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On 21 November 1879, Lancashire chemist John Hargreaves canvassed a meeting of chemists and managers in Widnes, St Helens and Runcorn to consider the formation of a chemical society. Modelled on the successful Tyne Chemical Society already operating in Newcastle, the newly proposed South Lancashire Chemical Society held its first meeting on 29 January 1880 in Liverpool, with the eminent industrial chemist and soda manufacturer Ludwig Mond presiding.
It was quickly decided that the society should not be limited to just the local region and the title the Society of Chemical Industry’ was finally settled upon at a meeting in London on 4 April 1881, as being more inclusive'. Held at the offices of the Chemical Society, now the headquarters of the Royal Society of Chemistry, in Burlington House, this meeting was presided over by Henry Roscoe, appointed first president of SCI, and attended by Eustace Carey, Ludwig Mond, FA Abel, Lowthian Bell, William H Perkin, Walter Weldon, Edward Rider Cook, Thomas Tyrer and George E Davis; all prominent scientists, industrialists and MPs of the time.
The society grew rapidly, launching international and regional sections. In 1881 Ivan Levinstein was a founder of the Manchester Section of the Society of Chemical Industry, later following Sir Henry Roscoe as chair of the Section. Levinstein also served as President of the Society of Chemical Industry between 1901 and 1903.
Prominent early members included William Lever, George Matthey, Ludwig Mond, [https://www.soci.org/about-us/history/notable-scientists-and-inventors Henry Armstrong], Leo Baekeland, [https://www.soci.org/about-us/history/notable-scientists-and-inventors Rudolph Messel], Charles Tennant, Richard Seligman, Ferdinand Hurter and Marie Stopes. | 1 | Applied and Interdisciplinary Chemistry |
Stereoisomers have the same atoms or isotopes connected by bonds of the same type, but differ in their shapes – the relative positions of those atoms in space – apart from rotations and translations.
In theory, one can imagine any arrangement in space of the atoms of a molecule or ion to be gradually changed to any other arrangement in infinitely many ways, by moving each atom along an appropriate path. However, changes in the positions of atoms will generally change the internal energy of a molecule, which is determined by the angles between bonds in each atom and by the distances between atoms (whether they are bonded or not).
A conformational isomer is an arrangement of the atoms of the molecule or ion for which the internal energy is a local minimum; that is, an arrangement such that any small changes in the positions of the atoms will increase the internal energy, and hence result in forces that tend to push the atoms back to the original positions. Changing the shape of the molecule from such an energy minimum to another energy minimum will therefore require going through configurations that have higher energy than and . That is, a conformation isomer is separated from any other isomer by an energy barrier: the amount that must be temporarily added to the internal energy of the molecule in order to go through all the intermediate conformations along the "easiest" path (the one that minimizes that amount).
A classic example of conformational isomerism is cyclohexane. Alkanes generally have minimum energy when the angles are close to 110 degrees. Conformations of the cyclohexane molecule with all six carbon atoms on the same plane have a higher energy, because some or all the angles must be far from that value (120 degrees for a regular hexagon). Thus the conformations which are local energy minima have the ring twisted in space, according to one of two patterns known as chair (with the carbons alternately above and below their mean plane) and boat (with two opposite carbons above the plane, and the other four below it).
If the energy barrier between two conformational isomers is low enough, it may be overcome by the random inputs of thermal energy that the molecule gets from interactions with the environment or from its own vibrations. In that case, the two isomers may as well be considered a single isomer, depending on the temperature and the context. For example, the two conformations of cyclohexane convert to each other quite rapidly at room temperature (in the liquid state), so that they are usually treated as a single isomer in chemistry.
In some cases, the barrier can be crossed by quantum tunneling of the atoms themselves. This last phenomenon prevents the separation of stereoisomers of fluorochloroamine or hydrogen peroxide , because the two conformations with minimum energy interconvert in a few picoseconds even at very low temperatures.
Conversely, the energy barrier may be so high that the easiest way to overcome it would require temporarily breaking and then reforming one or more bonds of the molecule. In that case, the two isomers usually are stable enough to be isolated and treated as distinct substances. These isomers are then said to be different configurational isomers or "configurations" of the molecule, not just two different conformations. (However, one should be aware that the terms "conformation" and "configuration" are largely synonymous outside of chemistry, and their distinction may be controversial even among chemists.)
Interactions with other molecules of the same or different compounds (for example, through hydrogen bonds) can significantly change the energy of conformations of a molecule. Therefore, the possible isomers of a compound in solution or in its liquid and solid phases many be very different from those of an isolated molecule in vacuum. Even in the gas phase, some compounds like acetic acid will exist mostly in the form of dimers or larger groups of molecules, whose configurations may be different from those of the isolated molecule. | 0 | Theoretical and Fundamental Chemistry |
Primary minerals are the minerals that crystalize during the formation of Earths crust, and their typical δSi isotopic value is in the range of −0.9‰ – +1.4‰. Earths crust is constantly undergoing weathering processes, which dissolve Si and produce secondary Si minerals simultaneously. The formation of secondary Si discriminates against the heavy Si isotope (Si), creating minerals with relatively low δSi isotopic values (−3‰ – +2.5‰, mean: −1.1‰). It has been suggested that this isotopic fractionation is controlled by the kinetic isotope effect of Si adsorption to Aluminum hydroxides, which takes place in early stages of weathering. As a result of incorporation of lighter Si isotopes into secondary minerals, the remaining dissolved Si will be relative enriched in the heavy Si isotope (Si), and associated with relatively high δSi isotopic values (−1‰ – +2‰, mean: +0.8‰). The dissolved Si is often transported by rivers to the oceans. | 0 | Theoretical and Fundamental Chemistry |
The first step should always be an investigation to determine the cause of the deterioration. The general principles of repair include arresting and preventing further degradation; treating exposed steel reinforcement; and filling fissures or holes caused by cracking or left after the loss of spalled or damaged concrete.
Various techniques are available for the repair, protection and rehabilitation of concrete structures, and specifications for repair principals have been defined systematically. The selection of the appropriate approach will depend on the cause of the initial damage (e.g. impact, excessive loading, movement, corrosion of the reinforcement, chemical attack, or fire) and whether the repair is to be fully load bearing or simply cosmetic.
Repair principles which do not improve the strength or performance of concrete beyond its original (undamaged) condition include replacement and restoration of concrete after spalling and delamination; strengthening to restore structural load-bearing capacity; and increasing resistance to physical or mechanical attack.
Repair principles for arresting and preventing further degradation include control of anodic areas; cathodic protection, cathodic control; increasing resistivity; preserving or restoring passivity; increasing resistance to chemical attack; protection against ingress of adverse agents; and moisture control.
Techniques for filling holes left by the removal of spalled or damaged concrete include mortar repairs; flowing concrete repairs and sprayed concrete repairs. The filling of cracks, fissures or voids in concrete for structural purposes (restoration of strength and load-bearing capability), or non-structural reasons (flexible repairs where further movement is expected, or alternately to resist water and gas permeation) typically involves the injection of low viscosity resins or grouts based on epoxy, PU or acrylic resins, or micronised cement slurries.
One novel proposal for the repair of cracks is to use bacteria. BacillaFilla is a genetically engineered bacterium designed to repair damaged concrete, filling in the cracks, and making them whole again. | 1 | Applied and Interdisciplinary Chemistry |
Water rockets use compressed air to power their water jet and generate thrust, they are used as toys.
Air Hogs, a toy brand, also uses compressed air to power piston engines in toy airplanes (and some other toy vehicles). | 1 | Applied and Interdisciplinary Chemistry |
In molecular physics and chemistry, the van der Waals force is a distance-dependent interaction between atoms or molecules. Unlike ionic or covalent bonds, these attractions do not result from a chemical electronic bond; they are comparatively weak and therefore more susceptible to disturbance. The van der Waals force quickly vanishes at longer distances between interacting molecules.
Named after Dutch physicist Johannes Diderik van der Waals, the van der Waals force plays a fundamental role in fields as diverse as supramolecular chemistry, structural biology, polymer science, nanotechnology, surface science, and condensed matter physics. It also underlies many properties of organic compounds and molecular solids, including their solubility in polar and non-polar media.
If no other force is present, the distance between atoms at which the force becomes repulsive rather than attractive as the atoms approach one another is called the van der Waals contact distance; this phenomenon results from the mutual repulsion between the atoms' electron clouds.
The van der Waals forces are usually described as a combination of the London dispersion forces between "instantaneously induced dipoles", Debye forces between permanent dipoles and induced dipoles, and the Keesom force between permanent molecular dipoles whose rotational orientations are dynamically averaged over time. | 0 | Theoretical and Fundamental Chemistry |
The spectroscopic notation of molecules uses Greek letters to represent the modulus of the orbital angular momentum along the internuclear axis.
The quantum number that represents this angular momentum is Λ.
: Λ = 0, 1, 2, 3, ...
: Symbols: Σ, Π, Δ, Φ
For Σ states, one denotes if there is a reflection in a plane containing the nuclei (symmetric), using the + above. The − is used to indicate that there is not.
For homonuclear diatomic molecules, the index g or u denotes the existence of a center of symmetry (or inversion center) and indicates the symmetry of the vibronic wave function with respect to the point-group inversion operation i. Vibronic states that are symmetric with respect to i are denoted g for (German for "even"), and unsymmetric states are denoted u for (German for "odd"). | 0 | Theoretical and Fundamental Chemistry |
In order to understand how life arose, knowledge is required of the chemical pathways that permit formation of the key building blocks of life under plausible prebiotic conditions. The RNA world hypothesis holds that in the primordial soup there existed free-floating ribonucleotides, the fundamental molecules that combine in series to form RNA. Complex molecules such as RNA must have emerged from relatively small molecules whose reactivity was governed by physico-chemical processes. RNA is composed of pyrimidine and purine nucleotides, both of which are necessary for reliable information transfer, and thus natural selection and Darwinian evolution. Becker et al. showed how pyrimidine nucleosides can be synthesized from small molecules and ribose, driven solely by wet-dry cycles. Purine nucleosides can be synthesized by a similar pathway. 5’-mono-and diphosphates also form selectively from phosphate-containing minerals, allowing concurrent formation of polyribonucleotides with both the pyrimidine and purine bases. Thus a reaction network towards the pyrimidine and purine RNA building blocks can be established starting from simple atmospheric or volcanic molecules. | 1 | Applied and Interdisciplinary Chemistry |
Chloride is an anion in the human body needed for metabolism (the process of turning food into energy). It also helps keep the body's acid-base balance. The amount of serum chloride is carefully controlled by the kidneys.
Chloride ions have important physiological roles. For instance, in the central nervous system, the inhibitory action of glycine and some of the action of GABA relies on the entry of Cl into specific neurons. Also, the chloride-bicarbonate exchanger biological transport protein relies on the chloride ion to increase the blood's capacity of carbon dioxide, in the form of the bicarbonate ion; this is the mechanism underpinning the chloride shift occurring as the blood passes through oxygen-consuming capillary beds.
The normal blood reference range of chloride for adults in most labs is 96 to 106 milliequivalents (mEq) per liter. The normal range may vary slightly from lab to lab. Normal ranges are usually shown next to results in the lab report. A diagnostic test may use a chloridometer to determine the serum chloride level.
The North American Dietary Reference Intake recommends a daily intake of between 2300 and 3600 mg/day for 25-year-old males. | 1 | Applied and Interdisciplinary Chemistry |
INT (iodonitrotetrazolium or 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl-2H-tetrazolium) is a commonly used tetrazolium salt (usually prepared with chloride ions), similar to tetrazolium chloride that on reduction produces a red formazan dye that can be used for quantitative redox assays. It is also toxic to prokaryotes.
