text stringlengths 105 4.57k | label int64 0 1 | label_text stringclasses 2
values |
|---|---|---|
In the case of internal exposure, the dose is not received at the moment of exposure, as happens with external exposure, since the incorporated radionuclide irradiates the various organs and tissues during the time it is present in the body. By definition, the committed dose equivalent corresponds to the received dose integrated over 50 years from the date of intake. In order to calculate it, one has to know the intake activity and the value of the committed dose equivalent per unit of intake activity. The uncertainties of the first parameter are such that the committed dose equivalent can only be regarded as an order of magnitude and not as a very accurate quantity. The use of it is justified, however, for, like the dose equivalent for external exposure, it expresses the risk of stochastic effects for the individual concerned since these effects, should they appear, would do so only after a latent period which is generally longer than the dose integration time. Moreover, the use of the committed dose equivalent offers certain advantages for dosimetric management, especially when it is simplified. A practical problem which may arise is that the annual dose limit is apparently exceeded by virtue of the fact that one is taking account, in the first year, of doses which will actually be received only in the following years. These problems are rare enough in practice to be dealt with individually in each case. | 0 | Theoretical and Fundamental Chemistry |
Outside of the industrial sector, cracking of C-C and C-H bonds are rare chemical reactions. In principle, ethane can undergo homolysis:
:CHCH → 2 CH•
Because C-C bond energy is so high (377 kJ/mol), this reaction is not observed under laboratory conditions. More common examples of cracking reactions involve retro-Diels-Alder reactions. Illustrative is the thermal cracking of dicyclopentadiene to produce cyclopentadiene. | 0 | Theoretical and Fundamental Chemistry |
The energy loss of a backscattered ion is dependent on two processes: the energy lost in scattering events with sample nuclei, and the energy lost to small-angle scattering from the sample electrons. The first process is dependent on the scattering cross-section of the nucleus and thus on its mass and atomic number. For a given measurement angle, nuclei of two different elements will therefore scatter incident ions to different degrees and with different energies, producing separate peaks on an N(E) plot of measurement count versus energy. These peaks are characteristic of the elements contained in the material, providing a means of analyzing the composition of a sample by matching scattered energies to known scattering cross-sections. Relative concentrations can be determined by measuring the heights of the peaks.
The second energy loss process, the stopping power of the sample electrons, does not result in large discrete losses such as those produced by nuclear collisions. Instead it creates a gradual energy loss dependent on the electron density and the distance traversed in the sample. This energy loss will lower the measured energy of ions which backscatter from nuclei inside the sample in a continuous manner dependent on the depth of the nuclei. The result is that instead of the sharp backscattered peaks one would expect on an N(E) plot, with the width determined by energy and angular resolution, the peaks observed trail off gradually towards lower energy as the ions pass through the depth occupied by that element. Elements which only appear at some depth inside the sample will also have their peak positions shifted by some amount which represents the distance an ion had to traverse to reach those nuclei.
In practice, then, a compositional depth profile can be determined from an RBS N(E) measurement. The elements contained by a sample can be determined from the positions of peaks in the energy spectrum. Depth can be determined from the width and shifted position of these peaks, and relative concentration from the peak heights. This is especially useful for the analysis of a multilayer sample, for example, or for a sample with a composition which varies more continuously with depth.
This kind of measurement can only be used to determine elemental composition; the chemical structure of the sample cannot be determined from the N(E) profile. However, it is possible to learn something about this through RBS by examining the crystal structure. This kind of spatial information can be investigated by taking advantage of blocking and channeling. | 0 | Theoretical and Fundamental Chemistry |
Pol I is a 590 kDa enzyme that consists of 14 protein subunits (polypeptides), and its crystal structure in the yeast Saccharomyces cerevisiae was solved at 2.8Å resolution in 2013. Twelve of its subunits have identical or related counterparts in RNA polymerase II (Pol II) and RNA polymerase III (Pol III). The other two subunits are related to Pol II initiation factors and have structural homologues in Pol III.
Ribosomal DNA transcription is confined to the nucleolus, where about 400 copies of the 42.9-kb rDNA gene are present, arranged as tandem repeats in nucleolus organizer regions. Each copy contains a ~13.3 kb sequence encoding the 18S, the 5.8S, and the 28S RNA molecules, interlaced with two internal transcribed spacers, ITS1 and ITS2, and flanked upstream by a 5 external transcribed spacer and a downstream 3 external transcribed spacer. These components are transcribed together to form the 45S pre-rRNA. The 45S pre-rRNA is then post-transcriptionally cleaved by C/D box and H/ACA box snoRNAs, removing the two spacers and resulting in the three rRNAs by a complex series of steps. The 5S ribosomal RNA is transcribed by Pol III. Because of the simplicity of Pol I transcription, it is the fastest-acting polymerase and contributes up to 60% of cellular transcription levels in exponentially growing cells.
In Saccharomyces cerevisiae, the 5S rDNA has the unusual feature of lying inside the rDNA repeat. It is flanked by non-transcribed spacers NTS1 and NTS2, and is transcribed backwards by Pol III, separately from the rest of the rDNA. | 1 | Applied and Interdisciplinary Chemistry |
SCI America also works with the ACS and the AIChE to support scholars in chemistry and chemical engineering. | 1 | Applied and Interdisciplinary Chemistry |
The target DNA undergoes the first run of polymerase chain reaction with the first set of primers, shown in green. The selection of alternative and similar primer binding sites gives a selection of products, only one containing the intended sequence.
The product from the first reaction undergoes a second run with the second set of primers, shown in red. It is very unlikely that any of the unwanted PCR products contain binding sites for both the new primers, ensuring the product from the second PCR has little contamination from unwanted products. | 1 | Applied and Interdisciplinary Chemistry |
* Sweden is the leader in Europe to put ecosan into practice at a larger scale. For example, Tanum Municipality in Sweden has introduced urine separation toilets due to their very rocky and challenging terrain initially, and later also to recover phosphorus.
* Sweden has also made it possible in 2013 to certify safe and sanitized blackwater (urine and human excreta) from blackwater systems and for further use as a recognized fertilizer. Such blackwater systems could be vacuum toilets or septic tanks. The criteria for the certification have been developed by the Swedish Institute for Agricultural and Environmental Engineering and may pave the way for farmers to use human waste for agricultural production. The Federation of Swedish Farmers have been active in this development. Furthermore, the Swedish EPA in their last proposal in 2014 has downgraded the hygiene risk associated with urine.
* Stockholm Environment Institute (SEI) ran a large worldwide ecosan research programme called "Ecosanres" from 2001 to 2011. One of the "dry ecosan" pilot projects (i.e. with using dry toilets) of this programme was a large scale implementation of UDDTs in multi-story buildings together with other technologies to allow resource recovery from excreta. This project was called the Erdos Eco-Town Project in a town called Erdos in the Inner Mongolia Autonomous Region of China. It was a collaboration between the Dongsheng District government in Erdos and the Stockholm Environment Institute and aimed to save water and provide sanitation services in this drought-stricken and rapidly urbanizing area of northern China. For a variety of technical, social and institutional reasons, the UDDTs were removed after only a few years and the project failed to deliver in the area of nutrient recovery. This project is now well documented and has raised more awareness of the challenges and disadvantages of "urban ecosan".
*The Rich Earth Institute in Brattleboro, Vermont, US, is an NGO dedicated to reclaiming human urine as fertilizer. They have established the only community-scale urine nutrient reclamation program in the United States and are researching and developing treatment technologies to optimize the use of urine as fertilizer.
* SOIL in Haiti built what they call "ecosan toilets" (UDDTs) as part of the emergency relief effort following the 2010 Haiti earthquake. More than 20,000 Haitians are currently using SOIL ecological sanitation toilets and SOIL has produced over 400,000 liters of compost as a result. The compost is used for agricultural and reforestation projects. SOILs composting process is effective in inactivating Ascaris' eggs – an indicator for helminth eggs in general – in the excreta collected from the dry toilets within 16 weeks. The composting and monitoring methods used by SOIL in Haiti may serve as an example for other international settings.
* Sanitation First, an NGO in the UK is building ecosan facilities (UDDTs) in various parts of the developing world. They predominantly work in Tamil Nadu (India), where the Tamil Nadu State Government provides subsidies for their work. They have also constructed ecosan in other parts of rural India, Kenya and Sierra Leone. According to their website, 58,000 people worldwide are using their ecosan toilets in 2021.
* The NGO CREPA which was operating in the French-speaking West Africa region (now called WSA – Water and Sanitation in Africa) was very active in ecosan promotion from 2002 to 2010 with a strong focus on UDDTs coupled with reuse in agriculture, especially in Burkina Faso. | 1 | Applied and Interdisciplinary Chemistry |
An ISASMELT furnace is an upright-cylindrical shaped steel vessel that is lined with refractory bricks. There is a molten bath of slag, matte or metal (depending on the application) at the bottom of the furnace. A steel lance is lowered into the bath through a hole in the roof of the furnace, and air or oxygen-enriched air that is injected through the lance into the bath causes vigorous agitation of the bath.
Mineral concentrates or materials for recycling are dropped into the bath through another hole in the furnace roof or, in some cases, injected down the lance. These feed materials react with the oxygen in the injected gas, resulting in an intensive reaction in a small volume (relative to other smelting technologies).
ISASMELT lances contain one or more devices called "swirlers" that cause the injected gas to spin within the lance, forcing it against the lance wall, cooling it. The swirler consists of curved vanes around a central pipe forming an annular flow. They are designed to minimize pressure losses changing the angle from axial to tangential thus creating a strong vortex. The vortex helps mix liquids and solids with oxygen in the bath. The cooling effect results in a layer of slag "freezing" on the outside of the lance. This layer of solid slag protects the lance from the high temperatures inside the furnace. The tip of the lance that is submerged in the bath eventually wears out, and the worn lance is easily replaced with a new one when necessary. The worn tips are subsequently cut off and a new tip welded onto the lance body before it is returned to the furnace.
ISASMELT furnaces typically operate in the range of 1000–1200 °C, depending on the application. The refractory bricks that form the internal lining of the furnace protect the steel shell from the heat inside the furnace.
The products are removed from the furnace through one or more "tap holes" in a process called "tapping". This can be either continuous removal or in batches, with the tap holes being blocked with clay at the end of a tap, and then reopened by drilling or with a thermic lance when it is time for the next tap.
The products are allowed to separate in a settling vessel, such as a rotary holding furnace or an electric furnace.
While smelting sulfide concentrates, most of the energy needed to heat and melt the feed materials is derived from the reaction of oxygen with the sulfur and iron in the concentrate. However, a small amount of supplemental energy is required. ISASMELT furnaces can use a variety of fuels, including coal, coke, petroleum coke, oil and natural gas. The solid fuel can be added through the top of the furnace with the other feed materials, or it can be injected down the lance. Liquid and gaseous fuels are injected down the lance. | 1 | Applied and Interdisciplinary Chemistry |
A miniature animal PET has been constructed that is small enough for a fully conscious rat to be scanned. This RatCAP (Rat Conscious Animal PET) allows animals to be scanned without the confounding effects of anesthesia. PET scanners designed specifically for imaging rodents, often referred to as microPET, as well as scanners for small primates, are marketed for academic and pharmaceutical research. The scanners are based on microminiature scintillators and amplified avalanche photodiodes (APDs) through a system that uses single-chip silicon photomultipliers.
