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Iron is usually found as iron ore on Earth, except for one deposit of native iron in Greenland, which was used by the Inuit. Native copper, however, was found worldwide, along with silver, gold, and platinum, which were also used to make tools, jewelry, and other objects since Neolithic times. Copper was the hardest of these metals, and the most widely distributed. It became one of the most important metals to the ancients. Around 10,000 years ago in the highlands of Anatolia (Turkey), humans learned to smelt metals such as copper and tin from ore. Around 2500 BC, people began alloying the two metals to form bronze, which was much harder than its ingredients. Tin was rare, however, being found mostly in Great Britain. In the Middle East, people began alloying copper with zinc to form brass. Ancient civilizations took into account the mixture and the various properties it produced, such as hardness, toughness and melting point, under various conditions of temperature and work hardening, developing much of the information contained in modern alloy phase diagrams. For example, arrowheads from the Chinese Qin dynasty (around 200 BC) were often constructed with a hard bronze-head, but a softer bronze-tang, combining the alloys to prevent both dulling and breaking during use. | 1 | Applied and Interdisciplinary Chemistry |
Androgens, antiandrogens, estrogens, gonadotropin, corticosteroids, human growth hormone, insulin, antidiabetics (sulfonylureas, biguanides/metformin, thiazolidinediones, insulin), thyroid hormones, antithyroid drugs, calcitonin, diphosphonate, vasopressin analogues. | 1 | Applied and Interdisciplinary Chemistry |
Quantitative filter paper, also called ash-free filter paper, is used for quantitative and gravimetric analysis. During the manufacturing, producers use acid to make the paper ash-less and achieve high purity. | 0 | Theoretical and Fundamental Chemistry |
The above systems produce an economizer effect by using compressors, meters, valves and heat exchangers within the refrigeration cycle. In some refrigeration systems the economizer can be an independent refrigeration mechanism. Such is the case of subcooling the liquid line by any other means that draws the heat out of the main system. For example, a heat exchanger that preheats cold water needed for another process or human use, may take heat from the liquid line, effectively subcooling it and increasing the system's capacity.
Recently, machines exclusively designed for this purpose have been developed. In Chile, the manufacturer EcoPac Systems developed a cycle optimizer able to stabilize the temperature of the liquid line and allow either an increase in the refrigeration capacity of the system, or a reduction of the power consumption. Such systems have the advantage of not interfering with the original design of the refrigeration system and are a way to expand a single staged system that does not possess an economizer compressor. | 0 | Theoretical and Fundamental Chemistry |
Drospirenone (DRSP) is used by itself as a progestogen-only birth control pill, in combination with the estrogens ethinylestradiol (EE) or estetrol (E4), with or without supplemental folic acid (vitamin B), as a combined birth control pill, and in combination with the estrogen estradiol (E2) for use in menopausal hormone therapy. A birth control pill with low-dose ethinylestradiol is also indicated for the treatment of moderate acne, premenstrual syndrome (PMS), premenstrual dysphoric disorder (PMDD), and dysmenorrhea (painful menstruation). For use in menopausal hormone therapy, E2/DRSP is specifically approved to treat moderate to severe vasomotor symptoms (hot flashes), vaginal atrophy, and postmenopausal osteoporosis. The drospirenone component in this formulation is included specifically to prevent estrogen-induced endometrial hyperplasia. Drospirenone has also been used in combination with an estrogen as a component of hormone therapy for transgender women.
Studies have found that EE/DRSP is superior to placebo in reducing premenstrual emotional and physical symptoms while also improving quality of life. E2/DRSP has been found to increase bone mineral density and to reduce the occurrence of bone fractures in postmenopausal women. In addition, E2/DRSP has a favorable influence on cholesterol and triglyceride levels and decreases blood pressure in women with high blood pressure. Due to its antimineralocorticoid activity, drospirenone opposes estrogen-induced salt and water retention and maintains or slightly reduces body weight. | 0 | Theoretical and Fundamental Chemistry |
Lipophosphoglycan (LPG) is a class of molecules found on the surface of some eukaryotes, in particular protozoa. Each is made up of two parts, lipid and polysaccharide (also called glycan). They are bonded by a phosphodiester, hence the name lipo-phospho-glycan.
One species with extensive lipophosphoglycan coating is Leishmania, a group of single-celled protozoan parasite which cause leishmaniasis in many mammals, including humans. Their coats help modulate their hosts' immunological responses. | 1 | Applied and Interdisciplinary Chemistry |
In April 2011, elevated levels of caesium-137 were also being found in the environment after the Fukushima Daiichi nuclear disasters in Japan. In July 2011, meat from 11 cows shipped to Tokyo from Fukushima Prefecture was found to have 1,530 to 3,200 becquerels per kilogram of Cs, considerably exceeding the Japanese legal limit of 500 becquerels per kilogram at that time. In March 2013, a fish caught near the plant had a record 740,000 becquerels per kilogram of radioactive caesium, above the 100 becquerels per kilogram government limit. A 2013 paper in Scientific Reports found that for a forest site 50 km from the stricken plant, Cs concentrations were high in leaf litter, fungi and detritivores, but low in herbivores. By the end of 2014, "Fukushima-derived radiocaesium had spread into the whole western North Pacific Ocean", transported by the North Pacific current from Japan to the Gulf of Alaska. It has been measured in the surface layer down to 200 meters and south of the current area down to 400 meters.
Cesium-137 is reported to be the major health concern in Fukushima. A number of techniques are being considered that will be able to strip out 80% to 95% of the caesium from contaminated soil and other materials efficiently and without destroying the organic material in the soil. These include hydrothermal blasting. The caesium precipitated with ferric ferrocyanide (Prussian blue) would be the only waste requiring special burial sites. The aim is to get annual exposure from the contaminated environment down to 1 mSv above background. The most contaminated area where radiation doses are greater than 50 mSv/year must remain off limits, but some areas that are currently less than 5 mSv/year may be decontaminated, allowing 22,000 residents to return. | 0 | Theoretical and Fundamental Chemistry |
* Sivaramakrishna Chandrasekhar (1992) Liquid Crystals, 2nd edition, Cambridge University Press .
* David Dunmur & Tim Sluckin (2011) Soap, Science, and Flat-screen TVs: a history of liquid crystals, Oxford University Press .
* J. Prost & C.E. Williams (1999) "Liquid Crystals: Between Order and Disorder", pp 289–315 in Soft Matter Physics, Mohamed Daoud & Claudine E. Williams, editors, translated by Stephen N. Lyle from La Just Argile (1995), Springer Verlag . | 0 | Theoretical and Fundamental Chemistry |
Among the array of substrates that can be altered by CK2 many of them have been found in increased prevalence in cancers of the breast, lung, colon, and prostate. An increased concentration of substrates in cancerous cells infers a likely survival benefit to the cell, and activation of many of these substrates requires CK2. As well the anti-apoptotic function of CK2 allows the cancerous cell to escapes cell death and continue proliferating. Having roles in cell cycle regulation may also indicate CK2's role in allowing cell cycle progression when normally it should have been ceased. This also promotes CK2 as a possible therapeutic target for cancer drugs. When added with other potent anti-cancer therapies, a CK2 inhibitor may increase the effectiveness of the other therapy by allowing drug-induced apoptosis to occur at a normal rate. | 1 | Applied and Interdisciplinary Chemistry |
The density of a gas is calculated using the ideal gas law and an equation of state calculation such as the one described in AGA Report No. 8. | 1 | Applied and Interdisciplinary Chemistry |
Many proteins may adopt a beta sheet as part of their secondary structure. In beta sheets, sections of a single polypeptide may run side-by-side and antiparallel to each other, to allow for hydrogen bonding between their backbone chains. Beta sheets can also be either a parallel or anti-parallel secondary structure. However, an anti-parallel beta sheet is significantly more stable than a parallel structure due to their well aligned H-bonds, which are at a 90° angle. | 1 | Applied and Interdisciplinary Chemistry |
The cage is a part of the valve that surrounds the plug and is located inside the body of the valve. Typically, the cage is one of the greatest determiners of flow within the valve. As the plug is moved more of the openings in the cage are exposed and flow is increased and vice versa. The design and layout of the openings can have a large effect on flow of material (the flow characteristics of different materials at temperatures, pressures that are in a range). Cages are also used to guide the plug to the seat of the valve for a good shutoff, substituting the guiding from the bonnet. | 1 | Applied and Interdisciplinary Chemistry |
# Prepare a series of standards diluted with 0.15 M NaCl to final concentrations of 0 (blank = No protein), 250, 500, 750 and 1500 µg/mL. Also prepare serial dilutions of the unknown sample to be measured.
