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In 2022, it was found that levels of at least four perfluoroalkyl acids (PFAAs) in rainwater worldwide ubiquitously and often greatly exceeded the EPA's lifetime drinking water health advisories as well as comparable Danish, Dutch, and European Union safety standards, leading to the conclusion that "the global spread of these four PFAAs in the atmosphere has led to the planetary boundary for chemical pollution being exceeded". There are some moves to restrict and replace their use. | 0 | Theoretical and Fundamental Chemistry |
* Passau, Germany, sometimes called the (City of Three Rivers), is the site of a triple confluence, described thus in a guidebook: "from the north the little Ilz sluices brackish water down from the peat-rich Bavarian Forest, meeting the cloudy brown of the Danube as it flows from the west and the pale snow-melt jade of the Inn from the south [i.e., the Alps] to create a murky tricolour."
* The Thaya flows into the Morava in a rural location near Hohenau an der March in Austria, forming the tripoint of Austria, Czechia, and Slovakia.
* The Morava flows into the Danube at Devín, on the border between Slovakia and Austria.
* The Sava flows into the Danube at Belgrade, the capital of Serbia.
* In karst topography, which arises in soluble rock, rivers sometimes flow underground and form subterranean confluences, as at Planina Cave in Slovenia, where the Pivka and Rak merge to form the Unica. | 1 | Applied and Interdisciplinary Chemistry |
Despite its demise, Cement is an important part of California's history and culture. The remaining ruins serve as a reminder of the impact that the cement industry had on the region and the lives of its residents. Cement still interests people wondering about the history of the cement industry, the American West, the ghost town, and its past.
Cement is privately owned land and the owner's permission is required to visit the property that is approximately . | 1 | Applied and Interdisciplinary Chemistry |
A range of different methods exist for the measurement of sound in air.
The earliest reasonably accurate estimate of the speed of sound in air was made by William Derham and acknowledged by Isaac Newton. Derham had a telescope at the top of the tower of the Church of St Laurence in Upminster, England. On a calm day, a synchronized pocket watch would be given to an assistant who would fire a shotgun at a pre-determined time from a conspicuous point some miles away, across the countryside. This could be confirmed by telescope. He then measured the interval between seeing gunsmoke and arrival of the sound using a half-second pendulum. The distance from where the gun was fired was found by triangulation, and simple division (distance/time) provided velocity. Lastly, by making many observations, using a range of different distances, the inaccuracy of the half-second pendulum could be averaged out, giving his final estimate of the speed of sound. Modern stopwatches enable this method to be used today over distances as short as 200–400 metres, and not needing something as loud as a shotgun. | 1 | Applied and Interdisciplinary Chemistry |
Fas forms the death-inducing signaling complex (DISC) upon ligand binding. Membrane-anchored Fas ligand trimer on the surface of an adjacent cell causes oligomerization of Fas.
Recent studies which suggested the trimerization of Fas could not be validated. Other models suggested the oligomerization up to 5–7 Fas molecules in the DISC.
This event is also mimicked by binding of an agonistic Fas antibody, though some evidence suggests that the apoptotic signal induced by the antibody is unreliable in the study of Fas signaling. To this end, several clever ways of trimerizing the antibody for in vitro research have been employed.
Upon ensuing death domain (DD) aggregation, the receptor complex is internalized via the cellular endosomal machinery. This allows the adaptor molecule FADD to bind the death domain of Fas through its own death domain.
FADD also contains a death effector domain (DED) near its amino terminus, which facilitates binding to the DED of FADD-like interleukin-1 beta-converting enzyme (FLICE), more commonly referred to as caspase-8. FLICE can then self-activate through proteolytic cleavage into p10 and p18 subunits, two each of which form the active heterotetramer enzyme. Active caspase-8 is then released from the DISC into the cytosol, where it cleaves other effector caspases, eventually leading to DNA degradation, membrane blebbing, and other hallmarks of apoptosis.
Recently, Fas has also been shown to promote tumor growth, since during tumor progression, it is frequently downregulated or cells are rendered apoptosis resistant. Cancer cells in general, regardless of their Fas apoptosis sensitivity, depend on constitutive activity of Fas. This is stimulated by cancer-produced Fas ligand for optimal growth.
Although Fas has been shown to promote tumor growth in the above mouse models, analysis of the human cancer genomics database revealed that FAS is not significantly focally amplified across a dataset of 3131 tumors (FAS is not an oncogene), but is significantly focally deleted across the entire dataset of these 3131 tumors, suggesting that FAS functions as a tumor suppressor in humans.
In cultured cells, FasL induces various types of cancer cell apoptosis through the Fas receptor. In AOM-DSS-induced colon carcinoma and MCA-induced sarcoma mouse models, it has been shown that Fas acts as a tumor suppressor. Furthermore, the Fas receptor also mediates tumor-specific cytotoxic T lymphocyte (CTL) anti-tumor cytotoxicity. In addition to the well-described on-target CTL anti-tumor cytotoxicity, Fas has been ascribed with a distinct function – the induction of bystander tumor cell death even amongst cognate antigen non-expressing (bystander) cells. CTL-mediated bystander killing was described by the Fleischer Lab in 1986 and later attributed to fas-mediated lysis in vitro by the Austin Research Institute, Cellular Cytotoxicity Laboratory. More recently, fas-mediated bystander tumor cell killing was demonstrated in vivo by the Lymphoma Immunotherapy Program at Mount Sinai School of Medicine using T cells and CAR-T cells, similar to additional in vitro work using bispecific antibodies performed at Amgen. | 1 | Applied and Interdisciplinary Chemistry |
A hydrogen bond (H-bond), is a specific type of interaction that involves dipole–dipole attraction between a partially positive hydrogen atom and a highly electronegative, partially negative oxygen, nitrogen, sulfur, or fluorine atom (not covalently bound to said hydrogen atom). It is not a covalent bond, but instead is classified as a strong non-covalent interaction. It is responsible for why water is a liquid at room temperature and not a gas (given water's low molecular weight). Most commonly, the strength of hydrogen bonds lies between 0–4 kcal/mol, but can sometimes be as strong as 40 kcal/mol In solvents such as chloroform or carbon tetrachloride one observes e.g. for the interaction between amides additive values of about 5 kJ/mol. According to Linus Pauling the strength of a hydrogen bond is essentially determined by the electrostatic charges. Measurements of thousands of complexes in chloroform or carbon tetrachloride have led to additive free energy increments for all kind of donor-acceptor combinations. | 0 | Theoretical and Fundamental Chemistry |
By analogy to the above, one can use an anion exchange (positively charged) column surface chemistry to reduce the influence on retention of cationic (positively charged) functional groups for a set of analytes, such as when selectively isolating phosphorylated peptides or sulfated polysaccharide molecules. Use of a pH between 1 and 2 pH units will reduce the polarity of two of the three ionizable oxygens of the phosphate group, and thus will allow easy desorption from the (oppositely charged) surface chemistry. It will also reduce the influence of negatively charged carboxyls in the analytes, since they will be protonated at this low a pH value, and thus contribute less overall polarity to the molecule. Any common, positively charged amino groups will be repelled from the column surface chemistry and thus these conditions enhance the role of the phosphate's polarity (as well as other neutral polar groups) in the separation. | 1 | Applied and Interdisciplinary Chemistry |
Sintering or frittage is the process of compacting and forming a solid mass of material by pressure or heat without melting it to the point of liquefaction. Sintering happens as part of a manufacturing process used with metals, ceramics, plastics, and other materials. The nanoparticles in the sintered material diffuse across the boundaries of the particles, fusing the particles together and creating a solid piece.
Since the sintering temperature does not have to reach the melting point of the material, sintering is often chosen as the shaping process for materials with extremely high melting points, such as tungsten and molybdenum. The study of sintering in metallurgical powder-related processes is known as powder metallurgy.
An example of sintering can be observed when ice cubes in a glass of water adhere to each other, which is driven by the temperature difference between the water and the ice. Examples of pressure-driven sintering are the compacting of snowfall to a glacier, or the formation of a hard snowball by pressing loose snow together.
The material produced by sintering is called sinter. The word sinter comes from the Middle High German , a cognate of English cinder. | 1 | Applied and Interdisciplinary Chemistry |
* Orbifold signature:
* Coxeter notation (rhombic): [∞,2,∞]
* Coxeter notation (square): [(4,4,2)]
* Lattice: rhombic
* Point group: D
* The group cmm has reflections in two perpendicular directions, and a rotation of order two (180°) whose centre is not on a reflection axis. It also has two rotations whose centres are on a reflection axis.
*This group is frequently seen in everyday life, since the most common arrangement of bricks in a brick building (running bond) utilises this group (see example below).
The rotational symmetry of order 2 with centres of rotation at the centres of the sides of the rhombus is a consequence of the other properties.
The pattern corresponds to each of the following:
*symmetrically staggered rows of identical doubly symmetric objects
*a checkerboard pattern of two alternating rectangular tiles, of which each, by itself, is doubly symmetric
*a checkerboard pattern of alternatingly a 2-fold rotationally symmetric rectangular tile and its mirror image
;Examples of group cmm | 0 | Theoretical and Fundamental Chemistry |
The most studied mesoionic carbenes are based on imidazole and are referred to as imidazolin-4-ylidenes. These complexes were first reported by Crabtree in 2001. The formation of imidazolin-4-ylidenes (MIC) instead of imidazolin-2-ylidenes (NHC) is typically a matter of blocking the C2 position. Most imidazolin-4-ylidenes are trisubstituted in the N1, C2, and N3 positions or tetrasubstituted. Electron-withdrawing groups in the N3 and C5 positions stabilize the carbenes more than electron-donating groups. Free carbenes as well as numerous transition metal complexes have been synthesized. | 0 | Theoretical and Fundamental Chemistry |
In 2006 Goossen et al. proposed a reaction to synthesize biaryl compounds via catalytic decarboxylative cross coupling.
The mechanism involves two overlapping cycles, one using a copper halide and the other using palladium. The decarboxylation step occurs between the substituted benzoic acid and copper halide to form the intermediate aryl copper species. The palladium initially undergoes oxidative addition from the aryl halide to form a Pd(II) aryl complex. After both of these initial steps, the substituted aryl copper undergoes trans-metalation with the palladium complex. This step forms the copper halide, which then undergoes anion exchange with the substituted benzoic acid to reform the aryl copper intermediate, continuing the catalytic cycle. The other complex formed in the trans-metalation step is a bis-aryl palladium(II), which then undergoes reductive elimination to form the desired bis-aryl species as well as the starting Pd(0) complex, thus completing the catalytic cycle. | 0 | Theoretical and Fundamental Chemistry |
Typically, supercritical fluids are completely miscible with each other, so that a binary mixture forms a single gaseous phase if the critical point of the mixture is exceeded. However, exceptions are known in systems where one component is much more volatile than the other, which in some cases form two immiscible gas phases at high pressure and temperatures above the component critical points. This behavior has been found for example in the systems N-NH, NH-CH, SO-N and n-butane-HO.
The critical point of a binary mixture can be estimated as the arithmetic mean of the critical temperatures and pressures of the two components,
where χ denotes the mole fraction of component i.
