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Homogentisic acid (2,5-dihydroxyphenylacetic acid) is a phenolic acid usually found in Arbutus unedo (strawberry-tree) honey. It is also present in the bacterial plant pathogen Xanthomonas campestris pv. phaseoli as well as in the yeast Yarrowia lipolytica where it is associated with the production of brown pigments. It is oxidatively dimerised to form hipposudoric acid, one of the main constituents of the blood sweat of hippopotamuses.
It is less commonly known as melanic acid, the name chosen by William Prout. | 1 | Applied and Interdisciplinary Chemistry |
The identification of RBSs is used to determine the site of translation initiation in an unannotated sequence. This is referred to as N-terminal prediction. This is especially useful when multiple start codons are situated around the potential start site of the protein coding sequence.
Identification of RBSs is particularly difficult, because they tend to be highly degenerated. One approach to identifying RBS in E.coli is using neural networks. Another approach is using the Gibbs sampling method. | 1 | Applied and Interdisciplinary Chemistry |
Alfred Werner (12 December 1866 – 15 November 1919) was a Swiss chemist who was a student at ETH Zurich and a professor at the University of Zurich. He won the Nobel Prize in Chemistry in 1913 for proposing the octahedral configuration of transition metal complexes. Werner developed the basis for modern coordination chemistry. He was the first inorganic chemist to win the Nobel Prize, and the only one prior to 1973. | 0 | Theoretical and Fundamental Chemistry |
Gammaretroviral and lentiviral vectors for gene therapy have been developed that mediate stable genetic modification of treated cells by chromosomal integration of the transferred vector genomes. This technology is of use, not only for research purposes, but also for clinical gene therapy aiming at the long-term correction of genetic defects, e.g., in stem and progenitor cells. Retroviral vector particles with tropism for various target cells have been designed. Gammaretroviral and lentiviral vectors have so far been used in more than 300 clinical trials, addressing treatment options for various diseases. Retroviral mutations can be developed to make transgenic mouse models to study various cancers and their metastatic models. | 1 | Applied and Interdisciplinary Chemistry |
In human biology, footedness is the natural preference of one's left or right foot for various purposes. It is the foot equivalent of handedness. While purposes vary, such as applying the greatest force in a certain foot to complete the action of kick as opposed to stomping, footedness is most commonly associated with the preference of a particular foot in the leading position while engaging in foot- or kicking-related sports, such as association football and kickboxing. A person may thus be left-footed, right-footed or ambipedal (able to use both feet equally well). | 0 | Theoretical and Fundamental Chemistry |
The current interest in nontraditional methods for the generation of hydrogen has prompted a revisit of radiolytic splitting of water, where the interaction of various types of ionizing radiation (α, β, and γ) with water produces molecular hydrogen. This reevaluation was further prompted by the current availability of large amounts of radiation sources contained in the fuel discharged from nuclear reactors. This spent fuel is usually stored in water pools, awaiting permanent disposal or reprocessing. The yield of hydrogen resulting from the irradiation of water with β and γ radiation is low (G-values = <1 molecule per 100 electronvolts of absorbed energy) but this is largely due to the rapid reassociation of the species arising during the initial radiolysis. If impurities are present or if physical conditions are created that prevent the establishment of a chemical equilibrium, the net production of hydrogen can be greatly enhanced.
Another approach uses radioactive waste as an energy source for regeneration of spent fuel by converting sodium borate into sodium borohydride. By applying the proper combination of controls, stable borohydride compounds may be produced and used as hydrogen fuel storage medium.
A study conducted in 1976 found an order-of-magnitude estimate can be made of the average hydrogen production rate that could be obtained by utilizing the energy liberated via radioactive decay. Based on the primary molecular hydrogen yield of 0.45 molecules/100 eV, it would be possible to obtain 10 tons per day. Hydrogen production rates in this range are not insignificant, but are small compared with the average daily usage (1972) of hydrogen in the U.S. of about 2 x 10^4 tons. Addition of a hydrogen-atom donor could increase this about a factor of six. It was shown that the addition of a hydrogen-atom donor such as formic acid enhances the G value for hydrogen to about 2.4 molecules per 100 eV absorbed. The same study concluded that designing such a facility would likely be too unsafe to be feasible. | 0 | Theoretical and Fundamental Chemistry |
The Athinoula A. Martinos Center for Biomedical Imaging, usually referred to as just the "Martinos Center," is a major hub of biomedical imaging technology development and translational research. The Center is part of the Department of Radiology at Massachusetts General Hospital and is affiliated with both Harvard University and MIT. Bruce Rosen is the Director of the Center and Monica Langone is the Administrative Director.
The core technologies being developed and used at the Center are magnetic resonance imaging (MRI) and in vivo magnetic resonance spectroscopy (MRS), magnetoencephalography (MEG) and electroencephalography (EEG), optical imaging techniques (microscopy and near-infrared spectroscopy), positron emission tomography (PET), molecular imaging, medical image computing (MIC), health informatics, artificial intelligence in healthcare, and transcranial magnetic stimulation. A particular area of innovation at the Center is Multimodal Functional Neuroimaging, which involves the integration of imaging technologies for neuroscience applications. Major areas of research at the Center include: psychiatric, neurologic and neurovascular disorders; basic and cognitive neuroscience; cardiovascular disease; cancer; and more. Scientific investigation and technology development is funded through government, industry and other research grants.
The center is located in the Massachusetts General Hospital (MGH) East Campus in the Charlestown Navy Yard, 149 13th St. Charlestown, MA 02129. Separately, Massachusetts Institute of Technology (MIT) is home to its own Martinos Imaging Center.
The Martinos Center is home to approximately 120 faculty members and more than 100 postdoctoral research fellows and graduate students, and is a resource to hundreds of researchers and students throughout Boston, the United States and the world. The research faculty are basic scientists and clinicians interested in a broad range of biologically and medically important questions. They work in conjunction with physical scientists, computer scientists, and engineers to develop new imaging technologies and research applications, and to bring these developments to the sphere of medical care. Some of the prominent faculty at the Center include Bruce Rosen, Lawrence Wald, David Boas, Jacob Hooker, Julie C. Price, Peter Caravan, Anna Moore, Umar Mahmood, Randy Buckner, Matthew S. Rosen, Maria Angela Franceschini, Bruce Fischl and Marco Loggia.
The Center includes investigators and their laboratories based at the MGH research campus in Charlestown, as well as numerous other researchers from various departments within MGH, and other local, national and international institutions. Most Martinos Center-based faculty members have primary appointments in Radiology at MGH and Harvard, some with secondary appointments at MIT. Several of the investigators from other MGH departments and other institutions work at the Center, while even more conduct long- and short-term imaging studies at the Center and maintain their base elsewhere.
The center is a member or collaborator with NCRR (and BIRN), NIDA, NIBIB, National Cancer Institute, NINDS, NCCAM, ONDCP, and The MIND Institute. The center also has a strategic corporate partnerships with Siemens Medical Solutions, Pfizer Inc., and Canon Inc. It is also a Harvard Catalyst site, and incorporates research projects from Boston University, McLean Hospital, and other Boston institutions.
At the MGH Navy Yard site, there are eight large bore and five small bore MRI scanning bays used primarily for research, including the high-gradient field Human Connectome Project scanner, a 7 Tesla magnet for human radiography, and a combined PET-MRI. The Martinos Center also served as the site for the development of magnetoencephalography (MEG), and software development for analysis of MEG data is ongoing at the facility. New MRI and MRS sequences are developed in conjunction with Martinos, Harvard, and MIT faculty. In addition, the Center serves as a development site for new Siemens equipment, such as 32, 64, and 128 channel MRI coils which were designed and prototyped there. | 0 | Theoretical and Fundamental Chemistry |
Cobalt(II) chloride is an inorganic compound, a salt of cobalt and chlorine, with the formula . The compound forms several hydrates ·n, for n = 1, 2, 6, and 9. Claims of the formation of tri- and tetrahydrates have not been confirmed. The anhydrous form is a blue crystalline solid; the dihydrate is purple and the hexahydrate is pink. Commercial samples are usually the hexahydrate, which is one of the most commonly used cobalt salts in the lab. | 0 | Theoretical and Fundamental Chemistry |
These include genotoxicity testing, human biomonitoring and molecular epidemiology, ecogenotoxicology, as well as fundamental research in DNA damage and repair. For example, Swain and Rao, using the comet assay reported marked increases in several types of DNA damages in rat brain neurons and astrocytes during aging, including single-strand breaks, double-strand breaks and modified bases (8-OHdG and uracil). | 1 | Applied and Interdisciplinary Chemistry |
An alternating copolymer has regular alternating A and B units, and is often described by the formula: -A-B-A-B-A-B-A-B-A-B-, or -(-A-B-)-. The molar ratio of each monomer in the polymer is normally close to one, which happens when the reactivity ratios r and r are close to zero, as can be seen from the Mayo–Lewis equation. For example, in the free-radical copolymerization of styrene maleic anhydride copolymer, r = 0.097 and r = 0.001, so that most chains ending in styrene add a maleic anhydride unit, and almost all chains ending in maleic anhydride add a styrene unit. This leads to a predominantly alternating structure.
A step-growth copolymer -(-A-A-B-B-)- formed by the condensation of two bifunctional monomers A–A and B–B is in principle a perfectly alternating copolymer of these two monomers, but is usually considered as a homopolymer of the dimeric repeat unit A-A-B-B. An example is nylon 66 with repeat unit -OC-( CH)-CO-NH-(CH)-NH-, formed from a dicarboxylic acid monomer and a diamine monomer. | 0 | Theoretical and Fundamental Chemistry |
Sodium tetrachloroaurate is an inorganic compound with the chemical formula NaAuCl. It is composed of the ions Na and AuCl. It exists in the anhydrous and dihydrate states. At room temperature, it exists as a golden-orange solid. The anhydrous and dihydrate forms are available commercially.
__TOC__ | 0 | Theoretical and Fundamental Chemistry |
Click chemistry is a method for attaching a probe or substrate of interest to a specific biomolecule, a process called bioconjugation. The possibility of attaching fluorophores and other reporter molecules has made click chemistry a very powerful tool for identifying, locating, and characterizing both old and new biomolecules.
