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Topic Review
Geopolymer Concrete
Geopolymer concrete is a type of concrete that is made by reacting aluminate and silicate bearing materials with a caustic activator, such as fly ash or slag from iron and metal production. It can be a suitable substitute for ordinary Portland cement (OPC). 
  • 27.5K
  • 18 Feb 2022
Topic Review
Uncompetitive Inhibitor
Uncompetitive inhibition, also known as anti-competitive inhibition, takes place when an enzyme inhibitor binds only to the complex formed between the enzyme and the substrate (the E-S complex). Uncompetitive inhibition typically occurs in reactions with two or more substrates or products. While uncompetitive inhibition requires that an enzyme-substrate complex must be formed, non-competitive inhibition can occur with or without the substrate present. Uncompetitive inhibition is distinguished from competitive inhibition by two observations: first uncompetitive inhibition cannot be reversed by increasing [S] and second, as shown, the Lineweaver–Burk plot yields parallel rather than intersecting lines. This behavior is found in the inhibition of acetylcholinesterase by tertiary amines (R3N). Such compounds bind to the enzyme in its various forms, but the acyl-intermediate-amine complex cannot break down into enzyme plus product.
  • 19.2K
  • 16 Nov 2022
Topic Review
Two-Dimensional Materials
Two-dimensional (2D) materials are defined as crystalline materials consisting of single- or few-layer atoms, in which the in-plane interatomic interactions are much stronger than those along the stacking direction. Since the success of monolayer graphene exfoliation, 2D materials have been extensively studied due to their unique structures and unprecedented properties. Among these fascinating studies, the most predominant focus has been on their atomic structures, defects, and mechanical behaviors and properties, which serve as the basis for the practical applications of 2D materials.
  • 15.7K
  • 07 Jan 2022
Topic Review
Pi-Stacking
In chemistry, pi stacking (also called π–π stacking) refers to the presumptive attractive, noncovalent interactions (orbital overlap) between the pi bonds of aromatic rings. However this is a misleading description of the phenomena since direct stacking of aromatic rings (the "sandwich interaction") is electrostatically repulsive. What is more commonly observed (see figure to the right) is either a staggered stacking (parallel displaced) or pi-teeing (perpendicular T-shaped) interaction both of which are electrostatic attractive For example, the most commonly observed interactions between aromatic rings of amino acid residues in proteins is a stagered stacked followed by a perpendular orientation. Sandwiched orientations are relatively rare. Pi stacking is repulsive as it places carbon atoms with partial negative charges from one ring on top of other partial negatively charged carbon atoms from the second ring and hydrogen atoms with partial postive charges on top of other hydrogen atoms that likewise carry partial positive charges. In staggered stacking, one of the two aromatic rings is offset sideways so that the carbon atoms with partial negative charge in the first ring are placed above hydrogen atoms with partial positive charge in the second ring so that the electrostatic interactions become attractive. Likewise, pi-teeing interactions in which the two rings are oriented perpendicultar to either other is electrostatically attractive as it places partial postively charged hydrogen atoms in close proximity to partially negatively charged carbon atoms. An alternative explanation for the preference for staggered stacking is due to the balance between van der Waals interactions (attractive dispersion plus Pauli repulsion). These staggered stacking and π-teeing interactions between aromatic rings are important in nucleobase stacking within DNA and RNA molecules, protein folding, template-directed synthesis, materials science, and molecular recognition. Despite the wide use of term pi stacking in the scientific literature, there is no theoretical justification for its use.
  • 14.0K
  • 12 Oct 2022
Topic Review
List of Oxidation States of the Elements
This is a list of known oxidation states of the chemical elements, excluding nonintegral values. The most common states appear in bold. The table is based on that of Greenwood and Earnshaw, with additions noted. Oxidation state 0, which occurs for all elements, is implied by the column with the symbol of the element. The format of the table, which was devised by Dmitri Mendeleev in 1889, shows the periodicity of the oxidation states of the elements.
  • 13.4K
  • 18 Oct 2022
Topic Review
Computational Chemistry Methods
The main objective of computational chemistry is to solve chemical problems by simulating chemical systems (molecular, biological, materials) in order to provide reliable, accurate and comprehensive information at an atomic level. To this end, there are two main methodological families: those based on quantum chemical methods and those based on molecular mechanics. The former are methods in which the electrons are explicitly accounted for, while in the latter their presence is hidden in the force field. 
  • 11.8K
  • 17 Jun 2021
Topic Review
6061 Aluminium Alloy
6061 (Unified Numbering System (UNS) designation A96061) is a precipitation-hardened aluminium alloy, containing magnesium and silicon as its major alloying elements. Originally called "Alloy 61S", it was developed in 1935. It has good mechanical properties, exhibits good weldability, and is very commonly extruded (second in popularity only to 6063). It is one of the most common alloys of aluminum for general-purpose use. It is commonly available in pre-tempered grades such as 6061-O (annealed), tempered grades such as 6061-T6 (solutionized and artificially aged) and 6061-T651 (solutionized, stress-relieved stretched and artificially aged).
