articles |
A signal containing the address of the intended receiving machine travels from a source machine in both directions to all machines connected to the bus until it finds the intended recipient, which then accepts the data. If the machine address does not match the intended address for the data, the data portion of the sig... | Network topology | Wikipedia | 453 | 41413 | https://en.wikipedia.org/wiki/Network%20topology | Technology | Networks | null | vital_articles |
Extended star
The extended star network topology extends a physical star topology by one or more repeaters between the central node and the peripheral (or 'spoke') nodes. The repeaters are used to extend the maximum transmission distance of the physical layer, the point-to-point distance between the central node and th... | Network topology | Wikipedia | 503 | 41413 | https://en.wikipedia.org/wiki/Network%20topology | Technology | Networks | null | vital_articles |
In a fully connected network, all nodes are interconnected. (In graph theory this is called a complete graph.) The simplest fully connected network is a two-node network. A fully connected network doesn't need to use packet switching or broadcasting. However, since the number of connections grows quadratically with the... | Network topology | Wikipedia | 509 | 41413 | https://en.wikipedia.org/wiki/Network%20topology | Technology | Networks | null | vital_articles |
If the central node is passive, the originating node must be able to tolerate the reception of an echo of its own transmission, delayed by the two-way round trip transmission time (i.e. to and from the central node) plus any delay generated in the central node. An active star network has an active central node that us... | Network topology | Wikipedia | 428 | 41413 | https://en.wikipedia.org/wiki/Network%20topology | Technology | Networks | null | vital_articles |
Decentralization
In a partially connected mesh topology, there are at least two nodes with two or more paths between them to provide redundant paths in case the link providing one of the paths fails. Decentralization is often used to compensate for the single-point-failure disadvantage that is present when using a sing... | Network topology | Wikipedia | 262 | 41413 | https://en.wikipedia.org/wiki/Network%20topology | Technology | Networks | null | vital_articles |
Noise is sound, chiefly unwanted, unintentional, or harmful sound considered unpleasant, loud, or disruptive to mental or hearing faculties. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium, such as air or water. The difference arises when the b... | Noise | Wikipedia | 503 | 41415 | https://en.wikipedia.org/wiki/Noise | Physical sciences | Waves | null | vital_articles |
In audio engineering it can refer either to the acoustic noise from loudspeakers or to the unwanted residual electronic noise signal that gives rise to acoustic noise heard as hiss. This signal noise is commonly measured using A-weighting or ITU-R 468 weighting
Noise is often generated deliberately and used as a test ... | Noise | Wikipedia | 453 | 41415 | https://en.wikipedia.org/wiki/Noise | Physical sciences | Waves | null | vital_articles |
The National Institute for Occupational Safety and Health (NIOSH) provides recommendation on noise exposure in the workplace. In 1972 (revised in 1998), NIOSH published a document outlining recommended standards relating to the occupational exposure to noise, with the purpose of reducing the risk of developing permanen... | Noise | Wikipedia | 416 | 41415 | https://en.wikipedia.org/wiki/Noise | Physical sciences | Waves | null | vital_articles |
Noise exposure has increasingly been identified as a public health issue, especially in an occupational setting, as demonstrated with the creation of NIOSH's Noise and Hearing Loss Prevention program. Noise has also proven to be an occupational hazard, as it is the most common work-related pollutant. Noise-induced hea... | Noise | Wikipedia | 506 | 41415 | https://en.wikipedia.org/wiki/Noise | Physical sciences | Waves | null | vital_articles |
An optical disc is a flat, usually disc-shaped object that stores information in the form of physical variations on its surface that can be read with the aid of a beam of light. Optical discs can be reflective, where the light source and detector are on the same side of the disc, or transmissive, where light shines th... | Optical disc | Wikipedia | 511 | 41458 | https://en.wikipedia.org/wiki/Optical%20disc | Technology | Data storage | null | vital_articles |
Recording types
An optical disc is designed to support one of three recording types: read-only (such as CD and CD-ROM), recordable (write-once, like CD-R), or re-recordable (rewritable, like CD-RW). Write-once optical discs commonly have an organic dye (may also be a (phthalocyanine) azo dye, mainly used by Verbatim, ... | Optical disc | Wikipedia | 507 | 41458 | https://en.wikipedia.org/wiki/Optical%20disc | Technology | Data storage | null | vital_articles |
File operations of traditional mass storage devices such as flash drives, memory cards and hard drives can be simulated using a UDF live file system.