One of the earliest and most important methods in bioconjugation was to express a reporter on the same open reading frame as a biomolecule of interest. Notably, green fluorescent protein (GFP) was first (and still is) expressed in this way at the N- or C- terminus of many proteins. However, this approach comes with several difficulties. For instance, GFP is a very large unit and can often affect the folding of the protein of interest. Moreover, by being expressed at either terminus, the GFP adduct can also affect the targeting and expression of the desired protein. Finally, using this method, GFP can only be attached to proteins, and not post-translationally, leaving other important biomolecular classes (nucleic acids, lipids, carbohydrates, etc.) out of reach.
To overcome these challenges, chemists have opted to proceed by identifying pairs of bioorthogonal reaction partners, thus allowing the use of small exogenous molecules as biomolecular probes. A fluorophore can be attached to one of these probes to give a fluorescence signal upon binding of the reporter molecule to the target—just as GFP fluoresces when it is expressed with the target.
Now limitations emerge from the chemistry of the probe to its target. In order for this technique to be useful in biological systems, click chemistry must run at or near biological conditions, produce little and (ideally) non-toxic byproducts, have (preferably) single and stable products at the same conditions, and proceed quickly to high yield in one pot. Existing reactions, such as Staudinger ligation and the Huisgen 1,3-dipolar cycloaddition, have been modified and optimized for such reaction conditions. Today, research in the field concerns not only understanding and developing new reactions and repurposing and re-understanding known reactions, but also expanding methods used to incorporate reaction partners into living systems, engineering novel reaction partners, and developing applications for bioconjugation.
Biotech company Shasqi is a company leveraging click chemistry in humans. | 0 | Theoretical and Fundamental Chemistry |
In order of net exports in 2011, 2009 and 2006 in thousand bbl/d and thousand m/d:
Source: [http://www.eia.gov/countries/index.cfm?topL=exp US Energy Information Administration]
peak production already passed in this state</small>
Canadian statistics are complicated by the fact it is both an importer and exporter of crude oil, and refines large amounts of oil for the U.S. market. It is the leading source of U.S. imports of oil and products, averaging in August 2007.</small>
Total world production/consumption (as of 2005) is approximately . | 0 | Theoretical and Fundamental Chemistry |
Several other methods for the electrophilic formation of C-N bonds are available. Nitrites and nitrates can be used to form oximes and nitro compounds, respectively. Additionally, organoboranes can serve the role of the nucleophile and often provide higher yields with fewer complications than analogous carbanions. The Neber rearrangement offers an alternative to electrophilic amination through the intermediacy of an azirine. | 0 | Theoretical and Fundamental Chemistry |
The French chemist Louis Pasteur founded zymology, when in 1856 he connected yeast to fermentation.
When studying the fermentation of sugar to alcohol by yeast, Pasteur concluded that the fermentation was catalyzed by a vital force, called "ferments", within the yeast cells. The "ferments" were thought to function only within living organisms. Pasteur wrote that "Alcoholic fermentation is an act correlated with the life and organization of the yeast cells, not with the death or putrefaction of the cells." | 1 | Applied and Interdisciplinary Chemistry |
In momentum transfer, the fluid is treated as a continuous distribution of matter. The study of momentum transfer, or fluid mechanics can be divided into two branches: fluid statics (fluids at rest), and fluid dynamics (fluids in motion).
When a fluid is flowing in the x-direction parallel to a solid surface, the fluid has x-directed momentum, and its concentration is υρ. By random diffusion of molecules there is an exchange of molecules in the z-direction. Hence the x-directed momentum has been transferred in the z-direction from the faster- to the slower-moving layer.
The equation for momentum transfer is Newton's law of viscosity written as follows:
where τ is the flux of x-directed momentum in the z-direction, ν is μ/ρ, the momentum diffusivity, z is the distance of transport or diffusion, ρ is the density, and μ is the dynamic viscosity. Newtons law of viscosity is the simplest relationship between the flux of momentum and the velocity gradient. It may be useful to note that this is an unconventional use of the symbol τ'; the indices are reversed as compared with standard usage in solid mechanics, and the sign is reversed. | 1 | Applied and Interdisciplinary Chemistry |
In their largest application, an oxime is an intermediate in the industrial production of caprolactam, a precursor to Nylon 6. About half of the world's supply of cyclohexanone, more than a million tonnes annually, is converted to the oxime. In the presence of sulfuric acid catalyst, the oxime undergoes the Beckmann rearrangement to give the cyclic amide caprolactam: | 0 | Theoretical and Fundamental Chemistry |
Most enzymes cannot tolerate extremely high salt concentrations. The ions interfere with the weak ionic bonds of proteins. Typical enzymes are active in salt concentrations of 1-500 mM. As usual there are exceptions such as the halophilic algae and bacteria. | 1 | Applied and Interdisciplinary Chemistry |
The first ARDD conference was held in 2014 at Basel, Switzerland. Then, this conference was known as Aging Forum and it was a part of MipTec and Basel Life Congresses. The conference was intended to bring together the Pharmaceutical industry, leading academics, Investors and Startups. | 1 | Applied and Interdisciplinary Chemistry |
Roshko determined the correlation below from experiments on the flow of air around circular cylinders over range Re=50 to Re=2000:
: valid over [ 50 <= Re < 200]
: valid over [200 <= Re < 2000]
Ormières and Provansal investigated vortex shedding in the wake of a sphere and found a relationship between Re and Ro in the range 280 < Re < 360. | 1 | Applied and Interdisciplinary Chemistry |
The UK government aims to decarbonize all rail transport by 2040, a measure that has broad parliamentary support. In September 2019, Transport Scotland announced the goal of having Scottish transport net carbon neutral by the year 2035. This would be achieved by a rolling programme of electrification; where that is not feasible, using battery and other emerging technology such as hydrogen.
In an attempt to mitigate and improve the cost situation and thus persuade the government to backtrack on its electrification cancellations, the Railway Industry Association published a report in March 2019 detailing why costs had risen and suggested ways forward. Campaign to Electrify Britain's Railway heavily circulated and advertised this report. The answer to a written question in parliament regarding route miles electrified in the years 1997-2019 made rather stark reading. It has been mainly agreed that electrification costs in the UK are too high though.
Railways in Scotland are a devolved matter but all parties including the Green Party are vigorously campaigning for electrification.
Roger Ford, the technical editor of Modern Railways, often writes about similar themes and coined the phrase “Bionic duckweed". This refers to putting off what needs to be done today because something new in the future may be just around the corner to refer to schemes that are not based on electrification but alternative technologies such as biodiesel and Hydrogen. Other writers have done likewise. Other authors also cite issues with the huge inefficiency of hydrogen as opposed to electrification and the safety of using hydrogen fuel.
In September 2020 the Traction Decarbonisation Network Strategy Interim Business case was published. The principal recommendation was further electrification of 13,000 km (single track kilometres) of UK railways. As of November 2022, the TDNS has been quietly abandoned.
On 23 March 2021, the Transport Select Committee published a report in the 'Trains Fit for the Future" enquiry, which recommended a rolling programme of electrification that allowed for battery and hydrogen. Greater cost scrutiny was also recommended. The report was also highlighted in the mainstream press, featuring how Members of Parliament were calling for a rolling programme of electrification. In March 2021, in the April issue of Modern Railways magazine also reported that work was underway to extend OHL electrification to Market Harborough, but that the SPL Powerlines contractor was working in conjunction with Network Rail to extend wires beyond this to Sheffield and Nottingham. It was reported that the scheme was being divided into eight distinct route sections. On 22 April 2021, along with an open letter to Grant Shapps with fifteen signatures, the Railway Industry Association published their report "Why Rail Electrification". It was produced in conjunction with their RailDecarb21 campaign. These set out the case for a rolling programme of rail electrification. Both main political parties agree.
In July 2021, the UK Government released the document "Decarbonising transport – a better greener Britain" and at the same time released the supporting Rail environmental policy document. These were welcomed by the CEBR. These documents stated that rail electrification had a major role to play in the decarbonising agenda.
On 18 November 2021 the Integrated Rail Plan (IRP) was published. This included full Midland Main Line electrification and upgrades. In addition, full Transpennine North electrification was included. However, in December 2021 plans were leaked showing the treasury had declined to provide funding to electrify and decarbonise the railways. Further outcry came after it was revealed in The Guardian that the majority of civil servants who wrote the plan don't even live in the North or Midlands.
The Railway Industry Association continues to carry out reviews on decarbonisation in an effort to hold both the government and the industry to account. Although not the same as electrification, the organisation and others suggest modal shift away from roads to an electrified railway, will also help the climate. | 1 | Applied and Interdisciplinary Chemistry |
In cylindrical coordinates, the divergence of the velocity field u becomes:
as expected for an incompressible flow.
And in spherical coordinates: | 1 | Applied and Interdisciplinary Chemistry |
The sum of molar concentrations gives the total molar concentration, namely the density of the mixture divided by the molar mass of the mixture or by another name the reciprocal of the molar volume of the mixture. In an ionic solution, ionic strength is proportional to the sum of the molar concentration of salts. | 0 | Theoretical and Fundamental Chemistry |
Mathematical predictions by H. Peregrine had initially been established in the domain of hydrodynamics. This is however very different from where the Peregrine soliton has been for the first time experimentally generated and characterized. | 1 | Applied and Interdisciplinary Chemistry |
The element carbon plays a central role in climate and life on Earth. It is capable of moving among and between the geosphere, cryosphere, atmosphere, biosphere and hydrosphere. This flow of carbon is referred to as the Earths carbon cycle. It is also intimately linked to the cycling of other elements and compounds. The ocean plays a fundamental role in Earths carbon cycle, helping to regulate atmospheric CO concentration. The biological pump is a set of processes that transfer organic carbon from the surface to the deep ocean, and is at the heart of the ocean carbon cycle.
