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This involved the development and integration of an automated spotting system to spot multiple single molecules on a slide (like a microarray) for parallel enzymatic processing, automated fluorescence microscopy for image acquisition, image procession vision to handle images, algorithms for optical map construction, cluster computing for processing large amounts of data | 1 | Applied and Interdisciplinary Chemistry |
3-Methylglutaconyl-CoA (MG-CoA), also known as β-methylglutaconyl-CoA, is an intermediate in the metabolism of leucine. It is metabolized into HMG-CoA. | 1 | Applied and Interdisciplinary Chemistry |
In the Arrhenius theory, acids are defined as substances that dissociate in aqueous solutions to give H (hydrogen ions or protons), while bases are defined as substances that dissociate in aqueous solutions to give OH (hydroxide ions).
In 1923 physical chemists Johannes Nicolaus Brønsted in Denmark and Thomas Martin Lowry in England both independently proposed the theory named after them. In the Brønsted–Lowry theory acids and bases are defined by the way they react with each other, generalising them. This is best illustrated by an equilibrium equation.
: acid + base ⇌ conjugate base + conjugate acid.
With an acid, HA, the equation can be written symbolically as:
The equilibrium sign, ⇌, is used because the reaction can occur in both forward and backward directions (is reversible). The acid, HA, is a proton donor which can lose a proton to become its conjugate base, A. The base, B, is a proton acceptor which can become its conjugate acid, HB. Most acid–base reactions are fast, so the substances in the reaction are usually in dynamic equilibrium with each other. | 0 | Theoretical and Fundamental Chemistry |
Another regulatory element located upstream of the gene is an enhancer. Enhancers function as a "turn on" switch in gene expression and will activate the promoter region of a particular gene while silencers act as the "turn off" switch. Though these two regulatory elements work against each other, both sequence types affect the promoter region in very similar ways. Because silencers have not been thoroughly identified and analyzed, the extensive research on enhancers has aided biologists in understanding the mechanics of the silencer. Enhancers can be found in many of the same areas that silencers are found, such as upstream of the promoter by many kilobase pairs, or even downstream within the intron of the gene. DNA looping is also a model function used by enhancers in order to shorten the proximity of the promoter to the enhancer. Enhancers also function with transcription factors in order to initiate expression, much like silencers can with repressors. | 1 | Applied and Interdisciplinary Chemistry |
For pure elements or compounds, e.g. pure copper, pure water, etc. the liquidus and solidus are at the same temperature, and the term melting point may be used.
There are also some mixtures which melt at a particular temperature, known as congruent melting. One example is eutectic mixture. In a eutectic system, there is particular mixing ratio where the solidus and liquidus temperatures coincide at a point known as the invariant point. At the invariant point, the mixture undergoes a eutectic reaction where both solids melt at the same temperature. | 0 | Theoretical and Fundamental Chemistry |
The use of microorganisms to degrade PCBs from contaminated sites, relying on multiple microorganisms co-metabolism, is known as bioremediation of polychlorinated biphenyl. Some micro-organisms degrade PCBs by reducing the C-Cl bonds. Microbial dechlorination tends to be rather slow-acting in comparison to other methods. Enzymes extracted from microbes can show PCB activity. In 2005, Shewanella oneidensis' biodegraded a high percentage of PCBs in soil samples. A low voltage current can stimulate the microbial degradation of PCBs. | 1 | Applied and Interdisciplinary Chemistry |
The entrance to the active site for this enzyme is made up mainly of several arginine, histidine, serine, and aspartate side-chains, with a glutamate side-chain playing a secondary role. These side-chains, to be specific Arg359, Arg528, His469, and Ser386, are conserved within each transketolase enzyme and interact with the phosphate group of the donor and acceptor substrates. Because the substrate channel is so narrow, the donor and acceptor substrates cannot be bound simultaneously. Also, the substrates conform into a slightly extended form upon binding in the active site to accommodate this narrow channel.
Although this enzyme is able to bind numerous types of substrates, such as phosphorylated and nonphosphorylated monosaccharides including the keto and aldosugars fructose, ribose, etc., it has a high specificity for the stereoconfiguration of the hydroxyl groups of the sugars. These hydroxyl groups at C-3 and C-4 of the ketose donor must be in the D-threo configuration in order to correctly correspond to the C-1 and C-2 positions on the aldose acceptor. Also they stabilize the substrate in the active site by interacting with the Asp477, His30, and His263 residues. Disruption of this configuration, both the placement of hydroxyl groups or their stereochemistry, would consequently alter the H-bonding between the residues and substrates thus causing a lower affinity for the substrates.
In the first half of this pathway, His263 is used to effectively abstract the C3 hydroxyl proton, which thus allows a 2-carbon segment to be cleaved from fructose 6-phosphate. The cofactor necessary for this step to occur is thiamin pyrophosphate (TPP). The binding of TPP to the enzyme incurs no major conformational change to the enzyme; instead, the enzyme has two flexible loops at the active site that make TPP accessible and binding possible. Thus, this allows the active site to have a "closed" conformation rather than a large conformational change. Later in the pathway, His263 is used as a proton donor for the substrate acceptor-TPP complex, which can then generate erythrose-4-phosphate.
The histidine and aspartate side-chains are used to effectively stabilize the substrate within the active site and also participate in deprotonation of the substrate. To be specific, the His 263 and His30 side-chains form hydrogen bonds to the aldehyde end of the substrate, which is deepest into the substrate channel, and Asp477 forms hydrogen bonds with the alpha hydroxyl group on the substrate, where it works to effectively bind the substrate and check for proper stereochemistry. It is also thought that Asp477 could have important catalytic effects because of its orientation in the middle of the active site and its interactions with the alpha hydroxyl group of the substrate. Glu418, which is located in the deepest region of the active site, plays a critical role in stabilizing the TPP cofactor. To be specific, it is involved in the cofactor-assisted proton abstraction from the substrate molecule.
The phosphate group of the substrate also plays an important role in stabilizing the substrate upon its entrance into the active site. The tight ionic and polar interactions between this phosphate group and the residues Arg359, Arg528, His469, and Ser386 collectively work to stabilize the substrate by forming H-bonds to the oxygen atoms of the phosphate. The ionic nature is found in the salt bridge formed from Arg359 to the phosphate group. | 0 | Theoretical and Fundamental Chemistry |
Ocean acidification is caused by the equilibration of the atmosphere with the ocean, a process that occurs worldwide. Carbon dioxide in the atmosphere equilibrates and dissolves into the ocean. During this reaction, carbon dioxide reacts with water to form carbonic acid. The carbonic acid then dissociates into bicarbonate ions and hydrogen ions. This reaction causes the pH of the water to lower, effectively acidifying it. Ocean acidification is occurring in every ocean across the world. Since the beginning of the Industrial Revolution, the World's oceans have absorbed approximately 525 billion tons of carbon dioxide. During this time, world ocean pH has collectively decreased from 8.2 to 8.1, with climatic modeling predicting a further decrease of pH by 0.3 units by 2100. However, the Arctic Ocean has been affected more due to the cold water temperatures and increased solubility of gases as water temperature decreases. The cold Arctic water is able to absorb higher amounts of carbon dioxide compared to the warmer Pacific and Atlantic Oceans.
The chemical changes caused by the acidification of the Arctic Ocean are having negative ecological and socioeconomic repercussions. With the changes in the chemistry of their environment, arctic organisms are challenged with new stressors. These stressors can have damaging effects on these organisms, with some being affected more than others. Calcifying organisms specifically appear to be the most impacted by this changing water composition, as they rely on carbonate availability to survive. Dissolved carbonate concentrations decrease with increasing carbon dioxide and lowered pH in the water.
Ecological food webs are also altered by the acidification. Acidification lowers the ability of many fish to grow, which not only impacts food webs but humans that rely on these fisheries as well. Economic effects are resulting from shifting food webs that decrease popular fish populations. These fish populations provide jobs to people who work in the fisheries industry. As is apparent, ocean acidification lacks any positive benefits, and as a result has been placed high on a priority list within the United States and other organizations such as the Scientific Committee on Oceanic Research, UNESCO's Intergovernmental Oceanographic Commission, the Ocean Carbon and Biogeochemistry Program, the Integrated Marine Biogeochemistry and Ecosystem Research Project, and the Consortium for Ocean Leadership. | 0 | Theoretical and Fundamental Chemistry |
Mediator was originally discovered because it was important for RNA polymerase II function, but it has many more functions than just interactions at the transcription start site. | 1 | Applied and Interdisciplinary Chemistry |
In the periodogram approach to calculating the power spectra, the sample autocorrelation function is multiplied by some window function and then Fourier transformed. The window is applied to provide statistical stability as well as to avoid leakage from other parts of the spectrum. However, the window limits the spectral resolution.
Maximum entropy method attempts to improve the spectral resolution by extrapolating the correlation function beyond the maximum lag in such a way that the entropy of the corresponding probability density function is maximized in each step of the extrapolation.
The maximum entropy rate stochastic process that satisfies the given empirical autocorrelation and variance constraints is an autoregressive model with independent and identically distributed zero-mean Gaussian input.
