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*Tacke, Ida, and D. Holde. 1921. Über Anhydride höherer aliphatischer Fettesäuren. Berlin, TeH., Diss., 1921. (On higher aliphatic fatty acid anhydrides )
*Noddack, Walter, Otto Berg, and Ida Tacke. 1925. Zwei neue Elemente der Mangangruppe, Chemischer Teil. [Berlin: In Kommission bei W. de Gruyter]. (Two new elements of the manganese chemical group)
*Noddack, Ida, and Walter Noddack. 1927. Das Rhenium. Ergebnisse Der Exakten Naturwissenschaften. 6. Bd. (1927) (Rhenium)
*Noddack, Ida, and Walter Noddack. 1933. Das Rhenium. Leipzig: Leopold Foss. (Rhenium)
*Noddack, Ida (1934). Über das Element 93. Angewandte Chemie. 47(37): 653-655. (On Element 93).
*Noddack, Walter, and Ida Noddack. 1937. Aufgaben und Ziele der Geochemie. Freiburger wissenschaftliche Gesellschaft, Hft. 26. Freiburg im Breisgau: H. Speyer, H.F. Schulz. (Tasks and goals of Geochemistry)
*Noddack, Ida, and Walter Noddack. 1939. Die Häufigkeiten der Schwermetalle in Meerestieren. Arkiv för zoologi, Bd. 32, A, Nr. 4. Stockholm: Almqvist & Wiksell. (The frequency of heavy metals in marine animals)
*Noddack, Ida. 1942. Entwicklung und Aufbau der chemischen Wissenschaft. Freiburg i.Br: Schulz. (The development and structure of chemical science) | 1 | Applied and Interdisciplinary Chemistry |
The term "autapse" was first coined in 1972 by Van der Loos and Glaser, who observed them in Golgi preparations of the rabbit occipital cortex while originally conducting a quantitative analysis of neocortex circuitry. Also in the 1970s, autapses have been described in dog and rat cerebral cortex, monkey neostriatum, and cat spinal cord.
In 2000, they were first modeled as supporting persistence in recurrent neural networks. In 2004, they were modeled as demonstrating oscillatory behavior, which was absent in the same model neuron without autapse. More specifically, the neuron oscillated between high firing rates and firing suppression, reflecting the spike bursting behavior typically found in cerebral neurons. In 2009, autapses were, for the first time, associated with sustained activation. This proposed a possible function for excitatory autapses within a neural circuit. In 2014, electrical autapses were shown to generate stable target and spiral waves in a neural model network. This indicated that they played a significant role in stimulating and regulating the collective behavior of neurons in the network. In 2016, a model of resonance was offered.
Autapses have been used to simulate "same cell" conditions to help researchers make quantitative comparisons, such as studying how N-methyl-D-aspartate receptor (NMDAR) antagonists affect synaptic versus extrasynaptic NMDARs. | 1 | Applied and Interdisciplinary Chemistry |
The adsorption of particles to bubbles is essential to separating the minerals from the slurry, but the minerals must be purified from the additives used in separation, such as the collectors, frothers, and modifiers. The product of the cleaning, or desorption process, is known as the cleaner concentrate.
The detachment of a particle and bubble requires adsorption bond cleavage driven by shear forces. Depending on the flotation cell type, shear forces are applied by a variety of mechanical systems. Among the most common are impellers and mixers. Some systems combine the functionalities of these components by placing them at key locations where they can take part in multiple froth flotation mechanisms. Cleaning cells also take advantage of gravitational forces to improve separation efficiency.
Desorption itself is a chemical phenomenon where compounds are just physically attached to each other without having any chemical bond. | 1 | Applied and Interdisciplinary Chemistry |
Synthesis of xenon trioxide is by aqueous hydrolysis of :
: + 3 → + 6 HF
The resulting xenon trioxide crystals are a strong oxidising agent and can oxidise most substances that are at all oxidisable. However, it is slow-acting and this reduces its usefulness.
Above 25 °C, xenon trioxide is very prone to violent explosion:
:2 XeO → 2 Xe + 3 O (ΔH = −403 kJ/mol)
When it dissolves in water, an acidic solution of xenic acid is formed:
:XeO(aq) + HO → HXeO H +
This solution is stable at room temperature and lacks the explosive properties of xenon trioxide. It oxidises carboxylic acids quantitatively to carbon dioxide and water.
Alternatively, it dissolves in alkaline solutions to form xenates. The anion is the predominant species in xenate solutions. These are not stable and begin to disproportionate into perxenates (+8 oxidation state) and xenon and oxygen gas. Solid perxenates containing have been isolated by reacting with an aqueous solution of hydroxides. Xenon trioxide reacts with inorganic fluorides such as KF, RbF, or CsF to form stable solids of the form . | 0 | Theoretical and Fundamental Chemistry |
A cascade reaction, also known as a domino reaction or tandem reaction, is a chemical process that comprises at least two consecutive reactions such that each subsequent reaction occurs only in virtue of the chemical functionality formed in the previous step. In cascade reactions, isolation of intermediates is not required, as each reaction composing the sequence occurs spontaneously. In the strictest definition of the term, the reaction conditions do not change among the consecutive steps of a cascade and no new reagents are added after the initial step. By contrast, one-pot procedures similarly allow at least two reactions to be carried out consecutively without any isolation of intermediates, but do not preclude the addition of new reagents or the change of conditions after the first reaction. Thus, any cascade reaction is also a one-pot procedure, while the reverse does not hold true. Although often composed solely of intramolecular transformations, cascade reactions can also occur intermolecularly, in which case they also fall under the category of multicomponent reactions.
The main benefits of cascade sequences include high atom economy and reduction of waste generated by the several chemical processes, as well as of the time and work required to carry them out. The efficiency and utility of a cascade reaction can be measured in terms of the number of bonds formed in the overall sequence, the degree of increase in the structural complexity via the process, and its applicability to broader classes of substrates.
The earliest example of a cascade reaction is arguably the synthesis of tropinone reported in 1917 by Robinson. Since then, the use of cascade reactions has proliferated in the area of total synthesis. Similarly, the development of cascade-driven organic methodology has also grown tremendously. This increased interest in cascade sequences is reflected by the numerous relevant review articles published in the past couple of decades. A growing area of focus is the development of asymmetric catalysis of cascade processes by employing chiral organocatalysts or chiral transition-metal complexes.
Classification
of cascade reactions is sometimes difficult due to the diverse nature of the many
steps in the transformation. K. C. Nicolaou labels the cascades as
nucleophilic/electrophilic, radical, pericyclic or transition-metal-catalyzed,
based on the mechanism of the steps involved. In the cases in which two or more
classes of reaction are included in a cascade, the distinction becomes rather
arbitrary and the process is labeled according to what can be arguably
considered the “major theme”. In order to highlight the remarkable
synthetic utility of cascade reactions, the majority of the examples below come
from the total syntheses of complex molecules. | 0 | Theoretical and Fundamental Chemistry |
Gun development and design in Europe reached its "classic" form in the 1480s – longer, lighter, more efficient, and more accurate compared to its predecessors only three decades prior. The design persisted, and cannons of the 1480s show little difference and surprising similarity with cannons three centuries later in the 1750s. This 300-year period during which the classic cannon dominated gives it its moniker.
The early classical European guns are exemplified by two cannons from 1488 now preserved in a plaza in Neuchâtel, Switzerland. The Neuchâtel guns are 224 centimeters long, with a bore of 6.2 centimeters and the other is slightly longer, 252 centimeters, with the same bore size. They are differentiated from older firearms by an assortment of improvements. Their longer length-to-bore ratio imparts more energy into the shot, enabling the projectile to shoot further. Not only longer, they were also lighter as the barrel walls were made thinner to allow for faster dissipation of heat. They also no longer needed the help of a wooden plug to load since they offered a tighter fit between projectile and barrel, further increasing the accuracy of gunpowder warfare – and were deadlier due to developments such as gunpowder corning and iron shot. When these guns reached China in the 1510s, the Chinese were highly impressed by them, primarily for their longer and thinner barrels.
The two primary theories for the appearance of the classic gun involve the development of gunpowder corning and a new method for casting guns.
The corning hypothesis stipulates that the longer barrels came about as a reaction to the development of corned gunpowder. Not only did "corned" powder keep better, because of its reduced surface area, but gunners also found that it was more powerful and easier to load into guns. Prior to corning, gunpowder would also frequently demix into its constitutive components and was therefore unreliable. The faster gunpowder reaction was suitable for smaller guns, since large ones had a tendency to crack, and the more controlled reaction allowed large guns to have longer, thinner walls. However, the corning hypothesis has been argued against on two grounds: One, the powder makers were probably more worried about spoilage than the effect of corned gunpowder on guns; and two, corning as a practice had existed in China (for explosives) since the 1370s.
The second theory is that the key to developing the classic gun may have been a new method of gun casting, muzzle side up. Smith observes: "The surviving pieces of ordnance from earlier in the 15th century are big pieces with large bore sizes. They do not look like the long thin gun.… Essentially they are parallel-sided tubes with flat ends. The explanation is, probably, that they were cast muzzle down in the traditional bell-founding method whereas the long thin guns were cast muzzle up.… Perhaps this marks the real revolution in artillery. Once the technique of casting muzzle up with the attendant advantages, and it is not clear what those are at present, had been mastered by cannon founders, the way was open for the development of the classic form of artillery." However, Smith himself states that it is not clear what advantages this technique would have conferred, despite its widespread adoption. | 1 | Applied and Interdisciplinary Chemistry |
Membrane osmometry measurements are best used for 30,000 1,000,000 grams/mole. For above 1,000,000 grams/mole, the solute is too dilute to create a measurable osmotic pressure. For below 30,000 grams per mole, the solute permeates through the membrane and the measurements are inaccurate.
Another issue for membrane osmometer is the limited membrane types. The most common membrane used is cellulose acetate; however, cellulose acetate can only be used with toluene and water. While toluene and water are useful solvent for many compounds, not all polymers are miscible in toluene or water. Regenerated cellulose membranes can be used for many other solvents, but are hard to obtain. | 0 | Theoretical and Fundamental Chemistry |
The indenyl effect refers to an explanation for the enhanced rates of substitution exhibited by η-indenyl complexes vs the related η-cyclopentadienyl complexes.
Associative substitution occurs by the addition of a ligand to a metal complex followed by dissociation of an original ligand. Associative pathways are not typically seen in 18-electron complexes due to the requisite intermediates having more than 18 electrons associated with the metal atom. 18 electron indenyl complexes; however, have been shown to undergo substitution via associative pathways quite readily. This is attributed to the relative ease of η to η rearrangement due to stabilization by the arene. This stabilization is responsible for substitution rate enhancements of about 10 for the substitution of indenyl complexes compared to the corresponding cyclopentadienyl complex.
Kinetic data support two proposed mechanisms for associative ligand substitution. The first mechanism, proposed by Hart-Davis and Mawby, is a concerted attack by the nucleophile and η to η transition followed by loss of a ligand and a η to η transition.
