Model Experiments on Melting of Alloys with Low Melting Temperature in a Medium with High Melting Temperature

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Brownian motion on a square Lennard-Jones lattice: Trapping, hopping, and diffusion

Previously we showed that cGMP hydrolysis in rat whole retinal homogenates exhibited a dose-dependent inhibition following developmental lead exposure and a concentration-dependent inhibition with direct Pb2+ exposure. Additionally, developmental lead exposure resulted in a dose-dependent increase in retinal cGMP and rod Ca2+ levels. To determine whether Pb2+ or Ca2+ directly inhibited the rod-specific cGMP phosphodiesterase (PDE) and to examine the kinetic mechanism of this inhibition, purified bovine rod cGMP PDE was assayed in the presence of varying concentrations of cGMP, and Mg2+, Pb2+, and/or Ca2+. Increasing concentrations of the substrate, cGMP, resulted in a shift of the Pb2+ and Ca2+ concentration-response curves to the left, indicating a decrease in the half-maximal inhibitory concentrations of Pb2+ from nanomolar to picomolar levels. Increasing concentrations of the cofactor, Mg2+, resulted in a shift of the Pb2+ and Ca2+ concentration-response curves to the right, indicating a decrease in the inhibition of PDE activity by Pb2+ or Ca2+. A plot of 1/velocity vs 1/Mg2+ as a function of Pb2+ revealed that picomolar concentrations of Pb2+ competitively inhibited PDE relative to millimolar concentrations of Mg2+. Consistent with this finding, Mg2+ reversed the Pb(2+)-induced inhibition of PDE. Our recent kinetic analysis showed that Mg2+ and cGMP bind at interacting sites on the PDE in a random order. The present results reveal that Pb2+ may bind at the same site but with 4-6 log units higher affinity than Mg2+, thus preventing the hydrolysis of cGMP. These findings provide a novel mechanism for understanding the Pb(2+)-induced inhibition of cGMP PDE. These results may have implications for other enzymes using Mg2+ as a cofactor and suggest that Mg2+ may be useful in these situations for reversing the inhibition by Pb2+.     

Analysis of distribution of alternating-sign charged clusters on the surface of globular proteins

PURPOSE: In vitro evaluation of three prototype devices designed to trap emboli that are generated by intravascular procedures. MATERIALS AND METHODS: Three prototypes of the safety net were tested in a water flow model. Angioplasty of human endarterectomy specimens was performed upstream of the device (n = 8). In other tests, polyvinyl alcohol particles were injected into the water flow model upstream of the device (n = 15). The safety nets and the effluent that passed through them were examined for embolic particles. A third prototype was tested (n = 5) to evaluate whether the device could be deployed and retrieved as designed. RESULTS: The safety net was able to trap debris released by angioplasty of endarterectomy specimens in every case. Most, but not all, polyvinyl alcohol particles were trapped by the safety net. Four of five devices tested were deployed and retrieved as designed. One became caught in the introducing valve, which prevented deployment. CONCLUSION: The vascular safety net is effective in trapping small volumes of emboli. It can be deployed and retrieved as designed.     

等温熔炼炉开创铝熔炼技术新时代

节约两源（资源与能源）与减少污染物排放是一个永恒的话题。铝工业特别是原铝生产工业既是高能耗工业又是高污染行业，节能减排有着重要意义。铝工业下游产品行业的单位产品平均能耗虽然还不到上游产品的1/18，但由于产量大，总能耗高，也应是节能重点行业之一。由美国能源部拨款，阿波格技术公司、爱励公司、德雷克塞尔大学、阿贡国家实验室联合研发的铝合金等温熔炼炉（ITM）在铝及铝合金熔炼技术发展史上有着划时代的意义，与当前的常规反射炉相比，可节能70％，减排80％，铝的烧损下降4个百分点，在节源（资源与能源）减排方面意义重大。等温熔炼炉在美国已商业化试生产成功，正在作扩大试生产工作，并开发大的商业化生产炉，预计2010年美国可能有20％左右的下游铝产品是用此项技术熔炼的，首先得到应用的是铸造行业与压铸件生产行业。此技术不但适合于铝工业，也适用于其他冶金部门，还可用于熔化玻璃。