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A Ludwieg tube is a cheap and efficient way of producing supersonic flow. Mach numbers up to 4 in air are easily obtained without any additional heating of the flow. With heating, Mach numbers of up to 11 can be reached. | 1 | Applied and Interdisciplinary Chemistry |
Certain M┄H−C interactions are not classified as agostic but are described by the term anagostic. Anagostic interactions are more electrostatic in character. In terms of structures of anagostic interactions, the M┄H distances and M┄H−C angles fall into the ranges 2.3–2.9 Å and 110°–170°, respectively. | 0 | Theoretical and Fundamental Chemistry |
For the calculation strategy of CASTp, alpha-shape and discrete-flow methods are applied to the protein binding site, also the measurement of pocket size by the program of CAST by Liang et al. in 1998, then updated by Tian et al. in 2018. Firstly, CAST identifies atoms which form the protein pocket, then calculates the volume and area, identifies the atoms forming the rims of pocket mouth, computes how many mouth openings for each pocket, predict the area and circumference of mouth openings, finally locates cavities and calculate their size. The secondary structures were calculated by DSSP. The single amino acid annotations were fetched from UniProt database, then mapped to PDB structures following residue-level information from SIFTS database. | 1 | Applied and Interdisciplinary Chemistry |
Crucibles used for copper smelting were generally wide shallow vessels made from clay that lacks refractory properties which is similar to the types of clay used in other ceramics of the time. During the Chalcolithic period, crucibles were heated from the top by using blowpipes. Ceramic crucibles from this time had slight modifications to their designs such as handles, knobs or pouring spouts allowing them to be more easily handled and poured. Early examples of this practice can be seen in Feinan, Jordan. These crucibles have added handles to allow for better manipulation, however, due to the poor preservation of the crucibles there is no evidence of a pouring spout. The main purpose of the crucible during this period was to keep the ore in the area where the heat was concentrated to separate it from impurities before shaping.
A crucible furnace dating to 2300–1900 BC for bronze casting has been found at a religious precinct of Kerma. | 0 | Theoretical and Fundamental Chemistry |
* [http://www.cis.rit.edu/htbooks/nmr/inside.htm NMR/MRI tutorial]
* [https://web.archive.org/web/20100108014732/http://nmr.chinanmr.cn/guide/eNMR/eNMRindex.html NMR Library] NMR Concepts
* [http://www.grandinetti.org/Teaching/Chem7160/Notes NMR Course Notes]
* [https://www.nmr.tips/indexe.html Downloadable NMR exercises as PowerPoint (english/german) and PDF (german only) files] | 0 | Theoretical and Fundamental Chemistry |
A body-centered cubic unit cell has six octahedral voids located at the center of each face of the unit cell, and twelve further ones located at the midpoint of each edge of the same cell, for a total of six net octahedral voids. Additionally, there are 24 tetrahedral voids located in a square spacing around each octahedral void, for a total of twelve net tetrahedral voids. These tetrahedral voids are not local maxima and are not technically voids, but they do occasionally appear in multi-atom unit cells. | 0 | Theoretical and Fundamental Chemistry |
Litmus is a water-soluble mixture of different dyes extracted from lichens. It is often absorbed onto filter paper to produce one of the oldest forms of pH indicator, used to test materials for acidity. In an acidic medium, blue litmus paper turns red, while in a basic or alkaline medium, red litmus paper turns blue. In short, it is a dye and indicator which is used to place substances on a pH scale. | 0 | Theoretical and Fundamental Chemistry |
The number needed to treat (NNT) or number needed to treat for an additional beneficial outcome (NNTB) is an epidemiological measure used in communicating the effectiveness of a health-care intervention, typically a treatment with medication. The NNT is the average number of patients who need to be treated to prevent one additional bad outcome (e.g. the number of patients that need to be treated for one of them to benefit compared with a control in a clinical trial). It is defined as the inverse of the absolute risk reduction, and computed as , where is the incidence in the control (unexposed) group, and is the incidence in the treated (exposed) group. This calculation implicitly assumes monotonicity, that is, no individual can be harmed by treatment. The modern approach, based on counterfactual conditionals, relaxes this assumption and yields bounds on NNT.
A type of effect size, the NNT was described in 1988 by McMaster University's Laupacis, Sackett and Roberts. While theoretically, the ideal NNT is 1, where everyone improves with treatment and no one improves with control, in practice, NNT is always rounded up to the nearest round number
and so even a NNT of 1.1 becomes a NNT of 2
. A higher NNT indicates that treatment is less effective.
NNT is similar to number needed to harm (NNH), where NNT usually refers to a therapeutic intervention and NNH to a detrimental effect or risk factor. A combined measure, the number needed to treat for an additional beneficial or harmful outcome (NNTB/H), is also used. | 1 | Applied and Interdisciplinary Chemistry |
Levetiracetam is effective for treatment of generalized tonic-clonic epilepsy. It has been approved in the United States as add-on treatment for myoclonic, and tonic-clonic seizures. Levetiracetam has been approved in the European Union as a monotherapy treatment for epilepsy in the case of partial seizures or as an adjunctive therapy for partial, myoclonic, and tonic-clonic seizures.
Levetiracetam is sometimes used off label to treat status epilepticus. | 0 | Theoretical and Fundamental Chemistry |
The term glycosynthase refers to a class of proteins that have been engineered to catalyze the formation of a glycosidic bond. Glycosynthase are derived from glycosidase enzymes, which catalyze the hydrolysis of glycosidic bonds. They were traditionally formed from retaining glycosidase by mutating the active site nucleophilic amino acid (usually an aspartate or glutamate) to a small non-nucleophilic amino acid (usually alanine or glycine). More modern approaches use directed evolution to screen for amino acid substitutions that enhance glycosynthase activity. | 0 | Theoretical and Fundamental Chemistry |
The coefficients are calculated by fitting to experimentally measured masses of nuclei. Their values can vary depending on how they are fitted to the data and which unit is used to express the mass. Several examples are as shown below.
The formula does not consider the internal shell structure of the nucleus.
The semi-empirical mass formula therefore provides a good fit to heavier nuclei, and a poor fit to very light nuclei, especially He. For light nuclei, it is usually better to use a model that takes this shell structure into account. | 0 | Theoretical and Fundamental Chemistry |
Since the EPA methods are created by different regulatory departments within the EPA, finding methods on the EPA website itself can be challenging. To make finding methods easier, some organizations have created method search databases that organize all the methods into one place and link to actual test methods. Some allow searching by method number, analyte, or other keywords in the method. | 0 | Theoretical and Fundamental Chemistry |
Landes joined the University of Houston at an assistant professor in 2006, and moved to Rice University in 2009. She was appointed Kenneth S. Pitzer-Schlumberger Chair in 2021. Her early independent work considered super-resolution single molecule spectroscopy for the characterization of biomolecules using FRET with membrane receptors and diffusion within polymer brushes and porous hydrogel materials. She has pioneered the application of super-resolution microscopy to understand chromatography and has focused on tuning the plasmonic properties of nanomaterials using electrochemistry and stimuli-responsive polymers. She has also shown how silver ions disperse from the tips of gold-silver nanoparticle alloys, which may improve catalytic activity. Her biophysical chemistry work has demonstrated that single-molecule approaches could be used to better understand cancer metastasis.
Landes established the NSF Center for Adapting Flaws into Features (CAFF) in 2021 and serves as its director. The center investigates the defects in silicon-based electronics that hold promise for improving device performance, explore the structural and optoelectronic processes that make these flaws influential, and realize technologies that incorporate and exploit these flaws.
Landes was elected Chair of the Physical Chemistry Division in 2020.
Landes joined the University of Illinois Urbana-Champaign in 2023. | 0 | Theoretical and Fundamental Chemistry |
The Blueprint Initiative started as a research program in the lab of Dr. Christopher Hogue at the Samuel Lunenfeld Research Institute at Mount Sinai Hospital in Toronto. On December 14, 2005, Unleashed Informatics Limited acquired the commercial rights to The Blueprint Initiative intellectual property. This included rights to the protein interaction database BIND, the small molecule interaction database SMID, as well as the data warehouse SeqHound. Unleashed Informatics is a data management service provider and is overseeing the management and curation of The Blueprint Initiative under the guidance of Dr. Hogue. | 1 | Applied and Interdisciplinary Chemistry |
* Calculation of rainfall.
* Calculation of Evapotranspiration
* Calculating surface runoff and precipitation.
* Determining the water balance of a region.
* Determining the agricultural water balance.
* Designing riparian-zone restoration projects.
* Mitigating and predicting flood, landslide and Drought risk.
* Real-time flood forecasting, flood warning, Flood Frequency Analysis
* Designing irrigation schemes and managing agricultural productivity.
* Part of the hazard module in catastrophe modeling.
* Providing drinking water.
* Designing dams for water supply or hydroelectric power generation.
* Designing bridges.
* Designing sewers and urban drainage systems.
* Analyzing the impacts of antecedent moisture on sanitary sewer systems.
* Predicting geomorphologic changes, such as erosion or sedimentation.
* Assessing the impacts of natural and anthropogenic environmental change on water resources.
* Assessing contaminant transport risk and establishing environmental policy guidelines.
* Estimating the water resource potential of river basins.
* Water resources management. | 1 | Applied and Interdisciplinary Chemistry |
Cost of power generation by solar power projects would be below Rs. 1.0 per Kwh in few years. Availability of cheaper, clean and perennial/renewable power would favour more water lifting/pumping and tunnels in the river link projects rather than purely gravity links to economize on cost, reduce construction time and reduce land submergence by optimum use of existing reservoirs/less storage, etc. Tunnelling technology/methodology has also undergone drastic improvements to make them alternate choice to the gravity open canal links with shortest distance and cost effective manner. | 1 | Applied and Interdisciplinary Chemistry |
The Earth-based rectenna would likely consist of many short dipole antennas connected via diodes. Microwave broadcasts from the satellite would be received in the dipoles with about 85% efficiency. With a conventional microwave antenna, the reception efficiency is better, but its cost and complexity are also considerably greater. Rectennas would likely be several kilometers across. | 0 | Theoretical and Fundamental Chemistry |
BSA is prepared by treating acetamide with trimethylsilyl chloride in the presence of a base (Me = CH, Et = CH):
The reaction of BSA with alcohols gives the corresponding trimethylsilyl ether, together with acetamide as a byproduct (Me = CH): | 0 | Theoretical and Fundamental Chemistry |
Eating a variety of foods that contain potassium is the best way to get an adequate amount.
Foods with high sources of potassium include kiwifruit, orange juice, potatoes, coconut, avocados, apricots, parsnips and turnips, although many other fruits, vegetables, legumes, and meats contain potassium.
Common foods very high in potassium:
* beans (white beans and others)
* dark leafy greens (spinach, Swiss chard, and others)
* baked potatoes
* dried fruit (apricots, peaches, prunes, raisins; figs and dates)
* baked squash
* yogurt
* fish (salmon)
* avocado
* nuts (pistachios, almonds, walnuts, etc.)
* seeds (squash, pumpkin, sunflower)
Foods containing the highest concentration:
* dried herbs
* sun dried tomatoes
* cocoa solids
* whey powder
* paprika
* yeast extract
* rice bran
* molasses
* dry roasted soybeans | 1 | Applied and Interdisciplinary Chemistry |
Volcanic gases were collected and analysed as long ago as 1790 by Scipione Breislak in Italy. The composition of volcanic gases is dependent on the movement of magma within the volcano. Therefore, sudden changes in gas composition often presage a change in volcanic activity. Accordingly, a large part of hazard monitoring of volcanoes involves regular measurement of gaseous emissions. For example, an increase in the CO content of gases at Stromboli has been ascribed to injection of fresh volatile-rich magma at depth within the system.
Volcanic gases can be sensed (measured in-situ) or sampled for further analysis. Volcanic gas sensing can be:
* within the gas by means of electrochemical sensors and flow-through infrared-spectroscopic gas cells
* outside the gas by ground-based or airborne remote spectroscopy e.g., Correlation spectroscopy (COSPEC), Differential Optical Absorption Spectroscopy (DOAS), or Fourier Transform Infrared Spectroscopy (FTIR).