Therefore, the maximum entropy method is equivalent to least-squares fitting the available time series data to an autoregressive model
where the are independent and identically distributed as . The unknowns coefficients are found using least-square method. Once the autoregressive coefficients have been determined, the spectrum of the time series data is estimated by evaluating the power spectral density function of the fitted autoregressive model
where is the sampling period and is the imaginary unit. | 0 | Theoretical and Fundamental Chemistry |
1966-1979: University of Vienna<br />
Starting in 1966 Falk was an assistant at the [http://www.univie.ac.at/orgchem/ Institute of Organic Chemistry] at the University of Vienna. In 1975 he was promoted to associate professor of physical organic chemistry at the University of Vienna. In the summer of 1978 Falk was invited to speak at the Gordon Research Conference in Wolfeboro.<br />
1979–present: Johannes Kepler University of Linz<br />
In 1979 Falk received a call to become full professor of organic chemistry at Johannes Kepler University of Linz, where he founded the new
[http://www.orc.uni-linz.ac.at/ Institute of Organic Chemistry]. From 1989 through 1991 he was elected Dean of the Faculty of Engineering and Natural Sciences ([http://www.tn.jku.at/ TNF]) at Johannes Kepler University of Linz. In 2005 Falk was ranked #3 among the "Top 10" scientists in Upper Austria by the newspaper "OÖ Nachrichten". In 2008 he retired as Professor emeritus at the Institute of Organic chemistry of the JKU. | 0 | Theoretical and Fundamental Chemistry |
Of the three types of naturally occurring radioactivities (α, β, and γ), only alpha decay is a type of decay resulting from the nuclear strong force. The other proton and neutron decays occurred much earlier in the life of the atomic species and before the earth was formed. Thus, alpha decay can be considered either a form of particle decay or, less frequently, as a special case of nuclear fission. The timescale for the nuclear strong force is much faster than that of the nuclear weak force or the electromagnetic force, so the lifetime of nuclei past the drip lines are typically on the order of nanoseconds or less. For alpha decay, the timescale can be much longer than for proton or neutron emission owing to the high Coulomb barrier seen by an alpha-cluster in a nucleus (the alpha particle must tunnel through the barrier). As a consequence, there are no naturally-occurring nuclei on Earth that undergo proton or neutron emission; however, such nuclei can be created, for example, in the laboratory with accelerators or naturally in stars. The Facility for Rare Isotope Beams (FRIB) at Michigan State University came online in mid-2022 and is slated to create novel radioisotopes, which will be extracted in a beam and used for study. It uses a process of running a beam of relatively stable isotopes through a medium, which disrupts the nuclei and creating numerous novel nuclei, which are then extracted. | 0 | Theoretical and Fundamental Chemistry |
Mixtures of different solvents can have interesting features like anomalous conductivity (electrolytic) of particular lyonium ions and lyate ions generated by molecular autoionization of protic and aprotic solvents due to Grotthuss mechanism of ion hopping depending on the mixing ratios. Examples may include hydronium and hydroxide ions in water and water alcohol mixtures, alkoxonium and alkoxide ions in the same mixtures, ammonium and amide ions in liquid and supercritical ammonia, alkylammonium and alkylamide ions in ammines mixtures, etc.... | 0 | Theoretical and Fundamental Chemistry |
The CD V-710 was another high range survey meter, however, unlike the CD V-720, CD V-715, and CD V-717 its scale is only 0-50 R/H (0-0.5, 0–5, and 0-50) making it more of a mid range meter, however it is still far too high to respond to any exempt sources. The CD V-710 was made in 5 different versions from 1955 to at least 1958, the model 1 was produced by El-Tronics, models 2 and 4 were produced by Jorden Electronics, and models 3 and 5 were produced by Victoreen Instruments, models 1-3 were metal, and 4 and 5 were plastic. All versions of the CD V-710 use a combination of D batteries and obsolete 22.5 volt B batteries. By 1959, 170,750 were procured, however the model was ultimately superseded by the CD V-715 and in September 1985 FEMA issued instructions that remaining CD V-710s should be disposed of as obsolete. | 0 | Theoretical and Fundamental Chemistry |
The term molecular recognition refers to the specific interaction between two or more molecules through noncovalent bonding such as hydrogen bonding, metal coordination, hydrophobic forces, van der Waals forces, π-π interactions, halogen bonding, or resonant interaction
effects. In addition to these direct interactions, solvents can play a dominant indirect role in driving molecular recognition in solution. The host and guest involved in molecular recognition exhibit molecular complementarity. Exceptions are molecular containers, including, e.g., nanotubes, in which portals essentially control selectivity. | 0 | Theoretical and Fundamental Chemistry |
A DNA machine is a molecular machine constructed from DNA. Research into DNA machines was pioneered in the late 1980s by Nadrian Seeman and co-workers from New York University. DNA is used because of the numerous biological tools already found in nature that can affect DNA, and the immense knowledge of how DNA works previously researched by biochemists.
DNA machines can be logically designed since DNA assembly of the double helix is based on strict rules of base pairing that allow portions of the strand to be predictably connected based on their sequence. This "selective stickiness" is a key advantage in the construction of DNA machines.
An example of a DNA machine was reported by Bernard Yurke and co-workers at Lucent Technologies in the year 2000, who constructed molecular tweezers out of DNA.
The DNA tweezers contain three strands: A, B and C. Strand A latches onto half of strand B and half of strand C, and so it joins them all together. Strand A acts as a hinge so that the two "arms" — AB and AC — can move. The structure floats with its arms open wide. They can be pulled shut by adding a fourth strand of DNA (D) "programmed" to stick to both of the dangling, unpaired sections of strands B and C. The closing of the tweezers was proven by tagging strand A at either end with light-emitting molecules that do not emit light when they are close together. To re-open the tweezers add a further strand (E) with the right sequence to pair up with strand D. Once paired up, they have no connection to the machine BAC, so float away. The DNA machine can be opened and closed repeatedly by cycling between strands D and E. These tweezers can be used for removing drugs from inside fullerenes as well as from a self assembled DNA tetrahedron. The state of the device can be determined by measuring the separation between donor and acceptor fluorophores using FRET.
DNA walkers are another type of DNA machine. | 0 | Theoretical and Fundamental Chemistry |
Carmalt was made a Royal Society Dorothy Hodgkin Research Fellow at University College London in 1997. She has held many positions at UCL, including lecturer, professor, vice dean and eventually Head of Department. When she was made Head of Department in 2016 she was the first woman to hold the position.
Carnalt specialises in the synthesis of highly volatile, non-toxic molecular precursors for the growth of thin films of transparent conducting oxides (TCOs). TCOs are used in a range of different technologies, including computers, mobile phones and photovoltaic devices. The materials most commonly used to make TCOs (indium and tin) are available in limited quantities, expensive and complicated to process. Carmalt is interested in thin film deposition techniques, including chemical vapour deposition, aerosol-assisted chemical vapour deposition (AACVD) and atomic layer deposition. In particular, AACVD offers the potential for large-area TCO coatings based on nanoparticle dispersions. | 0 | Theoretical and Fundamental Chemistry |
Arsenicals are chemical compounds that contain arsenic. In a military context, the term arsenical refer to toxic arsenic compounds that are used as chemical warfare agents. This include blister agents, blood agents and vomiting agents. Historically, they were used extensively as insecticides, especially lead arsenate. | 1 | Applied and Interdisciplinary Chemistry |
The Conodont Alteration Index (CAI) is used to estimate the maximum temperature reached by a sedimentary rock using thermal alteration of conodont fossils. Conodonts in fossiliferous carbonates are prepared by dissolving the matrix with weak acid, since the conodonts are composed of apatite and thus do not dissolve as readily as carbonate. The fossils are then compared to the index under a microscope. The index was first developed by Anita Epstein and colleagues at the United States Geological Survey.
The CAI ranges from 1 to 6, as follows:
The CAI is commonly used by paleontologists due to its ease of measurement and the abundance of Conodonta throughout marine carbonates of the Paleozoic. However, the organism disappears from the fossil record after the Triassic period, so the CAI is not available to analyze rocks younger than . Additionally, the index can be positively skewed in regions of hydrothermal alteration. | 0 | Theoretical and Fundamental Chemistry |
The equation is derived by solving a linearized version of the Navier–Stokes equation for the perturbation velocity field
where is the unperturbed or basic flow. The perturbation velocity has the wave-like solution (real part understood). Using this knowledge, and the streamfunction representation for the flow, the following dimensional form of the Orr–Sommerfeld equation is obtained:
where is the dynamic viscosity of the fluid, is its density, and is the potential or stream function. In the case of zero viscosity (), the equation reduces to Rayleigh's equation. The equation can be written in non-dimensional form by measuring velocities according to a scale set by some characteristic velocity , and by measuring lengths according to channel depth . Then the equation takes the form
where
is the Reynolds number of the base flow. The relevant boundary conditions are the no-slip boundary conditions at the channel top and bottom and ,
: at and in the case where is the potential function.
Or:
: at and in the case where is the stream function.
The eigenvalue parameter of the problem is and the eigenvector is . If the imaginary part of the wave speed is positive, then the base flow is unstable, and the small perturbation introduced to the system is amplified in time. | 1 | Applied and Interdisciplinary Chemistry |
Bioreactor landfills accelerate the process of decomposition. As decomposition progresses, the mass of biodegradable components in the landfill declines, creating more space for dumping garbage. Bioreactor landfills are expected to increase this rate of decomposition and save up to 30% of space needed for landfills. With increasing amounts of solid waste produced every year and scarcity of landfill spaces, bioreactor landfill can thus provide a significant way of maximising landfill space. This is not just cost effective, but since less land is needed for the landfills, this is also better for the environment.
Furthermore, most landfills are monitored for at least 3 to 4 decades to ensure that no leachate or landfill gases escape into the community surrounding the landfill site. In contrast, bioreactor landfill are expected to decompose to level that does not require monitoring in less than a decade. Hence, the landfill land can be used for other purposes such as reforestation or parks, depending on the location at an earlier date. In addition, re-using leachate to moisturise the landfill filters it. Thus, less time and energy is required to process the leachate, making the process more efficient. | 1 | Applied and Interdisciplinary Chemistry |
Tributyltin azide is an organotin compound with the formula (CH)SnN. It is a colorless solid although older samples can appear as yellow oils. The compound is used as a reagent in organic synthesis. | 0 | Theoretical and Fundamental Chemistry |
Kenneth John Packer FRS (18 May 1938 – 18 September 2021) was a British nuclear magnetic resonance (NMR) scientist who was amongst the pioneers of NMR application in the second half of the 20th century.
Born in Kettering, Packer studied chemistry at Imperial College London, before embarking on a PhD at the University of Cambridge, where his career in the field of NMR and its applications would begin. His NMR research was established at the School of Chemistry at the University of East Anglia (UEA), where he remained for twenty years from 1964 to 1984. He then left academia for almost a decade, working for BP Research, before returning as research chair in the chemistry department of the University of Nottingham, where he remained until retirement in 2001.
He received the Royal Society of Chemistry's Medal for Analytical Spectroscopy in 1986. He was elected Fellow of the Royal Society in 1991. | 0 | Theoretical and Fundamental Chemistry |
Heating in diamond-anvil cells is typically done by two means, external or internal heating. External heating is defined as heating the anvils and would include a number of resistive heaters that are placed around the diamonds or around the cell body. The complementary method does not change the temperature of the anvils and includes fine resistive heaters placed within the sample chamber and laser heating. The main advantage to resistive heating is the precise measurement of temperature with thermocouples, but the temperature range is limited by the properties of the diamond which will oxidize in air at 700 °C The use of an inert atmosphere can extend this range above 1000 °C. A tungsten ring-wire resistive heater inside a BX90 DAC filled with Ar gas was reported to reach 1400 °C. With laser heating the sample can reach temperature above 5000 °C, but the minimum temperature that can be measured when using a laser-heating system is ~1200 °C and the measurement is much less precise. Advances in resistive heating are closing the gap between the two techniques so that systems can be studied from room temperature to beyond 5700 °C with the combination of the two. | 0 | Theoretical and Fundamental Chemistry |
Because methylmercury is formed in aquatic systems, and because it is not readily eliminated from organisms, it is biomagnified in aquatic food chains from bacteria, to plankton, through macroinvertebrates, to herbivorous fish and to piscivorous (fish-eating) fish. At each step in the food chain, the concentration of methylmercury in the organism increases. The concentration of methylmercury in the top-level aquatic predators can reach a level a million times higher than the level in the water. This is because methylmercury has a half-life of about 72 days in aquatic organisms resulting in its bioaccumulation within these food chains. Organisms, including humans, fish-eating birds, and fish-eating mammals such as otters and cetaceans (i.e. whales and dolphins) that consume fish from the top of the aquatic food chain receive the methylmercury that has accumulated through this process, plus the toxins in their habitat. Fish and other aquatic species are the main source of human methylmercury exposure.
