Variations of physical properties in pellets containing alumina/carbon powder mixtures during reduction and nitridation

Surface area and porosity of pellets containing alumina/carbon powder mixtures during reduction and nitridation were determined. The experimental results indicated that surface area and porosity of solid samples were decreased by increasing the reaction temperature, grain size, forming pressure and the amount of catalyst. Increasing the molar ratio of C/Al₂O₃ and gas flow rate could decrease the surface area and increase the porosity of the solid sample.     

Management of lymphoproliferative disorders after cardiac transplantation

We conducted a retrospective study of 516 cardiac recipients who underwent transplantation between April 1983 and April 1992, 19 of whom had development of post-transplantation lymphoproliferative disorders (PTLDs). These 19 patients presented with involvement of lung (5), gastrointestinal tract (5), disseminated disease (6), and adenoids and lymph nodes (3). B-cell proliferations ranging from an atypical hyperplasia to malignant lymphoma developed in 18 patients, and mixed cellularity Hodgkin's disease developed in 1 patient. The 19 patients with PTLD displayed a predominance of both women and cardiomyopathy as the indication for transplantation when compared with two separate control populations. No correlation was found between demographic criteria analyzed and (1) early versus late diagnosis of PTLD after transplantation, (2) the site of PTLD involvement, or (3) the histopathologic category of the PTLD lesion. Patients with gastrointestinal tract and lung PTLD involvement enjoyed an improved survival after both transplantation and PTLD diagnosis when compared with patients with PTLD involvement of all other extranodal sites. We report a high incidence of PTLD involving the lung and gastrointestinal tract in our cohort study. These sites of involvement responded better to a reduction in immunosuppression than did the other extranodal sites of involvement.     

鸡烟碱样胆碱能受体与[~(125)I]-α-银环蛇毒素结合动力学的研究

从鸡脑及骨骼肌中分离提取烟碱样胆碱能受体,用[~(125)I]-α一银环蛇毒素进行受体-配体结合动力学研究。结果表明,这种结合呈二级动力学反应性质。脑视叶中提纯的受体和骨骼肌中分离的受体,K_D值分别为129pM及4pM(25℃)。烟碱、箭毒碱等可抑制受体-配体的结合反应并测得各自的抑制常数及Hill系数。     

High-transconductance insulating-gate InP/InGaAs buried p-bufferDH-MODFETs grown by MOVPE

Buried p-buffer double heterostructure modulation-doped field-effect transistors (BP DH-MODFETs) with an InGaAs quantum-well channel were fabricated with high transconductance and good breakdown voltage, by placing the metal gate directly on Fe-doped InP insulating layer. Excellent extrinsic DC transconductance of 560 mS/mm and a high gate-to-drain diode breakdown voltage (greater than 20 V) were achieved at room temperature with FETs of 1.2-μm gate length. Unity currently gain cutoff frequency f_T of 24 GHz and maximum oscillation frequency f_max of 60 GHz were demonstrated for a drain to source voltage V_DS=4 V, which corresponds to an average electron velocity of 2.2×10⁷ cm/s in the quantum well     

激光熔覆用钴基合金粉末的研究

对激光熔覆用WFLC－11钴基合金粉末的激光熔覆工艺和熔覆层性能进行了研究，获得了WFLC－11钴基合金粉末激光熔覆层厚度与最小比能量关系曲线和熔覆层的组织、高温硬度等性能数据，为选择和使用WFLC－11钴基合金粉末提供了依据。     

离散效应存在时孤子脉冲的增强压缩

在群速度不匹配的条件下，提出一种提高孤子脉冲压缩效应的新方法．研究表明，若使信号脉冲与泵浦脉冲存在一适当的初始延时，则不但可以提高离散效应单独存在时信号脉冲的压缩比，而且可以提高孤子脉冲的压缩质量．     

EM发酵饲料中主要微生物类群的动态变化

对EM发酵饲料中乳酸杆菌、酵母菌、大肠菌群、腐败菌等微生物类群的动态变化进行了研究。结果表明 :饲料经EM发酵后 ,乳酸杆菌大量增加 ,发酵第4天达到最大值(9.5×108CFU·g-1 饲料) ,大肠菌群与腐败菌被明显抑制。并认为细菌总数与酵母菌数量不能作为评价EM发酵饲料质量好坏的指标。     

管杆漏磁探伤现场应用中的问题及对策

阐述了漏磁探伤漏磁场沿管、杆径向的分布特征 ,分析了影响探伤装置漏磁检测准确性的 4个因素 ,验证了信号提离距离的变化对传感器和探伤装置灵敏度的影响。针对在用的大多数浮动式传感器固定机构存在的两个严重缺点 ,提出采用自定位传感器固定机构 ,可消除机械装置对传感器灵敏度的影响。提出了一套标定和校验检测装置的方法 ,以保证探伤仪器的检测灵敏度始终恒定 ,提高检测结果的准确性和可靠性。     

我国车用无铅汽油的质量状况及分析

对1998－2001年间生产领域和流通领域的近500批次汽油产品检验数据进行了总结和分析，表明我国汽油的实物质量正在不断提高，但从环保要求出发还需不断向国际水平靠扰，尤其应进一步降低烯烃含量，硫含量。