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41,459,446 | https://en.wikipedia.org/wiki/HD%20112410 | HD 112410 is a star in the southern constellation of Musca. It has a yellow hue and is too dim to be readily visible to the average sight, having an apparent visual magnitude of 6.86. The distance to this star is 513 light years based on parallax, and it is drifting further away from the Sun with a radial velocity of 73 km/s. It has an absolute magnitude of 1.22.
This is an aging giant star with a stellar classification of G8III. It is cooling and expanding along the red giant branch, having evolved off the main sequence after exhausting its core supply of hydrogen fuel. At present it has 10 times the Sun's radius. Mass estimates range from 1.21 up to 2.32 times the mass of the Sun. The star has a lower metallicity the Sun – what astronomers term the abundance of elements with more mass than helium – and it is spinning with a projected rotational velocity of 3.3 km/s. It is radiating 50.5 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,793 K.
Planetary system
HD 112410 has a substellar companion calculated to have a mass at least 9.2 times that of Jupiter and an orbital period of 124.6 days at a typical separation of approximately 0.57 astronomical units (AU). As of 2013, this is the nearest exoplanet orbiting around any ascending red giant branch star, and second-closest planet to a giant star after the companion of HIP 13044.
References
G-type giants
Planetary systems with one confirmed planet
Musca
CD −64 676
112410
063242 | HD 112410 | Astronomy | 345 |
77,142,795 | https://en.wikipedia.org/wiki/Pamapimod | Pamapimod is an investigational drug which is being evaluated for the treatment of autoimmune diseases. It is a p38 mitogen-activated protein kinase inhibitor. It has been evaluated in a phase 2 clinical trial for the treatment of rheumatoid arthritis, but was found not to be effective. It has subsequently been investigated as a possible treatment for osteoarthritis.
See also
NJK14047
PH-797804
References
Pyridopyrimidines
Fluoroarenes
Aromatic ethers
Diols
Secondary amines | Pamapimod | Chemistry | 117 |
61,605,645 | https://en.wikipedia.org/wiki/CAgNO | The molecular formula CAgNO (molar mass: 149.89 g/mol, exact mass: 148.9031 u) may refer to:
Silver cyanate, cyanate salt of silver
Silver fulminate, highly explosive silver salt of fulminic acid | CAgNO | Chemistry | 59 |
5,944,092 | https://en.wikipedia.org/wiki/List%20of%20gotras | A gotra is equivalent to a lineage, akin to a family name, but the given name of a family is often different from its gotra, and may reflect the traditional occupation, place of residence or other important family characteristic rather than the lineage.
People belonging to a particular gotra may not be of the same caste (as there are many gotras which are part of different castes) in the Hindu social system. However, there is a notable exception among matrilineal Tulu speakers, for whom the lineages are the same across the castes.
People of the same gotra are generally not allowed to marry. At weddings, the gotras of the bride and the groom are read aloud to verify that they are not breaking this rule.
Main Brahmin Gotras
A list of major Brahmin gotras according to the Sutras:
Bhr̥gu (Jamadagni)
Bhārgava
Cyāvana
Aurva
Jāmadagnya
Vātsa
Kevala Bhr̥gu
Bhārgava
Daivodāsa
Vainya
Pārtha
Śaunaka
Gārtsamada
Gautama
Āṅgirasa
Gautama
Kākṣīvata
Dairghatamasa
Auśanasa
Bharadvāja
Āṅgirasa
Bārhaspatya
Bhāradvāja
Gārgya
Kevala Aṅgiras
Āṅgirasa
Āmbarīṣa
Māndhātra
Kautsa
Kāṇva
Maudgalya
Sāṁkr̥tya
Śāktya
Atri
Ātreya
Viśvāmitra
Vaiśvāmitra
Daivarāta
Mādhucchandasa
Kauśika
Gāthina
Aindra
Kaśyapa
Kāśyapa
Āvatsāra
Āsita
Śāṇḍila
Daivala
Vasiṣṭha
Vāsiṣṭha
Maitrāvaruṇa
Aupamanyava
Pārāśarya
Śāktya
Sāṁkr̥tya
Agastya
Āgastya
References
Indian castes
Gotras
Kinship and descent
Indian culture-related lists | List of gotras | Biology | 380 |
37,918,911 | https://en.wikipedia.org/wiki/Progress%20in%20Polymer%20Science | Progress in Polymer Science is a peer-reviewed scientific journal publishing review articles on topics broadly related to polymer chemistry. The 2022 impact factor of this journal was 27.1, ranking it the highest in the subject category "Polymer Science". The journal is available since 1967. Currently it is edited by Editor-in-Chief Jean-Francois Lutz and Senior Editors Michael Bockstaller and Chuanbing Tang. Honorary Editors-in-Chief include Krzysztof "Kris" Matyjaszewski and Guy C. Berry from Carnegie Mellon University.
References
Chemistry journals
Materials science journals
English-language journals
Elsevier academic journals | Progress in Polymer Science | Materials_science,Engineering | 130 |
23,715,461 | https://en.wikipedia.org/wiki/Limnological%20Review | The Limnological Reviewis an official journal of Polish Limnological Society and covers theoretical and applied freshwater research, including such topics as limnology, ecohydrology, aquatic biology, aquatic ecology, ecotoxicology, sedimentology, hydrogeology and environmental engineering. The journal is led by two editors-in-chief: Dariusz Borowiak (University of Gdańsk) and Piotr Rzymski (Poznan University of Medical Sciences)
External links
Limnology
Earth and atmospheric sciences journals
Hydrology journals | Limnological Review | Environmental_science | 108 |
8,121,479 | https://en.wikipedia.org/wiki/Quasi-set%20theory | Quasi-set theory is a formal mathematical theory for dealing with collections of objects, some of which may be indistinguishable from one another. Quasi-set theory is mainly motivated by the assumption that certain objects treated in quantum physics are indistinguishable and don't have individuality.
Motivation
The American Mathematical Society sponsored a 1974 meeting to evaluate the resolution and consequences of the 23 problems Hilbert proposed in 1900. An outcome of that meeting was a new list of mathematical problems, the first of which, due to Manin (1976, p. 36), questioned whether classical set theory was an adequate paradigm for treating collections of indistinguishable elementary particles in quantum mechanics. He suggested that such collections cannot be sets in the usual sense, and that the study of such collections required a "new language".
The use of the term quasi-set follows a suggestion in da Costa's 1980 monograph Ensaio sobre os Fundamentos da Lógica (see da Costa and Krause 1994), in which he explored possible semantics for what he called "Schrödinger Logics". In these logics, the concept of identity is restricted to some objects of the domain, and has motivation in Schrödinger's claim that the concept of identity does not make sense for elementary particles (Schrödinger 1952). Thus in order to provide a semantics that fits the logic, da Costa submitted that "a theory of quasi-sets should be developed", encompassing "standard sets" as particular cases, yet da Costa did not develop this theory in any concrete way. To the same end and independently of da Costa, Dalla Chiara and di Francia (1993) proposed a theory of quasets to enable a semantic treatment of the language of microphysics. The first quasi-set theory was proposed by D. Krause in his PhD thesis, in 1990 (see Krause 1992). A related physics theory, based on the logic of adding fundamental indistinguishability to equality and inequality, was developed and elaborated independently in the book The Theory of Indistinguishables by A. F. Parker-Rhodes.
Summary of the theory
We now expound Krause's (1992) axiomatic theory , the first quasi-set theory; other formulations and improvements have since appeared. For an updated paper on the subject, see French and Krause (2010). Krause builds on the set theory ZFU, consisting of Zermelo-Fraenkel set theory with an ontology extended to include two kinds of urelements:
m-atoms, whose intended interpretation is elementary quantum particles;
M-atoms, macroscopic objects to which classical logic is assumed to apply.
Quasi-sets (q-sets) are collections resulting from applying axioms, very similar to those for ZFU, to a basic domain composed of m-atoms, M-atoms, and aggregates of these. The axioms of include equivalents of extensionality, but in a weaker form, termed "weak extensionality axiom"; axioms asserting the existence of the empty set, unordered pair, union set, and power set; the axiom of separation; an axiom stating the image of a q-set under a q-function is also a q-set; q-set equivalents of the axioms of infinity, regularity, and choice. Q-set theories based on other set-theoretical frameworks are, of course, possible.
has a primitive concept of quasi-cardinal, governed by eight additional axioms, intuitively standing for the quantity of objects in a collection. The quasi-cardinal of a quasi-set is not defined in the usual sense (by means of ordinals) because the m-atoms are assumed (absolutely) indistinguishable. Furthermore, it is possible to define a translation from the language of ZFU into the language of in such a way so that there is a 'copy' of ZFU in . In this copy, all the usual mathematical concepts can be defined, and the 'sets' (in reality, the '-sets') turn out to be those q-sets whose transitive closure contains no m-atoms.
In there may exist q-sets, called "pure" q-sets, whose elements are all m-atoms, and the axiomatics of provides the grounds for saying that nothing in distinguishes the elements of a pure q-set from one another, for certain pure q-sets. Within the theory, the idea that there is more than one entity in x is expressed by an axiom stating that the quasi-cardinal of the power quasi-set of x has quasi-cardinal 2qc(x), where qc(x) is the quasi-cardinal of x (which is a cardinal obtained in the 'copy' of ZFU just mentioned).
What exactly does this mean? Consider the level 2p of a sodium atom, in which there are six indiscernible electrons. Even so, physicists reason as if there are in fact six entities in that level, and not only one. In this way, by saying that the quasi-cardinal of the power quasi-set of x is 2qc(x) (suppose that qc(x) = 6 to follow the example), we are not excluding the hypothesis that there can exist six subquasi-sets of x that are 'singletons', although we cannot distinguish among them. Whether there are or not six elements in x is something that cannot be ascribed by the theory (although the notion is compatible with the theory). If the theory could answer this question, the elements of x would be individualized and hence counted, contradicting the basic assumption that they cannot be distinguished.
In other words, we may consistently (within the axiomatics of ) reason as if there are six entities in x, but x must be regarded as a collection whose elements cannot be discerned as individuals. Using quasi-set theory, we can express some facts of quantum physics without introducing symmetry conditions (Krause et al. 1999, 2005). As is well known, in order to express indistinguishability, the particles are deemed to be individuals, say by attaching them to coordinates or to adequate functions/vectors like |ψ>. Thus, given two quantum systems labeled |ψ1⟩ and |ψ2⟩ at the outset, we need to consider a function like |ψ12⟩ = |ψ1⟩|ψ2⟩ ± |ψ2⟩|ψ1⟩ (except for certain constants), which keep the quanta indistinguishable by permutations; the probability density of the joint system independs on which is quanta #1 and which is quanta #2. (Note that precision requires that we talk of "two" quanta without distinguishing them, which is impossible in conventional set theories.) In , we can dispense with this "identification" of the quanta; for details, see Krause et al. (1999, 2005) and French and Krause (2006).
Quasi-set theory is a way to operationalize Heinz Post's (1963) claim that quanta should be deemed indistinguishable "right from the start."
See also
Multisets
Quantum physics
Quantum logic
References
Newton da Costa (1980) Ensaio sobre os Fundamentos da Lógica. São Paulo: Hucitec.
Manin, Yuri (1976) "Problems in Present Day Mathematics: Foundations," in Felix Browder, ed., Proceedings of Symposia in Pure Mathematics, Vol. XXVIII. Providence RI: American Mathematical Society.
Reprinted in
Set theory
Quantum mechanics | Quasi-set theory | Physics,Mathematics | 1,605 |
55,635,955 | https://en.wikipedia.org/wiki/Dropel%20Fabrics | Dropel Fabrics is an American technology company that develops, manufactures, and licenses sustainable treatments for natural fabrics to make spill proof and stain proof threads. The company is known for creating the world's first water and stain repellent naturals fabrics that maintain their softness and breathability.
History
Dropel was founded in 2015 by Sim Gulati following his research in material sciences and innovative textile processes. In 2014, after observing a broader need in apparel for innovation in natural fabrics, Gulati developed cotton fabrics using sustainable nanotechnology treatments for cotton in an effort to supplant less durable and less environmentally friendly clothing applications for polyester and other synthetics. In 2015 the company consulted with Amanda Parkes, Ph.D., termed a “fashion scientist” from Massachusetts Institute of Technology by Industry magazine.
Dropel incubated in New York based fashion accelerator, New York Fashion Tech Lab, and launched at the incubator's June 2015 demonstration day.
The New York Times reported that Dropel “patented a nanotechnology process that bonds hydrophobic polymers with natural fibers on the molecular level to make them water- and stain-repellent, a process that can be licensed by clothing brands.” The company has integrated its technology with brands AREA NYC, CEAM and Mister French. Dropel was part of the inaugural class of Fashion For Good, a sustainable fashion accelerator led by Kering, Plug and Play Ventures, Galleries Lafayette and the C&A Foundation. Fashion Tech Lab, a venture-capital accelerator led by Russian retail entrepreneur Miroslava Duma, Gaetan Bonhomme, Alex Moore, Cybernaut Venture Capital, and Full Tilt Capital invested in Dropel's seed round of funding. In 2015, Business Insider named Dropel Fabrics one of the “100 most exciting startups in New York City.”
References
External links
Textile companies of the United States
Biodegradable materials | Dropel Fabrics | Physics,Chemistry | 389 |
23,590,452 | https://en.wikipedia.org/wiki/Irreversible%20antagonist | An irreversible antagonist is a type of antagonist that binds permanently to a receptor, either by forming a covalent bond to the active site, or alternatively just by binding so tightly that the rate of dissociation is effectively zero at relevant time scales. This permanently deactivates the receptor and is usually followed by rapid internalisation and recycling of the non-functional receptor protein. Irreversible enzyme inhibitors that act similarly are clinically used and include drugs such as aspirin, omeprazole and monoamine oxidase inhibitors.
Examples
Naloxazone
Phenoxybenzamine
See also
Irreversible agonist
Irreversible enzyme inhibitor
References
Receptor antagonists | Irreversible antagonist | Chemistry | 143 |
8,177,517 | https://en.wikipedia.org/wiki/Pithecometra%20principle | The Pithecometra principle or Pithecometra thesis () describes the evolution of humans; the pithecometra law is analogous to the concept that "man evolved within apes" or "man descended from apes" as advocated by Thomas Henry Huxley.
In evolution, Huxley first developed the concept of the "Pithecometra principle" which was discussed by Charles Darwin and Ernst Haeckel, when Huxley wrote the 1863 essay "On the Origin of Species" stating that humanity was more closely related to apes than the apes were to monkeys.
Huxley added that to hunt evidence of this close ancestry between apes and humans, the regions where modern apes are found should be the focal point, hence, Africa.
The pithecometra principle has been most notable in evolution theory by placing humanity as an offshoot of animal species, rather than a separate divine creation, and thus pithecometra has generated intense religious controversy for decades.
Impact
Another of Darwin's colleagues was Ernst Heinrich Haeckel (1834–1919). Haeckel agreed with Huxley on several aspects of the pithecometra thesis. However, Haeckel frequently lectured on the Asian origin of the "missing link" between apes and humans. Consequently, Eugene Dubois, a student of Haeckel's indoctrinated with the idea of Asian hominid origins, traveled to Java, Indonesia in 1890–1892. It was during this expedition when Dubois made the incredible discovery of Homo erectus fossils in Asia. Also known as Java Man, that specimen was validation of humanity's deep ancestry outside of Europe.
The pithecometra thesis with the work of Darwin, Huxley and Haeckel helped liberate the European scientific community of its Eurocentric biases. However, their work did not directly produce a change. It required the later revolution in evolutionary thought, of the Neo-Darwinian Synthesis of the mid-20th century, to cause a change in the recovery of fossils from regions outside Europe. Evidence of refusals to accept the fossils that began to be found in Asia and Africa after the late 19th century was the Piltdown Hoax.
The perpetrator of the Piltdown hoax is uncertain but the year and location indicate a rejection of growing evidence for man's ancestry outside of Europe. In 1912 in England, a fossil was presented and named Piltdown Man. This specimen was the combination of ape and human features the scientific community had been seeking in order to argue human/ape affinities. The high, globular braincase signified human-like features while the robust jaw and molars resembled ape skulls. This fossil was used as proof of human evolution having occurred in England. With the discovery of the Piltdown specimen, actual fossil specimens of the prehistoric australopithecine genus coming from Africa were being ignored. Raymond Dart, who obtained a fossil skull of an actual hominid showing human-ape affinities from South Africa was treated with disdain. Later in the 1950s, as the Neo-Darwinian Synthesis had thoroughly saturated the European scientific community, fewer people chose to ignore the significant Australopithecus fossils coming from Africa, and the Piltdown Man fossil was re-examined. Upon closer inspection, the cranium was judged to be of a modern human and the jaw matched a modern orangutan. The molars had been filed down to appear like human upper molars, and the surface of the Piltdown specimen had been painted to give it the illusion of having been buried a long time. The rejection of the Piltdown fossil in the 1950s removed a significant barrier that had blocked the European scientific community's view of more accurate human origins.
See also
On the Origin of Species - 1859 book by Charles Darwin.
Notes
References
Joshua Barbach and Craig Byron, "Cultural Biases in Fossil Record" (impact of Pithecometra), 2005, ArchaeologyInfo.com webpage: ArchaeologyInfo-3.
Selection
Evolutionary biology | Pithecometra principle | Biology | 827 |
56,251,479 | https://en.wikipedia.org/wiki/Anti-exhaustion%20hypothesis | The anti-exhaustion hypothesis is a possible explanation for the existence of large repertoires and the song switching behaviour exhibited in birds. This hypothesis states that muscle exhaustion occurring due to repeating song bouts can be avoided by switching to a different song in the bird's repertoire. The anti-exhaustion hypothesis therefore predicts that birds with larger repertoires are less susceptible to exhaustion because they can readily change the song that they are producing.
The anti-exhaustion hypothesis was first proposed by Marcel Lambrechts and André Dhondt in 1988 after they carried out a study using recordings from great tits, Parus major, during the dawn chorus. There have been several studies carried out in which results have contradicted the anti-exhaustion hypothesis. Recent studies have shown that there is no evidence that the anti-exhaustion hypothesis is the cause of large repertoires in birds. Since the proposal of the anti-exhaustion hypothesis, several hypotheses have been proposed to explain the existence of repertoires and song switching behaviour in birds, including the motivation hypothesis and the warm-up hypothesis.
Anti-exhaustion hypothesis in great tits
The great tit, Parus major, is a passerine bird belonging to the family Paridae. Passerines are commonly referred to as songbirds, with most passerines singing multiple species-specific songs making a repertoire. Birds can be ranked depending on how they perform the songs in their repertoire. On one side, there are birds that sing with eventual variety and have small repertoires, meaning that each song type in their repertoire is repeated before they switch to a different song type.
On the other side, there are birds that sing with immediate variety and have larger repertoires, meaning that they switch song types continuously. The great tit, in particular, sings with eventual variety and has a small repertoire, usually consisting of two to seven different song types. Songs can be broken down into several simpler components. Songs are made up of bouts which last from about 30 seconds-600 seconds.
A bout is a stereotyped repetition of one to five notes which are called a phrase. Between two and 20 phrases are sung are short bursts which are called strophes. In-between strophes are periods of silence, and this is referred to as the inter-strophe pause. Therefore, a great tit sings several strophes of one song type before switching to a bout of another song type from their repertoire.
Biologically, having a large repertoire is advantageous in territorial defence and larger repertoires are also correlated with higher reproductive success. Marcel Lambrechts and André Dhondt proved that average strophe length and repertoire size can be used as proxies for male quality. Male quality refers to the fitness of the bird, measuring how well it survives and its reproductive success. Lambrechts and Dhondt set out to find the answers to four questions also pertaining to percentage performance time and male quality in the great tit.
The first of four questions they sought out to determine was if high quality males, those with a higher fitness, have a higher percentage performance time in their bouts compared to lower quality males, with percentage performance time meaning the percentage of time during which song was being produced. The second was if high quality males sing longer bouts than low quality males. The third answer they sought was whether the percentage performance time changed or stayed the same during a bout. The final question they sought the answer to was whether or not the percentage performance time changed after a bird switches song types.
In order to determine the answer to the four proposed questions, Marcel and André recorded male great tits from 1983–1986 in two plots (L and B) in the Peerdsbos and another plot (U) on campus at the University of Antwerp in Wilrijk. They came up with the anti-exhaustion hypothesis as an explanation for the results obtained from their study. Their results showed that high quality males, as predicted, had a higher percentage performance time than low quality males. Lambrechts and Dhondt also found that all great tits can show a systematic decrease in the percentage performance time during a bout, which is also known as drift.
The finding that drove their hypothesis was that the males were able to recover a high percentage performance by switching song types. If the male was producing shorter strophes and having longer inter-strophe pauses (low percentage performance), then by switching to a different song type the bird would once again be able to produce longer strophes and have shorter inter-strophe pauses. Lambrechts and Dhondt proposed the anti-exhaustion hypothesis, which provided both a functional and casual explanation for the song switching behaviour in birds along with having song repertoires.
The anti-exhaustion hypothesis stated that when it is necessary for a bird to sing for a prolonged period of time at a high rate, it must continuously switch song types. The hypothesis was focused around the idea that extended bouts of singing would lead to neuromuscular exhaustion because of the repetitive and stereotyped fashion of song bouts. Marcel and André proposed that the male great tits would have longer inter-strophe pauses towards the end of a song due to this exhaustion. By switching song types, the birds would be using alternative sound-producing muscles and nerves, therefore they would be able to recover a high percentage performance once again.
Anti-exhaustion hypothesis in blue tits
A study completed by Angelika Poesel and Bart Kempenaers (2002) was aimed at explaining drift during blue tit (Cyanistes caeruleus) song and among other Parus species and to also explain their findings in relation to the anti-exhaustion hypothesis and the motivation hypothesis. They studied a group of 20 male blue tits at Kolbeterberg in Vienna, Austria that were living in mixed deciduous woods. The results from their study showed that male blue tits did show a decrease in performance output (percentage performance time) the longer that they performed one song typed, which was illustrated by an increase in inter-strophe pauses.
In order to confirm the anti-exhaustion hypothesis, the two factors proposed by Lambrechts and Dhondt that influenced a low percentage performance time needed to be confirmed. These two factors are the initial level of song output (the greater the initial output, the greater the drift would be), and the number of switches between song types (after a switch in song types, performance output was increased). The results from this study could conclude that a repeated stereotyped song is difficult to maintain over a long period of time, which supported the anti-exhaustive hypothesis.
Motivation hypothesis
The motivation hypothesis was a competing hypothesis of the anti-exhaustion hypothesis. The motivation hypothesis, proposed by Weary in 1988, explained that drift may be due to a lack of motivation to keep singing the same song, not because of neuromuscular exhaustion. This study also worked with great tits, playing song to them during the day. Weary suggested that if drift was due to a lack of motivation, then if a bird was presented with the song of a rival, for example, then the bird should be able to increase its song output because of the motivational stimulus.
Weary also argued that if drift was caused by neuromuscular exhaustion, then birds would not be able to increase song output if they did not switch song types, which was not the case in all birds.
Lambrechts argued back that the test completed by Weary was not appropriate, as it was completed during the day, not during the dawn chorus when song output is at its maximum. In order to solve this conflict, Weary and Lambrechts got together and performed a series of tests during the day and during the dawn chorus testing the responsiveness to playback.
Their results showed that both hypotheses were supported, with drift being more common during the dawn chorus (supporting the anti-exhaustive hypothesis), but also that the increase in song output was similar during periods of high and low output (supporting the motivation hypothesis). These results concluded that the anti-exhaustive hypothesis and the motivation hypothesis are both possible and can both occur at the same time.
Warm-up hypothesis
The warm-up hypothesis proposed by Schraft et al. (2016) seems to contradict the anti-exhaustion hypothesis . This hypothesis foresees that birds have greater singing performance depending on the number of songs the bird has sung that day, known as recent practice, regardless of song type. This study was carried out between March and June 2012 at the Cabo Rojo National Wildlife Refuge in Puerto Rico. Male Adelaide's warblers, Setophaga adelaidae, recorded during their breeding season in their resident woods were found to have an average repertoire of 29 songs/male.
Schraft et al. tested several hypotheses, each with a different prediction and a different independent variable. The song type specific hypothesis predicted performance would decrease with consecutive repetitions of a song type, the independent variable being the run number. This hypothesis is consistent with the anti-exhaustion hypothesis. The song type general hypothesis predicted performance would increase with a higher latency period between songs, the independent variable being latency.
The warm-up hypothesis predicted performance would increase with number of songs sung, the independent variable being order. The Type I singing showcases higher performance predicted Type I songs would have higher performance than Type II songs, the independent variable. The vocal interaction hypothesis predicted performance would increase when countersinging. It was also hypothesized that time-dependent factors influenced performance, the independent variable being time.
The results from the study showed that singing performance improves with time throughout the morning. This was explained only by the warm-up hypothesis, the cumulative number of songs that the bird had sung that morning. The other hypotheses were found to have no effect on singing performance, including the song type specific hypothesis which is consistent with the anti-exhaustion hypothesis. Schraft et al. proposed that the anti-exhaustion hypothesis and the warm-up hypothesis are not mutually exclusive as the birds that warm up still may need to switch song types because of fatigue.
See also
Bird vocalization
f_tyieefrjxudu%4dtdu== References ==
Bird sounds
Ethology | Anti-exhaustion hypothesis | Biology | 2,076 |
36,443,306 | https://en.wikipedia.org/wiki/Clavulina%20ramosior | Clavulina ramosior is a species of coral fungus in the family Clavulinaceae. It occurs in Africa.
References
External links
Fungi described in 1966
Fungi of Africa
ramosior
Fungus species | Clavulina ramosior | Biology | 41 |
60,075,763 | https://en.wikipedia.org/wiki/CDV3%20%28gene%29 | Protein CDV3 homolog also known as carnitine deficiency-associated gene expressed in ventricle 3 is a protein that in humans is encoded by the CDV3 gene.
CDV3 is a biomarker for hepatocellular carcinoma. CDV3 has been considered as a potential target for gene therapy. Related gene families include plasma proteins and predicted intracellular proteins.
Gene
Aliases
The CDV3 protein is also commonly known as tyrosine-phosphorylated protein 36 (TPP36). TPP36 isoforms have been found to be substrates of Abl tyrosine kinase.
Locus
The CDV3 gene is on chromosome 3 (3q22.1).
Exons
There were variations in the listed number of exons in CDV3 between genetic databases. The number of exons vary based on the isoform in question, with most transcript isoforms having 5 exons.
Span
The exons of human CDV3 gene's longest transcript isoform span 16,711 bp.
Transcripts
Isoforms
CDV3 has seven isoforms, and more are continuously added to databases as they are discovered. Currently there are isoforms a-f.
Protein
Molecular weight: 27.3 kD
Protein length: 258 aa
Isoelectric point: 5.89
Motifs
A SAPS analysis on the human CDV3 protein sequence found one uncharged cluster segment from 28-75 aa. There were no signs of high scoring hydrophobic segments. One high scoring transmembrane segment was found from 28-55 aa. CDV3 was found to have significant maximal spacing from 27-76 aa.
Repeats
The following repetitive structures were found for the protein.
Aligned matching blocks:
[45-52] AGAAGGGA
[66-73] AGAAGPGA
with superset:
[32-36] AGAAG
[45-49] AGAAG
[ 66- 70] AGAAG
__
[134-137] MEKS
[213-216] MEKS
__
Simple tandem repeat:
[31-43] AAGAA_GSAGGSSG
[44-54] AAGAAGGGAGA
Predicted Motifs
PROSITE found several potential motifs in CDV3.
Predicted Secondary Structure
The following programs were used to develop this figure: JPred, CFSSP, and GOR4. The majority of the CDV3 structure is hypothesized to be alpha helices and random coil.
Predicted 3D Structure
The 3D structure of CDV3 was predicted through amino acid submission to the Zhang Lab and their I-TASSER program.
Gene regulation
Promoter
There are currently six different predicted promoters based on supporting transcripts. The following promoters were found using Genomatix . Promoter GXP_141972 was chosen for further analysis because of the large number of supporting transcripts, and it was found to be conserved in 14 of 14 orth. loci.
*No transcript assigned.
Expression patterns
CDV3 is ubiquitously expressed, and at relatively high levels, in all tissues examined in the humans. Higher expression existed in certain diseases.
Gene profile
Various experiments showing expression of CDV3 demonstrated different patterns of tissue expression; however, it is concluded that the gene is expressed ubiquitously throughout all tissue types with more expression within tissues involved in the immune system and skeletal muscle tissue.
The expression of CDV3 generally decreases throughout fetal development, but expression levels remain high.
Protein Level Regulation
A conceptual translation was made from NCBI reference sequence NM_017548.4. Amino acids conserved in at least 70% of vertebrate orthologous proteins are bolded (seen in the section below).
Evolution
Orthologs
The following orthologs were found through the NCBI database. The date of divergence between species and Homo sapies was determined using TimeTree. The sequence identity and similarity were found using BLAST.
Paralogs
No human paralogs were found for CDV3 GeneCards and GenesLikeMe databases through the Weizmann Institute of Science. There were not any other relevant sources when the Google Search was conducted.
Phylogenetic tree
A phylogenetic tree was developed from the species listed in the table above using "One Click Mode" on Phylogeny.fr.
Interacting proteins
Clinical significance
As earlier in the article, CDV3 has been found to be expressed in patients with various cancers and HIV. CDV3 has also been found to interact with Pr55 in the HIV retrovirus. Without further testing in expression, it is hard to determine how levels alter depending on disease state or the role this gene plays in these illnesses.
References
Proteins
Biomarkers | CDV3 (gene) | Chemistry,Biology | 953 |
50,918,386 | https://en.wikipedia.org/wiki/Placental%20microbiome | The placental microbiome is the nonpathogenic, commensal bacteria claimed to be present in a healthy human placenta and is distinct from bacteria that cause infection and preterm birth in chorioamnionitis. Until recently, the healthy placenta was considered to be a sterile organ but now genera and species have been identified that reside in the basal layer.
It should be stressed that the evidence for a placental microbiome is controversial. Most studies supporting the existence of a placental microbiome lack the appropriate experimental controls, and it has been found that contamination is most likely responsible for reports of a placental microbiome.
The placental microbiome more closely resembles that of the oral microbiome than either the vaginal or rectal microbiome.
Bacterial species and genera
Culturable and non-culturable bacterial species in the placenta obtained following normal term pregnancy have been identified.
In a healthy placental microbiome, the diversity of the species and genera is extensive. A change in the composition of the microbiota in the placenta is associated with excess gestational weight gain, and pre-term birth.
The placental microbiota varies between low birth weight infants and those infants with normal birth weights.
While bacteria are often found in the amniotic fluid of failed pregnancies, they are also found in particulate matter that is found in about 1% of healthy pregnancies.
In non-human animals, part of the microbiome is passed onto offspring even before the offspring are born. Bacteriologists assume that the same probably holds true for humans.
Research
The fact that germ free animals can be routinely generated by sterile cesarean section provides strong experimental evidence for the sterile womb hypothesis.
Future research may find that the microbiota of the female reproductive tract may be related to pregnancy, conception, and birth. Animal studies have been used to investigate the relationship between oral microbiota and the placental microbiota. Mice inoculated with species of oral bacteria demonstrated placental colonization soon afterwards.
History
Investigations into reproductive-associated microbiomes began around 1885 by Theodor Escherich. He wrote that meconium from the newborn was free of bacteria. This was interpreted as the uterine environment being sterile. Other investigations used sterile diapers for meconium collection. No bacteria were able to be cultured from the samples. Bacteria were detected and were directly proportional to the time between birth and the passage of meconium. A 1927 study demonstrated the presence of bacteria in the amniotic fluid of those that were in labor for longer than six hours.
See also
Human microbiome
Human microbiome project
Human virome
List of bacterial vaginosis microbiota
Microbiota of the lower reproductive tract of women
Vaginal microbiota in pregnancy
References
Placenta
Bacteriology
Microbiology
Feminine hygiene
Vagina
Microbiomes | Placental microbiome | Chemistry,Biology,Environmental_science | 592 |
367,371 | https://en.wikipedia.org/wiki/Pyrethrin | The pyrethrins are a class of organic compounds normally derived from Chrysanthemum cinerariifolium that have potent insecticidal activity by targeting the nervous systems of insects. Pyrethrin naturally occurs in chrysanthemum flowers and is often considered an organic insecticide when it is not combined with piperonyl butoxide or other synthetic adjuvants. Their insecticidal and insect-repellent properties have been known and used for thousands of years.
Pyrethrins are gradually replacing organophosphates and organochlorides as the pesticides of choice as the latter compounds have been shown to have significant and persistent toxic effects to humans. They first appeared on markets in the 1900s and have been continually used since then in products such as bug bombs, building insect sprays, and even to spray animals so that they do not get infectious diseases.
Chemistry
History
The pyrethrins occur in the seed cases of the perennial plant pyrethrum (Chrysanthemum cinerariaefolium), which has long been grown commercially to supply the insecticide. Pyrethrins have been used as an insecticide for thousands of years. It is believed that the Chinese crushed chrysanthemum plants and used the powder as an insecticide as early as 1000 BC. It was widely known that the Zhou dynasty in China widely used pyrethrin for its insecticide properties. For centuries, crushed Chrysanthemum flowers have been used in Iran to produce Persian Powder, an insecticide for household use. Pyrethrins were identified as the potent chemical in the Chrysanthemum plants responsible for the insecticidal properties in the crushed flowers around 1800 in Asia. In the Napoleonic Wars, French soldiers used the flowers to keep away fleas and body lice.
Biosynthesis
Well after their use as insecticides began, their chemical structures were determined by Hermann Staudinger and Lavoslav Ružička in 1924. Pyrethrin I (CnH28O3) and pyrethrin II (CnH28O5) are structurally related esters with a cyclopropane core. Pyrethrin I is a derivative of (+)-trans-chrysanthemic acid. Pyrethrin II is closely related, but one methyl group is oxidized to a carboxymethyl group, the resulting core being called pyrethric acid. Knowledge of their structures opened the way for the production of synthetic analogues, which are called pyrethroids. Pyrethrins are classified as terpenoids. The key step in the biosynthesis of the naturally occurring pyrethrins involves two molecules of dimethylallyl pyrophosphate, which join to form a cyclopropane ring by the action of the enzyme chrysanthemyl diphosphate synthase.
Production
Commercial pyrethrin production mainly takes place in mountainous equatorial zones. The commercial cultivation of the Dalmatian chrysanthemum (C. cinerariifolium) takes place at an altitude of 1600 to 3000 meters above sea level. This is done because pyrethrin concentration has been shown to increase as elevation increases to this level. Growing these plants does not require much water because semiarid conditions and a cool winter deliver optimal pyrethrin production. The Persian chrysanthemum C. coccineum also produces pyrethrins but at a much lower level. Both may be planted in low-altitude zones in dry soil, but the pyrethrin level is lower.
Pyrethrum extracted of the Persian chrysanthemum (painted daisy) was already imported to central Europe from Georgia in the middle of the 19th century.
Most of the world's supply of pyrethrin and C. cinerariaefolium today comes from Kenya, which produces the most potent flowers. Other countries include Croatia (in Dalmatia) and Japan. The flower was first introduced into Kenya and the highlands of Eastern Africa during the late 1920s. Since the 2000s, Kenya has produced about 70% of the world's supply of pyrethrum. A substantial amount of the flowers are cultivated by small-scale farmers who depend on it as a source of income. It is a major source of export income for Kenya and source of over 3,500 additional jobs. About 23,000 tons were harvested in 1975. The active ingredients are extracted with organic solvents to give a concentrate containing the six types of pyrethrins: pyrethrin I, pyrethrin II, cinerin I, cinerin II, jasmolin I, and jasmolin II.
Processing the flowers to cultivate the pyrethrin is often a lengthy process, and one that varies from area to area. For instance, in Japan, the flowers are hung upside down to dry which increases pyrethrin concentration slightly. To process pyrethrin, the flowers must be crushed. The degree to which the flower is crushed has an effect on both the longevity of the pyrethrin usage and the quality. The finer powder produced is better suited for use as an insecticide than the more coarsely crushed flowers. However, the more coarsely crushed flowers have a longer shelf life and deteriorate less.
Use as an insecticide
Pyrethrin is most commonly used as an insecticide and has been used for this purpose since the 1900s. In the 1800s, it was known as "Persian powder", "Persian pellitory", and "zacherlin". Pyrethrins delay the closure of voltage-gated sodium channels in the nerve cells of insects, resulting in repeated and extended nerve firings. This hyperexcitation causes the death of the insect due to loss of motor coordination and paralysis. Resistance to pyrethrin has been bypassed by pairing the insecticide with synthetic synergists such as piperonyl butoxide. Together, these two compounds prevent detoxification in the insect, ensuring insect death. Synergists make pyrethrin more effective, allowing lower doses to be effective. Pyrethrins are effective insecticides because they selectively target insects rather than mammals due to higher insect nerve sensitivity, smaller insect body size, lower mammalian skin absorption, and more efficient mammalian hepatic metabolism. Also, mammals are able to process pyrethrin quickly and have higher body temperatures which prevent pyrethrin from working effectively
Although pyrethrin is a potent insecticide, it also functions as an insect repellent at lower concentrations. Observations in food establishments demonstrate that flies are not immediately killed, but are found more often on windowsills or near doorways. This suggests, due to the low dosage applied, that insects are driven to leave the area before dying. Because of their insecticide and insect repellent effect, pyrethrins have been very successful in reducing insect pest populations that affect humans, crops, livestock, and pets, such as ants, spiders, and lice, as well as potentially disease-carrying mosquitoes, fleas, and ticks.
As pyrethrins and pyrethroids are increasingly being used as insecticides, the number of illnesses and injuries associated with exposure to these chemicals is also increasing. However, few cases leading to serious health effects or mortality in humans have occurred, which is why pyrethroids are labeled "low-toxicity" chemicals and are ubiquitous in home-care products. Pyrethrins are widely regarded as better for the environment, and can be harmless if used only in the field with localized sprays, as UV exposure breaks them down into harmless compounds. Additionally, they have little lasting effect on plants, degrading naturally or being degraded by the cooking process.
Specific pest species that have been successfully controlled by pyrethrum include: potato, beet, grape, and six-spotted leafhopper, cabbage looper, celery leaf tier, Say's stink bug, twelve-spotted cucumber beetle, lygus bugs on peaches, grape and flower thrips, and cranberry fruitworm.
Toxicity
Pyrethrins are among the safest insecticides on the market due to their rapid degradation in the environment.
Similarities between the chemistry of pyrethrins and synthetic pyrethroids include a similar mode of action and almost identical toxicity to insects (i.e., both pyrethrins and pyrethroids induce a toxic effect within the insect by acting on sodium channels).
Some differences in the chemistry between pyrethrins and synthetic pyrethroids have the result that synthetic pyrethroids have relatively longer environmental persistence than do pyrethrins. Pyrethrins have shorter environmental persistence than synthetic pyrethroids because their chemical structure is more susceptible to the presence of UV light and changes in pH.
The use of pyrethrin in products such as natural insecticides and pet shampoo, for its ability to kill fleas, increases the likelihood of toxicity in mammals that are exposed. Medical cases have emerged showing fatalities from the use of pyrethrin, prompting many organic farmers to cease use. One fatal case of an 11-year-old girl with a known asthmatic condition and who used shampoo containing only a small amount (0.2% pyrethrin) to wash her dog was documented.
Chronic pyrethrin toxicity in humans
Chronic toxicity in humans occurs most quickly through respiration into the lungs, or more slowly through absorption through the skin. Allergic reactions may occur after exposure, leading to itching and irritated skin as well as burning sensations. These types of reactions are rare because the allergenic component of pyrethrin in semi-synthetic pyrethroids has been removed. The metabolite compounds of pyrethrin are less toxic to mammals than their originators, and compounds are either broken down in the liver or gastrointestinal tract, or excreted through feces; no evidence of storage in tissues has been found .
Pyrethrum toxicity
Exposure to pyrethrum, the crude form of pyrethrin, causes harmful health effects for mammals. Pyrethrum also has an allergenic effect that commercial pyrethroids don't have.
In mammals, toxic exposure to pyrethrum can lead to tongue and lip numbness, drooling, lethargy, muscle tremors, respiratory failure, vomiting, diarrhea, seizures, paralysis, and death.
Exposure to pyrethrum in high levels in humans may cause symptoms such as asthmatic breathing, sneezing, nasal stuffiness, headache, nausea, loss of coordination, tremors, convulsions, facial flushing, and swelling. A possibility of damage to the immune system exists that leads to a worsening of allergies following toxicity. Infants are unable to resourcefully break down pyrethrum due to the ease of skin penetration, causing similar symptoms as adults, but with an increased risk of death.
Environmental effects
Aquatic habitats
In aquatic settings, toxicity of pyrethrin fluctuates, increasing with rising temperatures, water, and acidity. Run-off after application has become a concern for sediment-dwelling aquatic organisms because pyrethroids can accumulate in these areas. Aquatic life is extremely susceptible to pyrethrin toxicity, and has been documented in species such as the lake trout. Although pyrethrins are quickly metabolized by birds and most mammals, fish and aquatic invertebrates lack the ability to metabolize these compounds, leading to a toxic accumulation of byproducts. To combat the accumulation of pyrethroids in bodies of water, the Environmental Protection Agency (EPA) has introduced two labeling initiatives. The Environmental Hazard and General Labeling for Pyrethroid and Synergized Pyrethrins Non-Agricultural Outdoor Products was revised in 2013 to reduce runoff into bodies of water after use in residential, commercial, institutional, and industrial areas. The Pyrethroid Spray Drift Initiative updated language for labeling all pyrethroid products to be used on agricultural crops. Because of its high toxicity to fish and aquatic invertebrates even at low doses, the EPA recommends alternatives such as pesticide-free methods or alternative chemicals that are less harmful to the surrounding aquatic environment.
Terrestrial Habitats
Pyrethrin is mainly used on land and can also have impacts in the places that it is used. For instance pyrethrin has the ability to be persistent in the fields that it is sprayed on. This persistence in crops can lead to negative effects for meat production.
Bees
Pyrethrins are applied broadly as nonspecific insecticides. Bees have been shown to be particularly sensitive to pyrethrin, with fatal doses as small as 0.02 micrograms. Due to this sensitivity and pollinator decline, pyrethrins are recommended to be applied at night to avoid typical pollinating hours, and in liquid rather than dust form.
References
External links
International Center for Pyrethrum research
Pyrethrins and Pyrethroids Fact Sheet - National Pesticide Information Center
Pyrethrins and pyrethroids on the EXTOXNET
Pyrethrin and Permethrin Toxicity in Dogs and Cats
Allethrins
Plant toxin insecticides
Biological pest control | Pyrethrin | Chemistry | 2,769 |
30,426,748 | https://en.wikipedia.org/wiki/Kitzb%C3%BCheler%20Horn%20Transmitter | The Kitzbüheler Horn Transmitter () is a transmission tower made of reinforced concrete on the summit of the Kitzbüheler Horn near Kitzbühel in Austria. The Kitzbühler Horn Transmitter does not have a cylindrical shaft. It broadcasts TV and VHF radio programmes.
The tower was taken into service on 12 December 1969 as a combined radio and television transmission facility for the ORF after a difficult two-year-long construction period, preceded by lengthy and intensive negotiations with local authorities and land owners.
To facilitate the switchover to DVB-T, the analogue channels ORF 1 (Channel 5, 3 kW) and ORF 2 - Tirol (Channel 24, 30 kW) were switched off on 22 October 2007.
Frequencies and programmes
Analogue radio (VHF)
Digital television (DVB-T)
External links
Buildings and structures in Tyrol (federal state)
Radio technology
Kitzbühel | Kitzbüheler Horn Transmitter | Technology,Engineering | 186 |
39,836,130 | https://en.wikipedia.org/wiki/Strelka%20Institute | Strelka Institute for Media, Architecture and Design is a non-profit international educational project, founded in 2009 and located in Moscow. Strelka incorporates an education programme on urbanism and urban development aimed at professionals with a higher education, a public summer programme, the Strelka Press publishing house, and KB Strelka, the consulting arm of the Institute. Strelka has been listed among the top-100 best architecture schools in 2014, according to Domus magazine.
The Institute has been directed since 2013 by Varvara Melnikova. After the start of the Russo-Ukrainian war in 2022, Strelka suspended its operations.
Education programme
The Institute aims to educate the next generation of architects, designers and media professionals, enabling them to shape the 21st century world. Each year, Strelka welcomes young professionals and gives them the opportunity to work together with experts in the fields of urbanism, architecture and communications from all over the world. During this nine-month post-graduate programme, the researchers explore the issues related to Russia's urban development through a multidisciplinary method conducted in English. Experimental methods, a holistic approach to architecture, media and design, and an emphasis on research are the main characteristics of the programme. The prominent architect and architecture theorist, Rem Koolhaas (AMO/OMA), contributed to the designing of the Institute's education programme.
Since 2016, Benjamin H. Bratton, design theorist and author of The Stack: On Software and Sovereignty, is programme director. The program theme, The New Normal, focuses on long-term urban futures in relation to technological, geographic and ecological complexities.
Some notable faculty at the Strelka Institute has been : Keller Easterling, Benjamin H. Bratton, Winy Maas, Joseph Grima, Reinier De Graaf, Carlo Ratti, and Rem Koolhaas.
KB Strelka
KB Strelka provides strategic consulting services in the fields of architecture and urban planning, as well as cultural and spatial programming. The company was founded in 2013 by the executive board of the Strelka Institute. KB’s method is based on the implementation of transparent competition procedures, involving international experts, forecasting of expenses, and risk analysis at the early stages of project realisation. In 2013, KB organised several key international competitions for Russia: Zaryadye Park, the National Centre for Contemporary Arts, the Museum and Educational Centre of the Polytechnic Museum and Lomonosov Moscow State University, and the International Financial Centre in Rublyovo-Arkhangelskoye. Despite transparency efforts, KB Strelka's urbanisation projects in different cities in Russia have received criticism for the costs and the methods employed; such as the violent clearing of small street kiosks, corruption or incompetent design.
Summer at Strelka
From the end of May until mid September, Strelka’s courtyard hosts a public programme that is open to all. Its programme includes: lectures by prominent architects, urbanists, designers, social activists and scholars; discussions on topical urban issues; workshops; film screenings; theatre performances; concerts and fairs.
Strelka Press
Strelka Press publishes books and essays on modern issues of architecture, design and urban development in both English and Russian. The publishing house releases both printed and digital books. Strelka Press is based in London and Moscow. Strelka Press has published books by Donald Norman, Keller Easterling, and others.
Other information
Strelka is curating the Russian pavilion for the XIV Venice Architectural Biennale.
Strelka took part in the renovation of Moscow’s Gorky Park, designed the concept for Big Moscow development project, and framed the programme for the Moscow Urban Forum 2012-2013.
In 2013, Strelka launched What Moscow Wants, an on-line platform to crowdsource ideas for improving the development of Moscow.
References
External links
Official website
Architecture schools in Russia
Art schools in Russia
Education in Moscow
Urban planning
Educational institutions established in 2009
2009 establishments in Russia | Strelka Institute | Engineering | 826 |
78,238,636 | https://en.wikipedia.org/wiki/Collybia%20phyllophila | Collybia phyllophila, commonly known as the frosty funnel or the leaf-loving clitocybe, is a fungus in the family Tricholomataceae. Its epithet, meaning leaf-loving comes from its preference for leaf litter. It is common among forests in the Northern Hemisphere, and is poisonous.
Taxonomy
Collybia phyllophila was first described by Christiaan Hendrik Persoon as Agaricus phyllophilus in his work "Synopsis methodica fungorum" in 1801. In 1871, it was renamed to Clitocybe phyllophila by Paul Kummer in his book "Der Führer in die Pilzkunde" (The Guide to Fungi). However, a study in 2023 moved this species to the genus Collybia after phylogenetic analysis.
Description
Macroscopic characteristics
Collybia phyllophila forms medium-sized to relatively large fruiting bodies. The cap is up to wide. It is initially convex, later flat and slightly depressed in the center, although it does not become funnel-shaped. The cap is white to yellow and has a silvery to chalky white, pruinose coating, especially when young. The cap margins are rolled or curved to broadly wavy, with irregularly raised lobes when mature. When wet, the cap shows pinkish-buff or pale-brown spots.
The gills are initially whitish-yellowish, later cream-colored and with a more or less pronounced pinkish tone. They are dense and are broadly attached to the stalk or slightly decurrent. They are 2-7 mm thick, smooth and not forked. The spore print is cream-colored and often with pink or buff tones.
The stalk is long and cm thick. It is cylindrical in shape, though occasionally widening at the base. It is dirty white but becomes more beige-brownish with age. Its surface is fibrillose, and silky at the top. Dense, wooly, white mycelium surrounds the base. The flesh is watery and white, but slightly gray-brownish, especially in the cap.
It has a mild, to later rancid or astringent taste and a strong, spicy odour.
Microscopic characteristics
The hyaline spores are elliptical and measure 4-5.5 × 2.5-4 μm. Their surface is smooth and they do not glow under UV light. They are inamyloid and cyanophilous. In exsiccates they are usually connected in tetrahedrons. The basidia are club-shaped and measure 18-25 × 4.5-5.5 μm. They each have four spores. Cystidia are not present. The top layer of the cap consists of irregularly arranged, 2-4 μm wide hyphae. These usually have short nodular outgrowths or short branches. The flesh of the cap is composed of cylindric or inflated hyphae that are 4-13 μm wide. The septa have clamp connections.
Ecology and distribution
Collybia phyllophila is a common saprotrophic species in deciduous and coniferous forests. It grows on the decaying needles of white and red pine, and occasionally on mixed leaf litter pine and birch. Collybia phyllophila fruits in clusters or tufts from September to November. It is widespread in temperate and subtropical zones of the Northern Hemisphere.
Edibility
The fruiting bodies of Collybia phyllophila are poisonous as they, similar to other clitocyboid mushrooms contain muscarine. In one study, the amount of muscarine per kilogram varied between 19 and 86 mg. Symptoms of muscarinic poisoning include vomiting, diarrhea, constricted pupils sweating, bradycardia, hypotension.
Similar species
Collybia phyllophila can be confused with other white clitocyboid mushrooms such as Collybia rivulosa, Clitocybe dealbata or Clitocybe candicans. These look-a-likes are usually smaller, have white spore powder, more decurrent gills and a differently structured cap top layer. Collybia rivulosa's spores are not cyanophilous, and are single in exsiccates. Clitopilus prunulus, is also very similar, though it can be distinguished by its strong floury odour, and larger spores, as well as pink gills that separate easily from the cap. Collybia alboclitocyboides can be distinguished from C. phyllophila by the subregular flesh of its gills and by how the hyphae in the top layer of its cap run completely parallel to the cap's surface
Leucocybe connata can also be confused with it, though unlike it, the frosty funnel does not react to ferrous sulfate. Faded fruiting bodies of Clitocybe odora also sometimes look similar to it, but smell distinctly of aniseed. Clitocybe odora also differs through its blue-green tinted cap, and the absence of fine white hairs or wet spots on its cap.
