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The biosynthesis of N-linked glycans occurs via 3 major steps:
#Synthesis of dolichol-linked precursor oligosaccharide
#En bloc transfer of precursor oligosaccharide to protein
#Processing of the oligosaccharide
Synthesis, en bloc transfer and initial trimming of precursor oligosaccharide occurs in the endoplasmic reticulum (ER). Subsequent processing and modification of the oligosaccharide chain are carried out in the Golgi apparatus.
The synthesis of glycoproteins is thus spatially separated in different cellular compartments. Therefore, the type of N-glycan synthesized, depends on its accessibility to the different enzymes present within these cellular compartments.
However, in spite of the diversity, all N-glycans are synthesized through a common pathway with a common core glycan structure.
The core glycan structure is essentially made up of two N-acetyl glucosamine and three mannose residues. This core glycan is then elaborated and modified further, resulting in a diverse range of N-glycan structures. | 0 | Theoretical and Fundamental Chemistry |
Machine learning is a powerful tool that can be used in metabolomics analysis. Recently, scientists have developed retention time prediction software. These tools allow researchers to apply artificial intelligence to the retention time prediction of small molecules in complex mixture, such as human plasma, plant extracts, foods, or microbial cultures. Retention time prediction increases the identification rate in liquid chromatography and can lead to an improved biological interpretation of metabolomics data. | 1 | Applied and Interdisciplinary Chemistry |
Metal oxides excel at catalyzing gas phase reactions by photo-activation, as well as thermal activation of the catalyst. Oxidation of hydrocarbons, alcohols, carbon monoxide, and ammonia occurs when stimulated with light of greater energy than the band gap of the metal oxide. Homophasic and heterophasic light-induced oxygen isotope exchange has also been observed over TiO and ZnO. Homophasic isotope exchange is the production of from and . Heterophasic isotope exchange is the chemisorption of an oxygen isotope to the lattice of the metal oxide (lat), and replacement of one of the oxygens in the gas phase with the lattice oxygen as shown in the following reaction. | 0 | Theoretical and Fundamental Chemistry |
Photosynthetic carbohydrate synthesis in plants and certain bacteria is an anabolic process that produces glucose, cellulose, starch, lipids, and proteins from CO. It uses the energy produced from the light-driven reactions of photosynthesis, and creates the precursors to these large molecules via carbon assimilation in the photosynthetic carbon reduction cycle, a.k.a. the Calvin cycle. | 1 | Applied and Interdisciplinary Chemistry |
Hans Gross applied scientific methods to crime scenes and was responsible for the birth of criminalistics.
Edmond Locard expanded on Gross work with Locards Exchange Principle which stated "whenever two objects come into contact with one another, materials are exchanged between them". This means that every contact by a criminal leaves a trace.
Alexander Lacassagne, who taught Locard, produced autopsy standards on actual forensic cases.
Alphonse Bertillon was a French criminologist and founder of Anthropometry (scientific study of measurements and proportions of the human body). He used anthropometry for identification, stating that, since each individual is unique, by measuring aspects of physical difference there could be a personal identification system. He created the Bertillon System around 1879, a way of identifying criminals and citizens by measuring 20 parts of the body. In 1884, over 240 repeat offenders were caught using the Bertillon system, but the system was largely superseded by fingerprinting.
Frances Glessner Lee, known as "the mother of forensic science", was instrumental in the development of forensic science in the US. She lobbied to have coroners replaced by medical professionals, endowed the Harvard Associates in Police Science, and conducted many seminars to educate homicide investigators. She also created the Nutshell Studies of Unexplained Death, intricate crime scene dioramas used to train investigators, which are still in use today. | 0 | Theoretical and Fundamental Chemistry |
The drug flux represents the slope of the linear regression of the accumulated mass (Q) over time (t) normalized over the permeation area (A), i.e., the surface area of the barrier available for permeation.
Equation 1:
The drug apparent permeability (P) is calculated by normalizing the drug flux (j) over the initial concentration of the API in the donor compartment (c) as:
Equation 2:
Dimensionally, the P represents a velocity, and it is normally expressed in cm/sec. The highest is the permeability, the highest is expected to be the bioavailability of the drug after oral administration. | 1 | Applied and Interdisciplinary Chemistry |
Neutron tools are based on the measurement of a neutron cloud of different energy levels within the investigated volume. Epithermal-neutron tools measure epithermal neutron density with energy levels between 100eV and 0.1eV in the formation. Thermal-neutron tools only measure the population of neutrons with a thermal energy level, and Neutron-gamma tools measure the intensity of gamma flux generated by thermal neutron capture. The tools usually have two detectors (or more) with different spacings from the source to produce ratio of count rates, which theoretically reduce borehole effects.
A Helium-3 (He-3) filled proportional counter is the most common epithermal and thermal neutron detector. Helium has a high neutron capture cross section and produces the following reaction when interacting with a neutron.
He + n → H + H + 764keV energy
To boost the charge produced by the interaction between helium and a neutron, a high voltage is applied to the anode of the counter. A high operating voltage is chosen to give enough gain for counting purposes. Most helium-3 counters use a quench gas to stabilize high voltage performance and prevent run-away. | 0 | Theoretical and Fundamental Chemistry |
Globo H (globohexaosylceramide) is a globo-series glycosphingolipid antigen that is present on the outer membrane of some cancer cells. Globo H is not expressed in normal tissue cells, but is expressed in a number of types of cancers, including cancers of the breast, prostate, and pancreas. Globo H's exclusivity for cancer cells makes it a target of interest for cancer therapies. | 1 | Applied and Interdisciplinary Chemistry |
* Cell wall reinforcement (cellulose, lignin, suberin, callose, cell wall proteins)
* Antimicrobial chemicals, including reactive oxygen species such as hydrogen peroxide or peroxynitrite, or more complex phytoalexins such as genistein or camalexin
* Antimicrobial proteins such as defensins, thionins, or PR-1
* Antimicrobial enzymes such as chitinases, beta-glucanases, or peroxidases
* Hypersensitive response – a rapid host cell death response associated with defence induction. | 1 | Applied and Interdisciplinary Chemistry |
Although freeze fracture studies have revealed that the nodal axolemma in both the CNS and PNS is enriched in intra-membranous particles (IMPs) compared to the internode, there are some structural differences reflecting their cellular constituents. In the PNS, specialized microvilli project from the outer collar of Schwann cells and come very close to nodal axolemma of large fibers. The projections of the Schwann cells are perpendicular to the node and are radiating from the central axons. However, in the CNS, one or more of the astrocytic processes come in close vicinity of the nodes. Researchers declare that these processes stem from multi-functional astrocytes, as opposed to from a population of astrocytes dedicated to contacting the node. On the other hand, in the PNS, the basal lamina that surrounds the Schwann cells is continuous across the node. | 1 | Applied and Interdisciplinary Chemistry |
The Wu theory provides more accurate results than do the other two component theories, particularly for high surface energies. It does, however, suffer from one complication: because of the mathematics involved, the Wu theory yields two results for each component, one being the true result, and one being simply a consequence of the mathematics. The challenge at this point lies in interpreting which is the true result. Sometimes this is as simple as eliminating the result that makes no physical sense (a negative surface energy) or the result that is clearly incorrect by virtue of being many orders of magnitude larger or smaller than it should be. Sometimes interpretation is more tricky. | 0 | Theoretical and Fundamental Chemistry |
The carbon-silicon bond is highly electron-releasing and can stabilize a positive charge in the β position through hyperconjugation. Electrophilic additions to allyl- and vinylsilanes take advantage of this, and site selectivity generally reflects this property—electrophiles become bound to the carbon γ to the silyl group. The electron-donating strength of the carbon-silicon bond is similar to that of an acetamide substituent and equal to roughly two alkyl groups. After formation of the carbon-electrophile bond, silicon elimination is assisted by a nucleophile.
A model of the most likely reactive conformation of the allylsilane (see below) suggests that the new double bond that forms will predominantly possess the (E) configuration. However, addition of a nucleophile (such as the counterion of the electrophile) to the intermediate silyl-stabilized carbocation complicates this picture. Because the elimination to generate the double bond is stereospecifically anti, nucleophilic addition to either face of the silyl-stabilized carbanion leads to the formation of mixtures of double bond isomers. Diastereomeric mixtures of double bond isomers are common when Lewis acids are used to activate the electrophile.
Under conditions of nucleophilic catalysis, any intermediate along the reaction pathway may incorporate a silicon-nucleophile bond. This factor does not affect the outcome unless nucleophilic attack liberates free anions or allylic transposition occurs. The latter is known to occur for hypervalent allylsilanes incorporating fluoride. | 0 | Theoretical and Fundamental Chemistry |
Also called a tee with a diverter baffle, a waste tee or an end-outlet tee, it typically connects waste lines before they enter the trap and has a baffle to keep water from one waste pipe from entering the other at the connection. | 1 | Applied and Interdisciplinary Chemistry |
Many structural domains have been conserved through evolution, as prokaryotic initiation factors share similar structures with eukaryotic factors. The prokaryotic initiation factor, IF3, assists with start site specificity, as well as mRNA binding. This is in comparison with the eukaryotic initiation factor, eIF1, who also performs these functions. The elF1 structure is similar to the C-terminal domain of IF3, as they each contain a five-stranded beta sheet against two alpha helices.
The prokaryotic initiation factors IF1 and IF2 are also homologs of the eukaryotic initiation factors eIF1A and eIF5B. IF1 and eIF1A, both containing an OB-fold, bind to the A site and assist in the assembly of initiation complexes at the start codon. IF2 and eIF5B assist in the joining of the small and large ribosomal subunits. The eIF5B factor also contains elongation factors. Domain IV of eIF5B is closely related to the C-terminal domain of IF2, as they both consist of a beta-barrel. The elF5B also contains a GTP-binding domain, which can switch from an active GTP to an inactive GDP. This switch helps to regulate the affinity of the ribosome for the initiation factor.
A eukaryotic initiation factor eIF3 plays an important role in translational initiation. It has a complex structure, composed of 13 subunits. It helps to create the 43S pre-initiation complex, composed of the small 40S subunit attached to other initiation factors. It also helps to create the 48S pre-initiation complex, consisting of the 43S complex with the mRNA. The eIF3 factor can also be used post-translation in order to separate the ribosomal complex and keep the small and large subunits apart. The initiation factor interacts with the eIF1 and eIF5 factors used for scanning and selection of the start codons. This can create changes in the selection of the factors, binding to different codons.
Another important eukaryotic initiation factor, eIF2, binds the tRNA containing methionine to the P site of the small ribosome. The P site is where the tRNA carrying an amino acid forms a peptide bond with the incoming amino acids and carries the peptide chain. The factor consists of an alpha, beta, and gamma subunit. The eIF2 gamma subunit is characterized by a GTP-binding domain and beta-barrel folds. It binds to the tRNA through GTP. Once the initiation factor helps the tRNA bind, the GTP hydrolyzes and is released the eIF2. The eIF2 beta subunit is identified by its Zn-finger. The eIF2 alpha subunit is characterized by an OB-fold domain and two beta strands. This subunit helps to regulate translation, as it becomes phosphorylated to inhibit protein synthesis.
