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In phytopharmaceutical or herbal medicine, the active ingredient may be either unknown or may require cofactors in order to achieve therapeutic goals. This leads to complications in labelling. One way manufacturers have attempted to indicate strength is to engage in standardization to a marker compound. Standardization has not been achieved yet, however, with different companies using different markers, or different levels of the same markers, or different methods of testing for marker compounds. For example, St John's wort is often standardized to the hypericin that is now known not to be the "active ingredient" for antidepressant use. Other companies standardize to hyperforin or both, ignoring some 24 known additional possible active constituents. Many herbalists believe that the active ingredient in a plant is the plant itself. | 1 | Applied and Interdisciplinary Chemistry |
Protofection is a developing technique and is continuously being improved. A specific protein transduction system has been created that is complexed with mtDNA, which enables the mtDNA to move across the targeted cell's membrane and specifically target mitochondria. The transduction system used consists of a protein transduction domain, mitochondrial localization sequences, and mitochondrial transcription factor A. Each of these play a specific role in protofection:
* A protein transduction domain is needed because they are small regions of proteins that can cross the cell membrane of cells, independently.
* A specific mitochondrial localization sequences is used for protofection because it permits mtDNA to enter the mitochondria.
* Mitochondrial transcription factor A is used because it unwinds the mtDNA that enters the mitochondria, which is critical for mtDNA replication.
This process can lead to an increase in the amount of mtDNA present in the mitochondria of the target cells.
The transduction system has been tweaked and modified, since the first use of protofection. To shorten the name of the complex, which was previously called PTD-MLS-TFAM complex, it is now named MTD-TFAM. MTD stands for mitochondrial transduction domain and it includes the protein transduction domain and the mitochondrial localization sequences. | 1 | Applied and Interdisciplinary Chemistry |
The ohmic resistance appears in series with the electrode impedance of the reaction and the Nyquist diagram is translated to the right. | 0 | Theoretical and Fundamental Chemistry |
Polariton superfluid is predicted to be a state of the exciton-polaritons system that combines the characteristics of lasers with those of excellent electrical conductors. Researchers look for this state in a solid state optical microcavity coupled with quantum well excitons. The idea is to create an ensemble of particles known as exciton-polaritons and trap them.
Wave behavior in this state results in a light beam similar to that from a laser but possibly more energy efficient.
Unlike traditional superfluids that need temperatures of approximately ~4 K, the polariton superfluid could in principle be stable at much higher temperatures, and might soon be demonstrable at room temperature. Evidence for polariton superfluidity was reported in by Alberto Amo and coworkers, based on the suppressed scattering of the polaritons during their motion.
Although several other researchers are working in the same field, the terminology and conclusions are not completely shared by the different groups. In particular, important properties of superfluids, such as zero viscosity, and of lasers, such as perfect optical coherence, are a matter of debate. Although, there is clear indication of quantized vortices when the pump beam has orbital angular momentum.
Furthermore, clear evidence has been demonstrated also for superfluid motion of polaritons, in terms of the Landau criterion and the suppression of scattering from defects when the flow velocity is slower than the speed of sound in the fluid.
The same phenomena have been demonstrated in an organic exciton polariton fluid, representing the first achievement of room-temperature superfluidity of a hybrid fluid of photons and excitons. | 0 | Theoretical and Fundamental Chemistry |
Because of the relatively long residence time of the ocean's thermohaline circulation, carbon transported as marine snow into the deep ocean by the biological pump can remain out of contact with the atmosphere for more than 1000 years. That is, when the marine snow is finally decomposed to inorganic nutrients and dissolved carbon dioxide, these are effectively isolated from the surface ocean for relatively long time scales related to ocean circulation. Consequently, enhancing the quantity of marine snow that reaches the deep ocean is the basis of several geoengineering schemes to enhance carbon sequestration by the ocean. Ocean nourishment and iron fertilisation seek to boost the production of organic material in the surface ocean, with a concomitant rise in marine snow reaching the deep ocean. These efforts have not yet produced a sustainable fertilization that effectively transports carbon out of the system.
Increases in ocean temperatures, a projected indicator of climate change, may result in a decrease in the production of marine snow due to the enhanced stratification of the water column. Increasing stratification decreases the availability of phytoplankton nutrients such as nitrate, phosphate and silicic acid, and could lead to a decrease in primary production and, thus, marine snow.
The microbial communities associated with marine snow are also interesting to microbiologists. Recent research indicates transported bacteria may exchange genes with previously thought to be isolated populations of bacteria inhabiting the breadth of the ocean floor. In such an immense area there may be as yet undiscovered species tolerant of high pressures and extreme cold, perhaps finding use in bioengineering and pharmacy. | 0 | Theoretical and Fundamental Chemistry |
The discovery of NS5A inhibitors took place within the context of a pursuit for a treatment for HCV. NS5A is among the seven nonstructural proteins that form a complex with viral RNA within infected cells to initiate HCV replication. HCV research has produced several DAAs including NS3A, NS4A and NS5B inhibitors, as well as NS5A inhibitors. | 1 | Applied and Interdisciplinary Chemistry |
The entire process of rolling hairpin replication, which has distinct, sequential stages, can be summarized as follows:
*1. The coding portion of the genome is replicated, starting from the 3′-end of the 3′ hairpin, which acts as a primer, and continues until the newly synthesized strand is connected to the 5′-end of the 5′ hairpin, producing a duplex DNA molecule that has two strands of the coding portion of the genome.
*2. mRNA that encodes the viral replication initiator protein is transcribed and subsequently translated to synthesize the protein.
*3. The initiator protein binds to and cleaves the DNA within a region called the origin, which results in the hairpin unfolding into a linear, extended form. At the same time, the initiator protein establishes a replication fork with its helicase activity.
*4. The extended-form hairpin is replicated to create an inverted copy of the telomere on the newly synthesized strand.
*5. The two strands of that end refold back into two hairpins, which repositions the replication fork to switch templates and move in the opposite direction.
*6. DNA replication continues in a linear manner from one end to the other using the opposite strand as a template.
*7. Upon reaching the other end, that end's hairpin is unfolded and refolded to replicate the terminus and once again swap templates and change the direction of replication. This back-and-forth replication is continually repeated, producing a concatemer of multiple copies of the genome.
*8. The viral initiator protein periodically excises individual genomic strands of DNA from the replicative concatemer.
*9. Excised ssDNA genomes are packaged into newly constructed viral capsids. | 1 | Applied and Interdisciplinary Chemistry |
GPCRs include one or more receptors for the following ligands:
sensory signal mediators (e.g., light and olfactory stimulatory molecules);
adenosine, bombesin, bradykinin, endothelin, γ-aminobutyric acid (GABA), hepatocyte growth factor (HGF), melanocortins, neuropeptide Y, opioid peptides, opsins, somatostatin, GH, tachykinins, members of the vasoactive intestinal peptide family, and vasopressin;
biogenic amines (e.g., dopamine, epinephrine, norepinephrine, histamine, serotonin, and melatonin);
glutamate (metabotropic effect);
glucagon;
acetylcholine (muscarinic effect);
chemokines;
lipid mediators of inflammation (e.g., prostaglandins, prostanoids, platelet-activating factor, and leukotrienes);
peptide hormones (e.g., calcitonin, C5a anaphylatoxin, follicle-stimulating hormone [FSH], gonadotropin-releasing hormone [GnRH], neurokinin, thyrotropin-releasing hormone [TRH], and oxytocin);
and endocannabinoids.
GPCRs that act as receptors for stimuli that have not yet been identified are known as orphan receptors.
However, in contrast to other types of receptors that have been studied, wherein ligands bind externally to the membrane, the ligands of GPCRs typically bind within the transmembrane domain. However, protease-activated receptors are activated by cleavage of part of their extracellular domain. | 1 | Applied and Interdisciplinary Chemistry |
In addition to the active metal (usually Fe or Co), two other components comprise the catalyst: promoters and the catalyst support. Promoters are additives that enhance the behavior of the catalyst. For F-T catalysts, typical promoters including potassium and copper, which are usually added as salts. The choice of promoters depends on the primary metal, iron vs cobalt. Iron catalysts need alkali promotion to attain high activity and stability (e.g. 0.5 wt% ). Potassium-doped α-FeO are synthesized under variable calcination temperatures (400–800 °C). Addition of Cu for reduction promotion, addition of , for structural promotion and maybe some manganese can be applied for selectivity control (e.g. high olefinicity). The choice of promoters depends on the primary metal, i.e., iron vs cobalt. While group 1 alkali metals (e.g., potassium), help iron catalysts, they poison cobalt catalysts.
Catalysts are supported on high-surface-area binders/supports such as silica, alumina, or zeolites. | 0 | Theoretical and Fundamental Chemistry |
The endophenotype concept has also been used in suicide studies. Personality characteristics can be viewed as endophenotypes that may exert a diathesis effect on an individual's susceptibility to suicidal behavior. Although the exact identification of these endophenotypes is controversial, certain traits such as impulsivity and aggression are commonly cited risk factors.
One such genetic basis for one of these at-risk endophenotypes has been suggested in 2007 to be the gene coding for the serotonin receptor 5-HT, known to be relevant in aggressive behaviors. | 1 | Applied and Interdisciplinary Chemistry |
Diethyl dixanthogen disulfide is a component for froth flotations used, inter alia, for the separation of sulfide minerals like pyrrhotite. Diisopropyl dixanthogen disulfide is a reagent in the synthesis of sulfur heterocycles.
Dialkoxy dixanthogen disulfides undergo desulfurization by cyanide to give bis(alkoxythiocarbonyl)sulfides:
Dixanthogens are also ectoparasiticides. | 0 | Theoretical and Fundamental Chemistry |
Sewage may contain high levels of the nutrients nitrogen and phosphorus. Typical values for nutrient loads per person and nutrient concentrations in raw sewage in developing countries have been published as follows: 8 g/person/d for total nitrogen (45 mg/L), 4.5 g/person/d for ammonia-N (25 mg/L) and 1.0 g/person/d for total phosphorus (7 mg/L). The typical ranges for these values are: 6-10 g/person/d for total nitrogen (35–60 mg/L), 3.5-6 g/person/d for ammonia-N (20–35 mg/L) and 0.7-2.5 g/person/d for total phosphorus (4–15 mg/L).
Excessive release to the environment can lead to nutrient pollution, which can manifest itself in eutrophication. This process can lead to algal blooms, a rapid growth, and later decay, in the population of algae. In addition to causing deoxygenation, some algal species produce toxins that contaminate drinking water supplies.
Ammonia nitrogen, in the form of free ammonia (NH) is toxic to fish. Ammonia nitrogen, when converted to nitrite and further to nitrate in a water body, in the process of nitrification, is associated with the consumption of dissolved oxygen. Nitrite and nitrate may also have public health significance if concentrations are high in drinking water, because of a disease called metahemoglobinemia.
Phosphorus removal is important as phosphorus is a limiting nutrient for algae growth in many fresh water systems. Therefore, an excess of phosphorus can lead to eutrophication. It is also particularly important for water reuse systems where high phosphorus concentrations may lead to fouling of downstream equipment such as reverse osmosis.