References
Poisonous fungi
Fungi of Europe
Fungus species
Tricholomataceae | Collybia phyllophila | Biology,Environmental_science | 1,080 |
64,685,180 | https://en.wikipedia.org/wiki/Renata%20Gomes | Renata Gomes is a cardiovascular specialist who focusses her work on the use of molecular biology, imaging and nanotechnology applications for regeneration purposes. She is a Professor of Veteran's Health and Biomedical Research and the Chief Scientific Officer of veteran health charity BRAVO VICTOR.
Renata Gomes (born in 1985) was born in Barcelos, Portugal. At a young age she was dissecting birds that had been shot by hunters in her village. In her choice of career, she was also influenced by an uncle who was a forensic doctor at the Institute of Legal Medicine at the University of Minho in the northern Portuguese town of Braga. Her academic training was in the United Kingdom, where she received a Forensic Medicine and Forensic Sciences Degree from the University of Bradford, before doing post-graduate research and training in Cardiovascular Biochemistry and Medicine at University College London and an international PhD on Cardiovascular Regeneration and Nanotechnology with University of Coimbra in Portugal, the University of Oxford and the University of Eastern Finland (Kupio). Her work with the Universities of Coimbra, Oxford and Kupio on a nanoparticle that can contribute to cardiovascular regeneration placed her first in the 2011 Science-Image Competition organised by the British Heart Foundation.
Among the people with whom she has worked was the Nobel Prize winner, Professor Oliver Smithies. In Bradford, she worked over the holidays with Professor Karin Schallreuter on plastic surgery. While working with Professor Lino Ferreira at the Centre for Neuroscience and Cell Biology at Coimbra University, they had an idea to combine stem cell technology with nanotechnology. The research took place between 2008 and 2012. After the results were published, Gomes was nominated for and won the Science, Engineering and Technology for Britain 2012 award, given annually by the British Parliament. In 2013 her home town of Barcelos awarded her the title of Professional of the Year.
Part of her time is devoted to community and humanitarian causes. She has worked with the Small Scientists Network, based in her home town of Barcelos, which is aimed at promoting scientific curiosity among young people. Although having been treated for cancer, Gomes ran the London Marathon to raise money for the British Heart Foundation. While on a visit to Israel she contributed to a vaccination campaign among Bedouins. In Israel she met Henrique Cymerman, an Israeli journalist of Portuguese descent, with whom she decided to set up a Task Force called Knowledge for the Benefit of Mankind, to bring together religious leaders of various faiths and other influential thinkers and young people, to find realistic solutions in favour of peace.
Based in London, she then worked as Head of Research and Innovation for the charity Blind Veterans UK (formerly St Dunstan's), seeking to find regenerative-medicine solutions to benefit blind veterans. In 2020 she became its Chief Scientific Officer, before the Directorate became BRAVO VICTOR.
References
1985 births
Living people
People from Barcelos, Portugal
Nanotechnologists
Cardiovascular researchers
Alumni of the University of Bradford
Alumni of University College London
University of Coimbra alumni | Renata Gomes | Materials_science | 622 |
47,372,547 | https://en.wikipedia.org/wiki/Truncated%20Newton%20method | The truncated Newton method, originated in a paper by Ron Dembo and Trond Steihaug, also known as Hessian-free optimization, are a family of optimization algorithms designed for optimizing non-linear functions with large numbers of independent variables. A truncated Newton method consists of repeated application of an iterative optimization algorithm to approximately solve Newton's equations, to determine an update to the function's parameters. The inner solver is truncated, i.e., run for only a limited number of iterations. It follows that, for truncated Newton methods to work, the inner solver needs to produce a good approximation in a finite number of iterations; conjugate gradient has been suggested and evaluated as a candidate inner loop. Another prerequisite is good preconditioning for the inner algorithm.
References
Further reading
Optimization algorithms and methods | Truncated Newton method | Mathematics | 175 |
24,029,204 | https://en.wikipedia.org/wiki/C15H11O5 | {{DISPLAYTITLE:C15H11O5}}
The molecular formula C15H11O5 (or C15H11O5+, molar mass: 271.24 g/mol, exact mass: 271.0606 u) may refer to:
Fisetinidin, an anthocyanidin
Luteolinidin, an anthocyanidin
Pelargonidin, an anthocyanidin
Molecular formulas | C15H11O5 | Physics,Chemistry | 98 |
51,274,994 | https://en.wikipedia.org/wiki/Augusta-Priolo | The petrochemical complex of Augusta-Priolo (called Polo petrolchimico siracusano in Italian) is a vast industrialized coastal area in eastern Sicily including the territory of the municipalities of Augusta, Priolo Gargallo and Melilli. Main industrial activities are oil refining, processing of oil derivatives and energy production.
The complex, whose beginnings date back to 1949, has produced significant environmental problems for the coastline and the entire area, as well as health issues and an increased death rate. The area is therefore often dubbed triangolo della morte (triangle of death).
Among the companies in the region are ExxonMobil, Sasol, Erg, Polimeri Europa and Syndial.
See also
Triangle of death (Italy)
Angelo Moratti
Port of Augusta
References
External links
Chemical industry in Italy
Petrochemical industry
Pollution in Italy
Petroleum industry in Italy
Province of Syracuse | Augusta-Priolo | Chemistry | 183 |
20,556,915 | https://en.wikipedia.org/wiki/Boson | In particle physics, a boson ( ) is a subatomic particle whose spin quantum number has an integer value (0, 1, 2, ...). Bosons form one of the two fundamental classes of subatomic particle, the other being fermions, which have odd half-integer spin (, , , ...). Every observed subatomic particle is either a boson or a fermion. Paul Dirac coined the name boson to commemorate the contribution of Satyendra Nath Bose, an Indian physicist.
Some bosons are elementary particles occupying a special role in particle physics, distinct from the role of fermions (which are sometimes described as the constituents of "ordinary matter"). Certain elementary bosons (e.g. gluons) act as force carriers, which give rise to forces between other particles, while one (the Higgs boson) contributes to the phenomenon of mass. Other bosons, such as mesons, are composite particles made up of smaller constituents.
Outside the realm of particle physics, multiple identical composite bosons (in this context sometimes known as 'bose particles') behave at high densities or low temperatures in a characteristic manner described by Bose–Einstein statistics: for example a gas of helium-4 atoms becomes a superfluid at temperatures close to absolute zero. Similarly, superconductivity arises because some quasiparticles, such as Cooper pairs, behave in the same way.
Name
The name boson was coined by Paul Dirac to commemorate the contribution of Satyendra Nath Bose, an Indian physicist. When Bose was a reader (later professor) at the University of Dhaka, Bengal (now in Bangladesh), he and Albert Einstein developed the theory characterising such particles, now known as Bose–Einstein statistics and Bose–Einstein condensate.
Elementary bosons
All observed elementary particles are either bosons (with integer spin) or fermions (with odd half-integer spin). Whereas the elementary particles that make up ordinary matter (leptons and quarks) are fermions, elementary bosons occupy a special role in particle physics. They act either as force carriers which give rise to forces between other particles, or in one case give rise to the phenomenon of mass.
According to the Standard Model of Particle Physics there are five elementary bosons:
One scalar boson (spin = 0)
Higgs boson – the particle that contributes to the phenomenon of mass via the Higgs mechanism
Four vector bosons (spin = 1) that act as force carriers. These are the gauge bosons:
Photon – the force carrier of the electromagnetic field
Gluons (eight different types) – force carriers that mediate the strong force
Neutral weak boson – the force carrier that mediates the weak force
Charged weak bosons (two types) – also force carriers that mediate the weak force
A second order tensor boson (spin = 2) called the graviton (G) has been hypothesised as the force carrier for gravity, but so far all attempts to incorporate gravity into the Standard Model have failed.
Composite bosons
Composite particles (such as hadrons, nuclei, and atoms) can be bosons or fermions depending on their constituents. Since bosons have integer spin and fermions odd half-integer spin, any composite particle made up of an even number of fermions is a boson.
Composite bosons include:
All mesons of every type
Stable nuclei with even mass numbers such as deuterium, helium-4 (the alpha particle), carbon-12, lead-208, and many others.
As quantum particles, the behaviour of multiple indistinguishable bosons at high densities is described by Bose–Einstein statistics. One characteristic which becomes important in superfluidity and other applications of Bose–Einstein condensates is that there is no restriction on the number of bosons that may occupy the same quantum state. As a consequence, when for example a gas of helium-4 atoms is cooled to temperatures very close to absolute zero and the kinetic energy of the particles becomes negligible, it condenses into a low-energy state and becomes a superfluid.
Quasiparticles
Certain quasiparticles are observed to behave as bosons and to follow Bose–Einstein statistics, including Cooper pairs, plasmons and phonons.
See also
Explanatory notes
References
Quantum field theory
Atomic physics
Condensed matter physics | Boson | Physics,Chemistry,Materials_science,Engineering | 918 |
47,552,633 | https://en.wikipedia.org/wiki/List%20of%20people%20associated%20with%20PARC | Many notable computer scientists and others have been associated with the Palo Alto Research Center Incorporated (PARC), formerly Xerox PARC. They include:
Nina Amenta (at PARC 1996–1997), researcher in computational geometry and computer graphics
Anne Balsamo (at PARC 1999–2002), media studies scholar of connections between art, culture, gender, and technology
Patrick Baudisch (at PARC 2000–2001), in human–computer interaction
Daniel G. Bobrow (at PARC 1972–2017), artificial intelligence researcher
Susanne Bødker (at PARC 1982–1983), researcher in human–computer interaction
David Boggs (at PARC 1972–1982), computer network pioneer, coinventor of Ethernet
Anita Borg (at PARC 1997–2003), computer systems researcher, advocate for women in computing
John Seely Brown (at PARC 1978–2000), researcher in organizational studies, chief scientist of Xerox
Bill Buxton (at PARC 1989–1994), pioneer in human–computer interaction
Stuart Card (at PARC 1974-2010), applied human factors in human–computer interaction
Robert Carr (at PARC in late 1970s), CAD and office software designer
Ed Chi (at PARC 1997–2011), researcher in information visualization and the usability of web sites
Elizabeth F. Churchill (at PARC 2004–2006), specialist in human-computer interaction and social computing
Lynn Conway (at PARC 1973–1982), VLSI design pioneer and transgender activist
Franklin C. Crow (at PARC circa 1982–1990), computer graphics expert who did early research in antialiasing
Pavel Curtis (at PARC 1983–1996), pioneer in text-based online virtual reality systems
Doug Cutting (at PARC 1990-1994), creator of Nutch, Lucene, and Hadoop
Steve Deering (at PARC circa 1990–1996), internet engineer, lead designer of IPv6
L Peter Deutsch (at PARC 1971–1986), implementor of LISP 1.5, Smalltalk, and Ghostscript
David DiFrancesco (at PARC 1972–1974), worked with Richard Shoup on PAINT, cofounded Pixar
Paul Dourish (at PARC mid-1990s), researcher at the intersection of computer science and social science
W. Keith Edwards (at PARC 1996–2004), researcher in human-computer interaction and ubiquitous computing
Jerome I. Elkind (at PARC 1971–1978), head of the Computer Science Laboratory at PARC
Clarence Ellis (at PARC 1976–1984), first African American CS PhD, pioneered computer-supported cooperative work
David Em (at PARC 1975), computer artist, first fine artist to create a computer model of a 3d character
Bill English (at PARC 1971–1989), co-invented computer mouse
David Eppstein (at PARC 1989–1990), researcher in computational geometry and graph algorithms
John Ellenby (at PARC 1975–1978), Led AltoII development, 1979 founded GRID Systems
Matthew K. Franklin (at PARC 1998–2000), developed pairing-based elliptic-curve cryptography
Gaetano Borriello (at PARC 1980–1987), developed Open Data Kit
Richard Fikes (at PARC 1976-1983), leader in representation and use of knowledge in computer systems, Professor Emeritus, Stanford University
Sean R. Garner (at PARC circa 2009– ), researcher in photovoltaics and sustainable engineering
Charles Geschke (at PARC 1972–1980), invented page description languages, cofounded Adobe
Adele Goldberg (at PARC 1973–1986), codesigned Smalltalk, president of ACM
Jack Goldman (at PARC 1970–), Xerox chief scientist 1968–1982, founded PARC in 1970
Bill Gosper (at PARC 1977–1981), founded the hacker community, pioneered symbolic computation
Rich Gossweiler (at PARC 1997–2000), software engineer, expert in interaction design
Rebecca Grinter (at PARC 2000–2004), researcher in human-computer interaction and computer-supported cooperative work
Neil Gunther (at PARC 1982–1990), developed open-source performance modeling software
Jürg Gutknecht (at PARC 1984–1985), programming language researcher, designer, with Niklaus Wirth
Marti Hearst (at PARC 1994–1997), expert in computational linguistics and search engine user interfaces
Jeffrey Heer (at PARC 2001-2005), expert in information visualization and interactive data analysis
Bruce Horn (at PARC 1973–1981), member of original Apple Macintosh design team
Bernardo Huberman (at PARC circa 1982–2000), applied chaos theory to web dynamics
Dan Ingalls (at PARC circa 1972–1984), implemented Smalltalk virtual machine, invented bit blit
Van Jacobson (at PARC 2006– ), developed internet congestion control protocols and diagnostics
Natalie Jeremijenko (at PARC 1995), installation artist
Ted Kaehler (at PARC 1972–1985), developed key systems for original Smalltalk, later Apple HyperCard, Squeak
Ronald Kaplan (at PARC 1974–2006), expert in natural language processing, helped develop Interlisp
Jussi Karlgren (at PARC 1991-1992), known for work on stylistics, evaluation of search technology, and statistical semantics
Lauri Karttunen (at PARC 1987–2011), developed finite state morphology in computational linguistics
Alan Kay (at PARC 1971–1981), pioneered object-oriented programming and graphical user interfaces
Martin Kay (at PARC 1974–2002 ), expert on machine translation and computational linguistics
Gregor Kiczales (at PARC 1984–2002), invented aspect-oriented programming
Ralph Kimball (at PARC 1972–1982), designed first commercial workstation with mice, icons, and windows
András Kornai (at PARC 1988-1991), mathematical linguist
Butler Lampson (at PARC 1971–1983), won Turing Award for his development of networked personal computers
David M. Levy (at PARC 1984–1999), researcher on information overload
Jia Li (at PARC 1999–2000), researcher in computer vision and image retrieval
Cristina Lopes (at PARC 1995–2002), researcher in aspect-oriented programming and ubiquitous computing
Richard Francis Lyon (at PARC 1977–1981), built the first optical mouse
Jock D. Mackinlay (at PARC 1986–2004) researcher in information visualization
Cathy Marshall (at PARC circa 1989–2000), researcher on hypertext and personal archiving
Edward M. McCreight (at PARC 1971–1989) co-invented B-trees
Scott A. McGregor (at PARC 1978–1983) worked on Xerox Star, Viewers for Cedar and then Windows 1.0 at Microsoft
Sheila McIlraith (at PARC 1997–1998), researcher in artificial intelligence and the semantic web
Ralph Merkle (at PARC 1988–1999), invented public key cryptography and cryptographic hashing
Diana Merry (at PARC circa 1971–1986), helped develop Smalltalk, co-invented bit blit
Robert Metcalfe (at PARC 1972–1979), co-invented Ethernet, formulated Metcalfe's Law
James G. Mitchell (at PARC 1971–1984), developed WATFOR compiler, Mesa (programming language), Spring (operating system), ARM RISC chip
Louis Monier (at PARC 1983–1989), founded AltaVista search engine
J Strother Moore (at PARC 1973-1976), text editing, Interlisp VM, string searching, theorem proving
Thomas P. Moran (at PARC 1974–2001), founded journal Human-Computer Interaction
James H. Morris (at PARC 1974–1982), co-invented KMP string matching algorithm and lazy evaluation
Elizabeth Mynatt (at PARC 1995–1998), studied digital family portraits and ubiquitous computing
Greg Nelson (at PARC 1980–1981), satisfiability modulo theories, extended static checking, program verification, Modula-3, theorem prover
Martin Newell (at PARC 1979–1981), graphics expert who created the Utah teapot
William Newman (at PARC 1973–1979), Graphics and HCI researcher, developed drawing and page description software
Tina Ng (at PARC 2006–2015), expert on additive manufacture of flexible electronics
Geoffrey Nunberg (at PARC 1987–2001), linguist known for his work on lexical semantics
Severo Ornstein (at PARC 1976–1983), founding head of Computer Professionals for Social Responsibility
Valeria de Paiva (at PARC 2000–2008), uses logic and category theory to model natural language
George Pake (at PARC 1970–1986), pioneer in nuclear magnetic resonance, founding director of PARC
Jan O. Pedersen (at PARC circa 1990-1996), researcher in search system technology and algorithms
Peter Pirolli (at PARC 1991–2016 ), developed information foraging theory
Calvin Quate (at PARC 1983–1994), invented the atomic force microscope
Ashwin Ram (at PARC circa 2011–2016 ), researcher on artificial intelligence for health applications
Trygve Reenskaug (at PARC 1978–1979), formulated model–view–controller user interface design
George G. Robertson (at PARC circa 1988–1995), information visualization expert
Daniel M. Russell (at PARC 1982–1993), AI and UI research; later at Apple, then at Google, where he calls himself a search anthropologist
Eric Schmidt (at PARC 1982–1983), CEO of Google and chairman of Alphabet
Ronald V. Schmidt (at PARC 1980–1985), computer network engineer who founded SynOptics
Michael Schroeder (at PARC circa 1977–1985), co-invented Needham–Schroeder protocol for encrypted networking
Bertrand Serlet (at PARC 1985–1989), led the Mac OS X team
Scott Shenker (at PARC 1984–1998), leader in software-defined networking
John Shoch (at PARC 1971–1980), developed an important predecessor of TCP/IP networking
Richard Shoup (at PARC 1971–1978), invented SUPERPAINT and the first 8 bit Frame Buffer (picture memory), 1979 cofounded Aurora
Charles Simonyi (at PARC 1972-1981), led the creation of Microsoft Office
Alvy Ray Smith (at PARC 1974), cofounded Pixar
Brian Cantwell Smith (at PARC 1982–1996), invented introspective programming and researches computational metaphors
David Canfield Smith (at PARC 1975), invented interface icons, programming by demonstration, worked on graphical user interface, Xerox Star
Robert Spinrad (at PARC 1978–1982), designed vacuum tube computers, directed PARC
Bob Sproull (at PARC 1973–1977), designed early head-mounted display, wrote widely used computer graphics textbook
Jessica Staddon (at PARC 2001–2010), information privacy researcher
Gary Starkweather (at PARC 1970–1988), invented laser printers and color management
Maureen C. Stone (at PARC circa 1980–1998), expert in color modeling
Lucy Suchman (at PARC 1980–2000), researcher on human factors, cybercultural anthropology, and feminist theory
Bert Sutherland (at PARC 1975–1981), brought social scientists to PARC
Robert Taylor (at PARC 1970–1983), managed early ARPAnet development, founded DEC Systems Research Center
Warren Teitelman (at PARC 1972–1984), designed Interlisp
Shang-Hua Teng (at PARC 1991–1992), invented smoothed analysis of algorithms and near-linear-time Laplacian solvers
Larry Tesler (at PARC 1973–1980), developed Object Pascal and Apple Newton
Chuck Thacker (at PARC 1971–1983), chief designer of Alto, co-invented Ethernet
John Warnock (at PARC 1978–1982), cofounded Adobe
Mark Weiser (at PARC 1987–1999), invented ubiquitous computing
Niklaus Wirth (at PARC 1976–1977 and 1984–1985), designed Pascal and other programming languages
Frances Yao (at PARC 1979–1999), researcher in computational geometry and combinatorial algorithms
Nick Yee (at PARC 2005-2012), researcher in psychology and sociology of virtual environments
Annie Zaenen (at PARC 2001–2011), researcher on linguistic encoding of temporal and spatial information
Lixia Zhang (at PARC 1989–1996), computer networking pioneer
References
PARC | List of people associated with PARC | Technology | 2,486 |
712,775 | https://en.wikipedia.org/wiki/Frank%20Bunker%20Gilbreth | Frank Bunker Gilbreth (July 7, 1868 – June 14, 1924) was an American engineer, consultant, and author known as an early advocate of scientific management and a pioneer of time and motion study, and is perhaps best known as the father and central figure of Cheaper by the Dozen.
Both he and his wife Lillian Moller Gilbreth were industrial engineers and efficiency experts who contributed to the study of industrial engineering in fields such as motion study and human factors.
Biography
Early life and education
Gilbreth was born in Fairfield, Maine, on July 7, 1868. He was the third child and only son of John Hiram Gilbreth and Martha Bunker Gilbreth. His mother had been a schoolteacher. His father owned a hardware store and was a stockbreeder. When Gilbreth was three and a half years old his father died suddenly from pneumonia.
After his father's death his mother moved the family to Andover, Massachusetts, to find better schools for her children. The substantial estate left by her husband was managed by her husband's family. By the fall of 1878 the money had been lost or stolen and Martha Gilbreth had to find a way to make a living. She moved the family to Boston where good public schools existed. She opened a boarding house since a schoolteacher's salary would not support the family.
Gilbreth was not a good student. He attended Rice Grammar School, but his mother was concerned enough to teach him at home for a year. He attended Boston's English High School, and his grades improved when he became interested in his science and math classes. He took the entrance examinations for the Massachusetts Institute of Technology, but wanted his mother to be able to give up the boarding house. He decided to go to work rather than to college.
Whidden Construction Company
Renton Whidden, Gilbreth's old Sunday School teacher, hired him for his building company. He was to start as a laborer, learn the various building trades, and work his way up in the firm. In July 1885 at age 17 he started as a bricklayer's helper. As he learned bricklaying he noticed the many variations in the bricklayers' methods and efficiency. This began his interest in finding "the one best way" of executing any task. He quickly learned every part of building work and contracting, and advanced rapidly. He took night school classes to learn mechanical drawing. After five years he was a superintendent, which allowed his mother to give up her boarding house.
Using his observations of workmen laying brick, Gilbreth developed a multilevel scaffold that kept the bricks within easy reach of the bricklayer. He began patenting his innovations with this "Vertical Scaffold", then developed and patented the "Gilbreth Waterproof Cellar". He made innovations in concrete construction, as well. After ten years, at age 27, he was the chief superintendent. When after ten years the Whiddens were unwilling to make him a partner, he resigned to start his own company.
Career as general contractor
Gilbreth founded his own commercial contracting firm on April 1, 1895. For the next fifteen years, "Frank B. Gilbreth, General Contractor" and two subsidiary companies would build some 100 large-scale projects across the United States (along with two in Canada), including full scale factories, paper mills, canals, dams and powerhouses. The largest such project was a complete paper mill constructed in 1907–08 in Canton, North Carolina. It was a $2 million facility consisting of more than thirty full-scale industrial buildings.
One Gilbreth construction project was the Simmons Hardware Company's Sioux City Warehouse. The architects had specified that hundreds of hardened concrete piles (based on Gibreth's own patents for design and installation) were to be driven in to allow the soft ground to take the weight of two million bricks required to construct the building. The "Time and Motion" approach could be applied to the bricklaying and the transportation. The building was also required to support efficient input and output of deliveries via its own railroad switching facilities.
Gilbreth held thirteen patents as an inventor, beginning in his years with the Whiddens, and had patent and product management offices in London and Berlin. Other than two projects in Ontario, Canada, and a third that was abandoned after initial construction, he did not build any projects outside the United States.
Career as efficiency expert
Gilbreth changed careers to efficiency and management engineering with the close of his construction companies in about 1912. He eventually became an occasional lecturer at Purdue University, which houses his papers.
Gilbreth discovered his vocation as efficiency expert while still a young construction worker, when he sought ways to make bricklaying faster and easier. During the later part of his contracting career, this grew into a collaboration with his wife, Lillian Moller Gilbreth. Together they studied the work habits of manufacturing and clerical employees in all sorts of industries to find ways to increase output and make their jobs easier. He and Lillian founded a management consulting firm, Frank B. Gilbreth, Inc. (renamed Gilbreth, Inc. after his death), focusing on such endeavors.
Gilbreth was also an adamant champion of the "cost-plus-a-fixed sum" contract in his building contracting business. He described this method in an article in Industrial Magazine in 1907, comparing it to fixed price and guaranteed maximum price methods. Many of his prolific advertisements throughout the era boast of and recommend this as "their special method of construction."
Family
Gilbreth married Lillian Evelyn Moller on October 19, 1904, in Oakland, California; they had 12 children. Their names were Anne Moller Gilbreth Barney (1905–1987), Mary Elizabeth Gilbreth (1906–1912), Ernestine Moller Gilbreth Carey (1908–2006), Martha Bunker Gilbreth Tallman (1909–1968), Frank Bunker Gilbreth Jr. (1911–2001), William Moller Gilbreth (1912–1990), Lillian Gilbreth Johnson (1914–2001), Frederick Moller Gilbreth (1916–2015), Daniel Bunker Gilbreth (1917–2006), John Moller Gilbreth (1919–2002), Robert Moller Gilbreth (1920–2007), and Jane Moller Gilbreth Heppes (1922–2006); there was also a stillborn daughter (1915) who was not named.
Death
Gilbreth died of a heart attack on June 14, 1924, at age 55. He was at the Lackawanna Terminal in Montclair, New Jersey, talking with his wife by telephone. In accordance with his wishes, his brain was donated to Harvard University, and his ashes were scattered in the Atlantic Ocean. Lillian outlived him by 48 years.
Work
Motion studies
Gilbreth served as a major in the U.S. Army during World War I. His assignment was to find quicker and more efficient means of assembling and disassembling small arms. However, he was stricken with rheumatic fever and then pneumonia just weeks into his service, and spent four months in recovery before being discharged. The heart damage from this episode would contribute to his premature death six years later. According to Claude George (1968), Gilbreth reduced all motions of the hand into some combination of 17 basic motions. These included grasp, transport loaded, and hold. Gilbreth named the motions therbligs — "Gilbreth" spelled (approximately) backwards. He used a motion picture camera that was calibrated in fractions of minutes to time the smallest of motions in workers.
Their emphasis on the "one best way" and therbligs predates the development of continuous quality improvement (CQI), and the late 20th century understanding that repeated motions can lead to workers experiencing repetitive motion injuries.
Gilbreth was the first to propose the position of "caddy" (Gilbreth's term) to a surgeon, who handed surgical instruments to the surgeon as needed. Gilbreth also devised the standard techniques used by armies around the world to teach recruits how to rapidly disassemble and reassemble their weapons even when blindfolded or in total darkness.
Scientific management
The work of the Gilbreths is often associated with that of Frederick Winslow Taylor, yet there was a substantial philosophical difference between the Gilbreths and Taylor. The symbol of Taylorism was the stopwatch; Taylor was concerned primarily with reducing process times. The Gilbreths, in contrast, sought to make processes more efficient by reducing the motions involved. They saw their approach as more concerned with workers' welfare than Taylorism, which workers themselves often perceived as concerned mainly with profit. This difference led to a personal rift between Taylor and the Gilbreths which, after Taylor's death, turned into a feud between the Gilbreths and Taylor's followers. After Frank's death, Lillian Gilbreth took steps to heal the rift; however, some friction remains over questions of history and intellectual property.
Fatigue study
In conducting their Motion Study method to work, they found that the key to improving work efficiency was in reducing unnecessary motions. Not only were some motions unnecessary, but they caused employee fatigue. Their efforts to reduce fatigue included reduced motions, tool redesign, parts placement, and bench and seating height, for which they began to develop workplace standards. The Gilbreths' work broke ground for contemporary understanding of ergonomics.
Legacy
Frank and Lillian Gilbreth often used their large family (and Frank himself) as guinea pigs in experiments. Their family exploits are lovingly detailed in the 1948 book Cheaper by the Dozen, written by son Frank Jr. and daughter Ernestine (Ernestine Gilbreth Carey). The book inspired a film and the title inspired a second and third unrelated film of the same name. The first, in 1950, starred Clifton Webb and Myrna Loy. The second, in 2003, starred comedians Steve Martin and Bonnie Hunt, and bears no resemblance to the book, except that it features a family with twelve children, and the wife's maiden name is Gilbreth. The third, in 2022, also bears no relation to the book and starred Gabrielle Union and Zach Braff. A 1952 sequel titled Belles on Their Toes chronicled the adventures of the Gilbreth family after Frank's 1924 death. A later biography of his parents, Time Out For Happiness, was written by Frank Bunker Gilbreth, Jr. alone in 1962.
The award for lifetime achievement by the Institute of Industrial and Systems Engineers (IISE) is named in Frank and Lillian Gilbreth's honor.
His maxim of "I will always choose a lazy person to do a difficult job, because a lazy person will find an easy way to do it" is still commonly used today, although it is often misattributed to Bill Gates, who merely repeated the quote but did not originate it.
Selected publications
Frank and Lillian Gilbreth wrote in collaboration, but Lillian's name was not included on the title page until after she earned her PhD.
References
Further reading
Frank Gilbreth Jr. makes several errors of recollection in this otherwise significant letter-memoire.
External links
, comprehensive family and professional history.
, books by and about the Gilbreths and Scientific Management
An updated history of the Gilbreth family vacation home.
1868 births
1924 deaths
American industrial engineers
American business theorists
People from Fairfield, Maine
Military personnel from Maine
Purdue University faculty
People from Montclair, New Jersey
American bricklayers
Time and motion study
Articles containing video clips
Henry Laurence Gantt Medal recipients
Engineers from New Jersey
Writers from Maine
English High School of Boston alumni | Frank Bunker Gilbreth | Engineering | 2,406 |
52,991 | https://en.wikipedia.org/wiki/Pressure%20cooker | A pressure cooker is a sealed vessel for cooking food with the use of high pressure steam and water or a water-based liquid, a process called pressure cooking. The high pressure limits boiling and creates higher temperatures not possible at lower pressures, allowing food to be cooked faster than at normal pressure.
The prototype of the modern pressure cooker was the steam digester invented in the seventeenth century by the physicist Denis Papin. It works by expelling air from the vessel and trapping steam produced from the boiling liquid. This is used to raise the internal pressure up to one atmosphere above ambient and gives higher cooking temperatures between . Together with high thermal heat transfer from steam it permits cooking in between a half and a quarter the time of conventional boiling as well as saving considerable energy.
Almost any food that can be cooked in steam or water-based liquids can be cooked in a pressure cooker. Modern pressure cookers have many safety features to prevent the pressure cooker from holding too much pressure causing an explosion. After cooking, the steam pressure is lowered back to ambient atmospheric pressure so that the vessel can be opened. On all modern devices, a safety lock prevents opening while under pressure.
According to the New York Times Magazine, 37% of U.S. households owned at least one pressure cooker in 1950. By 2011, that rate dropped to only 20%. Part of the decline has been attributed to fear of explosion (although this is extremely rare with modern pressure cookers) along with competition from other fast cooking devices such as the microwave oven. However, third-generation pressure cookers have many more safety features and digital temperature control, do not vent steam during cooking, and are quieter and more efficient, and these conveniences have helped make pressure cooking more popular.
History
In 1679, French physicist Denis Papin, better known for his studies on steam, invented the steam digester in an attempt to reduce the cooking time of food. His airtight cooker used steam pressure to raise the water's boiling point, thus cooking food more quickly. In 1681 Papin presented his invention to the Royal Society of London as a scientific study; he was later elected as a member.
In 1864, Georg Gutbrod of Stuttgart began manufacturing pressure cookers made of tinned cast iron.
Although the concept of cooking with pressurized steam had been known for two centuries, the term “pressure cooker” was not commonly used until the early 20th century. The earliest citation of the phrase given in the Oxford English Dictionary is from a Lincoln, Nebraska, newspaper in 1914. However, the Dictionary editors apparently overlooked or did not have access to certain Colorado newspapers from a few years earlier than that. As early as 1910, the inventor Zeno E. Crook founded a business called “The Pressure Cooker Company” in Denver, Colorado. Crook had developed an aluminum cooker of a size practical for home use, and soon began marketing it to communities in the high country of Colorado, where the device proved to be well suited for use in high-altitude cooking. In many of these communities, Crook's pressure cooker was hailed as a marvelous new invention, until 1918, when Popular Science Monthly broke the news that this “invention” was actually more than 200 years old.
In 1918, Spain granted a patent for the pressure cooker to José Alix Martínez from Zaragoza. Martínez named it the olla exprés, literally "express cooking pot", under patent number 71143 in the Boletín Oficial de la Propiedad Industrial. In 1924, the first pressure cooking pot recipe book was published, written by José Alix and titled "360 fórmulas de cocina Para guisar con la 'olla expres'", or 360 recipes for cooking with a pressure cooker.
In 1935, the Automa pressure cooker was introduced. Mountaineers attempting to climb Mount Everest took it along with them to cook in higher altitudes.
In 1938, Alfred Vischer presented his invention, the Flex-Seal Speed Cooker, in New York City. Vischer's pressure cooker quickly gained popularity, and its success led to competition among American and European manufacturers. At the 1939 New York World's Fair, the National Pressure Cooker Company, later renamed National Presto Industries, introduced its own pressure cooker.
First generation
Also known as "old type" pressure cookers, these operate with a weight-modified or "jiggler" valve, which releases pressure during operation. Some people consider them loud because the valve rattles as excess steam is released. Older pressure cookers typically offered only one pressure level, but from the 1960s onwards some allow the operator to change the weight of the valve, thus changing the pressure.
Today most pressure cookers are variations on the first-generation cookers, with the addition of new safety features such as a mechanism that prevents the cooker from being opened until it is entirely depressurized.
Second generation
These operate with a spring-loaded valve that is often hidden from view in a proprietary mechanism. This generation is characterized by two or more pressure settings. Some of these pressure cookers do not release any steam during operation (non-venting) and instead use a rising indicator with markings to show the pressure level. These only release steam when the pan is opened, or as a safety precaution if the heat source is not reduced enough when the pan reaches the required cooking pressure. Others use a dial that the operator can advance by a few clicks (which alters the spring tension) to change the pressure setting or release pressure; these release steam during operation (venting).
Third generation "electric pressure cookers"
After the stove-top pressure cookers came the electric pressure cookers in 1991, called the "third generation" pressure cookers.
These include an electric heat source that is automatically regulated to maintain the operating temperature and pressure. They also include a spring-loaded valve (as described above) and are typically non venting during cooking.
An electric pressure cooker integrates a timer. Depending on cooking control capability, there are three generations of electric pressure cookers:
First-generation electric, with mechanical timer. There is no delayed cooking capability.
Second-generation electric, with digital controller. Delayed cooking becomes possible and the controller shows a countdown timer when working pressure is reached.
Third-generation electric, with smart programming, which includes pre-set cooking times and settings based on heating intensity, temperature, pressure and duration.
Some pressure cookers are multifunctional (multicookers): pressure cooker, saute/browning, slow cooker, rice cooker, egg cooker, yogurt maker, steamer, sous vide, canner, and stockpot warmer that can also be used to keep cooked food warm. Since 2018, with the release of the Ninja Foodi pressure cooker, which was the first pressure cooker that could also air fry, several other pressure cooker manufacturers, including Instant Pot, have come out with their own pressure cookers that can air fry, which are now known as air fryer pressure cookers. Air fryer pressure cookers generally have two separate lids, one for pressure cooking, and one for air frying.
Theory
At standard pressure the boiling point of water is . With any food containing or cooked with water, once the temperature reaches the boiling point, any excess heat causes some of the water to vaporize into steam efficiently carrying away heat keeping the food temperature at 100 °C.
In a sealed pressure cooker, as the water boils, the steam is trapped in the cooker which raises the pressure. However, the boiling point of water increases with pressure resulting in superheated water.
The equation for the pressure, temperature and volume of the steam is given by the ideal gas law:
or
where , and are the pressure, volume and temperature; is the amount of substance; and is the ideal gas constant.
In a sealed pressure cooker the volume and amount of steam is fixed, so the temperature can be controlled either directly or by setting the pressure, such as with a pressure release valve.
For example, if the pressure reaches 1 bar or above the existing atmospheric pressure, the water will have reached a temperature of approximately which cooks the food much faster.
Pressure cookers also use steam and water to rapidly transfer the heat to the food and all parts of the vessel. While compared to an oven, a pressure cooker's 120 °C is not particularly high, ovens contain air which is subject to thermal boundary layer effects which greatly slows heating, whereas pressure cookers flush air from the cooking vessel during warm up and replace it with hot steam. For items not placed within the liquid, as this steam condenses on the food it transfers water's latent heat of vaporization, which is extremely large (2.275 kJ/g), to the surface, rapidly bringing the surface of the food up to cooking temperature. Because the steam condenses and drips away, no significant boundary layer forms and heat transfer is exceptionally efficient, and food heats much faster and more evenly.
However some recipes require browning to develop flavors as during roasting or frying. Higher temperatures are attainable with conventional cooking where the surface of the food can dry out. Such browning occurs via the Maillard reaction, at temperatures higher than the roughly achieved in pressure cooking. Because those temperatures are not reached in pressure cooking, foods are generally browned by searing them, either in the open pressure cooker or another pan beforehand.
High altitudes
A pressure cooker can be used to compensate for lower atmospheric pressure at high elevations. The boiling point of water drops by approximately 1 °C per every 294 metres of altitude (see: High-altitude cooking), causing the boiling point of water to be significantly below the at standard pressure. This is problematic because temperatures above roughly 90 °C are necessary to cook many common vegetables in a reasonable time. For example, on the summit of Everest (), the boiling point of water would be only . Without the use of a pressure cooker, many boiled foods may remain undercooked, as described in Charles Darwin's The Voyage of the Beagle (chapter XV, March 20, 1835):
When pressure cooking at high altitudes, cooking times need to be increased by approximately 5% for every above elevation. Since the regulators work off the pressure differential between interior and ambient pressure, the absolute pressure in the interior of a pressure cooker will always be lower at higher altitudes.
Weight is a concern with backpackers, so mountaineering pressure cookers are designed to operate at a lower differential pressure than stove-top units. This enables them to use thinner, and therefore lighter materials. Generally, the goal is to raise the cooking temperature enough to make cooking possible and to conserve fuel by reducing heat lost through boiling. Lightweight pressure cookers as small as weighing are available for mountain climbers. Sherpas often use pressure cookers in base camp.
Health benefits
Some food toxins can be reduced by pressure cooking. A Korean study of aflatoxins in rice (associated with Aspergillus fungus) showed that pressure cooking was capable of reducing aflatoxin concentrations to 32% of the amount in the uncooked rice, compared to 77% from ordinary cooking.
Design
Pressure cookers employ one or more regulators to control the pressure/temperature. All types have a calibrated pressure relief valve, as well as one or more emergency valves.
With the simplest types, once the desired pressure is reached, the valve opens, and steam escapes cooling the vessel and limiting the temperature. More advanced stovetop models have pressure indicators that permit the user to adjust the heat to prevent the steam from escaping. Third generation types automatically measure the state of the vessel and control the power so as to not release steam in operation.
Capacity
Pressure cookers are available in different capacities for cooking larger or smaller amounts, with 6 litres' capacity being common. The maximum capacity of food is less than the advertised capacity because pressure cookers can only be filled up to 2/3 full, depending on ingredients and liquid (see Safety features section).
Pan
Metal pan body
Pan handles, usually one each on opposite ends, for carrying the cooker with both hands
Because of the forces that pressure cookers must withstand, they are usually heavier than conventional pots of similar size. The increased weight of conventional pressure cookers makes them unsuitable for applications in which saving weight is a priority, such as camping. Nonetheless, small, lightweight pressure cookers are available for mountain climbers (see High altitudes).
Lid
Lids usually have a number of features:
Lid handle, usually with a locking device button or slider that "clicks" shut and prevents removal while cooking
Gasket (also known as a "sealing ring") that seals the cooker airtight
Steam vent with a pressure regulator on top (either a weight or spring device) that maintains the pressure level in the pan
Pressure indicator pin, for showing the presence or absence of any pressure, however slight
Safety devices on the lid (typically over-pressure and/or over-temperature pressure release valves)
Gasket
A gasket or sealing ring, made from either rubber or silicone, forms a gas-tight seal that does not allow air or steam to escape between the lid and pan. Normally, the only way steam can escape is through a regulator on the lid while the cooker is pressurized. If the regulator becomes blocked, a safety valve provides a backup escape route for steam.
To seal the gasket there are several main methods used. Each determines the design of the pressure cooker:
The twist-on design has slots on the lid engaging with flanges on the body, similar to a lid on a glass jar, that works by placing the lid on the pot and twisting it about 30° to lock it in place. A common modern design, it has easily implemented locking features that prevent the removal of the lid while under pressure.
The center screw design has a bar that is slotted in place over the lid and a screw tightened downward to hold the lid on. Though an older design, it is still produced due to its ease of construction and simplicity.
The bolt-down design has flanges on both its lid and its body for bolts to be passed through, and usually uses wingnuts that hinge on the body and so are never fully removed from the cooker; this sealing design is typically used for larger units such as canning retorts and autoclaves. It is very simple to produce, and it can seal with simple and inexpensive gaskets.
The internally fitted lid design employs an oval lid that is placed inside and presses outward; the user inserts the lid at an angle, then turns the lid to align it with the pot opening on top because the lid is larger than the opening. A spring arrangement holds the lid in place until the pressure forms and holds the lid tightly against the body, preventing removal until the pressure is released.
Gaskets (sealing rings) require special care when cleaning (e.g., not washed with kitchen knives), unlike a standard lid for a saucepan. Food debris, fats, and oils must be cleaned from the gasket after every use. Gasket/sealing rings need replacing with a new one about once a year (or sooner if it is damaged e.g. a small split). A very dry gasket can make it difficult or impossible to close the lid. Smearing the gasket sparingly with vegetable oil alleviates this problem (using too much vegetable oil can make the gasket swell and prevent it sealing properly). A gasket that has lost its flexibility makes bringing the cooker up to pressure difficult as steam can escape before sufficient pressure is generated to provide an adequate seal; this is usually a sign that the gasket needs replacing with a new one. Oiling the gasket with vegetable oil may alleviate the problem temporarily, but a new gasket is often required.
Pressure cooker manufacturers sell replacement gaskets and recommend their replacement at regular intervals e.g. annually.
If the pressure cooker has not been used for a long time, the gasket and other rubber or silicone parts will dry out and will likely need replacing.
Safety features
Early pressure cookers equipped with only a primary safety valve risked explosion from food blocking the release valve. On modern pressure cookers, food residues blocking the steam vent or the liquid boiling dry will trigger additional safety devices. Modern pressure cookers sold from reputable manufacturers have sufficient safety features to prevent the pressure cooker itself from exploding. When excess pressure is released by a safety mechanism, debris of food being cooked may also be ejected with the steam, which is loud and forceful. This can be avoided if the pressure cooker is regularly cleaned and maintained in accordance with the manufacturer's instructions and never overfilled with food and/or liquid.
Modern pressure cookers typically have two or three redundant safety valves and additional safety features, such as an interlock lid that prevents the user from opening the lid when the internal pressure exceeds atmospheric pressure, preventing accidents from a sudden release of hot liquid, steam and food. If safety mechanisms are not correctly in place, the cooker will not pressurize the contents. Pressure cookers should be operated only after reading the instruction manual, to ensure correct usage. Pressure cooker failure is dangerous: a large quantity of scalding steam and water will be forcefully ejected and if the lid separates it may be propelled with considerable force. Some cookers with an internally fitted lid may be particularly dangerous upon failure as the lid fits tighter with increasing pressure, preventing the lid from deforming and venting around the edges. Due to these dangers pressure cookers are generally over-engineered in a safety regard and some countries even have regulations to prevent the sale of non-compliant cookers.
For first generation pressure cookers with a weighted valve or "jiggler", the primary safety valve or regulator is usually a weighted stopper, commonly called "the rocker" or "vent weight". This weighted stopper is lifted by the steam pressure, allowing excess pressure to be released. There is a backup pressure release mechanism that releases pressure quickly if the primary pressure release mechanism fails (e.g., food jams the steam discharge path). One such method is a hole in the lid that is blocked by a low melting point alloy plug and another is a rubber grommet with a metal insert at the center. At a sufficiently high pressure, the grommet will distort and the insert will blow out of its mounting hole to release pressure. If the pressure continues to increase, the grommet itself will blow out to release pressure. These safety devices usually require replacement when activated by excess pressure. Newer pressure cookers may have a self-resettable spring device, fixed onto the lid, that releases excess pressure.
On second generation pressure cookers, a common safety feature is the gasket, which expands to release excess pressure downward between the lid and the pot. This release of excess pressure is forceful and sufficient to extinguish the flame of a gas stove.
Pressure cookers sold in the European Union (EU) must comply with the Pressure Equipment Directive.
Maximum fill levels
The recommended maximum fill levels of food/liquid avoids blockage of the steam valve or developing excess pressure: two-thirds full with solid food, half full for liquids and foods that foam and froth (e.g., rice, pasta; adding a tablespoon of cooking oil minimizes foaming), and no more than one-third full for pulses (e.g., lentils).
Accessories
Steamer basket
Trivet for keeping the steamer basket above liquid
Metal divider, for separating different foods in the steamer basket e.g. vegetables
Inner pot, for pot-in-pot pressure steaming
Materials
Pressure cookers are typically made of aluminum (aluminium) or stainless steel. Aluminum pressure cookers may be stamped, polished, or anodized, but all are unsuitable for the dishwasher. They are cheaper, but the aluminum is reactive to acidic foods, whose flavors are changed in the reactions, and are less durable than stainless steel pressure cookers. Some aluminum pressure cookers from Afghanistan are known to be contaminated with lead and imported pots were responsible for the lead poisoning of Afghani refugees in Washington state in 2019.
Higher-quality stainless steel pressure cookers are made with heavy, three-layer, or copper-clad bottoms (heat spreader) for uniform heating because stainless steel has lower thermal conductivity. Most modern stainless steel cookers are dishwasher safe, although some manufacturers may recommend washing by hand. Some pressure cookers have a non-stick interior.
Operation
Liquid
Pressure cooking always requires a water-based liquid to generate the steam to raise the pressure within the cooker. Pressure cooking cannot be used for cooking methods that produce little steam such as roasting, pan frying, or deep frying. A minimum quantity of liquid is required to create and maintain pressure, as indicated in the manufacturer's instruction manual. For venting cookers more liquid is required for longer cooking times. This is not desirable for food requiring much less liquid, but recipes and books for pressure cookers take this into account.
Assembling
Food is placed inside the pressure cooker with a small amount of water or other liquid such as stock. Food is either cooked in the liquid or above the liquid for steaming; the latter method prevents the transfer of flavors from the liquid.
Sauces which contain starch thickeners can tend to burn onto the interior base of the pressure cooker which may prevent the cooker from reaching operating pressure. Because of this issue, sauces may require thickening or reduction after pressure cooking.
With pot in pot pressure cooking, some or all of the food is placed in an elevated pot on a trivet above water or another food item which generates the steam. This permits the cooking of multiple foods separately, and allows for minimal water mixed with the food, and thicker sauces, which would otherwise scorch onto the bottom of the pan.
Bringing to pressure
The lid is closed, the pressure setting is chosen and the pressure cooker is heated to boil the liquid. The cooker fills with steam and vents air. As the internal temperature rises, the pressure rises until it reaches the desired gauge pressure.
It usually takes several minutes for the pressure cooker to reach the selected pressure level. It can take 10 minutes or longer depending on the quantity of food, the temperature of the food (cold or frozen food delays pressurization), the amount of liquid, the power of the heat source, and the size of the pressure cooker. There is typically a pop-up indicator that shows that the cooker has pressure inside, but it does not reliably signal that the cooker has reached the selected pressure. The pop-up indicator shows the state of the interlock which prevents the lid from being opened while there is any internal pressure. Manufacturers may use their own terminology for this, such as calling it a "locking indicator."
Timing the recipe begins when the selected pressure/pressure is reached. Once the cooker reaches full pressure, the heat is lowered to maintain the pressure. With pressure cookers accurate timing is essential using an audible timer.
With first generation designs, the pressure regulator weight begins levitating above its nozzle, allowing excess steam to escape. In second generation pressure cookers, either a relief valve subsequently opens, releasing steam to prevent the pressure from rising any further or a rod rises with markers to indicate the pressure level, without constantly venting steam. At this stage, the heat source is reduced to the lowest possible heat that still maintains pressure, as extra heat wastes energy and increases liquid loss. In third generation pressure cookers, the device will detect the vessel has reached the required cooking temperature/pressure and will maintain it for the programmed time, generally without further loss of steam.
Recipes for foods using raising agents such as steamed puddings call for gentle pre-steaming, without pressure, in order to activate the raising agents prior to cooking and achieve a light, fluffy texture.
Food containers
Small containers such as plastic pudding containers can be used in a pressure cooker, if the containers (and any covering used) can withstand temperatures of and are not placed directly on the interior base. The containers can be used for cooking foods that are prone to burning on the base of the pressure cooker. A lid for the container may be used if the lid allows some steam to come into contact with the food and the lid is securely fitted; an example is foil or greaseproof paper, pleated in the center and tied securely with string. Containers that are cracked or have otherwise sustained damage are not suitable. Cooking time is longer when using covered containers because the food is not in direct contact with the steam. Since non-metal containers are poorer heat conductors, the type of container material stated in the recipe cannot be substituted without affecting the outcome. For example, if the recipe time is calculated using a stainless steel container and a plastic container is used instead, the recipe will be undercooked, unless the cooking time is increased. Containers with thicker sides, e.g., oven-proof glass or ceramic containers, which are slower to conduct heat, will add about 10 minutes to the cooking time. Liquid can be added inside the container when pressure cooking foods such as rice, which need to absorb liquid in order to cook properly.
Pre-frying ingredients
The flavor of some foods, such as meat and onions, can be improved by gently cooking with a little pre-heated cooking oil, butter or other fat in the open pressure cooker over medium heat for stove-top models (unless the manufacturer advises against this) before pressure cooking, while avoiding overheating the empty pressure cooker not heating the empty cooker with the lid and gasket in place to avoid damage. Electric pressure cookers usually have a "saute" or "brown" option for frying ingredients. The pressure cooker needs to cool briefly before adding liquid; otherwise some of the liquid will evaporate instantly, possibly leaving insufficient liquid for the entire pressure cooking time; if deglazing the pan, more liquid may need to be added.
Pressure release methods
After cooking, there are three ways of releasing the pressure, either quickly or slowly, before the lid can be opened. Recipes for pressure cookers state which release method is required at the end of the cooking time for proper results. Failure to follow the recommendation may result in food that is under-cooked or over-cooked.
