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Intermediate positional identities between the stump and the distal tip are then filled in through a process called intercalation. Motor neurons, muscle, and blood vessels grow with the regenerated limb, and reestablish the connections that were present prior to amputation. The time that this entire process takes varies according to the age of the animal, ranging from about a month to around three months in the adult and then the limb becomes fully functional. Researchers at Australian Regenerative Medicine Institute at Monash University have published that when macrophages, which eat up material debris, were removed, salamanders lost their ability to regenerate and formed scarred tissue instead. The axolotl salamander Ambystoma mexicanum, an organism with exceptional limb regenerative capabilities, likely undergoes epigenetic alterations in its blastema cells that enhance expression of genes involved in limb regeneration. The Axolotl has very little blood and has an excess of epidermal cells. This allows the affected area to then flourish with epidermal cells and continued gene expression allows the area to regenerate to its natural being. In spite of the historically few researchers studying limb regeneration, remarkable progress has been made recently in establishing the neotenous amphibian the axolotl (Ambystoma mexicanum) as a model genetic organism. This progress has been facilitated by advances in genomics, bioinformatics, and somatic cell transgenesis in other fields, that have created the opportunity to investigate the mechanisms of important biological properties, such as limb regeneration, in the axolotl. The Ambystoma Genetic Stock Center (AGSC) is a self-sustaining, breeding colony of the axolotl supported by the National Science Foundation as a Living Stock Collection. Located at the University of Kentucky, the AGSC is dedicated to supplying genetically well-characterized axolotl embryos, larvae, and adults to laboratories throughout the United States and abroad. An NIH-funded NCRR grant has led to the establishment
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"page_id": 854081,
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"title": "Regeneration (biology)"
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of the Ambystoma EST database, the Salamander Genome Project (SGP) that has led to the creation of the first amphibian gene map and several annotated molecular data bases, and the creation of the research community web portal. In 2022, a first spatiotemporal map revealed key insights about axolotl brain regeneration, also providing the interactive Axolotl Regenerative Telencephalon Interpretation via Spatiotemporal Transcriptomic Atlas. ==== Frog model ==== Anurans (frogs) can only regenerate their limbs during embryonic development. Reactive oxygen species (ROS) appear to be required for a regeneration response in the anuran larvae. ROS production is essential to activate the Wnt signaling pathway, which has been associated with regeneration in other systems. Once the limb skeleton has developed in frogs, regeneration does not occur (Xenopus can grow a cartilaginous spike after amputation). The adult Xenopus laevis is used as a model organism for regenerative medicine. In 2022, a cocktail of drugs and hormones (1,4-DPCA, BDNF, growth hormone, resolvin D5, and retinoic acid), in a single dose lasting 24 hours, was shown to trigger long-term leg regeneration in adult X. laevis. Instead of a single spike, a paddle-shaped growth is obtained at the end of the limb by 18 months. === Hydra === Hydra is a genus of freshwater polyp in the phylum Cnidaria with highly proliferative stem cells that gives them the ability to regenerate their entire body. Any fragment larger than a few hundred epithelial cells that is isolated from the body has the ability to regenerate into a smaller version of itself. The high proportion of stem cells in the hydra supports its efficient regenerative ability. Regeneration among hydra occurs as foot regeneration arising from the basal part of the body, and head regeneration, arising from the apical region. Regeneration tissues that are cut from the gastric region contain
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{
"page_id": 854081,
"source": null,
"title": "Regeneration (biology)"
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polarity, which allows them to distinguish between regenerating a head in the apical end and a foot in the basal end so that both regions are present in the newly regenerated organism. Head regeneration requires complex reconstruction of the area, while foot regeneration is much simpler, similar to tissue repair. In both foot and head regeneration, however, there are two distinct molecular cascades that occur once the tissue is wounded: early injury response and a subsequent, signal-driven pathway of the regenerating tissue that leads to cellular differentiation. This early-injury response includes epithelial cell stretching for wound closure, the migration of interstitial progenitors towards the wound, cell death, phagocytosis of cell debris, and reconstruction of the extracellular matrix. Regeneration in hydra has been defined as morphallaxis, the process where regeneration results from remodeling of existing material without cellular proliferation. If a hydra is cut into two pieces, the remaining severed sections form two fully functional and independent hydra, approximately the same size as the two smaller severed sections. This occurs through the exchange and rearrangement of soft tissues without the formation of new material. During Hydra head regeneration there are coordinated gene expression and chromatin regulation changes. An enhancer is a short DNA sequence (50–1500 base pairs) that can be bound by transcription factors to increase the transcription of a particular gene. In the enhancer regions that are activated during head regeneration, a set of transcription factor motifs commonly occur that appear to facilitate coordinated gene expression. === Aves (birds) === Owing to a limited literature on the subject, birds are believed to have very limited regenerative abilities as adults. Some studies on roosters have suggested that birds can adequately regenerate some parts of the limbs and depending on the conditions in which regeneration takes place, such as age of the
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{
"page_id": 854081,
"source": null,
"title": "Regeneration (biology)"
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animal, the inter-relationship of the injured tissue with other muscles, and the type of operation, can involve complete regeneration of some musculoskeletal structure. Werber and Goldschmidt (1909) found that the goose and duck were capable of regenerating their beaks after partial amputation and Sidorova (1962) observed liver regeneration via hypertrophy in roosters. Birds are also capable of regenerating the hair cells in their cochlea following noise damage or ototoxic drug damage. Despite this evidence, contemporary studies suggest reparative regeneration in avian species is limited to periods during embryonic development. An array of molecular biology techniques have been successful in manipulating cellular pathways known to contribute to spontaneous regeneration in chick embryos. For instance, removing a portion of the elbow joint in a chick embryo via window excision or slice excision and comparing joint tissue specific markers and cartilage markers showed that window excision allowed 10 out of 20 limbs to regenerate and expressed joint genes similarly to a developing embryo. In contrast, slice excision did not allow the joint to regenerate due to the fusion of the skeletal elements seen by an expression of cartilage markers. Similar to the physiological regeneration of hair in mammals, birds can regenerate their feathers in order to repair damaged feathers or to attract mates with their plumage. Typically, seasonal changes that are associated with breeding seasons will prompt a hormonal signal for birds to begin regenerating feathers. This has been experimentally induced using thyroid hormones in the Rhode Island Red Fowls. === Mammals === Mammals are capable of cellular and physiological regeneration, but have generally poor reparative regenerative ability across the group. Examples of physiological regeneration in mammals include epithelial renewal (e.g., skin and intestinal tract), red blood cell replacement, antler regeneration and hair cycling. Male deer lose their antlers annually during the months
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{
"page_id": 854081,
"source": null,
"title": "Regeneration (biology)"
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of January to April then through regeneration are able to regrow them as an example of physiological regeneration. A deer antler is the only appendage of a mammal that can be regrown every year. While reparative regeneration is a rare phenomenon in mammals, it does occur. A well-documented example is regeneration of the digit tip distal to the nail bed. Reparative regeneration has also been observed in rabbits, pikas and African spiny mice. In 2012, researchers discovered that two species of African spiny mice, Acomys kempi and Acomys percivali, were capable of completely regenerating the autotomically released or otherwise damaged tissue. These species can regrow hair follicles, skin, sweat glands, fur and cartilage. In addition to these two species, subsequent studies demonstrated that Acomys cahirinus could regenerate skin and excised tissue in the ear pinna. Despite these examples, it is generally accepted that adult mammals have limited regenerative capacity compared to most vertebrate embryos/larvae, adult salamanders and fish. But the regeneration therapy approach of Robert O. Becker, using electrical stimulation, has shown promising results for rats and mammals in general. Some researchers have also claimed that the MRL mouse strain exhibits enhanced regenerative abilities. Work comparing the differential gene expression of scarless healing MRL mice and a poorly-healing C57BL/6 mouse strain, identified 36 genes differentiating the healing process between MRL mice and other mice. Study of the regenerative process in these animals is aimed at discovering how to duplicate them in humans, such as deactivation of the p21 gene. However, recent work has shown that MRL mice actually close small ear holes with scar tissue, rather than regeneration as originally claimed. MRL mice are not protected against myocardial infarction; heart regeneration in adult mammals (neocardiogenesis) is limited, because heart muscle cells are nearly all terminally differentiated. MRL mice show the
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{
"page_id": 854081,
"source": null,
"title": "Regeneration (biology)"
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same amount of cardiac injury and scar formation as normal mice after a heart attack. However, recent studies provide evidence that this may not always be the case, and that MRL mice can regenerate after heart damage. ==== Humans ==== The regrowth of lost tissues or organs in the human body is being researched. Some tissues such as skin regrow quite readily; others have been thought to have little or no capacity for regeneration, but ongoing research suggests that there is some hope for a variety of tissues and organs. Human organs that have been regenerated include the bladder, vagina and the penis. As are all metazoans, humans are capable of physiological regeneration (i.e. the replacement of cells during homeostatic maintenance that does not necessitate injury). For example, the regeneration of red blood cells via erythropoiesis occurs through the maturation of erythrocytes from hematopoietic stem cells in the bone marrow, their subsequent circulation for around 90 days in the blood stream, and their eventual cell-death in the spleen. Another example of physiological regeneration is the sloughing and rebuilding of a functional endometrium during each menstrual cycle in females in response to varying levels of circulating estrogen and progesterone. However, humans are limited in their capacity for reparative regeneration, which occurs in response to injury. One of the most studied regenerative responses in humans is the hypertrophy of the liver following liver injury. For example, the original mass of the liver is re-established in direct proportion to the amount of liver removed following partial hepatectomy, which indicates that signals from the body regulate liver mass precisely, both positively and negatively, until the desired mass is reached. This response is considered cellular regeneration (a form of compensatory hypertrophy) where the function and mass of the liver is regenerated through the proliferation of
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"page_id": 854081,
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existing mature hepatic cells (mainly hepatocytes), but the exact morphology of the liver is not regained. This process is driven by growth factor and cytokine regulated pathways. The normal sequence of inflammation and regeneration does not function accurately in cancer. Specifically, cytokine stimulation of cells leads to expression of genes that change cellular functions and suppress the immune response. Adult neurogenesis is also a form of cellular regeneration. For example, hippocampal neuron renewal occurs in normal adult humans at an annual turnover rate of 1.75% of neurons. Cardiac myocyte renewal has been found to occur in normal adult humans, and at a higher rate in adults following acute heart injury such as infarction. Even in adult myocardium following infarction, proliferation is only found in around 1% of myocytes around the area of injury, which is not enough to restore function of cardiac muscle. However, this may be an important target for regenerative medicine as it implies that regeneration of cardiomyocytes, and consequently of myocardium, can be induced. Another example of reparative regeneration in humans is fingertip regeneration, which occurs after phalanx amputation distal to the nail bed (especially in children) and rib regeneration, which occurs following osteotomy for scoliosis treatment (though usually regeneration is only partial and may take up to one year). Yet another example of regeneration in humans is vas deferens regeneration, which occurs after a vasectomy and which results in vasectomy failure. === Reptiles === The ability and degree of regeneration in reptiles differs among the various species (see ), but the most notable and well-studied occurrence is tail-regeneration in lizards. In addition to lizards, regeneration has been observed in the tails and maxillary bone of crocodiles and adult neurogenesis has also been noted. Tail regeneration has never been observed in snakes, but see. Lizards possess the
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{
"page_id": 854081,
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highest regenerative capacity as a group. Following autotomous tail loss, epimorphic regeneration of a new tail proceeds through a blastema-mediated process that results in a functionally and morphologically similar structure. === Chondrichthyes === It has been estimated that the average shark loses about 30,000 to 40,000 teeth in a lifetime. Leopard sharks routinely replace their teeth every 9–12 days and this is an example of physiological regeneration. This can occur because shark teeth are not attached to a bone, but instead are developed within a bony cavity. Rhodopsin regeneration has been studied in skates and rays. After complete photo-bleaching, rhodopsin can completely regenerate within 2 hours in the retina. White bamboo sharks can regenerate at least two-thirds of their liver and this has been linked to three micro RNAs, xtr-miR-125b, fru-miR-204, and has-miR-142-3p_R-. In one study, two-thirds of the liver was removed and within 24 hours more than half of the liver had undergone hypertrophy. Some sharks can regenerate scales and even skin following damage. Within two weeks of skin wounding, mucus is secreted into the wound and this initiates the healing process. One study showed that the majority of the wounded area was regenerated within 4 months, but the regenerated area also showed a high degree of variability. == See also == Autotomy Cloning Regenerative medicine Neuroregeneration Organ transplantation Epimorphosis Morphallaxis Polyphyodont == Notes == == Sources == == Further reading == Kevin Strange and Viravuth Yin, "A Shot at Regeneration: A once abandoned drug compound shows an ability to rebuild organs damaged by illness and injury", Scientific American, vol. 320, no. 4 (April 2019), pp. 56–61. == External links == Rines, George Edwin, ed. (1920). "Regeneration, in zoology" . Encyclopedia Americana.