A range of treatment processes are available to remove nitrogen and phosphorus. Biological nutrient removal (BNR) is regarded by some as a type of secondary treatment process, and by others as a tertiary (or advanced) treatment process. | 1 | Applied and Interdisciplinary Chemistry |
Ultraviolet radiation (UVR) is part of the electromagnetic spectrum, just beyond visible light. Ultraviolet wavelengths are 100 to 400 nanometres (nm, billionths of a metre) and are divided into three bands: A, B and C. UVA wavelengths are the longest, 315 to 400 nm; UVB are 280 to 315 nm, and UVC wavelengths are the shortest, 100 to 280 nm.
About 95% of the UVR that reaches the earth from the sun is UVA and 5% UVB; no appreciable UVC reaches the earth. While tanning systems before the 1970s produced some UVC, modern tanning devices produce no UVC, a small amount of UVB and mostly UVA. Classified by the WHO as a group 1 carcinogen, UVR has "complex and mixed effects on human health". While it causes skin cancer and other damage, including wrinkles, it also triggers the synthesis of vitamin D and endorphins in the skin. | 0 | Theoretical and Fundamental Chemistry |
β-Catenin has been shown to interact with:
* APC,
* AXIN1,
* Androgen receptor,
* CBY1,
* CDH1,
* CDH2,
* CDH3,
* CDK5R1,
* CHUK,
* CTNND1,
* CTNNA1,
* EGFR,
* Emerin
* ESR1
* FHL2,
* GSK3B,
* HER2/neu,
* HNF4A,
* IKK2,
* LEF1 including transgenically,
* MAGI1,
* MUC1,
* NR5A1,
* PCAF,
* PHF17,
* Plakoglobin,
* PTPN14,
* PTPRF,
* PTPRK (PTPkappa),
*PTPRT (PTPrho),
*PTPRU (PCP-2),
* PSEN1,
* PTK7
* RuvB-like 1,
* SMAD7,
* SMARCA4
* SLC9A3R1,
* USP9X, and
* VE-cadherin.
* XIRP1 | 1 | Applied and Interdisciplinary Chemistry |
Throughout recorded history, attempts at producing a state of general anesthesia can be traced back to the writings of ancient Sumerians, Babylonians, Assyrians, Egyptians, Indians, and Chinese. Despite significant advances in anatomy and surgical technique during the Renaissance, surgery remained a last-resort treatment largely due to the pain associated with it. However, scientific discoveries in the late 18th and early 19th centuries paved the way for the development of modern anesthetic techniques.
In the late 19th century, two major advances enabled the transition to modern surgery: the development and application of antiseptic techniques as a result of the germ theory of disease, which reduced morbidity and mortality rates, and the advances in pharmacology and physiology that led to the development of general anesthesia and pain control. In the 20th century, general anesthesia's safety and efficacy were further improved with the routine use of tracheal intubation and advanced airway management techniques, monitoring, and new anesthetic agents with improved characteristics. Standardized training programs for anesthesiologists and nurse anesthetists emerged during this period.
Moreover, the application of economic and business administration principles to healthcare in the late 20th and early 21st centuries led to the introduction of management practices, such as transfer pricing, to improve the efficiency of anesthetists. | 1 | Applied and Interdisciplinary Chemistry |
Solubilization is distinct from dissolution because the resulting fluid is a colloidal dispersion involving an association colloid. This suspension is distinct from a true solution, and the amount of the solubilizate in the micellar system can be different (often higher) than the regular solubility of the solubilizate in the solvent.
In non-chemical literature and in everyday language, the term "solubilization" is sometimes used in a broader meaning as "to bring to a solution or (non-sedimenting) suspension" by any means, e.g., leaching by a reaction with an acid. | 0 | Theoretical and Fundamental Chemistry |
The Gaia theorem states that the Earth's atmospheric composition is kept at a dynamically steady state by the presence of life. The atmospheric composition provides the conditions that contemporary life has adapted to. All the atmospheric gases other than noble gases present in the atmosphere are either made by organisms or processed by them.
The stability of the atmosphere in Earth is not a consequence of chemical equilibrium. Oxygen is a reactive compound, and should eventually combine with gases and minerals of the Earth's atmosphere and crust. Oxygen only began to persist in the atmosphere in small quantities about 50 million years before the start of the Great Oxygenation Event. Since the start of the Cambrian period, atmospheric oxygen concentrations have fluctuated between 15% and 35% of atmospheric volume. Traces of methane (at an amount of 100,000 tonnes produced per year) should not exist, as methane is combustible in an oxygen atmosphere.
Dry air in the atmosphere of Earth contains roughly (by volume) 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases including methane. Lovelock originally speculated that concentrations of oxygen above about 25% would increase the frequency of wildfires and conflagration of forests. This mechanism, however, would not raise oxygen levels if they became too low. If plants can be shown to robustly over-produce O then perhaps only the high oxygen forest fires regulator is necessary. Recent work on the findings of fire-caused charcoal in Carboniferous and Cretaceous coal measures, in geologic periods when O did exceed 25%, has supported Lovelock's contention. | 0 | Theoretical and Fundamental Chemistry |
FACSS presents several awards to both students and professionals. These awards honor scientists who have made significant contributions to the field of Analytical Chemistry.
*FACSS Student Award and Tomas A. Hirshfeld Award [https://web.archive.org/web/20130901023114/http://www.scixconference.org/awards/facss-2012-student-award-and-tomas-a-hirschfeld-award ]
*SAS Student Poster Awards and FACSS Student Poster Awards [http://www.scixconference.org/awards/sas-student-poster-awards-and-facss-poster-awards ]
*FACSS Distinguished Service Award [http://www.scixconference.org/awards/facss-distinguished-service-award ]
*FACSS Innovation Award [http://www.scixconference.org/awards/facss-innovation-awards-paper ]
*Charles Mann Award for Applied Raman Spectroscopy [http://www.scixconference.org/awards/charles-mann-award ]
*Anachem Award [http://www.scixconference.org/awards/anachem-award ]
*Lester W. Strock Award [http://www.scixconference.org/awards/lester-w-strock-award ]
*Applied Spectroscopy William F. Meggers Award [http://www.scixconference.org/awards/applied-spectroscopy-william-f-meggers-award ]
*Ellis R. Lippincott Award [http://www.scixconference.org/awards/ellis-r-lippincott-award ]
* William G. Fateley Student Award
*Coblentz Society Craver Award [http://www.scixconference.org/awards/coblentz-society-craver-award ]
*ACS Div of Analytical Chem Arthur F. Findeis Award for Achievements by a Young Analytical Scientist [http://www.scixconference.org/awards/acs-division-of-analytical-chemistry-award ]
The FACSS Innovation Award was started in 2011 at the Reno meeting. [http://www.spectroscopynow.com/coi/cda/home.cda;jsessionid=D0EEB34B346A80BAF002DDCA366D8255?chId=6] [http://www.spectroscopyeurope.com/] | 0 | Theoretical and Fundamental Chemistry |
Although the energy formula of Rydberg series is a result of hydrogen-like atom structure, Rydberg states are also present in molecules. Wave functions of high Rydberg states are very diffuse and span diameters that approach infinity. As a result, any isolated neutral molecule behaves like a hydrogen-like atom at the Rydberg limit. For molecules with multiple stable monovalent cations, multiple Rydberg series may exist. Because of the complexity of molecular spectra, low-lying Rydberg states of molecules are often mixed with valence states with similar energy and are thus not pure Rydberg states. | 0 | Theoretical and Fundamental Chemistry |
The photochlorination of benzene proceeds also via a radical chain reaction:
In some applications, the reaction is carried out at 15 to 20 °C. At a conversion of 12 to 15% the reaction is stopped and the reaction mixture is worked up. | 0 | Theoretical and Fundamental Chemistry |
An event-specific detection searches for the presence of a DNA sequence unique to a certain GMO, usually the junction between the transgene and the organism's original DNA. This approach is ideal to precisely identify a GMO, yet highly similar GMOs will pass completely unnoticed. Event-specific detection is PCR-based. | 1 | Applied and Interdisciplinary Chemistry |
Compressors pump gas for a wide variety of applications each of which has its own flow resistance which the compressor has to meet to keep the gas flowing. A map shows the pumping characteristics for the complete range of flows and pressure requirements for its application. The map may be produced by driving the compressor with an electric motor with the flow resistance selected artificially using a variable area throttle valve. The compressor may also be mapped if it is part of a gas generator with a valve at the turbine exit. Campbell shows a General Electric J79 compressor mapped in this way. | 0 | Theoretical and Fundamental Chemistry |
In one dimension, a differential form
is exact if and only if has an antiderivative (but not necessarily one in terms of elementary functions). If has an antiderivative and let be an antiderivative of so , then obviously satisfies the condition for exactness. If does not have an antiderivative, then we cannot write with for a differentiable function so is inexact. | 0 | Theoretical and Fundamental Chemistry |
Ovarian hyperstimulation is the stimulation to induce development of multiple follicles of the ovaries. It should start with response prediction by e.g. age, antral follicle count and level of anti-Müllerian hormone. The resulting prediction of e.g. poor or hyper-response to ovarian hyperstimulation determines the protocol and dosage for ovarian hyperstimulation.
Ovarian hyperstimulation also includes suppression of spontaneous ovulation, for which two main methods are available: Using a (usually longer) GnRH agonist protocol or a (usually shorter) GnRH antagonist protocol. In a standard long GnRH agonist protocol the day when hyperstimulation treatment is started and the expected day of later oocyte retrieval can be chosen to conform to personal choice, while in a GnRH antagonist protocol it must be adapted to the spontaneous onset of the previous menstruation. On the other hand, the GnRH antagonist protocol has a lower risk of ovarian hyperstimulation syndrome (OHSS), which is a life-threatening complication.
For the ovarian hyperstimulation in itself, injectable gonadotropins (usually FSH analogues) are generally used under close monitoring. Such monitoring frequently checks the estradiol level and, by means of gynecologic ultrasonography, follicular growth. Typically approximately 10 days of injections will be necessary.
When stimulating ovulation after suppressing endogenous secretion, it is necessary to supply exogenous gonadotropines. The most common one is the human menopausal gonadotropin (hMG), which is obtained by donation of menopausal women. Other pharmacological preparations are FSH+LH or coripholitropine alpha. | 1 | Applied and Interdisciplinary Chemistry |
Fish are exposed to large oxygen fluctuations in their aquatic environment since the inherent properties of water can result in marked spatial and temporal differences in the concentration of oxygen (see oxygenation and underwater). Fish respond to hypoxia with varied behavioral, physiological, and cellular responses to maintain homeostasis and organism function in an oxygen-depleted environment. The biggest challenge fish face when exposed to low oxygen conditions is maintaining metabolic energy balance, as 95% of the oxygen consumed by fish is used for ATP production releasing the chemical energy of nutrients through the mitochondrial electron transport chain. Therefore, hypoxia survival requires a coordinated response to secure more oxygen from the depleted environment and counteract the metabolic consequences of decreased ATP production at the mitochondria. | 0 | Theoretical and Fundamental Chemistry |
Cyclohexane is considered a benchmark in determining ring strain in cycloalkanes and it is commonly accepted that there is little to no strain energy. In comparison, smaller cycloalkanes are much higher in energy due to increased strain. Cyclopropane is analogous to a triangle and thus has bond angles of 60°, much lower than the preferred 109.5° of an sp hybridized carbon. Furthermore, the hydrogens in cyclopropane are eclipsed. Cyclobutane experiences similar strain, with bond angles of approximately 88° (it isn't completely planar) and eclipsed hydrogens. The strain energy of cyclopropane and cyclobutane are 27.5 and 26.3 kcal mol, respectively. Cyclopentane experiences much less strain, mainly due to torsional strain from eclipsed hydrogens: its preferred conformations interconvert by a process called pseudorotation.
