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Support of hardware T&L assured the GeForce and Radeon of a strong future, unlike its Direct3D 6 predecessors which relied upon software T&L. While hardware T&L does not add new rendering features, the extra performance allowed for much more complex scenes and an increasing number of games recommended it anyway to run ... | Transform, clipping, and lighting | Wikipedia | 197 | 6961053 | https://en.wikipedia.org/wiki/Transform%2C%20clipping%2C%20and%20lighting | Technology | Computer science | null |
A rivet gun, also known as a rivet hammer or a pneumatic hammer, is a type of tool used to drive rivets. The rivet gun is used on rivet's factory head (the head present before riveting takes place), and a bucking bar is used to support the tail of the rivet. The energy from the hammer in the rivet gun drives the wor... | Rivet gun | Wikipedia | 444 | 14419104 | https://en.wikipedia.org/wiki/Rivet%20gun | Technology | Hydraulics and pneumatics | null |
Fast-hitting gun
The fast-hitting gun strikes multiple light-weight blows at a high rate as long as the trigger is held down. These are repeated in the range of 2,500 to 5,000 bpm. The fast-hitting gun, sometimes referred to as a vibrator, is generally used with softer rivets.
Corner riveter
The corner riveter is a co... | Rivet gun | Wikipedia | 437 | 14419104 | https://en.wikipedia.org/wiki/Rivet%20gun | Technology | Hydraulics and pneumatics | null |
A hinny is a domestic equine hybrid, the offspring of a male horse (a stallion) and a female donkey (a jenny). It is the reciprocal cross to the more common mule, which is the product of a male donkey (a jack) and a female horse (a mare). The hinny is distinct from the mule both in physiology and temperament as a conse... | Hinny | Wikipedia | 400 | 156739 | https://en.wikipedia.org/wiki/Hinny | Biology and health sciences | Hybrids | Animals |
Hypochondriasis or hypochondria is a condition in which a person is excessively and unduly worried about having a serious illness. Hypochondria is an old concept whose meaning has repeatedly changed over its lifespan. It has been claimed that this debilitating condition results from an inaccurate perception of the cond... | Hypochondriasis | Wikipedia | 425 | 156778 | https://en.wikipedia.org/wiki/Hypochondriasis | Biology and health sciences | Mental disorders | Health |
Hypochondria is often characterized by fears that minor bodily or mental symptoms may indicate a serious illness, constant self-examination and self-diagnosis, and a preoccupation with one's body. Many individuals with hypochondriasis express doubt and disbelief in the doctors' diagnosis, and report that doctors’ reass... | Hypochondriasis | Wikipedia | 502 | 156778 | https://en.wikipedia.org/wiki/Hypochondriasis | Biology and health sciences | Mental disorders | Health |
Hypochondriasis is often accompanied by other psychological disorders. Bipolar disorder, clinical depression, obsessive-compulsive disorder (OCD), phobias, and somatization disorder,
panic disorder are the most common accompanying conditions in people with hypochondriasis, as well as a generalized anxiety disorder dia... | Hypochondriasis | Wikipedia | 444 | 156778 | https://en.wikipedia.org/wiki/Hypochondriasis | Biology and health sciences | Mental disorders | Health |
Cause
The genetic contribution to hypochondriasis is probably moderate, with heritability estimates around 10–37%. Non-shared environmental factors (i.e., experiences that differ between twins in the same family) explain most of the variance in key components of the condition such as the fear of illness and disease con... | Hypochondriasis | Wikipedia | 476 | 156778 | https://en.wikipedia.org/wiki/Hypochondriasis | Biology and health sciences | Mental disorders | Health |
B. Preoccupation with the belief and the symptoms causes persistent distress or interference with personal functioning in daily living and leads the patient to seek medical treatment or investigations (or equivalent help from local healers).