The eIF4F complex supports the cap-dependent translation initiation process and is composed of the initiation factors eIF4A, eIF4E, and eIF4G. The cap end of the mRNA, being the 5’ end, is brought to the complex where the 43S ribosomal complex can bind and scan the mRNA for the start codon. During this process, the 60S ribosomal subunit binds and the large 80S ribosomal complex is formed. The eIF4G plays a role, as it interacts with the polyA-binding protein, attracting the mRNA. The eIF4E then binds the cap of the mRNA and the small ribosomal subunit binds to the eIF4G to begin the process of creating the 80S ribosomal complex. The eIF4A works to make this process more successful, as it is a DEAD box helicase. It allows for the unwinding of the untranslated regions of the mRNA to allow for ribosomal binding and scanning. | 1 | Applied and Interdisciplinary Chemistry |
In crystallography, materials science and metallurgy, Vegards law is an empirical finding (heuristic approach) resembling the rule of mixtures. In 1921, Lars Vegard discovered that the lattice parameter of a solid solution of two constituents is approximately a weighted mean of the two constituents lattice parameters at the same temperature:
e.g., in the case of a mixed oxide of uranium and plutonium as used in the fabrication of MOX nuclear fuel:
Vegards law assumes that both components A and B in their pure form (i.e.', before mixing) have the same crystal structure. Here, is the lattice parameter of the solid solution, and are the lattice parameters of the pure constituents, and is the molar fraction of B in the solid solution.
Vegard's law is seldom perfectly obeyed; often deviations from the linear behavior are observed. A detailed study of such deviations was conducted by King. However, it is often used in practice to obtain rough estimates when experimental data are not available for the lattice parameter for the system of interest.
For systems known to approximately obey Vegard's law, the approximation may also be used to estimate the composition of a solution from knowledge of its lattice parameters, which are easily obtained from diffraction data. For example, consider the semiconductor compound . A relation exists between the constituent elements and their associated lattice parameters, , such that:
When variations in lattice parameter are very small across the entire composition range, Vegards law becomes equivalent to Amagats law. | 1 | Applied and Interdisciplinary Chemistry |
The importance of an antiparallel DNA double helix structure is because of its hydrogen bonding between the complementary nitrogenous base pairs. If the DNA structure were to be parallel, the hydrogen bonding would not be possible, as the base pairs would not be paired in the known way. The four base pairs are: adenine, guanine, cytosine, and thymine, where adenine complements thymine, and guanine complements cytosine. Transcription would be another problem if the DNA structure were to be parallel, making no sense of the information being read from the DNA. This would further lead to the production of incorrect proteins. | 1 | Applied and Interdisciplinary Chemistry |
Purple of Cassius is a purple pigment formed by the reaction of gold salts with tin(II) chloride. It has been used to impart glass with a red coloration (see cranberry glass), as well as to determine the presence of gold as a chemical test.
Generally, the preparation of this material involves gold being dissolved in aqua regia, then reacted with a solution of tin(II) chloride. The tin(II) chloride reduces the chloroauric acid from the dissolution of gold in aqua regia to a colloid of elemental gold supported on tin dioxide to give a purple precipitate or coloration.
When used as a test, the intensity of the color correlates with the concentration of gold present. This test was first observed and refined by a German physician and alchemist, Andreas Cassius (1600–1676) of Hamburg, in 1665. Berzelius later made a detailed study of the purple of Cassius. The colour also attracted attention from Faraday.
Richard Adolf Zsigmondy, who earned the 1926 Nobel Prize for chemistry, says that "Several of the red gold divisions prepared with formaldehyde as well as those reduced with phosphorus appeared perfectly clear in ordinary daylight (like good red wine). They did not settle out their gold, and I was therefore able to call them rightly chemical solutions. In Thomas Graham’s dialysis, however, they behaved like colloidal suspensions: the gold particles did not pass through the parchment membrane. This showed my gold divisions their proper place, namely, that they belonged to the colloidal suspensions." | 0 | Theoretical and Fundamental Chemistry |
A common simplification to (14) is the harmonic approximation, in which the probability density function is modeled as a Gaussian. Under this approximation, static displacive disorder is ignored and it is assumed that atomic displacements are determined entirely by motion (alternative models in which the Gaussian approximation is invalid have been considered elsewhere).
From equations (7) and (14), the Debye–Waller factor contributes to the observed intensity of a diffraction experiment. And based on (16), we see that our anisotropic displacement factor is responsible for determining . Additionally, (15) shows that may be directly related to the probability density function for a nuclear displacement from the mean position. As a result, its possible to conduct a scattering experiment on a crystal, fit the resulting spectrum for the various atomic values, and derive each atoms tendency for nuclear displacement from . | 0 | Theoretical and Fundamental Chemistry |
End-sequence profiling (ESP) (sometimes "Paired-end mapping (PEM)") is a method based on sequence-tagged connectors developed to facilitate de novo genome sequencing to identify high-resolution copy number and structural aberrations such as inversions and translocations. <br />
Briefly, the target genomic DNA is isolated and partially digested with restriction enzymes into large fragments. Following size-fractionation, the fragments are cloned into plasmids to construct artificial chromosomes such as bacterial artificial chromosomes (BAC) which are then sequenced and compared to the reference genome. The differences, including orientation and length variations between constructed chromosomes and the reference genome, will suggest copy number and structural aberration. | 1 | Applied and Interdisciplinary Chemistry |
Neutrons undergo many types of scattering, including both elastic and inelastic scattering. Whether elastic or inelastic scatter occurs is dependent on the speed of the neutron, whether fast or thermal, or somewhere in between. It is also dependent on the nucleus it strikes and its neutron cross section. In inelastic scattering, the neutron interacts with the nucleus and the kinetic energy of the system is changed. This often activates the nucleus, putting it into an excited, unstable, short-lived energy state which causes it to quickly emit some kind of radiation to bring it back down to a stable or ground state. Alpha, beta, gamma, and protons may be emitted. Particles scattered in this type of nuclear reaction may cause the nucleus to recoil in the other direction. | 0 | Theoretical and Fundamental Chemistry |
Laser-heated pedestal growth (LHPG) or laser floating zone (LFZ) is a crystal growth technique. A narrow region of a crystal is melted with a powerful CO or YAG laser. The laser and hence the floating zone, is moved along the crystal. The molten region melts impure solid at its forward edge and leaves a wake of purer material solidified behind it. This technique for growing crystals from the melt (liquid/solid phase transition) is used in materials research. | 0 | Theoretical and Fundamental Chemistry |
Mutagens may be of physical, chemical or biological origin. They may act directly on the DNA, causing direct damage to the DNA, and most often result in replication error. Some however may act on the replication mechanism and chromosomal partition. Many mutagens are not mutagenic by themselves, but can form mutagenic metabolites through cellular processes, for example through the activity of the cytochrome P450 system and other oxygenases such as cyclooxygenase. Such mutagens are called promutagens. | 0 | Theoretical and Fundamental Chemistry |
Lithium is a teratogen, causing birth defects in a small number of newborn babies. Case reports and several retrospective studies have demonstrated possible increases in the rate of a congenital heart defect known as Ebsteins anomaly, if taken during a womans pregnancy. As a consequence, fetal echocardiography is routinely performed in pregnant women taking lithium to exclude the possibility of cardiac anomalies. Lamotrigine seems to be a possible alternative to lithium in pregnant women for the treatment of acute bipolar depression or for the management of bipolar patients with normal mood. Gabapentin and clonazepam are also indicated as antipanic medications during the childbearing years and during pregnancy. Valproic acid and carbamazepine also tend to be associated with teratogenicity.
While it appears to be safe to use while breastfeeding a number of guidelines list it as a contraindication including the British National Formulary. | 1 | Applied and Interdisciplinary Chemistry |
* Elected a Fellow of the Royal Society of Medicine (FRSM)
* Awarded Fellowship of the International Society for Science and Religion
* 2010 James Gregory Medal
* 2010 Agilent Thought Leader Award
* 2012 Waters Corporation Center of Innovation Program Honors
* 2014 University of Gothenburg Sahlgrenska institute Honorary Doctorate
* 2016 The Analytical Scientist Power List
* 2017 International glycoconjugate organisation award | 1 | Applied and Interdisciplinary Chemistry |
Sea foam also acts as a mode of transport for both organisms and nutrients within the marine environment and, at times, into the intertidal or terrestrial environments. Wave action can deposit foam into intertidal areas where it can remain when the tide recedes, bringing nutrients to the intertidal zone. Additionally, sea foam can become airborne in windy conditions, transporting materials between marine and terrestrial environments. The ability of sea foam to transport materials is also thought to benefit macroalgal organisms, as macroalgae propagules can be carried to different microenvironments, thus influencing the tidal landscape and contributing to new possible ecological interactions. As sea foam is a wet environment, it is conducive habitat to algal spores where propagules can attach to the substrate and avoid risk of dissemination. When sea foam contains fungi, it can also aid in the decomposition of plant and animal remains in coastal ecosystems. | 0 | Theoretical and Fundamental Chemistry |
ITS-90 is designed to represent the thermodynamic temperature scale (referencing absolute zero) as closely as possible throughout its range. Many different thermometer designs are required to cover the entire range. These include helium vapor pressure thermometers, helium gas thermometers, standard platinum resistance thermometers (known as SPRTs, PRTs or Platinum RTDs) and monochromatic radiation thermometers.
Although the Kelvin and Celsius scales are defined using absolute zero (0 K) and the triple point of water (273.16 K and 0.01 °C), it is impractical to use this definition at temperatures that are very different from the triple point of water. Accordingly, ITS–90 uses numerous defined points, all of which are based on various thermodynamic equilibrium states of fourteen pure chemical elements and one compound (water). Most of the defined points are based on a phase transition; specifically the melting/freezing point of a pure chemical element. However, the deepest cryogenic points are based exclusively on the vapor pressure/temperature relationship of helium and its isotopes whereas the remainder of its cold points (those less than room temperature) are based on triple points. Examples of other defining points are the triple point of hydrogen (−259.3467 °C) and the freezing point of aluminum (660.323 °C).
Thermometers calibrated per ITS–90 use complex mathematical formulas to interpolate between its defined points. ITS–90 specifies rigorous control over variables to ensure reproducibility from lab to lab. For instance, the small effect that atmospheric pressure has upon the various melting points is compensated for (an effect that typically amounts to no more than half a millikelvin across the different altitudes and barometric pressures likely to be encountered). The standard even compensates for the pressure effect due to how deeply the temperature probe is immersed into the sample. ITS–90 also draws a distinction between "freezing" and "melting" points. The distinction depends on whether heat is going into (melting) or out of (freezing) the sample when the measurement is made. Only gallium is measured while melting, all the other metals are measured while the samples are freezing.
There are often small differences between measurements calibrated per ITS–90 and thermodynamic temperature. For instance, precise measurements show that the boiling point of VSMOW water under one standard atmosphere of pressure is actually 373.1339 K (99.9839 °C) when adhering strictly to the two-point definition of thermodynamic temperature. When calibrated to ITS–90, where one must interpolate between the defining points of gallium and indium, the boiling point of VSMOW water is about 10 mK less, about 99.974 °C. The virtue of ITS–90 is that another lab in another part of the world will measure the very same temperature with ease due to the advantages of a comprehensive international calibration standard featuring many conveniently spaced, reproducible, defining points spanning a wide range of temperatures. | 0 | Theoretical and Fundamental Chemistry |
The Mixtec civilization have long been thought to be the dominant goldsmiths of post-classic Mesoamerica. A large number of gold artifacts found in central and southern Mexico have been attributed to the Mixtec. | 1 | Applied and Interdisciplinary Chemistry |
Born in Sydney, Cornforth was the son and the second of four children of English-born, Oxford-educated schoolmaster and teacher John Warcup Cornforth and Hilda Eipper (1887–1969), a granddaughter of pioneering missionary and Presbyterian minister Christopher Eipper. Before her marriage, Eipper had been a maternity nurse.
