水合作用与pH调控聚电解质刷的构象转变

我们基于Flory-Huggins理论,建立理论模型研究水合作用与pH调控聚电解质刷的构象转变.理论模型考虑聚电解质链与水分子间的作用(聚电解质链的水合作用)、体系中的静电作用.研究发现,随着水合作用的改变,聚电解质刷出现由溶胀到塌缩的构象转变.由此表明了水合作用可在很大程度调节聚电解质刷的相变.通过分析pH的调控效应我们还发现,在碱性环境中(pH=8),聚电解质链单体的解离度增大,静电排斥会使得聚电解质刷溶胀.由此表明,聚电解质刷内水合作用与静电效应的耦合,将会共同决定聚电解质刷的构象转变特性.理论结果深刻揭示了水合作用的改变,会使得聚电解质刷体系发生相变,pH可在很大程度上改变其相变特性.     

具有双网络结构高强度和形状记忆水凝胶

本文将形状记忆功能引入到双网络水凝胶设计之中.首先合成了聚乙二醇-聚丙烯酰氧乙基三甲基氯化铵/聚（丙烯酰胺-co-丙烯酸）（PEG-PDAC/P（AAm-co-AAc））双网络水凝胶,其中第一套网络由交联的聚乙二醇（PEG）链组成,包埋着聚电解质聚丙烯酰氧乙基三甲基氯化铵（PDAC）;第二套网络由丙烯酰胺（AAm）和丙烯酸（AAc）的共聚物交联组成,交联剂为N,N''-亚甲基双丙烯酰胺（MBAA）.结果表明,双网络水凝胶显示出高强度的特点,其断裂应力和韧性分别达到了0.9 MPa和3.8 MJ/m³.和传统地利用中性高分子作为柔软和韧性的第二套网络相比较,本文选择将具有弱电解质特性的丙烯酸单体引入到第二套网络中,利用丙烯酸与三价铁离子的络合作用,成功地赋予水凝胶在氧化环氧反应条件下的形状记忆功能.结果表明,只要巧妙地引入响应性单体,高强度和形状记忆这两种最重要的特性可以同时被引入到双网络水凝胶的设计之中.     

聚丙烯酰胺水凝胶的核磁共振微成象

用核磁共振微成象中的自旋回波成象方法研究了γ辐射交联聚丙烯酰胺水凝胶体系,得到PAMG样品中交联网络的质子自旋密度分布之直观图象.对4个不同溶胀度的PAMG样品进行了实验测量,其实验结果清晰而直观地显示出样品中的交联网络随样品溶胀度的不同而变化的情况.     

聚天门冬氨酸水凝胶对Zn2＋的吸附行为

以聚丁二酰亚胺为原料,以戊二醛为交联剂制备聚天门冬氨酸水凝胶.研究了聚天门冬氨酸水凝胶对Zn2＋的吸附性能.结果表明：聚天门冬氨酸水凝胶对Zn2＋的吸附满足Langmuir等温方程,且吸附行为为吸热过程,聚天门冬氨酸水凝胶对Zn2＋的吸附能力较强.     

离子液体凝胶聚合物电解质PP13TFSI-LiTFSI-P(VdF-HFP)的电化学性能 (cited: 1)

采用溶液浇铸法将N-甲基-N-丙基哌啶二(三氟甲基磺)亚胺(PP13TFSI)、二(三氟甲基磺)亚胺锂与偏氟乙烯-六氟丙烯共聚物(P(VdF-HFP))混合制备离子液体凝胶聚合物电解质(ILGPEs). 通过扫描电子显微镜观察发现,这种离子液体凝胶聚合物电解质由于液体相的均匀分布而具有疏松的结构. 采用电化学阻抗、计时电流法、线性扫描伏安法测试了电解质的离子电导率、锂离子迁移数和电化学窗口. 室温下离子液体凝胶聚合物电解质的离子电导率和锂离子迁移数分别是0.79 mS/cm和0.71,电化学窗口为0～5.1 Vvs. Li⁺/Li. 电池性能测试表明,这种离子液体凝胶聚合物电解质在Li/LiFePO₄电池中是稳定的,放电容量在30、75和150mA/g倍率下分别为135、117和100 mAh/g,电池经100个循环后容量保持在100%而几乎没有衰减.     