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"page_id": 854081,
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"title": "Regeneration (biology)"
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These Solar System minor planets are the furthest from the Sun as of December 2021. The objects have been categorized by their approximate current distance from the Sun, and not by the calculated aphelion of their orbit. The list changes over time because the objects are moving in their orbits. Some objects are inbound and some are outbound. It would be difficult to detect long-distance comets if it were not for their comas, which become visible when heated by the Sun. Distances are measured in astronomical units (AU, Sun–Earth distances). The distances are not the minimum (perihelion) or the maximum (aphelion) that may be achieved by these objects in the future. This list does not include near-parabolic comets of which many are known to be currently more than 100 AU (15 billion km) from the Sun, but are currently too far away to be observed by telescope. Trans-Neptunian objects are typically announced publicly months or years after their discovery, so as to make sure the orbit is correct before announcing it. Due to their greater distance from the Sun and slow movement across the sky, trans-Neptunian objects with observation arcs less than several years often have poorly constrained orbits. Particularly distant objects take several years of observations to establish a crude orbit solution before being announced. For instance, the most distant known trans-Neptunian object 2018 AG37 was discovered by Scott Sheppard in January 2018 but was announced three years later in February 2021. == Noted objects == One particularly distant body is 90377 Sedna, which was discovered in November 2003. It has an extremely eccentric orbit that takes it to an aphelion of 937 AU. It takes over 10,000 years to orbit, and during the next 50 years it will slowly move closer to the Sun as it comes to
|
{
"page_id": 48534508,
"source": null,
"title": "List of Solar System objects most distant from the Sun"
}
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perihelion at a distance of 76 AU from the Sun. Sedna is the largest known sednoid, a class of objects that play an important role in the Planet Nine hypothesis. Pluto (30–49 AU, about 34 AU in 2015) was the first Kuiper belt object to be discovered (1930) and is the largest known dwarf planet. == Gallery == Notable trans-Neptunian objects == Known distant objects == This is a list of known objects at heliocentric distances of more than 65 AU. In theory, the Oort cloud could extend over 120,000 AU (2 ly) from the Sun. == See also == List of artificial objects leaving the Solar System Lists of astronomical objects List of Solar System objects by greatest aphelion List of hyperbolic comets List of trans-Neptunian objects == References ==
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{
"page_id": 48534508,
"source": null,
"title": "List of Solar System objects most distant from the Sun"
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Peritoneal recesses (or peritoneal gutters) are the spaces formed by peritoneum draping over viscera. The term refers mainly to four spaces in the abdominal cavity; the two paracolic gutters and the two paramesenteric gutters. There are other smaller recesses including those around the duodenojejunal flexure, cecum, and the sigmoid colon. These gutters are clinically important because they allow a passage for infectious fluids from different compartments of the abdomen. For example; fluid from an infected appendix can track up the right paracolic gutter to the hepatorenal recess. The four peritoneal recesses are: The left and right paracolic gutters. The left and right paramesenteric gutters. == Duodenal recesses == To the left side of the duodenojejunal flexure, recesses or fossae may be created by peritoneal folds. The paraduodenal recess proper is situated posterior to the superior extremity of the inferior mesenteric vein. This paraduodenal recess is clinically and surgically important: an internal hernia protruding into the recess may obstruct the inferior mesenteric vein or cause a thrombus to form within it, and the vein may be sectioned during surgical repair of such a hernia. A superior and an inferior duodenal recess may be created by horizontal peritoneal folds. A retroduodenal recess may occur posterior to the duodenojejunal flexure. The small intestine may herniate (a condition known as an "internal hernia") into these recesses, and such hernias may then strangulate. == See also == Hepatorenal recess == References == == External links == Anatomy photo:37:14-0100 at the SUNY Downstate Medical Center — "Abdominal Cavity: Peritoneal Gutters" page 1 Anatomy photo:37:14-0200 at the SUNY Downstate Medical Center — "Abdominal Cavity: Peritoneal Gutters" page 2 Anatomy photo:37:14-0300 at the SUNY Downstate Medical Center — "Abdominal Cavity: Peritoneal Gutters" page 3
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{
"page_id": 24053827,
"source": null,
"title": "Peritoneal recesses"
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Butylthiol may refer to: Butanethiol (1-butylthiol) tert-Butylthiol (TBM)
|
{
"page_id": 36177988,
"source": null,
"title": "Butylthiol"
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In theory of vibrations, Duhamel's integral is a way of calculating the response of linear systems and structures to arbitrary time-varying external perturbation. It is named after Jean-Marie Duhamel. == Introduction == === Background === The response of a linear, viscously damped single-degree of freedom (SDOF) system to a time-varying mechanical excitation p(t) is given by the following second-order ordinary differential equation m d 2 x ( t ) d t 2 + c d x ( t ) d t + k x ( t ) = p ( t ) {\displaystyle m{\frac {d^{2}x(t)}{dt^{2}}}+c{\frac {dx(t)}{dt}}+kx(t)=p(t)} where m is the (equivalent) mass, x stands for the amplitude of vibration, t for time, c for the viscous damping coefficient, and k for the stiffness of the system or structure. If a system initially rests at its equilibrium position, from where it is acted upon by a unit-impulse at the instance t=0, i.e., p(t) in the equation above is a Dirac delta function δ(t), x ( 0 ) = d x d t | t = 0 = 0 {\textstyle x(0)=\left.{\frac {dx}{dt}}\right|_{t=0}=0} , then by solving the differential equation one can get a fundamental solution (known as a unit-impulse response function) h ( t ) = { 1 m ω d e − ς ω n t sin ω d t , t > 0 0 , t < 0 {\displaystyle h(t)={\begin{cases}{\frac {1}{m\omega _{d}}}e^{-\varsigma \omega _{n}t}\sin \omega _{d}t,&t>0\\0,&t<0\end{cases}}} where ς = c 2 k m {\textstyle \varsigma ={\frac {c}{2{\sqrt {km}}}}} is called the damping ratio of the system, ω n = k m {\textstyle \omega _{n}={\sqrt {\frac {k}{m}}}} is the natural angular frequency of the undamped system (when c=0) and ω d = ω n 1 − ς 2 {\textstyle \omega _{d}=\omega _{n}{\sqrt {1-\varsigma ^{2}}}} is the angular frequency when damping
|
{
"page_id": 4917315,
"source": null,
"title": "Duhamel's integral"
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|
effect is taken into account (when c ≠ 0 {\displaystyle c\neq 0} ). If the impulse happens at t=τ instead of t=0, i.e. p ( t ) = δ ( t − τ ) {\displaystyle p(t)=\delta (t-\tau )} , the impulse response is h ( t − τ ) = 1 m ω d e − ς ω n ( t − τ ) sin [ ω d ( t − τ ) ] {\displaystyle h(t-\tau )={\frac {1}{m\omega _{d}}}e^{-\varsigma \omega _{n}(t-\tau )}\sin[\omega _{d}(t-\tau )]} ， t ≥ τ {\displaystyle t\geq \tau } === Conclusion === Regarding the arbitrarily varying excitation p(t) as a superposition of a series of impulses: p ( t ) ≈ ∑ τ < t p ( τ ) ⋅ Δ τ ⋅ δ ( t − τ ) {\displaystyle p(t)\approx \sum _{\tau <t}{p(\tau )\cdot \Delta \tau \cdot \delta }(t-\tau )} then it is known from the linearity of system that the overall response can also be broken down into the superposition of a series of impulse-responses: x ( t ) ≈ ∑ τ < t p ( τ ) ⋅ Δ τ ⋅ h ( t − τ ) {\displaystyle x(t)\approx \sum _{\tau <t}{p(\tau )\cdot \Delta \tau \cdot h}(t-\tau )} Letting Δ τ → 0 {\displaystyle \Delta \tau \to 0} , and replacing the summation by integration, the above equation is strictly valid x ( t ) = ∫ 0 t p ( τ ) h ( t − τ ) d τ {\displaystyle x(t)=\int _{0}^{t}{p(\tau )h(t-\tau )d\tau }} Substituting the expression of h(t-τ) into the above equation leads to the general expression of Duhamel's integral x ( t ) = 1 m ω d ∫ 0 t p ( τ ) e − ς ω n ( t − τ ) sin [
|
{
"page_id": 4917315,
"source": null,
"title": "Duhamel's integral"
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|
ω d ( t − τ ) ] d τ {\displaystyle x(t)={\frac {1}{m\omega _{d}}}\int _{0}^{t}{p(\tau )e^{-\varsigma \omega _{n}(t-\tau )}\sin[\omega _{d}(t-\tau )]d\tau }} === Mathematical proof === The above SDOF dynamic equilibrium equation in the case p(t)=0 is the homogeneous equation: d 2 x ( t ) d t 2 + c ¯ d x ( t ) d t + k ¯ x ( t ) = 0 {\displaystyle {\frac {d^{2}x(t)}{dt^{2}}}+{\bar {c}}{\frac {dx(t)}{dt}}+{\bar {k}}x(t)=0} , where c ¯ = c m , k ¯ = k m {\displaystyle {\bar {c}}={\frac {c}{m}},{\bar {k}}={\frac {k}{m}}} The solution of this equation is: x h ( t ) = C 1 ⋅ e − 1 2 ( c ¯ + c ¯ 2 − 4 ⋅ k ¯ ) t + C 2 ⋅ e 1 2 ( − c ¯ + c ¯ 2 − 4 ⋅ k ¯ ) t {\displaystyle x_{h}(t)=C_{1}\cdot e^{-{\frac {1}{2}}\left({\bar {c}}+{\sqrt {{\bar {c}}^{2}-4\cdot {\bar {k}}}}\right)t}+C_{2}\cdot e^{{\frac {1}{2}}\left(-{\bar {c}}+{\sqrt {{\bar {c}}^{2}-4\cdot {\bar {k}}}}\right)t}} The substitution: A = 1 2 ( c ¯ − c ¯ 2 − 4 k ¯ ) , B = 1 2 ( c ¯ + c ¯ 2 − 4 k ¯ ) , P = c ¯ 2 − 4 k ¯ , P = B − A {\displaystyle A={\frac {1}{2}}\left({\bar {c}}-{\sqrt {{\bar {c}}^{2}-4{\bar {k}}}}\right),\;B={\frac {1}{2}}\left({\bar {c}}+{\sqrt {{\bar {c}}^{2}-4{\bar {k}}}}\right),\;P={\sqrt {{\bar {c}}^{2}-4{\bar {k}}}},\;P=B-A} leads to: x h ( t ) = C 1 e − B ⋅ t + C 2 e − A ⋅ t {\displaystyle x_{h}(t)=C_{1}e^{-B\cdot t}\;+\;C_{2}e^{-A\cdot t}} One partial solution of the non-homogeneous equation: d 2 x ( t ) d t 2 + c ¯ d x ( t ) d t + k ¯ x ( t ) = p ¯ ( t ) {\textstyle {\frac {d^{2}x(t)}{dt^{2}}}+{\bar {c}}{\frac
|
{
"page_id": 4917315,
"source": null,
"title": "Duhamel's integral"
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|
{dx(t)}{dt}}+{\bar {k}}x(t)={\bar {p}}(t)} , where p ¯ ( t ) = p ( t ) m {\textstyle {\bar {p}}(t)={\frac {p(t)}{m}}} , could be obtained by the Lagrangian method for deriving partial solution of non-homogeneous ordinary differential equations. This solution has the form: x p ( t ) = ∫ p ( t ) ¯ ⋅ e A t d t ⋅ e − A t − ∫ p ( t ) ¯ ⋅ e B t d t ⋅ e − B t P {\displaystyle x_{p}(t)={\frac {\int {{\bar {p(t)}}\cdot e^{At}dt}\cdot e^{-At}-\int {{\bar {p(t)}}\cdot e^{Bt}dt}\cdot e^{-Bt}}{P}}} Now substituting: ∫ p ( t ) ¯ ⋅ e A t d t | t = z = Q z , ∫ p ( t ) ¯ ⋅ e B t d t | t = z = R z {\textstyle \left.\int {{\bar {p(t)}}\cdot e^{At}dt}\right|_{t=z}=Q_{z},\left.\int {{\bar {p(t)}}\cdot e^{Bt}dt}\right|_{t=z}=R_{z}} ,where ∫ x ( t ) d t | t = z {\textstyle \left.\int x(t)dt\right|_{t=z}} is the primitive of x(t) computed at t=z, in the case z=t this integral is the primitive itself, yields: x p ( t ) = Q t ⋅ e − A t − R t ⋅ e − B t P {\displaystyle x_{p}(t)={\frac {Q_{t}\cdot e^{-At}-R_{t}\cdot e^{-Bt}}{P}}} Finally the general solution of the above non-homogeneous equation is represented as: x ( t ) = x h ( t ) + x p ( t ) = C 1 ⋅ e − B t + C 2 ⋅ e − A t + Q t ⋅ e − A t − R t ⋅ e − B t P {\displaystyle x(t)=x_{h}(t)+x_{p}(t)=C_{1}\cdot e^{-Bt}+C_{2}\cdot e^{-At}+{\frac {Q_{t}\cdot e^{-At}-R_{t}\cdot e^{-Bt}}{P}}} with time derivative: d x d t = − A e − A t ⋅ C 2 − B e − B t ⋅ C 1 +
|
{
"page_id": 4917315,
"source": null,
"title": "Duhamel's integral"
}
|
1 P [ Q t ˙ ⋅ e − A t − A Q t ⋅ e − A t − R t ˙ ⋅ e − B t + B R t ⋅ e − B t ] {\displaystyle {\frac {dx}{dt}}=-Ae^{-At}\cdot C_{2}-Be^{-Bt}\cdot C_{1}+{\frac {1}{P}}\left[{\dot {Q_{t}}}\cdot e^{-At}-AQ_{t}\cdot e^{-At}-{\dot {R_{t}}}\cdot e^{-Bt}+BR_{t}\cdot e^{-Bt}\right]} , where Q t ˙ = p ( t ) ⋅ e A t , R t ˙ = p ( t ) ⋅ e B t {\displaystyle {\dot {Q_{t}}}=p(t)\cdot e^{At},{\dot {R_{t}}}=p(t)\cdot e^{Bt}} In order to find the unknown constants C 1 , C 2 {\displaystyle C_{1},C_{2}} , zero initial conditions will be applied: x ( t ) | t = 0 = 0 : C 1 + C 2 + Q 0 ⋅ 1 − R 0 ⋅ 1 P = 0 {\displaystyle x(t)|_{t=0}=0:C_{1}+C_{2}+{\frac {Q_{0}\cdot 1-R_{0}\cdot 1}{P}}=0} ⇒ C 1 + C 2 = R 0 − Q 0 P {\displaystyle C_{1}+C_{2}={\frac {R_{0}-Q_{0}}{P}}} d x d t | t = 0 = 0 : − A ⋅ C 2 − B ⋅ C 1 + 1 P ⋅ [ − A ⋅ Q 0 + B ⋅ R 0 ] = 0 {\displaystyle \left.{\frac {dx}{dt}}\right|_{t=0}=0:-A\cdot C_{2}-B\cdot C_{1}+{\frac {1}{P}}\cdot [-A\cdot Q_{0}+B\cdot R_{0}]=0} ⇒ A ⋅ C 2 + B ⋅ C 1 = 1 P ⋅ [ B ⋅ R 0 − A ⋅ Q 0 ] {\displaystyle A\cdot C_{2}+B\cdot C_{1}={\frac {1}{P}}\cdot [B\cdot R_{0}-A\cdot Q_{0}]} Now combining both initial conditions together, the next system of equations is observed: C 1 + C 2 = R 0 − Q 0 P B ⋅ C 1 + A ⋅ C 2 = 1 P ⋅ [ B ⋅ R 0 − A ⋅ Q 0 ] | C 1 = R 0 P C 2 = − Q 0 P {\displaystyle
|
{
"page_id": 4917315,
"source": null,
"title": "Duhamel's integral"
}
|
\left.{\begin{alignedat}{5}C_{1}&&\;+&&\;C_{2}&&\;=&&\;{\frac {R_{0}-Q_{0}}{P}}&\\B\cdot C_{1}&&\;+&&\;A\cdot C_{2}&&\;=&&\;{\frac {1}{P}}\cdot [B\cdot R_{0}-A\cdot Q_{0}]\end{alignedat}}\right|{\begin{alignedat}{5}C_{1}&&\;=&&\;{\frac {R_{0}}{P}}&\\C_{2}&&\;=&&\;-{\frac {Q_{0}}{P}}\end{alignedat}}} The back substitution of the constants C 1 {\displaystyle C_{1}} and C 2 {\displaystyle C_{2}} into the above expression for x(t) yields: x ( t ) = Q t − Q 0 P ⋅ e − A ⋅ t − R t − R 0 P ⋅ e − B ⋅ t {\displaystyle x(t)={\frac {Q_{t}-Q_{0}}{P}}\cdot e^{-A\cdot t}-{\frac {R_{t}-R_{0}}{P}}\cdot e^{-B\cdot t}} Replacing Q t − Q 0 {\displaystyle Q_{t}-Q_{0}} and R t − R 0 {\displaystyle R_{t}-R_{0}} (the difference between the primitives at t=t and t=0) with definite integrals (by another variable τ) will reveal the general solution with zero initial conditions, namely: x ( t ) = 1 P ⋅ [ ∫ 0 t p ¯ ( τ ) ⋅ e A τ d τ ⋅ e − A t − ∫ 0 t p ¯ ( τ ) ⋅ e B τ d τ ⋅ e − B t ] {\displaystyle x(t)={\frac {1}{P}}\cdot \left[\int _{0}^{t}{{\bar {p}}(\tau )\cdot e^{A\tau }d\tau }\cdot e^{-At}-\int _{0}^{t}{{\bar {p}}(\tau )\cdot e^{B\tau }d\tau }\cdot e^{-Bt}\right]} Finally substituting c = 2 ξ ω m , k = ω 2 m {\displaystyle c=2\xi \omega m,\;k=\omega ^{2}m} , accordingly c ¯ = 2 ξ ω , k ¯ = ω 2 {\displaystyle {\bar {c}}=2\xi \omega ,{\bar {k}}=\omega ^{2}} , where ξ<1 yields: P = 2 ω D i , A = ξ ω − ω D i , B = ξ ω + ω D i {\displaystyle P=2\omega _{D}i,\;A=\xi \omega -\omega _{D}i,\;B=\xi \omega +\omega _{D}i} , where ω D = ω ⋅ 1 − ξ 2 {\displaystyle \omega _{D}=\omega \cdot {\sqrt {1-\xi ^{2}}}} and i is the imaginary unit. Substituting this expressions into the above general solution with zero initial conditions and using the Euler's exponential formula will lead
|
{
"page_id": 4917315,
"source": null,
"title": "Duhamel's integral"
}
|
to canceling out the imaginary terms and reveals the Duhamel's solution: x ( t ) = 1 ω D ∫ 0 t p ¯ ( τ ) e − ξ ω ( t − τ ) sin ( ω D ( t − τ ) ) d τ {\displaystyle x(t)={\frac {1}{\omega _{D}}}\int _{0}^{t}{{\bar {p}}(\tau )e^{-\xi \omega (t-\tau )}\sin(\omega _{D}(t-\tau ))d\tau }} == See also == Duhamel's principle == References == R. W. Clough, J. Penzien, Dynamics of Structures, Mc-Graw Hill Inc., New York, 1975. Anil K. Chopra, Dynamics of Structures - Theory and applications to Earthquake Engineering, Pearson Education Asia Limited and Tsinghua University Press, Beijing, 2001 Leonard Meirovitch, Elements of Vibration Analysis, Mc-Graw Hill Inc., Singapore, 1986 == External links == Duhamel's formula at "Dispersive Wiki".
