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For patients who have achieved long term remission, it is recommended to discontinue lithium gradually and in a controlled fashion.
Discontinuation symptoms may occur in patients stopping the medication including irritability, restlessness and somatic symptoms like vertigo, dizziness or lightheadedness. Symptoms occur within the first week and are generally mild and self-limiting within weeks. | 1 | Applied and Interdisciplinary Chemistry |
Chemical exothermic reactions are generally more spontaneous than their counterparts, endothermic reactions.
In a thermochemical reaction that is exothermic, the heat may be listed among the products of the reaction. | 0 | Theoretical and Fundamental Chemistry |
CRISPR-associated transposons or CASTs are mobile genetic elements (MGEs) that have evolved to make use of minimal CRISPR systems for RNA-guided transposition of their DNA. Unlike traditional CRISPR systems that contain interference mechanisms to degrade targeted DNA, CASTs lack proteins and/or protein domains responsible for DNA cleavage. Specialized transposon machinery, similar to that of the well characterized Tn7 transposon, complexes with the CRISPR RNA (crRNA) and associated Cas proteins for transposition. CAST systems have been characterized in a wide range of bacteria and make use of variable CRISPR configurations including Type I-F, Type I-B, Type I-C, Type I-D, Type I-E, Type IV, and Type V-K. MGEs remain an important part of genetic exchange by horizontal gene transfer and CASTs have been implicated in the exchange of antibiotic resistance and antiviral defense mechanisms, as well as genes involved in central carbon metabolism. These systems show promise for genetic engineering due to their programmability, PAM flexibility, and ability to insert directly into the host genome without double strand breaks requiring activation of host repair mechanisms. They also lack Cas1 and Cas2 proteins and so rely on other more complete CRISPR systems for spacer acquisition in trans. | 1 | Applied and Interdisciplinary Chemistry |
Evelyn B. Man was born in Lawrence, New York, but she grew up in North Stonington, Connecticut. Man's father, Edward Man, was an attorney from New York City and her mother was Mary Hewitt Man.
Man graduated from Wheeler High School, and then, in 1925, she graduated from Wellesley College with a degree in chemistry. Man graduated from Yale with a doctorate degree in physiological chemistry in 1932. | 1 | Applied and Interdisciplinary Chemistry |
Type-II superconductivity is characterized by two critical fields called B and B. At a magnetic field B the applied magnetic field starts to penetrate the sample, but the sample is still superconducting. Only at a field of B the sample is completely normal. For fields in between B and B magnetic flux penetrates the superconductor in well-organized patterns, the so-called Abrikosov vortex lattice similar to the pattern shown in Fig. 2. A cross section of the superconducting plate is given in Fig. 7. Far away from the plate the field is homogeneous, but in the material superconducting currents flow which squeeze the field in bundles of exactly one flux quantum. The typical field in the core is as big as 1 tesla. The currents around the vortex core flow in a layer of about 50 nm with current densities on the order of 15 A/m. That corresponds with 15 million ampère in a wire of one mm. | 0 | Theoretical and Fundamental Chemistry |
The Newbery-Vautin process and other processes based on chlorination were replaced by processes based on cyanidation, which used fewer reagents. Processes that are free of cyanide and emit less toxic byproducts have also been developed. | 1 | Applied and Interdisciplinary Chemistry |
Thioesters have general structure R−C(O)−S−R. They are related to regular esters (R−C(O)−O−R) but are more susceptible to hydrolysis and related reactions. Thioesters formed from coenzyme A are prominent in biochemistry, especially in fatty acid synthesis. | 0 | Theoretical and Fundamental Chemistry |
Mecillinam (INN) or amdinocillin (USAN) is an extended-spectrum penicillin antibiotic of the amidinopenicillin class that binds specifically to penicillin binding protein 2 (PBP2), and is only considered to be active against Gram-negative bacteria. It is used primarily in the treatment of urinary tract infections, and has also been used to treat typhoid and paratyphoid fever. Because mecillinam has very low oral bioavailability, an orally active prodrug was developed: pivmecillinam. | 0 | Theoretical and Fundamental Chemistry |
The Marilyn and Sturges W. Bailey Distinguished Member Award, is the highest honor of The Clay Minerals Society, based in Virginia, United States. It is awarded solely for scientific eminence in clay mineralogy (in its broadest sense) as evidenced by the publication of outstanding original scientific research and by the impact of this research on the clay sciences. It is endowed by Linda and David Bailey and replaces The Clay Mineral Society's Distinguished Member Award. It is not restricted to members of the CMS.
The award is presented at the CMS annual meeting. | 0 | Theoretical and Fundamental Chemistry |
N-Iodosuccinimide (NIS) is a reagent used in organic chemistry for the iodination of alkenes and as a mild oxidant.
NIS is the iodine analog of N-chlorosuccinimide (NCS) and N-bromosuccinimide (NBS) which are used for similar applications. | 0 | Theoretical and Fundamental Chemistry |
Perrys Chemical Engineers Handbook (also known as Perrys Handbook, Perrys, or The Chemical Engineers Bible') was first published in 1934 and the most current ninth edition was published in July 2018. It has been a source of chemical engineering knowledge for chemical engineers, and a wide variety of other engineers and scientists, through eight previous editions spanning more than 80 years. | 1 | Applied and Interdisciplinary Chemistry |
Chambers isolated by filters are proper tools for accurate determination of chemotactic behavior. The pioneer type of these chambers was constructed by Boyden. The motile cells are placed into the upper chamber, while fluid containing the test substance is filled into the lower one. The size of the motile cells to be investigated determines the pore size of the filter; it is essential to choose a diameter which allows active transmigration. For modelling in vivo conditions, several protocols prefer coverage of filter with molecules of extracellular matrix (collagen, elastin etc.) Efficiency of the measurements was increased by development of multiwell chambers (e.g. NeuroProbe), where 24, 96, 384 samples are evaluated in parallel. Advantage of this variant is that several parallels are assayed in identical conditions. | 1 | Applied and Interdisciplinary Chemistry |
A thermodynamic instrument is any device for the measurement of thermodynamic systems. In order for a thermodynamic parameter or physical quantity to be truly defined, a technique for its measurement must be specified. For example, the ultimate definition of temperature is "what a thermometer reads". The question follows – what is a thermometer?
There are two types of thermodynamic instruments: the meter and the reservoir. A thermodynamic meter is any device which measures any parameter of a thermodynamic system. A thermodynamic reservoir is a system which is so large that it does not appreciably alter its state parameters when brought into contact with the test system. | 0 | Theoretical and Fundamental Chemistry |
French chemist Louis Pasteur was the first zymologist when in 1857 he connected yeast to fermentation. Pasteur originally defined fermentation as "respiration without air".
Pasteur performed careful research and concluded:
The German Eduard Buchner, winner of the 1907 Nobel Prize in chemistry, later determined that fermentation was actually caused by a yeast secretion, which he termed zymase.
The research efforts undertaken by the Danish Carlsberg scientists greatly accelerated understanding of yeast and brewing. The Carlsberg scientists are generally acknowledged as having jump-started the entire field of molecular biology. | 1 | Applied and Interdisciplinary Chemistry |
S. pneumoniae is human pathogenic bacterium in which the process of genetic transformation was first described in the 1930s. In order for a bacterium to take up exogenous DNA from its surroundings, it must become competent. In S. pneumoniae, a number of complex events must occur to achieve a competent state, but it is believed that quorum sensing plays a role. Competence stimulating peptide (CSP) is a 17-amino acid peptide autoinducer required for competency and subsequent genetic transformation. CSP is produced by proteolytic cleavage of a 41-amino acid precursor peptide (ComC); is secreted by an ABC transporter (ComAB); and is detected by a sensor kinase protein (ComD) once it has reached a threshold concentration. Detection is followed by autophosphorylation of ComD, which in turn, phosphorylates ComE. ComE is a response regulator responsible for activating transcription of comX, the product of which is required to activate transcription of a number of other genes involved in the development of competence. | 1 | Applied and Interdisciplinary Chemistry |
There are many species of bacteria and other microorganisms that live on or inside the healthy human body. In fact, there are roughly as many microbial as human cells in the human body by number.
(much less by mass or volume). Some of these symbionts are necessary for our health. Those that neither help nor harm humans are called commensal organisms. | 1 | Applied and Interdisciplinary Chemistry |
Cheon enrolled in Yonsei University in 1981 majoring in chemistry. He later obtained a Bachelor of Science and Master of Science in 1985 and 1987, respectively. Studying under Professor Gregory S. Girolami, Cheon received a Ph.D. in chemistry from the University of Illinois at Urbana-Champaign in 1993. Staying in the U.S., he did postdoc work in the University of California Berkeley | 0 | Theoretical and Fundamental Chemistry |
The Reformatsky reaction (sometimes transliterated as Reformatskii reaction) is an organic reaction which condenses aldehydes or ketones with α-halo esters using metallic zinc to form β-hydroxy-esters:
The organozinc reagent, also called a Reformatsky enolate, is prepared by treating an alpha-halo ester with zinc dust. Reformatsky enolates are less reactive than lithium enolates or Grignard reagents and hence nucleophilic addition to the ester group does not occur. The reaction was discovered by Sergey Nikolaevich Reformatsky.
Some reviews have been published.
In addition to aldehydes and ketones, it has also been shown that the Reformatsky enolate is able to react with acid chlorides, imines, nitriles (see Blaise reaction), and nitrones. Moreover, metals other than zinc have also been used, including magnesium, iron, cobalt, nickel, germanium, cadmium, indium, barium, and cerium. Additionally, metal salts are also applicable in place of metals, notably samarium(II) iodide, chromium(II) chloride, titanium(II) chloride, cerium(III) halides such as cerium(III) iodide, and titanocene(III) chloride. | 0 | Theoretical and Fundamental Chemistry |
Uridine-5′-triphosphate (UTP) is a pyrimidine nucleoside triphosphate, consisting of the organic base uracil linked to the 1′ carbon of the ribose sugar, and esterified with tri-phosphoric acid at the 5′ position. Its main role is as substrate for the synthesis of RNA during transcription. UTP is the precursor for the production of CTP via CTP synthetase. UTP can be biosynthesized from UDP by Nucleoside Diphosphate Kinase after using the phosphate group from ATP. UDP + ATP ⇌ UTP + ADP; both UTP and ATP are energetically equal.
