Laser-induced suppression effect on the sublimation of BCl3-Xe solid mixtures

Changes in the vacuum pressure over BCl₃-Xe solid mixtures by cw CO₂ laser irradiation have been investigated. For a sample of low dilution condensed at 68 K, sublimation of Xe is suppressed more than 30% by exciting the BCl₃ ν₃ vibration. Formation of a BCl₃ layer in the solid seems to play an important role in this phenomenon.     

Relaxation mode analysis of nonlinear birth and death processes

Nonlinear birth and death processes with one variable are considered. The general master equations describing these processes are analyzed in terms of their eigenmodes and eigenvalues using the method of a WKB approximation. Formulas for the density of eigenstates are obtained. The lower lying eigenmodes are calculated to investigate long-time relaxation, such as relaxations of metastable and unstable states. Anomalous accumulation of the lower lying eigenvalues is shown to exist when the system is infinitesimally close to a critical or marginal state. The general results obtained are applied to some instructive examples, such as the kinetic Weiss-Ising model and a stochastic model of nonlinear chemical reactions.The work at UCSD was supported in part by the National Science Foundation under Grants MPS72-04363A03 and CHE75-20624.Adapted from the author's Ph.D. dissertation at University of Tokyo, December 1974.     

Efficient determination and characterization of transition states using ab-initio methods

The gradient of the potential energy with respect to nuclear coordinates has been calculated using ab-initio single determinant molecular orbital methods. The calculated gradient is used together with very efficient minimization methods to locate and characterize transition states on many-dimensional potential energy surfaces. Previously such methods have only been applied to semi-empirical potential functions. Although the calculation of the gradient in addition to the energy increases the computational time by about a factor of four, we have demonstrated the feasibility of these calculations by locating the transition state for the model rearrangement of HNC to HCN using both minimal (STO-3G) and split valence shell (4-31G) basis sets. Further use of such methods in the direct application of ab-initio wavefunctions to dynamical investigations is discussed.     

Silicon-based liquid-crystal cell for self-branching of optical packets

Self-controlled photonic switching was achieved by combining the photoconductivity of a semiconductor and the electrical tunability of a liquid crystal (LC). Pulse packets of 1.06 μm wavelength created free carriers in a silicon electrode of an LC cell, which triggered voltage application for LC reorientation. Consequently, polarization direction of the succeeding packets became perpendicular to that of the preceding packets, and they progressed in different directions after passing through a polarization beam splitter. The cascade LC cells divided a series of packets one by one in a self-controlled manner.     

Evaluation of electrodeposited gold nanostructures for applications in QCM sensing

The electrodeposition of gold nanostructures increases the surface area of a biosensor, which brings an enhancement of the sensitivity by increasing the amount of analyte binding to the surface. To evaluate the relationship among the surface structure, the area and the analyte binding, we quantitatively analyzed them for quartz crystal microbalance (QCM) sensing by scanning electron microscopy and cyclic voltammetry measurements. The results indicate a several-times increase of analyte bindings, and also the limitation of the sensing performance.     

Concise total synthesis of (-)-myxalamide A

The MIDA touch: A concise and highly convergent protecting-group-free total synthesis of (-)-myxalamide?A involves a stereoselective vinylogous Mukaiyama aldol reaction of a vinylketene silyl N,O-acetal, together with a one-pot Stille/Suzuki-Miyaura cross-coupling reaction using Burke's N-methyliminodiacetic acid (MIDA) boronate to connect left- and right-hand fragments of the molecule (see scheme).     

Micro fluorescent analysis system integrating GaN-light-emitting-diode on a silicon platform

A micro fluorescent analysis system is proposed using silicon micromachining. GaN blue light-emitting diode (LED) monolithically integrated on a silicon substrate is used as a light source for the fluorescent analysis system. The blue light suits the excitation of several dyes used commonly in fluorescent analysis. Silicon photodiode (Si-PD) that matches the visible and near infrared fluorescent wavelengths of dyes is integrated on a silicon substrate. Polydimethylsiloxane (PDMS) micro-channels are also stacked for flowing dye-sensitized liquid. Therefore, the proposed system is an integrated system that can be composed on a silicon platform, i.e. a bottom layer of Si-PD, a middle layer of GaN-LED on silicon substrate and a top layer of micro PDMS channel. An aperture is opened into the GaN-LED layer by deep reactive ion etching to create a ring-shaped GaN-LED and a through-hole for detection. The light from the ring-shaped GaN-LED in the middle layer excites the dye-sensitized liquid in the top micro-channel layer. The fluorescence emitted from dye is detected by the Si-PD on the bottom layer at an angle larger than 90 degrees from the direction of excitation. Therefore, the detection optics consist basically of a dark-field illumination optical system. In order to evaluate the performance of the integrated system, fluorescence of fluorescein isothiocyanate (FITC) solution flowing in the micro channel is measured. From the measurement, the noise, sensitivity and limit of detection in the fabricated system are evaluated for FITC dye to be 0.57 pA, 1.21 pA μM(-1) and 469 nM, respectively. From these results, a compact fluorescence analysis system is demonstrated.