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Papers published prior to a recent community consensus employ differing sets of nomenclature. The precursor peptide has been referred to previously as prepeptide, prepropeptide, or structural peptide. The leader peptide has been referred to as a propeptide, pro-region, or intervening region. Historical alternate terms for core peptide included propeptide, structural peptide, and toxin region (for conopeptides, specifically). | 1 | Applied and Interdisciplinary Chemistry |
Accelerated testing of adhesives is used to predict long term performance of adhesive exposed to a variety of environmental factors. Adhesives are sometimes used as load bearing and sealing joints, which points great stress on them. In accelerated testing, factors like the temperature, moisture, vibrations, voltage, and UV light are greatly increased over a short period so long term predictions can be made about the effect of the aforementioned factors. | 0 | Theoretical and Fundamental Chemistry |
HIV protease inhibitors are used to treat patients having AIDS virus by preventing its DNA replication. HIV protease is used by the virus to cleave Gag-Pol polyprotein into 3 smaller proteins that are responsible for virion assembly, package and maturation. This enzyme targets the specific phenylalanine-proline cleave site within the target protein. If HIV protease is switched off the virion particle will lose function and cannot infect patients. Since it is essential in viral replication and is absent in healthy human, it is an ideal target for drug development.
HIV protease belongs to aspartic protease family and has a similar mechanism. Firstly the aspartate residue activates a water molecule and turns it into a nucleophile. Then it attacks the carbonyl group within the peptide bond (NH-CO) to form a tetrahedral intermediate. The nitrogen atom within the intermediate receives a proton, forming an amide group and subsequent rearrangement leads to the breakdown of the bond between it and the intermediate and forms two products.
Inhibitors usually contain a nonhydrolyzable hydroxyethylene or hydroxyethylamine groups that mimic the tetrahedral intermediate. Since they share a similar structure and electrostatic arrangement to the transition state of substrates they can still fit into the active site but cannot be broken down, so hydrolysis cannot occur. | 1 | Applied and Interdisciplinary Chemistry |
Retinaldehyde is a retinol (vitamin A) derivative responsible for vision. It binds rhodopsin, a well-characterized GPCR that binds all-cis retinal in its inactive state. Upon photoisomerization by a photon the cis-retinal is converted to trans-retinal causing activation of rhodopsin which ultimately leads to depolarization of the neuron thereby enabling visual perception. | 1 | Applied and Interdisciplinary Chemistry |
The occurrence of amorphous phases turned out to be a phenomenon of particular interest for the studying of thin-film growth. The growth of polycrystalline films is often used and preceded by an initial amorphous layer, the thickness of which may amount to only a few nm. The most investigated example is represented by the unoriented molecules of thin polycrystalline silicon films. Wedge-shaped polycrystals were identified by transmission electron microscopy to grow out of the amorphous phase only after the latter has exceeded a certain thickness, the precise value of which depends on deposition temperature, background pressure, and various other process parameters. The phenomenon has been interpreted in the framework of Ostwald's rule of stages that predicts the formation of phases to proceed with increasing condensation time towards increasing stability. | 0 | Theoretical and Fundamental Chemistry |
In a hydrogen bond, the electronegative atom not covalently attached to the hydrogen is named the proton acceptor, whereas the one covalently bound to the hydrogen is named the proton donor. This nomenclature is recommended by the IUPAC. The hydrogen of the donor is protic and therefore can act as a Lewis acid and the acceptor is the Lewis base. Hydrogen bonds are represented as system, where the dots represent the hydrogen bond. Liquids that display hydrogen bonding (such as water) are called associated liquids.
Hydrogen bonds arise from a combination of electrostatics (multipole-multipole and multipole-induced multipole interactions), covalency (charge transfer by orbital overlap), and dispersion (London forces).
In weaker hydrogen bonds, hydrogen atoms tend to bond to elements such as sulfur (S) or chlorine (Cl); even carbon (C) can serve as a donor, particularly when the carbon or one of its neighbors is electronegative (e.g., in chloroform, aldehydes and terminal acetylenes). Gradually, it was recognized that there are many examples of weaker hydrogen bonding involving donor other than N, O, or F and/or acceptor Ac with electronegativity approaching that of hydrogen (rather than being much more electronegative). Although weak (≈1 kcal/mol), "non-traditional" hydrogen bonding interactions are ubiquitous and influence structures of many kinds of materials.
The definition of hydrogen bonding has gradually broadened over time to include these weaker attractive interactions. In 2011, an IUPAC Task Group recommended a modern evidence-based definition of hydrogen bonding, which was published in the IUPAC journal Pure and Applied Chemistry. This definition specifies: | 0 | Theoretical and Fundamental Chemistry |
SR deficiency is currently being treated using a combination therapy of levodopa and carbidopa. These treatments are also used for individuals suffering from Parkinson's. The treatment is noninvasive and only requires the patient to take oral tablets 3 or 4 times a day, where the dosage of levodopa and carbidopa is determined by the severity of the symptoms. Levodopa is in a class of medications called central nervous system agents where its main function is to become dopamine in the brain. Carbidopa is in a class of medications called decarboxylase inhibitors and it works by preventing levodopa from being broken down before it reaches the brain. This treatment is effective in mitigating motor symptoms, but it does not totally eradicate them and it is not as effective on cognitive problems. Patients who have been diagnosed with SR deficiency and have undergone this treatment have shown improvements with most motor impairments including oculogyric crises, dystonia, balance, and coordination. | 1 | Applied and Interdisciplinary Chemistry |
Similar to the process of distillation, gas-liquid chromatography (typically referred to as gas chromatography, or, more simply, GC) utilises a distillation tower to separate the petroleum. However, compared to distillation's 2 to 300 theoretical plates, gas chromatography includes more than 25,000. This provides a greater degree of separation.
In order to achieve more complete analyses, gas chromatography is used along with mass spectrometry (to make gas chromatography/mass spectrometry, or GCMS), with infrared spectrometry (to make gas chromatography/infrared spectrometry, or GCIR), and with isotope ratio mass spectrometry (to make gas chromatography/isotope ratio mass spectrometry, or GSIRMS). | 0 | Theoretical and Fundamental Chemistry |
The chloroplasts of some hornworts and algae contain structures called pyrenoids. They are not found in higher plants. Pyrenoids are roughly spherical and highly refractive bodies which are a site of starch accumulation in plants that contain them. They consist of a matrix opaque to electrons, surrounded by two hemispherical starch plates. The starch is accumulated as the pyrenoids mature. In algae with carbon concentrating mechanisms, the enzyme RuBisCO is found in the pyrenoids. Starch can also accumulate around the pyrenoids when CO is scarce. Pyrenoids can divide to form new pyrenoids, or be produced "de novo". | 0 | Theoretical and Fundamental Chemistry |
Masri was born and raised in Nablus, Palestine. After leaving Nablus, Masri continued his education in Egypt, before moving to the United States, where he graduated from Virginia Tech with a B.S. in Chemical Engineering in 1983. | 1 | Applied and Interdisciplinary Chemistry |
Micro-sized ZnO tetrapodal particles added to pilot paper production. The most common are one-dimensional nanostructures, such as nanorods, nanotubes, nanofibers, nanowires, but also nanoplates, nanosheets, nanospheres, tetrapods. ZnO is strongly oxidative, chemically stable, with enhanced photocatalytic activity, and has a large free-exciton binding energy. It is non-toxic, abundant, biocompatible, biodegradable, environmentally friendly, low cost, and compatible with simple chemical synthesis. ZnO faces limits to its widespread use in photocatalysis under solar radiation. Several approaches have been suggested to overcome this limitation, including doping for reducing the band gap and improving charge carrier separation. | 0 | Theoretical and Fundamental Chemistry |
A kodecyte (ko•de•cyte) is a living cell that has been modified (koded) by the incorporation of one or more function-spacer-lipid constructs (FSL constructs) to gain a new or novel biological, chemical or technological function. The cell is modified by the lipid tail of the FSL construct incorporating into the bilipid membrane of the cell.
All kodecytes retain their normal vitality and functionality while gaining the new function of the inserted FSL constructs. The combination of dispersibility in biocompatible media, spontaneous incorporation into cell membranes, and apparent low toxicity, makes FSL constructs suitable as research tools and for the development of new diagnostic and therapeutic applications. | 1 | Applied and Interdisciplinary Chemistry |
*Hony. dean, College of Chemical Sciences and chairman – academic board: Prof J N Oleap Fernando, C.Chem. (Chartered Chemist), C.Sci.
*Vice-chairman, academic board: Prof. G M K B Gunaherath, C.Chem. (Chartered Chemist)
*Secretary for educational affairs: Ms. P M Jayasinha, C.Chem. (Chartered Chemist)
*Asst. secretary for educational affairs: Ms. M N K de S Goonatillake, C.Chem. (Chartered Chemist)
*Course co-ordinator (Kandy): Dr (Ms) A D L C Perera, C.Chem.
*Academic laboratory co-ordinator: Mr. M R M Haniffa, C.Chem. (Chartered Chemist)
*Visiting professor: Prof. S Sotheeswaran, D.Sc. (Hull), C.Chem. (Chartered Chemist)
*Full-time lecturers: Dr U S K Weliwegamage, C.Chem., Dr. (Ms.) V M Thadhani
*Registrar and registrar/College of Chemical Sciences: Mr. N I N S Nadarasa, C.Chem. (Chartered Chemist)
*Deputy registrar/DLTC co-ordinator: Mr J M Ranasinghe Banda, C.Chem. (Chartered Chemist)
*Asst. librarian/College of Chemical Sciences: Mr K G B Wimalasena | 1 | Applied and Interdisciplinary Chemistry |
The first reported use of a PPG in the scientific literature was by Barltrop and Schofield, who in 1962 used 253.7 nm light to release glycine from N-benzylglycine. Following this initial report, the field rapidly expanded throughout the 1970s as Kaplan and Epstein studied PPGs in a variety of biochemical systems. During this time, a series of standards for evaluating PPG performance was compiled. An abbreviated list of these standards, which are commonly called the Lester rules, or Sheehan criteria are summarized below:
* In biological systems, the protected substrate, as well as the photoproducts should be highly soluble in water; in synthesis, this requirement is not as strict
* The protected substrate, as well as the photoproducts should be stable in the photolysis environment
* Separation of the PPG should exhibit a quantum yield greater than 0.10
* Separation of the PPG should occur through a primary photochemical process
* The chromophore should absorb incident light with reasonable absorptivity
* The excitation wavelength of light should be greater than 300 nm
* The media and photoproducts should not absorb the incident light
* A general, high-yield synthetic procedure should exist for attaching the PPG to an unprotected substrate
* The protected substrate and the photoproducts should be easily separated | 0 | Theoretical and Fundamental Chemistry |
The oldest cast iron water pipes date from the 17th century and were installed to distribute water throughout the gardens of the Chateau de Versailles. These amount to some 35 km of pipe, typically 1 m lengths with flanged joints. The extreme age of these pipes make them of considerable historical value. Despite extensive refurbishment in 2008 by Saint-Gobain PAM, 80% remain original.
