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* An exergonic reaction is a spontaneous chemical reaction that releases energy. It is thermodynamically favored, indexed by a negative value of ΔG (Gibbs free energy). Over the course of a reaction, energy needs to be put in, and this activation energy drives the reactants from a stable state to a highly energetically unstable transition state to a more stable state that is lower in energy (see: reaction coordinate). The reactants are usually complex molecules that are broken into simpler products. The entire reaction is usually catabolic. The release of energy (called Gibbs free energy) is negative (i.e. −ΔG) because energy is released from the reactants to the products.
* An endergonic reaction is an anabolic chemical reaction that consumes energy. It is the opposite of an exergonic reaction. It has a positive ΔG because it takes more energy to break the bonds of the reactant than the energy of the products offer, i.e. the products have weaker bonds than the reactants. Thus, endergonic reactions are thermodynamically unfavorable. Additionally, endergonic reactions are usually anabolic.
The free energy (ΔG) gained or lost in a reaction can be calculated as follows: ΔG = ΔH − TΔS
where ∆G = Gibbs free energy, ∆H = enthalpy, T = temperature (in kelvins), and ∆S = entropy. | 1 | Applied and Interdisciplinary Chemistry |
Celsius (known until 1948 as centigrade) is a temperature scale that is named after the Swedish astronomer Anders Celsius (1701–1744), who developed a similar temperature scale two years before his death. The degree Celsius (°C) can refer to a specific temperature on the Celsius scale as well as a unit to indicate a temperature interval (a difference between two temperatures).
From 1744 until 1954, 0 °C was defined as the freezing point of water and 100 °C was defined as the boiling point of water, both at a pressure of one standard atmosphere.
Although these defining correlations are commonly taught in schools today, by international agreement, between 1954 and 2019 the unit degree Celsius and the Celsius scale were defined by absolute zero and the triple point of VSMOW (specially prepared water). This definition also precisely related the Celsius scale to the Kelvin scale, which defines the SI base unit of thermodynamic temperature with symbol K. Absolute zero, the lowest temperature possible, is defined as being exactly 0 K and −273.15 °C. Until 19 May 2019, the temperature of the triple point of water was defined as exactly 273.16 K (0.01 °C). This means that a temperature difference of one degree Celsius and that of one kelvin are exactly the same.
On 20 May 2019, the kelvin was redefined so that its value is now determined by the definition of the Boltzmann constant rather than being defined by the triple point of VSMOW. This means that the triple point is now a measured value, not a defined value. The newly-defined exact value of the Boltzmann constant was selected so that the measured value of the VSMOW triple point is exactly the same as the older defined value to within the limits of accuracy of contemporary metrology. The degree Celsius remains exactly equal to the kelvin, and 0 K remains exactly −273.15 °C. | 0 | Theoretical and Fundamental Chemistry |
Fluorescence polarization was first observed by F. Weigert in 1920. He experimented with solutions of fluorescein, eosin, and other dyes at various temperatures and viscosities. Observing that polarization increased with viscosity of the solvent and the size of the dye molecule, but decreased with an increase in temperature, he deduced that polarization increased with a decrease in mobility of the emitting species. From 1925 to 1926 Francis Perrin detailed a quantitative theory for fluorescence polarization in multiple significant publications which remain relevant to this day.
Since Perrin's contribution, the technique has grown from determining binding isotherms under heavily controlled parameters, to the study of antigen-antibody, small molecule-protein, and hormone-receptor binding interactions. A fluorescence polarization immunoassay was first described and used in the 1960s. The competitive homogenous characteristic allowed for the fluorescence polarization immunoassay to be automated much easier than other immunoassay techniques such as radioimmunoassays or enzyme-linked immunoassays.
Despite originating as a method for direct interaction studies, the technique has been adopted by high-throughput screening (HTS) since the mid 1990s to help facilitate the drug discovery process by studying complex enzymatic interaction. | 1 | Applied and Interdisciplinary Chemistry |
Size of sea salt aerosols ranges widely from ~0.05 to 10 μm in diameter, with most of masses concentrated in super-micron range (coarse mode), and highest number concentration in sub-micron range. Correspondingly, sea salt aerosols have a wide range of atmospheric lifetimes. As the sea salt aerosols are hygroscopic, their particle sizes may vary with humidity by up to a factor of 2. Sea salt aerosols influence the sulfate aerosol formation in different ways due to the different sizes. Very small sea salt aerosols, which are below the critical diameter for droplet activation at low supersaturations, can serve as nuclei for the growth of sulfate particles, while larger sea salt particles serve as a sink for gaseous hydrogen sulfate (HSO) molecules, reducing the amount of sulfate available for the formation of accumulation mode particles. | 0 | Theoretical and Fundamental Chemistry |
pHydrion is the trademarked name for a popular line of chemical test products, marketed by Micro Essential Laboratory, Inc., the original manufacturer of Hydrion and pHydrion products. The trademarked pHydrion product line comprises chemical test papers, chemical indicators, chemical test kits, chemical indicator kits, pH indicator pencils, chemical buffers, buffer salts, buffer preservatives, dispensers, color charts, and testing products, for use in testing, detecting, identifying, measuring, and indicating levels of pH, of sanitizers, and of other substances. | 0 | Theoretical and Fundamental Chemistry |
The model is based on seasonal input data and returns seasonal outputs. The number of seasons per year can be chosen between a minimum of one and a maximum of four. One can distinguish for example dry, wet, cold, hot, irrigation or fallow seasons. Reasons of not using smaller input/output periods are:
#short-term (e.g., daily) inputs would require much information, which, in large areas, may not be readily available;
#short-term outputs would lead to immense output files, which would be difficult to manage and interpret;
#this model is especially developed to predict long-term trends, and predictions for the future are more reliably made on a seasonal (long-term) than on a daily (short-term) basis, due to the high variability of short-term data;
#though the precision of the predictions for the future may be limited, a lot is gained when the trend is sufficiently clear. For example, it need not be a major constraint to the design of appropriate soil salinity control measures when a certain salinity level, predicted by SahysMod to occur after 20 years, will in reality occur after 15 or 25 years. | 0 | Theoretical and Fundamental Chemistry |
DNA methylation is the process in which a methyl group is added to either a cytosine or adenine. This process causes the activation or inactivation of gene expression, thereby resulting in gene regulation in eukaryotic cells. DNA methylation process is also known to be involved in certain types of cancer formation. In order for this chemical modification to occur, it is necessary that the target base flips out of the DNA double helix to allow the methyltransferases to catalyze the reaction. | 1 | Applied and Interdisciplinary Chemistry |
Technically, ceramics are composed of raw materials such as powders and natural or synthetic chemical additives, favouring either compaction (hot, cold or isostatic), setting (hydraulic or chemical), or accelerating sintering processes. According to the formulation and shaping process used, bioceramics can vary in density and porosity as cements, ceramic depositions, or ceramic composites. Porosity is often desired in bioceramics including bioglasses. Towards improving the performance of transplanted porous bioceramics, numerous processing techniques are available for the control of porosity, pore size distribution and pore alignment. For crystalline materials, grain size and crystalline defects provide further pathways to enhance biodegradation and osseointegration, which are key for effective bone graft and bone transplant materials. This can be achieved by the inclusion of grain refining dopants and by imparting defects in the crystalline structure through various physical means.
A developing material processing technique based on the biomimetic processes aims to imitate natural and biological processes and offer the possibility of making bioceramics at ambient temperature rather than through conventional or hydrothermal processes [GRO 96]. The prospect of using these relatively low processing temperatures opens up possibilities for mineral organic combinations with improved biological properties through the addition of proteins and biologically active molecules (growth factors, antibiotics, anti-tumor agents, etc.). However, these materials have poor mechanical properties which can be improved, partially, by combining them with bonding proteins. | 0 | Theoretical and Fundamental Chemistry |
In freshwater or marine systems apparent oxygen utilization (AOU) is the difference between oxygen gas solubility (i.e. the concentration at saturation) and the measured oxygen concentration in water with the same physical and chemical properties. | 0 | Theoretical and Fundamental Chemistry |
Similar to microbial fuel cells, biological photovoltaic systems which employ whole organisms have the advantage over non-biological fuel cells and photovoltaic systems of being able to self-assemble and self-repair (i.e. the photosynthetic organism is able to reproduce itself). The ability of the organism to store energy allows for power generation from biological photovoltaic systems in the dark, circumventing the grid supply and demand problems sometimes faced by conventional photovoltaics. Additionally, the use of photosynthetic organisms that fix carbon dioxide means the assembly of the light harvesting material in a biological photovoltaic system could have a negative carbon footprint.
Compared to microbial fuel cells, which use heterotrophic microorganisms, biological photovoltaic systems need no input of organic compounds to supply reducing equivalents to the system. This improves the efficiency of light-to-electricity conversion by minimising the number of reactions separating the capture of light energy and reduction of the anode. A disadvantage of using oxygenic photosynthetic material in bioelectrochemical systems is that the production of oxygen in the anodic chamber has a detrimental effect on the cell voltage. | 0 | Theoretical and Fundamental Chemistry |
An example of a publication using live IGSNs can be found here:
This paper contains several samples identified by IGSN. One of them is IGSN: 10.58052/SSH000SUA. Information about this sample can be obtained by resolving the IGSN by adding the URL of the resolver before the IGSN: https://doi.org/10.58052/SSH000SUA.
IGSN can be used to identify samples and sampling features, such as boreholes or outcrops. The IGSN [https://doi.org/10.60510/ICDP5054ESYI201 10.60510/ICDP5054ESYI201] identifies a core section from core [https://doi.org/10.60510/ICDP5054ECYD101 5054_1_A_658_Z (IGSN 10.60510/ICDP5054ECYD101)] of the COSC Expedition of the International Continental Scientific Drilling Program. The corresponding drill hole (sampling feature) [https://doi.org/10.60510/ICDP5054EEW1001 5054_1_A] is identified by IGSN [https://doi.org/10.60510/ICDP5054EEW1001 10.60510/ICDP5054EEW1001]. | 0 | Theoretical and Fundamental Chemistry |
Meitner was born Elise Meitner on 7 November 1878 into a Jewish upper-middle-class family at the family home in 27 Kaiser Josefstraße in the Leopoldstadt district of Vienna, the third of eight children of chess master Philipp Meitner and his wife Hedwig. The birth register of Vienna's Jewish community lists her as being born on 17 November 1878, but all other documents list her date of birth as 7 November, which is what she used. Her father was one of the first Jewish lawyers admitted to practice in Austria. She had two older siblings, Gisela and Auguste (Gusti), and four younger: Moriz (Fritz), Carola (Lola), Frida and Walter; all ultimately pursued an advanced education. Her father was a confirmed freethinker, and she was brought up as such. As an adult, she converted to Christianity, following Lutheranism, and was baptised in 1908; her sisters Gisela and Lola converted to Catholic Christianity that same year. She also adopted a shortened name "Lise". | 1 | Applied and Interdisciplinary Chemistry |
Silver ions form alkene complexes. The binding is reversible, but sufficient to impede the elution of the alkene-containing analytes. | 0 | Theoretical and Fundamental Chemistry |
In 1992, the Moscow Institute of Fine Chemical Technology named after M. V. Lomonosov has received a new, higher educational status – status of the academy. With the name change has changed the status and range of activities of the institute along with old technology, new specialty Humanitarian – Management Profile: "Economics and Management (chemical industry)", "Environmental Protection", "Standardization and Certification". These specialties are subject to major technologies and solve their narrow-profile tasks.