In a mechanism proposed by Basolo, η and η isomers exist in rapid chemical equilibrium. The rate-limiting step occurs with the attack of the nucleophile on a η isomer. The nature of the substituents of the allyl group can strongly affect the kinetics and regiochemistry of the nucleophilic attack. | 0 | Theoretical and Fundamental Chemistry |
A Luggin capillary (also Luggin probe, Luggin tip, or Luggin-Haber capillary) is a small tube that is used in electrochemistry. The capillary defines a clear sensing point for the reference electrode near the working electrode. This is in contrast to the poorly defined, large reference electrode. | 0 | Theoretical and Fundamental Chemistry |
In medicine, a biomarker is a measurable indicator of the severity or presence of some disease state. It may be defined as a "cellular, biochemical or molecular alteration in cells, tissues or fluids that can be measured and evaluated to indicate normal biological processes, pathogenic processes, or pharmacological responses to a therapeutic intervention." More generally a biomarker is anything that can be used as an indicator of a particular disease state or some other physiological state of an organism. According to the WHO, the indicator may be chemical, physical, or biological in nature - and the measurement may be functional, physiological, biochemical, cellular, or molecular.
A biomarker can be a substance that is introduced into an organism as a means to examine organ function or other aspects of health. For example, rubidium chloride is used in isotopic labeling to evaluate perfusion of heart muscle. It can also be a substance whose detection indicates a particular disease state, for example, the presence of an antibody may indicate an infection. More specifically, a biomarker indicates a change in expression or state of a protein that correlates with the risk or progression of a disease, or with the susceptibility of the disease to a given treatment. Biomarkers can be characteristic biological properties or molecules that can be detected and measured in parts of the body like the blood or tissue. They may indicate either normal or diseased processes in the body. Biomarkers can be specific cells, molecules, or genes, gene products, enzymes, or hormones. Complex organ functions or general characteristic changes in biological structures can also serve as biomarkers. Although the term biomarker is relatively new, biomarkers have been used in pre-clinical research and clinical diagnosis for a considerable time. For example, body temperature is a well-known biomarker for fever. Blood pressure is used to determine the risk of stroke. It is also widely known that cholesterol values are a biomarker and risk indicator for coronary and vascular disease, and that C-reactive protein (CRP) is a marker for inflammation.
Biomarkers are useful in a number of ways, including measuring the progress of disease, evaluating the most effective therapeutic regimes for a particular cancer type, and establishing long-term susceptibility to cancer or its recurrence. Biomarkers characterize disease progression starting from the earliest natural history of the disease. Biomarkers assess disease susceptibility and severity, which allows one to predict outcomes, determine interventions and evaluate therapeutic responses. From a forensics and epidemiologic perspective, biomarkers offer unique insight about the relationships between environmental risk factors. The parameter can be chemical, physical or biological. In molecular terms biomarker is "the subset of markers that might be discovered using genomics, proteomics technologies or imaging technologies. Biomarkers play major roles in medicinal biology. Biomarkers help in early diagnosis, disease prevention, drug target identification, drug response etc. Several biomarkers have been identified for many diseases such as serum LDL for cholesterol, blood pressure, and P53 gene and MMPs as tumor markers for cancer. | 1 | Applied and Interdisciplinary Chemistry |
Bjerknes writes:This principle is analogous to Archimedes' principle. Based on this principle the force acting on a particle of volume is . Where is the fluid velocity and is the fluid density.
Using conservation of momentum for incompressible non-viscous fluid one can find that to first order: , Concluding that . | 1 | Applied and Interdisciplinary Chemistry |
A tidal bore, often simply given as bore in context, is a tidal phenomenon in which the leading edge of the incoming tide forms a wave (or waves) of water that travels up a river or narrow bay, reversing the direction of the river or bay's current. It is a strong tide that pushes up the river, against the current. | 1 | Applied and Interdisciplinary Chemistry |
The concentration of CDOM can have a significant effect on biological activity in aquatic systems. CDOM diminishes light intensity as it penetrates water. Very high concentrations of CDOM can have a limiting effect on photosynthesis and inhibit the growth of phytoplankton, which form the basis of oceanic food chains and are a primary source of atmospheric oxygen. However, the influence of CDOM on algal photosynthesis can be complex in other aquatic systems like lakes where CDOM increases photosynthetic rates at low and moderate concentrations, but decreases photosynthetic rates at high concentrations. CDOM concentrations reflect hierarchical controls. Concentrations vary among lakes in close proximity due to differences in lake and watershed morphometry, and regionally because of difference in climate and dominant vegetation. CDOM also absorbs harmful UVA/B radiation, protecting organisms from DNA damage.
Absorption of UV radiation causes CDOM to "bleach", reducing its optical density and absorptive capacity. This bleaching (photodegradation) of CDOM produces low-molecular-weight organic compounds which may be utilized by microbes, release nutrients that may be used by phytoplankton as a nutrient source for growth, and generates reactive oxygen species, which may damage tissues and alter the bioavailability of limiting trace metals.
CDOM can be detected and measured from space using satellite remote sensing and often interferes with the use of satellite spectrometers to remotely estimate phytoplankton populations. As a pigment necessary for photosynthesis, chlorophyll is a key indicator of the phytoplankton abundance. However, CDOM and chlorophyll both absorb light in the same spectral range so it is often difficult to differentiate between the two.
Although variations in CDOM are primarily the result of natural processes including changes in the amount and frequency of precipitation, human activities such as logging, agriculture, effluent discharge, and wetland drainage can affect CDOM levels in fresh water and estuarine systems. | 0 | Theoretical and Fundamental Chemistry |
Various analytical methods approved by the United States Environmental Protection Agency (EPA) for measuring mercury in wastewater are in common use. EPA Methods 245.7 and 1631 are commonly used for measurement of industrial wastewater using CVAFS. | 0 | Theoretical and Fundamental Chemistry |
Carbon sequestration - when acting as a carbon sink - helps to mitigate climate change and thus reduce harmful effects of climate change. It helps to slow the atmospheric and marine accumulation of greenhouse gases, which are released by burning fossil fuels and industrial livestock production.
Carbon sequestration, when applied for climate change mitigation, can either build on enhancing naturally occurring carbon sequestration or use technology for carbon sequestration processes.
Within the carbon capture and storage approaches, carbon sequestration refers to the storage component. Artificial carbon storage technologies can be applied, such as gaseous storage in deep geological formations (including saline formations and exhausted gas fields), and solid storage by reaction of CO with metal oxides to produce stable carbonates.
For carbon to be sequestered artificially (i.e. not using the natural processes of the carbon cycle) it must first be captured, or it must be significantly delayed or prevented from being re-released into the atmosphere (by combustion, decay, etc.) from an existing carbon-rich material, by being incorporated into an enduring usage (such as in construction). Thereafter it can be passively stored or remain productively utilized over time in a variety of ways. For instance, upon harvesting, wood (as a carbon-rich material) can be incorporated into construction or a range of other durable products, thus sequestering its carbon over years or even centuries. | 0 | Theoretical and Fundamental Chemistry |
The Bioinorganic Chemistry Award has been awarded by the Dalton division of the Royal Society of Chemistry every two years since 2009. The winner receives £2000 and undertakes a lecture tour in the UK. The award was discontinued in 2020. | 0 | Theoretical and Fundamental Chemistry |
Air supply to a building is generally performed by an air handling unit. The process may include for filtering, heating, cooling, humidification, or dehumidification, all of which processes consume energy. Since the fresh air demand for the building occupants may be less than that is required for air conditioning purposes, it would be wasteful if 100% fresh air were used, with wholesome treated air rejected to the atmosphere in its place. Therefore, mixing is used to balance the needs between the occupants requirements for fresh air and the air conditioning process for the building.
Enhanced controls systems may monitor the return air quality or carbon dioxide concentration in order to automatically modulate the air mix for optimum energy efficiency whilst maintaining desired fresh air requirements. Such systems work very well in buildings where the occupancy rate can vary greatly throughout the day, or seasonally. Additionally, when outside air conditions are such, typically mid-season weather conditions, it may be that ambient temperatures are suitable for free cooling purposes. In such conditions the mixing damper will be set to close and the system use full fresh air for optimum energy efficiency. Where fresh air is not required, such as early morning pre-heat or pre-conditioning periods, the mixing damper can be automatically set to full recirculation, again for optimum energy efficiency. | 1 | Applied and Interdisciplinary Chemistry |
The purest copper is obtained by an electrolytic process, undertaken using a slab of impure copper as the anode and a thin sheet of pure copper as the cathode. The electrolyte is an acidic solution of copper sulphate. By passing electricity through the cell, copper is dissolved from the anode and deposited on the cathode. However impurities either remain in solution or collect as an insoluble sludge. This process only became possible following the invention of the dynamo; it was first used in South Wales in 1869. | 1 | Applied and Interdisciplinary Chemistry |
Iodine is an essential trace element in biological systems. It has the distinction of being the heaviest element commonly needed by living organisms as well as the second-heaviest known to be used by any form of life (only tungsten, a component of a few bacterial enzymes, has a higher atomic number and atomic weight). It is a component of biochemical pathways in organisms from all biological kingdoms, suggesting its fundamental significance throughout the evolutionary history of life.
Iodine is critical to the proper functioning of the vertebrate endocrine system, and plays smaller roles in numerous other organs, including those of the digestive and reproductive systems. An adequate intake of iodine-containing compounds is important at all stages of development, especially during the fetal and neonatal periods, and diets deficient in iodine can present serious consequences for growth and metabolism. | 1 | Applied and Interdisciplinary Chemistry |
* Manfred Schidlowski: [https://link.springer.com/chapter/10.1007%2F978-3-642-59381-9_24 Search for Morphological and Biogeochemical Vestiges of Fossil Life in Extraterrestrial Settings: Utility of Terrestrial Evidence]. In: Horneck G., Baumstark-Khan C. (eds) Astrobiology. Springer, Berlin, Heidelberg 2002, pages 373–386.
* Pitawala, A., Schidlowski, M., Dahanayake, K. et al.: [https://link.springer.com/article/10.1007%2Fs00126-002-0327-y Geochemical and petrological characteristics of Eppawala phosphate deposits, Sri Lanka]. In: Miner Deposita, Vol. 38, September 2002, pages 505–515.
* Manfred Schidlowski: [https://www.sciencedirect.com/science/article/abs/pii/S0301926800001285 Carbon isotopes as biogeochemical recorders of life over 3.8 Ga of Earth history: evolution of a concept]. In: Precambrian Research, Vol. 106, Issues 1–2, 1 February 2001, pages 117-134
* Yanan Shen, Manfred Schidlowski: [https://pubs.geoscienceworld.org/gsa/geology/article-abstract/28/7/623/191927/New-C-isotope-stratigraphy-from-southwest-China?redirectedFrom=fulltext New C isotope stratigraphy from southwest China: Implications for the placement of the Precambrian-Cambrian boundary on the Yangtze Platform and global correlations ]. In: Geology, Vol. 28, Issue 7, 1 July 2000, pages 623–626.
* B. Nagy, R. Weber, J.C. Guerrero, M. Schidlowski: [https://www.elsevier.com/books/developments-and-interactions-of-the-precambrian-atmosphere-lithosphere-and-biosphere/nagy/978-0-444-42240-8 Developments and Interactions of the Precambrian Atmosphere, Lithosphere and Biosphere]. Latest Edition, 1 April 2000.
* Manfred Schidlowski, Stjepko Golubic, Michael M. Kimberley, David M. McKirdy Sr.: [https://link.springer.com/book/10.1007/978-3-642-76884-2 Early Organic Evolution - Implications for Mineral and Energy Resources: A Farewell Address to IGCP Project 157]. Springer, Berlin, Heidelberg 1992. [https://link.springer.com/chapter/10.1007/978-3-642-76884-2_1#citeas PDF].
* Manfred Schidlowski: [https://www.nature.com/articles/333313a0 A 3,800-million-year isotopic record of life from carbon in sedimentary rocks]. In: Nature 333, 26 May 1988, pages 313–318.