Cast iron proved to be a beneficial material for the manufacture of water pipes and was used as a replacement for the original elm pipelines utilized earlier. These water pipelines were composed of individually cast pipe sections, often termed sticks, jointed together by a variety of joint mechanisms. Flanged joints consisted of flat machined surfaces that were tightly bolted together with a gasket between them to prevent leakage. This type of pipe joint is still in use today, typically for above-ground pipelines in water treatment and manufacturing plants.
Cast iron pipe was frequently used uncoated, although later coatings and linings reduced corrosion and improved hydraulics. In cast iron pipe, the graphite forms flakes during the casting process, when examined under a microscope. Cast iron pipe was superseded by ductile iron pipe, which is a direct development, with most existing manufacturing plants transitioning to the new material during the 1970s and 1980s. Ductile iron pipe is different than cast iron, because the introduction of magnesium during the casting process causes the graphite to form spheres (graphite nodules) rather than flakes. While this allows the material to remain castable, the end product is much tougher than cast iron, and allows elastic behavior at lower stress levels. Little cast iron pipe is currently manufactured, since ductile iron pipe is widely accepted as a superior product. Many public utilities, municipalities, and private industries still have functional cast iron pipe in service to this day. | 1 | Applied and Interdisciplinary Chemistry |
A shear layer develops viscous instability and forms Tollmien–Schlichting waves which grow, while still laminar, into finite amplitude (1 to 2 percent of the freestream velocity) three-dimensional fluctuations in velocity and pressure to develop three-dimensional unstable waves and hairpin eddies. From then on, the process is more a breakdown than a growth. The longitudinally stretched vortices begin a cascading breakdown into smaller units, until the relevant frequencies and wave numbers are approaching randomness. Then in this diffusively fluctuating state, intense local changes occur at random times and locations in the shear layer near the wall. At the locally intense fluctuations, turbulent spots are formed that burst forth in the form of growing and spreading spots — the result of which is a fully turbulent state downstream. | 1 | Applied and Interdisciplinary Chemistry |
For transition metals, oxidative reaction results in the decrease in the d to a configuration with fewer electrons, often 2e fewer. Oxidative addition is favored for metals that are (i) basic and/or (ii) easily oxidized. Metals with a relatively low oxidation state often satisfy one of these requirements, but even high oxidation state metals undergo oxidative addition, as illustrated by the oxidation of Pt(II) with chlorine:
:[PtCl] + Cl → [PtCl]
In classical organometallic chemistry, the formal oxidation state of the metal and the electron count of the complex both increase by two. One-electron changes are also possible and in fact some oxidative addition reactions proceed via series of 1e changes. Although oxidative additions can occur with the insertion of a metal into many different substrates, oxidative additions are most commonly seen with H–H, H–X, and C–X bonds because these substrates are most relevant to commercial applications.
Oxidative addition requires that the metal complex have a vacant coordination site. For this reason, oxidative additions are common for four- and five-coordinate complexes.
Reductive elimination is the reverse of oxidative addition. Reductive elimination is favored when the newly formed X–Y bond is strong. For reductive elimination to occur the two groups (X and Y) should be mutually adjacent on the metal's coordination sphere. Reductive elimination is the key product-releasing step of several reactions that form C–H and C–C bonds. | 0 | Theoretical and Fundamental Chemistry |
There are relatively few published examples of demonstrations or recreation of the experiment. Two physicists in the University of Washington system reported on demonstrations to students and colleagues and produced directions for re-creating the experiment in 1985 as part of an investigation into the role of the experiment in the history of physics. Physicists at Sofia University in Bulgaria reported on reproducing the experiment for high school students in 2017. | 0 | Theoretical and Fundamental Chemistry |
Biopolymers are polymers produced by living organisms. Cellulose and starch, proteins and peptides, and DNA and RNA are all examples of biopolymers, in which the monomeric units, respectively, are sugars, amino acids, and nucleotides. Cellulose is both the most common biopolymer and the most common organic compound on Earth. About 33% of all plant matter is cellulose. On a similar manner, silk (proteinaceous biopolymer) has garnered tremendous research interest in a myriad of domains including tissue engineering and regenerative medicine, microfluidics, drug delivery. | 1 | Applied and Interdisciplinary Chemistry |
* Biological Aerated (or Anoxic) Filter (BAF) or Biofilters combine filtration with biological carbon reduction, nitrification or denitrification. BAF usually includes a reactor filled with a filter media. The media is either in suspension or supported by a gravel layer at the foot of the filter. The dual purpose of this media is to support highly active biomass that is attached to it and to filter suspended solids. Carbon reduction and ammonia conversion occurs in aerobic mode and sometime achieved in a single reactor while nitrate conversion occurs in anoxic mode. BAF is operated either in upflow or downflow configuration depending on design specified by manufacturer.
* Integrated Fixed-Film Activated Sludge
* Moving Bed Biofilm Reactors (MBBRs) typically requires smaller footprint than suspended-growth systems. | 1 | Applied and Interdisciplinary Chemistry |
The breakdown of phytoplankton in the environment depends on the presence of oxygen, and once oxygen is no longer in the bodies of water, ligninperoxidases cannot continue to break down the lignin. When oxygen is not present in the water, the time required for breakdown of phytoplankton changes from 10.7 days to a total of 160 days.
The rate of phytoplankton breakdown can be represented using this equation:
In this equation, G(t) is the amount of particulate organic carbon (POC) overall at a given time, t. G(0) is the concentration of POC before breakdown takes place. k is a rate constant in year-1, and t is time in years. For most POC of phytoplankton, the k is around 12.8 years-1, or about 28 days for nearly 96% of carbon to be broken down in these systems. Whereas for anoxic systems, POC breakdown takes 125 days, over four times longer. It takes approximately 1 mg of oxygen to break down 1 mg of POC in the environment, and therefore, hypoxia takes place quickly as oxygen is used up quickly to digest POC. About 9% of POC in phytoplankton can be broken down in a single day at 18 °C. Therefore, it takes about eleven days to completely break down phytoplankton.
After POC is broken down, this particulate matter can be turned into other dissolved carbon, such as carbon dioxide, bicarbonate ions, and carbonate. As much as 30% of phytoplankton can be broken down into dissolved carbon. When this particulate organic carbon interacts with 350 nm ultraviolet light, dissolved inorganic carbon is formed, removing even more oxygen from the environment in the forms of carbon dioxide, bicarbonate ions, and carbonate. Dissolved inorganic carbon is made at a rate of 2.3–6.5 mg/(m⋅day).
As phytoplankton breakdown, free phosphorus and nitrogen become available in the environment, which also fosters hypoxic conditions. As the breakdown of this phytoplankton takes place, the more phosphorus turns into phosphates, and nitrogens turn into nitrates. This depletes the oxygen even more so in the environment, further creating hypoxic zones in higher quantities. As more minerals such as phosphorus and nitrogen are displaced into these aquatic systems, the growth of phytoplankton greatly increases, and after their death, hypoxic zones are formed. | 0 | Theoretical and Fundamental Chemistry |
7-Methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (mTBD) is a bicyclic strong guanidine base (pK = 25.43 in CHCN and pK = 17.9 in THF). mTBD, like [[Triazabicyclodecene|1,5,7-triazabicyclo[4.4.0]dec-5-ene]] and other guanidine super bases, can be used as a catalyst in a variety of chemical reactions. It also reacts with CO, which could make it useful for carbon capture and storage.
When brought into contact with some acids, mTBD reacts to form an ionic liquid. Some of these ionic liquids can dissolve cellulose. | 0 | Theoretical and Fundamental Chemistry |
Imidazolidinones are catalysts for many transformations such as asymmetric Diels-Alder reactions and Michael additions. Chiral catalysts induce asymmetric reactions, often with high enantioselectivities. This catalyst works by forming an iminium ion with carbonyl groups of α,β-unsaturated aldehydes (enals) and enones in a rapid chemical equilibrium. This iminium activation is similar to activation of carbonyl groups by a Lewis acid and both catalysts lower the substrate's LUMO:
The transient iminium intermediate is chiral which is transferred to the reaction product via chiral induction. The catalysts have been used in Diels-Alder reactions, Michael additions, Friedel-Crafts alkylations, transfer hydrogenations and epoxidations.
One example is the asymmetric synthesis of the drug warfarin (in equilibrium with the hemiketal) in a Michael addition of 4-hydroxycoumarin and benzylideneacetone:
A recent exploit is the vinyl alkylation of crotonaldehyde with an organotrifluoroborate salt:
For other examples of its use: see organocatalytic transfer hydrogenation and asymmetric Diels-Alder reactions. | 0 | Theoretical and Fundamental Chemistry |
A stepwise model for the emergence of chemiosmosis, a key element in the origin of life on earth, proposes that primordial organisms used thermal cycling as an energy source (thermosynthesis), functioning essentially as a heat engine:
:self-organized convection in natural waters causing thermal cycling →
:: added β-subunit of F ATP Synthase
:: (generated ATP by thermal cycling of subunit during suspension in convection cell: thermosynthesis) →
::: added membrane and F ATP Synthase moiety
::: (generated ATP by change in electrical polarization of membrane during thermal cycling: thermosynthesis) →
:::: added metastable, light-induced electric dipoles in membrane
:::: (primitive photosynthesis) →
::::: added quinones and membrane-spanning light-induced electric dipoles
::::: (today's bacterial photosynthesis, which makes use of chemiosmosis). | 1 | Applied and Interdisciplinary Chemistry |
Polyadenylation is the addition of a poly(A) tail to an RNA transcript, typically a messenger RNA (mRNA). The poly(A) tail consists of multiple adenosine monophosphates; in other words, it is a stretch of RNA that has only adenine bases. In eukaryotes, polyadenylation is part of the process that produces mature mRNA for translation. In many bacteria, the poly(A) tail promotes degradation of the mRNA. It, therefore, forms part of the larger process of gene expression.
The process of polyadenylation begins as the transcription of a gene terminates. The 3′-most segment of the newly made pre-mRNA is first cleaved off by a set of proteins; these proteins then synthesize the poly(A) tail at the RNA's 3′ end. In some genes these proteins add a poly(A) tail at one of several possible sites. Therefore, polyadenylation can produce more than one transcript from a single gene (alternative polyadenylation), similar to alternative splicing.
