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Particle size analysis, particle size measurement, or simply particle sizing, is the collective name of the technical procedures, or laboratory techniques which determines the size range, and/or the average, or mean size of the particles in a powder or liquid sample.
Particle size analysis is part of particle science, and it is generally carried out in particle technology laboratories.
The particle size measurement is typically achieved by means of devices, called Particle Size Analyzers (PSA), which are based on different technologies, such as high definition image processing, analysis of Brownian motion, gravitational settling of the particle and light scattering (Rayleigh and Mie scattering) of the particles.
The particle size can have considerable importance in a number of industries including the chemical, food, mining, forestry, agriculture, cosmetics, pharmaceutical, energy, and aggregate industries. | 0 | Theoretical and Fundamental Chemistry |
Stereochemical information of a chiral monomer can be expressed in a supramolecular polymer. Helical supramolecular polymer with P-and M-conformation are widely seen, especially those composed of disc-shaped monomers. When the monomers are achiral, both P-and M-helices are formed in equal amounts. When the monomers are chiral, typically due to the presence of one or more stereocenters in the side chains, the diastereomeric relationship between P- and M-helices leads to the preference of one conformation over the other. Typical example is a C-symmetric disk-shaped chiral monomer that forms helical supramolecular polymers via the "majority rule". A slight excess of one enantiomer of the chiral monomer resulted in a strong bias to either the right-handed or left-handed helical geometry at the supramolecular polymer level. In this case, a characteristic nonlinear dependence of the anisotropic factor, g, on the enantiomeric excess of a chiral monomer can be generally observed. Like in small molecule based chiral system, chirality of a supramolecular polymer also affected by chiral solvents. Some application such as a catalyst for asymmetric synthesis and circular polarized luminescence are observed in chiral supramolecular polymers too. | 0 | Theoretical and Fundamental Chemistry |
From 1897-1898, she was granted a graduate scholarship to pursue her PhD. Upon completion of her PhD, she was granted one of Yales University Fellowships to continue work in Goochs laboratory until 1899. | 0 | Theoretical and Fundamental Chemistry |
Architect Jay Swayze stated that the idea for the Atomitat was born when he attended a civil defense discussion on fallout shelters. The home completed in 1962 and it was designed during the cold war when Americans feared nuclear war. Swayze said that the Atomitat was designed to be an atomic habitat which met the civil defense specifications. The cost of the furnished Atomitat with two vehicles was estimated to be $135,000. The Swayze's also stated that because the Atomitat home was secure against damaging weather, their home insurance rate was about 87.5% less than the rate of an above ground home.
In 1967 the Atomitat was featured in a U.S. Information Agency propaganda film. The film was part of a series showing scenes of American life, and it would be shown in Arab countries. | 0 | Theoretical and Fundamental Chemistry |
Moving-boundary electrophoresis was developed by Arne Tiselius in 1930. Tiselius was awarded the 1948 Nobel Prize in chemistry for his work on the separation of colloids through electrophoresis, the motion of charged particles through a stationary liquid under the influence of an electric field. | 0 | Theoretical and Fundamental Chemistry |
Sodium dithionite finds widespread use in industry as a reducing agent. It is for example used in bleaching of pulp and some dyes. | 1 | Applied and Interdisciplinary Chemistry |
The most common case is case (a) in which is electrostatically coupled to the internuclear axis, and is coupled to by spin-orbit coupling. Then both and have well-defined axial components, and respectively. As they are written with the same Greek symbol, the spin component should not be confused with states, which are states with orbital angular component equal to zero. defines a vector of magnitude pointing along the internuclear axis. Combined with the rotational angular momentum of the nuclei , we have . In this case, the precession of and around the nuclear axis is assumed to be much faster than the nutation of and around .
The good quantum numbers in case (a) are , , , and . However is not a good quantum number because the vector is strongly coupled to the electrostatic field and therefore precesses rapidly around the internuclear axis with an undefined magnitude. We express the rotational energy operator as , where is a rotational constant. There are, ideally, fine-structure states, each with rotational levels having relative energies starting with . For example, a Π state has a Π term (or fine structure state) with rotational levels = 1/2, 3/2, 5/2, 7/2, ... and a Π term with levels = 3/2, 5/2, 7/2, 9/2.... Case (a) requires > 0 and so does not apply to any Σ states, and also > 0 so that it does not apply to any singlet states.
The selection rules for allowed spectroscopic transitions depend on which quantum numbers are good. For Hund's case (a), the allowed transitions must have and and and and . In addition, symmetrical diatomic molecules have even (g) or odd (u) parity and obey the Laporte rule that only transitions between states of opposite parity are allowed. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, isotopologues are molecules that differ only in their isotopic composition. They have the same chemical formula and bonding arrangement of atoms, but at least one atom has a different number of neutrons than the parent.
An example is water, whose hydrogen-related isotopologues are: "light water" (HOH or ), "semi-heavy water" with the deuterium isotope in equal proportion to protium (HDO or ), "heavy water" with two deuterium isotopes of hydrogen per molecule ( or ), and "super-heavy water" or tritiated water ( or , as well as and , where some or all of the hydrogen atoms are replaced with the radioactive tritium isotope). Oxygen-related isotopologues of water include the commonly available form of heavy-oxygen water () and the more difficult to separate version with the isotope. Both elements may be replaced by isotopes, for example in the doubly labeled water isotopologue . All taken together, there are 9 different stable water isotopologues, and 9 radioactive isotopologues involving tritium, for a total of 18. However only certain ratios are possible in mixture, due to prevalent hydrogen swapping.
The atom(s) of the different isotope may be anywhere in a molecule, so the difference is in the net chemical formula. If a compound has several atoms of the same element, any one of them could be the altered one, and it would still be the same isotopologue. When considering the different locations of the same isotopically modified element, the term isotopomer, first proposed by Seeman and Paine in 1992, is used.
Isotopomerism is analogous to constitutional isomerism of different elements in a structure. Depending on the formula and the symmetry of the structure, there might be several isotopomers of one isotopologue. For example, ethanol has the molecular formula . Mono-deuterated ethanol, , is an isotopologue of it. The structural formulas and are two isotopomers of that isotopologue. | 0 | Theoretical and Fundamental Chemistry |
The company XeelTech and CK Materials Lab in Korea use magnetorheological fluid to generate the haptic feedback of their HAPTICORE rotary switches. The MR actuators are primarily used as input devices with adaptive haptic feedback to enable new possibilities in user interface design. The HAPTICORE technology functions like a miniature MR brake. By changing the magnetic field created by a small electromagnet inside the rotary knob, the friction between the outer shell and the stator is modified in such a way that the user perceives the braking effect as haptic feedback.
By modifying the rheological state of the fluid in near real time, a variety of mechanical rotary knob and cam switch haptic patterns such as ticks, grids, and barriers or limits can be simulated. In addition, it is also possible to generate new forms of haptic feedback, such as speed-adaptive and direction-dependent haptic feedback modes. This technology is used, for example, in HMIs of industrial equipment, household appliances or computer peripherals. | 1 | Applied and Interdisciplinary Chemistry |
A phosphorylation cascade is a sequence of signaling pathway events where one enzyme phosphorylates another, causing a chain reaction leading to the phosphorylation of thousands of proteins. This can be seen in signal transduction of hormone messages. A signaling pathway begins at the cell surface where a hormone or protein binds to a receptor at the extracellular matrix. The interactions between the molecule and receptor cause a conformational change at the receptor, which activates multiple enzymes or proteins. These enzymes activate secondary messengers, which leads to the phosphorylation of thousands of proteins. The end product of a phosphorylation cascade is the changes occurring inside the cell.
One best example that explains this phenomenon is mitogen-activated protein (MAP) kinase or ERK kinase. MAP kinase not only plays an important function during growth of cell in the M phase phosphorylation cascade but also plays an important role during the sequence of signaling pathway. In order to regulate its functions so it does not cause chaos, it can only be active when both tyrosine and threonine/serine residues are phosphorylated. | 1 | Applied and Interdisciplinary Chemistry |
As electrons from the cathode gain more energy, they tend to ionize, rather than excite atoms. Excited atoms quickly fall back to ground level emitting light, however, when atoms are ionized, the opposite charges are separated, and do not immediately recombine. This results in more ions and electrons, but no light. This region is sometimes called Crookes dark space, and sometimes referred to as the cathode fall, because the largest voltage drop in the tube occurs in this region. | 0 | Theoretical and Fundamental Chemistry |
IBX dehydrogenation (oxidation) of cycloheptanone (suberone) to 2,6-cycloheptadienone [1192-93-4] followed by reaction with an amine is versatile a way of forming tropinones. The mechanism evoked is clearly delineated to be a double Michael reaction (i.e. conjugate addition). | 0 | Theoretical and Fundamental Chemistry |
Electron backscatter diffraction (EBSD) is a scanning electron microscopy (SEM) technique used to study the crystallographic structure of materials. EBSD is carried out in a scanning electron microscope equipped with an EBSD detector comprising at least a phosphorescent screen, a compact lens and a low-light camera. In the microscope an incident beam of electrons hits a tilted sample. As backscattered electrons leave the sample, they interact with the atoms and are both elastically diffracted and lose energy, leaving the sample at various scattering angles before reaching the phosphor screen forming Kikuchi patterns (EBSPs). The EBSD spatial resolution depends on many factors, including the nature of the material under study and the sample preparation. They can be indexed to provide information about the material's grain structure, grain orientation, and phase at the micro-scale. EBSD is used for impurities and defect studies, plastic deformation, and statistical analysis for average misorientation, grain size, and crystallographic texture. EBSD can also be combined with energy-dispersive X-ray spectroscopy (EDS), cathodoluminescence (CL), and wavelength-dispersive X-ray spectroscopy (WDS) for advanced phase identification and materials discovery.
The change and sharpness of the electron backscatter patterns (EBSPs) provide information about lattice distortion in the diffracting volume. Pattern sharpness can be used to assess the level of plasticity. Changes in the EBSP zone axis position can be used to measure the residual stress and small lattice rotations. EBSD can also provide information about the density of geometrically necessary dislocations (GNDs). However, the lattice distortion is measured relative to a reference pattern (EBSP). The choice of reference pattern affects the measurement precision; e.g., a reference pattern deformed in tension will directly reduce the tensile strain magnitude derived from a high-resolution map while indirectly influencing the magnitude of other components and the spatial distribution of strain. Furthermore, the choice of EBSP slightly affects the GND density distribution and magnitude. | 0 | Theoretical and Fundamental Chemistry |
In 2013 Green and a team of researchers launched the BabySeq Project to study the ethical and medical consequences of sequencing a newborn´s DNA.
