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In concert with the primary surface forces described above, there are several circumstantial effects in play. While the forces themselves each contribute to the magnitude of the adhesion between the surfaces, the following play a crucial role in the overall strength and reliability of an adhesive device. | 0 | Theoretical and Fundamental Chemistry |
Bacterial anaerobic corrosion typically impacts metallic substrates but may also occur in concrete. Corrosion of concrete mediums leads to considerable losses in industrial settings. When considering the corrosion of concrete there is significant documentation of structural degradation in concrete wastewater infrastructure where wastewater is collected or treated. Similarly, biofilms are important for bacterial anaerobic corrosion of metals in wastewater pipes.
For bacterial anaerobic corrosion there is general corrosion of substrates as well as another form of corrosion known as pitting. In both general or pitting corrosion, the breakdown process occurs in aqueous conditions. Bacteria tend to form biofilms as their primary means of corroding metals, with different bacteria dominating across different settings. In municipal wastewater, Desulfovibrio desulfuricans is the main contributor to corrosion. | 1 | Applied and Interdisciplinary Chemistry |
CGL (congenital generalized lipodystrophy) is a heterogeneous genetic disorder characterized by almost complete loss of adipose tissue (both metabolic and mechanical adipose depots) and an increase of ectopic fat storage in liver and muscle. Of the four CGL types, BSCL2 (Berardinelli-Seip Congenital lipodystrophy type 2), resulting from mutations in the BSCL2/seipin gene, exhibits the most severe lipodystrophic phenotype.
Furthermore, these patients could suffer dyslipidemia, hepatic steatosis, insulin resistance and hypertrophic cardiomyopathy due to a cell-autonomous defect in cardiomyocytes. | 1 | Applied and Interdisciplinary Chemistry |
Enzymes can catalyze up to several million reactions per second. Enzyme rates depend on solution conditions and substrate concentration. Like other enzymes POLR2 has a saturation curve and a maximum velocity (V). It has a K (substrate concentration required for one-half V) and a k (the number of substrate molecules handled by one active site per second). The specificity constant is given by k/K. The theoretical maximum for the specificity constant is the diffusion limit of about 10 to 10 (Ms), where every collision of the enzyme with its substrate results in catalysis. In yeast, mutation in the Trigger-Loop domain of the largest subunit can change the kinetics of the enzyme.
Bacterial RNA polymerase, a relative of RNA Polymerase II, switches between inactivated and activated states by translocating back and forth along the DNA. Concentrations of [NTP] = 10 μM GTP, 10 μM UTP, 5 μM ATP and 2.5 μM CTP, produce a mean elongation rate, turnover number, of ~1 bp (NTP) for bacterial RNAP, a relative of RNA polymerase II.
RNA polymerase II undergoes extensive co-transcriptional pausing during transcription elongation. This pausing is especially pronounced at nucleosomes, and arises in part through the polymerase entering a transcriptionally incompetent backtracked state. The duration of these pauses ranges from seconds to minutes or longer, and exit from long-lived pauses can be promoted by elongation factors such as TFIIS. In turn, the transcription rate influences whether the histones of transcribed nucleosomes are evicted from chromatin, or reinserted behind the transcribing polymerase. | 1 | Applied and Interdisciplinary Chemistry |
It was the second stop codon mutation to be discovered. Reminiscent of the usual yellow-orange-brown color associated with amber, this second stop codon was given the name of "ochre", an orange-reddish-brown mineral pigment.
Ochre mutant viruses had a property similar to amber mutants in that they recovered infectious ability within certain suppressor strains of bacteria. The set of ochre suppressors was distinct from amber suppressors, so ochre mutants were inferred to correspond to a different nucleotide triplet. Through a series of mutation experiments comparing these mutants with each other and other known amino acid codons, Sydney Brenner concluded that the amber and ochre mutations corresponded to the nucleotide triplets "UAG" and "UAA". | 1 | Applied and Interdisciplinary Chemistry |
Urea-containing creams are used as topical dermatological products to promote rehydration of the skin. Urea 40% is indicated for psoriasis, xerosis, onychomycosis, ichthyosis, eczema, keratosis, keratoderma, corns, and calluses. If covered by an occlusive dressing, 40% urea preparations may also be used for nonsurgical debridement of nails. Urea 40% "dissolves the intercellular matrix" of the nail plate. Only diseased or dystrophic nails are removed, as there is no effect on healthy portions of the nail. This drug (as carbamide peroxide) is also used as an earwax removal aid.
Urea has also been studied as a diuretic. It was first used by Dr. W. Friedrich in 1892. In a 2010 study of ICU patients, urea was used to treat euvolemic hyponatremia and was found safe, inexpensive, and simple.
Like saline, urea has been injected into the uterus to induce abortion, although this method is no longer in widespread use.
The blood urea nitrogen (BUN) test is a measure of the amount of nitrogen in the blood that comes from urea. It is used as a marker of renal function, though it is inferior to other markers such as creatinine because blood urea levels are influenced by other factors such as diet, dehydration, and liver function.
Urea has also been studied as an excipient in Drug-coated Balloon (DCB) coating formulation to enhance local drug delivery to stenotic blood vessels. Urea, when used as an excipient in small doses (~3 μg/mm) to coat DCB surface was found to form crystals that increase drug transfer without adverse toxic effects on vascular endothelial cells.
Urea labeled with carbon-14 or carbon-13 is used in the urea breath test, which is used to detect the presence of the bacterium Helicobacter pylori (H. pylori) in the stomach and duodenum of humans, associated with peptic ulcers. The test detects the characteristic enzyme urease, produced by H. pylori, by a reaction that produces ammonia from urea. This increases the pH (reduces the acidity) of the stomach environment around the bacteria. Similar bacteria species to H. pylori can be identified by the same test in animals such as apes, dogs, and cats (including big cats). | 0 | Theoretical and Fundamental Chemistry |
Yoon was born in Montreal, Quebec and grew up in Blacksburg, VA. As an undergraduate at Harvard University, he became fascinated by organic chemistry working in the laboratories of leading experts in contemporary asymmetric synthesis. Specifically, Yoon first experienced research in David A. Evans's lab studying stereocontrolled aldol reactions.
After earning his A.B. in chemistry from Harvard in 1996, he proceeded to earn his M.S. under the guidance of Erick M. Carreira, who introduced Yoon to synthesis of complex natural products through applied photochemistry. Yoon was then accepted as Dave MacMillan's first graduate student, initially at UC Berkeley and later at Caltech, where he earned his Ph.D. investigating methods to control the stereochemistry of pericyclic reactions. He returned to Harvard in 2002 as a postdoc to research the use of hydrogen bonding urea catalysts in asymmetric synthesis in the laboratory of Eric Jacobsen. | 0 | Theoretical and Fundamental Chemistry |
Sometimes, special circuits are built for the purpose of sensing and controlling the temperature or voltage status. Devices such as thermistors, voltage-dependent resistors, thermostats and sensors such as infrared thermometers are used to modify the current upon different conditions such as circuit-temperature and input voltage. | 0 | Theoretical and Fundamental Chemistry |
* Georges Friedel (1904) "Étude sur les groupements cristallins", Extrait du Bulletin de la Société de lIndustrie minérale', Quatrième série, Tomes III e IV. Saint-Étienne, Société de l’Imprimerie Théolier J. Thomas et C., 485 pp.
* Georges Friedel (1920) "Contribution à létude géométrique des macles", Bulletin de la Société française de Minéralogie' 43: 246-295.
* Georges Friedel (1926) Leçons de Cristallographie, Berger-Levrault, Nancy, Paris, Strasbourg XIX+602 pp.
* Georges Friedel (1933) "Sur un nouveau type de macles", Bulletin de la Société française de Minéralogie 56: 262-274.
* J.D.H. Donnay (1940) "Width of Albite-Twinning Lamellae", Am. Mineral., 25: 578-586. | 0 | Theoretical and Fundamental Chemistry |
In stereochemistry, mutarotation is the change in optical rotation of a chiral material in a solution due to a change in proportion of the two constituent anomers (i.e. the interconversion of their respective stereocenters) until equilibrium is reached. Cyclic sugars show mutarotation as α and β anomeric forms interconvert.
The optical rotation of the solution depends on the optical rotation of each anomer and their ratio in the solution.
Mutarotation was discovered by French chemist Augustin-Pierre Dubrunfaut in 1844, when he noticed that the specific rotation of aqueous sugar solution changes with time. | 0 | Theoretical and Fundamental Chemistry |
Metal carbonyl hydrides are complexes of transition metals with carbon monoxide and hydride as ligands. These complexes are useful in organic synthesis as catalysts in homogeneous catalysis, such as hydroformylation. | 0 | Theoretical and Fundamental Chemistry |
Electrochemical impedance spectroscopy is used in a wide range of applications.
In the paint and coatings industry, it is a useful tool to investigate the quality of coatings and to detect the presence of corrosion.
It is used in many biosensor systems as a label-free technique to measure bacterial concentration and to detect dangerous pathogens such as Escherichia coli O157:H7 and Salmonella, and yeast cells.
Electrochemical impedance spectroscopy is also used to analyze and characterize different food products. Some examples are the assessment of food–package interactions, the analysis of milk composition, the characterization and the determination of the freezing end-point of ice-cream mixes, the measure of meat ageing, the investigation of ripeness and quality in fruits and the determination of free acidity in olive oil.
In the field of human health monitoring is better known as bioelectrical impedance analysis (BIA) and is used to estimate body composition as well as different parameters such as total body water and free fat mass.
Electrochemical impedance spectroscopy can be used to obtain the frequency response of batteries and electrocatalytic systems at relatively high temperatures.
Biomedical sensors working in the microwave range relies on dielectric spectroscopy to detect changes in the dielectric properties over a frequency range, such as non-invasive continuous blood glucose monitoring. The IFAC database can be used as a resource to get the dielectric properties for human body tissues.
For heterogenous mixtures like suspensions impedance spectroscopy can be used to monitor the particle sedimentation process. | 0 | Theoretical and Fundamental Chemistry |
In some countries, such as the EU, smokestack measurements from individual power plants must be published. Meanwhile, in some countries, such as Turkey, they are only reported to the government, not the public. However, since the late 2010s satellite measurements of some pollutants have been available. | 1 | Applied and Interdisciplinary Chemistry |
Also, alkaline lysis is sometimes used to extract plant genetic material. The plant cells are subjected to a strongly alkaline solution containing a detergent (usually a zwitterionic or nonionic detergent such as Tween 20), and the mixture is incubated at high temperature. This method is not used as often due to the sodium hydroxide's tendency to damage genetic material, reducing DNA fragment size. | 1 | Applied and Interdisciplinary Chemistry |
Yuri Berlin received his master's degree in Physics from the Moscow Engineering Physics Institute in 1968, studying luminescence of aromatic molecules dissolved in organic liquids. During the period 1968-1974, Berlin worked as a research fellow at the Institute of Chemical Physics, the USSR Academy of Science, and in 1974 completed his PhD studies at the Moscow Institute for Physics and Technology under the supervision of Victor Talrose. His thesis was focused on the development of theory for the ion-pair mechanism of radiolysis of non-polar liquids. | 0 | Theoretical and Fundamental Chemistry |
This clock reaction uses sodium, potassium or ammonium persulfate to oxidize iodide ions to iodine. Sodium thiosulfate is used to reduce iodine back to iodide before the iodine can complex with the starch to form the characteristic blue-black color.
