text
stringlengths 105
4.57k
| label
int64 0
1
| label_text
stringclasses 2
values |
|---|---|---|
As a liquid or semisolid dosage, gels are typically used where a solid form would affect the patient’s comfort. As a trade-off, conventional gels have poor retention rates. This results in unpredictable losses of the drug, as the non-solid dosage is unable to maintain its position at the site of administration. Mucoadhesives increase retention by dynamically increasing the viscosity of the gel after application. This allows the gel to effectively administer the drug at the local site while maintaining the comfort of the patient. | 1 | Applied and Interdisciplinary Chemistry |
The necessity of obtaining accurate thermodynamic quantities for the actinide elements and their compounds was recognized at the outset of the Manhattan Project, when a dedicated team of scientists and engineers initiated the program to exploit nuclear energy for military purposes. Since the end of World War II, both fundamental and applied objectives have motivated a great deal of further study of actinide thermodynamics. | 0 | Theoretical and Fundamental Chemistry |
Key thermophysical properties of phase-change materials include: Melting point (T), Heat of fusion (ΔH), Specific heat (c) (of solid and liquid phase), Density (ρ) (of solid and liquid phase) and thermal conductivity. Values such as volume change and volumetric heat capacity can be calculated there from. | 0 | Theoretical and Fundamental Chemistry |
Russell demonstrated that alkaline vents created an abiogenic proton motive force chemiosmotic gradient, ideal for abiogenesis. Their microscopic compartments "provide a natural means of concentrating organic molecules," composed of iron-sulfur minerals such as mackinawite, endowed these mineral cells with the catalytic properties envisaged by Günter Wächtershäuser. This movement of ions across the membrane depends on a combination of two factors:
# Diffusion force caused by concentration gradient—all particles including ions tend to diffuse from higher concentration to lower.
# Electrostatic force caused by electrical potential gradient—cations like protons H tend to diffuse down the electrical potential, anions in the opposite direction.
These two gradients taken together can be expressed as an electrochemical gradient, providing energy for abiogenic synthesis. The proton motive force can be described as the measure of the potential energy stored as a combination of proton and voltage gradients across a membrane (differences in proton concentration and electrical potential).
The surfaces of mineral particles inside deep-ocean hydrothermal vents have catalytic properties similar to those of enzymes and can create simple organic molecules, such as methanol (CHOH) and formic, acetic, and pyruvic acids out of the dissolved CO in the water, if driven by an applied voltage or by reaction with H or HS.
The research reported by Martin in 2016 supports the thesis that life arose at hydrothermal vents, that spontaneous chemistry in the Earths crust driven by rock–water interactions at disequilibrium thermodynamically underpinned lifes origin and that the founding lineages of the archaea and bacteria were H-dependent autotrophs that used CO as their terminal acceptor in energy metabolism. Martin suggests, based upon this evidence, that the LUCA "may have depended heavily on the geothermal energy of the vent to survive". Pores at deep sea hydrothermal vents are suggested to have been occupied by membrane-bound compartments which promoted biochemical reactions. Metabolic intermediates in the Krebs cycle, gluconeogenesis, amino acid bio-synthetic pathways, glycolysis, the pentose phosphate pathway, and including sugars like ribose, and lipid precursors can occur non-enzymatically at conditions relevant to deep-sea alkaline hydrothermal vents.
If the deep marine hydrothermal setting was the site for the origin of life, then abiogenesis could have happened as early as 4.0-4.2 Gya. If life evolved in the ocean at depths of more than ten meters, it would have been shielded both from impacts and the then high levels of ultraviolet radiation from the sun. The available energy in hydrothermal vents is maximized at 100–150 °C, the temperatures at which hyperthermophilic bacteria and thermoacidophilic archaea live. Arguments against a hydrothermal origin of life state that hyperthermophily was a result of convergent evolution in bacteria and archaea, and that a mesophilic environment would have been more likely. This hypothesis, suggested in 1999 by Galtier, was proposed one year before the discovery of the Lost City Hydrothermal Field, where white-smoker hydrothermal vents average ~45-90 °C. Moderate temperatures and alkaline seawater at Lost City are now the favoured hydrothermal vent setting in contrast to acidic, high temperature (~350 °C) black-smokers. | 0 | Theoretical and Fundamental Chemistry |
The U.S.-based company Sedron Technologies (formerly Janicki Bioenergy) presented in 2014 a prototype using combustion. Their process is a sewage sludge treatment system that produces drinking water and electrical energy as end products from sewage sludge. Manufactured by Sedron Technologies, the proof of concept model was funded by the Bill and Melinda Gates Foundation. The S100 prototype model can produce 10,800 liters of drinking water per day and 100 kW net electricity. A larger model under development, the S200, is designed to handle the waste from 100,000 people, produce 86,000 liters of drinking water per day and 250 kW net output electricity. These systems are designed to provide a "self-sustaining bioenergy" process.
The treatment process first involves boiling (or thermally drying) the sewage sludge, during which water vapor is boiled off and recovered. A dry sludge is left behind which is then combusted as fuel to heat a boiler. This boiler produces steam and the heat necessary for the boiling process. The steam is then used to generate electrical energy. Some of this electrical energy is used for the final water reverse osmosis purification stages to produce safe drinking water, and to power ancillary pumps, fans and motors. The process immediately uses the solid fuel it produces, and therefore the process does not make a solid fuel product as an end product.
A pilot project of Sedron Technologies' omni processor was installed in Dakar, Senegal, in 2015 and can now treat the fecal sludge of 50,000-100,000 people. | 1 | Applied and Interdisciplinary Chemistry |
Common adverse drug reactions (ADRs) associated with the use of dicloxacillin include: diarrhea, nausea, rash, urticaria, pain and inflammation at injection site, superinfection (including candidiasis), allergy, and transient increases in liver enzymes and bilirubin.
On rare occasions, cholestatic jaundice (also referred to as cholestatic hepatitis) has been associated with dicloxacillin therapy. The reaction may occur up to several weeks after treatment has stopped, and takes weeks to resolve. The estimated incidence is 1 in 15,000 exposures, and is more frequent in people over 55 years old, females, and those with treatment longer than 2 weeks.
It should be used with caution and monitored in the elderly, particularly with intravenous administration, due to a risk of thrombophlebitis.
Dicloxacillin can also lower the effectiveness of birth control pills and pass into breast milk. | 0 | Theoretical and Fundamental Chemistry |
Naomi Chayen is a biochemist and structural biologist. She is a professor of Biomedical Sciences at Imperial College London, where she leads the Crystallization Group in Computational and Systems Medicine. She is best known for developing the microbatch method and inventing novel nucleants for protein crystallization which have been applied to high-throughput screening for rational drug design. | 1 | Applied and Interdisciplinary Chemistry |
Tetrasulfur tetranitride is an inorganic compound with the formula . This gold-poppy coloured solid is the most important binary sulfur nitride, which are compounds that contain only the elements sulfur and nitrogen. It is a precursor to many S-N compounds and has attracted wide interest for its unusual structure and bonding.
Nitrogen and sulfur have similar electronegativities. When the properties of atoms are so highly similar, they often form extensive families of covalently bonded structures and compounds. Indeed, a large number of S-N and S-NH compounds are known with as their parent. | 0 | Theoretical and Fundamental Chemistry |
Carbaminohemoglobin (carbaminohaemoglobin BrE) (COHb, also known as carbhemoglobin and carbohemoglobin) is a compound of hemoglobin and carbon dioxide, and is one of the forms in which carbon dioxide exists in the blood. Twenty-three percent of carbon dioxide is carried in blood this way (70% is converted into bicarbonate by carbonic anhydrase and then carried in plasma, 7% carried as free CO, dissolved in plasma). | 1 | Applied and Interdisciplinary Chemistry |
Curing is a chemical process employed in polymer chemistry and process engineering that produces the toughening or hardening of a polymer material by cross-linking of polymer chains. Even if it is strongly associated with the production of thermosetting polymers, the term "curing" can be used for all the processes where a solid product is obtained from a liquid solution, such as with PVC plastisols. | 0 | Theoretical and Fundamental Chemistry |
Various methods for the production of singlet oxygen exist. Irradiation of oxygen gas in the presence of an organic dye as a sensitizer, such as rose bengal, methylene blue, or porphyrins—a photochemical method—results in its production. Large steady state concentrations of singlet oxygen are reported from the reaction of triplet excited state pyruvic acid with dissolved oxygen in water. Singlet oxygen can also be produced in non-photochemical, preparative chemical procedures. One chemical method involves the decomposition of triethylsilyl hydrotrioxide generated in situ from triethylsilane and ozone.
:(CH)SiH + O → (CH)SiOOOH → (CH)SiOH + O(Δ)
Another method uses the aqueous reaction of hydrogen peroxide with sodium hypochlorite:
: HO + NaOCl → O(Δ) + NaCl + HO
A third method liberates singlet oxygen via phosphite ozonides, which are, in turn, generated in situ such as triphenyl phosphite ozonide. Phosphite ozonides will decompose to give singlet oxygen:
:(RO)P + O → (RO)PO
:(RO)PO → (RO)PO + O(Δ)
An advantage of this method is that it is amenable to non-aqueous conditions. | 0 | Theoretical and Fundamental Chemistry |
The protein encoded by this gene mediates transcriptional control by interaction with the activation function 2 (AF2) region of several nuclear receptors, including the estrogen, retinoic acid, and vitamin D receptors. The protein localizes to nuclear bodies and is thought to associate with chromatin and heterochromatin-associated factors. The protein is a member of the tripartite motif (TRIM) family. The TRIM motif includes three zinc-binding domains – a RING, a B-box type 1 and a B-box type 2 – and a coiled-coil region. Two alternatively spliced transcript variants encoding different isoforms have been described for this gene. | 1 | Applied and Interdisciplinary Chemistry |
Using simplifying assumptions, the spectroscopic parameters (absorption, remission, and transmission fractions) of a plane parallel layer can be built from the refractive index of the material making up the layer, the linear absorption coefficient (absorbing power) of the material, and the thickness of the layer. While other assumptions could be made, those most often used are those of normal incidence of a directed beam of light, with internal and external reflection from the surface being the same. | 0 | Theoretical and Fundamental Chemistry |
Ribosomal RNA (rRNA) intergenic spacer analysis (RISA) is a method of microbial community analysis that provides a means of comparing differing environments or treatment impacts without the bias imposed by culture- dependent approaches. RISA involves PCR amplification of a region of the rRNA gene operon between the small (16S) and large (23S) subunits called the intergenic spacer region ISR.
By using oligonucleotide primers targeted to conserved regions in the 16S and 23S genes, RISA fragments can be generated from most of the dominant bacteria in an environmental sample. While the majority of the rRNA operon serves a structural function, portions of the 16S-23S intergenic region can encode tRNAs depending on the bacterial species. However the taxonomic value of the ISR lies in the significant heterogeneity in both length and nucleotide sequence. In RISA, we attempt to exploit the length heterogeneity of the ISR, which has been shown to range between 150 and 1500 bp with the majority of the ISR lengths being between 150 and 500 bp.
