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The precise physiological role of uteroglobin is not yet known. Putative functions are:
# Immunomodulation
# Progesterone binding: weak in some animals, especially weak in humans. (Note: UGB is itself progesterone induced gene in the endometrium in Lagomorphs)
# Inhibits phospholipase A2 in vitro
# Binds phosphatidylcholine, phosphatidylinositol
# Binds to fibronectin: The uteroglobulin knockout mice on the inbred C57Bl6 strain develop Goodpasture's syndrome like glomerulopathy due to fibronectin binding of IgA which might potentially be prevented by uteroglobin replacement. However contrary to the animal model claims, human genetic data might suggest that the effect may be indirect
# Uteroglobin knockout mice on the inbred 129 strain appear to have healthy phenotype (no glomerulopathy development), but show physiological differences in their responses to respiratory challenges. The phenotype exhibited by these mice are; decreased bioaccumulation of biphenyls, susceptibility and increased IL-13, and IL-6 following hyperoxic challenge, and changes in the club cell morphology.
# Target of polychlorinated biphenyl (pcb) binding | 1 | Applied and Interdisciplinary Chemistry |
Dimensional correctness as part of type checking has been studied since 1977.
Implementations for Ada and C++ were described in 1985 and 1988.
Kennedy's 1996 thesis describes an implementation in Standard ML, and later in F#. There are implementations for Haskell, OCaml, and Rust, Python, and a code checker for Fortran.<br />
Griffioens 2019 thesis extended Kennedys Hindley–Milner type system to support Hart's matrices.
McBride and Nordvall-Forsberg show how to use dependent types to extend type systems for units of measure.
Mathematica 13.2 has a function for transformations with quantities named NondimensionalizationTransform that applies a nondimensionalization transform to an equation. Mathematica also has a function to find the dimensions of a unit such as 1 J named UnitDimensions. Mathematica also has a function that will find dimensionally equivalent combinations of a subset of physical quantities named DimensionalCombations. Mathematica can also factor out certain dimension with UnitDimensions by specifying an argument to the function UnityDimensions. For example, you can use UnityDimensions to factor out angles. In addition to UnitDimensions, Mathematica can find the dimensions of a QuantityVariable with the function QuantityVariableDimensions. | 1 | Applied and Interdisciplinary Chemistry |
Glycoside hydrolases are found in essentially all domains of life. In prokaryotes, they are found both as intracellular and extracellular enzymes that are largely involved in nutrient acquisition. One of the important occurrences of glycoside hydrolases in bacteria is the enzyme beta-galactosidase (LacZ), which is involved in regulation of expression of the lac operon in E. coli. In higher organisms glycoside hydrolases are found within the endoplasmic reticulum and Golgi apparatus where they are involved in processing of N-linked glycoproteins, and in the lysosome as enzymes involved in the degradation of carbohydrate structures. Deficiency in specific lysosomal glycoside hydrolases can lead to a range of lysosomal storage disorders that result in developmental problems or death. Glycoside hydrolases are found in the intestinal tract and in saliva where they degrade complex carbohydrates such as lactose, starch, sucrose and trehalose. In the gut they are found as glycosylphosphatidyl anchored enzymes on endothelial cells. The enzyme lactase is required for degradation of the milk sugar lactose and is present at high levels in infants, but in most populations will decrease after weaning or during infancy, potentially leading to lactose intolerance in adulthood. The enzyme O-GlcNAcase is involved in removal of N-acetylglucosamine groups from serine and threonine residues in the cytoplasm and nucleus of the cell. The glycoside hydrolases are involved in the biosynthesis and degradation of glycogen in the body. | 0 | Theoretical and Fundamental Chemistry |
Two methods for the synthesis of haloalkanes from carboxylic acids are Hunsdiecker reaction and Kochi reaction. | 0 | Theoretical and Fundamental Chemistry |
The high functional group tolerance of the intramolecular Heck reaction allows it to be used at a very late stage in synthetic routes. In a synthesis of (±)-FR900482, IMHR establishes a tricyclic ring system in high yield without disturbing any of the sensitive functionality nearby.
Intramolecular Heck reactions have been employed for the construction of complex natural products. An example is the late-stage, macrocyclic ring closure in the total synthesis of the cytotoxic natural product (–)-Mandelalide A.
In another example a fully intramolecular tandem Heck reaction is used in a synthesis of (–)-scopadulcic acid. A 6-exo cyclization sets the quaternary center and provides a neopentyl σ-palladium intermediate, which undergoes a 5-exo reaction to provide the ring system. | 0 | Theoretical and Fundamental Chemistry |
Fluorescence spectroscopy (also known as fluorimetry or spectrofluorometry) is a type of electromagnetic spectroscopy that analyzes fluorescence from a sample. It involves using a beam of light, usually ultraviolet light, that excites the electrons in molecules of certain compounds and causes them to emit light; typically, but not necessarily, visible light. A complementary technique is absorption spectroscopy. In the special case of single molecule fluorescence spectroscopy, intensity fluctuations from the emitted light are measured from either single fluorophores, or pairs of fluorophores.
Devices that measure fluorescence are called fluorometers. | 0 | Theoretical and Fundamental Chemistry |
The six factor formula effective neutron multiplication factor, k, is the average number of neutrons from one fission that cause another fission. The remaining neutrons either are absorbed in non-fission reactions or leave the system without being absorbed. The value of k determines how a nuclear chain reaction proceeds:
* k < 1 (subcriticality): The system cannot sustain a chain reaction, and any beginning of a chain reaction dies out over time. For every fission that is induced in the system, an average total of 1/(1 − k) fissions occur. Proposed subcritical reactors make use of the fact that a nuclear reaction sustained by an external neutron source can be "switched off" when the neutron source is removed. This provides a certain degree of inherent safety.
* k = 1 (criticality): Every fission causes an average of one more fission, leading to a fission (and power) level that is constant. Nuclear power plants operate with k = 1 unless the power level is being increased or decreased.
* k > 1 (supercriticality): For every fission in the material, it is likely that there will be "k" fissions after the next mean generation time (Λ). The result is that the number of fission reactions increases exponentially, according to the equation , where t is the elapsed time. Nuclear weapons are designed to operate under this state. There are two subdivisions of supercriticality: prompt and delayed.
When describing kinetics and dynamics of nuclear reactors, and also in the practice of reactor operation, the concept of reactivity is used, which characterizes the deflection of reactor from the critical state: ρ = (k − 1)/k. InHour (from inverse of an hour, sometimes abbreviated ih or inhr) is a unit of reactivity of a nuclear reactor.
In a nuclear reactor, k will actually oscillate from slightly less than 1 to slightly more than 1, due primarily to thermal effects (as more power is produced, the fuel rods warm and thus expand, lowering their capture ratio, and thus driving k lower). This leaves the average value of k at exactly 1. Delayed neutrons play an important role in the timing of these oscillations. | 0 | Theoretical and Fundamental Chemistry |
Double bond isomers are always considered diastereomers, not enantiomers. Diastereomerism can also occur at a double bond, where the cis vs trans relative positions of substituents give two non-superposable isomers. Many conformational isomers are diastereomers as well.
In the case of diastereomerism occurring at a double bond, E-Z, or entgegen and zusammen (German), is used in notating nomenclature of alkenes. | 0 | Theoretical and Fundamental Chemistry |
The harmful effects of glutamate on the central nervous system were first observed in 1954 by T. Hayashi, a Japanese scientist who stated that direct application of glutamate caused seizure activity, though this report went unnoticed for several years. D. R. Lucas and J. P. Newhouse, after noting that "single doses of [20–30 grams of sodium glutamate in humans] have ... been administered intravenously without permanent ill-effects", observed in 1957 that a subcutaneous dose described as "a little less than lethal", destroyed the neurons in the inner layers of the retina in newborn mice. In 1969, John Olney discovered that the phenomenon was not restricted to the retina, but occurred throughout the brain, and coined the term excitotoxicity. He also assessed that cell death was restricted to postsynaptic neurons, that glutamate agonists were as neurotoxic as their efficiency to activate glutamate receptors, and that glutamate antagonists could stop the neurotoxicity.
In 2002, Hilmar Bading and co-workers found that excitotoxicity is caused by the activation of NMDA receptors located outside synaptic contacts. The molecular basis for toxic extrasynaptic NMDA receptor signaling was uncovered in 2020 when Hilmar Bading and co-workers described a death signaling complex that consists of extrasynaptic NMDA receptor and TRPM4. Disruption of this complex using NMDAR/TRPM4 interface inhibitors (also known as ‚interface inhibitors‘) renders extrasynaptic NMDA receptor non-toxic. | 1 | Applied and Interdisciplinary Chemistry |
Treatment of a Grignard reagent with oxygen gives the magnesium organoperoxide. Hydrolysis of this material yields hydroperoxides or alcohol. These reactions involve radical intermediates.
The simple oxidation of Grignard reagents to give alcohols is of little practical importance as yields are generally poor. In contrast, two-step sequence via a borane (vide supra) that is subsequently oxidized to the alcohol with hydrogen peroxide is of synthetic utility.
The synthetic utility of Grignard oxidations can be increased by a reaction of Grignard reagents with oxygen in presence of an alkene to an ethylene extended alcohol. This modification requires aryl or vinyl Grignards. Adding just the Grignard and the alkene does not result in a reaction demonstrating that the presence of oxygen is essential. The only drawback is the requirement of at least two equivalents of Grignard although this can partly be circumvented by the use of a dual Grignard system with a cheap reducing Grignard such as n-butylmagnesium bromide. | 0 | Theoretical and Fundamental Chemistry |
Kobayashi et al. isolated callystatin A in 1997 from the marine sponge Callyspongia truncata using acetone extraction. This marine sponge was discovered near the Goto Islands of the Nagasaki Prefecture in Japan. Kobayashi also reported the isolation of callystatin A from another marine sponge Stelletta sp. and an unidentified marine tunicate, both of which were collected at the same site as Callyspongia truncata. It is possible that there is a symbiotic relationship among these microorganisms which can explain their biosynthesis of callystatin A.
The leptomycin family of molecules that callystatin belongs to includes several well-known molecules with cytotoxic properties. such as leptomycins A and B, anguinomycins A and B, kazusamycin, and leptofuranins A-D. All of these molecules were isolated from various strains of Streptomyces sp. and share a common structural motif consisting of a terminal α,β-unsaturated lactone group attached to a long unsaturated fatty acid chain which includes two diene systems separated by two sp-hybridized carbons. It is believed that this highly conserved structural motif is important for biological target recognition with the α,β-unsaturated lactone moiety serving as the pharmacophore of the molecule. | 0 | Theoretical and Fundamental Chemistry |
In 2009, Ted Ellis produced an exhibit focusing on the theme of African-American history in light of slavery and emancipation. The exhibit, American Slavery: The Reason Why Were Here, tied into the Juneteenth commemoration of slaverys abolition in the State of Texas. It was located at and included tours of the historic residence of horticulturist Henry Stringfellow, an innovator in organic gardening who was enlightened in how he employed of freedmen. Ellis began the series of works at a 2006 exhibition at the same house.
The exhibit's more than 20 paintings were painted with brush and fingers, and Ellis sometimes added a collage of documents. The exhibit included images of the transportation of slaves, the industry of slavery in crop production, and the abolition of slavery.
The painting Free At Last includes depictions of Buffalo soldiers, Harriet Tubman, the year "1865", a mighty oak, and in the background, their heads bowed in prayer, the figures of the current owner and restorer of the house, Sam Collins III, and his wife and children. The exhibit also displayed Ellis famous depiction of Barack Obama, Obama, the 44th President'.
Ellis art was featured at a 2011 exhibition at the Rosa Parks Library and Museum. The Museum, at Troy University in Montgomery, Alabama, hosted the exhibit, called Our History, Heritage, and Culture: An American Story, the Art of Ted Ellis', as part of its celebration of Black History Month.
