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Nanofluids are primarily used for their enhanced thermal properties as coolants in heat transfer equipment such as heat exchangers, electronic cooling system(such as flat plate) and radiators. Heat transfer over flat plate has been analyzed by many researchers. However, they are also useful for their controlled optical properties. Graphene based nanofluid has been found to enhance Polymerase chain reaction efficiency. Nanofluids in solar collectors is another application where nanofluids are employed for their tunable optical properties. Nanofluids have also been explored to enhance thermal desalination technologies, by altering thermal conductivity and absorbing sunlight, but surface fouling of the nanofluids poses a major risk to those approaches. Researchers proposed nanofluids for electronics cooling. Nanofluids also can be used in machining. | 0 | Theoretical and Fundamental Chemistry |
Favipiravir, as an antiviral drug, has been authorized for treating COVID-19 in several countries including Japan, Russia, Serbia, Turkey, India, and Thailand, under emergency provisions. A rapid meta-review in September 2020 (analyzing four studies) noted that the drug led to clinical and radiological improvements; however, no reduction in mortality or differences in oxygen-support requirement were observed and more rigorous studies were sought. A Cochrane Systematic review published in Feb 2024, noted that there is actually no real benefit with Favipiravir in treating Covid-19 in terms of mortality benefits, or admission to mechanical ventillation, or hospitalisation, and it may not make any difference in adverse effects or serious adverse effects.
, large-cohort clinical trials are underway. | 0 | Theoretical and Fundamental Chemistry |
Sulfoxides, especially DMSO, form coordination complexes with transition metals. Depending on the hard-soft properties of the metal, the sulfoxide binds through either the sulfur or the oxygen atom. The latter is particularly common. | 0 | Theoretical and Fundamental Chemistry |
The College Board's recommended preparation was a one-year college preparatory course in chemistry, a one-year course in algebra, and experience in the laboratory. However, some second-year algebra concepts (including logarithms) were tested on this subject test. Given the timed nature of the test, one of the keys of the mathematics that appeared on the SAT II in Chemistry was not the difficulty, but rather the speed at which it had to have been completed. Furthermore, the oft-quoted prerequisite of lab-experience was sometimes unnecessary for the SAT Subject Test in Chemistry due to the nature of the questions concerning experiments; most laboratory concepts could simply be memorized beforehand. Some lab-based questions used diagrams, and thus it was helpful to know what common glassware looks like and how the different pieces are used. | 1 | Applied and Interdisciplinary Chemistry |
* Office of the Administrator (also CDC Director)
* Office of the Director (also NCEH (National Center for Environmental Health) head)
** Office of Communications
** Office of Science
** Office of Management and Analytics
** Office of Policy, Partnerships, and Planning
* Office of the Associate Director
** Office of Innovation and Analytics (OIA)
** Office of Community Health Hazard Assessment (OCHHA)
** Office of Capacity Development and Applied Prevention Science (OCDAPS)
The Office of the Director (of ASTDR) is joint with that of NCEH; it also contains seven functional units, five offices, five program-specific divisions to support and implement six program areas:
* [https://wwwn.cdc.gov/TSP/PHA/PHALanding.aspx Public Health Assessments]
* [https://www.atsdr.cdc.gov/toxprofiledocs/index.html Toxicological Profiles]
* [https://www.atsdr.cdc.gov/emergencyresponse/index.html Emergency Response]
* [https://www.atsdr.cdc.gov/dataresources.html Exposure and Disease Registries]
* [https://www.atsdr.cdc.gov/dataresources.html Health Effects Research]
* [https://www.atsdr.cdc.gov/environmentaleducation.html Health Education] | 1 | Applied and Interdisciplinary Chemistry |
R-12 was used in most refrigeration and vehicle air conditioning applications prior to 1994 before being replaced by 1,1,1,2-tetrafluoroethane (R-134a), which has an insignificant ozone depletion potential. Automobile manufacturers started using R-134a instead of R-12 in 1992–1994. When older units leak or require repair involving removal of the refrigerant, retrofitment to a refrigerant other than R-12 (most commonly R-134a which has a global warming potential 3,400 times that of carbon dioxide) is required in some jurisdictions. The United States does not require automobile owners to retrofit their systems; however, taxes on ozone-depleting chemicals coupled with the relative scarcity of the original refrigerants on the open market make retrofitting the only economical option. Retrofitment requires a system flush and a new filter/dryer or accumulator, and may also involve the installation of new seals and/or hoses made of materials compatible with the refrigerant being installed. Mineral oil used with R-12 is not compatible with R-134a. Some oils designed for conversion to R-134a are advertised as compatible with residual R-12 mineral oil. Another replacement for R-12 is the highly flammable, but truly drop-in HC-12a, whose flammability has led to injuries and deaths in a bus fire in 2006. | 1 | Applied and Interdisciplinary Chemistry |
Within the realm of bioorganometallic chemistry is the study of the fates of synthetic organometallic compounds. Tetraethyllead has received considerable attention in this regard as has its successors such as methylcyclopentadienyl manganese tricarbonyl. Methylmercury is a particularly infamous case; this cation is produced by the action of vitamin B-related enzymes on mercury. | 0 | Theoretical and Fundamental Chemistry |
This method uses in vivo and silico ctDNA fragment length selection to enrich the variant proportion in the plasma. The method is decided on size selection criteria based on blood ctDNA fragment length properties, so it may not generalize well for other non-invasive sampling methods. Furthermore, it employs supervised machine learning methods like Random Forest and Logistic Regression on shallow WGS to classify cancer and healthy patients. The method can be used for different cancer types. | 1 | Applied and Interdisciplinary Chemistry |
Retinal (also known as retinaldehyde) is a polyene chromophore. Retinal, bound to proteins called opsins, is the chemical basis of visual phototransduction, the light-detection stage of visual perception (vision).
Some microorganisms use retinal to convert light into metabolic energy. In fact, a recent study suggests most living organisms on our planet ~3 billion years ago used retinal to convert sunlight into energy rather than chlorophyll. Since retinal absorbs mostly green light and transmits purple light, this gave rise to the Purple Earth Hypothesis.
Retinal itself is considered to be a form of vitamin A when eaten by an animal. There are many forms of vitamin A, all of which are converted to retinal, which cannot be made without them. The number of different molecules that can be converted to retinal varies from species to species. Retinal was originally called retinene, and was renamed after it was discovered to be vitamin A aldehyde.
Vertebrate animals ingest retinal directly from meat, or they produce retinal from carotenoids — either from α-carotene or β-carotene — both of which are carotenes. They also produce it from β-cryptoxanthin, a type of xanthophyll. These carotenoids must be obtained from plants or other photosynthetic organisms. No other carotenoids can be converted by animals to retinal. Some carnivores cannot convert any carotenoids at all. The other main forms of vitamin A — retinol and a partially active form, retinoic acid — may both be produced from retinal.
Invertebrates such as insects and squid use hydroxylated forms of retinal in their visual systems, which derive from conversion from other xanthophylls. | 1 | Applied and Interdisciplinary Chemistry |
Fogbank (stylized as FOGBANK) is a code name given to a secret material used in the W76, W78 and W88 nuclear warheads that are part of the United States nuclear arsenal. The process to create Fogbank was lost by 2000, when it was needed for the refurbishment of old warheads. Fogbank was then reverse engineered by the National Nuclear Security Administration (NNSA) over five years and at the cost of tens of millions of dollars.
Fogbank's precise nature is classified; in the words of former Oak Ridge general manager Dennis Ruddy, "The material is classified. Its composition is classified. Its use in the weapon is classified, and the process itself is classified." Department of Energy Nuclear Explosive Safety documents simply describe it as a material "used in nuclear weapons and nuclear explosives" along with lithium hydride (LiH) and lithium deuteride (LiD), beryllium (Be), uranium hydride (UH), and plutonium hydride.
However, NNSA Administrator Tom DAgostino disclosed the role of Fogbank in the weapon: "Theres another material in the—its called interstage material, also known as Fogbank", and arms experts believe that Fogbank is an aerogel material which acts as an interstage material in a nuclear warhead; i.e., a material designed to become a superheated plasma following the detonation of the weapons fission stage, the plasma then triggering the fusion-stage detonation. | 0 | Theoretical and Fundamental Chemistry |
Experimental data on association reactions of H and HO suggest that radiative association involving atomic and diatomic neutral radicals may be considered as an effective mechanism for the production of small neutral molecules in the interstellar clouds. The formation of O occurs in the gas phase via the neutral exchange reaction between O and HO, which is also the main sink for HO in dense regions.
We can see that atomic oxygen takes part both in the production and destruction of HO, so the abundance of HO depends mainly on the H abundance. Then, important chemical pathways leading from HO radicals are:
HO + O → O + H (1A) Neutral-neutral
HO + C → CO + H (2A) Ion-neutral
HO + N → NO + H (3A) Neutral-neutral
HO + C → CO + H (4A) Neutral-neutral
HO + H → HO + photon (5A) Neutral-neutral | 1 | Applied and Interdisciplinary Chemistry |
One form of Cannabis defense is the up-regulation of cannabinoids and specialized terpenes in response to differing biotic stressors in the environment such as pests and predation. In a study from 2019, tobacco hornworm larvae were fed on an artificial diet of wheat germ containing a cannabis agent. The results showed that on average, significantly high dosages of CBD in the new diet may have decreased survival rates of the larvae. In addition, Maduca sexta larvae avoids eating plants containing high amounts of CBD, allowing for the indication that CBD may be a natural pest deterrent. However, research also has shown when the plant is subjected to mechanical wounds from certain insects, CBD levels were unchanged and even decreased. This observation may be due to difference in the species of insect and chemical secretions, thus providing a new hypothesis that CBD levels vary in response to certain species or even have no effect.
Phytocannabinoid and terpene content in the leaves and flowers of C. sativa rises when under attack by Tetranychus urticae, a common pest for the genus. When compared to a control of Cannabis sativa without any pest damage, research from 2022 demonstrated an overall increase of secondary metabolites in plants exposed to Tetranychus urtivae infestation and measured this metabolite rise using liquid and gas chromatograph mass spectrometers. The increase was found to be significant, and is attributed as a defense mechanism in the plant.
The induction and up-regulation of cannabinoids as defense genes in Cannabis can be induced by elicitors. In a study from 2019, salicylic acid (SA) was used with GABA as an elicitor to determine its effects on the expression of metabolites involved in THC and CBD biosynthesis. SA and GABA were demonstrated to effectively up-regulate the expression of THCAS, a cannabigerolic acid used to form THC, which resulted in higher levels of THC. These results support the mechanism in which cannabis elicitors such as salicylic acid and GABA triggers a signal cascade for increased expression of defense genes in response to stress.
One line of defense is the release of volatile organic compounds (VOCs) into the air to defend against herbivores by warning neighboring plants. The release of VOCs may begin with the jasmonic (JA) pathway pathway which up-regulates defensive genes. Jasmonic acid, also called jasmonate, is a hormone linked to wound signaling in plants. Rapid wound signaling involves an influx of calcium after the arrival of an action potential. The increase of calcium triggers a regulatory protein, calmodulin, to turn on a protein kinase releasing JASMONATE-ASSOCIATED VQ-MOTIF GENE1 (JAV1) by combining it with phosphoric acid. From a study in 2020, in response to the necrotrophic pathogen gray mold, JA mediated markers were up-regulated in the leaves that were infected, from beginning of infection to the end. Through a series of signals, the plant detects the presence of fungal elicitors/pathogens, then through the JA pathway the expression of defense genes are increased. | 1 | Applied and Interdisciplinary Chemistry |
About 860 communities in the US have combined sewer systems, serving about 40million people. Pollutants from CSO discharges can include bacteria and other pathogens, toxic chemicals, and debris. These pollutants have also been linked with antimicrobial resistance, posing serious public health concerns. The U.S. Environmental Protection Agency (EPA) issued a policy in 1994 requiring municipalities to make improvements to reduce or eliminate CSO-related pollution problems. The policy is implemented through the National Pollutant Discharge Elimination System (NPDES) permit program. The policy defined water quality parameters for the safety of an ecosystem; it allowed for action that are site specific to control CSOs in most practical way for community; it made sure the CSO control is not beyond a communitys budget; and allowed water quality parameters to be flexible, based upon the site specific conditions. The CSO Control Policy' required all publicly owned treatment works to have "nine minimum controls" in place by January 1, 1997, in order to decrease the effects of sewage overflow by making small improvements in existing processes. In 2000 Congress amended the Clean Water Act to require the municipalities to comply with the EPA policy. | 1 | Applied and Interdisciplinary Chemistry |
Spermatozoon is the male gamete. After ejaculation this cell is not mature, so it can not fertilize the oocyte. To have the ability to fertilize the female gamete, this cell suffers capacitation and acrosome reaction in female reproductive tract. The signaling pathways best described for spermatozoon involve these processes. The cAMP/PKA signaling pathway leads to sperm cells capacitation; however, adenylyl cyclase in sperm cells is different from the somatic cells. Adenylyl cyclase in spermatozoon does not recognize G proteins, so it is stimulated by bicarbonate and Ca ions. Then, it converts adenosine triphosphate into cyclic AMP, which activates Protein kinase A. PKA leads to protein tyrosine phosphorylation.
