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991.
The electrochemical response of carbon paste electrode was investigated containing an inorganic and a non-electroactive compound on which an electro- active organic molecule was adsorbed. Alizarin S was chosen as the test molecule adsorbed on 150 m2/g of alumina, because this molecule is either easily reduced or oxidized on carbon. The electrode response was found to be linear for low amounts of alumina containing a known amount of Alizarin S. The electrical yield was never higher than 50%, but was reproducible. An increasing alumina amount in the paste increased the response, but lowered the electrical yield. 相似文献
992.
Finite linear spaces on v points with v–2 mutually intersecting long lines are completely characterized.Dedicated to Professor Giuseppe Tallini on the occasion of his 60th birthday.Work supported by Italian M.P.I. 8nd by GNSAGA of CNR 相似文献
993.
Varilová T Vránková A Pacáková V Tichá M Stulík K 《Journal of chromatography. A》2005,1084(1-2):207-213
Three stationary phases have been prepared for affinity liquid chromatography isolation and separation of porcine and human pepsin. The phases contain 3,5-diiodo-L-tyrosine (DIT) bound to the supports HEMA BIO VS, HEMA BIO E and EPOXY TOYOPEARL. These phases have been tested on a model sample of porcine pepsin A and applied to human pepsin. Fractions have been collected and the chymase activity determined in selected analyses. For affinity CE, capillaries have been prepared by modifying the wall with 3-aminopropyltriethoxysilane, followed either by direct binding of DIT, or by binding L-tyrosine that was subsequently iodated. The dissociation constant K(d) has been determined for the pepsin-DIT complex from the changes in the electrophoretic mobilities. 相似文献
994.
995.
The results of a numerical calculation which extends Scheraga's calculation on the non-Newtonian behavior of the viscosity factor v of rigid ellipsoid solutions are given here and compared to experimental data obtained on different poly(γ-benzyl L -glutamate) samples in helical configuration, over a wide range of molecular weight, up to 980,000. Relations for the axial ratio p, the rotary diffusion constant D, and a test of the deformability of the polymer under shear, are given as functions of the shear-rate dependence of the intrinsic viscosity. The experimental behavior under shear shows that PBLG becomes somewhat flexible in dichloroethane, but not in m-cresol. The dimensions calculated from the viscometric results suggest discrete changes in the length per monomeric unit of the helix at different well defined molecular weights. 相似文献
996.
We report on a computer simulation study of the early stages of the crystallization of molecular nitrogen. First, we study how homogeneous nucleation takes place in supercooled liquid N(2) for a moderate degree of supercooling. Using the umbrella sampling technique, we determine the free energy barrier of formation for a critical nucleus of N(2). We show that, in accord with Ostwald's rule of stages, the structure of the critical nucleus is predominantly that of a metastable polymorph (alpha-N(2) for the state point investigated). We then monitor the evolution of several critical nuclei through a series of unbiased molecular dynamics trajectories. The growth of N(2) crystallites is accompanied by a structural evolution toward the stable polymorph beta-N(2). The microscopic mechanism underlying this evolution qualitatively differs from that reported previously. We do not observe any dissolution or reorganization of the alpha-like core of the nucleus. On the contrary, we show that alpha-like and beta-like blocks coexist in postcritical nuclei. We relate the structural evolution to a greater adsorption rate of beta-like molecules on the surface and show that this transition actually starts well within the precritical regime. We also carefully investigate the effect of the system size on the height of the free energy barrier of nucleation and on the structure and size of the critical nucleus. 相似文献
997.
998.
Bernard Cathala Claude Picard Louis Cazaux Pierre Tisnès 《Journal of Molecular Structure》1996,385(3):353-174
Doubly-armed diazatetralactams constitute a new series of easily synthesized tetralactams. The structural study of the calcium complexes of their N,N′-dimethyl acetamido and (2-pyridylmethyl) derivatives was performed by IR, 1H, 13C NMR spectroscopies and molecular modeling. These complexes showed a C2 symmetry and a high number (8–9) of coordination around the calcium atom. 相似文献
999.
Collisions ot fast metastable beams of Ar, H, and D atoms, and H2 and D2 molecules with NO2 producing positive ions and NO?2 were studied. The ratio of the 3B1-1A1 NO?2 cross sections is a linear function of the projectile velocity. This finding is tentatively interpreted in the framework of a Landau-Zener model Earlier results on O?2 are re-examined. 相似文献
1000.
Claude Biran Blaise Efendene Jacques Dunogues 《Journal of organometallic chemistry》1983,253(2):C13-C17
Direct polysilylation of bicyclic heterosubstrates was performed without (in the case of indole or its N-methyl or N-trimethylsilyl derivatives) or with (benzothiophene, benzofuranne) ring-opening. Hexasilylation from benzothiophene occurred with desulfurization. 相似文献