|
{
"page_id": 4917315,
"source": null,
"title": "Duhamel's integral"
}
|
Dark radiation (also dark electromagnetism) is a postulated type of radiation that mediates interactions of dark matter. By analogy to the way photons mediate electromagnetic interactions between particles in the Standard Model (called baryonic matter in cosmology), dark radiation is proposed to mediate interactions between dark matter particles. Similar to dark matter particles, the hypothetical dark radiation does not interact with Standard Model particles. There has been no notable evidence for the existence of such radiation; baryonic matter contains multiple interacting particle types, but it is not known if dark matter does. Cosmic microwave background data may indicate that the number of effective neutrino degrees of freedom is more than 3.046, which is slightly more than the standard case for 3 types of neutrino. This extra degree of freedom could arise from having a non-trivial amount of dark radiation in the universe. One possible candidate for dark radiation is the sterile neutrino. == See also == Dark photon – Hypothetical force carrier particle connected to dark matter Fifth force – Speculative physics theory Dual photon – Hypothetical particle dual to the photon Photino – Hypothetical superpartner of the photon Dark sector – Hypothetical collections of yet-unobserved quantum fields and particles == References ==
|
{
"page_id": 36177989,
"source": null,
"title": "Dark radiation"
}
|
In organic chemistry, hydrocarbons (compounds composed solely of carbon and hydrogen) are divided into two classes: aromatic compounds and aliphatic compounds (; G. aleiphar, fat, oil). Aliphatic compounds can be saturated (in which all the C-C bonds are single, requiring the structure to be completed, or 'saturated', by hydrogen) like hexane, or unsaturated, like hexene and hexyne. Open-chain compounds, whether straight or branched, and which contain no rings of any type, are always aliphatic. Cyclic compounds can be aliphatic if they are not aromatic. == Structure == Aliphatics compounds can be saturated, joined by single bonds (alkanes), or unsaturated, with double bonds (alkenes) or triple bonds (alkynes). If other elements (heteroatoms) are bound to the carbon chain, the most common being oxygen, nitrogen, sulfur, and chlorine, it is no longer a hydrocarbon, and therefore no longer an aliphatic compound. However, such compounds may still be referred to as aliphatic if the hydrocarbon portion of the molecule is aliphatic, e.g. aliphatic amines, to differentiate them from aromatic amines. The least complex aliphatic compound is methane (CH4). == Properties == Most aliphatic compounds are flammable, allowing the use of hydrocarbons as fuel, such as methane in natural gas for stoves or heating; butane in torches and lighters; various aliphatic (as well as aromatic) hydrocarbons in liquid transportation fuels like petrol/gasoline, diesel, and jet fuel; and other uses such as ethyne (acetylene) in welding. == Examples of aliphatic compounds == The most important aliphatic compounds are: n-, iso- and cyclo-alkanes (saturated hydrocarbons) n-, iso- and cyclo-alkenes and -alkynes (unsaturated hydrocarbons). Important examples of low-molecular aliphatic compounds can be found in the list below (sorted by the number of carbon-atoms): == References ==
|
{
"page_id": 2120,
"source": null,
"title": "Aliphatic compound"
}
|
Granomarginata is a genus of spherical Cambrian acritarchs interpreted as a phytoplankton. == References ==
|
{
"page_id": 45025353,
"source": null,
"title": "Granomarginata"
}
|
Bronchus-associated lymphoid tissue (BALT) is a tertiary lymphoid structure. It is a part of mucosa-associated lymphoid tissue (MALT), and it consists of lymphoid follicles in the lungs and bronchus. BALT is an effective priming site of the mucosal and systemic immune responses. == Structure == BALT is similar in most mammal species, but it differs in its maintenance and inducibility. While it is normal component of lungs and bronchus in rabbits or pigs, in mice or humans it appears only after infection or inflammation. In mice and humans it is thus called inducible BALT (iBALT). BALT and iBALT are structurally and functionally very similar, so in this article only BALT is used for both structures. BALT is found along the bifurcations of the upper bronchi directly beneath the epithelium and generally lying between an artery and a bronchus. It is also in perivascular, peribronchial and even interstitial areas in the lower airways of the lung. To call it BALT it has to be structured accumulation of lymphocytes and other immune cells. There are lymphoid follicles with apparent germinal centres with most B-cells surrounded by T-cell area. In interfollicular T-cell area, there are many dendritic cells presenting antigen to T-cells and in germinal centres, there are follicular dendritic cells. There are CD4+ Th lymphocytes in germinal centres and interfollicular area and CD8+ T cells mainly in interfollicular area. High endothelial venules (HEVs) are also present in BALT in T/B-cell interface, allowing for the recruitment of naive T cells. These HEV are the only entry site for lymphocytes to migrate into the BALT and leave by efferent lymphatic vessels. In some species, M cells have been described in epithelium above BALT similar to M cells in the dome epithelium of Peyer’s patches, although the dome epithelium is not typical for BALT. For
|
{
"page_id": 54397002,
"source": null,
"title": "Bronchus-associated lymphoid tissue"
}
|
formation of BALT in mice is necessary inteleukin-17 and VCAM-1, PNAd and LFA-1 and it is lymphotoxin-α independent whereas the development of secondary lymphoid organs (such as lymph nodes and Peyer’s patches) is typically dependent on LTα. Formation of BALT may be caused by disabled in situ function of Treg cells. == Function == Function and purpose of BALT is not completely known yet. It is also unclear if its formation is part of normal immune response or if it is pathologic and should be suppressed. BALT is included in the efficient priming of adaptive B-cell and T-cell responses directed against airborne antigens. It needs dendritic cells to its maintenance and function. Inducible BALT is formed after infection, e.g. influenza, and peak in size between 1 and 2 weeks after infection and diminish thereafter. Immune responses initiated in iBALT are delayed relative to the immune response in the draining lymph nodes, owing to the time it takes to form iBALT. However, in chronic disease iBALT may be a component of the pathology. BALT can be induced even in fetal lungs after chorioamnionitis or intrauterine pneumonia. Also there is an evidence that cigarette smoke can induce formation of BALT in humans and rats. BALT can also occur after other stimuli, e.g. inflammation caused by rheumatoid arthritis or other autoimmune lung disease or mechanic damage by dust particles. == References ==
|
{
"page_id": 54397002,
"source": null,
"title": "Bronchus-associated lymphoid tissue"
}
|
The molecular formula C16H23NO3 (molar mass: 277.36 g/mol) may refer to: Pargolol N-Ethylheptylone
|
{
"page_id": 41551947,
"source": null,
"title": "C16H23NO3"
}
|
The Fries rearrangement, named for the German chemist Karl Theophil Fries, is a rearrangement reaction of a phenolic ester to a hydroxy aryl ketone by catalysis of Lewis acids. It involves migration of an acyl group of phenol ester to the aryl ring. The reaction is ortho and para selective and one of the two products can be favoured by changing reaction conditions, such as temperature and solvent. == Mechanism == Despite many efforts, a definitive reaction mechanism for the Fries rearrangement has not been determined. Evidence for inter- and intramolecular mechanisms have been obtained by crossover experiments with mixed reactants.The reaction progress is not dependent on solvent or substrate. A widely accepted mechanism involves a carbocation intermediate. In the first reaction step a Lewis acid for instance aluminium chloride AlCl3 co-ordinates to the carbonyl oxygen atom of the acyl group. This oxygen atom is more electron rich than the phenolic oxygen atom and is the preferred Lewis base. This interaction polarizes the bond between the acyl residue and the phenolic oxygen atom and the aluminium chloride group rearranges to the phenolic oxygen atom. This generates a free acylium carbocation which reacts in a classical electrophilic aromatic substitution with the aromatic ring. The abstracted proton is released as hydrochloric acid where the chlorine is derived from aluminium chloride. The orientation of the substitution reaction is temperature dependent. A low reaction temperature favors para substitution and with high temperatures the ortho product prevails, this can be rationalised as exhibiting classic thermodynamic versus kinetic reaction control as the ortho product can form a more stable bidentate complex with the aluminium. Formation of the ortho product is also favoured in non-polar solvents; as the solvent polarity increases, the ratio of the para product also increases. == Scope == Phenols react to form esters
|
{
"page_id": 2820171,
"source": null,
"title": "Fries rearrangement"
}
|
instead of hydroxyarylketones when reacted with acyl halides under Friedel-Crafts acylation conditions. Therefore, this reaction is of industrial importance for the synthesis of hydroxyarylketones, which are important intermediates for several pharmaceuticals. As an alternative to aluminium chloride, other Lewis acids such as boron trifluoride and bismuth triflate or strong protic acids such as hydrogen fluoride and methanesulfonic acid can also be used. In order to avoid the use of these corrosive and environmentally unfriendly catalysts altogether research into alternative heterogeneous catalysts is actively pursued. == Limits == In all instances only esters can be used with stable acyl components that can withstand the harsh conditions of the Fries rearrangement. If the aromatic or the acyl component is heavily substituted then the chemical yield will drop due to steric constraints. Deactivating meta-directing groups on the benzene group will also have an adverse effect as can be expected for a Friedel–Crafts acylation. == Photo-Fries rearrangement == In addition to the ordinary thermal phenyl ester reaction a photochemical variant is possible. The photo-Fries rearrangement can likewise give [1,3] and [1,5] products, which involves a radical reaction mechanism. This reaction is also possible with deactivating substituents on the aromatic group. Because the yields are low this procedure is not used in commercial production. However, photo-Fries rearrangement may occur naturally, for example when a plastic object made of aromatic polycarbonate, polyester or polyurethane, is exposed to the sun (aliphatic carbonyls undergo Norrish reactions, which are somewhat similar). In this case, photolysis of the ester groups would lead to leaching of phthalate from the plastic. == Anionic Fries rearrangement == In the anionic Fries rearrangement ortho-metalation of aryl esters, carbamates and carbonates with a strong base results in a rearrangement to give ortho-carbonyl species. == See also == Friedel–Crafts alkylation-like reactions: Hofmann–Martius rearrangement Fischer–Hepp rearrangement Duff
|
{
"page_id": 2820171,
"source": null,
"title": "Fries rearrangement"
}
|
reaction == References ==
|
{
"page_id": 2820171,
"source": null,
"title": "Fries rearrangement"
}
|
Trimethoxyphenethylamines (TMPEA) are a group of positional isomers of the psychedelic cactus alkaloid mescaline. Some of them are described in the book PiHKAL by Alexander Shulgin and Ann Shulgin. 2,3,4-trimethoxyphenethylamine (Isomescaline) 2,3,5-trimethoxyphenethylamine (2C-TMA-4) 2,3,6-trimethoxyphenethylamine (2C-TMA-5) 2,4,5-trimethoxyphenethylamine (2C-O) 2,4,6-trimethoxyphenethylamine (2C-TMA-6) 3,4,5-trimethoxyphenethylamine (Mescaline) 4-bromo-2,5,beta-trimethoxyphenethylamine (BOB (psychedelic)) 4-methyl-2,5,β-trimethoxyphenethylamine (BOD (psychedelic)) N-(2-methoxybenzyl)-3,4,5-trimethoxyphenethylamine (NBOMe-mescaline) == See also == Substituted methoxyphenethylamine Methoxyphenethylamine Dimethoxyphenethylamine Methoxyamphetamine Dimethoxyamphetamine Trimethoxyamphetamine
|
{
"page_id": 10815565,
"source": null,
"title": "Trimethoxyphenethylamine"
}
|
Endocardial cushions project into the atrial canal, and, meeting in the middle line, unite to form the septum intermedium which divides the canal into two channels, the future right and left atrioventricular orifices. == References == This article incorporates text in the public domain from page 512 of the 20th edition of Gray's Anatomy (1918) == External links == Overview at edu.mt
|
{
"page_id": 4786259,
"source": null,
"title": "Septum intermedium"
}
|
Vacuum evaporation is the process of causing the pressure in a liquid-filled container to be reduced below the vapor pressure of the liquid, causing the liquid to evaporate at a lower temperature than normal. Although the process can be applied to any type of liquid at any vapor pressure, it is generally used to describe the boiling of water by lowering the container's internal pressure below standard atmospheric pressure and causing the water to boil at room temperature. The vacuum evaporation treatment process consists of reducing the interior pressure of the evaporation chamber below atmospheric pressure. This reduces the boiling point of the liquid to be evaporated, thereby reducing or eliminating the need for heat in both the boiling and condensation processes. There are other advantages, such as the ability to distill liquids with high boiling points and avoiding decomposition of substances that are heat sensitive. == Application == === Food === When the process is applied to food and the water is evaporated and removed, the food can be stored for long periods without spoiling. It is also used when boiling a substance at normal temperatures would chemically change the consistency of the product, such as egg whites coagulating when attempting to dehydrate the albumen into a powder. This process was invented by Henri Nestlé in 1866, of Nestlé Chocolate fame, although the Shakers were already using a vacuum pan before that (see condensed milk). This process is used industrially to make such food products as evaporated milk for milk chocolate and tomato paste for ketchup. In the sugar industry vacuum evaporation is used in the crystallization of sucrose solutions. Traditionally this process was performed in batch mode, but nowadays continuous vacuum pans are available. === Wastewater treatment === Vacuum evaporators are used in a wide range of industrial
|
{
"page_id": 3672150,
"source": null,
"title": "Vacuum evaporation"
}
|
sectors to treat industrial wastewater. It represents a clean, safe and very versatile technology with low management costs, which in most cases serves as a zero-discharge treatment system. === Thin film deposition === Vacuum evaporation is also a form of physical vapor deposition used in the semiconductor, microelectronics, and optical industries. In this context it is used to deposit thin films of material onto surfaces. Such a technique consists of pumping a vacuum chamber to low pressures (<10−5 torr) and heating a material to produce vapor to deposit the material onto a cold surface. The material to be vaporized is typically heated until its vapor pressure is high enough to produce a flux of several Angstroms per second by using an electrically resistive heater or bombardment by a high voltage beam. === Electronics === Thermal evaporation has been investigated for the production of organic light-emitting diodes (OLEDs) and organic photovoltaic cells. In organic photovoltaic cells, the purity of the organic semiconductor layers influences the device’s energy conversion efficiency and stability. == See also == Freeze drying List of waste-water treatment technologies Vacuum deposition == References == == External links == Vacuum evaporation manufacturer
|
{
"page_id": 3672150,
"source": null,
"title": "Vacuum evaporation"
}
|
Sampson (later renamed Mammoth) was a Shire horse gelding born in 1846 and bred by Thomas Cleaver at Toddington Mills, Bedfordshire, England. According to Guinness World Records (1986) he was the tallest horse ever recorded, by 1850 measuring 219.7 centimetres (7 ft 2.5 in) or 21.2½ hands in height. His peak weight was estimated at 3,360 lb (1,524 kg), making him the heaviest horse ever recorded. == See also == List of historical horses == References ==
|
{
"page_id": 5572696,
"source": null,
"title": "Sampson (horse)"
}
|
The Liberator is a superhero from the Golden Age of Comics. His first appearance was in Exciting Comics #15 (December 1941), published by Nedor Comics. The character was later revived by writer Alan Moore for America's Best Comics. == Nedor Comics == The Liberator is the secret identity of Dr. Nelson Drew, a chemistry teacher at fictional Claflin University (as in, not to be confused with the historically black college affiliated with South Carolina State University). He discovers an ancient Egyptian formula called Lamesis that gives him superhuman strength and speed. Drew uses his powers as the Liberator to fight Nazi saboteurs during World War II. The formula sometimes wears off, turning the Liberator back into Dr. Drew at inopportune moments. The Liberator debuted in Exciting Comics #15, and appeared regularly in that title and America's Best Comics (not to be confused with the later DC Comics imprint). His last Golden Age appearance was in Exciting Comics #35 (October 1944). == America's Best Comics == Alan Moore revived the Liberator, along with many other Nedor Comics characters, for his Tom Strong series. In Tom Strong #12 (June 2001), the Liberator was revealed to have been one of the members of SMASH that had been placed in suspended animation after an alien invasion from the Moon in 1969. Awakened 30 years later, the Liberator joined his former comrades in the fight against the alien. SMASH disbanded shortly thereafter, but reformed three years later. The Liberator is a member of the reformed group. == Dynamite Entertainment == Currently, The Liberator is one of dozens of Golden Age superhero characters appearing in Dynamite Entertainment's Project Superpowers line of comics. The basic premise is that The Fighting Yank spent years imprisoning all of his fellow heroes in the mystical Urn of Pandora, mistakenly thinking
|
{
"page_id": 9504861,
"source": null,
"title": "Liberator (Nedor Comics)"
}
|
that it would bring about the end of all evil; The Liberator was one of those heroes. Decades later, the Urn was broken and the heroes freed. As seen in the Black Terror miniseries, The Liberator is now one of several patriotic-themed heroes who protect the U.S. president and America's interests, even if this pits them against their fellow heroes. == See also == Nedor Comics == References == == External links == The Liberator at International Hero.co.uk
|
{
"page_id": 9504861,
"source": null,
"title": "Liberator (Nedor Comics)"
}
|
The molecular formula C16H26N2O4 (molar mass: 310.39 g/mol, exact mass: 310.1893 u) may refer to: Cetamolol Pamatolol
|
{
"page_id": 41551965,
"source": null,
"title": "C16H26N2O4"
}
|
Major General William Luther Sibert (October 12, 1860 – October 16, 1935) was a senior United States Army officer who commanded the 1st Division on the Western Front during World War I. Sibert was the first division commander of the "Big Red One," leading the 1st Infantry from June to January 1918. Sibert was nearly 58 when appointed to command an infantry division going into combat, a challenging task for which he acknowledged he had no prior experience, as his background was with the Engineers. He was relieved by General John J. Pershing and appointed to lead the new Chemical Warfare Service, a task far more suited to his background and talents. After retiring as a major general in 1920, concluding 36 years on active duty in the U.S. Army, Sibert oversaw a project modernizing the docks and waterways in Mobile, Alabama, and served on the Presidential Commission that led to the construction of Hoover Dam. He died in 1935 in Bowling Green, Kentucky, where he had lived out most of his retirement. == Early life and education == Sibert was born in Gadsden, Alabama, on October 12, 1860. After attending the University of Alabama from 1879 to 1880, he entered the United States Military Academy and was appointed a second lieutenant of Engineers, United States Army, on June 15, 1884. His appointment was a distinction as only the top 10 percent of each West Point class was then commissioned into the Engineers. == Military career == He graduated from the Engineer School of Applications in 1887 and went on to hold several engineer positions in the United States and overseas. In 1899, he was assigned as the chief engineer of the 8th Army Corps and the chief engineer and general manager of the Manila and Dagupan Railroad during the