In 2018 the UC Davis School of Veterinary Medicine became the first veterinary center to employ a small clinical PET scanner as a scanner for clinical (rather than research) animal diagnosis. Because of cost as well as the marginal utility of detecting cancer metastases in companion animals (the primary use of this modality), veterinary PET scanning is expected to be rarely available in the immediate future. | 1 | Applied and Interdisciplinary Chemistry |
TEOS-10 includes the Gibbs Seawater (GSW) Oceanographic Toolbox which is available as open source software in MATLAB, Fortran, Python, C, C++, R, Julia and PHP. While TEOS-10 is generally expressed in basic SI-units, the GSW package uses input and output data in commonly used oceanographic units (such as g/kg for Absolute Salinity S and dbar for pressure p).
In addition to the GSW Oceanographic Toolbox, the Seawater-Ice-Air (SIA) Library is available for Fortran and VBA (for the use in Excel), and covers the thermodynamic properties of seawater, ice and (moist) air. In contrast to the GSW Toolbox, the SIA-Library exclusively uses basic SI-units. | 0 | Theoretical and Fundamental Chemistry |
In 2012, a team of scientists used NMR spectroscopy to measure all of the position-specific carbon isotope abundances of glucose and other sugars. It was shown that the isotope abundances are heterogeneous. Different portions of the sugar molecules are used for biosynthesis based on the metabolic pathway an organism uses. Therefore, any interpretations of position-specific isotopes of molecules downstream of glucose have to consider this intramolecular heterogeneity.
Glucose is the monomer of cellulose, the polymer that makes plants and trees rigid. After the advent of position-specific analyses of glucose, biogeochemists from Sweden looked the concentric tree rings of a Pinus nigra that recorded yearly growth between 1961 and 1995. They digested the cellulose down to its glucose units and used NMR spectroscopy to analyze its intramolecular isotopic patterns. They found correlations with position-specific isotope enrichments that were not apparent with whole molecule carbon isotope analysis of glucose. By measuring position-specific enrichments in the 6-carbon glucose molecule, they gathered six times more information from the same sample. | 0 | Theoretical and Fundamental Chemistry |
The Pedersen Process was invented by Harald Pedersen in the 1920s and used in Norway for over 40 years before shutting down due to the Pedersen Process being less economically competitive than the Bayer Process. However, it is believed a modern Pedersen process could be economically viable with "low-quality" bauxite, as even though "low-quality" bauxite has less alumina in the form of trihydrate gibbsite, it has more iron oxide which would be converted to pig iron in the smelting process instead of red mud. | 1 | Applied and Interdisciplinary Chemistry |
The Hartmann number (Ha) is the ratio of electromagnetic force to the viscous force, first introduced by Julius Hartmann (18811951) of Denmark. It is frequently encountered in fluid flows through magnetic fields. It is defined by:
where
* B is the magnetic field intensity
* L is the characteristic length scale
* σ is the electrical conductivity
* μ is the dynamic viscosity | 1 | Applied and Interdisciplinary Chemistry |
Tempered glass pipes are used for specialized applications, such as corrosive liquids, medical or laboratory wastes, or pharmaceutical manufacturing. Connections are generally made using specialized gasket or O-ring fittings. | 1 | Applied and Interdisciplinary Chemistry |
Consider a sample consisting of observations (for example, objects of unknown volume). Both assays (for example, different methods of volume measurement) are performed on each sample, resulting in data points. Each of the samples is then represented on the graph by assigning the mean of the two measurements as the -value, and the difference between the two values as the -value.
The Cartesian coordinates of a given sample with values of and determined by the two assays is
For comparing the dissimilarities between the two sets of samples independently from their mean values, it is more appropriate to look at the ratio of the pairs of measurements. Log transformation (base 2) of the measurements before the analysis will enable the standard approach to be used; so the plot will be given by the following equation:
This version of the plot is used in MA plot. | 0 | Theoretical and Fundamental Chemistry |
The Kelvin–Helmholtz instability (after Lord Kelvin and Hermann von Helmholtz) is a fluid instability that occurs when there is velocity shear in a single continuous fluid or a velocity difference across the interface between two fluids. Kelvin-Helmholtz instabilities are visible in the atmospheres of planets and moons, such as in cloud formations on Earth or the Red Spot on Jupiter, and the atmospheres of the Sun and other stars. | 1 | Applied and Interdisciplinary Chemistry |
After securing the fellowship of the Pakistan Academy of Sciences, Rahman had been affiliated with the Pakistan government regarding education and science affairs. From 1996 until 2012, Rahman served in the board of directors of the Committee on Scientific and Technological Cooperation, representing Pakistans delegation. In 1997, Rahman served as the Coordinator General of the Organisation of Islamic Cooperations (OIC) Committee on Scientific and Technological Cooperation (COMSTECH) that comprised 57 Ministers of Science and Technology from 57 OIC member countries. In recognition of his scientific transformation of Pakistan and building a large number of Centers of Excellence in the country as well as promoting scientific research, Rahman was conferred the TWAS Prize in Institution Building, in Durban, South Africa in 2009. Atta-ur-Rahman has seved as the co-chairman of UN ESCAP.
In 1999, he joined the Ministry of Science and Technology (MoSci) as its minister, assisting in drafting the official science policy of the country. In 2002, he was appointed as minister of the Ministry of Education (MoEd) as well as becoming the chairman of the Higher Education Commission (HEC) until resigning in 2008. Atta-ur-Rahman has also served as Chairman of the Prime Ministers National Task Force on Science and Technology, Co Chairman of Prime Ministers National Task Force on Information Technology and Telecommunications, and Vice Chairman of the Prime Ministers Task Force on Technology Driven Knowledge Economy during the years 2019 to 2022. He is the President of the Network of Science of Organisation of Islamic Countries (NASIC) | 0 | Theoretical and Fundamental Chemistry |
In physics, natural abundance (NA) refers to the abundance of isotopes of a chemical element as naturally found on a planet. The relative atomic mass (a weighted average, weighted by mole-fraction abundance figures) of these isotopes is the atomic weight listed for the element in the periodic table. The abundance of an isotope varies from planet to planet, and even from place to place on the Earth, but remains relatively constant in time (on a short-term scale).
As an example, uranium has three naturally occurring isotopes: U, U, and U. Their respective natural mole-fraction abundances are 99.2739–99.2752%, 0.7198–0.7202%, and 0.0050–0.0059%. For example, if 100,000 uranium atoms were analyzed, one would expect to find approximately 99,274 U atoms, approximately 720 U atoms, and very few (most likely 5 or 6) U atoms. This is because U is much more stable than U or U, as the half-life of each isotope reveals: 4.468 × 10 years for U compared with 7.038 × 10 years for U and 245,500 years for U.
Exactly because the different uranium isotopes have different half-lives, when the Earth was younger, the isotopic composition of uranium was different. As an example, 1.7×10 years ago the NA of U was 3.1% compared with today's 0.7%, and that allowed a natural nuclear fission reactor to form, something that cannot happen today.
However, the natural abundance of a given isotope is also affected by the probability of its creation in nucleosynthesis (as in the case of samarium; radioactive Sm and Sm are much more abundant than stable Sm) and by production of a given isotope as a daughter of natural radioactive isotopes (as in the case of radiogenic isotopes of lead). | 0 | Theoretical and Fundamental Chemistry |
*Sonogashira coupling
*Glaser coupling
*Cadiot–Chodkiewicz coupling
*Castro–Stephens coupling
*A3 coupling reaction | 0 | Theoretical and Fundamental Chemistry |
ISO 20815 defines "downstream" in its definition section as:<br>
3.1.8 downstream<br>
business process, most commonly in petroleum industry, associated with post-production activities.
::Example: refining, transportation and marketing of petroleum products. | 1 | Applied and Interdisciplinary Chemistry |
The axisymmetric inviscid equation is governed by the Hicks equation, that reduces when no swirl is present (i.e., zero circulation) to
where is the stream function, is the radial distance from the axis, and is the axial distance measured from the closed end of the cylinder. The function is found to predict the correct solution. The solution satisfying the required boundary conditions is given by
where is the radius of the cylinder and is the injection velocity at the wall. Despite the simple-looking formula, the solution has been experimentally verified to be accurate. The solution is wrong for distances of order since boundary layer separation at is inevitable; that is, the Taylor–Culick profile is correct for . The Taylor–Culick profile with injection at the closed end of the cylinder can also be solved analytically.
Although the solution is derived for the inviscid equation, it satisfies the non-slip condition at the wall since, as Taylor argued, any boundary layer at the sidewall will be blown off by flow injection. Hence, the flow is referred to as quasi-viscous. | 1 | Applied and Interdisciplinary Chemistry |
Global sales of proprietary drugs are estimated $735 billion in 2010, or almost 90% of the total pharma market. Global sales of generics are about $100 billion, or just over 10% of the total pharma market. Due to the much lower unit price, their market share will be close to 30% on an API volume/volume basis. | 0 | Theoretical and Fundamental Chemistry |
Marine chemistry, also known as ocean chemistry or chemical oceanography, is the study of chemical content in marine environments as influenced by plate tectonics and seafloor spreading, turbidity, currents, sediments, pH levels, atmospheric constituents, metamorphic activity, and ecology. Marine life has adapted to the chemistries unique to Earth's oceans, and marine ecosystems are sensitive to changes in ocean chemistry.
The impact of human activity on the chemistry of the Earths oceans has increased over time, with pollution from industry and various land-use practices significantly affecting the oceans. Moreover, increasing levels of carbon dioxide in the Earths atmosphere have led to ocean acidification, which has negative effects on marine ecosystems. The international community has agreed that restoring the chemistry of the oceans is a priority, and efforts toward this goal are tracked as part of Sustainable Development Goal 14.
Chemical oceanography is the study of the chemistry of Earth's oceans. An interdisciplinary field, chemical oceanographers study the distributions and reactions of both naturally occurring and anthropogenic chemicals from molecular to global scales.
Due to the interrelatedness of the ocean, chemical oceanographers frequently work on problems relevant to physical oceanography, geology and geochemistry, biology and biochemistry, and atmospheric science. Many chemical oceanographers investigate biogeochemical cycles, and the marine carbon cycle in particular attracts significant interest due to its role in carbon sequestration and ocean acidification. Other major topics of interest include analytical chemistry of the oceans, marine pollution, and anthropogenic climate change. | 0 | Theoretical and Fundamental Chemistry |
Dissolved load is the portion of a streams total sediment load that is carried in solution, especially ions from chemical weathering. It is a major contributor to the total amount of material removed from a rivers drainage basin, along with suspended load and bed load. The amount of material carried as dissolved load is typically much smaller than the suspended load, though this is not always the case, particularly when the available river flow is mostly harnessed for purposes such as irrigation or industrial uses. Dissolved load comprises a significant portion of the total material flux out of a landscape, and its composition is important in regulating the chemistry and biology of the stream water.