For computer data backup and physical data transfer, optical discs such as CDs and DVDs are gradually being replaced with faster, smaller solid-state devices, especially... | Optical disc | Wikipedia | 354 | 41458 | https://en.wikipedia.org/wiki/Optical%20disc | Technology | Data storage | null | vital_articles |
Optical discs are typically stored in special cases, sometimes called jewel cases. Discs should not have any stickers and should not be stored together with paper; papers must be removed from the jewel case before storage. Discs should be handled by the edges to prevent scratching, with the thumb on the inner edge of t... | Optical disc | Wikipedia | 490 | 41458 | https://en.wikipedia.org/wiki/Optical%20disc | Technology | Data storage | null | vital_articles |
The first recorded historical use of an optical disc was in 1884 when Alexander Graham Bell, Chichester Bell and Charles Sumner Tainter recorded sound on a glass disc using a beam of light.
Optophonie is a very early (1931) example of a recording device using light for both recording and playing back sound signals on ... | Optical disc | Wikipedia | 456 | 41458 | https://en.wikipedia.org/wiki/Optical%20disc | Technology | Data storage | null | vital_articles |
Most first-generation disc devices had an infrared laser reading head. The minimum size of the laser spot is proportional to the wavelength of the laser, so wavelength is a limiting factor upon the amount of information that can be stored in a given physical area on the disc. The infrared range is beyond the long-wavel... | Optical disc | Wikipedia | 401 | 41458 | https://en.wikipedia.org/wiki/Optical%20disc | Technology | Data storage | null | vital_articles |
In 1979, Exxon STAR Systems in Pasadena, CA built a computer controlled WORM drive that utilized thin film coatings of Tellurium and Selenium on a 12" diameter glass disk. The recording system utilized blue light at 457 nm to record and red light at 632.8 nm to read. STAR Systems was bought by Storage Technology Corpor... | Optical disc | Wikipedia | 376 | 41458 | https://en.wikipedia.org/wiki/Optical%20disc | Technology | Data storage | null | vital_articles |
Sony and Philips developed the first generation of the CDs in the mid-1980s with the complete specifications for these devices. With the help of this kind of technology the possibility of representing the analog signal into digital signal was exploited to a great level. For this purpose, the 16-bit samples of the analo... | Optical disc | Wikipedia | 495 | 41458 | https://en.wikipedia.org/wiki/Optical%20disc | Technology | Data storage | null | vital_articles |
Blu-ray and derivatives (up to 400 GB - experimental)
BD-R and BD-RE
High Fidelity Pure Audio
AVCHD and AVCREC
BDXL and Blu-ray 3D
4K Blu-ray and 8K Blu-ray
Wii U Optical Disc (25 GB per layer)
HD DVD (discontinued disc format, up to 51 GB triple layer)
CBHD (a derivative of the HD DVD format)
HD VMD
Professi... | Optical disc | Wikipedia | 440 | 41458 | https://en.wikipedia.org/wiki/Optical%20disc | Technology | Data storage | null | vital_articles |
An optical isolator, or optical diode, is an optical component which allows the transmission of light in only one direction. It is typically used to prevent unwanted feedback into an optical oscillator, such as a laser cavity.
The operation of conventional optical isolators relies on the Faraday effect (which in turn ... | Optical isolator | Wikipedia | 456 | 41460 | https://en.wikipedia.org/wiki/Optical%20isolator | Technology | Optical components | null | vital_articles |
Figure 2 shows a Faraday rotator with an input polarizer, and an output analyzer. For a polarization dependent isolator, the angle between the polarizer and the analyzer, , is set to 45°. The Faraday rotator is chosen to give a 45° rotation.
