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61.
Samy Skander Bahoura 《Comptes Rendus Mathematique》2006,342(10):755-758
We give some results concerning inequalities for some elliptic operators of order 2 and 4. With those inequalities and the concentration phenomena we can describe the asymptotic behavior of those PDE solutions. To cite this article: S.S. Bahoura, C. R. Acad. Sci. Paris, Ser. I 342 (2006). 相似文献
62.
Glaspell G Hassan HM Elzatahry A Fuoco L Radwan NR El-Shall MS 《The journal of physical chemistry. B》2006,110(43):21387-21393
Active gold and palladium nanoparticles supported on MgO nanocubes and ZnO nanobelts and transition-metal-containing MgO nanobelts were synthesized by combining evaporation and deposition-precipitation techniques. The high activity and stability of the Au/CeO2 and Pd/CeO2 nanoparticle catalysts deposited on the MgO cubes are remarkable and imply that a variety of efficient catalysts can be designed and tested using this approach. The significant increase in the concentration of corner and edge sites in MgO nanocubes make them well-defined supports to study the detailed mechanism of the catalytic activity enhancement. 相似文献
63.
Samy A. Madbouly Tsuneo Chiba Toshiaki Ougizawa Takashi Inoue 《Journal of Macromolecular Science: Physics》2013,52(1-2):79-92
The effect of simple shear flow on the miscibility and morphology of blends of poly(methyl methacrylate) (PMMA) and a styrene-acrylonitrile random copoly-mer with 29.5 wt% acrylonitrile (SAN-29.5) has been investigated using shear apparatus and transmission electron microscopy (TEM). The obtained data showed that only shear-induced mixing was observed for all of the composition ratios. The increase of the cloud point (or homogenization temperature) ΔT(γdot; = T(γdot;) - T(0) was investigated as a function of shear rate γdot;; in addition, the normalized shift in the cloud point ΔT(γdot;)/T(0) versus γdot; was also studied and compared with that of simple liquid mixtures and polymer solutions. The results showed that the polymer blends were more sensitive to the shear rate than both simple-liquid mixtures and polymer solutions. The morphology of the PMMN SAN(= 75/25) blend (the critical composition) indicated that shear-induced phase mixing occurred at a critical shear rate value, below which the two phases were highly oriented and elongated in the flow direction. Three regimes, depending on the applied shear rate values, were detected that were in good agreement with the literature data for polymer solutions. The effect of relaxation times after shear cessation showed a decrease in the orientation of the elongated particles, but it did not completely vanish even for 10 min after the shear cessation. 相似文献
64.
Ali Fouad Adel A. Marzouk Montaser Sh. A. Shaykoon Samy M. Ibrahim Sobhy M. El-Adl Ashraf Ghanem 《Molecules (Basel, Switzerland)》2021,26(12)
Daptomycin, a macrocyclic antibiotic, is here used as a new chiral selector in preparation of chiral stationary phase (CSP) in a recently prepared polymer monolithic capillary. The latter is prepared using the copolymerization of the monomers glycidyl methacrylate (GMA) and ethylene glycol dimethacrylate (EGDMA) in the presence of daptomycin in water. Under reversed phase conditions (RP), the prepared capillaries were tested for the enantioselective nanoliquid chromatographic separation of fifty of the racemic drugs of different pharmacological groups, such as adrenergic blockers, H1-blockers, NSAIDs, antifungal drugs, and others. Baseline separation was attained for many drugs under RP-HPLC. Daptomycin expands the horizon of chiral selectors in HPLC. 相似文献
65.
Meroueh SO Minasov G Lee W Shoichet BK Mobashery S 《Journal of the American Chemical Society》2003,125(32):9612-9618
Penicillin-binding proteins (PBPs), biosynthetic enzymes of bacterial cell wall assembly, and beta-lactamases, resistance enzymes to beta-lactam antibiotics, are related to each other from an evolutionary point of view. Massova and Mobashery (Antimicrob. Agents Chemother. 1998, 42, 1-17) have proposed that for beta-lactamases to have become effective at their function as antibiotic resistance enzymes, they would have had to undergo structure alterations such that they would not interact with the peptidoglycan, which is the substrate for PBPs. A cephalosporin analogue, 7beta-[N-Acetyl-L-alanyl-gamma-D-glutamyl-L-lysine]-3-acetoxymethyl-3-cephem-carboxylic acid (compound 6), was conceived and synthesized to test this notion. The X-ray structure of the complex of this cephalosporin bound to the active site of the deacylation-deficient Q120L/Y150E variant of the class C AmpC beta-lactamase from Escherichia coli was solved at 1.71 A resolution. This complex revealed that the surface for interaction with the strand of peptidoglycan that acylates the active site, which is present in PBPs, is absent in the -lactamase active site. Furthermore, insertion of a peptide in the beta-lactamase active site at a location where the second strand of peptidoglycan in some PBPs binds has effectively abolished the possibility for such interaction with the beta-lactamase. A 2.6 ns dynamics simulation was carried out for the complex, which revealed that the peptidoglycan surrogate (i.e., the active-site-bound ligand) undergoes substantial motion and is not stabilized for binding within the active site. These factors taken together disclose the set of structure modifications in the antibiotic resistance enzyme that prevent it from interacting with the peptidoglycan, en route to achieving catalytic proficiency for their intended function. 相似文献
66.
[reaction: see text] An efficient method for the synthesis of diaryl ethers under particularly mild conditions is described. Inexpensive ligands were found to greatly accelerate the Ullmann-type coupling of aryl bromides or iodides with phenols. A series of diaryl ethers were obtained with excellent yields in acetonitrile in the presence of Cs(2)CO(3) and catalytic copper(I) oxide. The reaction tolerates substrates with unfavorable substitution patterns, such as sterically hindered coupling partners or electron-rich aryl halides. 相似文献
67.
Klaus Burger Christoph B?ttcher Lothar Hennig Samy A. Essawy 《Monatshefte für Chemie / Chemical Monthly》2004,8(2):865-877
A preparatively simple synthesis of N-linked glycopeptoids starting from iminodiacetic acid and glycosylamines, using hexafluoroacetone as protecting and activating reagent is described. 相似文献
68.
M. Samy Modeliar 《Journal of Algebra》2008,319(11):4472-4484
Let k be a field of positive characteristic p, and let P be a finite p-group. In this paper, I state a combinatorial characterization of finite dimensional permutation kP-modules. 相似文献
69.
70.
[reaction: see text] A synthesis for oligodeoxynucleotides with a 3'-terminal 2'-N-methyl-2'-acylamido-2'-deoxyuridine residue was developed. Unlike their unmethylated counterparts, these oligodeoxynucleotides can be stably immobilized on aldehyde-displaying glass surfaces to provide DNA microarrays. An anthraquinone carboxamido group as a 2'-substituent doubled the capture efficiency of an immobilized tetradecamer. 相似文献