The homologue in DNA is thymidine triphosphate (TTP or dTTP). UTP also has a deoxyribose form (dUTP). | 1 | Applied and Interdisciplinary Chemistry |
Copper is the eighth most abundant metal in the Earth's crust, is available all over the world, and is one of the few that can appear in a pure state. It is not complicated to work with, and a bare hammering can be enough to transform a nugget into a bead. The eye-catching look of native copper makes it easy to recognize, and even flashier if converted into jewelry, a possible motivation for humankind to start metallurgy with it. An evolutive technological process has been described, although there are authors like Javinovic, who think that it is not necessary to pass through the first stages to reach the last one. | 1 | Applied and Interdisciplinary Chemistry |
In one study, it was estimated that for every dollar ($1) that is spent on pesticides for crops can yield up to four dollars ($4) in crops saved. This means based that, on the amount of money spent per year on pesticides, $10 billion, there is an additional $40 billion savings in crop that would be lost due to damage by insects and weeds. In general, farmers benefit from having an increase in crop yield and from being able to grow a variety of crops throughout the year. Consumers of agricultural products also benefit from being able to afford the vast quantities of produce available year-round. | 1 | Applied and Interdisciplinary Chemistry |
Serial analysis of gene expression (SAGE) is an alternate method of analysis based on RNA sequencing rather than hybridization. SAGE relies on the sequencing of 10–17 base pair tags which are unique to each gene. These tags are produced from poly-A mRNA and ligated end-to-end before sequencing. SAGE gives an unbiased measurement of the number of transcripts per cell, since it does not depend on prior knowledge of what transcripts to study (as microarrays do). | 1 | Applied and Interdisciplinary Chemistry |
Acidifiers are inorganic chemicals that, put into a human (or other mammalian) body, either produce or become acid.
These chemicals increase the level of gastric acid in the stomach when ingested, thus decreasing the stomach pH.
Out of many types of acidifiers, the main four are:
* Gastric acidifiers, these are the drugs which are used to restore temporarily the acidity of stomach in patient suffering from hypochlorhydria
* Urinary acidifiers, used to control pH in urine
* Systemic acidifiers, used to control pH in the overall body
* Acids, mostly used in laboratory experiments
Acidifier performance in distal stomach is debatable.
Patients who suffer from achlorhydria have deficient secretion of hydrochloric acid in their stomach. In such cases, acidifiers may provide sufficient acidity for proper digestion of food. Systemic acidifiers, usually given by injection, act by reducing the alkali reserve in the body, and are also useful in reducing metabolic alkalosis. | 0 | Theoretical and Fundamental Chemistry |
To date, OTTR has been used for quantifying tRNA species. This method provides a reliable and precise quantification of tRNAs and allows for the detection of changes in tRNA levels under different physiological conditions. Therefore, this method is useful for a variety of research applications in the field of molecular biology and genetics.
As tRNAs are essential components of translation, the ability to quantify tRNA levels accurately is crucial for understanding how the translation machinery is regulated. Using OTTR, researchers can determine changes in tRNA levels in response to different growth conditions, environmental stress, or genetic modifications. This information can help to identify factors that affect tRNA abundance and their potential roles in modulating translation.
In particular, the OTTR protocol has been used to characterize the small RNA composition of mammalian sperm populations. This work revealed that sperm small RNA pools are composed largely of rRNA fragments and both 5 and 3 tRNA halves from the majority of tRNAs. This improved understanding of sperm payload composition has implications for our understanding of the biogenesis of structural RNA fragments in the male germline, as well as the biochemical nature of the RNAs delivered to the zygote upon fertilization.
The OTTR protocol could also be used in the study of piwi-interacting RNAs (piRNAs), which is another important classes of small RNAs. While the applications of OTTR have mainly been focused on tRNA fragment detection, OTTR has also been shown to perform well in the capture of miRNAs which could be useful for the study of miRNA expression patterns in different cell types or under different conditions.
Future applications of protocols similar to OTTR are also being considered in the development of diagnostic assays for small RNAs. The high fidelity of the OTTR protocol in capturing small RNAs could make it an attractive option when paired with liquid biopsy assays, where circulating small RNAs are analyzed as biomarkers for various diseases. | 1 | Applied and Interdisciplinary Chemistry |
Prime editing is a search-and-replace genome editing technology in molecular biology by which the genome of living organisms may be modified. The technology directly writes new genetic information into a targeted DNA site. It uses a fusion protein, consisting of a catalytically impaired Cas9 endonuclease fused to an engineered reverse transcriptase enzyme, and a prime editing guide RNA (pegRNA), capable of identifying the target site and providing the new genetic information to replace the target DNA nucleotides. It mediates targeted insertions, deletions, and base-to-base conversions without the need for double strand breaks (DSBs) or donor DNA templates.
The technology has received mainstream press attention due to its potential uses in medical genetics. It utilizes methodologies similar to precursor genome editing technologies, including CRISPR/Cas9 and base editors. Prime editing has been used on some animal models of genetic disease and plants. | 1 | Applied and Interdisciplinary Chemistry |
Hemamala Indivari Karunadasa is an assistant professor of chemistry at Stanford University. She works on hybrid organic – inorganic materials, such as perovskites, for clean energy and large area lighting. | 0 | Theoretical and Fundamental Chemistry |
*NASA, Vortex-lattice utilization. NASA SP-405, NASA-Langley, Washington, 1976.
*Prandtl. L, Applications of modern hydrodynamics to aeronautics, NACA-TR-116, NASA, 1923.
*Falkner. V.M., The Accuracy of Calculations Based on Vortex Lattice Theory, Rep. No. 9621, British A.R.C., 1946.
*J. Katz, A. Plotkin, Low-Speed Aerodynamics, 2nd ed., Cambridge University Press, Cambridge, 2001.
*J.D. Anderson Jr, Fundamentals of aerodynamics, 2nd ed., McGraw-Hill Inc, 1991.
*J.J. Bertin, M.L. Smith, Aerodynamics for Engineers, 3rd ed., Prentice Hall, New Jersey, 1998.
*E.L. Houghton, P.W. Carpenter, Aerodynamics for Engineering Students, 4th ed., Edward Arnold, London, 1993.
*Lamar, J. E., Herbert, H. E., Production version of the extended NASA-Langley vortex lattice FORTRAN computer program. Volume 1: Users guide', NASA-TM-83303, NASA, 1982
*Lamar, J. E., Herbert, H. E., Production version of the extended NASA-Langley vortex lattice FORTRAN computer program. Volume 2: Source code, NASA-TM-83304, NASA, 1982
*Melin, Thomas, A Vortex Lattice MATLAB Implementation for Linear Aerodynamic Wing Applications, Royal Institute of Technology (KTH), Sweden, December, 2000
*M. Drela, Flight Vehicle Aerodynamics, MIT Press, Cambridge, MA, 2014. | 1 | Applied and Interdisciplinary Chemistry |
The most popular protein stain is Coomassie brilliant blue. It is an anionic dye, which non-specifically binds to proteins. Proteins in the gel are fixed by acetic acid and simultaneously stained. The excess dye incorporated into the gel can be removed by destaining with the same solution without the dye. The proteins are detected as blue bands on a clear background.
When more sensitive method than staining by Coomassie is needed, silver staining is usually used. Silver staining is a sensitive procedure to detect trace amounts of proteins in gels, but can also visualize nucleic acid or polysaccharides.
Visualization methods without using a dye such as Coomassie and silver are available on the market. For example Bio-Rad Laboratories markets ”stain-free” gels for SDS-PAGE gel electrophoresis. Alternatively, reversible fluorescent dyes, such as those from Azure Biosystems such as AzureRed or Azure TotalStain Q can be used.
Similarly as in nucleic acid gel electrophoresis, tracking dye is often used. Anionic dyes of a known electrophoretic mobility are usually included in the sample buffer. A very common tracking dye is Bromophenol blue. This dye is coloured at alkali and neutral pH and is a small negatively charged molecule that moves towards the anode. Being a highly mobile molecule it moves ahead of most proteins. | 1 | Applied and Interdisciplinary Chemistry |
The Helferich method may refer to:
#Glycosylation of an alcohol using a glycosyl acetate as glycosyl donor and a Lewis acid (e.g. a metal halide) as promoter
#Glycosylation of an alcohol using a glycosyl halide as a glycosyl donor and a mercury salt as promoter (cf the Koenigs-Knorr reaction, which uses silver salts as promoters). | 0 | Theoretical and Fundamental Chemistry |
Label the hydrogen spin as , and the carbon spin by . For illustrative purposes, we assume that the equilibrium state only has polarisation on the -spin (in reality, there will also be polarisation on the spin, with the relative populations determined by the thermal Boltzmann factors). The -coupling Hamiltonian is
which gives the following evolution
The non-trivial commutators used to identify the cyclic subspace for are
and consequently the next cyclic rotation
where we used the mixed-product identity , which relates the matrix and Kronecker products for compatible dimensions of , and also the fact that since the two eigenvalues of any of the spin-1/2 operators are , any of their squares are given by by the Cayley–Hamilton theorem.
Note also that the term is invariant under the -coupling evolution. That is that the term commutes with the Hamiltonian, and in this case, that can be manually confirmed by evaluating the commutator using the matrix representations of the spin operators. | 0 | Theoretical and Fundamental Chemistry |
The Pearson symbol should only be used to designate simple structures (elements, some binary compound) where the number of atoms per unit cell equals, ideally, the number of translationally equivalent points. | 0 | Theoretical and Fundamental Chemistry |
4-Dimethylaminopyridine (DMAP) is a derivative of pyridine with the chemical formula (CH)NCHN. This white solid is of interest because it is more basic than pyridine, owing to the resonance stabilisation from the NMe substituent.
Because of its basicity, DMAP is a useful nucleophilic catalyst for a variety of reactions such as esterifications with anhydrides, the Baylis-Hillman reaction, hydrosilylations, tritylation, the Steglich rearrangement, Staudinger synthesis of β-lactams and many more. Chiral DMAP analogues are used in kinetic resolution experiments of mainly secondary alcohols and Evans auxiliary type amides. | 0 | Theoretical and Fundamental Chemistry |
Crosslinking generally involves covalent bonds that join two polymer chains. The term curing refers to the crosslinking of thermosetting resins, such as unsaturated polyester and epoxy resin, and the term vulcanization is characteristically used for rubbers. When polymer chains are crosslinked, the material becomes more rigid. The mechanical properties of a polymer depend strongly on the cross-link density. Low cross-link densities increase the viscosities of polymer melts. Intermediate cross-link densities transform gummy polymers into materials that have elastomeric properties and potentially high strengths. Very high cross-link densities can cause materials to become very rigid or glassy, such as phenol-formaldehyde materials.