Before the transition to a tiered structure the education of students was carried out in one direction, "Chemical Technology and Biotechnology", which consists of seven specialties. After the transition academy led training in seven areas of undergraduate, graduate five areas (including 26 master's programs) and 13 majors (including 25 majors) in full-time and part-correspondence courses, and conducted post-graduate education in 24 specialties and additional education in primary educational programs MITHT.
To implement in MITHT a tiered system of higher education were opened new training units. Along with main faculties teaching of students was performed at the Faculty of Natural Science, Faculty of Humanities, Faculty of Management, Economics and Environment, Faculty of Engineering, Faculty of further education at the Institute of Distance Education.
According to the Federal Agency for Supervision in Education and Science in 2008 in MITHT worked one of the most highly qualified scientific and technical teaching staff of universities and academies of Russia: doctors and candidates of sciences accounted for about 80% of the teachers. At the academy a total enrollment of 4,500 undergraduate and graduate students, taught 119 professors, doctors, and 218 associate professors, candidates of sciences. | 1 | Applied and Interdisciplinary Chemistry |
Hemithioacetals ordinarily readily dissociate into thiol and aldehyde, however, some have been isolated. In general, these isolable hemithioacetals are cyclic, which disfavors dissociation, and can often be further stabilized by the presence of acid. An important class are S-glycosides, such as octylthioglucoside, which are formed by a reaction between thiols and sugars. Other examples include 2-hydroxytetrahydrothiophene and the anti-HIV drug Lamivudine. Another class of isolable hemithioacetals are derived from carbonyl groups that form stable hydrates. For example, thiols react with hexafluoroacetone trihydrate to give hemithioacetals, which can be isolated. | 0 | Theoretical and Fundamental Chemistry |
Although anthocyanins have been shown to have antioxidant properties in vitro, there is no evidence for antioxidant effects in humans after consuming foods rich in anthocyanins. Unlike controlled test-tube conditions, the fate of anthocyanins in vivo shows they are poorly conserved (less than 5%), with most of what is absorbed existing as chemically modified metabolites that are excreted rapidly. The increase in antioxidant capacity of blood seen after the consumption of anthocyanin-rich foods may not be caused directly by the anthocyanins in the food, but instead by increased uric acid levels derived from metabolizing flavonoids (anthocyanin parent compounds) in the food. It is possible that metabolites of ingested anthocyanins are reabsorbed in the gastrointestinal tract from where they may enter the blood for systemic distribution and have effects as smaller molecules.
In a 2010 review of scientific evidence concerning the possible health benefits of eating foods claimed to have "antioxidant properties" due to anthocyanins, the European Food Safety Authority concluded that 1) there was no basis for a beneficial antioxidant effect from dietary anthocyanins in humans, 2) there was no evidence of a cause-and-effect relationship between the consumption of anthocyanin-rich foods and protection of DNA, proteins, and lipids from oxidative damage, and 3) there was no evidence generally for consumption of anthocyanin-rich foods having any "antioxidant", "anti-cancer", "anti-aging", or "healthy aging" effects. | 0 | Theoretical and Fundamental Chemistry |
The Johns Hopkins School of Public Health Department of Biochemistry and Molecular Biology (BMB) was established in 1916, as the Department of Chemical Hygiene. That same year, the Johns Hopkins School of Hygiene and Public Health was founded, as it was named then. Today, the school is named the Bloomberg School of Public Health and is part of the Johns Hopkins University in Baltimore, Maryland, United States.
The Department has changed names three times in its history from the Department of Chemical Hygiene, when it was founded, to the Department of Biochemistry by the time Roger H. Herriott was its Chair in 1948, to the Department of Biochemistry and Molecular Biology by the time Roger McMacken was its chair in 1990. Yet, since that time it has remained as the Department of Biochemistry and Molecular Biology.
As of 2019, BMB is chaired by Ashani Weeraratna. | 1 | Applied and Interdisciplinary Chemistry |
Research has shown that applying 5 to 15 volts of electricity for 50 ms to the segmental nerve that innervates the light organ leads to a glow 1.5 seconds after that lasts for five to ten seconds. Stimulation of the segmental nerve has been found to lead to several different nerve impulses, and frequency of nervous impulses has been found to be proportional to the intensity of the stimulus applied. A high frequency of nervous impulse was found to lead to a constant latency. The light organ is inactive in the absence of nerve impulses. Constant nerve signaling was shown to coincide with constant emission of light from the light organ with a higher frequency coinciding with a higher amplitude of light emitted up to 30 impulses per second. Impulses beyond this frequency were not found to be associated with a more intense glow. The fact that the frequency of nerve impulses was able to exceed beyond the maximum intensity of light emission suggests some limitations in the mechanism either arising from the synapse or the cell's light producing process. Additionally, a series of action potentials have been shown to lead to the sporadic, discontinuous emission to light. It was also found that a higher frequency of action potentials lead to a higher likelihood of any emission of light. Nerve impulses are associated with a depolarization of the photocyte which plays a role in its light emitting mechanism, and greater depolarization events were found to be associated with more intense lightning. The nerve innervating the light organ containing photocytes has only two axons, but they branch repeatedly allowing the numerous photocytes to be innervated with each cell being associated with several nerve terminals with each terminal possibly being associated with several synapses.
It was found that the junction between at the end of the neuron innervating the light organ differs from the kind of junction found between two different neurons or between neurons and muscles in the neuromuscular junction. The depolarization of the photocyte following nervous stimulation was found to be one-hundred times slower than the with the other two kinds of junctions and this slow response cannot be attributed to the rate of diffusion because the synapse between the neuron and photocyte is relatively small. It has been found that the neurons that control the light mechanism terminate at the tracheal cells rather than the photocytes themselves. | 1 | Applied and Interdisciplinary Chemistry |
As a scientist with the American Red Cross, Fahy was the originator of the first practical method of cryopreservation by vitrification and the inventor of computer-based systems to apply this technology to whole organs. Before joining Twenty-First Century Medicine, he was the chief scientist for Organ, Inc and of LRT, Inc. He was also Head of the Tissue Cryopreservation Section of the Transfusion and Cryopreservation Research Program of the U.S. Naval Medical Research Institute in Bethesda, Maryland where he spearheaded the original concept of ice blocking agents. In 2014, he was named a Fellow of the Society for Cryobiology in recognition of the impact of his work in low temperature biology.
In 2015–2017, Fahy led the TRIIM (Thymus Regeneration, Immunorestoration, and Insulin Mitigation) human clinical trial, designed to reverse aspects of human aging. The purpose of the TRIIM trial was to investigate the possibility of using recombinant human growth hormone (rhGH) to prevent or reverse signs of immunosenescence in ten 51‐ to 65‐year‐old putatively healthy men. The study: | 1 | Applied and Interdisciplinary Chemistry |
Non-ferrous extractive metallurgy is one of the two branches of extractive metallurgy which pertains to the processes of reducing valuable, non-iron metals from ores or raw material. Metals like zinc, copper, lead, aluminium as well as rare and noble metals are of particular interest in this field, while the more common metal, iron, is considered a major impurity. Like ferrous extraction, non-ferrous extraction primarily focuses on the economic optimization of extraction processes in separating qualitatively and quantitatively marketable metals from its impurities (gangue).
Any extraction process will include a sequence of steps or unit processes for separating highly pure metals from undesirables in an economically efficient system. Unit processes are usually broken down into three categories: pyrometallurgy, hydrometallurgy, and electrometallurgy. In pyrometallurgy, the metal ore is first oxidized through roasting or smelting. The target metal is further refined at high temperatures and reduced to its pure form. In hydrometallurgy, the object metal is first dissociated from other materials using a chemical reaction, which is then extracted in pure form using electrolysis or precipitation. Finally, electrometallurgy generally involves electrolytic or electrothermal processing. The metal ore is either distilled in an electrolyte or acid solution, then magnetically deposited onto a cathode plate (electrowinning); or smelted then melted using an electric arc or plasma arc furnace (electrothermic reactor).
Another major difference in non-ferrous extraction is the greater emphasis on minimizing metal losses in slag. This is widely due to the exceptional scarcity and economic value of certain non-ferrous metals which are, inevitably, discarded during the extraction process to some extent. Thus, material resource scarcity and shortages are of great concern to the non-ferrous industry. Recent developments in non-ferrous extractive metallurgy now emphasize the reprocessing and recycling of rare and non-ferrous metals from secondary raw materials (scrap) found in landfills. | 1 | Applied and Interdisciplinary Chemistry |
A nanofountain probe (NFP) is a device for drawing micropatterns of liquid chemicals at extremely small resolution. An NFP contains a cantilevered micro-fluidic device terminated in a nanofountain. The embedded microfluidics facilitates rapid and continuous delivery of molecules from the on-chip reservoirs to the fountain tip. When the tip is brought into contact with the substrate, a liquid meniscus forms, providing a path for molecular transport to the substrate. By controlling the geometry of the meniscus through hold time and deposition speed, various inks and biomolecules could be patterned on a surface, with sub 100 nm resolution. | 1 | Applied and Interdisciplinary Chemistry |
A B2 intermetallic compound has equal numbers of atoms of two metals such as aluminium and iron, arranged as two interpenetrating simple cubic lattices of the component metals. | 1 | Applied and Interdisciplinary Chemistry |
In larger urban centres, studies have noted that lesbian, gay, bisexual, transgender and queer (LGBTQ+) populations are among the fastest-growing users of fertility care. IVF is increasingly being used to allow lesbian and other LGBT couples to share in the reproductive process through a technique called reciprocal IVF. The eggs of one partner are used to create embryos which the other partner carries through pregnancy. For gay male couples, many elect to use IVF through gestational surrogacy, where one partners sperm is used to fertilise a donor ovum, and the resulting embryo is transplanted into a surrogate carriers womb. There are various IVF options available for same-sex couples including, but not limited to, IVF with donor sperm, IVF with a partners oocytes, reciprocal IVF, IVF with donor eggs, and IVF with gestational surrogate. IVF with donor sperm can be considered traditional IVF for lesbian couples, but reciprocal IVF or using a partners oocytes are other options for lesbian couples trying to conceive to include both partners in the biological process. Using a partners oocytes is an option for partners who are unsuccessful in conceiving with their own, and reciprocal IVF involves undergoing reproduction with a donor egg and sperm that is then transferred to a partner who will gestate. Donor IVF involves conceiving with a third partys eggs. Typically, for gay male couples hoping to use IVF, the common techniques are using IVF with donor eggs and gestational surrogates. | 1 | Applied and Interdisciplinary Chemistry |
Integral skin foam, also known as self-skin foam, is a type of foam with a high-density skin and a low-density core. It can be formed in an open-mold process or a closed-mold process. In the open-mold process, two reactive components are mixed and poured into an open mold. The mold is then closed and the mixture is allowed to expand and cure. Examples of items produced using this process include arm rests, baby seats, shoe soles, and mattresses. The closed-mold process, more commonly known as reaction injection molding (RIM), injects the mixed components into a closed mold under high pressures. | 0 | Theoretical and Fundamental Chemistry |
As in any power cycle, the most important indicator of its performance is the thermal efficiency. The thermal efficiency of a transcritical cycle is computed as:
where is the thermal input of the cycle, provided by either combustion or with a heat exchanger, and is the power produced by the cycle.
The power produced is considered comprehensive of the produced power during the expansion process of the working fluid and the one consumed during the compression step.