C. Persistent refusal to accept medical advice that there is no adequate phys... | Hypochondriasis | Wikipedia | 432 | 156778 | https://en.wikipedia.org/wiki/Hypochondriasis | Biology and health sciences | Mental disorders | Health |
In the case of the DSM, the first and second versions listed hypochondriasis as a neurosis, whereas the third and fourth versions listed hypochondriasis as a somatoform disorder. The current version of the DSM (DSM-5) lists somatic symptom disorder (SSD) under the heading of "somatic symptom and related disorders", and... | Hypochondriasis | Wikipedia | 446 | 156778 | https://en.wikipedia.org/wiki/Hypochondriasis | Biology and health sciences | Mental disorders | Health |
Etymology
Among the regions of the abdomen, the hypochondrium is the uppermost part. The word derives from the Greek term ὑποχόνδριος hypokhondrios, meaning "of the soft parts between the ribs and navel" from ὑπό hypo ("under") and χόνδρος khondros, or cartilage (of the sternum). Hypochondria in Late Latin meant "the a... | Hypochondriasis | Wikipedia | 386 | 156778 | https://en.wikipedia.org/wiki/Hypochondriasis | Biology and health sciences | Mental disorders | Health |
Desalination is a process that removes mineral components from saline water. More generally, desalination is the removal of salts and minerals from a substance. One example is soil desalination. This is important for agriculture. It is possible to desalinate saltwater, especially sea water, to produce water for human c... | Desalination | Wikipedia | 477 | 156787 | https://en.wikipedia.org/wiki/Desalination | Technology | Food, water and health | null |
Numerous examples of experimentation in desalination appeared throughout Antiquity and the Middle Ages, but desalination became feasible on a large scale only in the modern era. A good example of this experimentation comes from Leonardo da Vinci (Florence, 1452), who realized that distilled water could be made cheaply ... | Desalination | Wikipedia | 458 | 156787 | https://en.wikipedia.org/wiki/Desalination | Technology | Food, water and health | null |
Beginning about 1800, things started changing as a consequence of the appearance of the steam engine and the so-called age of steam. Knowledge of the thermodynamics of steam processes and the need for a pure water source for its use in boilers generated a positive effect regarding distilling systems. Additionally, the ... | Desalination | Wikipedia | 507 | 156787 | https://en.wikipedia.org/wiki/Desalination | Technology | Food, water and health | null |
By the late 1960s and the early 1970s, RO started to show promising results to replace traditional thermal desalination units. Research took place at state universities in California, at the Dow Chemical Company and DuPont. Many studies focus on ways to optimize desalination systems. The first commercial RO plant, the ... | Desalination | Wikipedia | 500 | 156787 | https://en.wikipedia.org/wiki/Desalination | Technology | Food, water and health | null |
While noting costs are falling, and generally positive about the technology for affluent areas in proximity to oceans, a 2005 study argued, "Desalinated water may be a solution for some water-stress regions, but not for places that are poor, deep in the interior of a continent, or at high elevation. Unfortunately, that... | Desalination | Wikipedia | 485 | 156787 | https://en.wikipedia.org/wiki/Desalination | Technology | Food, water and health | null |
There are currently two technologies with a large majority of the world's desalination capacity: multi-stage flash distillation and reverse osmosis.
Distillation
Solar distillation
Solar distillation mimics the natural water cycle, in which the sun heats sea water enough for evaporation to occur. After evaporation, t... | Desalination | Wikipedia | 437 | 156787 | https://en.wikipedia.org/wiki/Desalination | Technology | Food, water and health | null |
Multiple-effect distillation
Multiple-effect distillation (MED) works through a series of steps called "effects". Incoming water is sprayed onto pipes which are then heated to generate steam. The steam is then used to heat the next batch of incoming sea water. To increase efficiency, the steam used to heat the sea wat... | Desalination | Wikipedia | 458 | 156787 | https://en.wikipedia.org/wiki/Desalination | Technology | Food, water and health | null |
Reverse osmosis uses a thin-film composite membrane, which comprises an ultra-thin, aromatic polyamide thin-film. This polyamide film gives the membrane its transport properties, whereas the remainder of the thin-film composite membrane provides mechanical support. The polyamide film is a dense, void-free polymer with ... | Desalination | Wikipedia | 487 | 156787 | https://en.wikipedia.org/wiki/Desalination | Technology | Food, water and health | null |
Freeze–thaw
Freeze–thaw desalination (or freezing desalination) uses freezing to remove fresh water from salt water. Salt water is sprayed during freezing conditions into a pad where an ice-pile builds up. When seasonal conditions warm, naturally desalinated melt water is recovered. This technique relies on extended p... | Desalination | Wikipedia | 476 | 156787 | https://en.wikipedia.org/wiki/Desalination | Technology | Food, water and health | null |
Other techniques
In a April 2024, researchers from the Australian National University published experimental results of a novel technique for desalination. This technique, thermodiffusive desalination, passes saline water through a channel with a temperature gradient. Species migrate under this temperature gradient in... | Desalination | Wikipedia | 437 | 156787 | https://en.wikipedia.org/wiki/Desalination | Technology | Food, water and health | null |
Cogeneration
Cogeneration is generating useful heat energy and electricity from a single process. Cogeneration can provide usable heat for desalination in an integrated, or "dual-purpose", facility where a power plant provides the energy for desalination. Alternatively, the facility's energy production may be dedicated... | Desalination | Wikipedia | 484 | 156787 | https://en.wikipedia.org/wiki/Desalination | Technology | Food, water and health | null |
Factors that determine the costs for desalination include capacity and type of facility, location, feed water, labor, energy, financing, and concentrate disposal. Costs of desalinating sea water (infrastructure, energy, and maintenance) are generally higher than fresh water from rivers or groundwater, water recycling, ... | Desalination | Wikipedia | 421 | 156787 | https://en.wikipedia.org/wiki/Desalination | Technology | Food, water and health | null |
Intake
In the United States, cooling water intake structures are regulated by the Environmental Protection Agency (EPA). These structures can have the same impacts on the environment as desalination facility intakes. According to EPA, water intake structures cause adverse environmental impact by sucking fish and shellf... | Desalination | Wikipedia | 465 | 156787 | https://en.wikipedia.org/wiki/Desalination | Technology | Food, water and health | null |
Another possibility is making the desalination plant movable, thus avoiding that the brine builds up into a single location (as it keeps being produced by the desalination plant). Some such movable (ship-connected) desalination plants have been constructed.