# Add 100 µL of each of the above to a separate test tube (or spectrophotometer tube if using a Spectronic 20).
# Add 5.0 mL of Coomassie Blue to each tube and mix by vortex, or inversion.
# Adjust the spectrophotometer to a wavelength of 595 nm, using the tube which contains no protein (blank).
# Wait 5 minutes and read each of the standards and each of the samples at 595 nm wavelength.
# Plot the absorbance of the standards vs. their concentration. Compute the extinction coefficient and calculate the concentrations of the unknown samples. | 0 | Theoretical and Fundamental Chemistry |
*2001 M J Pettifor
*2000 Terry Gladman
*1999 Etham T Turkdogan
*1998 R Baker
*1997 F Kenneth Iverson
*1996 Sir Brian Moffat
*1995 P Wright
*1994 F B Pickering
*1993 H Saito | 1 | Applied and Interdisciplinary Chemistry |
In the setting of standards, agencies make political and technical/scientific decisions based on how the water will be used. In the case of natural water bodies, agencies also make some reasonable estimate of pristine conditions. Natural water bodies will vary in response to a region's environmental conditions, whereby water composition is influenced by the surrounding geological features, sediments, and rock types, topography, hydrology, and climate. Environmental scientists and aqueous geochemists work to interpret the parameters and environmental conditions that impact the water quality of a region, which in turn helps to identify the sources and fates of contaminants. Environmental lawyers and policymakers work to define legislation with the intention that water is maintained at an appropriate quality for its identified use.
Another general perception of water quality is that of a simple property that tells whether water is polluted or not. In fact, water quality is a complex subject, in part because water is a complex medium intrinsically tied to the ecology, geology, and anthropogenic activities of a region. Industrial and commercial activities (e.g. manufacturing, mining, construction, transport) are a major cause of water pollution as are runoff from agricultural areas, urban runoff and discharge of treated and untreated sewage. | 0 | Theoretical and Fundamental Chemistry |
The inverse sixth-power distance dependence of Förster resonance energy transfer was experimentally confirmed by Wilchek, Edelhoch and Brand using tryptophyl peptides. Stryer, Haugland and Yguerabide also experimentally demonstrated the theoretical dependence of Förster resonance energy transfer on the overlap integral by using a fused indolosteroid as a donor and a ketone as an acceptor. Calculations on FRET distances of some example dye-pairs can be found here.
However, a lot of contradictions of special experiments with the theory was observed under complicated environment when the orientations and quantum yields of the molecules are difficult to estimate. | 1 | Applied and Interdisciplinary Chemistry |
Carbohydrate macromolecules (polysaccharides) are formed from polymers of monosaccharides. Because monosaccharides have multiple functional groups, polysaccharides can form linear polymers (e.g. cellulose) or complex branched structures (e.g. glycogen). Polysaccharides perform numerous roles in living organisms, acting as energy stores (e.g. starch) and as structural components (e.g. chitin in arthropods and fungi). Many carbohydrates contain modified monosaccharide units that have had functional groups replaced or removed.
Polyphenols consist of a branched structure of multiple phenolic subunits. They can perform structural roles (e.g. lignin) as well as roles as secondary metabolites involved in signalling, pigmentation and defense. | 0 | Theoretical and Fundamental Chemistry |
Untranslated regions (UTRs) are sections of the mRNA before the start codon and after the stop codon that are not translated, termed the five prime untranslated region (5 UTR) and three prime untranslated region (3 UTR), respectively. These regions are transcribed with the coding region and thus are exonic as they are present in the mature mRNA. Several roles in gene expression have been attributed to the untranslated regions, including mRNA stability, mRNA localization, and translational efficiency. The ability of a UTR to perform these functions depends on the sequence of the UTR and can differ between mRNAs. Genetic variants in 3' UTR have also been implicated in disease susceptibility because of the change in RNA structure and protein translation.
The stability of mRNAs may be controlled by the 5 UTR and/or 3 UTR due to varying affinity for RNA degrading enzymes called ribonucleases and for ancillary proteins that can promote or inhibit RNA degradation. (See also, C-rich stability element.)
Translational efficiency, including sometimes the complete inhibition of translation, can be controlled by UTRs. Proteins that bind to either the 3 or 5 UTR may affect translation by influencing the ribosomes ability to bind to the mRNA. MicroRNAs bound to the 3 UTR also may affect translational efficiency or mRNA stability.
Cytoplasmic localization of mRNA is thought to be a function of the 3 UTR. Proteins that are needed in a particular region of the cell can also be translated there; in such a case, the 3 UTR may contain sequences that allow the transcript to be localized to this region for translation.
Some of the elements contained in untranslated regions form a characteristic secondary structure when transcribed into RNA. These structural mRNA elements are involved in regulating the mRNA. Some, such as the SECIS element, are targets for proteins to bind. One class of mRNA element, the riboswitches, directly bind small molecules, changing their fold to modify levels of transcription or translation. In these cases, the mRNA regulates itself. | 1 | Applied and Interdisciplinary Chemistry |
In combustion, Clarke–Riley diffusion flame is a diffusion flame that develops inside a naturally convected boundary layer on a hot fuel surface with quiescent oxidizer environment, first studied and experimentally verified by John Frederick Clarke and Norman Riley in 1976. This problem is an extension of Emmons problem. | 1 | Applied and Interdisciplinary Chemistry |
Similar to copper oxide heap leaching, also using dilute sulfuric acid. Rio Tinto is commercializing this technology in Namibia and Australia; the French nuclear fuel company Orano, in Niger with two mines and Namibia; and several other companies are studying its feasibility.
The final product is yellowcake and requires significant further processing to produce fuel-grade feed. | 1 | Applied and Interdisciplinary Chemistry |
Acetone (propanone) is the simplest ketone and is separated into three groups in the Joback method: two methyl groups (−CH) and one ketone group (C=O). Since the methyl group is present twice, its contributions have to be added twice. | 0 | Theoretical and Fundamental Chemistry |
Depending upon the desired product, either the solvent or solute stream of RO will be waste. For food concentration applications, the concentrated solute stream is the product and the solvent stream is waste. For water treatment applications, the solvent stream is purified water and the solute stream is concentrated waste. The solvent waste stream from food processing may be used as reclaimed water, but there may be fewer options for disposal of a concentrated waste solute stream. Ships may use marine dumping and coastal desalination plants typically use marine outfalls. Landlocked RO plants may require evaporation ponds or injection wells to avoid polluting groundwater or surface runoff. | 0 | Theoretical and Fundamental Chemistry |
At equilibrium the rate of the forward reaction is equal to the backward reaction rate. A simple reaction, such as ester hydrolysis
has reaction rates given by expressions
According to Guldberg and Waage, equilibrium is attained when the forward and backward reaction rates are equal to each other. In these circumstances, an equilibrium constant is defined to be equal to the ratio of the forward and backward reaction rate constants
The concentration of water may be taken to be constant, resulting in the simpler expression
This particular concentration quotient, , has the dimension of concentration, but the thermodynamic equilibrium constant, , is always dimensionless. | 0 | Theoretical and Fundamental Chemistry |
Similar to single-stage impactors in collection methods, cascade impactors have multiple size cuts (PM, PM), allowing for bioaerosols to separate according to size. Separating biological material by aerodynamic diameter is useful due to size ranges being dominated by specific types of organisms (bacteria exist range from 1–20 micrometers and pollen from 10–100 micrometers). The Andersen line of cascade impactors are most widely used to test air particles. | 0 | Theoretical and Fundamental Chemistry |
Vacuum pyrolysis, with the removal of neutral volatile byproducts i.e. methanol or chloroform, has been used to prepare dihydroimidazole and triazole based carbenes. Historically the removal of chloroform by vacuum pyrolysis of adducts A was used by Wanzlick in his early attempts to prepare dihydroimidazol-2-ylidenes but this method is not widely used. The Enders laboratory has used vacuum pyrolysis of adduct B to generate a triazol-5-ylidene. | 0 | Theoretical and Fundamental Chemistry |
The BGIT is based on empirical data and heat of formation. Some groups are too hard to measure, so not all the existing groups are available in the table. Sometimes approximation should be made when those unavailable groups are encountered. For example, we need to approximate C as C and N as N in C≡N, which clearly cause more inaccuracy, which is another drawback. | 0 | Theoretical and Fundamental Chemistry |
Following her formal retirement, Waters continued part-time research and teaching activities at Massey Albany. Her husband, Neil Waters, died in Auckland in 2018. | 0 | Theoretical and Fundamental Chemistry |
The first polar FOCE (antFOCE) experiment was awarded funding in November 2012, followed by design and concept studies initiated in 2013. Installation and initial science experiments are planned for 2014. antFOCE is a collaborative effort between the University of Tasmania, Australian Antarctic Division, Antarctic Climate & Ecosystems Cooperative Research Centre, Monterey Bay Aquarium Research Institute and specialist ocean acidification policy advisors from the International Ocean Acidification Reference Users Group (IOA-RUG). The IOA-RUG will take the lead in communicating the outcomes of the FOCE experiment to global climate and ocean policy related organizations. | 0 | Theoretical and Fundamental Chemistry |
Succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate (SMCC) is a heterobifunctional amine-to-sulfhydryl crosslinker, which contains two reactive groups at opposite ends: N-hydroxysuccinimide-ester and maleimide, reactive with amines and thiols respectively. SMCC is often used in bioconjugation to link proteins with other functional entities (fluorescent dyes, tracers, nanoparticles, cytotoxic agents). For example, a targeted anticancer agent – trastuzumab emtansine (antibody-drug conjugate containing an antibody trastuzumab chemically linked to a highly potent drug DM-1) – is prepared using SMCC reagent. | 1 | Applied and Interdisciplinary Chemistry |
The presence of waters near the freezing point alters the balance of the relative effects of contrasts in salinity and temperature on sea water density. This is described in the equation,
where is the thermal expansion coefficient and is the haline contraction coefficient. In particular, the ratio is crucial. Using the observed temperatures and salinities, in the modern ocean, is about 10 whilst at the LGM it is estimated to have been closer to 25. The modern thermohaline circulation is thus more controlled by density contrasts due to thermal differences, whereas during the LGM the oceans were more than twice as sensitive to differences in salinity rather than temperature. In this way, the thermohaline circulation can be considered to have been less "thermo" and more "haline". | 0 | Theoretical and Fundamental Chemistry |
In simple cases there is only one grain or one type of material in the area used for collecting a diffraction pattern. However, often there is more than one. If they are in different areas then the diffraction pattern will be a combination. In addition there can be one grain on top of another, in which case the electrons that go through the first are diffracted by the second. Electrons have no memory (like many of us), so after they have gone through the first grain and been diffracted, they traverse the second as if their current direction was that of the incident beam. This leads to diffraction spots which are the vector sum of those of the two (or even more) reciprocal lattices of the crystals, and can lead to complicated results. It can be difficult to know if this is real and due to some novel material, or just a case where multiple crystals and diffraction is leading to odd results. | 0 | Theoretical and Fundamental Chemistry |
Tilth is a physical condition of soil, especially in relation to its suitability for planting or growing a crop. Factors that determine tilth include the formation and stability of aggregated soil particles, moisture content, degree of aeration, soil biota, rate of water infiltration and drainage. Tilth can change rapidly, depending on environmental factors such as changes in moisture, tillage and soil amendments. The objective of tillage (mechanical manipulation of the soil) is to improve tilth, thereby increasing crop production; in the long term, however, conventional tillage, especially plowing, often has the opposite effect, causing the soil carbon sponge to oxidize, break down and become compacted.