The typical conceptual configuration of a transcritical cycle employs a single heater, thanks to the absence of drastic phase change from one state to another, being the pressure above the critical one. In subcritical cycles, instead, the heating process of the working fluid occurs in three different heat exchangers: in economizers the working fluid is heated (while remaining in the liquid phase) up to a condition approaching the saturated liquid conditions. Evaporators accomplish fluid evaporation process (typically up to the saturated vapour conditions) and in superheaters the working fluid is heated form the saturated vapour conditions to a superheated vapor. Moreover, using Rankine cycles as bottoming cycles in the context of combined gas-steam cycles keeps the configuration of the former ones as always subcritical. Therefore, there will be multiple pressure levels and hence multiple evaporators, economizers and superheaters, which introduces a significant complication to the heat injection process in the cycle. | 0 | Theoretical and Fundamental Chemistry |
Heterogeneous photocatalysis is the process that underpins the activity of most architectural materials, such as glass, ceramic tiles, roof tiles, concrete, paint, and fabrics which are promoted as being self-cleaning (or air-purifying). These photocatalytic materials facilitate the oxidative mineralisation of organic and inorganic species by ambient oxygen on their surfaces, rendering the surfaces clean and, usually, hydrophilic. In most commercial photocatalytic products the active layer is a thin, clear, colourless coating of the semiconductor anatase titania, which requires UV light to photogenerate the necessary electrons (e) and holes (h), in its conductance and valence bands, respectively, to promote the photocatalytic process. A schematic of the key processes behind the photocatalytic mineralisation of an organic pollutant on the surface of a titania photocatalyst film is illustrated in figure 1 and the overall reaction is summarised by:
Water molecules—adsorbed to the photocatalyst—are also needed to generate the hydroxyl groups on the surface.
The marketing of photocatalytic products and prevention of counterfeiting is made difficult because the photocatalytic coatings are usually and necessarily invisible to the eye. One way to achieve a visual demonstration of photocatalysis is to use a dyestuff, like methylene blue, dissolved in water, as the organic species to be mineralised, since, as the photocatalytic process proceeds, the colour of the dye disappears as it is oxidised. This approach forms the basis of a well-established ISO test for photocatalytic activity of films ISO. However, most photocatalyst commercial products use only a thin layer of titania (e.g. ca. 15 nm thick in self-cleaning glass) and ambient UV levels are often low (e.g. for a sunny day in the UK the UVA irradiance is only ca. 4 mW/cm). As a consequence, the photocatalytic oxidative bleaching of methylene blue is usually very slow, taking many hours, and so inappropriate for marketing at least. | 0 | Theoretical and Fundamental Chemistry |
The GC–MS is composed of two major building blocks: the gas chromatograph and the mass spectrometer. The gas chromatograph utilizes a capillary column whose properties regarding molecule separation depend on the column's dimensions (length, diameter, film thickness) as well as the phase properties (e.g. 5% phenyl polysiloxane). The difference in the chemical properties between different molecules in a mixture and their relative affinity for the stationary phase of the column will promote separation of the molecules as the sample travels the length of the column. The molecules are retained by the column and then elute (come off) from the column at different times (called the retention time), and this allows the mass spectrometer downstream to capture, ionize, accelerate, deflect, and detect the ionized molecules separately. The mass spectrometer does this by breaking each molecule into ionized fragments and detecting these fragments using their mass-to-charge ratio.
These two components, used together, allow a much finer degree of substance identification than either unit used separately. It is not possible to make an accurate identification of a particular molecule by gas chromatography or mass spectrometry alone. The mass spectrometry process normally requires a very pure sample while gas chromatography using a traditional detector (e.g. Flame ionization detector) cannot differentiate between multiple molecules that happen to take the same amount of time to travel through the column (i.e. have the same retention time), which results in two or more molecules that co-elute. Sometimes two different molecules can also have a similar pattern of ionized fragments in a mass spectrometer (mass spectrum). Combining the two processes reduces the possibility of error, as it is extremely unlikely that two different molecules will behave in the same way in both a gas chromatograph and a mass spectrometer. Therefore, when an identifying mass spectrum appears at a characteristic retention time in a GC–MS analysis, it typically increases certainty that the analyte of interest is in the sample. | 0 | Theoretical and Fundamental Chemistry |
Methanesulfonic acid (MsOH) or methanesulphonic acid (in British English) is an organosulfuric, colorless liquid with the molecular formula and structure . It is the simplest of the alkylsulfonic acids (). Salts and esters of methanesulfonic acid are known as mesylates (or methanesulfonates, as in ethyl methanesulfonate). It is hygroscopic in its concentrated form. Methanesulfonic acid can dissolve a wide range of metal salts, many of them in significantly higher concentrations than in hydrochloric acid (HCl) or sulfuric acid (). | 0 | Theoretical and Fundamental Chemistry |
In contrast with jawed vertebrates whose immunity is based on variable, diverse, and joining gene segments (VDJs) of immunoglobulins, the jawless invertebrates, such as lamprey and hagfish, create a receptor diversity by somatic DNA rearrangement of leucine-rich repeat (LRR) modules that are incorporate in *vlr* genes (variable leukocyte receptors). Those LRR form 3D structures resembling curved solenoids that selectively bind specific glycans.
A study from University of Maryland has shown that lamprey antibodies (lambodies) could selectively bind to tumor-associated carbohydrate antigens (such as Tn and TF) at nanomolar affinities. The T-nouvelle antigen (Tn) and TF are present in proteins in as much as 90% of different cancer cells after post-translational modification, whereas in healthy cells those antigens are much more complex. A selection of lambodies that could bind to aGPA, a human erythrocyte membrane glycoprotein that is covered with 16 TF moieties, through magnetic-activated cell sorting (MACS) and fluorescence-activated cell sorting (FACS) has yielded a leucine-rich lambody VLRB.aGPA.23. This lambody selectively stained (over healthy samples) cells from 14 different types of adenocarcinomas: bladder, esophagus, ovary, tongue, cheek, cervix, liver, nose, nasopharynx, greater omentum, colon, breast, larynx, and lung. Moreover, patients whose tissues stained positive with VLRB.aGPA.23 had a significantly smaller survival rate.
A close look at the crystal structure of VLRB.aGPA.23 reveals a tryptophan residue at position 187 right over the carbohydrate binding pocket. | 1 | Applied and Interdisciplinary Chemistry |
As mentioned in the previous section, early repolarization is known as appearing as elevated wave segments on ECGs. Recent studies have shown a connection between early repolarization and sudden cardiac death, which is identified as early repolarization syndrome. The condition is shown in both ventricular fibrillation without other structural heart defects as well as an early depolarization pattern, which can be seen on ECG.
The primary root of early repolarization syndrome stems from malfunctions of electrical conductance in ion channels, which may be due to genetic factors. Malfunctions of the syndrome include fluctuating sodium, potassium, and calcium currents. Changes in these currents may result in overlap of myocardial regions undergoing different phases of the action potential simultaneously, leading to risk of ventricular fibrillation and arrhythmias.
Upon being diagnosed, most individuals do not need immediate intervention, as early repolarization on an ECG does not indicate any life-threatening medical emergency. Three to thirteen percent of healthy individuals have been observed to have early repolarization on an ECG. However, patients who display early repolarization after surviving an event of early repolarization syndrome (a sudden-cardiac death experience), an implantable cardioverter-defibrillator (ICD) is strongly recommended. In addition, a patient may be more prone to atrial fibrillation if the individual has early repolarization syndrome and is under sixty years of age. | 0 | Theoretical and Fundamental Chemistry |
Photon upconversion is the process of using two low-energy (e.g., infrared) photons to produce one higher energy photon; downconversion is the process of using one high energy photon (e.g., ultraviolet) to produce two lower energy photons. Either of these techniques could be used to produce higher efficiency solar cells by allowing solar photons to be more efficiently used. The difficulty, however, is that the conversion efficiency of existing phosphors exhibiting up- or down-conversion is low, and is typically narrow band.
One upconversion technique is to incorporate lanthanide-doped materials (Erbium|, Ytterbium|, Holmium| or a combination), taking advantage of their luminescence to convert infrared radiation to visible light. Upconversion process occurs when two infrared photons are absorbed by rare-earth ions to generate a (high-energy) absorbable photon. As example, the energy transfer upconversion process (ETU), consists in successive transfer processes between excited ions in the near infrared. The upconverter material could be placed below the solar cell to absorb the infrared light that passes through the silicon. Useful ions are most commonly found in the trivalent state. ions have been the most used. ions absorb solar radiation around 1.54 µm. Two ions that have absorbed this radiation can interact with each other through an upconversion process. The excited ion emits light above the Si bandgap that is absorbed by the solar cell and creates an additional electron–hole pair that can generate current. However, the increased efficiency was small. In addition, fluoroindate glasses have low phonon energy and have been proposed as suitable matrix doped with ions. | 0 | Theoretical and Fundamental Chemistry |
Samoa, a former German colony, had been RHT for more than a century, but switched to LHT in 2009, making it the first territory in almost 30 years to change sides. The move was legislated in 2008 to allow Samoans to use cheaper vehicles imported from Australia, New Zealand, or Japan, and to harmonise with other South Pacific nations. A political party, The Peoples Party, was formed by the group People Against Switching Sides (PASS) to protest against the change, with PASS launching a legal challenge; in April 2008 an estimated 18,000 people attended demonstrations against switching. The motor industry was also opposed, as 14,000 of Samoas 18,000 vehicles were designed for RHT and the government refused to meet the cost of conversion. After months of preparation, the switch from right to left happened in an atmosphere of national celebration. There were no reported incidents. At 05:50 local time, Monday 7 September, a radio announcement halted traffic, and an announcement at 6:00 ordered traffic to switch to LHT. The change coincided with more restrictive enforcement of speeding and seat-belt laws. That day and the following were declared public holidays, to reduce traffic. The change included a three-day ban on alcohol sales, while police mounted dozens of checkpoints, warning drivers to drive slowly. | 0 | Theoretical and Fundamental Chemistry |
Wetting is the ability of a liquid to maintain contact with a solid surface, resulting from intermolecular interactions when the two are brought together. This happens in presence of a gaseous phase or another liquid phase not miscible with the first one. The degree of wetting (wettability) is determined by a force balance between adhesive and cohesive forces. There are two types of wetting: non-reactive wetting and reactive wetting.
Wetting is important in the bonding or adherence of two materials. Wetting and the surface forces that control wetting are also responsible for other related effects, including capillary effects. Surfactants can be used to increase the wetting power of a liquid like water.
Wetting is a focus of research attention in nanotechnology and nanoscience studies due to the advent of many nanomaterials in the past two decades (e.g. graphene, carbon nanotube, boron nitride nanomesh). | 0 | Theoretical and Fundamental Chemistry |
In 1838, Justus von Liebig proposed that an acid is a hydrogen-containing compound whose hydrogen can be replaced by a metal. This redefinition was based on his extensive work on the chemical composition of organic acids, finishing the doctrinal shift from oxygen-based acids to hydrogen-based acids started by Davy. Liebig's definition, while completely empirical, remained in use for almost 50 years until the adoption of the Arrhenius definition. | 0 | Theoretical and Fundamental Chemistry |
Porphyrin complexes consist of a square planar MN core. The periphery of the porphyrins, consisting of sp-hybridized carbons, generally display only small deviations from planarity. Additionally, the metal is often not centered in the N plane.
