Study of the effect of noble metal promotion in Ni-based catalyst for the Sabatier reaction

This paper reports the preparation and the evaluation of the performance of Ni-based powder catalysts with low nickel loading on the CO2 methanation reaction, that is an integral part of the power-to-gas (PtG) technology. CeO₂, CeZrO₄ and CeO₂/SiO₂ were selected as possible supports, and the results of this first screening pointed out that 10%Ni/CeO₂ catalyst could offer the best reaction performances because of ceria's peculiar characteristics. Moreover, the promotion of this promising formulation with the addition of a small amount of noble metals (Pt, Ru, Rh) was investigated, showing that platinum in particular can enhance the catalyst performances. A further study related to the noble metal loading pointed out that platinum and ruthenium have a different optimum loading condition: this result, together with the activity tests performed on monometallic formulations with only the noble metal, suggested that the two metals are able to catalyse two different reactions, thus promoting two different reaction mechanisms.     

Red clays from Central and Eastern Crete: geochemical and mineralogical properties in view of provenance studies on ancient ceramics

The existing geochemical diversity of clay deposits consists the underlying assumption for the determination of provenance of archaeological ceramics on the basis of their chemical composition. This assumption was tested on Quarternary red clayey alluviums from Central and Eastern Crete (Greece), an area rich in archaeological pottery and very popular for ceramics provenance studies. This type of clay has been used for pottery production on the island since the antiquity and it is still in use by traditional workshops. Altogether, 17 samples of clayey raw materials were collected from 7 different locations in Central and Eastern Crete, and characterised by chemistry, mineralogy and petrography. The study was focussed on the internal variability within deposits and the diversity among different deposits.It was possible to distinguish all seven deposits from each other on the basis of their chemical composition, taking into account the available mineralogical and petrographical information, although some deposits presented compositional relations. Compared to Neogene clay deposits in the same area, the variability among the examined red clayey deposits was clearly higher and exceeded by far the intra-deposit variability.     

Cation Effect on the Binary and Ternary Phase Behaviors of Double-Tailed Methanesulfonate Amphiphiles

A series of symmetrical dialkyl methanesulfonate amphiphiles [DiC _n CHSO ₃ ] _m M (n = 6, 7, 8) with different counter cations (M^m+ = H⁺, Li⁺, Na⁺, K⁺, Cu²⁺, Zn²⁺, Mg²⁺, Ca²⁺, Sc³⁺) were synthesized in five steps. Their solubility and critical micelle concentration (CMC) in water were determined highlighting a huge effect of the chain length and the nature of the cation. The hydrophilic–lipophilic balance of the surfactants were assessed with the phase inversion temperature (PIT)-slope method based on the deviation from the PIT of the reference C₁₀E₄/n-octane/0.01 M NaCl_(aq) emulsion through addition of increasing amounts of the dialkyl methanesulfonates. The hydrophilicity of the surfactants was thus ranked in terms of dPIT/dx_sulfonate. A “cation” scan with the [DiC ₆ CHSO ₃ ] _m M /benzene/water systems at f_w = 0.5 was finally performed confirming the hydrophilicity ranking obtained with the PIT-slope method. It revealed that the [DiC ₆ CHSO ₃ ] ₂ Mg behaves as a “Balanced Surfactant” able to form spontaneously a three-phase microemulsion system (Winsor III) just in the presence of water and oil, in the same way as the catalytic surfactant dimethyldioctylammonium molybdate, which has the same PIT-slope.     

GaAsSb/InAlAs PA DHBTs Grown by Production MBE

The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4 × 100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor. The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb. A Sb composition variation of less than ± 0.1 atomic percent across a 4 × 100mm platen configuration has been achieved. The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO＞6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm × 50μm. The devices have a 40nm thick GaAsSb base with p-doping of 4. 5 × 1019cm-3 . Devices with an emitter size of 4μm × 30μm have a current gain variation less than 2% across the fully processed 100mm wafer. ft and fmax are over 50GHz,with a power efficiency of 50% ,which are comparable to standard power GaAs HBT results. These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs.     

