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Friedrich Otto Schott (1851–1935) was a German chemist, glass technologist, and the inventor of borosilicate glass. Schott systematically investigated the relationship between the chemical composition of the glass and its properties. In this way, he solved fundamental problems in glass properties, identifying compositions with optical properties that approach the theoretical limit. Schott's findings were a major advance in the optics for microscopy and optical astronomy. His work has been described as "a watershed in the history of glass composition".
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Theoretical and Fundamental Chemistry
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Older gamma-ray detectors use the Geiger-Mueller counter principle, but have been mostly replaced thallium-doped sodium-iodide (NaI) scintillation detector, which has a higher efficiency. NaI detectors are usually composed of a NaI crystal coupled with a photomultiplier. When gamma ray from formation enters the crystal, it undergoes successive collisions with the atoms of the crystal, resulting in a short flashes of light when the gamma-ray is absorbed. The light is detected by the photomultiplier, which converts the energy into an electric pulse with amplitude proportional to the gamma-ray energy. The number of electric pulses is recorded in counts per seconds (CPS). The higher the gamma-ray count rate, the larger the clay content and vice versa.
Primary calibration of gamma-ray tool is the test pit at the University of Houston. The artificial formation simulate about twice the radioactivity of a shale, which generates 200 API units of gamma radiation. The detector crystal is affected by hydration and its response changes with time. Consequently, a secondary and a field calibration is achieved with a portable jig carrying a small radioactive source.
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Theoretical and Fundamental Chemistry
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The imidazol-2-ylidenes are strong bases, having pK ≈ 24 for the conjugate acid in dimethyl sulfoxide (DMSO):
However, further work showed that diaminocarbenes will deprotonate the DMSO solvent, with the resulting anion reacting with the resulting amidinium salt.
Reaction of imidazol-2-ylidenes with 1-bromohexane gave 90% of the 2-substituted adduct, with only 10% of the corresponding alkene, indicating that these molecules are also reasonably nucleophilic.
pK values for the conjugate acids of several NHC families have been examined in aqueous solution. pKa values of triazolium ions lie in the range 16.5–17.8, around 3 pK units more acidic than related imidazolium ions.
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Theoretical and Fundamental Chemistry
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Brian Halton (9 March 1941 – 23 February 2019) was a New Zealand organic chemist. He is noted for his investigation of highly strained and fused aromatic compounds, and was also active as an historian of chemistry.
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Theoretical and Fundamental Chemistry
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Reoviridae are currently classified into nine genera. The genomes of these viruses consist of 10 to 12 segments of dsRNA, each generally encoding one protein. The mature virions are non-enveloped. Their capsids, formed by multiple proteins, have icosahedral symmetry and are arranged generally in concentric layers.
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Applied and Interdisciplinary Chemistry
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Ambergris has been mostly known for its use in creating perfume and fragrance much like musk. Perfumes based on ambergris still exist.
Ambergris has historically been used in food and drink. A serving of eggs and ambergris was reportedly King Charles II of Englands favorite dish. A recipe for Rum Shrub liqueur from the mid 19th century called for a thread of ambergris to be added to rum, almonds, cloves, cassia, and the peel of oranges in making a cocktail from The English and Australian Cookery Book'. It has been used as a flavoring agent in Turkish coffee and in hot chocolate in 18th century Europe. The substance is considered an aphrodisiac in some cultures.
Ancient Egyptians burned ambergris as incense, while in modern Egypt ambergris is used for scenting cigarettes. The ancient Chinese called the substance "dragon's spittle fragrance". During the Black Death in Europe, people believed that carrying a ball of ambergris could help prevent them from contracting plague. This was because the fragrance covered the smell of the air which was believed to be a cause of plague.
During the Middle Ages, Europeans used ambergris as a medication for headaches, colds, epilepsy, and other ailments.
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Applied and Interdisciplinary Chemistry
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The North Atlantic Gyre is located in the northern hemisphere in the Atlantic Ocean, between the Intertropical Convergence Zone (ITCZ) in the south and Iceland in the north. The North Equatorial Current brings warm waters west towards the Caribbean and defines the southern edge of the North Atlantic Gyre. Once these waters reach the Caribbean they join the warm waters in the Gulf of Mexico and form the Gulf Stream, a western boundary current. This current then heads north and east towards Europe, forming the North Atlantic Current. The Canary Current flows south along the western coast of Europe and north Africa, completing the gyre circulation. The center of the gyre is the Sargasso Sea, which is characterized by the dense accumulation of Sargassum seaweed.
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Applied and Interdisciplinary Chemistry
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Mieli is now considered one of the founders of the discipline of the history of science, as one of the first to consider it a discipline it its own right.
His history of science career began whilst a chemistry lecturer in Rome, building on interest stimulated in his studies in Germany.
In 1912, he founded, and briefly maintained, a section in the journal Rivista di filosofia for the history of science. He edited the Italian bibliography for the then new journal Isis, and in 1916, published a pamphlet calling for a chair of history of science to be created in Italian universities. He also wrote several books on history of science topics, and edited a series on classic texts in science and philosophy for Laterza, an Italian publisher.
He taught history of science at the University of Rome between 1919 and 1928, and the University of Perugia in 1926. He was elected a member of Deutsche Akademie der Naturforscher Leopoldina in 1925.
In 1919, he founded the journal Archeion (later renamed Archives internationales dhistoire des sciences' and still published), which he continued to edit until three years before he died. Many organisations, including UNESCO, provided funding for the journal, which he also subsidised from his own finances.
In 1928 he moved to Paris. There, Mieli co-founded, and served as permanent secretary of the Comite International dHistoire des Sciences (the International Committee for the History of Science), renamed the International Academy of the History of Science at its First International Congress of the History of Science, held in Paris in May 1929. At that meeting, Archeion' became the official journal of the Academy.
That same year, Mieli was invited to create and direct a Unit for the History of Science at the Centre international de synthèse, which had been created in 1925 by Henri Berr. The Unit officially opened on 22 January 1930. He worked there, collaborating with Helene Metzger until 1939, when he moved to Argentina. He was very ill when he arrived in Argentina, and spent several months in hospital.
He worked at the Universidad Nacional del Litoral in Santa Fé, from 1940 to 1943 where he founded an Institute for the History and Philosophy of Science and continued to edit Archeion. Following the 1943 Argentine coup détat and the new Governments intervention in the university, his employment contract was cancelled, and he retired to Florida, near Buenos Aires.
In poor health, and without the financial backing of the university, he ceased being editor of Archeion, which was subsequently relaunched as Archives internationales dhistoire des sciences. He began to write Panorama general de historia de la ciencia,' a survey of the history of science, intended to be an eight-volume set. He completed and published the first two volumes, and had proofs of the third, fourth and fifth, by the time he died.
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Applied and Interdisciplinary Chemistry
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Based on STANDARD ANSI/ISA S5.1 and ISO 14617-6, the P&ID is used for the identification of measurements within the process. The identifications consist of up to 5 letters. The first identification letter is for the measured value, the second is a modifier, 3rd indicates passive/readout function, 4th - active/output function, and the 5th is the function modifier. This is followed by loop number, which is unique to that loop. For instance FIC045 means it is the Flow Indicating Controller in control loop 045. This is also known as the "tag" identifier of the field device, which is normally given to the location and function of the instrument. The same loop may have FT045 - which is the flow transmitter in the same loop.
For reference designation of any equipment in industrial systems the standard IEC 61346 (Industrial systems, installations and equipment and industrial products — Structuring principles and reference designations) can be applied. For the function Measurement the reference designator B is used, followed by the above listed letter for the measured variable.
For reference designation of any equipment in a power station the KKS Power Plant Classification System can be applied.
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Applied and Interdisciplinary Chemistry
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Past studies suggest that repeats are a common feature of eukaryotes unlike the prokaryotes and archaea. Other reports suggest that irrespective of the comparative shortage of repeat elements in prokaryotic genomes, they nevertheless contain hundreds or even thousands of large repeats. Current genomic analysis seem to suggest the existence of a large excess of perfect inverted repeats in many prokaryotic genomes as compared to eukaryotic genomes.
For quantification and comparison of inverted repeats between several species, namely on archaea, see
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Applied and Interdisciplinary Chemistry
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In case of a sudden reduction of pipe diameter, without streamlining, the flow is not able to follow the sharp bend into the narrower pipe. As a result, there is flow separation, creating recirculating separation zones at the entrance of the narrower pipe. The main flow is contracted between the separated flow areas, and later on expands again to cover the full pipe area.
There is not much head loss between cross section 1, before the contraction, and cross section 3, the vena contracta at which the main flow is contracted most. But there are substantial losses in the flow expansion from cross section 3 to 2. These head losses can be expressed by using the Borda–Carnot equation, through the use of the coefficient of contraction μ:
with A the cross-sectional area at the location of strongest main flow contraction 3, and A the cross-sectional area of the narrower part of the pipe. Since A ≤ A, the coefficient of contraction is less than one: μ ≤ 1. Again there is conservation of mass, so the volume fluxes in the three cross sections are a constant (for constant fluid density ρ):
with v, v and v the mean flow velocity in the associated cross sections. Then, according to the Borda–Carnot equation (with loss coefficient ξ=1), the energy loss ΔE per unit of fluid volume and due to the pipe contraction is:
The corresponding loss of total head ΔH can be computed as ΔH = ΔE/(ρg).
According to measurements by Weisbach, the contraction coefficient for a sharp-edged contraction is approximately:
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Applied and Interdisciplinary Chemistry
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Professor Mukherjee proposed the idea of making the Indian Agricultural Research Institute,(IARI) a regular University. In 1958, on the recommendation of
the Indo-American Team on Agricultural Research and Education and with the generous aid of the Rockefeller Foundation, the Post-Graduate School was established
at this Institute by the Governmental of India. The Institute now enjoys the status of a University under the University Grants Commission Act of 1956.
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Theoretical and Fundamental Chemistry
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Natural isotopes must be either stable, have a half-life exceeding about 7 years (there are 35 isotopes in this category, see stable isotope for more details) or are generated in large amounts cosmogenically (such as C, which has a half-life of only 6000 years but is made by cosmic rays colliding with N).
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Theoretical and Fundamental Chemistry
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The Memorial Lecture Award was established in the year 1979 in the honour of Professor Kotcherlakota Rangadhama Rao by the students of Prof. K.Rangadhama Rao and Indian National Science Academy, formerly National Institute of Sciences of India, Calcutta. The lecture is awarded for outstanding contributions in the field of Spectroscopy. The award carries an honorarium of Rs. 25,000/- and a citation.