For greater accuracy, the critical point can be calculated using equations of state, such as the Peng–Robinson, or group-contribution methods. Other properties, such as density, can also be calculated using equations of state. | 0 | Theoretical and Fundamental Chemistry |
Ulrike Diebold (born 12 December 1961, in Kapfenberg, Austria) is an Austrian physicist and materials scientist who is a professor of surface science at TU Vienna. She is known for her groundbreaking research on the atomic scale geometry and electronic structure of metal-oxide surfaces. | 0 | Theoretical and Fundamental Chemistry |
If the solubility, S, of an organic compound is known or predicted in both water and 1-octanol, then log P can be estimated as
There are a variety of approaches to predict solubilities, and so log S. | 0 | Theoretical and Fundamental Chemistry |
Electron scattering occurs when electrons are displaced from their original trajectory. This is due to the electrostatic forces within matter interaction or, if an external magnetic field is present, the electron may be deflected by the Lorentz force. This scattering typically happens with solids such as metals, semiconductors and insulators; and is a limiting factor in integrated circuits and transistors.
The application of electron scattering is such that it can be used as a high resolution microscope for hadronic systems, that allows the measurement of the distribution of charges for nucleons and nuclear structure. The scattering of electrons has allowed us to understand that protons and neutrons are made up of the smaller elementary subatomic particles called quarks.
Electrons may be scattered through a solid in several ways:
*Not at all: no electron scattering occurs at all and the beam passes straight through.
*Single scattering: when an electron is scattered just once.
*Plural scattering: when electron(s) scatter several times.
*Multiple scattering: when electron(s) scatter many times over.
The likelihood of an electron scattering and the degree of the scattering is a probability function of the specimen thickness to the mean free path. | 0 | Theoretical and Fundamental Chemistry |
Microbial biodegradation is the use of bioremediation and biotransformation methods to harness the naturally occurring ability of microbial xenobiotic metabolism to degrade, transform or accumulate environmental pollutants, including hydrocarbons (e.g. oil), polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), heterocyclic compounds (such as pyridine or quinoline), pharmaceutical substances, radionuclides and metals.
Interest in the microbial biodegradation of pollutants has intensified in recent years, and recent major methodological breakthroughs have enabled detailed genomic, metagenomic, proteomic, bioinformatic and other high-throughput analyses of environmentally relevant microorganisms, providing new insights into biodegradative pathways and the ability of organisms to adapt to changing environmental conditions.
Biological processes play a major role in the removal of contaminants and take advantage of the catabolic versatility of microorganisms to degrade or convert such compounds. In environmental microbiology, genome-based global studies are increasing the understanding of metabolic and regulatory networks, as well as providing new information on the evolution of degradation pathways and molecular adaptation strategies to changing environmental conditions. | 1 | Applied and Interdisciplinary Chemistry |
* Killick, D. 2004. Review Essay: "What Do We Know About African Iron Working?" Journal of African Archaeology. Vol 2 (1) pp. 135–152
* Bocoum, H. (ed.), 2004, The origins of iron metallurgy in Africa – New lights on its antiquity, H. Bocoum (ed.), UNESCO publishing
* Schmidt, P.R., Mapunda, B.B., 1996. "Ideology and the Archaeological Record in Africa: Interpreting Symbolism in Iron Smelting Technology". Journal of Anthropological Archaeology. Vol 16, pp. 73–102
* Rehren, T., Charlton, M., Shadrek, C., Humphris, J., Ige, A., Veldhuijen, H.A. "Decisions set in slag: the human factor in African iron smelting". La Niece, S., Hook, D., and Craddock, P., (eds). Metals and mines : studies in archaeometallurgy. 2007, pp. 211–218.
* Okafor, E.E., 1993. "New Evidence on Early Iron-Smelting from Southeastern Nigeria". Shaw, T., Sinclair, P., Bassey, A., Okpoko, A (eds). The Archaeology of Africa Food, Metals and Towns. London, Routledge, pp. 432–448
* Kense, F.J., and Okora, J.A., 1993. "Changing Perspectives on Traditional Iron Production in West Africa". Shaw, T., Sinclair, P., Bassey, A., Okpoko, A (eds). The Archaeology of Africa Food, Metals and Towns. London, Routledge, pp. 449– 458
* Muhammed, I.M., 1993. "Iron Technology in the Middle Sahel/Savanna: With Emphasis on Central Darfur". Shaw, T., Sinclair, P., Bassey, A., Okpoko, A (eds). The Archaeology of Africa Food, Metals and Towns. London, Routledge, pp. 459–467
* Buleli, NS., 1993. Iron-Making Techniques in the Kivu Region of Zaire: Some of the Differences Between the South Maniema Region and North Kivu. Shaw, T., Sinclair, P., Bassey, A., Okpoko, A (eds). The Archaeology of Africa Food, Metals and Towns'. London, Routledge, pp. 468–477
* Radimilahy, C., 1993 "Ancient Iron-Working in Madagascar". Shaw, T., Sinclair, P., Bassey, A., Okpoko, A (eds). The Archaeology of Africa Food, Metals and Towns. London, Routledge, pp. 478–473
* Kiriama, H.O., 1993. "The Iron Using Communities in Kenya". Shaw, T., Sinclair, P., Bassey, A., Okpoko, A (eds). The Archaeology of Africa Food, Metals and Towns. London, Routledge, pp. 484–498
* Martinelli, B., 1993, "Fonderies ouest-africaines. Classement comparatif et tendances", in Atouts et outils de lethnologie des techniques – Sens et tendance en technologie comparée, Revue Techniques et culture', n 21 : 195–221.
* Martinelli, B., 2004, "On the Threshold of Intensive Metallurgy – The choice of Slow Combustion in the Niger River Bend (Burkina Faso and Mali)" in The origins of iron metallurgy in Africa – New lights on its antiquity, H. Bocoum (ed.), UNESCO publishing : pp. 216–247
* Collet, D.P., 1993. "Metaphors and Representations Associated with Precolonial Iron-Smelting in Eastern and Southern Africa". Shaw, T., Sinclair, P., Bassey, A., Okpoko, A (eds). The Archaeology of Africa Food, Metals and Towns. London, Routledge, pp. 499–511 | 1 | Applied and Interdisciplinary Chemistry |
Two Soviet scientists, B. R. Lazarenko and N. I. Lazarenko, were tasked in 1943 to investigate ways of preventing the erosion of tungsten electrical contacts due to sparking. They failed in this task but found that the erosion was more precisely controlled if the electrodes were immersed in a dielectric fluid. This led them to invent an EDM machine used for working difficult-to-machine materials such as tungsten. The Lazarenkos' machine is known as an R-C-type machine, after the resistor–capacitor circuit (RC circuit) used to charge the electrodes.
Simultaneously but independently, an American team, Harold Stark, Victor Harding, and Jack Beaver, developed an EDM machine for removing broken drills and taps from aluminium castings. Initially constructing their machines from under-powered electric-etching tools, they were not very successful. But more powerful sparking units, combined with automatic spark repetition and fluid replacement with an electromagnetic interrupter arrangement produced practical machines. Stark, Harding, and Beaver's machines produced 60 sparks per second. Later machines based on their design used vacuum tube circuits that produced thousands of sparks per second, significantly increasing the speed of cutting. | 1 | Applied and Interdisciplinary Chemistry |
Magnetometers are used extensively in experimental particle physics to measure the magnetic field of pivotal components such as the concentration or focusing beam-magnets. | 0 | Theoretical and Fundamental Chemistry |
Capsaicin, the active ingredient in chili pepper, was first isolated over a century ago. In 1919 the exact chemical structure of capsaicin was determined and the complete synthesis of the compound was achieved a decade later. Capsaicin has been used as an analgesic for decades, but the therapeutic potential of capsaicin was first recognized as early as 1850. The discovery that the pungency of capsaicin is mediated through TRPV1 set the stage for further research of the function of the TRPV1 receptor, and preclinical studies showed evidence of its importance in numerous human diseases. These are the first agents acting by this mechanism that made their way into clinic for evaluation of their use as possible analgesics and therefore important targets for drug development. Many discoveries are yet to be made, both in terms of the range of potential therapeutic applications in addition to analgesia for TRPV1 antagonists and it was only in the last decade where there has been a full understanding of the molecular mechanism. In the years to come it will be clearer if TRPV1 antagonists can fulfill their potential. | 1 | Applied and Interdisciplinary Chemistry |
20 people directly from the Winter School 1 and 20 people from the Test 3 will join the Summer School 2, which is held at the same place with Summer School 1. In the school, students stay two weeks; studying theories in the morning and learning experiments in afternoon. Almost of the theories are related to Organic Chemistry. One person gets a Best Graduation, 14 people get a Merit, and some of the leftovers get an Honorable Mention. 15 people-Best Graduation and Merit-can join the Winter School 2. These students have to take the Test 4, but the result doesn't matter of choosing students joining the Test 4. They can directly go to the Winter School 2. | 1 | Applied and Interdisciplinary Chemistry |
In statistical mechanics, the following molecular equation is derived from first principles
where is the absolute pressure of the gas, is the number density of the molecules (given by the ratio , in contrast to the previous formulation in which is the number of moles), is the absolute temperature, and is the Boltzmann constant relating temperature and energy, given by:
where is the Avogadro constant.
From this we notice that for a gas of mass , with an average particle mass of times the atomic mass constant, , (i.e., the mass is Da) the number of molecules will be given by
and since , we find that the ideal gas law can be rewritten as
In SI units, is measured in pascals, in cubic metres, in kelvins, and in SI units. | 0 | Theoretical and Fundamental Chemistry |
Metallacrown nomenclature has been developed to mimic the nomenclature of crown ethers, which are named by the total number of atoms in the ring, followed by "C" for "crown," and the number of oxygen atoms in the ring. For example, 12-crown-4 or 12-C-4 describes Figure 2a. When naming metallacrowns, a similar format is followed. However, the C becomes "MC" for "metallacrown" and the "MC" is followed by the ring metal, other heteroatom, and the ligand used to make the metallacrown. For example, metallacrown b in the figure above is named [12-MC-4], where "shi" is the ligand, salicylhydroxamic acid. | 0 | Theoretical and Fundamental Chemistry |
Sulfolipids are sulfur containing lipids. Sulfoquinovosyl diacylglycerols are the predominant sulfolipids present in plants. In leaves its content comprises up to 3 - 6% of the total sulfur present. This sulfolipid is present in plastid membranes and likely is involved in chloroplast functioning. The route of biosynthesis and physiological function of sulfoquinovosyl diacylglycerol is still under investigation. From recent studies it is evident that sulfite it the likely sulfur precursor for the formation of the sulfoquinovose group of this lipid. | 1 | Applied and Interdisciplinary Chemistry |
The concept of residence time originated in models of chemical reactors. The first such model was an axial dispersion model by Irving Langmuir in 1908. This received little attention for 45 years; other models were developed such as the plug flow reactor model and the continuous stirred-tank reactor, and the concept of a washout function (representing the response to a sudden change in the input) was introduced. Then, in 1953, Peter Danckwerts resurrected the axial dispersion model and formulated the modern concept of residence time. | 0 | Theoretical and Fundamental Chemistry |
Ion exchange chromatography can be used to separate proteins because they contain charged functional groups. The ions of interest (in this case charged proteins) are exchanged for another ions (usually H) on a charged solid support. The solutes are most commonly in a liquid phase, which tends to be water. Take for example proteins in water, which would be a liquid phase that is passed through a column. The column is commonly known as the solid phase since it is filled with porous synthetic particles that are of a particular charge. These porous particles are also referred to as beads, may be aminated (containing amino groups) or have metal ions in order to have a charge. The column can be prepared using porous polymers, for macromolecules of a mass of over 100 000 Da, the optimum size of the porous particle is about 1 μm. This is because slow diffusion of the solutes within the pores does not restrict the separation quality. The beads containing positively charged groups, which attract the negatively charged proteins, are commonly referred to as anion exchange resins. The amino acids that have negatively charged side chains at pH 7 (pH of water) are glutamate and aspartate. The beads that are negatively charged are called cation exchange resins, as positively charged proteins will be attracted. The amino acids that have positively charged side chains at pH 7 are lysine, histidine and arginine.
