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Bimodal AFM is applied to characterize a large variety of surfaces and interfaces. Some applications exploit the sensitivity of bimodal observables to enhance spatial resolution. However, the full capabilities of bimodal AFM are shown in the generation of quantitative maps of material properties. The section is divided in terms of the achieved spatial resolution, atomic-scale or nanoscale. | 6 | Supramolecular Chemistry |
The enthalpy is , and the product is just . Then is simplyThis is the enthalpic equation of state for a perfect vdW fluid, or in reduced form | 7 | Physical Chemistry |
Microcystins cannot be broken down by standard proteases like pepsin, trypsin, collagenase, and chymotrypsin due to their cyclic chemical nature. They are hepatotoxic, i.e., able to cause serious damage to the liver. Once ingested, microcystin travels to the liver via the bile acid transport system, where most is stored, though some remains in the blood stream and may contaminate tissue.
Acute health effects of Microcystin-LR are abdominal pain, vomiting and nausea, diarrhea, headache, blistering around the mouth, and after inhalation sore throat, dry cough, and pneumonia.
Studies suggest that the absorption of microcystins occurs in the gastrointestinal tract. Furthermore, it was found that these hepatotoxins inhibit the activity of protein enzymes phosphatase PP1 and PP2A causing hemorrhagic shock and were found to kill within 45 minutes in mice studies.
There appears to be inadequate information to assess the carcinogenic potential of microcystins by applying EPA Guidelines for Carcinogen Risk Assessment. A few studies suggest a relationship may exist between liver and colorectral cancers and the occurrence of cyanobacteria in drinking water in China. Evidence is, however, limited due to limited ability to accurately assess and measure exposure. | 2 | Environmental Chemistry |
The sulfur isotopic composition of natural samples can be determined by Elemental Analysis-Isotope Ratio Mass Spectrometry (EA-IRMS), by Dual Inlet-Isotope Ratio Mass Spectrometry (DI-IRMS), by Multi-Collector-Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS), by Secondary Ion Mass Spectrometry (SIMS), or by Nanoscale secondary ion mass spectrometry (NanoSIMS). MC-ICPMS can be paired with gas chromatography (GC-MC-ICPMS) to separate certain volatile compounds in a sample and measure the sulfur isotopic composition of individual compounds.
The sulfur isotopic compositions of minerals and porewater in sediment are subject to accumulation and diffusion after burial. Reactive transport models are often used to account for the effect of such physical processes and find out the isotopic effect of the process studied. | 9 | Geochemistry |
The mathematical function used to model cross-correlation curves in FCCS is slightly more complex compared to that used in FCS. One of the primary differences is the effective superimposed observation volume, denoted as in which the G and R channels form a single observation volume:
where and are radial parameters and and are the axial parameters for the G and R channels respectively.
The diffusion time, for a doubly (G and R) fluorescent species is therefore described as follows:
where is the diffusion coefficient of the doubly fluorescent particle.
The cross-correlation curve generated from diffusing doubly labelled fluorescent particles can be modelled in separate channels as follows:
In the ideal case, the cross-correlation function is proportional to the concentration of the doubly labeled fluorescent complex:
with
The cross-correlation amplitude is directly proportional to the concentration of double-labeled (red and green) species. | 7 | Physical Chemistry |
Hemoglobin (Hb) is the primary vehicle for transporting oxygen in the blood. Each hemoglobin molecule has the capacity to carry four oxygen molecules. These molecules of oxygen bind to the iron of the heme prosthetic group.
When hemoglobin has no bound oxygen, nor bound carbon dioxide, it has the unbound conformation (shape). The binding of the first oxygen molecule induces change in the shape of the hemoglobin that increases its ability to bind to the other three oxygen molecules.
In the presence of dissolved carbon dioxide, the pH of the blood changes; this causes another change in the shape of hemoglobin, which increases its ability to bind carbon dioxide and decreases its ability to bind oxygen. With the loss of the first oxygen molecule, and the binding of the first carbon dioxide molecule, yet another change in shape occurs, which further decreases the ability to bind oxygen, and increases the ability to bind carbon dioxide. The oxygen bound to the hemoglobin is released into the blood's plasma and absorbed into the tissues, and the carbon dioxide in the tissues is bound to the hemoglobin.
In the lungs the reverse of this process takes place. With the loss of the first carbon dioxide molecule the shape again changes and makes it easier to release the other three carbon dioxides.
Oxygen is also carried dissolved in the bloods plasma, but to a much lesser degree. Hemoglobin is contained in red blood cells. Hemoglobin releases the bound oxygen when carbonic acid is present, as it is in the tissues. In the capillaries, where carbon dioxide is produced, oxygen bound to the hemoglobin is released into the bloods plasma and absorbed into the tissues.
How much of that capacity is filled by oxygen at any time is called the oxygen saturation. Expressed as a percentage, the oxygen saturation is the ratio of the amount of oxygen bound to the hemoglobin, to the oxygen-carrying capacity of the hemoglobin. The oxygen-carrying capacity of hemoglobin is determined by the type of hemoglobin present in the blood. The amount of oxygen bound to the hemoglobin at any time is related, in large part, to the partial pressure of oxygen to which the hemoglobin is exposed. In the lungs, at the alveolar–capillary interface, the partial pressure of oxygen is typically high, and therefore the oxygen binds readily to hemoglobin that is present. As the blood circulates to other body tissue in which the partial pressure of oxygen is less, the hemoglobin releases the oxygen into the tissue because the hemoglobin cannot maintain its full bound capacity of oxygen in the presence of lower oxygen partial pressures. | 1 | Biochemistry |
Liquids are useful as lubricants due to their ability to form a thin, freely flowing layer between solid materials. Lubricants such as oil are chosen for viscosity and flow characteristics that are suitable throughout the operating temperature range of the component. Oils are often used in engines, gear boxes, metalworking, and hydraulic systems for their good lubrication properties. | 7 | Physical Chemistry |
Pit water, mine water or mining water is water that collects in a mine and which has to be brought to the surface by water management methods in order to enable the mine to continue working. | 9 | Geochemistry |
L1 activity has been observed in numerous types of cancers, with particularly extensive insertions found in colorectal and lung cancers. It is currently unclear if these insertions are causes or secondary effects of cancer progression. However, at least two cases have found somatic L1 insertions causative of cancer by disrupting the coding sequences of genes APC and PTEN in colon and endometrial cancer, respectively.
Quantification of L1 copy number by qPCR or L1 methylation levels with bisulfite sequencing are used as diagnostic biomarkers in some types of cancers. L1 hypomethylation of colon tumor samples is correlated with cancer stage progression. Furthermore, less invasive blood assays for L1 copy number or methylation levels are indicative of breast or bladder cancer progression and may serve as methods for early detection. | 1 | Biochemistry |
The EBF organizes annual symposia to involve the bioanalytical community: pharmaceutical industry, academia, CRO, instrument providers and regulatory agencies. It is the intention of the organisation to inform their business partners and peers about the discussion held and agreements achieved and to open the forum for challenging procedures or techniques as well as for new regulatory requirements.
The EBF has also reached out to participate in international scientific meetings representing the bioanalytical voice of the European pharmaceutical industry. Selective examples are: American Association of Pharmaceutical Scientists meetings, The Boston Society Applied Pharmaceutical Analysis meetings, and Canadian Validation Group meeting. | 3 | Analytical Chemistry |
The chemistry component incorporates both bioavailability and potential effects on benthic community. The potential of sediment toxicity for a given site is based on a linear regression model (LRM). A chemical score index (CSI) of the contaminant describes the magnitude of exposure relative to benthic community disturbance. An optimal set of index-specific thresholds are selected for the chemistry component by statistically comparing several candidates to evaluate which set exhibited greatest overall agreement (Bay and Weisberg, 2012). The magnitude of sediment toxicity is determined by multiple toxicity tests conducted in the lab to complement chemistry component. Toxicity LOE are determined by the mean of toxicity category score from all relevant tests. Development of LOE for benthic component is based on community metrics and abundance. Several indices such as benthic response index (BRI), benthic biotic integrity (IBI), and relative biotic index (RBI) are utilized to assess biological response of the benthic community. The median score of all individual indices will establish benthic LOE.
Each component of the triad is assigned a response category: minimal, low, moderate, or high disturbance relative to background conditions. Individual LOEs are ranked into categories by comparing test results of each component to established thresholds (Bay and Weisberg, 2012). Integration of benthos and toxicity LOE classify the severity and effects of contamination. LOE of chemistry and toxicity are combined to assign the potential of chemically-mediated effects.
A site is assigned an impact category by integrating the severity of effect and the potential of chemically mediated effects. The conditions of individual sites of concern are assigned an impact category between 1 and 5 (with 1 being unimpacted and 5 being clearly impacted by contamination). The SQT triad can also classify impact as inconclusive in cases when LOE between components are in disagreement or additional information is required (Bay and Weisberg, 2012). | 2 | Environmental Chemistry |
Calcareous grassland is a form of grassland characteristic of soils containing much calcium carbonate from underlying chalk or limestone rock. | 9 | Geochemistry |
Potent, bioactive natural products like triptolide that inhibit mammalian transcription via inhibition of the XPB subunit of the general transcription factor TFH has been recently reported as a glucose conjugate for targeting hypoxic cancer cells with increased glucose transporter expression. | 1 | Biochemistry |
Cefuroxime, sold under the brand name Zinacef among others, is a second-generation cephalosporin antibiotic used to treat and prevent a number of bacterial infections. These include pneumonia, meningitis, otitis media, sepsis, urinary tract infections, and Lyme disease. It is used by mouth or by injection into a vein or muscle.
Common side effects include nausea, diarrhea, allergic reactions, and pain at the site of injection. Serious side effects may include Clostridium difficile infection, anaphylaxis, and Stevens–Johnson syndrome. Use in pregnancy and breastfeeding is believed to be safe. It is a second-generation cephalosporin and works by interfering with a bacteria's ability to make a cell wall resulting in its death.
Cefuroxime was patented in 1971, and approved for medical use in 1977. It is on the World Health Organization's List of Essential Medicines. In 2020, it was the 325th most commonly prescribed medication in the United States, with more than 800thousand prescriptions. | 4 | Stereochemistry |
In electrochemistry, the faradaic current is the electric current generated by the reduction or oxidation of some chemical substance at an electrode. The net faradaic current is the algebraic sum of all the faradaic currents flowing through an indicator electrode or working electrode. | 7 | Physical Chemistry |
Underwater corrosion engineers apply the same principals used in underground corrosion control but use specially trained and certified scuba divers for condition assessment, and corrosion control system installation and commissioning. The main difference being in the type of reference cells used to collect voltage readings. Corrosion of piles and the legs of oil and gas rigs are of particular concern. This includes rigs in the North Sea off the coast of the United Kingdom and the Gulf of Mexico. | 8 | Metallurgy |
Recombinase polymerase amplification (RPA) is a single tube, isothermal alternative to the polymerase chain reaction (PCR). By adding a reverse transcriptase enzyme to an RPA reaction it can detect RNA as well as DNA, without the need for a separate step to produce cDNA,. Because it is isothermal, RPA can use much simpler equipment than PCR, which requires a thermal cycler. Operating best at temperatures of 37–42 °C and still working, albeit more slowly, at room temperature means RPA reactions can in theory be run quickly simply by holding a tube. This makes RPA an excellent candidate for developing low-cost, rapid, point-of-care molecular tests. An international quality assessment of molecular detection of Rift Valley fever virus performed as well as the best RT-PCR tests, detecting less concentrated samples missed by some PCR tests and an RT-LAMP test.
