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Levobupivacaine is a drug that has analgesic, motor blocking, and sensory blocking effects on the human body, whose properties are dictated by its chemical characteristics, such as pK, which has a value of 8.1. The pK of a drug can be informative information that indicates its ionisation under physiological conditions. For example, drugs with a high pK, such as that of levobupivacaine, tend to be their ionised form under physiological state, meaning that they would not easily cross the hydrophobic plasma membrane of cells. This, however, is counteracted by the high lipid solubility of levobupivacaine, which increases the ease with which it can diffuse through the phospholipid bilayer. Additionally, high-protein binding quality (97%) is characteristic of levobupivacaine, which strengthens its binding to cell surface proteins, thereby lengthening the binding, and thus action time.
The S(-)-enantiomer of levobupivacaine is a high-potency, long-acting anaesthetic with a relatively slow onset of action. Indeed, it has been found in certain studies that, as a surgical anaesthetic, it has a sensory ad motor blocking activity for over 90% of adult patients who received appropriate doses for their bodily composition, and duration of the surgery, with an onset time of 15 minutes.
More specifically, levobupivacaine achieves its effects by acting on the neuronal voltage-sensitive sodium channels, where it prevents the transmission of nerve impulses. The normal function of these sodium channels is halted temporarily, as the drug interferes with their opening, thereby inhibiting the conduction of action potentials in nerves involved in sympathetic, sensory, and motor activity. This interruption results in decreased muscle control, and overall analgesic effects which allow for levobupivacaine to act as a local anaesthetic.
Levobupivacaine varies slightly in its effects depending on the characteristics of the neuron in question. For example, in myelinated neurons, the nodes of Ranvier are targeted and more easily blocked than unmyelinated neurons, and small nerves are more easily blocked than large nerves.
When compared to the racemic bupivacaine mixture, levobupivacaine generally has been shown to have similar effects. As an anaesthetic, it is similar in nerve-blocking potency compared to its R(+)-enantiomer and racemic mixture, although its effects are affected by the route of administration and the concentration, however, they were ultimately similar among the three. Some animal studies indicate that among the three, levobupivacaine shows an increased duration of anaesthesia and/or greater potency, and there is evidence that in humans it is as potent as bupivacaine. | 0 | Theoretical and Fundamental Chemistry |
The principle of the electron was first theorised in the period of 1838-1851 by a natural philosopher by the name of Richard Laming who speculated the existence of sub-atomic, unit charged particles; he also pictured the atom as being an electrosphere of concentric shells of electrical particles surrounding a material core.
It is generally accepted that J. J. Thomson first discovered the electron in 1897, although other notable members in the development in charged particle theory are George Johnstone Stoney (who coined the term "electron"), Emil Wiechert (who was first to publish his independent discovery of the electron), Walter Kaufmann, Pieter Zeeman and Hendrik Lorentz.
Compton scattering was first observed at Washington University in St. Louis in 1923 by Arthur Compton who earned the 1927 Nobel Prize in Physics for the discovery; his graduate student Y. H. Woo who further verified the results is also of mention. Compton scattering is usually cited in reference to the interaction involving the electrons of an atom, however nuclear Compton scattering does exist.
The first electron diffraction experiment was conducted in 1927 by Clinton Davisson and Lester Germer using what would come to be a prototype for modern LEED system. The experiment was able to demonstrate the wave-like properties of electrons, thus confirming the de Broglie hypothesis that matter particles have a wave-like nature. However, after this the interest in LEED diminished in favour of High-energy electron diffraction until the early 1960s when an interest in LEED was revived; of notable mention during this period is H. E. Farnsworth who continued to develop LEED techniques.
High energy electron-electron colliding beam history begins in 1956 when K. O'Neill of Princeton University became interested in high energy collisions, and introduced the idea of accelerator(s) injecting into storage ring(s). While the idea of beam-beam collisions had been around since approximately the 1920s, it was not until 1953 that a German patent for colliding beam apparatus was obtained by Rolf Widerøe. | 0 | Theoretical and Fundamental Chemistry |
The journal was established in 1963 as Clinical Chemistry/Klinische Chemie. In 1991 it was renamed to European Journal of Clinical Chemistry and Clinical Biochemistry. In 1998 it obtained its present name. | 1 | Applied and Interdisciplinary Chemistry |
Born in Pittsburg, Kansas, in 1914, Corson received a B.A. degree from the College of Emporia in 1934, his M.A. degree from the University of Kansas in 1935, and his Ph.D. in physics from the University of California, Berkeley, in 1938. | 1 | Applied and Interdisciplinary Chemistry |
Since 2016, Mahdi as served as the Secretary-General of the Supreme Council for Planning and Development in the Government of Kuwait. Prior to this appointment, he was the Assistant Secretary General for the Follow-up and Future Forecasting besides being the Acting Assistant Secretary General for Planning.
Mahdi sits in several government boards and higher committees, mainly the Public Authority for Industry (PAI), Kuwait Institute for Scientific Research (KISR), Public Authority for Civil Information (PACI), and the Public Authority for Housing and Welfare (PAHW).He is a member of the Supreme Council for Education and is on the Board of Trustees of the National Center for Education Development (NCED). He serves as member in high-level committees such as the Economic and Fiscal Reform Monitoring Committee , the Humanitarian Foreign Aid Committee, Fiscal Budgeting Framework, Kuwait Demographic Disparities Committee, the Development of Kuwait Islands Committee, the Executive Committee of the Silk City, Kuwait Master Plan 2040 Committee, Kuwait Bond Debut Roadshow, and the Kuwait University Mega Projects Committee.
He also serves other government sub-committees and leading government work groups, and has spoken extensively at national and international conferences, such as the Kuwait Housing & Residential Development Forum and Kuwait Infrastructure Week in 2017.
Mahdi chairs the Consultants Selection Committee during the period 2016-2017 and is the National Director of the Country Program Action Plan of the United Nations Development Programme in Kuwait, and currently presides over the National Committee for the Implementation of Agenda 2030.
Mahdi steers chairs the national SDGs 2030 permanent standing committee and leads the vision of the state, “New Kuwait 2035”. He established the Kuwait Public Policy Center (KPPC) and its Nudge Unit; also oversees the research centers including The National Knowledge Economy Center, the National Sustainable Development Observatory and the National Development Research Center. He also led the initiative to produce Kuwait’s first Macro-Economic Model by collaborating with Oxford Economics. He has also hosted the IPIECA’s report “the Mapping the Oil and Gas Industry to the SDGs: An Atlas”, and the World Energy Outlook 2018’s report of the IEO. Mahdi has also developed strategic partnerships with local, regional and international organizations to support knowledge sharing and development. | 1 | Applied and Interdisciplinary Chemistry |
Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and for many other biological effects. In humans, the most important compounds in this group are vitamin D (cholecalciferol) and vitamin D (ergocalciferol).
The major natural source of vitamin D is synthesis of cholecalciferol in the lower layers of the epidermis of the skin, through a photochemical reaction with Ultraviolet B (UV-B) radiation from sun exposure or UV-B lamps. Cholecalciferol and ergocalciferol can be ingested from the diet and supplements. Only a few foods, such as the flesh of fatty fish, naturally contain significant amounts of vitamin D. In the U.S. and other countries, cows milk and plant-derived milk substitutes are fortified with vitamin D, as are many breakfast cereals. Mushrooms exposed to ultraviolet light contribute useful amounts of vitamin D. Dietary recommendations typically assume that all of a persons vitamin D is taken by mouth, because sun exposure in the population is variable and recommendations about the amount of sun exposure that is safe are uncertain in view of the associated risks of skin cancer.
Vitamin D from the diet, or from skin synthesis, is biologically inactive. It is activated by two protein enzyme hydroxylation steps, the first in the liver and the second in the kidneys. Because vitamin D can be synthesized in adequate amounts by most mammals if they get enough sunlight, it is not essential and therefore is technically not a vitamin. Instead it can be considered a hormone, with activation of the vitamin D pro-hormone resulting in the active form, calcitriol, which then produces effects via a nuclear receptor in multiple locations.
Cholecalciferol is converted in the liver to calcifediol (25-hydroxycholecalciferol); ergocalciferol is converted to 25-hydroxyergocalciferol. These two vitamin D metabolites (called 25-hydroxyvitamin D or 25(OH)D) are measured in serum to determine a person's vitamin D status. Calcifediol is further hydroxylated by the kidneys and some of the immune system cells to form calcitriol (1,25-dihydroxycholecalciferol), the biologically active form of vitamin D. Calcitriol circulates as a hormone in the blood, having a major role regulating the concentration of calcium and phosphate, and promoting the healthy growth and remodeling of bone. Calcitriol also has other effects, including some on cell growth, neuromuscular and immune functions, and reduction of inflammation.
Vitamin D has a significant role in calcium homeostasis and metabolism. Its discovery was due to effort to find the dietary substance lacking in children with rickets (the childhood form of osteomalacia). Vitamin D supplements are given to treat or to prevent osteomalacia and rickets. The evidence for other health effects of vitamin D supplementation in vitamin D–replete individuals is inconsistent. The effect of vitamin D supplementation on mortality is not clear, with one meta-analysis finding a small decrease in mortality in elderly people. Except for the prevention of rickets and osteomalacia in high-risk groups, any benefit of vitamin D supplements to musculoskeletal or general health may be small. | 1 | Applied and Interdisciplinary Chemistry |
Ronald W. Davis first discovered sticky ends as the product of the action of EcoRI, the restriction endonuclease. | 1 | Applied and Interdisciplinary Chemistry |
Normally the heat transfer between airstreams provided by the device is termed as sensible, which is the exchange of energy, or enthalpy, resulting in a change in temperature of the medium (air in this case), but with no change in moisture content. | 0 | Theoretical and Fundamental Chemistry |
There are several PREN formulas. They commonly range from:
: PREN = %Cr + 3.3 × %Mo + 16 × %N
to:
: PREN = %Cr + 3.3 × %Mo + 30 × %N.
There are a few stainless steels which add tungsten (W), for those the following formula is used:
: PREN = %Cr + 3.3 × (%Mo + 0.5 × %W ) + 16 × %N
All % values of elements must be expressed by mass, or weight (wt. %), and not by volume. Tolerance on element measurements could be ignored as the PREN value is indicative only. | 1 | Applied and Interdisciplinary Chemistry |
The gene silencing effects of transfected designed siRNA are generally transient, but this difficulty can be overcome through an RNAi approach. Delivering this siRNA from DNA templates can be done through several recombinant viral vectors based on retrovirus, adeno-associated virus, adenovirus, and lentivirus. The latter is the most efficient virus that stably delivers siRNA to target cells as it can transduce nondividing cells as well as directly target the nucleus. These specific viral vectors have been synthesized to effectively facilitate siRNA that is not viable for transfection into cells. Another aspect is that in some cases synthetic viral vectors can integrate siRNA into the cell genome which allows for stable expression of siRNA and long-term gene knockdown. This technique is advantageous because it is in vivo and effective for difficult to transfect cell. However problems arise because it can trigger antiviral responses in some cell types leading to mutagenic and immunogenic effects.
This method has potential use in gene silencing of the central nervous system for the treatment of Huntington's disease. | 1 | Applied and Interdisciplinary Chemistry |
A grain boundary (GB) is the transition area or interface between adjacent crystallites (or grains) of the same chemical and lattice composition, not to be confused with a phase boundary. The adjacent grains do not have the same orientation of the lattice, thus giving the atoms in GB shifted positions relative to the lattice in the crystals. Due to the shifted positioning of the atoms in the GB they have a higher energy state when compared with the atoms in the crystal lattice of the grains. It is this imperfection that makes it possible to selectively etch the GBs when one wants the microstructure to be visible.