Phospholipase C (PLC) is involved in acrosome reaction. ZP3 is a glycoprotein present in zona pelucida and it interacts with receptors in spermatozoon. So, ZP3 can activate G protein coupled receptors and tyrosine kinase receptors, that leads to production of PLC. PLC cleaves the phospholipid phosphatidylinositol 4,5-bisphosphate (PIP2) into diacyl glycerol (DAG) and inositol 1,4,5-trisphosphate. IP3 is released as a soluble structure into the cytosol and DAG remains bound to the membrane. IP3 binds to IP3 receptors, present in acrosome membrane. In addition, calcium and DAG together work to activate protein kinase C, which goes on to phosphorylate other molecules, leading to altered cellular activity. These actions cause an increase in cytosolic concentration of Ca that leads to dispersion of actin and consequently promotes plasmatic membrane and outer acrosome membrane fusion.
Progesterone is a steroid hormone produced in cumulus oophorus. In somatic cells it binds to receptors in nucleus; however, in spermatozoon its receptors are present in plasmatic membrane. This hormone activates AKT that leads to activation of other protein kinases, involved in capacitation and acrosome reaction.
When ROS (reactive oxygen species) are present in high concentration, they can affect the physiology of cells, but when they are present in moderated concentration they are important for acrosome reaction and capacitation. ROS can interact with cAMP/PKA and progesterone pathway, stimulating them. ROS also interacts with ERK pathway that leads to activation of Ras, MEK and MEK-like proteins. These proteins activate protein tyrosine kinase (PTK) that phosphorylates various proteins important for capacitation and acrosome reaction. | 0 | Theoretical and Fundamental Chemistry |
Protein adsorption influences the interactions that occur at the tissue-implant interface. Protein adsorption can lead to blood clots, the foreign-body response and ultimately the degradation of the device. In order to counter-act the effects of protein adsorption, implants are often coated with a polymer coating to decrease protein adsorption.
Polyethylene glycol (PEG) coatings have been shown to minimize protein adsorption in the body. The PEG coating consists of hydrophilic molecules that are repulsive to protein adsorption. Proteins consist of hydrophobic molecules and charge sites that want to bind to other hydrophobic molecules and oppositely charged sites. By applying a thin monolayer coating of PEG, protein adsorption is prevented at the device site. Furthermore, the device's resistance to protein adsorption, fibroblast adhesion and bacteria adhesion are increased. | 0 | Theoretical and Fundamental Chemistry |
Many health departments require a percolation test ("perc" test) to establish the suitability of drain field soil to receive septic tank effluent. An engineer, soil scientist, or licensed designer may be required to work with the local governing agency to design a system that conforms to these criteria.
A more progressive way to determine leach field sizing is by direct observation of the soil profile. In this observation, the engineer evaluates many features of the soil such as texture, structure, consistency, pores/roots, etc.
The goal of percolation testing is to ensure the soil is permeable enough for septic tank effluent to percolate away from the drain field, but fine grained enough to filter out pathogenic bacteria and viruses before they travel far enough to reach a water well or surface water supply. Coarse soils – sand and gravel – can transmit wastewater away from the drain field before pathogens are destroyed. Silt and clay effectively filter out pathogens but allow very limited wastewater flow rates. Percolation tests measure the rate at which clean water disperses through a disposal trench into the soil. Several factors may reduce observed percolation rates when the drain field receives anoxic septic tank effluent:
*Microbial colonies catabolizing soluble organic compounds from the septic tank effluent will adhere to soil particles and reduce the interstitial area available for water flow between soil particles. These colonies tend to form a low-permeability biofilm of gelatinous slime at the soil interface of the disposal trench.
*Insoluble particles small enough to be carried through the septic tank will accumulate at the soil interface of the disposal trench; non-biodegradable particles like synthetic fiber lint from laundry, mineral soil from washing, or bone and eggshell fragments from garbage disposals will remain to fill interstitial areas formerly available for water flow out of the trench.
*Cooking fats or petroleum products emulsified by detergents or dissolved by solvents can flow through prior to anaerobic liquefaction when septic tank volume is too small to offer adequate residence time, and may congeal as a hydrophobic layer on the soil interface of the disposal trench.
*Rising groundwater levels may reduce the available hydraulic head (or vertical distance) causing gravitational water flow away from the disposal trench. Effluent initially flowing downward from the disposal trench might ultimately encounter groundwater or impermeable rock or clay requiring a directional shift to horizontal movement away from the drain field. A certain vertical distance is required between the effluent level in the disposal trench and the water level applicable when the effluent leaves the drain field in order for gravitational force to overcome viscous frictional forces resisting flow through porous soil. Effluent levels in the vicinity of the drain field will rise toward the ground surface to preserve that vertical distance difference if groundwater levels surrounding the drain field approach the level of effluent in the disposal trench.
*Frozen ground may seasonally reduce the cross-sectional area available for flow or evaporation. | 1 | Applied and Interdisciplinary Chemistry |
The 146 even-proton, even-neutron (EE) nuclides comprise ~58% of all stable nuclides and all have spin 0 because of pairing. There are also 24 primordial long-lived even-even nuclides. As a result, each of the 41 even-numbered elements from 2 to 82 has at least one stable isotope, and most of these elements have several primordial isotopes. Half of these even-numbered elements have six or more stable isotopes. The extreme stability of helium-4 due to a double pairing of 2 protons and 2 neutrons prevents any nuclides containing five (, ) or eight () nucleons from existing long enough to serve as platforms for the buildup of heavier elements via nuclear fusion in stars (see triple alpha process).
Only five stable nuclides contain both an odd number of protons and an odd number of neutrons. The first four "odd-odd" nuclides occur in low mass nuclides, for which changing a proton to a neutron or vice versa would lead to a very lopsided proton-neutron ratio (, , , and ; spins 1, 1, 3, 1). The only other entirely "stable" odd-odd nuclide, (spin 9), is thought to be the rarest of the 251 stable nuclides, and is the only primordial nuclear isomer, which has not yet been observed to decay despite experimental attempts.
Many odd-odd radionuclides (such as the ground state of tantalum-180) with comparatively short half-lives are known. Usually, they beta-decay to their nearby even-even isobars that have paired protons and paired neutrons. Of the nine primordial odd-odd nuclides (five stable and four radioactive with long half-lives), only is the most common isotope of a common element. This is the case because it is a part of the CNO cycle. The nuclides and are minority isotopes of elements that are themselves rare compared to other light elements, whereas the other six isotopes make up only a tiny percentage of the natural abundance of their elements. | 0 | Theoretical and Fundamental Chemistry |
* by drugs: pharmacotherapy, chemotherapy (also, medical therapy often means specifically pharmacotherapy)
* by medical devices: implantation
** cardiac resynchronization therapy
* by specific molecules: molecular therapy (although most drugs are specific molecules, molecular medicine refers in particular to medicine relying on molecular biology)
** by specific biomolecular targets: targeted therapy
*** molecular chaperone therapy
** by chelation: chelation therapy
* by specific chemical elements:
** by metals:
*** by heavy metals:
**** by gold: chrysotherapy (aurotherapy)
**** by platinum-containing drugs: platin therapy
*** by biometals
**** by lithium: lithium therapy
**** by potassium: potassium supplementation
**** by magnesium: magnesium supplementation
**** by chromium: chromium supplementation; phonemic neurological hypochromium therapy
**** by copper: copper supplementation
** by nonmetals:
*** by diatomic oxygen: oxygen therapy, hyperbaric oxygen therapy (hyperbaric medicine)
**** transdermal continuous oxygen therapy
*** by triatomic oxygen (ozone): ozone therapy
*** by fluoride: fluoride therapy
*** by other gases: medical gas therapy
* by water:
** hydrotherapy
** aquatic therapy
** rehydration therapy
*** oral rehydration therapy
** water cure (therapy)
* by biological materials (biogenic substances, biomolecules, biotic materials, natural products), including their synthetic equivalents: biotherapy
** by whole organisms
*** by viruses: virotherapy
*** by bacteriophages: phage therapy
*** by animal interaction: see animal interaction section
** by constituents or products of organisms
*** by plant parts or extracts (but many drugs are derived from plants, even when the term phytotherapy is not used)
**** scientific type: phytotherapy
**** traditional (prescientific) type: herbalism
*** by animal parts: quackery involving shark fins, tiger parts, and so on, often driving threat or endangerment of species
*** by genes: gene therapy
**** gene therapy for epilepsy
**** gene therapy for osteoarthritis
**** gene therapy for color blindness
**** gene therapy of the human retina
**** gene therapy in Parkinson's disease
*** by epigenetics: epigenetic therapy
*** by proteins: protein therapy (but many drugs are proteins despite not being called protein therapy)
*** by enzymes: enzyme replacement therapy
*** by hormones: hormone therapy
**** hormonal therapy (oncology)
**** hormone replacement therapy
***** estrogen replacement therapy
***** androgen replacement therapy
***** hormone replacement therapy (menopause)
***** transgender hormone therapy
****** feminizing hormone therapy
****** masculinizing hormone therapy
**** antihormone therapy
***** androgen deprivation therapy
*** by whole cells: cell therapy (cytotherapy)
**** by stem cells: stem cell therapy
**** by immune cells: see immune system products below
*** by immune system products: immunotherapy, host modulatory therapy
**** by immune cells:
***** T-cell vaccination
***** cell transfer therapy
***** autologous immune enhancement therapy
***** TK cell therapy
**** by humoral immune factors: antibody therapy
***** by whole serum: serotherapy, including antiserum therapy
***** by immunoglobulins: immunoglobulin therapy
****** by monoclonal antibodies: monoclonal antibody therapy
** by urine: urine therapy (some scientific forms; many prescientific or pseudoscientific forms)
** by food and dietary choices:
*** medical nutrition therapy
*** grape therapy (quackery)
* by salts (but many drugs are the salts of organic acids, even when drug therapy is not called by names reflecting that)
** by salts in the air
*** by natural dry salt air: "taking the cure" in desert locales (especially common in prescientific medicine; for example, one 19th-century way to treat tuberculosis)
*** by artificial dry salt air:
**** low-humidity forms of speleotherapy
**** negative air ionization therapy
*** by moist salt air:
**** by natural moist salt air: seaside cure (especially common in prescientific medicine)
**** by artificial moist salt air: water vapor forms of speleotherapy
** by salts in the water
*** by mineral water: spa cure ("taking the waters") (especially common in prescientific medicine)
*** by seawater: seaside cure (especially common in prescientific medicine)
* by aroma: aromatherapy
* by other materials with mechanism of action unknown
** by occlusion with duct tape: duct tape occlusion therapy | 1 | Applied and Interdisciplinary Chemistry |
The collective effective dose, dose quantity S, is calculated as the sum of all individual effective doses over the time period or during the operation being considered due to ionizing radiation. It can be used to estimate the total health effects of a process or accidental release involving ionizing radiation to an exposed population. The total collective dose is the dose to the exposed human population between the time of release until its elimination from the environment, perhaps integrating to time equals infinity. However, doses are generally reported for specific populations and a stated time interval. The International Commission on Radiological Protection (ICRP) states: "To avoid aggregation of low individual doses over extended time periods and wide geographical regions the range in effective dose and the time period should be limited and specified. | 0 | Theoretical and Fundamental Chemistry |
Sensor-based ore sorting is the terminology used in the mining industry. It is a coarse physical coarse particle separation technology usually applied in the size range for . Aim is either to create a lumpy product in ferrous metals, coal or industrial minerals applications or to reject waste before it enters production bottlenecks and more expensive comminution and concentration steps in the process.