The concentration of mercury in any given fish depends on the species of fish, the age and size of the fish and the type of water body in which it is found. In general, fish-eating fish such as shark, swordfish, marlin, larger species of tuna, walleye, largemouth bass, and northern pike, have higher levels of methylmercury than herbivorous fish or smaller fish such as tilapia and herring. Within a given species of fish, older and larger fish have higher levels of methylmercury than smaller fish. Fish that develop in water bodies that are more acidic also tend to have higher levels of methylmercury. | 0 | Theoretical and Fundamental Chemistry |
The Qubit assays (formerly known as Quant-iT) were previously developed and manufactured by Molecular Probes (now part of Life Technologies). Each dye is specialized for one type of molecule (DNA, RNA, or protein). These dyes exhibit extremely low fluorescence until bound to their target molecule. Upon binding to DNA, the dye molecules assume a more rigid shape and increase in fluorescence by several orders of magnitude, most likely due to intercalation between the bases.
The Qubit fluorometer, a device designed to measure fluorescence signals from samples, operates by correlating these signals with known concentrations of probes. This process enables it to transform the fluorescence data into a quantified concentration measurement. The device uses this established relationship to accurately determine the concentration of a sample.
A specific instance of this technology is the Qubit 2.0 fluorometer, which is often used in conjunction with the "dsDNA BR Assay Kit." This kit, along with others in the Qubit quantification system, incorporates dyes. These dyes are sensitive to different biomolecules and their concentrations. In this context, "ds" denotes double-stranded and "ss" signifies single-stranded DNA, indicating the specific types of DNA that the dyes can detect. | 0 | Theoretical and Fundamental Chemistry |
There are a number of factors that can affect the meaning of the NNT depending on the situation. The treatment may be a drug in the form of a pill or injection, a surgical procedure, or many other possibilities. The following examples demonstrate how NNT is determined and what it means. In this example, it is important to understand that every participant has the condition being treated, so there are only "diseased" patients who received the treatment or did not. This is typically a type of study that would occur only if both the control and the tested treatment carried significant risks of serious harm, or if the treatment was unethical for a healthy participant (for example, chemotherapy drugs or a new method of appendectomy - surgical removal of the appendix). Most drug trials test both the control and the treatment on both healthy and "diseased" participants. Or, if the treatment's purpose is to prevent a condition that is fairly common (an anticoagulant to prevent heart attack for example), a prospective study may be used. A study which starts with all healthy participants is termed a prospective study, and is in contrast to a retrospective study, in which some participants already have the condition in question. Prospective studies produce much higher quality evidence, but are much more difficult and time-consuming to perform.
In the table below:
* is the probability of seeing no improvement after receiving the treatment (this is 1 minus the probability of seeing improvement with the treatment). This measure applies only to the treated group.
* is the probability of seeing no improvement after receiving the control (this is 1 minus the probability of seeing improvement with only the control). This measure applies only to the control (unexposed) group. The control group may receive a placebo treatment, or in cases where the goal is to find evidence that a new treatment is more effective than an existing treatment, the control group will receive the existing treatment. The meaning of the NNT is dependent on whether the control group received a placebo treatment or an existing treatment, and, in cases where a placebo treatment is given, the NNT is also affected to the quality of the placebo (i.e. for participants, is the placebo completely indistinguishable from the tested treatment. | 1 | Applied and Interdisciplinary Chemistry |
Many radical processes involve chain reactions or chain propagation with disproportionation and recombination occurring in the terminal step of the reaction. Terminating chain propagation is often most significant during polymerization as the desired chain propagation cannot take place if disproportionation and recombination reactions readily occur. Controlling termination products and regulating disproportionation and recombination reactions in the terminal step are important considerations in radical chemistry and polymerization. In some reactions (such as the one shown below) one or both of the termination pathways can be hindered by steric or solvent effects. | 0 | Theoretical and Fundamental Chemistry |
Valine is produced by a four-enzyme pathway. It begins with the condensation of two equivalents of pyruvate catalyzed by acetohydroxy acid synthase yielding α-acetolactate. The second step involves the NADPH-dependent reduction of α-acetolactate and migration of methyl groups to produce α, β-dihydroxyisovalerate. This is catalyzed by acetohydroxy isomeroreductase. The third step is the dehydration of α, β-dihydroxyisovalerate catalyzed by dihydroxy acid dehydrase. In the fourth and final step, the resulting α-ketoisovalerate undergoes transamination catalyzed either by an alanine-valine transaminase or a glutamate-valine transaminase. Valine biosynthesis is subject to feedback inhibition in the production of acetohydroxy acid synthase. | 1 | Applied and Interdisciplinary Chemistry |
Methylene blue is a dye behaving as a redox indicator that is commonly used in the food industry to test the freshness of milk and dairy products. A few drops of methylene blue solution added to a sample of milk should remain blue (oxidized form in the presence of enough dissolved ), otherwise (discoloration caused by the reduction of methylene blue into its colorless reduced form) the dissolved concentration in the milk sample is low indicating that the milk is not fresh (already abiotically oxidized by whose concentration in solution decreases) or could be contaminated by bacteria also consuming the atmospheric dissolved in the milk. In other words, aerobic conditions should prevail in fresh milk and methylene blue is simply used as an indicator of the dissolved oxygen remaining in the milk. | 0 | Theoretical and Fundamental Chemistry |
Deoxyinosine monophosphate (dIMP) is a nucleoside monophosphate and a derivative of inosinic acid. It can be formed by the deamination of the purine base in deoxyadenosine monophosphate (dAMP). The enzyme deoxyribonucleoside triphosphate pyrophosphohydrolase, encoded by YJR069C in S. cerevisiae and containing (d)ITPase and (d)XTPase activities, hydrolyses dITP, resulting in the release of pyrophosphate and dIMP. | 1 | Applied and Interdisciplinary Chemistry |
A Gran plot (also known as Gran titration or the Gran method) is a common means of standardizing a titrate or titrant by estimating the equivalence volume or end point in a strong acid-strong base titration or in a potentiometric titration. Such plots have been also used to calibrate glass electrodes, to estimate the carbonate content of aqueous solutions, and to estimate the K values (acid dissociation constants) of weak acids and bases from titration data.
Gran plots use linear approximations of the a priori non-linear relationships between the measured quantity, pH or electromotive potential (emf), and the titrant volume. Other types of concentration measures, such as spectrophotometric absorbances or NMR chemical shifts, can in principle be similarly treated. These approximations are only valid near, but not at, the end point, and so the method differs from end point estimations by way of first- and second-derivative plots, which require data at the end point. Gran plots were originally devised for graphical determinations in pre-computer times, wherein an x-y plot on paper would be manually extrapolated to estimate the x-intercept. The graphing and visual estimation of the end point have been replaced by more accurate least-squares analyses since the advent of modern computers and enabling software packages, especially spreadsheet programs with built-in least-squares functionality. | 0 | Theoretical and Fundamental Chemistry |
Many coactivators also function as corepressors under certain circumstances. Cofactors such as TAF1 and BTAF1 can initiate transcription in the presence of an activator (act as a coactivator) and repress basal transcription in the absence of an activator (act as a corepressor). | 1 | Applied and Interdisciplinary Chemistry |
Baking powder is used to cause the dough for breads and cakes to "rise" by creating millions of tiny carbon dioxide bubbles. Baking powder is not to be confused with baking soda, which is sodium bicarbonate (). Baking powder is a mixture of baking soda (sodium bicarbonate) and acidic salts. The bubbles are created because, when the baking powder is combined with water, the sodium bicarbonate and acid salts react to produce gaseous carbon dioxide.
Whether commercially or domestically prepared, the principles behind baking powder formulations remain the same. The acid–base reaction can be generically represented as shown:
The real reactions are more complicated because the acids are complicated. For example, starting with sodium bicarbonate and monocalcium phosphate (), the reaction produces carbon dioxide by the following stoichiometry:
A typical formulation (by weight) could call for 30% sodium bicarbonate, 5–12% monocalcium phosphate, and 21–26% sodium aluminium sulfate. Alternately, a commercial baking powder might use sodium acid pyrophosphate as one of the two acidic components instead of sodium aluminium sulfate. Another typical acid in such formulations is cream of tartar (), a derivative of tartaric acid. | 0 | Theoretical and Fundamental Chemistry |
End groups are an important aspect of polymer synthesis and characterization. In polymer chemistry, they are functional groups that are at the very ends of a macromolecule or oligomer (IUPAC). In polymer synthesis, like condensation polymerization and free-radical types of polymerization, end-groups are commonly used and can be analyzed by nuclear magnetic resonance (NMR) to determine the average length of the polymer. Other methods for characterization of polymers where end-groups are used are mass spectrometry and vibrational spectrometry, like infrared and raman spectroscopy. These groups are important for the analysis of polymers and for grafting to and from a polymer chain to create a new copolymer. One example of an end group is in the polymer poly(ethylene glycol) diacrylate where the end-groups are circled. | 0 | Theoretical and Fundamental Chemistry |
Starting in the 2010s, despite a global ban on the production of CFCs, five of these ozone-damaging emissions were on the rise.
The atmospheric abundance of CFC-13 rose from 3.0 parts per trillion (ppt) in year 2010 to 3.3 ppt in year 2020 based on analysis of air samples gathered from sites around the world.
Contrary to the Montreal Protocol, the atmospheric emissions of CFC-13 and four other chlorofluorocarbons (CFCs), increased between 2010 and 2020.
As of 2023, the drivers behind the increase in CFC-13 and CFC-112a emissions were not certain. | 1 | Applied and Interdisciplinary Chemistry |
Peptidoglycan is immunologically active, which can stimulate immune cells to increase the expression of cytokines and enhance antibody-dependent specific response when combined with vaccine or as adjuvant alone. MDP, which is the basic unit of peptidoglycan, was initially used as the active component of Freunds adjuvant. Peptidoglycan from Staphylococcus aureus was used as a vaccine to protect mice, showing that after vaccine injection for 40 weeks, the mice survived from S. aureus' challenge at an increased lethal dose. | 1 | Applied and Interdisciplinary Chemistry |
In neutron stars, neutron heavy nuclei are found as relativistic electrons penetrate the nuclei and produce inverse beta decay, wherein the electron combines with a proton in the nucleus to make a neutron and an electron-neutrino:
As more and more neutrons are created in nuclei the energy levels for neutrons get filled up to an energy level equal to the rest mass of a neutron. At this point any electron penetrating a nucleus will create a neutron, which will "drip" out of the nucleus. At this point we have:
And from this point onwards the equation
applies, where p is the Fermi momentum of the neutron. As we go deeper into the neutron star the free neutron density increases, and as the Fermi momentum increases with increasing density, the Fermi energy increases, so that energy levels lower than the top level reach neutron drip and more and more neutrons drip out of nuclei so that we get nuclei in a neutron fluid. Eventually all the neutrons drip out of nuclei and we have reached the neutron fluid interior of the neutron star. | 0 | Theoretical and Fundamental Chemistry |
Hemoglobin (Hb) is the primary vehicle for transporting oxygen in the blood. Each hemoglobin molecule has the capacity to carry four oxygen molecules. These molecules of oxygen bind to the iron of the heme prosthetic group.