The dissolved load is primarily controlled by the rate of chemical weathering, which depends on climate and weather conditions such as moisture and temperature. Dissolved load has many useful applications within the field of geology, including erosion, denudation, and reconstructing climate in the past. | 0 | Theoretical and Fundamental Chemistry |
DVS measurement has applications over a wide range of industries. Both equilibrium vapor sorption isotherms and vapor sorption kinetic results can yield vital information for materials ranging from pharmaceuticals to fuel cells. Although water sorption experiments are most common, the use of organic vapor in DVS experiments can reveal additional sample properties. The below sections highlight how DVS experiments are utilized in several industries. | 0 | Theoretical and Fundamental Chemistry |
Broadly neutralizing HIV-1 antibodies (bNAbs) are neutralizing antibodies which neutralize multiple HIV-1 viral strains. bNAbs are unique in that they target conserved epitopes of the virus, meaning the virus may mutate, but the targeted epitopes will still exist. In contrast, non-bNAbs are specific for individual viral strains with unique epitopes. The discovery of bNAbs has led to an important area of research, namely, discovery of a vaccine, not only limited to HIV, but also other rapidly mutating viruses like influenza. | 1 | Applied and Interdisciplinary Chemistry |
In veterinary medicine, ampicillin is used in cats, dogs, and farm animals to treat:
* Anal gland infections
* Cutaneous infections, such as abscesses, cellulitis, and pustular dermatitis
* E. coli and Salmonella infections in cattle, sheep, and goats (oral form). Ampicillin use for this purpose had declined as bacterial resistance has increased.
* Mastitis in sows
* Mixed aerobic–anaerobic infections, such as from cat bites
* Multidrug-resistant Enterococcus faecalis and E. faecium
* Prophylactic use in poultry against Salmonella and sepsis from E. coli or Staphylococcus aureus
* Respiratory tract infections, including tonsilitis, bovine respiratory disease, shipping fever, bronchopneumonia, and calf and bovine pneumonia
* Urinary tract infections in dogs
Horses are generally not treated with oral ampicillin, as they have low bioavailability of beta-lactams.
The half-life in animals is around that same of that in humans (just over an hour). Oral absorption is less than 50% in cats and dogs, and less than 4% in horses. | 0 | Theoretical and Fundamental Chemistry |
Chitosan is a polysaccharide composed of randomly distributed β-(1-4)-linked D-glucosamine (deacetylated unit) and N-acetyl-D-glucosamine (acetylated unit). It is derived from the N-deacetylation of chitin and has been used for several applications such as drug delivery, space-filling implants and in wound dressings. However, one drawback of this polymer is its weak mechanical properties and is thus often combined with other polymers such collagen to form a polymer with stronger mechanical properties for cell encapsulation applications. | 1 | Applied and Interdisciplinary Chemistry |
Lovastatin, sold under the brand name Mevacor among others, is a statin medication, to treat high blood cholesterol and reduce the risk of cardiovascular disease. Its use is recommended together with lifestyle changes. It is taken by mouth.
Common side effects include diarrhea, constipation, headache, muscles pains, rash, and trouble sleeping. Serious side effects may include liver problems, muscle breakdown, and kidney failure. Use during pregnancy may harm the baby and use during breastfeeding is not recommended. It works by decreasing the liver's ability to produce cholesterol by blocking the enzyme HMG-CoA reductase.
Lovastatin was patented in 1979 and approved for medical use in 1987. It is on the World Health Organization's List of Essential Medicines. It is available as a generic medication. In 2021, it was the 100th most commonly prescribed medication in the United States, with more than 6million prescriptions. | 0 | Theoretical and Fundamental Chemistry |
Reduction is often expressed as a percentage. The closer it is to 100%, the better.
Letting and be as before, a reduction by % is achieved, where
;Example:
Let, as in the earlier example, the concentration of some contaminant be 580 ppm before and 0.725 ppm after treatment. Then
So this is (better than) a 99% reduction, but not yet quite a 99.9% reduction.
The following table summarizes the most common cases.
In general, if is a whole number, an -log reduction corresponds to a percentage reduction with leading digits "9" in the percentage (provided that it is at least 10%). | 0 | Theoretical and Fundamental Chemistry |
Some researchers suggest that the exclusion zone is due to a change in the geometrical structure of water, induced by the surface of the hydrophilic (or metal) solid water's structure.
In this model, the water in the exclusion zone has a structure of hexagonal sheets, where the hydrogen atoms are positioned between oxygen atoms. Moreover, hydrogen atoms bond to the oxygens atoms lying in the layer above and below so that in total each hydrogen forms three bonds. This structure can be considered as an intermediate between ice and water. However, the hexagonal sheet hypothesis does not account for all aspects of the exclusion zone, and it is not supported by the majority of physicists. | 1 | Applied and Interdisciplinary Chemistry |
Transport Phenomena contains many instances of hidden messages and other word play.
For example, the first letters of each sentence of the Preface spell out "This book is dedicated to O. A. Hougen." while in the revised second edition, the first letters of each paragraph spell out "Welcome". The first letters of each paragraph in the Postface spell out "On Wisconsin". In the first printing, in Fig. 9.L (p. 305) "Bird" is typeset safely outside the furnace wall. | 1 | Applied and Interdisciplinary Chemistry |
The Management Committee is responsible for the general management of the IIR in between Executive Committee meetings. It includes:
* the President of the Executive Committee
* three members elected every four years by the Executive Committee
* three members elected every four years by the Science and Technology Council | 0 | Theoretical and Fundamental Chemistry |
Aside from chemical requirements several key factors influence extraction efficiency:
* Retention time - refers to the time spent in the leaching system by the solids. This is calculated as the total volumetric capacity of the leach tank/s divided by the volumetric throughput of the solid/liquid slurry. Retention time is commonly measured in hours for precious metals recovery. A sequence of leach tanks is referred to as a leach "train", and retention time is measured considering the total volume of the leach train. The desired retention time is determined during the testing phase, and the system is then designed to achieve this.
* Size - The ore must be ground to a size that exposes the desired mineral to the leaching agent (referred to as “liberation”), and in tank leaching this must be a size that can be suspended by the agitator. In vat leaching this is the size that is the most economically viable, where the recovery achieved as ore is ground finer is balanced against the increased cost of processing the material.
* Slurry density - The slurry density (percent solids) determines retention time. The settling rate and viscosity of the slurry are functions of the slurry density. The viscosity, in turn, controls the gas mass transfer and the leaching rate.
* Numbers of tanks - Agitated tank leach circuits are typically designed with no less than four tanks and preferably more to prevent short-circuiting of the slurry through the tanks.
* Dissolved gas - Gas is often injected below the agitator or into the vat to obtain the desired dissolved gas levels – typically oxygen, in some base metal plants sulphur dioxide may be required.
* Reagents - Adding and maintaining the appropriate amount of reagents throughout the leach circuit is critical to a successful operation. Adding insufficient quantities of reagents reduces the metal recovery but adding excess reagents increases the operating costs without recovering enough additional metal to cover the cost •of the reagents.
The tank leaching method is commonly used to extract gold and silver from ore, such as with the Sepro Leach Reactor. | 1 | Applied and Interdisciplinary Chemistry |
The process of spliceosome formation involves the U4 and U6 snRNPs associating and forming a di-snRNP in the cell nucleus. This di-snRNP then recruits another member (U5) to become a tri-snRNP. U6 must then dissociate from U4 to bond with U2 and become catalytically active. Once splicing has been done, U6 must dissociate from the spliceosome and bond back with U4 to restart the cycle.
Prp24 has been shown to promote the binding of U4 and U6 snRNPs. Removing Prp24 results in the accumulation of free U4 and U6, and the subsequent addition of Prp24 regenerates U4/U6 and reduces the amount of free U4 and U6. Naked U6 snRNA is very compact and has little room to form base pairs with other RNA. However, when U6 snRNP associates with proteins such as Prp24, the structure is much more open, thus facilitating the binding to U4. Prp24 is not present in the U6/U4 duplex itself, and it has been suggested that Prp24 must leave the complex in order for proper base pairs to be formed. It has also been suggested that Prp24 may play a role in destabilizing U4/U6 in order for U6 to pair bases with U2. | 1 | Applied and Interdisciplinary Chemistry |
Brass was used in Lothal and Atranjikhera in the 3rd and 2nd millennium BCE. Brass and probably zinc was also found at Taxila in 4th to 3rd century BCE contexts. | 1 | Applied and Interdisciplinary Chemistry |
BioModels is a free and open-source repository for storing, exchanging and retrieving quantitative models of biological interest created in 2006. All the models in the curated section of BioModels Database have been described in peer-reviewed scientific literature.
The models stored in BioModels' curated branch are compliant with MIRIAM, the standard of model curation and annotation. The models have been simulated by curators to check that when run in simulations, they provide the same results as described in the publication. Model components are annotated, so the users can conveniently identify each model element and retrieve further information from other resources.
Modellers can submit the models in SBML and CellML. Models can subsequently be downloaded in SBML, [http://www.nrcam.uchc.edu/ VCML] , [http://www.math.pitt.edu/~bard/xpp/xpp.html XPP], SciLab, Octave, BioPAX and RDF/XML. The reaction networks of models are presented in some graphic formats, such as PNG, SVG and graphic Java applet, in which some networks were presented by following Systems Biology Graphical Notation. And a human readable summary of each model is available in PDF. | 1 | Applied and Interdisciplinary Chemistry |
Due to the relatively small sample size achievable with dealloying, the mechanical properties of these materials are often probed using the following techniques:
* Nanoindentation
* Micropillar compression
* Deflection testing of bridges
* Thin-film wrinkling | 1 | Applied and Interdisciplinary Chemistry |
The first reported synthesis and characterisation of phosphaethynolate came from Becker et al. in 1992. They were able to isolate the anion as a lithium salt (in 87% yield) by reacting lithium bis(trimethylsilyl)phosphide with dimethyl carbonate . The x-ray crystallographic analysis of the anion determined the bond length to be (indicative of a phosphorus-carbon triple bond) and the bond length to be . Similar studies were performed on derivatives of this structure and the results indicated that dimerisation to form a four-membered Li ring is favoured by this molecule.
Ten years later, in 2002, Westerhausen et al. published the use of Becker's method to make a family of alkaline earth metal salts of PCO ; this work involved the synthesis of the magnesium, calcium, strontium and barium bis-phosphaethynolates. Like the salts previously reported by Becker, the alkali-earth metal analogues were unstable to moisture and air and thus were required to be stored at low temperatures (around ) in dimethoxyethane solutions.
It was not until 2011 that the first stable salt of the phosphaethynolate anion was reported by Grutzmacher and co-workers . They managed to isolate the compound as a brown solid in 28% yield. The structure of the stable sodium salt, formed by carbonylation of sodium phosphide, contains bridging PCO units in contrast to the terminal anions found in the previously reported structures. The authors noted that this sodium salt could be handled in air as well as water without major decomposition; this emphasises the significance of the accompanying counter cation in stabilisation of PCO.
Direct carbonylation was a method also employed by Goicoechea in 2013 in order to synthesis a phosphaethynolate anion stabilised by a potassium cation sequestered in 18-crown-6 . This method required the carbonylation of solutions of at and produced by-products that were readily separated during aqueous work ups. The use of aqueous work ups reflects the high stability of the salt in water. This method afforded the PCO anion in reasonable yields around 43%. Characterisation of the compound involved infra-red spectroscopy; the band indicative of the triple bond stretch was observed at . | 0 | Theoretical and Fundamental Chemistry |
* Neutral counting assumes each bond is equally split between two atoms.
