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Following the total synthesis of bottromycin, Kobayashi and colleagues synthesized a series of bottromycin derivatives and evaluated their anti-MRSA and anti-VRE activity. Only derivatives of the methyl ester moiety were explored, as they found that the methyl ester was both important for antibacterial activity and unstable in blood plasma. A series of seventeen derivatives were synthesized, with derivatives falling into three general categories: amide derivatives, urea derivatives, and ketone derivatives. All analogs except the carboxylic acid and hydrazide analogs were derivatized from isolated bottromycin A2 using an activated azide ester. The derivatives were tested against six Gram-positive bacterial strains: Staphylococcus aureus FDA209P, S. aureus Smith, MRSA HH-1, MRSA 92-1191, Enterococcus faecalis NCTC12201, and E. faecalis NCTC12203 (both VRE).
Bottromycin A2 had low micromolar activity against all the strains tested, ranging from an MIC of 0.5 μg/mL in E. faecalis NCTC12203 to 2 μg/mL in MRSA HH-1. The amide and urea derivative families were found to have weaker antibacterial activity than bottromycin A2 against S. aureus, MRSA, and VRE. The MIC values for the amide and urea derivatives were generally four times greater than those for bottromycin A2. They were, however, significantly more stable in mouse plasma than bottromycin A2. Bottromycin A2 completely degraded in mouse plasma after 10 minutes and exhibited 0% residual activity after exposure to rat serum. Only one derivative had lower than 50% residual activity. In contrast, many derivatives retained a significant percentage of residual anti-MRSA activity following exposure to serum. Thioester intermediates to the ketone derivatives were found to be unstable, exhibiting 0% residual activity, although they had improved antibacterial activity, exhibiting sub-micromolar MIC values. The propyl ketone was found to be the most promising derivative of all the analogs obtained, both exhibiting antibacterial activity against the bacterial strains tested and stability in plasma, retaining 100% residual activity. The MIC values obtained for the propyl derivative were the same as those found for bottromycin A2 except in the case of NCTC12201, which had an MIC of 2 μg/mL for the derivative and an MIC of 1 μg/mL for bottromycin A2. A summary of MIC values for tested bacterial strains is shown below.
Even the least active bottromycin derivatives exhibited greater anti-VRE activity than vancomycin, which was used as a control antibiotic in this study. The propyl derivative and bottromycin A2 had similar antimicrobial activity to linezolid, a synthetic antibiotic active against Gram-positive bacteria including MRSA and VRE, across all the bacterial strains studied. Overall, the results of this study suggested that further modifications of bottromycin may lead to a more stable, effective antibiotic.
A natural derivative of bottromycin, bottromycin D, has also been identified. It is produced in a marine Streptomyces species, strain WMMB272. Although the methyl ester is still present in bottromycin D, one of the macrocyclic valines is mutated to an alanine. The minimum inhibitory concentration (MIC) for bottromycin D was determined and found to be only slightly less active than bottromycin A2 (2 μg/mL for bottromycin D vs. 1 μg/mL for bottromycin A2). The authors postulated that greater conformational flexibility of bottromycin D may be responsible for its lower activity.
No further antibacterial studies of synthetic or biosynthetic bottromycin derivatives have been reported in the literature as of 2013. The search for efficacious analogs will be enabled by bottromycin’s status as a ribosomal peptide. Analogs may be explored biosynthetically by changing the sequence of the precursor peptide; a change in amino acid sequence will lead directly to a modified bottromycin structure. | 0 | Organic Chemistry |
One of the first DREADDs was based on the human M muscarinic receptor (hM). Only two point mutations of hM were required to achieve a mutant receptor with nanomolar potency for CNO, insensitivity to acetylcholine and low constitutive activity and this DREADD receptor was named hM3Dq. M and M muscarinic receptors have been mutated to create DREADDs hM1Dq and hM5Dq respectively.
The most commonly used inhibitory DREADD is hM4Di, derived from the M muscarinic receptor that couples with the G protein. Another G coupled human muscarinic receptor, M, was also mutated to obtain the DREADD receptor hM2D. Another inhibitory G-DREADD is the kappa-opioid-receptor (KOR) DREADD (KORD) which is selectively activated by salvinorin B (SalB).
G-coupled DREADDs have also been developed. These receptors are also known as GD and are chimeric receptors containing intracellular regions of the turkey erythrocyte β-adrenergic receptor substituted into the rat M DREADD. | 1 | Biochemistry |
Alloenzymes (or also called allozymes) are variant forms of an enzyme which differ structurally but not functionally from other allozymes coded for by different alleles at the same locus. These are opposed to isozymes, which are enzymes that perform the same function, but which are coded by genes located at different loci.
Alloenzymes are common biological enzymes that exhibit high levels of functional evolutionary conservation throughout specific phyla and kingdoms. They are used by phylogeneticists as molecular markers to gauge evolutionary histories and relationships between different species. This can be done because allozymes do not have the same structure. They can be separated by capillary electrophoresis. However, some species are monomorphic for many of their allozymes which would make it difficult for phylogeneticists to assess the evolutionary histories of these species. In these instances, phylogeneticists would have to use another method to determine the evolutionary history of a species.
These enzymes generally perform very basic functions found commonly throughout all lifeforms, such as DNA polymerase, the enzyme that repairs and copies DNA. Significant changes in this enzyme reflect significant events in evolutionary history of organisms. As expected DNA polymerase shows relatively small differences in its amino acid sequence between phyla and even kingdoms.
The key to choosing which alloenzyme to use in a comparison between multiple species is to choose one that is as variable as possible while still being present in all the organisms. By comparing the amino acid sequence of the enzyme in the species, more amino acid similarities should be seen in species that are more closely related, and fewer between those that are more distantly related. The less well conserved the enzyme is, the more amino acid differences will be present in even closely related species. | 1 | Biochemistry |
Artifact replication plays an important role in comparing artifact use. Often objects are made not just to prove a manufacturing process or to sit in a display case, but to show that a given object will show signs of wear that are similar to those present in the archaeological record. Roberts and Ottaway conducted such experimental reconstructions by casting bronze axes using them in a preconceived manner and then comparing the results against known archaeological remains. Results gathered from such experimentation have found that objects have comparable wear patterns and there are European socketed axes that were deposited used as well as unused. Tool mark identification can also go the opposite ways using experimental reconstruction to show the difference between various material media and the wear patterns they leave. Greenfield gives one such experiment where steel, bronze, and stone tool marks on bone are all researched and examples are given for how they might be seen in the archaeological record.
Energy consumption and efficiency is another topic of interest in archaeometallurgy. Tree felling and land clearing experiments involving comparison of stone, bronze, and steel axes are popular with a number of archaeologists In these types of experiments, factors such as time spent and oxygen intake of the researchers are taken into account to try to find similarities in past life ways use of energy. | 8 | Metallurgy |
For a normal crystalline ice far below its melting point, there will be some relaxation of the atoms near the surface. Simulations of ice near to its melting point show that there is significant melting of the surface layers rather than a symmetric relaxation of atom positions. Nuclear magnetic resonance provided evidence for a liquid layer on the surface of ice. In 1998, using atomic force microscopy, Astrid Döppenschmidt and Hans-Jürgen Butt measured the thickness of the liquid-like layer on ice to be roughly 32 nm at −1 °C, and 11 nm at −10 °C.
The surface melting can account for the following:
*Low coefficient of friction of ice, as experienced by skaters.
*Ease of compaction of ice
*High adhesion of ice surfaces | 7 | Physical Chemistry |
David Eusthatios Manolopoulos (born 14 December 1961) is a Professor of Theoretical Chemistry at University of Oxford. His research focuses on the computational modeling of the dynamics of elementary chemical reactions in the gas phase and quantum mechanical effects in chemical dynamics. His research highlights include work on path integral approach to molecular dynamics and chemical topics as diverse as fullerenes, ring polymers, reactive scattering, and more recently, the molecular and quantum mechanism of avian magnetoreception.
He was awarded the Marlow Award and the Corday–Morgan Prize. He has been involved with editing the Journal of Chemical Physics. | 7 | Physical Chemistry |
;Myoglobin: Found in the muscle tissue of many vertebrates, including humans, it gives muscle tissue a distinct red or dark gray color. It is very similar to hemoglobin in structure and sequence, but is not a tetramer; instead, it is a monomer that lacks cooperative binding. It is used to store oxygen rather than transport it.
;Hemocyanin: The second most common oxygen-transporting protein found in nature, it is found in the blood of many arthropods and molluscs. Uses copper prosthetic groups instead of iron heme groups and is blue in color when oxygenated.
;Hemerythrin: Some marine invertebrates and a few species of annelid use this iron-containing non-heme protein to carry oxygen in their blood. Appears pink/violet when oxygenated, clear when not.
;Chlorocruorin: Found in many annelids, it is very similar to erythrocruorin, but the heme group is significantly different in structure. Appears green when deoxygenated and red when oxygenated.
;Vanabins: Also known as vanadium chromagens, they are found in the blood of sea squirts. They were once hypothesized to use the metal vanadium as an oxygen binding prosthetic group. However, although they do contain vanadium by preference, they apparently bind little oxygen, and thus have some other function, which has not been elucidated (sea squirts also contain some hemoglobin). They may act as toxins.
;Erythrocruorin: Found in many annelids, including earthworms, it is a giant free-floating blood protein containing many dozens—possibly hundreds—of iron- and heme-bearing protein subunits bound together into a single protein complex with a molecular mass greater than 3.5 million daltons.
;Leghemoglobin: In leguminous plants, such as alfalfa or soybeans, the nitrogen fixing bacteria in the roots are protected from oxygen by this iron heme containing oxygen-binding protein. The specific enzyme protected is nitrogenase, which is unable to reduce nitrogen gas in the presence of free oxygen.
