火焰原子吸收光谱法测定高纯石英粉中痕量钙

系统地研究了用空气——乙炔火焰原子吸收光谱分析法测定高纯石英粉中钙的最佳条件，建立了14％的乙醇作为增感剂，在2％盐酸介质中，0．4％ LaCl3溶液作为释放剂，用塞曼火焰原子吸收法测定的可行性方案，探讨了共存元素对钙的干扰及其消除。方法操作简便快速，干扰少，方法相对标准偏差小于3％，适用于日常分析石英粉中的杂质。     

Selective oxidation of styrenes under oxygen catalyzed by cobalt chloride

The cobalt(II) chloride-catalyzed oxidative cleavage of -methylstyrene with oxygen in t-BuOH gives acetophenone and formaldehyde in good yield. The competing reactions between C=C cleavage and formation of polymeric products are strongly affected by the solvent, cobalt catalyst and concentration used, as well as the reaction temperature. A free radical mechanism involving a cyclic peroxide intermediate is proposed to give the cleavage products. Oxidation of various alkenes using CoCl₂/t-BuOH/O₂ system shows that only activated styrenes can be oxidized effectively. The reactivity of various styrenes and their selectivity towards giving cleavage products or polymers are strongly influenced by the electronic and steric properties of the substrate.     

20＂通径中压球阀的设计和三维数值模拟

介绍了通径为20＂（1＂=25．4mm）的大口径中压球阀阀体、新型C形金属密封环组件等的结构设计；在阀座与球体之间采用整体碟形弹簧和新型阀座密封填料，以保证高压密封，提高使用寿命；阀芯采用空心球体结构和分段冲压成形加工工艺，有效地保证了球体的加工精度和质量，降低了生产成本；在结构设计中，充分考虑了球阀的密封、防火、启闭传动及制造工艺的要求；对其中结构复杂的球阀阀体和空心球形阀芯进行了强度计算和ANSYS应力、应变模拟分析计算，二者计算结果一致，并认为阀体的厚度由其大开孔处局部应力的整体补强确定。     

大型机械轴承相对标高测试系统

介绍了一种使用连通管、电涡流传感器测量轴承相对标高的测试系统,它能准确测量大型机械相邻轴承的相对标高变化.文中叙述了其测量原理、特点以及系统的硬件电路和软件设计,最后给出一个测试实例,并对测量结果进行了简要分析.     

熔块中的气泡缺陷及其解决办法

分析了熔块生产中气泡缺陷产生的各种原因．提出了实际生产中的注意事项和具体的解决办法。     

Effect of Pretreatment Atmosphere on CuO/TiO2 Activities in NO + CO Reaction

Using TiO₂ as carrier, CuO/TiO₂ catalysts with different CuO loading were prepared by the impregnation method. The catalytic activities in NO+CO reaction were examined with a micro-reactor gas chromatography reaction system and the methods of TPR, XPS and NO-TPD. It was found that the catalytic activities were affected by pretreatment atmosphere, i.e. H₂ atmosphere > reduction–reoxidation > 10%CO/He > reaction gas (fresh sample). NO decomposition was better by low-valence Cu species than by high-valence Cu species, i.e. Cu⁰>Cu⁺>Cu²⁺. The XPS results indicated that Cu species on CuO/TiO₂ were Cu⁰, Cu⁺, normal Cu²⁺(Cu²⁺(I)) and chain-structured Cu²⁺(Cu²⁺(II)) as –Cu–O–Ti–O–. The activities of Cu²⁺(II) were much higher than that of Cu²⁺(I), but both species were very unstable in the reaction atmosphere and easily reduced by CO, which accounted for the variable activities of fresh catalysts with increasing reaction temperature. In NO+CO reaction, the redox process was a cycle of Cu⁺–Cu²⁺(I) at low reaction temperature but was a cycle of Cu⁰–Cu⁺ at high reaction temperature. As shown by NO-TPD, high catalytic activities could be attributed to the following factors, e.g. oxygen caves on the catalyst’s surface after pretreatment with H₂ and reduction–reoxidation, formation of Cu⁰ after pretreatment with H₂, and increment of Cu species dispersion and formation of Cu²⁺(II) after pretreatment with reduction–reoxidation.     

细胞固定化催化生产精细化学品的研究进展Q

摘要：细胞固定化技术具有流程简单、生物相容、操作稳定等优点，可有效保证细胞活性，实现高效的细胞催化生产精细化学品。本文介绍了表面附着、凝胶包埋、聚电解质层层自组装膜等多细胞固定化方法，及其在二元醇、生物乙醇、乳酸、酯、多糖等精细化学品生产中的研究现状和进展，并分析讨论了各种方法存在的问题。同时，总结了近年来新发展的单细胞纳米涂层固定化方法的机理、趋势及应用于精细化学品生产的可能性。最后对细胞固定化催化生产精细化学品面临的技术挑战及研究方向做出展望，以期为精细化学品生产提供一定的技术支持。     

等离子硅刻蚀及其工艺参数的多尺度优化

用CFD-ACE+和CFD-TOPO分别对容性耦合等离子体反应腔室放电和等离子硅刻蚀过程进行仿真,讨论不同射频电压和腔室条件对等离子体特性的影响.结果表明:随着射频电压的升高,离子的通量增大;在低射频电压时,离子通量随腔室压强的升高而减小,而在高射频电压时趋势则相反.用Kriging模型对影响刻蚀形貌的参数(腔室压强和射频电压)进行优化,结果表明该优化方法可以为工艺条件相近的刻蚀机设备的设计提供参考.     

Synthesis and characterization of a new water-soluble endohedral metallofullerene for MRI contrast agents

Water-soluble amino acid derivatives of gadolinium (Gd) endohedral metallofullerenes (AAD-EMFs), Gd@C₈₂O_m(OH)_n(NHCH₂CH₂COOH)_l (m ≈ 6, n ≈ 16 and l ≈ 8) are synthesized by a direct reaction of the pure endohedral metallofullerene Gd@C₈₂ with an excess of alkaline solution of β-alanine. The structure of the AAD-EMFs is characterized by FTIR, XPS and laser-desorption time-of-flight (LD-TOF) mass spectrometries. Water proton relaxivity analysis indicates that the longitudinal relaxivity R₁ (the effect on 1/T₁, 9.1 mM⁻¹ s⁻¹) of AAD-EMFs is higher than that of the commercial MRI contrast agent, Magnevist (gadolinium-diethylenetriaminepentaacetic acid, Gd-DTPA, 5.6 mM⁻¹ s⁻¹). The MRI phantom studies are performed to confirm the high efficiency of this sample as MRI contrast agents.     

Morphologic study of electrochemically formed lead dioxide

Various electrochemical methods with different conditions were used to prepare lead dioxide (PbO₂). The observation revealed that the morphology of deposited PbO₂ could be controlled by simply changing deposition parameters. Under the condition of oxygen evolution, which dominates the electrode process, uniformly distributed high porous structured PbO₂ was formed. The results indicated that large current density or high potential polarization should be one of the most important and necessary factors for forming high surface area PbO₂ deposit. Only β-PbO₂ was identified by X-ray diffraction measurement for the deposit prepared by present methods and solution. One potential application of this method is to prepare nanoscaled PbO₂ parallel lines.