The isoelectric point is the pH at which a compound - in this case a protein - has no net charge. A protein's isoelectric point or PI can be determined using the pKa of the side chains, if the amino (positive chain) is able to cancel out the carboxyl (negative) chain, the protein would be at its PI. Using buffers instead of water for proteins that do not have a charge at pH 7, is a good idea as it enables the manipulation of pH to alter ionic interactions between the proteins and the beads. Weakly acidic or basic side chains are able to have a charge if the pH is high or low enough respectively. Separation can be achieved based on the natural isoelectric point of the protein. Alternatively a peptide tag can be genetically added to the protein to give the protein an isoelectric point away from most natural proteins (e.g., 6 arginines for binding to a cation-exchange resin or 6 glutamates for binding to an anion-exchange resin such as DEAE-Sepharose).
Elution by increasing ionic strength of the mobile phase is more subtle. It works because ions from the mobile phase interact with the immobilized ions on the stationary phase, thus "shielding" the stationary phase from the protein, and letting the protein elute.
Elution from ion-exchange columns can be sensitive to changes of a single charge- chromatofocusing. Ion-exchange chromatography is also useful in the isolation of specific multimeric protein assemblies, allowing purification of specific complexes according to both the number and the position of charged peptide tags. | 0 | Theoretical and Fundamental Chemistry |
Instead of the hemiacetal hydroxyl group, a hydrogen atom can be removed to form a substituent, for example the hydrogen from the C3 hydroxyl of a glucose molecule. Then the substituent is called D-glucopyranos-3-O-yl as it appears in the name of the drug Mifamurtide.
Recent detection of the Au in living organism was possible through the use of C-glycosyl pyrene, where its permeability through cell membrane and fluorescence properties were used to detect Au. | 0 | Theoretical and Fundamental Chemistry |
Like most of the SAT Subject Tests, the Chemistry SAT Test was relatively difficult. It tested a very wide breadth of content and expected students to formulate answers in a very short period of time. Many high school students found themselves picking up extra resource material, like prep books and online aids, to help them prepare for the SAT Chemistry test.
While the test was challenging, there were distinctions between the SAT Chemistry Test and the AP Chemistry exam, which is a more critical-thinking exam that is used not for college admissions but rather for college placement. Still, an AP course in Chemistry is sufficient preparation for the Chemistry SAT. | 1 | Applied and Interdisciplinary Chemistry |
In 1923, Debye and Hückel reported the first successful theory for the distribution of charges in ionic solutions.
The framework of linearized Debye–Hückel theory subsequently was applied to colloidal dispersions by Levine and Dube
who found that charged colloidal particles should experience a strong medium-range repulsion and a weaker long-range attraction.
This theory did not explain the observed instability of colloidal dispersions against irreversible aggregation in solutions of high ionic strength.
In 1941, Derjaguin and Landau introduced a theory for the stability of colloidal dispersions that invoked a fundamental instability driven by strong but short-ranged van der Waals attractions countered by the stabilizing influence of electrostatic repulsions.
In 1948, Verwey and Overbeek independently arrived at the same result.
This so-called DLVO theory resolved the failure of the Levine–Dube theory to account for the dependence of colloidal dispersions' stability on the ionic strength of the electrolyte. | 0 | Theoretical and Fundamental Chemistry |
A surrogate to BOD has been developed using a resazurin derivative which reveals the extent of oxygen uptake by micro-organisms for organic matter mineralization. A cross-validation performed on 109 samples in Europe and the United-States showed a strict statistical equivalence between results from both methods.
An electrode has been developed based on the luminescence emission of a photo-active chemical compound and the quenching of that emission by oxygen. This quenching photophysics mechanism is described by the Stern–Volmer equation for dissolved oxygen in a solution:
* : Luminescence in the presence of oxygen
* : Luminescence in the absence of oxygen
* : Stern-Volmer constant for oxygen quenching
* : Dissolved oxygen concentration
The determination of oxygen concentration by luminescence quenching has a linear response over a broad range of oxygen concentrations and has excellent accuracy and reproducibility. | 0 | Theoretical and Fundamental Chemistry |
Factors which influence this include the atmospheric abundance of the two gases, the supply of the gases to the site of fixation (i.e. in land plants: whether the stomata are open or closed), the length of the liquid phase (how far these gases have to diffuse through water in order to reach the reaction site). For example, when the stomata are closed to prevent water loss during drought: this limits the supply, while production within the leaf will continue. In algae (and plants which photosynthesise underwater); gases have to diffuse significant distances through water, which results in a decrease in the availability of relative to . It has been predicted that the increase in ambient concentrations predicted over the next 100 years may lower the rate of photorespiration in most plants by around 50%. However, at temperatures higher than the photosynthetic thermal optimum, the increases in turnover rate are not translated into increased assimilation because of the decreased affinity of Rubisco for . | 0 | Theoretical and Fundamental Chemistry |
In a simple picture of an electron-nucleus two-spin system, the solid effect occurs when a transition involving an electron-nucleus mutual flip (called zero quantum or double quantum) is excited by a microwave irradiation, in the presence of relaxation. This kind of transition is in general weakly allowed, meaning that the transition moment for the above microwave excitation results from a second-order effect of the electron-nuclear interactions and thus requires stronger microwave power to be significant, and its intensity is decreased by an increase of the external magnetic field B. As a result, the DNP enhancement from the solid effect scales as B when all the relaxation parameters are kept constant. Once this transition is excited and the relaxation is acting, the magnetization is spread over the "bulk" nuclei (the major part of the detected nuclei in an NMR experiment) via the nuclear dipole network.
This polarizing mechanism is optimal when the exciting microwave frequency shifts up or down by the nuclear Larmor frequency from the electron Larmor frequency in the discussed two-spin system. The direction of frequency shifts corresponds to the sign of DNP enhancements.
Solid effect exist in most cases but is more easily observed if the linewidth of the EPR spectrum of involved unpaired electrons is smaller than the nuclear Larmor frequency of the corresponding nuclei. | 0 | Theoretical and Fundamental Chemistry |
Echoes were first detected in nuclear magnetic resonance by Erwin Hahn in 1950, and spin echoes are sometimes referred to as Hahn echoes. In nuclear magnetic resonance and magnetic resonance imaging, radiofrequency radiation is most commonly used.
In 1972 F. Mezei introduced spin-echo neutron scattering, a technique that can be used to study magnons and phonons in single crystals. The technique is now applied in research facilities using triple axis spectrometers.
In 2020 two teams demonstrated that when strongly coupling an ensemble of spins to a resonator, the Hahn pulse sequence does not just lead to a single echo, but rather to a whole train of periodic echoes. In this process the first Hahn echo acts back on the spins as a refocusing pulse, leading to self-stimulated secondary echoes. | 0 | Theoretical and Fundamental Chemistry |
Psoralens are materials that make the skin more sensitive to UV light. They are photosensitizing agents found in plants naturally and manufactured synthetically. Psoralens are taken as pills (systemically) or can be applied directly to the skin, by soaking the skin in a solution that contains the psoralens. They allow UVA energy to be effective at lower doses. When combined with exposure to the UVA in PUVA, psoralens are highly effective at clearing psoriasis and vitiligo. In the case of vitiligo, they work by increasing the sensitivity of melanocytes, the cells that manufacture skin color, to UVA light. Melanocytes have sensors that detect UV light and trigger the manufacture of brown skin color. This color protects the body from the harmful effects of UV light. It can also be connected to the skin's immune response.
LED PUVA lamps give much more intense light compared to fluorescent type lamps. This reduces the treatment time, makes the treatment more effective, and enables the use of a weaker psoralen.
The physician and physiotherapists can choose a starting dose of UV based on the patient's skin type. The UV dose will be increased in every treatment until the skin starts to respond, normally when it becomes a little bit pink.
Normally the UVA dose is increased slowly, starting from 10 seconds and increased by 10 seconds a day, until the skin becomes a little bit pink. When the skin is little bit pink the time should be steady.
To reduce the number of treatments, some clinics test the skin before the treatments, by exposing a small area of the patient's skin to UVA, after ingestion of psoralen. The dose of UVA that produces redness 12 hours later, called the minimum phototoxic dose (MPD), or minimal erythema dose (MED) becomes the starting dose for treatment. | 0 | Theoretical and Fundamental Chemistry |
To allow prediction of the cell potential, tabulations of standard electrode potential are available. Such tabulations are referenced to the standard hydrogen electrode (SHE). The standard hydrogen electrode undergoes the reaction
:2 H + 2 e → H
which is shown as a reduction but, in fact, the SHE can act as either the anode or the cathode, depending on the relative oxidation/reduction potential of the other electrode/electrolyte combination. The term standard in SHE requires a supply of hydrogen gas bubbled through the electrolyte at a pressure of 1 atm and an acidic electrolyte with H activity equal to 1 (usually assumed to be [H] = 1 mol/liter, i.e. pH = 0).
The SHE electrode can be connected to any other electrode by a salt bridge and an external circuit to form a cell. If the second electrode is also at standard conditions, then the measured cell potential is called the standard electrode potential for the electrode. The standard electrode potential for the SHE is zero, by definition. The polarity of the standard electrode potential provides information about the relative reduction potential of the electrode compared to the SHE. If the electrode has a positive potential with respect to the SHE, then that means it is a strongly reducing electrode which forces the SHE to be the anode (an example is Cu in aqueous CuSO with a standard electrode potential of 0.337 V). Conversely, if the measured potential is negative, the electrode is more oxidizing than the SHE (such as Zn in ZnSO where the standard electrode potential is −0.76 V).
Standard electrode potentials are usually tabulated as reduction potentials. However, the reactions are reversible and the role of a particular electrode in a cell depends on the relative oxidation/reduction potential of both electrodes. The oxidation potential for a particular electrode is just the negative of the reduction potential. A standard cell potential can be determined by looking up the standard electrode potentials for both electrodes (sometimes called half cell potentials). The one that is smaller will be the anode and will undergo oxidation. The cell potential is then calculated as the sum of the reduction potential for the cathode and the oxidation potential for the anode.
