儿童血铅与其它微量元素水平的关系

为探讨儿童血铅与血锌、铁、铜、钙、锰含量的相互消长关系 ,利用多元线性回归分析对 2 1 72名儿童的血微量元素及血铅进行了分析。结果显示 ,被调查儿童中 47 5 6%的儿童血铅升高 ,全部呈轻 中度升高 ( 0 1 0～ 0 44μg/mL) ;钙、铁、锰对血铅值的倒数 (PB1)的作用显著 (P<0 0 1 ) ,但相关并不密切 ,偏相关系数分别为 -0 0 79,0 0 7,0 0 6;血钙与血锌、铜之间有明显的交互作用 ,儿童体内血钙对血铅的影响依赖于血铜、锌的含量 ;血铁和锰含量与PB1呈正相关 ,即与血铅水平呈负相关 ,两者的部分作用又被它们之间的交互作用所减弱。结果提示 ,轻 中度铅中毒仍是城市儿童中普遍存在的一个重要问题 ,除了控制铅污染源外 ,还要注意适当补充铁剂 ,合理饮食以保持机体内钙锰等各种微量元素间的平衡也是重要的防治措施。     

24万深圳市学童铅中毒的筛查

为给深圳市儿童铅中毒的防治提供基础资料和指导,对深圳市学童的铅中毒进行了大规模的筛查,从2001年10月至2004年1月,分五个阶段,总检测人数达241283人,检测主要采用ZPP,血锌原卟啉测定法。结果表明,五个阶段铅偏高和超高总人数为110140人,铅超标比例为45．65％。对300名家长和23880名筛查儿童进行了电话调查和访问。对筛查结果的准确性、铅中毒筛查方法、儿童铅中毒形势、环境与铅中毒的关系等进行了讨论。并采取了一些防治措施,给有关方面提出了防治铅中毒的建议,对铅防治工作作出了贡献。     

高温超导体在未来聚变装置中的应用

简要地介绍了磁约束托卡马克装置中用超导磁体代替常规磁体的发展方向 ;叙述了可能用在聚变中的两类高温超导材料 ,并讨论了托卡马克磁体对高温超导体的特殊要求 ;描述了高温超导体的聚变应用进展 ;介绍了高温超导电流引线以及 A- SSTR2反应堆高温超导环场 (TF)线圈的概念设计     

Growth of ultra‐high purity PbI2 single crystal: (1) Preparation of high purity PbI2

In order to prepare high purity lead iodide (PbI₂) single crystals, the starting material‐iodine (I) has been purified by the sublimation method, and the PbI₂ polycrystalline by the normal freezing method. The purification effect of these methods has been confirmed by evaluating the impurity concentration in ingot by glow discharge mass spectrometry (GDMS) analysis. By comparing the purity of three different starting materials, non‐purified iodine+6N‐Pb, purified iodine+6N‐Pb and commercial 6N‐PbI₂, PbI₂ synthesized by purified iodine in the present experiment has the highest purity. This indicates that these purification methods are suitable. The present research results are expected to prepare high‐resistivity PbI₂ used in radiation detector. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

(K_(0.485)Na_(0.485)Li_(0.03))NbO_3-Pb(Zr_(0.53)Ti_(0.47))O_3陶瓷的介电铁电性能

采用传统电子陶瓷工艺制备新型钙钛矿体系(1-x)(K_(0.485)Na_(0.485)Li_(0.03))NbO_3-Pb(Zr_(0.53)Ti_(0.47))O_3陶瓷,研究了该体系陶瓷的介电铁电性能.X射线衍射分析表明:所有陶瓷样品都具有单一的钙钛矿结构,在0.65≤x≤0.75时,出现明显的正交相和四方相的准同型相界区.测试结果表明:陶瓷具有高介电常数.低介质损耗,良好的温度稳定性;获得了饱和的电滞回线,显示了优良的铁电性能.尤其在x=0.75时各项性能达到最佳,其中介电常数ε_r=1590,介电损耗tan δ=0.017,居里温度T_c=295℃,剩余极化强度P,=28.6 μC·cm~(-1),矫顽场强E_c=0.89 kV·mm~(-1).     