Ring strain can be considerably higher in bicyclic systems. For example, bicyclobutane, CH, is noted for being one of the most strained compounds that is isolatable on a large scale; its strain energy is estimated at 63.9 kcal mol (267 kJ mol). | 0 | Theoretical and Fundamental Chemistry |
Contamination of the lake environment by chromium started in the 1950s, and has increased dramatically until at least 2005, reaching 20 times natural background levels. It originates in industrial activities that involve leather tanning in the shoe factory of Calzado Cobán. The chromium does not seem to accumulate along the food chain, as it is not found in fishes and crayfishes. However, it accumulates massively in water hyacinth roots and, from there, is transferred to lake sediments through shedding of roots to the lake floor. Most of the water hyacinth biomass is actually extracted from the lake to fight eutrophication and turned into horticultural fertilizer. | 1 | Applied and Interdisciplinary Chemistry |
This section lists only historical data. For recent data, see Abundance of elements in Earth's crust.
Technical definition of "clarke", "Earth's crust" and "lithosphere" differ among authors, and the actual numbers vary accordingly, sometimes by several times. Even the same author presents multiple versions, with various estimation parameters or knowledge refinements. Yet they are often quoted without source, rendering the data unverifiable.
Clarke & Washington presented estimations of the average composition of outer part of Earth with four variants:
# 10-mile crust, hydrosphere and atmosphere.
# 20-mile crust, hydrosphere and atmosphere.
# 10-mile crust, only igneous rocks and sedimentary rocks. (i.e. exclude hydrosphere and atmosphere)
# 10-mile crust, only igneous rocks. (i.e. exclude hydrosphere and atmosphere)
"The earth's crust" in Clarke and Washington works can mean two different things: (a) The whole outer part of Earth, ie. lithosphere, hydrosphere and atmosphere; (b) Only the lithosphere, which in their works just meant "the rocky crust of the earth". "Crust" here means (b).
* Following tables do not cover all elements. Some elements not on the table may have larger abundance. Some minor elements are listed here to aid identifying the origin of unsourced documents.
* Some entries contain data for the disputed element 43 masurium.
* Precision (number of digits) may be adjusted to improve legibility. | 0 | Theoretical and Fundamental Chemistry |
The encapsulins are a family of bacterial proteins that serve as the main structural components of encapsulin nanocompartments. There are several different encapsulin proteins, including EncA, which forms the shell, and EncB, EncC, and EncD, which form the core.
Encapsulins are also used in synthetic biology. They are hard to discover due to their similarity to phage proteins. | 1 | Applied and Interdisciplinary Chemistry |
The acentric factor is a conceptual number introduced by Kenneth Pitzer in 1955, proven to be useful in the description of fluids. It has become a standard for the phase characterization of single & pure components, along with other state description parameters such as molecular weight, critical temperature, critical pressure, and critical volume (or critical compressibility). The acentric factor is also said to be a measure of the non-sphericity (centricity) of molecules.
Pitzer defined from the relationship
where
is the reduced saturation vapor pressure and
is the reduced temperature.
For a series of fluids, as the acentric factor increases the vapor curve is "pulled" down, resulting in higher boiling points. For many monatomic fluids,
is close to 0.1, which leads to . In many cases, lies above the boiling temperature of liquids at atmosphere pressure.
Values of can be determined for any fluid from accurate experimental vapor pressure data. The definition of gives values which are close to zero for the noble gases argon, krypton, and xenon. is also very close to zero for molecules which are nearly spherical. Values of correspond to vapor pressures above the critical pressure, and are non-physical.
The acentric factor can be predicted analytically from some equations of state. For example, it can be easily shown from the above definition that a van der Waals fluid has an acentric factor of about −0.302024, which if applied to a real system would indicate a small, ultra-spherical molecule. | 0 | Theoretical and Fundamental Chemistry |
Traditional urban drainage systems are limited by various factors including volume capacity, damage or blockage from debris and contamination of drinking water. Many of these issues are addressed by SuDS systems by bypassing traditional drainage systems altogether and returning rainwater to natural water sources or streams as soon as possible. Increasing urbanisation has caused problems with increased flash flooding after sudden rain. As areas of vegetation are replaced by concrete, asphalt, or roofed structures, leading to impervious surfaces, the area loses its ability to absorb rainwater. This rain is instead directed into surface water drainage systems, often overloading them and causing floods.
The goal of all sustainable drainage systems is to use rainfall to recharge the water sources of a given site. These water sources are often underlying the water table, nearby streams, lakes, or other similar freshwater sources. For example, if a site is above an unconsolidated aquifer, then SuDS will aim to direct all rain that falls on the surface layer into the underground aquifer as quickly as possible. To accomplish this, SuDS use various forms of permeable layers to ensure the water is not captured or redirected to another location. Often these layers include soil and vegetation, though they can also be artificial materials.
The paradigm of SuDS solutions should be that of a system that is easy to manage, requiring little or no energy input (except from environmental sources such as sunlight, etc.), resilient to use, and being environmentally as well as aesthetically attractive. Examples of this type of system are basins (shallow landscape depressions that are dry most of the time when it is not raining), rain gardens (shallow landscape depressions with shrub or herbaceous planting), swales (shallow normally-dry, wide-based ditches), filter drains (gravel filled trench drain), bioretention basins (shallow depressions with gravel and/or sand filtration layers beneath the growing medium), reed beds and other wetland habitats that collect, store, and filter dirty water along with providing a habitat for wildlife.
A common misconception of SuDS is that they reduce flooding on the development site. In fact the SuDS is designed to reduce the impact that the surface water drainage system of one site has on other sites. For instance, sewer flooding is a problem in many places. Paving or building over land can result in flash flooding. This happens when flows entering a sewer exceed its capacity and it overflows. The SuDS system aims to minimise or eliminate discharges from the site, thus reducing the impact, the idea being that if all development sites incorporated SuDS then urban sewer flooding would be less of a problem. Unlike traditional urban stormwater drainage systems, SuDS can also help to protect and enhance ground water quality. | 1 | Applied and Interdisciplinary Chemistry |
The general mathematical concept embodied in a Wigner–Seitz cell is more commonly called a Voronoi cell, and the partition of the plane into these cells for a given set of point sites is known as a Voronoi diagram.
The cell may be chosen by first picking a lattice point. After a point is chosen, lines are drawn to all nearby lattice points. At the midpoint of each line, another line is drawn normal to each of the first set of lines. The smallest area enclosed in this way is called the Wigner–Seitz primitive cell.
For a 3-dimensional lattice, the steps are analogous, but in step 2 instead of drawing perpendicular lines, perpendicular planes are drawn at the midpoint of the lines between the lattice points.
As in the case of all primitive cells, all area or space within the lattice can be filled by Wigner–Seitz cells and there will be no gaps.
Nearby lattice points are continually examined until the area or volume enclosed is the correct area or volume for a primitive cell. Alternatively, if the basis vectors of the lattice are reduced using lattice reduction only a set number of lattice points need to be used. In two-dimensions only the lattice points that make up the 4 unit cells that share a vertex with the origin need to be used. In three-dimensions only the lattice points that make up the 8 unit cells that share a vertex with the origin need to be used. | 0 | Theoretical and Fundamental Chemistry |
Enantiomers, also known as optical isomers, are two stereoisomers that are related to each other by a reflection: they are mirror images of each other that are non-superposable. Human hands are a macroscopic analog of this. Every stereogenic center in one has the opposite configuration in the other. Two compounds that are enantiomers of each other have the same physical properties, except for the direction in which they rotate polarized light and how they interact with different optical isomers of other compounds. As a result, different enantiomers of a compound may have substantially different biological effects. Pure enantiomers also exhibit the phenomenon of optical activity and can be separated only with the use of a chiral agent. In nature, only one enantiomer of most chiral biological compounds, such as amino acids (except glycine, which is achiral), is present. An optically active compound shows two forms: -(+) form and -(−) form. | 0 | Theoretical and Fundamental Chemistry |
The Orr–Sommerfeld equation, in fluid dynamics, is an eigenvalue equation describing the linear two-dimensional modes of disturbance to a viscous parallel flow. The solution to the Navier–Stokes equations for a parallel, laminar flow can become unstable if certain conditions on the flow are satisfied, and the Orr–Sommerfeld equation determines precisely what the conditions for hydrodynamic stability are.
The equation is named after William McFadden Orr and Arnold Sommerfeld, who derived it at the beginning of the 20th century. | 1 | Applied and Interdisciplinary Chemistry |
Palmitoylcarnitine has demonstrated potential as a diagnostic marker in newborns for the medical condition of primary carnitine deficiency.
Levels of palmitoylcarnitine (palcar) demonstrated significant correlation with dihydrotestosterone (DHT) and its effects in prostate cancer models, suggesting a similar role between the two molecules. | 1 | Applied and Interdisciplinary Chemistry |
Insects most often use sugars or polyols as cryoprotectants. One species that uses cryoprotectant is Polistes exclamans (a wasp). In this species, the different levels of cryoprotectant can be used to distinguish between morphologies. | 1 | Applied and Interdisciplinary Chemistry |
At least three plausible mechanisms for the Elbs reaction have been suggested. The first mechanism, suggested by Fieser, begins with a heat-induced cyclisation of the benzophenone, followed by a [[Sigmatropic reaction#%5B1,3%5D-shifts|[1,3]-hydride shift]] to give the compound . A dehydration reaction then affords the polyaromatic.
Alternatively, in the second mechanism, due to Cook, the methylated aromatic compound instead first undergoes a tautomerization followed by an electrocyclic reaction to give the same intermediate, which then similarly undergoes a [1,3]-hydride shift and dehydration.
A third mechanism has also been proposed, involving pyrolytic radical generation. | 0 | Theoretical and Fundamental Chemistry |
* Recherches sur les composés octyliques (1870).
* Application du sulfure de manganèse comme conleur plastique (1890). | 0 | Theoretical and Fundamental Chemistry |
Zhong Zhong and Hua Hua were produced by scientists from the Institute of Neuroscience of the Chinese Academy of Sciences in Shanghai, led by Qiang Sun and Mu-ming Poo. They extracted nuclei from the fibroblasts of an aborted fetal monkey (a crab-eating macaque or Macaca fascicularis) and inserted them into egg cells (ova) that had had their own nuclei removed. The team used two enzymes to erase the epigenetic memory of the transferred nuclei of being somatic cells. This crucial reprogramming step allowed the researchers to overcome the main obstacle that had precluded the successful cloning of primates until now. They then placed 21 of these ova into surrogate mother monkeys, resulting in six pregnancies, two of which produced living animals. The monkeys were named Zhong Zhong and Hua Hua, a reference to Zhonghua (, a Chinese name for China). Although the success rate was still low, the methods could be improved to increase survival rate in the future. By comparison, the Scotland-based team that created Dolly the sheep in 1996 required 277 attempts and produced only one lamb.
