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111.
Metal-ceramic composites produced by melt infiltration of the ceramic preform were studied. The ceramic preform of these materials is manufactured through freeze-casting process and the microstructure can be presented as distribution of the lamellar domains. Micromechanical models were used for the calculation of the effective elastic properties of the domains. The minimum compliance problem was solved for sample subjected to the four-point bending test. The optimal orientation and volume fracture of the micro constituents were identified using different models. The difference between the initial and optimized design was analyzed. The convergence of the provided optimization procedure was very rapid. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
112.
Guan Y Zakrevskyy Y Stumpe J Antonietti M Faul CF 《Chemical communications (Cambridge, England)》2003,(7):894-895
In this communication we present the facile preparation and characterisation of thermotropic liquid-crystalline materials from the ionic self-assembly of a charged perylenediimide derivative and oppositely charged surfactants. 相似文献
113.
The first synthesis of the common trisaccharide of glycoforms of the outer core region of the Pseudomonas aeruginosa lipopolysaccharide is reported. A fully protected trisaccharide precursor was prepared via a highly efficient α-(1→4)-glucosylation of a β-(1→3)-linked 6-O-benzyl-2-azido-2-deoxy-3-O-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)-α-d-galactopyranoside. In contrast, an alternative sequence of glycosylations, which involves β-glucosylation of an α-(1→4)-linked Glc-GalN3 unit, did not lead to the target trisaccharide backbone. Further O-deacetylation, azido group reduction and debenzylation of the protected trisaccharide precursor gave the corresponding trisaccharide amine. The latter structure was used in the synthesis of a series of trisaccharides bearing an acetyl group, an l-alanine or an N-acetylated l-alanine residue on its amino group at C-2 of GalN. 相似文献
114.
Sergiy S. Mikhailichenko Vadim M. Timoshenko Yuriy G. Shermolovich Fabienne Grellepois 《Journal of fluorine chemistry》2007,128(7):703-709
Reactions of N-alkyl- or N-aryl(perfluoroalkyl)thiocarboxamides with alkyl lithium reagents are described. Trifluorothioacetamides are converted into the corresponding lithium salts. Compounds bearing a long polyfluorinated chain terminated by a CHF2 group and compounds containing an N-alkyl substituent with a proton adjacent to nitrogen react further via a multi-step reaction sequence involving HF elimination and then vinylic fluorine substitution and/or SN′ type fluorine substitution. These transformations led to unsaturated N-monosubstituted polyfluorinated thioamides. 相似文献
115.
Yuriy V. Lisnyak Arthur V. Martynov Vyacheslav N. Baumer Oleg V. Shishkin Anna V. Gubskaya 《Journal of inclusion phenomena and macrocyclic chemistry》2007,58(3-4):367-375
The crystal complex of β-cyclodextrin with succinic acid, intermediate product of hydrolysis reaction of succinic anhydride in the presence of β-cyclodextrin, was isolated and studied by X-ray analysis (monoclinic, space group P21, a = 15.1977(7) Å, b = 10.1763(5) Å, c = 20.6943(6) Å, β = 109.239(4)°, V = 3021.8(2) Å3, Z = 2, R 1 = 0.0359, wR 2 = 0.0947). It was proved that β-cyclodextrin and succinic acid form an inclusion complex, which exists in crystal state as a heptahydrate. The molecule of succinic acid is fully included in the β-cyclodextrin cavity with its carboxyl groups accessible for water molecules. Water molecules located at borders of cavity rims and in interstices between molecules of β-cyclodextrin participate in formation of intermolecular hydrogen bonds. The overall structure does not contain disordered fragments. The crystal conformation of succinic acid corresponds to one of possible conformers of the molecule in vacuo and is almost not disturbed by intermolecular interactions in crystal. Based on the analysis of structural features of the crystal conformation of succinic acid and character of its location in the β-cyclodextrin cavity, it was suggested that hydrolysis of succinic anhydride via ring opening and formation of succinic acid is mediated by cyclodextrin microenvironment and it likely occurs near the narrow rim of the macrocycle cavity. 相似文献
116.
Kondakova AN Vinogradov EV Knirel YA Lindner B 《Rapid communications in mass spectrometry : RCM》2005,19(16):2343-2349
Electrospray ionization with Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS) was used for screening and structural elucidation of core oligosaccharides isolated from lipopolysaccharides of bacteria of the genus Proteus. Mass spectra allowed the determination of the molecular masses with high accuracy and the estimation of the chemical heterogeneity of the samples. They did not, however, provide sufficient information to identify structural details of the branched oligosaccharides. Therefore, various fragmentation techniques for determining such details were examined. Infrared multiphoton dissociation tandem mass spectrometry (IRMPD-MS/MS) experiments in negative ion mode resulted in cleavage between the structurally conserved inner core region and the variable outer core region. Positive ion capillary skimmer dissociation mass spectra showed numerous fragment ion peaks, including those corresponding to the subsequent cleavage of the glycosidic linkages starting from the non-reducing end of the oligosaccharide. Despite their complexity, these mass spectrometric studies allowed confirmation of previously determined Proteus lipopolysaccharide core structures, and identification of new related structures in other strains of these bacteria. 相似文献
117.