Sulphur dioxide (SO) absorbs strongly in the ultraviolet wavelengths and has low background concentrations in the atmosphere. These characteristics make sulphur dioxide a good target for volcanic gas monitoring. It can be detected by satellite-based instruments, which allow for global monitoring, and by ground-based instruments such as DOAS. DOAS arrays are placed near some well-monitored volcanoes and used to estimate the flux of SO emitted. The Multi-Component Gas Analyzer System (Multi-GAS) is also used to remotely measure CO, SO and HS. The fluxes of other gases are usually estimated by measuring the ratios of different gases within the volcanic plume, e.g. by FTIR, electrochemical sensors at the volcano crater rim, or direct sampling, and multiplying the ratio of the gas of interest to SO by the SO flux.
Direct sampling of volcanic gas sampling is often done by a method involving an evacuated flask with caustic solution, first used by Robert W. Bunsen (1811-1899) and later refined by the German chemist Werner F. Giggenbach (1937-1997), dubbed Giggenbach-bottle. Other methods include collection in evacuated empty containers, in flow-through glass tubes, in gas wash bottles (cryogenic scrubbers), on impregnated filter packs and on solid adsorbent tubes.
Analytical techniques for gas samples comprise gas chromatography with thermal conductivity detection (TCD), flame ionization detection (FID) and mass spectrometry (GC-MS) for gases, and various wet chemical techniques for dissolved species (e.g., acidimetric titration for dissolved CO, and ion chromatography for sulfate, chloride, fluoride). The trace metal, trace organic and isotopic composition is usually determined by different mass spectrometric methods. | 1 | Applied and Interdisciplinary Chemistry |
Isolobal fragments of tetrahedral and octahedral molecules can be related. Structures with the same number of frontier orbitals are isolobal to one another. For example, the methane with two hydrogen atoms removed, CH is isolobal to a d ML complex formed from an octahedral starting complex (Figure 4). | 0 | Theoretical and Fundamental Chemistry |
Slender-body theory in Stokes flow is a simple approximate method of determining the irrotational flow field around bodies whose length is large compared with their width. The basis of the method is to choose a distribution of flow singularities along a line (since the body is slender) so that their irrotational flow in combination with a uniform stream approximately satisfies the zero normal velocity condition. | 1 | Applied and Interdisciplinary Chemistry |
Validations can be broken into three stages: validating the raw data collected (data validation), the interpretation of the data into the atomic model (model-to-data validation), and finally validation on the model itself. While the first two steps are specific to the technique used, validating the arrangement of atoms in the final model is not. | 1 | Applied and Interdisciplinary Chemistry |
The word "emulsion" comes from the Latin emulgere "to milk out", from ex "out" + mulgere "to milk", as milk is an emulsion of fat and water, along with other components, including colloidal casein micelles (a type of secreted biomolecular condensate). | 0 | Theoretical and Fundamental Chemistry |
Persistent triplet state carbenes are likely to have very similar reactivity as other non-persistent triplet state carbenes. | 0 | Theoretical and Fundamental Chemistry |
One field where these are found is nuclear magnetic resonance (NMR) spectroscopy, where it identifies radio frequency (RF) coils that are smaller than 1 mm.
The detection limits of micro-MRI or MRM can be pushed further by taking advantage of microsystem fabrication techniques. In general, the RF receiver coil should closely conform to the sample to ensure good detection sensitivity. A properly designed NMR probe will maximize both the observe factor, which is the ratio of the sample volume being observed by the RF coil to the total sample volume required for analysis, and the filling factor, the ratio of the sample volume being observed by the RF coil to the coil volume.
The miniaturization of NMR probes thus involves two advantages:
# Increased sensitivity without which the analysis of such low concentration compounds would be impossible, and
# Increase of filling factor by matching the probe to the sample volume. Still, the extraction of the NMR spectra of samples having smaller and smaller volumes is a real challenge. Either these reductions of volume are dictated by the difficulties of production of sufficiently large samples or by the necessities of miniaturization of the analysing system, in both cases a careful design of the radiofrequency coils, ensuring an optimum reception of the NMR signal, are required. | 0 | Theoretical and Fundamental Chemistry |
Plant stress responses can be observed in plants that are under- or over-supplied with Mg. The first observable signs of Mg stress in plants for both starvation and toxicity is a depression of the rate of photosynthesis, it is presumed because of the strong relationships between Mg and chloroplasts/chlorophyll. In pine trees, even before the visible appearance of yellowing and necrotic spots, the photosynthetic efficiency of the needles drops markedly. In Mg deficiency, reported secondary effects include carbohydrate immobility, loss of RNA transcription and loss of protein synthesis. However, due to the mobility of Mg within the plant, the deficiency phenotype may be present only in the older parts of the plant. For example, in Pinus radiata starved of Mg, one of the earliest identifying signs is the chlorosis in the needles on the lower branches of the tree. This is because Mg has been recovered from these tissues and moved to growing (green) needles higher in the tree.
A Mg deficit can be caused by the lack of the ion in the media (soil), but more commonly comes from inhibition of its uptake. Mg binds quite weakly to the negatively charged groups in the root cell walls, so that excesses of other cations such as K, NH, Ca, and Mn can all impede uptake.(Kurvits and Kirkby, 1980; In acid soils Al is a particularly strong inhibitor of Mg uptake. The inhibition by Al and Mn is more severe than can be explained by simple displacement, hence it is possible that these ions bind to the Mg uptake system directly. In bacteria and yeast, such binding by Mn has already been observed. Stress responses in the plant develop as cellular processes halt due to a lack of Mg (e.g. maintenance of ΔpH across the plasma and vacuole membranes). In Mg-starved plants under low light conditions, the percentage of Mg bound to chlorophyll has been recorded at 50%. Presumably, this imbalance has detrimental effects on other cellular processes.
Mg toxicity stress is more difficult to develop. When Mg is plentiful, in general the plants take up the ion and store it (Stelzer et al., 1990). However, if this is followed by drought then ionic concentrations within the cell can increase dramatically. High cytoplasmic Mg concentrations block a K channel in the inner envelope membrane of the chloroplast, in turn inhibiting the removal of H ions from the chloroplast stroma. This leads to an acidification of the stroma that inactivates key enzymes in carbon fixation, which all leads to the production of oxygen free radicals in the chloroplast that then cause oxidative damage. | 1 | Applied and Interdisciplinary Chemistry |
Select filter cloth to obtain solid binding resistance and good cake release. Use coated fabric for more effective cake release and have a longer-lasting cloth media due to solid binding filter cloth. Both the discharge roll speed and drum speed must be the same. Adjust the scraper knife to leave a significant heal on discharge roll to produce a continuous cake transfer. | 0 | Theoretical and Fundamental Chemistry |
The position of Whitley Professor of Biochemistry at the University of Oxford is one of the permanent chairs of the university, and the first in the field of biochemistry at the university. It is associated with a fellowship at Trinity College, Oxford, and was established with an endowment of £10,000 by Edward Whitley of Trinity College. Benjamin Moore was nominated by Whitley, a former student of Moore, as the first professor. Since its creation, the position has been held by:
* Benjamin Moore 1920–22
* Sir Rudolph Peters 1923–54
* Sir Hans Adolf Krebs 1954–67
* Rodney Robert Porter 1967–85
* Sir Edwin Southern 1985–2005
* Kim Nasmyth 2006-2022
* Dame Amanda Fisher 2023 onwards | 1 | Applied and Interdisciplinary Chemistry |
Despite dicloxacillin being insensitive to beta-lactamases, some organisms have developed resistance to other narrow-spectrum β-lactam antibiotics including methicillin. Such organisms include methicillin-resistant Staphylococcus aureus (MRSA). | 0 | Theoretical and Fundamental Chemistry |
Various magnetic particles (magnetic carrier) coated with silica are often used as silica coated beads
Maghemite particle (γ-FeO) and magnetite particle (FeO),
as well as an intermediate iron oxide particle thereof, are most suitable as magnetic carriers.
Generally, the quality of the magnetic beads is characterized by
following parameters:
* saturation magnetization (～10-80 A m2/kg (emu/g):Superparamagnetic),
* coercive force (～ 0.80-15.92 kA/m),
* size diameter (～ 0.1-0.5 μm),
* mass of each particle (～ 2.7 ng),
* ease of collection (to be mentioned later),
* capture ability (to be mentioned later),
* Sedimentation rate (～4% in 30 min),
* Area ratio (> 100 m/g),
* Effective density (～ 2.5 g/cm), and
* Particle counts (～ 1 x 10 particles/mg).
Here, "ease of collection" is defined and compared by while capture ability are defined and compared by | 1 | Applied and Interdisciplinary Chemistry |
The mimic poison frog Ranitomeya (Dendrobates) imitator is polymorphic, with a striped morph that imitates the black and yellow striped morph of Ranitomeya variabilis, a spotted morph that imitates the largely blue-green highland spotted morph also of R. variabilis, and a banded morph that imitates the red and black banded Ranitomeya summersi.
R. imitator has thus apparently evolved in separate populations to resemble different targets, i.e. it has changed to resemble (adverged on) those target species, rather than both R. imitator and the other species mutually converging in the way that Müller supposed for tropical butterflies.
Such advergence may be common. The mechanism was proposed by the entomologist F. A. Dixey in 1909 and has remained controversial; the evolutionary biologist James Mallet, reviewing the situation in 2001, suggested that in Müllerian mimicry, advergence may be more common than convergence. In advergent evolution, the mimicking species responds to predation by coming to resemble the model more and more closely. Any initial benefit is thus to the mimic, and there is no implied mutualism, as there would be with Müllers original convergence theory. However, once model and mimic have become closely similar, some degree of mutual protection becomes likely. This theory would predict that all mimicking species in an area should converge on a single pattern of coloration. This does not appear to happen in nature, however, as Heliconius' butterflies form multiple Müllerian mimicry rings in a single geographical area. The finding implies that additional evolutionary forces are probably at work. | 1 | Applied and Interdisciplinary Chemistry |
In high-throughput screening (HTS), one of the major goals is to select compounds (including small molecules, siRNAs, shRNA, genes, et al.) with a desired size of inhibition or activation effects. A compound with a desired size of effects in an HTS screen is called a hit. The process of selecting hits is called hit selection. | 1 | Applied and Interdisciplinary Chemistry |
Strychnine total synthesis in chemistry describes the total synthesis of the complex biomolecule strychnine. The first reported method by the group of Robert Burns Woodward in 1954 is considered a classic in this research field.
At the time it formed the natural conclusion to an elaborate process of molecular structure elucidation that started with the isolation of strychnine from the beans of Strychnos ignatii by Pierre Joseph Pelletier and Joseph Bienaimé Caventou in 1818. Major contributors to the entire effort were Sir Robert Robinson with over 250 publications and Hermann Leuchs with another 125 papers in a time span of 40 years. Robinson was awarded the Nobel Prize in Chemistry in 1947 for his work on alkaloids, strychnine included.
The process of chemical identification was completed with publications in 1946 by Robinson and later confirmed by Woodward in 1947. X-ray structures establishing the absolute configuration became available between 1947 and 1951 with publications from Johannes Martin Bijvoet and J. H. Robertson
Woodward published a very brief account on the strychnine synthesis in 1954 (just 3 pages) and a lengthy one (42 pages) in 1963.
Many more methods exist and reported by the research groups of Magnus, Overman, Kuehne, Rawal, Bosch, Vollhardt, Mori, Shibasaki, Li, Fukuyama Vanderwal and MacMillan. Synthetic (+)-strychnine is also known. Racemic synthesises were published by Padwa in 2007 and in 2010 by Andrade and by Reissig.
In his 1963 publication Woodward quoted Sir Robert Robinson who said for its molecular size it is the most complex substance known. | 0 | Theoretical and Fundamental Chemistry |
Lugol's iodine, also known as aqueous iodine and strong iodine solution, is a solution of potassium iodide with iodine in water. It is a medication and disinfectant used for a number of purposes. Taken by mouth it is used to treat thyrotoxicosis until surgery can be carried out, protect the thyroid gland from radioactive iodine, and to treat iodine deficiency. When applied to the cervix it is used to help in screening for cervical cancer. As a disinfectant it may be applied to small wounds such as a needle stick injury. A small amount may also be used for emergency disinfection of drinking water.