;Coboglobin: A synthetic cobalt-based porphyrin. Coboprotein would appear colorless when oxygenated, but yellow when in veins. | 7 | Physical Chemistry |
Sidney Gilchrist Thomas, a Londoner with a Welsh father, was an industrial chemist who decided to tackle the problem of phosphorus in iron, which resulted in the production of low grade steel. Believing that he had discovered a solution, he contacted his cousin, Percy Gilchrist, who was a chemist at the Blaenavon Ironworks. The manager at the time, Edward Martin, offered Sidney equipment for large-scale testing and helped him draw up a patent that was taken out in May 1878. Sidney Gilchrist Thomass invention consisted of using dolomite or sometimes limestone linings for the Bessemer converter rather than clay, and it became known as the basic Bessemer rather than the acid' Bessemer process. An additional advantage was that the processes formed more slag in the converter, and this could be recovered and used very profitably as a phosphate fertilizer. | 8 | Metallurgy |
PKM2 is a cytosolic enzyme that is associated with other glycolytic enzymes, i.e., hexokinase, glyceraldehyde 3-P dehydrogenase, phosphoglycerate kinase, phosphoglyceromutase, enolase, and lactate dehydrogenase within a so-called glycolytic enzyme complex.
However, PKM2 contains an inducible nuclear localization signal in its C-terminal domain. The role of PKM2 within the nucleus is complex, since pro-proliferative but also pro-apoptotic stimuli have been described. On the one hand, nuclear PKM2 was found to participate in the phosphorylation of histone 1 by direct phosphate transfer from PEP to histone 1. On the other hand, nuclear translocation of PKM2 induced by a somatostatin analogue, HO, or UV light has been linked with caspase-independent programmed cell death. | 1 | Biochemistry |
A test is done by taking a small scraping from a pill and placing it in the reagent testing liquid or dropping the reagent onto the scraping. The liquid will change colour when reacting with different chemicals to indicate the presence of certain substances.
Testing with a reagent kit does not indicate the pill is safe. While the testing process does show some particular substances are present, it may not show a harmful substance that is also present and unaccounted for by the testing process. Some substances that cause strong colour changes can also mask the presence of other substances that cause weaker colour changes. Thin layer chromatography is used with reagent testing to separate substances before testing and prevent this "masking" effect.
Ehrlich reagent can only detect drugs with an indole moiety, but this is useful because drugs from the NBOMe class do not have an indole and are often sold as LSD which does. The Ehrlich reagent has an additional benefit over other reagents in that it does not react with the paper on which LSD is often distributed.
Reagent tests are often limited to target specific chemicals, and when these substances are mis-sold it is usually by substitution of a different substance in the same chemical family, rendering the test unuseful for consumers. However, reagent tests for chemicals families also exist.
Lacing agents are often used to cut the weight of substances. Some of the most available and non-suspicious cutting agents are reducing sugars: The common dietary monosaccharides galactose, glucose and fructose are all reducing sugars. Sugar is the generic name for sucrose, a disaccharide composed of glucose and fructose. | 3 | Analytical Chemistry |
Production of CPs for industrial use started in the 1930s, with global production in 2000 being about 2 million tonnes. Currently, over 200 CP formulations are in use for a wide range of industrial applications, such as flame retardants and plasticisers, as additives in metal working fluids, in sealants, paints, adhesives, textiles, leather fat and coatings. | 2 | Environmental Chemistry |
Pertactin adheres to only ciliated epithelial cells of B. bronchiseptica in vivo. However, in vitro, PRN does not adhere to either. PRN does however help provide resistance towards a hyperinflammatory response of innate immunity for B. bronchiseptica. With respect to the adaptive immunity, studies show that PRN plays a role in combating neutrophil-mediated clearance of B. bronchiseptica. | 1 | Biochemistry |
The collision/reaction cell is used to remove interfering ions through ion/neutral reactions. Collision/reaction cells are known under several names. The dynamic reaction cell is located before the quadrupole in the ICP-MS device. The chamber has a quadrupole and can be filled with reaction (or collision) gases (ammonia, methane, oxygen or hydrogen), with one gas type at a time or a mixture of two of them, which reacts with the introduced sample, eliminating some of the interference.
The integrated Collisional Reaction Cell (iCRC) used by Analytik Jena ICP-MS is a mini-collision cell installed in front of the parabolic ion mirror optics that removes interfering ions by injecting a collisional gas (He), or a reactive gas (H), or a mixture of the two, directly into the plasma as it flows through the skimmer cone and/or the sampler cone. The iCRC removed interfering ions using a collisional kinetic energy discrimination (KED) phenomenon and chemical reactions with interfering ions similarly to traditionally used larger collision cells. | 3 | Analytical Chemistry |
Diel vertically migrating krill, salps, smaller zooplankton and fish can actively transport carbon to depth by consuming POC in the surface layer at night, and metabolising it at their daytime, mesopelagic residence depths. Depending on species life history, active transport may occur on a seasonal basis as well.
Without vertical migration the biological pump wouldn't be nearly as efficient. Organisms migrate up to feed at night so when they migrate back to depth during the day they defecate large sinking fecal pellets. Whilst some larger fecal pellets can sink quite fast, the speed that organisms move back to depth is still faster. At night organisms are in the top 100 metres of the water column, but during the day they move down to between 800 and 1000 metres. If organisms were to defecate at the surface it would take the fecal pellets days to reach the depth that they reach in a matter of hours. Therefore, by releasing fecal pellets at depth they have almost 1000 metres less to travel to get to the deep ocean. This is something known as active transport. The organisms are playing a more active role in moving organic matter down to depths. Because a large majority of the deep sea, especially marine microbes, depends on nutrients falling down, the quicker they can reach the ocean floor the better.
Zooplankton and salps play a large role in the active transport of fecal pellets. 15–50% of zooplankton biomass is estimated to migrate, accounting for the transport of 5–45% of particulate organic nitrogen to depth. Salps are large gelatinous plankton that can vertically migrate 800 metres and eat large amounts of food at the surface. They have a very long gut retention time, so fecal pellets usually are released at maximum depth. Salps are also known for having some of the largest fecal pellets. Because of this they have a very fast sinking rate, small detritus particles are known to aggregate on them. This makes them sink that much faster. So while currently there is still much research being done on why organisms vertically migrate, it is clear that vertical migration plays a large role in the active transport of dissolved organic matter to depth. | 9 | Geochemistry |
The difference between reversible and irreversible events has particular explanatory value in complex systems (such as living organisms, or ecosystems). According to the biologists Humberto Maturana and Francisco Varela, living organisms are characterized by autopoiesis, which enables their continued existence. More primitive forms of self-organizing systems have been described by the physicist and chemist Ilya Prigogine. In the context of complex systems, events which lead to the end of certain self-organising processes, like death, extinction of a species or the collapse of a meteorological system can be considered as irreversible. Even if a clone with the same organizational principle (e.g. identical DNA-structure) could be developed, this would not mean that the former distinct system comes back into being. Events to which the self-organizing capacities of organisms, species or other complex systems can adapt, like minor injuries or changes in the physical environment are reversible. However, adaptation depends on import of negentropy into the organism, thereby increasing irreversible processes in its environment. Ecological principles, like those of sustainability and the precautionary principle can be defined with reference to the concept of reversibility. | 7 | Physical Chemistry |
Modafinil was considered for the treatment of ADHD because of its lower abuse potential than conventional psychostimulants like methylphenidate and amphetamines. In 2008, an application to market modafinil for pediatric ADHD was submitted to the Food and Drug Administration in the US.
However, evidence of modafinil for treatment of adult ADHD is mixed, and a 2016 systematic review of alternative drug therapies for adult ADHD did not recommend its use in this context. In a later large phase 3 clinical trial of modafinil for adult ADHD, modafinil was not effective in improving symptoms, and there was a high rate of side effects (86%) and discontinuation (47%). The poor tolerability of modafinil in this study was possibly due to the use of high doses (). Another reason for the denial of the approval was due to concerns about rare but serious dermatological toxicity in Stevens–Johnson syndrome). | 4 | Stereochemistry |
Studies published in 1992 and 1997 indicate that the level of aerobic fitness of an individual does not have any correlation with the level of resting metabolism. Both studies find that aerobic fitness levels do not improve the predictive power of fat free mass for resting metabolic rate.
However, recent research from the Journal of Applied Physiology, published in 2012, compared resistance training and aerobic training on body mass and fat mass in overweight adults (STRRIDE AT/RT). When you consider time commitments against health benefits, aerobic training is the optimal mode of exercise for reducing fat mass and body mass as a primary consideration, resistance training is good as a secondary factor when aging and lean mass are a concern. Resistance training causes injuries at a much higher rate than aerobic training. Compared to resistance training, it was found that aerobic training resulted in a significantly more pronounced reduction of body weight by enhancing the cardiovascular system which is what is the principal factor in metabolic utilization of fat substrates. Resistance training if time is available is also helpful in post-exercise metabolism, but it is an adjunctive factor because the body needs to heal sufficiently between resistance training episodes, whereas with aerobic training, the body can accept this every day. RMR and BMR are measurements of daily consumption of calories. The majority of studies that are published on this topic look at aerobic exercise because of its efficacy for health and weight management.
Anaerobic exercise, such as weight lifting, builds additional muscle mass. Muscle contributes to the fat-free mass of an individual and therefore effective results from anaerobic exercise will increase BMR. However, the actual effect on BMR is controversial and difficult to enumerate. Various studies suggest that the resting metabolic rate of trained muscle is around 55 kJ/kg per day. Even a substantial increase in muscle mass, say 5 kg, would make only a minor impact on BMR. | 1 | Biochemistry |
Anti-double stranded DNA (anti-dsDNA) antibodies are highly associated with SLE. They are a very specific marker for the disease, with some studies quoting nearly 100%. Data on sensitivity ranges from 25 to 85%. Anti-dsDNA antibody levels, known as titres, correlate with disease activity in SLE; high levels indicate more active lupus. The presence of anti-dsDNA antibodies is also linked with lupus nephritis and there is evidence they are the cause. Some anti-dsDNA antibodies are cross reactive with other antigens found on the glomerular basement membrane (GBM) of the kidney, such as heparan sulphate, collagen IV, fibronectin and laminin. Binding to these antigens within the kidney could cause inflammation and complement fixation, resulting in kidney damage. Presence of high DNA-binding and low C3 levels have been shown to have extremely high predictive value (94%) for the diagnosis of SLE. It is also possible that the anti-dsDNA antibodies are internalised by cells when they bind membrane antigens and then are displayed on the cell surface. This could promote inflammatory responses by T-cells within the kidney. It is important to note that not all anti-dsDNA antibodies are associated with lupus nephritis and that other factors can cause this symptom in their absence. The antigen of anti-dsDNA antibodies is double stranded DNA. | 1 | Biochemistry |
Construction of a 15 t/h demonstration copper ISASMELT plant began in 1986. The design was based on MIM's 250 kg/h test work and operating experience with the lead ISASMELT pilot plant. It cost A$11 million and was commissioned in April 1987. The initial capital cost was recovered in the first 14 months of operation.