:E° = E° (cathode) – E° (anode) = E° (cathode) + E° (anode)
For example, the standard electrode potential for a copper electrode is:
Cell diagram
:Pt | H (1 atm) | H (1 M) || Cu (1 M) | Cu
:E° = E° (cathode) – E° (anode)
At standard temperature, pressure and concentration conditions, the cell's emf (measured by a multimeter) is 0.34 V. By definition, the electrode potential for the SHE is zero. Thus, the Cu is the cathode and the SHE is the anode giving
:E = E°(Cu/Cu) – E°(H/H)
Or,
:E°(Cu/Cu) = 0.34 V
Changes in the stoichiometric coefficients of a balanced cell equation will not change the E° value because the standard electrode potential is an intensive property. | 0 | Theoretical and Fundamental Chemistry |
Before monosaccharide units are incorporated into glycoproteins, polysaccharides, or lipids in living organisms, they are typically first "activated" by being joined via a glycosidic bond to the phosphate group of a nucleotide such as uridine diphosphate (UDP), guanosine diphosphate (GDP), thymidine diphosphate (TDP), or cytidine monophosphate (CMP). These activated biochemical intermediates are known as sugar nucleotides or sugar donors. Many biosynthetic pathways use mono- or oligosaccharides activated by a diphosphate linkage to lipids, such as dolichol. These activated donors are then substrates for enzymes known as glycosyltransferases, which transfer the sugar unit from the activated donor to an accepting nucleophile (the acceptor substrate). | 0 | Theoretical and Fundamental Chemistry |
Ferromanganese is an alloy of iron and manganese, with other elements such as silicon, carbon, sulfur, nitrogen and phosphorus. The primary use of ferromanganese is as a type of processed manganese source to add to different types of steel, such as stainless steel. Global production of low-carbon ferromanganese (i.e. alloys with less than 2% carbon content) reached 1.5 megatons in 2010. | 1 | Applied and Interdisciplinary Chemistry |
In dimensional analysis, the Strouhal number (St, or sometimes Sr to avoid the conflict with the Stanton number) is a dimensionless number describing oscillating flow mechanisms. The parameter is named after Vincenc Strouhal, a Czech physicist who experimented in 1878 with wires experiencing vortex shedding and singing in the wind. The Strouhal number is an integral part of the fundamentals of fluid mechanics.
The Strouhal number is often given as
where f is the frequency of vortex shedding, L is the characteristic length (for example, hydraulic diameter or the airfoil thickness) and U is the flow velocity. In certain cases, like heaving (plunging) flight, this characteristic length is the amplitude of oscillation. This selection of characteristic length can be used to present a distinction between Strouhal number and reduced frequency:
where k is the reduced frequency, and A is amplitude of the heaving oscillation.
For large Strouhal numbers (order of 1), viscosity dominates fluid flow, resulting in a collective oscillating movement of the fluid "plug". For low Strouhal numbers (order of 10 and below), the high-speed, quasi-steady-state portion of the movement dominates the oscillation. Oscillation at intermediate Strouhal numbers is characterized by the buildup and rapidly subsequent shedding of vortices.
For spheres in uniform flow in the Reynolds number range of 8×10 there co-exist two values of the Strouhal number. The lower frequency is attributed to the large-scale instability of the wake, is independent of the Reynolds number Re and is approximately equal to 0.2. The higher-frequency Strouhal number is caused by small-scale instabilities from the separation of the shear layer. | 1 | Applied and Interdisciplinary Chemistry |
Inositol trisphosphate receptor (InsP3R) is a membrane glycoprotein complex acting as a Ca channel activated by inositol trisphosphate (InsP3). InsP3R is very diverse among organisms, and is necessary for the control of cellular and physiological processes including cell division, cell proliferation, apoptosis, fertilization, development, behavior, learning and memory. Inositol triphosphate receptor represents a dominant second messenger leading to the release of Ca from intracellular store sites. There is strong evidence suggesting that the InsP3R plays an important role in the conversion of external stimuli to intracellular Ca signals characterized by complex patterns relative to both space and time, such as Ca waves and oscillations. | 1 | Applied and Interdisciplinary Chemistry |
Silicon carbide can be used in the production of graphene because of its chemical properties that promote the production of graphene on the surface of SiC nanostructures.
When it comes to its production, silicon is used primarily as a substrate to grow the graphene. But there are actually several methods that can be used to grow the graphene on the silicon carbide. The confinement controlled sublimation (CCS) growth method consists of a SiC chip that is heated under vacuum with graphite. Then the vacuum is released very gradually to control the growth of graphene. This method yields the highest quality graphene layers. But other methods have been reported to yield the same product as well.
Another way of growing graphene would be thermally decomposing SiC at a high temperature within a vacuum. But this method turns out to yield graphene layers that contain smaller grains within the layers. So there have been efforts to improve the quality and yield of graphene. One such method is to perform ex situ graphitization of silicon terminated SiC in an atmosphere consisting of argon. This method has proved to yield layers of graphene with larger domain sizes than the layer that would be attainable via other methods. This new method can be very viable to make higher quality graphene for a multitude of technological applications.
When it comes to understanding how or when to use these methods of graphene production, most of them mainly produce or grow this graphene on the SiC within a growth enabling environment. It is utilized most often at rather higher temperatures (such as 1300 °C) because of SiC thermal properties. However, there have been certain procedures that have been performed and studied that could potentially yield methods that use lower temperatures to help manufacture graphene. More specifically this different approach to graphene growth has been observed to produce graphene within a temperature environment of around 750 °C. This method entails the combination of certain methods like chemical vapor deposition (CVD) and surface segregation. And when it comes to the substrate, the procedure would consist of coating a SiC substrate with thin films of a transition metal. And after the rapid heat treating of this substance, the carbon atoms would then become more abundant at the surface interface of the transition metal film which would then yield graphene. And this process was found to yield graphene layers that were more continuous throughout the substrate surface. | 1 | Applied and Interdisciplinary Chemistry |
The CBS catalyst or Corey–Bakshi–Shibata catalyst is an asymmetric catalyst derived from proline. It finds many uses in organic reactions such as the CBS reduction, Diels-Alder reactions and (3+2) cycloadditions. Proline, a naturally occurring chiral compound, is readily and cheaply available. It transfers its stereocenter to the catalyst which in turn is able to drive an organic reaction selectively to one of two possible enantiomers. This selectivity is due to steric strain in the transition state that develops for one enantiomer but not for the other. | 0 | Theoretical and Fundamental Chemistry |
Regelation is the phenomenon of ice melting under pressure and refreezing when the pressure is reduced. This can be demonstrated by looping a fine wire around a block of ice, with a heavy weight attached to it. The pressure exerted on the ice slowly melts it locally, permitting the wire to pass through the entire block. The wire's track will refill as soon as pressure is relieved, so the ice block will remain intact even after wire passes completely through. This experiment is possible for ice at −10 °C or cooler, and while essentially valid, the details of the process by which the wire passes through the ice are complex. The phenomenon works best with high thermal conductivity materials such as copper, since latent heat of fusion from the top side needs to be transferred to the lower side to supply latent heat of melting. In short, the phenomenon in which ice converts to liquid due to applied pressure and then re-converts to ice once the pressure is removed is called regelation.
Regelation was discovered by Michael Faraday. It occurs only for substances such as ice, that have the property of expanding upon freezing, for the melting points of those substances decrease with the increasing external pressure. The melting point of ice falls by 0.0072 °C for each additional atm of pressure applied. For example, a pressure of 500 atmospheres is needed for ice to melt at −4 °C. | 0 | Theoretical and Fundamental Chemistry |
Some pairs of minerals that are not related structurally or compositionally may also exhibit epitaxy. A common example is rutile TiO on hematite FeO. Rutile is tetragonal and hematite is trigonal, but there are directions of similar spacing between the atoms in the (100) plane of rutile (perpendicular to the a axis) and the (001) plane of hematite (perpendicular to the c axis). In epitaxy these directions tend to line up with each other, resulting in the axis of the rutile overgrowth being parallel to the c axis of hematite, and the c axis of rutile being parallel to one of the axes of hematite. | 0 | Theoretical and Fundamental Chemistry |
The fluid motion in a vortex creates a dynamic pressure (in addition to any hydrostatic pressure) that is lowest in the core region, closest to the axis, and increases as one moves away from it, in accordance with Bernoulli's principle. One can say that it is the gradient of this pressure that forces the fluid to follow a curved path around the axis.
In a rigid-body vortex flow of a fluid with constant density, the dynamic pressure is proportional to the square of the distance from the axis. In a constant gravity field, the free surface of the liquid, if present, is a concave paraboloid.
In an irrotational vortex flow with constant fluid density and cylindrical symmetry, the dynamic pressure varies as , where is the limiting pressure infinitely far from the axis. This formula provides another constraint for the extent of the core, since the pressure cannot be negative. The free surface (if present) dips sharply near the axis line, with depth inversely proportional to . The shape formed by the free surface is called a hyperboloid, or "Gabriel's Horn" (by Evangelista Torricelli).
The core of a vortex in air is sometimes visible because water vapor condenses as the low pressure of the core causes adiabatic cooling; the funnel of a tornado is an example. When a vortex line ends at a boundary surface, the reduced pressure may also draw matter from that surface into the core. For example, a dust devil is a column of dust picked up by the core of an air vortex attached to the ground. A vortex that ends at the free surface of a body of water (like the whirlpool that often forms over a bathtub drain) may draw a column of air down the core. The forward vortex extending from a jet engine of a parked airplane can suck water and small stones into the core and then into the engine. | 1 | Applied and Interdisciplinary Chemistry |
Another area of research within artificial photosynthesis is the selection and manipulation of photosynthetic microorganisms, namely green microalgae and cyanobacteria, for the production of solar fuels. Many strains produce hydrogen naturally. Algae biofuels such as butanol and methanol have been produced at various scales. This method has benefited from the development of synthetic biology, Diverse biofuels have been developed, e.g., acetic acid from carbon dioxide using "cyborg bacteria".
Some solar cells are capable of splitting water into oxygen and hydrogen, approximately ten times more efficient than natural photosynthesis. Sun Catalytix, the startup based on the artificial leaf, stated that it will not be scaling up the prototype as the device offers few savings over other ways to make hydrogen from sunlight.
Some photoautotrophic microorganisms can, under certain conditions, produce hydrogen. Nitrogen-fixing microorganisms, such as filamentous cyanobacteria, possess the enzyme nitrogenase, responsible for conversion of atmospheric N into ammonia; molecular hydrogen is a byproduct of this reaction, and is many times not released by the microorganism, but rather taken up by a hydrogen-oxidizing (uptake) hydrogenase. One way of forcing these organisms to produce hydrogen is then to annihilate uptake hydrogenase activity. This has been done on a strain of Nostoc punctiforme: one of the structural genes of the NiFe uptake hydrogenase was inactivated by insertional mutagenesis, and the mutant strain showed hydrogen evolution under illumination.