In one implementation, unpolymerized or partially polymerized resin is treated with a crosslinking reagent. In vulcanization, sulfur is the cross-linking agent. Its introduction changes rubber to a more rigid, durable material associated with car and bike tires. This process is often called sulfur curing. In most cases, cross-linking is irreversible, and the resulting thermosetting material will degrade or burn if heated, without melting. Chemical covalent cross-links are stable mechanically and thermally. Therefore, cross-linked products like car tires cannot be recycled easily. A class of polymers known as thermoplastic elastomers rely on physical cross-links in their microstructure to achieve stability, and are widely used in non-tire applications, such as snowmobile tracks, and catheters for medical use. They offer a much wider range of properties than conventional cross-linked elastomers because the domains that act as cross-links are reversible, so can be reformed by heat. The stabilizing domains may be non-crystalline (as in styrene-butadiene block copolymers) or crystalline as in thermoplastic copolyesters.
Alkyd enamels, the dominant type of commercial oil-based paint, cure by oxidative crosslinking after exposure to air. | 0 | Theoretical and Fundamental Chemistry |
On a daily scale, GPP rates are most affected by the diel cycle of photosynthetically active radiation while ER is largely affected by changes in water temperature. Additionally, ER rates are also tied to the quantity or quality of the organic substrate and relative contributions of autotrophic and heterotrophic respiration, as indicated by studies of the patterns of night-time respiration (e.g. Sadro et al. 2014). For example, bacterioplankton respiration can be higher during the day and in the first hours of the night, due to the higher availability of labile dissolved organic matter produced by phytoplankton. As the sun rises, there is a rapid increase in primary production in the lake, often making it autotrophic (NEP > 0) and reducing dissolved that was produced from carbon mineralization that occurred during the night. This behavior continues until reaching a peak in NEP, typically around the maximum light availability. Then there is a tendency for the NEP to fall steadily between the hours of maximum light availability until the next day's sunrise.
Day-to-day differences in incoming light and temperature, due to differences in the weather, such as cloud cover and storms, affect rates of primary production and, to a lesser extent, respiration. These weather variations also cause short-term variability in mixed layer depth, which in turn affects nutrients, organic matter, and light availability, as well as vertical and horizontal gas exchanges. Deep mixing reduces light availability but also increases nutrients and organic matter availability in the upper layers. Thus the effects of short-term variability in mixed layer depth on gross primary production (GPP) will depend on which are the limiting factors on each lake at a given period. Thus a deeper mixing layer could either increase or decrease GPP rates depending on the balance between nutrient and light limitation of photosynthesis ().
Responses in metabolic rates are as dynamic as the physical and chemical processes occurring in the lake, but changes in algal biomass are less variable, involving growth and loss over longer periods. High light and nutrients availability are associated with the formation of algal blooms in lakes; during these blooms GPP rates are very high, and ER rates usually increase almost as much as GPP rates, and the balance of GPP and ER is close to 1. Right after the bloom, GPP rates start to decrease but ER rates continue higher due to the high availability of labile organic matter, which can lead to a fast depletion of dissolved oxygen concentration in the water column, resulting in fish kills. | 1 | Applied and Interdisciplinary Chemistry |
In the first few decades of nuclear magnetic resonance, spectrometers used a technique known as continuous-wave (CW) spectroscopy, where the transverse spin magnetization generated by a weak oscillating magnetic field is recorded as a function of the oscillation frequency or static field strength B. When the oscillation frequency matches the nuclear resonance frequency, the transverse magnetization is maximized and a peak is observed in the spectrum. Although NMR spectra could be, and have been, obtained using a fixed constant magnetic field and sweeping the frequency of the oscillating magnetic field, it was more convenient to use a fixed frequency source and vary the current (and hence magnetic field) in an electromagnet to observe the resonant absorption signals. This is the origin of the counterintuitive, but still common, "high field" and "low field" terminology for low frequency and high frequency regions, respectively, of the NMR spectrum.
As of 1996, CW instruments were still used for routine work because the older instruments were cheaper to maintain and operate, often operating at 60 MHz with correspondingly weaker (non-superconducting) electromagnets cooled with water rather than liquid helium. One radio coil operated continuously, sweeping through a range of frequencies, while another orthogonal coil, designed not to receive radiation from the transmitter, received signals from nuclei that reoriented in solution. As of 2014, low-end refurbished 60 MHz and 90 MHz systems were sold as FT-NMR instruments, and in 2010 the "average workhorse" NMR instrument was configured for 300 MHz.
CW spectroscopy is inefficient in comparison with Fourier analysis techniques (see below) since it probes the NMR response at individual frequencies or field strengths in succession. Since the NMR signal is intrinsically weak, the observed spectrum suffers from a poor signal-to-noise ratio. This can be mitigated by signal averaging, i.e. adding the spectra from repeated measurements. While the NMR signal is the same in each scan and so adds linearly, the random noise adds more slowly – proportional to the square root of the number of spectra (see random walk). Hence the overall signal-to-noise ratio increases as the square-root of the number of spectra measured. However, monitoring an NMR signal at a single frequency as a function of time may be better suited for kinetic studies than pulsed Fourier-transform NMR spectrosocopy. | 0 | Theoretical and Fundamental Chemistry |
The concept of cone angle is most easily visualized with symmetrical ligands, e.g. PR. But the approach has been refined to include less symmetrical ligands of the type PRR′R″ as well as diphosphines. In such asymmetric cases, the substituent angles half angles, , are averaged and then doubled to find the total cone angle, θ'. In the case of diphosphines, the of the backbone is approximated as half the chelate bite angle, assuming a bite angle of 74°, 85°, and 90° for diphosphines with methylene, ethylene, and propylene backbones, respectively. The Manz cone angle is often easier to compute than the Tolman cone angle: | 0 | Theoretical and Fundamental Chemistry |
RIC wettability characterization technique is based on a modified form of Washburn's equation (1921). The technique enables relatively quick and accurate measurements of wettability in terms of contact angle while requiring no complex equipment. The method is applicable for any set of reservoir fluids, on any type of reservoir rock and at any heterogeneity level. It characterizes wettability across the board from strongly water to strongly oil wet conditions.
The step of deriving the modified form of Washburn equation for a rock/liquid/liquid system involves acquiring a Washburn equation for a rock/air/liquid system. The Washburn equation for a rock/air/liquid system is represented by:
Herein, "t" is the penetration rate of liquid into a porous sample, "μ" is the liquids viscosity, "ρ" is the liquids density, "γ" is the liquids surface tension, "θ" is the liquids contact angle, "m" is the mass of the liquid that penetrates the porous sample and "C" is the constant of characterization of the porous sample. evaluating a value of "γ" using a young’s equation for a rock surface/water/air system (Figure 2) and a value of "γ" using young’s equation for a liquid/liquid/rock system is represented as:
"γ" is the surface tension between the oil and water system, "γ" is the surface tension between oil and solid system and "γ" is the surface tension between water and the solid system. Using Young's equation for a rock surface/ water/air system and substituting in equation (2) to obtain equation 3:
Rearranging equation (1) to factor out γ obtains equation (4), wherein γ a liquid-vapor surface tension is:
Realizing that γ (liquid–vapor surface tension) is equivalent to γ (oil–air surface tension), or γ (water–air-surface tension), substituting equation (4) in equation (3) and cancelling out similar terms obtains equation (5):
Therein, γ is liquid-vapor surface tension, γis oil-air surface tension, γ is water-air surface tension, µ is viscosity of oil and µ is viscosity of water. cosθ is contact angle between water and oil; representing a relationship between a mass of water imbibed into the core sample and a mass of oil imbibed in the core sample with an equation (6):
Therein ρ is density of water and V is volume of water imbibed, ρ is density of oil and V is volume of oil imbibed, the amount of water imbibed and amount of oil imbibed under gravity are same; and air behaves as a strong non-wetting phase in both an oil–air–solid and a water–air–solid systems, thereby indicating that both oil and water behave as strong wetting phases, resulting in equal air/oil and air/water capillary forces for the same porous media and for a given pore size distribution. Thus, a mass change of a core sample due to water imbibition is equal to a mass change of a core sample due to oil imbibition, because water or oil penetration of the porous media at any time is a function of a balance between gravity and capillary forces. The mass of water imbibed into a core sample is approximately equal to a mass of oil imbibed in the core sample core samples of a same rock type and dimensions, and for equal capillary forces;
Cancelling out g in equation(6) gives equation (7):
which means
Therein, m is mass of water and m is mass of oil. Factoring out </small> from Eq. 5 to obtain Eq. 9, gives Modified Washburn Equation:
Therein θ is the contact angle of liquid/liquid/rock system, μ is a viscosity of oil phase, μ is a viscosity of water phase, ρ is density of oil phase in g/cm, ρ is density of water phase in g/cm, m is mass of fluid penetrated into a porous rock, t is time in min, γ_ is the surface tension between an oil and a water in dyne/cm, and ∁ is a characteristic constant of the porous rock. | 1 | Applied and Interdisciplinary Chemistry |
Gear meters differ from oval gear meters in that the measurement chambers are made up of the gaps between the teeth of the gears. These openings divide up the fluid stream and as the gears rotate away from the inlet port, the meter's inner wall closes off the chamber to hold the fixed amount of fluid. The outlet port is located in the area where the gears are coming back together. The fluid is forced out of the meter as the gear teeth mesh and reduce the available pockets to nearly zero volume. | 1 | Applied and Interdisciplinary Chemistry |
There are actually several physical mechanisms that produce the elastic forces within the network chains as a rubber sample is stretched. Two of these arise from entropy changes and one is associated with the distortion of the molecular bond angles along the chain backbone. These three mechanisms are immediately apparent when a moderately thick rubber sample is stretched manually. Initially, the rubber feels quite stiff, i.e. the force must be increased at a high rate with respect to the strain. At intermediate strains, the required increase in force is much lower to cause the same amount of stretch. Finally, as the sample approaches the breaking point, its stiffness increases markedly. What the observer is noticing are the changes in the modulus of elasticity that are due to the different molecular mechanisms. These regions can be seen in Fig. 1, a typical stress vs. strain measurement for natural rubber. The three mechanisms (labelled Ia, Ib and II) predominantly correspond to the regions shown on the plot. The concept of entropy comes to us from the area mathematical physics called statistical mechanics which is concerned with the study of large thermal systems, e.g. rubber networks at room temperature. Although the detailed behavior of the constituent chains are random and far too complex to study individually, we can obtain very useful information about their average behavior from a statistical mechanics analysis of a large sample. There are no other examples of how entropy changes can produce a force in our everyday experience. One may regard the entropic forces in polymer chains as arising from the thermal collisions that their constituent atoms experience with the surrounding material. It is this constant jostling that produces a resisting (elastic) force in the chains as they are forced to become straight. While stretching a rubber sample is the most common example of elasticity, it also occurs when rubber is compressed. Compression may be thought of as a two dimensional expansion as when a balloon is inflated. The molecular mechanisms that produce the elastic force are the same for all types of strain.