Side effects may include allergic reactions, headache, vomiting, and conjunctivitis. Long term use may result in trouble sleeping and depression. It should not typically be used during pregnancy or breastfeeding. Lugol's iodine is a liquid made up of two parts potassium iodide for every one part elemental iodine in water.
Lugols iodine was first made in 1829 by the French physician Jean Lugol. It is on the World Health Organizations List of Essential Medicines. Lugols iodine is available as a generic medication and over the counter. Lugols solution is available in different strengths of iodine. Large volumes of concentrations more than 2.2% may be subject to regulation. | 0 | Theoretical and Fundamental Chemistry |
Per Teodor Cleve (10 February 1840 – 18 June 1905) was a Swedish chemist, biologist, mineralogist and oceanographer. He is best known for his discovery of the chemical elements holmium and thulium.
Born in Stockholm in 1840, Cleve earned his BSc and PhD from Uppsala University in 1863 and 1868, respectively. After receiving his PhD, he became an assistant professor of chemistry at the university. He later became professor of general and agricultural chemistry. In 1874 he theorised that didymium was in fact two elements; this theory was confirmed in 1885 when Carl Auer von Welsbach discovered neodymium and praseodymium.
In 1879 Cleve discovered holmium and thulium. His other contributions to chemistry include the discovery of aminonaphthalenesulfonic acids, also known as Cleve's acids. From 1890 on he focused on biological studies. He developed a method of determining the age and order of late glacial and postglacial deposits from the types of diatom fossils in the deposits, and wrote a seminal text in the field of oceanography. He died in 1905 at age 65. | 1 | Applied and Interdisciplinary Chemistry |
The spectrum of action includes many Gram-positive and Gram-negative bacteria (including Pseudomonas) and anaerobic bacteria. The overall spectrum is similar to that of imipenem, although meropenem is more active against Enterobacteriaceae and less active against Gram-positive bacteria. It works against extended-spectrum β-lactamases, but may be more susceptible to metallo-β-lactamases. Meropenem is frequently given in the treatment of febrile neutropenia. This condition frequently occurs in patients with hematological malignancies and cancer patients receiving anticancer drugs that suppress bone marrow formation. It is approved for complicated skin and skin structure infections, complicated intra-abdominal infections and bacterial meningitis.
In 2017, the U.S. Food and Drug Administration (FDA) granted approval for the combination of meropenem and vaborbactam to treat adults with complicated urinary tract infections. | 0 | Theoretical and Fundamental Chemistry |
Given the advantages of , a group of scientists from institutions around the world are working on the Rice Project to produce a strain of rice, naturally a plant, that uses the pathway by studying the plants maize and Brachypodium. As rice is the world's most important human food—it is the staple food for more than half the planet—having rice that is more efficient at converting sunlight into grain could have significant global benefits towards improving food security. The team claims rice could produce up to 50% more grain—and be able to do it with less water and nutrients.
The researchers have already identified genes needed for photosynthesis in rice and are now looking towards developing a prototype rice plant. In 2012, the Government of the United Kingdom along with the Bill & Melinda Gates Foundation provided US$14 million over three years towards the Rice Project at the International Rice Research Institute. In 2019, the Bill & Melinda Gates Foundation granted another US$15 million to the Oxford-University-led C4 Rice Project. The goal of the 5-year project is to have experimental field plots up and running in Taiwan by 2024.
C photosynthesis, an intermediate step between and Kranz , may be preferred over for rice conversion. The simpler system is less optimized for high light and high temperature conditions than , but has the advantage of requiring fewer steps of genetic engineering and performing better than under all temperatures and light levels. In 2021, the UK Government provided £1.2 million on studying C engineering. | 0 | Theoretical and Fundamental Chemistry |
Flux is a reducing agent designed to help reduce (return oxidized metals to their metallic state) metal oxides at the points of contact to improve the electrical connection and mechanical strength. The two principal types of flux are acid flux (sometimes called "active flux"), containing strong acids, used for metal mending and plumbing, and rosin flux (sometimes called "passive flux"), used in electronics. Rosin flux comes in a variety of "activities", corresponding roughly to the speed and effectiveness of the organic acid components of the rosin in dissolving metallic surface oxides, and consequently the corrosiveness of the flux residue.
Due to concerns over atmospheric pollution and hazardous waste disposal, the electronics industry has been gradually shifting from rosin flux to water-soluble flux, which can be removed with deionized water and detergent, instead of hydrocarbon solvents. Water-soluble fluxes are generally more conductive than traditionally used electrical / electronic fluxes and so have more potential for electrically interacting with a circuit; in general it is important to remove their traces after soldering. Some rosin type flux traces likewise should be removed, and for the same reason.
In contrast to using traditional bars or coiled wires of all-metal solder and manually applying flux to the parts being joined, much hand soldering since the mid-20th century has used flux-core solder. This is manufactured as a coiled wire of solder, with one or more continuous bodies of inorganic acid or rosin flux embedded lengthwise inside it. As the solder melts onto the joint, it frees the flux and releases that on it as well. | 1 | Applied and Interdisciplinary Chemistry |
London dispersion forces arise from instantaneous dipoles between two nonpolar molecules close together. The random nature of electron orbit allows moments in which the charge distribution in a molecule is unevenly distributed, allowing an electrostatic attraction to another molecule with a temporary dipole. A larger molecule allows for a larger dipole, and thus will have stronger dispersion forces. | 0 | Theoretical and Fundamental Chemistry |
Proline isomerization of certain prolines in RNA polymerase II is key in the process of recruiting and placing processing factors during transcription. PPIases target RNA polymerase II by interacting with the Rpb1 carboxy terminal domain, or CTD. Proline isomerization is then used as part of the mechanism of the CTD to recruit co-factors required for co-transcriptional RNA processing, regulating RNA polymerase II activity. Nrd1 is a protein that is responsible for many of the transcriptional activities of RNAP II, specifically through the Nrd1- dependent termination pathway. This pathway requires the parvulin Ess1, or Pin1 depending on the organism, to isomerize the pSer5-Pro6 bond in the CTD. Without the cis conformation of the pSer5-Pro6 bond, created by Ess1/Pin1, Nrd1 cannot bind to RNAP II. Any variation from this process leads to a decrease in Nrd1 binding affinity, lowering the ability of RNAP II to process and degrade noncoding RNAs. | 0 | Theoretical and Fundamental Chemistry |
Specific control of the lac genes depends on the availability of the substrate lactose to the bacterium. The proteins are not produced by the bacterium when lactose is unavailable as a carbon source.
The lac genes are organized into an operon; that is, they are oriented in the same direction immediately adjacent on the chromosome and are co-transcribed into a single polycistronic mRNA molecule. Transcription of all genes starts with the binding of the enzyme RNA polymerase (RNAP), a DNA-binding protein, which binds to a specific DNA binding site, the promoter, immediately upstream of the genes. Binding of RNA polymerase to the promoter is aided by the cAMP-bound catabolite activator protein (CAP, also known as the cAMP receptor protein). However, the lacI gene (regulatory gene for lac operon) produces a protein that blocks RNAP from binding to the operator of the operon. This protein can only be removed when allolactose binds to it, and inactivates it. The protein that is formed by the lacI gene is known as the lac repressor. The type of regulation that the lac operon undergoes is referred to as negative inducible, meaning that the gene is turned off by the regulatory factor (lac repressor) unless some molecule (lactose) is added. Once the repressor is removed, RNAP then proceeds to transcribe all three genes (lacZYA) into mRNA. Each of the three genes on the mRNA strand has its own Shine-Dalgarno sequence, so the genes are independently translated. The DNA sequence of the E. coli lac operon, the lacZYA mRNA, and the lacI genes are available from GenBank [https://www.ncbi.nlm.nih.gov/entrez/viewer.fcgi?db=nucleotide&val=146575 (view)].
The first control mechanism is the regulatory response to lactose, which uses an intracellular regulatory protein called the lactose repressor to hinder production of β-galactosidase in the absence of lactose. The lacI gene coding for the repressor lies nearby the lac operon and is always expressed (constitutive). If lactose is missing from the growth medium, the repressor binds very tightly to a short DNA sequence just downstream of the promoter near the beginning of lacZ called the lac operator. The repressor binding to the operator interferes with binding of RNAP to the promoter, and therefore mRNA encoding LacZ and LacY is only made at very low levels. When cells are grown in the presence of lactose, however, a lactose metabolite called allolactose, made from lactose by the product of the lacZ gene, binds to the repressor, causing an allosteric shift. Thus altered, the repressor is unable to bind to the operator, allowing RNAP to transcribe the lac genes and thereby leading to higher levels of the encoded proteins.
The second control mechanism is a response to glucose, which uses the catabolite activator protein (CAP) homodimer to greatly increase production of β-galactosidase in the absence of glucose. Cyclic adenosine monophosphate (cAMP) is a signal molecule whose prevalence is inversely proportional to that of glucose. It binds to the CAP, which in turn allows the CAP to bind to the CAP binding site (a 16 bp DNA sequence upstream of the promoter on the left in the diagram below, about 60 bp upstream of the transcription start site), which assists the RNAP in binding to the DNA. In the absence of glucose, the cAMP concentration is high and binding of CAP-cAMP to the DNA significantly increases the production of β-galactosidase, enabling the cell to hydrolyse lactose and release galactose and glucose.
More recently inducer exclusion was shown to block expression of the lac operon when glucose is present. Glucose is transported into the cell by the PEP-dependent phosphotransferase system. The phosphate group of phosphoenolpyruvate is transferred via a phosphorylation cascade consisting of the general PTS (phosphotransferase system) proteins HPr and EIA and the glucose-specific PTS proteins EIIA and EIIB, the cytoplasmic domain of the EII glucose transporter. Transport of glucose is accompanied by its phosphorylation by EIIB, draining the phosphate group from the other PTS proteins, including EIIA. The unphosphorylated form of EIIA binds to the lac permease and prevents it from bringing lactose into the cell. Therefore, if both glucose and lactose are present, the transport of glucose blocks the transport of the inducer of the lac operon. | 1 | Applied and Interdisciplinary Chemistry |
2-C-Methyl--erythritol 4-phosphate (MEP) is an intermediate on the MEP pathway (non-mevalonate pathway) of isoprenoid precursor biosynthesis. It is the first committed metabolite on that pathway on the route to IPP and DMAPP. | 1 | Applied and Interdisciplinary Chemistry |
During early 2016, science writers and bloggers speculated that one of the superheavy elements would be named oganessium or oganesson. The International Union of Pure and Applied Chemistry (IUPAC) announced in November 2016 that element 118 would be named oganesson to honor Oganessian. It was first observed in 2002 at JINR, by a joint team of Russian and American scientists. Directed by Oganessian, the team included American scientists of the Lawrence Livermore National Laboratory, California. Prior to this announcement, a dozen elements had been named after people, but of those, only seaborgium was likewise named while its namesake (Glenn T. Seaborg) was alive. As Seaborg died in 1999, Oganessian is the only currently living namesake of an element. | 1 | Applied and Interdisciplinary Chemistry |
In developing countries many governments are corrupt and poor and they respond to these problems with frequently changing policies and non clear agreements. Water demand exceeds supply, and household and industrial water supplies are prioritised over other uses, which leads to water stress. Potable water has a price in the market; water often becomes a business for private companies, which earn a profit by putting a higher price on water, which imposes a barrier for lower-income people. The Millennium Development Goals propose the changes required.
Goal 6 of the United Nations' Sustainable Development Goals is to "Ensure availability and sustainable management of water and sanitation for all". This is in recognition of the human right to water and sanitation, which was formally acknowledged at the United Nations General Assembly in 2010, that "clean drinking water and sanitation are essential to the recognition of all human rights". Sustainable water supply includes ensuring availability, accessibility, affordability and quality of water for all individuals.