Large metals such as zirconium, tantalum, and molybdenum tend to bind two porphyrin ligands. Some [M(OEP)] feature a multiple bonds between the metals. | 1 | Applied and Interdisciplinary Chemistry |
A small scale study of 289 Japanese patients suggested a minor increased predisposition from an amino acid substitution of the 196 allele at exon 6. Genomic testing of 81 SLE patients and 207 healthy patients in a Japanese study showed 37% of SLE patients had a polymorphism on position 196 of exon 6 compared to 18.8% of healthy patients. The TNFR2 196R allele polymorphism suggests that even one 196R allele results in increased risk for SLE. | 1 | Applied and Interdisciplinary Chemistry |
A primary antibody can be very useful for the detection of biomarkers for diseases such as cancer, diabetes, Parkinson’s and Alzheimer’s disease and they are used for the study of absorption, distribution, metabolism, and excretion (ADME) and multi-drug resistance (MDR) of therapeutic agents. | 1 | Applied and Interdisciplinary Chemistry |
Pratyakṣa (perception) occupies the foremost position in the Nyāya epistemology. Perception can be of two types, laukika (ordinary) and alaukika (extraordinary). Ordinary perception is defined by Akṣapāda Gautama in his Nyāya Sutra (I, i.4) as a non-erroneous cognition which is produced by the intercourse of sense-organs with the objects.
Indian texts identify four requirements for correct perception: Indriyarthasannikarsa (direct experience by ones sensory organ(s) with the object, whatever is being studied), Avyapadesya (non-verbal; correct perception is not through hearsay, according to ancient Indian scholars, where ones sensory organ relies on accepting or rejecting someone elses perception), Avyabhicara (does not wander; correct perception does not change, nor is it the result of deception because ones sensory organ or means of observation is drifting, defective, suspect) and Vyavasayatmaka (definite; correct perception excludes judgments of doubt, either because of one's failure to observe all the details, or because one is mixing inference with observation and observing what one wants to observe, or not observing what one does not want to observe).
Ordinary perception to Nyāya scholars was based on direct experience of reality by eyes, ears, nose, touch and taste. Extraordinary perception included yogaja or pratibha (intuition), samanyalaksanapratyaksa (a form of induction from perceived specifics to a universal), and jnanalaksanapratyaksa (a form of perception of prior processes and previous states of a topic of study by observing its current state). | 1 | Applied and Interdisciplinary Chemistry |
The pharmaceutical industry constitutes the most important customer base for the fine chemical industry (see Table 4). The largest companies are Pfizer, USA; Roche, Switzerland, GlaxoSmithKline, UK; Sanofi Aventis, France, and Novartis, Switzerland. All are active in R&D, manufacturing and marketing. Pharmaceuticals containing more than 2000 different active ingredients are in commerce today; a sizable number of them are sourced from the fine chemical industry. The industry also has a track record of above-average growth.
The fine chemical industry has a keen interest in the top-selling or "blockbuster drugs", i.e. those with worldwide annual sales in excess of $1 billion. Their number has increased steadily, from 27 in 1999 to 51 in 2001, 76 in 2003, and then levelled off.
Sales of the top 20 blockbuster drugs are reported in Table 6. The APIs of 12 of them are "small" (LMW) molecules. Averaging a MW of 477, they have quite complex structures. They typically show three cyclic moieties. 10 of them exhibit at least one N-heterocyclic moiety. Five of the top 10, up from none in 2005, are biopharmaceuticals. The largest-selling non-proprietary drugs are paracetamol, omeprazole, ethinylestradiol, amoxicillin, pyridoxine, and ascorbic acid.
The innovator pharma companies require mainly custom manufacturing services for their proprietary drug substances. The demand is driven primarily by the number of new drug launches, the volume requirements and the industrys "make or buy" strategy. A summary of the pros and cons for outsourcing from the pharma industrys perspective is given in Table 7. As extended studies at the Stern Business School of the New York City University have shown, financial considerations clearly favor the "buy" option.
Teva and Sandoz are by far the largest generics companies (see also chapter 6.3.2). They differ from their competitors not only in sales revenues but also because they are strongly backwards integrated and have proprietary drugs in their portfolios. They also vie for the promising biosimilars market.
Several thousand small or virtual pharma companies focus on R&D. albeit on just a few lead compounds. They typically originate mostly from academia. Therefore, their R&D strategy is more focused on the elucidation of the biological roots of diseases rather than developing synthesis methods. | 0 | Theoretical and Fundamental Chemistry |
Adding more mirrors does not add more possibilities (in the plane), because they can always be rearranged to cause cancellation. | 0 | Theoretical and Fundamental Chemistry |
* At Lokoja, Nigeria, the Benue River flows into the Niger.
* At Kazungula in Zambia, the Chobe River flows into the Zambezi. The confluence defines the tripoint of Zambia (north of the rivers), Botswana (south of the rivers) and Namibia (west of the rivers). The land border between Botswana and Zimbabwe to the east also reaches the Zambezi at this confluence, so there is a second tripoint (Zambia-Botswana-Zimbabwe) only 150 meters downstream from the first. See Kazungula and Quadripoint, and Gallery below for image.
* The Sudanese capital of Khartoum is located at the confluence of the White Nile and the Blue Nile, the beginning of the Nile. | 1 | Applied and Interdisciplinary Chemistry |
In general, volatility tends to decrease with increasing molecular mass because larger molecules can participate in more intermolecular bonding, although other factors such as structure and polarity play a significant role. The effect of molecular mass can be partially isolated by comparing chemicals of similar structure (i.e. esters, alkanes, etc.). For instance, linear alkanes exhibit decreasing volatility as the number of carbons in the chain increases. | 0 | Theoretical and Fundamental Chemistry |
The dyes used in early experimental cells (circa 1995) were sensitive only in the high-frequency end of the solar spectrum, in the UV and blue. Newer versions were quickly introduced (circa 1999) that had much wider frequency response, notably "triscarboxy-ruthenium terpyridine" [Ru(4,4',4"-(COOH)-terpy)(NCS)], which is efficient right into the low-frequency range of red and IR light. The wide spectral response results in the dye having a deep brown-black color, and is referred to simply as "black dye". The dyes have an excellent chance of converting a photon into an electron, originally around 80% but improving to almost perfect conversion in more recent dyes, the overall efficiency is about 90%, with the "lost" 10% being largely accounted for by the optical losses in top electrode.
A solar cell must be capable of producing electricity for at least twenty years, without a significant decrease in efficiency (life span). The "black dye" system was subjected to 50 million cycles, the equivalent of ten years' exposure to the sun in Switzerland. No discernible performance decrease was observed. However the dye is subject to breakdown in high-light situations. Over the last decade an extensive research program has been carried out to address these concerns. The newer dyes included 1-ethyl-3 methylimidazolium tetrocyanoborate [EMIB(CN)] which is extremely light- and temperature-stable, copper-diselenium [Cu(In,GA)Se] which offers higher conversion efficiencies, and others with varying special-purpose properties.
DSSCs are still at the start of their development cycle. Efficiency gains are possible and have recently started more widespread study. These include the use of quantum dots for conversion of higher-energy (higher frequency) light into multiple electrons, using solid-state electrolytes for better temperature response, and changing the doping of the TiO to better match it with the electrolyte being used. | 0 | Theoretical and Fundamental Chemistry |
Non-nucleoside reverse-transcriptase inhibitors (NNRTIs) are antiretroviral drugs used in the treatment of human immunodeficiency virus (HIV). NNRTIs inhibit reverse transcriptase (RT), an enzyme that controls the replication of the genetic material of HIV. RT is one of the most popular targets in the field of antiretroviral drug development.
Discovery and development of NNRTIs began in the late 1980s and in the end of 2009 four NNRTI had been approved by regulatory authorities and several others were undergoing clinical development. Drug resistance develops quickly if NNRTIs are administered as monotherapy and therefore NNRTIs are always given as part of combination therapy, the highly active antiretroviral therapy (HAART). | 1 | Applied and Interdisciplinary Chemistry |
Bioavailability is the measure by which various substances in the environment may enter into living organisms. It is commonly a limiting factor in the production of crops (due to solubility limitation or absorption of plant nutrients to soil colloids) and in the removal of toxic substances from the food chain by microorganisms (due to sorption to or partitioning of otherwise degradable substances into inaccessible phases in the environment). A noteworthy example for agriculture is plant phosphorus deficiency induced by precipitation with iron and aluminum phosphates at low soil pH and precipitation with calcium phosphates at high soil pH. Toxic materials in soil, such as lead from paint may be rendered unavailable to animals ingesting contaminated soil by supplying phosphorus fertilizers in excess. Organic pollutants such as solvents or pesticides may be rendered unavailable to microorganisms and thus persist in the environment when they are adsorbed to soil minerals or partition into hydrophobic organic matter. | 1 | Applied and Interdisciplinary Chemistry |
If a reaction occurs through these steps:
: A + S ⇌ AS → Products
where A is the reactant and S is an adsorption site on the surface and the respective rate constants for the adsorption, desorption and reaction are k, k and k, then the global reaction rate is:
where:
* r is the rate, mol·m·s
*is the concentration of adsorbate, mol·m
* is the surface concentration of occupied sites, mol·m
* is the concentration of all sites (occupied or not), mol·m
* is the surface coverage, (i.e. ) defined as the fraction of sites which are occupied, which is dimensionless
* is time, s
* is the rate constant for the surface reaction, s.
*is the rate constant for surface adsorption, m·mol·s
*is the rate constant for surface desorption, s
is highly related to the total surface area of the adsorbent: the greater the surface area, the more sites and the faster the reaction. This is the reason why heterogeneous catalysts are usually chosen to have great surface areas (in the order of a hundred m/gram)
If we apply the steady state approximation to AS, then:
: so
and
The result is equivalent to the Michaelis–Menten kinetics of reactions catalyzed at a site on an enzyme. The rate equation is complex, and the reaction order is not clear. In experimental work, usually two extreme cases are looked for in order to prove the mechanism. In them, the rate-determining step can be:
*Limiting step: adsorption/desorption
The order respect to A is 1. Examples of this mechanism are NO on gold and HI on platinum
*Limiting step: reaction of adsorbed species
The last expression is the Langmuir isotherm for the surface coverage. The adsorption equilibrium constant , and the numerator and denominator have each been divided by . The overall reaction rate becomes .
Depending on the concentration of the reactant the rate changes:
:* Low concentrations, then , that is to say a first order reaction in component A.
:* High concentration, then . It is a zeroth order reaction in component A. | 0 | Theoretical and Fundamental Chemistry |
Symmetry elements are denoted by i for centers of inversion, C for proper rotation axes, σ for mirror planes, and S for improper rotation axes (rotation-reflection axes). C and S are usually followed by a subscript number (abstractly denoted n) denoting the order of rotation possible.
By convention, the axis of proper rotation of greatest order is defined as the principal axis. All other symmetry elements are described in relation to it. A vertical mirror plane (containing the principal axis) is denoted σ; a horizontal mirror plane (perpendicular to the principal axis) is denoted σ. | 0 | Theoretical and Fundamental Chemistry |
A daily challenge in attosecond science is to characterize the temporal proprieties of the attosecond pulses used in any pump-probe experiments with atoms, molecules or solids.
The most used technique is based on the frequency-resolved optical gating for a complete reconstruction of attosecond bursts (FROG-CRAB).
The main advantage of this technique is that it allows to exploit the corroborated frequency-resolved optical gating (FROG) technique, developed in 1991 for picosecond-femtosecond pulse characterization, to the attosecond field.
Complete reconstruction of attosecond bursts (CRAB) is an extension of FROG and it is based on the same idea for the field reconstruction.
In other words, FROG-CRAB is based on the conversion of an attosecond pulse into an electron wave-packet that is freed in the continuum by atomic photoionization, as already described with Eq..
The role of the low-frequency driving laser pulse( e.g. infra-red pulse) is to behave as gate for the temporal measurement.
Then, by exploring different delays between the low-frequency and the attosecond pulse a streaking trace (or streaking spectrogram) can be obtained.
