Anticipated backward stochastic differential equations driven by the Teugels martingales

In this paper, a class of anticipated backward stochastic differential equations driven by Teugels martingales associated with Lévy process is investigated. We obtain the existence and uniqueness of solutions to these equations by means of the fixed-point theorem. We show that a comparison theorem for this type of ABSDEs also holds under some slight stronger conditions.     

Expression,Purification, and Characterization of a Recombinant Methionine Adenosyltransferase pDS16 in Pichia pastoris

Methionine adenosyltransferase (MAT, EC2.5.1.6) catalyzes the synthesis of S-adenosylmethionine (SAM) using l-methionine and adenosine triphosphate (ATP) as substrates. The mutant MAT pDS16 was obtained through DNA shuffling previously in our lab. Overexpression of pDS16 in Pichia pastoris led to about 65 % increase of MAT activity and SAM accumulation, compared with the strain overexpressing Saccharomyces cerevisiae MAT gene SAM2. Different strategies were tested to facilitate the expression and purification of pDS16. However, addition of the hexahistidine tag to pDS16 was shown to decrease the enzyme activity, and the yeast α-factor signal sequence could not effectivley direct the secretion of pDS16. The intracellular pDS16 was purified by a simple two-step procedure combining an ion exchange and hydrophobic interaction chromatography. Protein purity was verified by sodium dodecyl sulfate polyacrylamide gel electrophoresis to be 93 %, with the specific activity of 1.828 U/mg. Two-dimensional electrophoresis revealed pI of ～5.5. The purified enzyme followed Michaelis kinetics with a Km of 1.72 and 0.85 mM, and Vmax of 1.54 and 1.15 μmol/min/mg for ATP and L-methionine, respectively. pDS16 exhibited optimal activity at pH 8.5 and 45 °C with the requirement of divalent cation Mg²⁺ and was slightly stimulated by the monovalent cation K⁺. It showed an improved thermostability, about 50 % of the enzyme activity was retained even after preincubation at 50 °C for 2 h.     

巴拿哈空间中随机年龄结构种群方程的数值分析

本文研究年龄结构随机种群方程的离散误差,在空间离散中用到Galerkin公式,时间离散中用到显式欧拉公式.     

Detection of a semirough target in turbulent atmosphere by a partially coherent beam

The inverse problem of the interaction of an isotropic Gaussian Schell-model beam with a semirough target in turbulent atmosphere is investigated. It is found that we can determine the target size and the transverse correlation width of the target by measuring the transverse beam widths and the transverse coherence widths of the beams at the source plane and the receiver plane. Our results are useful for remote sensing and bistatic LIDAR system.     

Enhancement on interlaminar shear strength and water‐lubricated tribological performance of high‐strength glass fabric/phenolic laminate by the incorporation of carbon nanotubes

High‐strength glass fabric (HSGF)/phenolic laminates modified with different contents of carbon nanotubes (CNTs) were fabricated by hot‐compression technique. The effects of CNTs on the interface of HSGF/phenolic, interlaminar shear strength (ILSS) and water‐lubricated tribological performance of HSGF/phenolic laminate were investigated. The ILSS of the laminates were tested on a universal testing machine (DY35), and the tribological properties were evaluated by a block‐on‐ring tribo‐tester. The interfaces of HSGF/phenolic and the worn surfaces of the laminates were analyzed by scanning electron microscope. The results showed that the moderate incorporation of CNTs improved the interface of HSGF/phenolic and accordingly enhanced the ILSS of the laminate. Besides, the friction coefficient of HSGF/phenolic laminate sliding against stainless steel in water can be remarkably stabilized and lowered by the incorporation of CNTs due to the better water lubrication induced by added CNTs and the intrinsic self‐lubrication of CNTs which were further graphitized during the friction and wear process. And the wear rate of the laminate can be accordingly reduced by 1 order of magnitude. The results indicate that CNTs have excellent potential in enhancing both ILSS and tribological fabric/polymer laminate composite, which will greatly improve the current situation of deterioration on mechanical properties by adding traditional solid lubricants. Copyright © 2014 John Wiley & Sons, Ltd.     

基于卷积神经网络和松鼠优化算法的机翼结构混合优化设计#br#

针对大展弦比机翼的结构轻量化优化设计,提出了一种高效的布局和尺寸混合优化方法．在CFD/CSD气动弹性计算的基础上,对不同的结构变量进行统一编码,使用一维卷积神经网络建立代理模型,并使用松鼠优化算法建立了混合优化模型进行搜索寻优．以某型太阳能无人机的机翼结构优化为例,优化结果表明翼肋的布局变量和翼梁的尺寸变量之间存在着耦合关系,使用松鼠优化算法相比于遗传算法节省了35 %~45 %的计算成本,且混合优化后的结构比原始结构减重4.1 %,验证了该方法的有效性．     

Loading of free radicals on the functional graphene combined with liquid chromatography–tandem mass spectrometry screening method for the detection of radical-scavenging natural antioxidants