The resulting PCR product will be a mixture of fragments contributed by several dominant community members. This product is electrophoresed in a polyacrylamide gel, and the DNA is visualized following staining. The result is a complex banding pattern that provides a community-specific profile, with each DNA band corresponding to a bacterial population on the original assemblage. | 1 | Applied and Interdisciplinary Chemistry |
This research, published in 2017, aimed to search for the solar neutrino effective magnetic moment. The search was completed using data from exposure from the Borexino experiment's second phase which consisted of data over 1291.5 days (3.54 years). The results yielded that the electron recoil spectrum shape was as expected with no major changes or deviations from it. | 0 | Theoretical and Fundamental Chemistry |
Following the action potential, characteristically generated by the influx of Na through voltage gated Na channels, there is a period of repolarization in which the Na channels are inactivated while K channels are activated. Further study of K channels shows that there are four types which influence the repolarization of the cell membrane to re-establish the resting potential. The four types are K1, K2, K3 and K4. The K1 channel primarily influences the repolarization of the axon. The K2 channel is characteristically activated slower. The K4 channels are characteristically activated rapidly. When K2 and K4 channels are blocked, the action potential predictably widens. The K3 channels open at a more positive membrane potential and deactivate 10 times faster than the other K channels. These properties allow for the high-frequency firing that mammalian neurons require. Areas with dense K3 channels include the neocortex, basal ganglia, brain stem and hippocampus as these regions create microsecond action potentials that requires quick repolarization.
Utilizing voltage-clamp data from experiments based on rodent neurons, the K4 channels are associated with the primary repolarization conductance following the depolarization period of a neuron. When the K4 channel is blocked, the action potential becomes broader, resulting in an extended repolarization period, delaying the neuron from being able to fire again. The rate of repolarization closely regulates the amount of Ca ions entering the cell. When large quantities of Ca ions enter the cell due to extended repolarization periods, the neuron may die, leading to the development of stroke or seizures.
The K1 channels are found to contribute to repolarization of pyramidal neurons, likely associated with an upregulation of the K4 channels. The K2 channels were not found to contribute to repolarization rate as blocking these channels did not result in changes in neuron repolarization rates. | 0 | Theoretical and Fundamental Chemistry |
The two-way shape-memory effect is the effect that the material remembers two different shapes: one at low temperatures, and one at the high temperature.
A material that shows a shape-memory effect during both heating and cooling is said to have two-way shape memory. This can also be obtained without the application of an external force (intrinsic two-way effect).
The reason the material behaves so differently in these situations lies in training. Training implies that a shape memory can "learn" to behave in a certain way.
Under normal circumstances, a shape-memory alloy "remembers" its low-temperature shape, but upon heating to recover the high-temperature shape, immediately "forgets" the low-temperature shape. However, it can be "trained" to "remember" to leave some reminders of the deformed low-temperature condition in the high-temperature phases. One way of training the SMA consists in applying a cyclic thermal load under constant stress field. During this process, internal defects are introduced into the microstructure which generates internal permanent stresses that facilitate the orientation of the martensitic crystals. Therefore, while cooling a trained SMA in austenitic phase under no applied stress, the martensite is formed detwinned due to the internal stresses, which leads to the material shape change. And while heating back the SMA into austenite, it recovers its initial shape.
There are several ways of doing this. A shaped, trained object heated beyond a certain point will lose the two-way memory effect. | 1 | Applied and Interdisciplinary Chemistry |
P300/CBP-associated factor (PCAF), also known as K(lysine) acetyltransferase 2B (KAT2B), is a human gene and transcriptional coactivator associated with p53. | 1 | Applied and Interdisciplinary Chemistry |
The head loss (or ) expresses the pressure loss due to friction in terms of the equivalent height of a column of the working fluid, so the pressure drop is
: = The head loss due to pipe friction over the given length of pipe (SI units: m);
: = The local acceleration due to gravity (m/s).
It is useful to present head loss per length of pipe (dimensionless):
where is the pipe length (m).
Therefore, the Darcy–Weisbach equation can also be written in terms of head loss: | 1 | Applied and Interdisciplinary Chemistry |
Historically, probably the most commonly studied cases of two-phase flow are in large-scale power systems. Coal and gas-fired power stations used very large boilers to produce steam for use in turbines. In such cases, pressurised water is passed through heated pipes and it changes to steam as it moves through the pipe. The design of boilers requires a detailed understanding of two-phase flow heat-transfer and pressure drop behaviour, which is significantly different from the single-phase case. Even more critically, nuclear reactors use water to remove heat from the reactor core using two-phase flow. A great deal of study has been performed on the nature of two-phase flow in such cases, so that engineers can design against possible failures in pipework, loss of pressure, and so on (a loss-of-coolant accident (LOCA)).
Another case where two-phase flow can occur is in pump cavitation. Here a pump is operating close to the vapor pressure of the fluid being pumped. If pressure drops further, which can happen locally near the vanes for the pump, for example, then a phase change can occur and gas will be present in the pump. Similar effects can also occur on marine propellers; wherever it occurs, it is a serious problem for designers. When the vapor bubble collapses, it can produce very large pressure spikes, which over time will cause damage on the propeller or turbine.
The above two-phase flow cases are for a single fluid occurring by itself as two different phases, such as steam and water. The term two-phase flow is also applied to mixtures of different fluids having different phases, such as air and water, or oil and natural gas. Sometimes even three-phase flow is considered, such as in oil and gas pipelines where there might be a significant fraction of solids. Although oil and water are not strictly distinct phases (since they are both liquids) they are sometimes considered as a two-phase flow; and the combination of oil, gas and water (e.g. the flow from an offshore oil well) may also be considered a three-phase flow.
Other interesting areas where two-phase flow is studied includes water electrolysis, climate systems such as clouds, and in groundwater flow, in which the movement of water and air through the soil is studied.
Other examples of two-phase flow include bubbles, rain, waves on the sea, foam, fountains, mousse, cryogenics, and oil slicks. One final example is in the electrical explosion of metal. | 1 | Applied and Interdisciplinary Chemistry |
An alternative approach called Hydrothermal liquefaction employs a continuous process that subjects harvested wet algae to high temperatures and pressures— and .
Products include crude oil, which can be further refined into aviation fuel, gasoline, or diesel fuel using one or many upgrading processes. The test process converted between 50 and 70 percent of the algae's carbon into fuel. Other outputs include clean water, fuel gas and nutrients such as nitrogen, phosphorus, and potassium. | 1 | Applied and Interdisciplinary Chemistry |
The following table lists the sensitivity of different types of ANAs for different diseases.
Some ANAs appear in several types of disease, resulting in lower specificity of the test. For example, IgM-rheumatoid factor (IgM-RF) have been shown to cross-react with ANA giving falsely positive immunofluorescence. Positive ANA as well as anti-DNA antibodies have been reported in patients with autoimmune thyroid disease. ANA can have a positive test result in up to 45% of people with autoimmune thyroid conditions or rheumatoid arthritis and up to 15% of people with HIV or hepatitis C. As per Lupus Foundation of America, "about 5% of the general population will have a positive ANA. However, at least 95% of the people who have a positive ANA do not have lupus. A positive ANA test can sometimes run in families, even if family members have no evidence of lupus." On the other hand, they say, although 95% of the patients who actually have lupus test positive for ANA, "Only a small percentage have a negative ANA, and many of those have other antibodies (such as anti-phospholipid antibodies, anti-Ro, anti-SSA) or their ANA converted from positive to negative from steroids, cytotoxic medications, or uremia (kidney failure)." | 1 | Applied and Interdisciplinary Chemistry |
Several methods exist to measure the inclusion content in liquid aluminium. The most common methods are PoDFA, Prefil, K-Mold and LiMCA. Measuring the inclusions is of great help to understand the impact of furnace preparation, alloying practice, feedstock mix, settling time, and similar parameters on melt cleanliness. | 1 | Applied and Interdisciplinary Chemistry |
The development of the helium–neon laser (He-Ne) in 1962 at the Bell Telephone Laboratories provided the optics community with a continuous wave electromagnetic radiation source that was highly concentrated at a wavelength of 632.8 nanometers (nm) in the red portion of the visible spectrum. It was discovered that fluid flow measurements could be made using the Doppler effect on a He-Ne beam scattered by small polystyrene spheres in the fluid.
At the Research Laboratories of Brown Engineering Company (later Teledyne Brown Engineering), this phenomenon was used to develop the first laser Doppler flowmeter using heterodyne signal processing. This instrument became known as the laser Doppler velocimeter and the technique was called laser Doppler velocimetry. It is also referred to as laser Doppler anemometry.
Early laser Doppler velocimetry applications included measuring and mapping the exhaust from rocket engines with speeds up to 1000 m/s, as well as determining flow in a near-surface blood artery. Similar instruments were also developed for solid surface monitoring, with applications ranging from measuring product speeds in production lines of paper and steel mills to measuring vibration frequency and amplitude of surfaces. | 1 | Applied and Interdisciplinary Chemistry |
Soft laser desorption is a soft ionization technique which desorbs and ionizes molecules from surfaces with minimal fragmentation. This is useful for a broad range of small and large molecules and molecules that fragment easily. The first soft laser desorption techniques included matrix-assisted laser desorption/ionization (MALDI) nanoparticles in glycerol. In MALDI, the analyte is first mixed with a matrix solution. The matrix absorbs energy from the laser pulse and transfers it to the analyte, causing desorption and ionization of the sample. MALDI generates [M+H] ions.
DIOS was first reported by Gary Siuzdak, Jing Wei and Jillian M. Buriak in 1999. It was developed as a matrix-free alternative to MALDI for smaller molecules. Because MALDI uses a matrix, background ions are introduced due to ionization of the matrix. These ions reduce the usefulness of MALDI for small molecules. In contrast, DIOS uses a porous silicon surface to trap the analyte. This surface is not ionized by the laser, therefore creating minimal background ionization and thus allowing for the analysis of small molecules. | 0 | Theoretical and Fundamental Chemistry |
Phytoremediation is the use of plant-based technologies to decontaminate an area.
Most land plants can form a symbiotic relationship with fungi which is advantageous for both organisms. This relationship is called mycorrhiza. Researchers found that phytoremediation is enhanced by mycorrhizae. Mycorrhizal fungis symbiotic relationships with plant roots help with the uptake of nutrients and the plants ability to resist biotic and abiotic stress factors such as heavy metals bioavailable in the rhizosphere. Arbuscular mycorrhizal fungi (AMF) produce proteins that bind heavy metals and thereby decrease their bioavailability. The removal of soil contaminants by mycorrhizal fungi is called mycorrhizoremediation.
Mycorrhizal fungi, especially AMF, can greatly improve the phytoremediation capacity of some plants. This is mostly due to the stress the plants suffer because of the pollutants is greatly reduced in the presence of AMF, so they can grow more and produce more biomass. The fungi also provide more nutrition, especially phosphorus, and promote the overall health of the plants. The mycelium's quick expansion can also greatly extend the rhizosphere influence zone (hyphosphere), providing the plant with access to more nutrients and contaminants. Increasing the rhizosphere overall health also means a rise in the bacteria population, which can also contribute to the bioremediation process.
