罗尔中值定理的一些新证法

给出了罗尔微分中值定理的三种新的证明方法,其中第二种很简便的方法仅依赖于大家熟知的Heine-Borel有限覆盖定理.由此可见罗尔微分中值定理可以是实数的完备性的直接推论.     

高温高压合成CeTbO3+δ的XPS研究

 经过高温高压合成的CeTbO_3+δ进行了XPS研究，发现在1.0 GPa下，Tb⁴⁺在~600 ℃开始转变成Tb³⁺，而Ce⁴⁺在~800 ℃开始向Ce³⁺转变。在1 000~1 200 ℃形成单相萤石结构化合物CeTbO_3+δ的Ce是以Ce³⁺、Ce⁴⁺混合价形式存在，Tb全部变成Tb³⁺。实验表明，用Ce_3d谱上~888 eV峰的峰位及其与882 eV峰的相对强度变化可以定性判断化合物中是否含有Ce³⁺。研究了高温高压合成的CeTbO_3+δ的稳定性随时间的变化问题。     

Candida Rugosa lipase-catalyzed kinetic resolution of β-hydroxy-β-arylpropionates and δ-hydroxy-δ-aryl-β-oxo-pentanoates

A simple and convenient method was reported for the preparation of optically active β-hydroxy-β-arylpropionates, δ-hydroxy-δ-aryl-β-oxo-pentanoates and their butyryl derivatives via CRL-catalyzed hydrolysis. The optically active products are potential precursors of some chiral pharmaceuticals and natural products.     

A method of detecting capture γ-rays in a strong pulsed radiation field

We present a technology for diagnosing the D－T fusion process by detecting capture γ-rays. This technology provides an alternative route to diagnosing the D－T reaction process when a great deal of heavy Z materials surrounds the D－T region. A very important aspect of this paper is to focus on the methods of shielding low-energy γ-rays whose radiation intensity is 10⁶ times higher than that of the capture γ-rays. Another aspect is about how to distinguish signal from noise. The result of a 50/1 signal-to-noise ratio indicates that the designed double-magnetic spectrograph is very successful for diagnosing the D－T fusion reaction process.     

光合细菌产生5-氨基乙酰丙酸(ALA)的研究

从36个光合细菌菌株中筛选出的7株紫色非硫红假单胞菌有产ALA能力，其中菌株99-28ALA产量最高 用紫外线对菌株99-28进行诱变处理，筛选出产量比野生菌株高1倍多的菌株L-1，对影响菌株的生长和ALA产量的因子进行了探索，抑制剂加入时间和加入次数对ALA产量有显著影响，在最佳条件下（pH7.5，培养对数生长期加入ALA脱水酶抑制剂乙酰丙酸30mmol，ALA生物合成前体甘氨酸30mmol和琥珀酸30mmol，3000lx光照），菌株L-1的ALA产量可达22.15mg/L。     

NMR metabolic profiling of organic and aqueous sea bass extracts: implications in the discrimination of wild and cultured sea bass

The nuclear magnetic resonance (NMR) technique was used as analytical tool to determine the complete metabolic profiling of sea bass extracts: water-soluble metabolites belonging to different classes such as sugars, amino acids, dipeptides and organic acids as well as metabolites soluble in organic solvent such as lipids, sterols and fatty acids were identified. The metabolite profiling together with a suitable statistical analysis were used to discriminate between wild and cultured sea bass samples. Preliminary results show that discrimination between wild and cultured sea bass was obtained not only using fatty acid composition but also cholesterol and phosphatidylethanolamine and some water-soluble metabolites such as choline, trimethylamine oxide, glutamine, fumaric and malic acids.     

A general synthetic approach for the synthesis of β-hydroxy-δ-lactones: asymmetric total synthesis of prelactones and epi-prelactones V and E

A general synthetic approach for the synthesis of prelactones and epi-prelactones V and E has been reported using an Evans’ aldol reaction as the key step.     

