text
stringlengths 105
4.44k
| label
int64 0
9
| label_text
stringclasses 10
values |
|---|---|---|
Pirkle and co-workers pioneered the development of a variety of CSPs based on charge-transfer complexation and simultaneous hydrogen bonding. These phases are also referred to as Brush-type CSPs. The Pirkle phases are based on aromatic π-acid (3,5-dinitrobenzoyI ring) and π- basic (naphthalene) derivative. In addition to π-π interaction sites, they have hydrogen-bonding and dipole-dipole interaction sites provided by an amide, urea or ester functionality. Strong three-point interaction, according to Dalgleish's model, enables enantioseparation. These phases are classified into π-electron-acceptor, π-electron-donor or π-electron acceptor-donor phase.
A number of Pirkle-type CSPs are commercially available. They are used most often in the normal phase mode. The ionic form of the DNPBG (3,5-dinitrobenzoyl-phenylglycine) CSP has been successfully employed to achieve separation of racemic propranolol in biological fluid. Many compounds of pharmaceutical interest including enantiomers of naproxen and metoprolol has been separated using Pirkle CSP. | 4 | Stereochemistry |
From 1901 to 1938, Sørensen was head of the prestigious Carlsberg Laboratory, Copenhagen. While working at the Carlsberg Laboratory he studied the effect of ion concentration on proteins and, because the concentration of hydrogen ions was particularly important, he introduced the pH-scale as a simple way of expressing it in 1909. The article in which he introduced the scale (using the notation ) was published in French and Danish as well as in German described two methods for measuring acidity which Sørensen and his students had refined. The first method was based on electrodes, whereas the second involved comparing the colours of samples and a preselected set of indicators. (Sørensen, 1909).
:From p. 134: "Die Größe der Wasserstoffionenkonzentration … und die Bezeichnung für den numerischen Wert des Exponent dieser Potenz benütze." (The magnitude of the hydrogen ion concentration is accordingly expressed by the normality factor of the solution concerned, based on the hydrogen ions, and this factor is written in the form of a negative power of 10. By the way, as I refer [to it] in a following section (see p. 159), I just want to point out here that I use the name "hydrogen ion exponent" and the notation for the numerical value of the exponent of this power.)
:From pp. 159–160: "Für die Zahl p schlage ich den Namen "Wasserstoffionenexponent" … Normalitätsfaktors der Lösung verstanden." (For the number p I suggest the name "hydrogen ion exponent" and the notation . By the hydrogen ion exponent () of a solution is thus understood the Briggsian logarithm of the reciprocal value of the normality factor of the solution, based on the hydrogen ions, and this factor is written in the form of a negative power of 10).
:Starting on p. 139, "4. Meßmethoden zur Bestimmung der Wasserstoffionenkonzentration." (4. Methods of measurement for the determination of hydrogen ion concentration.), Sørensen reviewed a series of methods for measuring hydrogen ion concentration. He rejected all of them except two.
:From p. 144: "Es gibt noch zwei Verfahrungsweisen, … bzw. die colorimetrische Methode genannt." (There are still two procedures by which the hydrogen or hydroxyl ion concentration of a solution can be determined; namely, gas chain measurement and determination by means of indicators, also called the electrometric or colorimetric method.) On pp. 145–146, Sørensen outlined the electrometric and colorimetric methods:
::From p. 145: "Die elektrometrische Methode. Wird eine mit Platin-schwarz bedeckte Platinplatte in eine wäßerige … von der Wasserstoffionenkonzentration der Lösung abhängt.)" (The electrometric method. If a platinum plate that's covered with platinum black is dipped into an aqueous – acidic, neutral, or alkaline – solution and if the solution is saturated with hydrogen, then one finds, between the platinum plate and the solution, a voltage difference whose magnitude depends on the hydrogen ion concentration of the solution according to a law.
::From pp. 145: "Die colorimetrische Methode. Der Umschlag des Indicators bei einer gewöhnlichen Titrierung bedeutet ja, wie bekannt, daß die Konzentration der Wasserstoffionen der vorliegenden Lösung eine gewisse Größe von der einen oder der anderen Seite her erreicht oder überschritten hat." (The colorimetric method. The sudden change of the indicator during a typical titration means, as is known, that the concentration of hydrogen ions in the solution at hand has reached or exceeded – from one direction or the other – a certain magnitude.)
: p. 146: "Die Grundlage ist seit langer Zeit bekannt, … eine vollständige Reihe Indikatoren mit Umschlagspunkten bei den verschiedensten Ionenkonzentrationen zusammenzustellen." (The basis [of the colorimetric method] has been known for a long time, but the scattered material was first struggled through and perfected at certain points by the beautiful investigations of Hans Friedenthal [1870-1942] and Eduard Salm, so that it became possible for them to assemble a complete series of indicators with transition points at the most varied ion concentrations.)
:On pp. 150ff, the electrometric method is detailed; and on pp. 201ff, the colorimetric method is detailed. | 3 | Analytical Chemistry |
As the tartrate salt, levorphanol is marketed by Hikma Pharmaceuticals USA Inc. and Virtus Pharmaceuticals in the U.S., and Canada under the brand name Levo-Dromoran. | 4 | Stereochemistry |
Arsenic poisoning (or arsenicosis) is a medical condition that occurs due to elevated levels of arsenic in the body. If arsenic poisoning occurs over a brief period of time, symptoms may include vomiting, abdominal pain, encephalopathy, and watery diarrhea that contains blood. Long-term exposure can result in thickening of the skin, darker skin, abdominal pain, diarrhea, heart disease, numbness, and cancer.
The most common reason for long-term exposure is contaminated drinking water. Groundwater most often becomes contaminated naturally; however, contamination may also occur from mining or agriculture. It may also be found in the soil and air. Recommended levels in water are less than 10–50 µg/L (10–50 parts per billion). Other routes of exposure include toxic waste sites and pseudo-medicine. Most cases of poisoning are accidental. Arsenic acts by changing the functioning of around 200 enzymes. Diagnosis is by testing the urine, blood, or hair.
Prevention is by using water that does not contain high levels of arsenic. This may be achieved by the use of special filters or using rainwater. There is not good evidence to support specific treatments for long-term poisoning. For acute poisonings treating dehydration is important. Dimercaptosuccinic acid or dimercaptopropane sulfonate may be used while dimercaprol (BAL) is not recommended. Hemodialysis may also be used.
Through drinking water, more than 200 million people globally are exposed to higher-than-safe levels of arsenic. The areas most affected are Bangladesh and West Bengal. Exposure is also more common in people of low income and minorities. Acute poisoning is uncommon. The toxicity of arsenic has been described as far back as 1500 BC in the Ebers papyrus. | 1 | Biochemistry |
The mechanism proceeds in two stages: β-nucleophilic addition to the unsaturated carbonyl compound, followed by electrophilic substitution at the α-carbon of the resulting enolate.
When the nucleophile is an organometallic reagent, the mechanisms of the first step can vary. Whether reactions take place by ionic or radical mechanisms is unclear in some cases. Research has shown that the second step may even proceed via single-electron transfers when the reduction potential of the electrophile is low. A general scheme involving ionic intermediates is shown below.
Lithium organocuprates undergo oxidative addition to enones to give, after reductive elimination of an organocopper(III) species, β-substituted lithium enolates.
In any case, the second step is well described in all cases as the reaction of an enolate with an electrophile. The two steps may be carried out as distinct experimental operations if the initially formed enolate is protected after β-addition. If the two steps are not distinct, however, the counterion of the enolate is determined by the counterion of the nucleophilic starting material and can influence the reactivity of the enolate profoundly. | 0 | Organic Chemistry |
The production of bottromycin by S. bottropensis and S. scabies, as well as the production of a bottromycin analog termed bottromycin D, has been studied. It was independently confirmed in 2012 by multiple groups that bottromycin is produced as a ribosomal peptide natural product that it subsequently post-translationally modified. Before this, it was unclear whether bottromycin was produced by nonribosomal peptide synthetase machinery (NRPS). The presence of amino acids other than the 20 proteinogenic amino acids is often a feature of NRPS products because NRPS machinery can directly incorporate other amino acids, among other chemical building blocks. Ribosomal peptide synthesis, which is the same machinery that produces all proteins found in the cell, is limited to the 20 proteinogenic amino acids. However, bottromycin was found to be a highly modified ribosomal peptide by a combination of genome mining and gene deletion studies.
In ribosomal peptide synthesis, the final product results from modifications to a linear peptide starting material translated by the ribosome from an mRNA transcript. In S. scabies the precursor peptide, termed BtmD, is a 44-amino acid peptide. The precursor peptide is termed BmbC in S. bottropensis. The amino acids forming the bottromycin core are residues 2-9 in BtmD: Gly-Pro-Val-Val-Val-Phe-Asp-Cys. In bottromycin D, the sequence is Gly-Pro-Ala-Val-Val-Phe-Asp-Cys, and the precursor peptide is termed BstA. BstA shares high sequence homology with BtmD in the follower peptide region. Unlike other ribosomal peptide natural products, which are normally synthesized with a leader peptide that is cleaved, bottromycin is synthesized with a follower peptide. The presence of a follower peptide was identified by bioinformatic analysis of the bottromycin biosynthetic cluster.
The complete biosynthetic gene cluster for bottromycin has been identified. It is predicted to contain 13 genes, including the precursor peptide (notation will follow Crone and colleagues; other studies had similar results). One of the genes in the cluster, btmL, is proposed to be a transcriptional regulator. Another gene, btmA, is proposed to export bottromycin. The remaining ten genes are expected to modify the precursor peptide btmD from a linear peptide to the final macrocyclic product.
A biosynthetic pathway has been hypothesized based on proposed gene functions (see figure). btmM, with homology to Zn+2 aminopeptidases, is predicted to cleave the N-terminal methionine residue, which is not present in the bottromycin final product. btmE and btmF both contain YcaO-like domains. It is believed that one Although it is unclear which enzyme is responsible for which step, it is hypothesized that one catalyzes macrocyclic amidine formation while the other catalyzes thiazoline formation. btmJ, encoding an enzyme with cytochrome P450 homology, may oxidize the thiazoline to the thiazole. btmH or btmI both have homology to hydrolytic enzymes (α/β hydrolase and metallo-dependent hydrolase, respectively) may catalyze follower peptide hydrolysis. An alternative proposed role for btmH or btmI is to function as a cyclodehydratase in macrocyclization. Gene deletion studies failed to elucidate the function of other proteins within the cluster. | 0 | Organic Chemistry |
Ultraviolet radiation can aggravate several skin conditions and diseases, including systemic lupus erythematosus, Sjögrens syndrome, Sinear Usher syndrome, rosacea, dermatomyositis, Dariers disease, Kindler–Weary syndrome and Porokeratosis. | 5 | Photochemistry |
Sodium amide is mainly used as a strong base in organic chemistry, often in liquid ammonia solution. It is the reagent of choice for the drying of ammonia (liquid or gaseous). One of the main advantages to the use of sodium amide is its relatively low nucleophilicity. In the industrial production of indigo, sodium amide is a component of the highly basic mixture that induces cyclisation of N-phenylglycine. The reaction produces ammonia, which is recycled typically. | 0 | Organic Chemistry |
Acid guanidinium thiocyanate-phenol-chloroform extraction (abbreviated AGPC) is a liquid–liquid extraction technique in biochemistry. It is widely used in molecular biology for isolating RNA (as well as DNA and protein in some cases). This method may take longer than a column-based system such as the silica-based purification, but has higher purity and the advantage of high recovery of RNA: an RNA column is typically unsuitable for purification of short (<200 nucleotides) RNA species, such as siRNA, miRNA, gRNA and tRNA.