Polarization dependent isolators are typically used in free space optical sy... | Optical isolator | Wikipedia | 465 | 41460 | https://en.wikipedia.org/wiki/Optical%20isolator | Technology | Optical components | null | vital_articles |
Figure 3 shows the propagation of light through a polarization independent isolator. The forward travelling light is shown in blue, and the backward propagating light is shown in red. The rays were traced using an ordinary refractive index of 2, and an extraordinary refractive index of 3. The wedge angle is 7°.
The Fa... | Optical isolator | Wikipedia | 506 | 41460 | https://en.wikipedia.org/wiki/Optical%20isolator | Technology | Optical components | null | vital_articles |
In optics, optical path length (OPL, denoted Λ in equations), also known as optical length or optical distance, is the length that light needs to travel through a vacuum to create the same phase difference as it would have when traveling through a given medium. It is calculated by taking the product of the geometric le... | Optical path length | Wikipedia | 509 | 41461 | https://en.wikipedia.org/wiki/Optical%20path%20length | Physical sciences | Optics | Physics | vital_articles |
The visible spectrum is the band of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light (or simply light).
The optical spectrum is sometimes considered to be the same as the visible spectrum, but some authors define the term more ... | Visible spectrum | Wikipedia | 455 | 41464 | https://en.wikipedia.org/wiki/Visible%20spectrum | Physical sciences | Electrodynamics | null | vital_articles |
In the 17th century, Isaac Newton discovered that prisms could disassemble and reassemble white light, and described the phenomenon in his book Opticks. He was the first to use the word spectrum (Latin for "appearance" or "apparition") in this sense in print in 1671 in describing his experiments in optics. Newton obser... | Visible spectrum | Wikipedia | 404 | 41464 | https://en.wikipedia.org/wiki/Visible%20spectrum | Physical sciences | Electrodynamics | null | vital_articles |
In the 18th century, Johann Wolfgang von Goethe wrote about optical spectra in his Theory of Colours. Goethe used the word spectrum (Spektrum) to designate a ghostly optical afterimage, as did Schopenhauer in On Vision and Colors. Goethe argued that the continuous spectrum was a compound phenomenon. Where Newton narrow... | Visible spectrum | Wikipedia | 465 | 41464 | https://en.wikipedia.org/wiki/Visible%20spectrum | Physical sciences | Electrodynamics | null | vital_articles |
Before reaching the retina, light must first transmit through the cornea and lens. UVB light (< 315 nm) is filtered mostly by the cornea, and UVA light (315–400 nm) is filtered mostly by the lens. The lens also yellows with age, attenuating transmission most strongly at the blue part of the spectrum. This can cause xan... | Visible spectrum | Wikipedia | 504 | 41464 | https://en.wikipedia.org/wiki/Visible%20spectrum | Physical sciences | Electrodynamics | null | vital_articles |
Vision outside the visible spectrum
Under ideal laboratory conditions, subjects may perceive infrared light up to at least 1,064 nm. While 1,050 nm NIR light can evoke red, suggesting direct absorption by the L-opsin, there are also reports that pulsed NIR lasers can evoke green, which suggests two-photon absorption m... | Visible spectrum | Wikipedia | 497 | 41464 | https://en.wikipedia.org/wiki/Visible%20spectrum | Physical sciences | Electrodynamics | null | vital_articles |
Mammals
Most mammals have retained only two opsin classes (LWS and VS), due likely to the nocturnal bottleneck. However, old world primates (including humans) have since evolved two versions in the LWS class to regain trichromacy. Unlike most mammals, rodents' UVS opsins have remained at shorter wavelengths. Along with... | Visible spectrum | Wikipedia | 463 | 41464 | https://en.wikipedia.org/wiki/Visible%20spectrum | Physical sciences | Electrodynamics | null | vital_articles |
Invertebrates
The visual systems of invertebrates deviate greatly from vertebrates, so direct comparisons are difficult. However, UV sensitivity has been reported in most insect species.
Bees and many other insects can detect ultraviolet light, which helps them find nectar in flowers. Plant species that depend on insec... | Visible spectrum | Wikipedia | 339 | 41464 | https://en.wikipedia.org/wiki/Visible%20spectrum | Physical sciences | Electrodynamics | null | vital_articles |
Cod (: cod) is the common name for the demersal fish genus Gadus, belonging to the family Gadidae. Cod is also used as part of the common name for a number of other fish species, and one species that belongs to genus Gadus is commonly not called cod (Alaska pollock, Gadus chalcogrammus).