|
{
"page_id": 13305949,
"source": null,
"title": "William L. Sibert"
}
|
Philippine Insurrection. Later, he returned to the United States where he was in charge of river and harbor districts and headquarters in Louisville and Pittsburgh. From 1907 through 1914, Sibert was a member of the Panama Canal Commission and was responsible for the building of a number of critical parts of the Panama Canal, including the Gatun Locks and Dam, the West Breakwater in Colon, and the channel from Gatun Lake to the Pacific Ocean. On March 15, 1915, Sibert, by now a lieutenant colonel, was promoted to the rank of brigadier general. This promotion, while not an uncommon practice in the Regular Army of the time, was still unusual. Congress wanted to make Sibert a brigadier general, but the Engineer Corps was only authorized one, so instead of expanding the Corps, they appointed Sibert to a line officer slot (i.e., Infantry). The Army not knowing what to do with an engineer who had never led troops or trained for combat suddenly elevated to a general of infantry, decided to assign Sibert, who had been working on canal projects in the Mid-West and advisory missions to China, to command the Pacific Coast's Coastal Artillery. Here, it was felt he could do little harm. Unfortunately for Sibert, when the United States entered World War I in April 1917, Brigadier General Sibert was one of the only senior infantry officers on active duty. He was duly breveted to major general and deployed with the initial four regiments of the American Expeditionary Forces (AEF) which formed the 1st Division (nicknamed "The Big Red One") once in France. The AEF's Commander-in-Chief (C-in-C), General John J. Pershing, a long serving cavalry officer famous for his exploits at San Juan Hill in the Spanish–American War, and recently in charge of the campaign against Pancho Villa, was
|
{
"page_id": 13305949,
"source": null,
"title": "William L. Sibert"
}
|
short on qualified general officers (he himself had only recently been promoted to his position) so Sibert was placed in charge of the 1st Division. To his credit, Sibert opposed his own promotion as a line officer, protesting his own lack of experience. In the peacetime Army prior to 1917, though, it was relatively harmless. In the cauldron of the Western Front, it was a serious problem. The AEF suffered a serious leadership problem throughout the final year of the war, as officers were rapidly promoted to positions with little or no experience. The American Army was singularly unprepared for the war, and the strain of its rapid expansion created many personnel problems like Sibert's. Part of the problem was the Army's promotion system, which continued to cause problems into World War II. The rank a Regular Army officer might hold, and their official rank were not always the same. Thus a "peacetime rank" and a "wartime" rank differed. An officer might start the war as a lieutenant colonel, end the war as a major general, and then revert to being a lieutenant colonel after the war. Incidentally, pay was not necessarily tied to rank, but depended on time in service and an individual's official rank. In the small Regular Army of 1917, most officers were below the rank of colonel, and few serving in general officer billets actually were recognized by Congress as holding the rank of general, rather, they were "breveted" to the higher rank. Actual promotion required Congressional approval, the number of positions limited by law, and was based solely on seniority. Breveting allowed the Army to bypass these restrictions, for better or worse. Thus, the problem of promoting Sibert to brigadier general in the Engineer Corps and the subsequent trouble it caused. Sibert led the 1st
|
{
"page_id": 13305949,
"source": null,
"title": "William L. Sibert"
}
|
Infantry Division during its initial training by French and British forces. In October 1917, Pershing wrote an extensive letter to Secretary of War Newton D. Baker expressing his concerns about some of his generals, "I hope you will permit me to speak very frankly and quite confidentially, but I fear that we have some general officers who have neither the experience, the energy, nor the aggressive spirit to prepare their units or to handle them under battle conditions, as they exist today. I shall comment in an enclosure on the individuals to whom I refer particularly." In January 1918, the first elements of the AEF, part of the 1st Infantry Division, prepared to deploy into the line at Ansauville. MG Sibert was relieved by General John J. Pershing before the Division's deployment to the front. Pershing was dissatisfied with the Division's progress and elevated Brigadier General Robert Lee Bullard, a true line officer, to replace Sibert. Sibert returned to the United States in January 1918 where he became the commanding general of the Army Corps of Engineers Southeastern Department located at Charleston, South Carolina. Sibert was not alone in his relief, as Secretary Baker had approved Pershing's relief of a number of individuals. Pershing showed some measure of respect for Sibert, who was pushing 58 years old (a contributing factor to his relief), recognizing that the position Sibert was in, was not entirely of his own making. Pershing was not nearly as kind to others he removed from command during the war. When the War Department created the Chemical Warfare Service (CWS) later that spring, Pershing was asked to name a general officer to head it. Pershing recommended Sibert to the War Department, demonstrating his understanding of Sibert's true ability as an engineer and project manager. Following his assignment to
|
{
"page_id": 13305949,
"source": null,
"title": "William L. Sibert"
}
|
the CWS on June 28, 1918, Congress promoted Sibert to the rank of Major General, making the earlier brevet promotion official. Sibert led the CWS from May 1918 to February 1920. During that period the CWS in the United States focused on production and equipment. As commander of the CWS he oversaw the production of America's first chemical warfare agent, Lewisite, and the development of the US Army's chemical defense equipment, including the first US protective (or "gas") masks, the M-1 and M-2. The CWS in Europe, part of the AEF, did not fall under Sibert's control. Instead, that was led by Colonel Amos Fries, part of Pershing's Command Staff. When Sibert announced his retirement in 1919, Amos Fries, still in Europe, was selected to replace him. Today the US Army considers Sibert the "father of the US Army Chemical Corps" because he was the first commander of the CWS. Of course, he was also the first commanding officer of the 1st Infantry Division, the oldest continually serving Division in the United States Army. Sibert retired from active duty in February 1920 and settled in Bowling Green, Kentucky. Following his retirement from the Army, Sibert led the modernization of the docks and waterways in Mobile, Alabama, and served on the Presidential Commission that led to the building of Hoover Dam. He was elected to the University of Alabama Engineering Hall of Fame in 1961. For his services during World War I he was awarded the Army Distinguished Service Medal, the citation for which reads: The President of the United States of America, authorized by Act of Congress, July 9, 1918, takes pleasure in presenting the Army Distinguished Service Medal to Major General William Luther Sibert, United States Army, for exceptionally meritorious and distinguished services to the Government of the United
|
{
"page_id": 13305949,
"source": null,
"title": "William L. Sibert"
}
|
States, in a duty of great responsibility during World War I, in the organization and administration of the Chemical Warfare Service, contributory to the successful prosecution of the war. == Personal life == Sibert married Mary Margaret Cummings in September 1887, with whom he had five sons and one daughter. After Mary's death in 1915, General Sibert married Juliette Roberts in June 1917. She died 15 months later and in 1922 Sibert married Evelyn Clyne Bairnsfather of Edinburgh, Scotland who remained his wife until his death on October 16, 1935, in Bowling Green. General Sibert is buried at Arlington National Cemetery. Two of his five sons, Edwin L. Sibert and Franklin C. Sibert, each retired as Major Generals in the Army. == Decorations == == References == == External links == Works by or about William L. Sibert at the Internet Archive William Luther Sibert in the Alabama Hall of Fame Archived 2008-01-10 at the Wayback Machine US Army Chemical Corps Regimental Association Biography of MG William L. Sibert Archived 2012-03-05 at the Wayback Machine
|
{
"page_id": 13305949,
"source": null,
"title": "William L. Sibert"
}
|
DNA ligase (NAD+) (EC 6.5.1.2, polydeoxyribonucleotide synthase (NAD+), polynucleotide ligase (NAD+), DNA repair enzyme, DNA joinase, polynucleotide synthetase (nicotinamide adenine dinucleotide), deoxyribonucleic-joining enzyme, deoxyribonucleic ligase, deoxyribonucleic repair enzyme, deoxyribonucleic joinase, DNA ligase, deoxyribonucleate ligase, polynucleotide ligase, deoxyribonucleic acid ligase, polynucleotide synthetase, deoxyribonucleic acid joinase, DNA-joining enzyme, polynucleotide ligase (nicotinamide adenine dinucleotide)) is an enzyme with systematic name poly(deoxyribonucleotide):poly(deoxyribonucleotide) ligase (AMP-forming, NMN-forming). This enzyme catalyses the following chemical reaction NAD+ + (deoxyribonucleotide)n + (deoxyribonucleotide)m ⇌ {\displaystyle \rightleftharpoons } AMP + beta-nicotinamide D-ribonucleotide + (deoxyribonucleotide)n+m Catalyses the formation of a phosphodiester at the site of a single-strand break in duplex DNA. == See also == DNA ligase == References == == External links == DNA+ligase+(NAD+) at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
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{
"page_id": 5507168,
"source": null,
"title": "DNA ligase (NAD+)"
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This is a list of common household pests – undesired animals that have a history of living, invading, causing damage, eating human foods, acting as disease vectors or causing other harms in human habitation. == Mammals == Mice Field mice House mice Possums Brushtail possum Ringtail possum Rats Black rats Brown rats Wood rats Cotton rats == Invertebrates == Ants Argentine ants Carpenter ants Fire ants Odorous house ants Pharaoh ants Thief ants Bed bugs Beetles Woodworms Death watch beetles Furniture beetles Weevils Maize weevil Rice weevil Carpet beetles Fur beetles Varied carpet beetles Spider beetles Mealworm beetles Centipedes House centipedes Cockroaches Brown-banded cockroaches German cockroaches American cockroaches Oriental cockroaches Dust mites Earwigs Crickets House crickets Firebrats Flies Bottle flies Blue bottle flies Green bottle flies House flies Fruit flies Mosquitoes Moths Almond moths Indianmeal moths Clothes moths Common clothes moths Brown house moths Paper Lice Red spiders Silverfish Spiders Termites Dampwood termites Subterranean termites Woodlouse == See also == Home-stored product entomology List of notifiable diseases Noxious weed Pest (organism) == References ==
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{
"page_id": 2099301,
"source": null,
"title": "List of common household pests"
}
|
Particulate inorganic carbon (PIC) can be contrasted with dissolved inorganic carbon (DIC), the other form of inorganic carbon found in the ocean. These distinctions are important in chemical oceanography. Particulate inorganic carbon is sometimes called suspended inorganic carbon. In operational terms, it is defined as the inorganic carbon in particulate form that is too large to pass through the filter used to separate dissolved inorganic carbon. Most PIC is calcium carbonate, CaCO3, particularly in the form of calcite, but also in the form of aragonite. Calcium carbonate makes up the shells of many marine organisms. It also forms during whiting events and is excreted by marine fish during osmoregulation. == Overview == Carbon compounds can be distinguished as either organic or inorganic, and dissolved or particulate, depending on their composition. Organic carbon forms the backbone of key component of organic compounds such as – proteins, lipids, carbohydrates, and nucleic acids. Inorganic carbon is found primarily in simple compounds such as carbon dioxide, carbonic acid, bicarbonate, and carbonate (CO2, H2CO3, HCO3−, CO32− respectively). Marine carbon is further separated into particulate and dissolved phases. These pools are operationally defined by physical separation – dissolved carbon passes through a 0.2 μm filter, and particulate carbon does not. There are two main types of inorganic carbon that are found in the oceans. Dissolved inorganic carbon (DIC) is made up of bicarbonate (HCO3−), carbonate (CO32−) and carbon dioxide (including both dissolved CO2 and carbonic acid H2CO3). DIC can be converted to particulate inorganic carbon (PIC) through precipitation of CaCO3 (biologically or abiotically). DIC can also be converted to particulate organic carbon (POC) through photosynthesis and chemoautotrophy (i.e. primary production). DIC increases with depth as organic carbon particles sink and are respired. Free oxygen decreases as DIC increases because oxygen is consumed during aerobic respiration. Particulate
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{
"page_id": 67766374,
"source": null,
"title": "Particulate inorganic carbon"
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inorganic carbon (PIC) is the other form of inorganic carbon found in the ocean. Most PIC is the CaCO3 that makes up shells of various marine organisms, but can also form in whiting events. Marine fish also excrete calcium carbonate during osmoregulation. Some of the inorganic carbon species in the ocean, such as bicarbonate and carbonate, are major contributors to alkalinity, a natural ocean buffer that prevents drastic changes in acidity (or pH). The marine carbon cycle also affects the reaction and dissolution rates of some chemical compounds, regulates the amount of carbon dioxide in the atmosphere and Earth's temperature. == Calcium carbonate == Particulate inorganic carbon (PIC) usually takes the form of calcium carbonate (CaCO3), and plays a key part in the ocean carbon cycle. This biologically fixed carbon is used as a protective coating for many planktonic species (coccolithophores, foraminifera) as well as larger marine organisms (mollusk shells). Calcium carbonate is also excreted at high rates during osmoregulation by fish, and can form in whiting events. While this form of carbon is not directly taken from the atmospheric budget, it is formed from dissolved forms of carbonate which are in equilibrium with CO2 and then responsible for removing this carbon via sequestration. CO2 + H2O → H2CO3 → H+ + HCO3− Ca2+ + 2HCO3− → CaCO3 + CO2 + H2O While this process does manage to fix a large amount of carbon, two units of alkalinity are sequestered for every unit of sequestered carbon. The formation and sinking of CaCO3 therefore drives a surface to deep alkalinity gradient which serves to raise the pH of surface waters, shifting the speciation of dissolved carbon to raise the partial pressure of dissolved CO2 in surface waters, which actually raises atmospheric levels. In addition, the burial of CaCO3 in sediments serves
|
{
"page_id": 67766374,
"source": null,
"title": "Particulate inorganic carbon"
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to lower overall oceanic alkalinity, tending to raise pH and thereby atmospheric CO2 levels if not counterbalanced by the new input of alkalinity from weathering. The portion of carbon that is permanently buried at the sea floor becomes part of the geologic record. Calcium carbonate often forms remarkable deposits that can then be raised onto land through tectonic motion as in the case with the White Cliffs of Dover in Southern England. These cliffs are made almost entirely of the plates of buried coccolithophores. === Carbonate pump === The carbonate pump, sometimes called the carbonate counter pump, starts with marine organisms at the ocean's surface producing particulate inorganic carbon (PIC) in the form of calcium carbonate (calcite or aragonite, CaCO3). This CaCO3 is what forms hard body parts like shells. The formation of these shells increases atmospheric CO2 due to the production of CaCO3 in the following reaction with simplified stoichiometry:Coccolithophores, a nearly ubiquitous group of phytoplankton that produce shells of calcium carbonate, are the dominant contributors to the carbonate pump. Due to their abundance, coccolithophores have significant implications on carbonate chemistry, in the surface waters they inhabit and in the ocean below: they provide a large mechanism for the downward transport of CaCO3. The air-sea CO2 flux induced by a marine biological community can be determined by the rain ratio - the proportion of carbon from calcium carbonate compared to that from organic carbon in particulate matter sinking to the ocean floor, (PIC/POC). The carbonate pump acts as a negative feedback on CO2 taken into the ocean by the solubility pump. It occurs with lesser magnitude than the solubility pump. The carbonate pump is sometimes referred to as the "hard tissue" component of the biological pump. Some surface marine organisms, like coccolithophores, produce hard structures out of calcium carbonate,
|
{
"page_id": 67766374,
"source": null,
"title": "Particulate inorganic carbon"
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a form of particulate inorganic carbon, by fixing bicarbonate. This fixation of DIC is an important part of the oceanic carbon cycle. Ca2+ + 2 HCO3− → CaCO3 + CO2 + H2O While the biological carbon pump fixes inorganic carbon (CO2) into particulate organic carbon in the form of sugar (C6H12O6), the carbonate pump fixes inorganic bicarbonate and causes a net release of CO2. In this way, the carbonate pump could be termed the carbonate counter pump. It works counter to the biological pump by counteracting the CO2 flux from the biological pump. == Calcite and aragonite seas == An aragonite sea contains aragonite and high-magnesium calcite as the primary inorganic calcium carbonate precipitates. The chemical conditions of the seawater must be notably high in magnesium content relative to calcium (high Mg/Ca ratio) for an aragonite sea to form. This is in contrast to a calcite sea in which seawater low in magnesium content relative to calcium (low Mg/Ca ratio) favors the formation of low-magnesium calcite as the primary inorganic marine calcium carbonate precipitate. The Early Paleozoic and the Middle to Late Mesozoic oceans were predominantly calcite seas, whereas the Middle Paleozoic through the Early Mesozoic and the Cenozoic (including today) are characterized by aragonite seas. Aragonite seas occur due to several factors, the most obvious of these is a high seawater Mg/Ca ratio (Mg/Ca > 2), which occurs during intervals of slow seafloor spreading. However, the sea level, temperature, and calcium carbonate saturation state of the surrounding system also determine which polymorph of calcium carbonate (aragonite, low-magnesium calcite, high-magnesium calcite) will form. Likewise, the occurrence of calcite seas is controlled by the same suite of factors controlling aragonite seas, with the most obvious being a low seawater Mg/Ca ratio (Mg/Ca < 2), which occurs during intervals of rapid seafloor