To avoid opening the pressure cooker too often while cooking different vegetables with varying cooking times, the vegetables that take longer to cook can be cut into smaller pieces and vegetables that cook faster can be cut into larger pieces.
To inspect the food, the pressure cooker needs to be opened, which halts the cooking process. With a conventional saucepan, this can be done in a matter of seconds by visually inspecting the food.
Manual, normal, regular, or automatic release
This method is sometimes called a quick release, not to be confused with the cold water release (mentioned below). It involves the quick release of vapor by gradually lifting (or removing) the valve, pushing a button, or turning a dial. It is most suitable to interrupt cooking to add food that cooks faster than what is already in the cooker. For example, since meat takes longer to cook than vegetables, it is necessary to add vegetables to stew later so that it will cook only for the last few minutes. Releasing the steam with care avoids the risk of being scalded by the rapid release of hot steam. This release method is not suitable for foods that foam and froth while cooking; the hot contents might spray outwards due to the pressure released from the steam vent. Pressure cookers should be operated with caution when releasing vapour through the valve, especially while cooking foamy foods and liquids (lentils, beans, grains, milk, gravy, etc.) This release method takes about two minutes to release the pressure before the lid can be opened.
Natural release
The natural release method allows the pressure to drop slowly. This is achieved by removing the pressure cooker from the heat source and allowing the pressure to lower without action. It takes approximately 10 to 15 minutes (possibly longer) for the pressure to disappear before the lid can be opened. On many pressure cookers, a coloured indicator pin will drop when the pressure has gone. This natural release method is recommended for foods that foam and froth during cooking, such as rice, legumes, or recipes with raising agents such as steamed puddings. The texture and tenderness of meat cooked in a pressure cooker can be improved by using the natural release method. The natural release method finishes cooking foods or recipes that have longer cooking times because the inside of the pressure cooker stays hot. This method is not recommended for foods that require very short cooking times, otherwise the food overcooks.
Cold water quick release
This method is the fastest way of releasing pressure with portable pressure cookers, but can be dangerous if performed incorrectly. Hence it is safer to release pressure by using the other methods. The manufacturer's instruction book may advise against the cold water release or require it to be performed differently.
The cold water release method involves using slow running cold tap water, over the edge of the pressure cooker lid, being careful to avoid the steam vent or any other valves or outlets, and never immersing the pressure cooker under water, otherwise steam can be ejected from under the lid, which could cause scalding injury to the user; also the pressure cooker lid can be permanently damaged by an internal vacuum if water gets sucked into the pressure cooker, since the incoming water blocks the inrush of air.
The cold water release is most suitable for foods with short cooking times. It takes about 20 seconds for the cooker to cool down enough to lower the pressure so that it can be safely opened. This method is not suitable for electric pressure cookers, as they are not immersible. This type of pressure cooker cannot be opened with a cold water quick-release method.
The cold water release method is not recommended when cooking pulses e.g. red kidney beans, as the sudden release of pressure can cause the bean to burst its skin.
Pressure settings
Most pressure cookers have a cooking (operating) pressure setting between 0.8–1 bar (11.6–15 psi) (gauge) so the pressure cooker operates at 1.8 to 2.0 bar (absolute). The standard cooking pressure of 15 psi gauge was determined by the United States Department of Agriculture in 1917. At this pressure, water boils at (described in vapour pressure of water article).
The higher temperature causes food to cook faster; cooking times can typically be reduced to one-third of the time for conventional cooking methods. The actual cooking time also depends on the pressure release method used after timing (see Pressure release methods for details) and the thickness and density of the food, since thicker (and denser) foods take longer to cook. Meat joints and some other foods like sponge puddings and Christmas puddings are typically timed according to their weight. Frozen foods need extra cooking time to allow for thawing.
When pressure cooking at 1 bar/15 psi (gauge), approximate cooking times are one minute for shredded cabbage, seven minutes for boiled potatoes (if cut small, not diced) and three minutes for fresh green beans. If the pressure is released naturally after timing (see Pressure release methods for details), cooking times are even shorter. Food cooks more quickly when cut into smaller pieces.
Some recipes may require cooking at lower than 1 bar/15 psi (gauge) e.g. fresh vegetables, as these can easily overcook. Many pressure cookers have 2 or more selectable pressure settings or weights.
Some pressure cookers have a lower or higher maximum pressure than 1 bar/15 psi (gauge) or can be adjusted to different pressures for some recipes; cooking times will increase or decrease accordingly. This is typically done by having different regulator weights or different pressure or temperature settings. Some pressure cookers operate at lower pressures than others. If the recipe is devised for a higher pressure and the pressure cooker does not reach that pressure, the cooking time can be increased to compensate.
Efficiency
Pressure cookers are considerably more expensive than conventional saucepans of the same size.
The minimum quantity of water or liquid that keeps pressure cooker filled with steam is sufficient, so pressure cookers can use much less liquid than the amount required for conventional cooking. When less water or liquid is heated, the food reaches its cooking temperature faster and less energy is required than that of boiling, steaming, or oven cooking. It is also not necessary to immerse food in water. Additionally, with non venting pressure cookers, steam isn't continually escaping, thus evaporation losses are non existent once it has reached pressure. Overall, energy used by third generation pressure cookers can be as much as 70% lower than conventional pan cooking.
Effect on food
Pressure cooking requires much less water than conventional boiling, so food can be ready sooner.
Because of this, vitamins and minerals are not leached (dissolved) away by water, as they would be if food were boiled in large amounts of water. Due to the shorter cooking time, vitamins are preserved relatively well during pressure cooking.
Several foods can be cooked together in the pressure cooker, either for the same amount of time or added later for different times. Manufacturers provide steamer baskets to allow more foods to be cooked together inside the pressure cooker.
Not only is this steam energy transmitted quickly to food, it is also transmitted rapidly to any micro-organisms that are present, easily killing even the deadliest types that are able to survive at the boiling point. Because of this enhanced germ killing ability, a pressure cooker can be used as an effective sanitizer for jam pots, glass baby bottles, or for water while camping.
Foods unsuitable for pressure cooking
Some foods are not recommended for pressure cooking. Foods such as noodles, pasta, cranberries, cereals and oatmeal can expand too much, froth and sputter, potentially blocking the steam vent and creating an unsafe condition.
Use as weapons
The appliance has been adapted as a crude type of bomb, which has been used in terrorist attacks.
2006 Mumbai train bombings
2010 Stockholm bombings (failed to explode)
2010 Times Square car bombing attempt (failed to explode)
2013 Boston Marathon bombing
2016 New York and New Jersey bombings
2017 Manchester Arena bombing
Pressure cookers are allowed on airplanes but may be better in your checked luggage.
Related devices
An autoclave () is a type of pressure cooker used by laboratories and hospitals to sterilize equipment. A stovetop autoclave is essentially a higher-pressure cooker with a gauge, used as an autoclave in poorer areas.
Pressure canners are large pressure cookers which have the capacity to hold jars used in home canning. Pressure canners are specifically designed for canning, whereas ordinary pressure cookers are not recommended for canning due to the risk of botulism poisoning. Pressure canners hold heat () and pressure for much longer than ordinary pressure cookers; these factors are a critical part of the total processing time required to destroy harmful microbes such as bacterial spores.
Pressure fryers are used for deep fat frying under pressure, because ordinary pressure cookers are not suitable for pressure frying.
An air fryer pressure cooker (not to be confused with a pressure fryer) is a recent combination of a pressure cooker and an air fryer, with two separate lids, one for pressure cooking and one for air frying. The air frying lid has a convection fan inside that allows it to air fry foods, similar to an air fryer oven. This innovation was popularized by the Ninja Foodi Pressure Cooker, marketed as the first pressure cooker that can crisp and air fry.
A pressure oven is a recent combination of an oven and pressure cooker, usually as a countertop convection oven. Pressure ovens operate at low pressures, , compared to other pressure cookers. Their main function is as an enhanced oven or broiler for meat and poultry, avoiding drying. As such, they often include a rotisserie. Although having insufficient pressure for most conventional pressure cooking functions, they do also have non-pressure oven modes.
See also
List of cooking appliances
Explanatory notes
References
External links
Cooking appliances
Cooking techniques
Cooking vessels
Culinary terminology
French inventions
Pressure | Pressure cooker | Physics | 7,456 |
14,119,867 | https://en.wikipedia.org/wiki/P2RX7 | P2X purinoceptor 7 is a protein that in humans is encoded by the P2RX7 gene.
The product of this gene belongs to the family of purinoceptors for ATP. Multiple alternatively spliced variants which would encode different isoforms have been identified although some fit nonsense-mediated decay criteria.
The receptor is found in the central and peripheral nervous systems, in microglia, in macrophages, in uterine endometrium, and in the retina. The P2X7 receptor also serves as a pattern recognition receptor for extracellular ATP-mediated apoptotic cell death, regulation of receptor trafficking, mast cell degranulation, and inflammation. Regarding inflammation, P2X7 receptor induces the NLRP3 inflammasome in myeloid cells and leads to interleukin-1beta release.
Structure and kinetics
The P2X7 subunits can form homomeric receptors only with a typical P2X receptor structure.
The P2X7 receptor is a ligand-gated cation channel that opens in response to ATP binding and leads to cell depolarization. The P2X7 receptor requires higher levels of ATP than other P2X receptors; however, the response can be potentiated by reducing the concentration of divalent cations such as calcium or magnesium. Continued binding leads to increased permeability to N-methyl-D-glucamine (NMDG+). P2X7 receptors do not become desensitized readily and continued signaling leads to the aforementioned increased permeability and an increase in current amplitude.
Pharmacology
Agonists
P2X7 receptors respond to BzATP more readily than ATP.
ADP and AMP are weak agonists of P2X7 receptors, but a brief exposure to ATP can increase their effectiveness.
Glutathione has been proposed to act as a P2X7 receptor agonist when present at milimolar levels, inducing calcium transients and GABA release from retinal cells.
Antagonists
The P2X7 receptor current can be blocked by zinc, calcium, magnesium, and copper.
P2X7 receptors are sensitive to pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) and relatively insensitive to suramin, but the suramin analog, NF279, is much more effective.
Oxidized ATP (OxATP) and Brilliant Blue G has also been used for blocking P2X7 in inflammation.
Other blockers include the large organic cations calmidazolium (a calmodulin antagonist) and KN-62 (a CaM kinase II antagonist).
JNJ-54175446 and JNJ-55308942 are selective antagonists
Receptor trafficking
In microglia, P2X7 receptors are found mostly on the cell surface. Conserved cysteine residues located in the carboxyl terminus seem to be important for receptor trafficking to the cell membrane. These receptors are upregulated in response to peripheral nerve injury.
In melanocytic cells P2X7 gene expression may be regulated by MITF.
Recruitment of pannexin
Activation of the P2X7 receptor by ATP leads to recruitment of pannexin pores which allow small molecules such as ATP to leak out of cells. This allows further activation of purinergic receptors and physiological responses such a spreading cytoplasmic waves of calcium. Moreover, this could be responsible for ATP-dependent lysis of macrophages through the formation of membrane pores permeable to larger molecules.
Clinical significance
Inflammation
On T cells activation of P2X7 receptors can activate the T cells or cause T cell differentiation, can affect T cell migration or (at high extracellular levels of ATP and/or NAD+) can induce cell death. The CD38 enzyme on B lymphocytes and macrophages reduces extracellular NAD+, promoting the survival of T cells.
Neuropathic pain
Microglial P2X7 receptors are thought to be involved in neuropathic pain because blockade or deletion of P2X7 receptors results in decreased responses to pain, as demonstrated in vivo. Moreover, P2X7 receptor signaling increases the release of proinflammatory molecules such as IL-1β, IL-6, and TNF-α. In addition, P2X7 receptors have been linked to increases in proinflammatory cytokines such as CXCL2 and CCL3. P2X7 receptors are also linked to P2X4 receptors, which are also associated with neuropathic pain mediated by microglia.
Osteoporosis
Mutations in this gene have been associated to low lumbar spine bone mineral density and accelerated bone loss in post-menopausal women.
Diabetes
The ATP/P2X7R pathway may trigger T-cell attacks on the pancreas, rendering it unable to produce insulin. This autoimmune response may be an early mechanism by which the onset of diabetes is caused.
Research
Possible link to hepatic fibrosis
One study in mice showed that blockade of P2X7 receptors attenuates onset of liver fibrosis.
See also
Purinergic receptor
P2X receptor
References
Further reading
External links
Ion channels | P2RX7 | Chemistry | 1,117 |
2,629,937 | https://en.wikipedia.org/wiki/Feature%20connector | The feature connector was an internal connector found mostly in some older ISA, VESA Local Bus, and PCI graphics cards, but also on some early AGP ones. It was intended for use by devices that needed to exchange large amounts of data with the graphics card without hogging a computer system's CPU or data bus, such as TV tuner cards, video capture cards, MPEG video decoders (e.g. SGS Thomson MPEG Decoder), and first generation 3D graphic accelerator cards. Early examples include the IBM EGA video adapter.
Several standards existed for feature connectors, depending on the bus and graphics card type. Most of them were simply an 8, 16 or 32-bit wide internal connector, transferring data between the graphics card and another device, bypassing the system's CPU and memory completely.
Their speeds often far exceeded the speed of normal ISA or even early PCI buses, e.g. 40 MB/s for a standard ISA-based SVGA, up to 150 MB/s for a VESA-based or PCI-based one, while the standard 16 bit ISA bus ran at ~5.3 MB/s and the VESA bus at up to 160 MB/s bandwidth. The feature connector bandwidths were far beyond the capabilities of e.g. a 386, 486 and barely handled by an early Pentium.
Depending on the implementation, it could be uni or bi-directional, and carry analog color information as well as data. Unlike analog overlay devices however, a feature connector carried mainly data and essentially allowed an expansion card to access the graphics card Video RAM directly, although directing this data stream to the system's CPU and RAM was not always possible, limiting its usefulness mainly to display purposes.
Although its use rapidly declined after the introduction of the faster AGP internal bus, it was, at its time, the only feasible way to connect certain types of graphics-intensive devices to an average computing system without exceeding the available CPU power and memory bandwidth, and without the disadvantages and limitations of a purely analog overlay.
The idea of accessing a video card's memory directly resurfaced with the introduction of the Scan-Line Interleave (3dfx SLI) technology, although this technology is aimed at connecting two equally powered and complete graphic cards to produce a single, increased performance visual output, and not e.g. directly interfacing TV tuner cards.
PCMCIA card
A variant of that idea, born for PCMCIA Card, is named Zoomed video port.
References
External links
Definition of VESA Advanced feature connection at thefreedictionary.com
Definition of VGA feature connection at thefreedictionary.com
AMC, an ATI extension of the Feature Connector
Computer buses
Display technology
VESA | Feature connector | Engineering | 577 |
73,397,196 | https://en.wikipedia.org/wiki/X%20Herculis | X Herculis is a star about 400 light years from the Earth in the constellation Hercules. It is a semiregular variable star, ranging in brightness from magnitude 5.8 to 7.0 over a period of about 102 days. It is rarely visible to the naked-eye, but can be seen easily with a small telescope, or binoculars.
X Herculis was discovered to be a variable star by John Gore, in 1890. Variability was quickly confirmed by two other observers. Although it was known by a variety of names at the time of the discovery of its variability, the star was immediately given the variable star designation X Herculis. Subsequent studies found periods of , and days in the light curve.
X Herculis is an oxygen-rich AGB star, losing mass at a rate of per year via a stellar wind. In 1986 Benjamin Zuckerman et al. detected the J=2→1 line of carbon monoxide (CO) in the stellar wind. The shape of the CO line profile shows that the wind has two components, one of which leaves the vicinity of the star at a speed of km/sec, and another which has a speed of km/sec. The slow wind appears to arise from a disk surrounding, and possibly orbiting X Herculis. The faster wind appears to arise from a bipolar outflow. The stellar winds have produced a large circumstellar shell. Studies of such a shell using molecular spectroscopy can only probe the inner region of the shell, because as the stellar wind expands and becomes less dense, the molecules in the gas are dissociated by the interstellar radiation field. Luckily, the high galactic latitude (48°) of X Herculis allows the 21 cm line of atomic hydrogen (HI) to be observed without contamination from unrelated material in the galactic plane. Lynn Matthews et al. mapped the HI shell, and found it to be at least 0.8 light years across, with a comet-like tail produced by the motion of the star through the interstellar medium (ISM). The mass of HI in the shell is about , but the total mass of the shell may be significantly larger, because much of the hydrogen may be in molecular form.
Near-infrared radiation from X Herculis was detected in the first Two-Micron Sky Survey, published in 1969. The stellar winds from AGB stars contain dust and that dust was detected in the far-infrared by the IRAS satellite. The dust emission was resolved by IRAS, showing the same large shell that is seen in HI observations. X Herculis is moving through the ISM at a speed of 108 km/sec. Herschel Space Observatory images show a bow shock in the region where the stellar wind collides with the ISM, but they show no evidence of the bipolar flow seen in high resolution maps of the molecular line emission.
References
Hercules (constellation)
Herculis, X
144205
78574
Semiregular variable stars
M-type giants | X Herculis | Astronomy | 615 |
12,307,690 | https://en.wikipedia.org/wiki/Harry%20B.%20Gray | Harry Barkus Gray (born November 14, 1935) is the Arnold O. Beckman Professor of Chemistry at California Institute of Technology.
Career
Gray received his B.S. in chemistry from Western Kentucky University in 1957. He began his work in inorganic chemistry at Northwestern University, where he earned his Ph.D. in 1960 working under Fred Basolo and Ralph Pearson. He was initiated into the Upsilon chapter of Alpha Chi Sigma at Northwestern University in 1958. After that, he spent a year (1960–61) as an NSF Postdoctoral Fellow at the University of Copenhagen, where, along with Walter A. Manch, he collaborated with Carl J. Ballhausen on studies of the electronic structures of metal complexes.
After completing his NSF Postdoctoral Fellow at the University of Copenhagen, he relocated to New York City to take up a faculty appointment at Columbia University. He served as an assistant professor from 1961 to 1963 and as an associate professor from 1963 to 1965.
In 1966, he became the Arnold O. Beckman Professor of Chemistry at California Institute of Technology, and founding director of the Beckman Institute. He also served on the Physical Sciences jury for the Infosys Prize from 2010 to 2013.
Gray also trained future leaders of several major science research universities. Four of his doctoral students became presidents or chancellors of University of Rhode Island, Iowa State University, University of North Carolina at Chapel Hill, and Washington University in St. Louis.
Research
Gray's interdisciplinary research program addresses a wide range of fundamental problems in inorganic chemistry, biochemistry, and biophysics. Electron transfer (ET) chemistry is a unifying theme for much of this research.
Over the past twenty-five years the Gray group has been measuring the kinetics of long-range ET reactions in metalloproteins labeled with inorganic redox reagents. Early research by his lab members showed that details of the internal structures of the proteins dominate the ET rates. Current research is aimed at understanding how intermediate protein radicals accelerate long-range ET. In collaboration with Jay R. Winkler of the Beckman Institute at Caltech they have developed new techniques for measuring ET rates in crystals of Ru-, Os-, and Re-modified azurins, as well as crystals of Fe(III)-cytochrome c doped with Zn(II)-cytochrome c. This method of integrating photosensitizers into protein crystals has provided a powerful new tool for studying biochemical reaction dynamics. The Gray/Winkler group is also using ET chemistry to probe the dynamics of protein folding in cytochrome c.
Major publications
Awards and honors
His accolades include:
1970 ACS Award in Pure Chemistry
1979 Tolman Award
1986 National Medal of Science
1990 AIC Gold Medal
1992 Priestley Medal
2000 Harvey Prize
2000 Foreign Member of the Royal Society
2004 The Benjamin Franklin Medal in Chemistry
2004 Wolf Prize in Chemistry
2009 Welch Award
2012 Inducted into the Alpha Chi Sigma Hall of Fame
2013 Othmer Gold Medal for outstanding contribution to chemistry and science.
Wolf Prize
He was awarded the Wolf Prize in Chemistry in 2004 for his pioneering work in bioinorganic chemistry, unraveling novel principles of structure and long-range electron transfer in proteins.
Gray has made generative contributions to the understanding of chemical bonding of metal complexes, mechanisms of inorganic reactions, spectroscopy and magneto-chemistry of inorganic compounds. His study of the first trigonal prismatic complexes is one such example. Harry Gray's most significant work lies at the interface between chemistry and biology. As a pioneer of the important and thriving field of bioinorganic chemistry, he has made many key contributions, the most important of which is the development of fundamental understanding of electron transfer in biological systems, at the atomic level.
References
External Links
Interview with Harry Barkus Gray, 2017. Caltech Oral Histories
1935 births
Living people
People from Warren County, Kentucky
21st-century American chemists
American inorganic chemists
Foreign members of the Royal Society
Northwestern University alumni
Columbia University faculty
California Institute of Technology faculty
Wolf Prize in Chemistry laureates
National Medal of Science laureates
Western Kentucky University alumni
Members of the United States National Academy of Sciences
Benjamin Franklin Medal (Franklin Institute) laureates | Harry B. Gray | Chemistry | 840 |
14,455,119 | https://en.wikipedia.org/wiki/GPR179 | Probable G-protein coupled receptor 179 is a protein that in humans is encoded by the GPR179 gene.
Clinical relevance
Mutations in this gene have been associated to cases of congenital stationary Night Blindness.
References
Further reading
G protein-coupled receptors | GPR179 | Chemistry | 50 |
14,817,974 | https://en.wikipedia.org/wiki/KCNJ15 | Potassium inwardly-rectifying channel, subfamily J, member 15, also known as KCNJ15 is a human gene, which encodes the Kir4.2 protein.
Function
Potassium channels are present in most mammalian cells, where they participate in a wide range of physiologic responses. Kir4.2 is an integral membrane protein and inward-rectifier type potassium channel. Kir4.2 has a greater tendency to allow potassium to flow into a cell rather than out of a cell. Three transcript variants encoding the same protein have been found for this gene.
The existing literature describing KCNJ15 and Kir4.2 is sparse. In spite of some initial channel nomenclature confusion, in which the gene was referred to as Kir1.3 the channel was first cloned from human kidney by Shuck and coworkers in 1997. Shortly thereafter it was shown that mutation of an extracellular lysine residue resulted in 6-fold increase in K+ current. Two years later, in 1999, voltage clamp measurements in xenopus oocytes found that intracellular acidification decreased the potassium current of Kir4.2. Also activation of protein kinase C decreased the current although in a non-reversible fashion. Furthermore, it was found that coexpression with related potassium channel Kir5.1, changed these results somewhat, which the authors concluded was likely to be a result of heterodimerization. Further voltage clamp investigations found the exact pH sensitivity (pKa = 7.1), open probability (high) and conductance of ~25 pS. In 2007 the channel was found to interact with the Calcium-sensing receptor in human kidney, using a yeast-two-hybrid system. This co-localization was verified at the protein level using both immunofluorescence techniques and coimmunoprecipitation of Kir4.2 and the Calcium-sensing receptor. Also a mutational study of Kir4.2 has demonstrated that removal of a c-terminal tyrosine increased the K+ current more than 10-fold. Because the channel has a very high open probability, the authors of this last article conclude that this increase is mediated by increased trafficking of the protein to the membrane and not increased single-channel conductance. This same line of reasoning is applicable to the initial work of Derst and coworkers.
Interactions
KCNJ15 has been shown to interact with Interleukin 16.
See also
Inward-rectifier potassium ion channel
References
Ion channels | KCNJ15 | Chemistry | 526 |
9,214,162 | https://en.wikipedia.org/wiki/Turritopsis%20dohrnii | Turritopsis dohrnii, also known as the immortal jellyfish, is a species of small, biologically immortal jellyfish found worldwide in temperate to tropic waters. It is one of the few known cases of animals capable of reverting completely to a sexually immature, colonial stage after having reached sexual maturity as a solitary individual.
Like most other hydrozoans, T. dohrnii begin their lives as tiny, free-swimming larvae known as planulae. As a planula settles down, it gives rise to a colony of polyps that are attached to the sea floor. All the polyps and jellyfish arising from a single planula are genetically identical clones. The polyps form into an extensively branched form, which is not commonly seen in most jellyfish. Jellyfish, also known as medusae, then bud off these polyps and continue their life in a free-swimming form, eventually becoming sexually mature. When sexually mature, they have been known to prey on other jellyfish species at a rapid pace. If the T. dohrnii jellyfish is exposed to environmental stress, physical assault, or is sick or old, it can revert to the polyp stage, forming a new polyp colony. It does this through the cell development process of transdifferentiation, which alters the differentiated state of the cells and transforms them into new types of cells.
Theoretically, this process can go on indefinitely, effectively rendering the jellyfish biologically immortal, although in practice individuals can still die. In nature, most Turritopsis dohrnii are likely to succumb to predation or disease in the medusa stage without reverting to the polyp form.
The capability of biological immortality with no maximum lifespan makes T. dohrnii an important target of basic biological aging and pharmaceutical research.
Taxonomy
The species was formerly considered conspecific with T. nutricula before being reclassified as a separate species. It was named in 1883 in honour of Anton Dohrn, the founder of the Stazione Zoologica Anton Dohrn in Naples, Italy.
Until a 2006 study, it was thought that Turritopsis rubra and Turritopsis nutricula were the same species as Turritopsis dohrnii. It is not known whether or not T. rubra medusae can also transform back into polyps, however further research is still to be done.
Description
The medusa of Turritopsis dohrnii is bell-shaped, with a maximum diameter of about and is about as tall as it is wide. The mesoglea in the walls of the bell is uniformly thin, except for some thickening at the apex. The relatively large stomach is bright red and has a cruciform shape in cross section. Young specimens 1 mm in diameter have only eight tentacles evenly spaced out along the edge, whereas adult specimens have 80–90 tentacles. The medusa (jellyfish) is free-living in the plankton. Dense nerve net cells are also present in the epidermis in the cap. They form a large ring-like structure above the radial canal commonly presented in cnidarians.
Turritopsis dohrnii also has a bottom-living polyp form, or hydroid, which consists of stolons that run along the substrate and upright branches with feeding polyps that can produce medusa buds. These polyps develop over a few days into tiny 1 mm medusae, which are liberated and swim free from the parent hydroid colony.
Distribution and invasion
Turritopsis is believed to have originated in the Pacific, but has spread all over the world through trans-Arctic migrations, and has speciated into several populations that are easy to distinguish morphologically, but whose species distinctions have recently been verified by a study and comparison of mitochondrial ribosomal gene sequences. Turritopsis are found in temperate to tropical regions in all of the world's oceans. Turritopsis is believed to be spreading across the world through ballast water discharge. Unlike other species invasions which caused serious economic and ecological consequences, T. dohrnii's invasion around the world was unnoticed due to their tiny size and innocuity. "We are looking at a worldwide silent invasion", said Smithsonian Tropical Marine Institute scientist Maria Miglietta.
Life cycle
The eggs develop in gonads of female medusae, which are located in the walls of the manubrium (stomach). Mature eggs are presumably spawned and fertilized in the sea by sperm produced and released by male medusae, as is the case for most hydromedusae. However, the related species Turritopsis rubra seems to retain fertilized eggs until the planula stage. Fertilized eggs develop into planula larvae, which settle onto the sea floor (or even the rich marine communities that live on floating docks), and develop into polyp colonies (hydroids). The hydroids bud new jellyfishes, which are released at about one millimetre in size and then grow and feed in the plankton, becoming sexually mature after a few weeks (the exact duration depends on the ocean temperature; at it is 25 to 30 days and at it is 18 to 22 days). Medusae of T. dohrnii are able to survive between 14 °C and 25 °C.
Biological immortality
Most jellyfish species have a relatively fixed lifespan, which varies by species from hours to many months (long-lived mature jellyfish spawn every day or night; the time is also fairly fixed and species-specific). The medusa of Turritopsis dohrnii is the only form known to have the ability to return to a polyp state, by a specific transformation process that requires the presence of certain cell types (tissue from both the jellyfish bell surface and the circulatory canal system).
Experiments have revealed that all stages of the medusae, from newly released to fully mature individuals, can transform back into polyps under the conditions of starvation, sudden temperature change, reduction of salinity, and artificial damage of the bell with forceps or scissors. The transforming medusa is characterized first by deterioration of the bell, mesoglea, and tentacles. All immature medusa (with 12 tentacles at most) then turned into a cyst-like stage and then transformed into stolons and polyps. However, about 20%-40% of mature medusa went into the stolons and polyps stage without passing the cyst-like stage. Polyps were formed after 2 days since stolons had developed and fed on food. Polyps further multiply by growing additional stolons, branches, and then polyps to form colonial hydroids. In the experiment, they would eventually transform into stolons and polyps and begin their lives once again, even without environmental changes or injury.
This ability to reverse the biotic cycle (in response to adverse conditions) is unique in the animal kingdom. It allows the jellyfish to bypass death, rendering Turritopsis dohrnii potentially biologically immortal. The process has not been observed in their natural habitat, in part because the process is quite rapid and because field observations at the right moment are unlikely. Regardless, most individual medusae are likely to fall victim to the general hazards of life as mesoplankton, including being eaten by predators or succumbing to disease.
The species possesses unique mechanisms related to telomere maintenance, which play a significant role in its regenerative abilities. T. dohrnii maintains telomere length through specific cellular processes during its life cycle reversal, effectively resetting cellular aging.
The species' cell development method of transdifferentiation has inspired scientists to find a way to make stem cells using this process for renewing damaged or dead tissue in humans.
Ecology
Diet
Turritopsis dohrnii are a carnivorous species that commonly feed on zooplankton. Their diet mainly consists of plankton, fish eggs and small mollusks. T. dohrnii ingests food and excretes waste through the mouth. T. dohrnii hunts by using its tentacles as it drifts through the water. Its tentacles, which contain stinging cells called nematocysts, spread and sting its prey. The tentacles can then flex to direct its prey to the mouth. T. dohrnii, like other jellyfish, may use its bell to catch its prey. T. dohrnii's bell will expand, sucking in water, as it propels itself to swim. This expansion of the bell brings potential prey in closer reach of the tentacles.
Predation
Turritopsis dohrnii, like other jellyfish, are preyed on most commonly by other jellyfish. Other predators of T. dohrnii include sea anemones, tuna, sharks, swordfish, sea turtles, and penguins. Many species prey on T. dohrnii and other jellyfish due to their simple composition. They are only approximately 5% non-aqueous matter, and the remaining part is composed of water. They are composed of three layers. An outer layer (the epidermis), a middle layer (mesoglea; a thick, jelly-like substance), and an inner layer (gastrodermis).
Habitat
Turritopsis dohrnii was first discovered in the Mediterranean Sea, but has since been found worldwide. T. dohrnii is generally found living in temperate to tropical waters. They can be found in marinas or docks, on vessel hulls, and on the ocean floor. They typically live in a salinity range of polyhaline (18–30 PSU) and euhaline (30-40 PSU).
Genomic analysis
Genomic analyses such as sequence analysis on mRNA or mitochondria DNA have been employed to investigate its lifecycle. mRNA analysis of each life stage showed that a stage-specific gene in the medusae stage is expressed tenfold more than in other stages. This gene is relative to a Wnt signal that can induce a regeneration process upon injury.
Analysis of nucleotide sequence homologs and protein homologs identified Nemopsis bachei as the species' closest relative. None of the closely related species display biological immortality.
In 2022, a study reported the key molecular mechanisms of rejuvenation they found in a comparison of the newly presented genomes of this biologically immortal jellyfish and a similar but non-rejuvenating jellyfish, involving e.g. DNA replication and repair, and stem cell renewal.
Culturing
Keeping T. dohrnii in captivity is quite difficult. Currently, only one scientist, Shin Kubota from Kyoto University, has managed to sustain a group of these jellyfish for a prolonged period of time. The plankton must be inspected daily to ensure that they have properly digested the Artemia cysts they are being fed.
Kubota reported that during a two-year period, his colony rebirthed itself 11 times. Kubota regularly appears on Japanese television to talk about his immortal jellyfish and has recorded several songs about them, often singing them at the end of his conference presentations.
See also
Hydra – another kind of cnidarian that is claimed to be immortal
List of longest-living organisms
References
Further reading
.
.
External links
Cheating Death: The Immortal Life Cycle of Turritopsis
Telomerase activity is not related to life-history stage in the jellyfish Cassiopea sp.
Scientists are Close to Finding a Way to be Immortal
Oceaniidae
Immortality
Negligibly senescent organisms
Animals described in 1883 | Turritopsis dohrnii | Biology | 2,418 |
38,451,608 | https://en.wikipedia.org/wiki/Inforg | An inforg is an informationally embodied organism, entity made up of information, that exists in the infosphere. These informationally embodied organisms are also called natural agents.
Description
Inforgs was used by Luciano Floridi to describe what makes up an infosphere. The usage of the word describes organisms that are made up of information rather than "standalone and unique entities". This description of inforgs allows them to exist in the infosphere as natural agents alongside artificial agents. Inforgs can be part of a hybrid agent that is, for example, a family with digital devices such as digital cameras, cell phones, tablets, and laptops.
Norbert Wiener describes organisms as entities defined by patterns of persisting Shannon information. Shannon information, named after Claude Shannon, places information in the physical realm allowing it to be manipulated by the laws of nature and science. Thus, inforgs are composed of matter, energy, and Shannon information. An experiment that supports inforgs and the component of Shannon information is the use of DNA as a medium for data storage. Encoding DNA, which is considered to be the building blocks of organisms, to hold binary information reinforces the idea that living organisms are "persisting patterns of Shannon information encoded within an ever-changing flux of matter-energy".
The Shannon information that is found within an inforg also contains the identity of said organism. For example, A human being's identity is not matter or energy but rather encoded by patterns of Shannon information within his/her body. While a person's body may change over time, his/her identity persists through time. The manipulation of Shannon information in an inforg is under what is called the metaphysical realm.
See also
Luciano Floridi
Infosphere
Information
Shannon information
Metaphysics
Information Revolution
Information Age
Digital Transformation
References
Information society | Inforg | Technology | 370 |
22,449,768 | https://en.wikipedia.org/wiki/Coprinellus%20ellisii | Coprinellus ellisii is a species of mushroom in the family Psathyrellaceae. Found in Europe, it was first described as Coprinus ellisii by Peter D. Orton in 1960, and later transferred to the genus Coprinellus in 2001. The specific epithet ellisii honours E.A. Ellis, who, according to Orton, was "the Norfolk naturalist and mycologist who collected this and who brought me many puzzling and apparently undescribed agarics."
References
ellisii
Fungi described in 1960
Fungi of Europe
Fungus species | Coprinellus ellisii | Biology | 115 |
14,357,725 | https://en.wikipedia.org/wiki/In%20vivo%20magnetic%20resonance%20spectroscopy | In vivo magnetic resonance spectroscopy (MRS) is a specialized technique associated with magnetic resonance imaging (MRI).
Magnetic resonance spectroscopy (MRS), also known as nuclear magnetic resonance (NMR) spectroscopy, is a non-invasive, ionizing-radiation-free analytical technique that has been used to study metabolic changes in brain tumors, strokes, seizure disorders, Alzheimer's disease, depression, and other diseases affecting the brain. It has also been used to study the metabolism of other organs such as muscles. In the case of muscles, NMR is used to measure the intramyocellular lipids content (IMCL).
Magnetic resonance spectroscopy is an analytical technique that can be used to complement the more common magnetic resonance imaging (MRI) in the characterization of tissue. Both techniques typically acquire signal from hydrogen protons (other endogenous nuclei such as those of Carbon, Nitrogen, and Phosphorus are also used), but MRI acquires signal primarily from protons which reside within water and fat, which are approximately a thousand times more abundant than the molecules detected with MRS. As a result, MRI often uses the larger available signal to produce very clean 2D images, whereas MRS very frequently only acquires signal from a single localized region, referred to as a "voxel". MRS can be used to determine the relative concentrations and physical properties of a variety of biochemicals frequently referred to as "metabolites" due to their role in metabolism.
Data Acquisition
Acquiring an MRS scan is very similar to that of MRI with a few additional steps preceding data acquisition. These steps include:
Shimming the magnetic field: this step is taken to correct for the inhomogeneity of the magnetic field by tuning different pulses in the x, y, and z directions. This step is usually automated but can be performed manually.
Suppressing the water signal: because water molecules contain hydrogen, and the relative concentration of water to metabolite is about 10,000:1, the water signal is often suppressed or the metabolite peaks will not be discernible in the spectra. This is achieved by adding water suppression pulses. Recent advances allow proton MRS without water suppression.
Choosing a spectroscopic technique: careful planning of measurements is important in the context of a specific experiment.
Single Voxel Spectroscopy (SVS): has a minimum spatial resolution of approximately 1 cm3, and has the cleanest spectrum free from unwanted artifacts due to the small acquired volume leading to easy shim and less unwanted signals from outside the voxel.
Magnetic Resonance Spectroscopic Imaging (MRSI): a 2-dimensional (or 3-dimensional) MRS technique which uses two/three phase-encoding directions to create a two/three-dimensional map of spectra. The drawbacks of this technique is that having two/three phase encoding directions requires lengthy scan time, and the larger volume of acquisition is more likely to introduce artefacts due to poorer shimming, unsuppressed water, as well as the inherent sinc point-spread-function due to the finite sampling of k-space which results in the signal from one voxel bleeding into all others.
Data Quantification
During data acquisition, the scan acquires raw data in the form of spectra. This raw data must be quantified to achieve a meaningful understanding of the spectrum. This quantification is achieved via linear combination. Linear combination requires knowledge of the underlying spectral shapes, referred to as basis sets. Basis sets are acquired either via numerical simulation or experimentally measured in phantoms. There are numerous packages available to numerically simulate basis sets, including MARSS, FID-A, among others such as GAMMA, VESPA and Spinach. With the basis sets, the raw data can now be quantified as measured concentrations of different chemical species. Software is used to complete this. LCModel, a commercial software, has been for most of the field's history the standard software quantification package. However, now there are many freeware packages for quantification: AMARES, AQSES, Gannet, INSPECTOR, jMRUI, TARQUIN, and more.
Before linear combination, peak extraction used to be used for data quantification. However, this is no longer popular nor recommended. Peak extraction is a technique which integrates the area underneath a signal. Despite its seemingly straightforwardness, there are several confounds with this technique. Chiefly, the individual Lorentzian shapes employed do not scale up to match the complexity of the spectral shapes of J-coupled metabolites and is too simple to discern between overlapping peaks.
Pulse Sequences
Similar to MRI, MRS uses pulse sequences to acquire signal from several different molecules to generate a spectra instead of an image. In MRS, STEAM (Stimulated Echo Acquisition Method) and PRESS (Point Resolved Spectroscopy) are the two primary pulse sequence techniques used. In terms of advantages, STEAM is best for imaging metabolites with shorter T2 and has lower SAR, while PRESS has higher SNR than STEAM. STEAM and PRESS are most widely used due to their implementation on the major vendors of MR scanners. Beyond STEAM and PRES there are sequences which utilize adiabatic pulses. Adiabatic pulses produce uniform flip angles even when there is extreme B1 inhomogeneity. Thus, these sequences allow us to achieve excitation that achieves the sought-for B1 insensitivity and off-resonance in the RF coil and sampled object. Specifically, adiabatic pulses solve the problem of signal dropout that comes from the different B1 flux patterns that result from the surface transmit coils used and the usage of normal pulses. Adiabatic pulses are also useful for constraints on RF peak power for excitation and lowering tissue heating. Additionally, adiabatic pulses have substantially higher bandwidth, which reduces chemical shift displacement artefact, which is particularly important at high field strengths and when a large range of frequencies are desired to be measured (i.e., measuring both the signals upfield and downfield of water in proton MRS).
Spatial Localization Sequences
In PRESS, the two chief drawbacks are lengthy echo time (TE) and chemical shift displacement (CSD) artifacts. Lengthy echo time arises from the fact that PRESS uses two 180° pulses, unlike STEAM which uses exclusively 90° pulses. The duration of 180° pulses are generally longer than 90° pulses because it takes more energy to flip a net magnetization vector completely as opposed to only 90°. Chemical shift displacement artifacts arises partly because of less optimal slice selection profiles. Multiple 180° pulses does not allow a very short TE, resulting in less optimal slice selection profile. Additionally, multiple 180° pulses means smaller bandwidth and thus larger chemical shift displacement. Specifically, the chemical shift displacement artifacts occur because signals with different chemical shifts experience different frequency-encoded slice selections and thus do not originate from same volume. Additionally, this effect becomes greater at higher magnetic field strengths.
SPECIAL consists of a spatially selective pre-excitation inversion pulse (typically AFP) followed by spatially selective excitation and refocusing pulses, both of which are usually SLR or truncated sinc pulses.
SPECIAL is a hybrid of PRESS and Image-Selected In Vivo Spectroscopy (ISIS). ISIS achieves spatial localization in the three spatial dimensions through a series of eight slice-selective preinversion pulses that can be appropriately positioned so that the sum of the eight cycles removes all signal outside the desired 3D region. SPECIAL obtains spatial localization from only a single dimension with pre-excitation inversion pulses (cycled on and off every other repetition time [TR]), making it a two-cycle sequence.
The use of the preinversion pulse to remove one refocusing pulse (as compared with PRESS) is what allows SPECIAL to achieve a short TE, reaching a minimum of 2.2 msec on a preclinical scanner in rat brain while being able to recover the full signal and as low as 6 msec on a clinical 3T scanner.
The largest drawback of SPECIAL and SPECIAL-sLASER is that they are two-cycle schemes, and systematic variations between cycles will manifest in their difference spectrum. Lipid contamination is a particularly large problem with SPECIAL and similar sequences.
The state-of-the-art localization sequence is sLASER, which utilizes two pairs of adiabatic refocusing pulses. This has recently been recommended by consensus.
The first is through OVS, which will reduce the contamination of lipid signals that originate from outside the voxel, although this comes at the cost of an increase in SAR. The second is not to set the amplitude of the pre-excitation inversion pulse to zero every other TR, but instead to shift the location of this ISIS plane such that the excited volume for the off condition is outside the object. This has been shown to greatly reduce lipid contamination, speculated to have arisen from the interaction between the RF pulse and lipid compartments due to incomplete relaxation, magnetization transfer, or the homonuclear Overhauser effect, although the exact mechanism remains unknown. The third is to use an echo-planar readout that dephases magnetization from outside the voxel, also shown to substantially reduce lipid artifacts. All three methods could be combined to overcome lipid contamination.
One of the dimensions to understand about a pulse sequence is its coherence pathway. The coherence pathway is the sequence of quantum coherence number(s) the signal takes prior to its acquisition. All coherence pathways end in -1, as this is the only coherence pathway detected by quadrature coils. The spin echo-type sequences (PRESS, sLASER, LASER) simply alternate between +1 and -1. For example, the coherence pathway for PRESS (expressed as a vector) is [-1, 1, -1]. This indicates that after the initial RF pulse (excitation pulse) the spins have a -1 quantum coherence. The refocusing pulses then swap the -1 to +1, then back from +1 to -1 (where it is then detected). Similarly for sLASER the coherence pathway is [-1, 1, -1, 1, -1]. The coherence pathway for LASER is [-1, 1, -1, 1, -1, 1, -1]. The coherence pathway for sPECIAL is [0, 1, -1]. This indicates that after the first RF pulse the signal resides as a population, due to its 0 quantum coherence number. Coherence pathways are critical as the explain how the sequences are affected by crushers and phase cycling. As such, coherence pathway analysis has been used to develop optimized crusher schemes and phase cycling schemes for an arbitrary MRS experiment.
Uses
MRS allows doctors and researchers to obtain biochemical information about the tissues of the human body in a non-invasive way (without the need for a biopsy), whereas MRI only gives them information about the structure of the body (the distribution of water and fat).
For example, whereas MRI can be used to assist in the diagnosis of cancer, MRS could potentially be used to assist in information regarding to the aggressiveness of the tumor. Furthermore, because many pathologies appear similar in diagnostic imaging (such as radiation-induced necrosis and recurring tumor following radiotherapy), MRS may in the future be used to assist in distinguishing between similarly appearing prognoses.
MRS equipment can be tuned (just like a radio receiver) to pick up signals from different chemical nuclei within the body. The most common nuclei to be studied are protons (hydrogen), phosphorus, carbon, sodium and fluorine.
The types of biochemicals (metabolites) which can be studied include choline-containing compounds (which are used to make cell membranes), creatine (a chemical involved in energy metabolism), inositol and glucose (both sugars), N-acetylaspartate, and alanine and lactate which are elevated in some tumors.
At present MRS is mainly used as a tool by scientists (e.g. medical physicists and biochemists) for medical research projects, but it is becoming clear that it also has the ability to give doctors useful clinical information, especially with the discovery that it can be used to probe the concentration of alpha-Hydroxyglutaric acid, which is only present in IDH1 and IDH2 mutated gliomas, which alters the prescribed treatment regimen.
MRS is currently used to investigate a number of diseases in the human body, most notably cancer (in brain, breast and prostate), epilepsy, Alzheimer's disease, Parkinson's disease, and Huntington's chorea. MRS has been used to diagnose pituitary tuberculosis.
Prostate cancer: Combined with a magnetic resonance imaging (MRI) and given equal results, then the three-dimensional MRS can predict the prevalence of a malignant degeneration of prostate tissue by approximately 90%. The combination of both methods may be helpful in the planning of biopsies and therapies of the prostate, as well as to monitor the success of a therapy.
Example
Shown below is an MRI brain scan (in the axial plane, that is slicing from front-to-back and side-to-side through the head) showing a brain tumor (meningioma) at the bottom right. The red box shows the volume of interest from which chemical information was obtained by MRS (a cube with 2 cm sides which produces a square when intersecting the 5 mm thick slice of the MRI scan).
Each biochemical, or metabolite, has a different peak in the spectrum which appears at a known frequency. The peaks corresponding to the amino acid alanine, are highlighted in red (at 1.4 ppm). This is an example of the kind of biochemical information which can help doctors to make their diagnosis. Other metabolites of note are choline (3.2 ppm) and creatine (3.0 ppm).
Applications of MRS
In 1H Magnetic Resonance Spectroscopy each proton can be visualized at a specific chemical shift (peak position along x-axis) depending on its chemical environment. This chemical shift is dictated by neighboring protons within the molecule. Therefore, metabolites can be characterized by their unique set of 1H chemical shifts. The metabolites that MRS probes for have known (1H) chemical shifts that have previously been identified in NMR spectra. These metabolites include:
N-acetyl Aspartate (NAA): with its major resonance peak at 2.02 ppm, decrease in levels of NAA indicate loss or damage to neuronal tissue, which results from many types of insults to the brain. Its presence in normal conditions indicates neuronal and axonal integrity.
Choline: with its major peak at 3.2 ppm, choline is known to be associated with membrane turnover, or increase in cell division. Increased choline indicates increase in cell production or membrane breakdown, which can suggest demyelination or presence of malignant tumors.
Creatine and phosphocreatine: with its major peak at 3.0 ppm, creatine marks metabolism of brain energy. Gradual loss of creatine in conjunction with other major metabolites indicates tissue death or major cell death resulting from disease, injury or lack of blood supply. Increase in creatine concentration could be a response to cranialcerebral trauma. Absence of creatine may be indicative of a rare congenital disease.
Lipids: with their major aliphatic peaks located in the 0.9–1.5 ppm range, increase in lipids is seen is also indicative of necrosis. These spectra are easily contaminated, as lipids are not only present in the brain, but also in other biological tissue such as the fat in the scalp and area between the scalp and skull.
Lactate: Is an AX3 system which results in a doublet (two symmetric peaks) centered about 1.31 ppm, and a quartet (four peaks with relative peak heights of 1:2:2:1) centered about 4.10 ppm. The doublet at 1.31 ppm is typically quantified as the quartet may be suppressed through water saturation or obscured by residual water. In healthy subjects lactate is not visible, for its concentration is lower than the detection limit of MRS; however, presence of this peak indicates glycolysis has been initiated in an oxygen-deficient environment. Several causes of this include ischemia, hypoxia, mitochondrial disorders, and some types of tumors.
Myo-inositol: with its major peak at 3.56 ppm, an increase in Myo-inositol has been seen to be disrupted in patients with Alzheimer's, dementia, and HIV patients.
Glutamate and glutamine: these amino acids are marked by a series of resonance peaks between 2.2 and 2.4 ppm. Hyperammonemia, hepatic encephalopathy are two major conditions that result in elevated levels of glutamine and glutamate. MRS, used in conjunction with MRI or some other imaging technique, can be used to detect changes in the concentrations of these metabolites, or significantly abnormal concentrations of these metabolites.
GABA can be detected primarily from its peaks at approximately 3.0 ppm, however because creatine has a strong singlet at 3.0 ppm with approximately 20x the amplitude a technique which exploits J-coupling must be used to accurately quantify GABA. The most common techniques for this are J-difference editing (MEGA), or J-resolved (as used in JPRESS)
Glutathione can also be detected from its peak at peak at 3.0 ppm, however similar to GABA it also must use a method which exploits J-coupling to remove the overlaying creatine signal.
Limitations of MRS
The major limitation to MRS is its low available signal due to the low concentration of metabolites as compared to water. As such, it has inherently poor temporal and spatial resolution. Nevertheless, no alternate technique is able to quantify metabolism in vivo non-invasively and thus MRS remains a valuable tool for research and clinical scientists.
In addition, despite recent efforts toward international expert consensus on methodological details like shimming, motion correction, spectral editing, spectroscopic neuroimaging, other advanced acquisition methods, data processing and quantification, application to brain, proton spectroscopy application to skeletal muscle, phosphorus application to skeletal muscle, methods description, results reporting, and other considerations, currently published implementations of in vivo magnetic resonance spectroscopy cluster into literatures exhibiting a broad variety of individualized acquisition, processing, quantification, and reporting techniques. This situation may contribute to a low sensitivity and specificity of, for example, in vivo proton magnetic resonance spectroscopy to disorders such as multiple sclerosis, that continue to fall below clinically beneficial thresholds for, e.g., diagnosis.
Non-Proton (1H) MRS
31Phosphorus Magnetic Resonance Spectroscopy
1H MRS's clinical success is only rivaled by 31P MRS. This is in large part because of the relatively high sensitivity of phosphorus NMR (7% of protons) combined with a 100% natural abundance.
Consequently, high-quality spectra are acquired within minutes. Even at low field strengths, great spectra resolution is obtained because of the relatively large (~30 ppm) chemical shift dispersion for in vivo phosphates. Clinically, phosphorus NMR excels because it detects all metabolites playing key roles in tissue energy metabolism and can indirectly deduce intracellular pH. However, phosphorus NMR is chiefly challenged by the limited number of metabolites it can detect.
