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Topic Review
Commercially Important Chlorinated Phenols
Phenols are compounds having a hydroxyl group attached to an aromatic ring such as a benzene or naphthalene ring. Several phenols that also possess one or more chlorine substituents attached to the aromatic ring have significant commercial importance, and these are the subject of this entry.
  • 3.3K
  • 08 Jan 2022
Topic Review
Purple Drank
Purple drank is a recreational drug, created by combining prescription-grade cough syrup with a soft drink and hard candy. The concoction originated in Houston, Texas, and is popular among those who belong to the hip hop subculture or reside in the southern United States.
  • 3.2K
  • 02 Nov 2022
Topic Review
Strychnine Poisoning
Strychnine poisoning can be fatal to humans and other animals and can occur by inhalation, swallowing or absorption through eyes or mouth. It produces some of the most dramatic and painful symptoms of any known toxic reaction, making it quite noticeable and a common choice for assassinations and poison attacks. For this reason, strychnine poisoning is often portrayed in literature and film, such as the murder mysteries written by Agatha Christie. The probable lethal oral dose in humans is 1.5 to 2 mg/kg. Similarly, the median lethal dose for dogs, cats, and rats ranges from 0.5 to 2.35 mg/kg.
  • 3.2K
  • 01 Dec 2022
Topic Review
Sulfonamide
Sulfonamide is a functional group (a part of a molecule) that is the basis of several groups of drugs, which are called sulphonamides, sulfa drugs or sulpha drugs. The original antibacterial sulfonamides are synthetic (nonantibiotic) antimicrobial agents that contain the sulfonamide group. Some sulfonamides are also devoid of antibacterial activity, e.g., the anticonvulsant sultiame. The sulfonylureas and thiazide diuretics are newer drug groups based upon the antibacterial sulfonamides. Allergies to sulfonamides are common. The overall incidence of adverse drug reactions to sulfa antibiotics is approximately 3%, close to penicillin; hence medications containing sulfonamides are prescribed carefully. Sulfonamide drugs were the first broadly effective antibacterials to be used systemically, and paved the way for the antibiotic revolution in medicine.
  • 3.2K
  • 23 Nov 2022
Topic Review
Azeotropes for Waste Recovery
Aiming for more sustainable chemical production requires an urgent shift towards synthetic approaches designed for waste minimization. In this context the use of azeotropes can be an effective tool for “recycling” and minimizing the large volumes of solvents, especially in aqueous mixtures, used. This review discusses the implementation of different kinds of azeotropic mixtures in relation to the environmental and economic benefits linked to their recovery and re-use. Examples of the use of azeotropes playing a role in the process performance and in the purification steps maximizing yields while minimizing waste. 
  • 3.2K
  • 11 Aug 2021
Topic Review
The Application of Food-Grade Emulsions
Briefly, an emulsion is simply a mixture of two (or more) liquids that are otherwise immiscible. The detailed investigation of food-grade emulsions, which possess considerable structural and functional advantages, remains ongoing to enhance people's understanding of these dispersion systems and to expand their application scope. 
  • 3.2K
  • 30 Sep 2022
Topic Review
Potential Energy of Protein
In the context of chemistry and molecular modelling, a force field is a computational method that is used to estimate the forces between atoms within molecules and also between molecules. More precisely, the force field refers to the functional form and parameter sets used to calculate the potential energy of a system of atoms or coarse-grained particles in molecular mechanics, molecular dynamics, or Monte Carlo simulations. The parameters for a chosen energy function may be derived from experiments in physics and chemistry, calculations in quantum mechanics, or both. Force fields are interatomic potentials and utilize the same concept as force fields in classical physics, with the difference that the force field parameters in chemistry describe the energy landscape, from which the acting forces on every particle are derived as a gradient of the potential energy with respect to the particle coordinates. All-atom force fields provide parameters for every type of atom in a system, including hydrogen, while united-atom interatomic potentials treat the hydrogen and carbon atoms in methyl groups and methylene bridges as one interaction center. Coarse-grained potentials, which are often used in long-time simulations of macromolecules such as proteins, nucleic acids, and multi-component complexes, sacrifice chemical details for higher computing efficiency.
  • 3.2K
  • 23 Nov 2022
Topic Review
Dielectric Materials
Owing to their insulating properties, dielectric materials are known as electrically insulating materials. According to the different dielectric materials, traditional dielectric capacitors can be divided into three categories. Firstly, there are polymer-based dielectric capacitors. The dielectric materials of this type of capacitors are mainly polymer materials. Second, there are ceramic-based dielectric capacitors. The dielectric materials of such capacitors include multi-phase ceramics, glass ceramics, ceramic films, etc. Third is the polymer ceramic composite dielectric capacitors, using a variety of polymer and ceramic composite materials as storage medium.