In advanced economies, the problems are about optimising existing supply networks. These economies have usually had continuing evolution, which allowed them to construct infrastructure to supply water to people. The European Union has developed a set of rules and policies to overcome expected future problems.
There are many international documents with interesting, but not very specific, ideas and therefore they are not put into practice. Recommendations have been made by the United Nations, such as the Dublin Statement on Water and Sustainable Development. | 1 | Applied and Interdisciplinary Chemistry |
In statistical mechanics, the thermodynamic limit or macroscopic limit, of a system is the limit for a large number of particles (e.g., atoms or molecules) where the volume is taken to grow in proportion with the number of particles.
The thermodynamic limit is defined as the limit of a system with a large volume, with the particle density held fixed.
In this limit, macroscopic thermodynamics is valid. There, thermal fluctuations in global quantities are negligible, and all thermodynamic quantities, such as pressure and energy, are simply functions of the thermodynamic variables, such as temperature and density. For example, for a large volume of gas, the fluctuations of the total internal energy are negligible and can be ignored, and the average internal energy can be predicted from knowledge of the pressure and temperature of the gas.
Note that not all types of thermal fluctuations disappear in the thermodynamic limit—only the fluctuations in system variables cease to be important.
There will still be detectable fluctuations (typically at microscopic scales) in some physically observable quantities, such as
* microscopic spatial density fluctuations in a gas scatter light (Rayleigh scattering)
* motion of visible particles (Brownian motion)
* electromagnetic field fluctuations, (blackbody radiation in free space, Johnson–Nyquist noise in wires)
Mathematically an asymptotic analysis is performed when considering the thermodynamic limit. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, inherent chirality is a property of asymmetry in molecules arising, not from a stereogenic or chiral center, but from a twisting of the molecule in 3-D space. The term was first coined by Volker Boehmer in a 1994 review, to describe the chirality of calixarenes arising from their non-planar structure in 3-D space.
This phenomenon was described as resulting from "the absence of a place of symmetry or an inversion center in the molecule as a whole". Boehmer further explains this phenomenon by suggesting that if an inherently chiral calixarene macrocycle were opened up it would produce an "achiral linear molecule". There are two commonly used notations to describe a molecules inherent chirality: cR/cS (arising from the notation used for classically chiral compounds, with c denoting curvature) and P/M. Inherently chiral molecules, like their classically chiral counterparts, can be used in chiral host–guest chemistry, enantioselective synthesis, and other applications. There are naturally occurring inherently chiral molecules as well. Retinal, a chromophore in rhodopsin. exists in solution as a racemic pair of enantiomers due to the curvature of an achiral polyene chain. | 0 | Theoretical and Fundamental Chemistry |
Gamma-ray detected by Gamma-ray detector in an oil or gas wells, is not only a function of radioactivity of the formations, but also other factors as follows:
* Borehole Fluid: the influence of borehole fluid depends on its volume (i.e. hole size), the position of the tool, its density, and composition. Potassium chloride (KCl) in mud, for example, flows into permeable sections, resulting in an increase in gamma ray activity.
* Tubing, Casing, etc.: Their effect depend on the thickness, density, and nature of the materials (e.g. steel, aluminum). Steel reduces the gamma-ray level, but can be corrected once the density and thickness of the casing, cement sheath and borehole fluid are known.
* Cement: Its impact is determined by the type of cement, additives, density and thickness
* Bed Thickness: Gamma-ray reading does not reflect the true value in a bed with a thickness less than the diameter of the sphere of investigation. In a series of thin beds, the log reading is a volume average of the contributions within the sphere.
In addition, all radioactive phenomena are random in nature. Count rates vary about a mean value, and counts must be averaged over time to obtain a reasonable estimate of the mean. The longer the averaged period and the higher the count rate, the more precise the estimate.
Sample of corrections required for different gamma-ray tools are available from [https://web.archive.org/web/20071020141209/http://www.slb.com/content/services/resources/books/log_charts/gamma_ray.asp Schlumberger].
Gamma ray log interpretation show different peaks in well. Shale are represent the Sharp Peaks and its range is 40-140 API and contain the high amount of potassium. | 0 | Theoretical and Fundamental Chemistry |
Nanoparticle tracking analysis (NTA) is a method for visualizing and analyzing particles in liquids that relates the rate of Brownian motion to particle size. The rate of movement is related only to the viscosity and temperature of the liquid; it is not influenced by particle density or refractive index. NTA allows the determination of a size distribution profile of small particles with a diameter of approximately 10–1000 nanometers (nm) in liquid suspension.
The technique is used in conjunction with an ultramicroscope and a laser illumination unit that together allow small particles in liquid suspension to be visualized moving under Brownian motion. The light scattered by the particles is captured using a CCD or EMCCD camera over multiple frames. Computer software is then used to track the motion of each particle from frame to frame. The rate of particle movement is related to a sphere equivalent hydrodynamic radius as calculated through the Stokes–Einstein equation. The technique calculates particle size on a particle-by particle basis, overcoming inherent weaknesses in ensemble techniques such as dynamic light scattering. Since video clips form the basis of the analysis, accurate characterization of real time events such as aggregation and dissolution is possible. Samples require minimal preparation, minimizing the time required to process each sample. Speculators suggest that eventually the analysis may be done in real-time with no preparation, e.g. when detecting the presence of airborne viruses or biological weapons.
NTA currently operates for particles from about 10 to 1000 nm in diameter, depending on particle type. Analysis of particles at the lowest end of this range is possible only for particles composed of materials with a high refractive index, such gold and silver. The upper size limit is restricted by the limited Brownian motion of large particles; because a large particle moves very slowly, accuracy is diminished. The viscosity of the solvent also influences the movement of particles, and it, too, plays a part in determining the upper size limit for a specific system. | 0 | Theoretical and Fundamental Chemistry |
The structure of a protein-coding gene consists of many elements of which the actual protein coding sequence is often only a small part. These include introns and untranslated regions of the mature mRNA. Noncoding genes can also contain introns that are removed during processing to produce the mature functional RNA.
All genes are associated with regulatory sequences that are required for their expression. First, genes require a promoter sequence. The promoter is recognized and bound by transcription factors that recruit and help RNA polymerase bind to the region to initiate transcription. The recognition typically occurs as a consensus sequence like the TATA box. A gene can have more than one promoter, resulting in messenger RNAs (mRNA) that differ in how far they extend in the 5' end. Highly transcribed genes have "strong" promoter sequences that form strong associations with transcription factors, thereby initiating transcription at a high rate. Others genes have "weak" promoters that form weak associations with transcription factors and initiate transcription less frequently. Eukaryotic promoter regions are much more complex and difficult to identify than prokaryotic promoters.
Additionally, genes can have regulatory regions many kilobases upstream or downstream of the gene that alter expression. These act by binding to transcription factors which then cause the DNA to loop so that the regulatory sequence (and bound transcription factor) become close to the RNA polymerase binding site. For example, enhancers increase transcription by binding an activator protein which then helps to recruit the RNA polymerase to the promoter; conversely silencers bind repressor proteins and make the DNA less available for RNA polymerase.
The mature messenger RNA produced from protein-coding genes contains untranslated regions at both ends which contain binding sites for ribosomes, RNA-binding proteins, miRNA, as well as terminator, and start and stop codons. In addition, most eukaryotic open reading frames contain untranslated introns, which are removed and exons, which are connected together in a process known as RNA splicing. Finally, the ends of gene transcripts are defined by cleavage and polyadenylation (CPA) sites, where newly produced pre-mRNA gets cleaved and a string of ~200 adenosine monophosphates is added at the 3 end. The poly(A) tail protects mature mRNA from degradation and has other functions, affecting translation, localization, and transport of the transcript from the nucleus. Splicing, followed by CPA, generate the final mature mRNA, which encodes the protein or RNA product. Although the general mechanisms defining locations of human genes are known, identification of the exact factors regulating these cellular processes is an area of active research. For example, known sequence features in the 3-UTR can only explain half of all human gene ends.
Many noncoding genes in eukaryotes have different transcription termination mechanisms and they do not have poly(A) tails.
Many prokaryotic genes are organized into operons, with multiple protein-coding sequences that are transcribed as a unit. The genes in an operon are transcribed as a continuous messenger RNA, referred to as a polycistronic mRNA. The term cistron in this context is equivalent to gene. The transcription of an operon's mRNA is often controlled by a repressor that can occur in an active or inactive state depending on the presence of specific metabolites. When active, the repressor binds to a DNA sequence at the beginning of the operon, called the operator region, and represses transcription of the operon; when the repressor is inactive transcription of the operon can occur (see e.g. Lac operon). The products of operon genes typically have related functions and are involved in the same regulatory network. | 1 | Applied and Interdisciplinary Chemistry |
Two monosaccharides with equivalent molecular graphs (same chain length and same carbonyl position) may still be distinct stereoisomers, whose molecules differ in spatial orientation. This happens only if the molecule contains a stereogenic center, specifically a carbon atom that is chiral (connected to four distinct molecular sub-structures). Those four bonds can have any of two configurations in space distinguished by their handedness. In a simple open-chain monosaccharide, every carbon is chiral except the first and the last atoms of the chain, and (in ketoses) the carbon with the keto group.
For example, the triketose H(CHOH)(C=O)(CHOH)H (glycerone, dihydroxyacetone) has no stereogenic center, and therefore exists as a single stereoisomer. The other triose, the aldose H(C=O)(CHOH)H (glyceraldehyde), has one chiral carbon—the central one, number 2—which is bonded to groups −H, −OH, −C(OH)H, and −(C=O)H. Therefore, it exists as two stereoisomers whose molecules are mirror images of each other (like a left and a right glove). Monosaccharides with four or more carbons may contain multiple chiral carbons, so they typically have more than two stereoisomers. The number of distinct stereoisomers with the same diagram is bounded by 2, where c is the total number of chiral carbons.
The Fischer projection is a systematic way of drawing the skeletal formula of an acyclic monosaccharide so that the handedness of each chiral carbon is well specified. Each stereoisomer of a simple open-chain monosaccharide can be identified by the positions (right or left) in the Fischer diagram of the chiral hydroxyls (the hydroxyls attached to the chiral carbons).
Most stereoisomers are themselves chiral (distinct from their mirror images). In the Fischer projection, two mirror-image isomers differ by having the positions of all chiral hydroxyls reversed right-to-left. Mirror-image isomers are chemically identical in non-chiral environments, but usually have very different biochemical properties and occurrences in nature.
While most stereoisomers can be arranged in pairs of mirror-image forms, there are some non-chiral stereoisomers that are identical to their mirror images, in spite of having chiral centers. This happens whenever the molecular graph is symmetrical, as in the 3-ketopentoses H(CHOH)(CO)(CHOH)H, and the two halves are mirror images of each other. In that case, mirroring is equivalent to a half-turn rotation. For this reason, there are only three distinct 3-ketopentose stereoisomers, even though the molecule has two chiral carbons.
Distinct stereoisomers that are not mirror-images of each other usually have different chemical properties, even in non-chiral environments. Therefore, each mirror pair and each non-chiral stereoisomer may be given a specific monosaccharide name. For example, there are 16 distinct aldohexose stereoisomers, but the name "glucose" means a specific pair of mirror-image aldohexoses. In the Fischer projection, one of the two glucose isomers has the hydroxyl at left on C3, and at right on C4 and C5; while the other isomer has the reversed pattern. These specific monosaccharide names have conventional three-letter abbreviations, like "Glu" for glucose and "Thr" for threose.
Generally, a monosaccharide with n asymmetrical carbons has 2 stereoisomers. The number of open chain stereoisomers for an aldose monosaccharide is larger by one than that of a ketose monosaccharide of the same length. Every ketose will have 2 stereoisomers where n > 2 is the number of carbons. Every aldose will have 2 stereoisomers where n > 2 is the number of carbons.