The below lists the recipients of the Memorial Award since its inception in the year 1979.
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Theoretical and Fundamental Chemistry
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Because of the way ESTs are sequenced, many distinct expressed sequence tags are often partial sequences that correspond to the same mRNA of an organism. In an effort to reduce the number of expressed sequence tags for downstream gene discovery analyses, several groups assembled expressed sequence tags into EST contigs. Example of resources that provide EST contigs include: TIGR gene indices, Unigene, and STACK
Constructing EST contigs is not trivial and may yield artifacts (contigs that contain two distinct gene products). When the complete genome sequence of an organism is available and transcripts are annotated, it is possible to bypass contig assembly and directly match transcripts with ESTs. This approach is used in the TissueInfo system (see below) and makes it easy to link annotations in the genomic database to tissue information provided by EST data.
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Applied and Interdisciplinary Chemistry
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Since there is no single experimental feature which identifies a material as a spin liquid, several experiments have to be conducted to gain information on different properties which characterize a spin liquid.
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Theoretical and Fundamental Chemistry
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The publication of the NAPAP-fIIa crystal structure triggered many researches on thrombin inhibitors. NAPAP is an active site thrombin inhibitor. It fills the S3 and S2 pockets with its naphthalene and piperidine groups. AstraZeneca used the information to develop melagatran. The compound was poorly orally available, but after renovation they got a double prodrug which was the first oral DTI in clinical trials, ximelagatran. Ximelagatran was on the European market for approximately 20 months when it was suspended. Studies showed that treatment for over 35 days was linked with the risk of hepatic toxicity. It was never approved by the FDA.
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Applied and Interdisciplinary Chemistry
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The phenomenon of predissociation occurs when an electronic transition results in dissociation of the molecule at an excitation energy less than the normal dissociation limit of the upper state. This can occur when the potential energy curve of the upper state crosses the curve for a repulsive state, so that the two states have equal energy at some internuclear distance. This allows the possibility of a radiationless transition to the repulsive state whose energy levels form a continuum, so that there is blurring of the particular vibrational band in the vibrational progression.
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Theoretical and Fundamental Chemistry
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Thousands of residents assembled to pay respects to Tom at his funeral filling the south end of Stockton High Street and the entire length of Bridge Road. His funeral procession, was four deep and numbered about two thousand people – an unusual turnout for a 40 year old industrialist and engineer.
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Applied and Interdisciplinary Chemistry
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The pH of the extracellular fluid, including the blood plasma, is normally tightly regulated between 7.32 and 7.42 by the chemical buffers, the respiratory system, and the renal system. The normal pH in the fetus differs from that in the adult. In the fetus, the pH in the umbilical vein pH is normally 7.25 to 7.45 and that in the umbilical artery is normally 7.18 to 7.38.
Aqueous buffer solutions will react with strong acids or strong bases by absorbing excess ions, or ions, replacing the strong acids and bases with weak acids and weak bases. This has the effect of damping the effect of pH changes, or reducing the pH change that would otherwise have occurred. But buffers cannot correct abnormal pH levels in a solution, be that solution in a test tube or in the extracellular fluid. Buffers typically consist of a pair of compounds in solution, one of which is a weak acid and the other a weak base. The most abundant buffer in the ECF consists of a solution of carbonic acid (HCO), and the bicarbonate () salt of, usually, sodium (Na). Thus, when there is an excess of ions in the solution carbonic acid partially neutralizes them by forming HO and bicarbonate () ions. Similarly an excess of H ions is partially neutralized by the bicarbonate component of the buffer solution to form carbonic acid (HCO), which, because it is a weak acid, remains largely in the undissociated form, releasing far fewer H ions into the solution than the original strong acid would have done.
The pH of a buffer solution depends solely on the ratio of the molar concentrations of the weak acid to the weak base. The higher the concentration of the weak acid in the solution (compared to the weak base) the lower the resulting pH of the solution. Similarly, if the weak base predominates the higher the resulting pH.
This principle is exploited to regulate the pH of the extracellular fluids (rather than just buffering the pH). For the carbonic acid-bicarbonate buffer, a molar ratio of weak acid to weak base of 1:20 produces a pH of 7.4; and vice versa—when the pH of the extracellular fluids is 7.4 then the ratio of carbonic acid to bicarbonate ions in that fluid is 1:20.
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Theoretical and Fundamental Chemistry
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This is a modification of the method of oxidative tethering to a para-methoxybenzyl ether. The difference here is that the para-alkoxybenzyl group is attached to a solid support; the β-mannoside product is released into the solution phase in the last step, while the by-products remain attached to the solid phase. This makes the purification of the β-glycoside easier; it is formed as the almost exclusive product.
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Theoretical and Fundamental Chemistry
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The Graduate Institute of Ferrous Technology (GIFT POSTECH) is an institute for graduate-level education and research in the field of iron and steel technology at Pohang University of Science and Technology, South Korea. It has nine specialized laboratories covering all sides of metallurgy. However, the Institute now has a reduced focus on steels, having introduced laboratories on battery electronics,.
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Applied and Interdisciplinary Chemistry
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Alternative non-helical models were briefly considered in the late 1970s as a potential solution to problems in DNA replication in plasmids and chromatin. However, the models were set aside in favor of the double-helical model due to subsequent experimental advances such as X-ray crystallography of DNA duplexes and later the nucleosome core particle, and the discovery of topoisomerases. Also, the non-double-helical models are not currently accepted by the mainstream scientific community.
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Theoretical and Fundamental Chemistry
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Historically, two conventions for sign for the electrode potential have formed:
# convention "Nernst–Lewis–Latimer" (sometimes referred to as "American"),
# convention "Gibbs–Ostwald–Stockholm" (sometimes referred to as "European").
In 1953 in Stockholm IUPAC recognized that either of the conventions is permissible; however, it unanimously recommended that only the magnitude expressed according to the convention (2) be called "the electrode potential". To avoid possible ambiguities, the electrode potential thus defined can also be referred to as Gibbs–Stockholm electrode potential. In both conventions, the standard hydrogen electrode is defined to have a potential of 0 V. Both conventions also agree on the sign of for a half-cell reaction when it is written as a reduction.
The main difference between the two conventions is that upon reversing the direction of a half-cell reaction as written, according to the convention (1) the sign of also switches, whereas in the convention (2) it does not. The logic behind switching the sign of is to maintain the correct sign relationship with the Gibbs free energy change, given by where is the number of electrons involved and is the Faraday constant. It is assumed that the half-reaction is balanced by the appropriate SHE half-reaction. Since switches sign when a reaction is written in reverse, so too, proponents of the convention (1) argue, should the sign of . Proponents of the convention (2) argue that all reported electrode potentials should be consistent with the electrostatic sign of the relative potential difference.
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Theoretical and Fundamental Chemistry
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* 1984 "Physics Award" of the German Physical Society (together with Gottfried Münzenberg, Willibrord Reisdorf and Karl-Heinz Schmidt)
* 1996 Otto Hahn Prize of the City of Frankfurt am Main (together with Gottfried Münzenberg)
* 1996 "Doctor honoris causa" of the Faculty of Mathematics and Physics, Comenius University of Bratislava, Slovakia
* 1997 "G.N. Flerov Prize" of the Joint Institute for Nuclear Research (JINR) in Dubna, Russia
* 1998 "Honorary Professor" of the Goethe University in Frankfurt am Main, Germany
* 1998 "SUN-AMCO Medal" of the International Union of Pure and Applied Physics
* 2001 "Doctor honoris causa" of the Joint Institute for Nuclear Research (JINR) in Dubna, Russia
* 2002 "First Prize" of the Joint Institute for Nuclear Research (JINR) in Dubna, Russia
* 2004 "Distinguished Professor" of the Josef Buchmann Foundation and the Department of Physics of the Goethe University in Frankfurt am Main, Germany
* 2006 "Roentgen Medal" of the City of Remscheid-Lennep, Germany, place of birth of Conrad Roentgen
* 2009 "Helmholtz Professor" of the Helmholtz Association of German Research Centres (HGF)
* 2011 "Nicolaus Copernicus Medal" of the Polish Academy of Sciences in Warsaw, Poland
* 2011 "Medal of the City of Torun" and Nicolaus Copernicus University in Torun, Poland
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Applied and Interdisciplinary Chemistry
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Artificial photosynthesis was first anticipated by the Italian chemist Giacomo Ciamician during 1912. In a lecture that was later published in Science he proposed a switch from the use of fossil fuels to radiant energy provided by the sun and captured by technical photochemistry devices. In this switch he saw a possibility to lessen the difference between the rich north of Europe and poor south and ventured a guess that this switch from coal to solar energy would "not be harmful to the progress and to human happiness."
During the late 1960s, Akira Fujishima discovered the photocatalytic properties of titanium dioxide, the so-called Honda-Fujishima effect, which could be used for hydrolysis.
Visible light water splitting with a one piece multijunction semiconductor device (vs. UV light with titanium dioxide semiconductors) was first demonstrated and patented by William Ayers at Energy Conversion Devices during 1983. This group demonstrated water photolysis into hydrogen and oxygen, now referred to as an "artificial leaf" with a low cost, thin film amorphous silicon multijunction sheet immersed directly in water. Hydrogen evolved on the front amorphous silicon surface decorated with various catalysts while oxygen evolved from the back side metal substrate which also eliminated the hazard of mixed hydrogen/oxygen gas evolution. A polymer membrane above the immersed device provided a path for proton transport. The higher photovoltage available from the multijunction thin film device with visible light was a major advance over previous photolysis attempts with UV or other single junction semiconductor photoelectrodes. The group's patent also lists several other semiconductor multijunction compositions in addition to amorphous silicon.
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Theoretical and Fundamental Chemistry
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It is important to recognize that while iron production had great influence over Africa both culturally in trade and expansion (Martinelli, 1993, 1996, 2004), as well as socially in beliefs and rituals, there is great regional variation. Much of the evidence for cultural significance comes from the practises still carried out today by different African cultures. Ethnographical information has been very useful in reconstructing the events surrounding iron production in the past, however the reconstructions could have become distorted through time and influence by anthropologist's studies.
The control of iron production was often by ironworkers themselves, or a "central power" in larger societies such as kingdoms or states (Barros 2000, p. 154). The demand for trade is believed to have resulted in some societies working only as smelters or smiths, specialising in just one of the many skills necessary to the production process. It is possible that this also led to tradesmen specialising in transporting and trading iron (Barros 2000, pg152). However, not every region benefited from industrialising iron production, others created environmental problems that arose due to the massive deforestation required to provide the charcoal for fuelling furnaces (for example the ecological crisis of the Mema Region (Holl 2000, pg48)).