13Carbon Magnetic Resonance Spectroscopy
In contrast to phosphorus NMR, carbon NMR is an insensitive technique. This arises from the fact that 13C NMR has a low abundance (1.1%) and carbon's low gyromagnetic ratio. This low abundance is because 12C does not have a magnetic moment, making it not NMR active, leading to 13C's use for spectroscopy purposes. However, this low sensitivity can be improved via decoupling, averaging, polarization transfer, and larger volumes. Despite the low natural abundance and sensitivity of 13C, 13C MRS has been used to study several metabolites, especially glycogen and triglycerides. It has proven especially useful at providing insight on the metabolic fluxes from 13C-labeled precursors. There is great overlap in what 1H MRS and 13C MRS can obtain spectra-wise and large reason, combined with 1H MRS's high sensitivity, why 13C MRS has never seen wide application like 1H MRS. See also Hyperpolarized carbon-13 MRI.
23Sodium Magnetic Resonance Spectroscopy
Sodium NMR is infamous for its low sensitivity (9.2% relative to proton sensitivity) and low SNR because of its low sodium concentration (30 - 100 mM), especially compared to protons (40 - 50 M). However, interest in sodium NMR has been reinspired by recent significant gains in SNR at high magnetic fields, along with improved coil designs and optimized pulse sequences. There is much hope for sodium NMR's clinical potential because the detection of abnormal intracellular sodium in vivo may have significant diagnostic potential and reveal new insights into tissue electrolysis homeostasis.
19Fluorine Magnetic Resonance Spectroscopy
Fluorine NMR has high sensitivity (82% relative to proton sensitivity) and 100% natural abundance. However, it is important to note that no endogenous 19F containing compounds are found in biological tissues and thus the fluorine signal comes from an external reference compound. Because19F is not found in biological tissues, 19F does not have to deal with interference from background signals like in vivo 1H MRS does with water, making it especially powerful for pharmacokinetic studies. 1H MRI provides the anatomical landmarks, while 19F MRI/MRS allows us to follow and map the specific interactions of specific compounds. in vivo 19F MRS can be used to monitor the uptake and metabolism of drugs, study the metabolism of anesthetic, determine cerebral blood flow, and measure, via fluorinated compounds ("probes"), various parameters like pH, oxygen levels, and metal concentration.
See also
Functional magnetic resonance spectroscopy of the brain
Magnetic resonance imaging
Magnetization transfer
NMR
NMR spectroscopy
References
External links
Online Physics Tutorial for MRI and MRS
https://aclarion.com/
NOCISCAN (aclarion) – The first, evidence-supported, SaaS platform to leverage MR Spectroscopy to noninvasively help physicians distinguish between painful and nonpainful discs in the spine.
In vivo
Nuclear magnetic resonance spectroscopy | In vivo magnetic resonance spectroscopy | Physics,Chemistry | 4,724 |
20,796,420 | https://en.wikipedia.org/wiki/The%20Year%20of%20the%20Angry%20Rabbit | The Year of the Angry Rabbit is a science fiction novel by Australian author Russell Braddon, in which giant mutant rabbits run amok in Australia while the Prime Minister uses a new superweapon to dominate the planet.
The pulp narrative was played for laughs, and designed as an indictment of war, nationalism and capitalism. The novel was also notable as being part of a small revival of Australian science fiction in the 1960s. Its comic-horror tone was well received and a movie version was released in 1972 titled Night of the Lepus – a straight-faced monster movie that dropped the humor of the book.
Summary
Sir Alfred – who engineered Fitzgerald's election to prime minister – calls Fitzgerald one evening with a complaint: his Bludgerton property has been infested with rabbits that are immune to myxomatosis. Fearing another rabbit epidemic, Fitzgerald tasks Professor Welch and his scientists with inventing super myxomatosis, or Supermyx, to control the growing rabbit population. They test the first batch of Supermyx on a male and female rabbit, with disastrous results: Supermyx does not kill rabbits, and merely makes them savage, as if infected with rabies. Supermyx is, however, instantly lethal to humans, as demonstrated when Sir Alfred is brutally killed by the test cases, which then escape and turn the entire rabbit brood into flesh-rending Supermyx carriers.
In a temporary lapse of brilliance, Sir Alan Jacks suggests that Fitzgerald weaponize Supermyx and conquer the world. Fitzgerald does just that: after nuking the Bludgerton property to prevent the rabbit outbreak (and having the scientists committed so that word of the threat never comes to light), he has Supermyx bombs planted in every country; as a demonstration of power, he wipes out the entire populations of two countries who refuse to stop warring with each other. This results in total nuclear disarmament, the exile of all nuclear physicists to a doomed island, and an eventual end to conventional warfare. Wars are soon conducted as harmless arena games which are heavily promoted like the Olympics. Fitzgerald has all weapon factories shut down, but this quickly threatens the world economy, so he decrees the factories continue producing weapons of warfare, which are then summarily dumped into the ocean. Surprisingly, Fitzgerald's seemingly ridiculous plans actually work: world peace finally becomes a reality for three years.
As Supermyx cannot travel across bodies of water, Australia is completely safe from its own superweapons; however, the Supermyx-carrying Bludgerton Rabbits (now giant from atomic radiation) refuse to go away, and keep resurfacing time and again, threatening to overwhelm Australia and wipe out its population. The rabbits eventually become too numerous to contain, and Australia wages a one-sided war against the numberless brood. Fitzgerald is killed, and the entire continent is evacuated, leaving Australia to the aborigines, who eventually summon a flood to destroy the rabbits. The novel ends with the implication that the remaining Supermyx bombs will be detonated, wiping humanity from the face of the earth.
Characters
Kevin Sean Aloysius "Ella" Fitzgerald: Prime Minister of Australia, and the novel's protagonist. An archetypal scheming politician.
Major General Sir Alan Jacks: Notoriously incompetent Minister of Defence whose predictions are always wrong, except for one temporary lapse of brilliance when he suggests using Supermyx as a world-dominating weapon.
Sir Alfred Hill G.C.B.: Wealthy landowner, habitual blackmailer, and the story's catalyst. After discovering oil on his property he used his wealth to dominate two boroughs (pocket boroughs), which won Fitzgerald the last election by a two-seat majority. When rabbits begin spawning on his property, Alfred threatens to use the same trick to lose Fitzgerald the next election if he can't find a way to get rid of the rabbits.
Professor Welch: Leader of the team that is tasked to develop Supermyxomatosis, in the hope of annihilating the rabbit plague on Sir Alfred's ranch.
Les Dorfmann: Welch's second-in-command, who becomes a hunted fugitive, and later becomes Fitzgerald's last hope at defeating the deadly rabbits.
Dr Miller: Assistant to professor Golovin, who helps Dorfmann escape the authorities, and later marries him.
Flo Hill, AKA "Ladyill": Wife of Sir Alfred, who Fitzgerald was once infatuated with.
Major Gary Cooper Hill: Son of Ladyill and Sir Alfred. Military man in the Australian army. Unlike the Minister of Defence, Gary is a highly competent and very effective leader.
The Bludgerton Rabbits: Initially normal rabbits infesting Sir Alfred's Bludgerton property, they become savage plague-carriers when infected with Supermyx. They are the only thing that threatens Australia's total world dominance, and each time they resurface, they are larger, nastier, and more numerous.
Background
Braddon said he wrote the book "as a joke" and says it took him four weeks to complete.
References
External links
Serialised in Australia Women's weekly - Part One 21 October 1964, Part Two 28 October 1964, Part Three 4 November 1964
1964 Australian novels
1964 science fiction novels
Australian science fiction novels
Comic science fiction novels
Australian satirical novels
Australian novels adapted into films
Novels about rabbits and hares
Fiction about size change
Novels set in Australia
Heinemann (publisher) books | The Year of the Angry Rabbit | Physics,Mathematics | 1,119 |
3,251,941 | https://en.wikipedia.org/wiki/Orion%20molecular%20cloud%20complex | The Orion molecular cloud complex (or, simply, the Orion complex) is a star-forming region with stellar ages ranging up to 12 Myr. Two giant molecular clouds are a part of it, Orion A and Orion B. The stars currently forming within the complex are located within these clouds. A number of other somewhat older stars no longer associated with the molecular gas are also part of the complex, most notably the Orion's Belt (Orion OB1b), as well as the dispersed population north of it (Orion OB1a). Near the head of Orion there is also a population of young stars that is centered on Meissa. The complex is between 1 000 and 1 400 light-years away, and hundreds of light-years across.
The Orion complex is one of the most active regions of nearby stellar formation visible in the night sky, and is home to both protoplanetary discs and very young stars. Much of it is bright in infrared wavelengths due to the heat-intensive processes involved in stellar formation, though the complex contains dark nebulae, emission nebulae, reflection nebulae, and H II regions. The presence of ripples on the surface of Orion's molecular clouds was discovered in 2010. The ripples are a result of the expansion of the nebulae gas over pre-existing molecular gas.
The Orion complex includes a large group of bright nebulae, dark clouds in the Orion constellation. Several nebulae can be observed through binoculars and small telescopes, and some parts (such as the Orion Nebula) are visible to the naked eye.
Nebulae within the complex
The following is a list of notable regions within the larger complex:
Orion A molecular cloud
The Orion Nebula, also known as M42 (part of Orion's Sword)
M43, which is part of the Orion Nebula
Sh2-279 (part of Orion's Sword)
NGC 1980 (part of Orion's Sword)
Orion molecular cloud 1 (OMC-1) with the Becklin–Neugebauer Object and the Kleinmann–Low Nebula
Orion molecular cloud 2 (OMC-2)
Orion molecular cloud 3 (OMC-3)
Orion molecular cloud 4 (OMC-4)
NGC 1981
NGC 1999
the Waterfall nebula (HH-222), above NGC 1999
HH 34 a Herbig–Haro object with symmetric bow shocks
LDN 1641
HH 1/2, the first recognized Herbig–Haro objects
Orion B molecular cloud
Flame Nebula (NGC 2024)
IC 434, which contains the Horsehead Nebula
The Horsehead Nebula (Barnard 33)
M78, a reflection nebula (NGC 2068)
McNeil's Nebula is a variable nebula discovered in 2004 near M78
Orion East Cloud (LDN 1621 + LDN 1622)
HH 24-26 this group contains three Herbig–Haro objects
HH 111 one of the most well-known Herbig–Haro objects
Orion OB1 association
Orion's Belt
Sigma Ori cluster
25 Ori cluster
Lambda Orionis molecular ring (Sh2-264)
Lambda Ori cluster
Barnard 30
Barnard 35 (Angelfish nebula)
Orion-Eridanus superbubble
Barnard's Loop (Sh2-276)
IC 2118
Eridanus Loop
Arc A
Arc B
Arc C
A more complete list can be found for example in Maddalena et al. (1986) Table 1
Individual components
Orion A
The giant molecular cloud Orion A is the most active star-forming region in the local neighbourhood of the Sun. In the last few million years about 3000 young stellar objects were formed in this region, including about 190 protostars and about 2600 pre-main sequence stars. The Orion A cloud has a mass in the order of 105 . The stars in Orion A do not have the same distance to us. The "head" of the cloud, which also contains the Orion Nebula is about 1300 light-years (400 parsecs) away from the Sun. The "tail" however is up to 1530 light-years (470 parsecs) away from the Sun. The Orion A cloud is therefore longer than the projected length of 130 light-years (40 parsecs) and has a true length of 290 light-years (90 parsecs).
Orion Molecular Clouds
The Orion Molecular Clouds (OMC 1 to OMC 4) are molecular clouds located behind the Orion Nebula. Most of the light from the OMCs are blocked by material from the Orion Nebula, but some features like the Kleinmann-Low Nebula and the Becklin-Neugebauer object can be seen in the infrared. The clouds can be seen in the far-infrared and in radio wavelengths. The Trapezium Cluster has a small angular separation from the Kleinmann-Low Nebula, but the Trapezium Cluster is located inside the Orion Nebula, which is closer towards Earth.
Orion B
Orion B is about 1370 light-years (420 parsecs) from Earth. It has a size of about 1.5 kpc² and a mass in the order of 105 . It contains several star forming regions with the star cluster inside the Flame Nebula being the largest cluster.
Orion OB1 association
The Orion OB1 association represents different stellar populations that are superimposed along our line of sight. The oldest group with 8-10 million years is Orion OB1a, northwest of Orion's Belt, and the youngest group with less than 2 million years is Orion OB1d, which contains the Orion Nebula cluster and NGC 2024.
Lambda Orionis molecular ring
The Lambda Orionis ring is a large molecular ring, centered around Lambda Orioinis (Meissa). It was suggested that this ring formed after a supernova occurred inside the central star-forming region that once surrounded the Lambda Orionis Cluster, dispersing the material into the ring seen today. Star-formation is still continuing in regions of the ring.
Superbubble
Parts of the Orion-Eridanus superbubble were first seen as Barnard's Loop in Hydrogen-alpha images that warp around the eastern portion of Orion. The other part of the superbubble that is seen in H-alpha is the Eridanus Loop. The walls of the entire bubble are seen in far-infrared and HI. Some features of the Eridanus Loop might be as close as 590 light-years (180 parsecs) to the Sun.
Gallery
See also
Runaway star
Rho Ophiuchi cloud complex
Taurus molecular cloud
Perseus molecular cloud
Scorpius–Centaurus association
References
External links
Orion Cloud Complex
SEDS website
ESO: Hidden Secrets of Orion’s Clouds incl. Photos & Animations
Orion (constellation)
Molecular clouds | Orion molecular cloud complex | Astronomy | 1,360 |
51,838,790 | https://en.wikipedia.org/wiki/V528%20Carinae | V528 Carinae (V528 Car, HD 95950, HIP 54021) is a variable star in the constellation Carina.
V528 Carinae has an apparent visual magnitude that varies between about 6.3 and 6.8. When it is near its maximum brightness, it is very faintly visible to the naked eye under ideal observing conditions. It is a distant star but the exact distance is uncertain. The Hipparcos satellite gives a negative annual parallax and is not helpful, while the Gaia Data Release 3 parallax of implies a distance of around (2,200 parsecs). Assuming membership of the Carina OB2 membership would give a distance of about .
V528 Carinae is a red supergiant of spectral type M2 Ib with an effective temperature of . It has a radius of 700 solar radii. In the visible spectrum, its luminosity is 11,900 times higher than the Sun, but the bolometric luminosity considering all wavelengths reaches around . It loses mass at per year.
It was found to be a variable star when the Hipparcos data was analyzed, and for that reason it was given its variable star designation in 1999. It is classified as a slow irregular variable whose prototype is TZ Cassiopeiae.
See also
List of largest known stars
References
Carina (constellation)
Slow irregular variables
Carinae, V528
M-type supergiants
CD−60 3327
095950
054021
J11030616-6054387
IRAS catalogue objects | V528 Carinae | Astronomy | 323 |
8,567,475 | https://en.wikipedia.org/wiki/Roller-compacted%20concrete | Roller-compacted concrete (RCC) or rolled concrete (rollcrete) is a special blend of concrete that has essentially the same ingredients as conventional concrete but in different ratios, and increasingly with partial substitution of fly ash for portland cement. The partial substitution of fly ash for Portland Cement is an important aspect of RCC dam construction because the heat generated by fly ash hydration is significantly less than the heat generated by portland cement hydration. This in turn reduces the thermal loads on the concrete and reduces the potential for thermal cracking to occur. RCC is a mix of cement/fly ash, water, sand, aggregate and common additives, but contains much less water. The produced mix is drier and essentially has no slump. RCC is placed in a manner similar to road paving; the material is delivered by dump trucks or conveyors, spread by small bulldozers or specially modified asphalt pavers, and then compacted by vibratory rollers.
In dam construction, roller-compacted concrete began its initial development with the construction of the Alpe Gera Dam near Sondrio in North Italy between 1961 and 1964. Concrete was laid in a similar form and method but not rolled. RCC had been touted in engineering journals during the 1970s as a revolutionary material suitable for, among other things, dam construction. Initially and generally, RCC was used for backfill, sub-base and concrete pavement construction, but increasingly it has been used to build concrete gravity dams because the low cement content and use of fly ash cause less heat to be generated while curing than do conventional mass concrete placements. Roller-compacted concrete has many time and cost benefits over conventional mass concrete dams; these include higher rates of concrete placement, lower material costs and lower costs associated with post-cooling and formwork.
Dam applications
For dam applications, RCC sections are built lift-by-lift in successive horizontal layers resulting in a downstream slope that resembles a concrete staircase. Once a layer is placed, it can immediately support the earth-moving equipment to place the next layer. After RCC is deposited on the lift surface, small dozers typically spread it in one-foot-thick (about 30 cm) layers.
The first RCC dam built in the United States was the Willow Creek Dam on Willow Creek, a tributary in Oregon of the Columbia River. It was constructed by the US Army Corps of Engineers between November 1981 and February 1983. Construction proceeded well, within a fast schedule and under budget (estimated US$50 million, actual US$35 million). On initial filling though, it was found that the leakage between the compacted layers within the dam body was unusually high. This condition was treated by traditional remedial grouting at a further cost of US$2 million, which initially reduced the leakage by nearly 75%; over the years, seepage has since decreased to less than 10% of its initial flow. Concern over the dam's long-term safety has continued however, although only indirectly related to its RCC construction. Within a few years of construction, problems were noted with stratification of the reservoir water, caused by upstream pollution and anoxic decomposition, which produced hydrogen sulfide gas. Concerns were expressed that this could in turn give rise to sulfuric acid, and thus accelerate damage to the concrete. The controversy itself, as well as its handling, continued for some years. In 2004 an aeration plant was installed to address the root cause in the reservoir, as had been suggested 18 years earlier.
In the quarter century following the construction of the Willow Creek Dam, considerable research and experimentation yielded many improvements in concrete mix designs, dam designs and construction methods for roller-compacted concrete dams. By 2008, about 350 RCC dams existed worldwide. As of 2018, the highest dam of this type was the Gilgel Gibe III Dam in Ethiopia, at , with the Pakistani Diamer-Bhasha Dam under construction at .
See also
List of roller-compacted concrete dams
Asphalt concrete
Further reading
References
External links
History of Concrete
Database of Worldwide Roller Compacted Concrete Dams
Concrete
Concrete buildings and structures
Building materials | Roller-compacted concrete | Physics,Engineering | 842 |
51,065,855 | https://en.wikipedia.org/wiki/RepRap%20Ormerod | The RepRap Ormerod is an open-source fused deposition modeling 3D printer and is part of the RepRap project. The RepRap Ormerod is named after the English entomologist Eleanor Anne Ormerod, it was designed by RepRapPro. There have been two versions of the Ormerod, the Ormerod 1 was released in December 2013 and the Ormerod 2 released in December 2014.
The RepRap Ormerod has a 200 mm × 200 mm × 200 mm build volume, uses a Bowden extruder, it also has a micro SD card and USB and Ethernet connections allowing it to be connected to a network. The printer was praised for the simplicity of construction and its low cost.
See also
RepRap
Prusa i3
Prusa Mini
References
External links
RepRap Ormerod page on RepRap.org
Open Source repository on Github by RepRapPro
Open hardware electronic devices
3D printers
RepRap project
2013 introductions | RepRap Ormerod | Engineering,Biology | 206 |
185,820 | https://en.wikipedia.org/wiki/Physics%20and%20Beyond | Physics and Beyond () is a book by Werner Heisenberg, the German physicist who discovered the uncertainty principle. It tells, from his point of view, the history of exploring atomic science and quantum mechanics in the first half of the 20th century.
As the subtitle "Encounters and Conversations" suggests, the core part of this book takes the form of discussions between himself and other scientists. Heisenberg says: "I wanted to show that science is done by people, and the most wonderful ideas come from dialog".
With chapters like "The first encounter with the science about atoms", "Quantum mechanics and conversations with Einstein", "Conversation about the relation between biology, physics and chemistry" or "Conversations about language" and "The behavior of an individual during a political disaster", dated 1937–1941, a reader can hear speaking such persons as Erwin Schrödinger, Niels Bohr, Albert Einstein or Max Planck, not only about physics, but also about many other questions related to biology, humans, philosophy, and politics.
Not only that, these conversations are often situated in detailed description of the historical atmosphere and a beautiful scenery, as many of them were led in nature during the many journeys they made, backpacking or sailing. "'Do you see whales, Heisenberg?', 'Yes, I see only whales, but I hope they are only big waves.'", is one of humorous scenes when the author, Bohr and other friends were sailing in a dark night.
The book provides a first-hand account about how science is done and how quantum physics, especially the Copenhagen interpretation, emerged.
"Nobody can reproduce these conversations verbatim, but I believe that the spirit of what the people said, and how they did, is conserved," the author tries to explain in the preface.
Many believe that the golden years of physics around 1925, when "even small people could do big things" are gone. But the people who had been there continue to speak to us through this book.
The book was published first in German 1969, in English as Physics and Beyond (1971) and in French in 1972 (La partie et le tout).
References
Bibliography
Science books
Books about the history of physics
Quantum mechanics
1969 non-fiction books
Werner Heisenberg | Physics and Beyond | Physics | 469 |
20,982,853 | https://en.wikipedia.org/wiki/Effluent%20spreading | Effluent spreading is a process in which a slurry of effluent from a dairy farm's milking parlor is pumped and spread on pasture. Commonly a rotating sprinkler is used. Dairy manure contains ammonium NH4-N.
In New Zealand the application of effluent is a permitted activity, although spreading in excess is an environmental hazard.
Organic fertilizers | Effluent spreading | Chemistry | 87 |
75,659,158 | https://en.wikipedia.org/wiki/DBOS | DBOS (Database-Oriented Operating System) is a database-oriented operating system meant to simplify and improve the scalability, security and resilience of large-scale distributed applications. It started in 2020 as a joint open source project with MIT, Stanford and Carnegie Mellon University, after a brainstorm between Michael Stonebraker and Matei Zaharia on how to scale and improve scheduling and performance of millions of Apache Spark tasks.
The basic idea is to run a multi-node multi-core, transactional, highly-available distributed database, such as VoltDB, as the only application for a microkernel, and then to implement scheduling, messaging, file systems and other operating system services on top of the database.
The architectural philosophy is described by this quote from the abstract of their initial preprint: All operating system state should be represented uniformly as database tables, and operations on this state should be made via queries from otherwise stateless tasks. This design makes it easy to scale and evolve the OS without whole-system refactoring, inspect and debug system state, upgrade components without downtime, manage decisions using machine learning, and implement sophisticated security features.Stonebraker claims a variety of security benefits, from a "smaller, less porous attack surface", to the ability to log and analyze how the system state changes in real-time due to the transactional nature of the OS. Recovery from a severe bug or an attack can be as simple as rolling back the database to a previous state. And since the database is already distributed, the complexity of orchestration systems like Kubernetes can be avoided.
A prototype was built with competitive performance to existing systems.
DBOS Cloud
In March of 2024, DBOS Cloud became the first commercial service from DBOS Inc. It provides transactional Functions as a Service (FaaS), and is positioned as a competitor to serverless computing architectures like AWS Lambda. DBOS Cloud is currently based on FoundationDB, a fast ACID NoSQL database, running on the Firecracker service from AWS. It provides built-in support for features like multinode scaling and a "time-traveler" debugger that can help track down elusive heisenbugs and works in Visual Studio Code. Another feature is reliable execution, allowing a program to continue running even if the operating system needs to be restarted, and ensuring that no work is repeated.
Firecracker runs on stripped down Linux microkernel via a stripped down KVM hypervisor, so parts of the Linux kernel are still under the covers, but work is ongoing to eliminate them.
DBOS Cloud has been tested running across 1,000 cores running applications. The first API provided is for TypeScript, via the open-source DBOS Transact framework. It provides a runtime with built-in reliable message delivery and idempotency.
Holger Mueller of Constellation Research wondered how well DBOS the company can scale. “Will a small team at DBOS be able to run an OS, database, observability, workflow and cyber stack as good as the combination of the best of breed vendors?”
See also
PICK OS, another implementation of an operating system based on a DB.
References
External links
Operating systems | DBOS | Technology | 670 |
71,601,495 | https://en.wikipedia.org/wiki/Lingzi | (), also called (), refers to a traditional Chinese ornament which uses long pheasant tail feather appendages to decorate some headdress in , Chinese opera costumes. In Chinese opera, the not only decorative purpose but are also used express thoughts, feelings, and the drama plot. They are typically used on the helmets of warriors, where a pair of pheasant feathers extensions are the indicators that the character is a warrior figure; the length of the feathers, on the other hand, is an indicator of the warrior's rank. The are generally about five or six feet long. Most of the time, are used to represent handsome military commanders.
Origins
It is suggested that the use of originated from the (), a form of used by the military officials since the ancient times. Similar headgear decorated with pairs of worn the military can be seen in paintings dating to the Ming dynasty.
Wuguan
During the Warring States period, King Wuling of Zhao adopted the policy and a -style which looks similar to the conical hat of the Scythian was adopted. King Wuling's -style was less pointy than the actual Scythian hat and he decorated his hat with a marten tail to denote his noble status. The King of Qin later give the -style of King Wuling to his servant as an insult to King Wuling after the latter had destroyed the regime of the Zhao state.
King Huiwen of Zhao later wore the same -style as his father, King Wuling; and therefore this type of was named (). Many years later, the evolved into the military cap called .
By the Han dynasty, a decorated with pheasant feathers became known as () and was used by the military officials of the Han dynasty. The was first worn in the state of Zhao to distinguish military officers during the Warring States period. The was possibly itself derived from the -style adopted by King Wuling through policy. The snow pheasant () was a symbolism of martial valour and courage due to its association with the snow pheasant which would fight its opponent until death.
Skills and manipulation
The skills required to manipulate the two pheasant feathers are known as . These skills include shaking and swinging; sometimes the are shaken with one hand but sometimes two hands are used. The skills of are used by many roles; however, they are especially used in the role.
When combined the movements of the head and body of the actor, the movement of the express the feelings and dispositions of the character, which include the expression of surprise, hatred, happiness, and frivolity.
See also
Chinese opera
– Chinese opera costume
Hanfu
Guzhuang
Gallery
Notes
References
Chinese traditional clothing
Chinese opera
Costume design | Lingzi | Engineering | 557 |
75,512,019 | https://en.wikipedia.org/wiki/TurkHackTeam | TurkHackTeam is a Turkish nationalist hacker group founded in 2002. Ideologically they are Kemalists and define themselves as the "Turkish Cyber Army".
They state that their goal is to fight against all kinds of cyber threats against Turkey. They have appeared on news headlines on many international news portals.
History
The group claimed responsibility for the hacking of the pro-Kurdish Democratic Society Party's website in 2008.
TurkHackTeam went on a spree of attacking Iranian and Russian websites in 2016 amid the Syrian civil war. During rising tensions in the Nagorno-Karabakh conflict, they participated in cyberwarfare against Armenian hackers. In 2017, for unknown reasons, they hacked the official website of the UK Police. In March 2017, during a brief period of tensions between the Netherlands and Turkey, the TurkHackTeam launched their "Netherlands Operation" where they hacked and defaced over 250 Dutch websites in less than a month.
They also hacked Star Alliance. TurkHackTeam is also a platform that prepares social projects. The first of the projects was to send morale letters to the soldiers and police after the 2016 Turkish coup attempt. In the same year, they distributed food in Africa through an association. Later, some group members gathered on 10 November and went to visit Anıtkabir, the mausoleum of Mustafa Kemal Atatürk. In 2017, the group, which collected books from its members, donated these books to secondary and high schools, and created libraries.
At the beginning of February 2024, the hacker group claimed responsibility for the attack on La Poste and Crédit Agricole. According to the first elements this is a Denial-of-service attack. They also stood out in 2023 for hacking the ANSSI Telegram page.
References
Information society
Internet-based activism
Internet-related activism
Intellectual property activism
Internet culture
Internet vigilantism
Internet trolling
Hacker groups
Turkish nationalism
Organizations established in 2002 | TurkHackTeam | Technology | 396 |
26,568,934 | https://en.wikipedia.org/wiki/Sturm%20series | In mathematics, the Sturm series associated with a pair of polynomials is named after Jacques Charles François Sturm.
Definition
Let and two univariate polynomials. Suppose that they do not have a common root and the degree of is greater than the degree of . The Sturm series is constructed by:
This is almost the same algorithm as Euclid's but the remainder has negative sign.
Sturm series associated to a characteristic polynomial
Let us see now Sturm series associated to a characteristic polynomial in the variable :
where for in are rational functions in with the coordinate set . The series begins with two polynomials obtained by dividing by where represents the imaginary unit equal to and separate real and imaginary parts:
The remaining terms are defined with the above relation. Due to the special structure of these polynomials, they can be written in the form:
In these notations, the quotient is equal to which provides the condition . Moreover, the polynomial replaced in the above relation gives the following recursive formulas for computation of the coefficients .
If for some , the quotient is a higher degree polynomial and the sequence stops at with .
References
Mathematical series | Sturm series | Mathematics | 229 |
20,155,706 | https://en.wikipedia.org/wiki/Self%20Winding%20Clock%20Company | The Self Winding Clock Company (SWCC) was a major manufacturer of electromechanical clocks from 1886 until about 1970. Based in New York City, the company was one of the first to power its clocks with an electric motor instead of winding by hand.
A patented clock mechanism automatically rewinds the main spring each hour by the small electric motor. A contact switch mounted on the clock's center shaft is activated after the clock has run for one hour and the main spring is rewound one revolution. This rewinding occurs each hour. The power for the motor is supplied by batteries and the batteries last about one year.
History
The Self Winding Clock Company clock movement was patented by one of the company founders, Chester Henry Pond (1844–1912) in 1884 (Patent No. 308,521). Pond was also a principal in the Gamewell Fire Alarm-Telegraph Company. He was an accomplished instrument maker and a pioneer in the developing field of electricity. He designed a small electric motor and matched it with a conventional clock mechanism.
In 1886, Pond patented a correction device that used an electric current to activate a mechanical lever attached to the clock movement. This correction attachment would move the clock hands precisely to the hour (Patent No. 339,688). If the clock is not absolutely accurate, it would be corrected when receiving the hourly time signal over a telegraph line from a master clock calibrated to the US Naval Observatory. This correction was referred to as synchronizing, and many SWCC clocks were fitted with this option.
The original SWCC factory was located at 205 Willoughby Avenue in Brooklyn, New York. This site was across from the Pratt Institute, and now is part of the Pratt Institute campus. Charles Pratt (1830–1891), the founder of Pratt Institute, was also one of SWCC's original founders and the company started business in his buildings. The SWCC factory remained in Brooklyn until they moved to 75 Varick Street, New York at some time in the 1950s, to apparently make room for expansion at the Pratt Institute. In addition to doing the clock manufacturing in Brooklyn, SWCC had business offices at various locations in New York City throughout its long history.
Clock movements
When Self Winding Clock Company started producing clocks, the vast majority of the actual clock movements were made by the Seth Thomas Clock Company and the remainder were made by the E. Howard & Co. The most expensive clocks could be equipped with the higher grade movement made by E. Howard. SWCC then fitted their motor-winding components and synchronizing apparatus to the movements. The movements were mounted in cases of various designs, often in case styles similar to those of companies like Seth Thomas and E. Howard. The SWCC appears to have been manufacturing their own clock movements by 1892, for they are all stamped "Self Winding Clock Co". Earlier movements were stamped with Seth Thomas or E. Howard markings.
The unique feature of SWCC clocks was that the clocks were wound electrically. The success of SWCC depended upon the clocks being reliably wound every hour without failure. The hourly winding motor was the one element of the clock that was most likely to fail. Over a span of about 15 years, the design of the SWCC movements went through a series of modifications aimed at improving reliability. The first six different styles all had the winding motor added to the SWCC movement. The final design, termed the "F" movement or Vibrator movement, was a major improvement. This movement, with minor modifications, was used for the next 60 plus years. In this design, the motor proved to be much more reliable and was now an integral part of the movement rather than added on below the clock works. The "F" movement motor employed a vibrating up and down motion rather than rotary motion to re-wind the mainspring.
SWCC imprinted all of their movements with serial numbers. The serial numbers were used for inventory purposes and were assigned in ascending order. It is possible to approximately date the time of manufacture of a movement based on the serial number. The first "F" movements were made in 1898 and were made into the 1940s. However, it is not possible to automatically date a particular clock by the movement serial number. SWCC had a practice of exchanging clock movements rather than servicing a movement and then returning it to the same clock. This results in rarely finding a SWCC clock with its original movement. Identification tag numbers also often do not match movement serial numbers because the tags were not changed when the movement was exchanged. The total number of "F" movements manufactured could be confusing. The lowest serial numbers are in the 33,000 range and the highest is in the 402,000 range. There were large numbering gaps and it has been calculated that probably around 200,000 movements were produced.
Western Union time service
The relationship of the Self Winding Clock Company with Western Union (WU) began with an agreement between the companies of June 1889. Its subject matter was for the transmission of time signals over Western Union telegraph lines to synchronize clocks made by SWCC. The company owned the clocks and WU installed and maintained them for a monthly fee, ranging from $1.25 to $2.00 per clock. SWCC was paid a percentage of the rental fee for providing clocks for WU customers. If the clock movements required major repairs, they were sent to a SWCC repair facility and a replacement movement was installed by WU at the customer location. The partnership between SWCC and WU ended in 1963 when, as part of a lawsuit settlement, WU purchased all the rental clocks from SWCC. By the late 1960s, the time-service business had run its course and ceased to be profitable. Most of the clocks were simply abandoned.
Notable clock designs
The SWCC clock's were usually used in synchronized time systems. Time systems that consisted of many clocks linked electrically to a master clock. The majority of the systems were installed in businesses, factories, banks, schools, and universities. Many railroads also relied on SWCC synchronized clock systems. Some clocks were sold as individual timepieces but most clocks were a part of time systems. SWCC offered many very elegant designs for their clocks and the clocks could be purchased to match any decor. These were essentially catalog items. There were however many special one-of-a-kind clocks and clock systems that were installed by SWCC. These were intended to be very important architectural statements. Two of the most significant installations were the clocks at Grand Central Terminal and the enormous four-dial clock and lighting system for the Metropolitan Life Insurance Company Tower. The two pictured clocks of the Grand Central Terminal and the outside clocks on the Metropolitan Life Insurance Tower were just part of each property's very complex synchronized time systems. Grand Central Terminal had a master clock that controlled all the clocks at the terminal. Metropolitan Life had two separate master clocks. One controlled the motors for the four outside clocks, rang the bells in the bell tower and controlled the spectacular and very complex outside lighting system. Another SWCC master clock controlled 184 slave clocks throughout the original building. Complex SWCC synchronized systems were also installed in the London Underground. The underground installation started in 1905 and eventually included about 600 SWCC clocks.
References
External links
Master Clocks in Central Offices, Connections Museum. Video detailing a SWCC clock used in telephone service.
Clock brands
Horology
Defunct manufacturing companies based in New York City
MetLife
Western Union | Self Winding Clock Company | Physics | 1,502 |
60,345,032 | https://en.wikipedia.org/wiki/NGC%204144 | NGC 4144 is a barred spiral galaxy in the constellation Ursa Major. It was discovered by William Herschel on April 10, 1788.
Gallery
References
External links
Ursa Major
Astronomical objects discovered in 1788
Barred spiral galaxies
Discoveries by William Herschel
4144
038688 | NGC 4144 | Astronomy | 56 |
10,415,613 | https://en.wikipedia.org/wiki/Schwinger%20variational%20principle | Schwinger variational principle is a variational principle which expresses the scattering T-matrix as a functional depending on two unknown wave functions. The functional attains stationary value equal to actual scattering T-matrix. The functional is stationary if and only if the two functions satisfy the Lippmann-Schwinger equation. The development of the variational formulation of the scattering theory can be traced to works of L. Hultén and J. Schwinger in 1940s.
Linear form of the functional
The T-matrix expressed in the form of stationary value of the functional reads
where and are the initial and the final states respectively, is the interaction potential and is the retarded Green's operator for collision energy . The condition for the stationary value of the functional is that the functions and satisfy the Lippmann-Schwinger equation
and
Fractional form of the functional
Different form of the stationary principle for T-matrix reads
The wave functions and must satisfy the same Lippmann-Schwinger equations to get the stationary value.
Application of the principle
The principle may be used for the calculation of the scattering amplitude in the similar way like the variational principle for bound states, i.e. the form of the wave functions is guessed, with some free parameters, that are determined from the condition of stationarity of the functional.
See also
Lippmann-Schwinger equation
Quantum scattering theory
T-matrix method
Green's operator
References
Bibliography
Scattering | Schwinger variational principle | Physics,Chemistry,Materials_science | 300 |
1,066,948 | https://en.wikipedia.org/wiki/Modus%20vivendi | Modus vivendi (plural modi vivendi) is a Latin phrase that means "mode of living" or "way of life". In international relations, it often is used to mean an arrangement or agreement that allows conflicting parties to coexist in peace. In science, it is used to describe lifestyles.
Modus means "mode", "way", "method", or "manner". Vivendi means "of living". The phrase is often used to describe informal and temporary arrangements in political affairs. For example, if two sides reach a modus vivendi regarding disputed territories, despite political, historical or cultural incompatibilities, an accommodation of their respective differences is established for the sake of contingency.
In diplomacy, a modus vivendi is an instrument for establishing an international accord of a temporary or provisional nature, intended to be replaced by a more substantial and thorough agreement, such as a treaty. Armistices and instruments of surrender are intended to achieve a modus vivendi.
Examples
The term often refers to Anglo-French relations from the 1815 end of the Napoleonic Wars to the 1904 Entente Cordiale.
On 7 January 1948, the United States, Britain and Canada, concluded an agreement known as the modus vivendi, that allowed for limited sharing of technical information on nuclear weapons which officially repealed the Quebec Agreement.
See also
References
External links
Definition of key terms used in the UN Treaty Collection
Behavior
Latin political words and phrases | Modus vivendi | Biology | 307 |
61,555,473 | https://en.wikipedia.org/wiki/TSUBAME%20%28satellite%29 | TSUBAME was a microsatellite developed by the Tokyo Institute of Technology and Tokyo University of Science from a student design concept in 2004. The satellite was designed to demonstrate new technologies for rapid attitude control, observing gamma ray bursts, and Earth observation. The name, TSUBAME, means swift in Japanese and was chosen both because of the experimental attitude control system and to invoke another gamma ray observatory, the Swift Gamma-Ray Burst Mission, which launched shortly after TSUBAME's first design concept was published in 2004.
TSUBAME was launched with four other satellites from Yasny Cosmodrome on a Dnepr rocket on November 6, 2014. It was placed in a 500 km altitude Sun-synchronous orbit. A week after the launch, problems were reported with communication hardware and communication was lost with the satellite after three months of recovery efforts.
Objectives
The TSUBAME mission included both engineering and scientific objectives. Primarily engineering objectives were successful demonstration of new compact control moment gyroscopes for rapid changes in spacecraft attitude and demonstration of a compact, 14-meter resolution optical camera. In addition to these engineering objectives, the mission also included a primarily scientific objective to observe ephemeral, high-energy phenomena, such as gamma ray bursts, using polarimetry of hard X-rays. Early concepts of the mission also included tether formation control experiments but this objective appears to have been dropped from the final design.
History
The Matunaga space systems lab at the Tokyo Institute of Technology had launched several student-designed satellites before TSUBAME, including CUTE-1 in 2003, CUTE-1.7 + APD in 2006, and CUTE-1.7 + APD II in 2007. The first design concepts for the TSUBAME mission were entered into a student satellite design contest in 2004, where it won Grand Prix. TSUBAME was one of four small satellites to launch piggyback with ASNARO 1. The mission was launched from Yasny Cosmodrome on a Dnepr rocket on November 6, 2014. It was deployed into a 500 km Sun synchronous orbit.
Initially, TSUBAME's mission was expected to last one year. Early results from the check-in phase, where hardware is activated and vital functions checked, were positive, but a week after launch issues with RF command receiver (in the FM broadcast band) were observed. Later, issues developed with the satellite spin rate, S-band communications, GPS receiver, and battery voltage and temperature. About three months after launch, all communication was lost with the failure of the continuous wave transceiver. Subsequent analysis of communications with the satellite and laboratory reproduction have revealed that the ultimate loss of contact and some of the other issues were caused by a failure in a DC-DC converter. Several other issues and design flaws were revealed in the failure analysis.
Description
The satellite bus was a rectangular prism assembled from an internal structure of metal panels an exterior covered with carbon fibre reinforced polymer lattice. The spacecraft mass was approximately .
The miniature control moment gyroscopes demonstrated in TSUBAME each had a rotating flywheel driven by a synchronous motor, and a single stepper motor, which controlled the gimbal. These control moment gyros were arranged in a pyramid. The flywheels were 7.35 cm in diameter and weighed 1 kg. In addition to the control moment gyros, a magnetorquer was also used for attitude control. Navigation and attitude determination used a number of sensors including six Sun sensors, a three-direction magnetometer, three MEMS gyroscopes, and two star trackers. A field-programmable gate array contained the software for the attitude determination and control systems.
TSUBAME had multiple communication systems to cope with the limitations of the radio equipment available on the ground. Similar to other satellites developed by the space systems laboratory at Tokyo Institute of Technology, TSUBAME had an FM band receiver and ultra high frequency transmitter which could communicate with the university's ground station. The UHF transmitter broadcast continuously after deployment so that amateur radio operators could assist in tracking the satellite. The volume of data that TSUBAME was expected to produce (on the order of tens of megabytes) could not be quickly broadcast by the radio transmitter, so an additional S-band transceiver was also included, even though an S-band antenna was not immediately available to the university; it was hoped that Fukui University of Technology would allow use of a 10m parabolic antenna after the launch. Poor design of the antennas on TSUBAME were found to be a likely cause of many of the failures that occurred on orbit. The first communication issues that were observed were attributed to interference from radio waves reflected off the solar panels. Subsequent failures were attributed to a failure of a DC-DC converter powering the communication systems.
Instruments
The primary science objective measuring polarization of gamma ray bursts required two instruments. The Wide-Field Burst Monitors (WBMs) were used to help detect and localize events so the spacecraft can be pointed in the correct direction, while the Hard X-ray Compton Polarimeter (HXCP) was designed to make observations once correctly oriented. There were five WBM units at diverse locations on the TSUBAME. Each WBM was a tile of caesium iodide scintillator. When an increase in the count rate was detected by one or more scintillators, the main processor would determine the direction, initiate control systems of the satellite. The HXCP could measure polarization for photons from 30 to 200 keV. It comprised tiles of plastic scintillator to scatter incident photons, photomultiplier tubes, and a second caesium iodide based scintillator used as an absorber. Each scintillator tile was attached to an avalanche photodiode, which converts photons to an electric signal. To mitigate background noise, the HXCP was surrounded by metal composite shielding, and coincidence between the two scintillating materials could be compared and processed by onboard computers. The optical camera was developed by the Tokyo University of Science. It had a ground resolution of 14 meters per pixel and could take up to five images each second.
References
Space telescopes
Satellites of Japan
Spacecraft launched in 2014
Microsatellites | TSUBAME (satellite) | Astronomy | 1,299 |
13,007,260 | https://en.wikipedia.org/wiki/Bis%28chloromethyl%29%20ether | Bis(chloromethyl) ether is an organic compound with the chemical formula (ClCH2)2O. It is a colourless liquid with an unpleasant suffocating odour and it is one of the chloroalkyl ethers. Bis(chloromethyl) ether was once produced on a large scale, but was found to be highly carcinogenic and thus such production has ceased.
Synthesis
It was produced industrially from paraformaldehyde and a mixture of chlorosulfonic acid and sulfuric acid. It is also produced as a byproduct in the Blanc chloromethylation reaction, formed when formaldehyde (the monomer, paraformaldehyde or formalin) and concentrated hydrochloric acid are mixed, and is a known impurity in technical grade chloromethyl methyl ether.
Because of their carcinogenic potency, the industrial production of chloromethyl ethers ended in most countries in the early 1980s. Bis(chloromethyl) ether was no exception to this with production in the U.S.A. ending in 1982.
Uses
Bis(chloromethyl) ether has been extensively used in chemical synthesis, primarily as a crosslinking agent in the manufacture of ion-exchange resins and in the textile industry. It was also used as a linker in the synthesis of certain nerve agent antidotes (asoxime chloride, obidoxime).
Bis(chloromethyl) was also effective for chloromethylation of aromatic substrates.
Safety
Bis(chloromethyl) ether is carcinogenic. It is one of 13 chemicals considered an OSHA-regulated occupational carcinogen. Chronic exposure has been linked to in increased risk of lung cancer.
It is classified as an extremely hazardous substance in the United States as defined in Section 302 of the U.S. Emergency Planning and Community Right-to-Know Act (42 U.S.C. 11002), and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities.
See also
Chloromethyl methyl ether - ClCH2OCH3
Bis(chloroethyl) ether - (ClCH2CH2)2O
References
IARC Group 1 carcinogens
Alkylating agents
Organochlorides
Ethers
Reagents for organic chemistry
Foul-smelling chemicals | Bis(chloromethyl) ether | Chemistry | 503 |
55,796,756 | https://en.wikipedia.org/wiki/Zwicky%20Transient%20Facility | The Zwicky Transient Facility (ZTF, obs. code: I41) is a wide-field sky astronomical survey using a new camera attached to the Samuel Oschin Telescope at Palomar Observatory in San Diego County, California, United States. Commissioned in 2018, it supersedes the (Intermediate) Palomar Transient Factory (2009–2017) that used the same observatory code. It is named after the Swiss astronomer Fritz Zwicky.
Description
Observing in visible and infrared wavelengths, the Zwicky Transient Facility is designed to detect transient objects that rapidly change in brightness, for example supernovae, gamma ray bursts, and collision between two neutron stars, and moving objects like comets and asteroids.
The new camera is made of 16 CCDs of 6144×6160 pixels each, enabling each exposure to cover an area of 47 square degrees. The Zwicky Transient Facility is designed to image the entire northern sky in three nights and scan the plane of the Milky Way twice each night to a limiting magnitude of 20.5 (r band, 5σ).
The amount of data produced by ZTF is expected to be ten times larger than its predecessor, the Intermediate Palomar Transient Factory. ZTF's large data will allow it to act as a prototype for the Vera C. Rubin Observatory (formerly Large Synoptic Survey Telescope) that is expected to be in full operation in 2024 and will accumulate ten times more data than ZTF.
First light was recorded of an area in the constellation Orion on November 1, 2017.
The first confirmed findings from the ZTF project were reported on 7 February 2018, with the discovery of 2018 CL, a small near-Earth asteroid.
Discoveries
On 9 May 2019, ZTF discovered its first comet, C/2019 J2 (Palomar), a long-period comet.
A search of the ZTF's archive identified images of the interstellar comet 2I/Borisov as early as December 13, 2018, extending observations back eight months.
594913 ꞌAylóꞌchaxnim, the first asteroid discovered whose orbit is entirely within the orbit of Venus, was discovered by ZTF during its Twilight Survey.
A search from ZTF's images identified Cataclysmic variable, ZTF J1813+4251 a binary with a period of under 1 hour.
AT2021lwx, a long-lasting high-energy transient with a redshift of 0.9945, was discovered on 13 April 2021.
A very bright tidal disruption event called AT2022cmc with a redshift of 1.19325, among the brightest astronomical events ever observed.
Comet C/2022 E3 (ZTF), which reached naked eye visibility in early 2023
See also
OGLE survey
GOTO (telescope array)
References
Astronomical surveys
Palomar Observatory | Zwicky Transient Facility | Astronomy | 573 |
26,179,180 | https://en.wikipedia.org/wiki/Activated%20sludge%20model | Activated sludge model is a generic name for a group of mathematical methods to model activated sludge systems. The research in this area is coordinated by a task group of the International Water Association (IWA). Activated sludge models are used in scientific research to study biological processes in hypothetical systems. They can also be applied on full scale wastewater treatment plants for optimisation, when carefully calibrated with reference data for sludge production and nutrients in the effluent.
Around 1983 a task group of the International Association on Water Quality (one of the associations that formed IWA) was formed. They started creating on a generalised framework for mathematical models that could be used to model activated sludge for nitrogen removal. One of the main goals was to develop a model of which the complexity was as low as possible and simple to represent, though still able to accurately predict the biological processes. After four years, the first IAWQ model, named ASM1 was ready and incorporated a basic model taking into account chemical oxygen demand (COD), bacterial growth, and biomass degradation.
An activated sludge model consists of:
state variables: these include the different fractions of COD, biomass and different types of nutrients, both organic and inorganic
a description of the dynamic processes: lists the different biological processes that are modelled, together with their formulae
parameters: variables that describe the circumstances of the biological system, such as growth and decay rate, half-saturation coefficient for hydrolysis, etc.
History
Before work on ASM1 started in 1983, there were already some 15 years of experience in activated sludge modelling, although every research group that worked on mathematical systems of activated sludge created its own model framework, incompatible to all others. ASM1 therefore catalysed the research and had a major impact on activated sludge modelling.
ASM1 was the foundation for numerous extensions. These extensions include for example better prediction of nitrogen and phosphorus removal. Widely used extended models include ASM2, ASM2d, and ASM3P. At the time of publication of the ASM1 model, biological phosphorus removal was already used although this process was not completely understood at that time. Basic knowledge of phosphorus removing bacteria was included in the ASM1 model and parameters were adjusted accordingly. Hence after 8 years, ASM2 was published in 1995.
ASM1 does not include the role of phosphorus accumulating organisms nor the relationship between biological phosphorus removal and removal of nitrogen. An enhanced version of ASM1, simply named ASM2, was developed to include biological and chemical phosphorus removal. As scientific understanding grew in the late 1990s, ASM2 was extended into ASM2d, principally by the addition of anoxic as well as aerobic uptake of phosphorus.
Availability
The IWA activated sludge models are commonly used in existing programs. The most common are Biowin, GPS-X, WEST, STOAT, SIMBA#, SUMO, and ASIM. In addition there are Matlab implementations, Fortran code in the COST 682 Benchmarking report, and Modelica code in the Modelica WasteWater library.
See also
Activated sludge
Bacterial growth
Membrane bioreactors
Michaelis-Menten kinetics
Monod equation
References
External links
Various PhD theses on modelling activated sludge systems
Detailed algorithms for ASM1 and Takacs settling tank model
Sewerage | Activated sludge model | Chemistry,Engineering,Environmental_science | 686 |
71,865,156 | https://en.wikipedia.org/wiki/Gaia%20BH1 | Gaia BH1 (Gaia DR3 4373465352415301632) is a binary system consisting of a G-type main-sequence star and a likely stellar-mass black hole, located about away from the Solar System in the constellation of Ophiuchus. , it is the nearest known system that astronomers are reasonably confident contains a black hole, followed by Gaia BH3, Gaia BH2 and A0620-00.
Characteristics
The star and black hole orbit each other with a period of 185.59 days and an eccentricity of 0.45. The star is similar to the Sun, with about and , and a temperature of about , while the black hole has a mass of about . Given this mass, the black hole's Schwarzschild radius should be about .