These are also referred to as epimers which have the different arrangement of −OH and −H groups at the asymmetric or chiral carbon atoms (this does not apply to those carbons having the carbonyl functional group). | 0 | Theoretical and Fundamental Chemistry |
Many river systems are shaped by human activity and through anthropogenic forces. The process of human influence on nature, including rivers, is stated with the beginning of the Anthropocene, which has replaced the Holocene. This long-term impact is analyzed and explained by a wide range of sciences and stands in an interdisciplinary context. The natural water cycle and stream flow is globally influenced and linked to global interconnections. Rivers are an essential component of the terrestrial realm and have been a preferable location for human settlements during history. River is the main expression used for river channels themselves, riparian zones<nowiki/>, floodplains<nowiki/> and terraces, adjoining uplands dissected by lower channels and river deltas<nowiki/>. | 1 | Applied and Interdisciplinary Chemistry |
UV disinfection is most effective for treating high-clarity, purified reverse osmosis distilled water. Suspended particles are a problem because microorganisms buried within particles are shielded from the UV light and pass through the unit unaffected. However, UV systems can be coupled with a pre-filter to remove those larger organisms that would otherwise pass through the UV system unaffected. The pre-filter also clarifies the water to improve light transmittance and therefore UV dose throughout the entire water column. Another key factor of UV water treatment is the flow rate—if the flow is too high, water will pass through without sufficient UV exposure. If the flow is too low, heat may build up and damage the UV lamp.
A disadvantage of UVGI is that while water treated by chlorination is resistant to reinfection (until the chlorine off-gasses), UVGI water is not resistant to reinfection. UVGI water must be transported or delivered in such a way as to avoid reinfection. | 0 | Theoretical and Fundamental Chemistry |
Genes interact in the sense that they affect each others function. For instance, a mutation may be harmless, but when it is combined with another mutation, the combination may turn out to be lethal. Such genes are said to "interact genetically". Genes that are connected in such a way form genetic interaction networks. Some of the goals of these networks are: develop a functional map of a cells processes, drug target identification using chemoproteomics, and to predict the function of uncharacterized genes.
In 2010, the most "complete" gene interactome produced to date was compiled from about 5.4 million two-gene comparisons to describe "the interaction profiles for ~75% of all genes in the budding yeast", with ~170,000 gene interactions. The genes were grouped based on similar function so as to build a functional map of the cells processes. Using this method the study was able to predict known gene functions better than any other genome-scale data set as well as adding functional information for genes that hadnt been previously described. From this model genetic interactions can be observed at multiple scales which will assist in the study of concepts such as gene conservation. Some of the observations made from this study are that there were twice as many negative as positive interactions, negative interactions were more informative than positive interactions, and genes with more connections were more likely to result in lethality when disrupted. | 1 | Applied and Interdisciplinary Chemistry |
Inner sphere electron transfer (IS ET) or bonded electron transfer is a redox chemical reaction that proceeds via a covalent linkage—a strong electronic interaction—between the oxidant and the reductant reactants. In inner sphere electron transfer, a ligand bridges the two metal redox centers during the electron transfer event. Inner sphere reactions are inhibited by large ligands, which prevent the formation of the crucial bridged intermediate. Thus, inner sphere ET is rare in biological systems, where redox sites are often shielded by bulky proteins. Inner sphere ET is usually used to describe reactions involving transition metal complexes and most of this article is written from this perspective. However, redox centers can consist of organic groups rather than metal centers.
The bridging ligand could be virtually any entity that can convey electrons. Typically, such a ligand has more than one lone electron pair, such that it can serve as an electron donor to both the reductant and the oxidant. Common bridging ligands include the halides and the pseudohalides such as hydroxide and thiocyanate. More complex bridging ligands are also well known including oxalate, malonate, and pyrazine. Prior to ET, the bridged complex must form, and such processes are often highly reversible. Electron transfer occurs through the bridge once it is established. In some cases, the stable bridged structure may exist in the ground state; in other cases, the bridged structure may be a transiently-formed intermediate, or else as a transition state during the reaction.
The alternative to inner sphere electron transfer is outer sphere electron transfer. In any transition metal redox process, the mechanism can be assumed to be outer sphere unless the conditions of the inner sphere are met. Inner sphere electron transfer is generally enthalpically more favorable than outer sphere electron transfer due to a larger degree of interaction between the metal centers involved, however, inner sphere electron transfer is usually entropically less favorable since the two sites involved must become more ordered (come together via a bridge) than in outer sphere electron transfer. | 0 | Theoretical and Fundamental Chemistry |
The most known methods used in microanalysis include:
* Most of the spectroscopy methods: ultraviolet–visible spectroscopy, infrared spectroscopy, nuclear magnetic resonance, X-ray fluorescence, Energy-dispersive X-ray spectroscopy, Wavelength-dispersive X-ray spectroscopy, and mass spectrometry
* Most of the chromatography methods : high-performance liquid chromatography, Gel permeation chromatography;
* Some thermal analysis methods: differential scanning calorimetry, thermogravimetric analysis;
* Electrophoresis;
* Field flow fractionation;
* X-ray diffraction;
* Combustion analysis. | 0 | Theoretical and Fundamental Chemistry |
* The Charlotte, North Carolina Mint – 1835 to 1861. After the Civil War, the plant was reopened in 1868 as an assay office until 1913, when it was ultimately closed.
* The New Orleans, Louisiana Mint – 1835 to 1942. Coinage operations were conducted here from 1838, but were suspended from 1861 until 1879; assay functions were performed from 1876. Coinage resumed in 1879 and continued until 1909. The facility operated as an assay office from 1909 until 1942, when it was closed.
* The U.S. Assay Office, St. Louis, Missouri – 1881 to 1911
* The U.S. Assay Office, Helena, Montana – 1874 to 1933
* The U.S. Assay Office, Salt Lake City, Utah – 1909 to 1933
* The U.S. Assay Office, Deadwood, South Dakota – 1898 to 1927
* The U.S. Assay Office, Boise, Idaho – 1869 to 1933
* The U.S. Assay Office, New York, New York – 1854 to 1982
* The U.S. Assay Office, Seattle, Washington – 1898 to 1955 | 0 | Theoretical and Fundamental Chemistry |
This effect occurs with class-a metals such as iron(II). The Cyclopentadienyl complex (CH)Fe(CO)(SCN) is an example of chemical symbiosis. The cyclopentadienyl directs the thiocyanate to bond through its softer Sulphur donor. A more definitive example are the halopentamminocobalt(III) ions, Co(NH)X, which are more stable when the halogen, X, is fluoride than with iodide, and the halopentcyanocobalt(III) ions, Co(CN)X, which are most stable when the halogen is iodine. | 0 | Theoretical and Fundamental Chemistry |
There are two types of pumps available for uniform delivery of relatively small liquid volumes for GPC: piston or peristaltic pumps. The delivery of a constant flow free of fluctuations is especially important to the precision of the GPC analysis, as the flow-rate is used for the calibration of the molecular weight, or diameter. | 0 | Theoretical and Fundamental Chemistry |
Preliminary treatment (sometimes called pretreatment) removes coarse materials that can be easily collected from the raw sewage before they damage or clog the pumps and sewage lines of primary treatment clarifiers. | 1 | Applied and Interdisciplinary Chemistry |
Organisms that rely on light energy to fix carbon, and thus participate in primary production, are referred to as photoautotrophs.
Photoautotrophs exists across the tree of life. Many bacterial taxa are known to be photoautotrophic such as cyanobacteria and some Pseudomonadota (formerly proteobacteria). Eukaryotic organisms gained the ability to participate in photosynthesis through the development of plastids derived from endosymbiotic relationships. Archaeplastida, which includes red algae, green algae, and plants, have evolved chloroplasts originating from an ancient endosymbiotic relationship with an Alphaproteobacteria. The productivity of plants, while being photoautotrophs, is also dependent on factors such as salinity and abiotic stressors from the surrounding environment. The rest of the eukaryotic photoautotrophic organisms are within the SAR clade (Comprising Stramenopila, Alveolata, and Rhizaria). Organisms in the SAR clade that developed plastids did so through a secondary or a tertiary endosymbiotic relationships with green algae and/or red algae. The SAR clade includes many aquatic and marine primary producers such as Kelp, Diatoms, and Dinoflagellates. | 0 | Theoretical and Fundamental Chemistry |
Culminating in the 1930s, the British chemists Christopher Ingold and Robert Robinson among others had investigated the mechanisms of organic reactions, and had come up with empirical rules which could predict reactivity of organic molecules. Woodward was perhaps the first synthetic organic chemist who used these ideas as a predictive framework in synthesis. Woodward's style was the inspiration for the work of hundreds of successive synthetic chemists who synthesized medicinally important and structurally complex natural products. | 0 | Theoretical and Fundamental Chemistry |
Amines are the most prevalent absorbent in postcombustion carbon capture technology today. In particular, monoethanolamine (MEA) has been used in industrial scales in postcombustion carbon capture, as well as in other CO separations, such as "sweetening" of natural gas. However, amines are corrosive, degrade over time, and require large industrial facilities. Ionic liquids on the other hand, have low vapor pressures . This property results from their strong Coulombic attractive force. Vapor pressure remains low through the substance's thermal decomposition point (typically >300 °C). In principle, this low vapor pressure simplifies their use and makes them "green" alternatives. Additionally, it reduces risk of contamination of the CO gas stream and of leakage into the environment.
The solubility of CO in ionic liquids is governed primarily by the anion, less so by the cation. The hexafluorophosphate (PF) and tetrafluoroborate (BF) anions have been shown to be especially amenable to CO capture.
Ionic liquids have been considered as solvents in a variety of liquid-liquid extraction processes, but never commercialized. Beside that, ionic liquids have replaced the conventional volatile solvents in industry such as absorption of gases or extractive distillation. Additionally, ionic liquids are used as co-solutes for the generation of aqueous biphasic systems, or purification of biomolecules. | 0 | Theoretical and Fundamental Chemistry |
PDE5 inhibitors have shown promise in the treatment of heart failure with reduced ejection fraction through several beneficial effects on lung vasculature, cardiac remodelling and diastolic function. A study showed that effective treatment of pulmonary arterial hypertension with sildenafil improved functional capacity and reduced right ventricular mass in patients. The effects on right ventricular remodeling were significantly greater in comparison with the non-selective endothelial receptor antagonist bosentan. However, PDE5 inhibitors may be harmful in patients with heart failure with preserved ejection fraction due to potential negative inotropic effects. | 1 | Applied and Interdisciplinary Chemistry |
In gel electrophoresis proteins are normally separated by charge, size, or shape. The aim of isoelectric focusing (IEF), for example, is to separate proteins according to their isoelectric point (pI), thus, according to their charge at different pH values. Here, a similar mechanism is accomplished in a commercially available electrophoresis chamber (cf. fig. Equipment) for separating charged biomolecules, for example, superoxide dismutase (SOD) or allergens, at constant pH conditions and different velocities of migration depending on different isoelectric points of zwitterions. The separated (metal) proteins elute sequentially, starting with the lowest (pI > 2–4) and ending with the highest pI (pI < 10.0) of the dissolved protein molecules to be analyzed.
Due to the specific properties of the prepared gel and electrophoresis buffer solution which is basic and contains Tris-HCl and NaN, most proteins of a biological system (e.g., Helicobacter pylori) are charged negatively in the solution, and will migrate from the cathode to the anode due to the electric field. In general, reaction equation (1) shows that the carboxyl side group of a proteinogenic amino acid is negatively charged, equation (2) that the amino side groups are electrically neutral under these conditions:
(1) R-COOH + OH → R-COO + HO
(2) R-NH + OH → R-NH + HO
At the anode, electrochemically-generated hydrogen ions react with Tris molecules to form monovalent Tris ions (3). The positively charged Tris ions migrate through the gel to the cathode where they neutralise hydroxide ions to form Tris molecules and water (4):
(3) (HOCH)CNH + H → [(HOCH)CNH]
(4) [(HOCH)CNH] + OH → (HOCH)CNH + HO
Thus, the Tris-based buffering mechanism causes a constant pH in the continuous buffer system with a high buffer capacity.
At 25 °C Tris buffer has an effective pH range between 7.5 and 9.0. Under the conditions given here (addressing the concentration of buffer components, buffering mechanism, pH and temperature) the effective pH is shifted in the range of about 10.0 to 10.5. Native buffer systems all have low conductivity and range in pH from 3.8 to 10.2. Continuous native buffer systems are thus used to separate proteins according their pI.