|
{
"page_id": 67766374,
"source": null,
"title": "Particulate inorganic carbon"
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spreading. == Whiting events == A whiting event is a phenomenon that occurs when a suspended cloud of fine-grained calcium carbonate precipitates in water bodies, typically during summer months, as a result of photosynthetic microbiological activity or sediment disturbance. The phenomenon gets its name from the white, chalky color it imbues to the water. These events have been shown to occur in temperate waters as well as tropical ones, and they can span for hundreds of meters. They can also occur in both marine and freshwater environments. The origin of whiting events is debated among the scientific community, and it is unclear if there is a single, specific cause. Generally, they are thought to result from either bottom sediment re-suspension or by increased activity of certain microscopic life such as phytoplankton. Because whiting events affect aquatic chemistry, physical properties, and carbon cycling, studying the mechanisms behind them holds scientific relevance in various ways. == Great Calcite Belt == The Great Calcite Belt (GCB) of the Southern Ocean is a region of elevated summertime upper ocean calcite concentration derived from coccolithophores, despite the region being known for its diatom predominance. The overlap of two major phytoplankton groups, coccolithophores and diatoms, in the dynamic frontal systems characteristic of this region provides an ideal setting to study environmental influences on the distribution of different species within these taxonomic groups. The Great Calcite Belt, defined as an elevated particulate inorganic carbon (PIC) feature occurring alongside seasonally elevated chlorophyll a in austral spring and summer in the Southern Ocean, plays an important role in climate fluctuations, accounting for over 60% of the Southern Ocean area (30–60° S). The region between 30° and 50° S has the highest uptake of anthropogenic carbon dioxide (CO2) alongside the North Atlantic and North Pacific oceans. Knowledge of the impact
|
{
"page_id": 67766374,
"source": null,
"title": "Particulate inorganic carbon"
}
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of interacting environmental influences on phytoplankton distribution in the Southern Ocean is limited. For example, more understanding is needed of how light and iron availability or temperature and pH interact to control phytoplankton biogeography. Hence, if model parameterizations are to improve to provide accurate predictions of biogeochemical change, a multivariate understanding of the full suite of environmental drivers is required. The Southern Ocean has often been considered as a microplankton-dominated (20–200 μm) system with phytoplankton blooms dominated by large diatoms and Phaeocystis sp. However, since the identification of the GCB as a consistent feature and the recognition of picoplankton (< 2 μm) and nanoplankton (2–20 μm) importance in high-nutrient, low-chlorophyll (HNLC) waters, the dynamics of small (bio)mineralizing plankton and their export need to be acknowledged. The two dominant biomineralizing phytoplankton groups in the GCB are coccolithophores and diatoms. Coccolithophores are generally found north of the polar front, though Emiliania huxleyi has been observed as far south as 58° S in the Scotia Sea, at 61° S across Drake Passage, and at 65°S south of Australia. Diatoms are present throughout the GCB, with the polar front marking a strong divide between different size fractions. North of the polar front, small diatom species, such as Pseudo-nitzschia spp. and Thalassiosira spp., tend to dominate numerically, whereas large diatoms with higher silicic acid requirements (e.g., Fragilariopsis kerguelensis) are generally more abundant south of the polar front. High abundances of nanoplankton (coccolithophores, small diatoms, chrysophytes) have also been observed on the Patagonian Shelf and in the Scotia Sea. Currently, few studies incorporate small biomineralizing phytoplankton to species level. Rather, the focus has often been on the larger and noncalcifying species in the Southern Ocean due to sample preservation issues (i.e., acidified Lugol’s solution dissolves calcite, and light microscopy restricts accurate identification to cells > 10
|
{
"page_id": 67766374,
"source": null,
"title": "Particulate inorganic carbon"
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μm. In the context of climate change and future ecosystem function, the distribution of biomineralizing phytoplankton is important to define when considering phytoplankton interactions with carbonate chemistry, and ocean biogeochemistry. The Great Calcite Belt spans the major Southern Ocean circumpolar fronts: the Subantarctic front, the polar front, the Southern Antarctic Circumpolar Current front, and occasionally the southern boundary of the Antarctic Circumpolar Current. The subtropical front (at approximately 10 °C) acts as the northern boundary of the GCB and is associated with a sharp increase in PIC southwards. These fronts divide distinct environmental and biogeochemical zones, making the GCB an ideal study area to examine controls on phytoplankton communities in the open ocean. A high PIC concentration observed in the GCB (1 μmol PIC L−1) compared to the global average (0.2 μmol PIC L−1) and significant quantities of detached E. huxleyi coccoliths (in concentrations > 20,000 coccoliths mL−1) both characterize the GCB. The GCB is clearly observed in satellite imagery spanning from the Patagonian Shelf across the Atlantic, Indian, and Pacific oceans and completing Antarctic circumnavigation via the Drake Passage. == Coccolithophores == Since the industrial revolution 30% of the anthropogenic CO2 has been absorbed by the oceans, resulting in ocean acidification, which is a threat to calcifying alga. As a result, there has been profound interest in these calcifying algae, boosted by their major role in the global carbon cycle. Globally, coccolithophores, particularly Emiliania huxleyi, are considered to be the most dominant calcifying algae, which blooms can even be seen from outer space. Calcifying algae create an exoskeleton from calcium carbonate platelets (coccoliths), providing ballast which enhances the organic and inorganic carbon flux to the deep sea. Organic carbon is formed by means of photosynthesis, where CO2 is fixed and converted into organic molecules, causing removal of CO2 from
|
{
"page_id": 67766374,
"source": null,
"title": "Particulate inorganic carbon"
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the seawater. Counterintuitively, the production of coccoliths leads to the release of CO2 in the seawater, due to removal of carbonate from the seawater, which reduces the alkalinity and causes acidification. Therefore, the ratio between particulate inorganic carbon (PIC) and particulate organic carbon (POC) is an important measure for the net release or uptake of CO2. In short, the PIC:POC ratio is a key characteristic required to understand and predict the impact of climate change on the global ocean carbon cycle. == Calcium particle morphologies == Protist shells == See also == carbonate compensation depth aragonite compensation depth lysocline calcareous ooze Carbonate pump Marine biogenic calcification snowline: the depth at which carbonate disappear from sediments under steady-state conditions == References == == Sources == Adabi, Mohammad H. (2004), "A re-evaluation of aragonite versus calcite seas", Carbonates and Evaporites, 19 (2): 133–141, Bibcode:2004CarEv..19..133A, doi:10.1007/BF03178476, S2CID 128955184 Hardie, Lawrence A (1996), "Secular variation in seawater chemistry: An explanation for the coupled secular variation in the mineralogies of marine limestones and potash evaporites over the past 600 my", Geology, 24 (3), Geological Society of America: 279–283, Bibcode:1996Geo....24..279H, doi:10.1130/0091-7613(1996)024<0279:svisca>2.3.co;2 Hardie, Lawrence A. (2003), "Secular variations in Precambrian seawater chemistry and the timing of Precambrian aragonite seas and calcite seas", Geology, 31 (9): 785–788, Bibcode:2003Geo....31..785H, doi:10.1130/g19657.1 Lowenstein, T.K.; Timofeeff, M.N.; Brennan, S.T.; Hardie, L.A.; Demicco, R.V. (2001), "Oscillations in Phanerozoic seawater chemistry: evidence from fluid inclusions", Science, 294 (5544): 1086–1088, Bibcode:2001Sci...294.1086L, doi:10.1126/science.1064280, PMID 11691988, S2CID 2680231 Morse, J.W.; Mackenzie, F.T. (1990). "Geochemistry of sedimentary carbonates". Developments in Sedimentology. 48: 1–707. doi:10.1016/S0070-4571(08)70330-3. Palmer, T.J.; Wilson, M.A. (2004). "Calcite precipitation and dissolution of biogenic aragonite in shallow Ordovician calcite seas". Lethaia. 37 (4): 417–427 [1]. Bibcode:2004Letha..37..417P. doi:10.1080/00241160410002135. Wilkinson, B.H.; Given, K.R. (1986). "Secular variation in abiotic marine carbonates: constraints on Phanerozoic atmospheric carbon dioxide contents and oceanic
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{
"page_id": 67766374,
"source": null,
"title": "Particulate inorganic carbon"
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Mg/Ca ratios". Journal of Geology. 94 (3): 321–333. Bibcode:1986JG.....94..321W. doi:10.1086/629032. S2CID 128840375. Wilkinson, B.H.; Owen, R.M.; Carroll, A.R. (1985). "Submarine hydrothermal weathering, global eustacy, and carbonate polymorphism in Phanerozoic marine oolites". Journal of Sedimentary Petrology. 55: 171–183. doi:10.1306/212f8657-2b24-11d7-8648000102c1865d.
|
{
"page_id": 67766374,
"source": null,
"title": "Particulate inorganic carbon"
}
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A synaptic transistor is an electrical device that can learn in ways similar to a neural synapse. It optimizes its own properties for the functions it has carried out in the past. The device mimics the behavior of the property of neurons called spike-timing-dependent plasticity, or STDP. == Structure == Its structure is similar to that of a field effect transistor, where an ionic liquid takes the place of the gate insulating layer between the gate electrode and the conducting channel. That channel is composed of samarium nickelate (SmNiO3, or SNO) rather than the field effect transistor's doped silicon. == Function == A synaptic transistor has a traditional immediate response whose amount of current that passes between the source and drain contacts varies with voltage applied to the gate electrode. It also produces a much slower learned response such that the conductivity of the SNO layer varies in response to the transistor's STDP history, essentially by shuttling oxygen ions between the SNO and the ionic liquid. The analog of strengthening a synapse is to increase the SNO's conductivity, which essentially increases gain. Similarly, weakening a synapse is analogous to decreasing the SNO's conductivity, lowering the gain. The input and output of the synaptic transistor are continuous analog values, rather than digital on-off signals. While the physical structure of the device has the potential to learn from history, it contains no way to bias the transistor to control the memory effect. An external supervisory circuit converts the time delay between input and output into a voltage applied to the ionic liquid that either drives ions into the SNO or removes them. A network of such devices can learn particular responses to "sensory inputs", with those responses being learned through experience rather than explicitly programmed. == References ==
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{
"page_id": 41027689,
"source": null,
"title": "Synaptic transistor"
}
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Activated carbon, also called activated charcoal, is a form of carbon commonly used to filter contaminants from water and air, among many other uses. It is processed (activated) to have small, low-volume pores that greatly increase the surface area available for adsorption or chemical reactions. (Adsorption, not to be confused with absorption, is a process where atoms or molecules adhere to a surface). The pores can be thought of as a microscopic "sponge" structure. Activation is analogous to making popcorn from dried corn kernels: popcorn is light, fluffy, and its kernels have a high surface-area-to-volume ratio. Activated is sometimes replaced by active. Because it is so porous on a microscopic scale, one gram of activated carbon has a surface area of over 3,000 square metres (32,000 square feet), as determined by gas absorption. Researchers at Cornell University synthesized an ultrahigh surface area activated carbon with a BET area of 4,800 m2 (52,000 sq ft). This BET area value is the highest reported in the literature for activated carbon to date. For charcoal, the equivalent figure before activation is about 2–5 square metres (22–54 sq ft). A useful activation level may be obtained solely from high surface area. Further chemical treatment often enhances adsorption properties. Activated carbon is usually derived from waste products such as coconut husks; waste from paper mills has been studied as a source. These bulk sources are converted into charcoal before being activated. When derived from coal, it is referred to as activated coal. Activated coke is derived from coke. == Uses == Activated carbon is used in methane and hydrogen storage, air purification, capacitive deionization, supercapacitive swing adsorption, solvent recovery, decaffeination, gold purification, metal extraction, water purification, medicine, sewage treatment, air filters in respirators, filters in compressed air, teeth whitening, production of hydrogen chloride, edible electronics,
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{
"page_id": 395375,
"source": null,
"title": "Activated carbon"
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and many other applications. === Industrial === One major industrial application involves use of activated carbon in metal finishing for purification of electroplating solutions. For example, it is the main purification technique for removing organic impurities from bright nickel plating solutions. A variety of organic chemicals are added to plating solutions for improving their deposit qualities and for enhancing properties like brightness, smoothness, ductility, etc. Due to passage of direct current and electrolytic reactions of anodic oxidation and cathodic reduction, organic additives generate unwanted breakdown products in solution. Their excessive build up can adversely affect plating quality and physical properties of deposited metal. Activated carbon treatment removes such impurities and restores plating performance to the desired level. === Medical === Activated carbon is used to treat poisonings and overdoses following oral ingestion. Tablets or capsules of activated carbon are used in many countries as an over-the-counter drug to treat diarrhea, indigestion, and flatulence. However, activated charcoal shows no effect on intestinal gas and diarrhea, is ordinarily medically ineffective if poisoning resulted from ingestion of corrosive agents, boric acid, or petroleum products, and is particularly ineffective against poisonings of strong acids or bases, cyanide, iron, lithium, arsenic, methanol, ethanol, or ethylene glycol. Activated carbon will not prevent these chemicals from being absorbed into the human body. It is on the World Health Organization's List of Essential Medicines. Incorrect application (e.g. into the lungs) results in pulmonary aspiration, which can sometimes be fatal if immediate medical treatment is not initiated. === Analytical chemistry === Activated carbon, in 50% w/w combination with celite, is used as stationary phase in low-pressure chromatographic separation of carbohydrates (mono-, di-, tri-saccharides) using ethanol solutions (5–50%) as mobile phase in analytical or preparative protocols. Activated carbon is useful for extracting the direct oral anticoagulants (DOACs) such as dabigatran,
|
{
"page_id": 395375,
"source": null,
"title": "Activated carbon"
}
|
apixaban, rivaroxaban and edoxaban from blood plasma samples. For this purpose it has been made into "minitablets", each containing 5 mg activated carbon for treating 1ml samples of DOAC. Since this activated carbon has no effect on blood clotting factors, heparin or most other anticoagulants this allows a plasma sample to be analyzed for abnormalities otherwise affected by the DOACs. === Environmental === Carbon adsorption has numerous applications in removing pollutants from air or water streams both in the field and in industrial processes such as: Spill cleanup Groundwater remediation Drinking water filtration Wastewater treatment Air purification Volatile organic compounds capture from painting, dry cleaning, gasoline dispensing operations, and other processes Volatile organic compounds recovery (SRU, Solvent Recovery Unit; SRP, Solvent Recovery Plant; SRS, Solvent Recovery System) from flexible packaging, converting, coating, and other processes. During early implementation of the 1974 Safe Drinking Water Act in the US, EPA officials developed a rule that proposed requiring drinking water treatment systems to use granular activated carbon. Because of its high cost, the so-called GAC rule encountered strong opposition across the country from the water supply industry, including the largest water utilities in California. Hence, the agency set aside the rule. Activated carbon filtration is an effective water treatment method due to its multi-functional nature. There are specific types of activated carbon filtration methods and equipment that are indicated – depending upon the contaminants involved. Activated carbon is also used for the measurement of radon concentration in air. Biomass waste-derived activated carbons were also successfully used for the removal of caffeine and paracetamol from water. === Agricultural === Activated carbon (charcoal) is an allowed substance used by organic farmers in both livestock production and wine making. In livestock production it is used as a pesticide, animal feed additive, processing aid, nonagricultural ingredient
|
{
"page_id": 395375,
"source": null,
"title": "Activated carbon"
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and disinfectant. In organic winemaking, activated carbon is allowed for use as a processing agent to adsorb brown color pigments from white grape concentrates. It is sometimes used as biochar. === Distilled alcoholic beverage purification === Activated carbon filters (AC filters) can be used to filter vodka and whiskey of organic impurities which can affect color, taste, and odor. Passing an organically impure vodka through an activated carbon filter at the proper flow rate will result in vodka with an identical alcohol content and significantly increased organic purity, as judged by odor and taste. === Fuel storage === Research is being done testing various activated carbons' ability to store natural gas and hydrogen gas. The porous material acts like a sponge for different types of gases. The gas is attracted to the carbon material via Van der Waals forces. Some carbons have been able to achieve binding energies of 5–10 kJ per mol. The gas may then be desorbed when subjected to higher temperatures and either combusted to do work or in the case of hydrogen gas extracted for use in a hydrogen fuel cell. Gas storage in activated carbons is an appealing gas storage method because the gas can be stored in a low pressure, low mass, low volume environment that would be much more feasible than bulky on-board pressure tanks in vehicles. The United States Department of Energy has specified certain goals to be achieved in the area of research and development of nano-porous carbon materials. All of the goals are yet to be satisfied but numerous institutions, including the ALL-CRAFT program, are continuing to conduct work in this field. === Gas purification === Filters with activated carbon are usually used in compressed air and gas purification to remove oil vapors, odor, and other hydrocarbons from the air.
