Effects of initial crystal size of diamond powder on surface residual stress and morphology in polycrystalline diamond (PCD) layer

Polycrystalline diamond compacts (PDC) were synthesized using diamond powder of average crystal size 3-20 μm by the Ni 70 Mn 25 Co 5 alloy infiltration technique at high temperature and high pressure (HPHT).The surface residual stress of polycrystalline diamond (PCD) layer was measured using micro-Raman spectroscopy with hydrostatic stress model and X-ray diffraction (XRD).Measurements of the stress levels of PCDs show that the residual compressive stresses range from 0.12 to 0.22 GPa,which increase with th...     

The dependence of structure and properties of polycrystalline diamonds (PCD) on the conditions of their production

Abstract

AES and SIMS were used to analyze the diamond powders surface composition using LAS-3000 device. It is found that impurities on diamond particles surfaces have a detrimental effect on the PCD sintering and physico-mechanical properties of the product.     

三种细胞质雄性不育水稻小孢子发育过程的研究

运用ＤＮＡ荧光探针结合显微荧光术，系统地研究了３种水稻细胞质雄性不育系的败育过程、时期和特点．结果表明，珍汕９７不育系不能完成小孢子第一次有丝分裂；马协不育系小孢子可完成第一次有丝分裂，但不能进入第二次有丝分裂；广丛４１不育系部分小孢子可完成第二次有丝分裂，因此可看到许多三核花粉，但因核行为异常而败育．小孢子的败育过程可能是一种程序性细胞死亡（ＰＣＤ）的过程     

细胞凋亡分析测试方法的研究进展*

本文对细胞凋亡的测试方法进行了较全面的综述, 介绍了细胞凋亡的形态学特征和生化特征, 重点评述了细胞凋亡的各种分析测试方法, 包括形态学观察法、琼脂糖凝胶电泳法、流式细胞计数法、原位DNA 标记检测法、anti-ssDNA MAbs 分析和PCR 技术。对细胞凋亡测试方法的发展趋势作了讨论。     

Active control schemes for aseismic base-isolated structures

Summary  Active control schemes are used for the protection of base-isolated and seismically excited buildings. The desired control objective is to keep the whole structure arbitrarily close to its initial configuration prior to the earthquake. The proposed methods require control force application only at the base of the structure. The controllers developed may depend on information obtained from all the floors or just the first (base) floor alone. Received 13 September 2000; accepted for publication 26 June 2001 RID=" ID=" Dedicated to the memory of Professor P.D. Panagiotopoulos with our warmest prayers. RID=" ID=" The first author wishes to thank Prof. G. Leitmann and Prof. E. Papadopoulos for the numerous helpful discussions. The same author is supported in part by the Institute of Communication and Computer Systems, NTUA, under the program Archimedes 65/1017.     

二阶偏振模色散矢量致脉冲展宽的理论分析

我们首次提出了消偏矢量的概念，并用它来描述二阶偏振模色散中偏振模色散矢量方向的变化。本文导出了由于二阶偏振模色散所引起的脉冲展宽的解析表达式，结论指出，偏振相关的本征色散总是使脉冲展宽加剧；而偏振模色散矢量方向的变化（消偏矢量），却是使脉冲展宽减弱。二阶偏振模色散对脉冲的展宽，不仅与偏振相关的本征色散和消偏矢量有关，而且还与信号的传输速率以及初始一阶偏振模色散的大小有关。信号速率的提高，将明显的使二阶偏振模色散的影响增强。在偏振相关的本征色散不为零的情况下，通过调整初始偏振态矢量、初始一阶偏振模色散矢量以及消偏矢量三者的方向，使它们互相平行，可以获得最佳的色散补偿。但是却不能获得完全的色散补偿。在最佳色散补偿时的最小脉冲展宽为σ= (2^1/2/4)( DCF/T₀).     

Natural limit of the number of copper ions chemisorbed on the surface of a detonation nanodiamond

The upper limit of the amount of copper ions that can be grafted to the detonation nanodiamond surface has been calculated. A maximum of 34 wt% copper can be grafted to carboxylated and hydroxylated 5 nm nanodiamonds. The results of calculations have been compared with the experimental and published data.     

烧结多晶钻石的压力、温度与压力场、温度场

本文根据钻石自体烧结、生成碳化物烧结、扫越催化再结晶方式与石墨一次生长多晶钻石四种不同方法的烧结机制,论述了相应的压力场、温场及压力温度工艺条件.     

动物细胞凋亡相关基因p53和c-myc在大麦中的染色体定位

以人的原癌基因c myc和抑癌基因p53的cDNA为探针,经Southern杂交证明,它们在大麦基因组中存在同源序列.利用荧光原位杂交技术(FISH)进一步对大麦进行了染色体定位.在大麦有丝分裂中期染色体上p53有3个位点被检出,分别位于2L(第二染色体长臂)、2S(第二染色体短臂)和6L上,相应百分距离为84.27±0.75、46.24±15.44和19.23±0.53;c myc有2个位点被检出,分别位于5L和3S上,百分距离相应为75.90±6.62和47.63±5.20.利用改进的荧光原位杂交技术,使异源单拷贝或低拷贝基因在大麦姐妹染色单体上,同时出现信号的检出率达到了30%以上.