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排序方式: 共有3140条查询结果,搜索用时 31 毫秒
991.
聚乳酸组织工程支架表面涂覆钙磷盐的工艺研究 总被引:3,自引:0,他引:3
提出了以聚乳酸/钙磷盐/胶原的骨组织工程支架快速成形制造的材料系统,对比了两种在聚乳酸(PLA)表面涂覆钙磷盐的工艺.一种是将聚乳酸组织工程支架浸泡在模拟体液中采用平衡反应法沉积钙磷盐;另一种是在聚乳酸薄膜上采用非平衡反应法沉积钙磷盐;系统地研究了沉积时间和沉积量、钙磷摩尔比和相结构演变的关系;通过控制反应时间和调整反应物配比获得磷酸四钙(TetCP)-PLA和无定形磷酸钙(ACP)—PLA等材料组合;并对所获得的复合材料进行生物相容性试验.对比试验证明细胞在材料表面生长良好,采用两种方法涂覆钙磷盐均改进了聚乳酸的生物相容性. 相似文献
992.
承德低品位钙基膨润土制备高效活性白土的工艺研究 总被引:6,自引:1,他引:5
以河北承德产低品位钙基膨润土为原料 ,直接用于制备活性白土 ,成功地制备了脱色率大于 99% ,活性度为 2 18,过滤速度达 2 7 3ml/min的高效活性白土 ,并对影响活性白土质量的条件进行了探讨。 相似文献
993.
The experimental investigation of concrete carbonation depth 总被引:2,自引:0,他引:2
Phenolphthalein indicator has traditionally been used to determine the depth of carbonation in concrete. This investigation uses the thermalgravimetric analysis (TGA) method, which tests the concentration distribution of Ca(OH)2 and CaCO3, while the X-ray diffraction analysis (XRDA) tests the intensity distribution of Ca(OH)2 and CaCO3. The Fourier transformation infrared spectroscopy (FTIR) test method detects the presence of C-O in concrete samples as a basis for determining the presence of CaCO3. Concrete specimens were prepared and subjected to accelerated carbonation under conditions of 23 °C temperature, 70% RH and 20% concentration of CO2. The test results of TGA and XRDA indicate that there exist a sharp carbonation front. Three zones of carbonation were identified according to the degree of carbonation and pH in the pore solutions. The TGA, XRDA and FTIR results showed the depth of carbonation front is twice of that determined from phenolphthalein indicator. 相似文献
994.
H. P. M. Vijverberg T. Leinders‐Zufall R. H. S. Westerink 《Materialwissenschaft und Werkstofftechnik》2002,33(12):751-755
From a neurotoxicological perspective, we have investigated effects of Pb2+ and other divalent metal ions on membrane signaling by voltage‐, Ca2+‐ and ligand‐gated ion channels using voltage clamp and patch clamp techniques. The results from our and other studies of the effects of metal ions reported in the literature are summarized here and demonstrate that metal ions cause multiple, distinct effects on a variety of membrane signaling processes. A situation similar to that with membrane ion channels applies to the effects of metal ions on intracellular signaling. Effects on exocytosis, a resultant of highly integrated and complex intracellular signaling, indicate that Pb2+ is a substitute for intracellular Ca2+ in the triggering the fusion and release of exocytotic vesicles. Despite the relatively detailed knowledge of metal effects at the molecular level, few specific cellular targets associated with specific toxic effects of metals have been identified. Such knowledge is essential for the understanding of metal toxicity. 相似文献
995.
Thermodynamic calculation of Sn (Ⅳ)-NH4+-Cl--H2O system 总被引:1,自引:0,他引:1
According to the principles of simultaneous equilibrium and electronic charge neutrality, the thermodynamics of Sn(Ⅳ)-NH4 -Cl- -H2O system under normal condition was calculated. Relation between all sorts of complex of Sn4 and pH was plotted. Based on thermodynamics analysis and calculation, some experiments were done to validate the relation between the total concentration of tin ion and pH in this system. The results suggest that the total concentration of ammonium and pH are the most important factors which determine whether (NH4)2SnCl6 or Sn(OH)4 exists in this system. Results further suggest when contnet of HCl is more than 6 mol/L, Sn4 in this system will be also precipitated in the form of (NH4)2SnCl6. These results lay the solid theory foundation to preindium tin oxide(ITO), from the tinny material. 相似文献
996.
本文根据引黄国际Ⅰ标工程的具体情况,合理地选用导爆管起爆法,对影响导爆管起爆的因素进行了分析,得出了起爆网路雷管段别的最佳选配方案。 相似文献
997.
小鼠精子附睾成熟过程中Ca^2+及Ca^2+—ATPase的研究 总被引:1,自引:0,他引:1
利用焦锑酸钾方法和电镜酶组织化学定位方法,研究了小鼠精子在附睾成熟过程中的Ca^2+及Ca^2+-ATPase变化。结果发现:附睾头中的精子内元Ca^2+或极低,而Ca^2+-ATPase活性极强,可能是由于Ca^2+-ATPase的作用将Ca^2+从精子内排出了精子外;在附睾体中,精子Ca^2+-ATPase活性降低,而Ca^2+浓度迅速上升,并且发现Ca^2+来自于附睾管细胞;到了附睾尾部,精 相似文献
998.
Under bump metallurgy study for Pb-free bumping 总被引:1,自引:0,他引:1
The demand for Pb-free and high-density interconnection technology is rapidly growing. The electroplating-bumping method is
a good approach to meet finepitch requirements, especially for high-volume production, because to volume change of patterned-solder
bumps during reflow is not so large compared with the stencil-printing method. This paper proposes a Sn/3.5 Ag Pb-free electroplating-bumping
process for high-density Pb-free interconnects. It was found that a plated Sn/Ag bump becomes Sn/Ag/Cu by reflowing when Cu
containing under bump metallurgy (UBM) is used. Another important issue for future flip-chip interconnects is to optimize
the UBM system for high-density and Pb-free solder bumps. In this work, four UBM systems, sputtered TiW 0.2 μm/Cu 0.3 μm/electroplated
Cu 5 μm, sputtered Cr 0.15 μm/Cr-Cu 0.3 μm/Cu 0.8 μm, sputtered NiV 0.2 μm/Cu 0.8 μm, and sputtered TiW 0.2 μm/NiV 0.8 μm,
were investigated for interfacial reaction with electroplated Pb/63Sn and Sn/3.5Ag solder bumps. Both Cu-Sn and Ni-Sn intermetallic
compound (IMC) growth were observed to spall-off from the UBM/solder interface when the solder-wettable layer is consumed
during a liquid-state “reflow” process. This IMC-spalling mechanism differed depending on the barrier layer material. 相似文献
999.
1000.