Method for determination of association and dissociation rate constants of reversible bimolecular reactions by isothermal titration calorimeters

The rate law equation for reversible bimolecular reactions, which are describable by association and dissociation rate constants (k1 and k-1), is not solvable to a plain formula under stoichiometric reaction conditions. Therefore, it is a general technique to observe such reactions under pseudo first-order conditions, which make the reactions a single-exponential process, and enable us to determine k1 and k-1 without any complicated iterative computations needed to analyze the same reactions under stoichiometric reaction conditions. However, the accelerated reaction rates under pseudo first-order conditions are not always favorable to the physicochemical tools employing a slow or medium response time, such as thermal analysis instruments. In this study, we have developed a simple non-iterative analytical method to determine k1 and k-1 of reversible bimolecular reactions under stoichiometric conditions on the basis of experimental data of isothermal titration calorimetry (ITC), which is generally used to determine thermodynamic parameters rather than kinetic constants. Our method is principally based on the general principle of chemical bindings caused along with the titration processes, that is, the chemical relaxation kinetics, which had been hitherto considered in the analysis on the ITC data.     

基于漩流的细胞姿态控制方法

细胞姿态调整是生物工程显微操作中一项非常重要的工作。提出通过两微管喷射流体产生漩流,漩流带动细胞转动,进行非接触式的细胞姿态控制的方法。改变微管之间的相对位置、喷射速度和微管内径等参数,可以控制微管之间产生的漩流强度、尺寸,以适应不同尺寸、形状的细胞以及培养溶液的变化,使显微操作更为方便。建立显微操作环境下微流场漩流中细胞运动模型,模拟微观尺度下利用微流体产生漩流和细胞在漩流中的运动,仿真分析微管相对位置、喷射速度等参数对漩流及细胞运动特性的影响。通过试验进一步研究微流场中漩流的产生以及不同形状漩流作用下细胞的运动特性,得到与数值计算结果相一致的结论。     

Synthesis of molybdenum carbide nanoparticles using pulsed wire discharge in mixed atmosphere of kerosene and argon

Pulsed wire discharge was used to prepare nanoparticles of molybdenum and its carbides from Mo wires in a gas mixture of argon and kerosene at pressures of 100, 50, and 25 kPa. The different pressures affected the carburization process and particle formation. The most effective pressure was 25 kPa, where the volume fraction of MoC was identified by Rietveld refinement of X-ray diffraction data to be 98.4%. The particle size distribution was also obtained from transmission electron microscopy measurements, and the smallest geometric mean diameter was determined tobe 24.3 nm for the sample prepared at 25 kPa.     

Analysis of semiconductor intersectional waveguide opticalswitch-modulator

Transmission and reflection characteristics and wavelength chirping of a guided mode in a semiconductor intersectional optical switch-modulator are analyzed by considering the electric field-induced refractive index variation along with the absorption loss variation. The refractive index and absorption ratio, α¯_p, is shown to determine the performance of the switch-modulator. A transmission port is suitable for a modulation with a high extinction ratio, low insertion loss, and small wavelength chirping. The insertion loss at the reflection port depends heavily on α¯_p. A low insertion loss and high extinction ratio intersectional optical switch is possible when -α¯_p is higher than 10, which can be realized with a quantum box structure     

Increase in Phase Transition Temperature of Activated Alumina with Nano-Zirconia Synthesized by Pulsed Wire Discharge

Activated alumina powders have been synthesized by using a novel dry process of pulsed wire discharge. The temperature of phase transition from activated alumina to α-alumina and its variation caused by adding zirconia have been investigated. A mixture of activated alumina and zirconia was formed by mixing zirconium plasma with aluminum plasma and cooling together in an oxygen atmosphere. It was found that the transition temperature increased when the zirconia content ratio was increased. On the other hand, results of X-ray diffraction and X-ray photoelectron spectroscopy analysis indicated no substitution of zirconium in an alumina lattice. Thus, most of the zirconium atoms were located in zirconia particles on the surface and/or the grain boundary of alumina grains. Thus, it appears that the increase in the phase transition was caused by retardation of atomic diffusion at zirconia particles.     

Noise in semiconductor laser amplifiers with quantum box structure

The low-noise properties of a quantum-box traveling-wave semiconductor laser amplifier (QB-TW-SLA) are discussed. The gain and population-inversion parameter of a quantum-box structure are precisely expressed using density matrix theory. Due to sharp gain characteristics as well as a small population inversion parameter, dominant two-beat noise is significantly reduced, even in a solitary device without a narrow bandpass filter. The noise figure can be reduced to 3.5 dB     

Analysis of electric field effect in quantum box structure and itsapplication to low-loss intersectional type optical switch

The electric field induced refractive-index variation and the refractive-index variation-absorption loss variation ratio in a GaInAs/InP quantum box (QB) structure are analyzed and applied to an intersectional type optical switch. The large index variation of a few percent with low absorption characteristics in a QB structure, is found to be very useful to decrease the insertion loss at both the ON and OFF state of a QB intersectional-type optical switch. It is shown that in such a switch the loss can be decreased to less than 1 dB. The QB size dependence and fluctuations in QB size on QB-intersectional type optical switch are also discussed     

Platelet-activating factor and granulocyte-mediated oxidative stress. Strategy forin vivo oxyradical visualization

Platelet-activating factor (PAF) and leukotriene B₄ are potent lipid mediators of endothelium-granulocyte interaction which results in granulocyte-dependent increased microvascular permeability. The specific mechanism by which PAF induces granulocyte-mediated endothelial injury has not been fully investigated. Digital imaging photonic intensified microscopy has revealed that PAF effectively induces granulocyte-mediated oxidative stress on microvascular beds. The method has made it possible to visualize luminol-dependent photonic burst released from PAF-treated microvascular beds in the rat mesentery. The photonic activities clearly corresponded to the localization of sticking granulocytes in post-capillary venules. By contrast, no significant chemilumigenic response could be detected in the leukotriene B₄-induced activation of endothelium-granulocyte interactionin vivo. The present findings suggest that oxygen radicals are not prerequisites for granulocyte adhesion in the microcirculation and provide evidence for a dissociation ofin vivo granulocyte function between leukotactic and oxidative activation in leukotriene B₄-induced microvascular changes. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Axial mode selectivity in active distributed-reflector for dynamic-single-mode lasers

The theory for design of active distributed-reflector lasers is discussed from the point of view of dynamic-single-mode (DSM) characteristics. Optimum conditions and fabrication tolerances of coupling coefficient, cavity length, length and location of phase-shifted region, and the effect of the reflection at the end mirrors are discussed. Asymmetric active distributed-reflector laser with different coupling coefficients and lengths of two corrugation regions is also proposed to improve the efficiency of the front facet output.