T. Ellis has been pictorially documenting African-American lifestyle, history and culture for thirty years. Ellis paintings are in the permanent collection of the DuSable museum, Charles Wright museum, the McKenna museum, Free People of Color Museum, and the Amistad Research Center. The City of Selma, Alabama, commissioned T. Ellis as the official artist for the 50th anniversary for the civil rights march, known as "Bloody Sunday". The City and County of Galveston, Texas, recognized T. Ellis for the 150th anniversary of Juneteenth. The Juneteenth Freedom Project was exhibited at the State Capitol in Washington, DC at the U.S. Senate Rotunda and House of Representatives Rayburn Building. President Barack Obama and the First Lady, Michelle Obama of the White House has thanked T. Ellis for his art and giving.
T.Ellis painting of the Tuskegee airmen, "The Lonely Angels" was signed by all the Tuskegge Airmen who were in attendance to receive their Congressional Medal of Honor from the President. President George W. Bush and Speaker of the House of Representatives Nancy Pelosi stand amidst 300 Tuskegee Airmen during a photo opportunity Thursday, March 29, 2007, in Statuary Hall at the U.S. Capitol. White House. | 0 | Theoretical and Fundamental Chemistry |
The medium in which a sound wave is travelling does not always respond adiabatically, and as a result, the speed of sound can vary with frequency.
The limitations of the concept of speed of sound due to extreme attenuation are also of concern. The attenuation which exists at sea level for high frequencies applies to successively lower frequencies as atmospheric pressure decreases, or as the mean free path increases. For this reason, the concept of speed of sound (except for frequencies approaching zero) progressively loses its range of applicability at high altitudes. The standard equations for the speed of sound apply with reasonable accuracy only to situations in which the wavelength of the sound wave is considerably longer than the mean free path of molecules in a gas.
The molecular composition of the gas contributes both as the mass (M) of the molecules, and their heat capacities, and so both have an influence on speed of sound. In general, at the same molecular mass, monatomic gases have slightly higher speed of sound (over 9% higher) because they have a higher γ (...) than diatomics do (). Thus, at the same molecular mass, the speed of sound of a monatomic gas goes up by a factor of
This gives the 9% difference, and would be a typical ratio for speeds of sound at room temperature in helium vs. deuterium, each with a molecular weight of 4. Sound travels faster in helium than deuterium because adiabatic compression heats helium more since the helium molecules can store heat energy from compression only in translation, but not rotation. Thus helium molecules (monatomic molecules) travel faster in a sound wave and transmit sound faster. (Sound travels at about 70% of the mean molecular speed in gases; the figure is 75% in monatomic gases and 68% in diatomic gases).
Note that in this example we have assumed that temperature is low enough that heat capacities are not influenced by molecular vibration (see heat capacity). However, vibrational modes simply cause gammas which decrease toward 1, since vibration modes in a polyatomic gas give the gas additional ways to store heat which do not affect temperature, and thus do not affect molecular velocity and sound velocity. Thus, the effect of higher temperatures and vibrational heat capacity acts to increase the difference between the speed of sound in monatomic vs. polyatomic molecules, with the speed remaining greater in monatomics. | 1 | Applied and Interdisciplinary Chemistry |
As of 2017 there are no peer-reviewed scientific studies available regarding the efficacy of the technique. A few university student projects investigate Hügelkultur but have not been published in scientific journals.
One small scale and short term student project investigated the Hügelkultur method as a potential use for yard trimmings waste, and also if lima beans, kale and okra planted on a Hügelkultur mound showed any signs of nutrient deficiency compared to a non-raised control bed. It was found that over 11 tons of yard trimmings were used in the mound, and no evidence of macronutrient deficiency could be detected in the crops in the short term. Indeed, despite concerns that incorporation of large quantities of high carbon woody matter would lead to nitrogen immobilization and hence nitrogen deficiency in the crop, a higher level of nitrogen was found in the raised bed. However, the micronutrient iron was lower relative to the control bed. The author speculated that no nitrogen deficiency occurred since the roots of the plants did not penetrate past the superficial layers of the mound into the deeper wood-containing region.
A student thesis investigated the water holding capacity of Hügelkultur beds and whether the technique could be useful to prevent karst rocky desertification in China. Over 3 months of measurements, water concentration in hügel mounds remained high. Samples from hügel sites contained almost twice as much water as those from flat control plots. It was suggested that of hügels has 3-10 times more water than a flat plot affected by karst rocky desertification. | 1 | Applied and Interdisciplinary Chemistry |
There has been increasing controversy surrounding pharmaceutical marketing and influence. There have been accusations and findings of influence on doctors and other health professionals through drug reps including the constant provision of marketing gifts and biased information to health professionals; highly prevalent advertising in journals and conferences; funding independent healthcare organizations and health promotion campaigns; lobbying physicians and politicians (more than any other industry in the US); sponsorship of medical schools or nurse training; sponsorship of continuing educational events, with influence on the curriculum; and hiring physicians as paid consultants on medical advisory boards.
Some advocacy groups, such as No Free Lunch and AllTrials, have criticized the effect of drug marketing to physicians because they say it biases physicians to prescribe the marketed drugs even when others might be cheaper or better for the patient.
There have been related accusations of disease mongering (over-medicalising) to expand the market for medications. An inaugural conference on that subject took place in Australia in 2006. In 2009, the Government-funded National Prescribing Service launched the "Finding Evidence – Recognising Hype" program, aimed at educating on methods for independent drug analysis.
Meta-analyses have shown that psychiatric studies sponsored by pharmaceutical companies are several times more likely to report positive results, and if a drug company employee is involved the effect is even larger. Influence has also extended to the training of doctors and nurses in medical schools, which is being fought.
It has been argued that the design of the Diagnostic and Statistical Manual of Mental Disorders and the expansion of the criteria represents an increasing medicalization of human nature, or "disease mongering", driven by drug company influence on psychiatry. The potential for direct conflict of interest has been raised, partly because roughly half the authors who selected and defined the DSM-IV psychiatric disorders had or previously had financial relationships with the pharmaceutical industry.
In the US, starting in 2013, under the Physician Financial Transparency Reports (part of the Sunshine Act), the Centers for Medicare & Medicaid Services has to collect information from applicable manufacturers and group purchasing organizations in order to report information about their financial relationships with physicians and hospitals. Data are made public in the Centers for Medicare & Medicaid Services website. The expectation is that relationship between doctors and Pharmaceutical industry will become fully transparent.
In a report conducted by OpenSecrets, there were more than 1,100 lobbyists working in some capacity for the pharmaceutical business in 2017. In the first quarter of 2017, the health products and pharmaceutical industry spent $78 million on lobbying members of the United States Congress. | 1 | Applied and Interdisciplinary Chemistry |
Measurement of natural variations in the abundances of stable isotopes of the same element is normally referred to as stable isotope analysis. This field is of interest because the differences in mass between different isotopes leads to isotope fractionation, causing measurable effects on the isotopic composition of samples, characteristic of their biological or physical history.
As a specific example, the hydrogen isotope deuterium (heavy hydrogen) is almost double the mass of the common hydrogen isotope. Water molecules containing the common hydrogen isotope (and the common oxygen isotope, mass 16) have a mass of 18. Water incorporating a deuterium atom has a mass of 19, over 5% heavier. The energy to vaporise the heavy water molecule is higher than that to vaporize the normal water so isotope fractionation occurs during the process of evaporation. Thus a sample of sea water will exhibit a quite detectable isotopic-ratio difference when compared to Antarctic snowfall.
Samples must be introduced to the mass spectrometer as pure gases, achieved through combustion, gas chromatographic feeds, or chemical trapping. By comparing the detected isotopic ratios to a measured standard, an accurate determination of the isotopic make up of the sample is obtained. For example, carbon isotope ratios are measured relative to the international standard for C. The C standard is produced from a fossil belemnite found in the Peedee Formation, which is a limestone formed in the Cretaceous period in South Carolina, U.S.A. The fossil is referred to as VPDB (Vienna Pee Dee Belemnite) and has C:C ratio of 0.0112372. Oxygen isotope ratios are measured relative the standard, V-SMOW (Vienna Standard Mean Ocean Water).
It is critical that the sample be processed before entering the mass spectrometer so that only a single chemical species enters at a given time. Generally, samples are combusted or pyrolyzed and the desired gas species (usually hydrogen (H), nitrogen (N), carbon dioxide (CO), or sulfur dioxide (SO)) is purified by means of traps, filters, catalysts and/or chromatography.
The two most common types of IRMS instruments are continuous flow and dual inlet. In dual inlet IRMS, purified gas obtained from a sample is alternated rapidly with a standard gas (of known isotopic composition) by means of a system of valves, so that a number of comparison measurements are made of both gases. In continuous flow IRMS, sample preparation occurs immediately before introduction to the IRMS, and the purified gas produced from the sample is measured just once. The standard gas may be measured before and after the sample or after a series of sample measurements. While continuous-flow IRMS instruments can achieve higher sample throughput and are more convenient to use than dual inlet instruments, the yielded data is of approximately 10-fold lower precision. | 0 | Theoretical and Fundamental Chemistry |
Atmospheric particulate matter, also known as particulate matter, or PM, describes solids and/or liquid particles suspended in a gas, most commonly the Earth's atmosphere. Particles in the atmosphere can be divided into two types, depending on the way they are emitted. Primary particles, such as mineral dust, are emitted into the atmosphere. Secondary particles, such as ammonium nitrate, are formed in the atmosphere through gas-to-particle conversion. | 1 | Applied and Interdisciplinary Chemistry |
The term was used as early as 1973, when scientist Carl Sagan described it and other human chauvinisms that limit imagination of possible extraterrestrial life. It suggests that human beings, as carbon-based life forms who have never encountered any life that has evolved outside the Earth's environment, may find it difficult to envision radically different biochemistries. | 1 | Applied and Interdisciplinary Chemistry |
The full width at half maximum (FWHM) of the Voigt profile can be found from the
widths of the associated Gaussian and Lorentzian widths. The FWHM of the Gaussian profile
is
The FWHM of the Lorentzian profile is
An approximate relation (accurate to within about 1.2%) between the widths of the Voigt, Gaussian, and Lorentzian profiles is:
By construction, this expression is exact for a pure Gaussian or Lorentzian.
A better approximation with an accuracy of 0.02% is given by (originally found by Kielkopf)
Again, this expression is exact for a pure Gaussian or Lorentzian.
In the same publication, a slightly more precise (within 0.012%), yet significantly more complicated expression can be found. | 0 | Theoretical and Fundamental Chemistry |
Potassium ethyl xanthate (KEX) is an organosulfur compound with the chemical formula . It is a pale yellow powder that is used in the mining industry for the separation of ores. It is a potassium salt of ethyl xanthic acid. | 1 | Applied and Interdisciplinary Chemistry |
A salamander (or deadman's foot or furnace bear) in the metallurgy dialect means all liquid and solidified
materials in the hearth of a blast furnace below the tap hole.
The target of the salamander tapping is to remove the remaining hot metal and slag from the blast furnace to allow a safe and efficient intermediate repair and blow-in of the blast furnace.
During blowing down of the furnace the salamander is tapped by drilling a hole in the blast furnace hearth. | 1 | Applied and Interdisciplinary Chemistry |
Percentages are dimensionless quantities, since they are ratios of two quantities with the same dimensions. In other words, the % sign can be read as "hundredths", since .
Taking a derivative with respect to a quantity divides the dimension by the dimension of the variable that is differentiated with respect to. Thus:
* position () has the dimension L (length);
* derivative of position with respect to time (, velocity) has dimension TL—length from position, time due to the gradient;
* the second derivative , acceleration) has dimension .
Likewise, taking an integral adds the dimension of the variable one is integrating with respect to, but in the numerator.
* force has the dimension (mass multiplied by acceleration);
* the integral of force with respect to the distance () the object has travelled (, work) has dimension .
In economics, one distinguishes between stocks and flows: a stock has a unit (say, widgets or dollars), while a flow is a derivative of a stock, and has a unit of the form of this unit divided by one of time (say, dollars/year).