Iron smelters and smiths received different social status depending on their culture. Some were lower in society due to the aspect of manual labour and associations with witchcraft, for example in the Maasai and Tuareg (Childs et al. 2005 pg 288). In other cultures the skills are often passed down through family and would receive great social status (sometimes even considered as witchdoctors) within their community. Their powerful knowledge allowed them to produce materials on which the whole community relied. In some communities they were believed to have such strong supernatural powers that they were regarded as highly as the king or chief. For example, an excavation at the royal tomb of King Rugira (Great Lakes, Eastern Africa) found two iron anvils placed at his head (Childs et al. 2005, p. 288 in Herbert 1993:ch.6). In some cultures mythical stories have been built around the premise of the iron smelter emphasising their godlike significance.
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Applied and Interdisciplinary Chemistry
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Unlike alkyl halide refrigerants that contain bromine or chlorine, R-410A (which contains only fluorine) does not contribute to ozone depletion and is therefore becoming more widely used as ozone-depleting refrigerants like R-22 are phased out. However, like methane, its global warming potential (GWP) is appreciably worse than CO for the time it persists. Because R410A is a 50% combination of CHF (HFC-32) and 50% CHFCF (HFC-125), it is not easy to express their combined effects in a single global warming potential (GWP), However, HFC-32 has a 4.9 year lifetime and a 100-year GWP of 675 and HFC-125 has a 29-year lifetime and a 100-year GWP of 3500. The combination has a GWP of 2088, higher than that of R-22 (100-year GWP=1810), and an atmospheric lifetime of nearly 30 years compared with the 12-year lifetime of R-22.
Since R-410A allows for higher SEER ratings than an R-22 system by reducing power consumption, the overall impact on global warming of R-410A systems can, in some cases, be lower than that of R-22 systems due to reduced greenhouse gas emissions from power plants. This assumes that the atmospheric leakage will be sufficiently managed. Under the assumption that preventing ozone depletion is more important in the short term than GWP reduction, R-410A is preferable to R-22.
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Applied and Interdisciplinary Chemistry
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Furthermore, the method showed consistent performance in cancer identification, classification, and treatment effect problems like NSCLC and DLBCL identification, histological classification of subtypes of NSCLC, molecular classification of subtypes of DLBCL, DLBCL COO detection, programmed death-ligand 1 immune-checkpoint inhibition response prediction against advanced NSCLC cases, and prognostic value detection of individual genes.
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Applied and Interdisciplinary Chemistry
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Typically plugs are made from a soft material, such as rubber, or have a soft outer rim, so that they can be fitted to holes slightly smaller than their diameter; this ensures a tight seal. They are often connected by a ball chain which ensures the plug may be pulled from the drain with relative ease.
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Applied and Interdisciplinary Chemistry
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In molecular biology, a hybridization probe (HP) is a fragment of DNA or RNA, usually 15–10000 nucleotides long, which can be radioactively or fluorescently labeled. HPs can be used to detect the presence of nucleotide sequences in analyzed RNA or DNA that are complementary to the sequence in the probe. The labeled probe is first denatured (by heating or under alkaline conditions such as exposure to sodium hydroxide) into single stranded DNA (ssDNA) and then hybridized to the target ssDNA (Southern blotting) or RNA (northern blotting) immobilized on a membrane or in situ.
To detect hybridization of the probe to its target sequence, the probe is tagged (or "labeled") with a molecular marker of either radioactive or (more recently) fluorescent molecules. Commonly used markers are P (a radioactive isotope of phosphorus incorporated into the phosphodiester bond in the probe DNA), digoxigenin, a non-radioactive, antibody-based marker, biotin or fluorescein. DNA sequences or RNA transcripts that have moderate to high sequence similarity to the probe are then detected by visualizing the hybridized probe via autoradiography or other imaging techniques. Normally, either X-ray pictures are taken of the filter, or the filter is placed under UV light. Detection of sequences with moderate or high similarity depends on how stringent the hybridization conditions were applied—high stringency, such as high hybridization temperature and low salt in hybridization buffers, permits only hybridization between nucleic acid sequences that are highly similar, whereas low stringency, such as lower temperature and high salt, allows hybridization when the sequences are less similar.
Hybridization probes used in DNA microarrays refer to DNA covalently attached to an inert surface, such as coated glass slides or gene chips, to which a mobile cDNA target is hybridized. Depending on the method, the probe may be synthesized using the phosphoramidite method, or it can be generated and labeled by PCR amplification or cloning (both are older methods). In order to increase the in vivo stability of the probe RNA is not used. Instead, RNA analogues may be used, in particular morpholino- derivatives. Molecular DNA- or RNA-based probes are routinely used in screening gene libraries, detecting nucleotide sequences with blotting methods, and in other gene technologies, such as nucleic acid and tissue microarrays.
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Applied and Interdisciplinary Chemistry
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Greg N. Stephanopoulos (born 1950) is an American chemical engineer and the Willard Henry Dow Professor in the department of chemical engineering at the Massachusetts Institute of Technology. He has worked at MIT, Caltech, and the University of Minnesota in the areas of biotechnology, bioinformatics, and metabolic engineering especially in the areas of bioprocessing for biochemical and biofuel production. Stephanopoulos is the author of over 400 scientific publications with more than 35,000 citations (h index = 97) as of April 2018. In addition, Greg has supervised more than 70 graduate students and 50 post-docs whose research has led to more than 50 patents. He was elected a fellow of the American Association for the Advancement of Science (2005), a member of the National Academy of Engineering (2003), and received the ENI Prize on Renewable Energy 2011.
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Applied and Interdisciplinary Chemistry
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This system is the best understood of the plasmid partition system.
It is composed of an actin-like ATPAse, ParM, and a CBP called ParR. The centromere like site, parC contains two sets of five 11 base pair direct repeats separated by the parMR promoter.
The amino-acid sequence identity can go down to 15% between ParM and other actin-like ATPase.
The mechanism of partition involved here is a pushing mechanism:
# ParR binds to parC and pairs plasmids which form a nucleoprotein complex, or partition complex
# The partition complex serves as nucleation point for the polymerization of ParM; ParM-ATP complex inserts at this point and push plasmids apart
# The insertion leads to hydrolysis of ParM-ATP complex, leading to depolymerization of the filament
# At cell division, plasmids copies are at each cell extremity, and will end up in future daughter cell
The filament of ParM is regulated by the polymerization allowed by the presence the partition complex (ParR-parC), and by the depolymerization controlled by the ATPase activity of ParM.
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Applied and Interdisciplinary Chemistry
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Some other methods to produce LAGP materials have been reported in literature works, including liquid-based techniques, spark plasma sintering, and co-precipitation.
In the following table, some ionic conductivity values are reported for LAGP materials produced with different synthesis routes, in the case of optimized production and annealing conditions.
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Theoretical and Fundamental Chemistry
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The use of molten CaCl is important because this molten salt can dissolve and transport the "O" ions to the anode to be discharged. The anode reaction depends on the material of the anode. Depending on the system it is possible to produce either CO or CO or a mixture at the carbon anode:
However, if an inert anode is used, such as that of high density SnO, the discharge of the O ions leads to the evolution of oxygen gas. However the use of an inert anode has disadvantages. Firstly, when the concentration of CaO is low, Cl evolution at the anode becomes more favourable. In addition, when compared to a carbon anode, more energy is required to achieve the same reduced phase at the cathode. Inert anodes suffer from stability issues.
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Theoretical and Fundamental Chemistry
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The Curtin–Hammett principle can explain the observed dynamics in transformations employing dynamic kinetic resolution, such as the Noyori asymmetric hydrogenation and enantioselective lithiation.
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Theoretical and Fundamental Chemistry
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Frémys work included investigations of osmic acid, the ferrates, stannates, plumbates, and other oxometallates, as well as ozone; attempts to obtain free fluorine by the electrolysis of fused fluorides; and the discovery of anhydrous hydrofluoric acid and a series of acides sulphazotés, the precise nature of which long remained a matter of discussion. He also studied the coloring of leaves and flowers, the composition of bone, cerebral matter, and other animal substances, and the processes of fermentation, in which he was an opponent of Pasteurs views.
Keenly alive to the importance of the technical applications of chemistry, Frémy devoted special attention as a teacher to the training of industrial chemists. In this field he contributed to our knowledge of the manufacture of iron and steel, sulfuric acid, glass, and paper, and in particular worked at the saponification of fats with sulfuric acid and the utilization of palmitic acid for candle-making. In the later years of his life he applied himself to the problem of obtaining alumina in the I crystalline form, and succeeded in making rubies identical with the natural gem not merely in chemical composition but also in physical properties.
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Theoretical and Fundamental Chemistry
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The order of ligands which possess cis-labilizing effects are as follows:
CO, AuPPh, H, SnPh, GePh, SO, NCH CO , NCO
Anionic ligands such as F, Cl, OH, and SH have particularly strong CO labilizing effects in complexes. This is because these ligands will stabilize the 16 e intermediate by electron donation from the p-pi lone pair donor orbital. Other sulfur-containing ligands, particularly thiobenzoate, are other examples of particularly useful CO cis-labilizing ligands, which can be explained by stabilization of the intermediate that results upon CO dissociation. This can be attributed to the partial interaction of the oxygen from the thiobenzoate and the metal, which can eliminate solvent effects that can occur during ligand dissociation in transition metal complexes.
Note that the strongest labilizing effects come from ligands that are weak sigma donors with virtually no pi-accepting behavior. The cis effect can be attributed to the role of ligand X in stabilizing the transition state. It has also been determined that labilizing X ligands do in fact strengthen the M-CO bond trans to X, which is hypothesized to be due to the weak pi-accepting and/or sigma donating behavior of ligand X. This lack of strong sigma donation/pi-accepting will allow the CO (a strong pi-acceptor) trans to ligand X to pull electron density toward it, strengthening the M-CO bond. This phenomenon is further supported by the evidence from extensive studies on the trans effect, which in turn shows how ligands that are actually strong sigma donors and pi-acceptors weaken the M-L bond trans to them. Since the cis and trans effects seem to have generally opposite trends, the electronic argument supports both phenomena. Further evidence for cis labilization of CO can be attributed to the CO ligands being in competition for the d, d, and d orbitals. This argument especially holds true when the X is a halogen.
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Theoretical and Fundamental Chemistry
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Three key points are taken into consideration regarding MRL values in the EU regulation:
1) the amounts of residues found in food must be safe for consumers and must be as low as possible,
2) the European Commission fixes MRLs for all food and animal feed, and 3) the MRLs for all crops and all pesticides can be found in the MRL database on the Commission website.