As of 2015, whole genome and exome sequencing as a newborn screening tool were deliberated. and in 2021, further discussed.
In 2021, the NIH funded BabySeq2, an implementation study that expanded the BabySeq project, enrolling 500 infants from diverse families and track the effects of their genomic sequencing on their pediatric care.
In 2023, the Lancet opined that in the UK "focusing on improving screening by upgrading targeted gene panels might be more sensible in the short term. Whole genome sequencing in the long term deserves thorough examination and universal caution." | 1 | Applied and Interdisciplinary Chemistry |
When combined with a thermoelectric generator, a passive daytime radiative cooling surface can be used to generate electricity during the daytime and nighttime, although the power generated in tests has been relatively low. Research and development is preliminary. | 0 | Theoretical and Fundamental Chemistry |
Polarized light (PL) is very useful when studying the structure of metals with non-cubic crystal structures (mainly metals with hexagonal close-packed (hcp) crystal structures). If the specimen is prepared with minimal damage to the surface, the structure can be seen vividly in cross-polarized light (the optic axis of the polarizer and analyzer are 90 degrees to each other, i.e., crossed). In some cases, an hcp metal can be chemically etched and then examined more effectively with PL. Tint etched surfaces, where a thin film (such as a sulfide, molybdate, chromate or elemental selenium film) is grown epitaxially on the surface to a depth where interference effects are created when examined with BF producing color images, can be improved with PL. If it is difficult to get a good interference film with good coloration, the colors can be improved by examination in PL using a sensitive tint (ST) filter. | 1 | Applied and Interdisciplinary Chemistry |
A three-axis fluxgate magnetometer was part of the Mariner 2 and Mariner 10 missions. A dual technique magnetometer is part of the Cassini–Huygens mission to explore Saturn. This system is composed of a vector helium and fluxgate magnetometers. Magnetometers were also a component instrument on the Mercury MESSENGER mission. A magnetometer can also be used by satellites like GOES to measure both the magnitude and direction of the magnetic field of a planet or moon. | 0 | Theoretical and Fundamental Chemistry |
Without oxygen, pyruvate (pyruvic acid) is not metabolized by cellular respiration but undergoes a process of fermentation. The pyruvate is not transported into the mitochondrion but remains in the cytoplasm, where it is converted to waste products that may be removed from the cell. This serves the purpose of oxidizing the electron carriers so that they can perform glycolysis again and removing the excess pyruvate. Fermentation oxidizes NADH to NAD so it can be re-used in glycolysis. In the absence of oxygen, fermentation prevents the buildup of NADH in the cytoplasm and provides NAD for glycolysis. This waste product varies depending on the organism. In skeletal muscles, the waste product is lactic acid. This type of fermentation is called lactic acid fermentation. In strenuous exercise, when energy demands exceed energy supply, the respiratory chain cannot process all of the hydrogen atoms joined by NADH. During anaerobic glycolysis, NAD regenerates when pairs of hydrogen combine with pyruvate to form lactate. Lactate formation is catalyzed by lactate dehydrogenase in a reversible reaction. Lactate can also be used as an indirect precursor for liver glycogen. During recovery, when oxygen becomes available, NAD attaches to hydrogen from lactate to form ATP. In yeast, the waste products are ethanol and carbon dioxide. This type of fermentation is known as alcoholic or ethanol fermentation. The ATP generated in this process is made by substrate-level phosphorylation, which does not require oxygen.
Fermentation is less efficient at using the energy from glucose: only 2 ATP are produced per glucose, compared to the 38 ATP per glucose nominally produced by aerobic respiration. Glycolytic ATP, however, is produced more quickly. For prokaryotes to continue a rapid growth rate when they are shifted from an aerobic environment to an anaerobic environment, they must increase the rate of the glycolytic reactions. For multicellular organisms, during short bursts of strenuous activity, muscle cells use fermentation to supplement the ATP production from the slower aerobic respiration, so fermentation may be used by a cell even before the oxygen levels are depleted, as is the case in sports that do not require athletes to pace themselves, such as sprinting. | 1 | Applied and Interdisciplinary Chemistry |
Many acetylations are achieved using these three reagents:
*Acetic anhydride. This reagent is common in the laboratory; its use cogenerates acetic acid.
*Acetyl chloride. This reagent is also common in the laboratory, but its use cogenerates hydrogen chloride, which can be undesirable.
*Ketene. At one time acetic anhydride was prepared by the reaction of ketene with acetic acid: | 0 | Theoretical and Fundamental Chemistry |
The first scientific concept of acids and bases was provided by Lavoisier in around 1776. Since Lavoisiers knowledge of strong acids was mainly restricted to oxoacids, such as (nitric acid) and (sulfuric acid), which tend to contain central atoms in high oxidation states surrounded by oxygen, and since he was not aware of the true composition of the hydrohalic acids (HF, HCl, HBr, and HI), he defined acids in terms of their containing oxygen', which in fact he named from Greek words meaning "acid-former" (). The Lavoisier definition held for over 30 years, until the 1810 article and subsequent lectures by Sir Humphry Davy in which he proved the lack of oxygen in hydrogen sulfide (), hydrogen telluride (), and the hydrohalic acids. However, Davy failed to develop a new theory, concluding that "acidity does not depend upon any particular elementary substance, but upon peculiar arrangement of various substances". One notable modification of oxygen theory was provided by Jöns Jacob Berzelius, who stated that acids are oxides of nonmetals while bases are oxides of metals. | 0 | Theoretical and Fundamental Chemistry |
Relative entropy can also be interpreted as the expected discrimination information for over : the mean information per sample for discriminating in favor of a hypothesis against a hypothesis , when hypothesis is true. Another name for this quantity, given to it by I. J. Good, is the expected weight of evidence for over to be expected from each sample.
The expected weight of evidence for over is not the same as the information gain expected per sample about the probability distribution of the hypotheses,
Either of the two quantities can be used as a utility function in Bayesian experimental design, to choose an optimal next question to investigate: but they will in general lead to rather different experimental strategies.
On the entropy scale of information gain there is very little difference between near certainty and absolute certainty—coding according to a near certainty requires hardly any more bits than coding according to an absolute certainty. On the other hand, on the logit scale implied by weight of evidence, the difference between the two is enormous – infinite perhaps; this might reflect the difference between being almost sure (on a probabilistic level) that, say, the Riemann hypothesis is correct, compared to being certain that it is correct because one has a mathematical proof. These two different scales of loss function for uncertainty are both useful, according to how well each reflects the particular circumstances of the problem in question. | 0 | Theoretical and Fundamental Chemistry |
Homoleptic complexes (complexes with only chloride ligands) are often common reagents. Almost all examples are anions. | 0 | Theoretical and Fundamental Chemistry |
Bromine water is an oxidizing, intense brown mixture containing diatomic bromine (Br) dissolved in water (HO). It is often used as a reactive in chemical assays of recognition for substances which react with bromine in an aqueous environment with the halogenation mechanism, mainly unsaturated carbon compounds (carbon compounds with 1 or more double or triple bond(s)). The most common compounds that react well with bromine water are phenols, alkenes, enols, the acetyl group, aniline, and glucose. In addition, bromine water is commonly used to test for the presence of an alkene which contains a double covalent bond, reacting with the bromine water, changing its color from an intense yellow to a colorless solution. Bromine water is also commonly used to check for the presence of an aldehyde group in compounds. In this reaction, the color of bromine water is changed to yellow from colorless (oxidation process). | 0 | Theoretical and Fundamental Chemistry |
There are three major approaches to single-cell proteomics: antibody based methods, fluorescent protein based methods, and mass-spectroscopy based methods. | 1 | Applied and Interdisciplinary Chemistry |
Dicloxacillin is commercially available as the sodium salt, dicloxacillin sodium, in capsules and as a powder for reconstitution. | 0 | Theoretical and Fundamental Chemistry |
Hypersensitive sites are found on every active gene, and many of these genes often have more than one hypersensitive site. Most often, hypersensitive sites are found only in chromatin of cells in which the associated gene is being expressed, and do not occur when the gene is inactive.
In DNA being transcribed, 5'hypersensitive sites appear before transcription begins, and the DNA sequences within the hypersensitive sites are required for gene expression. Note: hypersensitive sites precede active promoters.
Hypersensitive sites are generated as a result of the binding of transcription factors that displace histone octamers.
They can also be located by indirect end labelling. A fragment of DNA is cut once at the hypersensitive site with DNase and at another site with a restriction enzyme. The distance from the known restriction site to the DNase cut is then measured to give the location. | 1 | Applied and Interdisciplinary Chemistry |
Piping or tubing is usually inserted into fittings to make connections. Connectors are assigned a gender, abbreviated M or F. An example of this is a "-inch female adapter NPT", which would have a corresponding male connection of the same size and thread standard (in this case also NPT). | 1 | Applied and Interdisciplinary Chemistry |
* Cooper M. B., “Naturally Occurring Radioactive Material (NORM) in Australian Industries”, EnviroRad report ERS-006 prepared for the Australian Radiation Health and Safety Advisory Council (2005).
* Agrawal, K. K. Sahu, B. D. Pandey, "Solid waste management in non-ferrous industries in India", Resources, Conservation and Recycling 42 (2004), 99–120.
* Jongyeong Hyuna, Shigehisa Endoha, Kaoru Masudaa, Heeyoung Shinb, Hitoshi Ohyaa, "Reduction of chlorine in bauxite residue by fine particle separation", Int. J. Miner. Process., 76, 1–2, (2005), 13–20.
* Claudia Brunori, Carlo Cremisini, Paolo Massanisso, Valentina Pinto, Leonardo Torricelli, "Reuse of a treated red mud bauxite waste: studies on environmental compatibility", Journal of Hazardous Materials, 117(1), (2005), 55–63.
* Genc¸-Fuhrman H., TjellJ. C., McConchie D., "Increasing the arsenate adsorption capacity of neutralized red mud (Bauxsol™)", J. Colloid Interface Sci. 271 (2004) 313–320.
* Genc¸-Fuhrman H., Tjell J. C., McConchie D., Schuiling O., "Adsorption of arsenate from water using neutralized red mud", J. Colloid Interface Sci. 264 (2003) 327–334. | 1 | Applied and Interdisciplinary Chemistry |
In mammals, CPSF is a protein complex, consisting of six subunits: CPSF-160 (CPSF1), CPSF-100 (CPSF2), CPSF-73 (CPSF3), and CPSF-30 (CPSF4) kDa subunits, WDR33 and Fip1 (FIP1L1).
