Coexistence of ergodicity and nonergodicity in LaFeO(3)-modified Bi(1/2)(Na(0.78)K(0.22))(1/2)TiO(3) relaxors

The effect of LaFeO(3) addition to Bi(1/2)(Na(0.78)K(0.22))(1/2)TiO(3) ceramics on the phase stability and macroscopic functional properties was investigated. Similarly to other chemical modifiers known in the literature, LaFeO(3) addition suppresses an electric-field-induced long-range ferroelectric order, giving rise to a giant unipolar strain of ～0.3% at 2?mol% LaFeO(3) addition. Time-dependent changes in polarization and strain hysteresis loops both during successive electrical cycling and after removal of the electric field suggest that a specimen with 2?mol% LaFeO(3) consists of both ergodic and nonergodic phases, which is unique among the known relaxor materials.     

Absolute mean square exponential stability of Lur’e stochastic distributed parameter control systems

In this work the absolute mean square exponential stability of Lur’e stochastic distributed parameter control systems has been addressed. Delay-dependent sufficient conditions for the stochastic stability in Hilbert spaces are established in terms of linear operator inequalities (LOIs). Finally, the stochastic wave equation illustrates our result.     

Synthesis of three novel anionic gemini surfactants and comparative studies of their assemble behavior in the presence of bovine serum albumin

Three novel anionic sulfonate gemini surfactants, sodium 4,4'-(10,19-dioxo-9,11,18,20-tetraazaoctacosane-9,20-diyl) dibenzenesulfonate (Surfactant I), sodium 4,4'-(12,21-dioxo-11,13,20,22-tetraazadotriacontane-11,22-diyl) dibenzenesulfonate (Surfactant II), and sodium 4,4'-(14,23-dioxo-13,15,22,24-tetraazahezatriacontane-13,24-diyl) dibenzenesulfonate (Surfactant III), with different lengths of hydrophobic tail have been synthesized, and their assembly behavior in the presence of bovine serum albumin (BSA) has been studied using spectral methods and molecular modeling methods at physiological pH and 298 K. Critical micelle concentrations (CMCs) of the three surfactants have been determined by surface tension measurements. Despite the obvious decrease of CMC with the increase of tail length, fluorescence spectra have shown much closer CAC in the presence of BSA. Surfactant II shows the highest CAC of 3.19 × 10(-5) mol L(-1) compared with the other two. The polarity of the microenvironment in BSA-surfactant systems has been investigated using pyrene as the probe. In addition, far-UV CD spectra studied the change of the secondary structure content of BSA caused by the three surfactants. The features of the assembly behavior were discussed by three concentration regions. Surfactant II could unfold the protein much more efficiently than the other two surfactants at low concentration, but at high concentration, the change of the secondary structure and the formation of hydrophobic microenvironment show a direct relationship to the length of the hydrophobic tail with the increase of the surfactant concentration.     

Surface tension and aggregation properties of novel cationic gemini surfactants with diethylammonium headgroups and a diamido spacer

A series of novel cationic gemini surfactants with diethylammonium headgroups and a diamido spacer were synthesized, and their surface and bulk properties were investigated by surface tension, electrical conductivity, fluorescence, viscosity, dynamic light scattering (DLS), and transmission electron microscopy (TEM) measurements. An interesting phenomenon, that is, the obvious decline in surface tension upon increasing concentration above the critical micelle concentration (cmc), was found in these gemini surfactant solutions, and two explanations were proposed. This surface tension behavior could be explained by the rapid increase in the counterion activity in the bulk phase or the continued filling of the interface with increasing surfactant concentration above the cmc. More interestingly, not only vesicles but also the surfactant-concentration-induced vesicle to larger aggregate (spongelike aggregate) transition and the salt-induced vesicle and spongelike aggregate to micelle transition were found in the aqueous solutions of these gemini surfactants. The spongelike aggregate that is first reported in the cationic gemini surfactant-water binary system is probably caused by the adhesion and fusion of vesicles at high surfactant concentration.     

利用ICCD定位宇宙线来测量探测器时间分辨的方法研究

本研究采用双层150 mm×150 mm闪烁条阵列定位宇宙线的入射和出射位置. 阵列信号光使用波移光纤吸收传输,在ICCD相机前插入前置像增强器,使信号光延迟大于200 ns, 使ICCD可以由外部高速触发信号控制,有效记录随机触发事例.该宇宙线定位系统可以同时多点密集测量 通用探测器测试平台的时间分辨和闪烁光的渡越时间.该新方法与传统时间分辨测量方法相比提高了30倍以上 的效率.实验结果显示:时间探测器的时间分辨好于200 ps,满足通用探测器测试平台的设计要求.     

Saturable absorber at 940 nm using single wall carbon nanotubes deposited by vertical evaporation technique

The vertical evaporation technique allows us to fabricate aligned single wall carbon saturable absorbers. The nonlinear parameters of the absorber at the wavelength of 940 nm were measured. The measured bi-exponential lifetimes of the absorber are 330 fs and 850 fs, respectively. The saturation intensity and modulation depth were found to be 2000 μJ/cm² and 10% for SWCNT absorber at the direction of alignment, in comparison to 950 μJ/cm² and 7% for the SWCNT solution.     

注凝成型制备氧化锆增韧氧化铝陶瓷

采用低毒单体N,N-二甲基丙烯酰胺(DMAA)制备了氧化锆增韧氧化铝(ZrO2/Al2O3,ZTA)陶瓷,氧化铝与氧化锆的质量比为3∶1,浆料的固相体积分数为50 vol%。讨论了不同干燥方式对干燥速率以及坯体性能的影响,研究了不同成型温度对坯体性能的影响。通过研究发现,在湿热烘箱中干燥的坯体强度最高,成型温度应控制在65℃附近。通过对不同单体含量的坯体烧结后陶瓷性能的对比,发现单体的加入量为10wt%左右较好,通过与干压成型陶瓷性能的对比,发现注凝成型得到的陶瓷强度和韧性分别提高了42.2%和23.5%,达到640 MPa和6.3MPa.m1/2,通过扫描电镜图片分析发现,注凝成型制得的陶瓷结构更均匀。     

Water assisted growth of C₆₀ rods and tubes by liquid-liquid interfacial precipitation method

C?? nanorods with hexagonal cross sections are grown using a static liquid-liquid interfacial precipitation method in a system of C??/m-dichlorobenzene solution and ethanol. Adding water to the ethanol phase leads instead to C?? tubes where both length and diameter of the C?? tubes can be controlled by the water content in the ethanol. Based on our observations we find that the diameter of the rods/tubes strongly depends on the nucleation step. We propose a liquid-liquid interface growth model of C?? rods and tubes based on the diffusion rate of the good C?? containing solvent into the poor solvent as well as on the size of the crystal seeds formed at the interface between the two solvents. The grown rods and tubes exhibit a hexagonal solvate crystal structure with m-dichlorobenzene solvent molecules incorporated into the crystal structure, independent of the water content. An annealing step at 200 °C at a pressure < 1 kPa transforms the grown structures into a solvent-free face centered cubic structure. Both the hexagonal and the face centered cubic structures are very stable and neither morphology nor structure shows any signs of degradation after three months of storage.