Striving to minimize its energy leads to the coarsening of the microstructure to reach a metastable state within the specimen. This involves minimizing its GB area and changing its topological structure to minimize its energy. This grain growth can either be normal or abnormal, a normal grain growth is characterized by the uniform growth and size of all the grains in the specimen. Abnormal grain growth is when a few grains grow much larger than the remaining majority. | 1 | Applied and Interdisciplinary Chemistry |
Ethanol precipitation is a method used to purify and/or concentrate RNA, DNA, and polysaccharides such as pectin and xyloglucan from aqueous solutions by adding ethanol as an antisolvent. | 1 | Applied and Interdisciplinary Chemistry |
Phase contrast MRI (PC-MRI) is used to measure flow velocities in the body. It is used mainly to measure blood flow in the heart and throughout the body. PC-MRI may be considered a method of magnetic resonance velocimetry. Since modern PC-MRI typically is time-resolved, it also may be referred to as 4-D imaging (three spatial dimensions plus time). | 0 | Theoretical and Fundamental Chemistry |
The and pH of a solution are related by the Nernst equation as commonly represented by a Pourbaix diagram . For a half cell equation, conventionally written as a reduction reaction (i.e., electrons accepted by an oxidant on the left side):
The half-cell standard reduction potential is given by
where is the standard Gibbs free energy change, is the number of electrons involved, and is Faraday's constant. The Nernst equation relates pH and :
where curly braces { } indicate activities, and exponents are shown in the conventional manner. as a function of pH with a slope of volt (pH has no units).
This equation predicts lower at higher pH values. This is observed for the reduction of O into HO, or OH, and for reduction of H into H. | 1 | Applied and Interdisciplinary Chemistry |
The primary structure of the SUI1 protein is made up of 108 amino acids. The protein domain has a structure made of a seven-bladed beta-propeller and it also contains a C-terminal alpha helix. Homologues of SUI1 have been found in mammals, insects and plants. SUI1 is also evolutionary related to proteins from Escherichia coli (yciH), Haemophilus influenzae (HI1225) and Methanococcus vannielii. | 1 | Applied and Interdisciplinary Chemistry |
or
This exact result can be obtained from the general BAR method, using (for example) the Metropolis function, in the limit . Indeed, in that case, the denominator of the general case expression above tends to 1, while the numerator tends to .
A direct derivation from the definitions is more straightforward, though. | 0 | Theoretical and Fundamental Chemistry |
The light reactions of photosynthesis generate ATP by the action of chemiosmosis. The photons in sunlight are received by the antenna complex of Photosystem II, which excites electrons to a higher energy level. These electrons travel down an electron transport chain, causing protons to be actively pumped across the thylakoid membrane into the thylakoid lumen. These protons then flow down their electrochemical potential gradient through an enzyme called ATP-synthase, creating ATP by the phosphorylation of ADP to ATP. The electrons from the initial light reaction reach Photosystem I, then are raised to a higher energy level by light energy and then received by an electron acceptor and reduce NADP to NADPH. The electrons lost from Photosystem II get replaced by the oxidation of water, which is "split" into protons and oxygen by the oxygen-evolving complex (OEC, also known as WOC, or the water-oxidizing complex). To generate one molecule of diatomic oxygen, 10 photons must be absorbed by Photosystems I and II, four electrons must move through the two photosystems, and 2 NADPH are generated (later used for carbon dioxide fixation in the Calvin Cycle). | 1 | Applied and Interdisciplinary Chemistry |
The term microemulsion was first used by T. P. Hoar and J. H. Shulman, professors of chemistry at Cambridge University, in 1943. Alternative names for these systems are often used, such as transparent emulsion, swollen micelle, micellar solution, and solubilized oil. More confusingly still, the term microemulsion can refer to the single isotropic phase that is a mixture of oil, water and surfactant, or to one that is in equilibrium with coexisting predominantly oil and/or aqueous phases, or even to other non-isotropic phases. As in the binary systems (water/surfactant or oil/surfactant), self-assembled structures of different types can be formed, ranging, for example, from (inverted) spherical and cylindrical micelles to lamellar phases and bicontinuous microemulsions, which may coexist with predominantly oil or aqueous phases. | 0 | Theoretical and Fundamental Chemistry |
The Shapiro–Senapathy algorithm has been used to determine the various aberrant splicing mechanisms in genes due to deleterious mutations in the splice sites, which cause numerous diseases. Deleterious splice site mutations impair the normal splicing of the gene transcripts, and thereby make the encoded protein defective. A mutant splice site can become “weak” compared to the original site, due to which the mutated splice junction becomes unrecognizable by the spliceosomal machinery. This can lead to the skipping of the exon in the splicing reaction, resulting in the loss of that exon in the spliced mRNA (exon-skipping). On the other hand, a partial or complete intron could be included in the mRNA due to a splice site mutation that makes it unrecognizable (intron inclusion). A partial exon-skipping or intron inclusion can lead to premature termination of the protein from the mRNA, which will become defective leading to diseases. The S&S has thus paved the way to determine the mechanisms by which a deleterious mutation could lead to a defective protein, resulting in different diseases depending on which gene is affected. | 1 | Applied and Interdisciplinary Chemistry |
Many protein-containing solutions have the highest absorption at 280 nm in the spectrophotometer, the UV range. This requires spectrophotometers capable of measuring in the UV range, which many cannot. Additionally, the absorption maxima at 280 nm requires that proteins contain aromatic amino acids such as tyrosine (Y), phenylalanine (F) and/or tryptophan (W). Not all proteins contain these amino acids, a fact which will skew the concentration measurements. If nucleic acids are present in the sample, they would also absorb light at 280 nm, skewing the results further. By using the Bradford protein assay, one can avoid all of these complications by simply mixing the protein samples with the Coomassie brilliant blue G-250 dye (Bradford reagent) and measuring their absorbances at 595 nm, which is in the visible range and may be accurately measured by the use of a mobile smartphone camera.
The procedure for Bradford protein assay is very easy and simple to follow. It is done in one step where the Bradford reagent is added to a test tube along with the sample. After mixing well, the mixture almost immediately changes to a blue color. When the dye binds to the proteins through a process that takes about 2 minutes, a change in the absorption maximum of the dye from 465 nm to 595 nm in acidic solutions occurs. This dye creates strong noncovalent bonds with the proteins, via electrostatic interactions with the amino and carboxyl groups, as well as Van Der Waals interactions. Only the molecules that bind to the proteins in solution exhibit this change in absorption, which eliminates the concern that unbound molecules of the dye might contribute to the experimentally obtained absorption reading. This process is more beneficial since it is less pricey than other methods, easy to use, and has high sensitivity of the dye for protein.
After 5 minutes of incubation, the absorbance can be read at 595 nm using a spectrophotometer or a mobile smartphone camera (RGBradford method).
This assay is one of the fastest assays performed on proteins. The total time it takes to set up and complete the assay is under 30 minutes. The entire experiment is done at room temperature.
The Bradford protein assay can measure protein quantities as little as 1 to 20 μg. It is an extremely sensitive technique.
The dye reagent is a stable ready to use product prepared in phosphoric acid. It can remain at room temperature for up to 2 weeks before it starts to degrade.
Protein samples usually contain salts, solvents, buffers, preservatives, reducing agents and metal chelating agents. These molecules are frequently used for solubilizing and stabilizing proteins. Other protein assay like BCA and Lowry are ineffective because molecules like reducing agents interfere with the assay. Using Bradford can be advantageous against these molecules because they are compatible to each other and will not interfere.
The linear graph acquired from the assay (absorbance versus protein concentration in μg/mL) can be easily extrapolated to determine the concentration of proteins by using the slope of the line.
It is a sensitive technique. It is also very simple: measuring the OD at 595 nm after 5 minutes of incubation. This method can also make use of a Vis spectrophotometer or a mobile smartphone camera (RGBradford method). | 0 | Theoretical and Fundamental Chemistry |
Unilever PLC in the United Kingdom is developing a pyrolysis-based fecal sludge treatment unit designed to serve over 2000 people. | 1 | Applied and Interdisciplinary Chemistry |
On instroke, the same relationship between force exerted, pressure and effective cross sectional area applies as discussed above for outstroke. However, since the cross sectional area is less than the piston area the relationship between force, pressure and radius is different. The calculation isn't more complicated though, since the effective cross sectional area is merely that of the piston surface minus the cross sectional area of the piston rod.
For instroke, therefore, the relationship between force exerted, pressure, radius of the piston, and radius of the piston rod, is as follows:
Where:
: represents the resultant force
: represents the radius of the piston
: represents the radius of the piston rod
: is pi, approximately equal to 3.14159. | 1 | Applied and Interdisciplinary Chemistry |
BANs are unique in that names are assigned for combination preparations as well as single-drug preparations. For example, the BAN Co-amoxiclav is assigned to preparations containing amoxicillin and clavulanic acid. Most other pharmacopoeias simply refer to combination products by both ingredients in the preparation, in this example "amoxicillin with clavulanic acid".
The prefix of "co-" is used for many combination drugs, including opioid with paracetamol or aspirin analgesics (e.g., Co-codamol, Co-codaprin, Co-dydramol, Co-proxamol). The other commonly encountered opioid combination is the anti-diarrhoeal, non-analgesic mixture of diphenoxylate and atropine, Co-phenotrope (a.k.a. Lomotil). Also antibiotics (e.g., Co-fluampicil and Co-trimoxazole), drugs to lower blood pressure (e.g., Co-tenidone), diuretics (e.g., Co-amilofruse and Co-amilozide), gastrointestinal drugs (e.g., Co-danthrusate), and anti-Parkinsonism agents such as Co-careldopa, Co-beneldopa, and others (e.g., Co-cyprindiol). | 1 | Applied and Interdisciplinary Chemistry |
In 1941, the year in which they graduated from the University of Oxford, Cornforth married Rita Harriet Harradence (b. 1915), with whom he had one son, John, and two daughters, Brenda and Philippa. Cornforth had met Harradence after she had broken a Claisen flask in their second year at the University of Sydney; Cornforth, with his expertise of glassblowing and the use of a blowpipe, mended the break. Rita Cornforth died on 6 November 2012, at home with her family around her, following a long illness.
On an important author or paper that was integral to his success, Cornforth stated that he was particularly impressed by the works of German chemist Hermann Emil Fischer.