This relationship has been proven useful with many pollutants, such as Rhizophagus intraradices and Robinia pseudoacacia in lead contaminated soil, Rhizophagus intraradices with Glomus versiforme inoculated into vetiver grass for lead removal, AMF and Calendula officinalis in cadmium and lead contaminated soil, and in general was effective in increasing the plant bioremediation capacity for metals, petroleum fuels, and PAHs. In wetlands AMF greatly promote the biodegradation of organic pollutants like benzene-, methyl tert-butyl ether- and ammonia from groundwater when inoculated into Phragmites australis. | 1 | Applied and Interdisciplinary Chemistry |
Ötzi is a Neolithic man who, in 1991, was found in an Alpine glacier between Austria and Italy. Ötzi is exceptionally well preserved since his body was dehydrated and encapsulated in glacial ice. Radiocarbon dating gave an age of approximately 5,200 years old. TIMS, ICP-MS and gas mass spectrometry have all been applied to the strontium, lead, and oxygen isotopes in Ötzis bones and teeth. His teeth indicated a likely birth and early childhood near to where the Eisack and Rienz rivers confluence. In his adulthood, however, Ötzis bones suggest that he moved to the lower Vinschgau and Etsch valley. More recent isotopic data, gathered from his gut contents, provides yet another timescale and hint that Ötzi's movement could be attributable to seasonal migration. | 0 | Theoretical and Fundamental Chemistry |
In polymer physics, the coil–globule transition is the collapse of a macromolecule from an expanded coil state through an ideal coil state to a collapsed globule state, or vice versa. The coil–globule transition is of importance in biology due to the presence of coil-globule transitions in biological macromolecules such as proteins and DNA. It is also analogous with the swelling behavior of a crosslinked polymer gel and is thus of interest in biomedical engineering for controlled drug delivery. A particularly prominent example of a polymer possessing a coil-globule transition of interest in this area is that of Poly(N-isopropylacrylamide) (PNIPAAm). | 0 | Theoretical and Fundamental Chemistry |
Clumped isotopes present a distinct set of challenges for isotopic reference materials. By convention the clumped isotope composition of CO liberated from CaCO (Δ) and CH (Δ/ΔCH3DCH2D2CO for carbon dioxide and CH for methane. Standard isotopic reference materials are still required in clumped isotope analysis for measuring the bulk δ values of a sample, which are used to calculate the expected stochastic distribution and subsequently to infer clumped isotope temperatures. However, the clumped isotope composition of most samples are altered in the mass spectrometer during ionization, meaning that post-measurement data correction requires having measured materials of known clumped isotope composition. At a given temperature equilibrium thermodynamics predicts the distribution of isotopes among possible isotopologues, and these predictions can be calibrated experimentally. To generate a standard of known clumped isotope composition, current practice is to internally equilibrate analyte gas at high temperatures in the presence of a metal catalyst and assume that it has the Δ value predicted by equilibrium calculations. Developing isotopic reference materials specifically for clumped isotope analysis remains an ongoing goal of this rapidly developing field and was a major discussion topic during the 6th [http://www.ipgp.fr/en/iciw International Clumped Isotopes Workshop] in 2017. It is possible that researchers in the future will measure clumped isotope ratios against internationally distributed reference materials, similar to the current method of measuring the bulk isotope composition of unknown samples. | 0 | Theoretical and Fundamental Chemistry |
Housed in a plastic container, the bomb has a metal partition that separates two liquid reagents. Once the partition is removed, the liquids mix and react, causing them to rapidly expand and then solidify, creating a physical barrier blocking the tunnel. The device is either set at its target by an individual or thrown.
In 2021, testing of sponge bombs was reportedly conducted by IDF in simulated tunnels.
During initial testing of these bombs, the liquid emulsion was found to be hazardous to work with when mishandled – some Israeli soldiers lost their eyesight. | 0 | Theoretical and Fundamental Chemistry |
Zubbles were invented by Tim Kehoe, a toy creator from St. Paul, Minnesota. After an unexplained breakthrough in his kitchen, he was able to produce blue bubbles, that, unsuitably for a toy, stained clothing. After an eight-year-long delay in developing the idea further, he recommenced his investigations after forming a new toy company.
In the process of trying to rediscover the recipe, he changed the formula, making the coloring water-soluble. However, having to wash off the color from the bubbles rendered them unsuited to a mass-market toy. Kehoe hired the dye chemist Ram Sabnis, who arrived at a formula where the color would disappear on its own, with sufficient exposure to air, and without washing or staining.
The company entered into a global license agreement with Spin Master Ltd. for Zubbles Colored Bubbles in December 2005. Despite announcements of expected release dates, Spin Master dropped plans for commercial production due to complexities in the manufacturing process.
In 2008, the company reached a licensing agreement with a new toy company called Jamm Company. Zubbles commenced commercial sales in June 2009.
In 2011, Crayola disputed the patent given to Kehoe/C2C Technologies in a lawsuit which claimed that colored bubbles should be in the public domain.
Kehoe died unexpectedly at the age of 43 in 2014. | 0 | Theoretical and Fundamental Chemistry |
In a quantum-mechanical description of matter, the electrons confined to a material (such as those in individual atoms, molecules or crystals) are limited to a discrete set of energy values. The ground state of such a material system is such that the most energetic electron has its minimal energy. In photoluminescence, energy is transferred from light incident on the material and absorbed to electrons. The light is absorbed in minimal "quanta" or "packets" of energy of the electromagnetic radiation called photons. The amount of energy carried by a photon is proportional to its frequency. The electron is then in an excited state of higher energy. Such states are not stable and with time the material system will return to its ground state and the electron will lose its energy. Luminescence is the process whereby light is emitted when the electron drops to a lower energy level.
Often when a photon is absorbed, the system is excited in the corresponding excited state, then it relaxes in an intermediate lower energy state, with a "non-radiative relaxation" (a relaxation that doesn't involve the emission of a photon, but e.g. involves the emission of vibrational energy) and then there is the emission of a photon with a lower energy than the absorbed one, because of the relaxation from the intermediate, lower energy state to the "ground state". Usually the strongest luminescence of the material is from the lower levels to the ground state. This process is called fluorescence. For instance, in semiconductors, most of the light emitted is at the frequency corresponding to the bandgap energy, i.e. from the bottom of the conduction band to the top of the valence band. In such systems, more light absorbed by the material, results in more electrons decaying non-radiatively to the lower states, and more luminescence in the emission wavelength. | 0 | Theoretical and Fundamental Chemistry |
Phenolics are formed by three different biosynthetic pathways: (i) the shikimate/chorizmate or succinylbenzoate pathway, which produces the phenyl propanoid derivatives (C6–C3); (ii) the acetate/malonate or polyketide pathway, which produces the side-chain-elongated phenyl propanoids, including the large group of flavonoids (C6–C3–C6) and some quinones; and (iii) the acetate/mevalonate pathway, which produces the aromatic terpenoids, mostly monoterpenes, by dehydrogenation reactions. The aromatic amino acid phenylalanine, synthesized in the shikimic acid pathway, is the common precursor of phenol containing amino acids and phenolic compounds.
In plants, the phenolic units are esterified or methylated and are submitted to conjugation, which means that the natural phenols are mostly found in the glycoside form instead of the aglycone form.
In olive oil, tyrosol forms esters with fatty acids. In rye, alkylresorcinols are phenolic lipids.
Some acetylations involve terpenes like geraniol. Those molecules are called meroterpenes (a chemical compound having a partial terpenoid structure).
Methylations can occur by the formation of an ether bond on hydroxyl groups forming O-methylated polyphenols. In the case of the O-methylated flavone tangeritin, all of the five hydroxyls are methylated, leaving no free hydroxyls of the phenol group. Methylations can also occur on directly on a carbon of the benzene ring like in the case of poriol, a C-methylated flavonoid. | 0 | Theoretical and Fundamental Chemistry |
In nuclear physics, the island of stability is a predicted set of isotopes of superheavy elements that may have considerably longer half-lives than known isotopes of these elements. It is predicted to appear as an "island" in the chart of nuclides, separated from known stable and long-lived primordial radionuclides. Its theoretical existence is attributed to stabilizing effects of predicted "magic numbers" of protons and neutrons in the superheavy mass region.
Several predictions have been made regarding the exact location of the island of stability, though it is generally thought to center near copernicium and flerovium isotopes in the vicinity of the predicted closed neutron shell at N = 184. These models strongly suggest that the closed shell will confer further stability towards fission and alpha decay. While these effects are expected to be greatest near atomic number Z = 114 (flerovium) and N = 184, the region of increased stability is expected to encompass several neighboring elements, and there may also be additional islands of stability around heavier nuclei that are doubly magic (having magic numbers of both protons and neutrons). Estimates of the stability of the nuclides within the island are usually around a half-life of minutes or days; some optimists think half-lives of millions of years.
Although the nuclear shell model predicting magic numbers has existed since the 1940s, the existence of long-lived superheavy nuclides has not been definitively demonstrated. Like the rest of the superheavy elements, the nuclides within the island of stability have never been found in nature; thus, they must be created artificially in a nuclear reaction to be studied. Scientists have not found a way to carry out such a reaction, for it is likely that new types of reactions will be needed to populate nuclei near the center of the island. Nevertheless, the successful synthesis of superheavy elements up to Z = 118 (oganesson) with up to 177 neutrons demonstrates a slight stabilizing effect around elements 110 to 114 that may continue in heavier isotopes, consistent with the existence of the island of stability. | 0 | Theoretical and Fundamental Chemistry |
Perfusion storage methods can mechanically injury the vascular endothelium of the kidney, which leads to arterial thrombosis or fibrin deposition after reimplantation. Hill noted that, in human kidneys, fibrin deposition in the glomerulus after reimplantation and postoperative function, correlated with the length of perfusion storage. He had taken biopsies at revascularisation from human kidneys preserved by perfusion or ice storage, and showed by electron microscopy that endothelial disruption only occurred in those kidneys that had been perfused. Biopsies taken one hour after revascularisation showed platelets and fibrin adherent to any areas of denuded vascular basement membrane. A different type of vascular damage was described by Sheil who showed how a jet lesion could be produced distal to the cannula tied into the renal artery, leading to arterial thrombosis approximately 1 cm distal to the cannula site. | 1 | Applied and Interdisciplinary Chemistry |
It is also used in molecular biology as an oxidising agent, for example to oxidise free thiols to form disulfide bonds in proteins. | 0 | Theoretical and Fundamental Chemistry |
Surface plasmon resonance (SPR) is a phenomenon that occurs where electrons in a thin metal sheet become excited by light that is directed to the sheet with a particular angle of incidence, and then travel parallel to the sheet. Assuming a constant light source wavelength and that the metal sheet is thin, the angle of incidence that triggers SPR is related to the refractive index of the material and even a small change in the refractive index will cause SPR to not be observed. This makes SPR a possible technique for detecting particular substances (analytes) and SPR biosensors have been developed to detect various important biomarkers. | 0 | Theoretical and Fundamental Chemistry |
Several clinical studies have shown that MFGM could positively affect circulating lipids. A single-blind RCT in overweight adults has shown that the effects of milk fat on plasma lipids were modulated by the MFGM content; compared to butter oil (control diet), consumption of whipping cream (MFGM diet) for 8 weeks did not impair the lipoprotein profile. Another double-blind RCT in overweight and obese adults has also shown that MFGM attenuated the negative effects of a high-saturated fats meal by reducing postprandial cholesterol, inflammatory markers and insulin response. A double-blind RCT in normal healthy adults has indicated that one month consumption of buttermilk rich in MFGM led to reduction in serum cholesterol and triacylglycerol levels as well as blood pressure.
