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排序方式: 共有548条查询结果,搜索用时 15 毫秒
71.
Douglas L. Cassimiro Clóvis A. Ribeiro Jorge M. V. Capela Marisa S. Crespi Marisa V. Capela 《Journal of Thermal Analysis and Calorimetry》2011,105(2):405-410
Meglumine, (2R,3R,4R,5S)-6-methylaminohexane-1,2,3,4,5-pentol, is a carbohydrate derived from sorbitol in which the hydroxyl group in position one
is replaced by a methylamine group. It forms binary adducts with substances having carboxyl groups, which have in common the
presence of hydrogen bonding as the main force in the stabilization of these species. During melting, adducts of meglumine
with flunixin (2-[[2-methyl-3-(trifluoromethyl)phenyl]amino]pyridine-3-carboxylic acid) polymerize or self-assemble in amorphous
supramolecular structures with molecular weights around 2.0 × 105 kDa. DSC curves, in a first heating, show isomorphic transitions where the last one at 137 °C for the flunixin-meglumine
adduct originated the supramolecular amorphous polymers with glass transition around 49.5 °C. The kinetic parameters for the
thermal decomposition step of the polymers were determined by the Capela-Ribeiro non-linear isoconversional method. From data
for the TG curves in nitrogen atmosphere and heating rates of 5, 10, 15, and 20 °C min−1, the E
α and B
α terms could be determined and, consequently, the pre-exponential factor, Aα, as well as the kinetic model, g(α). 相似文献
72.
It is well known that any symplectic manifold (M,Ω) has an almost complex structure J which is compatible with Ω. In this paper, we deal with the existence of compatible pairs (J,Ω) on nilpotent Lie algebras
of dimension ≤6, J being an integrable almost complex structure. We prove that if such a pair exists, J must satisfy some extra conditions, namely J must be nilpotent in the sense of [Trans. Am. Math. Soc. 352 (2000) 5405]. Associated to any such a compatible pair, there is a pseudo-Kähler metric g which cannot be positive definite unless
be abelian. All these metrics are Ricci flat, although many of them are nonflat, and we study the behaviour of its curvature tensor under deformation. 相似文献
73.
An improved method of sample injection was demonstrated for introducing ultra-low volume liquid on a microfabricated device. In our previous study, a pressure-driven injection method has been introduced and was applied to on-chip electrophoresis. In this study, the need for control of the air vent, which was indispensable for sample injection in the previous study, was completely eliminated, facilitating sample injection with great simplicity and high accuracy. This was realized by altering the topology of the air vent channel, which is connected to a hydrophobic and narrow channel (called a passive valve). Several types of air vent channels were designed and their injection performances were tested. In addition, by modifying the shape and the position of air vent channel and passive valve, the residual liquid volume inside the passive valve after sample injection was decreased to approximately 0.5% of the injected volume, a value which showed high reproducibility. 相似文献
74.
75.
Koji Ishida Yoshiaki Uchida Shuji Ninomiya Masumi Osawa 《Fresenius' Journal of Analytical Chemistry》1990,336(5):419-422
Summary The thin-layer chromatographic behaviour of all the rare earths except Pm on silica gel in aqueous solutions of five alkali metal chlorides has been surveyed. The Rf-values and the logarithms of the separation factors relative to Gd vary in a regular and peculiar way with increasing atomic number, through a reflection of the strong tetrad effect. A discussion concerning the effects on the Rf-values of the solvent cations and the solvent anions, and typical chromatograms for the separations of multi-component mixtures containing adjacent lanthanoids are also presented. 相似文献
76.
77.
78.
Masumi Sato 《等离子体物理论文集》1973,13(1):9-25
Evolution from the linear growth to the nonlinearly saturated state of ionization waves (moving striations) is investigated from a viewpoint of an instability which appears in a plasma. The experiments were performed observing backward waves excited below the upper critical current Ic in xenon, argon, and argon-mercury gases at pressures of the order of Torr. It is found that (1) the behavior of the evolution obeys the Landau amplitude equation; (2) the saturated amplitude does not depend on an initial value, but only on plasma parameters; (3) the linear growth and squared saturation level are proportional to the excess over Ic, and when frequency-controlled, they have a parabolic dependence on the frequency; and (4) nonuniform axial changes in the dc state due to the nonlinear effects appear in a form of enhanced ionization in the plasma where the electron temperature and density are increased. The way of these behavior can be applied to a large number of spatially or temporally unstable modes. 相似文献
79.