Cornforth died in Sussex on 8 December 2013. at the age of 96. Cornforth is survived by his three children and four grandchildren. He was a sceptic and an atheist. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, phosphinites are organophosphorus compounds with the formula . They are used as ligands in homogeneous catalysis and coordination chemistry. | 0 | Theoretical and Fundamental Chemistry |
Small Tim proteins are synthesised lacking a cleavable presequence, but instead containing internal targeting information and need to be imported to the intermembrane space. The intermembrane space import and assembly machinery (MIA) is believed to mediate transport of the small Tim precursors into the intermembrane space subcompartment. MIA is composed of two main essential cysteine-rich proteins; Mia40 and Erv1. Mia40 is also referred to as Tim40 in yeast and deficiency of Mia40 has been reported to affect import of the small Tims. Mia40 is anchored to the mitochondrial inner membrane via an N-terminal hydrophobic segment, exposing a large domain to the intermembrane space. It contains 6 conserved cysteine residues, which allow the binding of incoming Tim precursor proteins. Following import of small Tim proteins into the intermembrane space Mia40 interacts with small Tim proteins via disulfide bonds. Following isomerisation of the disulfide bridge, the polypeptide is released. Mia40 which is now in reduced state, is then oxidised by Erv1. This oxidation step is vital to facilitate further rounds of precursor protein import. Without Erv1 activity, reduced Mia40 accumulates and is in inactive conformation. Interaction between the incoming precursor proteins, Mia40 and Erv1, is maintained as a result of a flow of electrons that are transferred from the incoming protein to Mia40 and from reduced Mia40 to oxidised Erv1. Precursors are then released in oxidised state and form disulfide bridges which prevents their escape out of the intermembrane space. Small Tim proteins are then maintained in active conformation within the intermembrane space by Hot13 (helper of Tims). It is possible that Hot13 may have reducing effects on small Tim proteins as they counterbalance the harmful effects that oxidative agents exhibit. | 1 | Applied and Interdisciplinary Chemistry |
Glycan-Protein interactions represent a class of biomolecular interactions that occur between free or protein-bound glycans and their cognate binding partners. Intramolecular glycan-protein (protein-glycan) interactions occur between glycans and proteins that they are covalently attached to. Together with protein-protein interactions, they form a mechanistic basis for many essential cell processes, especially for cell-cell interactions and host-cell interactions. For instance, SARS-CoV-2, the causative agent of COVID-19, employs its extensively glycosylated spike (S) protein to bind to the ACE2 receptor, allowing it to enter host cells. The spike protein is a trimeric structure, with each subunit containing 22 N-glycosylation sites, making it an attractive target for vaccine search.
Glycosylation, i.e., the addition of glycans (a generic name for monosaccharides and oligosaccharides) to a protein, is one of the major post-translational modification of proteins contributing to the enormous biological complexity of life. Indeed, three different hexoses could theoretically produce from 1056 to 27,648 unique trisaccharides in contrast to only 6 peptides or oligonucleotides formed from 3 amino acids or 3 nucleotides respectively. In contrast to template-driven protein biosynthesis, the "language" of glycosylation is still unknown, making glycobiology a hot topic of current research given their prevalence in living organisms.
The study of glycan-protein interactions provides insight into the mechanisms of cell-signaling and allows to create better-diagnosing tools for many diseases, including cancer. Indeed, there are no known types of cancer that do not involve erratic patterns of protein glycosylation. | 1 | Applied and Interdisciplinary Chemistry |
Solvation significantly affects the basicity of amines. N-H groups strongly interact with water, especially in ammonium ions. Consequently, the basicity of ammonia is enhanced by 10 by solvation. The intrinsic basicity of amines, i.e. the situation where solvation is unimportant, has been evaluated in the gas phase. In the gas phase, amines exhibit the basicities predicted from the electron-releasing effects of the organic substituents. Thus tertiary amines are more basic than secondary amines, which are more basic than primary amines, and finally ammonia is least basic. The order of pK's (basicities in water) does not follow this order. Similarly aniline is more basic than ammonia in the gas phase, but ten thousand times less so in aqueous solution.
In aprotic polar solvents such as DMSO, DMF, and acetonitrile the energy of solvation is not as high as in protic polar solvents like water and methanol. For this reason, the basicity of amines in these aprotic solvents is almost solely governed by the electronic effects. | 0 | Theoretical and Fundamental Chemistry |
The Journal of Chemical Education is a monthly peer-reviewed academic journal available in both print and electronic versions. It is published by the Division of Chemical Education of the American Chemical Society and was established in 1924 by Neil Gordon. The journal covers research on chemical education, and its target audience includes instructors of chemistry from middle school through graduate school and some scientists in commerce, industry, and government. | 1 | Applied and Interdisciplinary Chemistry |
For air with a pressure of 1 bar, the Prandtl numbers in the temperature range between −100 °C and +500 °C can be calculated using the formula given below. The temperature is to be used in the unit degree Celsius. The deviations are a maximum of 0.1% from the literature values.
The Prandtl numbers for water (1 bar) can be determined in the temperature range between 0 °C and 90 °C using the formula given below. The temperature is to be used in the unit degree Celsius. The deviations are a maximum of 1% from the literature values. | 1 | Applied and Interdisciplinary Chemistry |
Another form of bioprinting involves an inkjet printer, which is primarily utilized in biomedical settings. This method prints detailed proteins and nucleic acids. Hydrogels are commonly selected as the bioink. Cells can be printed on to a selected surface media to proliferate and ultimately differentiate. A drawback of this printing method is the ability of the bioinks such as hydrogels to clog the printing nozzle, due to their high viscosity. Ideal inkjet bioprinting involves using a low polymer viscosity (ideally below 10 centipoise), low cell density (<10 million cells/mL), and low structural heights (<10 million cells/mL). | 1 | Applied and Interdisciplinary Chemistry |
Foldits toolbox is mainly for the design of protein molecules. The games creator announced the plan to add, by 2013, the chemical building blocks of organic subcomponents to enable players to design small molecules. The small molecule design system termed Drugit was tested on the Von Hippel-Lindau tumor suppressor (VHL). Results of the VHL experiment were presented in a March 2023 preprint paper and at an August 2023 American Chemical Society conference session. | 1 | Applied and Interdisciplinary Chemistry |
The Venetian blind design is a type of electrostatic direct collector. The Venetian Blind design name comes from the visual similarity of the ribbons to venetian window blinds. Designs in the early 1970s by William Barr and Ralph Moir used repeating metal ribbons at a specified angle as the ion collector plates. These metal ribbon-like surfaces are more transparent to ions going forward than to ions going backward. Ions pass through surfaces of successively increasing potential until they turn and start back, along a parabolic trajectory. They then see opaque surfaces and are caught. Thus ions are sorted by energy with high-energy ions being caught on high-potential electrodes.
William Barr and Ralph Moir then ran a group which did a series of direct energy conversion experiments through the late 1970s and early 1980s. The first experiments used beams of positives and negatives as fuel, and demonstrated energy capture at a peak efficiency of 65 percent and a minimum efficiency of 50 percent. The following experiments involved a true plasma direct converter that was tested on the Tandem Mirror Experiment (TMX), an operating magnetic mirror fusion reactor. In the experiment, the plasma moved along diverging field lines, spreading it out and converting it into a forward moving beam with a Debye length of a few centimeters. Suppressor grids then reflect the electrons, and collector anodes recovered the ion energy by
slowing them down and collecting them at high-potential plates. This machine demonstrated an energy capture efficiency of 48 percent. However, Marshall Rosenbluth argued that keeping the plasma's neutral charge over the very short Debye length distance would be very challenging in practice, though he said that this problem would not occur in every version of this technology.
The Venetian Blind converter can operate with 100 to 150 keV D-T plasma, with an efficiency of about 60% under conditions compatible with economics, and an upper technical conversion efficiency up to 70% ignoring economic limitations. | 0 | Theoretical and Fundamental Chemistry |
Cell proliferation is often regulated by not only external mitogens but also by anti-mitogens, which inhibit cell cycle progression past G1. In normal cells, anti-mitogenic signaling as a result of DNA damage, preventing the cells from replicating and dividing. Tumor cells that are resistant to anti-mitogens allow the cell cycle to move forward when it should be prevented by some anti-mitogenic mechanism. This resistance to anti-mitogens might simply arise from overstimulation by positive mitogens. In other cases, tumor cells possess loss-of-function mutations in some part of the anti-mitogenic pathway. For example, consider the well-known anti-mitogen, transforming growth factor (TGF-𝝱). TGF-𝝱 works by binding to cell-surface receptors and activating the Smad gene regulatory proteins. Smad proteins then trigger an increase in p15, which inhibits cyclin D1 and prevents cell cycle progression. In many cancers, there is a loss-of-function mutation in the Smad proteins, thus negating the entire anti-mitogenic pathway. | 1 | Applied and Interdisciplinary Chemistry |
The introduction of the iron bomb was significant to the history of gunpowder weaponry. Traditionally the inspiration for the development of the iron bomb is ascribed to the tale of a fox hunter named Iron Li. According to the story, around the year 1189 Iron Li developed a new method for hunting foxes which used a ceramic explosive to scare foxes into his nets. The explosive consisted of a ceramic bottle with a mouth, stuffed with gunpowder, and attached with a fuse. Explosive and net were placed at strategic points of places such as watering holes frequented by foxes, and when they got near enough, Iron Li would light the fuse, causing the ceramic bottle to explode and scaring the frightened foxes right into his nets. While a fanciful tale, it's not exactly certain why this would cause the development of the iron bomb, given the explosive was made using ceramics, and other materials such as bamboo or even leather would have done the same job, assuming they made a loud enough noise. Nonetheless, the iron bomb made its first appearance in 1221 at the siege of Qizhou (in modern Hubei), and this time it would be the Jin who possessed the technological advantage. The Song commander Zhao Yurong (趙與褣) survived and was able to relay his account for posterity.
Qizhou was a major fortress city situated near the Yangtze and a 25 thousand strong Jin army advanced on it in 1221. News of the approaching army reached Zhao Yurong in Qizhou, and despite being outnumbered nearly eight to one, he decided to hold the city. Qizhous arsenal consisted of some three thousand thunderclap bombs, twenty thousand "great leather bombs" (皮大炮), and thousands of gunpowder arrows and gunpowder crossbow bolts. While the formula for gunpowder had become potent enough to consider the Song bombs to be true explosives, they were unable to match the explosive power of the Jin iron bombs. Yurong describes the uneven exchange thus, "The barbaric enemy attacked the Northwest Tower with an unceasing flow of catapult projectiles from thirteen catapults. Each catapult shot was followed by an iron fire bomb [catapult shot], whose sound was like thunder. That day, the city soldiers in facing the catapult shots showed great courage as they maneuvered [our own] catapults, hindered by injuries from the iron fire bombs. Their heads, their eyes, their cheeks were exploded to bits, and only one half [of the face] was left." Jin artillerists were able to successfully target the command center itself: "The enemy fired off catapult stones ... nonstop day and night, and the magistrates headquarters [帳] at the eastern gate, as well as my own quarters ..., were hit by the most iron fire bombs, to the point that they struck even on top of [my] sleeping quarters and [I] nearly perished! Some said there was a traitor. If not, how would they have known the way to strike at both of these places?"
Zhao was able to examine the new iron bombs himself and described thus, "In shape they are like gourds, but with a small mouth. They are made with pig iron, about two inches thick, and they cause the city's walls to shake." Houses were blown apart, towers battered, and defenders blasted from their placements. Within four weeks all four gates were under heavy bombardment. Finally the Jin made a frontal assault on the walls and scaled them, after which followed a merciless hunt for soldiers, officers, and officials of every level. Zhao managed an escape by clambering over the battlement and making a hasty retreat across the river, but his family remained in the city. Upon returning at a later date to search the ruins, he found that the "bones and skeletons were so mixed up that there was no way to tell who was who." | 1 | Applied and Interdisciplinary Chemistry |
RNA polymerase II holoenzyme is a form of eukaryotic RNA polymerase II that is recruited to the promoters of protein-coding genes in living cells. It consists of RNA polymerase II, a subset of general transcription factors, and regulatory proteins known as SRB proteins.
Part of the assembly of the holoenzyme is referred to as the preinitiation complex, because its assembly takes place on the gene promoter before the initiation of transcription. The mediator complex acts as a bridge between RNA polymerase II and the transcription factors. | 1 | Applied and Interdisciplinary Chemistry |
In Japan, modafinil is Schedule I psychotropic drug. This means that it is considered to have a high potential for abuse and dependence, and is therefore subject to strict regulations. The use of Schedule I drugs in Japan is generally prohibited, except under certain circumstances, such as for medical purposes. It can only be prescribed by a doctor. It cannot be imported or exported without a permit.