|
{
"page_id": 395375,
"source": null,
"title": "Activated carbon"
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The most common designs use a 1-stage or 2 stage filtration principle in which activated carbon is embedded inside the filter media. Activated carbon filters are used to retain radioactive gases within the air vacuumed from a nuclear boiling water reactor turbine condenser. The large charcoal beds adsorb these gases and retain them while they rapidly decay to nonradioactive solid species. The solids are trapped in the charcoal particles, while the filtered air passes through. === Chemical purification === Activated carbon is commonly used on the laboratory scale to purify solutions of organic molecules containing unwanted colored organic impurities. Filtration over activated carbon is used in large scale fine chemical and pharmaceutical processes for the same purpose. The carbon is either mixed with the solution then filtered off or immobilized in a filter. === Mercury scrubbing === Activated carbon, often infused with sulfur or iodine, is widely used to trap mercury emissions from coal-fired power stations, medical incinerators, and from natural gas at the wellhead. However, despite its effectiveness, activated carbon is expensive to use. Since it is often not recycled, the mercury-laden activated carbon presents a disposal dilemma. If the activated carbon contains less than 260 ppm mercury, United States federal regulations allow it to be stabilized (for example, trapped in concrete) for landfilling. However, waste containing greater than 260 ppm is considered to be in the high-mercury subcategory and is banned from landfilling (Land-Ban Rule). This material is now accumulating in warehouses and in deep abandoned mines at an estimated rate of 100 tons per year. The problem of disposal of mercury-laden activated carbon is not unique to the United States. In the Netherlands, this mercury is largely recovered and the activated carbon is disposed of by complete burning, forming carbon dioxide (CO2). === Food additive === Activated,
|
{
"page_id": 395375,
"source": null,
"title": "Activated carbon"
}
|
food-grade charcoal became a food trend in 2016, being used as an additive to impart a "slightly smoky" taste and a dark coloring to products including hotdogs, ice cream, pizza bases, and bagels. People taking medication, including birth control pills and antidepressants, are advised to avoid novelty foods or drinks that use activated charcoal coloring since it can render the medication ineffective. === Smoking filtration === Activated charcoal is used in smoking filters as a way to reduce the tar content and other chemicals present in smoke, which is a result of combustion, wherein it has been found to reduce the toxicants from tobacco smoke, in particular the free radicals. == Structure of activated carbon == The structure of activated carbon has long been a subject of debate. In a book published in 2006, Harry Marsh and Francisco Rodríguez-Reinoso considered more than 15 models for the structure, without coming to a definite conclusion about which was correct. Recent work using aberration-corrected transmission electron microscopy has suggested that activated carbons may have a structure related to that of the fullerenes, with pentagonal and heptagonal carbon rings. == Production == Activated carbon is carbon produced from carbonaceous source materials such as bamboo, coconut husk, willow peat, wood, coir, lignite, coal, and petroleum pitch. It can be produced (activated) by one of the following processes: Physical activation: The source material is developed into activated carbon using hot gases. Air is then introduced to burn out the gases, creating a graded, screened and de-dusted form of activated carbon. This is generally done by using one or more of the following processes: Carbonization: Material with carbon content is pyrolyzed at temperatures in the range 600–900 °C, usually in an inert atmosphere with gases such as argon or nitrogen Activation/oxidation: Raw material or carbonized material is
|
{
"page_id": 395375,
"source": null,
"title": "Activated carbon"
}
|
exposed to oxidizing atmospheres (oxygen or steam) at temperatures above 250 °C, usually in the temperature range of 600–1200 °C. The activation is performed by heating the sample for 1 h in a muffle furnace at 450 °C in the presence of air. Chemical activation: The carbon material is impregnated with certain chemicals. The chemical is typically an acid, strong base, or a salt (phosphoric acid 25%, potassium hydroxide 5%, sodium hydroxide 5%, potassium carbonate 5%, calcium chloride 25%, and zinc chloride 25%). The carbon is then subjected to high temperatures (250–600 °C). It is believed that the temperature activates the carbon at this stage by forcing the material to open up and have more microscopic pores. Chemical activation is preferred to physical activation owing to the lower temperatures, better quality consistency, and shorter time needed for activating the material. The Dutch company Norit NV, part of the Cabot Corporation, is the largest producer of activated carbon in the world. Haycarb, a Sri Lankan coconut shell-based company, controls 16% of the global market share. == Classification == Activated carbons are complex products which are difficult to classify on the basis of their behaviour, surface characteristics and other fundamental criteria. However, some broad classification is made for general purposes based on their size, preparation methods, and industrial applications. === Powdered activated carbon (PAC) === Normally, activated carbons (R 1) are made in particulate form as powders or fine granules less than 1.0 mm in size with an average diameter between 0.15 and 0.25 mm. Thus they present a large surface to volume ratio with a small diffusion distance. Activated carbon (R 1) is defined as the activated carbon particles retained on a 50-mesh sieve (0.297 mm). Powdered activated carbon (PAC) material is finer material. PAC is made up of crushed or
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"page_id": 395375,
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ground carbon particles, 95–100% of which will pass through a designated mesh sieve. The ASTM classifies particles passing through an 80-mesh sieve (0.177 mm) and smaller as PAC. It is not common to use PAC in a dedicated vessel, due to the high head loss that would occur. Instead, PAC is generally added directly to other process units, such as raw water intakes, rapid mix basins, clarifiers, and gravity filters. === Granular activated carbon (GAC) === Granular activated carbon (GAC) has a relatively larger particle size compared to powdered activated carbon and consequently, presents a smaller external surface. Diffusion of the adsorbate is thus an important factor. These carbons are suitable for adsorption of gases and vapors, because gaseous substances diffuse rapidly. Granulated carbons are used for air filtration and water treatment, as well as for general deodorization and separation of components in flow systems and in rapid mix basins. GAC can be obtained in either granular or extruded form. GAC is designated by sizes such as 8×20, 20×40, or 8×30 for liquid phase applications and 4×6, 4×8 or 4×10 for vapor phase applications. A 20×40 carbon is made of particles that will pass through a U.S. Standard Mesh Size No. 20 sieve (0.84 mm) (generally specified as 85% passing) but be retained on a U.S. Standard Mesh Size No. 40 sieve (0.42 mm) (generally specified as 95% retained). AWWA (1992) B604 uses the 50-mesh sieve (0.297 mm) as the minimum GAC size. The most popular aqueous-phase carbons are the 12×40 and 8×30 sizes because they have a good balance of size, surface area, and head loss characteristics. === Extruded activated carbon (EAC) === Extruded activated carbon (EAC) combines powdered activated carbon with a binder, which are fused together and extruded into a cylindrical shaped activated carbon block with diameters
|
{
"page_id": 395375,
"source": null,
"title": "Activated carbon"
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from 0.8 to 130 mm. These are mainly used for gas phase applications because of their low pressure drop, high mechanical strength and low dust content. Also sold as CTO filter (Chlorine, Taste, Odor). === Bead activated carbon (BAC) === Bead activated carbon (BAC) is made from petroleum pitch and supplied in diameters from approximately 0.35 to 0.80 mm. Similar to EAC, it is also noted for its low pressure drop, high mechanical strength and low dust content, but with a smaller grain size. Its spherical shape makes it preferred for fluidized bed applications such as water filtration. === Impregnated carbon === Porous carbons containing several types of inorganic impregnate such as iodine and silver. Cations such as aluminium, manganese, zinc, iron, lithium, and calcium have also been prepared for specific application in air pollution control especially in museums and galleries. Due to its antimicrobial and antiseptic properties, silver loaded activated carbon is used as an adsorbent for purification of domestic water. Drinking water can be obtained from natural water by treating the natural water with a mixture of activated carbon and aluminium hydroxide (Al(OH)3), a flocculating agent. Impregnated carbons are also used for the adsorption of hydrogen sulfide (H2S) and thiols. Adsorption rates for H2S as high as 50% by weight have been reported. === Polymer coated carbon === This is a process by which a porous carbon can be coated with a biocompatible polymer to give a smooth and permeable coat without blocking the pores. The resulting carbon is useful for hemoperfusion. Hemoperfusion is a treatment technique in which large volumes of the patient's blood are passed over an adsorbent substance in order to remove toxic substances from the blood. === Woven carbon === There is a technology of processing technical rayon fiber into activated carbon cloth for
|
{
"page_id": 395375,
"source": null,
"title": "Activated carbon"
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carbon filtering. Adsorption capacity of activated cloth is greater than that of activated charcoal (BET theory) surface area: 500–1500 m2/g, pore volume: 0.3–0.8 cm3/g). Thanks to the different forms of activated material, it can be used in a wide range of applications (supercapacitors, odor absorbers, CBRN-defense industry etc.). == Properties == A gram of activated carbon can have a surface area in excess of 500 m2 (5,400 sq ft), with 3,000 m2 (32,000 sq ft) being readily achievable. Carbon aerogels, while more expensive, have even higher surface areas, and are used in special applications. Under an electron microscope, the high surface-area structures of activated carbon are revealed. Individual particles are intensely convoluted and display various kinds of porosity; there may be many areas where flat surfaces of graphite-like material run parallel to each other, separated by only a few nanometres or so. These micropores provide superb conditions for adsorption to occur, since adsorbing material can interact with many surfaces simultaneously. Tests of adsorption behaviour are usually done with nitrogen gas at 77 K under high vacuum, but in everyday terms activated carbon is perfectly capable of producing the equivalent, by adsorption from its environment, liquid water from steam at 100 °C (212 °F) and a pressure of 1/10,000 of an atmosphere. James Dewar, the scientist after whom the Dewar (vacuum flask) is named, spent much time studying activated carbon and published a paper regarding its adsorption capacity with regard to gases. In this paper, he discovered that cooling the carbon to liquid nitrogen temperatures allowed it to adsorb significant quantities of numerous air gases, among others, that could then be recollected by simply allowing the carbon to warm again and that coconut-based carbon was superior for the effect. He uses oxygen as an example, wherein the activated carbon would typically
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{
"page_id": 395375,
"source": null,
"title": "Activated carbon"
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adsorb the atmospheric concentration (21%) under standard conditions, but release over 80% oxygen if the carbon was first cooled to low temperatures. Physically, activated carbon binds materials by van der Waals force or London dispersion force. Activated carbon does not bind well to certain chemicals, including alcohols, diols, strong acids and bases, metals and most inorganics, such as lithium, sodium, iron, lead, arsenic, fluorine, and boric acid. Activated carbon adsorbs iodine very well. The iodine capacity, mg/g, (ASTM D28 Standard Method test) may be used as an indication of total surface area. Carbon monoxide is not well adsorbed by activated carbon. This should be of particular concern to those using the material in filters for respirators, fume hoods, or other gas control systems because the gas is undetectable to the human senses, toxic to the metabolism, and neurotoxic. Substantial lists of the common industrial and agricultural gases adsorbed by activated carbon can be found online. Activated carbon can be used as a substrate for the application of various chemicals to improve the adsorptive capacity for some inorganic (and problematic organic) compounds such as hydrogen sulfide (H2S), ammonia (NH3), formaldehyde (HCOH), mercury (Hg) and radioactive iodine-131(131I). This property is known as chemisorption. === Iodine number === Many carbons preferentially adsorb small molecules. Iodine number is the most fundamental parameter used to characterize activated carbon performance. It is a measure of activity level (higher number indicates higher degree of activation) often reported in mg/g (typical range 500–1200 mg/g). It is a measure of the micropore content of the activated carbon (0 to 20 Å, or up to 2 nm) by adsorption of iodine from solution. It is equivalent to surface area of carbon between 900 and 1100 m2/g. It is the standard measure for liquid-phase applications. Iodine number is defined as the
|
{
"page_id": 395375,
"source": null,
"title": "Activated carbon"
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milligrams of iodine adsorbed by one gram of carbon when the iodine concentration in the residual filtrate is at a concentration of 0.02 normal (i.e. 0.02N). Basically, iodine number is a measure of the iodine adsorbed in the pores and, as such, is an indication of the pore volume available in the activated carbon of interest. Typically, water-treatment carbons have iodine numbers ranging from 600 to 1100. Frequently, this parameter is used to determine the degree of exhaustion of a carbon in use. However, this practice should be viewed with caution, as chemical interactions with the adsorbate may affect the iodine uptake, giving false results. Thus, the use of iodine number as a measure of the degree of exhaustion of a carbon bed can only be recommended if it has been shown to be free of chemical interactions with adsorbates and if an experimental correlation between iodine number and the degree of exhaustion has been determined for the particular application. === Molasses === Some carbons are more adept at adsorbing large molecules. Molasses number or molasses efficiency is a measure of the mesopore content of the activated carbon (greater than 20 Å, or larger than 2 nm) by adsorption of molasses from solution. A high molasses number indicates a high adsorption of big molecules (range 95–600). Caramel dp (decolorizing performance) is similar to molasses number. Molasses efficiency is reported as a percentage (range 40%–185%) and parallels molasses number (600 = 185%, 425 = 85%). The European molasses number (range 525–110) is inversely related to the North American molasses number. Molasses Number is a measure of the degree of decolorization of a standard molasses solution that has been diluted and standardized against standardized activated carbon. Due to the size of color bodies, the molasses number represents the potential pore volume available
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{
"page_id": 395375,
"source": null,
"title": "Activated carbon"
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for larger adsorbing species. As all of the pore volume may not be available for adsorption in a particular waste water application, and as some of the adsorbate may enter smaller pores, it is not a good measure of the worth of a particular activated carbon for a specific application. Frequently, this parameter is useful in evaluating a series of active carbons for their rates of adsorption. Given two active carbons with similar pore volumes for adsorption, the one having the higher molasses number will usually have larger feeder pores resulting in more efficient transfer of adsorbate into the adsorption space. === Tannin === Tannins are a mixture of large and medium size molecules. Carbons with a combination of macropores and mesopores adsorb tannins. The ability of a carbon to adsorb tannins is reported in parts per million concentration (range 200 ppm–362 ppm). === Methylene blue === Some carbons have a mesopore (20 Å to 50 Å, or 2 to 5 nm) structure which adsorbs medium size molecules, such as the dye methylene blue. Methylene blue adsorption is reported in g/100g (range 11–28 g/100g). === Dechlorination === Some carbons are evaluated based on the dechlorination half-life length, which measures the chlorine-removal efficiency of activated carbon. The dechlorination half-value length is the depth of carbon required to reduce the chlorine concentration by 50%. A lower half-value length indicates superior performance. === Apparent density === The solid or skeletal density of activated carbons will typically range between 2000 and 2100 kg/m3 (125–130 lbs./cubic foot). However, a large part of an activated carbon sample will consist of air space between particles, and the actual or apparent density will therefore be lower, typically 400 to 500 kg/m3 (25–31 lbs./cubic foot). Higher density provides greater volume activity and normally indicates better-quality activated carbon. ASTM D
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{
"page_id": 395375,
"source": null,
"title": "Activated carbon"
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2854 -09 (2014) is used to determine the apparent density of activated carbon. === Hardness/abrasion number === It is a measure of the activated carbon's resistance to attrition. It is an important indicator of activated carbon to maintain its physical integrity and withstand frictional forces. There are large differences in the hardness of activated carbons, depending on the raw material and activity levels (porosity). === Ash content === Ash reduces the overall activity of activated carbon and reduces the efficiency of reactivation. The amount is exclusively dependent on the base raw material used to produce the activated carbon (e.g., coconut, wood, coal, etc.). The metal oxides (Fe2O3) can leach out of activated carbon resulting in discoloration. Acid/water-soluble ash content is more significant than total ash content. Soluble ash content can be very important for aquarists, as ferric oxide can promote algal growths. A carbon with a low soluble ash content should be used for marine, freshwater fish and reef tanks to avoid heavy metal poisoning and excess plant/algal growth. ASTM (D2866 Standard Method test) is used to determine the ash content of activated carbon. === Carbon tetrachloride activity === Measurement of the porosity of an activated carbon by the adsorption of saturated carbon tetrachloride vapour. === Particle size distribution === The finer the particle size of an activated carbon, the better the access to the surface area and the faster the rate of adsorption kinetics. In vapour phase systems this needs to be considered against pressure drop, which will affect energy cost. Careful consideration of particle size distribution can provide significant operating benefits. However, in the case of using activated carbon for adsorption of minerals such as gold, the particle size should be in the range of 3.35–1.4 millimetres (0.132–0.055 in). Activated carbon with particle size less than 1 mm
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{
"page_id": 395375,
"source": null,
"title": "Activated carbon"
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would not be suitable for elution (the stripping of mineral from an activated carbon). Researchers at Cornell University synthesized an ultrahigh surface area activated carbon with a BET area of 4800 m2 g–1 and a total pore volume of 2.7 cm3 g–1. This BET area value is the highest reported in the literature for activated carbon to date. == Modification of properties and reactivity == Acid-base, oxidation-reduction and specific adsorption characteristics are strongly dependent on the composition of the surface functional groups. The surface of conventional activated carbon is reactive, capable of oxidation by atmospheric oxygen and oxygen plasma steam, and also carbon dioxide and ozone. Oxidation in the liquid phase is caused by a wide range of reagents (HNO3, H2O2, KMnO4). Through the formation of a large number of basic and acidic groups on the surface of oxidized carbon to sorption and other properties can differ significantly from the unmodified forms. Activated carbon can be nitrogenated by natural products or polymers or processing of carbon with nitrogenating reagents. Activated carbon can interact with chlorine, bromine and fluorine. Surface of activated carbon, like other carbon materials can be fluoralkylated by treatment with (per)fluoropolyether peroxide in a liquid phase, or with wide range of fluoroorganic substances by CVD-method. Such materials combine high hydrophobicity and chemical stability with electrical and thermal conductivity and can be used as electrode material for super capacitors. Sulfonic acid functional groups can be attached to activated carbon to give "starbons" which can be used to selectively catalyse the esterification of fatty acids. Formation of such activated carbons from halogenated precursors gives a more effective catalyst which is thought to be a result of remaining halogens improving stability. It is reported about synthesis of activated carbon with chemically grafted superacid sites –CF2SO3H. Some of the chemical properties of
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{
"page_id": 395375,
"source": null,
"title": "Activated carbon"