* Manfred Schildlowski: [https://link.springer.com/chapter/10.1007%2F978-94-009-9085-2_14 Antiquity and Evolutionary Status of Bacterial Sulfate Reduction: Sulfur Isotope Evidence]. In: Limits of Life, 1980, pages 159–171.
* Manfred Schidlowski, Rudolf Eichmann, Christian E. Junge: [https://www.sciencedirect.com/science/article/abs/pii/0301926875900182 Precambrian sedimentary carbonates: carbon and oxygen isotope geochemistry and implications for the terrestrial oxygen budget]. In: Precambrian Research, Vol 2, Issue 1, February 1975, pages 1-69.
* Manfred Schidlowski: [https://www.nature.com/articles/205895a0 Probable Life-forms from the Precambrian of the Witwatersrand System (South Africa)]. In: Nature, Vol. 205, 27 February 1965, pages 895–896. | 0 | Theoretical and Fundamental Chemistry |
Despite formal recommendation to the contrary, the term partition coefficient remains the predominantly used term in the scientific literature.
In contrast, the IUPAC recommends that the title term no longer be used, rather, that it be replaced with more specific terms. For example, partition constant, defined as
where K is the process equilibrium constant, [A] represents the concentration of solute A being tested, and "org" and "aq" refer to the organic and aqueous phases respectively. The IUPAC further recommends "partition ratio" for cases where transfer activity coefficients can be determined, and "distribution ratio" for the ratio of total analytical concentrations of a solute between phases, regardless of chemical form. | 0 | Theoretical and Fundamental Chemistry |
Liver of sulfur is a loosely defined mixture of potassium sulfide, potassium polysulfide, potassium thiosulfate, and likely potassium bisulfide. Synonyms include hepar sulfuris, sulfur, sulfurated potash and sulfurated potassa. There are two distinct varieties: "potassic liver of sulfur" and "ammoniacal liver of sulfur". | 0 | Theoretical and Fundamental Chemistry |
Howard E. Zimmerman was a native of Connecticut. During World War II, he served in the U.S. Armored Corps in Europe where he was a tank gunner. His final rank was technical sergeant. He obtained a B. S. in Chemistry in 1950 and a Ph.D. in 1953 both from Yale University. He was a Postdoctoral Research Fellow with a National Research Council fellowship from 1953 to 1954 working with R. B. Woodward (Harvard). From 1954 to 1960 he was assistant professor at Northwestern University. Beginning in 1960 he was Associate Professor and then Professor at the University of Wisconsin, and from 1990 he was Hilldale and A. C. Cope Professor of Chemistry. His publications number over 285 (including 11 chapters).
Zimmerman gave ACS Short Courses on organic quantum chemistry and molecular orbital theory. He authored a 1975 textbook entitled Quantum Mechanics for Organic Chemists. Zimmerman was the organizer of the 1972 IUPAC Photochemistry Symposium (Baden-Baden) and of five Pacifichem Symposia – the last being Pacifichem 2010. | 0 | Theoretical and Fundamental Chemistry |
There is a market for vials of processed sperm and for various reasons a sperm bank may sell-on stocks of vials which it holds known as onselling. The costs of screening of donors and storage of frozen donor sperm vials are not insignificant and in practice most sperm banks will try to dispose of all samples from an individual donor. The onselling of sperm therefore enables a sperm bank to maximize the sale and disposal of sperm samples which it has processed. The reasons for onselling may also be where part of, or even the main business of, a particular sperm bank is to process and store sperm rather than to use it in fertility treatments, or where a sperm bank is able to collect and store more sperm than it can use within nationally set limits. In the latter case a sperm bank may onsell sperm from a particular donor for use in another jurisdiction after the number of pregnancies achieved from that donor has reached its national maximum.
Sperm banks may supply other sperm banks or a fertility clinic with donor sperm to be used for achieving pregnancies.
Sperm banks may also supply sperm for research or educational purposes. | 1 | Applied and Interdisciplinary Chemistry |
* Preliminary round: Usually held around the end of August and the beginning of September each year.
* Final round: Usually held around the end of November and the start of December.
(An interesting fact is that before 2011 the final round took part in the next January after the preliminary round, but some reforms were launched and consequently the time was altered to the end of the year in 2011.) | 1 | Applied and Interdisciplinary Chemistry |
Aliphatic compounds can be saturated, joined by single bonds (alkanes), or unsaturated, with double bonds (alkenes) or triple bonds (alkynes). If other elements (heteroatoms) are bound to the carbon chain, the most common being oxygen, nitrogen, sulfur, and chlorine, it is no longer a hydrocarbon, and therefore no longer an aliphatic compound. However, such compounds may still be referred to as aliphatic if the hydrocarbon portion of the molecule is aliphatic, e.g. aliphatic amines, to differentiate them from aromatic amines.
The least complex aliphatic compound is methane (CH). | 0 | Theoretical and Fundamental Chemistry |
Primary sources from the group of Irma Rantanen at University of Turku, Finland claim that SLS-containing pastes cause more dry mouth (xerostomia) than their proposed alternative. However, a 2011 Cochrane review of these studies, and of the more general area, concludes that there "is no strong evidence... that any topical therapy is effective for relieving the symptom of dry mouth." | 1 | Applied and Interdisciplinary Chemistry |
Sodium iodide activated with thallium, NaI(Tl), when subjected to ionizing radiation, emits photons (i.e., scintillate) and is used in scintillation detectors, traditionally in nuclear medicine, geophysics, nuclear physics, and environmental measurements. NaI(Tl) is the most widely used scintillation material. The crystals are usually coupled with a photomultiplier tube, in a hermetically sealed assembly, as sodium iodide is hygroscopic. Fine-tuning of some parameters (i.e., radiation hardness, afterglow, transparency) can be achieved by varying the conditions of the crystal growth. Crystals with a higher level of doping are used in X-ray detectors with high spectrometric quality. Sodium iodide can be used both as single crystals and as polycrystals for this purpose. The wavelength of maximum emission is 415 nm. | 0 | Theoretical and Fundamental Chemistry |
* The novel The Dervish House by Ian McDonald features a hunt for a mellified man.
* A segment of the eighth episode of the fourth series of the British childrens historical sketch show Horrible Histories' features this concept.
* The song "Sweet Bod" by Neil Cicierega (also known as Lemon Demon) on the 2016 album Spirit Phone is about this concept, containing many lyrics revolving around a corpse being mummified in honey, and the sale of said honey for medicinal purposes. | 1 | Applied and Interdisciplinary Chemistry |
Xanthosine monophosphate (xanthylate) is an intermediate in purine metabolism. It is a ribonucleoside monophosphate. It is formed from IMP via the action of IMP dehydrogenase, and it forms GMP via the action of GMP synthase. Also, XMP can be released from XTP by enzyme deoxyribonucleoside triphosphate pyrophosphohydrolase containing (d)XTPase activity.
It is abbreviated XMP. | 1 | Applied and Interdisciplinary Chemistry |
Because nitrenes are so reactive, they are not isolated. Instead, they are formed as reactive intermediates during a reaction. There are two common ways to generate nitrenes:
* From azides by thermolysis or photolysis, with expulsion of nitrogen gas. This method is analogous to the formation of carbenes from diazo compounds.
* From isocyanates, with expulsion of carbon monoxide. This method is analogous to the formation of carbenes from ketenes. | 0 | Theoretical and Fundamental Chemistry |
In the 1980s, Lehn observed that Co(I) species were produced in solutions containing CoCl, 2,2'-bipyridine (bpy), a tertiary amine, and a Ru(bpy)Cl photosensitizer. The high affinity of CO to cobalt centers led both him and Ziessel to study cobalt centers as electrocatalysts for reduction. In 1982, they reported CO and H as products from the irradiation of a solution containing 700ml of CO, Ru(bpy) and Co(bpy).
Since the work of Lehn and Ziessel, several catalysts have been paired with the Ru(bpy) photosensitizer.
When paired with methylviologen, cobalt, and nickel-based catalysts, carbon monoxide and hydrogen gas are observed as products.
Paired with rhenium catalysts, carbon monoxide is observed as the major product, and with ruthenium catalysts formic acid is observed. Some product selection is attainable through tuning of the reaction environment. Other photosensitizers have also been employed as catalysts. They include FeTPP (TPP=5,10,15,20-tetraphenyl-21H,23H-porphine) and CoTPP, both of which produce CO while the latter produces formate also. Non-metal photocatalysts include pyridine and N-heterocyclic carbenes.
In August 2022, it was developed a photocatalyst based on lead–sulfur (Pb–S) bonds, with promising results. | 0 | Theoretical and Fundamental Chemistry |
Amyloid precursor protein has been shown to interact with:
* APBA1,
* APBA2,
* APBA3,
* APBB1,
* APPBP1,
* APPBP2,
* BCAP31,
* BLMH
* CLSTN1,
* CAV1,
* COL25A1,
* FBLN1,
* GSN,
* HSD17B10, and
* SHC1.
APP interacts with reelin, a protein implicated in a number of brain disorders, including Alzheimer's disease. | 1 | Applied and Interdisciplinary Chemistry |
The initiation time is related to the rate at which carbonation propagates in the concrete cover thickness. Once that carbonation reaches the steel surface, altering the local pH value of the environment, the protective thin film of oxides on the steel surface becomes instable, and corrosion initiates involving an extended portion of the steel surface. One of the most simplified and accredited models describing the propagation of carbonation in time is to consider penetration depth proportional to the square root of time, following the correlation
where is the carbonation depth, is time, and is the carbonation coefficient. The corrosion onset takes place when the carbonation depth reaches the concrete cover thickness, and therefore can be evaluated as
where is the concrete cover thickness.
is the key design parameter to assess initiation time in the case of carbonation-induced corrosion. It is expressed in mm/year and depends on the characteristics of concrete and the exposure conditions. The penetration of gaseous CO in a porous medium such as concrete occurs via diffusion. The humidity content of concrete is one of the main influencing factors of CO diffusion in concrete. If concrete pores are completely and permanently saturated (for instance in submerged structures) CO diffusion is prevented. On the other hand, for completely dry concrete, the chemical reaction of carbonation cannot occur. Another influencing factor for CO diffusion rate is concrete porosity. Concrete obtained with higher w/c ratio or obtained with an incorrect curing process presents higher porosity at hardened state, and is therefore subjected to a higher carbonation rate. The influencing factors concerning the exposure conditions are the environmental temperature, humidity and concentration of CO. Carbonation rate is higher for environments with higher humidity and temperature, and increases in polluted environments such as urban centres and inside close spaces as tunnels.