Cornforth was raised in Sydney as well as Armidale, in the north of New South Wales, where he undertook primary school education.
At about 10 years old, Cornforth had noted signs of deafness, which led to a diagnosis of otosclerosis, a disease of the middle ear which causes progressive hearing loss. This left him completely deaf by the age of 20 but also fatefully influenced his career direction away from law, his original intended field of study, and towards chemistry. In an interview with Sir Harry Kroto for the Vega Science Trust, Cornforth explained: | 0 | Theoretical and Fundamental Chemistry |
Lauterbur was of Luxembourgish ancestry. Born and raised in Sidney, Ohio, Lauterbur graduated from Sidney High School, where a new Chemistry, Physics, and Biology wing was dedicated in his honor. As a teenager, he built his own laboratory in the basement of his parents' house. His chemistry teacher at school understood that he enjoyed experimenting on his own, so the teacher allowed him to do his own experiments at the back of class.
When he was drafted into the United States Army in the 1953 and was assigned to the Army Chemical Center in Edgewood, Maryland. His superiors allowed him to spend his time working on an early nuclear magnetic resonance (NMR) machine; he had published four scientific papers by the time he left the Army. Paul became an atheist later on. | 0 | Theoretical and Fundamental Chemistry |
* Van der Roest H., de Bruin B., van Dalen R., Uijterlinde C. (2012) Maakt Nereda-installatie Epe hooggespannen verwachtingen waar?, Vakblad H2O, nr.23, 2012, p30-p34.
* Giesen A., van Loosdrecht M.C.M., Niermans R. (2012) Aerobic granular biomass: the new standard for domestic and industrial wastewater treatment?, Water21, April 2012, p28-p30.
* Zilverentant A., de Bruin B., Giesen A. (2011) [http://skiw.nl/open.php?do=document&id=2a79ea27c279e471f4d180b08d62b00a Nereda: The new Standard for Energy and Cost Effective Industrial and Municipal Wastewater treatment], SKIW, Het National Water Symposium, May 2011.
* Water Sewage & Effluent (2010) Water Nymph at Gansbaai, Water Sewage & Effluent, Water Management solutions for Africa, Volume 30 no.2, 2010, p50-p53.
* Gao D. Liu L. Liang H. Wu W.M. (2010), Aerobic granular sludge: characterization, mechanism of granulation and application to wastewater treatment, Critical reviews in Biotechnology
* Dutch Water Sector (2012), [https://archive.today/20130121175432/http://www.dutchwatersector.com/news/news/2012/05/official-commissioning-nereda-at-wwtp-epe-wonder-granule-keeps-its-promise/ Commissioning Nereda at wwtp Epe: Wonder granule keeps its promise]
* Kolver (2012), [http://www.engineeringnews.co.za/article/success-at-gansbaai-leads-to-construction-of-another-nereda-plant-2012-06-01 Success at Gansbaai leads to construction of another Nereda plant], engineeringnews
* Nadaba (2009), [http://www.engineeringnews.co.za/article/new-innovation-2009-11-06 Gansbaai wastewater project incorporates techno innovation ], engineeringnews
* Euronews (2012), [http://www.euronews.com/2012/05/22/dutch-inventor-cleans-up-water-treatment/ Dutch Investor cleans up water treatment] | 1 | Applied and Interdisciplinary Chemistry |
Folin's reagent or sodium 1,2-naphthoquinone-4-sulfonate is a chemical reagent used as a derivatizing agent to measure levels of amines and amino acids. The reagent reacts with them in alkaline solution to produce a fluorescent material that can be easily detected.
This should not be confused with Folin-Ciocalteu reagent, that is used to detect phenolic compounds.
The Folin reagent can be used with an acidic secondary reagent to distinguish MDMA and related compounds from PMMA and related compounds. | 0 | Theoretical and Fundamental Chemistry |
As fusion time begins, there is an incubation period where no strength develops. Once enough time has passed for the molten material to begin solidifying, the joint strength begins to develop before plateauing at the maximum strength. If power is applied after full joint strength is achieved, the strength will start to decline slowly. | 0 | Theoretical and Fundamental Chemistry |
The evolution of interactome complexity is delineated in a study published in Nature. In this study it is first noted that the boundaries between prokaryotes, unicellular eukaryotes and multicellular eukaryotes are accompanied by orders-of-magnitude reductions in effective population size, with concurrent amplifications of the effects of random genetic drift. The resultant decline in the efficiency of selection seems to be sufficient to influence a wide range of attributes at the genomic level in a nonadaptive manner. The Nature study shows that the variation in the power of random genetic drift is also capable of influencing phylogenetic diversity at the subcellular and cellular levels. Thus, population size would have to be considered as a potential determinant of the mechanistic pathways underlying long-term phenotypic evolution. In the study it is further shown that a phylogenetically broad inverse relation exists between the power of drift and the structural integrity of protein subunits. Thus, the accumulation of mildly deleterious mutations in populations of small size induces secondary selection for protein–protein interactions that stabilize key gene functions, mitigating the structural degradation promoted by inefficient selection. By this means, the complex protein architectures and interactions essential to the genesis of phenotypic diversity may initially emerge by non-adaptive mechanisms. | 1 | Applied and Interdisciplinary Chemistry |
Demasculinization refers to the reversal of virilization. Some but not all aspects of virilization are reversible. Demasculinization occurs naturally with andropause, pathologically with hypogonadism, and artificially or medically with antiandrogens, estrogens, and orchiectomy. It is desired by many transgender women who have undergone the changes of pubertal masculinization, to restore and induce feminine physical traits that would otherwise be masked or never occur. Some virilized traits remain though (such as body hair, a hard jawline and an enlarged larynx), due to the fashion in which virilization affects a body's physiology. | 1 | Applied and Interdisciplinary Chemistry |
CLIPZ is a database of post-transcriptional regulatory elements (RNA-binding proteins) built from cross-linking and immunoprecipitation data. | 1 | Applied and Interdisciplinary Chemistry |
Mitogen-activated protein kinases are catalytically inactive in their base form. In order to become active, they require (potentially multiple) phosphorylation events in their activation loops. This is conducted by specialized enzymes of the STE protein kinase group. In this way protein dynamics can induce a conformational change in the structure of the protein via long-range allostery.
In the case of classical MAP kinases, the activation loop contains a characteristic TxY (threonine-x-tyrosine) motif (TEY in mammalian ERK1 and ERK2, TDY in ERK5, TPY in JNKs, TGY in p38 kinases) that needs to be phosphorylated on both the threonine and the tyrosine residues in order to lock the kinase domain in a catalytically competent conformation. In vivo and in vitro, phosphorylation of tyrosine oftentimes precedes phosphorylation of threonine, although phosphorylation of either residue can occur in the absence of the other.
This tandem activation loop phosphorylation (that was proposed to be either distributive or processive, dependent on the cellular environment) is performed by members of the Ste7 protein kinase family, also known as MAP2 kinases. MAP2 kinases in turn, are also activated by phosphorylation, by a number of different upstream serine-threonine kinases (MAP3 kinases). Because MAP2 kinases display very little activity on substrates other than their cognate MAPK, classical MAPK pathways form multi-tiered, but relatively linear pathways. These pathways can effectively convey stimuli from the cell membrane (where many MAP3Ks are activated) to the nucleus (where only MAPKs may enter) or to many other subcellular targets.
In comparison to the three-tiered classical MAPK pathways, some atypical MAP kinases appear to have a more ancient, two-tiered system. ERK3 (MAPK6) and ERK4 (MAPK4) were recently shown to be directly phosphorylated and thus activated by PAK kinases (related to other MAP3 kinases). In contrast to the classical MAP kinases, these atypical MAPKs require only a single residue in their activation loops to be phosphorylated. The details of NLK and ERK7 (MAPK15) activation remain unknown.
Inactivation of MAPKs is performed by a number of phosphatases. A very conserved family of dedicated phosphatases is the so-called MAP kinase phosphatases (MKPs), a subgroup of dual-specificity phosphatases (DUSPs). As their name implies, these enzymes are capable of hydrolyzing the phosphate from both phosphotyrosine and the phosphothreonine residues. Since removal of either phosphate groups will greatly reduce MAPK activity, essentially abolishing signaling, some tyrosine phosphatases are also involved in inactivating MAP kinases (e.g. the phosphatases HePTP, STEP and PTPRR in mammals). | 1 | Applied and Interdisciplinary Chemistry |
Fracturing is a brittle deformation process that creates permanent linear breaks, that are not accompanied by displacement within materials. These linear breaks or openings can be independent or interconnected. For fracturing to occur, the ultimate strength of the materials need to be exceeded to a point where the material ruptures. Rupturing is aided by the accumulations of high differential stress (the difference between the maximum and minimum stress acting on the object). Most fracture grow into faults. However, the term fault is only used when the fracture plane accommodate some degree of movement. Fracturing can happen across all scales, from microfractures to macroscopic fractures and joints in the rocks. | 1 | Applied and Interdisciplinary Chemistry |
Albert Fredrick Ottomar Germann (February 18, 1886 – December 22, 1976) was an American physical chemist, university professor, and chemical entrepreneur. | 0 | Theoretical and Fundamental Chemistry |
Nitrification in nature is a two-step oxidation process of ammonium () or ammonia () to nitrite () and then to nitrate () catalyzed by two ubiquitous bacterial groups growing together. The first reaction is oxidation of ammonium to nitrite by ammonia oxidizing bacteria (AOB) represented by members of Betaproteobacteria and Gammaproteobacteria. Further organisms able to oxidize ammonia are Archaea (AOA).
The second reaction is oxidation of nitrite () to nitrate by nitrite-oxidizing bacteria (NOB), represented by the members of Nitrospinota, Nitrospirota, Pseudomonadota, and Chloroflexota.
This two-step process was described already in 1890 by the Ukrainian microbiologist Sergei Winogradsky.
Ammonia can be also oxidized completely to nitrate by one comammox bacterium. | 1 | Applied and Interdisciplinary Chemistry |
The revival of the woolly mammoth is a proposed hypothetical that frozen soft-tissue remains and DNA from extinct woolly mammoths could be a means of regenerating the species. Several methods have been proposed to achieve this goal, including cloning, artificial insemination, and genome editing. Whether or not it is ethical to create a live mammoth is debated.
In 2003, the Pyrenean ibex was briefly revived, giving credence to the idea that the mammoth could be successfully revived. | 1 | Applied and Interdisciplinary Chemistry |
It carried out work on reactors for the British civil and military (submarine fleet) nuclear energy programmes, investigating metallurgy. In the first ten years, it carried out research on materials for fast breeder reactors; it was the first time that niobium had been part of a fast breeder reactor. The site investigated fracture mechanics, nuclear reactor physics and hydraulics.