The biological pump depends on the fraction of primary produced organic matter that survives degradation in the euphotic zone and that is exported from surface water to the ocean interior, where it is mineralized to inorganic carbon, with the result that carbon is transported against the gradient of dissolved inorganic carbon (DIC) from the surface to the deep ocean. This transfer occurs through physical mixing and transport of dissolved and particulate organic carbon (POC), vertical migrations of organisms (zooplankton, fish) and through gravitational settling of particulate organic carbon.
The biological pump can be divided into three distinct phases, the first of which is the production of fixed carbon by planktonic phototrophs in the euphotic (sunlit) surface region of the ocean. In these surface waters, phytoplankton use carbon dioxide (CO), nitrogen (N), phosphorus (P), and other trace elements (barium, iron, zinc, etc.) during photosynthesis to make carbohydrates, lipids, and proteins. Some plankton, (e.g. coccolithophores and foraminifera) combine calcium (Ca) and dissolved carbonates (carbonic acid and bicarbonate) to form a calcium carbonate (CaCO) protective coating.
Once this carbon is fixed into soft or hard tissue, the organisms either stay in the euphotic zone to be recycled as part of the regenerative nutrient cycle or once they die, continue to the second phase of the biological pump and begin to sink to the ocean floor. The sinking particles will often form aggregates as they sink, greatly increasing the sinking rate. It is this aggregation that gives particles a better chance of escaping predation and decomposition in the water column and eventually making it to the sea floor.
The fixed carbon that is decomposed by bacteria either on the way down or once on the sea floor then enters the final phase of the pump and is remineralized to be used again in primary production. The particles that escape these processes entirely are sequestered in the sediment and may remain there for millions of years. It is this sequestered carbon that is responsible for ultimately lowering atmospheric CO.
The diagram immediately above illustrates the components of the biological pump. Biology, physics and gravity interact to pump organic carbon into the deep sea. The processes of fixation of inorganic carbon in organic matter during photosynthesis, its transformation by food web processes (trophodynamics), physical mixing, transport and gravitational settling are referred to collectively as the biological pump.
The biological pump is responsible for transforming dissolved inorganic carbon (DIC) into organic biomass and pumping it in particulate or dissolved form into the deep ocean. Inorganic nutrients and carbon dioxide are fixed during photosynthesis by phytoplankton, which both release dissolved organic matter (DOM) and are consumed by herbivorous zooplankton. Larger zooplankton - such as copepods - egest fecal pellets which can be reingested and sink or collect with other organic detritus into larger, more-rapidly-sinking aggregates. DOM is partially consumed by bacteria (black dots) and respired; the remaining refractory DOM is advected and mixed into the deep sea. DOM and aggregates exported into the deep water are consumed and respired, thus returning organic carbon into the enormous deep ocean reservoir of DIC. About 1% of the particles leaving the surface ocean reach the seabed and are consumed, respired, or buried in the sediments. There, carbon is stored for millions of years. The net effect of these processes is to remove carbon in organic form from the surface and return it to DIC at greater depths, maintaining the surface-to-deep ocean gradient of DIC. Thermohaline circulation returns deep-ocean DIC to the atmosphere on millennial timescales. | 0 | Theoretical and Fundamental Chemistry |
This cost/benefit tradeoff of alarm calling behaviour has sparked many interest debates among evolutionary biologists seeking to explain the occurrence of such apparently "self-sacrificing" behaviour. The central question is this: "If the ultimate purpose of any animal behaviour is to maximize the chances that an organism's own genes are passed on, with maximum fruitfulness, to future generations, why would an individual deliberately risk destroying itself (their entire genome) for the sake of saving others (other genomes)?". | 1 | Applied and Interdisciplinary Chemistry |
Lipotropic compounds are those that help catalyse the breakdown of fat during metabolism in the body. A lipotropic nutrient promotes or encourages the export of fat from the liver. Lipotropics are necessary for maintenance of a healthy liver, and for burning the exported fat for additional energy. Without lipotropics, such as choline and inositol, fats and bile can become trapped in the liver, causing severe problems such as cirrhosis and blocking fat metabolism.
Choline is the major lipotrope in mammals and other known lipotropes are important only insofar as they contribute to the synthesis of choline. Choline is essential for fat metabolism. Choline functions as a methyl donor and it is required for proper liver function. Though choline can be synthesized from methionine or serine, mammals don't produce a sufficient amount on their own. Liver, eggs, wheat bran, meat, and broccoli are dietary sources of choline.
Inositol exerts lipotropic effects as well. Oranges and cantaloupe are high in inositol.
Methionine, an essential amino acid, is a major lipotropic compound in humans. When estrogen levels are high, the body requires more methionine. Estrogens reduce bile flow through the liver and increase bile cholesterol levels. Methionine helps deactivate estrogens. Egg whites are high in methionine.
Methionine levels also affect the amount of sulfur-containing compounds, such as glutathione, in the liver. Glutathione and other sulfur-containing peptides play a critical role in defending against toxic compounds. Supplementation with vitamin C, vitamin D, and NAC can increase glutathione levels.
Betaine hydrochloride is a lipotropic and increases gastric acid. Betaine itself (in a non-hydrochloric form, also known as TMG or Trimethylglycine) also has a lipotropic effect. Quinoa is high in betaine. | 1 | Applied and Interdisciplinary Chemistry |
Total suspended solids (TSS) is the dry-weight of suspended particles, that are not dissolved, in a sample of water that can be trapped by a filter that is analyzed using a filtration apparatus known as sintered glass crucible. TSS is a water quality parameter used to assess the quality of a specimen of any type of water or water body, ocean water for example, or wastewater after treatment in a wastewater treatment plant. It is listed as a conventional pollutant in the U.S. Clean Water Act. Total dissolved solids is another parameter acquired through a separate analysis which is also used to determine water quality based on the total substances that are fully dissolved within the water, rather than undissolved suspended particles.
TSS is also referred to using the terms total suspended matter (TSM) and suspended particulate matter (SPM). All three terms describe the same essential measurement. TSS was previously called non-filterable residue (NFR), but was changed to TSS because of ambiguity in other scientific disciplines. | 0 | Theoretical and Fundamental Chemistry |
While disposal into exhausted open pits is generally a straightforward operation, disposal into underground voids is more complex. A common modern approach is to mix a certain quantity of tailings with waste aggregate and cement, creating a product that can be used to backfill underground voids and stopes. A common term for this is HDPF – High Density Paste Fill. HDPF is a more expensive method of tailings disposal than pond storage, however it has many other benefits – not just environmental but it can significantly increase the stability of underground excavations by providing a means for ground stress to be transmitted across voids – rather than having to pass around them – which can cause mining induced seismic events like that suffered previously at the Beaconsfield Mine Disaster. | 1 | Applied and Interdisciplinary Chemistry |
In proton NMR spectroscopy, deuterated solvent (enriched to >99% deuterium) is typically used to avoid recording a large interfering signal or signals from the proton(s) (i.e., hydrogen-1) present in the solvent itself. If nondeuterated chloroform (containing a full equivalent of protium) were used as solvent, the solvent signal would almost certainly overwhelm and obscure any nearby analyte signals. In addition, modern instruments usually require the presence of deuterated solvent, as the field frequency is locked using the deuterium signal of the solvent to prevent frequency drift. Commercial chloroform-d does, however, still contain a small amount (0.2% or less) of non-deuterated chloroform; this results in a small singlet at 7.26 ppm, known as the residual solvent peak, which is frequently used as an internal chemical shift reference.
In carbon-13 NMR spectroscopy, the sole carbon in deuterated chloroform shows a triplet at a chemical shift of 77.16 ppm with the three peaks being about equal size, resulting from splitting by spin coupling to the attached spin-1 deuterium atom ( has a chemical shift of 77.36 ppm).
Deuterated chloroform is a general purpose NMR solvent, as it is not very chemically reactive and unlikely to exchange its deuterium with its solute, and its low boiling point allows for easy sample recovery. It, however, it is incompatible with strongly basic, nucleophilic, or reducing analytes, including many organometallic compounds. | 0 | Theoretical and Fundamental Chemistry |
Although additional research is required to improve the efficiency of prime editing, the technology offers promising scientific improvements over other gene editing tools. The prime editing technology has the potential to correct the vast majority of pathogenic alleles that cause genetic diseases, as it can repair insertions, deletions, and nucleotide substitutions. | 1 | Applied and Interdisciplinary Chemistry |
MIKE FLOOD can be used for river-flood plain interaction, integrated urban drainage and river modeling, urban flood analysis and detailed dam break studies. | 1 | Applied and Interdisciplinary Chemistry |
* DUSP1, DUSP2, DUSP3, DUSP4, DUSP5, DUSP6, DUSP7, DUSP8, DUSP9
* DUSP10, DUSP11, DUSP12, DUSP13, DUSP14, DUSP15, DUSP16, DUSP18, DUSP19
* DUSP21, DUSP22, DUSP23, DUSP26, DUSP27, DUSP28 | 1 | Applied and Interdisciplinary Chemistry |
Metals, and specifically rare-earth elements, form numerous chemical complexes with boron. Their crystal structure and chemical bonding depend strongly on the metal element M and on its atomic ratio to boron. When B/M ratio exceeds 12, boron atoms form B icosahedra which are linked into a three-dimensional boron framework, and the metal atoms reside in the voids of this framework. Those icosahedra are basic structural units of most allotropes of boron and boron-rich rare-earth borides. In such borides, metal atoms donate electrons to the boron polyhedra, and thus these compounds are regarded as electron-deficient solids.
The crystal structures of many boron-rich borides can be attributed to certain types including MgAlB, YB, REBSi, BC and other, more complex types such as REBCSi. Some of these formulas, for example BC, YB and MgAlB, historically reflect the idealistic structures, whereas the experimentally determined composition is nonstoichiometric and corresponds to fractional indexes. Boron-rich borides are usually characterized by large and complex unit cells, which can contain more than 1500 atomic sites and feature extended structures shaped as "tubes" and large modular polyhedra ("superpolyhedra"). Many of those sites have partial occupancy, meaning that the probability to find them occupied with a certain atom is smaller than one and thus that only some of them are filled with atoms. Scandium is distinguished among the rare-earth elements by that it forms numerous borides with uncommon structure types; this property of scandium is attributed to its relatively small atomic and ionic radii.