It cannot be used while driving or operating machinery. Cephalon licensed Alfresa Corporation to produce, and Mitsubishi Tanabe Pharma to sell modafinil products under the trade name Modiodal in Japan. There have been arrests of people who imported modafinil for personal use. | 0 | Theoretical and Fundamental Chemistry |
Solvated electrons are involved in the reaction of alkali metals with water, even though the solvated electron has only a fleeting existence. Below pH = 9.6 the hydrated electron reacts with the hydronium ion giving atomic hydrogen, which in turn can react with the hydrated electron giving hydroxide ion and usual molecular hydrogen H.
Solvated electrons can be found even in the gas phase. This implies their possible existence in the upper atmosphere of Earth and involvement in nucleation and aerosol formation.
Its standard electrode potential value is -2.77 V. The equivalent conductivity of 177 Mho cm is similar to that of hydroxide ion. This value of equivalent conductivity corresponds to a diffusivity of 4.75 cms. | 0 | Theoretical and Fundamental Chemistry |
The voltaic pile stimulated a series of improved batteries, such as the Daniell cell, fuel cell and lead acid battery. Their operation was largely understood in the late 1800s from the theories by Wilhelm Ostwald and Walther Nernst. In 1894 Ostwald explained the energy conversion in a fuel cell and stressed that its efficiency was not limited by thermodynamics. Ostwald, together with Jacobus Henricus van 't Hoff, and Svante Arrhenius, was a founding father of electrochemistry and chemical ionic theory, and received a Nobel prize in chemistry in 1909.
His work was continued by Walther Nernst, who derived the Nernst equation and described ionic conduction in heterovalently doped zirconia, which he used in his Nernst lamp. Nernst was inspired by the dissociation theory of Arrhenius published in 1887, which relied on ions in solution. In 1889 he realized the similarity between electrochemical and chemical equilibria, and formulated his famous equation that correctly predicted the output voltage of various electrochemical cells based on liquid electrolytes from the thermodynamic properties of their components.
Besides his theoretical work, in 1897 Nernst patented the first lamp that used a solid electrolyte. Contrary to the existing carbon-filament lamps, Nernst lamp could operate in air and was twice more efficient as its emission spectrum was closer to that of daylight. AEG, a lighting company in Berlin, bought the Nernst’s patent for one million German gold marks, which was a fortune at the time, and used 800 of Nernst lamps to illuminate their booth at the world’s fair Exposition Universelle (1900). | 0 | Theoretical and Fundamental Chemistry |
These are based upon study of the terminal velocity acquired by particles suspended in a viscous liquid. Sedimentation time is longest for the finest particles, so this technique is useful for sizes below 10 μm, but sub-micrometer particles cannot be reliably measured due to the effects of Brownian motion. Typical apparatus disperses the sample in liquid, then measures the density of the column at timed intervals. Other techniques determine the optical density of successive layers using visible light or x-rays.
Advantages: this technique determines particle size as a function of settling velocity.
Disadvantages: Sample must be dispersed in a liquid medium... some particles may (partially or fully) dissolve in the medium altering the size distribution, requiring careful selection of the dispersion media.
Density is highly dependent upon fluid temperature remaining constant.
X-Rays will not count carbon (organic) particles.
Many of these instruments can require a bulk sample (e.g. two to five grams). | 0 | Theoretical and Fundamental Chemistry |
George W. Corner and Willard M. Allen discovered the hormonal action of progesterone in 1929. By 1931–1932, nearly pure crystalline material of high progestational activity had been isolated from the corpus luteum of animals, and by 1934, pure crystalline progesterone had been refined and obtained and the chemical structure of progesterone was determined. This was achieved by Adolf Butenandt at the Chemisches Institut of Technical University in Danzig, who extracted this new compound from several thousand liters of urine.
Chemical synthesis of progesterone from stigmasterol and pregnanediol was accomplished later that year. Up to this point, progesterone, known generically as corpus luteum hormone, had been being referred to by several groups by different names, including corporin, lutein, luteosterone, and progestin. In 1935, at the time of the Second International Conference on the Standardization of Sex Hormones in London, England, a compromise was made between the groups and the name progesterone (progestational steroidal ketone) was created. | 0 | Theoretical and Fundamental Chemistry |
A fresnel is a unit of frequency equal to 10 s. It was occasionally used in the field of spectroscopy, but its use has been superseded by terahertz (with the identical value 10 hertz). It is named for Augustin-Jean Fresnel the physicist whose expertise in optics led to the creation of Fresnel lenses. | 0 | Theoretical and Fundamental Chemistry |
To see this unstable behavior more quantitatively, consider the equations of motion for a fluid element mass in circular motion with an angular velocity In general will be a function of the distance from the rotation axis and we assume that the orbital radius is The centripetal acceleration required to keep the mass in orbit is ; the minus sign indicates a direction toward the center. If this force is gravity from a point mass at the center, then the centripetal acceleration is simply where is the gravitational constant and is the central mass.
Let us now consider small departures from the circular motion of the orbiting mass element caused by some perturbing force. We transform variables into a rotating frame moving with the orbiting mass element at angular velocity with origin located at the unperturbed, orbiting location of the mass element. As usual when working in a rotating frame, we need to add to the equations of motion a Coriolis force plus a centrifugal force The velocity is the velocity as measured in the rotating frame. Furthermore, we restrict our attention to a small neighborhood near say with much smaller than Then the sum of the centrifugal and centripetal forces is
to linear order in With our axis pointing radial outward from the unperturbed location of the fluid element and our axis pointing in the direction of increasing azimuthal angle (the direction of the unperturbed orbit), the and equations of motion for a small departure from a circular orbit are:
where and are the forces per unit mass in the and directions, and a dot indicates a time derivative (i.e., is the velocity, is the acceleration, etc.). Provided that and are either 0 or linear in x and y, this is a system of coupled second-order linear differential equations that can be solved analytically.
In the absence of external forces, and , the equations of motion have solutions with the time dependence where the angular frequency satisfies the equation
where is known as the epicyclic frequency. In our solar system, for example, deviations from a sun-centered circular orbit that are familiar ellipses when viewed by an external viewer at rest, appear instead as small radial and azimuthal oscillations of the orbiting element when viewed by an observer moving with the undisturbed circular motion.
These oscillations trace out a small retrograde ellipse (i.e. rotating in the opposite sense of the large circular orbit), centered on the undisturbed orbital location of the mass element.
The epicyclic frequency may equivalently be written which shows that it is proportional to the radial derivative of the angular momentum per unit mass, or specific angular momentum. The specific angular momentum must increase outward if stable epicyclic oscillations are to exist, otherwise displacements would grow exponentially, corresponding to instability. This is a very general result known as the Rayleigh criterion (Chandrasekhar 1961) for stability. For orbits around a point mass, the specific angular momentum is proportional to so the Rayleigh criterion is well satisfied.
Consider next the solutions to the equations of motion if the mass element is subjected to an external restoring force, where is an arbitrary constant (the "spring constant"). If we now seek solutions for the modal displacements in and with time dependence we find a much more complex equation for
Even though the spring exerts an attractive force, it may destabilize. For example, if the spring constant is sufficiently weak, the dominant balance will be between the final two terms on the left side of the equation. Then, a decreasing outward angular velocity profile will produce negative values for and both positive and negative imaginary values for The negative imaginary root results not in oscillations, but in exponential growth of very small displacements. A weak spring therefore causes the type of instability described qualitatively at the end of the previous section. A strong spring on the other hand, will produce oscillations, as one intuitively expects. | 1 | Applied and Interdisciplinary Chemistry |
The gabT gene encodes for GABA transaminase, an enzyme that catalyzes the conversion of GABA and 2-oxoglutarate into succinate semialdehyde and glutamate. Succinate semialdehyde is then oxidized into succinate by succinate semialdehyde dehydrogenase which is encoded by the gabP gene, thereby entering the TCA cycle as a usable source of energy. The gab operon contributes to homeostasis of polyamines such as putrescine, during nitrogen-limited growth. It is also known to maintain high internal glutamate concentrations under stress conditions. | 1 | Applied and Interdisciplinary Chemistry |
Upon illumination with blue-green light, OCP switches from an orange form (OCP) to a red form (OCP). The reversion of OCP to OCP is light independent and occurs slowly in darkness. OCP is considered the dark, stable form of the protein, and does not contribute to phycobilisome quenching. OCP is considered to be essential for induction of the photoprotection mechanism. The photoconversion from the orange to red form has a poor light efficiency (very low quantum yield), which helps to ensure the protein's photoprotective role only functions during high light conditions; otherwise, the dissipative NPQ process could unproductively divert light energy away from photosynthesis under light-limiting conditions. | 0 | Theoretical and Fundamental Chemistry |
Water is an excellent solvent due to its high dielectric constant. Substances that mix well and dissolve in water are known as hydrophilic ("water-loving") substances, while those that do not mix well with water are known as hydrophobic ("water-fearing") substances. The ability of a substance to dissolve in water is determined by whether or not the substance can match or better the strong attractive forces that water molecules generate between other water molecules. If a substance has properties that do not allow it to overcome these strong intermolecular forces, the molecules are precipitated out from the water. Contrary to the common misconception, water and hydrophobic substances do not "repel", and the hydration of a hydrophobic surface is energetically, but not entropically, favorable.
When an ionic or polar compound enters water, it is surrounded by water molecules (hydration). The relatively small size of water molecules (~ 3 angstroms) allows many water molecules to surround one molecule of solute. The partially negative dipole ends of the water are attracted to positively charged components of the solute, and vice versa for the positive dipole ends.
In general, ionic and polar substances such as acids, alcohols, and salts are relatively soluble in water, and nonpolar substances such as fats and oils are not. Nonpolar molecules stay together in water because it is energetically more favorable for the water molecules to hydrogen bond to each other than to engage in van der Waals interactions with non-polar molecules.
An example of an ionic solute is table salt; the sodium chloride, NaCl, separates into cations and anions, each being surrounded by water molecules. The ions are then easily transported away from their crystalline lattice into solution. An example of a nonionic solute is table sugar. The water dipoles make hydrogen bonds with the polar regions of the sugar molecule (OH groups) and allow it to be carried away into solution. | 1 | Applied and Interdisciplinary Chemistry |
An episome is a special type of plasmid, which remains as a part of the eukaryotic genome without integration. Episomes manage this by replicating together with the rest of the genome and subsequently associating with metaphase chromosomes during mitosis. Episomes do not degrade, unlike standard plasmids, and can be designed so that they are not epigenetically silenced inside the eukaryotic cell nucleus. Episomes can be observed in nature in certain types of long-term infection by adeno-associated virus or Epstein-Barr virus. In 2004, it was proposed that non-viral episomes might be used in genetic therapy for long-term change in gene expression.
As of 1999, there were many known sequences of DNA (deoxyribonucleic acid) that allow a standard plasmid to become episomally retained. One example is the S/MAR sequence.
The length of episomal retention is fairly variable between different genetic constructs and there are many known features in the sequence of an episome which will affect the length and stability of genetic expression of the carried transgene. Among these features is the number of CpG sites which contribute to epigenetic silencing of the transgene carried by the episome. | 1 | Applied and Interdisciplinary Chemistry |
The structure of the open channel structure was solved by two independent research teams in 2009 at low pH values of 4-4.6 (GLIC being proton-gated). | 1 | Applied and Interdisciplinary Chemistry |
The 1993 Chemical Weapons Convention (CWC) is the most recent arms control agreement with the force of International law. Its full name is the Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on their Destruction. That agreement outlaws the production, stockpiling and use of chemical weapons. It is administered by the Organisation for the Prohibition of Chemical Weapons (OPCW), which is an independent organization based in The Hague.