To evaluate propagation time in the case of carbonation-induced corrosion, several models have been proposed. In a simplified but commonly accepted method, the propagation time is evaluated as function of the corrosion propagation rate. If the corrosion rate is considered constant, t can be estimated as:
where is the limit corrosion penetration in steel and is the corrosion propagation rate.
must be defined in function of the limit state considered. Generally for carbonation-induced corrosion the concrete cover cracking is considered as limit state, and in this case a equal to 100 μm is considered. depends on the environmental factors in proximity of the corrosion process, such as the availability of oxygen and water at concrete cover depth. Oxygen is generally available at the steel surface, except for submerged structures. If pores are constantly fully saturated, a very low amount of oxygen reaches the steel surface and corrosion rate can be considered negligible. For very dry concretes is negligible due to the absence of water which prevents the chemical reaction of corrosion. For intermediate concrete humidity content, corrosion rate increases with increasing the concrete humidity content. Since the humidity content in a concrete can significantly vary along the year, it is general not possible to define a constant . One possible approach is to consider a mean annual value of . | 1 | Applied and Interdisciplinary Chemistry |
Zhao Jincai (; born December 1960) is a Chinese environmental chemist and researcher of the Institute of Chemistry of the Chinese Academy of Sciences. In April 1994, he obtained a doctorate from Meisei University in Japan. In 2011 he was elected as an academician of CAS. He is a professor at the Institute of Chemistry, CAS; Deputy Director of Key Laboratory of Photochemistry; Deputy Director of Science Committee of Molecular Sciences Centre, CAS. His research mainly focuses on the photocatalytic degradation of toxic and persistent organic pollutants. Zhao introduced -based photocatalyst under visible light, and discovered a new way for oxygen atom transfer during photocatalytic reactions. | 1 | Applied and Interdisciplinary Chemistry |
Carotenoderma, also referred to as carotenemia, is a benign and reversible medical condition where an excess of dietary carotenoids results in orange discoloration of the outermost skin layer. It is associated with a high blood β-carotene value. This can occur after a month or two of consumption of beta-carotene rich foods, such as carrots, carrot juice, tangerine juice, mangos, or in Africa, red palm oil. β-carotene dietary supplements can have the same effect. The discoloration extends to palms and soles of feet, but not to the white of the eye, which helps distinguish the condition from jaundice. Consumption of greater than 30 mg/day for a prolonged period has been confirmed as leading to carotenemia. | 1 | Applied and Interdisciplinary Chemistry |
Armodafinil exhibits linear time-independent kinetics following single and multiple oral dose administration. Increase in systemic exposure is proportional over the dose range of 50–400 mg. No time-dependent change in kinetics was observed through 12 weeks of dosing. Apparent steady state for armodafinil was reached within 7 days of dosing. At steady state, the systemic exposure for armodafinil is 1.8 times the exposure observed after a single dose. The concentration-time profiles of the (R)-(−)-enantiomer following a single dose of 50 mg Nuvigil or 100 mg Provigil (modafinil being a 1:1 mixture of (R)-(−)- and (S)-(−)- enantiomers) are nearly superimposable. However, the C of armodafinil at steady state was 37% higher following administration of 200 mg Nuvigil than the corresponding value of modafinil following administration of 200 mg Provigil due to the more rapid clearance of the (S)-(+)-enantiomer. | 0 | Theoretical and Fundamental Chemistry |
The German physicist Rudolf Clausius, in the 1850s, was the first to mathematically quantify the discovery of irreversibility in nature through his introduction of the concept of entropy. In his 1854 memoir "On a Modified Form of the Second Fundamental Theorem in the Mechanical Theory of Heat," Clausius states:
Simply, Clausius states that it is impossible for a system to transfer heat from a cooler body to a hotter body. For example, a cup of hot coffee placed in an area of room temperature will transfer heat to its surroundings and thereby cool down with the temperature of the room slightly increasing (to ). However, that same initial cup of coffee will never absorb heat from its surroundings, causing it to grow even hotter, with the temperature of the room decreasing (to ). Therefore, the process of the coffee cooling down is irreversible unless extra energy is added to the system.
However, a paradox arose when attempting to reconcile microanalysis of a system with observations of its macrostate. Many processes are mathematically reversible in their microstate when analyzed using classical Newtonian mechanics. This paradox clearly taints microscopic explanations of macroscopic tendency towards equilibrium, such as James Clerk Maxwells 1860 argument that molecular collisions entail an equalization of temperatures of mixed gases. From 1872 to 1875, Ludwig Boltzmann reinforced the statistical explanation of this paradox in the form of Boltzmanns entropy formula, stating that an increase of the number of possible microstates a system might be in, will increase the entropy of the system, making it less likely that the system will return to an earlier state. His formulas quantified the analysis done by William Thomson, 1st Baron Kelvin, who had argued that:
Another explanation of irreversible systems was presented by French mathematician Henri Poincaré. In 1890, he published his first explanation of nonlinear dynamics, also called chaos theory. Applying chaos theory to the second law of thermodynamics, the paradox of irreversibility can be explained in the errors associated with scaling from microstates to macrostates and the degrees of freedom used when making experimental observations. Sensitivity to initial conditions relating to the system and its environment at the microstate compounds into an exhibition of irreversible characteristics within the observable, physical realm. | 0 | Theoretical and Fundamental Chemistry |
With regard to the risk of proliferation and use by terrorists, the relatively simple design is a concern, as it does not require as much fine engineering or manufacturing as other methods. With enough highly enriched uranium, nations or groups with relatively low levels of technological sophistication could create an inefficient—though still quite powerful—gun-type nuclear weapon. | 0 | Theoretical and Fundamental Chemistry |
Polymeric materials have widespread application due to their versatile characteristics, cost-effectiveness, and highly tailored production. The science of polymer synthesis allows for excellent control over the properties of a bulk polymer sample. However, surface interactions of polymer substrates are an essential area of study in biotechnology, nanotechnology, and in all forms of coating applications. In these cases, the surface characteristics of the polymer and material, and the resulting forces between them largely determine its utility and reliability. In biomedical applications for example, the bodily response to foreign material, and thus biocompatibility, is governed by surface interactions. In addition, surface science is integral part of the formulation, manufacturing, and application of coatings.
__TOC__ | 0 | Theoretical and Fundamental Chemistry |
Hemoglobin acts to transport oxygen which the body receives to all body tissue via blood vessels. Over time, when red blood cells need to be replenished, the hemoglobin is broken down in the spleen; it breaks down into two parts: heme group consisting of iron and bile and protein fraction. While protein and iron are utilized to renew red blood cells, pigments that make up the red color in blood are deposited into the bile to form bilirubin. Jaundice leads to raised bilirubin levels that in turn negatively remove elastin-rich tissues. Jaundice may be noticeable in the sclera of the eyes at levels of about 2 to 3 mg/dl (34 to 51 μmol/L), and in the skin at higher levels.
Jaundice is classified, depending upon whether the bilirubin is free or conjugated to glucuronic acid, into conjugated jaundice or unconjugated jaundice. | 1 | Applied and Interdisciplinary Chemistry |
Palmitoylethanolamide was discovered in 1957. Indications for its use as an anti-inflammatory and analgesic date from before 1980. In that year, researchers described what they called "N-(2-hydroxyethyl)-palmitamide" as a natural anti-inflammatory agent, stating, "We have succeeded in isolating a crystalline anti-inflammatory factor from soybean lecithin and identifying it as (S)-(2-hydroxyethyl)-palmitamide. The compound also was isolated from a phospholipid fraction of egg yolk and from hexane-extracted peanut meal."
In 1975, Czech physicians described the results of a clinical trial looking at joint pain, where the analgesic action of aspirin versus PEA were tested; both drugs were reported to enhance joint movements and decrease pain. In 1970 the drug manufacturer Spofa in Czechoslovakia introduced Impulsin, a tablet dose of PEA, for the treatment and prophylaxis of influenza and other respiratory infections. In Spain, the company Almirall introduced Palmidrol in tablet and suspension forms in 1976, for the same indications.
In the mid-1990s, the relationship between anandamide and PEA was described; the expression of mast cell receptors sensitive to the two molecules was demonstrated by Levi-Montalcini and coworkers. During this period, more insight into the functions of endogenous fatty acid derivatives emerged, and compounds such as oleamide, palmitoylethanolamide, 2-lineoylglycerol and 2-palmitoylglycerol were explored for their capacity to modulate pain sensitivity and inflammation via what at that time was thought to be the endocannabinoid signalling pathway.
Primary reports also have provided evidence that PEA downregulates hyperactive mast cells in a dose-dependent manner, and that it alleviates pain elicited in mouse models. PEA and related compounds such as anandamide also seem to have synergistic effects in models of pain and analgesia. | 1 | Applied and Interdisciplinary Chemistry |
There are three types of persistent infections, latent, chronic and slow, in which the virus stays inside the host cell for prolonged periods of time. During latent infections there is minimal to no expression of infected viral genome. The genome remains within the host cell until the virus is ready for replication. Chronic infections have similar cellular effects as acute cytocidal infections but there is a limited number of progeny and viruses involved in transformation. Lastly, slow infections have a longer incubation period in which no physiological, morphological or subcellular changes may be involved. | 1 | Applied and Interdisciplinary Chemistry |
Photon anti-bunching is the process in Resonance Fluorescence through which rate at which photons are emitted by a two-level atom is limited. A two-level atom is only capable of absorbing a photon from the driving electromagnetic field after a certain period of time has passed. This time period is modeled as a probability distribution where as . As the atom cannot absorb a photon, it is unable to emit one and thus there is a restriction on the spectral density. This is illustrated by the second order correlation function
From the above equation it is clear that and thus resulting in the relation that describes photon antibunching
This shows that the power cannot be anything other than zero for . In the weak field approximation can only increase monotonically as increases, however in the strong field approximation oscillates as it increases. These oscillations die off as .
The physical idea behind photon anti-bunching is that while the atom itself is ready to be excited as soon as it releases its previous photon, the electromagnetic field created by the laser takes time to excite the atom. | 0 | Theoretical and Fundamental Chemistry |
The intrinsic viscosity is very sensitive to the axial ratio of spheroids, especially of prolate spheroids. For example, the intrinsic viscosity can provide rough estimates of the number of subunits in a protein fiber composed of a helical array of proteins such as tubulin. More generally, intrinsic viscosity can be used to assay quaternary structure. In polymer chemistry intrinsic viscosity is related to molar mass through the Mark–Houwink equation. A practical method for the determination of intrinsic viscosity is with a Ubbelohde viscometer. | 1 | Applied and Interdisciplinary Chemistry |
Because many reagents exist for radical generation and trapping, establishing a single prevailing mechanism is not possible. However, once a radical is generated, it can react with multiple bonds in an intramolecular fashion to yield cyclized radical intermediates. The two ends of the multiple bond constitute two possible sites of reaction. If the radical in the resulting intermediate ends up outside of the ring, the attack is termed "exo"; if it ends up inside the newly formed ring, the attack is called "endo." In many cases, exo cyclization is favored over endo cyclization (macrocyclizations constitute the major exception to this rule). 5-hexenyl radicals are the most synthetically useful intermediates for radical cyclizations, because cyclization is extremely rapid and exo selective. Although the exo radical is less thermodynamically stable than the endo radical, the more rapid exo cyclization is rationalized by better orbital overlap in the chair-like exo transition state (see below).
Substituents that affect the stability of these transition states can have a profound effect on the site selectivity of the reaction. Carbonyl substituents at the 2-position, for instance, encourage 6-endo ring closure. Alkyl substituents at positions 2, 3, 4, or 6 enhance selectivity for 5-exo closure.
Cyclization of the homologous 6-heptenyl radical is still selective, but is much slower—as a result, competitive side reactions are an important problem when these intermediates are involved. Additionally, 1,5-shifts can yield stabilized allylic radicals at comparable rates in these systems. In 6-hexenyl radical substrates, polarization of the reactive double bond with electron-withdrawing functional groups is often necessary to achieve high yields. Stabilizing the initially formed radical with electron-withdrawing groups provides access to more stable 6-endo cyclization products preferentially.
Cyclization reactions of vinyl, aryl, and acyl radicals are also known. Under conditions of kinetic control, 5-exo cyclization takes place preferentially. However, low concentrations of a radical scavenger establish thermodynamic control and provide access to 6-endo products—not via 6-endo cyclization, but by 5-exo cyclization followed by 3-exo closure and subsequent fragmentation (Dowd-Beckwith rearrangement). Whereas at high concentrations of the exo product is rapidly trapped preventing subsequent rearrangement to the endo product Aryl radicals exhibit similar reactivity.