RPA was developed and launched by TwistDx Ltd. (formerly known as ASM Scientific Ltd), a biotechnology company based in Cambridge, UK. | 1 | Biochemistry |
Several models attempt to account for the bulk properties of water by assuming that they are dominated by cluster formation within the liquid. According to the quantum cluster equilibrium (QCE) theory of liquids, n=8 clusters dominate the liquid water bulk phase, followed by n=5 and n=6 clusters. Near the triple point, the presence of an n=24 cluster is invoked. In another model, bulk water is built up from a mixture of hexamer and pentamer rings containing cavities capable of enclosing small solutes. In yet another model an equilibrium exists between a cubic water octamer and two cyclic tetramers. However, no model yet has reproduced the experimentally-observed density maximum of water as a function of temperature. | 7 | Physical Chemistry |
Whereas FCS is a point measurement providing diffusion time at a given observation volume, svFCS is a technique where the observation spot is varied in order to measure diffusion times at different spot sizes. The relationship between the diffusion time and the spot area is linear and could be plotted in order to decipher the major contribution of confinement. The resulting curve is called the diffusion law.
This technique is used in Biology to study the plasma membrane organization on living cells.
where is the y axis intercept. In case of Brownian diffusion, . In case of a confinement due to isolated domains, whereas in case of isolated domains, .
svFCS studies on living cells and simulation papers
Sampling-Volume-Controlled Fluorescence Correlation Spectroscopy (SVC-FCS):
z-scan FCS
FCS with Nano-apertures: breaking the diffraction barrier
STED-FCS: | 7 | Physical Chemistry |
Adenosine-to-inosine (A-to-I) modifications contribute to nearly 90% of all editing events in RNA. The deamination of adenosine is catalyzed by the double-stranded RNA-specific adenosine deaminase (ADAR), which typically acts on pre-mRNAs. The deamination of adenosine to inosine disrupts and destabilizes the dsRNA base pairing, therefore rendering that particular dsRNA less able to produce siRNA, which interferes with the RNAi pathway.
The wobble base pairing causes deaminated RNA to have a unique but different structure, which may be related to the inhibition of the initiation step of RNA translation. Studies have shown that I-RNA (RNA with many repeats of the I-U base pair) recruits methylases that are involved in the formation of heterochromatin and that this chemical modification heavily interferes with miRNA target sites. There is active research into the importance of A-to-I modifications and their purpose in the novel concept of epitranscriptomics, in which modifications are made to RNA that alter their function. A long established consequence of A-to-I in mRNA is the interpretation of I as a G, therefore leading to functional A-to-G substitution, e.g. in the interpretation of the genetic code by ribosomes. Newer studies, however, have weakened this correlation by showing that inosines can also be decoded by the ribosome (although in a lesser extent) as adenosines or uracils. Furthermore, it was shown that I's lead to the stalling of ribosomes on the I-rich mRNA.
The development of high-throughput sequencing in recent years has allowed for the development of extensive databases for different modifications and edits of RNA. RADAR (Rigorously Annotated Database of A-to-I RNA editing) was developed in 2013 to catalog the vast variety of A-to-I sites and tissue-specific levels present in humans, mice, and flies. The addition of novel sites and overall edits to the database are ongoing. The level of editing for specific editing sites, e.g. in the filamin A transcript, is tissue-specific. The efficiency of mRNA-splicing is a major factor controlling the level of A-to-I RNA editing. Interestingly, ADAR1 and ADAR2 also affect alternative splicing via both A-to-I editing ability and dsRNA binding ability. | 1 | Biochemistry |
A spot assay or spot test can also refer to a specific test in microbiology. This test is often used to check the growth rate of bacterial or yeast cells on different media or to perform serial dilution tests of micro-organisms. Usually a 96-pinner (often called frogger) is used to perform these spot assay.
Another application is high-throughput screening, whichoften uses spot assays to determine the growth of eg. mated cells or to check for protein-protein interactions in a yeast two-hybrid test. This is often done with a robot. | 3 | Analytical Chemistry |
In the short flap pathway in eukaryotes the lagging strand of DNA is primed in short intervals. In the short pathway only, the nuclease FEN1 is involved. Pol δ frequently encounters the downstream primed Okazaki fragment and displaces the RNA/DNA initiator primer into a 5′ flap. The FEN1 5’-3’ endonuclease recognizes that the 5’ flap is displaced, and it cleaves, creating a substrate for ligation. In this method the Pol a-synthesized primer is removed. Studies show that in the FEN1 suggest a ‘tracking; model where the nuclease moves from the 5’ flap to its base to preform cleavage. The Pol δ does not process a nuclease activity to cleave the displaced flap. The FEN1 cleaves the short flap immediately after they form. The cleavage is inhibited when the 5’ end of the DNA flap is blocked either with a complementary primer or a biotin-conjugated streptavidin moiety. DNA ligase seals the nick made by the FEN1 and it creates a functional continuous double strand of DNA. PCNA simulates enzymatic functions of proteins for both FEN1 and DNA ligase. The interaction is crucial in creating proper ligation of the lagging DNA strand. Sequential strand displacement and cleavage by Pol δ and FEN1, respectively, helps to remove the entire initiator RNA before ligation. Many displacements need to take place and cleavage reactions are required to remove the initiator primer. The flap that is created and processes and it is matured by the short flap pathway. | 1 | Biochemistry |
The main application of Ellingham diagrams is in the extractive metallurgy industry, where it helps to select the best reducing agent for various ores in the extraction process, purification and grade setting for steel manufacturing. It also helps to guide the purification of metals, especially the removal of trace elements. The direct reduction process for making iron rests firmly on the guidance of Ellingham diagrams, which show that hydrogen by itself can reduce iron oxides to the metal. | 8 | Metallurgy |
Neutron activation analysis (NAA) is a nuclear process used for determining the concentrations of elements in many materials. NAA allows discrete sampling of elements as it disregards the chemical form of a sample, and focuses solely on atomic nuclei. The method is based on neutron activation and thus requires a neutron source. The sample is bombarded with neutrons, causing its constituent elements to form radioactive isotopes. The radioactive emissions and radioactive decay paths for each element have long been studied and determined. Using this information, it is possible to study spectra of the emissions of the radioactive sample, and determine the concentrations of the various elements within it. A particular advantage of this technique is that it does not destroy the sample, and thus has been used for the analysis of works of art and historical artifacts. NAA can also be used to determine the activity of a radioactive sample.
If NAA is conducted directly on irradiated samples it is termed instrumental neutron activation analysis (INAA). In some cases, irradiated samples are subjected to chemical separation to remove interfering species or to concentrate the radioisotope of interest; this technique is known as radiochemical neutron activation analysis (RNAA).
NAA can perform non-destructive analyses on solids, liquids, suspensions, slurries, and gases with no or minimal preparation. Due to the penetrating nature of incident neutrons and resultant gamma rays, the technique provides a true bulk analysis. As different radioisotopes have different half-lives, counting can be delayed to allow interfering species to decay eliminating interference. Until the introduction of ICP-AES and PIXE, NAA was the standard analytical method for performing multi-element analyses with minimum detection limits in the sub-ppm range. Accuracy of NAA is in the region of 5%, and relative precision is often better than 0.1%. There are two noteworthy drawbacks to the use of NAA; even though the technique is essentially non-destructive, the irradiated sample will remain radioactive for many years after the initial analysis, requiring handling and disposal protocols for low-level to medium-level radioactive material; also, the number of suitable activation nuclear reactors is declining; with a lack of irradiation facilities, the technique has declined in popularity and become more expensive. | 3 | Analytical Chemistry |
The odds for relatedness are calculated from log odd ratio, which are then rounded off to get the substitution matrices BLOSUM matrices. | 1 | Biochemistry |
*5'-nuclease TaqMan assay
*Exciton-controlled hybridization-sensitive fluorescent oligonucleotide (ECHO) probes.
*Dual Hybridization (LightCycler®) probes
*Scorpions® Probes
*LUX (Light Upon Extension) Probes
*DNA binding dye assays (e.g., SYBR Green, SYTO9, Melt Doctor, LCGreen Plus, etc.) | 1 | Biochemistry |
3-Methylfentanyl was also reported by media as the identity of the anaesthetic "gas" Kolokol-1 delivered as an aerosol during the Moscow theater hostage crisis in 2002 in which many hostages died from accidental overdoses, 3-methylfentanyl was later ruled out as the primary agent used. The opiate antidote naloxone was on-hand to treat the victims of the crisis, but, whether due to their incarceration, lack of food, or water, or sleep, or due to the novel nature of the still-unconfirmed compound used, acute symptoms continued to develop, resulting in many fatalities despite the administration of naloxone. | 1 | Biochemistry |
Silyl enol ethers are neutral, mild nucleophiles (milder than enamines) that react with good electrophiles such as aldehydes (with Lewis acid catalysis) and carbocations. Silyl enol ethers are stable enough to be isolated, but are usually used immediately after synthesis. | 0 | Organic Chemistry |
Modifications can also happen in short non-coding RNAs, including small nuclear RNA (snRNA) and microRNA (miRNA). However, these modifications are less common than those in mRNA, tRNA, and rRNA. | 1 | Biochemistry |
Consider a classical measurement where a single particle is scattered off a single stationary target particle. Conventionally, a spherical coordinate system is used, with the target placed at the origin and the axis of this coordinate system aligned with the incident beam. The angle is the scattering angle, measured between the incident beam and the scattered beam, and the is the azimuthal angle.
The impact parameter is the perpendicular offset of the trajectory of the incoming particle, and the outgoing particle emerges at an angle . For a given interaction (Coulombic, magnetic, gravitational, contact, etc.), the impact parameter and the scattering angle have a definite one-to-one functional dependence on each other. Generally the impact parameter can neither be controlled nor measured from event to event and is assumed to take all possible values when averaging over many scattering events. The differential size of the cross section is the area element in the plane of the impact parameter, i.e. . The differential angular range of the scattered particle at angle is the solid angle element . The differential cross section is the quotient of these quantities, .
It is a function of the scattering angle (and therefore also the impact parameter), plus other observables such as the momentum of the incoming particle. The differential cross section is always taken to be positive, even though larger impact parameters generally produce less deflection. In cylindrically symmetric situations (about the beam axis), the azimuthal angle is not changed by the scattering process, and the differential cross section can be written as
In situations where the scattering process is not azimuthally symmetric, such as when the beam or target particles possess magnetic moments oriented perpendicular to the beam axis, the differential cross section must also be expressed as a function of the azimuthal angle.
For scattering of particles of incident flux off a stationary target consisting of many particles, the differential cross section at an angle is related to the flux of scattered particle detection in particles per unit time by
Here is the finite angular size of the detector (SI unit: sr), is the number density of the target particles (SI units: m), and is the thickness of the stationary target (SI units: m). This formula assumes that the target is thin enough that each beam particle will interact with at most one target particle.
The total cross section may be recovered by integrating the differential cross section over the full solid angle ( steradians):
It is common to omit the “differential” qualifier when the type of cross section can be inferred from context. In this case, may be referred to as the integral cross section or total cross section. The latter term may be confusing in contexts where multiple events are involved, since “total” can also refer to the sum of cross sections over all events.
The differential cross section is extremely useful quantity in many fields of physics, as measuring it can reveal a great amount of information about the internal structure of the target particles. For example, the differential cross section of Rutherford scattering provided strong evidence for the existence of the atomic nucleus.
Instead of the solid angle, the momentum transfer may be used as the independent variable of differential cross sections.
Differential cross sections in inelastic scattering contain resonance peaks that indicate the creation of metastable states and contain information about their energy and lifetime. | 7 | Physical Chemistry |
9-BBN is prepared by the reaction of 1,5-cyclooctadiene and borane usually in ethereal solvents, for example:
The compound is commercially available as a solution in tetrahydrofuran and as a solid. 9-BBN is especially useful in Suzuki reactions.