* This method begins with locating the central atom on the periodic table and determining the number of its valence electrons. One counts valence electrons for main group elements differently from transition metals, which use d electron count.
:E.g. in period 2: B, C, N, O, and F have 3, 4, 5, 6, and 7 valence electrons, respectively.
:E.g. in period 4: K, Ca, Sc, Ti, V, Cr, Fe, Ni have 1, 2, 3, 4, 5, 6, 8, 10 valence electrons respectively.
* One is added for every halide or other anionic ligand which binds to the central atom through a sigma bond.
* Two is added for every lone pair bonding to the metal (e.g. each Lewis base binds with a lone pair). Unsaturated hydrocarbons such as alkenes and alkynes are considered Lewis bases. Similarly Lewis and Bronsted acids (protons) contribute nothing.
* One is added for each homoelement bond.
* One is added for each negative charge, and one is subtracted for each positive charge. | 0 | Theoretical and Fundamental Chemistry |
In 1831, the East India Company officer William Elliott made a facsimile of the inscription. Based on this facsimile, in 1834, James Prinsep published a lithograph in the Journal of the Royal Asiatic Society of Great Britain and Ireland. However, this lithograph did not represent every single word of the inscription correctly. Some years later, British engineer T. S. Burt made an ink impression of the inscription. Based on this, in 1838, Prinsep published an improved lithograph in the same journal, with his reading of the script and translation of the text.
Decades later, Bhagwan Lal Indraji made another copy of the inscription on a cloth. Based on this copy, Bhau Daji Lad published a revised text and translation in 1875, in Journal of the Bombay Branch of the Royal Asiatic Society. This reading was the first one to correctly mention the kings name as Chandra. In 1888, John Faithfull Fleet published a critical edition of the text in Corpus Inscriptionum Indicarum'.
In 1945, Govardhan Rai Sharma dated the inscription to the first half of the 5th century CE, on paleographic grounds. He observed that its script was similar to the writing on other Gupta-Era inscriptions, including the ones discovered at Bilsad (415 CE), Baigram (449 CE), and Kahanum (449 CE). R. Balasubramaniam (2005) noted that the characters of the Delhi inscription closely resembled the dated inscriptions of Chandragupta II, found at Udayagiri in Madhya Pradesh. | 1 | Applied and Interdisciplinary Chemistry |
Cis-action or cis-acting is a vague term that, in general, means "an action on the same" in contrast to trans-action "an action on a different". In other words, the initiator of the action is affected by it. Cis-actions occur wherever circular dependencies are present. Most notably in:
* biology, where it refers to life itself as in the selfish gene, cis-acting genetic elements and self-maintenance as a trait of self-replicating entities;
* chemistry, where it is known as autocatalytic set.
* Software engineering, as in computer viruses. | 1 | Applied and Interdisciplinary Chemistry |
Inorganic ions in animals and plants are ions necessary for vital cellular activity. In body tissues, ions are also known as electrolytes, essential for the electrical activity needed to support muscle contractions and neuron activation. They contribute to osmotic pressure of body fluids as well as performing a number of other important functions. Below is a list of some of the most important ions for living things as well as examples of their functions:
* Cacalcium ions are a component of bones and teeth. They also function as biological messengers, as do most of the ions listed below. (See Hypocalcaemia.)
*Zn - zinc ions are found in very small concentrations in the body, and their main purpose is that of an antioxidant; the zinc ions act as antioxidants both generally and for liver specific pro-oxidants. Zinc ions can also act as an antioxidant-like stabilizer for some macro-molecules which bind zinc ions with high affinity, especially in cysteine-rich binding sites. These binding sites use these zinc ions as a stabilizer to protein folds, making these protein motifs more rigid in structure. These structures include zinc fingers, and have several different conformations.
* Kpotassium ions' main function in animals is osmotic balance, particularly in the kidneys. (See Hypokalemia.)
* Nasodium ions have a similar role to potassium ions. (See Sodium deficiency.)
*Mn- manganese ions are seen being used as stabilizer for varying protein configurations. However, manganese ion overexposure is linked to several neurodegenerative diseases such as Parkinson's disease.
* Mg magnesium ions are a component of chlorophyll. (See Magnesium deficiency (plants))
* Cl inability to transport chloride ions in humans manifests itself as cystic fibrosis (CF)
* Carbonate| the shells of sea creatures are calcium carbonate. In blood approximately 85% of carbon dioxide, is converted into aqueous carbonate ions (an acidic solution), allowing a greater rate of transportation.
*Co- cobalt ions are present in the human body in amounts from 1 to 2 mg. Cobalt is observed in the heart, liver, kidney, and spleen, and considerably smaller quantities in the pancreas, brain, and serum. Cobalt is a necessary component of vitamin B and a fundamental coenzyme of cell mitosis. Cobalt is crucial for amino acid formation and some proteins to create myelin sheath in nerve cells. Cobalt also plays a role in creating neurotransmitters, which are vital for proper function within the organism.
* Phosphate|adenosine triphosphate (ATP) is a common molecule which stores energy in an accessible form. Bone is calcium phosphate.
* Fe/Feas found in haemoglobin, the main oxygen carrying molecule has a central iron ion.
* Nitrate| source of nitrogen in plants for the synthesis of proteins. | 0 | Theoretical and Fundamental Chemistry |
The following are examples of sulfotransferases:
* carbohydrate sulfotransferase: CHST1, CHST2, CHST3, CHST4, CHST5, CHST6, CHST7, CHST8, CHST9, CHST10, CHST11, CHST12, CHST13, CHST14
* galactose-3-O-sulfotransferase: GAL3ST1, GAL3ST2, GAL3ST3, GAL3ST4
* heparan sulfate 2-O-sulfotransferase: HS2ST1
* heparan sulfate 3-O-sulfotransferase: HS3ST1, HS3ST2, HS3ST3A1, HS3ST3B1, HS3ST4, HS3ST5, HS3ST6
* heparan sulfate 6-O-sulfotransferase: HS6ST1, HS6ST2, HS6ST3
* N-deacetylase/N-sulfotransferase: NDST1, NDST2, NDST3, NDST4
* tyrosylprotein sulfotransferase: TPST1, TPST2
* uronyl-2-sulfotransferase
* Estrone sulfotransferase
* Chondroitin 4-sulfotransferase
* other: SULT1A1, SULT1A2, SULT1A3, SULT1A4, SULT1B1, SULT1C2, SULT1C3, SULT1C4, SULT1D1P, SULT1E1, SULT2A1, SULT2B1, SULT4A1, SULT6B1 | 1 | Applied and Interdisciplinary Chemistry |
Rofecoxib was the second selective COX-2 inhibitor to be marketed, and the first one to be taken off the market. When the pharmacokinetics were studied in healthy human subjects, the peak concentration was achieved in 9 hours with effective half-life of approximately 17 hours. A secondary peak has been observed, which might suggest that the absorption of rofecoxib varies with intestinal motility, hence leading to high variability in time until peak concentration is met. Seventy-one and a half percent of the dose was recovered in urine (less than 1% unmetabolised) and 14.2% was recovered in feces (approximately 1.8% in the bile). Among the metabolites were rofecoxib-3’,4’-dihydrodiol, 4’-hydroxyrofecoxib-O-β-D-glucuronide, 5-hydroxyrofecoxib-O-β-D-glucuronide, 5-hydroxyrofecoxib, rofecoxib-erythro-3,4-dihydrohydroxy acid, rofecoxib-threo-3,4-dihydrohydroxy acid, cis-3,4-dihydrorofecoxib and trans-3,4-dihydrorofecoxib. | 1 | Applied and Interdisciplinary Chemistry |
In zero field NMR all magnetic fields are shielded such that magnetic fields below 1 nT (nanotesla) are achieved and the nuclear precession frequencies of all nuclei are close to zero and indistinguishable. Under those circumstances the observed spectra are no-longer dictated by chemical shifts but primarily by J-coupling interactions which are independent of the external magnetic field. Since inductive detection schemes are not sensitive at very low frequencies, on the order of the J-couplings (typically between 0 and 1000 Hz), alternative detection schemes are used. Specifically, sensitive magnetometers turn out to be good detectors for zero field NMR. A zero magnetic field environment does not provide any polarization hence it is the combination of zero field NMR with hyperpolarization schemes that makes zero field NMR desirable. | 0 | Theoretical and Fundamental Chemistry |
* 1977–1983 Assistant Professor: Department of Chemistry, SUNY at Albany, Albany, NY
* 1983–1987 Associate Professor: Department of Chemistry, SUNY at Albany, Albany, NY
* 1987–1990 Professor: Department of Chemistry, SUNY at Albany, Albany, NY
* 1990–present Professor: Department of Chemistry, Johns Hopkins University, Baltimore, MD
* 2009–present Professor: Department of Bioinspired Science, WCU Program, MOBIC (Metal Oxygen BioInspired Chemistry) Group Ewha Womans University Seoul, KOREA | 0 | Theoretical and Fundamental Chemistry |
The US Environmental Protection Agency (EPA) lists the following criteria for an organism to be an ideal indicator of fecal contamination:
# The organism should be present whenever enteric pathogens are present
# The organism should be useful for all types of water
# The organism should have a longer survival time than the hardiest enteric pathogen
# The organism should not grow in water
# The organism should be found in warm-blooded animals' intestines.
None of the types of indicator organisms that are currently in use fit all of these criteria perfectly, however, when cost is considered, use of indicators becomes necessary. | 0 | Theoretical and Fundamental Chemistry |
Thure E. Cerling received his Bachelor of Science degree in geology and chemistry from Iowa State University, in Ames, Iowa, in 1972, and, in 1973, his Master of Science in geology from Iowa State. In 1977 he was awarded a Ph.D. in geology from the University of California at Berkeley. From 1977 to 1979 he worked as a research scientist at Oak Ridge National Laboratory and, from 1979 he has been a member of the University of Utah's faculty. | 0 | Theoretical and Fundamental Chemistry |
After receiving his Ph.D., he became a group leader at the Fermi Institute for Nuclear Studies at the University of Chicago and also took up a position at the Air Force Cambridge Research Laboratory in Bedford, Massachusetts. He managed radiation-effects projects studying a series of nuclear weapons tests in Nevada and the 1954 hydrogen bomb tests at the Bikini Atoll in the South Pacific.
In 1962, after witnessing the devastating effects of nuclear weapons, Martell decided to pursue a different direction in his life and took up a position as a radiochemist in the Atmospheric Chemistry Division at NCAR in Boulder, Colorado.
In 1980 he published a paper in Newscript in which he argued that radium progeny, particularly polonium-210, are responsible for the cancer-causing effects of cigarettes. He followed this up in 1983 with a [http://www.pnas.org/cgi/content/abstract/80/5/1285 subsequent research paper] in which he calculated that smokers who die of lung cancer have been exposed to 80-100 rads of radiation.