As with the lead ISASMELT pilot plant, the copper ISASMELT demonstration plant was integrated into copper smelter operations and justified by the 20% (30,000 t/y) increase in copper production that it provided. It quickly treated the entire backlog of converter slag concentrate, which could not be treated at high rates in the reverberatory furnaces without generating magnetite ("FeO") accretions that would necessitate shutting down the reverberatory furnaces for their removal.
The demonstration copper ISASMELT plant was used to further develop the copper process. Refractory life was initially shorter than expected and considerable effort was devoted to understanding the reasons and attempting to extend the life of the refractories. At the end of the life of the demonstration plant, the longest refractory life achieved was 90 weeks.
Lance life was also low initially. Inexperienced operators could destroy a lance in as little as 10 minutes. However, as a result of modifications to the lance design, the development of techniques to determine the position of the lance in the bath, and a rise in the operating experience, the typical lance life was extended to a week.
The demonstration plant was commissioned with high-pressure (700 kPag) air injected down the lance. Later, after extensive testing of low-pressure lance designs and trials using oxygen enrichment of the lance air, a 70 t/d oxygen plant and a 5 Nm3/s blower with a discharge pressure of 146 kPag were purchased. The new lance design was capable of operating at pressures below 100 kPag. Using enrichment of the oxygen in the lance air to 35%, the demonstration plant throughput was lifted to 48 t/h of concentrate, and the gross energy used during smelting was reduced from 25.6 GJ/t of contained copper to 4.1 GJ/t. | 8 | Metallurgy |
*CUT&RUN sequencing, antibody-targeted controlled cleavage by micrococcal nuclease for transcriptomic profiling.
*Hydrolysis of nucleic acids in crude cell-free extracts.
*Sequencing of RNA.
*Preparation of rabbit reticulocyte lysates.
*Studies of chromatin structure.
*Removal of nucleic acids from laboratory protein preparations allowing for protein folding and structure-function studies.
*Research on the mechanisms of protein folding. | 1 | Biochemistry |
Levetiracetam has not been found to be useful for treatment of neuropathic pain, nor for treatment of essential tremors. Levetiracetam has not been found to be useful for treating all developmental disorders within the autism spectrum; studies have only proven to be an effective treatment for partial, myoclonic, or tonic-clonic seizures associated with autism spectrum disorder. | 4 | Stereochemistry |
In 1878 Josiah Willard Gibbs proposed that a droplet or crystal will arrange itself such that its surface Gibbs free energy is minimized by assuming a shape of low surface energy. He defined the quantity
Here represents the surface (Gibbs free) energy per unit area of the th crystal face and is the area of said face. represents the difference in energy between a real crystal composed of molecules with a surface and a similar configuration of molecules located inside an infinitely large crystal. This quantity is therefore the energy associated with the surface. The equilibrium shape of the crystal will then be that which minimizes the value of .
In 1901 Russian scientist George Wulff stated (without proof) that the length of a vector drawn normal to a crystal face will be proportional to its surface energy : . The vector is the "height" of the th face, drawn from the center of the crystal to the face; for a spherical crystal this is simply the radius. This is known as the Gibbs-Wulff theorem.
In 1943 Laue gave a simple proof, which was extended in 1953 by Herring with a proof of the theorem and a method for determining the equilibrium shape of a crystal, consisting of two main exercises. To begin, a polar plot of surface energy as a function of orientation is made. This is known as the gamma plot and is usually denoted as , where denotes the surface normal, e.g., a particular crystal face. The second part is the Wulff construction itself in which the gamma plot is used to determine graphically which crystal faces will be present. It can be determined graphically by drawing lines from the origin to every point on the gamma plot. A plane perpendicular to the normal is drawn at each point where it intersects the gamma plot. The inner envelope of these planes forms the equilibrium shape of the crystal.
The Wulff construction is for the equilibrium shape, but there is a corresponding form called the "kinetic Wulff construction" where the surface energy is replaced by a growth velocity. There are also variants that can be used for particles on surfaces and with twin boundaries. | 7 | Physical Chemistry |
Examples of studies involving putative genes include the discovery of 30 putative receptor genes found in rat vomeronasal organ (VNO) and the identification of 79 putative TATA boxes found in many plant genomes. | 1 | Biochemistry |
Medications that contain more than 10% pseudoephedrine are prohibited under the Stimulants Control Law in Japan. | 4 | Stereochemistry |
The detected hemolithin protein was reported to have been found inside two CV3 meteorites Allende and Acfer 086. Acfer-086, where the complete molecule was detected rather than fragments (Allende), was discovered in Agemour, Algeria in 1990. | 9 | Geochemistry |
In summary, in order to find a standard curve, one must use varying concentrations of BSA (Bovine Serum Albumin) in order to create a standard curve with concentration plotted on the x-axis and absorbance plotted on the y-axis. Only a narrow concentration of BSA is used (2-10 ug/mL) in order to create an accurate standard curve. Using a broad range of protein concentration will make it harder to determine the concentration of the unknown protein. This standard curve is then used to determine the concentration of the unknown protein. The following elaborates on how one goes from the standard curve to the concentration of the unknown.
First, add a line of best fit, or Linear regression and display the equation on the chart. Ideally, the R value will be as close to 1 as possible. R represents the sum of the square values of the fit subtracted from each data point. Therefore, if R is much less than one, consider redoing the experiment to get one with more reliable data.
The equation displayed on the chart gives a means for calculating the absorbance and therefore concentration of the unknown samples. In Graph 1, x is concentration and y is absorbance, so one must rearrange the equation to solve for x and enter the absorbance of the measured unknown. It is likely that the unknown will have absorbance numbers outside the range of the standard. These should not be included calculations, as the equation given cannot apply to numbers outside of its limitations.
In a large scale, one must compute the extinction coefficient using the Beer-Lambert Law A=εLC in which A is the measured absorbance, ε is the slope of the standard curve, L is the length of the cuvette, and C is the concentration being determined. In a micro scale, a cuvette may not be used and therefore one only has to rearrange to solve for x.
In order to attain a concentration that makes sense with the data, the dilutions, concentrations, and units of the unknown must be normalized (Table 1). To do this, one must divide concentration by volume of protein in order to normalize concentration and multiply by amount diluted to correct for any dilution made in the protein before performing the assay. | 3 | Analytical Chemistry |
is the total angular momentum,
is the azimuthal quantum number,
is the spin quantum number, and
is the secondary total angular momentum quantum number.
Which transitions are allowed is based on the hydrogen-like atom. The symbol is used to indicate a forbidden transition.
In hyperfine structure, the total angular momentum of the atom is where is the nuclear spin angular momentum and is the total angular momentum of the electron(s). Since has a similar mathematical form as it obeys a selection rule table similar to the table above. | 7 | Physical Chemistry |
Where a given letter is used in both capital and lower case form (, and , ) the capital letter refers to the macroscopic observable and the lower case letter to the corresponding variable for an individual particle or layer of the material. Greek symbols are used for properties of a single particle.
* – absorption fraction of a single layer
* – remission fraction of a single layer
* – transmission fraction of a single layer
* A, R, T – The absorption, remission, and transmission fractions for a sample composed of n layers
* α – absorption fraction of a particle
* β – back-scattering from a particle
* σ – isotropic scattering from a particle
*– absorption coefficient defined as the fraction of incident light absorbed by a very thin layer divided by the thickness of that layer
* – scattering coefficient defined as the fraction of incident light scattered by a very thin layer divided by the thickness of that layer | 7 | Physical Chemistry |
Achinewhu married Eunice Achinewhu (nee Eunice Nyema Otto) in 1972 and they have four children.
He is a reverend canon of the Church of Nigeria Anglican Communion. He is a crown of peace, justice of peace, and the national president of Peace Builders Association (Council of Ambassadors for Peace and Unification) | 1 | Biochemistry |
The VSEPR theory also predicts that substitution of a ligand at a central atom by a lone pair of valence electrons leaves the general form of the electron arrangement unchanged with the lone pair now occupying one position. For molecules with five pairs of valence electrons including both bonding pairs and lone pairs, the electron pairs are still arranged in a trigonal bipyramid but one or more equatorial positions is not attached to a ligand atom so that the molecular geometry (for the nuclei only) is different.
The seesaw molecular geometry is found in sulfur tetrafluoride (SF) with a central sulfur atom surrounded by four fluorine atoms occupying two axial and two equatorial positions, as well as one equatorial lone pair, corresponding to an AXE molecule in the AXE notation. A T-shaped molecular geometry is found in chlorine trifluoride (ClF), an AXE molecule with fluorine atoms in two axial and one equatorial position, as well as two equatorial lone pairs. Finally, the triiodide ion () is also based upon a trigonal bipyramid, but the actual molecular geometry is linear with terminal iodine atoms in the two axial positions only and the three equatorial positions occupied by lone pairs of electrons (AXE); another example of this geometry is provided by xenon difluoride, XeF. | 4 | Stereochemistry |
Volume number density is the number of specified objects per unit volume:
where N is the total number of objects in a volume V.
Here it is assumed that N is large enough that rounding of the count to the nearest integer does not introduce much of an error, however V is chosen to be small enough that the resulting n does not depend much on the size or shape of the volume V because of large-scale features.