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Applied and Interdisciplinary Chemistry
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Recovery is sometimes impossible in subsonic aircraft; however, as an aircraft descends into lower, warmer, denser air, control authority (meaning the ability to control the aircraft) may return because drag tends to slow the aircraft while the speed of sound and control authority both increase.
To prevent Mach stall from progressing, the pilot should keep the airspeed below the type's critical Mach number by reducing thrust, extending air brakes, and if possible, extending the landing gear.
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Applied and Interdisciplinary Chemistry
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Tides in marginal seas are tides affected by their location in semi-enclosed areas along the margins of continents and differ from tides in the open oceans. Tides are water level variations caused by the gravitational interaction between the Moon, the Sun and the Earth. The resulting tidal force is a secondary effect of gravity: it is the difference between the actual gravitational force and the centrifugal force. While the centrifugal force is constant across the Earth, the gravitational force is dependent on the distance between the two bodies and is therefore not constant across the Earth. The tidal force is thus the difference between these two forces on each location on the Earth.
In an idealized situation, assuming a planet with no landmasses (an aqua planet), the tidal force would result in two tidal bulges on opposite sides of the earth. This is called the equilibrium tide. However, due to global and local ocean responses different tidal patterns are generated. The complicated ocean responses are the result of the continental barriers, resonance due to the shape of the ocean basin, the tidal waves impossibility to keep up with the Moons tracking, the Coriolis acceleration and the elastic response of the solid earth.
In addition, when the tide arrives in the shallow seas it interacts with the sea floor which leads to the deformation of the tidal wave. As a results, tides in shallow waters tend to be larger, of shorter wavelength, and possibly nonlinear relative to tides in the deep ocean.
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Applied and Interdisciplinary Chemistry
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A sand rammer is a piece of equipment used in foundry sand testing to make test specimen of molding sand by compacting bulk material by free fixed height drop of fixed weight for 3 times. It is also used to determine compactibility of sands by using special specimen tubes and a linear scale.
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Applied and Interdisciplinary Chemistry
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In order to understand how life arose, knowledge is required of the chemical pathways that permit formation of the key building blocks of life under plausible prebiotic conditions. Nam et al. demonstrated the direct condensation of purine and pyrimidine nucleobases with ribose to give ribonucleosides in aqueous microdroplets, a key step leading to RNA formation. Also, a plausible prebiotic process for synthesizing purine ribonucleosides was presented by Becker et al.
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Applied and Interdisciplinary Chemistry
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Wild Fermentation: The Flavor, Nutrition, and Craft of Live-Culture Foods is a 2003 book by Sandor Katz that discusses the ancient practice of fermentation. While most of the conventional literature assumes the use of modern technology, Wild Fermentation focuses more on the practice and culture of fermenting food.
The term "wild fermentation" refers to the reliance on naturally occurring bacteria and yeast to ferment food. For example, conventional bread making requires the use of a commercial, highly specialized yeast, while wild-fermented bread relies on naturally occurring cultures that are found on the flour, in the air, and so on. Similarly, the book's instructions on sauerkraut require only cabbage and salt, relying on the cultures that naturally exist on the vegetable to perform the fermentation.
The book also discusses some foods that are not, strictly speaking, wild ferments such as miso, yogurt, kefir, and nattō.
Beyond food, the book includes some discussion of social, personal, and political issues, such as the legality of raw milk cheeses in the United States.
Newsweek has referred to Wild Fermentation as the "fermentation bible".
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Applied and Interdisciplinary Chemistry
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Surfactants play an important role in droplet-based microfluidics in the stabilization of the droplets, and the prevention of the fusion of droplets during incubation.
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Theoretical and Fundamental Chemistry
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Karl Norris pioneered the field of near-infrared spectroscopy. He began by using log(1/R) as a metric of absorption. While often the samples examined were “infinitely thick”, partially transparent samples were analyzed (especially later) in cells that had a rear reflecting surface (reflector) in a mode called "transflectance". Therefore, the remission from the sample contained light that was back-scattered from the sample, as well as light that was transmitted through the sample, then reflected back to be transmitted through the sample again, thereby doubling the path length. Having no sound theoretical basis for data treatment, Norris used the same electronic processing that was used for absorption data collected in transmission. He pioneered the use of multiple linear regression for analysis of data.
Gerry Birth was the founder of the International Diffuse Reflectance Conference (IDRC). He also worked at the USDA. He was known to have a deep desire to have a better understanding of the process of light scattering. He teamed up with Harry Hecht (who was active in the early meetings of IDRC) to write the Physics theory chapter, with many photographic illustrations, in an influential Handbook edited by Phil Williams and Karl Norris: Nearinfrared Technology in the Agriculture and Food Industries.
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Theoretical and Fundamental Chemistry
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Protein phosphatases remove phosphates from proteins, usually on Serine, Threonine, and Tyrosine residues, reversing the action of protein kinases. The PTP family of protein phosphatases is tyrosine-specific, and several other families (PPPL, PPM, HAD) appear to be serine/threonine specific, while other families are unknown or have a variety of substrates (DSPs dephosphorylate any amino acid, while some protein phosphatases also have non-protein substrates). In the human genome, 20 different folds of protein are known to be phosphatases, of which 10 include protein phosphatases.
Protein phosphatomes have been cataloged for human and 8 other key eukaryotes, for Plasmodium and Trypanosomes
and phosphatomes have been used for functional analysis, by experimentally investing all known protein phosphatases, in the yeast Fusarium, in Plasmodium and in human cancer
Large scale databases exist for human and animal phosphatomes [http://phosphatome.net/wiki/index.php Phosphatome.net], parasitic protozoans [http://202.41.10.46/ProtozPhosDB/ ProtozPhosDB] and for the substrates of human phosphatases [http://www.koehn.embl.de/depod/ DEPOD].
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Applied and Interdisciplinary Chemistry
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Anti-anti-sigma factors allow for the dissociation of the matching anti-sigma factor from its sigma factors, thought binding to the anti-sigma factor, forcing its release from the sigma factor. This allows for tighter regulation of the transcription of genes as a response to environmental conditions. Anti-anti-sigma factors can thereby function as negative or positive regulatory elements, depending on the corroding sigma factor and gene involved.
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Applied and Interdisciplinary Chemistry
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In cold weather the blood flow to the limbs of birds and mammals is reduced on exposure to cold environmental conditions, and returned to the trunk via the deep veins which lie alongside the arteries (forming venae comitantes). This acts as a counter-current exchange system which short-circuits the warmth from the arterial blood directly into the venous blood returning into the trunk, causing minimal heat loss from the extremities in cold weather. The subcutaneous limb veins are tightly constricted, thereby reducing heat loss via this route, and forcing the blood returning from the extremities into the counter-current blood flow systems in the centers of the limbs. Birds and mammals that regularly immerse their limbs in cold or icy water have particularly well developed counter-current blood flow systems to their limbs, allowing prolonged exposure of the extremities to the cold without significant loss of body heat, even when the limbs are as thin as the lower legs, or tarsi, of a bird, for instance.
When animals like the leatherback turtle and dolphins are in colder water to which they are not acclimatized, they use this CCHE mechanism to prevent heat loss from their flippers, tail flukes, and dorsal fins. Such CCHE systems are made up of a complex network of peri-arterial venous plexuses, or venae comitantes, that run through the blubber from their minimally insulated limbs and thin streamlined protuberances. Each plexus consists of a central artery containing warm blood from the heart surrounded by a bundle of veins containing cool blood from the body surface. As these fluids flow past each other, they create a heat gradient in which heat is transferred and retained inside the body. The warm arterial blood transfers most of its heat to the cool venous blood now coming in from the outside. This conserves heat by recirculating it back to the body core. Since the arteries give up a good deal of their heat in this exchange, there is less heat lost through convection at the periphery surface.
Another example is found in the legs of an Arctic fox treading on snow. The paws are necessarily cold, but blood can circulate to bring nutrients to the paws without losing much heat from the body. Proximity of arteries and veins in the leg results in heat exchange, so that as the blood flows down it becomes cooler, and does not lose much heat to the snow. As the (cold) blood flows back up from the paws through the veins, it picks up heat from the blood flowing in the opposite direction, so that it returns to the torso in a warm state, allowing the fox to maintain a comfortable temperature, without losing it to the snow. This system is so efficient that the Arctic fox does not begin to shiver until the temperature drops to .
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Applied and Interdisciplinary Chemistry
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The AFM-IR technique based on a pulsed infrared laser source was commercialized by Anasys Instruments, a company founded by Reading, Hammiche and Pollock in the United Kingdom in 2004; a sister, United States corporation was founded a year later. Anasys Instruments developed its product with support from the National Institute of Standards and Technology and the National Science Foundation. Since free electron lasers are rare and available only at select institutions, a key to enabling a commercial AFM-IR was to replace them with a more compact type of infrared source. Following the lead given by Hammiche et al in 2001 and Hill et al in 2008, Anasys Instruments introduced an AFM-IR product in early 2010, using a tabletop laser source based on a nanosecond optical parametric oscillator. The OPO source enabled nanoscale infrared spectroscopy over a tuning range of roughly 1000–4000 cm or 2.5-10 μm.
The initial product required samples to be mounted on infrared-transparent prisms, with the infrared light being directed from below in the manner of Dazzi et al. For best operation, this illumination scheme required thin samples, with optimal thickness of less than 1 μm, prepared on the surface of the prism. In 2013, Anasys released an AFM-IR instrument based on the work of Hill et al. that supported top-side illumination. "By eliminating the need to prepare samples on infrared-transparent prisms and relaxing the restriction on sample thickness, the range of samples that could be studied was greatly expanded. The CEO of Anasys Instruments recognised this achievement by calling it " an exciting major advance" in a letter written to the university and included in the final report of EPSRC project EP/C007751/1. The UEA technique went on to become Anasys Instruments' flagship product.
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Theoretical and Fundamental Chemistry
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Salbutamol is sold as a racemic mixture. The (R)-(−)-enantiomer (CIP nomenclature) is shown in the image at right (top), and is responsible for the pharmacologic activity; the (S)-(+)-enantiomer (bottom) blocks metabolic pathways associated with elimination of itself and of the pharmacologically active enantiomer (R). The slower metabolism of the (S)-(+)-enantiomer also causes it to accumulate in the lungs, which can cause airway hyperreactivity and inflammation. Potential formulation of the R form as an enantiopure drug is complicated by the fact that the stereochemistry is not stable, but rather the compound undergoes racemization within a few days to weeks, depending on pH.
The direct separation of Salbutamol enantiomers and the control of enantiomeric purity has been described by thin-layer chromatography.