MFGM supplementation in infancy is hypothesized to have programming effects that may influence circulating lipid levels later in life. Breastfed infants are known to have a higher total serum cholesterol and LDL cholesterol than formula-fed infants in infancy, but lower levels in adulthood. A clinical study in infants has suggested that MFGM supplementation could narrow the gap between breastfed and formula-fed infants with regard to serum lipid status. Specifically, as compared with a control formula, infants receiving MFGM-supplemented formula had higher total serum cholesterol until 6 months of age, similar to breastfed infants. The LDL:HDL ratio did not differ between the formula-fed groups and was significantly higher in the breastfed reference group as compared with both formula-fed groups. | 1 | Applied and Interdisciplinary Chemistry |
Grignard reagents, given by RMgX, with R being a monoanionic organic substituent and X being a halide, are thought to proceed through some magnesium(I) intermediates, such as RMgMgX. It is believed that some of the transformations that occur with Grignard reagents may proceed via single electron transfer. This proceeds from the RMg to the substrate. Organic one electron reductions are also believed to be in equilibrium with a univalent magnesium compounds such as XMgMgX. This reagent could have potential to be more selective when compared to other reducing agents, such as samarium(II) Iodide, SmI, that also acts as a one electron reductant. | 0 | Theoretical and Fundamental Chemistry |
Located in the East San Francisco Bay, the neighborhood of West Oakland is home to mainly low-income African American and Latino residents who are exposed to a disproportionate amount of airborne toxins as compared to the rest of the surrounding Alameda County. West Oakland's close proximity to highways and the Port of Oakland leave residents highly exposed to pollutants caused by moving and stationary sources of diesel pollution, thus leaving them at higher risk for health complications such as asthma and even shorter life expectancy than surrounding neighborhoods averages.
High emissions of toxic chemicals and airborne particulate matter in West Oakland that cause health issues are due to diesel fuels used for transportation in the Port of Oakland and surrounding highways. Traffic and transportation-related air pollutants include carbon monoxide, nitrogen dioxide, black carbon, and diesel particulate matter. Residents are more exposed to harmful pollutants compared to other areas of the Bay Area and Oakland and therefore more at risk for harmful health effects. Compared to the State of California, West Oakland produces 90 times more diesel emission particulates per square mile per day. These pollutants have detrimental health effects such as asthma and reduced life expectancy while putting children at higher susceptibility for health complications.
Inequitable economic, residential, and environmental conditions in this low-income community of color leave residents of West Oakland with poor and inequitable health outcomes. African-American and Latino children of 10–18 years in West Oakland are more susceptible to onset lung defects such as asthma. According to Alameda County Vital Statistics, an African American child born in West Oakland is expected to live 14 fewer years than a white child born in the more wealthy Oakland Hills. Children 5 and under in west Oakland visit the emergency room for asthma three times more often than children in the county as a whole.
There are multiple efforts and strategies to spur legislation for equitable environmental conditions in low-income communities. There are many environmental justice groups and organizations in the Bay Area that encourage community participation in pursuing environmental justice. For example, data is collected by a Community-based participatory research (CBPR) and collaborated with West Oakland Environmental Indicators Project (WOEIP) in order to find effective and accurate findings to prove injustice and eventually spur reform in environmental policy. These research efforts can be used to document and communicate trends in air quality in West Oakland to policymakers. Effectiveness of efforts by these groups are multiplied by and increasing availability of environmental poverty lawyers who empower legislation in the legal system. | 1 | Applied and Interdisciplinary Chemistry |
The touchstone method is most common by far and does not damage the item in question. A rubbing of the item is made on a special stone, treated with acids and the result is compared to the result of the same process done on a sample of gold with a known purity. Red radiolarian chert or black siliceous slate were used for this. Differences in precious metal content as small as 10 to 20 parts per thousand can often be established with confidence by the test, using acids and gold samples both of a specific, known concentration. | 1 | Applied and Interdisciplinary Chemistry |
The first-generation of Glycoazodyes was first reported in 2007. These Glycoazodyes use a diester linker, specifically a succinyl bridge. An ester group bonds the sugar to an n-alkane spacer, and the spacer bonds to the dye through another ester group. | 0 | Theoretical and Fundamental Chemistry |
Owing to the ability of nitrido ligands to serve as a bridging ligand, several metal clusters are known to contain nitride ligands at their center. Such nitrido ligands are termed interstitial. In some cases, the nitride is completely encased in the center of six or more metals and cannot undergo reactions, although it contributes to the intermetallic bonding. | 0 | Theoretical and Fundamental Chemistry |
Before exploring Rietveld refinement, it is necessary to establish a greater understanding of powder diffraction data and what information is encoded therein in order to establish a notion of how to create a model of a diffraction pattern, which is of course necessary in Rietveld refinement. A typical diffraction pattern can be described by the positions, shapes, and intensities of multiple Bragg reflections. Each of the three mentioned properties encodes some information relating to the crystal structure, the properties of the sample, and the properties of the instrumentation. Some of these contributions are shown in Table 1, below.
<br />
The structure of a powder pattern is essentially defined by instrumental parameters and two crystallographic parameters: unit cell dimensions, and atomic content and coordination. So, a powder pattern model can be constructed as follows:
# Establish peak positions: Bragg peak positions are established from Bragg's law using the wavelength and d-spacing for a given unit cell.
# Determine peak intensity: Intensity depends on the structure factor, and can be calculated from the structural model for individual peaks. This requires knowledge of the specific atomic coordination in the unit cell and geometrical parameters.
# Peak shape for individual Bragg peaks: Represented by functions of the FWHM (which vary with Bragg angle) called the peak shape functions. Realistically ab initio modelling is difficult, and so empirically selected peak shape functions and parameters are used for modelling.
# Sum: The individual peak shape functions are summed and added to a background function, leaving behind the resultant powder pattern.
It is easy to model a powder pattern given the crystal structure of a material. The opposite, determining the crystal structure from a powder pattern, is much more complicated. A brief explanation of the process follows, though it is not the focus of this article.
To determine structure from a powder diffraction pattern the following steps should be taken. First, Bragg peak positions and intensities should be found by fitting to a peak shape function including background. Next, peak positions should be indexed and used to determine unit cell parameters, symmetry, and content. Third, peak intensities determine space group symmetry and atomic coordination. Finally, the model is used to refine all crystallographic and peak shape function parameters. To do this successfully, there is a requirement for excellent data which means good resolution, low background, and a large angular range. | 0 | Theoretical and Fundamental Chemistry |
In the gas phase sulfur dioxide is oxidized by reaction with the hydroxyl radical via an intermolecular reaction:
:SO + OH· → HOSO·
which is followed by:
:HOSO· + O → HO· + SO
In the presence of water, sulfur trioxide (SO) is converted rapidly to sulfuric acid:
:SO (g) + HO (l) → HSO (aq)
Nitrogen dioxide reacts with OH to form nitric acid:
:NO + OH· → HNO | 1 | Applied and Interdisciplinary Chemistry |
Many TRIM proteins are induced by interferons, which are important component of resistance to pathogens and several TRIM proteins are known to be required for the restriction of infection by lentiviruses. TRIM proteins are involved in pathogen-recognition and by regulation of transcriptional pathways in host defence. | 1 | Applied and Interdisciplinary Chemistry |
The active ingredient in pepper spray is capsaicin, which is derived from the fruit of plants in the genus Capsicum, including chilis in the form of oleoresin capsicum (OC). Extraction of OC from peppers requires capsicum to be finely ground, from which capsaicin is then extracted using an organic solvent such as ethanol. The solvent is then evaporated, and the remaining waxlike resin is the oleoresin capsaicin.
An emulsifier such as propylene glycol is used to suspend OC in water, and the suspension is then pressurized to make an aerosol pepper spray. Other sprays may use an alcohol (such as isopropyl alcohol) base for a more penetrating product, but a risk of fire is present if combined with a taser.
Determining the strength of pepper sprays made by different manufacturers can be confusing and difficult. Statements a company makes about their product strength are not regulated.
* The US federal government uses CRC (capsaicin and related capsaicinoids) content for regulation. CRC is the pain-producing component of the OC that produces the burning sensation. Personal pepper sprays can range from a low of 0.18% to a high of 3%. Most law enforcement pepper sprays use between 1.3% and 2%. The federal government of the United States has determined that bear attack deterrent sprays must contain at least 1.0% and not more than 2% CRC. Because the six different types of capsaicinoids under the CRC heading has different levels of potency (up to 2× on the SHU scale), the measurement does not fully represent the strength. Manufacturers do not state which particular type of capsaicinoids are used.
* Using the OC concentration is unreliable because the concentration of CRC (and potency of these compounds) can vary. Some manufacturers may show a very high percentage of OC, but the resin itself may not be spicy enough. Higher OC content only reliably implies a higher oil content, which may be undesirable as the hydrophobic oil is less able to soak and penetrate skin. Solutions of more than 5% OC may not spray properly.
* Scoville heat units (SHU) is a common indication of pepper spiciness. It does take into account the different potency of CRC compounds, but it cannot be reliably used in pepper spray because it measures the strength of the dry product, i.e. the OC resin and not what comes in the aerosol spray. As the resin is always diluted to make it spray-able, the SHU rating is not useful on its own. | 1 | Applied and Interdisciplinary Chemistry |
This idea, drug to metabolite switching, is an extension of the chiral switch concept. The purpose of the switching is to develop an active metabolite which will be devoid of the side-effects and have an improved therapeutic profile compared to the parent chiral drug. Some examples of chiral drug to metabolite switches, (those in the market and others under investigation) include terfenadine to fexofenadine, halofantrine to desbutylhalofantrine, and cisapride to norcisapride. A summary is presented in the table below. | 0 | Theoretical and Fundamental Chemistry |
In the limiting case of no interaction, the system is an ideal gas and the structure factor is completely featureless: , because there is no correlation between the positions and of different particles (they are independent random variables), so the off-diagonal terms in Equation () average to zero: . | 0 | Theoretical and Fundamental Chemistry |
The Ferrier rearrangement is an organic reaction that involves a nucleophilic substitution reaction combined with an allylic shift in a glycal (a 2,3-unsaturated glycoside). It was discovered by the carbohydrate chemist Robert J. Ferrier. | 0 | Theoretical and Fundamental Chemistry |
In most cases this decay mode is masked by other, more probable modes involving fewer particles, such as single electron capture. When all other modes are “forbidden” (strongly suppressed) double electron capture becomes the main mode of decay. There exist 34 naturally occurring nuclei that are believed to undergo double electron capture, but the process has been confirmed by observation in the decay of only three nuclides: , , and .
One reason is that the probability of double electron capture is stupendously small; the half-lives for this mode lie well above 10 years. A second reason is that the only detectable particles created in this process are X-rays and Auger electrons that are emitted by the excited atomic shell. In the range of their energies (~1–10 keV), the background is usually high. Thus, the experimental detection of double electron capture is more difficult than that for double beta decay.