Viktor Pogorilyy Anna Plyutinskaya Nikita Suvorov Ekaterina Diachkova Yuriy Vasilev Andrei Pankratov Andrey Mironov Mikhail Grin 《Molecules (Basel, Switzerland)》2021,26(23)
In this work, we obtained the first selenium-containing chlorin with a chalcogen atom in exlocycle E. It was shown that the spectral properties were preserved in the target compound and the stability increased at two different pH values, in comparison with the starting purpurin-18. The derivatives have sufficiently high fluorescence and singlet oxygen quantum yields. The photoinduced cytotoxicity of sulfur- and selenium-anhydrides of chlorin p6 studied for the first time in vitro on the S37 cell line was found to be two times higher that of purpurin-18 and purpurinimide studied previously. Moreover, the dark cytotoxicity increased four-fold in comparison with the latter compounds. Apparently, the increase in the dark cytotoxicity is due to the interaction of the pigments studied with sulfur- and selenium-containing endogenous intracellular compounds. Intracellular distributions of thioanhydride and selenoanhydride chlorin p6 in S37 cells were shown in cytoplasm by diffusion distribution. The intracellular concentration of the sulfur derivative turned out to be higher and, as a consequence, its photoinduced cytotoxicity was higher as well. 相似文献
118.
Yuriy Povstenko Tamara Kyrylych Boena Wo
na-Szczeniak Renata Kawa Andrzej Yatsko 《Entropy (Basel, Switzerland)》2022,24(1)
In a real solid there are different types of defects. During sudden cooling, near cracks, there can appear high thermal stresses. In this paper, the time-fractional heat conduction equation is studied in an infinite space with an external circular crack with the interior radius R in the case of axial symmetry. The surfaces of a crack are exposed to the constant heat flux loading in a circular ring . The stress intensity factor is calculated as a function of the order of time-derivative, time, and the size of a circular ring and is presented graphically. 相似文献
119.
Vitaliy Smokal Oksana Kharchenko Yuriy Karabets Andrii Kysil Oksana Krupka 《Molecular Crystals and Liquid Crystals》2018,672(1):11-17
ABSTRACTIn this work we report preliminary results obtained for methacrylic polymers incorporating aurone side-group as photochemical active molecule. The aurone polymers were obtained by a three-step synthetic approach: (2Z)-6-hydroxy-2-(4-R-benzyliden)-1-benzofuran-3(2H)-ones were synthesized by using condensation reation of 6-hydroxybenzofuran-3-one with benzaldehydes; then methacrylate monomers were synthesized by reaction the alcohols with methacryloyl chloride; and the polymers were synthesized by free radical polymerization. Polymers were characterized by 1HNMR spectroscopy and DSC techniques. Their physicochemical properties are determined by absorption, fluorescence excitation and emission spectroscopies. 相似文献
120.
Fologea D Al Faori R Krueger E Mazur YI Kern M Williams M Mortazavi A Henry R Salamo GJ 《Analytical and bioanalytical chemistry》2011,401(6):1871-1879
Transmembrane protein transporters possessing binding sites for ions, toxins, pharmaceutical drugs, and other molecules constitute
excellent candidates for developing sensitive and selective biosensing devices. Their attractiveness for analytical purposes
is enhanced by the intrinsic amplification capabilities shown when the binding event leads to major changes in the transportation
of ions or molecules other than the analyte itself. The large-scale implementation of such transmembrane proteins in biosensing
devices is limited by the difficulties encountered in inserting functional transporters into artificial bilayer lipid membranes
and by the limitations in understanding and exploiting the changes induced by the interaction with the analyte for sensing
purposes. Here, we show that lysenin, a pore-forming toxin extracted from earthworm Eisenia foetida, which inserts stable and large conductance channels into artificial bilayer lipid membranes, functions as a multivalent
ion-sensing device. The analytical response consists of concentration and ionic-species-dependent macroscopic conductance
inhibition most probably linked to a ligand-induced gating mechanism. Multivalent ion removal by chelation or precipitation
restores, in most cases, the initial conductance and demonstrates reversibility. Changes in lipid bilayer membrane compositions
leading to the absence of voltage-induced gating do not affect the analytical response to multivalent ions. Microscopic current
analysis performed on individual lysenin channels in the presence of Cu2+ revealed complex open–closed transitions characterized by unstable intermediate sub-conducting states. Lysenin channels provide
an analytical tool with a built-in sensing mechanism for inorganic and organic multivalent ions, and the excellent stability
in an artificial environment recommend lysenin as a potential candidate for single-molecule detection and analysis. 相似文献