In some contexts, dimensional quantities are expressed as dimensionless quantities or percentages by omitting some dimensions. For example, debt-to-GDP ratios are generally expressed as percentages: total debt outstanding (dimension of currency) divided by annual GDP (dimension of currency)—but one may argue that, in comparing a stock to a flow, annual GDP should have dimensions of currency/time (dollars/year, for instance) and thus debt-to-GDP should have the unit year, which indicates that debt-to-GDP is the number of years needed for a constant GDP to pay the debt, if all GDP is spent on the debt and the debt is otherwise unchanged. | 1 | Applied and Interdisciplinary Chemistry |
Endogenous template-independent primer-primer interaction is due to the random design of hexamer primers. One possible solution is to design constrained-randomized hexanucleotide primers that do not cross-hybridize. | 1 | Applied and Interdisciplinary Chemistry |
The recommendations include a flow chart which can be summarised very briefly:
*identify the central atom,
*identify and name the ligands,
*specify coordination mode of ligands i.e. using kappa and/or eta conventions
*sequence the ligands
*specify coordination geometry i.e polyhedral symbol, configuration index (using CIP rules and absolute configuration for optically active compounds. | 0 | Theoretical and Fundamental Chemistry |
Fluctuation electron microscopy is another transmission electron microscopy based technique that is sensitive to the medium range order of amorphous materials. Structural fluctuations arising from different forms of medium range order can be detected with this method. Fluctuation electron microscopy experiments can be done in conventional or scanning transmission electron microscope mode. | 0 | Theoretical and Fundamental Chemistry |
Bauxite tailings is a waste product generated in the industrial production of aluminium. Making provision for the approximately 77 million tons that is produced annually is one of the most significant problems for the aluminium mining industry. | 1 | Applied and Interdisciplinary Chemistry |
Sulfuric acid acts as the electrolyte in lead–acid batteries (lead-acid accumulator):
At anode:
At cathode:
Overall: | 0 | Theoretical and Fundamental Chemistry |
Carbon dioxide occupies a different binding site on the hemoglobin. At tissues, where carbon dioxide concentration is higher, carbon dioxide binds to allosteric site of hemoglobin, facilitating unloading of oxygen from hemoglobin and ultimately its removal from the body after the oxygen has been released to tissues undergoing metabolism. This increased affinity for carbon dioxide by the venous blood is known as the Bohr effect. Through the enzyme carbonic anhydrase, carbon dioxide reacts with water to give carbonic acid, which decomposes into bicarbonate and protons:
:CO + HO → HCO → HCO + H
Hence, blood with high carbon dioxide levels is also lower in pH (more acidic). Hemoglobin can bind protons and carbon dioxide, which causes a conformational change in the protein and facilitates the release of oxygen. Protons bind at various places on the protein, while carbon dioxide binds at the α-amino group. Carbon dioxide binds to hemoglobin and forms carbaminohemoglobin. This decrease in hemoglobins affinity for oxygen by the binding of carbon dioxide and acid is known as the Bohr effect. The Bohr effect favors the T state rather than the R state. (shifts the O-saturation curve to the right'). Conversely, when the carbon dioxide levels in the blood decrease (i.e., in the lung capillaries), carbon dioxide and protons are released from hemoglobin, increasing the oxygen affinity of the protein. A reduction in the total binding capacity of hemoglobin to oxygen (i.e. shifting the curve down, not just to the right) due to reduced pH is called the root effect. This is seen in bony fish.
It is necessary for hemoglobin to release the oxygen that it binds; if not, there is no point in binding it. The sigmoidal curve of hemoglobin makes it efficient in binding (taking up O in lungs), and efficient in unloading (unloading O in tissues).
In people acclimated to high altitudes, the concentration of 2,3-Bisphosphoglycerate (2,3-BPG) in the blood is increased, which allows these individuals to deliver a larger amount of oxygen to tissues under conditions of lower oxygen tension. This phenomenon, where molecule Y affects the binding of molecule X to a transport molecule Z, is called a heterotropic allosteric effect. Hemoglobin in organisms at high altitudes has also adapted such that it has less of an affinity for 2,3-BPG and so the protein will be shifted more towards its R state. In its R state, hemoglobin will bind oxygen more readily, thus allowing organisms to perform the necessary metabolic processes when oxygen is present at low partial pressures.
Animals other than humans use different molecules to bind to hemoglobin and change its O affinity under unfavorable conditions. Fish use both ATP and GTP. These bind to a phosphate "pocket" on the fish hemoglobin molecule, which stabilizes the tense state and therefore decreases oxygen affinity. GTP reduces hemoglobin oxygen affinity much more than ATP, which is thought to be due to an extra hydrogen bond formed that further stabilizes the tense state. Under hypoxic conditions, the concentration of both ATP and GTP is reduced in fish red blood cells to increase oxygen affinity.
A variant hemoglobin, called fetal hemoglobin (HbF, αγ), is found in the developing fetus, and binds oxygen with greater affinity than adult hemoglobin. This means that the oxygen binding curve for fetal hemoglobin is left-shifted (i.e., a higher percentage of hemoglobin has oxygen bound to it at lower oxygen tension), in comparison to that of adult hemoglobin. As a result, fetal blood in the placenta is able to take oxygen from maternal blood.
Hemoglobin also carries nitric oxide (NO) in the globin part of the molecule. This improves oxygen delivery in the periphery and contributes to the control of respiration. NO binds reversibly to a specific cysteine residue in globin; the binding depends on the state (R or T) of the hemoglobin. The resulting S-nitrosylated hemoglobin influences various NO-related activities such as the control of vascular resistance, blood pressure and respiration. NO is not released in the cytoplasm of red blood cells but transported out of them by an anion exchanger called AE1. | 0 | Theoretical and Fundamental Chemistry |
* In 1963 he was awarded an Honorary Doctor of Science from the University of British Columbia.
* In 1965 he was awarded an Honorary Doctor of Science from Carleton University.
* In 1967 he was made a Companion of the Order of Canada.
* In 1968 he was awarded an Honorary Doctor of Laws from the University of Saskatchewan. | 0 | Theoretical and Fundamental Chemistry |
Haptophytes are similar and closely related to cryptophytes or heterokontophytes. Their chloroplasts lack a nucleomorph, their thylakoids are in stacks of three, and they synthesize chrysolaminarin sugar, which they store completely outside of the chloroplast, in the cytoplasm of the haptophyte. | 0 | Theoretical and Fundamental Chemistry |
Another possibility is chain transfer to a second polymer molecule, result in the formation of a product macromolecule with a branched structure. In this case the growing chain takes an atom X from a second polymer chain whose growth had been completed. The growth of the first polymer chain is completed by the transfer of atom X. However the second molecule loses an atom X from the interior of its polymer chain to form a reactive radical (or ion) which can add more monomer molecules. This results in the addition of a branch or side chain and the formation of a product macromolecule with a branched structure. | 0 | Theoretical and Fundamental Chemistry |
Since mesoionic carbene ligands are very strong σ-donors and make it easier for a metal center to undergo oxidative addition, MIC ligands have the potential to be useful in catalysis. MIC transition metal complexes have been tested as catalysts in olefin metathesis, ring closure metathesis, and ring opening polymerization metathesis. The MIC complexes work very well, and in many cases, they outperform their NHC counterparts. MIC complexes have been successful as catalysts for Suzuki-Miyaura and Heck-Mizoroki cross-coupling reactions. Again, in many cases, MIC catalysts are superior to their NHC counterparts. For example, in olefin metathesis, MIC catalysts are active at room temperature after simply addition of a Brønsted acid, such as hydrochloric acid or trifluoroacetic acid, compared to the large amount of thermal activation required for NHC catalysts. MIC complexes have found use as catalysts in olefin hydrogenation. They have been shown to hydrogenate terminal and cis-alkenes. They work better than their NHC counterparts due to the MIC ligand’s stronger electron-donating properties. They are better able to provide electron density to promote hydrogen gas oxidative addition to the metal. MIC complexes have been used in transfer hydrogenation reactions. For example, they have been used to hydrogenate a diaryl ketone using isopropanol as a hydrogen source., MIC complexes are being considered as green chemistry catalysts. They act as catalysts for base- and oxidant-free oxidation of alcohols and amines. Some complexes have also been shown to synthesize certain aryl amides. Other MIC complexes have been used in hydroarylation, involving the addition of an electron-rich aryl group and a hydrogen across a multiple bond. The reactions that mesoionic carbene complexes catalyze will continue to expand as more research is done. | 0 | Theoretical and Fundamental Chemistry |
The PCR method is extremely sensitive, requiring only a few DNA molecules in a single reaction for amplification across several orders of magnitude. Therefore, adequate measures to avoid contamination from any DNA present in the lab environment (bacteria, viruses, or human sources) are required. Because products from previous PCR amplifications are a common source of contamination, many molecular biology labs have implemented procedures that involve dividing the lab into separate areas. One lab area is dedicated to preparation and handling of pre-PCR reagents and the setup of the PCR reaction, and another area to post-PCR processing, such as gel electrophoresis or PCR product purification. For the setup of PCR reactions, many standard operating procedures involve using pipettes with filter tips and wearing fresh laboratory gloves, and in some cases a laminar flow cabinet with UV lamp as a work station (to destroy any extraneomultimer formation). PCR is routinely assessed against a negative control reaction that is set up identically to the experimental PCR, but without template DNA, and performed alongside the experimental PCR. | 1 | Applied and Interdisciplinary Chemistry |
Recent research has focused on the in-place remediation of trichloroethylene in soil and groundwater using potassium permanganate instead of removal for off-site treatment and disposal. Naturally occurring bacteria have been identified with the ability to degrade TCE. Dehalococcoides sp. degrade trichloroethylene by reductive dechlorination under anaerobic conditions. Under aerobic conditions, Pseudomonas fluorescens can co-metabolize TCE. Soil and groundwater contamination by TCE has also been successfully remediated by chemical treatment and extraction. The bacteria Nitrosomonas europaea can degrade a variety of halogenated compounds including trichloroethylene. Toluene dioxygenase has been reported to be involved in TCE degradation by Pseudomonas putida. In some cases, Xanthobacter autotrophicus can convert up to 51% of TCE to CO and . | 1 | Applied and Interdisciplinary Chemistry |
Flortaucipir (aka F-T807) was discovered by the Siemens biomarker research group, headed by Hartmuth Kolb and Katrin Szardenings, who also conducted first in human trials. Flortaucipir (F) was approved for medical use in the United States in May 2020.
The safety and effectiveness of flortaucipir (F) imaging was evaluated in two clinical studies. In each study, five evaluators read and interpreted the flortaucipir (F) imaging. The evaluators were blinded to clinical information and interpreted the imaging as positive or negative.
The first study enrolled 156 participants who were terminally ill and agreed to undergo flortaucipir (F) imaging and participate in a post-mortem brain donation program. In 64 of the participants who died within nine months of the flortaucipir (F) brain scan, evaluators' reading of the flortaucipir (F) scan was compared to post-mortem readings from independent pathologists who evaluated the density and distribution of neurofibrillary tangles (NFTs) in the same brain. The study showed evaluators reading the flortaucipir (F) images had a high probability of correctly evaluating participants with tau pathology and had an average-to-high probability of correctly evaluating participants without tau pathology.
The second study included the same participants with terminal illness as the first study, plus 18 additional participants with terminal illness, and 159 participants with cognitive impairment being evaluated for Alzheimers disease (the indicated patient population). The study gauged how well flortaucipir (F) evaluators readings agreed with each other's assessments of the readings. Perfect reader agreement would be 1, while no reader agreement would be 0. In this study, reader agreement was 0.87 across all 241 participants. In a separate subgroup analysis that included the 82 terminally ill participants diagnosed after death and the 159 participants with cognitive impairment, reader agreement was 0.90 for the participants in the indicated population and 0.82 in the terminally ill participants.
The FDA approved flortaucipir (F) based on evidence of 1921 participants from 19 trials conducted at 322 sites in the United States, Australia, Belgium, Canada, France, Japan, Netherlands and Poland.
The ability of flortaucipir (F) to detect tau pathology was assessed in participants with generally severe stages of dementia and may be lower in participants in earlier stages of cognitive decline than in the participants with terminal illness who were studied.