It was originally devised by Piotr Chomczynski and Nicoletta Sacchi, who published their protocol in 1987. The reagent is sold by Sigma-Aldrich by the name TRI Reagent; by Invitrogen under the name TRIzol; by Bioline as Trisure; and by Tel-Test as STAT-60. | 1 | Biochemistry |
With the development of microfabrication and nanotechnology, the study of microfluidics and nanofluidics is drawing more attention. Research on microfluidic found its advantages in DNA analysis, lab-on-a-chip, and micro-TAS. Devices in a microfluidic system include channels, valves, mixers, and pumps. Integration of these microfluidic devices enables sorting, transporting, and mixing of substances within fluids. However, the failure of moving parts in these systems is usually the critical issue and the main drawback. Mechanisms to control flow without using mechanical parts are always desired for reliability and lifetime.
In 1997, Wei, Bard and Feldberg discovered that ion rectification occurs at the tip of a nano-sized pipe. They observed that the surface charge at the wall of a nano-pipet induced a non-neutral electrical potential within the orifice. The electrical potential then modifies the concentration of ion species, resulting in an asymmetric current-voltage characteristic for the current through the pipet.
Transport of ions in the electrolyte can be adjusted by tuning the pH value in a dilute ionic solution, or by introducing an external electrical potential to change the surface charge density of the wall. As an analogy to semiconductor devices, the mechanism to control charge carrier transport in electronic devices was established in the area of nanofluidics. In nanofluidics, the active control of ion transport is realized using nano-scale channels or pores.
Research efforts on micro-scaled fluidic systems started to focus on the rectifying phenomena, which can be seen only in nano-scaled systems. In 2006, Professor Majumdar and Professor Yang in University of California, Berkeley built the first "nanofluidic" transistor. The transistor can be turn on or off by an external electrical signal, allowing the control of ionic fluids in a nano-scaled channel. Their work implies a possibility to create a nanofluidic circuitry with logic functions.
The main researchers in the area of nanofluidic devices include Arun Majumdar and Peidong Yang in University of California - Berkeley, Harold Craighead and Brian Kirbyat Cornell University, Juan Santiago at Stanford University, Albert van den Berg in University of Twente, Zuzanna Siwy in University of California - Irvine, and Mark Shannon in University of Illinois - Urbana-Champaign. | 7 | Physical Chemistry |
For the incompressible Arruda–Boyce model to be consistent with linear elasticity, with as the shear modulus of the material, the following condition has to be satisfied:
From the Arruda–Boyce strain energy density function, we have,
Therefore, at ,
Substituting in the values of leads to the consistency condition | 7 | Physical Chemistry |
Arctic sea ice has experienced an extreme reduction over the past few decades, with the minimum area of sea ice being 4.32 million km in 2019, a sharp 38% decrease from 1980, when the minimum area was 7.01 million km. Sea ice plays an important role in the health of the Arctic Ocean, and its decline has had detrimental effects on Arctic Ocean chemistry. All oceans equilibrate with the atmosphere by pulling carbon dioxide out of the atmosphere and into the ocean, which lowers the pH of the water. Sea ice limits the air-sea gas exchange with carbon dioxide by protecting the water from being completely exposed to the atmosphere. Low carbon dioxide levels are important to the Arctic Ocean due to intense cooling, fresh water runoff, and photosynthesis from marine organisms. Reductions in sea ice have allowed more carbon dioxide to equilibrate with the arctic water, resulting in increased acidification. The decrease in sea ice has also allowed more Pacific Ocean water to flow into in the Arctic Ocean during the winter, called Pacific winter water. Pacific Ocean water is high in carbon dioxide, and with decreased amounts of sea ice, more Pacific Ocean water has been able to enter the Arctic Ocean, carrying carbon dioxide with it. This Pacific winter water has further acidified the Arctic Ocean, as well as increased the depth of acidified water. | 9 | Geochemistry |
Robert Stirlings innovative contribution to the design of hot air engines of 1816 was what he called the Economiser'. Now known as the regenerator, it stored heat from the hot portion of the engine as the air passed to the cold side, and released heat to the cooled air as it returned to the hot side. This innovation improved the efficiency of the Stirling engine enough to make it commercially successful in particular applications, and has since been a component of every air engine that is called a Stirling engine. | 7 | Physical Chemistry |
The equivalent carbon content concept is used on ferrous materials, typically steel and cast iron, to determine various properties of the alloy when more than just carbon is used as an alloyant, which is typical. The idea is to convert the percentage of alloying elements other than carbon to the equivalent carbon percentage, because the iron-carbon phases are better understood than other iron-alloy phases. Most commonly this concept is used in welding, but it is also used when heat treating and casting cast iron. | 8 | Metallurgy |
Depending on how the experiment is carried out, DamID can be subject to plasmid methylation biases. Because plasmids are usually amplified in E. coli where Dam is naturally expressed, they are methylated on every GATC. In transient transfection experiments, the DNA of those plasmids is recovered along with the DNA of the transfected cells, meaning that fragments of the plasmid are amplified in the methyl PCR. Every sequence of the genome that shares homology or identity with the plasmid may thus appear to be bound by the protein of interest. In particular, this is true of the open reading frame of the protein of interest, which is present in both the plasmid and the genome. In microarray experiments, this bias can be used to ensure that the proper material was hybridized. In stable cell lines or fully transgenic animals, this bias is not observed as no plasmid DNA is recovered. | 1 | Biochemistry |
Before 1960, virtually all measurements of photoelectron kinetic energies were for electrons emitted from metals and other solid surfaces. In about 1956, Kai Siegbahn developed X-ray photoelectron spectroscopy (XPS) for surface chemical analysis. This method uses x-ray sources to study energy levels of atomic core electrons, and at the time had an energy resolution of about 1 eV (electronvolt).
The ultraviolet photoelectron spectroscopy (UPS) was pioneered by Feodor I. Vilesov, a physicist at St. Petersburg (Leningrad) State University in Russia (USSR) in 1961 to study the photoelectron spectra of free molecules in the gas phase. The early experiments used monochromatized radiation from a hydrogen discharge and a retarding potential analyzer to measure the photoelectron energies.
The PES was further developed by David W. Turner, a physical chemist at Imperial College in London and then at Oxford University, in a series of publications from 1962 to 1967. As a photon source, he used a helium discharge lamp which emits a wavelength of 58.4 nm (corresponding to an energy of 21.2 eV) in the vacuum ultraviolet region. With this source, Turner's group obtained an energy resolution of 0.02 eV. Turner referred to the method as "molecular photoelectron spectroscopy", now usually "ultraviolet photoelectron spectroscopy" or UPS. As compared to XPS, UPS is limited to energy levels of valence electrons, but measures them more accurately. After 1967, commercial UPS spectrometers became available. One of the latest commercial devices was the Perkin Elmer PS18. For the last twenty years, the systems have been homemade. One of the latest in progress - Phoenix II - is that of the laboratory of Pau, IPREM developed by Dr. Jean-Marc Sotiropoulos. | 7 | Physical Chemistry |
UV pinning is the process of applying a dose of low intensity ultraviolet (UV) light to a UV curable ink (UV ink). The lights wavelengths must be correctly matched to the inks photochemical properties. As a result, the ink droplets move to a higher viscosity state, but stop short of full cure. This is also referred to as the "gelling" of the ink.
UV pinning is typically used in UV ink jet applications (e.g. the printing of labels, the printing of electronics, and the fabrication of 3-D microstructures). | 5 | Photochemistry |
In the first step of the porphyrin biosynthesis pathway, porphobilinogen is generated from aminolevulinate (ALA) by the enzyme ALA dehydratase. | 1 | Biochemistry |
Biomonitoring involves the use of organisms to assess environmental contamination, such as of surrounding air or water. It can be done qualitatively by observing and noting changes in organisms, or quantitatively by measuring accumulation of chemicals in organism tissues. By observing or measuring the effects the environment has on its resident organisms, pollution may be suspected or inferred.
Historically, public health regulations have been based on theoretical risk calculations according to known levels of chemical substances in air, water, soil, food, other consumer products and other sources of potential exposure. Human biomonitoring offers the opportunity to analyze the actual internal levels of bodily substances from all potential routes of exposure at one time, which may contribute to improving risk assessments.
Scientific advancements have made it possible to detect a greater number of chemical substances in smaller concentrations in the body, with some chemicals detectable at levels as low as parts per trillion. A single biomonitoring measurement is only one snapshot in time and may not accurately reflect the level of exposure over longer periods.
The presence of an environmental chemical in the body does not necessarily indicate harm. The analytical chemistry of detecting chemicals has advanced more rapidly than the ability to interpret the potential health consequences. Health risks are usually established from toxicity studies in laboratory animals and epidemiological evidence in humans. Lead is a well studied chemical with a CDC action level of concern, currently at 10 µg/dL, or 100 parts per billion, in blood; however, neurobehavioral impairment has been noted below this level. Because this approach requires establishment of cause and effect in epidemiological studies and a thorough understanding of human dose response, data to support these types of action levels exist for only a few environmental chemicals. The concept of Biomonitoring Equivalents (BEs) has been developed as an alternative approach to aid in interpreting and communicating biomonitoring results in the context of potential risks to health.
There are different types of biomarkers that indicate exposure, effect, or susceptibility. | 2 | Environmental Chemistry |
Photoactive catalysts have been introduced over the last decade, such as and ZnO nano rodes. Most suffer from the fact that they can only perform under UV irradiation due to their band structure. Other photocatalysts, including a graphene-ZnO nanocompound counter this problem. | 5 | Photochemistry |
The applications of photophoresis expand into the various divisions of science, thus physics, chemistry as well as in biology. Photophoresis is applied in particle trapping and levitation, in the field flow fractionation of particles, in the determination of thermal conductivity and temperature of microscopic grains and also in the transport of soot particles in the atmosphere. The use of light in the separation of particles aerosols based on their optical properties, makes possible the separation of organic and inorganic particles of the same aerodynamic size.
Recently, photophoresis has been suggested as a chiral sorting mechanism for single walled carbon nanotubes. The proposed method would utilise differences in the absorption spectra of semiconducting carbon nanotubes arising from optically excited transitions in electronic structure. If developed the technique would be orders of magnitudes faster than currently established ultracentrifugation techniques.