Iodine is generated:
And is then removed:
Once all the thiosulfate is consumed the iodine may form a complex with the starch. Potassium persulfate is less soluble (cfr. Salters website) while ammonium persulfate has a higher solubility and is used instead in the reaction described in examples from Oxford University. | 0 | Theoretical and Fundamental Chemistry |
Propanephosphonic acid anhydride (PPAA, T3P) is an anhydride of propanephosphonic acid. Its structure is a cyclic trimer, with a phosphorus–oxygen core and propyl groups and additional oxygens attached. The chemical is a useful reagent for peptide synthesis reactions, where it activates the carboxylic acid partner for subsequent reaction with amines. It is commercially available as 50 % solution in DMF or ethyl acetate as a slightly yellow mixture. | 0 | Theoretical and Fundamental Chemistry |
Pelletizing is done in a pellet mill, where feed is normally conditioned and thermal-treated in the fitted conditioners of a pellet mill. The feed is then pushed through the holes and exit the pellet mill as pelleted feed. | 1 | Applied and Interdisciplinary Chemistry |
Negishi died in Indianapolis, Indiana, on June 6, 2021. He was 85 years old. No funeral services took place in the United States, but his family planned to lay him to rest in Japan in 2022. | 0 | Theoretical and Fundamental Chemistry |
Avogadros law (sometimes referred to as Avogadros hypothesis or Avogadros principle) or Avogadro-Ampères hypothesis is an experimental gas law relating the volume of a gas to the amount of substance of gas present. The law is a specific case of the ideal gas law. A modern statement is:
The law is named after Amedeo Avogadro who, in 1812, hypothesized that two given samples of an ideal gas, of the same volume and at the same temperature and pressure, contain the same number of molecules. As an example, equal volumes of gaseous hydrogen and nitrogen contain the same number of molecules when they are at the same temperature and pressure, and observe ideal gas behavior. In practice, real gases show small deviations from the ideal behavior and the law holds only approximately, but is still a useful approximation for scientists. | 0 | Theoretical and Fundamental Chemistry |
The flux of the entire pathway is regulated by the rate-determining steps. These are the slowest steps in a network of reactions. The rate-limiting step occurs near the beginning of the pathway and is regulated by feedback inhibition, which ultimately controls the overall rate of the pathway. The metabolic pathway in the cell is regulated by covalent or non-covalent modifications. A covalent modification involves an addition or removal of a chemical bond, whereas a non-covalent modification (also known as allosteric regulation) is the binding of the regulator to the enzyme via hydrogen bonds, electrostatic interactions, and Van Der Waals forces.
The rate of turnover in a metabolic pathway, also known as the metabolic flux, is regulated based on the stoichiometric reaction model, the utilization rate of metabolites, and the translocation pace of molecules across the lipid bilayer. The regulation methods are based on experiments involving 13C-labeling, which is then analyzed by Nuclear Magnetic Resonance (NMR) or gas chromatography-mass spectrometry (GC-MS)-derived mass compositions. The aforementioned techniques synthesize a statistical interpretation of mass distribution in proteinogenic amino acids to the catalytic activities of enzymes in a cell. | 1 | Applied and Interdisciplinary Chemistry |
In Complex I (NADH ubiquinone oxidoreductase, Type I NADH dehydrogenase, or mitochondrial complex I; ), two electrons are removed from NADH and transferred to a lipid-soluble carrier, ubiquinone (Q). The reduced product, ubiquinol (QH), freely diffuses within the membrane, and Complex I translocates four protons (H) across the membrane, thus producing a proton gradient. Complex I is one of the main sites at which premature electron leakage to oxygen occurs, thus being one of the main sites of production of superoxide.
The pathway of electrons is as follows:
NADH is oxidized to NAD, by reducing flavin mononucleotide to FMNH in one two-electron step. FMNH is then oxidized in two one-electron steps, through a semiquinone intermediate. Each electron thus transfers from the FMNH to an Fe–S cluster, from the Fe-S cluster to ubiquinone (Q). Transfer of the first electron results in the free-radical (semiquinone) form of Q, and transfer of the second electron reduces the semiquinone form to the ubiquinol form, QH. During this process, four protons are translocated from the mitochondrial matrix to the intermembrane space. As the electrons move through the complex an electron current is produced along the 180 Angstrom width of the complex within the membrane. This current powers the active transport of four protons to the intermembrane space per two electrons from NADH. | 1 | Applied and Interdisciplinary Chemistry |
Potential application as long-lasting dyes is based on the enhanced stability of the inner portion of the dumbbell-shaped molecule. Studies with cyclodextrin-protected rotaxane azo dyes established this characteristic. More reactive squaraine dyes have also been shown to have enhanced stability by preventing nucleophilic attack of the inner squaraine moiety. The enhanced stability of rotaxane dyes is attributed to the insulating effect of the macrocycle, which is able to block interactions with other molecules. | 0 | Theoretical and Fundamental Chemistry |
Edward Mills Purcell (August 30, 1912 – March 7, 1997) was an American physicist who shared the 1952 Nobel Prize for Physics for his independent discovery (published 1946) of nuclear magnetic resonance in liquids and in solids. Nuclear magnetic resonance (NMR) has become widely used to study the molecular structure of pure materials and the composition of mixtures. Friends and colleagues knew him as Ed Purcell. | 0 | Theoretical and Fundamental Chemistry |
Brown was born in 1934 in The Bronx, New York. According to Brown, when she was young, she contracted tuberculosis, and was treated by Arthur Logan. Logan was a young African-American in his intern year of residency, and lived in Browns building. Browns later inspiration to study science came from asking Logan how one could become a doctor. He replied, "Oh, you study science". Brown excelled in particular in chemistry, scoring 98 out of 100 on the New York State Regents chemistry exam. She attended New Dorp High School on Staten Island, and graduated in 1952. Brown earned her bachelors degree in chemistry at Hunter College in 1956, one of two African Americans in the inaugural class of Hunters chemistry program. In 1958, she became the first African American woman to achieve a masters degree from the University of Minnesota in organic chemistry. Her masters thesis was entitled, “Study of Dye and Ylide Formation in Salts of 9-(P-dimethylaminophenyl) Fluorene.” | 1 | Applied and Interdisciplinary Chemistry |
Nikolai Timofeevich Beliaev or Nicholas Timothy Belaiew (26 June 1878 – 5 November 1955) was a Russian metallurgist. He was famous for his studies on Damascus steel and the idea of crystallization in metals and the production of Widmanstatten structures. He also wrote on the history of steel making.
Beliaev was born in St. Petersburg to General T. M. Beliaev and Maria Nikolayevna Septjurina. He was educated at Mikhailovskaya Artilleriiskaya Academy and was trained under Dmitry Konstantinovich Chernov and Henry Le Chatelier. He became a professor of metallurgy in 1909. During World War I he was wounded and he was sent to England in 1915. He received a Bessemer Gold Medal in 1937 from the British Institute of Steel and Iron in London. A major contribution was on the studies of crystal structure in steels both man-made and of meteoric origin and examined their mechanical properties. He also took an interest in Icelandic research. | 1 | Applied and Interdisciplinary Chemistry |
Concentration polarization is a term used in the scientific fields of electrochemistry and membrane science. | 0 | Theoretical and Fundamental Chemistry |
Gray molasses is a method of sub-Doppler laser cooling of atoms. It employs principles from Sisyphus cooling in conjunction with a so-called "dark" state whose transition to the excited state is not addressed by the resonant lasers. Ultracold atomic physics experiments on atomic species with poorly-resolved hyperfine structure, like isotopes of lithium
and potassium,
often utilize gray molasses instead of Sisyphus cooling as a secondary cooling stage after the ubiquitous magneto-optical trap (MOT) to achieve temperatures below the Doppler limit. Unlike a MOT, which combines a molasses force with a confining force, a gray molasses can only slow but not trap atoms; hence, its efficacy as a cooling mechanism lasts only milliseconds before further cooling and trapping stages must be employed. | 0 | Theoretical and Fundamental Chemistry |
Maintaining the water seal is critical to trap operation; traps might dry out, and poor venting can suction or blow water out of the traps. This is usually avoided by venting the drain pipes downstream of the trap; by being vented to the atmosphere outside the building, the drain lines never operate at a pressure much higher or lower than atmospheric pressure. In the United States, plumbing codes usually provide strict limitations on how far a trap may be located from the nearest vent stack.
When a vent cannot be provided, an air admittance valve may be used instead. These devices avoid negative pressure in the drain pipe by venting room air into the drain pipe (behind the trap). A "Chicago Loop" is another alternative.
When a trap is installed on a fixture that is not routinely used—such as a floor drain—the eventual evaporation of the water in the trap must be considered. In these cases, a trap primer may be installed; these are devices that automatically recharge traps with water to maintain their water seals. | 1 | Applied and Interdisciplinary Chemistry |
Phytoreoviruses are non-turreted reoviruses that are major agricultural pathogens, particularly in Asia. One member of this family, Rice Dwarf Virus (RDV), has been extensively studied by electron cryomicroscopy and x-ray crystallography. From these analyses, atomic models of the capsid proteins and a plausible model for capsid assembly have been derived. While the structural proteins of RDV share no sequence similarity to other proteins, their folds and the overall capsid structure are similar to those of other Reoviridae. | 1 | Applied and Interdisciplinary Chemistry |
The Kapitza number (Ka) is a dimensionless number named after the prominent Russian physicist Pyotr Kapitsa (Peter Kapitza). He provided the first extensive study of the ways in which a thin film of liquid flows down inclined surfaces. Expressed as the ratio of surface tension forces to inertial forces, the Kapitza number acts as an indicator of the hydrodynamic wave regime in falling liquid films. Liquid film behavior represents a subset of the more general class of free boundary problems. and is important in a wide range of engineering and technological applications such as evaporators, heat exchangers, absorbers, microreactors, small-scale electronics/microprocessor cooling schemes, air conditioning and gas turbine blade cooling.
After World War II Kapitza was removed from all his positions, including director of his Institute for Physical Problems, for refusing to work on nuclear weapons. He was at his country house and devised experiments to work on there, including his experiments on falling films of liquid.
