Bone indentation recovery time correlates with bond reforming time.

Despite centuries of work, dating back to Galileo, the molecular basis of bone's toughness and strength remains largely a mystery. A great deal is known about bone microsctructure and the microcracks that are precursors to its fracture, but little is known about the basic mechanism for dissipating the energy of an impact to keep the bone from fracturing. Bone is a nanocomposite of hydroxyapatite crystals and an organic matrix. Because rigid crystals such as the hydroxyapatite crystals cannot dissipate much energy, the organic matrix, which is mainly collagen, must be involved. A reduction in the number of collagen cross links has been associated with reduced bone strength and collagen is molecularly elongated ('pulled') when bovine tendon is strained. Using an atomic force microscope, a molecular mechanistic origin for the remarkable toughness of another biocomposite material, abalone nacre, has been found. Here we report that bone, like abalone nacre, contains polymers with 'sacrificial bonds' that both protect the polymer backbone and dissipate energy. The time needed for these sacrificial bonds to reform after pulling correlates with the time needed for bone to recover its toughness as measured by atomic force microscope indentation testing. We suggest that the sacrificial bonds found within or between collagen molecules may be partially responsible for the toughness of bone.     

失能眩光形成机理的研究

由视觉可靠性的要求,分析了阈对比和背景亮度之间的关系;根据夜间行车时前照灯的实际照明环境,讨论了眩光在人眼视网膜上形成的等效光幕亮度及产生的失能眩光;等效光幕亮度的增加导致对比度下降并使眼睛出现失能;最后给出了当光强增大时由于对比度下降而造成失能眩光出现的实验结果。     

恢复类中具有分布时滞的传染病模型

研究了具有非线性接触率βＩ＾ｐＳ＾ｑ／（１＋αＩ）和恢复类中具有分布时滞的ＳＩＲＳ传染病模型的解的存在性和平衡位置以及平凡平衡位置的稳定性。     

磁共振短时反转恢复序列在骨肉瘤诊断中的应用

目的 探讨骨肉瘤的MRI特征,提高对骨肉瘤的认识.方法 回顾性分析24例经手术或穿刺病理证实的骨肉瘤患者的MRI影像资料.结果 胫骨上端11例,股骨下端10例,肱骨2例,跟骨1例,所有患者在常规MRI检查序列中均显示为T1及T2低信号且在T2低信号中出现不规则高信号,边缘及软组织显示较清晰,在短时反转恢复序列中,所有病变均表现为不规则高信号改变,显示的病变范围及周边侵蚀更明显.结论 骨肉瘤在MRI/STIR检查中有一定的影像特征,有助于骨肉瘤的诊断,尤其对于早期骨肉瘤的诊断.     

磁共振短时反转恢复序列在骨肉瘤诊断中的应用

目的 探讨骨肉瘤的MRI特征，提高对骨肉瘤的认识。方法回顾性分析24例经手术或穿刺病理证实的骨肉瘤患者的MRI影像资料。结果胫骨上端11例，股骨下端10例，肱骨2例，跟骨1例，所有患者在常规MRI检查序列中均显示为T1及T2低信号且在T2低信号中出现不规则高信号，边缘及软组织显示较清晰，在短时反转恢复序列中，所有病变均表现为不规则高信号改变，显示的病变范围及周边侵蚀更明显。结论骨肉瘤在MRI／SnR检查中有一定的影像特征，有助于骨肉瘤的诊断，尤其对于早期骨肉瘤的诊断。     

The time course of visual categorization： Electrophysiological evidence from ERP

Categorization is the process to ascertain the identity of an object by a specific standard[1,2]. Categorization isa fundamental cognitive process; in fact, the raw per- ception would be of little use without the effective clas- sification of original inf…     

Channel kinetics determine the time course of NMDA receptor-mediated synaptic currents