In 2021 Azadi, Popov et al. report "light-driven levitation of macroscopic polymer films with nanostructured surface as candidates for long-duration near-space flight" Using a light intensity comparable to sunlight, they levitated centimeter-scale disks made of commercial 0.5-micron-thick mylar film coated with carbon nanotubes on one side. Experiments by Schafer, Kim, Vlassak and Keith suggest that photophoretic forces could levitate thin 10 centimetre-scale structures in Earth′s stratosphere indefinitely for the purpose of atmospheric science, especially monitoring high-altitude weather. They describe in 2022 a preliminary design fabricated with available methods of a 10 cm diameter device combining a levitating structure of two membranes 2 μm apart in a stiff support structure tested to have sufficient strength to withstand transport, deployment, and flight at 25 km altitude. Payload capacity is 300 mg and could support bidirectional radio communication at over 10 Mb/s and some navigational control. By upscaling the structure it might carry payloads of a few grams. They suggest uses for telecommunications, and deployment on Mars. | 7 | Physical Chemistry |
Compressor performance changes, day to day, with changes in the ambient pressure and temperature. Woolenweber shows the change in performance of a turbocharger compressor when the inlet temperature varies between 70 and 100 deg F. In the case of aircraft compressors, inlet pressure and temperature also change with altitude and airspeed. The presentation of different performance for every combination of inlet temperature and pressure would be unmanageable but it is possible to collapse it all onto a single map, which is applicable to a wide range of inlet conditions, using dimensional analysis. In dimensional analysis individual quantities such as rotor speed, mass flow and delivery pressure are each grouped with other relevant quantities in such a way that the groups have no dimensions but still have a physical meaning. For example rotor speed , inlet temperature , compressor diameter and gas properties and are grouped together as dimensionless which is equivalent to the blade mach number.
Parameter groups which are used as the basis for gas turbine engine compressor maps are total-pressure ratio (P/P), <math>w
\sqrt{\gamma \ R \ T}/{AP} and efficiency. , for example, is simplified below while still being representative of mach number. Maps for other applications use head or discharge pressure and volume flow.
For a particular compressor and gas the flow and speed groups are simplified, by deleting the terms which are constant for a particular compressor and application, namely compressor dimensions and gas properties , , and . They are named pseudo-non-dimensional parameters and .
A final step is to give the pseudo-non-dimensional parameters standard units for mass flow and speed and more recognizable numerical values by applying pressure and temperature ratio correction factors, also derived as part of the dimensional analysis.
The corrected parameters are and . They have the same units as the original observed values and are corrected to agreed standard conditions, the International Standard Atmosphere at sea level (ISA SL). Alternatively they may be shown relative to the design value where the design value is specified as either 100% or 1.0.
The fuel burned in a gas turbine engine sets the compressor running line and also has to be used in non-dimensional form to show its effect on engine operation. It is used as a ratio with combustor pressure when shown on a compressor map. Corrected fuel flow is shown as . Although both air and fuel are flows of fluid their non-dimensional parameters are different, and , because non-dimensional airflow is a form of fluid Mach number while fuel is flow of an incompressible energy source. The dimensions of airflow are M/t and those of fuel-flow are ML/t, where M, L and t are mass, length and time.
Fuel flow is also shown on a compressor map, but in the form of its effect, ie turbine inlet temperature. This effect is shown, again non-dimensionally, as the ratio of turbine inlet temperature to compressor inlet temperature, and known as engine temperature ratio. Grandcoing shows the constant temperature lines crossed as a helicopter compressor goes from no-load to full-load with increasing fuel flow. | 7 | Physical Chemistry |
The impact of an ethanol-based universal indicator may seem negligible at first glance. However, in the case of dilute solutions prepared with bidistilled water, this influence becomes readily discernible and measurable. [https://github.com/ddiesing/universal_indicator_conductivity/blob/main/indicator_conc_conduct.csv] | 3 | Analytical Chemistry |
NCOA6 has been shown to interact with:
* ASCL2 and
* Activating transcription factor 2,
* Androgen receptor,
* CREB-binding protein,
* DNA-PKcs,
* E2F1,
* EP300,
* Estrogen receptor alpha,
* Estrogen receptor beta,
* HBXIP,
* HIST2H3C,
* HSF1,
* Ku70,
* Ku80,
* Liver X receptor beta,
* MLL3,
* RBBP5,
* Retinoblastoma protein,
* Retinoic acid receptor alpha,
* Retinoid X receptor alpha,
* Src,
* TGS1,
* TUBA4A,
* TUBB,
* Thyroid hormone receptor alpha, and
* Thyroid hormone receptor beta. | 1 | Biochemistry |
Bisulfite sequencing applies routine sequencing methods on bisulfite-treated genomic DNA to determine methylation status at CpG dinucleotides. Other non-sequencing strategies are also employed to interrogate the methylation at specific loci or at a genome-wide level. All strategies assume that bisulfite-induced conversion of unmethylated cytosines to uracil is complete, and this serves as the basis of all subsequent techniques. Ideally, the method used would determine the methylation status separately for each allele. Alternative methods to bisulfite sequencing include Combined Bisulphite Restriction Analysis and methylated DNA immunoprecipitation (MeDIP).
Methodologies to analyze bisulfite-treated DNA are continuously being developed. To summarize these rapidly evolving methodologies, numerous review articles have been written.
The methodologies can be generally divided into strategies based on methylation-specific PCR (MSP) (Figure 4), and strategies employing polymerase chain reaction (PCR) performed under non-methylation-specific conditions (Figure 3). Microarray-based methods use PCR based on non-methylation-specific conditions also. | 1 | Biochemistry |
There are at least five hormones that aid and regulate the digestive system in mammals. There are variations across the vertebrates, as for instance in birds. Arrangements are complex and additional details are regularly discovered. Connections to metabolic control (largely the glucose-insulin system) have been uncovered.
* Gastrin – is in the stomach and stimulates the gastric glands to secrete pepsinogen (an inactive form of the enzyme pepsin) and hydrochloric acid. Secretion of gastrin is stimulated by food arriving in stomach. The secretion is inhibited by low pH.
* Secretin – is in the duodenum and signals the secretion of sodium bicarbonate in the pancreas and it stimulates the bile secretion in the liver. This hormone responds to the acidity of the chyme.
* Cholecystokinin (CCK) – is in the duodenum and stimulates the release of digestive enzymes in the pancreas and stimulates the emptying of bile in the gall bladder. This hormone is secreted in response to fat in chyme.
* Gastric inhibitory peptide (GIP) – is in the duodenum and decreases the stomach churning in turn slowing the emptying in the stomach. Another function is to induce insulin secretion.
* Motilin – is in the duodenum and increases the migrating myoelectric complex component of gastrointestinal motility and stimulates the production of pepsin. | 1 | Biochemistry |
Biochemical differences between different organisms and humans are useful for drug development. For instance, penicillin kills bacteria by inhibiting the bacterial enzyme DD-transpeptidase, destroying the development of the bacterial cell wall and inducing cell death. Thus, the study of binding sites is relevant to many fields of research, including cancer mechanisms, drug formulation, and physiological regulation. The formulation of an inhibitor to mute a protein's function is a common form of pharmaceutical therapy.
In the scope of cancer, ligands that are edited to have a similar appearance to the natural ligand are used to inhibit tumor growth. For example, Methotrexate, a chemotherapeutic, acts as a competitive inhibitor at the dihydrofolate reductase active site. This interaction inhibits the synthesis of tetrahydrofolate, shutting off production of DNA, RNA and proteins. Inhibition of this function represses neoplastic growth and improves severe psoriasis and adult rheumatoid arthritis.
In cardiovascular illnesses, drugs such as beta blockers are used to treat patients with hypertension. Beta blockers (β-Blockers) are antihypertensive agents that block the binding of the hormones adrenaline and noradrenaline to β1 and β2 receptors in the heart and blood vessels. These receptors normally mediate the sympathetic "fight or flight" response, causing constriction of the blood vessels.
Competitive inhibitors are also largely found commercially. Botulinum toxin, known commercially as Botox, is a neurotoxin that causes flaccid paralysis in the muscle due to binding to acetylcholine dependent nerves. This interaction inhibits muscle contractions, giving the appearance of smooth muscle. | 1 | Biochemistry |
Typical arene tricarbonyl piano stool complexes of Mn(I) and Re(I) are cationic and thus exhibit enhanced reactivity toward nucleophiles. Subsequent to nucleophilic addition, the modified arene can be recovered from the metal. | 0 | Organic Chemistry |
The Graduate Institute of Ferrous Technology has nine laboratories with key areas of expertise:
* [https://web.archive.org/web/20110728031933/http://www.postech.ac.kr/mse/axal/ Alternative Technology Lab]:
**Continuous casting-related innovation
**Texture control
**Alternative alloying and processing
* [https://web.archive.org/web/20100325004541/http://controllab.postech.ac.kr/ Control and Automation Lab]:
**Computer control system
**Process automation
**Control theory & Applications
**Measurement
* [http://gift.webteem.co.kr/jdboard/club/main.php?page=club&code=csl&group_a=csl Clean Steel Lab]:
**Thermochemistry
**Physico-chemical properties
**Fluid dynamics
**Solidification and casting
* Environmental Metallurgy Lab:
**Reduction of CO emission
**Improvement of energy efficiency
**Gas alloying technology
* [http://cml.postech.ac.kr/ Computational Metallurgy Lab]:
**Classical modeling and experiments
**Phase field modeling and experiments
**First principle calculation, quantum mechanical modeling
* Microstructure Control Lab:
**Phase transformation / electron microscopy
**Microscopic deformation behavior
**Toughness enhancement via microstructure control
**Innovative processing (e.g., twin-roll casting)
* Materials Design Lab:
**[http://www.worldsteel.org/?action=storypages&id=242 Automotive Steels], Galvanized/Galvannealed Products
**Electrical Steels
**Stainless steels
**Steel grades related to power generation
* [http://mml.postech.ac.kr/ Materials Mechanics Lab]:
**Net Shape Forming (sheet forming, other forming)
**Performance in service (fracture, crashworthiness, fatigue)
* [http://sel.postech.ac.kr/ Surface Engineering Lab]:
**Composite coatings
** Corrosion mechanism & lifetime prediction
**Corrosion resistant alloy design
**Metallic coatings | 8 | Metallurgy |
When stored in the presence of air or oxygen, ethers tend to form explosive peroxides, such as diethyl ether hydroperoxide. The reaction is accelerated by light, metal catalysts, and aldehydes. In addition to avoiding storage conditions likely to form peroxides, it is recommended, when an ether is used as a solvent, not to distill it to dryness, as any peroxides that may have formed, being less volatile than the original ether, will become concentrated in the last few drops of liquid. The presence of peroxide in old samples of ethers may be detected by shaking them with freshly prepared solution of a ferrous sulfate followed by addition of KSCN. Appearance of blood red color indicates presence of peroxides. The dangerous properties of ether peroxides are the reason that diethyl ether and other peroxide forming ethers like tetrahydrofuran (THF) or ethylene glycol dimethyl ether (1,2-dimethoxyethane) are avoided in industrial processes. | 0 | Organic Chemistry |
In computational biology, protein pK calculations are used to estimate the pK values of amino acids as they exist within proteins. These calculations complement the pK values reported for amino acids in their free state, and are used frequently within the fields of molecular modeling, structural bioinformatics, and computational biology. | 7 | Physical Chemistry |
Threonine proteases use the amino acid threonine as their catalytic nucleophile. Unlike cysteine and serine, threonine is a secondary hydroxyl (i.e. has a methyl group). This methyl group greatly restricts the possible orientations of triad and substrate as the methyl clashes with either the enzyme backbone or histidine base. When the nucleophile of a serine protease was mutated to threonine, the methyl occupied a mixture of positions, most of which prevented substrate binding. Consequently, the catalytic residue of a threonine protease is located at its N-terminus.