  • 3.2K
  • 19 Feb 2021
Topic Review
Nonaqueous Titration
Nonaqueous titration is the titration of substances dissolved in solvents other than water. It is the most common titrimetric procedure used in pharmacopoeial assays and serves a double purpose: it is suitable for the titration of very weak acids and very weak bases, and it provides a solvent in which organic compounds are soluble. The most commonly used procedure is the titration of organic bases with perchloric acid in anhydrous acetic acid. These assays sometimes take some perfecting in terms of being able to judge the endpoint precisely. The Karl Fischer titration for water content is another nonaqueous titration, usually done in methanol or sometimes in ethanol. Since water is the analyte in this method, it cannot also be used as the solvent.
  • 3.2K
  • 14 Oct 2022
Topic Review
SO2 Poisoning Mechanism
The selective catalytic reduction (SCR) has been widely used in industrial denitrification owing to its high denitrification efficiency, low operating costs, and simple operating procedures. However, coal containing a large amount of sulfur will produce SO2 during combustion, which makes the catalyst easy to be deactivated, thus limiting the application of this technology. This review summarizes the latest NH3-SCR reaction mechanisms and the deactivation mechanism of catalyst in SO2-containing flue gas. Some strategies are summarized for enhancing the poison-resistance through modification, improvement of support, the preparation of complex oxide catalyst, optimizing the preparation methods, and acidification. The mechanism of improving sulfur resistance of catalysts at low temperatures is summarized, and the further development of the catalyst is also prospected. This paper could provide a reference and guidance for the development of SO2 resistance of the catalyst at low temperatures.
  • 3.1K
  • 09 Nov 2020
Topic Review
Conjugate Acid
A conjugate acid, within the Brønsted–Lowry acid–base theory, is a chemical compound formed when an acid donates a proton (H+) to a base—in other words, it is a base with a hydrogen ion added to it, as in the reverse reaction it loses a hydrogen ion. On the other hand, a conjugate base is what is left over after an acid has donated a proton during a chemical reaction. Hence, a conjugate base is a species formed by the removal of a proton from an acid, as in the reverse reaction it is able to gain a hydrogen ion. Because some acids are capable of releasing multiple protons, the conjugate base of an acid may itself be acidic. In summary, this can be represented as the following chemical reaction: Johannes Nicolaus Brønsted and Martin Lowry introduced the Brønsted–Lowry theory, which proposed that any compound that can transfer a proton to any other compound is an acid, and the compound that accepts the proton is a base. A proton is a nuclear particle with a unit positive electrical charge; it is represented by the symbol H+ because it constitutes the nucleus of a hydrogen atom, that is, a hydrogen cation. A cation can be a conjugate acid, and an anion can be a conjugate base, depending on which substance is involved and which acid–base theory is the viewpoint. The simplest anion which can be a conjugate base is the solvated electron whose conjugate acid is the atomic hydrogen.
  • 3.1K
  • 28 Nov 2022
Topic Review
Water Ionizer
A water ionizer (also known as an alkaline ionizer) is a home appliance which claims to raise the pH of drinking water by using electrolysis to separate the incoming water stream into acidic and alkaline components. The alkaline stream of the treated water is called alkaline water. Proponents claim that consumption of alkaline water results in a variety of health benefits, making it similar to the alternative health practice of alkaline diets. Such claims violate basic principles of chemistry and physiology. There is no medical evidence for any health benefits of alkaline water. Extensive scientific evidence has completely debunked these claims. The machines originally became popular in Japan and other East Asian countries before becoming available in the United States and Europe.
  • 3.1K
  • 07 Nov 2022
Topic Review
Compounds of Aluminium
Aluminium (or aluminum) combines characteristics of pre- and post-transition metals. Since it has few available electrons for metallic bonding, like its heavier group 13 congeners, it has the characteristic physical properties of a post-transition metal, with longer-than-expected interatomic distances. Furthermore, as Al3+ is a small and highly charged cation, it is strongly polarizing and aluminium compounds tend towards covalency; this behaviour is similar to that of beryllium (Be2+), an example of a diagonal relationship. However, unlike all other post-transition metals, the underlying core under aluminium's valence shell is that of the preceding noble gas, whereas for gallium and indium it is that of the preceding noble gas plus a filled d-subshell, and for thallium and nihonium it is that of the preceding noble gas plus filled d- and f-subshells. Hence, aluminium does not suffer the effects of incomplete shielding of valence electrons by inner electrons from the nucleus that its heavier congeners do. Aluminium's electropositive behavior, high affinity for oxygen, and highly negative standard electrode potential are all more similar to those of scandium, yttrium, lanthanum, and actinium, which have ds2 configurations of three valence electrons outside a noble gas core: aluminium is the most electropositive metal in its group. Aluminium also bears minor similarities to the metalloid boron in the same group; AlX3 compounds are valence isoelectronic to BX3 compounds (they have the same valence electronic structure), and both behave as Lewis acids and readily form adducts. Additionally, one of the main motifs of boron chemistry is regular icosahedral structures, and aluminium forms an important part of many icosahedral quasicrystal alloys, including the Al–Zn–Mg class.
  • 3.1K
  • 07 Nov 2022
Topic Review
Corroles and Hexaphyrins
Recent developments in the synthesis of corroles and hexaphyrins are reviewed, highlighting their potential application in photodynamic therapy.