In 1993 he published a paper in which he theorized that ionizing radiation in artesian groundwater was the energy source which fueled the evolution of DNA and the first living cells, after exchanging ideas with the University of Colorado's Nobel prize-winning chemist Tom Cech. At the time of his death, he was working on a book called "Natural Radionuclides and Life". | 0 | Theoretical and Fundamental Chemistry |
Continuing his work studying the prebiotic synthesis of RNA, Orgel explored mechanisms by which inorganic phosphate and nucleotide phosphoryl groups could be chemically activated for condensation into nucleic acid polymers. Starting in the 1960s, Orgel explored a variety of cyanide-based activating agents which could have plausibly been present on a young earth. A carbodiimide reagent was found to be effective at activating nucleotide phosphoryl groups and promoting the formation of short Adenosine dimers and trimers. In 2018, John D. Sutherland and co-workers proposed that methyl isocyanide and acetaldehyde could combine to form a pre-biotic phosphate activating agent which could plausibly have formed under early-earth conditions.
Orgel also theorised that one single strand of RNA could have been the template for the first life on Earth and that these imidazole-activated nucleotides could have used this RNA template strand to polymerise and replicate. Lohrmann and Orgel reported that the phosphorimidazolide derivative of adenosine monophosphate (in which a phosphoryl group oxygen is substituted by an imidazole ring) forms short adenosine oligomers in the presence of poly-uridine templates. They further discovered that the divalent metal cation used to catalyze the reaction influenced the regiochemistry of the inter-nucleotide linkage. Pb gave primarily 5’-2’ linked nucleotides while Zn gave primarily 5’-3’ linked nucleotides from guanosine phosphorimidazolides in the presence of a poly-cytidine template. Montmorillonite clay was also shown to promote the polymerization of adenosine phosphorimidazolide into oligonucleotides tens of bases in length starting from a poly-adenosine 10-mer primer. In the absence of montmorillonite, the primer was capped through the formation of a 5’ adenosine pyrophosphate.
The oligonucleotide products in early studies were typically characterized through a combination of C radiolabeling, gel electrophoresis, and paper electrophoresis. Enzymatic digestion was used to differentiate regioisomers. The advent of HPLC allowed the characterization of long oligomers of guanosine. | 0 | Theoretical and Fundamental Chemistry |
A xerogel is a solid formed from a gel by drying with unhindered shrinkage. Xerogels usually retain high porosity (15–50%) and enormous surface area (150–900 m/g), along with very small pore size (1–10 nm). When solvent removal occurs under supercritical conditions, the network does not shrink and a highly porous, low-density material known as an aerogel is produced. Heat treatment of a xerogel at elevated temperature produces viscous sintering (shrinkage of the xerogel due to a small amount of viscous flow) which results in a denser and more robust solid, the density and porosity achieved depend on the sintering conditions. | 0 | Theoretical and Fundamental Chemistry |
A practical example used very widely in areas drawing drinking water from chalk or limestone aquifers is the addition of sodium carbonate to the raw water to reduce the hardness of the water. In the water treatment process, highly soluble sodium carbonate salt is added to precipitate out sparingly soluble calcium carbonate. The very pure and finely divided precipitate of calcium carbonate that is generated is a valuable by-product used in the manufacture of toothpaste.
The salting-out process used in the manufacture of soaps benefits from the common-ion effect. Soaps are sodium salts of fatty acids. Addition of sodium chloride reduces the solubility of the soap salts. The soaps precipitate due to a combination of common-ion effect and increased ionic strength.
Sea, brackish and other waters that contain appreciable amount of sodium ions (Na) interfere with the normal behavior of soap because of common-ion effect. In the presence of excess Na, the solubility of soap salts is reduced, making the soap less effective. | 0 | Theoretical and Fundamental Chemistry |
The following equation illustrates the relation between shear rate and shear stress for a fluid with laminar flow only in the direction x:
where:
* is the shear stress in the components x and y, i.e. the force component on the direction x per unit surface that is normal to the direction y (so it is parallel to the direction x)
* is the viscosity, and
* is the flow velocity gradient along the direction y, that is normal to the flow velocity .
If viscosity is constant, the fluid is Newtonian. | 1 | Applied and Interdisciplinary Chemistry |
Nitrification is the process by which ammonia () is converted to nitrate (). Nitrification is actually the net result of two distinct processes: oxidation of ammonia to nitrite () by nitrosifying bacteria (e.g. Nitrosomonas) and oxidation of nitrite to nitrate by the nitrite-oxidizing bacteria (e.g. Nitrobacter). Both of these processes are extremely energetically poor leading to very slow growth rates for both types of organisms. Biochemically, ammonia oxidation occurs by the stepwise oxidation of ammonia to hydroxylamine () by the enzyme ammonia monooxygenase in the cytoplasm, followed by the oxidation of hydroxylamine to nitrite by the enzyme hydroxylamine oxidoreductase in the periplasm.
Electron and proton cycling are very complex but as a net result only one proton is translocated across the membrane per molecule of ammonia oxidized. Nitrite oxidation is much simpler, with nitrite being oxidized by the enzyme nitrite oxidoreductase coupled to proton translocation by a very short electron transport chain, again leading to very low growth rates for these organisms. Oxygen is required in both ammonia and nitrite oxidation, meaning that both nitrosifying and nitrite-oxidizing bacteria are aerobes. As in sulfur and iron oxidation, NADH for carbon dioxide fixation using the Calvin cycle is generated by reverse electron flow, thereby placing a further metabolic burden on an already energy-poor process.
In 2015, two groups independently showed the microbial genus Nitrospira is capable of complete nitrification (Comammox). | 1 | Applied and Interdisciplinary Chemistry |
Tetrabutylammonium tribromide, abbreviated to TBATB, is a pale orange solid with the formula [N(CH)]Br. It is a salt of the lipophilic tetrabutylammonium cation and the linear tribromide anion. The salt is sometimes used as a reagent used in organic synthesis as a conveniently weighable, solid source of bromine. | 0 | Theoretical and Fundamental Chemistry |
In chemical thermodynamics, isothermal titration calorimetry (ITC) is a physical technique used to determine the thermodynamic parameters of interactions in solution. It is most often used to study the binding of small molecules (such as medicinal compounds) to larger macromolecules (proteins, DNA etc.) in a label-free environment. It consists of two cells which are enclosed in an adiabatic jacket. The compounds to be studied are placed in the sample cell, while the other cell, the reference cell, is used as a control and contains the buffer in which the sample is dissolved.
The technique was developed by H. D. Johnston in 1968 as a part of his Ph.D. dissertation at Brigham Young University, and was considered niche until introduced commercially by MicroCal Inc. in 1988. Compared to other calorimeters, ITC has an advantage in not requiring any correctors since there was no heat exchange between the system and the environment. | 0 | Theoretical and Fundamental Chemistry |
The most influential names in the history of alchemy include:
*Hermes Trismegistus – by tradition, the founder of Western alchemy; many alchemical works were attributed to him.
*Wei Boyang – authored the earliest known book on theoretical alchemy in China.
*Pseudo-Democritus – anonymous author of the oldest extant works of Greco-Egyptian alchemy.
*Zosimos of Panopolis – influential Greco-Egyptian alchemist.
*Khālid ibn Yazīd – credited with introducing alchemy to the Islamic world.
*Pseudo-Apollonius of Tyana – earliest known source of the sulfur-mercury theory of metals and the Emerald Tablet.
*Jābir ibn Hayyān – notable for the theory of the balance (ʿilm al-mīzān), the theory of artificial generation (ʿilm al-takwīn), and a general emphasis on experimental science.
**Pseudo-Geber – later Latin alchemist who wrote the influential Summa perfectionis.
*Roger Bacon – staunch proponent of the use of alchemy.
*Paracelsus – developer of iatrochemistry.
*Robert Boyle – alchemist critical of Paracelsus, credited as the father of modern chemistry.
*Mary Anne Atwood – key figure in the occult revival of alchemy.
*Carl Jung – merged alchemy and psychoanalytic thought. | 1 | Applied and Interdisciplinary Chemistry |
Fluids are substances that do not permanently change under an enormous amount of stress. A solid tends to deform in order to remain at equilibrium under a great deal of stress. Fluids are defined as both liquids and gases because the molecules inside the fluid are much weaker than those molecules contained in a solid. When referring to the density of a fluid in terms of a liquid, there is a small percentage of change to the liquid’s density as pressure is increased. If the fluid is referred to as a gas, the density will change greatly depending on the amount of pressure applied due to the equation of state for gases (p=ρRT). In the study of the flow of liquids, the term used while referring to the little change in density is called incompressible flow. In the study of the flow of gases, the rapid increase due to an increase of pressure is called compressible flow. | 1 | Applied and Interdisciplinary Chemistry |
Density functional theory states that when any fluid is exposed to an external potential, , then all equilibrium quantities become functions of number density profile, . As a result, the total free energy is minimized. The Grand canonical potential, , is then written
where is the chemical potential, is the temperature, and is the helmholtz free energy. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, the equivalent concentration or normality () of a solution is defined as the molar concentration divided by an equivalence factor or -factor : | 0 | Theoretical and Fundamental Chemistry |
Common synthetic polymers have main chains composed of carbon, i.e. C-C-C-C.... Examples include polyolefins such as polyethylene ((CHCH)) and many substituted derivative ((CHCH(R))) such as polystyrene (R = CH), polypropylene (R = CH), and acrylates (R = COR').
Other major classes of organic polymers are polyesters and polyamides. They have respectively -C(O)-O- and -C(O)-NH- groups in their backbones in addition to chains of carbon. Major commercial products are polyethyleneterephthalate ("PET"), ((CHCOCHOC(O))) and nylon-6 ((NH(CH)C(O))). | 0 | Theoretical and Fundamental Chemistry |
Iodine-123 (I-123) is a gamma emitter. It is used only diagnostically, as its radiation is penetrating and short-lived. | 0 | Theoretical and Fundamental Chemistry |
Despo C. Fatta-Kassinos is a chemical and environmental engineer, academic and author. She is a professor in the Department of Civil and Environmental Engineering and the first director of Nireas-International Water Research Center (Nireas-IWRC) at the University of Cyprus (2010–2022). She has been named a Highly Cited Researcher by Web of Science, Clarivate Analytics.
Best known for her work in wastewater treatment and reuse; Fatta-Kassinos co-edited Xenobiotics in the Urban Water Cycle: Mass Flows, Environmental Processes, Mitigation, and Treatment strategies, and also authored a childrens book on water titled The Secret Handbook of the Blue Circle'.