Two evolutionarily independent enzyme superfamilies with different protein folds are known to use the N-terminal residue as a nucleophile: Superfamily PB (proteasomes using the Ntn fold) and Superfamily PE (acetyltransferases using the DOM fold) This commonality of active site structure in completely different protein folds indicates that the active site evolved convergently in those superfamilies.
Families of threonine proteases | 1 | Biochemistry |
The current production method includes two reaction steps with potentially hazardous azides. A reported azide-free Roche synthesis of tamiflu is summarised graphically below:
The synthesis commences from naturally available (−)-shikimic acid. The 3,4-pentylidene acetal mesylate is prepared in three steps: esterification with ethanol and thionyl chloride; ketalization with p-toluenesulfonic acid and 3-pentanone; and mesylation with triethylamine and methanesulfonyl chloride. Reductive opening of the ketal under modified Hunter conditions in dichloromethane yields an inseparable mixture of isomeric mesylates. The corresponding epoxide is formed under basic conditions with potassium bicarbonate. Using the inexpensive Lewis acid magnesium bromide diethyl etherate (commonly prepared fresh by the addition of magnesium
turnings to 1,2-dibromoethane in benzene:diethyl ether), the epoxide is opened with allyl amine to yield the corresponding 1,2-amino alcohol. The water-immiscible solvents methyl tert-butyl ether and acetonitrile are used to simplify the workup procedure, which involved stirring with 1 M aqueous ammonium sulfate. Reduction on palladium, promoted by ethanolamine, followed by acidic workup yielded the deprotected 1,2-aminoalcohol. The aminoalcohol was converted directly to the corresponding allyl-diamine in an interesting cascade sequence that commences with the unselective imination of benzaldehyde with azeotropic water removal in methyl tert-butyl ether. Mesylation, followed by removal of the solid byproduct triethylamine hydrochloride, results in an intermediate that was poised to undergo aziridination upon transimination with another equivalent of allylamine. With the librated methanesulfonic acid, the
aziridine opens cleanly to yield a diamine that immediately undergoes a second transimination. Acidic hydrolysis then removed the imine. Selective acylation with acetic anhydride (under buffered conditions, the 5-amino group is protonated owing to a considerable difference in pK, 4.2 vs 7.9, preventing acetylation) yields the desired N-acetylated product in crystalline form upon extractive workup. Finally, deallylation as above, yielded the freebase of oseltamivir, which was converted to the desired oseltamivir phosphate by treatment with phosphoric acid. The final product is obtained in high purity (99.7%) and an overall yield of 17-22% from (−)-shikimic acid. It is noted that the synthesis avoids the use of potentially explosive azide reagents and intermediates; however, the synthesis actually used by Roche uses azides. Roche has other routes to
oseltamivir that do not involve the use of (−)-shikimic acid as a chiral pool starting material, such as a Diels-Alder route involving furan and ethyl acrylate or an isophthalic acid route, which involves catalytic hydrogenation and enzymatic desymmetrization. | 0 | Organic Chemistry |
During the 1950s, Bernard Katz and Paul Fatt observed spontaneous miniature synaptic currents at the frog neuromuscular junction. Based on these observations, they developed the quantal hypothesis that is the basis for our current understanding of neurotransmitter release as exocytosis and for which Katz received the Nobel Prize in Physiology or Medicine in 1970. In the late 1960s, Ricardo Miledi and Katz advanced the hypothesis that depolarization-induced influx of calcium ions triggers exocytosis.
Sir Charles Scott Sherringtonin coined the word synapse and the history of the word was given by Sherrington in a letter he wrote to John Fulton: | 1 | Biochemistry |
Recently, Gregory Fu and colleagues reported a modification of their earlier kinetic resolution work to produce an effective dynamic kinetic resolution. Using the ruthenium racemization catalyst shown to the right, and his planar chiral DMAP catalyst, Fu has demonstrated the dynamic kinetic resolution of secondary alcohols yielding up to 99% and 93% ee, as shown below. Work is ongoing to further develop the applications of the widely used DMAP catalyst to dynamic kinetic resolution. | 4 | Stereochemistry |
Chloroplasts make all of a cell's purines and pyrimidines—the nitrogenous bases found in DNA and RNA. They also convert nitrite (NO) into ammonia (NH) which supplies the plant with nitrogen to make its amino acids and nucleotides. | 5 | Photochemistry |
Bases: adenine (A), cytosine (C), guanine (G) and thymine (T) or uracil (U).
Amino acids: Alanine (Ala, A), Arginine (Arg, R), Asparagine (Asn, N), Aspartic acid (Asp, D), Cysteine (Cys, C), Glutamic acid (Glu, E), Glutamine (Gln, Q), Glycine (Gly, G), Histidine (His, H), Isoleucine (Ile, I), Leucine (Leu, L), Lysine (Lys, K), Methionine (Met, M), Phenylalanine (Phe, F), Proline (Pro, P), Serine (Ser, S), Threonine (Thr, T), Tryptophan (Trp, W), Tyrosine (Tyr, Y), and Valine (Val, V). | 1 | Biochemistry |
*Rutherford Memorial Medal (2009)
*OMCOS Award (2009)
*Sloan Research Fellowship (2008)
*Merck Process Award (2008)
*Eli Lilly Grantee (2007–2009)
*NSERC Discovery Accelerator Supplement Award (2007–2009)
*Amgen Young Investigator's Award (2007)
*Astra Zeneca Award for Chemistry (2007)
*University of Ottawa Research Chair in Novel Catalytic Transformations (2007–2012)
*Merck Process Research Award (2007)
*University of Ottawa Young Researcher of the Year (2006)
*Ichikizaki Travel Grant Award (2006)
*Boehringer Ingelheim Young Investigator Award in Organic Chemistry (2005)
*Cottrell Scholar Award (2005)
*Ichikizaki Travel Grant Award (2005)
*Premier's Research Excellence Award (2003)
*John C. Polanyi Award in Chemistry (2003) | 0 | Organic Chemistry |
Wood dust is known to be a human carcinogen, based on sufficient evidence of carcinogenicity from studies in humans. It has been demonstrated through human epidemiologic studies that exposure to wood dust increases the occurrence of cancer of the nose (nasal cavities and paranasal sinuses). An association of wood dust exposure and cancers of the nose has been observed in numerous case reports, cohort studies, and case control studies specifically addressing nasal cancer. | 2 | Environmental Chemistry |
CrysTBox is freely available on demand for non-commercial use by non-commercial subjects. The only safe way to download CrysTBox installers is via a request form on the official website. Commercial use is not allowed due to the license of MATLAB used for CrysTBox compilation. | 3 | Analytical Chemistry |
Zuclopenthixol antagonises both dopamine D and D receptors, α-adrenoceptors and 5-HT receptors with a high affinity, but has no affinity for muscarinic acetylcholine receptors. It weakly antagonises the histamine (H) receptor but has no α-adrenoceptor blocking activity .
Evidence from in vitro work and clinical sources (i.e. therapeutic drug monitoring databases) suggests that both CYP2D6 and CYP3A4 play important roles in zuclopenthixol metabolism. | 4 | Stereochemistry |
In the United States, sperm banks maintain lists or catalogs of donors which provide basic information about the donor such as racial origin, skin color, height, weight, color of eyes, and blood group. Some of these catalogs are available for browsing on the Internet, while others are made available to patients only when they apply to a sperm bank for treatment. Some sperm banks make additional information about each donor available for an additional fee, and others make additional basic information known to children produced from donors when those children reach the age of 18. Some clinics offer "exclusive donors" whose sperm is used to produce pregnancies for only one recipient woman. How accurate this is, or can be, is not known, and neither is it known whether the information produced by sperm banks, or by the donors themselves, is true. Many sperm banks will, however, carry out whatever checks they can to verify the information they request, such as checking the identity of the donor and contacting his own doctor to verify medical details.
In the United Kingdom, most donors are anonymous at the point of donation and recipients can see only non-identifying information about their donor (height, weight, ethnicity etc.). Donors need to provide identifying information to the clinic and clinics will usually ask the donors doctor to confirm any medical details they have been given. Donors are asked to provide a pen portrait of themselves which is held by the HFEA and can be obtained by the adult conceived from the donation at the age of 18, along with identifying information such as the donors name and last known address. Known donation is permitted and it is not uncommon for family or friends to donate to a recipient couple.
Qualities that potential recipients typically prefer in donors include the donors being tall, college educated, and with a consistently high sperm count.
A review came to the result that 68% of donors had given information to the clinical staff regarding physical characteristics and education but only 16% had provided additional information such as hereditary aptitudes and temperament or character. | 1 | Biochemistry |
* Journal of Agricultural and Food Chemistry
* Journal of the American Oil Chemists Society'
* [http://www.elsevier.com/wps/find/journaldescription.cws_home/522499/description#description Biophysical Chemistry journal]
* Magnetic Resonance in Chemistry
* Starke/ Starch Journal
* [http://journalofdairyscience.org/ Journal of Dairy Science (JDS)]
* Chemical Physics Letters
* Zeitschrift für Physikalische Chemie (1887)
* Biopolymers
* Journal of Food Science (IFT, USA)
* [http://www.wiley.com/bw/journal.asp?ref=0950-5423 International Journal of Food Science & Technology]
* Macromolecular Chemistry and Physics (1947)
* [http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1097-0010 Journal of the Science of Food and Agriculture]
* [http://www.polyacs.org/11.html Polymer Preprints] (ACS)
* [http://pubs.rsc.org/en/journals/journalissues/ib Integrative Biology] Journal of the Royal Society of Chemistry
* [http://pubs.rsc.org/en/journals/journalissues/ob Organic & Biomolecular Chemistry] (An RSC Journal)
* Nature
** Nature Precedings
* Journal of Biological Chemistry
* Proceedings of the National Academy of Sciences of the United States of America | 7 | Physical Chemistry |
HPTLC comprises three modes: linear mode, circular mode, and anticircular mode. Among these modes, the anticircular mode stands out as the fastest in theory and practice within the realm of HPTLC. This mode achieves separation by allowing the mobile phase to enter the plate layer precisely along an outer circular path, after which it flows toward the center at a nearly constant speed. This approach maximizes sample capacity while minimizing time, layer, and mobile phase consumption, making it the most cost-effective HPTLC technique. The narrow spot-path unique to anticircular HPTLC facilitates automated quantification. When compared to the linear and circular modes, the anticircular mode demonstrates superior separation and significantly heightened sensitivity, especially at higher Rf-values. | 3 | Analytical Chemistry |
In organic chemistry, organic peroxides are organic compounds containing the peroxide functional group (). If the R′ is hydrogen, the compounds are called hydroperoxides, which are discussed in that article. The O−O bond of peroxides easily breaks, producing free radicals of the form (the dot represents an unpaired electron). Thus, organic peroxides are useful as initiators for some types of polymerization, such as the acrylic, unsaturated polyester, and vinyl ester resins used in glass-reinforced plastics. MEKP and benzoyl peroxide are commonly used for this purpose. However, the same property also means that organic peroxides can explosively combust. Organic peroxides, like their inorganic counterparts, are often powerful bleaching agents. | 0 | Organic Chemistry |
Thomas Gilbert Henry Jones (1895–1970) was an Australian organic chemist and academic, notable for his pioneering work in the field of essential oils from Queensland flora natural products. | 0 | Organic Chemistry |
* Ewald, M., Fechner, P. & Gauglitz, G. Anal Bioanal Chem (2015) 407: 4005. doi:10.1007/s00216-015-8562-0
* Bleher, O., Schindler, A., Yin, MX. et al. Anal Bioanal Chem (2014) 406: 3305. doi:10.1007/s00216-013-7504-y
* Schindler, A., Bleher, O., Thaler, M., et al. (2014). Diagnostic performance study of an antigen microarray for the detection of antiphospholipid antibodies in human serum. Clinical Chemistry and Laboratory Medicine, 53(5), pp. 801–808. Retrieved 2 Mar. 2017, from doi:10.1515/cclm-2014-0569
* Ewald, M., Le Blanc, A.F., Gauglitz, G. et al. Anal Bioanal Chem (2013) 405: 6461. doi:10.1007/s00216-013-7040-9
* Rüdiger Frank ; Bernd Möhrle ; Dieter Fröhlich and Günter Gauglitz, "A transducer-independent optical sensor system for the detection of biochemical binding reactions", Proc. SPIE 5993, Advanced Environmental, Chemical, and Biological Sensing Technologies III, 59930A (November 8, 2005); doi:10.1117/12.633881; https://dx.doi.org/10.1117/12.633881
* SLAS Technol. 2017 Aug;22(4):437-446. doi: 10.1177/2211068216657512. Low-Volume Label-Free Detection of Molecule-Protein Interactions on Microarrays by Imaging Reflectometric Interferometry. Burger J, Rath C, Woehrle J, Meyer PA, Ben Ammar N, Kilb N, Brandstetter T, Pröll F, Proll G, Urban G, Roth G. | 7 | Physical Chemistry |
IPM is used in agriculture, horticulture, forestry, human habitations, preventive conservation of cultural property and general pest control, including structural pest management, turf pest management and ornamental pest management. IPM practices help to prevent and slow the development of resistance, known as resistance management. | 9 | Geochemistry |
The molecule malabaricane and its derivatives, the malabaricanes, are triterpene and triterpenoid compounds found in various organisms. They are named after the rain forest tree Ailanthus malabarica (Ailanthus triphysa), from which they were first isolated in 1967 by scientists at the National Chemical Laboratory in Pune, India. Later, great varieties of malabaricanes were discovered in other organisms, mostly in marine sponges such as Rhabdastrella globostellata.