Crystals of the specific rare-earth boride YB are used as X-ray monochromators for selecting X-rays with certain energies (in the 1–2 keV range) out of synchrotron radiation. Other rare-earth borides may find application as thermoelectric materials, owing to their low thermal conductivity; the latter originates from their complex, "amorphous-like", crystal structure. | 0 | Theoretical and Fundamental Chemistry |
The advantage in atom economy of using NCAs for peptide formation is that there is no need for a protecting group on the functional group reacted with the amino acid. For example, the Merrifield synthesis depends on the use of Boc and Bzl protecting groups, which need be removed after the reaction. In the case of Bailey peptide synthesis, the free peptide is directly obtained after the reaction. However, unwanted and difficult to remove by-products may be formed. An N-substitution of the NCA (for example, by an o-nitrophenylsulfenyl group) can simplify the subsequent purification process, but on the other hand deteriorates the atom economy of the reaction. The synthesis of NCAs can be carried out by the Leuchs reaction or by the reaction of N-(benzyloxycarbonyl)-amino acids with oxalyl chloride. In the latter case, again the procedure is less efficient in the sense of atom economy. | 1 | Applied and Interdisciplinary Chemistry |
A melt inclusion is a small parcel or "blobs" of melt(s) that is entrapped by crystals growing in magma and eventually forming igneous rocks. In many respects it is analogous to a fluid inclusion within magmatic hydrothermal systems. Melt inclusions tend to be microscopic in size and can be analyzed for volatile contents that are used to interpret trapping pressures of the melt at depth. | 0 | Theoretical and Fundamental Chemistry |
In general, the free-stream velocity is uniform, in other words , but here a small vorticity is imposed in the outer flow. | 1 | Applied and Interdisciplinary Chemistry |
Hydrophobic interactions in protein SEC are relatively weak at low ionic strength, electrostatic effects may contribute significantly to retention, and this allows us to use an SEC column as a weak ion exchanger. | 0 | Theoretical and Fundamental Chemistry |
Ortho esters are readily hydrolyzed in mild aqueous acid to form esters:
: RC(OR′) + HO → RCOR′ + 2 R′OH
For example, trimethyl orthoformate CH(OCH) may be hydrolyzed (under acidic conditions) to methyl formate and methanol; and may be further hydrolyzed (under alkaline conditions) to salts of formic acid and methanol. | 0 | Theoretical and Fundamental Chemistry |
Engineers can use the Brinell hardness of materials in their calculations to avoid this mode of failure. A rolling element bearing's static load rating is defined to avoid this failure type. Increasing the number of elements can provide better distribution of the load, so bearings intended for a large load may have many balls, or use needles instead. This decreases the chances of brinelling, but increases friction and other factors. However, although roller and ball bearings work well for radial and thrust loading, they are often prone to brinelling when very high impact loading, lateral loading, or vibration are experienced. Babbitt bearings or bronze bushings are often used instead of roller bearings in applications where such loads exist, such as in automotive crankshafts or pulley sheaves, to decrease the possibility of brinelling by distributing the force over a very large surface area.
A common cause of brinelling is the use of improper installation procedures. Brinelling often occurs when pressing bearings into holes or onto shafts. Care must usually be taken to ensure that pressure is applied to the proper bearing race to avoid transferring the pressure from one race to the other through the balls or rollers. If pressing force is applied to the wrong race, brinelling can occur to either or both of the races. The act of pressing or clamping can also leave brinell marks, especially if the vise or press has serrated jaws or roughened surfaces. Flat pressing plates are often used in the pressing of bearings, while soft copper, brass, or aluminum jaw covers are often used in vises to help avoid brinell marks from being forced into the workpiece. | 1 | Applied and Interdisciplinary Chemistry |
He studied philosophy and law in Vienna. After finishing his studies he started further studies at the Bergakademie (Mining Academy) in Schemnitz (Selmecbánya), Lower Hungary (today Banská Štiavnica, Slovakia) in 1763. He studied mining, mechanics, mineralogy and chemistry and after graduating he became a Markscheider (official mine surveyor) in 1768. In 1770 he joined the Hofcommission für die Regulierung der Banater Berg und Hüttenwerke (royal commission for mining in the Banat) where he gained a lot of knowledge on mining in the Banat. He was promoted to the rank of an Oberbergmeister (senior mining official) and became a mine manager in the same year.
In 1775 he became Oberbergmeister in the Tyrol town of Schwaz. Schwaz was one of the largest centres of silver and copper mining in Austria-Hungary in that time. In 1778 he discovered an occurrence of tourmaline in the Zillertal.
Müller became one of seven Thesaurariats councillor in Transylvania responsible for the supervision of all mining and coinage activities in Transylvania in 1778. After the dissolution of the Thesaurariat Müller became Oberinspector (chief surveyor) of all mining, smelting and salt production in Transylvania. | 1 | Applied and Interdisciplinary Chemistry |
Anions with the general formula are called sulfonates. They are the conjugate bases of sulfonic acids with formula . As sulfonic acids tend to be strong acids, the corresponding sulfonates are weak bases. Due to the stability of sulfonate anions, the cations of sulfonate salts such as scandium triflate have application as Lewis acids.
A classic preparation of sulfonates is the Strecker sulfite alkylation, in which an alkali sulfite salt displaces a halide, typically in the presence of an iodine catalyst:
An alternative is the condensation of a sulfonyl halide with an alcohol in pyridine: | 0 | Theoretical and Fundamental Chemistry |
The Uranium Medical Research Centre (UMRC) is an independent non-profit organization founded in 1997 to provide objective and expert scientific and medical research into the effects of uranium, transuranium elements, and radionuclides produced by the process of radioactive decay and fission. UMRC is also a registered charity in the United States and Canada. The founder of UMRC, Asaf Durakovic, claimed on CNN that: "Inhalation of uranium dust is harmful.... Even in the amount of one atom". | 0 | Theoretical and Fundamental Chemistry |
Vilma Lucila Espín Guillois (7 April 1930 – 18 June 2007) was a Cuban revolutionary, feminist, and chemical engineer. She helped supply and organize the 26th of July Movement as an underground spy, and took an active role in many branches of the Cuban government from the conclusion of the revolution to her death. Espín helped found the Federation of Cuban Women and promoted equal rights for Cuban women in all spheres of life. | 1 | Applied and Interdisciplinary Chemistry |
In many supramolecular catalytic systems designed to work with bimolecular addition reactions like the Diels-Alder, the product of the reaction binds more strongly to the supramolecular host than the two substrates do, consequently leading to inhibition by the product. As a result, these catalysts has a turnover number of one and are not truly catalytic. A stoichiometric quantity of the catalysts is needed for a full conversion. | 0 | Theoretical and Fundamental Chemistry |
EPIC-seq, (short for Epigenetic Expression Inference by Cell-free DNA Sequencing), is a high-throughput method that specifically targets gene promoters using cell-free DNA (cfDNA) sequencing. By employing non-invasive techniques such as blood sampling, it infers the expression levels of targeted genes. It consists of both wet and dry lab stages.
EPIC-seq involves deep sequencing of the transcription start sites (TSS). It hypothesizes that with deep sequencing of these TSSs, usage of fragmentomic features, chromatin fragmentation patterns or properties, can allow high-resolution analyses, as opposed to its alternatives.
The method has been shown effective for gene-level expression inference, molecular subtyping of diffuse large B cell lymphoma (DLBCL), histological classification of nonsmall-cell lung cancer (NSCLC), evaluation of results of immunotherapy agents, and assessment of the genes' prognostic importance. EPIC-seq uses machine learning to deduce the RNA expression of the genes and proposes two new metrics: promoter fragmentation entropy (PFE), an adjusted Shannon Index for entropy, and nucleosome-depleted region (NDR) score, the depth of sequencing in NDR regions. PFE showed superior performance compared to earlier metrics for fragmentomic features.
Additionally, EPIC-seq has been mentioned as a possible solution for detecting tissue damage and esophagus cancer using methylation profiles of cfDNAs, profiling of donor liver molecular networks, and inflammatory bowel disease (IBD) detection. | 1 | Applied and Interdisciplinary Chemistry |
A sophorolipid is a surface-active glycolipid compound that can be synthesized by a selected number of non-pathogenic yeast species. They are potential bio-surfactants due to their biodegradability and low eco-toxicity. | 0 | Theoretical and Fundamental Chemistry |
Endiandric acid C, isolated from the tree Endiandra introrsa, is a well characterized chemical compound. Endiadric acid C is reported to have better antibiotic activity than ampicillin.
This genus of trees is in the family Lauraceae. These trees are found in the north-eastern Australian rainforests and other tropical and subtropical regions. However, they are also found in southern Canada and in Chile. Endiandric acid C is also isolated from the species E. xanthocarpa. Endiandric acids are also found in Beilschmiedia trees, which were categorized under the genus Endiandra, but moved to their own genus as they found in cold, high latitude areas, and even in New Zealand. Other endiandric acids are found in B. oligandra and B. anacardioides, which are found in the Western Province of Cameroon. | 0 | Theoretical and Fundamental Chemistry |
Metal-alkene complexes are uncommon in nature, with one exception. Ethene affects the ripening of fruit and flowers by complexation to a Cu(I) center in a transcription factor. | 0 | Theoretical and Fundamental Chemistry |
In 1979, the ACS formed a task force chaired by Ned D. Heindel to look at creating a national center for the history of chemistry. Arnold Thackray, a professor in the Department of History and Sociology of Science at the University of Pennsylvania, and curator of the Edgar Fahs Smith Memorial Collection on the history of chemistry at the University of Pennsylvania, argued for the formation of such a center in Philadelphia. Thackray obtained promises of private support from chemist John C. Haas and institutional support from the Dow Chemical Company and DuPont. In December 1981, the ACS approved the establishment of the Center for the History of Chemistry, with support of $50,000 per year for five years, in cooperation with the University of Pennsylvania, which was to provide an equivalent in goods and services. An agreement to create the Center for the History of Chemistry was signed by officers of the American Chemical Society and the University of Pennsylvania on January 22 and 26, 1982. A policy council was appointed by the sponsoring institutions to oversee routine operations of the center, and Arnold Thackray was appointed part-time director of the center on April 29, 1982. The center was inaugurated on March 11, 1983, in several vacant basement rooms on the University of Pennsylvania campus. Its "immediate aims" included gathering oral histories of important chemists and inventorying papers and manuscripts in repositories throughout the country to map "the largely unexplored territory of the history of chemistry and chemical technology."