The U.S. Food and Drug Administration (FDA) granted the application for flortaucipir (F) priority review and it granted approval of Tauvid to Avid Radiopharmaceuticals, Inc. | 1 | Applied and Interdisciplinary Chemistry |
For shallow water waves, such as tsunamis and hydraulic jumps, the characteristic velocity is the average flow velocity, averaged over the cross-section perpendicular to the flow direction. The wave velocity, termed celerity , is equal to the square root of gravitational acceleration , times cross-sectional area , divided by free-surface width :
so the Froude number in shallow water is:
For rectangular cross-sections with uniform depth , the Froude number can be simplified to:
For the flow is called a subcritical flow, further for the flow is characterised as supercritical flow. When the flow is denoted as critical flow. | 1 | Applied and Interdisciplinary Chemistry |
C6; C7; 8A; 8B; C9; CD320; CFI;
CORIN; DGCR2; HSPG2; LDLR; LDLRAD2; LDLRAD3; LRP1; LRP10;
LRP11; LRP12; LRP1B; LRP2; LRP3; LRP4; LRP5; LRP6;
LRP8; MAMDC4; MFRP; PRSS7; RXFP1; RXFP2; SORL1; SPINT1;
SSPO; ST14; TMPRSS4; TMPRSS6; TMPRSS7; TMPRSS9 (serase-1B); VLDLR; | 1 | Applied and Interdisciplinary Chemistry |
Levobupivacaine is an amino-amide anaesthetic that is similar in structure to bupivacaine, namely the S-enantiomer of bupivacaine. A lipophilic aromatic ring is linked to a hydrocarbon chain by an amide bond. The lipophilic components of levobupivacaine allow it to cross cell membraness and exert its local anaesthetic effect by causing a reversible blockade of open neuronal sodium channels. | 0 | Theoretical and Fundamental Chemistry |
Synthetic repellents tend to be more effective and/or longer lasting than "natural" repellents.
For protection against mosquito bites, the U.S. Centers for Disease Control (CDC) recommends DEET, icaridin (picaridin, KBR 3023), oil of lemon eucalyptus (para-menthane-diol or PMD), IR3535 and 2-undecanone with the caveat that higher percentages of the active ingredient provide longer protection.
In 2015, Researchers at New Mexico State University tested 10 commercially available products for their effectiveness at repelling mosquitoes. On the mosquito Aedes aegypti, the vector of Zika virus, only one repellent that did not contain DEET had a strong effect for the duration of the 240 minutes test: a lemon eucalyptus oil repellent. All DEET-containing mosquito repellents were active.
In one comparative study from 2004, IR3535 was as effective or better than DEET in protection against Aedes aegypti and Culex quinquefasciatus mosquitoes. Other sources (official publications of the associations of German physicians as well as of German druggists) suggest the contrary and state DEET is still the most efficient substance available and the substance of choice for stays in malaria regions, while IR3535 has little effect. However, some plant-based repellents may provide effective relief as well. Essential oil repellents can be short-lived in their effectiveness.
A test of various insect repellents by an independent consumer organization found that repellents containing DEET or icaridin are more effective than repellents with "natural" active ingredients. All the synthetics gave almost 100% repellency for the first 2 hours, where the natural repellent products were most effective for the first 30 to 60 minutes, and required reapplication to be effective over several hours.
Although highly toxic to cats, permethrin is recommended as protection against mosquitoes for clothing, gear, or bed nets. In an earlier report, the CDC found oil of lemon eucalyptus to be more effective than other plant-based treatments, with a similar effectiveness to low concentrations of DEET. However, a 2006 published study found in both cage and field studies that a product containing 40% oil of lemon eucalyptus was just as effective as products containing high concentrations of DEET. Research has also found that neem oil is mosquito repellent for up to 12 hours. Citronella oils mosquito repellency has also been verified by research, including effectiveness in repelling Aedes aegypti', but requires reapplication after 30 to 60 minutes.
There are also products available based on sound production, particularly ultrasound (inaudibly high-frequency sounds) which purport to be insect repellents. However, these electronic devices have been shown to be ineffective based on studies done by the United States Environmental Protection Agency and many universities. | 1 | Applied and Interdisciplinary Chemistry |
According to food chemist Udo Pollmer of the European Institute of Food and Nutrition Sciences in Munich, alcohol can be molecularly encapsulated in cyclodextrines, a sugar derivate. In this way, encapsuled in small capsules, the fluid can be handled as a powder. The cyclodextrines can absorb an estimated 60 percent of their own weight in alcohol. A US patent has been registered for the process as early as 1974. | 0 | Theoretical and Fundamental Chemistry |
Amatoxins and phallotoxins are 8- and 7-membered natural products, respectively, characterized by N-to-C cyclization in addition to a tryptathionine motif derived from the crosslinking of Cys and Trp. The amatoxins and phallotoxins also differ from other RiPPs based on the presence of a C-terminal recognition sequence in addition to the N-terminal leader peptide. α-Amanitin, an amatoxin, has a number of posttranslational modifications in addition to macrocyclization and formation of the tryptathionine bridge: oxidation of the tryptathionine leads to the presence of a sulfoxide, and numerous hydroxylations decorate the natural product. As an amatoxin, α-amanitin is an inhibitor of RNA polymerase II. | 1 | Applied and Interdisciplinary Chemistry |
Homonuclear triatomic molecules contain three of the same kind of atom. That molecule will be an allotrope of that element.
Ozone, O is an example of a triatomic molecule with all atoms the same. Triatomic hydrogen, H, is unstable and breaks up spontaneously. H, the trihydrogen cation is stable by itself and is symmetric. He, the helium trimer is only weakly bound by van der Waals force and is in an Efimov state. Trisulfur (S) is analogous to ozone. | 0 | Theoretical and Fundamental Chemistry |
In July 1914—shortly before the outbreak of World War I in August—Hahn was called to active duty with the army in a Landwehr regiment. Meitner undertook X-ray technician training, and a course on anatomy at the city hospital in Lichterfelde. Meanwhile, she completed both the work on the beta ray spectrum that she had begun before the war with Hahn and Baeyer, and her own study of the uranium decay chain. In July 1915, she returned to Vienna, where she joined the Austrian Army as an X-ray nurse-technician. Her unit was soon deployed to the Eastern front in Poland, and she also served on the Italian front for a while before being discharged in September 1916.
Meitner returned to the KWI for Chemistry and her research in October. In January 1917, she was appointed the head of her own physics section. The Hahn-Meitner Laboratory was divided into separate Hahn and Meitner Laboratories, and her pay was increased to 4,000 marks. Hahn returned to Berlin on leave, and they discussed another loose end from their pre-war work: the search for the mother isotope of actinium. According to the radioactive displacement law of Fajans and Soddy, this had to be an isotope of the undiscovered element 91 on the periodic table that lay between thorium and uranium. Kasimir Fajans and Oswald Helmuth Göhring discovered this element in 1913, and named it brevium after its short half-life. However, the isotope they had found was a beta emitter, and therefore could not be the mother isotope of actinium. This had to be another isotope of the same element.
In 1914 Hahn and Meitner had developed a new technique for separating the tantalum group from pitchblende, which they hoped would speed the isolation of the new isotope. When Meitner resumed work in 1917, though, not only Hahn but most of the students, laboratory assistants and technicians had been called up, so Meitner had to do everything herself. In February, Meitner extracted 2 grams of silicon dioxide () from 21 grams of pitchblende. She set 1.5 grams aside and added a tantalum pentafluoride () carrier to the other 0.5 grams, which she dissolved in hydrogen fluoride (). She then boiled it in concentrated sulfuric acid (), precipitated what was believed to be element 91, and verified that it was an alpha emitter. Hahn came home on leave in April, and together they devised a series of indicator tests to eliminate other known alpha emitters. The only known ones with similar chemical behaviour were lead-210 (which decays to alpha emitter polonium-210) and thorium-230.
For this more pitchblende was required. Meitner went to Vienna, where she met with Stefan Meyer. The export of uranium from Austria was forbidden due to wartime restrictions, but Meyer was able to offer her a kilogram of uranium residue, pitchblende from which the uranium had been removed, which was actually better for her purpose. The indicator tests showed that the alpha activity was not due to these substances. All that now remained was to find evidence of actinium. For this more pitchblende was required, and this time Meyer was unable to assist, as the export was now prohibited. Meitner managed to obtain 100 g of "double residue"—pitchblende without uranium or radium—from Friedrich Oskar Giesel and began tests with 43 grams of it, but its composition was different, and at first her tests did not work. With Giesel's help, she was able to produce a pure product that was strongly radioactive. By December 1917 she was able to isolate both the mother isotope and its actinium daughter product. She submitted their findings for publication in March 1918.
Although Fajans and Göhring had been the first to discover the element, custom required that an element was represented by its longest-lived and most abundant isotope, and brevium did not seem appropriate. Fajans agreed to Meitner naming the element "protoactinium" (subsequently shortened to protactinium), and assigning it the chemical symbol Pa. In June 1918, Soddy and John Cranston announced that they had independently extracted a sample of the isotope, but unlike Meitner they were unable to describe its characteristics. They acknowledged Meitner's priority, and agreed to the name. The connection to uranium remained a mystery, as neither of the known isotopes of uranium decayed into protactinium. It remained unsolved until the mother isotope, uranium-235, was discovered in 1929. | 1 | Applied and Interdisciplinary Chemistry |
The Institute for Problems of Cryobiology and Cryomedicine in Kharkiv is one of the institutes of the National Academy of Science of Ukraine, and is the largest institute devoted to cryobiology research in the world. | 1 | Applied and Interdisciplinary Chemistry |
For several compounds containing both a nitrene group and a free radical group an ESR high-spin quartet has been recorded (matrix, cryogenic temperatures). One of these has an amine oxide radical group incorporated, another system has a carbon radical group.
In this system one of the nitrogen unpaired electrons is delocalized in the aromatic ring making the compound a σ–σ–π triradical. A carbene nitrogen radical (imidyl radical) resonance structure makes a contribution to the total electronic picture.
In 2019, an authentic triplet nitrene was isolated by Betley and Lancaster, stabilized by coordination to a copper center in a bulky ligand. | 0 | Theoretical and Fundamental Chemistry |
Interferome offers many ways of searching and retrieving data from the database:
*Identify interferon regulated gene signatures in microarray data;
*Gene Ontology analysis and annotation;
*Normal tissue expression of interferon regulated genes;
*Regulatory analysis of interferon regulated genes;
*BLAST (Basic Local Alignment Search Tool) analysis and orthologue sequence download; | 1 | Applied and Interdisciplinary Chemistry |
Stationary-wave integrated Fourier-transform spectrometry (SWIFTS), or standing-wave integrated Fourier-transform spectrometry, is an analytical technique used for measuring the distribution of light across an optical spectrum. SWIFTS technology is based on a near-field Lippmann architecture. An optical signal is injected into a waveguide and ended by a mirror (true Lippman configuration). The input signal interferes with the reflected signal, creating a standing, or stationary, wave.
In a counter-propagative architecture, the two optical signals are injected at the opposite ends of the waveguide. The evanescent waves propagating within the waveguide are then sampled by optical probes. This results in an interferogram. A mathematical function known as a Lippmann transform, similar to a Fourier transform, is later used to give the spectrum of the light. | 0 | Theoretical and Fundamental Chemistry |
Dixon rings have a similar design to Lessing rings. They are made of stainless steel mesh, giving Dixon rings a low pressure drop and after pre-wetting. Dixon rings have a very large surface area, which increases the rate of mass transfer. Dixon rings have a large liquid hold up, a low pressure drop and a large surface area, and have a high mass transfer rate. Dixon rings are used for laboratory distillation and scrubbing applications. | 1 | Applied and Interdisciplinary Chemistry |
Biometals are metals normally present, in small but important and measurable amounts, in biology, biochemistry, and medicine. The metals copper, zinc, iron, and manganese are examples of metals that are essential for the normal functioning of most plants and the bodies of most animals, such as the human body. A few (calcium, potassium, sodium) are present in relatively larger amounts, whereas most others are trace metals, present in smaller but important amounts (the image shows the percentages for humans). Approximately 2/3 of the existing periodic table is composed of metals with varying properties, accounting for the diverse ways in which metals (usually in ionic form) have been utilized in nature and medicine. | 1 | Applied and Interdisciplinary Chemistry |
In November 1804 Davy became a Fellow of the Royal Society, over which he would later preside. He was one of the founding members of the Geological Society in 1807 and was elected a foreign member of the Royal Swedish Academy of Sciences in 1810 and a Foreign Honorary Member of the American Academy of Arts and Sciences in 1822. | 1 | Applied and Interdisciplinary Chemistry |
Gear flow meters rely on internal gears rotating as fluid passes through them. There are various types of gear meters named mostly for the shape of the internal components
; Oval gear: Two rotating oval gears with synchronized teeth “squeeze” a finite amount of fluid through the meter for each revolution.