Brine is denser than seawater and therefore sinks to the ocea... | Desalination | Wikipedia | 408 | 156787 | https://en.wikipedia.org/wiki/Desalination | Technology | Food, water and health | null |
Iodine deficiency
Desalination removes iodine from water and could increase the risk of iodine deficiency disorders. Israeli researchers claimed a possible link between seawater desalination and iodine deficiency, finding iodine deficits among adults exposed to iodine-poor water concurrently with an increasing proport... | Desalination | Wikipedia | 450 | 156787 | https://en.wikipedia.org/wiki/Desalination | Technology | Food, water and health | null |
Low-temperature thermal
Originally stemming from ocean thermal energy conversion research, low-temperature thermal desalination (LTTD) takes advantage of water boiling at low pressure, even at ambient temperature. The system uses pumps to create a low-pressure, low-temperature environment in which water boils at a temp... | Desalination | Wikipedia | 428 | 156787 | https://en.wikipedia.org/wiki/Desalination | Technology | Food, water and health | null |
Ion concentration polarisation (ICP)
In 2022, using a technique that used multiple stages of ion concentration polarisation followed by a single stage of electrodialysis, researchers from MIT manage to create a filterless portable desalination unit, capable of removing both dissolved salts and suspended solids. Design... | Desalination | Wikipedia | 348 | 156787 | https://en.wikipedia.org/wiki/Desalination | Technology | Food, water and health | null |
The idea of the method is in the fact that when the hydrogel is put into contact with aqueous salt solution, it swells absorbing a solution with the ion composition different from the original one. This solution can be easily squeezed out from the gel by means of sieve or microfiltration membrane. The compression of th... | Desalination | Wikipedia | 413 | 156787 | https://en.wikipedia.org/wiki/Desalination | Technology | Food, water and health | null |
Passarell
The Passarell process uses reduced atmospheric pressure rather than heat to drive evaporative desalination. The pure water vapor generated by distillation is then compressed and condensed using an advanced compressor. The compression process improves distillation efficiency by creating the reduced pressure i... | Desalination | Wikipedia | 425 | 156787 | https://en.wikipedia.org/wiki/Desalination | Technology | Food, water and health | null |
Electrokinetic shocks
A process employing electrokinetic shock waves can be used to accomplish membraneless desalination at ambient temperature and pressure. In this process, anions and cations in salt water are exchanged for carbonate anions and calcium cations, respectively using electrokinetic shockwaves. Calcium a... | Desalination | Wikipedia | 328 | 156787 | https://en.wikipedia.org/wiki/Desalination | Technology | Food, water and health | null |
Perth began operating a reverse osmosis seawater desalination plant in 2006. The Perth desalination plant is powered partially by renewable energy from the Emu Downs Wind Farm.
A desalination plant now operates in Sydney, and the Wonthaggi desalination plant was under construction in Wonthaggi, Victoria. A wind farm a... | Desalination | Wikipedia | 440 | 156787 | https://en.wikipedia.org/wiki/Desalination | Technology | Food, water and health | null |
Before 2015, the largest desalination plant in the United States was at Tampa Bay, Florida, which began desalinizing 25 million gallons (95000 m3) of water per day in December 2007. In the United States, the cost of desalination is $3.06 for 1,000 gallons, or 81 cents per cubic meter. In the United States, California, ... | Desalination | Wikipedia | 155 | 156787 | https://en.wikipedia.org/wiki/Desalination | Technology | Food, water and health | null |
As of 2008, "World-wide, 13,080 desalination plants produce more than 12 billion gallons of water a day, according to the International Desalination Association." An estimate in 2009 found that the worldwide desalinated water supply will triple between 2008 and 2020.