The two most common species of... | Cod | Wikipedia | 477 | 41515 | https://en.wikipedia.org/wiki/Cod | Biology and health sciences | Acanthomorpha | null | vital_articles |
Related species
Cod forms part of the common name of many other fish no longer classified in the genus Gadus. Many are members of the family Gadidae; others are members of three related families within the order Gadiformes whose names include the word "cod": the morid cods, Moridae (100 or so species); the eel cods, Mu... | Cod | Wikipedia | 488 | 41515 | https://en.wikipedia.org/wiki/Cod | Biology and health sciences | Acanthomorpha | null | vital_articles |
Scorpaeniformes
From the order Scorpaeniformes:
Ling cod Ophiodon elongatus
Red rock cod Scorpaena papillosa
Rock cod Sebastes
Ophidiiformes
The tadpole cod family, Ranicipitidae, and the Eucla cod family, Euclichthyidae, were formerly classified in the order Ophidiiformes, but are now grouped with the Gadiformes.
... | Cod | Wikipedia | 438 | 41515 | https://en.wikipedia.org/wiki/Cod | Biology and health sciences | Acanthomorpha | null | vital_articles |
Atlantic cod could be further divided into several stocks, including the Arcto-Norwegian, North Sea, Baltic Sea, Faroe, Iceland, East Greenland, West Greenland, Newfoundland, and Labrador stocks. There seems to be little interchange between the stocks, although migrations to their individual breeding grounds may involv... | Cod | Wikipedia | 498 | 41515 | https://en.wikipedia.org/wiki/Cod | Biology and health sciences | Acanthomorpha | null | vital_articles |
In the Baltic Sea the most important prey species are herring and sprat. Many studies that analyze the stomach contents of these fish indicate that cod is the top predator, preying on the herring and sprat. Sprat form particularly high concentrations in the Bornholm Basin in the southern Baltic Sea. Although cod feed p... | Cod | Wikipedia | 425 | 41515 | https://en.wikipedia.org/wiki/Cod | Biology and health sciences | Acanthomorpha | null | vital_articles |
Aquaculture
Farming of Atlantic cod has received a significant amount of interest due to the overall trend of increasing cod prices alongside reduced wild catches. However, progress in creating large scale farming of cod has been slow, mainly due to bottlenecks in the larval production stage, where survival and growth... | Cod | Wikipedia | 433 | 41515 | https://en.wikipedia.org/wiki/Cod | Biology and health sciences | Acanthomorpha | null | vital_articles |
Apart from the long history, cod differ from most fish because the fishing grounds are far from population centres. The large cod fisheries along the coast of North Norway (and in particular close to the Lofoten islands) have been developed almost uniquely for export, depending on sea transport of stockfish over large ... | Cod | Wikipedia | 511 | 41515 | https://en.wikipedia.org/wiki/Cod | Biology and health sciences | Acanthomorpha | null | vital_articles |
The near-complete destruction of the Atlantic northwest cod biomass off the shores devastated coastal communities, which had been overexploiting the same cod population for decades. The fishermen along the Atlantic northwest had employed modern fishing technologies, including the ecologically-devastating practice of tr... | Cod | Wikipedia | 508 | 41515 | https://en.wikipedia.org/wiki/Cod | Biology and health sciences | Acanthomorpha | null | vital_articles |
The photic zone (or euphotic zone, epipelagic zone, or sunlight zone) is the uppermost layer of a body of water that receives sunlight, allowing phytoplankton to perform photosynthesis. It undergoes a series of physical, chemical, and biological processes that supply nutrients into the upper water column. The photic zo... | Photic zone | Wikipedia | 340 | 41519 | https://en.wikipedia.org/wiki/Photic%20zone | Physical sciences | Oceanography | Earth science | vital_articles |
Ninety percent of marine life lives in the photic zone, which is approximately two hundred meters deep. This includes phytoplankton (plants), including dinoflagellates, diatoms, cyanobacteria, coccolithophores, and cryptomonads. It also includes zooplankton, the consumers in the photic zone. There are carnivorous meat ... | Photic zone | Wikipedia | 378 | 41519 | https://en.wikipedia.org/wiki/Photic%20zone | Physical sciences | Oceanography | Earth science | vital_articles |
Nutrient uptake in the photic zone