In the majority of all mining processes, particles of sub-economic grade enter the traditional comminution, classification and concentration steps. If the amount of sub-economic material in the above-mentioned fraction is roughly 25% or more, there is good potential that sensor-based ore sorting is a technically and financially viable option. High added value can be achieved with relatively low capital expenditure, especially when increasing the productivity through downstream processing of higher grade feed and through increased overall recovery when rejecting deleterious waste. | 0 | Theoretical and Fundamental Chemistry |
The rapid neutron capture process is believed to operate very close to the neutron drip line, though the astrophysical site of the r-process, while widely believed to take place in core-collapse supernovae, is unknown. While the neutron drip line is very poorly determined experimentally, and the exact reaction flow is not precisely known, various models predict that nuclei along the r-process path have a two-neutron separation energy (S) of approximately 2 MeV. Beyond this point, stability is thought to rapidly decrease in the vicinity of the drip line, with beta decay occurring before further neutron capture. In fact, the nuclear physics of extremely neutron-rich matter is a fairly new subject, and already has led to the discovery of the island of inversion and halo nuclei such as Li, which has a very diffuse neutron skin leading to a total radius comparable to that of Pb. Thus, although the neutron drip line and the r-process are linked very closely in research, it is an unknown frontier awaiting future research, both from theory and experiment. | 0 | Theoretical and Fundamental Chemistry |
On blood tests, an elevated level of lactate dehydrogenase usually indicates tissue damage, which has multiple potential causes, reflecting its widespread tissue distribution:
*Hemolytic anemia
*Vitamin B12 deficiency anemia
*Infections such as infectious mononucleosis, meningitis, encephalitis, HIV/AIDS. It is notably increased in sepsis.
*Infarction, such as bowel infarction, myocardial infarction and lung infarction
*Acute kidney disease
*Acute liver disease
*Rhabdomyolysis
*Pancreatitis
*Bone fractures
*Cancers, notably testicular cancer and lymphoma. A high LDH after chemotherapy may indicate that it has not been successful.
*Severe shock
*Hypoxia
Low and normal levels of LDH do not usually indicate any pathology. Low levels may be caused by large intake of vitamin C.
LDH is a protein that normally appears throughout the body in small amounts. | 1 | Applied and Interdisciplinary Chemistry |
Propionyl-CoA production through the catabolism of fatty acids is also associated with thioesterifcation. In a study concerning Aspergillus nidulans, it was found that with the inhibition of a methylcitrate synthase gene, mcsA, of the pathway described above, production of distinct polyketides was inhibited as well. Therefore, the utilization of propionyl-CoA through the methylcitrate cycle decreases its concentration, while subsequently increasing the concentration of polyketides. A polyketide is a structure commonly found in fungi that is made of acetyl- and malonyl-CoAs, providing a product with alternating carbonyl groups and methylene groups. Polyketides and polyketide derivatives are often highly structurally complex, and several are highly toxic. This has led to research on limiting polyketide toxicity to crops in agriculture through phytopathogenic fungi. | 1 | Applied and Interdisciplinary Chemistry |
Gas kinetics is a science in the branch of fluid dynamics, concerned with the study of motion of gases and its effects on physical systems. Based on the principles of fluid mechanics and thermodynamics, gas dynamics arises from the studies of gas flows in transonic and supersonic flights. To distinguish itself from other sciences in fluid dynamics, the studies in gas dynamics are often defined with gases flowing around or within physical objects at speeds comparable to or exceeding the speed of sound and causing a significant change in temperature and pressure. Some examples of these studies include but are not limited to: choked flows in nozzles and valves, shock waves around jets, aerodynamic heating on atmospheric reentry vehicles and flows of gas fuel within a jet engine. At the molecular level, gas dynamics is a study of the kinetic theory of gases, often leading to the study of gas diffusion, statistical mechanics, chemical thermodynamics and non-equilibrium thermodynamics. Gas dynamics is synonymous with aerodynamics when the gas field is air and the subject of study is flight. It is highly relevant in the design of aircraft and spacecraft and their respective propulsion systems. | 1 | Applied and Interdisciplinary Chemistry |
The cost of a study depends on many factors, especially the number of sites conducting the study, the number of patients involved, and whether the study treatment is already approved for medical use.
The expenses incurred by a pharmaceutical company in administering a Phase III orIV clinical trial may include, among others:
* production of the drug(s) or device(s) being evaluated
* staff salaries for the designers and administrators of the trial
* payments to the contract research organization, the site management organization (if used) and any outside consultants
* payments to local researchers and their staff for their time and effort in recruiting test subjects and collecting data for the sponsor
* the cost of study materials and the charges incurred to ship them
* communication with the local researchers, including on-site monitoring by the CRO before and (in some cases) multiple times during the study
* one or more investigator training meetings
* expense incurred by the local researchers, such as pharmacy fees, IRB fees and postage
* any payments to subjects enrolled in the trial
* the expense of treating a test subject who develops a medical condition caused by the study drug
These expenses are incurred over several years.
In the US, sponsors may receive a 50 percent tax credit for clinical trials conducted on drugs being developed for the treatment of orphan diseases. National health agencies, such as the US National Institutes of Health, offer grants to investigators who design clinical trials that attempt to answer research questions of interest to the agency. In these cases, the investigator who writes the grant and administers the study acts as the sponsor, and coordinates data collection from any other sites. These other sites may or may not be paid for participating in the study, depending on the amount of the grant and the amount of effort expected from them. Using internet resources can, in some cases, reduce the economic burden. | 1 | Applied and Interdisciplinary Chemistry |
The Gowanus Canal, in Brooklyn, New York, is bounded by several communities including Park Slope, Cobble Hill, Carroll Gardens, and Red Hook. The canal empties into New York Harbor. Completed in 1869, the canal was once a major transportation route for the then separate cities of Brooklyn and New York City. Manufactured gas plants, mills, tanneries, and chemical plants are among the many facilities that operated along the canal. As a result of years of discharges, storm water runoff, sewer outflows, and industrial pollutants, the canal has become one of the nation's most extensively contaminated water bodies. Contaminants include PCBs, coal tar wastes, heavy metals, and volatile organics. On March 2, 2010, EPA added the canal to its Superfund National Priorities List (NPL). Placing the canal on the list allows the agency to further investigate contamination at the site and develop an approach to address the contamination.
After the NPL designation, several firms tried to redesign the area surrounding the canal to meet EPA's principles. One of the proposals was the Gowanus Canal Sponge Park, suggested by Susannah Drake of DLANDstudio, an architecture and landscape architecture firm based in Brooklyn. The firm designed a public open space system that slows, absorbs, and filters surface water runoff with the goal of remediating contaminated water, activating the private canal waterfront, and revitalizing the neighborhood. The unique feature of the park is its character as a working landscape that means the ability to improve the environment of the canal over time while simultaneously supporting public engagement with the canal ecosystem. The park was cited in a professional award by the American Society of Landscape Architects (ASLA), in the Analysis and Planning category, in 2010. | 1 | Applied and Interdisciplinary Chemistry |
Kiick designs polymer nanostructures for targeted therapies and hydrogel matrices for regenerative medicine. She makes use of biomimetic self-assembly, bioconjugation and biosynthesis. In particular, Kiick has worked on polymer-peptide macromolecular structures that can engage cellular targets. These include the use of polyethylene glycol (PEG) in click chemistry to form hydrogels that degrade selectively in response to molecules present in tissues and extracellular matrix. Kiick has shown it is possible to selectively release small molecule cargo with a tuned release for applications in targeted drug-delivery and vascular grafts. She has developed resilin-like polypeptides (RLP), elastomeric materials that can be cross-linked using small molecules, as well as hydrogels that contain nanoparticles for targeting tumors and inflammatory conditions. Resilin is a primary elastomeric protein that is found in insects, and helps them to jump long distances and produce sound.
She joined the faculty at the University of Delaware in 2001, and earned the rank of associate professor in 2007. In 2011 Kiick was promoted to the rank of professor of materials science and engineering and also named deputy dean of the University of Delaware’s college of engineering. In 2019-2020 she was awarded a Leverhulme Visiting Professorship from the Leverhulme Trust and a Fulbright Scholarship from the Fulbright Program to the University of Nottingham, to develop protocols for fabricating bioelastomeric materials. | 0 | Theoretical and Fundamental Chemistry |
Interferometric nanoparticle tracking analysis (iNTA) is the next generation of NTA technology. It is based on interferometric scattering microscopy (iSCAT), which enhances the signal of weak scatterers. In contrast to NTA, iNTA has a superior resolution based on a two-parameter analysis, including the size and the scattering cross-section of the particle. | 0 | Theoretical and Fundamental Chemistry |
The intuitive concept of the SFMs led to different versions of the visualization method established in different domains of materials science.
Structure field map was first introduced in 1954 by MacKenzie L. Keith and Rustum Roy to classify structural prototypes for the oxide perovskites of the chemical formula ABO. It was later popularized by a compiled handbook written by Olaf Muller and Rustum Roy, published in 1974 that included many more known materials. | 0 | Theoretical and Fundamental Chemistry |
Long-range order has been observed in thin films of colloidal liquids under oil—with the faceted edge of an emerging single crystal in alignment with the diffuse streaking pattern in the liquid phase. Structural defects have been directly observed in the ordered solid phase as well as at the interface of the solid and liquid phases. Mobile lattice defects have been observed via Bragg reflections, due to the modulation of the light waves in the strain field of the defect and its stored elastic strain energy. | 0 | Theoretical and Fundamental Chemistry |
Applications of dendrimers typically involve conjugating other chemical species to the dendrimer surface that can function as detecting agents (such as a dye molecule), affinity ligands, targeting components, radioligands, imaging agents, or pharmaceutically active compounds. Dendrimers have very strong potential for these applications because their structure can lead to multivalent systems. In other words, one dendrimer molecule has hundreds of possible sites to couple to an active species. Researchers aimed to utilize the hydrophobic environments of the dendritic media to conduct photochemical reactions that generate the products that are synthetically challenged. Carboxylic acid and phenol-terminated water-soluble dendrimers were synthesized to establish their utility in drug delivery as well as conducting chemical reactions in their interiors. This might allow researchers to attach both targeting molecules and drug molecules to the same dendrimer, which could reduce negative side effects of medications on healthy cells.
Dendrimers can also be used as a solubilizing agent. Since their introduction in the mid-1980s, this novel class of dendrimer architecture has been a prime candidate for host–guest chemistry. Dendrimers with hydrophobic core and hydrophilic periphery have shown to exhibit micelle-like behavior and have container properties in solution. The use of dendrimers as unimolecular micelles was proposed by Newkome in 1985. This analogy highlighted the utility of dendrimers as solubilizing agents. The majority of drugs available in pharmaceutical industry are hydrophobic in nature and this property in particular creates major formulation problems. This drawback of drugs can be ameliorated by dendrimeric scaffolding, which can be used to encapsulate as well as to solubilize the drugs because of the capability of such scaffolds to participate in extensive hydrogen bonding with water. Dendrimer labs are trying to manipulate dendrimer's solubilizing trait, to explore dendrimers for drug delivery and to target specific carriers.
For dendrimers to be able to be used in pharmaceutical applications, they must surmount the required regulatory hurdles to reach market. One dendrimer scaffold designed to achieve this is the polyethoxyethylglycinamide (PEE-G) dendrimer. This dendrimer scaffold has been designed and shown to have high HPLC purity, stability, aqueous solubility and low inherent toxicity. | 0 | Theoretical and Fundamental Chemistry |
Clean agent FS 49 C2 is an environmentally engineered, human safe, fast acting Clean Agent fire extinguishing gas for gaseous fire suppression installed in a suited fire suppression system. The gas consists of tetrafluoroethane, pentafluoroethane and carbon dioxide.
FS 49 C2 maintains breathable concentrations of oxygen in the air. It can extinguish a fire with less danger to people in the room at extinguishing concentrations in contrast to pure carbon dioxide based fire suppression system that is deadly to humans when released in extinguishing amounts.
The gas was initially called Halotron II B/FS49C2. | 1 | Applied and Interdisciplinary Chemistry |
Push–pull perfusion is an in vivo sampling method most commonly used for measuring neurotransmitters in the brain. Developed by J.H. Gaddum in 1960,
this technique replaced the cortical cup technique for observing neurotransmitters. The advent of concentric microdialysis probes in the 1980s resulted in push-pull sampling falling out of favor, as such probes require less monitoring, and are less invasive than the higher flow rate push-pull probes (>10 microliter/min), which could result in lesions if flow is unbalanced.
With the advent of microfluidics and miniaturized probes, low-flow push–pull sampling was developed in 2002. By using flow rates of ~50 nL/min, this technique minimizes tissue damage while providing finer spatial resolution than microdialysis sampling. | 1 | Applied and Interdisciplinary Chemistry |
The CD family of co-receptors are a well-studied group of extracellular receptors found in immunological cells. The CD receptor family typically act as co-receptors, illustrated by the classic example of CD4 acting as a co-receptor to the T cell receptor (TCR) to bind major histocompatibility complex II (MHC-II). This binding is particularly well-studied in T-cells where it serves to activate T-cells that are in their resting (or dormant) phase and to cause active cycling T-cells to undergo programmed cell death. Boehme et al. demonstrated this interesting dual outcome by blocking the binding of CD4 to MHC-II which prevented the programmed cell death reaction that active T-cells typically display.