Discovery
Gaia BH1 was discovered in 2022 via astrometric observations with Gaia, and also observed via radial velocity. The discovery team found no astrophysical scenario that could explain the observed motion of the G-type star, other than a black hole. The system differs from "black hole impostors" such as LB-1 and HR 6819 in that the evidence for a black hole does not depend on the mass of the star or the inclination of the orbit, and there is no evidence of mass transfer. The discovery team also found a second system that is a candidate for containing a black hole, which was also reported by another team of astronomers, and was confirmed in 2023 as Gaia BH2.
The black hole was also independently detected by a second team, who found slightly different parameters.
See also
GRS 1915+105
OGLE-2011-BLG-0462
VFTS 243
References
Ophiuchus
G-type main-sequence stars
Stellar black holes
Astrometric binaries
20220914 | Gaia BH1 | Physics,Astronomy | 383 |
31,868,890 | https://en.wikipedia.org/wiki/Profile%20diagram | In Unified Modeling Language
in the field of software engineering,
a profile diagram
operates at the metamodel level to show stereotypes as classes with the «stereotype» stereotype, and profiles as packages with the «profile» stereotype. The extension relation (solid line with closed, filled arrowhead) indicates what metamodel element a given stereotype is extending.
History
The profile diagram did not exist in UML 1.
Other diagrams had been used to display this issue.
It was introduced with UML 2 to display the usage of profiles.
See also
UML diagrams
References
External links
Christoph Kecher: "UML 2.0 - Das umfassende Handbuch" Galileo Computing, 2006,
Unified Modeling Language diagrams
Systems Modeling Language | Profile diagram | Engineering | 150 |
710,045 | https://en.wikipedia.org/wiki/Pulsed%20laser%20deposition | Pulsed laser deposition (PLD) is a physical vapor deposition (PVD) technique where a high-power pulsed laser beam is focused inside a vacuum chamber to strike a target of the material that is to be deposited. This material is vaporized from the target (in a plasma plume) which deposits it as a thin film on a substrate (such as a silicon wafer facing the target). This process can occur in ultra high vacuum or in the presence of a background gas, such as oxygen which is commonly used when depositing oxides to fully oxygenate the deposited films.
While the basic setup is simple relative to many other deposition techniques, the physical phenomena of laser-target interaction and film growth are quite complex (see Process below). When the laser pulse is absorbed by the target, energy is first converted to electronic excitation and then into thermal, chemical and mechanical energy resulting in evaporation, ablation, plasma formation and even exfoliation. The ejected species expand into the surrounding vacuum in the form of a plume containing many energetic species including atoms, molecules, electrons, ions, clusters, particulates and molten globules, before depositing on the typically hot substrate.
Process
The detailed mechanisms of PLD are very complex including the ablation process of the target material by the laser irradiation, the development of a plasma plume with high energetic ions, electrons as well as neutrals and the crystalline growth of the film itself on the heated substrate. The process of PLD can generally be divided into four stages:
Laser absorption on the target surface and laser ablation of the target material and creation of a plasma
Dynamic of the plasma
Deposition of the ablation material on the substrate
Nucleation and growth of the film on the substrate surface
Each of these steps is crucial for the crystallinity, uniformity and stoichiometry of the resulting film.
Laser ablation of the target material and creation of a plasma
The ablation of the target material upon laser irradiation and the creation of plasma are very complex processes. The removal of atoms from the bulk material is done by vaporization of the bulk at the surface region in a state of non-equilibrium. In this the incident laser pulse penetrates into the surface of the material within the penetration depth. This dimension is dependent on the laser wavelength and the index of refraction of the target material at the applied laser wavelength and is typically in the region of 10 nm for most materials. The strong electrical field generated by the laser light is sufficiently strong to remove the electrons from the bulk material of the penetrated volume. This process occurs within 10 ps of a ns laser pulse and is caused by non-linear processes such as multiphoton ionization which are enhanced by microscopic cracks at the surface, voids, and nodules, which increase the electric field. The free electrons oscillate within the electromagnetic field of the laser light and can collide with the atoms of the bulk material thus transferring some of their energy to the lattice of the target material within the surface region. The surface of the target is then heated up and the material is vaporized.
Dynamic of the plasma
In the second stage the material expands in a plasma parallel to the normal vector of the target surface towards the substrate due to Coulomb repulsion and recoil from the target surface. The spatial distribution of the plume is dependent on the background pressure inside the PLD chamber. The density of the plume can be described by a cosn(x) law with a shape similar to a Gaussian curve. The dependency of the plume shape on the pressure can be described in three stages:
The vacuum stage, where the plume is very narrow and forward directed; almost no scattering occurs with the background gases.
The intermediate region where a splitting of the high energetic ions from the less energetic species can be observed. The time-of-flight (TOF) data can be fitted to a shock wave model; however, other models could also be possible.
High pressure region where we find a more diffusion-like expansion of the ablated material. Naturally this scattering is also dependent on the mass of the background gas and can influence the stoichiometry of the deposited film.
The most important consequence of increasing the background pressure is the slowing down of the high energetic species in the expanding plasma plume. It has been shown that particles with kinetic energies around 50 eV can resputter the film already deposited on the substrate. This results in a lower deposition rate and can furthermore result in a change in the stoichiometry of the film.
Deposition of the ablation material on the substrate
The third stage is important to determine the quality of the deposited films. The high energetic species ablated from the target are bombarding the substrate surface and may cause damage to the surface by sputtering off atoms from the surface but also by causing defect formation in the deposited film. The sputtered species from the substrate and the particles emitted from the target form a collision region, which serves as a source for condensation of particles. When the condensation rate is high enough, a thermal equilibrium can be reached and the film grows on the substrate surface at the expense of the direct flow of ablation particles and the thermal equilibrium obtained.
Nucleation and growth of the film on the substrate surface
The nucleation process and growth kinetics of the film depend on several growth parameters including:
Laser parameters – several factors such as the laser fluence [Joule/cm2], laser energy, and ionization degree of the ablated material will affect the film quality, the stoichiometry, and the deposition flux. Generally, the nucleation density increases when the deposition flux is increased.
Surface temperature – The surface temperature has a large effect on the nucleation density. Generally, the nucleation density decreases as the temperature is increased. Heating of the surface can involve a heating plate or the use of a CO2 laser.
Substrate surface – The nucleation and growth can be affected by the surface preparation (such as chemical etching), the miscut of the substrate, as well as the roughness of the substrate.
Background pressure – Common in oxide deposition, an oxygen background is needed to ensure stoichiometric transfer from the target to the film. If, for example, the oxygen background is too low, the film will grow off stoichiometry which will affect the nucleation density and film quality.
In PLD, a large supersaturation occurs on the substrate during the pulse duration. The pulse lasts around 10–40 microseconds depending on the laser parameters. This high supersaturation causes a very large nucleation density on the surface as compared to molecular beam epitaxy or sputtering deposition. This nucleation density increases the smoothness of the deposited film.
In PLD, [depending on the deposition parameters above] three growth modes are possible:
Step-flow growth – All substrates have a miscut associated with the crystal. These miscuts give rise to atomic steps on the surface. In step-flow growth, atoms land on the surface and diffuse to a step edge before they have a chance to nucleated a surface island. The growing surface is viewed as steps traveling across the surface. This growth mode is obtained by deposition on a high miscut substrate, or depositing at elevated temperatures
Layer-by-layer growth – In this growth mode, islands nucleate on the surface until a critical island density is reached. As more material is added, the islands continue to grow until the islands begin to run into each other. This is known as coalescence. Once coalescence is reached, the surface has a large density of pits. When additional material is added to the surface the atoms diffuse into these pits to complete the layer. This process is repeated for each subsequent layer.
3D growth – This mode is similar to the layer-by-layer growth, except that once an island is formed an additional island will nucleate on top of the 1st island. Therefore, the growth does not persist in a layer by layer fashion, and the surface roughens each time material is added.
History
Pulsed laser deposition is only one of many thin film deposition techniques. Other methods include molecular beam epitaxy (MBE), chemical vapor deposition (CVD), sputter deposition (RF, magnetron, and ion beam). The history of laser-assisted film growth started soon after the technical realization of the first laser in 1960 by Maiman. Smith and Turner utilized a ruby laser to deposit the first thin films in 1965, three years after Breech and Cross studied the laser-vaporization and excitation of atoms from solid surfaces. However, the deposited films were still inferior to those obtained by other techniques such as chemical vapor deposition and molecular beam epitaxy. In the early 1980s, a few research groups (mainly in the former USSR) achieved remarkable results on manufacturing of thin film structures utilizing laser technology. The breakthrough came in 1987 when D. Dijkkamp, Xindi Wu and T. Venkatesan were able to laser deposit a thin film of YBa2Cu3O7, a high temperature superconductive material, which was of superior quality to that of films deposited with alternative techniques. Since then, the technique of pulsed laser deposition has been utilized to fabricate high quality crystalline films, such as doped garnet thin films for use as planar waveguide lasers. The deposition of ceramic oxides, nitride films, ferromagnetic films, metallic multilayers and various superlattices has been demonstrated. In the 1990s the development of new laser technology, such as lasers with high repetition rate and short pulse durations, made PLD a very competitive tool for the growth of thin, well defined films with complex stoichiometry.
Technical aspects
There are many different arrangements to build a deposition chamber for PLD. The target material which is evaporated by the laser is normally found as a rotating disc attached to a support. However, it can also be sintered into a cylindrical rod with rotational motion and a translational up and down movement along its axis. This special configuration allows not only the utilization of a synchronized reactive gas pulse but also of a multicomponent target rod with which films of different multilayers can be created.
Some factors that influence the deposition rate:
Target material
Pulse energy of laser
Repetition rate of the laser
Temperature of the substrate
Distance from target to substrate
Type of gas and pressure in chamber (oxygen, argon, etc.)
References
External links
Introduction to Pulsed Laser Deposition Introduction to Pulsed laser deposition
Laser-MBE: Pulsed Laser Deposition under Ultra-High Vacuum
A Brief Overview of Pulse Laser Deposition System
Physical vapor deposition techniques
Semiconductor device fabrication
Thin film deposition
Laser machining
Laser applications | Pulsed laser deposition | Chemistry,Materials_science,Mathematics | 2,196 |
1,121,231 | https://en.wikipedia.org/wiki/Electronic%20bill%20payment | Electronic bill payment is a feature of online, mobile and telephone banking, similar in its effect to a giro, allowing a customer of a financial institution to transfer money from their transaction or credit card account to a creditor or vendor such as a public utility, department store or an individual to be credited against a specific account. These payments are typically executed electronically as a direct deposit through a national payment system, operated by the banks or in conjunction with the government. Payment is typically initiated by the payer but can also be set up as a direct debit.
In addition to the bill payment facility, most banks will also offer various features with their electronic bill payment systems. These include the ability to schedule payments in advance to be made on a specified date (convenient for installments such as mortgage and support payments), to save the biller information for reuse at a future time and various options for searching the recent payment history. In many cases the payment data can also be downloaded and posted directly into the customer's accounting or personal finance software.
History
Although this technology was available from the mid 1990s, uptake was initially slow until internet access by households increased. By 2000, adoption of electronic bill payment systems started to dramatically increase.
Impact
From the consumer's point of view, electronic payment of bills is cheaper, faster, and more convenient than writing, posting and reconciling cheques. In addition, though limitations exist, a wider range of bank accounts or credit cards can be used for the electronic payment of bills. Paying bills online allows you to use a variety of payment methods rather than the traditional cheque.
Using electronic bill presentment and payment enables businesses to fast-track customer payments and get access to funds faster, which in turn results in cash flow improvement.
For banks the advantages of electronic bill payments are a reduction in processing costs minimizing paperwork and an increase in customer loyalty. In a 2003 study, the banks said that "customers who pay online show more loyalty and are more receptive to other offers".
Bill pay in the USA
In the United States, most banks and credit unions offer a free service typically called "bill pay." The banking customer logs into their online bank account, and submits a bill pay request, inputting all information that would be found on a physical check. Their bank will then pay the recipient electronically if they are connected to the system. Utilities are likely to be set up to receive bill pay electronically. Many recipients aren't, so for these recipients, the bank cuts a physical check, puts the check in a stamped and addressed envelope, puts the envelope in the mail, and then sends the check to the intended recipient. The recipient then deposits the check with their bank as usual.
See also
Direct credit
E-commerce payment system
E-commerce
Electronic billing
Digital wallet
Digital economy
Mobile banking
Online shopping
Unified Payments Interface
References
Payment systems
Banking technology
E-commerce
Electronics industry
Supply chain management | Electronic bill payment | Technology | 591 |
61,464,897 | https://en.wikipedia.org/wiki/PK-4%20%28ISS%20experiment%29 | The PK-4 or (Plasmakristall-4) laboratory is a joint Russian-European laboratory for the investigation of dusty/complex plasmas on board the International Space Station (ISS), with the principal investigators at the Institute of Materials Science at the German Aerospace Center (DLR) and the Russian Institute for High Energy Densities of the Russian Academy of Sciences. It is the third laboratory on board the ISS to study complex plasmas, after the PKE Nefedov and PK-3 Plus experiments. In contrast to the previous setups, the geometry was significantly changed and is more suited to study flowing complex plasmas.
Technical description
The heart of the PK-4 laboratory consists of a direct current (DC) discharge tube. A plasma is generated by applying an electric field between an anode and a cathode. Microparticles are then injected into the plasma and move through the tube into the working area where their motion is recorded with two cameras, the images of which are joined for analysis. The movement of the microparticles inside the fields of view of the cameras is followed by experimenters. The polarity of this electric field can be switched at a high frequency, so that the microparticles can be trapped in the working area.
A variety of manipulation techniques are available, for instance a manipulation laser that can produce shear flow, and a thermal manipulator which can trap microparticles with a thermal gradient. The optical observation of the microparticles is complemented by other diagnostics methods: a spectrometer and a glow camera that records the plasma glow in several spectral lines.
Scientific goals
As its predecessors, PK-4 Plus studies complex plasmas, which are low temperature plasmas that contain highly charged microparticles. The microparticles interact with each other and with the plasma and can be used to study a variety of topics, for instance waves, the influence of microparticles on the plasma, string formation, and shear flow.
External links
Forschungsgruppe komplexe Plasmen - DLR Oberpfaffenhofen
References
Plasma physics facilities
Science facilities on the International Space Station
International Space Station experiments | PK-4 (ISS experiment) | Physics | 452 |
54,140,642 | https://en.wikipedia.org/wiki/Perseus%E2%80%93Pegasus%20Filament | The Perseus–Pegasus Filament is a galaxy filament containing the Perseus–Pisces Supercluster and stretching for roughly a billion light-years (or over 300/h Mpc). Currently, it is considered to be one of the largest known structures in the universe. This filament is adjacent to the Pisces–Cetus Supercluster Complex.
Discovery
The Perseus–Pegasus Filament was discovered by David Batuski and Jack Burns of New Mexico State University in 1985.
It is likely that Clyde W. Tombaugh, of the Lowell Observatory, discovered its existence in 1936 while conducting his search for trans-Saturnian planets. He reported it as the Great Perseus-Andromeda stratum of Extra-Galactic Nebulae. Earlier still, parts of this clustering had been reported by .
See also
Abell catalogue
Large-scale structure of the universe
Galaxy filament
Supercluster
Big Ring
Notes
References
Galaxy filaments
Large-scale structure of the cosmos
Astronomical objects discovered in 1985 | Perseus–Pegasus Filament | Astronomy | 222 |
32,590,088 | https://en.wikipedia.org/wiki/Young-Tae%20Chang | Young-Tae Chang (born 1968) is a South Korean chemist. He is a professor of chemistry at Pohang University of Science and Technology (POSTECH) and Associate Director under Kim Kimoon at the Center for Self-assembly and Complexity at the Institute for Basic Science located on the POSTECH campus.
Young-Tae Chang was born in Busan, South Korea in 1968. He obtained a Bachelor of Science degree in chemistry from POSTECH, working on the divergent synthesis of all regioisomers of myo-inositol phosphates, under guide of Prof. Sung-Kee Chung. Doctoral requirements at POSTECH require a student study at least three years, but Young-Tae finished in two, requiring his advisor to appeal for a revision of the rules which allowed him to receive his doctorate in February 1997. He then engaged in postdoctoral research in the laboratory of Prof. Peter G. Schultz at University of California, Berkeley and Scripps Research in 2000.
He was appointed assistant professor at New York University (NYU) and promoted to associated professor in 2005. In September 2007, he moved to the National University of
Singapore and the Singapore Bioimaging Consortium at Biopolis. From 2017, he is a Full Professor in the Department of Chemistry, POSTECH and head of the Laboratory of Bioimaging Probe Development at SBIC. He pioneered diversity-oriented fluorescence library approach (DOFLA), and developed embryonic stem cell probe CDy1, neuronal stem cell probe CDr3, and neron specific probe, NeuO. He also developed a method for background-free live cell imaging with tamed fluorescent probe.
He is an editorial board member of MedChemComm and RSC Advances, Royal Society of Chemistry, and American Journal of Nuclear Medicine and Molecular Imaging. He has published more than 300 scientific papers and 3 books resulting in more than 22,000 citations. Additionally, he has filed more than 50 patents.
Honors and awards
2023: Yoshida Prize, International Organic Chemistry Foundation
2022: Sang-Chul Shim Academic Award, Korean Chemical Society
2007: NUS Young Investigator Award
2005: Career Award, National Science Foundation
References
External links
Professor CHANG Young-Tae, POSTECH
Associate Director - Center for Self-assembly and Complexity
Young-Tae Chang - Google Scholar
Living people
1968 births
Institute for Basic Science
Academic staff of the National University of Singapore
South Korean organic chemists
Pohang University of Science and Technology alumni
Academic staff of Pohang University of Science and Technology | Young-Tae Chang | Chemistry | 509 |
648,845 | https://en.wikipedia.org/wiki/Valdecoxib | Valdecoxib is a nonsteroidal anti-inflammatory drug (NSAID) used in the treatment of osteoarthritis, rheumatoid arthritis, and painful menstruation and menstrual symptoms. It is a selective cyclooxygenase-2 inhibitor. It was patented in 1995.
Valdecoxib was manufactured and marketed under the brand name Bextra by G. D. Searle & Company as an anti-inflammatory arthritis drug. It was approved by the United States Food and Drug Administration (FDA) on November 20, 2001, to treat arthritis and menstrual cramps, and was available by prescription in tablet form until 2005 when the FDA requested that Pfizer withdraw Bextra from the American market. The FDA cited "potential increased risk for serious cardiovascular (CV) adverse events," an "increased risk of serious skin reactions" and the "fact that Bextra has not been shown to offer any unique advantages over the other available NSAIDs."
In 2009, Bextra was at the center of the "largest health-care fraud settlement and the largest criminal fine of any kind ever." Pfizer paid a $2.3 billion civil and criminal fine. Pharmacia & Upjohn, a Pfizer subsidiary, violated the United States Food, Drug and Cosmetic Act for misbranding Bextra "with the intent to defraud or mislead."
A water-soluble and injectable prodrug of valdecoxib, parecoxib, is marketed in the European Union under the tradename Dynastat.
Uses until 2005
In the United States, the FDA approved valdecoxib for the treatment of osteoarthritis, adult rheumatoid arthritis, and primary dysmenorrhea.
Valdecoxib was also used off-label for controlling acute pain and various types of surgical pain.
Side effects and withdrawal from market
On April 7, 2005, Pfizer withdrew Bextra from the U.S. market on recommendation by the FDA, citing an increased risk of heart attack and stroke and also the risk of a serious, sometimes fatal, skin reaction. This was a result of recent attention to prescription NSAIDs, such as Merck's Vioxx. Other reported side effects were angina and Stevens–Johnson syndrome.
Pfizer first acknowledged cardiovascular risks associated with Bextra in October 2004. The American Heart Association soon after was presented with a report indicating patients using Bextra while recovering from heart surgery were 2.19 times more likely to suffer a stroke or heart attack than those taking placebos.
In a large study published in The Journal of the American Medical Association in 2006, valdecoxib appeared less adverse for renal (kidney) disease and heart arrhythmia compared to Vioxx, but elevated renal risks were slightly suggested.
2009 settlement for off-label uses promotions
On September 2, 2009, the United States Department of Justice fined Pfizer $2.3 billion after one of its subsidiaries, Pharmacia & Upjohn Company, pleaded guilty to marketing four drugs, including Bextra, "with the intent to defraud or mislead." Pharmacia & Upjohn admitted to criminal conduct in the promotion of Bextra, and agreed to pay the largest criminal fine ever imposed in the United States for any matter, $1.195 billion. A former Pfizer district sales manager was indicted and sentenced to home confinement for destroying documents regarding the illegal promotion of Bextra. In addition, a regional manager pleaded guilty to distribution of a misbranded product, and was fined $75,000 and 24 months on probation.
The remaining $1 billion of the fine were paid to resolve allegations under the civil False Claims Act case and is the largest civil fraud settlement against a pharmaceutical company. Six whistleblowers were awarded more than $102 million for their role in the investigation. Former Pfizer sales representative John Kopchinski acted as a qui tam relator and filed a complaint in 2004 outlining the illegal conduct in the marketing of Bextra. Kopchinski was awarded $51.5 million for his role in the case because the improper marketing of Bextra was the largest piece of the settlement at $1.8 billion.
Analytical methods
Several HPLC-UV methods have been reported for valdecoxib estimation in biological samples like human urine. Valdecoxib has analytical methods for bioequivalence studies, metabolite determination, estimation of formulation, and an HPTLC method for simultaneous estimation in tablet dosage form.
See also
Discovery and development of cyclooxygenase 2 inhibitors
Parecoxib
Apricoxib
References
External links
FDA Alert on Bextra withdrawal
Large systematic review of adverse renal and arrhythmia risk of valdcoxib and other COX-2 inhibitors, JAMA 2006
Dermatoxins
Nonsteroidal anti-inflammatory drugs
Withdrawn drugs
Isoxazoles
Drugs developed by Pfizer
COX-2 inhibitors
Sulfonamides | Valdecoxib | Chemistry | 1,064 |
22,853,958 | https://en.wikipedia.org/wiki/GridCase | GridCase (stylized as GRiDCASE) is a line of rugged tablets and laptops by Grid Systems Corporation released as a successor of the GRiD Compass line. The first model was released in 1985.
Models
Former line
GRiDCASE 2
1985; low-contrast LCD screen with green background (instead of orange/yellow plasma screen with black background on a Compass laptops).
This model was based on a MSDOS 2.11 and a bunch of apps burned on ROM that fit in the ROM tray in front.
GRiDCASE 3
1986; returning to a plasma screens (but with red/orange text color and wide aspect ratio). The internal power supply can be ejected and a battery-pack is installed in its place.
3D view: http://vintage-laptops.com/en/grid-case-3
GRiDCASE 3 Tempest
1986; the rugged version of GRiDCASE 3 with electromagnetic protection.
3D view: http://vintage-laptops.com/en/grid-case-tempest
GRiDCASE 1520
1988; can be equipped with plasma or LCD screen.
Was based on a 286 CPU.
3D view: http://vintage-laptops.com/en/grid-case-1520
GRiDCASE 1530
Source:
The modification of 1530 – the Grid GRiDCASE 1535EXP is a rugged laptop with a 80386 CPU, an optional 80387 floating-point processor and up to 8 Mbyte of DRAM. It was first flown into space in December 1992 on the STS-53 for use of the HERCULES geolocation device. The 1535EXP was also the first rugged portable PC to attain full TEMPEST accreditation from the NSA.
Another modification – the Grid GRiDCASE 1537EXP – has another screen (640×480 instead of 640×400, but with less physical size).
The power input is 100–240 V AC 50/60/400 Hz, 80 W. The 400 Hz utility frequency is common on airplanes and submarines.
3D view: http://vintage-laptops.com/en/grid-case-1537e
GRiDCASE 1550
1990; This model has an integrated pointing device, and was based on an Intel 80386sx processor.
The 1550sx version has 4 MB RAM, a 100 MB hard disk, a 1.44 MB floppy drive, a hardly visible B/W VGA-LCD screen, a built in 2400 bps modem and weights 5.5 kg (12 lbs.) without battery or power supply.
3D view: http://vintage-laptops.com/en/grid-case-1550sx
Tandy GRiD laptops
In the period from 1990–1994, the Tandy Corporation together with GRiD Systems Corporation produced the following models:
GRiD 1450SX – 3D view: http://vintage-laptops.com/en/grid-1450sx
GRiD 1810 – 3D view: http://vintage-laptops.com/en/grid-1810
GRiD 1660 and 1660C – 3D view: http://vintage-laptops.com/en/grid-1660
GRiD 1680 and 1680C – 3D view: http://vintage-laptops.com/en/grid-1680
GRiD 1720, 1750, 1755 – 3D view: http://vintage-laptops.com/en/grid-1755
GRiD 4025N and 4025NC – 3D view: http://vintage-laptops.com/en/grid-4025nc
GRiD Defence Systems GRiDCASE
Reintroduced in 1995 line.
GRiDCASE 1580
There is also a Tempest version of this model (1580T).
Pentium and pointing stick (initial model, 1995) or Pentium II and touchpad (1580 XGA, 1998).
3D view: http://vintage-laptops.com/en/grid-case-1580
3D view: http://vintage-laptops.com/en/grid-case-1580-tempest
3D view: https://vintage-laptops.com/en/grid-case-1580-XGA
GRiDCASE 1590
GRiDCASE 1510
See also
GridPad
Grid SE-T
Grid Lite
References
Grid Systems laptops
Computer-related introductions in 1985
Early laptops | GridCase | Technology | 876 |
16,855,056 | https://en.wikipedia.org/wiki/Mitochondrial%20ribosomal%20protein%20L17 | 39S ribosomal protein L17, mitochondrial is a protein that in humans is encoded by the MRPL17 gene.
Mammalian mitochondrial ribosomal proteins are encoded by nuclear genes and help in protein synthesis within the mitochondrion. Mitochondrial ribosomes (mitoribosomes) consist of a small 28S subunit and a large 39S subunit. They have an estimated 75% protein to rRNA composition compared to prokaryotic ribosomes, where this ratio is reversed. Another difference between mammalian mitoribosomes and prokaryotic ribosomes is that the latter contain a 5S rRNA. Among different species, the proteins comprising the mitoribosome differ greatly in sequence, and sometimes in biochemical properties, which prevents easy recognition by sequence homology. This gene encodes a 39S subunit protein.
References
Further reading
External links
Ribosomal proteins | Mitochondrial ribosomal protein L17 | Chemistry | 179 |
29,573,866 | https://en.wikipedia.org/wiki/SkillSlate | SkillSlate or SkillSlate.com was a New York City-based firm that matched individual service providers with customers via the Internet. The firm raised $1.1 million in capital in October 2010 with investments from Canaan Partners and First Round Capital.
SkillSlate helped small individual service providers, such as dog walkers, DJs, handymen, tutors and movers, market themselves on the web. According to a website description, SkillSlate helps the pages of service providers surface more prominently in search engine results. SkillSlate served the New York metropolitan area. Competitors included Craigslist, Geotoko, FoundTown, Closely, Proposable, Resource Nation, Flowtown, Buzzuka, Spoke, GoBuzz, Traindom, Hooray, Thumbtack, and others, as well as classified advertising in newspapers. According to Fortune Magazine, the idea for the site was conceived by venture capitalist Barkek Ringwelski while working at Canaan Partners when he found he could not find a cleaning person; he raised $50,000 from family and friends in May 2009 and launched the firm.
The company was acquired by TaskRabbit in early 2012.
References
External links
SkillSlate website
Online retailers of the United States
Companies based in New York City
Defunct online companies of the United States
Internet properties established in 2009
Business services companies established in 2009
Business services companies disestablished in 2012
Internet properties disestablished in 2012
2012 mergers and acquisitions
2009 establishments in New York City
2012 disestablishments in New York (state) | SkillSlate | Technology | 312 |
35,194,136 | https://en.wikipedia.org/wiki/Tate%27s%20isogeny%20theorem | In mathematics, Tate's isogeny theorem, proved by , states that two abelian varieties over a finite field are isogeneous if and only if their Tate modules are isomorphic (as Galois representations).
References
Abelian varieties
Theorems in algebraic geometry | Tate's isogeny theorem | Mathematics | 55 |
75,362,149 | https://en.wikipedia.org/wiki/Nitrolite | Nitrolite is an older form of powdery high explosive with an ammonium nitrate base, mixed with a smaller amount of TNT and nitroglycerin etc. It is used for mining, construction as well as military purposes. During World War II it came to be a budget replacement for more expensive TNT.
References
Explosives
Explosive chemicals | Nitrolite | Chemistry | 69 |
11,552,879 | https://en.wikipedia.org/wiki/Leptosphaeria%20acuta | Leptosphaeria acuta (also known as nettle rash) is a plant pathogen found on the dead stems of common nettle (Urtica dioica).
References
Pleosporales
Fungi described in 1818
Fungi of Europe
Fungal plant pathogens and diseases
Fungus species | Leptosphaeria acuta | Biology | 59 |
5,320 | https://en.wikipedia.org/wiki/Carbon%20nanotube | A carbon nanotube (CNT) is a tube made of carbon with a diameter in the nanometre range (nanoscale). They are one of the allotropes of carbon. Two broad classes of carbon nanotubes are recognized:
Single-walled carbon nanotubes (SWCNTs) have diameters around 0.5–2.0 nanometres, about 100,000 times smaller than the width of a human hair. They can be idealised as cutouts from a two-dimensional graphene sheet rolled up to form a hollow cylinder.
Multi-walled carbon nanotubes (MWCNTs) consist of nested single-wall carbon nanotubes in a nested, tube-in-tube structure. Double- and triple-walled carbon nanotubes are special cases of MWCNT.
Carbon nanotubes can exhibit remarkable properties, such as exceptional tensile strength and thermal conductivity because of their nanostructure and strength of the bonds between carbon atoms. Some SWCNT structures exhibit high electrical conductivity while others are semiconductors. In addition, carbon nanotubes can be chemically modified. These properties are expected to be valuable in many areas of technology, such as electronics, optics, composite materials (replacing or complementing carbon fibres), nanotechnology (including nanomedicine), and other applications of materials science.
The predicted properties for SWCNTs were tantalising, but a path to synthesising them was lacking until 1993, when Iijima and Ichihashi at NEC, and Bethune and others at IBM independently discovered that co-vaporising carbon and transition metals such as iron and cobalt could specifically catalyse SWCNT formation. These discoveries triggered research that succeeded in greatly increasing the efficiency of the catalytic production technique, and led to an explosion of work to characterise and find applications for SWCNTs.
History
The true identity of the discoverers of carbon nanotubes is a subject of some controversy. A 2006 editorial written by Marc Monthioux and Vladimir Kuznetsov in the journal Carbon described the origin of the carbon nanotube. A large percentage of academic and popular literature attributes the discovery of hollow, nanometre-size tubes composed of graphitic carbon to Sumio Iijima of NEC in 1991. His paper initiated a flurry of excitement and could be credited with inspiring the many scientists now studying applications of carbon nanotubes. Though Iijima has been given much of the credit for discovering carbon nanotubes, it turns out that the timeline of carbon nanotubes goes back much further than 1991.
In 1952, L. V. Radushkevich and V. M. Lukyanovich published clear images of 50-nanometre diameter tubes made of carbon in the Journal of Physical Chemistry Of Russia. This discovery was largely unnoticed, as the article was published in Russian, and Western scientists' access to Soviet press was limited during the Cold War. Monthioux and Kuznetsov mentioned in their Carbon editorial:
In 1976, Morinobu Endo of CNRS observed hollow tubes of rolled up graphite sheets synthesised by a chemical vapour-growth technique. The first specimens observed would later come to be known as single-walled carbon nanotubes (SWNTs). Endo, in his early review of vapor-phase-grown carbon fibers (VPCF), also reminded us that he had observed a hollow tube, linearly extended with parallel carbon layer faces near the fiber core. This appears to be the observation of multi-walled carbon nanotubes at the center of the fiber. The mass-produced MWCNTs today are strongly related to the VPGCF developed by Endo. In fact, they call it the "Endo-process", out of respect for his early work and patents. In 1979, John Abrahamson presented evidence of carbon nanotubes at the 14th Biennial Conference of Carbon at Pennsylvania State University. The conference paper described carbon nanotubes as carbon fibers that were produced on carbon anodes during arc discharge. A characterization of these fibers was given, as well as hypotheses for their growth in a nitrogen atmosphere at low pressures.
In 1981, a group of Soviet scientists published the results of chemical and structural characterization of carbon nanoparticles produced by a thermocatalytic disproportionation of carbon monoxide. Using TEM images and XRD patterns, the authors suggested that their "carbon multi-layer tubular crystals" were formed by rolling graphene layers into cylinders. They speculated that via this rolling, many different arrangements of graphene hexagonal nets are possible. They suggested two such possible arrangements: a circular arrangement (armchair nanotube); and a spiral, helical arrangement (chiral tube).
In 1987, Howard G. Tennent of Hyperion Catalysis was issued a U.S. patent for the production of "cylindrical discrete carbon fibrils" with a "constant diameter between about 3.5 and about 70 nanometers..., length 102 times the diameter, and an outer region of multiple essentially continuous layers of ordered carbon atoms and a distinct inner core...."
Helping to create the initial excitement associated with carbon nanotubes were Iijima's 1991 discovery of multi-walled carbon nanotubes in the insoluble material of arc-burned graphite rods; and Mintmire, Dunlap, and White's independent prediction that if single-walled carbon nanotubes could be made, they would exhibit remarkable conducting properties. Nanotube research accelerated greatly following the independent discoveries by Iijima and Ichihashi at NEC and Bethune et al. at IBM of methods to specifically produce single-walled carbon nanotubes by adding transition-metal catalysts to the carbon in an arc discharge. Thess et al. refined this catalytic method by vaporizing the carbon/transition-metal combination in a high-temperature furnace, which greatly improved the yield and purity of the SWNTs and made them widely available for characterization and application experiments. The arc discharge technique, well known to produce the famed Buckminsterfullerene, thus played a role in the discoveries of both multi- and single-wall nanotubes, extending the run of serendipitous discoveries relating to fullerenes. The discovery of nanotubes remains a contentious issue. Many believe that Iijima's report in 1991 is of particular importance because it brought carbon nanotubes into the awareness of the scientific community as a whole.
In 2020, during an archaeological excavation of Keezhadi in Tamil Nadu, India, ~2600-year-old pottery was discovered whose coatings appear to contain carbon nanotubes. The robust mechanical properties of the nanotubes are partially why the coatings have lasted for so many years, say the scientists.
Structure of SWCNTs
Basic details
The structure of an ideal (infinitely long) single-walled carbon nanotube is that of a regular hexagonal lattice drawn on an infinite cylindrical surface, whose vertices are the positions of the carbon atoms. Since the length of the carbon-carbon bonds is fairly fixed, there are constraints on the diameter of the cylinder and the arrangement of the atoms on it.
In the study of nanotubes, one defines a zigzag path on a graphene-like lattice as a path that turns 60 degrees, alternating left and right, after stepping through each bond. It is also conventional to define an armchair path as one that makes two left turns of 60 degrees followed by two right turns every four steps. On some carbon nanotubes, there is a closed zigzag path that goes around the tube. One says that the tube is of the zigzag type or configuration, or simply is a zigzag nanotube. If the tube is instead encircled by a closed armchair path, it is said to be of the armchair type, or an armchair nanotube. An infinite nanotube that is of one type consists entirely of closed paths of that type, connected to each other.
The zigzag and armchair configurations are not the only structures that a single-walled nanotube can have. To describe the structure of a general infinitely long tube, one should imagine it being sliced open by a cut parallel to its axis, that goes through some atom A, and then unrolled flat on the plane, so that its atoms and bonds coincide with those of an imaginary graphene sheet—more precisely, with an infinitely long strip of that sheet. The two halves of the atom A will end up on opposite edges of the strip, over two atoms A1 and A2 of the graphene. The line from A1 to A2 will correspond to the circumference of the cylinder that went through the atom A, and will be perpendicular to the edges of the strip. In the graphene lattice, the atoms can be split into two classes, depending on the directions of their three bonds. Half the atoms have their three bonds directed the same way, and half have their three bonds rotated 180 degrees relative to the first half. The atoms A1 and A2, which correspond to the same atom A on the cylinder, must be in the same class. It follows that the circumference of the tube and the angle of the strip are not arbitrary, because they are constrained to the lengths and directions of the lines that connect pairs of graphene atoms in the same class.
Let u and v be two linearly independent vectors that connect the graphene atom A1 to two of its nearest atoms with the same bond directions. That is, if one numbers consecutive carbons around a graphene cell with C1 to C6, then u can be the vector from C1 to C3, and v be the vector from C1 to C5. Then, for any other atom A2 with same class as A1, the vector from A1 to A2 can be written as a linear combination n u + m v, where n and m are integers. And, conversely, each pair of integers (n,m) defines a possible position for A2. Given n and m, one can reverse this theoretical operation by drawing the vector w on the graphene lattice, cutting a strip of the latter along lines perpendicular to w through its endpoints A1 and A2, and rolling the strip into a cylinder so as to bring those two points together. If this construction is applied to a pair (k,0), the result is a zigzag nanotube, with closed zigzag paths of 2k atoms. If it is applied to a pair (k,k), one obtains an armchair tube, with closed armchair paths of 4k atoms.
Types
The structure of the nanotube is not changed if the strip is rotated by 60 degrees clockwise around A1 before applying the hypothetical reconstruction above. Such a rotation changes the corresponding pair (n,m) to the pair (−2m,n+m). It follows that many possible positions of A2 relative to A1 — that is, many pairs (n,m) — correspond to the same arrangement of atoms on the nanotube. That is the case, for example, of the six pairs (1,2), (−2,3), (−3,1), (−1,−2), (2,−3), and (3,−1). In particular, the pairs (k,0) and (0,k) describe the same nanotube geometry. These redundancies can be avoided by considering only pairs (n,m) such that n > 0 and m ≥ 0; that is, where the direction of the vector w lies between those of u (inclusive) and v (exclusive). It can be verified that every nanotube has exactly one pair (n,m) that satisfies those conditions, which is called the tube's type. Conversely, for every type there is a hypothetical nanotube. In fact, two nanotubes have the same type if and only if one can be conceptually rotated and translated so as to match the other exactly. Instead of the type (n,m), the structure of a carbon nanotube can be specified by giving the length of the vector w (that is, the circumference of the nanotube), and the angle α between the directions of u and w,
may range from 0 (inclusive) to 60 degrees clockwise (exclusive). If the diagram is drawn with u horizontal, the latter is the tilt of the strip away from the vertical.
Chirality and mirror symmetry
A nanotube is chiral if it has type (n,m), with m > 0 and m ≠ n; then its enantiomer (mirror image) has type (m,n), which is different from (n,m). This operation corresponds to mirroring the unrolled strip about the line L through A1 that makes an angle of 30 degrees clockwise from the direction of the u vector (that is, with the direction of the vector u+v). The only types of nanotubes that are achiral are the (k,0) "zigzag" tubes and the (k,k) "armchair" tubes. If two enantiomers are to be considered the same structure, then one may consider only types (n,m) with 0 ≤ m ≤ n and n > 0. Then the angle α between u and w, which may range from 0 to 30 degrees (inclusive both), is called the "chiral angle" of the nanotube.
Circumference and diameter
From n and m one can also compute the circumference c, which is the length of the vector w, which turns out to be:
in picometres. The diameter of the tube is then , that is
also in picometres. (These formulas are only approximate, especially for small n and m where the bonds are strained; and they do not take into account the thickness of the wall.)
The tilt angle α between u and w and the circumference c are related to the type indices n and m by:
where arg(x,y) is the clockwise angle between the X-axis and the vector (x,y); a function that is available in many programming languages as atan2(y,x). Conversely, given c and α, one can get the type (n,m) by the formulas:
which must evaluate to integers.
Physical limits
Narrowest examples
If n and m are too small, the structure described by the pair (n,m) will describe a molecule that cannot be reasonably called a "tube", and may not even be stable. For example, the structure theoretically described by the pair (1,0) (the limiting "zigzag" type) would be just a chain of carbons. That is a real molecule, the carbyne; which has some characteristics of nanotubes (such as orbital hybridization, high tensile strength, etc.) — but has no hollow space, and may not be obtainable as a condensed phase. The pair (2,0) would theoretically yield a chain of fused 4-cycles; and (1,1), the limiting "armchair" structure, would yield a chain of bi-connected 4-rings. These structures may not be realizable.
The thinnest carbon nanotube proper is the armchair structure with type (2,2), which has a diameter of 0.3 nm. This nanotube was grown inside a multi-walled carbon nanotube. Assigning of the carbon nanotube type was done by a combination of high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and density functional theory (DFT) calculations.
The thinnest freestanding single-walled carbon nanotube is about 0.43 nm in diameter. Researchers suggested that it can be either (5,1) or (4,2) SWCNT, but the exact type of the carbon nanotube remains questionable. (3,3), (4,3), and (5,1) carbon nanotubes (all about 0.4 nm in diameter) were unambiguously identified using aberration-corrected high-resolution transmission electron microscopy inside double-walled CNTs.
Length
The observation of the longest carbon nanotubes grown so far, around 0.5 metre (550 mm) long, was reported in 2013. These nanotubes were grown on silicon substrates using an improved chemical vapor deposition (CVD) method and represent electrically uniform arrays of single-walled carbon nanotubes.
The shortest carbon nanotube can be considered to be the organic compound cycloparaphenylene, which was synthesized in 2008 by Ramesh Jasti. Other small molecule carbon nanotubes have been synthesized since.
Density
The highest density of CNTs was achieved in 2013, grown on a conductive titanium-coated copper surface that was coated with co-catalysts cobalt and molybdenum at lower than typical temperatures of 450 °C. The tubes averaged a height of 380 nm and a mass density of 1.6 g cm−3. The material showed ohmic conductivity (lowest resistance ~22 kΩ).
Variants
There is no consensus on some terms describing carbon nanotubes in the scientific literature: both "-wall" and "-walled" are being used in combination with "single", "double", "triple", or "multi", and the letter C is often omitted in the abbreviation, for example, multi-walled carbon nanotube (MWNT). The International Standards Organization typically uses "single-walled carbon nanotube (SWCNT)" or "multi-walled carbon nanotube (MWCNT)" in its documents.
Multi-walled
Multi-walled nanotubes (MWNTs) consist of multiple rolled layers (concentric tubes) of graphene. There are two models that can be used to describe the structures of multi-walled nanotubes. In the Russian Doll model, sheets of graphite are arranged in concentric cylinders, e.g., a (0,8) single-walled nanotube (SWNT) within a larger (0,17) single-walled nanotube. In the Parchment model, a single sheet of graphite is rolled in around itself, resembling a scroll of parchment or a rolled newspaper. The interlayer distance in multi-walled nanotubes is close to the distance between graphene layers in graphite, approximately 3.4 Å. The Russian Doll structure is observed more commonly. Its individual shells can be described as SWNTs, which can be metallic or semiconducting. Because of statistical probability and restrictions on the relative diameters of the individual tubes, one of the shells, and thus the whole MWNT, is usually a zero-gap metal.
Double-walled carbon nanotubes (DWNTs) form a special class of nanotubes because their morphology and properties are similar to those of SWNTs but they are more resistant to attacks by chemicals. This is especially important when it is necessary to graft chemical functions to the surface of the nanotubes (functionalization) to add properties to the CNT. Covalent functionalization of SWNTs will break some C=C double bonds, leaving "holes" in the structure on the nanotube and thus modifying both its mechanical and electrical properties. In the case of DWNTs, only the outer wall is modified. DWNT synthesis on the gram-scale by the CCVD technique was first proposed in 2003 from the selective reduction of oxide solutions in methane and hydrogen.
The telescopic motion ability of inner shells, allowing them to act as low-friction, low-wear nanobearings and nanosprings, may make them a desirable material in nanoelectromechanical systems (NEMS) . The retraction force that occurs to telescopic motion is caused by the Lennard-Jones interaction between shells, and its value is about 1.5 nN.
Junctions and crosslinking
Junctions between two or more nanotubes have been widely discussed theoretically. Such junctions are quite frequently observed in samples prepared by arc discharge as well as by chemical vapor deposition. The electronic properties of such junctions were first considered theoretically by Lambin et al., who pointed out that a connection between a metallic tube and a semiconducting one would represent a nanoscale heterojunction. Such a junction could therefore form a component of a nanotube-based electronic circuit. The adjacent image shows a junction between two multiwalled nanotubes.
Junctions between nanotubes and graphene have been considered theoretically and studied experimentally. Nanotube-graphene junctions form the basis of pillared graphene, in which parallel graphene sheets are separated by short nanotubes. Pillared graphene represents a class of three-dimensional carbon nanotube architectures.
Recently, several studies have highlighted the prospect of using carbon nanotubes as building blocks to fabricate three-dimensional macroscopic (>100 nm in all three dimensions) all-carbon devices. Lalwani et al. have reported a novel radical-initiated thermal crosslinking method to fabricate macroscopic, free-standing, porous, all-carbon scaffolds using single- and multi-walled carbon nanotubes as building blocks. These scaffolds possess macro-, micro-, and nano-structured pores, and the porosity can be tailored for specific applications. These 3D all-carbon scaffolds/architectures may be used for the fabrication of the next generation of energy storage, supercapacitors, field emission transistors, high-performance catalysis, photovoltaics, and biomedical devices, implants, and sensors.
Other morphologies
Carbon nanobuds are a newly created material combining two previously discovered allotropes of carbon: carbon nanotubes and fullerenes. In this new material, fullerene-like "buds" are covalently bonded to the outer sidewalls of the underlying carbon nanotube. This hybrid material has useful properties of both fullerenes and carbon nanotubes. In particular, they have been found to be exceptionally good field emitters. In composite materials, the attached fullerene molecules may function as molecular anchors preventing slipping of the nanotubes, thus improving the composite's mechanical properties.
A carbon peapod is a novel hybrid carbon material which traps fullerene inside a carbon nanotube. It can possess interesting magnetic properties with heating and irradiation. It can also be applied as an oscillator during theoretical investigations and predictions.
In theory, a nanotorus is a carbon nanotube bent into a torus (doughnut shape). Nanotori are predicted to have many unique properties, such as magnetic moments 1000 times larger than that previously expected for certain specific radii. Properties such as magnetic moment, thermal stability, etc. vary widely depending on the radius of the torus and the radius of the tube.
Graphenated carbon nanotubes are a relatively new hybrid that combines graphitic foliates grown along the sidewalls of multiwalled or bamboo-style CNTs. The foliate density can vary as a function of deposition conditions (e.g., temperature and time) with their structure ranging from a few layers of graphene (< 10) to thicker, more graphite-like. The fundamental advantage of an integrated graphene-CNT structure is the high surface area three-dimensional framework of the CNTs coupled with the high edge density of graphene. Depositing a high density of graphene foliates along the length of aligned CNTs can significantly increase the total charge capacity per unit of nominal area as compared to other carbon nanostructures.
Cup-stacked carbon nanotubes (CSCNTs) differ from other quasi-1D carbon structures, which normally behave as quasi-metallic conductors of electrons. CSCNTs exhibit semiconducting behavior because of the stacking microstructure of graphene layers.
Properties
Many properties of single-walled carbon nanotubes depend significantly on the (n,m) type, and this dependence is non-monotonic (see Kataura plot). In particular, the band gap can vary from zero to about 2 eV and the electrical conductivity can show metallic or semiconducting behavior.
Mechanical
Carbon nanotubes are the strongest and stiffest materials yet discovered in terms of tensile strength and elastic modulus. This strength results from the covalent sp2 bonds formed between the individual carbon atoms. In 2000, a multiwalled carbon nanotube was tested to have a tensile strength of . (For illustration, this translates into the ability to endure tension of a weight equivalent to on a cable with cross-section of ). Further studies, such as one conducted in 2008, revealed that individual CNT shells have strengths of up to ≈, which is in agreement with quantum/atomistic models. Because carbon nanotubes have a low density for a solid of 1.3 to 1.4 g/cm3, its specific strength of up to 48,000 kN·m/kg is the best of known materials, compared to high-carbon steel's 154 kN·m/kg.
Although the strength of individual CNT shells is extremely high, weak shear interactions between adjacent shells and tubes lead to significant reduction in the effective strength of multiwalled carbon nanotubes and carbon nanotube bundles down to only a few GPa. This limitation has been recently addressed by applying high-energy electron irradiation, which crosslinks inner shells and tubes, and effectively increases the strength of these materials to ≈60 GPa for multiwalled carbon nanotubes and ≈17 GPa for double-walled carbon nanotube bundles. CNTs are not nearly as strong under compression. Because of their hollow structure and high aspect ratio, they tend to undergo buckling when placed under compressive, torsional, or bending stress.
On the other hand, there is evidence that in the radial direction they are rather soft. The first transmission electron microscope observation of radial elasticity suggested that even van der Waals forces can deform two adjacent nanotubes. Later, nanoindentations with an atomic force microscope were performed by several groups to quantitatively measure the radial elasticity of multiwalled carbon nanotubes and tapping/contact mode atomic force microscopy was also performed on single-walled carbon nanotubes. Their high Young's modulus in the linear direction, of on the order of several GPa (and even up to an experimentally-measured 1.8 TPa, for nanotubes near 2.4 μm in length), further suggests they may be soft in the radial direction.
Electrical
Unlike graphene, which is a two-dimensional semimetal, carbon nanotubes are either metallic or semiconducting along the tubular axis. For a given (n,m) nanotube, if n = m, the nanotube is metallic; if n − m is a multiple of 3 and n ≠ m, then the nanotube is quasi-metallic with a very small band gap, otherwise the nanotube is a moderate semiconductor.
Thus, all armchair (n = m) nanotubes are metallic, and nanotubes (6,4), (9,1), etc. are semiconducting.
Carbon nanotubes are not semimetallic because the degenerate point (the point where the π [bonding] band meets the π* [anti-bonding] band, at which the energy goes to zero) is slightly shifted away from the K point in the Brillouin zone because of the curvature of the tube surface, causing hybridization between the σ* and π* anti-bonding bands, modifying the band dispersion.
The rule regarding metallic versus semiconductor behavior has exceptions because curvature effects in small-diameter tubes can strongly influence electrical properties. Thus, a (5,0) SWCNT that should be semiconducting in fact is metallic according to the calculations. Likewise, zigzag and chiral SWCNTs with small diameters that should be metallic have a finite gap (armchair nanotubes remain metallic). In theory, metallic nanotubes can carry an electric current density of 4 × 109 A/cm2, which is more than 1,000 times greater than those of metals such as copper, where for copper interconnects, current densities are limited by electromigration. Carbon nanotubes are thus being explored as interconnects and conductivity-enhancing components in composite materials, and many groups are attempting to commercialize highly conducting electrical wire assembled from individual carbon nanotubes. There are significant challenges to be overcome however, such as undesired current saturation under voltage, and the much more resistive nanotube-to-nanotube junctions and impurities, all of which lower the electrical conductivity of the macroscopic nanotube wires by orders of magnitude, as compared to the conductivity of the individual nanotubes.