Area number density is the number of specified objects per unit area, A:
Similarly, linear number density is the number of specified objects per unit length, L:
Column number density is a kind of areal density, the number or count of a substance per unit area, obtained integrating volumetric number density along a vertical path:
It's related to column mass density, with the volumetric number density replaced by the volume mass density. | 3 | Analytical Chemistry |
The three Laves phases are intermetallic compounds composed of CN12 and CN16 polyhedra with AB stoichiometry, commonly seen in binary metal systems like MgZn. Due to the small solubility of AB structures, Laves phases are almost line compounds, though sometimes they can have a wide homogeneity region. | 8 | Metallurgy |
Levocetirizine is an antihistamine. It acts as an inverse agonist that decreases activity at histamine H1 receptors. This in turn prevents the release of other allergy chemicals and increases the blood supply to the area, providing relief from the typical symptoms of hay fever. Levocetirizine, (R)-(-)-cetirizine, is essentially a chiral switch of (±)-cetirizine. This enantiomer, the eutomer, is more selective and the (S)-counterpart, the distomer, is inactive. | 4 | Stereochemistry |
In the gas phase, a single water molecule has an oxygen atom surrounded by two hydrogens and two lone pairs, and the geometry is simply described as bent without considering the nonbonding lone pairs.
However, in liquid water or in ice, the lone pairs form hydrogen bonds with neighboring water molecules. The most common arrangement of hydrogen atoms around an oxygen is tetrahedral with two hydrogen atoms covalently bonded to oxygen and two attached by hydrogen bonds. Since the hydrogen bonds vary in length many of these water molecules are not symmetrical and form transient irregular tetrahedra between their four associated hydrogen atoms. | 4 | Stereochemistry |
A feature of the LHPG technique is its high convection speed in the liquid phase due to Marangoni convection. It is possible to see that it spins very fast. Even when it appears to be standing still, it is in fact spinning fast on its axis. | 3 | Analytical Chemistry |
Photoluminescence excitation (abbreviated PLE) is a specific type of photoluminescence and concerns the interaction between electromagnetic radiation and matter. It is used in spectroscopic measurements where the frequency of the excitation light is varied, and the luminescence is monitored at the typical emission frequency of the material being studied. Peaks in the PLE spectra often represent absorption lines of the material. PLE spectroscopy is a useful method to investigate the electronic level structure of materials with low absorption due to the superior signal-to-noise ratio of the method compared to absorption measurements. | 7 | Physical Chemistry |
This equipment is a spectroscopic (light gathering) apparatus and corresponding method for rapidly detecting and analyzing analytes in a sample. The sample is irradiated by an excitation source in optical communication with the sample. The excitation source may include, but is not limited to, a laser, a flash lamp, an arc lamp, a light-emitting diode, or the like.
Figure 1 depicts the current version of the SOFIA system. Four linear arrays (101) extend from a sample holder (102), which houses an elongated, transparent sample container which is open at both ends, to an end port (103). The distal end of the endport (104) is inserted into an end port assembly (200). The linear arrays (101) comprise a plurality of optical fibers having a first end and a second end, the plurality of optical fibers optionally surrounded by a protective and/or insulating sheath. The optical fibers are linearly arranged, meaning that they are substantially coplanar with respect to one another so as to form an elongated row of fibers. | 1 | Biochemistry |
Warm spraying is a novel modification of high velocity oxy-fuel spraying, in which the temperature of combustion gas is lowered by mixing nitrogen with the combustion gas, thus bringing the process closer to the cold spraying. The resulting gas contains much water vapor, unreacted hydrocarbons and oxygen, and thus is dirtier than the cold spraying. However, the coating efficiency is higher. On the other hand, lower temperatures of warm spraying reduce melting and chemical reactions of the feed powder, as compared to HVOF. These advantages are especially important for such coating materials as Ti, plastics, and metallic glasses, which rapidly oxidize or deteriorate at high temperatures. | 8 | Metallurgy |
Vertebrate ferritin consists of two or three subunits which are named based on their molecular weight: L "light", H "heavy", and M "middle" subunits. The M subunit has only been reported in bullfrogs. In bacteria and archaea, ferritin consists of one subunit type. H and M subunits of eukaryotic ferritin and all subunits of bacterial and archaeal ferritin are H-type and have ferroxidase activity, which is the conversion of iron from the ferrous (Fe) to ferric (Fe) forms. This limits the deleterious reaction which occurs between ferrous iron and hydrogen peroxide known as the Fenton reaction which produces the highly damaging hydroxyl radical. The ferroxidase activity occurs at a diiron binding site in the middle of each H-type subunits. After oxidation of Fe(II), the Fe(III) product stays metastably in the ferroxidase center and is displaced by Fe(II), a mechanism that appears to be common among ferritins of all three domains of life. The light chain of ferritin has no ferroxidase activity but may be responsible for the electron transfer across the protein cage. | 1 | Biochemistry |
Hydrogenography is a combinatorial method based on the observation of optical changes on the metal surface by hydrogen absorption. The method allows the examination of thousands of combinations of alloy samples in a single batch. | 3 | Analytical Chemistry |
The reaction H + Br → 2 HBr proceeds by the following mechanism:
* Initiation
: Br → 2 Br• (thermal) or Br + hν → 2 Br• (photochemical)
: each Br atom is a free radical, indicated by the symbol "•" representing an unpaired electron.
* Propagation (here a cycle of two steps)
: Br• + H → HBr + H•
: H• + Br → HBr + Br•
: the sum of these two steps corresponds to the overall reaction H + Br → 2 HBr, with catalysis by Br• which participates in the first step and is regenerated in the second step.
* Retardation (inhibition)
: H• + HBr → H + Br•
: this step is specific to this example, and corresponds to the first propagation step in reverse.
* Termination 2 Br• → Br
: recombination of two radicals, corresponding in this example to initiation in reverse.
As can be explained using the steady-state approximation, the thermal reaction has an initial rate of fractional order (3/2), and a complete rate equation with a two-term denominator (mixed-order kinetics). | 7 | Physical Chemistry |
right|thumb|Example and diagram for p3
left|thumb|Cell structure for p3
* Orbifold signature:
* Coxeter notation: [(3,3,3)] or [3]
* Lattice: hexagonal
* Point group: C
* The group p3 has three different rotation centres of order three (120°), but no reflections or glide reflections.
Imagine a tessellation of the plane with equilateral triangles of equal size, with the sides corresponding to the smallest translations. Then half of the triangles are in one orientation, and the other half upside down. This wallpaper group corresponds to the case that all triangles of the same orientation are equal, while both types have rotational symmetry of order three, but the two are not equal, not each others mirror image, and not both symmetric (if the two are equal it is p6, if they are each others mirror image it is p31m, if they are both symmetric it is p3m1; if two of the three apply then the third also, and it is p6m). For a given image, three of these tessellations are possible, each with rotation centres as vertices, i.e. for any tessellation two shifts are possible. In terms of the image: the vertices can be the red, the blue or the green triangles.
Equivalently, imagine a tessellation of the plane with regular hexagons, with sides equal to the smallest translation distance divided by . Then this wallpaper group corresponds to the case that all hexagons are equal (and in the same orientation) and have rotational symmetry of order three, while they have no mirror image symmetry (if they have rotational symmetry of order six it is p6, if they are symmetric with respect to the main diagonals it is p31m, if they are symmetric with respect to lines perpendicular to the sides it is p3m1; if two of the three apply then the third also, it is p6m). For a given image, three of these tessellations are possible, each with one third of the rotation centres as centres of the hexagons. In terms of the image: the centres of the hexagons can be the red, the blue or the green triangles.
;Examples of group p3 | 3 | Analytical Chemistry |
One conducting polymer coating that has shown promising results for improving the performance of neural electrodes is polypyrrole (PPy). Polypyrrole has great biocompatibility and conductive properties, which makes it a good option for the use in neural electrodes. PPy has been shown to have a good interaction with biological tissues. This is due to the boundary it creates between the hard electrode and the soft tissue. PPy has been shown to support cell adhesion and growth of a number of different cell types including primary neurons which is important in neural implants. PPy also decreases the impedance of the electrode system by increasing the roughness on the surface. The roughness on the electrode surface is directly related to an increased surface area (increased neuron interface with electrode) which increases the signal conduction. In one paper, polypyrrole (PPy) was doped with polystyrene sulfonate (PSS) to electrochemically deposit a polypyrrole coating on the electrode surface. The film was coated onto the electrode at different thickness, increasing the roughness. The increased roughness (increased effective surface) leads to a decreased overall electrode impedance from about 400 kΩ (bare stent) to less than 10 kΩ (PPy/PSS coating) at 1 kHz. This decrease in impedance leads to improved charge transfer from the electrode to the tissue and an overall more effective electrode for recording and stimulating applications. | 7 | Physical Chemistry |
Polanyi described that the “turning point” of the acceptance of his model of adsorption occurred when Fritz Haber asked him to defend his theory in full in the Kaiser Wilhelm Institute for Physical Chemistry in Berlin, Germany. Many key players in the scientific world were present in this meeting including Albert Einstein. After hearing Polanyi's full explanation of his model, Haber and Einstein claimed that Polanyi “had displayed a total disregard for the scientifically established structure of the matter”. Years later, Polanyi described his ordeal by concluding,
Polanyi continued to provide supporting evidence in proving the validity of his model years after this meeting. | 7 | Physical Chemistry |
Mitochondrial diseases are usually detected by analysing muscle samples, where the presence of these organelles is higher. The most common tests for the detection of these diseases are:
# Southern blot to detect large deletions or duplications
# Polymerase chain reaction and specific mutation testing
# Sequencing | 1 | Biochemistry |
* Brazil: Classified as a weapon by Federal Act n° 3665/2000 (Regulation for Fiscalization of Controlled Products). Only law enforcement officers and private security agents with a recognized Less Lethal Weapons training certificate can carry it.
* Colombia: Can be sold without any kind of restriction to anyone older than 14 years.
** Use has not been inducted on the law enforcement officer's arsenal. | 1 | Biochemistry |
Planned
* EnMAP
Current and Past
*AVIRIS — airborne
*MODIS — on board EOS Terra and Aqua platforms
*MERIS — on board Envisat
*Hyperion — on board Earth Observing-1
*Several commercial manufacturers for laboratory, ground-based, aerial, or industrial imaging spectrographs | 7 | Physical Chemistry |
Chromids are elements that exist at the boundary between a chromosome and a plasmid, found in about 10% of bacterial species sequenced by 2009. These elements carry core genes and have codon usage similar to the chromosome, yet use a plasmid-type replication mechanism such as the low copy number RepABC. As a result, they have been variously classified as minichromosomes or megaplasmids in the past. In Vibrio, the bacterium synchronizes the replication of the chromosome and chromid by a conserved genome size ratio. | 1 | Biochemistry |
The leaf surface is also host to a large variety of microorganisms; in this context it is referred to as the phyllosphere.