The poly(A) tail is important for the nuclear export, translation and stability of mRNA. The tail is shortened over time, and, when it is short enough, the mRNA is enzymatically degraded. However, in a few cell types, mRNAs with short poly(A) tails are stored for later activation by re-polyadenylation in the cytosol. In contrast, when polyadenylation occurs in bacteria, it promotes RNA degradation. This is also sometimes the case for eukaryotic non-coding RNAs.
mRNA molecules in both prokaryotes and eukaryotes have polyadenylated 3′-ends, with the prokaryotic poly(A) tails generally shorter and fewer mRNA molecules polyadenylated. | 1 | Applied and Interdisciplinary Chemistry |
1,8-Diazabicyclo[5.4.0]undec-7-ene, or more commonly DBU, is a chemical compound and belongs to the class of amidine compounds. It is used in organic synthesis as a catalyst, a complexing ligand, and a non-nucleophilic base. | 0 | Theoretical and Fundamental Chemistry |
Even with current technologies, hECT structure and function is more at the level of newborn heart muscle than adult myocardium. Nonetheless, important advances have led to the generation of hECT patches for myocardial repair in animal models and use for in vitro models of drug screening. hECTs can also be used to experimentally model CVD using genetic manipulation and adenoviral-mediated gene transfer. In animal models of myocardial infarction (MI), hECT injection into the hearts of rats and mice reduces infarct size and improves heart function and contractility. As a proof of principle, grafts of engineered heart tissues have been implanted in rats following MI with beneficial effects on left ventricular function. The use of hECTs in generating tissue engineered heart valves is also being explored to improve current heart valve constructs for in vivo animal studies. As tissue engineering technology advances to overcome current limitations, hECTs are a promising avenue for experimental drug discovery, screening and disease modelling and in vivo repair. | 1 | Applied and Interdisciplinary Chemistry |
L. D. Landau's phenomenological and semi-microscopic theory of superfluidity of helium-4 earned him the Nobel Prize in physics, in 1962. Assuming that sound waves are the most important excitations in helium-4 at low temperatures, he showed that helium-4 flowing past a wall would not spontaneously create excitations if the flow velocity was less than the sound velocity. In this model, the sound velocity is the "critical velocity" above which superfluidity is destroyed. (Helium-4 actually has a lower flow velocity than the sound velocity, but this model is useful to illustrate the concept.) Landau also showed that the sound wave and other excitations could equilibrate with one another and flow separately from the rest of the helium-4, which is known as the "condensate".
From the momentum and flow velocity of the excitations he could then define a "normal fluid" density, which is zero at zero temperature and increases with temperature. At the so-called Lambda temperature, where the normal fluid density equals the total density, the helium-4 is no longer superfluid.
To explain the early specific heat data on superfluid helium-4, Landau posited the existence of a type of excitation he called a "roton", but as better data became available he considered that the "roton" was the same as a high momentum version of sound.
The Landau theory does not elaborate on the microscopic structure of the superfluid component of liquid helium. The first attempts to create a microscopic theory of the superfluid component itself were done by London and subsequently, Tisza.
Other microscopical models have been proposed by different authors. Their main objective is to derive the form of the inter-particle potential between helium atoms in superfluid state from first principles of quantum mechanics.
To date, a number of models of this kind have been proposed, including: models with vortex rings, hard-sphere models, and Gaussian cluster theories. | 1 | Applied and Interdisciplinary Chemistry |
Classical dyes and pigments produce color by the absorption and reflection of light; these are the materials that make a major impact on the color of our daily lives. In 2000, world production of organic dyes was 800,000 tonnes and of organic pigments, 250,000 tonnes and the volume has grown at a steady rate throughout the early years of this century. In 2019 the value of the organic dyes/pigments market is forecast to be $19.5bn. Their value is exceeded by the very large production of inorganic pigments. Organic dyes are used mainly to color textile fibers, paper, hair, leather, while pigments are used largely in inks, paints, plastic and cosmetics. Both are used in the growth area of the digital printing of textiles, paper and other surfaces.
Dyes are also made using the properties of chromic substances: Examples being
Photochromic dyes and
Thermochromic dyes | 0 | Theoretical and Fundamental Chemistry |
Enamines are labile and therefore chemically useful moieties which can be easily produced from commercially available starting reagents. A common route for enamine production is via an acid-catalyzed nucleophilic reaction of ketone or aldehyde species containing an α-hydrogen with secondary amines. Acid catalysis is not always required, if the pK of the reacting amine is sufficiently high (for example, pyrrolidine, which has a pK of 11.26). If the pK of the reacting amine is low, however, then acid catalysis is required through both the addition and the dehydration steps (common dehydrating agents include MgSO and NaSO). Primary amines are usually not used for enamine synthesis due to the preferential formation of the more thermodynamically stable imine species. Methyl ketone self-condensation is a side-reaction which can be avoided through the addition of TiCl into the reaction mixture (to act as a water scavenger). An example of an aldehyde reacting with a secondary amine to form an enamine via a carbinolamine intermediate is shown below: | 0 | Theoretical and Fundamental Chemistry |
Classical qualitative inorganic analysis is a method of analytical chemistry which seeks to find the elemental composition of inorganic compounds. It is mainly focused on detecting ions in an aqueous solution, therefore materials in other forms may need to be brought to this state before using standard methods. The solution is then treated with various reagents to test for reactions characteristic of certain ions, which may cause color change, precipitation and other visible changes.
Qualitative inorganic analysis is that branch or method of analytical chemistry which seeks to establish the elemental composition of inorganic compounds through various reagents. | 0 | Theoretical and Fundamental Chemistry |
The critical micelle concentration (CMC) in water at 25 °C is 8.2 mM, and the aggregation number at this concentration is usually considered to be about 62. The micelle ionization fraction (α) is around 0.3 (or 30%). | 1 | Applied and Interdisciplinary Chemistry |
In another study, Rollins and Dill (2014) introduces the Foldon Funnel Model, a new addition to previous folding funnels, in which secondary structures form sequentially along the folding pathway and are stabilized by tertiary interactions. The model predicts that the free energy landscape has a volcano shape instead of a simple funnel that is mentioned previously, in which the outer landscape is sloped uphill because protein secondary structures are unstable. These secondary structures are then stabilized by tertiary interactions, which, despite their increasingly native-like structures, are also increasing in free energy until the second-to-last to the last step that is downhill in free energy. The highest free energy on the volcano landscape is at the step with structure just before the native state. This prediction of energy landscape is consistent with experiments showing that most protein secondary structures are unstable on their own and with measured protein equilibrium cooperativities. Thus, all earlier steps before reaching the native state are in pre-equilibrium. Despite its model being different from other models before, the Foldon Funnel Model still divides conformational space into the two kinetic states: native versus all others. | 1 | Applied and Interdisciplinary Chemistry |
The mitochondrial calcium uniporter (MCU) is a protein complex located in the inner mitochondrial matrix that functions to take up calcium ions (Ca2+) into the matrix from the cytoplasm. The transport of calcium ions is specifically used in cellular function for regulating energy production in the mitochondria, cytosolic calcium signaling, and cell death. The uniporter becomes activated when cytoplasmic levels of calcium rise above 1 uM.
The MCU complex comprises 4 parts: the port-forming subunits, regulatory subunits MICU1 and MICU2, and an auxiliary subunit, EMRE. These subunits work together to regulate the uptake of calcium in the mitochondria. Specifically, the EMRE subunit functions for the transport of calcium, and the MICU subunit functions in tightly regulating the activity of MCU to prevent the overload of calcium concentrations in the cytoplasm. Calcium is fundamental for signaling pathways in cells, as well as for cell death pathways. The function of the mitochondrial uniporter is critical for maintaining cellular homeostasis.
The MICU1 and MICU2 subunits are a heterodimer connected by a disulfide bridge. When there are high levels of cytoplasmic calcium, the MICU1-MICU2 heterodimer undergoes a conformational change. The heterodimer subunits have cooperative activation, which means Ca binding to one MICU subunit in the heterodimer induces a conformational change on the other MICU subunits. The uptake of calcium is balanced by the sodium-calcium exchanger. | 1 | Applied and Interdisciplinary Chemistry |
The flammable nature of the exhalations of wine was already known to ancient natural philosophers such as Aristotle (384–322 BCE), Theophrastus (–287 BCE), and Pliny the Elder (23/24–79 CE). However, this did not immediately lead to the isolation of alcohol, even despite the development of more advanced distillation techniques in second- and third-century Roman Egypt. An important recognition, first found in one of the writings attributed to Jābir ibn Ḥayyān (ninth century CE), was that by adding salt to boiling wine, which increases the wines relative volatility, the flammability of the resulting vapors may be enhanced. The distillation of wine is attested in Arabic works attributed to al-Kindī (–873 CE) and to al-Fārābī (–950), and in the 28th book of al-Zahrāwīs (Latin: Abulcasis, 936–1013) Kitāb al-Taṣrīf (later translated into Latin as Liber servatoris). In the twelfth century, recipes for the production of aqua ardens ("burning water", i.e., alcohol) by distilling wine with salt started to appear in a number of Latin works, and by the end of the thirteenth century, it had become a widely known substance among Western European chemists.
The works of Taddeo Alderotti (1223–1296) describe a method for concentrating alcohol involving repeated fractional distillation through a water-cooled still, by which an alcohol purity of 90% could be obtained. The medicinal properties of ethanol were studied by Arnald of Villanova (1240–1311 CE) and John of Rupescissa (–1366), the latter of whom regarded it as a life-preserving substance able to prevent all diseases (the aqua vitae or "water of life", also called by John the quintessence of wine). | 0 | Theoretical and Fundamental Chemistry |
Zuzanna Stefania Siwy (born 1972) is a Polish–American chemist at the University of California, Irvine. Her research considers synthetic nanopores and their application in ionic devices. She is a Fellow of the American Physical Society, American Association for the Advancement of Science and Foundation for Polish Science. | 0 | Theoretical and Fundamental Chemistry |
EGF; LDLR; LRP1; LRP10; LRP1B; LRP2; LRP4; LRP5;
LRP5L; LRP6; LRP8; NID1; NID2; SORL1; VLDLR; | 1 | Applied and Interdisciplinary Chemistry |
Mechanical clock mechanisms are sensitive to temperature changes as each part has tiny tolerance and it leads to errors in time keeping. A bimetallic strip is used to compensate this phenomenon in the mechanism of some timepieces. The most common method is to use a bimetallic construction for the circular rim of the balance wheel. What it does is move a weight in a radial way looking at the circular plane down by the balance wheel, varying then, the momentum of inertia of the balance wheel. As the spring controlling the balance becomes weaker with the increasing temperature, the balance becomes smaller in diameter to decrease the momentum of inertia and keep the period of oscillation (and hence timekeeping) constant.
Nowadays this system is not used anymore since the appearance of low temperature coefficient alloys like nivarox, parachrom and many others depending on each brand. | 1 | Applied and Interdisciplinary Chemistry |
The SI-unit for mass concentration is kg/m (kilogram/cubic metre). This is the same as mg/mL and g/L. Another commonly used unit is g/(100 mL), which is identical to g/dL (gram/decilitre). | 0 | Theoretical and Fundamental Chemistry |
There is conflicting evidence about the benefits of interventions with vitamin D. Supplementation of between 800 and 1,000 IU is safe, but higher levels leading to blood levels of more than 50ng/mL (125nmol/L) may cause adverse effects.
