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In addition to being manipulated for medical and energy applications, capillary pressure is the cause behind various natural phenomena as well. For example, needle ice, seen in cold soil, occurs via capillary action. The first major contributions to the study of needle ice, or simply, frost heaving were made by Stephen Taber (1929) and Gunnar Beskow (1935), who independently aimed to understand soil freezing. Taber’s initial work was related to understanding how the size of pores within the ground influenced the amount of frost heave. He also discovered that frost heave is favorable for crystal growth and that a gradient of soil moisture tension drives water upward toward the freezing front near the top of the ground. In Beskow’s studies, he defined this soil moisture tension as “capillary pressure” (and soil water as “capillary water”). Beskow determined that the soil type and effective stress on the soil particles influenced frost heave, where effective stress is the sum of pressure from above ground and the capillary pressure.
In 1961, D.H. Everett elaborated on Taber and Beskow’s studies to understand why pore spaces filled with ice continue to experience ice growth. He utilized thermodynamic equilibrium principles, a piston cylinder model for ice growth and the following equation to understand the freezing of water in porous media (directly applicable to the formation of needle ice):
where:
: is the pressure of the solid crystal
: is the pressure in the surrounding liquid
: is the interfacial tension between the solid and the liquid
: is the surface area of the phase boundary
: is the volume of the crystal
: is the mean curvature of the solid/liquid interface
With this equation and model, Everett noted the behavior of water and ice given different pressure conditions at the solid-liquid interface. Everett determined that if the pressure of the ice is equal to the pressure of the liquid underneath the surface, ice growth is unable to continue into the capillary. Thus, with additional heat loss, it is most favorable for water to travel up the capillary and freeze in the top cylinder (as needle ice continues to grow atop itself above the soil surface). As the pressure of the ice increases, a curved interface between the solid and liquid arises and the ice will either melt, or equilibrium will be reestablished so that further heat loss again leads to ice formation. Overall, Everett determined that frost heaving (analogous to the development of needle ice) occurs as a function of the pore size in the soil and the energy at the interface of ice and water. Unfortunately, the downside to Everett's model is that he did not consider soil particle effects on the surface. | 1 | Applied and Interdisciplinary Chemistry |
The major steps in the Sulfo-TK pathway are:
* isomerization of sulfoquinovose to sulfofructose (catalyzed by sulfoquinovose isomerase);
* transketol reaction of sulfofructose to release erythrose (catalyzed by sulfofructose transketolase, a thiamine diphosphate dependent enzyme), and transfer of the C2-moiety to glyceraldehyde phosphate, yielding xylulose-5-phosphate (Xu5P).
* 4-Sulfoerythrose is isomerized to 4-sulfoerythrulose (SEu), whereupon a second round of transketolase catalyzed reaction cleaves SE to sulfoacetaldehyde, while the C2-moiety is again transferred to an acceptor molecule, glyceraldehyde phosphate (GAP), yielding a second molecule of xylulose-5-phosphate (Xu5P).
* Finally, the sulfoacetaldehyde is reduced to isethionate and excreted.
The sulfoacetaldehyde may be oxidized to sulfoacetate. | 1 | Applied and Interdisciplinary Chemistry |
Alpha-cleavage (α-cleavage) in organic chemistry refers to the act of breaking the carbon-carbon bond adjacent to the carbon bearing a specified functional group. | 0 | Theoretical and Fundamental Chemistry |
Technically, Hammonds postulate only describes the geometric structure of a chemical reaction. However, Hammonds postulate indirectly gives information about the rate, kinetics, and activation energy of reactions. Hence, it gives a theoretical basis for the understanding the Bell-Evans-Polanyi principle, which describes the experimental observation that the enthalpy change and rate of similar reactions were usually correlated.
The relationship between Hammond's postulate and the BEP principle can be understood by considering a S1 reaction. Although two transition states occur during a S1 reaction (dissociation of the leaving group and then attack by the nucleophile), the dissociation of the leaving group is almost always the rate-determining step. Hence, the activation energy and therefore rate of the reaction will depend only upon the dissociation step.
First, consider the reaction at secondary and tertiary carbons. As the BEP principle notes, experimentally S1 reactions at tertiary carbons are faster than at secondary carbons. Therefore, by definition, the transition state for tertiary reactions will be at a lower energy than for secondary reactions. However, the BEP principle cannot justify why the energy is lower.