Effects of excessive grain growth on the magnetic and mechanical properties of hot-deformed NdFeB magnets

The magnetic and mechanical properties of rare-earth magnets hot-deformed at temperature range 750-950 °C have been investigated. The grains tended to grow excessively from dozens of nanometers to several microns at the temperatures above 850 °C. The alignment of grains was disrupted by the hot deformation at the high temperatures. The Nd-rich phase was extruded at the temperatures which are higher than 850 °C. The Nd-rich phase extrusion resulted in the reduction of density by 1% and the reduction of remanence from 1.42 to 0.72 T. The reduction of grain boundaries caused by flat platelet-shaped grains changing to spherical grains and the weak binding strength among large grains of Nd₂Fe₁₄B phase may be the main reasons for the low mechanical strength of hot-deformed magnets.     

温度对铌酸锂电光相位调制特性的影响

利用折射率椭球基本理论对线性电光效应进行了分析,对单轴晶体铌酸锂电光相位调制器的温度特性进行了研究。通过计算机进行数值模拟计算,分析了加电场时光通过LiNbO3电光调制器后出射光的相位变化与温度间的关系,得出在横向和纵向调制中温度对相位改变的影响。研究发现,无论在横向还是在纵向调制下,入射光偏振方向不同但其各自受温度影响的相位变化趋势大体一致,即随着晶体中温度的增加而增大。计算结果表明,LiNbO3电光调制的最佳使用方案为：电场沿x主轴方向施加,入射光偏振方向为感应主轴x’方向,且LiNbO3电光调制器粟用横向相位调制方式。     

Investigation of nanostructural,thermal and magnetic properties of yttrium iron garnet synthesized by mechanochemical method

This paper focuses on the magnetic, structural and thermal properties of mechanically alloyed Y₂O₃/α-Fe₂O₃ mixed powders and investigates the effects of the mechanical milling and heat treatment on the synthesis of yttrium iron garnet from the primary materials. The morphological and structural studies were carried out by scanning electron microscope and X-ray diffraction, respectively. The thermal activities were measured by differential thermal analysis. The magnetic properties were studied by vibrating sample magnetometer. The results showed that high-energy milling does not lead to the garnet formation and even does not decrease the temperature of the garnet formation. Furthermore, the orthoferrite phase can be achieved slightly during the milling process (up to 96 h) and completely by the heat treatment at lower temperatures (850 °C).     

Dynamics of Controllable Optical Rogue Waves in Presence of Quintic Nonlinearity and Nonlinear Dispersion Effects

We analytically study optical rogue waves in the presence of quintic nonlinearity and nonlinear dispersion effects. Dynamics of the rogue waves are investigated through the precise expressions of their peak, valley, trajectory, and width. Based on this, the properties of a few specific rogue waves are demonstrated in detail, and the dynamical evolution of rogue waves can be well controlled under different nonlinearity management. It shows that the peak reaches its maximum and the valley becomes minimized when the width evolves to the minimum value. Moreover, we find that the higher-order effects here achieve balance due to the integrability, and they only influence the rogue waves' trajectory.     

Mechanical and optoelectric properties of post-annealed fluorine-doped tin oxide films by ultraviolet laser irradiation

The fluorine-doped tin oxide (FTO) thin film deposited on a soda-lime glass substrate was annealed by a defocus ultraviolet (UV) laser irradiation at ambient temperature. The mechanical and optoelectric properties of FTO films annealed by using the various laser processing parameters were reported. After the FTO films were subjected to laser post-annealing, the microhardness were slightly less but the reduced modulus values were larger than that of unannealed FTO films, respectively. The average optical transmittance in the visible waveband slightly increased with increasing the laser annealing energy and scan speed. Moreover, all the sheet resistance of laser annealed films was less than that of the unannealed ones. We found that the sheet resistance decrease was obviously influenced by annealing. The suitable annealing conditions could maintain the film thickness and relief the internal stress generated in the film preparation process to improve the electrical conductivity via decreasing laser energy or increasing scan speed.     