Fatta-Kassinos holds an appointment as a member of the Scientific Advisory Committee of the Catalan Institute for Water Research (ICRA), the SETAC Europe Council, and the Scientific Advisory Board of the CRETUS Research Center of the University of Santiago de Compostela in Spain. She had been appointed as a member of the Educational Council of the Diplomatic Academy of the Ministry of Foreign Affairs (Cyprus). She is the section editor for "Water and wastewater treatment" of PLOS Water. She formerly was an Associate Editor and since 2022 an Editor of Water Research, and previously served as Editor-in-Chief of the Journal of Environmental Chemical Engineering since its founding in 2012 until becoming an Executive Editor in September 2022. In 2014, she became a founding member of International Ph.D. School on Advanced Oxidation Processes, member of the Scientific and Management Committee. | 1 | Applied and Interdisciplinary Chemistry |
Iodine-131 (I, I-131) is an important radioisotope of iodine discovered by Glenn Seaborg and John Livingood in 1938 at the University of California, Berkeley. It has a radioactive decay half-life of about eight days. It is associated with nuclear energy, medical diagnostic and treatment procedures, and natural gas production. It also plays a major role as a radioactive isotope present in nuclear fission products, and was a significant contributor to the health hazards from open-air atomic bomb testing in the 1950s, and from the Chernobyl disaster, as well as being a large fraction of the contamination hazard in the first weeks in the Fukushima nuclear crisis. This is because I is a major fission product of uranium and plutonium, comprising nearly 3% of the total products of fission (by weight). See fission product yield for a comparison with other radioactive fission products. I is also a major fission product of uranium-233, produced from thorium.
Due to its mode of beta decay, iodine-131 causes mutation and death in cells that it penetrates, and other cells up to several millimeters away. For this reason, high doses of the isotope are sometimes less dangerous than low doses, since they tend to kill thyroid tissues that would otherwise become cancerous as a result of the radiation. For example, children treated with moderate dose of I for thyroid adenomas had a detectable increase in thyroid cancer, but children treated with a much higher dose did not. Likewise, most studies of very-high-dose I for treatment of Graves' disease have failed to find any increase in thyroid cancer, even though there is linear increase in thyroid cancer risk with I absorption at moderate doses. Thus, iodine-131 is increasingly less employed in small doses in medical use (especially in children), but increasingly is used only in large and maximal treatment doses, as a way of killing targeted tissues. This is known as "therapeutic use".
Iodine-131 can be "seen" by nuclear medicine imaging techniques (e.g., gamma cameras) whenever it is given for therapeutic use, since about 10% of its energy and radiation dose is via gamma radiation. However, since the other 90% of radiation (beta radiation) causes tissue damage without contributing to any ability to see or "image" the isotope, other less-damaging radioisotopes of iodine such as iodine-123 (see isotopes of iodine) are preferred in situations when only nuclear imaging is required. The isotope I is still occasionally used for purely diagnostic (i.e., imaging) work, due to its low expense compared to other iodine radioisotopes. Very small medical imaging doses of I have not shown any increase in thyroid cancer. The low-cost availability of I, in turn, is due to the relative ease of creating I by neutron bombardment of natural tellurium in a nuclear reactor, then separating I out by various simple methods (i.e., heating to drive off the volatile iodine). By contrast, other iodine radioisotopes are usually created by far more expensive techniques, starting with cyclotron radiation of capsules of pressurized xenon gas.
Iodine-131 is also one of the most commonly used gamma-emitting radioactive industrial tracer. Radioactive tracer isotopes are injected with hydraulic fracturing fluid to determine the injection profile and location of fractures created by hydraulic fracturing.
Much smaller incidental doses of iodine-131 than those used in medical therapeutic procedures, are supposed by some studies to be the major cause of increased thyroid cancers after accidental nuclear contamination. These studies suppose that cancers happen from residual tissue radiation damage caused by the I, and should appear mostly years after exposure, long after the I has decayed. Other studies did not find a correlation. | 0 | Theoretical and Fundamental Chemistry |
Most fundamental reactivity of bicarbonate/carbonato complexes is their interconversion. This acid-base reaction has been examined mainly for unimolecular complexes. Such reactions are molecular versions of the familiar reaction of acids with carbonate minerals.
Protonation of carbonato complexes gives the corresponding bicarbonate. The structure of bicarbonate complex indicates that protonation occurs at the coordinated oxygen. This process is the microscopic reverse or the first step in the carbonation of metal hydroxides. Protonation of bicarbonate ligands results in loss of carbon dioxide and formation of the metal hydroxide. Particularly well studied are the reactions of and its ethylenediamine analogue carbonatobis(ethylenediamine)cobalt(III). | 0 | Theoretical and Fundamental Chemistry |
EBSD is used in a wide range of applications, including materials science and engineering, geology, and biological research. In materials science and engineering, EBSD is used to study the microstructure of metals, ceramics, and polymers, and to develop models of material behaviour. In geology, EBSD is used to study the crystallographic structure of minerals and rocks. In biological research, EBSD is used to study the microstructure of biological tissues and to investigate the structure of biological materials such as bone and teeth. | 0 | Theoretical and Fundamental Chemistry |
In this method, the glycosyl donor is protected at C-2 by a para-methoxybenzyl (PMB) group. The glycosyl acceptor is then tethered at the benzylic position of the PMB protecting group in the presence of 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The anomeric leaving group (Y) is then activated, and the developing oxocarbenium ion is captured by the tethered aglycon alcohol (OR) to give 1,2-cis β-glycoside product. | 0 | Theoretical and Fundamental Chemistry |
Importantly, the rate of change in ocean acidification is much higher than in the geological past. This faster change prevents organisms from gradually adapting, and prevents climate cycle feedbacks from kicking in to mitigate ocean acidification. Ocean acidification is now on a path to reach lower pH levels than at any other point in the last 300 million years. The rate of ocean acidification (i.e. the rate of change in pH value) is also estimated to be unprecedented over that same time scale. These expected changes are considered unprecedented in the geological record. In combination with other ocean biogeochemical changes, this drop in pH value could undermine the functioning of marine ecosystems and disrupt the provision of many goods and services associated with the ocean, beginning as early as 2100.
The extent of further ocean chemistry changes, including ocean pH, will depend on climate change mitigation efforts taken by nations and their governments. Different scenarios of projected socioeconomic global changes are modelled by using the Shared Socioeconomic Pathways (SSP) scenarios.
Under a very high emission scenario (SSP5-8.5), model projections estimate that surface ocean pH could decrease by as much as 0.44 units by the end of this century, compared to the end of the 19th century. This would mean a pH as low as about 7.7, and represents a further increase in H+ concentrations of two to four times beyond the increase to date. | 0 | Theoretical and Fundamental Chemistry |
One fractionation schedule that is increasingly being used and continues to be studied is hypofractionation. This is a radiation treatment in which the total dose of radiation is divided into large doses. Typical doses vary significantly by cancer type, from 2.2 Gy/fraction to 20 Gy/fraction, the latter being typical of stereotactic treatments (stereotactic ablative body radiotherapy, or SABR – also known as SBRT, or stereotactic body radiotherapy) for subcranial lesions, or SRS (stereotactic radiosurgery) for intracranial lesions. The rationale of hypofractionation is to reduce the probability of local recurrence by denying clonogenic cells the time they require to reproduce and also to exploit the radiosensitivity of some tumors. In particular, stereotactic treatments are intended to destroy clonogenic cells by a process of ablation, i.e., the delivery of a dose intended to destroy clonogenic cells directly, rather than to interrupt the process of clonogenic cell division repeatedly (apoptosis), as in routine radiotherapy. | 0 | Theoretical and Fundamental Chemistry |
The prime editing tool offers advantages over traditional gene editing technologies. CRISPR/Cas9 edits rely on non-homologous end joining (NHEJ) or homology-directed repair (HDR) to fix DNA breaks, while the prime editing system employs DNA mismatch repair. This is an important feature of this technology given that DNA repair mechanisms such as NHEJ and HDR, generate unwanted, random insertions or deletions (INDELs). These are byproducts that complicate the retrieval of cells carrying the correct edit.
The prime system introduces single-stranded DNA breaks instead of the double-stranded DNA breaks observed in other editing tools, such as base editors. Collectively, base editing and prime editing offer complementary strengths and weaknesses for making targeted transition mutations. Base editors offer higher editing efficiency and fewer INDEL byproducts if the desired edit is a transition point mutation and a PAM sequence exists roughly 15 bases from the target site. However, because the prime editing technology does not require a precisely positioned PAM sequence to target a nucleotide sequence, it offers more flexibility and editing precision. Remarkably, prime editors allow all types of substitutions, transitions and transversions to be inserted into the target sequence. Cytosine base editing and adenine BE can already perform precise base transitions but for base transversions there have been no good options. Prime editing performs transversions with good usability. PE can insert up to 44bp, delete up to 80, or combinations thereof.
Because the prime system involves three separate DNA binding events (between (i) the guide sequence and the target DNA, (ii) the primer binding site and the target DNA, and (iii) the 3’ end of the nicked DNA strand and the pegRNA), it has been suggested to have fewer undesirable off-target effects than CRISPR/Cas9. | 1 | Applied and Interdisciplinary Chemistry |
The United States Environmental Protection Agency (EPA) maintains test methods, which are approved procedures for measuring the presence and concentration of physical, chemical and biological contaminants; evaluating properties, such as toxic properties, of chemical substances; or measuring the effects of substances under various conditions. The methods in the Agency index are known as EPA Methods. There are other types of methods such as the ASTM and United States Pharmacopeia, but the EPA Methods are the most widely accepted and used. | 0 | Theoretical and Fundamental Chemistry |
Calmodulin's ability to recognize a tremendous range of target proteins is due in large part to its structural flexibility. In addition to the flexibility of the central linker domain, the N- and C-domains undergo open-closed conformational cycling in the Ca-bound state. Calmodulin also exhibits great structural variability, and undergoes considerable conformational fluctuations, when bound to targets. Moreover, the predominantly hydrophobic nature of binding between calmodulin and most of its targets allows for recognition of a broad range of target protein sequences. Together, these features allow calmodulin to recognize some 300 target proteins exhibiting a variety of CaM-binding sequence motifs. | 1 | Applied and Interdisciplinary Chemistry |
Microfluidic fuel cells can use laminar flow to separate the fuel and its oxidant to control the interaction of the two fluids without the physical barrier that conventional fuel cells require. | 1 | Applied and Interdisciplinary Chemistry |
* Lyon, France lies where the Saône flows into the Rhone. A major new museum of science and anthropology, the Musée des Confluences, opened on the site in 2014.
* Near Toulouse, France lies where the Ariège (river) flows into the Garonne. Both take their source in the Pyrenees.
* The Lusatian Neisse flows into the Oder at a rural location in Poland opposite the German village of Ratzdorf. The two rivers form the Oder-Neisse line, the postwar boundary of Germany and Poland.
* The Triangle of Three Emperors, a former political tripoint, lies in present-day Poland. The empires that abutted (in the decades before World War I) were the Austrian, German, and Russian.
* Rovaniemi, the capital of Finnish Lapland and one of the largest towns above the Arctic Circle, is at the confluence of rivers Ounasjoki and Kemijoki.
* Kryvyi Rih, Ukraine is located (and named after) on the confluence of the Saksahan and Inhulets River.
* The Oka flows into the Volga at Nizhny Novgorod in Russia. The Alexander Nevsky Cathedral overlooks the site.