The OPCW administers the terms of the CWC to 192 signatories, which represents 98% of the global population. , 66,368 of 72,525 metric tonnes, (92% of chemical weapon stockpiles), have been verified as destroyed. The OPCW has conducted 6,327 inspections at 235 chemical weapon-related sites and 2,255 industrial sites. These inspections have affected the sovereign territory of 86 States Parties since April 1997. Worldwide, 4,732 industrial facilities are subject to inspection under provisions of the CWC. | 1 | Applied and Interdisciplinary Chemistry |
* Sherwood, L. (2004). Human Physiology From Cells to Systems, 5th Ed (p. 680). Belmont, CA: Brooks/Cole-Thomson Learning
* Wilmore, J., Costill, D. (2004). Physiology of Sport and Exercise, 3rd Ed (p. 164). Champaign, IL: Human Kinetics | 1 | Applied and Interdisciplinary Chemistry |
One example is the pair . The former has one water of crystallization but the latter does not.
Another example is the pair of titanium(III) chlorides, . The former is violet and the latter, with two molecules of water of crystallization, is green. | 0 | Theoretical and Fundamental Chemistry |
To determine the energy levels, the polygon corresponding to the cyclic annulene is desired is inscribed in the circle of radius 2β and centered at α (the energy of an isolated p orbital). The y-coordinate of the vertices of the polygon are the simple Hückel theory orbital energies. For systems with Hückel topology, the vertex is positioned at the circle bottom as suggested by Frost; for systems with Möbius topology, a polygon side is positioned at the circle bottom. In other words, for an N carbon system, the Möbius Frost circle is rotated by π/N radians compared to the Hückel system. It is seen that with one MO at the bottom and then groups of degenerate pairs, the Hückel systems will accommodate 4n + 2 electrons, following the ordinary Hückel rule. However, in contrast, the Möbius Systems have degenerate pairs of molecular orbitals starting at the circle bottom and thus will accommodate 4n electrons. For cyclic annulenes one then predicts which species will be favored. The method applies equally to cyclic reaction intermediates and transition states for pericyclic processes. | 0 | Theoretical and Fundamental Chemistry |
As well as the faecally derived stanol, two other isomers can be identified in the environment; 5α-cholestanol | 1 | Applied and Interdisciplinary Chemistry |
Human genes encoding KRAB-ZFPs include KOX1/ZNF10, KOX8/ZNF708, ZNF43, ZNF184, ZNF91, HPF4, HTF10 and HTF34. | 1 | Applied and Interdisciplinary Chemistry |
Nitriles are precursors to transition metal nitrile complexes, which are reagents and catalysts. Examples include tetrakis(acetonitrile)copper(I) hexafluorophosphate () and bis(benzonitrile)palladium dichloride (). | 0 | Theoretical and Fundamental Chemistry |
Alkyl sulfonates are esters of alkane sulfonic acids with the general formula R-SO-O-R'. They act as alkylating agents, some of them are used as alkylating antineoplastic agents in the treatment of cancer, e.g. Busulfan. | 0 | Theoretical and Fundamental Chemistry |
The five littoral states build consensus on legally binding governance of the Caspian Sea through Special Working Groups of a Convention on the Legal Status of the Caspian Sea. In advance of a Caspian Summit, the 51st Special Working Group took place in Astana in May 2018 and found consensus on multiple agreements: Agreements on cooperation in the field of transport; trade and economic cooperation; prevention of incidents on the sea; combating terrorism; fighting against organized crime; and border security cooperation.
The convention grants jurisdiction over of territorial waters to each neighboring country, plus an additional of exclusive fishing rights on the surface, while the rest is international waters. The seabed, on the other hand, remains undefined, subject to bilateral agreements between countries. Thus, the Caspian Sea is legally neither fully a sea nor a lake.
While the convention addresses caviar production, oil and gas extraction, and military uses, it does not touch on environmental issues. | 1 | Applied and Interdisciplinary Chemistry |
AMGs are not randomly distributed throughout genomes. Current research is being done to determine the genes that most commonly surround specific AMGs. Hyperplastic regions including the region between genes g15-g18 has been classified as locales where multiple AMGs have been inserted. Possible AMG contexts can be divided into locally collinear blocks (LCBs), or homologous regions shared by multiple viruses without rearrangements. AMGs have been found in just one or up to 14 LCBs. Those found in more diverse contexts have also shown up in variable locales within the LCB. | 1 | Applied and Interdisciplinary Chemistry |
Xerophthalmia, caused by a severe vitamin A deficiency, is described by pathologic dryness of the conjunctival epithelium and cornea. The conjunctiva becomes dry, thick, and wrinkled. Indicative is the appearance of Bitots spots, which are clumps of keratin debris that build up inside the conjunctiva. If untreated, xerophthalmia can lead to dry eye syndrome, corneal ulceration and ultimately to blindness as a result of cornea and retina damage. Although xerophthalmia is an eye-related issue, prevention (and reversal) are functions of retinoic acid having been synthesized from retinal rather than the 11-cis'-retinal to rhodopsin cycle.
Throughout southeast Asia, estimates are that more than half of children under the age of six years have subclinical vitamin A deficiency and night blindness, with progression to xerophthalmia being the leading cause of preventable childhood blindness. Estimates are that each year there are 350,000 cases of childhood blindness due to vitamin A deficiency. The causes are vitamin A deficiency during pregnancy, followed by low transfer of vitamin A during lactation and infant/child diets low in vitamin A or beta-carotene. The prevalence of pre-school age children who are blind due to vitamin A deficiency is lower than expected from incidence of new cases only because childhood vitamin A deficiency significantly increases all-cause mortality.
According to a 2017 Cochrane review, vitamin A deficiency, using serum retinol less than 0.70 µmol/L as a criterion, is a major public health problem affecting an estimated 190 million children under five years of age in low- and middle-income countries, primarily in Sub-Saharan Africa and Southeast Asia. In lieu of or in combination with food fortification programs, many countries have implemented public health programs in which children are periodically given very large oral doses of synthetic vitamin A, usually retinyl palmitate, as a means of preventing and treating VAD. Doses were 50,000 to 100,000 IU (International units) for children aged 6 to 11 months and 100,000 to 200,000 IU for children aged 12 months to five years, the latter typically every four to six months. In addition to a 24% reduction in all-cause mortality, eye-related results were reported. Prevalence of Bitot's spots at follow-up were reduced by 58%, night blindness by 68%, xerophthalmia by 69%. | 1 | Applied and Interdisciplinary Chemistry |
A mechanism involving arbitrium has recently been described in bacteriophages infecting several Bacillus species. The viruses communicate with each other to ascertain their own density compared to potential hosts. They use this information to decide whether to enter a lytic or lysogenic life-cycle.This decision is crucial as it affects their replication strategy and potential to spread within the host population, optimizing their survival and proliferation under varying environmental conditions. This communication mechanism enables a coordinated infection strategy, significantly enhancing the efficiency of phage proliferation. By synchronizing their life cycles, bacteriophages can maximize their impact on the host population, potentially leading to more effective control of bacterial densities. | 1 | Applied and Interdisciplinary Chemistry |
Articles relating to Tampa Bay, the body of water. For articles on the wider area, see :Category:Tampa Bay Area. | 1 | Applied and Interdisciplinary Chemistry |
Until recently thermodynamics has only considered systems coupled to a thermal bath and, therefore, satisfying Boltzmann statistics. However, some systems do not satisfy these conditions and are far from equilibrium such as living matter, for which fluctuations are expected to be non-Gaussian.
Active particle systems are able to take energy from their environment and drive themselves far from equilibrium. An important example of active matter is constituted by objects capable of self propulsion. Thanks to this property, they feature a series of novel behaviours that are not attainable by matter at thermal equilibrium, including, for example, swarming and the emergence of other collective properties. A passive particle is considered in an active bath when it is in an environment where a wealth of active particles are present. These particles will exert nonthermal forces on the passive object so that it will experience non-thermal fluctuations and will behave widely different from a passive Brownian particle in a thermal bath. The presence of an active bath can significantly influence the microscopic thermodynamics of a particle. Experiments have suggested that the Jarzynski equality does not hold in some cases due to the presence of non-Boltzmann statistics in active baths. This observation points towards a new direction in the study of non-equilibrium statistical physics and stochastic thermodynamics, where also the environment itself is far from equilibrium.
Active baths are a question of particular importance in biochemistry. For example, biomolecules within cells are coupled with an active bath due to the presence of molecular motors within the cytoplasm, which leads to striking and largely not yet understood phenomena such as the emergence of anomalous diffusion (Barkai et al., 2012). Also, protein folding might be facilitated by the presence of active fluctuations (Harder et al., 2014b) and active matter dynamics could play a central role in several biological functions (Mallory et al., 2015; Shin et al., 2015; Suzuki et al., 2015). It is an open question to what degree stochastic thermodynamics can be applied to systems coupled to active baths. | 0 | Theoretical and Fundamental Chemistry |
MMC Estates and Rathbone Jersey Limited purchased the site in May 2004, and said: "Any successful regeneration must find alternative uses and following discussions with the council, the site was defined as an area of opportunity for a mixed use urban village type development, comprising primarily employment and residential development supported by an appropriate level of ancillary uses. This will be supported by an environmental impact statement. MMC is a local developer responsible for the sympathetic council-backed regeneration of other sites within the borough, and has commenced some clearance works involving the felling of trees which are not protected by tree preservation orders." A Rochdale Council Draft Unitary Development Plan published earlier in the year had accepted that "the whole site is contaminated as a result of the industrial processes carried out there" and Administrators of Turner's considered the site "an asset of dubious value, (possibly even a liability)." The Administrators also stated that if mesothelioma or asbestos-related cancer deaths arose from any future development on the site, the liability for this would rest with the new owners and developers of the land. | 1 | Applied and Interdisciplinary Chemistry |
Some researchers have speculated that Earth may have been seeded by organic compounds early in its development by tholin-rich comets, providing the raw material necessary for life to develop (see Miller–Urey experiment for discussion related to this). Tholins do not exist naturally on present-day Earth due to the oxidizing properties of the free oxygen component of its atmosphere ever since the Great Oxygenation Event around 2.4 billion years ago.
Laboratory experiments suggest that tholins near large pools of liquid water that might persist for thousands of years could facilitate the formation of prebiotic chemistry to take place, and has implications on the origins of life on Earth and possibly other planets. Also, as particles in the atmosphere of an exoplanet, tholins affect the light scatter and act as a screen for protecting planetary surfaces from ultraviolet radiation, affecting habitability. Laboratory simulations found derived residues related to amino acids as well as urea, with important astrobiological implications.
On Earth, a wide variety of soil bacteria are able to use laboratory-produced tholins as their sole source of carbon. Tholins could have been the first microbial food for heterotrophic microorganisms before autotrophy evolved. | 0 | Theoretical and Fundamental Chemistry |
NETA is marketed in high-dose 5 mg oral tablets in the United States under the brand names Aygestin and Norlutate for the treatment of gynecological disorders. In addition, it is available under a large number of brand names at much lower dosages (0.1 to 1 mg) in combination with estrogens such as ethinylestradiol and estradiol as a combined oral contraceptive and for use in menopausal hormone therapy for the treatment of menopausal symptoms. | 1 | Applied and Interdisciplinary Chemistry |
Internal heat is the heat source from the interior of celestial objects, such as stars, brown dwarfs, planets, moons, dwarf planets, and (in the early history of the Solar System) even asteroids such as Vesta, resulting from contraction caused by gravity (the Kelvin–Helmholtz mechanism), nuclear fusion, tidal heating, core solidification (heat of fusion released as molten core material solidifies), and radioactive decay. The amount of internal heating depends on mass; the more massive the object, the more internal heat it has; also, for a given density, the more massive the object, the greater the ratio of mass to surface area, and thus the greater the retention of internal heat. The internal heating keeps celestial objects warm and active. | 0 | Theoretical and Fundamental Chemistry |
Asymmetrical flow field flow fractionation (AF4) is nowadays a common and state-of-the art method for fractionation and separation of macromolecules and particles in a suspension. AF4 is an alternative to HPLC and SEC in cases where column chromatography is not suitable for the analyte. HPLC or SEC would be used for liquid separations for molecules up to 1000 kDa and nanoparticles up to 10 nm. As the size increases above 10 nm, AF4 becomes superior in terms of resolution and recovery.