Unlike most dimensionless numbers used in the study of fluid mechanics, the Kapitza number represents a material property, as it is formed by combining powers of the surface tension, density, gravitational acceleration and kinematic viscosity.
where σ is the surface tension (SI units: N/m), g is gravitational acceleration (m/s), ρ is density (kg/m), β is inclination angle (rad), and ν is kinematic viscosity (m/s). | 1 | Applied and Interdisciplinary Chemistry |
Two single MYB transcription factors, CCA1 and LHY, activate expression of PRR7 and PRR9. In turn, PRR7 and PRR9 repress CCA1 and LHY through the binding of their promoters. This interaction forms the morning loop of the repressilator of the biological clock in A. thaliana. Chromatin immunoprecipitation demonstrates that LUX binds to the PRR9 promoter to repress it. Additionally, ELF3 has been shown to activate PRR9 and repress CCA1 and LHY. PRR9 is also activated by alternative RNA splicing. When PRMT5 (a methylation factor) is prevented from methylating intron 2 of PRR9, a frameshift resulting in premature truncation occurs.
PRR7 and PRR9 also play a role in the entrainment of A. thaliana to a temperature cycle. Double-mutant plants with inactivated PRR7 and PRR9 exhibit extreme period lengthening at high temperatures but show no change in period at low temperatures. However, the inactivation of CCA1 and LHY in the PRR7/PRR9 loss-of-function mutants shows no change in period at high temperatures—this suggests that PRR7 and PRR9 are acting by overcompensation. | 1 | Applied and Interdisciplinary Chemistry |
Temporary hardness is caused by the presence of dissolved bicarbonate minerals (calcium bicarbonate and magnesium bicarbonate). When dissolved, these types of minerals yield calcium and magnesium cations (Ca, Mg) and carbonate and bicarbonate anions ( and ). The presence of the metal cations makes the water hard. However, unlike the permanent hardness caused by sulfate and chloride compounds, this "temporary" hardness can be reduced either by boiling the water or by the addition of lime (calcium hydroxide) through the process of lime softening. Boiling promotes the formation of carbonate from the bicarbonate and precipitates calcium carbonate out of solution, leaving water that is softer upon cooling. | 0 | Theoretical and Fundamental Chemistry |
Hemoglobin concentration measurement is among the most commonly performed blood tests, usually as part of a complete blood count. For example, it is typically tested before or after blood donation. Results are reported in g/L, g/dL or mol/L. 1 g/dL equals about 0.6206 mmol/L, although the latter units are not used as often due to uncertainty regarding the polymeric state of the molecule. This conversion factor, using the single globin unit molecular weight of 16,000 Da, is more common for hemoglobin concentration in blood. For MCHC (mean corpuscular hemoglobin concentration) the conversion factor 0.155, which uses the tetramer weight of 64,500 Da, is more common. Normal levels are:
* Men: 13.8 to 18.0 g/dL (138 to 180 g/L, or 8.56 to 11.17 mmol/L)
* Women: 12.1 to 15.1 g/dL (121 to 151 g/L, or 7.51 to 9.37 mmol/L)
* Children: 11 to 16 g/dL (110 to 160 g/L, or 6.83 to 9.93 mmol/L)
* Pregnant women: 11 to 14 g/dL (110 to 140 g/L, or 6.83 to 8.69 mmol/L) (9.5 to 15 usual value during pregnancy)
Normal values of hemoglobin in the 1st and 3rd trimesters of pregnant women must be at least 11 g/dL and at least 10.5 g/dL during the 2nd trimester.
Dehydration or hyperhydration can greatly influence measured hemoglobin levels. Albumin can indicate hydration status.
If the concentration is below normal, this is called anemia. Anemias are classified by the size of red blood cells, the cells that contain hemoglobin in vertebrates. The anemia is called "microcytic" if red cells are small, "macrocytic" if they are large, and "normocytic" otherwise.
Hematocrit, the proportion of blood volume occupied by red blood cells, is typically about three times the hemoglobin concentration measured in g/dL. For example, if the hemoglobin is measured at 17 g/dL, that compares with a hematocrit of 51%.
Laboratory hemoglobin test methods require a blood sample (arterial, venous, or capillary) and analysis on hematology analyzer and CO-oximeter. Additionally, a new noninvasive hemoglobin (SpHb) test method called Pulse CO-Oximetry is also available with comparable accuracy to invasive methods.
Concentrations of oxy- and deoxyhemoglobin can be measured continuously, regionally and noninvasively using NIRS. NIRS can be used both on the head and on muscles. This technique is often used for research in e.g. elite sports training, ergonomics, rehabilitation, patient monitoring, neonatal research, functional brain monitoring, brain–computer interface, urology (bladder contraction), neurology (Neurovascular coupling) and more.
Hemoglobin mass can be measured in humans using the non-radioactive, carbon monoxide (CO) rebreathing technique that has been used for more than 100 years. With this technique, a small volume of pure CO gas is inhaled and rebreathed for a few minutes. During rebreathing, CO binds to hemoglobin present in red blood cells. Based on the increase in blood CO after the rebreathing period, the hemoglobin mass can be determined through the dilution principle. Although CO gas in large volumes is toxic to humans, the volume of CO used to assess blood volumes corresponds to what would be inhaled when smoking a cigarette. While researchers typically use custom-made rebreathing circuits, the Detalo Performance from Detalo Health has automated the procedure and made the measurement available to a larger group of users.
Long-term control of blood sugar concentration can be measured by the concentration of Hb A. Measuring it directly would require many samples because blood sugar levels vary widely through the day. Hb A is the product of the irreversible reaction of hemoglobin A with glucose. A higher glucose concentration results in more Hb A. Because the reaction is slow, the Hb A proportion represents glucose level in blood averaged over the half-life of red blood cells, is typically ~120 days. An Hb A proportion of 6.0% or less show good long-term glucose control, while values above 7.0% are elevated. This test is especially useful for diabetics.
The functional magnetic resonance imaging (fMRI) machine uses the signal from deoxyhemoglobin, which is sensitive to magnetic fields since it is paramagnetic. Combined measurement with NIRS shows good correlation with both the oxy- and deoxyhemoglobin signal compared to the BOLD signal. | 0 | Theoretical and Fundamental Chemistry |
*Reaction stoichiometry: In batch production this is defined by the concentration of chemical reagents and their volumetric ratio. In flow this is defined by the concentration of reagents and the ratio of their flow rate.
*Residence time: In batch production this is determined by how long a vessel is held at a given temperature. In flow the volumetric residence time is given by the ratio of the volume of the reactor and the overall flow rate, as most often, plug flow reactors are used. | 1 | Applied and Interdisciplinary Chemistry |
Aging-related preventive interventions are not possible without personal aging speed measurement. The most up to date and complex way to measure aging rate is by using varying biomarkers of human aging is based on the utilization of deep neural networks which may be trained on any type of omics biological data to predict the subject's age. Aging has been shown to be a strong driver of transcriptome changes. Aging clocks based on transcriptomes have suffered from considerable variation in the data and relatively low accuracy. However an approach that uses temporal scaling and binarization of transcriptomes to define a gene set that predicts biological age with an accuracy allowed to reach an assessment close to the theoretical limit. | 1 | Applied and Interdisciplinary Chemistry |
The chemical shift index or CSI is a widely employed technique in protein nuclear magnetic resonance spectroscopy that can be used to display and identify the location (i.e. start and end) as well as the type of protein secondary structure (beta strands, helices and random coil regions) found in proteins using only backbone chemical shift data The technique was invented by David S. Wishart in 1992 for analyzing Hα chemical shifts and then later extended by him in 1994 to incorporate C backbone shifts. The original CSI method makes use of the fact that Hα chemical shifts of amino acid residues in helices tends to be shifted upfield (i.e. towards the right side of an NMR spectrum) relative to their random coil values and downfield (i.e. towards the left side of an NMR spectrum) in beta strands. Similar kinds of upfield and downfield trends are also detectable in backbone C chemical shifts. | 0 | Theoretical and Fundamental Chemistry |
Hydrocyanation is important due to the versatility of alkyl nitriles (RCN), which are important intermediates for the syntheses of amides, amines, carboxylic acids and esters.
Naproxen, an anti-inflammatory drug, is prepared via an asymmetric hydrocyanation of a vinylnaphthalene utilizing a phosphinite () ligand, L . The enantioselectivity of this reaction is important because only the S enantiomer is medicinally desirable, whereas the R enantiomer produces harmful health effects. This reaction can produce the S enantiomer with >90% stereoselectivity. Upon recrystallization of the crude product, the optically pure nitrile can be obtained. | 0 | Theoretical and Fundamental Chemistry |
Dry granulation processes create granules by light compaction of the powder blend under low pressures. The compacts so-formed are broken up gently to produce granules (agglomerates). This process is often used when the product to be granulated is sensitive to moisture and heat. Dry granulation can be conducted on a tablet press using slugging tooling or on a roll press called a roller compactor. Dry granulation equipment offers a wide range of pressures to attain proper densification and granule formation. Dry granulation is simpler than wet granulation, therefore the cost is reduced. However, dry granulation often produces a higher percentage of fine granules, which can compromise the quality or create yield problems for the tablet. Dry granulation requires drugs or excipients with cohesive properties, and a dry binder may need to be added to the formulation to facilitate the formation of granules. | 1 | Applied and Interdisciplinary Chemistry |
Histamine has important roles in human physiology as both a hormone and a neurotransmitter. As a hormone, it is involved in the inflammatory response and itching. It regulates physiological functions in the gut and acts on the brain, spinal cord, and uterus. As a neurotransmitter, histamine promotes arousal and regulates appetite and the sleep-wake cycle. It also affects vasodilation, fluid production in tissues like the nose and eyes, gastric acid secretion, sexual function, and immune responses.
HNMT is the only enzyme in the human body responsible for metabolizing histamine within the CNS, playing a crucial role in brain function.
HNMT plays a crucial role in maintaining the proper balance of histamine in the human body. HNMT is responsible for the breakdown and metabolism of histamine, converting it into an inactive metabolite, N-methylhistamine, which inhibits HNMT gene expression in a negative feedback loop. By metabolizing histamine, HNMT helps prevent excessive levels of histamine from accumulating in various tissues and organs. This enzymatic activity ensures that histamine remains at appropriate levels to carry out its physiological functions without causing unwanted effects or triggering allergic reactions. In the central nervous system, HNMT plays an essential role in degrading histamine, where it acts as a neurotransmitter, since HNMT is the only enzyme in the body that can metabolize histamine in the CNS, ending its neurotransmitter activity.
HNMT also plays a role in the airway response to harmful particles, which is the body's physiological reaction to immune allergens, bacteria, or viruses in the respiratory system. Histamine is stored in granules in mast cells, basophils, and in the synaptic vesicles of histaminergic neurons of the airways. When exposed to immune allergens or harmful particles, histamine is released from these storage granules and quickly diffuses into the surrounding tissues. However, the released histamine needs to be rapidly deactivated for proper regulation, which is a function of HNMT. | 1 | Applied and Interdisciplinary Chemistry |
Clarice Phelps was raised in the American state of Tennessee. Her interest in chemistry began during her childhood when she was given a microscope and encyclopedia-based science kit by her mother. Her interest was further nurtured by her secondary school science teachers. She is an alumna of the Tennessee Aquatic Project and Development Group, a nonprofit organization for at-risk youth. Phelps completed a Bachelor of Science degree in chemistry from Tennessee State University in 2003.