Many of these photoautotrophs also have bidirectional hydrogenases, which can produce hydrogen under certain conditions. However, other energy-demanding metabolic pathways can compete with the necessary electrons for proton reduction, decreasing the efficiency of the overall process; also, these hydrogenases are very sensitive to oxygen.
Several carbon-based biofuels have also been produced using cyanobacteria, such as 1-butanol.
Synthetic biology techniques are predicted to be useful for this topic. Microbiological and enzymatic engineering have the potential of improving enzyme efficiency and robustness, as well as constructing new biofuel-producing metabolic pathways in photoautotrophs that previously lack them, or improving on the existing ones. Another topic being developed is the optimization of photobioreactors for commercial application. | 0 | Theoretical and Fundamental Chemistry |
* Eli Samuels: Eli is 18 years old, 6′9″ (201 centimeters) tall. Hes an A student, and is the salutatorian in high school. His mother has Huntingtons disease, which he could have too.
* Jonathan Samuels: Jonathan Samuels is Elis father, who loved his wife. He has a problem with Eli working at Wyatt Transgenics, because of things that went down in the past. He is initially completely unwilling to tell Eli anything about his mother's relationships with Dr. Wyatt.
* Dr. Quincy Wyatt: Dr. Quincy Wyatt is a famed geneticist, who is considered to be on par with Mendel, Watson, and Crick. He offers Eli a job. He displays an unexplained interest in Eli.
* Vivian Fadiman: Vivian Fadiman is Elis girlfriend and Valedictorian at his high school. All she wants is to be part of his life and she supports him in everything he does. Its hard for her to understand why Eli hides major parts of his life from her. Eli is devoted to her, though they do go through some rough times.
* Kayla Matheson: A year older than Eli, he gets to know her via Dr. Wyatt. He is attracted to her because of her beauty and athleticism.
* Ava Samuels: Ava Samuels was Elis mother and lived in a nursing home because of her Huntingtons disease. She had a mysterious connection with Dr. Wyatt. | 1 | Applied and Interdisciplinary Chemistry |
There are several on-line software and databases available for glycomic research. This includes:
* GlyCosmos
* GlyTouCan
* GlycomeDB
* UniCarb-DB | 0 | Theoretical and Fundamental Chemistry |
The initial stage of glass disease occurs when moisture causes alkali to be leached out of the glass. This becomes apparent when hygroscopic alkali deposits on the glass give it a cloudy or hazy appearance.
This may occur within as little as five to 10 years of the glass's manufacturing.
The glass may feel slippery or slimy
and tiny droplets, or weeping, may be seen in high humidity (above 55%).
The hydrated alkali can form fine crystals on the surface of the glass in low relative humidity (below 40%).
At this stage, it may be possible to gently wash the glass and remove the surface alkali.
This will help to stabilize the glass by reducing the surface pH, and by removing dust, soiling, and hygroscopic components that attract further moisture. | 0 | Theoretical and Fundamental Chemistry |
Assuming that the concentration is at equilibrium and the flow velocity is zero, meaning that only the ion species moves, the Nernst–Planck equation takes the form:
Rather than a general electric field, if we assume that only the electrostatic component is significant, the equation is further simplified by removing the time derivative of the magnetic vector potential:
Finally, in units of mol/(m·s) and the gas constant , one obtains the more familiar form:
where is the Faraday constant equal to ; the product of Avogadro constant and the elementary charge. | 0 | Theoretical and Fundamental Chemistry |
It is believed that thyroid hormones evolved in the Urbilaterian well before the development of the thyroid itself and molluscs, echinoderms, cephalochordates and ascidians all use such hormones. Cnidarians also respond to Thyroid hormone despite being parahoxozoans rather than bilaterians.
Insects use hormones similar to thyroid hormone using iodine.
Phosphorylated tyrosines created with tyrosine kinases are fundamental signalling molecules in all animals and in choanoflagellates. | 1 | Applied and Interdisciplinary Chemistry |
Alison Sarah Tomlin is a British physical chemist and applied mathematician whose research involves building detailed mathematical models of combustion, including uncertainty quantification for those models. She is a professor in the School of Chemical and Process Engineering at the University of Leeds, where she heads the Clean Combustion Research Group. | 0 | Theoretical and Fundamental Chemistry |
Hydrogen bonding is a strong intermolecular force that forms a special type of dipole-dipole attraction. Hydrogen bonds form when a hydrogen atom bonded to a strongly electronegative atom is around another electronegative atom with a lone pair of electrons. Hydrogen bonds are stronger than normal dipole-dipole interactions and dispersion forces but they remain weaker than covalent and ionic bonds. In hydrogels, structure and stability of water molecules are highly affected by the bonds. The polar groups in the polymer strongly bind water molecules and form hydrogen bonds which also cause hydrophobic effects to occur. These hydrophobic effects can be exploited to design physically crosslinked hydrogels that exhibit self healing abilities. The hydrophobic effects combined with the hydrophilic effects within the hydrogel structure can be balanced through dangling side chains that mediates the hydrogen bonding that occurs between two separate hydrogel pieces or across a ruptured hydrogel. | 0 | Theoretical and Fundamental Chemistry |
According to the Oxford English Dictionary, the suffix ‘omics’ refers to ‘the totality of some sort’. In biology, ‘omics’ techniques are used for the high-throughput analysis of DNA sequences and epigenetic modifications (genomics), mRNA and miRNA transcripts (transcriptomics), expressed proteins (proteomics), as well as synthesised metabolites (metabolomics) in a biological system (cell, tissue, organism, etc.) under a given set of experimental conditions.
Due to the high number of variables that are measured simultaneously, these techniques provide large and complex datasets that require adapted tools for data analysis and interpretation. | 0 | Theoretical and Fundamental Chemistry |
Recent advances in ultraviolet nanophotonics has led to development of single molecule study on label-free protein by exciting them with deep ultraviolet light and studying the dynamic processes. | 0 | Theoretical and Fundamental Chemistry |
The Bessemer process was the first inexpensive industrial process for the mass production of steel from molten pig iron before the development of the open hearth furnace. The key principle is removal of impurities from the iron by oxidation with air being blown through the molten iron. The oxidation also raises the temperature of the iron mass and keeps it molten.
Related decarburizing with air processes had been used outside Europe for hundreds of years, but not on an industrial scale. One such process (similar to puddling) was known in the 11th century in East Asia, where the scholar Shen Kuo of that era described its use in the Chinese iron and steel industry. In the 17th century, accounts by European travelers detailed its possible use by the Japanese.
The modern process is named after its inventor, the Englishman Henry Bessemer, who took out a patent on the process in 1856. The process was said to be independently discovered in 1851 by the American inventor William Kelly though the claim is controversial.
The process using a basic refractory lining is known as the "basic Bessemer process" or Gilchrist–Thomas process after the English discoverers Percy Gilchrist and Sidney Gilchrist Thomas. | 1 | Applied and Interdisciplinary Chemistry |
Helical wheels can be drawn by a variety of software packages including [https://CRAN.R-project.org/package=helixvis helixvis] in R, [https://github.com/smsaladi/heliquest heliquest] in R, or via the HELIQUEST server. | 1 | Applied and Interdisciplinary Chemistry |
There are a number of methods through which hypothermia is induced. These include: cooling catheters, cooling blankets, and application of ice applied around the body among others. As of 2013 it is unclear if one method is any better than the others. While cool intravenous fluid may be given to start the process, further methods are required to keep the person cold.
Core body temperature must be measured (either via the esophagus, rectum, bladder in those who are producing urine, or within the pulmonary artery) to guide cooling. A temperature below should be avoided, as adverse events increase significantly. The person should be kept at the goal temperature plus or minus half a degree Celsius for 24 hours. Rewarming should be done slowly with suggested speeds of per hour.
Targeted temperature management should be started as soon as possible. The goal temperature should be reached before 8 hours. Targeted temperature management remains partially effective even when initiated as long as 6 hours after collapse.
Prior to the induction of targeted temperature management, pharmacological agents to control shivering must be administered. When body temperature drops below a certain threshold—typically around —people may begin to shiver. It appears that regardless of the technique used to induce hypothermia, people begin to shiver when temperature drops below this threshold. Drugs commonly used to prevent and treat shivering in targeted temperature management include acetaminophen, buspirone, opioids including pethidine (meperidine), dexmedetomidine, fentanyl, and/or propofol. If shivering is unable to be controlled with these drugs, patients are often placed under general anesthesia and/or are given paralytic medication like vecuronium. People should be rewarmed slowly and steadily in order to avoid harmful spikes in intracranial pressure. | 1 | Applied and Interdisciplinary Chemistry |
This book covers underground mining and surveying. When a vein below ground is to be exploited a shaft is begun and a wooden shed with a windlass is placed above it. The tunnel dug at the bottom follows the vein and is just big enough for a man. The entire vein should be removed. Sometimes the tunnel eventually connects with a tunnel mouth in a hill side. Stringers and cross veins should be explored with cross tunnels or shafts when they occur. Agricola next describes that gold, silver, copper and mercury can be found as native metals, the others very rarely. Gold and silver ores are described in detail. Agricola then states that it is rarely worthwhile digging for other metals unless the ores are rich. Gems are found in some mines, but rarely have their own veins, lodestone is found in iron mines and emery in silver mines. Various minerals and colours of earths can be used to give indications of the presence of metal ores. The actual mineworking varies with the hardness of the rock, the softest is worked with a pick and requires shoring with wood, the hardest is usually broken with fire. Iron wedges, hammers and crowbars are used to break other rocks. Noxious gases and the ingress of water are described. Methods for lining tunnels and shafts with timber are described. The book concludes with a long treatise on surveying, showing the instruments required and techniques for determining the course of veins and tunnels. Surveyors allow veins to be followed, but also prevent mines removing ore from other claims and stop mine workings from breaking into other workings. | 1 | Applied and Interdisciplinary Chemistry |
In nuclear physics these methods are used to study properties of the nucleus itself.
Methods for studies of the nucleus:
* Gamma spectroscopy
* Hypernuclear spectroscopy
Methods for condensed matter studies:
* Nuclear magnetic resonance (NMR)
* Mössbauer spectroscopy
* Perturbed angular correlation (PAC, TDPAC, PAC spectroscopy)
* Muon spin spectroscopy
* Nuclear orientation
* Channeling
* Nuclear reaction analysis
* Nuclear quadrupole resonance (NQR)
Methods for trace element analysis:
* Neutron activation analysis (NAA)
* Associated particle imaging (API) | 0 | Theoretical and Fundamental Chemistry |
The complex ion can easily oxidize alcohol, aldehyde and amine, and capable of decarboxylating α-hydroxycarboxylic acids and phenylacetic acids to give the corresponding carbonyl compounds. Benzylic C-H bonds are oxidatively converted to carbonyl groups:
Aromatic thiols and allylaryl thioethers are oxidized to arylsulfonic acids, which gives an alternative route to produce arylsulfonic acids with mild conditions. | 0 | Theoretical and Fundamental Chemistry |
In biology, the SECIS element (SECIS: selenocysteine insertion sequence) is an RNA element around 60 nucleotides in length that adopts a stem-loop structure. This structural motif (pattern of nucleotides) directs the cell to translate UGA codons as selenocysteines (UGA is normally a stop codon). SECIS elements are thus a fundamental aspect of messenger RNAs encoding selenoproteins, proteins that include one or more selenocysteine residues.