AF4's applications are flexible for many analytical conditions where a column-based method would be unable to properly separate the desired particles. For macromolecules and nanoparticles AF4 is an alternative method especially when the stationary phase in columns interacts with the sample. AF4 is specifically powerful for inhomogeneous samples where it can separate soluble macromolecules from particles or aggregates.
AF4 and other FFF methods have been extensively used in environmental research on the impact of nano materials and to characterize condensed tannins oxidation.
For high molar mass and branched polymers, AF4 has been shown to achieve good separation, whereas SEC fails, and AF4 has been applied to polyolefines at temperatures above 150 C.
Detection methods are the same as for FFF in general, UV is most popular as a concentration detector, but most AF4 systems include a multi-angle light scattering detector for direct measurement or size and molar mass. | 0 | Theoretical and Fundamental Chemistry |
Colored dissolved organic matter (CDOM) is the optically measurable component of dissolved organic matter in water. Also known as chromophoric dissolved organic matter, yellow substance, and gelbstoff, CDOM occurs naturally in aquatic environments and is a complex mixture of many hundreds to thousands of individual, unique organic matter molecules, which are primarily leached from decaying detritus and organic matter. CDOM most strongly absorbs short wavelength light ranging from blue to ultraviolet, whereas pure water absorbs longer wavelength red light. Therefore, water with little or no CDOM, such as the open ocean, appears blue. Waters containing high amounts of CDOM can range from brown, as in many rivers, to yellow and yellow-brown in coastal waters. In general, CDOM concentrations are much higher in fresh waters and estuaries than in the open ocean, though concentrations are highly variable, as is the estimated contribution of CDOM to the total dissolved organic matter pool. | 0 | Theoretical and Fundamental Chemistry |
Cement, California is a mining and manufacturing ghost town in Solano County now enveloped within the boundaries of the United States city of Fairfield. Cement was established as a company town at the turn of the 20th century and it quickly became a boomtown. It was founded and owned by the Pacific Portland Cement Company, who produced Portland cement that was bagged and labeled under the company's "Golden Gate" trademarked brand. It was shuttered in 1927, structures and equipment were auctioned off, and its remains are now in ruins or were moved away. | 1 | Applied and Interdisciplinary Chemistry |
PELP1 is located on chromosome 17p13.2 and PELP1 is expressed in a wide variety of tissues; its highest expression levels are found in the brain, testes, ovaries, and uterus. Currently, there are two known isoforms (long 3.8 Kb and short 3.4 Kb) and short isoform is widely expressed in cancer cells. | 1 | Applied and Interdisciplinary Chemistry |
Flocculation is widely employed to measure the progress of curd formation in the initial stages of cheese making to determine how long the curds must set. The reaction involving the rennet micelles are modeled by Smoluchowski kinetics. During the renneting of milk the micelles can approach one another and flocculate, a process that involves hydrolysis of molecules and macropeptides.
Flocculation is also used during cheese wastewater treatment. Three different coagulants are mainly used:
* FeSO (iron(II) sulfate)
* Al(SO) (aluminium sulfate)
* FeCl (iron(III) chloride) | 1 | Applied and Interdisciplinary Chemistry |
The Cossee–Arlman mechanism in polymer chemistry is the main pathway for the formation of C–C bonds in the polymerization of alkenes. The mechanism features an intermediate coordination complex that contains both the growing polymer chain and the monomer (alkene). These ligands combine within the coordination sphere of the metal to form a polymer chain that is elongated by two carbons.
The details of this mechanism can be used to explain the stereoregularity of the polymerisation of alkenes using Ziegler–Natta or metallocene catalysts. Stereoregularity is relevant for unsymmetrical alkenes such as propylene. The coordination sphere of the metal ligands sterically influences which end of the propylene attaches to the growing polymer chain and the relative stereochemistry of the methyl groups on the polymer. The stereoregularity is influenced by the ligands. For the metallocene catalysts, the cyclopentadienyl ligands (or their surrogates) fulfill this role. For heterogeneous catalysts, the stereoregularity is determined by the surface structure around the active site on the catalyst particle, and can be influenced by additives such as succinates or phthalates, which tend to block specific sites, while leaving others (with different stereoreactivity) to catalyse the polymerization. | 0 | Theoretical and Fundamental Chemistry |
; Note
* There is no difference between the lower and higher heating values for the combustion of carbon, carbon monoxide and sulfur since no water is formed during the combustion of those substances.
* BTU/lb values are calculated from MJ/kg (1 MJ/kg = 430 BTU/lb). | 0 | Theoretical and Fundamental Chemistry |
Millon's reagent is an analytical reagent used to detect the presence of soluble proteins. A few drops of the reagent are added to the test solution, which is then heated gently. A reddish-brown coloration or precipitate indicates the presence of tyrosine residue which occur in nearly all proteins. The test was developed by the French chemist Auguste Nicolas Eugene Millon.
The reagent is made by dissolving metallic mercury in nitric acid and diluting with water, forming mercuric nitrate (Hg[NO]). In the test, the phenol group in the side chain of tyrosine gets nitrated, and that product then complexes with Hg(I) or Hg(II) ions to give a red colored precipitate. Millon's test is not specific for proteins; it also gives a positive test for other compounds containing the phenol functional group. Therefore, the biuret test or the ninhydrin reaction are used along with it to confirm the presence of proteins. | 0 | Theoretical and Fundamental Chemistry |
While at Loughborough, Scarlett served as a local councillor for Charnwood District Council and was appointed to represent Leicestershire County Council on the Trent River Authority, where he rose to the position of Chairman of Water Management. He contemplated a full-time career in politics, but decided to stay as an academic. | 1 | Applied and Interdisciplinary Chemistry |
The hemin/G-Quadruplex DNAzyme consists of G-Quadruplex forming DNA that can bind the co-factor hemin (a.k.a. Fe(III)Protoporphyrin IX), forming a complex that can perform certain oxidation reaction in the presence of hydrogen peroxide. This DNAzyme can oxidize small molecules, such as dopamine and adenosine triphosphate, but can also be used for the modification of peptides and proteins by attaching small molecules. | 0 | Theoretical and Fundamental Chemistry |
A given restriction enzyme cuts DNA segments within a specific nucleotide sequence, at what is called a restriction site. These recognition sequences are typically four, six, eight, ten, or twelve nucleotides long and generally palindromic (i.e. the same nucleotide sequence in the 5 – 3 direction). Because there are only so many ways to arrange the four nucleotides that compose DNA (Adenine, Thymine, Guanine and Cytosine) into a four- to twelve-nucleotide sequence, recognition sequences tend to occur by chance in any long sequence. Restriction enzymes specific to hundreds of distinct sequences have been identified and synthesized for sale to laboratories, and as a result, several potential "restriction sites" appear in almost any gene or locus of interest on any chromosome. Furthermore, almost all artificial plasmids include a (often entirely synthetic) polylinker (also called "multiple cloning site") that contains dozens of restriction enzyme recognition sequences within a very short segment of DNA. This allows the insertion of almost any specific fragment of DNA into plasmid vectors, which can be efficiently "cloned" by insertion into replicating bacterial cells.
After restriction digest, DNA can then be analysed using agarose gel electrophoresis. In gel electrophoresis, a sample of DNA is first "loaded" onto a slab of agarose gel (literally pipetted into small wells at one end of the slab). The gel is then subjected to an electric field, which draws the negatively charged DNA across it. The molecules travel at different rates (and therefore end up at different distances) depending on their net charge (more highly charged particles travel further), and size (smaller particles travel further). Since none of the four nucleotide bases carry any charge, net charge becomes insignificant and size is the main factor affecting rate of diffusion through the gel. Net charge in DNA is produced by the sugar-phosphate backbone. This is in contrast to proteins, in which there is no "backbone", and net charge is generated by different combinations and numbers of charged amino acids. | 1 | Applied and Interdisciplinary Chemistry |
The majority of synthetic ion channels follow an Eisenman I sequence (Cs > Rb > K > Na >> Li) in their selectivity for alkali metal cations, suggesting that the origin of the selectivity is governed by the difference in energy required to remove water from a fully hydrated cation. A few synthetic channels show other patterns of ion selectivity, and only a single instance in which a synthetic channel following the opposite selectivity sequence (Eisenman XI; Cs ) had been reported. | 0 | Theoretical and Fundamental Chemistry |
Copper and copper-based metals continued to be the major metal in use during the first part of the Iron Age (end of 2nd–beginning of 1st millennium BCE). Bronze scrap re-melting continued (mainly v-shaped clay crucibles, slags, clay tuyères) and structures of open campfires full of metal production remains were found in several sites in Israel associated mainly with the Philistines and the Sea People settlements on the northern Sharon coast between modern Tel Aviv and Haifa, e.g., Tel Qasile, Tel Gerisa, Tel Dor, and Tel Dan, in northern Israel. Only later in the Iron Age did metallic iron start to play a major role as a base metal for tools and weapons.
XRF analyses of metals, metallurgical remains, and FTIR + XRF analyses of archaeological sediments
from the open industrial area G in Tel Dor enabled the identification of the exact locations of metal working during the end of the Late Bronze Age and the Iron Age. It was also possible to partially reconstruct the pyrotechnological events that probably involved re-melting bronze in an open fireplace. Even after thousands of years the ash, charcoal, calcite, and burnt ground in the immediate vicinity of the metal work area retained significantly higher values of copper (circa 0.05 wt% Cu) than the surrounding archaeological layers.
During Iron Age II and III and the Persian Period (the first half of the first millennium BCE), copper-based objects continued to be present beside growing numbers of iron products. Silver hoards containing small tongueshaped bar chunks or scrapped jewellery became more and more common in the archaeological context in Israel as well as all over the Mediterranean. A similar phenomenon was evident during the Persian Period on the coast of Israel, where copper and copper-based objects were found in relatively large quantities and with parallels in other sites all around the Mediterranean Sea. What could be defined as a basic Phoenician metal “kit” is composed mainly of the “Irano–Scythian” shape of three winged and socketed arrowheads made mainly of tin bronze, sometimes with arsenic and/or lead and left as-cast, and “hand”-like decorated fibulae made of good quality (7 wt%–12 wt% Sn) tin bronze and lead (up to 17 wt% Pb). They underwent mechanical treatment after casting and an extensive final cold working in the area where the needle spring was fastened into the fibulae body. Long unalloyed copper nails that were found in coastal sites as well as part of the structure of ships were found in the shipwreck from Ma’agan Mikhael. | 1 | Applied and Interdisciplinary Chemistry |
The protons and neutrons that comprise an atomic nucleus behave almost identically within the nucleus. The approximate symmetry of isospin treats these particles as identical, but in a different quantum state. This symmetry is only approximate, however, and the nuclear force that binds nucleons together is a complicated function depending on nucleon type, spin state, electric charge, momentum, etc. and with contributions from non-central forces. The nuclear force is not a fundamental force of nature, but a consequence of the residual effects of the strong force that surround the nucleons. One consequence of these complications is that although deuterium, a bound state of a proton (p) and a neutron (n) is stable, exotic nuclides such as diproton or dineutron are unbound. The nuclear force is not sufficiently strong to form either p-p or n-n bound states, or equivalently, the nuclear force does not form a potential well deep enough to bind these identical nucleons.