Double electron capture can be accompanied by the excitation of the daughter nucleus. Its de-excitation, in turn, is accompanied by an emission of photons with energies of hundreds of keV. | 0 | Theoretical and Fundamental Chemistry |
During surface micromachining, stiction or adhesion between the substrate (usually silicon-based) and the microstructure occurs during the isotropic wet etching of the sacrificial layer. The capillary forces due to the surface tension of the liquid between the microstructure and substrate during drying of the wet etchant cause the two surfaces to adhere together. Separating the two surfaces is often complicated due to the fragile nature of the microstructure. Stiction is often circumvented by the use of a sublimating fluid (often supercritical CO, which has extremely low surface tension) drying process where the liquid phase is bypassed. CO displaces the rinsing fluid and is heated past the supercritical point. As the chamber pressure is slowly released the CO sublimates, thereby preventing stiction. | 0 | Theoretical and Fundamental Chemistry |
In medicine, protein electrophoresis is a method of analysing the proteins mainly in blood serum. Before the widespread use of gel electrophoresis, protein electrophoresis was performed as free-flow electrophoresis (on paper) or as immunoelectrophoresis.
Traditionally, two classes of blood proteins are considered: serum albumin and globulin. They are generally equal in proportion, but albumin as a molecule is much smaller and lightly, negatively-charged, leading to an accumulation of albumin on the electrophoretic gel. A small band before albumin represents transthyretin (also named prealbumin). Some forms of medication or body chemicals can cause their own band, but it usually is small. Abnormal bands (spikes) are seen in monoclonal gammopathy of undetermined significance and multiple myeloma, and are useful in the diagnosis of these conditions.
The globulins are classified by their banding pattern (with their main representatives):
* The alpha (α) band consists of two parts, 1 and 2:
** α - α-antitrypsin, α-acid glycoprotein.
** α - haptoglobin, α-macroglobulin, α-antiplasmin, ceruloplasmin.
* The beta (β) band - transferrin, LDL, complement
* The gamma (γ) band - immunoglobulin (IgA, IgD, IgE, IgG and IgM). Paraproteins (in multiple myeloma) usually appear in this band. | 1 | Applied and Interdisciplinary Chemistry |
FRET efficiencies can also be inferred from the photobleaching rates of the donor in the presence and absence of an acceptor. This method can be performed on most fluorescence microscopes; one simply shines the excitation light (of a frequency that will excite the donor but not the acceptor significantly) on specimens with and without the acceptor fluorophore and monitors the donor fluorescence (typically separated from acceptor fluorescence using a bandpass filter) over time. The timescale is that of photobleaching, which is seconds to minutes, with fluorescence in each curve being given by
where is the photobleaching decay time constant and depends on whether the acceptor is present or not. Since photobleaching consists in the permanent inactivation of excited fluorophores, resonance energy transfer from an excited donor to an acceptor fluorophore prevents the photobleaching of that donor fluorophore, and thus high FRET efficiency leads to a longer photobleaching decay time constant:
where and are the photobleaching decay time constants of the donor in the presence and in the absence of the acceptor respectively. (Notice that the fraction is the reciprocal of that used for lifetime measurements).
This technique was introduced by Jovin in 1989. Its use of an entire curve of points to extract the time constants can give it accuracy advantages over the other methods. Also, the fact that time measurements are over seconds rather than nanoseconds makes it easier than fluorescence lifetime measurements, and because photobleaching decay rates do not generally depend on donor concentration (unless acceptor saturation is an issue), the careful control of concentrations needed for intensity measurements is not needed. It is, however, important to keep the illumination the same for the with- and without-acceptor measurements, as photobleaching increases markedly with more intense incident light. | 1 | Applied and Interdisciplinary Chemistry |
Fatty acids from lipids are commonly used as an energy source by vertebrates as fatty acids are degraded through beta oxidation into acetate molecules. This acetate, bound to the active thiol group of coenzyme A, enters the citric acid cycle (TCA cycle) where it is fully oxidized to carbon dioxide. This pathway thus allows cells to obtain energy from fat. To use acetate from fat for biosynthesis of carbohydrates, the glyoxylate cycle, whose initial reactions are identical to the TCA cycle, is used.
Cell-wall containing organisms, such as plants, fungi, and bacteria, require very large amounts of carbohydrates during growth for the biosynthesis of complex structural polysaccharides, such as cellulose, glucans, and chitin. In these organisms, in the absence of available carbohydrates (for example, in certain microbial environments or during seed germination in plants), the glyoxylate cycle permits the synthesis of glucose from lipids via acetate generated in fatty acid β-oxidation.
The glyoxylate cycle bypasses the steps in the citric acid cycle where carbon is lost in the form of CO. The two initial steps of the glyoxylate cycle are identical to those in the citric acid cycle: acetate → citrate → isocitrate. In the next step, catalyzed by the first glyoxylate cycle enzyme, isocitrate lyase, isocitrate undergoes cleavage into succinate and glyoxylate (the latter gives the cycle its name). Glyoxylate condenses with acetyl-CoA (a step catalyzed by malate synthase), yielding malate. Both malate and oxaloacetate can be converted into phosphoenolpyruvate, which is the product of phosphoenolpyruvate carboxykinase, the first enzyme in gluconeogenesis. The net result of the glyoxylate cycle is therefore the production of glucose from fatty acids. Succinate generated in the first step can enter into the citric acid cycle to eventually form oxaloacetate. | 1 | Applied and Interdisciplinary Chemistry |
The relationship between mean flow velocity and volumetric flow rate is
: = The volumetric flow (m/s),
: = The cross-sectional wetted area (m).
In a full-flowing, circular pipe of diameter ,
Then the Darcy–Weisbach equation in terms of is | 1 | Applied and Interdisciplinary Chemistry |
NMO, as an N-oxide, is an oxidant in the Upjohn dihydroxylation. It is generally used in stoichiometric amounts as a secondary oxidant (a cooxidant) to regenerate a primary (catalytic) oxidant after the latter has been reduced by the substrate. Vicinal syn-dihydroxylation reactions for example, would, in theory, require stoichiometric amounts of toxic, volatile and expensive osmium tetroxide, but if continuously regenerated with NMO, the amount required can be reduced to catalytic quantities. | 0 | Theoretical and Fundamental Chemistry |
Major greenhouse gases are well mixed and take many years to leave the atmosphere.
The atmospheric lifetime of a greenhouse gas refers to the time required to restore equilibrium following a sudden increase or decrease in its concentration in the atmosphere. Individual atoms or molecules may be lost or deposited to sinks such as the soil, the oceans and other waters, or vegetation and other biological systems, reducing the excess to background concentrations. The average time taken to achieve this is the mean lifetime. This can be represented through the following formula, where the lifetime of an atmospheric species X in a one-box model is the average time that a molecule of X remains in the box.
can also be defined as the ratio of the mass (in kg) of X in the box to its removal rate, which is the sum of the flow of X out of the box
chemical loss of X
and deposition of X
(all in kg/s):
If input of this gas into the box ceased, then after time , its concentration would decrease by about 63%.
Changes to any of these variables can alter the atmospheric lifetime of a greenhouse gas. For instance, methanes atmospheric lifetime is estimated to have been lower in the 19th century than now, but to have been higher in the second half of the 20th century than after 2000. Carbon dioxide has an even more variable lifetime, which cannot be specified down to a single number. Scientists instead say that while the first 10% of carbon dioxides airborne fraction (not counting the ~50% absorbed by land and ocean sinks within the emission's first year) is removed "quickly", the vast majority of the airborne fraction – 80% – lasts for "centuries to millennia". The remaining 10% stays for tens of thousands of years. In some models, this longest-lasting fraction is as large as 30%. | 1 | Applied and Interdisciplinary Chemistry |
ppGpp directly inhibits transcription from ribosomal promoters. One model is ppGpp and DksA together and independently decrease the stability of the open complexes formed on DNA by RNAP. Another model is the trapping mechanism. In this model, RNAP is trapped by ppGpp in closed complexes and is unable to initiate transcription. Thus, ppGpp seems to act at many levels, and the mechanism of its action is a complex outcome of several factors, intrinsic promoter properties not being the least of them. The transcription activation by ppGpp can be direct or indirect. Direct activation occurs when RNAP interacts with effectors, such as ppGpp, DksA or both, to increase transcription from a given promoter. Indirect activation by these effectors of one promoter relies on inhibition of other (strong) promoters, leading to increased availability of RNAP that indirectly activates transcription initiation. The promoters that activated directly by ppGpp include PargI, PthrABC, PlivJ, and PhisG. The indirectly activation promoters include these dependent on sigma factors: S, H, N, E. When strong promoters, such as rrn, are inhibited, there more RNAP are available for these alternative sigma factors. | 1 | Applied and Interdisciplinary Chemistry |
In isotropic turbulence the Kármán–Howarth equation (after Theodore von Kármán and Leslie Howarth 1938), which is derived from the Navier–Stokes equations, is used to describe the evolution of non-dimensional longitudinal autocorrelation. | 1 | Applied and Interdisciplinary Chemistry |
The absorption of dietary iron is a variable and dynamic process. The amount of iron absorbed compared to the amount ingested is typically low, but may range from 5% to as much as 35% depending on circumstances and type of iron. The efficiency with which iron is absorbed varies depending on the source. Generally, the best-absorbed forms of iron come from animal products. Absorption of dietary iron in iron salt form (as in most supplements) varies somewhat according to the body's need for iron, and is usually between 10% and 20% of iron intake. Absorption of iron from animal products, and some plant products, is in the form of heme iron, and is more efficient, allowing absorption of from 15% to 35% of intake. Heme iron in animals is from blood and heme-containing proteins in meat and mitochondria, whereas in plants, heme iron is present in mitochondria in all cells that use oxygen for respiration.
Like most mineral nutrients, the majority of the iron absorbed from digested food or supplements is absorbed in the duodenum by enterocytes of the duodenal lining. These cells have special molecules that allow them to move iron into the body. To be absorbed, dietary iron can be absorbed as part of a protein such as heme protein or iron must be in its ferrous Fe form. A ferric reductase enzyme on the enterocytes brush border, duodenal cytochrome B (Dcytb), reduces ferric Fe to Fe. A protein called divalent metal transporter 1 (DMT1), which can transport several divalent metals across the plasma membrane, then transports iron across the enterocytes cell membrane into the cell. If the iron is bound to heme it is instead transported across the apical membrane by heme carrier protein 1 (HCP1).
These intestinal lining cells can then either store the iron as ferritin, which is accomplished by Fe binding to apoferritin (in which case the iron will leave the body when the cell dies and is sloughed off into feces), or the cell can release it into the body via the only known iron exporter in mammals, ferroportin. Hephaestin, a ferroxidase that can oxidize Fe to Fe and is found mainly in the small intestine, helps ferroportin transfer iron across the basolateral end of the intestine cells. In contrast, ferroportin is post-translationally repressed by hepcidin, a 25-amino acid peptide hormone. The body regulates iron levels by regulating each of these steps. For instance, enterocytes synthesize more Dcytb, DMT1 and ferroportin in response to iron deficiency anemia. Iron absorption from diet is enhanced in the presence of vitamin C and diminished by excess calcium, zinc, or manganese.
The human body's rate of iron absorption appears to respond to a variety of interdependent factors, including total iron stores, the extent to which the bone marrow is producing new red blood cells, the concentration of hemoglobin in the blood, and the oxygen content of the blood. The body also absorbs less iron during times of inflammation, in order to deprive bacteria of iron. Recent discoveries demonstrate that hepcidin regulation of ferroportin is responsible for the syndrome of anemia of chronic disease. | 1 | Applied and Interdisciplinary Chemistry |
Near the end of mitosis, p130 and p107 are dephosphorylated from their hyperphosphorylated state by the phosphatase PP2a. Inhibition of PP2a activity reduced promoter binding of some of the proteins of the DREAM complex in the subsequent G1 phase and de-repression of gene expression.