Although the pH value (10.00) of the electrophoresis buffer does not correspond to a physiological pH value within a cell or tissue type, the separated ring-shaped protein bands are eluted continuously into a physiological buffer solution (pH 8.00) and isolated in different fractions (cf. fig. Electropherogram). Provided that irreversible denaturation cannot be demonstrated by an independent procedure, most protein molecules are stable in aqueous solution, at pH values from 3 to 10 if the temperature is below 50 °C. As the Joule heat and temperature generated during electrophoresis may exceed 50 °C, and thus have a negative impact on the stability and migration behavior of proteins in the gel, the separation system, consisting of the electrophoresis chamber, fraction collector and other devices, is cooled in a refrigerator at 4 °C, thus greatly reducing the risk of heat convection currents. Overheating of the gel is impeded by internal cooling circuit of the gel column as an integrated part of the electrophoresis chamber and by generating a constant power by the power supply (cf. fig. Equipment). | 0 | Theoretical and Fundamental Chemistry |
On the cost side of pesticide use there can be costs to the environment and costs to human health. Pesticides safety education and pesticide applicator regulation are designed to protect the public from pesticide misuse, but do not eliminate all misuse. Reducing the use of pesticides and choosing less toxic pesticides may reduce risks placed on society and the environment from pesticide use. | 1 | Applied and Interdisciplinary Chemistry |
There is significant overlap in function with regards to some of these proteins. In particular, the Rho-related genes are important in nuclear trafficking (i.e.: mitosis) as well as with mobility along the cytoskeleton in general. These genes of particular interest in cancer research.
*ARHGAP35
*ARHGAP5
*ARHGDIA
*ARHGEF10L Rho guanine nucleotide exchange factor 10L
*ARHGEF11 Rho guanine nucleotide exchange factor 11
*ARHGEF40 Rho guanine nucleotide exchange factor 40
*ARHGEF7 Rho guanine nucleotide exchange factor 7
*RAB10 NM_016131 The small GTPases Rab are key regulators of intracellular membrane trafficking, from the formation of transport vesicles to their fusion with membranes
*RAB11A NM_004663
*RAB11B NM_004218
*RAB14 NM_016322
*RAB18 NM_021252
*RAB1A NM_004161 Homo sapiens RAB1A, member RAS oncogene family (RAB1A), mRNA
*RAB1B NM_030981
*RAB21 NM_014999
*RAB22A NM_020673
*RAB2A NM_002858
*RAB2B NM_001163380
*RAB3GAP1 NM_012233
*RAB3GAP2 NM_012414
*RAB40C NM_021168
*RAB4A NM_004578
*RAB5A NM_004162
*RAB5B NM_002865
*RAB5C NM_004583
*RAB6A NM_002868
*RAB7A NM_004637
*RAB9A NM_004251
*RABEP1 NM_004703
*RABEPK NM_005833
*RABGEF1 NM_014504
*RABGGTA NM_004581
*RABGGTB NM_004582
*CENPB Centromere protein B
*CTBP1 Centromere protein T
*CCNB1IP1 NM_021178 E3 ubiquitin-protein ligase. Modulates cyclin B levels and participates in the regulation of cell cycle progression through the G2 phase
*CCNDBP1 NM_012142 May negatively regulate cell cycle progression
*CCNG1 NM_004060 May play a role in growth regulation
*CCNH NM_001239 Involved in cell cycle control and in RNA transcription by RNA polymerase II. Its expression and activity are constant throughout the cell cycle
*CCNK NM_001099402 Regulatory subunit of cyclin-dependent kinases that mediates phosphorylation of the large subunit of RNA polymerase II
*CCNL1 NM_020307 Transcriptional regulator which participates in regulating the pre-mRNA splicing process
*CCNL2 NM_030937 Transcriptional regulator which participates in regulating the pre-mRNA splicing process. Also modulates the expression of critical apoptotic factor, leading to cell apoptosis.
*CCNY NM_145012 Positive regulatory subunit of the cyclin-dependent kinases CDK14/PFTK1 and CDK16. Acts as a cell-cycle regulator of Wnt signaling pathway during G2/M phase
*PPP1CA NM_002708 Protein phosphatase that associates with over 200 regulatory proteins to form highly specific holoenzymes which dephosphorylate hundreds of biological targets
*PPP1CC NM_002710
*PPP1R10 NM_002714
*PPP1R11 NM_021959 Homo sapiens protein phosphatase 1, regulatory (inhibitor) subunit 11 (PPP1R11),
*PPP1R15B NM_032833
*PPP1R37 NM_019121
*PPP1R7 NM_002712
*PPP1R8 NM_002713
*PPP2CA NM_002715
*PPP2CB NM_001009552
*PPP2R1A NM_014225 Negative regulator of growth and cell divisionHomo sapiens protein phosphatase 2 (formerly 2A), regulatory subunit A (PR 65),
*PPP2R2A NM_002717
*PPP2R2D NM_018461
*PPP2R3C NM_017917
*PPP2R4 NM_021131
*PPP2R5A NM_006243
*PPP2R5B NM_006244
*PPP2R5C NM_002719
*PPP2R5D NM_006245
*PPP2R5E NM_006246
*PPP4C NM_002720
*PPP4R1 NM_005134
*PPP4R2 NM_174907
*PPP5C NM_006247
*PPP6C NM_002721
*PPP6R2 NM_014678
*PPP6R3 NM_018312
*RAD1Homo sapiens ribonuclease/angiogenin inhibitor (RNH), mRNA
*RAD17 NM_002869 Essential for sustained cell growth, maintenance of chromosomal stability, and ATR-dependent checkpoint activation upon DNA damage
*RAD23B NM_002873
*RAD50 NM_005732
*RAD51C NM_002874
*IST1 (locates to central dividing line of dividing cells) | 1 | Applied and Interdisciplinary Chemistry |
Because of their wide needs, the overall chelating agents growth was 4 % annually during 2009-2014 and the trend is likely to increase. Aminopolycarboxylic acids chelators are the most widely consumed chelating agents; however, the percentage of the greener alternative chelators in this category continues to grow. The consumption of traditional aminopolycarboxylates chelators, in particular the EDTA (ethylenediaminetetraacetic acid) and NTA (nitrilotriacetic acid), is declining (–6% annually), because of the persisting concerns over their toxicity and negative environmental impact. In 2013, these greener alternative chelants represented approximately 15% of the total aminopolycarboxylic acids demand. This is expected to rise to around 21% by 2018, replacing and aminophosphonic acids used in cleaning applications. Examples of some Greener alternative chelating agents include ethylenediamine disuccinic acid (EDDS), polyaspartic acid (PASA), methylglycinediacetic acid (MGDA), glutamic diacetic acid (L-GLDA), citrate, gluconic acid, amino acids, plant extracts etc. | 0 | Theoretical and Fundamental Chemistry |
A program licensed and promoted by the Maine Department of Environmental Protection that provided free municipal wastewater sludge (biosolids) to farmers as fertilizer has resulted in PFAS contamination of local drinking water and farm-grown produce. | 0 | Theoretical and Fundamental Chemistry |
Extending the wavelength range for CD experiments had been both considered and instigated as far back as 1970. Three research groups had created their own "in-house" CD machines, with specialist lamps as their light source, to enable measurements in this range. Synchrotron radiation (SR) had been proposed for use as the light source at a meeting in Brookhaven National Laboratory on Long Island in 1972, however, it took a few years more before this came to fruition. Two research papers in 1980 reported the collection of CD data using SR as the light source for the experiments. Specifically, spectra were obtained in wavelength regions into the VUV range, from ~100 nanometers (nm) to ~200 nm, largely unavailable to laboratory-based bench-top spectrophotometers. Sutherland et. al. focussed on the development of a versatile spectrophotometer capable of measuring CD, amongst other properties, in the VUV region of the spectrum, while Snyder and Rowe collected CD data from a small organic compound in the wavelength range 130.5 nm to 205 nm. | 0 | Theoretical and Fundamental Chemistry |
A third perspective is chemistry education research (CER). CER is a type of discipline-based education research (DBER) focusing on the teaching and learning of chemistry. An overarching goal for chemistry education researchers is to help students develop expert-like (coherent and useful) knowledge of chemistry. Thus, the field of CER involves investigating:
* how students construct their understanding of chemical phenomena and develop practical skills relevant to the discipline;
* how CER findings can inform curriculum design, e.g. by suggesting certain learning objectives and instructional approaches;
and developing instruments to measure the above.
Following the example of physics education research (PER), CER tends to take the theories and methods developed in pre-college science education research, which generally takes place in Schools of Education, and applies them to understanding comparable problems in post-secondary settings (in addition to pre-college settings). Like science education researchers, CER practitioners tend to study the teaching practices of others as opposed to focusing on their own classroom practices. Chemistry education research is typically carried out in situ using human subjects from secondary and post-secondary schools. Chemistry education research utilizes both quantitative and qualitative data collection methods. Quantitative methods typically involve collecting data that can then be analyzed using various statistical methods. Qualitative methods include interviews, observations, document analysis, journaling, and other methods common to social science research. | 1 | Applied and Interdisciplinary Chemistry |
Certain lachrymatory agents, most notably tear gas, are often used by police to force compliance. In some countries (e.g., Finland, Australia, and United States), another common substance is mace. The self-defense weapon form of mace is based on pepper spray which comes in small spray cans. Versions including CS are manufactured for police use. Xylyl bromide, CN and CS are the oldest of these agents. CS is the most widely used. CN has the most recorded toxicity.
Typical manufacturer warnings on tear gas cartridges state "Danger: Do not fire directly at person(s). Severe injury or death may result." Tear gas guns do not have a manual setting to adjust the range of fire. The only way to adjust the projectile's range is to aim towards the ground at the correct angle. Incorrect aim will send the capsules away from the targets, causing risk for non-targets instead. | 1 | Applied and Interdisciplinary Chemistry |
The expansion of the corrosion products (iron oxides) of carbon steel reinforcement structures may induce internal mechanical stress (tensile stress) that cause the formation of cracks and disrupt the concrete structure. If rebars have been improperly installed or have inadequate concrete cover at surfaces exposed to the elements, oxide jacking and spalling can occur during the structures lifetime: flat fragments of concrete are detached from the concrete mass as a result of the rebars corrosion.
Concrete, like most consolidated hard rocks, is a material very resistant to compression but which cannot withstand tension, especially internal tensions. Its tensile strength is about 10 times lower than its compressive strength. In itself carbonated concrete is a very solid material because its compressive strength increases due to its porosity decrease by the precipitation of calcium carbonate (calcite, ). In the absence of steel reinforcement bars and without the formation of expansive reaction products inducing tensile stress inside the concrete matrix, pure concrete is most often a long-lasting material. An illustration of the concrete intrinsic durability is the dome of the Pantheon building in Rome made with Roman concrete more than 2000 years ago.