The CD4 receptor is composed of four concatamerized Ig-like domains and is anchored to the cell membrane by a single transmembrane domain. CD family receptors are typically monomers or dimers, though they are all primarily extracellular proteins. The CD4 receptor in particular interacts with murine MHC-II following the "ball-on-stick" model, where the Phe-43 ball fits into the conserved hydrophobic α2 and β2 domain residues. During binding with MHC-II, CD4 maintains independent structure and does not form any bonds with the TCR receptor.
The members of the CD family of co-receptors have a wide range of function. As well as being involved in forming a complex with MHC-II with TCR to control T-cell fate, the CD4 receptor is infamously the primary receptor that HIV envelope glycoprotein GP120 binds to. In comparison, CD28 acts as a ‘co-coreceptor’ (costimulatory receptor) for the MHC-II binding with TCR and CD4. CD28 increases the IL-2 secretion from the T-cells if it is involved in the initial activation; however, CD28 blockage has no effect on programmed cell death after the T-cell has been activated. | 1 | Applied and Interdisciplinary Chemistry |
Permeable pavements may give urban trees the rooting space they need to grow to full size. A "structural-soil" pavement base combines structural aggregate with soil; a porous surface admits vital air and water to the rooting zone. This integrates healthy ecology and thriving cities, with the living tree canopy above, the city's traffic on the ground, and living tree roots below. The benefits of permeables on urban tree growth have not been conclusively demonstrated and many researchers have observed tree growth is not increased if construction practices compact materials before permeable pavements are installed. | 1 | Applied and Interdisciplinary Chemistry |
Sir Walter Norman Haworth FRS (19 March 1883 – 19 March 1950) was a British chemist best known for his groundbreaking work on ascorbic acid (vitamin C) while working at the University of Birmingham. He received the 1937 Nobel Prize in Chemistry "for his investigations on carbohydrates and vitamin C". The prize was shared with Swiss chemist Paul Karrer for his work on other vitamins.
Haworth worked out the correct structure of a number of sugars, and is known among organic chemists for his development of the Haworth projection that translates three-dimensional sugar structures into convenient two-dimensional graphical form. | 0 | Theoretical and Fundamental Chemistry |
However, fluctuations that cause the correlations between pairs of atoms to decrease as their separation increases, causes the Bragg peaks in the structure factor of a crystal to broaden. To see how this works, we consider a one-dimensional toy model: a stack of plates with mean spacing . The derivation follows that in chapter 9 of Guinier's textbook. This model has been pioneered by and applied to a number of materials by Hosemann and collaborators over a number of years. Guinier and they termed this disorder of the second kind, and Hosemann in particular referred to this imperfect crystalline ordering as paracrystalline ordering. Disorder of the first kind is the source of the Debye–Waller factor.
To derive the model we start with the definition (in one dimension) of the
To start with we will consider, for simplicity an infinite crystal, i.e., . We will consider a finite crystal with disorder of the second-type below.
For our infinite crystal, we want to consider pairs of lattice sites. For large each plane of an infinite crystal, there are two neighbours planes away, so the above double sum becomes a single sum over pairs of neighbours either side of an atom, at positions and lattice spacings away, times . So, then
where is the probability density function for the separation of a pair of planes, lattice spacings apart. For the separation of neighbouring planes we assume for simplicity that the fluctuations around the mean neighbour spacing of a are Gaussian, i.e., that
and we also assume that the fluctuations between a plane and its neighbour, and between this neighbour and the next plane, are independent. Then is just the convolution of two s, etc. As the convolution of two Gaussians is just another Gaussian, we have that
The sum in is then just a sum of Fourier transforms of Gaussians, and so
for . The sum is just the real part of the sum and so the structure factor of the infinite but disordered crystal is
This has peaks at maxima , where . These peaks have heights
i.e., the height of successive peaks drop off as the order of the peak (and so ) squared. Unlike finite-size effects that broaden peaks but do not decrease their height, disorder lowers peak heights. Note that here we assuming that the disorder is relatively weak, so that we still have relatively well defined peaks. This is the limit , where . In this limit, near a peak we can approximate , with and obtain
which is a Lorentzian or Cauchy function, of FWHM , i.e., the FWHM increases as the square of the order of peak, and so as the square of the wave vector at the peak.
Finally, the product of the peak height and the FWHM is constant and equals , in the limit. For the first few peaks where is not large, this is just the limit. | 0 | Theoretical and Fundamental Chemistry |
Lecithin ( ; from the Ancient Greek "yolk") is a generic term to designate any group of yellow-brownish fatty substances occurring in animal and plant tissues which are amphiphilic – they attract both water and fatty substances (and so are both hydrophilic and lipophilic), and are used for smoothing food textures, emulsifying, homogenizing liquid mixtures, and repelling sticking materials.
Lecithins are mixtures of glycerophospholipids including phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, and phosphatidic acid.
Lecithin was first isolated in 1845 by the French chemist and pharmacist Théodore Gobley. In 1850, he named the phosphatidylcholine . Gobley originally isolated lecithin from egg yolk and established the complete chemical formula of phosphatidylcholine in 1874; in between, he demonstrated the presence of lecithin in a variety of biological materials, including venous blood, human lungs, bile, roe, and brains of humans, sheep and chicken.
Lecithin can easily be extracted chemically using solvents such as hexane, ethanol, acetone, petroleum ether or benzene; or extraction can be done mechanically. Common sources include egg yolk, marine foods, soybeans, milk, rapeseed, cottonseed, and sunflower oil. It has low solubility in water, but is an excellent emulsifier. In aqueous solution, its phospholipids can form either liposomes, bilayer sheets, micelles, or lamellar structures, depending on hydration and temperature. This results in a type of surfactant that usually is classified as amphipathic. Lecithin is sold as a food additive and dietary supplement. In cooking, it is sometimes used as an emulsifier and to prevent sticking, for example in non-stick cooking spray. | 0 | Theoretical and Fundamental Chemistry |
Coagulation is one of the most important physio-chemical reactions used in water treatment. Ions (heavy metals) and colloids (organic and inorganic) are mostly held in solution by electrical charges. The addition of ions with opposite charges destabilizes the colloids, allowing them to coagulate. Coagulation can be achieved by a chemical coagulant or by electrical methods. Alum [Al(SO)18HO] is such a chemical substance, which has been widely used for ages for wastewater treatment.
The mechanism of coagulation has been the subject of continual review. It is generally accepted that coagulation is brought about primarily by the reduction of the net surface charge to a point where the colloidal particles, previously stabilized by electrostatic repulsion, can approach closely enough for van der Waals forces to hold them together and allow aggregation. The reduction of the surface charge is a consequence of the decrease of the repulsive potential of the electrical double layer by the presence of an electrolyte having opposite charge. In the EC process, the coagulant is generated in situ by electrolytic oxidation of an appropriate anode material. In this process, charged ionic species—metals or otherwise—are removed from wastewater by allowing it to react with an ion having an opposite charge, or with floc of metallic hydroxides generated within the effluent.
Electrocoagulation offers an alternative to the use of metal salts or polymers and polyelectrolyte addition for breaking stable emulsions and suspensions. The technology removes metals, colloidal solids and particles, and soluble inorganic pollutants from aqueous media by introducing highly charged polymeric metal hydroxide species. These species neutralize the electrostatic charges on suspended solids and oil droplets to facilitate agglomeration or coagulation and resultant separation from the aqueous phase. The treatment prompts the precipitation of certain metals and salts: | 1 | Applied and Interdisciplinary Chemistry |
The potential difference at each pole of the BPE (which may or may not be enough for electrochemical reactions).
Note that the solution potential is not directly controlled by a power source (e.g. potentiostat) because it depends also on the solution composition. Therefore, for electrons to transfer to reduce species in the solution, the potential of the working electrode need to be set to a value more negative than of an electroactive molecule in the solution, and then – depending on the kinetics – electrons may transfer. In similar fashion, oxidation reactions occur. Also, according to Ohm’s law, the electric field and solution potential (V) will increase with increasing solution resistivity and the applied current at the outer-circuit. | 0 | Theoretical and Fundamental Chemistry |
2-Phosphoglyceric acid (2PG), or 2-phosphoglycerate, is a glyceric acid which serves as the substrate in the ninth step of glycolysis. It is catalyzed by enolase into phosphoenolpyruvate (PEP), the penultimate step in the conversion of glucose to pyruvate. | 1 | Applied and Interdisciplinary Chemistry |
Tammann was born in Yamburg (now Kingisepp, Leningrad Oblast). His father, Heinrich Tammann (1833–1864) was of Estonian peasant origin and his mother, Matilda Schünmann, was of German origin. Tammann graduated from University of Dorpat in chemistry. He came to Göttingen University in 1903 where he established the first Institute of Inorganic Chemistry in Germany. In 1908 he was appointed director of the Physico-Chemical Institute. His interests focused on the physics and physical chemistry of metals and alloys (metallurgy). In 1925, Tammann was awarded Liebig Medal. On 28 May 1936, Tammann was awarded the Eagle Shield of the German Empire (), with dedication "The Doyen of German Metallurgy". He was also known for the Vogel-Fulcher-Tammann equation, and the Tait-Tammann equation of state which seeks to account for the compressibility of liquids.
Tammann died in Göttingen at age 77. | 0 | Theoretical and Fundamental Chemistry |
Marques' father died when she was just eight years old. After high school she joined the University of Lisbon. From there she graduated in Physics and Chemistry from the Faculty of Sciences. Having turned down a chance to do geological work in Angola, she taught at the faculty after her graduation in 1926, where she was the only woman carrying out teaching or research in chemistry. She married António Silva Sousa Torres (1876-1958), professor at the Faculty of Sciences of the University of Lisbon, but only on condition that she could go to Paris to study for a Doctorate.
Wishing to specialize in radioactivity, she applied for and received a grant from the National Education Board () to study in 1931–32 at the Radium Institute in Paris (now the Curie Institute) on radioactivity topics. At her husbands request she was accompanied by her mother. Impressed by Marques’ work, Curie wrote to the Portuguese government in 1932 requesting an extension of her fellowship but the grant was not renewed. However, the Institute found a way to allow her to continue with her research, which was later turned into work on a doctoral thesis. In her first three years she worked under the guidance of Marie Curie and, in the last year, after Curies death, under the supervision of André-Louis Debierne. Her notes of classes given by Curie and Debierne form part of her valuable scientific estate. In 1935 she defended her doctoral thesis on Nouvelles recherches sur le fractionnement des sels de baryum radifère (New research on the fragmentation of radiferous barium salts) at the Sorbonne University. With the support of two Nobel Prize winners, Jean Baptiste Perrin and Frédéric Joliot-Curie, her Doctorate was awarded with three honourable mentions, the highest grade possible. She published her results in three articles in 1936 in the Journal de Chimie Physique and also published six articles in the Comptes rendus de l'Académie des Sciences of Paris.
Despite being invited to continue her research career in Paris, Marques chose to return to Lisbon and resumed her activity at the Faculty of Sciences, where she developed research in the field of radioactivity. In 1936, she created the Radiochemistry Laboratory, which led, in 1953, to the formation of the Centre for Radiochemistry Studies of the Nuclear Energy Studies Commission. She continued to be the director of the centre until well after her formal retirement from the university.
On her return to Lisbon Marques had been awarded a Doctorate in Physical-Chemical Sciences, on the strength of her French qualifications. She continued to do research on nuclear chemistry and radiochemistry and on the therapeutic applications of radioisotopes. She published regularly in Portuguese and international journals. However, despite her excellent qualifications, her career progression was relatively slow. The fact that she was a woman in a profession dominated by men appears to have been a major cause of this. She is quoted as saying that men considered it an insult to have to work with women. A contributory factor was that research was not a high priority in her university at that time: the laboratory she established was the first at the university. She finally became a full professor only in 1966, when she was the first woman to obtain a chair in chemistry at a Portuguese university. Towards the end of her professional life she developed serious problems with her eyesight. In October 1967, she attended ceremonies in Paris to mark the 100th anniversary of the birth of Marie Curie.
