羧酸加氢反应机理及催化剂的研究进展

生物质衍生羧酸化合物的加氢反应是生产生物质化学品的重要过程之一.我们从羧酸分子加氢反应机理与加氢催化剂两个方面进行概述,着重介绍了第VIII族金属,尤其贵金属作为活性金属的羧酸加氢反应机理,以及不同催化剂对羧酸加氢反应途径的影响.此外,还介绍了羧酸水相加氢反应中Ru基催化剂的研究进展.     

ICF研究中的Rayleigh-Taylor不稳定性实验用靶

 概述了当前研究Rayleigh-Taylor不稳定性增长实验所用的靶型情况。从实验用靶来看，调制靶的设计正从平面向立体发展，出现了球形和柱形等新靶形，制备手段包括精密机械微加工、激光束、电子束和离子束加工、半导体工艺和微米纳米技术加工等。根据对国外新靶型的研究，结合国内工艺条件和实验需求，对国内可能采用的靶型进行了研究探索。     

Algorithms for flattened Gaussian beams passing through apertured and unapertured paraxial ABCD optical systems

The propagation property of flattened Gaussian beams (FGBs) is studied based on the Collins formula, and analytical propagation equations for FGBs with and without an aperture are derived. It is shown that the closed-form expressions for the FGB of order N passing through paraxial ABCD optical systems without an aperture can be written as the combinations of Confluent Hyper-geometric Functions, and that the analytical equations for the FGB of order N passing through apertured paraxial ABCD optical systems may involve Error Functions. The proposed algorithms for the considered beams can save computing time, provide intuitive physical insights, and help to design optical systems. Our results are confirmed and illustrated with numerical examples.     

关于分光计调整方法的分析

本文对自准直调节方法的成像规律和光栅侧向倾斜对测量结果的影响等问题,进行了半定量分析,给出了相关的调节依据和正确的调节步骤     

Effects of fractal gating of potassium channels on neuronal behaviours

The classical model of voltage-gated ion channels assumes that according to a Markov process ion channels switch among a small number of states without memory, but a bunch of experimental papers show that some ion channels exhibit significant memory effects, and this memory effects can take the form of kinetic rate constant that is fractal. Obviously the gating character of ion channels will affect generation and propagation of action potentials, furthermore, affect generation, coding and propagation of neural information. However, there is little previous research on this series of interesting issues. This paper investigates effects of fractal gating of potassium channel subunits switching from closed state to open state on neuronal behaviours. The obtained results show that fractal gating of potassium channel subunits switching from closed state to open state has important effects on neuronal behaviours, increases excitability, rest potential and spiking frequency of the neuronal membrane, and decreases threshold voltage and threshold injected current of the neuronal membrane. So fractal gating of potassium channel subunits switching from closed state to open state can improve the sensitivity of the neuronal membrane, and enlarge the encoded strength of neural information.     

Thermal and Thermo-Oxidative Degradation of Biodegradable Poly(Ester Urethane) Containing Poly(L-Lactic Acid) and Poly(Butylene Succinate) Blocks

A novel biodegradable poly(ester urethane; PEU) was synthesized by chain extension reaction of dihydroxylated poly(L-lactic acid; PLLA) and poly(butylene succinate; PBS) using diisocyanate as a chain extender. The kinetics of thermal and thermo-oxidative degradation of PEU containing PLLA and PBS blocks were studied by thermogravimetric analysis (TGA). TGA results indicated that PEU was more stable in air than in nitrogen and went through a two-stage degradation process irrespective of the experimental atmosphere. Activation energy of each stage was calculated by means of Kissinger, Kim-Park, Friedman, Flynn-Wall-Ozawa, and Kissinger-Akahira-Sunose methods. For the first stage, the activation energy value obtained in air was slightly higher than the corresponding value obtained in nitrogen; and for the second stage, the activation energy showed a much higher value in air than in nitrogen. The Coats-Redfern method was employed to study the degradation mechanism of each stage. The results indicated that the degradation of the first stage follows the P3/4 mechanism irrespective of the experimental atmosphere; the degradation of the second stage of PEU obeys the P1 mechanism in nitrogen while P3/2 in air.     

Synthesis and catalytic activity of neutral salicylaldiminato nickel(II) complexes bearing a single N-heterocyclic carbene ligand

Neutral salicylaldiminato Ni(II) complexes bearing a single N-heterocyclic carbene (NHC) ligand [3,5-^tBu₂-2-(O)C₆H₂CHNAr]Ni(C{RNCHCHNⁱPr})Ph [Ar = 2,6-ⁱPr₂C₆H₃, R = Bn (1); Ar = 2,6-ⁱPr₂C₆H₃, R = ⁱPr (2)], have been synthesized via a one-pot procedure in high yield. The X-ray structure analysis reveals that both of 1 and 2 adopt distorted square-planar coordination geometry and NHC carbon (C_carbene) is trans to the ketimine nitrogen. Preliminary study indicates that complex 1 is inert toward the insertion of ethylene, however, it can catalyze the dimerization of ethylene in the presence of modified methylaluminoxane (MMAO) with a moderate activity of 3.05 × 10⁴ g(mol Ni)⁻¹ h ⁻¹ atm⁻¹ in a highly selective fashion.     

Unprecedented Quassinoids with Promising Biological Activity from Harrisonia perforata

Perforalactone A ( 1 ), a new 20S quassinoid with a unique cagelike 2,4‐dioxaadamantane ring system and a migrated side chain, was isolated from the plant Harrisonia perforata together with two biosynthetically related new quassinoids. The structures of these natural products were elucidated by NMR spectroscopy, X‐ray diffraction analysis, computational modeling, and the CD excitation chirality method. The compounds exhibited notable biological properties, including insecticidal activity against Aphis medicaginis Koch and antagonist activity at the nicotinic acetylcholine receptor of Drosophila melanogaster. The structural features of these compounds may be related to their promising biological characteristics. Their biosynthesis and an alternative origin of quassinoid‐type natural products are also discussed.     

Numerical study of the effects of scatterer sizes and distributions on multiple backscattered intensity patterns of polarized light

We investigate numerically the effects of scatterer sizes on backscattered polarization patterns using the third-order scattering model developed. The calculated results show that both parallel and cross polarization patterns from water suspensions of polystyrene spheres have four-lobe structures of the azimuth dependence of intensities. Particularly, the parallel polarization pattern is sensitive to scatterer sizes, exhibiting good agreement with prior experimental measurements. Furthermore, the polarization patterns from the dysplastic and normal cells with different size distribution widths are calculated and analyzed. The results show that the polarization patterns of dysplastic and normal cells have distinct differences, which might be used for identification of the morphological structure changes of cancer, dysplasia, and regeneration cells.     

Cationic Pd(II)-catalyzed enantioselective cyclization of aroylmethyl 2-alkynoates initiated by carbopalladation of alkynes with arylboronic acids

A cationic palladium(II)-catalyzed enantioselective intramolecular addition of vinylpalladium species to ketones initiated by the carbopalladation of alkynoates under mild conditions without a Pd(II)/Pd(0) redox system was developed with high yield and enantioselectivity. This cascade reaction provides an efficient method for the construction of optically active hydroxylactones.