The scientists also attempted to clone macaques using nuclei from adult donors, which is much more difficult. They implanted 42 surrogates, resulting in 22 pregnancies, but there were still only two infant macaques, and they died soon after birth. | 1 | Applied and Interdisciplinary Chemistry |
Another problem with plotting this (or any) type of count data is [http://en.wiktionary.org/wiki/overplotting overplotting] which is solved in the RA plot by jittering the points out away from each other but no so far as to merge with other coordinates. The result of this feature is a patchwork-like appearance to the plot that fades away as the A increases. | 1 | Applied and Interdisciplinary Chemistry |
Many common substances exhibit non-Newtonian flows. These include:
* Soap solutions, cosmetics, and toothpaste
* Food such as butter, cheese, jam, mayonnaise, soup, taffy, and yogurt
* Natural substances such as magma, lava, gums, honey, and extracts such as vanilla extract
* Biological fluids such as blood, saliva, semen, mucus, and synovial fluid
* Slurries such as cement slurry and paper pulp, emulsions such as mayonnaise, and some kinds of dispersions | 1 | Applied and Interdisciplinary Chemistry |
Gold mining began in Gedebey in 2009. In 2016, Azer Gold CJSC began gold mining in the Chovdar deposit. In 2017, 6,390.8 kg of gold was mined (which exceeded the 2016 production by 3.4 times. Gold production in January–May 2018 amounted to 2,081.7 kg, which exceeds last years data by 19.5%. In the first quarter of 2018, the companys exports amounted to $30 million. In 2017, 59,617 ounces of gold produces by Anglo Asian Mining PLC (the main gold producer in Azerbaijan) from Gadir Ugur and Gosha deposits. | 1 | Applied and Interdisciplinary Chemistry |
In recent years many industrial efforts have focused on tuning the color of lights using polyfluorenes. It was found that by doping green or red emitting materials into polyfluorenes one could tune the color emitted by the polymers. Since polyfluorene homopolymers emit higher energy blue light, they can transfer energy via Förster resonance energy transfer (FRET) to lower energy emitters. In addition to doping, color of polyfluorenes can be tuned by copolymerizing the fluorene monomers with other low band gap monomers. Researchers at the Dow Chemical Company synthesized several fluorene-based copolymers by alternating copolymerization using 5,5-dibromo-2,2-bithiophene which showed yellow emission and 4,7-dibromo-2,1,3-benzothiadiazole, which showed green emission. Other copolymerizations are also suitable; researchers at IBM performed random copolymerization of fluorene with 3,9(10)-dibromoperylene,4,4-dibromo-R-cyanostilbene, and 1,4-bis(2-(4-bromophenyl)-1-cyanovinyl)-2-(2-ethylhexyl)-5-methoxybenzene. Only a small amount of the co-monomer, approximately 5%, was needed to tune the emission of the polyfluorene from blue to yellow. This example further illustrates that by introducing monomers that have a lower band gap than the fluorene monomer, one can tune the color that is emitted by the polymer.
Substitution at the nine position with various moieties has also been examined as a means to control the color emitted by polyfluorene. In the past researchers have tried putting alkyl substituents on the ninth position, however it has been found that by putting bulkier groups, such as alkoxyphenyl groups, the polymers had enhanced blue emission stability and superior polymer light-emitting diode performance (compared to polymers which have alkyl substituents at the ninth position). | 0 | Theoretical and Fundamental Chemistry |
In catenane nomenclature, a number in square brackets precedes the word "catenane" in order to indicate how many rings are involved. Discrete catenanes up to a [7]catenane have been synthesised. | 0 | Theoretical and Fundamental Chemistry |
* Nigeria: Assistant Police Commissioner stated that pepper sprays are illegal for civilians to possess.
* South Africa: Pepper sprays are legal to own by civilians for self defense. | 1 | Applied and Interdisciplinary Chemistry |
The asymmetric hydrogenation of aromatic (especially heteroaromatic), substrates is a very active field of ongoing research. Catalysts in this field must contend with a number of complicating factors, including the tendency of highly stable aromatic compounds to resist hydrogenation, the potential coordinating (and therefore catalyst-poisoning) abilities of both substrate and product, and the great diversity in substitution patterns that may be present on any one aromatic ring. Of these substrates the most consistent success has been seen with nitrogen-containing heterocycles, where the aromatic ring is often activated either by protonation or by further functionalization of the nitrogen (generally with an electron-withdrawing protecting group). Such strategies are less applicable to oxygen- and sulfur-containing heterocycles, since they are both less basic and less nucleophilic; this additional difficulty may help to explain why few effective methods exist for their asymmetric hydrogenation. | 0 | Theoretical and Fundamental Chemistry |
Glycosyl iodides were first introduced for use in glycosylation reactions in 1901 by Koenigs and Knorr although were often considered too reactive for synthetic use. Recently several research groups have shown these donors to have unique reactive properties and can differ from other glycosyl chlorides or bromides with respect to reaction time, efficiency, and stereochemistry. Glycosyl iodides may be made under a variety of conditions, one method of note is the reaction of a 1-O-acetylpyranoside with TMSI.
Iodide donors may typically be activated under basic conditions to give β-glycosides with good selectivity. The use of tetraalkylammonium iodide salts such as tetrabutylammonium iodide (TBAI) allows for in-situ anomerization of the α-glycosyl halide to the β-glycosyl halide and provides the α-glycoside in good selectivity. | 0 | Theoretical and Fundamental Chemistry |
In cardiovascular physiology, the diagram is often applied to the left ventricle, and it can be mapped to specific events of the cardiac cycle. PV loop studies are widely used in basic research and preclinical testing, to characterize the intact heart's performance under various situations (effect of drugs, disease, characterization of mouse strains)
The sequence of events occurring in every heart cycle is as follows. The left figure shows a PV loop from a real experiment; letters refer to points.
* A is the end-diastolic point; this is the point where contraction begins. Pressure starts to increase, becomes rapidly higher than the atrial pressure, and the mitral valve closes. Since pressure is also lower than the aortic pressure, the aortic valve is closed as well.
* Segment AB is the contraction phase. Since both the mitral and aortic valves are closed, volume is constant. For this reason, this phase is called isovolumic contraction.
* At point B, pressure becomes higher than the aortic pressure and the aortic valve opens, initiating ejection.
* BC is the ejection phase, volume decreases. At the end of this phase, pressure lowers again and falls below aortic pressure. The aortic valve closes.
* Point C is the end-systolic point.
* Segment CD is the isovolumic relaxation. During this phase, pressure continues to fall. The mitral valve and aortic valve are both closed again so volume is constant.
* At point D pressure falls below the atrial pressure and the mitral valve opens, initiating ventricular filling.
* DA is the diastolic filling period. Blood flows from the left atrium to the left ventricle. Atrial contraction completes ventricular filling.
As it can be seen, the PV loop forms a roughly rectangular shape and each loop is formed in an anti-clockwise direction.
Very useful information can be derived by examination and analysis of individual loops or series of loops, for example:
* the horizontal distance between the top-left corner and the bottom-right corner of each loop is the stroke volume
* the line joining the top-left corner of several loops is the contractile or inotropic state.
See external links for a much more precise representation. | 0 | Theoretical and Fundamental Chemistry |
According to a laboratory procedure hydroxylamine-O-sulfonic acid can be prepared by treating hydroxylamine sulfate with fuming sulfuric acid (oleum). The industrial process is similar.
:(NHOH)SO + 2SO → 2HNOSOH + HSO
The sulfonation of hydroxylamine can also be effected with chlorosulfonic acid by a method first published in 1925 and refined for Organic Syntheses.
The hydroxylamine-O-sulfonic acid, which should be stored at 0 °C to prevent decomposition, can be checked by iodometric titration. | 0 | Theoretical and Fundamental Chemistry |
A constant magnetic force is applied to unzip the DNA hairpin, and reducing the force allows the hairpin to rezip. Prior to performing the downstream applications several unzipping and rezipping cycles are performed. While the magnetic force required to unzip and rezip may vary depending on the DNA sequence and hairpin length, their absolute values are not critical as long as they are consistent within a sequencing run. | 1 | Applied and Interdisciplinary Chemistry |
Cancer is a complex, heterogeneous disease that can be hereditary or the result of environmental stimuli. Minigenes are used to help oncologists understand the roles pre-mRNA splicing plays in different cancer types. Of particular interest are cancer specific genetic mutations that disrupt normal splicing events, including those affecting spliceosome components and RNA-binding proteins such as heterogeneous nuclear ribonucleoparticules (hnRNP), serine/arginine-rich (SR) proteins and small ribonucleoproteins (snRNP). Proteins encoded by aberrantly spliced pre-mRNAs are functionally different and contribute to the characteristic anomalies exhibited by cancer cells, including their ability to proliferate, invade and undergo angiogenesis, and metastasis. Minigenes help researchers identify genetic mutations in cancer that result in splicing errors and determine the downstream effects those splicing errors have on gene expression. Using knowledge obtained from studies employing minigenes, oncologists have proposed tests designed to detect products of abnormal gene expression for diagnostic purposes. Additionally, the prospect of using minigenes as a cancer immunotherapy is being explored. | 1 | Applied and Interdisciplinary Chemistry |
Flanges in the rest of the world are manufactured according to the ISO standards for materials, pressure ratings, etc. to which local standards including DIN, BS, and others, have been aligned. | 1 | Applied and Interdisciplinary Chemistry |
In polymers the glass transition temperature, T, is often expressed as the temperature at which the Gibbs free energy is such that the activation energy for the cooperative movement of 50 or so elements of the polymer is exceeded . This allows molecular chains to slide past each other when a force is applied. From this definition, we can see that the introduction of relatively stiff chemical groups (such as benzene rings) will interfere with the flowing process and hence increase T.
The stiffness of thermoplastics decreases due to this effect (see figure.) When the glass temperature has been reached, the stiffness stays the same for a while, i.e., at or near E, until the temperature exceeds T, and the material melts. This region is called the rubber plateau.
In ironing, a fabric is heated through this transition so that the polymer chains become mobile. The weight of the iron then imposes a preferred orientation. T can be significantly decreased by addition of plasticizers into the polymer matrix. Smaller molecules of plasticizer embed themselves between the polymer chains, increasing the spacing and free volume, and allowing them to move past one another even at lower temperatures. Addition of plasticizer can effectively take control over polymer chain dynamics and dominate the amounts of the associated free volume so that the increased mobility of polymer ends is not apparent. The addition of nonreactive side groups to a polymer can also make the chains stand off from one another, reducing T. If a plastic with some desirable properties has a T that is too high, it can sometimes be combined with another in a copolymer or composite material with a T below the temperature of intended use. Note that some plastics are used at high temperatures, e.g., in automobile engines, and others at low temperatures.