Synaptic release of glutamate results in a two component excitatory postsynaptic current (e.p.s.c.) at many vertebrate central synapses. Non-N-methyl-D-aspartate receptors mediate a component that has a rapid onset and decay while the component mediated by N-methyl-D-aspartate (NMDA) receptors has a slow rise-time and a decay of several hundred milliseconds, 100 times longer than the mean open time of NMDA channels. The slow decay of the NMDA-mediated e.p.s.c. could be due to residual glutamate in the synaptic cleft resulting in repeated binding and activation of NMDA receptors. However, in cultured hippocampal neurons, we find that the NMDA receptor antagonist D-2-amino-5-phosphonopentanoate has no effect on the slow e.p.s.c. when rapidly applied after activation of the synapse, suggesting that rebinding of glutamate does not occur. In addition, a brief pulse of glutamate to an outside-out membrane patch results in openings of NMDA channels that persist for hundreds of milliseconds, indicating that glutamate can remain bound for this period. These results imply that a brief pulse of glutamate in the synaptic cleft is sufficient to account for the slow e.p.s.c.     

粗波分复用技术在同城容灾系统中的应用

为满足降低数据丢失风险,提高数据和应用系统可用性的需要,在研究粗波分复用技术特点的基础上,利用粗波分复用光电转换模块设计了存储扩展接口,对接口的电气特性进行了测试.测试结果表明:接口的电气特性良好,对信号具有放大的作用.同时,对基于该接口构建的城域网范围内光纤通道存储扩展系统原型的读写性能进行了测试,测试结果显示,20 km距离的存储读写吞吐率达到了14 Mbit/s,为构建同城容灾系统提供了一种新方法.     

信息时代制图课教学体系的探讨与实践

探讨了当前新兴学科层出不穷与计算机飞速发展时代制图课程教学体系的调整、改进与变更.强调高科技条件下工程技术人员与军事指挥人员具备阅读、绘制工程技术图样与空间想像力、创造思维能力的重要性;在对计算机绘图与传统手工制图教学相辅相成与协调发展、教学课时与内容增减及合理安排、制图工具与理论创新的研究与实践的基础上,取得了实际经验和理论成果。初步形成了具有“多快好省”特点的制图课教学体系.对制图课程的未来发展做了客观展望.该研究对制图课程的教学、实际应用与发展有积极作用.     

Predicting spontaneous recovery of memory.

Long after a new language has been learned and forgotten, relearning a few words seems to trigger the recall of other words. Neural-network models indicate that this form of spontaneous recovery may result from the storage of distributed representations, which are thought to mediate human memory. Here we use a psychomotor learning task to show that a corresponding effect of spontaneous memory recovery occurs in human subjects.     

Human inspired lighting control in robot systems with the intention of glare avoidance

This paper presents some human-inspired strategies for lighting control in a robot system for best scene interpretation,where the main intention is to avoid possible glares or highlights occurring in images. It firstly compares the characteristics of human eyes and robot eyes. Then some evaluation criteria are addressed to assess the lighting conditions. A bio-inspired method is adopted to avoid the visual glare which is caused by either direct illumination from large light sources or indirect illumination reflected by smooth surfaces. Appropriate methods are proposed to optimize the pose and optical parameters of the light source and the vision camera.     

我校大学体育课程的现状及改革构想

针对我校大学体育课程的现状,依据教育部新<纲要>精神,结合当今大学体育教育思想和教学改革方向,提出课程改革的构想转变课程指导思想;调整课程设置、扩展教学内容;改革教学模式;加强师资建设、改善体育设施.     

我校大学体育课程的现状及改革构想

针对我校大学体育课程的现状,依据教育部新《纲要》精神,结合当今大学体育教育思想和教学改革方向,提出课程改革的构想:转变课程指导思想;调整课程设置、扩展教学内容;改革教学模式;加强师资建设、改善体育设施。     

我校大学体育课程的现状及改革构想

针对我校大学体育课程的现状,依据教育部新<纲要>精神,结合当今大学体育教育思想和教学改革方向,提出课程改革的构想:转变课程指导思想;调整课程设置、扩展教学内容;改革教学模式;加强师资建设、改善体育设施.