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21.
Bo Jiang Jeffrey L. Brown Jane Sheraton Nathalie Fortin Howard Bussey 《Yeast (Chichester, England)》1994,10(3):341-353
We have identified three yeast genes, KES1, HES1 and OSH1, whose products show homology to the human oxysterol binding protein (OSBP). Mutations in these genes resulted in pleiotropic sterol-related phenotypes. These include tryptophan-transport defects and nystatin resistance, shown by double and triple mutants. In addition, mutant combinations showed small but apparently cumulative reductions in membrane ergosterol levels. The three yeast genes are also functionally related as overexpression of HES1 or KES1 alleviated the tryptophan-transport defect in kes1Δ or osh1Δ mutants, respectively. Our study implicates this new yeast gene family in ergosterol synthesis and provides comparative evidence of a role for human OSBP in cholesterol synthesis. 相似文献
22.
求解机械装配规划的新方法 总被引:6,自引:0,他引:6
本文提出一个求解机械装配规划的算法,其计算量~O(sN~2),其中s是零件所有可能装配方向的个数,N是工件的零件数(一般s~O(N)).而现行的求机械装配规划的算法,其计算量均随N的增加按指数律增加. 相似文献
23.
An improved coupled-mode equation for nonlinear directional couplers (NLDC) with Kerr-like nonlinear media is proposed. The method is based on the generalized reciprocity relation in which two sets of field solutions satisfying Maxwell's equations are for the NLDC and for the isolated nonlinear waveguide. That leads to a reasonable result that all the coefficients in the coupled-mode equations, including the coupling coefficient, become power dependent. For the NLDC with a self-focusing or self-defocusing nonlinear material, the authors examine how the coupling coefficient, the coupling length, and the guided power depend on the input power in the range of coupling stronger than in previous reports. It is found that the critical power at which the coupling length becomes infinity does not increase as much with the two guides for the case of self-focusing media 相似文献
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Meng Yan Minyu Yao Hongming Zhang Li Xia Ye Zhang 《Photonics Technology Letters, IEEE》2008,20(10):788-790
A novel en/decoder for spectral phase-coded optical code-division multiple-access system based on amplitude sampled fiber Bragg grating (FBG) is proposed. Both equivalent chirp and equivalent phase shift are achieved by amplitude sampling. Compared with previous en/decoder based on step chirped FBG, it is easier to fabricate. The performance of the proposed en/decoder is verified by both numerical simulation and experimental demonstration. 相似文献
29.
Jinsheng Que Qing Wang Jianping Chen Bingfei Shi Qinghui Meng 《Bulletin of Engineering Geology and the Environment》2008,67(4):479-483
The paper describes some geotechnical properties of the soft soils in Guangzhou College City, China, which are difficult to
both sample and test. Laboratory and in situ tests were carried out to assess the physical and mechanical indices of the soils.
The data were statistically analyzed and linear regression undertaken such that equations could be developed by which the
geotechnical properties of the soft soils can be predicted. The statistical validity of the degree of correlation confirmed
that using these equations, the mechanical indices can be estimated from physical indices determined by routine testing.
相似文献
30.
A series of novel block polymers of polyurethane (PU) and chitosan have been prepared in two steps. The first step is the preparation of PU prepolymer, obtained from polytetramethylene oxide glycol (PTMO, Mn = 1000), isophrone diisocyanate (IPDI), and 2,2′-dimethylol propionic acid (DMPA), followed by ionizing PU prepolymer with triethylamine (TEA). The second step involves PU chain-extended by water-soluble chitosan of low molecular weight (Mn = 5000) by self-emulsion polymerization method. The sizes of the latex particles, morphology, and copolymer architecture have been characterized by dynamic light scattering (DLS), general tensile test, infrared spectroscopy (IR), surface contact angle measurement, and transmission electron microscopy (TEM). Furthermore, it shows that the addition of chitosan remarkably increases anticoagulative property of PU elastomers confirmed by the recalcification time. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献