The subunits form two components: mammalian polyadenylation specificity factors (mPSF) and mammalian cleavage factor (mCF). The mPSF is made up of CPSF-160, WDR33, CPSF-30, and Fip1. It is necessary for PAS recognition and polyadenylation. The mCF is made up of CPSF-73, CPSF-100, and symplekin. It catalyzes the cleavage reaction by recognizing the histone mRNA 3' processing site.
CPSF-73 is a zinc-dependent hydrolase which cleaves the mRNA precursor between a CA dinucleotide just downstream the polyadenylation signal sequence AAUAAA.
CPSF-100 contributes to the endonuclease activity of CPSF-73.
CPSF-160 (160 kDa) is the largest subunit of CPSF and directly binds to the AAUAAA polyadenylation signal. 160 kDa has three β-propeller domains and a C-terminal domain.
CPSF-30 (30 kDa) has five Cys-Cys-Cys-His (CCCH) zinc-finger motifs near the N terminus and a CCCH zinc knuckle at the C terminus. Two isoforms of CPSF-30 exist and can be found in CPSF complexes. The RNA binding activity of CPSF-30 is mediated by its zinc-fingers 2 and 3. WD repeat domain 33 (146 kDa) has a WD40 domain near the N terminus. The WD40 domain interacts with RNA. WDR33 and CPSF-30 recognize the polyadenylation signal (PAS) in pre-mRNA, which aids in defining the position of RNA cleavage. CPSF-30 recognizes the AU-rich hexamer region by a cooperative, metal-dependent binding mechanism.
Although CPSF-160 is the largest subunit of CPSF, a study conducted by Schönemann et al., debate that WDR33 is responsible for recognizing the PAS and not CPSF-160 as previously believed. The study concluded that the reason that CPSF-160 was believed to be responsible for recognizing the PAS was due to the fact that the WDR33 subunit had not been discovered at the time of the claim.
Fip1 binds to U-rich RNAs by its arginine-rich C-terminus. It binds to RNA sequences upstream of the AAUAAA hexamer region in vitro. Fip1 and CPSF-160 recruit poly(A) polymerase (PAP) to the 3' processing site. PAP is stimulated by Poly(A) binding protein nuclear one to add the poly(A) tail, a non-templated adenosine residues, at the cleavage site.
Only CPSF-160, CPSF-30, Fip1, and WDR33 are necessary and sufficient to form an active CPSF subcomplex in AAUAAA-dependent polyadenylation. CPSF-73 and CPSF-100 are disposable.
CPSF recruits proteins to the 3' region. Identified proteins that are coordinated by CPSF activity include: cleavage stimulatory factor and the two poorly understood cleavage factors. The binding of the polynucleotide adenylyltransferase responsible for actually synthesizing the tail is a necessary prerequisite for cleavage, thus ensuring that cleavage and polyadenylation are tightly coupled processes. | 1 | Applied and Interdisciplinary Chemistry |
eRNAs are transcribed from DNA sequences upstream and downstream of extragenic enhancer regions. Previously, several model enhancers have demonstrated the capability to directly recruit RNA Pol II and general transcription factors and form the pre-initiation complex (PIC) prior to the transcription start site at the promoter of genes. In certain cell types, activated enhancers have demonstrated the ability to both recruit RNA Pol II and also provide a template for active transcription of their local sequences.
Depending on the directionality of transcription, enhancer regions generate two different types of non-coding transcripts, 1D-eRNAs and 2D-eRNAs. The nature of the pre-initiation complex and specific transcription factors recruited to the enhancer may control the type of eRNAs generated. After transcription, the majority of eRNAs remain in the nucleus. In general, eRNAs are very unstable and actively degraded by the nuclear exosome. Not all enhancers are transcribed, with non-transcribed enhancers greatly outnumbering the transcribed ones in the order of magnitude of dozens of thousands in every given cell type. | 1 | Applied and Interdisciplinary Chemistry |
Besides the ex vivo approach by the City of Hope National Medical Center discussed above, the Center for Infection and Immunity Amsterdam (CINIMA), the University of Amsterdam, the Netherlands, is extensively researching the composition of multi-cassette DNA constructs to tackle HIV. | 1 | Applied and Interdisciplinary Chemistry |
53 stable nuclides have an even number of protons and an odd number of neutrons. They are a minority in comparison to the even-even isotopes, which are about 3 times as numerous. Among the 41 even-Z elements that have a stable nuclide, only two elements (argon and cerium) have no even-odd stable nuclides. One element (tin) has three. There are 24 elements that have one even-odd nuclide and 13 that have two odd-even nuclides. Of 35 primordial radionuclides there exist four even-odd nuclides (see table at right), including the fissile . Because of their odd neutron numbers, the even-odd nuclides tend to have large neutron capture cross-sections, due to the energy that results from neutron-pairing effects. These stable even-proton odd-neutron nuclides tend to be uncommon by abundance in nature, generally because, to form and enter into primordial abundance, they must have escaped capturing neutrons to form yet other stable even-even isotopes, during both the s-process and r-process of neutron capture, during nucleosynthesis in stars. For this reason, only and are the most naturally abundant isotopes of their element.
48 stable odd-proton-even-neutron nuclides, stabilized by their paired neutrons, form most of the stable isotopes of the odd-numbered elements; the very few odd-proton-odd-neutron nuclides comprise the others. There are 41 odd-numbered elements with Z = 1 through 81, of which 39 have stable isotopes (technetium () and promethium () have no stable isotopes). Of these 39 odd Z elements, 30 elements (including hydrogen-1 where 0 neutrons is even) have one stable odd-even isotope, and nine elements:
chlorine (),
potassium (),
copper (),
gallium (),
bromine (),
silver (),
antimony (),
iridium (), and
thallium (), have two odd-even stable isotopes each. This makes a total stable odd-even isotopes.
There are also five primordial long-lived radioactive odd-even isotopes, , , , , and . The last two were only recently found to decay, with half-lives greater than 10 years. | 0 | Theoretical and Fundamental Chemistry |
dPCR enables the absolute and reproducible quantification of target nucleic acids at single-molecule resolution. Unlike analogue quantitative PCR (qPCR), however, absolute quantification with dPCR does not require a standard curve. dPCR also has a greater tolerance for inhibitor substances and PCR assays that amplify inefficiently as compared to qPCR.
dPCR can quantify, for example, the presence of specific sequences from contaminating genetically modified organisms in foodstuffs, viral load in the blood, PBMCs, serum samples, chorionic villi tissues, biomarkers of neurodegenerative disease in cerebral spinal fluid, and fecal contamination in drinking water. | 1 | Applied and Interdisciplinary Chemistry |
A Latimer diagram of a chemical element is a summary of the standard electrode potential data of that element. This type of diagram is named after Wendell Mitchell Latimer, an American chemist. | 0 | Theoretical and Fundamental Chemistry |
In n dimensions, an affine space group, or Bieberbach group, is a discrete subgroup of isometries of n-dimensional Euclidean space with a compact fundamental domain. proved that the subgroup of translations of any such group contains n linearly independent translations, and is a free abelian subgroup of finite index, and is also the unique maximal normal abelian subgroup. He also showed that in any dimension n there are only a finite number of possibilities for the isomorphism class of the underlying group of a space group, and moreover the action of the group on Euclidean space is unique up to conjugation by affine transformations. This answers part of Hilberts eighteenth problem. showed that conversely any group that is the extension of Z by a finite group acting faithfully is an affine space group. Combining these results shows that classifying space groups in n dimensions up to conjugation by affine transformations is essentially the same as classifying isomorphism classes for groups that are extensions of Z by a finite group acting faithfully.
It is essential in Bieberbach's theorems to assume that the group acts as isometries; the theorems do not generalize to discrete cocompact groups of affine transformations of Euclidean space. A counter-example is given by the 3-dimensional Heisenberg group of the integers acting by translations on the Heisenberg group of the reals, identified with 3-dimensional Euclidean space. This is a discrete cocompact group of affine transformations of space, but does not contain a subgroup Z. | 0 | Theoretical and Fundamental Chemistry |
The atomization of molten materials produces a large amount of dust and fumes made up of very fine particles (ca. 80–95% of the particles by number <100 nm). Proper extraction facilities are vital not only for personal safety, but to minimize entrapment of re-frozen particles in the sprayed coatings. The use of respirators fitted with suitable filters is strongly recommended where equipment cannot be isolated.
Certain materials offer specific known hazards:. The Toxicity from thermal spray aerosols is dependent on the metal profile of the thermal spray.
#Finely divided metal particles are potentially pyrophoric and harmful when accumulated in the body.
#Certain materials e.g. aluminum, zinc and other base metals may react with water to evolve hydrogen. This is potentially explosive and special precautions are necessary in fume extraction equipment.
#Fumes of certain materials, notably zinc and copper alloys, have a disagreeable odour and may cause a fever-type reaction in certain individuals (known as metal fume fever). This may occur some time after spraying and usually subsides rapidly. If it does not, medical advice must be sought.
#Fumes of reactive compounds can dissociate and create harmful gasses. Respirators should be worn in these areas and gas meters should be used to monitor the air before respirators are removed. | 1 | Applied and Interdisciplinary Chemistry |
It is conventional if it can be explained by the BCS theory or its derivatives, or unconventional, otherwise. Alternatively, a superconductor is called unconventional if the superconducting order parameter transforms according to a non-trivial irreducible representation of the point group or space group of the system. | 0 | Theoretical and Fundamental Chemistry |
Venom in medicine is the medicinal use of venoms for therapeutic benefit in treating diseases.
