Entropy Structure Within a Cosserat Fluid Involving Chemical Reactions,Heat, and Mass Transfer

In this contribution, the entropy balance equation of a Cosserat-type fluid involving chemical reactions, heat and mass transfer is derived from Gibbs relation. To this aim, the balance equations of internal, kinetic, potential and total energies of a Cosserat-type fluid are derived. Some new terms appear in the aforementioned equations in comparison to the classical theory. In the case of kinetic energy, a new balance equation is derived from the conservation law of angular momentum. The obtained equations give a deep insight into the energy content and structure of entropy within such a continuum as well as the mechanisms of energy dissipation.     

Stylissatin A,a cyclic peptide that inhibits nitric oxide production from the marine sponge Stylissa massa

A new cyclic heptapeptide, stylissatin A (1), was isolated from the Papua New Guinean marine sponge Stylissa massa. Through the use of 1D and 2D NMR spectroscopic analysis, Marfey’s method, and MS/MS analysis, its structure was determined to be cyclo-[Tyr¹–Ile²–Phe³–Pro⁴–Ile⁵–Pro⁶–Phe⁷]. Stylissatin A inhibited nitric oxide production in LPS-stimulated murine macrophage RAW264.7 cells with an IC₅₀ value of 87 μM.     

Pd修饰对Cd0.8Zn0.2S/SiO2光催化甘油水溶液制氢性能的影响

用等体积浸渍法制备了不同Pd负载量的Pd/Cd_0.8Zn_0.2S/SiO₂光催化材料,采用XRD、H₂-TPR、XPS、UV-vis DRS和光催化反应评价等方法对光催化材料的表面结构、光吸收性能以及光催化甘油水溶液制氢反应性能进行了考察。研究结果表明,ZnS与CdS在SiO₂表面形成了Cd_0.8Zn_0.2S固溶体,金属Pd负载未对固溶体Cd_0.8Zn_0.2S/SiO₂的结构造成影响;金属Pd修饰明显地提高了原固溶体的光响应性能,拓展了其吸光域,增强了吸光效率。金属Pd修饰后,Cd_0.8Zn_0.2S/SiO₂的光解甘油水溶液产氢速率显著提高,Pd负载量为0.5%的Pd/Cd_0.8Zn_0.2S/SiO₂具有最佳的光催化甘油水溶液制氢性能,其在紫外光照射下的氢气生成速率为831 μmol/h,较未负载时提高了近四倍;模拟太阳光下为153 μmol/h,较未负载时提高了近两倍。     

催化氧化处理工业废气中高浓度甲醛

制备了用于温和条件下催化氧化去除工业废气中高浓度甲醛(HCHO)的1%Pt-4%CeO₂/AC催化剂. 将高浓度甲醛的催化氧化过程与双甘膦氧化制备草甘膦的反应过程集成在一起,使草甘膦合成过程中产生和排放出来的甲醛(100-300 mg/m³)在通过催化剂床层时被完全除去. 系统研究了温度、空速和甲醛含量对甲醛去除率的影响. 在气体空速(GHSV)低于20000 h^-1时废气中几乎所有的甲醛都被氧化,处理后的废气中的甲醛含量低于0.1 mg/m³,甲醛的转化率为99.1%-100%. 当GHSV为30000- h^-1,催化剂床层温度为12℃时,生产废气通过催化剂床层后的甲醛含量小于1.5 mg/m³,甲醛的转化率为97.56%-99.99%. 1%Pt-4%CeO₂/AC催化剂的中试试验结果表明,处理后最终尾气中甲醛含量小于10 mg/m³,有效地防止了甲醛对人们健康的危害,具有良好的产业化前景.     

磷酸缓冲盐和硫酸钠对洋葱假单胞菌脂肪酶的非水相激活

研究了kosmotropic型磷酸缓冲盐和硫酸钠对洋葱假单胞菌脂肪酶(Pseudomonas cepacia lipase, PCL)非水相催化性能的影响.以往磷酸缓冲盐被用来调控体系的pH值,其掺杂量对酶的催化活性无明显影响,而适量硫酸钠的掺杂则可有效提高酶在非水相的催化活性.本文研究发现,通过精确调控冻干过程,磷酸缓冲盐掺杂能够将PCL在有机相中的转酯化活性提高近10倍,达到其水相本征活性的50%,这一激活效果甚至高于硫酸钠掺杂.利用热重方法分析了盐掺杂PCL的含水量和蛋白结构,并将失重结果同其在有机相中的催化活性相关联,发现PCL在磷酸缓冲盐和硫酸钠掺杂下的催化构型与蛋白含水量及其周围盐环境具有不同的依赖关系.利用2-(4’-氨基-2’-羟基苯基)苯并恶唑作为荧光探针,研究了磷酸缓冲盐和硫酸钠掺杂的PCL悬浮于有机相时对荧光探针发射光谱的影响,发现盐掺杂酶制剂的存在能够大大增加荧光探针稳定于极性溶剂的构型含量,这可能与蛋白周围掺杂盐键和的水分子有关.如果用探针分子稳定于极性溶剂和非极性溶剂的构型比值间接表示悬浮酶制剂的极性结构,在正己烷体系中硫酸钠掺杂的PCL具有比磷酸缓冲盐掺杂的PCL大得多的极性,且酶制剂的极性大小与其非水相转酯化活性之间具有相似的变化趋势.上述研究结果表明,掺杂盐对粗PCL酶制剂的激活可能部分归因于掺杂盐键和的水分子在蛋白周围构筑的极性环境.     