Branca Edmée Marques died on 19 July 1986 at the age of 87. In September 2009, the Lisbon City Council approved the name Branca Edmée Marques for a street in the university area as a way to honour her achievements. | 0 | Theoretical and Fundamental Chemistry |
Salts of thioacetic acid such as potassium thioacetate can be used convert nitroarenes to aryl acetamides in one step. This is particularly useful in the preparation of pharmaceuticals, e.g., paracetamol. | 0 | Theoretical and Fundamental Chemistry |
The genome is the total genetic material of an organism and includes both the genes and non-coding sequences. Eukaryotic genes can be annotated using FINDER. | 1 | Applied and Interdisciplinary Chemistry |
If the "strange matter hypothesis" is true, then nuclear matter is metastable against decaying into strange matter. The lifetime for spontaneous decay is very long, so we do not see this decay process happening around us. However, under this hypothesis there should be strange matter in the universe:
# Quark stars (often called "strange stars") consist of quark matter from their core to their surface. They would be several kilometers across, and may have a very thin crust of nuclear matter.
# Strangelets are small pieces of strange matter, perhaps as small as nuclei. They would be produced when strange stars are formed or collide, or when a nucleus decays. | 0 | Theoretical and Fundamental Chemistry |
The relative importance-measuring property of the PageRank link analysis algorithm could be used to identify new possible drug targets in proteins. A PageRank-based algorithm could identify important protein targets in the pathogen organism better than a method considering only the number of incoming edges (in-degree) of a node in the metabolic network. The reason for this is that some already known, important protein targets do not have a high degree (are not hubs) and also, perturbing some hubs could result in unwanted physiological effects. | 1 | Applied and Interdisciplinary Chemistry |
A recent development in forensic science is the isotopic analysis of hair strands. Hair has a recognisable growth rate of 9-11mm per month or 15 cm per year. Human hair growth is primarily a function of diet, especially drinking water intake. The stable isotopic ratios of drinking water are a function of location, and the geology that the water percolates through. Sr, Sr and oxygen isotope variations are different all over the world. These differences in isotopic ratio are then biologically set in our hair as it grows and it has therefore become possible to identify recent geographic histories by the analysis of hair strands. For example, it could be possible to identify whether a terrorist suspect had recently been to a particular location from hair analysis. This hair analysis is a non-invasive method which is becoming very popular in cases that DNA or other traditional means are bringing no answers.
Isotope analysis can be used by forensic investigators to determine whether two or more samples of explosives are of a common origin. Most high explosives contain carbon, hydrogen, nitrogen and oxygen atoms and thus comparing their relative abundances of isotopes can reveal the existence of a common origin. Researchers have also shown that analysis of the C/C ratios can locate the country of origin for a given explosive.
Stable isotopic analysis has also been used in the identification of drug trafficking routes. Isotopic abundances are different in morphine grown from poppies in south-east Asia versus poppies grown in south-west Asia. The same is applied to cocaine that is derived from Bolivia and that from Colombia. | 0 | Theoretical and Fundamental Chemistry |
The word comes from Ancient Greek θίξις thixis touch (from thinganein to touch) and -tropy, -tropous, from Ancient Greek -τρόπος -tropos of turning, from τρόπος tropos a turn, from τρέπειν trepein, to turn. Hence, it can be translated as something that turns (or changes) when touched. It was invented by Herbert Freundlich originally for a sol-gel transformation. | 1 | Applied and Interdisciplinary Chemistry |
Recently, various carbonyls have been turned into organometallic reagent surrogates via hydrazone umpolung by C.-J. Li et al. In the presence of a catalyst, similar to organometallic reagents, hydrazones can undergo nucleophilic additions, conjugate additions, and transition-metal catalyzed cross-couplings with various electrophiles to form new C-C bonds. | 0 | Theoretical and Fundamental Chemistry |
James S. Robbins has argued that the advent of petroleum-refined kerosene saved some species of great whales from extinction by providing an inexpensive substitute for whale oil, thus eliminating the economic imperative for open-boat whaling, but others say that fossil fuels increased whaling with most whales being killed in the 20th century. | 0 | Theoretical and Fundamental Chemistry |
HeSE has been used to construct empirical helium-surface scattering potentials through the measurement of selective adsorption resonances (bound state resonances) on the clean LiF(001) surface and the hydrogenated Si(111) surface. | 0 | Theoretical and Fundamental Chemistry |
The coupling of proton translocation and electron transport in Complex I is currently proposed as being indirect (long range conformational changes) as opposed to direct (redox intermediates in the hydrogen pumps as in heme groups of Complexes III and IV). The architecture of the hydrophobic region of complex I shows multiple proton transporters that are mechanically interlinked. The three central components believed to contribute to this long-range conformational change event are the pH-coupled N2 iron-sulfur cluster, the quinone reduction, and the transmembrane helix subunits of the membrane arm. Transduction of conformational changes to drive the transmembrane transporters linked by a connecting rod during the reduction of ubiquinone can account for two or three of the four protons pumped per NADH oxidized. The remaining proton must be pumped by direct coupling at the ubiquinone-binding site. It is proposed that direct and indirect coupling mechanisms account for the pumping of the four protons.
The N2 cluster's proximity to a nearby cysteine residue results in a conformational change upon reduction in the nearby helices, leading to small but important changes in the overall protein conformation. Further electron paramagnetic resonance studies of the electron transfer have demonstrated that most of the energy that is released during the subsequent CoQ reduction is on the final ubiquinol formation step from semiquinone, providing evidence for the "single stroke" H translocation mechanism (i.e. all four protons move across the membrane at the same time). Alternative theories suggest a "two stroke mechanism" where each reduction step (semiquinone and ubiquinol) results in a stroke of two protons entering the intermembrane space.
The resulting ubiquinol localized to the membrane domain interacts with negatively charged residues in the membrane arm, stabilizing conformational changes. An antiporter mechanism (Na/H swap) has been proposed using evidence of conserved Asp residues in the membrane arm. The presence of Lys, Glu, and His residues enable for proton gating (a protonation followed by deprotonation event across the membrane) driven by the pK of the residues. | 1 | Applied and Interdisciplinary Chemistry |
For a light scattering instrument composed of many detectors placed at various angles, all the detectors need to respond the same way. Usually, detectors will have slightly different quantum efficiency, different gains, and are looking at different geometrical scattering volumes. In this case, a normalization of the detectors is absolutely needed. To normalize the detectors, a measurement of a pure solvent is made first. Then an isotropic scatterer is added to the solvent. Since isotropic scatterers scatter the same intensity at any angle, the detector efficiency and gain can be normalized with this procedure. It is convenient to normalize all the detectors to the 90° angle detector.
where I(90) is the scattering intensity measured for the Rayleigh scatterer by the 90° angle detector.
The most common equation to measure the weight-average molecular weight, M, is the Zimm equation (the right-hand side of the Zimm equation is provided incorrectly in some texts, as noted by Hiemenz and Lodge):
where
and
with
and the scattering vector for vertically polarized light is
with n the refractive index of the solvent, λ the wavelength of the light source, N the Avogadro constant, c the solution concentration, and dn/dc the change in the refractive index of the solution with change in concentration. The intensity of the analyte measured at an angle is I(θ). In these equations, the subscript A is for analyte (the solution) and T is for the toluene with the Rayleigh ratio of toluene, R being 1.35×10 cm for a HeNe laser. As described above, the radius of gyration, R, and the second virial coefficient, A, are also calculated from this equation. The refractive index increment dn/dc characterizes the change of the refractive index n with the concentration c and can be measured with a differential refractometer.
A Zimm plot is built from a double extrapolation to zero angle and zero concentration from many angles and many concentration measurements. In its simplest form, the Zimm equation is reduced to:
for measurements made at low angle and infinite dilution since P(0) = 1.
There are typically several analyses developed to analyze the scattering of particles in solution to derive the above-named physical characteristics of particles. A simple static light scattering experiment entails the average intensity of the sample that is corrected for the scattering of the solvent will yield the Rayleigh ratio, R as a function of the angle or the wave vector q as follows: | 0 | Theoretical and Fundamental Chemistry |
;Novels and poetry
*Davy is the subject of a humorous song by Richard Gendall, recorded in 1980 by folk-singer Brenda Wootton in the album Boy Jan Cornishman, the seven verses of which each recall a day of the week on which Davy purportedly made a particular discovery.
*English playwright Nick Darke wrote Laughing Gas (2005) a comedy script about the life of Sir Humphry Davy, unfinished at the time of Nick Darke's death; completed posthumously by actor and playwright Carl Grose and produced by the Truro-based production company O-region.
*Edmund Clerihew Bentley's first clerihew, published in 1905, was written about Sir Humphry Davy:
:Sir Humphry Davy
:Abominated gravy.
:He lived in the odium
:Of having discovered sodium.
* There is a humorous rhyme of unknown origin about the statue in Penzance:
:Sir Humphrey Davy's kindly face,
:Is turned away from Market Place
:Towards St Michael's Mount
:So, if he do want to tell the time
:He've got to wait till the clock do chime
:Then he's forced to count.
*Jules Verne refers to Davys geological theories in his 1864 novel Journey to the Centre of the Earth'
* On the 2021 TV show Avenue 5, when asked who he is referring to, Captain Ryan, played by Hugh Laurie, responds, "Who do you think? Sir Humphrey Davy?" | 1 | Applied and Interdisciplinary Chemistry |
A large compilation of Henry's law constants has been published by Sander (2023). A few selected values are shown in the table below: | 0 | Theoretical and Fundamental Chemistry |
In 1941, Kharash discovered that Grignard reagents add to cyclohexenone in presence of Cu(I) resulting in 1,4-addition instead of 1,2-addition. This work foreshadowed extensive studies on the conjugate additions to enones with organocuprates. Note that if a Grignard reagent (such as RMgBr) is used, the reaction with an enone would instead proceed through a 1,2-addition. The 1,4-addition mechanism of cuprates to enones goes through the nucleophilic addition of the Cu(I) species at the beta-carbon of the alkene to form a Cu(III) intermediate, followed by reductive elimination of Cu(I). In the original paper describing this reaction, methylmagnesium bromide is reacted with isophorone with and without 1 mole percent of added copper(I) chloride (see figure).
Without added salt the main products are alcohol B (42%) from nucleophilic addition to the carbonyl group and diene C (48%) as its dehydration reaction product. With added salt the main product is 1,4-adduct A (82%) with some C (7%).
A 1,6-addition is also possible, for example in one step of the commercial-scale production of fulvestrant: | 0 | Theoretical and Fundamental Chemistry |
The most frequently introduced forms are:where:
* is the absolute pressure of the gas,
* is the volume of the gas,
* is the amount of substance of gas (also known as number of moles),
* is the ideal, or universal, gas constant, equal to the product of the Boltzmann constant and the Avogadro constant,
* is the Boltzmann constant,
* is the Avogadro constant,
* is the absolute temperature of the gas,
* is the number of particles (usually atoms or molecules) of the gas.
In SI units, p is measured in pascals, V is measured in cubic metres, n is measured in moles, and T in kelvins (the Kelvin scale is a shifted Celsius scale, where 0.00 K = −273.15 °C, the lowest possible temperature). R has for value 8.314 J/(mol·K) = 1.989 ≈ 2 cal/(mol·K), or 0.0821 L⋅atm/(mol⋅K). | 0 | Theoretical and Fundamental Chemistry |
Speculation on the power of systems that have been called "molecular assemblers" has sparked a wider political discussion on the implication of nanotechnology. This is in part due to the fact that nanotechnology is a very broad term and could include "molecular assemblers". Discussion of the possible implications of fantastic molecular assemblers has prompted calls for regulation of current and future nanotechnology. There are very real concerns with the potential health and ecological impact of nanotechnology that is being integrated in manufactured products. Greenpeace for instance commissioned a report concerning nanotechnology in which they express concern into the toxicity of nanomaterials that have been introduced in the environment. However, it makes only passing references to "assembler" technology. The UK Royal Society and Royal Academy of Engineering also commissioned a report entitled "Nanoscience and nanotechnologies: opportunities and uncertainties" regarding the larger social and ecological implications of nanotechnology. This report does not discuss the threat posed by potential so-called "molecular assemblers". | 0 | Theoretical and Fundamental Chemistry |
Although originally referred to as AT-AC introns, not all these introns are delimited by AT-AC dinucleotides. Some of them have GT-AG or AT-AG ends, at least. Thus, it is more correct to speak about the splicing machinery which is used to process them, differentiating between U2-type (canonical or major) and U12-type (non-canonical or minor). The main determinants for distinguishing U2- and U12-type introns are 5' splice site and branch site sequences.