When atmospheric carbon dioxide (), or carbonate ions (, dissolved in water) diffuse into concrete from its external surface, they react with calcium hydroxide (portlandite, ) and the pH of the concrete pore water progressively decreases from 13.5 – 12.5 to 8.5 (pH of water in equilibrium with calcite). Below a pH value of about 9.5 – 10, the solubility of iron oxides present at the surface of carbon steel increases and they start to dissolve. As a consequence, they no longer protect the underlying metallic iron against oxidation by atmospheric oxygen and the reinforcement bars are no longer passivated against corrosion. It is the considerable forces internally created by the expansion of the iron corrosion products (about 6 – 7 times less dense than metallic iron, so 6 – 7 times more voluminous) that cause the cracks in the concrete matrix and destroy reinforced concrete. In the absence of iron (and without some harmful chemical degradation reactions also producing expansive products) concrete would probably be one of the most durable materials. However, steel reinforcement bars are necessary to take over the tensile efforts to which concrete is submitted in most engineering structures and stainless steel would be too costly a metal to replace carbon steel. Zinc-galvanization or epoxy-coating can improve the corrosion resistance of rebar, but have also other disadvantages such as their lower surface adhesion to concrete (risk of slip), the possible formation of cathodic and anodic zones conducive to galvanic corrosion if the protective coating is locally punctured or damaged, and their higher costs. | 1 | Applied and Interdisciplinary Chemistry |
A case–control study of hospitalized patients found that the blood plasma levels of CMTM5 protein and CMTM5 messenger RNA (i.e. mRNA) in 350 patients with coronary artery disease were significantly higher than a matched group of 350 patients without this disease. The same research group similarly studied 124 hospitalized patients who had in place a coronary artery stent. They found that high blood plasma levels of CMTM5 mRNA were associated with a higher rate of subsequently developing stenosis (i.e. narrowing) in their stents than patients with lower levels of this mRNA. Furthermore, the forced overexpression of the CMTM5 gene inhibited the proliferation and migration of cultured human endothelial cells, while the forced suppression of the CMTM5 gene promote the proliferation of these cells. These studies suggest that the CMTM5 gene, one of its mRNAs, and/or one of its CMTM5 proteins may promote atherosclerosis-based coronary artery disease and the stenosis of coronary artery stents and do so by inhibiting vascular endothelial cells from functioning to inhibit atherosclerosis and stent occlusion. More studies are necessary to confirm and further define these relationships; to determine if expression of the CMTM5 gene's or its products can be used as makers for patient susceptibilities to coronary artery/stent occlusions; and to determine if this gene or its products can be used clinically as targets for preventing or decreasing the frequency of these occlusions. | 1 | Applied and Interdisciplinary Chemistry |
Photolytic producers are similar to phototrophs, but source hydrogen from water molecules that are broken down as the organism interacts with light. Photolytic producers consist of algae and certain photosynthetic bacteria.
(algae)
(photolytic bacteria) | 1 | Applied and Interdisciplinary Chemistry |
The starting reactants for these reactions are hydrogen cyanide (HCN) as well as HCN derivatives and acetylene. Both of these are hypothesized to be present on the early Earth. The conditions this reaction occurs in are a relatively moderate temperature of 35 degrees C and in anoxic or oxygen free conditions. The early Earth was anoxic before the great oxidation event, making these conditions plausible. In the laboratory synthesis, a neutral phosphate buffer was used to maintain a stable, neutral pH. hydrogen sulfide (H2S) is used as a reductant in these reactions. The reactions are driven forward by ultraviolet radiation and catalyzed by Cu(I)-Cu(II) photoredox cycling. Some compounds in the system perform multiple roles. For example, phosphate serves as a buffer to maintain a neutral pH, acts as a catalyst in the synthesis of 2-aminooxazole and urea and serves as a reagent in the formation of glycerol-3-phosphate and ribonucleotides. The mechanisms involved in these reactions include reductive homologation processes to build larger, more complex molecules from the simple starting materials. The products of this reaction include the precursors of many amino acids, the precursors of lipids, and ribonucleotides. It is worth noting that most of the prebiotic monomers are not synthesized in their entirety by these reactions, only their precursors. The amino acid precursors would then be produced by Strecker synthesis reactions. Cyanosulfidic metabolism also does produce the precursors of both purines and pyrimidines ribonucleotides simultaneously. Many of the compounds produced also include intermediates in one-carbon metabolism. | 0 | Theoretical and Fundamental Chemistry |
Nuclear magnetic resonance (NMR) in porous materials covers the application of using NMR as a tool to study the structure of porous media and various processes occurring in them. This technique allows the determination of characteristics such as the porosity and pore size distribution, the permeability, the water saturation, the wettability, etc. | 0 | Theoretical and Fundamental Chemistry |
Tungsten plays a large and indispensable role in modern high-tech industry. Up to 500,000 tons of raw tungsten ore are mined each year by Wolfram Bergbau und Hütten AG (WHB)in Felbertal, Austria, which is the largest scheelite deposit in Europe. 25% of the run-of-mine ore are separated as waste before entering the mill. | 0 | Theoretical and Fundamental Chemistry |
Triple disc rolling contact fatigue (RCF) Rig is a specialised testing apparatus used in the field of tribology and materials science to evaluate the fatigue resistance and durability of materials subjected to rolling contact. This rig is designed for simulating the conditions encountered in various mechanical systems, such as rolling bearings, gears, and other components exposed to repeated rolling and sliding motions. The rig typically consists of three discs or rollers arranged in a specific configuration. These discs can represent the interacting components of interest, such as a rolling bearing. The rig also allows precise control over the loading conditions, including the magnitude of the load, contact pressure, and contact geometry.
PCS Instruments Micro-pitting Rig (MPR) is a specialised testing instrument used in the field of tribology and mechanical engineering to study micro-pitting, a type of surface damage that occurs in lubricated rolling and sliding contact systems. The MPR is designed to simulate real-world operating conditions by subjecting test specimens, often gears or rolling bearings, to controlled rolling and sliding contact under lubricated conditions. | 1 | Applied and Interdisciplinary Chemistry |
*1 kg/m = 1 g/L (exactly)
*1 kg/m = 0.001 g/cm (exactly)
*1 kg/m ≈ 0.06243 lb/ft (approximately)
*1 kg/m ≈ 0.1335 oz/US gal (approximately)
*1 kg/m ≈ 0.1604 oz/imp gal (approximately)
*1 g/cm = 1000 kg/m (exactly)
*1 lb/ft ≈ 16.02 kg/m (approximately)
*1 oz/(US gal) ≈ 7.489 kg/m (approximately)
*1 oz/(imp gal) ≈ 6.236 kg/m (approximately) | 0 | Theoretical and Fundamental Chemistry |
In vitro fertilization involves removing eggs from a woman, collecting sperm from a man, fertilizing the egg with the sperm, allowing the fertilized egg to form a blastocyst, and then transferring the blastocyst into the uterus. MRT involves an additional egg from a third person, and manipulation of both the recipient egg and the donor egg.
As of 2016 there were three MRT techniques in use: maternal spindle transfer (MST); pronuclear transfer (PNT); and the newest technique, polar body transfer (PBT). The original technique, in which mitochondria-containing cytoplasm taken from a donor egg is simply injected into the recipient egg, is no longer used.
In maternal spindle transfer, an oocyte is removed from the recipient, and when it is in the metaphase II stage of cell division, the spindle-chromosome complex is removed; some of the cytoplasm comes with it, so some mitochondria are likely to be included. The spindle-chromosome complex is inserted into a donor oocyte from which the nucleus has already been removed. This egg is fertilized with sperm and allowed to form a blastocyst, which can then be investigated with preimplantation genetic diagnosis to check for mitochondrial mutations, prior to being implanted in the recipient's uterus.
In pronuclear transfer, an oocyte is removed from the recipient and fertilized with sperm. The donor oocyte is fertilized with sperm from the same person. The male and female pronuclei are removed from each fertilized egg prior to their fusing, and the pronuclei from the recipients fertilized egg are inserted into the fertilized egg from the donor. As with MST, a small amount of cytoplasm from the recipient egg may be transferred, and as with MST, the fertilized egg is allowed to form a blastocyst, which can then be investigated with preimplantation genetic diagnosis to check for mitochondrial mutations before being implanted in the recipients uterus.
In polar body transfer, a polar body (a small cell with very little cytoplasm that is created when an egg cell divides) from the recipient is used in its entirety, instead of using nuclear material extracted from the recipients normal egg; this can be used in either MST or PNT. This technique was first published in 2014 and as of 2015 it had not been consistently replicated, but is considered promising as there is a greatly reduced chance for transmitting mitochondria from the recipient because polar bodies contain very few mitochondria, and it does not involve extracting material from the recipients egg. | 1 | Applied and Interdisciplinary Chemistry |
Other work has focused on predicting the gene expression levels in a gene regulatory network. The approaches used to model gene regulatory networks have been constrained to be interpretable and, as a result, are generally simplified versions of the network. For example, Boolean networks have been used due to their simplicity and ability to handle noisy data but lose data information by having a binary representation of the genes. Also, artificial neural networks omit using a hidden layer so that they can be interpreted, losing the ability to model higher order correlations in the data. Using a model that is not constrained to be interpretable, a more accurate model can be produced. Being able to predict gene expressions more accurately provides a way to explore how drugs affect a system of genes as well as for finding which genes are interrelated in a process. This has been encouraged by the DREAM competition which promotes a competition for the best prediction algorithms. Some other recent work has used artificial neural networks with a hidden layer. | 1 | Applied and Interdisciplinary Chemistry |
It is category A in Australia meaning that no evidence of harm has been found after being taken by many pregnant women. Use during breast feeding is generally safe. | 0 | Theoretical and Fundamental Chemistry |
The resulting flow from applying a voltage is a plug flow. Unlike a parabolic profile flow generated from a pressure differential, a plug flow’s velocity profile is approximately planar, with slight variation near the electric double layer. This offers significantly less deleterious dispersive effects and can be controlled without valves, offering a high-performance method for fluid separation, although many complex factors prove this control to be difficult. Because of difficulties measuring and monitoring flow in microfluidic channels, primarily disrupting the flow pattern, most analysis is done through numerical methods and simulation.
Electroosmotic flow through microchannels can be modeled after the Navier-Stokes equation with the driving force deriving from the electric field and the pressure differential. Thus it is governed by the continuity equation
and momentum
where is the velocity vector, is the density of the fluid, is the material derivative, is the viscosity of the fluid, is the electric charge density, is the applied electric field, is the electric field due to the zeta potential at the walls and is the fluid pressure.
Laplace’s equation can describe the external electric field
while the potential within the electric double layer is governed by
where is the dielectric constant of the electrolyte solution and is the vacuum permittivity. This equation can be further simplified using the Debye-Hückel approximation
where is the Debye length, used to describe the characteristic thickness of the electric double layer. The equations for potential field within the double layer can be combined as
The transport of ions in space can be modeled using the Nernst–Planck equation:
Where is the ion concentration, is the magnetic vector potential, is the diffusivity of the chemical species, is the valence of ionic species, is the elementary charge, is the Boltzmann constant, and is the absolute temperature. | 0 | Theoretical and Fundamental Chemistry |
Metal quenching is a transient heat transfer process in terms of the time temperature transformation (TTT). It is possible to manipulate the cooling process to adjust the phase of a suitable material. For example, appropriate quenching of steel can convert a desirable proportion of its content of austenite to martensite, creating a very hard and strong product. To achieve this, it is necessary to quench at the "nose" (or eutectic) of the TTT diagram. Since materials differ in their Biot numbers, the time it takes for the material to quench, or the Fourier number, varies in practice. In steel, the quenching temperature range is generally from 600 °C to 200 °C. To control the quenching time and to select suitable quenching media, it is necessary to determine the Fourier number from the desired quenching time, the relative temperature drop, and the relevant Biot number. Usually, the correct figures are read from a standard nomogram. By calculating the heat transfer coefficient from this Biot number, one can find a liquid medium suitable for the application. | 1 | Applied and Interdisciplinary Chemistry |
In bacteria, where two-component signaling is extremely common, about 25% of known histidine kinases are of the hybrid type. Two-component systems are much rarer in archaea and eukaryotes, and occur in lower eukaryotes and in plants but not in metazoans. Among known examples, most if not all eukaryotic two-component systems are hybrid kinase phosphorelays.
A bioinformatic census of bacterial genomes found large variations in the number of (monomeric) HPt domains identified in different bacterial phyla, with some genomes encoding no HPts at all. Relative to the number of histidine kinase and response regulators present in a genome, eukaryotes have more identifiable HPt domains than bacteria. In fungi, the genomic inventory of HPt proteins varies, with filamentous fungi generally possessing more HPt proteins than yeasts; only one is encoded in the well-characterized Saccharomyces cerevisiae genome. Plants generally have more than one HPt, but fewer HPts than response regulators. | 1 | Applied and Interdisciplinary Chemistry |
The Hepatitis C virus requires the CD81 co-receptor for infection. Studies suggest that the tight junction protein Claudin-1 (CLDN1) may also play a part in HCV entry. Claudin family abnormalities are also common in hepatocellular carcinoma, which can result from HPV infection. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, photoisomerization is molecular behavior in which structural change between isomers is caused by photoexcitation. Both reversible and irreversible photoisomerization reactions exist. However, the word "photoisomerization" usually indicates a reversible process. Photoisomerizable molecules are already put to practical use, for instance, in pigments for rewritable CDs, DVDs, and 3D optical data storage solutions. In addition, recent interest in photoisomerizable molecules has been aimed at molecular devices, such as molecular switches, molecular motors, and molecular electronics.