Soil with good tilth is spongy with large pore spaces for air infiltration and water movement. Roots only grow where the soil tilth allows for adequate levels of soil oxygen. Such soil also holds a reasonable supply of water and nutrients.
Tillage, organic matter amendments, fertilization and irrigation can each improve tilth, but when used excessively, can have the opposite effect. Crop rotation and cover crops can rebuild the soil carbon sponge and positively impact tilth. A combined approach can produce the greatest improvement. | 0 | Theoretical and Fundamental Chemistry |
Nucleosides are typically synthesized through the coupling of a nucleophilic pyrimidine, purine, or other basic heterocycle with a derivative of ribose or deoxyribose that is electrophilic at the anomeric carbon. When an acyl-protected ribose is employed, selective formation of the β-nucleoside (possessing the S configuration at the anomeric carbon) results from neighboring group participation. Stereoselective synthesis of deoxyribonucleosides directly from deoxyribose derivatives is more difficult to achieve because neighboring group participation cannot take place.
Three general methods have been used to synthesize nucleosides from nucleophilic bases and electrophilic sugars. The fusion method involves heating the base and acetyl-protected 1-acetoxyribose to 155 °C and results in the formation of the nucleoside with a maximum yield of 70%.
The metal salt method involves the combination of a metal salt of the heterocycle with a protected sugar halide. Silver and mercury salts were originally used; however, more recently developed methods use sodium salts.
The silyl-Hilbert-Johnson (SHJ) reaction (or Vorbrüggen reaction), the mildest general method for the formation of nucleosides, is the combination of a silylated heterocycle and protected sugar acetate (such as 1-O-acetyl-2,3,5-tri-O-benzoyl-beta-D-ribofuranose) in the presence of a Lewis acid. Problems associated with the insolubility of the heterocyclic bases and their metal salts are avoided; however, site selectivity is sometimes a problem when heterocycles containing multiple basic sites are used, as the reaction is often reversible. | 0 | Theoretical and Fundamental Chemistry |
The Macfarlane Burnet Medal and Lecture is a biennial award given by the Australian Academy of Science to recognise outstanding scientific research in the biological sciences.
It was established in 1971 and honours the memory of the Nobel laureate Sir Frank Macfarlane Burnet, OM KBE MD FAA FRS, the Australian virologist best known for his contributions to immunology and is the academy's highest award for biological sciences. | 1 | Applied and Interdisciplinary Chemistry |
Aerated solutions of Cr(CHCN)(NS) are highly photoactive and prone to rapid decomposition. Deaerated solutions of Cr(CHCN)(NS) in acetonitrile are stable as long as they are kept in the dark. Continuous photolysis using 366 nm light is slow, while using a 355 nm pulsed laser results in faster labilization of NS. | 0 | Theoretical and Fundamental Chemistry |
As enzymes have evolved to bind their substrates tightly, and most reversible inhibitors bind in the active site of enzymes, it is unsurprising that some of these inhibitors are strikingly similar in structure to the substrates of their targets. Inhibitors of dihydrofolate reductase (DHFR) are prominent examples. Other examples of these substrate mimics are the protease inhibitors, a therapeutically effective class of antiretroviral drugs used to treat HIV/AIDS. The structure of ritonavir, a peptidomimetic (peptide mimic) protease inhibitor containing three peptide bonds, as shown in the "competitive inhibition" figure above. As this drug resembles the peptide that is the substrate of the HIV protease, it competes with the substrate in the enzyme's active site.
Enzyme inhibitors are often designed to mimic the transition state or intermediate of an enzyme-catalysed reaction. This ensures that the inhibitor exploits the transition state stabilising effect of the enzyme, resulting in a better binding affinity (lower K) than substrate-based designs. An example of such a transition state inhibitor is the antiviral drug oseltamivir; this drug mimics the planar nature of the ring oxonium ion in the reaction of the viral enzyme neuraminidase.
However, not all inhibitors are based on the structures of substrates. For example, the structure of another HIV protease inhibitor tipranavir is not based on a peptide and has no obvious structural similarity to a protein substrate. These non-peptide inhibitors can be more stable than inhibitors containing peptide bonds, because they will not be substrates for peptidases and are less likely to be degraded.
In drug design it is important to consider the concentrations of substrates to which the target enzymes are exposed. For example, some protein kinase inhibitors have chemical structures that are similar to ATP, one of the substrates of these enzymes. However, drugs that are simple competitive inhibitors will have to compete with the high concentrations of ATP in the cell. Protein kinases can also be inhibited by competition at the binding sites where the kinases interact with their substrate proteins, and most proteins are present inside cells at concentrations much lower than the concentration of ATP. As a consequence, if two protein kinase inhibitors both bind in the active site with similar affinity, but only one has to compete with ATP, then the competitive inhibitor at the protein-binding site will inhibit the enzyme more effectively. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, the carbon-hydrogen bond ( bond) is a chemical bond between carbon and hydrogen atoms that can be found in many organic compounds. This bond is a covalent, single bond, meaning that carbon shares its outer valence electrons with up to four hydrogens. This completes both of their outer shells, making them stable.
Carbon–hydrogen bonds have a bond length of about 1.09 Å (1.09 × 10 m) and a bond energy of about 413 kJ/mol (see table below). Using Pauling's scale—C (2.55) and H (2.2)—the electronegativity difference between these two atoms is 0.35. Because of this small difference in electronegativities, the bond is generally regarded as being non-polar. In structural formulas of molecules, the hydrogen atoms are often omitted. Compound classes consisting solely of bonds and bonds are alkanes, alkenes, alkynes, and aromatic hydrocarbons. Collectively they are known as hydrocarbons.
In October 2016, astronomers reported that the very basic chemical ingredients of life—the carbon-hydrogen molecule (CH, or methylidyne radical), the carbon-hydrogen positive ion () and the carbon ion ()—are the result, in large part, of ultraviolet light from stars, rather than in other ways, such as the result of turbulent events related to supernovae and young stars, as thought earlier. | 0 | Theoretical and Fundamental Chemistry |
Superplasticizers (SPs), also known as high range water reducers, are additives used for making high-strength concrete or to place self-compacting concrete. Plasticizers are chemical compounds enabling the production of concrete with approximately 15% less water content. Superplasticizers allow reduction in water content by 30% or more. These additives are employed at the level of a few weight percent. Plasticizers and superplasticizers also retard the setting and hardening of concrete.
According to their dispersing functionality and action mode, one distinguishes two classes of superplasticizers:
# Ionic interactions (electrostatic repulsion): lignosulfonates (first generation of ancient water reducers), sulfonated synthetic polymers (naphthalene, or melamine, formaldehyde condensates) (second generation), and;
# Steric effects: Polycarboxylates-ether (PCE) synthetic polymers bearing lateral chains (third generation).
Superplasticizers are used when well-dispersed cement particle suspensions are required to improve the flow characteristics (rheology) of concrete. Their addition allows to decrease the water-to-cement ratio of concrete or mortar without negatively affecting the workability of the mixture. It enables the production of self-consolidating concrete and high-performance concrete. The water–cement ratio is the main factor determining the concrete strength and its durability. Superplasticizers greatly improve the fluidity and the rheology of fresh concrete. The concrete strength increases when the water-to-cement ratio decreases because avoiding to add water in excess only for maintaining a better workability of fresh concrete results in a lower porosity of the hardened concrete, and so to a better resistance to compression.