超声法制备硫化铅/二氧化硅核壳结构亚微米粒子

0 引言 纳米微粒具有的小尺寸效应,表面效应、量子尺寸效应及宏观量子隧道效应等导致纳米粒子的热、磁、光、敏感特性和表面稳定性等不同于常规粒子,这就使得它具有广阔的应用前景.     

Integrated capacity and inventory management with capacity acquisition lead times

We model a make-to-stock production system that utilizes permanent and contingent capacity to meet non-stationary stochastic demand, where a constant lead time is associated with the acquisition of contingent capacity. We determine the structure of the optimal solution concerning both the operational decisions of integrated inventory and flexible capacity management, and the tactical decision of determining the optimal permanent capacity level. Furthermore, we show that the inventory (either before or after production), the pipeline contingent capacity, the contingent capacity to be ordered, and the permanent capacity are economic substitutes. We also show that the stochastic demand variable and the optimal contingent capacity acquisition decisions are economic complements. Finally, we perform numerical experiments to evaluate the value of utilizing contingent capacity and to study the effects of capacity acquisition lead time, providing useful managerial insights.     

Characterization of mechanochemically synthesized lead selenide

Mechanochemical synthesis of lead selenide PbSe nanocrystals was performed by high-energy milling of lead and selenium powders in a planetary ball mill. The structure properties of synthesized lead selenide were characterized by XRD analysis that confirmed crystalline nature of PbSe nanocrystals. Calculated average size of PbSe crystallites was 37 nm. The methods of particle size distribution analysis, specific surface area measurement, SEM and TEM were used for the characterization of surface and morphology of PbSe nanocrystals. SEM analysis revealed agglomerates of PbSe particles. However, HRTEM analysis confirmed perfect stoichiometric PbSe cubes with NaCl structure as well. UV-VIS-NIR spectrophotometry was used to confirm the blue shift of the small particles occurring in the powder product obtained by the mechanochemical synthesis. Presented at the 8th Conference on Solid State Chemistry, Bratislava, Slovakia, 6–11 July 2008.     

杯[4]芳烃衍生物对Pb2＋的液膜传输动力学

以3类含不同基团的杯[4]芳烃衍生物作为离子载体在H2O-CHCl3-H2O液膜传输体系下分别对Pb2＋进行液膜传输实验. 简要讨论了以杯[4]芳烃衍生物作为离子载体对Pb2＋液膜传输的动力学机理. 重点研究了不同载体种类, 载体浓度, 搅拌速度, 传输时间等因素对Pb2＋传输的影响. 实验结果表明: 以含Br原子的杯[4]芳烃衍生物和含S原子的杯[4]芳烃衍生物作为离子载体对Pb2＋有明显的传输效果. 可以用本文的动力学模型来描述整个传输体系的动力学特性.     

绿色电化学水分解法制备臭氧: 机理研究

采用电催化剂通过水分解反应形成臭氧的绿色节能方法为常规耗能量大的冷电晕放电提供了非常具有吸引力的替代方法. 在大量研究的用于电化学合成臭氧的电催化剂中,β-氧化铅（β-PbO₂）和氧化锡（SnO₂）基催化剂在室温下最有效. 本工作通过密度泛函理论计算,研究了上述两种催化剂作用下臭氧的形成机制.两种催化剂β-PbO₂和镍/锡掺杂氧化锡（Ni/Sb-SnO₂）的(110) 晶面最稳定. 故作者特别关注β-PbO₂(110) and Ni/Sb-SnO₂(110)表面发生的最后两步反应,即氧气和臭氧的形成,模拟了可能的水分解机理. 结果表明,在β-PbO₂催化剂的作用下,臭氧是遵循 Eley-Rideal机理形成,与在 Ni/Sb-SnO₂,表面臭氧的形成机理相反,后者是通过Langmuir-Hinshelwood 机理形成. 将β-PbO₂主要模拟为固-液相,Ni/Sb-SnO₂主要模拟为气相,计算得到吸附能(E_ads)、吉布斯自由能(ΔG)和活化能(E_act)等热力学参数值,并进行了分析与比较. 这些结果为设计和研发新型的高电流效率电化学制臭氧用催化剂提供了依据.