From 2016 to 2020, Phelps earned a M.S. in mechanical engineering through the nuclear and radiochemistry program at the University of Texas at Austin. , Phelps is a PhD student in the nuclear engineering program at University of Tennessee. | 0 | Theoretical and Fundamental Chemistry |
Using antibody microarray in different medical diagnostic areas has attracted researchers attention. Digital bioassay is an example of such research domains. In this technology, an array of microwells on a glass/polymer chip are seeded with magnetic beads (coated with fluorescent tagged antibodies), subjected to targeted antigens and then characterised by a microscope through counting fluorescing wells. A cost-effective fabrication platform (using OSTE polymers) for such microwell arrays has been recently demonstrated and the bio-assay model system has been successfully characterised. Furthermore, immunoassays on thiol-ene "synthetic paper" micropillar scaffolds have shown to generate a superior fluorescence signal. | 1 | Applied and Interdisciplinary Chemistry |
Rain is generally mildly acidic, with a pH between 5.2 and 5.8 if not having any acid stronger than carbon dioxide. If high amounts of nitrogen and sulfur oxides are present in the air, they too will dissolve into the cloud and raindrops, producing acid rain. | 1 | Applied and Interdisciplinary Chemistry |
Thermocouples are suitable for measuring over a large temperature range, from −270 up to 3000 °C (for a short time, in inert atmosphere). Applications include temperature measurement for kilns, gas turbine exhaust, diesel engines, other industrial processes and fog machines. They are less suitable for applications where smaller temperature differences need to be measured with high accuracy, for example the range 0–100 °C with 0.1 °C accuracy. For such applications thermistors, silicon bandgap temperature sensors and resistance thermometers are more suitable. | 1 | Applied and Interdisciplinary Chemistry |
The following advantages have been reported for the BBOC:
* very high oxygen efficiency – the injection of oxygen directly into the reaction zone within the furnace results in much greater oxygen efficiency (close to 100%) than with reverberatory furnaces (8% for the Niihama furnace) or top-blown rotary converters (about 30%)
* reduced off-gas volume – the use of industrial oxygen and the high oxygen efficiency of the process means that excess air is not required to achieve the results. This reduces the off-gas volume and thus the cost of the off-gas train and handling equipment. Rand Refinery reported that the off-gas volume of the BBOC was about 75% of that of a TBRC with a special lance conversion and only 19% of that of top-submerged lance smelting. Niihama refinery reported that its BBOC had 15% of the off-gas volume of its reverberatory furnace while producing 1.8 times the product
* higher reaction rates – by injecting the oxygen directly into the reaction zone, the reaction rates are much higher than in reverberatory furnaces where the oxygen has first to penetrate the slag layer. BRM reported a reaction rate per unit of furnace volume of 10–20 times that of the reverberatory furnace
* lower refractory wear – Rand Refinery reported that the refractory linings of its TBRC furnaces needed replacing after approximately two weeks, while the linings of its BBOC furnace lasted about 14 weeks
* lower precious metal inventories – a consequence of the higher reaction rates is that smaller furnace volumes are required and there are smaller cycle times. This results in lower precious metal inventories. In lead slimes bullion processing, the silver inventory was reduced from 4.5 t to 1.25 t after replacing a reverberatory furnace with a BBOC and at BRM the silver inventory fell from 11.5 t to 3.1 t with the introduction of the BBOC furnace
* better energy efficiency – a supplementary burner is needed only during heating the charge and doré casting operations. During cupellation, the oxidation reactions provide sufficient heat to maintain temperature. There was a 92% reduction in fuel consumption per tonne of doré treated reported for the BBOC at the Niihama refinery
* better product quality – BHAS reported that lead and copper levels in silver produced from the BBOC of 0.01% and 0.1% respectively were possible when the furnace was operating under design conditions, compared to 0.04% and 0.2% for the old reverberatory furnace, and 0.8% and 0.4% for the Sirosmelt furnace. Rand Refinery reported that a doré bullion of 99.2% was achievable. BRM reported that its doré is 99.7% silver
* higher recoveries of precious metals – due to changes in the way the BBOC is operated compare to reverberatory furnaces, notably in being able to use deeper layers of slag, there is an increase in the recovery of precious metals compared to the reverberatory furnaces. Replacement of reverberatory furnaces with BBOC furnaces saw the direct silver recovery increase from 92.5% to 97.5% at BRM and from 70% to over 95% at Niihama
* simple vessel design – the BBOC has a relatively simple vessel design, without the complex moving parts of TBRCs
* good process control – the high oxygen utilization allows good process control, particularly when combined with an oxygen sensor in the off-gas system
* lower labor requirements – the BBOC has a lower labor requirement than reverberatory furnaces, top-submerged lance furnaces and TBRCs
* lower operating costs – lower labor requirements, lower fuel requirements and longer refractory life contributed to a 28.3% reduction in overall operating costs when the BBOC was installed at the Rand Refinery
* lower capital cost – the BBOC is a simpler furnace than TBRC or top-submerged lance furnaces. Rand Refinery reported a capital cost comparison indicating that its BBOC option was 67% of the cost of a top-submerged lance option. | 1 | Applied and Interdisciplinary Chemistry |
The species used in Germany to measure saprobic water quality tend to group around s = 2, while other countries like Austria and the Czech Republic use a more diverse list of organisms. | 1 | Applied and Interdisciplinary Chemistry |
Small molecule drugs, compounds typically <1 kD in mass, comprise a large portion of the therapeutic market. These drugs usually operate by agonizing or antagonizing the active site on a disease-linked protein of interest, though allosteric regulation is possible. With an estimated 93% of the human proteome lacking druggable binding sites, methods have been developed to modulate protein activity through binding of any available site rather than only the active site. These drugs contain a target protein binding warhead in addition to a linker-separated active domain. This domain may recruit a second protein to the proximity, induce protease-mediated degradation, or recruit a kinase for directed phosphorylation, among other functions. These drugs expand both the mechanism of action for small molecule therapeutics and the pool of potential protein targets. | 1 | Applied and Interdisciplinary Chemistry |
Mikhail Tsvet invented chromatography in 1900 during his research on plant pigments. He used liquid-adsorption column chromatography with calcium carbonate as adsorbent and petrol ether/ethanol mixtures as eluent to separate chlorophylls and carotenoids. The method was described on 30 December 1901 at the XI Congress of Naturalists and Physicians (XI съезд естествоиспытателей и врачей) in St. Petersburg. The first printed description was in 1905, in the Proceedings of the Warsaw Society of Naturalists, biology section. He first used the term "chromatography" in print in 1906 in his two papers about chlorophyll in the German botanical journal, Berichte der Deutschen botanischen Gesellschaft. In 1907 he demonstrated his chromatograph for the German Botanical Society.
For several reasons, Tsvets work was long ignored: the violent political upheaval in Russia at the beginning of the 20th century, the fact that Tsvet originally published only in Russian (making his results largely inaccessible to western scientists), and an article denying Tsvets findings. Richard Willstätter and Arthur Stoll tried to repeat Tsvets experiments, but because they used an overly aggressive adsorbent (destroying the chlorophyll), were not able to do so. They published their results and Tsvets chromatography method fell into obscurity. It was revived 10 years after his death thanks to Austrian biochemist Richard Kuhn and his student, German scientist Edgar Lederer as well as the work of A. J. Martin and R. L. Synge. | 0 | Theoretical and Fundamental Chemistry |
A semi sacrificial coating known as a safety shield acts as a penetrating sealer on the wall or surface protecting the surface pores. If the surface is vandalized the coating can be partially removed using a combination of graffiti removal solvent and high-pressure washer. The anti graffiti safety shield is generally reapplied every second attack. While it is possible to use only pressure to remove coating, this will cause additional surface erosion. | 0 | Theoretical and Fundamental Chemistry |
The 3′-UTR often contains microRNA response elements (MREs), which are sequences to which miRNAs bind. miRNAs are short, non-coding RNA molecules capable of binding to mRNA transcripts and regulating their expression. One miRNA mechanism involves partial base pairing of the 5' seed sequence of an miRNA to an MRE within the 3′-UTR of an mRNA; this binding then causes translational repression. | 1 | Applied and Interdisciplinary Chemistry |
Sala married three times; first to Maria Ennan, who gave birth to a sole child, daughter Maria, who on 5 January 1608 was baptized in Winterthur. She later married the Oldenburg physician Anton Günther Billich, who was friends with Sala. However they divorced in 1634, Sala's granddaughter Marie Sophie was never recognized by Billich.
Sala married a second time in the German Reformed Community in Hamburg on the 15 April 1621, to Cornelia de L'Hommels.
His third marriage was with Katharina von Brockdorff (born 1608) in Lübeck in 1628. Their descendants were confirmed in the Reich through the nobility in which the Sala family had been established in Italy. Sala's great-grandson Gerd Carl Graf von Sala even achieved entry to the imperial count in 1751. However, the German Sala branch died out with his son Hans Christian in 1806.
Sala died on the 2nd. October 1637 at the age of 61 in Bützow, after having cut himself three days earlier. He was buried on 20 October in the Cathedral of St. Maria, St. Johannes Evangelista and St. Cäcilia. | 1 | Applied and Interdisciplinary Chemistry |
Sameh Fahmi (born 14 August 1949) is an Egyptian engineer and politician who served as oil minister of Egypt for 12 years from 1999 to 2011. | 1 | Applied and Interdisciplinary Chemistry |
* Royal Society of Western Australia, University Medal for outstanding student in natural and earth sciences (2003)
* Society of Environmental Toxicology and Chemistry, Best Platform Presentation by a student (2008)
* FNR ATTRACT Fellowship for the development of new methods to identify unknown chemicals (2018)
*The Analytical Scientist, Top 40 under 40 Power List (2018) | 0 | Theoretical and Fundamental Chemistry |
Deuterium HCL or even hydrogen HCL and deuterium discharge lamps are used in LS AAS for background correction purposes. The radiation intensity emitted by these lamps decreases significantly with increasing wavelength, so that they can be only used in the wavelength range between 190 and about 320 nm. | 0 | Theoretical and Fundamental Chemistry |
An emerging body of work highlights the application potential for clumped isotopes to reconstruct temperature and fluid properties in hydrothermal ore deposits. In mineral exploration, delineation of the heat footprint around an ore body provides critical insight into the processes that drive transport and deposition of metals. During proof of concept studies, clumped isotopes were used to provide accurate temperature reconstructions in epithermal, sediment hosted, and Mississippi Valley Type (MVT) deposits. These case studies are supported by measurement of carbonates in active geothermal settings. | 0 | Theoretical and Fundamental Chemistry |
K. C. Nicolaou and coworkers at Scripps Research Institute generated the chiral hydrazone through Enders hydrazone alkylation reaction with high stereoselectivity (de' > 95%). The subsequent ozonolysis and Wittig reaction led to the side chain fragment of zaragozic acid A, which is a potent medicine for coronary heart disease. | 0 | Theoretical and Fundamental Chemistry |
Rotating their carbon–carbon bonds, the molecules ethane and propane have three local energy minima. They are structurally and energetically equivalent, and are called the staggered conformers. For each molecule, the three substituents emanating from each carbon–carbon bond are staggered, with each H–C–C–H dihedral angle (and H–C–C–CH dihedral angle in the case of propane) equal to 60° (or approximately equal to 60° in the case of propane). The three eclipsed conformations, in which the dihedral angles are zero, are transition states (energy maxima) connecting two equivalent energy minima, the staggered conformers.