Cyclization can involve heteroatom-containing multiple bonds such as nitriles, oximes, and carbonyls. Attack at the carbon atom of the multiple bond is almost always observed. In the latter case attack is reversible; however alkoxy radicals can be trapped using a stannane trapping agent. | 0 | Theoretical and Fundamental Chemistry |
There are many types of passive samplers used that specialize in absorbing different classes of aquatic contaminants found in the environment. Chemcatcher and SMPD are two types of passive samplers that are also commonly used. Monitoring programs use SMPDs to measure to hydrophobic organic contaminants. SPMDs are designed to mimic the bioconcentration of contaminants in fatty tissues (ITRC, 2006). Contaminants applicable to the use of an SPMD include, but are not limited to, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides, dioxins, and furans.
The SPMD consist of a thin-walled, nonporous, polyethylene membrane tube that is filled with high molecular weight lipid. These tubes are approximately 90 cm long and wrap around the inside of a stainless steel deployment canister. SMPDs are efficient at absorbing pollutants with a log Kow of 4-8. This slightly overlaps with the range of contaminants absorbed by POCIS. Because of this, SMPDs and POCIS devices are often used together in monitoring studies to achieve a more representative understanding of contamination. | 0 | Theoretical and Fundamental Chemistry |
The typical solution, historically, has been to use the Hall effect to create a current that flows with the fluid. (See illustration.) This design has arrays of short, segmented electrodes on the sides of the duct. The first and last electrodes in the duct power the load. Each other electrode is shorted to an electrode on the opposite side of the duct. These shorts of the Faraday current induce a powerful magnetic field within the fluid, but in a chord of a circle at right angles to the Faraday current. This secondary, induced field makes current flow in a rainbow shape between the first and last electrodes.
Losses are less than a Faraday generator, and voltages are higher because there is less shorting of the final induced current.
However, this design has problems because the speed of the material flow requires the middle electrodes to be offset to "catch" the Faraday currents. As the load varies, the fluid flow speed varies, misaligning the Faraday current with its intended electrodes, and making the generator's efficiency very sensitive to its load. | 1 | Applied and Interdisciplinary Chemistry |
The dominant application of metal carbenes involves none of the above classes of compounds, but rather heterogeneous catalysts used for alkene metathesis for the synthesis of higher alkenes. A variety of related reactions are used to interconvert light alkenes, e.g. butenes, propylene, and ethylene. Carbene complexes are invoked as intermediates in the Fischer–Tropsch route to hydrocarbons.
A variety of homogeneous carbene catalysts, especially the Grubbs' ruthenium and Schrock molybdenum-imido catalysts have been used for olefin metathesis in laboratory-scale synthesis of natural products and materials science. | 0 | Theoretical and Fundamental Chemistry |
Far-red
In efforts to increase photosynthetic efficiency, researchers have proposed extending the spectrum of light that is available for photosynthesis. One approach involves incorporating pigments like chlorophyll d and f, which are capable of absorbing far-red light, into the photosynthetic machinery of higher plants. Naturally present in certain cyanobacteria, these chlorophylls enable photosynthesis with far-red light that standard chlorophylls a and b cannot utilize. By adapting these pigments for use in higher plants, it is hoped that plants can be engineered to utilize a wider range of the light spectrum, potentially leading to increased growth rates and biomass production.
Green
Green light is considered the least efficient wavelength in the visible spectrum for photosynthesis and presents an opportunity for increased utilization. Chlorophyll c is a pigment found in marine algae with blue-green absorption and could be used to expand absorption in the green wavelengths in plants. Expression of the dinoflagellate CHLOROPHYLL C SYNTHASE gene in the plant Nicotiana benthamiana resulted in the heterologous production of chlorophyll c. This was the first successful introduction of a foreign chlorophyll molecule into a higher plant and is the first step towards bioengineering plants for improved photosynthetic performance across a variety of lighting conditions. | 0 | Theoretical and Fundamental Chemistry |
Factitious airs was a term used for synthetic gases which emerged around 1670 when Robert Boyle coined the term upon isolating what is now understood to be hydrogen. Factitious means "artificial, not natural", so the term means "man-made gases". | 1 | Applied and Interdisciplinary Chemistry |
Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic fields are expelled from the material. Any material exhibiting these properties is a superconductor. Unlike an ordinary metallic conductor, whose resistance decreases gradually as its temperature is lowered, even down to near absolute zero, a superconductor has a characteristic critical temperature below which the resistance drops abruptly to zero. An electric current through a loop of superconducting wire can persist indefinitely with no power source.
The superconductivity phenomenon was discovered in 1911 by Dutch physicist Heike Kamerlingh Onnes. Like ferromagnetism and atomic spectral lines, superconductivity is a phenomenon which can only be explained by quantum mechanics. It is characterized by the Meissner effect, the complete cancelation of the magnetic field in the interior of the superconductor during its transitions into the superconducting state. The occurrence of the Meissner effect indicates that superconductivity cannot be understood simply as the idealization of perfect conductivity in classical physics.
In 1986, it was discovered that some cuprate-perovskite ceramic materials have a critical temperature above . Such a high transition temperature is theoretically impossible for a conventional superconductor, leading the materials to be termed high-temperature superconductors. The cheaply available coolant liquid nitrogen boils at and thus the existence of superconductivity at higher temperatures than this facilitates many experiments and applications that are less practical at lower temperatures. | 0 | Theoretical and Fundamental Chemistry |
A beam origin (also beam source) is a river section that is in very good ecological condition. The river section may not necessarily be located in the main course but side waters. On the one hand, it shows structural, hydrological and hydraulic quality close to nature; on the other hand, it is the natural habitat of typical organisms that can drift and migrate to other sections. If a beam source only meets the prerequisites for an abiotic beam effect it is called a potential beam origin and it is assumed that in the long-term a typical inventory of species can be formed. | 1 | Applied and Interdisciplinary Chemistry |
The RNA coded by the short-interspersed nuclear element does not code for any protein product but is nonetheless reverse-transcribed and inserted back into an alternate region in the genome. For this reason, short interspersed nuclear elements are believed to have co-evolved with long interspersed nuclear element (LINEs), as LINEs do in fact encode protein products which enable them to be reverse- transcribed and integrated back into the genome. SINEs are believed to have co-opted the proteins coded by LINEs which are contained in 2 reading frames. Open reading frame 1 (ORF 1) encodes a protein which binds to RNA and acts as a chaperone to facilitate and maintain the LINE protein-RNA complex structure. Open reading frame 2 (ORF 2) codes a protein which possesses both endonuclease and reverse transcriptase activities. This enables the LINE mRNA to be reverse-transcribed into DNA and integrated into the genome based on the sequence-motifs recognized by the protein's endonuclease domain.
LINE-1 (L1) is transcribed and retrotransposed most frequently in the germ-line and during early development; as a result SINEs move around the genome most during these periods. SINE transcription is down-regulated by transcription factors in somatic cells after early development, though stress can cause up-regulation of normally silent SINEs. SINEs can be transferred between individuals or species via horizontal transfer through a viral vector.
SINEs are known to share sequence homology with LINES which gives a basis by which the LINE machinery can reverse transcribe and integrate SINE transcripts. Alternately, some SINEs are believed to use a much more complex system of integrating back into the genome; this system involves the use random double-stranded DNA breaks (rather than the endonuclease coded by related long-interspersed nuclear elements creating an insertion-site). These DNA breaks are utilized to prime reverse transcriptase, ultimately integrating the SINE transcript back into the genome. SINEs nonetheless depend on enzymes coded by other DNA elements and are thus known as non-autonomous retrotransposons as they depend on the machinery of LINEs, which are known as autonomous retrotransposons.<
The theory that short-interspersed nuclear elements have evolved to utilize the retrotransposon machinery of long-interspersed nuclear elements is supported by studies which examine the presence and distribution of LINEs and SINEs in taxa of different species. For example, LINEs and SINEs in rodents and primates show very strong homology at the insertion-site motif. Such evidence is a basis for the proposed mechanism in which integration of the SINE transcript can be co-opted with LINE-coded protein products. This is specifically demonstrated by a detailed analysis of over 20 rodent species profiled LINEs and SINEs, mainly L1s and B1s respectively; these are families of LINEs and SINEs found at high frequencies in rodents along with other mammals. The study sought to provide phylogenetic clarity within the context of LINE and SINE activity.
The study arrived at a candidate taxa believed to be the first instance of L1 LINE extinction; it expectedly discovered that there was no evidence to suggest that B1 SINE activity occurred in species which did not have L1 LINE activity. Also, the study suggested that B1 short-interspersed nuclear element silencing in fact occurred before L1 long-interspersed nuclear element extinction; this is due to the fact that B1 SINEs are silenced in the genus most-closely related to the genus which does not contain active L1 LINEs (though the genus with B1 SINE silencing still contains active L1 LINEs). Another genus was also found which similarly contained active L1 long-interspersed nuclear elements but did not contain B1 short-interspersed nuclear elements; the opposite scenario, in which active B1 SINEs were present in a genus which did not possess active L1 LINEs was not found. This result was expected and strongly supports the theory that SINEs have evolved to co-opt the RNA-binding proteins, endonucleases, and reverse-transcriptases coded by LINEs. In taxa which do not actively transcribe and translate long-interspersed nuclear elements protein-products, SINEs do not have the theoretical foundation by which to retrotranspose within the genome. The results obtained in Rinehart et al. are thus very supportive of the current model of SINE retrotransposition. | 1 | Applied and Interdisciplinary Chemistry |
A superconductor can be Type I, meaning it has a single critical field, above which all superconductivity is lost and below which the magnetic field is completely expelled from the superconductor; or Type II, meaning it has two critical fields, between which it allows partial penetration of the magnetic field through isolated points. These points are called vortices. Furthermore, in multicomponent superconductors it is possible to have a combination of the two behaviours. In that case the superconductor is of Type-1.5. | 0 | Theoretical and Fundamental Chemistry |
Most organisms synthesize NAD from simple components. The specific set of reactions differs among organisms, but a common feature is the generation of quinolinic acid (QA) from an amino acideither tryptophan (Trp) in animals and some bacteria, or aspartic acid (Asp) in some bacteria and plants. The quinolinic acid is converted to nicotinic acid mononucleotide (NaMN) by transfer of a phosphoribose moiety. An adenylate moiety is then transferred to form nicotinic acid adenine dinucleotide (NaAD). Finally, the nicotinic acid moiety in NaAD is amidated to a nicotinamide (Nam) moiety, forming nicotinamide adenine dinucleotide.
In a further step, some NAD is converted into NADP by NAD kinase, which phosphorylates NAD. In most organisms, this enzyme uses adenosine triphosphate (ATP) as the source of the phosphate group, although several bacteria such as Mycobacterium tuberculosis and a hyperthermophilic archaeon Pyrococcus horikoshii, use inorganic polyphosphate as an alternative phosphoryl donor. | 0 | Theoretical and Fundamental Chemistry |
*Continuous and short-term surface water runoff
*Stormwater prediction and management
*Flash flood forecasting
*Operational flood alert
*Flood event reconstruction
*Design Storm development
*Recharge estimation
*Soil moisture monitoring
*Hydrology and Hydraulics studies
*Land use planning scenarios
*Water quality studies
*Hydropower management
*Hydrology education
*Hydrologic research | 1 | Applied and Interdisciplinary Chemistry |
The dual ligation hybridization assay (DLA) extends the specificity of the hybridization-ligation assay to a specific method for the parent compound. Despite hybridization-ligation assays robustness, sensitivity and added specificity for the 3-end of the oligonculeotide analyte, the hybridization-ligation assay is not specific for the 5' end of the analyte.