One of the world's largest desalination hubs is the... | Desalination | Wikipedia | 498 | 156787 | https://en.wikipedia.org/wiki/Desalination | Technology | Food, water and health | null |
Micro ribonucleic acid (microRNA, miRNA, μRNA) are small, single-stranded, non-coding RNA molecules containing 21–23 nucleotides. Found in plants, animals, and even some viruses, miRNAs are involved in RNA silencing and post-transcriptional regulation of gene expression. miRNAs base-pair to complementary sequences in m... | MicroRNA | Wikipedia | 475 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
The first miRNA was discovered in 1993 by a group led by Victor Ambros and including Lee and Feinbaum. However, additional insight into its mode of action required simultaneously published work by Gary Ruvkun's team, including Wightman and Ha. These groups published back-to-back papers on the lin-4 gene, which was know... | MicroRNA | Wikipedia | 447 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
Nomenclature
Under a standard nomenclature system, names are assigned to experimentally confirmed miRNAs before publication. The prefix "miR" is followed by a dash and a number, the latter often indicating order of naming. For example, miR-124 was named and likely discovered prior to miR-456. A capitalized "miR-" refer... | MicroRNA | Wikipedia | 387 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
When two mature microRNAs originate from opposite arms of the same pre-miRNA and are found in roughly similar amounts, they are denoted with a -3p or -5p suffix. (In the past, this distinction was also made with "s" (sense) and "as" (antisense)). However, the mature microRNA found from one arm of the hairpin is usually... | MicroRNA | Wikipedia | 453 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
The DNA template is not the final word on mature miRNA production: 6% of human miRNAs show RNA editing (IsomiRs), the site-specific modification of RNA sequences to yield products different from those encoded by their DNA. This increases the diversity and scope of miRNA action beyond that implicated from the genome alo... | MicroRNA | Wikipedia | 319 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
The double-stranded RNA (dsRNA) structure of the hairpins in a pri-miRNA is recognized by a nuclear protein known as DiGeorge Syndrome Critical Region 8 (DGCR8 or "Pasha" in invertebrates), named for its association with DiGeorge Syndrome. DGCR8 associates with the enzyme Drosha, a protein that cuts RNA, to form the Mi... | MicroRNA | Wikipedia | 505 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
Cytoplasmic processing
In the cytoplasm, the pre-miRNA hairpin is cleaved by the RNase III enzyme Dicer. This endoribonuclease interacts with 5' and 3' ends of the hairpin and cuts away the loop joining the 3' and 5' arms, yielding an imperfect miRNA:miRNA* duplex about 22 nucleotides in length. Overall hairpin length ... | MicroRNA | Wikipedia | 477 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
The mature miRNA is part of an active RNA-induced silencing complex (RISC) containing Dicer and many associated proteins. RISC is also known as a microRNA ribonucleoprotein complex (miRNP); A RISC with incorporated miRNA is sometimes referred to as a "miRISC."
Dicer processing of the pre-miRNA is thought to be coupled... | MicroRNA | Wikipedia | 403 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
Additional RISC components include TRBP [human immunodeficiency virus (HIV) transactivating response RNA (TAR) binding protein], PACT (protein activator of the interferon-induced protein kinase), the SMN complex, fragile X mental retardation protein (FMRP), Tudor staphylococcal nuclease-domain-containing protein (Tudor... | MicroRNA | Wikipedia | 460 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
Decay of mature miRNAs in Caenorhabditis elegans is mediated by the 5'-to-3' exoribonuclease XRN2, also known as Rat1p. In plants, SDN (small RNA degrading nuclease) family members degrade miRNAs in the opposite (3'-to-5') direction. Similar enzymes are encoded in animal genomes, but their roles have not been described... | MicroRNA | Wikipedia | 399 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
For partially complementary microRNAs to recognise their targets, nucleotides 2–7 of the miRNA (its 'seed region') must be perfectly complementary. Animal miRNAs inhibit protein translation of the target mRNA (this is present but less common in plants). Partially complementary microRNAs can also speed up deadenylation,... | MicroRNA | Wikipedia | 464 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
Interactions between microRNAs and complementary sequences on genes and even pseudogenes that share sequence homology are thought to be a back channel of communication regulating expression levels between paralogous genes (genes having a similar structure indicating divergence from a common ancestral gene). Given the n... | MicroRNA | Wikipedia | 396 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
New microRNAs are created in multiple ways. Novel microRNAs can originate from the random formation of hairpins in "non-coding" sections of DNA (i.e. introns or intergene regions), but also by the duplication and modification of existing microRNAs. microRNAs can also form from inverted duplications of protein-coding se... | MicroRNA | Wikipedia | 497 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
Across all species, in excess of 5000 different miRNAs had been identified by March 2010. Whilst short RNA sequences (50 – hundreds of base pairs) of a broadly comparable function occur in bacteria, bacteria lack true microRNAs.