Venom is any poisonous compound secreted by an animal intended to harm or disable another. When an organism produces a venom, its final form may contain hundreds of different bioactive elements that interact with each other inevitably producing its toxic effects. This mixture of ingredients includes various proteins, peptides, and non-peptidic small molecules. The active components of these venoms are isolated, purified, and screened in assays. These may be either phenotypic assays to identify component that may have desirable therapeutic properties (forward pharmacology) or target directed assays to identify their biological target and mechanism of action (reverse pharmacology). | 1 | Applied and Interdisciplinary Chemistry |
A Web of Science search for the term multiferroic yields the year 2000 paper "Why are there so few magnetic ferroelectrics?" from N. A. Spaldin (then Hill) as the earliest result. This work explained the origin of the contraindication between magnetism and ferroelectricity and proposed practical routes to circumvent it, and is widely credited with starting the modern explosion of interest in multiferroic materials. The availability of practical routes to creating multiferroic materials from 2000 stimulated intense activity. Particularly key early works were the discovery of large ferroelectric polarization in epitaxially grown thin films of magnetic BiFeO, the observation that the non-collinear magnetic ordering in orthorhombic TbMnO and TbMnO causes ferroelectricity, and the identification of unusual improper ferroelectricity that is compatible with the coexistence of magnetism in hexagonal manganite YMnO. The graph to the right shows in red the number of papers on multiferroics from a Web of Science search until 2008; the exponential increase continues today. | 0 | Theoretical and Fundamental Chemistry |
For reversible reactions that do not occur in aqueous buffers, the pre-equilibrated DCC approach can be used. The DCL was initially generated (or pre-equilibrated) in organic solvent, and then diluted into aqueous buffer containing the protein target for selection. Organic based reversible reactions, including Diels-Alder and alkene cross metathesis reactions, have been proposed or applied to protein-directed DCC using this method. | 1 | Applied and Interdisciplinary Chemistry |
Mass spectrometry methods are generally used for analysis of environmental contaminant monitoring, particularly in aquatic environments (though they can be applied in non-aquatic environments, such as with screening pesticides on plant matter), paired with chromatography for separation. For target screening, this means using gas chromatography–mass spectrometry (GC-MS) or liquid chromatography–mass spectrometry (LC-MS) methods "that use single reaction monitoring (SIM) or selected reaction monitoring (SRM) modes." However, for suspect and non-target screening, these methods are inadequate due to recording only a limited number of compounds and insufficient useful information can be determined about unknown compounds, particularly given the dearth of LC-MS comparison libraries. For those non-targeted screening approaches, high-resolution mass spectrometry and high mass accuracy chromatography techniques are required. Combinations of quadrupole, time-of-flight, ion trap, and orbitrap mass spectrometry analyzers have emerged, along with high-performance liquid chromatography (and ultra-high-performance liquid chromatography), to more rapidly and effectively tackle suspect and non-target screening. | 0 | Theoretical and Fundamental Chemistry |
The Lemieux–Johnson or Malaprade–Lemieux–Johnson oxidation is a chemical reaction in which an olefin undergoes oxidative cleavage to form two aldehyde or ketone units. The reaction is named after its inventors, Raymond Urgel Lemieux and William Summer Johnson, who published it in 1956.
The reaction proceeds in a two step manner, beginning with dihydroxylation of the alkene by osmium tetroxide, followed by a Malaprade reaction to cleave the diol using periodate. Excess periodate is used to regenerate the osmium tetroxide, allowing it to be used in catalytic amounts. The Lemieux–Johnson reaction ceases at the aldehyde stage of oxidation and therefore produces the same results as ozonolysis.
The classical Lemieux–Johnson oxidation often generates many side products, resulting in low reaction yields; however the addition of non-nucleophilic bases, such as 2,6-lutidine, can improve on this.
OsO may be replaced with a number of other Osmium compounds. Periodate may also be replaced with other oxidising agents, such as oxone. | 0 | Theoretical and Fundamental Chemistry |
Screening falls under two general categories: dry screening, and wet screening. From these categories, screening separates a flow of material into grades, these grades are then either further processed to an intermediary product or a finished product. Additionally, the machines can be categorized into a moving screen and static screen machines, as well as by whether the screens are horizontal or inclined. | 1 | Applied and Interdisciplinary Chemistry |
CheB, when activated by CheA, acts as a methylesterase, removing methyl groups from glutamate residues on the cytosolic side of the receptor; it works antagonistically with CheR, a methyltransferase, which adds methyl residues to the same glutamate residues. If the level of an attractant remains high, the level of phosphorylation of CheA (and, therefore, CheY and CheB) will remain low, the cell will swim smoothly, and the level of methylation of the MCPs will increase (because CheB-P is not present to demethylate). The MCPs no longer respond to the attractant when they are fully methylated; therefore, even though the level of attractant might remain high, the level of CheA-P (and CheB-P) increases and the cell begins to tumble. The MCPs can be demethylated by CheB-P, and, when this happens, the receptors can once again respond to attractants. The situation is the opposite with regard to repellents: fully methylated MCPs respond best to repellents, while least-methylated MCPs respond worst to repellents. This regulation allows the bacterium to remember chemical concentrations from the recent past, a few seconds, and compare them to those it is currently experiencing, thus know whether it is traveling up or down a gradient.
that bacteria have to chemical gradients, other mechanisms are involved in increasing the absolute value of the sensitivity on a given background. Well-established examples are the ultra-sensitive response of the motor to the CheY-P signal, and the clustering of chemoreceptors. | 1 | Applied and Interdisciplinary Chemistry |
Benson and Buss originated the BGIT in a 1958 article. Within this manuscript, Benson and Buss proposed four approximations:
# A limiting law for additivity rules.
# Zero-order approximation. Additivity of atomic properties.
# First-order approximation. Additivity of bond properties.
# Second-order approximation. Additivity of group properties.
These approximations account for the atomic, bond, and group contributions to heat capacity (C), enthalpy (ΔH°), and entropy (ΔS°). The most important of these approximations to the group-increment theory is the second-order approximation, because this approximation "leads to the direct method of writing the properties of a compound as the sum of the properties of its group".
The second-order approximation accounts for two molecular atoms or structural elements that are within relative proximity to one another (approximately 3–5 ångstroms as proposed in the article). By using a series of disproportionation reactions of symmetrical and asymmetrical framework, Benson and Buss concluded that neighboring atoms within the disproportionation reaction under study are not affected by the change.
; Symmetrical
; Asymmetrical
In the symmetrical reaction the cleavage between the CH in both reactants leads to one product formation. that the neighboring carbons are not changed as the rearrangement occurs. In the asymmetrical reaction the hydroxyl–methyl bond is cleaved and rearranged on the ethyl moiety of the methoxyethane. The methoxy and hydroxyl rearrangement display clear evidence that the neighboring groups are not affected in the disproportionation reaction.
The "disproportionation" reactions that Benson and Buss refer to are termed loosely as "radical disproportionation" reactions. From this they termed a "group" as a polyvalent atom connected together with its ligands. However, they noted that under all approximations ringed systems and unsaturated centers do not follow additivity rules due to their preservation under disproportionation reactions. A ring must be broken at more than one site to actually undergo a disproportionation reaction. This holds true with double and triple bonds, as they must break multiple times to break their structure. They concluded that these atoms must be considered as distinct entities. Hence we see C and C groups, which take into account these groups as being individual entities. Furthermore, this leaves error for ring strain, as we will see in its limitations.
From this Benson and Buss concluded that the ΔH of any saturated hydrocarbon can be precisely calculated due to the only two groups being a methylene [C−(C)(H)] and the terminating methyl group [C−(C)(H)]. Benson later began to compile actual functional groups from the second-order approximation. Ansylyn and Dougherty explained in simple terms how the group increments, or Benson increments, are derived from experimental calculations. By calculating the ΔΔH between extended saturated alkyl chains (which is just the difference between two ΔH values), as shown in the table, one can approximate the value of the C−(C)(H) group by averaging the ΔΔH values. Once this is determined, all one needs to do is take the total value of ΔH, subtract the ΔH caused by the C−(C)(H) group(s), and then divide that number by two (due to two C−(C)(H) groups), obtaining the value of the C−(C)(H) group. From the knowledge of these two groups, Benson moved forward obtain and list functional groups derived from countless numbers of experimentation from many sources, some of which are displayed below. | 0 | Theoretical and Fundamental Chemistry |
The tail addition step in this synthesis (Scheme 6) was identical to that in the Nicolaou tail addition and was based on Oijma chemistry. The A ring was functionalized with a hydroxyl group through pyridinium chlorochromate oxidation of α-acylketone 49 to form ketone 50. Subsequent reduction using sodium borohydride produced alcohol 51 . Reaction of this alcohol with the Ojima lactam 52 and a concluding silyl deprotection step at two triethyl silyl positions in compound 53 gave Taxol. | 0 | Theoretical and Fundamental Chemistry |
Acrylonitrile butadiene styrene (ABS) is used for the conveyance of potable water, slurries and chemicals. Most commonly used for DWV (drain-waste-vent) applications. It has a wide temperature range, from -40 °C to +60 °C.
ABS is a thermoplastic material and was originally developed in the early 1950s for use in oil fields and the chemical industry. The variability of the material and its relative cost effectiveness has made it a popular engineering plastic. It can be tailored to a range of applications by modifying the ratio of the individual chemical components.
They are used mainly in industrial applications where high impact strength and rigidity are essential.
This material is also used in non-pressure piping systems for soil and waste. | 1 | Applied and Interdisciplinary Chemistry |
The law of gravitation is derived from classical statistical mechanics applied to the holographic principle, that states that the description of a volume of space can be thought of as bits of binary information, encoded on a boundary to that region, a closed surface of area . The information is evenly distributed on the surface with each bit requiring an area equal to , the so-called Planck area, from which can thus be computed:
where is the Planck length. The Planck length is defined as:
where is the universal gravitational constant, is the speed of light, and is the reduced Planck constant. When substituted in the equation for we find:
The statistical equipartition theorem defines the temperature of a system with degrees of freedom in terms of its energy such that:
where is the Boltzmann constant. This is the equivalent energy for a mass according to:
The effective temperature experienced due to a uniform acceleration in a vacuum field according to the Unruh effect is:
where is that acceleration, which for a mass would be attributed to a force according to Newton's second law of motion:
Taking the holographic screen to be a sphere of radius , the surface area would be given by:
From algebraic substitution of these into the above relations, one derives Newton's law of universal gravitation:
Note that this derivation assumes that the number of the binary bits of information is equal to the number of the degrees of freedom. | 0 | Theoretical and Fundamental Chemistry |
Two bands may overlap with the head of one on top of another band or close to each other. This may make a stepped appearance. The two band heads close to each other are called a double head. | 0 | Theoretical and Fundamental Chemistry |
and P benzyl ring and was shown to inhibit the hydrolysis of angiotensin I and bradykinin via the C-domain. The synthesis of keto-ACE analogues with Trp or Phe at the P’ position led to a marked increase in C-domain selectivity, but the introduction of an aliphatic P group conferred N-domain selectivity. Inhibitory potency may further be enhanced by the incorporation of hydrophobic substituent, such as phenyl group at the P’ position. P’ substituents with S-stereochemistry have also been shown to possess greater inhibitory potency than their R-counterparts.