Work on irradiation of metals was also carried out with the School of Materials, University of Manchester and the Department of Materials Science and Metallurgy, University of Cambridge. | 1 | Applied and Interdisciplinary Chemistry |
Enediols are alkenes with a hydroxyl group on each carbon of the C=C double bond. Normally such compounds are disfavored components in equilibria with acyloins. One special case is catechol, where the C=C subunit is part of an aromatic ring. In some other cases however, enediols are stabilized by flanking carbonyl groups. These stabilized enediols are called reductones. Such species are important in glycochemistry, e.g., the Lobry de Bruyn-van Ekenstein transformation.
Ribulose-1,5-bisphosphate is a key substrate in the Calvin cycle of photosynthesis. In the Calvin cycle, the ribulose equilibrates with the enediol, which then binds carbon dioxide. The same enediol is also susceptible to attack by oxygen (O) in the (undesirable) process called photorespiration. | 0 | Theoretical and Fundamental Chemistry |
Green leaf volatiles (GLV) are organic compounds released by plants.
Some of these chemicals function as signaling compounds between either plants of the same species, of other species, or even different lifeforms like insects.
Green leaf volatiles are involved in patterns of attack and protection between species. They have been found to increase the attractive effect of pheromones of cohabiting insect species that protect plants from attacking insect species. For example, corn plants that are being fed on by caterpillars will release GLVs that attract wasps, who then attack the caterpillars. GLVs also have antimicrobial properties that can prevent infection at the site of injury.
GLVs include C6-aldehydes [(Z)-3-hexenal, n-hexanal] and their derivatives such as (Z)-3-hexenol, (Z)-3-hexen-1-yl acetate, and the corresponding E-isomers. | 1 | Applied and Interdisciplinary Chemistry |
Many waters in both the UK and Europe are capable of supporting Type 1 pitting but no problems will be experienced unless a pit is initiated in the wall of the tube. When a copper tube is initially filled with a hard water salts deposit on the wall and the copper slowly reacts with the water producing a thin protective layer of mixed corrosion products and hardness scale. If any pitting of the tube is to occur then this film must be locally disrupted. There are three mechanisms that allow the disruption of the protective deposits. The most well known, although now the least common, is the presence of carbon films on the bore. Stagnation and flux residues are the most common initiation mechanisms that have led to Type 1 pitting failures in the last ten years. | 1 | Applied and Interdisciplinary Chemistry |
The Deborah number was originally proposed by Markus Reiner, a professor at Technion in Israel, who chose the name inspired by a verse in the Bible, stating "The mountains flowed before the Lord" in a song by the prophetess Deborah in the Book of Judges; הָרִ֥ים נָזְל֖וּ מִפְּנֵ֣י יְהוָ֑ה hā-rîm nāzəlū mippənê Yahweh). In his 1964 paper (a reproduction of his after-dinner speech to the Fourth International Congress on Rheology in 1962), Markus Reiner further elucidated the name's origin: | 1 | Applied and Interdisciplinary Chemistry |
The glyoxylate cycle is a variant of the citric acid cycle. It is an anabolic pathway occurring in plants and bacteria utilizing the enzymes isocitrate lyase and malate synthase. Some intermediate steps of the cycle are slightly different from the citric acid cycle; nevertheless oxaloacetate has the same function in both processes. This means that oxaloacetate in this cycle also acts as the primary reactant and final product. In fact the oxaloacetate is a net product of the glyoxylate cycle because its loop of the cycle incorporates two molecules of acetyl-CoA. | 1 | Applied and Interdisciplinary Chemistry |
When a continuum radiation source is used for AAS measurement it is indispensable to work with a high-resolution monochromator. The resolution has to be equal to or better than the half-width of an atomic absorption line (about 2 pm) in order to avoid losses of sensitivity and linearity of the calibration graph. The research with high-resolution (HR) CS AAS was pioneered by the groups of O’Haver and Harnly in the US, who also developed the (up until now) only simultaneous multi-element spectrometer for this technique. The breakthrough, however, came when the group of Becker-Ross in Berlin, Germany, built a spectrometer entirely designed for HR-CS AAS. The first commercial equipment for HR-CS AAS was introduced by Analytik Jena (Jena, Germany) at the beginning of the 21st century, based on the design proposed by Becker-Ross and Florek. These spectrometers use a compact double monochromator with a prism pre-monochromator and an echelle grating monochromator for high resolution. A linear charge-coupled device (CCD) array with 200 pixels is used as the detector. The second monochromator does not have an exit slit; hence the spectral environment at both sides of the analytical line becomes visible at high resolution. As typically only 3–5 pixels are used to measure the atomic absorption, the other pixels are available for correction purposes. One of these corrections is that for lamp flicker noise, which is independent of wavelength, resulting in measurements with very low noise level; other corrections are those for background absorption, as will be discussed later. | 0 | Theoretical and Fundamental Chemistry |
LHT was introduced by the U.K. in British India (now India, Pakistan, Myanmar, and Bangladesh), British Malaya and British Borneo (now Malaysia, Brunei and Singapore), and British Hong Kong. All are still LHT, as well as neighbour countries Bhutan and Nepal, except Myanmar, which switched to RHT in 1970, although much of its infrastructure is still geared to LHT and its neighbours India, Bangladesh and Thailand use LHT. Most cars are used RHD vehicles imported from Japan. Afghanistan was LHT until the 1950s, in line with Pakistan (former part of British India).
Although Portuguese Timor (present-day East Timor), which shares the island Timor with Indonesia with LHT, switched to RHT as Portugal in 1928, it switched back to LHT in 1976 during the Indonesian occupation of East Timor.
In the 1930s, parts of China like the Shanghai International Settlement, Canton and Japanese-occupied northeast China used LHT. However, in 1946 the Republic of China made RHT mandatory in China (including Taiwan, which used LHT under Japanese colonization 1895–1945), although Portuguese Macau (present-day Macau) remained LHT, as well as British Hong Kong, despite becoming transferred to China in 1999 and 1997 respectively.
Both North Korea and South Korea use RHT since 1946, after liberation from Japanese colonial power.
The Philippines was mostly LHT during its Spanish and American colonial periods, as well as during the Commonwealth era. During the Japanese occupation, the Philippines remained LHT, also because LHT had been required by the Japanese; but during the Battle of Manila, the liberating American forces drove their tanks to the right for easier facilitation of movement. RHT was formalized in 1945 through a decree by then-president Sergio Osmeña. Even though RHT was formalized, RHD vehicles such as public buses were still imported in the Philippines until a law was passed that banned the importation of RHD vehicles except for special cases. These RHD vehicles are required to be converted to LHD
Japan was never part of the British Empire, but its traffic also drives on the left. Although the origin of this habit goes back to the Edo period (1603–1868), it was not until 1872 – the year Japans first railway was introduced, built with technical aid from the British – that this unwritten rule received official acknowledgment. Gradually, a massive network of railways and tram tracks was built, with all railway vehicles driven on the left-hand side. However, it took another half-century, until 1924, until left-hand traffic was legally mandated. Post-World War II Okinawa was ruled by the United States Civil Administration of the Ryukyu Islands until 1972, and was RHT until 6 a.m. the morning of 30 July 1978, when it switched back to LHT. The conversion operation was known as 730 (Nana-San-Maru', which refers to the date of the changeover). Okinawa is one of few places to have changed from RHT to LHT in the late 20th century. While Japan drives on the left and most Japanese vehicles are RHD, imported vehicles (e.g. BMW, Mercedes-Benz, Porsche) are generally bought as LHD as LHD cars are considered to be status symbols.
Vietnam became RHT as part of French Indochina, as did Laos and Cambodia. In Cambodia, RHD cars, many of which were smuggled from Thailand, were banned in 2001, even though they accounted for 80% of vehicles in the country. | 0 | Theoretical and Fundamental Chemistry |
Alkylation with geminal dihalides gives 1,3-dithiepanes. Oxidation gives the cyclic disulfide 1,2-dithiane:
It forms self-assembled monolayers on gold.
It is also used in polyadditions along with 1,4-butanediol to form sulfur-containing polyester and polyurethanes containing diisocyanate. Several of these polymers are considered biodegradable and many of their components are sourced from non-petroleum oils. | 0 | Theoretical and Fundamental Chemistry |
In polymerase chain reaction (PCR) experiments, the GC-content of short oligonucleotides known as primers is often used to predict their annealing temperature to the template DNA. A higher GC-content level indicates a relatively higher melting temperature.
Many sequencing technologies, such as Illumina sequencing, have trouble reading high-GC-content sequences. Bird genomes are known to have many such parts, causing the problem of "missing genes" expected to be present from evolution and phenotype but never sequenced — until improved methods were used. | 1 | Applied and Interdisciplinary Chemistry |
SOCl is highly reactive and can violently release hydrochloric acid upon contact with water and alcohols. It is also a controlled substance under the Chemical Weapons Convention, where it is listed as a Schedule 3 substance, since it is used in the manufacture of G-series nerve agents and the Meyer and Meyer–Clarke methods of producing sulfur-based mustard gases. | 0 | Theoretical and Fundamental Chemistry |
Pyridine is a toxic, flammable liquid with a strong and unpleasant fishy odour. Its odour threshold of 0.04 to 20 ppm is close to its threshold limit of 5 ppm for adverse effects, thus most (but not all) adults will be able to tell when it is present at harmful levels. Pyridine easily dissolves in water and harms both animals and plants in aquatic systems. | 0 | Theoretical and Fundamental Chemistry |
Aggregating safety data across clinical trials during drug development is important because trials are generally designed to focus on determining how well the drug works. The safety data collected and aggregated across multiple trials as the drug is developed allows the sponsor, investigators and regulatory agencies to monitor the aggregate safety profile of experimental medicines as they are developed. The value of assessing aggregate safety data is: a) decisions based on aggregate safety assessment during development of the medicine can be made throughout the medicines development and b) it sets up the sponsor and regulators well for assessing the medicines safety after the drug is approved. | 1 | Applied and Interdisciplinary Chemistry |
Radiochemistry is the chemistry of radioactive materials, in which radioactive isotopes of elements are used to study the properties and chemical reactions of non-radioactive isotopes (often within radiochemistry the absence of radioactivity leads to a substance being described as being inactive as the isotopes are stable).
For further details please see the page on radiochemistry. | 0 | Theoretical and Fundamental Chemistry |
Respirometry is a general term that encompasses a number of techniques for obtaining estimates of the rates of metabolism of vertebrates, invertebrates, plants, tissues, cells, or microorganisms via an indirect measure of heat production (calorimetry). | 1 | Applied and Interdisciplinary Chemistry |
Modafinil, a eugeroic or wakefulness-promoting drug, is primarily used for treating narcolepsy, a sleep disorder characterized by excessive daytime sleepiness and sudden sleep attacks. Being a central nervous system (CNS) stimulant (psychostimulant) itself, modafinil has lower addictive potential than classical psychostimulants, such as amphetamines, cocaine or methylphenidate, but still produces psychoactive, euphoric, and subjective effects typical of classical stimulants.