This 2D-spectrogram is later analyzed by a reconstruction algorithm with the goal of retrieving both the attosecond pulse and the IR pulse, with no need of a prior knowledge on any of them.
However, as Eq. pinpoints, the intrinsic limits of this technique is the knowledge on atomic dipole proprieties, in particular on the atomic dipole quantum phase.
The reconstruction of both the low-frequency field and the attosecond pulse from a streaking trace is typically achieved through iterative algorithms, such as:
* Principal component generalized projections algorithm (PCGPA).
* Volkov transform generalized projection algorithm (VTGPA).
* extended ptychographic iterative engine (ePIE). | 0 | Theoretical and Fundamental Chemistry |
In 2005, British researchers noticed that the net flow of the northern Gulf Stream had decreased by about 30% since 1957. Coincidentally, scientists at Woods Hole had been measuring the freshening of the North Atlantic as Earth becomes warmer. Their findings suggested that precipitation increases in the high northern latitudes, and polar ice melts as a consequence. By flooding the northern seas with excessive fresh water, global warming could, in theory, divert the Gulf Stream waters that usually flow northward, past the British Isles and Norway, and cause them to instead circulate toward the equator. Were this to happen, Europe's climate would be seriously impacted.
Don Chambers from the USF College of Marine Science mentioned, "The major effect of a slowing AMOC is expected to be cooler winters and summers around the North Atlantic, and small regional increases in sea level on the North American coast." James Hansen and Makiko Sato stated, "AMOC slowdown that causes cooling ~1°C and perhaps affects weather patterns is very different from an AMOC shutdown that cools the North Atlantic several degrees Celsius; the latter would have dramatic effects on storms and be irreversible on the century time scale." Downturn of the Atlantic meridional overturning circulation, has been tied to extreme regional sea level rise. | 0 | Theoretical and Fundamental Chemistry |
Metal complexes, also known as coordination compounds, include virtually all metal compounds. The study of "coordination chemistry" is the study of "inorganic chemistry" of all alkali and alkaline earth metals, transition metals, lanthanides, actinides, and metalloids. Thus, coordination chemistry is the chemistry of the majority of the periodic table. Metals and metal ions exist, in the condensed phases at least, only surrounded by ligands.
The areas of coordination chemistry can be classified according to the nature of the ligands, in broad terms:
* Classical (or "Werner Complexes"): Ligands in classical coordination chemistry bind to metals, almost exclusively, via their lone pairs of electrons residing on the main-group atoms of the ligand. Typical ligands are HO, NH, Cl, CN, en. Some of the simplest members of such complexes are described in metal aquo complexes, metal ammine complexes,
: Examples: [Co(EDTA)], [[Cobalt(III) hexammine chloride|[Co(NH)]]], [[Potassium ferrioxalate|[Fe(CO)]]]
* Organometallic chemistry: Ligands are organic (alkenes, alkynes, alkyls) as well as "organic-like" ligands such as phosphines, hydride, and CO.
: Example: (CH)Fe(CO)CH
* Bioinorganic chemistry: Ligands are those provided by nature, especially including the side chains of amino acids, and many cofactors such as porphyrins.
: Example: hemoglobin contains heme, a porphyrin complex of iron
: Example: chlorophyll contains a porphyrin complex of magnesium
: Many natural ligands are "classical" especially including water.
* Cluster chemistry: Ligands include all of the above as well as other metal ions or atoms as well.
: Example Ru(CO)
* In some cases there are combinations of different fields:
:Example: [[Iron–sulfur protein|[FeS(Scysteinyl)]]], in which a cluster is embedded in a biologically active species.
Mineralogy, materials science, and solid state chemistry – as they apply to metal ions – are subsets of coordination chemistry in the sense that the metals are surrounded by ligands. In many cases these ligands are oxides or sulfides, but the metals are coordinated nonetheless, and the principles and guidelines discussed below apply. In hydrates, at least some of the ligands are water molecules. It is true that the focus of mineralogy, materials science, and solid state chemistry differs from the usual focus of coordination or inorganic chemistry. The former are concerned primarily with polymeric structures, properties arising from a collective effects of many highly interconnected metals. In contrast, coordination chemistry focuses on reactivity and properties of complexes containing individual metal atoms or small ensembles of metal atoms. | 0 | Theoretical and Fundamental Chemistry |
An alternative method used to create ATP is through oxidative phosphorylation, which takes place during cellular respiration. This process utilizes the oxidation of NADH to NAD, yielding 3 ATP, and of FADH to FAD, yielding 2 ATP. The potential energy stored as an electrochemical gradient of protons (H) across the inner mitochondrial membrane is required to generate ATP from ADP and P (inorganic phosphate molecule), a key difference from substrate-level phosphorylation. This gradient is exploited by ATP synthase acting as a pore, allowing H from the mitochondrial intermembrane space to move down its electrochemical gradient into the matrix and coupling the release of free energy to ATP synthesis. Conversely, electron transfer provides the energy required to actively pump H out of the matrix. | 1 | Applied and Interdisciplinary Chemistry |
An important piece of early evidence in support of the homotropylium cation structure that did not rely on the magnetic properties of the molecule involved the acquisition of its UV spectrum. Winstein et al. determined that the absorption maxima for the homotropylium cation exhibited a considerably shorter wavelength than would be precited for the classical cyclooctatrienyl cation or the bicyclo[5.1.0]octadienyl compound with the fully formed internal cyclopropane bond (and a localized electronic structure). Instead, the UV spectrum most resembled that of the aromatic tropylium ion. Further calculations allowed Winstein to determine that the bond order between the two carbon atoms adjacent to the outlying methylene bridge is comparable to that of the π-bond separating the corresponding carbon atoms in the tropylium cation. Although this experiment proved to be highly illuminating, UV spectra are generally considered to be poor indicators of aromaticity or homoaromaticity. | 0 | Theoretical and Fundamental Chemistry |
The U.S.-based NGO Climate Foundation, in collaboration with Stanford University, has built several pilot-scale reactors to treat human waste and turn it into biochar, which can be used as an agricultural soil amendment. | 1 | Applied and Interdisciplinary Chemistry |
Together with the benzyltriethylammonium salt, benzyltrimethylammonium hydroxide is a popular phase-transfer catalyst.
It is used in aldol condensation reactions and base-catalyzed dehydration reactions. It is also used as a base in Ando's Z-selective variant of Horner-Wadsworth-Emmons Olefination reactions.
Relative to tetramethylammonium hydroxide, benzyltriethylammonium hydroxide is more labile. In 6M NaOH at 160 °C their half-lives are 61.9 and 4 h, respectively. | 0 | Theoretical and Fundamental Chemistry |
Heterofermentative bacteria produce less lactate and less ATP, but produce several other end products:
:Glucose + ADP + P → Lactate + Ethanol + CO + ATP
Examples include Leuconostoc mesenteroides, Lactobacillus bifermentous, and Leuconostoc lactis. | 1 | Applied and Interdisciplinary Chemistry |
Scientists observed the thermogenic activity in brown adipose tissue, which eventually led to the discovery of UCP1, initially known as "Uncoupling Protein". The brown tissue revealed elevated levels of mitochondria respiration and another respiration not coupled to ATP synthesis, which symbolized strong thermogenic activity. UCP1 was the protein discovered responsible for activating a proton pathway that was not coupled to ADP phosphorylation (ordinarily done through ATP Synthase). | 1 | Applied and Interdisciplinary Chemistry |
Fajans was born May 27, 1887, in Warsaw, Congress Poland, to a family of Jewish background. After he had completed secondary school in Warsaw (1904), he studied chemistry in Germany, first at the University in Leipzig, and then in Heidelberg and Zürich. In 1909 he was awarded his PhD for research into the stereoselective synthesis of chiral compounds.
In 1910 Fajans took a job at the laboratory of Ernest Rutherford in Manchester, where the nucleus was discovered. He then returned to Germany, where he became an assistant and subsequently assistant professor at the Technical University of Karlsruhe, researching radioactivity. In 1917 he headed the Faculty of Physical Chemistry at Munich University, and in 1932 became the Head of the Institute of Physical Chemistry established by the Rockefeller Foundation. In 1935 he left Germany due to escalating Nazi persecution. He stayed for a while in Cambridge and then moved to the University of Michigan where he worked until his demise. In 1959 he became an honorary member of the Polish Chemical Society.
Fajans retired at age of seventy but never stopped working. He died May 18, 1975, in Ann Arbor, Michigan. | 1 | Applied and Interdisciplinary Chemistry |
Zanamivir analogues are designed to improve the therapeutic use. Replacing the carboxylate group at the C1 to phosphonate group led the drug to be more potent with high affinity to form ionic interaction with the active site. Additionally, the click-chemistry reaction was used to synthesize the C4-triazole-modified zanamivir analogue that shows inhibitory activity close to zanamivir. Laninamivir is designed by replacing C7 hydroxy moiety with small lipophilic group, -OCH3, which resulted in an excellent inhibitory activity. The C8 and C9 diol play an important role in the binding affinity with neuraminidase, prolonging the effect. The polymer scaffolds at the C7 position of zanamivir via an alkyl ether has gained more attention as this showed enhanced antiviral activity. | 1 | Applied and Interdisciplinary Chemistry |
The effect of friction, between the air and the land, breaks the geostrophic balance. Friction slows the flow, lessening the effect of the Coriolis force. As a result, the pressure gradient force has a greater effect and the air still moves from high pressure to low pressure, though with great deflection. This explains why high-pressure system winds radiate out from the center of the system, while low-pressure systems have winds that spiral inwards.
The geostrophic wind neglects frictional effects, which is usually a good approximation for the synoptic scale instantaneous flow in the midlatitude mid-troposphere. Although ageostrophic terms are relatively small, they are essential for the time evolution of the flow and in particular are necessary for the growth and decay of storms. Quasigeostrophic and semi geostrophic theory are used to model flows in the atmosphere more widely. These theories allow for a divergence to take place and for weather systems to then develop. | 1 | Applied and Interdisciplinary Chemistry |
Deoxyguanosine is composed of the purine nucleobase guanine linked by its N9 nitrogen to the C1 carbon of deoxyribose. It is similar to guanosine, but with one hydroxyl group removed from the 2 position of the ribose sugar (making it deoxyribose). If a phosphate group is attached at the 5 position, it becomes deoxyguanosine monophosphate.
Deoxyguanosine is one of the four deoxyribonucleosides that make up DNA. | 1 | Applied and Interdisciplinary Chemistry |
The increase of ocean acidity decelerates the rate of calcification in salt water, leading to smaller and slower growing coral reefs which supports approximately 25% of marine life. Impacts are far-reaching from fisheries and coastal environments down to the deepest depths of the ocean. The increase in ocean acidity in not only killing the coral, but also the wildly diverse population of marine inhabitants which coral reefs support. | 0 | Theoretical and Fundamental Chemistry |
UV light (specifically, UV‑B) causes the body to produce vitamin D, which is essential for life. Humans need some UV radiation to maintain adequate vitamin D levels. According to the World Health Organization:
Vitamin D can also be obtained from food and supplementation. Excess sun exposure produces harmful effects, however.