The US Office of Dietary Supplements established a Vitamin D Initiative over 2004–18 to track current research and provide education to consumers. As of 2022, the role of vitamin D in the prevention and treatment of diabetes, glucose intolerance, hypertension, multiple sclerosis, and other medical conditions remains under preliminary research.
Some preliminary studies link low vitamin D levels with disease later in life. One meta-analysis found a decrease in mortality in elderly people. Another meta-analysis covering over 350,000 people concluded that vitamin D supplementation in unselected community-dwelling individuals does not reduce skeletal (total fracture) or non-skeletal outcomes (myocardial infarction, ischemic heart disease, stroke, cerebrovascular disease, cancer) by more than 15%, and that further research trials with similar design are unlikely to change these conclusions. As of 2022, there is insufficient evidence for an effect of vitamin D supplementation on the risk of cancer. A 2019 meta-analysis found a small increase in risk of stroke when calcium and vitamin D supplements were taken together. | 1 | Applied and Interdisciplinary Chemistry |
PIV has been applied to a wide range of flow problems, varying from the flow over an aircraft wing in a wind tunnel to vortex formation in prosthetic heart valves. 3-dimensional techniques have been sought to analyze turbulent flow and jets.
Rudimentary PIV algorithms based on cross-correlation can be implemented in a matter of hours, while more sophisticated algorithms may require a significant investment of time. Several open source implementations are available. Application of PIV in the US education system has been limited due to high price and safety concerns of industrial research grade PIV systems. | 1 | Applied and Interdisciplinary Chemistry |
In petroleum industry parlance, production refers to the quantity of crude extracted from reserves, not the literal creation of the product. | 0 | Theoretical and Fundamental Chemistry |
Asymmetric Heck reactions establish quaternary or tertiary stereocenters. If migratory insertion generates a quaternary center adjacent to the palladium-carbon bond (as in reactions of trisubstituted or 1,1-disubstituted alkenes), β-hydride elimination toward that center is not possible and it is retained in the product. Similarly, β-hydride elimination is not possible if a hydrogen syn to the palladium-carbon bond is not available. Thus, tertiary stereocenters can be established in conformationally restricted systems. | 0 | Theoretical and Fundamental Chemistry |
The acceptable daily intake (ADI) is 0–4 mg/kg under both EU and WHO/FAO guidelines.
Sunset yellow FCF has no carcinogenicity, genotoxicity, or developmental toxicity in the amounts at which it is used.
It has been claimed since the late 1970s, under the advocacy of Benjamin Feingold, that sunset yellow FCF causes food intolerance and ADHD-like behavior in children, but there is no scientific evidence to support these broad claims. It is possible that certain food colorings may act as a trigger in those who are genetically predisposed, but the evidence is weak. | 0 | Theoretical and Fundamental Chemistry |
General Control Non-Derepressible 5 (Gcn5) –related N-Acetyltransferases (GNATs) is one of the many studied families with acetylation abilities. This superfamily includes the factors Gcn5 which is included in the SAGA, SLIK, STAGA, ADA, and A2 complexes, Gcn5L, p300/CREB-binding protein associated factor (PCAF), Elp3, HPA2 and HAT1. Major features of the GNAT family include HAT domains approximately 160 residues in length and a conserved bromodomain that has been found to be an acetyl-lysine targeting motif. Gcn5 has been shown to acetylate substrates when it is part of a complex. Recombinant Gcn5 has been found to be involved in the acetylation of the H3 histones of the nucleosome. To a lesser extent, it has been found to also acetylate H2B and H4 histones when involved with other complexes. PCAF has the ability to act as a HAT protein and acetylate histones, it can acetylate non-histone proteins related to transcription, as well as act as a coactivator in many processes including myogenesis, nuclear-receptor-mediated activation and growth-factor-signaled activation. Elp3 has the ability to acetylate all histone subunits and also shows involvement in the RNA polymerase II holoenzyme. | 0 | Theoretical and Fundamental Chemistry |
The hydrogen ion, or hydronium ion, is a Brønsted–Lowry acid when dissolved in HO and the hydroxide ion is a base because of the self-separating reaction
An analogous reaction occurs in liquid ammonia
Thus, the ammonium ion, , in liquid ammonia corresponds to the hydronium ion in water and the amide ion, in ammonia, to the hydroxide ion in water. Ammonium salts behave as acids, and amides behave as bases.
Some non-aqueous solvents can behave as bases, i.e. accept protons, in relation to Brønsted–Lowry acids.
where S stands for a solvent molecule. The most important of such solvents are dimethylsulfoxide, DMSO, and acetonitrile, , as these solvents have been widely used to measure the acid dissociation constants of carbon-containing molecules. Because DMSO accepts protons more strongly than the acid becomes stronger in this solvent than in water. Indeed, many molecules behave as acids in non-aqueous solutions but not in aqueous solutions. An extreme case occurs with carbon acids, where a proton is extracted from a bond.
Some non-aqueous solvents can behave as acids. An acidic solvent will make dissolved substances more basic. For example, the compound is known as acetic acid since it behaves as an acid in water. However it behaves as a base in liquid hydrogen chloride, a much more acidic solvent. | 0 | Theoretical and Fundamental Chemistry |
In the field of medicine, pelletization is referred to as the agglomeration process that converts fine powders or granules into more or less spherical pellets. The use of the technology increased because it allows for the controlled release of dosage form, which also lead to a uniform absorption with less mucosal irritation within the gastrointestinal tract. There are different pelletization processes applied in the pharmaceutical industry and these typically vary according to the bonding forces. Some examples of the processes include balling, compression, and spray congealing. Balling is similar to the wet (or green) pelletization used in the iron ore industry. | 1 | Applied and Interdisciplinary Chemistry |
The function of protein paucimannosylation remains largely unexplored in vertebrates. Recent literature however has emerged demonstrating that paucimannosylation play roles in mediating pathophysiological processes such as in inflammation, pathogen infection, cancer and in the development of stem cells and in normal homeostasis. For example, elevated expression of paucimannosidic proteins was shown in Mycobacterium tuberculosis infected macrophages, during preclampsia and on Tamm-Horsfall proteins secreted by human urothelial cells during urinary tract infections suggesting the involvement of paucimannosylation in those conditions. Additionally, sputum from individuals suffering from cystic fibrosis and airway infections were also observed to be rich in paucimannosidic proteins. Furthermore, paucimannosylation was reported to be prominent features of human neutrophils and in monocytes and macrophages. Recent literature have also demonstrated elevated signatures of paucimannosidic proteins associated with a range of human cancers including brain, breast, blood, melanoma, non-melanoma, liver, ovarian and prostate cancers. Enriched paucimannosidic glycoepitopes were found in the tumours when compared to the adjacent non-tumour tissues. Literature have also reported the presence of paucimannosylation in embryonic stem cells and neuronal stem cells, suggesting potential functional role(s) in these cells. Notably, deficiency of hexosaminidases results in clinically significant Tay-Sachs and Sandhoff diseases, which also implicates Hex and paucimannosidic proteins in those conditions.
Endogenous and exogenous binding partners of mammalian paucimannosidic glycans have been suggested, including the macrophage mannose receptor (CD206) and dectin-2. Other putative endogenous paucimannosidic protein receptors such as dectin-1, DC-SIGN and DC-SIGNR have been proposed, but experimental support is still lacking. Exogeneous binders of paucimannosidic glycans such as the Escherichia coli FimH and P. aeruginosa PA-IIL were also reported to play important roles in the adhesion and pathophysiology of these opportunistic pathogens. | 1 | Applied and Interdisciplinary Chemistry |
Metal dusting is "a catastrophic form of corrosion that occurs when susceptible materials are exposed to environments with high carbon activities." The corrosion manifests itself as a break-up of bulk metal to metal powder. The suspected mechanism is firstly the deposition of a graphite layer on the surface of the metal, usually from carbon monoxide (CO) in the vapour phase. This graphite layer is then thought to form metastable MC species (where M is the metal), which migrate away from the metal surface. However, in some regimes no MC species are observed indicating a direct transfer of metal atoms into the graphite layer.
The temperatures normally associated with metal dusting are high (300–850 °C). From a general understanding of chemistry, it can be deduced that at lower temperatures, the rate of reaction to form the metastable MC species is too low to be significant, and at much higher temperatures the graphite layer is unstable and so CO deposition does not occur (at least to any appreciable degree).
Very briefly, there are several proposed methods for prevention or reduction of metal dusting; the most common seem to be aluminide coatings, alloying with copper and addition of steam.
There is a significant amount of literature in existence that describes proposed mechanisms, prevention methods etc. There is also a good summary of metal dusting and some prevention methods in Corrosion by Carbon and Nitrogen - Metal Dusting, Carburisation and Nitridation | 1 | Applied and Interdisciplinary Chemistry |
If bodies are prepared with separately microscopically stationary states, and are then put into purely thermal connection with each other, by conductive or radiative pathways, they will be in thermal equilibrium with each other just when the connection is followed by no change in either body. But if initially they are not in a relation of thermal equilibrium, heat will flow from the hotter to the colder, by whatever pathway, conductive or radiative, is available, and this flow will continue until thermal equilibrium is reached and then they will have the same temperature.
One form of thermal equilibrium is radiative exchange equilibrium. Two bodies, each with its own uniform temperature, in solely radiative connection, no matter how far apart, or what partially obstructive, reflective, or refractive, obstacles lie in their path of radiative exchange, not moving relative to one another, will exchange thermal radiation, in net the hotter transferring energy to the cooler, and will exchange equal and opposite amounts just when they are at the same temperature. In this situation, Kirchhoff's law of equality of radiative emissivity and absorptivity and the Helmholtz reciprocity principle are in play. | 0 | Theoretical and Fundamental Chemistry |
Complex metallic alloys is an umbrella term for intermetallic compounds with a relatively large unit cell. There is no precise definition of how large the unit cell of a complex metallic alloy has to be, but the broadest definition includes Zintl phases, skutterudites, and Heusler compounds on the most simple end, and quasicrystals on the more complex end. | 1 | Applied and Interdisciplinary Chemistry |
A DNA-gelatin mixture may be used for printing onto a slide. Gelatin powder is first dissolved in sterile Milli-Q water to form a 0.2% gelatin solution. Purified DNA plasmid is then mixed with the gelatin solution, and the final gelatin concentration is kept greater than 0.17%. Besides gelatin, atelocollagen and fibronectin are also successful transfection vectors for introducing foreign DNA into the cell nucleus. | 1 | Applied and Interdisciplinary Chemistry |
Holmes undergraduate studies and masters research were conducted at the University of Melbourne where he was resident at Ormond College. Travelling to the UK on a Shell Overseas Science Scholarship, he performed his PhD work at University College London under the supervision of Franz Sondheimer. | 0 | Theoretical and Fundamental Chemistry |
The first protein complex of the photosynthesis component light-dependent reactions is referred to as photosystem II. The complex utilizes an enzyme to capture photons of light, providing the greater photosynthesis process with all of the electrons needed to produce ATP. Photosystem II is particularly temperature sensitive, and desphosphorylation has been implicated as a driver of plasticity in responding to varied temperature. Accelerated protein dephosphorylation in photosynthetic thylakoid membranes occurs at elevated temperatures, directly impacting the desphosphorylation of key proteins within the photosystem II complex. | 1 | Applied and Interdisciplinary Chemistry |
The recent development of electron spectroscopy makes it possible to reveal the electronic structures of molecules. Although this is mainly accomplished by electron analysers, electrostatic lenses also play a significant role in the development of electron spectroscopy.