;Lepidote: Covered with fine scurfy scales. | 5 | Photochemistry |
RNA spike-ins are samples of RNA at known concentrations that can be used as gold standards in experimental design and during downstream analyses for absolute quantification and detection of genome-wide effects.
* Absolute quantification: Absolute quantification of gene expression is not possible with most RNA-Seq experiments, which quantify expression relative to all transcripts. It is possible by performing RNA-Seq with spike-ins, samples of RNA at known concentrations. After sequencing, read counts of spike-in sequences are used to determine the relationship between each genes read counts and absolute quantities of biological fragments. In one example, this technique was used in Xenopus tropicalis' embryos to determine transcription kinetics.
* Detection of genome-wide effects: Changes in global regulators including chromatin remodelers, transcription factors (e.g., MYC), acetyltransferase complexes, and nucleosome positioning are not congruent with normalization assumptions and spike-in controls can offer precise interpretation. | 1 | Biochemistry |
Conformal compound coatings stop the whiskers from penetrating a barrier, reaching a nearby termination and forming a short. | 8 | Metallurgy |
The reaction of the CFCs which is responsible for the depletion of ozone, is the photo-induced scission of a C-Cl bond:
:CClF → CClF + Cl
The chlorine atom, written often as Cl, behaves very differently from the chlorine molecule (Cl). The radical Cl is long-lived in the upper atmosphere, where it catalyzes the conversion of ozone into O. Ozone absorbs UV-B radiation, so its depletion allows more of this high energy radiation to reach the Earth's surface. Bromine atoms are even more efficient catalysts; hence brominated CFCs are also regulated. | 2 | Environmental Chemistry |
The great oxygenation event began with the biologically induced appearance of oxygen in the Earth's atmosphere about 2.45 billion years ago. The rise of oxygen levels due to cyanobacterial photosynthesis in ancient microenvironments was probably highly toxic to the surrounding biota. Under these conditions, the selective pressure of oxidative stress is thought to have driven the evolutionary transformation of an archaeal lineage into the first eukaryotes. Oxidative stress might have acted in synergy with other environmental stresses (such as ultraviolet radiation and/or desiccation) to drive this selection. Selective pressure for efficient repair of oxidative DNA damages may have promoted the evolution of eukaryotic sex involving such features as cell-cell fusions, cytoskeleton-mediated chromosome movements and emergence of the nuclear membrane. Thus, the evolution of meiotic sex and eukaryogenesis may have been inseparable processes that evolved in large part to facilitate repair of oxidative DNA damages. | 1 | Biochemistry |
A new, effective and economical concept in pheromone delivery using a flowable formulation to create long lasting monolithic pheromone dispensers has been brought to the market in the past decade. These novel SPLAT pheromone mating disruption formulations can provide effective season long suppression effect (e.g., depending on the target pest a single application of SPLAT controls the target pest for a complete reproductive cycle, or for the entire season) and can be manually or mechanically applied. Although mechanical dispersal techniques require specialized off-the-shelf application technology and/or equipment, once the application system is made to work it allows protection of extensive areas using pheromones, one of the most benign and effective pest management techniques available today. A benefit of SPLAT is that the dollop anchors where it lands, avoiding unwanted drift of the formulation once applied in the field, and, depending on the mode of application, the cured dollops are retrievable. | 1 | Biochemistry |
UV curing (ultraviolet curing) is the process by which ultraviolet light initiates a photochemical reaction that generates a crosslinked network of polymers through radical polymerization or cationic polymerization. UV curing is adaptable to printing, coating, decorating, stereolithography, and in the assembly of a variety of products and materials. UV curing is a low-temperature, high speed, and solventless process as curing occurs via polymerization. Originally introduced in the 1960s, this technology has streamlined and increased automation in many industries in the manufacturing sector. | 5 | Photochemistry |
The symbol used to represent specific volume in equations is "v" with SI units of cubic meters per kilogram.
The symbol used to represent volume in equations is "V" with SI units of cubic meters.
When performing a thermodynamic analysis, it is typical to speak of intensive and extensive properties. Properties which depend on the amount of gas (either by mass or volume) are called extensive properties, while properties that do not depend on the amount of gas are called intensive properties. Specific volume is an example of an intensive property because it is the ratio of volume occupied by a unit of mass of a gas that is identical throughout a system at equilibrium. 1000 atoms a gas occupy the same space as any other 1000 atoms for any given temperature and pressure. This concept is easier to visualize for solids such as iron which are incompressible compared to gases. However, volume itself --- not specific --- is an extensive property. | 7 | Physical Chemistry |
The Latin word traces to the Proto-Indo-European root *gʷet- "pitch"; see that link for other cognates.
The expression "bitumen" originated in the Sanskrit, where we find the words "jatu", meaning "pitch", and "jatu-krit", meaning "pitch creating", "pitch producing" (referring to coniferous or resinous trees). The Latin equivalent is claimed by some to be originally "gwitu-men" (pertaining to pitch), and by others, "pixtumens" (exuding or bubbling pitch), which was subsequently shortened to "bitumen", thence passing via French into English. From the same root is derived the Anglo Saxon word "cwidu" (Mastix), the German word "Kitt" (cement or mastic) and the old Norse word "kvada".
The word "ašphalt" is claimed to have been derived from the Accadian term "asphaltu" or "sphallo," meaning "to split." It was later adopted by the Homeric Greeks in the form of the adjective ἄσφαλἤς, ἐς signifying "firm," "stable," "secure," and the corresponding verb ἄσφαλίξω, ίσω meaning "to make firm or stable," "to secure".
The word "asphalt" is derived from the late Middle English, in turn from French asphalte, based on Late Latin asphalton, asphaltum, which is the latinisation of the Greek (ásphaltos, ásphalton), a word meaning "asphalt/bitumen/pitch", which perhaps derives from , "not, without", i.e. the alpha privative, and (sphallein), "to cause to fall, baffle, (in passive) err, (in passive) be balked of".
The first use of asphalt by the ancients was as a cement to secure or join various objects, and it thus seems likely that the name itself was expressive of this application. Specifically, Herodotus mentioned that bitumen was brought to Babylon to build its gigantic fortification wall.
From the Greek, the word passed into late Latin, and thence into French (asphalte) and English ("asphaltum" and "asphalt"). In French, the term asphalte is used for naturally occurring asphalt-soaked limestone deposits, and for specialised manufactured products with fewer voids or greater bitumen content than the "asphaltic concrete" used to pave roads. | 7 | Physical Chemistry |
In 1832, the family settled in Mecklenburg County, Virginia, east of Christiansville (now Chase City). Although he arrived too late to obtain the prospective teaching position, John William established a laboratory in Christiansville. Here he conducted experiments and published eight papers before entering medical school. His sister Dorothy Catherine Draper provided finances through teaching drawing and painting for his medical education. In March 1836, he graduated from the University of Pennsylvania School of Medicine. That same year, he began teaching at Hampden–Sydney College in Virginia. | 5 | Photochemistry |
Hyperpolarization is a change in membrane potential. Neuroscientists measure it using a technique known as patch clamping that allows them to record ion currents passing through individual channels. This is done using a glass micropipette, also called a patch pipette, with a 1 micrometer diameter. There is a small patch that contains a few ion channels and the rest is sealed off, making this the point of entry for the current. Using an amplifier and a voltage clamp, which is an electronic feedback circuit, allows the experimenter to maintain the membrane potential at a fixed point and the voltage clamp then measures tiny changes in current flow. The membrane currents giving rise to hyperpolarization are either an increase in outward current or a decrease in inward current. | 7 | Physical Chemistry |
β-Thromboglobulin (β-TG), or beta-thromboglobulin, is a chemokine protein secreted by platelets. It is a type of chemokine (C-X-C motif) ligand 7. Along with platelet factor 4 (PF4), β-TG is one of the best-characterized platelet-specific proteins. β-TG and PF4 are stored in platelet alpha granules and are released during platelet activation. As a result, they are useful markers of platelet activation. β-TG also has multiple biological activities, for instance being involved in maturation of megakaryocytes. | 1 | Biochemistry |
Potential root causes of metallurgical failures are vast, spanning the lifecycle of component from design to manufacturing to usage. The most common reasons for failures can be classified into the following categories: | 8 | Metallurgy |
1,4-Butanedithiol is an organosulfur compound with the formula . It is a malodorous, colorless liquid that is highly soluble in organic solvents. The compound has found applications in biodegradable polymers. | 0 | Organic Chemistry |
From racemic acid found in grapes; from Latin racemus, meaning a bunch of grapes. This acid, when naturally produced in grapes, is only the right-handed version of the molecule, better known as tartaric acid. In many Germanic languages racemic acid is called “grape acid” e.g. German traubensäure and Swedish druvsyra. Carl von Linné gave red elderberry the scientific name Sambucus racemosa as the Swedish name, druvfläder, means grape elder, so called because its berries grow in a grape-like cluster. | 4 | Stereochemistry |
The eluent (mobile phase) should be the appropriate solvent to dissolve the polymer, should not interfere with the response of the polymer analyzed, and should wet the packing surface and make it inert to interactions with the polymers. The most common eluents for polymers that dissolve at room temperature GPC are tetrahydrofuran (THF), o-dichlorobenzene and trichlorobenzene at 130–150 °C for crystalline polyalkynes and hexafluoroisopropanol (HFIP) for crystalline condensation polymers such as polyamides and polyesters. | 3 | Analytical Chemistry |
The article has only treated the case in which particles have a parabolic relation between energy and momentum, as is the case in non-relativistic mechanics. For particles with energies close to their respective rest mass, the equations of special relativity are applicable. Where single-particle energy is given by:
For this system, the Fermi energy is given by:
where the equality is only valid in the ultrarelativistic limit, and
The relativistic Fermi gas model is also used for the description of massive white dwarfs which are close to the Chandrasekhar limit. For the ultrarelativistic case, the degeneracy pressure is proportional to . | 7 | Physical Chemistry |
Throughout this article, [RL] denotes the concentration of a receptor-ligand complex, [R] the concentration of free receptor, and [L] the concentration of free ligand (so that the total concentration of the receptor and ligand are [R]+[RL] and [L]+[RL], respectively). Let n be the number of binding sites for ligand on each receptor molecule, and let represent the average number of ligands bound to a receptor. Let K denote the dissociation constant between the ligand and receptor. The Scatchard equation is given by
By plotting /[L] versus , the Scatchard plot shows that the slope equals to -1/K while the x-intercept equals the number of ligand binding sites n. | 1 | Biochemistry |
The citric acid cycle, also known as the Krebs cycle or the TCA (tricarboxylic acid) cycle is an 8-step process that takes the pyruvate generated by glycolysis and generates 4 NADH, FADH2, and GTP, which is further converted to ATP. It is only in step 5, where GTP is generated, by succinyl-CoA synthetase, and then converted to ATP, that ADP is used (GTP + ADP → GDP + ATP). | 1 | Biochemistry |
Li(HMDS) can react with a wide range of metal halides, by a salt metathesis reaction, to give metal bis(trimethylsilyl)amides.