In bacteria the SECIS element appears soon after the UGA codon it affects. In archaea and eukaryotes, it occurs in the 3 UTR of an mRNA, and can cause multiple UGA codons within the mRNA to code for selenocysteine. One archaeal SECIS element, in Methanococcus, is located in the 5 UTR.
The SECIS element appears defined by sequence characteristics, i.e. particular nucleotides tend to be at particular positions in it, and a characteristic secondary structure. The secondary structure is the result of base-pairing of complementary RNA nucleotides, and causes a hairpin-like structure. The eukaryotic SECIS element includes non-canonical A-G base pairs, which are uncommon in nature, but are critically important for correct SECIS element function. Although the eukaryotic, archaeal and bacterial SECIS elements each share a general hairpin structure, they are not alignable, e.g. an alignment-based scheme to recognize eukaryotic SECIS elements will not be able to recognize archaeal SECIS elements. However, in Lokiarcheota, SECIS elements are more similar to eukaryotic elements.
In bioinformatics, several computer programs have been created that search for SECIS elements within a genome sequence, based on the sequence and secondary structure characteristics of SECIS elements. These programs have been used in searches for novel selenoproteins. | 1 | Applied and Interdisciplinary Chemistry |
A powder pattern arises in powdered samples where crystallites are randomly oriented relative to the magnetic field so that all molecular orientations are present. In presence of a chemical shift anisotropy interaction, each orientation with respect to the magnetic field gives a different resonance frequency. If enough crystallites are present, all the different contributions overlap continuously and lead to a smooth spectrum.
Fitting of the pattern in a static ssNMR experiment gives information about the shielding tensor, which are often described by the isotropic chemical shift , the chemical shift anisotropy parameter , and the asymmetry parameter . | 0 | Theoretical and Fundamental Chemistry |
Lanthanum also forms a diiodide, LaI. It is an electride and is best formulated {La,2I,e}, with the electron delocalised in a conduction band. Several other lanthanides form similar compounds, including CeI, PrI and GdI. Lanthanum diiodide adopts the same tetragonal crystal structure as PrI.
Lanthanum(III) iodide reacts with lanthanum metal under an argon atmosphere in a tantalum capsule at 1225 K to form the mixed-valence compound LaI.
Reduction of LaI or LaI with metallic sodium in an argon atmosphere at 550 °C gives lanthanum monoiodide, LaI, which has a hexagonal crystal structure. | 0 | Theoretical and Fundamental Chemistry |
There has been some confusion in the literature on the use of the term “M30”. Although it should be very clear that “M30” is a monoclonal antibody (“M”) that detects the antigen “ccK18”/“K18-Asp396” people sometimes refer to the antigen as “M30”. This is incorrect.
It is clear that the use of the term “M30” in connection with “keratin” means the monoclonal antibody M30® or (possibly, but erroneously) the neo-epitope DALD396 on K18 recognized by the M30® monoclonal. “M30” is not a biological entity expressed in cells but a (patent protected) monoclonal antibody.
Caspase-cleaved fragment of keratin 18 = ccK18
Keratin 18 = K18 (or CK18)
M30® = the antibody that recognizes a neoepitope on ccK18
M65® ELISA = an ELISA composed of two antibodies (M5 and M6) for conventional epitopes of K18
M30®, Apoptosense®, M65®, EpiDeath®, and PEVIVA® are registered trademarks, including U.S. Trademarks 4,577,969, 2,749,204, 1,009,048, and 896,269. Additionally, VLVBio™ holds additional Trademarks in most countries worldwide. | 1 | Applied and Interdisciplinary Chemistry |
Reacting an aldehyde with a Grignard reagent or organolithium and treating the resulting secondary alkoxide with N-tert-butylbenzenesulfinimidoyl chloride is a convenient one-pot reaction for converting aldehydes to ketones. While Grignards can be used for this reaction, organolithium compounds give higher yields, due to the higher reactivity of a lithium alkoxide compared to the corresponding magnesium salt. In some cases, an equivalent of DMPU, a Lewis base, will increase yields. For example, treating benzaldehyde with n-butyllithium and N-tert-butylbenzenesulfinimidoyl chloride in THF gives 1-phenyl-1-pentanone in good yield.
N-tert-Butylbenzenesulfinimidoyl chloride can also be used to synthesize imines from amines. Imines synthesized in this fashion have been shown to undergo a one-pot Mannich reaction with 1,3-dicarbonyl compounds, such as malonate esters and 1,3-diketones. In this example, Cbz-protected benzylamine is deprotonated using n-butyllithium, then treated with N-tert-butylbenzenesulfinimidoyl chloride to form the protected imine. Dimethyl malonate acts as the nucleophile and reacts with the imine to give the final product, a Mannich base. | 0 | Theoretical and Fundamental Chemistry |
Another identification mechanism is through immunoassay. Abbott Laboratories AxSYM is an immunoassay device utilizing Fluorescence Polarization Immunoassay (FPIA) technology that can determine the presence and quantify salicylates. The introduction of a salicylate specific antigen labeled with fluorescein into the sample will mark the sample. Upon irradiation with 490nm light, some of that light will be reflected back to a detector at 520nm. Polarization allows the machine to detect the difference between antibody bound, and unbound fluorescein. It is therefore possible to quantify the serum salicylate level through the signal strength—the amount of reflected light received. | 0 | Theoretical and Fundamental Chemistry |
Hydrogen is a chemical element with an atomic number of 1. It has just one proton and one electron. Deuterium is the heavier naturally occurring, non-radioactive, stable isotope of hydrogen. Deuterium contains one proton, one electron, and a neutron, effectively doubling the mass of the deuterium isotope without changing its properties significantly. Substituting deuterium for hydrogen yields deuterated compounds that are similar in size and shape to hydrogen-based compounds.
One of the most pernicious and irreparable types of oxidative damage inflicted by reactive oxygen species (ROS) upon biomolecules involves the carbon-hydrogen bond cleavage (hydrogen abstraction). In theory, replacing hydrogen with deuterium "reinforces" the bond due to the kinetic isotope effect, and such reinforced biomolecules taken up by the body will be more resistant to ROS.
The deuterium-reinforced lipids resists the non-enzymatic lipid peroxidation (LPO) through isotope effect — a non-antioxidant based mechanism that protects mitochondrial, neuronal and other lipid membranes, thereby greatly reducing the levels of numerous LPO-derived toxic products such as reactive carbonyls.
Treating cells with deuterium-containing PUFAs (D-PUFAs) can prevent of ferroptosis. This treatment stops the autoxidation process through the kinetic isotope effect (KIE), as shown in Table 1 [66]. The efficacy of D-PUFAs in preventing ferroptosis has been demonstrated in models induced by erastin and RSL3, and has shown promising results in various disease models, especially those related to neurodegenerative disorders. | 1 | Applied and Interdisciplinary Chemistry |
There are several techniques used to map out which phase is present during perturbations done on the lipid. These perturbations include pH changes, temperature changes, pressure changes, volume changes, etc.
The most common technique used to study phospholipid phase presence is phosphorus nuclear magnetic resonance (31P NMR). In this technique, different and unique powder diffraction patterns are observed for lamellar, hexagonal, and isotropic phases. Other techniques that are used and do offer definitive evidence of existence of lamellar and hexagonal phases include freeze-fracture electron microscopy, X-ray diffraction, differential scanning calorimetry (DSC), and deuterium nuclear magnetic resonance (2H NMR).
Additionally, negative staining transmission electron microscopy has been shown as a useful tool to study lipid bilayer phase behavior and polymorphism into lamellar phase, micellar, unilamellar liposome, and hexagonal aqueous-lipid structures, in aqueous dispersions of membrane lipids. As water-soluble negative stain is excluded from the hydrophobic part (fatty acyl chains) of lipid aggregates, the hydrophilic headgroup portions of the lipid aggregates stain dark and clearly mark the outlines of the lipid aggregates (see figure). | 0 | Theoretical and Fundamental Chemistry |
Flortaucipir (F), sold under the brand name Tauvid, is a radioactive diagnostic agent indicated for use with positron emission tomography (PET) imaging to image the brain.
The most common adverse reactions include headache, injection site pain and increased blood pressure.
Two proteins – tau and amyloid – are recognized as hallmarks of Alzheimers disease. In people with Alzheimers disease, pathological forms of tau proteins develop inside neurons in the brain, creating neurofibrillary tangles. After flortaucipir (F) is administered intravenously, it binds to sites in the brain associated with this tau protein misfolding. The brain can then be imaged with a PET scan to help identify the presence of tau pathology.
It is the first drug used to help image a distinctive characteristic of Alzheimer's disease in the brain called tau pathology. The U.S. Food and Drug Administration (FDA) considers it to be a first-in-class medication. | 1 | Applied and Interdisciplinary Chemistry |
Antanas Purėnas (16 February 1881 – 5 November 1962) was a famous Lithuanian organic chemist and politician. | 0 | Theoretical and Fundamental Chemistry |
Protein interactions: To screen for protein–protein interactions and protein interactions with other molecules such as metabolites, lipids, DNA and small molecules.; enzyme inhibition assay: for high throughput drug candidate screening and to discover novel enzymes for use in biotechnology; screening antibody specificity. | 1 | Applied and Interdisciplinary Chemistry |
For emulsions, flocculation describes clustering of individual dispersed droplets together, whereby the individual droplets do not lose their identity. Flocculation is thus the initial step leading to further ageing of the emulsion (droplet coalescence and the ultimate separation of the phases). Flocculation is used in mineral dressing, but can be also used in the design of physical properties of food and pharmaceutical products. | 1 | Applied and Interdisciplinary Chemistry |
Oxidation of phosphonites gives phosphonates:
:2 P(OR)R + O → 2 OP(OR)R
Phosphonites can function as ligands in homogeneous catalysis. | 0 | Theoretical and Fundamental Chemistry |
Solid-state sintering is the most used synthesis process to produce solid-state electrolytes. Powders of LAGP precursors, including oxides like GeO and AlO, are mixed, calcinated and densified at high temperature (700 - 1200 °C) and for long times (12 hours). Sintered LAGP is characterized by high crystalline quality, large grains, a compact microstructure, and high density, even if negative side effects such as loss of volatile lithium compounds and formation of secondary phases should be avoided while the material is kept at high temperature.
The sintering parameters affects LAGP microstructure and purity and, ultimately, its ionic conductivity and conduction performances. | 0 | Theoretical and Fundamental Chemistry |
In 1834, Théophile-Jules Pelouze distilled tartaric acid and isolated glutaric acid and another unknown organic acid. Jöns Jacob Berzelius characterized this other acid the following year and named pyruvic acid because it was distilled using heat. The correct molecular structure was deduced by the 1870s.