Stable nuclides require approximately equal numbers of protons and neutrons. The stable nuclide carbon-12 (C) is composed of six neutrons and six protons, for example. Protons have a positive charge, hence within a nuclide with many protons there are large repulsive forces between protons arising from the Coulomb force. By acting to separate protons from one another, the neutrons within a nuclide play an essential role in stabilizing nuclides. With increasing atomic number, even greater numbers of neutrons are required to obtain stability. The heaviest stable element, lead (Pb), has many more neutrons than protons. The stable nuclide Pb has Z = 82 and N = 124, for example. For this reason, the valley of stability does not follow the line Z = N for A larger than 40 (Z = 20 is the element calcium). Neutron number increases along the line of beta stability at a faster rate than atomic number.
The line of beta stability follows a particular curve of neutron–proton ratio, corresponding to the most stable nuclides. On one side of the valley of stability, this ratio
is small, corresponding to an excess of protons over neutrons in the nuclides. These nuclides tend to be unstable to β decay or electron capture, since such decay converts a proton to a neutron. The decay serves to move the nuclides toward a more stable neutron-proton ratio. On the other side of the valley of stability, this ratio is large, corresponding to an excess of neutrons over protons in the nuclides. These nuclides tend to be unstable to β decay, since such decay converts neutrons to protons. On this side of the valley of stability, β decay also serves to move nuclides toward a more stable neutron-proton ratio. | 0 | Theoretical and Fundamental Chemistry |
Rivers have always been a reliable source for human communities. They have been a preferable place for settlements in early history and still provide a rich environment for big cities. Many trade routes lead along rivers and build global connections. | 1 | Applied and Interdisciplinary Chemistry |
They directly damage DNA, but may or may not undergo metabolism to produce promutagens (metabolites that can have higher mutagenic potential than their substrates).
* Reactive oxygen species (ROS) – These may be superoxide, hydroxyl radicals and hydrogen peroxide, and large number of these highly reactive species are generated by normal cellular processes, for example as a by-products of mitochondrial electron transport, or lipid peroxidation. As an example of the latter, 15-hydroperoxyicosatetraenocic acid, a natural product of cellular cyclooxygenases and lipoxygenases, breaks down to form 4-hydroxy-2(E)-nonenal, 4-hydroperoxy-2(E)-nonenal, 4-oxo-2(E)-nonenal, and cis-4,5-epoxy-2(E)-decanal; these bifunctional electophils are mutagenic in mammalian cells and may contribute to the development and/or progression of human cancers (see 15-Hydroxyicosatetraenoic acid). A number of mutagens may also generate these ROS. These ROS may result in the production of many base adducts, as well as DNA strand breaks and crosslinks.
* Deaminating agents, for example nitrous acid which can cause transition mutations by converting cytosine to uracil.
* Polycyclic aromatic hydrocarbons (PAH), when activated to diol-epoxides can bind to DNA and form adducts.
* Alkylating agents such as ethylnitrosourea. The compounds transfer methyl or ethyl group to bases or the backbone phosphate groups. Guanine when alkylated may be mispaired with thymine. Some may cause DNA crosslinking and breakages. Nitrosamines are an important group of mutagens found in tobacco, and may also be formed in smoked meats and fish via the interaction of amines in food with nitrites added as preservatives. Other alkylating agents include mustard gas and vinyl chloride.
* Aromatic amines and amides have been associated with carcinogenesis since 1895 when German physician Ludwig Rehn observed high incidence of bladder cancer among workers in German synthetic aromatic amine dye industry. 2-Acetylaminofluorene, originally used as a pesticide but may also be found in cooked meat, may cause cancer of the bladder, liver, ear, intestine, thyroid and breast.
* Alkaloid from plants, such as those from Vinca species, may be converted by metabolic processes into the active mutagen or carcinogen.
* Bromine and some compounds that contain bromine in their chemical structure.
* Sodium azide, an azide salt that is a common reagent in organic synthesis and a component in many car airbag systems
* Psoralen combined with ultraviolet radiation causes DNA cross-linking and hence chromosome breakage.
* Benzene, an industrial solvent and precursor in the production of drugs, plastics, synthetic rubber and dyes. | 0 | Theoretical and Fundamental Chemistry |
Splat cooling is a method for quenching small droplets of molten materials by rapid contact with a cold surface. The particles undergo a characteristic cooling process, with the heat profile at for initial temperature as the maximum at and at and , and the heat profile at for as the boundary conditions. Splat cooling rapidly ends in a steady state temperature, and is similar in form to the Gaussian diffusion equation. The temperature profile, with respect to the position and time of this type of cooling, varies with:
Splat cooling is a fundamental concept that has been adapted for practical use in the form of thermal spraying. The thermal diffusivity coefficient, represented as , can be written as . This varies according to the material. | 1 | Applied and Interdisciplinary Chemistry |
Center of pressure is used in sailboat design to represent the position on a sail where the aerodynamic force is concentrated.
The relationship of the aerodynamic center of pressure on the sails to the hydrodynamic center of pressure (referred to as the center of lateral resistance) on the hull determines the behavior of the boat in the wind. This behavior is known as the "helm" and is either a weather helm or lee helm. A slight amount of weather helm is thought by some sailors to be a desirable situation, both from the standpoint of the "feel" of the helm, and the tendency of the boat to head slightly to windward in stronger gusts, to some extent self-feathering the sails. Other sailors disagree and prefer a neutral helm.
The fundamental cause of "helm", be it weather or lee, is the relationship of the center of pressure of the sail plan to the center of lateral resistance of the hull. If the center of pressure is astern of the center of lateral resistance, a weather helm, the tendency of the vessel is to want to turn into the wind.
If the situation is reversed, with the center of pressure forward of the center of lateral resistance of the hull, a "lee" helm will result, which is generally considered undesirable, if not dangerous. Too much of either helm is not good, since it forces the helmsman to hold the rudder deflected to counter it, thus inducing extra drag beyond what a vessel with neutral or minimal helm would experience. | 1 | Applied and Interdisciplinary Chemistry |
Vancomycin is one of the few antibiotics used in plant tissue culture to eliminate Gram-positive bacterial infection. It has relatively low toxicity to plants. | 0 | Theoretical and Fundamental Chemistry |
Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of both water clarity and water quality.
Fluids can contain suspended solid matter consisting of particles of many different sizes. While some suspended material will be large enough and heavy enough to settle rapidly to the bottom of the container if a liquid sample is left to stand (the settable solids), very small particles will settle only very slowly or not at all if the sample is regularly agitated or the particles are colloidal. These small solid particles cause the liquid to appear turbid.
Turbidity (or haze) is also applied to transparent solids such as glass or plastic. In plastic production, haze is defined as the percentage of light that is deflected more than 2.5° from the incoming light direction. | 0 | Theoretical and Fundamental Chemistry |
Carbon-carbon bond activation refers to the breaking of carbon-carbon bonds in organic molecules. This process is an important tool in organic synthesis, as it allows for the formation of new carbon-carbon bonds and the construction of complex organic molecules. However, C–C bond activation is challenging mainly for the following reasons: (1) C-H bond activation is a competitive process of C-C activation, which is both energetically and kinetically more favorable; (2) the accessibility of the transition metal center to C–C bonds is generally difficult due to its hidden nature; (3) relatively high stability of the C–C bond (90 kcal/mol). As a result, in the early stage, most examples of C-C activation are of stringed ring systems, which makes C-C activation more favorable by increasing the energy of the starting material. However, C-C activation of unstrained C-C bonds has remained challenging until the recent two decades. | 0 | Theoretical and Fundamental Chemistry |
Catholic Bishops in Kenya are among those who have spread a conspiracy theory asserting that HCG forms part of a covert sterilization program, forcing denials from the Kenyan government.
In order to induce a stronger immune response, some versions of human chorionic gonadotropin-based anti-fertility vaccines were designed as conjugates of the β subunit of HCG covalently linked to tetanus toxoid. It was alleged that a non-conjugated tetanus vaccine used in developing countries was laced with a human chorionic gonadotropin-based anti-fertility drug and was distributed as a means of mass sterilization. This charge has been vigorously denied by the World Health Organization (WHO) and UNICEF. Others have argued that a hCG-laced vaccine could not possibly be used for sterilization, since the effects of the anti-fertility vaccines are reversible (requiring booster doses to maintain infertility) and a non-conjugated vaccine is likely to be ineffective. Finally, independent testing of the tetanus vaccine by Kenya's health authorities revealed no traces of the human chorionic gonadotropin hormone. | 1 | Applied and Interdisciplinary Chemistry |
In quantum physics, the scattering amplitude is the probability amplitude of the outgoing spherical wave relative to the incoming plane wave in a stationary-state scattering process.
At large distances from the centrally symmetric scattering center, the plane wave is described by the wavefunction
where is the position vector; ; is the incoming plane wave with the wavenumber along the axis; is the outgoing spherical wave; is the scattering angle (angle between the incident and scattered direction); and is the scattering amplitude. The dimension of the scattering amplitude is length. The scattering amplitude is a probability amplitude; the differential cross-section as a function of scattering angle is given as its modulus squared,
The asymptotic form of the wave function in arbitrary external field takes the form
where is the direction of incidient particles and is the direction of scattered particles. | 0 | Theoretical and Fundamental Chemistry |
Photostimulation is the use of light to artificially activate biological compounds, cells, tissues, or even whole organisms. Photostimulation can be used to noninvasively probe various relationships between different biological processes, using only light. In the long run, photostimulation has the potential for use in different types of therapy, such as migraine headache. Additionally, photostimulation may be used for the mapping of neuronal connections between different areas of the brain by “uncaging” signaling biomolecules with light. Therapy with photostimulation has been called light therapy, phototherapy, or photobiomodulation.
Photostimulation methods fall into two general categories: one set of methods uses light to uncage a compound that then becomes biochemically active, binding to a downstream effector. For example, uncaging glutamate is useful for finding excitatory connections between neurons, since the uncaged glutamate mimics the natural synaptic activity of one neuron impinging upon another. The other major photostimulation method is the use of light to activate a light-sensitive protein such as rhodopsin, which can then excite the cell expressing the opsin.
Scientists have long postulated the need to control one type of cell while leaving those surrounding it untouched and unstimulated. Well-known scientific advancements such as the use of electrical stimuli and electrodes have succeeded in neural activation but fail to achieve the aforementioned goal because of their imprecision and inability to distinguish between different cell types. The use of optogenetics (artificial cell activation via the use of light stimuli) is unique in its ability to deliver light pulses in a precise and timely fashion. Optogenetics is somewhat bidirectional in its ability to control neurons. Channels can be either depolarized or hyperpolarized depending on the wavelength of light that targets them. For instance, the technique can be applied to channelrhodopsin cation channels to initiate neuronal depolarization and eventually activation upon illumination. Conversely, activity inhibition of a neuron can be triggered via the use of optogenetics as in the case of the chloride pump halorhodopsin which functions to hyperpolarize neurons.
Before optogenetics can be performed, however, the subject at hand must express the targeted channels. Natural and abundant in microbials, rhodopsins—including bacteriorhodopsin, halorhodopsin and channelrhodopsin—each have a different characteristic action spectrum which describes the set of colors and wavelengths that they respond to and are driven to function by.