When these elastic force models are combined with the complex morphology of the network, it is not possible to obtain simple analytic formulae to predict the macroscopic stress. It is only via numerical simulations on computers that it is possible to capture the complex interaction between the molecular forces and the network morphology to predict the stress and ultimate failure of a rubber sample as it is strained. | 0 | Theoretical and Fundamental Chemistry |
Its presence was identified by Nakabayashi and co-workers where the hybrid layer consists of demineralized intertubular dentin and infiltrated and polymerized adhesive resin.
The hybrid layer is hydrophobic, acid resistant and tough. The quality of hybrid layer formed decides the strength of resin dentin interface. When the hybrid layer becomes thicker and more uniform, the bond strength is better. | 0 | Theoretical and Fundamental Chemistry |
The convention surrounding P-NMR (and other nuclei) changed convention in 1975: "The dimensionless scale should be defined as positive in the high frequency (low field) direction." Therefore, note that manuscripts published before 1976 will generally have the opposite sign. | 0 | Theoretical and Fundamental Chemistry |
Cyclic α,β-unsaturated ketones are the most commonly employed substrates for vicinal difunctionalization. They tend to be more reactive than acyclic analogues and undergo less direct addition than aldehydes. Amides and esters can be used to encourage conjugate addition in cases when direct addition may be competitive (as in the addition of organolithium compounds).
Because the addition step is highly sensitive to steric effects, β-substituents are likely to slow the reaction. Acetylenic and allenic substrates react to give products with some retained unsaturation. | 0 | Theoretical and Fundamental Chemistry |
Dmitri Petrovich Konovalov (22 March 1856 – 6 January 1929) was a Russian-Soviet physical chemist who worked on gas-liquid phases of solutions in equilibrium and came up with several rules that were also independently worked on by J. Willard Gibbs and the rules are often called Gibbs-Konovalov rules. They provide the basis for distillation and separation of components that form azeotropes. | 0 | Theoretical and Fundamental Chemistry |
Recombinant DNA (rDNA) molecules are DNA molecules formed by laboratory methods of genetic recombination (such as molecular cloning) that bring together genetic material from multiple sources, creating sequences that would not otherwise be found in the genome.
Recombinant DNA is the general name for a piece of DNA that has been created by combining two or more fragments from different sources. Recombinant DNA is possible because DNA molecules from all organisms share the same chemical structure, differing only in the nucleotide sequence. Recombinant DNA molecules are sometimes called chimeric DNA because they can be made of material from two different species like the mythical chimera. rDNA technology uses palindromic sequences and leads to the production of sticky and blunt ends.
The DNA sequences used in the construction of recombinant DNA molecules can originate from any species. For example, plant DNA can be joined to bacterial DNA, or human DNA can be joined with fungal DNA. In addition, DNA sequences that do not occur anywhere in nature can be created by the chemical synthesis of DNA and incorporated into recombinant DNA molecules. Using recombinant DNA technology and synthetic DNA, any DNA sequence can be created and introduced into living organisms.
Proteins that can result from the expression of recombinant DNA within living cells are termed recombinant proteins. When recombinant DNA encoding a protein is introduced into a host organism, the recombinant protein is not necessarily produced. Expression of foreign proteins requires the use of specialized expression vectors and often necessitates significant restructuring by
foreign coding sequences.
Recombinant DNA differs from genetic recombination in that the former results from artificial methods while the latter is a normal biological process that results in the remixing of existing DNA sequences in essentially all organisms. | 1 | Applied and Interdisciplinary Chemistry |
The isomeric shift on atomic spectral lines is the energy or frequency shift in atomic spectra, which occurs when one replaces one nuclear isomer by another. The effect was predicted by Richard M. Weiner in 1956, whose calculations showed that it should be measurable by atomic (optical) spectroscopy (see also). It was observed experimentally for the first time in 1958. The theory of the atomic isomeric shift is also used in the interpretation of the Mössbauer isomeric shift. | 0 | Theoretical and Fundamental Chemistry |
Open PHACTS (Open Pharmacological Concept Triple Store) was a European initiative public–private partnership between academia, publishers, enterprises, pharmaceutical companies and other organisations working to enable better, cheaper and faster drug discovery. It has been funded by the Innovative Medicines Initiative, selected as part of three projects to "design methods for common standards and sharing of data for more efficient drug development and patient treatment in the future". | 1 | Applied and Interdisciplinary Chemistry |
Pipecolic acid (piperidine-2-carboxylic acid) is an organic compound with the formula HNCHCOH. It is a carboxylic acid derivative of piperidine and, as such, an amino acid, although not one encoded genetically. Like many other α-amino acids, pipecolic acid is chiral, although the S-stereoisomer is more common. It is a colorless solid.
Its biosynthesis starts from lysine. CRYM, a taxon-specific protein that also binds thyroid hormones, is involved in the pipecolic acid pathway. | 1 | Applied and Interdisciplinary Chemistry |
The experimental position improved dramatically after research by Henry Moseley in 1913. Moseley, after discussions with Bohr who was at the same lab (and who had used Van den Broeks hypothesis in his Bohr model of the atom), decided to test Van den Broeks and Bohrs hypothesis directly, by seeing if spectral lines emitted from excited atoms fitted the Bohr theorys postulation that the frequency of the spectral lines be proportional to the square of Z.
To do this, Moseley measured the wavelengths of the innermost photon transitions (K and L lines) produced by the elements from aluminium (Z = 13) to gold (Z = 79) used as a series of movable anodic targets inside an x-ray tube. The square root of the frequency of these photons increased from one target to the next in an arithmetic progression. This led to the conclusion (Moseleys law) that the atomic number does closely correspond (with an offset of one unit for K-lines, in Moseleys work) to the calculated electric charge of the nucleus, i.e. the element number Z. Among other things, Moseley demonstrated that the lanthanide series (from lanthanum to lutetium inclusive) must have 15 members—no fewer and no more—which was far from obvious from known chemistry at that time. | 0 | Theoretical and Fundamental Chemistry |
The gua operon is responsible for regulating the synthesis of guanosine mono phosphate (GMP), a purine nucleotide, from inosine monophosphate (IMP or inosinate). It consists of two structural genes guaB (encodes for IMP dehydrogenase or and guaA (encodes for GMP synthetase) apart from the promoter and operator region. | 1 | Applied and Interdisciplinary Chemistry |
In the first example, we will show how to use a mass balance to derive a relationship between the percent excess air for the combustion of a hydrocarbon-base fuel oil and the percent oxygen in the combustion product gas. First, normal dry air contains of oxygen per mole of air, so there is one mole of in of dry air. For stoichiometric combustion, the relationships between the mass of air and the mass of each combustible element in a fuel oil are:
Considering the accuracy of typical analytical procedures, an equation for the mass of air per mass of fuel at stoichiometric combustion is:
where refer to the mass fraction of each element in the fuel oil, sulfur burning to , and refers to the air-fuel ratio in mass units.
For of fuel oil containing 86.1% C, 13.6% H, 0.2% O, and 0.1% S the stoichiometric mass of air is , so AFR = 14.56. The combustion product mass is then . At exact stoichiometry, should be absent. At 15 percent excess air, the AFR = 16.75, and the mass of the combustion product gas is , which contains of excess oxygen. The combustion gas thus contains 2.84 percent by mass. The relationships between percent excess air and % in the combustion gas are accurately expressed by quadratic equations, valid over the range 0–30 percent excess air:
In the second example, we will use the law of mass action to derive the expression for a chemical equilibrium constant.
Assume we have a closed reactor in which the following liquid phase reversible reaction occurs:
The mass balance for substance A becomes
As we have a liquid phase reaction we can (usually) assume a constant volume and since we get
or
In many textbooks this is given as the definition of reaction rate without specifying the implicit assumption that we are talking about reaction rate in a closed system with only one reaction. This is an unfortunate mistake that has confused many students over the years.
According to the law of mass action the forward reaction rate can be written as
and the backward reaction rate as
The rate at which substance A is produced is thus
and since, at equilibrium, the concentration of A is constant we get
or, rearranged | 1 | Applied and Interdisciplinary Chemistry |
The potential energy and unique bonding structure contained in the bonds of molecules with ring strain can be used to drive reactions in organic synthesis. Examples of such reactions are ring opening metathesis polymerisation, photo-induced ring opening of cyclobutenes, and nucleophilic ring-opening of epoxides and aziridines.
Increased potential energy from ring strain also can be used to increase the energy released by explosives or increase their shock sensitivity. For example, the shock sensitivity of the explosive 1,3,3-Trinitroazetidine could partially or primarily explained by its ring strain. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, alpha-elimination refers to reactions of this type:
:RCHX → RC: + HX
The reaction is employed to generate carbenes and nitrenes. The formation of dichlorocarbene from chloroform is an example.
Alpha eliminations contrasts with beta eliminations, which are commonly used to generate alkenes:
:RCHCXR → RC=CR + HX
Both alpha- and beta-eliminations typically require strong base. | 0 | Theoretical and Fundamental Chemistry |
Unlike the other assimilatory pathways, bacteria using the RuBP pathway derive all of their organic carbon from assimilation. This pathway was first elucidated in photosynthetic autotrophs and is better known as the Calvin Cycle. Shortly thereafter, methylotrophic bacteria who could grow on reduced compounds were found using this pathway.
First, 3 molecules of ribulose 5-phosphate are phosphorylated to ribulose 1,5-bisphosphate (RuBP). The enzyme ribulose bisphosphate carboxylase (RuBisCO) carboxylates these RuBP molecules which produces 6 molecules of 3-phosphoglycerate (PGA). The enzyme phosphoglycerate kinase phosphorylates PGA into 1,3-diphosphoglycerate (DPGA). Reduction of 6 DPGA by the enzyme glyceraldehyde phosphate dehydrogenase generates 6 molecules of the compound glyceraldehyde-3-phosphate (GAP). One GAP molecule is diverted towards biomass while the other 5 molecules regenerate the 3 molecules of ribulose 5-phosphate. | 0 | Theoretical and Fundamental Chemistry |
In addition to his own activity as a chemist, Speter had a great interest in the study of the history of chemistry. The title of his doctoral dissertation, publish 1910, was "Lavoisier and his Forerunners"
. Later he studied various areas of chemistry, but his main interests were in the histories of sugar and superphosphate.
The history of sugar production.