The addition of SP in the truck during transit is a fairly modern development within the industry. Admixtures added in transit through automated slump management system, allow to maintain fresh concrete slump until discharge without reducing concrete quality. | 0 | Theoretical and Fundamental Chemistry |
Luminol (CHNO) is a chemical that exhibits chemiluminescence, with a blue glow, when mixed with an appropriate oxidizing agent. Luminol is a white-to-pale-yellow crystalline solid that is soluble in most polar organic solvents, but insoluble in water.
Forensic investigators use luminol to detect trace amounts of blood at crime scenes, as it reacts with the iron in hemoglobin. Biologists use it in cellular assays to detect copper, iron, cyanides, as well as specific proteins via western blotting.
When luminol is sprayed evenly across an area, trace amounts of an activating oxidant make the luminol emit a blue glow that can be seen in a darkened room. The glow only lasts about 30 seconds, but can be documented photographically. The glow is stronger in areas receiving more spray; the intensity of the glow does not indicate the amount of blood or other activator present. | 0 | Theoretical and Fundamental Chemistry |
A paper coauthored by Tomlin won the 1992 Sugden Award of The Combustion Institute. Tomlin was elected to the inaugural 2018 class of Fellows of The Combustion Institute, "for innovative research on the development and application of mechanism reduction, sensitivity analysis and uncertainty quantification in combustion models". | 0 | Theoretical and Fundamental Chemistry |
Mollapour is married to Dimitra Bourboulia, PhD, Associate Professor, Assistant Dean for Undergraduate and Graduate Medical Education Research, and Director for the Office of Research for Medical Students, at SUNY Upstate Medical University. | 1 | Applied and Interdisciplinary Chemistry |
Nanoparticles are classified as having at least one of its dimensions in the range of 1-100 nanometers (nm). The small size of nanoparticles allows them to have unique characteristics which may not be possible on the macro-scale. Self-assembly is the spontaneous organization of smaller subunits to form larger, well-organized patterns. For nanoparticles, this spontaneous assembly is a consequence of interactions between the particles aimed at achieving a thermodynamic equilibrium and reducing the system’s free energy. The thermodynamics definition of self-assembly was introduced by Professor Nicholas A. Kotov. He describes self-assembly as a process where components of the system acquire non-random spatial distribution with respect to each other and the boundaries of the system. This definition allows one to account for mass and energy fluxes taking place in the self-assembly processes.
This process occurs at all size scales, in the form of either static or dynamic self-assembly. Static self-assembly utilizes interactions amongst the nano-particles to achieve a free-energy minimum. In solutions, it is an outcome of random motion of molecules and the affinity of their binding sites for one another. A dynamic system is forced to not reach equilibrium by supplying the system with a continuous, external source of energy to balance attractive and repulsive forces. Magnetic fields, electric fields, ultrasound fields, light fields, etc. have all been used as external energy sources to program robot swarms at small scales. Static self-assembly is significantly slower compared to dynamic self-assembly as it depends on the random chemical interactions between particles.
Self assembly can be directed in two ways. The first is by manipulating the intrinsic properties which includes changing the directionality of interactions or changing particle shapes. The second is through external manipulation by applying and combining the effects of several kinds of fields to manipulate the building blocks into doing what is intended. To do so correctly, an extremely high level of direction and control is required and developing a simple, efficient method to organize molecules and molecular clusters into precise, predetermined structures is crucial. | 0 | Theoretical and Fundamental Chemistry |
Increasing the intensity of the electromagnetic field and the particle velocity, the emission of photons with energy comparable to the electron one becomes more probable and non-linear inverse Compton scattering starts to progressively differ from the classical limit because of quantum effects such as photon recoil. A dimensionless parameter, called electron quantum parameter, can be introduced to describe how far the physical condition are from the classical limit and how much non-linear and quantum effects matter. This parameter is given by the following expression:where V/m is the Schwinger field. In scientific literature, is also called . The Schwinger field , appearing in this definition, is a critical field capable of performing on electrons a work of over a reduced Compton length , where is the reduced Planck constant. The presence of such a strong field implies the instability of vacuum and it is necessary to explore non-linear QED effects, such as the production of pairs from vacuum. The Schwinger field corresponds to an intensity of nearly W/cm. Consequently, represents the work, in units of , performed by the field over the Compton length and in this way it also measures the importance of quantum non-linear effects since it compares the field strength in the rest frame of the electron with that of the critical field. Non-linear quantum effects, like the production of an electron-positron pair in vacuum, occur above the critical field , however, they can be observed also well below this limit since ultra-relativistic particles with Lorentz factor equal to see fields of the order of in their rest frame. is called also non-linear quantum parameter whereas it is a measure of the magnitude of non-linear quantum effects. The electron quantum parameter is linked to the magnitude of the Lorentz four-force acting on the particle due to the electromagnetic field and it is a Lorentz-invariant:The four-force acting on the particle is equal to the derivative of the four-momentum with respect to proper time. Using this fact in the classical limit, the radiated power according to the relativistic generalization of the Larmor formula becomes:<math display="block">
P=\dfrac{2}{3}\dfrac{e^2m^2c^3}{\hbar^2}\chi^2
and, therefore, some considerations can be done on which are the conditions for prolific emission, further evaluating the definition (). The electron quantum parameter increases with the energy of the electron (direct proportionality to ) and it is larger when the force exerted by the field perpendicularly to the particle velocity increases. | 0 | Theoretical and Fundamental Chemistry |
Mount Polley ships material, concentrated by floating, by truck to Vancouver when it is sent overseas to buyers who then smelt and refine the material. | 1 | Applied and Interdisciplinary Chemistry |
The instrumentation needed to perform capillary electrophoresis is relatively simple. A basic schematic of a capillary electrophoresis system is shown in figure 1. The systems main components are a sample vial, source and destination vials, a capillary, electrodes, a high voltage power supply, a detector, and a data output and handling device. The source vial, destination vial and capillary are filled with an electrolyte such as an aqueous buffer solution. To introduce the sample, the capillary inlet is placed into a vial containing the sample. Sample is introduced into the capillary via capillary action, pressure, siphoning, or electrokinetically, and the capillary is then returned to the source vial. The migration of the analytes is initiated by an electric field that is applied between the source and destination vials and is supplied to the electrodes by the high-voltage power supply. In the most common mode of CE, all ions, positive or negative, are pulled through the capillary in the same direction by electroosmotic flow. The analytes separate as they migrate due to their electrophoretic mobility, and are detected near the outlet end of the capillary. The output of the detector is sent to a data output and handling device such as an integrator or computer. The data is then displayed as an electropherogram, which reports detector response as a function of time. Separated chemical compounds appear as peaks with different migration times in an electropherogram. The technique is often attributed to James W. Jorgensen and Krynn DeArman Lukacs, who first demonstrated the capabilities of this technique. Capillary electrophoresis was first combined with mass spectrometry by Richard D. Smith and coworkers, and provides extremely high sensitivity for the analysis of very small sample sizes. Despite the very small sample sizes (typically only a few nanoliters of liquid are introduced into the capillary), high sensitivity and sharp peaks are achieved in part due to injection strategies that result in a concentration of analytes into a narrow zone near the inlet of the capillary. This is achieved in either pressure or electrokinetic injections simply by suspending the sample in a buffer of lower conductivity (e.g.' lower salt concentration) than the running buffer. A process called field-amplified sample stacking (a form of isotachophoresis) results in concentration of analyte in a narrow zone at the boundary between the low-conductivity sample and the higher-conductivity running buffer.
To achieve greater sample throughput, instruments with arrays of capillaries are used to analyze many samples simultaneously. Such capillary array electrophoresis (CAE) instruments with 16 or 96 capillaries are used for medium- to high-throughput capillary DNA sequencing, and the inlet ends of the capillaries are arrayed spatially to accept samples directly from SBS-standard footprint 96-well plates. Certain aspects of the instrumentation (such as detection) are necessarily more complex than for a single-capillary system, but the fundamental principles of design and operation are similar to those shown in Figure 1. | 0 | Theoretical and Fundamental Chemistry |
The only North American producer, Monsanto Company, marketed PCBs under the trade name Aroclor from 1930 to 1977. These were sold under trade names followed by a four-digit number. In general, the first two digits refer to the product series as designated by Monsanto (e.g. 1200 or 1100 series); the second two numbers indicate the percentage of chlorine by mass in the mixture. Thus, Aroclor 1260 is a 1200 series product and contains 60% chlorine by mass. It is a myth that the first two digits referred to the number of carbon atoms; the number of carbon atoms do not change in PCBs. The 1100 series was a crude PCB material which was distilled to create the 1200 series PCB product.
The exception to the naming system is Aroclor 1016 which was produced by distilling 1242 to remove the highly chlorinated congeners to make a more biodegradable product. "1016" was given to this product during Monsanto's research stage for tracking purposes but the name stuck after it was commercialized.
Different Aroclors were used at different times and for different applications. In electrical equipment manufacturing in the US, Aroclor 1260 and Aroclor 1254 were the main mixtures used before 1950; Aroclor 1242 was the main mixture used in the 1950s and 1960s until it was phased out in 1971 and replaced by Aroclor 1016.