Its highly regioselective addition on alkenes allows the preparation of terminal alcohols by subsequent oxidative cleavage with HO in aqueous KOH. The steric demand of 9-BBN greatly suppresses the formation of the 2-substituted isomer compared to the use of borane. | 0 | Organic Chemistry |
One of the main competing models for cpDNA asserts that most cpDNA is linear and participates in homologous recombination and replication structures similar to bacteriophage T4. It has been established that some plants have linear cpDNA, such as maize, and that more still contain complex structures that scientists do not yet understand; however, the predominant view today is that most cpDNA is circular. When the original experiments on cpDNA were performed, scientists did notice linear structures; however, they attributed these linear forms to broken circles. If the branched and complex structures seen in cpDNA experiments are real and not artifacts of concatenated circular DNA or broken circles, then a D-loop mechanism of replication is insufficient to explain how those structures would replicate. At the same time, homologous recombination does not explain the multiple A → G gradients seen in plastomes. This shortcoming is one of the biggest for the linear structure theory. | 5 | Photochemistry |
Clay chemistry is an applied subdiscipline of chemistry which studies the chemical structures, properties and reactions of or involving clays and clay minerals. It is a multidisciplinary field, involving concepts and knowledge from inorganic and structural chemistry, physical chemistry, materials chemistry, analytical chemistry, organic chemistry, mineralogy, geology and others.
The study of the chemistry (and physics) of clays and clay minerals is of great academic and industrial relevance as they are among the most widely used industrial minerals, being employed as raw materials (ceramics, pottery, etc.), adsorbents, catalysts, additives, mineral charges, medicines, building materials and others.
The unique properties of clay minerals including: nanometric scale layered construction, presence of fixed and interchangeable charges, possibility of adsorbing and hosting (intercalating) molecules, ability of forming stable colloidal dispersions, possibility of tailored surface and interlayer chemical modification and others, make the study of clay chemistry a very important and extremely varied field of research.
Many distinct fields and knowledge areas are impacted by the physico-chemical behavior of clay minerals, from environmental sciences to chemical process engineering, from pottery to nuclear waste management.
Their cation exchange capacity (CEC) is of great importance in the balance of the most common cations in soil (Na, K, NH, Ca, Mg) and pH control, with direct impact on the soil fertility. It also plays an important role in the fate of most Ca arriving from land (river water) into the seas.
The ability to change and control the CEC of clay minerals offers a valuable tool in the development of selective adsorbents with applications as varied as chemical sensors or pollution cleaning substances for contaminated water, for example.
The understanding of the reactions of clay minerals with water (intercalation, adsorption, colloidal dispersion, etc.) are indispensable for the ceramic industry (plasticity and flow control of ceramic raw mixtures, for example). Those interactions also influence a great number of mechanical properties of soils, being carefully studied by building and construction engineering specialists.
The interactions of clay minerals with organic substances in the soil also plays a vital role in the fixation of nutrients and fertility, as well as in the fixation or leaching of pesticides and other contaminants. Some clay minerals (kaolinite) are used as carrier material for fungicides and insecticides.
The weathering of many rock types produce clay minerals as one of its last products. The understanding of these geochemical processes is also important for the understanding of geological evolution of landscapes and macroscopic properties of rocks and sediments. Presence of clay minerals in Mars, detected by the Mars Reconnaissance Orbiter in 2009 was another strong evidence of the existence of water on the planet in previous geological eras.
The possibility to disperse nanometric scaled clay mineral particles into a matrix of polymer, with the formation of an inorganic-organic nanocomposite has prompted a large resurgence in the study of these minerals from the late 1990s.
In addition, study of clay chemistry is also of great relevance to the chemical industry, as many clay minerals are used as catalysts, catalyst precursors or catalyst substrates in a number of chemical processes, like automotive catalysts and oil cracking catalysts. | 9 | Geochemistry |
In some Asian cuisines, fish is traditionally fermented with rice to produce lactic acid that preserves the fish. Examples of these dishes include burong isda of the Philippines; narezushi of Japan; and pla ra of Thailand. The same process is also used for shrimp in the Philippines in the dish known as balao-balao. | 1 | Biochemistry |
By raising the water table, after damage has been inflicted due to over-intensive drainage, the soils can be restored.
The following table gives an example.
Drainage and yield of Malaysian oil palm on acid sulfate soils (after Toh Peng Yin and Poon Yew Chin, 1982)<br>
Yield in tons of fresh fruit per ha:
Drainage depth and intensity were increased in 1962. The water table was raised again in 1966 to counter negative effects.
In the "millennium drought" in the Murray-Darling Basin in Australia, exposure of acid sulfate soils occurred. Large scale engineering interventions were undertaken to prevent further acidification, including construction of a bund and pumping of water to prevent exposure and acidification of Lake Albert. Management of acidification in the Lower Lakes was also undertaken using aerial limestone dosing. | 9 | Geochemistry |
Anthropogenic changes to the natural greenhouse effect are sometimes referred to as the enhanced greenhouse effect.
This table shows the most important contributions to the overall greenhouse effect, without which the average temperature of Earths surface would be about , instead of around . This table also specifies tropospheric' ozone, because this gas has a cooling effect in the stratosphere, but a warming influence comparable to nitrous oxide and CFCs in the troposphere. | 2 | Environmental Chemistry |
The wavelengths are approximate; exact values depend on the particular instruments (e.g. characteristics of satellite's sensors for Earth observation, characteristics of illumination and sensors for document analysis):
* Blue, 450–515/520 nm, is used for atmosphere and deep water imaging, and can reach depths up to in clear water.
* Green, 515/520–590/600 nm, is used for imaging vegetation and deep water structures, up to in clear water.
* Red, 600/630–680/690 nm, is used for imaging man-made objects, in water up to deep, soil, and vegetation.
* Near infrared (NIR), 750–900 nm, is used primarily for imaging vegetation.
* Mid-infrared (MIR), 1550–1750 nm, is used for imaging vegetation, soil moisture content, and some forest fires.
* Far-infrared (FIR), 2080–2350 nm, is used for imaging soil, moisture, geological features, silicates, clays, and fires.
* Thermal infrared, 10,400–12,500 nm, uses emitted instead of reflected radiation to image geological structures, thermal differences in water currents, fires, and for night studies.
* Radar and related technologies are useful for mapping terrain and for detecting various objects. | 7 | Physical Chemistry |
A group of FeS ferredoxins, originally found in bacteria, has been termed "bacterial-type". Bacterial-type ferredoxins may in turn be subdivided into further groups, based on their sequence properties. Most contain at least one conserved domain, including four cysteine residues that bind to a [FeS] cluster. In Pyrococcus furiosus FeS ferredoxin, one of the conserved Cys residues is substituted with aspartic acid.
During the evolution of bacterial-type ferredoxins, intrasequence gene duplication, transposition and fusion events occurred, resulting in the appearance of proteins with multiple iron–sulfur centers. In some bacterial ferredoxins, one of the duplicated domains has lost one or more of the four conserved Cys residues. These domains have either lost their iron–sulfur binding property or bind to a [FeS] cluster instead of a [FeS] cluster and dicluster-type.
3-D structures are known for a number of monocluster and dicluster bacterial-type ferredoxins. The fold belongs to the α+β class, with 2-7 α-helices and four β-strands forming a barrel-like structure, and an extruded loop containing three "proximal" Cys ligands of the iron–sulfur cluster. | 5 | Photochemistry |
If there are additional factors preventing boundary movement, such as Zener pinning by particles, then the grain size may be restricted to a much lower value than might otherwise be expected. This is an important industrial mechanism in preventing the softening of materials at high temperature. | 8 | Metallurgy |
A study that utilized climate modeling to simulate the effects of predicted increases in water temperature and salinity as a result of climate change on C. finmarchicus of the eastern shelf of North America forecasts lower abundance of copepods. The decrease in favorable environmental conditions is expected to decrease the size and density of C. finmarchius, and will likely have negative effects on whales and other components of the food web that are inextricably tied to copepods. The impact of diapause and variation in seasonal productivity was not explicitly included as increasing model complexity and more accurate accounting for Calanus spp. metabolic processes during diapause is required. The importance of diapause timing with spring plankton blooms is well-established, suggesting that there is potential for additional population impacts as a result of climate change, which would further reverberate throughout the ecosystem. | 9 | Geochemistry |
Photoionization is the physical process in which an incident photon ejects one or more electrons from an atom, ion or molecule. This is essentially the same process that occurs with the photoelectric effect with metals. In the case of a gas or single atoms, the term photoionization is more common.
The ejected electrons, known as photoelectrons, carry information about their pre-ionized states. For example, a single electron can have a kinetic energy equal to the energy of the incident photon minus the electron binding energy of the state it left. Photons with energies less than the electron binding energy may be absorbed or scattered but will not photoionize the atom or ion.
For example, to ionize hydrogen, photons need an energy greater than 13.6 electronvolts (the Rydberg energy), which corresponds to a wavelength of 91.2 nm. For photons with greater energy than this, the energy of the emitted photoelectron is given by:
where h is the Planck constant and ν is the frequency of the photon.
This formula defines the photoelectric effect.
Not every photon which encounters an atom or ion will photoionize it. The probability of photoionization is related to the photoionization cross-section, which depends on the energy of the photon and the target being considered. For photon energies below the ionization threshold, the photoionization cross-section is near zero. But with the development of pulsed lasers it has become possible to create extremely intense, coherent light where multi-photon ionization may occur. At even higher intensities (around 10 - 10 W/cm of infrared or visible light), non-perturbative phenomena such as barrier suppression ionization and rescattering ionization are observed. | 7 | Physical Chemistry |
Atomic manipulation is the process of moving single atoms on a substrate using Scanning Tunneling Microscope (STM). The atomic manipulation is a surface science technique usually used to create artificial objects on the substrate made out of atoms and to study electronic behaviour of matter. These objects do not occur in nature and therefore need to be created artificially. The first demonstration of atomic manipulation was done by IBM scientists in 1989, when they created IBM in atoms. | 7 | Physical Chemistry |
Allison Hubel is an American mechanical engineer and cryobiologist who applies her expertise in heat transfer to study the cryopreservation of biological tissue. She is a professor of mechanical engineering at the University of Minnesota, where she directs the Biopreservation Core Resource and the Technological Leadership Institute, and is president-elect of the Society for Cryobiology. | 1 | Biochemistry |
Since the discovery of ribozymes that exist in living organisms, there has been interest in the study of new synthetic ribozymes made in the laboratory. For example, artificially produced self-cleaving RNAs with good enzymatic activity have been produced. Tang and Breaker isolated self-cleaving RNAs by in vitro selection of RNAs originating from random-sequence RNAs. Some of the synthetic ribozymes that were produced had novel structures, while some were similar to the naturally occurring hammerhead ribozyme.
In 2015, researchers at Northwestern University and the University of Illinois Chicago engineered a tethered ribosome that works nearly as well as the authentic cellular component that produces all the proteins and enzymes within the cell. Called Ribosome-T, or Ribo-T, the artificial ribosome was created by Michael Jewett and Alexander Mankin. The techniques used to create artificial ribozymes involve directed evolution. This approach takes advantage of RNA's dual nature as both a catalyst and an informational polymer, making it easy for an investigator to produce vast populations of RNA catalysts using polymerase enzymes. The ribozymes are mutated by reverse transcribing them with reverse transcriptase into various cDNA and amplified with error-prone PCR. The selection parameters in these experiments often differ. One approach for selecting a ligase ribozyme involves using biotin tags, which are covalently linked to the substrate. If a molecule possesses the desired ligase activity, a streptavidin matrix can be used to recover the active molecules.
Lincoln and Joyce used in vitro evolution to develop ribozyme ligases capable of self-replication in about an hour, via the joining of pre-synthesized highly complementary oligonucleotides.