基于非贵金属镍的金属有机大环的光解水放氢性能

将具有NN（氮氮）双齿配位点的席夫碱配体L2（L2=1,4-苯二-2''-吡啶腙）与镍构筑得到一例[2+2]型金属有机大环[Ni₂（L2）₂（CH₃CN）₄]（ClO₄）₄·4CH₃CN（2）,并将其用于可见光条件下的光解水产氢研究。该非贵金属光催化体系由催化剂、光敏剂（荧光素,Fl）和电子牺牲剂（三乙胺）三部分组成。相比于具有相同配位环境的单核配合物[Ni（L1）₂（CH₃CN）₂]（ClO₄）₂（1,L1=3-甲酰基苯-2''-吡啶腙）,金属有机大环2作为催化剂具有较高的光催化活性,其产氢TON值可以达到3 100 mol_H2·mol_cat^-1,归因于荧光素分子可能与金属有机大环2形成超分子配合物,提高了光致电子转移效率。     

Iridium and Rhodium Complexes within a Macroreticular Acidic Resin: A Heterogeneous Photocatalyst for Visible‐light Driven H2 Production without an Electron Mediator

Direct ion exchange of cyclometalated iridium(III) and tris‐2,2′‐bipyridyl rhodium(III) complexes, of which the former acts as a photosensitizer and the latter as a proton reduction catalyst, within a macroreticular acidic resin has been accomplished with the aim of developing a photocatalyst for H₂ production under visible‐light irradiation. Ir L_III‐edge and Rh K‐edge X‐ray absorption fine structure (XAFS) measurements suggest that the Ir and Rh complexes are easily accommodated in the macroreticular space without considerable structural changes. The photoluminescence emission of the exchanged Ir complex due to a triplet ligand charge‐transfer (³LC) and metal‐to‐ligand charge‐transfer (³MLCT) transition near 550 nm decreases with increasing the amount of the Rh complex, thus suggesting the occurrence of an electron transfer from Ir to Rh. The Ir‐Rh/resin catalyst behaves as a heterogeneous photocatalyst capable of both visible‐light sensitization and H₂ production in an aqueous medium in the absence of an electron mediator. The photocatalytic activitity is strongly dependent on the amount of the components and reaches a maximum at a molar ratio of 2:1 of Ir/Rh complexes. Moreover, leaching and agglomeration of the active metal complexes are not observed, and the recovered photocatalyst can be recycled without loss in catalytic activity.     

Gas analyzer for continuous monitoring of trace level methanethiol by microchannel collection and fluorescence detection

The highly odorous compound methanethiol, CH₃SH, is commonly produced in biodegradation of biomass and industrial processes, and is classed as 2000 times more odorous than NH₃. However, there is no simple analytical method for detecting low parts-per-billion in volume ratio (ppbv) levels of CH₃SH. In this study, a micro gas analysis system (μGAS) was developed for continuous or near real time measurement of CH₃SH at ppbv levels. In addition to a commercial fluorescence detector, a miniature high sensitivity fluorescence detector was developed using a novel micro-photomultiplier tube device. CH₃SH was collected by absorption into an alkaline solution in a honeycomb-patterned microchannel scrubber and then mixed with the fluorescent reagent, 4-(N,N-dimethylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (DBD-F). Gaseous CH₃SH was measured without serious interference from other sulfur compounds or amines. The limits of detection were 0.2 ppbv with the commercial detector and 0.3 ppbv with the miniature detector. CH₃SH produced from a pulping process was monitored with the μGAS system and the data agreed well with those obtained by collection with a silica gel tube followed by thermal desorption–gas chromatography–mass spectrometry. The portable system with the miniature fluorescence detector was used to monitor CH₃SH levels in near-real time in a stockyard and it was shown that the major odor component, CH₃SH, presented and its concentration varied dynamically with time.     

La-CoMoN_x/CNTs催化剂上氨分解反应的本征动力学

以La-CoMoNx/CNTs为催化剂,对氨分解制氢反应的本征动力学进行了研究。考察了N2浓度、H2浓度、NH3浓度以及反应温度对反应速率的影响。采用幂指数方程描述反应动力学,确定了本征动力学参数,推导出了本征动力学方程,得到反应的活化能为93.948 kJ/mol。同时对其反应机理进行了探讨,认为La-CoMoNx/CNTs催化剂上氨分解反应遵循Temkin-Pyzhev机理,即表面氮原子的结合脱附为反应的速率控制步骤。     

生产和运输成本问题的机会约束规划方法

当供应商的生产能力和销售商的需求量是随机参数时,建立了一类产品生产和运输成本问题的数学模型,它是一种随机优化模型.利用机会约束规划方法研究了在给定置信水平和其它相关约束条件时,此类随机优化问题的确定型等价式.给出了每个供应商给每个销售商的送货量,且达到了总运输成本最低.实际案例研究表明所建立的模型和求解方法有效,且分析了不同置信水平下最优值的变化,提供了选择最佳置信水平的方法.