Commercial production of PCBs was banned in the United States in 1979, with the passage of the Toxic Substances Control Act (TSCA). | 1 | Applied and Interdisciplinary Chemistry |
Some aircraft have been built to use the Magnus effect to create lift with a rotating cylinder instead of a wing, allowing flight at lower horizontal speeds. The earliest attempt to use the Magnus effect for a heavier-than-air aircraft was in 1910 by a US member of Congress, Butler Ames of Massachusetts. The next attempt was in the early 1930s by three inventors in New York state. | 1 | Applied and Interdisciplinary Chemistry |
Each process is one of the following:
*isothermal (at constant temperature, maintained with heat added or removed from a heat source or sink)
*isobaric (at constant pressure)
*isometric/isochoric (at constant volume), also referred to as iso-volumetric
*adiabatic (no heat is added or removed from the system during adiabatic process)
*isentropic (reversible adiabatic process, no heat is added or removed during isentropic process) | 0 | Theoretical and Fundamental Chemistry |
Let's assume that we understand mechanics well enough to understand and measure volume, area, mass, and force. These may be combined to understand the concept of pressure, which is force per unit area and density, which is mass per unit volume. It has been experimentally determined that, at low enough pressures and densities, all gases behave as ideal gases. The behavior of an ideal gas is given by the ideal gas law:
where P is pressure, V is volume, N is the number of particles (total mass divided by mass per particle), k is Boltzmanns constant, and T is temperature. In fact, this equation is more than a phenomenological equation, it gives an operational, or experimental, definition of temperature. A thermometer is a tool that measures temperature - a primitive thermometer would simply be a small container of an ideal gas, that was allowed to expand against atmospheric pressure. If we bring it into thermal contact with the system whose temperature we wish to measure, wait until it equilibrates, and then measure the volume of the thermometer, we will be able to calculate the temperature of the system in question via T=PV/Nk'. Hopefully, the thermometer will be small enough that it does not appreciably alter the temperature of the system it is measuring, and also that the atmospheric pressure is not affected by the expansion of the thermometer.
The ideal gas thermometer can be defined more precisely by saying it is a system containing an ideal gas, which is thermally connected to the system it is measuring, while being dynamically and materially insulated from it. It is simultaneously dynamically connected to an external pressure reservoir, from which it is materially and thermally insulated. Other thermometers (e.g. mercury thermometers, which display the volume of mercury to the observer), may now be constructed, and calibrated against the ideal gas thermometer. | 0 | Theoretical and Fundamental Chemistry |
Target proteins are functional biomolecules that are addressed and controlled by biologically active compounds. They are used in the processes of transduction, transformation and conjugation. The identification of target proteins, the investigation of signal transduction processes and the understanding of their interaction with ligands are key elements of modern biomedical research. Since the interaction with target proteins is the molecular origin of most drugs, their particular importance for molecular biology, molecular pharmacy and pharmaceutical sciences is obvious. Target proteins control the action and the kinetic behavior of drugs within the organism. The elucidation of structure, conformational signaling and catalytic properties of particular target proteins facilitates a rational design of drugs and biotechnological processes. Known as biologicals, target proteins can also be drugs by themselves when their modification and formulation is emphasized within the pharmaceutical sciences. Finally, target protein - inducer interactions can be exploited for biomolecular transcription regulating systems in order to control for example gene therapeutic approaches. | 1 | Applied and Interdisciplinary Chemistry |
Wind driven ventilation can be classified as cross ventilation and single-sided ventilation. Wind driven ventilation depends on wind behavior, on the interactions with the building envelope and on openings or other air exchange devices such as inlets or windcatchers.
The knowledge of the urban climatology i.e. the wind around the buildings is crucial when evaluating the air quality and thermal comfort inside buildings as air and heat exchange depends on the wind pressure on facades. As observed in the equation (1), the air exchange depends linearly on the wind speed in the urban place where the architectural project will be built. CFD (Computational Fluid Dynamics) tools and zonal modelings are usually used to design naturally ventilated buildings. Windcatchers are able to aid wind driven ventilation by directing air in and out of buildings. | 1 | Applied and Interdisciplinary Chemistry |
By February 1994, several regional landfills in Campania had become overfilled, and Prime Minister Carlo Azeglio Ciampi declared a state of emergency and created the Committee for the Waste Emergency in Campania (Commissariato di Governo per lemergenza rifiuti in Campania').
By December 1999, all regional landfills had reached capacity. Reports in 2008 stated that the crisis was caused at least in part by the Camorra, the powerful Campania-based mafia, which created a lucrative business in the municipal waste disposal sector, mostly in the triangle of death. With the complicity of industrial companies, the illegal dumpers frequently mix heavy metals, industrial waste, and chemicals and household waste together, and then dump them near roads and burn them to avoid detection, leading to severe soil and air pollution.
According to Giacomo D'Alisa et al., "the situation worsened during this period as the Camorra diversified their illegal waste disposal strategy: 1) transporting and dumping hazardous waste in the countryside by truck; 2) dumping waste in illegal caves or holes; 3) mixing toxic waste with textiles to avoid explosions and then burning it; and 4) mixing toxic with urban waste for disposal in landfills and incinerators."
A Camorra member, Nunzio Perella was arrested in 1992, and began collaborating with authorities; he had stated "the rubbish is gold." The boss of the Casalesi clan, Gaetano Vassallo, admitted to systematically working for 20 years to bribe local politicians and officials to gain their acquiescence to dumping toxic waste. Giorgio Napolitano, then President of Italian Republic, said in June 2008: | 1 | Applied and Interdisciplinary Chemistry |
The main component of a VIPA is a glass plate whose normal is slightly tilted with respect to the input light. One side (light input side) of the glass plate is coated with a 100% reflective mirror and the other side (light output side) is coated with a highly reflective but partially transmissive mirror. The side with the 100% reflective mirror has an anti-reflection coated light entrance area, through which a light beam enters the glass plate. The input light is line-focused to a line (focal line) on the partially transmissive mirror on the light output side. A typical line-focusing lens is a cylindrical lens, which is also part of the VIPA. The light beam is diverging after the beam waist located at the line-focused position.
After the light enters the glass plate through the light entrance area, the light is reflected at the partially transmissive mirror and the 100% reflective mirror, and thus the light travels back and forth between the partially transmissive mirror and the 100% reflective mirror.
It is noted that the glass plate is tilted as a result of its slight rotation where the axis of rotation is the focal line. This rotation/tilt prevents the light from leaving the glass plate out of the light entrance area. Therefore, in order for the optical system to work as a VIPA, there is a critical minimum angle of tilt that allows the light entering through the light entrance area to return only to the 100% reflective mirror. Below this angle, the function of the VIPA is severely impaired. If the tilting angle were zero, the reflected light from the partially transmissive mirror would travel exactly in reverse and exit the glass plate through the light entrance area without being reflected by the 100% reflective mirror. In the figure, refraction at the surfaces of the glass plate was ignored for simplicity.
When the light beam is reflected each time at the partially transmissive mirror, a small portion of the light power passes through the mirror and travels away from the glass plate. For a light beam passing through the mirror after multiple reflections, the position of the line-focus can be seen in the virtual image when observed from the light output side. Therefore, this light beam travels as if it originated at a virtual light source located at the position of the line-focus and diverged from the virtual light source. The positions of the virtual light sources for all the transmitted light beams automatically align along the normal to the glass plate with a constant spacing, that is, a number of virtual light sources are superimposed to create an optical phased array. Due to the interference of all the light beams, the phased array emits a collimated light beam in one direction, which is at a wavelength dependent angle, and therefore, an angular dispersion is produced. | 0 | Theoretical and Fundamental Chemistry |
Sigma-2 receptors have been found to be highly expressed in proliferating cells, including tumor cells, and to play a role in the differentiation, morphology, and survival of those cells. By interacting with EGFR membrane proteins sigma-2 receptors play a role in the regulation of signals further downstream such as PKC and RAF. Both PKC and Raf kinase up regulate transcription and cell proliferation. | 1 | Applied and Interdisciplinary Chemistry |
Carbamylation of the ε-amino group of Lys210 is stabilized by coordination with the . This reaction involves binding of the carboxylate termini of Asp203 and Glu204 to the ion. The substrate RuBP binds displacing two of the three aquo ligands. | 0 | Theoretical and Fundamental Chemistry |
The parent metallacyclopentane has the formula LM(CH). Such compounds are intermediates in the metal catalysed dimerization, trimerization, and tetramerization of ethylene to give but-1-ene, hex-1-ene and oct-1-ene, respectively. Metallacyclopentanes are invoked as intermediates in the evolution of heterogeneous alkene metathesis catalysts from ethylene and metal oxides. Metallacyclopentane intermediates are proposed to isomerize to metallacyclobutanes, which then eliminate propylene giving the alkylidene. | 0 | Theoretical and Fundamental Chemistry |
The most widely used electrode is the glass electrode, which is selective for the hydrogen ion. This is suitable for all acid–base equilibria. values between about 2 and 11 can be measured directly by potentiometric titration using a glass electrode. This enormous range of stability constant values (ca. 100 to 10) is possible because of the logarithmic response of the electrode. The limitations arise because the Nernst equation breaks down at very low or very high pH.
When a glass electrode is used to obtain the measurements on which the calculated equilibrium constants depend, the precision of the calculated parameters is limited by secondary effects such as variation of liquid junction potentials in the electrode. In practice it is virtually impossible to obtain a precision for log β better than ±0.001. | 0 | Theoretical and Fundamental Chemistry |
SaltMod is computer program for the prediction of the salinity of soil moisture, groundwater and drainage water, the depth of the watertable, and the drain discharge (hydrology) in irrigated agricultural lands, using different (geo)hydrologic conditions, varying water management options, including the use of ground water for irrigation, and several cropping rotation schedules.
