The use of nitride intermediates in the preparation of metals. A study of the reduction of Nb2O5 with NH3

A kinetics study of the reduction of Nb₂O₅ with NH₃ was conducted at 600° to 1300°C, using vertical fixed-bed, flow-through reactors, with the goal of using the nitride as an interme-diate in the preparation of niobium (columbium) metal via a thermal decomposition step. The effects of reactor materials (stainless steel, nickel, molybdenum, graphite, alumina, and Vycor) upon ammonia reactivity toward Nb₂O₅ were investigated. At low temperatures, the metal reactor systems were more catalytically reactive, yielding faster rates of reac-tion and a greater degree of nitride conversion, whereas at high temperatures, the non-metal reactor systems performed better. In general, the initial reaction rate-temperature data exhibited a maximum, associated with oxynitride formation, near 700°C for the metal reactor systems and 800° to 900°C for the nonmetal reactor systems, followed by a mini-mum, associated with NbO₂ formation, at 800° to 850°C for the metal reactor systems and 950° to 1000°C for the nonmetal reactor systems where NbN formation commences. A sec-ond maximum, associated with the hexagonal NbN phase, occurred at 1200°C. The ranges of activation energies for these regions were from 15 to 30 kcal/mole for region I, 8 to 22 kcal/mole for region II, and 10 to 22 kcal/mole for region III.     

Catalytic dehydrogenation of propane over cluster-derived Ir–Sn/SiO2 catalysts

The dehydrogenation of propane was studied in gas-phase at 773 K over two series of silica-deposited Ir–Sn systems: the bimetallic catalysts obtained from Ir–Sn carbonyl clusters precursors and the ones prepared by deposition of a metallorganic Sn precursor onto preformed Ir nanoparticles. In the comparison, cluster-derived catalysts showed good propane conversion, optimal selectivity to propene and high stability under the severe reaction conditions.     

Preparation and characterisation of mesoporous silica–alumina and silica–titania with a narrow pore size distribution

Amorphous mesoporous materials with a different degree of order in the arrangement of pores are outlined. Particularly, the synthesis of a class of mesoporous silica–alumina (MSA) materials with narrow pore size distribution and a disordered arrangement of pores is reported and discussed. Likewise, the preparation of titanium-containing ordered mesoporous silicates (Ti-MCM-41) and disordered mesoporous silica–titania (MST) are also described in detail. The structural properties of the solids are compared by means of X-ray diffraction and UV-Vis diffuse reflectance spectroscopy. The nitrogen adsorption–desorption measurements were performed and the textural properties are evaluated by the BET, DFT, BJH and t-plot methods.

The high specific surface area and pore volume, as well as the acidity, make MSA solids interesting catalysts in several petrochemical transformations, i.e. oligomerisation, alkylation, hydroisomerisation, rearrangement reactions. Besides, thanks to the width of the mesopores of such solids, the catalytic activity of titanium-containing silicates may have a potential application in the epoxidation of bulky unsaturated fine chemical substrates.     

CSF neuroactive steroids in affective disorders: pregnenolone, progesterone, and DBI

Recently several steroid compounds have been discovered to act as neuromodulators in diverse central nervous system (CNS) functions. We wondered if neuroactive steroids might be involved in affective illness or in the mode of action of mood-regulating medications such as carbamazepine. Levels of the neuroactive steroids pregnenolone and progesterone, as well as the neuropeptide diazepam binding inhibitor (DBI) (known to promote steroidogenesis), were analyzed from cerebrospinal fluid (CSF) obtained by lumbar puncture (LP) from 27 medication-free subjects with affective illness and 10 healthy volunteers. Mood-disordered subjects who were clinically depressed at the time of the LP had lower CSF pregnenolone (n = 9, 0.16 ng/ml) compared with euthymic volunteers (n = 10, 0.35 ng/ml; p < 0.01). In addition, pregnenolone was lower in all affectively ill subjects (n = 26, 0.21 ng/ml), regardless of mood state on the LP day, than healthy volunteers (p < 0.05). No differences were found for progesterone or DBI levels by mood state or diagnosis. Progesterone, pregnenolone, and DBI did not change significantly or consistently in affectively ill subjects after treatment with carbamazepine. CSF pregnenolone is decreased in subjects with affective illness, particularly during episodes of active depression. Further research into the role of neuroactive steroids in mood regulation is warranted.     