Experimental detection and manipulation
While researchers focused on miRNA expression in p... | MicroRNA | Wikipedia | 391 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
High-throughput quantification of miRNAs is error prone, for the larger variance (compared to mRNAs) that comes with methodological problems. mRNA-expression is therefore often analyzed to check for miRNA-effects in their levels (e.g. in). Databases can be used to pair mRNA- and miRNA-data that predict miRNA-targets ba... | MicroRNA | Wikipedia | 445 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
Furthermore, specific miRNAs may be associated with certain histological subtypes of colorectal cancer. For instance, expression levels of miR-205 and miR-373 have been shown to be increased in mucinous colorectal cancers and mucin-producing Ulcerative Colitis-associated colon cancers, but not in sporadic colonic adeno... | MicroRNA | Wikipedia | 490 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
Germline mutations in DNA repair genes cause only 2–5% of colon cancer cases. However, altered expression of microRNAs, causing DNA repair deficiencies, are frequently associated with cancers and may be an important causal factor. Among 68 sporadic colon cancers with reduced expression of the DNA mismatch repair protei... | MicroRNA | Wikipedia | 301 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
HMGA proteins (HMGA1a, HMGA1b and HMGA2) are implicated in cancer, and expression of these proteins is regulated by microRNAs. HMGA expression is almost undetectable in differentiated adult tissues, but is elevated in many cancers. HMGA proteins are polypeptides of ~100 amino acid residues characterized by a modular se... | MicroRNA | Wikipedia | 477 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
Murine microRNA-712 is a potential biomarker (i.e. predictor) for atherosclerosis, a cardiovascular disease of the arterial wall associated with lipid retention and inflammation. Non-laminar blood flow also correlates with development of atherosclerosis as mechanosenors of endothelial cells respond to the shear force o... | MicroRNA | Wikipedia | 480 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
TIMP3 also decreases the expression of TNFα (a pro-inflammatory regulator) during turbulent flow. Activity of TNFα in turbulent flow was measured by the expression of TNFα-converting enzyme (TACE) in blood. TNFα decreased if miR-712 was inhibited or TIMP3 overexpressed, suggesting that miR-712 and TIMP3 regulate TACE a... | MicroRNA | Wikipedia | 267 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
Kidney disease
Targeted deletion of Dicer in the FoxD1-derived renal progenitor cells in a murine model resulted in a complex renal phenotype including expansion of nephron progenitors, fewer renin cells, smooth muscle arterioles, progressive mesangial loss and glomerular aneurysms. High throughput whole transcriptome ... | MicroRNA | Wikipedia | 408 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
Nervous system
MiRNAs are crucial for the healthy development and function of the nervous system. Previous studies demonstrate that miRNAs can regulate neuronal differentiation and maturation at various stages. MiRNAs also play important roles in synaptic development (such as dendritogenesis or spine morphogenesis) and... | MicroRNA | Wikipedia | 504 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
miRNAs can be either upregulated or downregulated in response to chronic alcohol use. miR-206 expression increased in the prefrontal cortex of alcohol-dependent rats, targeting the transcription factor brain-derived neurotrophic factor (BDNF) and ultimately reducing its expression. BDNF plays a critical role in the for... | MicroRNA | Wikipedia | 474 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
Another class of miRNAs that regulate insulin resistance, obesity, and diabetes, is the let-7 family. Let-7 accumulates in human tissues during the course of aging. When let-7 was ectopically overexpressed to mimic accelerated aging, mice became insulin-resistant, and thus more prone to high fat diet-induced obesity an... | MicroRNA | Wikipedia | 477 | 156964 | https://en.wikipedia.org/wiki/MicroRNA | Biology and health sciences | Molecular biology | Biology |
The cytoskeleton is a complex, dynamic network of interlinking protein filaments present in the cytoplasm of all cells, including those of bacteria and archaea. In eukaryotes, it extends from the cell nucleus to the cell membrane and is composed of similar proteins in the various organisms. It is composed of three main... | Cytoskeleton | Wikipedia | 358 | 156970 | https://en.wikipedia.org/wiki/Cytoskeleton | Biology and health sciences | Organelles and other cell parts | null |
A large-scale example of an action performed by the cytoskeleton is muscle contraction. This is carried out by groups of highly specialized cells working together. A main component in the cytoskeleton that helps show the true function of this muscle contraction is the microfilament. Microfilaments are composed of the m... | Cytoskeleton | Wikipedia | 438 | 156970 | https://en.wikipedia.org/wiki/Cytoskeleton | Biology and health sciences | Organelles and other cell parts | null |
Eukaryotic cells contain three main kinds of cytoskeletal filaments: microfilaments, microtubules, and intermediate filaments. In neurons the intermediate filaments are known as neurofilaments. Each type is formed by the polymerization of a distinct type of protein subunit and has its own characteristic shape and intr... | Cytoskeleton | Wikipedia | 473 | 156970 | https://en.wikipedia.org/wiki/Cytoskeleton | Biology and health sciences | Organelles and other cell parts | null |
A number of small-molecule cytoskeletal drugs have been discovered that interact with actin and microtubules. These compounds have proven useful in studying the cytoskeleton, and several have clinical applications.
Microfilaments
Microfilaments, also known as actin filaments, are composed of linear polymers of G-acti... | Cytoskeleton | Wikipedia | 329 | 156970 | https://en.wikipedia.org/wiki/Cytoskeleton | Biology and health sciences | Organelles and other cell parts | null |
Intermediate filaments are a part of the cytoskeleton of many eukaryotic cells. These filaments, averaging 10 nanometers in diameter, are more stable (strongly bound) than microfilaments, and heterogeneous constituents of the cytoskeleton. Like actin filaments, they function in the maintenance of cell-shape by bearing ... | Cytoskeleton | Wikipedia | 507 | 156970 | https://en.wikipedia.org/wiki/Cytoskeleton | Biology and health sciences | Organelles and other cell parts | null |
Microtubules are hollow cylinders about 23 nm in diameter (lumen diameter of approximately 15 nm), most commonly comprising 13 protofilaments that, in turn, are polymers of alpha and beta tubulin. They have a very dynamic behavior, binding GTP for polymerization. They are commonly organized by the centrosome.