Vitamin D promotes the creation of serotonin. The production of serotonin is in direct proportion to the degree of bright sunlight the body receives. Serotonin is thought to provide sensations of happiness, well-being and serenity to human beings. | 0 | Theoretical and Fundamental Chemistry |
When it is time for a cell to enter S phase, complexes of cyclin-dependent kinases (CDK) and cyclins phosphorylate pRb, allowing E2F-DP to dissociate from pRb and become active. When E2F is free it activates factors like cyclins (e.g. cyclin E and cyclin A), which push the cell through the cell cycle by activating cyclin-dependent kinases, and a molecule called proliferating cell nuclear antigen, or PCNA, which speeds DNA replication and repair by helping to attach polymerase to DNA. | 1 | Applied and Interdisciplinary Chemistry |
3-Methyl-3-sulfanylhexan-1-ol is a primary alcohol that is hexan-1-ol which is substituted by a methyl group and a thiol group at position 3. It is the odor component of human axilla sweat and the major species at pH 7.3. | 1 | Applied and Interdisciplinary Chemistry |
The in vivo functionality and longevity of any implantable medical device is affected by the body's response to the foreign material. The body undergoes a cascade of processes defined under the foreign body response (FBR) in order to protect the host from the foreign material. The interactions between the device upon the host tissue/blood as well as the host tissue/blood upon the device must be understood in order to prevent complications and device failure.
Tissue injury caused by device implantation causes inflammatory and healing responses during FBR. The inflammatory response occurs within two time periods: the acute phase, and the chronic phase. The acute phase occurs during the initial hours to days of implantation, and is identified by fluid and protein exudation along with a neutrophilic reaction. During the acute phase, the body attempts to clean and heal the wound by delivering excess blood, proteins, and monocytes are called to the site. Continued inflammation leads to the chronic phase, which can be categorized by the presence of monocytes, macrophages, and lymphocytes. In addition, blood vessels and connective tissue form in order to heal the wounded area. | 1 | Applied and Interdisciplinary Chemistry |
This model suggests that enzymes exist in a variety of conformations, only some of which are capable of binding to a substrate. When a substrate is bound to the protein, the equilibrium in the conformational ensemble shifts towards those able to bind ligands (as enzymes with bound substrates are removed from the equilibrium between the free conformations). | 1 | Applied and Interdisciplinary Chemistry |
Polythiophene (PTh) and its derivatives-based polymers are also one kind of conjugated polymers for PTT. Polythiophene-based polymers usually exhibit excellent photostability, large light-harvesting ability, easy synthesis, and facile functionalization with different substituents.
Conjugated copolymer (C3) with promising photothermal properties can be prepared by linking 2-N,N′-bis(2-(ethyl)hexyl)-perylene-3,4,9,10-tetra-carboxylic acid bis-imide to a thienylvinylene oligomer. C3 was coprecipitated with PEG-PCL and indocyanine green (ICG) to obtain PEG-PCL-C3-ICG nanoparticles for fluorescence-guided photothermal/photodynamic therapy against oral squamous cell carcinoma (OSCC). A biodegradable PLGA-PEGylated DPPV (poly{2,2′-[(2,5-bis(2-hexyldecyl)-3,6-dioxo-2,3,5,6-tetrahydropyrrolo[3,4-c]-pyrrole-1,4-diyl)-dithiophene]-5,5′-diyl-alt-vinylene) conjugated polymer for PA-guided PTT with PCE 71% (@ 808 nm, 0.3 W cm−2). The vinylene bonds in the main chain improves the biodegradability, biocompatibility and photothermal conversion efficiency of CPs. | 0 | Theoretical and Fundamental Chemistry |
In reality, the Couette solution is not reached instantaneously. The "startup problem" describing the approach to steady state is given by
subject to the initial condition
and with the same boundary conditions as the steady flow:
The problem can be made homogeneous by subtracting the steady solution. Then, applying separation of variables leads to the solution:
The timescale describing relaxation to steady state is , as illustrated in the figure. The time required to reach the steady state depends only on the spacing between the plates and the kinematic viscosity of the fluid, but not on . | 1 | Applied and Interdisciplinary Chemistry |
Viral vectors are genetically engineered viruses carrying modified viral DNA or RNA that has been rendered noninfectious, but still contain viral promoters and also the transgene, thus allowing for translation of the transgene through a viral promoter. However, because viral vectors frequently are lacking infectious sequences, they require helper viruses or packaging lines for large-scale transfection. Viral vectors are often designed for permanent incorporation of the insert into the host genome, and thus leave distinct genetic markers in the host genome after incorporating the transgene. For example, retroviruses leave a characteristic retroviral integration pattern after insertion that is detectable and indicates that the viral vector has incorporated into the host genome. | 1 | Applied and Interdisciplinary Chemistry |
Excessive exposure or intake may lead to a condition known as manganism, a neurodegenerative disorder that causes dopaminergic neuronal death and symptoms similar to Parkinson's disease. | 1 | Applied and Interdisciplinary Chemistry |
He was born in Kraljske Bare, near Andrijevica, on 1 January 1896, to father Milonja and mother Ružica, nee Novović. He finished primary school in his native village (1903-1907), and three grades of the lower grammar school in Podgorica (1907-1910), where he sat on a bench with Risto Stijović. He continued his education in Belgrade, where he finished the grades from the fourth to the seventh (1910-1914) in the Second Mens Gymnasium. The First World War prevented him from finishing the eighth grade of high school because he joined the military in 1914 as a student sergeant in the Royal Battalion in Montenegro. In June 1916, he was taken prisoner in Hungary, where he spent time in the camp until 23 December 1918. In 1919, he finished the eighth grade of the Second Mens Gymnasium in Belgrade, passed the matriculation exam and enrolled at the Faculty of Philosophy, departments of chemistry and physics.
He was a professor in the Faculty of Natural Sciences and Mathematics in Belgrade. In 1921, he became the first assistant professor of chemistry, as a student, and after graduating in 1922, he became a teaching assistant. He worked on his doctoral dissertation for two years at the Institute of Chemistry of the University of Nancy (1926-1928) as a scholarship holder of the French government, with Professor Vavon. He received his doctorate in July 1928 and stayed in Nancy for another year to complete his research and work. After that, he spent a year in London doing scientific work in the Chemistry Laboratory of the University College London with Nobel Laureate Robert Robertson as a scholarship holder of the Serbian Support Fund. He returned to Belgrade in October 1930. He was elected assistant professor in 1931 and associate professor in 1938. Immediately after the war, only professors Milivoje Lozanić and Vukić Mićović and assistant Sergije Lebedev were at the Department of Chemistry. He became a full professor in 1950. He was the director of the Chemical Institute in the period 1949-1960. He retired in 1966, and from 1945 until his retirement he was the head of the Department of Chemistry at the Faculty of Natural Sciences and Mathematics.
He was the dean of the Faculty of Natural Sciences and Mathematics in Belgrade from 1949 to 1952. He was the rector of the University of Belgrade for two school years, 1952-1953 and 1953-1954. Mićović was popular with his many students from all over Yugoslavia.
He became a corresponding member of the Serbian Academy of Sciences and Arts on 30 Januar 1958, and a regular member on 20 December 1961. He was the secretary of the Department of Natural and Mathematical Sciences at SANU in 1963-1965, and the general secretary of SANU from 1965 to 1971.
Mićović published a large number of scientific papers in various fields of organic chemistry: the construction of alicyclic nuclei and synthetic glycerols of the structure of esters of dicarbonate acids, determination of the constitution of quinidine carbonic acids, systematic studies on reductions by means of lithium aluminum hydride, reactions of aliphatic alcohols with lead tetracitate, studies on the chemical composition of lichens of Serbia.
Mićović contributed to chemical nomenclature and terminology in the Serbian language. He wrote the university textbook "Stereochemistry", Scientific Book, Belgrade, 1948, 565 pages. He translated from the German books by Arnold Frederik Holleman: "Textbook of Organic Chemistry" and "Inorganic Chemistry". With a group of authors, he prepared a "Chemical textbook" for high schools, published in 1968.
In addition to Serbian, he spoke English, French, German, Russian and Italian. He was a member of the French Chemical Society (French: Société Chimique de France) from 1928 to 1941. He was the vice president of the Serbian Chemical Society and a member of the Croatian Chemical Society. He has won several awards and recognitions, including the Seventh of July Award of Serbia in 1965, the Order of Labor with a Red Flag (1964) and the Order of Merit for the People with a Golden Star (1979).
He died on 19 January 1981, in Belgrade and was buried in the Belgrade New Cemetery. His bust, together with the bust of George K. Stefanović, is in front of the entrance to the Great Chemical Amphitheater (WHA) of the Faculty of Chemistry.
He was married Magdalena "Lena" Sokić (1910-1993), the daughter of Milovan Sokić, an MP and cafe owner from Ivanjica. They had three children: Ruzica, Ivan and Milutin. | 0 | Theoretical and Fundamental Chemistry |
Gene targeting is a biotechnological tool used to change the DNA sequence of an organism (hence it is a form of Genome Editing). It is based on the natural DNA-repair mechanism of Homology Directed Repair (HDR), including Homologous Recombination. Gene targeting can be used to make a range of sizes of DNA edits, from larger DNA edits such as inserting entire new genes into an organism, through to much smaller changes to the existing DNA such as a single base-pair change. Gene targeting relies on the presence of a repair template to introduce the user-defined edits to the DNA. The user (usually a scientist) will design the repair template to contain the desired edit, flanked by DNA sequence corresponding (homologous) to the region of DNA that the user wants to edit; hence the edit is targeted to a particular genomic region. In this way Gene Targeting is distinct from natural homology-directed repair, during which the ‘natural’ DNA repair template of the sister chromatid is used to repair broken DNA (the sister chromatid is the second copy of the gene). The alteration of DNA sequence in an organism can be useful in both a research context – for example to understand the biological role of a gene – and in biotechnology, for example to alter the traits of an organism (e.g. to improve crop plants). | 1 | Applied and Interdisciplinary Chemistry |
Nucleic acids are generally very large molecules. Indeed, DNA molecules are probably the largest individual molecules known. Well-studied biological nucleic acid molecules range in size from 21 nucleotides (small interfering RNA) to large chromosomes (human chromosome 1 is a single molecule that contains 247 million base pairs).
In most cases, naturally occurring DNA molecules are double-stranded and RNA molecules are single-stranded. There are numerous exceptions, however—some viruses have genomes made of double-stranded RNA and other viruses have single-stranded DNA genomes, and, in some circumstances, nucleic acid structures with three or four strands can form.
Nucleic acids are linear polymers (chains) of nucleotides. Each nucleotide consists of three components: a purine or pyrimidine nucleobase (sometimes termed nitrogenous base or simply base), a pentose sugar, and a phosphate group which makes the molecule acidic. The substructure consisting of a nucleobase plus sugar is termed a nucleoside. Nucleic acid types differ in the structure of the sugar in their nucleotides–DNA contains 2'-deoxyribose while RNA contains ribose (where the only difference is the presence of a hydroxyl group). Also, the nucleobases found in the two nucleic acid types are different: adenine, cytosine, and guanine are found in both RNA and DNA, while thymine occurs in DNA and uracil occurs in RNA.
The sugars and phosphates in nucleic acids are connected to each other in an alternating chain (sugar-phosphate backbone) through phosphodiester linkages. In conventional nomenclature, the carbons to which the phosphate groups attach are the 3-end and the 5-end carbons of the sugar. This gives nucleic acids directionality, and the ends of nucleic acid molecules are referred to as 5-end and 3-end. The nucleobases are joined to the sugars via an N-glycosidic linkage involving a nucleobase ring nitrogen (N-1 for pyrimidines and N-9 for purines) and the 1' carbon of the pentose sugar ring.
