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1.
Microfluidic systems can conveniently be used for rapid analysis of biological samples. Here we describe a single re-circulating flow, or microvortex, that can generate a maximum fluid rotational velocity of up to 12 m s(-1) and a corresponding radial acceleration in excess of 10(6)g. Such microvortices may be exploited in centrifugal microdevices to investigate the effects of high radial acceleration on biological and chemical processes. 相似文献
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为解决深海X70管线钢在实际焊接中粗晶区(CGHAZ)的脆化问题,在不同热循环工艺下对X70管线钢进行了热模拟研究。采用Gleeble-3800热模拟机模拟X70管线钢CGHAZ,研究CGHAZ在10~60 kJ/cm不同热输入(HI)条件下组织和韧性的变化规律,并通过光学显微镜(OM)、扫描电镜(SEM)和夏比冲击试验等手段表征CGHAZ的组织和韧性。结果表明,不同热输入下试验钢的组织主要由粒状贝氏体(GB)、贝氏体铁素体(BF)和马-奥组元(M-A组元)组成;当HI不断增大时,BF比例减少,GB比例增加,M-A组元粗化,冲击吸收能先升高再降低;当HI为20 kJ/cm时,BF和GB可获得优异组合,断口为韧性断裂,冲击吸收能达到173.8 J;当HI大于20 kJ/cm时,断口解离断裂,冲击吸收能下降明显,最低为18.8 J。因此,较低的热输入可提高CGHAZ的韧性,使X70管线钢具有高强度、高韧性和良好的焊接性。研究结果可为优化焊接工艺提供理论依据。 相似文献
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针对高超声速飞行器在临近空间巡航时出现的通信"黑障"问题,根据RAM C提供的飞行试验数据,建立一维等离子体鞘套模型,通过数值计算分析了等离子体与太赫兹波的相互作用机理,并从等离子体厚度、等离子体电子密度、等离子体碰撞频率和太赫兹波入射角等条件得到了太赫兹波在等离子体鞘套中的传输特性曲线。仿真结果表明:把太赫兹波段作为临近空间平台通信,有利于解决"黑障"问题,其中在大气窗口0.22THz处的衰减均在30dB以下。此论证结果可为临近空间平台设计的高超声速飞行器选用通信频段时提供参考。 相似文献
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Carlton JM Angiuoli SV Suh BB Kooij TW Pertea M Silva JC Ermolaeva MD Allen JE Selengut JD Koo HL Peterson JD Pop M Kosack DS Shumway MF Bidwell SL Shallom SJ van Aken SE Riedmuller SB Feldblyum TV Cho JK Quackenbush J Sedegah M Shoaibi A Cummings LM Florens L Yates JR Raine JD Sinden RE Harris MA Cunningham DA Preiser PR Bergman LW Vaidya AB van Lin LH Janse CJ Waters AP Smith HO White OR Salzberg SL Venter JC Fraser CM Hoffman SL Gardner MJ Carucci DJ 《Nature》2002,419(6906):512-519
Species of malaria parasite that infect rodents have long been used as models for malaria disease research. Here we report the whole-genome shotgun sequence of one species, Plasmodium yoelii yoelii, and comparative studies with the genome of the human malaria parasite Plasmodium falciparum clone 3D7. A synteny map of 2,212 P. y. yoelii contiguous DNA sequences (contigs) aligned to 14 P. falciparum chromosomes reveals marked conservation of gene synteny within the body of each chromosome. Of about 5,300 P. falciparum genes, more than 3,300 P. y. yoelii orthologues of predominantly metabolic function were identified. Over 800 copies of a variant antigen gene located in subtelomeric regions were found. This is the first genome sequence of a model eukaryotic parasite, and it provides insight into the use of such systems in the modelling of Plasmodium biology and disease. 相似文献
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Van Eerdewegh P Little RD Dupuis J Del Mastro RG Falls K Simon J Torrey D Pandit S McKenny J Braunschweiger K Walsh A Liu Z Hayward B Folz C Manning SP Bawa A Saracino L Thackston M Benchekroun Y Capparell N Wang M Adair R Feng Y Dubois J FitzGerald MG Huang H Gibson R Allen KM Pedan A Danzig MR Umland SP Egan RW Cuss FM Rorke S Clough JB Holloway JW Holgate ST Keith TP 《Nature》2002,418(6896):426-430
Asthma is a common respiratory disorder characterized by recurrent episodes of coughing, wheezing and breathlessness. Although environmental factors such as allergen exposure are risk factors in the development of asthma, both twin and family studies point to a strong genetic component. To date, linkage studies have identified more than a dozen genomic regions linked to asthma. In this study, we performed a genome-wide scan on 460 Caucasian families and identified a locus on chromosome 20p13 that was linked to asthma (log(10) of the likelihood ratio (LOD), 2.94) and bronchial hyperresponsiveness (LOD, 3.93). A survey of 135 polymorphisms in 23 genes identified the ADAM33 gene as being significantly associated with asthma using case-control, transmission disequilibrium and haplotype analyses (P = 0.04 0.000003). ADAM proteins are membrane-anchored metalloproteases with diverse functions, which include the shedding of cell-surface proteins such as cytokines and cytokine receptors. The identification and characterization of ADAM33, a putative asthma susceptibility gene identified by positional cloning in an outbred population, should provide insights into the pathogenesis and natural history of this common disease. 相似文献
6.