where X = Cl, Br, I and sometimes F
Metal bis(trimethylsilyl)amide complexes are lipophilic due to the ligand and hence are soluble in a range of nonpolar organic solvents, this often makes them more reactive than the corresponding metal halides, which can be difficult to solubilise. The steric bulk of the ligands causes their complexes to be discrete and monomeric; further increasing their reactivity. Having a built-in base, these compounds conveniently react with protic ligand precursors to give other metal complexes and hence are important precursors to more complex coordination compounds. | 0 | Organic Chemistry |
The studies of rapamycin as immunosuppressive agent enabled us to understand its mechanism of action. It inhibits T-cell proliferation and proliferative responses induced by several cytokines, including interleukin 1 (IL-1), IL-2, IL-3, IL-4, IL-6, IGF, PDGF, and colony-stimulating factors (CSFs). Rapamycin inhibitors and rapalogs can target tumor growth both directly and indirectly. Direct impact of them on cancer cells depend on the concentration of the drug and certain cellular characteristics. The indirect way, is based on interaction with processes required for tumor angiogenesis. | 1 | Biochemistry |
An antibody that recognizes the protein can be added to this mixture to create an even larger complex with a greater shift. This method is referred to as a supershift assay, and is used to unambiguously identify a protein present in the protein – nucleic acid complex.
Often, an extra lane is run with a competitor oligonucleotide to determine the most favorable binding sequence for the binding protein. The use of different oligonucleotides of defined sequence allows the identification of the precise binding site by competition (not shown in diagram). Variants of the competition assay are useful for measuring the specificity of binding and for measurement of association and dissociation kinetics. Thus, EMSA might also be used as part of a SELEX experiment to select for oligonucleotides that do actually bind a given protein.
Once DNA-protein binding is determined in vitro, a number of algorithms can narrow the search for identification of the transcription factor. Consensus sequence oligonucleotides for the transcription factor of interest will be able to compete for the binding, eliminating the shifted band, and must be confirmed by supershift. If the predicted consensus sequence fails to compete for binding, identification of the transcription factor may be aided by Multiplexed Competitor EMSA (MC-EMSA), whereby large sets of consensus sequences are multiplexed in each reaction, and where one set competes for binding, the individual consensus sequences from this set are run in a further reaction.
For visualization purposes, the nucleic acid fragment is usually labelled with a radioactive, fluorescent or biotin label. Standard ethidium bromide staining is less sensitive than these methods and can lack the sensitivity to detect the nucleic acid if small amounts of nucleic acid or single-stranded nucleic acid(s) are used in these experiments. When using a biotin label, streptavidin conjugated to an enzyme such as horseradish peroxidase is used to detect the DNA fragment. While isotopic DNA labeling has little or no effect on protein binding affinity, use of non-isotopic labels including flurophores or biotin can alter the affinity and/or stoichiometry of the protein interaction of interest. Competition between fluorophore- or biotin-labeled probe and unlabeled DNA of the same sequence can be used to determine whether the label alters binding affinity or stoichiometry. | 1 | Biochemistry |
Biological carbon fixation or сarbon assimilation is the process by which inorganic carbon (particularly in the form of carbon dioxide) is converted to organic compounds by living organisms. The compounds are then used to store energy and as structure for other biomolecules. Carbon is primarily fixed through photosynthesis, but some organisms use a process called chemosynthesis in the absence of sunlight.
Organisms that grow by fixing carbon are called autotrophs, which include photoautotrophs (which use sunlight), and lithoautotrophs (which use inorganic oxidation). Heterotrophs are not themselves capable of carbon fixation but are able to grow by consuming the carbon fixed by autotrophs or other heterotrophs. "Fixed carbon", "reduced carbon", and "organic carbon" may all be used interchangeably to refer to various organic compounds. Chemosynthesis is carbon fixation driven by chemical energy, rather than from sunlight. Sulfur- and hydrogen-oxidizing bacteria often use the Calvin cycle or the reductive citric acid cycle. | 5 | Photochemistry |
Age at time of death: Stillborn fetuses and infants putrefy slowly due to their sterility. Otherwise, however, younger people generally putrefy more quickly than older people.
Condition of the body: A body with a greater fat percentage and less lean body mass will have a faster rate of putrefaction, as fat retains more heat and it carries a larger amount of fluid in the tissues.
Cause of death: The cause of death has a direct relationship to putrefaction speed, with bodies that died from acute violence or accident generally putrefying slower than those that died from infectious diseases. Certain poisons, such as potassium cyanide or strychnine, may also delay putrefaction, while chronic alcoholism and cocaine use will speed it.
External injuries: Antemortem or postmortem injuries can speed putrefaction as injured areas can be more susceptible to invasion by bacteria. | 1 | Biochemistry |
Column chromatography is an extremely time-consuming stage in any lab and can quickly become the bottleneck for any process lab. Many manufacturers like Biotage, Buchi, Interchim and Teledyne Isco have developed automated flash chromatography systems (typically referred to as LPLC, low pressure liquid chromatography, around ) that minimize human involvement in the purification process. Automated systems will include components normally found on more expensive high performance liquid chromatography (HPLC) systems such as a gradient pump, sample injection ports, a UV detector and a fraction collector to collect the eluent. Typically these automated systems can separate samples from a few milligrams up to an industrial many kilogram scale and offer a much cheaper and quicker solution to doing multiple injections on prep-HPLC systems.
The resolution (or the ability to separate a mixture) on an LPLC system will always be lower compared to HPLC, as the packing material in an HPLC column can be much smaller, typically only 5 micrometre thus increasing stationary phase surface area, increasing surface interactions and giving better separation. However, the use of this small packing media causes the high back pressure and is why it is termed high pressure liquid chromatography. The LPLC columns are typically packed with silica of around 50 micrometres, thus reducing back pressure and resolution, but it also removes the need for expensive high pressure pumps. Manufacturers are now starting to move into higher pressure flash chromatography systems and have termed these as medium pressure liquid chromatography (MPLC) systems which operate above . | 3 | Analytical Chemistry |
Etiocholanolone glucuronide (ETIO-G) is an endogenous, naturally occurring metabolite of testosterone. It is formed in the liver from etiocholanolone by UDP-glucuronyltransferases. ETIO-G has much higher water solubility than etiocholanolone and is eventually excreted in the urine via the kidneys. Along with androsterone glucuronide, it is one of the major inactive metabolites of testosterone. | 1 | Biochemistry |
A plastic crystal is a crystal composed of weakly interacting molecules that possess some orientational or conformational degree of freedom. The name plastic crystal refers to the mechanical softness of such phases: they resemble waxes and are easily deformed. If the internal degree of freedom is molecular rotation, the name rotor phase or rotatory phase is also used. Typical examples are the modifications Methane I and Ethane I.
In addition to the conventional molecular plastic crystals, there are also emerging ionic plastic crystals, particularly organic ionic plastic crystals (OIPCs) and protic organic ionic plastic crystals (POIPCs). POIPCs are solid protic organic salts formed by proton transfer from a Brønsted acid to a Brønsted base and in essence are protic ionic liquids in the molten state, have found to be promising solid-state proton conductors for high temperature proton-exchange membrane fuel cells. Examples include 1,2,4-triazolium perfluorobutanesulfonate and imidazolium methanesulfonate.
If the internal degree of freedom freezes in a disordered way, an orientational glass is obtained.
The orientational degree of freedom may be an almost free rotation, or it may be a jump diffusion between a restricted number of possible orientations, as was shown for carbon tetrabromide.
X- ray diffraction patterns of plastic crystals are characterized by strong diffuse intensity in addition to the sharp Bragg peaks. In a powder pattern this intensity appears to resemble an amorphous background as one would expect for a liquid, but for a single crystal the diffuse contribution reveals itself to be highly structured. The Bragg peaks can be used to determine an average structure but due to the large amount of disorder this is not very insightful. It is the structure of the diffuse scattering that reflects the details of the constrained disorder in the system. Recent advances in two-dimensional detection at synchrotron beam lines facilitate the study of such patterns. | 7 | Physical Chemistry |
Latia luciferin is, in terms of chemistry, (E)-2-methyl-4-(2,6,6-trimethyl-1-cyclohex-1-yl)-1-buten-1-ol formate and is from the freshwater snail Latia neritoides. | 1 | Biochemistry |
Monoamine nuclei are clusters of cells that primarily use monoamine neurotransmitters to communicate. The raphe nuclei, ventral tegmental area, and locus coeruleus have been included in texts about monoamine nuclei. These nuclei receive a variety of inputs including from other monoamines, as well as from glutaminergic, GABAergic, and substance p related pathways. The catacholaminergic pathways mainly project upwards into the cortical and limbic regions, power sparse descending axons have been observed in animals models. Both ascending and descending serotonergic pathways project from the raphe nuclei. Raphe nuclei in the obscurus, pallid us, and magnus descend into the brainstem and spinal cord, while the raphe ponds, raphe dorsals, and nucleus centralism superior projected up into the medial forebrain bundle before branching off. Monoamine nuclei have been studied in relation to major depressive disorder, with some abnormalities observed, however MAO-B levels appear to be normal during depression in these regions. | 1 | Biochemistry |
When the solute undergoes ionic dissociation in solution (for example a salt), the system becomes decidedly non-ideal and we need to take the dissociation process into consideration. One can define activities for the cations and anions separately ( and ).
