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El Sayed H. El Ashry

Bio: El Sayed H. El Ashry is an academic researcher from Alexandria University. The author has contributed to research in topics: Alkylation & Ring (chemistry). The author has an hindex of 30, co-authored 338 publications receiving 3903 citations. Previous affiliations of El Sayed H. El Ashry include University of Karachi & University of Konstanz.


Papers
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Journal ArticleDOI
TL;DR: In this article, the corrosion inhibition efficiency of triazole, oxadiazole and thiadiazoles derivatives for steel in presence of acidic medium have been studied by using AM1, PM3, MINDO/3 and MNDO semi-empirical SCF molecular orbital methods.

184 citations

Journal Article
TL;DR: The constituents of the volatile oil, the resin and the gum are outlined in detail and Myrrh has considerable antimicrobial activity and is medicinally used in a variety of diseases.
Abstract: Occurrence, constituents and medicinal use of myrrh, obtained from the stem of different Commiphora species are reviewed. The constituents of the volatile oil, the resin and the gum are outlined in detail. Myrrh has considerable antimicrobial activity and is medicinally used in a variety of diseases.

105 citations

Journal Article
TL;DR: In this paper, various compounds that have been investigated as glycosidase inhibitors are reviewed and the first three parts of this review article covers the following classes of compounds: sugar, lactones and hydroximolactones, glycoly halides, oligosaccharides, glycosides and their derivatives.
Abstract: The various compounds that have been investigated as glycosidase inhibitors are reviewed. The first of three parts of this review article covers the following classes of compounds: sugar, lactones and hydroximolactones, glycosyl halides, oligosaccharides, glycosides and their derivatives, deoxy thiosugar derivatives, thioglycosides, deoxy amino and guanidino sugars, glycosylamines, anhydrosugars and their analogues, deoxysugars, glycals, C-glycosides and C-nucleosides.

78 citations

Journal ArticleDOI
TL;DR: In this article, a correlation between quantum parameters obtained by AM1 calculation and experimental inhibition efficiency has been validated by single point calculations for the semi-empirical AM1 structure using B3LYP/6-31G* as a higher level of theory.

71 citations


Cited by
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Journal ArticleDOI
TL;DR: This review covers the literature published in 2014 for marine natural products, with 1116 citations referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms.

4,649 citations

Journal ArticleDOI
TL;DR: It is demonstrated that the optical absorption of carbon nitride semiconductor materials is extendable into the visible region up to about 750 nm by simple copolymerization with organic monomers like barbituric acid (BA).
Abstract: and nonmetallic elements (N, C, B) creates localized/ delocalized states in the band gap and thus extends its optical absorption to the visible region, but doping usually comes with accelerated charge recombination and lower stability of the doped materials. Meanwhile, various other inorganic, non-TiO2-based, visible-light catalysts have been developed (e.g., metal oxides, nitrides, sulfides, phosphides, and their mixed solid solutions), whereby Ga, Ge, In, Ta, Nb, and W are the main metal constituents. However, sustained utilization of solar energy calls for the development of more abundant and stable catalysts working with visible light, and this has remained challenging so far. Recently, a polymeric semiconductor on the basis of a defecteous graphitic carbon nitride (g-C3N4), was introduced as a metal-free photocatalyst which fulfills the basic requirements for a water-splitting catalyst, including being abundant, stable, and responsive to visible light. In the following, we use the notation “g-C3N4” to describe this class of materials rather than the idealized structure. The most active system is in fact presumably an N-bridged “poly(tri-s-triazine)”, already described by Liebig as “melon”. A semiconductor structure with band edges straddling the water redox potential was revealed for melon by DFT calculations, albeit electrochemical analysis is still awaited. g-C3N4 is considered to be the most stable phase of covalent carbon nitride, and facile synthesis of the melon substructure from simple liquid precursors and monomers allows easy engineering of carbon nitride materials to achieve the desired nanostructures via soft-chemical processing routes and methods. For instance, a high surface area (67–400 mg ) can be imparted on g-C3N4 materials by polymerization of cyanamide on a silica template, which results in photocatalytically more active g-C3N4 nanostructures. [8] Metal-doped gC3N4 can also be conveniently obtained by polymerization of dicyandiamine in the presence of metal salts, and thus multifunctionalization of such materials for a variety of applications can be achieved. Most importantly, the electronic and optical properties of carbon nitride, regarded as a polymer semiconductor, are in principle adjustable by organic protocols. Such organic protocols have been widely used to control the performance of traditional p-conjugated polymers, for example, to improve solar-cell efficiencies by constructing copolymerized donor–acceptor structures, or to modify electronic properties by co-blending with p/n-type organic dopants. Our aim was to use such organic modifications to extend the insufficient light absorption of g-C3N4 (a result of its large band gap of 2.7 eV, which corresponds to wavelengths shorter than 460 nm) towards the maximum of the solar spectrum. Here we demonstrate that the optical absorption of carbon nitride semiconductor materials is extendable into the visible region up to about 750 nm by simple copolymerization with organic monomers like barbituric acid (BA). The electronic and photoelectric properties of the modified carbon nitrides were then investigated to elucidate their enhanced activity for hydrogen production from water containing an appropriate sacrificial reagent with visible light. In principle, BA can be directly incorporated into the classical carbon nitride condensation scheme (Scheme 1). New carbon nitride structures were therefore synthesized by dissolving dicyandiamide with different amounts of BA in water, followed by thermally induced copolymerization at 823 K. For simplicity, the resulting samples are denoted CNBx, where x (0.05, 0.1, 0.2, 0.5, 1, 2) refers to the weighedin amount of BA. The structure, texture, and electrochemical properties of these materials were characterized, and their photochemical performance analyzed. Their XRD patterns (Figure S1, Supporting Information) are dominated by the characteristic (002) peak at 27.48 of a graphitic, layered structure with an interlayer distance of d = [*] J. Zhang, X. Chen , Prof. X. Fu, Prof. X. Wang State Key Laboratory Breeding Base of Photocatalysis Fuzhou University, Fuzhou 350002 (China) E-mail: xcwang@fzu.edu.cn

1,244 citations

Journal ArticleDOI
Gökhan Gece1
TL;DR: In this paper, a review of quantum chemical methods for corrosion inhibitor studies is presented, with a concise summary of the most used quantum chemical parameters and methods and then summarizes the results of research articles in corrosion science over the past 20 years.

1,034 citations

Journal ArticleDOI
01 Aug 1953-Nature
TL;DR: The Merck Index of Chemicals and Drugs is an encyclopedia for the Chemist, Pharmacist, Physician and Allied Professions and thumb-indexed, 8 dollars.
Abstract: The Merck Index of Chemicals and Drugs An Encyclopedia for the Chemist, Pharmacist, Physician and Allied Professions Sixth edition Pp xiv + 1167 (Rahway, NJ: Merck and Company, Inc, 1952) 750 dollars; thumb-indexed, 8 dollars

972 citations

Journal ArticleDOI
TL;DR: The development of N,N-dialkyl(thio)urea derivatives is charted, from early "proof-of-concept" materials to contemporary active chiral (bifunctional) promoters of highly selective asymmetric transformations.
Abstract: Over the last decade the potential for N,N-dialkyl(thio)urea derivatives to serve as active metal-free organocatalysts for a wide range of synthetically useful reactions susceptible to the influence of general acid catalysis has begun to be realised. This article charts the development of these catalysts (with emphasis on the design principles involved), from early "proof-of-concept" materials to contemporary active chiral (bifunctional) promoters of highly selective asymmetric transformations.

753 citations