变截面Euler-Bernoulli梁在轴力作用下固有振动的级数解

建立了截面特性、轴力和质量分布均连续变化的Euler-Bernoulli梁固有振动方程。采用Frobeniu方法求解方程,得到了方程的级数解析解;并计算了结构的振动频率与振型。算例证明了该方法的有效性,并表明轴向力的几何非线性效应对振动的低阶频率和自振振型有一定的影响,级数项数的取值对算法的收敛性有影响。     

A rapid h.p.l.c. method for the determination of methionine hydroxy analogue free acid in supplemented feeds

Two methods are described for determining methionine hydroxy analogue free acid (HMB) in supplemented poultry feeds. The procedure is based on extraction of analogue from the feed, followed by high-pressure liquid chromatographic measurement of the HMB directly after extraction or, more rigorously, after extraction and hydrolysis of oligomers to monomer. Recoveries of HMB over the supplementation range 0.08–0.25% (by wt) are 98% with coefficients of variation of 5.4% in commercial poultry feeds. A 98% correlation coefficient is obtained when the analyses are compared with the gas chromatographic method.     

Effects of nimesulide on constitutive and inducible prostanoid biosynthesis in human beings

BACKGROUND: The aim of this study was to test the hypothesis that nimesulide, a nonsteroidal antiinflammatory drug, or its principal metabolite 4-hydroxynimesulide, is a selective inhibitor of prostaglandin H synthase-2 in human beings. METHODS: Heparinized whole blood samples obtained from healthy subjects were incubated with lipopolysaccharide (10 micrograms/ml) for 24 hours at 37 degrees C and prostaglandin E2 was measured in plasma as an index of monocyte prostaglandin H synthase-2 activity. The production of thromboxane B2 in whole blood allowed to clot at 37 degrees C for 60 minutes was assessed as an index of platelet prostaglandin H synthase-1 activity. We also measured the urinary excretion of 11-dehydrothromboxane B2, prostaglandin E2, 6-ketoprostaglandin F1 alpha, and thromboxane B2 as in vivo indexes of cyclooxygenase activity. All prostanoids were measured by previously validated radioimmunoassay techniques. RESULTS: In the whole blood assays in vitro, nimesulide was twentyfold more potent than 4-hydroxynimesulide toward the two isozymes and both compounds displayed a twentyfold preference for prostaglandin H synthase-2 versus prostaglandin H synthase-1. The administration of a single oral dose of 100 mg nimesulide to six healthy subjects significantly (p < 0.01) reduced monocyte prostaglandin H synthase-2 and prostaglandin H synthase-1 activity ex vivo by more than 90% and 50%, respectively, up to 6 hours. At 24 hours, prostaglandin H synthase-2 but not prostaglandin H synthase-1 activity was significantly reduced by 49% (p < 0.05). Nimesulide significantly (p < 0.05) reduced the urinary excretion of 11-dehydrothromboxane B2 and 6-ketoprostaglandin F1 alpha by approximately 30% and 25%, respectively, while not affecting that of prostaglandin E2 and thromboxane B2. CONCLUSIONS: Nimesulide is a potent inhibitor of human monocyte prostaglandin H synthase-2. However, despite a twentyfold selectivity ratio, therapeutic plasma levels of nimesulide are sufficiently high to cause detectable inhibition of platelet prostaglandin H synthase-1.     

基于ANSYS的渐进结构拓扑优化方法比较

以大型有限元通用软件ANSYS作为平台进行二次开发,探索基于渐进结构优化方法的结构拓扑优化途径.通过直接删除单元和运用单元生死技术,发展了两种实现结构拓扑优化的途径,并与ANSYS自带的结构拓扑优化功能进行比较研究.结果表明,直接删除法和单元生死法均可用于工程实际,运用单元生死技术进行基于ESO的结构拓扑优化有更大的灵活性和实用性.     

高速铁路中承式钢箱混凝土系杆梁拱组合桥极限承载能力分析

采用有限元方法,结合高速铁路中某特大中承式钢箱混凝土系杆梁拱组合桥工程实际,建立了该组合体系桥梁的全桥有限元模型,进行了桥梁整体结构极限承载能力分析。分析过程中主要考虑了材料非线性、几何非线性、施工制造误差、荷载效应、钢与混凝土的组合效应等对桥梁极限承载能力的影响。研究结果表明,主拱肋、主纵梁及横梁固结形式的中承式钢箱混凝土系杆拱梁组合体系具有刚度大、承载能力高、美观经济等特点,在铁路尤其是高速铁路建设中具有良好的应用前景。所得结论对今后同类桥梁设计和分析具有指导意义。