Because of its nanoscale cross-section, electrons propagate only along the tube's axis. As a result, carbon nanotubes are frequently referred to as one-dimensional conductors. The maximum electrical conductance of a single-walled carbon nanotube is 2G0, where G0 = 2e2/h is the conductance of a single ballistic quantum channel.
Because of the role of the π-electron system in determining the electronic properties of graphene, doping in carbon nanotubes differs from that of bulk crystalline semiconductors from the same group of the periodic table (e.g., silicon). Graphitic substitution of carbon atoms in the nanotube wall by boron or nitrogen dopants leads to p-type and n-type behavior, respectively, as would be expected in silicon. However, some non-substitutional (intercalated or adsorbed) dopants introduced into a carbon nanotube, such as alkali metals and electron-rich metallocenes, result in n-type conduction because they donate electrons to the π-electron system of the nanotube. By contrast, π-electron acceptors such as FeCl3 or electron-deficient metallocenes function as p-type dopants because they draw π-electrons away from the top of the valence band.
Intrinsic superconductivity has been reported, although other experiments found no evidence of this, leaving the claim a subject of debate.
In 2021, Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering at MIT, published department findings on the use of carbon nanotubes to create an electric current. By immersing the structures in an organic solvent, the liquid drew electrons out of the carbon particles. Strano was quoted as saying, "This allows you to do electrochemistry, but with no wires," and represents a significant breakthrough in the technology. Future applications include powering micro- or nanoscale robots, as well as driving alcohol oxidation reactions, which are important in the chemicals industry.
Crystallographic defects also affect the tube's electrical properties. A common result is lowered conductivity through the defective region of the tube. A defect in metallic armchair-type tubes (which can conduct electricity) can cause the surrounding region to become semiconducting, and single monatomic vacancies induce magnetic properties.
Electromechanical
Semiconducting carbon nanotubes have shown piezoresistive property when applying mechanical force. The structural deformation causes a change in the band gap which effects the conductance. This property has the potential to be used in strain sensors.
Optical
Carbon nanotubes have useful absorption, photoluminescence (fluorescence), and Raman spectroscopy properties. Spectroscopic methods offer the possibility of quick and non-destructive characterization of relatively large amounts of carbon nanotubes. There is a strong demand for such characterization from the industrial point of view: numerous parameters of nanotube synthesis can be changed, intentionally or unintentionally, to alter the nanotube quality, such as the non-tubular carbon content, structure (chirality) of the produced nanotubes, and structural defects. These features then determine nearly all other significant optical, mechanical, and electrical properties.
Carbon nanotube optical properties have been explored for use in applications such as for light-emitting diodes (LEDs) and photo-detectors based on a single nanotube have been produced in the lab. Their unique feature is not the efficiency, which is yet relatively low, but the narrow selectivity in the wavelength of emission and detection of light and the possibility of its fine-tuning through the nanotube structure. In addition, bolometer and optoelectronic memory devices have been realised on ensembles of single-walled carbon nanotubes. Nanotube fluorescence has been investigated for the purposes of imaging and sensing in biomedical applications.
Thermal
All nanotubes are expected to be very good thermal conductors along the tube, exhibiting a property known as "ballistic conduction", but good insulators lateral to the tube axis. Measurements show that an individual SWNT has a room-temperature thermal conductivity along its axis of about 3500 W·m−1·K−1; compare this to copper, a metal well known for its good thermal conductivity, which transmits 385 W·m−1·K−1. An individual SWNT has a room-temperature thermal conductivity lateral to its axis (in the radial direction) of about 1.52 W·m−1·K−1, which is about as thermally conductive as soil. Macroscopic assemblies of nanotubes such as films or fibres have reached up to 1500 W·m−1·K−1 so far. Networks composed of nanotubes demonstrate different values of thermal conductivity, from the level of thermal insulation with the thermal conductivity of 0.1 W·m−1·K−1 to such high values. That is dependent on the amount of contribution to the thermal resistance of the system caused by the presence of impurities, misalignments and other factors. The temperature stability of carbon nanotubes is estimated to be up to 2800 °C in vacuum and about 750 °C in air.
Crystallographic defects strongly affect the tube's thermal properties. Such defects lead to phonon scattering, which in turn increases the relaxation rate of the phonons. This reduces the mean free path and reduces the thermal conductivity of nanotube structures. Phonon transport simulations indicate that substitutional defects such as nitrogen or boron will primarily lead to the scattering of high-frequency optical phonons. However, larger-scale defects such as Stone–Wales defects cause phonon scattering over a wide range of frequencies, leading to a greater reduction in thermal conductivity.
Antibacterial
Recently, carbon-nanotubes have been shown to have antibacterial properties. They disrupt normal bacterial function by causing physical/mechanical damage, facilitating oxidative stress or lipid extraction, inhibiting bacterial metabolism, and isolating functional sites via wrapping with CNM-containing nanomaterials.
Synthesis
Techniques have been developed to produce nanotubes in sizeable quantities, including arc discharge, laser ablation, chemical vapor deposition (CVD) and high-pressure carbon monoxide disproportionation (HiPCO). Among these arc discharge, laser ablation are batch by batch process, Chemical Vapor Deposition can be used both for batch by batch or continuous processes, and HiPCO is gas phase continuous process. Most of these processes take place in a vacuum or with process gases. The CVD growth method is popular, as it yields high quantity and has a degree of control over diameter, length and morphology. Using particulate catalysts, large quantities of nanotubes can be synthesized by these methods, and industrialisation is well on its way, with several CNT and CNT fibers factory around the world. One problem of CVD processes is the high variability in the nanotube's characteristics The HiPCO process advances in catalysis and continuous growth are making CNTs more commercially viable. The HiPCO process helps in producing high purity single-walled carbon nanotubes in higher quantity. The HiPCO reactor operates at high temperature 900–1100 °C and high pressure ~30–50 bar. It uses carbon monoxide as the carbon source and iron pentacarbonyl or nickel tetracarbonyl as a catalyst. These catalysts provide a nucleation site for the nanotubes to grow, while cheaper iron-based catalysts like Ferrocene can be used for CVD process.
Vertically aligned carbon nanotube arrays are also grown by thermal chemical vapor deposition. A substrate (quartz, silicon, stainless steel, carbon fibers, etc.) is coated with a catalytic metal (Fe, Co, Ni) layer. Typically that layer is iron and is deposited via sputtering to a thickness of 1–5 nm. A 10–50 nm underlayer of alumina is often also put down on the substrate first. This imparts controllable wetting and good interfacial properties.
When the substrate is heated to the growth temperature (~600 to 850 °C), the continuous iron film breaks up into small islands with each island then nucleating a carbon nanotube. The sputtered thickness controls the island size and this in turn determines the nanotube diameter. Thinner iron layers drive down the diameter of the islands and drive down the diameter of the nanotubes grown. The amount of time the metal island can sit at the growth temperature is limited as they are mobile and can merge into larger (but fewer) islands. Annealing at the growth temperature reduces the site density (number of CNT/mm2) while increasing the catalyst diameter.
The as-prepared carbon nanotubes always have impurities such as other forms of carbon (amorphous carbon, fullerene, etc.) and non-carbonaceous impurities (metal used for catalyst). These impurities need to be removed to make use of the carbon nanotubes in applications.
Purification
As-synthesized carbon nanotubes typically contain impurities and most importantly different chiralities of carbon nanotubes. Therefore, multiple methods have been developed to purify them including polymer-assisted, density gradient ultracentrifugation (DGU), chromatography and aqueous two-phase extraction (ATPE). These methods have been reviewed in multiple articles.
Certain polymers selectively disperse or wrap CNTs of a particular chirality, metallic character or diameter. For example, poly(phenylenevinylenes) disperses CNTs of specific diameters (0.75–0.84 nm) and polyfluorenes are highly selective for semiconducting CNTs. It involves mainly two steps, sonicate the mixture (CNTs and polymers in solvent), centrifuge and the supernatant are desired CNTs.
Density gradient ultracentrifugation is a method based on the density difference of CNTs, so that different components are layered in centrifuge tubes under centrifugal force. Chromatography-based methods include size exclusion (SEC), ion-exchange (IEX) and gel chromatography. For SEC, CNTs are separated due to the difference in size using a stationary phase with different pore size. As for IEX, the separation is achieved based on their differential adsorption and desorption onto chemically functionalized resins packed in an IEX column, so understanding the interaction between CNTs mixtures and resins is important. The first IEX is reported to separate DNA-SWCNTs. Gel chromatography is based on the partition of CNTs between stationary and mobile phase, it's found semiconducting CNTs are more strongly attracted by gel than metallic CNTs. While it shows potential, the current application is limited to the separation of semiconducting (n,m) species.
ATPE uses two water-soluble polymers such as polyethylene glycol (PEG) and dextran. When mixed, two immiscible aqueous phases form spontaneously, and each of the two phases shows a different affinity to CNTs. Partition depends on the solvation energy difference between two similar phases of microscale volumes. By changing the separation system or temperatures, and adding strong oxidants, reductants, or salts, the partition of CNTs species into the two phases can be adjusted.
Despite the progress that has been made to separate and purify CNTs, many challenges remain, such as the growth of chirality-controlled CNTs, so that no further purification is needed, or large-scale purification.
Advantages of monochiral CNTs
Monochiral CNTs have the advantage that they do contain less or no impurities, well-defined non-congested optical spectra. This allows to create for example CNT-based biosensors with higher sensitivity and selectivity. For example, monochiral SWCNTs are necessary for multiplexed and ratiometric sensing schemes, enhanced sensitivity of biocompatibility.
Functionalization
Carbon nanotubes can be functionalized to attain desired properties that can be used in a wide variety of applications. The two main methods of carbon nanotube functionalization are covalent and non-covalent modifications. Because of their apparent hydrophobic nature, carbon nanotubes tend to agglomerate hindering their dispersion in solvents or viscous polymer melts. The resulting nanotube bundles or aggregates reduce the mechanical performance of the final composite. The surface of the carbon nanotubes can be modified to reduce the hydrophobicity and improve interfacial adhesion to a bulk polymer through chemical attachment.
Chemical routes such as covalent functionalization have been studied extensively, which involves the oxidation of CNTs via strong acids (e.g. sulfuric acid, nitric acid, or a mixture of both) in order to set the carboxylic groups onto the surface of the CNTs as the final product or for further modification by esterification or amination. Free radical grafting is a promising technique among covalent functionalization methods, in which alkyl or aryl peroxides, substituted anilines, and diazonium salts are used as the starting agents.
Functionalization can improve CNTs characteristically weak dispersibility in many solvents, such as water - a consequence of their strong intermolecular p–p interactions. This can enhance the processing and manipulation of insoluble CNTs, rendering them useful for synthesizing innovative CNT nanofluids with impressive properties that are tunable for a wide range of applications.
Free radical grafting of macromolecules (as the functional group) onto the surface of CNTs can improve the solubility of CNTs compared to common acid treatments which involve the attachment of small molecules such as hydroxyl onto the surface of CNTs. The solubility of CNTs can be improved significantly by free-radical grafting because the large functional molecules facilitate the dispersion of CNTs in a variety of solvents even at a low degree of functionalization. Recently an innovative environmentally friendly approach has been developed for the covalent functionalization of multi-walled carbon nanotubes (MWCNTs) using clove buds. This approach is innovative and green because it does not use toxic and hazardous acids which are typically used in common carbon nanomaterial functionalization procedures. The MWCNTs are functionalized in one pot using a free radical grafting reaction. The clove-functionalized MWCNTs are then dispersed in water producing a highly stable multi-walled carbon nanotube aqueous suspension (nanofluids).
The surface of carbon nanotubes can be chemically modified by coating spinel nanoparticles by hydrothermal synthesis and can be used for water oxidation purposes.
In addition, the surface of carbon nanotubes can be fluorinated or halofluorinated by heating while in contact with a fluoroorganic substance, thereby forming partially fluorinated carbons (so-called Fluocar materials) with grafted (halo)fluoroalkyl functionality.
Modeling
Carbon nanotubes are modelled in a similar manner as traditional composites in which a reinforcement phase is surrounded by a matrix phase. Ideal models such as cylindrical, hexagonal and square models are common. The size of the micromechanics model is highly function of the studied mechanical properties. The concept of representative volume element (RVE) is used to determine the appropriate size and configuration of the computer model to replicate the actual behavior of the CNT-reinforced nanocomposite. Depending on the material property of interest (thermal, electrical, modulus, creep), one RVE might predict the property better than the alternatives. While the implementation of the ideal model is computationally efficient, they do not represent microstructural features observed in scanning electron microscopy of actual nanocomposites. To incorporate realistic modeling, computer models are also generated to incorporate variability such as waviness, orientation and agglomeration of multiwall or single-wall carbon nanotubes.
Metrology
There are many metrology standards and reference materials available for carbon nanotubes.
For single-wall carbon nanotubes, ISO/TS 10868 describes a measurement method for the diameter, purity, and fraction of metallic nanotubes through optical absorption spectroscopy, while ISO/TS 10797 and ISO/TS 10798 establish methods to characterize the morphology and elemental composition of single-wall carbon nanotubes, using transmission electron microscopy and scanning electron microscopy respectively, coupled with energy dispersive X-ray spectrometry analysis.
NIST SRM 2483 is a soot of single-wall carbon nanotubes used as a reference material for elemental analysis, and was characterized using thermogravimetric analysis, prompt gamma activation analysis, induced neutron activation analysis, inductively coupled plasma mass spectroscopy, resonant Raman scattering, UV-visible-near infrared fluorescence spectroscopy and absorption spectroscopy, scanning electron microscopy, and transmission electron microscopy. The Canadian National Research Council also offers a certified reference material SWCNT-1 for elemental analysis using neutron activation analysis and inductively coupled plasma mass spectroscopy. NIST RM 8281 is a mixture of three lengths of single-wall carbon nanotube.
For multiwall carbon nanotubes, ISO/TR 10929 identifies the basic properties and the content of impurities, while ISO/TS 11888 describes morphology using scanning electron microscopy, transmission electron microscopy, viscometry, and light scattering analysis. ISO/TS 10798 is also valid for multiwall carbon nanotubes.
Safety and health
The National Institute for Occupational Safety and Health (NIOSH) is the leading United States federal agency conducting research and providing guidance on the occupational safety and health implications and applications of nanomaterials. Early scientific studies have indicated that nanoscale particles may pose a greater health risk than bulk materials due to a relative increase in surface area per unit mass. Increase in length and diameter of CNT is correlated to increased toxicity and pathological alterations in lung. The biological interactions of nanotubes are not well understood, and the field is open to continued toxicological studies. It is often difficult to separate confounding factors, and since carbon is relatively biologically inert, some of the toxicity attributed to carbon nanotubes may be instead due to residual metal catalyst contamination. In previous studies, only Mitsui-7 was reliably demonstrated to be carcinogenic, although for unclear/unknown reasons. Unlike many common mineral fibers (such as asbestos), most SWCNTs and MWCNTs do not fit the size and aspect-ratio criteria to be classified as respirable fibers. In 2013, given that the long-term health effects have not yet been measured, NIOSH published a Current Intelligence Bulletin detailing the potential hazards and recommended exposure limit for carbon nanotubes and fibers. The U.S. National Institute for Occupational Safety and Health has determined non-regulatory recommended exposure limits (RELs) of 1 μg/m3 for carbon nanotubes and carbon nanofibers as background-corrected elemental carbon as an 8-hour time-weighted average (TWA) respirable mass concentration. Although CNT caused pulmonary inflammation and toxicity in mice, exposure to aerosols generated from sanding of composites containing polymer-coated MWCNTs, representative of the actual end-product, did not exert such toxicity.
As of October 2016, single-wall carbon nanotubes have been registered through the European Union's Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) regulations, based on evaluation of the potentially hazardous properties of SWCNT. Based on this registration, SWCNT commercialization is allowed in the EU up to 100 metric tons. Currently, the type of SWCNT registered through REACH is limited to the specific type of single-wall carbon nanotubes manufactured by OCSiAl, which submitted the application.
Applications
Carbon nanotubes are currently used in multiple industrial and consumer applications. These include battery components, polymer composites, to improve the mechanical, thermal and electrical properties of the bulk product, and as a highly absorptive black paint. Many other applications are under development, including field effect transistors for electronics, high-strength fabrics, biosensors for biomedical and agricultural applications, and many others.
Biomedical Applications
Because of their relatively large surface area, CNTs are capable of interacting with a wide variety of therapeutic and diagnostic agents (drugs, genes, vaccines, antibodies, biosensors, etc.). This can be utilized to assist in drug delivery directly into cells. In addition, CNTs have recently been used as reinforcements in implants and scaffolds due to their suitable reaction area, high elastic modulus, and load transfer capability.
CNTs have been shown to increase the effectiveness of bioactive coatings for the attachment, proliferation, and differentiation of osteoblasts, and has been used as a bone substitution material.
CNTs may be used as reinforcing materials for chitosan-containing coatings used on implants and medical scaffolds.
Biosensing
SWCNTs have nanoscale dimensions that fit to the size of biological species. Due to this size compatibility and their large surface-to-volume ratio, they are sensitive to changes in their chemical environment. Through covalent and non-covalent surface functionalization, SWCNTs can be precisely tailored for selective molecular interactions with a target analyte. The SWCNT represents the transduction unit that converts the interaction into a signal change (optical or electrical). Due to continuous progress in the development of detection strategies, there are numerous examples of the use of SWCNTs as highly sensitive nanosensors (even down to the single molecule level) for a variety of important biomolecules. Examples include the detection of reactive oxygen and nitrogen species, neurotransmitters, other small molecules, lipids, proteins, sugars, DNA/RNA, enzymes as well as bacteria.
The signal change manifests itself in an increase or decrease in the current (electrical) or in a change in the intensity or wavelength of the fluorescence emission (optical). Depending on the type of application, both electrical or optical signal transmission can be advantageous. For sensitive measurement of electronic changes, field-effect transistors (FET) are often used in which the flow of charges within the SWCNTs is measured. The FET structures allow easy on-chip integration and can be parallelized to detect multiple target analytes simultaneously. However, such sensors are more invasive for in vivo applications, as the entire device has to be inserted into the body. Optical detection with semiconducting SWCNTs is based on the radiative recombination of excitons in the near-infrared (NIR) by prior optical (fluorescence) or electrical excitation (electroluminescence). The emission in the NIR enables detection in the biological transparency window, where optical sensor applications benefit from reduced scattering and autofluorescence of biological samples and consequently a high signal-to-noise ratio. Compared to optical sensors in the UV or visible range, the penetration depth in biological tissue is also increased. In addition to the advantage of a contactless readout SWCNTs have excellent photostability, which enables long-term sensor applications. Furthermore, the nanoscale size of SWCNTs allows dense coating of surfaces which enables chemical imaging, e.g. of cellular release processes with high spatial and temporal resolution. Detection of several target analytes is possible by the spatial arrangement of different SWCNT sensors in arrays or by hyperspectral detection based on monochiral SWCNT sensors that emit at different emission wavelengths. For fluorescence applications, however, optical filters to distinguish between excitation and emission and a NIR-sensitive detector must be used. Standard silicon detectors can also be used if monochiral SWCNTs (extractable by special purification processes) emitting closer to the visible range (800 – 900 nm) are used. In order to avoid susceptibility of optical sensors to fluctuating ambient light, internal references such as SWCNTs that are modified to be non-responsive or stable NIR emitters can be used. An alternative is to measure fluorescence lifetimes instead of fluorescence intensities. Overall, SWCNTs therefore have great potential as building blocks for various biosensors.
To render SWCNTs suitable for biosensing, their surface needs to be modified to ensure colloidal stability and provide a handle for biological recognition. Therefore, biosensing and surface modifications (functionalization) are closely related.
Potential future applications include biomedical and environmental applications such as monitoring plant health in agriculture, standoff process control in bioreactors, research/diagnostics of neuronal communication and numerous diseases such as coagulation disorders, diabetes, cancer, microbial and viral infections, testing the efficacy of pharmaceuticals or infection monitoring using smart implants. In industry, SWCNTs are already used as sensors in the detection of gases and odors in the form of an electronic nose or in enzyme screening.
Other current applications
Easton-Bell Sports, Inc. have been in partnership with Zyvex Performance Materials, using CNT technology in a number of their bicycle components – including flat and riser handlebars, cranks, forks, seatposts, stems and aero bars.
Amroy Europe Oy manufactures Hybtonite carbon nano-epoxy resins where carbon nanotubes have been chemically activated to bond to epoxy, resulting in a composite material that is 20% to 30% stronger than other composite materials. It has been used for wind turbines, marine paints and a variety of sports gear such as skis, ice hockey sticks, baseball bats, hunting arrows, and surfboards.
Surrey NanoSystems synthesizes carbon nanotubes to create vantablack ultra-absorptive black paint.
"Gecko tape" (also called "nano tape") is often commercially sold as double-sided adhesive tape. It can be used to hang lightweight items such as pictures and decorative items on smooth walls without punching holes in the wall. The carbon nanotube arrays comprising the synthetic setae leave no residue after removal and can stay sticky in extreme temperatures.
Tips for atomic force microscope probes.
Applications under development
Applications of nanotubes in development in academia and industry include:
Medical devices: Using single wall carbon nanotubes in medical devices results in no skin contamination, high flexibility, and softness, which are crucial for healthcare applications.
Wearable electronics and 5G/6G communication: Electrodes with single wall carbon nanotubes (SWCNTs) exhibit excellent electrochemical properties and flexibility.
Bitumen and asphalt: The world's first test section of road pavement with single wall carbon nanotubes (SWCNTs) showed a 67% increase in resistance to cracks and ruts, increasing the lifespan of the materials.
Nanocomposites for aviation, automotive, and renewable energy markets: Modifying resin with just 0.02% single wall carbon nanotubes (SWCNTs) increases electrical conductivity by 276% without compromising the mechanical properties of fiber-reinforced polymers, also improving flexural properties and delaying thermal degradation.
Additive manufacturing: single wall carbon nanotubes (SWCNTs) are mixed with a suitable printing medium or used as a filler material in the printing process, creating complex structures with enhanced mechanical and electrical properties.
Utilizing carbon nanotubes as the channel material of carbon nanotube field-effect transistors.
Using carbon nanotubes as a scaffold for diverse microfabrication techniques.
Energy dissipation in self-organized nanostructures under the influence of an electric field.
Using carbon nanotubes for environmental monitoring due to their active surface area and their ability to absorb gases.
Jack Andraka used carbon nanotubes in his pancreatic cancer test. His method of testing won the Intel International Science and Engineering Fair Gordon E. Moore Award in the spring of 2012.
The Boeing Company has patented the use of carbon nanotubes for structural health monitoring of composites used in aircraft structures. This technology is hoped to greatly reduce the risk of an in-flight failure caused by structural degradation of aircraft.
Zyvex Technologies has also built a 54' maritime vessel, the Piranha Unmanned Surface Vessel, as a technology demonstrator for what is possible using CNT technology. CNTs help improve the structural performance of the vessel, resulting in a lightweight 8,000 lb boat that can carry a payload of 15,000 lb over a range of 2,500 miles.
IMEC is using carbon nanotubes for pellicles in semiconductor lithography.
In tissue engineering, carbon nanotubes have been used as scaffolding for bone growth.
Carbon nanotubes can serve as additives to various structural materials. For instance, nanotubes form a tiny portion of the material(s) in some (primarily carbon fiber) baseball bats, golf clubs, car parts, or damascus steel.
IBM expected carbon nanotube transistors to be used on Integrated Circuits by 2020.
SWCNTs have found use in long lasting, faster charged lithium ion batteries; polyamide car parts for e-painting; automotive primers for cost benefits and better aesthetics of topcoats; ESD floors; electrically conductive lining coatings for tanks and pipes; rubber parts with improved heat and oil aging stability; conductive gelcoats for ATEX requirements and tooling conductive gelcoats for increased safety and efficiency; and heating fiber coatings for infrastructure elements.
Potential/Future applications
The strength and flexibility of carbon nanotubes makes them of potential use in controlling other nanoscale structures, which suggests they will have an important role in nanotechnology engineering. The highest tensile strength of an individual multi-walled carbon nanotube has been tested to be 63 GPa. Carbon nanotubes were found in Damascus steel from the 17th century, possibly helping to account for the legendary strength of the swords made of it. Recently, several studies have highlighted the prospect of using carbon nanotubes as building blocks to fabricate three-dimensional macroscopic (>1mm in all three dimensions) all-carbon devices. Lalwani et al. have reported a novel radical initiated thermal crosslinking method to fabricated macroscopic, free-standing, porous, all-carbon scaffolds using single- and multi-walled carbon nanotubes as building blocks. These scaffolds possess macro-, micro-, and nano- structured pores and the porosity can be tailored for specific applications. These 3D all-carbon scaffolds/architectures may be used for the fabrication of the next generation of energy storage, supercapacitors, field emission transistors, high-performance catalysis, photovoltaics, and biomedical devices and implants.
CNTs are potential candidates for future via and wire material in nano-scale VLSI circuits. Eliminating electromigration reliability concerns that plague today's Cu interconnects, isolated (single and multi-wall) CNTs can carry current densities in excess of 1000 MA/cm2 without electromigration damage.
Single-walled nanotubes are likely candidates for miniaturizing electronics. The most basic building block of these systems is an electric wire, and SWNTs with diameters of an order of a nanometre can be excellent conductors. One useful application of SWNTs is in the development of the first intermolecular field-effect transistors (FET). The first intermolecular logic gate using SWCNT FETs was made in 2001. A logic gate requires both a p-FET and an n-FET. Because SWNTs are p-FETs when exposed to oxygen and n-FETs otherwise, it is possible to expose half of an SWNT to oxygen and protect the other half from it. The resulting SWNT acts as a not logic gate with both p- and n-type FETs in the same molecule.
Large quantities of pure CNTs can be made into a freestanding sheet or film by surface-engineered tape-casting (SETC) fabrication technique which is a scalable method to fabricate flexible and foldable sheets with superior properties. Another reported form factor is CNT fiber (a.k.a. filament) by wet spinning. The fiber is either directly spun from the synthesis pot or spun from pre-made dissolved CNTs. Individual fibers can be turned into a yarn. Apart from its strength and flexibility, the main advantage is making an electrically conducting yarn. The electronic properties of individual CNT fibers (i.e. bundle of individual CNT) are governed by the two-dimensional structure of CNTs. The fibers were measured to have a resistivity only one order of magnitude higher than metallic conductors at . By further optimizing the CNTs and CNT fibers, CNT fibers with improved electrical properties could be developed.
CNT-based yarns are suitable for applications in energy and electrochemical water treatment when coated with an ion-exchange membrane. Also, CNT-based yarns could replace copper as a winding material. Pyrhönen et al. (2015) have built a motor using CNT winding.
See also
Buckypaper
Carbide-derived carbon
Carbon nanocone
Carbon nanofibers
Carbon nanoscrolls
Carbon nanotube computer
Carbon nanotubes in photovoltaics
Colossal carbon tube
Diamond nanothread
Filamentous carbon
Molecular modelling
Nanoflower
Nano-I-beam
Ninithi (nanotube modelling software)
Optical properties of carbon nanotubes
Organic semiconductor
References
This article incorporates public domain text from the National Institute of Environmental Health Sciences (NIEHS) as quoted.
External links
Nanocarbon: From Graphene to Buckyballs. Interactive 3D models of cyclohexane, benzene, graphene, graphite, chiral & non-chiral nanotubes, and C60 Buckyballs – WeCanFigureThisOut.org.
C60 and Carbon Nanotubes a short video explaining how nanotubes can be made from modified graphite sheets and the three different types of nanotubes that are formed
Learning module for Bandstructure of Carbon Nanotubes and Nanoribbons
Selection of free-download articles on carbon nanotubes
WOLFRAM Demonstrations Project: Electronic Band Structure of a Single-Walled Carbon Nanotube by the Zone-Folding Method
WOLFRAM Demonstrations Project: Electronic Structure of a Single-Walled Carbon Nanotube in Tight-Binding Wannier Representation
Allotropes of carbon
Transparent electrodes
Refractory materials
Space elevator
Discovery and invention controversies
Nanomaterials | Carbon nanotube | Physics,Chemistry,Materials_science,Astronomy,Technology | 13,240 |
7,075,191 | https://en.wikipedia.org/wiki/Azrieli%20Center | Azrieli Center (; Merkaz Azrieli) is a complex of three skyscrapers in Tel Aviv. At the base of the complex lies a large shopping mall. The complex was designed by Israeli-American architect Eli Attia. After Attia and the developer of the complex David Azrieli (after whom it is named) fell out, completion of the project was passed on to the Tel Aviv firm of Moore Yaski Sivan Architects.
Site
The Azrieli Center is located on a site in Tel Aviv, Israel, which was previously used as Tel Aviv's dumpster-truck parking garage. The tower cost $420 million to build.
Circular Tower
The Azrieli Center Circular Tower is the tallest of the three towers, measuring in height. Construction of this tower began in 1996 and was completed in 1999. The tower has 49 floors, making it at the time of its construction the tallest building in Tel Aviv, only to be surpassed by the Moshe Aviv Tower in Ramat Gan in 2001. The top floor has an indoor observation deck and a high-end restaurant, and the 48th floor is home to Mr. Azrieli's personal office.
Each floor of the Circular Tower has 84 windows, giving the tower more than 4,000 windows. The tower's perimeter is ; its diameter is . Each floor covers .
On October 31, 2003, the first annual Azrieli Circular Tower run-up competition was held, in which the participants ran up the 1,144 stairs to the tower's roof. Winners of the contest had the chance to participate in the following year's Empire State Building run-up competition in New York City.
Triangular Tower
The Azrieli Center Triangular Tower has a height of . Construction of this tower, like the circular tower, began in 1996 and was completed in 1999. It has 46 floors and its main occupant is Bezeq, Israel's largest telecommunications company; Bezeq occupies 13 floors of the tower. The tower's cross-section is an equilateral triangle.
Square Tower
The Azrieli Center Square Tower was completed in June 2007. The tower has 42 floors, and is high. It is the shortest of the three towers in the Azrieli complex. Construction of the third tower was stopped in 1998 due to urban planning disagreements and was resumed in 2006.
The lower 13 floors house Africa Israel's Crowne Plaza business hotel. The upper floors are used as office space.
Shopping center
The Azrieli Center Mall is one of the largest in Israel. There are about 30 restaurants, fast-food counters, cafes and food stands in the mall. The top floor of the mall is a popular hangout spot for teens, and many online message boards arrange get-togethers there during national holidays. There are over 300 stores in the mall.
Due to high, constant terrorism threats, the Azrieli towers are guarded to deter terrorist action, like many buildings in Israel.
Other features
The large complex boasted an 8-screen cinema until 2010, when H&M took over the space. Azrieli also features a large fitness club, night schools, a small kid-focused amusement park and a pedestrian bridge leading to Tel Aviv HaShalom Railway Station. A second pedestrian bridge, completed in March 2003, connects the Azrieli Center with the other side of Begin Road, the Shaul HaMelech light rail station and HaKirya. It is expected that a connection between Kaplan underpass and the project's underground carpark, which is one of the largest ever built in the region, will be constructed. When completed, the plot which the Center occupies will offer a 400-seat, open air auditorium.
Access
The Azrieli Center is bordered by the Ayalon Highway that crosses Tel Aviv from North to South, Begin Road and Giv'at HaTahmoshet Street (a short section that connects Kaplan Street with HaShalom Road). It is situated next to the HaShalom Interchange on the Ayalon Highway.
The center can be easily accessed from most parts of Israel by train to the Tel Aviv HaShalom Railway Station which is connected to the center by an enclosed pedestrian bridge or by one of the many buses that stop on Begin Road. In addition, the Tel Aviv Arlozorov Bus Terminal is located north of the complex. Sha'ul HaMelekh LRT Station is located 5 minute walk from the complex.
Spiral Tower
The Spiral Tower is an under-construction 91-floor, 350 meter high skyscraper which will be incorporated into the Azrieli Center complex. The Azrieli Tower will be the second-tallest in Israel if completed (after Bein Arim tower), surpassing the current tallest skyscraper, Azrieli Sarona Tower, and ToHa Tower 2.
The building's floor area ratio will be 20.
Gallery
See also
List of skyscrapers in Israel
List of tallest buildings in Tel Aviv
List of shopping malls in Israel
YOO Towers
References
External links
Catch up for Tower 3 - World Architecture News
Office buildings completed in 1999
Skyscrapers in Tel Aviv
Postmodern architecture
Shopping malls in Israel
Tourist attractions in Tel Aviv
Skyscraper hotels
Skyscraper office buildings in Israel
Skyscrapers in Israel
Residential skyscrapers in Israel
1999 establishments in Israel
20th-century architecture in Israel | Azrieli Center | Engineering | 1,074 |
6,977,357 | https://en.wikipedia.org/wiki/Reboiler | Reboilers are heat exchangers typically used to provide heat to the bottom of industrial distillation columns. They boil the liquid from the bottom of a distillation column to generate vapors which are returned to the column to drive the distillation separation. The heat supplied to the column by the reboiler at the bottom of the column is removed by the condenser at the top of the column.
Proper reboiler operation is vital to effective distillation. In a typical classical distillation column, all the vapor driving the separation comes from the reboiler. The reboiler receives a liquid stream from the column bottom and may partially or completely vaporize that stream. Steam usually provides the heat required for the vaporization.
Types of reboilers
The most critical element of reboiler design is the selection of the proper type of reboiler for a specific service. Most reboilers are of the shell and tube heat exchanger type and normally steam is used as the heat source in such reboilers. However, other heat transfer fluids like hot oil or Dowtherm (TM) may be used. Fuel-fired furnaces may also be used as reboilers in some cases.
Commonly used heat exchanger type reboilers are:
Kettle Type reboilers
Kettle reboilers (Image 1) are very simple and reliable. they are similar to shell and tube type heat exchangers. They may require pumping of the column bottoms liquid into the kettle, or there may be sufficient liquid head to deliver the liquid into the reboiler. In this reboiler type, steam flows through the tube bundle and exits as condensate. The liquid from the bottom of the tower, commonly called the bottoms, flows through the shell side. There is a retaining wall or overflow weir separating the tube bundle from the reboiler section where the residual reboiled liquid (called the bottoms product) is withdrawn, so that the tube bundle is kept covered with liquid and reduce the amount of low-boiling compounds in the bottoms product.
Thermosyphon reboilers
Thermosyphon reboilers (Image 2) do not require pumping of the column bottoms liquid into the reboiler. Natural circulation is obtained by using the density difference between the reboiler inlet column bottoms liquid and the reboiler outlet liquid-vapor mixture to provide sufficient liquid head to deliver the tower bottoms into the reboiler. Thermosyphon reboilers (also known as calandrias) are more complex than kettle reboilers and require more attention from the plant operators. There are many types of thermosyphon reboilers including vertical, horizontal, once-through or recirculating.
Fired reboiler
Fired heaters (Image 3), also known as furnaces, may be used as a distillation column reboiler. A pump is required to circulate the column bottoms through the heat transfer tubes in the furnace's convection and radiant sections. The heat source for the fired heater reboiler may be either fuel gas or fuel oil.
Forced circulation reboilers
A forced circulation reboiler (Image 4) uses a pump to circulate the column bottoms liquid through the reboilers. This is useful if the reboiler must be located far from the column, or if the bottoms product is extremely viscous.
Some fluids are temperature sensitive such as those subject to polymerization by contact with high temperature heat transfer tube walls. High liquid recirculation rates are used to reduce tube wall temperatures, thereby reducing polymerization on the tube and associated fouling.
See also
Vaporization
Boiling
Further reading
External links
Column reboilers
Sketches and discussion of various reboiler types
Heat exchangers
Distillation
Industrial equipment
pl:Podgrzewacz cwu | Reboiler | Chemistry,Engineering | 820 |
4,222,668 | https://en.wikipedia.org/wiki/Witt%27s%20theorem | "Witt's theorem" or "the Witt theorem" may also refer to the Bourbaki–Witt fixed point theorem of order theory.
In mathematics, Witt's theorem, named after Ernst Witt, is a basic result in the algebraic theory of quadratic forms: any isometry between two subspaces of a nonsingular quadratic space over a field k may be extended to an isometry of the whole space. An analogous statement holds also for skew-symmetric, Hermitian and skew-Hermitian bilinear forms over arbitrary fields. The theorem applies to classification of quadratic forms over k and in particular allows one to define the Witt group W(k) which describes the "stable" theory of quadratic forms over the field k.
Statement
Let be a finite-dimensional vector space over a field k of characteristic different from 2 together with a non-degenerate symmetric or skew-symmetric bilinear form. If {{nowrap|f : U → ''U}} is an isometry between two subspaces of V then f extends to an isometry of V.
Witt's theorem implies that the dimension of a maximal totally isotropic subspace (null space) of V is an invariant, called the index or of b, and moreover, that the isometry group of acts transitively on the set of maximal isotropic subspaces. This fact plays an important role in the structure theory and representation theory of the isometry group and in the theory of reductive dual pairs.
Witt's cancellation theorem
Let , , be three quadratic spaces over a field k. Assume that
Then the quadratic spaces and are isometric:
In other words, the direct summand appearing in both sides of an isomorphism between quadratic spaces may be "cancelled".
Witt's decomposition theorem
Let be a quadratic space over a field k. Then
it admits a Witt decomposition:
where is the radical of q, is an anisotropic quadratic space and is a split quadratic space. Moreover, the anisotropic summand, termed the core form, and the hyperbolic summand in a Witt decomposition of are determined uniquely up to isomorphism.
Quadratic forms with the same core form are said to be similar or Witt equivalent'''.
Citations
References
Emil Artin (1957) Geometric Algebra, page 121 via Internet Archive
Theorems in linear algebra
Quadratic forms | Witt's theorem | Mathematics | 515 |
20,162,597 | https://en.wikipedia.org/wiki/Norwegian%20Ocean%20Industry%20Authority | The Norwegian Ocean Industry Authority () is a Norwegian governmental supervisory authority under the Norwegian Ministry of Labour and Social Inclusion. The authority has regulatory responsibility for safety, emergency preparedness and the working environment in petroleum-industry activities in Norway, both on land and offshore. The first director was Magne Ognedal, and since 2013 Anne Myhrvold.
The PSA was established on 1 January 2004 as an independent, governmental supervisory body, partitioned from the Norwegian Petroleum Directorate. Its headquarters are located in Stavanger.
In 2023, it was announced that it would change its name to the Norwegian Ocean Industry Authority effective 1 January 2024.
Responsibilities
The PSA has regulatory responsibility for safety, emergency preparedness and the working environment in the petroleum activities, including petroleum facilities and associated pipeline systems at Melkøya, Tjeldbergodden, Nyhamna, Kollsnes, Mongstad, Sture, Kårstø and Slagentangen, as well as any future, integrated petroleum facilities.
The regulatory responsibility covers all phases of the activities; such as planning, engineering, construction, use and finally, removal.
The Norwegian government has assigned the Petroleum Safety Authority Norway the following tasks:
The PSA shall, through its own supervision and through cooperation with other authorities in the HSE area, ensure that the petroleum activities and other associated activities are followed up in a comprehensive manner.
The PSA shall furthermore carry out information and advisory activities vis-à-vis the players in the industry, establish practical cooperative relationships with other national and international HSE authorities, as well as contribute actively to the transfer of knowledge in the area of health, safety and environment in society in general.
The PSA shall issue statements to its superior government ministry regarding matters which are under consideration and provide assistance to the ministry when requested.
In the broadest sense, the entire work and purpose of the Petroleum Safety Authority Norway is to ensure that the petroleum activities are conducted prudently as regards health, environment and safety. The ministry has issued the following guidelines for how the PSA should carry out its tasks:
Follow-up shall be system-oriented and risk-based. This follow-up must be in addition to, and not instead of, the follow-up which the industry carries out for its own part. There shall be a balanced consideration between the PSA's role as a high risk/technological supervisory body and as a labour inspection authority. Participation and cooperation between the parties are important principles and integral preconditions for the activities of the Petroleum Safety Authority Norway.
Activities
In 2005, the PSA was made part of the Coexistence Group II working group, a joint project of the Norwegian government, the Institute of Marine Research, the Norwegian Fishermen's Association, the Norwegian Foundation for Nature Research and the Norwegian Oil Industry Association. Coexistence Group II's mission is to explore the feasibility of coexistence between the fishing and petroleum industries in Norwegian waters. The PSA also coordinates supervisory responsibility with Norway's national Health Examination Survey (HES).
See also
History of the petroleum industry in Norway
Standardization in oil industry
References
External links
Official Petroleum Safety Authority Norway website—
Government agencies of Norway
Petroleum industry in Norway
Oil and gas law
Petroleum politics
Government agencies established in 2004
2004 establishments in Norway
Petroleum in Norway
Safety organizations
Energy organizations | Norwegian Ocean Industry Authority | Chemistry,Engineering | 676 |
9,361,016 | https://en.wikipedia.org/wiki/Chromodomain | A chromodomain (chromatin organization modifier) is a protein structural domain of about 40–50 amino acid residues commonly found in proteins associated with the remodeling and manipulation of chromatin. The domain is highly conserved among both plants and animals, and is represented in a large number of different proteins in many genomes, such as that of the mouse. Some chromodomain-containing genes have multiple alternative splicing isoforms that omit the chromodomain entirely. In mammals, chromodomain-containing proteins are responsible for aspects of gene regulation related to chromatin remodeling and formation of heterochromatin regions. Chromodomain-containing proteins also bind methylated histones and appear in the RNA-induced transcriptional silencing complex. In histone modifications, chromodomains are very conserved. They function by identifying and binding to methylated lysine residues that exist on the surface of chromatin proteins and thereby regulate gene transcription.
See also
Bromodomain
Chromo shadow domain
References
External links
Chromatin Remodeling: Chromodomains at cellsignal.com
Protein domains | Chromodomain | Chemistry,Biology | 251 |
52,135,992 | https://en.wikipedia.org/wiki/NGC%20330 | NGC 330 is an open cluster in the Small Magellanic Cloud. It is located in the constellation Tucana. It was discovered on 1 August 1826 by James Dunlop. It was described by Dreyer as "a globular cluster, very bright, small, a little extended, stars from 13th to 15th magnitude." At an aperture of 31.0 arcseconds, the apparent V-band magnitude is 9.60, but at this wavelength, it also has 0.36 magnitudes of interstellar extinction.
NGC 330 is quite young, at about 40 million years old, and has a large proportion of Be stars. Its estimated mass is , and its total luminosity is , leading to a mass-to-luminosity ratio of 0.06 /. All else equal, older star clusters have higher mass-to-luminosity ratios; that is, they have lower luminosities for the same mass. About 34% of the massive star population in NGC 330 is estimated to be in a close binary star system; this is lower than clusters in the Large Magellanic Cloud and the Milky Way, but it is unknown if this is because NGC 330 is metal-poor or is older than the compared clusters.
References
External links
0330
18260801
Tucana
Small Magellanic Cloud
Discoveries by James Dunlop
Open clusters | NGC 330 | Astronomy | 276 |
46,504,226 | https://en.wikipedia.org/wiki/Normal%20homomorphism | In algebra, a normal homomorphism is a ring homomorphism that is flat and is such that for every field extension L of the residue field of any prime ideal , is a normal ring.
References
Ring theory
Morphisms | Normal homomorphism | Mathematics | 46 |
76,803,836 | https://en.wikipedia.org/wiki/NGC%203751 | NGC 3751 is a type E-S0 lenticular galaxy located in the Leo constellation. It is located 450 million light-years away from the Solar System and was discovered by Ralph Copeland on April 5, 1874.
To date, a non-redshift measurement gives a distance of approximately 138,000 Mpc (450 million light-years) for NGC 3751. This value is within the Hubble Distance values.
Copeland Septet
NGC 3751 is a member of the Copeland Septet. The other members are NGC 3745, NGC 3746, NGC 3748, NGC 3750, NGC 3753 and NGC 3754.
Halton Arp noticed the 7 galaxies in which he published inside his article in 1966. This group is known as Arp 320 in which another galaxy, PGC 36010 is part of it.
This group was also observed by Paul Hickson, in which he included them inside his article which was published in 1982. It is noted that this group is designated as Hickson 57. NGC 3751 is known as HCG 57F.
References
3751
036017
06601
Leo (constellation)
Discoveries by Ralph Copeland
Astronomical objects discovered in 1874
Lenticular galaxies
2MASS objects
SDSS objects
320
Hickson Compact Groups
Copeland Septet | NGC 3751 | Astronomy | 259 |
762,804 | https://en.wikipedia.org/wiki/Sex%20assignment | Sex assignment (also known as gender assignment) is the discernment of an infant's sex, typically made at birth based on an examination of the baby's external genitalia by a healthcare provider such as a midwife, nurse, or physician. In the vast majority of cases (99.95%), sex is assigned unambiguously at birth. However, in about 1 in 2000 births, the baby's genitalia may not clearly indicate male or female, necessitating additional diagnostic steps, and deferring sex assignment.
In most countries the healthcare provider's determination, along with other details of the birth, is by law recorded on an official document and submitted to the government for later issuance of a birth certificate and for other legal purposes.
The prevalence of intersex conditions, where a baby's sex characteristics do not conform strictly to typical definitions of male or female, ranges between 0.018% and 1.7%. While some intersex conditions result in genital ambiguity (approximately 0.02% to 0.05% of births), others present genitalia that are distinctly male or female, which may delay the recognition of an intersex condition until later in life.
Societally and medically, it is generally assumed that a person's gender identity will align with the sex assigned at birth, making them cisgender. However, for a minority, assigned sex and gender identity do not coincide, leading to transgender identity experiences. When assigning sex to intersex individuals, some healthcare providers may consider the gender identity that most people with a similar intersex condition develop, although such assignments may be revised as the individual matures.
The use of surgical or hormonal interventions to reinforce sex assignments in intersex individuals without informed consent is considered a violation of human rights, according to the Office of the United Nations High Commissioner for Human Rights.
Terminology
Sex assignment refers to the identification of an infant's sex at birth, typically based on observable physical characteristics. This is also known as gender assignment.
In clinical and medical contexts, terms such as "birth-assigned sex" or "birth-assigned gender" are used to describe the sex identified at birth, while "assigned sex" and "assigned gender" may also refer to any subsequent reassignments, especially common among intersex individuals.
The terminology has evolved across various editions of the Diagnostic and Statistical Manual of Mental Disorders (DSM) maintained by the American Psychiatric Association. Initially, the third edition of the DSM referred to "anatomic sex". By the fourth edition in 1994, the term "assigned sex" was introduced, with subsequent editions also using "biological sex" and "natal gender". The latest revision in 2022 streamlined the language to consistently use "sex assignment".
A 2006 consensus statement on intersex conditions also adopted the terms "assigned sex" and "assigned gender". Sex is assigned as either male or female, leading to specific terms:
More visible adoption of the terminology of sex assignment has led to public debate and criticism. Mathematician Alan Sokal and biologist Richard Dawkins have argued against the "assigned at birth" terminology. In a 2024 op-ed for The Boston Globe, they contended that sex is an "objective biological reality" determined at conception and observed at birth, rather than assigned. They say that using "assigned" terminology, which they view as an example of "social constructionism gone amok", distorts scientific facts and could undermine trust in medical institutions.
There is a consensus in the use of the term "sex assignment" for newborns with intersex conditions; observed chromosomal sex and assigned sex may intentionally differ for medical reasons (based upon predictions of psychosocial and psychosexual health in later life).
Assignment in cases of infants with intersex traits, or cases of trauma
Observation or recognition of an infant's sex may be complicated in the case of intersex infants and children and in cases of early trauma. In such cases, the infant may be assigned male or female, and may receive intersex surgery to confirm that assignment. These medical interventions have increasingly been seen as a human rights violation due to their unnecessary nature and the potential for lifelong complications.
Cases of trauma include the famous John/Joan case, where sexologist John Money claimed successful reassignment from male to female of a 17-month-old boy whose penis was destroyed during circumcision. However, this claim was later shown to be largely false. The subject, David Reimer, later identified as a man.
The number of births with ambiguous genitals is in the range of 1 in 2,000 to 1 in 4,500 (0.05% to 0.02%). Typical examples would be an unusually prominent clitoris in an otherwise apparently typical girl, or complete cryptorchidism in an otherwise apparently typical boy. In most of these cases, a sex is tentatively assigned and the parents told that tests will be performed to confirm the apparent sex. Typical tests in this situation might include a pelvic ultrasound to determine the presence of a uterus, a testosterone or 17α-hydroxyprogesterone level, and/or a karyotype. In some of these cases a pediatric endocrinologist is consulted to confirm the tentative sex assignment. The expected assignment is usually confirmed within hours to a few days in these cases.
Some infants are born with enough ambiguity that assignment becomes a more drawn-out process of multiple tests and intensive education of the parents about sexual differentiation. In some of these cases, it is clear that the child will face physical difficulties or social stigma as they grow up, and deciding upon the sex of assignment involves weighing the advantages and disadvantages of either assignment. Intersex activists have criticised "normalising" procedures performed on infants and children, who are unable to provide informed consent.
History
In European societies, Roman law, post-classical canon law, and later common law, referred to a person's sex as male, female, or hermaphrodite, with legal rights as male or female depending on the characteristics that appeared most dominant. Under Roman law, a hermaphrodite had to be classed as either male or female. The 12th-century Decretum Gratiani states that "Whether a hermaphrodite may witness a testament, depends on which sex prevails". The foundation of common law, the 16th Century Institutes of the Lawes of England, described how a hermaphrodite could inherit "either as male or female, according to that kind of sexe which doth prevaile." Legal cases where sex assignment was placed in doubt have been described over the centuries.
With the medicalization of intersex, criteria for assignment have evolved over the decades, as clinical understanding of biological factors and diagnostic tests have improved, as surgical techniques have changed and potential complications have become clearer, and in response to the outcomes and opinions of adults who have grown up with various intersex conditions.
Before the 1950s, assignment was based almost entirely on the appearance of the external genitalia. Although physicians recognized that there were conditions in which the apparent secondary sexual characteristics could develop contrary to the person's sex, and conditions in which the gonadal sex did not match that of the external genitalia, their ability to understand and diagnose such conditions in infancy was too poor to attempt to predict future development in most cases.
In the 1950s, endocrinologists developed a basic understanding of the major intersex conditions such as congenital adrenal hyperplasia (CAH), androgen insensitivity syndrome, and mixed gonadal dysgenesis. The discovery of cortisone allowed survival of infants with severe CAH for the first time. New hormone tests and karyotypes allowed more confident diagnosis in infancy and prediction of future development.
Sex assignment became more than choosing a sex of rearing, but also began to include surgical treatment. Undescended testes could be retrieved. A greatly enlarged clitoris could be amputated to the usual size, but attempts to create a penis were unsuccessful. John Money and others controversially believed that children were more likely to develop a gender identity that matched sex of rearing than might be determined by chromosomes, gonads, or hormones. The resulting medical model was termed the "Optimal gender model".