Due to biological uptake, the photic zone has relatively low levels of nutrient concentrations. As a result, phytoplankton doesn't receive enough nutrients when there is high water-column stability. The spatial distribution of organisms can be controlled by a number of factors. Physi... | Photic zone | Wikipedia | 464 | 41519 | https://en.wikipedia.org/wiki/Photic%20zone | Physical sciences | Oceanography | Earth science | vital_articles |
Most of the solar energy reaching the Earth is in the range of visible light, with wavelengths between about 400-700 nm. Each colour of visible light has a unique wavelength, and together they make up white light. The shortest wavelengths are on the violet and ultraviolet end of the spectrum, while the longest waveleng... | Photic zone | Wikipedia | 433 | 41519 | https://en.wikipedia.org/wiki/Photic%20zone | Physical sciences | Oceanography | Earth science | vital_articles |
Water in the open ocean appears clear and blue because it contains much less particulate matter, such as phytoplankton or other suspended particles, and the clearer the water, the deeper the light penetration. Blue light penetrates deeply and is scattered by the water molecules, while all other colours are absorbed; th... | Photic zone | Wikipedia | 341 | 41519 | https://en.wikipedia.org/wiki/Photic%20zone | Physical sciences | Oceanography | Earth science | vital_articles |
Phytoplankton are unicellular microorganisms which form the base of the ocean food chains. They are dominated by diatoms, which grow silicate shells called frustules. When diatoms die their shells can settle on the seafloor and become microfossils. Over time, these microfossils become buried as opal deposits in the mar... | Photic zone | Wikipedia | 466 | 41519 | https://en.wikipedia.org/wiki/Photic%20zone | Physical sciences | Oceanography | Earth science | vital_articles |
Phytoplankton are restricted to the photo zone only. As its growth is completely dependent upon photosynthesis. This results in the 50–100 m water level inside the ocean. Growth can also come from land factors, for example minerals that are dissolved from rocks, mineral nutrients from generations of plants and animals ... | Photic zone | Wikipedia | 261 | 41519 | https://en.wikipedia.org/wiki/Photic%20zone | Physical sciences | Oceanography | Earth science | vital_articles |
The Avogadro constant, commonly denoted or , is an SI defining constant with an exact value of (reciprocal moles). It is this defined number of constituent particles (usually molecules, atoms, ions, or ion pairs—in general, entities) per mole (SI unit) and used as a normalization factor in relating the amount of subs... | Avogadro constant | Wikipedia | 444 | 41545 | https://en.wikipedia.org/wiki/Avogadro%20constant | Physical sciences | Substance | Chemistry | vital_articles |
The Avogadro constant was historically derived from the old definition of the mole as the amount of substance in 12 grams of carbon-12 (12C); or, equivalently, the number of daltons in a gram, where the dalton is defined as of the mass of a 12C atom. By this old definition, the numerical value of the Avogadro constant... | Avogadro constant | Wikipedia | 478 | 41545 | https://en.wikipedia.org/wiki/Avogadro%20constant | Physical sciences | Substance | Chemistry | vital_articles |
The name Avogadro's number was coined in 1909 by the physicist Jean Perrin, who defined it as the number of molecules in exactly 32 grams of oxygen gas. The goal of this definition was to make the mass of a mole of a substance, in grams, be numerically equal to the mass of one molecule relative to the mass of the hydro... | Avogadro constant | Wikipedia | 485 | 41545 | https://en.wikipedia.org/wiki/Avogadro%20constant | Physical sciences | Substance | Chemistry | vital_articles |
By this definition, one mole of any substance contained exactly as many elementary entities as one mole of any other substance. However, this number was a physical constant that had to be experimentally determined since it depended on the mass (in grams) of one atom of 12C, and therefore, it was known only to a limite... | Avogadro constant | Wikipedia | 407 | 41545 | https://en.wikipedia.org/wiki/Avogadro%20constant | Physical sciences | Substance | Chemistry | vital_articles |
In physics, a plane wave is a special case of a wave or field: a physical quantity whose value, at any given moment, is constant through any plane that is perpendicular to a fixed direction in space.