When hemoglobin has no bound oxygen, nor bound carbon dioxide, it has the unbound conformation (shape). The binding of the first oxygen molecule induces change in the shape of the hemoglobin that increases its ability to bind to the other three oxygen molecules.
In the presence of dissolved carbon dioxide, the pH of the blood changes; this causes another change in the shape of hemoglobin, which increases its ability to bind carbon dioxide and decreases its ability to bind oxygen. With the loss of the first oxygen molecule, and the binding of the first carbon dioxide molecule, yet another change in shape occurs, which further decreases the ability to bind oxygen, and increases the ability to bind carbon dioxide. The oxygen bound to the hemoglobin is released into the blood's plasma and absorbed into the tissues, and the carbon dioxide in the tissues is bound to the hemoglobin.
In the lungs the reverse of this process takes place. With the loss of the first carbon dioxide molecule the shape again changes and makes it easier to release the other three carbon dioxides.
Oxygen is also carried dissolved in the bloods plasma, but to a much lesser degree. Hemoglobin is contained in red blood cells. Hemoglobin releases the bound oxygen when carbonic acid is present, as it is in the tissues. In the capillaries, where carbon dioxide is produced, oxygen bound to the hemoglobin is released into the bloods plasma and absorbed into the tissues.
How much of that capacity is filled by oxygen at any time is called the oxygen saturation. Expressed as a percentage, the oxygen saturation is the ratio of the amount of oxygen bound to the hemoglobin, to the oxygen-carrying capacity of the hemoglobin. The oxygen-carrying capacity of hemoglobin is determined by the type of hemoglobin present in the blood. The amount of oxygen bound to the hemoglobin at any time is related, in large part, to the partial pressure of oxygen to which the hemoglobin is exposed. In the lungs, at the alveolar–capillary interface, the partial pressure of oxygen is typically high, and therefore the oxygen binds readily to hemoglobin that is present. As the blood circulates to other body tissue in which the partial pressure of oxygen is less, the hemoglobin releases the oxygen into the tissue because the hemoglobin cannot maintain its full bound capacity of oxygen in the presence of lower oxygen partial pressures. | 1 | Applied and Interdisciplinary Chemistry |
Carly Joanne Stevens has been awarded B.Sc. and M.Sc. degrees. In 2004 her PhD was awarded by the Open University for her work on the effects of nitrogen on grassland ecology supervised by Nancy Dise, David Gowing and Owen Mountford. It was carried out in collaboration with the NERC Centre for Ecology and Hydrology, Monks Wood. Prior to her appointment at University of Lancaster, Stevens was a research fellow at the Open University. | 0 | Theoretical and Fundamental Chemistry |
There are a number of ways to excite a population of vibrations, i.e., create a hot optical phonon population. For example, if the electron population is excited, using a laser or electric field, they will typically relax by emitting optical phonons. Additionally, a hot molecular gas can impart its vibrations to a crystal when chemisorbed. Regardless of method, the conversion efficiency is limited by the optical phonon temperature achieved as compared to the electron temperature within the device due to Carnot's theorem.
In a nanoscale device, this temperature is approximately equal to the temperature of the device itself. However, in a macroscale device the generated electrons accumulate faster than they are collected. Thus, the electron population is heated up to the optical phonon temperature and further generation is inhibited. The down-conversion is simultaneously inhibited as the acoustic phonon population is heated to the optical phonon temperature. Thus, the large pV cell develops a near-equilibrium state where it is heated. At best, it will act like a thermoelectric generator and exhibit thermoelectric effects. Such a device is called a thermovoltaic, rather than a phonovoltaic. | 0 | Theoretical and Fundamental Chemistry |
In any study, some of the protein domains, those under investigation, will be varied according to the goals of the study whereas other domains, those that are not themselves being investigated, will be kept constant. For example, in a two-hybrid study to select DNA-binding domains, the DNA-binding domain, BD, will be varied while the two interacting proteins, the bait and prey, must be kept constant to maintain a strong binding between the BD and AD. There are a number of domains from which to choose the BD, bait and prey and AD, if these are to remain constant. In protein–protein interaction investigations, the BD may be chosen from any of many strong DNA-binding domains such as Zif268. A frequent choice of bait and prey domains are residues 263–352 of yeast Gal11P with a N342V mutation and residues 58–97 of yeast Gal4, respectively. These domains can be used in both yeast- and bacterial-based selection techniques and are known to bind together strongly.
The AD chosen must be able to activate transcription of the reporter gene, using the cells own transcription machinery. Thus, the variety of ADs available for use in yeast-based techniques may not be suited to use in their bacterial-based analogues. The herpes simplex virus-derived AD, VP16 and yeast Gal4 AD have been used with success in yeast whilst a portion of the α-subunit of E. coli RNA polymerase has been utilised in E. coli'-based methods.
Whilst powerfully activating domains may allow greater sensitivity towards weaker interactions, conversely, a weaker AD may provide greater stringency. | 1 | Applied and Interdisciplinary Chemistry |
Of all commercialized pharmaceutical drugs, twenty percent contain fluorine, including important drugs in many different pharmaceutical classes. Fluorine is often added to drug molecules during drug design, as even a single atom can greatly change the chemical properties of the molecule in desirable ways.
Because of the considerable stability of the carbon–fluorine bond, many drugs are fluorinated to delay their metabolism, which is the chemical process in which the drugs are turned into compounds that allows them to be eliminated. This prolongs their half-lives and allows for longer times between dosing and activation. For example, an aromatic ring may prevent the metabolism of a drug, but this presents a safety problem, because some aromatic compounds are metabolized in the body into poisonous epoxides by the organisms native enzymes. Substituting a fluorine into a para' position, however, protects the aromatic ring and prevents the epoxide from being produced.
Adding fluorine to biologically active organic compounds increases their lipophilicity (ability to dissolve in fats), because the carbon–fluorine bond is even more hydrophobic than the carbon–hydrogen bond. This effect often increases a drug's bioavailability because of increased cell membrane penetration. Although the potential of fluorine being released in a fluoride leaving group depends on its position in the molecule, organofluorides are generally very stable, since the carbon–fluorine bond is strong.
Fluorines also find their uses in common mineralocorticoids, a class of drugs that increase the blood pressure. Adding a fluorine increases both its medical power and anti-inflammatory effects. Fluorine-containing fludrocortisone is one of the most common of these drugs. Dexamethasone and triamcinolone, which are among the most potent of the related synthetic corticosteroid class of drugs, contain fluorine as well.
Several inhaled general anesthetic agents, including the most commonly used inhaled agents, also contain fluorine. The first fluorinated anesthetic agent, halothane, proved to be much safer (neither explosive nor flammable) and longer-lasting than those previously used. Modern fluorinated anesthetics are longer-lasting still and almost insoluble in blood, which accelerates the awakening. Examples include sevoflurane, desflurane, enflurane, and isoflurane, all hydrofluorocarbon derivatives.
Prior to the 1980s, antidepressants altered not only serotonin uptake but also the uptake of altered norepinephrine; the latter caused most of the side effects of antidepressants. The first drug to alter only the serotonin uptake was Prozac; it gave birth to the extensive selective serotonin reuptake inhibitor (SSRI) antidepressant class and is the best-selling antidepressant. Many other SSRI antidepressants are fluorinated organics, including Celexa, Luvox, and Lexapro. Fluoroquinolones are a commonly used family of broad-spectrum antibiotics. | 1 | Applied and Interdisciplinary Chemistry |
Northup was an undergraduate student at West Virginia University, where she studied political science. She moved to the University of Illinois Urbana-Champaign for graduate studies, where she earned a Masters of Library Science in 1972. Northup moved to the University of New Mexico, where she earned a Masters degree in biology in 1988. She remained at the University of New Mexico for her doctoral research, where she studied the geomicrobiology of caves. | 0 | Theoretical and Fundamental Chemistry |
Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-containing compounds such as alkanes (e.g. methane ) and its derivatives are universally considered organic, but many others are sometimes considered inorganic, such as halides of carbon without carbon-hydrogen and carbon-carbon bonds (e.g. carbon tetrachloride ), and certain compounds of carbon with nitrogen and oxygen (e.g. cyanide ion , hydrogen cyanide , chloroformic acid , carbon dioxide , and carbonate ion ).
Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The study of the properties, reactions, and syntheses of organic compounds comprise the discipline known as organic chemistry. For historical reasons, a few classes of carbon-containing compounds (e.g., carbonate salts and cyanide salts), along with a few other exceptions (e.g., carbon dioxide, and even hydrogen cyanide despite the fact it contains a carbon-hydrogen bond), are generally considered inorganic. Other than those just named, little consensus exists among chemists on precisely which carbon-containing compounds are excluded, making any rigorous definition of an organic compound elusive.
Although organic compounds make up only a small percentage of Earth's crust, they are of central importance because all known life is based on organic compounds. Living things incorporate inorganic carbon compounds into organic compounds through a network of processes (the carbon cycle) that begins with the conversion of carbon dioxide and a hydrogen source like water into simple sugars and other organic molecules by autotrophic organisms using light (photosynthesis) or other sources of energy. Most synthetically-produced organic compounds are ultimately derived from petrochemicals consisting mainly of hydrocarbons, which are themselves formed from the high pressure and temperature degradation of organic matter underground over geological timescales. This ultimate derivation notwithstanding, organic compounds are no longer defined as compounds originating in living things, as they were historically.
In chemical nomenclature, an organyl group, frequently represented by the letter R, refers to any monovalent substituent whose open valence is on a carbon atom. | 0 | Theoretical and Fundamental Chemistry |
If one tries to predict the probability of collision with a classical model that treats the electron and atom as hard spheres, one finds that the probability of collision should be independent of the incident electron energy. However, Ramsauer and Townsend, independently observed that for slow-moving electrons in argon, krypton, or xenon, the probability of collision between the electrons and gas atoms obtains a minimum value for electrons with a certain amount of kinetic energy (about 1 electron volts for xenon gas).
No good explanation for the phenomenon existed until the introduction of quantum mechanics, which explains that the effect results from the wave-like properties of the electron. A simple model of the collision that makes use of wave theory can predict the existence of the Ramsauer–Townsend minimum. Niels Bohr presented a simple model for the phenomenon that considers the atom as a finite square potential well.