  • 10.6K
  • 22 Nov 2022
Topic Review
Kraft Pulp Mill Process
Kraft pulp mills produce a fibrous material composed of wood cellulose fibers, constituting the main raw material for papermaking. The kraft process is the dominant technology in the world to produce pulp, allowing the recycling of most of the pulping chemical in two loops, commonly referred to as the sodium cycle and calcium cycle. A third cycle is also relevant to sodium sulphate recovery. Meanwhile, significant amounts of solid, liquid and gaseous emissions are generated, requiring treatment before release into the environment. Some inorganic solid wastes are of particular concern due to the high quantities generated, which are landfilled: green liquor dregs, slaker grits, lime mud, and boiler fly ash.
  • 8.8K
  • 29 Oct 2020
Topic Review
Ingredients of Moisturizers
Moisturizers are one of the most widely used preparations in cosmetics and have been extensively used to soften the skin for consumers. Moisturizers work effectively in combating dry skin which may cause pain, tightness, itch, stinging, and/or tingling. Knowing the characteristics and interactions of active ingredients with the skin will allow for better utilization of available moisturizers.
  • 8.5K
  • 11 Jul 2022
Topic Review
Thermal Stability of Structural Materials
Thermal stability determines the material ability of retaining its properties at required temperatures over extended service time. In addition to temperature and time, thermal stability is affected by load conditions and environmental conditions.
  • 8.5K
  • 20 Aug 2020
Topic Review
Smart Textile Materials
In the last three decades, the development of new kinds of textiles, so-called smart and interactive textiles, has continued unabated. Smart textile materials and their applications are set to drastically boom as the demand for these textiles have been increasing with the emergence of new fibers, new fabrics, and innovative processing technologies. Moreover, people are eagerly demanding washable, flexible, lightweight, and robust e-textiles. These features depend on the properties of the starting material, the post-treatment, and the integration techniques. In this work, a comprehensive review has been conducted on the integration techniques of conductive materials in and onto a textile structure. The review showed that an e-textile can be developed by applying a conductive component on the surface of a textile substrate via plating, printing, coating, and other surface techniques, or by producing a textile substrate from metals and inherently conductive polymers via the creation of fibers and construction of yarns and fabrics with these. In addition, conductive filament fibers or yarns can be also integrated into conventional textile substrates during the fabrication like braiding, weaving, and knitting or as a post-fabrication of the textile fabric via embroidering. Additionally, layer-by-layer 3D printing of the entire smart textile components is possible, and the concept of 4D could play a significant role in advancing the status of smart textiles to a new level.
  • 8.4K
  • 29 Sep 2021
Topic Review
Paper
Paper is a thin material produced by pressing together moist fibres of cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets. It is a versatile material with many uses, including writing, printing, packaging, cleaning, decorating, and a number of industrial and construction processes. Papers are essential in legal or non-legal documentation. The pulp papermaking process is said to have been developed in China during the early 2nd century CE, possibly as early as the year 105 CE, by the Han court eunuch Cai Lun, although the earliest archaeological fragments of paper derive from the 2nd century BCE in China. The modern pulp and paper industry is global, with China leading its production and the United States right behind it.
  • 7.4K
  • 30 Oct 2022
Topic Review
Chemical Bonding of H2O
Water (H2O) is a simple triatomic bent molecule with C2v molecular symmetry and bond angle of 104.5° between the central oxygen atom and the hydrogen atoms. Despite being one of the simplest triatomic molecules, its chemical bonding scheme is nonetheless complex as many of its bonding properties such as bond angle, ionization energy, and electronic state energy cannot be explained by one unified bonding model. Instead, several traditional and advanced bonding models such as simple Lewis and VESPR structure, valence bond theory, molecular orbital theory, isovalent hybridization, and Bent's rule are discussed below to provide a comprehensive bonding model for H2O, explaining and rationalizing the various electronic and physical properties and features manifested by its peculiar bonding arrangements.
  • 6.9K
  • 18 Oct 2022
Topic Review
Perovskite Materials
In the development of hydrogen-based technology, a key challenge is the sustainable production of hydrogen in terms of energy consumption and environmental aspects. However, existing methods mainly rely on fossil fuels due to their cost efficiency, and as such, it is difficult to be completely independent of carbon-based technology. Electrochemical hydrogen production is essential, since it has shown the successful generation of hydrogen gas of high purity. Similarly, the photoelectrochemical (PEC) method is also appealing, as this method exhibits highly active and stable water splitting with the help of solar energy. We discuss the exceptional optical and electrical characteristics of perovskite materials which often dictate PEC performance. We further extend our discussion to the material limit of perovskite under a hydrogen production environment, i.e., that PEC reactions often degrade the contact between the electrode and the electrolyte.