INT is an artificial electron acceptor that can be utilized in a colorimetric assay to determine the concentration of protein in a solution. It can be reduced by succinate dehydrogenase to furazan, the formation of which can be measured by absorbance at 490 nm. The activity of succinate dehydrogenase is readily observed by the naked eye as the solution turns from colorless to rusty red. | 0 | Theoretical and Fundamental Chemistry |
This scan uses reverse-geometry (BE-type) instruments. These instruments use a front-end magnetic sector that allows for exclusive mass selection of the precursor ion. The fragmentation region is in-between the two analyzers. The electric sector scan gives the product-ion spectrum. MIKES can also be used for direct measurement of kinetic-energy release values. | 0 | Theoretical and Fundamental Chemistry |
Kirchhoff also worked in the mathematical field of graph theory, in which he proved Kirchhoff's matrix tree theorem. | 1 | Applied and Interdisciplinary Chemistry |
When transcription is arrested by the presence of a lesion in the transcribed strand of a gene, DNA repair proteins are recruited to the stalled RNA polymerase to initiate a process called transcription-coupled repair. Central to this process is the general transcription factor TFIIH that has ATPase activity. TFIIH causes a conformational change in the polymerase, to expose the transcription bubble trapped inside, in order for the DNA repair enzymes to gain access to the lesion. Thus, RNA polymerase serves as damage-sensing protein in the cell to target repair enzymes to genes that are being actively transcribed. | 1 | Applied and Interdisciplinary Chemistry |
In materials science, Ostwalds rule or Ostwalds step rule, conceived by Wilhelm Ostwald, describes the formation of polymorphs. The rule states that usually the less stable polymorph crystallizes first. Ostwald's rule is not a universal law but a common tendency observed in nature.
This can be explained on the basis of irreversible thermodynamics, structural relationships, or a combined consideration of statistical thermodynamics and structural variation with temperature. Unstable polymorphs more closely resemble the state in solution, and thus are kinetically advantaged.
For example, out of hot water, metastable, fibrous crystals of benzamide appear first, only later to spontaneously convert to the more stable rhombic polymorph. Another example is magnesium carbonate, which more readily forms dolomite. A dramatic example is phosphorus, which upon sublimation first forms the less stable white phosphorus, which only slowly polymerizes to the red allotrope. This is notably the case for the anatase polymorph of titanium dioxide, which having a lower surface energy is commonly the first phase to form by crystallisation from amorphous precursors or solutions despite being metastable, with rutile being the equilibrium phase at all temperatures and pressures. | 0 | Theoretical and Fundamental Chemistry |
A cis-regulatory element called the GAIT element is involved in the selective translational silencing of the Ceruloplasmin transcript.
The silencing requires binding of a cytosolic inhibitor complex called IFN-gamma-activated inhibitor of translation (GAIT) to the GAIT element. | 1 | Applied and Interdisciplinary Chemistry |
Ethers serve as Lewis bases. For instance, diethyl ether forms a complex with boron trifluoride, i.e. borane diethyl etherate (). Ethers also coordinate to the Mg center in Grignard reagents. Tetrahydrofuran is more basic than acyclic ethers. It forms with many complexes. | 0 | Theoretical and Fundamental Chemistry |
* pnictochalcogenides
** oxypnictides, including oxynitrides, oxyphosphides, oxyarsenides, oxyantimonides, oxybismuthides
* chalcohalides or chalcogenide halides
** oxohalides, including oxyfluorides, oxychlorides, oxybromides, oxyiodides
** fluorosulfides
** sulfide chlorides, selenide chlorides, telluride chlorides
** sulfide bromides, selenide bromides, telluride bromides
** sulfide iodides, selenide iodides, telluride iodides
* oxysulfides, oxyselenides
* oxyhydrides
* halopnictides
** fluoropnictides, including fluorophosphides, fluoroarsenides, fluoroantimonides, fluorobismuthides, arsenide chlorides | 0 | Theoretical and Fundamental Chemistry |
Completed genome sequences allow every open reading frame (ORF), the part of a gene that is likely to contain the sequence for the messenger RNA and protein, to be cloned and expressed as protein. These proteins are then purified and crystallized, and then subjected to one of two types of structure determination: X-ray crystallography and nuclear magnetic resonance (NMR). The whole genome sequence allows for the design of every primer required in order to amplify all of the ORFs, clone them into bacteria, and then express them. By using a whole-genome approach to this traditional method of protein structure determination, all of the proteins encoded by the genome can be expressed at once. This approach allows for the structural determination of every protein that is encoded by the genome. | 1 | Applied and Interdisciplinary Chemistry |
The first efforts that can be considered photogeochemical research can be traced to the "formaldehyde hypothesis" of Adolf von Baeyer in 1870, in which formaldehyde was proposed to be the initial product of plant photosynthesis, formed from carbon dioxide and water through the action of light on a green leaf. This suggestion inspired numerous attempts to obtain formaldehyde in vitro, which can retroactively be considered photogeochemical studies. Detection of organic compounds such as formaldehyde and sugars was reported by many workers, usually by exposure of a solution of carbon dioxide to light, typically a mercury lamp or sunlight itself. At the same time, many other workers reported negative results. One of the pioneer experiments was that of Bach in 1893, who observed the formation of lower uranium oxides upon irradiation of a solution of uranium acetate and carbon dioxide, implying the formation of formaldehyde. Some experiments included reducing agents such as hydrogen gas, and others detected formaldeyhde or other products in the absence of any additives, although the possibility was admitted that reducing power may have been produced from the decomposition of water during the experiment. In addition to the main focus on synthesis of formaldehyde and simple sugars, other light-assisted reactions were occasionally reported, such as the decomposition of formaldehyde and subsequent release of methane, or the formation of formamide from carbon monoxide and ammonia.
In 1912 Benjamin Moore summarized the main facet of photogeochemistry, that of inorganic photocatalysis: "the inorganic colloid must possess the property of transforming sunlight, or some other form of radiant energy, into chemical energy." Many experiments, still focused on how plants assimilate carbon, did indeed explore the effect of a "transformer" (catalyst); some effective "transformers" were similar to naturally occurring minerals, including iron(III) oxide or colloidal iron hydroxide; cobalt carbonate, copper carbonate, nickel carbonate; and iron(II) carbonate. Working with an iron oxide catalyst, Baly concluded in 1930 that "the analogy between the laboratory process and that in the living plant seems therefore to be complete," referring to his observation that in both cases, a photochemical reaction takes place on a surface, the activation energy is supplied in part by the surface and in part by light, efficiency decreases when the light intensity is too great, the optimal temperature of the reaction is similar to that of living plants, and efficiency increases from the blue to the red end of the light spectrum.
At this time, however, the intricate details of plant photosynthesis were still obscure, and the nature of photocatalysis in general was still actively being discovered; Mackinney in 1932 stated that "the status of this problem [photochemical CO reduction] is extraordinarily involved." As in many emerging fields, experiments were largely empirical, but the enthusiasm surrounding this early work did lead to significant advances in photochemistry. The simple but challenging principle of transforming solar energy into chemical energy capable of performing a desired reaction remains the basis of application-based photocatalysis, most notably artificial photosynthesis (production of solar fuels).
After several decades of experiments centered around the reduction of carbon dioxide, interest began to spread to other light-induced reactions involving naturally occurring materials. These experiments usually focused on reactions analogous to known biological processes, such as soil nitrification, for which the photochemical counterpart "photonitrification" was first reported in 1930. | 0 | Theoretical and Fundamental Chemistry |
Vitamin D is produced photochemically from 7-dehydrocholesterol in the skin of most vertebrate animals, including humans. The precursor of vitamin D, 7-dehydrocholesterol is produced in relatively large quantities. 7-Dehydrocholesterol reacts with UVB light at wavelengths of 290–315 nm. These wavelengths are present in sunlight, as well as in the light emitted by the UV lamps in tanning beds (which produce ultraviolet primarily in the UVA spectrum, but typically produce 4% to 10% of the total UV emissions as UVB, some tanning beds can use only separate UVB light bulbs specifically for vitamin D production). Exposure to light through windows is insufficient because glass almost completely blocks UVB light.
Adequate amounts of vitamin D can be produced with moderate sun exposure to the face, arms and legs (for those with the least melanin), averaging 5–30 minutes twice per week, or approximately 25% of the time for minimal sunburn. The darker the skin on the Fitzpatrick scale and the weaker the sunlight, the more minutes of exposure are needed. It also depends on parts of body exposed, all three factors affect minimal erythema dose (MED). Vitamin D overdose from UV exposure is impossible: the skin reaches an equilibrium where the vitamin D degrades as fast as it is created.
The skin consists of two primary layers: the inner layer called the dermis, and the outer, thinner epidermis. Vitamin D is produced in the keratinocytes of two innermost strata of the epidermis, the stratum basale and stratum spinosum, which also are able to produce calcitriol and express the VDR. | 1 | Applied and Interdisciplinary Chemistry |
Polymers such as PMMA and HEMA:MMA are used as matrices in the gain medium of solid-state dye lasers, also known as solid-state dye-doped polymer lasers. These polymers have a high surface quality and are also highly transparent so that the laser properties are dominated by the laser dye used to dope the polymer matrix. These type of lasers, that also belong to the class of organic lasers, are known to yield very narrow linewidths which is useful for spectroscopy and analytical applications. An important optical parameter in the polymer used in laser applications is the change in refractive index with temperature
also known as dn/dT. For the polymers mentioned here the (dn/dT) ~ −1.4 × 10 in units of K in the 297 ≤ T ≤ 337 K range. | 0 | Theoretical and Fundamental Chemistry |
Metabolic rates in lakes and reservoirs are controlled by many environmental factors, such as light and nutrient availability, temperature, and water column mixing regimes. Thus, spatial and temporal changes in those factors cause spatial and temporal variability in metabolic rates, and each of those factors affect metabolism at different spatial and temporal scales. | 1 | Applied and Interdisciplinary Chemistry |
Sufficiently dense matter containing protons experiences proton degeneracy pressure, in a manner similar to the electron degeneracy pressure in electron-degenerate matter: protons confined to a sufficiently small volume have a large uncertainty in their momentum due to the Heisenberg uncertainty principle. However, because protons are much more massive than electrons, the same momentum represents a much smaller velocity for protons than for electrons. As a result, in matter with approximately equal numbers of protons and electrons, proton degeneracy pressure is much smaller than electron degeneracy pressure, and proton degeneracy is usually modelled as a correction to the equations of state of electron-degenerate matter. | 0 | Theoretical and Fundamental Chemistry |
While the early work of Hillhouse focused on early-transition metal chemistry, his later career efforts were dedicated towards base metals. For example, in 2001 Hillhouse and co-workers synthesized a complex that refuted the notion that it was impossible for late transition metals like nickel to form multiple bonds with heteroatoms. The result was a molecule that he affectionately referred to as “Double Nickel,” which possessed an indisputable nickel-nitrogen double bond. Later the group published a study showcasing that one can also synthesize and isolated an electronically similar phosphinidine species. Additionally, using bulky N-heterocyclic carbene (NHC) ligands, Hillhouse and co-workers showed that one can stabilize a linear two-coordinate Ni-based imido species. His group has also showcased how some of these and similar complexes can undergo redox chemistry forming Ni(I) and Ni(III) species. | 0 | Theoretical and Fundamental Chemistry |
A rotameter is a device that measures the volumetric flow rate of fluid in a closed tube.
It belongs to a class of meters called variable-area flowmeters, which measure flow rate by allowing the cross-sectional area the fluid travels through to vary, causing a measurable effect. | 1 | Applied and Interdisciplinary Chemistry |
The synthesis reported by Bodwell/Li (racemic, 2002) was a formal synthesis as it produced a compound already prepared by Rawal (no. 5 in the Rawal synthesis). The key step was an inverse electron demand Diels–Alder reaction of cyclophane 1 by heating in N,N-diethylaniline (dinitrogen is expulsed) followed by reduction of double bond in 2 to 3 by sodium borohydride / triflic acid and removal of the carbamate protecting group (PDC / celite) to 4.
The method is disputed by Reissig (see Reissig synthesis). | 0 | Theoretical and Fundamental Chemistry |
This method relies on phase separation by centrifugation of a mixture of the aqueous sample and a solution containing water-saturated phenol and chloroform, resulting in an upper aqueous phase and a lower organic phase (mainly phenol). Guanidinium thiocyanate, a chaotropic agent, is added to the organic phase to aid in the denaturation of proteins (such as those that strongly bind nucleic acids or those that degrade RNA). The nucleic acids (RNA and/or DNA) partition into the aqueous phase, while protein partitions into the organic phase. The pH of the mixture determines which nucleic acids get purified. Under acidic conditions (pH 4-6), DNA partitions into the organic phase while RNA remains in the aqueous phase. Under neutral conditions (pH 7-8), both DNA and RNA partition into the aqueous phase. In a last step, the nucleic acids are recovered from the aqueous phase by precipitation with 2-propanol. The 2-propanol is then washed with ethanol and the pellet briefly air-dried and dissolved in TE buffer or RNAse free water.
