Topic Review
Black Soldier Fly
The black soldier fly (BSF), Hermetia illucens Linnaeus, is a large Stratiomyidae fly (13-20 mm in size) found worldwide, but it is believed to have originated in the Americas. It is frequently found in the tropics and temperate regions throughout the world. Although adapted primarily to these regions, it can tolerate wide extremes of temperature except when ovipositing. They are considered beneficial insects and non-pests. The adult fly does not have mouthparts, stingers, or digestive organs; thus, they do not bite or sting and do not feed during its short lifespan. They feed only as larvae and are, therefore, not associated with disease transmission. BSF larvae (BSFL) are voracious eaters of a wide range of organic wastes, decomposing and returning nutrients to the soil. Additionally, BSFL is an alternative protein source for aquaculture, pet food, livestock feed, and human nutrition.
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  • 25 Apr 2023
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). 
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  • 18 Feb 2022
Topic Review
Electronic Circular Dichroism
This entry provides an introduction to the basic concepts of Electronic Circular Dichroism (ECD) spectroscopy. It describes the fundamental principles, instrumentation, and different approaches for interpreting and predicting ECD spectra. It surveys the most popular modern applications of ECD for the structural analysis of organic compounds.
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  • 24 May 2022
Topic Review
Synthetic Dyes
Synthetic dyes are commonly used in food products like soft drinks, vegetable sauces, jellies, etc. Most artificial dyes can cause cancer, therefore it is very important to develop sensors to detect them in food samples.
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  • 09 Jun 2021
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.
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  • 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.
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  • 07 Jan 2022
Topic Review
Extraction Techniques in Sample Preparation
Sample preparation is the most crucial step in the analytical procedure designed for implementation in any analytical application (food analysis, bionalysis, forensics, toxicology, environmental monitoring etc). It is the limiting factor in chemical analysis since it is time consuming and it can potentially introduce errors. No one can doubt that the best approach would be the direct introduction of the sample to the instrument, however this is rarely feasible. Efficient sample pretreatment is inevitably required as the instrument technology has produced highly sophisticated and sensitive analytical equipment. Hence, the analytical scientists have to develop and apply a suitable sample preparation protocol that ensures that the composition of the sample remains unchanged, no impurities are introduced during handling, all interferences have been left back, the analytes’ concentration is not only at detectable levels, but it can also be quantified precisely and accurately and that the matrix of the sample is compatible with the analytical technique. Extraction techniques are the most powerful tool in hands of the analytical chemists and lab practitioners. Either sorbent based or solvent based, extraction techniques provide the necessary tool that can be used to handle the sample in a way that all information in it can be revealed, all advantages in instrumentation have been exploited to the fullest and the lifetime of the instrument is prolonged in a seamless operation mode.
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  • 28 Oct 2020
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.
  • 12.3K
  • 18 Oct 2022
Topic Review
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.
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  • 12 Oct 2022
Topic Review
Hydraulic Actuators
Hydraulic actuators are elements converting the energy of the working fluid into mechanical energy related to the reciprocating motion. The most frequently applied materials used in power hydraulics are described, and various surface modifications of the discussed elements, which are aimed at improving the operating parameters of actuators, are presented. The most frequently used materials for actuators elements are iron alloys. However, due to rising ecological requirements, there is a tendency to looking for modern replacements to obtain the same or even better mechanical or tribological parameters. Sealing systems are manufactured mainly from thermoplastic or elastomeric polymers, which are characterized by low friction and ensure the best possible interaction of seals with the cooperating element. In the field of surface modification, among others, the issue of chromium plating of piston rods has been discussed, which, due, to the toxicity of hexavalent chromium, should be replaced by other methods of improving surface properties.
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  • 23 Mar 2021
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