TDPAC and emission Mössbauer spectroscopy of99Ru in YBa2Cu3O7−x

The hyperfine interactions of⁹⁹Ru(⁹⁹Rh) in YBa₂Cu₃O_7–x withx<0.2 andx1 were studied by means of TDPAC and emission Mössbauer spectroscopy. The superconductor YBa₂Cu₃O_7–x withx<0.2 was prepared by conventional heat treatment in oxygen, the semiconductor withx1 by heating the superconductor under a reduced pressure. The TDPAC and Mössbauer measurements show that Ru ions exclusively occupy the Cu-1 site, which forms one-dimensional Cu-O chains in the orthorhombic phase.     

Carrier transport and its effect on the turn-on delay time in strained GalnAsP/InP multiple quantum well lasers

The effects of carrier transport on turn-on delay time in multiple quantum well lasers were investigated both theoretically and experimentally. By using rate equation analysis with two components of the carrier density inside and outside of the quantum wells, we found that carrier transport caused two important effects: one is the stationary effect of a significant reduction in carrier density in quantum wells; the other is an increase in differential carrier lifetime.As an experimental investigation, compressively strained 1.3 m GalnAsP/InP multiple quantum well (MQW) lasers were fabricated and their turn-on delay times were measured and investigated. The short-cavity buried-heterostructure lasers showed low-threshold current (2 to 3 mA) and small turn-on delay time (<200 ps) at biasless 30 mA pulse current. Although these performances are suitable for high-speed digital transmission, it was found that the carrier lifetimes derived from the turn-on delay measurement were larger for strained quantum well lasers than for conventional quantum well lasers and double heterostructure lasers. These phenomena are explained using the carrier transport model and are discussed. The solutions for further reduction in carrier lifetime and turn-on delay are discussed.     

Determination of carbon isotope ratios of methanol and acetaldehyde in air samples by gas chromatography-isotope ratio mass spectrometry combined with headspace solid-phase microextraction

Isotopic signatures of atmospheric methanol and acetaldehyde have the potential to improve our ability to quantitatively assess their importance in atmospheric chemistry. However, isotopic measurements of atmospheric methanol and acetaldehyde and their individual source and sink processes have been limited. In this study, we examined gas chromatography-isotope ratio mass spectrometry combined with headspace solid-phase microextraction to measure the carbon isotope ratios of methanol and acetaldehyde in air samples. The method enabled us to determine carbon isotope ratios with a precision (1 standard deviation) of±0.6 ‰ for 20 ml of air sample containing more than 3 ppm of methanol and±0.7 ‰ for 20 ml of air sample containing more than 2 ppm of acetaldehyde. Moreover, the applicability of this method to determine isotope ratios of methanol and acetaldehyde emitted from detached plant leaves was demonstrated.     

Iodine Intercalation of Bi2Sr2Ca(n−1)CunOy(N=2,3) Superconductors by Using Reactants I2 or FeI2

Abstract

The change of superconductivity induced by intercalation is very interesting We have investigated on intercalation into Bi2212 single crystal and Bi2223 polycrystalline superconductors using FeI₂ or I₂ as reactant. The iodine intercalation by using FeI₂ as a reactant into Bi2223 phase is reported for first time as long as we know. In iodine intercalation into Bi2212 by using FeI₂ as reactant, the critical tem T_Conset in out-of-plane measurement has suddenly decreased on X=0.95. Similar changes of T_Conset with higher X have been observed independent of directions and reactants. T_Conset of I_xBi₂Sr₂CaCu₂O_y intercalated by FeI₂ is a little lower than one of I_xBi₂Sr₂CaCu₂O_y intercalated by I₂. This is likely due to the change of hall concentration induced by reduction of host In iodine intercalation into Bi2223, the smaller change of T_Conset with increasing amount of intercalant is likely due to the number of CuO₂ planes between ntercalant layers.     

Grain-boundary faceting at a = 3, [110]/{112} grain boundary in a cubic zirconia bicrystal

The atomic structure of a = 3, [110]/{112} grain boundary in a yttria-stabilized cubic zirconia bicrystal has been investigated by high-resolution transmission electron microscopy (HRTEM). It was found that the grain boundary migrated to form periodic facets, although the bicrystal was initially joined so as to have the symmetric boundary plane of {112}. The faceted boundary planes were indexed as {111}/{115}. The structure of the {111}/{115} grain boundary was composed of an alternate array of two types of structure unit: {112}- and {111}-type structure units. HRTEM observations combined with lattice statics calculations verified that both crystals were relatively shifted by (α/4)[110] along the rotation axis to form a stable grain-boundary structure. A weak-beam dark-field image revealed that there was a periodic array of dislocations along the grain boundary. The grain-boundary dislocations were considered to be introduced by the slight misorientation from the perfect = 3 orientation. The fact that the periodicity of the facets corresponded to that of the grain-boundary dislocations must indicate that the introduction of the grain-boundary dislocations is closely related to the periodicity of the facets. An atomic flipping model has been proposed for the facet growth from the initial = 3, {112} grain boundary.     

Development of an ONU Using a Reflective Semiconductor Optical Amplifier Transmitter and Its Transmission Characteristic

We propose a WDM-PON system as one of the promising candidates for next generation high capacity,cost-effective and inter-operable optical access network system and develop an ONU using reflective SOA transmitter for the WDM-PON system.     

On a resolvent problem for the linearized system from the dynamical system describing the compressible viscous fluid motion

The linearized initial boundary value problem describing the motion of the viscous compressible fluid is studied under Dirichlet zero condition in bounded and unbounded domains. The resolvent estimate for the corresponding operator is proved in the L_p framework and the sharp inner estimate of the resolvent set is obtained. Copyright © 2004 John Wiley Sons, Ltd.     

Morphological studies of a hydrogen-bonded LC polymer obtained by photopolymerization in LC solvents

Anisotropic morphologies and the phase behaviour of a hydrogen-bonded LC polymer obtained by photopolymerization in two kinds of LC solvent are discussed. The hydrogen-bonded LC monomer, 4-(6-acryloyloxyhexyloxy) benzoic acid (A6OBA), was photopolymerized in 4-cyano-4'-hexyloxybiphenyl (6OCB) and in 4-cyano-4'-undecyloxybiphenyl (11OCB), which show a nematic phase and a smectic A phase, respectively. After photo-polymerization, the LC media were removed by extraction and the pure polymer was observed by scanning electron microscopy. SEM images showed that the polymer possessed fibrous morphology with a fibre diameter of a few micrometers, based on polymerization-induced phase separation. The overall geometries reflected typical LC characteristics such as schlieren and focal-conic fan textures. It was found that the hydrogen bond between benzoic acid groups in the monomer was rigid enough to fix the anisotropic phase-separated structure forming during the early stage of phase separation; however, it could not permanently maintain the fibre structure due to dissociation at elevated temperature. X-ray measurements revealed that a well developed layer structure of the hydrogen-bonded mesogen existed in the polymer obtained from the smectic phase of 11OCB, whereas a polymer layer structure could develop only partially from the nematic phase of 6OCB.