Although not true catalysts, the creation of artificial self-cleaving riboswitches, termed aptazymes, has also been an active area of research. Riboswitches are regulatory RNA motifs that change their structure in response to a small molecule ligand to regulate translation. While there are many known natural riboswitches that bind a wide array of metabolites and other small organic molecules, only one ribozyme based on a riboswitch has been described: glmS. Early work in characterizing self-cleaving riboswitches was focused on using theophylline as the ligand. In these studies, an RNA hairpin is formed which blocks the ribosome binding site, thus inhibiting translation. In the presence of the ligand, in these cases theophylline, the regulatory RNA region is cleaved off, allowing the ribosome to bind and translate the target gene. Much of this RNA engineering work was based on rational design and previously determined RNA structures rather than directed evolution as in the above examples. More recent work has broadened the ligands used in ribozyme riboswitches to include thymine pyrophosphate. Fluorescence-activated cell sorting has also been used to engineering aptazymes. | 7 | Physical Chemistry |
Electrochemical engineering is the branch of chemical engineering dealing with the technological applications of electrochemical phenomena, such as electrosynthesis of chemicals, electrowinning and refining of metals, flow batteries and fuel cells, surface modification by electrodeposition, electrochemical separations and corrosion.
According to the IUPAC, the term electrochemical engineering is reserved for electricity-intensive processes for industrial or energy storage applications and should not be confused with applied electrochemistry, which comprises small batteries, amperometric sensors, microfluidic devices, microelectrodes, solid-state devices, voltammetry at disc electrodes, etc.
More than 6% of the electricity is consumed by large-scale electrochemical operations in the US. | 7 | Physical Chemistry |
* CPPs have been used to transport a variety of biomolecules into cells in both vitro and in vivo. One must be cautious of which CPPs are used. For example, different CPPs promote movement into different cell types and cellular components.
* If the TIVA tag is not used within 3 months of synthesis, the FRET signal is weakened.
* The storage of TIVA tag requires a -80 °C freezer and should be in dried form. | 1 | Biochemistry |
In 2010 bay health improved slightly in terms of the overall health of its ecosystem, earning a rating of 31 out of 100, up from a 28 rating in 2008. An estimate in 2006 from a "blue ribbon panel" said cleanup costs would be $15 billion. Compounding the problem is that 100,000 new residents move to the area each year. A 2008 Washington Post report suggested that government administrators had overstated progress on cleanup efforts as a way to "preserve the flow of federal and state money to the project." In January 2011, there were reports that millions of fish had died, but officials suggested it was probably the result of extremely cold weather.
The health of the Chesapeake Bay improved in 2015, marking three years of gains over a four-year period, according to a 2016 report by the University of Maryland Center for Environmental Science (UMCES). In 2021 scientists at the UMCES reported slight improvements in bay water quality compared to levels measured in 2020. The greatest improvements were seen in the lower bay areas, while the Patapsco River and Back River (Maryland) regions showed minimal improvement. Positive indicators included decreased nitrogen levels and increases in dissolved oxygen.
The CBF reported that as of 2022 pollution control efforts in the bay have continued to show mixed results, with no improvement in levels of toxic contaminants, nitrogen and dissolved oxygen, and a small decrease in water clarity compared to 2020 levels (measured as Secchi depth). Oyster and rockfish populations in the bay have improved, but blue crab populations have continued to decline. | 2 | Environmental Chemistry |
To completely describe the state of a plasma, all of the particle locations and velocities that describe the electromagnetic field in the plasma region would need to be written down. However, it is generally not practical or necessary to keep track of all the particles in a plasma. Therefore, plasma physicists commonly use less detailed descriptions, of which there are two main types: | 7 | Physical Chemistry |
Polymer properties depend of their structure and they are divided into classes according to their physical bases. Many physical and chemical properties describe how a polymer behaves as a continuous macroscopic material. They are classified as bulk properties, or intensive properties according to thermodynamics. | 7 | Physical Chemistry |
oligo - oligodeoxyribonucleotide - oligonucleotide - oligosaccharide-transporting ATPase - oncogene - oncovirus - open reading frame - operator - operon - origin of replication - ornithine(lysine) transaminase - osteomimicry | 1 | Biochemistry |
Uteroglobin, or blastokinin, also known as secretoglobin family 1A member 1 (SCGB1A1), is a protein that in humans is encoded by the SCGB1A1 gene.
SCGB1A1 is the founding member of the secretoglobin family of small, secreted, disulfide-bridged dimeric proteins found only in mammals. This antiparallel disulfide linked homodimeric protein is multifunctional and found in various tissues in various names such as: uteroglobin (UG, UGB), uteroglobin-like antigen (UGL), blastokinin, club-cell secretory protein (CCSP), Clara-cell 16 kD protein (17 in rat/mice), club-cell-specific 10 kD protein (CC10), human protein 1, urine protein 1 (UP-1), polychlorinated biphenyl-binding protein (PCB-BP), human club cell phospholipid-binding protein (hCCPBP), secretoglobin 1A member 1 (SCGB1A1).
This protein is specifically expressed in club cells in the lungs. | 1 | Biochemistry |
Winter sea ice is a significant atmospheric contribution of bromine. Organic bromine gases such as CHBr, CHBr, CHIBr are emitted by microorganisms in sea ice and snow at ten-fold higher rates than from other environments. In polar areas, decreasing sea ice releases bromine and at the Arctic and Antarctic boundary layer, bromine is released in the spring when the ice melts.
Inorganic bromine is found in the atmosphere and is quickly cycled between its gas and its particulate phase. Bromine gas (Br) undergoes an autocatalytic cycle known as the bromine explosion, which occurs in the ocean and salt lakes such as the Dead Sea, where a high quantity of salts are exposed to the atmosphere. Bromine contributes to 5-15% of tropospheric ozone layer losses. | 9 | Geochemistry |
A melatonergic agent (or drug) is a chemical which functions to directly modulate the melatonin system in the body or brain. Examples include melatonin receptor agonists and melatonin receptor antagonists. | 1 | Biochemistry |
Sulfonic acids have functionality R−S(=O)−OH. They are strong acids that are typically soluble in organic solvents. Sulfonic acids like trifluoromethanesulfonic acid is a frequently used reagent in organic chemistry. Sulfinic acids have functionality R−S(O)−OH while sulfenic acids have functionality R−S−OH. In the series sulfonic—sulfinic—sulfenic acids, both the acid strength and stability diminish in that order. Sulfonamides, sulfinamides and sulfenamides, with formulas R−SONR′, R−S(O)NR′, and R−SNR′, respectively, each have a rich chemistry. For example, sulfa drugs are sulfonamides derived from aromatic sulfonation. Chiral sulfinamides are used in asymmetric synthesis, while sulfenamides are used extensively in the vulcanization process to assist cross-linking. Thiocyanates, R−S−CN, are related to sulfenyl halides and esters in terms of reactivity. | 9 | Geochemistry |
Agrochemical companies are the second largest users of fine chemicals. Most products have a "pharmaceutical heritage". As a consequence of an intensive M&A activity (Mergers and Acquisitions) over the past 10–20 years, the industry now is more consolidated than the pharmaceutical industry. The top 10 companies, led by Syngenta, Switzerland; Bayer Cropsciences, Germany: Monsanto, USA; BASF Crop Protection, Germany, and Dow Agrosciences, USA have a share of almost 95% of the total 2,000,000 tons / $48.5 billion pesticide output in 2010. Since the 1990s the R&D effort is focused mainly on gene modified (GM) seeds. At both Monsanto and DuPont's seed subsidiary, Pioneer Hi-Bred, GM seed businesses already account for more than 50% of total sales. 100 new LMW agrochemicals have been launched in the period 2000–2009. However, only 8 products achieved sales in excess of $100 million per year.
Generics play a bigger role in the agro than in the pharma industry. They represent some 70% of the global market. China National Chemical Corp, a.k.a. ChemChina Group, is the world's largest supplier of generic farm chemicals. Mahkteshim Agan, Israel, and Cheminova, Denmark follow on the ranks 2 and 3. Apart from these multibillion-dollar companies, there are hundreds of smaller firms with sales of less than $50 million per year, mainly in India and China. The incidence of the cost of the active ingredient is about 33%; i.e., much higher than in drugs. Depending on the climatic conditions affecting crop yields, consumption and prices of agrochemicals are subject to wide fluctuations from year to year, impacting also the suppliers.
The molecular structures of modern agrochemicals are much more complex than in older products, but lower than of their pharma counterparts. The average molecular weight of the top 10 is 330, as compared with 477 for the top 10. In comparison to reagents used in pharmaceutical fine chemical syntheses, hazardous chemicals, e.g. sodium azide, halogens, methyl sulfide, phosgene, phosphorus chlorides, are more frequently used. Agrochemical companies sometimes outsource just these steps, which require specialized equipment, on toll conversion deals. With exception of the pyrethroids, which are photostable modifications of naturally occurring pyrethrums, active ingredients of agrochemicals rarely are chiral. Examples within herbicides are the worlds longstanding top-selling product, Monsantos round-up (glyphosate). Syngentas cyclohexadione-type mesotrione and paraquat dichloride. Within insecticides, the traditional organophosphates, like malathion, and pyrethroids such as γ-cyhalotrin are being substituted for by neonicotinoids, like Bayers imidacloprid and Syngentas thiamethoxam and pyrazoles, such as BASFs fipronil. Chloranthaniliprole is the most important representative of Du Ponts award-winning anthranilic diamide family of broad spectrum insecticides. Within fungicides, the strobilurins, a new class, are growing rapidly and already have captured more than 30% of the $10 billion global fungicide market. Syngentas azoxystrobin was the first product launched. Also BASFs F-500 Series, a.o. pyraclostrobin and kresoxim-methyl, Bayer CropScience, and Monsanto are developing new compounds in this class. Combination pesticides, such as Monsantos Genuity and SmartStax are more and more frequently used. | 0 | Organic Chemistry |
Since their discovery in the 1970s, many restriction enzymes have been identified; for example, more than 3500 different Type II restriction enzymes have been characterized. Each enzyme is named after the bacterium from which it was isolated, using a naming system based on bacterial genus, species and strain. For example, the name of the EcoRI restriction enzyme was derived as shown in the box. | 1 | Biochemistry |
Particulate organic matter (POM) is a fraction of total organic matter operationally defined as that which does not pass through a filter pore size that typically ranges in size from 0.053 millimeters (53 μm) to 2 millimeters.
Particulate organic carbon (POC) is a closely related term often used interchangeably with POM. POC refers specifically to the mass of carbon in the particulate organic material, while POM refers to the total mass of the particulate organic matter. In addition to carbon, POM includes the mass of the other elements in the organic matter, such as nitrogen, oxygen and hydrogen. In this sense POC is a component of POM and there is typically about twice as much POM as POC. Many statements that can be made about POM apply equally to POC, and much of what is said in this article about POM could equally have been said of POC.
Particulate organic matter is sometimes called suspended organic matter, macroorganic matter, or coarse fraction organic matter. When land samples are isolated by sieving or filtration, this fraction includes partially decomposed detritus and plant material, pollen, and other materials. When sieving to determine POM content, consistency is crucial because isolated size fractions will depend on the force of agitation.
POM is readily decomposable, serving many soil functions and providing terrestrial material to water bodies. It is a source of food for both soil organisms and aquatic organisms and provides nutrients for plants. In water bodies, POM can contribute substantially to turbidity, limiting photic depth which can suppress primary productivity. POM also enhances soil structure leading to increased water infiltration, aeration and resistance to erosion. Soil management practices, such as tillage and compost/manure application, alter the POM content of soil and water. | 9 | Geochemistry |
Homing endonucleases differ from Type II restriction enzymes in the several respects:
* Whereas Type II restriction enzymes bind short, usually symmetric, recognition sequences of 4 to 8 bp, homing endonucleases bind very long and in many cases asymmetric recognition sequences spanning 12 to 40 bp.
* Homing endonucleases are generally more tolerant of substitutions in the recognition sequence. Minor variations in the recognition sequence usually decrease the activity of homing endonucleases, but often do not completely abolish it as often occurs with restriction enzymes.