In a liquid solution the activity coefficient of a given ion (e.g. Ca) isn't measurable because it is experimentally impossible to independently measure the electrochemical potential of an ion in solution. (One cannot add cations without putting in anions at the same time). Therefore, one introduces the notions of
;mean ionic activity
;mean ionic molality
;mean ionic activity coefficient
where represent the stoichiometric coefficients involved in the ionic dissociation process
Even though and cannot be determined separately, is a measurable quantity that can also be predicted for sufficiently dilute systems using Debye–Hückel theory. For electrolyte solutions at higher concentrations, Debye–Hückel theory needs to be extended and replaced, e.g., by a Pitzer electrolyte solution model (see external links below for examples). For the activity of a strong ionic solute (complete dissociation) we can write: | 7 | Physical Chemistry |
Water oxidation is a more complex chemical reaction than proton reduction. In nature, the oxygen-evolving complex performs this reaction by accumulating reducing equivalents (electrons) in a manganese-calcium cluster within photosystem II (PS II), then delivering them to water molecules, with the resulting production of molecular oxygen and protons:
:2 HO → O + 4 H + 4e
Without a catalyst (natural or artificial), this reaction is very endothermic, requiring high temperatures (at least 2500 K).
The exact structure of the oxygen-evolving complex has been hard to determine experimentally. As of 2011, the most detailed model was from a 1.9 Å resolution crystal structure of photosystem II. The complex is a cluster containing four manganese and one calcium ions, but the exact location and mechanism of water oxidation within the cluster is unknown. Nevertheless, bio-inspired manganese and manganese-calcium complexes have been synthesized, such as [MnO] cubane-type clusters, some with catalytic activity.
Some ruthenium complexes, such as the dinuclear µ-oxo-bridged "blue dimer" (the first of its kind to be synthesized), are capable of light-driven water oxidation, thanks to being able to form high valence states. In this case, the ruthenium complex acts as both photosensitizer and catalyst. This complexes and other molecular catalysts still attract researchers in the field, having different advantages such as clear structure, active site, and easy to study mechanism. One of the main challenges to overcome is their short-term stability and their effective heterogenization for applications in artificial photosynthesis devices.
Many metal oxides have been found to have water oxidation catalytic activity, including ruthenium(IV) oxide (RuO), iridium(IV) oxide (IrO), cobalt oxides (including nickel-doped CoO), manganese oxide (including layered MnO (birnessite), MnO), and a mix of MnO with CaMnO. Oxides are easier to obtain than molecular catalysts, especially those from relatively abundant transition metals (cobalt and manganese), but suffer from low turnover frequency and slow electron transfer properties, and their mechanism of action is hard to decipher and, therefore, to adjust. | 5 | Photochemistry |
Ketenes are highly electrophilic at the carbon atom bonded with the heteroatom, due to its sp character. Ketene can be formed with different heteroatom bonded to the sp carbon atom, such as O, S or Se, respectively named ketene, thioketene and selenoketene.
Ethenone, the simplest ketene, has different experimental lengths for each of the double bonds; the C=O bond is 1,160Å and the C=C bond is 1,314Å. The angle between the two H atoms is 121.5°, similar to the theoretically ideal angle formed in alkenes between sp carbon atom and H substituents.
Ketenes are unstable and cannot be stored. In the absence of nucleophiles with which to react, ethenone dimerises to give β-lactone, a cyclic ester. If the ketene is disubstituted, the dimerisation product is a substituted cyclobutadione. For monosubstituted ketenes, the dimerisation could afford either the ester or the diketone product. | 0 | Organic Chemistry |
π–π interactions are associated with the interaction between the π-orbitals of a molecular system. The high polarizability of aromatic rings lead to dispersive interactions as major contribution to so-called stacking effects. These play a major role for interactions of nucleobases e.g. in DNA. For a simple example, a benzene ring, with its fully conjugated π cloud, will interact in two major ways (and one minor way) with a neighboring benzene ring through a π–π interaction (see figure 3). The two major ways that benzene stacks are edge-to-face, with an enthalpy of ~2 kcal/mol, and displaced (or slip stacked), with an enthalpy of ~2.3 kcal/mol. The sandwich configuration is not nearly as stable of an interaction as the previously two mentioned due to high electrostatic repulsion of the electrons in the π orbitals. | 6 | Supramolecular Chemistry |
Genes nested opposite the coding sequences of their host genes are very rare, and have been observed in prokaryotes, and more recently, in yeast (S. cerevisiae) and in Tetrahymena thermophila. These non-intronic nested genes remain to be identified in metazoan genomes. As with intronic nested genes, nonintronic nested genes typically do not share functions or expression patterns with their host genes. | 1 | Biochemistry |
The Institute for Chemistry and Biology of the Marine Environment of the Carl von Ossietzky University of Oldenburg (, abbreviated ICBM)
is one of the marine science institutes at the German coast and the only university-based marine research institute in Lower Saxony, Germany.
The ICBM is located on the campus Wechloy in Oldenburg, with locations in Wilhelmshaven and on the island of Spiekeroog (in relation to the national park centre Wittbülten on the area of the Hermann Lietz School). The ICBM operates the Wadden Sea time series station Spiekeroog (WSS) and several research vessels. | 9 | Geochemistry |
Seventy percent of the worlds supply of ascorbic acid is produced in China. Ascorbic acid is prepared in industry from glucose in a method based on the historical Reichstein process. In the first of a five-step process, glucose is catalytically hydrogenated to sorbitol, which is then oxidized by the microorganism Acetobacter suboxydans' to sorbose. Only one of the six hydroxy groups is oxidized by this enzymatic reaction. From this point, two routes are available. Treatment of the product with acetone in the presence of an acid catalyst converts four of the remaining hydroxyl groups to acetals. The unprotected hydroxyl group is oxidized to the carboxylic acid by reaction with the catalytic oxidant TEMPO (regenerated by sodium hypochlorite bleaching solution). Historically, industrial preparation via the Reichstein process used potassium permanganate as the bleaching solution. Acid-catalyzed hydrolysis of this product performs the dual function of removing the two acetal groups and ring-closing lactonization. This step yields ascorbic acid. Each of the five steps has a yield larger than 90%.
A more biotechnological process, first developed in China in the 1960s, but further developed in the 1990s, bypasses the use of acetone-protecting groups. A second genetically modified microbe species, such as mutant Erwinia, among others, oxidises sorbose into 2-ketogluconic acid (2-KGA), which can then undergo ring-closing lactonization via dehydration. This method is used in the predominant process used by the ascorbic acid industry in China, which supplies 70% of world's ascorbic acid. Researchers are exploring means for one-step fermentation. | 1 | Biochemistry |
A fusible alloy is a metal alloy capable of being easily fused, i.e. easily meltable, at relatively low temperatures. Fusible alloys are commonly, but not necessarily, eutectic alloys.
Sometimes the term "fusible alloy" is used to describe alloys with a melting point below . Fusible alloys in this sense are used for solder. | 8 | Metallurgy |
In 1662, Robert Boyle systematically studied the relationship between the volume and pressure of a fixed amount of gas at a constant temperature. He observed that the volume of a given mass of a gas is inversely proportional to its pressure at a constant temperature.
Boyle's law, published in 1662, states that, at a constant temperature, the product of the pressure and volume of a given mass of an ideal gas in a closed system is always constant. It can be verified experimentally using a pressure gauge and a variable volume container. It can also be derived from the kinetic theory of gases: if a container, with a fixed number of molecules inside, is reduced in volume, more molecules will strike a given area of the sides of the container per unit time, causing a greater pressure. | 7 | Physical Chemistry |
Due to its inherent microbial nature, nitrification in soils is greatly susceptible to soil conditions. In general, soil nitrification will proceed at optimal rates if the conditions for the microbial communities foster healthy microbial growth and activity. Soil conditions that have an effect on nitrification rates include:
*Substrate availability (presence of NH)
*Aeration (availability of O)
*Soil moisture content (availability of HO)
*pH (near neutral)
*Temperature | 1 | Biochemistry |
Base saturation expresses the percentage of potential CEC occupied by the cations Ca, Mg, K or Na. These are traditionally termed "base cations" because they are non-acidic, although they are not bases in the usual chemical sense. Base saturation provides an index of soil weathering and reflects the availability of exchangeable cationic nutrients to plants. | 9 | Geochemistry |
Testing for gold with acid capitalizes on gold's status as a noble metal, resistant to corrosion, oxidation, or acid. The procedure includes rubbing the gold-colored item on black stone, leaving a visible mark. The mark undergoes scrutiny by applying nitric acid, which dissolves the mark of any item not gold, stainless steel, zinc, tungsten, aluminum, platinum, or palladium. If the mark persists, further testing involves aqua regia (nitric acid and hydrochloric acid). If the mark dissolves, the item proves to be genuine gold. More precise assessment of fineness or purity is achieved using varying strengths of aqua regia and comparative testing against known fineness. | 3 | Analytical Chemistry |
The genus was previously only known from two species from highly disjunct localities – Ancyronyx variegatus from North America (described in 1824) and Ancyronyx acaroides from Palembang in Sumatra (described in 1896). This strange distribution pattern (and the fact that there were no new specimens of A. acaroides recovered) initially led 20th century specialists to question whether A. acaroides was indeed collected from Sumatra, or whether it was correctly designated to the genus as originally described. However, in 1991, new specimens of A. acaroides were rediscovered from Sumatra by the Austrian coleopterologists Manfred A. Jäch and S. Schödl, confirming its type locality. In addition they also discovered the species in Southeast Asia, including West Malaysia, Sarawak and Bali during 1992 and 1993. The species was also subsequently found in Thailand, Indonesia and the Philippines. Since then, nineteen new species of the genus have been described from Southeast Asia and China. | 2 | Environmental Chemistry |
In biochemistry, a Janin plot, like a Ramachandran plot, is a way to visualize dihedral angle distributions in protein structures. While a Ramachandran plot relates the two backbone dihedral angles, a Janin plot relates the first side chain dihedral angle χ-1 against χ-2. Because not all amino acids have these dihedral angles, a Janin plot is not applicable to all such acids.
