ZG35CrMnSiRe热处理的试验研究

ZG35CrMnSiRe铸钢经不同的热处理,对其强度、硬度、塑性和冲击韧性等机械性能进行测定,实验结果表明其综合机械性能良好。     

Cloning of a representative genomic library of the human X chromosome after sorting by flow cytometry

A library of 50,000 recombinants representative of the human X chromosome has been constructed. Human X chromosomes were physically separated using a fluorescence-activated cell sorter. The DNA was purified from the chromosomes, digested to completion with the restriction enzyme EcoRI and cloned into the phage lambda gtWES.lambda B. The X-derived nature of the recombinants was confirmed by hybridization to rodent/human cell line DNA containing only the human X chromosome. Such libraries will be particularly useful for the investigation of genetic diseases such as Duchenne muscular dystrophy, where the basic defect has not been elucidated, and of neoplasia, where several specific chromosomal anomalies, particularly for the leukaemias, have been identified.     

锌精馏铅塔燃烧室热工问题诊断

针对韶关冶炼厂锌精馏过程中1号铅塔燃烧室内存在上、下空间温差较大,第2层空气助燃作用很小,第3层空气基本上失去助燃作用等问题,对铅塔燃烧室进行了热工测试.发现铅塔燃烧室内水平方向的温度并非均匀,而且其温差比上、下方向的温差更大.通过对铅塔燃烧室热工诊断及研究,得出导致铅塔燃烧室内烟气与塔盘外壁在水平和上、下方向温差大的原因是燃烧室内煤气、空气以及烟气在各喷口的分布,燃烧室和换热室间隔墙具有保温作用,燃烧室内烟气扰动,直升烟道对第2层煤气和第2,3层空气加热.其中,直升烟道对第2,3层空气的加热作用以及它们较大的沿程阻力导致第2层空气助燃作用小,第3层空气基本上失去助燃作用.这种诊断结果有利于铅塔燃烧室的正常运行和维护.     

苜蓿叶蛋白提取效果及叶蛋白氨基酸组成的研究

采用不同浓度的硫酸铵和不同组合的酸化、碱化方法,提取苜蓿叶蛋白研究发现:采用加热,加醇复合处理效果比单一酸碱处理效果好;优化处理组分析表明采用30%硫酸铵提取苜蓿叶蛋白效果最好;苜蓿叶中蛋白氨基酸种类齐全,含量高,比例协调,是一种蛋白含量高的植物蛋白.     

Persistence of soil organic matter as an ecosystem property

Globally, soil organic matter (SOM) contains more than three times as much carbon as either the atmosphere or terrestrial vegetation. Yet it remains largely unknown why some SOM persists for millennia whereas other SOM decomposes readily--and this limits our ability to predict how soils will respond to climate change. Recent analytical and experimental advances have demonstrated that molecular structure alone does not control SOM stability: in fact, environmental and biological controls predominate. Here we propose ways to include this understanding in a new generation of experiments and soil carbon models, thereby improving predictions of the SOM response to global warming.     

Experience-dependent plasticity of dendritic spines in the developing rat barrel cortex in vivo

Do changes in neuronal structure underlie cortical plasticity? Here we used time-lapse two-photon microscopy of pyramidal neurons in layer 2/3 of developing rat barrel cortex to image the structural dynamics of dendritic spines and filopodia. We found that these protrusions were highly motile: spines and filopodia appeared, disappeared or changed shape over tens of minutes. To test whether sensory experience drives this motility we trimmed whiskers one to three days before imaging. Sensory deprivation markedly (approximately 40%) reduced protrusive motility in deprived regions of the barrel cortex during a critical period around postnatal days (P)11-13, but had no effect in younger (P8-10) or older (P14-16) animals. Unexpectedly, whisker trimming did not change the density, length or shape of spines and filopodia. However, sensory deprivation during the critical period degraded the tuning of layer 2/3 receptive fields. Thus sensory experience drives structural plasticity in dendrites, which may underlie the reorganization of neural circuits.     

Angiotensin-converting enzyme 2 is an essential regulator of heart function

Cardiovascular diseases are predicted to be the most common cause of death worldwide by 2020. Here we show that angiotensin-converting enzyme 2 (ace2) maps to a defined quantitative trait locus (QTL) on the X chromosome in three different rat models of hypertension. In all hypertensive rat strains, ACE2 messenger RNA and protein expression were markedly reduced, suggesting that ace2 is a candidate gene for this QTL. Targeted disruption of ACE2 in mice results in a severe cardiac contractility defect, increased angiotensin II levels, and upregulation of hypoxia-induced genes in the heart. Genetic ablation of ACE on an ACE2 mutant background completely rescues the cardiac phenotype. But disruption of ACER, a Drosophila ACE2 homologue, results in a severe defect of heart morphogenesis. These genetic data for ACE2 show that it is an essential regulator of heart function in vivo.     

Genome sequencing in microfabricated high-density picolitre reactors

The proliferation of large-scale DNA-sequencing projects in recent years has driven a search for alternative methods to reduce time and cost. Here we describe a scalable, highly parallel sequencing system with raw throughput significantly greater than that of state-of-the-art capillary electrophoresis instruments. The apparatus uses a novel fibre-optic slide of individual wells and is able to sequence 25 million bases, at 99% or better accuracy, in one four-hour run. To achieve an approximately 100-fold increase in throughput over current Sanger sequencing technology, we have developed an emulsion method for DNA amplification and an instrument for sequencing by synthesis using a pyrosequencing protocol optimized for solid support and picolitre-scale volumes. Here we show the utility, throughput, accuracy and robustness of this system by shotgun sequencing and de novo assembly of the Mycoplasma genitalium genome with 96% coverage at 99.96% accuracy in one run of the machine.