* Homing endonucleases share structural motifs that suggest there are four families, whereas it has not been possible to determine simply recognisable and distinguishable families of Type II restriction enzymes.
* Homing endonucleases act as monomers or homodimers, and often require associated proteins to regulate their activity or form ribonucleoprotein complexes, wherein RNA is an integral component of the catalytic apparatus. Type II restriction enzymes can also function alone, as monomers or homodimers, or with additional protein subunits, but the accessory subunits differ from those of the homing endonucleases. Thus, they can require restriction, modification, and specificity subunits for their action.
* Finally, homing endonucleases have a broader phylogenetic distribution, occurring in all three biological domains—the archaea, bacteria and eukarya. Type II restriction enzymes occur only in archaea, bacteria and certain viruses. Homing endonucleases are also expressed in all three compartments of the eukaryotic cell: nuclei, mitochondria and chloroplasts. Open reading frames encoding homing endonucleases have been found in introns, inteins, and in freestanding form between genes, whereas genes encoding Type II restriction enzyme genes have been found only in freestanding form, almost always in close association with genes encoding cognate DNA modifying enzymes. Thus, while the Type II restriction enzymes and homing endonucleases share the function of cleaving double-stranded DNA, they appear to have evolved independently. | 1 | Biochemistry |
Treatment of high-silicon ferrosilicon with hydrogen chloride is the basis of the industrial synthesis of trichlorosilane.
Ferrosilicon is also used in a ratio of 3–3.5% in the manufacture of sheets for the magnetic circuit of electrical transformers. | 8 | Metallurgy |
Arsenic is an element with a vaporization point of 615 °C, such that arsenical oxide will be lost from the melt before or during casting, and fumes from fire setting for mining and ore processing have long been known to attack the nervous system, eyes, lungs, and skin.
Chronic arsenic poisoning leads to peripheral neuropathy, which can cause weakness in the legs and feet. It has been speculated that this lay behind the legend of lame smiths in many cultures and myths, such as the Greek god Hephaestus. As Hephaestus was an iron-age smith, not a bronze-age smith, the connection would be one from ancient folk memory.
A well-preserved mummy of a man who lived around 3,200 BC found in the Ötztal Alps, popularly known as Ötzi, showed high levels of both copper particles and arsenic in his hair. This, along with Ötzi's copper axe blade, which is 99.7% pure copper, has led scientists to speculate that he was involved in copper smelting. | 8 | Metallurgy |
SU-8 2000 series resists use cyclopentanone for the primary solvent and can be used to create films between 0.5 and 100 µm in thickness. This formulation may offer improved adhesion on some substrates versus the original formulation.
SU-8 3000 series resists also use cyclopentanone for the primary solvent and are designed to be spun into thicker films ranging from 2 to 75 µm in a single coat.
SU-8 GLM2060 series of low-stress photoresist consist of epoxy GBL and silica formulation CTE 14.
SU-8 GCM3060 Series of GERSTELTEC conductive SU8 with nanoparticles of silver.
SU-8 GMC10xx Series of GERSTELTEC colored SU8 Red, Bleau, Green, black and others.
SU-8 GMJB10XX Series of GERSTELTEC low viscosities epoxy for inkjet applications.
SU8 GM10XX Series of Classic GERSTELTEC epoxy.
Its polymerization process proceeds upon photoactivation of a photoacid generator (triarylsulfonium salts, for example) and subsequent post exposure baking. The polymerization process it a cationic chain growth, which takes place by ring opening polymerization of the epoxide groups.
SUEX is a Thick Dry Film Sheet (TDFS) which is a solventless formulation applied by lamination. As this formulation is a dry sheet, there is high uniformity, no edge-bead formation and very little waste. These sheets come in a range of thicknesses from 100 µm to over 1mm. DJMicrolaminates also sell a thinner range, ADEX TFDS, which are available in thicknesses from 5 µm through to 75 µm. | 7 | Physical Chemistry |
Palytoxin, PTX or PLTX is an intense vasoconstrictor, and is considered to be one of the most poisonous non-protein substances known, second only to maitotoxin in terms of toxicity in mice.
Palytoxin is a polyhydroxylated and partially unsaturated compound (8 double bonds) with a long carbon chain. It has water-soluble and fat-soluble parts, 40 hydroxy groups and 64 chiral centers. Due to chirality and possible double bond cis-trans isomerism, it has over 10 alternative stereoisomers. It is thermostable, and treatment with boiling water does not remove its toxicity. It remains stable in aqueous solutions for prolonged periods but rapidly decomposes and loses its toxicity in acidic or alkaline solutions. It has multiple analogues with a similar structure like ostreocin-D, mascarenotoxin-A and -B.
Palytoxin occurs at least in tropics and subtropics where it is made by Palythoa corals and Ostreopsis dinoflagellates, or possibly by bacteria occurring in these organisms. It can be found in many more species like fish and crabs due to the process of biomagnification. It can also be found in organisms living close to palytoxin producing organisms like sponges, mussels, starfish and cnidaria.
People are rarely exposed to palytoxin. Exposures have happened in people who have eaten sea animals like fish and crabs, but also in aquarium hobbyists who have handled Palythoa corals incorrectly and in those who have been exposed to certain algal blooms.
Palytoxin targets the sodium-potassium pump protein by locking it into a position where it allows passive transport of both sodium and potassium ions, thereby destroying the ion gradient that is essential for life. Because palytoxin can affect every type of cell in the body, the symptoms can be very different for the various routes of exposure.
Palytoxin's planar chemical structure was solved in 1981 by two research groups independently from each other. Stereochemistry was solved in 1982. Palytoxin carboxylic acid was synthesized by Yoshito Kishi and colleagues in 1989 and actual palytoxin in 1994 by Kishi and Suh. | 0 | Organic Chemistry |
Also at the Janelia Research Campus, a new fluorescent molecules known as CaMPARI (calcium-modulated photoactivatable ratiometric integrator) was developed using EosFP. The permanent green to red conversion signal was coupled with a calcium-sensitive protein, calmodulin, so that color change in the fusion construct depended on the release of calcium accompanied by neural activity. CaMPARI is able to permanently mark neurons that are active at an any time and can also be targeted to synapses. This visualization is possible across a wide amount of brain tissue as opposed to the limited view available with using a microscope. It also allows for the visualization of neural activity during complicated behaviors as the organism under study is allowed to move freely, rather than under a microscope. It also allows for the observation of neurons during specific behavior periods. CaMPARI has, thus far, been used to label active neural circuits in mice, zebrafish and fruit flies. | 1 | Biochemistry |
Mukaiyama has been recognized for his achievements in the form of seven honorary degrees and membership in the national academies of four nations. He is the namesake of the Mukaiyama Award, awarded by the Society of Synthetic Organic Chemistry, Japan since 2005. His major awards include:
* Chemical Society of Japan Award in 1973
* Imperial Prize and Academy Prize from the Japan Academy in 1983
* Nicholaus Copernicus Medal from the Polish Academy of Sciences in 1986
* Person of Cultural Merit from Japan in 1992
* Chevalier de l’Ordre National du Mérite from France in 1994
* ACS Award for Creative work in Synthetic Organic Chemistry from the American Chemical Society in 1996
* Order of Culture from Japan in 1997
* Tetrahedron Prize for Creativity in Organic Chemistry from Elsevier in 1998
* Sir Derek Barton Gold Medal from the Royal Society of Chemistry in 1998 | 0 | Organic Chemistry |
Anti-SSA autoantibodies (anti–Sjögrens-syndrome-related antigen A autoantibodies, also called anti-Ro, or similar names including anti-SSA/Ro, anti-Ro/SSA, anti–SS-A/Ro, and anti-Ro/SS-A) are a type of anti-nuclear autoantibodies that are associated with many autoimmune diseases, such as systemic lupus erythematosus (SLE), SS/SLE overlap syndrome, subacute cutaneous lupus erythematosus (SCLE), neonatal lupus and primary biliary cirrhosis. They are often present in Sjögrens syndrome (SS). Additionally, Anti-Ro/SSA can be found in other autoimmune diseases such as systemic sclerosis (SSc), polymyositis/dermatomyositis (PM/DM), rheumatoid arthritis (RA), and mixed connective tissue disease (MCTD), and are also associated with heart arrhythmia.
Anti-SSA/Ro autoantibodies are classified as extractable nuclear antigens. The Anti-SSA/Ro autoantibody targets Ro proteins, namely Ro52 and Ro60. Ro52 and Ro60 were originally thought to be one protein, however current findings show that they are two functionally distinct proteins encoded by genes on separate chromosomes. Anti-SSA/Ro autoantibodies are used in clinical settings as a diagnostic tool to identify patients with SLE and Sjögren's syndrome. In clinical tests for autoimmune disease, Anti-Ro antibodies are some of the most consistently and frequently detected among autoantibodies.
Anti-Ro autoantibodies are often found in conjunction with a similar antibody, Anti-La/SSB (also called anti–SS-B or anti–SS-B/La), in patients with SS. These two antibodies share pathological characteristics. | 1 | Biochemistry |
The physical process of non-linear inverse Compton scattering has been first introduced theoretically in different scientific articles starting from 1964. Before this date, some seminal works had emerged dealing with the description of the classical limit of NICS, called non-linear Thomson scattering or multiphoton Thomson scattering. In 1964, different papers were published on the topic of electron scattering in intense electromagnetic fields by L. S. Brown and T. W. B. Kibble, and by A. I. Nikishov and V. I. Ritus, among the others. The development of the high-intensity laser systems required to study the phenomenon has motivated the continuous advancements in the theoretical and experimental studies of NICS. At the time of the first theoretical studies, the terms non-linear (inverse) Compton scattering and multiphoton Compton scattering were not in use yet and they progressively emerged in later works. The case of an electron scattering off high-energy photons in the field of a monochromatic background plane wave with either circular or linear polarization was one of the most studied topics at the beginning. Then, some groups have studied more complicated non-linear inverse Compton scattering scenario, considering complex electromagnetic fields of finite spatial and temporal extension, typical of laser pulses.
The advent of laser amplification techniques and in particular of chirped pulse amplification (CPA) has allowed to reach sufficiently high-laser intensities to study new regimes of light-matter interaction and to significantly observe non-linear inverse Compton scattering and its peculiar effects. Non-linear Thomson scattering was first observed in 1983 with keV electron beam colliding with a Q-switched Nd:YAG laser delivering an intensity of W/cm (), photons of frequency two times the one of the laser were produced, then in 1995 with a CPA laser of peak intensity around W/cm interacting with neon gas, and in 1998 in the interaction of a mode-locked Nd:YAG laser ( W/cm, ) with plasma electrons from a helium gas jet, producing multiple harmonics of the laser frequency. NICS was detected for the first time in a pioneering experiment at the SLAC National Accelerator Laboratory at Stanford University, USA. In this experiment, the collision of an ultra-relativistic electron beam, with energy of about GeV, with a terawatt Nd:glass laser, with an intensity of W/cm (, ), produced NICS photons which were observed indirectly via a nonlinear energy shift in the spectrum of electrons in output; consequent positron generation was also observed in this experiment.