Using Hammond's postulate, the lower energy of the tertiary transition state means that its structure is relatively closer to its reactants R(tertiary)-X than to the carbocation "product" when compared to the secondary case. Thus, the tertiary transition state will be more geometrically similar to the R(tertiary)-X reactants than the secondary transition state is to its R(secondary)-X reactants. Hence, if the tertiary transition state is close in structure to the (low energy) reactants, then it will also be lower in energy because structure determines energy. Likewise, if the secondary transition state is more similar to the (high energy) carbocation "product," then it will be higher in energy. | 0 | Theoretical and Fundamental Chemistry |
Many S-N compounds are prepared from . Reaction with piperidine generates :
A related cation is also known, i.e. .
Treatment with tetramethylammonium azide produces the heterocycle :
Cyclo- has 10 pi-electrons.
In a related reaction, the use of the bis(triphenylphosphine)iminium azide gives a salt containing the blue anion:
The anion has a chain structure described using the resonance .
reacts with electron-poor alkynes.
Chlorination of gives thiazyl chloride.
Passing gaseous over silver metal yields the low temperature superconductor polythiazyl or polysulfurnitride (transition temperature (0.26±0.03) K), often simply called "(SN)". In the conversion, the silver first becomes sulfided, and the resulting silver sulfide| catalyzes the conversion of the into the four-membered ring , which readily polymerizes. | 0 | Theoretical and Fundamental Chemistry |
The Histone code hypothesis suggests the idea that patterns of post-translational modifications on histones, collectively, can direct specific cellular functions. Chemical modifications of histone proteins often occur on particular amino acids. This specific addition of single or multiple modifications on histone cores can be interpreted by transcription factors and complexes which leads to functional implications. This process is facilitated by enzymes such as HATs and HDACs that add or remove modifications on histones, and transcription factors that process and "read" the modification codes. The outcome can be activation of transcription or repression of a gene. For example, the combination of acetylation and phosphorylation have synergistic effects on the chromosomes overall structural condensation level and, hence, induces transcription activation of immediate early gene.
Experiments investigating acetylation patterns of H4 histones suggested that these modification patterns are collectively maintained in mitosis and meiosis in order to modify long-term gene expression. The acetylation pattern is regulated by HAT and HADC enzymes and, in turn, sets the local chromatin structure. In this way, acetylation patterns are transmitted and interconnected with protein binding ability and functions in subsequent cell generation. | 0 | Theoretical and Fundamental Chemistry |
The dominant luminous component in a cluster of galaxies is the 10 to 10 kelvin intracluster medium. The emission from the intracluster medium is characterized by thermal bremsstrahlung. This radiation is in the energy range of X-rays and can be easily observed with space-based telescopes such as Chandra X-ray Observatory, XMM-Newton, ROSAT, ASCA, EXOSAT, Suzaku, RHESSI and future missions like IXO [https://web.archive.org/web/20080303062108/http://constellation.gsfc.nasa.gov/] and Astro-H [https://web.archive.org/web/20071112015825/http://www.astro.isas.ac.jp/future/NeXT/].
Bremsstrahlung is also the dominant emission mechanism for H II regions at radio wavelengths. | 0 | Theoretical and Fundamental Chemistry |
Different blocking agents for isocyanates have different unblocking temperatures.
* Sodium bisulfite
* Diethyl malonate =
* 3,5-Dimethylpyrazole =
* MEKO =
* Phenol =
* Caprolactam = | 0 | Theoretical and Fundamental Chemistry |
Tollmien (1931) and Schlichting (1929) theorized that viscosity-induced grabbing and releasing of laminae created long-crested simple harmonic (SH) oscillations (vibrations) along a smooth flat boundary, at a flow rate approaching the onset of turbulence. These T-S waves would gradually increase in amplitude until they broke up into the vortices, noise and high resistance that characterize turbulent flow. Contemporary wind tunnels failed to show T-S waves.
In 1943, Schubauer and Skramstad (S and S) created a wind tunnel that went to extremes to damp mechanical vibrations and sounds that might affect the airflow studies along a smooth flat plate. Using a vertical array of evenly spaced hot wire anemometers in the boundary layer (BL) airflow, they substantiated the existence of T-S oscillations by showing SH velocity fluctuations in the BL laminae. The T-S waves gradually increased in amplitude until a few random spikes of in-phase amplitude appeared, triggering focal vortices (turbulent spots), with noise. A further increase in flow rate resulted suddenly in many vortices, aerodynamic noise and a great increase in resistance to flow. An oscillation of a mass in a fluid creates a sound wave; SH oscillations of a mass of fluid, flowing in that same fluid along a boundary, must result in SH sound, reflected off the boundary, transversely into the fluid.