A National Advisory Board was also formed from a wide-ranging group of people in academia and industry. In 1982, its members included John C. Haas, historians Margaret W. Rossiter and Alfred D. Chandler, Jr. and at least three Nobel Prize winners, Christian B. Anfinsen, Herbert C. Brown, and Glenn T. Seaborg. The American Institute of Chemical Engineers (AIChE) became a co-founder of the center, signing an agreement on August 27 and 28, 1984. In addition, the institution began to establish relationships with affiliated organizations such as The Chemists' Club, the American Society for Biochemistry and Molecular Biology, the American Association of Textile Chemists and Colorists, the Electrochemical Society and the American Society for Mass Spectrometry.
As early as 1983, the Center for the History of Chemistry expressed an interest in "The Conservation of Historic American Chemical Instruments", in discussions of a possible joint project with the Smithsonian. However, the center did not yet have exhibition or collections space to allow for the acquisition of any but the most limited quantities of documents. The center did curate a number of traveling exhibitions by collaborating with other organizations, including "Joseph Priestley: Enlightened Chemist", "Polymers and People", "Scaling Up", and "Chemical Education in the United States". | 1 | Applied and Interdisciplinary Chemistry |
The metal-carbon bond in organometallic compounds is generally highly covalent. For highly electropositive elements, such as lithium and sodium, the carbon ligand exhibits carbanionic character, but free carbon-based anions are extremely rare, an example being cyanide.
Most organometallic compounds are solids at room temperature, however some are liquids such as methylcyclopentadienyl manganese tricarbonyl, or even volatile liquids such as nickel tetracarbonyl. Many organometallic compounds are air sensitive (reactive towards oxygen and moisture), and thus they must be handled under an inert atmosphere. Some organometallic compounds such as triethylaluminium are pyrophoric and will ignite on contact with air. | 0 | Theoretical and Fundamental Chemistry |
Leu-enkephalin is an endogenous opioid peptide neurotransmitter with the amino acid sequence Tyr-Gly-Gly-Phe-Leu that is found naturally in the brains of many animals, including humans. It is one of the two forms of enkephalin; the other is met-enkephalin. The tyrosine residue at position 1 is thought to be analogous to the 3-hydroxyl group on morphine. Leu-enkephalin has agonistic actions at both the μ- and δ-opioid receptors, with significantly greater preference for the latter. It has little to no effect on the κ-opioid receptor. | 1 | Applied and Interdisciplinary Chemistry |
Cyclic sulfonic esters are called sultones. Two examples are propane-1,3-sultone and 1,4-butane sultone. Some sultones are short-lived intermediates, used as strong alkylating agents to introduce a negatively charged sulfonate group. In the presence of water, they slowly hydrolyze to the hydroxy sulfonic acids. Sultone oximes are key intermediates in the synthesis of the anti-convulsant drug zonisamide.
Tisocromide is an example of a sultone. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, the law of multiple proportions states that in compounds which contain two particular chemical elements, the amount of Element A per measure of Element B will differ across these compounds by ratios of small whole numbers. For instance, the ratio of the hydrogen content in methane and ethane per measure of carbon is 2:3. This law is also known as Daltons Law', named after John Dalton, the chemist who first expressed it. The discovery of this pattern led Dalton to develop the modern theory of atoms, as it suggested that the elements combine with each other in multiples of a basic quantity.
The law of multiple proportions often does not apply when comparing very large molecules. For example, if one tried to demonstrate it using the hydrocarbons decane (chemical formula CH) and undecane (CH), one would find that 100 grams of carbon could react with 18.46 grams of hydrogen to produce decane or with 18.31 grams of hydrogen to produce undecane, for a ratio of hydrogen masses of 121:120, which is hardly a ratio of "small" whole numbers. | 0 | Theoretical and Fundamental Chemistry |
In terms of commercial uses, 2-furoic acid is often used in the production of furoate esters, some of which are drugs and pesticides. | 0 | Theoretical and Fundamental Chemistry |
SI-compliant units that can be used as alternatives are shown in the chart below. Expressions that the BIPM explicitly does not recognize as being suitable for denoting dimensionless quantities with the SI are marked with .
Note that the notations in the "SI units" column above are for the most part dimensionless quantities; that is, the units of measurement factor out in expressions like "1 nm/m" (1 n/ =1 × 10) so the ratios are pure-number coefficients with values less than 1. | 1 | Applied and Interdisciplinary Chemistry |
The same way that RNA silencing regulates downstream target mRNAs, RNA silencing itself is regulated. For example, silencing signals get spread between cells by a group of enzymes called RdRPs (RNA-dependent RNA polymerases) or RDRs. | 1 | Applied and Interdisciplinary Chemistry |
Remineralisation refers to the breakdown or transformation of organic matter (those molecules derived from a biological source) into its simplest inorganic forms. These transformations form a crucial link within ecosystems as they are responsible for liberating the energy stored in organic molecules and recycling matter within the system to be reused as nutrients by other organisms. What fraction does escape remineralisation varies depending on the location. For example, in the North Sea, values of carbon deposition are ~1% of primary production while that value is <0.5% in the open oceans on average. Therefore, most of nutrients remain in the water column, recycled by the biota. Heterotrophic organisms will utilize the materials produced by the autotrophic (and chemotrophic) organisms and via respiration will remineralise the compounds from the organic form back to inorganic, making them available for primary producers again.
For most areas of the ocean, the highest rates of carbon remineralisation occur at depths between in the water column, decreasing down to about where remineralisation rates remain pretty constant at 0.1 μmol kg yr. This provides the most nutrients available for primary producers within the photic zone, though it leaves the upper surface waters starved of inorganic nutrients. Most remineralisation is done with dissolved organic carbon (DOC). Studies have shown that it is larger sinking particles that transport matter down to the sea floor while suspended particles and dissolved organics are mostly consumed by remineralisation. This happens in part due to the fact that organisms must typically ingest nutrients smaller than they are, often by orders of magnitude. With the microbial community making up 90% of marine biomass, it is particles smaller than the microbes (on the order of ) that will be taken up for remineralisation. | 0 | Theoretical and Fundamental Chemistry |
Developed by Julius Schäffer to help with the identification of Agaricus species. A positive reaction of Schaeffers test, which uses the reaction of aniline and nitric acid on the surface of the mushroom, is indicated by an orange to red color; it is characteristic of species in the section Flavescentes'. The compounds responsible for the reaction were named schaefferal A and B to honor Schäffer.
Two intersecting lines are drawn on the surface of the cap, the first with aniline or aniline water, the second with an aqueous solution of 65% nitric acid. The test is considered positive when a bright orange color forms where the lines cross.
Agaricus placomyces and Agaricus xanthodermus produce false negative reactions.
Sometimes referred to as "Schaeffers reaction", "Schaeffers cross reaction" or "Schaeffer's test". | 0 | Theoretical and Fundamental Chemistry |
Although ribozymes are quite rare in most cells, their roles are sometimes essential to life. For example, the functional part of the ribosome, the biological machine that translates RNA into proteins, is fundamentally a ribozyme, composed of RNA tertiary structural motifs that are often coordinated to metal ions such as Mg as cofactors. In a model system, there is no requirement for divalent cations in a five-nucleotide RNA catalyzing trans-phenylalanation of a four-nucleotide substrate with 3 base pairs complementary with the catalyst, where the catalyst/substrate were devised by truncation of the C3 ribozyme.
The best-studied ribozymes are probably those that cut themselves or other RNAs, as in the original discovery by Cech and Altman. However, ribozymes can be designed to catalyze a range of reactions, many of which may occur in life but have not been discovered in cells.
RNA may catalyze folding of the pathological protein conformation of a prion in a manner similar to that of a chaperonin. | 0 | Theoretical and Fundamental Chemistry |
In 2018 the Tantalum-Niobium International Study Center established The Anders Gustaf Ekeberg Tantalum Prize ("Ekeberg Prize"), an annual award to recognize excellence in tantalum research. The Prize will increase awareness of the many unique properties of tantalum products and the applications in which they excel.
The inaugural winner of the Ekeberg Prize was Yuri Freeman, for his book "Tantalum and Niobium-Based Capacitors" (Springer, 2018). | 1 | Applied and Interdisciplinary Chemistry |
This puzzle was mentioned by W. W. Rouse Ball in the third, 1896, edition of his book Mathematical Recreations And Problems Of Past And Present Times, and is said to have been a favorite problem of Lewis Carroll. | 0 | Theoretical and Fundamental Chemistry |
The Museum of the History of Donetsk Metallurgical Plant was created in 1955, and it is located in the Technology House. The idea for its creation came from the director of the DMZ, Pavel Vasilyevich Andreev. The museum consists of more than 3000 exhibits. In 1971 the museum was awarded the title of national museum. Among the exhibits are certificates for products manufactured by the plant in 1900, original photographs of the Nizhny Novgorod industrial exhibition in 1896 and others.