Speter studied the work of the two people who are considered the founding fathers of the production of sugar from sugar beets: Andreas Sigismund Marggraf and Franz Karl Achard. He published a comprehensive bibliography of Franz Karl Achard`s contributions, including more than 200 references, in the journal of the German sugar industry ("Die deutsche Zuckerindustrie"). He also published an illustrated account of Achard`s experiments in beet sugar production. Speter also studied other, less successful, efforts to produce sugar. The famous Justus von Liebig prepared sugar from 7 different species of maple and recommended extensive planting of maples in hope of making Germany self-sufficient in this respect. Another German, Ludwig Hofmann, tried to produce sugar from pumpkin.
Speter also studied and wrote about some more esoteric historic experiments with sugar. In 1932 he described the experiments with sugar Triboluminescence made by Francis Bacon and Otto von Guericke. In another publication, he described an anonymous German author who, in 1780, prepared Leyden jars where melted sugar served as an insulator.
The history of superphosphate.
In his study of the history of Superphosphate Speter collected information, including patents and notes, about 16 scientists and industrialists who contributed to the research and manufacture of the fertilizer. They include: Johann Tholde, a school principal from Brno; Johan Gottlieb Gahn; Carl Wilhelm Scheele; Anders Gustaf Ekeberg; A. Bergsteen; Louis-Nicolas Vauquelin; Antoine Fourcroy; George Pearson; Sir Humphry Davy; S. F. Hernbstädt; Justus von Liebig; Sir John Bennet Lawes and Sir James Murray (physician). The results of his studies were published in "Super-Phosphate", a monthly journal of the International Superphosphate Manufacturers' Association. The papers included detailed bibliographies and biographical notes.
The history of the match.
As a by-product of his interest in the history of superphosphate he became interested in another Phosphorus product, the match, and its predecessor the tinderbox. In the "Deutschen Zündwaren-Zeitung", the journal of the German match industry, he published an article about the matches of John Walker called "Congreves" or "friction lights". In the same journal he published an illustrated history of matches based on a translation from Hungarian. He also republished an early 19th-century account about tinderboxes, by Friedrich Hermbstädt.
Other topics in the history of chemistry.
Speter studied a variety of other topics in the history of chemistry, among them: plastic materials, explosives, materials for the photographic industry, Scientific instruments and life-saving equipment. The results of his studies were published in German and Austrian scientific and industrial journals. Translations also were printed in publications in the United States, The Netherlands and Hungary. | 1 | Applied and Interdisciplinary Chemistry |
In high energy particle physics nucleon-lepton scattering, the semi-inclusive deep inelastic scattering (SIDIS) is a method to obtain information on the nucleon structure. It expands the traditional method of deep inelastic scattering (DIS). In DIS, only the scattered lepton is detected while the remnants of the shattered nucleon are ignored (inclusive experiment). In SIDIS, a high momentum hadron, a.k.a. as the leading hadron is detected in addition to the scattered lepton. This allows us to obtain additional details about the scattering process kinematics. | 0 | Theoretical and Fundamental Chemistry |
Non-photochemical quenching is measured by the quenching of chlorophyll fluorescence and is distinguished from photochemical quenching by applying a bright light pulse under actinic light to transiently saturate photosystem II reaction center and compare the maximal yield of fluorescence emission under light and dark-adapted state. Non-photochemical quenching is not affected if the pulse of light is short. During this pulse, the fluorescence reaches the level reached in the absence of any photochemical quenching, known as maximum fluorescence, .
For further discussion, see Measuring chlorophyll fluorescence and Plant stress measurement.
Chlorophyll fluorescence can easily be measured with a chlorophyll fluorometer. Some fluorometers can calculate NPQ and photochemical quenching coefficients (including qP, qN, qE and NPQ), as well as light and dark adaptation parameters (including Fo, Fm, and Fv/Fm). | 0 | Theoretical and Fundamental Chemistry |
The second law of thermodynamics can be interpreted as quantifying state transformations which are statistically unlikely so that they become effectively forbidden. The second law typically applies to systems composed of many particles interacting; Quantum thermodynamics resource theory is a formulation of thermodynamics in the regime where it can be applied to a small number of particles interacting with a heat bath. For processes which are cyclic or very close to cyclic, the second law for microscopic systems takes on a very different form than it does at the macroscopic scale, imposing not just one constraint on what state transformations are possible, but an entire family of constraints. These second laws are not only relevant for small systems, but also apply to individual macroscopic systems interacting via long-range interactions, which only satisfy the ordinary second law on average. By making precise the definition of thermal operations, the laws of thermodynamics take on a form with the first law defining the class of thermal operations, the zeroth law emerging as a unique condition ensuring the theory is nontrivial, and the remaining laws being a monotonicity property of generalised free energies. | 0 | Theoretical and Fundamental Chemistry |
In organometallic chemistry, a metal–ligand multiple bond describes the interaction of certain ligands with a metal with a bond order greater than one. Coordination complexes featuring multiply bonded ligands are of both scholarly and practical interest. transition metal carbene complexes catalyze the olefin metathesis reaction. Metal oxo intermediates are pervasive in oxidation catalysis.
As a cautionary note, the classification of a metal–ligand bond as being "multiple" bond order is ambiguous and even arbitrary because bond order is a formalism. Furthermore, the usage of multiple bonding is not uniform. Symmetry arguments suggest that most ligands engage metals via multiple bonds. The term 'metal–ligand multiple bond" is often reserved for ligands of the type and (n = 0, 1, 2) and (n = 0, 1) where R is H or an organic substituent, or pseudohalide. Historically, and are not included in this classification, nor are halides. | 0 | Theoretical and Fundamental Chemistry |
Nanolithography is the technique to pattern materials and build devices under nano-scale. Nanolithography is often used together with thin-film-deposition, self-assembly, and self-organization techniques for various nanofabrications purpose. Many practical applications make use of nanolithography, including semiconductor chips in computers. There are many types of nanolithography, which include:
* Photolithography
* Electron-beam lithography
* X-ray lithography
* Extreme ultraviolet lithography
* Light coupling nanolithography
* Scanning probe microscope
* Nanoimprint lithography
* Dip-Pen nanolithography
* Soft lithography
Each nanolithography technique has varying factors of the resolution, time consumption, and cost. There are three basic methods used by nanolithography. One involves using a resist material that acts as a "mask", known as photoresists, to cover and protect the areas of the surface that are intended to be smooth. The uncovered portions can now be etched away, with the protective material acting as a stencil. The second method involves directly carving the desired pattern. Etching may involve using a beam of quantum particles, such as electrons or light, or chemical methods such as oxidation or Self-assembled monolayers. The third method places the desired pattern directly on the surface, producing a final product that is ultimately a few nanometers thicker than the original surface. To visualize the surface to be fabricated, the surface must be visualized by a nano-resolution microscope, which includes the scanning probe microscopy and the atomic force microscope. Both microscopes can also be engaged in processing the final product. | 0 | Theoretical and Fundamental Chemistry |
The higher heating value is experimentally determined in a bomb calorimeter. The combustion of a stoichiometric mixture of fuel and oxidizer (e.g. two moles of hydrogen and one mole of oxygen) in a steel container at is initiated by an ignition device and the reactions allowed to complete. When hydrogen and oxygen react during combustion, water vapor is produced. The vessel and its contents are then cooled to the original 25 °C and the higher heating value is determined as the heat released between identical initial and final temperatures.
When the lower heating value (LHV) is determined, cooling is stopped at 150 °C and the reaction heat is only partially recovered. The limit of 150 °C is based on acid gas dew-point.
Note: Higher heating value (HHV) is calculated with the product of water being in liquid form while lower heating value (LHV) is calculated with the product of water being in vapor form. | 0 | Theoretical and Fundamental Chemistry |
Most tanning beds are horizontal enclosures with a bench and canopy (lid) that house long, low-pressure fluorescent bulbs (100–200 watt) under an acrylic surface. The tanner is surrounded by bulbs when the canopy is closed. Modern tanning beds emit mostly UVA (the sun emits around 95% UVA and 5% UVB). One review of studies found that the UVB irradiance of beds was on average lower than the summer sun at latitudes 37°S to 35°N, but that UVA irradiance was on average much higher.
The user sets a timer (or it is set remotely by the salon operator), lies on the bed and pulls down the canopy. The maximum exposure time for most low-pressure beds is 15–20 minutes. In the US, maximum times are set by the manufacturer according to how long it takes to produce four "minimal erythema doses" (MEDs), an upper limit laid down by the FDA. An MED is the amount of UV radiation that will produce erythema (redness of the skin) within a few hours of exposure.
High-pressure beds use smaller, higher-wattage quartz bulbs and emit a higher percentage of UVA. They may emit 10–15 times more UVA than the midday sun, and have a shorter maximum exposure time (typically 10–12 minutes). UVA gives an immediate, short-term tan by bronzing melanin in the skin, but no new melanin is formed. UVB has no immediate bronzing effect, but with a delay of 72 hours makes the skin produce new melanin, leading to tans of longer duration. UVA is less likely to cause burning or dry skin than UVB, but is associated with wrinkling and loss of elasticity because it penetrates deeper.
Commercial tanning beds cost $6,000 to $30,000 as of 2006, with high-pressure beds at the high end. One Manhattan chain was charging $10 to $35 per session in 2016, depending on the number, strength, and type of bulbs. This is known as level 1–6 tanning; level 1 involves a basic low-pressure bed with 36 x 100-watt bulbs. Depending on the quality of the bed, it may contain a separate facial tanner, shoulder tanners, a choice of tanning levels and UVA/UVB combinations, sound system, MP3 connection, aromatherapy, air conditioning, a misting option and voice guide. There are also open-air beds, in which the tanner is not entirely enclosed. | 0 | Theoretical and Fundamental Chemistry |
Disulfide is also used to refer to compounds that contain two sulfide (S) centers. The compound carbon disulfide, CS is described with the structural formula i.e. S=C=S. This molecule is not a disulfide in the sense that it lacks a S-S bond. Similarly, molybdenum disulfide, MoS, is not a disulfide in the sense again that its sulfur atoms are not linked. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, the dodecahedral molecular geometry describes the shape of compounds where eight atoms or groups of atoms or ligands are arranged around a central atom defining the vertices of a snub disphenoid (also known as a trigonal dodecahedron). This shape has D symmetry and is one of the three common shapes for octacoordinate transition metal complexes, along with the square antiprism and the bicapped trigonal prism.
One example of the dodecahedral molecular geometry is the ion. | 0 | Theoretical and Fundamental Chemistry |
It is worthy to note that due to the multiple reactive sites of the multivinyl monomers, plenty of unreacted pendent vinyl groups are introduced to linear primary polymer chains. These pendent vinyl groups have the potential to react with propagating active centres either from their own polymer chain or others. Therefore, both of the intramolecular cyclization and intermolecular crosslinking might occur in this process.