* The English city of Southampton is built at the confluence of the tidal estuaries of the River Test and River Itchen which combine to form Southampton Water estuary. | 1 | Applied and Interdisciplinary Chemistry |
Bubbles can be effectively used to teach and explore a wide variety of concepts to even young children. Flexibility, colour formation, reflective or mirrored surfaces, concave and convex surfaces, transparency, a variety of shapes (circle, square, triangle, sphere, cube, tetrahedron, hexagon), elastic properties, and comparative sizing, as well as the more esoteric properties of bubbles listed on this page. Bubbles are useful in teaching concepts starting from 2 years old and into college years. A Swiss university professor, Dr. Natalie Hartzell, has theorized that the usage of artificial bubbles for entertainment purposes of young children has shown a positive effect in the region of the child's brain that controls motor skills and is responsible for coordination with children exposed to bubbles at a young age showing measurably better motion skills than those who were not. | 1 | Applied and Interdisciplinary Chemistry |
Frémy's salt was discovered in 1845 by Edmond Frémy (1814–1894). Its use in organic synthesis was popularized by Hans Teuber, such that an oxidation using this salt is called the Teuber reaction. | 0 | Theoretical and Fundamental Chemistry |
PKA is directed to specific sub-cellular locations after tethering to AKAPs. Ryanodine receptor (RyR) co-localizes with the muscle AKAP and RyR phosphorylation and efflux of Ca is increased by localization of PKA at RyR by AKAPs. | 1 | Applied and Interdisciplinary Chemistry |
Mutation studies in prokaryotes and eukaryotes show that ractopamine is not mutagenic. However, the results of several in vitro studies, including chromosome aberration tests in human lymphocytes, are positive. The positive genotoxic results are explained with limited evidence to be due to a secondary auto-oxidative mechanism from ractopamine-catechol-producing reactive intermediates. | 0 | Theoretical and Fundamental Chemistry |
The maximum residue limit (also maximum residue level, MRL) is the maximum amount of pesticide residue that is expected to remain on food products when a pesticide is used according to label directions, that will not be a concern to human health. | 1 | Applied and Interdisciplinary Chemistry |
* Hepatitis C infection
* Antisocial personality disorder
* Borderline personality traits
* Schizoid/avoidant behavior
Given that the A1+ allele is associated with antisocial personality disorder, one may infer that the allele is also associated with narcissistic personality disorder and histrionic personality disorder. However, these predictions have not yet been empirically verified. | 1 | Applied and Interdisciplinary Chemistry |
Cyclobutenone was originally synthesized from the 3-bromocyclobutanone and 3-chlorocyclobutanone precursors which were prepared from an allene and a ketene via two independent routes. Scheme 7 shows the preparation from cyclobutenone from an allene.
Activated alkyoxyacetylenes can be synthesized in a single-pot preparation of triisopropylsilyloxyacetylenes from esters. The silyloxyacetylenes are useful substitutes for alkoxyacetylenes in [2 + 2] cycloaddition reactions with ketenes and vinylketenes affording cyclobutenones (Scheme 8).
Diazoketones can be synthesized in one-step from readily available ketones or carboxylic acid precursors by the addition of diazomethane to acyl chlorides. A diazo group transfer method can be used to produce α,β-unsaturated ketones. The traditional method of the deformylative diazo transfer approach has been improved upon by substituting the trifluoroacetylation of generated lithium enolates for the Claisen formylation step. The key step in this procedure is activation of the ketone starting material to the corresponding α-trifluoroacetyl derivative using trifluoroethyltrifluoroacetate (TFEA) (Scheme 9).
Alkynes or ketenophiles can be synthesized by various methods. Trialkylsilyloxyalkynes have proven to be excellent ketenophiles. These alkynes react in the annulation reaction to form resorcinol monosilyl ethers which can be de-protected under mild reaction conditions.
Base-promoted dehydrohalogenation of (Z)-2-halovinyl ethers to form alkoxyacetylenes is one of the most well established routes of alkyne synthesis (Scheme 10).
The synthesized alkynes are then heated in benzene or toluene in presence of excess cyclobutenone initiating the benzannulation reaction. Treatment with n-BuNF in tetrahydrofuran removes the siloxy groups to form the desired diols. | 0 | Theoretical and Fundamental Chemistry |
* Kavli Frontiers of Science Fellow, National Academy of Sciences (1998)
*Fellow, American Association for the Advancement of Science (2015)
*Cesare Emiliani Lecturer, American Geophysical Union (2018)
*Fellow, American Geophysical Union (2019) | 0 | Theoretical and Fundamental Chemistry |
More sophisticated variants of sublimation apparatus include those that apply a temperature gradient so as to allow for controlled recrystallization of different fractions along the cold surface. Thermodynamic processes follow a statistical distribution, and suitably designed apparatus exploit this principle with a gradient that will yield different purities in particular temperature zones along the collection surface. Such techniques are especially helpful when the requirement is to refine or separate multiple products or impurities from the same mix of raw materials. It is necessary in particular when some of the required products have similar sublimation points or pressure curves. | 0 | Theoretical and Fundamental Chemistry |
First write down the equilibrium expression
This shows that when the acid dissociates, equal amounts of hydrogen ion and anion are produced. The equilibrium concentrations of these three components can be calculated in an ICE table (ICE standing for "initial, change, equilibrium").
The first row, labelled I, lists the initial conditions: the concentration of acid is C, initially undissociated, so the concentrations of A and H would be zero; y is the initial concentration of added strong acid, such as hydrochloric acid. If strong alkali, such as sodium hydroxide, is added, then y will have a negative sign because alkali removes hydrogen ions from the solution. The second row, labelled C for "change", specifies the changes that occur when the acid dissociates. The acid concentration decreases by an amount −x, and the concentrations of A and H both increase by an amount +x. This follows from the equilibrium expression. The third row, labelled E for "equilibrium", adds together the first two rows and shows the concentrations at equilibrium.
To find x, use the formula for the equilibrium constant in terms of concentrations:
Substitute the concentrations with the values found in the last row of the ICE table:
Simplify to
With specific values for C, K and y, this equation can be solved for x. Assuming that pH = −log[H], the pH can be calculated as pH = −log(x + y). | 0 | Theoretical and Fundamental Chemistry |
Some electronic components develop lower resistances or lower triggering voltages (for nonlinear resistances) as their internal temperature increases. If circuit conditions cause markedly increased current flow in these situations, increased power dissipation may raise the temperature further by Joule heating. A vicious circle or positive feedback effect of thermal runaway can cause failure, sometimes in a spectacular fashion (e.g. electrical explosion or fire). To prevent these hazards, well-designed electronic systems typically incorporate current limiting protection, such as thermal fuses, circuit breakers, or PTC current limiters.
To handle larger currents, circuit designers may connect multiple lower-capacity devices (e.g. transistors, diodes, or MOVs) in parallel. This technique can work well, but is susceptible to a phenomenon called current hogging, in which the current is not shared equally across all devices. Typically, one device may have a slightly lower resistance, and thus draws more current, heating it more than its sibling devices, causing its resistance to drop further. The electrical load ends up funneling into a single device, which then rapidly fails. Thus, an array of devices may end up no more robust than its weakest component.
The current-hogging effect can be reduced by carefully matching the characteristics of each paralleled device, or by using other design techniques to balance the electrical load. However, maintaining load balance under extreme conditions may not be straightforward. Devices with an intrinsic positive temperature coefficient (PTC) of electrical resistance are less prone to current hogging, but thermal runaway can still occur because of poor heat sinking or other problems.
Many electronic circuits contain special provisions to prevent thermal runaway. This is most often seen in transistor biasing arrangements for high-power output stages. However, when equipment is used above its designed ambient temperature, thermal runaway can still occur in some cases. This occasionally causes equipment failures in hot environments, or when air cooling vents are blocked. | 1 | Applied and Interdisciplinary Chemistry |
Vapor phase osmometry (VPO), also known as vapor-pressure osmometry, is an experimental technique for the determination of a polymer's number average molecular weight, M. It works by taking advantage of the decrease in vapor pressure that occurs when solutes are added to pure solvent. This technique can be used for polymers with a molecular weight of up to 20,000 though accuracy is best for those below 10,000. Although membrane osmometry is also based on the measurement of colligative properties, it has a lower bound of 25,000 for sample molecular weight that can be measured owing to problems with membrane permeation. | 0 | Theoretical and Fundamental Chemistry |
The gray is used to measure absorbed dose rates in non-tissue materials for processes such as radiation hardening, food irradiation and electron irradiation. Measuring and controlling the value of absorbed dose is vital to ensuring correct operation of these processes. | 0 | Theoretical and Fundamental Chemistry |
Small GTPases function as monomers and have a molecular weight of about 21 kilodaltons that consists primarily of the GTPase domain. They are also called small or monomeric guanine nucleotide-binding regulatory proteins, small or monomeric GTP-binding proteins, or small or monomeric G-proteins, and because they have significant homology with the first-identified such protein, named Ras, they are also referred to as Ras superfamily GTPases. Small GTPases generally serve as molecular switches and signal transducers for a wide variety of cellular signaling events, often involving membranes, vesicles or cytoskeleton. According to their primary amino acid sequences and biochemical properties, the many Ras superfamily small GTPases are further divided into five subfamilies with distinct functions: Ras, Rho ("Ras-homology"), Rab, Arf and Ran. While many small GTPases are activated by their GEFs in response to intracellular signals emanating from cell surface receptors (particularly growth factor receptors), regulatory GEFs for many other small GTPases are activated in response to intrinsic cell signals, not cell surface (external) signals. | 1 | Applied and Interdisciplinary Chemistry |
One suitable definition of organic matter is biological material in the process of decaying or decomposing, such as humus. A closer look at the biological material in the process of decaying reveals so-called organic compounds (biological molecules) in the process of breaking up (disintegrating).
The main processes by which soil molecules disintegrates are by bacterial or fungal enzymatic catalysis. If bacteria or fungi were not present on Earth, the process of decomposition would have proceeded much slower. | 0 | Theoretical and Fundamental Chemistry |
The protein has a short cytoplasmic region, a transmembrane alpha-helix, a water-soluble beta-sandwich domain located in endoplasmic reticulum, and second TM helix. | 1 | Applied and Interdisciplinary Chemistry |
Ingesting large amounts of arsenic can cause symptoms similar to food poisoning, with abdominal pain, nausea, vomiting, and diarrhea starting within hours. Bloody diarrhea can cause severe fluid loss, resulting in hypovolemic shock. The heart and nervous system can also be affected, causing disruption to heart rhythms (QT interval prolongation or tachycardia), heart failure, confusion, seizures, brain swelling, coma, and death. Inhaling arsine gas – the most toxic form of arsenic – causes a multisystem disease starting 2 to 24 hours after inhalation. Symptoms include gastrointestinal distress, headache, weakness, difficulty breathing, kidney and liver dysfunction, and the destruction of red blood cells.
Chronic ingestion of lower levels of arsenic causes visible changes in the skin, typically hyperpigmentation (dark areas), but sometimes hypopigmentation (light areas) or an alternating areas of each. Some experience general thickening of the skin on the palms and soles of the feet, or small thickened areas. Around 5% of those affected develop light-colored bands across the fingernail, called Mees' lines. Chronic exposure eventually causes disease across multiple body systems, including peripheral neuropathy (numbness and tingling), enlargement of the liver and spleen, diabetes, heart disease, cognitive impairment, and damage to the portal vein (Non-cirrhotic portal fibrosis and portal hypertension).