Pseudocompact groups: progress and problems

Several months ago the speaker and Jan van Mill gave a proof of this result [W.W. Comfort, J. van Mill, Extremal pseudocompact abelian groups are compact metrizable, Abstracts Amer. Math. Soc. 27 (2006) 78 (Abstract #1014-22-958); W.W. Comfort, J. van Mill, Extremal pseudocompact abelian groups are compact metrizable, Proc. Amer. Math. Soc. 135 (2007) 4039-4044]: A pseudocompact abelian group of uncountable weight admits both a proper dense pseudocompact subgroup and a strictly larger pseudocompact group topology.This presentation will describe both the necessary new details of the argument and the historical development (useful tools, special cases). Among those who contributed essentially are: K.A. Ross (1964, 1966); T. Soundararajan (1982); L.C. Robertson (1982, 1988); J. van Mill (1989); J. van Mill and H. Gladdines (1994); J. Galindo (2002).Several related unsolved problems will be cited.     

Selective CO2 Reduction to Ethylene Mediated by Adaptive Small-molecule Engineering of Copper-based Electrocatalysts

Electrochemical CO₂ reduction reaction (CO₂RR) over Cu catalysts exhibits enormous potential for efficiently converting CO₂ to ethylene (C₂H₄). However, achieving high C₂H₄ selectivity remains a considerable challenge due to the propensity of Cu catalysts to undergo structural reconstruction during CO₂RR. Herein, we report an in situ molecule modification strategy that involves tannic acid (TA) molecules adaptive regulating the reconstruction of a Cu-based material to a pathway that facilitates CO₂ reduction to C₂H₄ products. An excellent Faraday efficiency (FE) of 63.6 % on C₂H₄ with a current density of 497.2 mA cm⁻² in flow cell was achieved, about 6.5 times higher than the pristine Cu catalyst which mainly produce CH₄. The in situ X-ray absorption spectroscopy and Raman studies reveal that the hydroxyl group in TA stabilizes Cu^δ+ during the CO₂RR. Furthermore, theoretical calculations demonstrate that the Cu^δ+/Cu⁰ interfaces lower the activation energy barrier for *CO dimerization, and hydroxyl species stabilize the *COH intermediate via hydrogen bonding, thereby promoting C₂H₄ production. Such molecule engineering modulated electronic structure provides a promising strategy to achieve highly selective CO₂ reduction to value-added chemicals.     

A new generation of cyanide ion-selective membranes for flow injection application: part II. Comparative study of cyanide flow-injection detectors based on thin electroplated silver chalcogenide membranes

Using induced cathodic electrodeposition a number of silver chalcogenide thin layer membranes of non-trivial composition have been synthesized and their performance as ion-selective flow-injection potentiometric detectors (FIPDs) for free cyanide has been critically estimated in the context of the stringent requirements for toxic cyanide environmental monitoring. AgSCN/Ag₂S, Ag₂S, Ag_2+δSe, Ag_2+δSe_1−xTe_x (0 < δ < 0.25 and x ≈ 0.13), Ag₂Se and Ag₂Se_1−xTe_x electroplated membranes were selected for the present performance-based comparative study in order to obtain a feedback information about the effect of membrane composition. Both silver selenide and Te-doped silver selenide membranes, irrespective of their stoichiometry with respect to silver, exhibit the lowest detection limit for CN⁻ (52 ppb) with linear double-Nernstian response down to 130 ppb. The type of chalcogene anion in the membrane composition proves to exert dominant effect on the general performance characteristics of the newly developed FIPDs. The silver stoichiometry (intrinsic defects factor) and the inclusion of Te-dopant (extrinsic defects factor) have more pronounced effect on the profile of the output signal and exert moderate control on the detectors selectivity and baseline stability. This new generation of CN⁻—ion-selective membranes for FIPDs exhibits high selectivity against the common interferents present in cyanide effluents such as SCN⁻, S₂O₃²⁻, Cl⁻ and do not get poisoned in the presence of S²⁻. Moreover, their long-term stability and signal reproducibility, which make redundant the regular day-to-day calibration, coupled with the cost-effective technology for membranes preparation and easy re-generation make them attractive candidates for incorporation into automated in-field devices for in situ cyanide toxic species monitoring.