Production of light alkenes with low CO2 emission from gas phase oxidative cracking (GOC) of hexane

Compared with non-oxidative pyrolysis of hexane, the rupture of C-C bonds of hexane in the GOC process becomes rather easy due to the change of thermodynamics and kinetics of the reaction with introduction of oxygen. CO predominates in the COx produced, and the ratio CO/CO₂ can be as high as 16. The GOC process could be operated in an autothermic way, which would minimize energy consumption of the whole process and greatly decrease the CO₂ emission. GOC seems to be an environmentally benign and promising alternative route for light alkenes production using heavy feedstock. This revised version was published online in August 2006 with corrections to the Cover Date.     

人工神经网络的光学实现

本文讨论了光学神经网络的优势及其所面临的主要问题,简述了它近十年来的发展．光互连是光学实现神经网络最具吸引力的技术,光电混合集成的灵巧象素器件又融合了电子器件灵活、可编程、易控制的特点．二者的结合是当前光学神经网络发展的主要趋势,它们为神经网络的进一步发展和应用,为超大规模神经网络的实现和应用提供了一种很有前途的方案．     

静高压熔态淬火Al70Co15Ni10Tb5合金中十次准晶的相关晶体相C4和C5

 使用静高压熔态淬火方法，在Al₇₀Co₁₅Ni₁₀Tb₅合金中截获到两个新的十次准晶相关相C₄和C₅。其晶胞参数分别为：底心正交晶体（C₄），α=1.38 nm，b=1.60 nm，c=2.0 nm；简单正交晶体（C₅），α=1.20 nm，b=1.60 nm，c=2.30 mn。对二者的高分辨象进行了分析和研究，发现他们有着密切的关系，且可以认为是Penros拼图有序化的结果。     

Er：YLF晶体中Er^3＋离子的光谱特征

利用居地－奥非脱（Ｊｕｄｄ－Ｏｆｅｌｔ）理论计算了Ｅｒ＾３＋离了在氟化钇锂（ＬｉＹＦ４简写为ＹＬＦ）晶体中的辐射跃迁几率Ａｊｊ无辐射跃迁几率ωＪＪ及激发态荧光寿命τ，并根据荧光动力学方程计算出各激发态布居数ＮＪ与掺杂浓度ｘ的关系，对２．７μｍ激光（＾４Ｉ１１／２→＾４Ｉ１３／２）来说，掺杂浓度要大于～３ａｔ％，才能实现布居数反转，对波长为１．７３μｍ的＾４Ｉ１３／２→＾４Ｉ１５／２跃迁，存在荧光强     

怀孕期头发中一些元素含量的变化趋势

用同步辐射激发X射线荧光分析,对11个产妇怀孕期间头发内一些元素含量的变化趋势进行了测量,在各自对比的基础上,得到了一些结果。     

Kinetic and mechanistic studies of the photolysis of metronidazole in simulated aqueous environmental matrices using a mass spectrometric approach

Metronidazole is a nitroimidazole antibiotic derivative used in humans against anaerobic bacteria and protozoa. In light of the recent detection of metronidazole in hospital wastes, sewage treatment plants, and surface waters, along with its known sensitivity toward photolytical degradation, this study aimed to model the photolysis in environmental waters by sunlight as a natural attenuation process. To this end, the degradation of metronidazole in a photoreactor simulating solar radiation (Suntest CPS) was compared in five different aqueous matrices: deionized water, artificial freshwater (AFW), AFW supplemented with nitrate (5 mg/L), AFW containing humic acids, and AFW with both nitrate and humic acids. Irrespective of the test medium, the degradation of the metronidazole solutions (10 and 0.02 mg/L) was found to follow pseudo-first-order kinetics. Degradation rates were dependant on the matrix, with humic acids causing a two to threefold decrease in the rate constants while the presence of nitrate had no marked effect on the kinetics. Therefore, the direct photolysis of metronidazole was apparently attenuated through a filter effect of humic acids. Screening of the irradiated water samples by ultra performance liquid chromatography/quadrupole time-of-flight mass spectrometry allowed separation and characterisation of four principal phototransformation products of the antibiotic. The high-resolution MS data pointed to the formation of two rearrangement products (C₆H₁₀N₃O₃) isobaric with metronidazole, a third product deriving from the elimination of NO from the nitro group (C₆H₁₁N₂O₂), and a fourth unidentified degradate with a likely elemental composition of C₅H₁₀N₃O.     

