一种改进的耗散型接触力模型及实验验证

为了研究含间隙运动副对连杆机构动态性能的影响,基于能够描述碰撞过程中能量损失的连续接触模型,建立了一个新的耗散型接触力模型.在这个新模型下对含间隙连杆机构进行动力学仿真,并进行了实验研究.主要考察了间隙尺寸和加载强度对连杆受力的影响.结果表明:间隙的存在会影响传递力曲线,使机构产生明显的振动冲击,间隙大小和加载速度是影响机构动态响应的主要因素.该仿真结果得到了实验的验证.     

A worldwide survey of haplotype variation and linkage disequilibrium in the human genome

Recent genomic surveys have produced high-resolution haplotype information, but only in a small number of human populations. We report haplotype structure across 12 Mb of DNA sequence in 927 individuals representing 52 populations. The geographic distribution of haplotypes reflects human history, with a loss of haplotype diversity as distance increases from Africa. Although the extent of linkage disequilibrium (LD) varies markedly across populations, considerable sharing of haplotype structure exists, and inferred recombination hotspot locations generally match across groups. The four samples in the International HapMap Project contain the majority of common haplotypes found in most populations: averaging across populations, 83% of common 20-kb haplotypes in a population are also common in the most similar HapMap sample. Consequently, although the portability of tag SNPs based on the HapMap is reduced in low-LD Africans, the HapMap will be helpful for the design of genome-wide association mapping studies in nearly all human populations.     

基于频率变化平方比的压力管道损伤定位方法

利用摄动原理探讨了基于振动模态分析的结构无损检测技术,并把频率变化平方比应用于压力管道,从理论上验证了该参数的变化是结构损伤程度和位置的函数。并且利用该方法对一钢管进行了数值模拟和试验,结果表明方法简单可行,可为解决工程实际问题提供一定的参考。     

Generation of pluripotent stem cells from adult human testis

Human primordial germ cells and mouse neonatal and adult germline stem cells are pluripotent and show similar properties to embryonic stem cells. Here we report the successful establishment of human adult germline stem cells derived from spermatogonial cells of adult human testis. Cellular and molecular characterization of these cells revealed many similarities to human embryonic stem cells, and the germline stem cells produced teratomas after transplantation into immunodeficient mice. The human adult germline stem cells differentiated into various types of somatic cells of all three germ layers when grown under conditions used to induce the differentiation of human embryonic stem cells. We conclude that the generation of human adult germline stem cells from testicular biopsies may provide simple and non-controversial access to individual cell-based therapy without the ethical and immunological problems associated with human embryonic stem cells.     

诺丽 预防和治疗癌症的佳品

以目前的技术,人类还不能发明出有效并且安全无毒的药物,用来预防和治疗癌症。通用的化疗药物都有毒性,它们被用来杀死癌细胞,但同时也不同程度地杀死了人体内的健康组织。目标疗法,例如利用血管抑制剂对某一具体受体进行血管抑制或者有效生成基因,为控制癌症带来了极大的希望。血管生成是新血液管道生长的过程。成人的血管生长都是由疾病造成的,排除如月经和怀孕等少数的生理情况,肿瘤不可能长到0．08英寸这么大,除非是第一次形成时导致了新的血管扩张生成。因此,抑制血管生成就可以阻止癌细胞扩展,     

Observation of high-energy neutrinos using Cerenkov detectors embedded deep in Antarctic ice

Neutrinos are elementary particles that carry no electric charge and have little mass. As they interact only weakly with other particles, they can penetrate enormous amounts of matter, and therefore have the potential to directly convey astrophysical information from the edge of the Universe and from deep inside the most cataclysmic high-energy regions. The neutrino's great penetrating power, however, also makes this particle difficult to detect. Underground detectors have observed low-energy neutrinos from the Sun and a nearby supernova, as well as neutrinos generated in the Earth's atmosphere. But the very low fluxes of high-energy neutrinos from cosmic sources can be observed only by much larger, expandable detectors in, for example, deep water or ice. Here we report the detection of upwardly propagating atmospheric neutrinos by the ice-based Antarctic muon and neutrino detector array (AMANDA). These results establish a technology with which to build a kilometre-scale neutrino observatory necessary for astrophysical observations.     

基于数据挖掘对中医药治疗CKD合并脑卒中的组方用药分析

基于数据挖掘方法探讨中医药治疗慢性肾脏病(CKD)合并脑卒中(CS)的临床用药规律.收集2017 年10 月至2022 年10 月天津中医药大学第一附属医院门诊治疗CKD合并CS的处方,建立中药处方数据库.统计分析用药频次、性味及归经,对处方中的药物进行聚类分析,利用SPSS Modeler 18 Apriori算法对所有药物进行关联分析.最终纳入544 个处方,涉及中药258味,总用药频次8 886 次.药性以寒性、温性、平性居多;药味以苦味、甘味、辛味为主;归经多为脾经、肝经;得出13 个关联组合药对和5 个核心药物组合.中医药对CKD合并CS患者的治疗,根据气虚血瘀、脾肾两虚的病机特点,主要采用健脾益气、补肾活血的组方用药.     

强磁场对Ni-33Al-28Cr-5.0Mo-0.5Hf合金强化及其断裂特征影响

研究了N i-33A l-28C r-5.0M o-0.5H f高温合金在900℃经10 T强磁场处理后室温下的力学性能变化.发现合金经过强磁场处理后,抗弯强度增加了75%,但弹性模量几乎没有改变.对试样断口的观察表明,磁场使得试件呈现韧性断裂特征;而没经磁场处理的试件断口形貌呈现脆性断裂特征.微观分析表明,在强磁场和温度场的耦合作用下,原来在N iA l-C r(M o)相边界处析出的块状和细小颗粒状的H eusler相(N i2A lH f)因大量溶解而减少.     

电流变体单链的力学性质

研究了由微小潮湿玻璃球在硅油中加直流电场后形成的电为体单“链”的力学性质,发现受剪单链的剪切屈服应力与外加电场强度的１．４次幂成正比,剪切屈服应力与组成链的玻璃球的数量（３￣５个）无关。在较小的剪应变下,剪就力随剪应变的增加而增加;剪应力达到最大值（屈服点）以后又开始随剪应变的增大而减小。实测单链的剪切屈服应力及剪切模量随电场强度的变化与理论预报吻合良好。     

含裂纹的周期简支梁振动功率流特性

在周期简支梁中,利用周期结构理论、波在周期简支梁中的传播特性和裂纹受拉时的弯曲弹簧假设,推导了含裂纹梁单元受到激励时,单元左右两端输出的振动功率流计算公式;通过绘制的功率流比值曲线,给出了识别裂纹深度和位置的方法以及裂纹诊断的步骤和优势。