Since electron spectroscopy detects several physical phenomena from the electrons emitted from samples, it is necessary to transport the electrons to the electron analyser. Electrostatic lenses satisfy the general properties of lenses. | 0 | Theoretical and Fundamental Chemistry |
A hydrogen analyzer can be used for direct measurement of hydrogen in liquid aluminium. Direct monitoring of hydrogen is possible using an on-line quantitative measurement technology based on a closed-loop gas recirculation method though a porous ceramic probe.
Since its introduction in 1989, this gas recirculation method has been increasingly used by major aluminum producers.
An example of analyzer for direct hydrogen measurement in liquid aluminium is the Accurity. It works with a probe immersed in liquid aluminium and it uses the closed-loop recirculation method. | 1 | Applied and Interdisciplinary Chemistry |
Electrokinetic phenomena are a family of several different effects that occur in heterogeneous fluids, or in porous bodies filled with fluid, or in a fast flow over a flat surface. The term heterogeneous here means a fluid containing particles. Particles can be solid, liquid or gas bubbles with sizes on the scale of a micrometer or nanometer. There is a common source of all these effects—the so-called interfacial double layer of charges. Influence of an external force on the diffuse layer generates tangential motion of a fluid with respect to an adjacent charged surface. This force might be electric, pressure gradient, concentration gradient, or gravity. In addition, the moving phase might be either continuous fluid or dispersed phase. | 0 | Theoretical and Fundamental Chemistry |
The field of crystallography, where X-rays are shone through crystals of a solid material, was founded by William Henry Bragg and his son William Lawrence Bragg at the Institute of Physics during and after World War II. Materials science became a major established discipline following the onset of the Silicon Age and Information Age. This led to the development of modern computers and then mobile phones, with the need to make them smaller, faster and more powerful leading to materials science developing smaller and lighter materials capable of dealing with more complex calculations. This in turn enabled computers to be used to solve complex crystallographic calculations and automate crystallography experiments, allowing researchers to design more accurate and powerful techniques. Along with computers and crystallography, the development of laser technology from 1960 onwards led to the development of light-emitting diodes (used in DVD players and smartphones), fibre-optic communication (used in global telecommunications), and confocal microscopy, a key tool in materials science. | 1 | Applied and Interdisciplinary Chemistry |
Dialysis is useful for many of the same desalting and buffer exchange applications performed with gel filtration chromatography, as both methods are based on similar molecular weight cut-off limits. Gel filtration has the advantage of speed (a few minutes vs. hours for dialysis) along with the ability to remove contaminants from relatively small-volume samples compared to dialysis which is an important feature when working with toxic or radioactive substances. Dialysis, on the other hand, is much less dependent on sample size as related to device format. For dialysis applications, achieving a high percentage sample recovery and molecule removal is generally straight forward with little optimization. For gel filtration applications it is important to select a column size and format that is suitable for your sample. | 0 | Theoretical and Fundamental Chemistry |
EQCM can be used to ideally modify polymer membranes together with other electrochemical measurements or surface characterization methods. A team has used CV, UV-Vis, IR and EQCM studied irreversible changes of some polythiophenes in the electrochemical reduction process in acetonitrile. Later on they used AFM and EQCM investigated growth of polypyrrole film in anionic surfactant micellar solution. Then combing with CV, UV-Vis, FTIR, ESR, they used EQCM to study conductivity and magnetic properties of 3,4-dimethoxy and 3,4-ethylenedioxy-terminated polypyrrole and polythiophene. | 0 | Theoretical and Fundamental Chemistry |
Knock-in technology is different from knockout technology in that knockout technology aims to either delete part of the DNA sequence or insert irrelevant DNA sequence information to disrupt the expression of a specific genetic locus. Gene knock-in technology, on the other hand, alters the genetic locus of interest via a one-for-one substitution of DNA sequence information or by the addition of sequence information that is not found on said genetic locus. A gene knock-in therefore can be seen as a gain-of-function mutation and a gene knockout a loss-of-function mutation, but a gene knock-in may also involve the substitution of a functional gene locus for a mutant phenotype that results in some loss of function. | 1 | Applied and Interdisciplinary Chemistry |
Clay chemistry is an applied subdiscipline of chemistry which studies the chemical structures, properties and reactions of or involving clays and clay minerals. It is a multidisciplinary field, involving concepts and knowledge from inorganic and structural chemistry, physical chemistry, materials chemistry, analytical chemistry, organic chemistry, mineralogy, geology and others.
The study of the chemistry (and physics) of clays and clay minerals is of great academic and industrial relevance as they are among the most widely used industrial minerals, being employed as raw materials (ceramics, pottery, etc.), adsorbents, catalysts, additives, mineral charges, medicines, building materials and others.
The unique properties of clay minerals including: nanometric scale layered construction, presence of fixed and interchangeable charges, possibility of adsorbing and hosting (intercalating) molecules, ability of forming stable colloidal dispersions, possibility of tailored surface and interlayer chemical modification and others, make the study of clay chemistry a very important and extremely varied field of research.
Many distinct fields and knowledge areas are impacted by the physico-chemical behavior of clay minerals, from environmental sciences to chemical process engineering, from pottery to nuclear waste management.
Their cation exchange capacity (CEC) is of great importance in the balance of the most common cations in soil (Na, K, NH, Ca, Mg) and pH control, with direct impact on the soil fertility. It also plays an important role in the fate of most Ca arriving from land (river water) into the seas.
The ability to change and control the CEC of clay minerals offers a valuable tool in the development of selective adsorbents with applications as varied as chemical sensors or pollution cleaning substances for contaminated water, for example.
The understanding of the reactions of clay minerals with water (intercalation, adsorption, colloidal dispersion, etc.) are indispensable for the ceramic industry (plasticity and flow control of ceramic raw mixtures, for example). Those interactions also influence a great number of mechanical properties of soils, being carefully studied by building and construction engineering specialists.
The interactions of clay minerals with organic substances in the soil also plays a vital role in the fixation of nutrients and fertility, as well as in the fixation or leaching of pesticides and other contaminants. Some clay minerals (kaolinite) are used as carrier material for fungicides and insecticides.
The weathering of many rock types produce clay minerals as one of its last products. The understanding of these geochemical processes is also important for the understanding of geological evolution of landscapes and macroscopic properties of rocks and sediments. Presence of clay minerals in Mars, detected by the Mars Reconnaissance Orbiter in 2009 was another strong evidence of the existence of water on the planet in previous geological eras.
The possibility to disperse nanometric scaled clay mineral particles into a matrix of polymer, with the formation of an inorganic-organic nanocomposite has prompted a large resurgence in the study of these minerals from the late 1990s.
In addition, study of clay chemistry is also of great relevance to the chemical industry, as many clay minerals are used as catalysts, catalyst precursors or catalyst substrates in a number of chemical processes, like automotive catalysts and oil cracking catalysts. | 0 | Theoretical and Fundamental Chemistry |
Waters was born Joyce Mary Partridge in Auckland on 2 June 1931, the daughter of Mary Elizabeth Partridge (née Harrison) and Thomas Harold Charles Partridge. She was educated at Diocesan School for Girls, Auckland, from 1938 to 1949, and went on to study at Auckland University College, graduating Bachelor of Science in 1954, Master of Science with first-class honours in 1955, and PhD in 1960. The title of her doctoral thesis, supervised by John Llewellyn and David Hall, was A study of some co-ordination compounds formed between nickel diammines and the nitrite ion. She was the second woman to complete a PhD in chemistry at Auckland.
In 1959, she married fellow inorganic chemist Neil Waters, who was knighted in 1995. | 0 | Theoretical and Fundamental Chemistry |
Less ambiguous than the above ichnogenera, are the traces left behind by invertebrates such as Hibbertopterus, a giant "sea scorpion" or eurypterid of the early Paleozoic era. This marine arthropod produced a spectacular track preserved in Scotland.
Bioerosion through time has produced a magnificent record of borings, gnawings, scratchings and scrapings on hard substrates. These trace fossils are usually divided into macroborings and microborings. Bioerosion intensity and diversity is punctuated by two events. One is called the Ordovician Bioerosion Revolution (see Wilson & Palmer, 2006) and the other was in the Jurassic. For a comprehensive bibliography of the bioerosion literature, please see the External links below.
The oldest types of tetrapod tail-and-footprints date back to the latter Devonian period. These vertebrate impressions have been found in Ireland, Scotland, Pennsylvania, and Australia. A sandstone slab containing the track of tetrapod, dated to 400 million years, is amongst the oldest evidence of a vertebrate walking on land.
Important human trace fossils are the Laetoli (Tanzania) footprints, imprinted in volcanic ash 3.7 Ma (million years ago) – probably by an early Australopithecus. | 1 | Applied and Interdisciplinary Chemistry |
Fulmer Research Institute was founded in 1945 by Col W C (Dev) Devereux and incorporated in 1946. He had been a pioneer in the use of light metal alloys in aero engines and, in the Second World War, he had an important role in the UK Ministry of Aircraft Production, organizing the assembly in Britain of American aircraft and reorganizing the repair of aircraft and aero-engines.
After the war, in 1945, he set up a company called Almin Ltd (Associated Light Metal Industries) which brought together a group of companies mostly concerned with the production and processing of aluminium and magnesium alloys. He wanted Almin to have research facilities but he recognised that Almin's R&D needs alone were not sufficient to justify the investment in staff and capital equipment required for properly equipped laboratories. His answer was to establish a contract research organization
along the lines of Battelle Memorial Institute and The Mellon Institute of Industrial Research in the USA.
Thus he founded Fulmer Research Institute as one of the first contract research companies in Britain. Initially it was in temporary accommodation but he soon found a permanent base by purchasing a large Edwardian country house with ten acres of grounds, in the Buckinghamshire village of Stoke Poges. The name Fulmer was the name of the local telephone exchange and that of a nearby village. | 1 | Applied and Interdisciplinary Chemistry |
*Gamma (γ): This is the matrix phase. While Co-based superalloys are less-used commercially, alloying elements include C, Cr, W, Ni, Ti, Al, Ir, and Ta. As in stainless steels, Chromium is used (occasionally up to 20 wt.%) to improve resistance to oxidation and corrosion via the formation of a CrO passive layer, which is critical for use in gas turbines, but also provides solid-solution strengthening due to the mismatch in the atomic radii of Co and Cr, and precipitation hardening due to the formation of MC-type carbides.