Submicrometer organic silica gel fiber for oxygen sensing

We introduce the electrospinning method into fabricating oxygen-sensitive submicrometer scale optical fiber. Uniform tris (4,7-diphenyl-1,10-phenathroline) ruthenium(II) dichloride ([Ru(dpp)(3)](2+)Cl(2))-doped fibers with a diameter of 900 nm are obtained by electrospinning the organic silicon sol solution derived from tetraethyl orthosilicate and n-Octyltriethoxysilane (C(14)H(32)O(3)Si). The experimental results show that the single gel fiber exhibits excellent optical and sensing properties. A laser with a wavelength of 452 nm can be efficiently launched into the fiber and guide along the fiber to excite the fluorescence. Then, we find that [Ru(dpp)(3)](2+)-gel fiber has favorable optical and sensing characteristics, and the Stern-Volmer plots are linear in the full concentration range of O(2) (0-100 vol.?%). The ratio of I(0)/I(100), where I(0) and I(100) respectively represent the fluorescence intensities of the fiber exposed to 100% N(2) and 100% O(2), as the sensitivity of the fiber is 3.5. Simultaneously, the fiber can make a quick response within 100 ms. This method provides an effective and convenient way to fabricate highly uniform nanoscale or microscale optical waveguides for photonic devices.     

高岭土负载SO42-/ZrO2-TiO2催化剂的制备及其在缩酮合成中的应用

以经H2SO4处理焙烧的高岭土为载体,制备了以其负载的SO2-4/ZrO2-TiO2固体酸催化剂。 用FT-IR、XRD和NH3-TPD等测试技术表征了催化剂的微观结构及酸强度,考察了对环己酮乙二醇缩酮反应的催化活性及稳定性。 结果表明,酸化处理使高岭土表面酸量增加,但酸强度变化不大,而其负载SO2-4/ZrO2-TiO2后,经500 ℃焙烧3 h其酸量及酸强度显著升高。 环己酮用量为0.2 mol、乙二醇0.24 mol、催化剂1.2 g、带水剂环己烷15 mL,回流反应70 min后,缩酮收率可达96.8%,催化剂重复使用5次收率保持在90%以上。     

Semisynthesis and Cytotoxicity Evaluation of a Series of Ocotillol Type Saponins and Aglycones from 20(S)-Ginsenoside Rg2, Rh1, Protopanaxatriol and Their 20(R)-Epimers

With the oxidation treatment, eighteen compounds were separated from 20(S)-ginsenoside Rg₂, Rh₁, protopanaxatriol(PPT) and their 20(R)-epimers in total and cytotoxicity of most of them was evaluated against three human cancer cell lines HeLa, A549 and MCF-7 by 3-(4,5-dimetylthiazol-z-yl)-2,5-diphenyltetrazolium bromide(MTT) assay. Their structures were confirmed by means of nuclear magnetic resonance(NMR) and mass spectrometry and the results were compared with those of previous literature. In this study, we systematically semisynthesized all four ocotillol type saponins, i.e., (20S, 24S), (20S, 24R), (20R, 24S) and (20R, 24R). All the configurations at C20 kept the same with their starting materials. Meanwhile a pair of C24 epimers was generated in terms of ocotillol type saponins. In addition, seven compounds(4-8, 13 and 14) were reported firstly. The cytotoxic results distinguished the ocotillol type products(6, 7, 13 and 14) from 20(R)-PPT and 20(R)-ginsenoside Rh₁, which possessed better cytotoxicities than their correspondents from 20(S)-epimers against HeLa cells, and the carbonyl group at C3 can improve the cytotoxi-city, which helped us to gain deeper insight into Ocotillol type saponins.     

On the strain hardening and texture evolution in high manganese steels: Experiments and numerical investigation

We present a systematic investigation on the strain hardening and texture evolution in high manganese steels where twinning induced plasticity (TWIP) plays a significant role for the materials' plastic deformation. Motivated by the stress–strain behavior of typical TWIP steels with compositions of Fe, Mn, and C, we develop a mechanistic model to explain the strain-hardening in crystals where deformation twinning dominates the plastic deformation. The classical single crystal plasticity model accounting for both dislocation slip and deformation twinning are then employed to simulate the plastic deformation in polycrystalline TWIP steels. While only deformation twinning is activated for plasticity, the simulations with samples composed of voronoi grains cannot fully capture the texture evolution of the TWIP steel. By including both twinning deformation and dislocation slip, the model is able to capture both the stress–strain behaviors and the texture evolution in Fe–Mn–C TWIP steel in different boundary-value problems. Further analysis on the strain contributions by both mechanisms suggests that deformation twinning plays the dominant role at the initial stage of plasticity in TWIP steels, and dislocation slip becomes increasingly important at large strains.