Role of cyclic GMP-inhibitable phosphodiesterase and nitric oxide in the beta adrenoceptor control of renin secretion

We have reported that inhibition of nitric oxide synthesis with N(G)-nitro-L-arginine methyl ester (L-NAME) attenuates the renin secretory response to beta adrenoceptor stimulation. We proposed that the attenuation results from disinhibition of the cyclic GMP-inhibitable isoform of phosphodiesterase (PDE III) with a resultant increase in cyclic AMP hydrolysis in the juxtaglomerular cells. In our investigation, experiments were performed in conscious rabbits to test the effects of the specific PDE III inhibitor milrinone on resting renin secretion and on the renin responses to isoproterenol and L-NAME. In the first series of experiments, infusion of milrinone increased plasma renin activity from 5.4 +/- 0.6 to 10.2 +/- 1.4 ng/ml/2 hr (P < .01). Heart rate increased markedly, but arterial pressure did not change. In the second series, infusion of isoproterenol increased plasma renin activity from 6.3 +/- 1.1 to 15.0 +/- 1.0 ng/ml/2 hr (P < .01). The renin response to isoproterenol was increased (P < .01) in the presence of milrinone (15.3 +/- 3.7 to 38.4 +/- 6.2 ng/ml/2 hr, P < .01). In the third series, L-NAME alone decreased plasma renin activity from 5.0 +/- 1.0 to 3.3 +/- 1.0 ng/ml/2 hr (P < .01). Milrinone again increased plasma renin activity and prevented the suppression of plasma renin activity by L-NAME. By contrast, milrinone did not alter the suppression of plasma renin activity produced by infusion of phenylephrine. In addition, a PDE IV inhibitor failed to prevent the suppression of PRA by L-NAME. Finally, administration of milrinone completely reversed the L-NAME-induced suppression of the renin response to isoproterenol. These results provide evidence that PDE III participates in the regulation of renin secretion, and support the proposal that the L-NAME-induced reductions in renin secretion and in the renin response to beta adrenoceptor stimulation result from disinhibition of PDE III and increased hydrolysis of cyclic AMP in the juxtaglomerular cells.     

Quantitative gait analysis after bilateral total knee arthroplasty with two different systems within each subject

The functional behavior of two kinematically different knee arthroplasty systems within each subject was studied by gait analysis (three-dimensional kinematics, kinetics, dynamic electromyography) in five elderly patients, 2 to 5 years after bilateral surgery. Clinical results were good, yet gait velocity was reduced (range, 0.57-1.1 m/s), with a shortened stride length and a decreased duration of single-limb stance in all subjects. Force plate recordings revealed an undynamic gait with slow loading, reduced modulation of the vertical forces, and poor fore/aft shears. Sagittal plane knee motion during gait was reduced in all subjects, with trunk and pelvic compensation patterns for foot clearance. Muscle activity around the knee was prolonged bilaterally, with activity modulation related to the motion pattern. Although the stride parameters were quite symmetric, there was a marked asymmetry of the motion pattern, with a side-to-side difference of peak knee flexion during stance and swing phase of up to 15 degrees. This finding, however, was not clearly related to the type of prosthesis. Even within one subject, significant side-to-side variability may persist, which leads to asymmetry of the motion pattern, unrelated to the kinematic design of the implant. Other factors, such as the patella-extensor mechanism, ligament balancing, leg-length discrepancy, proprioception, continuation of a preoperative habit, or a contralateral influence, may explain part of the asymmetry seen in these subjects.     

基于水华爆发的水源地安全模糊评价

根据水源地频发的水华爆发现象,采用故障树分析法,分析导致水源地水华爆发的原因.根据故障树分析结果,结合2010—2011年东营市某水源地水源数据资料,建立评价指标体系.采用模糊综合评价分析法,从水华爆发的角度对东营市某水源地进行安全评价,最终确定该水源地的安全等级.     

修正时间硬化理论的PBX蠕变模型及其应用

利用基于修正时间硬化理论的蠕变模型来模拟炸药部件的短时蠕变行为。以HMX基PBX的15次单轴压缩蠕变实验数据确定了15组模型参数,抽取3组利用ANSYS软件进行模拟实验来验证模型。根据正态分布小概率原理最终确定了通用的蠕变模型参数。应用获得的蠕变模型对真空吸附作用下的该型PBX部件进行蠕变仿真,获得其在1h内的蠕变变形。理论分析和数值模拟结果表明,该模型能很好地描述HMX基PBX的蠕变特性,可以运用于机械加工过程中炸药部件受夹持力作用的短时蠕变仿真。     

转矩流变仪制备再生胶的工艺及性能

利用转矩流变仪的高温剪切作用并添加再生活化剂420对废旧轮胎胶粉(GTRP)进行了再生,讨论了活化剂用量和加工温度对再生胶再生程度及力学性能的影响。结果表明,随着活化剂用量的增大和温度的上升,GTRP溶胶含量明显上升,门尼粘度和交联密度均明显下降。转子转速为50r/min,加工时间为15min,加工温度为170℃,活化剂420用量为0.5份时,所得再生胶具有最佳综合力学性能。     

氨气预氮化制备超薄氮化硅薄膜及电学性能

为寻求制备性能良好的纳米厚度氮化硅(SiN_x)薄膜的方法,采用NH_3等离子体氮化、SiH_4/NH_3等离子增强化学淀积法及先氮化后淀积的方法制备了三种SiN_x薄膜,研究比较了三种薄膜的性质。用X射线光电子谱检测了NH_3等离子体氮化Si片得到的SiN_x薄膜的组分,利用椭圆偏振光谱仪测量薄膜厚度,估算了氮化速率。用NH_3和SiH_4作为反应气,分别在原始硅片和经过NH_3预氮化后的硅片上淀积厚度为5 nm、10 nm和50 nm的SiN_x薄膜。用电容-电压法研究了薄膜样品的电学性质,发现单纯用NH_3等离子体氮化的薄膜不适合做介质膜,而先用NH_3氮化再淀积SiN_x的样品比直接淀积SiN_x的样品界面性能明显改善,界面态密度降低到1～2×10~(11)eV~(-1) cm~(-2)。     

SiC衬底AlGaN/GaN HEMT的热分析与测试

对SiC衬底AlGaN/GaN HEMT的结温进行了理论计算与实测。计算中考虑了衬底材料热导率随温度的变化以及器件源、漏电阻上的热损耗,不同耗散功率下的理论计算与红外显微镜实测结果比较表明,两者相差最大不超过10℃。由于理论计算结果是在解析解的基础上运用计算机迭代计算获得,所耗时间较短,故这一结果对于改善器件结构以提高AlGaN/GaN HEMT及其MMIC电路的性能将有较大帮助。