索夹对自锚悬索桥成桥状态影响分析

基于有限单元法(FEMC)比较分析了索夹对自锚悬索桥成桥状态的影响.索夹能够提高中跨主缆的成桥线形,在维持索长不变的情况下,各吊杆的成桥索力会有所增大,若使各吊杆均达到设计成桥索力值,则需增大各吊杆的无应力长度值.基于计入索夹影响的FEMC模型分别讨论了索夹长度、截面面积和惯性矩等参数对结构成桥状态的影响,并且建立了根据索夹长度比和面积比计算得到的主缆中跨跨中控制点成桥高程提升量和吊杆索力平均增量值的简化计算公式.经工程实例验证,提出的索夹模型计算结果与结构实际变形接近.     

Development of planar patch clamp technology and its application in the analysis of cellular electrophysiology

A patch clamp chip, as a novel cell-based chip for electrophysiological recordings, has many prominent advantages such as high resolution, accuracy, high throughput and automation. It can be used to perform multivariate and real-time measurements of cell networks in situ. Therefore, this technology will dramatically promote the research on ionic channels, neuronal networks and the application of this technology in drug screening. This paper reviews the development of planar patch clamp technology and its applications in detail. The latest progress in the research of taste cells electrophysiology and taste transduction is also presented. Finally, this paper analyzes the methodology of neural chips. Based on the current research of our laboratory, the prospective applications of a patch clamp chip in the research of taste sensation and transduction mechanisms at molecular and cellular levels are discussed.     

Melittin Makes “Ion Channel” on the Membrane of Cells

ＩｎｔｒｏｄｕｃｔｉｏｎＭｅｌｉｔｉｎｉｓａｍａｊｏｒｐｒｏｔｅｉｎｉｎｔｈｅｖｅｎｏｍｏｆｔｈｅＥｕｒｏｐｅａｎｈｏｎｎｙｂｅｅ，ＡｐｉｓＭｅｌｉｆｅｒａ．Ｉｔｉｓａｐｅｐｔｉｄｅｗｉｔｈ２６ａｍｉｎｏａｃｉｄｓ，ａｎｄａｎＭＷｏｆ２８５０．Ｔｈｅ...     

江西玉山县王家坝晚奥陶世三衢山组点礁发育特征及其群落研究

本文研究了玉山王家坝晚奥陶世三衢山组的点礁,描记了三个生物群落:Sibiriolites jiangxiensis群落,Fletcheriella grandis-Pachystylostroma群落和Trocholites-Encrinuroides群落.依据造礁功能的不同,作者还简述了组成点礁的各种生物群团.     

C-peptide fragments stimulate glucose utilization in diabetic rats

Studies of C-peptide cellular effects show that not only the full-length native peptide but also specific C-terminal fragments are biologically active in in vitro systems. In the present study, the effect of five C-peptide fragments and the native peptide on whole-body glucose turnover was studied in streptozotocin diabetic rats using the insulin clamp technique. Insulin was infused intravenously at 18 pmol kg^–1 min^–1 for 90 min and blood glucose concentration was clamped at 8 and 4 mM in diabetic and non-diabetic animals. A steady state was reached during the last 30 min of the study period. Rat C-peptide II and fragments comprising residues 27–31 and 28–31 were effective in augmenting glucose turnover in diabetic rats (+100% to 150%), while no significant effects were seen for segments 1–26, 11–19 and 11–15. The metabolic clearance rate for glucose during infusion of C-peptide or fragments 27–31 and 28–31 in diabetic rats was similar to that seen in non-diabetic animals. We conclude that C-terminal tetra- and pentapeptides, but not fragments from the middle segment of C-peptide, are as effective as the full-length peptide in stimulating whole-body glucose turnover in diabetic rats.Received 18 December 2003; received after revision 19 January 2004; accepted 21 January 2004     

Relationship between action potential, contraction-relaxation pattern, and intracellular Ca2+ transient in cardiomyocytes of dogs with chronic heart failure