Multiple experiments have been then performed by crossing a high-energy laser pulse with a relativistic electron beam from a conventional linear electron accelerator, but a further achievement in the study of non-linear inverse Compton scattering has been achieved with the realization of all-optical setups. In these cases, a laser pulse is both responsible for the electron acceleration, through the mechanisms of plasma acceleration, and for the non-linear inverse Compton scattering occurring in the interaction of accelerated electrons with a laser pulse (possibly counter-propagating with respect to electrons). One of the first experiment of this type was made in 2006 producing photons of energy from to keV with a Ti:Sa laser beam (W/cm). Research is still ongoing and active in this field as attested by the numerous theoretical and experimental publications. | 7 | Physical Chemistry |
In biochemistry, an Eadie–Hofstee plot (or Eadie–Hofstee diagram) is a graphical representation of the Michaelis–Menten equation in enzyme kinetics. It has been known by various different names, including Eadie plot, Hofstee plot and Augustinsson plot. Attribution to Woolf is often omitted, because although Haldane and Stern credited Woolf with the underlying equation, it was just one of the three linear transformations of the Michaelis–Menten equation that they initially introduced. However, Haldane indicated latter that Woolf had indeed found the three linear forms: is plotted against , against , or against , the first plot being most convenient unless inhibition is being studied.</blockquote> | 1 | Biochemistry |
The body of living organisms are composed of many enantiopure chiral substances. For example, amino acids that make up the proteins in the body have the same configuration, L-absolute configuration. Because of this specificity, vital processes such as constructing proteins, rely on stereoselectivity to ensure that out of all the potential enantiomers available, the body is utilizing the correct enantiopure compound.
Selectivity is a very important part of organic synthesis. In scientific papers regarding synthesis, selectivity is often listed in data tables alongside percent yield and other reaction conditions. While selectivity is deemed important in scientific literature, it has been challenging to effectively implement selectivity in drug development and production. A major issue with selectivity in pharmaceuticals is that a large percentage of drug syntheses by nature are not selective reactions, racemic mixtures are formed as the products. Separating racemic mixtures into their respective enantiomers takes extra time, money, and energy. One way to separate enantiomers is to chemically convert them into species that can be separated: diastereomers. Diastereomers, unlike enantiomers, have entirely different physical properties—boiling points, melting points, NMR shifts, solubilities—and they can be separated by conventional means such as chromatography or recrystallization. This is a whole extra step in the synthesis process and not desirable from a manufacturing standpoint. As a result, a number of pharmaceuticals are synthesized and marketed as a racemic mixture of enantiomers in cases where the less-effective enantiomer is benign. However, by identifying and specifically purifying the enantiomer which effectively binds to its respective binding site in the body, less of the drug would be needed to achieve the desired effect. With the improvement of chiral technology, a rich repertoire of enantioselective chromatographic methods have become available for the separation of drug enantiomers on the analytical, preparative, and industrial scales. | 4 | Stereochemistry |
Due to its high relative density, it gathers in low-lying areas, and at high concentrations it can cause asphyxiation. Other health effects are similar to tetrafluoromethane. | 2 | Environmental Chemistry |
The direct approach measures the exposures to pollutants by monitoring the pollutant concentrations reaching the respondents. The pollutant concentrations are directly monitored on or within the person through point of contact, biological monitoring, or biomarkers. In a workplace setting, methods of workplace exposure monitoring are used.
The point of contact approach indicates the total concentration reaching the host, while biological monitoring and the use of biomarkers infer the dosage of the pollutant through the determination of the body burden. The respondents often record their daily activities and locations during the measurement of the pollutants to identify the potential sources, microenvironments, or human activities contributing the pollutant exposure. An advantage of the direct approach is that the exposures through multiple media (air, soil, water, food, etc.) are accounted for through one study technique. The disadvantages include the invasive nature of the data collection and associated costs. Point of contact is continuous measure of the contaminant reaching the target through all routes.
Biological monitoring is another approach to measuring exposure measures the amount of a pollutant within body tissues or fluids (such as blood or urine). Biological monitoring measures the body burden of a pollutant but not the source from whence it came. The substance measured may be either the contaminant itself or a biomarker which is specific to and indicative of an exposure to the contaminant. Biomarkers of exposure assessment is a measure of the contaminant or other proportionally related variable in the body.
Air sampling measures the contaminant in the air as concentration units of ppmv (parts per million by volume), mg/m (milligrams per cubic meter) or other mass per unit volume of air. Samplers can be worn by workers or researchers to estimate concentrations found in the breathing zone (personal) or samples collected in general areas can be used to estimate human exposure by integrating time and activity patterns. Validated and semi-validated air sampling methods are published by NIOSH, OSHA, ISO and other bodies.
Surface or dermal sampling measures of the contaminant on touchable surfaces or on skin. Concentrations are typically reported in mass per unit surface area such as mg/100 cm.
In general, direct methods tend to be more accurate but more costly in terms of resources and demands placed on the subject being measured and may not always be feasible, especially for a population exposure study.
Examples of direct methods include air sampling though a personal portable pump, split food samples, hand rinses, breath samples or blood samples. | 2 | Environmental Chemistry |
The existence of multiple possible tautomers for individual chemical substances can lead to confusion. For example, samples of 2-pyridone and 2-hydroxypyridine do not exist as separate isolatable materials: the two tautomeric forms are interconvertible and the proportion of each depends on factors such as temperature, solvent, and additional substituents attached to the main ring.
Historically, each form of the substance was entered into databases such as those maintained by the Chemical Abstracts Service and given separate CAS Registry Numbers. 2-Pyridone was assigned [142-08-5] and 2-hydroxypyridine [109-10-4]. The latter is now a "replaced" registry number so that look-up by either identifier reaches the same entry. The facility to automatically recognise such potential tautomerism and ensure that all tautomers are indexed together has been greatly facilitated by the creation of the International Chemical Identifier (InChI) and associated software. Thus the standard InChI for either tautomer is . | 4 | Stereochemistry |
The ENCyclOpedia of Rna Epitranscriptome (ENCORE) is an upgraded version of [https://rna.sysu.edu.cn/encore/index.php RMBase] that a comprehensive epitranscriptome platform with tens of new software and tools, to decode the distribution pattern, metagene profile, biogenesis mechanisms, regulatory functions, interactome, evolutional conservation and novel reader proteins of more than 70 different types of RNA modifications by analyzing thousands of high-throughput sequencing data. | 1 | Biochemistry |
Protein translation involves a set of twenty amino acids. Each of these amino acids is coded for by a sequence of three DNA base pairs called a codon. Because there are 64 possible codons, but only 20-22 encoded amino acids (in nature) and a stop signal (i.e. up to three codons that do not code for any amino acid and are known as stop codons, indicating that translation should stop), some amino acids are coded for by 2, 3, 4, or 6 different codons. For example, the codons TTT and TTC both code for the amino acid phenylalanine. This is often referred to as redundancy of the genetic code. There are two mechanisms for redundancy: several different transfer RNAs can deliver the same amino acid, or one tRNA can have a non-standard wobble base in position three of the anti-codon, which recognises more than one base in the codon.
In the above phenylalanine example, suppose that the base in position 3 of a TTT codon got substituted to a C, leaving the codon TTC. The amino acid at that position in the protein will remain a phenylalanine. Hence, the substitution is a synonymous one. | 1 | Biochemistry |
In 1986, a meeting at the Institute Of Medicine defined gene therapy as the addition or replacement of a gene in a targeted cell type. In the same year, the FDA announced that it had jurisdiction over approving "gene therapy" without defining the term. The FDA added a very broad definition in 1993 of any treatment that would ‘modify or manipulate the expression of genetic material or to alter the biological properties of living cells’. In 2018 this was narrowed to ‘products that mediate their effects by transcription or translation of transferred genetic material or by specifically altering host (human) genetic sequences’.
Writing in 2018, in the Journal of Law and the Biosciences, Sherkow et al. argued for a narrower definition of gene therapy than the FDAs in light of new technology that would consist of any treatment that intentionally and permanently modified a cells genome, with the definition of genome including episomes outside the nucleus but excluding changes due to episomes that are lost over time. This definition would also exclude introducing cells that did not derive from a patient themselves, but include ex vivo approaches, and would not depend on the vector used.
During the COVID-19 pandemic, some academics insisted that the mRNA vaccines for COVID were not gene therapy to prevent the spread of incorrect information that the vaccine could alter DNA, other academics maintained that the vaccines were a gene therapy because they introduced genetic material into a cell. Fact-checkers, such as Full Fact, Reuters, PolitiFact, and FactCheck.org said that calling the vaccines a gene therapy was incorrect. Podcast host Joe Rogan was criticized for calling mRNA vaccines gene therapy as was British politician Andrew Bridgen, with fact checker Full Fact calling for Bridgen to be removed from the conservative party for this and other statements. | 1 | Biochemistry |
The energy required to remove an atom from the surface depends on the number of bonds to other surface atoms which must be broken. For a simple cubic lattice in this model, each atom is treated as a cube and bonding occurs at each face, giving a coordination number of 6 nearest neighbors. Second-nearest neighbors in this cubic model are those that share an edge and third-nearest neighbors are those that share corners. The number of neighbors, second-nearest neighbors, and third-nearest neighbors for each of the different atom positions are given in Table 1.
Most crystals, however, are not arranged in a simple cubic lattice. The same ideas apply for other types of lattices where the coordination number is not six, but these are not as easy to visualize and work with in theory, so the remainder of the discussion will focus on simple cubic lattices. Table 2 indicates the number of neighboring atoms for a bulk atom in some other crystal lattices.
The kink site is of special importance when evaluating the thermodynamics of a variety of phenomena. This site is also referred to as the “half-crystal position” and energies are evaluated relative to this position for processes such as adsorption, surface diffusion, and sublimation. The term “half-crystal” comes from the fact that the kink site has half the number of neighboring atoms as an atom in the crystal bulk, regardless of the type of crystal lattice.
For example, the formation energy for an adatom—ignoring any crystal relaxation—is calculated by subtracting the energy of an adatom from the energy of the kink atom.
This can be understood as the breaking of all of the kink atom’s bonds to remove the atom from the surface and then reforming the adatom interactions. This is equivalent to a kink atom diffusing away from the rest of the step to become a step adatom and then diffusing away from the adjacent step onto the terrace to become an adatom. In the case where all interactions are ignored except for those with nearest neighbors, the formation energy for an adatom would be the following, where is the bond energy in the crystal is given by Equation 2.
This can be extended to a variety of situations, such as the formation of an adatom-surface vacancy pair on a terrace, which would involve the removal of a surface atom from the crystal and placing it as an adatom on the terrace. This is described by Equation 3.
The energy of sublimation would simply be the energy required to remove an atom from the kink site. This can be envisioned as the surface being disassembled one terrace at a time by removing atoms from the edge of each step, which is the kink position. It has been demonstrated that the application of an external electric field will induce the formation of additional kinks in a surface, which then leads to a faster rate of evaporation from the surface. | 7 | Physical Chemistry |
In thermodynamics, a partial molar property is a quantity which describes the variation of an extensive property of a solution or mixture with changes in the molar composition of the mixture at constant temperature and pressure. It is the partial derivative of the extensive property with respect to the amount (number of moles) of the component of interest. Every extensive property of a mixture has a corresponding partial molar property. | 7 | Physical Chemistry |
A large class of drugs are enzyme inhibitors that bind to enzymes in the body and inhibit their activity. In this case it is the drug-target residence time (the length of time the drug stays bound to the target) that is of interest. Drugs with long residence times are desirable because they remain effective for longer and therefore can be used in lower doses. This residence time is determined by the kinetics of the interaction, such as how complementary the shape and charges of the target and drug are and whether outside solvent molecules are kept out of the binding site (thereby preventing them from breaking any bonds formed), and is proportional to the half-life of the chemical dissociation. One way to measure the residence time is in a preincubation-dilution experiment where a target enzyme is incubated with the inhibitor, allowed to approach equilibrium, then rapidly diluted. The amount of product is measured and compared to a control in which no inhibitor is added.