The minor spliceosome consists of U11, U12, U4atac, and U6atac, together with U5 and an unknown number of non-snRNP proteins. The U11, U12 and U4atac/U6atac snRNPs are functional analogs of the U1, U2 and U4/U6 snRNPs in the major spliceosome. Although the minor U4atac and U6atac snRNAs are functional analogs of U4 and U6, respectively, they share only limited sequence homology (c. 40%). Furthermore, the sequence of U11 in comparison with U1, as well as U12 compared with U2, are completely unrelated. Despite this fact, the minor U11, U12, U4atac and U6atac snRNAs can be folded into structures similar to U1, U2, U4 and U6, respectively. | 1 | Applied and Interdisciplinary Chemistry |
Cholesterol, glycerophospholipids and sphingolipids are major constituents of the cell membrane and in certain cases function as second messengers in cell proliferation, apoptosis and cell adhesion in inflammation and tumor metastasis. Far-eastern blot was established as a method for transferring lipids from an HPTLC plate to a polyvinylidene difluoride (PVDF) membrane within a minute. Applications of this with other methods have been studied. Far-eastern blotting allows for the purification of glycosphingolipids and phospholipids, structural analysis of lipids in conjunction with direct mass spectrometry, binding studies using various ligands such as antibodies, lectins, bacterium, viruses, and toxins, and enzyme reaction on membranes.
Far-eastern blot is adaptable to the analysis of lipids as well as metabolites of drugs and natural compounds from plants and environmental hormones. | 1 | Applied and Interdisciplinary Chemistry |
To derive an energy equation, note that the advective acceleration term may be decomposed as:where is the vorticity of the flow and is the Euclidean norm. This leads to a form of the momentum equation, ignoring the external forces term, given by:Taking the dot product of with this equation leads to:This equation was arrived at using the scalar triple product . Define to be the energy density:Noting that is time-independent, we arrive at the equation:Assuming that the energy density is time-independent and the flow is one-dimensional leads to the simplification:with being a constant; this is equivalent to Bernoulli's principle. Of particular interest in open-channel flow is the specific energy , which is used to compute the hydraulic head that is defined as:with being the specific weight. However, realistic systems require the addition of a head loss term to account for energy dissipation due to friction and turbulence that was ignored by discounting the external forces term in the momentum equation. | 1 | Applied and Interdisciplinary Chemistry |
An open path detector usually costs more than a single point detector, so there is little incentive for applications that play to a point detector's strengths: where the point detector can be placed at the known location of the highest gas concentration, and a relatively slow response is acceptable. The open path detector excels in outdoor situations where, even if the likely source of the gas release is known, the evolution of the developing cloud or plume is unpredictable. Gas will almost certainly enter an extended linear beam before finding its way to any single chosen point. Also, point detectors in exposed outdoor locations require weather shields to be fitted, increasing the response time significantly. Open path detectors can also show a cost advantage in any application where a row of point detectors would be required to achieve the same coverage, for instance monitoring along a pipeline, or around the perimeter of a plant. Not only will one detector replace several, but the costs of installation, maintenance, cabling etc. are likely to be lower. | 1 | Applied and Interdisciplinary Chemistry |
Genes are regulated so that they are expressed only when the product is needed, since expression draws on limited resources. A cell regulates its gene expression depending on its external environment (e.g. available nutrients, temperature and other stresses), its internal environment (e.g. cell division cycle, metabolism, infection status), and its specific role if in a multicellular organism. Gene expression can be regulated at any step: from transcriptional initiation, to RNA processing, to post-translational modification of the protein. The regulation of lactose metabolism genes in E. coli (lac operon) was the first such mechanism to be described in 1961. | 1 | Applied and Interdisciplinary Chemistry |
These reagents were discovered by Henry Gilman and coworkers. Lithium dimethylcopper (CH)CuLi can be prepared by adding copper(I) iodide to methyllithium in tetrahydrofuran at −78 °C. In the reaction depicted below, the Gilman reagent is a methylating reagent reacting with an alkyne in a conjugate addition, and the negative charge is trapped in a nucleophilic acyl substitution with the ester group forming a cyclic enone. | 0 | Theoretical and Fundamental Chemistry |
The test was originally developed by Ludwig Wilhelm Winkler, in later literature referred to as Lajos Winkler, while working at Budapest University on his doctoral dissertation in 1888. The amount of dissolved oxygen is a measure of the biological activity of the water masses. Phytoplankton and macroalgae present in the water mass-produce oxygen by way of photosynthesis. Bacteria and eukaryotic organisms (zooplankton, fish) consume this oxygen through cellular respiration. The result of these two mechanisms determines the concentration of dissolved oxygen, which in turn indicates the production of biomass. The difference between the physical concentration of oxygen in the water (or the theoretical concentration if there were no living organisms) and the actual concentration of oxygen is called the biochemical demand in oxygen. The Winkler test is often controversial as it is not 100% accurate and the oxygen levels may fluctuate from test to test despite using the same constant sample. | 0 | Theoretical and Fundamental Chemistry |
One of the worst disasters caused by stress corrosion cracking was the fall of the Silver Bridge, WV in 1967, when a single brittle crack formed by rusting grew to criticality. The crack was on one of the tie bar links of one of the suspension chains, and the whole joint failed quickly by overload. The event escalated and the whole bridge disappeared in less than a minute, killing 46 drivers or passengers on the bridge at the time. | 1 | Applied and Interdisciplinary Chemistry |
Pseudotropine (3β-tropanol, ψ-tropine, 3-pseudotropanol, or PTO) is a derivative of tropane and an isomer of tropine. Pseudotropine can be found in the Coca plant along with several other alkaloids | 1 | Applied and Interdisciplinary Chemistry |
Crystalline thin-films from non-spherical colloids were produced using convective assembly techniques. Colloid shapes included dumbbell, hemisphere, disc, and sphero-cylinder shapes. Both purely crystalline and plastic crystal phases could be produced, depending on the aspect ratio of the colloidal particle. The low aspect ratio, such as bulge, eye-ball, and snowman-like non-spherical colloids, which spontaneously self-assembled to photonic crystal array with high uniformity. The particles were crystallized both as 2D (i.e., monolayer) and 3D (i.e., multilayer) structures. The observed lattice and particle orientations experimentally confirmed a body of theoretical work on the condensed phases of non-spherical objects. Assembly of crystals from non-spherical colloids can also be directed via the use of electrical fields. | 0 | Theoretical and Fundamental Chemistry |
Restriction enzymes likely evolved from a common ancestor and became widespread via horizontal gene transfer. In addition, there is mounting evidence that restriction endonucleases evolved as a selfish genetic element. | 1 | Applied and Interdisciplinary Chemistry |
The reaction steps are:
* hydrogenation of -glucose to -sorbitol, an organic reaction with nickel as a catalyst under high temperature and high pressure.
* Microbial oxidation or fermentation of sorbitol to -sorbose with acetobacter at pH 4-6 and 30 °C.
* protection of the 4 hydroxyl groups in sorbose by formation of the acetal with acetone and an acid to Diacetone-L-sorbose (2,3:4,6−Diisopropyliden−α−L−sorbose)
* Organic oxidation with potassium permanganate (to Diprogulic acid) followed by heating with water gives the 2-Keto-L-gulonic acid
* The final step is a ring-closing step or gamma lactonization with removal of water.
* Intermediate 5 can also be prepared directly from 3 with oxygen and platinum
The microbial oxidation of sorbitol to sorbose is important because it provides the correct stereochemistry. | 0 | Theoretical and Fundamental Chemistry |
Definitive mechanistic studies of rhodium-catalyzed cyclopropanation are lacking. However, the mechanism has been rationalized based on product distribution and stereoselectivity. Attack of the diazo compound on the metal center generates a zwitterionic metal alkyl complex, which expels nitrogen gas to afford a metal carbene intermediate. Concerted addition of the metal carbene to the olefin (without direct coordination of the olefin to the metal) generates the observed cyclopropane product. The configuration of the olefin is retained throughout the process; however, metal carbenes with heterotopic faces may generate a mixture of diastereomers, as shown at the right of Eq. (2).
The configuration of the product is determined by the trajectory of approach of the olefin to the metal carbene. In reactions of monosubstituted metal carbenes with terminal olefins, the olefin likely approaches "end-on" (with the carbon-carbon double bond of the olefin nearly parallel to the metal-carbon double bond of the carbene) with the olefin R group pointed away from the substituent of the carbene. A second transition state model has been proposed for reactions of vinyl-substituted carbenes. In this model, the olefin approaches "side-on" (with the carbon-carbon double bond of the olefin perpendicular to the metal-carbon double bond of the carbene) with the olefin R group far from the vinyl group. | 0 | Theoretical and Fundamental Chemistry |
Also known as retrotransposons, these employ a strategy of self-copying via RNA transcriptase and subsequently inserting themselves into a new site within the host genome. The presence or absence of transcriptase (the enzyme which allows for self-copying) within the coding of the transposon defines class I elements as autonomous or non-autonomous. Class I transposons can take the form of:
* LTRs, long terminal repeats, which contain immensely repetitive code (hundreds or thousands of the same few nucleotides)
* Non-LTRs, which lack lengthy repetitive coding, and can be LINEs, long interspersed nuclear elements, which code for their own transpositional machinery, and SINEs, short interspersed nuclear elements, which piggy-back off of LINE machinery
Curiously, retrotransposons have been discovered to be the predominant form of transpositional element in plants with large genomes, such as maize and wheat, potentially indicating rapid success of this class of transposon in the creation of hybrids, such as wheat, peppermint and, in the distant past, maize. Plant hybridization often creates polyploids, with double, triple, quadruple or more the number of chromosomes present in the parent generation. Polyploid hybrids seem to be particularly susceptible to genetic intrusion by retrotransposons, as supported by a study in sunflower hybridization, which showed that the hybridized flowers possessed genomes that were about 50% larger than that of their parents, with the majority of this increase linked to the amplification of a single retrotransposon class | 1 | Applied and Interdisciplinary Chemistry |
In 1970, lithium was approved by the United States Food and Drug Administration (FDA) for the treatment of bipolar disorder, which remains its primary use in the United States. It is sometimes used when other treatments are not effective in a number of other conditions, including major depression, schizophrenia, disorders of impulse control, and some psychiatric disorders in children. Because the FDA has not approved lithium for the treatment of other disorders, such use is off-label. | 1 | Applied and Interdisciplinary Chemistry |
A Rotary Vacuum Filter Drum consists of a cylindrical filter membrane that is partly sub-merged in a slurry to be filtered. The inside of the drum is held lower than the ambient pressure. As the drum rotates through the slurry, the liquid is sucked through the membrane, leaving solids to cake on the membrane surface while the drum is submerged. A knife or blade is positioned to scrape the product from the surface.
The technique is well suited to slurries, flocculated suspensions, and liquids with a high solid content, which could clog other forms of filter. It is common to pre-coated with a filter aid, typically of diatomaceous earth (DE) or Perlite. In some implementations, the knife also cuts off a small portion of the filter media to reveal a fresh media surface that will enter the liquid as the drum rotates. Such systems advance the knife automatically as the surface is removed. | 0 | Theoretical and Fundamental Chemistry |
Based on the NPS and schedule of a pipe, the pipe outside diameter (OD) and wall thickness can be obtained from reference tables such as those below, which are based on ASME standards B36.10M and B36.19M. For example, NPS 14 Sch 40 has an OD of and a wall thickness of . However, the NPS and OD values are not always equal, which can create confusion.
* For NPS to 12, the NPS and OD values are different. For example, the OD of an NPS 12 pipe is actually . To find the actual OD for each NPS value, refer to the tables below. (Note that for tubing, the size indicates actual dimensions, not nominal.)
* For NPS 14 and up, the NPS and OD values are equal. In other words, an NPS 14 pipe is actually OD.
The reason for the discrepancy for NPS to 12 inches is that these NPS values were originally set to give the same inside diameter (ID) based on wall thicknesses standard at the time. However, as the set of available wall thicknesses evolved, the ID changed and NPS became only indirectly related to ID and OD.
For a given NPS, the OD stays fixed and the wall thickness increases with schedule. For a given schedule, the OD increases with NPS while the wall thickness stays constant or increases. Using equations and rules in ASME B31.3 Process Piping, it can be shown that pressure rating decreases with increasing NPS and constant schedule.
Some specifications use pipe schedules called standard wall (STD), extra strong (XS), and double extra strong (XXS), although these actually belong to an older system called iron pipe size (IPS). The IPS number is the same as the NPS number. STD is identical to SCH 40S, and 40S is identical to 40 for NPS to NPS 10, inclusive. XS is identical to SCH 80S, and 80S is identical to 80 for NPS to NPS 8, inclusive. XXS wall is thicker than schedule 160 from NPS in to NPS 6 in inclusive, and schedule 160 is thicker than XXS wall for NPS 8 in and larger. | 1 | Applied and Interdisciplinary Chemistry |
Sarah Elaine B. Petrie is a Canadian and American physical chemist who worked for the research laboratories of Eastman Kodak and became known for her research on the thermal properties of glasses, polymers, and liquid crystals.