On February 16, 2012, a branch of the Museum of the History of the Donetsk Metallurgical Plant was opened in the lower floor of the St. Ignatius Church, which is dedicated to Ignatius of Mariupol. | 1 | Applied and Interdisciplinary Chemistry |
The journal is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2020 impact factor of 3.715. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, conformational isomerism is a form of stereoisomerism in which the isomers can be interconverted just by rotations about formally single bonds (refer to figure on single bond rotation). While any two arrangements of atoms in a molecule that differ by rotation about single bonds can be referred to as different conformations, conformations that correspond to local minima on the potential energy surface are specifically called conformational isomers or conformers. Conformations that correspond to local maxima on the energy surface are the transition states between the local-minimum conformational isomers. Rotations about single bonds involve overcoming a rotational energy barrier to interconvert one conformer to another. If the energy barrier is low, there is free rotation and a sample of the compound exists as a rapidly equilibrating mixture of multiple conformers; if the energy barrier is high enough then there is restricted rotation, a molecule may exist for a relatively long time period as a stable rotational isomer or rotamer (an isomer arising from hindered single-bond rotation). When the time scale for interconversion is long enough for isolation of individual rotamers (usually arbitrarily defined as a half-life of interconversion of 1000 seconds or longer), the isomers are termed atropisomers (see: atropisomerism). The ring-flip of substituted cyclohexanes constitutes another common form of conformational isomerism.
Conformational isomers are thus distinct from the other classes of stereoisomers (i. e. configurational isomers) where interconversion necessarily involves breaking and reforming of chemical bonds. For example, /- and R/S- configurations of organic molecules have different handedness and optical activities, and can only be interconverted by breaking one or more bonds connected to the chiral atom and reforming a similar bond in a different direction or spatial orientation. They also differ from geometric (cis/trans) isomers, another class of stereoisomers, which require the π-component of double bonds to break for interconversion. (Although the distinction is not always clear-cut, since certain bonds that are formally single bonds actually have double bond character that becomes apparent only when secondary resonance contributors are considered, like the C–N bonds of amides, for instance.) Due to rapid interconversion, conformers are usually not isolable at room temperature.
The study of the energetics between different conformations is referred to as conformational analysis. It is useful for understanding the stability of different isomers, for example, by taking into account the spatial orientation and through-space interactions of substituents. In addition, conformational analysis can be used to predict and explain product selectivity, mechanisms, and rates of reactions. Conformational analysis also plays an important role in rational, structure-based drug design. | 0 | Theoretical and Fundamental Chemistry |
The drug consists of exametazime as a chelating agent for the radioisotope technetium-99m. Both enantiomeric forms of exametazime are used—the drug is racemic. The third stereoisomer of this structure, the meso form, is not included. | 0 | Theoretical and Fundamental Chemistry |
The practice of alchemy in the Western world, based on a Hellenistic and Babylonian approach to planetary astronomy, often ascribed a symbolic association between the seven then-known celestial bodies and the metals known to the Greeks and Babylonians during antiquity. Additionally, some alchemists and astrologers believed there was an association, sometimes called a rulership, between days of the week, the alchemical metals, and the planets that were said to hold "dominion" over them. There was some early variation, but the most common associations since antiquity are the following: | 1 | Applied and Interdisciplinary Chemistry |
Like hot black oxide, mid-temperature black oxide converts the surface of the metal to magnetite (FeO). However, mid-temperature black oxide blackens at a temperature of , significantly less than hot black oxide. This is advantageous because it is below the solution's boiling point, meaning there are no caustic fumes produced.
Since mid-temperature black oxide is most comparable to hot black oxide, it also can meet the military specification MIL-DTL-13924, as well as AMS 2485. | 0 | Theoretical and Fundamental Chemistry |
A number of chemical reactions have water as a product. If the reactions take place at temperatures higher than the dew point of the surrounding air the water will be formed as vapor and increase the local humidity, if below the dew point local condensation will occur. Typical reactions that result in water formation are the burning of hydrogen or hydrocarbons in air or other oxygen containing gas mixtures, or as a result of reactions with oxidizers.
In a similar fashion other chemical or physical reactions can take place in the presence of water vapor resulting in new chemicals forming such as rust on iron or steel, polymerization occurring (certain polyurethane foams and cyanoacrylate glues cure with exposure to atmospheric humidity) or forms changing such as where anhydrous chemicals may absorb enough vapor to form a crystalline structure or alter an existing one, sometimes resulting in characteristic color changes that can be used for measurement. | 1 | Applied and Interdisciplinary Chemistry |
An MR fluid is used in one of three main modes of operation, these being flow mode, shear mode and squeeze-flow mode. These modes involve, respectively, fluid flowing as a result of pressure gradient between two stationary plates; fluid between two plates moving relative to one another; and fluid between two plates moving in the direction perpendicular to their planes. In all cases the magnetic field is perpendicular to the planes of the plates, so as to restrict fluid in the direction parallel to the plates. | 1 | Applied and Interdisciplinary Chemistry |
The antibody based methods use designed antibodies to bind to proteins of interest, allowing the relative abundance of multiple individual targets to be identified by one of several different techniques.
Imaging: Antibodies can be bound to fluorescent molecules such as quantum dots or tagged with organic fluorophores for detection by fluorescence microscopy. Since different colored quantum dots or unique fluorophores are attached to each antibody it is possible to identify multiple different proteins in a single cell. Quantum dots can be washed off of the antibodies without damaging the sample, making it possible to do multiple rounds of protein quantification using this method on the same sample. For the methods based on organic fluorophores, the fluorescent tags are attached by a reversible linkage such as a DNA-hybrid (that can be melted/dissociated under low-salt conditions) or chemically inactivated, allowing multiple cycles of analysis, with 3-5 targets quantified per cycle. These approaches have been used for quantifying protein abundance in patient biopsy samples (e.g. cancer) to map variable protein expression in tissues and/or tumors, and to measure changes in protein expression and cell signaling in response to cancer treatment.
Mass Cytometry: rare metal isotopes, not normally found in cells or tissues, can be attached to the individual antibodies and detected by mass spectrometry for simultaneous and sensitive identification of proteins. These techniques can be highly multiplexed for simultaneous quantification of many targets (panels of up to 38 markers) in single cells.
Antibody-DNA quantification: another antibody-based method converts protein levels to DNA levels. The conversion to DNA makes it possible to amplify protein levels and use NGS to quantify proteins. In one such approach, two antibodies are selected for each protein needed to be quantified. The two antibodies are then modified to have single stranded DNA connected to them that are complementary. When the two antibodies bind to a protein the complementary strands will anneal and produce a double stranded segment of DNA that can then be amplified using PCR. Each pair of antibodies designed for one protein is tagged with a different DNA sequence. The DNA amplified from PCR can then be sequenced, and the protein levels quantified. | 1 | Applied and Interdisciplinary Chemistry |
Osmolarity is distinct from molarity because it measures osmoles of solute particles rather than moles of solute. The distinction arises because some compounds can dissociate in solution, whereas others cannot.
Ionic compounds, such as salts, can dissociate in solution into their constituent ions, so there is not a one-to-one relationship between the molarity and the osmolarity of a solution. For example, sodium chloride (NaCl) dissociates into Na and Cl ions. Thus, for every 1 mole of NaCl in solution, there are 2 osmoles of solute particles (i.e., a 1 mol/L NaCl solution is a 2 osmol/L NaCl solution). Both sodium and chloride ions affect the osmotic pressure of the solution.
Another example is magnesium chloride (MgCl), which dissociates into Mg and 2Cl ions. For every 1 mole of MgCl in the solution, there are 3 osmoles of solute particles.
Nonionic compounds do not dissociate, and form only 1 osmole of solute per 1 mole of solute. For example, a 1 mol/L solution of glucose is 1 osmol/L.
Multiple compounds may contribute to the osmolarity of a solution. For example, a 3 Osm solution might consist of: 3 moles glucose, or 1.5 moles NaCl, or 1 mole glucose + 1 mole NaCl, or 2 moles glucose + 0.5 mole NaCl, or any other such combination. | 0 | Theoretical and Fundamental Chemistry |
The use of two wires of iridium/rhodium alloys can provide a thermocouple that can be used up to about 2000 °C in inert atmospheres. | 1 | Applied and Interdisciplinary Chemistry |
In cellular biology, proteins act as intracellular signaling molecules by activating another protein in a signaling pathway. In order to do this, proteins can switch between active and inactive states, thus acting as molecular switches in response to another signal. For example, phosphorylation of proteins can be used to activate or inactivate proteins. The external signal flipping the molecular switch could be a protein kinase, which adds a phosphate group to the protein, or a protein phosphatase, which removes phosphate groups. | 0 | Theoretical and Fundamental Chemistry |
Carbon–carbon bond-forming reactions are organic reactions in which a new carbon–carbon bond is formed. They are important in the production of many human-made chemicals such as pharmaceuticals and plastics. The reverse reaction, where a carbon-carbon bond is broken, is known as carbon-carbon bond activation.
Some examples of reactions which form carbon–carbon bonds are the aldol reaction, Diels–Alder reaction, Grignard reaction, cross-coupling reactions, the Michael reaction and the Wittig reaction.
The directed synthesis of desired three-dimensional structures for tertiary carbons was largely solved during the late 20th century, but the same ability to direct quaternary carbon synthesis did not start to emerge until the first decade of the 21st century. | 0 | Theoretical and Fundamental Chemistry |
Alcohol consumption increases the risk of hypothermia in two ways: vasodilation and temperature controlling systems in the brain. Vasodilation increases blood flow to the skin, resulting in heat being lost to the environment. This produces the effect of feeling warm, when one is actually losing heat. Alcohol also affects the temperature-regulating system in the brain, decreasing the body's ability to shiver and use energy that would normally aid the body in generating heat. The overall effects of alcohol lead to a decrease in body temperature and a decreased ability to generate body heat in response to cold environments. Alcohol is a common risk factor for death due to hypothermia. Between 33% and 73% of hypothermia cases are complicated by alcohol. | 1 | Applied and Interdisciplinary Chemistry |
Glass databases are a collection of glass compositions, glass properties, glass models, associated trademark names, patents etc. These data were collected from publications in scientific papers and patents, from personal communication with scientists and engineers, and other relevant sources. | 0 | Theoretical and Fundamental Chemistry |
Acta Sedimentologica Sinica (Chinese name: 沉积学报) is a peer-reviewed scientific journal covering the fields of sedimentology, sedimentary mineral deposits, and geochemistry. It is sponsored by the Professional Committee of Sedimentology of the Chinese Society of Mineral and Rock Geochemistry and the Professional Committee of Sedimentary Geology of the Chinese Geological Society. | 0 | Theoretical and Fundamental Chemistry |
By applying specific equipment and adapting measurement parameters several types of experiments can be performed.