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Theoretical and Fundamental Chemistry
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Argatroban is a small univalent DTI formed from P1 residue from arginine. It binds to the active site on thrombin. The X-ray crystal structure shows that the piperidine ring binds in the S2 pocket and the guanidine group binds with hydrogen bonds with Asp189 into the S1 pocket. It’s given as an intravenous bolus because the highly basic guanidine with pKa 13 prevents it to be absorbed from the gastrointestinal tract. The plasma half-life is approximately 45 minutes. As argatroban is metabolized via hepatic pathway and is mainly excreted through the biliary system, dose adjustments are necessary in patients with hepatic impairment but not renal damage. Argatroban has been approved in the USA since 2000 for the treatment of thrombosis in patients with HIT and 2002 for anticoagulation in patients with a history of HIT or are at risk of HIT undergoing percutaneous coronary interventions (PCI). It was first introduced in Japan in 1990 for treatment of peripheral vascular disorders.
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Applied and Interdisciplinary Chemistry
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Scintillation properties of organic-inorganic methylamonium (MA) lead halide perovskites under proton irradiation were first reported by Shibuya et al. in 2002 and the first γ-ray pulse height spectrum, although still with poor energy resolution, was reported on () by van Eijk et al. in 2008 . Birowosuto at al. studied the scintillation properties of 3-D and 2-D layered perovskites under X-ray excitation. MAPbBr () emits at 550 nm and MAPbI () at 750 nm which is attributed to exciton emission near the band gap of the compounds. In this first generation of Pb-halide perovskites the emission is strongly quenched at room temperature and less than 1 000 ph/MeV survive. At 10 K however intense emission is observed and write about yields up to 200 000 ph/MeV. The quenching is attributed to the small e-h binding energy in the exciton that decreases for Cl to Br to I . Interestingly one may replace the organic MA group with Cs+ to obtain full inorganic CsPbX halide perovskites. Depending on the Cl, Br, I content the triplet X-ray excited exciton emission can be tuned from 430 nm to 700 nm . One may also dilute Cs with Rb to obtain similar tuning. Above very recent developments demonstrate that the organic-inorganic and all inorganic Pb-halide perovskites have various interesting scintillation properties. However, the recent two-dimensional perovskite single crystals with light yields between 10 000 and 40 000 ph/MeV and decay times below 10 ns at room temperature will be more favorable as they may have much larger Stokes shift up to 200 nm in comparison with CsPbBr quantum dot scintillators and this is essential to prevent self reabsorption for scintillators.
More recently, a new material class first reported by Professor [https://www.chem.fsu.edu/~ma/ Biwu Ma's] research group, called 0D organic metal halide hybrid (OMHH), an extension of the perovskite materials. This class of materials exhibits strong exciton binding of hundreds of meV, resulting in their high photoluminescent quantum efficiency of almost unity. Their large stoke shift and reabsorption-free properties make them desirable. Their potential applications for scintillators have been reported by the same group, and others. In 2020,(C38H34P2)MnBr4 was reported to have a light yield up to 80 000 Photon/MeV despite its low Z compared to traditional all inorganic. Impressive light yields from other 0D OMHH have been reported. There is a great potential to realize new generation scintillators from this material class. However, they are limited by their relatively long response time in microseconds, which is an area of intense research.
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Theoretical and Fundamental Chemistry
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Sir James Whyte Black (1924–2010) held the Chair of Pharmacology from 1973 to 1978.
Jim Black and Heinz Schild knew each other well because Schild had acted as a consultant to the then Smith, Kline & French company during the time when Black was leading the team that developed the histamine receptor antagonists, H antagonists, which reduce secretion of gastric acid and which, at the time, transformed the treatment of gastric ulcers. Schild's methods for quantitative methods for analysis of drug antagonists were crucial for this work.
Black introduced many changes to teaching in the department. One of the most important was the introduction of a BSc course in Medicinal Chemistry. His long experience in the pharmaceutical industry had convinced him that organic and physical chemists working on drug development with pharmacologists and biochemists would benefit greatly from a substantial knowledge of biology, certainly enough to allow them to understand and assess the kinds of measurements that their biological colleagues undertook. Though the students were based in the Department of Chemistry, they took also courses in physiology and pharmacology, particularly its molecular aspects. This BSc course, like that in Pharmacology, also flourished and continues today. Another important change was a sharp reduction in the number of experiments with animal tissues undertaken by medical students during their course in pharmacology. At the same time, the emphasis on the importance of observations on human subjects was increased.
Black's appointment coincided with the onset of the straitened circumstances that all UK universities were to experience and that have continued in one form or another ever since. The changes he made helped the department to adjust to these harder times. To the regret of his Departmental staff, Black found that only the pharmaceutical industry could provide the facilities needed for the work he wished to pursue, and in 1978 he left to join the Wellcome Foundation.
Black was knighted in 1981 and in 1988 he got the Nobel Prize in Physiology or Medicine along with Gertrude B. Elion and George H. Hitchings for their work on drug development.
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Applied and Interdisciplinary Chemistry
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In organic chemistry, the propargyl group is a functional group of 2-propynyl with the structure . It is an alkyl group derived from propyne ().
The term propargylic refers to a saturated position (sp-hybridized) on a molecular framework next to an alkynyl group. The name comes from mix of propene and argentum, which refers to the typical reaction of the terminal alkynes with silver salts.
The term homopropargylic designates in the same manner
* a saturated position on a molecular framework next to a propargylic group and thus two bonds from an alkyne moiety.
* a 3-butynyl fragment, , or substituted homologue.
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Theoretical and Fundamental Chemistry
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In metallurgy, alpha case is the oxygen-enriched surface phase that occurs when titanium and its alloys are exposed to heated air or oxygen. Alpha case is hard and brittle, and tends to create a series of microcracks that will reduce the metal's performance and its fatigue properties. Alpha case can be minimized or avoided by processing titanium at very deep vacuum levels. However once present on the surface, the currently applied method to remove the alpha case is by the subtractive methods of machining and/or chemical milling.
An emerging technique is to subject the metal to an electrochemical treatment in molten salts, such as calcium chloride or lithium chloride at elevated temperatures. This method removes the dissolved oxygen from the alpha case, hence restoring the oxygen-free metal. However, an unwanted consequence of the high temperature treatment is the growth of the grains in the metal. Grain growth may be limited by lowering the molten salt temperature. Alternatively, the metal may be rolling-pressed again to break the large grains into smaller ones.
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Applied and Interdisciplinary Chemistry
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Once Wöhler became a professor at the University of Göttingen, students traveled from around the world to be instructed by him. Wöhler saw particular success in his students after giving them hands-on experience in the lab. This practice was later adopted around the world, becoming the chemistry lab co-requisite that is required at most universities today.
Wöhler also allowed his students to participate and aid him in his research, which was not typical at the time. This practice became nearly universal, normalizing the undergraduate and graduate-level research that is a requirement for numerous degrees today.
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Applied and Interdisciplinary Chemistry
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The Suess effect is a change in the ratio of the atmospheric concentrations of heavy isotopes of carbon (C and C) by the admixture of large amounts of fossil-fuel derived CO, which contains no CO and is depleted in CO relative to CO in the atmosphere and carbon in the upper ocean and the terrestrial biosphere . It was discovered by and is named for the Austrian chemist Hans Suess, who noted the influence of this effect on the accuracy of radiocarbon dating. More recently, the Suess effect has been used in studies of climate change. The term originally referred only to dilution of atmospheric CO relative to CO. The concept was later extended to dilution of CO and to other reservoirs of carbon such as the oceans and soils, again relative to C.
Although the ratio of atmospheric CO to CO decreased over the industrial era (prior to atmospheric testing of nuclear weapons, commencing about 1950), because of the increase, due to fossil fuel emissions, in the amount of atmospheric CO over this period, roughly 1850 to 1950, the amount of atmospheric CO actually increased over this period.
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Theoretical and Fundamental Chemistry
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CGC complexes feature a pi-bonded moiety (e.g. cyclopentadienyl) linked to one of the other ligands on the same metal centre in such a way that the angle at this metal between the centroid of the pi-system and the additional ligand is smaller than in comparable unbridged complexes. More specifically, the term CGC was used for ansa-bridged cyclopentadienyl amido complexes, although the definition goes far beyond this class of compounds. The term CGC is frequently used in connection with other more or less related ligand systems that may or may not be isolobal and/or isoelectronic with the ansa-bridged cyclopentadienyl amido ligand system. Furthermore, the term is frequently used for related complexes with long ansa-bridges that induce no strain. Ansa-bridged cyclopentadienyl amido complexes are known for the Group 3, 4, 5, 6 and some Group 8 metals, with the Group 4 congeners being the most studied ones.
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Theoretical and Fundamental Chemistry
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The following equation can be used to correct a measured pollutant concentration in an emitted gas (containing a measured CO content) to an equivalent pollutant concentration in an emitted gas containing a specified reference amount of CO:
As an example, a measured particulates concentration of 200 mg/m in a dry gas that has a measured 8 volume % CO is:
:200 × ( 12 ÷ 8 ) = 300 mg/m
when corrected to a dry gas having a specified reference CO content of 12 volume %.
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Applied and Interdisciplinary Chemistry
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Vibronic spectroscopy is a branch of molecular spectroscopy concerned with vibronic transitions: the simultaneous changes in electronic and vibrational energy levels of a molecule due to the absorption or emission of a photon of the appropriate energy. In the gas phase, vibronic transitions are accompanied by changes in rotational energy also.
Vibronic spectra of diatomic molecules have been analysed in detail; emission spectra are more complicated than absorption spectra. The intensity of allowed vibronic transitions is governed by the Franck–Condon principle. Vibronic spectroscopy may provide information, such as bond length, on electronic excited states of stable molecules. It has also been applied to the study of unstable molecules such as dicarbon, C, in discharges, flames and astronomical objects.
