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排序方式: 共有654条查询结果,搜索用时 15 毫秒
641.
Bangshao Dong Deren Li Shaoxiong Zhou Jingyu Qin Shaopeng Pan Zhengbang Li 《自然科学进展(英文版)》2013,23(2):216-219
The structure of Fe80Si10B10 alloy melt was investigated by ab initio molecular dynamic simulation from the local atomic environments. It presents that Fe80Si10B10 alloy can be considered as the combination of B-centered prism-like clusters and bcc-like Fe-Si solid solution. The poor glass-forming ability of the alloy has been investigated and can be attributed to the bcc-like environment around Si atoms and the relative high content of pure Fe clusters. 相似文献
642.
Zhou Junliang 《中国工程科学》2013,11(5):2-12
The study on slide stability of hydraulic structures on subbed soil was made. Using the slide test results of dragged concreting base plates on subbed soil pits,the decreased value of bearing capacity on slide after rebound and repression influence of subbed soil was determined,and the envelope of ultimate slide shear resistance was also quantitatively determined. Due to the lack of similar mechanisms of slide stability on subbed soil and base plate of hydraulic structures,different safety coefficients for the slide stability were adopted. It was suggested to use the maximum compressive stress σmaxof eccentric load to predict structure displacement,slide and creepy slippage of subbed soil,to determine the sliding creepy contour and limit the maximum load on subbed soil. Two hydraulic structures that had been put into operation were reviewed by this method,and the results accorded with the real conditions. 相似文献
643.
A review of research on hyste-resis and stick-slip is presented in this paper. Devices for investigating friction hysteresis and stick-slip of linear rolling guide ways are introduced,as well as some experiment results and conclusions,and some factors impacting on stick-slip are also exhibited. 相似文献
644.
This paper employs system dynamics to explore how the synergy between technology management and technological capability affects new product development.The results show that the synergy between technology management and technological capability has positive impact on new product development.Moreover, the leading synergy processes between technology management and technological capability in different new product development stages are different.This paper deepens the theoretical understanding of how to achieve new product development, and also provides useful guidance for firms to implement new product development. 相似文献
645.
George RE Sanda T Hanna M Fröhling S Luther W Zhang J Ahn Y Zhou W London WB McGrady P Xue L Zozulya S Gregor VE Webb TR Gray NS Gilliland DG Diller L Greulich H Morris SW Meyerson M Look AT 《Nature》2008,455(7215):975-978
Neuroblastoma, an embryonal tumour of the peripheral sympathetic nervous system, accounts for approximately 15% of all deaths due to childhood cancer. High-risk neuroblastomas are rapidly progressive; even with intensive myeloablative chemotherapy, relapse is common and almost uniformly fatal. Here we report the detection of previously unknown mutations in the ALK gene, which encodes a receptor tyrosine kinase, in 8% of primary neuroblastomas. Five non-synonymous sequence variations were identified in the kinase domain of ALK, of which three were somatic and two were germ line. The most frequent mutation, F1174L, was also identified in three different neuroblastoma cell lines. ALK complementary DNAs encoding the F1174L and R1275Q variants, but not the wild-type ALK cDNA, transformed interleukin-3-dependent murine haematopoietic Ba/F3 cells to cytokine-independent growth. Ba/F3 cells expressing these mutations were sensitive to the small-molecule inhibitor of ALK, TAE684 (ref. 4). Furthermore, two human neuroblastoma cell lines harbouring the F1174L mutation were also sensitive to the inhibitor. Cytotoxicity was associated with increased amounts of apoptosis as measured by TdT-mediated dUTP nick end labelling (TUNEL). Short hairpin RNA (shRNA)-mediated knockdown of ALK expression in neuroblastoma cell lines with the F1174L mutation also resulted in apoptosis and impaired cell proliferation. Thus, activating alleles of the ALK receptor tyrosine kinase are present in primary neuroblastoma tumours and in established neuroblastoma cell lines, and confer sensitivity to ALK inhibition with small molecules, providing a molecular rationale for targeted therapy of this disease. 相似文献
646.
647.
