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研究了盐浴软氮化对42CrMo钢的摩擦性能的影响.对42CrMo进行盐浴软氮化处理,处理过的试件和未处理试件分别在不同的载荷和润滑情况下进行摩擦试验.结果表明,盐浴软氮化处理过的试件比未处理过试件的抗胶合能力至少提高了500 N.盐浴软氮化工艺能够有效地改善机车用大齿轮使用中胶合破坏严重的现状. 相似文献
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JIA Wenyan KONG N MA Jun LIU Hesheng GAO Xiaorong GAO Shangkai YANG Fusheng 《自然科学进展(英文版)》2006,16(7):691-700
An important consideration in epileptic seizure prediction is proving the existence of a pre-seizure state that can be detected using various signal processing algorithms. In the analyses of intracranial electroencephalographic (EEG)recordings of four epilepsy patients, the short-term changes in the measures of complexity and synchrony were detected before the majority of seizure events across the sample patient population. A decrease in complexity and increase in phase synchrony appeared several minutes before seizure onset and the changes were more pronounced in the focal region than in the remote region. This result was also validated statistically using a surrogate data method. 相似文献
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高性能的癫痫脑电信号自动检测方法对减轻医生负担并提高癫痫的诊断效率具有重要临床研究意义。论文提出了一种能够区分正常、癫痫发作和发作间期脑电信号的高性能三分类系统。采用Daubechies 4小波构成的4级提升式小波变换将脑电信号分解为不同子带信号,求得不同子带信号的近似熵、Teager能量、局部波动率、自回归系数、Hurst指数特征值;利用Fisher得分法进行特征选择,提高分类精度同时减小计算复杂度;基于二叉树多分类支持矢量机(support vector machine, SVM)对脑电信号分类,实现正常、癫痫发作和发作间期信号的自动检测。实验表明,系统的准确率、灵敏度和特异性均达到100%,优于现有的分类识别方法,提出的三分类系统具有良好的分类性能,为癫痫及癫痫发作的临床检测提供了较好参考价值。 相似文献
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Meier S Bräuer AU Heimrich B Nitsch R Savaskan NE 《Cellular and molecular life sciences : CMLS》2004,61(9):1082-1094
Myelin is crucial for the stabilization of axonal projections in the developing and adult mammalian brain. However, myelin
components also act as a non-permissive and repellent substrate for outgrowing axons. Therefore, one major factor which accounts
for the lack of axonal regeneration in the mature brain is myelin. Here we report on the appearance of mature, fully myelinated
axons during hippocampal development and following entorhinal lesion with the myelin-specific marker Black Gold. Although
entorhinal axons enter the hippocampal formation at embryonic day 17, light and ultrastructural analysis revealed that mature
myelinated fibers in the hippocampus occur in the second postnatal week. During postnatal development, increasing numbers
of myelinated fibers appear and the distribution of myelinated fibers at postnatal day 25 was similar to that found in the
adult. After entorhinal cortex lesion, a specific anterograde denervation in the hippocampus takes place, accompanied by a
long-lasting loss of myelin. Quantitative analysis of myelin and myelin breakdown products at different time points after
lesion revealed a temporally close correlation to the degeneration and reorganization pha-ses in the hippocampus. In contrast,
electroconvulsive seizures resulted in brief demyelination and a faster recovery time course. In conclusion, we could show
that the appearance of mature axons in the hippocampus is temporally regulated during development. In the adult hippocampus,
demyelination was found after anterograde degeneration and also following seizures, suggesting that independent types of insult
lead to demyelination. Reappearing mature axons were found in the hippocampus following axonal sprouting. Therefore, our quantitative
analysis of mature axons and myelination effectively reflects the readjusted axonal density and possible electrophysiological
balance following lesion.
Received 22 December 2003; received after revision 11 February 2004; accepted 17 February 2004 相似文献
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摘要: 目的 探讨红藻氨酸( Kainic Acid,KA) 致癫痫大鼠癫痫发作过程中海马组织神经生长因子( nerve growth factor,NGF) 不同时间点表达量的变化。方法 腹腔注射 KA 建立大鼠癫痫模型。采用 TaqMan 探针实时定量 PCR ( Real-time quantitative PCR) 技术,检测注射 KA 后不同时点大鼠海马组织中 NGF 表达量的变化。结果 与 NGF 表达量与生理盐水对照组( NS) 相比,6 ~ 12 h NGF 表达量明显低于 NS 组( P < 0. 05) 、48 ~ 72 h NGF 表达量开始升高并高于 NS 组,在 24、72 h 时其表达量显著高于 NS 组( P < 0. 05) 。结论 NGF 对致癫大鼠的海马具有修复与保护作用。 相似文献
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近年来临床上越来越多采用中西医结合的方法控制癫痫疾病的发作;通过以灌胃给药的方式给予PTZ癫痫幼鼠不同浓度的榆叶粗提液,观察榆叶对PTZ幼鼠癫痫模型的癫痫行为和海马神经元的影响;结果发现:与PTZ癫痫模型组相比,高浓度榆叶粗提液干预将癫痫发生率降低了20%;榆叶粗提液中、高浓度组海马神经元数目明显增加;表明中、高浓度的榆叶粗提液对PTZ癫痫模型有一定的改善作用,一定程度上可以降低癫痫行为的发生率和抑制癫痫对海马神经元的损伤。 相似文献