’ and P’ substituent may be cyclized to form a lactam, where there is a correlation between the inhibitory potency and the ring size. In 2001 it was postulated that a substitution α to nitrogen and making of 3-methyl-substituted analog of A58365A, a pyridone acid isolated from the fermentation broth of the bacterium Streptomyces chromofuscus with ACE inhibitory activity, might influence the level of biological activity by steric or hydrophobic effect, and/or by preventing reactions at C3. It was also noticed during the synthetic work on A58365A that potential precursors were sensitive to oxidation of the five-membered ring and so the 3-methyl analogue might be more stable in this respect. | 1 | Applied and Interdisciplinary Chemistry |
DPP-4 inhibitors usually have an electrophilic group that can interact with the hydroxyl of the catalytic serine in the active binding site (Figure 3). Frequently that group is a nitrile group but can also be boronic acid or diphenyl phosphonate. This electrophilic group can bind to the imidate complex with covalent bonds and slow, tight-binding kinetics but this group is also responsible for stability issues due to reactions with the free amino group of the P2-amino acid. Therefore, inhibitors without the electrophilic group have also been developed, but these molecules have shown toxicity due to affinity to other dipeptidyl peptidases, e.g. DPP-2, DPP-8 and DPP-9.
DPP-4 inhibitors span diverse structural types. In 2007 few of the most potent compounds contain a proline mimetic cyanopyrrolidine P1 group. This group enhances the potency, probably due to a transient covalent trapping of the nitrile group by the active site Ser630 hydroxyl, leading to delayed dissociation and slow tight binding of certain inhibitors. When these potency enhancements were achieved, some chemical stability issues were noted and more advanced molecules had to be made. To avoid these stability issues, the possibility to exclude the nitrile group was investigated. Amino acids with aryl or polar side chains did not show appreciable DPP-4 inhibition and in fact, all compounds without the nitrile group in this research suffered a 20 to 50-fold loss of potency corresponding to the compounds containing the nitrile group. | 1 | Applied and Interdisciplinary Chemistry |
Rhenium and osmium are siderophile elements which are present at very low abundances in the crust. Rhenium undergoes radioactive decay to produce osmium. The ratio of non-radiogenic osmium to radiogenic osmium throughout time varies.
Rhenium prefers to enter sulfides more readily than osmium. Hence, during melting of the mantle, rhenium is stripped out, and prevents the osmium–osmium ratio from changing appreciably. This locks in an initial osmium ratio of the sample at the time of the melting event. Osmium–osmium initial ratios are used to determine the source characteristic and age of mantle melting events. | 0 | Theoretical and Fundamental Chemistry |
Rosenkranz was a world-class bridge player and one of the most successful in Mexico. He won 12 NABC-level events at thrice-annual North American Bridge Championships meets, including all four major titles: the Grand Nationals, Reisinger, Spingold and Vanderbilt. In world championship teams competition, he represented Mexico in the quadrennial World Team Olympiad three times from 1972 to 1996 and the United States in the 1983 Bermuda Bowl. In addition, he has made significant contributions to bidding theory. He created the Romex bidding system, an extension of Standard American with many gadgets. He invented the Rosenkranz double and Rosenkranz redouble, and wrote more than a dozen books on bridge. | 0 | Theoretical and Fundamental Chemistry |
Mitochondria are commonly referred to as the cells "powerhouses" because of their capacity to effectively produce ATP which is essential to maintain cellular homeostasis and metabolism. Moreover, researchers have gained a better knowledge of mitochondrias significance in cell biology because of the discovery of cell signaling pathways by mitochondria which are crucial platforms for cell function regulation such as apoptosis. Its physiological adaptability is strongly linked to the cell mitochondrial channels ongoing reconfiguration through a range of mechanisms known as mitochondrial membrane dynamics, which include endomembrane fusion and fragmentation (separation) as well as ultrastructural membrane remodeling. As a result, mitochondrial dynamics regulate and frequently choreograph not only metabolic but also complicated cell signaling processes such as cell pluripotent stem cells, proliferation, maturation, aging, and mortality. Mutually, post-translational alterations of mitochondrial apparatus and the development of transmembrane contact sites among mitochondria and other structures, which both have the potential to link signals from diverse routes that affect mitochondrial membrane dynamics substantially, Mitochondria are wrapped by two membranes: an inner mitochondrial membrane (IMM) and an outer mitochondrial membrane (OMM), each with a distinctive function and structure, which parallels their dual role as cellular powerhouses and signaling organelles. The inner mitochondrial membrane divides the mitochondrial lumen into two parts: the inner border membrane, which runs parallel to the OMM, and the cristae, which are deeply twisted, multinucleated invaginations that give room for surface area enlargement and house the mitochondrial respiration apparatus. The outer mitochondrial membrane, on the other hand, is soft and permeable. It, therefore, acts as a foundation for cell signaling pathways to congregate, be deciphered, and be transported into mitochondria. Furthermore, the OMM connects to other cellular organelles, such as the endoplasmic reticulum (ER), lysosomes, endosomes, and the plasma membrane. Mitochondria play a wide range of roles in cell biology, which is reflected in their morphological diversity. Ever since the beginning of the mitochondrial study, it has been well documented that mitochondria can have a variety of forms, with both their general and ultra-structural morphology varying greatly among cells, during the cell cycle, and in response to metabolic or cellular cues. Mitochondria can exist as independent organelles or as part of larger systems; they can also be unequally distributed in the cytosol through regulated mitochondrial transport and placement to meet the cells localized energy requirements. Mitochondrial dynamics refers to the adaptive and variable aspect of mitochondria, including their shape and subcellular distribution. | 1 | Applied and Interdisciplinary Chemistry |
Next-generation sequencing technologies such as pyrosequencing sequence less than 250 bases in a read which limits their ability to sequence whole genomes. However, their ability to generate results in real-time and their potential to be massively scaled up makes them a viable option for sequencing small regions to perform SNP genotyping. Compared to other SNP genotyping methods, sequencing is in particular, suited to identifying multiple SNPs in a small region, such as the highly polymorphic Major Histocompatibility Complex region of the genome. | 1 | Applied and Interdisciplinary Chemistry |
When the surface plasmon wave interacts with a local particle or irregularity, such as a rough surface, part of the energy can be re-emitted as light. This emitted light can be detected behind the metal film from various directions. | 0 | Theoretical and Fundamental Chemistry |
Commonly metal-imido complexes are generated from metal oxo complexes. They arise by condensation of amines and metal oxides and metal halides:
:LMO + HNR → LMNR + HO
This approach is illustrated by the conversion of MoOCl to the diimido derivative MoCl(NAr)(dimethoxyethane), precursors to the Schrock carbenes of the type Mo(OR)(NAr)(CH-t-Bu).
:LMCl + 3 HNR → LMNR + 2 RNHCl
Aryl isocyanates react with metal oxides concomitant with decarboxylation:
:LMO + O=C=NR → LMNR + CO | 0 | Theoretical and Fundamental Chemistry |
The insertion of ethylene and propylene into titanium alkyls is the cornerstone of Ziegler-Natta catalysis, the commercial route of polyethylene and polypropylene. This technology mainly involves heterogeneous catalysts, but it is widely assumed that the principles and observations on homogeneous systems are applicable to the solid-state versions. Related technologies include the Shell Higher Olefin Process which produces detergent precursors. the olefin can be coordinated to the metal before insertion. Depending on the ligand density of the metal, ligand dissociation may be necessary to provide a coordination site for the olefin. | 0 | Theoretical and Fundamental Chemistry |
Protein adsorption is critical for many industrial and biomedical applications. Accurate prediction of protein adsorption will enable progress to be made in these areas. | 1 | Applied and Interdisciplinary Chemistry |
Before the POCIS is constructed, all the hardware as well as the sorbents and membrane must be thoroughly cleaned so that any potential interference is removed. During and after sampling the only cleaning necessary is the removal of any sediment that has adhered to the surface of the sampler. After assembly, and prior to deployment, the samplers are stored in frozen airtight containers to avoid any contamination. The samplers should be kept in airtight containers during transportation both to and from the sampling site so that airborne contaminants do not contaminate the sampler. It is ideal to keep the samplers cold while transporting them in order to preserve the integrity of the samples.
After the POCIS is retrieved from the field, the membrane is gently cleaned to reduce the possibility of any contamination to the sorbent. The sorbent is placed into a chromatography column so that the chemicals that samples can be recovered using an organic solvent. The solvent used is specifically chosen based on the type of sorbent and chemicals sampled. The sample can go through further processing such as cleanup or fractionation depending on the desired use of the sample. | 0 | Theoretical and Fundamental Chemistry |
In 1866, Nilson became an associate professor of chemistry at Uppsala, with the responsibilities of chief assistant and demonstrator of chemistry for Svanberg's laboratory. He was a calm and patient teacher, relying more on demonstrations than on lectures. He insisted that after the work of the day was completed, it was to be left behind, and not discussed during leisure. His earliest papers mainly concerned sulfides, arsenical sulfosalt minerals, and selenous acid, extending the work of Berzelius. | 1 | Applied and Interdisciplinary Chemistry |
PCBs are toxic to bacterial communities above 1000 mg/kg. However, if the concentration is too low (lower than 50 mg/kg), the degradation slows down significantly, for there is not enough material to stimulate the expression of required genes and support the growth of competent microorganisms. PCBs includes various different compounds with slightly different structures. Those slight differences make big differences in metabolic rate. Generally speaking, the more chlorines in a PCB molecule, the harder for it to be degraded. In particular, microorganisms cannot degrade di- and tetra-ortho substituted well. It is possible that those structures prevent enzymes from accessing reaction sites. | 1 | Applied and Interdisciplinary Chemistry |
Born in Edinburgh, the third son of Juliana Stevenson and surgeon and botanist John Hope, he lived at High School Yards on the south side of the old town. He was educated next door to his house at the High School, the University of Edinburgh (MD 1787) and the University of Paris. At the university he was a student of Prof Joseph Black.
Hope was a nephew of the physician Alexander Stevenson FRSE. | 1 | Applied and Interdisciplinary Chemistry |
Chime was used by a wide range of biochemistry web sites for the visualization of macromolecules, many of which were linked to the World Index of Molecular Visualization Resources MolVisIndex.Org. Chime was also used until 2006 at the Protein Data Bank (PDB) to examine structures stored there.