* Gamma Prime (γ): Constitutes the precipitate used to strengthen the alloy. It is usually close-packed with a L1 structure of CoTi or FCC CoTa, though both W and Al integrate into these cuboidal precipitates. Ta, Nb, and Ti integrate into the γ phase and are stabilize it at high temperatures.
* Carbide Phases: Carbides strengthen the alloy through precipitation hardening but decrease low-temperature ductility.
* Topologically Close-Packed (TCP) phases may appear in some Co-based superalloys, but embrittle the alloy and are thus undesirable. | 1 | Applied and Interdisciplinary Chemistry |
Colorimetric assays use reagents that undergo a measurable color change in the presence of the analyte. They are widely used in biochemistry to test for the presence of enzymes, specific compounds, antibodies, hormones and many more analytes. For example,
*para-Nitrophenylphosphate is converted into a yellow product by alkaline phosphatase enzyme.
*Coomassie Blue is an aromatic dye that binds to aromatic proteins and positively charged amino acid residues within the protein structure. The binding interaction results in a spectrum shift, enabling quantitative measurement of the protein concentration. A similar colorimetric assay, the Bicinchoninic acid assay, uses a chemical reaction to determine protein concentration.
*The Biuret assay utilizes a biuret reagent which turns purple in the presence of proteins due to the chelation of copper salts in an alkaline solution.
*Enzyme linked immunoassays use enzyme-complexed-antibodies to detect antigens. Binding of the antibody is often inferred from the color change of reagents such as TMB. | 0 | Theoretical and Fundamental Chemistry |
Russell (1883) studied the chemical composition of the different tufa types in Lake Lahontan, a large Pleistocene system of multiple lakes in California, Nevada, and Oregon. Not surprisingly, it was found that the tufas consisted primarily of CaO and . However, they also contain minor constituents of MgO (~2 wt%), Fe/Al-oxides (.25-1.29 wt%), and PO (0.3 wt%). | 1 | Applied and Interdisciplinary Chemistry |
In medical terminology, the term photopigment is applied to opsin-type photoreceptor proteins, specifically rhodopsin and photopsins, the photoreceptor proteins in the retinal rods and cones of vertebrates that are responsible for visual perception, but also melanopsin and others. | 1 | Applied and Interdisciplinary Chemistry |
The two oil price shocks had many short- and long-term effects on global politics and the global economy. They led to sustained reductions in demand as a result of substitution to other fuels, especially coal and nuclear, and improvements in energy efficiency, facilitated by government policies. High oil prices also induced investment in oil production by non-OPEC countries, including Prudhoe Bay in Alaska, the North Sea offshore fields of the United Kingdom and Norway, the Cantarell offshore field of Mexico, and oil sands in Canada.
About 90 percent of vehicular fuel needs are met by oil. Petroleum also makes up 40 percent of total energy consumption in the United States, but is responsible for only one percent of electricity generation. Petroleums worth as a portable, dense energy source powering the vast majority of vehicles and as the base of many industrial chemicals makes it one of the worlds most important commodities.
The top three oil-producing countries as of 2018 are the United States, Russia, and Saudi Arabia. In 2018, due in part to developments in hydraulic fracturing and horizontal drilling, the United States became the world's largest producer.
About 80 percent of the worlds readily accessible reserves are located in the Middle East, with 62.5 percent coming from the Arab five: Saudi Arabia, United Arab Emirates, Iraq, Qatar, and Kuwait. A large portion of the worlds total oil exists as unconventional sources, such as bitumen in Athabasca oil sands and extra heavy oil in the Orinoco Belt. While significant volumes of oil are extracted from oil sands, particularly in Canada, logistical and technical hurdles remain, as oil extraction requires large amounts of heat and water, making its net energy content quite low relative to conventional crude oil. Thus, Canada's oil sands are not expected to provide more than a few million barrels per day in the foreseeable future. | 0 | Theoretical and Fundamental Chemistry |
In rare cases, carbido ligands are terminal. One example is with a Ru-C distance of 163 pm, typical for a triple bond. The complex can be obtained by metathesis of vinyl acetate to give results in a metastable complex, which eliminates acetic acid.
Such transition metal, one coordinate-carbon bonded complexes are comparable to carbon monoxide, cyanide, and isonitrile analogues. These carbides can be used as synthons to access a wide range of carbyne complexes, the most notable being Fischer carbynes. American chemist Christopher C. Cummins is one of the pioneers of this area. | 0 | Theoretical and Fundamental Chemistry |
A slurry is a mixture of denser solids suspended in liquid, usually water. The most common use of slurry is as a means of transporting solids or separating minerals, the liquid being a carrier that is pumped on a device such as a centrifugal pump. The size of solid particles may vary from 1 micrometre up to hundreds of millimetres.
The particles may settle below a certain transport velocity and the mixture can behave like a Newtonian or non-Newtonian fluid. Depending on the mixture, the slurry may be abrasive and/or corrosive. | 1 | Applied and Interdisciplinary Chemistry |
Simultaneous measurement of and for 1:1 adducts is routinely carried out using isothermal titration calorimetry. Extension to more complex systems is limited by the availability of suitable software. | 0 | Theoretical and Fundamental Chemistry |
The balance of dissimilatory nitrate reduction to ammonium and denitrification alters the accuracy of f-ratio calculations. The f-ratio is used to quantify the efficiency of the biological pump, which reflects sequestering of carbon from the atmosphere to the deep sea. The f-ratio is calculated using estimates of new production (primary productivity stimulated by nutrients entering the photic zone from outside the photic zone, for example from the deep ocean) and regenerated production (primary productivity stimulated by nutrients already in the photic zone, released by remineralisation). Calculations of the f-ratio use the nitrogen species stimulating primary productivity as a proxy for the type of production occurring; productivity stimulated by NH rather than NO is regenerated production. DNRA also produces NH (in addition to remineralisation) but from organic matter which has been exported from the photic zone; this may be subsequently reintroduced by mixing or upwelling of deeper water back to the surface, thereby, stimulating primary productivity; thus, in areas where high amounts of DNRA is occurring, f-ratio calculations will not be accurate. | 1 | Applied and Interdisciplinary Chemistry |
The FDA label contains warnings that rasagiline may cause severe hypertension or hypotension, may make people sleepy, may make motor control worse in some people, may cause hallucinations and psychotic-like behavior, may cause impulse control disorder, may increase the risk of melanoma, and upon withdrawal may cause high fever or confusion.
Side effects when the drug is taken alone include flu-like symptoms, joint pain, depression, stomach upset, headache, dizziness, and insomnia. When taken with L-DOPA, side effects include increased movement problems, accidental injury, sudden drops in blood pressure, joint pain and swelling, dry mouth, rash, abnormal dreams and digestive problems including vomiting, loss of appetite, weight loss, abdominal pain, nausea, constipation. When taken with Parkinson's drugs other than L-DOPA, side effects include peripheral edema, fall, joint pain, cough, and insomnia. | 0 | Theoretical and Fundamental Chemistry |
Indolicidin is an antimicrobial peptide isolated from neutrophil blood cells of cows. The mature peptide is just 13 amino acids, making it one of the smallest antimicrobial peptides known to be encoded as the primary product of the encoding antimicrobial peptide gene. Indolicidin is active against bacterial pathogens, but has also been shown to kill fungi and even HIV virus. | 0 | Theoretical and Fundamental Chemistry |
The first use of a bioassay dates back to the late 19th century, when the foundation of bioassays was laid down by German physician Paul Ehrlich. He introduced the concept of standardization by the reactions of living matter. His bioassay on diphtheria antitoxin was the first bioassay to receive recognition. His use of bioassay was able to discover that administration of gradually increasing dose of diphtheria in animals stimulated production of antiserum.
One well known example of a bioassay is the "canary in the coal mine" experiment. To provide advance warning of dangerous levels of methane in the air, miners would take methane-sensitive canaries into coal mines. If the canary died due to a build-up of methane, the miners would leave the area as quickly as possible.
Many early examples of bioassays used animals to test the carcinogenicity of chemicals. In 1915, Yamaigiwa Katsusaburo and Koichi Ichikawa tested the carcinogenicity of coal tar using the inner surface of rabbit's ears.
From the 1940s to the 1960s, animal bioassays were primarily used to test the toxicity and safety of drugs, food additives, and pesticides.
Beginning in the late 1960s and 1970s, reliance on bioassays increased as public concern for occupational and environmental hazards increased. | 1 | Applied and Interdisciplinary Chemistry |
The energy density of sound waves decreases as they become farther apart so increasing the distance between the receiver and source results in a progressively lesser intensity of sound at the receiver. In a normal three-dimensional setting, with a point source and point receptor, the intensity of sound waves will be attenuated according to the inverse square of the distance from the source. | 1 | Applied and Interdisciplinary Chemistry |
Alloying elements are added to a base metal, to induce hardness, toughness, ductility, or other desired properties. Most metals and alloys can be work hardened by creating defects in their crystal structure. These defects are created during plastic deformation by hammering, bending, extruding, et cetera, and are permanent unless the metal is recrystallized. Otherwise, some alloys can also have their properties altered by heat treatment. Nearly all metals can be softened by annealing, which recrystallizes the alloy and repairs the defects, but not as many can be hardened by controlled heating and cooling. Many alloys of aluminium, copper, magnesium, titanium, and nickel can be strengthened to some degree by some method of heat treatment, but few respond to this to the same degree as does steel.
The base metal iron of the iron-carbon alloy known as steel, undergoes a change in the arrangement (allotropy) of the atoms of its crystal matrix at a certain temperature (usually between and , depending on carbon content). This allows the smaller carbon atoms to enter the interstices of the iron crystal. When this diffusion happens, the carbon atoms are said to be in solution in the iron, forming a particular single, homogeneous, crystalline phase called austenite. If the steel is cooled slowly, the carbon can diffuse out of the iron and it will gradually revert to its low temperature allotrope. During slow cooling, the carbon atoms will no longer be as soluble with the iron, and will be forced to precipitate out of solution, nucleating into a more concentrated form of iron carbide (FeC) in the spaces between the pure iron crystals. The steel then becomes heterogeneous, as it is formed of two phases, the iron-carbon phase called cementite (or carbide), and pure iron ferrite. Such a heat treatment produces a steel that is rather soft. If the steel is cooled quickly, however, the carbon atoms will not have time to diffuse and precipitate out as carbide, but will be trapped within the iron crystals. When rapidly cooled, a diffusionless (martensite) transformation occurs, in which the carbon atoms become trapped in solution. This causes the iron crystals to deform as the crystal structure tries to change to its low temperature state, leaving those crystals very hard but much less ductile (more brittle).
