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91.
92.
Effects of fatty acyl chain length,double‐bond number and matrix on phosphatidylcholine responses in matrix‐assisted laser desorption/ionization on an Orbitrap mass spectrometer
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Vitaliy Chagovets Miroslav Lísa Michal Holčapek 《Rapid communications in mass spectrometry : RCM》2015,29(24):2374-2384
93.
Vitaliy Gerasimov Vladimir Mitsa Yuriy Babinets 《Fresenius' Journal of Analytical Chemistry》1996,355(3-4):404-405
The depth dependence of Raman spectra of a-GeS2-type films having a different optical thickness (/4 and /2) and their refractive index profile have been investigated. The model of a layered-inhomogeneous structure of films has been proposed. There have been distinguished three regions: near-surface region (up to 50 Å), central part and transition film-substrate region (up to 300 Å). 相似文献
94.
The depth dependence of Raman spectra of a-GeS(2)-type films having a different optical thickness (lambda/4 and lambda/2) and their refractive index profile have been investigated. The model of a layered-inhomogeneous structure of films has been proposed. There have been distinguished three regions: near-surface region (up to 50 A), central part and transition film-substrate region (up to 300 A). 相似文献
95.
Nesterenko V Putt KS Hergenrother PJ 《Journal of the American Chemical Society》2003,125(48):14672-14673
The selective induction of death in cancer cells is a major challenge in modern medicine. In this communication we describe the synthesis of an 88-membered combinatorial library, and the subsequent evaluation of these compounds for their ability to selectively induce apoptosis in cancerous cells. A compound was identified from the library that induces apoptosis in U-937 and HL-60 cell lines. This compound is a remarkably selective pro-apoptotic agent for these cancer cell lines, as it does not induce significant death in noncancerous white blood cells, even at concentrations as high as 1000 muM. 相似文献
96.
Ilia A. Guzei Vitaliy I. Timokhin Robert West 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(3):m90-m92
The title compound, [Sn(C10H21N2)(C6H18NSi2)], contains the SnII centre in a trigonal–pyramidal geometry. The basal plane is formed by three N atoms and the fourth apical position is occupied by a stereoactive lone pair. The Sn atom is displaced from the plane of the three N atoms by 1.1968 (12) Å. The Sn—N bonds are highly polarized toward the N atoms, as confirmed by natural bonding orbital analysis. 相似文献
97.
The effect of pH on the complexation of poly(acrylic acid) with poly(vinyl alcohol) in aqueous solution, the miscibility of these polymers in the solid state and the possibility for crosslinking the blends using gamma radiation has been studied. It is demonstrated that the complexation ability of poly(vinyl alcohol) with respect to poly(acrylic acid) is relatively low in comparison with some other synthetic non-ionic polymers. The precipitation of interpolymer complexes was observed below the critical pH of complexation (pH(crit1)), which characterizes the transition between a compact hydrophobic polycomplex and an extended hydrophilic interpolymer associate. Films prepared by casting from aqueous solutions at different pH values exhibited a transition from miscibility to immiscibility at a certain critical pH, pH(crit2), above which hydrogen bonding is prevented. It is shown here that gamma radiation crosslinking of solid blends is efficient and only results in the formation of hydrogel films for blends prepared between pH(crit1) and pH(crit2). The yield of the gel fraction and the swelling properties of the films depended on the absorbed radiation dose and the polymer ratio. [Diagram: see text] SEM image of an equimolar PAA-PVA blend cast from a pH 4.6 solution. 相似文献
98.
A microscopic approach to surface-enhanced Raman scattering (SERS) from molecules adsorbed on noble-metal nanoparticles is developed. For nanoparticle sizes smaller than 10 nm, the classical electromagnetic enhancement mechanism is modified by quantum-size effects. Using time-dependent local field approximation, we perform systematic analysis of SERS in nanometer-sized Ag nanoparticles. We find that, in small nanoparticles, Raman cross-section enhancement is governed by the interplay between Landau damping of the surface plasmon and interband screening in the nanoparticle surface layer. 相似文献
99.
Vadim V. Negrebetsky Aleksandr G. Shipov Evgeniya P. Kramarova Vitaliy V. Negrebetsky Yuri I. Baukov 《Journal of organometallic chemistry》1997,530(1-2):1-12
The structure and dynamic behavior of (O-Si)-chelate N-(dimethylhalogenosilyl)methyl acetamides of the type MeC(O)N(CH(Ph)Me)CH2 SiMe2 X, where X = F, Cl, Br with the OSiC3X coordination set, were studied by multinuclear (1H, 13C, 17O, 29Si) and dynamic 1H NMR spectroscopy. Ligand permutation at silicon was detected. The observed influence of the solvent, nucleofugacity of the X substituent and the external nucleophile on the calculated values of the free energies of activation testify to the dissociative and/or associative mechanisms of the process, but including the stages in which the regular (pseudo-rotation or ‘turnstile’) mechanism takes place. At lower temperatures (up to −90°C) the 1H, 13C, 29Si NMR spectra of N-(dimethylchlorosilyl)methyl acetamide contain the signals of two species of unequal intensity. This effect was explained by an equilibrium between monomers containing the intramolecular O → Si bond and dimers with a hexacoordinate silicon and the bridging chlorine atoms. 相似文献
100.
Chatgilialoglu C Ferreri C Guerra M Timokhin V Froudakis G Gimisis T 《Journal of the American Chemical Society》2002,124(36):10765-10772
Relative kinetic data were determined for the 5-endo-trig cyclization of radical 12 compared to hydrogen abstraction from (TMS)(3)SiH in the temperature range of 344-430 K, which allows for the estimation of a rate constant of 2 x 10(4) s(-)(1) at 298 K with an activation energy of ca. 9 kcal/mol for the cyclization process. The 5-endo-trig cyclization of a variety of radicals that afford five-membered nitrogen-containing heterocycles was addressed computationally at the UB3LYP/6-31G level. The 5-endo vs 4-exo mode of cyclication and the effect of delocalization of the unpaired electron in the transition state were investigated. Because the ring formed during cyclization contains five sp(2) centers, electrocyclization via a pentadienyl-like resonance form was also considered. For comparison, similar calculations were performed for 4-penten-1-yl and related radicals. The factors that affect the activation energies of homolytic 5-endo-trig cyclization were determined. In the absence of steric or conformational effects, the endo cyclization to form the five-membered ring was strongly favored over exo cyclization to form the four-membered ring not only on thermodynamic grounds but also kinetically. When a substituent on the double bond was able to delocalize the unpaired electron in the transition state of the 4-exo path, the two modes of cyclization became kinetically comparable. These results have an important bearing on the generalization of the Baldwin-Beckwith rules, which classified the 5-endo-trig radical cyclization as a "disfavored" process. 相似文献