Guanidinium thiocyanate denatures proteins, including RNases, and separates rRNA from ribosomal proteins, while phenol, isopropanol and water are solvents with poor solubility. In the presence of chloroform or BCP (bromochloropropane), these solvents separate entirely into two phases that are recognized by their color: a clear, upper aqueous phase (containing the nucleic acids) and a lower phase (containing the proteins dissolved in phenol and the lipids dissolved in chloroform).
Other denaturing chemicals such as 2-mercaptoethanol and sarcosine may also be used.
The major downside is that phenol and chloroform are both hazardous and inconvenient materials, and the extraction is often laborious, so in recent years many companies now offer alternative ways to isolate RNA. | 1 | Applied and Interdisciplinary Chemistry |
There are several software tools available for RNA velocity analysis.Each of these tools has its own strengths and applications, so the choice of tool would depend on the specific requirements of your analysis: | 1 | Applied and Interdisciplinary Chemistry |
Some synthetic macromolecules, such as catenanes and rotaxanes, dendrimers and hyperbranched polymers, and other assemblies, have molecular weights extending into the thousands or tens of thousands, where most ionization techniques have difficulty producing molecular ions. MALDI is a simple and fast analytical method that can allow chemists to rapidly analyze the results of such syntheses and verify their results. | 1 | Applied and Interdisciplinary Chemistry |
A lamella (: lamellae) in biology refers to a thin layer, membrane or plate of tissue. This is a very broad definition, and can refer to many different structures. Any thin layer of organic tissue can be called a lamella and there is a wide array of functions an individual layer can serve. For example, an intercellular lipid lamella is formed when lamellar disks fuse to form a lamellar sheet. It is believed that these disks are formed from vesicles, giving the lamellar sheet a lipid bilayer that plays a role in water diffusion.
Another instance of cellular lamellae can be seen in chloroplasts. Thylakoid membranes are actually a system of lamellar membranes working together, and are differentiated into different lamellar domains. This lamellar system allows plants to convert light energy into chemical energy. Chloroplasts are characterized by a system of membranes embedded in a hydrophobic proteinaceous matrix, or stroma. The basic unit of the membrane system is a flattened single vesicle called the thylakoid; thylakoids stack into grana. All the thylakoids of a granum are connected with each other, and the grana are connected by intergranal lamellae.
It is placed between the two primary cell walls of two plant cells and made up of intracellular matrix. The lamella comprises a mixture of polygalacturons (D-galacturonic acid) and neutral carbohydrates. It is soluble in the pectinase enzyme.
Lamella, in cell biology, is also used to describe the leading edge of a motile cell, of which the lamellipodia is the most forward portion.
The lipid bilayer core of biological membranes is also called lamellar phase. Thus, each bilayer of multilamellar liposomes and wall of a unilamellar liposome is also referred to as a lamella. | 0 | Theoretical and Fundamental Chemistry |
In addition to the Nobel Prize, his awards and distinctions include Sloan Fellow (1969); Fellow of American Academy of Arts and Sciences (1975); Fellow Am. Phys. Soc. (1976); Guggenheim Fellow (1977); Member National Academy of Sciences (1979); Member International Academy of Science, Munich, Member Academia Sinica (1980); E.O. Lawrence Award (1981); Miller Professor, Berkeley (1981); Fairchild Distinguished Scholar (1983); Harrison Howe Award (1983); Peter Debye Award (1986); National Medal of Science (1986); Golden Plate Award of the American Academy of Achievement (1987) and Faraday Lectureship Prize (1992). Yuan Tseh Lee was awarded the Othmer Gold Medal in 2008 in recognition of his outstanding contributions to progress in chemistry and science. His post-doctoral supervisor and fellow Nobel Laureate Dudley Herschbach congratulated Lee. In 2019 Yuan T. Lee was also awarded the Fray International Sustainability Award by FLOGEN Star Outreach at SIPS 2019. | 0 | Theoretical and Fundamental Chemistry |
If the fluid density is time-invariant at all points within the flow, i.e.,
then the continuity equation (e.g., see Continuity equation#Fluid dynamics) for two-dimensional plane flow becomes
In this case the stream function is defined such that
and represents the mass flux (rather than volumetric flux) per unit thickness through the test surface. | 1 | Applied and Interdisciplinary Chemistry |
Leishmania tarentolae (cannot infect mammals) expression systems allow stable and lasting production of proteins at high yield, in chemically defined media. Produced proteins exhibit fully eukaryotic post-translational modifications, including glycosylation and disulfide bond formation. | 1 | Applied and Interdisciplinary Chemistry |
The AMCA testing laboratory is an A2LA accredited laboratory that tests air control and air movement devices for members of the air control and air movement industry.
The AMCA lab comprises the following:
* Four Reverberant Sound Rooms ranging in size from 6,300 cu.ft. to 61,700 cu.ft.
* Two Water Test Facilities with chambers capable of simulating eight inches (203 mm) of rain-fall per hour and wind speeds of .
* Multi Nozzle Chambers that are capable of measuring airflow up to 88,000 cfm.
* Circulator Fan Facility capable of testing 96 inch fans.
* Acoustic Duct Silencer Facility
* ISO/IEC 17025 accredited
AMCA International also oversees 40 accredited laboratories and two independent, accredited laboratories located in Taiwan and Singapore. Additional independent AMCA accredited laboratories are under construction in Korea and China. | 1 | Applied and Interdisciplinary Chemistry |
For the measurement of the diversity of fragmentomic features, the PFE metric, derived from Shannons Index of entropy, is developed. The default number of 201 bins of lengths 100 to 300 are used for density estimation by the maximum likelihood method. The probability of having a fragment with size , () is computed by the division of the number of fragments with size by the total number of fragments. Shannons entropy is calculated with fthe formula: . | 1 | Applied and Interdisciplinary Chemistry |
Singlet and triplet carbenes exhibit divergent reactivity.
Triplet carbenes are diradicals, and participate in stepwise radical additions. Triplet carbene addition necessarily involves (at least one) intermediate with two unpaired electrons.
Singlet carbenes can (and do) react as electrophiles, nucleophiles, or ambiphiles. Their reactions are typically concerted and often cheletropic. Singlet carbenes are typically electrophilic, unless they have a filled p orbital, in which case they can react as Lewis bases. The Bamford-Stevens reaction gives carbenes in aprotic solvents and carbenium ions in protic ones.
The different mechanisms imply that singlet carbene additions are stereospecific but triplet carbene additions stereoselective. Methylene from diazomethane photolysis reacts with either cis- or trans-2-butene to give a single diastereomer of 1,2-dimethylcyclopropane: cis from cis and trans from trans. Thus methylene is a singlet carbene; if it were triplet, the product would not depend on the starting alkene geometry. | 0 | Theoretical and Fundamental Chemistry |
An off-line process is characterized by the fact that the system to be cleaned has to be taken out of operation in order to inject the cleaning body(ies) and to execute the cleaning procedure. An additional distinction must be made between active and passive cleaning bodies.
Passive cleaning bodies may be a matter of brushes or special constructions like scrapers or so-called "pigs", for instance, which are conveyed through the tubes by means of pressurized air, water, or other media. In most cases, cleaning is implemented through the oversize of the cleaning bodies compared to the tube inner diameter. The types range from brushes with bristles of plastic or steel to scrapers (with smaller tube diameters) and more expensive designs with spraying nozzles for pipelines. This method is applied for tube and pipe diameters from around 5 mm to several metres. Also belonging to this field is the cleaning of obstructed soil pipes of domestic sewage systems that is done by means of a rotating, flexible shaft.
The active cleaning bodies are more or less remote controlled robots that move through the tubes and fulfill their cleaning task, pulling along with them not only cables for power supply and communication but also hoses for the cleaning liquid. Also measuring devices or cameras are carried along to monitor the function. To date, such devices have still required minimum diameters of around 300 mm, however a further diminution is being worked on. The reasonable maximum diameter of this kind of devices is 2 m because above this diameter an inspection of the pipe would certainly be less expensive. For such large diameters a robot application is imaginable only if health-hazardous chemicals are in use. | 1 | Applied and Interdisciplinary Chemistry |
Biodegradable additives may be added to polymers to accelerate their degradation. In the case of photo-oxidation OXO-biodegradation additives are used. These are transition metal salts such as iron (Fe), manganese (Mn), and cobalt (Co). Fe complexes increase the rate of photooxidation by promoting the homolysis of hydroperoxides via Fenton reactions.
The use of such additives has been controversial due to concerns that treated plastics do not fully biodegrade and instead result in the accelerated formation of microplastics. Oxo-plastics would be difficult to distinguish from untreated plastic but their inclusion during plastic recycling can create a destabilised product with fewer potential uses, potentially jeopardising the business case for recycling any plastic. OXO-biodegradation additives were banned in the EU in 2019 | 0 | Theoretical and Fundamental Chemistry |
Staying in the U.S., Cheon was a postdoc in the University of California Berkeley. For the next three years, he was a staff research associate at UCLA before returning to Korea to work as an assistant and then associate professor at KAIST. His research at KAIST focused on geometrical shape control of nanoparticles and magnetic particles. This also marked his first publication on nanocrystals which is a reoccurring interest in his research career and a source of multiple highly cited articles.
He started working at Yonsei University as a full professor in 2002 and later became the Horace G. Underwood Professor in 2008. His research at Yonsei on nanoscale phenomena has led to nanomaterial applications in biology, including highly sensitive MRI contrast agents and nanoscale toolkits for cells. A notable study is from 2004, when he demonstrated the principle of size-dependent MRI contrast effects using nanoparticles which enabled the development of magnetism-engineered iron oxide (MEIO) as an ultra-sensitive nanoparticle MRI contrast agent which might help detect early stage cancer.
From 2010 to 2016, Cheon was the director of the National Creative Research Initiative Center for Evolutionary Nanoparticles. From 2015, he became the director of the newly established Yonsei-Institute of Basic Science Center for Nanomedicine at the Yonsei University Sinchon campus. | 0 | Theoretical and Fundamental Chemistry |
Resistance to mefloquine is common around the west border in Cambodia and other parts of Southeast Asia. The mechanism of resistance is by increase in Pfmdr1 copy number. | 0 | Theoretical and Fundamental Chemistry |
Sometimes the term point mutation is used to describe insertions or deletions of a single base pair (which has more of an adverse effect on the synthesized protein due to the nucleotides' still being read in triplets, but in different frames: a mutation called a frameshift mutation). | 1 | Applied and Interdisciplinary Chemistry |
An orphan drug is a pharmaceutical agent that is developed to treat certain rare medical conditions. An orphan drug would not be profitable to produce without government assistance, due to the small population of patients affected by the conditions. The conditions that orphan drugs are used to treat are referred to as orphan diseases. The assignment of orphan status to a disease and to drugs developed to treat it is a matter of public policy that depends on the legislation (if there is any) of the country.
Designation of a drug as an orphan drug has yielded medical breakthroughs that might not otherwise have been achieved, due to the economics of drug research and development. Examples of this can be that in the U.S. and the EU, it is easier to gain marketing approval for an orphan drug. There may be other financial incentives, such as an extended period of exclusivity, during which the producer has sole rights to market the drug. All are intended to encourage development of drugs which would otherwise lack sufficient profit motive to attract corporate research budgets and personnel. | 1 | Applied and Interdisciplinary Chemistry |
Inorganic Chemistry is a biweekly peer-reviewed scientific journal published by the American Chemical Society since 1962. It covers research in all areas of inorganic chemistry.
The current editor-in-chief is Stefanie Dehnen (Karlsruhe Institute of Technology). | 0 | Theoretical and Fundamental Chemistry |
The quenching process produces a high strength bar from inexpensive low carbon steel. The process quenches the surface layer of the bar, which pressurizes and deforms the crystal structure of intermediate layers, and simultaneously begins to temper the quenched layers using the heat from the bar's core.