Abnormalities of contractile function have been identified in cardiomyocytes isolated from failed human hearts and from hearts of animals with experimentally induced heart failure (HF). The mechanism(s) responsible for these functional abnormalities are not fully understood. In the present study, we examined the relationship between action potential duration, pattern of contraction and relaxation, and associated intracellular Ca²⁺ transients in single cardiomyocytes isolated from the left ventricle (LV) of dogs (n = 7) with HF produced by multiple sequential intracoronary microembolizations. Comparisons were made with LV cardiomyocytes isolated from normal dogs. Action potentials were measured in isolated LV cardiomyocytes by perforated patch clamp, Ca²⁺ transients by fluo 3 probe fluorescence, and cardiomyocyte contraction and relaxation by edge movement detector. HF cardiomyocytes exhibited an abnormal pattern of contraction and relaxation characterized by an attenuated initial twitch (spike) followed by a sustained contracture ('dome') of 1 to 8 s in duration and subsequent delayed relaxation. This pattern was more prominent at low stimulation rates (58% at 0.2 Hz, n = 211, 21% at 0.5 Hz, n = 185). Measurements of Ca²⁺ transients in HF cardiomyocytes at 0.2 Hz manifested a similar spike and dome configuration. The dome phase of both the contraction/relaxation pattern and Ca²⁺ transients seen in HF cardiomyocytes coincided with a sustained plateau of the action potential. Shortening of the action potential duration by administration of saxitoxin (100 nM) or lidocaine (30 μM) reduced the duration of the dome phase of both the contraction/relaxation profile as well as that of the Ca²⁺ transient profile. An increase of stimulation rate up to 1 Hz caused shortening of the action potential and disappearance of the spike-dome profile in the majority of HF cardiomyocytes. In HF cardiomyocytes, the action potential and Ca²⁺ transient duration were not significantly different from those measured in normal cells. However, the contraction-relaxation cycle was significantly longer in HF cells (314 ± 67 ms, n = 21, vs. 221 ± 38 ms, n = 46, mean ± SD), indicating impaired excitation-contraction uncou pling in HF cardiomyocytes. The results show that, in cardiomyocytes isolated from dogs with HF, contractile abnormalities and abnormalities of intracellular Ca²⁺ transients at low stimulation rates are characterized by a spike-dome configuration. This abnormal pattern appears to result from prolongation of the action potential. Received 22 January 1998; received after revision 16 March 1998; accepted 27 March 1998     

架空输电线紧线器的可靠性设计

本文对大负荷容量架空输电线紧线器设计中的可靠性问题作了深入讨论.对紧线器的结构与受力状态作了计算分析,并对所用铝合金材料进行了低循环疲劳、断裂及裂纹扩展速率等一系列力学性质的试验研究.采用有限元法和应变电测法,确定了紧线器钳体的应变幅值及高应变区域.对于这些区域按局部应力应变法进行了寿命估算,在此基础上改进了设计,将最高应变幅控制在许用应变幅以内,考察了钳体的损伤容限,使紧线器安全可靠性能得到充分保证,其重量也大幅度减轻.     

膜片钳仪的低噪声设计

本文研制的PC-Ⅰ型膜片钳可以分辨细胞膜上离子单通道电流信号(1pA,10kHz).在分析PC-Ⅰ原理的基础上讨论了其抑制噪声、扩展频带、输入杂散电容和输入电阻的补偿技术.给出了PC-Ⅰ的1GΩ/0.1GΩ探头内用机械开关切换对杂散电容敏感的高阻值反馈电阻的有效方法。在信噪比足够高的条件下,仪器的测量误差≤2％。     

从发明先进医学设备获诺贝尔医学奖中得到的启示

百年来的诺贝尔生理或医学奖中,因发明先进的仪器设备而获诺贝尔医学奖共有四次,它们是:1924年爱因托芬(荷兰)发明了心电图机;1979年科马克(美国)亨斯菲尔德(英国)发明了电脑辅助X线断层摄影(CT);1980年内尔(德国)萨克曼(德国)发明了应用膜片钳技术;2003年比德.曼斯菲尔德(英国)和保罗.劳特布尔在核磁共振成像技术领域的突破性成就。这些先进的仪器设备的发明对人类的科学与文明的贡献是巨大的,我们从多方面可以得到深刻的启示[1]。