Carlton JM Adams JH Silva JC Bidwell SL Lorenzi H Caler E Crabtree J Angiuoli SV Merino EF Amedeo P Cheng Q Coulson RM Crabb BS Del Portillo HA Essien K Feldblyum TV Fernandez-Becerra C Gilson PR Gueye AH Guo X Kang'a S Kooij TW Korsinczky M Meyer EV Nene V Paulsen I White O Ralph SA Ren Q Sargeant TJ Salzberg SL Stoeckert CJ Sullivan SA Yamamoto MM Hoffman SL Wortman JR Gardner MJ Galinski MR Barnwell JW Fraser-Liggett CM 《Nature》2008,455(7214):757-763
The human malaria parasite Plasmodium vivax is responsible for 25-40% of the approximately 515 million annual cases of malaria worldwide. Although seldom fatal, the parasite elicits severe and incapacitating clinical symptoms and often causes relapses months after a primary infection has cleared. Despite its importance as a major human pathogen, P. vivax is little studied because it cannot be propagated continuously in the laboratory except in non-human primates. We sequenced the genome of P. vivax to shed light on its distinctive biological features, and as a means to drive development of new drugs and vaccines. Here we describe the synteny and isochore structure of P. vivax chromosomes, and show that the parasite resembles other malaria parasites in gene content and metabolic potential, but possesses novel gene families and potential alternative invasion pathways not recognized previously. Completion of the P. vivax genome provides the scientific community with a valuable resource that can be used to advance investigation into this neglected species. 相似文献
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解体好氧颗粒污泥修复 总被引:3,自引:0,他引:3
考察了加入新的活性污泥使解体好氧颗粒污泥完成修复的可行性.解体好氧颗粒污泥对新加入的活性污泥进行吸附,在各种选择压力特别是水力剪切力作用下和原有颗粒污泥形成一个有机整体.大约3周时间,解体颗粒污泥被完全修复.扫描电镜观察发现,被修复后的颗粒污泥呈现非常规则的结构,微生物相十分致密.在解体颗粒污泥逐渐被修复的过程中,颗粒平均粒径仅从最初的2.8mm增至2.9mm,说明活性污泥在颗粒污泥上的附着主要发生在颗粒的空穴.而颗粒污泥的沉降性能和强度都得到了极大的改善,颗粒沉降速率和完整性系数分别由最初的72m/h和56.8%提高到110m/h和65.8%.新加入的活性污泥除了部分用于修复解体颗粒污泥,其余在选择压力等的作用下形成了新的好氧颗粒污泥. 相似文献
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Young ND Debellé F Oldroyd GE Geurts R Cannon SB Udvardi MK Benedito VA Mayer KF Gouzy J Schoof H Van de Peer Y Proost S Cook DR Meyers BC Spannagl M Cheung F De Mita S Krishnakumar V Gundlach H Zhou S Mudge J Bharti AK Murray JD Naoumkina MA Rosen B Silverstein KA Tang H Rombauts S Zhao PX Zhou P Barbe V Bardou P Bechner M Bellec A Berger A Bergès H Bidwell S Bisseling T Choisne N Couloux A Denny R Deshpande S Dai X Doyle JJ Dudez AM Farmer AD Fouteau S Franken C Gibelin C Gish J Goldstein S 《Nature》2011,480(7378):520-524
Legumes (Fabaceae or Leguminosae) are unique among cultivated plants for their ability to carry out endosymbiotic nitrogen fixation with rhizobial bacteria, a process that takes place in a specialized structure known as the nodule. Legumes belong to one of the two main groups of eurosids, the Fabidae, which includes most species capable of endosymbiotic nitrogen fixation. Legumes comprise several evolutionary lineages derived from a common ancestor 60 million years ago (Myr ago). Papilionoids are the largest clade, dating nearly to the origin of legumes and containing most cultivated species. Medicago truncatula is a long-established model for the study of legume biology. Here we describe the draft sequence of the M. truncatula euchromatin based on a recently completed BAC assembly supplemented with Illumina shotgun sequence, together capturing ~94% of all M. truncatula genes. A whole-genome duplication (WGD) approximately 58 Myr ago had a major role in shaping the M. truncatula genome and thereby contributed to the evolution of endosymbiotic nitrogen fixation. Subsequent to the WGD, the M. truncatula genome experienced higher levels of rearrangement than two other sequenced legumes, Glycine max and Lotus japonicus. M. truncatula is a close relative of alfalfa (Medicago sativa), a widely cultivated crop with limited genomics tools and complex autotetraploid genetics. As such, the M. truncatula genome sequence provides significant opportunities to expand alfalfa's genomic toolbox. 相似文献
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采用射频磁控溅射技术在聚酰亚胺柔性衬底上制备硅基薄膜太阳能电池用铝背电板,研究了不同溅射功率和工作气压条件对铝电极薄膜性能的影响.利用原子力显微镜分析表征了薄膜的表面形貌和粗糙度,薄膜的电学性能和光学性能分别采用四探针测量仪和紫外可见近红外分光光度计进行分析表征.测试结果表明:随着溅射功率的增加,薄膜表面均方根粗糙度迅... 相似文献