Predicting from theory the kinetic energy that will produce a Ramsauer–Townsend minimum is quite complicated since the problem involves understanding the wave nature of particles. However, the problem has been extensively investigated both experimentally and theoretically and is well understood. | 0 | Theoretical and Fundamental Chemistry |
Biuret is a chemical compound with the chemical formula . It is a white solid that is soluble in hot water. A variety of organic derivatives are known. The term "biuret" also describes a family of organic compounds with the chemical formula , where are hydrogen, organyl or other groups. Also known as carbamylurea, it results from the condensation of two equivalents of urea. It is a common undesirable impurity in urea-based fertilizers, as biuret is toxic to plants. | 0 | Theoretical and Fundamental Chemistry |
Some synthetic radioisotopes are extracted from spent nuclear reactor fuel rods, which contain various fission products. For example, it is estimated that up to 1994, about 49,000 terabecquerels (78 metric tons) of technetium were produced in nuclear reactors; as such, anthropogenic technetium is far more abundant than technetium from natural radioactivity.
Some synthetic isotopes are produced in significant quantities by fission but are not yet being reclaimed. Other isotopes are manufactured by neutron irradiation of parent isotopes in a nuclear reactor (for example, technetium-97 can be made by neutron irradiation of ruthenium-96) or by bombarding parent isotopes with high energy particles from a particle accelerator.
Many isotopes, including radiopharmaceuticals, are produced in cyclotrons. For example, the synthetic fluorine-18 and oxygen-15 are widely used in positron emission tomography. | 0 | Theoretical and Fundamental Chemistry |
Yttria-alumina melts are another system reported to exhibit polyamorphism. Observation of a liquid–liquid phase transition in the supercooled liquid has been reported. Though this is disputed in the literature. Polyamorphism has also been reported in Yttria-Alumina glasses. Yttria-Alumina melts quenched from about 1900 °C at a rate ~400 °C/s, can form glasses containing a second co-existing phase. This happens for certain Y/Al ratios (about 20–40 mol% YO). The two phases have the same average composition but different density, molecular structure and hardness. However whether the second phase is glassy or crystalline is also debated.
Continuous changes in density were observed upon cooling silicon dioxide or germanium dioxide. Although continuous density changes do not constitute a first order transition, they may be indicative of an underlying abrupt transition. | 0 | Theoretical and Fundamental Chemistry |
Direct comparison experiments are primarily used for measuring hydrogen/deuterium isotope effects in enzymatic reactions. The monoisotopic substrate and a deuterated form of the substrate are separately exposed to the enzyme of interest over a range of concentrations. The Michaelis-Menten kinetic parameters for both substrates are determined and the position-specific isotope effect at the site of deuteration is expressed as the ratio of the monoisotopic rate constant over the rare isotope rate constant. | 0 | Theoretical and Fundamental Chemistry |
It ranges from Ontario west to Alaska, and south to Missouri, north-central Nebraska, the northern half of Wyoming, and central Washington south through Idaho into north-central Utah. A disjunct subset of its range occurs from central Colorado to northwestern New Mexico. An isolated population was formerly found in Chihuahua, Mexico, but has since been extirpated. The United States portion of the Souris River is alternately known as the Mouse River because of the large numbers of field mice that lived along its banks. | 1 | Applied and Interdisciplinary Chemistry |
The kinesis strategy controlled by the locally and instantly evaluated well-being (fitness) can be described in simple words: Animals stay longer in good conditions and leave bad conditions more quickly. If the well-being is measured by the local reproduction coefficient then the minimal reaction-diffusion model of kinesis can be written as follows:
For each population in the biological community,
where:
is the population density of ith species,
represents the abiotic characteristics of the living conditions (can be multidimensional),
is the reproduction coefficient, which depends on all and on s,
is the equilibrium diffusion coefficient (defined for equilibrium ). The coefficient characterises dependence of the diffusion coefficient on the reproduction coefficient.
The models of kinesis were tested with typical situations. It was demonstrated that kinesis is beneficial for assimilation of both patches and fluctuations of food distribution. Kinesis may delay invasion and spreading of species with the Allee effect. | 1 | Applied and Interdisciplinary Chemistry |
Two early examples of scientifically designed bioswales for large scale applications are found in the western US. In 1996, for Willamette River Park in Portland, Oregon, a total of 2330 lineal feet of bioswale was designed and installed to capture and prevent pollutant runoff from entering the Willamette River. Intermittent check dams were installed to further abet silt capture, which reduced by 50% suspended solids entering the river system.
A second example of a large scale designed bioswale is at the Carneros Business Park, Sonoma County, California. Starting in 1997 the project design team worked with the California Department of Fish and Game and County of Sonoma to produce a detailed design to channel surface runoff at the perimeter of a large parking area. Surface runoff consists of building roof runoff, parking lot runoff and overland flow from properties to the north of the project site. A total of two lineal miles of bioswale was designed into the project. The purpose of the bioswale was to minimize runoff contaminants from entering Sonoma Creek. The bioswale channel is grass-lined and nearly linear in form. Downslope gradient is approximately 4% and cross-slope gradient is approximately 6%.
A relatively recent project established was the "Street Edge Alternatives" (SEA) project in Seattle, Washington, completed in 2001. Rather than using traditional piping, SEAs goal was to create a natural landscape that represented what the area was like before development. The street was 11% more pervious than a standard street and was characterized with evergreen trees and bioswales. The bioswales were planted on graded slopes with wetland and upland plants. Other landscaping also focused on native and salmon-friendly plants. SEA provided a strong benefit for stormwater runoff mitigation that helped continue to protect Seattles creek ecology. The project street also created a more inviting and aesthetically pleasing site as opposed to hard landscaping.
The New York City Department of Environmental Protection (NYC DEP) has built more than 11,000 curbside bioswales, which are referred to as rain gardens. Rain gardens are constructed throughout the city to manage storm water and to improve the water quality of city waterways. The care and tending of rain gardens is a partnership between the NYC DEP and a group of citizen volunteers called "harbor protectors". Rain gardens are inspected and cleaned at least once a week. | 1 | Applied and Interdisciplinary Chemistry |
As required for all separation techniques, ionic liquids exhibit selectivity towards one or more of the phases of a mixture. 1-Butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF) is a room-temperature ionic liquid that was identified early on as a viable substitute for volatile organic solvents in liquid-liquid separations. Other [PF]- and [BF]- containing ionic liquids have been studied for their CO absorption properties, as well as 1-ethyl-3-methylimidazolium (EMIM) and unconventional cations like trihexyl(tetradecyl) phosphonium ([P]). Selection of different anion and cation combinations in ionic liquids affects their selectivity and physical properties. Additionally, the organic cations in ionic liquids can be "tuned" by changing chain lengths or by substituting radicals. Finally, ionic liquids can be mixed with other ionic liquids, water, or amines to achieve different properties in terms of absorption capacity and heat of absorption. This tunability has led some to call ionic liquids "designer solvents." 1-butyl-3-propylamineimidazolium tetrafluoroborate was specifically developed for CO capture; it is designed to employ chemisorption to absorb CO and maintain efficiency under repeated absorption/regeneration cycles. Other ionic liquids have been simulated or experimentally tested for potential use as CO absorbents. | 0 | Theoretical and Fundamental Chemistry |
The reactions that occur with permeable reactive barriers and ferrous iron are surface based. The surface reactions take three different forms: direct reduction, electron shunting through ferrous iron, and reduction by production and reaction of hydrogen. Pathway A represents direct electron transfer (ET) for Fe to the adsorbed halocarbon (RX) at the metal/water point of contact, resulting in dechlorination and production of Fe. Pathway B shows that Fe (resulting from corrosion of Fe) may also dechlorinate RX, producing Fe. Pathway C shows that H from the anaerobic corrosion of Fe might react with RX if a catalyst is present. | 1 | Applied and Interdisciplinary Chemistry |
Alkyne activation with π–acidic metals such as Au or Pt is a conventional method in complex organic manifold synthesis, however how this activation exacts reactivity is not fully understood and thus mechanism is largely proposed on the basis of reaction outcome and theoretical calculations. Cationic Au(I) and Pt(II) catalyst are attractive choices as they display strong Lewis acid character and the ability to stabilize cationic intermediates while being bench stable.
A versatile function of Au(I) catalyzed enyne cycloisomerization is the construction of asymmetric medium–sized rings, which is a challenge in the synthesis of ornamented molecular design. Convenient access to asymmetric 7– and 8–membered carbocycles is possible using chiral BINAP Au(I) gold catalyst, giving a wide variety of products.
It is proposed that intramolecular cyclopropanation occurs via a 1,2–shift of the propargyl ester mediated by Au to give a syn–Au vinyl carbenoid species (29). Computational studies show that the syn–intermediate, 29, is formed under kinetic control and it is suggested that it is in equilibrium with the thermodynamically favorable cis–intermediate which may be intercepted by a nucleophile leading to vinyl cyclopropane diene products, however this is beyond the scope of this article.
Vinylcycloalkenes is another functional class of products accessible through alkyne activation of enynes with π–acidic metals. PtCl has been shown to catalyze the formation of a variety of exotic vinylcycloalkenes from readily accessible starting materials (figure 10).
Notably, a ring expansion is observed for enynes with cyclic alkene motifs. This is rationalized by a formal insertion of the methylene group of the olefin between the two carbons of the alkyne; a mechanistic reasoning for this ring expansion has also been proposed. The formation of these vinycloalkenes in concert with its ability to undergo a ring expansion was exploited to construct intermediate 36 en route to streptorubin B. A similar transformation is possible using cationic Au(I) complexes, however here one can select for vinycycloalkene products through a mechanism proceeding via an initial 5–exo–dig or bicyclopropanes can be produced via an initial 6–endo–dig. It is suggested through DFT calculations that the 5–exo–dig cyclization is favored for Au(I) complexes as it has a lower activation barrier relative to the 6–endo–dig and indeed numerous examples of vinylcycloalkenes products produced via an initial 5–exo–dig are given (figure 11).
The reactivity can be reversed by careful selection of reaction conditions, catalyst selection and substrate. The divergent reactivity of these transition metal catalyzed cycloisomerizations further demonstrates their synthetic utility in building unique molecular skeletons. | 0 | Theoretical and Fundamental Chemistry |
Before Jacobi, the Maclaurin spheroid, which was formulated in 1742, was considered to be the only type of ellipsoid which can be in equilibrium. Lagrange in 1811 considered the possibility of a tri-axial ellipsoid being in equilibrium, but concluded that the two equatorial axes of the ellipsoid must be equal, leading back to the solution of Maclaurin spheroid. But Jacobi realized that Lagrange's demonstration is a sufficiency condition, but not necessary. He remarked: | 1 | Applied and Interdisciplinary Chemistry |
Bene Meat Technologies a.s. (BMT) is a Czech biotechnology start-up focused on research and development of technology for the production of cultivated meat on an industrial scale. It cooperates with scientific institutions and companies in the Czech Republic and abroad. The company has its laboratories on the first floor of the Cube building in Vokovice, Prague. | 1 | Applied and Interdisciplinary Chemistry |
Polymer characterization spans many techniques for determining the chemical composition, molecular weight distribution, and physical properties. Select common techniques include the following:
*Size-exclusion chromatography (also called gel permeation chromatography), sometimes coupled with static light scattering, can used to determine the number-average molecular weight, weight-average molecular weight, and dispersity.