Isomalabaricanes are malabaricanes in which the three carbon rings of the molecule are connected in trans−syn−trans conformation, as opposed to other malabaricanes, where the rings are connected in trans−anti−trans conformation. They are of particular research interest because many of them have been reported to show anti-tumour activity in cell culture. | 1 | Biochemistry |
Every two anomers are designated alpha (α) or beta (β), according to the configurational relationship between the anomeric centre and the anomeric reference atom, hence they are relative stereodescriptors. The anomeric centre in hemiacetals is the anomeric carbon C-1; in hemiketals, it is the carbon derived from the carbonyl of the ketone (e.g. C-2 in -fructose). In aldohexoses the anomeric reference atom is the stereocenter that is farthest from anomeric carbon in the ring (the configurational atom, defining the sugar as or ). For example, in α--glucopyranose the reference atom is C-5.
If in the cyclic Fischer projection the exocyclic oxygen atom at the anomeric centre is cis (on the same side) to the exocyclic oxygen attached to the anomeric reference atom (in the OH group) the anomer is α. If the two oxygens are trans (on different sides) the anomer is β. Thus, the absolute configurations of the anomeric carbon and the reference atom are the same (both R or both S) in the α anomer and opposite (one R and the other S) in the β anomer. | 4 | Stereochemistry |
The reagent is prepared by dissolving 0.5–2.0 g of p–dimethylaminobenzaldehyde (DMAB) in 50 mL of 95% ethanol and 50 mL of concentrated hydrochloric acid and is best used when fresh. Other alcohols, such as 1-propanol, can also be used as well.
The Ehrlich reagent is similar to a number of other indole tests:
* The van Urk reagent, which uses 0.125 g of p-DMAB, 0.2 mL of ferric chloride solution (25 mg/mL) in 100 mL of 65% sulfuric acid. This is sometimes referred to as the Hofmann reagent or p-DMAB-TS (Test Solution) and gives slightly different colours with different indoles.
* The Renz and Loew reagent, which uses p-dimethylaminocinnamaldehyde and may also be used for the detection of flavonoids.
* The "improved hallucinogen reagent", which uses a 1:1 solution of 5% DMAB in concentrated phosphoric acid (specific gravity 1.45) to methanol. | 3 | Analytical Chemistry |
Three proteinaceous iron–sulfur reaction centers are found in PSI. Labeled F, F, and F, they serve as electron relays. F and F are bound to protein subunits of the PSI complex and F is tied to the PSI complex. Various experiments have shown some disparity between theories of iron–sulfur cofactor orientation and operation order. In one model, F passes an electron to F, which passes it on to F to reach the ferredoxin. | 5 | Photochemistry |
(Bis(trifluoroacetoxy)iodo)benzene, , is a hypervalent iodine compound used as a reagent in organic chemistry. It can be used to carry out the Hofmann rearrangement under acidic conditions. | 0 | Organic Chemistry |
CoQ taken as a pharmacological substance has potential to inhibit the effects of theophylline as well as the anticoagulant warfarin; CoQ may interfere with warfarins actions by interacting with cytochrome p450 enzymes thereby reducing the INR, a measure of blood clotting. The structure of CoQ is similar to that of vitamin K, which competes with and counteracts warfarins anticoagulation effects. CoQ is not recommended in people taking warfarin due to the increased risk of clotting. | 1 | Biochemistry |
Major greenhouse gases are well mixed and take many years to leave the atmosphere.
The atmospheric lifetime of a greenhouse gas refers to the time required to restore equilibrium following a sudden increase or decrease in its concentration in the atmosphere. Individual atoms or molecules may be lost or deposited to sinks such as the soil, the oceans and other waters, or vegetation and other biological systems, reducing the excess to background concentrations. The average time taken to achieve this is the mean lifetime. This can be represented through the following formula, where the lifetime of an atmospheric species X in a one-box model is the average time that a molecule of X remains in the box.
can also be defined as the ratio of the mass (in kg) of X in the box to its removal rate, which is the sum of the flow of X out of the box
chemical loss of X
and deposition of X
(all in kg/s):
If input of this gas into the box ceased, then after time , its concentration would decrease by about 63%.
Changes to any of these variables can alter the atmospheric lifetime of a greenhouse gas. For instance, methanes atmospheric lifetime is estimated to have been lower in the 19th century than now, but to have been higher in the second half of the 20th century than after 2000. Carbon dioxide has an even more variable lifetime, which cannot be specified down to a single number. Scientists instead say that while the first 10% of carbon dioxides airborne fraction (not counting the ~50% absorbed by land and ocean sinks within the emission's first year) is removed "quickly", the vast majority of the airborne fraction – 80% – lasts for "centuries to millennia". The remaining 10% stays for tens of thousands of years. In some models, this longest-lasting fraction is as large as 30%. | 2 | Environmental Chemistry |
First developed in 1836 by Danish archaeologist Christian Jürgensen Thomsen as a part of his "Three-age system", the term "Bronze Age" is used by archaeologists to refer to those societies which have developed bronze technology but not yet learned how to work the more complicated process involved in making iron objects. The European Bronze Age lasted from , when the Aegean civilizations of Greece first developed bronze technology, right through to , when the Nordic Bronze Age came to an end with the development of iron among Scandinavian communities.
The period known by archaeologists as Bronze Age Britain lasted from through to , and was defined by the adoption of copper and bronze technologies on the island. Bronze Age Ireland followed a similar, yet distinct course.
The Early Bronze Age in the British Isles was marked by the adoption of what archaeologists call the "Beaker culture", which had arrived from continental Europe. Eogan noted that the "evidence from archaeology is that Beaker-using communities were the earliest metallurgists in Britain and Ireland", with their produce including "copper artefacts such as tanged daggers but also gold objects as well as the use of gold for embellishment." | 8 | Metallurgy |
Digestion is the breakdown of large insoluble food compounds into small water-soluble components so that they can be absorbed into the blood plasma. In certain organisms, these smaller substances are absorbed through the small intestine into the blood stream. Digestion is a form of catabolism that is often divided into two processes based on how food is broken down: mechanical and chemical digestion. The term mechanical digestion refers to the physical breakdown of large pieces of food into smaller pieces which can subsequently be accessed by digestive enzymes. Mechanical digestion takes place in the mouth through mastication and in the small intestine through segmentation contractions. In chemical digestion, enzymes break down food into the small compounds that the body can use.
In the human digestive system, food enters the mouth and mechanical digestion of the food starts by the action of mastication (chewing), a form of mechanical digestion, and the wetting contact of saliva. Saliva, a liquid secreted by the salivary glands, contains salivary amylase, an enzyme which starts the digestion of starch in the food. The saliva also contains mucus, which lubricates the food; the electrolyte hydrogencarbonate (), which provides the ideal conditions of pH for amylase to work; and other electrolytes (, , ). About 30% of starch is hydrolyzed into disaccharide in the oral cavity (mouth). After undergoing mastication and starch digestion, the food will be in the form of a small, round slurry mass called a bolus. It will then travel down the esophagus and into the stomach by the action of peristalsis. Gastric juice in the stomach starts protein digestion. Gastric juice mainly contains hydrochloric acid and pepsin. In infants and toddlers, gastric juice also contains rennin to digest milk proteins. As the first two chemicals may damage the stomach wall, mucus and bicarbonates are secreted by the stomach. They provide a slimy layer that acts as a shield against the damaging effects of chemicals like concentrated hydrochloric acid while also aiding lubrication. Hydrochloric acid provides acidic pH for pepsin. At the same time protein digestion is occurring, mechanical mixing occurs by peristalsis, which is waves of muscular contractions that move along the stomach wall. This allows the mass of food to further mix with the digestive enzymes. Pepsin breaks down proteins into peptides or proteoses, which is further broken down into dipeptides and amino acids by enzymes in the small intestine. Studies suggest that increasing the number of chews per bite increases relevant gut hormones and may decrease self-reported hunger and food intake.