电极形状对GaN基发光二极管芯片性能的影响

采用Crosslight APSYS这一行业专业软件对p-GaN,InGaN/InGaN多量子阱,n-GaN和蓝宝石的芯片结构研究了不同电极形状与器件的光电性能之间的关系.优化设计了普通指形电极、对称型指形电极、h形指形电极、旋转形电极、中心环绕形电极、树形电极等6种电极结构.通过电极优化设计,电流分布更加均匀,减小了电流的聚集效应.优化后的电极结构结果表明:芯片的电特性得到了提高,芯片的光特性得到了明显改善,芯片的出光效率大幅度提高,芯片的转化效率得到了提升.     

Effects of therapeutic ultrasound on the nucleus and genomic DNA

In recent years, data have been accumulating on the ability of ultrasound to affect at a distance inside the cell. Previous conceptions about therapeutic ultrasound were mainly based on compromising membrane permeability and triggering some biochemical reactions. However, it was shown that ultrasound can access deep to the nuclear territory resulting in enhanced macromolecular localization as well as alterations in gene and protein expression. Recently, we have reported on the occurrence of DNA double-strand breaks in different human cell lines exposed to ultrasound in vitro with some insight into the subsequent DNA damage response and repair pathways. The impact of these observed effects again sways between extremes. It could be advantageous if employed in gene therapy, wound and bone fracture-accelerated healing to promote cellular proliferation, or in cancer eradication if the DNA lesions would culminate in cell death. However, it could be a worrying sign if they were penultimate to further cellular adaptations to stresses and thus shaking the safety of ultrasound application in diagnosis and therapy. In this review, an overview of the rationale of therapeutic ultrasound and the salient knowledge on ultrasound-induced effects on the nucleus and genomic DNA will be presented. The implications of the findings will be discussed hopefully to provide guidance to future ultrasound research.     

Quantification of frequency dependence of mechanical effects induced by ultrasound

The physical or mechanical effects induced by ultrasound were investigated through the viscosity change in degradation of polymers. The viscosity change was observed with polyethylene oxide in both aqueous and benzene solution; while polystyrene in only benzene solution. The frequency of ultrasound in these experiments varies from 20 kHz to 1 MHz, under a constant dissipated power. The viscosity ratio and the apparent degradation rate were obtained as a function of the irradiation frequency. From the analysis of these experiments, the mechanical effects are found to slow down above 100 kHz when the frequency increases. In case of the analysis of solution viscosity, since this method yields the same apparent results in both aqueous and benzene solutions, our study propose an alternative simple, cost effective method to quantify the mechanical effects in sonochemistry.     

Reflection of thermal atoms by a pulsed standing wave

Reflection of thermal atoms by a pulsed standing wave with a duration in the nanosecond range is studied. The momentum distribution of the reflected atoms is determined by calculations based on the adiabatic atom-photon interactions. It is shown that with a proper choice of the field intensity and the pulse duration the standing-wave pattern functions as a row of independent atom mirrors. At an optimum choice of the parameter values, the fraction of the elastically reflected atoms is more than 20%. Furthermore, we show that the pulsed standing-wave mirror can be used to manipulate their final momentum distribution. When using laser pulses with an intensity of several tens of MW/cm², tens of thousands of atoms can be reflected by a single laser pulse. Received 3 December 1999 and Received in final form 25 April 2000     

Control of Sudden Death of Entanglement by Transient Effects

We investigate the properties of entanglement between an isolated atom and a Jaynes-Cummings atom in the presence of transient effects. These effects are due to the modulation of the atom-field coupling whose explicit time-dependence is considered for the case of the linear sweep. We show that the sudden death of entanglement can be controlled by the transient effects. These effects can suppress the sudden death of entanglement in time.