For any position in space and any time , the value of such a field can be written as
where is a unit-length vector, ... | Plane wave | Wikipedia | 436 | 41559 | https://en.wikipedia.org/wiki/Plane%20wave | Physical sciences | Waves | Physics | vital_articles |
A true plane wave cannot physically exist, because it would have to fill all space. Nevertheless, the plane wave model is important and widely used in physics. The waves emitted by any source with finite extent into a large homogeneous region of space can be well approximated by plane waves when viewed over any part o... | Plane wave | Wikipedia | 386 | 41559 | https://en.wikipedia.org/wiki/Plane%20wave | Physical sciences | Waves | Physics | vital_articles |
(also ) is a property of transverse waves which specifies the geometrical orientation of the oscillations. In a transverse wave, the direction of the oscillation is perpendicular to the direction of motion of the wave. One example of a polarized transverse wave is vibrations traveling along a taut string (see image),... | Polarization (waves) | Wikipedia | 423 | 41564 | https://en.wikipedia.org/wiki/Polarization%20%28waves%29 | Physical sciences | Optics | null | vital_articles |
According to quantum mechanics, electromagnetic waves can also be viewed as streams of particles called photons. When viewed in this way, the polarization of an electromagnetic wave is determined by a quantum mechanical property of photons called their spin. A photon has one of two possible spins: it can either spin ... | Polarization (waves) | Wikipedia | 391 | 41564 | https://en.wikipedia.org/wiki/Polarization%20%28waves%29 | Physical sciences | Optics | null | vital_articles |
Electromagnetic waves (such as light), traveling in free space or another homogeneous isotropic non-attenuating medium, are properly described as transverse waves, meaning that a plane wave's electric field vector and magnetic field are each in some direction perpendicular to (or "transverse" to) the direction of wav... | Polarization (waves) | Wikipedia | 456 | 41564 | https://en.wikipedia.org/wiki/Polarization%20%28waves%29 | Physical sciences | Optics | null | vital_articles |
Knowing the propagation direction ( in this case) and , one can just as well specify the wave in terms of just and describing the electric field. The vector containing and (but without the component which is necessarily zero for a transverse wave) is known as a Jones vector. In addition to specifying the polarizat... | Polarization (waves) | Wikipedia | 321 | 41564 | https://en.wikipedia.org/wiki/Polarization%20%28waves%29 | Physical sciences | Optics | null | vital_articles |
Just considering electromagnetic waves, we note that the preceding discussion strictly applies to plane waves in a homogeneous isotropic non-attenuating medium, whereas in an anisotropic medium (such as birefringent crystals as discussed below) the electric or magnetic field may have longitudinal as well as transverse ... | Polarization (waves) | Wikipedia | 400 | 41564 | https://en.wikipedia.org/wiki/Polarization%20%28waves%29 | Physical sciences | Optics | null | vital_articles |
Polarization can be defined in terms of pure polarization states with only a coherent sinusoidal wave at one optical frequency. The vector in the adjacent diagram might describe the oscillation of the electric field emitted by a single-mode laser (whose oscillation frequency would be typically times faster). The field... | Polarization (waves) | Wikipedia | 477 | 41564 | https://en.wikipedia.org/wiki/Polarization%20%28waves%29 | Physical sciences | Optics | null | vital_articles |
Any pair of orthogonal polarization states may be used as basis functions, not just linear polarizations. For instance, choosing right and left circular polarizations as basis functions simplifies the solution of problems involving circular birefringence (optical activity) or circular dichroism.