It has been shown that channelrhodopsin-2, a monolithic protein containing a light sensor and a cation channel, provides electrical stimulation of appropriate speed and magnitude to activate neuronal spike firing. Recently, photoinhibition, the inhibition of neural activity with light, has become feasible with the application of molecules such as the light-activated chloride pump halorhodopsin to neural control. Together, blue-light activated channelrhodopsin-2 and the yellow light-activated chloride pump halorhodopsin enable multiple-color, optical activation and silencing of neural activity. (See also Photobiomodulation) | 1 | Applied and Interdisciplinary Chemistry |
Like all fluid dynamics-related disciplines, the modelling of particle-laden flows is an enormous challenge for researchers - this is because most flows of practical interest are turbulent.
Direct numerical simulations (DNS) for single-phase flow, let alone two-phase flow, are computationally very expensive; the computing power required for models of practical engineering interest are far out of reach. Since one is often interested in modeling only large scale qualitative behavior of the flow, a possible approach is to decompose the flow velocity into mean and fluctuating components, by the Reynolds-averaged Navier-Stokes (RANS) approach. A compromise between DNS and RANS is large eddy simulation (LES), in which the small scales of fluid motion are modeled and the larger, resolved scales are simulated directly.
Experimental observations, as well as DNS indicate that an important phenomenon to model is preferential concentration. Particles (particularly those with Stokes number close to 1) are known to accumulate in regions of high shear and low vorticity (such as turbulent boundary layers), and the mechanisms behind this phenomenon are not well understood. Moreover, particles are known to migrate down turbulence intensity gradients (this process is known as turbophoresis). These features are particularly difficult to capture using RANS or LES-based models since too much time-varying information is lost.
Due to these difficulties, existing turbulence models tend to be ad hoc, that is, the range of applicability of a given model is usually suited toward a highly specific set of parameters (such as geometry, dispersed phase mass loading and particle reaction time), and are also restricted to low Reynolds numbers (whereas the Reynolds number of flows of engineering interest tend to be very high). | 1 | Applied and Interdisciplinary Chemistry |
Liquids are often used in cooking due to their excellent heat-transfer capabilities. In addition to thermal conduction, liquids transmit energy by convection. In particular, because warmer fluids expand and rise while cooler areas contract and sink, liquids with low kinematic viscosity tend to transfer heat through convection at a fairly constant temperature, making a liquid suitable for blanching, boiling, or frying. Even higher rates of heat transfer can be achieved by condensing a gas into a liquid. At the liquid's boiling point, all of the heat energy is used to cause the phase change from a liquid to a gas, without an accompanying increase in temperature, and is stored as chemical potential energy. When the gas condenses back into a liquid this excess heat-energy is released at a constant temperature. This phenomenon is used in processes such as steaming. | 0 | Theoretical and Fundamental Chemistry |
Despite the name, siphonic roof drainage does not work as a siphon; the technology makes use of gravity induced vacuum pumping to carry water horizontally from multiple roof drains to a single downpipe and to increase flow velocity. Metal baffles at the roof drain inlets reduce the injection of air which increases the efficiency of the system. One benefit to this drainage technique is reduced capital costs in construction compared to traditional roof drainage. Another benefit is the elimination of pipe pitch or gradient required for conventional roof drainage piping. However this system of gravity pumping is mainly suitable for large buildings and is not usually suitable for residential properties. | 1 | Applied and Interdisciplinary Chemistry |
AMGs employ diverse functions including pathways not involved in metabolism despite what the name suggests. They are categorized in two classes based on their presence in the Kyoto Encyclopedia of Genes and Genomes (KEGG). AMGs do not encompass metabolic genes involved in typical viral functions, such as nucleotide and protein metabolism since their functions achieve direct viral reproduction, rather than augmenting host function to indirectly enhance it. | 1 | Applied and Interdisciplinary Chemistry |
In the following discussion, we define volumetric flow rate V̇ (i.e. volume of fluid flowing per time) as
where
: r = radius of the pipe (for a pipe of circular section, the internal radius of the pipe).
: v = mean velocity of fluid flowing through the pipe.
: A = cross sectional area of the pipe.
In long pipes, the loss in pressure (assuming the pipe is level) is proportional to the length of pipe involved.
Friction loss is then the change in pressure Δp per unit length of pipe L
When the pressure is expressed in terms of the equivalent height of a column of that fluid, as is common with water, the friction loss is expressed as S, the "head loss" per length of pipe, a dimensionless quantity also known as the hydraulic slope.
where
: ρ = density of the fluid, (SI kg / m)
: g = the local acceleration due to gravity; | 1 | Applied and Interdisciplinary Chemistry |
Thermochemistry is the study of the heat energy which is associated with chemical reactions and/or phase changes such as melting and boiling. A reaction may release or absorb energy, and a phase change may do the same. Thermochemistry focuses on the energy exchange between a system and its surroundings in the form of heat. Thermochemistry is useful in predicting reactant and product quantities throughout the course of a given reaction. In combination with entropy determinations, it is also used to predict whether a reaction is spontaneous or non-spontaneous, favorable or unfavorable.
Endothermic reactions absorb heat, while exothermic reactions release heat. Thermochemistry coalesces the concepts of thermodynamics with the concept of energy in the form of chemical bonds. The subject commonly includes calculations of such quantities as heat capacity, heat of combustion, heat of formation, enthalpy, entropy, and free energy.
Thermochemistry is one part of the broader field of chemical thermodynamics, which deals with the exchange of all forms of energy between system and surroundings, including not only heat but also various forms of work, as well the exchange of matter. When all forms of energy are considered, the concepts of exothermic and endothermic reactions are generalized to exergonic reactions and endergonic reactions. | 0 | Theoretical and Fundamental Chemistry |
Mechanical coalescers, which are the more common type of coalescers, operate by physically altering a droplet by mechanical means. They are commonly applied in the global oil and gas industries for the removal of water or hydrocarbon condensate. While coalescers by definition function as a separation tool for liquids, they are also used, and mistakenly referred to, as filters.
In the area of compressed air purification, coalescing filters are used to separate liquid water and oil from compressed air using a coalescing effect. Coalescence (physics) shows how coalescing filters operating at lower temperatures and high pressures work better. These filters additionally remove particles. The most commonly used media in this case is borosilicate micro-fiber.
In the Oil and Gas, Petrochemical and Oil Refining industries, liquid-gas coalescers are widely used to remove water and hydrocarbon liquids to less than 0.011 mW (plus particulate matter to less than 0.3 µm in size) from natural gas to ensure natural gas quality and protect downstream equipment such as compressors, gas turbines, amine or glycol absorbers, molecular sieves, PSA's, metering stations, mercury guard beds, gas fired heaters or furnaces, heat exchangers or gas-gas purification membranes.
In the natural gas industry, gas/liquid coalescers are used for recovery of lube oil downstream of a compressor. All liquids will be removed but lube oil recovery is the primary reason for installing a coalescer on the outlet of a compressor. Liquids from upstream of the compressor, which may include aerosol particles, entrained liquids or large volumes of liquids called "slugs" and which may be water and/or a combination of hydrocarbon liquids should be removed by a filter/coalescing vessel located upstream of the compressor. Efficiencies of gas/liquid coalescers are typically 0.3 µm (0.3 micron) liquid particles, with efficiencies to 99.98%.
Liquid-liquid coalescers can also be used to separate hydrocarbons from water phases such as oil removal from produced water. They have been also used in pyrolysis gasoline (benzene) removal from quench water in ethylene plants, although in this application, the constant changing of cartridges can lead to operator exposure to BTX (benzene, toluene and xylene), as well as disposal issues and high operating costs from frequent replacement. | 0 | Theoretical and Fundamental Chemistry |
As a byproduct of the ethoxylation process, a route to some ingredients found in cleansing and moisturizing products, dioxane can contaminate cosmetics and personal care products such as deodorants, perfumes, shampoos, toothpastes and mouthwashes. The ethoxylation process makes the cleansing agents, such as sodium laureth sulfate and ammonium laureth sulfate, less abrasive and offers enhanced foaming characteristics. 1,4-Dioxane is found in small amounts in some cosmetics, a yet unregulated substance used in cosmetics in both China and the U.S. Research has found the chemical in ethoxylated raw ingredients and in off-the-shelf cosmetic products. The Environmental Working Group (EWG) found that 97% of hair relaxers, 57% of baby soaps and 22 percent of all products in Skin Deep, their database for cosmetic products, are contaminated with 1,4-dioxane.
Since 1979 the U.S. Food and Drug Administration (FDA) have conducted tests on cosmetic raw materials and finished products for the levels of 1,4-dioxane. 1,4-Dioxane was present in ethoxylated raw ingredients at levels up to 1410 ppm (~0.14%wt), and at levels up to 279 ppm (~0.03%wt) in off the shelf cosmetic products. Levels of 1,4-dioxane exceeding 85 ppm (~0.01%wt) in children's shampoos indicate that close monitoring of raw materials and finished products is warranted. While the FDA encourages manufacturers to remove 1,4-dioxane, it is not required by federal law.
On 9 December 2019, New York passed a bill to ban the sale of cosmetics with more than 10 ppm of 1,4-dioxane as of the end of 2022. The law will also prevent the sale of household cleaning and personal care products containing more than 2 ppm of 1,4-dioxane at the end of 2022. | 0 | Theoretical and Fundamental Chemistry |
The growth of Alabamas iron and steel industry was significantly influenced by Tannehill iron-making practices, such as using distilled coal residues as a furnace fuel, making early experimentation with coke, and reducing red iron ore from Red Mountain in a blast furnace. Due to the significant role that Tannehill pays in Alabamas iron and steel industry, the Alabama Central District of Civitan International and the representatives of the University of Alabama first proposed in the late 1960s that a state park should be built to preserve the site of Tannehill Ironworks, the birthplace of the Birmingham Iron industry. The proposal was approved by the state in 1969, and in the following year 1970, the Tannehill Historical State Parkopened to the public. There are more than 45 historical buildings in this state park, including the May Plantation Cotton Gin House, the John Wesley Hall Gristmill, as well as a collection of log cabins that trace back to the nineteenth century. Among the efforts to preserve the historical buildings and Tannehill artifacts, the Iron and Steel Museum of Alabama was built, and it opened in 1981. At present, the Tannehill Ironworks state park has been listed on the National Register of Historic Places and the Civil War Discovery Trail. In particular, the museum demonstrates how 13 iron manufacturers and 6 rolling mills worked to produce iron during the Civil war, making the Tannehill Ironworks among the best-preserved and oldest historical sites in the Southeastern part of this country. From 2004 to 2005, the museum had a significant make-over to introduce more new exhibits to the site, including an old rice-plantation-owned power source, and one of the oldest steam engines in this country. In 2017, Tannehill Ironworks, containing the Iron and Steel Museum of Alabama, became one of the six Birmingham historical sites which contributed to the creation of the Birmingham Industrial Heritage Trail. More recently, the Tannehill Furnace memorial park has become one of the most visited sites in Alabama, and the number of visitors each year exceeds 425,000. This is mainly due to the park's organisation of a variety of outdoor events and activities; for example, the Trade Days event is organised monthly from March to November each year, and visitors also have an opportunity to participant in a Civil War battle re-enactment. | 1 | Applied and Interdisciplinary Chemistry |
Laid down in the environment, territorial pheromones mark the boundaries and identity of an organisms territory. In cats and dogs, these hormones are present in the urine, which they deposit on landmarks serving to mark the perimeter of the claimed territory. In social seabirds, the preen gland is used to mark nests, nuptial gifts, and territory boundaries with behavior formerly described as displacement activity'. | 1 | Applied and Interdisciplinary Chemistry |
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