Using the deactivation enhanced strategy, a relatively small instantaneous kinetic chain length limits the number of vinyl groups that can be added to a propagating chain end during each activation/deactivation cycles and thus keeps the polymer chains growing in a limited space. In this way, unlike what happens in free radical polymerization (FRP), the formation of huge polymer chains and large-scale combinations at early reaction stages is avoided. Therefore, a small instantaneous kinetic chain length is the prerequisite for further manipulation of intramolecular cyclization or intermolecular crosslinking. Based on the small instantaneous kinetic chain length, regulation of different chain dimensions and concentrations would lead to distinct reaction types. A low ratio of initiator to monomer would result in the formation of longer chains but of a lower chain concentration, This scenario would no doubt increases the chances of intramolecular cyclization due to the high local/spatial vinyl concentration within the growth boundary. Although the opportunity for intermolecular reactions can increase as the polymer chains grow, the likelihood of this occurring at the early stage of reactions is minimal due to the low chain concentration, which is why single chain cyclized/knotted polymers can form. However, in contrast, a high initiator concentration not only diminishes the chain dimension during the linear-growth phase thus suppressing the intramolecular cyclization, but it also increases the chain concentration within the system so that pendent vinyl groups in one chain are more likely to fall into the growth boundary of another chain. Once the monomers are converted to short chains, the intermolecular combination increases and allows the formation of hyperbranched structures with a high density of branching and vinyl functional groups. | 0 | Theoretical and Fundamental Chemistry |
A presumed blood sample is first collected with a swab. A drop of phenolphthalein reagent is added to the sample, and after a few seconds, a drop of hydrogen peroxide is applied to the swab. If the swab turns pink rapidly, it is said to test presumptive positive for blood. Waiting for periods over 30 seconds will result in most swabs turning pink naturally as they oxidize on their own in the air.
Optionally, the swab can first be treated with a drop of ethanol in order to lyse the cells present and gain increased sensitivity and specificity. This test is nondestructive to the sample, which can be kept and used in further tests at the lab; however, few labs would use the swab used for the Kastle–Meyer test in any further testing, opting instead to use a fresh swab of the original stain. | 0 | Theoretical and Fundamental Chemistry |
The Ohnesorge number (Oh) is a dimensionless number that relates the viscous forces to inertial and surface tension forces. The number was defined by Wolfgang von Ohnesorge in his 1936 doctoral thesis.
It is defined as:
Where
* μ is the dynamic viscosity of the liquid
* ρ is the density of the liquid
* σ is the surface tension
* L is the characteristic length scale (typically drop diameter)
* Re is the Reynolds number
* We is the Weber number | 1 | Applied and Interdisciplinary Chemistry |
When Criegee intermediates are formed, some portion of them will undergo prompt unimolecular decay, producing OH radicals and other products. However, they may instead become stabilized by interactions with other molecules or react with other chemicals to give different products.
Criegee intermediates may be collisionally stabilized via collisions with other molecules in the atmosphere. These stabilized Criegee intermediates may then undergo thermal unimolecular decay to OH radicals and other products, or may undergo bimolecular reactions with other atmospheric species.
In the ozonolysis reaction sequence, the Criegee intermediate reacts with another carbonyl compound (generally the aldehyde or ketone byproduct of the Criegee-intermediate formation reaction itself) to form an ozonide (1,2,4-trioxolane). | 1 | Applied and Interdisciplinary Chemistry |
Bioeffectors have a direct or indirect effect on plant performance by influencing the functional implementation or activation of biological mechanisms, particularly those interfering with soil-plant-microbe interactions.
In contrast to conventional fertilizers and pesticides, the effectiveness of bioeffectors is not based on a substantial direct input of mineral plant nutrients, either in inorganic or organic forms.
*Products in use are:
** Microbial residues,
** Composting and fermentation products,
** Plant and algae extracts
*Bioeffector-preparations (bio-agents) as ready-formulated products are applied:
** with the purpose of stimulating plant growth (bio-stimulants),
** to improve plant nutrient acquisition (bio-fertilizers),
** to protect plants from pathogens and pests (bio-control agents)
** or generally to advance cropping efficiency; they can contain one or more bio-effectors along with other substances”
*Well established bioeffectors with documented positive results in the field level are:
** Rhizobia strains for soil or seed inoculation as a prerequisite for symbiotic N2-fixation when establishing new legume species or varieties.
** positive effects of mycorrhiza inoculation for soils with a (temporarily) low potential for natural root mycorrhization.
** sufficient mycorrhization enhances nutrient (P) and water uptake and increases resistance to pathogenic fungi.
*Further mechanisms for the positive impact of bioeffectors on plant growth have postulated, promising a high potential for resource preservation due to reduction of fertiliser and pesticide use:
** Active nutrient mobilisation by exudation of acids and carboxylates (e.g. P-mobilisation),
** exudation of micro-nutrient mobilising siderophores/chelates (e.g. Fe),
** reduction of trace elements from less soluble oxidised to highly soluble reduced forms (e.g. Fe to Fe, Mn to Mn),
** associative/non-symbiotic N-fixation, protective antagonism to plant pathogens,
** enhancement of mycorrhizal infection and growth, and stimulating hormonal effects. | 1 | Applied and Interdisciplinary Chemistry |
Some microbes are heterotrophic (more precisely chemoorganoheterotrophic), using organic compounds as both carbon and energy sources. Heterotrophic microbes live off of nutrients that they scavenge from living hosts (as commensals or parasites) or find in dead organic matter of all kind (saprophages). Microbial metabolism is the main contribution for the bodily decay of all organisms after death. Many eukaryotic microorganisms are heterotrophic by predation or parasitism, properties also found in some bacteria such as Bdellovibrio (an intracellular parasite of other bacteria, causing death of its victims) and Myxobacteria such as Myxococcus (predators of other bacteria which are killed and lysed by cooperating swarms of many single cells of Myxobacteria). Most pathogenic bacteria can be viewed as heterotrophic parasites of humans or the other eukaryotic species they affect. Heterotrophic microbes are extremely abundant in nature and are responsible for the breakdown of large organic polymers such as cellulose, chitin or lignin which are generally indigestible to larger animals. Generally, the oxidative breakdown of large polymers to carbon dioxide (mineralization) requires several different organisms, with one breaking down the polymer into its constituent monomers, one able to use the monomers and excreting simpler waste compounds as by-products, and one able to use the excreted wastes. There are many variations on this theme, as different organisms are able to degrade different polymers and secrete different waste products. Some organisms are even able to degrade more recalcitrant compounds such as petroleum compounds or pesticides, making them useful in bioremediation.
Biochemically, prokaryotic heterotrophic metabolism is much more versatile than that of eukaryotic organisms, although many prokaryotes share the most basic metabolic models with eukaryotes, e. g. using glycolysis (also called EMP pathway) for sugar metabolism and the citric acid cycle to degrade acetate, producing energy in the form of ATP and reducing power in the form of NADH or quinols. These basic pathways are well conserved because they are also involved in biosynthesis of many conserved building blocks needed for cell growth (sometimes in reverse direction). However, many bacteria and archaea utilize alternative metabolic pathways other than glycolysis and the citric acid cycle. A well-studied example is sugar metabolism via the keto-deoxy-phosphogluconate pathway (also called ED pathway) in Pseudomonas. Moreover, there is a third alternative sugar-catabolic pathway used by some bacteria, the pentose phosphate pathway. The metabolic diversity and ability of prokaryotes to use a large variety of organic compounds arises from the much deeper evolutionary history and diversity of prokaryotes, as compared to eukaryotes. It is also noteworthy that the mitochondrion, the small membrane-bound intracellular organelle that is the site of eukaryotic oxygen-using energy metabolism, arose from the endosymbiosis of a bacterium related to obligate intracellular Rickettsia, and also to plant-associated Rhizobium or Agrobacterium. Therefore, it is not surprising that all mitrochondriate eukaryotes share metabolic properties with these Pseudomonadota. Most microbes respire (use an electron transport chain), although oxygen is not the only terminal electron acceptor that may be used. As discussed below, the use of terminal electron acceptors other than oxygen has important biogeochemical consequences. | 1 | Applied and Interdisciplinary Chemistry |
Physical, chemical, and biological processes combine in wetlands to remove contaminants from wastewater. An understanding of these processes is fundamental not only to designing wetland systems but to understanding the fate of chemicals once they enter the wetland. Theoretically, wastewater treatment within a constructed wetland occurs as it passes through the wetland medium and the plant rhizosphere. A thin film around each root hair is aerobic due to the leakage of oxygen from the rhizomes, roots, and rootlets. Aerobic and anaerobic micro-organisms facilitate decomposition of organic matter. Microbial nitrification and subsequent denitrification releases nitrogen as gas to the atmosphere. Phosphorus is coprecipitated with iron, aluminium, and calcium compounds located in the root-bed medium. Suspended solids filter out as they settle in the water column in surface flow wetlands or are physically filtered out by the medium within subsurface flow wetlands. Harmful bacteria, fungi, and viruses are reduced by filtration and adsorption by biofilms on the gravel or sand media in subsurface flow and vertical flow systems. | 1 | Applied and Interdisciplinary Chemistry |
Electrodialysis is a process of separation which uses ion-exchange membranes and an electrical potential as a driving force. It is mainly used to remove ions from aqueous solutions. There are three electrodialysis processes which are commonly used - Donnan dialysis, reverse electrodialysis, and electro-electrodialysis. These processes are explained below. | 1 | Applied and Interdisciplinary Chemistry |
Frictional forces play a role in determining the flow properties of compressible flow in ducts. In calculations, friction is either taken as inclusive or exclusive. If friction is inclusive, then the analysis of compressible flow becomes more complex as if friction is not inclusive. If the friction is exclusive to the analysis, then certain restrictions will be put into place. When friction is included on compressible flow, the friction limits the areas in which the results from analysis in be applied. As mentioned before, the shape of the duct, such as varying sizes or nozzles, effect the different calculations in between friction and compressible flow. | 1 | Applied and Interdisciplinary Chemistry |
In analytical chemistry, a standard solution (titrant or titrator) is a solution containing an accurately known concentration. Standard solutions are generally prepared by dissolving a solute of known mass into a solvent to a precise volume, or by diluting a solution of known concentration with more solvent.
Standard solutions are used to determine the concentration of solutions with unknown concentration, such as solutions in titrations. The concentrations of standard solutions are normally expressed in units of moles per litre (mol/L, often abbreviated to M for molarity), moles per cubic decimetre (mol/dm), kilomoles per cubic metre (kmol/m), grams per milliliters (g/mL), or in terms related to those used in particular titrations (such as titres). | 0 | Theoretical and Fundamental Chemistry |
In a solution that decreases in acidity, methyl orange moves from the color red to orange and finally to yellow with the opposite occurring for a solution increasing in acidity. This color change from yellow to red occurs because the protons in the acidic solution react with the N=N bond of the molecule, protonating one of them and changing the visible light absorption of the molecule to reflect more red light than orange/yellow.