In viscoelastic materials, the presence of liquid-like behavior depends on the properties of and so varies with rate of applied load, i.e., how quickly a force is applied. The silicone toy Silly Putty behaves quite differently depending on the time rate of applying a force: pull slowly and it flows, acting as a heavily viscous liquid; hit it with a hammer and it shatters, acting as a glass.
On cooling, rubber undergoes a liquid-glass transition, which has also been called a rubber-glass transition. | 0 | Theoretical and Fundamental Chemistry |
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The P promoter allows for tight regulation and control of a target gene in vivo. As explained above, P is regulated by the addition and absence of arabinose. As tested, the promoter can be further repressed with reduced levels of cAMP through the addition of glucose. Plasmid vectors have been constructed and tested with a selectable marker (Cm in this case), origin of replication, araC and operons, multiple cloning site and P promoter. Studies show that vectors are highly expressed and can be used, in combination with chromosomal null alleles, to study loss of function of essential genes. | 1 | Applied and Interdisciplinary Chemistry |
The eggs are retrieved from the patient using a transvaginal technique called transvaginal oocyte retrieval, involving an ultrasound-guided needle piercing the vaginal wall to reach the ovaries. Through this needle follicles can be aspirated, and the follicular fluid is passed to an embryologist to identify ova. It is common to remove between ten and thirty eggs. The retrieval process, which lasts approximately 20 to 40 minutes, is performed under conscious sedation or general anesthesia to ensure patient comfort. Following optimal follicular development, the eggs are meticulously retrieved using transvaginal ultrasound guidance with the aid of a specialised ultrasound probe and a fine needle aspiration technique. The follicular fluid, containing the retrieved eggs, is expeditiously transferred to the embryology laboratory for subsequent processing. | 1 | Applied and Interdisciplinary Chemistry |
Boyles law states that at constant temperature' the volume of a given mass of a dry gas is inversely proportional to its pressure.
Most gases behave like ideal gases at moderate pressures and temperatures. The technology of the 17th century could not produce very high pressures or very low temperatures. Hence, the law was not likely to have deviations at the time of publication. As improvements in technology permitted higher pressures and lower temperatures, deviations from the ideal gas behavior became noticeable, and the relationship between pressure and volume can only be accurately described employing real gas theory. The deviation is expressed as the compressibility factor.
Boyle (and Mariotte) derived the law solely by experiment. The law can also be derived theoretically based on the presumed existence of atoms and molecules and assumptions about motion and perfectly elastic collisions (see kinetic theory of gases). These assumptions were met with enormous resistance in the positivist scientific community at the time, however, as they were seen as purely theoretical constructs for which there was not the slightest observational evidence.
Daniel Bernoulli (in 1737–1738) derived Boyles law by applying Newtons laws of motion at the molecular level. It remained ignored until around 1845, when John Waterston published a paper building the main precepts of kinetic theory; this was rejected by the Royal Society of England. Later works of James Prescott Joule, Rudolf Clausius and in particular Ludwig Boltzmann firmly established the kinetic theory of gases and brought attention to both the theories of Bernoulli and Waterston.
The debate between proponents of energetics and atomism led Boltzmann to write a book in 1898, which endured criticism until his suicide in 1906. Albert Einstein in 1905 showed how kinetic theory applies to the Brownian motion of a fluid-suspended particle, which was confirmed in 1908 by Jean Perrin. | 0 | Theoretical and Fundamental Chemistry |
The Joback method is an extension of the Lydersen method and uses very similar groups, formulas, and parameters for the three properties the Lydersen already supported (critical temperature, critical pressure, critical volume).
Joback extended the range of supported properties, created new parameters and modified slightly the formulas of the old Lydersen method. | 0 | Theoretical and Fundamental Chemistry |
Normal metabolism of nucleotide sugars is very important. Any malfunction in any contributing enzyme will lead to a certain disease for example:
#Inclusion body myopathy: is a congenital disease resulted from altered function of UDP-GlcNAc epimerase .
#Macular corneal dystrophy: is a congenital disease resulted from malfunction of GlcNAc-6-sulfotransferase.
#Congenital disorder in α-1,3 mannosyl transferase will result in a variety of clinical symptoms, e.g. hypotonia, psychomotor retardation, liver fibrosis and various feeding problems. | 0 | Theoretical and Fundamental Chemistry |
There are three main metals used as galvanic anodes: magnesium, aluminum and zinc. They are all available as blocks, rods, plates or extruded ribbon. Each material has advantages and disadvantages.
Magnesium has the most negative electropotential of the three (see galvanic series) and is more suitable for areas where the electrolyte (soil or water) resistivity is higher. This is usually on-shore pipelines and other buried structures, although it is also used on boats in fresh water and in water heaters. In some cases, the negative potential of magnesium can be a disadvantage: if the potential of the protected metal becomes too negative, reduction of water or solvated protons may evolve hydrogen atoms on the cathode surface, for instance according to
leading to hydrogen embrittlement or to disbonding of the coating. Where this is a concern, zinc anodes may be used. An aluminum-zinc-tin alloy called KA90 is commonly used in marine and water heater applications.
Zinc and aluminium are generally used in salt water, where the resistivity is generally lower and magnesium dissolves relatively quickly by reaction with water under hydrogen evolution (self-corrosion). Typical uses are for the hulls of ships and boats, offshore pipelines and production platforms, in salt-water-cooled marine engines, on small boat propellers and rudders, and for the internal surface of storage tanks.
Zinc is considered a reliable material, but is not suitable for use at higher temperatures, as it tends to passivate (the oxide layer formed shields from further oxidation); if this happens, current may cease to flow and the anode stops working. Zinc has a relatively low driving voltage, which means in higher-resistivity soils or water it may not be able to provide sufficient current. However, in some circumstances — where there is a risk of hydrogen embrittlement, for example — this lower voltage is advantageous, as overprotection is avoided.
Aluminium anodes have several advantages, such as a lighter weight, and much higher capacity than zinc. However, their electrochemical behavior is not considered as reliable as zinc, and greater care must be taken in how they are used. Aluminium anodes will passivate where chloride concentration is below 1,446 parts per million.
One disadvantage of aluminium is that if it strikes a rusty surface, a large thermite spark may be generated, so its use is restricted in tanks where there may be explosive atmospheres and there is a risk of the anode falling.
Since the operation of a galvanic anode relies on the difference in electropotential between the anode and the cathode, practically any metal can be used to protect some other, providing there is a sufficient difference in potential. For example, iron anodes can be used to protect copper. | 0 | Theoretical and Fundamental Chemistry |
The lifetime of excited states results in natural broadening, also known as lifetime broadening. The uncertainty principle relates the lifetime of an excited state (due to spontaneous radiative decay or the Auger process) with the uncertainty of its energy.
Some authors use the term "radiative broadening" to refer specifically to the part of natural broadening caused by the spontaneous radiative decay.
A short lifetime will have a large energy uncertainty and a broad emission. This broadening effect results in an unshifted Lorentzian profile. The natural broadening can be experimentally altered only to the extent that decay rates can be artificially suppressed or enhanced. | 0 | Theoretical and Fundamental Chemistry |
* Sleeves must be sized such as to adequately allow the passage of the intended penetrant(s) plus enough room to permit the practical installation and mounting of the penetrants as well as adequate room for firestops. A general practice is to size the sleeve two NPS (pipe sizes) up from the diameter of the penetrant. For example, a 4" pipe, with 1" of thermal insulation makes a 6" penetrant (1" pipe covering on each side of the pipe), plus two pipe sizes = an 8" sleeve, creating a 1" annulus.
* In case of insulated piping, the size of the insulation must be taken into account for the intended firestop certification listing. | 1 | Applied and Interdisciplinary Chemistry |
The insertion of carbon monoxide and alkenes into metal-carbon bonds is a widely exploited reaction with major industrial applications.
Such reactions are subject to the usual parameters that affect other reactions in coordination chemistry, but steric effects are especially important in determining the stereochemistry and regiochemistry of the reactions. The reverse reaction, the de-insertion of CO and alkenes, are of fundamental significance in many catalytic cycles as well.
Widely employed applications of migratory insertion of carbonyl groups are hydroformylation and the carbonylative production of acetic acid. The former converts alkenes, hydrogen, and carbon monoxide into aldehydes. The production of acetic acid by carbonylation proceeds via two similar industrial processes. More traditional is the rhodium-based Monsanto acetic acid process, but this process has been superseded by the iridium-based Cativa process. By 2002, worldwide annual production of acetic acid stood at 6 million tons, of which approximately 60% is produced by the Cativa process.
The Cativa process catalytic cycle, shown above, includes both insertion and de-insertion steps. The oxidative addition reaction of methyl iodide with (1) involves the formal insertion of the iridium(I) centre into the carbon-iodine bond, whereas step (3) to (4) is an example of migratory insertion of carbon monoxide into the iridium-carbon bond. The active catalyst species is regenerated by the reductive elimination of acetyl iodide from (4), a de-insertion reaction. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, aldol reactions are acid- or base-catalyzed reactions of aldehydes or ketones.
Aldol addition or aldolization refers to the addition of an enolate or enolation as a nucleophile to a carbonyl moiety as an electrophile. This produces a β-hydroxyaldehyde or β-hydroxyketone. In an aldol condensation, water is subsequently eliminated and an α,β-unsaturated carbonyl is formed. The aldol cleavage or Retro-aldol reaction is the reverse reaction into the starting compounds.
The name aldehyde -alcohol reaction derives from the reaction product in the case of a reaction among aldehydes, a β-hydroxy aldehyde.
Aldol reactions are important reactions for carbon-carbon bond formation and a fundamental reaction principle in organic chemistry. | 0 | Theoretical and Fundamental Chemistry |
Humans can affect the production of humic substances via a variety of ways: by making use of natural processes by composting lignin or adding biochar (see soil rehabilitation), or by industrial synthesis of artificial humic substances from organic feedstocks directly. These artificial substances may be similarly divided into artificial humic acid (A-HA) and artificial fulvic acid (A-FA).
Lignosulfonates, a by-product from the sulfite pulping of wood, are valorized in the industrial fabrication of concrete where they serve as water reducer, or concrete superplasticizer, to decrease the water-cement ratio (w/c) of fresh concrete while preserving its workability. The w/c ratio of concrete is one of the main parameter controlling the mechanical strength of hardened concrete and its durability. The same wood pulping process can also be applied to obtain humus-like substances by hydrolysis and oxidation. A kind of artificial "lignohumate" can be directly produced from wood in this way.
Agricultural litter can be turned into an artificial humic substance by a hydrothermal reaction. The resulting mixture can increase the content of dissolved organic matter (DOM) and total organic carbon (TOC) in soil.
Lignite (brown coal) may also be oxidized to produce humic substances, reversing the natural process of coal formation under anoxic and reducing conditions. This form of "mineral-derived fulvic acid" is widely used in China. This process also occurs in nature, producing leonardite. | 0 | Theoretical and Fundamental Chemistry |
ATP hydrolysis is the catabolic reaction process by which chemical energy that has been stored in the high-energy phosphoanhydride bonds in adenosine triphosphate (ATP) is released after splitting these bonds, for example in muscles, by producing work in the form of mechanical energy. The product is adenosine diphosphate (ADP) and an inorganic phosphate (P). ADP can be further hydrolyzed to give energy, adenosine monophosphate (AMP), and another inorganic phosphate (P). ATP hydrolysis is the final link between the energy derived from food or sunlight and useful work such as muscle contraction, the establishment of electrochemical gradients across membranes, and biosynthetic processes necessary to maintain life.