Challenges to requirements for sex assignment
In recent years, the perceived need to legally assign sex is increasingly being challenged by transgender, transsexual, and intersex people. A report for the Dutch Ministry of Security and Justice states "Gender increasingly seems to be perceived as a 'sensitive' identity feature, but so far is not regarded, nor protected as such in privacy regulations". Australian government guidelines state that "departments and agencies that collect sex and/or gender information must not collect information unless it is necessary for, or directly related to, one or more of the agency's functions or activities"
Sex registration was introduced in the Netherlands in 1811 due to gender-specific rights and responsibilities, such as military conscription. Many gender-specific provisions in legislation no longer exist, but the provisions remain for rationales that include "speed of identification procedures".
References
Genital modification and mutilation
Human sexuality
Intersex healthcare
Sex-determination systems
Transgender health care | Sex assignment | Biology | 1,924 |
1,922,158 | https://en.wikipedia.org/wiki/Salix%20babylonica | Salix babylonica (Babylon willow or weeping willow; ) is a species of willow native to dry areas of northern China, Korea, Mongolia, Japan, and Siberia but cultivated for millennia elsewhere in Asia, being traded along the Silk Road to southwest Asia and Europe.
Description
Salix babylonica is a medium- to large-sized deciduous tree, growing up to tall. It grows rapidly, but has a short lifespan, between 40 and 75 years. The shoots are Yellowish-brown, with small buds. The leaves are alternate and spirally arranged, narrow, light green, long and broad, with finely serrate margins and long acuminate tips; they turn a gold-yellow in autumn. The flowers are arranged in catkins produced early in the spring; it is dioecious, with the male and female catkins on separate trees.
Taxonomy
Salix babylonica was described and named scientifically by Carl Linnaeus in 1736, who knew the species as the pendulous-branched ("weeping") variant then recently introduced into the Clifford garden in Hartekamp in The Netherlands.
Horticultural selections and related hybrids
Early Chinese cultivar selections include the original weeping willow, Salix babylonica 'Pendula', in which the branches and twigs are strongly pendulous, which was presumably spread along ancient trade routes. These distinctive trees were subsequently introduced into England from Aleppo in northern Syria in 1730, and have rapidly become naturalised, growing well along rivers and in parks. These plants are all females, readily propagated vegetatively, and capable of hybridizing with various other kinds of willows, but not breeding true from seed. This type of tree is grown very easily through plant propagation.
Two cultivated hybrids between pendulous Salix babylonica and other species of Salix willows also have pendulous branchlets, and are more commonly planted than S. babylonica itself:
Salix × pendulina, a hybrid with S. babylonica accepted as the female parent, but with the male parent unidentified, probably being either S. euxina or S. × fragilis, but perhaps S. pentandra. Of these possibilities, S. × fragilis is itself a hybrid, with S. alba and S. euxina as parental species.
Salix × sepulcralis, is a hybrid between S. alba and S. babylonica.
Cultivars derived from either of these hybrids are generally better adapted than S. babylonica to the more humid climates of most heavily populated regions of Europe and North America.
Relation to Salix matsudana
A similar willow species also native to northern China, Salix matsudana (Chinese willow), is now included in Salix babylonica as a synonym by many botanists, including the Russian willow expert Alexey Skvortsov. The only reported difference between the two species is S. matsudana has two nectaries in each female flower, whereas S. babylonica has only one; however, this character is variable in many willows (for example, crack willow, Salix × fragilis, can have either one or two), so even this difference may not be taxonomically significant.
A horticultural variant with twisted twigs and trunk, the corkscrew willow (S. matsudana var. tortuosa), is widely planted.
Cultivation
Salix babylonica, especially its pendulous-branched ("weeping") form, has been introduced into many other areas, including Europe and the southeastern United States, but beyond China, it has not generally been as successfully cultivated as some of its hybrid derivatives, being sensitive to late-spring frosts. In the more humid climates of much of Europe and eastern North America, it is susceptible to a canker disease, willow anthracnose (Marssonina salicicola), which makes infected trees very short-lived and unsightly.
Cultivars
Salix babylonica (Babylon willow) has many cultivars, including:
'Babylon' (synonym: 'Napoleon') is the most widely grown cultivar of S. babylonica, with its typical weeping branches.
'Crispa' (synonym: 'Annularis') is a mutant of 'Babylon', with spirally curled leaves.
Various cultivars of Salix matsudana (Chinese willow) are now often included within Salix babylonica, treated more broadly, including:
'Pendula' is one of the best weeping trees, with a silvery shine, hardier, and more disease resistant.
'Tortuosa' is an upright tree with twisted and contorted branches, marketed as corkscrew willow.
Yet other weeping willow cultivars are derived from interspecific Salix hybrids, including S. babylonica in their parentage. The most widely grown weeping willow cultivar is Salix × sepulcralis 'Chrysocoma', with bright yellowish branchlets.
Uses
Peking willow is a popular ornamental tree in northern China, and is also grown for wood production and shelterbelts there, being particularly important around the oases of the Gobi Desert, protecting agricultural land from desert winds.
Origin
The epithet babylonica in this Chinese species' scientific name (S. babylonica), as well as the related common names "Babylon willow" or "Babylon weeping willow", derive from a misunderstanding by Linnaeus that this willow was the tree described in the Bible in the opening of Psalm 137 (here in Latin and English translations):
From the Clementine Vulgate (Latin, 1592):
Super flumina Babylonis illic sedimus et flevimus, cum recordaremur Sion.
In salicibus in medio ejus suspendimus organa nostra....
Here, "salicibus" is the dative plural of the Latin noun salix, the willows, used by Linnaeus as the name for the willow genus Salix.
From the King James Version (English, 1611):
By the rivers of Babylon, there we sat down, yea, we wept, when we remembered Zion.
We hanged our harps upon the willows in the midst thereof.
From the Revised Standard Version (English, 1952):
By the waters of Babylon, there we sat down and wept, when we remembered Zion
On the willows there we hung up our lyres....
Despite these Biblical references to "willows", whether in Latin or English, the trees growing in Babylon along the Euphrates River in ancient Mesopotamia (modern Iraq) and named gharab in early Hebrew, are not willows (Salix) in either the modern or the classical sense, but the Euphrates poplar (Populus euphratica), with willow-like leaves on long, drooping shoots, in the related genus Populus. Both Populus and Salix are in the plant family Salicaceae, the willow family.
These Babylonian trees are correctly called poplars, not willows, in the New International Version of the Bible (English, 1978):
By the rivers of Babylon we sat and wept when we remembered Zion
There on the poplars we hung our harps.
Explanatory notes
References
Further reading
Flora of China:
External links
babylonica
Flora of China
Flora of Korea
Flora of Japan
Flora of Russia
Flora of Mongolia
Garden plants of Asia
Ornamental trees
Phytoremediation plants
Plants described in 1753
Taxa named by Carl Linnaeus
Trees of China
Weeping trees
Drought-tolerant trees
Trees of Siberia
Trees of Russia
Trees of continental subarctic climate | Salix babylonica | Biology | 1,544 |
3,704,756 | https://en.wikipedia.org/wiki/Snub%2024-cell | In geometry, the snub 24-cell or snub disicositetrachoron is a convex uniform 4-polytope composed of 120 regular tetrahedral and 24 icosahedral cells. Five tetrahedra and three icosahedra meet at each vertex. In total it has 480 triangular faces, 432 edges, and 96 vertices. One can build it from the 600-cell by diminishing a select subset of icosahedral pyramids and leaving only their icosahedral bases, thereby removing 480 tetrahedra and replacing them with 24 icosahedra.
Topologically, under its highest symmetry, [3+,4,3], as an alternation of a truncated 24-cell, it contains 24 pyritohedra (an icosahedron with Th symmetry), 24 regular tetrahedra, and 96 triangular pyramids.
Semiregular polytope
It is one of three semiregular 4-polytopes made of two or more cells which are Platonic solids, discovered by Thorold Gosset in his 1900 paper. He called it a tetricosahedric for being made of tetrahedron and icosahedron cells. (The other two are the rectified 5-cell and rectified 600-cell.)
Alternative names
Snub icositetrachoron
Snub demitesseract
Semi-snub polyoctahedron (John Conway)
Sadi (Jonathan Bowers) for snub disicositetrachoron
Tetricosahedric (Thorold Gosset)
Geometry
Coordinates
The vertices of a snub 24-cell centered at the origin of 4-space, with edges of length 2, are obtained by taking even permutations of
(0, ±1, ±φ, ±φ2)
where φ = ≈ 1.618 is the golden ratio.
The unit-radius coordinates of the snub 24-cell, with edges of length φ−1 ≈ 0.618, are the even permutations of
(±, ±, ±, 0)
These 96 vertices can be found by partitioning each of the 96 edges of a 24-cell in the golden ratio in a consistent manner dimensionally analogous to the way the 12 vertices of an icosahedron or "snub octahedron" can be produced by partitioning the 12 edges of an octahedron in the golden ratio. This can be done by first placing vectors along the 24-cell's edges such that each two-dimensional face is bounded by a cycle, then similarly partitioning each edge into the golden ratio along the direction of its vector. This is equivalent to the snub truncation construction of the 24-cell described below.
The 96 vertices of the snub 24-cell, together with the 24 vertices of a 24-cell, form the 120 vertices of the 600-cell.
Constructions
The snub 24-cell is derived from the 24-cell by a special form of truncation.
Truncations remove vertices by cutting through the edges incident to the vertex; forms of truncation differ by where on the edge the cut is made. The common truncations of the 24-cell include the rectified 24-cell (which cuts each edge at its midpoint, producing a polytope bounded by 24 cubes and 24 cuboctahedra), and the truncated 24-cell (which cuts each edge one-third of its length from the vertex, producing a polytope bounded by 24 cubes and 24 truncated octahedra). In these truncations a cube is produced in place of the removed vertex, because the vertex figure of the 24-cell is a cube and the cuts are equidistant from the vertex.
The snub truncation of the 24-cell cuts each edge into two golden sections (such that the larger section is in the golden ratio ~1.618 to the smaller section, and the original edge is in the golden ratio to the larger section). The cut must be made in alternate directions on alternate edges incident to each vertex, in order to have a coherent result. The edges incident to a vertex in the 24-cell are the 8 radii of its cubical vertex figure. The only way to choose alternate radii of a cube is to choose the four radii of a tetrahedron (inscribed in the cube) to be cut at the smaller section of their length from the vertex, and the opposite four radii (of the other tetrahedron that can be inscribed in the cube) to be cut at the larger section of their length from the vertex. There are of course two ways to do this; both produce a cluster of five regular tetrahedra in place of the removed vertex, rather than a cube.
This construction has an analogy in 3 dimensions: the construction of the icosahedron (the "snub octahedron") from the octahedron, by the same method. That is how the snub-24 cell's icosahedra are produced from the 24-cell's octahedra during truncation.
The snub 24-cell is related to the truncated 24-cell by an alternation operation. Half the vertices are deleted, the 24 truncated octahedron cells become 24 icosahedron cells, the 24 cubes become 24 tetrahedron cells, and the 96 deleted vertex voids create 96 new tetrahedron cells.
The snub 24-cell may also be constructed by a particular diminishing of the 600-cell: by removing 24 vertices from the 600-cell corresponding to those of an inscribed 24-cell, and then taking the convex hull of the remaining vertices. This is equivalent to removing 24 icosahedral pyramids from the 600-cell.
Conversely, the 600-cell may be constructed from the snub 24-cell by augmenting it with 24 icosahedral pyramids.
Weyl orbits
Another construction method uses quaternions and the Icosahedral symmetry of Weyl group orbits of order 120. The following describe and 24-cells as quaternion orbit weights of D4 under the Weyl group W(D4):
O(0100) : T = {±1,±e1,±e2,±e3,(±1±e1±e2±e3)/2}
O(1000) : V1
O(0010) : V2
O(0001) : V3
With quaternions where is the conjugate of and and , then the Coxeter group is the symmetry group of the 600-cell and the 120-cell of order 14400.
Given such that and as an exchange of within , we can construct the snub 24-cell as
Structure
The icosahedral cells fit together face-to-face leaving voids between them filled by clusters of five tetrahedral cells.
Each icosahedral cell is joined to 8 other icosahedral cells at 8 triangular faces in the positions corresponding to an inscribing octahedron. The remaining triangular faces are joined to tetrahedral cells, which occur in pairs that share an edge on the icosahedral cell.
The tetrahedral cells may be divided into two groups, of 96 yellow cells and 24 red cells respectively (as colored in the net illustration). Each yellow tetrahedral cell is joined via its triangular faces to 3 blue icosahedral cells and one red tetrahedral cell, while each red tetrahedral cell is joined to 4 yellow tetrahedra. Thus, the tetrahedral cells occur in clusters of five (four yellow cells face-bonded around a red central one, each red/yellow pair lying in a different hyperplane). The red central tetrahedron of the five shares each of its six edges with a different icosahedral cell, and with the pair of yellow tetrahedral cells which shares that edge on the icosahedral cell.
Symmetry
The snub 24-cell has three vertex-transitive colorings based on a Wythoff construction on a Coxeter group from which it is alternated: F4 defines 24 interchangeable icosahedra, while the B4 group defines two groups of icosahedra in an 8:16 counts, and finally the D4 group has 3 groups of icosahedra with 8:8:8 counts.
Projections
Orthographic projections
Perspective projections
Dual
The Dual snub 24-cell has 144 identical irregular cells. Each cell has faces of two kinds: 3 kites and 6 isosceles triangles. The polytope has a total of 432 faces (144 kites and 288 isosceles triangles) and 480 edges.
Related polytopes
The snub 24-cell can be obtained as a diminishing of the 600-cell at 24 of its vertices, in fact those of a vertex inscribed 24-cell. There is also a further such bi-diminishing, when the vertices of a second vertex inscribed 24-cell would be diminished as well. Accordingly, this one is known as the bi-24-diminished 600-cell.
The snub 24-cell is also called a semi-snub 24-cell because it is not a true snub (alternation of an omnitruncated 24-cell). The full snub 24-cell can also be constructed although it is not uniform, being composed of irregular tetrahedra on the alternated vertices.
The snub 24-cell is the largest facet of the 4-dimensional honeycomb, the snub 24-cell honeycomb.
The snub 24-cell is a part of the F4 symmetry family of uniform 4-polytopes.
See also
Snub 24-cell honeycomb
Dual snub 24-cell
Citations
References
External links
Snub icositetrachoron - Data and images
Uniform 4-polytopes | Snub 24-cell | Physics | 2,084 |
8,763,893 | https://en.wikipedia.org/wiki/Three%20Stars%20%28Chinese%20constellation%29 | The Three Stars mansion () is one of the twenty-eight mansions of the Chinese constellations. It is one of the western mansions of the White Tiger. This collection of seven bright stars is visible during winter in the Northern Hemisphere (summer in the Southern).
Asterisms
References
Chinese constellations | Three Stars (Chinese constellation) | Astronomy | 62 |
41,830,137 | https://en.wikipedia.org/wiki/Bubble%20oxygenator | A bubble oxygenator is an early implementation of the oxygenator used for cardiopulmonary bypass. It has since been supplanted by the membrane oxygenator
as a result of advances in material science. Some continue to promote it as a low-cost alternative allowing greater self-sufficiency.
History
Open-heart surgery developed rapidly beginning in the 1950s, and many methods were developed for oxygenating blood outside the body. A bubble oxygenator was introduced in 1950 by Clark, Gollan, and Gupta. The method faced initial skepticism but in 1956 the University of Minnesota's De-Wall-Lillehei bubble oxygenator was demonstrated to be relatively simple, inexpensive, and easy to operate.
The device faced competition from membrane oxygenators, which arrived within the same decade and were found to provide better oxygenation for periods over eight hours, and other advantages beyond six hours. However, most open-heart operations were substantially shorter, and by 1976 the bubble oxygenator was predominant.
In the 1980s, microporous membrane oxygenators were developed, and replaced bubble oxygenators in most applications.
References
Medical equipment | Bubble oxygenator | Biology | 226 |
21,599,341 | https://en.wikipedia.org/wiki/Medea%20hypothesis | The Medea hypothesis is a term coined by paleontologist Peter Ward for a hypothesis that contests the Gaian hypothesis and proposes that multicellular life, understood as a superorganism, may be self-destructive or suicidal.
The metaphor refers to the mythological Medea (representing the Earth), who kills her own children (multicellular life).
In this view, microbial-triggered mass extinctions result in returns to the microbial-dominated state Earth has been in for most of its history.
Examples
Possible examples of extinction events induced entirely or partially by biotic activities include:
The Great Oxidation Event, 2.45 billion years ago, believed to be responsible for the mass poisoning of anaerobic microbes to which oxygen was toxic, and for the Huronian glaciation that resulted from the reaction of methane with oxygen to form carbon dioxide (a less potent greenhouse gas than methane) and subsequent depletion of atmospheric carbon dioxide by aerobic photosynthesisers
The Sturtian and Marinoan Snowball Earth glaciations, 715 to 680 and 650 to 632.3 million years ago, respectively, resulting from the sequestration of atmospheric carbon dioxide during the Neoproterozoic Oxygenation Event
The Late Ordovician Mass Extinction (LOME), to , suggested by some studies to have been caused by glaciation resulting from carbon dioxide depletion driven by the radiation of land plants
Euxinic events, such as during the Great Dying, , and the aforementioned LOME, caused by sulphur-reducing prokaryotes that produce hydrogen sulphide
The list excludes the Cretaceous–Paleogene extinction event, since this was, at least partially, externally induced by a meteor impact.
Current status and future extinctions
Peter Ward proposes that the current man-made climate change and mass extinction event may be considered to be the most recent Medean event. As these events are anthropogenic, he postulates that Medean events are not necessarily caused by microbes, but by intelligent life as well and that the final mass extinction of complex life, roughly about 500–900 million years in the future, can also be considered a Medean event: "Plant life that still exists then will be forced to adapt to a warming and expanding Sun, causing them to remove even more carbon dioxide from the atmosphere (which in turn will have already been lowered due to the increasing heat from the Sun gradually speeding up the weathering process that removes these molecules from the atmosphere), and ultimately accelerating the complete extinction of complex life by making carbon dioxide levels drop down to just 10 ppm, below which plants can no longer survive." However, Ward simultaneously argues that intelligent life such as humans may not necessarily just trigger future Medean events, but may eventually prevent them from occurring.
See also
Death drive
Fermi paradox
References
External links
Biological hypotheses
Earth sciences
Ecological theories
Events that forced the climate
Evolutionary biology
Extinction events
Hypotheses
Medea
Meteorological hypotheses
Planetary science
Superorganisms
Words and phrases derived from Greek mythology | Medea hypothesis | Astronomy,Biology | 623 |
2,128,410 | https://en.wikipedia.org/wiki/Delamination | Delamination is a mode of failure where a material fractures into layers. A variety of materials, including laminate composites and concrete, can fail by delamination. Processing can create layers in materials, such as steel formed by rolling and plastics and metals from 3D printing which can fail from layer separation. Also, surface coatings, such as paints and films, can delaminate from the coated substrate.
In laminated composites, the adhesion between layers often fails first, causing the layers to separate. For example, in fiber-reinforced plastics, sheets of high strength reinforcement (e.g., carbon fiber, fiberglass) are bound together by a much weaker polymer matrix (e.g., epoxy). In particular, loads applied perpendicular to the high strength layers, and shear loads can cause the polymer matrix to fracture or the fiber reinforcement to debond from the polymer.
Delamination also occurs in reinforced concrete when metal reinforcements near the surface corrode. The oxidized metal has a larger volume causing stresses when confined by the concrete. When the stresses exceed the strength of the concrete, cracks can form and spread to join with neighboring cracks caused by corroded rebar creating a fracture plane that runs parallel to the surface. Once the fracture plane has developed, the concrete at the surface can separate from the substrate.
Processing can create layers in materials which can fail by delamination. In concrete, surfaces can flake off from improper finishing. If the surface is finished and densified by troweling while the underlying concrete is bleeding water and air, the dense top layer may separate from the water and air pushing upwards. In steels, rolling can create a microstructure when the microscopic grains are oriented in flat sheets which can fracture into layers. Also, certain 3D printing methods (e.g., Fused Deposition) builds parts in layers that can delaminate during printing or use. When printing thermoplastics with fused deposition, cooling a hot layer of plastic applied to a cold substrate layer can cause bending due to differential thermal contraction and layer separation.
Inspection methods
There are multiple nondestructive testing methods to detect delamination in structures including visual inspection, tap testing (i.e. sounding), ultrasound, radiography, and infrared imaging.
Visual inspection is useful for detecting delaminations at the surface and edges of materials. However, a visual inspection may not detect delamination within a material without cutting the material open.
Tap testing or sounding involves gently striking the material with a hammer or hard object to find delamination based on the resulting sound. In laminated composites, a clear ringing sound indicates a well bonded material whereas a duller sound indicates the presence of delamination due to the defect dampening the impact. Tap testing is well suited for finding large defects in flat panel composites with a honeycomb core whereas thin laminates may have small defects that are not discernible by sound. Using sound is also subjective and dependent on the inspector's quality of hearing as well as judgement. Any intentional variations in the part may also change the pitch of the produced sound, influencing the inspection. Some of these variations include ply overlaps, ply count change gores, core density change (if used), and geometry.
In reinforced concretes intact regions will sound solid whereas delaminated areas will sound hollow. Tap testing large concrete structures is carried about either with a hammer or with a chain dragging device for horizontal surfaces like bridge decks. Bridge decks in cold climate countries which use de-icing salts and chemicals are commonly subject to delamination and as such are typically scheduled for annual inspection by chain-dragging as well as subsequent patch repairs of the surface.
Delamination resistance testing methods
Coating delamination tests
ASTM provides standards for paint adhesion testing which provides qualitative measures for paints and coatings resistance to delamination from substrates. Tests include cross-cut test, scrape adhesion, and pull-off test.
Interlaminar fracture toughness testing
Fracture toughness is a material property that describes resistance to fracture and delamination. It is denoted by critical stress intensity factor or critical strain energy release rate . For unidirectional fiber reinforced polymer laminate composites, ASTM provides standards for determining mode I fracture toughness and mode II fracture toughness of the interlaminar matrix. During the tests load and displacement is recorded for analysis to determine the strain energy release rate from the compliance method. in terms of compliance is given by
where is the change in compliance (ratio of ), is the thickness of the specimen, and is the change in crack length.
Mode I interlaminar fracture toughness
ASTM D5528 specifies the use of the double cantilever beam (DCB) specimen geometry for determining mode I interlaminar fracture toughness. A double cantilever beam specimen is created by placing a non-stick film between reinforcement layers in the center of the beam before curing the polymer matrix to create an initial crack of length . During the test the specimen is loaded in tension from the end of the initial crack side of the beam opening the crack. Using the compliance method, the critical strain energy release rate is given by
where and are the maximum load and displacement respectively by determining when the load deflection curve has become nonlinear with a line drawn from the origin with a 5% increase in compliance. Typically, equation 2 overestimates the fracture toughness because the two cantilever beams of the DCB specimen will have a finite rotation at the crack. The finite rotation can be corrected for by calculating with a slightly longer crack with length giving
The crack length correction can be calculated experimentally by plotting the least squares fit of the cube root of the compliance vs. crack length . The correction is the absolute value of the x intercept. Fracture toughness can also be corrected with the compliance calibration method where given by
where is the slope of the least squares fit of vs. .
Mode II interlaminar fracture toughness
Mode II interlaminar fracture toughness can be determined by an edge notch flexure test specified by ASTM D7905. The specimen is prepared in a similar manner as the DCB specimen introducing an initial crack with length before curing the polymer matrix. If the test is performed with the initial crack (non-precracked method) the candidate fracture toughness is given by
where is the thickness of the specimen and is the max load and is a fitting parameter. is determined by experimental results with a least squares fit of compliance vs. the crack length cubed with the form of
.
The candidate fracture toughness equals the mode II fracture toughness if strain energy release rate falls within certain percentage of at different crack lengths specified by ASTM.
Interlaminar shear strength testing
Interlaminar shear strength is used as an additional measure of the strength of the fiber-matrix bond in fiber-reinforced composites. Shear-induced delamination is experienced in various loading conditions where the bending moment across the composite changes rapidly, such as in pipes with changes in thickness or bends. Multiple test architectures have been proposed for use in measuring interlaminar shear strength, including the short beam shear test, Iosipescu test, rail shear test, and asymmetrical four-point bending test. The goal of each of these tests is to maximize the ratio of shear stress to tensile stress exhibited in the sample, promoting failure via delamination of the fiber-matrix interface instead of through fiber tension or buckling. The orthotropic symmetry of fiber composite materials makes a state of pure shear stress difficult to obtain in sample testing; thin cylindrical specimens can be used but are costly to manufacture. Sample geometries are thus chosen for ease of machining and optimization of the stress state when loaded.
In addition to manufactured composites such as glass fiber-reinforced polymers, interlaminar shear strength is an important property in natural materials such as wood. The long, thin shape of floorboards, for example, may promote deformation that leads to vibrations.
Asymmetric four-point bending
Asymmetric four-point bending (AFPB) may be chosen to measure interlaminar shear strength over other procedures for a variety of reasons, including specimen machinability, test reproducibility, and equipment availability. For example, short-beam shear samples are constrained to a specific length-thickness ratio to prevent bending failure, and the shear stress distribution across the specimen is non-uniform, both of which contribute to a lack of reproducibility. Rail shear testing also produces a non-homogeneous shear stress state, making it appropriate for determining shear modulus, but not shear strength. The Iosipescu test requires special equipment in addition to the roller setup already used for other three- and four-point flexural tests.
ASTM C1469 outlines a standard for AFPB testing of advanced ceramic joints, and the method has been proposed to be adapted for use with continuous ceramic matrix composites. Rectangular samples can be used with or without notches machined at the center; the addition of notches helps to control the position of the failure along the length of the sample, but improper or nonsymmetrical machining can result in the addition of undesired normal stresses which reduce the measured strength. The sample is then loaded in compression in its test fixture, with loading applied directly to the sample from 4 loading pins arranged in a parallelogram-like configuration. The load applied from the test fixture is transferred unevenly to the top two pins; the ratio of the inner pin load and outer pin load is defined as the loading factor , such that
,
where and are the lengths from the inner pin to the applied point load and from the outer pin to the applied point load, respectively. The normal stress in the sample is maximized at the locations of the inner pins, and is equivalent to
,
where is the total applied load on the sample, is the sample length, is the sample width (into the page as seen in a 2D free-body diagram), and is the sample thickness. The shear stress in the sample is maximized in between the inner span of the pins and is given by
.
The ratio of normal to shear stress in the sample is given by
.
This ratio is dependent both on the loading factor of the sample and its length-thickness ratio; both of these quantities are important in determining the mode of failure of the sample in testing.
References
Composite materials
Mechanical failure modes | Delamination | Physics,Materials_science,Technology,Engineering | 2,151 |
1,197,643 | https://en.wikipedia.org/wiki/Minesweeping | Minesweeping is the practice of removing explosive naval mines, usually by a specially designed ship called a minesweeper using various measures to either capture or detonate the mines, but sometimes also with an aircraft made for that purpose. Minesweeping has been practiced since the advent of naval mining in 1855 during the Crimean War. The first minesweepers date to that war and consisted of British rowboats trailing grapnels to snag the mines.
By ship
A sweep is either a contact sweep, a wire dragged through the water by one or two ships to cut the mooring wire of floating mines, or a distance sweep that mimics a ship to detonate the mines. The sweeps are dragged by minesweepers, either purpose-built military ships or converted trawlers. Each run covers between , and the ships must move slowly in a straight line, making them vulnerable to enemy fire. This was exploited by the Turkish army in the Battle of Gallipoli in 1915, when mobile howitzer batteries prevented the British and French from clearing a path through minefields.
If a contact sweep hits a mine, the wire of the sweep rubs against the mooring wire until it is cut. Sometimes "cutters", explosive devices to cut the mine's wire, are used to lessen the strain on the sweeping wire. Mines cut free are recorded and collected for research or shot with a deck gun. Before the First World War, the Imperial Russian Navy officer Pyotr Kitkin invented "mine protectors" to break a sweeping wire before it could cut the mine's mooring wire.
Minesweepers protect themselves with an oropesa or paravane instead of a second minesweeper. These are torpedo-shaped towed bodies, similar in shape to a Harvey Torpedo, that are streamed from the sweeping vessel thus keeping the sweep at a determined depth and position. Some large warships were routinely equipped with paravane sweeps near the bows in case they inadvertently sailed into minefields—the mine would be deflected towards the paravane by the wire instead of towards the ship by its wake. More recently, heavy-lift helicopters have dragged minesweeping sleds, as in the 1991 Persian Gulf War.
The distance sweep mimics the sound and magnetism of a ship and is pulled behind the sweeper. It has floating coils and large underwater drums. It is the only sweep effective against bottom mines.
During the Second World War, RAF Coastal Command used Vickers Wellington bombers Wellington DW.Mk I fitted with degaussing coils to trigger magnetic mines.
Modern influence mines are designed to discriminate against false inputs and are much more difficult to sweep. They often contain inherent anti-sweeping mechanisms. For example, they may be programmed to respond to the unique noise of a particular ship-type, its associated magnetic signature and the typical pressure displacement of such a vessel. As a result, a mine-sweeper must accurately guess and mimic the required target signature to trigger detonation. The task is complicated by the fact that an influence mine may have one or more of a hundred different potential target signatures programmed into it.
Another anti-sweeping mechanism is a ship-counter in the mine fuze. When enabled, this allows detonation only after the mine fuze has been triggered a pre-set number of times. To further complicate matters, influence mines may be programmed to arm themselves (or disarm automatically—known as self-sterilization) after a pre-set time. During the pre-set arming delay (which could be days or weeks) the mine would remain dormant and ignore any target stimulus, whether genuine or faked.
When influence mines are laid in an ocean minefield, they may have various combinations of fuze settings configured. For example, some mines (with the acoustic sensor enabled) may become active within three hours of being laid, others (with the acoustic and magnetic sensors enabled) may become active after two weeks but have the ship-counter mechanism set to ignore the first two trigger events, and still others in the same minefield (with the magnetic and pressure sensors enabled) may not become armed until three weeks have passed. Groups of mines within this mine-field may have different target signatures which may or may not overlap. The fuzes on influence mines allow many different permutations, which complicates the clearance process.
Mines with ship-counters, arming delays, and highly specific target signatures in mine fuses can falsely convince a belligerent that a particular area is clear of mines or has been swept effectively because a succession of vessels have already passed through safely.
By aircraft
Aircraft can also be used for minesweeping. During the Second World War, fifteen British Vickers Wellington bombers were modified to carry a large magnetic induction loop and an electrical generator. The "Directional Wireless Installation" (DWI), a cover story for the true purpose of the magnetic loop, was used successfully on 10 May 1940, to sweep a path for the escape of the Dutch royal family to the UK. The DWI was used most successfully in the Mediterranean Theatre, particularly over the Suez Canal and Alexandria Harbour. Their use revealed the limitations of the technique, in that it only works effectively in very shallow water (such as canals and harbours). From about 1943, German Junkers Ju 52 transports were similarly converted. Blohm & Voss BV 138 MS tri-motor flying boats were also used for this purpose.
The MH-53E Sea Dragon helicopter is used primarily by the United States Navy to tow several types of mine hunting or mine sweeping gear through the water. It replaced the earlier, RH-53A and RH-53D variants of the Sikorsky CH-53 Sea Stallion. Other examples of minesweeping helicopters include the RH-3A variant of the Sikorsky SH-3 Sea King, as well as the Mi-14BT variant of the Mil Mi-14 and the MCH-101 variant of the AgustaWestland AW101.
See also
Minehunter
References
External links
Mine warfare
Mine action | Minesweeping | Engineering | 1,242 |
767,363 | https://en.wikipedia.org/wiki/United%20States%20astronaut%20badges | United States astronaut badges are the various badges of the United States which are awarded to military and civilian personnel of the National Aeronautics and Space Administration, the various child departments of the Department of Defense, or a private space-faring entity, who have performed (or in some cases, completed training for) a spaceflight. The military versions are among the least-awarded qualification badges of the United States armed forces.
History
The first astronaut badges were created by taking the astronauts' own aviator badges and overlaying the center shield with a design called the "astronaut device", a star with three trailing rays passing through an ellipse representing orbital flight.
In the 1960s, the United States Department of Defense awarded astronaut badges to military and civilian pilots who flew aircraft higher than . Seven USAF and NASA pilots qualified for the astronaut badge by flying the suborbital X-15 rocket spaceplane. American test pilots Michael Melvill and Brian Binnie were each awarded a commercial astronaut badge by the Federal Aviation Administration (FAA) when they flew sub-orbital missions aboard the Scaled Composites SpaceShipOne rocket spaceplane. All others who have been awarded the astronaut badge earned it travelling to space in non-winged rockets, the X-15, or the Space Shuttle. Three of the crew members aboard the Ax-1 flight aboard the Crew Dragon Capsule were awarded their civilian astronaut wings by their Mission commander upon becoming the first private citizens to travel to the International Space Station on April 9, 2022.
Military badges
Each of the military services issues its own version of the astronaut badge, which consists of a standard aviation badge with an astronaut device (shooting star through a halo) centered on the badge's shield, or escutcheon. The United States Air Force and United States Army astronaut badges are issued in three degrees: Basic, senior, and command (Air Force)/master (Army). The senior astronaut badge is denoted by a star centered above the decoration, while the command/master level is indicated by a star and wreath.
Eligibility
To earn an astronaut badge, a U.S. Air Force or U.S. Navy and Marine Corps officer must complete all required training and participate in a space flight more than above the Earth. The U.S. Army has awarded the badge to officers that have orbited the Earth.
U.S. Air Force astronauts
The U.S. Air Force Astronaut Badge consists of a standard USAF aeronautical badge upon which is centered the astronaut device. The Air Force does not consider Astronaut to be a separate rating from its six established rating badges, but as a "qualifier" to them, and may only be awarded by the Air Force Chief of Staff after written application upon completion of an operational space mission. The rating of Observer is used for USAF Mission Specialists who have completed training but not a mission and are not otherwise aeronautically rated as a USAF pilot, RPA pilot, combat systems officer, air battle manager, or flight surgeon. In 2007, the U.S. Air Force announced the opening of astronaut mission specialists positions to enlisted personnel who met certain eligibility requirements. These requirements include:
Be on active duty in the U.S. Air Force
Be a United States citizen
Have a minimum of a bachelor's degree in either engineering, mathematics, biological science, or physical science, with 3 years experience
Have a current Class II Flight Physical
Be between 62 and 75 inches tall
No enlisted astronaut badges are yet known to have been issued.
U.S. Army astronauts
The gold astronaut device is issued by the U.S. Army to Army aviators, flight surgeons, and aircrew members that qualify as astronauts. Army astronauts that have yet to fly a mission and have not previously been awarded any aviation badge are awarded the army aviation badge. Once they have flown a mission, they are awarded the astronaut device, which is affixed to the shield of their army aviation badge. The army astronaut device was approved on May 17, 1983. The black version of the device and its sew-on equivalent may be worn on the Army Combat Uniform (ACU); the silver wings with gold device version is authorized for wear on Army Service Uniforms. It is believed to be the rarest badge issued by the U.S. Army.
U.S. Navy, Marine Corps, and Coast Guard astronauts
The naval astronaut insignias are issued in a single degree to naval aviators and flight officers from the United States Navy, United States Marine Corps, and United States Coast Guard, with officers of all three branches receiving their designations as aviators or flight officers through the naval aviation flight training program. All three branches also wear the same insignia which consists of naval aviator insignia or naval flight officer insignia with a centered gold astronaut device. However, the Coast Guard only issues the naval aviator version of the astronaut insignia to its astronauts.
NASA badges
Civilian astronaut badge
NASA issues an astronaut badge to all civilian personnel who qualify as specialists on spaceflight missions.
The badge is embroidered in either silver or gold, at the astronaut's discretion, and feature the same astronaut device as the military versions. It is worn on flight suits and flight jackets.
Space Shuttle payload specialist badges
A unique badge was created for individuals serving as payload specialists on NASA Space Shuttle missions. Payload specialists were selected by a variety of organizations and included:
individuals selected by the research community, a company or consortium flying a commercial payload aboard the spacecraft
non-NASA astronauts selected by partner nations
U.S. legislative branch representatives
The payload specialist badge featured a silhouette of the Space Shuttle in place of the astronaut device.
The payload specialist badge of Ukrainian astronaut Leonid Kadenyuk
NASA astronaut pins
In addition to the astronaut badge, which is worn on a military uniform or NASA jumpsuit, astronauts also earn a pin to wear on civilian clothing, signifying their eligibility to take part in missions to space. These include flights to the International Space Station, and Artemis missions to the moon.
The first astronaut pin was created for the Mercury Seven astronauts, in the form of the symbol for the planet Mercury overlaid with the Arabic number "7." As the space program expanded, NASA realized it needed a new symbol to cover personnel on all missions, and created a new lapel pin isolating the "astronaut device" previously applied to flight wings.
The pin is issued in two grades, silver and gold, with the silver pin awarded to candidates who have successfully completed astronaut training and the gold pin to astronauts who have flown in space. Astronaut candidates are given the silver pin but are required to purchase the gold pin at a cost of approximately $400. The Mercury astronauts were the first to receive the pins.
A unique astronaut pin was made for NASA astronaut Deke Slayton in 1967. It was gold in color, like the ones given to astronauts who had flown, and it had a small diamond in place of the star. It was made at the request of the crew of the first crewed mission of the Apollo program as a tribute to Slayton's work at NASA. At the time it was thought that Slayton would never get to space himself, due to a heart condition. Believing that Slayton would refuse to wear exactly the same gold pin as veteran astronauts, the diamond was added. The pin was supposed to have been flown on board the Apollo 1 spacecraft, then given to Slayton after the mission was over. However, the Apollo 1 crew died in a fire during a training exercise on January 27, 1967 and the pin was presented to Slayton by the three widows of the dead crew. This diamond-studded gold pin was later flown to the Moon on board Apollo 11 in July 1969. Slayton would go on to earn a gold pin in 1975 as a docking module pilot on the Apollo-Soyuz Test Project.
A second unique pin was made for Nick Hague after he became the first NASA astronaut to experience an in-flight launch abort. On October 11, 2018, the Soyuz MS-10 mission, part of Expedition 57 to the International Space Station, aborted after one of the four boosters failed to separate properly from the first stage core. The abort happened late enough in the launch sequence that the Soyuz capsule coasted to an apogee of 93 km (58 mi) after separating from the disintegrating rocket. This was above the U.S. definition of the boundary of space at 50 miles (80 km) but below the FAI definition of 100 km (62 mi). In commemoration of his aborted flight, he was given a pin made of roughly-cast tin. He would later receive a gold pin after his successful mission as part of Expedition 59/60.
One silver astronaut pin currently rests on the surface of the Moon, the one that belonged to Clifton Williams, left there by astronaut Alan Bean during Apollo 12 in 1969. Williams was originally scheduled to fly to the Moon as Lunar Module Pilot on Apollo 12 but was killed in a plane crash before he was officially assigned to the flight. Bean was his replacement.
FAA Commercial Space Astronaut Wings
From 2004 through 2021 the U.S. Federal Aviation Administration created a program to encourage and recognize commercial astronauts, giving special wings to pilots and flight crew on all FAA-licensed commercial flight that exceeded 50 Mile above the surface of the Earth. The FAA Commercial Astronaut Wings design was changed in 2018, and the program opened up to all passengers on such flights.
The program was discontinued in 2021, with the rise of commercial space tourism. In total, 30 people were awarded Commercial Space Astronaut Wings.
See also
Military badges of the United States
Badges of the United States Air Force
Badges of the United States Army
Badges of the United States Coast Guard
Badges of the United States Marine Corps
Badges of the United States Navy
Human spaceflight
Mission patch
Edge of space
Pilot-Cosmonaut of the Russian Federation
References
United States military badges
Space program of the United States
Space-related awards | United States astronaut badges | Technology | 1,985 |
3,246,010 | https://en.wikipedia.org/wiki/HD%20196885 | HD 196885 is a binary star system in the northern constellation of Delphinus. It comprises a pair of stars HD 196885 A and HD 196885 B on a 69-years eccentric orbit.
The primary star is near the lower limit of visibility to the naked eye with an apparent visual magnitude of 6.39. It is located at a distance of 110.9 light years from the Sun. It is drifting closer with a radial velocity of −30 km/s, and is expected to come to within in 836,000 years.
The secondary, component B, is a red dwarf star separated by 0.6 arcseconds from the primary star that was discovered in 2006 with NaCo at VLT. It has a class in the range M1V to M3V with 51% of the Sun's mass.
The star BD+10 4351B, located 192 arcseconds away from HD 196885 is located at the same distance and may be a physically bound companion star, in which case HD 196885 is a trinary system. If it is bound, then the separation is at least 6,600 AU (the separation along the line-of-sight is unknown, so this value represents a lower limit on the true separation).
Planetary system
In 2004, a planet was announced to be orbiting the star HD 196885 A in a 386-day orbit. Follow-up work published in 2008 did not confirm the original candidate but instead found evidence of a planet in a . Perturbation by the secondary star in this system may have driven the planet into a high inclination orbit. The planetary existence was confirmed and parameters were refined by 2022.
See also
Epsilon Reticuli
GJ 3021
References
F-type main-sequence stars
M-type main-sequence stars
Planetary systems with one confirmed planet
Binary stars
Delphinus
BD+10 4351
196885
101966
7907
J20395188+1114588 | HD 196885 | Astronomy | 402 |
18,450,034 | https://en.wikipedia.org/wiki/Multicritical%20point | Multicritical points are special points in the parameter space of thermodynamic or
other systems with a continuous phase transition. At least two thermodynamic or other
parameters must be adjusted to reach a multicritical point. At a multicritical point the system belongs to a universality class different from the "normal" universality class.
A more detailed definition requires concepts from the theory of critical phenomena.
Definition
The union of all the points of the parameter space for which the system is critical is
called a critical manifold.
As an example consider a substance ferromagnetic below a
transition temperature , and paramagnetic above . The parameter space here is
the temperature axis, and the critical manifold consists of the point . Now add
hydrostatic pressure to the parameter space. Under hydrostatic pressure the substance
normally still becomes ferromagnetic below a temperature ().
This leads to a
critical curve in the () plane - a -dimensional critical manifold. Also taking into account
shear stress as a thermodynamic parameter leads to a critical surface () in the
() parameter space - a -dimensional critical manifold.
Critical manifolds of dimension and may have physically reachable borders of dimension
which in turn may have borders of dimension . The system still is critical at
these borders. However, criticality terminates for good reason, and the points on the
borders normally belong to another universality class than the universality class realized
within the critical manifold. All the points on the border of a critical manifold are
multicritical points.
Instead of terminating somewhere critical manifolds also may branch or intersect.
The points on the intersections or branch lines also are multicritical points.
At least two parameters must be adjusted to reach a multicritical point.
A -dimensional critical manifold may have two -dimensional borders intersecting at a point. Two parameters must be adjusted to reach such a border, three parameters must be adjusted to reach the intersection of the two borders. A system of this type represents up to four universality classes: one within the critical manifold, two on the borders and one on the intersection of the borders.
The gas-liquid critical point is not multicritical, because the phase transition at
the vapour pressure curve () is discontinuous and the critical manifold thus consists of a single point.
Examples
Tricritical Point and Multicritical Points of Higher Order
To reach a tricritical point the parameters must be tuned in such a way that the renormalized counterpart of the -term of the Hamiltonian vanishes. A well-known experimental realization is found in the mixture of Helium-3 and Helium-4.
Lifshitz Point
To reach a Lifshitz point the parameters must be tuned in such a way that the renormalized counterpart of the -term of the Hamiltonian vanishes. Consequently, at the Lifshitz point phases of uniform and modulated order meet the disordered phase. An experimental example is the magnet
MnP. A Lifshitz point is realized in a prototypical way in the ANNNI model. The Lifshitz point has been introduced by R.M. Hornreich, S. Shtrikman and M. Luban in 1975, honoring the research of
Evgeny Lifshitz.
Lifshitz Tricritical Point
This multicritical point is simultaneously tricritical and Lifshitz. Three parameters must be adjusted to reach
a Lifshitz tricritical point. Such a point has been discussed to occur in non-stoichiometric ferroelectrics.
Lee-Yang edge singularity
The critical manifold of an Ising model with zero external magnetic field consists of the point at the critical temperature on the temperature axis . In a purely imaginary external magnetic field this critical manifold ramifies into the two branches of the Lee-Yang type, belonging to a different universality class. The Ising critical point plays the role of a multicritical point in this situation (there are no imaginary magnetic fields, but there are equivalent physical situations).
References
Renormalization group | Multicritical point | Physics,Materials_science,Mathematics | 831 |
25,566,420 | https://en.wikipedia.org/wiki/Dronabinol | Dronabinol (), sold under the brand names Marinol and Syndros, is the generic name for the molecule of (−)-trans-Δ9-tetrahydrocannabinol (THC) in the pharmaceutical context. It has indications as an appetite stimulant, antiemetic, and sleep apnea reliever and is approved by the U.S. Food and Drug Administration (FDA) as safe and effective for HIV/AIDS-induced anorexia and chemotherapy-induced nausea and vomiting.
Dronabinol is the principal psychoactive constituent enantiomer form, (−)-trans-Δ9-tetrahydrocannabinol, found in Cannabis sativa L. plants, but can also be synthesized in laboratory. Dronabinol does not include any other tetrahydrocannabinol (THC) isomers or any cannabidiol.
Medical uses
Low appetite and nausea
Dronabinol is used to stimulate appetite and therefore weight gain in patients with HIV/AIDS and cancer. It is also used to treat chemotherapy-induced nausea and vomiting.
Pain
Dronabinol demonstrated analgesic efficacy in a majority of studies in chronic pain, the data in acute pain is less conclusive.
Cannabis use disorder
Dronabinol may be useful in treating cannabis addiction as it has been shown to reduce cannabis withdrawal symptoms and the subjective effects of cannabis.
Sleep apnea
Dronabinol demonstrates significant improvement in sleep apnea scores. Phase 2B clinical trials were completed in 2017 for FDA approval for this indication.
Adverse effects
Common side effects of dronabinol include euphoria, drowsiness, dizziness, decreased motor coordination, anxiety, paranoia, confusion, and a rapid heartbeat, among others.
Overdose
In a mild overdose of dronabinol, the typical side effects are exacerbated, whereas a severe overdose presents with lethargy, slurred speech, severe ataxia, and orthostatic hypotension.
Pharmacology
History
While dronabinol was initially approved by the United States Food and Drug Administration (FDA) on May 31, 1985, it was not until May 13, 1986, the Drug Enforcement Administration (DEA), issued a Final Rule and Statement of Policy authorizing the "rescheduling of synthetic dronabinol in sesame oil and encapsulated in soft gelatin capsules from Schedule I to Schedule II" (DEA 51 FR 17476-78). This permitted medical use of Marinol, albeit with the severe restrictions associated with Schedule II status. For instance, refills of Marinol prescriptions were not permitted.
On April 29, 1991, the Commission on Narcotic Drugs, in accordance with article 2, paragraphs 5 and 6, of the Convention on Psychotropic Substances of 1971, decided that Δ9-tetrahydrocannabinol (also referred to as Δ9-THC) and its stereochemical variants should be transferred from Schedule I to Schedule II of that Convention. This released Δ9-THC from many of the restrictions imposed by the convention, facilitating its marketing as medication.
An article published in the April–June 1998 issue of the Journal of Psychoactive Drugs found that "Healthcare professionals have detected no indication of script-chasing or doctor-shopping among the patients for whom they have prescribed dronabinol". The authors state that Marinol has a low potential for abuse.
In 1999, in the United States, Marinol was rescheduled from Schedule II to III of the Controlled Substances Act, reflecting a finding that THC had a potential for abuse less than that of cocaine and heroin. This rescheduling constituted part of the argument for a 2002 petition for removal of cannabis from Schedule I of the Controlled Substances Act, in which petitioner Jon Gettman noted, "Cannabis is a natural source of dronabinol (THC), the ingredient of Marinol, a Schedule III drug. There are no grounds to schedule cannabis in a more restrictive schedule than Marinol".
In 2003, the World Health Organization Expert Committee on Drug Dependence recommended transferring THC to Schedule IV of the convention, citing its medical uses and low abuse potential. In 2019, the Committee recommended transferring Δ9-THC to Schedule I of the Single Convention on Narcotic Drugs of 1961, but its recommendations were rejected by the United Nations Commission on Narcotic Drugs.
Society and culture
Brand names
Dronabinol is marketed as Marinol and Syndros, a registered trademark of Solvay Pharmaceuticals. Dronabinol is also marketed, sold, and distributed by PAR Pharmaceutical Companies under the terms of a license and distribution agreement with SVC pharma LP, an affiliate of Rhodes Technologies for Marinol and Insys Pharmaceuticals for Syndros. Dronabinol is available as a prescription drug (under Marinol and Syndros ) in several countries including the United States, Germany, South Africa and Australia. In Canada, Tetra Bio-Pharma filed a New Drug Submission (NDS) with Health Canada for its Dronabinol Soft Gel capsules to be marketed as REDUVO™. Tetra has two other dronabinol drugs with new routes of administration which limit first-pass metabolism; an inhaled THC-based dronabinol drug and their mucoadhesive-delivery dronabinol drug Adversa®, which are both in the accelerated 505(b)(2) New Drug Application (NDA) pathway for the U.S. and Canadian markets.
In the United States, Marinol is a Schedule III drug, available by prescription, considered to be non-narcotic and to have a low risk of physical or mental dependence. Efforts to get cannabis rescheduled as analogous to Marinol have not succeeded thus far, though a 2002 petition has been accepted by the DEA. As a result of the rescheduling of Marinol from Schedule II to Schedule III, refills are now permitted for this substance. Marinol's U.S. Food and Drug Administration (FDA) approval for medical use has raised much controversy as to why cannabis is still illegal at the federal level.
Comparisons with medical cannabis
Female cannabis plants not only contain dronabinol but at least 113 other cannabinoids, including cannabidiol (CBD), thought to be the major anticonvulsant that helps people with multiple sclerosis; and cannabichromene (CBC), an anti-inflammatory which may contribute to the pain-killing effect of cannabis.
It takes over one hour for Marinol to reach full systemic effect, compared to seconds or minutes for smoked or vaporized cannabis. Mark Kleiman, director of the Drug Policy Analysis Program at UCLA's School of Public Affairs said of Marinol, "it wasn't any fun and made the user feel bad, so it could be approved without any fear that it would penetrate the recreational market, and then used as a club with which to beat back the advocates of whole cannabis as a medicine."