*Scattering techniques, such as static light scattering and small-angle neutron scattering, are used to determine the dimensions (radius of gyration) of macromolecules in solution or in the melt. These techniques are also used to characterize the three-dimensional structure of microphase-separated block polymers, polymeric micelles, and other materials.
*Wide-angle X-ray scattering (also called wide-angle X-ray diffraction) is used to determine the crystalline structure of polymers (or lack thereof).
*Spectroscopy techniques, including Fourier-transform infrared spectroscopy, Raman spectroscopy, and nuclear magnetic resonance spectroscopy, can be used to determine the chemical composition.
*Differential scanning calorimetry is used to characterize the thermal properties of polymers, such as the glass-transition temperature, crystallization temperature, and melting temperature. The glass-transition temperature can also be determined by dynamic mechanical analysis.
*Thermogravimetry is a useful technique to evaluate the thermal stability of the polymer.
*Rheology is used to characterize the flow and deformation behavior. It can be used to determine the viscosity, modulus, and other rheological properties. Rheology is also often used to determine the molecular architecture (molecular weight, molecular weight distribution, branching) and to understand how the polymer can be processed. | 0 | Theoretical and Fundamental Chemistry |
Due to the unique temperature-dependent phase transition experienced by ELPs, in which they move from a linear state to a spherical aggregate state above their T, as well as the ability of ELPs to be easily conjugated with other compounds, these biopolymers hold numerous applications. Some of these applications involve ELP use in protein purification, cancer therapy, and tissue scaffolding. | 0 | Theoretical and Fundamental Chemistry |
When the single bond between the two centres is free to rotate, cis/trans descriptors become invalid. Two widely accepted prefixes used to distinguish diastereomers on sp³-hybridised bonds in an open-chain molecule are syn and anti. Masamune proposed the descriptors which work even if the groups are not attached to adjacent carbon atoms. It also works regardless of CIP priorities. Syn describes groups on the same face while anti describes groups on opposite faces. The concept applies only to the Zigzag projection. The descriptors only describe relative stereochemistry rather than absolute stereochemistry.
All isomers are same. | 0 | Theoretical and Fundamental Chemistry |
Direct factor Xa inhibitors are being used clinically and their usage is constantly increasing. They are gradually taking over warfarin usage and low molecular weight heparins (LMWH). Indication for Xa inhibitors is preventing deep vein thrombosis (DVT) which can lead to pulmonary embolism. It is also used to treat atrial fibrillation to lower the risk of stroke caused by a blood clot. Another indication is a prophylactic treatment for blood clotting (thrombosis) due to atherosclerosis. Rivaroxaban was the first FXa inhibitor on the market and then followed by apixaban, edoxaban and betrixaban. | 1 | Applied and Interdisciplinary Chemistry |
The UN and business communities developed an international standard for tailings management in 2020 after the critical failure of the Brumadinho dam disaster. The program was convened by United Nations Environment Programme (UNEP), International Council on Mining and Metals (ICMM) and the Principles for Responsible Investment. | 1 | Applied and Interdisciplinary Chemistry |
Despite most other life forms being killed by the lack of oxygen, jellyfish can thrive and are sometimes present in dead zones in vast numbers. Jellyfish blooms produce large quantities of mucus, leading to major changes in food webs in the ocean since few organisms feed on them. The organic carbon in mucus is metabolized by bacteria which return it to the atmosphere in the form of carbon dioxide in what has been termed a "jelly carbon shunt". The potential worsening of jellyfish blooms as a result of human activities has driven new research into the influence of dead zones on jelly populations. The primary concern is the potential for dead zones to serve as breeding grounds for jelly populations as a result of the hypoxic conditions driving away competition for resources and common predators of jellyfish. The increased population of jellyfish could have high commercial costs with loss of fisheries, destruction and contamination of trawling nets and fishing vessels, and lowered tourism revenue in coastal systems. | 0 | Theoretical and Fundamental Chemistry |
See Vitamin, Mineral (nutrient), Protein (nutrient)
An inadequate amount of a nutrient is a deficiency. Deficiencies can be due to a number of causes including an inadequacy in nutrient intake, called a dietary deficiency, or any of several conditions that interfere with the utilization of a nutrient within an organism. Some of the conditions that can interfere with nutrient utilization include problems with nutrient absorption, substances that cause a greater than normal need for a nutrient, conditions that cause nutrient destruction, and conditions that cause greater nutrient excretion. Nutrient toxicity occurs when excess consumption of a nutrient does harm to an organism.
In the United States and Canada, recommended dietary intake levels of essential nutrients are based on the minimum level that "will maintain a defined level of nutriture in an individual", a definition somewhat different from that used by the World Health Organization and Food and Agriculture Organization of a "basal requirement to indicate the level of intake needed to prevent pathologically relevant and clinically detectable signs of a dietary inadequacy".
In setting human nutrient guidelines, government organizations do not necessarily agree on amounts needed to avoid deficiency or maximum amounts to avoid the risk of toxicity. For example, for vitamin C, recommended intakes range from 40 mg/day in India to 155 mg/day for the European Union. The table below shows U.S. Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for vitamins and minerals, PRIs for the European Union (same concept as RDAs), followed by what three government organizations deem to be the safe upper intake. RDAs are set higher than EARs to cover people with higher than average needs. Adequate Intakes (AIs) are set when there is not sufficient information to establish EARs and RDAs. Countries establish tolerable upper intake levels, also referred to as upper limits (ULs), based on amounts that cause adverse effects. Governments are slow to revise information of this nature. For the U.S. values, with the exception of calcium and vitamin D, all of the data date from 1997 to 2004.
The daily recommended amounts of niacin and magnesium are higher than the tolerable upper limit because, for both nutrients, the ULs identify the amounts which will not increase risk of adverse effects when the nutrients are consumed as a serving of a dietary supplement. Magnesium supplementation above the UL may cause diarrhea. Supplementation with niacin above the UL may cause flushing of the face and a sensation of body warmth. Each country or regional regulatory agency decides on a safety margin below when symptoms may occur, so the ULs may differ based on source.
EAR U.S. Estimated Average Requirements.
RDA U.S. Recommended Dietary Allowances; higher for adults than for children, and may be even higher for women who are pregnant or lactating.
AI U.S. Adequate Intake; AIs established when there is not sufficient information to set EARs and RDAs.
PRI Population Reference Intake is European Union equivalent of RDA; higher for adults than for children, and may be even higher for women who are pregnant or lactating. For Thiamin and Niacin, the PRIs are expressed as amounts per megajoule (239 kilocalories) of food energy consumed.
Upper Limit Tolerable upper intake levels.
ND ULs have not been determined.
NE EARs, PRIs or AIs have not yet been established or will not be (EU does not consider chromium an essential nutrient). | 0 | Theoretical and Fundamental Chemistry |
According to the above rules, a carbon atom in a molecule, considered as a substituent, has the following names depending on the number of hydrogens bound to it, and the type of bonds formed with the remainder of the molecule: | 0 | Theoretical and Fundamental Chemistry |
Johann Chrysostom Magnenus ( – ) published his Democritus reviviscens in 1646. Magnenus was the first to arrive at a scientific estimate of the size of an "atom" (i.e. of what would today be called a molecule). Measuring how much incense had to be burned before it could be smelled everywhere in a large church, he calculated the number of molecules in a grain of incense to be of the order 10, only about one order of magnitude below the actual figure. | 1 | Applied and Interdisciplinary Chemistry |
Consider an infinitely long cylinder of radius exhibiting torsional oscillation with angular velocity where is the frequency. Then the velocity approaches after the initial transient phase to
where is the modified Bessel function of the second kind. This solution can be expressed with real argument as:
where
and are Kelvin functions and is to the dimensionless oscillatory Reynolds number defined as , being the kinematic viscosity. | 1 | Applied and Interdisciplinary Chemistry |
In particle tracking, the trajectories of a set of particles are measured, typically by applying particle tracking algorithms to movies.[http://www.physics.emory.edu/~weeks/idl/] Particle tracking has the advantage that all the dynamical information is maintained in the measurement, unlike FCS where correlation averages the dynamics to a single smooth curve. The advantage is apparent in systems showing complex diffusion, where directly computing the mean squared displacement allows straightforward comparison to normal or power law diffusion. To apply particle tracking, the particles have to be distinguishable and thus at lower concentration than required of FCS. Also, particle tracking is more sensitive to noise, which can sometimes affect the results unpredictably. | 0 | Theoretical and Fundamental Chemistry |
In the case of normal shock, flow is assumed to be in a steady state and thickness of shock is very small. It is further assumed that there is no friction or heat loss at the shock (because heat transfer is negligible because it occurs on a relatively small surface). It is customary in this field to denote x as the upstream and y as the downstream condition.
Since the mass flow rate from the two sides of the shock are constant, the mass balance becomes,
As there is no external force applied, momentum is conserved. Which give rises to the equation
Because heat flow is negligible, the process can be treated as adiabatic. So the energy equation will be
From the equation of state for perfect gas,
P=ρRT
As the temperature from both sides of the shock wave is discontinues, the speed of sound is different in these adjoining medium. So it is convenient to define the star mach number that will be independent of the specific mach number. From star condition, the speed of sound at the critical condition can also be a good reference velocity. Speed of sound at that temperature is,
And additional Mach number which is independent of specific mach number is,
Since energy remains constant across the shock,
dividing mass equation by momentum equation we will get
From above equations,
it will give rises to
Which is called the prandtl condition in normal shock | 1 | Applied and Interdisciplinary Chemistry |
In the final stages of the synthesis (Scheme 5), the hydroxyl group in 46 was deprotected to give alcohol 47. Reaction of the lithium alkoxide of 47 with the Ojima lactam 48 adds the tail in 49. Deprotection of the triethylsilyl ether with hydrofluoric acid and removal of the BOM group under reductive conditions gave (−)-Taxol 51 in 46 steps. | 0 | Theoretical and Fundamental Chemistry |
Restriction digest is most commonly used as part of the process of the molecular cloning of DNA fragment into a vector (such as a cloning vector or an expression vector). The vector typically contains a multiple cloning site where many restriction site may be found, and a foreign piece of DNA may be inserted into the vector by first cutting the restriction sites in the vector as well the DNA fragment, followed by ligation of the DNA fragment into the vector.
Restriction digests are also necessary for performing any of the following analytical techniques:
*RFLP – Restriction fragment length polymorphism
*AFLP – Amplified fragment length polymorphism
*STRP – Short tandem repeat polymorphism | 1 | Applied and Interdisciplinary Chemistry |
A good jug should, regardless of fashion, have a spout with a tear-off edge (i.e. no rounded edge) to make it more difficult to run around the edge. And – even more important - after the edge, the spout should first lead upwards (regardless of the position in which the jug is held). As a result, the liquid would be forced to flow upwards after going around the edge of the spout when pouring, but this is prevented by gravity. The flow can thus resist wetting even when pouring slowly and the liquid does not reach the downwardly inclined part of the spout and the body of the jug.