The butane molecule is the simplest molecule for which single bond rotations result in two types of nonequivalent structures, known as the anti- and gauche-conformers (see figure).
For example, butane has three conformers relating to its two methyl (CH) groups: two gauche conformers, which have the methyls ±60° apart and are enantiomeric, and an anti conformer, where the four carbon centres are coplanar and the substituents are 180° apart (refer to free energy diagram of butane). The energy difference between gauche and anti is 0.9 kcal/mol associated with the strain energy of the gauche conformer. The anti conformer is, therefore, the most stable (≈ 0 kcal/mol). The three eclipsed conformations with dihedral angles of 0°, 120°, and 240° are transition states between conformers. Note that the two eclipsed conformations have different energies: at 0° the two methyl groups are eclipsed, resulting in higher energy (≈ 5 kcal/mol) than at 120°, where the methyl groups are eclipsed with hydrogens (≈ 3.5 kcal/mol).
While simple molecules can be described by these types of conformations, more complex molecules require the use of the Klyne–Prelog system to describe the different conformers.
More specific examples of conformational isomerism are detailed elsewhere:
*Ring conformation
**Cyclohexane conformations, including with chair and boat conformations among others.
**Cycloalkane conformations, including medium rings and macrocycles
**Carbohydrate conformation, which includes cyclohexane conformations as well as other details.
*Allylic strain – energetics related to rotation about the single bond between an sp carbon and an sp carbon.
*Atropisomerism – due to restricted rotation about a bond.
*Folding, including the secondary and tertiary structure of biopolymers (nucleic acids and proteins).
*Akamptisomerism – due to restricted inversion of a bond angle. | 0 | Theoretical and Fundamental Chemistry |
The camera, attached to a long chord, is fed through an access point on the property. It is then maneuvered through the pipes to the point of damage of obstruction. The captured footage is sent directly to a screen, giving the plumber a live view of the affected area. | 1 | Applied and Interdisciplinary Chemistry |
High-throughput screening (HTS) is a method for scientific discovery especially used in drug discovery and relevant to the fields of biology, materials science and chemistry. Using robotics, data processing/control software, liquid handling devices, and sensitive detectors, high-throughput screening allows a researcher to quickly conduct millions of chemical, genetic, or pharmacological tests. Through this process one can quickly recognize active compounds, antibodies, or genes that modulate a particular biomolecular pathway. The results of these experiments provide starting points for drug design and for understanding the noninteraction or role of a particular location. | 1 | Applied and Interdisciplinary Chemistry |
Intermediate band photovoltaics in solar cell research provides methods for exceeding the Shockley–Queisser limit on the efficiency of a cell. It introduces an intermediate band (IB) energy level in between the valence and conduction bands. Theoretically, introducing an IB allows two photons with energy less than the bandgap to excite an electron from the valence band to the conduction band. This increases the induced photocurrent and thereby efficiency.
Luque and Marti first derived a theoretical limit for an IB device with one midgap energy level using detailed balance. They assumed no carriers were collected at the IB and that the device was under full concentration. They found the maximum efficiency to be 63.2%, for a bandgap of 1.95eV with the IB 0.71eV from either the valence or conduction band.
Under one sun illumination the limiting efficiency is 47%. Several means are under study to realize IB semiconductors with such optimum 3-bandgap configuration, namely via materials engineering (controlled inclusion of deep level impurities or highly-mismatched alloys) and nano-structuring (quantum-dots in host hetero-crystals). | 0 | Theoretical and Fundamental Chemistry |
Supplementation with vitamin D is a reliable method for preventing or treating rickets. On the other hand, the effects of vitamin D supplementation on non-skeletal health are uncertain. A review did not find any effect from supplementation on the rates of non-skeletal disease, other than a tentative decrease in mortality in the elderly. Vitamin D supplements do not alter the outcomes for myocardial infarction, stroke or cerebrovascular disease, cancer, bone fractures or knee osteoarthritis.
A US Institute of Medicine (IOM) report states: "Outcomes related to cancer, cardiovascular disease and hypertension, and diabetes and metabolic syndrome, falls and physical performance, immune functioning and autoimmune disorders, infections, neuropsychological functioning, and preeclampsia could not be linked reliably with intake of either calcium or vitamin D, and were often conflicting." Some researchers claim the IOM was too definitive in its recommendations and made a mathematical mistake when calculating the blood level of vitamin D associated with bone health. Members of the IOM panel maintain that they used a "standard procedure for dietary recommendations" and that the report is solidly based on the data. | 1 | Applied and Interdisciplinary Chemistry |
The Annual Review of Chemical and Biomolecular Engineering is helmed by the editor or the co-editors. The editor is assisted by the editorial committee, which includes associate editors, regular members, and occasionally guest editors. Guest members participate at the invitation of the editor, and serve terms of one year. All other members of the editorial committee are appointed by the Annual Reviews board of directors and serve five-year terms. The editorial committee determines which topics should be included in each volume and solicits reviews from qualified authors. Unsolicited manuscripts are not accepted. Peer review of accepted manuscripts is undertaken by the editorial committee. | 1 | Applied and Interdisciplinary Chemistry |
In biology, translation is the process in living cells in which proteins are produced using RNA molecules as templates. The generated protein is a sequence of amino acids. This sequence is determined by the sequence of nucleotides in the RNA. The nucleotides are considered three at a time. Each such triple results in addition of one specific amino acid to the protein being generated. The matching from nucleotide triple to amino acid is called the genetic code. The translation is performed by a large complex of functional RNA and proteins called ribosomes. The entire process is called gene expression.
In translation, messenger RNA (mRNA) is decoded in a ribosome, outside the nucleus, to produce a specific amino acid chain, or polypeptide. The polypeptide later folds into an active protein and performs its functions in the cell. The ribosome facilitates decoding by inducing the binding of complementary transfer RNA (tRNA) anticodon sequences to mRNA codons. The tRNAs carry specific amino acids that are chained together into a polypeptide as the mRNA passes through and is "read" by the ribosome.
Translation proceeds in three phases:
# Initiation: The ribosome assembles around the target mRNA. The first tRNA is attached at the start codon.
# Elongation: The last tRNA validated by the small ribosomal subunit (accommodation) transfers the amino acid. It carries to the large ribosomal subunit which binds it to the one of the preceding admitted tRNA (transpeptidation). The ribosome then moves to the next mRNA codon to continue the process (translocation), creating an amino acid chain.
# Termination: When a stop codon is reached, the ribosome releases the polypeptide. The ribosomal complex remains intact and moves on to the next mRNA to be translated.
In prokaryotes (bacteria and archaea), translation occurs in the cytosol, where the large and small subunits of the ribosome bind to the mRNA. In eukaryotes, translation occurs in the cytoplasm or across the membrane of the endoplasmic reticulum in a process called co-translational translocation. In co-translational translocation, the entire ribosome/mRNA complex binds to the outer membrane of the rough endoplasmic reticulum (ER), and the new protein is synthesized and released into the ER; the newly created polypeptide can be stored inside the ER for future vesicle transport and secretion outside the cell, or immediately secreted.
Many types of transcribed RNA, such as tRNA, ribosomal RNA, and small nuclear RNA, do not undergo a translation into proteins.
Several antibiotics act by inhibiting translation. These include anisomycin, cycloheximide, chloramphenicol, tetracycline, streptomycin, erythromycin, and puromycin. Prokaryotic ribosomes have a different structure from that of eukaryotic ribosomes, and thus antibiotics can specifically target bacterial infections without any harm to a eukaryotic host's cells. | 1 | Applied and Interdisciplinary Chemistry |
Chartered Chemist (CChem) is a chartered status awarded by the Royal Society of Chemistry (RSC) in the United Kingdom, the Royal Australian Chemical Institute (RACI) in Australia, by the Ministry of Education in Italy, the Institute of Chemistry Ceylon (IChemC), Sri Lanka, and the Institute of Chartered Chemists of Nigeria in Nigeria.
Achieving chartered status in any profession denotes to the wider community a high level of specialised subject knowledge and professional competence. The award of the Chartered Chemist (CChem) designation recognises the experienced practising chemist who has demonstrated an in-depth knowledge of chemistry, significant personal achievements based upon chemistry, professionalism in the workplace and a commitment to maintaining technical expertise through continuing professional development. | 1 | Applied and Interdisciplinary Chemistry |
Most VOCs in Earth's atmosphere are biogenic, largely emitted by plants.
Biogenic volatile organic compounds (BVOCs) encompass VOCs emitted by plants, animals, or microorganisms, and while extremely diverse, are most commonly terpenoids, alcohols, and carbonyls (methane and carbon monoxide are generally not considered). Not counting methane, biological sources emit an estimated 760 teragrams of carbon per year in the form of VOCs. The majority of VOCs are produced by plants, the main compound being isoprene. Small amounts of VOCs are produced by animals and microbes. Many VOCs are considered secondary metabolites, which often help organisms in defense, such as plant defense against herbivory. The strong odor emitted by many plants consists of green leaf volatiles, a subset of VOCs. Although intended for nearby organisms to detect and respond to, these volatiles can be detected and communicated through wireless electronic transmission, by embedding nanosensors and infrared transmitters into the plant materials themselves.
Emissions are affected by a variety of factors, such as temperature, which determines rates of volatilization and growth, and sunlight, which determines rates of biosynthesis. Emission occurs almost exclusively from the leaves, the stomata in particular. VOCs emitted by terrestrial forests are often oxidized by hydroxyl radicals in the atmosphere; in the absence of NO pollutants, VOC photochemistry recycles hydroxyl radicals to create a sustainable biosphere-atmosphere balance. Due to recent climate change developments, such as warming and greater UV radiation, BVOC emissions from plants are generally predicted to increase, thus upsetting the biosphere-atmosphere interaction and damaging major ecosystems. A major class of VOCs is the terpene class of compounds, such as myrcene.