When the pyloric sphincter valve opens, partially digested food (chyme) enters the duodenum where it mixes with digestive enzymes from the pancreas and bile juice from the liver and then passes through the small intestine, in which digestion continues. When the chyme is fully digested, it is absorbed into the blood. 95% of nutrient absorption occurs in the small intestine. Water and minerals are reabsorbed back into the blood in the colon (large intestine) where the pH is slightly acidic (about 5.6 ~ 6.9). Some vitamins, such as biotin and vitamin K (KMK7) produced by bacteria in the colon are also absorbed into the blood in the colon. Absorption of water, simple sugar and alcohol also takes place in stomach. Waste material (feces) is eliminated from the rectum during defecation. | 1 | Biochemistry |
Japan, which had permitted its feed additive use at least until 2009, and South Korea only allow import of meat with ractopamine residues up to the maximum residue limit (MRL), but do not permit its use in beef production. | 4 | Stereochemistry |
In Sweden, it is legal to produce fermented water and there is no upper limit on the alcohol volume produced from the yeast. | 1 | Biochemistry |
Ca currents through cardiomyocyte gap junctions mediate synchronized contraction of cardiac tissue. As a result, GCaMP expression in cardiomyocytes, both in vitro and in vivo, has been used to study Ca-influx-dependent excitation and contraction in zebrafish and mice. For instance, Tallini et al. (2006) expressed GCaMP2 in mouse embryos to show that, at embryonic day 10.5, electrical conduction was rapid in the atria and ventricles but slow in the atrioventricular canal. Chi et al. (2008) used a transgenic cardiac-specific GCaMP zebrafish line to image cardiomyocyte activation throughout the cardiac cycle; from their results, they characterized four developmental stages of the zebrafish cardiac conduction system and identified 17 novel mutations affecting cardiac conduction. However, uncontrolled expression of GCaMP leads to cardiac hypertrophy due to overexpression of the calmodulin motif, which interferes with intracellular calcium signaling. As a result, experiments using cardiac tissue should carefully control the level of GCaMP expression. | 1 | Biochemistry |
Sarıçiftçi specializes in the field of organic semiconductors and their applications. In particular, he has worked in the field of organic solar cells. Chemical energy storage of solar energy by means of CO recycling recycling is in its research increasingly important. | 7 | Physical Chemistry |
LAs may enhance the effects of depolarisation and nondepolarising NMBAs through pre and post-synaptic interactions at the NMJ. It may result in blood levels high enough to potentiate NMBA-induced neuromuscular block. Epidurally administered levobupivacaine and mepivacaine potentiate amino-steroidal NMBAs and delay recovery from neuromuscular blockade. | 1 | Biochemistry |
On this scale, pure HSO (18.4 M) has a H value of −12, and pyrosulfuric acid has H ~ −15. Take note that the Hammett acidity function clearly avoids water in its equation. It is a generalization of the pH scale—in a dilute aqueous solution (where B is HO), pH is very nearly equal to H. By using a solvent-independent quantitative measure of acidity, the implications of the leveling effect are eliminated, and it becomes possible to directly compare the acidities of different substances (e.g. using pK, HF is weaker than HCl or HSO in water but stronger than HCl in glacial acetic acid.)
H for some concentrated acids:
* Helonium: −63
* Fluoroantimonic acid (1990): −23 > H > −28
* Magic acid (1974): −23
* Carborane superacids: H < −18.0
* Fluorosulfuric acid (1944): −15.1
*Hydrogen fluoride: −15.1
*Trifluoromethanesulfonic acid (1940): −14.9
*Perchloric acid: −13
* Sulfurochloridic acid: −13.8; −12.78
* Sulfuric acid: −12.0
For mixtures (e.g., partly diluted acids in water), the acidity function depends on the composition of the mixture and has to be determined empirically. Graphs of H vs mole fraction can be found in the literature for many acids. | 7 | Physical Chemistry |
Due to sulfur's high covalence, it can form up to 6 chemical bonds with other elements such as oxygen, resulting in a large number of oxidation states. Thus, there exist several redox reactions involving sulfur compounds. This freedom allows numerous chemical steps with different entropy changes, increasing the odds of meeting the criteria for a thermochemical cycle.
Much of the initial research was conducted in the United States, with sulfate- and sulfide-based cycles studied at Kentucky University, the Los Alamos National Laboratory and General Atomics. Significant research based on sulfates (e.g., FeSO and CuSO) was conducted in Germany and Japan. The sulfur-iodine cycle, discovered by General Atomics, has been proposed as a way of supplying a hydrogen economy without the need for hydrocarbons. | 7 | Physical Chemistry |
Ender's hydrazone alkylation reaction is usually run through a sequence of three steps. The first step should always be the synthesis of the hydrazones. The ketone or aldehyde is mixed with either SAMP or RAMP and allowed to react under argon for 12 hours. The crude hydrazone obtained is purified by distillation or recrystallization. At 0 degree celsius, the hydrazone is transferred into the ether solution of lithium diisopropylamide. Then this mixture is cooled down to -110 degree celsius and is slowly added the alkyl halide. This mixture is then allowed to warm up to room temperature. After 12 hours of reaction at room temperature, the crude alkylated hydrazone is allowed to react with ozone in a Schlenk tube to cleave the C=N bond. After distillation or column chromatography, pure alkylation product can be obtained. | 0 | Organic Chemistry |
LaNi is an intermetallic compound with a CaCu structure. It belongs to the hexagonal crystal system. It can be oxidized by air above 200 °C, and react with hydrochloric acid, sulfuric acid or nitric acid above 20 °C. LaNi can be used as a catalyst for hydrogenation reactions. | 8 | Metallurgy |
This machine uses a motor-driven plate to hold a precisely flat disk (known as a "lap") for the purpose of cutting or polishing. Diamond abrasives bonded to metal or resin are typically used for cutting laps, and a wide variety of materials are used for polishing laps in conjunction with either very fine diamond powder or oxide-based polishes. Water is typically used for cutting, while either oil or water is used for the polishing process.
The machine uses a system generally called a "mast" which consists of an angle readout, height adjustment and typically a gear (called an "index gear") with a particular number of teeth is used as a means of setting the rotational angle. The angles of rotation are evenly divided by the number of teeth present on the gear, though many machines include additional means of adjusting the rotational angle in finer increments, often called a "cheater". The stone is bonded to a (typically metal) rod known as a "dop" or "dop stick" and is held in place by part of the mast referred to as the "quill". | 3 | Analytical Chemistry |
Like pheromones (communication chemicals used within a species), kairomones can be utilized as an attracticide to lure a pest species to a location containing pesticide. However, they might also be used to lure desired species. Kairomones produced by the hosts of parasitic wasps have been used in an attempt to attract them and keep them around in crops where they reduce herbivory, but this could instead result in fewer attacks on the herbivorous pest if the applied kairomone distracts them from finding real hosts. For example, studies have shown that kairomones are effective in attracting female African sugarcane borers to deposit eggs on dead leaf material.
Recent discoveries have highlighted that predators are attracted to the odour of co-existing predators.
Kairomones have been extensively studied, and some are in successful usage, in Floridas Anastrepha suspensa' eradication zone in support of the citrus, and various other orchard industries there. | 1 | Biochemistry |
* TEs are also a widely used tool for mutagenesis of most experimentally tractable organisms. The Sleeping Beauty transposon system has been used extensively as an insertional tag for identifying cancer genes.
* The Tc1/mariner-class of TEs Sleeping Beauty transposon system, awarded Molecule of the Year in 2009, is active in mammalian cells and is being investigated for use in human gene therapy.
* TEs are used for the reconstruction of phylogenies by the means of presence/absence analyses. Transposons can act as biological mutagen in bacteria.
* Common organisms which the use of Transposons has been well developed are:
**Drosophila
** Arabidopsis thaliana
** Escherichia coli | 1 | Biochemistry |
A typical sublimation apparatus separates a mix of appropriate solid materials in a vessel in which it applies heat under a controllable atmosphere (air, vacuum or inert gas). If the material is not at first solid, then it may freeze under reduced pressure. Conditions are so chosen that the solid volatilizes and condenses as a purified compound on a cooled surface, leaving the non-volatile residual impurities or solid products behind.
The form of the cooled surface often is a so-called cold finger which for very low-temperature sublimation may actually be cryogenically cooled. If the operation is a batch process, then the sublimed material can be collected from the cooled surface once heating ceases and the vacuum is released. Although this may be quite convenient for small quantities, adapting sublimation processes to large volume is generally not practical with the apparatus becoming extremely large and generally needing to be disassembled to recover products and remove residue.
Among the advantages of applying the principle to certain materials are the comparatively low working temperatures, reduced exposure to gases such as oxygen that might harm certain products, and the ease with which it can be performed on extremely small quantities. The same apparatus may also be used for conventional distillation of extremely small quantities due to the very small volume and surface area between evaporating and condensing regions, although this is generally only useful if the cold finger can be cold enough to solidify the condensate. | 3 | Analytical Chemistry |
The Pho regulon is controlled by a two-component regulatory system composed of a histidine kinase sensor protein (PhoR) within the inner membrane and a transcriptional response regulator (PhoB/PhoR) on the cytoplasmic side of the membrane. These proteins bind to upstream promoters in the pho regulon in order to induce a general change in gene transcription. This occurs when the cell senses low concentrations of phosphate within its internal environment causing the response regulator to be phosphorylated inducing an overall decrease in gene transcription. This mechanism is ubiquitous within gram-positive, gram-negative, cyanobacteria, yeasts, and archaea. | 1 | Biochemistry |
Alkyl radical disproportionation has been studied extensively in scientific literature. During alkyl radical disproportionation, an alkane and an alkene are the end products and the bond order of the products increases by one over the reactants. Thus the reaction is exothermic (ΔH = ) and proceeds rapidly. | 0 | Organic Chemistry |
Research has shown that cells undergoing rapid growth have shown changes in their metabolism. These changes are observed with regards to glucose metabolism. The changes in metabolism occur because the rate of metabolism controls various signal transduction pathways that coordinate the activation of transcription factors as well as determining cell-cycle progress.
Growing cells require synthesis of new nucleotides, membranes and protein components. These materials can be obtained from carbon metabolism (e.g. glucose metabolism) or from peripheral metabolism. The enhanced flux observed in abnormally growing cells is brought about by high glucose uptake. | 1 | Biochemistry |
Since the late 1990s product analysis via SYBR Green, other double-strand specific dyes, or probe-based melting curve analysis has become nearly ubiquitous. The probe-based technique is sensitive enough to detect single-nucleotide polymorphisms (SNP) and can distinguish between homozygous wildtype, heterozygous and homozygous mutant alleles by virtue of the dissociation patterns produced. Without probes, amplicon melting (melting and analysis of the entire PCR product) was not generally successful at finding single base variants through melting profiles. With higher resolution instruments and advanced dyes, amplicon melting analysis of one base variants is now possible with several commercially available instruments. For example: Applied Biosystems 7500 Fast System and the 7900HT Fast Real-Time PCR System, Idaho Technologys LightScanner (the first plate-based high resolution melting device), Qiagens Rotor-Gene instruments, and Roche's LightCycler 480 instruments.
Many research and clinical examples exist in the literature that show the use of melting curve analysis to obviate or complement sequencing efforts, and thus reduce costs.
While most quantitative PCR machines have the option of melting curve generation and analysis, the level of analysis and software support varies. High Resolution Melt (known as either Hi-Res Melting, or HRM) is the advancement of this general technology and has begun to offer higher sensitivity for SNP detection within an entire dye-stained amplicon. It is less expensive and simpler in design to develop probeless melting curve systems. However, for genotyping applications, where large volumes of samples must be processed, the cost of development may be less important than the total throughput and ease of interpretation, thus favoring probe-based genotyping methods.