Narcolepsy causes a strong urge to sleep during the day and can include symptoms like cataplexy (sudden muscle weakness), sleep paralysis (inability to move or speak while falling asleep or waking up), and hallucinations. Narcolepsy is linked to a lack of the brain chemical hypocretin (or orexin), primarily produced in the hypothalamus. Modafinil is not a cure for narcolepsy, but it can help manage the symptoms. While modafinil is primarily used to treat excessive sleepiness, it may also help reduce the frequency and severity of cataplexy attacks in some people. Modafinil is approved for management of narcolepsy with or without cataplexy. However, it is not specifically approved for the treatment of cataplexy.
Modafinil is also prescribed for shift work sleep disorder and excessive daytime sleepiness caused by obstructive sleep apnea, though it is recommended that people with apnea use continuous positive airway pressure (CPAP) therapy before starting modafinil.
Modafinil's use varies by region. In the US, it is approved for adult narcolepsy, shift work sleep disorder, and obstructive sleep apnea, but not for children. In the UK and the EU, since 2014, it is approved solely for narcolepsy, including in children (pediatric narcolepsy), with its use for other conditions restricted by the European Medicines Agency.
both the French and the American Academy of Sleep Medicine strongly recommend modafinil as the first-choice treatment for narcolepsy. In Europe, modafinil is considered one of the primary drugs recommended for treating narcolepsy according to the guidelines. | 0 | Theoretical and Fundamental Chemistry |
Based on the physical method of electroporation, nucleofection uses a combination of electrical parameters, generated by a device called Nucleofector, with cell-type specific reagents. The substrate is transferred directly into the cell nucleus and the cytoplasm. In contrast, other commonly used non-viral transfection methods rely on cell division for the transfer of DNA into the nucleus. Thus, nucleofection provides the ability to transfect even non-dividing cells, such as neuron and resting blood cells. Before the introduction of the Nucleofector Technology, efficient gene transfer into primary cells had been restricted to the use of viral vectors, which typically involve disadvantages such as safety risks, lack of reliability, and high cost. The non-viral gene transfer methods available were not suitable for the efficient transfection of primary cells. Non-viral delivery methods may require cell division for completion of transfection, since the DNA enters the nucleus during breakdown of the nuclear envelope upon cell division or by a specific localization sequence.
Optimal nucleofection conditions depend upon the individual cell type, not on the substrate being transfected. This means that identical conditions are used for the nucleofection of DNA, RNA, siRNAs, shRNAs, mRNAs and pre-mRNAs, BACs, peptides, morpholinos, PNA, or other biologically active molecules. | 1 | Applied and Interdisciplinary Chemistry |
The next table gives the terrestrial isotope distributions for some elements. Some elements, such as phosphorus and fluorine, only exist as a single isotope, with a natural abundance of 100%. | 0 | Theoretical and Fundamental Chemistry |
Entropic gravity, also known as emergent gravity, is a theory in modern physics that describes gravity as an entropic force—a force with macro-scale homogeneity but which is subject to quantum-level disorder—and not a fundamental interaction. The theory, based on string theory, black hole physics, and quantum information theory, describes gravity as an emergent phenomenon that springs from the quantum entanglement of small bits of spacetime information. As such, entropic gravity is said to abide by the second law of thermodynamics under which the entropy of a physical system tends to increase over time.
The theory has been controversial within the physics community but has sparked research and experiments to test its validity. | 0 | Theoretical and Fundamental Chemistry |
In immunology, activation is the transition of leucocytes and other cell types involved in the immune system. On the other hand, deactivation is the transition in the reverse direction. This balance is tightly regulated, since a too small degree of activation causes susceptibility to infections, while, on the other hand, a too large degree of activation causes autoimmune diseases.
Activation and deactivation results from a variety of factors, including cytokines, soluble receptors, arachidonic acid metabolites, steroids, receptor antagonists, adhesion molecules, bacterial products and viral products. | 0 | Theoretical and Fundamental Chemistry |
The ECW model created by Russell S. Drago is a quantitative model that describes and predicts the strength of Lewis acid base interactions, . The model assigned and parameters to many Lewis acids and bases. Each acid is characterized by an and a . Each base is likewise characterized by its own and . The and parameters refer, respectively, to the electrostatic and covalent contributions to the strength of the bonds that the acid and base will form. The equation is
The term represents a constant energy contribution for acid–base reaction such as the cleavage of a dimeric acid or base. The equation predicts reversal of acids and base strengths. The graphical presentations of the equation show that there is no single order of Lewis base strengths or Lewis acid strengths. | 0 | Theoretical and Fundamental Chemistry |
During World War II, various chloroalkanes were in standard use in military aircraft, although these early halons suffered from excessive toxicity. Nevertheless, after the war they slowly became more common in civil aviation as well. In the 1960s, fluoroalkanes and bromofluoroalkanes became available and were quickly recognized as being highly effective fire-fighting materials. Much early research with Halon 1301 was conducted under the auspices of the US Armed Forces, while Halon 1211 was, initially, mainly developed in the UK. By the late 1960s they were standard in many applications where water and dry-powder extinguishers posed a threat of damage to the protected property, including computer rooms, telecommunications switches, laboratories, museums and art collections. Beginning with warships, in the 1970s, bromofluoroalkanes also progressively came to be associated with rapid knockdown of severe fires in confined spaces with minimal risk to personnel.
By the early 1980s, bromofluoroalkanes were in common use on aircraft, ships, and large vehicles as well as in computer facilities and galleries. However, concern was beginning to be expressed about the impact of chloroalkanes and bromoalkanes on the ozone layer. The Vienna Convention for the Protection of the Ozone Layer did not cover bromofluoroalkanes under the same restrictions, instead, the consumption of bromofluoroalkanes was frozen at 1986 levels. This is due to the fact that emergency discharge of extinguishing systems was thought to be too small in volume to produce a significant impact, and too important to human safety for restriction. | 1 | Applied and Interdisciplinary Chemistry |
The Max Planck Institute for Terrestrial Microbiology () is a research institute for terrestrial microbiology in Marburg, Germany. It was founded in 1991 by Rudolf K. Thauer and is one of 80 institutes in the Max Planck Society (Max-Planck-Gesellschaft). Its sister institute is the Max Planck Institute for Marine Microbiology, which was founded a year later in 1992 in Bremen. | 0 | Theoretical and Fundamental Chemistry |
Throughout the years there have been a few mass bleaching events that have affected the Great Barrier Reef. In particular, the years of 2016 and 2017, saw the reef sustain two years of back to back bleaching periods. This long period accounted for an estimated loss of half of the coral life in the Great Barrier Reef. The parts of the reef that did survive were damaged, leading to an overall period of low coral reproduction. This was later followed by another bleaching event in 2020, making it the third bleaching event in five years. Studies found however that the results of the 2020 bleaching were not too severe, as it only affected a minimal amount of reefs, with most being in the lower to moderate levels of bleaching.
In early 2022 a study showed, 91% of coral in the Great Barrier Reef, have experienced some degree of coral bleaching. The reefs that had higher levels of bleaching, often were accompanied by higher overall air temperature. These temperature levels lasted all through the summer season in Australia, attributing to prolonged coral bleaching periods. Prolonged periods raise concern, as corals would not be able to reproduce and die out, leading to more loss of the reefs. However, recent reports from June 2022, have stated that the Great Barrier Reef, is currently recovering. Reefs affected by bleaching have lowered to 16% along different areas of the Australian Coast. As ocean temperatures continue to drop, we can expect bleaching levels to go down, and coral levels to increase. Though coral bleaching has gone down, predators of the coral reef, Crown-of-thorns starfish, are still impacting coral growth and development. | 0 | Theoretical and Fundamental Chemistry |
The methylium cation () exists in the gas phase, but is otherwise not encountered. Some compounds are considered to be sources of the cation, and this simplification is used pervasively in organic chemistry. For example, protonation of methanol gives an electrophilic methylating reagent that reacts by the S2 pathway:
Similarly, methyl iodide and methyl triflate are viewed as the equivalent of the methyl cation because they readily undergo S2 reactions by weak nucleophiles.
The methyl cation has been detected in interstellar space. | 0 | Theoretical and Fundamental Chemistry |
The phase diagram shows the importance of the electrode gap distance to the performance of electrochemical reactions. For traditional macrosystems, where the electrode gap distance is much larger than the Debye-length, two half-reactions are decoupled and cannot influence each other. Normally the electrochemical current is limited by a slow diffusion step. When the gap distance is reduced to around the Debye-length, a large electric field can form between the two electrodes (due to double layers and the two regions overlapping with each other); this enhances the mass transport rate. In this region the electrolysis current is very sensitive to the gap distance and the reactions are migration-rate limited. When the gap distance is further reduced to the deep-sub-Debye-length region, the mass transport can be enhanced further to a level even faster than the electron-transfer step. In this region, even when we shrink the gap distance further, the current cannot be enlarged any more, meaning that the current has reached saturation. Here the two half-reactions are coupled together and the reactions are limited by the electron-transfer steps.
Therefore, by just adjusting the gap distance, the fundamental performance of the electrochemical reactions can be significantly changed. | 0 | Theoretical and Fundamental Chemistry |
Genes of all organisms, except bacteria, consist of short protein-coding regions (exons) interrupted by long sequences (introns). When a gene is expressed, its DNA sequence is copied into a “primary RNA” sequence by the enzyme RNA polymerase. Then the “spliceosome” machinery physically removes the introns from the RNA copy of the gene by the process of splicing, leaving only a contiguously connected series of exons, which becomes messenger RNA (mRNA). This mRNA is now read by the ribosome, which produces the encoded protein. Thus, although introns are not physically removed from a gene, a gene's sequence is read as if introns were not present.
Exons are usually short, with an average length of about 120 bases (e.g. in human genes). Intron lengths vary widely from 10 to 500,000, but exon lengths have an upper bound of about 600 bases in most eukaryotes. Because exons code for protein sequences, they are important for the cell, yet constitute only ~2% of the sequences. Introns, in contrast, constitute 98% of the sequences but seem to have few crucial functions, except for enhancer sequences and developmental regulators in rare instances.
Until Philip Sharp and Richard Roberts discovered introns within eukaryotic genes in 1977, it was believed that the coding sequence of all genes was always in one single stretch, bounded by a single long ORF. The discovery of introns was a profound surprise, which instantly brought up the questions of how, why and when the introns came into the eukaryotic genes.
It soon became apparent that a typical eukaryotic gene was interrupted at many locations by introns, dividing the coding sequence into many short exons. Also surprising was that the introns were long, as long as hundreds of thousands of bases. These findings prompted the questions of why many introns occur within a gene (for example, ~312 introns occur in the human gene TTN), why they are long, and why exons are short.
It was also discovered that the spliceosome machinery was large and complex with ~300 proteins and several SnRNA molecules. The questions extended to the origin of the spliceosome. Soon after the discovery of introns, it became apparent that the junctions between exons and introns on either side exhibited specific sequences that directed the spliceosome machinery to the exact base position for splicing. How and why these splice junction signals came into being was another important question. | 1 | Applied and Interdisciplinary Chemistry |
Many metering pumps are piston-driven. Piston pumps are positive displacement pumps which can be designed to pump at practically constant flow rates (averaged over time) against a wide range of discharge pressure, including high discharge pressures of thousands of psi.