Although available in 1996 in both Windows 95 and classic Mac OS versions for both Netscape and Internet Explorer browsers, development of Chime did not follow the move to Mac OS X for the Mac and support for Windows-based browsers other than Internet Explorer was limited (although it works well in Mozilla Firefox). One significant feature added in 1997 was the ability to display spectroscopic data in the form of the IUPAC JCAMP-DX protocols. Apart from this, most subsequent updates were for the installation package to follow the development of Windows and Internet Explorer. Accelrys announced in 2012 that Chime was no longer supported and would remain available for download until the end of 2012. Chime was part of the ISIS product line acquired by Symyx Technologies from scientific publisher Elsevier in October 2007. Now Chime is owned by Dassault Systemes BIOVIA (formerly Accelrys), and has been merged into Discovery Studio, but no longer exists as a free browser plugin.
Chime largely has been superseded by Jmol, a non-proprietary open-source Java molecular visualization application and JavaScript applet that has maintained most Chime command compatibility while adding numerous features. | 0 | Theoretical and Fundamental Chemistry |
Atom optics (or atomic optics) "refers to techniques to manipulate the trajectories and exploit the wave properties of neutral atoms". Typical experiments employ beams of cold, slowly moving neutral atoms, as a special case of a particle beam. Like an optical beam, the atomic beam may exhibit diffraction and interference, and can be focused with a Fresnel zone plate or a concave atomic mirror.
For comprehensive overviews of atom optics, see the 1994 review by Adams, Sigel, and Mlynek or the 2009 review by Cronin, Jörg, and Pritchard. More bibliography about Atom Optics can be found in the 2017 Resource Letter in the American Journal of Physics. For quantum atom optics see the 2018 review by Pezzè et al. | 0 | Theoretical and Fundamental Chemistry |
AC-IV was first reported in the bacterium Aeromonas hydrophila, and the structure of the AC-IV from Yersinia pestis has been reported. These are the smallest of the AC enzyme classes; the AC-IV (CyaB) from Yersinia is a dimer of 19 kDa subunits with no known regulatory components (). AC-IV forms a superfamily with mammalian thiamine-triphosphatase called CYTH (CyaB, thiamine triphosphatase). | 1 | Applied and Interdisciplinary Chemistry |
Atomic spectroscopy was the first application of spectroscopy. Atomic absorption spectroscopy and atomic emission spectroscopy involve visible and ultraviolet light. These absorptions and emissions, often referred to as atomic spectral lines, are due to electronic transitions of outer shell electrons as they rise and fall from one electron orbit to another. Atoms also have distinct x-ray spectra that are attributable to the excitation of inner shell electrons to excited states.
Atoms of different elements have distinct spectra and therefore atomic spectroscopy allows for the identification and quantitation of a sample's elemental composition. After inventing the spectroscope, Robert Bunsen and Gustav Kirchhoff discovered new elements by observing their emission spectra. Atomic absorption lines are observed in the solar spectrum and referred to as Fraunhofer lines after their discoverer. A comprehensive explanation of the hydrogen spectrum was an early success of quantum mechanics and explained the Lamb shift observed in the hydrogen spectrum, which further led to the development of quantum electrodynamics.
Modern implementations of atomic spectroscopy for studying visible and ultraviolet transitions include flame emission spectroscopy, inductively coupled plasma atomic emission spectroscopy, glow discharge spectroscopy, microwave induced plasma spectroscopy, and spark or arc emission spectroscopy. Techniques for studying x-ray spectra include X-ray spectroscopy and X-ray fluorescence. | 0 | Theoretical and Fundamental Chemistry |
Karel František Wiesner (November 25, 1919 – November 28, 1986) was a Canadian chemist of Czech origin known for his contributions to the chemistry of natural products, notably aconitum alkaloids and digitalis glycosides. | 0 | Theoretical and Fundamental Chemistry |
A Mössbauer spectrograph was made of the dust that gathered on Opportunity's capture magnet. The results suggested that the magnetic component of the dust was titanomagnetite, rather than just plain magnetite, as was once thought. A small amount of olivine was also detected which was interpreted as indicating a long arid period on the planet. On the other hand, a small amount of hematite that was present meant that there may have been liquid water for a short time in the early history of the planet.
Because the Rock Abrasion Tool (RAT) found it easy to grind into the bedrocks, it is thought that the rocks are much softer than the rocks at Gusev crater. | 0 | Theoretical and Fundamental Chemistry |
The capping enzyme is part of the covalent nucleotidyl transferases superfamily, which also includes DNA ligases and RNA ligases. The enzymes of this superfamily share the following similarities:
* Conserved regions known as motifs I, II, III, IIIa, IV, V and VI, which are arranged in the same order and similar spacing
* A lysine containing motif KxDG (motif I)
* A covalent lysyl-NMP intermediate
The capping enzyme is composed of two domains, a nucleotidyl transferase (NTase) domain and a C-terminal oligonucleotide binding (OB) domain. The NTase domain, conserved in capping enzymes, DNA and RNA ligases, is made up 5 motifs, I, III, IIIa, IV and V. Motif I or KxDG is the active site where the covalent (lysyl)-N-GMP intermediate is formed. Both the NTase and OB domains undergo conformational changes that assist in the capping reaction.
Capping enzymes are found in the nucleus of eukaryotic cells. Depending on the organism, the capping enzyme is either a monofunctional or bifunctional polypeptide. The guanylyltransferases (Ceg1) of Saccharomyces cerevisiae is encoded by the CEG1 gene and is composed of 459 amino acids (53-kD). The RNA triphosphatase (Cet1) is a separate 549 amino acid polypeptide (80-kD), encoded by the CET1 gene. The human capping enzyme is an example of a bifunctional polypeptide, which has both triphosphatase (N-terminal) and guanylyltransferase (C-terminal) domains. The human mRNA guanylyltransferase domain of the capping enzyme is composed of seven helices and fifteen β strands that are grouped into three, five and seven strands, arranged as antiparallel β sheets. The enzyme structure has three sub-domains referred to hinge, base and lid. The GTP binding site is located between the hinge and base domain. The lid domain determines the conformation of the active site cleft, which consists of the GTP binding site, phosphoamide linking lysine and surrounding residues. The guanylyltransferase domain is linked to the triphosphatase domain via a 25 amino acid flexible loop structure. | 1 | Applied and Interdisciplinary Chemistry |
For free convection near a vertical wall, the Rayleigh number is defined as:
where:
*x is the characteristic length
*Ra is the Rayleigh number for characteristic length x
*g is acceleration due to gravity
*β is the thermal expansion coefficient (equals to 1/T, for ideal gases, where T is absolute temperature).
* is the kinematic viscosity
*α is the thermal diffusivity
*T is the surface temperature
*T is the quiescent temperature (fluid temperature far from the surface of the object)
*Gr is the Grashof number for characteristic length x
*Pr is the Prandtl number
In the above, the fluid properties Pr, ν, α and β are evaluated at the film temperature, which is defined as:
For a uniform wall heating flux, the modified Rayleigh number is defined as:
where:
*q″ is the uniform surface heat flux
*k is the thermal conductivity. | 1 | Applied and Interdisciplinary Chemistry |
PAR1, PAR3, and PAR4 are activated by thrombin. There are species-specific differences in thrombin receptor expression in platelets and other cell types, in which differences in thrombin concentrations may considerably affect platelet activation of distinct PARs. As seen in human platelets, PAR1 and PAR4 are the functional thrombin receptors, whereas PAR3 and PAR4 are functional thrombin receptors in mouse platelets
Thrombin receptors are also differentially expressed in cell types, e.g. PAR1 is expressed in fibroblasts, smooth muscle cells, sensory neurons and glial cells, whereas the other two are less clearly defined.
There are various roles depending on location of activation. Fibroblasts and smooth muscle cells induces growth factor and matrix production, migration and proliferation. Sensory neurons induces proliferation and release of neuroactive agents. | 1 | Applied and Interdisciplinary Chemistry |
The Hiyama coupling was developed to combat the issues associated with other organometallic reagents. The initial reactivity of organosilicon was not actually first reported by Hiyama, as Kumada reported a coupling reaction using organofluorosilicates shown below. Organosilanes were then discovered, by Hiyama, to have reactivity when activated by a fluoride source. This reactivity, when combined with a palladium salt, creates a carbon-carbon bond with an electrophillic carbon, like an organic halide. Compared to the inherent issues of well-used organometalics reagents, such as organomagnesium (Grignard reagents) and organocopper reagents, which are very reactive and are known to have low chemoselectivity, enough to destroy functional groups on both coupling partners, organosilicon compounds are inactive. Other organometallic reagents using metals such as zinc, tin, and boron, reduce the reactivity issue, but have other problems associated with each reagent. Organozinc reagents are moisture sensitive, organotin compounds are toxic, and organoboron reagents are not readily available, are expensive, and aren't often stable. Organosilanes are readily available compounds that, upon activation (much like organotin or organoboron compounds) from fluoride or a base, can react with organohalides to form C-C bonds in a chemo- and regioselective manner. The reaction first reported was used to couple easily made (and activated) organosilicon nucleophiles and organohalides (electrophiles) in the presence of a palladium catalyst. Since this discovery, work has been done by various groups to expand the scope of this reaction and to "fix" the issues with this first coupling, such as the need for fluoride activation of the organosilane. | 0 | Theoretical and Fundamental Chemistry |
Organometallic compounds undergo several important reactions:
* associative and dissociative substitution
* oxidative addition and reductive elimination
* transmetalation
* migratory insertion
* β-hydride elimination
* electron transfer
* carbon-hydrogen bond activation
* carbometalation
* hydrometalation
* cyclometalation
* nucleophilic abstraction
The synthesis of many organic molecules are facilitated by organometallic complexes. Sigma-bond metathesis is a synthetic method for forming new carbon-carbon sigma bonds. Sigma-bond metathesis is typically used with early transition-metal complexes that are in their highest oxidation state. Using transition-metals that are in their highest oxidation state prevents other reactions from occurring, such as oxidative addition. In addition to sigma-bond metathesis, olefin metathesis is used to synthesize various carbon-carbon pi bonds. Neither sigma-bond metathesis or olefin metathesis change the oxidation state of the metal. Many other methods are used to form new carbon-carbon bonds, including beta-hydride elimination and insertion reactions. | 0 | Theoretical and Fundamental Chemistry |
Overdose of levonorgestrel as an emergency contraceptive has not been described. Nausea and vomiting might be expected. | 0 | Theoretical and Fundamental Chemistry |
Tanmay A. M. Bharat is a programme leader in the Structural Studies Division of the MRC Laboratory of Molecular Biology. He and his group use electron tomography, together with several structural and cell biology methods to study the cell surfaces of bacteria and archaea. His work has increased the understanding of how surface molecules help in the formation of multicellular communities of prokaryotes, examples of which include biofilms and microbiomes. He has been awarded several prizes and fellowships for his work. | 1 | Applied and Interdisciplinary Chemistry |
3D EBSD combines EBSD with serial sectioning methods to create a three-dimensional map of a material's crystallographic structure. The technique involves serially sectioning a sample into thin slices, and then using EBSD to map the crystallographic orientation of each slice. The resulting orientation maps are then combined to generate a 3D map of the crystallographic structure of the material. The serial sectioning can be performed using a variety of methods, including mechanical polishing, focused ion beam (FIB) milling, or ultramicrotomy. The choice of sectioning method depends on the size and shape of the sample, on its chemical composition, reactivity and mechanical properties, as well as the desired resolution and accuracy of the 3D map.
