天然气汽车加气站的发展趋势

文章对L-CNG加气站的特点和工艺流程进行了介绍,分析了其相对于传统CNG加气站和LNG加气站的优点,有巨大的应用前景和可观的经济、社会效益。最后提出L-CNG加气站是未来LNG汽车加气站的一个过渡阶段,对已建的CNG进行改造也比较经济。     

CNG 汽车加气站消防和给排水

文章分析了 CNG 汽车加气站火灾特点和给排水方面的需求,根据国家现行的相关设计规范,对 CNG加气站消防设施和给排水设施提出设计方案     

提高矿井主排水系统管网运行效率的探讨

矿井排水系统是保证井下的矿工人身和生产安全的重要保证。在保证安全和高效运行的同时,应最大限度提高综合效率,达到降低排水电耗的目标。为保证换后流速在经济流速范围内,即管网的造价和运行费用之和最小,我们做了大量的工作,在对不同的管路口径和排水模式进行了详细的对比和分析基础上,以经济流速为目标,对提高矿井主排水系统管网运行效率进行了探讨,得出运行节电结论。     

对选择热水供暖循环泵几个问题的分析和探讨

本文对选择供暖循环泵的几个主要问题进行了分析和探讨。例如,选择循环泵时是否要在管网总设计流量和总压力损失基数上乘以１．１－１．２的系数;高温水锅炉低温水运行时锅炉本体水流阻力的估定;关于对循环泵入口和出口压力的限定;多台泵并联运行时其单台泵的流量,是否要比单台泵独立运行时减少;以及循环泵的节能指标等问题。     

套期保值原理及其应用

本文介绍了期货套期保值的概念、基本原理、作用、实现条件、操作原则、类型及特征 ,列举了金银期货套期保值实际应用方法及注意事项。     

国内外通用型金属封闭开关设备技术动态（一）

本文介绍通用型金属封闭关设备的国内外总本技术水平,目前产品的结构与特点,国内 自行设计和引进技术以及今后产品发展的前景。     

Absence of vitamin D deficiency in young Nigerian children

OBJECTIVE: To determine the prevalence of vitamin D deficiency in young Nigerian children residing in an area where nutritional rickets is common. Study design: A randomized cluster sample of children aged 6 to 35 months in Jos, Nigeria. RESULTS: Of 218 children evaluated, no child in the study had a 25-hydroxyvitamin D (25-OHD) concentration <10 ng/mL (the generally held definition of vitamin D deficiency). Children spent an average of 8.3 hours per day outside of the home. Twenty children (9.2%) had clinical findings of rickets. Children with clinical signs of rickets were more likely to be not currently breast fed and have significantly lower serum calcium concentrations than those without signs of rickets (9.1 vs 9.4 mg/dL, respectively, P =.01). Yet, 25-OHD levels were not significantly different between those children with clinical signs of rickets and those without such clinical signs. CONCLUSION: Vitamin D deficiency was not found in this population of young children in whom clinical rickets is common. This is consistent with the hypothesis that dietary calcium insufficiency, without preexisting vitamin D deficiency, accounts for the development of clinical rickets in Nigerian children.     

Differential activation of NAD kinase by plant calmodulin isoforms. The critical role of domain I

NAD kinase is a Ca2+/calmodulin (CaM)-dependent enzyme capable of converting cellular NAD to NADP. The enzyme purified from pea seedlings can be activated by highly conserved soybean CaM, SCaM-1, but not by the divergent soybean CaM isoform, SCaM-4 (Lee, S. H., Kim, J. C., Lee, M. S., Heo, W. D., Seo, H. Y., Yoon, H. W., Hong, J. C., Lee, S. Y., Bahk, J. D., Hwang, I., and Cho, M. J. (1995) J. Biol. Chem. 270, 21806-21812). To determine which domains were responsible for this differential activation of NAD kinase, a series of chimeric SCaMs were generated by exchanging functional domains between SCaM-4 and SCaM-1. SCaM-4111, a chimeric SCaM-1 that contains the first domain of SCaM-4, was severely impaired (only 40% of maximal) in its ability to activate NAD kinase. SCaM-1444, a chimeric SCaM-4 that contains the first domain of SCaM-1 exhibited nearly full ( approximately 70%) activation of NAD kinase. Only chimeras containing domain I of SCaM-1 produced greater than half-maximal activation of NAD kinase. To define the amino acid residue(s) in domain I that were responsible for this differential activation, seven single residue substitution mutants of SCaM-1 were generated and tested for NAD kinase activation. Among these mutants, only K30E and G40D showed greatly reduced NAD kinase activation. Also a double residue substitution mutant, K30E/G40D, containing these two mutations in combination was severely impaired in its NAD kinase-activating potential, reaching only 20% of maximal activation. Furthermore, a triple mutation, K30E/M36I/G40D, completely abolished NAD kinase activation. Thus, our data suggest that domain I of CaM plays a key role in the differential activation of NAD kinase exhibited by SCaM-1 and SCaM-4. Further, the residues Lys30 and Glu40 of SCaM-1 are critical for this function.