Other components have been shown to be phosphorylated for DREAM complex assembly to occur. Of these, LIN52 phosphorylation on its S28 residue is the most well-understood. Substitution of this serine to alanine led to reduced binding of the MuvB core to p130 and impaired the ability of cells to enter quiescence. This indicates that LIN52 S28 phosphorylation is required for proper association and function of the DREAM complex via binding with p130.
One known regulator of phosphorylation of the S28 residue is the DYRK1A. The loss of this kinase leads to decreased phosphorylation of the S28 residue and association of p130 with MuvB. DYRK1A was also found to degrade cyclin D1, which would increase p21 levels – both of which contribute to cell cycle exit.
The DREAM complex was also shown to regulate cytokinesis through GAS2L3. | 1 | Applied and Interdisciplinary Chemistry |
An oligoester is an ester oligomer chain containing a small number of repeating ester units (monomers). Oligoesters are short analogs of polymeric polyesters.
An example is oligo-(R)-3-hydroxybutyrate. | 0 | Theoretical and Fundamental Chemistry |
Diols react as alcohols, by esterification and ether formation.
Diols such as ethylene glycol are used as co-monomers in polymerization reactions forming polymers including some polyesters and polyurethanes. A different monomer with two identical functional groups, such as a dioyl dichloride or dioic acid is required to continue the process of polymerization through repeated esterification processes.
A diol can be converted to cyclic ether by using an acid catalyst, this is diol cyclization. Firstly, it involves protonation of the hydroxyl group. Then, followed by intramolecular nucleophilic substitution, the second hydroxyl group attacks the electron deficient carbon. Provided that there are enough carbon atoms that the angle strain is not too much, a cyclic ether can be formed.
1,2-diols and 1,3-diols can be protected using a protecting group. Protecting groups are used so that the functional group does not react to future reactions. Benzylidene groups are used to protect 1,3-diols. There are extremely useful in biochemistry as shown below of a carbohydrate derivative being protected.
Diols can also be used to protect carbonyl groups. They are commonly used and are quite efficient at synthesizing cyclic acetals. These protect the carbonyl groups from reacting from any further synthesis until it is necessary to remove them. The reaction below depicts a diol being used to protect a carbonyl using zirconium tetrachloride.
Diols can also be converted to lactones employing the Fétizon oxidation reaction. | 0 | Theoretical and Fundamental Chemistry |
Some mammals can emit foul smelling liquids from anal glands, such as the pangolin and some members of families Mephitidae and Mustelidae including skunks, weasels, and polecats. Monotremes have venomous spurs used to avoid predation and slow lorises (Primates: Nycticebus) produce venom which appears to be effective at deterring both predators and parasites. It has also been demonstrated that physical contact with a slow loris (without being bitten) can cause a reaction in humans – acting as a contact poison. | 1 | Applied and Interdisciplinary Chemistry |
Overloading peaks should not cause performance problems while continuous overloading lead to a loss of treatment capacity through too much suspended solids, sludge or fats.
Subsurface flow wetlands require the following maintenance tasks: regular checking of the pretreatment process, of pumps when they are used, of influent loads and distribution on the filter bed. | 1 | Applied and Interdisciplinary Chemistry |
An ylide () or ylid () is a neutral dipolar molecule containing a formally negatively charged atom (usually a carbanion) directly attached to a heteroatom with a formal positive charge (usually nitrogen, phosphorus or sulfur), and in which both atoms have full octets of electrons. The result can be viewed as a structure in which two adjacent atoms are connected by both a covalent and an ionic bond; normally written X–Y. Ylides are thus 1,2-dipolar compounds, and a subclass of zwitterions. They appear in organic chemistry as reagents or reactive intermediates.
The class name "ylide" for the compound should not be confused with the suffix "-ylide". | 0 | Theoretical and Fundamental Chemistry |
IIR Working Groups operate on a temporary basis, bringing together specialists, to work on projects arising from current issues.
Their aim is to promote development, provide knowledge and give recommendations in these spheres. In order to achieve these objectives, they hold conferences and workshops, write publications and provide recommendations. Members of WGs are IIR members from industry, academia, national administrations and research. | 0 | Theoretical and Fundamental Chemistry |
Side effects of gestonorone caproate have been reported to include worsened glucose tolerance, decreased libido in men, and local injection site reactions such as irritation. | 0 | Theoretical and Fundamental Chemistry |
A pheromone (from Greek phero "to bear" + hormone from Greek – "impetus") is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individual. There are alarm pheromones, food trail pheromones, sex pheromones, and many others that affect behavior or physiology. Their use among insects has been particularly well documented. In addition, some vertebrates and plants communicate by using pheromones. A notable example of pheromone usage to indicate sexual receptivity in insects can be seen in the female Dawsons burrowing bee, which uses a particular mixture of cuticular hydrocarbons to signal sexual receptivity to mating, and then another mixture to indicate sexual disinterest. These hydrocarbons, in association with other chemical signals produced in the Dufours gland, have been implicated in male repulsion signaling as well.
The term "pheromone" was introduced by Peter Karlson and Martin Lüscher in 1959, based on the Greek word pherein (to transport) and hormone (to stimulate). They are also sometimes classified as ecto-hormones. German Biochemist Adolf Butenandt characterized the first such chemical, Bombykol (a chemically well-characterized pheromone released by the female silkworm to attract mates). | 1 | Applied and Interdisciplinary Chemistry |
The following list describes a viewpoint on the interdisciplinary relationships between molecular biology and other related fields.
* Molecular biology is the study of the molecular underpinnings of the biological phenomena, focusing on molecular synthesis, modification, mechanisms and interactions.
* Biochemistry is the study of the chemical substances and vital processes occurring in living organisms. Biochemists focus heavily on the role, function, and structure of biomolecules such as proteins, lipids, carbohydrates and nucleic acids.
* Genetics is the study of how genetic differences affect organisms. Genetics attempts to predict how mutations, individual genes and genetic interactions can affect the expression of a phenotype
While researchers practice techniques specific to molecular biology, it is common to combine these with methods from genetics and biochemistry. Much of molecular biology is quantitative, and recently a significant amount of work has been done using computer science techniques such as bioinformatics and computational biology. Molecular genetics, the study of gene structure and function, has been among the most prominent sub-fields of molecular biology since the early 2000s. Other branches of biology are informed by molecular biology, by either directly studying the interactions of molecules in their own right such as in cell biology and developmental biology, or indirectly, where molecular techniques are used to infer historical attributes of populations or species, as in fields in evolutionary biology such as population genetics and phylogenetics. There is also a long tradition of studying biomolecules "from the ground up", or molecularly, in biophysics. | 1 | Applied and Interdisciplinary Chemistry |
Cross sections commonly calculated using Mie theory include efficiency coefficients for extinction , scattering , and Absorption cross sections. These are normalized by the geometrical cross sections of the particle as
The cross section is defined by
where is the energy flow through the surrounding surface, and is the intensity of the incident wave. For a plane wave the intensity is going to be , where is the impedance of the host medium.
The main approach is based on the following. Firstly, we construct an imaginary sphere of radius (surface ) around the particle (the scatterer). The net rate of electromagnetic energy crosses the surface is
where is the time averaged Poynting vector. If energy is absorbed within the sphere, otherwise energy is being created within the sphere. We will not consider this case here. If the host medium is non-absorbing, the energy must be absorbed by the particle. We decompose the total field into incident and scattered parts , and the same for the magnetic field . Thus, we can decompose into the three terms , where
Where , , and .
All the field can be decomposed into the series of vector spherical harmonics (VSH). After that, all the integrals can be taken.
In the case of a uniform sphere of radius , permittivity , and permeability the problem has a precise solution. The scattering and extinction coefficients are | 0 | Theoretical and Fundamental Chemistry |
Four broad classes of biomarkers are diagnostic biomarkers, prognostic biomarkers, predictive biomarkers and pharmacodynamic biomarkers. | 1 | Applied and Interdisciplinary Chemistry |
Shortly after its inauguration the society began publishing the Journal of Exploration Geochemistry in 1972. Today the societys flagship journal is Geochemistry: Exploration, Environment, Analysis, co-published with the Geological Society of London. The journal covers fields relating to the application of geochemistry to the exploration and study of mineral resources. It aims to promote interchange between exploration and environmental geochemistry. The journal is a hybrid open-access journal, publishing both subscription and open access articles. It also publishes Explore, a newsletter, and co-publishes Elements', a membership magazine. | 0 | Theoretical and Fundamental Chemistry |
The micelle velocity is defined by:
where is the electrophoretic velocity of a micelle.
The retention time of a given sample should depend on the capacity factor, :
where is the total number of moles of solute in the micelle and is the total moles in the aqueous phase. The retention time of a solute should then be within the range:
Charged analytes have a more complex interaction in the capillary because they exhibit electrophoretic mobility, engage in electrostatic interactions with the micelle, and participate in hydrophobic partitioning.
The fraction of the sample in the aqueous phase, , is given by:
where is the migration velocity of the solute. The value can also be expressed in terms of the capacity factor:
Using the relationship between velocity, tube length from the injection end to the detector cell (), and retention time, , and , a relationship between the capacity factor and retention times can be formulated:
The extra term enclosed in parentheses accounts for the partial mobility of the hydrophobic phase in MEKC. This equation resembles an expression derived for in conventional packed bed chromatography:
A rearrangement of the previous equation can be used to write an expression for the retention factor:
From this equation it can be seen that all analytes that partition strongly into the micellar phase (where is essentially ∞) migrate at the same time, . In conventional chromatography, separation of similar compounds can be improved by gradient elution. In MEKC, however, techniques must be used to extend the elution range to separate strongly retained analytes.
Elution ranges can be extended by several techniques including the use of organic modifiers, cyclodextrins, and mixed micelle systems. Short-chain alcohols or acetonitrile can be used as organic modifiers that decrease and to improve the resolution of analytes that co-elute with the micellar phase. These agents, however, may alter the level of the EOF. Cyclodextrins are cyclic polysaccharides that form inclusion complexes that can cause competitive hydrophobic partitioning of the analyte. Since analyte-cyclodextrin complexes are neutral, they will migrate toward the cathode at a higher velocity than that of the negatively charged micelles. Mixed micelle systems, such as the one formed by combining SDS with the non-ionic surfactant Brij-35, can also be used to alter the selectivity of MEKC. | 0 | Theoretical and Fundamental Chemistry |
The first stable carbenes to be isolated were based on an imidazole ring, with the hydrogen in carbon 2 of the ring (between the two nitrogen atoms) removed, and other hydrogens replaced by various groups. These imidazol-2-ylidenes are still the most stable and the most well studied and understood family of persistent carbenes.
A considerable range of imidazol-2-ylidenes have been synthesised, including those in which the 1,3-positions have been functionalised with alkyl, aryl, alkyloxy, alkylamino, alkylphosphino and even chiral substituents:
In particular, substitution of two chlorine atoms for the two hydrogens at ring positions 4 and 5 yielded the first air-stable carbene. Its extra stability probably results from the electron-withdrawing effect of the chlorine substituents, which reduce the electron density on the carbon atom bearing the lone pair, via induction through the sigma-backbone.