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activated carbon have been attributed to presence of the surface active carbon double bond. The Polyani adsorption theory is a popular method for analyzing adsorption of various organic substances to their surface. == Examples of adsorption == === Heterogeneous catalysis === The most commonly encountered form of chemisorption in industry, occurs when a solid catalyst interacts with a gaseous feedstock, the reactant/s. The adsorption of reactant/s to the catalyst surface creates a chemical bond, altering the electron density around the reactant molecule and allowing it to undergo reactions that would not normally be available to it. == Reactivation and regeneration == The reactivation or the regeneration of activated carbons involves restoring the adsorptive capacity of saturated activated carbon by desorbing adsorbed contaminants on the activated carbon surface. === Thermal reactivation === The most common regeneration technique employed in industrial processes is thermal reactivation. The thermal regeneration process generally follows three steps: Adsorbent drying at approximately 105 °C (221 °F) High temperature desorption and decomposition (500–900 °C (932–1,652 °F)) under an inert atmosphere Residual organic gasification by a non-oxidising gas (steam or carbon dioxide) at elevated temperatures (800 °C (1,470 °F)) The heat treatment stage utilises the exothermic nature of adsorption and results in desorption, partial cracking and polymerization of the adsorbed organics. The final step aims to remove charred organic residue formed in the porous structure in the previous stage and re-expose the porous carbon structure regenerating its original surface characteristics. After treatment the adsorption column can be reused. Per adsorption-thermal regeneration cycle between 5–15 wt% of the carbon bed is burnt off resulting in a loss of adsorptive capacity. Thermal regeneration is a high energy process due to the high required temperatures making it both an energetically and commercially expensive process. Plants that rely on thermal regeneration of activated
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{
"page_id": 395375,
"source": null,
"title": "Activated carbon"
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carbon have to be of a certain size before it is economically viable to have regeneration facilities onsite. As a result, it is common for smaller waste treatment sites to ship their activated carbon cores to specialised facilities for regeneration. === Other regeneration techniques === Current concerns with the high energy/cost nature of thermal regeneration of activated carbon has encouraged research into alternative regeneration methods to reduce the environmental impact of such processes. Though several of the regeneration techniques cited have remained areas of purely academic research, some alternatives to thermal regeneration systems have been employed in industry. Current alternative regeneration methods are: TSA (thermal swing adsorption) and/or PSA (pressure swing adsorption) processes: through convection (heat transfer) using steam, "hot" inert gas (typically heated nitrogen (150–250 °C (302–482 °F))), or vacuum (T+VSA or TVSA, combining TSA and VSA processes) in situ regeneration MWR (microwave regeneration) Chemical and solvent regeneration Microbial regeneration Electrochemical regeneration Ultrasonic regeneration Wet air oxidation == See also == Activated charcoal cleanse Biochar Bamboo charcoal Binchōtan Bone char Carbon filtering Carbocatalysis Conjugated microporous polymer Hydrogen storage Kværner process Onboard refueling vapor recovery == References == == External links == "Imaging the atomic structure of activated carbon" – Journal of Physics: Condensed Matter "How Does Activated Carbon Work?" at Slate "Worshiping the False Idols of Wellness" on activated charcoal as a useless wellness practice at the New York Times
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{
"page_id": 395375,
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Hesseltinella is a genus of fungi belonging to the family Cunninghamellaceae. The genus name of Hesseltinella is in honour of Clifford William Hesseltine (1917–1999), who was an American botanist (Mycology), Microbiologist, from the University of Wisconsin. The genus was circumscribed by Harbansh Prasad Upadhyay in Persoonia vol.6 (issue 1) on pages 111, 116-117 in 1970. The genus has cosmopolitan distribution. It has one known species; Hesseltinella vesiculosa H.P.Upadhyay == References ==
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{
"page_id": 67635312,
"source": null,
"title": "Hesseltinella"
}
|
The Ornithological Council is an association of ornithological organisations based in the Americas involved in bird study and conservation. It was established by Richard C. Banks and incorporated in Washington, D.C. in 1992 as a nonprofit organization. Its original members comprised the American Ornithologists' Union, Association of Field Ornithologists, Colonial Waterbirds Society (now the Waterbird Society), Cooper Ornithological Society, Pacific Seabird Group, Raptor Research Foundation and Wilson Ornithological Society. Since then they have been joined by CIPAMEX, the Neotropical Ornithological Society, the Society of Canadian Ornithologists and the Society for the Conservation and Study of Caribbean Birds. The Council focuses not only on issues affecting birds and their survival, but also the needs of ornithologists. It tries to resolve conflicts and promotes sound management and the sustainable use of natural resources. Issues include funding for research and educational programs; government regulations and permits for research activities; decision-making in habitat and biodiversity management; the impacts of birds on fisheries, in agriculture, and in urban areas; threatened species; the role of birds in ecosystems; and standards concerning the use and maintenance of live birds in research. == References == BIRDNET
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{
"page_id": 22808689,
"source": null,
"title": "Ornithological Council"
}
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The Letts nitrile synthesis is a chemical reaction of aromatic carboxylic acids with metal thiocyanates to form nitriles. The reaction includes the loss of carbon dioxide and potassium hydrosulfide. The polar basic substitution reaction was discovered in 1872 by Edmund A. Letts. == History == In 1857 Hugo Schiff observed that the reaction between benzoyl chloride with potassium cyanide produced the desired benzonitrile. Work done later by British chemist Edmund A. Letts delved much deeper into the synthesis of nitriles. Attempting first to add cyano-groups to acetic acid, he obtained a mixture of acetamide and carbonyl sulfide. However, in 1872 he showed that treating a 2:1 molecular ratio of benzoic acid and potassium thiocyanate with heat for several hours also produced nitriles with only a small amount of amide with about 40% yield. G. Krüss expanded on Letts' work in 1884, producing better yields by utilizing lead(II) thiocyanate. In 1916, E.E. Reid found that showed that dry distillation of the zinc(II) salt of the acid with a 20% excess of lead(II) thiocyanate gave an 86% conversion and 91% yield, almost double of that produced by Letts. == Mechanism == Kekulé proposed the reaction mechanism in 1873. In this polar basic substitution reaction mechanism, thiocyanate ion extracts the acidic proton from benzoic acid while heated. This yields the conjugate base (stabilized by resonance structures) and thiocyanic acid. The next step involves the evolution of carbon dioxide, where a lone pair of electrons moves from the negatively charged oxygen to form a double bond with the carboxylic carbon. The sigma bond between the ring and carboxyl group is then severed, the electron pair moving to the ring and delocalized through resonance structures. The final step of the mechanism involves the attack of the phenyl anion attacking the cyano-carbon, pushing the electron pair
|
{
"page_id": 5900402,
"source": null,
"title": "Letts nitrile synthesis"
}
|
over to the sulfur, which readily diffuses the negative charge and is further stabilized by the potassium ion, resulting in the final benzonitrile product and potassium hydrosulfide. == Applications == Aromatic nitriles have a few applications, including polyrecombination to form polymers, are sometimes studied as biologically active molecules and undergoing Ritter reactions to form amides. Benzonitrile, the original product of Letts, has multiple uses as a versatile reagent and as a solvent. Substituted benzonitriles are important in many fields including pharmaceuticals. Benzonitrile is a precursor in the synthesis of Fadrozole, an aromatase inhibitor used in the treatment of breast cancer. 4-(trifluoromethyl)benzonitrile, produced by the Nickel catalyzed cyanation of 4-chlorobenzotrifluoride is a precursor for the antidepressant Fluvoxamine. Benzonitrile can also act a ligand in asymmetric catalysis, coordinating to transition metals and forming Lewis acids. == See also == For synthesis of nitriles: Kolbe nitrile synthesis Rosenmund-von Braun reaction For reactions of nitriles: Pinner reaction Stephen aldehyde synthesis == References ==
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{
"page_id": 5900402,
"source": null,
"title": "Letts nitrile synthesis"
}
|
Paul Kunz (December 20, 1942 – September 12, 2018) was an American particle physicist and software developer, who initiated the deployment of the first web server outside of Europe. After a meeting in September 1991 with Tim Berners-Lee of CERN, he returned to the Stanford Linear Accelerator Center (SLAC) with word of the World Wide Web. By Thursday, December 12, 1991, there was an active Web server installed and operational at SLAC, establishing the first Web server in the US, the SPIRES HEP, connected to the SPIRES High Energy Physics database, thanks to the efforts of Kunz, Louise Addis, and Terry Hung. He was also the originator of the free/open source GNUstep implementation of the NeXTSTEP framework and also at the basis of the idea for objcX (objective-C for the X Window System). He was the chief developer of HippoDraw, a statistical analysis software, primarily intended for the analysis and presentation of particle physics and astrophysics data at SLAC. == External links == "GNUstep: Who's Who Developers" "Early World Wide Web at SLAC" == References ==
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{
"page_id": 1968245,
"source": null,
"title": "Paul Kunz"
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Detritivores (also known as detrivores, detritophages, detritus feeders or detritus eaters) are heterotrophs that obtain nutrients by consuming detritus (decomposing plant and animal parts as well as feces). There are many kinds of invertebrates, vertebrates, and plants that eat detritus or carry out coprophagy. By doing so, all these detritivores contribute to decomposition and the nutrient cycles. Detritivores should be distinguished from other decomposers, such as many species of bacteria, fungi and protists, which are unable to ingest discrete lumps of matter. Instead, these other decomposers live by absorbing and metabolizing on a molecular scale (saprotrophic nutrition). The terms detritivore and decomposer are often used interchangeably, but they describe different organisms. Detritivores are usually arthropods and help in the process of remineralization. Detritivores perform the first stage of remineralization, by fragmenting the dead plant matter, allowing decomposers to perform the second stage of remineralization. Plant tissues are made up of resilient molecules (e.g. cellulose, lignin, xylan) that decay at a much lower rate than other organic molecules. The activity of detritivores is the reason why there is not an accumulation of plant litter in nature. Detritivores are an important aspect of many ecosystems. They can live on any type of soil with an organic component, including marine ecosystems, where they are termed interchangeably with bottom feeders. Typical detritivorous animals include millipedes, springtails, woodlice, dung flies, slugs, many terrestrial worms, sea stars, sea cucumbers, fiddler crabs, and some sedentary marine Polychaetes such as worms of the family Terebellidae. Detritivores can be classified into more specific groups based on their size and biomes. Macrodetritivores are larger organisms such as millipedes, springtails, and woodlouse, while microdetritivores are smaller organisms such as bacteria. Scavengers are not typically thought to be detritivores, as they generally eat large quantities of organic matter, but both detritivores and
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{
"page_id": 723067,
"source": null,
"title": "Detritivore"
}
|
scavengers are the same type of cases of consumer-resource systems. The consumption of wood, whether alive or dead, is known as xylophagy. The activity of animals feeding only on dead wood is called sapro-xylophagy and those animals, sapro-xylophagous. == Ecology == Detritivores play an important role as recyclers in the ecosystem's energy flow and biogeochemical cycles. Alongside decomposers, they reintroduce vital elements such as carbon, nitrogen, phosphorus, calcium, and potassium back into the soil, allowing plants to take in these elements and use them for growth. They shred the dead plant matter which releases the trapped nutrients in the plant tissues. An abundance of detritivores in the soil allows the ecosystem to efficiently recycle nutrients. Many detritivores live in mature woodland, though the term can be applied to certain bottom-feeders in wet environments. These organisms play a crucial role in benthic ecosystems, forming essential food chains and participating in the nitrogen cycle. Detritivores and decomposers that reside in the desert live in burrows underground to avoid the hot surface since underground conditions provide favorable living conditions for them. Detritivores are the main organisms in clearing plant litter and recycling nutrients in the desert. Due to the limited vegetation available in the desert, desert detritivores adapted and evolved ways to feed in the extreme conditions of the desert. Detritivore feeding behaviour is affected by rainfall; moist soil increases detritivore feeding and excretion. Fungi, acting as decomposers, are important in today's terrestrial environment. During the Carboniferous period, fungi and bacteria had yet to evolve the capacity to digest lignin, and so large deposits of dead plant tissue accumulated during this period, later becoming the fossil fuels. By feeding on sediments directly to extract the organic component, some detritivores incidentally concentrate toxic pollutants. == See also == Decomposer Saprotrophic nutrition Nepenthes ampullaria Consumer-resource
|
{
"page_id": 723067,
"source": null,
"title": "Detritivore"
}
|
systems == References ==
|
{
"page_id": 723067,
"source": null,
"title": "Detritivore"
}
|
A deer horn, or deer whistle, is a whistle mounted on automobiles intended to help prevent collisions with deer. Air moving through the device produces sound (ultrasound in some models), intended to warn deer of a vehicle's approach. Deer are highly unpredictable, skittish animals whose normal reaction to an unfamiliar sound is to stop, look and listen to determine if they are being threatened. If the whistle gives them advance warning, they may freeze on the roadside, rather than running across the road into the path of the vehicle. In Australia, a different product, with electrically powered speakers (Shu Roo), is used to decrease collisions with kangaroos. Researchers with the University of Wisconsin–Madison measured three devices and a press report said they found these three devices produced "low-pitched and ultrasonic sounds at speeds of 30 to 70 miles per hour; however, researchers were unable to verify that deer responded to the sounds." Researchers with the Georgia Game and Fish Department have pointed out several reasons for ultrasound devices not to work as advertised: Some deer whistles do not emit any ultrasonic sound under the advertised operating conditions (typically when the vehicle exceeds 30 mph). Ultrasonic sound does not carry very well. It does not travel a long enough distance to provide adequate warning, and also is stopped by virtually any intervening object, so any curves in a road will block the sound. Little is known about the auditory limits of deer, but current knowledge indicates that deer hear approximately the same frequencies as humans, and thus if humans can't hear a sound, deer probably can't either. If deer could hear ultrasound, it is unknown if it would alarm them or induce a flight response. In addition to the Georgia and Wisconsin studies, a study by the Ohio State Police Department
|
{
"page_id": 3147902,
"source": null,
"title": "Deer horn"
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indicated the whistles are ineffective. The Department of Zoology at the University of Melbourne did independent testing, funded by the Royal Automobile Club of Victoria, New South Wales Road Traffic Authority, National Roads and Motorists’ Association Limited, and Transport South Australia. They bought one Shu Roo and tested it on a sedan, a 4x4, an 18-seat bus, and a cargo truck. The Shu Roo could be heard by their test equipment above the sound of wind and vehicle engines at up to 30 meters (98 ft). Wind on test days ranged from 0 to 57 kilometres per hour (35 mph). They also compared road collisions among fleet vehicles with and without Shu Roos, especially targeting bus and truck companies. They used pre-existing installations of Shu Roos at the participating companies, not random assignment. Vehicles averaged one collision with a kangaroo per 50,000 kilometres (31,000 mi), the same value with and without Shu Roos. They excluded two vehicles with Shu Roos which hit 39 and 25 kangaroos respectively, each in one night. The collisions of non-Shu Roo vehicles were concentrated in fewer vehicles than the collisions of Shu Roo vehicles, which may reflect routes or drivers. Fleet managers reported some Shu Roos did not stay on. It was hard to recruit professional drivers willing to report their mileage to the survey. An alternative in future studies would be to enlist a car hire company, since they already track mileage, could randomly assign devices to cars, and benefit from accurate results. == References == == Further reading == "Blowing the Whistle on Deer Scare Devices". Farm Journal (Mid–February). 1993. Schwalbach, Randall P. (November 1989). "Whistles and Whitetails". Deer and Deer Hunting. Archived from the original on 2016-03-03. Retrieved 2005-11-13. "Advisory #31" (PDF). Insurance Institute for Highway Safety. Archived from the original (PDF)
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{
"page_id": 3147902,
"source": null,
"title": "Deer horn"
}
|
on 2006-09-27. "Deer-Vehicle Collisions are Numerous and Costly. Do Countermeasures Work?". Road Management and Engineering Journal. 1997. Archived from the original on 1998-05-29.
|
{
"page_id": 3147902,
"source": null,
"title": "Deer horn"
}
|
The molecular formula C23H24N2O4 may refer to: 25N-NBPh PD-102,807
|
{
"page_id": 35063935,
"source": null,
"title": "C23H24N2O4"
}
|
A defense wound or self-defense wound is an injury received by the victim of an attack while trying to defend against the assailant(s). Defensive wounds are often found on the hands and forearms if a victim raised them to protect the head and face or to fend off an assault, but may also be present on the feet and legs if a victim attempted defense while lying down and kicking out at an assailant. The appearance and nature of the wound varies with the type of weapon used and the location of the injury, and may present as a laceration, abrasion, contusion or bone fracture. Where a victim has time to raise hands or arms before being shot by an assailant, the injury may also present as a gunshot wound. Severe laceration of the palmar surface of the hand or partial amputation of fingers may result from the victim grasping the blade of a weapon during an attack. In forensic pathology the presence of defense wounds is highly indicative of homicide and also proves that the victim was, at least initially, conscious and able to offer some resistance during the attack. Defense wounds may be classified as active or passive. A victim of a knife attack, for example, would receive active defense wounds from grasping at the knife's blade, and passive defense wounds on the back of the hand if it was raised up to protect the face. == References ==
|
{
"page_id": 34211972,
"source": null,
"title": "Defense wound"
}
|
The molecular formula C14H16N2 (molar mass: 212.29 g/mol) may refer to: Atipamezole Diphenylethylenediamine Ergoline Naphthylpiperazines 1-(1-Naphthyl)piperazine 1-(2-Naphthyl)piperazine RS134-49 Tolidine
|
{
"page_id": 24053892,
"source": null,
"title": "C14H16N2"
}
|
Metal whiskering is a phenomenon that occurs in electrical devices when metals form long whisker-like projections over time. Tin whiskers were noticed and documented in the vacuum tube era of electronics early in the 20th century in equipment that used pure, or almost pure, tin solder in their production. It was noticed that small metal hairs or tendrils grew between metal solder pads, causing short circuits. Metal whiskers form in the presence of compressive stress. Germanium, zinc, cadmium, and even lead whiskers have been documented. Many techniques are used to mitigate the problem, including changes to the annealing process (heating and cooling), the addition of elements like copper and nickel, and the inclusion of conformal coatings. Traditionally, lead has been added to slow down whisker growth in tin-based solders. Following the Restriction of Hazardous Substances Directive (RoHS), the European Union banned the use of lead in most consumer electronic products from 2006 due to health problems associated with lead and the "high-tech trash" problem, leading to a re-focusing on the issue of whisker formation in lead-free solders. == Mechanism == Metal whiskering is a crystalline metallurgical phenomenon involving the spontaneous growth of tiny, filiform hairs from a metallic surface. The effect is primarily seen on elemental metals but also occurs with alloys. The mechanism behind metal whisker growth is not well understood, but seems to be encouraged by compressive mechanical stresses including: energy gained due to electrostatic polarization of metal filaments in the electric field, residual stresses caused by electroplating, mechanically induced stresses, stresses induced by diffusion of different metals, thermally induced stresses, and strain gradients in materials. Metal whiskers differ from metallic dendrites in several respects: dendrites are fern-shaped and grow across the surface of the metal, while metal whiskers are hair-like and project normal to the surface. Dendrite
|
{
"page_id": 1378439,
"source": null,
"title": "Whisker (metallurgy)"
}
|
