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871.
Maria Szymonowicz Stanisław Pielka Artur Owczarek Dorota Haznar Janusz Pluta 《Macromolecular Symposia》2007,253(1):71-76
Summary: The paper presents evaluation hemolytic and hemostatic activity of gelatin-alginate matrixes in contact with human blood in vitro studies. The percentage of hemolysis and free hemoglobin concentration were normal. The blood recalcyfication time (CT) was shortened and activated partial thromboplastin time (APTT) was prolonged. That sugested that coagulation processes were activated. Discrabed changes were depended an component composition of sponge. 相似文献
872.
Ana M. Reis Marcos V. D. Vermelho D rio L. Nic cio Evandro A. Gouveia Artur S. Gouveia-neto 《Fiber and Integrated Optics》1995,14(2):179-193
The generation of near-infrared and intense visible light through stimulated multi-wave mixing processes in single-mode silica-based optical fibers pumped by a Q-switched and mode-locked Nd:YAG laser operated at 1.319 μm is described. The experimental results show that intense infrared light around 1.2 μm is produced via selp-hase-matched four-photon mixing at the minimum group velocity dispersion region of pure SiO2-core and P2O5-doped silica fibers. In the visible spectral region, from 580 nm to 600 nm, 20 W peak power 100-ps pulses were generated by pumping single spans of single-mode P2O5-doped and undoped SiO2-core fibers with 1.319-μm laser pulses. The signal light generated in such fibers propagated in the LP02 fiber mode and exhibited a threshold power that depended upon the fiber length and a critical length that was power dependent. Also, it exhibited an asymmetrical spectrum of a few nanometers bandwidth, with a long tail toward high frequencies. For GeO2-doped silica-based fibers, a multiple-wavelength visible signal propagating in several high-order fiber modes was generated. 相似文献
873.
New enantioselective method for hydration of alkenes using cyclodextrins as phase transfer catalyst 总被引:1,自引:0,他引:1
A new enantioselective/inverse phase transfer catalysis (IPTC) reaction for the Markovnikov hydration of double bounds by an oxymercuration-demercuration reaction with cyclodextrins as catalysts was disclosed. Moderate ee (up to 32%) and yields (14-60%) were obtained for allylic amines and protected allylic alcohols as starting materials. 相似文献
874.
A new procedure for determining the structural heterogeneity of microporous solids is presented. Applying the concept of a general adsorption isotherm equation, a method for solving this equation for adsorption in micropores is developed, and the applicability of a new simple algorithm for determining the parameters of microporous structure of two commercial carbons is shown. Copyright 2001 Academic Press. 相似文献
875.
Although the swelling of clay during moistening is a broadly experienced occurrence, the mechanisms driving it and especially the reason for the existence of a peculiar gap between crystalline and osmotic swelling of Na-montmorillonite are not yet fully understood. We obtained a deeper insight by means of Monte Carlo simulations of Na-montmorillonite swelling, which yield the swelling curve, interaction energies between and characteristic positions of structural atoms and water molecules. We find that a chainlike structure consisting of Na cations, water molecules, and oxygens of substituted tetrahedrons of neighboring mineral layers is formed in the interlayer space of Na-montmorillonite at a layer spacing of approximately 19 A, where experimental investigations show termination of crystalline swelling. Such a persistent structure may lock the interlayer space, until excess water is able to break this chain by osmotic forces. We suggest that its formation is the reason for the existence of a gap in layer spacings between approximately 19 and approximately 40 A, which have been named "forbidden" layer spacings in experimental studies. 相似文献
876.
Ana L. Cardoso Artur M.S. Silva Teresa M.V.D. Pinho e Melo António M. d'A. Rocha Gonsalves 《Tetrahedron》2006,62(42):9861-9871
The 1,3-dipolar cycloaddition of dimethyl acetylenedicarboxylate with nonstabilized azomethine ylides, generated via the decarboxylative condensation of 1,3-thiazolidine-4-carboxylic acids with aldehydes, afforded 5,7a-dihydro-1H,3H-pyrrolo[1,2-c]thiazole derivatives. 2-Substituted-1,3-thiazolidine-4-carboxylic acids led to the stereoselective formation of 5,7a-dihydro-1H,3H-pyrrolo[1,2-c]thiazoles. Quantum-chemistry calculations were carried out allowing the rationalization of the observed stereoselective formation of the anti-dipole. 相似文献
877.
878.
The results are presented of measurements of protonation constants (potentiometry and NMR), UV spectroscopic properties and redox potentials of GSH and its five analogues, which are modified at the C-terminal glycine residue (gammaGlu-Cys-X, X = Gly, Gly-NH2, Gly-OEt, Ala, Glu, Ser). Strong linear correlations were found between various properties of the thiol and other functions of these peptides. These results allow discussion of the relationships between the structures and properties in glutathione and its analogues, and provide a novel chemical background for the issue of control of GSH reactivity. 相似文献
879.
Artur M. S. Silva Jos A. S. Cavaleiro Georges Tarrago Claude Marzin 《Journal of heterocyclic chemistry》1994,31(1):97-103
Bis(dimethyl sulfoxide)bis(flavonato)ruthenium(II) complexes, RuL2(DMSO)2, were synthesized by the reaction of dichlorotetrakis(dimethyl sulfoxide)ruthenium(II) with the sodium salts of 5-hydroxyflavone, 5-hydroxy-4′-methoxyflavone and 5-hydroxy-3′,4′,5′,7-tetramethoxyflavone, ( L ). The complexation was followed by 1H nmr spectroscopy. The 1:1 kinetically favoured tris(dimethyl sulfoxide)chloroflavonatoruthenium(II) complexes, RuLCl(DMSO)3, were initially formed and then transformed into the thermodynamically more stable ones. Each one of these complexes, by reacting with another equivalent of lig-and L, also gave rise to a mixture of 1:2 kinetic species, from which the 1:2 thermodynamically more stable bis(dimethyl sulfoxide)bis(flavonato)ruthenium(II) complexes, RuL2(DMSO)2, were formed. The complexes were characterized by extensive studies involving 1H, 13C nuclear magnetic resonance, infrared and ultraviolet-visible spectroscopy, mass spectrometry, cyclic voltammetry and elemental analysis. Such 1:2 complexes exhibited properties of two nonequivalent flavonate ligands and also of two non-equivalent dimethyl sulfoxide ligands; one of these dimethyl sulfoxide ligands is considered to be S-bonded and the other O-bonded. Also two quasireversible one-electron redox steps were observed at 0.53 to 0.57 and 0.44 to 0.41 V (vs Saturated Calomel Electrode). The spectroscopic results obtained allow for the discussion of stereochemistry of each bis(dimethyl sulfoxide)bis(flavonato)ruthenium(II) complex and to postulate its possible structure as one corresponding to the more anisochronous species. 相似文献
880.
A new xanthone (2), 3-(2-hydroxyethoxy)xanthone, and three known compounds, 1-hydroxyxanthone, salicylic acid and the sesquiterpene oplopanone, were isolated for the first time from the rhizomes of Hedychium gardnerianum Rosc. The structures of these compounds were elucidated on the basis of detailed spectral analysis, including 2D NMR experiments. 相似文献