Polarization ellipse
... | Polarization (waves) | Wikipedia | 365 | 41564 | https://en.wikipedia.org/wiki/Polarization%20%28waves%29 | Physical sciences | Optics | null | vital_articles |
Here and denote the amplitude of the wave in the two components of the electric field vector, while and represent the phases. The product of a Jones vector with a complex number of unit modulus gives a different Jones vector representing the same ellipse, and thus the same state of polarization. The physical electr... | Polarization (waves) | Wikipedia | 337 | 41564 | https://en.wikipedia.org/wiki/Polarization%20%28waves%29 | Physical sciences | Optics | null | vital_articles |
Another coordinate system frequently used relates to the plane of incidence. This is the plane made by the incoming propagation direction and the vector perpendicular to the plane of an interface, in other words, the plane in which the ray travels before and after reflection or refraction. The component of the electri... | Polarization (waves) | Wikipedia | 479 | 41564 | https://en.wikipedia.org/wiki/Polarization%20%28waves%29 | Physical sciences | Optics | null | vital_articles |
where is the wavenumber. As noted above, the instantaneous electric field is the real part of the product of the Jones vector times the phase factor When an electromagnetic wave interacts with matter, its propagation is altered according to the material's (complex) index of refraction. When the real or imaginary part... | Polarization (waves) | Wikipedia | 400 | 41564 | https://en.wikipedia.org/wiki/Polarization%20%28waves%29 | Physical sciences | Optics | null | vital_articles |
In a birefringent substance, electromagnetic waves of different polarizations travel at different speeds (phase velocities). As a result, when unpolarized waves travel through a plate of birefringent material, one polarization component has a shorter wavelength than the other, resulting in a phase difference between t... | Polarization (waves) | Wikipedia | 445 | 41564 | https://en.wikipedia.org/wiki/Polarization%20%28waves%29 | Physical sciences | Optics | null | vital_articles |
One can visualize the case of linear birefringence (with two orthogonal linear propagation modes) with an incoming wave linearly polarized at a 45° angle to those modes. As a differential phase starts to accrue, the polarization becomes elliptical, eventually changing to purely circular polarization (90° phase differen... | Polarization (waves) | Wikipedia | 382 | 41564 | https://en.wikipedia.org/wiki/Polarization%20%28waves%29 | Physical sciences | Optics | null | vital_articles |
Devices that block nearly all of the radiation in one mode are known as or simply "polarizers". This corresponds to in the above representation of the Jones matrix. The output of an ideal polarizer is a specific polarization state (usually linear polarization) with an amplitude equal to the input wave's original ampl... | Polarization (waves) | Wikipedia | 469 | 41564 | https://en.wikipedia.org/wiki/Polarization%20%28waves%29 | Physical sciences | Optics | null | vital_articles |
In the important special case of reflection at normal incidence (not involving anisotropic materials) there is no particular s- or p-polarization. Both the and polarization components are reflected identically, and therefore the polarization of the reflected wave is identical to that of the incident wave. However, in... | Polarization (waves) | Wikipedia | 501 | 41564 | https://en.wikipedia.org/wiki/Polarization%20%28waves%29 | Physical sciences | Optics | null | vital_articles |
Ellipsometry can be used to model the (complex) refractive index of a surface of a bulk material. It is also very useful in determining parameters of one or more thin film layers deposited on a substrate. Due to their reflection properties, not only are the predicted magnitude of the p and s polarization components, bu... | Polarization (waves) | Wikipedia | 343 | 41564 | https://en.wikipedia.org/wiki/Polarization%20%28waves%29 | Physical sciences | Optics | null | vital_articles |
Chemistry
We have seen (above) that the birefringence of a type of crystal is useful in identifying it, and thus detection of linear birefringence is especially useful in geology and mineralogy. Linearly polarized light generally has its polarization state altered upon transmission through such a crystal, making it st... | Polarization (waves) | Wikipedia | 498 | 41564 | https://en.wikipedia.org/wiki/Polarization%20%28waves%29 | Physical sciences | Optics | null | vital_articles |