S and S found foci of in-phase spiking amplitude in the T-S waves; these must create bursts of high amplitude sound, with high energy oscillation of fluid molecules transversely through the BL laminae. This has the potential to freeze laminar slip (laminar interlocking) in these spots, transferring the resistance to the boundary: this breaking at the boundary could rip out pieces of T-S long-crested waves which would tumble head-over-heels downstream in the boundary layer as the vortices of turbulent spots. With further increase in flow rate, there is an explosion into turbulence, with many random vortices and the noise of aerodynamic sound.
Schubauer and Skramstad overlooked the significance of the co-generation of transverse SH sound by the T-S waves in transition and turbulence. However, John Tyndall (1867) in his transition-to-turbulence flow studies using flames, deduced that SH waves were created during transition by viscosity acting around the walls of a tube and these could be amplified by blending with similar SH sound waves (from a whistle), triggering turbulence at lower flow rates. Schubauer and Skramstad introduced SH sound into the boundary layer by creating SH fluttering vibrations of a BL ferromagnetic ribbon in their 1941 experiments, similarly triggering turbulence at lower flow rates.
Tyndall’s contribution towards explaining the mystery of transition to turbulence 150 years ago is beginning to gain recognition. | 1 | Applied and Interdisciplinary Chemistry |
″There was once a time when sawmill operators could barely give away their sawdust. They dumped it in the woods or incinerated it just to get rid of the stuff. These days, they have ready markets for sawdust…″, according to a report in 2008. For example, sawdust is used by biomass power plants as fuel or is sold to dairy farmers as animal bedding. | 1 | Applied and Interdisciplinary Chemistry |
Iron is an essential bioelement for most forms of life, from bacteria to mammals. Its importance lies in its ability to mediate electron transfer. In the ferrous state (Fe), iron acts as an electron donor, while in the ferric state (Fe) it acts as an acceptor. Thus, iron plays a vital role in the catalysis of enzymatic reactions that involve electron transfer (reduction and oxidation, redox). Proteins can contain iron as part of different cofactors, such as iron–sulfur clusters (Fe-S) and heme groups, both of which are assembled in mitochondria. | 1 | Applied and Interdisciplinary Chemistry |
The main subprocesses of sensor-based sorting are material conditioning, material presentation, detection, data processing and separation.
* Material conditioning includes all operations which prepare the particles for being detected by the sensor. All optical sensors need clean material to be able to detect optical characteristics. Conditioning includes screening and cleaning of the feed material.
* The aim of the material presentation is the isolation of the particles by creating a single particle layer with the densest surface cover possible without particles touching each other and enough distance to each other allowing for a selective detection and rejection of each single particle.
There are two types of sensor-based sorters: the chute type and the belt type. For both types the first step in acceleration is spreading out the particles by a vibrating feeder followed by either a fast belt or a chute. On the belt type the sensor usually detects the particles horizontally while they pass it on the belt. For the chute type the material detection is usually done vertically while the material passes the sensor in a free fall. The data processing is done in real time by a computer. The computer transfers the result of the data processing to an ultra fast ejection unit which, depending on the sorting decision, ejects a particle or lets it pass. | 0 | Theoretical and Fundamental Chemistry |
Quantitative PCR (Q-PCR) is used to measure the quantity of a PCR product (preferably real-time, QRT-PCR). It is the method of choice to quantitatively measure amounts of transgene DNA in a food or feed sample. Q-PCR is commonly used to determine whether a DNA sequence is present in a sample and the number of its copies in the sample. The method with currently the highest level of accuracy is quantitative real-time PCR. QRT-PCR methods use fluorescent dyes, such as Sybr Green, or fluorophore-containing DNA probes, such as TaqMan, to measure the amount of amplified product in real time. If the targeted genetic sequence is unique to a certain GMO, a positive PCR test proves that the GMO is present in the sample. | 1 | Applied and Interdisciplinary Chemistry |
In the 1960s and 1970s various groups reported the ring-opening polymerization of norbornene catalyzed by hydrated trichlorides of ruthenium and other late transition metals in polar, protic solvents. This prompted Robert H. Grubbs and coworkers to search for well-defined, functional group tolerant catalysts based on ruthenium. The Grubbs group successfully polymerized the 7-oxo norbornene derivative using ruthenium trichloride, osmium trichloride as well as tungsten alkylidenes. They identified a Ru(II) carbene as an effective metal center and in 1992 published the first well-defined, ruthenium-based olefin metathesis catalyst, (PPh)ClRu=CHCH=CPh:
The corresponding tricyclohexylphosphine complex (PCy)ClRu=CHCH=CPh was also shown to be active. This work culminated in the now commercially available 1st generation Grubbs catalyst. | 0 | Theoretical and Fundamental Chemistry |
Wide varieties of aromatic compounds are enzymatically reduced to form free radicals that contain one more electron than their parent compounds. In general, the electron donor is any of a wide variety of flavoenzymes and their coenzymes. Once formed, these anion free radicals reduce molecular oxygen to superoxide and regenerate the unchanged parent compound. The net reaction is the oxidation of the flavoenzyme's coenzymes and the reduction of molecular oxygen to form superoxide. This catalytic behavior has been described as a futile cycle or redox cycling. | 0 | Theoretical and Fundamental Chemistry |
Since 2011, the MOSE control centre and management functions for the lagoon system have been located in the Venice Arsenal, symbol of the former trading and military might of the historic Serenissima or "Serene Republic". Numerous historical buildings, in a state of decay and abandonment for decades, have already been restored and reorganisation of the area is underway to accommodate these new activities.