With oval gear flow meters, two oval gears or rotors are mounted inside a cylinder. As the fluid flows through the cylinder, the pressure of the fluid causes the rotors to rotate. As flow rate increases, so does the rotational speed of the rotors.
; Helical gear: Helical gear flow meters get their name from the shape of their gears or rotors. These rotors resemble the shape of a helix, which is a spiral-shaped structure. As the fluid flows through the meter, it enters the compartments in the rotors, causing the rotors to rotate. Flowrate is calculated from the speed of rotation. | 1 | Applied and Interdisciplinary Chemistry |
Melainabacteria can be found in a range of environments, including soil, water, and animal habitats. They can be often be found in the gut of humans and in the respiratory tract, oral environments, and skin surface, though rarely. Melainabacteria is often found in natural environments such as groundwater aquifers and lake sediment, as well as soil and bioreactors. Melainabacteria are also found in the aphotic zone of aquatic environments such as lake sediment and aquifers. Cyanobacteria bloom in freshwater systems as a result of excess nutrients and high temperatures, resulting in a scum on the water surface that resembles spilled paint. Because Melainabacteria and Cyanobacteria are related, it has raised concern because Melainabacteria thrive in groundwater systems. The genomes of Melainabacteria were found to be bigger when found in aquifer systems and algal cultivation ponds than when in the mammalian gut environment. | 1 | Applied and Interdisciplinary Chemistry |
It is believed that an alternative visual cycle exists, which uses Müller glial cells instead of Retinal Pigment Epithelium. In this pathway, cones reduce all-trans retinal to all-trans retinol via all-trans Retinol Dehydrogenase, then transport all-trans retinol to Müller cells. There, it is transformed into 11-cis retinol by all-trans retinol isomerase, and can either be stored as retinyl esters within Müller cells, or transported back to the cone photoreceptors, where it is transformed from 11-cis retinol to 11-cis retinal by 11-cis Retinal Dehydrogenase. This pathway helps explain the rapid dark adaptation in the cone system, and the presence of 11-cis Retinal Dehydrogenase in cone photoreceptors, as it is not found in rods, only in the RPE. | 1 | Applied and Interdisciplinary Chemistry |
* Incomplete denitrification is often observed in the B-stage if the influent C/N ratio is low. Direct by-pass of a part of A-stage influent with high organic matter content to the B-stage is used to increase the C/N ratio.
* High sludge production in the A-stage is a drawback for WWTPs that are not equipped with anaerobic digestion of sludge because it increases sludge treatment costs.
* Sludge from A-stage has poor settling properties.
* High retention times cause an increased need for additional reactors to maintain throughput increasing equipment costs | 1 | Applied and Interdisciplinary Chemistry |
The process of microalgae cultivation is highly water-intensive. Life cycle studies estimated that the production of 1 liter of microalgae based biodiesel requires between 607 and 1944 liters of water. That said, abundant wastewater and/or seawater, which also contain various nutrients, can theoretically be used for this purpose instead of freshwater. | 1 | Applied and Interdisciplinary Chemistry |
The two most prevalent shape-memory alloys are copper-aluminium-nickel and nickel-titanium (NiTi), but SMAs can also be created by alloying zinc, copper, gold and iron.
Although iron-based and copper-based SMAs, such as Fe-Mn-Si, Cu-Zn-Al and Cu-Al-Ni, are commercially available and cheaper than NiTi, NiTi-based SMAs are preferable for most applications due to their stability and practicability as well as their superior thermo-mechanical performance. SMAs can exist in two different phases, with three different crystal structures (i.e. twinned martensite, detwinned martensite, and austenite) and six possible transformations. The thermo-mechanic behavior of the SMAs is governed by a phase transformation between the austenite and the martensite.
; M is the temperature at which the transition to martensite completes upon cooling. Accordingly, during heating A and A are the temperatures at which the transformation from martensite to austenite starts and finishes.
Applying a mechanical load to the martensite leads to a re-orientation of the crystals, referred to as “de-twinning”, which results in a deformation which is not recovered (remembered) after releasing the mechanical load. De-twinning starts at a certain stress σ and ends at σ above which martensite continue exhibiting only elastic behavior (as long as the load is below the yield stress). The memorized deformation from detwinning is recovered after heating to austenite.
The phase transformation from austenite to martensite can also occur at constant temperature by applying a mechanical load above a certain level. The transformation is reversed when the load is released.
The transition from the martensite phase to the austenite phase is only dependent on temperature and stress, not time, as most phase changes are, as there is no diffusion involved. Similarly, the austenite structure receives its name from steel alloys of a similar structure. It is the reversible diffusionless transition between these two phases that results in special properties. While martensite can be formed from austenite by rapidly cooling carbon-steel, this process is not reversible, so steel does not have shape-memory properties.
In this figure the vertical axis represents the martensite fraction. The difference between the heating transition and the cooling transition gives rise to hysteresis where some of the mechanical energy is lost in the process. The shape of the curve depends on the material properties of the shape-memory alloy, such as the alloy's composition and work hardening. | 1 | Applied and Interdisciplinary Chemistry |
Thermal spraying involves heating a feedstock of precursor material and spraying it on a surface. Specific techniques depend on desired particle size, coat thickness, spray speed, desired area, etc. Thermal spraying relies on adhesion to the surface. As a result, the surface of the superalloy must be cleaned and prepared, and usually polished, before application. | 1 | Applied and Interdisciplinary Chemistry |
After his PhD, Green undertook a postdoctoral research year with Wilkinson before moving to the University of Cambridge in 1960 as Assistant Lecturer and being appointed a Fellow of Corpus Christi College, Cambridge in 1961. In 1963 he was appointed a Septcentenary Fellow of Inorganic Chemistry at Balliol College, Oxford and a Departmental Demonstrator at the University of Oxford. In 1965 he was made a Lecturer and he was also a Royal Society Senior Research Fellow in Oxford 1979–86. In 1989 he was appointed Professor of Inorganic Chemistry and Head of the Inorganic Chemistry Laboratory at Oxford and Fellow of St Catherine's College, Oxford. In 2004 he became an Emeritus Research Professor. He was a co-founder of the Oxford Catalysts Group plc in 2006.
Green held many visiting positions including: Visiting Professor, Ecole de Chimie and Institute des Substances Naturelles, Paris (1972), Alfred P. Sloan Visiting Professor, Harvard University (1975), Sherman Fairchild Visiting Scholar at the California Institute of Technology (1981), and Walter Hieber Gastprofessor, University of Munich, Germany (1991). | 0 | Theoretical and Fundamental Chemistry |
These substances have some common attributes or gunas such as:
*Astitva (existence): indestructibility; permanence; the capacity by which a substance cannot be destroyed.
*Vastutva (functionality): capacity by which a substance has function.
*Dravyatva (changeability): capacity by which it is always changing in modifications.
*Prameyatva (knowability): capacity by which it is known by someone, or of being the subject-matter of knowledge.
*Agurulaghutva (individuality): capacity by which one attribute or substance does not become another and the substance does not lose the attributes whose grouping forms the substance itself.
*Pradeshatva (spatiality): capacity of having some kind of location in space.
There are some specific attributes that distinguish the dravyas from each other:
*Chetanatva (consciousness) and amurtavta (immateriality) are common attributes of the class of substances soul or jiva.
*Achetanatva (non-consciousness) and murtatva (materiality) are attributes of matter.
*Achetanatva (non-consciousness) and amurtavta (immateriality) are common to Motion, Rest, Time and Space. | 1 | Applied and Interdisciplinary Chemistry |
The fact that carbon and silicone have similar, but also dissimilar, characteristics triggered the interest in substituting carbon with silanediol as a central, zinc chelating group. Silicone forms a dialkylsilanediol compound that is sufficiently hindered so the formation of a siloxane polymer does not occur. Silanediols are more stable than carbon diols so they are expected to have longer half-life. Silanediols are also neutral at physiological pH (do not ionize).
Four stereoisomers of Phe-Ala silanediol were compared to ketone-based inhibitors and the silanediol were found to be fourfold less potent than the ketone analogue. This is because silanediols are weaker zinc chelators compared with ketones. Replacement of the silanediol, with a methylsilano group gave little enzyme inhibition. This confirms that the silanediol group interacts with ACE as a transition state analogue and the interaction is in a manner similar to that of ketone. If the benzyl group of silanediol is replaced by an i-butyl group it gives a weaker ACE inhibitor. Introduction of a hydrophobic methyl phenyl gives a little more potency than an analogue with a tert-butyl-group at P. That suggests that methyl phenyl gives a better S1 recognition than a tert-butyl group. | 1 | Applied and Interdisciplinary Chemistry |
4-Maleylacetoacetate (4-maleylacetoacetatic acid) is an intermediate in the metabolism of tyrosine. It is converted to fumarylacetoacetate by the enzyme 4-maleylacetoacetate cis-trans-isomerase. Gluthathione coenzymatically helps in conversion to fumarylacetoacetic acid. | 1 | Applied and Interdisciplinary Chemistry |
Reptiles need UVB for biosynthesis of vitamin D, and other metabolic processes. Specifically cholecalciferol (vitamin D3), which is needed for basic cellular / neural functioning as well as the utilization of calcium for bone and egg production. The UVA wavelength is also visible to many reptiles and might play a significant role in their ability survive in the wild as well as in visual communication between individuals. Therefore, in a typical reptile enclosure, a fluorescent UV a/b source (at the proper strength / spectrum for the species), must be available for many captive species to survive. Simple supplementation with cholecalciferol (Vitamin D3) will not be enough as there's a complete biosynthetic pathway that is "leapfrogged" (risks of possible overdoses), the intermediate molecules and metabolites also play important functions in the animals health. Natural sunlight in the right levels is always going to be superior to artificial sources, but this might not be possible for keepers in different parts of the world.
It is a known problem that high levels of output of the UVa part of the spectrum can both cause cellular and DNA damage to sensitive parts of their bodies – especially the eyes where blindness is the result of an improper UVa/b source use and placement photokeratitis. For many keepers there must also be a provision for an adequate heat source this has resulted in the marketing of heat and light "combination" products. Keepers should be careful of these "combination" light/ heat and UVa/b generators, they typically emit high levels of UVa with lower levels of UVb that are set and difficult to control so that animals can have their needs met. A better strategy is to use individual sources of these elements and so they can be placed and controlled by the keepers for the max benefit of the animals. | 0 | Theoretical and Fundamental Chemistry |
Radiolysis is the dissociation of molecules by ionizing radiation. It is the cleavage of one or several chemical bonds resulting from exposure to high-energy flux. The radiation in this context is associated with ionizing radiation; radiolysis is therefore distinguished from, for example, photolysis of the Cl molecule into two Cl-radicals, where (ultraviolet or visible spectrum) light is used.
The chemistry of concentrated solutions under ionizing radiation is extremely complex. Radiolysis can locally modify redox conditions, and therefore the speciation and the solubility of the compounds. | 0 | Theoretical and Fundamental Chemistry |
Vitamin A is a fat-soluble vitamin and an essential nutrient for animals. The term "vitamin A" encompasses a group of chemically related organic compounds that includes retinol, retinal (also known as retinaldehyde), retinoic acid, and several provitamin (precursor) carotenoids, most notably beta-carotene. Vitamin A has multiple functions: it is essential for embryo development and growth, for maintenance of the immune system, and for vision, where it combines with the protein opsin to form rhodopsin the light-absorbing molecule necessary for both low-light (scotopic vision) and color vision.
Vitamin A occurs as two principal forms in foods: A) retinol, found in animal-sourced foods, either as retinol or bound to a fatty acid to become a retinyl ester, and B) the carotenoids alpha-carotene, β-carotene, gamma-carotene, and the xanthophyll beta-cryptoxanthin (all of which contain β-ionone rings) that function as provitamin A in herbivore and omnivore animals which possess the enzymes that cleave and convert provitamin carotenoids to retinal and then to retinol. Some carnivore species lack this enzyme. The other carotenoids have no vitamin activity.