While the high strength of steel results when diffusion and precipitation is prevented (forming martensite), most heat-treatable alloys are precipitation hardening alloys, that depend on the diffusion of alloying elements to achieve their strength. When heated to form a solution and then cooled quickly, these alloys become much softer than normal, during the diffusionless transformation, but then harden as they age. The solutes in these alloys will precipitate over time, forming intermetallic phases, which are difficult to discern from the base metal. Unlike steel, in which the solid solution separates into different crystal phases (carbide and ferrite), precipitation hardening alloys form different phases within the same crystal. These intermetallic alloys appear homogeneous in crystal structure, but tend to behave heterogeneously, becoming hard and somewhat brittle.
In 1906, precipitation hardening alloys were discovered by Alfred Wilm. Precipitation hardening alloys, such as certain alloys of aluminium, titanium, and copper, are heat-treatable alloys that soften when quenched (cooled quickly), and then harden over time. Wilm had been searching for a way to harden aluminium alloys for use in machine-gun cartridge cases. Knowing that aluminium-copper alloys were heat-treatable to some degree, Wilm tried quenching a ternary alloy of aluminium, copper, and the addition of magnesium, but was initially disappointed with the results. However, when Wilm retested it the next day he discovered that the alloy increased in hardness when left to age at room temperature, and far exceeded his expectations. Although an explanation for the phenomenon was not provided until 1919, duralumin was one of the first "age hardening" alloys used, becoming the primary building material for the first Zeppelins, and was soon followed by many others. Because they often exhibit a combination of high strength and low weight, these alloys became widely used in many forms of industry, including the construction of modern aircraft. | 1 | Applied and Interdisciplinary Chemistry |
In deeper water, Stokes waves are unstable. This was shown by T. Brooke Benjamin and Jim E. Feir in 1967. The Benjamin–Feir instability is a side-band or modulational instability, with the side-band modulations propagating in the same direction as the carrier wave; waves become unstable on deeper water for a relative depth (with k the wavenumber and h the mean water depth). The Benjamin–Feir instability can be described with the nonlinear Schrödinger equation, by inserting a Stokes wave with side bands. Subsequently, with a more refined analysis, it has been shown – theoretically and experimentally – that the Stokes wave and its side bands exhibit Fermi–Pasta–Ulam–Tsingou recurrence: a cyclic alternation between modulation and demodulation.
In 1978 Longuet-Higgins, by means of numerical modelling of fully non-linear waves and modulations (propagating in the carrier wave direction), presented a detailed analysis of the region of instability in deep water: both for superharmonics (for perturbations at the spatial scales smaller than the wavelength ) and subharmonics (for perturbations at the spatial scales larger than ).
With increase of Stokes wave's amplitude, new modes of superharmonic instability appear. Appearance of a new branch of instability happens when the energy of the wave passes extremum. Detailed analysis of the mechanism of appearance of the new branches of instability has shown that their behavior follows closely a simple law, which allows to find with a good accuracy instability growth rates for all known and predicted branches.
In Longuet-Higgins studies of two-dimensional wave motion, as well as the subsequent studies of three-dimensional modulations by McLean et al., new types of instabilities were found – these are associated with resonant wave interactions between five (or more) wave components. | 1 | Applied and Interdisciplinary Chemistry |
Rain gardens are a form of stormwater management using water capture. Rain gardens are shallow depressed areas in the landscape, planted with shrubs and plants that are used to collect rainwater from roofs or pavement and allows for the stormwater to slowly infiltrate into the ground . Rain gardens mimic natural landscape functions by capturing stormwater, filtering out pollutants, and recharging groundwater. A study done in 2008 explains how rain gardens and stormwater planters are easy to incorporate into urban areas where they will improve the streets by minimizing the effects of drought and helping out with stormwater runoff. Stormwater planters can easily fit between other street landscapes and ideal in areas where spacing is tight. | 1 | Applied and Interdisciplinary Chemistry |
CerMet fuel consists of ceramic fuel particles (usually uranium oxide) embedded in a metal matrix. It is hypothesized that this type of fuel is what is used in United States Navy reactors. This fuel has high heat transport characteristics and can withstand a large amount of expansion. | 0 | Theoretical and Fundamental Chemistry |
Operational backscattering spectrometers at reactors include IN10, IN13, and IN16B at the Institut Laue-Langevin, the High Flux Backscattering Spectrometer (HFBS) at the NIST Center for Neutron Research,
the SPHERES instrument of Forschungszentrum Jülich at FRM II
and EMU at ANSTO. | 0 | Theoretical and Fundamental Chemistry |
This family of clusters includes the closo cages and their derivatives.
Isomerism is well established in this family:
*2,3- and 2,4-
*2,3- and 2,4-
*1,2- and 1,6-
*1,10-, 1,6-, and 1,2-
*1,2 and 1,3-. | 0 | Theoretical and Fundamental Chemistry |
Human perilipin-1 is composed by 522 amino acids, which add up to a molecular mass of 55.990 kDa. It presents an estimated number of 15 phosphorylation sites (residues 81, 85, 126, 130, 132, 137, 174, 299, 301, 382, 384, 408, 436, 497, 499 and 522) from which 3 -those in bold- have been suggested to be relevant for stimulated-lipolysis through PKA phosphorylation - they correspond respectively to PKA Phosphorylation sites 1, 5 and 6. A compositional bias of Glutamic acid can be found between residues 307 and 316. Its secondary structure has been suggested to be conformed exclusively by partially hydrophobic α-helixes, as well as the respective coils and bends.
Whereas perilipin-1 is coded by a single gene, alternative mRNA splicing processes can lead to three protein isoforms (Perilipin A, B and C). Both Perilipin A and B present common N-terminal regions, differing in the C-terminal ones. Concretely, beginning from the N-terminal of Perilipin-1, a PAT domain—characteristic of its protein family—can be found, followed by an also characteristic repeated sequence of 13 residues which form amphipathic helixes with an active role in linking membranes and a 4-helix bundle before the C-terminal carbon. In Perilipin A, lipophile nature is conferred by the slightly hydrophobic amino acids concentrated in the central 25% of the sequence, region that anchors the protein to the core of the lipid droplet. | 1 | Applied and Interdisciplinary Chemistry |
Selenizza is a naturally occurring solid hydrocarbon bitumen found in native deposits in Selenice, in Albania, the only European asphalt mine still in use. The bitumen is found in the form of veins, filling cracks in a more or less horizontal direction. The bitumen content varies from 83% to 92% (soluble in carbon disulphide), with a penetration value near to zero and a softening point (ring and ball) around 120 °C. The insoluble matter, consisting mainly of silica ore, ranges from 8% to 17%.
Albanian bitumen extraction has a long history and was practiced in an organized way by the Romans. After centuries of silence, the first mentions of Albanian bitumen appeared only in 1868, when the Frenchman Coquand published the first geological description of the deposits of Albanian bitumen. In 1875, the exploitation rights were granted to the Ottoman government and in 1912, they were transferred to the Italian company Simsa. Since 1945, the mine was exploited by the Albanian government and from 2001 to date, the management passed to a French company, which organized the mining process for the manufacture of the natural bitumen on an industrial scale.
Today the mine is predominantly exploited in an open pit quarry but several of the many underground mines (deep and extending over several km) still remain viable. Selenizza is produced primarily in granular form, after melting the bitumen pieces selected in the mine.
Selenizza is mainly used as an additive in the road construction sector. It is mixed with traditional bitumen to improve both the viscoelastic properties and the resistance to ageing. It may be blended with the hot bitumen in tanks, but its granular form allows it to be fed in the mixer or in the recycling ring of normal asphalt plants. Other typical applications include the production of mastic asphalts for sidewalks, bridges, car-parks and urban roads as well as drilling fluid additives for the oil and gas industry. Selenizza is available in powder or in granular material of various particle sizes and is packaged in sacks or in thermal fusible polyethylene bags.
A life-cycle assessment study of the natural selenizza compared with petroleum bitumen has shown that the environmental impact of the selenizza is about half the impact of the road asphalt produced in oil refineries in terms of carbon dioxide emission. | 0 | Theoretical and Fundamental Chemistry |
Halothane is an ozone depleting substance with an ODP of 1.56 and it is calculated to be responsible for 1% of total stratospheric ozone layer depletion. | 0 | Theoretical and Fundamental Chemistry |
The radioactivity of all radioactive waste weakens with time. All radionuclides contained in the waste have a half-life — the time it takes for half of the atoms to decay into another nuclide. Eventually, all radioactive waste decays into non-radioactive elements (i.e., stable nuclides). Since radioactive decay follows the half-life rule, the rate of decay is inversely proportional to the duration of decay. In other words, the radiation from a long-lived isotope like iodine-129 will be much less intense than that of a short-lived isotope like iodine-131. The two tables show some of the major radioisotopes, their half-lives, and their radiation yield as a proportion of the yield of fission of uranium-235.
The energy and the type of the ionizing radiation emitted by a radioactive substance are also important factors in determining its threat to humans. The chemical properties of the radioactive element will determine how mobile the substance is and how likely it is to spread into the environment and contaminate humans. This is further complicated by the fact that many radioisotopes do not decay immediately to a stable state but rather to radioactive decay products within a decay chain before ultimately reaching a stable state. | 0 | Theoretical and Fundamental Chemistry |
In real-life situations, particles in solution do not have a fixed size, resulting in the probability that a particle that would otherwise be hampered by a pore passing right by it. Also, the stationary-phase particles are not ideally defined; both particles and pores may vary in size. Elution curves, therefore, resemble Gaussian distributions. The stationary phase may also interact in undesirable ways with a particle and influence retention times, though great care is taken by column manufacturers to use stationary phases that are inert and minimize this issue.
Like other forms of chromatography, increasing the column length enhances resolution, and increasing the column diameter increases column capacity. Proper column packing is important for maximum resolution: An over-packed column can collapse the pores in the beads, resulting in a loss of resolution. An under-packed column can reduce the relative surface area of the stationary phase accessible to smaller species, resulting in those species spending less time trapped in pores. Unlike affinity chromatography techniques, a solvent head at the top of the column can drastically diminish resolution as the sample diffuses prior to loading, broadening the downstream elution. | 1 | Applied and Interdisciplinary Chemistry |
Schlichting jet is a steady, laminar, round jet, emerging into a stationary fluid of the same kind with very high Reynolds number. The problem was formulated and solved by Hermann Schlichting in 1933, who also formulated the corresponding planar Bickley jet problem in the same paper. The Landau-Squire jet from a point source is an exact solution of Navier-Stokes equations, which is valid for all Reynolds number, reduces to Schlichting jet solution at high Reynolds number, for distances far away from the jet origin. | 1 | Applied and Interdisciplinary Chemistry |
DN does not exactly correspond to a size in millimeters, because ISO 6708 defines it as being a dimensionless specification only indirectly related to a diameter. The ISO 6708 sizes provide a metric name for existing inch sizes, resulting in a 1:1 correlation between NPS and DN sizes. ISO 6708 does not include values for "DN 6" or "DN 8", however ASME B36.10M list the "DN 6" and "DN 8" . Also, the European Standard [https://www.techstreet.com/standards/din-en-12516-1?product_id=2027332 EN 12 516-1] (Industrial valves - Shell design strength - Part 1: Tabulation method for steel valve shells) specifies the dimensions "DN 6" and "DN 8", respectively their equivalents NPS "and NPS ".