Restoration has enabled a heritage of extraordinary historical and architectural value to be safeguarded and allowed buildings to be recovered and re-utilised. As home to MOSE management and control the arsenal will receive a new lease of life after years of abandonment, allowing its renaissance as a place of innovation and production, with important economic repercussions for the city and local area.
The historic arsenal buildings before and after restoration and construction of infrastructure to accommodate the new functions are shown below.
In the control centre, key decisions will be taken on raising and lowering the mobile barriers according to measurements made by tide gauges positioned in front of the lagoon inlets to record the rising tide in real time. The command to raise the gate will be given when water reaches the level established by the procedure to begin the manoeuvre and guarantee that the water level in the lagoon does not exceed the requisite safe level. | 1 | Applied and Interdisciplinary Chemistry |
In fluid dynamics, a blast wave is the increased pressure and flow resulting from the deposition of a large amount of energy in a small, very localised volume. The flow field can be approximated as a lead shock wave, followed by a self-similar subsonic flow field. In simpler terms, a blast wave is an area of pressure expanding supersonically outward from an explosive core. It has a leading shock front of compressed gases. The blast wave is followed by a blast wind of negative gauge pressure, which sucks items back in towards the center. The blast wave is harmful especially when one is very close to the center or at a location of constructive interference. High explosives that detonate generate blast waves. | 1 | Applied and Interdisciplinary Chemistry |
Gene symbols are italicised and all letters are in lowercase (shh). Protein designations are the same as the gene symbol, but are not italicised; the first letter is in uppercase and the remaining letters are in lowercase (Shh). | 1 | Applied and Interdisciplinary Chemistry |
A half-life often describes the decay of discrete entities, such as radioactive atoms. In that case, it does not work to use the definition that states "half-life is the time required for exactly half of the entities to decay". For example, if there is just one radioactive atom, and its half-life is one second, there will not be "half of an atom" left after one second.
Instead, the half-life is defined in terms of probability: "Half-life is the time required for exactly half of the entities to decay on average". In other words, the probability of a radioactive atom decaying within its half-life is 50%.
For example, the accompanying image is a simulation of many identical atoms undergoing radioactive decay. Note that after one half-life there are not exactly one-half of the atoms remaining, only approximately, because of the random variation in the process. Nevertheless, when there are many identical atoms decaying (right boxes), the law of large numbers suggests that it is a very good approximation to say that half of the atoms remain after one half-life.
Various simple exercises can demonstrate probabilistic decay, for example involving flipping coins or running a statistical computer program. | 0 | Theoretical and Fundamental Chemistry |
Surface or ground water abstracted for the supply of drinking water must be capable of meeting rigorous chemical standards following treatment. This requires a detailed knowledge of the water entering the treatment plant. In addition to the normal suite of environmental chemical parameters, other parameters such as hardness, phenol, oil and in some cases a real-time organic profile of the incoming water as in the River Dee regulation scheme. | 0 | Theoretical and Fundamental Chemistry |
The clinical use of most antibiotics result in a mutation of the pathogen organism leading to their resistance against the drug. Therefore, development of new drugs is always needed. A potential first step in developing new drugs against currently threatening diseases (e.g. tuberculosis) is to find new drug targets in the causative agent of the disease, i.e. the pathogen microorganism, let it be either a bacterium, or a protozoan parasite. After finding the target protein in the bacterium (or protozoan parasite), one could design small molecular drug compounds that bind to the protein and inhibit it.