Dietary retinol is absorbed from the digestive tract via passive diffusion. Unlike retinol, β-carotene is taken up by enterocytes by the membrane transporter protein scavenger receptor B1 (SCARB1), which is upregulated in times of vitamin A deficiency. Storage of retinol is in lipid droplets in the liver. A high capacity for long-term storage of retinol means that well-nourished humans can go months on a vitamin A- and β-carotene-deficient diet, while maintaining blood levels in the normal range. Only when the liver stores are nearly depleted will signs and symptoms of deficiency show. Retinol is reversibly converted to retinal, then irreversibly to retinoic acid, which activates hundreds of genes.
Vitamin A deficiency is common in developing countries, especially in Sub-Saharan Africa and Southeast Asia. Deficiency can occur at any age but is most common in pre-school age children and pregnant women, the latter due to a need to transfer retinol to the fetus. Vitamin A deficiency is estimated to affect approximately one-third of children under the age of five around the world, resulting in hundreds of thousands of cases of blindness and deaths from childhood diseases because of immune system failure. Reversible night blindness is an early indicator of low vitamin A status. Plasma retinol is used as a biomarker to confirm vitamin A deficiency. Breast milk retinol can indicate a deficiency in nursing mothers. Neither of these measures indicates the status of liver reserves.
The European Union and various countries have set recommendations for dietary intake, and upper limits for safe intake. Vitamin A toxicity also referred to as hypervitaminosis A, occurs when there is too much vitamin A accumulating in the body. Symptoms may include nervous system effects, liver abnormalities, fatigue, muscle weakness, bone and skin changes, and others. The adverse effects of both acute and chronic toxicity are reversed after consumption of high dose supplements is stopped. | 1 | Applied and Interdisciplinary Chemistry |
Jones married Vera Haines, a dispensing chemist in Gympie in 1923. They had two children. He died on 11 August 1970 in Brisbane. | 0 | Theoretical and Fundamental Chemistry |
The basis of ferroics is to understand the large changes in physical characteristics that occur over a very narrow temperature range. The changes in physical characteristics occur when phase transitions take place around some critical temperature value, normally denoted by . Above this critical temperature, the crystal is in a nonferroic state and does not exhibit the physical characteristic of interest. Upon cooling the material down below it undergoes a spontaneous phase transition. Such a phase transition typically results in only a small deviation from the nonferroic crystal structure, but in altering the shape of the unit cell the point symmetry of the material is reduced. This breaking of symmetry is physically what allows the formation of the ferroic phase.
In ferroelectrics, upon lowering the temperature below , a spontaneous dipole moment is induced along an axis of the unit cell. Although individual dipole moments can sometimes be small, the effect of unit cells gives rise to an electric field that over the bulk substance that is not insignificant. An important point about ferroelectrics is that they cannot exist in a centrosymmetric crystal. A centrosymmetric crystal is one where a lattice point can be mapped onto a lattice point .
Ferromagnets is a term that most people are familiar with, and, as with ferroelastics, the spontaneous magnetization of a ferromagnet can be attributed to a breaking of point symmetry in switching from the paramagnetic to the ferromagnetic phase. In this case, is normally known as the Curie Temperature.
In ferroelastic crystals, in going from the nonferroic (or prototypic phase) to the ferroic phase, a spontaneous strain is induced. An example of a ferroelastic phase transition is when the crystal structure spontaneously changes from a tetragonal structure (a square prism shape) to a monoclinic structure (a general parallelepiped). Here the shapes of the unit cell before and after the phase transition are different, and hence a strain is induced within the bulk.
In recent years, multiferroics have been attracting increased interest. These materials exhibit more than one ferroic property simultaneously in a single phase. A fourth ferroic order termed ferrotoroidic order has also been proposed. | 0 | Theoretical and Fundamental Chemistry |
Johnson et al. describe two isoforms of succinyl-CoA synthetase in amniotes, one that specifies synthesis of ATP, and one that synthesises GTP.
* - ATP-forming - SUCLA2
* - GTP-forming - SUCLG2
In amniotes, the enzyme is a heterodimer of an α- and a β-subunit. The specificity for either adenosine or guanosine phosphates is defined by the β-subunit, which is encoded by 2 genes. SUCLG2 is GTP-specific and SUCLA2 is ATP-specific, while SUCLG1 encodes the common α-subunit. β variants are produced at different amounts in different tissues, causing GTP or ATP substrate requirements.
Mostly consuming tissues such as heart and brain have more ATP-specific succinyl-CoA synthetase (ATPSCS), while synthetic tissues such as kidney and liver have the more GTP-specific form (GTPSCS). Kinetics analysis of ATPSCS from the breast muscle of pigeons and GTPSCS from pigeon liver showed that their apparent Michaelis constants were similar for CoA, but different for the nucleotides, phosphate, and succinate. The largest difference was for succinate: Kapp of ATPSCS = 5mM versus that of GTPSCS = 0.5mM. | 1 | Applied and Interdisciplinary Chemistry |
Early evolution is defined as beginning with the origin of life and ending with the last universal common ancestor (LUCA). According to the iron–sulfur world theory it covers a coevolution of cellular organization (cellularization), the genetic machinery and enzymatization of the metabolism. | 1 | Applied and Interdisciplinary Chemistry |
During exercise when the ATP reservoir is low (ADP>ATP), the purine nucleotide cycle produces ammonia (NH) when it converts AMP into IMP. (With the exception of AMP deaminase deficiency, where ammonia is produced during exercise when adenosine, from AMP, is converted into inosine). During rest (ADP<ATP), ammonia is produced from the conversion of adenosine into inosine by adenosine deaminase.
:AMP + HO + H → IMP + NH (catalyzed by AMP deaminase in skeletal muscle)
:Adenosine + HO → Inosine + NH (catalyzed by adenosine deaminase in skeletal muscle, blood, liver)
Ammonia is toxic, disrupts cell function, and permeates cell membranes. Ammonia becomes ammonium (NH) depending on the pH of the cell or plasma. Ammonium is relatively non-toxic and does not readily permeate cell membranes. + H ⇌ NH) diffuses into the blood, circulating to the liver to be neutralized by the urea cycle. (N.b. urea is not the same as uric acid, though both are end products of the purine nucleotide cycle, from ammonia and nucleotides respectively.) When the skeletal muscles are at rest (ADP) combines with glutamate to produce glutamine, which is an energy-consuming step, and the glutamine enters the blood. + ATP → Glutamine + ADP + P (catalyzed by glutamine synthetase in resting skeletal muscle) molecules neutralise the organic acids (lactic acid and ketone bodies) produced in the muscles.O → Glutamate + NH (catalyzed by glutaminase in the kidneys)</blockquote> | 1 | Applied and Interdisciplinary Chemistry |
*1985: Pittsburgh Analytical Chemistry Award
*1988: Malcolm E. Pruitt Award from the Council for Chemical Research
*1989: Theophilus Redwood Endowed Lectureship from the Royal Society of Chemistry
*1991: Endowed Professor of Analytical Chemistry, University of Washington
*1993: Torbern Bergman Medal from the Swedish Chemical Society’s analytical division | 0 | Theoretical and Fundamental Chemistry |
* 1932 Robert Hutton (retired 1942)
* 1945 George Wesley Austin
* 1958 Sir Alan Cottrell (resigned 1965)
* 1966 Robert Honeycombe
* 1984 Derek Hull (retired 1991)
* 1990 Sir Colin John Humphreys
* 2008 Anthony Cheetham | 1 | Applied and Interdisciplinary Chemistry |
Salen refers to a tetradentate C-symmetric ligand synthesized from salicylaldehyde (sal) and ethylenediamine (en). It may also refer to a class of compounds, which are structurally related to the classical salen ligand, primarily bis-Schiff bases. Salen ligands are notable for coordinating a wide range of different metals, which they can often stabilise in various oxidation states. For this reason salen-type compounds are used as metal deactivators. Metal salen complexes also find use as catalysts. | 0 | Theoretical and Fundamental Chemistry |
Consider a cuboid immersed in a fluid, its top and bottom faces orthogonal to the direction of gravity (assumed constant across the cube's stretch). The fluid will exert a normal force on each face, but only the normal forces on top and bottom will contribute to buoyancy. The pressure difference between the bottom and the top face is directly proportional to the height (difference in depth of submersion). Multiplying the pressure difference by the area of a face gives a net force on the cuboid — the buoyancy — equaling in size the weight of the fluid displaced by the cuboid. By summing up sufficiently many arbitrarily small cuboids this reasoning may be extended to irregular shapes, and so, whatever the shape of the submerged body, the buoyant force is equal to the weight of the displaced fluid.
The weight of the displaced fluid is directly proportional to the volume of the displaced fluid (if the surrounding fluid is of uniform density). The weight of the object in the fluid is reduced, because of the force acting on it, which is called upthrust. In simple terms, the principle states that the buoyant force (F) on an object is equal to the weight of the fluid displaced by the object, or the density (ρ) of the fluid multiplied by the submerged volume (V) times the gravity (g)
We can express this relation in the equation:
where denotes the buoyant force applied onto the submerged object, denotes the density of the fluid, represents the volume of the displaced fluid and is the acceleration due to gravity.
Thus, among completely submerged objects with equal masses, objects with greater volume have greater buoyancy.
Suppose a rock's weight is measured as 10 newtons when suspended by a string in a vacuum with gravity acting on it. Suppose that, when the rock is lowered into the water, it displaces water of weight 3 newtons. The force it then exerts on the string from which it hangs would be 10 newtons minus the 3 newtons of buoyant force: 10 − 3 = 7 newtons. Buoyancy reduces the apparent weight of objects that have sunk completely to the sea-floor. It is generally easier to lift an object through the water than it is to pull it out of the water.
For a fully submerged object, Archimedes' principle can be reformulated as follows:
then inserted into the quotient of weights, which has been expanded by the mutual volume
yields the formula below. The density of the immersed object relative to the density of the fluid can easily be calculated without measuring any volume is
(This formula is used for example in describing the measuring principle of a dasymeter and of hydrostatic weighing.)
Example: If you drop wood into water, buoyancy will keep it afloat.
Example: A helium balloon in a moving car. When increasing speed or driving in a curve, the air moves in the opposite direction to the cars acceleration. However, due to buoyancy, the balloon is pushed "out of the way" by the air and will drift in the same direction as the cars acceleration.
When an object is immersed in a liquid, the liquid exerts an upward force, which is known as the buoyant force, that is proportional to the weight of the displaced liquid. The sum force acting on the object, then, is equal to the difference between the weight of the object (down force) and the weight of displaced liquid (up force). Equilibrium, or neutral buoyancy, is achieved when these two weights (and thus forces) are equal. | 1 | Applied and Interdisciplinary Chemistry |
In X-ray crystallography, crystallographic disorder describes the cocrystallization of more than one rotamer, conformer, or isomer where the center of mass of each form is identical or unresolvable. As a consequence of disorder, the crystallographic solution is the sum of the various forms. In many cases, the components of the disorder are equally abundant, and, in other cases, the weighting coefficients for each component differ. Disorder can entail a pair or several components, and usually arises when the forms are nearly equal in energy and the crystal lattice is sufficiently spacious to accommodate the various components. | 0 | Theoretical and Fundamental Chemistry |
Atomicity is the total number of atoms present in a molecule of an element. For example, each molecule of oxygen (O) is composed of two oxygen atoms. Therefore, the atomicity of oxygen is 2.