用于系统级封装的毫米波介质填充波导的研究

基于不断发展的系统级封装技术,提出了一种用于芯片间高速互连的新型可集成的物理器件:硅基毫米波介质填充波导。文中阐述了该器件的物理原理,采用建模、仿真相结合的方法对该模块进行了结构设计,利用新的设计思路结合半导体工艺解决了毫米波互连结构内部的反射、电压驻波比(VSWR)、信号耦合、准TEM-TE-准TEM转换传输问题以及毫米波互连结构阵列中信号泄露的问题,并利用半导体与MEMS加工工艺加以实现。测试结果表明宽度为680μm的单通道矩形波导,-10 d B带宽为9.8 GHz,相对带宽为12.56%;传输损耗为1 d B/cm,工作频带内相邻波导之间串扰低于-40 d B,可以形成大阵列并进行集成,从而实现芯片间数据的并行传输。     

Mechanisms of class I restricted immunopathology. A transgenic mouse model of fulminant hepatitis

The molecular and cellular mechanisms responsible for cytotoxic T lymphocyte (CTL)-induced immunopathology are not well defined. Using a model in which hepatitis B surface antigen (HBsAg)-specific CTL cause an acute necroinflammatory liver disease in HBsAg transgenic mice, we demonstrate that class I-restricted disease pathogenesis is an orderly, multistep process that involves direct as well as indirect consequences of CTL activation. It begins (step 1) almost immediately as a direct antigen-specific CTL-target cell interaction that triggers the HBsAg-positive hepatocyte to undergo programmed cell death (apoptosis). It progresses (step 2) within hours to a focal inflammatory response in which antigen-nonspecific lymphocytes and neutrophils amplify the local cytopathic effect of the CTL. The most destructive pathogenetic function of the CTL, however, is to secrete interferon gamma when they encounter antigen in vivo, thereby activating the intrahepatic macrophage and inducing a delayed-type hypersensitivity response (step 3) that destroys the liver and kills the mouse. We propose that the principles illustrated in this study are generally applicable to other models of class I-restricted, CTL-induced immunopathology, and we suggest that they contribute to the immunopathogenesis of viral hepatitis during hepatitis B virus infection in humans.     

Thermal activated (“thermal”) battery technology : Part IIIb. Sulfur and oxide-based cathode materials

This article presents an overview of cathode materials (except the pyrite FeS₂) used or envisaged in thermally activated (“thermal”) batteries. The physicochemical properties and electrochemical performance of different cathode families (oxides, sulfides) are reviewed, including discharge mechanisms, when known.     

Performance of thermal cells and batteries made with plasma-sprayed cathodes and anodes

Cathodes for thermally activated (“thermal”) batteries based on CoS₂ and LiCl–LiBr–LiF electrolyte and FeS₂ (pyrite) and LiCl–KCl eutectic were prepared by thermal spraying catholyte mixtures onto graphite–paper substrates. Composite separator-cathode deposits were also prepared in the same manner by sequential thermal spraying of LiCl–KCl-based separator material onto a pyrite-cathode substrate. These materials were then tested in single cells over a temperature range of 400–600 °C and in 5-cell and 15-cell batteries. A limited number of battery tests were conducted with the separator-cathode composites and plasma-sprayed Li(Si) anodes—the first report of an all-plasma-sprayed thermal battery. Thermal-spraying offers distinct advantages over conventional pressed-powder parts for fabrication of thin electrodes for short-life thermal batteries. The plasma-sprayed electrodes have lower impedances than the corresponding pressed-powder parts due to improved particle–particle contact.