机械活化粉末制备W-Cu合金的微观组织

为了改善制备工艺和提高W-Cu合金的密度与性能,对原料粉末进行了机械活化处理,通过成形和烧结制备了W-Cu合金,考察了活化后粉末的变化,观察了合金的烧结组织并测量了密度.结果表明,机械活化能增大钨铜粉末的表面能和晶格畸变能,有效地促进烧结,改善烧结组织;烧结体中存在大量团絮状组织,团粒内部钨颗粒主要以固相方式烧结在一起,而团粒之间则以液相烧结为主.烧结组织细密、均匀,相对密度达98%以上;烧结组织中钨铜两相在微米尺度下仍然结合良好,部分界面出现了互溶.     

断陷盆地构造枢纽部位油气富集规律

以十屋断陷为例,根据其构造演化、主要断层特征及油气成藏条件分析,揭示多旋回断陷盆地构造枢纽带与油气富集关系.结果表明:十屋断陷枢纽部位经历了断陷期、断拗过渡期、拗陷期、萎缩隆升期等复杂的构造演化,多期差异构造变形及断裂活动导致了小宽枢纽带南段和北段具有相似性及差异性,后期构造反转发育部位多为早期断层发育部位,且主要集中在主干断层上,构造运动产生位移被断裂和褶皱吸收;不同阶段的隆起部位相叠加,使枢纽部位与构造高点相对位置发生变化,枢纽部位相对位置由原来的古隆起演变为斜坡部位;枢纽部位早期为油气的有利指向区,晚期具有良好的保存条件,同时发育多类型圈闭、有利沉积相组合及生储盖组合,围绕枢纽带可形成复式油气聚集带.     

A candidate for the cystic fibrosis locus isolated by selection for methylation-free islands

A genomic sequence close to the cystic fibrosis locus with the characteristics of an HTF island has been selectively cloned and characterized. Two markers flanking this sequence, which is conserved throughout mammalian evolution, show a very much greater disequilibrium than that found with any existing marker. A single mutational event accounts for most cases of cystic fibrosis. The sequence is expressed, and is a candidate for the cystic fibrosis gene.     

Testimony and knowing how

Much of what we learn from talking and listening does not qualify as testimonial knowledge: we can learn a great deal from other people without simply accepting what they say as being true. In this article, I examine the ways in which we acquire skills or knowledge how from our interactions with other people, and I discuss whether there is a useful notion of testimonial knowledge how.     

Transfer of a cloned immunoglobulin light-chain gene to mutant hybridoma cells restores specific antibody production

The expression of immunoglobulin (Ig) genes is regulated at several levels. For example, although kappa-chain production requires a DNA rearrangement that juxtaposes variable and joining segments, this rearrangement is not sufficient for kappa-chain gene expression; that is, some cell types do not permit immunoglobulin production. The mechanisms responsible for the regulation of the expression of rearranged immunoglobulin genes are poorly understood. The technique of modifying cloned genes in vitro and transferring the modified genes to cells in culture provides a tool for identifying the structural features required for gene expression. To analyse immunoglobulin genes in this manner, however, it is first necessary to use, as recipients, cells that normally permit immunoglobulin production. We report here that a cloned kappa-chain gene is expressed in immunoglobulin-producing hybridoma cells. Furthermore, the product of the transferred kappa-chain gene is capable of restoring specific antibody production to the transformed cells.     

浅谈高校图书馆服务模式创新和形象塑造

网络化、信息化、数字化时代的到来改变了图书馆的运行环境,使高校图书馆的信息服务出现了危机,因此需要创新服务模式,优化服务流程,即开展个性化服务,设立学科信息服务中心,开展层次化信息服务。     

Rat navigation guided by remote control

Free animals can be 'virtually' trained by microstimulating key areas of their brains.     

Common variants near ATM are associated with glycemic response to metformin in type 2 diabetes

Metformin is the most commonly used pharmacological therapy for type 2 diabetes. We report a genome-wide association study for glycemic response to metformin in 1,024 Scottish individuals with type 2 diabetes with replication in two cohorts including 1,783 Scottish individuals and 1,113 individuals from the UK Prospective Diabetes Study. In a combined meta-analysis, we identified a SNP, rs11212617, associated with treatment success (n = 3,920, P = 2.9 × 10(-9), odds ratio = 1.35, 95% CI 1.22-1.49) at a locus containing ATM, the ataxia telangiectasia mutated gene. In a rat hepatoma cell line, inhibition of ATM with KU-55933 attenuated the phosphorylation and activation of AMP-activated protein kinase in response to metformin. We conclude that ATM, a gene known to be involved in DNA repair and cell cycle control, plays a role in the effect of metformin upstream of AMP-activated protein kinase, and variation in this gene alters glycemic response to metformin.     

某型航空发动机对插板式进气畸变的响应

为得到较为准确的发动机对进气畸变的稳定性响应模型,首先分析了由实验所得到的某型航空涡扇发动机进口扰流插板产生的稳态总压畸变和紊流分布。相对于压气机转子进口,将周向分布的稳态总压畸变和截面脉动压力处理成为一组不同频率的压力激励波形分布。通过频谱分析得到:在发动机失稳前,稳态畸变形成的波形频率最低,幅值最大,是引起发动机失稳的主要原因。对该组合畸变激励波用一阶响应模型进行动态修正并使用平行压气机分析模型,得到了经修正的压气机喘振边界和得到改善的发动机进气畸变响应模型。最后分别计算了高、低压压气机逐步失稳的工作点移动过程。结果表明:与压气机出口实验失稳波形十分接近,该模型准确可行。     

局部固支功能梯度板的横向弯曲研究

研究了局部固支功能梯度方板在横向均布载荷作用下的静力学问题。假设功能梯度材料由陶瓷和钢组成，材料弹性模量设计为沿着板的厚度方向按照幂指数形式连续变化，功能梯度方板的四个边均为局部固支，应用Kirchhoff薄板理论和虚功原理推导了板的静力学有限元方程。另分别考虑了各边50%固支和25%固支两种情况，在板材料为纯陶瓷和纯钢时，将所得结果与ANSYS软件结果对比，验证了所建模型的准确性。最后，重点分析了梯度指数对板面和边界最大挠度的影响。结果表明梯度指数和固支范围是决定最大挠度的关键参数，其中固支范围对边界上最大挠度的影响更大。