The water management options include irrigation, drainage, and the use of subsurface drainage water from pipe drains, ditches or wells for irrigation. | 0 | Theoretical and Fundamental Chemistry |
Changes in Arc mRNA and/or protein are correlated with a number of behavioral changes including cued fear conditioning, contextual fear conditioning, spatial memory, operant conditioning, and inhibitory avoidance. The mRNA is notably upregulated following electrical stimulation in LTP-induction procedures such as high frequency stimulation (HFS), and is massively and globally induced by maximal electroconvulsive shock (MECS). | 1 | Applied and Interdisciplinary Chemistry |
Evidence that eRNAs cause downstream effects on the efficiency of enhancer activation and gene transcription suggests its functional capabilities and potential importance.
The transcription factor p53 has been demonstrated to bind enhancer regions and generate eRNAs in a p53-dependent manner. In cancer, p53 plays a central role in tumor suppression as mutations of the gene are shown to appear in 50% of tumors. These p53-bound enhancer regions (p53BERs) are shown to interact with multiple local and distal gene targets involved in cell proliferation and survival. Furthermore, eRNAs generated by the activation of p53BERs are shown to be required for efficient transcription of the p53 target genes, indicating the likely important regulatory role of eRNAs in tumor suppression and cancer. Generally, mutations in eRNA have been shown to demonstrate similar phenotypic behavior in oncogenesis as compared to protein-coding RNA.
Variations in enhancers have been implicated in human disease but a therapeutic approach to manipulate enhancer activity is currently not possible. With the emergence of eRNAs as important components in enhancer activity, powerful therapeutic tools such as RNAi may provide promising routes to target disruption of gene expression. | 1 | Applied and Interdisciplinary Chemistry |
Common thermodynamic equations and quantities in thermodynamics, using mathematical notation, are as follows: | 0 | Theoretical and Fundamental Chemistry |
The control of enzymatic browning has always been a challenge for the food industry. A variety of approaches are used to prevent or slow down enzymatic browning of foods, each method aimed at targeting specific steps of the chemical reaction. The different types of enzymatic browning control can be classified into two large groups: physical and chemical. Usually, multiple methods are used. The use of sulfites (powerful anti-browning chemicals) have been reconsidered due to the potential hazards that it causes along with its activity. Much research has been conducted regarding the exact types of control mechanisms that take place when confronted with the enzymatic process. Besides prevention, control over browning also includes measures intended to recover the food color after its browning. For instance, ion exchange filtration or ultrafiltration can be used in winemaking to remove the brown color sediments in the solution. | 1 | Applied and Interdisciplinary Chemistry |
It is also possible to synthesise heterocyclic compounds via the Elbs reaction. In 1956 an Elbs reaction of a thiophene derivative was published. The expected linear product was not obtained due to a change in reaction mechanism after formation of the first intermediate which caused multiple free radical reaction steps. | 0 | Theoretical and Fundamental Chemistry |
Weak affinity chromatography (WAC) is an affinity chromatography technique for affinity screening in drug development. WAC is an affinity-based liquid chromatographic technique that separates chemical compounds based on their different weak affinities to an immobilized target. The higher affinity a compound has towards the target, the longer it remains in the separation unit, and this will be expressed as a longer retention time. The affinity measure and ranking of affinity can be achieved by processing the obtained retention times of analyzed compounds. Affinity chromatography is part of a larger suite of techniques used in chemoproteomics based drug target identification.
The WAC technology is demonstrated against a number of different protein targets – proteases, kinases, chaperones and protein–protein interaction (PPI) targets. WAC has been shown to be more effective than established methods for fragment based screening. | 0 | Theoretical and Fundamental Chemistry |
NAPQI becomes toxic when GSH is depleted by an overdose of acetaminophen, Glutathione is an essential antidote to overdose. Glutathione conjugates to NAPQI and helps to detoxify it. In this capacity, it protects cellular protein thiol groups, which would otherwise become covalently modified; when all GSH has been spent, NAPQI begins to react with the cellular proteins, killing the cells in the process. The preferred treatment for an overdose of this painkiller is the administration of N-acetyl--cysteine (either via oral or IV administration)), which is processed by cells to -cysteine and used in the de novo synthesis of GSH. | 1 | Applied and Interdisciplinary Chemistry |
This is the earliest theory specifically for grain boundaries, in which McLean uses a model of P solute atoms distributed at random amongst N lattice sites and p solute atoms distributed at random amongst n independent grain boundary sites. The total free energy due to the solute atoms is then:
where E and e are energies of the solute atom in the lattice and in the grain boundary, respectively and the kln term represents the configurational entropy of the arrangement of the solute atoms in the bulk and grain boundary. McLean used basic statistical mechanics to find the fractional monolayer of segregant, , at which the system energy was minimized (at the equilibrium state), differentiating G with respect to p, noting that the sum of p and P is constant. Here the grain boundary analogue of Langmuir adsorption at free surfaces becomes:
Here, is the fraction of the grain boundary monolayer available for segregated atoms at saturation, is the actual fraction covered with segregant, is the bulk solute molar fraction, and is the free energy of segregation per mole of solute.
Values of were estimated by McLean using the elastic strain energy, , released by the segregation of solute atoms. The solute atom is represented by an elastic sphere fitted into a spherical hole in an elastic matrix continuum. The elastic energy associated with the solute atom is given by:
where is the solute bulk modulus, is the matrix shear modulus, and and are the atomic radii of the matrix and impurity atoms, respectively. This method gives values correct to within a factor of two (as compared with experimental data for grain boundary segregation), but a greater accuracy is obtained using the method of Seah and Hondros, described in the following section. | 0 | Theoretical and Fundamental Chemistry |
3M produces perfluoro(2-methyl-3-pentanone) under different brand names of Novec 1230 and Novec 649. These two products have different purity grades (>99% and >99.9%, respectively) intended for different industrial applications. | 1 | Applied and Interdisciplinary Chemistry |
In June 1955 Bussard moved to Los Alamos and joined the Nuclear Propulsion Divisions Project Rover designing nuclear thermal rocket engines. Bussard and R.D. DeLauer wrote two important monographs on nuclear propulsion, Nuclear Rocket Propulsion and Fundamentals of Nuclear Flight'. | 0 | Theoretical and Fundamental Chemistry |
Polymerized ionic liquids, poly(ionic liquid)s or polymeric ionic liquids, all abbreviated as PIL is the polymeric form of ionic liquids. They have half of the ionicity of ionic liquids since one ion is fixed as the polymer moiety to form a polymeric chain. PILs have a similar range of applications, comparable with those of ionic liquids but the polymer architecture provides a better chance for controlling the ionic conductivity. They have extended the applications of ionic liquids for designing smart materials or solid electrolytes. | 0 | Theoretical and Fundamental Chemistry |
Periodic Videos (also known as The Periodic Table of Videos) is a video project and YouTube channel on chemistry. It consists of a series of videos about chemical elements and the periodic table, with additional videos on other topics in chemistry and related fields. They are published on YouTube and produced by Brady Haran, a former BBC video journalist, mainly featuring Sir Martyn Poliakoff, Peter Licence, Stephen Liddle, Debbie Kays, Neil Barnes, Sam Tang, and other scientists at the University of Nottingham. | 1 | Applied and Interdisciplinary Chemistry |
Similar projects have been undertaken in Finland, which requires all buildings with area over 600 m to have an NBC (nuclear-biological-chemical) shelter, and Norway, which requires all buildings with an area over 1000 m to have a shelter.
The former Soviet Union and other Eastern Bloc countries often designed their underground mass-transit and subway tunnels to serve as bomb and fallout shelters in the event of an attack. Currently, the deepest subway line in the world is situated in St Petersburg in Russia, with an average depth of 60 meters, while the deepest subway station is Arsenalna in Kyiv, at 105.5 meters.
Germany has protected shelters for 3% of its population, Austria for 30%, Finland for 70%, Sweden for 81%, and Switzerland for 114%. | 0 | Theoretical and Fundamental Chemistry |
In 1989, the center received a further challenge grant, this time from Donald F. Othmer and his wife, Mildred Topp Othmer. Donald Othmer was a quiet chemical engineering professor from Polytechnic University in Brooklyn. The Othmers donated $5 million towards the creation of the Othmer Library of Chemical History. Again, efforts to match the grant were supported by the National Foundation for History of Chemistry and the American Chemical Societys Campaign for Chemistry. The new library was further supported by the donation of 8,500 monographs, textbooks and reference works from The Chemists Club of New York. | 1 | Applied and Interdisciplinary Chemistry |
Actinide chemistry (or actinoid chemistry) is one of the main branches of nuclear chemistry that investigates the processes and molecular systems of the actinides. The actinides derive their name from the group 3 element actinium. The informal chemical symbol An is used in general discussions of actinide chemistry to refer to any actinide. All but one of the actinides are f-block elements, corresponding to the filling of the 5f electron shell; lawrencium, a d-block element, is also generally considered an actinide. In comparison with the lanthanides, also mostly f-block elements, the actinides show much more variable valence. The actinide series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium. | 0 | Theoretical and Fundamental Chemistry |
In environmental chemistry, the term "contamination" is in some cases virtually equivalent to pollution, where the main interest is the harm done on a large scale to humans, organisms, or environments. An environmental contaminant may be chemical in nature, though it may also be a biological (pathogenic bacteria, virus, invasive species) or physical (energy) agent. Environmental monitoring is one mechanism available to scientists to detect contamination activities early before they become too detrimental. | 0 | Theoretical and Fundamental Chemistry |
Aqueous biphasic systems (ABS) or aqueous two-phase systems (ATPS) are clean alternatives for traditional organic-water solvent extraction systems.