Anhydridic bonds are often labelled as "high-energy bonds". P-O bonds are in fact fairly strong (~30 kJ/mol stronger than C-N bonds) and themselves not particularly easy to break. As noted below, energy is released by the hydrolysis of ATP. However, when the P-O bonds are broken, input of energy is required. It is the formation of new bonds and lower-energy inorganic phosphate with a release of a larger amount of energy that lowers the total energy of the system and makes it more stable.
Hydrolysis of the phosphate groups in ATP is especially exergonic, because the resulting inorganic phosphate molecular ion is greatly stabilized by multiple resonance structures, making the products (ADP and P) lower in energy than the reactant (ATP). The high negative charge density associated with the three adjacent phosphate units of ATP also destabilizes the molecule, making it higher in energy. Hydrolysis relieves some of these electrostatic repulsions, liberating useful energy in the process by causing conformational changes in enzyme structure.
In humans, approximately 60 percent of the energy released from the hydrolysis of ATP produces metabolic heat rather than fuel the actual reactions taking place.
Due to the acid-base properties of ATP, ADP, and inorganic phosphate, the hydrolysis of ATP has the effect of lowering the pH of the reaction medium. Under certain conditions, high levels of ATP hydrolysis can contribute to lactic acidosis. | 1 | Applied and Interdisciplinary Chemistry |
Chayen earned her first degree in pharmacy at the Hebrew University of Jerusalem. During her undergraduate studies, she visited the Kennedy Institute of Rheumatology to learn histochemistry. She subsequently pursued MSc and PhD research at the Kennedy Institute. In 1983, Chayen submitted her thesis on stimulus-response coupling in smooth muscle cells and received a PhD from Brunel University London.
Chayen began her first postdoctoral fellowship at Imperial College London, where she studied the biophysics of muscle proteins. When her grant was not renewed, she joined the lab of David Mervyn Blow to develop novel protein crystallization techniques. There, she began her influential work of utilizing phase diagrams to optimize conditions for crystal growth.
Currently, Chayen is a professor of Biomedical Sciences and head of the Crystallization Group in Computational and Systems Medicine at Imperial College London. | 1 | Applied and Interdisciplinary Chemistry |
The synapse contains at least two clusters of synaptic vesicles, the readily releasable pool and the reserve pool. The readily releasable pool is located within the active zone and connected directly to the presynaptic membrane while the reserve pool is clustered by cytoskeletal and is not directly connected to the active zone. | 1 | Applied and Interdisciplinary Chemistry |
The Clausius–Clapeyron relation leads to another equation also attributed to Kelvin, as the Kelvin equation. It explains why, because of surface tension, the vapor pressure for small droplets of liquid in suspension is greater than standard vapor pressure of that same liquid when the interface is flat. That is to say that when a liquid is forming small droplets, the equilibrium concentration of its vapor in its surroundings is greater. This arises because the pressure inside the droplet is greater than outside.
* is the standard vapor pressure for that liquid at that temperature and pressure.
* is the molar volume.
* is the gas constant
* is the Kelvin radius, the radius of the droplets.
The effect explains supersaturation of vapors. In the absence of nucleation sites, tiny droplets must form before they can evolve into larger droplets. This requires a vapor pressure many times the vapor pressure at the phase transition point.
This equation is also used in catalyst chemistry to assess mesoporosity for solids.
The effect can be viewed in terms of the average number of molecular neighbors of surface molecules (see diagram).
The table shows some calculated values of this effect for water at different drop sizes:
The effect becomes clear for very small drop sizes, as a drop of 1 nm radius has about 100 molecules inside, which is a quantity small enough to require a quantum mechanics analysis. | 0 | Theoretical and Fundamental Chemistry |
Aside from its synthetic versatility (see above), sulfolene is used as an additive in electrochemical fluorination. It can increase the yield of perfluorooctanesulfonyl fluoride by about 70%. It is "highly soluble in anhydrous HF and increases the conductivity of the electrolyte solution". In this application, it undergoes a ring opening and is fluorinated to form perfluorobutanesulfonyl fluoride. | 0 | Theoretical and Fundamental Chemistry |
A protein phosphatase is a phosphatase enzyme that removes a phosphate group from the phosphorylated amino acid residue of its substrate protein. Protein phosphorylation is one of the most common forms of reversible protein posttranslational modification (PTM), with up to 30% of all proteins being phosphorylated at any given time. Protein kinases (PKs) are the effectors of phosphorylation and catalyse the transfer of a γ-phosphate from ATP to specific amino acids on proteins. Several hundred PKs exist in mammals and are classified into distinct super-families. Proteins are phosphorylated predominantly on Ser, Thr and Tyr residues, which account for 79.3, 16.9 and 3.8% respectively of the phosphoproteome, at least in mammals. In contrast, protein phosphatases (PPs) are the primary effectors of dephosphorylation and can be grouped into three main classes based on sequence, structure and catalytic function. The largest class of PPs is the phosphoprotein phosphatase (PPP) family comprising PP1, PP2A, PP2B, PP4, PP5, PP6 and PP7, and the protein phosphatase Mg- or Mn-dependent (PPM) family, composed primarily of PP2C. The protein Tyr phosphatase (PTP) super-family forms the second group, and the aspartate-based protein phosphatases the third. The protein pseudophosphatases form part of the larger phosphatase family, and in most cases are thought to be catalytically inert, instead functioning as phosphate-binding proteins, integrators of signalling or subcellular traps. Examples of membrane-spanning protein phosphatases containing both active (phosphatase) and inactive (pseudophosphatase) domains linked in tandem are known, conceptually similar to the kinase and pseudokinase domain polypeptide structure of the JAK pseudokinases. A complete comparative analysis of human phosphatases and pseudophosphatases has been completed by Manning and colleagues, forming a companion piece to the ground-breaking analysis of the human kinome, which encodes the complete set of ~536 human protein kinases. | 1 | Applied and Interdisciplinary Chemistry |
Rasaratna Samuccaya ( Devanagari: रसरत्न समुच्चय) is an Indian Sanskrit treatise on alchemy. The text is dated between 13th to 16th century CE.
The text contains detailed descriptions of various complex metallurgical processes, as well as descriptions of how to set up and equip a laboratory and other topics concerning Indian alchemy. It is a work that synthesises the writings and opinions of several earlier authors and presents a coherent account of medieval Indian alchemy. | 1 | Applied and Interdisciplinary Chemistry |
Johann Moriaen (born Nuremberg c.1591-1668) was a German alchemist and early chemist, known as an associate of Samuel Hartlib. He was active in recruiting for Hartlib's network of intellectuals, the Hartlib Circle, and communicating with them. He was a convinced pansophist.
With no published works, his activities have been uncovered by recent scholarship. He operated from Amsterdam.
He matriculated at Heidelberg University in 1611, where he knew Georg Vechner, later an associate of Johann Amos Comenius. He then became a Calvinist minister. He moved to Cologne, where he perhaps met Theodore Haak who was there in 1626. He gave up the ministry and returned to his native Nuremberg in 1627, then full of refugees from the Thirty Years War.
He met Isaac Beeckman in Dordrecht in 1633. He at this time was involved in practical aspects of optics and Paracelsian chemistry and medicine. He moved permanently to the Netherlands five years later.
In 1657 he is recorded as the owner of a scarlet dye works in Hulkestein near Arnhem.
His Dutch connections included the Hebraist Adam Boreel, and businessman Louis de Geer, a supporter of Comenius. His correspondents included George Starkey. | 1 | Applied and Interdisciplinary Chemistry |
Potassium ion channels play a key role in maintaining the membrane's electric potential. These ion channels are present in many various biological systems. They frequently play a role in regulation of cellular level processes, many of these processes including muscle relaxation, hypertension, insulin secretion etc. Some examples of potassium ion channels within biological systems include K channels, BK channels, and ether-a-go-go potassium channels | 0 | Theoretical and Fundamental Chemistry |
Knowledge of its value in agriculture is also ancient, but agricultural use only became widely possible when the use of coal made it cheap in the coalfields in the late 13th century, and an account of agricultural use was given in 1523. The earliest descriptions of lime kilns differ little from those used for small-scale manufacture a century ago. Because land transportation of minerals like limestone and coal was difficult in the pre-industrial era, they were distributed by sea, and lime was most often manufactured at small coastal ports. Many preserved kilns are still to be seen on quaysides around the coasts of Britain. | 1 | Applied and Interdisciplinary Chemistry |
Under Marie Curies guidance at the Radium Institute, Perey learned how to isolate and purify radioactive elements, focusing on the chemical element actinium (discovered in Curies laboratory in 1899 by chemist André-Louis Debierne). Perey spent a decade sifting out actinium from all the other components of uranium ore, which Curie then used in her study of the decay of the element. Marie Curie died of aplastic anemia only five years after Perey began working with her, but Perey and Debierne continued their research on actinium and Perey was promoted to radiochemist. | 1 | Applied and Interdisciplinary Chemistry |
Most commonly the term is used for the piles of waste earth materials removed during an excavation process.
* In surface mining (commonly called strip mining) for coal or other underground deposits, earth materials removed to expose the targeted deposit are piled up alongside the excavation site (commonly a strip mining pit) in spoil banks.
* A dredge in placer mining is used to dig up volumes of gravel and other earth materials, which are sent through sluices to remove gold or other minerals, and the remaining earth materials ("tailings") are deposited behind the dredge in spoil banks.
* In hydraulic mining, high-pressure jets of water dislodge earth materials, which are put through sluices to sort out gold or other minerals, and the residual earth materials are left in spoil banks.
* The excavation of ditches and canals results in spoil banks being left along the side of the canal or ditch.
Spoil banks can also refer to refuse heaps formed from removal of excess surface materials. For example, alongside livestock lots, spoil banks are formed of manure and other slurry periodically removed from the surface of the livestock lot areas. | 1 | Applied and Interdisciplinary Chemistry |
In the United States, the Clean Water Act requires all direct effluent discharges to surface waters to be regulated with permits under the National Pollutant Discharge Elimination System (NPDES). Indirect dischargers–facilities which send their wastewater to municipal sewage treatment plants–may be subject to pretreatment requirements. NPDES permits require discharging facilities to limit or treat effluent to the levels that result from using the most effective treatment technologies possible at a practical cost to mitigate the effects of discharges on the receiving waters. EPA has published technology-based regulations, called "effluent guidelines", for 59 industrial categories. The agency reviews the standards annually, conducts research on various categories, and makes revisions as appropriate. Noncompliance with these standards and all other conditions in the permits is punishable by law. Each year, effluent guidelines regulations prevent billions of pounds of contaminants from being released into bodies of water.