The image on the right shows three vessels with poor pouring behavior. Even in a horizontal position, that is standing on the table, the bottom edges of the spouts do not point upwards. Behind are four vessels with good flow characteristics resulting from well formed tips. Here, the liquid rises at the lower edge of the spout at an angle of less than 45°. In part, this only becomes apparent when one considers the normal maximum fill level: the glass carafe on the far right, for example, appears at first glance to be a poor pourer because of its slender neck. However, since such vessels are generally filled at most up to the edge of the round part of the flask, an advantageous rise at the neck is then obtained when pouring horizontally.Upward angle for the liquid when pouring. With the two lower jugs on the right, the high position of the spout (above the maximum filling level) means that the vessel has to be tilted quite a bit before pouring, so that the spout can also be pushed up directly after the edge (against gravity). indicates.
To avoid the teapot effect, the pot can be filled less, so that a larger tilting angle is necessary from the start. However, the effect or the ideal filling level again depends on the can geometry.
The teapot effect does not occur with bottles because the slender neck of the bottle always points upwards when pouring; the current would therefore have to "flow uphill" a long way. Bottle-like containers are therefore often used for liquid chemicals in the laboratory. Certain materials are also used there to prevent dripping, for example glass, which can be easily shaped or even ground to create the sharpest possible edges, or Teflon, for example, which reduces the adhesion effect described above. | 1 | Applied and Interdisciplinary Chemistry |
Recent attempts have been made to relabel antifreeze proteins as ice structuring proteins to more accurately represent their function and to dispose of any assumed negative relation between AFPs and automotive antifreeze, ethylene glycol. These two things are completely separate entities, and show loose similarity only in their function. | 1 | Applied and Interdisciplinary Chemistry |
In 2020 scientists showed, with an experiment with different gravity environments on the ISS, that microorganisms could be employed to mine useful elements from basaltic rocks via bioleaching in space. | 1 | Applied and Interdisciplinary Chemistry |
Electrofiltration is a method that combines membrane filtration and electrophoresis in a dead-end process.
Electrofiltration is regarded as an appropriate technique for concentration and fractionation of biopolymers. The film formation on the filter membrane which hinders filtration can be minimized or completely avoided by the application of electric field, improving filtration’s performance and increasing selectivity in case of fractionation. This approach reduces significantly the expenses for downstream processing in bioprocesses. | 0 | Theoretical and Fundamental Chemistry |
While the Flory–Fox equation describes many polymers very well, it is more reliable for large values of M and samples of narrow weight distribution. As a result, other equations have been proposed to provide better accuracy for certain polymers. For example:
This minor modification of the Flory–Fox equation, proposed by Ogawa, replaces the inverse dependence on M with the square of the product of the number-average molecular weight, M , and weight-average molecular weight, M . Additionally, the equation:
was proposed by Fox and Loshaek, and has been applied to polystyrene, polymethylmethacrylate, and polyisobutylene, among others.
However, it is important to note that despite the dependence of T on molecular weight that the Flory-Fox and related equations describe, molecular weight is not necessarily a practical design parameter for controlling T because the range over which it can be changed without altering the physical properties of the polymer due to molecular weight change is small. | 0 | Theoretical and Fundamental Chemistry |
The protein content of peroxisomes varies across species or organism, but the presence of proteins common to many species has been used to suggest an endosymbiotic origin; that is, peroxisomes evolved from bacteria that invaded larger cells as parasites, and very gradually evolved a symbiotic relationship. However, this view has been challenged by recent discoveries. For example, peroxisome-less mutants can restore peroxisomes upon introduction of the wild-type gene.
Two independent evolutionary analyses of the peroxisomal proteome found homologies between the peroxisomal import machinery and the ERAD pathway in the endoplasmic reticulum, along with a number of metabolic enzymes that were likely recruited from the mitochondria. The peroxisome may have had an Actinomycetota origin; however, this is controversial. | 1 | Applied and Interdisciplinary Chemistry |
The third law of thermodynamics states: As the temperature of a system approaches absolute zero, all processes cease and the entropy of the system approaches a minimum value.
This law of thermodynamics is a statistical law of nature regarding entropy and the impossibility of reaching absolute zero of temperature. This law provides an absolute reference point for the determination of entropy. The entropy determined relative to this point is the absolute entropy. Alternate definitions include "the entropy of all systems and of all states of a system is smallest at absolute zero," or equivalently "it is impossible to reach the absolute zero of temperature by any finite number of processes".
Absolute zero, at which all activity would stop if it were possible to achieve, is −273.15 °C (degrees Celsius), or −459.67 °F (degrees Fahrenheit), or 0 K (kelvin), or 0° R (degrees Rankine). | 0 | Theoretical and Fundamental Chemistry |
In 1815 the French physicist Jean-Baptiste Biot showed that certain chemicals could rotate the plane of a beam of polarised light, a property called optical activity.
The nature of this property remained a mystery until 1848, when Louis Pasteur proposed that it had a molecular basis originating from some form of dissymmetry,
with the term chirality being coined by Lord Kelvin a year later.
The origin of chirality itself was finally described in 1874, when Jacobus Henricus van t Hoff and Joseph Le Bel independently proposed the tetrahedral geometry of carbon. Structural models prior to this work had been two-dimensional, and van t Hoff and Le Bel theorized that the arrangement of groups around this tetrahedron could dictate the optical activity of the resulting compound through what became known as the Le Bel–van 't Hoff rule.
In 1894 Hermann Emil Fischer outlined the concept of asymmetric induction; in which he correctly ascribed selective the formation of -glucose by plants to be due to the influence of optically active substances within chlorophyll. Fischer also successfully performed what would now be regarded as the first example of enantioselective synthesis, by enantioselectively elongating sugars via a process which would eventually become the Kiliani–Fischer synthesis.
The first enantioselective chemical synthesis is most often attributed to Willy Marckwald, Universität zu Berlin, for a brucine-catalyzed enantioselective decarboxylation of 2-ethyl-2-methylmalonic acid reported in 1904. A slight excess of the levorotary form of the product of the reaction, 2-methylbutyric acid, was produced; as this product is also a natural product—e.g., as a side chain of lovastatin formed by its diketide synthase (LovF) during its biosynthesis—this result constitutes the first recorded total synthesis with enantioselectivity, as well other firsts (as Koskinen notes, first "example of asymmetric catalysis, enantiotopic selection, and organocatalysis"). This observation is also of historical significance, as at the time enantioselective synthesis could only be understood in terms of vitalism. At the time many prominent chemists such as Jöns Jacob Berzelius argued that natural and artificial compounds were fundamentally different and that chirality was simply a manifestation of the vital force which could only exist in natural compounds. Unlike Fischer, Marckwald had performed an enantioselective reaction upon an achiral, un-natural starting material, albeit with a chiral organocatalyst (as we now understand this chemistry). | 0 | Theoretical and Fundamental Chemistry |
Total soil alkalinity increases with:
* Weathering of silicate, aluminosilicate and carbonate minerals containing , , and ;
* Addition of silicate, aluminosilicate and carbonate minerals to soils; this may happen by deposition of material eroded elsewhere by wind or water, or by mixing of the soil with less weathered material (such as the addition of limestone to acid soils);
* Addition of water containing dissolved bicarbonates (as occurs when irrigating with high-bicarbonate waters).
The accumulation of alkalinity in a soil (as carbonates and bicarbonates of Na, K, Ca and Mg) occurs when there is insufficient water flowing through the soils to leach soluble salts. This may be due to arid conditions, or poor internal soil drainage; in these situations most of the water that enters the soil is transpired (taken up by plants) or evaporates, rather than flowing through the soil.
The soil pH usually increases when the total alkalinity increases, but the balance of the added cations also has a marked effect on the soil pH. For example, increasing the amount of sodium in an alkaline soil tends to induce dissolution of calcium carbonate, which increases the pH. Calcareous soils may vary in pH from 7.0 to 9.5, depending on the degree to which or dominate the soluble cations. | 0 | Theoretical and Fundamental Chemistry |
The term (hydro)static pressure is sometimes used in fluid statics to refer to the pressure of a fluid at a nominated depth in the fluid. In fluid statics the fluid is stationary everywhere and the concepts of dynamic pressure and total pressure are not applicable. Consequently, there is little risk of ambiguity in using the term pressure, but some authors choose to use static pressure in some situations. | 1 | Applied and Interdisciplinary Chemistry |
Native silver is a rare element. Although it exists as such, it is usually found in nature combined with other metals, or in minerals that contain silver compounds, generally in the form of sulfides such as galena (lead sulfide) or cerussite (lead carbonate). So the primary production of silver requires the smelting and then cupellation of argentiferous lead ores.
Lead melts at 327 °C, lead oxide at 888 °C, and silver melts at 960 °C. To separate the silver, the alloy is melted again at the high temperature of 960 °C to 1000 °C in an oxidizing environment. The lead oxidises to lead monoxide, then known as litharge, which captures the oxygen from the other metals present. The liquid lead oxide is removed or absorbed by capillary action into the hearth linings. This chemical reaction may be viewed as
: (s) + 2 (s) + (g) → 2 (absorbed) + Ag(l)
The base of the hearth was dug in the form of a saucepan and covered with an inert and porous material rich in calcium or magnesium such as shells, lime, or bone ash. The lining had to be calcareous because lead reacts with silica (clay compounds) to form viscous lead silicate that prevents the needed absorption of litharge, whereas calcareous materials do not react with lead. Some of the litharge evaporates, and the rest is absorbed by the porous earth lining to form "litharge cakes".
Litharge cakes are usually circular or concavo-convex, about 15 cm in diameter. They are the most common archaeological evidence of cupellation in the Early Bronze Age. By analyzing their chemical composition, archaeologists can discern what kind of ore was treated, its main components, and the chemical conditions used in the process. This permits insights about production process, trade, social needs or economic situations. | 1 | Applied and Interdisciplinary Chemistry |
Electrostatic precipitators, ESPs, have recently gained renewed interest for bioaerosol sampling due to their highly efficient particle removal efficiencies and gentler sampling method as compared with impinging. ESPs charge and remove incoming aerosol particles from an air stream by employing a non-uniform electrostatic field between two electrodes, and a high field strength. This creates a region of high density ions, a corona discharge, which charges incoming aerosol droplets, and the electric field deposits the charges particles onto a collection surface.
