Dual nature of the electronic structure of (La(2--x--y)Nd(y)Sr(x))CuO(4) and La(1.85)Sr(0.15)CuO(4).

High resolution angle-resolved photoemission measurements have been carried out on (La(1.4--x)-Nd(0.6)Sr(x))CuO(4), a model system with static one-dimensional (1D) charge ordering (stripe), and (La(1.85)-Sr(0.15))CuO(4), a high temperature superconductor (T(c) = 40 K) with possible dynamic stripes. In addition to the straight segments near ( pi,0) and ( 0,pi) antinodal regions, we have identified the existence of spectral weight along the [1,1] nodal direction in the electronic structure of both systems. This observation of nodal state, together with the straight segments near antinodal regions, reveals the dual nature of the electronic structure of stripes due to the competition of order and disorder.     

Plasma polymerization of fluoromethanes

Methane and fluoromethanes (CH_nF_4−n, 1 ≤ n ≤ 3) were subjected to an rf glow discharge plasma. All the fluoromethanes (including methane) polymerized in the plasma and formed thin films. The deposition rate of the fluoromethanes depended on their monomer structure: CH₂F₂, of which the F/H ratio is unity, showed the greatest deposition rate. The elimination of H and F atoms as H—F was found to be a key factor for the polymerization of fluoromethanes. The chemical composition of the polymerized film, measured with X-ray photoelectron spectroscopy and glow discharge emission spectroscopy, was also found to be strongly dependent on monomer structure. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2043–2050, 1998     

Fiber devices using polarization- maintaining fibers

Fiber devices using polarization-maintaining fibers called PANDA fibers are presented. They are polarization-maintaining couplers and polarization-splitting couplers, optical isolators and optical circulators, and multi/demultiplexers designed for 1.3 μm wavelength. Crosstalk of-32 dB and excess loss of 0.03 dB for the polarization-maintaining coupler, and polarization-splitting ratio of 17 dB and excess loss of 0.5 dB for the polarization-splitting coupler have been fabricated by a fusion-elongation method. A fiber polarizer with the extinction ratio of more than 40 dB has been presented by using the difference of bending loss between the orthogonal modes in the PANDA fibers. Multi/demultiplexer with narrow band-pass of 1.4 nm utilizing combination of PANDA fiber polarization dispersion and the polarization-splitting coupler has been realized. An optical isolator consisting of fiber polarizers and a spherical YIG with a lens function and an optical circulator consisting of polarizing-splitting couplers and spherical YIGs have been achieved.     

Neutron spin-wave scattering from a Heusler alloy Pd2MnSn

Spin-wave dispersion relations have been determined in three principal symmetry directions for Heusler-type alloy Pd₂MnSn. Analysis shows that the exchange parameters at large distances have an oscillatory character which can be interpreted in terms of the s-d interaction model. However the n.n and n.n.n. interactions have the opposite sign to that expected from the model and should be attributed to other mechanisms.     

Mapping peroxidase in plant tissues by scanning electrochemical microscopy.

Scanning electrochemical microscopy has been firstly used to map the enzymatic activity in natural plant tissues. The peroxidase (POD) was maintained in its original state in the celery (Apium graveolens L.) tissues and electrochemically visualized under its native environment. Ferrocenemethanol (FMA) was selected as a mediator to probe the POD in celery tissues based on the fact that POD catalyzed the oxidation of FMA by H(2)O(2) to increase FMA(+) concentration. Two-dimensional reduction current profiles for FMA(+) produced images indicating the distribution and activity of the POD at the surface of the celery tissues. These images showed that the POD was widely distributed in the celery tissues, and larger amounts were found in some special regions such as the center of celery stem and around some vascular bundles.     

Enhancement of high energy proton yield with a polystyrene-coated metal target driven by a high-intensity femtosecond laser

We present experimental results on protons accelerated up to 950 keV from a 3-μm thick tantalum foil with a 133-nm thick polystyrene layer on its rear surface, irradiated with a laser pulse having the duration of 70 fs and the intensity of 2.7×10¹⁸ W/cm². The energy distribution of fast protons was measured simultaneously with that of the hot-electrons from the rear surface. The proton yield from the polystyrene-coated target is about 10 times as high as that from the uncoated metal target. This enhancement of the proton yield is roughly proportional to the increase of hydrogen atoms given by the 133-nm thick polystyrene layer, assuming a contaminant layer of ∼10-nm thickness is on the metal surface without coating. This result shows that the polystyrene layer contributes to the yield enhancement. PACS 52.38.Kd; 52.50.Jm; 52.59.-f     

Inelastic scattering processes in GaAs/n-AlGaAs selectively doped heterojunctions with InGaAs quantum dots

Inelastic scattering processes of the two-dimensional electron gas (2DEG) in both normal and inverted n-AlGaAs/GaAs heterojunction FET structures have been studied, for the case where InGaAs dots are embedded in the vicinity of GaAs channel. By analyzing the magnetoresistance data, the inelastic scattering time τ_in is determined as a function of the concentration N_2D of 2D electrons and shown to be reduced by 10–40% by the presence of InGaAs dots. By investigating a GaAs/n-AlGaAs inverted heterojunction FET with embedded InGaAs dots, we have varied the percentage P_oc of charged dots filled with an electron and found that τ_in decreases as P_oc increases, indicating that the inelastic scattering rate of 2DEG by charged dots is higher than that by the neutral ones.     

A Green's function approach to the deflection of a FGM plate under transient thermal loading

Summary  Green's function approach is adopted for analyzing the deflection and the transient temperature distribution of a plate made of functionally graded materials (FGMs). The governing equations for the deflection and the transient temperature are formulated into eigenvalue problems by using the eigenfunction expansion theory. Green's functions for solving the deflection and the transient temperature are obtained by using the Galerkin method and the laminate theory, respectively. The eigenfunctions of Green's function for the deflection are approximated in terms of a series of admissible functions that satisfy the homogeneous boundary conditions of the plate. The eigenfunctions of Green's function for the temperature are determined from the continuity conditions of the temperature and the heat flux at interfaces. Received 9 October 2000; accepted for publication 3 April 2001     

Stoichiometric and ultra-stable nanoparticles of II-VI compound semiconductors

Nanoparticles of (CdSe)_n are found extremely stable at n = 33 and 34 with structures distinctively different from the bulk fragments. They grow exclusively in large amount with a simple solution method. The diameter is determined as 1.5 nm. Such ultra-stable nanoparticles had been predicted both theoretically and experimentally after the discovery of carbon fullerenes, but not been produced macroscopically in any other element or compound system. First-principles calculations predict that the structures of (CdSe)₃₃ and (CdSe)₃₄ are puckered (CdSe)₂₈-cages accommodating respectively (CdSe)₅ an (CdSe)₆ inside to form a three-dimensional network of essentially hetero-polar sp³-bonding.