3D EBSD has several advantages over traditional 2D EBSD. First, it provides a complete picture of a material's crystallographic structure, allowing for a more accurate and detailed analysis of the microstructure. Second, it can be used to study complex microstructures, such as those found in composite materials or multi-phase alloys. Third, it can be used to study the evolution of microstructure over time, such as during deformation or heat treatment.
However, 3D EBSD also has some limitations. It requires extensive data acquisition and processing, proper alignment between slices, and can be time-consuming and computationally intensive. In addition, the quality of the 3D map depends on the quality of the individual EBSD maps, which can be affected by factors such as sample preparation, data acquisition parameters, and analysis methods. Overall, 3D EBSD is a powerful technique for studying the crystallographic structure of materials in three dimensions, and is widely used in materials science and engineering research and development. | 0 | Theoretical and Fundamental Chemistry |
Honeycomb refers to bioinspired patterns that provide a lightweight design for energy absorbing structures. Honeycomb design can be found in different structural biological components such as spongy bone and plant vasculature. Biologically inspired honeycomb structures include Kelvin, Weaire and Floret honeycomb (see Figure 2); each with a slightly different structure in comparison to the natural hexagonal honeycomb. These variations on the biological design have yielded significantly improved energy absorption results in comparison to traditional hexagonal honeycomb biofoam.
Due to these increased energy absorption performances, honeycomb inspired structures are being researched for use inside vehicle crumple zones. By using honeycomb structures as the inner core and surrounding the structure with a more rigid structural shell, these components can absorb impact energy during a crash and reduce the amount of energy the driver experiences. | 0 | Theoretical and Fundamental Chemistry |
DNA extraction is frequently a preliminary step in many diagnostic procedures used to identify environmental viruses and bacteria and diagnose illnesses and hereditary diseases. These methods consist of, but are not limited to:
Fluorescence In Situ Hybridization (FISH) technique was developed in the 1980s. The basic idea is to use a nucleic acid probe to hybridize nuclear DNA from either interphase cells or metaphase chromosomes attached to a microscopic slide. It is a molecular method used, among other things, to recognize and count particular bacterial groupings.
To recognize, define, and quantify the geographical and temporal patterns in marine bacterioplankton communities, researchers employ a technique called terminal restriction fragment length polymorphism (T-RFLP).
Sequencing: Whole or partial genomes and other chromosomal components, ended for comparison with previously published sequences. | 1 | Applied and Interdisciplinary Chemistry |
A photolabile protecting group (PPG; also known as: photoremovable, photosensitive, or photocleavable protecting group) is a chemical modification to a molecule that can be removed with light. PPGs enable high degrees of chemoselectivity as they allow researchers to control spatial, temporal and concentration variables with light. Control of these variables is valuable as it enables multiple PPG applications, including orthogonality in systems with multiple protecting groups. As the removal of a PPG does not require chemical reagents, the photocleavage of a PPG is often referred to as "traceless reagent processes", and is often used in biological model systems and multistep organic syntheses. Since their introduction in 1962, numerous PPGs have been developed and utilized in a variety of wide-ranging applications from protein science to photoresists. Due to the large number of reported protecting groups, PPGs are often categorized by their major functional group(s); three of the most common classifications are detailed below. | 0 | Theoretical and Fundamental Chemistry |
SMIE is less common that LMIE and much less common that other failure mechanisms such as hydrogen embrittlement, fatigue, and stress-corrosion cracking. Still, embrittlement mechanisms can be introduced during fabrication, coatings, testing or during service of the material components. Susceptibility for SMIE increases with the following material characteristics:
* Increase in strength of high-strength material
* Increasing grain size
* Materials with more planar-slip than wavy-slip | 1 | Applied and Interdisciplinary Chemistry |
In general, a water distribution system can be classified as having a grid, ring, radial or dead end layout.
A grid system follows the general layout of the road grid with water mains and branches connected in rectangles. With this topology, water can be supplied from several directions allowing good water circulation and redundancy if a section of the network has broken down. Drawbacks of this topology include difficulty sizing the system.
A ring system has a water main for each road, and there is a sub-main branched off the main to provide circulation to customers. This topology has some of the advantages of a grid system, but it is easier to determine sizing.
A radial system delivers water into multiple zones. At the center of each zone, water is delivered radially to the customers.
A dead end system has water mains along roads without a rectangular pattern. It is used for communities whose road networks are not regular. As there are no cross-connections between the mains, water can have less circulation and therefore stagnation may be a problem. | 1 | Applied and Interdisciplinary Chemistry |
The unscaled elasticities can be depicted in matrix form, called the unscaled elasticity matrix, . Given a network with molecular species and reactions, the unscaled elasticity matrix is defined as:
Likewise, is it also possible to define the matrix of scaled elasticities: | 0 | Theoretical and Fundamental Chemistry |
NADK phosphorylates NAD at the 2’ position of the ribose ring that carries the adenine moiety. It is highly selective for its substrates, NAD and ATP, and does not tolerate modifications either to the phosphoryl acceptor, NAD, or the pyridine moiety of the phosphoryl donor, ATP. NADK also uses metal ions to coordinate the ATP in the active site. In vitro studies with various divalent metal ions have shown that zinc and manganese are preferred over magnesium, while copper and nickel are not accepted by the enzyme at all. A proposed mechanism involves the 2' alcohol oxygen acting as a nucleophile to attack the gamma-phosphoryl of ATP, releasing ADP. | 1 | Applied and Interdisciplinary Chemistry |
For preparation of [(Co(NCS))(TPT)] crystalline sponges, the methanol solution of Co(NCS) was added into the TPT solution in 1,2-dichlorobenzene/methanol. After 7 days, the [(Co(NCS))(TPT)] would form and can be isolated by filtration.
For preparation of [(ZnI)(TPT)] crystalline sponges, the methanol solution of ZnI was added onto the top of TPT in nitrobenzene solution. After 7 days, the [(ZnI)(TPT)] would form and can be isolated by filtration.
Once the feedstocks were mixed, crystalline sponges would be produced via self-assembling processes, forming the thermodynamically stable organized network structures. | 0 | Theoretical and Fundamental Chemistry |
Due to their penetrating nature, gamma rays require large amounts of shielding mass to reduce them to levels which are not harmful to living cells, in contrast to alpha particles, which can be stopped by paper or skin, and beta particles, which can be shielded by thin aluminium. Gamma rays are best absorbed by materials with high atomic numbers (Z) and high density, which contribute to the total stopping power. Because of this, a lead (high Z) shield is 20–30% better as a gamma shield than an equal mass of another low-Z shielding material, such as aluminium, concrete, water, or soil; lead's major advantage is not in lower weight, but rather its compactness due to its higher density. Protective clothing, goggles and respirators can protect from internal contact with or ingestion of alpha or beta emitting particles, but provide no protection from gamma radiation from external sources.
The higher the energy of the gamma rays, the thicker the shielding made from the same shielding material is required. Materials for shielding gamma rays are typically measured by the thickness required to reduce the intensity of the gamma rays by one half (the half value layer or HVL). For example, gamma rays that require 1 cm (0.4 inch) of lead to reduce their intensity by 50% will also have their intensity reduced in half by of granite rock, 6 cm (2.5 inches) of concrete, or 9 cm (3.5 inches) of packed soil. However, the mass of this much concrete or soil is only 20–30% greater than that of lead with the same absorption capability. Depleted uranium is used for shielding in portable gamma ray sources, but here the savings in weight over lead are larger, In a nuclear power plant, shielding can be provided by steel and concrete in the pressure and particle containment vessel, while water provides a radiation shielding of fuel rods during storage or transport into the reactor core. The loss of water or removal of a "hot" fuel assembly into the air would result in much higher radiation levels than when kept under water. | 0 | Theoretical and Fundamental Chemistry |
Preparing standard solutions require standards with known amount of analyte. Analytical standards can be categorized into Primary or Secondary standards. | 0 | Theoretical and Fundamental Chemistry |
Not all supernovae are triggered by runaway nuclear fusion. Type Ib, Ic and type II supernovae also undergo core collapse, but because they have exhausted their supply of atomic nuclei capable of undergoing exothermic fusion reactions, they collapse all the way into neutron stars, or in the higher-mass cases, stellar black holes, powering explosions by the release of gravitational potential energy (largely via release of neutrinos). It is the absence of runaway fusion reactions that allows such supernovae to leave behind compact stellar remnants. | 1 | Applied and Interdisciplinary Chemistry |
As other species of sulfur at intermediate oxidation state, such as thiosulfate, tetrathionate can be responsible for the pitting corrosion of carbon steel and stainless steel.
Tetrathionate has also been found to serve as a terminal electron acceptor for Salmonella enterica serotype Typhimurium, whereas existing thiosulfate in the small intestines of mammals is oxidized by reactive oxygen species released by the immune system (mainly NADPH oxidase produced superoxide) to form tetrathionate. This aids in the growth of the bacterium, helped by the inflammatory response. | 1 | Applied and Interdisciplinary Chemistry |
Strict carnivores manage vitamin A differently than omnivores and herbivores. Carnivores are more tolerant of high intakes of retinol because those species have the ability to excrete retinol and retinyl esters in urine. Carnivores also have the ability to store more in the liver, due to a higher ratio of liver HSCs to hepatocytes compared to omnivores and herbivores. For humans, liver content can range from 20 to 30 μg/gram wet weight. Notoriously, polar bear liver is acutely toxic to humans because content has been reported in range of 2,215 to 10,400 μg/g wet weight. As noted, in humans, retinol circulates bound to RBP4. Carnivores maintain R-RBP4 within a tight range while also having retinyl esters in circulation. Bound retinol is delivered to cells while the esters are excreted in the urine. In general, carnivore species are poor converters of ionone-containing carotenoids, and pure carnivores such as felidae (cats) lack the cleaving enzyme entirely. They must have retinol or retinyl esters in their diet. | 1 | Applied and Interdisciplinary Chemistry |
Archaerhodopsin 1 and 2 (AR1 and AR2) were the first archaerhodopsins to be identified and are expressed by Halobacterium sp. Aus-1 and Aus-2 respectively. Both species were first isolated in Western Australia in the late 1980s. The crystal structures of both proteins were solved by Kunio Ihara, Tsutomo Kouyama and co-workers at Nagoya University, together with collaborators at the Spring-8 synchrotron. | 0 | Theoretical and Fundamental Chemistry |
Niobium-95, with a half-life of 35 days, is initially present as a fission product. The only stable isotope of niobium has mass number 93, and fission products of mass 93 first decay to long-lived zirconium-93 (half-life 1.53 Ma). Niobium-95 will decay to molybdenum-95 which is stable. | 0 | Theoretical and Fundamental Chemistry |
On the door
*Giuliano Kremmerz, La porta ermetica, Edizioni Studio Tesi, 1982.