Piston-driven metering pumps commonly work as follows: There is a piston (sometimes called plunger), typically cylindrical, which can go in and out of a correspondingly shaped chamber in the pump head. The inlet and outlet lines are joined to the piston chamber. There are two check valves, often ball check valves, attached to the pump head, one at the inlet line and the other at the outlet line. The inlet valve allows flow from the inlet line to the piston chamber, but not in the reverse direction. The outlet valve allows flow from the chamber to the outlet line, but not in reverse. The motor repeatedly moves the piston into and out of the piston chamber, causing the volume of the chamber to repeatedly become smaller and larger. When the piston moves out, a vacuum is created. Low pressure in the chamber causes liquid to enter and fill the chamber through the inlet check valve, but higher pressure at the outlet causes the outlet valve to shut. Then when the piston moves in, it pressurizes the liquid in the chamber. High pressure in the chamber causes the inlet valve to shut and forces the outlet valve to open, forcing liquid out at the outlet. These alternating suction and discharge strokes are repeated over and over to meter the liquid. In the back of the chamber, there is packing around the piston or a doughnut-shaped seal with a toroid-shaped sphincter-like spring inside compressing the seal around the piston. This holds the fluid pressure when the piston slides in and out and makes the pump leak-tight. The packing or seals can wear out after prolonged use and can be replaced. The metering rate can be adjusted by varying the strokelength by which the piston moves back and forth or varying the speed of the piston motion.
A single-piston pump delivers liquid to the outlet only during the discharge stroke. If the piston's suction and discharge strokes occur at the same speed and liquid is metered out half the time the pump is working, then the overall metering rate averaged over time equals half the average flow rate during the discharge stroke. Some single-piston pumps may have a constant slow piston motion for discharge and a quick retract motion for refilling the pump head. In such cases, the overall metering rate is practically equal to the pumping rate during the discharge stroke. | 1 | Applied and Interdisciplinary Chemistry |
Vancomycin is made by the soil bacterium Amycolatopsis orientalis.
Vancomycin biosynthesis occurs primarily via three nonribosomal protein syntheses (NRPSs) VpsA, VpsB, and VpsC. The enzymes determine the amino acid sequence during its assembly through its 7 modules. Before vancomycin is assembled through NRPS, the non-proteinogenic amino acids are first synthesized. -tyrosine is modified to become the β-hydroxytyrosine (β-HT) and 4-hydroxyphenylglycine (4-Hpg) residues. 3,5 dihydroxyphenylglycine ring (3,5-DPG) is derived from acetate.
Nonribosomal peptide synthesis occurs through distinct modules that can load and extend the protein by one amino acid per module through the amide bond formation at the contact sites of the activating domains. Each module typically consists of an adenylation (A) domain, a peptidyl carrier protein (PCP) domain, and a condensation (C) domain. In the A domain, the specific amino acid is activated by converting into an aminoacyl adenylate enzyme complex attached to a 4phosphopantetheine cofactor by thioesterification. The complex is then transferred to the PCP domain with the expulsion of AMP. The PCP domain uses the attached 4-phosphopantethein prosthetic group to load the growing peptide chain and their precursors. The organization of the modules necessary to biosynthesize Vancomycin is shown in Figure 1. In the biosynthesis of Vancomycin, additional modification domains are present, such as the epimerization (E) domain, which isomerizes the amino acid from one stereochemistry to another, and a thioesterase domain (TE) is used as a catalyst for cyclization and releases of the molecule via a thioesterase scission.
A set of NRPS enzymes (peptide synthase VpsA, VpsB, and VpsC) are responsible for assembling the heptapeptide. (Figure 2). VpsA codes for modules 1, 2, and 3. VpsB codes for modules 4, 5, and 6, and VpsC codes for module 7. The vancomycin aglycone contains 4 D-amino acids, although the NRPSs only contain 3 epimerization domains. The origin of D-Leu at residue 1 is not known. The three peptide syntheses are located at the start of the region of the bacterial genome linked with antibiotic biosynthesis, and span 27 kb.
β-hydroxytyrosine (β-HT) is synthesized prior to incorporation into the heptapeptide backbone. L-tyrosine is activated and loaded on the NRPS VpsD, hydroxylated by OxyD, and released by the thioesterase Vhp. The timing of the chlorination by halogenase VhaA during biosynthesis is currently undetermined, but is proposed to occur before the complete assembly of the heptapeptide.
After the linear heptapeptide molecule is synthesized, vancomycin has to undergo further modifications, such as oxidative cross-linking and glycosylation, in trans by distinct enzymes, referred to as tailoring enzymes, to become biologically active (Figure 3). To convert the linear heptapeptide to cross-linked, glycosylated vancomycin, six enzymes, are required. The enzymes OxyA, OxyB, OxyC, and OxyD are cytochrome P450 enzymes. OxyB catalyzes oxidative cross-linking between residues 4 and 6, OxyA between residues 2 and 4, and OxyC between residues 5 and 7. This cross-linking occurs while the heptapeptide is covalently bound to the PCP domain of the 7th NRPS module. These P450s are recruited by the X domain present in the 7th NRPS module, which is unique to glycopeptide antibiotic biosynthesis. The cross-linked heptapeptide is then released by the action of the TE domain, and methyltransferase Vmt then N-methylates the terminal leucine residue. GtfE then joins D-glucose to the phenolic oxygen of residue 4, followed by the addition of vancosamine catalyzed by GtfD.
Some of the glycosyltransferases capable of glycosylating vancomycin and related nonribosomal peptides display notable permissivity and have been employed for generating libraries of differentially glycosylated analogs through a process known as glycorandomization. | 0 | Theoretical and Fundamental Chemistry |
Tramadol, sold under the brand name Ultram among others, is an opioid pain medication and a serotonin–norepinephrine reuptake inhibitor (SNRI) used to treat moderately severe pain. When taken by mouth in an immediate-release formulation, the onset of pain relief usually begins within an hour. It is also available by injection. It is available in combination with paracetamol (acetaminophen).
As is typical of opioids, common side effects include constipation, itchiness, and nausea. Serious side effects may include hallucinations, seizures, increased risk of serotonin syndrome, decreased alertness, and drug addiction. A change in dosage may be recommended in those with kidney or liver problems. It is not recommended in those who are at risk of suicide or in those who are pregnant. While not recommended in women who are breastfeeding, those who take a single dose should not generally have to stop breastfeeding. Tramadol is converted in the liver to O-desmethyltramadol (desmetramadol), an opioid with a stronger affinity for the μ-opioid receptor.
Tramadol was patented in 1972 and launched under the name "Tramal" in 1977 by the West German pharmaceutical company Grünenthal GmbH. In the mid-1990s, it was approved in the United Kingdom and the United States. It is available as a generic medication and marketed under many brand names worldwide. In 2021, it was the 41st most commonly prescribed medication in the United States, with more than 15million prescriptions. | 0 | Theoretical and Fundamental Chemistry |
The recovery and use of urine and feces in "dry sanitation systems", i.e. without sewers or without mixing substantial amounts of water with the excreta, has been practiced by almost all cultures. The reuse was not limited to agricultural production. The Romans, for example, were aware of the bleaching attribute of the ammonia within urine and used it to whiten clothing.
Many traditional agricultural societies recognized the value of human waste for soil fertility and practised the "dry" collection and reuse of excreta. This enabled them to live in communities in which nutrients and organic matter contained in excreta were returned to the soil. Historical descriptions about these practices are sparse, but it is known that excreta reuse was practiced widely in Asia (for example in China, Japan, Vietnam, Cambodia, Korea) but also in Central and South America. However, the most renowned example of the organised collection and use of human excreta to support food production is that of China. The value of "night soil" as a fertilizer was recognized with well-developed systems in place to enable the collection of excreta from cities and its transportation to fields. The Chinese were aware of the benefits of using excreta in crop production more than 2500 years ago, enabling them to sustain more people at a higher density than any other system of agriculture.
In Mexico the Aztec culture collected human excreta for agricultural use. One example of this practice has been documented for the Aztec city of Tenochtitlan which was founded in 1325 and was one of the last cities of pre-Hispanic Mexico (conquered in 1521 by the Spanish): The population placed the sweepings in special boats moored at docks around the city. Mixtures of sweepings and excreta were used to fertilize the chinampas (agricultural fields) or to bolster the banks bordering the lake. Urine was collected in containers in all houses, then mixed with mud and used as a fabric dye. The Aztecs recognized the importance of recycling nutrients and compounds contained in wastewater.
In Peru, the Incas had a high regard for excreta as a fertilizer, which was stored, dried and pulverized to be utilized when planting maize.
In the Middle Ages, the use of excreta and greywater in agricultural production was the norm. European cities were rapidly urbanizing and sanitation was becoming an increasingly serious problem, whilst at the same time the cities themselves were becoming an increasingly important source of agricultural nutrients. The practice of directly using the nutrients in excreta and wastewater for agriculture therefore continued in Europe into the middle of the 19th century. Farmers, recognizing the value of excreta, were eager to get these fertilizers to increase production and urban sanitation benefited. This practice was also called gong farmer in England but carried many health risks for those involved with transporting the excreta and fecal sludge.
Besides direct use, excreta was also processed to produce pure chemicals. Using nitraries and nitre beds, one extract the nitrogen within as potassium nitrate (KNO), a key ingredient in gunpowder. KNO was also responsible for the discovery of nitric acid in the 17th century.
Traditional forms of sanitation and excreta reuse have continued in various parts of the world for centuries and were still common practice at the advent of the Industrial Revolution. Even as the world became increasingly more urbanised, the nutrients in excreta collected from urban sanitation systems without mixing with water were still used in many societies as a resource to maintain soil fertility, despite rising population densities. | 1 | Applied and Interdisciplinary Chemistry |
A limepit is either a place where limestone is quarried, or a man-made pit used to burn lime stones in the same way that modern-day kilns and furnaces constructed of brick are now used above ground for the calcination of limestone (calcium carbonate, CaCO) and by which quicklime (calcium oxide, CaO) is produced, an essential component in waterproofing and in wall plastering (plaster skim). | 1 | Applied and Interdisciplinary Chemistry |
Several biomolecules, including PUFAs and some amino acids, cannot be made by human beings and must be supplied in the diet. These molecules are termed “essential dietary components” and serve as building blocks that are incorporated into larger structures such as proteins and cell membranes. PUFA membrane components are particularly vulnerable to damage (oxidation) by reactive oxygen species (ROS) as part of both normal and pathological
metabolism. Unlike catabolic oxidation of drugs, or oxidative damage to DNA or proteins (which occurs stoichiometrically), oxidation of PUFAs is particularly pernicious, proceeding through a non-enzymatic lipid peroxidation chain reaction (LPO), whereby a single ROS species can initiate a runaway autoxidation process that does not need any additional ROS to propagate.