In an acid, it is reddish and in alkali, it is yellow. Methyl orange has a pK of 3.47 in water at . | 0 | Theoretical and Fundamental Chemistry |
Georg-Maria Schwab (, ; 3 February 1899 – 23 December 1984) was a German-Greek physical chemist recognised for his important contributions in the field of catalysis and the kinetics thereof.
Schwab's early academic career in Berlin and Würzburg (1923–1928) was characterised by meticulous experimental work as a kineticist, before starting his specialisation in heterogeneous catalysis in Munich (1928–1938). Dismissed by Nazi Germany on anti-Semitic grounds, he emigrated to Greece with the help of his future wife Elly Schwab-Agallidis, where together, they continued conducting physico-chemical research (1939–1950). Eventually returning to West Germany in the 1950s, Schwab served as professor of physical chemistry in the University of Munich until retirement (1951–1967). | 0 | Theoretical and Fundamental Chemistry |
* Autologous MDSC Injections to Treat Urinary Incontinence: an in vivo injection technique for pure stress incontinence in female subjects in which defective muscle cells were replaced with stem cells that would differentiate to become functioning smooth muscle cells in the urinary sphincter
* Vascular Smooth Muscle regeneration using induced pluripotent stem cells (iPSCs); an in vitro technique in which iPSCs were differentiated into proliferative smooth muscle cells using a nanofibrous scaffold.
* Formation of coiled three-dimensional (3D) cellular constructs containing smooth muscle-like cells differentiated from dedifferentiated fat (DFAT) cells: an in vitro technique for controlling the 3D organization of smooth muscle cells in which DFAT cells are suspended in a mixture of extracellular proteins with optimized stiffness so that they differentiate into smooth muscle-like cells with specific 3D orientation; a muscle tissue engineered construct for a smooth muscle cell precursor | 1 | Applied and Interdisciplinary Chemistry |
In crystallography, a periodic graph or crystal net is a three-dimensional periodic graph, i.e., a three-dimensional Euclidean graph whose vertices or nodes are points in three-dimensional Euclidean space, and whose edges (or bonds or spacers) are line segments connecting pairs of vertices, periodic in three linearly independent axial directions. There is usually an implicit assumption that the set of vertices are uniformly discrete, i.e., that there is a fixed minimum distance between any two vertices. The vertices may represent positions of atoms or complexes or clusters of atoms such as single-metal ions, molecular building blocks, or secondary building units, while each edge represents a chemical bond or a polymeric ligand.
Although the notion of a periodic graph or crystal net is ultimately mathematical (actually a crystal net is nothing but a periodic realization of an abelian covering graph over a finite graph
), and is closely related to that of a Tessellation of space (or honeycomb) in the theory of polytopes and similar areas, much of the contemporary effort in the area is motivated by crystal engineering and prediction (design), including metal-organic frameworks (MOFs) and zeolites. | 0 | Theoretical and Fundamental Chemistry |
Ethanol is obtained by fermentation of glucose (which is often obtained from starch) in the presence of yeast. Carbon dioxide is cogenerated. Like ethanol, butanol can be produced by fermentation processes. Saccharomyces yeast are known to produce these higher alcohols at temperatures above . The bacterium Clostridium acetobutylicum can feed on cellulose (also an alcohol) to produce butanol on an industrial scale. | 0 | Theoretical and Fundamental Chemistry |
Fatta-Kassinos has worked in the area of environmental science and authored numerous publications. Her research spans the fields of wastewater treatment and reuse, with a particular focus on Advanced Oxidation Processes (AOP), and on the development, and use of techniques for identifying contaminants of emerging concern in wastewater and crops, as well as antimicrobial resistance in the environment and wastewater technical systems. Among various honors, she is the recipient of the highest national research recognition award, the Nikos Symeonides National Research Award, and most recently was awarded the Noack Laboratorien Outstanding Science Career Award by the Society of Environmental Toxicology and Chemistry (SETAC). She was the Proposer, and Chair of the European COST Action NEREUS ES1403, "New and emerging challenges and opportunities in wastewater reuse" from 2014 till 2018, and later, became the Project coordinator of "Antibiotics and mobile resistance elements in wastewater reuse applications: risks and innovative solutions" (ANSWER) Project. | 1 | Applied and Interdisciplinary Chemistry |
Hydrogen-bonded organic frameworks are crystalline porous polymers assembled from organic monomers linked through hydrogen bonds. | 0 | Theoretical and Fundamental Chemistry |
On 17 October 1898, Humphrey matriculated for chemistry at the University of Zurich. She joined a growing band of Alfred Werners students, working in the inadequate cellars known as the "Katakomben" (catacombs). Humphrey was awarded a grant of £60 a year for three years by the Technical Education Board of the London County Council, but studying in Switzerland was expensive, and Humphrey was "hard up". Werner recognised Humphreys ability and appointed her as his assistant, with a salary, the first woman to occupy the post. Humphrey worked hard, and her account of the time suggests that she found the social life disappointing.
Humphrey was "the first of his students to succeed in preparing Werners first new series of geometrically isomeric cobalt complexes, a class of compounds that were crucial in his development and proof of his coordination theory." One of these compounds, the cis-bis(ethylenediamine)dinitrocobalt(III) bromide, was the first synthesis of a chiral octahedral cobalt complex. In 1991, the Swiss Committee on Chemistry donated Humphreys chiral crystals to the Royal Society of Chemistry, and they are now at Burlington House, in London.
"What a pity for Miss Humphrey that it was not recognized at the time, because she would then have been responsible for an unequivocal proof of the soundness of Werners coordination theory and the subsequent award of the Nobel prize to him." While one later study has cast doubt on the quality of the sample, Humphreys status as a pioneer woman scientist remains significant.
Her doctoral thesis Über die Bindungsstelle der Metalle in ihren Verbindungen und über Dinitritoäthylendiaminkobaltisalze was accepted by the University of Zurich in 1901. Humphrey was the first British woman to obtain a doctorate in chemistry, though not the first in Zurich. An American chemist, Rachel Holloway Lloyd, had already done so in 1887, and it had become "a haven for women students from all over Europe".
On completion of her thesis, Humphrey was recommended to move to Leipzig University to continue research under Wilhelm Ostwald. However, the attitude to women there was quite different from Zurich, and she would not tolerate a regime where she was not allowed to work in the laboratories in case her presence distracted the men from their work. | 0 | Theoretical and Fundamental Chemistry |
Composite materials contain two or more macroscopic phases, one of which is often ceramic. For example, a continuous matrix, and a dispersed phase of ceramic particles or fibers.
Applications of composite materials range from structural elements such as steel-reinforced concrete, to the thermally insulative tiles that play a key and integral role in NASAs Space Shuttle thermal protection system, which is used to protect the surface of the shuttle from the heat of re-entry into the Earths atmosphere. One example is Reinforced Carbon-Carbon (RCC), the light gray material that withstands reentry temperatures up to 1510 °C (2750 °F) and protects the nose cap and leading edges of Space Shuttle's wings. RCC is a laminated composite material made from graphite rayon cloth and impregnated with a phenolic resin. After curing at high temperature in an autoclave, the laminate is pyrolized to convert the resin to carbon, impregnated with furfural alcohol in a vacuum chamber, and cured/pyrolized to convert the furfural alcohol to carbon. In order to provide oxidation resistance for reuse capability, the outer layers of the RCC are converted to silicon carbide.
Domestic examples of composites can be seen in the "plastic" casings of television sets, cell-phones and so on. These plastic casings are usually a composite made up of a thermoplastic matrix such as acrylonitrile butadiene styrene (ABS) in which calcium carbonate chalk, talc, glass fibers or carbon fibers have been added for strength, bulk, or electro-static dispersion. These additions may be referred to as reinforcing fibers, or dispersants, depending on their purpose.
Thus, the matrix material surrounds and supports the reinforcement materials by maintaining their relative positions. The reinforcements impart their special mechanical and physical properties to enhance the matrix properties. A synergism produces material properties unavailable from the individual constituent materials, while the wide variety of matrix and strengthening materials provides the designer with the choice of an optimum combination. | 0 | Theoretical and Fundamental Chemistry |
* BMS-986121: μ-PAM
* BMS-986122: μ-PAM
* Ignavine
* Oxytocin: μ-PAM
* δ-PAM (see reference)
* Cannabidiol
* Tetrahydrocannabinol
* Sodium (Na) | 1 | Applied and Interdisciplinary Chemistry |
Minerals are naturally occurring solids formed through various geological processes under high pressures. To be classified as a true mineral, a substance must have a crystal structure with uniform physical properties throughout. Minerals range in composition from pure elements and simple salts to very complex silicates with thousands of known forms. In contrast, a rock sample is a random aggregate of minerals and/or mineraloids, and has no specific chemical composition. The vast majority of the rocks of the Earth's crust consist of quartz (crystalline SiO), feldspar, mica, chlorite, kaolin, calcite, epidote, olivine, augite, hornblende, magnetite, hematite, limonite and a few other minerals. Some minerals, like quartz, mica or feldspar are common, while others have been found in only a few locations worldwide. The largest group of minerals by far is the silicates (most rocks are ≥95% silicates), which are composed largely of silicon and oxygen, with the addition of ions of aluminium, magnesium, iron, calcium and other metals. | 0 | Theoretical and Fundamental Chemistry |
Targeting of TNRF2 in tumor cells is associated with increased tumor cell death and decreased progression of tumor cell growth.
Increased expression of TNFR2 is found in breast cancer, cervical cancer, colon cancer, and renal cancer. A link between the expression of TNRF2 in tumor cells and late-stage cancer has been discovered. TNFR2 plays a significant role in tumor cell growth as it has been found that the loss of TNFR2 expression is linked with increased death of associated tumor cells and a significant standstill of further growth. There is therapeutic potential in the targeting of TNFR2 for cancer treatments through TNFR2 inhibition. | 1 | Applied and Interdisciplinary Chemistry |
The homologous series of straight-chained alkanes begins methane (CH), ethane (CH), propane (CH), butane (CH), and pentane (CH). In that series, successive members differ in mass by an extra methylene bridge (-CH- unit) inserted in the chain. Thus the molecular mass of each member differs by 14 atomic mass units. Adjacent members in such a series, such as methane and ethane, are known as "adjacent homologues".
Within that series, many physical properties such as boiling point gradually change with increasing mass. For example, ethane (CH), has a higher boiling point than methane (CH). This is because the London dispersion forces between ethane molecules are higher than that between methane molecules, resulting in stronger forces of intermolecular attraction, raising the boiling point.