ABS are formed when either two polymers, one polymer and one kosmotropic salt, or two salts (one chaotropic salt and the other a kosmotropic salt) are mixed at appropriate concentrations or at a particular temperature. The two phases are mostly composed of water and non volatile components, thus eliminating volatile organic compounds. They have been used for many years in biotechnological applications as non-denaturing and benign separation media. Recently, it has been found that ATPS can be used for separations of metal ions like mercury and cobalt, carbon nanotubes, environmental remediation, metallurgical applications and as a reaction media. | 0 | Theoretical and Fundamental Chemistry |
For clarification, a distinction between the two corresponding cases is needed. With reference to a phase diagram, the sublimation that occurs left of the solid-gas boundary, the triple point or the solid-liquid boundary (corresponding to evaporation in vaporization) may be called gradual sublimation; and the substance sublimes gradually, regardless of rate. The sublimation that occurs at the solid-gas boundary (critical sublimation point) (corresponding to boiling in vaporization) may be called rapid sublimation, and the substance sublimes rapidly. The words "gradual" and "rapid" have acquired special meanings in this context and no longer describe the rate of sublimation. | 0 | Theoretical and Fundamental Chemistry |
In an endothermic reaction or system, energy is taken from the surroundings in the course of the reaction, usually driven by a favorable entropy increase in the system. An example of an endothermic reaction is a first aid cold pack, in which the reaction of two chemicals, or dissolving of one in another, requires calories from the surroundings, and the reaction cools the pouch and surroundings by absorbing heat from them.
Photosynthesis, the process that allows plants to convert carbon dioxide and water to sugar and oxygen, is an endothermic process: plants absorb radiant energy from the sun and use it in an endothermic, otherwise non-spontaneous process. The chemical energy stored can be freed by the inverse (spontaneous) process: combustion of sugar, which gives carbon dioxide, water and heat (radiant energy). | 0 | Theoretical and Fundamental Chemistry |
The Richtmyer–Meshkov instability (RMI) occurs when two fluids of different density are impulsively accelerated. Normally this is by the passage of a shock wave. The development of the instability begins with small amplitude perturbations which initially grow linearly with time. This is followed by a nonlinear regime with bubbles appearing in the case of a light fluid penetrating a heavy fluid, and with spikes appearing in the case of a heavy fluid penetrating a light fluid. A chaotic regime eventually is reached and the two fluids mix. This instability can be considered the impulsive-acceleration limit of the Rayleigh–Taylor instability. | 1 | Applied and Interdisciplinary Chemistry |
For fluorene, there are 6 apparent double bonds (three pi bonds in each side benzene-like ring); the central ring has one secondary carbon and is non-aromatic. Therefore: | 0 | Theoretical and Fundamental Chemistry |
The HiFIT hammer operates with a hardened pin with a ball resting on the workpiece with a diameter D of 3 mm.
This pin is hammered with an adjustable intensity at around 180–300 Hz at the weld toe. Local mechanical deformations occur in the form of a treatment track. The weld toe is deformed plastically. The induced compressive residual stress prevents the track cracking and the crack propagation on the surface. | 1 | Applied and Interdisciplinary Chemistry |
Artificial photosynthesis is a chemical process that biomimics the natural process of photosynthesis. The term artificial photosynthesis is used loosely, refer to any scheme for capturing and storing energy from sunlight by producing a fuel, specifically a solar fuel. An advantage of artificial photosynthesis is that the solar energy can be immediately converted and stored. By contrast, using photovoltaic cells, sunlight is converted into electricity and then converted again into chemical energy for storage, with some necessary losses of energy associated with the second conversion. The byproducts of these reactions are environmentally friendly. Artificially photosynthesized fuel would be a carbon-neutral source of energy, which could be used for transportation or homes. The economics of artificial photosynthesis are not competitive. | 0 | Theoretical and Fundamental Chemistry |
Imido ligands, also known as imides or nitrenes, most commonly form "linear six electron bonds" with metal centers. Bent imidos are a rarity limited by complexes electron count, orbital bonding availability, or some similar phenomenon. It is common to draw only two lines of bonding for all imidos, including the most common linear imidos with a six electron bonding interaction to the metal center. Similarly amido complexes are usually drawn with a single line even though most amido bonds involve four electrons. Alkoxides are generally drawn with a single bond although both two and four electron bonds are common. Oxo can be drawn with two lines regardless of whether four electrons or six are involved in the bond, although it is not uncommon to see six electron oxo bonds represented with three lines. | 0 | Theoretical and Fundamental Chemistry |
The minimum total potential energy principle is a fundamental concept used in physics and engineering. It dictates that at low temperatures a structure or body shall deform or displace to a position that (locally) minimizes the total potential energy, with the lost potential energy being converted into kinetic energy (specifically heat). | 0 | Theoretical and Fundamental Chemistry |
Wild aquatic birds are the natural hosts for a large variety of influenza A viruses. Occasionally viruses are transmitted from this reservoir to other species and may then cause devastating outbreaks in domestic poultry or give rise to human influenza pandemics. | 1 | Applied and Interdisciplinary Chemistry |
The green patina that forms naturally on copper and bronze, sometimes called verdigris, usually consists of varying mixtures of copper chlorides, sulfides, sulfates, and carbonates, depending upon environmental conditions such as sulfur-containing acid rain. In clean air rural environments, the patina is created by the slow chemical reaction of copper with carbon dioxide and water, producing a basic copper carbonate. In industrial and urban air environments containing sulfurous acid rain from coal-fired power plants or industrial processes, the final patina is primarily composed of sulphide or sulphate compounds.
A patina layer takes many years to develop under natural weathering. Buildings in damp coastal or marine environments will develop patina layers faster than ones in dry inland areas.
Façade cladding (copper cladding; copper wall cladding) with alloys of copper, like brass or bronze, will weather differently from "pure" copper cladding. Even a lasting gold colour is possible with copper-alloy cladding, for example Bristol Beacon in Bristol, or the Novotel at Paddington Central, London.
Antique and well-used firearms will often develop a layer of rust on the action, barrel, or other steel parts after the original finish has worn. On this subject gunsmith Mark Novak says "... This is what everybody calls patina, I call it a nice thick coat of rust..." The removal of such rust is often necessary for a firearm conservation to prevent further decay of the firearm. | 1 | Applied and Interdisciplinary Chemistry |
Most Grignard reactions are conducted in ethereal solvents, especially diethyl ether and THF. Grignard reagents react with 1,4-dioxane to give the diorganomagnesium compounds and insoluble coordination polymer and (R = organic group, X = halide):
This reaction exploits the Schlenk equilibrium, driving it toward the right. | 0 | Theoretical and Fundamental Chemistry |
For a two-phase system consisting of the and phase in equilibrium with a surface dividing the phases, the total Gibbs free energy of a system can be written as:
where is the Gibbs free energy.
The equation of the Gibbs Adsorption Isotherm can be derived from the “particularization to the thermodynamics of the Euler theorem on homogeneous first-order forms.” The Gibbs free energy of each phase , phase , and the surface phase can be represented by the equation:
where is the internal energy, is the pressure, is the volume, is the temperature, is the entropy, and is the chemical potential of the -th component.
By taking the total derivative of the Euler form of the Gibbs equation for the phase, phase and the surface phase:
where is the area of the dividing surface, and is the surface tension.
For reversible processes, the first law of thermodynamics requires that:
where is the heat energy and is the work.
Substituting the above equation into the total derivative of the Gibbs energy equation and by utilizing the result is equated to the non-pressure volume work when surface energy is considered:
by utilizing the fundamental equation of Gibbs energy of a multicomponent system:
The equation relating the phase, phase and the surface phase becomes:
When considering the bulk phases ( phase, phase), at equilibrium at constant temperature and pressure the Gibbs–Duhem equation requires that:
The resulting equation is the Gibbs adsorption isotherm equation:
The Gibbs adsorption isotherm is an equation which could be considered an adsorption isotherm that connects surface tension of a solution with the concentration of the solute.
For a binary system containing two components the Gibbs Adsorption Equation in terms of surface excess is: | 0 | Theoretical and Fundamental Chemistry |
Cubosomes are discrete, sub-micron, nanostructured particles of the bicontinuous cubic liquid crystalline phase. The term "bicontinuous" refers to two distinct hydrophilic regions separated by the bilayer. Bicontinuous cubic crystalline materials have been an active research topic because their structure lends itself well to controlled-release applications.
Cubosomes are liquid crystalline nano-structures formed from the cubic phase of lipids, such as monooleate, or any other amphiphilic macromolecules with the unique property to be dispersed into particles. Nano-vehicles are generated from a self-assembled lipid mixture and studied by means of high-resolution cryogenic transmission electron microscope (cryo-TEM). These structures have been observed to naturally occur in mitochondrial membranes and in stressed cells.