Unpolarized light, after being reflected by a specular (shiny) surface, generally obtains a degree of polarization. This phenomenon was observed in the early 1800s by the mathematician Étienne-Louis Malus, after whom Malus's law is named. Polarizing sunglasses exploit this effect to reduce glare from reflections by hor... | Polarization (waves) | Wikipedia | 409 | 41564 | https://en.wikipedia.org/wiki/Polarization%20%28waves%29 | Physical sciences | Optics | null | vital_articles |
Display technologies
The principle of liquid-crystal display (LCD) technology relies on the rotation of the axis of linear polarization by the liquid crystal array. Light from the backlight (or the back reflective layer, in devices not including or requiring a backlight) first passes through a linear polarizing sheet.... | Polarization (waves) | Wikipedia | 375 | 41564 | https://en.wikipedia.org/wiki/Polarization%20%28waves%29 | Physical sciences | Optics | null | vital_articles |
In a totally different sense, polarization encoding has become the leading (but not sole) method for delivering separate images to the left and right eye in stereoscopic displays used for 3D movies. This involves separate images intended for each eye either projected from two different projectors with orthogonally orie... | Polarization (waves) | Wikipedia | 509 | 41564 | https://en.wikipedia.org/wiki/Polarization%20%28waves%29 | Physical sciences | Optics | null | vital_articles |
All radio (and microwave) antennas used for transmitting or receiving are intrinsically polarized. They transmit in (or receive signals from) a particular polarization, being totally insensitive to the opposite polarization; in certain cases that polarization is a function of direction. Most antennas are nominally line... | Polarization (waves) | Wikipedia | 479 | 41564 | https://en.wikipedia.org/wiki/Polarization%20%28waves%29 | Physical sciences | Optics | null | vital_articles |
Especially due to the presence of the ground, there are some differences in propagation (and also in reflections responsible for TV ghosting) between horizontal and vertical polarizations. AM and FM broadcast radio usually use vertical polarization, while television uses horizontal polarization. At low frequencies espe... | Polarization (waves) | Wikipedia | 405 | 41564 | https://en.wikipedia.org/wiki/Polarization%20%28waves%29 | Physical sciences | Optics | null | vital_articles |
Polarization and vision
Many animals are capable of perceiving some of the components of the polarization of light, e.g., linear horizontally polarized light. This is generally used for navigational purposes, since the linear polarization of sky light is always perpendicular to the direction of the sun. This ability i... | Polarization (waves) | Wikipedia | 387 | 41564 | https://en.wikipedia.org/wiki/Polarization%20%28waves%29 | Physical sciences | Optics | null | vital_articles |
In medicine, the pulse is the rhythmic throbbing of each artery in response to the cardiac cycle (heartbeat). The pulse may be palpated in any place that allows an artery to be compressed near the surface of the body, such as at the neck (carotid artery), wrist (radial artery or ulnar artery), at the groin (femoral art... | Pulse | Wikipedia | 462 | 41600 | https://en.wikipedia.org/wiki/Pulse | Biology and health sciences | Medical procedures | null | vital_articles |
In healthy people, the pulse rate is close to the heart rate, as measured by ECG. Measuring the pulse rate is therefore a convenient way to estimate the heart rate. Pulse deficit is a condition in which a person has a difference between their pulse rate and heart rate. It can be observed by simultaneous palpation at th... | Pulse | Wikipedia | 483 | 41600 | https://en.wikipedia.org/wiki/Pulse | Biology and health sciences | Medical procedures | null | vital_articles |
The strength of the pulse can also be reported:
0 = Absent
1 = Barely palpable
2 = Easily palpable
3 = Full
4 = Aneurysmal or bounding pulse
Force
Also known as compressibility of pulse. It is a rough indication of systolic blood pressure.
Tension
Determined mainly by mean arterial blood pressure [edited by Elmo... | Pulse | Wikipedia | 422 | 41600 | https://en.wikipedia.org/wiki/Pulse | Biology and health sciences | Medical procedures | null | vital_articles |
Patterns
Several pulse patterns can be of clinical significance. These include:
Anacrotic pulse: notch on the upstroke of the carotid pulse. Two distinct waves (slow initial upstroke and delayed peak, which is close to S2). Present in AS.
Dicrotic pulse: is characterized by two beats per cardiac cycle, one systolic a... | Pulse | Wikipedia | 496 | 41600 | https://en.wikipedia.org/wiki/Pulse | Biology and health sciences | Medical procedures | null | vital_articles |
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