Steel billets 130mm² ("pencil ingots") are heated to approximately 1200°C to 1250°C in a reheat furnace. Then, they are progressively rolled to reduce the billets to the final size and shape of reinforcing bar. After the last rolling stand, the billet moves through a quench box. The quenching converts the billet's surface layer to martensite, and causes it to shrink. The shrinkage pressurizes the core, helping to form the correct crystal structures. The core remains hot, and austenitic. A microprocessor controls the water flow to the quench box, to manage the temperature difference through the cross-section of the bars. The correct temperature difference assures that all processes occur, and bars have the necessary mechanical properties.
The bar leaves the quench box with a temperature gradient through its cross section. As the bar cools, heat flows from the bars centre to its surface so that the bars heat and pressure correctly tempers an intermediate ring of martensite and bainite.
Finally, the slow cooling after quenching automatically tempers the austenitic core to ferrite and pearlite on the cooling bed.
These bars therefore exhibit a variation in microstructure in their cross section, having strong, tough, tempered martensite in the surface layer of the bar, an intermediate layer of martensite and bainite, and a refined, tough and ductile ferrite and pearlite core.
When the cut ends of TMT bars are etched in Nital (a mixture of nitric acid and methanol), three distinct rings appear: 1. A tempered outer ring of martensite, 2. A semi-tempered middle ring of martensite and bainite, and 3. a mild circular core of bainite, ferrite and pearlite. This is the desired micro structure for quality construction rebar.
In contrast, lower grades of rebar are twisted when cold, work hardening them to increase their strength. However, after thermo mechanical treatment (TMT), bars do not need more work hardening. As there is no twisting during TMT, no torsional stress occurs, and so torsional stress cannot form surface defects in TMT bars. Therefore TMT bars resist corrosion better than cold, twisted and deformed (CTD) bars.
After thermomechanical processing, some grades in which TMT Bars can be covered includes Fe: 415 /500 /550/ 600. These are much stronger compared with conventional CTD Bars and give up to 20% more strength to concrete structure with same quantity of steel. | 1 | Applied and Interdisciplinary Chemistry |
Aquatic invertebrates, most popularly the larvae of the caddis fly sp., are responsive to climate change, low levels of pollution and temperature change. As a result, they have the longest history of use in biomonitoring programs. Additionally, macroscopic species: frogs, fish, and some plant species, as well as, many forms of microscopic life, like bacteria and protozoa are used as indicator organisms in a variety of applications, storm water run-off among them.
Many species of Macroalgae (including Cyanobacteria, though not technically a true algae) are also used in biomonitoring for both aquatic and marine environments, as their short lifespan makes them very reactive to changes. | 1 | Applied and Interdisciplinary Chemistry |
The Executive Committee of the IIR handles the administrative and financial aspects of the daily running of the IIR, and meets once per year. It includes one delegate per member country, a president and three to six vice-presidents. | 0 | Theoretical and Fundamental Chemistry |
For an enzyme immobilised on an electrode, the value of the current at a certain potential equates , where is the number of electrons exchanged in the catalytic reaction, is the electrode surface, is the electroactive coverage, and TOF is the turnover frequency (or "turnover number"), that is, the number of substrate molecules transformed per second and per molecule of adsorbed enzyme).The latter can be deduced from the absolute value of the current only on condition that is known, which is rarely the case. However, information is obtained by analysing the relative change in current that results from changing the experimental conditions.
The factors that may influence the TOF are (i) the mass transport of substrate towards the electrode where the enzyme is immobilised (diffusion and convection), (ii) the rate of electron transfer between the electrode and the enzyme (interfacial electron transfer), and (iii) the "intrinsic" activity of the enzyme, all of which may depend on electrode potential.
The enzyme is often immobilized on a rotating disk working electrode (RDE) that is spun quickly to prevent the depletion of the substrate near the electrode. In that case, mass transport of substrate towards the electrode where the enzyme is adsorbed may not be influential. | 0 | Theoretical and Fundamental Chemistry |
The FeMo cofactor is a cluster with composition FeMoSC. Fe is the chemical symbol for the element iron (ferrum), and Mo is the symbol for molybdenum. This large cluster can be viewed as two subunits composed of one FeS (iron(III) sulfide) cluster and one MoFeS cluster. The two clusters are linked by three sulfide ligands and a bridging carbon atom. The unique iron (Fe) is anchored to the protein by a cysteine. It is also bound to three sulfides, resulting in tetrahedral molecular geometry. The additional six Fe centers in the cluster are each bonded to three sulfides. These six internal Fe centers define a trigonal prismatic arrangement around a central carbide center. The molybdenum is attached to three sulfides and is anchored to the protein by the imidazole group of a histidine residue. Also bound to Mo is a bidentate homocitrate cofactor, leading to octahedral geometry. Crystallographic analysis of the MoFe protein initially revealed the geometry and chemical composition of FeMoco, later confirmed by extended X-ray absorption fine-structure (EXAFS) studies. The Fe-S, Fe-Fe and Fe-Mo distances were determined to be 2.32, 2.64, and 2.73 Å respectively. | 0 | Theoretical and Fundamental Chemistry |
Atmospheric methane is the methane present in Earths atmosphere. The concentration of atmospheric methane is increasing due to methane emissions, and is causing climate change. Methane is one of the most potent greenhouse gases. Methanes radiative forcing (RF) of climate is direct, and it is the second largest contributor to human-caused climate forcing in the historical period. Methane is a major source of water vapour in the stratosphere through oxidation; and water vapour adds about 15% to methane's radiative forcing effect. The global warming potential (GWP) for methane is about 84 in terms of its impact over a 20-year timeframe, and 28 in terms of its impact over a 100-year timeframe.
Since the beginning of the Industrial Revolution (around 1750) the methane concentration in the atmosphere has increased by about 160%, and this increase is almost entirely caused by human activities. Since 1750 methane has contributed 3% of greenhouse gas (GHG) emissions in terms of mass but is responsible for approximately 23% of radiative or climate forcing. By 2019, global methane concentrations had risen from 722 parts per billion (ppb) in pre-industrial times to 1866 ppb. This is an increase by a factor of 2.6 and the highest value in at least 800,000 years.
Methane increases the amount of ozone (O) in the troposphere ( to from the Earths surface) and also in the stratosphere (from the troposphere to above the Earths surface). Both water vapour and ozone are GHGs, which in turn add to climate warming. | 1 | Applied and Interdisciplinary Chemistry |
Of all the radiation-based chemical reactions that have been studied, the most important is the decomposition of water. When exposed to radiation, water undergoes a breakdown sequence into hydrogen peroxide, hydrogen radicals, and assorted oxygen compounds, such as ozone, which when converted back into oxygen releases great amounts of energy. Some of these are explosive. This decomposition is produced mainly by alpha particles, which can be entirely absorbed by very thin layers of water.
Summarizing, the radiolysis of water can be written as: | 0 | Theoretical and Fundamental Chemistry |
Among these four moisture condition of aggregates, saturated surface dry is the condition that has the most applications in laboratory experiments, researches and studies, especially these related to water absorption, composition ratio or shrinkage test in materials like concrete. For many related experiments, a saturated surface dry condition is a premise that must be realize before the experiment. In saturated surface dry condition, the aggregate's water content is in a relatively stable and static situation where it would not be affected by its environment. Therefore, in experiments and tests where aggregates are in saturated surface dry condition, there would be fewer disrupting factors than in other three conditions. | 0 | Theoretical and Fundamental Chemistry |
One major area of application for microfluidic devices is the separation and sorting of different fluids or cell types. Recent developments in the microfluidics field have seen the integration of microfluidic devices with magnetophoresis: the migration of particles by a magnetic field. This can be accomplished by sending a fluid containing at least one magnetic component through a microfluidic channel that has a magnet positioned along the length of the channel. This creates a magnetic field inside the microfluidic channel which draws magnetically active substances towards it, effectively separating the magnetic and non-magnetic components of the fluid. This technique can be readily utilized in industrial settings where the fluid at hand already contains magnetically active material. For example, a handful of metallic impurities can find their way into certain consumable liquids, namely milk and other dairy products. Conveniently, in the case of milk, many of these metal contaminants exhibit paramagnetism. Therefore, before packaging, milk can be flowed through channels with magnetic gradients as a means of purifying out the metal contaminants.
Other, more research-oriented applications of microfluidic-assisted magnetophoresis are numerous and are generally targeted towards cell separation. The general way this is accomplished involves several steps. First, a paramagnetic substance (usually micro/nanoparticles or a paramagnetic fluid) needs to be functionalized to target the cell type of interest. This can be accomplished by identifying a transmembranal protein unique to the cell type of interest and subsequently functionalizing magnetic particles with the complementary antigen or antibody. Once the magnetic particles are functionalized, they are dispersed in a cell mixture where they bind to only the cells of interest. The resulting cell/particle mixture can then be flowed through a microfluidic device with a magnetic field to separate the targeted cells from the rest.
Conversely, microfluidic-assisted magnetophoresis may be used to facilitate efficient mixing within microdroplets or plugs. To accomplish this, microdroplets are injected with paramagnetic nanoparticles and are flowed through a straight channel which passes through rapidly alternating magnetic fields. This causes the magnetic particles to be quickly pushed from side to side within the droplet and results in the mixing of the microdroplet contents. This eliminates the need for tedious engineering considerations that are necessary for traditional, channel-based droplet mixing. Other research has also shown that the label-free separation of cells may be possible by suspending cells in a paramagnetic fluid and taking advantage of the magneto-Archimedes effect. While this does eliminate the complexity of particle functionalization, more research is needed to fully understand the magneto-Archimedes phenomenon and how it can be used to this end. This is not an exhaustive list of the various applications of microfluidic-assisted magnetophoresis; the above examples merely highlight the versatility of this separation technique in both current and future applications. | 1 | Applied and Interdisciplinary Chemistry |
In 1887, Heinrich Hertz observed that when light with sufficient frequency hits a metallic surface, the surface emits cathode rays. Ten years later, J. J. Thomson showed that the many reports of cathode rays were actually "corpuscles" and they quickly came to be called electrons. In 1902, Philipp Lenard discovered that the maximum possible energy of an ejected electron is unrelated to its intensity. This observation is at odds with classical electromagnetism, which predicts that the electron's energy should be proportional to the intensity of the incident radiation.
In 1905, Albert Einstein suggested that even though continuous models of light worked extremely well for time-averaged optical phenomena, for instantaneous transitions the energy in light may occur a finite number of energy quanta.
From the introduction section of his March 1905 quantum paper "On a heuristic viewpoint concerning the emission and transformation of light", Einstein states:
This statement has been called the most revolutionary sentence written by a physicist of the twentieth century.
The energy of a single quantum of light of frequency is given by the frequency multiplied by Planck's constant (an extremely tiny positive number):
Einstein assumed a light quanta transfers all of its energy to a single electron imparting at most an energy to the electron. Therefore, only the light frequency determines the maximum energy that can be imparted to the electron; the intensity of the photoemission is proportional to the light beam intensity.
Einstein argued that it takes a certain amount of energy, called the work function and denoted by , to remove an electron from the metal. This amount of energy is different for each metal. If the energy of the light quanta is less than the work function, then it does not carry sufficient energy to remove the electron from the metal. The threshold frequency, , is the frequency of a light quanta whose energy is equal to the work function:
If is greater than , the energy is enough to remove an electron. The ejected electron has a kinetic energy, , which is, at most, equal to the light energy minus the energy needed to dislodge the electron from the metal:
Einsteins description of light as being composed of energy quanta extended Plancks notion of quantized energy, which is that a single quanta of a given frequency, , delivers an invariant amount of energy, .
In nature, single quanta are rarely encountered. The Sun and emission sources available in the 19th century emit vast amount of energy every second. Planck's constant, , is so tiny that the amount of energy in each quanta, is very very small. Light we see includes many trillions of such quanta. | 1 | Applied and Interdisciplinary Chemistry |
Chloroeremomycin is composed of seven amino acids (three non-proteinogenic, and four proteinogenic) and three saccharide units. From N-terminus to C-terminus, the order is: Me--Leu, -Tyr, -Asn, -4-hydroxyphenylglycine (HPG), -HPG, -Tyr, and -3,5-dihydroxyphenylglycine (DHPG). When referring to specific amino acids, this article will reference the amino acid in the order it appears within the heptapeptide. Chloroeremomycin is glycosylated at aa4 with a Glc-(2→α1)-epivancosamine disaccharide and at aa6 with a -BHT-(→α1)-epivancosamine saccharide.