Pyruvic acid is a colorless liquid with a smell similar to that of acetic acid and is miscible with water. In the laboratory, pyruvic acid may be prepared by heating a mixture of tartaric acid and potassium hydrogen sulfate, by the oxidation of propylene glycol by a strong oxidizer (e.g., potassium permanganate or bleach), or by the hydrolysis of acetyl cyanide, formed by reaction of acetyl chloride with potassium cyanide:
:CHCOCl + KCN → CHCOCN + KCl
:CHCOCN → CHCOCOOH | 1 | Applied and Interdisciplinary Chemistry |
In thermodynamics and thermal physics, the Gouy-Stodola theorem is an important theorem for the quantification of irreversibilities in an open system, and aids in the exergy analysis of thermodynamic processes. It asserts that the rate at which work is lost during a process, or at which exergy is destroyed, is proportional to the rate at which entropy is generated, and that the proportionality coefficient is the temperature of the ambient heat reservoir. In the literature, the theorem often appears in a slightly modified form, changing the proportionality coefficient.
The theorem is named jointly after the French physicist Georges Gouy and Slovak physicist Aurel Stodola, who demonstrated the theorem in 1889 and 1905 respectively. Gouy used it while working on exergy and utilisable energy, and Stodola while working on steam and gas engines. | 0 | Theoretical and Fundamental Chemistry |
Complexes of the transition metals are usually generated simply by treating the appropriate metal complex with SO. The adducts are often weak. In some cases, SO displaces other ligands.
A large number of labile O-bonded SO complexes arise from the oxidation of a suspension of the metals in liquid SO, an excellent solvent. | 0 | Theoretical and Fundamental Chemistry |
In the early 1960s, Woodward began work on what was the most complex natural product synthesized to date—vitamin B. In a remarkable collaboration with his colleague Albert Eschenmoser in Zurich, a team of almost one hundred students and postdoctoral workers worked for many years on the synthesis of this molecule. The work was finally published in 1973, and it marked a landmark in the history of organic chemistry. The synthesis included almost a hundred steps, and involved the characteristic rigorous planning and analyses that had always characterised Woodwards work. This work, more than any other, convinced organic chemists that the synthesis of any complex substance was possible, given enough time and planning (see also palytoxin, synthesized by the research group of Yoshito Kishi, one of Woodwards postdoctoral students). As of 2019, no other total synthesis of Vitamin B has been published.
That same year, based on observations that Woodward had made during the B synthesis, he and Roald Hoffmann devised rules (now called the Woodward–Hoffmann rules) for elucidating the stereochemistry of the products of organic reactions. Woodward formulated his ideas (which were based on the symmetry properties of molecular orbitals) based on his experiences as a synthetic organic chemist; he asked Hoffman to perform theoretical calculations to verify these ideas, which were done using Hoffmann's Extended Hückel method. The predictions of these rules, called the "Woodward–Hoffmann rules" were verified by many experiments. Hoffmann shared the 1981 Nobel Prize for this work along with Kenichi Fukui, a Japanese chemist who had done similar work using a different approach; Woodward had died in 1979 and Nobel Prizes are not awarded posthumously. | 0 | Theoretical and Fundamental Chemistry |
Optical rotatory dispersion is the variation of the specific rotation of a medium with respect to the wavelength of light. Usually described Drude's empirical relation,
where is the specific rotation at temperature and wavelength , and and are constants that depend on the properties of the medium.
Optical rotatory dispersion has applications in organic chemistry regarding determining the structure of organic compounds. | 0 | Theoretical and Fundamental Chemistry |
The space occupied by a polymer molecule is generally expressed in terms of radius of gyration, which is an average distance from the center of mass of the chain to the chain itself. Alternatively, it may be expressed in terms of pervaded volume, which is the volume spanned by the polymer chain and scales with the cube of the radius of gyration.
The simplest theoretical models for polymers in the molten, amorphous state are ideal chains. | 0 | Theoretical and Fundamental Chemistry |
The origin of the hydrophobic effect is not fully understood.
Some argue that the hydrophobic interaction is mostly an entropic effect originating from the disruption of highly dynamic hydrogen bonds between molecules of liquid water by the nonpolar solute. A hydrocarbon chain or a similar nonpolar region of a large molecule is incapable of forming hydrogen bonds with water. Introduction of such a non-hydrogen bonding surface into water causes disruption of the hydrogen bonding network between water molecules. The hydrogen bonds are reoriented tangentially to such surface to minimize disruption of the hydrogen bonded 3D network of water molecules, and this leads to a structured water "cage" around the nonpolar surface. The water molecules that form the "cage" (or clathrate) have restricted mobility. In the solvation shell of small nonpolar particles, the restriction amounts to some 10%. For example, in the case of dissolved xenon at room temperature a mobility restriction of 30% has been found. In the case of larger nonpolar molecules, the reorientational and translational motion of the water molecules in the solvation shell may be restricted by a factor of two to four; thus, at 25 °C the reorientational correlation time of water increases from 2 to 4-8 picoseconds. Generally, this leads to significant losses in translational and rotational entropy of water molecules and makes the process unfavorable in terms of the free energy in the system. By aggregating together, nonpolar molecules reduce the surface area exposed to water and minimize their disruptive effect.
The hydrophobic effect can be quantified by measuring the partition coefficients of non-polar molecules between water and non-polar solvents. The partition coefficients can be transformed to free energy of transfer which includes enthalpic and entropic components, ΔG = ΔH - TΔS. These components are experimentally determined by calorimetry. The hydrophobic effect was found to be entropy-driven at room temperature because of the reduced mobility of water molecules in the solvation shell of the non-polar solute; however, the enthalpic component of transfer energy was found to be favorable, meaning it strengthened water-water hydrogen bonds in the solvation shell due to the reduced mobility of water molecules. At the higher temperature, when water molecules become more mobile, this energy gain decreases along with the entropic component. The hydrophobic effect depends on the temperature, which leads to "cold denaturation" of proteins.
The hydrophobic effect can be calculated by comparing the free energy of solvation with bulk water. In this way, the hydrophobic effect not only can be localized but also decomposed into enthalpic and entropic contributions. | 0 | Theoretical and Fundamental Chemistry |
The families lawyer, Des Collins, said: "Prior to the trial, the council maintained that a thorough investigation had led it to the conclusion that there was no link between the reclamation work and the childrens birth defects. It also maintained that had any convincing evidence been shown that the children had good claims then the council would have wanted to compensate them appropriately without going to trial. Today that link has been established and the evidence provided. The children now call upon the council to fulfil their pre-trial promises without delay." Collins said of the legal battle: "Ive been made out to be a shyster and an ambulance-chaser. The council has stonewalled, obstructed and prevaricated all the way through this. They didnt need to. If theyd ever said to us, Look, were not admitting liability, but well co-operate with you to find out what really happened, I wouldnt have minded. Instead, they tried to shut us out and paint us as the baddies... Theyve tried at every turn to stop us getting at the truth. Now they claim they cant afford to pay. I'm not impressed."
Corby Borough Councils Chief Executive Chris Mallender said: "We are obviously very disappointed and very surprised at the outcome of this trial. Our position has always been that there was no link between the reclamation work that was carried out in Corby in past decades and these childrens birth defects. That is still our position." He also said they were "prepared to apologise for mistakes that had been made but could not apologise until a causal link was proved between the works and the defects... We are not yet at the point of saying sorry because nobody yet is responsible."
The council's legal representatives said they were asked to advise on an appeal but had over 400 pages of judgment to review and also their client had to consider its position. The firm said it would be a few weeks before it has instructions. The statement added: "There are however some clear points to note at this stage. The case involves reclamation work going back to the 1980s. The judge concluded that this contamination affected pregnant women. A child, so affected, has 21 years from birth to make a claim and thus any work since the late 1980s which has not met the standard of care indicated in this judgment could be challenged in this way. For both local authorities and developers alike this is a significant concern because the standard of care has been drawn very highly, and could cause a rethink of the way that reclamation is carried out in the UK even though the facts of the case are historic."
Kelvin Glendenning, leader of Corby Borough Council between 1984 and 1995, said "I dont think that Corby Council has anything to regret... If there was toxic waste - and I am sure there wasnt any toxic waste at all that was floating about in the air - they shouldn't be blaming us." | 1 | Applied and Interdisciplinary Chemistry |
Oligosaprobes include some green and diatomaceous algae, flowering plants (for example, European white water lilies), some rotifers, Bryozoa, sponges, mollusks of the genus Dreissena, cladocerans (daphnids, bithotrephes), dragonfly and mayfly larvae, sterlets, trout, minnows, and newts.
Oligosaprobes also embrace a few saprophytes, including bacteria (scores and hundreds per 1 cu mm of water) and organisms that feed on bacteria. The term “oligosaprobe” is usually applied only to freshwater organisms. | 0 | Theoretical and Fundamental Chemistry |
Metal nitrito complexes figure prominently in the nitrogen cycle, which describes the relationships and interconversions of ammonia up to nitrate. Because nitrogen is often a limiting nutrient, this cycle is important. Nitrite itself does not readily undergo redox reactions, but its metal complexes do. | 0 | Theoretical and Fundamental Chemistry |
A heat engine is a system that converts heat to usable energy, particularly mechanical energy, which can then be used to do mechanical work. While originally conceived in the context of mechanical energy, the concept of the heat engine has been applied to various other kinds of energy, particularly electrical, since at least the late 19th century. The heat engine does this by bringing a working substance from a higher state temperature to a lower state temperature. A heat source generates thermal energy that brings the working substance to the higher temperature state. The working substance generates work in the working body of the engine while transferring heat to the colder sink until it reaches a lower temperature state. During this process some of the thermal energy is converted into work by exploiting the properties of the working substance. The working substance can be any system with a non-zero heat capacity, but it usually is a gas or liquid. During this process, some heat is normally lost to the surroundings and is not converted to work. Also, some energy is unusable because of friction and drag.
In general, an engine is any machine that converts energy to mechanical work. Heat engines distinguish themselves from other types of engines by the fact that their efficiency is fundamentally limited by Carnot's theorem of thermodynamics. Although this efficiency limitation can be a drawback, an advantage of heat engines is that most forms of energy can be easily converted to heat by processes like exothermic reactions (such as combustion), nuclear fission, absorption of light or energetic particles, friction, dissipation and resistance. Since the heat source that supplies thermal energy to the engine can thus be powered by virtually any kind of energy, heat engines cover a wide range of applications.
Heat engines are often confused with the cycles they attempt to implement. Typically, the term "engine" is used for a physical device and "cycle" for the models. | 0 | Theoretical and Fundamental Chemistry |
The energy of the third much-smaller product usually ranges between 10 and 20 MeV. In keeping with their origin, alpha particles produced by ternary fission typically have mean energies of about ~ 16 MeV (energies this great are never seen in alpha decay). Since these typically have significantly more energy than the ~ 5 MeV alpha particles from alpha decay, they are accordingly called "long-range alphas" (referring to their longer range in air or other media).