Molecules containing two and even three imidazol-2-ylidene groups have also been synthesised.
Imidazole-based carbenes are thermodynamically stable and generally have diagnostic C NMR chemical shift values between 210 and 230 ppm for the carbenic carbon. Typically, X-ray structures of these molecules show N–C–N bond angles of 101–102°. | 0 | Theoretical and Fundamental Chemistry |
Integrating the equations obtained at the second order, we find
where is an unknown at this order.
Now collecting terms of order , we find
The solvability condition of the above equation yields the governing equation for as follows | 1 | Applied and Interdisciplinary Chemistry |
Post-translational regulation refers to the control of the levels of active protein.
There are several forms.
It is performed either by means of reversible events (posttranslational modifications, such as phosphorylation or sequestration) or by means of irreversible events (proteolysis). | 1 | Applied and Interdisciplinary Chemistry |
The Papkovich–Neuber solution is a technique for generating analytic solutions to the Newtonian incompressible Stokes equations, though it was originally developed to solve the equations of linear elasticity.
It can be shown that any Stokes flow with body force can be written in the form:
where is a harmonic vector potential and is a harmonic scalar potential. The properties and ease of construction of harmonic functions makes the Papkovich–Neuber solution a powerful technique for solving the Stokes Equations in a variety of domains. | 1 | Applied and Interdisciplinary Chemistry |
Potential applications include herbicides and pesticides formulations, detergents, healthcare and cosmetics, pulp and paper, coal, textiles, ceramic processing and food industries, uranium ore-processing, and mechanical dewatering of peat. | 0 | Theoretical and Fundamental Chemistry |
With few exceptions, most chloroplasts have their entire chloroplast genome combined into a single large circular DNA molecule, typically 120,000–170,000 base pairs long. They can have a contour length of around 30–60 micrometers, and have a mass of about 80–130 million daltons.
While usually thought of as a circular molecule, there is some evidence that chloroplast DNA molecules more often take on a linear shape. | 0 | Theoretical and Fundamental Chemistry |
Gene nomenclature has been established by the HUGO Gene Nomenclature Committee (HGNC), a committee of the Human Genome Organisation, for each known human gene in the form of an approved gene name and symbol (short-form abbreviation), which can be accessed through a database maintained by HGNC. Symbols are chosen to be unique, and each gene has only one symbol (although approved symbols sometimes change). Symbols are preferably kept consistent with other members of a gene family and with homologs in other species, particularly the mouse due to its role as a common model organism. | 1 | Applied and Interdisciplinary Chemistry |
Chilton–Colburn J-factor analogy (also known as the modified Reynolds analogy) is a successful and widely used analogy between heat, momentum, and mass transfer. The basic mechanisms and mathematics of heat, mass, and momentum transport are essentially the same. Among many analogies (like Reynolds analogy, Prandtl–Taylor analogy) developed to directly relate heat transfer coefficients, mass transfer coefficients and friction factors, Chilton and Colburn J-factor analogy proved to be the most accurate.
It is written as follows,
This equation permits the prediction of an unknown transfer coefficient when one of the other coefficients is known. The analogy is valid for fully developed turbulent flow in conduits with Re > 10000, 0.7 < Pr < 160, and tubes where L/d > 60 (the same constraints as the Sieder–Tate correlation). The wider range of data can be correlated by Friend–Metzner analogy.
Relationship between Heat and Mass; | 1 | Applied and Interdisciplinary Chemistry |
Owing to its high reactivity and the ability to tune its endcap groups, PPA has been lately utilized in drug delivery applications. In one recent study, UV-sensitive PPA microcapsules containing different types of drugs were prepared. Once the capsules were subjected to a UV-light trigger, an unzipping reaction took place and the shell ruptured which led to the release of the core contain of these microcapsules. A unique advantage of these microcapsules is that they allow the immediate release of the drug upon exposure to the trigger rather than its continuous release over a period of time ranging from minutes to hours as other common microcapsules function. In an earlier publication, DiLauro et al. reported the ability to predesign and control the thickness of the microcapsule shells and length of the PPA used to form the shell, which have stimuli-responsive endcaps allowing head-to-tail fluoride-triggered depolymerization. | 0 | Theoretical and Fundamental Chemistry |
The rust resistance of EPS-processed steel strip is superior to that of acid pickled steel strip primarily because acid pickling imposes a corrosion "penalty" on the steel which EPS processing does not. This penalty is a result of chemical reactions that occur after acid pickling and serve as a catalyst for oxidation. The primary pickling agent is hydrochloric acid (HCl). Although the steel strip is thoroughly rinsed with clean water after immersion in the HCl bath, some residual amount of chlorine (Cl) remains on the surface of the strip. Chlorine reacts very readily with oxygen to form chlorides, so the free Cl acts as something of a "magnet" for oxygen. This mechanism makes acid-pickled steel more prone to picking up oxygen, whereas there is no comparable mechanism at work with EPS mechanical pickling.
In addition to the free Cl, compounds known as "chloride salts" remain on the surface of acid pickled steel in trace amounts, even after rinsing. Chloride salts react rapidly with moisture and accelerate oxidation of iron on the steel's surface. To prevent oxidation of the iron in the acid pickled strip, a thin film of oil is applied to the surface to serve as a barrier between the free Cl, chloride salts and oxygen. No such protective barrier is needed for EPS-processed steel, as no free Cl or chloride salts are present.
However, an additive is used in the EPS slurry blast carrier liquid to reduce the "smut" that would otherwise remain on the surface and dull the appearance of EPS-processed strip. This additive contains a rust inhibitor, a residual amount of which remains on the surface even after rinsing. It is believed that the presence of the rust inhibitor adds to the overall EPS-processed strip's ability to resist rusting. The additive has been demonstrated to have no impact on paint performance. | 1 | Applied and Interdisciplinary Chemistry |
Nicholas J. Turro (May 18, 1938 – November 24, 2012) was an American chemist, Wm. P. Schweitzer Professor of Chemistry at Columbia University. He was a world renowned organic chemist and leading world expert on organic photochemistry. He was the recipient of the 2011 Arthur C. Cope Award in Organic Chemistry, given annually "to recognize outstanding achievement in the field of organic chemistry, the significance of which has become apparent within the five years preceding the year in which the award will be considered." He was also the recipient of the 2000 Willard Gibbs Award, which recognizes "eminent chemists who...have brought to the world developments that enable everyone to live more comfortably and to understand this world better."
He received his B.A. degree summa cum laude from Wesleyan University in 1960. He attended graduate school at Caltech where he received his Ph.D. degree with George S. Hammond in 1963. Following a postdoctoral year at Harvard with P. D. Bartlett, he joined the faculty at Columbia University where he was the Wm. P. Schweitzer Professor of Chemistry.
Although he worked in many areas of chemistry, he was most well known for his work in photochemistry and spectroscopy, which he applied to studies involving small molecules in solution, interfaces, thin films, polymers, biological systems including DNA and carbohydrates, nanomaterials, supramolecular and "super-duper" molecular systems. His success in these areas is evident by his co-authorship of over 1000 papers. His expertise in photochemistry, spectroscopy and organic chemistry lead to a large network of international collaborators, including Fortune 500 companies such as Procter and Gamble.
He authored the influential books Molecular Photochemistry published in 1965, considered the "bible" of the field for several generations by organic photochemists, and Modern Molecular Photochemistry published in 1978. The latter was comprehensively revised as Principles of Molecular Photochemistry: An Introduction in 2008 and later as Modern Molecular Photochemistry of Organic Molecules in 2010 both of which were co-authored with V. Ramamurthy at University of Miami and J.C. Scaiano at the University of Ottawa. Turro has been selected as one of the most highly cited chemists for the past two decades, and has published over 900 research papers. He was a member of both the National Academy of Sciences and the American Academy of Arts and Sciences. | 0 | Theoretical and Fundamental Chemistry |
The fundamental series lines for rubidium appear in the near infrared. The valence electron moves from the 4d level as the 3d is contained in an inner shell. They were observed by R von Lamb.
Relevant energy levels are 4p4d j=5/2 19,355.282 cm and j=3/2 19,355.623 cm, and the first f levels at 4p4f j=5/2 26,792.185 cm and j=7/2 26,792.169 cm. | 0 | Theoretical and Fundamental Chemistry |
Garson was born in Rugby, England, the daughter of an engineer and botanist. She took her B.A with Honours from the University of Cambridge, Newnham College in 1974. Garson's focus was the natural sciences, specializing in chemistry. She obtained an MA in Natural Sciences and she took her PhD in organic chemistry from Cambridge in 1977. | 0 | Theoretical and Fundamental Chemistry |
Ultrafine particles (UFPs) are particulate matter of nanoscale size (less than 0.1 μm or 100 nm in diameter). Regulations do not exist for this size class of ambient air pollution particles, which are far smaller than the regulated PM and PM particle classes and are believed to have several more aggressive health implications than those classes of larger particulates.
Although they remain largely unregulated, the World Health Organization has published good practice statements regarding measuring UFPs.
There are two main divisions that categorize types of UFPs. UFPs can either be carbon-based or metallic, and then can be further subdivided by their magnetic properties. Electron microscopy and special physical lab conditions allow scientists to observe UFP morphology. Airborne UFPs can be measured using a condensation particle counter, in which particles are mixed with alcohol vapor and then cooled, allowing the vapor to condense around them, after which they are counted using a light scanner. UFPs are both manufactured and naturally occurring. UFPs are the main constituent of airborne particulate matter. Owing to their large quantity and ability to penetrate deep within the lung, UFPs are a major concern for respiratory exposure and health. | 0 | Theoretical and Fundamental Chemistry |
Hart graduated from MIT with a bachelors degree in geology in 1956 and a masters degree in geochemistry in 1957 from Caltech. In 1960 he received his doctorate in geochemistry from MIT with thesis Mineral ages and metamorphism under the supervision of Patrick M. Hurley. After a year as a Carnegie Fellow, Hart was from 1961 to 1975 at the Carnegie Institution in Washington, D.C. in the Department of Terrestrial Magnetism. From 1975 to 1989 he was a professor of Earth, Atmospheric and Planetary Sciences at MIT and from 1989 to 1992 a visiting professor there. From 1989 to 2007 he was a Senior Scientist in geology and geophysics at Woods Hole Oceanographic Institution. He retired from Woods Hole in 2007 as Scientist Emeritus.
Hart is a leading pioneer in the introduction of geochemistry into the Earth sciences. He developed comparative geochronology, which accounts for geological perturbations in various geochronometers. At the Carnegie Institution of Washington, he worked with George Wetherill, George Tilton, L. T. Aldrich, and G. L. Davis on mapping Precambrian rocks in the USA using comparative geochronology. There Hart became the leader of a group including Thomas Krogh, Albrecht Hofmann, Christopher Brooks, and others.