Some amino acids are modified prior to the completion of the heptapeptide (in cis) and some are modified after the heptapeptide is formed (in trans). During the synthesis of the heptapeptide, the stereocenters of aa3, aa4, aa6, and aa7 are changed from L to D. Both Tyr residues are hydroxylated and chlorinated after the amino acids have been incorporated to the growing polypeptide to form 4-chloro-β-hydroxytyrosine (BHT). The now-BHT residues are then crosslinked to the aa4 HPG through aryl-ether linkages. An aryl-aryl bond is formed between aa5 and aa7 at the aa5-C3 and aa7-C2 positions on the aromatic rings. Finally, the N-terminus Leu is methylated.
In addition to the presence of -amino acids, the molecule has atropisomer chemistry. The orientations of the chloro-substituted phenyl rings add another aspect of stereochemistry to the molecule. | 0 | Theoretical and Fundamental Chemistry |
While all the metals of antiquity but tin and lead occur natively, only gold and silver are commonly found as the native metal.
* Gold and silver occur frequently in their native form
* Mercury compounds are reduced to elemental mercury simply by low-temperature heating (500 °C).
* Tin and iron occur as oxides and can be reduced with carbon monoxide (produced by, for example, burning charcoal) at 900 °C.
* Copper and lead compounds can be roasted to produce the oxides, which are then reduced with carbon monoxide at 900 °C.
* Meteoric iron is often found as the native metal and it was the earliest source for iron objects known to humanity | 1 | Applied and Interdisciplinary Chemistry |
A hydrogencarbonate indicator (hydrogencarbonate indicator) is a type of pH indicator that is sensitive enough to show a color change as the concentration of carbon dioxide gas in an aqueous solution increases. The indicator is used in photosynthesis and respiration experiments to find out whether carbon dioxide is being liberated. It is also used to test the carbon dioxide content during gaseous exchange of organisms. When the carbon dioxide content is higher than 0.04%, the initial red colour changes to yellow as the pH becomes more acidic. If the carbon dioxide content is lower than 0.04%, it changes from red to magenta and, in relatively very low carbon dioxide concentrations, to purple. Carbon dioxide, even in the concentrations found in exhaled air, will dissolve in the indicator to form carbonic acid, a weak acid, which will lower the pH and give the characteristic colour change. A colour change to purple during photosynthesis shows a reduction in the percentage of carbon dioxide and is sometimes inferred as production of oxygen, but there is not actually any direct evidence for it.
Great care must be taken to avoid acidic or alkaline contamination of the apparatus in such experiments, since the test is not directly specific to gases like carbon dioxide. | 0 | Theoretical and Fundamental Chemistry |
A simple example can illustrate the concept. Consider the situation in which a slurry is flowing into a settling tank to remove the solids in the tank. Solids are collected at the bottom by means of a conveyor belt partially submerged in the tank, and water exits via an overflow outlet.
In this example, there are two substances: solids and water. The water overflow outlet carries an increased concentration of water relative to solids, as compared to the slurry inlet, and the exit of the conveyor belt carries an increased concentration of solids relative to water.
Assumptions
*Steady state
*Non-reactive system
Analysis
Suppose that the slurry inlet composition (by mass) is 50% solid and 50% water, with a mass flow of . The tank is assumed to be operating at steady state, and as such accumulation is zero, so input and output must be equal for both the solids and water. If we know that the removal efficiency for the slurry tank is 60%, then the water outlet will contain of solids (40% times times 50% solids). If we measure the flow rate of the combined solids and water, and the water outlet is shown to be , then the amount of water exiting via the conveyor belt must be . This allows us to completely determine how the mass has been distributed in the system with only limited information and using the mass balance relations across the system boundaries. The mass balance for this system can be described in a tabular form: | 1 | Applied and Interdisciplinary Chemistry |
COLACRO (Congreso Latinoamericano de Cromatografia) Merit Medal; Pittsburgh Analytical Chemistry Award; Eastern Analytical Symposium Award for Outstanding Achievements in the Fields of Analytical Chemistry; Tracy M. Sonneborn Award for Outstanding Research and Teaching, Indiana University; Dal Nogare Award in Chromatography; CaSSS (California Separation Science Society) Award for Excellence in Separation Science; Honorary Member of the Slovak Pharmaceutical Society; Foreign Member of the Learned Society of the Czech Republic (Czech Academy of Sciences); American Chemical Society Award in Analytical Chemistry; Jan Weber Prize and Medal, Slovak Pharmaceutical Society, Slovakia; Ralph N. Adams Award in Bioanalytical Chemistry. | 0 | Theoretical and Fundamental Chemistry |
Ex situ conservation (literally "off-site conservation") is the process of protecting an endangered species, variety or breed, of plant or animal outside its natural habitat. For example, by removing part of the population from a threatened habitat and placing it in a new location, an artificial environment which is similar to the natural habitat of the respective animal and within the care of humans, such as a zoological park or wildlife sanctuary. The degree to which humans control or modify the natural dynamics of the managed population varies widely, and this may include alteration of living environments, reproductive patterns, access to resources, and protection from predation and mortality.
Ex situ management can occur within or outside a species natural geographic range. Individuals maintained ex situ exist outside an ecological niche. This means that they are not under the same selection pressures as wild populations, and they may undergo artificial selection if maintained ex situ' for multiple generations.
Agricultural biodiversity is also conserved in ex situ collections. This is primarily in the form of gene banks where samples are stored in order to conserve the genetic resources of major crop plants and their wild relatives. | 1 | Applied and Interdisciplinary Chemistry |
Water-use efficiency (WUE) refers to the ratio of plant biomass to water lost by transpiration, can be defined either at the leaf, at the whole plant or a population/stand/field level:
*leaf level : photosynthetic water-use efficiency (also called instantaneous water-use efficiency WUE), which is defined as the ratio of the rate of net CO carbon assimilation (photosynthesis) to the rate of transpiration or stomatal conductance, then called intrinsic water-use efficiency (iWUE or W)
*plant level : water-use efficiency of productivity (also called integrated water-use efficiency or transpiration efficiency,TE), which is typically defined as the ratio of dry biomass produced to the rate of transpiration.
* field level : based on measurements of CO and water fluxes over a field of a crop or a forest, using the eddy covariance technique
Research to improve the water-use efficiecy of crop plants has been ongoing from the early 20th century, however with difficulties to actually achieve crops with increased water-use efficiency.
Intrinsic water-use efficiency W usually increases during soil drought, due to stomatal closure and a reduction in transpiration, and is therefore often linked to drought tolerance. Observatios from several authors have however suggested that WUE would rather be linked to different drought response strategies, where
* low WUE plants could either correspond to a drought tolerance strategy, for example by anatomical adaptations reducing vulnerability to xylem cavitation, or to a drought avoidance/water spender strategy through a wide soil exploration by roots or a drought escape strategy due to early flowering
* whereas high WUE plants could correspond to a drought avoidance/water saving strategy, through drought-sensitive, early closing stomata.
Increases in water-use efficiency are commonly cited as a response mechanism of plants to moderate to severe soil water deficits and have been the focus of many programs that seek to increase crop tolerance to drought. However, there is some question as to the benefit of increased water-use efficiency of plants in agricultural systems, as the processes of increased yield production and decreased water loss due to transpiration (that is, the main driver of increases in water-use efficiency) are fundamentally opposed. If there existed a situation where water deficit induced lower transpirational rates without simultaneously decreasing photosynthetic rates and biomass production, then water-use efficiency would be both greatly improved and the desired trait in crop production.
Water-use efficiency is also a much studied trait in Plant ecology, where it has been used already in the early 20th century to study the ecological requirements of Herbaceous plants or forest trees, and is still used today, for example related to a drought-induced limitation of tree growth | 0 | Theoretical and Fundamental Chemistry |
Thiosulfonates are organosulfur compounds with the formula RSOSR'. Thiosulfonate esters are produced by oxidation of disulfides or the nucleophilic attack of thiolates on organosulfonyl halides.
Alkali metal thiosulfonates are the conjugate base of thiosulfuric acid. They are prepared by the reaction of organosulfonyl chlorides with sources of sulfide.
Oxidation with mCPBA gives disulfones. | 0 | Theoretical and Fundamental Chemistry |
EPIC-seq inherits the advantages of high-throughput sequencing: fast sequencing times, high scalability, higher sequencing depths, lower costs, and low error rates. Another advantage of EPIC-seq is that it is non-invasive. This also eliminates the risks of invasive methods done over risky tissues and allows scientists to study tissues that are too dangerous or difficult to do so. | 1 | Applied and Interdisciplinary Chemistry |
N NMR has complications not encountered in H and C NMR spectroscopy. The 0.36% natural abundance of N results in a major sensitivity penalty. Sensitivity is made worse by its low gyromagnetic ratio (γ = −27.126 × 10 Ts), which is 10.14% that of H. The signal-to-noise ratio for H is about 300-fold greater than N at the same magnetic field strength. | 0 | Theoretical and Fundamental Chemistry |
Melanocytes are commonly known as cells that are responsible for producing the pigment melanin which gives coloration to the hair, skin, and nails. The exact mechanisms of how exactly melanocytes become cancerous are relatively unclear, but there is ongoing research to gain more information about the process. For example, it has been uncovered that the DNA of certain genes is often damaged in melanoma cells, most likely as a result of damage from UV radiation, and in turn increases the likelihood of developing melanoma. Specifically, it has been found that a large percentage of melanomas have mutations in the B-RAF gene which leads to melanoma by causing an MEK-ERK kinase cascade when activated. In addition to B-RAF, MITF is also known to play a crucial role in melanoma progression. Since it is a transcription factor that is involved in the regulation of genes related to invasiveness, migration, and metastasis, it can play a role in the progression of melanoma. | 1 | Applied and Interdisciplinary Chemistry |
Experimentation with respiratory oxidase inhibitors (for instance, cyanide) on unicellular algae has revealed interactive pathways to be present between chloroplasts and mitochondria. Metabolic pathways responsible for photosynthesis are present in chloroplasts, whereas respiratory metabolic pathways are present in mitochondria. In these pathways, metabolic carriers (like phosphate) exchange NAD(P)H molecules between photosynthetic and respiratory ETCs. Evidence using mass spectrometry on algae and photosynthetic mutants of Chlamydomonas, discovered that oxygen molecules were also being exchanged between photosynthetic and chlororespiratory ETCs. The mutant Chlamydomonas alga species, lacks photosystems one and two (PS I and PS II), so when the alga underwent flash-induced PS I activity, it resulted in no effect on mitochondrial pathways of respiration. Instead, this flash-induced PS I activity caused an exchange between photosynthetic and chlororespiratory ETCs, which was observed using polarography. This flash of PS I activity is triggered by an over-reduction of the PQ pool and/or lack of the pyridine nucleotide in the thylakoid membrane. A reduction in such molecules then stimulates NADPH and PTOX molecules to trigger chlororespiratory pathways.
Furthermore, in the absence of light (and thus photosynthesis), chlororespiration plays an integral role in enabling metabolic pathways to compensate for chemical energy synthesis. This is achieved through the oxidation of stromal compounds, which increases the PQ pool and allows for the chlororespiratory ETC to take place. | 1 | Applied and Interdisciplinary Chemistry |
Years of research and experience with the unusual conditions of supersonic flow have led to some interesting conclusions about airfoil design. Considering a rectangular wing, the pressure at a point P with coordinates (x,y) on the wing is defined only by the pressure disturbances originated at points within the upstream Mach cone emanating from point P. As result, the wing tips modify the flow within their own rearward Mach cones. The remaining area of the wing does not suffer any modification by the tips and can be analyzed with two-dimensional theory. For an arbitrary planform the supersonic leading and trailing are those portions of the wing edge where the components of the freestream velocity normal to the edge are supersonic. Similarly the subsonic leading and trailing are those portions of the wing edge where the components of the free stream velocity normal to the edge are subsonic.