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Theoretical and Fundamental Chemistry
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The following example deals with a beam of light scattering off a circle with radius and a perfectly reflecting boundary. The beam consists of a uniform density of parallel rays, and the beam-circle interaction is modeled within the framework of geometric optics. Because the problem is genuinely two-dimensional, the cross section has units of length (e.g., meters). Let be the angle between the light ray and the radius joining the reflection point of the ray with the center point of the mirror. Then the increase of the length element perpendicular to the beam is
The reflection angle of this ray with respect to the incoming ray is , and the scattering angle is
The differential relationship between incident and reflected intensity is
The differential cross section is therefore ()
Its maximum at corresponds to backward scattering, and its minimum at corresponds to scattering from the edge of the circle directly forward. This expression confirms the intuitive expectations that the mirror circle acts like a diverging lens. The total cross section is equal to the diameter of the circle:
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Theoretical and Fundamental Chemistry
|
In radiation physics, kerma is an acronym for "kinetic energy released per unit mass" (alternately, "kinetic energy released in matter", "kinetic energy released in material", or "kinetic energy released in materials"), defined as the sum of the initial kinetic energies of all the charged particles liberated by uncharged ionizing radiation (i.e., indirectly ionizing radiation such as photons and neutrons) in a sample of matter, divided by the mass of the sample. It is defined by the quotient
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Theoretical and Fundamental Chemistry
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While the dimensions of the individual channels are small, a micro process engineering device ("microstructured reactor") can contain many thousands of such channels, and the overall size of a microstructured reactor can be on the scale of meters. The objective of micro process engineering is not primarily to miniaturize production plants, but to increase yields and selectivities of chemical reactions, thus reducing the cost of chemical production. This goal can be achieved by either using chemical reactions that cannot be conducted in larger volumina, or by running chemical reactions at parameters (temperatures, pressures, concentrations) that are inaccessible in larger volumina due
to safety constraints. For example, the detonation of the stoichiometric mixture of two volume unit of hydrogen gas and
one volume unit of oxygen gas does not propagate in microchannels
with a sufficiently small diameter. This property is referred to as the
"intrinsic safety" of microstructured reactors. The improvement of yields and selectivities by using novel reactions or running reactions at more extreme parameters is known as "process intensification".
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Applied and Interdisciplinary Chemistry
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In toxicology, the lowest published toxic dose (Toxic Dose Low, TD) is the lowest dosage per unit of bodyweight (typically stated in milligrams per kilogram) of a substance known to have produced signs of toxicity in a particular animal species. When quoting a TD, the particular species and method of administration (e.g. ingested, inhaled, intravenous) are typically stated.
The TD is different from the LD (lethal dose) which is the dose causing death in 50% of people who are exposed or who consume the substance.
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Applied and Interdisciplinary Chemistry
|
Nuclear weapons use fission as either the partial or the main energy source. Depending on the weapon design and where it is exploded, the relative importance of the fission product radioactivity will vary compared to the activation product radioactivity in the total fallout radioactivity.
The immediate fission products from nuclear weapon fission are essentially the same as those from any other fission source, depending slightly on the particular nuclide that is fissioning. However, the very short time scale for the reaction makes a difference in the particular mix of isotopes produced from an atomic bomb.
For example, the Cs/Cs ratio provides an easy method of distinguishing between fallout from a bomb and the fission products from a power reactor. Almost no caesium-134 is formed by nuclear fission (because xenon-134 is stable). The Cs is formed by the neutron activation of the stable Cs which is formed by the decay of isotopes in the isobar (A = 133). So in a momentary criticality, by the time that the neutron flux becomes zero too little time will have passed for any Cs to be present. While in a power reactor plenty of time exists for the decay of the isotopes in the isobar to form Cs, the Cs thus formed can then be activated to form Cs only if the time between the start and the end of the criticality is long.
According to Jiri Hala's textbook, the radioactivity in the fission product mixture in an atom bomb is mostly caused by short-lived isotopes such as iodine-131 and barium-140. After about four months, cerium-141, zirconium-95/niobium-95, and strontium-89 represent the largest share of radioactive material. After two to three years, cerium-144/praseodymium-144, ruthenium-106/rhodium-106, and promethium-147 are responsible for the bulk of the radioactivity. After a few years, the radiation is dominated by strontium-90 and caesium-137, whereas in the period between 10,000 and a million years it is technetium-99 that dominates.
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Theoretical and Fundamental Chemistry
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Strontium-90 is a "bone seeker" that exhibits biochemical behavior similar to calcium, the next lighter group 2 element. After entering the organism, most often by ingestion with contaminated food or water, about 70–80% of the dose gets excreted. Virtually all remaining strontium-90 is deposited in bones and bone marrow, with the remaining 1% remaining in blood and soft tissues. Its presence in bones can cause bone cancer, cancer of nearby tissues, and leukemia. Exposure to Sr can be tested by a bioassay, most commonly by urinalysis.
The biological half-life of strontium-90 in humans has variously been reported as from 14 to 600 days, 1000 days, 18 years, 30 years and, at an upper limit, 49 years. The wide-ranging published biological half life figures are explained by strontium's complex metabolism within the body. However, by averaging all excretion paths, the overall biological half life is estimated to be about 18 years.
The elimination rate of strontium-90 is strongly affected by age and sex, due to differences in bone metabolism.
Together with the caesium isotopes Cs and Cs, and the iodine isotope I, it was among the most important isotopes regarding health impacts after the Chernobyl disaster.
As strontium has an affinity to the calcium-sensing receptor of parathyroid cells that is similar to that of calcium, the increased risk of liquidators of the Chernobyl power plant to suffer from primary hyperparathyroidism could be explained by binding of strontium-90.
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Theoretical and Fundamental Chemistry
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A Chromatography column is a device used in chromatography for the separation of chemical compounds. A chromatography column contains the stationary phase, allowing the mobile phase to pass through it. Chromatography columns of different types are used in both gas and liquid chromatography.
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Theoretical and Fundamental Chemistry
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Many photosynthetic life forms (plants, algae, phototrophic and chemoautotrophic bacteria, and archaea) require a way to utilize carbon into their metabolic pathways. This usually occurs in pathways that fix carbon from carbon dioxide (CO). In the 3-hydroxypropionate bicycle, photosynthetic organisms like Chloroflexus aurantiacus, fix CO and bicarbonate (HCO ) as part of their metabolic processes.
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Applied and Interdisciplinary Chemistry
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It has been known since the early 1930s that the salts of certain lanthanides are fluorescent. The reaction of lanthanide salts with nucleic acids was discussed in a number of publications during the 1930s and the 1940s where lanthanum-containing reagents were employed for the fixation of nucleic acid structures. In 1942 complexes of europium, terbium, and samarium were discovered to exhibit unusual luminescence properties when excited by UV light. However, the first staining of biological cells with lanthanides occurred twenty years later when bacterial smears of E. coli were treated with aqueous solutions of a europium complex, which under mercury lamp illumination appeared as bright red spots. Attention to lanthanide probes increased greatly in the mid-1970s when Finnish researchers proposed Eu(III), Sm(III), Tb(III), and Dy(III) polyaminocarboxylates as luminescent sensors in time-resolved luminescent (TRL) immunoassays. Optimization of analytical methods from the 1970s onward for lanthanide chelates and time-resolved luminescence microscopy (TRLM) resulted in the use of lanthanide probes in many scientific, medical and commercial fields.
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Applied and Interdisciplinary Chemistry
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UV-sensitive syndrome is a cutaneous condition inherited in an autosomal recessive fashion, characterized by photosensitivity and solar lentigines. Recent research identified that mutations of the KIAA1530 (UVSSA) gene as cause for the development of UV-sensitive syndrome. Furthermore, this protein was identified as a new player in the Transcription-coupled repair (TC-NER).
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Theoretical and Fundamental Chemistry
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In chemistry, a glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. These can be activated by enzyme hydrolysis, which causes the sugar part to be broken off, making the chemical available for use. Many such plant glycosides are used as medications. Several species of Heliconius butterfly are capable of incorporating these plant compounds as a form of chemical defense against predators. In animals and humans, poisons are often bound to sugar molecules as part of their elimination from the body.
In formal terms, a glycoside is any molecule in which a sugar group is bonded through its anomeric carbon to another group via a glycosidic bond. Glycosides can be linked by an O- (an O-glycoside), N- (a glycosylamine), S-(a thioglycoside), or C- (a C-glycoside) glycosidic bond. According to the IUPAC, the name "C-glycoside" is a misnomer; the preferred term is "C-glycosyl compound". The given definition is the one used by IUPAC, which recommends the Haworth projection to correctly assign stereochemical configurations.
Many authors require in addition that the sugar be bonded to a non-sugar for the molecule to qualify as a glycoside, thus excluding polysaccharides. The sugar group is then known as the glycone and the non-sugar group as the aglycone or genin part of the glycoside. The glycone can consist of a single sugar group (monosaccharide), two sugar groups (disaccharide), or several sugar groups (oligosaccharide).
The first glycoside ever identified was amygdalin, by the French chemists Pierre Robiquet and Antoine Boutron-Charlard, in 1830.
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Theoretical and Fundamental Chemistry
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Recently, it has been shown that trabectedin blocks DNA binding of the oncogenic transcription factor FUS-CHOP and reverses the transcriptional program in myxoid liposarcoma. By reversing the genetic program created by this transcription factor, trabectedin promotes differentiation and reverses the oncogenic phenotype in these cells.
Other than transcriptional interference, the mechanism of action of trabectedin is complex and not completely understood. The compound is known to bind and alkylate DNA at the N2 position of guanine. It is known from in vitro work that this binding occurs in the minor groove, spans approximately three to five base pairs and is most efficient with CGG sequences. Additional favorable binding sequences are TGG, AGC, or GGC. Once bound, this reversible covalent adduct bends DNA toward the major groove, interferes directly with activated transcription, poisons the transcription-coupled nucleotide excision repair complex, promotes degradation of RNA polymerase II, and generates DNA double-strand breaks.
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Theoretical and Fundamental Chemistry
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For an infinite two-dimensional lattice, defined by its primitive vectors , its reciprocal lattice can be determined by generating its two reciprocal primitive vectors, through the following formulae,
where is an integer and
Here represents a 90 degree rotation matrix, i.e. a quarter turn. The anti-clockwise rotation and the clockwise rotation can both be used to determine the reciprocal lattice: If is the anti-clockwise rotation and is the clockwise rotation, for all vectors . Thus, using the permutation
we obtain
Notably, in a 3D space this 2D reciprocal lattice is an infinitely extended set of Bragg rods—described by Sung et al.
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Theoretical and Fundamental Chemistry
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Protein crystallization is the process of formation of a regular array of individual protein molecules stabilized by crystal contacts. If the crystal is sufficiently ordered, it will diffract. Some proteins naturally form crystalline arrays, like aquaporin in the lens of the eye.
In the process of protein crystallization, proteins are dissolved in an aqueous environment and sample solution until they reach the supersaturated state. Different methods are used to reach that state such as vapor diffusion, microbatch, microdialysis, and free-interface diffusion. Developing protein crystals is a difficult process influenced by many factors, including pH, temperature, ionic strength in the crystallization solution, and even gravity. Once formed, these crystals can be used in structural biology to study the molecular structure of the protein, particularly for various industrial or medical purposes.