EPA regulations require effluent limitations to be expressed as mass-based limits (rather than concentration-based limits) in the permits, so that discharging facilities will not use dilution as a substitute for treatment. In cases where setting mass-based limits are infeasible, the permit authority must set conditions in the permit that prohibit dilution. | 1 | Applied and Interdisciplinary Chemistry |
Compared to both healthy volunteers and subjects with hypothyroidism and hyperthyroidism, SPINA-GD is reduced in subacute thyroiditis. In this condition, it has a higher specificity, positive and negative likelihood ratio than serum concentrations of thyrotropin, free T4 or free T3. These measures of diagnostic utility are also high in nodular goitre, where SPINA-GD is elevated. Among subjects with subclinical thyrotoxicosis, calculated deiodinase activity is significantly lower in exogenous thyrotoxicosis (resulting from therapy with levothyroxine) than in true hyperthyroidism (ensuing from toxic adenoma, toxic multinodular goitre or Graves' disease). SPINA-GD may therefore be an effective biomarker for the differential diagnosis of thyrotoxicosis.
Compared to healthy subjects, SPINA-GD is significantly reduced in euthyroid sick syndrome. | 1 | Applied and Interdisciplinary Chemistry |
Carbon tetraiodide is slightly reactive towards water, giving iodoform and I. It is soluble in nonpolar organic solvents. It decomposes thermally and photochemically to , CI. Its synthesis entails AlCl-catalyzed halide exchange, which is conducted at room temperature:
The product crystallizes from the reaction solution.
Carbon tetraiodide is used as an iodination reagent, often upon reaction with bases. Ketones are converted to 1,1-diiodoalkenes upon treatment with triphenylphosphine (PPh) and carbon tetraiodide. Alcohols are converted in and to iodide, by a mechanism similar to the Appel reaction. In an Appel reaction, carbon tetrachloride is used to generate alkyl chlorides from alcohols. | 0 | Theoretical and Fundamental Chemistry |
In 1940, Melhase was an undergraduate in the college of chemistry at the University of California, Berkeley. She was president of the Student Affiliates of the American Chemical Society and was considering doctoral studies and a career in chemistry. Honors students typically took on research projects at the time, and she sought advice from her close friend, nuclear chemist Gerhart Friedlander; Friedlander was then a graduate student under the supervision of Glenn T. Seaborg, and he suggested she approach him for a project. She spoke to Seaborg in his lab, and he proposed they work together to search for a Group 1 element among the fission products of uranium. Her laboratory was above those of Nobel Prize winners Willard Libby and Melvin Calvin.
In March 1941, Melhase worked with Art Wahl. He handed her 100 grams of a uranium compound (uranyl nitrate) that had been neutron-irradiated by a cyclotron. Using a Lauritzen quartz fiber electroscope, she discovered the Cs-137 several months later. Despite establishing herself as a promising young experimental scientist, nuclear research during World War II was treated with strict secrecy and it was not publicized. Significant research on the isotope followed, but their results were not made available until after the war.
Melhase received a bachelor's degree in nuclear chemistry and planned to apply for graduate studies at UC Berkeley. However, the head of the chemistry department, Gilbert N. Lewis, was refusing entry to women; the last woman the department admitted had gotten married shortly after her graduation and he considered her education a "waste". She worked for the Philadelphia Quartz Company in El Cerrito, California. She rejoined the Manhattan Project from 1944 to 1946. Without an advanced degree, she did not continue her career in science.
Though references to her work are scant, Seaborg shares credit of his discovery of Cs-137 with her. Writing in 1961, he stated:
He also wrote in 1990 that "it is appropriate to credit both G. T. Seaborg and M. Melhase for the birth of cesium 137." | 0 | Theoretical and Fundamental Chemistry |
Vancomycin is a branched tricyclic glycosylated nonribosomal peptide produced by the Actinomycetota species Amycolatopsis orientalis (formerly designated Nocardia orientalis).
Vancomycin exhibits atropisomerism—it has multiple chemically distinct rotamers owing to the rotational restriction of some of the bonds. The form present in the drug is the thermodynamically more stable conformer. | 0 | Theoretical and Fundamental Chemistry |
For a support material to be ideal, it must be hydrophilic, inert towards enzymes, biocompatible, microbial attack and compression resistant, and must be affordable. Support materials can be organic or inorganic, synthetic or natural (depending on the composition), since they are biomaterial types at the end. There is no universal type of a support material to be used for the immobilization of all enzymes. However, there are some commonly used supports such as silica-based carriers, acrylic resins, synthetic polymers, active membranes and exchange resins. One of the hardest processes before the immobilization process itself, is the selection of support material since it relies on the enzyme type, reaction of media, safety policy of hydrodynamic and reaction conditions. As different types of support give different physical and chemical characteristics and properties, which would effect enzyme function, such as: Hydrophilicity/hydrophobicity, surface chemistry, and pore size. | 0 | Theoretical and Fundamental Chemistry |
In thermodynamics, superheating (sometimes referred to as boiling retardation, or boiling delay) is the phenomenon in which a liquid is heated to a temperature higher than its boiling point, without boiling. This is a so-called metastable state or metastate, where boiling might occur at any time, induced by external or internal effects. Superheating is achieved by heating a homogeneous substance in a clean container, free of nucleation sites, while taking care not to disturb the liquid.
This may occur by microwaving water in a very smooth container. Disturbing the water may cause an unsafe eruption of hot water and result in burns. | 0 | Theoretical and Fundamental Chemistry |
PHBV find its application in controlled release of drugs, medical implants and repairs, specialty packaging, orthopedic devices and manufacturing bottles for consumer goods. It is also biodegradable which can be used as an alternative to non biodegradable plastics | 1 | Applied and Interdisciplinary Chemistry |
Cristina Nevado (born 1977) is a Spanish chemist who is a Professor of Organic Chemistry at the University of Zurich. Her research considers chemical synthesis and organometallic reactions. She received the 2021 Margaret Faul Women in Chemistry Award. | 0 | Theoretical and Fundamental Chemistry |
Huntingtons disease is characterized by cognitive impairments. There is increased expression of p75NTR in the hippocampus of Huntingtons disease patients (including mice models and humans). Over expression of p75NTR in mice causes cognitive impairments similar to Huntingtons disease. p75NTR is linked to reduced numbers of dendritic spines in the hippocampus, likely through p75NTR interactions with Transforming protein RhoA. Modulating p75NTR function could be a future direction in treating Huntingtons disease. | 1 | Applied and Interdisciplinary Chemistry |
*David R. Bundle, former postdoctoral fellow with Prof. Lemieux, currently professor of chemistry, the Raymond U. Lemieux Chair in Carbohydrate Chemistry, and a distinguished university professor at the University of Alberta, founder and former director of the Alberta Glycomics Centre (formerly known as Alberta Ingenuity Centre for Carbohydrate Science). http://www.chem.ualberta.ca/~glyco/who/index.htm
*Ole Hindsgaul, former PhD student with Prof. Lemieux, currently a distinguished professor at the Carlsberg Laboratory, Copenhagen, Denmark, and an adjunct professor, Department of Chemistry, University of Alberta, Canada. http://www.crc.dk/carbochem/oledraft2.htm | 0 | Theoretical and Fundamental Chemistry |
Similar to hydrogen bonds, a C–H···O interaction involves interactions of dipoles and therefore has directionality. The directionality of a C–H···O interaction is usually defined by the angle α between the С, Н and О atoms, and the distance d between the O and C atoms. In a С–Н···О interaction, the angle α is in the range between 90 and 180°, and the distance d is usually smaller than 3.2 Å. Bond strength is less than 1 kcal/mol. In the case of aromatic C–H donors, C–H···O interactions are not linear due to influence of aromatic ring substituents near the interacting C-H group. If aromatic molecules involved in С–Н···О interaction belong to the group of polycyclic aromatic hydrocarbons, the strength of C–H···O interactions increases with the number of aromatic rings.
C–H···O interactions can be important in drug design, being present in structures of therapeutic proteins, and nucleic acids.
O-H···C and N-H···C type interactions could also play a significant role and were first analyzed in 1993. | 0 | Theoretical and Fundamental Chemistry |
is shock-sensitive. Purer samples are more shock-sensitive than those contaminated with elemental sulfur. | 0 | Theoretical and Fundamental Chemistry |
The Mattauch isobar rule, formulated by Josef Mattauch in 1934, states that if two adjacent elements on the periodic table have isotopes of the same mass number, one of these isotopes must be radioactive. Two nuclides that have the same mass number (isobars) can both be stable only if their atomic numbers differ by more than one. In fact, for currently observationally stable nuclides, the difference can only be 2 or 4, and in theory, two nuclides that have the same mass number cannot be both stable (at least to beta decay or double beta decay), but many such nuclides which are theoretically unstable to double beta decay have not been observed to decay, e.g. Xe. However, this rule cannot make predictions on the half-lives of these radioisotopes. | 0 | Theoretical and Fundamental Chemistry |
In 1937, Hans Adolf Krebs, who discovered the citric acid cycle bearing his name, confirmed the anaerobic dismutation of pyruvic acid into lactic acid, acetic acid and CO by certain bacteria according to the global reaction:
The dismutation of pyruvic acid in other small organic molecules (ethanol + CO, or lactate and acetate, depending on the environmental conditions) is also an important step in fermentation reactions. Fermentation reactions can also be considered as disproportionation or dismutation biochemical reactions. Indeed, the donor and acceptor of electrons in the redox reactions supplying the chemical energy in these complex biochemical systems are the same organic molecules simultaneously acting as reductant or oxidant.
Another example of biochemical dismutation reaction is the disproportionation of acetaldehyde into ethanol and acetic acid.
While in respiration electrons are transferred from substrate (electron donor) to an electron acceptor, in fermentation part of the substrate molecule itself accepts the electrons. Fermentation is therefore a type of disproportionation, and does not involve an overall change in oxidation state of the substrate. Most of the fermentative substrates are organic molecules. However, a rare type of fermentation may also involve the disproportionation of inorganic sulfur compounds in certain sulfate-reducing bacteria. | 0 | Theoretical and Fundamental Chemistry |
The total complement of genes in an organism or cell is known as its genome, which may be stored on one or more chromosomes. A chromosome consists of a single, very long DNA helix on which thousands of genes are encoded. The region of the chromosome at which a particular gene is located is called its locus. Each locus contains one allele of a gene; however, members of a population may have different alleles at the locus, each with a slightly different gene sequence.
The majority of eukaryotic genes are stored on a set of large, linear chromosomes. The chromosomes are packed within the nucleus in complex with storage proteins called histones to form a unit called a nucleosome. DNA packaged and condensed in this way is called chromatin. The manner in which DNA is stored on the histones, as well as chemical modifications of the histone itself, regulate whether a particular region of DNA is accessible for gene expression. In addition to genes, eukaryotic chromosomes contain sequences involved in ensuring that the DNA is copied without degradation of end regions and sorted into daughter cells during cell division: replication origins, telomeres and the centromere. Replication origins are the sequence regions where DNA replication is initiated to make two copies of the chromosome. Telomeres are long stretches of repetitive sequences that cap the ends of the linear chromosomes and prevent degradation of coding and regulatory regions during DNA replication. The length of the telomeres decreases each time the genome is replicated and has been implicated in the aging process. The centromere is required for binding spindle fibres to separate sister chromatids into daughter cells during cell division.