In nine ... | Cytoskeleton | Wikipedia | 399 | 156970 | https://en.wikipedia.org/wiki/Cytoskeleton | Biology and health sciences | Organelles and other cell parts | null |
Septins are a group of the highly conserved GTP binding proteins found in eukaryotes. Different septins form protein complexes with each other. These can assemble to filaments and rings. Therefore, septins can be considered part of the cytoskeleton. The function of septins in cells include serving as a localized attach... | Cytoskeleton | Wikipedia | 366 | 156970 | https://en.wikipedia.org/wiki/Cytoskeleton | Biology and health sciences | Organelles and other cell parts | null |
Prior to the work of Jones et al., 2001, the cell wall was believed to be the deciding factor for many bacterial cell shapes, including rods and spirals. When studied, many misshapen bacteria were found to have mutations linked to development of a cell envelope. The cytoskeleton was once thought to be a feature only of... | Cytoskeleton | Wikipedia | 470 | 156970 | https://en.wikipedia.org/wiki/Cytoskeleton | Biology and health sciences | Organelles and other cell parts | null |
Some plasmids encode a separate system that involves an actin-like protein ParM. Filaments of ParM exhibit dynamic instability, and may partition plasmid DNA into the dividing daughter cells by a mechanism analogous to that used by microtubules during eukaryotic mitosis.
Crescentin
The bacterium Caulobacter crescentus... | Cytoskeleton | Wikipedia | 503 | 156970 | https://en.wikipedia.org/wiki/Cytoskeleton | Biology and health sciences | Organelles and other cell parts | null |
The cytoskeleton changes the mechanics of the cell in response to detected forces. For example, increasing tension within the plasma membrane makes it more likely that ion channels will open, which increases ion conductance and makes cellular change ion influx or efflux much more likely. Moreover, the mechanical proper... | Cytoskeleton | Wikipedia | 481 | 156970 | https://en.wikipedia.org/wiki/Cytoskeleton | Biology and health sciences | Organelles and other cell parts | null |
Tubulin-like proteins are tubulin in eukaryotes and FtsZ, TubZ, RepX in prokaryotes. Actin-like proteins are actin in eukaryotes and MreB, FtsA in prokaryotes. An example of a WACA-proteins, which are mostly found in prokaryotes, is MinD. Examples for intermediate filaments, which have almost exclusively been found in ... | Cytoskeleton | Wikipedia | 473 | 156970 | https://en.wikipedia.org/wiki/Cytoskeleton | Biology and health sciences | Organelles and other cell parts | null |
In probability theory, the law of large numbers (LLN) is a mathematical law that states that the average of the results obtained from a large number of independent random samples converges to the true value, if it exists. More formally, the LLN states that given a sample of independent and identically distributed value... | Law of large numbers | Wikipedia | 464 | 157055 | https://en.wikipedia.org/wiki/Law%20of%20large%20numbers | Mathematics | Statistics and probability | null |
For example, a fair coin toss is a Bernoulli trial. When a fair coin is flipped once, the theoretical probability that the outcome will be heads is equal to . Therefore, according to the law of large numbers, the proportion of heads in a "large" number of coin flips "should be" roughly . In particular, the proportion o... | Law of large numbers | Wikipedia | 486 | 157055 | https://en.wikipedia.org/wiki/Law%20of%20large%20numbers | Mathematics | Statistics and probability | null |
The Italian mathematician Gerolamo Cardano (1501–1576) stated without proof that the accuracies of empirical statistics tend to improve with the number of trials. This was then formalized as a law of large numbers. A special form of the LLN (for a binary random variable) was first proved by Jacob Bernoulli. It took him... | Law of large numbers | Wikipedia | 485 | 157055 | https://en.wikipedia.org/wiki/Law%20of%20large%20numbers | Mathematics | Statistics and probability | null |
(Lebesgue integrability of Xj means that the expected value E(Xj) exists according to Lebesgue integration and is finite. It does not mean that the associated probability measure is absolutely continuous with respect to Lebesgue measure.)
Introductory probability texts often additionally assume identical finite varian... | Law of large numbers | Wikipedia | 301 | 157055 | https://en.wikipedia.org/wiki/Law%20of%20large%20numbers | Mathematics | Statistics and probability | null |
As mentioned earlier, the weak law applies in the case of i.i.d. random variables, but it also applies in some other cases. For example, the variance may be different for each random variable in the series, keeping the expected value constant. If the variances are bounded, then the law applies, as shown by Chebyshev as... | Law of large numbers | Wikipedia | 494 | 157055 | https://en.wikipedia.org/wiki/Law%20of%20large%20numbers | Mathematics | Statistics and probability | null |
The strong law applies to independent identically distributed random variables having an expected value (like the weak law). This was proved by Kolmogorov in 1930. It can also apply in other cases. Kolmogorov also showed, in 1933, that if the variables are independent and identically distributed, then for the average t... | Law of large numbers | Wikipedia | 510 | 157055 | https://en.wikipedia.org/wiki/Law%20of%20large%20numbers | Mathematics | Statistics and probability | null |
This result is useful to derive consistency of a large class of estimators (see Extremum estimator).