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Theoretical and Fundamental Chemistry
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Like many other databases that store protein association knowledge, STRING imports data from experimentally derived protein–protein interactions through literature curation. Furthermore, STRING also store computationally predicted interactions from: (i) text mining of scientific texts, (ii) interactions computed from genomic features, and
(iii) interactions transferred from model organisms based on orthology.
All predicted or imported interactions are benchmarked against a common reference of functional partnership as annotated by KEGG (Kyoto Encyclopedia of Genes and Genomes).
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Applied and Interdisciplinary Chemistry
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Dalton's law expresses the fact that the total pressure of a mixture of ideal gases is equal to the sum of the partial pressures of the individual gases in the mixture. This equality arises from the fact that in an ideal gas, the molecules are so far apart that they do not interact with each other. Most actual real-world gases come very close to this ideal. For example, given an ideal gas mixture of nitrogen (N), hydrogen (H) and ammonia (NH):
where:
* = total pressure of the gas mixture
* = partial pressure of nitrogen (N)
* = partial pressure of hydrogen (H)
* = partial pressure of ammonia (NH)
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Theoretical and Fundamental Chemistry
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(LAP-A), a product of the octadecanoid pathway in some solanaceous plants, has been shown by Fowler et al. to have a regulatory role in the late wound response of tomato. Experiments were conducted using three genotypes of tomato plants: wildtype (WT), (LapA-SI) plants that were silenced for LAP-A, and LapA-OX that constitutively expressed LAP-A. Late-gene expression was inhibited in wounded LapA-SI plants, and the LapA-SI plants were also more susceptible to tobacco hornworm feeding, relative to wildtype (WT) plants. In comparison, the wounded LapA-OX leaves exhibited heightened levels of late gene RNA accumulation, an increased resistance to herbivory, and extended expression of late wound-response genes. These data suggest that LAP-A functions in regulating both the intensity and the persistence of the late wound response. However, unwounded LapA-OX did not accumulate late gene RNA transcripts, suggesting that presence of LAP-A alone is not sufficient to induce late gene expression. LAP-A is the first plant aminopeptidase shown to have a regulatory role in signal transduction pathway.
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Applied and Interdisciplinary Chemistry
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Classical analysis methods involve basic analytical methods widely used in laboratories. Gravimetric analysis measures the weight of the sample. Titrimetry is a family of techniques used to determine the concentration of an analyte.
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Theoretical and Fundamental Chemistry
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Dividing () by and substituting into () gives:
In this context, is the force field acting on the particles in the fluid, and is the mass of the particles. The term on the right hand side is added to describe the effect of collisions between particles; if it is zero then the particles do not collide. The collisionless Boltzmann equation, where individual collisions are replaced with long-range aggregated interactions, e.g. Coulomb interactions, is often called the Vlasov equation.
This equation is more useful than the principal one above, yet still incomplete, since cannot be solved unless the collision term in is known. This term cannot be found as easily or generally as the others – it is a statistical term representing the particle collisions, and requires knowledge of the statistics the particles obey, like the Maxwell–Boltzmann, Fermi–Dirac or Bose–Einstein distributions.
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Applied and Interdisciplinary Chemistry
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Nanofluidics is the study of the behavior, manipulation, and control of fluids that are confined to structures of nanometer (typically 1–100 nm) characteristic dimensions (1 nm = 10 m). Fluids confined in these structures exhibit physical behaviors not observed in larger structures, such as those of micrometer dimensions and above, because the characteristic physical scaling lengths of the fluid, (e.g. Debye length, hydrodynamic radius) very closely coincide with the dimensions of the nanostructure itself.
When structures approach the size regime corresponding to molecular scaling lengths, new physical constraints are placed on the behavior of the fluid. For example, these physical constraints induce regions of the fluid to exhibit new properties not observed in bulk, e.g. vastly increased viscosity near the pore wall; they may effect changes in thermodynamic properties and may also alter the chemical reactivity of species at the fluid-solid interface. A particularly relevant and useful example is displayed by electrolyte solutions confined in nanopores that contain surface charges, i.e. at electrified interfaces, as shown in the nanocapillary array membrane (NCAM) in the accompanying figure.
All electrified interfaces induce an organized charge distribution near the surface known as the electrical double layer. In pores of nanometer dimensions the electrical double layer may completely span the width of the nanopore, resulting in dramatic changes in the composition of the fluid and the related properties of fluid motion in the structure. For example, the drastically enhanced surface-to-volume ratio of the pore results in a preponderance of counter-ions (i.e. ions charged oppositely to the static wall charges) over co-ions (possessing the same sign as the wall charges), in many cases to the near-complete exclusion of co-ions, such that only one ionic species exists in the pore. This can be used for manipulation of species with selective polarity along the pore length to achieve unusual fluidic manipulation schemes not possible in micrometer and larger structures.
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Theoretical and Fundamental Chemistry
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Littrow expansion and its counterpart Littrow compression are optical effects associated with slitless imaging spectrographs. These effects are named after austrian physicist Otto von Littrow.
In a slitless imaging spectrograph, light is focused with a conventional optical system, which includes a transmission or reflection grating as in a conventional spectrograph. This disperses the light, according to wavelength, in one direction; but no slit is interposed into the beam. For pointlike objects (such as distant stars) this results in a spectrum on the focal plane of the instrument for each imaged object. For distributed objects with emission-line spectra (such as the Sun in extreme ultraviolet), it results in an image of the object at each wavelength of interest, overlapping on the focal plane, as in a spectroheliograph.
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Theoretical and Fundamental Chemistry
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Space is a substance that accommodates the living souls, the matter, the principle of motion, the principle of rest and time. It is all-pervading, infinite and made of infinite space-points.
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Applied and Interdisciplinary Chemistry
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For each uniform structure, there also exists a related but different structure, called a line-slip arrangement.
The differences between uniform and line-slip structures are marginal and difficult to spot from images of the sphere packings. However, by comparing their rolled-out contact networks, one can spot that certain lines (which represent contacts) are missing.
All spheres in a uniform structure have the same number of contacts, but the number of contacts for spheres in a line slip may differ from sphere to sphere. For the example line slip in the image on the right side, some spheres count five and others six contacts. Thus a line slip structure is characterised by these gaps or loss of contacts.
Such a structure is termed line slip because the losses of contacts occur along a line in the rolled-out contact network. It was first identified by Picket et al., but not termed line slip.
The direction, in which the loss of contacts occur can be denoted in the phyllotactic notation , since each number represents one of the lattice vectors in the hexagonal lattice. This is usually indicated by a bold number.
By shearing the row of spheres below the loss of contact against a row above the loss of contact, one can regenerate two uniform structures related to this line slip. Thus, each line slip is related to two adjacent uniform structures, one at a higher and one at a lower diameter ratio .
Winkelmann et al. were the first to experimentally realise such a structure using soap bubbles in a system of deformable spheres.
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Theoretical and Fundamental Chemistry
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Generally, the role of the arginine finger in catalysis is to function in transition state stabilization to allow water to perform a nucleophilic attack to cleave off a number of phosphate groups. However, there are exceptions, and arginine fingers can assist in other roles. Additionally, arginine fingers may be attached to different subunits or other proteins in a multiprotein complex. Arginine fingers sometimes interact with guanidinium during their role in catalysis.
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Applied and Interdisciplinary Chemistry
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For U.S. food and dietary supplement labeling purposes, the amount in a serving is expressed as a percent of Daily Value (%DV). For vitamin A labeling purposes 100% of the Daily Value was set at 5,000 IU, but it was revised to 900 μg RAE on 27 May 2016. A table of the old and new adult daily values is provided at Reference Daily Intake.
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Applied and Interdisciplinary Chemistry
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In the United States, eszopiclone is a schedule IV controlled substance under the Controlled Substances Act. Use of eszopiclone may lead to physical and psychological dependence. The risk of non-medical use and dependence increases with the dose and duration of usage and concomitant use of other psychoactive substances. The risk is also greater in patients with a history of alcohol use disorder or other substance use disorder or history of psychiatric disorders. Tolerance may develop after repeated use of benzodiazepines and benzodiazepine-like drugs for a few weeks.
A study funded and carried out by Sepracor, the manufacturer of eszopiclone, found no signs of tolerance or dependence in a group of patients followed for up to six months.
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Theoretical and Fundamental Chemistry
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Most drains have a single large exit at their point of discharge (often covered by a grating) into a canal, river, lake, reservoir, sea or ocean. Other than catchbasins, typically there are no treatment facilities in the piping system. Small storm drains may discharge into individual dry wells. Storm drains may be interconnected using slotted pipe, to make a larger dry well system. Storm drains may discharge into human-made excavations known as recharge basins or retention ponds.
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Applied and Interdisciplinary Chemistry
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When a protein folds, the titratable amino acids in the protein are transferred from a solution-like environment to an environment determined by the 3-dimensional structure of the protein. For example, in an unfolded protein, an aspartic acid typically is in an environment which exposes the titratable side chain to water. When the protein folds, the aspartic acid could find itself buried deep in the protein interior with no exposure to solvent.
Furthermore, in the folded protein, the aspartic acid will be closer to other titratable groups in the protein and will also interact with permanent charges (e.g. ions) and dipoles in the protein. All of these effects alter the pK value of the amino acid side chain, and pK calculation methods generally calculate the effect of the protein environment on the model pK value of an amino acid side chain.
Typically, the effects of the protein environment on the amino acid pK value are divided into pH-independent effects and pH-dependent effects. The pH-independent effects (desolvation, interactions with permanent charges and dipoles) are added to the model pK value to give the intrinsic pK value. The pH-dependent effects cannot be added in the same straightforward way and have to be accounted for using Boltzmann summation, Tanford–Roxby iterations or other methods.
The interplay of the intrinsic pK values of a system with the electrostatic interaction energies between titratable groups can produce quite spectacular effects such as non-Henderson–Hasselbalch titration curves and even back-titration effects.
The image on the right shows a theoretical system consisting of three acidic residues. One group is displaying a back-titration event (blue group).
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Theoretical and Fundamental Chemistry
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In 1942 Harder and Von Witsch were the first to propose that microalgae be grown as a source of lipids for food or fuel. Following World War II, research began in the US, Germany, Japan, England, and Israel on culturing techniques and engineering systems for growing microalgae on larger scales, particularly species in the genus Chlorella. Meanwhile, H. G. Aach showed that Chlorella pyrenoidosa could be induced via nitrogen starvation to accumulate as much as 70% of its dry weight as lipids. Since the need for alternative transportation fuel had subsided after World War II, research at this time focused on culturing algae as a food source or, in some cases, for wastewater treatment.