The DLA is intended to quantify the full-length, parent oligonucleotide compound only, with both intact 5 and 3 ends. DLA probes are ligated at the 5 and 3 ends of the analyte by the joint action of T4 DNA ligase and T4 polynucleotide kinase. The kinase phosphorylates the 5-end of the analyte and the ligase will join the capture probe to the analyte to the detection probe. The capture and detection probes in the DLA can thus be termed ligation probes. As for the hybridization-ligation assay, the DLA is specific for the parent compound because the efficiency of ligation over a bulge loop is low, and thus the DLA detects the full-length analyte with both intact 5 and 3'-ends. The DLA can also be used for the determination of individual metabolites in biological matrices.
The limitations with the hybridization-ligation assay also apply to the dual ligation assay, with the 5-end in addition to the 3-end requiring to have a free hydroxyl (or a phosphate group). Further, T4 DNA ligases are incompatible with ligation of RNA molecules as a donor (i.e. RNA at the 5 end of the ligation). Therefore, second generation antisense that comprise 2-O-methyl RNA, 2'-O-methoxyethyl or locked nucleic acids may not be compatible with the dual ligation assay. | 1 | Applied and Interdisciplinary Chemistry |
Radioactive isotope labeling experiments provide a powerful tool for determining the structure of organic molecules. By systematically decomposing the 2-norbornyl cation and analyzing the amount of radioactive isotope in each decomposition product, researchers were able to show further evidence for the non-classical picture of delocalized bonding (see Figure 9). Proponents of the nonclassical picture would expect 50% of the generated CO in the decomposition in Figure 9 to contain C, while proponents of the classical picture would expect more of the generated CO to be radioactive due to the short-lived nature of the cation. 40% of the carbon dioxide produced via decomposition has been observed to be radioactive, suggesting that the non-classical picture is more correct.
Further distinction between non-classical and classical structures of the 2-norbornyl cation is possible by combining NMR experiments with isotope-labeling experiments. Isotopic substitution of one of two deuterium atoms for a hydrogen atom causes the environment of nearby NMR-active atoms to change dramatically. Asymmetric deuterium isotope labeling (substitution) will cause a set of carbons that were all equivalent in the all-hydrogen species to be split into two or more sets of equivalent carbons in the deutero-labeled species; this will be manifested in the NMR spectrum as one peak in the all-hydrogen species' spectrum becoming at least two "split" peaks in the deutero-labeled species. If a system is undergoing a rapid equilibrium at a rate faster than the timescale of a C NMR experiment, the relevant peak will be split dramatically (on the order of 10-100 ppm). If the system is instead static, the peak will be split very little. The C NMR spectrum of the 2-norbornyl cation at -150 °C shows that the peaks corresponding to carbons 1 and 2 are split by less than 10 ppm (parts per million) when this experiment is carried out, indicating that the system is not undergoing a rapid equilibrium as in the classical picture. | 0 | Theoretical and Fundamental Chemistry |
A mitochondrion (; : mitochondria) is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used throughout the cell as a source of chemical energy. They were discovered by Albert von Kölliker in 1857 in the voluntary muscles of insects. The term mitochondrion was coined by Carl Benda in 1898. The mitochondrion is popularly nicknamed the "powerhouse of the cell", a phrase coined by Philip Siekevitz in a 1957 article of the same name.
Some cells in some multicellular organisms lack mitochondria (for example, mature mammalian red blood cells). The multicellular animal Henneguya salminicola is known to have retained mitochondrion-related organelles in association with a complete loss of their mitochondrial genome. A large number of unicellular organisms, such as microsporidia, parabasalids and diplomonads, have reduced or transformed their mitochondria into other structures, e.g. hydrogenosomes and mitosomes. The oxymonads Monocercomonoides, Streblomastix, and Blattamonas have completely lost their mitochondria.
Mitochondria are commonly between 0.75 and 3 μm in cross section, but vary considerably in size and structure. Unless specifically stained, they are not visible. In addition to supplying cellular energy, mitochondria are involved in other tasks, such as signaling, cellular differentiation, and cell death, as well as maintaining control of the cell cycle and cell growth. Mitochondrial biogenesis is in turn temporally coordinated with these cellular processes. Mitochondria have been implicated in several human disorders and conditions, such as mitochondrial diseases, cardiac dysfunction, heart failure and autism.
The number of mitochondria in a cell can vary widely by organism, tissue, and cell type. A mature red blood cell has no mitochondria, whereas a liver cell can have more than 2000. The mitochondrion is composed of compartments that carry out specialized functions. These compartments or regions include the outer membrane, intermembrane space, inner membrane, cristae, and matrix.
Although most of a eukaryotic cell's DNA is contained in the cell nucleus, the mitochondrion has its own genome ("mitogenome") that is substantially similar to bacterial genomes. This finding has led to general acceptance of the endosymbiotic hypothesis - that free-living prokaryotic ancestors of modern mitochondria permanently fused with eukaryotic cells in the distant past, evolving such that modern animals, plants, fungi, and other eukaryotes are able to respire to generate cellular energy. | 1 | Applied and Interdisciplinary Chemistry |
The formation of a glycosidic linkage results in the formation of a new stereogenic centre and therefore a mixture of products may be expected to result. The linkage formed may either be axial or equatorial (α or β with respect to glucose). To better understand this, the mechanism of a glycosylation reaction must be considered. | 0 | Theoretical and Fundamental Chemistry |
With GM corn being a common feedstock, it is unsurprising that some bioplastics are made from this.
Under the bioplastics manufacturing technologies there is the "plant factory" model, which uses genetically modified crops or genetically modified bacteria to optimise efficiency. | 0 | Theoretical and Fundamental Chemistry |
The use of the recycled glass as aggregate in concrete has become popular, with large-scale research on that application being carried out at Columbia University in New York. Recycled glass greatly enhances the aesthetic appeal of the concrete. Recent research has shown that concrete made with recycled glass aggregates have better long-term strength and better thermal insulation, due to the thermal properties of the glass aggregates. Glass which is not recycled, but crushed, reduces the volume of waste sent to landfill. Waste glass may also be kept out of landfill by using it for roadbed aggregate.
Glass aggregate, a mix of colors crushed to a small size, is substituted for pea gravel or crushed rock in many construction and utility projects, saving municipalities, such as the City of Tumwater, Washington Public Works, thousands of dollars (depending on the size of the project). Glass aggregate is not sharp to handle. In many cases, the state Department of Transportation has specifications for use, size and percentage of quantity for use. Common applications are as pipe bedding—placed around sewer, storm water or drinking water pipes, to transfer weight from the surface and protect the pipe. Another common use is as fill to bring the level of a concrete floor even with a foundation. Foam glass gravel provides a lighter aggregate with other useful properties.
Other uses for recycled glass include:
*Fiberglass insulation products
*Ceramic production
*As a flux in brick manufacture
*Astroturf
*Agriculture and landscape applications, such as top dressing, root zone material or golf bunker sand
*Recycled glass countertops
*As water filtration media
*Abrasives
Mixed waste streams may be collected from materials recovery facilities or mechanical biological treatment systems. Some facilities can sort mixed waste streams into different colours using electro-optical sorting units. | 0 | Theoretical and Fundamental Chemistry |
The compound has two commercial uses.
It is used as an ingredient in Fluosol, artificial blood. This application exploits the high solubility of oxygen and carbon dioxide in the solvent, as well as the low viscosity and toxicity. It is also a component of Fluorinert coolant liquids. CPUs of some computers are immersed in this liquid to facilitate cooling. | 1 | Applied and Interdisciplinary Chemistry |
An inclusion is a solid particle in liquid aluminium alloy. It is usually non-metallic and can be of different nature depending on its source. | 1 | Applied and Interdisciplinary Chemistry |
Research into algae for the mass-production of oil focuses mainly on microalgae (organisms capable of photosynthesis that are less than 0.4 mm in diameter, including the diatoms and cyanobacteria) as opposed to macroalgae, such as seaweed. The preference for microalgae has come about due largely to their less complex structure, fast growth rates, and high oil-content (for some species). However, some research is being done into using seaweeds for biofuels, probably due to the high availability of this resource.
researchers across various locations worldwide have started investigating the following species for their suitability as a mass oil-producers:
* Botryococcus braunii
* Chlorella
* Dunaliella tertiolecta
* Gracilaria
* Pleurochrysis carterae (also called CCMP647).
* Sargassum, with 10 times the output volume of Gracilaria.
The amount of oil each strain of algae produces varies widely. Note the following microalgae and their various oil yields:
*Ankistrodesmus TR-87: 28–40% dry weight
*Botryococcus braunii: 29–75% dw
*Chlorella sp.: 29%dw
*Chlorella protothecoides(autotrophic/heterotrophic): 15–55% dw
*Crypthecodinium cohnii: 20%dw
*Cyclotella DI- 35: 42%dw
*Dunaliella tertiolecta : 36–42%dw
*Hantzschia DI-160: 66%dw
*Nannochloris: 31(6–63)%dw
*Nannochloropsis : 46(31–68)%dw
** Nannochloropsis and biofuels
*Neochloris oleoabundans: 35–54%dw
*Nitzschia TR-114: 28–50%dw
*Phaeodactylum tricornutum: 31%dw
*Scenedesmus TR-84: 45%dw
*Schizochytrium 50–77%dw
*Stichococcus: 33(9–59)%dw
*Tetraselmis suecica: 15–32%dw
*Thalassiosira pseudonana: (21–31)%dw
In addition, due to its high growth-rate, Ulva has been investigated as a fuel for use in the SOFT cycle, (SOFT stands for Solar Oxygen Fuel Turbine), a closed-cycle power-generation system suitable for use in arid, subtropical regions.
Other species used include Clostridium saccharoperbutylacetonicum, Sargassum, Gracilaria, Prymnesium parvum, and Euglena gracilis. | 1 | Applied and Interdisciplinary Chemistry |
Given a set of structurally diverse ligands that binds to a receptor, a model of the receptor can be built by exploiting the collective information contained in such set of ligands. Different computational techniques explore the structural, electronic, molecular shape, and physicochemical similarities of different ligands that could imply their mode of action against a specific molecular receptor or cell lines. A candidate ligand can then be compared to the pharmacophore model to determine whether it is compatible with it and therefore likely to bind. Different 2D chemical similarity analysis methods have been used to scan a databases to find active ligands. Another popular approach used in ligand-based virtual screening consist on searching molecules with shape similar to that of known actives, as such molecules will fit the target's binding site and hence will be likely to bind the target. There are a number of prospective applications of this class of techniques in the literature. Pharmacophoric extensions of these 3D methods are also freely-available as webservers. Also shape based virtual screening has gained significant popularity. | 1 | Applied and Interdisciplinary Chemistry |
Photosynthetic water splitting (or oxygen evolution) is one of the most important reactions on the planet, since it is the source of nearly all the atmosphere's oxygen. Moreover, artificial photosynthetic water-splitting may contribute to the effective use of sunlight as an alternative energy-source.
The mechanism of water oxidation is understood in substantial detail. The oxidation of water to molecular oxygen requires extraction of four electrons and four protons from two molecules of water. The experimental evidence that oxygen is released through cyclic reaction of oxygen evolving complex (OEC) within one PSII was provided by Pierre Joliot et al. They have shown that, if dark-adapted photosynthetic material (higher plants, algae, and cyanobacteria) is exposed to a series of single turnover flashes, oxygen evolution is detected with typical period-four damped oscillation with maxima on the third and the seventh flash and with minima on the first and the fifth flash (for review, see). Based on this experiment, Bessel Kok and co-workers introduced a cycle of five flash-induced transitions of the so-called S-states, describing the four redox states of OEC: When four oxidizing equivalents have been stored (at the S-state), OEC returns to its basic S-state. In the absence of light, the OEC will "relax" to the S state; the S state is often described as being "dark-stable". The S state is largely considered to consist of manganese ions with oxidation states of Mn, Mn, Mn, Mn. Finally, the intermediate S-states were proposed by Jablonsky and Lazar as a regulatory mechanism and link between S-states and tyrosine Z.