Tolerance: The tolerance on pipe OD is + (0.0156) inch (), − (0.0312) inch ().
As per [https://www.asme.org/products/codes-standards/b3610m-2018-welded-seamless-wrought-steel-pipe ASME B36.10M -2018] Pipe wall thickness are rounded to nearest , while converting wall thickness from inch to millimetre. | 1 | Applied and Interdisciplinary Chemistry |
For standards relating to ventilation rates, in the United States refer to ASHRAE Standard 62.1-2010: Ventilation for Acceptable Indoor Air Quality. These requirements are for "all spaces intended for human occupancy except those within single-family houses, multifamily structures of three stories or fewer above grade, vehicles, and aircraft." In the revision to the standard in 2010, Section 6.4 was modified to specify that most buildings designed to have systems to naturally condition spaces must also "include a mechanical ventilation system designed to meet the Ventilation Rate or IAQ procedures [in ASHRAE 62.1-2010]. The mechanical system is to be used when windows are closed due to extreme outdoor temperatures noise and security concerns". The standard states that two exceptions in which naturally conditioned buildings do not require mechanical systems are when:
* Natural ventilation openings that comply with the requirements of Section 6.4 are permanently open or have controls that prevent the openings from being closed during period of expected occupancy, or
* The zone is not served by heating or cooling equipment.
Also, an authority having jurisdiction may allow for the design of conditioning system that does not have a mechanical system but relies only on natural systems. In reference for how controls of conditioning systems should be designed, the standard states that they must take into consideration measures to "properly coordinate operation of the natural and mechanical ventilation systems."
Another reference is ASHRAE Standard 62.2-2010: Ventilation and Acceptable Indoor Air Quality in low-rise Residential Buildings. These requirements are for "single-family houses and multifamily structures of three stories or fewer above grade, including manufactured and modular houses," but is not applicable "to transient housing such as hotels, motels, nursing homes, dormitories, or jails."
For standards relating to ventilation rates, in the United States refer to ASHRAE Standard 55-2010: Thermal Environmental Conditions for Human Occupancy. Throughout its revisions, its scope has been consistent with its currently articulated purpose, “to specify the combinations of indoor thermal environmental factors and personal factors that will produce thermal environmental conditions acceptable to a majority of the occupants within the space.” The standard was revised in 2004 after field study results from the ASHRAE research project, RP-884: developing an adaptive model of thermal comfort and preference, indicated that there are differences between naturally and mechanically conditioned spaces with regards to occupant thermal response, change in clothing, availability of control, and shifts in occupant expectations. The addition to the standard, 5.3: Optional Method For Determining Acceptable Thermal Conditions in Naturally Ventilated Spaces, uses an adaptive thermal comfort approach for naturally conditioned buildings by specifying acceptable operative temperature ranges for naturally conditioned spaces. As a result, the design of natural ventilation systems became more feasible, which was acknowledged by ASHRAE as a way to further sustainable, energy efficient, and occupant-friendly design. | 1 | Applied and Interdisciplinary Chemistry |
Also called Chimney effect or Stack effect, observes that warm air (from the hot shower) rises out over the shower curtain as cooler air (near the floor) pushes in under the curtain to replace the rising air. By pushing the curtain in towards the shower, the (short range) vortex and Coandă effects become more significant. However, the shower-curtain effect persists when cold water is used, implying that this is not the sole mechanism. | 1 | Applied and Interdisciplinary Chemistry |
The self-information, also known as the information content of a signal, random variable, or event is defined as the negative logarithm of the probability of the given outcome occurring.
When applied to a discrete random variable, the self-information can be represented as
is the relative entropy of the probability distribution from a Kronecker delta representing certainty that — i.e. the number of extra bits that must be transmitted to identify if only the probability distribution is available to the receiver, not the fact that . | 0 | Theoretical and Fundamental Chemistry |
ETF-QO consists of one structural domain with three functional domains packed in close proximity: a FAD domain, a 4Fe4S cluster domain, and a UQ-binding domain. FAD is in an extended conformation and is buried deeply within its functional domain. Multiple hydrogen bonds and a positive helix dipole modulate the redox potential of FAD and can possibly stabilize the anionic semiquinone intermediate. The 4Fe4S cluster is also stabilized by extensive hydrogen bonding around the cluster and its cysteine components. Ubiquinone binding is achieved through a deep hydrophobic binding pocket which is a different mode than other UQ-binding proteins such as succinate-Q oxidoreductase. Although ETF-QO is an integral membrane protein, it does not traverse the entire membrane unlike other UQ-binding proteins. | 1 | Applied and Interdisciplinary Chemistry |
An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the agonist, while an inverse agonist causes an action opposite to that of the agonist. | 1 | Applied and Interdisciplinary Chemistry |
The alpha process, also known as alpha capture or the alpha ladder, is one of two classes of nuclear fusion reactions by which stars convert helium into heavier elements. The other class is a cycle of reactions called the triple-alpha process, which consumes only helium, and produces carbon. The alpha process most commonly occurs in massive stars and during supernovae.
Both processes are preceded by hydrogen fusion, which produces the helium that fuels both the triple-alpha process and the alpha ladder processes. After the triple-alpha process has produced enough carbon, the alpha-ladder begins and fusion reactions of increasingly heavy elements take place, in the order listed below. Each step only consumes the product of the previous reaction and helium. The later-stage reactions which are able to begin in any particular star, do so while the prior stage reactions are still under way in outer layers of the star.
The energy produced by each reaction, , is mainly in the form of gamma rays (), with a small amount taken by the byproduct element, as added momentum.
It is a common misconception that the above sequence ends at (or , which is a decay product of ) because it is the most tightly bound nuclide – i.e., the nuclide with the highest nuclear binding energy per nucleon – and production of heavier nuclei would consume energy (be endothermic) instead of release it (exothermic). (Nickel-62) is actually the most tightly bound nuclide in terms of binding energy (though has a lower energy or mass per nucleon). The reaction is actually exothermic, and indeed adding alphas continues to be exothermic all the way to , but nonetheless the sequence does effectively end at iron. The sequence stops before producing because conditions in stellar interiors cause the competition between photodisintegration and the alpha process to favor photodisintegration around iron. This leads to more being produced than
All these reactions have a very low rate at the temperatures and densities in stars and therefore do not contribute significant energy to a star's total output. They occur even less easily with elements heavier than neon due to the increasing Coulomb barrier. | 0 | Theoretical and Fundamental Chemistry |
Strange quarks are naturally radioactive and decay by weak interactions into lighter quarks on a timescale that is extremely long compared with the nuclear-collision times. This makes it relatively easy to detect strange particles through the tracks left by their decay products. Consider as an example the decay of a negatively charged baryon (green in figure, dss), into a negative pion (d) and a neutral (uds) baryon. Subsequently, the decays into a proton and another negative pion. In general this is the signature of the decay of a . Although the negative (sss) baryon has a similar final state decay topology, it can be clearly distinguished from the because its decay products are different.
Measurement of abundant formation of (uss/dss), (sss) and especially their antiparticles is an important cornerstone of the claim that quark–gluon plasma has been formed. This abundant formation is often presented in comparison with the scaled expectation from normal proton–proton collisions; however, such a comparison is not a necessary step in view of the large absolute yields which defy conventional model expectations. The overall yield of strangeness is also larger than expected if the new form of matter has been achieved. However, considering that the light quarks are also produced in gluon fusion processes, one expects increased production of all hadrons. The study of the relative yields of strange and non strange particles provides information about the competition of these processes and thus the reaction mechanism of particle production. | 0 | Theoretical and Fundamental Chemistry |
There will be two rows of gates at the Lido inlet (21 mobile gates for the North barrier Lido-Treporti and 20 mobile gates for the South barrier Lido-San Nicolò).
To the north of the inlet (Treporti), a small craft harbour consisting of two basins communicating through a lock, will allow small craft and emergency vessels to shelter and transit when the gates are raised. The sea-side basin was temporarily drained and sealed for use as the site to construct the gate housing structures for this barrier. Once the housing structures had been completed, the area was flooded with water to allow the housing structures to be floated out.
The housing structures for the gates in the north barrier (seven housing structures and two for the abutment connections) were positioned on the seabed. Four of this barrier's gates were installed and manoeuvred for the first time in October 2013; at the end of 2014, the installation of 21 gates was completed and operational for functional testing purposes (the so-called "blank tests").
At the south of the inlet (San Nicolò), the launch and the positioning of seven housing structures and two for the abutment connections has been completed (the structures have been fabricated on a temporary raised area in the Malamocco inlet and will be taken out to sea by a giant mobile platform which functions as a giant elevator).
At the centre of the inlet, a new island has been constructed to act as an intermediate structure between the two rows of mobile gates. This island will accommodate the buildings and plant for operating the gates (construction underway).
Outside the inlet, a long curved breakwater is almost complete. | 1 | Applied and Interdisciplinary Chemistry |
In the marine environment, nitrogen is often the limiting nutrient, so the nitrogen cycle in the ocean is of particular interest. The nitrification step of the cycle is of particular interest in the ocean because it creates nitrate, the primary form of nitrogen responsible for "new" production. Furthermore, as the ocean becomes enriched in anthropogenic CO, the resulting decrease in pH could lead to decreasing rates of nitrification. Nitrification could potentially become a "bottleneck" in the nitrogen cycle.
Nitrification, as stated above, is formally a two-step process; in the first step ammonia is oxidized to nitrite, and in the second step nitrite is oxidized to nitrate. Diverse microbes are responsible for each step in the marine environment. Several groups of ammonia-oxidizing bacteria (AOB) are known in the marine environment, including Nitrosomonas, Nitrospira, and Nitrosococcus. All contain the functional gene ammonia monooxygenase (AMO) which, as its name implies, is responsible for the oxidation of ammonia. Subsequent metagenomic studies and cultivation approaches have revealed that some Thermoproteota (formerly Crenarchaeota) possess AMO. Thermoproteota are abundant in the ocean and some species have a 200 times greater affinity for ammonia than AOB, contrasting with the previous belief that AOB are primarily responsible for nitrification in the ocean. Furthermore, though nitrification is classically thought to be vertically separated from primary production because the oxidation of nitrate by bacteria is inhibited by light, nitrification by AOA does not appear to be light inhibited, meaning that nitrification is occurring throughout the water column, challenging the classical definitions of "new" and "recycled" production.
In the second step, nitrite is oxidized to nitrate. In the oceans, this step is not as well understood as the first, but the bacteria Nitrospina and Nitrobacter are known to carry out this step in the ocean. | 1 | Applied and Interdisciplinary Chemistry |
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