  • 3.1K
  • 24 Aug 2020
Topic Review
Relaxor Ferroelectrics for Energy Storage
Ferroelectrics (FE) are polar materials with spontaneous polarization that can be reoriented by changing the direction of the external applied electric field.
  • 3.0K
  • 08 Feb 2021
Topic Review
Enzymatic Interesterification
Enzymatic Interesterification (EIE) is the catalytic reaction that occurs when an enzyme is introduced into oil and rearranges the fatty acids on the glycerol backbone of a triglyceride. Triglycerides are either liquid or solid at room temperature. The rearrangement of the fatty acids that occurs with enzymatic interesterification provides structure and functionality to triglycerides at room temperature. This process adjusts the melting properties, increasing functionality and plasticity in food production applications. One of five different ways of altering melting property profiles, enzymatic interesterification is unlike the more widely used partial hydrogenation method in that it produces no trans fatty acids and lowers saturated fat content.
  • 3.0K
  • 12 Oct 2022
Topic Review
Sodium Cyclamate
Sodium cyclamate (sweetener code 952) is an artificial sweetener. It is 30–50 times sweeter than sucrose (table sugar), making it the least potent of the commercially used artificial sweeteners. It is often used with other artificial sweeteners, especially saccharin; the mixture of 10 parts cyclamate to 1 part saccharin is common and masks the off-tastes of both sweeteners. It is less expensive than most sweeteners, including sucralose, and is stable under heating. Safety concerns led to it being banned in a few countries, though the European Union considers it safe.
  • 3.0K
  • 08 Oct 2022
Topic Review
Additively Manufactured Aluminium Alloys
Metal additive manufacturing (MAM), also known as metal 3D printing, is a rapidly growing industry based on the fabrication of complex metal parts with improved functionalities. During MAM, metal parts are produced in a layer by layer fashion using 3D computer–aided design models. The advantages of using this technology includes the reduction of materials waste, high efficiency for small production runs, near net shape manufacturing, ease of change or revision of versions of a product, support of lattice structures, and rapid prototyping. Numerous metals and alloys can nowadays be processed by additive manufacturing techniques. Among them, Al-based alloys are of great interest for the automotive and aeronautic industry due to their relatively high strength and stiffness to weight ratio, good wear and corrosion resistance, and recycling potential. The special conditions associated with the MAM processes are known to produce in these materials a very fine microstructure with unique directional growth features far from equilibrium. This distinctive microstructure, together with other special features and microstructural defects originating from the additive manufacturing process are known to greatly influence the corrosion behavior of these materials. Several works have already been conducted in this direction. However, a number of issues concerning the corrosion and corrosion protection of these materials are still not well understood. This work reviews the main studies to date investigating the corrosion aspects of additively manufactured aluminium alloys. It also provides a summary and outlook of relevant directions to be explored in future research.
  • 3.0K
  • 13 Jan 2021
Topic Review
Basis Set
A basis set in theoretical and computational chemistry is a set of functions (called basis functions) that is used to represent the electronic wave function in the Hartree–Fock method or density-functional theory in order to turn the partial differential equations of the model into algebraic equations suitable for efficient implementation on a computer. The use of basis sets is equivalent to the use of an approximate resolution of the identity: the orbitals [math]\displaystyle{ |\psi_i\rangle }[/math] are expanded within the basis set as a linear combination of the basis functions [math]\displaystyle{ |\psi_i\rangle \approx \sum_\mu c_{\mu i} |\mu\rangle }[/math], where the expansion coefficients [math]\displaystyle{ c_{\mu i} }[/math] are given by [math]\displaystyle{ c_{\mu i} = \sum_{\nu} \langle \mu|\nu \rangle^{-1} \langle \nu |\psi_i \rangle }[/math]. The basis set can either be composed of atomic orbitals (yielding the linear combination of atomic orbitals approach), which is the usual choice within the quantum chemistry community; plane waves which are typically used within the solid state community, or real-space approaches. Several types of atomic orbitals can be used: Gaussian-type orbitals, Slater-type orbitals, or numerical atomic orbitals. Out of the three, Gaussian-type orbitals are by far the most often used, as they allow efficient implementations of Post-Hartree–Fock methods.
  • 3.0K
  • 17 Oct 2022
Topic Review
Mushroom Poisoning
Mushroom poisoning is poisoning resulting from the ingestion of mushrooms that contain toxic substances. Its symptoms can vary from slight gastrointestinal discomfort to death in about 10 days. Mushroom toxins are secondary metabolites produced by the fungus. Mushroom poisoning is usually the result of ingestion of wild mushrooms after misidentification of a toxic mushroom as an edible species. The most common reason for this misidentification is a close resemblance in terms of color and general morphology of the toxic mushrooms species with edible species. To prevent mushroom poisoning, mushroom gatherers familiarize themselves with the mushrooms they intend to collect, as well as with any similar-looking toxic species. The safety of eating wild mushrooms may depend on methods of preparation for cooking.
  • 3.0K
  • 19 Oct 2022
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