WANG Jian LIU Hong XUE JinPing JIANG Zhou CHEN NaiSheng HUANG JinLing 《科学通报(英文版)》2008,53(11):1657-1664
Sulfonate and/or phthalimidomethyl phthalocyanine zincs are obtained by the condensation reaction of anhydrous zinc acetate and two precursors, i.e. 4-phthalimidomethyl phthalonitrile and 4-(potassium sulfonated) phthalonitrile. The ZnPCSnPm mixture was separated into 5 components according to the number of substituted sulfonate groups and each component which has the same chemical constituent consists of different regioisomers. An HPLC method in isocratic conditions was developed to exercise quality control and make quantitative analysis of the photosensitizer, di-(potassium sulfonate)-diphthalimidomethyl phthalocyanine zinc (abbreviated as ZnPcS2P2, here, S represents sulfonate group, P the phthalimidomethyl group and ZnPc the phthalocyanine zinc). Furthermore, by comparing the retention behavior of ZnPcS2P2 with that of ZnPcS2, positional structure of isomers of ZnPcS2P2 was speculated. Reversed-phase HPLC method with TEA-phosphate buffer and DMF as eluents in gradient conditions has been proved to be a powerful tool for the separation of such complex system. 相似文献
648.
T-DNA transfer and integration as a tool for insertional mutagenesis in the taxol-producing fungus 总被引:1,自引:0,他引:1
Agrobacterium tumefaciens-mediated DNA transformation method was applied to transform Nodulisporium sylviforme fusant HDF-68, a taxol-producing fungus. We constructed a binary vector pBI121-43 carrying a hygromycin-resistant gene cassette between the right and left borders of T-DNA. Optimal co-cultivation of N.sylviforme with A.tumefaciens containing pBI121-43 led to 110~130 hygromycin-resistant transformants per million conidia. Putative transformants were found to be mitotically stable. The molecular analysis of transformants demonstrated the random integration of single copy of the T-DNA into the host genome. This transformation system serves as a basic tool for insertional mutagenesis in N.sylviforme fusant HDF-68, and the development of such system lays a solid foundation for constructing high-yied gene engineering strain and clarifying taxol biosynthesis pathway in this fungus. 相似文献
649.
Based on the principle of Lorentz force induced acoustic vibration, radiation theory comparison between acoustic point and dipole sources was conducted for magnetoacoustic tomography with magnetic induction (MAT-MI). It is proved that each acoustic source of MAT- MI is produced by the divergence of the magnetically induced Lorentz force, and the detected acoustic pressure is the integral of all diffraction sources inside the object. Wave clusters are produced by abrupt pressure changes at conductivity boundaries, and only the configurations in terms of shape and size of phantom models can be recon- structed. However, different from point source, positive and negative pressures are generated by the radiation pat- tern of dipole sources. Reverse vibration phases of wave clusters in collected waveforms and opposite polarities of borderline stripes in reconstructed images are produced at conductivity boundaries, representing the direction of conductivity changes. The experimentally collected wave- forms and reconstructed images of the aluminum foil cylinder and cylindrical saline gel phantom model agree well with simulated results. The favorable results prove the validity of the radiation theory of acoustic dipole source and provide basis for further investigation of conductivity reconstruction for MAT-MI. 相似文献
650.
Graphene is an ideal reinforcing phase for a high-performance composite filler, which is of great theoretical and practical significance for improving the wettability and reliability of the filler. However, the poor adsorption characteristics between graphene and the silver base filler significantly affect the application of graphene filler in the brazing field. It is a great challenge to improve the adsorption characteristics between a graphene and silver base filler. To solve this issue, the adsorption characteristic between graphene and silver was studied with first principle calculation. The effects of Ga, Mo, and W on the adsorption properties of graphene were explored. There are three possible adsorbed sites, the hollow site (H), the bridge site (B), and the top site (T). Based on this research, the top site is the most preferentially adsorbed site for Ag atoms, and there is a strong interaction between graphene and Ag atoms. Metal element doping enhances local hybridization between C or metal atoms and Ag. Furthermore, compared with other doped structures (Ga and Mo), W atom doping is the most stable adsorption structure and can also improve effective adsorption characteristic performance between graphene and Ag. 相似文献