LPO may damage hundreds to thousands of PUFA residues in PUFA-rich neuronal, mitochondrial and retinal membranes. The chain oxidation proceeds inexorably through multiple steps, destroying lipid membranes and generating highly reactive toxic secondary products that damage numerous biomolecules, such as proteins and DNA, irreversibly. This makes LPO one of the most detrimental processes that occur in the body. LPO is not controlled by enzymes, so evolution could not have provided a straightforward solution. Antioxidants cannot efficiently stop the incipient chain reaction because their maximal achievable concentration in lipid membranes is orders of magnitude lower than the PUFA concentration (typically, 1 tocopherol moiety per 2000 PUFA residues in a bilayer). Numerous neuronal and retinal diseases have LPO in their etiology. To put things in perspective, the brain makes up 1.5–2% of body weight yet consumes about a fifth of the body’s total energy output. A quarter of this 20%, i.e. 5% of the total body energy expenditure, is used by the brain to recycle damaged lipids in neuronal membranes. | 0 | Theoretical and Fundamental Chemistry |
In flowers, the coloration that is provided by anthocyanin accumulation may attract a wide variety of animal pollinators, while in fruits, the same coloration may aid in seed dispersal by attracting herbivorous animals to the potentially-edible fruits bearing these red, blue, or purple colors. | 0 | Theoretical and Fundamental Chemistry |
Researchers at Abbott Laboratories identified three novel series of DPP-4 inhibitors using HTS. After more research and optimization ABT-341 was discovered (Figure 8). It is a potent and selective DPP-4 inhibitor with a 2D-structure very similar to sitagliptin. However, the 3D-structure is quite different. ABT-341 also has a trifluorophenyl group that occupies the S1-pocket and the free amino group, but the two carbonyl groups are orientated 180° away from each other. ABT-341 is also believed to interact with the Tyr547, probably because of steric hindrance between the cyclohexenyl ring and the tyrosine side-chain. Omarigliptin is one of such compound which is in Phase-III development by Merck & Co. | 1 | Applied and Interdisciplinary Chemistry |
In resting cells, axin molecules oligomerize with each other through their C-terminal DIX domains, which have two binding interfaces. Thus they can build linear oligomers or even polymers inside the cytoplasm of cells. DIX domains are unique: the only other proteins known to have a DIX domain are Dishevelled and DIXDC1. (The single Dsh protein of Drosophila corresponds to three paralogous genes, Dvl1, Dvl2 and Dvl3 in mammals.) Dsh associates with the cytoplasmic regions of Frizzled receptors with its PDZ and DEP domains. When a Wnt molecule binds to Frizzled, it induces a poorly known cascade of events, that result in the exposure of dishevelleds DIX domain and the creation of a perfect binding site for axin. Axin is then titrated away from its oligomeric assemblies – the β-catenin destruction complex – by Dsh. Once bound to the receptor complex, axin will be rendered incompetent for β-catenin binding and GSK3 activity. Importantly, the cytoplasmic segments of the Frizzled-associated LRP5 and LRP6 proteins contain GSK3 pseudo-substrate sequences (Pro-Pro-Pro-Ser-Pro-x-Ser), appropriately "primed" (pre-phosphorylated) by CKI, as if it were a true substrate of GSK3. These false target sites greatly inhibit GSK3 activity in a competitive manner. This way receptor-bound axin will abolish mediating the phosphorylation of β-catenin. Since β-catenin is no longer marked for destruction, but continues to be produced, its concentration will increase. Once β-catenin levels rise high enough to saturate all binding sites in the cytoplasm, it will also translocate into the nucleus. Upon engaging the transcription factors LEF1, TCF1, TCF2 or TCF3, β-catenin forces them to disengage their previous partners: Groucho proteins. Unlike Groucho', that recruit transcriptional repressors (e.g. histone-lysine methyltransferases), β-catenin will bind transcriptional activators, switching on target genes. | 1 | Applied and Interdisciplinary Chemistry |
1,1 carboboration delivers both the carbon-carbon bond and the carbon-boron bond to the same carbon in the substrate. It requires a 1,2-migration of a substituent from one carbon to the other in the double bond. The Wrackmeyer reaction is typically credited as being the pioneering example of 1,1 carboboration and utilizes a metal migrating group to help facilitate the transformation. However, there are several modern examples of carboboration with a variety of migrating groups.
The Wrackmeyer reaction involves 1,1 carboboration of a 1-alkynylmetal compound to yield alkenylborane compounds. [M] can be silicon, germanium, tin, or lead compounds with various substituents or ligands. [M] and BR are typically cis to one another in the Wrackmeyer reaction, with some exceptions. | 0 | Theoretical and Fundamental Chemistry |
Ptaquiloside is a norsesquiterpene glucoside produced by bracken ferns (majorly Pteridium aquilinum) during metabolism. It is identified to be the main carcinogen of the ferns and to be responsible for their biological effects, such as haemorrhagic disease and bright blindness in livestock and oesophageal, gastric cancer in humans. Ptaquiloside has an unstable chemical structure and acts as a DNA alkylating agent under physiological conditions. It was first isolated and characterized by Yamada and co-workers in 1983.
The pure form ptaquiloside is a colorless amorphous compound. It is readily soluble in water and fairly soluble in ethyl acetate. Except in the plants, ptaquiloside has been detected in the milk and meat of affected livestock, as well as in the underground water and dry soil around bracken fern vegetation. The prevalence of ptaquiloside in daily sources along with its carcinogenic effects make it an increasing biological hazard in modern days. | 0 | Theoretical and Fundamental Chemistry |
In oceanography, a prime example of a limiting factor is a limiting nutrient. Nutrient availability in freshwater and marine environments plays a critical role in determining what organisms survive and thrive. Nutrients are the building blocks of all living organisms, as they support biological activity. They are required to make proteins, DNA, membranes, organelles, and exoskeletons. The major elements that constitute >95% of organic matter mass are carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus. Minor elements are iron, manganese, cobalt, zinc and copper. These minor elements are often only present in trace amounts but they are key as co-limiting factors as parts of enzymes, transporters, vitamins and amino acids. Within aquatic environments, nitrogen and phosphorus are leading contenders for most limiting nutrients.
Discovery of the Redfield ratio was a major insight that helped understand the relationship between nutrient availability in seawater and their relative abundance in organisms. Redfield was able to notice elemental consistencies between carbon, nitrogen and phosphorus when looking at larger organisms living in the ocean (C:N:P = 106:16:1). He also observed consistencies in nutrients within the water column; nitrate to phosphate ratio was 16:1. The overarching idea was that the environment fundamentally influences the organisms that grow in it and the growing organisms fundamentally influence the environment. Redfield's opening statement in his 1934 paper explains "It is now well recognized that the growth of plankton in the surface layers of the sea is limited in part by the quantities of phosphate and nitrate available for their use and that the changes in the relative quantities of certain substances in seawater are determined in their relative proportions by biological activity". Deviations from Redfield can be used to infer elemental limitations. Limiting nutrients can be discussed in terms of dissolved nutrients, suspended particles and sinking particles, among others. When discussing dissolved nutrient stoichiometry, large deviations from the original Redfield ratio can determine if an environment is phosphorus limited or nitrogen limited. When discussing suspended particle stoichiometry, higher N:P ratios are noted in oligotrophic waters (environments dominated by cyanobacteria; low latitudes/equator) and lower N:P ratios are noted in nutrient rich ecosystems (environments dominated by diatoms; high latitudes/poles).
Many areas are severely nitrogen limited, but phosphorus limitation has also been observed. In many instances trace metals or co-limitation occur. Co-limitations refer to where two or more nutrients simultaneously limit a process. Pinpointing a single limiting factor can be challenging, as nutrient demand varies between organisms, life cycles, and environmental conditions (e.g. thermal stress can increase demand on nutrients for biological repairs). | 0 | Theoretical and Fundamental Chemistry |
Chiral resolution, or enantiomeric resolution, is a process in stereochemistry for the separation of racemic mixture into their enantiomers. It is an important tool in the production of optically active compounds, including drugs. Another term with the same meaning is optical resolution.
The use of chiral resolution to obtain enantiomerically pure compounds has the disadvantage of necessarily discarding at least half of the starting racemic mixture. Asymmetric synthesis of one of the enantiomers is one means of avoiding this waste. | 0 | Theoretical and Fundamental Chemistry |
During the development of this technology, several modifications were done to the components, in order to increase its effectiveness. | 1 | Applied and Interdisciplinary Chemistry |
While at University of Michigan, Omar M. Yaghi (currently at UCBerkeley) and Adrien P Cote published the first paper of COFs in 2005, reporting a series of 2D COFs. They reported the design and successful synthesis of COFs by condensation reactions of phenyl diboronic acid (CH[B(OH)]) and hexahydroxytriphenylene (CH(OH)). Powder X-ray diffraction studies of the highly crystalline products having empirical formulas (CHBO)·(CH) (COF-1) and CHBO (COF-5) revealed 2-dimensional expanded porous graphitic layers that have either staggered conformation (COF-1) or eclipsed conformation (COF-5). Their crystal structures are entirely held by strong bonds between B, C, and O atoms to form rigid porous architectures with pore sizes ranging from 7 to 27 Angstroms. COF-1 and COF-5 exhibit high thermal stability (to temperatures up to 500 to 600 °C), permanent porosity, and high surface areas (711 and 1590 square meters per gram, respectively).
The synthesis of 3D COFs has been hindered by longstanding practical and conceptual challenges until it was first achieved in 2007 by Omar M. Yaghi and colleagues, which received the Newcomb Cleveland Prize. The research team synthesized and designed the first 3D-COF ever; COF-103 and COF-108, helping unleash this new field. Unlike 0D and 1D systems, which are soluble, the insolubility of 2D and 3D structures precludes the use of stepwise synthesis, making their isolation in crystalline form very difficult. This first challenge, however, was overcome by judiciously choosing building blocks and using reversible condensation reactions to crystallize COFs. | 0 | Theoretical and Fundamental Chemistry |
The conversion of the amino acid glutamine to α-ketoglutarate takes place in two reaction steps:
1. Hydrolysis of the amino group of glutamine yielding glutamate and ammonium.
Catalyzing enzyme: glutaminase (EC 3.5.1.2)
2. Glutamate can be excreted or can be further metabolized to α-ketoglutarate.
For the conversion of glutamate to α-ketoglutarate three different reactions are possible:
Catalyzing enzymes:
*glutamate dehydrogenase (GlDH), EC 1.4.1.2
*glutamate pyruvate transaminase (GPT), also called alanine transaminase (ALT), EC 2.6.1.2
*glutamate oxaloacetate transaminase (GOT), also called aspartate transaminase (AST), EC 2.6.1.1 (component of the malate aspartate shuttle) | 1 | Applied and Interdisciplinary Chemistry |
Copper is found in association with many other metals and deposit styles. Commonly, copper is either formed within sedimentary rocks, or associated with igneous rocks.
The world's major copper deposits are formed within the granitic porphyry copper style. Copper is enriched by processes during crystallisation of the granite and forms as chalcopyrite — a sulfide mineral, which is carried up with the granite.
Sometimes granites erupt to surface as volcanoes, and copper mineralisation forms during this phase when the granite and volcanic rocks cool via hydrothermal circulation.
Sedimentary copper forms within ocean basins in sedimentary rocks. Generally this forms by brine from deeply buried sediments discharging into the deep sea, and precipitating copper and often lead and zinc sulfides directly onto the sea floor. This is then buried by further sediment. This is a process similar to SEDEX zinc and lead, although some carbonate-hosted examples exist.