In 2012, Renger expressed the idea of internal changes of water molecules into typical oxides in different S-states during water splitting. | 0 | Theoretical and Fundamental Chemistry |
Per meg equals 0.001 permil or 0.0001 percent or parts per million ppm. The unit is typically used in isotope analysis by multiplying an isotope ratio in delta annotation, for example δO, by 1000000.
This annotation is typically used in studies of atmospheric trace gases, where a high precision is needed for a significant interpretation of results. | 0 | Theoretical and Fundamental Chemistry |
Thomas Haines was born on August 9, 1933, to Elsie Cubbon Haines (1894–1955) and Charles Haines, who deserted when Haines was two. In 1937, "by reason of the insanity of the mother", a judge placed him at the Graham School, an orphanage in Hastings-on-Hudson, New York. The orphanage, now a social services and foster care agency, was founded in 1806 by Isabella Graham and Elizabeth Hamilton, the recently widowed wife of Alexander Hamilton. Haines remained at the orphanage until high school, when he became a resident houseboy and gardener for a wealthy Hastings family. The story of Haines early life appears as "From the Orphanage to the Lab" in the Story Collider podcast. and in his autobiography with Mindy Lewis, A Curious Life: From Rebel Orphan to Innovative Scientist'.
Haines attended the City College of New York, with a B.S. in chemistry in 1957 and an M.S. in education in 1959. During that time he worked as live-in baby sitter for then-blacklisted American songwriter Jay Gorney (co-writer with Yip Harburg of the Depression era anthem, “Brother, Can You Spare a Dime?”) and his wife Sondra. There Haines came to know many other blacklisted professionals including actors Zero Mostel, Paul Robeson, and Lionel Stander, philosopher Barrows Dunham, and Bella Abzug, then a young lawyer defending blacklisted artists and intellectuals at HUAC hearings. | 1 | Applied and Interdisciplinary Chemistry |
Smooth mirror-like surfaces provide specular reflections, allowing easy detection of the acoustic wave. However, as surfaces become rougher the reflections become more diffuse, making detection of the acoustic wave more challenging for two reasons. Firstly, the reflected beam is spread out in a cone, as this cone increases in diameter less light is returned to the system - decreasing detection efficiency. Secondly, the light which is returned to the detector no longer exabits a gaussian intensity, instead the interfering wave fronts create a stochastic speckle pattern. However, many engineering processes impart an optically rough surface, for example additive manufacturing or forging, and there is a desire to make measurements on such components in their as manufactured state. To achieve this, an interferometric technique compatible with rough surfaces is required. For example, a Fabry–Pérot interferometer - which is inherently tolerant to speckle, two-wave mixing - which can adapt to the speckle pattern, or a speckle knife edge detector. With the use of such detection techniques, it is possible to make SRAS measurements on optically rough surfaces. | 0 | Theoretical and Fundamental Chemistry |
In 1889, Ludwig Mond discovered that the combustion of coal with air and steam produced ammonia along with an extra gas, which was named the Mond gas. He discovered this while looking for a process to form ammonium sulfate, which was useful in agriculture. The process involved reacting low-quality coal with superheated steam, which produced the Mond gas. The gas was then passed through dilute sulfuric acid spray, which ultimately removed the ammonia, forming ammonium sulfate.
Mond modified the gasification process by restricting the air supply and filling the air with steam, providing a low working temperature. This temperature was below ammonia's point of dissociation, maximizing the amount of ammonia that could be produced from the nitrogen, a product from superheating coal. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, anilides (or phenylamides) are a class of organic compounds with the general structure . They are amide derivatives of aniline (). | 0 | Theoretical and Fundamental Chemistry |
A quasiperiodic crystal, or quasicrystal, is a structure that is ordered but not periodic. A quasicrystalline pattern can continuously fill all available space, but it lacks translational symmetry. While crystals, according to the classical crystallographic restriction theorem, can possess only two-, three-, four-, and six-fold rotational symmetries, the Bragg diffraction pattern of quasicrystals shows sharp peaks with other symmetry orders—for instance, five-fold.
Aperiodic tilings were discovered by mathematicians in the early 1960s, and, some twenty years later, they were found to apply to the study of natural quasicrystals. The discovery of these aperiodic forms in nature has produced a paradigm shift in the field of crystallography. In crystallography the quasicrystals were predicted in 1981 by a five-fold symmetry study of Alan Lindsay Mackay,—that also brought in 1982, with the crystallographic Fourier transform of a Penrose tiling, the possibility of identifying quasiperiodic order in a material through diffraction.
Quasicrystals had been investigated and observed earlier, but, until the 1980s, they were disregarded in favor of the prevailing views about the atomic structure of matter. In 2009, after a dedicated search, a mineralogical finding, icosahedrite, offered evidence for the existence of natural quasicrystals.
Roughly, an ordering is non-periodic if it lacks translational symmetry, which means that a shifted copy will never match exactly with its original. The more precise mathematical definition is that there is never translational symmetry in more than n – 1 linearly independent directions, where n is the dimension of the space filled, e.g., the three-dimensional tiling displayed in a quasicrystal may have translational symmetry in two directions. Symmetrical diffraction patterns result from the existence of an indefinitely large number of elements with a regular spacing, a property loosely described as long-range order. Experimentally, the aperiodicity is revealed in the unusual symmetry of the diffraction pattern, that is, symmetry of orders other than two, three, four, or six. In 1982, materials scientist Dan Shechtman observed that certain aluminium–manganese alloys produced the unusual diffractograms which today are seen as revelatory of quasicrystal structures. Due to fear of the scientific community's reaction, it took him two years to publish the results for which he was awarded the Nobel Prize in Chemistry in 2011.
On 25 October 2018, Luca Bindi and Paul Steinhardt were awarded the Aspen Institute 2018 Prize for collaboration and scientific research between Italy and the United States, after they discovered icosahedrite, the first quasicrystal known to occur naturally. | 0 | Theoretical and Fundamental Chemistry |
* [https://web.archive.org/web/20130801074010/http://www.ccattbrams.org/wiki/index.php?title=About-CCATT-BRAMS CCATT-BRAMS]
* [http://ruc.noaa.gov/wrf/WG11/ WRF-Chem]
* CMAQ, [https://www.cmascenter.org/cmaq/ CMAQ Website]
* [http://www.camx.com/ CAMx]
* [http://www.geos-chem.org/ GEOS-Chem]
* [https://web.archive.org/web/20110724160533/http://www.lotos-euros.nl/index.html LOTOS-EUROS]
* [http://www.smhi.se/en/research/research-departments/air-quality/match-transport-and-chemistry-model-1.6831 MATCH]
* MOZART: (Model for OZone And Related chemical Tracers) is developed jointly by the (US) National Center for Atmospheric Research (NCAR), the Geophysical Fluid Dynamics Laboratory (GFDL), and the Max Planck Institute for Meteorology (MPI-Met) to simulate changes in ozone concentrations in the Earths atmosphere. MOZART was designed to simulate tropospheric chemical and transport processes, but has been extended (MOZART3) into the stratosphere and mesosphere. It can be driven by standard meteorological fields from, for example, the National Centers for Environmental Prediction (NCEP), the European Centre for Medium-Range Weather Forecasts (ECMWF) and the Global Modeling and Assimilation Office (GMAO), or by fields generated from general circulation models. MOZART4 improves MOZART2s chemical mechanisms, photolysis scheme, dry deposition mechanism, biogenic emissions and handling of tropospheric aerosols.
* TOMCAT/SLIMCAT
* [http://www.lmd.polytechnique.fr/chimere CHIMERE]
* [http://cerea.enpc.fr/polyphemus/ POLYPHEMUS]
* TCAM (Transport Chemical Aerosol Model; TCAM): a mathematical modelling method (computer simulation) designed to model certain aspects of the Earth's atmosphere. TCAM is one of several chemical transport models, all of which are concerned with the movement of chemicals in the atmosphere, and are thus used in the study of air pollution.
::TCAM is a multiphase three-dimensional eulerian grid model (as opposed to lagrangian or other modeling methods). It is designed for modelling dispersion of pollutants (in particular photochemical and aerosol) at mesoscales (medium scale, generally concerned with systems a few hundred kilometers in size).
::TCAM was developed at the University of Brescia in Italy. | 1 | Applied and Interdisciplinary Chemistry |
Utilizing powder metallurgy routes for titanium foam fabrication allows for production at lower temperatures than those required through a melt process and reduces overall risks for contamination. In loose-powder sintering (also known as gravity sintering), pores are created through diffusion bonding arising from the voids existing between packed powder particles. Axial compaction followed by sintering follows the same procedure as above, but pressures is applied for compaction of the precursor material. For both compaction methods, the resulting pore morphology is dependent upon the morphology of the metallic powder, making it difficult to control the size, shape, and distribution of the pores. Another disadvantage includes the relatively high probability of pore collapse and limited achievable porosity levels. | 0 | Theoretical and Fundamental Chemistry |
Sapropel (a contraction of Ancient Greek words sapros and pelos, meaning putrefaction and mud (or clay), respectively) is a term used in marine geology to describe dark-coloured sediments that are rich in organic matter. Organic carbon concentrations in sapropels commonly exceed 2 wt.% in weight.
The term sapropel events may also refer to cyclic oceanic anoxic event (OAE), in particular those affecting the Mediterranean Sea with a periodicity of about 21,000 years. | 0 | Theoretical and Fundamental Chemistry |
The Jameson Cell grew out of a long-term research program aimed at improving the recovery of fine particles by flotation. The work started at Imperial College London, and continued when Jameson moved in 1978 to the University of Newcastle, NSW, Australia, where he is Laureate Professor (2015). | 1 | Applied and Interdisciplinary Chemistry |
A cyclone sampler consists of a circular chamber with the aerosol stream entering through one or more tangential nozzles. Like an impactor, a cyclone sampler depends upon the inertia of the particle to cause it to deposit on the sampler wall as the air stream curves around inside the chamber. Also like an impactor, the collection efficiency depends upon the flow rate. Cyclones are less prone to particle bounce than impactors and can collect larger quantities of material. They also may provide a more gentle collection than impactors, which can improve the recovery of viable microorganisms. However, cyclones tend to have collection efficiency curves that are less sharp than impactors, and it is simpler to design a compact cascade impactor compared to a cascade of cyclone samplers. | 0 | Theoretical and Fundamental Chemistry |
The investigations in capillarity stem back as far as Leonardo da Vinci, however the idea of capillary length was not developed until much later. Fundamentally the capillary length is a product of the work of Thomas Young and Pierre Laplace. They both appreciated that surface tension arose from cohesive forces between particles and that the shape of a liquids surface reflected the short range of these forces. At the turn of the 19th century they independently derived pressure equations, but due to notation and presentation, Laplace often gets the credit. The equation showed that the pressure within a curved surface between two static fluids is always greater than that outside of a curved surface, but the pressure will decrease to zero as the radius approached infinity. Since the force is perpendicular to the surface and acts towards the centre of the curvature, a liquid will rise when the surface is concave and depress when convex. This was a mathematical explanation of the work published by James Jurin in 1719, where he quantified a relationship between the maximum height taken by a liquid in a capillary tube and its diameter – Jurins law. The capillary length evolved from the use of the Laplace pressure equation at the point it balanced the pressure due to gravity, and is sometimes called the Laplace capillary constant, after being introduced by Laplace in 1806. | 1 | Applied and Interdisciplinary Chemistry |
Bacterial adhesion involves the attachment (or deposition) of bacteria on the surface (solid, gel layer, etc.). This interaction plays an important role in natural system as well as in environmental engineering.
