Synthesis of α‐Willemite Nanoparticles by Post‐calcination of Flame‐made Zinc Oxide/Silica Composites

Composite ZnO/SiO₂ nanoparticles were made by flame spray pyrolysis (FSP). Characteristics of the product powder and its crystallization behavior on post‐calcination were evaluated. Polyhedral aggregates of nano‐sized primary particles consisting of ZnO nano‐crystals 1–3 nm in size and amorphous SiO₂ were obtained by FSP. A short residence time in the flame can result in the co‐existence of the ZnO and SiO₂ clusters without substitution or reaction hindering each other's grain growth. There was almost no change in the XRD pattern by calcination at 600 °C for 2 h, suggesting a high thermal stability of the ZnO nano‐crystals in the composite particles. A pure α‐willemite phase was obtained at 900 °C. At this calcination temperature, d_C and d_BET of the powder were 63 and 44 nm, respectively. The nano‐composite structure of the FSP‐made particles can suppress crystalline growth of ZnO during calcination to maintain a high reactivity of ZnO with SiO₂, obtaining pure α‐willemite with high specific surface area at low calcination temperatures.     

All-Optical Holographic Label Processing for Photonic Packet Switching

A holographic label processor for photonic packet switching is proposed. We observe the process of time-to-space conversion for an optical code consisting of 2 ps pulses at a wavelength of 1.55 $mUm with 100 km fiber transmission. Label recognition using an angular multiplexed spectral hologram (AMSH) as a label bank is experimentally demonstrated. We also investigate the AMSH by CGH and confirm its feasibility in computer simulations.     

Simultaneous determination of choline and acetylcholine based on a trienzyme chemiluminometric biosensor in a single line flow injection system.

A detector for the simultaneous determination of choline (Ch) and acetylcholine (ACh) based on a sensitive trienzyme chemiluminometric biosensor in a single line flow injection (FI) system is described. Immobilized choline oxidase (ChOx), immobilized peroxidase (POx), immobilized acetylcholinesterase, and coimmobilized ChOx/POx were packed, in turn, in a transparent ETFE tube (1 mm i.d., 75 cm) and the tube was placed in front of a photomultipier tube as a flow cell. Two-peak response was obtained by one injection of the sample solution. The first and second peaks were dependent on the concentrations of Ch and ACh, respectively. The influence of some experimental parameters such as flow rate, amounts of immobilized enzymes on the behavior of the sensor was studied in order to optimize the sensitivity, sample throughput and resolution. Calibration curves were linear at 1 - 1000 nM for Ch and 3 - 3000 nM for ACh. The sample throughput was 25/h without carryover. The FI system was applied to the simultaneous determination of Ch and ACh in rabbit brain tissue homogenates.     

NOVEL TERAHERTZ PHOTOCONDUCTIVE ANTENNAS

The photoconductive (PC) antenna is a key device for the recent terahertz (THz) photonics based on laser-pumped generation and detection of THz radiation. In this paper we report on two new types of PC antennas: the Schottky PC antenna and the multi-contacts PC antenna. The former one is able to detect THz radiation intensity without the time-delay scan and useful for applications where spectroscopic information is not important, such as the THz intensity imaging. The latter one is useful for the polarization sensitive THz spectroscopy, such as the THz ellipsometry. The characteristic features of these new types of PC antennas are studied by using a THz time-domain spectroscopy system.     

Steady-State Solutions to the Equations of Motion of Second-Grade Fluids with General Navier Type Slip Boundary Conditions in Holder Spaces

We consider a boundary-value problem for the stationary flow of an incompressible second-grade fluid in a bounded domain. The boundary condition allows for no-slip, Navier type slip, and free slip on different parts of the boundary. We first establish the well-posedness of a linear auxiliary problem by means of a fixed-point argument in which the problem is decomposed into a Stokes-type problem and two transport equations. Then we use the method of successive approximations to prove the unique solvability of the nonlinear problem with a sufficiently small body force in Holder spaces. Bibliography: 17 titles.Dedicated to Professor Vsevolod A. Solonnikov on his seventieth birthday__________Published in Zapiski Nauchnykh Seminarov POMI, Vol. 306, 2003, pp. 210–228.     

Surface Waves for a Compressible Viscous Fluid

In this paper, we are concerned with free boundary problem for compressible viscous isotropic Newtonian fluid. Our problem is to find the three-dimensional domain occupied by the fluid which is bounded below by the fixed bottom and above by the free surface together with the density, the velocity vector field and the absolute temperature of the fluid satisfying the system of Navier-Stokes equations and the initial-boundary conditions. The Navier-Stokes equations consist of the conservations of mass, momentum under the gravitational field in a downward direction and energy. The effect of the surface tension on the free surface is taken into account. The purpose of this paper is to establish two existence theorems to the problem mentioned above: the first concerns with the temporary local solvability in anisotropic Sobolev-Slobodetskiĭ spaces and the second the global solvability near the equilibrium rest state. Here the equilibrium rest state (heat conductive state) means that the temperature distribution is a linear function with respect to a vertical direction and the density is determined by an ordinary differential equation which involves equation of state. For the proof, we rely on the methods due to Solonnikov in the case of incompressible fluid with some modifications, since our problem is hyperbolic-parabolic coupled system. Dedicated to Professors Takaaki Nishida and Masayasu Mimura on their sixtieth birthdays