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排序方式: 共有75条查询结果,搜索用时 15 毫秒
51.
20世纪后期目睹了一场技术爆炸,这是自伽俐略和范列文虎克震撼了17世纪的智力基础以来的空前未有的事件。20世纪后期,天文学推出它的大爆炸、黑洞和重力波理论,无疑是在作一种极为微妙的理论冒险.然而,让我们来思考一下哈佛大学天文物理学家帕特里克·撒迪厄斯(Patriek Thaddeus)这个深知内情的人的看法吧t他总喜欢这样说:"在天文学的每 相似文献
52.
在北欧战争爆发以后,欧战会不会迅速扩大的问题,受到了普遍的注意。下面是美国国际问题及经济问题专家 Emeny 博士在过东京时对英文「日本时报」记者的谈话,刊于四月十二日该报。Emeny 这次是由美国俄亥俄省克里夫兰外交研究会及美国太平洋关系学院派来远东考察,他的观察是比较中立的。 相似文献
53.
功能级故障测试由于特大规模集成电路技术的发展而变得越来越重要.和门级的固定为0(s-a-0)或固定为1(s-a-1)故障模型及D-算法相对应,本文对于用寄存器传输语言描述的数字系统,给出一个功能级的故障模型及测试产生的算法. 相似文献
54.
Stoetzel C Laurier V Davis EE Muller J Rix S Badano JL Leitch CC Salem N Chouery E Corbani S Jalk N Vicaire S Sarda P Hamel C Lacombe D Holder M Odent S Holder S Brooks AS Elcioglu NH Silva ED Da Silva E Rossillion B Sigaudy S de Ravel TJ Lewis RA Leheup B Verloes A Amati-Bonneau P Mégarbané A Poch O Bonneau D Beales PL Mandel JL Katsanis N Dollfus H 《Nature genetics》2006,38(5):521-524
Bardet-Biedl syndrome (BBS) is a genetically heterogeneous ciliopathy. Although nine BBS genes have been cloned, they explain only 40-50% of the total mutational load. Here we report a major new BBS locus, BBS10, that encodes a previously unknown, rapidly evolving vertebrate-specific chaperonin-like protein. We found BBS10 to be mutated in about 20% of an unselected cohort of families of various ethnic origins, including some families with mutations in other BBS genes, consistent with oligogenic inheritance. In zebrafish, mild suppression of bbs10 exacerbated the phenotypes of other bbs morphants. 相似文献
55.
Electroless copper-phosphorus coatings with the addition of silicon carbide (SiC) particles 下载免费PDF全文
Soheila Faraji Afidah Abdul Rahim Norita Mohamed Coswald Stephen Sipaut 《矿物冶金与材料学报》2011,18(5):615-622
Cu-P-silicon carbide (SiC) composite coatings were deposited by means of electroless plating. The effects of pH values, temperature, and different concentrations of sodium hypophosphite (NaH2PO2·H2O), nickel sulfate (NiSO4·6H2O), sodium citrate (C6H5Na3O7·2H2O) and SiC on the deposition rate and coating compositions were evaluated, and the bath formulation for Cu-P-SiC composite coatings was optimised. The coating compositions were determined using energy-dispersive X-ray analysis (EDX). The corresponding optimal operating parameters for depositing Cu-P-SiC are as follows: pH 9; temperature, 90℃; NaH2PO2·H2O concentration, 125 g/L; NiSO4·6H2O concentration, 3.125 g/L; SiC concentration, 5 g/L; and C6H5Na3O7·2H2O concentration, 50 g/L. The surface morphology of the coatings analysed by scanning electron microscopy (SEM) shows that Cu particles are uniformly distributed. The hardness and wear resistance of Cu-P composite coatings are improved with the addition of SiC particles and increase with the increase of SiC content. 相似文献
56.
Ludovic Dume′ e Aaron Thornton Kallista Sears Ju¨ rg Schu¨ tz Niall Finn Steven Spoljari Robert Shanks Chris Skourtis Mikel Duke Stephen Gray 《自然科学进展(英文版)》2012,22(6):673-683
In-situ thermal expansion tests on a series of carbon nanotube bucky-paper composites
were performed with direct heating within a synchrotron SAXS source. The impact of the samples
density and morphology as well as the chemistry and degree of decoration of the carbon nanotubes
on the scattering patterns were investigated and correlated to the materials macro-properties. The
results demonstrate that simple densification techniques, such as acetone dipping or gold electroless
deposition, could reduce greatly the displacements of the carbon nanotubes within the structure
and lead to more thermally stable material. 相似文献
57.
Karnoub AE Dash AB Vo AP Sullivan A Brooks MW Bell GW Richardson AL Polyak K Tubo R Weinberg RA 《Nature》2007,449(7162):557-563
Mesenchymal stem cells have been recently described to localize to breast carcinomas, where they integrate into the tumour-associated stroma. However, the involvement of mesenchymal stem cells (or their derivatives) in tumour pathophysiology has not been addressed. Here, we demonstrate that bone-marrow-derived human mesenchymal stem cells, when mixed with otherwise weakly metastatic human breast carcinoma cells, cause the cancer cells to increase their metastatic potency greatly when this cell mixture is introduced into a subcutaneous site and allowed to form a tumour xenograft. The breast cancer cells stimulate de novo secretion of the chemokine CCL5 (also called RANTES) from mesenchymal stem cells, which then acts in a paracrine fashion on the cancer cells to enhance their motility, invasion and metastasis. This enhanced metastatic ability is reversible and is dependent on CCL5 signalling through the chemokine receptor CCR5. Collectively, these data demonstrate that the tumour microenvironment facilitates metastatic spread by eliciting reversible changes in the phenotype of cancer cells. 相似文献
58.
59.
Replicating genotype-phenotype associations 总被引:1,自引:0,他引:1
NCI-NHGRI Working Group on Replication in Association Studies Chanock SJ Manolio T Boehnke M Boerwinkle E Hunter DJ Thomas G Hirschhorn JN Abecasis G Altshuler D Bailey-Wilson JE Brooks LD Cardon LR Daly M Donnelly P Fraumeni JF Freimer NB Gerhard DS Gunter C Guttmacher AE Guyer MS Harris EL Hoh J Hoover R Kong CA Merikangas KR Morton CC Palmer LJ Phimister EG Rice JP Roberts J Rotimi C Tucker MA Vogan KJ Wacholder S Wijsman EM Winn DM Collins FS 《Nature》2007,447(7145):655-660
60.
利用从音乐分析中所获得的技术,天文学家一直在对星系如何会逐渐构成更大的星团这一问题进行研究甚至在绝大多数的天文学家看来,一个星系也是个相当大的物体,它是在一个可达数十万光年的区域中,由数千亿个穿行于浩瀚的气尘云之间的恒星所组成的星群,但是,对于那些从事垦系极限规模性质研究的宇宙学家看来,一个星系仅是所研究物质的基本单位。而在这可观测宇宙中充满了无数这样的物质。它们聚集成可达300万或更多光年的星团,这是些依次逐渐构成的更大的星族。迄今,由天文学家就宏观上所做的观测看来,星系大概是通过先期宇宙扩展和… 相似文献