In older contexts, atomicity is sometimes equivalent to valency. Some authors also use the term to refer to the maximum number of valencies observed for an element. | 0 | Theoretical and Fundamental Chemistry |
While Diaconescu is best known for her work on the reactivity of early transition metals, lanthanides, and actinides, she has also contributed to the field of redox active ligand systems for small molecule activation. Her group has exploited ferrocenes electronic and redox properties to enable catalytic transformations with electrophilic transition metal centers. Diaconescus research on redox active systems is studying how ferrocene's electronic and redox properties when strategically incorporated into a ligand affect the reactivity of d-block metal complexes. This extends to redox switchable catalysis and small molecule activation with applications in polyaniline nanofiber supporting metal catalysis and bioorganometallic polymers. She recognized that redox-switchable catalysis can generate multiple catalytically active species with varying reactivity. The idea is that a compound can have orthogonal reactivity between the oxidized and reduced forms of the catalyst. The ring-opening polymerization of cyclic ethers and esters as well as the polymerization of alkenes has been exploited with catalysts containing ferrocene. | 0 | Theoretical and Fundamental Chemistry |
Essential in synergetics is the order-parameter concept which was originally introduced in the Ginzburg–Landau theory in order to describe phase transitions in thermodynamics. The order parameter concept is generalized by Haken to the "enslaving-principle" saying that the dynamics of fast-relaxing (stable) modes is completely determined by the slow dynamics of, as a rule, only a few order-parameters (unstable modes). The order parameters can be interpreted as the amplitudes of the unstable modes determining the macroscopic pattern.
As a consequence, self-organization means an enormous reduction of degrees of freedom (entropy) of the system which macroscopically reveals an increase of order (pattern-formation). This far-reaching macroscopic order is independent of the details of the microscopic interactions of the subsystems. This supposedly explains the self-organization of patterns in so many different systems in physics, chemistry and biology. | 0 | Theoretical and Fundamental Chemistry |
Banhart describes two dominating perspectives in which cellular metals are characterized, referring to them as atomistic and macroscopic. The atomistic (or molecular) perspective holds that a cellular material is a construction of struts, membranes, and other elements which possess mechanical properties of their bulk metal counterpart. Indeed, the physical, mechanical, and thermal properties of titanium foams are commonly measured using the same methods as that of their solid counterparts. However, special precautions must be taken due to the cellular structure of metal foams. From a macroscopic perspective, the cellular structure is perceived as a homogeneous structure and characterized by considering the effective (or averaged) material parameters. | 0 | Theoretical and Fundamental Chemistry |
The doubly labeled water method is particularly useful for measuring average metabolic rate (field metabolic rate) over relatively long periods of time (a few days or weeks), in subjects for which other types of direct or indirect calorimetric measurements of metabolic rate would be difficult or impossible. For example, the technique can measure the metabolism of animals in the wild state, with the technical problems being related mainly to how to administer the dose of isotope, and collect several samples of body water at later times to check for differential isotope elimination.
Most animal studies involve capturing the subject animals and injecting them, then holding them for a variable period before the first blood sample has been collected. This period depends on the size of the animal involved and varies between 30 minutes for very small animals to 6 hours for much larger animals. In both animals and humans, the test is made more accurate if a single determination of respiratory quotient has been made for the organism eating the standard diet at the time of measurement, since this value changes relatively little (and more slowly) compared with the much larger metabolic rate changes related to thermoregulation and activity.
Because the heavy hydrogen and oxygen isotopes used in the standard doubly labeled water measurement are non-radioactive, and also non-toxic in the doses used (see heavy water), the doubly labeled water measurement of mean metabolic rate has been used extensively in human volunteers, and even in infants and pregnant women. The technique has been used on over 200 species of wild animals (mostly birds, mammals and some reptiles). Applications of the method to animals have been reviewed. A paper by Pontzer, Yamada, Sagayama and colleagues in 2021 summarized the results of over 6400 measurements using the technique in humans aged between 8 days and 96 years old.
Doubly labeled water (HO) can also be used for unusually warm ice and unusually dense water, as it has a higher melting point than and is denser than either light water or what is normally meant by "heavy water" (HO). HO melts at 4.00~4.04 °C (39.2 °F~39.27 °F) and the liquid reaches its maximum density of 1.21684~1.21699 g/cm at 11.43~11.49 °C (52.57 °F~52.68 °F). | 0 | Theoretical and Fundamental Chemistry |
In 1903 Auer von Welsbach won another patent for a fire striker ("flint") composition named ferrocerium. It takes its name from its two primary components: iron (from ), and the rare-earth element cerium. It is also known in Europe as "Auermetall" after its inventor. Three different Auermetalls were developed: the first was iron and cerium, the second also included lanthanum to produce brighter sparks, and the third added other heavy metals. In Auer von Welsbach's first alloy, 30% iron (ferrum) was added to purified cerium, hence the name "ferro-cerium".
Welsbach's flints consisted of pyrophoric alloys, 70% cerium and 30% iron, which when scratched or struck would give off sparks. This system remains in wide use in cigarette lighters today. In 1907 he formed Treibacher Chemische Werke GesmbH to build and market the devices. | 1 | Applied and Interdisciplinary Chemistry |
As a result of extensive cultivation of legumes (particularly soy, alfalfa, and clover), growing use of the Haber–Bosch process in the production of chemical fertilizers, and pollution emitted by vehicles and industrial plants, human beings have more than doubled the annual transfer of nitrogen into biologically available forms. In addition, humans have significantly contributed to the transfer of nitrogen trace gases from Earth to the atmosphere and from the land to aquatic systems. Human alterations to the global nitrogen cycle are most intense in developed countries and in Asia, where vehicle emissions and industrial agriculture are highest.
Generation of Nr, reactive nitrogen, has increased over 10 fold in the past century due to global industrialisation. This form of nitrogen follows a cascade through the biosphere via a variety of mechanisms, and is accumulating as the rate of its generation is greater than the rate of denitrification.
Nitrous oxide () has risen in the atmosphere as a result of agricultural fertilization, biomass burning, cattle and feedlots, and industrial sources. has deleterious effects in the stratosphere, where it breaks down and acts as a catalyst in the destruction of atmospheric ozone. Nitrous oxide is also a greenhouse gas and is currently the third largest contributor to global warming, after carbon dioxide and methane. While not as abundant in the atmosphere as carbon dioxide, it is, for an equivalent mass, nearly 300 times more potent in its ability to warm the planet.
Ammonia () in the atmosphere has tripled as the result of human activities. It is a reactant in the atmosphere, where it acts as an aerosol, decreasing air quality and clinging to water droplets, eventually resulting in nitric acid (HNO) that produces acid rain. Atmospheric ammonia and nitric acid also damage respiratory systems.
The very high temperature of lightning naturally produces small amounts of , , and , but high-temperature combustion has contributed to a 6- or 7-fold increase in the flux of to the atmosphere. Its production is a function of combustion temperature - the higher the temperature, the more is produced. Fossil fuel combustion is a primary contributor, but so are biofuels and even the burning of hydrogen. However, the rate that hydrogen is directly injected into the combustion chambers of internal combustion engines can be controlled to prevent the higher combustion temperatures that produce .
Ammonia and nitrous oxides actively alter atmospheric chemistry. They are precursors of tropospheric (lower atmosphere) ozone production, which contributes to smog and acid rain, damages plants and increases nitrogen inputs to ecosystems. Ecosystem processes can increase with nitrogen fertilization, but anthropogenic input can also result in nitrogen saturation, which weakens productivity and can damage the health of plants, animals, fish, and humans.
Decreases in biodiversity can also result if higher nitrogen availability increases nitrogen-demanding grasses, causing a degradation of nitrogen-poor, species-diverse heathlands. | 1 | Applied and Interdisciplinary Chemistry |
The RNAP occasionally stops and starts moving backwards when it encounters a roadblock or some difficult sequences. When this happens, the EC gets stuck because the reactive 3 edge of the RNA is out of the active site. The transcript cleavage factor TFS (a TFIIS homolog) helps resolve this issue by generating a cut so that a new 3 end is available in the active site. Some archaeon have up to 4 paralogs of TFS with divergent functions. | 1 | Applied and Interdisciplinary Chemistry |
For the pinhole configuration the width of the beam (which we aim to minimise) is largely given by geometrical optics. The size of the beam at the sample plane is given by the lines connecting the skimmer edges with the pinhole edges. When the Fresnel number is very small (), the beam width is also affected by Fraunhofer diffraction (see equation below).
In this equation is the Full Width at Half Maximum of the beam, is the geometrical projection of the beam and is the Airy diffraction term. is the Heaviside step function used here to indicate that the presence of the diffraction term depends on the value of the Fresnel number. Note that there are variations of this equation depending on what is defined as the "beam width" (for details compare and ). Due to the small wavelength of the helium beam, the Fraunhofer diffraction term can usually be omitted.
The intensity of the beam (which we aim to maximise) is given by the following equation (according to the Sikora and Andersen model):
Where is the total intensity stemming from the supersonic expansion nozzle (taken as a constant in the optimisation problem), is the radius of the pinhole, S is the speed ratio of the beam, is the radius of the skimmer, is the radius of the supersonic expansion quitting surface (the point in the expansion from which atoms can be considered to travel in a straight line), is the distance between the nozzle and the skimmer and is the distance between the skimmer and the pinhole. There are several other versions of this equation that depend on the intensity model, but they all show a quadratic dependency on the pinhole radius (the bigger the pinhole, the more intensity) and an inverse quadratic dependency with the distance between the skimmer and the pinhole (the more the atoms spread, the less intensity).
By combining the two equations shown above, one can obtain that for a given beam width for the geometrical optics regime the following values correspond to intensity maxima:
In here, represents the working distance of the microscope and is a constant that stems from the definition of the beam width. Note that both equations are given with respect to the distance between the skimmer and the pinhole, a. The global maximum of intensity can then be obtained numerically by replacing these values in the intensity equation above. In general, smaller skimmer radii coupled with smaller distances between the skimmer and the pinhole are preferred, leading in practice to the design of increasingly smaller pinhole microscopes. | 0 | Theoretical and Fundamental Chemistry |
In heterocyclic chemistry, organic reactions are classified by the type of heterocycle formed with respect to ring-size and type of heteroatom. See for instance the chemistry of indoles. Reactions are also categorized by the change in the carbon framework. Examples are ring expansion and ring contraction, homologation reactions, polymerization reactions, insertion reactions, ring-opening reactions and ring-closing reactions.
Organic reactions can also be classified by the type of bond to carbon with respect to the element involved. More reactions are found in organosilicon chemistry, organosulfur chemistry, organophosphorus chemistry and organofluorine chemistry. With the introduction of carbon-metal bonds the field crosses over to organometallic chemistry. | 0 | Theoretical and Fundamental Chemistry |
After the discovery of the lux operon, the use of bioluminescent bacteria as a laboratory tool is claimed to have revolutionized the area of environmental microbiology. The applications of bioluminescent bacteria include biosensors for detection of contaminants, measurement of pollutant toxicity and monitoring of genetically engineered bacteria released into the environment. Biosensors, created by placing a lux gene construct under the control of an inducible promoter, can be used to determine the concentration of specific pollutants. Biosensors are also able to distinguish between pollutants that are bioavailable and those that are inert and unavailable. For example, Pseudomonas fluorescens has been genetically engineered to be capable of degrading salicylate and naphthalene, and is used as a biosensor to assess the bioavailability of salicylate and naphthalene. Biosensors can also be used as an indicator of cellular metabolic activity and to detect the presence of pathogens. | 1 | Applied and Interdisciplinary Chemistry |
Flanges are flat rings around the end of pipes which mate with an equivalent flange from another pipe, the two being held together by bolts usually passed through holes drilled through the flanges. A deformable gasket, usually elastomeric, placed between raised faces on the mating flanges provides the seal. Flanges are designed to a large number of specifications that differ because of dimensional variations in pipes sizes and pressure requirements, and because of independent standards development. In the US, flanges are either threaded or welded onto the pipe. In the European market flanges are usually welded onto the pipe. In the US, flanges are available in a standard 125 lb bolt pattern as well as a 250 lb (and heavier) bolt pattern (steel bolt pattern). Both are usually rated at . A flanged joint is rigid and can bear both tension and compression as well as a limited degree of shear and bending. It also can be dismantled after assembly. Due to the rigid nature of the joint and the risk of excessive bending moment being imposed, it is advised that flanged pipework not be buried.