Delta wings have supersonic leading and trailing edges; in contrast arrow wings have a subsonic leading edge and a supersonic trailing edge.
When designing a supersonic airfoil two factors that must be considered are shock and expansion waves. Whether a shock or expansion wave is generated at different locations along an airfoil depends on the local flow speed and direction along with the geometry of the airfoil. | 1 | Applied and Interdisciplinary Chemistry |
Wilhelm Röntgen discovered X-rays on November 8, 1895, and their use spread very quickly for medical diagnostics, particularly broken bones and embedded foreign objects where they were a revolutionary improvement over previous techniques.
Due to the wide use of X-rays and the growing realisation of the dangers of ionizing radiation, measurement standards became necessary for radiation intensity and various countries developed their own, but using differing definitions and methods. Eventually, in order to promote international standardisation, the first International Congress of Radiology (ICR) meeting in London in 1925, proposed a separate body to consider units of measure. This was called the International Commission on Radiation Units and Measurements, or ICRU, and came into being at the Second ICR in Stockholm in 1928, under the chairmanship of Manne Siegbahn.
One of the earliest techniques of measuring the intensity of X-rays was to measure their ionising effect in air by means of an air-filled ion chamber. At the first ICRU meeting it was proposed that one unit of X-ray dose should be defined as the quantity of X-rays that would produce one esu of charge in one cubic centimetre of dry air at 0 °C and 1 standard atmosphere of pressure. This unit of radiation exposure was named the roentgen in honour of Wilhelm Röntgen, who had died five years previously. At the 1937 meeting of the ICRU, this definition was extended to apply to gamma radiation. This approach, although a great step forward in standardisation, had the disadvantage of not being a direct measure of the absorption of radiation, and thereby the ionisation effect, in various types of matter including human tissue, and was a measurement only of the effect of the X-rays in a specific circumstance; the ionisation effect in dry air.
In 1940, Louis Harold Gray, who had been studying the effect of neutron damage on human tissue, together with William Valentine Mayneord and the radiobiologist John Read, published a paper in which a new unit of measure, dubbed the gram roentgen (symbol: gr) was proposed, and defined as "that amount of neutron radiation which produces an increment in energy in unit volume of tissue equal to the increment of energy produced in unit volume of water by one roentgen of radiation". This unit was found to be equivalent to 88 ergs in air, and made the absorbed dose, as it subsequently became known, dependent on the interaction of the radiation with the irradiated material, not just an expression of radiation exposure or intensity, which the roentgen represented. In 1953 the ICRU recommended the rad, equal to 100 erg/g, as the new unit of measure of absorbed radiation. The rad was expressed in coherent cgs units.
In the late 1950s, the CGPM invited the ICRU to join other scientific bodies to work on the development of the International System of Units, or SI. The CCU decided to define the SI unit of absorbed radiation as energy deposited by reabsorbed charged particles per unit mass of absorbent material, which is how the rad had been defined, but in MKS units it would be equivalent to the joule per kilogram. This was confirmed in 1975 by the 15th CGPM, and the unit was named the "gray" in honour of Louis Harold Gray, who had died in 1965. The gray was thus equal to 100 rad. Notably, the centigray (numerically equivalent to the rad) is still widely used to describe absolute absorbed doses in radiotherapy.
The adoption of the gray by the 15th General Conference on Weights and Measures as the unit of measure of the absorption of ionizing radiation, specific energy absorption, and of kerma in 1975 was the culmination of over half a century of work, both in the understanding of the nature of ionizing radiation and in the creation of coherent radiation quantities and units. | 0 | Theoretical and Fundamental Chemistry |
For a given structure, the shear center is the point in space at which shear force could be applied without causing torsional deformation (e.g. twisting) of the cross-section of the structure. The shear center is an imaginary point, but does not vary with the magnitude of the shear force - only the cross-section of the structure. The shear center always lies along the axis of symmetry, and can be found using the following method:
# Apply an arbitrary resultant shear force
# Calculate the shear flows from this shear force
# Choose a reference point o an arbitrary distance e from the point of application of the load
# Calculate the moment about o using both shear flows and the resultant shear force, and equate the two expressions. Solve for e
# The distance e and the axis of symmetry give the coordinate for the shear center, independent of the shear force magnitude. | 1 | Applied and Interdisciplinary Chemistry |
Hyperconjugation affects several properties.
# Bond length: Hyperconjugation is suggested as a key factor in shortening of sigma bonds (σ bonds). For example, the single C–C bonds in 1,3-butadiene and propyne are approximately 1.46 Å in length, much less than the value of around 1.54 Å found in saturated hydrocarbons. For butadiene, this can be explained as normal conjugation of the two alkenyl parts. But for propyne, it is generally accepted that this is due to hyperconjugation between the alkyl and alkynyl parts.
# Dipole moments: The large increase in dipole moment of 1,1,1-trichloroethane as compared with chloroform can be attributed to hyperconjugated structures.
# The heat of formation of molecules with hyperconjugation are greater than sum of their bond energies and the heats of hydrogenation per double bond are less than the heat of hydrogenation of ethylene.
# Stability of carbocations:
#:(CH)C > (CH)CH > (CH)CH > CH
#: The three C–H σ bonds of the methyl group(s) attached to the carbocation can undergo the stabilization interaction but only one of them can be aligned perfectly with the empty p-orbital, depending on the conformation of the carbon–carbon bond. Donation from the two misaligned C–H bonds is weaker. The more adjacent methyl groups there are, the larger hyperconjugation stabilization is because of the increased number of adjacent C–H bonds. | 0 | Theoretical and Fundamental Chemistry |
Blow-off panels are used in ammunition compartments of some tanks to protect the crew in case of ammunition explosion, turning a catastrophic kill into a lesser firepower kill. Blowout panels are installed in several modern main battle tanks, including the M1 Abrams.
In military ammunition storage, blowout panels are included in the design of the bunkers which house explosives. Such bunkers are designed, typically, with concrete walls on four sides, and a roof made of a lighter material covered with earth. In some cases this lighter material is wood, though metal sheeting is also employed. The design is such that if an explosion or fire in the ammunition bunker (also called a locker) were to occur, the force of the blast would be directed vertically, and away from other structures and personnel.
Blowout panels had been in the past been considered as a possible solution to magazine explosions on battleships. However battleship designs since the 1920s instead used the all or nothing armor scheme, particularly with its armored citadel encompassing the battleships vitals including machinery and magazines, and in the case of magazine penetration the only recourse is to flood the magazine. The lack of blowout panels has resulted in catastrophic damage during the magazine explosions of several battleships including Tirpitz and Yamato'. | 1 | Applied and Interdisciplinary Chemistry |
Defining a drag coefficient, , as the ratio of the force experienced by the particle divided by the impact pressure of the fluid, a coefficient that can be considered as the transfer of available fluid force into drag is established. In this region the inertia of the impacting fluid is responsible for the majority of force transfer to the particle.
For a spherical particle in the Stokes regime this value is not constant, however in the Newtonian drag regime the drag on a sphere can be approximated by a constant, 0.44. This constant value implies that the efficiency of transfer of energy from the fluid to the particle is not a function of fluid velocity.
As such the terminal velocity of a particle in a Newtonian regime can again be obtained by equating the drag force to the applied force, resulting in the following expression | 0 | Theoretical and Fundamental Chemistry |
In crystallography, the transition temperature is the temperature at which a material changes from one crystal state (allotrope) to another. More formally, it is the temperature at which two crystalline forms of a substance can co-exist in equilibrium. For example, when rhombic sulfur is heated above 95.6 °C, it changes form into monoclinic sulfur; when cooled
below 95.6 °C, it reverts to rhombic sulfur. At 95.6 °C the two forms can co-exist. Another example is tin, which transitions from a cubic crystal below 13.2 °C to a tetragonal crystal above that temperature.
In the case of ferroelectric or ferromagnetic crystals, a transition temperature may be known as the Curie temperature. | 0 | Theoretical and Fundamental Chemistry |
The Renner-Teller effect is a phenomenon in molecular spectroscopy where a pair of electronic states that become degenerate at linearity are coupled by rovibrational motion.
The Renner-Teller effect is observed in the spectra of molecules that have electronic states that allow vibration through a linear configuration. For such molecules electronic states that are doubly degenerate at linearity (Π, Δ, ..., etc.) will split into two close-lying nondegenerate states for non-linear configurations. As part of the Renner–Teller effect, the rovibronic levels of such a pair of states will be strongly Coriolis coupled by the rotational kinetic energy operator causing a breakdown of the Born–Oppenheimer approximation. This is to be contrasted with the Jahn–Teller effect which occurs for polyatomic molecules in electronic states that allow vibration through a symmetric nonlinear configuration, where the electronic state is degenerate, and which further involves a breakdown of the Born-Oppenheimer approximation but here caused by the vibrational kinetic energy operator.
In its original formulation, the Renner–Teller effect was discussed for a triatomic molecule in an electronic state that is a linear Π-state at equilibrium. The 1934 article by Rudolf Renner was one of the first that considered dynamic effects that go beyond the Born–Oppenheimer approximation, in which the nuclear and electronic motions in a molecule are uncoupled. Renner chose an electronically excited state of the carbon dioxide molecule (CO) that is a linear Π-state at equilibrium for his studies. The products of purely electronic and purely nuclear rovibrational states served as the zeroth-order (no rovibronic coupling) wave functions in Renner's study. The rovibronic coupling acts as a perturbation.
Renner is the only author of the 1934 paper that first described the effect, so it can be called simply the Renner effect. Renner did this work as a PhD student under the supervision of Edward Teller and presumably Teller was perfectly happy not to be a coauthor. However, in 1933 Gerhard Herzberg and Teller had recognized that the potential of a triatomic linear molecule in a degenerate electronic state at linearity splits into two when the molecule is bent. A year later this effect was worked out in detail by Renner. Herzberg refers to this as the "Renner–Teller" effect in one of his influential books, and this name is most commonly used.
While Renner's theoretical study concerns an excited electronic state of carbon dioxide that is linear at equilibrium, the first observation of the Renner–Teller effect was in an electronic state of the NH molecule that is bent at equilibrium.
Much has been published about the Renner–Teller effect since its first experimental observation in 1959; see the bibliography on pages 412-413 of the textbook by Bunker and Jensen. Section 13.4 of this textbook discusses both the Renner–Teller effect (called the Renner effect) and the Jahn–Teller effect. | 0 | Theoretical and Fundamental Chemistry |
The gem-diol intermediate cleaves at the C2-C3 bond to form one molecule of glycerate-3-phosphate and a negatively charged carboxylate. Stereo specific protonation of C2 of this carbanion results in another molecule of glycerate-3-phosphate. This step is thought to be facilitated by Lys175 or potentially the carbamylated Lys210. | 0 | Theoretical and Fundamental Chemistry |
Many carboxylic acids are produced industrially on a large scale. They are also frequently found in nature. Esters of fatty acids are the main components of lipids and polyamides of aminocarboxylic acids are the main components of proteins.
Carboxylic acids are used in the production of polymers, pharmaceuticals, solvents, and food additives. Industrially important carboxylic acids include acetic acid (component of vinegar, precursor to solvents and coatings), acrylic and methacrylic acids (precursors to polymers, adhesives), adipic acid (polymers), citric acid (a flavor and preservative in food and beverages), ethylenediaminetetraacetic acid (chelating agent), fatty acids (coatings), maleic acid (polymers), propionic acid (food preservative), terephthalic acid (polymers). Important carboxylate salts are soaps. | 0 | Theoretical and Fundamental Chemistry |
Because the ability of a surface to adsorb molecules onto its surface depends on energies of interaction, thermodynamics of adsorption can be used to understand the driving forces for adsorption. To measure the thermodynamics of polymer surfaces, contact angles are often used to easily obtain useful information. The thermodynamic description of contact angles of a drop of liquid on a solid surface are derived from the equilibrium formed between the chemical potentials of the solid–liquid, solid–vapor, and liquid–vapor interfaces.
At equilibrium, the contact angle of a liquid drop on a surface does not change. Therefore, the Gibbs free energy is equal to 0:
The chemical potentials of the three interfaces must cancel out, producing Young's equation for the relationship between surface energies and contact angles:
where:
:is the surface tension of the liquid
: is the contact angle of the liquid
: is the surface tension of the solid–vapor interface
: is the surface tension of the solid–liquid interface
: is the vapor pressure of the liquid at equilibrium.