Petrie earned a Ph.D. in chemistry in 1957 from the University of Toronto, with the dissertation Dielectric behaviour of vapours adsorbed on porous and non-porous adsorbents, supervised by Robert L. McIntosh. By the same year she was working for the Kodak Research Laboratories. In 1977 she was appointed to a panel on polymers in the National Bureau of Standards and as an advisor to the office of chemistry and chemical technology of the National Research Council. She also served as a councilor to the American Chemical Society Division of Polymer Chemistry from 1979 to 1981. By 1994, when she served on the Committee on Polymer Science and Engineering of the National Research Council, she was listed as retired from Kodak.
In 1976, Petrie was named a Fellow of the American Physical Society (APS), after a nomination from the APS Division of Polymer Physics. | 0 | Theoretical and Fundamental Chemistry |
Olefin and alkyne metathesis refers to a carbon–carbon bond forming reaction. In the case of olefin metathesis, the bond forms between two sp-hybridized carbon centers. In alkyne metathesis it forms between two sp-hybridized carbon centers. Ring opening metathesis polymerization (ROMP) can be used in polymerization and macrocycle synthesis. | 0 | Theoretical and Fundamental Chemistry |
The Bionic Leaf is a biomimetic system that gathers solar energy via photovoltaic cells that can be stored or used in a number of different functions. Bionic leaves can be composed of both synthetic (metals, ceramics, polymers, etc.) and organic materials (bacteria), or solely made of synthetic materials. The Bionic Leaf has the potential to be implemented in communities, such as urbanized areas to provide clean air as well as providing needed clean energy. | 0 | Theoretical and Fundamental Chemistry |
It was in Munich (1928–1938) that Schwab started systematic work on heterogeneous catalysis which marked the rest of his career. Among the catalysis-related topics he studied in Munich were the kinetics of heterogeneously catalysed reactions, the nature of the heat of adsorption, the poisoning of catalysts and the spatial distribution of active catalytic sites. He also collaborated with his future wife Elly on her research about the influence of free radicals on parahydrogen, a work which they completed in Greece.
In the Kanellopoulos Institute (1939–1950), with the academic freedom he was given Schwab produced research on various occasional topics such as inorganic chromatography (which he is credited with inventing), turn-over transitions, carbon adsorption and properties of parahydrogen. He also built on his previous work with a series of kinetic studies, which eventually led to his theory on the electronic mechanisms of metal catalysis.
In later years, after returning to Munich as professor of physical chemistry, Schwab discovered the surface catalytic influence of a metal in contact with a semiconductor catalyst or an insulator in contact with a metal catalyst (occasionally referred to as Schwab effects of the 1st and of the 2nd type, respectively). | 0 | Theoretical and Fundamental Chemistry |
All bacterial luciferases are approximately 80 KDa heterodimers containing two subunits: α and β. The α subunit is responsible for light emission. The luxA and luxB genes encode for the α and β subunits, respectively. In most bioluminescent bacteria, the luxA and luxB genes are flanked upstream by luxC and luxD and downstream by luxE.
The bioluminescent reaction is as follows:
FMNH + O + R-CHO -> FMN + HO + R-COOH + Light (~ 495 nm)
Molecular oxygen reacts with FMNH (reduced flavin mononucleotide) and a long-chain aldehyde to produce FMN (flavin mononucleotide), water and a corresponding fatty acid. The blue-green light emission of bioluminescence, such as that produced by Photobacterium phosphoreum and Vibro harveyi, results from this reaction. Because light emission involves expending six ATP molecules for each photon, it is an energetically expensive process. For this reason, light emission is not constitutively expressed in bioluminescent bacteria; it is expressed only when physiologically necessary. | 1 | Applied and Interdisciplinary Chemistry |
This proof of the Hellmann–Feynman theorem requires that the wave function be an eigenfunction of the Hamiltonian under consideration; however, it is also possible to prove more generally that the theorem holds for non-eigenfunction wave functions which are stationary (partial derivative is zero) for all relevant variables (such as orbital rotations). The Hartree–Fock wavefunction is an important example of an approximate eigenfunction that still satisfies the Hellmann–Feynman theorem. Notable example of where the Hellmann–Feynman is not applicable is for example finite-order Møller–Plesset perturbation theory, which is not variational.
The proof also employs an identity of normalized wavefunctions – that derivatives of the overlap of a wave function with itself must be zero. Using Dirac's bra–ket notation these two conditions are written as
The proof then follows through an application of the derivative product rule to the expectation value of the Hamiltonian viewed as a function of : | 0 | Theoretical and Fundamental Chemistry |
Dithiocarbamates are described by invoking resonance structures that emphasize the pi-donor properties of the amine group. This bonding arrangement is indicated by a short C–N distance and the coplanarity of the NCS core as well as the atoms attached to N.
Because of the pi-donation from nitrogen, dithiocarbamates are more basic than structurally related anions such as dithiocarboxylates and xanthates. Consequently, they tend to bind as bidentate ligands. Another consequence of the C–N multiple bonding is that rotation about that bond is subject to a high barrier. | 0 | Theoretical and Fundamental Chemistry |
Piping components can be bolted together between flanges. Flanges are used to connect pipes with each other, to valves, to fittings, and to specialty items such as strainers and pressure vessels. A cover plate can be connected to create a "blind flange". Flanges are joined by bolting, and sealing is often completed with the use of gaskets or other methods. Mechanical means to mitigate effects of leaks, like spray guards or specific spray flanges, may be included. Industries where flammable, volatile, toxic or corrosive substances are being processed have greater need of special protection at flanged connections.
Flange guards can provide that added level of protection to ensure safety.
There are many different flange standards to be found worldwide. To allow easy functionality and interchangeability, these are designed to have standardised dimensions. Common world standards include ASA/ASME (USA), PN/DIN (European), BS10 (British/Australian), and JIS/KS (Japanese/Korean). In the USA, the standard is ASME B16.5 (ANSI stopped publishing B16.5 in 1996). ASME B16.5 covers flanges up to 24 inches size and up to pressure rating of Class 2500. Flanges larger than 24 inches are covered in ASME B16.47.
In most cases, standards are interchangeable, as most local standards have been aligned to ISO standards; however, some local standards still differ. For example, an ASME flange will not mate against an ISO flange. Further, many of the flanges in each standard are divided into "pressure classes", allowing flanges to be capable of taking different pressure ratings. Again these are not generally interchangeable (e.g. an ASME 150 will not mate with an ASME 300).
These pressure classes also have differing pressure and temperature ratings for different materials. Unique pressure classes for piping can also be developed for a process plant or power generating station; these may be specific to the corporation, engineering procurement and construction (EPC) contractor, or the process plant owner. The ASME pressure classes for flat-face flanges are Class 125 and Class 250. The classes for ring-joint, tongue and groove, and raised-face flanges are Class 150, Class 300, Class 400 (unusual), Class 600, Class 900, Class 1500, and Class 2500.
The flange faces are also made to standardized dimensions and are typically "flat face", "raised face", "tongue and groove", or "ring joint" styles, although other obscure styles are possible.
Flange designs are available as "weld neck", "slip-on", "lap joint", "socket weld", "threaded", and also "blind". | 1 | Applied and Interdisciplinary Chemistry |
One of the most critical processes determining cyanobacterial eco-physiology is cellular death. Evidence supports the existence of controlled cellular demise in cyanobacteria, and various forms of cell death have been described as a response to biotic and abiotic stresses. However, cell death research in cyanobacteria is a relatively young field and understanding of the underlying mechanisms and molecular machinery underpinning this fundamental process remains largely elusive. However, reports on cell death of marine and freshwater cyanobacteria indicate this process has major implications for the ecology of microbial communities/ Different forms of cell demise have been observed in cyanobacteria under several stressful conditions, and cell death has been suggested to play a key role in developmental processes, such as akinete and heterocyst differentiation, as well as strategy for population survival. | 0 | Theoretical and Fundamental Chemistry |
Ordering is the regularity in which atoms appear in a predictable lattice, as measured from one point. In a highly ordered, perfectly crystalline material, or single crystal, the location of every atom in the structure can be described exactly measuring out from a single origin. Conversely, in a disordered structure such as a liquid or amorphous solid, the location of the nearest and, perhaps, second-nearest neighbors can be described from an origin (with some degree of uncertainty) and the ability to predict locations decreases rapidly from there out. The distance at which atom locations can be predicted is referred to as the correlation length . A paracrystalline material exhibits a correlation somewhere between the fully amorphous and fully crystalline.
The primary, most accessible source of crystallinity information is X-ray diffraction and cryo-electron microscopy, although other techniques may be needed to observe the complex structure of paracrystalline materials, such as fluctuation electron microscopy in combination with density of states modeling of electronic and vibrational states. Scanning transmission electron microscopy can provide real-space and reciprocal space characterization of paracrystallinity in nanoscale material, such as quantum dot solids.
The scattering of X-rays, neutrons and electrons on paracrystals is quantitatively described by the theories of the ideal and real paracrystal.
Numerical differences in analyses of diffraction experiments on the basis of either of these two theories of paracrystallinity can often be neglected.
Just like ideal crystals, ideal paracrystals extend theoretically to infinity. Real paracrystals, on the other hand, follow the empirical α*-law, which restricts their size. That size is also indirectly proportional to the components of the tensor of the paracrystalline distortion. Larger solid state aggregates are then composed of micro-paracrystals. | 0 | Theoretical and Fundamental Chemistry |
A cyanohydrin reaction is an organic chemical reaction in which an aldehyde or ketone reacts with a cyanide anion or a nitrile to form a cyanohydrin. This nucleophilic addition is a reversible reaction but with aliphatic carbonyl compounds equilibrium is in favor of the reaction products. The cyanide source can be potassium cyanide, sodium cyanide or trimethylsilyl cyanide. With aromatic aldehydes such as benzaldehyde, the benzoin condensation is a competing reaction. The reaction is used in carbohydrate chemistry as a chain extension method for example that of D-xylose. | 0 | Theoretical and Fundamental Chemistry |
In Chapter 12 of The Conservation of Orbital Symmetry, entitled "Violations," Woodward and Hoffmann famously stated:This pronouncement notwithstanding, it is important to recognize that the Woodward–Hoffmann rules are used to predict relative barrier heights, and thus likely reaction mechanisms, and that they only take into account barriers due to conservation of orbital symmetry. Thus it is not guaranteed that a WH symmetry-allowed reaction actually takes place in a facile manner. Conversely, it is possible, upon enough energetic input, to achieve an anti-Woodward-Hoffmann product. This is especially prevalent in sterically constrained systems, where the WH-product has an added steric barrier to overcome. For example, in the electrocyclic ring-opening of the dimethylbicyclo[0.2.3]heptene derivative (1), a conrotatory mechanism is not possible due to resulting angle strain and the reaction proceeds slowly through a disrotatory mechanism at 400 C to give a cycloheptadiene product. Violations may also be observed in cases with very strong thermodynamic driving forces. The decomposition of dioxetane-1,2-dione to two molecules of carbon dioxide, famous for its role in the luminescence of glowsticks, has been scrutinized computationally. In the absence of fluorescers, the reaction is now believed to proceed in a concerted (though asynchronous) fashion, via a retro-[2+2]-cycloaddition that formally violates the Woodward–Hoffmann rules.
Similarly, a recent paper describes how mechanical stress can be used to reshape chemical reaction pathways to lead to products that apparently violate Woodward–Hoffman rules. In this paper, they use ultrasound irradiation to induce a mechanical stress on link-functionalized polymers attached syn or anti on the cyclobutene ring. Computational studies predict that the mechanical force, resulting from friction of the polymers, induces bond lengthening along the reaction coordinate of the conrotatory mechanism in the anti-bisubstituted-cyclobutene, and along the reaction coordinate of the disrotatory mechanism in the syn-bisubstituted-cyclobutene. Thus in the syn-bisubstituted-cyclobutene, the anti-WH product is predicted to be formed.
This computational prediction was backed up by experiment on the system below. Link-functionalized polymers were conjugated to cis benzocyclobutene in both syn- and anti- conformations. As predicted, both products gave the same (Z,Z) product as determined by quenching by a stereospecific Diels-Alder reaction with the substituted maleimide. In particular, the syn-substituted product gave the anti-WH product, presumably as the mechanical stretching along the coordinate of the disrotatory pathway lowered the barrier of the reaction under the disrotatory pathway enough to bias that mechanism. | 0 | Theoretical and Fundamental Chemistry |
Depending on the type of end-products produced, the zinc cathodes coming out of the electro-winning plant can undergo an additional transformation step in a foundry. Zinc cathodes are melted in induction furnaces and cast into marketable products such as ingots. Other metals and alloy components may be added to produce zinc containing alloys used in die-casting or general galvanization applications. Finally, molten zinc may be transported to nearby conversion plants or third parties using specially-designed insulated containers. | 1 | Applied and Interdisciplinary Chemistry |
During the process of lake stratification, shallow areas generally become stratified before deeper areas. In large lakes this condition may persist for weeks, during which a temperature front known as a thermal bar forms between the stratified and unstratified areas of the lake. The thermal bar generally forms parallel to shore and moves toward the lake center as deeper areas of the lake stratify. While thermal bars can form in both fall and spring, most studies of the thermal bar have investigated aspects of the feature in the spring, when the lake is warming up and the summer thermocline is beginning to form.