growth requires moisture capable of dissolving the metal into a solution of metal ions, which are then redistributed by electromigration in the presence of an electromagnetic field. While the precise mechanism for whisker formation remains unknown, it is known that whisker formation does not require either dissolution of the metal or the presence of an electromagnetic field. == Effects == Whiskers can cause short circuits and arcing in electrical equipment. The phenomenon was discovered by telephone companies in the late 1940s and it was later found that the addition of lead to tin solder provided mitigation. The European Restriction of Hazardous Substances Directive (RoHS), which took effect on July 1, 2006, restricted the use of lead in various types of electronic and electrical equipment. This has driven the use of lead-free alloys with a focus on preventing whisker formation (see § Mitigation and elimination). Others have focused on the development of oxygen-barrier coatings to prevent whisker formation. Airborne zinc whiskers have been responsible for increased system failure rates in computer server rooms. Zinc whiskers grow from galvanized (electroplated) metal surfaces at a rate of up to a millimeter per year with a diameter of a few micrometers. Whiskers can form on the underside of zinc electroplated floor tiles on raised floors. These whiskers can then become airborne within the floor plenum when the tiles are disturbed, usually during maintenance. Whiskers can be small enough to pass through air filters and can settle inside equipment, resulting in short circuits and system failure. Tin whiskers do not have to be airborne to damage equipment, as they are typically already growing directly in the environment where they can produce short circuits, i.e., the electronic equipment itself. At frequencies above 6 gigahertz or in fast digital circuits, tin whiskers can act like miniature antennas,
|
{
"page_id": 1378439,
"source": null,
"title": "Whisker (metallurgy)"
}
|
affecting the circuit impedance and causing reflections. In computer disk drives they can break off and cause head crashes or bearing failures. Tin whiskers often cause failures in relays and have been found upon examination of failed relays in nuclear power facilities. Pacemakers have been recalled due to tin whiskers. Research has also identified a particular failure mode for tin whiskers in vacuum (such as in space), where in high-power components a short-circuiting tin whisker is ionized into a plasma that is capable of conducting hundreds of amperes of current, massively increasing the damaging effect of the short circuit. The possible increase in the use of pure tin in electronics due to the RoHS directive drove the Joint Electron Device Engineering Council (JEDEC) and IPC electronic trade association to release a tin whisker acceptance testing standard and mitigation practices guideline intended to help manufacturers reduce the risk of tin whiskers in lead-free products. Silver whiskers often appear in conjunction with a layer of silver sulfide, which forms on the surface of silver electrical contacts operating in an atmosphere rich in hydrogen sulfide and high humidity. Such atmospheres can exist in sewage treatment plants and paper mills. Whiskers over 20 micrometres (μm) in length were observed on gold-plated surfaces and noted in a 2003 NASA internal memorandum. The effects of metal whiskering were chronicled on History Channel's program Engineering Disasters 19. == Mitigation and elimination == Several approaches are used to reduce or eliminate whisker growth, with ongoing research in the area. === Conformal coatings === Conformal compound coatings stop the whiskers from penetrating a barrier, reaching a nearby termination and forming a short. === Altering plating chemistry === Termination finishes of nickel, gold or palladium have been shown to eliminate whisker formation in controlled trials. == Tin whisker examples and
|
{
"page_id": 1378439,
"source": null,
"title": "Whisker (metallurgy)"
}
|
incidents == === Galaxy IV === Galaxy IV was a telecommunications satellite that was disabled and lost due to short circuits caused by tin whiskers in 1998. It was initially thought that space weather contributed to the failure, but later it was discovered that a conformal coating had been misapplied, allowing whiskers to form in the pure tin plating, find their way through a missing coating area, and cause a failure of the main control computer. The manufacturer, Hughes, has moved to nickel plating, rather than tin, to reduce the risk of whisker growth. The trade-off has been an increase in weight, adding 50 to 100 kilograms (110 to 220 lb) per payload. === Millstone Nuclear Power Plant === On April 17, 2005, the Millstone Nuclear Power Plant in Connecticut was shut down due to a "false alarm" that indicated an unsafe pressure drop in the reactor's steam system when the steam pressure was actually nominal. The false alarm was caused by a tin whisker that short circuited the logic board responsible for monitoring the steam pressure lines in the power plant. === Toyota accelerator position sensors false positive === In September 2011, three NASA investigators claimed that they identified tin whiskers on the accelerator position sensors of sampled Toyota Camry models that could contribute to the "stuck accelerator" crashes affecting certain Toyota models during 2005–2010. This contradicted an earlier 10-month joint investigation by the National Highway Traffic Safety Administration (NHTSA) and a large group of other NASA researchers that found no electronic defects. In 2012, NHTSA maintained: "We do not believe that tin whiskers are a plausible explanation for these incidents...[the likely cause was] pedal misapplication." Toyota also maintains that tin whiskers were not the cause of any stuck accelerator issues: "In the words of U.S. Transportation Secretary Ray
|
{
"page_id": 1378439,
"source": null,
"title": "Whisker (metallurgy)"
}
|
LaHood, 'The verdict is in. There is no electronic-based cause for unintended high-speed acceleration in Toyotas. Period.'" According to a Toyota press release, "no data indicates that tin whiskers are more prone to occur in Toyota vehicles than any other vehicle in the marketplace." Toyota also states that "their systems are designed to reduce the risk that tin whiskers will form in the first place." == See also == Monocrystalline whisker Dendrite (metal) Crystal growth Gold-aluminium intermetallic Impurity == References == == External links == Images of silver whiskers NASA
|
{
"page_id": 1378439,
"source": null,
"title": "Whisker (metallurgy)"
}
|
Preslav Nakov (born on 26 January 1977 in Veliko Turnovo, Bulgaria) is a computer scientist who works on natural language processing. He is particularly known for his research on fake news detection, automatic detection of offensive language, and biomedical text mining. Nakov obtained a PhD in computer science under the supervision of Marti Hearst from the University of California, Berkeley. He was the first person to receive the prestigious John Atanasov Presidential Award for achievements in the development of the information society by the President of Bulgaria. == Education == Preslav Nakov grew up in Veliko Turnovo, Bulgaria, where he attended primary and secondary school, obtaining a Diploma in Mathematics from the Secondary School of Mathematics and Natural Sciences 'Vassil Drumev' in 1996. He then obtained a MSc degree in Informatics (Computer Science) with specialisations in Artificial Intelligence and Information and Communication Technologies from Sofia University in 2011. During his MSc studies, he worked as a teaching assistant at Sofa University and the Bulgarian Academy of Sciences, as well as a guest lecturer at University College London during a visit in Spring 1999. Subsequently, he enrolled into the PhD program at the Department of Electrical Engineering and Computer Science, University of California, Berkeley, partly supported by a Fulbright Scholarship. Under the supervision of Marti Hearst, he wrote a thesis on the topic of text mining from the Web, and graduated with a PhD in Computer Science from UC Berkeley in 2007. == Career == Upon graduating from the University of California, Berkeley, Nakov started work as a Research Fellow at the National University of Singapore. Since 2012, he has been a Senior Scientist at the Qatar Computing Research Institute (QCRI). He maintains a position as an honorary lecturer at Sofia University. == Research == Preslav Nakov works in the area
|
{
"page_id": 66848907,
"source": null,
"title": "Preslav Nakov"
}
|
of natural language processing and text mining. He has published over 300 peer-reviewed research papers. Preslav Nakov's early research was on lexical semantics and text mining. He published influential papers on biomedical text mining, most prominently on methods to identify citation sentences in biomedical papers. He is though most well-known for his research on fake news detection, such as his work on predicting the factuality and bias of news sources, as well as for his research on the automatic detection of offensive language. Nakov also previously led the organisation of a popular evaluation campaign on sentiment analysis systems as part of SemEval between the years of 2015 and 2017. He currently coordinates the Tanbih News Aggregator project, a large project with partners at the Qatar Computing Research Institute and the MIT Computer Science and Artificial Intelligence Laboratory, which aims to uncover stance, bias and propaganda in news. == Selected honors and distinctions == 2003 John Atanasov Presidential Award for achievements in the development of the information society 2011 RANLP 2011 Young Researcher Award 2020 Conference on Information and Knowledge Management, best paper award == References ==
|
{
"page_id": 66848907,
"source": null,
"title": "Preslav Nakov"
}
|
Random chimeragenesis on transient templates (RACHITT) is a method to perform molecular mutagenesis at a high recombination rate. For example, RACHITT can be used to generate increased rate and extent of biodesulfurization of diesel by modification of dibenzothiophene mono-oxygenase. DNA shuffling is a similar but less powerful method used in directed evolution experiments. == References ==
|
{
"page_id": 6883469,
"source": null,
"title": "Random chimeragenesis on transient templates"
}
|
Breastmilk medicine refers to the non-nutritional usage of human breast milk (HBM) as a medicine or therapy to cure diseases. Breastmilk is perceived as an important food that provides essential nutrition to infants. It also provides protection in terms of immunity by direct transfer of antibodies from mothers to infants. The immunity developed via this mean protects infants from diseases such as respiratory diseases, middle ear infections, and gastrointestinal diseases. HBM can also produce lifelong positive therapeutic effects on a number of chronic diseases, including diabetes mellitus, obesity, hyperlipidemia, hypertension, cardiovascular diseases, autoimmunity, and asthma. Therapeutic use of breastmilk has long been a part of natural pharmacopeia, and ethnomedicine. The effectiveness of HBM and fresh colostrum as a treatment for inflammatory disorders such as rhinitis, skin infection, soring nipples, and conjunctivitis has been reported by public health nurses. Currently, many breastmilk components have shown therapeutic benefits in preclinical studies and are being evaluated by clinical studies. == Anti-inflammatory effects == HBM can be used to treat inflammations. Breastfeeding has an anti-inflammatory effect that is conveyed by its chemical components’ interaction with body cells. The major chemical component that produces the anti-inflammatory effect in both colostrum and transitional milk are glycoprotein and lactoferrin. Lactoferrin has multiple actions including lymph-stimulatory, anti-inflammatory, anti-bacterial, anti-viral, and anti-fungal effects. The anti-inflammatory effects of lactoferrin are attributed to its iron-binding properties, inhibition of inflammation-causing molecules including interleukin-1β (IL-1β) and tumor necrosis factor-alpha (TNF-α), stimulation of the activity and maturation of lymphocytes as well as preservation of an antioxidant environment. Besides, lactoferrin protects infants against bacterial and fungal infections in combination with other peptides present in HBM. === Respiratory viral infection in infants === Lactoferrin in HBM can also inhibit the invasion and proliferation of respiratory syncytial virus (RSV), which is a virus commonly found in the
|
{
"page_id": 73402513,
"source": null,
"title": "Breastmilk medicine"
}
|
human respiratory tract and causes mild cold-like symptoms. Lactoferrin can interact directly with the F glycoprotein which is a protein on the surface of the virus that is responsible for presenting the virus to body cells and causing infections. Adenovirus is another group of viruses that targets the mucosal membrane of the human respiratory tract. It usually causes mild to severe infection with symptoms like the common cold or flu. Lactoferrin can prevent infection of adenovirus since it can interfere with the primary receptors of the virus. HBM regurgitation into the nose after breastfeeding is a way to eliminate these mucosal bacteria and protect infants against recurring nose infections in breastfed infants in the long term. === Skin Problems: atopic eczema and diaper dermatitis === Atopic eczema is an inflammatory disorder that occurs in the outermost skin layer called the epidermis. This skin disorder affects 50% of infants in the first year after birth. Infants suffering from atopic eczema are characterized by intense itching, redness, and crusting in their skin. Skin thickening may result in chronic or sub-acute patients due to scratching and fissuring over time. One of the commonly used medications for atopic eczema is non-prescription cream containing an anti-inflammatory agent 1% hydrocortisone. On the other hand, applying HBM on the skin as ointments is therapeutically beneficial to infants with mild to moderate atopic eczema. It is evidenced that, compared to 1% hydrocortisone, HBM has similar effectiveness as 1% hydrocortisone to relieve infants’ inflaming skin conditions. Diaper dermatitis is another prevalent infant dermatological disorder. Common clinical features of diaper dermatitis include inflamed, itchy, tender skin and soreness in the diaper area. Study results have shown that human breastmilk is highly effective in healing diaper rash. There is much evidence supporting the anti-inflammatory effect of HBM. The immunological components in
|
{
"page_id": 73402513,
"source": null,
"title": "Breastmilk medicine"
}
|
HBM help strengthen the baby’s immune system. These immunological components include antimicrobial proteins that can inhibit or kill a wide range of pathogens whose invasion may lead to an inflammatory response. This antimicrobial effect could be achieved by indirectly creating an unfavorable environment for the growth of pathogens by modifying commensal flora, pH, or level of bacterial substrates. The antimicrobial effect is also brought by an antibody immunoglobulin A (IgA) which is the prenominal immunoglobulin present in HBM that can protect infants from a variety of skin infections. === Nipple problems: sore nipples === The painful nipple is a common difficulty confronted by mothers who decided to carry out breastfeeding. Topical application of expressed breastmilk has long been a non-pharmacological intervention to reduce nipple pain. According to the research outcome of many studies, topical application of HBM can help reduce the perception of nipple pain in a treatment course of 4 to 5 days. It is also stated that HBM is more effective in lowering pain perception than Lanolin. However, another study indicates that Lanolin produces lower pain levels in mothers with nipple pain than HBM. This study stated that lanolin shows a better therapeutic effect for healing rates, nipple trauma, and nipple pain. Although lanolin may be more efficacious than HBM to cure nipple problems, HBM is not proven to be ineffective to treat nipple pain. Considering HBM is more easily available than Lanolin, it is still useful for treating nipple problems in a practical sense. === Eye Problems === ==== Traditional uses ==== The topical application of breastmilk as a treatment for an infectious disease called conjunctivitis has been present since ancient times in different nations such as ancient Egypt, Rome, Greece, etc. HBM was also recommended by the Greek physician Galen as a remedy for conjunctivitis. Physicians
|
{
"page_id": 73402513,
"source": null,
"title": "Breastmilk medicine"
}
|
in early modern England recommended human milk for conditions ranging from mild symptoms such as soreness to even blindness. Healers in that era even believed that a mixture of HBM with other components could restore eyesight. ==== Scientific findings ==== Evidence from clinical research has shown that applying HBM can prevent people from getting conjunctivitis infections. Gonorrhea is a sexually transmitted infection. Besides sex-borne transmission, it can also be transmitted to babies during childbirth. This infectious disease can cause neonatal conjunctivitis, which could lead to blindness, if untreated. Hospitals in the United States are required to apply antibiotics to the eyes of new-born within one hour of childbirth to prevent the development of conjunctivitis. This is because certain bacteria in HBM are found to be effective against gonorrhea bacteria and may serve as a convenient and readily available substitute for antibiotics in places where antibiotics are not widely available. == Breastmilk in umbilical cord care == After labor in childbirth, the umbilical cord is clamped and cut, and part of it stays in contact with the infant. The remaining part of the umbilical cord dries out and eventually separates after 5–15 days. In taking care of the umbilical cord, the dry care method involving soap and water is recommended by the WHO and many national health organizations. For the use of HBM in umbilical cord care, clinical studies found that topical application of breast milk will lead to a shorter time of cord separation than other methods including ethanol and dry cord care. == Anti tumoricidal and anti-bacterial effects == Human alpha-lactalbumin is a natural protein component of HBM. It can be extracted by chromatography from breast milk. It complexes with oleic acid to form a protein called the “human alpha-lactalbumin made lethal to tumor cells” (HAMLET). The HAMLET complex
|
{
"page_id": 73402513,
"source": null,
"title": "Breastmilk medicine"
}
|
induces apoptosis in lung carcinoma cells. In in vitro and animal model studies, HAMLET has shown preventative and therapeutic effects in reducing and controlling tumor growth. The physiological effects of HAMLET may explain the proposal that breastfeeding has protective effects for mothers and children against cancer, as shown by the association length of breastfeeding and childhood cancer incidence. The HAMLET has also been found to have anti-bacterial effects through the inhibition of enzymes in glycolysis. == Role in society == Researchers’ interest in HBM is led by the discovery of a number of chemical components in HBM. These components include growth factors, cytokines, and a heterogeneous population of cells which are stem cells, probiotic bacteria, and the HAMLET complex. By considering the easy accessibility of HBM and high prevalence of infant inflammation disorders, breastmilk may be a cheap and convenient ways to relieve inflammatory symptoms. The prophylactic antibiotic use of human milk may be important in areas where mothers and infants do not have easy access to medicine, such as people living in developing countries. Under these circumstances, practice of HBM therapy as medicine will be a determining factor in infant recovery and survival. == General limitations == === Breastfeeding difficulties === Breastfeeding may not be feasible and easy for some mothers due to psychological or physiological reasons. For instance, breastfeeding self-efficacy, the mother's confidence in her breastfeeding abilities, is positively associated with exclusive breastfeeding while postpartum depression makes it more difficult to breastfeed. Mothers who have undergone breast surgeries such as mastectomy may have reduced capabilities of HBM production. === Suitability of breastmilk === For some individuals, HBM may not be suitable for use, as it may transmit of viruses and other pathogens to infants. For instance, cytomegalovirus, HIV, and bacterial infections from the mother may be transmitted through
|
{
"page_id": 73402513,
"source": null,
"title": "Breastmilk medicine"
}
|
HBM, causing complications for infants. === Evaluation of medical effectiveness of breastmilk === There is difficulty in the generalization of study results in evidence-based practice due to inconsistencies in the clinical study findings on breastfeeding medicine. HBM compositions are diverse among different individuals, or the same individual at various times. It is influenced by factors such as maternal diet and changes at various times after pregnancy. For instance, protein composition in HBM is higher in the earlier stages of lactation. Gradually, the mother produces more mature milk, which is whiter in color, compared to the yellowish colostrum. These changes may affect the effectiveness of HBM in medical use. == References ==
|
{
"page_id": 73402513,
"source": null,
"title": "Breastmilk medicine"
}
|
Continuum (pl.: continua or continuums) theories or models explain variation as involving gradual quantitative transitions without abrupt changes or discontinuities. In contrast, categorical theories or models explain variation using qualitatively different states. == In physics == In physics, for example, the space-time continuum model describes space and time as part of the same continuum rather than as separate entities. A spectrum in physics, such as the electromagnetic spectrum, is often termed as either continuous (with energy at all wavelengths) or discrete (energy at only certain wavelengths). In contrast, quantum mechanics uses quanta, certain defined amounts (i.e. categorical amounts) which are distinguished from continuous amounts. == In mathematics and philosophy == A good introduction to the philosophical issues involved is John Lane Bell's essay in the Stanford Encyclopedia of Philosophy. A significant divide is provided by the law of excluded middle. It determines the divide between intuitionistic continua such as Brouwer's and Lawvere's, and classical ones such as Stevin's and Robinson's. Bell isolates two distinct historical conceptions of infinitesimal, one by Leibniz and one by Nieuwentijdt, and argues that Leibniz's conception was implemented in Robinson's hyperreal continuum, whereas Nieuwentijdt's, in Lawvere's smooth infinitesimal analysis, characterized by the presence of nilsquare infinitesimals: "It may be said that Leibniz recognized the need for the first, but not the second type of infinitesimal and Nieuwentijdt, vice versa. It is of interest to note that Leibnizian infinitesimals (differentials) are realized in nonstandard analysis, and nilsquare infinitesimals in smooth infinitesimal analysis". == In social sciences, psychology and psychiatry == In social sciences in general, psychology and psychiatry included, data about differences between individuals, like any data, can be collected and measured using different levels of measurement. Those levels include dichotomous (a person either has a personality trait or not) and non-dichotomous approaches. While the non-dichotomous approach
|
{
"page_id": 20646034,
"source": null,
"title": "Continuum (measurement)"
}
|
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