Borel's law of large numbers
Borel's law of large numbers, named after Émile Borel, states that if an experiment is repeated a large number of times, independently under identical conditions, then the proportion of tim... | Law of large numbers | Wikipedia | 497 | 157055 | https://en.wikipedia.org/wiki/Law%20of%20large%20numbers | Mathematics | Statistics and probability | null |
μ is a constant, which implies that convergence in distribution to μ and convergence in probability to μ are equivalent (see Convergence of random variables.) Therefore,
This shows that the sample mean converges in probability to the derivative of the characteristic function at the origin, as long as the latter exists... | Law of large numbers | Wikipedia | 493 | 157055 | https://en.wikipedia.org/wiki/Law%20of%20large%20numbers | Mathematics | Statistics and probability | null |
Applications
One application of the LLN is an important method of approximation known as the Monte Carlo method, which uses a random sampling of numbers to approximate numerical results. The algorithm to compute an integral of f(x) on an interval [a,b] is as follows:
Simulate uniform random variables X1, X2, ..., Xn... | Law of large numbers | Wikipedia | 405 | 157055 | https://en.wikipedia.org/wiki/Law%20of%20large%20numbers | Mathematics | Statistics and probability | null |
In statistics, correlation or dependence is any statistical relationship, whether causal or not, between two random variables or bivariate data. Although in the broadest sense, "correlation" may indicate any type of association, in statistics it usually refers to the degree to which a pair of variables are linearly r... | Correlation | Wikipedia | 452 | 157057 | https://en.wikipedia.org/wiki/Correlation | Mathematics | Statistics and probability | null |
The most familiar measure of dependence between two quantities is the Pearson product-moment correlation coefficient (PPMCC), or "Pearson's correlation coefficient", commonly called simply "the correlation coefficient". It is obtained by taking the ratio of the covariance of the two variables in question of our numeric... | Correlation | Wikipedia | 479 | 157057 | https://en.wikipedia.org/wiki/Correlation | Mathematics | Statistics and probability | null |
For example, suppose the random variable is symmetrically distributed about zero, and . Then is completely determined by , so that and are perfectly dependent, but their correlation is zero; they are uncorrelated. However, in the special case when and are jointly normal, uncorrelatedness is equivalent to independ... | Correlation | Wikipedia | 508 | 157057 | https://en.wikipedia.org/wiki/Correlation | Mathematics | Statistics and probability | null |
(0, 1), (10, 100), (101, 500), (102, 2000).
As we go from each pair to the next pair increases, and so does . This relationship is perfect, in the sense that an increase in is always accompanied by an increase in . This means that we have a perfect rank correlation, and both Spearman's and Kendall's correlation coef... | Correlation | Wikipedia | 483 | 157057 | https://en.wikipedia.org/wiki/Correlation | Mathematics | Statistics and probability | null |
One important disadvantage of the alternative, more general measures is that, when used to test whether two variables are associated, they tend to have lower power compared to Pearson's correlation when the data follow a multivariate normal distribution. This is an implication of the No free lunch theorem. To detect al... | Correlation | Wikipedia | 503 | 157057 | https://en.wikipedia.org/wiki/Correlation | Mathematics | Statistics and probability | null |
Various correlation measures in use may be undefined for certain joint distributions of and . For example, the Pearson correlation coefficient is defined in terms of moments, and hence will be undefined if the moments are undefined. Measures of dependence based on quantiles are always defined. Sample-based statisti... | Correlation | Wikipedia | 489 | 157057 | https://en.wikipedia.org/wiki/Correlation | Mathematics | Statistics and probability | null |
In exploratory data analysis, the iconography of correlations consists in replacing a correlation matrix by a diagram where the "remarkable" correlations are represented by a solid line (positive correlation), or a dotted line (negative correlation).
Nearest valid correlation matrix
In some applications (e.g., buildin... | Correlation | Wikipedia | 493 | 157057 | https://en.wikipedia.org/wiki/Correlation | Mathematics | Statistics and probability | null |
The Pearson correlation coefficient indicates the strength of a linear relationship between two variables, but its value generally does not completely characterize their relationship. In particular, if the conditional mean of given , denoted , is not linear in , the correlation coefficient will not fully determine the... | Correlation | Wikipedia | 507 | 157057 | https://en.wikipedia.org/wiki/Correlation | Mathematics | Statistics and probability | null |
where and are the expected values of and respectively, and and are the standard deviations of and respectively.
The empirical correlation is an estimate of the correlation coefficient A distribution estimate for is given by
where is the Gaussian hypergeometric function.
This density is both a Bayesia... | Correlation | Wikipedia | 66 | 157057 | https://en.wikipedia.org/wiki/Correlation | Mathematics | Statistics and probability | null |
In probability theory and statistics, covariance is a measure of the joint variability of two random variables.