Providing a sense of scale, a forest in area, the size of the US state of Pennsylvania, is estimated to emit of terpenes on a typical August day during the growing season. Researchers investigating mechanisms of induction of genes producing volatile organic compounds, and the subsequent increase in volatile terpenes, has been achieved in maize using (Z)-3-hexen-1-ol and other plant hormones. | 0 | Theoretical and Fundamental Chemistry |
NMR spectroscopic research includes the following steps:
*Extraction of carbohydrate material (for natural glycans)
*Chemical removal of moieties masking regularity (for polymers)
*Separation and purification of carbohydrate material (for 2D NMR experiments, 10 mg or more is recommended)
*Sample preparation (usually in DO)
*Acquisition of 1D spectra
*Planning, acquisition and processing of other NMR experiments (usually requires from 5 to 20 hours)
*Assignment and interpretation of spectra (see exemplary figure)
*If a structural problem could not be solved: chemical modification/degradation and NMR analysis of products
*Acquisition of spectra of the native (unmasked) compound and their interpretation based on modified structure
*Presentation of results | 0 | Theoretical and Fundamental Chemistry |
When laser cooling of atoms was first proposed in 1975, the only cooling mechanism considered was Doppler cooling. As such the limit on the temperature was predicted to be the Doppler limit:
Here k is the Boltzmann constant, T is the temperature of the atoms, and Γ is the inverse of the excited state's radiative lifetime.
Early experiments seemed to be in agreement with this limit. However, in 1988 experiments began to report temperatures below the Doppler limit. These observations would take the theory of PG cooling to explain. | 0 | Theoretical and Fundamental Chemistry |
The VAR process is used on many different materials. Certain applications almost always use a material that has been VAR treated. A list of materials that may be VAR treated include:
*Stainless Steel
*Alloy Steel
**4340 & 4330+V
**300M
**AF1410
**Aermet 100
**M50
**BG42
**Nitralloy
**16NCD13
**35NCD16
**HY-100
**HY-180
**HY-TUF
**D6AC
**Maraging steels
**UT-18
**HP 9-4-30
*Titanium
**Ti-6Al-4V
**Ti-10V-2Al-3Fe
**Ti-5Al-5V-5Mo-3Cr
*Invar
*Nitinol
*Nickel superalloys
**Inconel alloys
**Hastelloy alloys
**Rene alloys
**RR1000
*Zirconium
*Niobium
*Platinum
*Tantalum
*Rhodium
Note that pure titanium and most titanium alloys are double or triple VAR processed. Nickel-based super alloys for aerospace applications are usually VAR processed. Zirconium and niobium alloys used in the nuclear industry are routinely VAR processed. Pure platinum, tantalum, and rhodium may be VAR processed. | 1 | Applied and Interdisciplinary Chemistry |
The electrical and thermal conductivity and magnetic property of metals enhance the electrical conductivity and antibacterial property of nanocomposite hydrogels when incorporated. The electrical conducting property is necessary for the hydrogels to start forming functional tissues and be used as imaging agents, drug delivery systems, conductive scaffolds, switchable electronics, actuators, and sensors. | 0 | Theoretical and Fundamental Chemistry |
The Division of Community Health Investigations manages an office in Washington, D.C., as well as offices in each of the 10 EPA regions:
:* Boston (Region 1: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, Vermont)
:* New York and Edison, New Jersey (Region 2: New Jersey, New York, Puerto Rico, U.S. Virgin Islands)
:* Philadelphia (Region 3: Delaware, District of Columbia, Maryland, Pennsylvania, Virginia, West Virginia)
:* Atlanta (Region 4: Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, South Carolina, Tennessee)
:* Chicago (Region 5: Illinois, Indiana, Michigan, Minnesota, Ohio, Wisconsin)
:* Dallas (Region 6: Arkansas, Louisiana, New Mexico, Oklahoma, Texas)
:* Kansas City, Kansas (Region 7: Iowa, Kansas, Missouri, Nebraska)
:* Denver and Helena, Montana (Region 8: Colorado, Montana, North Dakota, South Dakota, Utah, Wyoming)
:* San Francisco (Region 9: American Samoa, Arizona, California, Guam, Hawaii, Nevada, Northern Mariana Islands, Trust Territories)
:* Seattle and Anchorage, Alaska (Region 10: Alaska, Idaho, Oregon, Washington)
The regional offices work cooperatively with EPA, state and local health departments, health professionals, community groups, and other partners to implement programs and initiatives. | 1 | Applied and Interdisciplinary Chemistry |
Land animals, including livestock and pets have been affected. Dogs have died from the toxins after swimming in algal blooms. Warnings have come from government agencies in the state of Ohio, which noted that many dogs and livestock deaths resulted from HAB exposure in the U.S. and other countries. They also noted in a 2003 report that during the previous 30 years, they have seen more frequent and longer-lasting harmful algal blooms." In 50 countries and 27 states that year there were reports of human and animal illnesses linked to algal toxins. In Australia, the department of agriculture warned farmers that the toxins from a HAB had the "potential to kill large numbers of livestock very quickly."
Marine mammals have also been seriously harmed, as over 50 percent of unusual marine mammal deaths are caused by harmful algal blooms. In 1999, over 65 bottlenose dolphins died during a coastal HAB in Florida. In 2013 a HAB in southwest Florida killed a record number of Manatee. Whales have also died in large numbers. During the period from 2005 to 2014, Argentina reported an average 65 baby whales dying which experts have linked to algal blooms. A whale expert there expects the whale population to be reduced significantly. In 2003 off Cape Cod in the North Atlantic, at least 12 humpback whales died from toxic algae from a HAB. In 2015 Alaska and British Columbia reported many humpback whales had likely died from HAB toxins, with 30 having washed ashore in Alaska. "Our leading theory at this point is that the harmful algal bloom has contributed to the deaths," said a NOAA spokesperson.
Birds have died after eating dead fish contaminated with toxic algae. Rotting and decaying fish are eaten by birds such as pelicans, seagulls, cormorants, and possibly marine or land mammals, which then become poisoned. The nervous systems of dead birds were examined and had failed from the toxin's effect. On the Oregon and Washington coast, a thousand scoters, or sea ducks, were also killed in 2009. "This is huge," said a university professor. As dying or dead birds washed up on the shore, wildlife agencies went into "an emergency crisis mode."
It has even been suggested that harmful algal blooms are responsible for the deaths of animals found in fossil troves, such as the dozens of cetacean skeletons found at Cerro Ballena. | 0 | Theoretical and Fundamental Chemistry |
Prof. David Baker, a protein research scientist at the University of Washington, founded the Foldit project. Seth Cooper was the lead game designer. Before starting the project, Baker and his laboratory coworkers relied on another research project named Rosetta to predict the native structures of various proteins using special computer protein structure prediction algorithms. Rosetta was eventually extended to use the power of distributed computing: The Rosetta@home program was made available for public download, and displayed its protein-folding progress as a screensaver. Its results were sent to a central server for verification.
Some Rosetta@home users became frustrated when they saw ways to solve protein structures, but could not interact with the program. Hoping that humans could improve the computers' attempts to solve protein structures, Baker approached David Salesin and Zoran Popović, computer science professors at the same university, to help conceptualize and build an interactive program, a video game, that would appeal to the public and help efforts to find native protein structures. | 1 | Applied and Interdisciplinary Chemistry |
Type J (iron–constantan) has a more restricted range (−40 °C to +750 °C) than type K but higher sensitivity of about 50 μV/°C. The Curie point of the iron (770 °C) causes a smooth change in the characteristic, which determines the upper temperature limit. Note, the European/German Type L is a variant of the type J, with a different specification for the EMF output (reference DIN 43712:1985-01). | 1 | Applied and Interdisciplinary Chemistry |
Silicon-germanium (SiGe) thermoelectrics have been used for converting heat into electrical power in spacecraft designed for deep-space NASA missions since 1976. This material is used in the radioisotope thermoelectric generators (RTGs) that power Voyager 1, Voyager 2, Galileo, Ulysses, Cassini, and New Horizons spacecraft. SiGe thermoelectric material converts enough radiated heat into electrical power to fully meet the power demands of each spacecraft. The properties of the material and the remaining components of the RTG contribute towards the efficiency of this thermoelectric conversion. | 0 | Theoretical and Fundamental Chemistry |
Abnormal or discontinuous grain growth, also referred to as exaggerated or secondary recrystallisation grain growth, is a grain growth phenomenon in which certain energetically favorable grains (crystallites) grow rapidly in a matrix of finer grains, resulting in a bimodal grain-size distribution.
In ceramic materials, this phenomenon can result in the formation of elongated prismatic, acicular (needle-like) grains in a densified matrix. This microstructure has the potential to improve fracture toughness by impeding the propagation of cracks. | 0 | Theoretical and Fundamental Chemistry |
It is synthesised by the deprotonation of 2,2,6,6-tetramethylpiperidine with n-butyllithium at −78 °C. Recent reports show that this reaction can also be performed 0 °C. The compound is stable in a THF/ethylbenzene solvent mixture and is commercially available as such. | 0 | Theoretical and Fundamental Chemistry |
The only first-principles calculational tool currently available is lattice QCD, i.e. brute-force computer calculations. Because of a technical obstacle known as the fermion sign problem, this method can only be used at low density and high temperature (μ < T), and it predicts that the crossover to the quark–gluon plasma will occur around T = 150 MeV However, it cannot be used to investigate the interesting color-superconducting phase structure at high density and low temperature. | 0 | Theoretical and Fundamental Chemistry |
As coal is mostly carbon, burning it produces a lot of carbon dioxide. The IEA said in 2022 that ‘achieving a swift reduction in global coal emissions is the central challenge for reaching international climate targets’.
Carbon sequestration technology, to remove significant quantities of carbon dioxide from the air, has yet to be tested on a large scale and may not be safe or successful. Sequestered CO2 may eventually leak up through the ground, may lead to unexpected geological instability or may cause contamination of aquifers used for drinking water supplies. Carbon capture and storage is applied at large point emitters of carbon dioxide with the objective of preventing it from entering the atmosphere.
