EXISTENCE AND UNIQUENESS OF SOLUTIONS TO A NONLINEAR FRACTIONAL DIFFERENTIAL EQUATION

The initial value problem of a nonlinear fractional differential equation is discussed in this paper. Using the nonlinear alternative of Leray-Schauder type and the contraction mapping principle,we obtain the existence and uniqueness of solutions to the fractional differential equation,which extend some results of the previous papers.     

Evidence of negative-index refraction in nonlinear chemical waves

The negative index of refraction of nonlinear chemical waves has become a recent focus in nonlinear dynamics researches. Theoretical analysis and computer simulations have predicted that the negative index of refraction can occur on the interface between antiwaves and normal waves in a reaction-diffusion (RD) system. However, no experimental evidence has been found so far. In this Letter, we report our experimental design in searching for such a phenomenon in a chlorite-iodide-malonic acid (CIMA) reaction. Our experimental results demonstrate that competition between waves and antiwaves at their interface determines the fate of the wave interaction. The negative index of refraction was only observed when the oscillation frequency of a normal wave is significantly smaller than that of the antiwave. All experimental results were supported by simulations using the Lengyel-Epstein RD model which describes the CIMA reaction-diffusion system.     

空心阴极放电条纹特性的光谱诊断

利用发射光谱法,研究了圆柱型空心阴极放电条纹的特性.测量了条纹区的发射光谱,在此基础E计算得到r电子激发温度、相对电子密度和电子平均能量的空间分布特性.结果表明条纹区的光强、电子激发温度和电子密度均呈非等幅的周期性变化.与暗纹中心处相比,明纹中心具有较高的电子激发温度和较低的电子密度.由阴极向阳极,明纹中心处的电子激发温度幅值逐渐减小.此外,条纹区的电子激发温度随着电流的增加而增加.     

强辐射环境下高能脉冲裂变中子探测方法

在研究通道衰减、探测方法分离和探测器中子/射线本征分辨的基础上,研究了测量高能脉冲裂变中子数目的探测技术。基于电流型Si-PIN探测器,设计了减本底的背靠背探测结构,给出了测量强射线和低能散射中子干扰信号及有效扣除强辐射本底的实现方法,最终实现了高n/n和n/分辨测量和强裂变中子、射线混合场中的高能脉冲裂变中子数目探测,探测系统的信号/辐射本底比可达到10倍以上。     

A strategy for liquid chromatography/tandem mass spectrometry based quantitation of pegylated protein drugs in plasma using plasma protein precipitation with water-miscible organic solvents and subsequent trypsin digestion to generate surrogate peptides for detection

Recently, we have developed liquid chromatography/tandem mass spectrometry (LC/MS/MS)-based methods for the quantitation of pegylated therapeutic proteins in plasma. The methods are based on the LC/MS/MS detection of a surrogate peptide generated from trypsin digestion of the therapeutic protein. Various parameters related to the bioanalytical methods were evaluated and optimized, including the preparation of calibration standards and quality control samples, sample extraction, internal standard selection and its stage of addition, trypsin digestion, and non-specific binding. In this paper, we report the development of a method for a specific pegylated therapeutic protein and detail the various optimization steps undertaken. Simple extraction of the pegylated therapeutic protein from plasma was achieved via the precipitation of the endogenous proteins in plasma using acidic isopropanol and the resulting supernatant extract was subjected to trypsin digestion. A unique tryptic peptide arising from the pegylated therapeutic protein was used for LC/MS/MS-based detection and quantitation. A protein and a peptide were used as internal standards, with the former added before the sample extraction and the latter after the sample extraction. The method developed is simple, sensitive, specific and rugged, and has been implemented in a high throughput 96-well format to analyze plasma samples from in vivo studies. A required lower limit of quantitation (LLOQ) of 10 ng/mL, expressed in terms of the concentration of the protein drug, was easily achieved.     

Design,synthesis, and pesticidal activities of novel pyrimidin-4-amine derivatives containing trifluoroethyl sulfide moiety

In order to overcome the problem of pesticide resistance, it is necessary to discover novel pesticides with new mechanisms of action. Herein, a series of novel pyrimidin-4-amine derivatives containing trifluoroethyl sulfide moiety were designed and synthesized. Bioassays indicated that the title compounds synthesized possessed excellent acaricidal activity against Tetranychus urticae and fungicidal activity against Erysiphe graminis and Puccinia sorghi. Especially, the acaricidal activity of 5-chloro-6-(difluoromethyl)-N-(2-(2-fluoro-4-methyl-5-((2,2,2-trifluoroethyl)thio)phenoxy)ethyl)pyrimidin-4-amine (compound T4 , LC₅₀ = 0.19 mg/L) against T. urticae was close to commercial acaricide cyenopyrafen, and the fungicidal activity of 5-chloro-6-(difluoromethyl)-2-methyl-N-(2-(3-((2,2,2-trifluoroethyl)thio)phenoxy)ethyl)pyrimidin-4-amine (compound T15 , EC₅₀ = 1.32 mg/L) against P. sorghi. was superior to commercial fungicide tebuconazole. The synthesis and characterization of these compounds were given and the structure–activity relationships were discussed.     

离子辐照对磷烯热导率的影响及其机制分析

通过离子辐照产生缺陷,可以非常有效地调控磷烯诸多物理性质.本文应用分子动力学方法模拟离子辐照磷烯的过程,给出了缺陷的形成概率与入射离子能量、离子种类以及离子入射角度之间的关系,并且应用非平衡态分子动力学计算辐照后磷烯热导率的变化.以缺陷形成概率为切入点,系统地研究了辐照离子的能量、辐照剂量、离子的种类以及离子的入射角度对磷烯热导率的影响.应用晶格动力学方法研究了空位缺陷对磷烯声子参与率的影响,并计算了声子局域模式的空间分布.基于量子微扰和键弛豫理论,指出空位缺陷明显降低磷烯热导率的最重要物理机制是空位缺陷附近的低配位原子对声子强烈散射.本文研究可为缺陷工程调控磷烯的热输运性质提供理论参考.     

Enhancing thermal transport in multilayer structures: A molecular dynamics study on Lennard−Jones solids

We investigate the thermal transport properties of three kinds of multilayer structures: a perfect superlattice (SL) structure, a quasi-periodic multilayer structure consisted of two superlattice (2SL) structures with different periods, and a random multilayer (RML) structure. Our simulation results show that there exists a large number of aperiodic multilayer structures that have effective thermal conductivity higher than that of the SL counterpart, showing enhancement ratio in the effective thermal conductivity up to 193%. Surprisingly, some RML structures also exhibit enhanced thermal transport than the SL counterpart even in the presence of phonon localization. The detailed analysis on the underlying mechanism reveals that such peculiar enhancement is caused by the synergistic effect of coherent and incoherent phonon transport, which can be tuned by the structural configuration. Combined with molecular dynamics simulations and the machine learning technique, we further reveal that the enhancement effect of the effective thermal conductivity by 2SL structure is more significant when the period of SL structure is close to the critical transition period between the coherent and incoherent phonon transport regimes. Our study proposes a novel strategy to enhance the thermal transport in multilayer structures by regulating the wave-particle duality of phonons via the structure optimization, which might provide valuable insights to the thermal management in devices with densely packed interfaces.