At the lake surface, the thermal bar may be visible as a foam line between the stratified water shoreward of the thermal bar and unstratified water on the offshore side. At this convergence, waters mix and sink when they reach the temperature of maximum density, roughly 4 degrees Celsius for freshwater, a process known as cabbeling.
The downwelling of dense water at the thermal bar acts as a barrier to horizontal mixing. In spring, this concentrates warm water and suspended materials in the near shore waters around the edge of the lake. Satellite imagery has been used to identify thermal bars using their thermal characteristics as well as the concentration of suspended materials on their shoreward side, typically due to surface runoff to the lake.
Isotherms on the stratified side of the thermal bar slope away from the bar, producing a pressure gradient force that when balanced by the Coriolis force produces a cyclonic coastal geostrophic current that transports water and suspended matter along the shore.
The thermal bar phenomena was first described by François-Alphonse Forel in his study of Lac Leman. Additional studies have been carried out in Lake Ladoga, Lake Baikal and the Laurentian Great Lakes. | 1 | Applied and Interdisciplinary Chemistry |
Thiolactones are a class of heterocyclic compounds in organic chemistry. They are analogs of the more common lactones in which an oxygen atom is replaced with a sulfur atom. The sulfur atom is within the ring system and adjacent to a carbonyl group. | 0 | Theoretical and Fundamental Chemistry |
Metals and metal working had been known to the people of modern Italy since the Bronze Age. By 53 BC, Rome had expanded to control an immense expanse of the Mediterranean. This included Italy and its islands, Spain, Macedonia, Africa, Asia Minor, Syria and Greece; by the end of the Emperor Trajan's reign, the Roman Empire had grown further to encompass parts of Britain, Egypt, all of modern Germany west of the Rhine, Dacia, Noricum, Judea, Armenia, Illyria, and Thrace (Shepard 1993). As the empire grew, so did its need for metals.
Central Italy itself was not rich in metal ores, leading to necessary trade networks in order to meet the demand for metal. Early Italians had some access to metals in the northern regions of the peninsula in Tuscany and Cisalpine Gaul, as well as the islands Elba and Sardinia. With the conquest of Etruria in 275 BC and the subsequent acquisitions due to the Punic Wars, Rome had the ability to stretch further into Transalpine Gaul and Iberia, both areas rich in minerals. At the height of the Empire, Rome exploited mineral resources from Tingitana in north western Africa to Egypt, Arabia to North Armenia, Galatia to Germania, and Britannia to Iberia, encompassing all of the Mediterranean coast. Britannia, Iberia, Dacia, and Noricum were of special significance, as they were very rich in deposits and became major sites of resource exploitation (Shepard, 1993).
There is evidence that after the middle years of the Empire there was a sudden and steep decline in
mineral extraction. This was mirrored in other trades and industries.
One of the most important Roman sources of information is the Naturalis Historia of Pliny the Elder. Several books (XXXIII–XXXVII) of his encyclopedia cover metals and metal ores, their occurrence, importance and development. | 1 | Applied and Interdisciplinary Chemistry |
In addition to philosophy, Boyle devoted much time to theology, showing a very decided leaning to the practical side and an indifference to controversial polemics. At the Restoration of the king in 1660, he was favourably received at court and in 1665 would have received the provostship of Eton College had he agreed to take holy orders, but this he refused to do on the ground that his writings on religious subjects would have greater weight coming from a layman than a paid minister of the Church.
Moreover, Boyle incorporated his scientific interests into his theology, believing that natural philosophy could provide powerful evidence for the existence of God. In works such as Disquisition about the Final Causes of Natural Things (1688), for instance, he criticised contemporary philosophers – such as René Descartes – who denied that the study of nature could reveal much about God. Instead, Boyle argued that natural philosophers could use the design apparently on display in some parts of nature to demonstrate Gods involvement with the world. He also attempted to tackle complex theological questions using methods derived from his scientific practices. In Some Physico-Theological Considerations about the Possibility of the Resurrection' (1675), he used a chemical experiment known as the reduction to the pristine state as part of an attempt to demonstrate the physical possibility of the resurrection of the body. Throughout his career, Boyle tried to show that science could lend support to Christianity.
As a director of the East India Company he spent large sums in promoting the spread of Christianity in the East, contributing liberally to missionary societies and to the expenses of translating the Bible or portions of it into various languages. Boyle supported the policy that the Bible should be available in the vernacular language of the people. An Irish language version of the New Testament was published in 1602 but was rare in Boyles adult life. In 1680–85 Boyle personally financed the printing of the Bible, both Old and New Testaments, in Irish. In this respect, Boyles attitude to the Irish language differed from the Protestant Ascendancy class in Ireland at the time, which was generally hostile to the language and largely opposed the use of Irish (not only as a language of religious worship).
Boyle also had a monogenist perspective about race origin. He was a pioneer studying races, and he believed that all human beings, no matter how diverse their physical differences, came from the same source: Adam and Eve. He studied reported stories of parents giving birth to different coloured albinos, so he concluded that Adam and Eve were originally white and that Caucasians could give birth to different coloured races. Boyle also extended the theories of Robert Hooke and Isaac Newton about colour and light via optical projection (in physics) into discourses of polygenesis, speculating that maybe these differences were due to "seminal impressions". Taking this into account, it might be considered that he envisioned a good explanation for complexion at his time, due to the fact that now we know that skin colour is disposed by genes, which are actually contained in the semen. Boyles writings mention that at his time, for "European Eyes", beauty was not measured so much in colour of skin, but in "stature, comely symmetry of the parts of the body, and good features in the face". Various members of the scientific community rejected his views and described them as "disturbing" or "amusing".
In his will, Boyle provided money for a series of lectures to defend the Christian religion against those he considered "notorious infidels, namely atheists, deists, pagans, Jews and Muslims", with the provision that controversies between Christians were not to be mentioned (see Boyle Lectures). | 1 | Applied and Interdisciplinary Chemistry |
Photosensitizers are light absorbers that alter the course of a photochemical reaction. They usually are catalysts. They can function by many mechanisms, sometimes they donate an electron to the substrate, sometimes they abstract a hydrogen atom from the substrate. At the end of this process, the photosensitizer returns to its ground state, where it remains chemically intact, poised to absorb more light. One branch of chemistry which frequently utilizes photosensitizers is polymer chemistry, using photosensitizers in reactions such as photopolymerization, photocrosslinking, and photodegradation. Photosensitizers are also used to generate prolonged excited electronic states in organic molecules with uses in photocatalysis, photon upconversion and photodynamic therapy. Generally, photosensitizers absorb electromagnetic radiation consisting of infrared radiation, visible light radiation, and ultraviolet radiation and transfer absorbed energy into neighboring molecules. This absorption of light is made possible by photosensitizers' large de-localized π-systems, which lowers the energy of HOMO and LUMO orbitals to promote photoexcitation. While many photosensitizers are organic or organometallic compounds, there are also examples of using semiconductor quantum dots as photosensitizers. | 0 | Theoretical and Fundamental Chemistry |
The Stark effect originates from the interaction between a charge distribution (atom or molecule) and an external electric field.
The interaction energy of a continuous charge distribution , confined within a finite volume , with an external electrostatic potential is
This expression is valid classically and quantum-mechanically alike.
If the potential varies weakly over the charge distribution, the multipole expansion converges fast, so only a few first terms give an accurate approximation. Namely, keeping only the zero- and first-order terms,
where we introduced the electric field and assumed the origin 0 to be somewhere within .
Therefore, the interaction becomes
where and are, respectively, the total charge (zero moment) and the dipole moment of the charge distribution.
Classical macroscopic objects are usually neutral or quasi-neutral (), so the first, monopole, term in the expression above is identically zero. This is also the case for a neutral atom or molecule. However, for an ion this is no longer true. Nevertheless, it is often justified to omit it in this case, too. Indeed, the Stark effect is observed in spectral lines, which are emitted when an electron "jumps" between two bound states. Since such a transition only alters the internal degrees of freedom of the radiator but not its charge, the effects of the monopole interaction on the initial and final states exactly cancel each other. | 0 | Theoretical and Fundamental Chemistry |
Cholesterol regulates the function of several membrane proteins associated with lipid rafts. It does so by controlling the formation or depletion of lipid rafts in the plasma membrane. The lipid rafts house the membrane proteins and forming or depleting the lipid rafts moves the proteins in or out of the raft environment, thereby exposing them to a new environment that can activate or deactivate the proteins. For example, cholesterol directly regulates the affinity of palmitoylated proteins for GM1 containing lipid rafts. Cholesterol signaling through lipid rafts can be attenuated by phosphatidylinositol 4,5 bisphosphate signaling (PIP2). PIP2 contains mostly polyunsaturated lipids that partition away from saturated lipids. Proteins that bind both lipid rafts and PIP2 are negatively regulated by high levels of PIP2. This effect was observed with phospholipase D.
In the brain, astrocytes make the cholesterol and transport it to nerves to control their function. In this sense, cholesterol functions as a hormone. | 1 | Applied and Interdisciplinary Chemistry |
A high pressure jet is a stream of pressurized fluid that is released from an environment at a significantly higher pressure than ambient pressure from a nozzle or orifice, due to operational or accidental release. In the field of safety engineering, the release of toxic and flammable gases has been the subject of many R&D studies because of the major risk that they pose to the health and safety of workers, equipment and environment. Intentional or accidental release may occur in an industrial settings like natural gas processing plants, oil refineries and hydrogen storage facilities.
A main focus during a risk assessment process is the estimation of the gas cloud extension and dissipation, important parameters that allow to evaluate and establish safety limits that must be respected in order to minimize the possible damage after a high pressure release. | 1 | Applied and Interdisciplinary Chemistry |
Most (but not all; see minimalist channels) synthetic channels have chemical structures substantially larger than typical small molecules (molecular weights ~1-5kDa). This originates from the need to be amphiphilic, that is, have both sufficient hydrophobic portions to allow partitioning into lipid bilayer, as well as polar or charged "headgroups" to assert a defined orientation and geometry with respect to the membrane. | 0 | Theoretical and Fundamental Chemistry |
A simple body or a complex thermodynamic system can also be in a stationary state with non-zero rates of flow and chemical reaction; sometimes the word "equilibrium" is used in reference to such a state, though by definition it is not a thermodynamic equilibrium state. Sometimes, it is proposed to consider Le Chateliers principle for such states. For this exercise, rates of flow and of chemical reaction must be considered. Such rates are not supplied by equilibrium thermodynamics. For such states, there are no simple statements that echo Le Chateliers principle. Prigogine and Defay demonstrate that such a scenario may exhibit moderation, or may exhibit a measured amount of anti-moderation, though not a run-away anti-moderation that goes to completion. The example analysed by Prigogine and Defay is the Haber process.
This situation is clarified by considering two basic methods of analysis of a process. One is the classical approach of Gibbs, the other uses the near- or local- equilibrium approach of De Donder. The Gibbs approach requires thermodynamic equilibrium. The Gibbs approach is reliable within its proper scope, thermodynamic equilibrium, though of course it does not cover non-equilibrium scenarios. The De Donder approach can cover equilibrium scenarios, but also covers non-equilibrium scenarios in which there is only local thermodynamic equilibrium, and not thermodynamic equilibrium proper. The De Donder approach allows state variables called extents of reaction to be independent variables, though in the Gibbs approach, such variables are not independent. Thermodynamic non-equilibrium scenarios can contradict an over-general statement of Le Chatelier's Principle. | 0 | Theoretical and Fundamental Chemistry |
In the vast majority of accidents, and in all atomic bomb blasts, the threat due to beta and gamma emitters is greater than that posed by the alpha emitters in the fallout. Alpha particles are identical to a helium-4 nucleus (two protons and two neutrons), and travel at speeds in excess of 5% of the speed of light. Alpha particles have little penetrating power; most cannot penetrate through human skin. Avoiding direct exposure with fallout particles will prevent injury from alpha radiation. | 0 | Theoretical and Fundamental Chemistry |
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