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Topic Review
Atomic Radius
The atomic radius of a chemical element is a measure of the size of its atom, usually the mean or typical distance from the center of the nucleus to the outermost isolated electron. Since the boundary is not a well-defined physical entity, there are various non-equivalent definitions of atomic radius. Four widely used definitions of atomic radius are: Van der Waals radius, ionic radius, metallic radius and covalent radius. Typically, because of the difficulty to isolate atoms in order to measure their radii separately, atomic radius is measured in a chemically bonded state; however theoretical calculations are simpler when considering atoms in isolation. The dependencies on environment, probe, and state lead to a multiplicity of definitions. Depending on the definition, the term may apply to atoms in condensed matter, covalently bonding in molecules, or in ionized and excited states; and its value may be obtained through experimental measurements, or computed from theoretical models. The value of the radius may depend on the atom's state and context. Electrons do not have definite orbits nor sharply defined ranges. Rather, their positions must be described as probability distributions that taper off gradually as one moves away from the nucleus, without a sharp cutoff; these are referred to as atomic orbitals or electron clouds. Moreover, in condensed matter and molecules, the electron clouds of the atoms usually overlap to some extent, and some of the electrons may roam over a large region encompassing two or more atoms. Under most definitions the radii of isolated neutral atoms range between 30 and 300 pm (trillionths of a meter), or between 0.3 and 3 ångströms. Therefore, the radius of an atom is more than 10,000 times the radius of its nucleus (1–10 fm), and less than 1/1000 of the wavelength of visible light (400–700 nm). For many purposes, atoms can be modeled as spheres. This is only a crude approximation, but it can provide quantitative explanations and predictions for many phenomena, such as the density of liquids and solids, the diffusion of fluids through molecular sieves, the arrangement of atoms and ions in crystals, and the size and shape of molecules.
  • 1.6K
  • 18 Oct 2022
Topic Review
Anticancer Effects of Royal Jelly
Royal jelly (RJ) is produced by the hypopharyngeal and mandibular salivary glands of young nurse honeybees. RJ contains bioactive substances, such as carbohydrates, protein, lipids, peptides, mineral salts and polyphenols which contribute to the appreciated biological and pharmacological activities. Antioxidant, anticancer, anti-inflammatory, antidiabetic, and antibacterial impacts are among the well-recognized benefits. The combination of RJ or its constituents with anticancer drugs has synergistic effects on cancer disorders, enhancing the drug’s effectiveness or reducing its side effects. 
  • 1.3K
  • 18 Oct 2022
Topic Review
Application of Graphene in Electronic Devices
Graphene achieved a peerless level among nanomaterials in terms of its application in electronic devices, owing to its fascinating and novel properties. Its large surface area and high electrical conductivity combine to create high-power batteries. In addition, because of its high optical transmittance, low sheet resistance, and the possibility of transferring it onto plastic substrates, graphene is also employed as a replacement for indium tin oxide (ITO) in making electrodes for touch screens. Moreover, it was observed that graphene enhances the performance of transparent flexible electronic modules due to its higher mobility, minimal light absorbance, and superior mechanical properties. Graphene is even considered a potential substitute for the post-Si electronics era, where a high-performance graphene-based field-effect transistor (GFET) can be fabricated to detect the lethal SARS-CoV-2. Hence, graphene incorporation in electronic devices can facilitate immense device structure/performance advancements.
  • 1.6K
  • 18 Oct 2022
Topic Review
Synthesis of Pyran Derivatives
Heterogeneous catalysis (HC) has become a valuable means for designing sustainable production protocols to obtain superior intermediates, synthons, and potent bioactive heterocycles. The heterogeneous catalysts proved economical and eco-friendly due to the effectiveness of non-hazardous metals for constructing nanomaterials for atom-economical organic reactions. Heterogeneous catalysts significantly affected scientific and industrial innovations due to their tuneable textural properties, flexible acid-base characteristics, higher thermal stability, and improved reusability, with their excellent performance over their enormous counterparts.
  • 588
  • 18 Oct 2022
Topic Review
Organometallic Chemistry of Guanidines
Guanidines, nitrogen-rich compounds, appear as one such potential alternatives as ligands or proligands. In addition to occurring in a plethora of natural compounds, and thus in compounds of pharmacological use, guanidines allow a wide variety of coordination modes to different metal centers along the periodic table, with their monoanionic chelate derivatives being the most common.
  • 612
  • 18 Oct 2022
Topic Review
Willardiine and Its Analogues
Willardiine was first identified by Rolf Gimelin in 1959 from the extracts of seeds of Acacia willardiana. Structurally it corresponds to (2S)-2-amino-3-(2,4-dioxopyrimidin-1-yl)propanoic acid (1) and carrying an uracil moiety it can be ascribed to the category of nucleoamino acids. Willardiine is synthesized by the single specific enzyme uracilylalanine synthase, and the N–heterocyclic moiety uracil obtained by the orotate pathway proved to be an effective bioisostere for the distal carboxyl group of L-glutamate. Different  aspects on both chemistry and biotechnological applications of willardine/willardine-analogues and nucleopeptides will be reviewed herein.
  • 593
  • 18 Oct 2022
Topic Review
Strain Study of Cuprate Superconductors
Cuprate superconductors have attracted extensive attention due to their broad promising application prospects. Among the factors affecting superconductivity, the effect of strain cannot be ignored, which can significantly enhance or degrade superconductivity. The method of strain application, measurement techniques, and influences in detail are described.
  • 375
  • 18 Oct 2022
Topic Review
Mechanism of Action of Thiazolidin-2,4-dione
The thiazolidin-2,4-dione (TZD) moiety plays a central role in the biological functioning of several essential molecules. The availability of substitutions at the third and fifth positions of the Thiazolidin-2,4-dione (TZD) scaffold makes it a highly utilized and versatile moiety that exhibits a wide range of biological activities.
  • 1.2K
  • 18 Oct 2022
Topic Review
Intracellular Enzyme-Instructed Self-Assembly of Peptides
Despite the remarkable significance and encouraging breakthroughs of intracellular enzyme-instructed self-assembly of peptides (IEISAP) in disease diagnosis and treatment, a comprehensive review that focuses on this topic is still desirable.
  • 308
  • 18 Oct 2022
Topic Review
Carbon Dots Composites
Among carbon-based nanomaterials, carbon dots (CDs) have received a surge of interest in recent years due to their attractive features such as tunable photoluminescence, cost effectiveness, nontoxic renewable resources, quick and direct reactions, chemical and superior water solubility, good cell-membrane permeability, and simple operation. CDs and their composites have a large potential for sensing contaminants present in physical systems such as water resources as well as biological systems. Tuning the properties of CDs is a very important subject.
  • 745
  • 17 Oct 2022
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