Residence time can also refer to the amount of time that a drug spends in the part of the body where it needs to be absorbed. The longer the residence time, the more of it can be absorbed. If the drug is delivered in an oral form and destined for the upper intestines, it usually moves with food and its residence time is roughly that of the food. This generally allows 3 to 8 hours for absorption. If the drug is delivered through a mucous membrane in the mouth, the residence time is short because saliva washes it away. Strategies to increase this residence time include bioadhesive polymers, gums, lozenges and dry powders. | 9 | Geochemistry |
Polymerization, an anabolic pathway used to build macromolecules such as nucleic acids, proteins, and polysaccharides, uses condensation reactions to join monomers. Macromolecules are created from smaller molecules using enzymes and cofactors. | 1 | Biochemistry |
The hardness of a material can be measured in many ways. The Knoop hardness test, a method of microindentation hardness, is the most reproducible for dense ceramics. The Vickers hardness test and superficial Rockwell scales (e.g., 45N) can also be used, but tend to cause more surface damage than Knoop. The Brinell test is suitable for ductile metals, but not ceramics. In the Knoop test, a diamond indenter in the shape of an elongated pyramid is forced into a polished (but not etched) surface under a predetermined load, typically 500 or 1000 g. The load is held for some amount of time, say 10 s, and the indenter is retracted. The indention long diagonal (d, μm, in Fig. 4) is measured under a microscope, and the Knoop hardness (HK) is calculated from the load (P, g) and the square of the diagonal length in the equations below. The constants account for the projected area of the indenter and unit conversion factors. Most oxide ceramics have a Knoop hardness in the range of 1000–1500 kg/mm (10 – 15 GPa), and many carbides are over 2000 (20 GPa). The method is specified in ASTM C849, C1326 & E384. Microindentation hardness is also called microindentation hardness or simply microhardness. The hardness of very small particles and thin films of ceramics, on the order of 100 nm, can be measured by nanoindentation methods that use a Berkovich indenter.
: (kg/mm) and (GPa)
The toughness of ceramics can be determined from a Vickers test under a load of 10 – 20 kg. Toughness is the ability of a material to resist crack propagation. Several calculations have been formulated from the load (P), elastic modulus (E), microindentation hardness (H), crack length (c in Fig. 5) and flexural strength (σ). Modulus of rupture (MOR) bars with a rectangular cross-section are indented in three places on a polished surface. The bars are loaded in 4-point bending with the polished, indented surface in tension, until fracture. The fracture normally originates at one of the indentions. The crack lengths are measured under a microscope. The toughness of most ceramics is 2–4 MPa, but toughened zirconia is as much as 13, and cemented carbides are often over 20. The toughness-by-indention methods have been discredited recently and are being replaced by more rigorous methods that measure crack growth in a notched beam in bending.
: initial crack length
: indention strength in bending | 8 | Metallurgy |
Hypothetically, it should be possible to recreate an entire ecosystem from the bottom up, in mirror form.
Advances in synthetic biology, like synthesizing viruses since 2002, partially synthetic bacteria in 2010, or synthetic ribosomes in 2013, may lead to the possibility of fully synthesizing a living cell from small molecules, where we could use mirror-image versions (enantiomers) of life's building-block molecules, in place of the standard ones. Some proteins have been synthesized in mirror-image versions, including polymerase in 2016.
Reconstructing regular lifeforms in mirror-image form, using the mirror-image (chiral) reflection of their cellular components, could be achieved by substituting left-handed amino acids with right-handed ones, in order to create mirror reflections of all regular proteins. Analogously, we could get reflected sugars, DNA, etc., on which reflected enzymes would work perfectly. Finally we would get a normally functioning mirror reflection of a natural organism—a chiral counterpart organism.
Electromagnetic force (chemistry) is unchanged under such molecular reflection transformation (P-symmetry). There is a small alteration of weak interactions under reflection, which can produce very small corrections, but these corrections are many orders of magnitude lower than thermal noise—almost certainly too tiny to alter any biochemistry. However, there are also theories that weak interactions can have a greater effect on longer nucleic acids or protein chains, resulting in much less efficient conversion of mirror ribozymes or enzymes than normal ribozymes or enzymes.
Mirror animals would need to feed on reflected food, produced by reflected plants. Mirror viruses would not be able to attack natural cells, just as natural viruses would not be able to attack mirror cells.
Mirror life presents potential dangers. For example, a chiral-mirror version of cyanobacteria, which only needs achiral nutrients and light for photosynthesis, could take over Earth's ecosystem due to lack of natural enemies, disturbing the bottom of the food chain by producing mirror versions of the required sugars. Some bacteria can digest L-glucose; exceptions like this would give some rare lifeforms an unanticipated advantage. | 4 | Stereochemistry |
Monochromatic light is illuminated vertically on the rear side of a transparent multi-layer substrate. The partial beams of the monochromatic light are transmitted and reflected at each interphase of the multi-layer system. Superimposition of the reflected beams result in destructive or constructive interference (depending on wavelength of the used light and the used substrate/multi-layer system materials) that can be detected in an intensity change of the reflected light using a photodiode, CCD, or CMOS element.
The sensitive layer on top of the multi-layer system can be (bio-)chemically modified with receptor molecules, e.g. antibodies. Binding of specific ligands to the immobilised receptor molecules results in a change refractive index n and physical thickness d of the sensitive layer. The product of n and d results in the optical thickness (n*d) of the sensitive layer.
Monitoring the change of the reflected intensity of the used light over time results in binding curves that provide information on:
* concentration of used ligand
* binding kinetics (association and dissociation rate constants) between receptor and ligand
* binding strength (affinity) between receptor and ligand
* specificity of the interaction between receptor and ligand
Compared to bio-layer interferometry, which monitors the change of the interference pattern of reflected white light, SCORE only monitors the intensity change of the reflected light using a photodiode, CCD, or CMOS element. Thus, it is possible to analyse not only a single interaction but high-density arrays with up to 10,000 interactions per cm.
Compared to surface plasmon resonance (SPR), which penetration depth is limited by the evanescent field, SCORE is limited by the coherence length of the light source, which is typically a few micrometers. This is especially relevant when investigating whole cell assays. Also, SCORE (as well as BLI) is not influenced by temperature fluctuations during the measurement, while SPR needs thermostabilisation. | 7 | Physical Chemistry |
Metanil Yellow (Acid Yellow 36) is a dye of the azo class. In analytical chemistry, it is used as a pH indicator and it has a color change from red to yellow between pH 1.2 and 3.2.
Although it is an unpermitted food dye, because of its bright yellow color, Metanil Yellow has been used as an adulterant in turmeric powder and arhar dal, particularly in India.
Animal studies have suggested that Metanil Yellow is neurotoxic and hepatotoxic. | 3 | Analytical Chemistry |
A usually desired consecutive reaction is the hydrogenation of the aldehydes to alcohols. Higher temperatures and hydrogen partial pressures favor the hydrogenation of the resulting aldehyde to the alcohol. For the reaction mechanism it is believed that the aldehyde initially forms a CO-π-complex with the catalyst. This is rearranged to the alkoxide complex and by subsequent oxidative addition of hydrogen the alcohol is eliminated and the starting complex is formed.
The aldehydic carbon-oxygen double bond can also be subject to hydroformylation, which leads to formic acid and its esters. The reaction requires the carbon monoxide insertion into the oxygen-metal bond of the alkoxide complex. The resulting formyl complex can converted into the formic acid esters and the starting complex by oxidative addition of hydrogen. The initially produced aldehydes can react further by aldol condensation to either target product precursors like 2-ethylhexenal or higher molecular weight condensation products, so-called thick oil. | 0 | Organic Chemistry |
A bioinformatic search of the sequence databases identified one homologue of the MRS2 gene of yeast in a range of metazoans. The protein has a very similar sequence and predicted TM topology to the yeast protein, and the GMN motif is intact at the end of the first TM domain. The human protein, hsaMrs2p, has been localised to the mitochondrial membrane in mouse cells using a GFP fusion protein.
Very little is known about the Mg transport characteristics of the protein in mammals, but Zsurka et al. (2001) has shown that the human Mrs2p complements the mrs2 mutants in the yeast mitochondrial Mg uptake system. | 1 | Biochemistry |
Cooling curves are important in controlling the quality of a casting. The most important part of the cooling curve is the cooling rate which affects the microstructure and properties. Generally speaking, an area of the casting which is cooled quickly will have a fine grain structure and an area which cools slowly will have a coarse grain structure. Below is an example cooling curve of a pure metal or eutectic alloy, with defining terminology.
Note that before the thermal arrest the material is a liquid and after it the material is a solid; during the thermal arrest the material is converting from a liquid to a solid. Also, note that the greater the superheat the more time there is for the liquid material to flow into intricate details.
The above cooling curve depicts a basic situation with a pure metal, however, most castings are of alloys, which have a cooling curve shaped as shown below.
Note that there is no longer a thermal arrest, instead there is a freezing range. The freezing range corresponds directly to the liquidus and solidus found on the phase diagram for the specific alloy. | 8 | Metallurgy |
In the basic electroforming process, an electrolytic bath is used to deposit nickel or other electroformable metal onto a conductive surface of a model (mandrel). Once the deposited material has been built up to the desired thickness, the electroform is parted from the substrate. This process allows precise replication of the mandrel surface texture and geometry at low unit cost with high repeatability and excellent process control.
If the mandrel is made of a non-conductive material it can be coated with a thin conductive layer. | 8 | Metallurgy |
C terminus - Can f 1 - cancer - candidate gene - Canonical sequence - cap - cap site - carbon-monoxide dehydrogenase (cytochrome b-561) - carboxyl terminus - carcinoma - carnitine dehydratase - carrier - carveol dehydrogenase - CAT assay - CAT RNA-binding domain - catalase-related immune-responsive domain - CCAAT box - Cd2+-exporting ATPase - cDNA - cDNA clone - cDNA library - CDP-acylglycerol O-arachidonoyltransferase - cell - centimorgan - centromere - chain terminator - channel-conductance-controlling ATPase - chaperone protein - chlordecone reductase - chloroplast protein-transporting ATPase - cholestanetriol 26-monooxygenase - cholesterol 7alpha-monooxygenase - chromosome - chromosomal translocation - chromosome walking - CIS - cistron - clone (genetics) - clone (noun) - clone (verb) - cloning - coding sequence - coding strand - codon - codon usage bias - competent - complementary - conformational epitope - congenital - consensus sequence - conservative substitution - conserved - contig - coproporphyrinogen dehydrogenase - cortisone alpha-reductase - cosmid - costunolide synthase - CpG - craniosynostosis - crp domain - Cu2+-exporting ATPase - cyclodeaminase domain - cyclohexanol dehydrogenase - cystic fibrosis - cytogenetic map - cytosine - | 1 | Biochemistry |
C3 plants use the Calvin cycle to fix carbon. C4 plants use a modified Calvin cycle in which they separate Ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCO) from atmospheric oxygen, fixing carbon in their mesophyll cells and using oxaloacetate and malate to ferry the fixed carbon to RuBisCO and the rest of the Calvin cycle enzymes isolated in the bundle-sheath cells. The intermediate compounds both contain four carbon atoms, which gives C4. In Crassulacean acid metabolism (CAM), time isolates functioning RuBisCO (and the other Calvin cycle enzymes) from high oxygen concentrations produced by photosynthesis, in that O is evolved during the day, and allowed to dissipate then, while at night atmospheric CO is taken up and stored as malic or other acids. During the day, CAM plants close stomata and use stored acids as carbon sources for sugar, etc. production.
The C3 pathway requires 18 ATP and 12 NADPH for the synthesis of one molecule of glucose (3 ATP + 2 NADPH per fixed) while the C4 pathway requires 30 ATP and 12 NADPH (C3 + 12 ATP per fixed). In addition, we can take into account that each NADPH is equivalent to 3 ATP, that means both pathways require 36 additional (equivalent of) ATP [better citation needed]. Despite this reduced ATP efficiency, C4 is an evolutionary advancement, adapted to areas of high levels of light, where the reduced ATP efficiency is more than offset by the use of increased light. The ability to thrive despite restricted water availability maximizes the ability to use available light. The simpler C3 cycle which operates in most plants is adapted to wetter darker environments, such as many northern latitudes. Maize, sugar cane, and sorghum are C4 plants. These plants are economically important in part because of their relatively high photosynthetic efficiencies compared to many other crops. Pineapple is a CAM plant. | 5 | Photochemistry |
A drive designed to read and write to 3D optical data storage media may have a lot in common with CD/DVD drives, particularly if the form factor and data structure of the media is similar to that of CD or DVD. However, there are a number of notable differences that must be taken into account when designing such a drive. | 5 | Photochemistry |
The vibrational properties of LAGP could be directly probed using Raman spectroscopy. LAGP shows the Raman features characteristic of all the NASICON-type materials, most of which caused by the vibrational motions of PO units. The main spectral regions in a Raman spectrum of NASICON-type materials are summarized in the following table.