Photoisomerization behavior can be roughly categorized into several classes. Two major classes are trans-cis (or E-Z) conversion, and open-closed ring transition. Examples of the former include stilbene and azobenzene. This type of compounds has a double bond, and rotation or inversion around the double bond affords isomerization between the two states. Examples of the latter include fulgide and diarylethene. This type of compounds undergoes bond cleavage and bond creation upon irradiation with particular wavelengths of light. Still another class is the di-π-methane rearrangement. | 0 | Theoretical and Fundamental Chemistry |
Heat can flow into or out of a closed system by way of thermal conduction or of thermal radiation to or from a thermal reservoir, and when this process is effecting net transfer of heat, the system is not in thermal equilibrium. While the transfer of energy as heat continues, the system's temperature can be changing. | 0 | Theoretical and Fundamental Chemistry |
As early as 1754, the Swiss mathematician Leonhard Euler (1707–1783) speculated about the possibility of cavitation. In 1859, the English mathematician William Henry Besant (1828–1917) published a solution to the problem of the dynamics of the collapse of a spherical cavity in a fluid, which had been presented by the Anglo-Irish mathematician George Stokes (1819–1903) as one of the Cambridge [University] Senate-house problems and riders for the year 1847. In 1894, Irish fluid dynamicist Osborne Reynolds (1842–1912) studied the formation and collapse of vapor bubbles in boiling liquids and in constricted tubes.
The term cavitation first appeared in 1895 in a paper by John Isaac Thornycroft (1843–1928) and Sydney Walker Barnaby (1855–1925)—son of Sir Nathaniel Barnaby (1829 – 1915), who had been Chief Constructor of the Royal Navy—to whom it had been suggested by the British engineer Robert Edmund Froude (1846–1924), third son of the English hydrodynamicist William Froude (1810–1879). Early experimental studies of cavitation were conducted in 1894-5 by Thornycroft and Barnaby and by the Anglo-Irish engineer Charles Algernon Parsons (1854-1931), who constructed a stroboscopic apparatus to study the phenomenon. Thornycroft and Barnaby were the first researchers to observe cavitation on the back sides of propeller blades.
In 1917, the British physicist Lord Rayleigh (1842–1919) extended Besants work, publishing a mathematical model of cavitation in an incompressible fluid (ignoring surface tension and viscosity), in which he also determined the pressure in the fluid. The mathematical models of cavitation which were developed by British engineer Stanley Smith Cook (1875–1952) and by Lord Rayleigh revealed that collapsing bubbles of vapor could generate very high pressures, which were capable of causing the damage that had been observed on ships propellers. Experimental evidence of cavitation causing such high pressures was initially collected in 1952 by Mark Harrison (a fluid dynamicist and acoustician at the U.S. Navy's David Taylor Model Basin at Carderock, Maryland, USA) who used acoustic methods and in 1956 by Wernfried Güth (a physicist and acoustician of Göttigen University, Germany) who used optical Schlieren photography.
In 1944, Soviet scientists Mark Iosifovich Kornfeld (1908–1993) and L. Suvorov of the Leningrad Physico-Technical Institute (now: the Ioffe Physical-Technical Institute of the Russian Academy of Sciences, St. Petersburg, Russia) proposed that during cavitation, bubbles in the vicinity of a solid surface do not collapse symmetrically; instead, a dimple forms on the bubble at a point opposite the solid surface and this dimple evolves into a jet of liquid. This jet of liquid damages the solid surface. This hypothesis was supported in 1951 by theoretical studies by Maurice Rattray Jr., a doctoral student at the California Institute of Technology. Kornfeld and Suvorov's hypothesis was confirmed experimentally in 1961 by Charles F. Naudé and Albert T. Ellis, fluid dynamicists at the California Institute of Technology.
A series of experimental investigations of the propagation of strong shock wave (SW) in a liquid with gas bubbles, which made it possible to establish the basic laws governing the process, the mechanism for the transformation of the energy of the SW, attenuation of the SW, and the formation of the structure, and experiments on the analysis of the attenuation of waves in bubble screens with different acoustic properties were begun by pioneer works of Soviet scientist prof.V.F. Minin at the Institute of Hydrodynamics (Novosibirsk, Russia) in 1957–1960, who examined also the first convenient model of a screen - a sequence of alternating flat one-dimensional liquid and gas layers. In an experimental investigations of the dynamics of the form of pulsating gaseous cavities and interaction of SW with bubble clouds in 1957–1960 V.F. Minin discovered that under the action of SW a bubble collapses asymmetrically with the formation of a cumulative jet, which forms in the process of collapse and causes fragmentation of the bubble. | 1 | Applied and Interdisciplinary Chemistry |
Originally, the Van den Bergh reaction was used for a qualitative estimate of bilirubin.
This test is performed routinely in most medical laboratories and can be measured by a variety of methods.
Total bilirubin is now often measured by the 2,5-dichlorophenyldiazonium (DPD) method, and direct bilirubin is often measured by the method of Jendrassik and Grof. | 1 | Applied and Interdisciplinary Chemistry |
This naming has been developed principally for coordination compounds although it can be more widely applied. Examples are:
*Si(OH) tetrahydroxidosilicon (additive), or silanetetrol (substitutive) (note silicic acid is an acceptable name—orthosilicic has been dropped).
*[CoCl(NH)]Cl pentaamminechloridocobalt(2+) chloride | 0 | Theoretical and Fundamental Chemistry |
A biomonitoring assessment requires a baseline dataset which, ideally, defines the environment in its natural or default state. This is then used for comparison against any subsequent measurements, in order to assess potential alterations or trends.
In some cases, these datasets are used to create standardised tools for assessing water quality via biomonitoring data, such as the Specific Pollution Index (SPI) and South African Diatom Index (SADI). | 1 | Applied and Interdisciplinary Chemistry |
Even though the van der Waals interaction is attractive, as the adsorbed atom moves closer to the surface the wavefunction of electron starts to overlap with that of the surface atoms. Further the energy of the system will increase due to the orthogonality of wavefunctions of the approaching atom and surface atoms.
This Pauli exclusion and repulsion are particularly strong for atoms with closed valence shells that dominate the surface interaction. As a result, the minimum energy of physisorption must be found by the balance between the long-range van der Waals attraction and short-range Pauli repulsion. For instance, by separating the total interaction of physisorption into two contributions—a short-range term depicted by Hartree–Fock theory and a long-range van der Waals attraction—the equilibrium position of physisorption for rare gases adsorbed on jellium substrate can be determined. Fig. 2 shows the physisorption potential energy of He adsorbed on Ag, Cu, and Au substrates which are described by the jellium model with different densities of smear-out background positive charges. It can be found that the weak van der Waals interaction leads to shallow attractive energy wells (<10 meV). One of the experimental methods for exploring physisorption potential energy is the scattering process, for instance, inert gas atoms scattered from metal surfaces. Certain specific features of the interaction potential between scattered atoms and surface can be extracted by analyzing the experimentally determined angular distribution and cross sections of the scattered particles. | 0 | Theoretical and Fundamental Chemistry |
In chemical reaction engineering, "yield", "conversion" and "selectivity" are terms used to describe ratios of how much of a reactant has reacted—conversion, how much of a desired product was formed—yield, and how much desired product was formed in ratio to the undesired product—selectivity, represented as X, S, and Y.
According to the Elements of Chemical Reaction Engineering manual, yield refers to the amount of a specific product formed per mole of reactant consumed. In chemistry, mole is used to describe quantities of reactants and products in chemical reactions.
The Compendium of Chemical Terminology defined yield as the "ratio expressing the efficiency of a mass conversion process. The yield coefficient is defined as the amount of cell mass (kg) or product formed (kg,mol) related to the consumed substrate (carbon or nitrogen source or oxygen in kg or moles) or to the intracellular ATP production (moles)."
In the section "Calculations of yields in the monitoring of reactions" in the 1996 4th edition of Vogels Textbook of Practical Organic Chemistry (1978), the authors write that, "theoretical yield in an organic reaction is the weight of product which would be obtained if the reaction has proceeded to completion according to the chemical equation. The yield is the weight of the pure product which is isolated from the reaction." In the 1996 edition of Vogels Textbook', percentage yield is expressed as,
According to the 1996 edition of Vogels Textbook, yields close to 100% are called quantitative, yields above 90% are called excellent, yields above 80% are very good, yields above 70% are good, yields above 50% are fair, and yields below 40% are called poor. In their 2002 publication, Petrucci, Harwood, and Herring wrote that Vogels Textbook names were arbitrary, and not universally accepted, and depending on the nature of the reaction in question, these expectations may be unrealistically high. Yields may appear to be 100% or above when products are impure, as the measured weight of the product will include the weight of any impurities.
In their 2016 laboratory manual, Experimental Organic Chemistry, the authors described the "reaction yield" or "absolute yield" of a chemical reaction as the "amount of pure and dry product yielded in a reaction". They wrote that knowing the stoichiometry of a chemical reaction—the numbers and types of atoms in the reactants and products, in a balanced equation "make it possible to compare different elements through stoichiometric factors." Ratios obtained by these quantitative relationships are useful in data analysis. | 0 | Theoretical and Fundamental Chemistry |
Glendenin was born in Bay City, Michigan on November 8, 1918. He attended the University of Chicago, graduating in 1941. | 1 | Applied and Interdisciplinary Chemistry |
The measurement of unconjugated bilirubin (UCB) is underestimated by measurement of indirect bilirubin, as unconjugated bilirubin (without/yet glucuronidation) reacts with diazosulfanilic acid to create azobilirubin which is measured as direct bilirubin. | 1 | Applied and Interdisciplinary Chemistry |
Ketoacidosis is a pathological state of uncontrolled production of ketones that results in a metabolic acidosis, with serum ketone levels typically in excess of 3 mM. Ketoacidosis is most commonly caused by a deficiency of insulin in type 1 diabetes or late stage type 2 diabetes but can also be the result of chronic heavy alcohol use, salicylate poisoning, or isopropyl alcohol ingestion. Ketoacidosis causes significant metabolic derangements and is a life-threatening medical emergency. Ketoacidosis is distinct from physiological ketosis as it requires failure of the normal regulation of ketone body production. | 1 | Applied and Interdisciplinary Chemistry |
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 | Applied and Interdisciplinary Chemistry |
In response to a systemic bacterial infection, the immune system initiates a process known as "iron withholding". If bacteria are to survive, then they must obtain iron from their environment. Disease-causing bacteria do this in many ways, including releasing iron-binding molecules called siderophores and then reabsorbing them to recover iron, or scavenging iron from hemoglobin and transferrin. The harder the bacteria have to work to get iron, the greater a metabolic price they must pay. That means that iron-deprived bacteria reproduce more slowly. So, control of iron levels appears to be an important defense against many bacterial infections. Certain bacteria species have developed strategies to circumvent that defense, TB causing bacteria can reside within macrophages, which present an iron rich environment and Borrelia burgdorferi uses manganese in place of iron. People with increased amounts of iron, as, for example, in hemochromatosis, are more susceptible to some bacterial infections.
Although this mechanism is an elegant response to short-term bacterial infection, it can cause problems when it goes on so long that the body is deprived of needed iron for red cell production. Inflammatory cytokines stimulate the liver to produce the iron metabolism regulator protein hepcidin, that reduces available iron. If hepcidin levels increase because of non-bacterial sources of inflammation, like viral infection, cancer, auto-immune diseases or other chronic diseases, then the anemia of chronic disease may result. In this case, iron withholding actually impairs health by preventing the manufacture of enough hemoglobin-containing red blood cells. | 1 | Applied and Interdisciplinary Chemistry |
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