However, this equation cannot be used to determine the surface energy of a solid surface by itself. It can be used in conjunction with the following equation to determine the relationship between contact angle and surface energy of the solid, as surface tension ≈ surface energy for a solid:
where
: is the surface energy of the solid
: is the surface tension of the liquid.
: and are the dispersive and polar components of the surface energy of the solid
Using these two equations, the surface energy of a solid can be determined simply by measuring the contact angle of two different liquids of known surface tension on that solid's surface. | 0 | Theoretical and Fundamental Chemistry |
Tramadol can have pharmacodynamic, pharmacokinetic, and pharmacogenetic interactions.
Tramadol is metabolized by CYP2D6 enzymes which contribute to the metabolism of approximately 25% of all medications. Any medications with the ability to inhibit or induce these enzymes may interact with tramadol. These include common antiarrhythmics, antiemetics, antidepressants (sertraline, paroxetine, and fluoxetine in particular), antipsychotics, analgesics, and tamoxifen.
Due to tramadols serotonergic effects, tramadol has the potential to contribute to the development of an acute or chronic hyper-serotonin state called serotonin syndrome when used concurrently with other pro-serotonergic medications such as antidepressants (SSRIs, SNRIs, tricyclics, MAOIs), antipsychotics, triptans, cold medications containing dextromethorphan, and some herbal products such as St. Johns wort.
Concurrent use of 5-HT3 antagonists such as ondansetron, dolasetron, and palonosetron may reduce the effectiveness of both drugs.
Tramadol also acts as an opioid agonist and thus can increase the risk for side effects when used with other opioid and opioid-containing analgesics (such as morphine, pethidine, tapentadol, oxycodone, fentanyl, and Tylenol 3).
Tramadol increases the risk for seizures by lowering the seizure threshold. Using other medications that lower seizure threshold - such as antipsychotic medications, bupropion (an anti-depressant and smoking cessation drug), and amphetamines - can further increases this risk. | 0 | Theoretical and Fundamental Chemistry |
Enalapril is used to treat hypertension, symptomatic heart failure, and asymptomatic left ventricular dysfunction. ACE-inhibitors (including enalapril) have demonstrated ability to reduce the progression and worsening of existing chronic kidney disease in the presence of proteinuria/microalbuminuria (protein in the urine, a biomarker for chronic kidney disease). This renal protective effect is not seen in the absence of proteinuria/microalbuminuria, including in diabetic populations. The benefit has been particularly demonstrated in patients with hypertension and/or diabetes, and is likely to be seen in other populations (although further studies and subgroup analyses of existing studies are needed) It is widely used in chronic kidney failure. Furthermore, enalapril is an emerging treatment for psychogenic polydipsia. A double-blind, placebo-controlled trial showed that when used for this purpose, enalapril led to decreased water consumption (determined by urine output and osmolality) in 60% of patients. | 0 | Theoretical and Fundamental Chemistry |
Static devolatilizers include:
* Falling strand devolatilizers: Polymer is partitioned into many individual strands which fall down in a vacuum chamber. Diffusion moves volatiles into the gas phase, which are then collected via a vacuum system. This is usually the last stage of a devolatizing process, when vapor pressure is low.
* Falling film evaporator: Polymer falls down vertical walls, volatiles diffusing on the side that is not in contact with the walls.
* Tube evaporators: A boiling polymer solution flows downward in a vertical shell and tube heat exchanger into a separator. Polymer is collected at the bottom, vapor is collected via a vacuum system and condensers.
* Flash evaporators: A polymer solution is preheated and brought into a separator, where pressure below the vapor pressure of the solution leads to a part of the volatiles evaporating | 1 | Applied and Interdisciplinary Chemistry |
Many industries such as food, beverages, cosmetics, and even medicine utilize levan in their products. One of the reasons levan is able to be used in such a versatile way is that it fulfills all safety guidelines. Levan does not cause any form of skin or eye irritation, has not shown any allergenic effects, and poses no threat of cytotoxicity. | 1 | Applied and Interdisciplinary Chemistry |
There are many ways to accurately manipulate single molecules. Prominent among these are optical or magnetic tweezers, atomic-force-microscope (AFM) cantilevers and acoustic force spectroscopy. In all of these techniques, a biomolecule, such as protein or DNA, or some other biopolymer has one end bound to a surface or micrometre-sized bead and the other to a force sensor. The force sensor is usually a micrometre-sized bead or a cantilever, whose displacement can be measured to determine the force. | 0 | Theoretical and Fundamental Chemistry |
Electroforming is a metal forming process in which parts are fabricated through electrodeposition on a model, known in the industry as a mandrel. Conductive (metallic) mandrels are treated to create a mechanical parting layer, or are chemically passivated to limit electroform adhesion to the mandrel and thereby allow its subsequent separation. Non-conductive (glass, silicon, plastic) mandrels require the deposition of a conductive layer prior to electrodeposition. Such layers can be deposited chemically, or using vacuum deposition techniques (e.g., gold sputtering). The outer surface of the mandrel forms the inner surface of the form.
The process involves passing direct current through an electrolyte containing salts of the metal being electroformed. The anode is the solid metal being electroformed, and the cathode is the mandrel, onto which the electroform gets plated (deposited). The process continues until the required electroform thickness is achieved. The mandrel is then either separated intact, melted away, or chemically dissolved.
The surface of the finished part that was in intimate contact with the mandrel is replicated in fine detail with respect to the original, and is not subject to the shrinkage that would normally be experienced in a foundry cast metal object, or the tool marks of a milled part. The solution side of the part is less well defined, and that loss of definition increases with thickness of the deposit. In extreme cases, where a thickness of several millimetres is required, there is preferential build-up of material on sharp outside edges and corners. This tendency can be reduced by shielding, or a process known as periodic reverse, where the electroforming current is reversed for short periods and the excess is preferentially dissolved electrochemically. The finished form can either be the finished part, or can be used in a subsequent process to produce a positive of the original mandrel shape, such as with vinyl records or CD and DVD stamper manufacture.
In recent years, due to its ability to replicate a mandrel surface with practically no loss of fidelity, electroforming has taken on new importance in the fabrication of micro and nano-scale metallic devices and in producing precision injection molds with micro- and nano-scale features for production of non-metallic micro-molded objects. | 1 | Applied and Interdisciplinary Chemistry |
In some clinical circumstances, succinylcholine may be administered before and after a nondepolarising NMBA or two different nondepolarising NMBAs are administered in sequence. Combining different NMBAs can result in different degrees of neuromuscular block and management should be guided with the use of a neuromuscular function monitor.
The administration of nondepolarising neuromuscular blocking agent has an antagonistic effect on the subsequent depolarising block induced by succinylcholine. If a nondepolarising NMBA is administered prior to succinycholine, the dose of succinylcholine must be increased.
The administration of succinylcholine on the subsequent administration of a nondepolarising neuromuscular block depends on the drug used. Studies have shown that administration of succinylcholien before a nondepolarising NMBA does not affect the potency of mivacurium or rocuronium. But for vecuronium and cisatracurium, it speeds up the onset, increases the potency and prolongs the duration of action.
Combining two nondepolarising NMBAs of the same chemical class (e.g. rocuronium and vecuronium) produces an additive effect, while combining two nondepolarising NMBAs of different chemical class (e.g. rocuronium and cisatracurium) produces a synergistic response. | 1 | Applied and Interdisciplinary Chemistry |
The bias error in particle tracking discussed in the previous section is evident in the frequency domain, but it can be difficult to appreciate in cases where the particle motion is being tracked to perform flow field measurements (like in particle image velocimetry). A simple but insightful solution to the above-mentioned differential equation is possible when the forcing function is a Heaviside step function; representing particles going through a shockwave. In this case, is the flow velocity upstream of the shock; whereas is the velocity drop across the shock.
The step response for a particle is a simple exponential:
To convert the velocity as a function of time to a particle velocity distribution as a function of distance, lets assume a 1-dimensional velocity jump in the direction. Lets assume is positioned where the shock wave is, and then integrate the previous equation to get:
Considering a relaxation time of (time to 95% velocity change), we have:
This means the particle velocity would be settled to within 5% of the downstream velocity at from the shock. In practice, this means a shock wave would look, to a PIV system, blurred by approximately this distance.
For example, consider a normal shock wave of Mach number at a stagnation temperature of 298 K. A propylene glycol particle of would blur the flow by ; whereas a would blur the flow by (which would, in most cases, yield unacceptable PIV results).
Although a shock wave is the worst-case scenario of abrupt deceleration of a flow, it illustrates the effect of particle tracking error in PIV, which results in a blurring of the velocity fields acquired at the length scales of order . | 1 | Applied and Interdisciplinary Chemistry |
Enantioselective cycloaddition of azomethine ylides using chiral catalysts was first described in a seminal work by Allway and Grigg in 1991. This powerful method was further developed by Jørgensen and Zhang. These reactions generally use zinc, silver, copper, nickel, and calcium complexes.
Using chiral phosphine catalysts, enantiomerically pure spiroindolinones can be synthesized. The method described by Gong, et al. leads to an unexpected regiochemical outcome that does not follow electronic effects. This is attributed to favorable pi stacking with the catalyst. | 0 | Theoretical and Fundamental Chemistry |
With aqueous pK values of around 16–19, they are, in general, slightly weaker acids than water. With strong bases such as sodium hydride or sodium they form salts called alkoxides, with the general formula (where R is an alkyl and M is a metal).
The acidity of alcohols is strongly affected by solvation. In the gas phase, alcohols are more acidic than in water. In DMSO, alcohols (and water) have a pK of around 29–32. As a consequence, alkoxides (and hydroxide) are powerful bases and nucleophiles (e.g., for the Williamson ether synthesis) in this solvent. In particular, or in DMSO can be used to generate significant equilibrium concentrations of acetylide ions through the deprotonation of alkynes (see Favorskii reaction). | 0 | Theoretical and Fundamental Chemistry |
* Aronson, S. and Ludlam, T.: [https://searchworks.stanford.edu/view/11327941 "Hunting the quark gluon plasma"], U.S. Dept. of Energy (2005)
* Letessier, Jean: [https://searchworks.stanford.edu/view/4807502 Hadrons and quark-gluon plasma], Cambridge monographs on particle physics, nuclear physics, and cosmology (Vol. 18), Cambridge University Press (2002) | 0 | Theoretical and Fundamental Chemistry |
The deformation fields around large (over 1 μm) non-deformable particles are characterised by high dislocation densities and large orientation gradients and so are ideal sites for the development of recrystallization nuclei. This phenomenon, called particle stimulated nucleation (PSN), is notable as it provides one of the few ways to control recrystallization by controlling the particle distribution.
The size and misorientation of the deformed zone is related to the particle size and so there is a minimum particle size required to initiate nucleation. Increasing the extent of deformation will reduce the minimum particle size, leading to a PSN regime in size-deformation space.
If the efficiency of PSN is one (i.e. each particle stimulates one nuclei), then the final grain size will be simply determined by the number of particles. Occasionally the efficiency can be greater than one if multiple nuclei form at each particle but this is uncommon. The efficiency will be less than one if the particles are close to the critical size and large fractions of small particles will actually prevent recrystallization rather than initiating it (see above). | 1 | Applied and Interdisciplinary Chemistry |
Total viable count (TVC), gives a quantitative estimate of the concentration of microorganisms such as bacteria, yeast or mould spores in a sample. The count represents the number of colony forming units (cfu) per g (or per ml) of the sample.
A TVC is achieved by plating serial tenfold dilutions of the sample until between 30 and 300 colonies can be counted on a single plate. The reported count is the number of colonies counted multiplied by the dilution used for the counted plate
A high TVC count indicates a high concentration of micro-organisms which may indicate poor quality for drinking water or foodstuff.