Prokaryotes (bacteria and archaea) typically store their genomes on a single large, circular chromosome. Similarly, some eukaryotic organelles contain a remnant circular chromosome with a small number of genes. Prokaryotes sometimes supplement their chromosome with additional small circles of DNA called plasmids, which usually encode only a few genes and are transferable between individuals. For example, the genes for antibiotic resistance are usually encoded on bacterial plasmids and can be passed between individual cells, even those of different species, via horizontal gene transfer.
Whereas the chromosomes of prokaryotes are relatively gene-dense, those of eukaryotes often contain regions of DNA that serve no obvious function. Simple single-celled eukaryotes have relatively small amounts of such DNA, whereas the genomes of complex multicellular organisms, including humans, contain an absolute majority of DNA without an identified function. This DNA has often been referred to as "junk DNA". However, more recent analyses suggest that, although protein-coding DNA makes up barely 2% of the human genome, about 80% of the bases in the genome may be expressed, so the term "junk DNA" may be a misnomer. | 1 | Applied and Interdisciplinary Chemistry |
# [http://www.uq.edu.au/gilbertgroup]
# Theory of unimolecular and recombination reactions. RG Gilbert, SC Smith. Oxford: Blackwell Scientific Publications (1990)
# "Theory of thermal unimolecular reactions in the fall-off range. II. Weak collision rate constants". RG Gilbert, K Luther, J Troe, Ber Bunsenges Phys Chem, 87, 169–77 (1982)
# Emulsion polymerization: a mechanistic approach. RG Gilbert. London: Academic Press (1995)
# "The entry of free radicals into latex particles in emulsion polymerization". IA Maxwell, BR Morrison, DH Napper, RG Gilbert, Macromolecules, 24, 1629–40 (1991)
# "First-principles calculation of particle formation in emulsion polymerization: pseudo-bulk systems". EM Coen, S Peach, BR Morrison, RG Gilbert. Polymer, 45, 3595–3608 (2004)
# "Molecular weight distributions in free-radical polymerizations. Understanding the effects of chain-length-dependent termination". PA Clay, RG Gilbert. Macromolecules, 28, 552–69 (1995)
# "Critically evaluated rate coefficients for free-radical polymerization. 1. Propagation rate coefficients for styrene". M Buback, RG Gilbert, RA Hutchinson, B Klumperman, F-D Kuchta, BG Manders, KF O’Driscoll, GT Russell, J Schweer. Macromol. Chem. Phys., 196, 3267–80 (1995)
# "A priori prediction of propagation rate coefficients in free radical polymerizations: propagation of ethylene". JPA Heuts, RG Gilbert, L Radom. Macromolecules, 28, 8771–81 (1995)
# "Mechanistic information from analysis of molecular weight distributions of starch". JV Castro, C Dumas, H Chiou, MA Fitzgerald, RG Gilbert, Biomacromolecules, 6, 2248–59 (2005) | 0 | Theoretical and Fundamental Chemistry |
High amount of aerobic glycolysis (also known as the Warburg effect) distinguishes cancer cells from normal cells. The conversion of glucose to lactate rather than metabolizing it in the mitochondria through oxidative phosphorylation, (which can also occur in hypoxic normal cells) persists in malignant tumor despite the presence of oxygen. This process normally inhibits glycolysis which is also known as Pasteur effect. One of the reasons it is observed is because of the malfunction of mitochondria. Although ATP production by glycolysis can be more rapid than by oxidative phosphorylation, it is far less efficient in terms of ATP generated per unit of glucose consumed. Rather than oxidizing glucose for ATP production, glucose in cancer cells tends to be used for anabolic processes, such as ribose production, protein glycosylation and serine synthesis. This shift therefore demands that tumor cells implement an abnormally high rate of glucose uptake to meet their increased needs.
As neoplastic cells accumulate in three-dimensional multicellular masses, local low nutrient and oxygen levels trigger the growth of new blood vessels into the neoplasm. The imperfect neovasculature in the tumor bed is poorly formed and is inefficient. It therefore, causes nutrient and hypoxic stress (or a state of hypoxia). In this regard, cancer cells and stromal cells can symbiotically recycle and maximize the use of nutrients. Hypoxic adaptation by cancer cells is essential for survival and progression of a tumor. In addition to cell-autonomous changes that drive a cancer cell to proliferate and contribute to tumorigenesis, it has also been observed that alterations in whole-organism metabolism such as obesity are associated with heightened risks for a variety of cancers. | 1 | Applied and Interdisciplinary Chemistry |
After the war, Birger Solberg resumed control, but the economics and equipment of the facility had become unfavorable. Feeling empathy for the former workers, he devised a new business plan based on collecting German plane wrecks and other debris in middle-Norway and re-melting them.
The facility was closed on December 20, 2002 and production moved to Mo i Rana. | 1 | Applied and Interdisciplinary Chemistry |
Molecules in distant astronomical regions can be identified based on their unique rotational transitions, of which the corresponding microwave frequencies are detectable by antennae on Earth. The presence of interstellar sulfur mononitride was first reported in 1975 by back to back letters published in the Astrophysical Journal.
Interstellar NS was first identified in the giant molecular cloud Sagittarius B2 (Sgr B2). Its presence was reported in two concurrent articles. Measurements conducted with the National Radia Astronomy Observatory telescope at Kitt Peak, Arizona, picked up millimeter-wavelength radiation in Sgr B2 attributed to c-state transitions of NS in the Π state from J=5/2 to J=3/2 at 115.16 GHz. This assignment was confirmed by measurements conducted at University of Texas Millimeter Wave Observatory on Mount Locke as well, demonstrating J=5/2 to J=3/2 c-state and d-state transitions at 115.16 GHz and 115.6 GHz, respectively. Hyperfine interactions arise from N magnetic and electric-quadrupole moments.
NS has been detected in regions responsible for forming massive stars, such as giant molecular clouds like Sg B2 and cold, dark clouds such as L134N and TMC-1. One survey found NS in 12 out of 14 GMC studied, additionally observing the J=7/2 to J=5/2 and J=3/2 to J=1/2 transitions at 161 and 69 GHz, respectively. The abundance of NS in these regions was approximated based on the ratio of observed to intrinsic hyperfine line strengths as well as modeling using a statistical equilibrium program, finding low abundance in all except the Orion molecular cloud.
NS was also observed in the coma of the comets Hyakutake and Hale-Bopp. It's believed that the observed abundance is higher than gas-phase, ion-molecule models due to an unidentified species X-NS photo-dissociating to release NS. | 0 | Theoretical and Fundamental Chemistry |
Once transferred to the nascent peptide chain, N-linked glycans, in general, undergo extensive processing reactions, whereby the three glucose residues are removed, as well as several mannose residues, depending on the N-linked glycan in question. The removal of the glucose residues is dependent on proper protein folding. These processing reactions occur in the Golgi apparatus. Modification reactions may involve the addition of a phosphate or acetyl group onto the sugars, or the addition of new sugars, such as neuraminic acid. Processing and modification of N-linked glycans within the Golgi does not follow a linear pathway. As a result, many different variations of N-linked glycan structure are possible, depending on enzyme activity in the Golgi. | 0 | Theoretical and Fundamental Chemistry |
Oftentimes, ELPs are not used in isolation, but are rather fused with other proteins to become functionally active. The structure of these other proteins will have a certain effect on transition temperature. It is important to be able to predict the transition temperature that these fusion proteins will have relative to the free ELPs, as this temperature will determine the fused protein's applicability and phase transition. A theoretical model is available that relates the change in T of the fused protein to the varying ratios of each individual amino acid found in the fused protein. The model involves calculating a surface index (SI) associated with each amino acid and then extrapolating, based on the ratio of each amino acid present in the fused protein, the total change in the T associated with the fusion protein, ΔT:
SI=(ASA/ ASA)(T)
where ASA refers to the area of the entire fused protein that is available to the solvent that is being used, ASA refers to the area of the guest residue on the ELP that is available to the solvent, and T is the transition temperature that is unique to the amino acid. Summing up the contribution of each potential guest residue (XAA) will yield an SI index that is directly proportional to ΔT It was found that the amino acids that are charged under a physiological pH of 7.4 have the greatest impact on the overall SI of a fused protein. This is due to the fact that they are more accessible to water-containing solvents, thereby increasing the ASA and also have high T values. Hence, knowledge of the transition temperature of a fused protein is highly dependent on the presence of these charged residues. | 0 | Theoretical and Fundamental Chemistry |
The concept of emission and transmission tomography was introduced by David E. Kuhl, Luke Chapman and Roy Edwards in the late 1950s. Their work later led to the design and construction of several tomographic instruments at the University of Pennsylvania. In 1975 tomographic imaging techniques were further developed by Michel Ter-Pogossian, Michael E. Phelps, Edward J. Hoffman and others at Washington University School of Medicine.
Work by Gordon Brownell, Charles Burnham and their associates at the Massachusetts General Hospital beginning in the 1950s contributed significantly to the development of PET technology and included the first demonstration of annihilation radiation for medical imaging. Their innovations, including the use of light pipes and volumetric analysis, have been important in the deployment of PET imaging. In 1961, James Robertson and his associates at Brookhaven National Laboratory built the first single-plane PET scan, nicknamed the "head-shrinker."
One of the factors most responsible for the acceptance of positron imaging was the development of radiopharmaceuticals. In particular, the development of labeled 2-fluorodeoxy-D-glucose (FDG-firstly synthethized and described by two Czech scientists from Charles University in Prague in 1968) by the Brookhaven group under the direction of Al Wolf and Joanna Fowler was a major factor in expanding the scope of PET imaging. The compound was first administered to two normal human volunteers by Abass Alavi in August 1976 at the University of Pennsylvania. Brain images obtained with an ordinary (non-PET) nuclear scanner demonstrated the concentration of FDG in that organ. Later, the substance was used in dedicated positron tomographic scanners, to yield the modern procedure.
The logical extension of positron instrumentation was a design using two 2-dimensional arrays. PC-I was the first instrument using this concept and was designed in 1968, completed in 1969 and reported in 1972. The first applications of PC-I in tomographic mode as distinguished from the computed tomographic mode were reported in 1970. It soon became clear to many of those involved in PET development that a circular or cylindrical array of detectors was the logical next step in PET instrumentation. Although many investigators took this approach, James Robertson and Zang-Hee Cho were the first to propose a ring system that has become the prototype of the current shape of PET.
The PET-CT scanner, attributed to David Townsend and Ronald Nutt, was named by Time as the medical invention of the year in 2000. | 1 | Applied and Interdisciplinary Chemistry |
The general continuity equation, describing the conservation of mass, takes the form:where is the fluid density and is the divergence operator. Under the assumption of incompressible flow, with a constant control volume , this equation has the simple expression . However, it is possible that the cross-sectional area can change with both time and space in the channel. If we start from the integral form of the continuity equation:it is possible to decompose the volume integral into a cross-section and length, which leads to the form:Under the assumption of incompressible, 1D flow, this equation becomes:By noting that and defining the volumetric flow rate , the equation is reduced to:Finally, this leads to the continuity equation for incompressible, 1D open-channel flow: | 1 | Applied and Interdisciplinary Chemistry |
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