Public availability of biological network data makes the process of searching for new drug targets easier than it was before. By using the available metabolic networks, it is possible to find important nodes with link analysis algorithms, like PageRank. In a recently published paper, biochemical reactions are treated as nodes of the metabolic network. In this directed network, reaction A has a directed edge towards reaction B if the product of the former enters the latter reaction as a substrate or co-factor.
To select important nodes that could serve as drug targets, we might think of selecting high in-degree nodes (hubs; nodes with many incoming edges). It was shown however[2], that targeting hub proteins with many vital functions may unintentionally harm the living cell as well. A PageRank-based scoring method could detect important nodes that are not hubs and therefore might be better drug targets.
The PageRank of a node A is the stationary limit probability distribution that the random walker is at node A. In its original application, the personalization vector w captured the personal interest of a web-surfer: interesting websites to a surfer appeared with a higher probability in the distribution given in vector w. In this metabolic network, w is personalized to proteins; w is larger for those proteins that appear in higher concentrations in the proteomics analysis of certain diseases. This personalized PageRank may identify other related proteins to the disease.
However, by using only the personalized PageRank to identify important nodes, hubs still get a high score on average. To find non-hub important nodes instead, we should consider scoring the nodes by their "relativized personalized PageRank"; i.e. their personalized PageRank scores over the number of edges pointing towards them (over their in-degree):
The relativized personalized PageRank (rPPR(v)) for a node v is given by:
where PpageRank(v) is the personalized PageRank score of node v, and d_(v) is its in-degree. It was shown, that by using this method, numerous already validated drug targets can be found (e.g. in the Mycobacterium tuberculosis), therefore, new, currently unknown targets might be detected as well. | 1 | Applied and Interdisciplinary Chemistry |
*Materials Performance magazine
*CoatingsPro magazine
*CORROSION journal
*technical and reference books
*podcasts and webcasts | 1 | Applied and Interdisciplinary Chemistry |
The term agostic, derived from the Ancient Greek word for "to hold close to oneself", was coined by Maurice Brookhart and Malcolm Green, on the suggestion of the classicist Jasper Griffin, to describe this and many other interactions between a transition metal and a C−H bond. Often such agostic interactions involve alkyl or aryl groups that are held close to the metal center through an additional σ-bond.
Short interactions between hydrocarbon substituents and coordinatively unsaturated metal complexes have been noted since the 1960s. For example, in tris(triphenylphosphine) ruthenium dichloride, a short interaction is observed between the ruthenium(II) center and a hydrogen atom on the ortho position of one of the nine phenyl rings. Complexes of borohydride are described as using the three-center two-electron bonding model.
The nature of the interaction was foreshadowed in main group chemistry in the structural chemistry of trimethylaluminium. | 0 | Theoretical and Fundamental Chemistry |
The outbreak of hostilities in eastern Ukraine in 2014 complicated the activities of the enterprise. As a result, the plant ended 2014 with a net loss of UAH 4,871.533 million. In the first nine months of 2015, the plant produced 426 thousand tons of pig iron and 1.664 million tons of grade K coal concentrate, but losses continued to increase.
In June 2016, the leadership of the unrecognized DPR introduced external management at the plant, by which time its communications and a significant part of the equipment had become unusable due to repeated shutdowns and long downtime.
Also in June 2016, on the basis of the Donetsk Electrometallurgical Plant (DEMP), the state enterprise Yuzovsky Metallurgical Plant was opened. The YuMZ industrial complex is located on the same territory as the Donetsk Metallurgical Plant, which, in turn, is located in three districts of the DPR capital at once - Voroshilovsky, Budenovsky, Leninsk.
It was Re-launched on October 5, 2017.
In 2018 YuMZ began to supply products to Turkey, Iran and Syria.
Since May 1, 2019, blast-furnace production has been stopped. The company does not manufacture products. During the heating period of 2019–2020, only the factory CHPP-PVS and related power plants worked, in order to supply heat to part of the above three districts of the city of Donetsk.
From March to August 2020, the plant suspended work due to a shortage of raw materials. As of November 2020, the YuMZ complex, separated from the main part of the plant, continues to produce steel, specializing in the production of continuously cast square billets. The workforce consists of 858 people.
At the DMZ, there are energy workshops that provide transit and supply to factory consumers and sub-consumers of drinking and industrial water, electricity, natural gas, steam and hot water. | 1 | Applied and Interdisciplinary Chemistry |
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