Current flange standards used in the water industry are ANSI B16.1 in the US, EN 1092 in Europe, and AS/NZS 4087 in Australia and New Zealand. | 1 | Applied and Interdisciplinary Chemistry |
In flow chemistry, also called reactor engineering, a chemical reaction is run in a continuously flowing stream rather than in batch production. In other words, pumps move fluid into a reactor, and where tubes join one another, the fluids contact one another. If these fluids are reactive, a reaction takes place. Flow chemistry is a well-established technique for use at a large scale when manufacturing large quantities of a given material. However, the term has only been coined recently for its application on a laboratory scale by chemists and describes small pilot plants, and lab-scale continuous plants. Often, microreactors are used. | 1 | Applied and Interdisciplinary Chemistry |
The conversion equations depend on the temperature at which the conversion is wanted (usually about 20 to 25 degrees Celsius). At an ambient air pressure of 1 atmosphere (101.325 kPa), the general equation is:
and for the reverse conversion:
Notes:
* Pollution regulations in the United States typically reference their pollutant limits to an ambient temperature of 20 to 25 °C as noted above. In most other nations, the reference ambient temperature for pollutant limits may be 0 °C or other values.
* 1 percent by volume = 10,000 ppmv (i.e., parts per million by volume).
* atm = absolute atmospheric pressure in atmospheres
* mol = gram mole | 1 | Applied and Interdisciplinary Chemistry |
HMB is eliminated via the kidneys, with roughly of an ingested dose being excreted unchanged in urine. The remaining of the dose is retained in tissues or excreted as HMB metabolites. The fraction of a given dose of HMB that is excreted unchanged in urine increases with the dose. | 1 | Applied and Interdisciplinary Chemistry |
* Clinistrips quantitatively test for sugar in urine
* The Kastle-Meyer test tests for the presence of hemoglobin
* Salicylate testing is a category of drug testing that is focused on detecting salicylates such as acetylsalicylic acid for either biochemical or medical purposes.
* The Phadebas test tests for the presence of saliva for forensic purposes
* Iodine solution tests for starch
* The Van Slyke determination tests for specific amino acids
* The Zimmermann test tests for ketosteroids
* Seliwanoff's test differentiates between aldose and ketose sugars
* Test for lipids: add ethanol to sample, then shake; add water to the solution, and shake again. If fat is present, the product turns milky white.
*The Sakaguchi test detects the presence of arginine in protein
*The Hopkins–Cole reaction tests for the presence of tryptophan in proteins
*The nitroprusside reaction tests for the presence of free thiol groups of cysteine in proteins
*The Sullivan reaction tests for the presence of cysteine and cystine in proteins
*The Acree–Rosenheim reaction tests for the presence of tryptophan in proteins
*The Pauly reaction tests for the presence of tyrosine or histidine in proteins
*Heller's test tests for the presence of albumin in urine
*Gmelin's test tests for the presence of bile pigments in urine
*Hay's test tests for the presence of bile pigments in urine | 0 | Theoretical and Fundamental Chemistry |
The Butler–Volmer equation is:
or in a more compact form:
where:
* : electrode current density, A/m (defined as j = I/S)
*: exchange current density, A/m
* : electrode potential, V
* : equilibrium potential, V
* : absolute temperature, K
* : number of electrons involved in the electrode reaction
* : Faraday constant
* : universal gas constant
*: so-called cathodic charge transfer coefficient, dimensionless
*: so-called anodic charge transfer coefficient, dimensionless
* : activation overpotential (defined as ).
The right hand figure shows plots valid for . | 0 | Theoretical and Fundamental Chemistry |
MFGM is a structurally complex bioactive milk component, found in human milk as well as the milk of other mammalian species. The MFGM in human milk contains many bioactive components with diverse functions and has been linked to cognitive and health benefits to infants. Some compositional differences are reported to exist between species, but bovine MFGM, the best-studied non-human source, generally contains a lipid and protein composition, which is similar to that of human MFGM.
MFGM makes up an estimated 2-6% of the total fat globules. As raw milk has an average total fat content around 4%, it therefore contains around 0.08-0.24% of MFGM. In other words, 417–1250 kg of raw milk is needed to supply 1 kg of MFGM. The content of MFGM in dairy products varies depending on the processing involved. During dairy processing such as churning or decreaming, the MFGM is disrupted and preferentially distributed into aqueous phases such as buttermilk, butter serum, or certain type of whey. Thus they can be a good source of MFGM for addition into food products.
For example, infant formulas traditionally were lacking the MFGM because this fraction is lost during regular dairy processing. However, more recent advances in technology have facilitated the separation of MFGM from the fat globule, allowing bovine MFGM to be added in concentrated form. The MFGM fraction is now commercially available and can be added to infant formula or other nutritional products. | 1 | Applied and Interdisciplinary Chemistry |
Indoline 9 was acetylated to N-acetyl compound 10 (acetic anhydride, pyridine) and then the veratryl group was then ring-opened with ozone in aqueous acetic acid to muconic ester 11 (made possible by the two electron-donating methoxide groups). This is an example of bioinspired synthesis already proposed by Woodward in 1948. Cleavage of the acetyl group and ester hydrolysis with HCl in methanol resulted in formation of pyridone ester 12 with additional isomerization of the exocyclic double bond to an endocyclic double bond (destroying one asymmetric center). Subsequent treatment with hydrogen iodide and red phosphorus removed the tosyl group and hydrolysed both remaining ester groups to form diacid 13. Acetylation and esterification (diazomethane) produced acetyl diester 14 which was then subjected to a Dieckman condensation with sodium methoxide in methanol to enol 15. | 0 | Theoretical and Fundamental Chemistry |
Isodesmosine is a lysine derivative found in elastin. Isodesmosine is an isomeric pyridinium-based amino acid resulting from the condensation of four lysine residues between elastin proteins by lysyl-oxidase. These represent ideal biomarkers for monitoring elastin turnover because these special cross-links are only found in mature elastin in mammals. | 1 | Applied and Interdisciplinary Chemistry |
Internal coordinates are of the following types, illustrated with reference to the planar molecule ethylene,
* Stretching: a change in the length of a bond, such as C–H or C–C
* Bending: a change in the angle between two bonds, such as the HCH angle in a methylene group
* Rocking: a change in angle between a group of atoms, such as a methylene group and the rest of the molecule.
* Wagging: a change in angle between the plane of a group of atoms, such as a methylene group and a plane through the rest of the molecule,
* Twisting: a change in the angle between the planes of two groups of atoms, such as a change in the angle between the two methylene groups.
* Out-of-plane: a change in the angle between any one of the C–H bonds and the plane defined by the remaining atoms of the ethylene molecule. Another example is in BF when the boron atom moves in and out of the plane of the three fluorine atoms.
In a rocking, wagging or twisting coordinate the bond lengths within the groups involved do not change. The angles do. Rocking is distinguished from wagging by the fact that the atoms in the group stay in the same plane.
In ethylene there are 12 internal coordinates: 4 C–H stretching, 1 C–C stretching, 2 H–C–H bending, 2 CH rocking, 2 CH wagging, 1 twisting. Note that the H–C–C angles cannot be used as internal coordinates as well as the H-C-H angle because the angles at each carbon atom cannot all increase at the same time.
Note that these coordinates do not correspond to normal modes (see #Normal coordinates). In other words, they do not correspond to particular frequencies or vibrational transitions. | 0 | Theoretical and Fundamental Chemistry |
A recent study shows that conformational proofreading is used by human DNA repair mechanisms. The research focused on the question of how DNA-repair proteins scan the human genome for UV-induced damage during the initial step of nucleotide excision repair (NER). Detailed single-molecule measurements revealed how the human UV-damaged DNA-binding protein (UV-DDB) performs a 3D search. The authors find that "UV-DDB examines sites on DNA in discrete steps before forming long-lived, nonmotile UV-DDB dimers (DDB1-DDB2) at sites of damage. Analysis of the rates of dissociation for the transient binding molecules on both undamaged and damaged DNA show multiple dwell times over three orders of magnitude... These intermediate states are believed to represent discrete UV-DDB conformers on the trajectory to stable damage detection." The authors conclude from their detailed kinetic measurements that UV-DDB recognizes lesions using a conformational proofreading mechanism via multiple intermediates. | 1 | Applied and Interdisciplinary Chemistry |
A natural ECM scaffold provides the necessary physical and biochemical environment to facilitate the growth and specialization of potent progenitor and stem cells. Acellular matrices have been isolated in vitro and in vivo in a number of different tissues and organs. Decellularized ECM can be used to prepare bio-ink for 3D bioprinting. The most applicable success from decellularized tissues has come from symmetrical tissues that have less specialization, such as bone and dermal grafts; however, research and success are ongoing at the organ level.
Acellular dermal matrices have been successful in a number of different applications. For example, skin grafts are used in cosmetic surgery and burn care. The decellularized skin graft provides mechanical support to the damaged area while supporting the development of host-derived connective tissue. Cardiac tissue has clinical success in developing human valves from natural ECM matrices. A technique known as the Ross procedure uses an acellular heart valve to replace a defective valve, allowing native cells to repopulate a newly functioning valve. Decellularized allografts have been critical in bone grafts that function in bone reconstruction and replacing of deformed bones in patients.
The limits to myocardial tissue engineering come from the ability to immediately perfuse and seed and implemented heart into a patient. Though the ECM scaffold maintains the protein and growth factors of the natural tissue, the molecular level specialization has not yet been harnessed by researchers using decellularized heart scaffolds. Better success at using a whole organ from decellularization techniques has been found in pulmonary research. Scientists have been able to regenerate whole lungs in vitro from rat lungs using perfusion-decellularization. By seeding the matrix with fetal rat lung cells, a functioning lung was produced. The in vitro-produced lung was successfully implemented into a rat, which attests to the possibilities of translating an in vitro produced organ into a patient.
Other success for decellularization has been found in small intestinal submucosa (SIS), renal, hepatic, and pancreatic engineering. Because it is a thin material, the SIS matrix can be decellularized through immersing the tissue in chemical and enzymatic treatments. Renal tissue engineering is still developing, but cadaveric kidney matrices have been able to support development of potent fetal kidney cells. Pancreatic engineering is a testament to the molecular specificity of organs. Scientists have not yet been able to produce an entirely functioning pancreas, but they have had success in producing an organ that functions at specific segments. For example, diabetes in rats was shown to decrease by seeding a pancreatic matrix at specific sites. The future applications of decellularized tissue matrix is still being discovered and is considered one of the most hopeful areas in regenerative research. | 1 | Applied and Interdisciplinary Chemistry |
In early "straight-through" urea plants, reactant recovery (the first step in "recycling") was done by letting down the system pressure to atmospheric to let the carbamate decompose back to ammonia and carbon dioxide. Originally, because it was not economic to recompress the ammonia and carbon dioxide for recycle, the ammonia at least would be used for the manufacture of other products such as ammonium nitrate or ammonium sulfate, and the carbon dioxide was usually wasted. Later process schemes made recycling unused ammonia and carbon dioxide practical. This was accomplished by the "total recycle process", developed in the 1940s to 1960s and now called the "conventional recycle process". It proceeds by depressurizing the reaction solution in stages (first to 18–25 bar and then to 2–5 bar) and passing it at each stage through a steam-heated carbamate decomposer, then recombining the resulting carbon dioxide and ammonia in a falling-film carbamate condenser and pumping the carbamate solution back into the urea reaction vessel. | 0 | Theoretical and Fundamental Chemistry |
A type of electrophoretic mobility shift assay (AMSA), agarose gel electrophoresis is used to separate protein-bound amino acid complexes from free amino acids. Using a low voltage (~10 V/cm) to minimize the risk for heat damage, electricity is run across an agarose gel. When dissolved in a hot buffered solution (50 to 55 degrees Celsius), it produces a viscous solution, but when cooled, it solidifies as a gel. Serum proteins, hemoglobin, nucleic acids, polymerase chain reaction products, etc. are all separated using this method. Agarose's fixed sulfate groups can cause enhanced electroendosmosis, which lowers band resolution. Utilizing ultrapure agarose gel with little sulfate content can stop this. | 1 | Applied and Interdisciplinary Chemistry |
Microbial food cultures are considered as traditional food ingredients and are permitted in the production of foodstuffs all over the world under general food laws.
Commercially available microbial food cultures are sold as preparations, which are formulations, consisting of concentrates of one or more microbial species and/or strains including unavoidable media components carried over from the fermentation and components, which are necessary for their survival, storage, standardisation and to facilitate their application in the food production process.
Safety of microbial food cultures, depending on their characteristics and use, can be based on genus, species or strain levels. | 1 | Applied and Interdisciplinary Chemistry |
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