According to Claude Allègre:
Hart focused on the application of isotopic chemistry to age determination in geology, the geochemical evolution of mantle and oceanic lithosphere, and the geochemistry of strontium, neodymium, and lead isotopes in volcanic rocks. He also studied the long-term behavior of the chemical composition of the oceans due to their interaction with the oceanic crust and the experimental determination of fundamental geochemical properties such as mineral-melt partition coefficients in silicates and solid-state diffusion rates. In 1968, together with John S. Steinhart, he published the Steinhart-Hart equation, which provides a mathematical model of how the temperature and the electrical resistance of a thermistor vary, based upon 3 so-called Steinhart-Hart coefficients.
He was a co-editor from 1970 to 1972 of the Reviews of Geophysics, from 1970 to 1976 of the Geochimica et Cosmochimica Acta, and from 1975 to 1992 of Physics of the Earth and Planetary Interiors. In 1975/76 he chaired the US National Committee for Geochemistry. His doctoral students include Erik Hauri.
Hart has three children, one daughter from his first marriage, which ended in divorce in 1978, and a son and a daughter from his second marriage which began in 1980. | 0 | Theoretical and Fundamental Chemistry |
Junwang Tang, MAE, FRSC and FIMMM, is the Founding Director of Industrial Catalysis Center, and Carbon Neutrality Chair Professor of Materials Chemistry and Catalysis at the Department of Chemical Engineering, Tsinghua University and Visiting Professor at University College London (UCL). He also served as the Director of the University Material Hub at UCL (2016–2019). | 0 | Theoretical and Fundamental Chemistry |
Phosphorus-32 is widely used for labeling nucleic acids and phosphoproteins. It has the highest emission energy (1.7 MeV) of all common research radioisotopes. This is a major advantage in experiments for which sensitivity is a primary consideration, such as titrations of very strong interactions (i.e., very low dissociation constant), footprinting experiments, and detection of low-abundance phosphorylated species. Phosphorus-32 is also relatively inexpensive. Because of its high energy, however, its safe use requires a number of engineering controls (e.g., acrylic glass) and administrative controls. The half-life of phosphorus-32 is 14.2 days, and its maximum specific activity is .
Phosphorus-33 is used to label nucleotides. It is less energetic than phosphorus-32 and does not require protection with plexiglass. A disadvantage is its higher cost compared to phosphorus-32, as most of the bombarded phosphorus-31 will have acquired only one neutron, while only some will have acquired two or more. Its maximum specific activity is . | 0 | Theoretical and Fundamental Chemistry |
Moreover, because the assembly of the full-length gene product relies on the efficient and specific alignment of long single stranded oligonucleotides, critical parameters for synthesis success include extended sequence regions comprising secondary structures caused by inverted repeats, extraordinary high or low GC-content, or repetitive structures. Usually these segments of a particular gene can only be synthesized by splitting the procedure into several consecutive steps and a final assembly of shorter sub-sequences, which in turn leads to a significant increase in time and labor needed for its production.
The result of a gene synthesis experiment depends strongly on the quality of the oligonucleotides used. For these annealing based gene synthesis protocols, the quality of the product is directly and exponentially dependent on the correctness of the employed oligonucleotides. Alternatively, after performing gene synthesis with oligos of lower quality, more effort must be made in downstream quality assurance during clone analysis, which is usually done by time-consuming standard cloning and sequencing procedures.
Another problem associated with all current gene synthesis methods is the high frequency of sequence errors because of the usage of chemically synthesized oligonucleotides. The error frequency increases with longer oligonucleotides, and as a consequence the percentage of correct product decreases dramatically as more oligonucleotides are used.
The mutation problem could be solved by shorter oligonucleotides used to assemble the gene. However, all annealing based assembly methods require the primers to be mixed together in one tube. In this case, shorter overlaps do not always allow precise and specific annealing of complementary primers, resulting in the inhibition of full length product formation.
Manual design of oligonucleotides is a laborious procedure and does not guarantee the successful synthesis of the desired gene. For optimal performance of almost all annealing based methods, the melting temperatures of the overlapping regions are supposed to be similar for all oligonucleotides. The necessary primer optimisation should be performed using specialized oligonucleotide design programs. Several solutions for automated primer design for gene synthesis have been presented so far. | 1 | Applied and Interdisciplinary Chemistry |
Four of the main types of molecular biomarkers are genomic biomarkers, transcriptomic biomarkers, proteomic biomarkers and metabolic biomarkers. | 1 | Applied and Interdisciplinary Chemistry |
For membrane proteins, the situation is more complicated because the system that is being crystallized is not the membrane protein itself but the micellar system in which the membrane protein is embedded.
The size of the protein-detergent mixed micelles are affected by both additives and detergents which will strongly influence the crystals obtained. In addition to varying the concentration of primary detergents, additives (lipids and alcohols) and secondary detergents can be used to modulate the size and shape of the detergent micelles. By reducing the size of the mixed micelles lattice forming protein-protein contacts are encouraged. Lipid cubic phases, spontaneous self-assembling liquid crystals or lipid mesophases have been used successfully in the crystallization of integral membrane proteins.
Temperature, salts, detergents, various additives are used in this system to tailor the cubic phase to suit the target protein. Typical detergents used are n-dodecyl-β-d-maltopyranoside, n-decyl-β-d-glucopyranoside, lauryldimethylamine oxide LDAO, n-hexyl-β-d-glucopyranoside, n-nonyl-β-d-glucopyranoside and n-octyl-β-d-glucopyranoside; the various lipids are dioleoyl phosphatidylcholine, dioleoyl phosphatidylethanolamine and monoolein. | 0 | Theoretical and Fundamental Chemistry |
The resting potential of photocytes was found to exist in a range between 50 and 65 millivolts. It is generally accepted that the emission of light was found to occur after depolarization of the photocyte membrane although some have argued that the depolarization follows the emission of light. The depolarization of the membrane results in an increase of the rate of diffusion of ions across it. The depolarization of the photocyte was found to occur 0.5 seconds following nervous impulse culminating at one second with the maximum degree of depolarization observed. A higher frequency of nervous stimulation was associated with a smaller depolarization event. Exposure to neurotransmitters including epinephrine, norepinephrine, and synephrine, results in the emission of light but without any corresponding depolarization of the photocyte membrane. | 1 | Applied and Interdisciplinary Chemistry |
The number of two-component systems present in a bacterial genome is highly correlated with genome size as well as ecological niche; bacteria that occupy niches with frequent environmental fluctuations possess more histidine kinases and response regulators. New two-component systems may arise by gene duplication or by lateral gene transfer, and the relative rates of each process vary dramatically across bacterial species. In most cases, response regulator genes are located in the same operon as their cognate histidine kinase; lateral gene transfers are more likely to preserve operon structure than gene duplications. The small number of two-component systems present in eukaryotes most likely arose by lateral gene transfer from endosymbiotic organelles; in particular, those present in plants likely derive from chloroplasts. | 1 | Applied and Interdisciplinary Chemistry |
Unlike in solid mechanics where shear flow is the shear stress force per unit length, in fluid mechanics, shear flow (or shearing flow) refers to adjacent layers of fluid moving parallel to each other with different speeds. Viscous fluids resist this shearing motion. For a Newtonian fluid, the stress exerted by the fluid in resistance to the shear is proportional to the strain rate or shear rate.
A simple example of a shear flow is Couette flow, in which a fluid is trapped between two large parallel plates, and one plate is moved with some relative velocity to the other. Here, the strain rate is simply the relative velocity divided by the distance between the plates.
Shear flows in fluids tend to be unstable at high Reynolds numbers, when fluid viscosity is not strong enough to dampen out perturbations to the flow. For example, when two layers of fluid shear against each other with relative velocity, the Kelvin–Helmholtz instability may occur. | 1 | Applied and Interdisciplinary Chemistry |
In the Northwest Pacific, where the term for strong tropical cyclones is typhoon, the concept of typhoon engineering, which is very similar to Hurricane Engineering, is being proposed. | 1 | Applied and Interdisciplinary Chemistry |
On 29 November 2018, Chinese authorities suspended all of Hes research activities, saying his work was "extremely abominable in nature" and a violation of Chinese law. He was sequestered in a university apartment under some sort of surveillance. On 21 January 2019, He was fired from his job at SUSTech and his teaching and research work at the university was terminated. The same day, the Guangdong Province administration investigated the "gene editing baby incident", which is explicitly prohibited by the state. On 30 December 2019, the Shenzhen Nanshan District Peoples Court sentenced He Jiankui to three years in prison and with a fine of 3 million RMB (about US$ in 2019).
Among the collaborators, only two were indicted – Zhang Renli of the Guangdong Academy of Medical Sciences and Guangdong General Hospital, received a two-year prison sentence and a 1-million RMB (about US$) fine, and Qin Jinzhou of the Southern University of Science and Technology received an 18-month prison sentence and a 500,000 RMB (about US$) fine. The three were found guilty of having "forged ethical review documents and misled doctors into unknowingly implanting gene-edited embryos into two women." Zhang and Qin were officially banned from working in assisted reproductive technology for life. In April 2022, He was released from prison.
On 26 November 2018, The CRISPR Journal published ahead of print an article by He, Ryan Ferrell, Chen Yuanlin, Qin Jinzhou, and Chen Yangran in which the authors justified the ethical use of CRISPR gene editing in humans. As the news of CRISPR babies broke out, the editors reexamined the paper and retracted it on 28 December, announcing:Michael W. Deem, an American bioengineering professor at Rice University and his doctoral advisor was involved in the research, and was present when people involved in the study gave consent. He was the only non-Chinese out of 10 authors listed in the manuscript submitted to Nature'. Deem came under investigation by Rice University after news of the work was made public. As of 2022, the university never issued any information on his conduct. He resigned from the university in 2020, and pursued a business by creating a bioengineering and energy consultant company called Certus LLC.
Stanford University also investigated its faculty of Hes confidants including William Hurlbut, Matthew Porteus, and Stephen Quake, his main mentor in gene editing. The universitys review committee concluded that the accused "were not participants in [He Jiankui’s] research regarding genome editing of human embryos for intended implantation and birth and that they had no research, financial or organizational ties to this research."
In response to He's work, the World Health Organization, formed a committee comprising "a global, multi-disciplinary expert panel" called the Expert Advisory Committee on Developing Global Standards for Governance and Oversight of Human Genome Editing "to examine the scientific, ethical, social and legal challenges associated with human genome editing (both somatic and germline)" in December 2018. In 2019, it issued a call to halt all work on human genome editing, and launched a global registry to track research in the field. It had issued three reports for the recommended guidelines on human genome editing since 2019. As of 2021, the committee stood by the grounds that while somatic gene therapies have become useful in several disease, germline and heritable human genome editing is still with risks, and should be banned.
In May 2019, Chinese government prepared gene-editing regulations stressing that anyone found manipulating the human genome by genome-editing techniques would be held responsible for any related adverse consequences. The Civil Code of the People's Republic of China was amended in 2020 that added Article 1009 which states: "any medical research activity associated with human gene and human embryo must comply with the relevant laws, administrative regulations and national regulation, must not harm individuals and violate ethical morality and public interest." It was enacted on 1 January 2021. A draft of the 11th Amendment to the Chinese Criminal Code in 2020 has incorporated three types of crime: the illegal practice of human gene editing, human embryo cloning and severe endangering of the security of human genetic resources; with penalties of imprisonment of up to 7 years and a fine.
As of December 2021, Vivien Marx reported in the Nature Biotechnology article that both children are healthy. | 1 | Applied and Interdisciplinary Chemistry |
Subsets and Splits