Repeated arsenic exposure also increases the risk for developing several cancers, particularly of the skin, lung, liver, bladder, prostate, and blood vessels. The most common arsenic-induced skin cancer is squamous cell carcinoma in situ which typically occurs 2 to 20 years after arsenic exposure. | 1 | Applied and Interdisciplinary Chemistry |
Through the dissimilatory sulfate reduction pathway, sulfate can be reduced either bacterially (bacterial sulfate reduction) or inorganically (thermochemical sulfate reduction). This pathway involves the reduction of sulfate by organic compounds to produce hydrogen sulfide, which occurs in both processes.
The main products and reactants of bacterial sulfate reduction (BSR) and thermochemical sulfate reduction (TSR) are very similar. For both, various organic compounds and dissolved sulfate are the reactants, and the products or by-products are as follows: HS, CO, carbonates, elemental sulfur and metal sulfides. However, the reactive organic compounds differ for BSR and TSR because of the mutually exclusive temperature regimes. Organic acids are the main organic reactants for BSR and branched/n-alkanes are the main organic reactants for TSR. The inorganic reaction products in BSR and TSR are HS (HS) and (CO).
These processes occur because there are two very different thermal regimes in which sulfate is reduced, particularly in low-temperature and high-temperature environments. BSR usually occurs at lower temperatures from 0−80 °C, while TSR happens at much higher temperatures around 100–140 °C. Temperatures for TSR are not as well defined; the lowest confirmed temperature is 127 °C and the highest temperatures occur in settings around 160−180 °C. These two different regimes appear because at higher temperatures most sulfate-reducing microbes can no longer metabolize due to the denaturation of proteins or deactivation of enzymes, so TSR takes over. However, in hot sediments around hydrothermal vents BSR can happen at temperatures up to 110 °C.
BSR and TSR occur at different depths. BSR takes place in low-temperature environments, which are shallower settings such as oil and gas fields. BSR can also take place in modern marine sedimentary environments such as stratified inland seas, continental shelves, organic-rich deltas, and hydrothermal sediments which have intense microbial sulfate reduction because of the high concentration of dissolved sulfate in the seawater. Additionally, the high amounts of hydrogen sulfide found in oil and gas fields is thought to arise from the oxidation of petroleum hydrocarbons by sulfate. Such reactions are known to occur by microbial processes but it is generally accepted that TSR is responsible for the bulk of these reactions, especially in deep or hot reservoirs. Thus, TSR occurs in deep reservoirs where the temperatures are much higher. BSR is geologically instantaneous in most geologic settings, while TSR occurs at rates in the order of hundreds of thousands of years. Although much slower than BSR, even TSR appears to be a geologically fairly fast process.
BSR in shallow environments and TSR in deep reservoirs are key processes in the oceanic sulfur cycle. Approximately, 10% (of the total gas) of HS is produced in BSR settings, whereas 90% of the HS is produced in TSR settings. If there is more than a few percent of HS in any deep reservoir, then it is assumed that TSR has taken over. This is due to the fact that thermal cracking of hydrocarbons doesn't provide more than 3% of HS. The amount of HS is affected by several factors such as, the availability of organic reactants and sulfate and the presence/availability of base and transition metals. | 0 | Theoretical and Fundamental Chemistry |
The specificity constant (also known as the catalytic efficiency) is a measure of how efficiently an enzyme converts a substrate into product. Although it is the ratio of and it is a parameter in its own right, more fundamental than . Diffusion limited enzymes, such as fumarase, work at the theoretical upper limit of , limited by diffusion of substrate into the active site.
If we symbolize the specificity constant for a particular substrate A as the Michaelis–Menten equation can be written in terms of and as follows:
At small values of the substrate concentration this approximates to a first-order dependence of the rate on the substrate concentration:
Conversely it approaches a zero-order dependence on when the substrate concentration is high:
The capacity of an enzyme to distinguish between two competing substrates that both follow Michaelis–Menten kinetics depends only on the specificity constant, and not on either or alone. Putting for substrate and for a competing substrate , then the two rates when both are present simultaneously are as follows:
Although both denominators contain the Michaelis constants they are the same, and thus cancel when one equation is divided by the other:
and so the ratio of rates depends only on the concentrations of the two substrates and their specificity constants. | 0 | Theoretical and Fundamental Chemistry |
Evans was born in Nottingham, England on 28 March 1928. His father George Frederick Evans was a master carpenter and his mother (née Gladys Martha Taylor) was a dressmaker. He was educated at Huntingdon Street Junior School and then won a scholarship to Nottingham High School. In 1946 he entered Oxford with a scholarship to Lincoln College where his tutor was Rex Richards (later Sir Rex Richards FRS). He won the university Gibbs Prize in Chemistry in 1949, and in that year started DPhil work with Richards on calorimetry and the magnetic properties of clathrates containing nitric oxide or oxygen; nine papers resulted from this work. He was an ICI Research Fellow from 1952-5. In 1953-4 he became a postdoctoral research associate at the University of Chicago with Robert S. Mulliken working on the electronic spectra of halogens in organic solvents, producing four papers under his own name. | 0 | Theoretical and Fundamental Chemistry |
Sperm DNA fragmentation appears to be an important factor in the cause of male infertility, since men with high DNA fragmentation levels have significantly lower odds of conceiving. Oxidative stress is the major cause of DNA fragmentation in spermatozoa. A high level of the oxidative DNA damage 8-oxo-2'-deoxyguanosine is associated with abnormal spermatozoa and male infertility. | 1 | Applied and Interdisciplinary Chemistry |
In Orgel diagrams, the magnitude of the splitting energy exerted by the ligands on d orbitals, as a free ion approach a ligand field, is compared to the electron-repulsion energy, which are both sufficient at providing the placement of electrons. However, if the ligand field splitting energy, 10Dq, is greater than the electron-repulsion energy, then Orgel diagrams fail in determining electron placement. In this case, Orgel diagrams are restricted to only high spin complexes.
Tanabe–Sugano diagrams do not have this restriction, and can be applied to situations when 10Dq is significantly greater than electron repulsion. Thus, Tanabe–Sugano diagrams are utilized in determining electron placements for high spin and low spin metal complexes. However, they are limited in that they have only qualitative significance. Even so, Tanabe–Sugano diagrams are useful in interpreting UV-vis spectra and determining the value of 10Dq. | 0 | Theoretical and Fundamental Chemistry |
The Collaborative Computing project for NMR spectroscopy was set up in with three main aims; to create a common standard for representing NMR spectroscopy related data, to create a suite of new open-source NMR software packages and to arrange meetings for the NMR community, including conferences, workshops and courses in order to discuss and spread best-practice within the NMR community, for both computational and non-computational aspects. Primary financial support for CCPN comes from the BBSRC; the UK Biotechnology and Biological Sciences Research Council. CCPN is part of an array of collaborative computing projects (CCP) and follows in a similar vein to the successful and well-established CCP4 project for X-ray crystallography. CCPN is also supported by European Union grants, most recently as part of the Extend-NMR project; which links together several software producing groups from across Europe.
CCPN is governed by an executive committee which draws its members from academics throughout the UK NMR community. This committee is chosen at the CCPN Assembly Meeting where all UK based NMR groups may participate and vote. The day-to-day work of CCPN, including the organisation of meetings and software development, is handled by an informal working group, coordinated by Ernest Laue at the University of Cambridge, which comprises the core group of staff and developers, as well as a growing number of collaborators throughout the world who contribute to coordinated NMR software development. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, the Galilei number (Ga), sometimes also referred to as Galileo number (see discussion), is a dimensionless number named after Italian scientist Galileo Galilei (1564-1642).
It may be regarded as proportional to gravity forces divided by viscous forces. The Galilei number is used in viscous flow and thermal expansion calculations, for example to describe fluid film flow over walls. These flows apply to condensers or chemical columns.
* g: gravitational acceleration, (SI units: m/s)
* L: characteristic length, (SI units: m)
* ν: characteristic kinematic viscosity, (SI units: m/s) | 1 | Applied and Interdisciplinary Chemistry |
The Great Calcite Belt can be defined as an elevated particulate inorganic carbon (PIC) feature occurring alongside seasonally elevated chlorophyll a in austral spring and summer in the Southern Ocean. It plays an important role in climate fluctuations, accounting for over 60% of the Southern Ocean area (30–60° S). The region between 30° and 50° S has the highest uptake of anthropogenic carbon dioxide (CO) alongside the North Atlantic and North Pacific oceans. Knowledge of the impact of interacting environmental influences on phytoplankton distribution in the Southern Ocean is limited. For example, more understanding is needed of how light and iron availability or temperature and pH interact to control phytoplankton biogeography. Hence, if model parameterizations are to improve to provide accurate predictions of biogeochemical change, a multivariate understanding of the full suite of environmental drivers is required.
The Southern Ocean has often been considered as a microplankton-dominated (20–200 µm) system with phytoplankton blooms dominated by large diatoms and Phaeocystis sp. However, since the identification of the Great Calcite Belt (GCB) as a consistent feature and the recognition of picoplankton (< 2 µm) and nanoplankton (2–20 µm) importance in high-nutrient, low-chlorophyll (HNLC) waters, the dynamics of small (bio)mineralizing plankton and their export need to be acknowledged. The two dominant biomineralizing phytoplankton groups in the GCB are coccolithophores and diatoms. Coccolithophores are generally found north of the polar front, though Emiliania huxleyi has been observed as far south as 58° S in the Scotia Sea, at 61° S across Drake Passage, and at 65°S south of Australia.
Diatoms are present throughout the GCB, with the polar front marking a strong divide between different size fractions. North of the polar front, small diatom species, such as Pseudo-nitzschia spp. and Thalassiosira spp., tend to dominate numerically, whereas large diatoms with higher silicic acid requirements (e.g., Fragilariopsis kerguelensis) are generally more abundant south of the polar front. High abundances of nanoplankton (coccolithophores, small diatoms, chrysophytes) have also been observed on the Patagonian Shelf and in the Scotia Sea. Currently, few studies incorporate small biomineralizing phytoplankton to species level. Rather, the focus has often been on the larger and noncalcifying species in the Southern Ocean due to sample preservation issues (i.e., acidified Lugol’s solution dissolves calcite, and light microscopy restricts accurate identification to cells > 10 µm. In the context of climate change and future ecosystem function, the distribution of biomineralizing phytoplankton is important to define when considering phytoplankton interactions with carbonate chemistry, and ocean biogeochemistry.
The Great Calcite Belt spans the major Southern Ocean circumpolar fronts: the Subantarctic front, the polar front, the Southern Antarctic Circumpolar Current front, and occasionally the southern boundary of the Antarctic Circumpolar Current. The subtropical front (at approximately 10 °C) acts as the northern boundary of the GCB and is associated with a sharp increase in PIC southwards. These fronts divide distinct environmental and biogeochemical zones, making the GCB an ideal study area to examine controls on phytoplankton communities in the open ocean. A high PIC concentration observed in the GCB (1 µmol PIC L) compared to the global average (0.2 µmol PIC L) and significant quantities of detached E. huxleyi coccoliths (in concentrations > 20,000 coccoliths mL) both characterize the GCB. The GCB is clearly observed in satellite imagery spanning from the Patagonian Shelf across the Atlantic, Indian, and Pacific oceans and completing Antarctic circumnavigation via the Drake Passage. | 0 | Theoretical and Fundamental Chemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.