Often copper is associated with gold, lead, zinc, and nickel deposits. | 0 | Theoretical and Fundamental Chemistry |
Accumulation of tau protein is associated with neurodegenerative diseases including Alzheimers and Parkinsons diseases as well as other tauopathies. Tau protein isoforms are created by alternative splicing of exons 2, 3 and 10. The regulation of tau splicing is specific to stage of development, physiology and location. Errors in tau splicing can occur in both exons and introns and, depending on the error, result in changes to protein structure or loss of function. Aggregation of these abnormal tau proteins correlates directly with pathogenesis and disease progression. Minigenes have been used by several researchers to help understand the regulatory components responsible for mRNA splicing of the TAU gene. | 1 | Applied and Interdisciplinary Chemistry |
Frequently used SI prefixes are the millisievert (1 mSv = 0.001 Sv) and microsievert (1 μSv = 0.000 001 Sv) and commonly used units for time derivative or "dose rate" indications on instruments and warnings for radiological protection are μSv/h and mSv/h. Regulatory limits and chronic doses are often given in units of mSv/a or Sv/a, where they are understood to represent an average over the entire year. In many occupational scenarios, the hourly dose rate might fluctuate to levels thousands of times higher for a brief period of time, without infringing on the annual limits. The conversion from hours to years varies because of leap years and exposure schedules, but approximate conversions are:
: 1 mSv/h = 8.766 Sv/a
: 114.1 μSv/h = 1 Sv/a
Conversion from hourly rates to annual rates is further complicated by seasonal fluctuations in natural radiation, decay of artificial sources, and intermittent proximity between humans and sources. The ICRP once adopted fixed conversion for occupational exposure, although these have not appeared in recent documents:
: 8 h = 1 day
: 40 h = 1 week
: 50 weeks = 1 year
Therefore, for occupation exposures of that time period,
: 1 mSv/h = 2 Sv/a
: 500 μSv/h = 1 Sv/a | 0 | Theoretical and Fundamental Chemistry |
Aside from molecular metal phosphate complexes, the topic of this article, many or most transition metal phosphates are nonmolecular, being coordination polymers or dense ternary or quaternary phases. Iron(III) phosphate, contemplated as a cathode material for batteries, is one example. Vanadyl phosphate () is a commercial catalyst for oxidation reactions. Many metal phosphates occur as minerals. | 0 | Theoretical and Fundamental Chemistry |
Present-day methods of steel and alloy production are unable to attain completely pure metal without any non-metallic inclusions. Inclusions are present in any steel to a greater or lesser extent according to the mixture and conditions of production. Usually the amount of non-metallic inclusions in steel is not higher than 0.1%. However, the number of inclusions in metal is very high because of their extremely small size.
Non-metallic inclusions in steel are foreign substances. They disrupt the homogeneity of structure, so their influence on the mechanical and other properties can be considerable. During deformation, which occurs from flatting, forging, and stamping, non-metallic inclusions can cause cracks and fatigue failure in steel.
When investigating the influence of non-metallic inclusions on the quality of steel, of great importance are the properties of these inclusions: size, shape, chemical and physical characteristics. All these properties depend on the chemical composition of steel, method of smelting and for certain steel grade. These properties can change within wide limits even within the same mode of production.
Different methods for analysis of non-metallic inclusions have been developed and are now in use. These make it possible to determine content, structure and amount of non-metallic inclusions in steel and alloys with high accuracy. | 1 | Applied and Interdisciplinary Chemistry |
The surface advances normal to itself without the necessity of a stepwise growth mechanism. This means that in the presence of a sufficient thermodynamic driving force, every element of surface is capable of a continuous change contributing to the advancement of the interface. For a sharp or discontinuous surface, this continuous change may be more or less uniform over large areas for each successive new layer. For a more diffuse surface, a continuous growth mechanism may require changes over several successive layers simultaneously.
Non-uniform lateral growth is a geometrical motion of steps—as opposed to motion of the entire surface normal to itself. Alternatively, uniform normal growth is based on the time sequence of an element of surface. In this mode, there is no motion or change except when a step passes via a continual change. The prediction of which mechanism will be operative under any set of given conditions is fundamental to the understanding of crystal growth. Two criteria have been used to make this prediction:
Whether or not the surface is diffuse: a diffuse surface is one in which the change from one phase to another is continuous, occurring over several atomic planes. This is in contrast to a sharp surface for which the major change in property (e.g. density or composition) is discontinuous, and is generally confined to a depth of one interplanar distance.
Whether or not the surface is singular: a singular surface is one in which the surface tension as a function of orientation has a pointed minimum. Growth of singular surfaces is known to requires steps, whereas it is generally held that non-singular surfaces can continuously advance normal to themselves. | 0 | Theoretical and Fundamental Chemistry |
Cavitation has been applied to Biodiesel production since 2011 and is considered a proven and standard technology in this application. The implementation of hydrodynamic cavitation in the transesterification process allows for a significant reduction in catalyst use, quality improvement and production capacity increase. | 1 | Applied and Interdisciplinary Chemistry |
Yoon is openly gay and has been a vocal advocate for greater inclusion of and support for diverse members of the STEM community throughout his career. Yoon is a long time member of the UW-Madison Committee on LGBT Issues, which he chaired between 2013 and 2014. He has also given numerous invited lectures on topics relating to being LGBTQIA+ in STEM. Yoon lives in Madison, Wisconsin with his husband, Michael Velliquette, who is an artist. | 0 | Theoretical and Fundamental Chemistry |
François Charles Léon Moureu (19 April 1863, in Mourenx – 13 June 1929, in Biarritz) was a French organic chemist and pharmacist. In 1902 Charles Moureu published , translated into English as Fundamental principles of organic chemistry (1921).
During World War I, Charles Moureu was vice-chairman of France's Committee for Gas Warfare. In this role, he established 16 chemistry laboratories in Paris, supervising their work until 1918. Moureu also became chairman of the Committee of National Defence when it was established in 1925, leading it until his death in 1929.
During the war, he researched acrolein and sulfur mustard gas, working with Charles Dufraisse. This work led them to pioneering research into autoxidation and antioxidants.
Moureu supported initiatives for international cooperation and standardization among chemists. He was one of the vice-presidents of the (SCF) in 1910, and the founding President of the International Union of Pure and Applied Chemistry (IUPAC) from 1920 to 1922. | 0 | Theoretical and Fundamental Chemistry |
The Drug Discovery Initiative (DDI) was launched in 2018 to develop new drugs by working with clinicians and industry in infectious diseases, cancer, inflammation, neurodegenerative disorders, and metabolic diseases. However, the DDI is not limited to these areas and its research has contributed to antibiotics, cardiovascular diseases, and other health issues. Much of the research of the DDI uses facilities made available by Sydney Analytical such as X-ray scattering techniques and various types of spectroscopy, usually for characterisation of new drugs or proteins. Recent research within the DDI include Alzheimer's disease, malaria, and tuberculosis.
The current Academic Director of the DDI is Prof. Michael Kassiou. | 1 | Applied and Interdisciplinary Chemistry |
A vacuum coffee maker brews coffee using two chambers where vapor pressure and gravity produce coffee. This type of coffee maker is also known as vac pot, siphon or syphon coffee maker, and was invented by Loeff of Berlin in the 1830s. These devices have since been used for more than a century in many parts of the world. Design and composition of the vacuum coffee maker varies. The chamber material is borosilicate glass, metal, or plastic, and the filter can be either a glass rod or a screen made of metal, cloth, paper, or nylon. The Napier Vacuum Machine by James Robert Napier, presented in 1840, was an early example of this technique. While vacuum coffee makers generally were excessively complex for everyday use, they were prized for producing a clear brew, and were quite popular until the middle of the twentieth century. Vacuum coffee makers remain popular in some parts of Asia, including Japan and Taiwan. The Bauhaus interpretation of this device can be seen in Gerhard Marcks' coffee maker of 1925. | 1 | Applied and Interdisciplinary Chemistry |
Pseudin is a peptide derived from Pseudis paradoxa. Pseudins have some antimicrobial function.
There are several different forms:
* pseudin-1
* pseudin-2 -- has been proposed as a treatment for type 2 diabetes.
* pseudin-4 | 1 | Applied and Interdisciplinary Chemistry |
The method is made understandable by the figure. A 27-member peptide library is synthesized from three amino acids. After the first (A) and second (B) cycles samples were set aside before mixing them. The products of the third cycle (C) are cleaved down before mixing then are tested for activity. Suppose the group labeled by + sign is active. All members have the red amino acid at the last coupling position (CP). Consequently, the active member also has the red amino acid at the last CP. Then the red amino acid is coupled to the three samples set aside after the second cycle (B) to get samples D. After cleaving, the three E samples are formed. If after testing the sample marked by + is the active one it shows that the blue amino acid occupies the second CP in the active component. Then to the three A samples first the blue then the red amino acid is coupled (F) then tested again after cleaving (G). If the + component proves to be active, the sequence of the active component is determined and shown in H. | 1 | Applied and Interdisciplinary Chemistry |
Hope's apparatus consists of a vertical vessel full of water surrounded round the middle by a trough of cooling ice. Two thermometers, one above and one below the trough, measure the temperature of the water. It is designed to demonstrate that water reaches its maximum density at .
As the water in the central part of the vessel cools towards (and thus becomes denser) it sinks to the bottom of the vessel, displacing the warmer water. The lower thermometer will then read a constant . Further cooling towards will cause the now less dense water to rise to the top of the vessel, where the upper thermometer will then read a constant . | 1 | Applied and Interdisciplinary Chemistry |
Euxinia or euxinic conditions occur when water is both anoxic and sulfidic. This means that there is no oxygen (O) and a raised level of free hydrogen sulfide (HS). Euxinic bodies of water are frequently strongly stratified; have an oxic, highly productive, thin surface layer; and have anoxic, sulfidic bottom water. The word "euxinia" is derived from the Greek name for the Black Sea (Εὔξεινος Πόντος (Euxeinos Pontos)) which translates to "hospitable sea". Euxinic deep water is a key component of the Canfield ocean, a model of oceans during part of the Proterozoic eon (a part specifically known as the Boring Billion) proposed by Donald Canfield, an American geologist, in 1998. There is still debate within the scientific community on both the duration and frequency of euxinic conditions in the ancient oceans. Euxinia is relatively rare in modern bodies of water, but does still happen in places like the Black Sea and certain fjords. | 0 | Theoretical and Fundamental Chemistry |
Trisoxazolines (Often abbreviated TRISOX or TOX) are a class of tridentate, chiral ligands composed of three oxazoline rings. Despite being neutral they are able to form stable complexes with high oxidation state metals, such as rare earths, due to the chelate effect. The ligands have been investigated for molecular recognition and their complexes are used in asymmetric catalysts and polymerisation. | 0 | Theoretical and Fundamental Chemistry |
Ekman theory explains the theoretical state of circulation if water currents were driven only by the transfer of momentum from the wind. In the physical world, this is difficult to observe because of the influences of many simultaneous current driving forces (for example, pressure and density gradients). Though the following theory technically applies to the idealized situation involving only wind forces, Ekman motion describes the wind-driven portion of circulation seen in the surface layer.
Surface currents flow at a 45° angle to the wind due to a balance between the Coriolis force and the drags generated by the wind and the water. If the ocean is divided vertically into thin layers, the magnitude of the velocity (the speed) decreases from a maximum at the surface until it dissipates. The direction also shifts slightly across each subsequent layer (right in the northern hemisphere and left in the southern hemisphere). This is called the Ekman spiral. The layer of water from the surface to the point of dissipation of this spiral is known as the Ekman layer. If all flow over the Ekman layer is integrated, the net transportation is at 90° to the right (left) of the surface wind in the northern (southern) hemisphere. | 1 | Applied and Interdisciplinary Chemistry |
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