Since biological particles are typically analysed using liquid-based assays (PCR, immunoassays, viability assay) it is preferable to sample directly into a liquid volume for downstream analysis. For example, Pardon et al. show sampling of aerosols down to a microfluidic air-liquid interface, and Ladhani et al., show sampling of airborne Influenza down to a small liquid droplet. The use of low-volume liquids is ideal for minimising sample dilution, and has the potential to be couple to lab-on-chip technologies for rapid point-of-care analysis. | 0 | Theoretical and Fundamental Chemistry |
Transacetylation uses vinyl acetate as an acetyl donor and lipase as a catalyst. This methodology allows the preparation of enantio-enriched alcohols and acetates. | 0 | Theoretical and Fundamental Chemistry |
SahysMod is a computer program for the prediction of the salinity of soil moisture, groundwater and drainage water, the depth of the watertable, and the drain discharge in irrigated agricultural lands, using different hydrogeologic and aquifer conditions, varying water management options, including the use of ground water for irrigation, and several crop rotation schedules, whereby the spatial variations are accounted for through a network of polygons. | 0 | Theoretical and Fundamental Chemistry |
In the secondary structure of proteins, hydrogen bonds form between the backbone oxygens and amide hydrogens. When the spacing of the amino acid residues participating in a hydrogen bond occurs regularly between positions i and , an alpha helix is formed. When the spacing is less, between positions i and , then a 3 helix is formed. When two strands are joined by hydrogen bonds involving alternating residues on each participating strand, a beta sheet is formed. Hydrogen bonds also play a part in forming the tertiary structure of protein through interaction of R-groups. (See also protein folding).
Bifurcated H-bond systems are common in alpha-helical transmembrane proteins between the backbone amide of residue i as the H-bond acceptor and two H-bond donors from residue : the backbone amide and a side-chain hydroxyl or thiol . The energy preference of the bifurcated H-bond hydroxyl or thiol system is -3.4 kcal/mol or -2.6 kcal/mol, respectively. This type of bifurcated H-bond provides an intrahelical H-bonding partner for polar side-chains, such as serine, threonine, and cysteine within the hydrophobic membrane environments.
The role of hydrogen bonds in protein folding has also been linked to osmolyte-induced protein stabilization. Protective osmolytes, such as trehalose and sorbitol, shift the protein folding equilibrium toward the folded state, in a concentration dependent manner. While the prevalent explanation for osmolyte action relies on excluded volume effects that are entropic in nature, circular dichroism (CD) experiments have shown osmolyte to act through an enthalpic effect. The molecular mechanism for their role in protein stabilization is still not well established, though several mechanisms have been proposed. Computer molecular dynamics simulations suggest that osmolytes stabilize proteins by modifying the hydrogen bonds in the protein hydration layer.
Several studies have shown that hydrogen bonds play an important role for the stability between subunits in multimeric proteins. For example, a study of sorbitol dehydrogenase displayed an important hydrogen bonding network which stabilizes the tetrameric quaternary structure within the mammalian sorbitol dehydrogenase protein family.
A protein backbone hydrogen bond incompletely shielded from water attack is a dehydron. Dehydrons promote the removal of water through proteins or ligand binding. The exogenous dehydration enhances the electrostatic interaction between the amide and carbonyl groups by de-shielding their partial charges. Furthermore, the dehydration stabilizes the hydrogen bond by destabilizing the nonbonded state consisting of dehydrated isolated charges.
Wool, being a protein fibre, is held together by hydrogen bonds, causing wool to recoil when stretched. However, washing at high temperatures can permanently break the hydrogen bonds and a garment may permanently lose its shape. | 0 | Theoretical and Fundamental Chemistry |
FSM is but one aspect of citywide sanitation that also includes:
* Municipal solid waste management;
* Drainage and greywater management;
* Wastewater collection and treatment including effluent overflows from on-site systems where soils based dispersal systems are insufficient to assimilate the volume;
* Water safety; and
* Food safety.
There are important synergies between many of these services and FSM, and investigating co-management opportunities can yield benefits. MSW can often be co-managed with fecal waste, especially when thermal treatment technologies are used. Food waste from restaurants and markets can be co-composted with fecal waste to produce a high value soils amendment. Fats, Oil and Grease (FOG) from commercial grease traps can be added to biodigesters to increase methane production, or used in conjunction with fecal sludge as a feedstock for biodiesel production. Water supply is also closely linked with FSM as it is often the water utility that will manage programs and their customers that will pay for services through tariffs. | 1 | Applied and Interdisciplinary Chemistry |
The microscopic features of liquids derive from an interplay between attractive intermolecular forces and entropic forces.
The attractive forces tend to pull molecules close together, and along with short-range repulsive interactions, they are the dominant forces behind the regular structure of solids. The entropic forces are not "forces" in the mechanical sense; rather, they describe the tendency of a system to maximize its entropy at fixed energy (see microcanonical ensemble). Roughly speaking, entropic forces drive molecules apart from each other, maximizing the volume they occupy. Entropic forces dominant in gases and explain the tendency of gases to fill their containers. In liquids, by contrast, the intermolecular and entropic forces are comparable, so it is not possible to neglect one in favor of the other. Quantitatively, the binding energy between adjacent molecules is the same order of magnitude as the thermal energy . | 0 | Theoretical and Fundamental Chemistry |
The extracellular type II and type I kinase receptors binding to the TGF-β ligands. Transforming growth factor-β (TGF-β) is a superfamily of cytokines that play a significant upstream role in regulating of morphogenesis, homeostasis, cell proliferation, and differentiation. The significance of TGF-β is apparent with the human diseases that occur when TGF-β processes are disrupted, such as cancer, and skeletal, intestinal and cardiovascular diseases. TGF-β is pleiotropic and multifunctional, meaning they are able to act on a wide variety of cell types. | 1 | Applied and Interdisciplinary Chemistry |
Gecko feet are the most famous reversible adhesion mechanism in nature. The anti-fouling ability of feet allows geckos to run on dusty ceilings and corners without the accumulation of dirt on their feet. In 2000, Autumn et al. revealed the origin of gecko’s strong adhesion by investigating the surface features of the toes under electron microscope. They observed a hierarchical morphology of each foot which is composed of millions of small hair called setae. Moreover, each setae is composed of a smaller hair, and each hair is tailed with a flat spatula and these spatulae are bonded by the van der Waals forces. This surface feature, regardless of the surface type (hydrophobic, hydrophilic, dry, wet, rough etc.), enables geckos to stick the surface. In addition to strong adhesion, the gecko foot has a unique self-cleaning property which does not require water as the lotus leaf. | 0 | Theoretical and Fundamental Chemistry |
Darwins Black Box: The Biochemical Challenge to Evolution (1996; second edition 2006) is a book by Michael J. Behe, a professor of biochemistry at Lehigh University in Pennsylvania and a senior fellow of the Discovery Institutes Center for Science and Culture. In the book Behe presents his notion of irreducible complexity and argues that its presence in many biochemical systems therefore indicates that they must be the result of intelligent design rather than evolutionary processes. In 1993, Behe had written a chapter on blood clotting in Of Pandas and People, presenting essentially the same arguments but without the name "irreducible complexity," which he later presented in very similar terms in a chapter in Darwins Black Box. Behe later agreed that he had written both and agreed to the similarities when he defended intelligent design at the Kitzmiller v. Dover Area School District' trial.
The book has received highly critical reviews by many scientists, arguing that the assertions made by Behe fail with logical scrutiny and amount to pseudoscience. For example, in a review for Nature, Jerry Coyne panned the book for what he saw as usage of quote mining and spurious ad hominem attacks. The New York Times also, in a critique written by Richard Dawkins, condemned the book for having promoted discredited arguments. Despite this, the book has become a commercial success, and, as a bestseller, it received a mostly supportive review from Publishers Weekly, which described it as having a "spirited, witty critique of neo-Darwinian thinking" that may "spark interest." The politically conservative magazine National Review also voted Darwins Black Box' one of their top 100 non-fiction books of the century, using a panel that included Discovery Institute member George Gilder. | 1 | Applied and Interdisciplinary Chemistry |
It can occur because of a change in environmental conditions: for example, a change in solvent polarity will result in solvatochromism.
A series of structurally-related molecules in a substitution series can also show a bathochromic shift. Bathochromic shift is a phenomenon seen in molecular spectra, not atomic spectra; it is thus more common to speak of the movement of the peaks in the spectrum rather than lines.
where is the wavelength of the spectral peak of interest and | 0 | Theoretical and Fundamental Chemistry |
The journal includes an annual issue on a specific theme. Past theme issues are listed on the journal website. | 1 | Applied and Interdisciplinary Chemistry |
Site-specific pollution induced degradation is measured through the combination of the three portions of the sediment quality triad. The sediment chemistry, sediment toxicity, and the field effects to benthic organisms are compared quantitatively. Data is most useful when it has been normalized to reference site values by converting them to reference-to-ratio values (Chapman et al. 1986; Chapman 1989). The reference site is chosen to be the site with the least contamination with respect to the other sites sampled. Once normalized, data between portions of the triad are able to be compared even when large differences in measurements or units exits (Chapman, 1990). From the combination of the results from each portion of the triad a multivariate figure is developed and used to determine the level of degradation. | 1 | Applied and Interdisciplinary Chemistry |
Actinic inspection of masks in computer chip manufacture refers to inspecting the mask with the same wavelength of light that the lithography system will use. | 0 | Theoretical and Fundamental Chemistry |
Two salt metathesis reactions are popular for laboratory scale reactions. In the Kolbe nitrile synthesis, alkyl halides undergo nucleophilic aliphatic substitution with alkali metal cyanides. Aryl nitriles are prepared in the Rosenmund-von Braun synthesis.
In general, metal cyanides combine with alkyl halides to give a mixture of the nitrile and the isonitrile, although appropriate choice of counterion and temperature can minimize the latter. An alkyl sulfate obviates the problem entirely, particularly in nonaqueous conditions (the Pelouze synthesis). | 0 | Theoretical and Fundamental Chemistry |
In 1950, first experimental evidence for the existence of photophosphorylation in vivo was presented by Otto Kandler using intact Chlorella cells and interpreting his findings as light-dependent ATP formation.
In 1954, Daniel I. Arnon et.al. discovered photophosphorylation in vitro in isolated chloroplasts with the help of P.
His first review on the early research of photophosphorylation was published in 1956. | 0 | Theoretical and Fundamental Chemistry |
The journal is abstracted and indexed in:
*Aquatic Sciences & Fisheries Abstracts
*Chemical Abstracts Service
*Current Contents/Physical, Chemical & Earth Sciences
*Ei-Compendex
*Science Citation Index Expanded
*Scopus
According to the Journal Citation Reports, the journal has a 2022 impact factor of 0.7. | 0 | Theoretical and Fundamental Chemistry |
Generally, nucleophilic epoxidations are carried out under inert atmosphere in anhydrous conditions. For zinc-mediated epoxidations, diethylzinc and ligand are first mixed and oxidized, then the enone is introduced. Lanthanide-mediated epoxidations typically require an additive to stabilize the catalyst; this is most commonly triphenylphosphine oxide or triphenylarsine oxide.
Phase-transfer catalyzed epoxidations may be carried out using one of three possible sets of reaction conditions: (1) sodium hypochlorite at room temperature, (2) freshly prepared 8 M potassium hypochlorite, or (3) trichloroisocyanuric acid in aqueous or non-aqueous conditions.
Among polypeptide-based methods, employing a phase transfer catalyst and triphasic media permits lower catalyst loadings. Biphasic conditions using an organic base in conjunction with urea/HO may also be used. | 0 | Theoretical and Fundamental Chemistry |
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