Non-standard nucleosides are also found in both RNA and DNA and usually arise from modification of the standard nucleosides within the DNA molecule or the primary (initial) RNA transcript. Transfer RNA (tRNA) molecules contain a particularly large number of modified nucleosides. | 1 | Applied and Interdisciplinary Chemistry |
The severity of injuries to the mucosa of the gastrointestinal tract is commonly rated using the Zargar criteria. | 1 | Applied and Interdisciplinary Chemistry |
A Hoffmann kiln consists of a main fire passage surrounded on each side by several small rooms. Each room contains a pallet of bricks. In the main fire passage there is a fire wagon, that holds a fire that burns continuously. Each room is fired for a specific time, until the bricks are vitrified properly, and thereafter the fire wagon is rolled to the next room to be fired.
Each room is connected to the next room by a passageway carrying hot gases from the fire. In this way, the hottest gases are directed into the room that is currently being fired. Then the gases pass into the adjacent room that is scheduled to be fired next. There the gases preheat the brick. As the gases pass through the kiln circuit, they gradually cool as they transfer heat to the brick as it is preheated and dried. This is essentially a counter-current heat exchanger, which makes for a very efficient use of heat and fuel. This efficiency is a principal advantage of the Hoffmann kiln, and is one of the reasons for its original development and continued use throughout history. In addition to the inner opening to the fire passage, each room also has an outside door, through which recently fired brick is removed, and replaced with wet brick to be dried and then fired in the next firing cycle.
In a classic Hoffmann kiln, the fire may burn continuously for years, even decades; in Iran, there are kilns that are still active and have been working continuously for 35 years. Any fuel may be used in a Hoffmann kiln, including gasoline, natural gas, heavy petroleum and wood fuel. The dimensions of a typical Hoffmann kiln are completely variable, but in average about 5 m (height) x 15 m (width) x 150 m (length). | 1 | Applied and Interdisciplinary Chemistry |
The most common side effects are fine tremor, anxiety, headache, muscle cramps, dry mouth, and palpitation. Other symptoms may include tachycardia, arrhythmia, flushing of the skin, myocardial ischemia (rare), and disturbances of sleep and behaviour. Rarely occurring, but of importance, are allergic reactions of paradoxical bronchospasms, urticaria (hives), angioedema, hypotension, and collapse. High doses or prolonged use may cause hypokalemia, which is of concern especially in patients with kidney failure and those on certain diuretics and xanthine derivatives.
Salbutamol metered dose inhalers have been described as the "single biggest source of carbon emissions from NHS medicines prescribing" due to the propellants used in the inhalers. Dry powder inhalers are recommended as a low-carbon alternative. | 0 | Theoretical and Fundamental Chemistry |
For most crystalline solid solutions, there is a variation of lattice parameters with the composition. If the lattice of such a solution is to remain coherent in the presence of a composition modulation, mechanical work has to be done to strain the rigid lattice structure. The maintenance of coherency thus affects the driving force for diffusion.
Consider a crystalline solid containing a one-dimensional composition modulation along the x-direction. We calculate the elastic strain energy for a cubic crystal by estimating the work required to deform a slice of material so that it can be added coherently to an existing slab of cross-sectional area. We will assume that the composition modulation is along the x' direction and, as indicated, a prime will be used to distinguish the reference axes from the standard axes of a cubic system (that is, along the <100>).
Let the lattice spacing in the plane of the slab be a and that of the undeformed slice a. If the slice is to be coherent after the addition of the slab, it must be subjected to a strain ε in the z and y directions which is given by:
In the first step, the slice is deformed hydrostatically in order to produce the required strains to the z and y directions. We use the linear compressibility of a cubic system 1 / ( c + 2 c ) where the c's are the elastic constants. The stresses required to produce a hydrostatic strain of δ are therefore given by:
The elastic work per unit volume is given by:
where the ε's are the strains. The work performed per unit volume of the slice during the first step is therefore given by:
In the second step, the sides of the slice parallel to the x direction are clamped and the stress in this direction is relaxed reversibly. Thus, ε = ε = 0. The result is that:
The net work performed on the slice in order to achieve coherency is given by:
or
The final step is to express c in terms of the constants referred to the standard axes. From the rotation of axes, we obtain the following:
where l, m, n are the direction cosines of the x' axis and, therefore the direction cosines of the composition modulation. Combining these, we obtain the following:
The existence of any shear strain has not been accounted for. Cahn considered this problem, and concluded that shear would be absent for modulations along <100>, <110>, <111> and that for other directions the effect of shear strains would be small. It then follows that the total elastic strain energy of a slab of cross-sectional area A is given by:
We next have to relate the strain δ to the composition variation. Let a be the lattice parameter of the unstrained solid of the average composition c. Using a Taylor series expansion about c yields the following:
in which
where the derivatives are evaluated at c. Thus, neglecting higher-order terms, we have:
Substituting, we obtain:
This simple result indicates that the strain energy of a composition modulation depends only on the amplitude and is independent of the wavelength. For a given amplitude, the strain energy W is proportional to Y. Consider a few special cases.
For an isotropic material:
so that:
This equation can also be written in terms of Youngs modulus E and Poissonss ratio υ using the standard relationships:
Substituting, we obtain the following:
For most metals, the left-hand side of this equation
is positive, so that the elastic energy will be a minimum for those directions that minimize the term: lm + mn + ln. By inspection, those are seen to be <100>. For this case:
the same as for an isotropic material. At least one metal (molybdenum) has an anisotropy of the opposite sign. In this case, the directions for minimum W will be those that maximize the directional cosine function. These directions are <111>, and
As we will see, the growth rate of the modulations will be a maximum in the directions that minimize Y. These directions, therefore, determine the morphology and structural characteristics of the decomposition in cubic solid solutions.
Rewriting the diffusion equation and including the term derived for the elastic energy yields the following:
or
which can alternatively be written in terms of the diffusion coefficient D as:
The simplest way of solving this equation is by using the method of Fourier transforms. | 0 | Theoretical and Fundamental Chemistry |
A metaborate is a borate anion consisting of boron and oxygen, with empirical formula . Metaborate also refers to any salt or ester of such anion (e.g. salts such as sodium metaborate or calcium metaborate , and esters such as methyl metaborate ). Metaborate is one of the boron's oxyanions. Metaborates can be monomeric, oligomeric or polymeric.
In aqueous solutions metaborate anion hydrolyzes to tetrahydroxyborate . For this reason, solutions or hydrated salts of the latter are often improperly named "metaborates". | 0 | Theoretical and Fundamental Chemistry |
A study on molecular markers in human aortic endothelial cells published that aglycone stopped cell migration but not monocyte adhesion, which is the initial step of atherosclerotic plaque formation. Another study exploring the benefits of extra virgin olive oil consumption in preventing age-related neurodegenerative diseases found aglycone greatly increased the cognitive performance of mice. The aglycone-fed mice displayed strong autophagic reactions, mTOR regulation, and reduced plaque deposits and ß-amyloid levels. | 0 | Theoretical and Fundamental Chemistry |
Both the term and concept of hypervalency still fall under criticism. In 1984, in response to this general controversy, Paul von Ragué Schleyer proposed the replacement of hypervalency with use of the term hypercoordination because this term does not imply any mode of chemical bonding and the question could thus be avoided altogether.
The concept itself has been criticized by Ronald Gillespie who, based on an analysis of electron localization functions, wrote in 2002 that "as there is no fundamental difference between the bonds in hypervalent and non-hypervalent (Lewis octet) molecules there is no reason to continue to use the term hypervalent."
For hypercoordinated molecules with electronegative ligands such as PF, it has been demonstrated that the ligands can pull away enough electron density from the central atom so that its net content is again 8 electrons or fewer. Consistent with this alternative view is the finding that hypercoordinated molecules based on fluorine ligands, for example PF do not have hydride counterparts, e.g. phosphorane (PH) which is unknown.
The ionic model holds up well in thermochemical calculations. It predicts favorable exothermic formation of from phosphorus trifluoride PF and fluorine F whereas a similar reaction forming is not favorable. | 0 | Theoretical and Fundamental Chemistry |
The Wöhler synthesis is the conversion of ammonium cyanate into urea. This chemical reaction was described in 1828 by Friedrich Wöhler. It is often cited as the starting point of modern organic chemistry. Although the Wöhler reaction concerns the conversion of ammonium cyanate, this salt appears only as an (unstable) intermediate. Wöhler demonstrated the reaction in his original publication with different sets of reactants: a combination of cyanic acid and ammonia, a combination of silver cyanate and ammonium chloride, a combination of lead cyanate and ammonia and finally from a combination of mercury cyanate and cyanatic ammonia (which is again cyanic acid with ammonia). | 0 | Theoretical and Fundamental Chemistry |
Some carboxylases, particularly RuBisCO, preferentially bind the lighter carbon stable isotope carbon-12 over the heavier carbon-13. This is known as carbon isotope discrimination and results in carbon-12 to carbon-13 ratios in the plant that are higher than in the free air. Measurement of this ratio is important in the evaluation of water use efficiency in plants, and also in assessing the possible or likely sources of carbon in global carbon cycle studies. | 0 | Theoretical and Fundamental Chemistry |
Water can be classified by the level of total dissolved solids (TDS) in the water:
*Fresh water: TDS is less than 1,000 ppm
*Brackish water: TDS = 1,000 to 10,000 ppm
*Saline water: TDS = 10,000 to 35,000 ppm
*Hypersaline: TDS greater than 35,000 ppm
Drinking water generally has a TDS below 500 ppm. Higher TDS Fresh Water is drinkable but taste may be objectionable. | 1 | Applied and Interdisciplinary Chemistry |
The citrate test detects the ability of an organism to use citrate as the sole source of carbon and energy. | 0 | Theoretical and Fundamental Chemistry |
G proteins are important signal transducing molecules in cells. "Malfunction of GPCR [G Protein-Coupled Receptor] signaling pathways are involved in many diseases, such as diabetes, blindness, allergies, depression, cardiovascular defects, and certain forms of cancer. It is estimated that about 30% of the modern drugs' cellular targets are GPCRs." The human genome encodes roughly 800 G protein-coupled receptors, which detect photons of light, hormones, growth factors, drugs, and other endogenous ligands. Approximately 150 of the GPCRs found in the human genome still have unknown functions.
Whereas G proteins are activated by G protein-coupled receptors, they are inactivated by RGS proteins (for "Regulator of G protein signalling"). Receptors stimulate GTP binding (turning the G protein on). RGS proteins stimulate GTP hydrolysis (creating GDP, thus turning the G protein off). | 1 | Applied and Interdisciplinary Chemistry |
Stainless steel contains additives which are highly oxidizable, such as chromium and molybdenum. Such steels can only be decarburized by reacting with dry hydrogen, which has no water content, unlike wet hydrogen, which is produced in a way that includes some water and can otherwise be used for decarburization. | 1 | Applied and Interdisciplinary Chemistry |
According to the nuclear shell model, there exists a class of isomers, for which, in a first approximation, it is sufficient to consider one single nucleon, called the "optical" nucleon, to get an estimate of the difference between the charge distributions of the two isomer states, the rest of the nucleons being filtered out. This applies in particular for isomers in odd-proton–even-neutron nuclei, with nearly closed shells. Indium-115, for which the effect was calculated, is such an example. The result of the calculation was that the isomeric shift on atomic spectral lines, although rather small, turned out to be two orders of magnitude bigger than a typical natural line width, which constitutes the limit of optical measurability.