*Henry Carrington Bolton (gennaio-marzo 1895). The Porta Magica - Rome. The Journal of American Folk-Lore 8 (28): pp. 73–78.
*Pietro Bornia, La Porta Magica di Roma: studio storico, Luce ed Ombra (1915).
*Teodoro Brescia, Il Segno del Messia: lenigma svelato - LOlismo Originario, la Porta Alchemica e larcheoastronomia', Battaglia Terme (Padova), Nexus, 2012.
*Eugène Canseliet, Deux logis alchimiques en marge de la science et de lhistoire', Paris, Jean Schemit, 1945
*Luciano Pirrotta, La Porta Ermetica, Roma, Athanor, 1979.
*Nicoletta Cardano (a cura di), La Porta Magica. Luoghi e memorie nel giardino di piazza Vittorio, Roma, Palombi Editori, 1990.
*Maria Fiammetta Iovine, Gli Argonauti a Roma. Alchimia, ermetismo e storia inedita del Seicento nei Dialoghi eruditi di Giuseppe Giusto Guaccimanni, Roma, La Lepre Edizioni, 2014.
*Mino Gabriele, La porta magica di Roma simbolo dellalchimia occidentale', Firenze, Leo S. Olschki, 2015.
On Massimiliano Palombara
*Marchese Massimiliano Palombara, La Bugia: Rime ermetiche e altri scritti. Da un Codice Reginense del sec. XVII, a cura di Anna Maria Partini, Roma, ed. Mediterranee, 1983.
*Mino Gabriele, Il giardino di Hermes: Massimiliano Palombara alchimista e rosacroce nella Roma del Seicento. Con la prima edizione del codice autografo della Bugia, 1656, Roma, editrice Ianua, 1986.
*Maria Fiammetta Iovine, Massimiliano Palombara filosofo incognito. Appunti per una biografia di un alchimista rosacrociano del XVII secolo, Roma, La Lepre Edizioni, 2016. | 1 | Applied and Interdisciplinary Chemistry |
On a streamlined body fully immersed in a potential flow, there are two stagnation points—one near the leading edge and one near the trailing edge. On a body with a sharp point such as the trailing edge of a wing, the Kutta condition specifies that a stagnation point is located at that point. The streamline at a stagnation point is perpendicular to the surface of the body. | 1 | Applied and Interdisciplinary Chemistry |
Police forces may collect DNA samples without a suspect's knowledge, and use it as evidence. The legality of the practice has been questioned in Australia.
In the United States, where it has been accepted, courts often rule that there is no expectation of privacy and cite California v. Greenwood (1988), in which the Supreme Court held that the Fourth Amendment does not prohibit the warrantless search and seizure of garbage left for collection outside the curtilage of a home. Critics of this practice underline that this analogy ignores that "most people have no idea that they risk surrendering their genetic identity to the police by, for instance, failing to destroy a used coffee cup. Moreover, even if they do realize it, there is no way to avoid abandoning one's DNA in public."
The United States Supreme Court ruled in Maryland v. King (2013) that DNA sampling of prisoners arrested for serious crimes is constitutional.
In the United Kingdom, the Human Tissue Act 2004 prohibits private individuals from covertly collecting biological samples (hair, fingernails, etc.) for DNA analysis but exempts medical and criminal investigations from the prohibition. | 1 | Applied and Interdisciplinary Chemistry |
A 1935 paper published by Lev Landau and Evgeny Lifshitz predicted the existence of ferromagnetic resonance of the Larmor precession, which was independently verified in experiments by J. H. E. Griffiths (UK) and E. K. Zavoiskij (USSR) in 1946.
Larmor precession is important in nuclear magnetic resonance, magnetic resonance imaging, electron paramagnetic resonance, muon spin resonance, and neutron spin echo. It is also important for the alignment of cosmic dust grains, which is a cause of the polarization of starlight.
To calculate the spin of a particle in a magnetic field, one must in general also take into account Thomas precession if the particle is moving. | 0 | Theoretical and Fundamental Chemistry |
SP-B is a critical protein for lung function, and is found in the context of pulmonary surfactant. Understanding surfactant is important to gaining a full understanding of SP-B. Surfactant is a mixture of lipids and proteins that coats the inside of alveoli and is essential for life due to its key role in preventing alveolar collapse at low lung volumes. In the absence of surfactant, the surface tension at the gas/fluid interface prevents inhalation at standard pressure, but surfactant minimizes surface tension to values near zero and allows for normal breathing. It is also known to have a role in both the immune response and inflammation control.
Surfactant deficiency is a common cause of respiratory disease. Respiratory distress syndrome (RDS) is a particularly well-known instance of surfactant deficiency because it has a high mortality rate among preterm babies, a variety of other conditions are related to surfactant levels and composition.
Surfactant is composed of primarily lipids (90% by weight), and proteins make up only the remaining 10%. The following two sections will address the lipid and protein components respectively. | 0 | Theoretical and Fundamental Chemistry |
The hydrophobic effect is the desire for non-polar molecules to aggregate in aqueous solutions in order to separate from water. This phenomenon leads to minimum exposed surface area of non-polar molecules to the polar water molecules (typically spherical droplets), and is commonly used in biochemistry to study protein folding and other various biological phenomenon. The effect is also commonly seen when mixing various oils (including cooking oil) and water. Over time, oil sitting on top of water will begin to aggregate into large flattened spheres from smaller droplets, eventually leading to a film of all oil sitting atop a pool of water. However the hydrophobic effect is not considered a non-covalent interaction as it is a function of entropy and not a specific interaction between two molecules, usually characterized by entropy.enthalpy compensation. An essentially enthalpic hydrophobic effect materializes if a limited number of water molecules are restricted within a cavity; displacement of such water molecules by a ligand frees the water molecules which then in the bulk water enjoy a maximum of hydrogen bonds close to four. | 0 | Theoretical and Fundamental Chemistry |
* Nitinat Lake on Vancouver Island has a sometimes dangerous tidal bore at Nitinat Narrows where the lake meets the Pacific Ocean. The lake is popular with windsurfers due to its consistent winds. | 1 | Applied and Interdisciplinary Chemistry |
Trees absorb carbon dioxide (CO2) from the atmosphere through the process of photosynthesis. Throughout this biochemical process, chlorophyll in the tree's leaves harnesses sunlight to convert CO2 and water into glucose and oxygen. While glucose serves as a source of energy for the tree, oxygen is released into the atmosphere as a byproduct. Trees store carbon in the form of biomass, encompassing roots, stems, branches, and leaves. Throughout their lifespan, trees continue to sequester carbon, acting as long-term storage units for atmospheric CO. Sustainable forest management, afforestration, reforestation and proforestation are therefore important contributions to climate change mitigation. Afforestation is the establishment of a forest in an area where there was no previous tree cover. Proforestation is the practice of growing an existing forest intact toward its full ecological potential. An important consideration in such efforts is that the carbon sink potential of forests will saturate and forests can turn from sinks to carbon sources. The Intergovernmental Panel on Climate Change (IPCC) concluded that a combination of measures aimed at increasing forest carbon stocks, and sustainable timber offtake will generate the largest carbon sequestration benefit.
In terms of carbon retention on forest land, it is better to avoid deforestation than to remove trees and subsequently reforest, as deforestation leads to irreversible effects e.g. biodiversity loss and soil degradation. Additionally, the effects of af- or reforestation will be farther in the future compared to keeping existing forests intact. It takes much longer − several decades − for reforested areas to return to the same carbon sequestration levels found in mature tropical forests.
There are four primary ways in which reforestation and reducing deforestation can increase carbon sequestration. First, by increasing the volume of existing forest. Second, by increasing the carbon density of existing forests at a stand and landscape scale. Third, by expanding the use of forest products that will sustainably replace fossil-fuel emissions. Fourth, by reducing carbon emissions that are caused from deforestation and degradation.
The planting of trees on marginal crop and pasture lands helps to incorporate carbon from atmospheric into biomass. For this carbon sequestration process to succeed the carbon must not return to the atmosphere from biomass burning or rotting when the trees die. To this end, land allotted to the trees must not be converted to other uses and management of the frequency of disturbances might be necessary in order to avoid extreme events. Alternatively, the wood from them must itself be sequestered, e.g., via biochar, bio-energy with carbon storage (BECS), landfill or stored by use in construction.
Reforestation with long-lived trees (>100 years) will sequester carbon for substantial periods and be released gradually, minimizing carbon's climate impact during the 21st century. Earth offers enough room to plant an additional 1.2 trillion trees. Planting and protecting them would offset some 10 years of CO emissions and sequester 205 billion tons of carbon. This approach is supported by the Trillion Tree Campaign. Restoring all degraded forests world-wide would capture about 205 billion tons of carbon in total, which is about two-thirds of all carbon emissions.
Although a bamboo forest stores less total carbon than a mature forest of trees, a bamboo plantation sequesters carbon at a much faster rate than a mature forest or a tree plantation. Therefore, the farming of bamboo timber may have significant carbon sequestration potential.
During a 30-year period to 2050 if all new construction globally utilized 90% wood products, largely via adoption of mass timber in low rise construction, this could sequester 700 million net tons of carbon per year, thus negating approximately 2% of annual carbon emissions as of 2019. This is in addition to the elimination of carbon emissions from the displaced construction material such as steel or concrete, which are carbon-intense to produce.
As enforcement of forest protection may not sufficiently address the drivers behind deforestation – the largest of which being the production of beef in the case of the Amazon rainforest – it may also need policies. These could effectively ban and/or progressively discourage deforestation-associated trade via e.g. product information requirements, satellite monitoring like the Global Forest Watch, related eco-tariffs, and product certifications. | 0 | Theoretical and Fundamental Chemistry |
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