Digital High Resolution Melting (dHRM) is also used in conjunction with digital PCR (dPCR) to improve quantitative power by providing additional information on the melting behavior of the amplified DNA, which can help in distinguishing between different genetic variants and in ensuring the accuracy of the quantification. dHRM is enabled by the use of sensitive DNA-binding dyes and digital PCR instrumentation, which allows for the collection of high-density data points to generate detailed melt profiles. These profiles can be used to identify even subtle differences in nucleic acid sequences, making dHRM a powerful tool for genotyping, mutation scanning, and methylation analysis
dHRM is an advanced molecular technique used for the analysis of genetic variations, such as single nucleotide polymorphisms (SNPs), mutations, and methylations, by monitoring the melting behavior of double-stranded DNA. It is a post-PCR method that involves the gradual heating of PCR-amplified DNA in the presence of intercalating dyes that fluoresce when bound to double-stranded DNA. As the DNA melts, the fluorescence decreases, and the changes in fluorescence are monitored in real-time with digital PCR system. The resulting melting curves are then analyzed to detect genetic differences based on the melting temperatures of the DNA fragments.
The technique has been further advanced by its application on digital microfluidics platforms, which can facilitate the analysis of single-nucleotide polymorphisms (SNPs) with high accuracy and sensitivity. Additionally, massively parallel dHRM has been developed to enable rapid and absolutely quantitative sequence profiling, which can be particularly useful in clinical and industrial settings where accurate quantification of nucleic acids is critical. | 1 | Biochemistry |
* Loading: The first amino acid is activated with ATP as a mixed acyl-phosphoric acid anhydride with AMP by the A-domain and loaded onto the serine-attached 4-phospho-pantethine (4PP) sidechain of the PCP-domain catalyzed by the PCP-domain (thiolation).
* Some A domains require interaction with MbtH-like proteins for their activity.
* Sometimes the amino group of the bound amino acid is formylated by an F-domain or methylated by an NMT-domain. | 1 | Biochemistry |
Infrared absorption band positions may be given either in wavelength (usually in micrometers, μm) or wavenumber (usually in reciprocal centimeters, cm) scale. | 7 | Physical Chemistry |
Brazing (sometimes known as silver soldering or hard soldering) requires a higher temperature than soft soldering (> 450 °C). As well as removing existing oxides, rapid oxidation of the metal at the elevated temperatures has to be avoided. This means that fluxes need to be more aggressive and to provide a physical barrier. Traditionally borax was used as a flux for brazing, but there are now many different fluxes available, often using active chemicals such as fluorides as well as wetting agents. Many of these chemicals are toxic and due care should be taken during their use. | 8 | Metallurgy |
Magnesium is the most abundant free cation in plant cytosol, is the central atom in chlorophyll and offers itself as a bridging ion for the aggregation of ribosomes in plants. Even small changes in the concentration of magnesium in plant cytosol or chloroplasts can drastically affect the key enzymes present in the chloroplasts. It is most commonly used as a co-factor in eukaryotes and functions as an important functional key in enzymes like RNA Polymerase and ATPase. In phosphorylating enzymes like ATPase or kinases and phosphates, magnesium acts as a stabilizing ion in polyphosphate compounds due its Lewis acidity. Magnesium has also been noted as a possible secondary messenger for neural transmissions. Magnesium acts as an allosteric inhibitor for the enzyme vacuolar pyrophosphatase (V-PPase). In vitro, the concentration of free magnesium acts as a strict regulator and stabilizer for the enzyme activity of V-PPase. | 1 | Biochemistry |
Virtually all TOC analysers measure the CO formed when organic carbon is oxidized and/or when inorganic carbon is acidified. Oxidation is performed either through Pt-catalyzed combustion, by heated persulfate, or with a UV/persulfate reactor. Once the CO is formed, it is measured by a detector: either a conductivity cell (if the CO is aqueous) or a non-dispersive infrared cell (after purging the aqueous CO into the gaseous phase). Conductivity detection is only desirable in the lower TOC ranges in deionized waters, whereas NDIR detection excels in all TOC ranges. A variation described as "membrane conductometric detection can allow for measurement of TOC across a wide analytical range in both deionized and non-deionized water samples. Modern high-performance TOC instruments are capable of detecting carbon concentrations well below 1 µg/L (1 part per billion or ppb).
A total organic carbon analyser determines the amount of carbon in a water sample. By acidifying the sample and flushing with nitrogen or helium the sample removes inorganic carbon, leaving only organic carbon sources for measurement. There are two types of analysers. One uses combustion and the other chemical oxidation. This is used as a water purity test, as the presence of bacteria introduces organic carbon. | 3 | Analytical Chemistry |
Liquid water is essential for carbon-based life. Chemical bonding of carbon molecules requires liquid water. Water has the chemical property to make compound-solvent pairing. In humans, 55% to 60% of the body is water. Water provides the reversible hydration of carbon dioxide. Hydration of carbon dioxide is needed in carbon-based life. All life on Earth uses the same biochemistry of carbon. Water is important in life's carbonic anhydrase the interaction of between carbon dioxide and water. Carbonic anhydrase needs a family of carbon base enzymes for the hydration of carbon dioxide and acid–base homeostasis, that regulates PH levels in life. In plant life, liquid water is needed for photosynthesis, the biological process plants use to convert light energy and carbon dioxide into chemical energy. | 1 | Biochemistry |
Since the mid-20th century, it has been discerned from population studies (though incompletely understood) that fluoride reduces tooth decay. Initially, researchers hypothesized that fluoride helped by converting tooth enamel from the more acid-soluble mineral hydroxyapatite to the less acid-soluble mineral fluorapatite. However, more recent studies showed no difference in the frequency of caries (cavities) between teeth that were pre-fluoridated to different degrees. Current thinking is that fluoride prevents cavities primarily by helping teeth that are in the very early stages of tooth decay.
When teeth begin to decay from the acid produced by sugar-consuming bacteria, calcium is lost (demineralization). However, teeth have a limited ability to recover calcium if decay is not too far advanced (remineralization). Fluoride appears to reduce demineralization and increase remineralization. Also, there is some evidence that fluoride interferes with the bacteria that consume sugars in the mouth and make tooth-destroying acids. In any case, it is only the fluoride that is directly present in the mouth (topical treatment) that prevents cavities; fluoride ions that are swallowed do not benefit the teeth.
Water fluoridation is the controlled addition of fluoride to a public water supply in an effort to reduce tooth decay in people who drink the water. Its use began in the 1940s, following studies of children in a region where water is naturally fluoridated. It is now used widely in public water systems in the United States and some other parts of the world, such that about two-thirds of the U.S. population is exposed to fluoridated water supplies and about 5.7% of people worldwide. Although the best available evidence shows no association with adverse effects other than fluorosis (dental and, in worse cases, skeletal), most of which is mild, water fluoridation has been contentious for ethical, safety, and efficacy reasons, and opposition to water fluoridation exists despite its widespread support by public health organizations. The benefits of water fluoridation have lessened recently, presumably because of the availability of fluoride in other forms, but are still measurable, particularly for low-income groups. Systematic reviews in 2000 and 2007 showed significant reduction of cavities in children exposed to water fluoridation.
Sodium fluoride, tin difluoride, and, most commonly, sodium monofluorophosphate, are used in toothpaste. In 1955, the first fluoride toothpaste was introduced in the United States. Now, almost all toothpaste in developed countries is fluoridated. For example, 95% of European toothpaste contains fluoride. Gels and foams are often advised for special patient groups, particularly those undergoing radiation therapy to the head (cancer patients). The patient receives a four-minute application of a high amount of fluoride. Varnishes, which can be more quickly applied, exist and perform a similar function. Fluoride is also often present in prescription and non-prescription mouthwashes and is a trace component of foods manufactured using fluoridated water supplies. | 1 | Biochemistry |
Lithium tetramethylpiperidide (often abbreviated LiTMP or LTMP) is a chemical compound with the molecular formula . It is used as a non-nucleophilic base, being comparable to LiHMDS in terms of steric hindrance. | 0 | Organic Chemistry |
The conventional method of performing laser-induced fluorescence, as well as other types of spectroscopic measurements, such as infrared, ultraviolet-visible spectroscopy, phosphorescence, etc., is to use a small transparent laboratory vessel, a cuvette, to contain the sample to be analyzed.
To perform a measurement, the cuvette is filled with the liquid to be investigated and then illuminated with a laser focused through one of the cuvette's faces. A lens is placed in line with one of the faces of the cuvette located at 90° from the input window to collect the laser-induced fluorescent light. Only a small volume of the cuvette is actually illuminated by the laser and produces a detectable spectroscopic emission. The output signal is significantly reduced because the lens picks up only about 10% of the spectroscopic emission due to solid angle considerations. This technique has been used for at least 75 years; even before the laser existed, when conventional light sources were used to excite the fluorescence.
SOFIA solves the problem of low collection efficiency, as it collects nearly all of the fluorescent light produced from the sample being analyzed, increasing the amount of fluorescence signal by around a factor of 10 over conventional apparatus. | 1 | Biochemistry |
The Caspian Sea region presently is a significant, but not major, supplier of crude oil to world markets, based upon estimates by BP Amoco and the U.S. Energy Information Administration, U.S. Department of Energy. The region output about 1.4–1.5 million barrels per day plus natural gas liquids in 2001, 1.9% of total world output. More than a dozen countries output more than this top figure. Caspian region production has been higher, but waned during and after the collapse of the Soviet Union. Kazakhstan accounts for 55% and Azerbaijan for about 20% of the states' oil output.
The world's first offshore wells and machine-drilled wells were made in Bibi-Heybat Bay, near Baku, Azerbaijan. In 1873, exploration and development of oil began in some of the largest fields known to exist in the world at that time on the Absheron Peninsula near the villages of Balakhanli, Sabunchi, Ramana, and Bibi Heybat. Total recoverable reserves were more than 500 million tons. By 1900, Baku had more than 3,000 oil wells, 2,000 of which were producing at industrial levels. By the end of the 19th century, Baku became known as the "black gold capital", and many skilled workers and specialists flocked to the city.
By the beginning of the 20th century, Baku was the center of the international oil industry. In 1920, when the Bolsheviks captured Azerbaijan, all private property, including oil wells and factories, was confiscated. Rapidly the republics oil industry came under the control of the Soviet Union. By 1941, Azerbaijan was producing a record 23.5 million tons of oil per year – its Baku region output was nearly 72 percent of the Soviet Unions oil.
In 1994, the "Contract of the Century" was signed, heralding extra-regional development of the Baku oil fields. The large Baku–Tbilisi–Ceyhan pipeline conveys Azeri oil to the Turkish Mediterranean port of Ceyhan and opened in 2006.