Most common AUC experiments are sedimentation velocity and sedimentation equilibrium experiments. | 1 | Applied and Interdisciplinary Chemistry |
* Food chemistry
* Food physics and Rheology
* Biophysical chemistry
* Physical chemistry
** Spectroscopy-applied
** Intermolecular forces
** Nanotechnology and nanostructures
* Chemical physics
** Molecular dynamics
** Surface chemistry and Van der Waals forces
** Chemical reactions and Reaction chemistry
* Quantum chemistry
** Quantum genetics
** Molecular models of DNA and Molecular modelling of proteins and viruses
* Bioorganic chemistry
* Polymer chemistry
* Biochemistry and Biological chemistry
** Enzymology
** Protein–protein interactions
** Biomembranes
* Complex system biology
** Integrative biology
** Mathematical biophysics
** Systems biology
** Genomics, Proteomics, Interactomics, Structural bioinformatics and Cheminformatics
* Food technology, Food engineering, Food safety and Food biotechnology
** Agricultural biotechnology
****Immobilized cells and enzymes
****Microencapsulation of food additives and vitamins, etc.
* Chemical engineering
* Plant biology and Crop sciences
* Animal sciences | 0 | Theoretical and Fundamental Chemistry |
Details of the fabrication and resulting microstructure of the glass membrane of the pH electrode are maintained as trade secrets by the manufacturers. However, certain aspects of design are published. Glass is a solid electrolyte, for which alkali-metal ions can carry current. The pH-sensitive glass membrane is generally spherical to simplify the manufacture of a uniform membrane. These membranes are up to 0.4 millimeters in thickness, thicker than original designs, so as to render the probes durable. The glass has silicate chemical functionality on its surface, which provides binding sites for alkali-metal ions and hydrogen ions from the solutions. This provides an ion-exchange capacity in the range of 10 to 10 mol/cm. Selectivity for hydrogen ions (H) arises from a balance of ionic charge, volume requirements versus other ions, and the coordination number of other ions. Electrode manufacturers have developed compositions that suitably balance these factors, most notably lithium glass.
The silver chloride electrode is most commonly used as a reference electrode in pH meters, although some designs use the saturated calomel electrode. The silver chloride electrode is simple to manufacture and provides high reproducibility. The reference electrode usually consists of a platinum wire that has contact with a silver/silver chloride mixture, which is immersed in a potassium chloride solution. There is a ceramic plug, which serves as a contact to the test solution, providing low resistance while preventing mixing of the two solutions.
With these electrode designs, the voltmeter is detecting potential differences of ±1400 millivolts. The electrodes are further designed to rapidly equilibrate with test solutions to facilitate ease of use. The equilibration times are typically less than one second, although equilibration times increase as the electrodes age. | 0 | Theoretical and Fundamental Chemistry |
If a solvent is precisely poor enough to cancel the effects of excluded volume expansion, the theta (θ) condition is satisfied. For a given polymer-solvent pair, the theta condition is satisfied at a certain temperature, called the theta (θ) temperature or theta point. A solvent at this temperature is called a theta solvent.
In general, measurements of the properties of polymer solutions depend on the solvent. However, when a theta solvent is used, the measured characteristics are independent of the solvent. They depend only on short-range properties of the polymer such as the bond length, bond angles, and sterically favorable rotations. The polymer chain will behave exactly as predicted by the random walk or ideal chain model. This makes experimental determination of important quantities such as the root mean square end-to-end distance or the radius of gyration much simpler.
Additionally, the theta condition is also satisfied in the bulk amorphous polymer phase. Thus, the conformations adopted by polymers dissolved in theta solvents are identical to those adopted in bulk polymer polymerization . | 0 | Theoretical and Fundamental Chemistry |
Due to the polar nature of the water molecule itself, other polar molecules are generally able to dissolve in water. Most nonpolar molecules are water-insoluble (hydrophobic) at room temperature. Many nonpolar organic solvents, such as turpentine, are able to dissolve nonpolar substances. | 0 | Theoretical and Fundamental Chemistry |
Amdoxovir is a guanosine analogue NRTI prodrug that has good bioavailability. It is deaminated intracellularly by adenosine deaminase to dioxolane guanine (DXG). DXG-triphosphate, the active form of the drug, has greater activity than DAPD-triphosphate. Amdoxovir is currently in phasa II clinical trials. | 1 | Applied and Interdisciplinary Chemistry |
In sweetgum (Liquidambar styraciflua), sinapaldehyde arises in two steps from coniferyl aldehyde beginning with hydroxylation mediated by coniferyl aldehyde 5-hydroxylase. The diphenol is then methylated at the 5-OH by the action of caffeate O-methyltransferase.
Sinapaldehyde is reduced to the alcohol by the action of dehydrogenase enzymes. In Arabidopsis thaliana, the enzyme dihydroflavonol 4-reductase uses NADP to reduce sinapaldehyde to sinapyl alcohol.
It is found in Senra incana (Hibisceae). It is a low molecular weight phenol that is susceptible to extraction from cork stoppers into wine. | 1 | Applied and Interdisciplinary Chemistry |
Prior to its widespread use in the past three decades radioactivity was the most common label.
The advantages of fluorescence over radioactive labels are as follows:
* Fluorescence is safer to use and does not require radiological controls.
* Several fluorescent molecules can be used simultaneously given that they do not overlap, cf. FRET, whereas with radioactivity two isotopes can be used (tritium and a low energy isotope such as P due to different intensities) but require special machinery (a tritium screen and a regular phosphor-imaging screen or a specific dual channel detector).
Note: a channel is similar to "colour" but distinct, it is the pair of excitation and emission filters specific for a dye, e.g. agilent microarrays are dual channel, working on cy3 and cy5, these are colloquially referred to as green and red.
Fluorescence is not necessarily more convenient to use because it requires specialized detection equipment of its own. For non-quantitative or relative quantification applications it can be useful but it is poorly suited for making absolute measurement because of fluorescence quenching, whereas measuring radioactively labeled molecules is always direct and highly sensitive.
Disadvantages of fluorophores include:
* Significantly changes the properties of a fluorescently-labeled molecule
* Interference with normal biological processes
* Toxicity | 1 | Applied and Interdisciplinary Chemistry |
Null mutants die at an early gestational age (embryonic day 11.5). By investigating hypomorphic mutants (which can survive 2 days longer), it was found that placental defects were primarily lethal and that there were also defects in cardiac and hepatic development, but many other organs were normal | 1 | Applied and Interdisciplinary Chemistry |
The SBSP concept is attractive because space has several major advantages over the Earth's surface for the collection of solar power:
* It is always solar noon in space and full sun.
* Collecting surfaces could receive much more intense sunlight, owing to the lack of obstructions such as atmospheric gasses, clouds, dust and other weather events. Consequently, the intensity in orbit is approximately 144% of the maximum attainable intensity on Earth's surface.
* A satellite could be illuminated over 99% of the time and be in Earth's shadow a maximum of only 72 minutes per night at the spring and fall equinoxes at local midnight. Orbiting satellites can be exposed to a consistently high degree of solar radiation, generally for 24 hours per day, whereas earth surface solar panels currently collect power for an average of 29% of the day.
* Power could be relatively quickly redirected directly to areas that need it most. A collecting satellite could possibly direct power on demand to different surface locations based on geographical baseload or peak load power needs.
* Reduced plant and wildlife interference. | 0 | Theoretical and Fundamental Chemistry |
The density of water is about : this relationship was originally used to define the gram. The density varies with temperature, but not linearly: as the temperature increases, the density rises to a peak at and then decreases; the initial increase is unusual because most liquids undergo thermal expansion so that the density only decreases as a function of temperature. The increase observed for water from to and for a few other liquids is described as negative thermal expansion. Regular, hexagonal ice is also less dense than liquid water—upon freezing, the density of water decreases by about 9%.
These peculiar effects are due to the highly directional bonding of water molecules via the hydrogen bonds: ice and liquid water at low temperature have comparatively low-density, low-energy open lattice structures. The breaking of hydrogen bonds on melting with increasing temperature in the range 0–4 °C allows for a denser molecular packing in which some of the lattice cavities are filled by water molecules. Above 4 °C, however, thermal expansion becomes the dominant effect, and water near the boiling point (100 °C) is about 4% less dense than water at .
Under increasing pressure, ice undergoes a number of transitions to other polymorphs with higher density than liquid water, such as ice II, ice III, high-density amorphous ice (HDA), and very-high-density amorphous ice (VHDA).
The unusual density curve and lower density of ice than of water is essential for much of the life on earth—if water were most dense at the freezing point, then in winter the cooling at the surface would lead to convective mixing. Once 0 °C are reached, the water body would freeze from the bottom up, and all life in it would be killed. Furthermore, given that water is a good thermal insulator (due to its heat capacity), some frozen lakes might not completely thaw in summer. As it is, the inversion of the density curve leads to a stable layering for surface temperatures below 4 °C, and with the layer of ice that floats on top insulating the water below, even e.g., Lake Baikal in central Siberia freezes only to about 1 m thickness in winter. In general, for deep enough lakes, the temperature at the bottom stays constant at about 4 °C (39 °F) throughout the year (see diagram). | 1 | Applied and Interdisciplinary Chemistry |
Before any calculations can be made, a tie line is drawn on the phase diagram to determine the mass fraction of each element; on the phase diagram to the right it is line segment LS. This tie line is drawn horizontally at the compositions temperature from one phase to another (here the liquid to the solid). The mass fraction of element B at the liquidus is given by w (represented as w in this diagram) and the mass fraction of element B at the solidus is given by w (represented as w' in this diagram). The mass fraction of solid and liquid can then be calculated using the following lever rule equations:
where w is the mass fraction of element B for the given composition (represented as w in this diagram).