The Raman spectra of LAGP are usually characterized by broad peaks, even when the material is in its crystalline form. Indeed, both the presence of aluminium ions in place of germanium ions and the extra lithium ions introduce structural and compositional disorder in the sublattice, resulting in peak broadening. | 7 | Physical Chemistry |
P680 receives excitation energy either by directly absorbing a photon of suitable frequency or indirectly from other chlorophylls within photosystem II, thereby exciting an electron to a higher energy level. The resulting P680 with a loosened electron is designated as P680*, which is a strong reducing agent. | 5 | Photochemistry |
Tethered intramolecular [2+2] reactions entail the formation of cyclobutane and cyclobutanone via intramolecular 2+2 photocycloadditions. Tethering ensures formation of a multi-cyclic system.
The length of the tether affects the stereochemical outcome of the [2+2] reaction. Longer tethers tend to generate the "straight" product where the terminal carbon of the alkene is linked to the -carbon of the enone. When the tether consists only two carbons, the “bent” product is generated where the -carbon of the enone is connected to the terminal carbon of the alkene.
Tethered [2+2] reactions have been used to synthesize organic compounds with interesting ring systems and topologies. For example, [2+2] photocyclization was used to construct the tricyclic core structure in ginkgolide B. | 0 | Organic Chemistry |
Examples of intermetallics through history include:
# Roman yellow brass, CuZn
# Chinese high tin bronze, CuSn
# Type metal, SbSn
# Chinese white copper, CuNi
German type metal is described as breaking like glass, not bending, softer than copper but more fusible than lead. The chemical formula does not agree with the one above; however, the properties match with an intermetallic compound or an alloy of one. | 8 | Metallurgy |
The Hildebrand solubility parameter is the square root of the cohesive energy density:
The cohesive energy density is the amount of energy needed to completely remove unit volume of molecules from their neighbours to infinite separation (an ideal gas). This is equal to the heat of vaporization of the compound divided by its molar volume in the condensed phase. In order for a material to dissolve, these same interactions need to be overcome, as the molecules are separated from each other and surrounded by the solvent. In 1936 Joel Henry Hildebrand suggested the square root of the cohesive energy density as a numerical value indicating solvency behavior. This later became known as the "Hildebrand solubility parameter". Materials with similar solubility parameters will be able to interact with each other, resulting in solvation, miscibility or swelling. | 7 | Physical Chemistry |
*Bailyn, M. (1994). A Survey of Thermodynamics, American Institute of Physics Press, New York, .
*Callen, H.B. (1960/1985). Thermodynamics and an Introduction to Thermostatistics, (1st edition 1960) 2nd edition 1985, Wiley, New York, .
* A translation may be found [http://neo-classical-physics.info/uploads/3/0/6/5/3065888/caratheodory_-_thermodynamics.pdf here]. A mostly reliable translation is to be found at Kestin, J. (1976). The Second Law of Thermodynamics, Dowden, Hutchinson & Ross, Stroudsburg PA.
*Eu, B.C. (2002). Generalized Thermodynamics. The Thermodynamics of Irreversible Processes and Generalized Hydrodynamics, Kluwer Academic Publishers, Dordrecht, .
*Jaynes, E.T. (1965). Gibbs vs. Boltzmann entropies, Am. J. Phys., 33: 391–398.
*Marsland, R. , Brown, H.R., Valente, G. (2015). [https://aapt.scitation.org/doi/abs/10.1119/1.4914528 Time and irreversibility in axiomatic thermodynamics], Am. J. Phys., 83(7): 628–634.
*Planck, M., (1923/1927). Treatise on Thermodynamics, translated by A. Ogg, third English edition, Longmans, Green and Co., London.
*Prigogine, I., Defay, R. (1950/1954). Chemical Thermodynamics, Longmans, Green & Co, London.
*Tisza, L. (1966). Generalized Thermodynamics, M.I.T. Press, Cambridge MA.
*Zemanksy, M.W., Dittman, R.H. (1937/1981). Heat and Thermodynamics. An Intermediate Textbook, sixth edition, McGraw-Hill Book Company, New York, ISNM 0-07-072808-9. | 7 | Physical Chemistry |
Parvoviruses are a family of DNA viruses that have single-stranded DNA (ssDNA) genomes enclosed in rugged, icosahedral protein capsids 18–26 nanometers (nm) in diameter. Unlike most other ssDNA viruses, which have circular genomes that form a loop, parvoviruses have linear genomes with short terminal sequences at each end of the genome. These termini are capable of being formed into structures called hairpins or hairpin loops and consist of short, imperfect palindromes. Varying from virus to virus, the coding region of the genome is 4–6 kilobases (kb) in length, and the termini are 116–550 nucleotides (nt) in length each. The hairpin sequences provide most of the cis-acting information needed for DNA replication and packaging.
Parvovirus genomes may be either positive-sense or negative-sense. Some species, such as adeno-associated viruses (AAV) like AAV2, package a roughly equal number of positive-sense and negative-sense strands into virions, others, such as minute virus of mice (MVM), show preference toward packaging negative-sense strands, and others have varying proportions. Because of this disparity, the 5′-end (usually pronounced "five prime end") of the strand that encodes the non-structural proteins is called the "left end", and the 3′-end (usually pronounced "three prime end") is called the "right end". In reference to the negative-sense strand, the 3′-end is the left side and the 5′-end is the right side.
Parvoviruses replicate their genomes through a process called rolling hairpin replication (RHR), which is a unidirectional, strand displacement form of DNA replication. Before replication, the coding portion of the ssDNA genome is converted to a double-strand DNA (dsDNA) form, which is then cleaved by a viral protein to initiate replication. Sequential unfolding and refolding of the hairpin termini acts to reverse the direction of synthesis, which allows replication to go back and forth along the genome to synthesize a continuous duplex replicative form (RF) DNA intermediate. Progeny ssDNA genomes are then excised from the RF intermediate. While the general aspects of RHR are conserved across genera and species, the exact details likely vary.
Parvovirus genomes have distinct starting points of replication that contain palindromic DNA sequences. These sequences are able to alternate between inter- and intrastrand basepairing throughout replication, and they serve as self-priming telomeres at each end of the genome. They also contain two key sites necessary for replication used by the initiator protein: a binding site and a cleavage site. Telomere sequences have significant complexity and diversity, suggesting that they perform additional functions for many species. In MVM, for example, the left-end hairpin contains binding sites for transcription factors that modulate gene expression from an adjacent promoter. For AAV, the hairpins can bind to MRE11/Rad50/NBS1 (MRN) complexes and Ku70/80 heterodimers, which are involved in sensing and repairing DNA. In general, however, they have the same basic structure: imperfect palindromes in which a fully or primarily basepaired region terminates into an axial symmetry. These palindromes can fold into a variety of structures such as a Y-shaped structure and a cruciform-shaped structure. During replication, the termini act as hinges in which the imperfectly basepaired or partial cruciform regions surrounding the axis provide a favorable environment for unfolding and refolding of the hairpin.
Some parvoviruses, such as AAV2, are homotelomeric, meaning the two palindromic telomeres are similar or identical and form part of larger (inverted) terminal repeat sequences. Replication at each terminal ending is therefore similar. Other parvoviruses, such as MVM, are heterotelomeric, meaning they have two physically different telomeres. As a result, heterotelomeric parvoviruses tend to have a more complex replication process since the two telomeres have different replication processes. In general, homotelomeric parvoviruses replicate both ends via a process called terminal resolution, whereas heterotelomeric parvoviruses replicate one end by terminal resolution and the other end by an asymmetric process called junction resolution. Whether a genus is hetero- or homotelomeric, along with other genomic characteristics, is shown in the following table. | 1 | Biochemistry |
Flutamide, sold under the brand name Eulexin among others, is a nonsteroidal antiandrogen (NSAA) which is used primarily to treat prostate cancer. It is also used in the treatment of androgen-dependent conditions like acne, excessive hair growth, and high androgen levels in women. It is taken by mouth, usually three times per day.
Side effects in men include breast tenderness and enlargement, feminization, sexual dysfunction, and hot flashes. Conversely, the medication has fewer side effects and is better-tolerated in women with the most common side effect being dry skin. Diarrhea and elevated liver enzymes can occur in both sexes. Rarely, flutamide can cause liver damage, lung disease, sensitivity to light, elevated methemoglobin, elevated sulfhemoglobin, and deficient neutrophils. Numerous cases of liver failure and death have been reported, which has limited the use of flutamide.
Flutamide acts as a selective antagonist of the androgen receptor (AR), competing with androgens like testosterone and dihydrotestosterone (DHT) for binding to ARs in tissues like the prostate gland. By doing so, it prevents their effects and stops them from stimulating prostate cancer cells to grow. Flutamide is a prodrug to a more active form. Flutamide and its active form stay in the body for a relatively short time, which makes it necessary to take flutamide multiple times per day.
Flutamide was first described in 1967 and was first introduced for medical use in 1983. It became available in the United States in 1989. The medication has largely been replaced by newer and improved NSAAs, namely bicalutamide and enzalutamide, due to their better efficacy, tolerability, safety, and dosing frequency (once per day), and is now relatively little-used. It is on the World Health Organization's List of Essential Medicines. | 4 | Stereochemistry |
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. | 7 | Physical Chemistry |
Aciculitins are antifungal cyclic peptides isolated from a marine sponge. There are 3 Aciculitins that are isolated from the Lithistid sponge Aciculites orientalis that differ by their homologous lipid residues.
Aciculitin D is a similar cyclic peptide to Aciculitin A-C. It was isolated from Poecillastra sp. marine sponge that is collected from the deep sea. Based on its molecular formula, Aciculitin D is the most similar to Aciculitin B structure wise since they only differ in one amino acid substitution. The structure of Aciculitin B contains one extra glutamine while the structure of Aciculitin D has one extra L-Threonine. Although the two cyclic peptides contain slightly different amino acids, they still have the same overall charge because both glutamine and L-Threonine are considered neutral amino acids. | 1 | Biochemistry |
Following the procedure described in the gas in a box article, we can apply the Thomas–Fermi approximation which assumes that the average energy is large compared to the energy difference between levels so that the above sum may be replaced by an integral. This replacement gives the macroscopic grand potential function , which is close to :
The degeneracy dg may be expressed for many different situations by the general formula:
where α is a constant, E is a critical energy, and Γ is the Gamma function. For example, for a massive Bose gas in a box, α=3/2 and the critical energy is given by:
where Λ is the thermal wavelength, and f is a degeneracy factor (f=1 for simple spinless bosons). For a massive Bose gas in a harmonic trap we will have α=3 and the critical energy is given by:
where V(r)=mωr/2 is the harmonic potential. It is seen that E is a function of volume only.
This integral expression for the grand potential evaluates to:
where Li(x) is the polylogarithm function.
The problem with this continuum approximation for a Bose gas is that the ground state has been effectively ignored, giving a degeneracy of zero for zero energy. This inaccuracy becomes serious when dealing with the Bose–Einstein condensate and will be dealt with in the next sections. As will be seen, even at low temperatures the above result is still useful for accurately describing the thermodynamics of just the un-condensed portion of the gas. | 7 | Physical Chemistry |
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