The oil field in the Russian section of the body of water was discovered in 2005. It is reportedly the largest found in 25 years. It was announced in October 2016 that Lukoil would start production from it. | 2 | Environmental Chemistry |
*ALAS1 Aminolevulinic Acid Synthase type 1 (type 2 is erythroid and associated with porphyria)
*ARHGEF2 Rho guanine nucleotide exchange factor
*ARMET Mesencephalic astrocyte-derived neurotrophic factor
*AES amino terminal enhancer of split
*BECN1 involved in autophagy and partners with PI3K
*BUD31 formerly Maternal G10 transcript
*Creatine kinase CKB (ATP reservoir)
*Cytidine deaminase questionable: not present in very high levels at all
*CPNE1
*ENSA (gene)
*FTH1 Heavy chain of Ferritin
*GDI2 rab/ras vesicular trafficking
*GUK1 Guanylate kinase transfers phosphate from ATP to GMP
*HPRT Hypoxanthine-guanine phosphoribosyltransferase
*IFITM1 Induced by interferon, transmembrane protein
*JTB (gene) Jumping translocation breakpoint
*MMPL2
*NME2 (formerly NM23B) Nucleoside diphosphate kinase
*NONO
*P4HB
*PRDX1 peroxiredoxin (reduces peroxides)
*PTMA Prothymosin
*RPA2 Binds DNA during replication to keep it straightened out
*SULT1A3 Sulfate conjugation (note: SULT1C is cited in earlier literature as being ubiquitous but this may be an example of different tags being used to refer to a common area of 2 closely related genes. If the tag is too short, then it may not be specific enough to truly specify one member of a gene family from another)
*SYNGR2 Synaptogyrin (may participate in vesicle translocation)
*Tetratricopeptide, TTC1 small glutamine rich tetratricopeptide | 1 | Biochemistry |
Adenine nucleotide translocator (ANT), also known as the ADP/ATP translocase (ANT), ADP/ATP carrier protein (AAC) or mitochondrial ADP/ATP carrier, exchanges free ATP with free ADP across the inner mitochondrial membrane. ANT is the most abundant protein in the inner mitochondrial membrane and belongs to mitochondrial carrier family.
Free ADP is transported from the cytoplasm to the mitochondrial matrix, while ATP produced from oxidative phosphorylation is transported from the mitochondrial matrix to the cytoplasm, thus providing the cells with its main energy currency. ADP/ATP translocases are exclusive to eukaryotes and are thought to have evolved during eukaryogenesis. Human cells express four ADP/ATP translocases: SLC25A4, SLC25A5, SLC25A6 and SLC25A31, which constitute more than 10% of the protein in the inner mitochondrial membrane. These proteins are classified under the mitochondrial carrier superfamily. | 1 | Biochemistry |
Increasing the pressure in a gaseous reaction will increase the number of collisions between reactants, increasing the rate of reaction. This is because the activity of a gas is directly proportional to the partial pressure of the gas. This is similar to the effect of increasing the concentration of a solution.
In addition to this straightforward mass-action effect, the rate coefficients themselves can change due to pressure. The rate coefficients and products of many high-temperature gas-phase reactions change if an inert gas is added to the mixture; variations on this effect are called fall-off and chemical activation. These phenomena are due to exothermic or endothermic reactions occurring faster than heat transfer, causing the reacting molecules to have non-thermal energy distributions (non-Boltzmann distribution). Increasing the pressure increases the heat transfer rate between the reacting molecules and the rest of the system, reducing this effect.
Condensed-phase rate coefficients can also be affected by pressure, although rather high pressures are required for a measurable effect because ions and molecules are not very compressible. This effect is often studied using diamond anvils.
A reaction's kinetics can also be studied with a pressure jump approach. This involves making fast changes in pressure and observing the relaxation time of the return to equilibrium. | 7 | Physical Chemistry |
Bilirubin is created by the activity of biliverdin reductase on biliverdin, a green tetrapyrrolic bile pigment that is also a product of heme catabolism. Bilirubin, when oxidized, reverts to become biliverdin once again. This cycle, in addition to the demonstration of the potent antioxidant activity of bilirubin, has led to the hypothesis that bilirubins main physiologic role is as a cellular antioxidant. Consistent with this, animal studies suggest that eliminating bilirubin results in endogenous oxidative stress. Bilirubins antioxidant activity may be particularly important in the brain, where it prevents excitotoxicity and neuronal death by scavenging superoxide during N-methyl-D-aspartic acid neurotransmission. | 1 | Biochemistry |
Thermal plasmas. can be technically generated, for example, by inductive coupling of high-frequency fields in the MHz range (ICP: Inductively coupled plasma) or by direct current coupling (arc discharges). A thermal plasma is characterized by the fact that electrons, ions and neutral particles are in thermodynamic equilibrium. For atmospheric-pressure plasmas, the temperatures in thermal plasmas are usually above 6000 K. This corresponds to average kinetic energies of less than 1 eV.
Nonthermal plasmas are found in low-pressure arc discharges, such as fluorescent lamps, in dielectrically barrier discharges (DBD), such as ozone tubes, in microwave plasmas (plasma torches, i.e. PLexc oder MagJet) or in GHz-plasmajets. A non-thermal plasma shows a significant difference between the electron and gas temperature. For example, the electron temperature can be several 10,000 K, which corresponds to average kinetic energies of more than 1 eV while a gas temperature close to room temperature is measured. Despite their low temperature, such plasmas can trigger chemical reactions and excitation states via electron collisions. Pulsed coronal and dielectrically impeded discharges belong to the family of nonthermal plasmas. Here the electrons are much hotter (several eV) than the ions/neutral gas particles (room temperature). | 7 | Physical Chemistry |
Diboryne or a compound with boron-boron triple bond was first isolated as a N-heterocyclic carbene supported complex (NHC-BB-NHC) in the Braunschweig group, and its unique, peculiar bonding structure thereupon catalyzed new research to computationally assess the nature of this at that time controversial triple bond.
A few years later, Köppe and Schnöckel published an article arguing that the B-B bond should be defined as a 1.5 bond based on thermodynamic view and rigid force constant calculations. That same year, Grunenberg reassessed the B-B bond using generalized compliance constants of which he claimed better suited as a bond strength descriptor.
The calculated relaxed force constants show a clear trend as the bond order between the B-B bond increases, which advocates the existence of the triple bond in Braunschweig's compound. | 6 | Supramolecular Chemistry |
The usage of multiple reading frames leads to the possibility of overlapping genes; there may be many of these in viral, prokaryote, and mitochondrial genomes. Some viruses, e.g. hepatitis B virus and BYDV, use several overlapping genes in different reading frames.
In rare cases, a ribosome may shift from one frame to another during translation of an mRNA (translational frameshift). This causes the first part of the mRNA to be translated in one reading frame, and the latter part to be translated in a different reading frame. This is distinct from a frameshift mutation, as the nucleotide sequence (DNA or RNA) is not altered—only the frame in which it is read. | 1 | Biochemistry |
Poaceae (grasses) including agriculturally important species such as barley and wheat are able to efficiently sequester iron by releasing phytosiderophores via their root into the surrounding soil rhizosphere. Chemical compounds produced by microorganisms in the rhizosphere can also increase the availability and uptake of iron. Plants such as oats are able to assimilate iron via these microbial siderophores. It has been demonstrated that plants are able to use the hydroxamate-type siderophores ferrichrome, rhodotorulic acid and ferrioxamine B; the catechol-type siderophores, agrobactin; and the mixed ligand catechol-hydroxamate-hydroxy acid siderophores biosynthesized by saprophytic root-colonizing bacteria. All of these compounds are produced by rhizospheric bacterial strains, which have simple nutritional requirements, and are found in nature in soils, foliage, fresh water, sediments, and seawater.
Fluorescent pseudomonads have been recognized as biocontrol agents against certain soil-borne plant pathogens. They produce yellow-green pigments (pyoverdines) which fluoresce under UV light and function as siderophores. They deprive pathogens of the iron required for their growth and pathogenesis. | 1 | Biochemistry |
For plasma to exist, ionization is necessary. The term "plasma density" by itself usually refers to the electron density , that is, the number of charge-contributing electrons per unit volume. The degree of ionization is defined as fraction of neutral particles that are ionized:
where is the ion density and the neutral density (in number of particles per unit volume). In the case of fully ionized matter, . Because of the quasineutrality of plasma, the electron and ion densities are related by , where is the average ion charge (in units of the elementary charge). | 7 | Physical Chemistry |
Detrimental secondary phases can also form because of thermal treatments or during the material production. Excessively high sintering/annealing temperatures or long dwelling times will result in the loss of volatile species (especially LiO) and in the decomposition of LAGP main phase into AlPO and GeO. LAGP bulk samples and thin films are typically stable up to 700-750 °C; if this temperature is exceeded, volatile lithium is lost and the impurity phase GeO forms. If the temperature is further increased beyond 950 °C, also AlPO appears.
Raman spectroscopy and in situ X-ray diffraction (XRD) are useful techniques that can be employed to recognise the phase purity of LAGP samples during and after the heat treatments. | 7 | Physical Chemistry |
A hemichrome (FeIII) is a form of low-spin methemoglobin (metHb).
Hemichromes, which precede the denaturation processes of hemoglobin (Hb), are mainly produced by partially denaturated hemoglobins and form histidine complexes.
Hemichromes are usually associated with blood disorders. | 1 | Biochemistry |
In chemistry, polarity is a separation of electric charge leading to a molecule or its chemical groups having an electric dipole moment, with a negatively charged end and a positively charged end.
Polar molecules must contain one or more polar bonds due to a difference in electronegativity between the bonded atoms. Molecules containing polar bonds have no molecular polarity if the bond dipoles cancel each other out by symmetry.
Polar molecules interact through dipole-dipole intermolecular forces and hydrogen bonds. Polarity underlies a number of physical properties including surface tension, solubility, and melting and boiling points. | 7 | Physical Chemistry |
The equilibrium reaction involving diamond is
Examining the oxygen fugacity of the upper mantle and transition enables us to compare it with the conditions (equilibrium reaction shown above) required for diamond formation. The results show that the is usually 2 units lower than the carbonate-carbon reaction which means favoring the formation of diamond at transition zone conditions.
It has also been reported that pH decrease would also facilitate the formation of diamond in Mantle conditions.
where the subscript aq means aqueous, implying H is dissolved in the solution.
Deep diamonds have become important windows to look into the mineralogy of the Earth's interior. Minerals not stable at the surface could possibly be found within inclusions of superdeep diamonds-- implying they were stable where these diamond crystallized. Because of the hardness of diamonds, the high pressure environment is retained even after transporting to the surface. So far, these superdeep minerals brought by diamonds include ringwoodite, ice-VII, cubic δ-N and Ca-perovskite. | 9 | Geochemistry |
The first useful addition polymer was made by accident in 1933 by ICI chemists Reginald Gibson and Eric Fawcett. They were carrying out a series of experiments that involved reacting organic compounds under high temperatures and high pressures. They set up an experiment to react ethene with benzaldehyde in the hope of producing a ketone. They left the reaction vessel overnight, and the next morning they found a small amount of a white waxy solid. It was shown later that this solid was polyethylene.
The term "addition polymerization" is deprecated by IUPAC (International Union of Pure and Applied Chemistry) which recommends the alternative term chain polymerization. | 7 | Physical Chemistry |
Aequorin is presumably encoded in the genome of Aequorea. At least four copies of the gene were recovered as cDNA from the animal. Because the genome has not been sequenced, it is unclear if the cDNA variants can account for all of the isoforms of the protein. | 1 | Biochemistry |
Although this page is devoted to genes that should be ubiquitously expressed, this section is for genes whose current name reflects their relative upregulation in testes
*SPAG7
*SRM Spermidine synthase
*TEGT Bax-1 inhibitor
*DAZAP2 Deleted in azoospermia
*MEA1 Male enhanced antigen | 1 | Biochemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.