  • 6.8K
  • 30 Jul 2021
Topic Review
Rice Hulls
Rice hulls (or rice husks) are the hard protecting coverings of grains of rice. In addition to protecting rice during the growing season, rice hulls can be put to use as building material, fertilizer, insulation material, or fuel. Rice hulls are part of the chaff of the rice.
  • 6.8K
  • 10 Oct 2022
Topic Review
Brilliant Blue FCF
Brilliant Blue FCF (Blue 1) is a synthetic organic compound used primarily as a blue colorant for processed foods, medications, dietary supplements, and cosmetics. It is classified as a triarylmethane dye and is known under various names, such as FD&C Blue No. 1 or Acid Blue 9. It is denoted by E number E133 and has a color index of 42090. It has the appearance of a blue powder and is soluble in water and glycerol, with a maximum absorption at about 628 nanometers. It is one of the oldest FDA-approved color additives and is generally considered nontoxic and safe.
  • 6.7K
  • 17 Nov 2022
Topic Review
Acid Throwing
Acid throwing, also called an acid attack, a vitriol attack or vitriolage, is a form of violent assault defined as the act of throwing acid or a similarly corrosive substance onto the body of another "with the intention to disfigure, maim, torture, or kill". Perpetrators of these attacks throw corrosive liquids at their victims, usually at their faces, burning them, and damaging skin tissue, often exposing and sometimes dissolving the bones. The most common types of acid used in these attacks are sulfuric and nitric acid. Hydrochloric acid is sometimes used, but is much less damaging. Aqueous solutions of strongly alkaline materials, such as caustic soda (sodium hydroxide), are used as well, particularly in areas where strong acids are controlled substances. The long term consequences of these attacks may include blindness, as well as permanent scarring of the face and body, along with far-reaching social, psychological, and economic difficulties. Today, acid attacks are reported in many parts of the world. Since the 1990s, Bangladesh has been reporting the highest number of attacks and highest incidence rates for women, with 3,512 Bangladeshi people acid attacked between 1999 and 2013, and in Pakistan and India acid attacks are at an all-time high and increasing every year. Although acid attacks occur all over the world, this type of violence is most common in South Asia. The UK has one of the highest rates of acid attacks per capita in the world, according to Acid Survivors Trust International (ASTI). In 2016 there were over 601 acid attacks in the UK based on ASTI figures. Over 1,200 cases were recorded over the past 5 years. From 2011 to 2016 there were 1,464 crimes involving acid or corrosive substance in London alone.
  • 6.2K
  • 21 Oct 2022
Topic Review
Unbiunium
Check temperatures Ubu: no input for C, K, F. Check temperatures Ubu: no input for C, K, F. Unbiunium, also known as eka-actinium or simply element 121, is the hypothetical chemical element with symbol Ubu and atomic number 121. Unbiunium and Ubu are the temporary systematic IUPAC name and symbol respectively, until a permanent name is decided upon. In the periodic table of the elements, it is expected to be the first of the superactinides, and the third element in the eighth period: analogously to lanthanum and actinium, it could be considered the fifth member of group 3 and the first member of the fifth-row transition metals. It has attracted attention because of some predictions that it may be in the island of stability, although newer calculations expect the island to actually occur at a slightly lower atomic number, closer to copernicium and flerovium. Unbiunium has not yet been synthesized. Nevertheless, because it is only three elements away from the heaviest known element, oganesson (element 118), its synthesis may come in the near future; it is expected to be one of the last few reachable elements with current technology, and the limit may be anywhere between element 120 and 124. It will also likely be far more difficult to synthesize than the elements known so far up to 118, and still more difficult than elements 119 and 120. The team at RIKEN in Japan has plans to attempt the synthesis of element 121 in the future after its attempts on elements 119 and 120. The position of unbiunium in the periodic table suggests that it would have similar properties to its lighter congeners, scandium, yttrium, lanthanum, and actinium; however, relativistic effects may cause some of its properties to differ from those expected from a straight application of periodic trends. For example, unbiunium is expected to have a s2p valence electron configuration instead of the s2d of its lighter congeners in group 3, but this is not expected to significantly affect its chemistry, which is predicted to be that of a normal group 3 element; it would on the other hand significantly lower its first ionisation energy beyond what would be expected from periodic trends.
  • 6.2K
  • 25 Oct 2022
Topic Review
Properties of Phase Change Materials
The main drawback of phase change materials (PCMs) is their low thermal conductivity, which limits the possibilities of a wide range of implementations. Therefore, the researchers, as found in the literature, proposed several methods to improve the thermal conductivity of PCMs, including inserting high thermal conductivity materials in nano-, micro-, and macro-scales, as well as encapsulation of PCMs. However, these inserts impact the other properties of PCMs like latent heat, melting temperature, thermal stability, and cycling stability. 
  • 5.6K
  • 18 Sep 2021
Topic Review
Glass–Ceramics
Owing to their combinations of unique properties of sintered ceramics and the distinctive characteristics of glasses, glass-ceramics have attracted great interest from both academia and industry worldwide since their accidental discovery in 1953.
  • 5.3K
  • 27 Oct 2020
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