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371.
介绍了开滦煤矿马家沟矿新型建材分公司使用台式振动小型砌块成型机全自动生产线中的煤矸石的主要指标及特性,及利用煤矸石生产砌块的可行性,并分析了其产品性能。 相似文献
372.
373.
A dispersion-strengthened copper alloy with 1 wt% TiC for commercial electrical-contact wires was prepared by in-situ reaction casting, grain-ultrafining by equal-channel angular pressing (ECAP) and subsequent annealing with aim to obtain excellent comprehensive performance. The results showed that fine TiC particles were in-situ synthesized in the as-cast Cu matrix and aggregated in clusters, and thus mechanical properties of the as-cast alloy deemed insufficient. Continued ECAP at 473 K significantly refined the grains of the as-cast alloy and improved the distribution of TiC particles. Due to multiple strengthening mechanisms, the ECAP-processed alloys maintained good conductivity with obviously enhanced tensile strength and hardness values. After post-ECAP annealing, the elongation and conductivity of the fine-grained copper alloy increased with the adequate tensile strength. The novel combined process endows the alloy appropriate performance to serve current high-frequency electrification railway systems. 相似文献
374.
BAI1 is an engulfment receptor for apoptotic cells upstream of the ELMO/Dock180/Rac module 总被引:1,自引:0,他引:1
Park D Tosello-Trampont AC Elliott MR Lu M Haney LB Ma Z Klibanov AL Mandell JW Ravichandran KS 《Nature》2007,450(7168):430-434
Engulfment and subsequent degradation of apoptotic cells is an essential step that occurs throughout life in all multicellular organisms. ELMO/Dock180/Rac proteins are a conserved signalling module for promoting the internalization of apoptotic cell corpses; ELMO and Dock180 function together as a guanine nucleotide exchange factor (GEF) for the small GTPase Rac, and thereby regulate the phagocyte actin cytoskeleton during engulfment. However, the receptor(s) upstream of the ELMO/Dock180/Rac module are still unknown. Here we identify brain-specific angiogenesis inhibitor 1 (BAI1) as a receptor upstream of ELMO and as a receptor that can bind phosphatidylserine on apoptotic cells. BAI1 is a seven-transmembrane protein belonging to the adhesion-type G-protein-coupled receptor family, with an extended extracellular region and no known ligands. We show that BAI1 functions as an engulfment receptor in both the recognition and subsequent internalization of apoptotic cells. Through multiple lines of investigation, we identify phosphatidylserine, a key 'eat-me' signal exposed on apoptotic cells, as a ligand for BAI1. The thrombospondin type 1 repeats within the extracellular region of BAI1 mediate direct binding to phosphatidylserine. As with intracellular signalling, BAI1 forms a trimeric complex with ELMO and Dock180, and functional studies suggest that BAI1 cooperates with ELMO/Dock180/Rac to promote maximal engulfment of apoptotic cells. Last, decreased BAI1 expression or interference with BAI1 function inhibits the engulfment of apoptotic targets ex vivo and in vivo. Thus, BAI1 is a phosphatidylserine recognition receptor that can directly recruit a Rac-GEF complex to mediate the uptake of apoptotic cells. 相似文献
375.
Mullighan CG Goorha S Radtke I Miller CB Coustan-Smith E Dalton JD Girtman K Mathew S Ma J Pounds SB Su X Pui CH Relling MV Evans WE Shurtleff SA Downing JR 《Nature》2007,446(7137):758-764
Chromosomal aberrations are a hallmark of acute lymphoblastic leukaemia (ALL) but alone fail to induce leukaemia. To identify cooperating oncogenic lesions, we performed a genome-wide analysis of leukaemic cells from 242 paediatric ALL patients using high-resolution, single-nucleotide polymorphism arrays and genomic DNA sequencing. Our analyses revealed deletion, amplification, point mutation and structural rearrangement in genes encoding principal regulators of B lymphocyte development and differentiation in 40% of B-progenitor ALL cases. The PAX5 gene was the most frequent target of somatic mutation, being altered in 31.7% of cases. The identified PAX5 mutations resulted in reduced levels of PAX5 protein or the generation of hypomorphic alleles. Deletions were also detected in TCF3 (also known as E2A), EBF1, LEF1, IKZF1 (IKAROS) and IKZF3 (AIOLOS). These findings suggest that direct disruption of pathways controlling B-cell development and differentiation contributes to B-progenitor ALL pathogenesis. Moreover, these data demonstrate the power of high-resolution, genome-wide approaches to identify new molecular lesions in cancer. 相似文献
376.
用模型论的方法证明了一类不定方程a1xr11 a2xr22 ... anxrnn=bys(其中a1,...,an,b为任意整数,r1,...,rn,s为任意正整数)有解.进一步地,我们用相同的方法解决了一个猜想. 相似文献
377.
JIANG Huiming ZHANG Shubiao JIN Rongchao MA Yunhua 《武汉大学学报:自然科学英文版》2007,12(6):1099-1104
Piperidine absorbs CO2 and H2O in air to form a molecular complex: piperidium-l-piperidinecarboxylate-H2O. The structure of the complex was characterized by X-ray single crystal diffraction. The crystal structure was determined to be triclinic, space group P1^-with a=0.648 6(8) nm, b=0.809 200) nm, c= 1.357 1(16) nm, a=96.96706)°, β =102.506(15)°,γ=104.202 05)°, Z=2. The complex is stabilized via five hydrogen bonds between the three components, N-O electrostatic interaction and O-O interaction (electron transfer) betweenl-piperidinecarboxylate and H2O. Due to electron transference of carbamate ion, the oxygen atom in water molecule is strongly negatively charged and the O-H bond is considerably shorter than that of the free molecule of water. The formation of the molecular complex is a reversible process and will decompose upon heating. The mechanism of formation and stabilization is further investigated herein. 相似文献
378.
379.
2003年SARS是中国公众健康的“灾难”,交通旅客运输因此蒙受巨大损失。依据本底趋势线理论,
对此次危机的交通客运量损失进行了定量估算。结果显示:2003年SARS共造成交通旅客损失10畅07亿人次,其
中,公路损失8畅88亿人次,铁路损失1畅05亿人次,航空损失1611畅7万人次,水运损失1943万人次;危机的生命
周期从2003年4月开始,5~6月全面爆发,7~8月消减衰退,11~12月有一定的补偿;由于交通区位和SARS
疫情的差异,全国28个省(市)自治区客运量损失可划分为4个等级,其中,广东、 相似文献
380.
快速切换是移动IPv6技术的关键问题之一.为了改善移动IPv6的快速切换性能,文中提出一个基于分层移动的快速切换方案HMFH.该方案基于微移动和链路层触发的思想,重点针对切换过程中的切换延迟、切换丢包、可扩展性以及路由影响等移动特性进行设计.仿真结果表明,HMFH具有切换延迟短、切换丢包少、可扩展性好、路由效率高等优点... 相似文献