The numerator of each equation is the original composition that we are interested in is +/- the opposite lever arm. That is if you want the mass fraction of solid then take the difference between the liquid composition and the original composition. And then the denominator is the overall length of the arm so the difference between the solid and liquid compositions. If youre having difficulty realising why this is so, try visualising the composition when w approaches w'. Then the liquid concentration will start increasing. | 1 | Applied and Interdisciplinary Chemistry |
For stationary, creeping, incompressible flow, i.e. , the Navier–Stokes equation simplifies to the Stokes equation, which by neglecting the bulk term is:
where is the viscosity, is the velocity in the direction, and is the pressure. Assuming the viscous resisting force is linear with the velocity we may write:
where is the porosity, and is the second order permeability tensor. This gives the velocity in the direction,
which gives Darcy's law for the volumetric flux density in the direction,
In isotropic porous media the off-diagonal elements in the permeability tensor are zero, for and the diagonal elements are identical, , and the common form is obtained as below, which enables the determination of the liquid flow velocity by solving a set of equations in a given region.
The above equation is a governing equation for single-phase fluid flow in a porous medium. | 1 | Applied and Interdisciplinary Chemistry |
The composition of a nuclide (atomic nucleus) is defined by the number of protons Z and the number of neutrons N, which sum to mass number A. Proton number Z, also named the atomic number, determines the position of an element in the periodic table. The approximately 3300 known nuclides are commonly represented in a chart with Z and N for its axes and the half-life for radioactive decay indicated for each unstable nuclide (see figure). , 251 nuclides are observed to be stable (having never been observed to decay); generally, as the number of protons increases, stable nuclei have a higher neutron–proton ratio (more neutrons per proton). The last element in the periodic table that has a stable isotope is lead (Z = 82), with stability (i.e., half-lives of the longest-lived isotopes) generally decreasing in heavier elements, especially beyond curium (Z = 96). The half-lives of nuclei also decrease when there is a lopsided neutron–proton ratio, such that the resulting nuclei have too few or too many neutrons to be stable.
The stability of a nucleus is determined by its binding energy, higher binding energy conferring greater stability. The binding energy per nucleon increases with atomic number to a broad plateau around A = 60, then declines. If a nucleus can be split into two parts that have a lower total energy (a consequence of the mass defect resulting from greater binding energy), it is unstable. The nucleus can hold together for a finite time because there is a potential barrier opposing the split, but this barrier can be crossed by quantum tunneling. The lower the barrier and the masses of the fragments, the greater the probability per unit time of a split.
Protons in a nucleus are bound together by the strong force, which counterbalances the Coulomb repulsion between positively charged protons. In heavier nuclei, larger numbers of uncharged neutrons are needed to reduce repulsion and confer additional stability. Even so, as physicists started to synthesize elements that are not found in nature, they found the stability decreased as the nuclei became heavier. Thus, they speculated that the periodic table might come to an end. The discoverers of plutonium (element 94) considered naming it "ultimium", thinking it was the last. Following the discoveries of heavier elements, of which some decayed in microseconds, it then seemed that instability with respect to spontaneous fission would limit the existence of heavier elements. In 1939, an upper limit of potential element synthesis was estimated around element 104, and following the first discoveries of transactinide elements in the early 1960s, this upper limit prediction was extended to element 108. | 0 | Theoretical and Fundamental Chemistry |
Alkali metal and alkaline earth metal acetylides of the general formula MC≡CM are salt-like Zintl phase compounds, containing ions. Evidence for this ionic character can be seen in the ready hydrolysis of these compounds to form acetylene and metal oxides, there is also some evidence for the solubility of ions in liquid ammonia. The ion has a closed shell ground state of Σ, making it isoelectronic to a neutral molecule N, which may afford it some stability.
Analogous acetylides prepared from other metals, particularly transition metals, show covalent character and are invariably associated with their metal centers. This can be seen in their general stability to water (such as silver acetylide, copper acetylide) and radically different chemical applications.
Acetylides of the general formula RC≡CM (where R = H or alkyl) generally show similar properties to their doubly substituted analogues. In the absence of additional ligands, metal acetylides adopt polymeric structures wherein the acetylide groups are bridging ligands. | 0 | Theoretical and Fundamental Chemistry |
The Public Analyst runs a laboratory which will:
* Analyse food:
** for composition: many foods have legally defined, customary or expected compositions
** for additives: which must be legally permitted and within prescribed concentrations
** for contamination: chemical, microbiological
** to assess the accuracy of labelling
** to investigate whether complaints by the public are justified
* Interpret relevant law passed by the EU and UK or Ireland:
** act as expert witness in prosecutions
In addition to their central rôle in relation to food law enforcement, Public Analysts provide expert scientific support to local authorities and the private sector in various other areas, for example they:
* analyse drinking, bathing water including swimming pools, industrial effluents, industrial process waters and other waters
* investigate environmental products and processes including assessing land contamination, building materials and examining fuels
* advise on waste management
* investigate and monitor air pollution
* advise on consumer safety - in particular consumer products such as toys
* monitor asbestos and other hazards
* carry out toxicological work to assist HM Coroners | 1 | Applied and Interdisciplinary Chemistry |
Metallurgical failure analysis is the process to determine the mechanism that has caused a metal component to fail. It can identify the cause of failure, providing insight into the root cause and potential solutions to prevent similar failures in the future, as well as culpability, which is important in legal cases. Resolving the source of metallurgical failures can be of financial interest to companies. The annual cost of corrosion (a common cause of metallurgical failures) in the United States was estimated by NACE International in 2012 to be $450 billion a year, a 67% increase compared to estimates for 2001. These failures can be analyzed to determine their root cause, which if corrected, would save reduce the cost of failures to companies.
Failure can be broadly divided into functional failure and expected performance failure. Functional failure occurs when a component or process fails and its entire parent system stops functioning entirely. This category includes the common idea of a component fracturing rapidly. Expected performance failures are when a component causes the system to perform below a certain performance criterion, such as life expectancy, operating limits, or shape and color. Some performance criteria are documented by the supplier, such as maximum load allowed on a tractor, while others are implied or expected by the customer, such gas consumption (miles per gallon for automobiles).
Often a combination of both environmental conditions and stress will cause failure. Metal components are designed to withstand the environment and stresses that they will be subjected to. The design of a metal component involves not only a specific elemental composition but also specific manufacturing process such as heat treatments, machining processes, etc. The huge arrays of different metals that result all have unique physical properties. Specific properties are designed into metal components to make them more robust to various environmental conditions. These differences in physical properties will exhibit unique failure modes. A metallurgical failure analysis takes into account as much of this information as possible during analysis. The ultimate goal of failure analysis is to provide a determination of the root cause and a solution to any underlying problems to prevent future failures. | 1 | Applied and Interdisciplinary Chemistry |
Barbara McClintock discovered the first TEs in maize (Zea mays) at the Cold Spring Harbor Laboratory in New York. McClintock was experimenting with maize plants that had broken chromosomes.
In the winter of 1944–1945, McClintock planted corn kernels that were self-pollinated, meaning that the silk (style) of the flower received pollen from its own anther. These kernels came from a long line of plants that had been self-pollinated, causing broken arms on the end of their ninth chromosomes. As the maize plants began to grow, McClintock noted unusual color patterns on the leaves. For example, one leaf had two albino patches of almost identical size, located side by side on the leaf. McClintock hypothesized that during cell division certain cells lost genetic material, while others gained what they had lost. However, when comparing the chromosomes of the current generation of plants with the parent generation, she found certain parts of the chromosome had switched position. This refuted the popular genetic theory of the time that genes were fixed in their position on a chromosome. McClintock found that genes could not only move but they could also be turned on or off due to certain environmental conditions or during different stages of cell development.
McClintock also showed that gene mutations could be reversed. She presented her report on her findings in 1951, and published an article on her discoveries in Genetics in November 1953 entitled "Induction of Instability at Selected Loci in Maize".
At the 1951 Cold Spring Harbor Symposium where she first publicized her findings, her talk was met with dead silence. Her work was largely dismissed and ignored until the late 1960s–1970s when, after TEs were found in bacteria, it was rediscovered. She was awarded a Nobel Prize in Physiology or Medicine in 1983 for her discovery of TEs, more than thirty years after her initial research. | 1 | Applied and Interdisciplinary Chemistry |
DPN is emerging as a powerful research tool for manipulating cells at subcellular resolution
* Stem cell differentiation
* Subcellular drug delivery
* Cell sorting
* Surface gradients
* Subcellular ECM protein patterns
* Cell adhesion | 1 | Applied and Interdisciplinary Chemistry |
Oxidation with dioxiranes refers to the introduction of oxygen into organic molecules through the action of a dioxirane. Dioxiranes are well known for their oxidation of alkenes to epoxides; however, they are also able to oxidize other unsaturated functionality, heteroatoms, and alkane C-H bonds. | 0 | Theoretical and Fundamental Chemistry |
Tammann was awarded the following prizes:
* Liebig Medal of the Association of German Chemists () in 1925
* Heyn Medal of the German Society for Materials Science () in 1929
* Eagle Shield of the German Empire in 1936
The Tammann Commemorative Medal of the Deutsche Gesellschaft für Materialkunde is named after him. | 0 | Theoretical and Fundamental Chemistry |
SQUIDs, or superconducting quantum interference devices, measure extremely small changes in magnetic fields. They are very sensitive vector magnetometers, with noise levels as low as 3 fT Hz in commercial instruments and 0.4 fT Hz in experimental devices. Many liquid-helium-cooled commercial SQUIDs achieve a flat noise spectrum from near DC (less than 1 Hz) to tens of kilohertz, making such devices ideal for time-domain biomagnetic signal measurements. SERF atomic magnetometers demonstrated in laboratories so far reach competitive noise floor but in relatively small frequency ranges.
SQUID magnetometers require cooling with liquid helium () or liquid nitrogen () to operate, hence the packaging requirements to use them are rather stringent both from a thermal-mechanical as well as magnetic standpoint. SQUID magnetometers are most commonly used to measure the magnetic fields produced by laboratory samples, also for brain or heart activity (magnetoencephalography and magnetocardiography, respectively). Geophysical surveys use SQUIDs from time to time, but the logistics of cooling the SQUID are much more complicated than other magnetometers that operate at room temperature. | 0 | Theoretical and Fundamental Chemistry |
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