In food microbiology it is used as a benchmark for the evaluation of the shelf-life of foodstuffs | 0 | Theoretical and Fundamental Chemistry |
Chemical WorkBench can be used by researchers and engineers working in the following fields:
*General chemical kinetics and thermodynamics
*Kinetic mechanisms development
*Thin films growth for microelectronics
*Nanotechnology
*Catalysis and chemical engineering
*Combustion, detonation and pollution control
*Waste treatment and recovering
*Plasma light sources and plasma chemistry
*High-temperature chemistry
*Education
*Combustion and detonation, clean power-generation technologies, safety analysis, CVD, heterogeneous and catalytic reactions and processes, and processes in non-equilibrium plasmas are the main areas of interest. | 0 | Theoretical and Fundamental Chemistry |
Mond gas is a cheap coal gas that was used for industrial heating purposes. Coal gases are made by decomposing coal through heating it to a high temperature. Coal gases were the primary source of gas fuel during the 1940s and 1950s until the adoption of natural gas. They were used for lighting, heating, and cooking, typically being supplied to households through pipe distribution systems. The gas was named after its discoverer, Ludwig Mond. | 0 | Theoretical and Fundamental Chemistry |
The first generation of the Edwards equation was
where k and k are the rate constants for a nucleophile and a standard (HO). H is a measure of the basicity of the nucleophile relative to protons, as defined by the equation:
where the pK is that of the conjugate acid of the nucleophile and the constant 1.74 is the correction for the pK of HO.
E is the term Edwards introduced to account for the polarizability of the nucleophile. It is related to the oxidation potential (E) of the reaction (oxidative dimerization of the nucleophile) by the equation:
where 2.60 is the correction for the oxidative dimerization of water, obtained from a least-squares correlation of data in Edwards’ first paper on the subject. α and β are then parameters unique to specific nucleophiles that relate the sensitivity of the substrate to the basicity and polarizability factors.
However, because some β's appeared to be negative as defined by the first generation of the Edwards equation, which theoretically should not occur, Edwards adjusted his equation. The term E was determined to have some dependence on the basicity relative to protons (H) due to some factors that affect basicity also influencing the electrochemical properties of the nucleophile. To account for this, E was redefined in terms of basicity and polarizability (given as molar refractivity, R):
: where
The values of a and b, obtained by the method of least squares, are 3.60 and 0.0624 respectively. With this new definition of E, the Edwards equation can be rearranged:
where A= αa and B = β + αb. However, because the second generation of the equation was also the final one, the equation is sometimes written as , especially since it was republished in that form in a later paper of Edwards’, leading to confusion over which parameters are being defined. | 0 | Theoretical and Fundamental Chemistry |
Surface roughness scattering or interface roughness scattering is the elastic scattering of particles against a rough solid surface or imperfect interface between two different materials. This effect has been observed in classical systems, such as microparticle scattering, as well as quantum systems, where it arises electronic devices, such as field effect transistors and quantum cascade lasers. | 0 | Theoretical and Fundamental Chemistry |
In the diagram on the right, phytoplankton convert CO, which has dissolved from the atmosphere into the surface oceans (90 Gt yr), into particulate organic carbon (POC) during primary production (~ 50 Gt C yr). Phytoplankton are then consumed by copepods, krill and other small zooplankton grazers, which in turn are preyed upon by higher trophic levels. Any unconsumed phytoplankton form aggregates, and along with zooplankton faecal pellets, sink rapidly and are exported out of the mixed layer ( 14). Krill, copepods, zooplankton and microbes intercept phytoplankton in the surface ocean and sinking detrital particles at depth, consuming and respiring this POC to CO (dissolved inorganic carbon, DIC), such that only a small proportion of surface-produced carbon sinks to the deep ocean (i.e., depths > 1000 m). As krill and smaller zooplankton feed, they also physically fragment particles into small, slower- or non-sinking pieces (via sloppy feeding, coprorhexy if fragmenting faeces), retarding POC export. This releases dissolved organic carbon (DOC) either directly from cells or indirectly via bacterial solubilisation (yellow circle around DOC). Bacteria can then remineralise the DOC to DIC (CO, microbial gardening).
The biological carbon pump is one of the chief determinants of the vertical distribution of carbon in the oceans and therefore of the surface partial pressure of CO governing air-sea CO exchange. It comprises phytoplankton cells, their consumers and the bacteria that assimilate their waste and plays a central role in the global carbon cycle by delivering carbon from the atmosphere to the deep sea, where it is concentrated and sequestered for centuries. Photosynthesis by phytoplankton lowers the partial pressure of CO in the upper ocean, thereby facilitating the absorption of CO from the atmosphere by generating a steeper CO gradient. It also results in the formation of particulate organic carbon (POC) in the euphotic layer of the epipelagic zone (0–200 m depth). The POC is processed by microbes, zooplankton and their consumers into fecal pellets, organic aggregates (“marine snow”) and other forms, which are thereafter exported to the mesopelagic (200–1000 m depth) and bathypelagic zones by sinking and vertical migration by zooplankton and fish. Although primary production includes both dissolved and particulate organic carbon (DOC and POC respectively), only POC leads to efficient carbon export to the ocean interior, whereas the DOC fraction in surface waters is mostly recycled by bacteria. However, a more biologically resistant DOC fraction produced in the euphotic zone (accounting for 15–20% of net community productivity), is not immediately mineralized by microbes and accumulates in the ocean surface as biologically semi-labile DOC. This semi-labile DOC undergoes net export to the deep ocean, thus constituting a dynamic part of the biological carbon pump. The efficiency of DOC production and export varies across oceanographic regions, being more prominent in the oligotrophic subtropical oceans. The overall efficiency of the biological carbon pump is mostly controlled by the export of POC. | 0 | Theoretical and Fundamental Chemistry |
Walter Noddack (17 August 1893 – 7 December 1960) was a German chemist. He, Ida Tacke (who later married Noddack), and Otto Berg reported the discovery of element 43 and element 75 in 1925. | 1 | Applied and Interdisciplinary Chemistry |
Advantages of the copper–chlorine cycle include lower operating temperatures, the ability to use low-grade waste heat to improve energy efficiency, and potentially lower cost materials. In comparison with other thermochemical cycles, the Cu–Cl process requires relatively low temperatures of up to .
Another significant merit of this cycle is a relatively low voltage (thus low electrical energy expenditure) that is required for the electrochemical step (0.6 to 1.0 V, perhaps even 0.5 if lower current density can be achieved). The overall efficiency of the Cu–Cl cycle has been estimated to be just over 43%, excluding the additional potential gains of utilizing waste heat in the cycle.
Solids handling between processes and corrosive working fluids present unique challenges for the engineering equipment development. Among others, the following materials are being currently used: spray coatings, nickel alloys, glass-lined steel, refractory materials, and other advanced materials. | 0 | Theoretical and Fundamental Chemistry |
Because primers are designed to have low complementarity to each other, they may anneal (step I in the figure) only at low temperature, e.g. room temperature, such as during the preparation of the reaction mixture. Although DNA polymerases used in PCR are most active around 70 °C, they have some polymerizing activity also at lower temperatures, which can cause DNA synthesis from primers after annealing to each other. Several methods have been developed to prevent PDs formation until the reaction reaches working temperature (60-70 °C), and these include initial inhibition of the DNA polymerase, or physical separation of reaction components reaction until the reaction mixture reaches the higher temperatures. These methods are referred to as hot-start PCR.
Wax: in this method the enzyme is spatially separated from the reaction mixture by wax that melts when the reaction reaches high temperature.
Slow release of magnesium: DNA polymerase requires magnesium ions for activity, so the magnesium is chemically separated from the reaction by binding to a chemical compound, and is released into the solution only at high temperature
Non-covalent binding of inhibitor: in this method a peptide, antibody or aptamer are non-covalently bound to the enzyme at low temperature and inhibit its activity. After an incubation of 1–5 minutes at 95 °C, the inhibitor is released and the reaction starts.
Cold-sensitive Taq polymerase: is a modified DNA polymerase with almost no activity at low temperature.
Chemical modification: in this method a small molecule is covalently bound to the side chain of an amino acid in the active site of the DNA polymerase. The small molecule is released from the enzyme by incubation of the reaction mixture for 10–15 minutes at 95 °C. Once the small molecule is released, the enzyme is activated. | 1 | Applied and Interdisciplinary Chemistry |
Andrée Marquet studied engineering at the École nationale supérieure de chimie de Paris, then defended a thesis prepared at the Collège de France under the direction of Jean Jacques (1961), followed by a post-doctoral internship at the ETH in Zurich with Professor Duilio Arigoni. After a career at the CNRS, she was appointed professor at the Pierre-et-Marie-Curie University (1978) and founded the organic biological chemistry laboratory there. She contributed, with a few others, to the development of this interface sub-discipline at the national level, which was still in its infancy, and created at UPMC adapted teaching courses where chemists and biochemists could meet.
In addition to her work as a teacher-researcher, she has held various positions of general interest.
Between 1984 and 1986, she chaired the organic chemistry division of the Société chimique de France, and from 1987 to 1991, the Société Franco-japonaise de chimie fine et thérapeutique. She chaired section 20 of the CNRS National Committee (1991-1995) and was a member of the CNRS Scientific Council from 1992 to 1997. In 1998, she became Scientific Director of the Chemistry Department at the Research Department of the MENRT. Between 1999 and 2003, she was a member of the Board of Directors of the Palais de la Découverte, and between 2007 and 2008, she was a member of the Board of Directors of the MENRT.
2011, member of the Ethics Committee of the CNRS. In 2002, she founded the "Chemistry and Society" Commission, within the Fondation de la Maison de la Chimie, of which she remains president until 2011. This commission seeks to analyse the origin of the misunderstanding that has developed between chemistry and society, and to contribute to the search for solutions by organising actions resolutely directed towards the general public. | 0 | Theoretical and Fundamental Chemistry |
A plasmid is a small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently. They are most commonly found as small circular, double-stranded DNA molecules in bacteria; however, plasmids are sometimes present in archaea and eukaryotic organisms. In nature, plasmids often carry genes that benefit the survival of the organism and confer selective advantage such as antibiotic resistance. While chromosomes are large and contain all the essential genetic information for living under normal conditions, plasmids are usually very small and contain only additional genes that may be useful in certain situations or conditions. Artificial plasmids are widely used as vectors in molecular cloning, serving to drive the replication of recombinant DNA sequences within host organisms. In the laboratory, plasmids may be introduced into a cell via transformation. Synthetic plasmids are available for procurement over the internet.
Plasmids are considered replicons, units of DNA capable of replicating autonomously within a suitable host. However, plasmids, like viruses, are not generally classified as life. Plasmids are transmitted from one bacterium to another (even of another species) mostly through conjugation. This host-to-host transfer of genetic material is one mechanism of horizontal gene transfer, and plasmids are considered part of the mobilome. Unlike viruses, which encase their genetic material in a protective protein coat called a capsid, plasmids are "naked" DNA and do not encode genes necessary to encase the genetic material for transfer to a new host; however, some classes of plasmids encode the conjugative "sex" pilus necessary for their own transfer. Plasmids vary in size from 1 to over 400 kbp, and the number of identical plasmids in a single cell can range anywhere from one to thousands under some circumstances. | 1 | Applied and Interdisciplinary Chemistry |
The basic apothecaries system consists of the units pound, ounce, and scruple from the classical Roman weight system, together with the originally Greek drachm and a new subdivision of the scruple into either 20 ("barley") or 24 ("wheat") grains (). In some countries other units of the original system remained in use, for example in Spain the and . In some cases the apothecaries and civil weight systems had the same ounces ("an ounce is an ounce"), but the civil pound consisted of 16 ounces. is Latin for the seed of the carob tree.
Many attempts were made to reconstruct the exact mass of the Roman pound. One method for doing this consists in weighing old coins; another uses the fact that Roman weight units were derived from Roman units of length similar to the way the kilogramme was originally derived from the metre, i.e. by weighing a known volume of water. Nowadays the Roman pound is often given as 327.45 g, but one should keep in mind that (apart from the other uncertainties that come with such a reconstruction) the Roman weight standard is unlikely to have remained constant to such a precision over the centuries, and that the provinces often had somewhat inexact copies of the standard. The weight and subdivision of the pound in the Holy Roman Empire were reformed by Charlemagne, but in the Byzantine Empire it remained essentially the same. Since Byzantine coins circulated up to Scandinavia, the old Roman standard continued to be influential through the Middle Ages. | 1 | Applied and Interdisciplinary Chemistry |
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