Some important classes of organic molecules are derivatives of alkanes, such as the primary alcohols, aldehydes, and (mono)carboxylic acids form analogous series to the alkanes. The corresponding homologous series of primary straight-chained alcohols comprises methanol (CHO), ethanol (CHO), 1-propanol (CHO), 1-butanol, and so on. The single-ring cycloalkanes form another such series, starting with cyclopropane.
Biopolymers also form homologous series, for example the polymers of glucose such as cellulose oligomers starting with cellobiose, or the series of amylose oligomers starting with maltose, which are sometimes called maltooligomers. Homooligopeptides, oligopeptides made up of repetitions of only one amino acid can also be studied as homologous series. | 0 | Theoretical and Fundamental Chemistry |
An experiment for the preparation of mercuric oxide was first described by 11th century Arab-Spanish alchemist, Maslama al-Majriti, in Rutbat al-hakim. It was historically called red precipitate (as opposed to white precepitate being the mercuric amidochloride).
In 1774, Joseph Priestley discovered that oxygen was released by heating mercuric oxide, although he did not identify the gas as oxygen (rather, Priestley called it "dephlogisticated air," as that was the paradigm that he was working under at the time). | 0 | Theoretical and Fundamental Chemistry |
A transition metal alkoxide complex is a kind of coordination complex containing one or more alkoxide ligands, written as , where R is the organic substituent. Metal alkoxides are used for coatings and as catalysts. | 0 | Theoretical and Fundamental Chemistry |
Since the separation of biological molecules such as proteins would be better served by isocratic elution with an aqueous solvent, resolution of HPLC analysis should be tweaked in the area of stationary phases to elute such analytes that may be sensitive to organic solvents. Kanazawa et al. recognized the possibility of changing the LCST parameter through the addition of different moieties. Kanazawa’s group investigated the reversible changes of PNIPAAm once modifying it with a carboxyl end. It was suggested that the modification leads to faster changes in conformation due to the restrictions introduced by the carboxyl group. They attached the carboxyl-terminated PNIPAAm chains to (aminopropyl)silica and used it as packing material for HPLC analysis of steroids. The separation took place under isocratic conditions using pure water as the mobile phase, and controlled the temperature using a water bath. They were able to shift the LCST from 32 °C to 20 °C by making the solution 1M in NaCl concentration. Of the 5 steroids and benzene, only testosterone could be resolved from the other peaks below the LCST (5 °C, LCST=20 °C in 1M NaCl). Above the LCST (25 °C, LCST=20 °C in 1M NaCl), all of the peaks are well resolved, and there is an increasing trend of retention time versus temperature up to 50 °C. | 0 | Theoretical and Fundamental Chemistry |
The Sudbury Neutrino Observatory (SNO), a underground observatory in Sudbury, Canada, is the other site where neutrino oscillation research was taking place in the late 1990s and early 2000s. The results from experiments at this observatory along with those at Super-Kamiokande are what helped solve the solar neutrino problem.
The SNO is also a heavy-water Cherenkov detector and designed to work the same way as the Super-Kamiokande. The Neutrinos when reacted with heavy water produce the blue Cherenkov light, signaling the detection of neutrinos to researchers and observers. | 0 | Theoretical and Fundamental Chemistry |
For a fully filled duct or pipe whose cross-section is a regular polygon, the hydraulic diameter is equivalent to the diameter of a circle inscribed within the wetted perimeter.
This can be seen as follows: The -sided regular polygon is a union of triangles, each of height and base .
Each such triangle contributes to the total area and to the total perimeter, giving
for the hydraulic diameter. | 1 | Applied and Interdisciplinary Chemistry |
[https://www.epw.senate.gov/public/index.cfm/superfund-sites-identified-by-epa-to-have-pfas-contamination Five military installations] in Washington State have been identified by the U.S. Senate Committee on Environment and Public Works as having PFAS contamination. Toward environmental and consumer protections, the Washington State Department of Ecology published a [https://apps.ecology.wa.gov/publications/summarypages/2104048.html Chemical Action Plan] in November 2021, and in June 2022 the governor tasked the Washington State Department of Ecology with [https://app.leg.wa.gov/RCW/default.aspx?cite=70A.350.090 phasing out manufacture and import of products containing PFASs]. Initial steps taken by the Washington State Department of Health to protect the public from exposure through drinking water have included setting [https://doh.wa.gov/sites/default/files/2022-02/PFAS%20Rule%20Adoption%20Notice%20and%20Adopted%20Rule%20Language.pdf?uid=62c866e64514c State Action Levels] for five PFASs (PFOA, PFOS, PFNA, PFHxS, and PFBS), which were implemented in November 2021. | 0 | Theoretical and Fundamental Chemistry |
Transcriptomics methods are highly parallel and require significant computation to produce meaningful data for both microarray and RNA-Seq experiments. Microarray data is recorded as high-resolution images, requiring feature detection and spectral analysis. Microarray raw image files are each about 750 MB in size, while the processed intensities are around 60 MB in size. Multiple short probes matching a single transcript can reveal details about the intron-exon structure, requiring statistical models to determine the authenticity of the resulting signal. RNA-Seq studies produce billions of short DNA sequences, which must be aligned to reference genomes composed of millions to billions of base pairs. De novo assembly of reads within a dataset requires the construction of highly complex sequence graphs. RNA-Seq operations are highly repetitious and benefit from parallelised computation but modern algorithms mean consumer computing hardware is sufficient for simple transcriptomics experiments that do not require de novo assembly of reads. A human transcriptome could be accurately captured using RNA-Seq with 30 million 100 bp sequences per sample. This example would require approximately 1.8 gigabytes of disk space per sample when stored in a compressed fastq format. Processed count data for each gene would be much smaller, equivalent to processed microarray intensities. Sequence data may be stored in public repositories, such as the Sequence Read Archive (SRA). RNA-Seq datasets can be uploaded via the Gene Expression Omnibus. | 1 | Applied and Interdisciplinary Chemistry |
The Leimgruber–Batcho, Bartoli and Baeyer–Emmerling indole syntheses begin with aromatic nitro compounds. Indigo can be synthesized in a condensation reaction from ortho-nitrobenzaldehyde and acetone in strongly basic conditions in a reaction known as the Baeyer–Drewson indigo synthesis. | 0 | Theoretical and Fundamental Chemistry |
Elizabeth A. Canuel is a chemical oceanographer known for her work on organic carbon cycling in aquatic environments. She is the Chancellor Professor of Marine Science at the College of William & Mary and is an elected fellow of the Geochemical Society and the European Association of Geochemistry. | 0 | Theoretical and Fundamental Chemistry |
The Benesi–Hildebrand method is a mathematical approach used in physical chemistry for the determination of the equilibrium constant K and stoichiometry of non-bonding interactions. This method has been typically applied to reaction equilibria that form one-to-one complexes, such as charge-transfer complexes and host–guest molecular complexation.
The theoretical foundation of this method is the assumption that when either one of the reactants is present in excess amounts over the other reactant, the characteristic electronic absorption spectra of the other reactant are transparent in the collective absorption/emission range of the reaction system. Therefore, by measuring the absorption spectra of the reaction before and after the formation of the product and its equilibrium, the association constant of the reaction can be determined. | 0 | Theoretical and Fundamental Chemistry |
An April paper reported that gene therapy addressed achromatopsia (color blindness) in dogs by targeting cone photoreceptors. Cone function and day vision were restored for at least 33 months in two young specimens. The therapy was less efficient for older dogs.
In September it was announced that an 18-year-old male patient in France with beta thalassemia major had been successfully treated. Beta thalassemia major is an inherited blood disease in which beta haemoglobin is missing and patients are dependent on regular lifelong blood transfusions. The technique used a lentiviral vector to transduce the human β-globin gene into purified blood and marrow cells obtained from the patient in June 2007. The patient's haemoglobin levels were stable at 9 to 10 g/dL. About a third of the hemoglobin contained the form introduced by the viral vector and blood transfusions were not needed. Further clinical trials were planned. Bone marrow transplants are the only cure for thalassemia, but 75% of patients do not find a matching donor.
Cancer immunogene therapy using modified antigene, antisense/triple helix approach was introduced in South America in 2010/11 in La Sabana University, Bogota (Ethical Committee 14 December 2010, no P-004-10). Considering the ethical aspect of gene diagnostic and gene therapy targeting IGF-I, the IGF-I expressing tumors i.e. lung and epidermis cancers were treated (Trojan et al. 2016). | 1 | Applied and Interdisciplinary Chemistry |
there was no evidence that an increase in physical performance occurs after inhaling salbutamol, but there are various reports for benefit when delivered orally or intravenously. In spite of this, salbutamol required "a declaration of Use in accordance with the International Standard for Therapeutic Use Exemptions" under the 2010 WADA prohibited list. This requirement was relaxed when the 2011 list was published to permit the use of "salbutamol (maximum 1600 micrograms over 24 hours) and salmeterol when taken by inhalation in accordance with the manufacturers' recommended therapeutic regimen."
Abuse of the drug may be confirmed by detection of its presence in plasma or urine, typically exceeding 1,000 ng/mL. The window of detection for urine testing is on the order of just 24 hours, given the relatively short elimination half-life of the drug, estimated at between 5 and 6 hours following oral administration of 4 mg. | 0 | Theoretical and Fundamental Chemistry |
Coefficient of discharge for sharp-edged orifice plates with corner, flange or D and D/2 tappings and no drain or vent hole (Reader-Harris/Gallagher equation):
:and if D < 71.2mm in which case this further term is added to C:
:In the equation for C,
::and only the three following pairs of values for L and L' are valid:
:::corner tappings:
:::flange tappings:
:::D and D/2 tappings: | 1 | Applied and Interdisciplinary Chemistry |
The nuclear drip line is the boundary beyond which atomic nuclei are unbound with respect to the emission of a proton or neutron.
An arbitrary combination of protons and neutrons does not necessarily yield a stable nucleus. One can think of moving up or to the right across the table of nuclides by adding a proton or a neutron, respectively, to a given nucleus. However, adding nucleons one at a time to a given nucleus will eventually lead to a newly formed nucleus that immediately decays by emitting a proton (or neutron). Colloquially speaking, the nucleon has leaked or dripped out of the nucleus, hence giving rise to the term drip line.
Drip lines are defined for protons and neutrons at the extreme of the proton-to-neutron ratio; at p:n ratios at or beyond the drip lines, no bound nuclei can exist. While the location of the proton drip line is well known for many elements, the location of the neutron drip line is only known for elements up to neon. | 0 | Theoretical and Fundamental Chemistry |
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