A novel free radical reaction combined with liquid chromatography electrospray ionization tandem mass spectrometry (FRR-LC–PDA-ESI/APCI-MS/MS) screening method was developed for the detection and identification of radical-scavenging natural antioxidants. Functionalized graphene was prepared by chemical method for loading free radicals (superoxide radical, peroxyl radical and PAHs free radical). Separation was performed with and without a preliminary exposure of the sample to specific free radicals on the functionalized graphene, which can facilitate reaction kinetics (charge transfers) between free radicals and potential antioxidants. The difference in chromatographic peak areas is used to identify potential antioxidants. The structure of the antioxidants in one sample (Swertia chirayita) is identified using MS/MS and comparison with standards. Thirteen compounds were found to possess potential antioxidant activity, and their free radical-scavenging capacities were investigated. The thirteen compounds were identified as 1,3,5-trihydroxyxanthone-8-O-β-d-glucopyranoside (PD1), norswertianin (PD2), 1,3,5,8-tetrahydroxyxanthone (PD3), 3, 3′, 4′, 5, 8-penta hydroxyflavone-6-β-d-glucopyranosiduronic acid-6′-pentopyranose-7-O-glucopyranoside (PD4), 1,5,8-trihydroxy-3-methoxyxanthone (PD5), swertiamarin (PS1), 2-C-β-d-glucopyranosyl-1,3,7-trihydroxylxanthone (PS2), 1,3,7-trihydroxylxanthone-8-O-β-d-glucopyranoside (PL1), 1,3,8-trihydroxyl xanthone-5-O-β-d-glucopyranoside (PL2), 1,3,7-trihydroxy-8-methoxyxanthone (PL3), 1,2,3-trihydroxy-7,8-dimethoxyxanthone (PL4), 1,8-dihydroxy-2,6-dimethoxy xanthone (PL5) and 1,3,5,8-tetramethoxydecussatin (PL6). The reactivity and SC₅₀ values of those compounds were investigated, respectively. PD4 showed the strongest capability for scavenging PAHs free radical; PL4 showed prominent scavenging capacities in the lipid peroxidation processes; it was found that all components in S. chirayita exhibited weak reactivity in the superoxide radical scavenging capacity. The use of the free radical reaction screening method based on LC–PDA-ESI/APCI-MS/MS would provide a new approach for rapid detection and identification of radical-scavenging natural antioxidants from complex matrices.     

Time domain transmission properties of multi-vias

The time domain transmission properties of multi-vias in MCM-C and MCM-D packages are investigated by the FDTD method. The results demonstrate that the crosstalk between two vias is negligible when their distance is larger than their width and excellent transmission properties can be achieved below 10GHz.This work was supported by the National Natural Science Fund of China and by the Fok Ying Tung Education Foundation.     

Electrochemical detection of L-cysteine using a glassy carbon electrode modified with a two-dimensional composite prepared from platinum and Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles on reduced graphene oxide

We report on an electrochemical sensor for L-cysteine that consists of a glassy carbon electrode modified with a two-dimensional ternary nanocomposite prepared from platinum, magnetite, and reduced graphene oxide (referred to as Pt-Fe₃O₄/rGO). It was prepared by a solvothermal method and characterized by X-ray powder diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. Electrochemical detection processes were investigated by cyclic voltammetry, amperometry, double potential step chronoamperometry and differential pulse voltammetry. The diffusion coefficient (7.41 × 10^?7 cm² s^?1) and reaction rate constant (9.96 × 10⁷ cm³ mol^?1 s^?1) were calculated via the Cottrell equation. The sensor, best operated in 0.1 M NaOH solution at a working voltage of 0.65 V vs. SCE, has a 10 μM detection limit and an analytical range that extends from 0.10 to 1.0 mM. The method is acceptably selective, stable, repeatable and reproducible due to the synergistic effect of the various components applied. The detection limit is 1.0 × 10^?5 M.

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Graphical abstract The electrochemical detection of L-cysteine based on a two-dimensional Pt-Fe₃O₄/reduced graphene oxide modified glassy carbon electrode has a detection limit of 1.0 × 10^-5 M in the range of 0.10 - 1.0 mM due to the synergistic effect of each component.

     

Targeted therapy of SMMC-7721 liver cancer in vitro and in vivo with carbon nanotubes based drug delivery system

A new type of drug delivery system (DDS) involved chitosan (CHI) modified single walled carbon nanotubes (SWNTs) for controllable loading/release of anti-cancer doxorubicin (DOX) was constructed. CHI was non-covalently wrapped around SWNTs, imparting water-solubility and biocompatibility to the nanotubes. Folic acid (FA) was also bounded to the outer CHI layer to realize selective killing of tumor cells. The targeting DDS could effectively kill the HCC SMMC-7721 cell lines and depress the growth of liver cancer in nude mice, showing superior pharmaceutical efficiency to free DOX. The results of the blood routine and serum biochemical parameters, combined with the histological examinations of vital organs, demonstrating that the targeting DDS had negligible in vivo toxicity. Thus, this DDS is promising for high treatment efficacy and low side effects for future cancer therapy.