This correlation is different for the various amino acids and can depend on the type of secondary structure (Helix, Sheet, etc.) local to that residue. The plot is named for Joël Janin, who studied these correlations in 1978 with Shoshana Wodak. | 1 | Biochemistry |
TFH is a ten‐subunit complex; seven of these subunits comprise the “core” whereas three comprise the dissociable “CAK” (CDK Activating Kinase) module. The core consists of subunits XPB, XPD, p62, p52, p44, p34 and p8 while CAK is composed of CDK7, cyclin H, and MAT1. | 1 | Biochemistry |
* Hoffman-La Roche Award from the Canadian Society for Chemistry (1997)
* Ottawa Life Sciences Council Achievement Award (2001)
* Rotary International Paul Harris Fellowship (2001)
* National Research Council of Canada Royalty Sharing Award (2001)
* Melville L. Wolfrom Award from the American Chemical Society Division of Carbohydrate Chemistry (2003)
* Gold Medal from the World Intellectual Property Organization (WIPO) (2005)
* Tech Museum Award – Technology Benefiting Humanity the Hib Vaccine team (2005)
* Probst Memorial Lecturer – Southern Illinois University (2006)
* Award of Excellence in research from the Foundation of Stars - Montreal Children’s Hospital (2008)
* Médaille (medal) de l’Université du Québec À Montréal (UQAM) (2009)
* Léo-Pariseau Prize of the Association francophone pour le savoir (2010)
* "Prix Cercle d’Excellence” of the Université du Québec (2011)
* Canada Research Chair in Medicinal Chemistry (2004-2017) | 0 | Organic Chemistry |
These tests validated the system for planetary exploration. Some improvements to be addressed in the future are instrument miniaturization, extraction protocols, and antibody stability under outer space conditions. SOLID would be one of the payloads of the proposed Icebreaker Life to Mars, or a lander to Europa. | 1 | Biochemistry |
A 1995 review study found that there is no clinical benefit to the use of CoQ in the treatment of periodontal disease. | 1 | Biochemistry |
Increasing the intensity of the electromagnetic field and the particle velocity, the emission of photons with energy comparable to the electron one becomes more probable and non-linear inverse Compton scattering starts to progressively differ from the classical limit because of quantum effects such as photon recoil. A dimensionless parameter, called electron quantum parameter, can be introduced to describe how far the physical condition are from the classical limit and how much non-linear and quantum effects matter. This parameter is given by the following expression:where V/m is the Schwinger field. In scientific literature, is also called . The Schwinger field , appearing in this definition, is a critical field capable of performing on electrons a work of over a reduced Compton length , where is the reduced Planck constant. The presence of such a strong field implies the instability of vacuum and it is necessary to explore non-linear QED effects, such as the production of pairs from vacuum. The Schwinger field corresponds to an intensity of nearly W/cm. Consequently, represents the work, in units of , performed by the field over the Compton length and in this way it also measures the importance of quantum non-linear effects since it compares the field strength in the rest frame of the electron with that of the critical field. Non-linear quantum effects, like the production of an electron-positron pair in vacuum, occur above the critical field , however, they can be observed also well below this limit since ultra-relativistic particles with Lorentz factor equal to see fields of the order of in their rest frame. is called also non-linear quantum parameter whereas it is a measure of the magnitude of non-linear quantum effects. The electron quantum parameter is linked to the magnitude of the Lorentz four-force acting on the particle due to the electromagnetic field and it is a Lorentz-invariant:The four-force acting on the particle is equal to the derivative of the four-momentum with respect to proper time. Using this fact in the classical limit, the radiated power according to the relativistic generalization of the Larmor formula becomes:<math display="block">
P=\dfrac{2}{3}\dfrac{e^2m^2c^3}{\hbar^2}\chi^2
and, therefore, some considerations can be done on which are the conditions for prolific emission, further evaluating the definition (). The electron quantum parameter increases with the energy of the electron (direct proportionality to ) and it is larger when the force exerted by the field perpendicularly to the particle velocity increases. | 7 | Physical Chemistry |
If an infinitesimally small amount of heat is supplied to a system in a reversible way then, according to the second law of thermodynamics, the entropy change of the system is given by:
Since
where C is the heat capacity, it follows that:
The heat capacity depends on how the external variables of the system are changed when the heat is supplied. If the only external variable of the system is the volume, then we can write:
From this follows:
Expressing dS in terms of dT and dP similarly as above leads to the expression:
One can find the above expression for by expressing dV in terms of dP and dT in the above expression for dS.
results in
and it follows:
Therefore,
The partial derivative can be rewritten in terms of variables that do not involve the entropy using a suitable Maxwell relation. These relations follow from the fundamental thermodynamic relation:
It follows from this that the differential of the Helmholtz free energy is:
This means that
and
The symmetry of second derivatives of F with respect to T and V then implies
allowing one to write:
The r.h.s. contains a derivative at constant volume, which can be difficult to measure. It can be rewritten as follows. In general,
Since the partial derivative is just the ratio of dP and dT for dV = 0, one can obtain this by putting dV = 0 in the above equation and solving for this ratio:
which yields the expression:
The expression for the ratio of the heat capacities can be obtained as follows:
The partial derivative in the numerator can be expressed as a ratio of partial derivatives of the pressure w.r.t. temperature and entropy. If in the relation
we put and solve for the ratio we obtain . Doing so gives:
One can similarly rewrite the partial derivative by expressing dV in terms of dS and dT, putting dV equal to zero and solving for the ratio . When one substitutes that expression in the heat capacity ratio expressed as the ratio of the partial derivatives of the entropy above, it follows:
Taking together the two derivatives at constant S:
Taking together the two derivatives at constant T:
From this one can write: | 7 | Physical Chemistry |
The Fourier-domain version of the a/LCI system uses a superluminescent diode (SLD) with a fiber-coupled output as the light source. A fiber splitter separates the signal path at 90% intensity and the reference path at 10%.
The light from the SLD passes through an optical isolator and subsequently a polarization controller. It has been shown that control of light polarization is important for maximizing optical signal and comparing angular scattering with the Mie scattering model. A polarization-maintaining fiber is used to carry the illumination light to the sample. A second polarization controller is similarly used to control the polarization of the light passing through the reference path.
The output of the fiber on the right is collimated using lens L1 and illuminates the tissue. But because the delivery fiber is offset from the optical axis of the lens, the beam is delivered to the sample at an oblique angle. Backscattered light is then collimated by the same lens and collected by the fiber bundle. The fibers are one focal length from the lens, and the sample is one focal length on the other side. This configuration captures light from the maximum range of angles and minimizes light noise due to specular reflections.
At the distal end of the fiber bundle, light from each fiber is imaged onto the spectrometer. Light from the sample and reference arms are mixed by a beamsplitting cube (BS), and are incident on the entrance slit of an imaging spectrometer. Data from the imaging spectrometer are transferred to a computer via USB interface for signal processing and display of results. The computer also provides control of the imaging spectrometer. | 7 | Physical Chemistry |
Cyanobacteria contain both PSI and PSII. Their light-harvesting system is different from that found in plants (they use phycobilins, rather than chlorophylls, as antenna pigments), but their electron transport chain
→ PSII → plastoquinol → bf → cytochrome c → PSI → ferredoxin → NADPH
bf ← plastoquinol
is, in essence, the same as the electron transport chain in chloroplasts. The mobile water-soluble electron carrier is cytochrome c in cyanobacteria, having been replaced by plastocyanin in plants.
Cyanobacteria can also synthesize ATP by oxidative phosphorylation, in the manner of other bacteria. The electron transport chain is
NADH dehydrogenase → plastoquinol → bf → cyt c → cyt aa →
where the mobile electron carriers are plastoquinol and cytochrome c, while the proton pumps are NADH dehydrogenase, cyt bf and cytochrome aa (member of the COX3 family).
Cyanobacteria are the only bacteria that produce oxygen during photosynthesis. Earth's primordial atmosphere was anoxic. Organisms like cyanobacteria produced our present-day oxygen-containing atmosphere.
The other two major groups of photosynthetic bacteria, purple bacteria and green sulfur bacteria, contain only a single photosystem and do not produce oxygen. | 5 | Photochemistry |
Krister Holmberg, born 1946, is a Swedish chemist.
Holmberg took a PhD in Organic Chemistry from Chalmers University of Technology in Gothenburg, Sweden in 1974. He then worked in industry for many years and he was R&D Director of Berol Nobel in Stenungsund, Sweden. During the period 1991-1998 he was Director of the Institute for Surface Chemistry in Stockholm. Since 1998 he has been Professor of Surface Chemistry at Chalmers University of Technology. His recent research has focussed on the behavior of surface active compounds in solution and at interfaces. He has been active in a number of industrial applications of surface and colloid chemistry.
Holmberg has been visiting professor at universities in the EU, the US and China: P. et M. Curie in Paris, the University of Florence, the University of California at Santa Barbara and the Chinese Academy of Sciences in Beijing. He is a member of the Royal Swedish Academy of Engineering Sciences (Kungliga Ingenjörsvetenskapsakademien), of the Royal Swedish Academy of Sciences (Kungliga Vetenskapsakademin) and of the Royal Academy of Arts and Sciences in Gothenburg (Kungliga Vetenskaps- och Vitterhetssamhället i Göteborg). He was chairman of the latter academy during 2014.
In 2000, Holmberg was awarded the French National Order of Merit (lOrdre National du Mérite au grade de Chevalier), and in 2006 he won the Oscar Carlson medal from the Swedish Chemical Society. He received the JCIS Life-Time Achievement Award in 2008, the Kash Mittal Award in 2018 and the Quancheng Friendship Award' by the city of Jinan, China in 2019. In 2021 he received the Friendship Award of China from the Chinese Government. | 0 | Organic Chemistry |
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