The shift measured three years later in Hg-197 was quite close to that calculated for In-115, although in Hg-197, unlike in In-115, the optical nucleon is a neutron instead of a proton, and the electron–free-neutron interaction is much smaller than the electron—free-proton interaction. This is a consequence of the fact that the optical nucleons are not free, but bound particles. Thus the results could be explained within the theory by associating with the odd optical neutron an effective electric charge of Z/A. | 0 | Theoretical and Fundamental Chemistry |
The most commonly used and commercially available fluorescent base analogue, 2-aminopurine (2-AP), has a high-fluorescence quantum yield free in solution (0.68) that is considerably reduced (appr. 100 times but highly dependent on base sequence) when incorporated into nucleic acids. The emission sensitivity of 2-AP to immediate surroundings is shared by other promising and useful fluorescent base analogues like 3-MI, 6-MI, 6-MAP, pyrrolo-dC (also commercially available), modified and improved derivatives of pyrrolo-dC, furan-modified bases and many other ones (see recent reviews). This sensitivity to the microenvironment has been utilized in studies of e.g. structure and dynamics within both DNA and RNA, dynamics and kinetics of DNA-protein interaction and electron transfer within DNA.
A newly developed and very interesting group of fluorescent base analogues that has a fluorescence quantum yield that is nearly insensitive to their immediate surroundings is the tricyclic cytosine family. 1,3-Diaza-2-oxophenothiazine, tC, has a fluorescence quantum yield of approximately 0.2 both in single- and in double-strands irrespective of surrounding bases. Also the oxo-homologue of tC called tC (both commercially available), 1,3-diaza-2-oxophenoxazine, has a quantum yield of 0.2 in double-stranded systems. However, it is somewhat sensitive to surrounding bases in single-strands (quantum yields of 0.14–0.41). The high and stable quantum yields of these base analogues make them very bright, and, in combination with their good base analogue properties (leaves DNA structure and stability next to unperturbed), they are especially useful in fluorescence anisotropy and FRET measurements, areas where other fluorescent base analogues are less accurate. Also, in the same family of cytosine analogues, a FRET-acceptor base analogue, tC, has been developed. Together with tC as a FRET-donor this constitutes the first nucleic acid base analogue FRET-pair ever developed. The tC-family has, for example, been used in studies related to polymerase DNA-binding and DNA-polymerization mechanisms. | 1 | Applied and Interdisciplinary Chemistry |
This derivation
based on statistical mechanics was originally provided by Volmer and Mahnert in 1925. The partition function of the finite number of adsorbents adsorbed on a surface, in a canonical ensemble, is given by
where is the partition function of a single adsorbed molecule, is the number of adsorption sites (both occupied and unoccupied), and is the number of adsorbed molecules which should be less than or equal to . The terms in the bracket give the total partition function of the adsorbed molecules by taking a product of the individual partition functions (refer to Partition function of subsystems). The factor accounts for the overcounting arising due to the indistinguishable nature of the adsorbates. The grand canonical partition function is given by
is the chemical potential of an adsorbed molecule. As it has the form of binomial series, the summation is reduced to
where
The grand canonical potential is
based on which the average number of occupied sites is calculated
which gives the coverage
Now, invoking the condition that the system is in equilibrium, that is, the chemical potential of the adsorbed molecules is equal to that of the molecules in gas phase, we have
The chemical potential of an ideal gas is
where is the Helmholtz free energy of an ideal gas with its partition function
is the partition function of a single particle in the volume of (only consider the translational freedom here).
We thus have , where we use Stirling's approximation.
Plugging to the expression of , we have
which gives the coverage
By defining
and using the identity , finally, we have
It is plotted in the figure alongside demonstrating that the surface coverage increases quite rapidly with the partial pressure of the adsorbants, but levels off after P reaches P. | 0 | Theoretical and Fundamental Chemistry |
If the post-synaptic cell is a sensory neuron, then an increased firing rate in that neuron will transmit the signal to the central nervous system for integration. Whereas, if the post-synaptic cell is a connective pillar cell or a vascular smooth muscle cell, then the serotonin will cause vasoconstriction and previously unused lamellae will be recruited through recruitment of more capillary beds, and the total surface area for gas exchange per lamella will be increased.
In fish, the hypoxic signal is carried up to the brain for processing by the glossopharyngeal (cranial nerve IX) and vagus (cranial nerve X) nerves. The first branchial arch is innervated by the glossopharyngeal nerve (cranial nerve IX); however all four arches are innervated by the vagus nerve (cranial nerve X). Both the glossopharyngeal and vagus nerves carry sensory nerve fibres into the brain and central nervous system. | 0 | Theoretical and Fundamental Chemistry |
Some common analytes that clinical chemistry tests analyze include:
;Electrolytes
*Sodium
*Potassium
*Chloride
*Bicarbonate
;Renal (kidney) function tests
*Creatinine
*Blood urea nitrogen
;Liver function tests
*Total protein (serum)
**Albumin
**Globulins
**A/G ratio (albumin-globulin)
**Protein electrophoresis
**Urine protein
*Bilirubin; direct; indirect; total
*Aspartate transaminase (AST)
*Alanine transaminase (ALT)
*Gamma-glutamyl transpeptidase (GGT)
*Alkaline phosphatase (ALP)
;Cardiac markers
*H-FABP
*Troponin
*Myoglobin
*CK-MB
*B-type natriuretic peptide (BNP)
;Minerals
*Calcium
*Magnesium
*Phosphate
*Potassium
;Blood disorders
*Iron
*Transferrin
*TIBC
*Vitamin B12
*Vitamin D
*Folic acid
;Miscellaneous
*Glucose
*C-reactive protein
*Glycated hemoglobin (HbA1c)
*Uric acid
*Arterial blood gases ([H], P</sub>)
*Adrenocorticotropic hormone (ACTH)
*Toxicological screening and forensic toxicology (drugs and toxins)
*Neuron-specific enolase (NSE)
*fecal occult blood test (FOBT) | 1 | Applied and Interdisciplinary Chemistry |
Inland acid sulfate soil systems across Australia: CRC LEME Open File Report 249 (Fitzpatrick and Shand, 2008) provides a comprehensive introduction to the subject as well as more detailed discussion on select aspects such as the mineralogy of and toxic gas emissions from acid sulfate soils. The report also contains a range of Australian case studies that demonstrate environmental and community health hazards posed by acid sulfate soils, and how these hazards were or were not effectively managed. | 0 | Theoretical and Fundamental Chemistry |
In the idealized model, the chemical components of the and bulk phases remain unchanged except when approaching the dividing surface. The total moles of any component (Examples include: water, ethylene glycol etc.) remains constant in the bulk phases but varies in the surface phase for the real system model as shown below.
In the real system, however, the total moles of a component varies depending on the arbitrary placement of the dividing surface. The quantitative measure of adsorption of the -th component is captured by the surface excess quantity. The surface excess represents the difference between the total moles of the -th component in a system and the moles of the -th component in a particular phase (either or ) and is represented by:
where is the surface excess of the -th component, are the moles, and are the phases, and is the area of the dividing surface.
represents excess of solute per unit area of the surface over what would be present if the bulk concentration prevailed all the way to the surface, it can be positive, negative or zero. It has units of mol/m. | 0 | Theoretical and Fundamental Chemistry |
Bisulfite sequencing applies routine sequencing methods on bisulfite-treated genomic DNA to determine methylation status at CpG dinucleotides. Other non-sequencing strategies are also employed to interrogate the methylation at specific loci or at a genome-wide level. All strategies assume that bisulfite-induced conversion of unmethylated cytosines to uracil is complete, and this serves as the basis of all subsequent techniques. Ideally, the method used would determine the methylation status separately for each allele. Alternative methods to bisulfite sequencing include Combined Bisulphite Restriction Analysis and methylated DNA immunoprecipitation (MeDIP).
Methodologies to analyze bisulfite-treated DNA are continuously being developed. To summarize these rapidly evolving methodologies, numerous review articles have been written.
The methodologies can be generally divided into strategies based on methylation-specific PCR (MSP) (Figure 4), and strategies employing polymerase chain reaction (PCR) performed under non-methylation-specific conditions (Figure 3). Microarray-based methods use PCR based on non-methylation-specific conditions also. | 1 | Applied and Interdisciplinary Chemistry |
CK1δ and CK1ε were thought to be generally redundant in circadian cycle length and protein stability. Recent research, however, has shown that CK1δ deficiency lengthens circadian period while CK1ε deficiency does not. Also, CK1α has recently been suggested to play a role redundant to CK1δ in phosphorylating PER1 although this is not consistent with other data | 1 | Applied and Interdisciplinary Chemistry |
Generally, synthetic schemes that begin with ketones () involve conversion of the ketone with the desired substituents to diaziridines (). These diaziridenes are then subsequently oxidized to form the desired diazirines.
Diaziridines can be prepared from ketones by oximation, followed by tosylation (or mesylation), and then finally by treatment with ammonia (). Generally, oximation reactions are performed by reacting the ketone with hydroxylammonium chloride () under heat in the presence of a base such as pyridine. Subsequent tosylation or mesylation of the alpha-substituted oxygen with tosyl or mesyl chloride in the presence of base yields the tosyl or mesyl oxime. The final treatment of the tosyl or mesyl oxime with ammonia produces the diaziridine.
Diaziridines can be also produced directly by the reaction of ketones with ammonia in the presence of an aminating agent such as a monochloramine or hydroxyl amine O-sulfonic acid.
Diaziridines can be oxidized to diazirines by a number of methods. These include oxidation by chromium-based reagents such as the Jones oxidation, oxidation by iodine and triethylamine, oxidation by silver oxide, oxidation by oxalyl chloride, or even electrochemical oxidation on a platinum-titanium anode. | 0 | Theoretical and Fundamental Chemistry |
In electrochemistry, electrosynthesis is the synthesis of chemical compounds in an electrochemical cell. Compared to ordinary redox reactions, electrosynthesis sometimes offers improved selectivity and yields. Electrosynthesis is actively studied as a science and also has industrial applications. Electrooxidation has potential for wastewater treatment as well. | 0 | Theoretical and Fundamental Chemistry |
Hormonal imprinting (HI) is a phenomenon which takes place at the first encounter between a hormone and its developing receptor in the critical periods of life (in unicellulars during the whole life) and determines the later signal transduction capacity of the cell. The most important period in mammals is the perinatal one, however this system can be imprinted at weaning, at puberty and in case of continuously dividing cells during the whole life. Faulty imprinting is caused by drugs, environmental pollutants and other hormone-like molecules present in excess at the critical periods with lifelong receptorial, morphological, biochemical and behavioral consequences. HI is transmitted to the hundreds of progeny generations in unicellulars and (as proved) to a few generations also in mammals. | 1 | Applied and Interdisciplinary Chemistry |
Many different fusion proteins have been created using EosFP and its engineered variants. These fusion proteins allow for the tracking of proteins within living cells while retaining complex biological functions like protein-protein interactions and protein-DNA interactions. Eos fusion constructs include those with recombination signal-binding protein (RBP) and cytokeratin. Studies have shown that it is favourable to attach the protein of interest to the N-terminal side of the EosFP label. These fusion constructs have been used to visualize nuclear translocation with androgen receptors, dynamics of the cytoskeleton with actin and vinculin and intranuclear protein movement with RBP. | 1 | Applied and Interdisciplinary Chemistry |
While there are myriad sites that have been analyzed to date within the United States, the following list will serve as examples of the subject matter:
*Auke Bay U.S. Postal Facility, Juneau, Alaska
*Esso Canada Ltd. Former Bulk Fuels Facility, Owen Sound, Ontario, Canada
*Dakin Building, Brisbane, California
*East Elk Grove Specific Plan, Elk Grove, California
*Mariners Marsh Park, Staten Island, New York
*Richmond State Hospital Farm Industrial Park, Wayne County, Indiana
*Sydney Steel Plant Lands, Sydney, Nova Scotia
*Weyerhauser Technology Center, Federal Way, Washington | 1 | Applied and Interdisciplinary Chemistry |
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