Interest in the application of algae for biofuels was rekindled during the oil embargo and oil price surges of the 1970s, leading the US Department of Energy to initiate the Aquatic Species Program in 1978. The Aquatic Species Program spent $25 million over 18 years with the goal of developing liquid transportation fuel from algae that would be price competitive with petroleum-derived fuels. The research program focused on the cultivation of microalgae in open outdoor ponds, systems which are low in cost but vulnerable to environmental disturbances like temperature swings and biological invasions. 3,000 algal strains were collected from around the country and screened for desirable properties such as high productivity, lipid content, and thermal tolerance, and the most promising strains were included in the SERI microalgae collection at the Solar Energy Research Institute (SERI) in Golden, Colorado and used for further research. Among the program's most significant findings were that rapid growth and high lipid production were "mutually exclusive", since the former required high nutrients and the latter required low nutrients. The final report suggested that genetic engineering may be necessary to be able to overcome this and other natural limitations of algal strains, and that the ideal species might vary with place and season. Although it was successfully demonstrated that large-scale production of algae for fuel in outdoor ponds was feasible, the program failed to do so at a cost that would be competitive with petroleum, especially as oil prices sank in the 1990s. Even in the best case scenario, it was estimated that unextracted algal oil would cost $59–186 per barrel, while petroleum cost less than $20 per barrel in 1995. Therefore, under budget pressure in 1996, the Aquatic Species Program was abandoned.
Other contributions to algal biofuels research have come indirectly from projects focusing on different applications of algal cultures. For example, in the 1990s Japan's Research Institute of Innovative Technology for the Earth (RITE) implemented a research program with the goal of developing systems to fix using microalgae. Although the goal was not energy production, several studies produced by RITE demonstrated that algae could be grown using flue gas from power plants as a source, an important development for algal biofuel research. Other work focusing on harvesting hydrogen gas, methane, or ethanol from algae, as well as nutritional supplements and pharmaceutical compounds, has also helped inform research on biofuel production from algae.
Following the disbanding of the Aquatic Species Program in 1996, there was a relative lull in algal biofuel research. Still, various projects were funded in the US by the Department of Energy, Department of Defense, National Science Foundation, Department of Agriculture, National Laboratories, state funding, and private funding, as well as in other countries. More recently, rising oil prices in the 2000s spurred a revival of interest in algal biofuels and US federal funding has increased, numerous research projects are being funded in Australia, New Zealand, Europe, the Middle East, and other parts of the world.
In March 2023, researchers said that the commercialization of biofuels would require several billion dollars of funding, plus a long-term dedication to overcoming what appear to be fundamental biological limitations of wild organisms. Most researchers believe that large scale production of biofuels is either "a decade, and more likely two decades, away."
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Applied and Interdisciplinary Chemistry
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The amount of calcium in blood (more specifically, in blood plasma) can be measured as total calcium, which includes both protein-bound and free calcium. In contrast, ionized calcium is a measure of free calcium. An abnormally high level of calcium in plasma is termed hypercalcemia and an abnormally low level is termed hypocalcemia, with "abnormal" generally referring to levels outside the reference range.
The main methods to measure serum calcium are:
* O-Cresolphalein Complexone Method; A disadvantage of this method is that the volatile nature of the 2-amino-2-methyl-1-propanol used in this method makes it necessary to calibrate the method every few hours in a clinical laboratory setup.
* Arsenazo III Method; This method is more robust, but the arsenic in the reagent is a health hazard.
The total amount of Ca present in a tissue may be measured using Atomic absorption spectroscopy, in which the tissue is vaporized and combusted. To measure Ca concentration or spatial distribution within the cell cytoplasm in vivo or in vitro, a range of fluorescent reporters may be used. These include cell permeable, calcium-binding fluorescent dyes such as Fura-2 or genetically engineered variant of green fluorescent protein (GFP) named Cameleon.
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Applied and Interdisciplinary Chemistry
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Compounds that obey the 18-electron rule are typically "exchange inert". Examples include [[Hexamminecobalt(III) chloride|[Co(NH)]Cl]], Mo(CO), and [[Ferrocyanide|[Fe(CN)]]]. In such cases, in general ligand exchange occurs via dissociative substitution mechanisms, wherein the rate of reaction is determined by the rate of dissociation of a ligand. On the other hand, 18-electron compounds can be highly reactive toward electrophiles such as protons, and such reactions are associative in mechanism, being acid-base reactions.
Complexes with fewer than 18 valence electrons tend to show enhanced reactivity. Thus, the 18-electron rule is often a recipe for non-reactivity in either a stoichiometric or a catalytic sense.
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Theoretical and Fundamental Chemistry
|
The term organic herbicide has come to mean herbicides intended for organic farming. Few natural herbicides rival the effectiveness of synthetics. Some plants also produce their own herbicides, such as the genus Juglans (walnuts), or the tree of heaven; such actions of natural herbicides, and other related chemical interactions, is called allelopathy. The applicability of these agents is unclear.
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Applied and Interdisciplinary Chemistry
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Rapid equilibration between enantiomeric conformers and irreversible hydrogenation place the reaction under Curtin–Hammett control. The use of a chiral catalyst results in a higher-energy and a lower-energy transition state for hydrogenation of the two enantiomers. The transformation occurs via the lower-energy transition state to form the product as a single enantiomer.
Consistent with the Curtin–Hammett principle, the ratio of products depends on the absolute energetic barrier of the irreversible step of the reaction, and does not reflect the equilibrium distribution of substrate conformers. The relative free energy profile of one example of the Noyori asymmetric hydrogenation is shown below:
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Theoretical and Fundamental Chemistry
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A bilayer is a double layer of closely packed atoms or molecules.
The properties of bilayers are often studied in condensed matter physics, particularly in the context of semiconductor devices, where two distinct materials are united to form junctions, such as p–n junctions, Schottky junctions, etc. Layered materials, such as graphene, boron nitride, or transition metal dichalcogenides, have unique electronic properties as a bilayer system and are an active area of current research.
In biology, a common example is the lipid bilayer, which describes the structure of multiple organic structures, such as the membrane of a cell.
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Theoretical and Fundamental Chemistry
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Traditionally, the Cohn process incorporating cold ethanol fractionation has been used for albumin purification. However, chromatographic methods for separation started being adopted in the early 1980s. Developments were ongoing in the time period between when Cohn fractionation started being used, in 1946, and when chromatography started being used, in 1983. In 1962, the Kistler & Nistchmann process was created which was a spinoff of the Cohn process. Chromatographic processes began to take shape in 1983. In the 1990s, the Zenalb and the CSL Albumex processes were created which incorporated chromatography with a few variations.
The general approach to using chromatography for plasma fractionation for albumin is: recovery of supernatant I, delipidation, anion exchange chromatography, cation exchange chromatography, and gel filtration chromatography.
The recovered purified material is formulated with combinations of sodium octanoate and sodium N-acetyl tryptophanate and then subjected to viral inactivation procedures, including pasteurisation at 60 °C.
This is a more efficient alternative than the Cohn process for four main reasons:
1) smooth automation and a relatively inexpensive plant was needed,
2) easier to sterilize equipment and maintain a good manufacturing environment,
3) chromatographic processes are less damaging to the albumin protein, and
4) a more successful albumin end result can be achieved.
Compared with the Cohn process, the albumin purity went up from about 95% to 98% using chromatography, and the yield increased from about 65% to 85%. Small percentage increases make a difference in regard to sensitive measurements like purity. There is one big drawback in using chromatography, which has to do with the economics of the process. Although the method was efficient from the processing aspect, acquiring the necessary equipment is a big task. Large machinery is necessary, and for a long time the lack of equipment availability was not conducive to its widespread use. The components are more readily available now but it is still a work in progress and will possibly be ready in the future to help the world.
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Theoretical and Fundamental Chemistry
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Luciferase can function in two different pathways: a bioluminescence pathway and a CoA-ligase pathway. In both pathways, luciferase initially catalyzes an adenylation reaction with MgATP. However, in the CoA-ligase pathway, CoA can displace AMP to form luciferyl CoA.
Fatty acyl-CoA synthetase similarly activates fatty acids with ATP, followed by displacement of AMP with CoA. Because of their similar activities, luciferase is able to replace fatty acyl-CoA synthetase and convert long-chain fatty acids into fatty-acyl CoA for beta oxidation.
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Applied and Interdisciplinary Chemistry
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A concept that began in Prince George's County, Maryland in 1990, LID began as an alternative to traditional stormwater best management practices (BMPs) installed at construction projects. Officials found that the traditional practices such as detention ponds and retention basins were not cost-effective and the results did not meet water quality goals. The Low Impact Development Center, Inc., a non-profit water resources research organization, was formed in 1998 to work with government agencies and institutions to further the science, understanding, and implementation of LID and other sustainable environmental planning and design approaches, such as Green Infrastructure and the Green Highways Partnership.
The LID design approach has received support from the U.S. Environmental Protection Agency (EPA) and is being promoted as a method to help meet goals of the Clean Water Act. Various local, state, and federal agency programs have adopted LID requirements in land development codes and implemented them in public works projects. LID techniques can also play an important role in Smart Growth and Green infrastructure land use planning.
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Applied and Interdisciplinary Chemistry
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One major advantage of the Stöber process is that it can produce silica particles that are nearly monodisperse, and thus provides an ideal model for use in studying colloidal phenomena. It was a pioneering discovery when first published, allowing synthesis of spherical monodisperse silica particles of controlled sizes, and in 2015 remains the most widely used wet chemistry approach to silica nanoparticles.
The process provides a convenient approach to preparing silica nanoparticles for applications including intracellular drug delivery and biosensing. The mesoporous silica nanoparticles prepared by modified Stöber processes have applications in the field of catalysis and liquid chromatography. In addition to monodispersity, these materials have very large surface areas as well as uniform, tunable, and highly ordered pore structures, which makes mesoporous silica uniquely attractive for these applications.
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Theoretical and Fundamental Chemistry
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Kinesin-13 MCAK (Mitotic Centromere-Associated Kinesin) is a KRP that is involved in resolving errors during mitosis involving kinetochore-microtubules. This process is associated with Aurora B Protein Kinase. When Aurora Bs function is disrupted, MCAK ability to locate centromeres, which play a critical role in separation of chromosomes during mitosis, was suppressed. There are other environments in which MCAKs function is impaired, absent impact on its associated kinase. For example, alpha-tubulin detyrosination has been demonstrated to impact MCAK's mitotic repair capabilities, suggesting a potential cause of chromosomal instability.
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Applied and Interdisciplinary Chemistry
|
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