The sign of the covariance, therefore, shows the tendency in the linear relationship between the variables. If greater values of one variable mainly correspond with greater values of the other variable, and ... | Covariance | Wikipedia | 506 | 157059 | https://en.wikipedia.org/wiki/Covariance | Mathematics | Statistics and probability | null |
It can also be equivalently expressed, without directly referring to the means, as
More generally, if there are possible realizations of , namely but with possibly unequal probabilities for , then the covariance is
In the case where two discrete random variables and have a joint probability distribution, represe... | Covariance | Wikipedia | 508 | 157059 | https://en.wikipedia.org/wiki/Covariance | Mathematics | Statistics and probability | null |
and whose covariance is positive are called positively correlated, which implies if then likely . Conversely, and with negative covariance are negatively correlated, and if then likely .
Relationship to inner products
Many of the properties of covariance can be extracted elegantly by observing that it satisfies ... | Covariance | Wikipedia | 491 | 157059 | https://en.wikipedia.org/wiki/Covariance | Mathematics | Statistics and probability | null |
This is a direct result of the linearity of expectation and is useful
when applying a linear transformation, such as a whitening transformation, to a vector.
Cross-covariance matrix of real random vectors
For real random vectors and , the cross-covariance matrix is equal to
where is the transpose of the vector (... | Covariance | Wikipedia | 465 | 157059 | https://en.wikipedia.org/wiki/Covariance | Mathematics | Statistics and probability | null |
In the theory of evolution and natural selection, the price equation describes how a genetic trait changes in frequency over time. The equation uses a covariance between a trait and fitness, to give a mathematical description of evolution and natural selection. It provides a way to understand the effects that gene tran... | Covariance | Wikipedia | 385 | 157059 | https://en.wikipedia.org/wiki/Covariance | Mathematics | Statistics and probability | null |
In mathematics, the cross product or vector product (occasionally directed area product, to emphasize its geometric significance) is a binary operation on two vectors in a three-dimensional oriented Euclidean vector space (named here ), and is denoted by the symbol . Given two linearly independent vectors and , the c... | Cross product | Wikipedia | 397 | 157092 | https://en.wikipedia.org/wiki/Cross%20product | Mathematics | Algebra | null |
The product can be generalized in various ways, using the orientation and metric structure just as for the traditional 3-dimensional cross product; one can, in dimensions, take the product of vectors to produce a vector perpendicular to all of them. But if the product is limited to non-trivial binary products with ve... | Cross product | Wikipedia | 503 | 157092 | https://en.wikipedia.org/wiki/Cross%20product | Mathematics | Algebra | null |
As the cross product operator depends on the orientation of the space, in general the cross product of two vectors is not a "true" vector, but a pseudovector. See for more detail.
Names and origin
In 1842, William Rowan Hamilton first described the algebra of quaternions and the non-commutative Hamilton product. In... | Cross product | Wikipedia | 447 | 157092 | https://en.wikipedia.org/wiki/Cross%20product | Mathematics | Algebra | null |
These equalities, together with the distributivity and linearity of the cross product (though neither follows easily from the definition given above), are sufficient to determine the cross product of any two vectors a and b. Each vector can be defined as the sum of three orthogonal components parallel to the standard b... | Cross product | Wikipedia | 498 | 157092 | https://en.wikipedia.org/wiki/Cross%20product | Mathematics | Algebra | null |
Since the result of the scalar triple product may be negative, the volume of the parallelepiped is given by its absolute value:
Because the magnitude of the cross product goes by the sine of the angle between its arguments, the cross product can be thought of as a measure of perpendicularity in the same way that the d... | Cross product | Wikipedia | 512 | 157092 | https://en.wikipedia.org/wiki/Cross%20product | Mathematics | Algebra | null |
More generally, the cross product obeys the following identity under matrix transformations:
where is a 3-by-3 matrix and is the transpose of the inverse and is the cofactor matrix. It can be readily seen how this formula reduces to the former one if is a rotation matrix. If is a 3-by-3 symmetric matrix applied t... | Cross product | Wikipedia | 508 | 157092 | https://en.wikipedia.org/wiki/Cross%20product | Mathematics | Algebra | null |
For the cross product , there are multiple vectors that give the same value of . As a result, it is not possible to rearrange this equation to yield a unique solution for in terms of and . Nevertheless, it is possible to find a family of solutions for , which are
where is an arbitrary constant.
This can be derive... | Cross product | Wikipedia | 487 | 157092 | https://en.wikipedia.org/wiki/Cross%20product | Mathematics | Algebra | null |
The columns [a]×,i of the skew-symmetric matrix for a vector a can be also obtained by calculating the cross product with unit vectors. That is,
or
where is the outer product operator.
Also, if a is itself expressed as a cross product:
then
This result can be generalized to higher dimensions using geometric algeb... | Cross product | Wikipedia | 483 | 157092 | https://en.wikipedia.org/wiki/Cross%20product | Mathematics | Algebra | null |
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