Cubosomes are formed at controlled temperatures into lipid bi-layer twisted into three dimension with minimal surface forming a tightly packed structure with bicontinuous domains of water and lipid.
There are three different proposed phases that these cubic structures can be in: the P-surface, G-surface and D-surface for primitive, gyroid and diamond structures respectively. This variation in structure allows for cubosomes to be the ultimate drug delivery system due to its ability to maintain the structural integrity of the ingredients that it carries. The uses of cubosomes are still being researched but they range from systems for efficient drug delivery into specific body systems to stabilizing and producing palladium nanoparticles. | 0 | Theoretical and Fundamental Chemistry |
Abrasion is the property of the coal which describes its propensity and ability to wear away machinery and undergo autonomous grinding. While carbonaceous matter in coal is relatively soft, quartz and other mineral constituents in coal are quite abrasive. This is tested in a calibrated mill, containing four blades of known mass. The coal is agitated in the mill for 12,000 revolutions at a rate of 1,500 revolutions per minute.(I.E 1500 revolution for 8 min.) The abrasion index is determined by measuring the loss of mass of the four metal blades. | 0 | Theoretical and Fundamental Chemistry |
Several other quantities can be used to describe the composition of a mixture. These should not be called concentrations. | 0 | Theoretical and Fundamental Chemistry |
Brigitte Zanda was a student at the École normale supérieure de jeunes filles from 1978 to 1982. She continued her education at the École nationale supérieure des mines de Paris where she was a research fellow from 1982 to 1984. From 1984 to 1989, she worked as a research engineer at the Institut d'astrophysique de Paris, affiliated with the CNRS.
She defended her doctoral thesis in fundamental geochemistry, entitled Les réactions nucléaires induites par le rayonnement cosmique dans les météorites de fer, at the University of Paris VII in 1988, under the supervision of Jean Audouze. A year later, Brigitte Zanda became an associate professor at the National Museum of Natural History, where she was responsible for the conservation of the national meteorite collection.
As part of her professional activities at the Museum, Brigitte Zanda is involved in the dissemination of scientific culture. She also works in the scientific direction of the Astronomy Festival of Fleurance and is responsible for the scientific organization of the AstroNomades festival. She also co-pilots the ANR FRIPON project and directs the / project "Vigie-Ciel". | 0 | Theoretical and Fundamental Chemistry |
This resonant process occurs in a neutral atom when the electric field displaces the electron density relative to the nucleus it surrounds.
This displacement occurs due to the equilibrium between restoration and electric forces.
Electronic polarization may be understood by assuming an atom as a point nucleus surrounded by spherical electron cloud of uniform charge density. | 0 | Theoretical and Fundamental Chemistry |
In his autobiography, What Mad Pursuit, Crick wrote about his choice of the word dogma and some of the problems it caused him:
Similarly, Horace Freeland Judson records in The Eighth Day of Creation: | 1 | Applied and Interdisciplinary Chemistry |
Henrys law states that P=Kx where P is the partial pressure of gas above the solution. K is Henrys law constant. K increases as temperature increases. x is the mole fraction of gas in the solution. According to Henry's law carbonation increases in a solution as temperature decreases.
Since carbonation is the process of giving compounds like carbonic acid (liq) from CO (gas) {i.e. making liquid from gasses} thus the partial pressure of CO has to decrease or the mole fraction of CO in solution has to increase {P/x = K} and both these two conditions support increase in carbonation. | 0 | Theoretical and Fundamental Chemistry |
In the field of formation evaluation, porosity is one of the key measurements to quantify oil and gas reserves. Neutron porosity measurement employs a neutron source to measure the hydrogen index in a reservoir, which is directly related to porosity. The Hydrogen Index (HI) of a material is defined as the ratio of the concentration of hydrogen atoms per cm in the material, to that of pure water at 75 °F. As hydrogen atoms are present in both water and oil-filled reservoirs, measurement of the amount allows estimation of the amount of liquid-filled porosity. | 0 | Theoretical and Fundamental Chemistry |
In fluorescence microscopy, fluorescence confocal laser scanning microscopy, as well as in molecular biology, FRET is a useful tool to quantify molecular dynamics in biophysics and biochemistry, such as protein-protein interactions, protein–DNA interactions, and protein conformational changes. For monitoring the complex formation between two molecules, one of them is labeled with a donor and the other with an acceptor. The FRET efficiency is measured and used to identify interactions between the labeled complexes. There are several ways of measuring the FRET efficiency by monitoring changes in the fluorescence emitted by the donor or the acceptor. | 1 | Applied and Interdisciplinary Chemistry |
A comet assay can determine the degree of DNA fragmentation in sperm cells. The degree of DNA fragmentation has been associated with outcomes of in vitro fertilization.
The comet has been modified for use with sperm cells as a tool for male infertility diagnosis
To break down these tightly bound protamine proteins in order to use the comet for sperm, additional steps in the de-condensation protocol are required. | 1 | Applied and Interdisciplinary Chemistry |
* Honorary Member of the Academy of Sciences of the Armenian SSR
* Honorary Member of Academy of Sciences of the Tajik SSR
* Honorary member of Academy of Sciences of the Turkmen SSR
* Honorary Member of Bulgarian Academy of Sciences (1952)
* Honorary Member of Hungarian Academy of Sciences (1953)
* Honorary Member of the Romanian Academy of Sciences (1957)
* Honorary Member of New York Academy of Sciences USA (1958)
* Honorary Member of American Academy of Arts and Sciences in Boston (1960)
* Honorary Member of the London Chemical Society
* Honorary Member of the Chemical Industry Society of Great Britain
* Honorary Member of the Polish Chemical Society
* Honorary Member of National Institute of Sciences of India
* Honorary Member of the Royal Society of Edinburgh
* Full member of German Academy of Naturalists "Leopoldina" (1959)
* Full member of International Academy of Astronautics (1966)
* Member of the Polish Academy of Sciences (1954)
* Full member of Czechoslovak Academy of Sciences (1957)
* Foreign Member Royal Society of London (1961)
* Foreign member GDR Academy of Sciences (1950)
* Member of the European Society of Cultural Workers
* Doctor "honoris causa" University of Paris (1964)
* Doctor "honoris causa" University of Bordeaux (1966)
* Doctor "honoris causa" University of Jena
* Doctor "honoris causa" University of Calcutta
* Doctor Iasi Polytechnic Institute
* Member of World Peace Council (1950) | 0 | Theoretical and Fundamental Chemistry |
The involvement of toll signalling in immunity was first demonstrated in the fruit fly, Drosophila melanogaster. Fruit flies have only innate immune responses allowing studies to avoid interference of adaptive immune mechanisms on signal transduction. The fly response to fungal or bacterial infection occurs through two distinct signalling cascades, one of which is the toll pathway and the other is the immune deficiency pathway. The toll pathway is similar to mammalian TLR signalling, but unlike mammalian TLRs, toll is not activated directly by pathogen-associated molecular patterns (PAMPs). Its receptor ectodomain recognizes the cleaved form of the cytokine spätzle, which is secreted in the haemolymph as an inactive dimeric precursor. The toll receptor shares the cytoplasmatic TIR domain with mammalian TLRs, but the ectodomain and intracytoplasmatic tail are different. This difference might reflect a function of these receptors as cytokine receptors rather than PRRs.
The toll pathway is activated by different stimuli, such as Gram positive bacteria, fungi and virulence factors. First, the Spätzle processing enzyme (SPE) is activated in response to infection and cleaves spätzle (spz). Cleaved spätzle then binds to the toll receptor and crosslinks its ectodomains. This triggers conformational changes in the receptor resulting in signalling through toll. From this point forward, the signalling cascade is very similar to mammalian signalling through TLRs. The toll-induced signalling complex (TICS) is composed of MyD88, Tube, and Pelle (the orthologue of mammalian IRAK). Signal from TICS is then transduced to Cactus (homologue of mammalian IκB), phosphorylated Cactus is polyubiquitylated and degraded, allowing nuclear translocation of DIF (dorsal-related immunity factor; a homologue of mammalian NF-κB) and induction of transcription of genes for antimicrobial peptides (AMPs) such as drosomycin.
Drosophila have a total of 9 toll family and 6 spz family genes that interact with each other to differing degrees. | 1 | Applied and Interdisciplinary Chemistry |
Acetyl phosphate (AcP), a precursor to ATP, can readily be synthesized at modest yields from thioacetate in pH 7 and 20 °C and pH 8 and 50 °C, although acetyl phosphate is less stable in warmer temperatures and alkaline conditions than in cooler and acidic to neutral conditions. It is unable to promote polymerization of ribonucleotides and amino acids and was only capable of phosphorylation of organic compounds. It was shown that it can promote aggregation and stabilization of AMP in the presence of Na, aggregation of nucleotides could promote polymerization above 75 °C in the absence of Na. It is possible that polymerization promoted by AcP could occur at mineral surfaces. It was shown that ADP can only be phosphorylated to ATP by AcP and other nucleoside triphosphates were not phosphorylated by AcP. This might explain why all lifeforms use ATP to drive biochemical reactions. | 1 | Applied and Interdisciplinary Chemistry |
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