As approximately 37% of the world energy consumption in 2022 was from coal, reaching the carbon dioxide reduction targets of the Paris Agreement will require modifications to how coal is used. | 1 | Applied and Interdisciplinary Chemistry |
Early in her career, Soderholm focused on the characterizing the magnetic and electronic behavior of compounds containing f-ions (lanthanides and actinides) with a focus on high-T materials, compounds that are superconducting under usually high temperatures. She was part of the research group that first determined the structure of YBaCuO. Their discovery formed the foundation for the further developments in the broad field of superconductivity. | 0 | Theoretical and Fundamental Chemistry |
A glycosidase is an enzyme that catalyzes the breakdown of a glycosidic linkage to produce two smaller sugars. This process has important implications in the utilization of stored energy, like glycogen in animals, as well as in the breakdown of cellulose by organisms that feed on plants. In general, aspartic or glutamic acid residues in the active site of the enzyme catalyze the hydrolysis of the glycosidic bond. The mechanism of these enzymes involves an oxocarbenium ion intermediate, a general example of which is shown below. | 0 | Theoretical and Fundamental Chemistry |
Electrons can be scattered by other charged particles through the electrostatic Coulomb forces. Furthermore, if a magnetic field is present, a traveling electron will be deflected by the Lorentz force. An extremely accurate description of all electron scattering, including quantum and relativistic aspects, is given by the theory of quantum electrodynamics. | 0 | Theoretical and Fundamental Chemistry |
Pure organochlorides like polyvinyl chloride (PVC) do not absorb any light above 220 nm. The initiation of photo-oxidation is instead caused by various irregularities in the polymer chain, such as structural defects as well as hydroperoxides, carbonyl groups, and double bonds.
Hydroperoxides formed during processing are the most important initiator to begin with, however their concentration decreases during photo-oxidation whereas carbonyl concentration increases, as such carbonyls may become the primary initiator over time.
Propagation steps involve the hydroperoxyl radical, which can abstract hydrogen from both hydrocarbon (-CH-) and organochloride (-CHCl-) sites in the polymer at comparable rates. Radicals formed at hydrocarbon sites rapidly convert to alkenes with loss of radical chlorine. This forms allylic hydrogens (shown in red) which are more susceptible to hydrogen abstraction leading to the formation of polyenes in zipper-like reactions.
When the polyenes contain at least eight conjugated double bonds they become coloured, leading to yellowing and eventual browning of the material. This is off-set slightly by longer polyenes being photobleached with atmospheric oxygen, however PVC does eventually discolour unless polymer stabilisers are present. Reactions at organochloride sites proceed via the usual hydroperoxyl and hydroperoxide before photolysis yields the α-chloro-alkoxyl radical. This species can undergo various reactions to give carbonyls, peroxide cross-links and beta scission products. | 0 | Theoretical and Fundamental Chemistry |
Tar is a dark brown or black viscous liquid of hydrocarbons and free carbon, obtained from a wide variety of organic materials through destructive distillation. Tar can be produced from coal, wood, petroleum, or peat.
Mineral products resembling tar can be produced from fossil hydrocarbons, such as petroleum. Coal tar is produced from coal as a byproduct of coke production. | 0 | Theoretical and Fundamental Chemistry |
Sendai virus (family Paramyxoviridae) has a linear, single stranded, negative-sense, nonsegmented RNA genome. The viral RdRp consists of two virus-encoded subunits, a smaller one P and a larger one L. When different inactive RdRp mutants with defects throughout the length of the L subunit where tested in pairwise combinations, restoration of viral RNA synthesis was observed in some combinations. This positive L–L interaction is referred to as intragenic complementation and indicates that the L protein is an oligomer in the viral RNA polymerase complex. | 1 | Applied and Interdisciplinary Chemistry |
The PUREX process is a liquid–liquid extraction ion-exchange method used to reprocess spent nuclear fuel, in order to extract primarily uranium and plutonium, independent of each other, from the other constituents. The current method of choice is to use the PUREX liquid–liquid extraction process which uses a tributyl phosphate/hydrocarbon mixture to extract both uranium and plutonium from nitric acid. This extraction is of the nitrate salts and is classed as being of a solvation mechanism. For example, the extraction of plutonium by an extraction agent (S) in a nitrate medium occurs by the following reaction.
: + 4 + 2 S → []
A complex bond is formed between the metal cation, the nitrates and the tributyl phosphate, and a model compound of a dioxouranium(VI) complex with two nitrates and two triethyl phosphates has been characterised by X-ray crystallography. After the dissolution step it is normal to remove the fine insoluble solids, because otherwise they will disturb the solvent extraction process by altering the liquid-liquid interface. It is known that the presence of a fine solid can stabilize an emulsion. Emulsions are often referred to as third phases in the solvent extraction community.
An organic solvent composed of 30% tributyl phosphate (TBP) in a hydrocarbon solvent, such as kerosene, is used to extract the uranium as UO(NO)·2TBP complexes, and plutonium as similar complexes, from other fission products, which remain in the aqueous phase. The transuranium elements americium and curium also remain in the aqueous phase. The nature of the organic soluble uranium complex has been the subject of some research. A series of complexes of uranium with nitrate and trialkyl phosphates and phosphine oxides have been characterized.
Plutonium is separated from uranium by treating the kerosene solution with aqueous ferrous sulphamate, which selectively reduces the plutonium to the +3 oxidation state. The plutonium passes into the aqueous phase. The uranium is stripped from the kerosene solution by back-extraction into nitric acid at a concentration of ca. . | 0 | Theoretical and Fundamental Chemistry |
MFGM bioactive protein components, including the glycoproteins lactadherin, MUC-1, and butyrophilin, have been shown in preclinical studies to affect immune response. These components influence the immune system by several mechanisms, including interference with microbe adhesion to intestinal epithelia, bacteriocidal action, support of beneficial microbiota, and modulation of other parts of the immune system.
MFGM phospholipid components such as phosphatidylcholine are a key constituent of the intestinal mucus barrier, and therefore may contribute to intestinal defense against invasive pathogens. Sphingolipids, including sphingomyelin, are present in the apical membrane of the gut epithelia, and are also important for maintaining membrane structure, modulating growth factor receptors, and serving competitive binding inhibitors for microorganisms, microbial toxins, and viruses. Gangliosides are also present in intestinal mucosa and may possibly contribute to improved gut microflora and antibacterial defense. | 1 | Applied and Interdisciplinary Chemistry |
The CD V-700 (often written as "CDV-700") is a Geiger counter employing a probe equipped with a Geiger–Müller tube, manufactured by several companies under contract to United States federal civil defense agencies in the 1950s and 1960s. While all models adhere to a similar size, shape, coloring and form-factor, there were substantial differences between various models and manufacturers over the years the CD V-700 was in production. Many of the earlier units required the use of now-obsolete high-voltage batteries, and were declared obsolete by the end of the 1970s.
Tens of thousands of these units were distributed to US state civil defense agencies. Even though large numbers have been sold off as surplus to civilian users, many remain in use with first responders and state emergency management agencies today. | 0 | Theoretical and Fundamental Chemistry |
Duplex sequencing is a library preparation and analysis method for next-generation sequencing (NGS) platforms that employs random tagging of double-stranded DNA to detect mutations with higher accuracy and lower error rates.
This method uses degenerate molecular tags in addition to sequencing adapters to recognize reads originating from each strand of DNA. The generated sequencing reads then will be analyzed using two methods: single-strand consensus sequences (SSCS) and duplex consensus sequences (DCS) assembly. Duplex sequencing theoretically can detect mutations with frequencies as low as 5 x 10 --that is more than 10,000 times higher in accuracy compared to the conventional next-generation sequencing methods.
The estimated error rate of standard next-generation sequencing platforms is 10 to 10 per base call. With this error rate, billions of base calls that are produced by NGS will result in millions of errors. The errors are introduced during sample preparation and sequencing such as polymerase chain reaction, sequencing, and image analysis errors. While the NGS platforms' error rate is acceptable in some applications such as detection of clonal variants, it is a major limitation for applications that require higher accuracy for detection of low-frequency variants such as detection of intra-organismal mosaicism, subclonal variants in genetically heterogeneous cancers, or circulating tumor DNA.
Several library preparation strategies have been developed that increase accuracy of NGS platforms such as molecular barcoding and circular consensus sequencing method. Like NGS platforms, the data generated by these methods originates from a single strand of DNA, and therefore the errors that are introduced during PCR amplification, tissue processing, DNA extraction, hybridization capture (where used) or DNA sequencing itself can still be distinguished as a true variant. The duplex sequencing method addresses this problem by taking advantage of the complementary nature of two strands of DNA and confirming only variants that are present in both strands of DNA. Because the probability of two complementary errors arising at the same location in both strands is exceedingly low, duplex sequencing increases the accuracy of sequencing significantly. | 1 | Applied and Interdisciplinary Chemistry |
Chlorarachniophytes are a rare group of organisms that also contain chloroplasts derived from green algae, though their story is more complicated than that of the euglenophytes. The ancestor of chlorarachniophytes is thought to have been a eukaryote with a red algal derived chloroplast. It is then thought to have lost its first red algal chloroplast, and later engulfed a green alga, giving it its second, green algal derived chloroplast.
Chlorarachniophyte chloroplasts are bounded by four membranes, except near the cell membrane, where the chloroplast membranes fuse into a double membrane. Their thylakoids are arranged in loose stacks of three. Chlorarachniophytes have a form of polysaccharide called chrysolaminarin, which they store in the cytoplasm, often collected around the chloroplast pyrenoid, which bulges into the cytoplasm.
Chlorarachniophyte chloroplasts are notable because the green alga they are derived from has not been completely broken down—its nucleus still persists as a nucleomorph found between the second and third chloroplast membranes—the periplastid space, which corresponds to the green alga's cytoplasm. | 0 | Theoretical and Fundamental Chemistry |
DMDO is not commercially available because of its instability. DMDO can be prepared as dilute solutions (~0.1 M) by treatment of acetone with potassium peroxymonosulfate , usually in the form of Oxone (2KHSO·KHSO·KSO).
The preparation of DMDO is rather inefficient (typical yields < 3%) and typically only yields a relatively dilute solution in acetone (only up to approximately 0.1 M). This is tolerable as preparation uses inexpensive substances: acetone, sodium bicarbonate, and potassium peroxymonosulfate (commercially known as "oxone"). The solution can be stored at low temperatures and its concentration may be assayed immediately prior to its use.
The more active compound methyl(trifluoromethyl)dioxirane can be similarly prepared from methyl trifluoromethyl ketone. | 0 | Theoretical and Fundamental Chemistry |
Phytoecdysteroids are plant-derived ecdysteroids. Phytoecdysteroids are a class of chemicals that plants synthesize for defense against phytophagous (plant eating) insects. These compounds are mimics of hormones used by arthropods in the molting process known as ecdysis. When insects eat the plants with these chemicals they may prematurely molt, lose weight, or suffer other metabolic damage and die.
Chemically, phytoecdysteroids are classed as triterpenoids, the group of compounds that includes triterpene saponins, phytosterols, and phytoecdysteroids. Plants, but not animals, synthesize phytoecdysteroids from mevalonic acid in the mevalonate pathway of the plant cell using acetyl-CoA as a precursor.
Over 250 ecdysteroid analogs have been identified so far in plants, and it has been theorized that there are over 1,000 possible structures which might occur in nature. Many more plants have the ability to "turn on" the production of phytoecdysteroids when under stress, animal attack or other conditions.
The term phytoecdysteroid can also apply to ecdysteroids found in fungi, even though fungi are not plants.