The attachment of biomass on the membrane surface will result in membrane fouling, which can significantly reduce the efficiency of the treatment system using membrane filtration process in wastewater treatment plants. The low adhesion of bacteria to soil is essential key for the success of in-situ bioremediation in groundwater treatment. However, the contamination of pathogens in drinking water could be linked to the transportation of microorganisms in groundwater and other water sources.
Controlling and preventing the adverse impact of the bacterial deposition on the aquatic environment need a deeply understanding about the mechanisms of this process. DLVO theory has been used extensively to describe the deposition of bacteria in many current researches. | 0 | Theoretical and Fundamental Chemistry |
Pyruvate dehydrogenase complex (PDC) is a complex of three enzymes that converts pyruvate into acetyl-CoA by a process called pyruvate decarboxylation. Acetyl-CoA may then be used in the citric acid cycle to carry out cellular respiration, and this complex links the glycolysis metabolic pathway to the citric acid cycle. Pyruvate decarboxylation is also known as the "pyruvate dehydrogenase reaction" because it also involves the oxidation of pyruvate.
This multi-enzyme complex is related structurally and functionally to the oxoglutarate dehydrogenase and branched-chain oxo-acid dehydrogenase multi-enzyme complexes. | 1 | Applied and Interdisciplinary Chemistry |
Ligands can be attached to liposomes through ligation to create ligand-targeted liposomes in a variety of ways. Liposomes have a lipid outer layer that can be used to bind ligands. Conjugation of the ligand to the surface of a liposome can be achieved through multiple routes. Covalent binding is a prominent way due to the anchoring between the long-chain fatty acids and the ligand. Combinations of covalent binding through disulfide linkages, heating, and hydrophobic interactions can be used depending on the properties of the liposome and ligand. Adsorption and membrane fusion are non-covalent methods for the attachment of monoclonal antibodies. Chemical linkages such as covalent bonds are more effective at increasing the amount of attached ligand to the carrier as opposed to non-covalent methods. During chemical coupling for manufacturing, it is crucial that ligands maintain their integrity when attached to the liposome surface. If ligands, such as antibodies, do not maintain binding specificity, proper orientation, and coupling efficiency the liposome will not be effective. | 1 | Applied and Interdisciplinary Chemistry |
Through the seasonal vertical migration of zooplankton, the lipid pump creates a net difference between lipids transported to the deep during the fall (when zooplankton enter diapause) and what returns to the surface during the spring, resulting in the sequestration of lipid carbon at depth. The biological pump encompasses many processes that sequester the CO taken up in the surface ocean by phytoplankton through the export of POC to the deep ocean. Although zooplankton are known to play important roles in the biological pump through grazing and the repackaging of particulate matter, the active transport of seasonally-migrating zooplankton through the lipid pump has not been incorporated into global estimates of the biological pump. | 0 | Theoretical and Fundamental Chemistry |
Several ECS journals which have ceased publication are now preserved as an archive. These archived publications are available through the Digital Library. | 0 | Theoretical and Fundamental Chemistry |
Ernst was married to Magdalena until his death. Together, they had three children: Anna Magdalena, Katharina Elisabeth and Hans-Martin Walter.
Besides toiling with his work, Ernst also enjoyed music and art, specifically Tibetan scroll art. Using scientific techniques, Ernst would research the pigments on the scrolls to learn about their geographic origin and age.
Ernst died on 4 June 2021 in Winterthur at the age of 87. | 0 | Theoretical and Fundamental Chemistry |
Hydroperoxides are mildly acidic. The range is indicated by 11.5 for Methyl hydroperoxide| to 13.1 for .
Hydroperoxides can be reduced to alcohols with lithium aluminium hydride, as described in this idealized equation:
This reaction is the basis of methods for analysis of organic peroxides. Another way to evaluate the content of peracids and peroxides is the volumetric titration with alkoxides such as sodium ethoxide.
The phosphite esters and tertiary phosphines also effect reduction: | 0 | Theoretical and Fundamental Chemistry |
Despite its increased efficacy, the edit inserted by PE2 might still be removed due to DNA mismatch repair of the edited strand. To avoid this problem during DNA heteroduplex resolution, an additional single guide RNA (sgRNA) is introduced. This sgRNA is designed to match the edited sequence introduced by the pegRNA, but not the original allele. It directs the Cas9 nickase portion of the fusion protein to nick the unedited strand at a nearby site, opposite to the original nick. Nicking the non-edited strand causes the cell's natural repair system to copy the information in the edited strand to the complementary strand, permanently installing the edit. However, there are drawbacks to this system as nicking the unaltered strand can lead to additional undesired indels. | 1 | Applied and Interdisciplinary Chemistry |
Abhik Ghosh (Bengali: অভীক ঘোষ) is an Indian inorganic chemist and materials scientist and a professor of chemistry at UiT – The Arctic University of Norway in Tromsø, Norway. | 0 | Theoretical and Fundamental Chemistry |
The first synthesis of tropinone was by Richard Willstätter in 1901. It started from the seemingly related cycloheptanone, but required many steps to introduce the nitrogen bridge; the overall yield for the synthesis path is only 0.75%. Willstätter had previously synthesized cocaine from tropinone, in what was the first synthesis and elucidation of the structure of cocaine. | 0 | Theoretical and Fundamental Chemistry |
According to the extremum principle of thermodynamics and , namely that at equilibrium the entropy is a maximum. This leads to a requirement that . This mathematical criterion expresses a physical condition which Epstein described as follows:
"It is obvious that this middle part, dotted in our curves [the place where the requirement is violated, dashed gray in Fig. 1 and repeated here], can have no physical reality. In fact, let us imagine the fluid in a state corresponding to this part of the curve contained in a heat conducting vertical cylinder whose top is formed by a piston. The piston can slide up and down in the cylinder, and we put on it a load exactly balancing the pressure of the gas. If we take a little weight off the piston, there will no longer be equilibrium and it will begin to move upward. However, as it moves the volume of the gas increases and with it its pressure. The resultant force on the piston gets larger, retaining its upward direction. The piston will, therefore, continue to move and the gas to expand until it reaches the state represented by the maximum of the isotherm. Vice versa, if we add ever so little to the load of the balanced piston, the gas will collapse to the state corresponding to the minimum of the isotherm"
While on an isotherm this requirement is satisfied everywhere so all states are gas, those states on an isotherm, which lie between the local minimum, , and local maximum, , for which (shown dashed gray in Fig. 1), are unstable and thus not observed. This is the genesis of the phase change; there is a range , for which no observable states exist. The states for are liquid and for are vapor; due to gravity the denser liquid lies below the vapor. The transition points, states with zero slope, are called spinodal points. Their locus is the spinodal curve that separates the regions of the plane for which liquid, vapor, and gas exist from a region where no observable states exist. This spinodal curve is obtained here from the vdW equation by differentiation (or equivalently from ) as
A projection of this space curve is plotted in Fig. 1 as the black dash dot curve. It passes through the critical point which is also a spinodal point. | 0 | Theoretical and Fundamental Chemistry |
Researchers in the field have developed approaches to produce living organs that are constructed with the appropriate biological and mechanical properties. 3D bioprinting is based on three main approaches: biomimicry, autonomous self-assembly and mini-tissue building blocks. | 1 | Applied and Interdisciplinary Chemistry |
* Oswald Helmuth Göhring: Über das neue Element Brevium und Versuche zur Auffindung seiner Isotopen. (About the new element brevium and attempts to locate its isotopes). PhD Thesis, Karlsruhe Technische Hochschule zu Fridericiana, 1914. 58 p.
* K. Fajans and OH Göhring, "Über das Uran X2-das neue Element der Uranreihe." ("Uranium X2, the new element in the uranium series") Phys. Zeitschrift, 1913, 14, 877-884. | 1 | Applied and Interdisciplinary Chemistry |
The Elbs reaction is an organic reaction describing the pyrolysis of an ortho methyl substituted benzophenone to a condensed polyaromatic. The reaction is named after its inventor, the German chemist Karl Elbs, also responsible for the Elbs oxidation. The reaction was published in 1884. Elbs however did not correctly interpret the reaction product due to a lack of knowledge about naphthalene structure. | 0 | Theoretical and Fundamental Chemistry |
Thioacetic acid is an organosulfur compound with the molecular formula . It is a thioic acid: the sulfur analogue of acetic acid (), as implied by the thio- prefix. It is a yellow liquid with a strong thiol-like odor. It is used in organic synthesis for the introduction of thiol groups () in molecules. | 0 | Theoretical and Fundamental Chemistry |
Solid supports for peptide synthesis are selected for physical stability, to permit the rapid filtration of liquids. Suitable supports are inert to reagents and solvents used during SPPS and allow for the attachment of the first amino acid. Swelling is of great importance because peptide synthesis takes place inside the swollen pores of the solid support.
Three primary types of solid supports are: gel-type supports, surface-type supports, and composites. Improvements to solid supports used for peptide synthesis enhance their ability to withstand the repeated use of TFA during the deprotection step of SPPS. Two primary resins are used, based on whether a C-terminal carboxylic acid or amide is desired. The Wang resin was, , the most commonly used resin for peptides with C-terminal carboxylic acids. | 1 | Applied and Interdisciplinary Chemistry |
In the late 19th century, scientists experimentally discovered that and do not absorb infrared radiation (called, at that time, "dark radiation"), while water (both as true vapor and condensed in the form of microscopic droplets suspended in clouds) and and other poly-atomic gaseous molecules do absorb infrared radiation. In the early 20th century, researchers realized that greenhouse gases in the atmosphere made Earths overall temperature higher than it would be without them. The term greenhouse' was first applied to this phenomenon by Nils Gustaf Ekholm in 1901.
During the late 20th century, a scientific consensus evolved that increasing concentrations of greenhouse gases in the atmosphere cause a substantial rise in global temperatures and changes to other parts of the climate system, with consequences for the environment and for human health. | 1 | Applied and Interdisciplinary Chemistry |
In biochemistry, saccharification is a term for denoting any chemical change wherein a monosaccharide molecule remains intact after becoming unbound from another saccharide.
For example, when a carbohydrate is broken into its component sugar molecules by hydrolysis (e.g., sucrose being broken down into glucose and fructose).
Enzymes such as amylases (e.g. in saliva) and glycoside hydrolase (e.g. within the brush border of the small intestine) are able to perform exact saccharification through enzymatic hydrolysis.
Through thermolysis, saccharification can also occur as a transient result, among many other possible effects, during caramelization. | 0 | Theoretical and Fundamental Chemistry |
In cellulose, glycosyl groups link together 1,4-β-D-glucosyl units to form chains of (1,4-β-D-glucosyl).
Other examples include ribityl in 6,7-Dimethyl-8-ribityllumazine, and glycosylamines. | 0 | Theoretical and Fundamental Chemistry |
* Cathodic reduction of carbon dioxide and anodic oxidation of acetonitrile afford cyanoacetic acid.
* An electrosynthesis employing alternating current prepares phenol at both the cathode and the anode. | 0 | Theoretical and Fundamental Chemistry |
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