Clinical trials comparing the use of cannabis extracts with Marinol in the treatment of cancer cachexia have demonstrated equal efficacy and well-being among subjects in the two treatment arms. United States federal law currently registers dronabinol as a Schedule III controlled substance, but all other cannabinoids remain Schedule I, except various synthetic cannabinoids like nabilone and HU-308.
See also
Cannabinoids
11-Hydroxy-THC, metabolite of THC
Anandamide, 2-Arachidonoylglycerol, endogenous cannabinoids
Tetrahydrocannabinol
Cannabidiol (CBD)
Cannabinol (CBN), a metabolite of THC
Dimethylheptylpyran
Parahexyl
Tetrahydrocannabinolic acid, the biosynthetic precursor for THC
HU-210, WIN 55,212-2, JWH-133, synthetic cannabinoid agonists (neocannabinoids)
Medical cannabis (pharmaceutical cannabinoids)
Epidiolex (prescription form of purified cannabidiol derived from hemp used for treating some rare neurological diseases)
Sativex (nabiximols)
Nabilone, a novel synthetic cannabinoid
HU-308, a highly potent synthetic cannabinoid CB2 receptor agonist
References
External links
Medlineplus.gov on Dronabinol
Acetylcholinesterase inhibitors
Amorphous solids
Antiemetics
Appetite stimulants
Aromatase inhibitors
Benzochromenes
Drugs developed by AbbVie
Entheogens
Euphoriants
Social problems in medicine
Tetrahydrocannabinol | Dronabinol | Physics | 1,814 |
937,971 | https://en.wikipedia.org/wiki/Endemism | Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. For example, the Cape sugarbird is found exclusively in southwestern South Africa and is therefore said to be endemic to that particular part of the world. An endemic species can also be referred to as an endemism or, in scientific literature, as an endemite. Similarly, many species found in the Western ghats of India are examples of endemism.
Endemism is an important concept in conservation biology for measuring biodiversity in a particular place and evaluating the risk of extinction for species. Endemism is also of interest in evolutionary biology, because it provides clues about how changes in the environment cause species to undergo range shifts (potentially expanding their range into a larger area, or becoming extirpated from an area they once lived), go extinct, or diversify into more species.
The extreme opposite of an endemic species is one with a cosmopolitan distribution, having a global or widespread range.
A rare alternative term for a species that is endemic is "precinctive", which applies to species (and other taxonomic levels) that are restricted to a defined geographical area. Other terms that sometimes are used interchangeably, but less often, include autochthonal, autochthonic, and indigenous; however, these terms do not reflect the status of a species that specifically belongs only to a determined place.
Etymology
History of the concept
The word endemic is from Neo-Latin endēmicus, from Greek ἔνδημος, éndēmos, "native". Endēmos is formed of en meaning "in", and dēmos meaning "the people". The word entered the English language as a loan word from French endémique, and originally seems to have been used in the sense of diseases that occur at a constant amount in a country, as opposed to epidemic diseases, which are exploding in cases. The word was used in biology in 1872 to mean a species restricted to a specific location by Charles Darwin.
The less common term 'precinctive' has been used by some entomologists as the equivalent of 'endemic'. Precinctive was coined in 1900 by David Sharp when describing the Hawaiian insects, as he was uncomfortable with the fact that the word 'endemic' is often associated with diseases. 'Precinctive' was first used in botany by Vaughan MacCaughey in Hawaii in 1917.
Overview
A species is considered to be endemic to the area where it is found naturally, to the exclusion of other areas; presence in captivity or botanical gardens does not disqualify a species from being endemic. In theory, the term "endemic" could be applied on any scale; for example, the cougar is endemic to the Americas, and all known life is endemic to Earth. However, endemism is normally used only when a species has a relatively small or restricted range. This usage of "endemic" contrasts with "cosmopolitan." Endemics are not necessarily rare; some might be common where they occur. Likewise, not all rare species are endemics; some may have a large range but be rare throughout this range.
Origins
The evolutionary history of a species can lead to endemism in multiple ways. Allopatric speciation, or geographic speciation, is when two populations of a species become geographically separated from each other and as a result develop into different species. In isolated areas where there is little possibility for organisms to disperse to new places, or to receive new gene flow from outside, the rate of endemism is particularly high. For example, many endemic species are found on remote islands, such as Hawaii, the Galápagos Islands and Socotra. Populations on an island are isolated, with little opportunity to interbreed with outside populations, which eventually causes reproductive isolation and separation into different species. Darwin's finches in the Galápagos archipelago are examples of species endemic to islands. Similarly, isolated mountainous regions like the Ethiopian Highlands, or large bodies of water far from other lakes, like Lake Baikal, can also have high rates of endemism.
Endemism can also be created in areas which act as refuges for species during times of climate change like ice ages. These changes may have caused species to become repeatedly restricted to regions with unusually stable climate conditions, leading to high concentrations of endemic species in areas resistant to climate fluctuations. Endemic species that used to exist in a much larger area, but died out in most of their range, are called paleoendemic, in contrast to neoendemic species, which are new species that have not dispersed beyond their range. The ginkgo tree, Ginkgo biloba, is one example of a paleoendemic species.
In many cases, biological factors, such as low rates of dispersal or returning to the spawning area (philopatry), can cause a particular group of organisms to have high speciation rates and thus many endemic species. For example, cichlids in the East African Rift Lakes have diversified into many more endemic species than the other fish families in the same lakes, possibly due to such factors. Plants that become endemic on isolated islands are often those which have a high rate of dispersal and are able to reach such islands by being dispersed by birds. While birds are less likely to be endemic to a region based on their ability to disperse via flight, there are over 2,500 species which are considered endemic, meaning that the species is restricted to an area less than .
Microorganisms were traditionally not believed to form endemics. The hypothesis 'everything is everywhere', first stated in Dutch by Lourens G.M. Baas Becking in 1934, describes the theory that the distribution of organisms smaller than 2 mm is cosmopolitan where habitats occur that support their growth.
Subtypes and definitions
Endemism can reflect a wide variety of evolutionary histories, so researchers often use more specialized terms that categorize endemic species based upon how they came to be endemic to an area. Different categorizations of endemism also capture the uniqueness and irreplaceability of biodiversity hotspots differently and impact how those hotspots are defined, affecting how resources for conservation are allocated.
The first subcategories were first introduced by Claude P. E. Favager and Juliette Contandriopoulis in 1961: schizoendemics, apoendemics and patroendemics. Using this work, Ledyard Stebbins and Jack Major then introduced the concepts of neoendemics and paleoendemics in 1965 to describe the endemics of California. Endemic taxa can also be classified into autochthonous, allochthonous, taxonomic relicts and biogeographic relicts.
Paleoendemism refers to species that were formerly widespread but are now restricted to a smaller area. Neoendemism refers to species that have recently arisen, such as through divergence and reproductive isolation or through hybridization and polyploidy in plants, and have not dispersed beyond a limited range.
Paleoendemism is more or less synonymous with the concept of a 'relict species': a population or taxon of organisms that were more widespread or more diverse in the past. A 'relictual population' is a population that currently occurs in a restricted area, but whose original range was far wider during a previous geologic epoch. Similarly, a 'relictual taxon' is a taxon (e.g. species or other lineage) that is the sole surviving representative of a formerly diverse group.
The concept of phylogenetic endemism has also been used to measure the relative uniqueness of the species endemic to an area. In measurements that incorporate phylogenetic endemism, branches of the evolutionary tree are weighted by how narrowly they are distributed. This captures not only the total number of taxa endemic to the area (taxonomic endemism), but also how distant those species are from their living relatives.
Schizoendemics, apoendemics and patroendemics can all be classified as types of neoendemics. Schizoendemics arise from a wider distributed taxon that has become reproductively isolated without becoming (potentially) genetically isolated – a schizoendemic has the same chromosome count as the parent taxon it evolved from. An apoendemic is a polyploid of the parent taxon (or taxa in the case of allopolyploids), whereas a patroendemic has a lower, diploid chromosome count than the related, more widely distributed polyploid taxon. Mikio Ono coined the term 'aneuendemics' in 1991 for species that have more or fewer chromosomes than their relatives due to aneuploidy.
Pseudoendemics are taxa that have possibly recently evolved from a mutation. Holoendemics is a concept introduced by Richardson in 1978 to describe taxa that have remained endemic to a restricted distribution for a very long time.
In a 2000 paper, Myers and de Grave further attempted to redefine the concept. In their view, everything is endemic, even cosmopolitan species are endemic to Earth, and earlier definitions restricting endemics to specific locations are wrong. Thus the subdivisions neoendemics and paleoendemics are without merit regarding the study of distributions, because these concepts consider that an endemic has a distribution limited to one place. Instead, they propose four different categories: holoendemics, euryendemics, stenoendemics and rhoendemics. In their scheme cryptoendemics and euendemics are further subdivisions of rhoendemics. In their view, a holoendemic is a cosmopolitan species. Stenoendemics, also known as local endemics, have a reduced distribution and are synonymous with the word 'endemics' in the traditional sense, whereas euryendemics have a larger distribution -both these have distributions that are more or less continuous. A rhoendemic has a disjunct distribution. Where this disjunct distribution is caused by vicariance, in a euendemic the vicariance was geologic in nature, such as the movement of tectonic plates, but in a cryptoendemic the disjunct distribution was due to the extinction of the intervening populations. There is yet another possible situation that can cause a disjunct distribution, where a species is able to colonize new territories by crossing over areas of unsuitable habitat, such as plants colonizing an island – this situation they dismiss as extremely rare and do not devise a name for. Traditionally, none of Myers and de Grave's categories would be considered endemics except stenoendemics.
Environments
Some environments are particularly conducive to the development of endemic species, either because they allow the persistence of relict taxa that were extirpated elsewhere, or because they provide mechanisms for isolation and opportunities to fill new niches.
Soil
Serpentine soils act as 'edaphic islands' of low fertility and these soils lead to high rates of endemism. These soils are found in the Balkan Peninsula, Turkey, Alps, Cuba, New Caledonia, South Africa, Zimbabwe, the North American Appalachians, and scattered distribution in California, Oregon, and Washington and elsewhere. For example, Mayer and Soltis considered the widespread subspecies Streptanthus glandulosus subsp. glandulosus which grows on normal soils, to be a paleoendemic, whereas closely related endemic forms of S. glandulosus occurring on serpentine soil patches are neoendemics which recently evolved from subsp. glandulosus.
Caves
Obligate cave-dwelling species, known as troglobites, are often endemic to small areas, even to single individual caves, because cave habitats are by nature restricted, isolated, and fragmented. A high level of adaptation to a cave environment limits an organism's ability to disperse, since caves are often not connected to each other. One hypothesis for how closely related troglobite species could become isolated from one another in different caves is that their common ancestor may have been less restricted to cave habitats. When climate conditions became unfavorable, the ancestral species was extirpated from the surface, but some populations survived in caves, and diverged into different species due to lack of gene flow between them.
Islands
Isolated islands commonly develop a number of endemics. Many species and other higher taxonomic groups exist in very small terrestrial or aquatic islands, which restrict their distribution. The Devil's Hole pupfish, Cyprinodon diabolis, has its whole native population restricted to a spring that is 20 x 3 meters, in Nevada's Mojave Desert. This 'aquatic island' is connected to an underground basin; however, the population present in the pool remains isolated.
Other areas very similar to the Galapagos Islands of the Pacific Ocean exist and foster high rates of endemism. The Socotra Archipelago of Yemen, located in the Indian Ocean, has seen a new endemic species of parasitic leech, Myxobdella socotrensis, appear. This species is restricted to freshwater springs, where it may attach to and feed upon native crabs.
Mountains
Mountains can be seen as 'sky islands': refugia of endemics because species that live in the cool climates of mountain peaks are geographically isolated. For example, in the Alpes-Maritimes department of France, Saxifraga florulenta is an endemic plant that may have evolved in the Late Miocene and could have once been widespread across the Mediterranean Basin.
Volcanoes also tend to harbor a number of endemic species. Plants on volcanoes tend to fill a specialized ecological niche, with a very restrictive range, due to the unique environmental characteristics. The Kula Volcano, one of the fourteen volcanoes in Turkey, is home to 13 endemic species of plants.
Conservation
Endemics might more easily become endangered or extinct because they are already restricted in distribution. This puts endemic plants and animals at greater risk than widespread species during the rapid climate change of this century. Some scientists claim that the presence of endemic species in an area is a good method to find geographical regions that can be considered priorities for conservation. Endemism can thus be studied as a proxy for measuring biodiversity of a region.
The concept of finding endemic species that occur in the same region to designate 'endemism hotspots' was first proposed by Paul Müller in a 1973 book. According to him, this is only possible where 1.) the taxonomy of the species in question is not in dispute; 2.) the species distribution is accurately known; and 3.) the species have relatively small distributional ranges.
In a 2000 article, Myers et al. used the standard of having more than 0.5% of the world's plant species being endemic to the region to designate 25 geographical areas of the world as biodiversity hotspots.
In response to the above, the World Wildlife Fund has split the world into a few hundred geographical 'ecoregions'. These have been designed to include as many species as possible that only occur in a single ecoregion, and these species are thus 'endemics' to these ecoregions. Since plenty of these ecoregions have a high prevalence of endemics existing within them, many National Parks have been formed around or within them to further promote conservation. The Caparaó National Park was formed in the Atlantic Forest, a biodiversity hotspot located in Brazil, in order to help protect valuable and vulnerable species.
Other scientists have argued that endemism is not an appropriate measure of biodiversity, because the levels of threat or biodiversity are not actually correlated to areas of high endemism. When using bird species as an example, it was found that only 2.5% of biodiversity hotspots correlate with endemism and the threatened nature of a geographic region. A similar pattern had been found regarding mammals, Lasioglossum bees, Plusiinae moths, and swallowtail butterflies in North America: these different groups of taxa did not correlate geographically with each other regarding endemism and species richness. Especially using mammals as flagship species proved to be a poor system of identifying and protecting areas of high invertebrate biodiversity. In response to this, other scientists again defended the concept by using WWF ecoregions and reptiles, finding that most reptile endemics occur in WWF ecoregions with high biodiversity.
Other conservation efforts for endemics include keeping captive and semi-captive populations in zoological parks and botanical gardens. These methods are ex situ ("off-site") conservation methods. The use of such methods may not only offer refuge and protection for individuals of declining or vulnerable populations, but it may also allow biologists valuable opportunities to research them as well.
References
External links
Biodiversity
Habitat
Ecology terminology
Evolutionary biology terminology | Endemism | Biology | 3,468 |
28,255,598 | https://en.wikipedia.org/wiki/Triglycine%20sulfate | Triglycine sulfate (TGS) is a chemical compound with a formula (NH2CH2COOH)3·H2SO4. The empirical formula of TGS does not represent the molecular structure, which contains protonated glycine moieties and sulfate ions. TGS with protons replaced by deuterium is called deuterated TGS or DTGS; alternatively, DTGS may refer to doped TGS. By doping the DTGS with the amino acid L-Alanine, the crystal properties are improved and the new material is called Deuterated L-Alanine doped Triglycine Sulfate (DLATGS or DLTGS). These crystals are pyroelectric and ferroelectric which allows their use as photodetector elements in infrared spectroscopy and night vision applications. TGS detectors have also been used as the target in vidicon cathode ray imager tubes.
TGS has a critical point for the order parameter of polarization, at 322.5 K.
Crystal structure and properties
TGS crystals may be formed by evaporation of an aqueous solution of sulfuric acid and a greater than three-fold excess of glycine. They belong to the polar space group P21 and therefore are pyroelectric and ferroelectric at room temperature, exhibiting spontaneous polarization along the b-axis ([010] direction). The Curie temperature of the ferroelectric transition is 49 °C for TGS and 62 °C for DTGS. The crystal structure consists of SO42−, 2(N+H3CH2COOH) (G1 and G2 in the crystal-structure diagram), and +NH3CH2COO− (G3) species held together by hydrogen bonds. These bonds are easily broken by the polar molecules of water, which leads to the hygroscopicity of TGS – its crystals are easily etched by water. Along the b-axis, the G1-SO4 and G2-G3 layers are stacked alternately. The nearest two neighboring layers with identical chemical composition are rotated 180° around the b-axis against each other. DTGS and DLATGS materials are derivatives of TGS which have better pyroelectric properties and give less detector noise as can be shown in the following table.
Typical performance of DLATGS detectors
The typical performance and pyroelectric properties of DLATGS detectors of 1.3 and 2.0 mm in diameter of the element size are shown in the table below.
References
Infrared sensor materials
Sulfates | Triglycine sulfate | Chemistry | 535 |
319,610 | https://en.wikipedia.org/wiki/Biological%20life%20cycle | In biology, a biological life cycle (or just life cycle when the biological context is clear) is a series of stages of the life of an organism, that begins as a zygote, often in an egg, and concludes as an adult that reproduces, producing an offspring in the form of a new zygote which then itself goes through the same series of stages, the process repeating in a cyclic fashion.
"The concept is closely related to those of the life history, development and ontogeny, but differs from them in stressing renewal." Transitions of form may involve growth, asexual reproduction, or sexual reproduction.
In some organisms, different "generations" of the species succeed each other during the life cycle. For plants and many algae, there are two multicellular stages, and the life cycle is referred to as alternation of generations. The term life history is often used, particularly for organisms such as the red algae which have three multicellular stages (or more), rather than two.
Life cycles that include sexual reproduction involve alternating haploid (n) and diploid (2n) stages, i.e., a change of ploidy is involved. To return from a diploid stage to a haploid stage, meiosis must occur. In regard to changes of ploidy, there are three types of cycles:
haplontic life cycle — the haploid stage is multicellular and the diploid stage is a single cell, meiosis is "zygotic".
diplontic life cycle — the diploid stage is multicellular and haploid gametes are formed, meiosis is "gametic".
haplodiplontic life cycle (also referred to as diplohaplontic, diplobiontic, or dibiontic life cycle) — multicellular diploid and haploid stages occur, meiosis is "sporic".
The cycles differ in when mitosis (growth) occurs. Zygotic meiosis and gametic meiosis have one mitotic stage: mitosis occurs during the n phase in zygotic meiosis and during the 2n phase in gametic meiosis. Therefore, zygotic and gametic meiosis are collectively termed "haplobiontic" (single mitotic phase, not to be confused with haplontic). Sporic meiosis, on the other hand, has mitosis in two stages, both the diploid and haploid stages, termed "diplobiontic" (not to be confused with diplontic).
Discovery
The study of reproduction and development in organisms was carried out by many botanists and zoologists.
Wilhelm Hofmeister demonstrated that alternation of generations is a feature that unites plants, and published this result in 1851 (see plant sexuality).
Some terms (haplobiont and diplobiont) used for the description of life cycles were proposed initially for algae by Nils Svedelius, and then became used for other organisms. Other terms (autogamy and gamontogamy) used in protist life cycles were introduced by Karl Gottlieb Grell. The description of the complex life cycles of various organisms contributed to the disproof of the ideas of spontaneous generation in the 1840s and 1850s.
Haplontic life cycle
A zygotic meiosis is a meiosis of a zygote immediately after karyogamy, which is the fusion of two cell nuclei. This way, the organism ends its diploid phase and produces several haploid cells. These cells divide mitotically to form either larger, multicellular individuals, or more haploid cells. Two opposite types of gametes (e.g., male and female) from these individuals or cells fuse to become a zygote.
In the whole cycle, zygotes are the only diploid cell; mitosis occurs only in the haploid phase.
The individuals or cells as a result of mitosis are haplonts, hence this life cycle is also called haplontic life cycle. Haplonts are:
In archaeplastidans: some green algae (e.g., Chlamydomonas, Zygnema, Chara)
In stramenopiles: some golden algae
In alveolates: many dinoflagellates, e.g., Ceratium, Gymnodinium, some apicomplexans (e.g., Plasmodium)
In rhizarians: some euglyphids, ascetosporeans
In excavates: some parabasalids
In amoebozoans: Dictyostelium
In opisthokonts: most fungi (some chytrids, zygomycetes, some ascomycetes, basidiomycetes)
Diplontic life cycle
In gametic meiosis, instead of immediately dividing meiotically to produce haploid cells, the zygote divides mitotically to produce a multicellular diploid individual or a group of more unicellular diploid cells. Cells from the diploid individuals then undergo meiosis to produce haploid cells or gametes. Haploid cells may divide again (by mitosis) to form more haploid cells, as in many yeasts, but the haploid phase is not the predominant life cycle phase. In most diplonts, mitosis occurs only in the diploid phase, i.e. gametes usually form quickly and fuse to produce diploid zygotes.
In the whole cycle, gametes are usually the only haploid cells, and mitosis usually occurs only in the diploid phase.
The diploid multicellular individual is a diplont, hence a gametic meiosis is also called a diplontic life cycle. Diplonts are:
In archaeplastidans: some green algae (e.g., Cladophora glomerata, Acetabularia)
In stramenopiles: some brown algae (the Fucales, however, their life cycle can also be interpreted as strongly heteromorphic-diplohaplontic, with a highly reduced gametophyte phase, as in the flowering plants), some xanthophytes (e.g., Vaucheria), most diatoms, some oomycetes (e.g., Saprolegnia, Plasmopara viticola), opalines, some "heliozoans" (e.g., Actinophrys, Actinosphaerium)
In alveolates: ciliates
In excavates: some parabasalids
In opisthokonts: animals, some fungi (e.g., some ascomycetes)
Haplodiplontic life cycle
In sporic meiosis (also commonly known as intermediary meiosis), the zygote divides mitotically to produce a multicellular diploid sporophyte. The sporophyte creates spores via meiosis which also then divide mitotically producing haploid individuals called gametophytes. The gametophytes produce gametes via mitosis. In some plants the gametophyte is not only small-sized but also short-lived; in other plants and many algae, the gametophyte is the "dominant" stage of the life cycle.
Haplodiplonts are:
In archaeplastidans: red algae (which have two sporophyte generations), some green algae (e.g., Ulva), land plants
In stramenopiles: most brown algae
In rhizarians: many foraminiferans, plasmodiophoromycetes
In amoebozoa: myxogastrids
In opisthokonts: some fungi (some chytrids, some ascomycetes like the brewer's yeast)
Other eukaryotes: haptophytes
Some animals have a sex-determination system called haplodiploid, but this is not related to the haplodiplontic life cycle.
Vegetative meiosis
Some red algae (such as Bonnemaisonia and Lemanea) and green algae (such as Prasiola) have vegetative meiosis, also called somatic meiosis, which is a rare phenomenon. Vegetative meiosis can occur in haplodiplontic and also in diplontic life cycles. The gametophytes remain attached to and part of the sporophyte. Vegetative (non-reproductive) diploid cells undergo meiosis, generating vegetative haploid cells. These undergo many mitosis, and produces gametes.
A different phenomenon, called vegetative diploidization, a type of apomixis, occurs in some brown algae (e.g., Elachista stellaris). Cells in a haploid part of the plant spontaneously duplicate their chromosomes to produce diploid tissue.
Parasitic life cycle
Parasites depend on the exploitation of one or more hosts. Those that must infect more than one host species to complete their life cycles are said to have complex or indirect life cycles. Dirofilaria immitis, or the heartworm, has an indirect life cycle, for example. The microfilariae must first be ingested by a female mosquito, where it develops into the infective larval stage. The mosquito then bites an animal and transmits the infective larvae into the animal, where they migrate to the pulmonary artery and mature into adults.
Those parasites that infect a single species have direct life cycles. An example of a parasite with a direct life cycle is Ancylostoma caninum, or the canine hookworm. They develop to the infective larval stage in the environment, then penetrate the skin of the dog directly and mature to adults in the small intestine.
If a parasite has to infect a given host in order to complete its life cycle, then it is said to be an obligate parasite of that host; sometimes, infection is facultative—the parasite can survive and complete its life cycle without infecting that particular host species. Parasites sometimes infect hosts in which they cannot complete their life cycles; these are accidental hosts.
A host in which parasites reproduce sexually is known as the definitive, final or primary host. In intermediate hosts, parasites either do not reproduce or do so asexually, but the parasite always develops to a new stage in this type of host. In some cases a parasite will infect a host, but not undergo any development, these hosts are known as paratenic or transport hosts. The paratenic host can be useful in raising the chance that the parasite will be transmitted to the definitive host. For example, the cat lungworm (Aelurostrongylus abstrusus) uses a slug or snail as an intermediate host; the first stage larva enters the mollusk and develops to the third stage larva, which is infectious to the definitive host—the cat. If a mouse eats the slug, the third stage larva will enter the mouse's tissues, but will not undergo any development.
Evolution
The primitive type of life cycle probably had haploid individuals with asexual reproduction. Bacteria and archaea exhibit a life cycle like this, and some eukaryotes apparently do too (e.g., Cryptophyta, Choanoflagellata, many Euglenozoa, many Amoebozoa, some red algae, some green algae, the imperfect fungi, some rotifers and many other groups, not necessarily haploid). However, these eukaryotes probably are not primitively asexual, but have lost their sexual reproduction, or it just was not observed yet. Many eukaryotes (including animals and plants) exhibit asexual reproduction, which may be facultative or obligate in the life cycle, with sexual reproduction occurring more or less frequently.
Individual organisms participating in a biological life cycle ordinarily age and die, while cells from these organisms that connect successive life cycle generations (germ line cells and their descendants) are potentially immortal. The basis for this difference is a fundamental problem in biology. The Russian biologist and historian Zhores A. Medvedev considered that the accuracy of genome replicative and other synthetic systems alone cannot explain the immortality of germlines. Rather Medvedev thought that known features of the biochemistry and genetics of sexual reproduction indicate the presence of unique information maintenance and restoration processes at the gametogenesis stage of the biological life cycle. In particular, Medvedev considered that the most important opportunities for information maintenance of germ cells are created by recombination during meiosis and DNA repair; he saw these as processes within the germ line cells that were capable of restoring the integrity of DNA and chromosomes from the types of damage that cause irreversible ageing in non-germ line cells, e.g. somatic cells.
The ancestry of each present day cell presumably traces back, in an unbroken lineage for over 3 billion years to the origin of life. It is not actually cells that are immortal but multi-generational cell lineages. The immortality of a cell lineage depends on the maintenance of cell division potential. This potential may be lost in any particular lineage because of cell damage, terminal differentiation as occurs in nerve cells, or programmed cell death (apoptosis) during development. Maintenance of cell division potential of the biological life cycle over successive generations depends on the avoidance and the accurate repair of cellular damage, particularly DNA damage. In sexual organisms, continuity of the germline over successive cell cycle generations depends on the effectiveness of processes for avoiding DNA damage and repairing those DNA damages that do occur. Sexual processes in eukaryotes provide an opportunity for effective repair of DNA damages in the germ line by homologous recombination.
See also
Metamorphosis – Profound change in body structure during the postembryonic development of an organism
References
Sources
Further reading
Reproduction | Biological life cycle | Biology | 2,948 |
2,394,731 | https://en.wikipedia.org/wiki/Zoophily | Zoophily, or zoogamy, is a form of pollination whereby pollen is transferred by animals, usually by invertebrates but in some cases vertebrates, particularly birds and bats, but also by other animals. Zoophilous species frequently have evolved mechanisms to make themselves more appealing to the particular type of pollinator, e.g. brightly colored or scented flowers, nectar, and appealing shapes and patterns. These plant-animal relationships are often mutually beneficial because of the food source provided in exchange for pollination.
Pollination is defined as the transfer of pollen from the anther to the stigma. There are many vectors for pollination, including abiotic (wind and water) and biotic (animal). There are benefits and costs associated with any vector. For instance, using animal pollination is beneficial because the process is more directed and often results in pollination. At the same time it is costly for the plant to produce rewards, such as nectar, to attract animal pollinators. Not producing such rewards is one benefit of using abiotic pollinators, but a cost associated with this approach is that the pollen may be distributed more randomly. In general, pollination by animals occurs after they reach inside the flowers for nectar. While feeding on the nectar, the animal rubs or touches the stamens and is covered in pollen. Some of this pollen will be deposited on the stigma of the next flower it visits, pollinating the flower.
Insect pollination
This is known as entomophily. There are many different subtypes.
Bee pollination (melittophily)
There are diverse types of bees (such as honeybees, bumblebees, and orchid bees), forming large groups that are quite distinctive in size, tongue length and behaviour (some solitary, some colonial); thus generalization about bee pollination is difficult. Some plants can only be pollinated by bees because their anthers release pollen internally, and it must be shaken out by buzz pollination (also known as "sonication"). Bees are the only animals that perform this behaviour. Bumblebees and solitary bees sonicate, but honeybees do not. About 9% of the flowers of the world are primarily pollinated using buzz pollination.
Wasp pollination
Wasps are also responsible for the pollination of several plants species, being important pollen vectors, and in some cases, even more efficient pollinators than bees.
Butterfly pollination (psychophily)
Despite their complete dependence on flowers for sustenance as imagoes, butterflies are generally poor pollinators, lacking specific structures to carry pollen. Nonetheless, some plants appear to have specialised on attracting butterflies. Buddleja is a well-known example. The species in the orchid genus Bonatea are all pollinated by moths, except for Bonatea cassidea which has evolved into a psychophile. This orchid affixes its pollinaria firmly between the palpi of visiting butterflies. Unlike its relatives, this orchid species exhibits diurnal anthesis, a weak scent which is virtually absent at night, and has short spurs containing small amounts of relatively dilute sucrose-rich nectar -these are all considered psychophilous traits. B. cassidea has white flowers, but butterfly-attracting flowers are often coloured. Unlike bees and wasps, some butterflies such as swallowtails are able to see the colour red. Butterflies also require a platform on which to land.
Moth pollination (phalaenophily)
Among the more important moth pollinators are the hawk moths (Sphingidae). Their behaviour is similar to hummingbirds: they hover in front of flowers with rapid wingbeats. Most are nocturnal or crepuscular.
Other moths (Noctuids, Geometrids, Pyralids, for example) fly slowly and settle on the flower. They do not require as much nectar as the fast-flying hawk moths, and the flowers tend to be small (though they may be aggregated in heads).
Fly pollination (myophily and sapromyophily)
Flies tend to be important pollinators in high-altitude and high-latitude systems, where they are numerous and other insect groups may be lacking. There are two main types of fly pollination: myophily and sapromyophily.
Myophily includes flies that feed on nectar and pollen as adults - particularly bee flies (Bombyliidae), hoverflies (Syrphidae), and others - and these regularly visit flowers. In contrast, male fruit flies (Tephritidae) are enticed by specific floral attractants emitted by some wild orchids which do not produce nectar. Chemicals emitted by the orchid act as the fly's sex pheromone precursor or booster.
Sapromyophiles, on the other hand, normally visit dead animals or dung. They are attracted to flowers which mimic the odor of such objects. The plant provides them with no reward and they leave quickly unless it has traps to slow them down. Such plants are far less common than myophilous ones.
Beetle pollination (cantharophily)
Beetles are particularly important in some parts of the world such as semi-arid areas of Southern Africa and southern California and the montane grasslands of KwaZulu-Natal in South Africa.
Cantharophily is often the main pollination system in the Araceae family. It occurs in genera such as Amorphophallus, Dieffenbachia, Monstera, Philodendron and Theriophonum. A well-known example is the gigantic inflorescence of Amorphophallus titanum. This bloom appears like column sticking out of a vast sheet of rotting flesh. It is able to generate heat, which it uses to exude a powerful foetid and revolting odour at night. This attracts necrophagous beetles, and also specialised beetle predators of these beetles -the plant is essentially tricking the beetles into believing that there is food or a place to lay their eggs. Araceae flowers often trap beetles in a compartment with the pollen: the beetles must pass through a constriction of the spathe to get inside, but the plant can tighten the spathe against the spadix and thus close the constriction for a time. There is also some evidence that the giant inflorescence, which heats itself to , thus shines like an invisible infrared beacon in the dark of night on the jungle floor, unseen by humans but detectable by insects. The blooms of Philodendron adamantinum are able to stick a glob of resin on the otherwise smooth back of the beetles it attracts, modifying them so they are better equipped to carry pollen to the next inflorescence.
Other
In Dioscorea chouardii, pollination is performed by ants.
Lizard pollination
According to one 2003 paper, it is possible that lizard pollination is underestimated. Lizards have been known to feed on nectar since 1977. However, only two species of lizard from New Zealand has been shown to carry pollen as of 2003, although it is unknown if they actually pollinate flowers. There is also circumstantial evidence Podarcis lilfordi may help pollinate Euphorbia dendroides on the Balearic Islands; one study found seed set higher in areas with a higher lizard density. Both these species are not dependant on nectar as a food source, and do not appear to have evolved specific adaptations to exploit it. Despite the lack of evidence, the authors nonetheless theorise that some plants on small islands may have mutualistically evolved to accommodate lizard pollination.
The lizards known to carry pollen are the geckoes Hoplodactylus duvauceli and Dactylocnemis pacificus. Between them, they visit the flowers of at least four species of plant: Metrosideros excelsa, Phormium tenax, Myoporum laetum and in one case Hebe bollonsii, although the structure of the flowers of the last three species do not allow pollen transfer to occur during feeding by lizards, which are better seen as robbers of nectar, these plants are adapted for bird or insect pollination. The only pollen ever found on these lizards is that of Metrosideros excelsa, which has been found on 3% to 47% of the lizards caught on these trees, depending on the night. These lizards are only attracted to the nectar on flowers, not the pollen. If it is proved that lizards are the main pollinators of these plants, the authors of the study theorise that the possible pollination syndrome associated with lizard pollination could be copious nectar and possibly scented flowers in the case of nocturnal lizards. Flowers or inflorescences must also be robust enough to support the weight of the pollinator while feeding. They also theorise that the colour red that the flowers of most species Metrosideros have, which generally attracts birds, might somehow also serve to repel insects and thus leave more nectar for the geckoes. Metrosideros excelsa is a generalist, which is pollinated by both birds and insects. There does not appear to be any mutualistic relationship between the geckoes and Metrosideros excelsa, neither species requires the presence of the other to thrive.
Bird pollination
The term ornithophily is used to describe pollination specifically by birds. Bird pollination is done primarily by bird species that specialize on eating nectar, which is known as nectarivory. Hummingbirds, found only in the Americas, and many other bird species throughout the world are obligate nectarivores and important pollinators. These include sunbirds, sugarbirds, honeyeaters, flowerpeckers and honeycreepers, these have long narrow bills suited for probing flowers. However, many shorter-billed birds can also pollinate, including white-eyes, bananaquits, flowerpiercers, lories and lorikeets, many of which have more generalist diets and also feed on insects, fruits, and seeds (short-billed birds can also steal nectar from long flowers, as suggested by the name 'flowerpiercer'). Hummingbirds are the oldest group of nectar-specialist birds, with the greatest degree of specialization on nectar. The trumpet creeper (Campsis radicans) is a plant species adapted specifically for hummingbirds.
Plants pollinated by birds often have elongated or tube-shaped, brightly colored diurnal flowers that are red or orange, but no odor because birds have a poor sense of smell.
Some 500 genera of plants are pollinated by birds.
Bat pollination
Bat pollination is called chiropterophily. Hundreds of tropical plant species completely, or partially, dependent on bats for pollination in tropical regions. As of 2009, 28 orders, 67 families and about 528 species of angiosperms in some 250 genera are known to be pollinated by nectar-feeding bats. In some cases nectivorous bats are do not pollinate certain species, even while they do pollinate others, but instead act as 'nectar robbers' and exploit other pollination systems. Only two families of bats (not including the somewhat bizarre Mystacinidae) contain nectivores, and morphologically specialized nectivores are in the minority in both of these families, Pteropodidae (15 species) and Phyllostomidae (perhaps up to 38 species in the subfamily called Glossophaginae). Pteropodidae are large fruit bats from the Old World which must perch on the plant to access the nectar and do not have the ability to echolocate, whereas the much smaller Phyllostomidae only occur in the New World and have the ability to hover and echolocate.
Plants pollinated by bats often have white or pale nocturnal flowers that are large and bell shaped. Many of these flowers have large amounts of nectar, and emit a smell that attracts bats, such as a strong fruity or musky odor. Bats use certain chemical cues to locate food sources. They are attracted to odors that contain esters, alcohols, aldehydes, and aliphatic acids. Bats often have excellent spatial memory and will visit specific flowering plants repeatedly.
Pollination by other mammals
Non-flying mammals (i.e. all mammals except bats) have been found to feed on the nectar of several species of plant. This is known as therophily. Though some of these mammals are pollinators, others do not carry or transfer enough pollen to be considered pollinators. The group of non-flying pollinators is composed of marsupials, lemurs, rodents, shrews, and elephant shrews. As of 1997 studies have documented non-flying mammal pollination involving at least 59 species of mammal distributed among 19 families and six orders. As of 1997, there were 85 species of plants from 43 genera and 19 families which were visited by these mammals. In many cases, a plant species is visited by a range of mammals. Two examples of multiple mammal pollination are the genus Quararibea which is visited by twelve species and Combretum which is visited by eight (although not all these animals actually pollinate the flowers).
The honey possum from southwestern Australia is the only entirely nectarivorous mammal which is not a bat.
One example of a plant using animal pollinators is the bulb Massonia depressa. At least four rodent species were found to be visiting M. depressa during the night. Traits of the M. depressa flowers support non-flying mammal pollination: it has a dull-colored and very sturdy inflorescence at ground level, has a strong yeasty odor, and secretes copious amounts of sucrose-dominant nectar during the night. The nectar of M. depressa was also found to be 400 times as viscous, i.e. sticky, as an equivalent sugar solution. This jelly-like consistency of the nectar may discourage insect consumption while also facilitating lapping by rodents.
See also
Pollination syndrome
References
Plant morphology
Pollination | Zoophily | Biology | 2,918 |
15,456,399 | https://en.wikipedia.org/wiki/Bacteriuria | Bacteriuria is the presence of bacteria in urine. Bacteriuria accompanied by symptoms is a urinary tract infection while that without is known as asymptomatic bacteriuria. Diagnosis is by urinalysis or urine culture. Escherichia coli is the most common bacterium found. People without symptoms should generally not be tested for the condition. Differential diagnosis include contamination.
If symptoms are present, treatment is generally with antibiotics. Bacteriuria without symptoms generally does not require treatment. Exceptions may include pregnant women, those who have had a recent kidney transplant, young children with significant vesicoureteral reflux, and those undergoing surgery of the urinary tract.
Bacteriuria without symptoms is present in about 3% of otherwise healthy middle aged women. In nursing homes rates are as high as 50% among women and 40% in men. In those with a long term indwelling urinary catheter rates are 100%. Up to 10% of women have a urinary tract infection in a given year and half of all women have at least one infection at some point in their lives. There is an increased risk of asymptomatic or symptomatic bacteriuria in pregnancy due to physiological changes that occur in a pregnant woman which promotes unwanted pathogen growth in the urinary tract.
Signs and symptoms
Asymptomatic
Asymptomatic bacteriuria is bacteriuria without accompanying symptoms of a urinary tract infection and is commonly caused by the bacterium Escherichia coli. Other potential pathogens are Klebsiella spp., and group B streptococci. It is more common in women, in the elderly, in residents of long-term care facilities, and in people with diabetes, bladder catheters, and spinal cord injuries. People with a long-term Foley catheter always show bacteriuria. Chronic asymptomatic bacteriuria occurs in as many as 50% of the population in long-term care.
There is an association between asymptomatic bacteriuria in pregnant women with low birth weight, preterm delivery, cystitis, infection of the newborn and fetus death. However, most of these studies were graded as poor quality. Bacteriuria in pregnancy also increases the risk of preeclampsia.
Symptomatic
Symptomatic bacteriuria is bacteriuria with the accompanying symptoms of a urinary tract infection (such as frequent urination, painful urination, fever, back pain, abdominal pain and blood in the urine) and includes pyelonephritis or cystitis. The most common cause of urinary tract infections is Escherichia coli.
Diagnosis
Testing for bacteriuria is usually performed in people with symptoms of a urinary tract infection. Certain populations that cannot feel or express symptoms of infection are also tested when showing nonspecific symptoms. For example, confusion or other changes in behaviour can be a sign of an infection in the elderly. Screening for asymptomatic bacteriuria in pregnancy is a common routine in many countries, but controversial.
The gold standard for detecting bacteriuria is a bacterial culture which identifies the concentration of bacterial cells in the urine. The culture is usually combined with subsequent testing using biochemical methods or MALDI-TOF, which allows to identify the bacterial species, and antibiotic susceptibility testing. Urine culture is quantitative and very reliable, but can take at least one day to obtain a result and it is expensive. Miniaturization of bacterial culture within dipstick format, Digital Dipstick, allows bacterial detection, identification and quantification for bacteriuria within 10–12 hours at the point-of-care. Clinicians will often treat symptomatic bacteriuria based on the results of the urine dipstick test while waiting for the culture results.
Bacteriuria can usually be detected using a urine dipstick test. The nitrite test detects nitrate-reducing bacteria if growing in high numbers in urine. A negative dipstick test does not exclude bacteriuria, as not all bacteria which can colonise the urinary tract are nitrate-reducing. The leukocyte esterase test indirectly detects the presence of leukocytes (white blood cells) in urine which can be associated with a urinary tract infection. In the elderly, the leukocyte esterase test is often positive even in the absence of an infection. The urine dipstick test is readily available and provides fast, but often unreliable results. Some organisms such as chlamydia and Ureaplasma urealyticum will produce a negative leukocyte esterase reaction.
Microscopy can also be used to detect bacteriuria. It is rarely used in clinical routine since it requires more time and equipment and does not allow reliable identification or quantification of the causal bacterial species.
Bacteriuria is assumed if a single bacterial species is isolated in a concentration greater than 100,000 colony forming units per millilitre of urine in clean-catch midstream urine specimens. In urine samples obtained from women, there is a risk for bacterial contamination from the vaginal flora. Therefore, in research, usually a second specimen is analysed to confirm asymptomatic bacteriuria in women. For urine collected via bladder catheterization in men and women, a single urine specimen with greater than 100,000 colony forming units of a single species per millilitre is considered diagnostic. The threshold for women displaying UTI symptoms can be as low as 100 colony forming units of a single species per millilitre. However, bacteria below a threshold of 10000 colony forming units per millilitre are usually reported as "no growth" by clinical laboratories.
Using special techniques certain non-disease causing bacteria have also been found in the urine of healthy people. These are part of the resident microbiota.
Screening
Although controversial, many countries including the United States recommend a one time screening for bacteriuria during mid pregnancy. The screening method is by urine culture. Screening non-pregnant adults is recommended against by the United States Preventive Task Force.
Treatment
The decision to treat bacteriuria depends on the presence of accompanying symptoms and comorbidities.
Asymptomatic
Asymptomatic bacteriuria generally does not require treatment. Exceptions include those undergoing surgery of the urinary tract, children with vesicoureteral reflux or others with structural abnormalities of the urinary tract. In many countries, regional guidelines recommend treatment of pregnant women.
There is no indication to treat asymptomatic bacteriuria in diabetics, renal transplant recipients, and in those with spinal cord injuries.
The overuse of antibiotics to treat asymptomatic bacteriuria has many adverse effects such as an increased risk of diarrhea, the spread of antimicrobial resistance, and infection due to Clostridioides difficile.
Symptomatic
Symptomatic bacteriuria is synonymous with urinary tract infection and typically treated with antibiotics. Common choices include nitrofurantoin and trimethoprim/sulfamethoxazole.
Epidemiology
References
External links
Bacteria and humans
Abnormal clinical and laboratory findings for urine
Wikipedia medicine articles ready to translate
nl:Bacteriurie | Bacteriuria | Biology | 1,541 |
3,028,786 | https://en.wikipedia.org/wiki/Drafted%20masonry | Drafted masonry, in architecture, is the term given to large stones, the face of which has been dressed round the edge in a draft or sunken surface, leaving the centre portion as it came from the quarry. The dressing is worked with an adze of eight teeth to the inch, used in a vertical direction and to a width of two to four inches.
The earliest example of drafted masonry is found in the immense platform built by Cyrus in 530 BC at Pasargadae in Persia. It occurs again in the palace of Hyrcanus, known as the Arak-el-Emir (176 BC), but is there inferior in execution.
The finest drafted masonry is that dating from the time of Herod the Great, in the tower of David and the walls of the Haram in Jerusalem, and at Hebron. In the castles built by the Crusaders, the adze has been worked in a diagonal direction instead of vertically. In all these examples the size of the stones employed is sometimes enormous, so that the traditional influence of the Phoenician stonemasons seems to have lasted till the twelfth century.
References
Masonry | Drafted masonry | Engineering | 230 |
78,338,372 | https://en.wikipedia.org/wiki/Boris%20Bakra%C4%8D | Boris Bakrač (25 March 1912 in Požega – 29 November 1989 in Zagreb) was a Croatian civil engineer and politician. Bakrač graduated from the University of Zagreb in 1936 before starting a career in civil engineering. After the outbreak of the World War II and the Invasion of Yugoslavia, he joined the Communist Party of Yugoslavia, as its covert agent in Zagreb in 1942. A year later, the Partisan resistance command in Croatia appointed Bakrač the chief negotiator for prisoner exchanges with the Axis powers within the framework of the German–Yugoslav Partisan negotiations. He oversaw exchange of a total of 700 to 800 Axis-held prisoners of war in the process. He conducted the negotiations under the pseudonym Ivo Zuljević to conceal his identity.
In 1944, following the Belgrade offensive, Bakrač evacuated Mišo Broz, the youngest son of the Yugoslav Partisan leader Josip Broz Tito, from Zagreb to Belgrade. Mišo was born in Zagreb shortly after the outbreak of the war. He and his mother Herta Haas remained in the city and in the nearby area of Hrvatsko Zagorje aided by Partisan supporters.
After the war, Bakrač was the deputy minister and then minister of construction in the government of the People's Republic of Croatia between 1945 and 1951. From 1958 to 1963, Bakrač again became a member of the Croatian government. He was a member of the Croatian Sabor until 1974, serving as the deputy president of its Executive Committee from 1969 to 1972, and the deputy Speaker from 1972 to 1974. In 1975–1978, he was a member of the Presidnecy of Croatia tasked with international relations. Bakrač was also a member of the Assembly of Yugoslavia from 1953 to 1957, and a member of the Central Committee of the League of Communists of Croatia from 1954 to 1974.
At various times, Bakrač was the President of the Association of Engineers and Technicians of Croatia, the President of the Tourist Association of Croatia, the President of the Federal Chamber of Civil Engineers of Yugoslavia, the President of the Croatian Football Federation, the President of the Croatian Sports Association, and the President of the Yugoslav Olympic Committee. In 1960, he became a permanent member of the International Olympic Committee. In 1987, Bakrač received the Silver Olympic Order.
References
1912 births
1989 deaths
League of Communists of Croatia politicians
Croatian people of World War II
International Olympic Committee members
Recipients of the Olympic Order
Representatives in the modern Croatian Parliament
Members of the Assembly of the Socialist Federal Republic of Yugoslavia
Civil engineers
People from Požega, Croatia
University of Zagreb alumni | Boris Bakrač | Engineering | 523 |
52,432,145 | https://en.wikipedia.org/wiki/Rodney%20John%20Allam | Rodney John Allam, MBE (born 1940 in St Helens, Lancashire) is an English chemical engineer and fellow of the Institution of Chemical Engineers who is credited with inventions related to power generation, notably the Allam power cycle, which is a generation process for fossil fuels, with integrated carbon dioxide capture.
Career
Allam was employed by Air Products & Chemicals for 44 years, most recently as Director of Technology Development. In 2004, he was appointed member of the Order of the British Empire for services to the environment. He has also been a visiting professor at the Imperial College of Science and Technology and a lead author of the IPCC special report on carbon dioxide capture and storage, released in 2005. In 2007, the IPCC, along with Al Gore, was awarded with the Nobel Peace Prize.
His work has included new processes and equipment for production of gases and cryogenic liquids, such as oxygen, nitrogen, argon, carbon monoxide, carbon dioxide, hydrogen and helium. Several of these gases are generally produced through air separation, which is also a necessary step in the practical application of the Allam cycle, in which gaseous fossil fuels, for example natural gas or gasified coal, are combusted with pure oxygen. A 50 MW demonstration plant being built in Texas is expected to start operating in 2017.
In 2012, Allam was awarded the Global Energy Prize, for his work on processes and power generation, along with Russian scientists Valery Kostuk and Boris Katorgin. , he is chairman of the international award committee for the prize.
, Allam works for 8 Rivers Capital, with among other things the commercialisation of the Allam cycle.
See also
Allam power cycle
References
External links
Description of the Allam power cycle
1940 births
Living people
British chemical engineers
21st-century English engineers
20th-century British inventors
Intergovernmental Panel on Climate Change lead authors
Members of the Order of the British Empire
Environmental engineers
People from St Helens, Merseyside | Rodney John Allam | Chemistry,Engineering | 398 |
29,744,149 | https://en.wikipedia.org/wiki/Nickel-dependent%20hydrogenase | Hydrogenases are enzymes that catalyze the reversible activation of hydrogen and which occur widely in prokaryotes as well as in some eukaryotes. There are various types of hydrogenases, but all of them seem to contain at least one iron-sulphur cluster. They can be broadly divided into two groups: hydrogenases containing nickel and, in some cases, also selenium (the [NiFe] and [NiFeSe] hydrogenases) and those lacking nickel (the [Fe] hydrogenases).
The [NiFe] and [NiFeSe] hydrogenases are heterodimer that consist of a small subunit that contains a signal peptide and a large subunit. All the known large subunits seem to be evolutionary related; they contain two Cys-x-x-Cys motifs; one at their N-terminal end; the other at their C-terminal end. These four cysteines are involved in the binding of nickel. In the [NiFeSe] hydrogenases the first cysteine of the C-terminal motif is a selenocysteine which has experimentally been shown to be a nickel ligand.
References
Protein domains
Enzymes | Nickel-dependent hydrogenase | Biology | 253 |
33,300,502 | https://en.wikipedia.org/wiki/Beryllium%20monohydride | Beryllium monohydride (BeH) is an example of a molecule with a half-bond order according to molecular orbital theory. It is a metastable monoradical species which has only been observed in the gas phase. In beryllium monohydride, beryllium has a valency of one, and hydrogen has a valency of one.
BeH has only 5 electrons and is the simplest open shell neutral molecule, and is therefore extremely important for the benchmarking of ab initio methods. With such a light mass, it is also an important benchmark system for studying the breakdown of the Born–Oppenheimer approximation. Due to its simplicity, BeH is expected to be present in astronomical contexts such as exoplanetary atmospheres, cool stars, and the interstellar medium, but so far has only been found on the Sun. Because of the long lifetime (by nuclear physics standards) of 11Be, 11BeH is the leading candidate for the formation of the first halo nucleonic molecule.
BeH has been studied spectroscopically since 1928 and in over 80 theoretical studies (see for a review).
The bond length is 134.2396(3) pm and the dissociation energy is 17702(200) cm−1.
The dimeric molecule Be2H2 has also been observed in an argon matrix at 10 K
References
Beryllium compounds
Metal hydrides | Beryllium monohydride | Chemistry | 297 |
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