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71.
In this report, the dynamic behaviour of a tractor-vibrating subsoiler system was analysed theoretically and experimentally. From a simulation using a mathematical model of this system and some field experiments, it was determined that the Virtual Hitch Point (VHP) is the parameter that most affects the vibrations of a tractor's body. By setting the VHP at an optimal position, the acceleration of a tractor's body was reduced considerably. 相似文献
72.
Jun Terao 《Tetrahedron》2004,60(6):1301-1308
Reaction pathways as well as stereochemistries and stoichiometries of zirconocene-catalyzed silylation of olefins with chlorosilanes in the presence of nBuMgCl were studied and discussed in detail. Rate determining steps were examined by kinetic studies and labeling experiments. 相似文献
73.
n-Octyl fluoride underwent a cross-coupling reaction with n-propylmagnesium bromide in the presence of 1,3-butadiene using NiCl2 as a catalyst at room temperature to give undecane in moderate yields. This alkyl-alkyl cross-coupling proceeded more efficiently when CuCl2 was employed instead of NiCl2. Addition of 1,3-butadiene dramatically improved the yields of the coupling products from primary alkyl Grignard reagents in both Ni- and Cu-catalyzed reactions. Alkyl fluorides efficiently reacted with tertiary alkyl and phenyl Grignard reagents using CuCl2 in the absence of 1,3-butadiene to afford the coupling products in high yields. The competitive reaction of a mixture of alkyl halides (R-X; X = F, Cl, Br) with nC5H11MgBr showed that the reactivities of the halides increase in the order R-Cl < R-F < R-Br. In contrast, in the Cu-catalyzed reaction with PhMgBr, the reactivities increase in the order R-Cl < R-Br < R-F. 相似文献
74.
In high resolution solid-state CP/MAS13C NMR spectra of several hydroxybenzaldehydes, the downfield shifts due to hydrogen bonding for the vary inversely with the O...O hydrgen-bonddistances. Conformations of the aldehyde groups in the solid state are determined by the chemical shifts of the ortho carbons. 相似文献
75.
C Danyoshi Y Terao K Achiwa H Okumura T Kurihara A Matsuura F Kobayashi 《Chemical & pharmaceutical bulletin》1989,37(7):1969-1970
Newly synthesized pyrrolidine derivatives inhibited rabbit platelet aggregation induced by platelet activating factor. 相似文献
76.
We examined the effect of staurosporine on cytosolic calcium response in rat basophilic leukemia (RBL-2H3) cells using fura-2 as a fluorescent indicator of calcium ion. Staurosporine at a dose of 30 nM inhibited antigen-stimulated Ca2(+)-influx into the cells from the extracellular environment. In contrast, the drug at this concentration inhibited neither the mobilization of Ca2+ from intracellular stores nor inositol 1,4,5-trisphosphate (IP3) formation. At a high concentration (300 nM), however, staurosporine completely inhibited the cytosolic calcium responses as well as IP3 formation. These results indicate that staurosporine, if used at an appropriate concentration, can be used to discriminate Ca2(+)-influx from extracellular environment from mobilization of the ion from intracellular stores. These results also suggest that protein kinases, possibly protein kinase C, are involved in the calcium influx of RBL-2H3 cells from the extracellular environment. Serotonin release was strongly inhibited by the drug at 30 nM staurosporine. Since the inhibition of serotonin release and suppression of cytosolic calcium increase in response to the antigen were in parallel, we concluded that the inhibition of serotonin release from RBL-2H3 cells caused by the drug was elicited by the suppression of Ca2(+)-influx into the cells. 相似文献
77.
A chiral building block, (R)-2-(2,2-diethoxyethyl)-1,3-propanediol monoacetate was synthesized in high optical and chemical yields by lipase-catalyzed transesterification. From this compound, we synthesized chiral 3-substituted gamma-lactones and a new nucleoside with antiviral activity. 相似文献
78.
S Ohkawa T Terao M Murakami T Matsumoto G Goto 《Chemical & pharmaceutical bulletin》1991,39(4):917-921
2,3,5-Trimethyl-6-(3-pyridylmethyl)-1,4-benzoquinone (CV-6504) has inhibitory activities on both thromboxane A2 synthase and 5-lipoxygenase as well as scavenging activity against active oxygen species. The latter two activities are closely related to the quinone moiety, which is reduced to a hydroquinone in the living body. Comparison of these two activities for both the quinone and hydroquinone showed that the hydroquinone form had superior activities. Concerning the reduction mechanism by PB-3c cells we can see that superoxide dismutase (SOD) has no influence on the rate of reduction, but dicumarol almost completely inhibits the reduction at a concentration greater than 1 x 10(-6) M. Therefore, it can be concluded that CV-6504 is reduced mainly by two electron donating enzymes without the intermediary of a semiquinone radical and that the resulting hydroquinone inhibits lipid peroxidation as well as 5-lipoxygenase activity. 相似文献
79.
Application of conventional cross polarization (CP) to (2)H results in only a narrowband enhancement of the powder line shape due to the quadrupole interaction. We propose a CP scheme to uniformly enhance (2)H spectra in static powders. In this method, a Hartmann-Hahn matched (2)H rf field is applied on the Lee-Goldburg (LG) condition to remove the zeroth-order quadrupole interaction. In order to achieve a uniformly enhanced (2)H powder line shape with a limited (2)H rf intensity, the (1)H rf amplitude in CP is stepwise altered during the contact time. We develop a spin-thermodynamic theory to describe polarization transfer due to CP with LG irradiation (LG-CP) under the influence of the quadrupole interaction, which can successfully reproduce the LG-CP line shapes observed under various experimental conditions. Experimental and simulated (2)H powder spectra are reported for some compounds. 相似文献
80.
New catalytic C--Si bond-forming reactions using chlorosilanes are described. These reactions proceed efficiently under mild conditions by the combined use of Grignard reagents and transition metal catalysts, such as Ti, Zr, Ni, and Pd. It is proposed that ate complex intermediates formed by the reaction of transition metals with Grignard reagents play important roles as the active catalytic species. The present study demonstrates the practical use of chlorosilanes in transition metal catalyzed silylation reactions providing convenient methods for allyl- or vinylsilane synthesis. The reaction pathways of these transformations as well as the scope and limitations are discussed. 相似文献