Some plants or fungi that produce phytoecdysteroids include Achyranthes bidentata, Tinospora cordifolia, Pfaffia paniculata, Leuzea carthamoides, Rhaponticum uniflorum, Serratula coronata, Cordyceps, and Asparagus. | 1 | Applied and Interdisciplinary Chemistry |
All SOCS have certain structures in common. This includes a varying N-terminal domain involved in protein-protein interactions, a central SH2 domain, which can bind to molecules that have been phosphorylated by tyrosine kinases, and a SOCS box located at the C-terminal that enables recruitment of E3 ligases and ubiquitin signaling molecules. | 1 | Applied and Interdisciplinary Chemistry |
Scientists use this beam of charged particles to determine the elemental composition of solid materials (minerals, glasses, metals). The chemical composition of the target can be found from the elemental data extracted through emitted X-rays (in the case where the primary beam consists of charged electrons) or measurement of an emitted secondary beam of material sputtered from the target (in the case where the primary beam consists of charged ions).
When the ion energy is in the range of a few tens of keV (kilo-electronvolt) these microprobes are usually called FIB (Focused ion beam). An FIB makes a small portion of the material into a plasma; the analysis is done by the same basic techniques as the ones used in mass spectrometry.
When the ion energy is higher, hundreds of keV to a few MeV (mega-electronvolt) they are called nuclear microprobes. Nuclear microprobes are extremely powerful tools that utilize ion beam analysis techniques as microscopies with spot sizes in the micro-/nanometre range. These instruments are applied to solve scientific problems in a diverse range of fields, from microelectronics to biomedicine. In addition to the development of new ways to exploit these probes as analytical tools (this application area of the nuclear microprobes is called nuclear microscopy), strong progress has been made in the area of materials modification recently (most of which can be described as PBW, proton beam writing).
The nuclear microprobe's beam is usually composed of protons and alpha particles. Some of the most advanced nuclear microprobes have beam energies in excess of 2 MeV. This gives the device very high sensitivity to minute concentrations of elements, around 1 ppm at beam sizes smaller than 1 micrometer. This elemental sensitivity exists because when the beam interacts with the a sample it gives off characteristic X-rays of each element present in the sample. This type of detection of radiation is called PIXE. Other analysis techniques are applied to nuclear microscopy including Rutherford backscattering(RBS), STIM, etc.
Another use for microprobes is the production of micro and nano sized devices, as in microelectromechanical systems and nanoelectromechanical systems. The advantage that microprobes have over other lithography processes is that a microprobe beam can be scanned or directed over any area of the sample. This scanning of the microprobe beam can be imagined to be like using a very fine tipped pencil to draw your design on a paper or in a drawing program. Traditional lithography processes use photons which cannot be scanned and therefore masks are needed to selectively expose your sample to radiation. It is the radiation that causes changes in the sample, which in turn allows scientists and engineers to develop tiny devices such as microprocessors, accelerometers (like in most car safety systems), etc. | 0 | Theoretical and Fundamental Chemistry |
Curie visited Poland for the last time in early 1934. A few months later, on 4 July 1934, she died aged 66 at the Sancellemoz sanatorium in Passy, Haute-Savoie, from aplastic anemia believed to have been contracted from her long-term exposure to radiation, causing damage to her bone marrow.
The damaging effects of ionising radiation were not known at the time of her work, which had been carried out without the safety measures later developed. She had carried test tubes containing radioactive isotopes in her pocket, and she stored them in her desk drawer, remarking on the faint light that the substances gave off in the dark. Curie was also exposed to X-rays from unshielded equipment while serving as a radiologist in field hospitals during the First World War. When Curies body was exhumed in 1995, the French Office de Protection contre les Rayonnements Ionisants (OPRI') "concluded that she could not have been exposed to lethal levels of radium while she was alive". They pointed out that radium poses a risk only if it is ingested, and speculated that her illness was more likely to have been due to her use of radiography during the First World War.
She was interred at the cemetery in Sceaux, alongside her husband Pierre. Sixty years later, in 1995, in honour of their achievements, the remains of both were transferred to the Paris Panthéon. Their remains were sealed in a lead lining because of the radioactivity. She became the second woman to be interred at the Panthéon (after Sophie Berthelot) and the first woman to be honoured with interment in the Panthéon on her own merits.
Because of their levels of radioactive contamination, her papers from the 1890s are considered too dangerous to handle. Even her cookbooks are highly radioactive. Her papers are kept in lead-lined boxes, and those who wish to consult them must wear protective clothing. In her last year, she worked on a book, Radioactivity, which was published posthumously in 1935. | 0 | Theoretical and Fundamental Chemistry |
Time resolved microwave conductivity (TRMC) is an experimental technique used to evaluate the electronic properties of semiconductors. Specifically, it is used to evaluate a proxy for charge carrier mobility and a representative carrier lifetime from light-induced changes in conductance. The technique works by photo-generating electrons and holes in a semiconductor, allowing these charge carriers to move under a microwave field, and detecting the resulting changes in the electric field. TRMC systems cannot be purchased as a single unit, and are generally "home-built" from individual components. One advantage of TRMC over alternative techniques is that it does not require direct physical contact to the material. | 0 | Theoretical and Fundamental Chemistry |
The earliest measurements combining AFM with infrared spectroscopy were performed in 1999 by Hammiche et al. at the University of Lancaster in the United Kingdom, in an EPSRC-funded project led by M Reading and H M Pollock. Separately, Anderson at the Jet Propulsion Laboratory in the United States made a related measurement in 2000. Both groups used a conventional Fourier transform infrared spectrometer (FTIR) equipped with a broadband thermal source, the radiation was focused near the tip of a probe that was in contact with a sample. The Lancaster group obtained spectra by detecting the absorption of infrared radiation using a temperature sensitive thermal probe. Anderson took the different approach of using a conventional AFM probe to detect the thermal expansion. He reported an interferogram but not a spectrum; the first infrared spectrum obtained in this way was reported by Hammiche et al. in 2004: this represented the first proof that spectral information about a sample could be obtained using this approach.
Both of these early experiments used a broadband source in conjunction with an interferometer; these techniques could, therefore, be referred to as AFM-FTIR although Hammiche et al. coined the more general term photothermal microspectroscopy or PTMS in their first paper. PTMS has various subgroups; including techniques that measure temperature measure thermal expansion use broadband sources. use lasers excite the sample using evanescent waves, illuminate the sample directly from above etc. and different combinations of these. Fundamentally, they all exploit the photothermal effect. Different combinations of sources, methods, methods of detection and methods of illumination have benefits for different applications. Care should be taken to ensure that it is clear which form of PTMS is being used in each case. Currently there is no universally accepted nomenclature. The original technique dubbed AFM-IR that induced resonant motion in the probe using a Free Electron Laser has developed by exploiting the foregoing permutations so that it has evolved into various forms.
The pioneering experiments of Hammiche et al and Anderson had limited spatial resolution due to thermal diffusion - the spreading of heat away from the region where the infrared light was absorbed. The thermal diffusion length (the distance the heat spreads) is inversely proportional to the root of the modulation frequency. Consequently, the spatial resolution achieved by the early AFM-IR approaches was around one micron or more, due to the low modulation frequencies of the incident radiation created by the movement of the mirror in the interferometer. Also, the first thermal probes were Wollaston wire devices that were developed originally for Microthermal analysis (in fact PTMS was originally considered to be one of a family of microthermal techniques). The comparatively large size of these probes also limited spatial resolution. Bozec et al. and Reading et al. used thermal probes with nanoscale dimensions and demonstrated higher spatial resolution. Ye et al described a MEM-type thermal probe giving sub-100 nm spatial resolution, which they used for nanothermal analysis. The process of exploring laser sources began in 2001 by Hammiche et al when they acquired the first spectrum using a tuneable laser (see Resolution improvement with pulsed laser source).
A significant development was the creation by Reading et al. in 2001 of a custom interface that allowed measurements to be made while illuminating the sample from above; this interface focused the infrared beam to a spot of circa 500μm diameter, close to the theoretical maximum. The use of top-down or top-side illumination has the important benefit that samples of arbitrary thickness can be studied on arbitrary substrates. In many cases this can be done without any sample preparation. All subsequent experiments by Hammiche, Pollock, Reading and their co-workers were made using this type of interface including the instrument constructed by Hill et al. for nanoscale imaging using a pulsed laser. The work of the University of Lancaster group in collaboration with workers from the University of East Anglia led to the formation of a company, Anasys Instruments, to exploit this and related technologies (see Commercialization). | 0 | Theoretical and Fundamental Chemistry |
Acid secretion by the human stomach results in a median diurnal pH of 1.4. This very large (>10-fold) H gradient is generated by the gastric H/K ATPase which is an ATP-driven proton pump. Hydrolysis of one ATP molecule is used to catalyse the electroneutral exchange of two luminal potassium ions for two cytoplasmic protons through the gastric membrane. | 1 | Applied and Interdisciplinary Chemistry |
Injury in plants is damage caused by other organisms or by the non-living (abiotic) environment to plants. Animals that commonly cause injury to plants include insects, mites, nematodes, and herbivorous mammals; damage may also be caused by plant pathogens including fungi, bacteria, and viruses. Abiotic factors that can damage plants include heat, freezing, flooding, lightning, ozone gas, and pollutant chemicals.
Plants respond to injury by signalling that damage has occurred, by secreting materials to seal off the damaged area, by producing antimicrobial chemicals, and in woody plants by regrowing over wounds. | 1 | Applied and Interdisciplinary Chemistry |
The sampler can be deployed in the field for extended periods of time ranging from days to weeks. The specific pollutants of interest are sequestered by the samplers and these are retained on the receiving phase disk. After retrieval from the environment the pollutants are eluted from the disk and analysed in the laboratory using conventional instrumental methods. In order to obtain TWA concentrations the sampler must first be calibrated in the laboratory so as to ascertain the uptake rate (usually measured as the volume of water cleared per unit time i.e. L/h for the analyte) of the pollutant of interest. Chemcatcher® has been used in a range of aquatic environments; however, most work to date has been in monitoring the TWA concentrations of priority and emerging pollutants in surface waters.
The use of passive sampling devices, such as Chemcatcher® or polar organic chemical integrative sampler (POCIS), has a number of advantages over the use of spot or bottle sampling for monitoring pollutants in the aquatic environment. The latter technique gives only an instantaneous concentration of the pollutant as the specific time of sampling. Passive samplers, depending on their mode of use, can give either the TWA or equilibrium concentration of the pollutant over the deployment period. The measurement of TWA concentrations can give a better indication of the long-term environmental conditions and enables improved risk assessment. Chemcatcher® can be used to monitor both polar and non-polar compounds. | 0 | Theoretical and Fundamental Chemistry |
These polymers are commercially used in optical films, lenses, touch screens, light guide panels, reflection films, and other components for mobile devices, displays, cameras, copiers and other optical assemblies. | 0 | Theoretical and Fundamental Chemistry |
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