The other two larger fragments carry away, in their kinetic energies, the remainder of the fission kinetic energy (typically totalling ~ 170 MeV in heavy element fission) that does not appear as the 10 to 20 MeV kinetic energy carried away by the third smaller product. Thus, the larger fragments in ternary fission are each less energetic, by a typical 5 to 10 MeV, than they are seen to be in binary fission. | 0 | Theoretical and Fundamental Chemistry |
Aluminum based nanogalvanic alloys are characterized by the size of their galvanic microstructure and consist of particles with a mesh size of -325, which is equivalent to a diameter of around 50 microns. Since the grain size of the powders is in the nanometer scale and the particle size is tens of microns similar to conventional powders, no additional health hazards are associated with the handling of the nanogalvanic powders. The by-products of the powder reaction with water is non-toxic and occurs naturally. The aluminum based nanogalvanic alloys were also demonstrated to produce 1000 ml. of hydrogen gas per gram of aluminum in less than 1 minute and 1340 ml—100% of the theoretical yield at 295 K and 1 atm.—in 3 minutes without the need for hazardous or costly materials, or additional processes. These nanogalvanic structured powders can be manufactured by means of high energy ball milling at room temperature or at lower temperatures. The powders may be compacted in the form of tablets for ease of transportation, which would reduce reliance on high-pressure or liquid hydrogen cylinders traditionally used for shipment. Additionally, they are stable in the atmosphere at standard temperature, pressure, and humidity levels, allowing for convenient storage. | 1 | Applied and Interdisciplinary Chemistry |
In the 1740s, Benjamin Huntsman found a means of melting blister steel, made by the cementation process, in crucibles. The resulting crucible steel, usually cast in ingots, was more homogeneous than blister steel. | 1 | Applied and Interdisciplinary Chemistry |
During plastic deformation the work performed is the integral of the stress and strain in the plastic deformation regime. Although the majority of this work is converted to heat, some fraction (~1–5%) is retained in the material as defects—particularly dislocations. The rearrangement or elimination of these dislocations will reduce the internal energy of the system and so there is a thermodynamic driving force for such processes. At moderate to high temperatures, particularly in materials with a high stacking fault energy such as aluminium and nickel, recovery occurs readily and free dislocations will readily rearrange themselves into subgrains surrounded by low-angle grain boundaries.
The driving force is the difference in energy between the deformed and recrystallized state ΔE which can be determined by the dislocation density or the subgrain size and boundary energy (Doherty, 2005):
where ρ is the dislocation density, G is the shear modulus, b is the Burgers vector of the dislocations, γ is the subgrain boundary energy and d is the subgrain size. | 1 | Applied and Interdisciplinary Chemistry |
A riser clamp is a type of hardware used by mechanical building trades for pipe support in vertical runs of piping (risers) at each floor level. The devices are placed around the pipe, and integral fasteners are then tightened to clamp them onto the pipe. The friction between the pipe and riser clamp transfers the weight of the pipe through the riser clamp to the building structure. Risers are generally located at floor penetrations, particularly for continuous floor slabs such as concrete. They may also be located at some other interval as dictated by local building codes or at intermediate intervals to support plumbing which has been altered or repaired. Heavier piping types, such as cast iron, require more frequent support. Ordinarily, riser clamps are made of carbon steel and individually sized to fit certain pipe sizes.
There are at least two types of riser clamp: the two-bolt pipe clamp and the yoke clamp. | 1 | Applied and Interdisciplinary Chemistry |
Several thermodynamic definitions are very useful in thermochemistry. A system is the specific portion of the universe that is being studied. Everything outside the system is considered the surroundings or environment. A system may be:
* a (completely) isolated system which can exchange neither energy nor matter with the surroundings, such as an insulated bomb calorimeter
* a thermally isolated system which can exchange mechanical work but not heat or matter, such as an insulated closed piston or balloon
* a mechanically isolated system which can exchange heat but not mechanical work or matter, such as an uninsulated bomb calorimeter
* a closed system which can exchange energy but not matter, such as an uninsulated closed piston or balloon
* an open system which it can exchange both matter and energy with the surroundings, such as a pot of boiling water | 0 | Theoretical and Fundamental Chemistry |
Chlorosulfonyl isocyanate is the chemical compound ClSONCO, known as CSI. This compound is a versatile reagent in organic synthesis. | 0 | Theoretical and Fundamental Chemistry |
Human cancellous bone possesses a stiffness ranging from 12 to 23 GPa; careful control and modification of manufacturing parameters to achieve similar strengths is imperative for practicality of integration. Correctly predicting the Youngs modulus for foams is imperative for actual biomedical integration; a mismatch of Youngs moduli between the implant and the bone can result in stress-shielding effects from a disproportional handling of stress. The implant which typically exhibits a higher Young's modulus than the bone will absorb most of the load. As a result of this imbalance, the starting bone density will be reduced, there will be tissue death and, eventually, implant failure.
Natural bone exhibits the ability to adjust local fiber away from the low-stress regions toward high stress regions through the distribution of porosity, thus maximizing overall comfort. Using finite element analysis, researchers examined the effect of filling pores with bone on mechanical properties. They concluded that bone ingrowth significantly improved the mechanical properties, evidenced by decreased localized plasticity and stress concentrations. In effect, the titanium foam in the study allowed the bone to exhibit its natural ability to adjust local fiber away from the low-stress regions toward high stress regions.
Experiments demonstrated that random combinations of pore size and shape result in lower Youngs moduli. Theoretical models for the quantification of Youngs moduli do not account for random pore size and shape distribution, so experimental measurements must be conducted in the presence of heterogeneous pore size and distribution. This is a limitation of the micro-mechanical models discussed above. | 0 | Theoretical and Fundamental Chemistry |
The classic method of nonlinear absorption used by microscopists is conventional two-photon fluorescence, in which two photons from a single source interact to excite a photoelectron. The electron then emits a photon as it transitions back to its ground state. This microscopy method has been revolutionary in biological sciences because of its inherent three-dimensional optical sectioning capabilities.
Two-photon absorption is inherently a nonlinear process: fluorescent output intensity is proportional to the square of the excitation light intensity. This ensures that fluorescence is only generated within the focus of a laser beam, as the intensity outside of this plane is insufficient to excite a photoelectron.
However, this microscope modality is inherently limited by the number of biological molecules that can undergo both two-photon excitation and fluorescence.
Pump–probe microscopy circumvents this limitation by directly measuring excitation light. This expands the number of potential targets to any molecule capable of two-photon absorption, even if it does not fluoresce upon relaxation. The method modulates the amplitude of a pulsed laser beam, referred to as the pump, to bring the target molecule to an excited state. This will then affect the properties of a second coherent beam, referred to as the probe, based on the interaction of the two beams with the molecule. These properties are then measured by a detector to form an image. | 0 | Theoretical and Fundamental Chemistry |
Mitochondrial disease is a group of disorders caused by mitochondrial dysfunction. Mitochondria are the organelles that generate energy for the cell and are found in every cell of the human body except red blood cells. They convert the energy of food molecules into the ATP that powers most cell functions.
Mitochondrial diseases take on unique characteristics both because of the way the diseases are often inherited and because mitochondria are so critical to cell function. A subclass of these diseases that have neuromuscular symptoms are known as mitochondrial myopathies. | 1 | Applied and Interdisciplinary Chemistry |
These names are used to refer to the moieties themselves or to radical species, and also to form the names of halides and substituents in larger molecules.
When the parent hydrocarbon is unsaturated, the suffix ("-yl", "-ylidene", or "-ylidyne") replaces "-ane" (e.g. "ethane" becomes "ethyl"); otherwise, the suffix replaces only the final "-e" (e.g. "ethyne" becomes "ethynyl").
When used to refer to moieties, multiple single bonds differ from a single multiple bond. For example, a methylene bridge (methanediyl) has two single bonds, whereas a methylene group (methylidene) has one double bond. Suffixes can be combined, as in methylidyne (triple bond) vs. methylylidene (single bond and double bond) vs. methanetriyl (three double bonds).
There are some retained names, such as methylene for methanediyl, 1,x-phenylene for phenyl-1,x-diyl (where x is 2, 3, or 4), carbyne for methylidyne, and trityl for triphenylmethyl. | 0 | Theoretical and Fundamental Chemistry |
In any real moving fluid, energy is dissipated due to friction; turbulence dissipates even more energy for high Reynolds number flows. This dissipation, called head loss, is divided into two main categories, "major losses" associated with energy loss per length of pipe, and "minor losses" associated with bends, fittings, valves, etc. The most common equation used to calculate major head losses is the Darcy–Weisbach equation. Older, more empirical approaches are the Hazen–Williams equation and the Prony equation.
For relatively short pipe systems, with a relatively large number of bends and fittings, minor losses can easily exceed major losses. In design, minor losses are usually estimated from tables using coefficients or a simpler and less accurate reduction of minor losses to equivalent length of pipe, a method often used for shortcut calculations of pneumatic conveying lines pressure drop. | 1 | Applied and Interdisciplinary Chemistry |
Christina Lampe-Önnerud was born in Sweden. Her father, Wolfgang Lampe, was a power engineer. Lampe-Önnerud had an interest in science early on, making fireworks in a basement bathtub and playing with chemistry and electrical kits as a child. She was also trained as an opera singer. | 0 | Theoretical and Fundamental Chemistry |
The Hill coefficient is a measure of ultrasensitivity (i.e. how steep is the response curve).
The Hill coefficient, or , may describe cooperativity (or possibly other biochemical properties, depending on the context in which the Hill equation is being used). When appropriate, the value of the Hill coefficient describes the cooperativity of ligand binding in the following way:
*. Positively cooperative binding: Once one ligand molecule is bound to the enzyme, its affinity for other ligand molecules increases. For example, the Hill coefficient of oxygen binding to haemoglobin (an example of positive cooperativity) falls within the range of 1.7–3.2.
*. Negatively cooperative binding: Once one ligand molecule is bound to the enzyme, its affinity for other ligand molecules decreases.
*. Noncooperative (completely independent) binding: The affinity of the enzyme for a ligand molecule is not dependent on whether or not other ligand molecules are already bound. When n=1, we obtain a model that can be modeled by Michaelis–Menten kinetics, in which , the Michaelis–Menten constant.
The Hill coefficient can be calculated approximately in terms of the cooperativity index of Taketa and Pogell as follows:
where and are the input values needed to produce the 10% and 90% of the maximal response, respectively. | 1 | Applied and Interdisciplinary Chemistry |
For a spherical particle the surface area will scale as the square of the size, while the volume scales as the cube. Therefore surface contributions to the energy can become important at small sizes in nanoparticles. If the energy of the surface atoms is lower when they are closer, this can be accomplished by shrinking the whole particle. The gain in energy from the surface stress will scale as the area, balanced by an energy cost for the shrinking (deformation) that scales as the volume. Combined these lead to a change in the lattice parameter that scales inversely with size. This has been measured for many materials using either electron diffraction or x-ray diffraction. This phenomenon has sometimes been written as equivalent to the Laplace pressure, also called the capillary pressure, in both cases with a surface tension. This is not correct since these are terms that apply to liquids.
One complication is that the changes in lattice parameter lead to more involved forms for nanoparticles with more complex shapes or when surface segregation can occur. | 0 | Theoretical and Fundamental Chemistry |
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