Pseudomorphic InGaAs quantum-wire FETs with negative differential resistance

Pseudomorphic trench-type InGaAs/InAlAs quantum-wire field-effect transistors (QWR-FET) are realized by selective molecular beam epitaxy. The pseudomorphic QWR-FET has a negative differential resistance (NDR) effect with a low source–drain voltage (0.3 V). The NDR spectra are clearly observed in the 50–220 K temperature range. The operating current of the pseudomorphic QWR-FET is twice that of a lattice-matched QWR-FET, and this is thought to be due to the higher electron mobility.     

Experimental studies on E×B drift rotational transform andconfinement in the bumpy torus NBT-1M

Experimental studies on E×B drift rotational transform for toroidal plasma confinement were carried out using a bumpy torus NBT-1M. An inward radial electric field was observed, which induced E×B poloidal precession and formed closed drift surfaces in a conventional ECH configuration. However, the confinement was degraded by the plasma convective loss due to the asymmetric potential profile and core electrostatic fluctuations. By the use of a combination of two frequencies for ECH (18 GHz and 8.5 GHz), we could reduce both the potential asymmetry and the fluctuation. In this operation, the plasma confinement by E×B drift rotational transform was demonstrated more clearly than that in the conventional single frequency operation     

Control of heme peptide activity by using phase transition polymers modified with inhibitors

Catalytic activity of a heme peptide (HP) modified-electrode for H(2)O(2) reduction was controlled by use of poly(N-isopropylacrylamide) modified with an inhibitory moiety, imidazole group. The polymers inhibited the catalytic activity below their lower critical solution temperature (LCST) where the polymers were dissolved and did not inhibit the activity above the LCST where the polymers were precipitated. A polymer with a longer side chain connecting with the imidazole group was more inhibitory than a polymer with a shorter side chain at temperatures below the LCST. Formation constants of dissolved HP-imidazole complexes were evaluated by spectroscopic means, and it was found that the polymers were more inhibitory than the corresponding monomers.     

Flip motion of heterogeneous buckled dimers on Ge(0 0 1) by electron injection from STM tip

Surface motion of a topological defect between p(2×2) and c(4×2) structures, a “kink”, across buckled Sn-Ge and Si-Ge dimers on Ge(0 0 1) surfaces was investigated using scanning tunneling microscopy. Energy thresholds of π^∗ electrons for flipping these dimers in the kink are obtained by analyzing the kink surface motion. Electronic states of these systems and energy barriers for flipping the dimers are examined by first-principles calculations for considering elementary processes of the electronically-excited flip motion of the dimers. We propose that the flip motion is caused by a resonant scattering of the π^∗ electrons with localized electronic states at the kink.     

Weak first- or second-order implicit Runge–Kutta methods for stochastic differential equations with a scalar Wiener process

New fully implicit stochastic Runge–Kutta schemes of weak order 1 or 2 are proposed for stochastic differential equations with sufficiently smooth drift and diffusion coefficients and a scalar Wiener process, which are derivative-free and which are A-stable in mean square for a linear test equation in some general settings. They are sought in a transparent way and their convergence order and stability properties are confirmed in numerical experiments.     

Direct determination of bromine in plastics by electrothermal vaporization/inductively coupled plasma mass spectrometry using a tungsten boat furnace vaporizer and an exchangeable sample cuvette system

A tungsten boat furnace vaporization inductively coupled plasma mass spectrometry (TBF/ICP‐MS) method has been applied to the direct determination of bromine in plastic samples. In the pretreatment, the plastic sample is spread over a small sample cuvette made of tungsten by treating it with a strongly basic organic solution, e.g., octanol or diisobutyl ketone in the presence of potassium hydroxide. The cuvette is placed on a tungsten boat furnace, with which the electrothermal vaporizer is equipped. At the vaporization step, a widely spread thin layer of the sample facilitates its efficient evaporation and introduction into an ICP mass spectrometer. The most remarkable feature is that all the bromine species in plastic samples are decomposed to form a thermally stable inorganic salt during the pretreatment procedure. Therefore, the bromine content in plastic samples can be measured by a calibration curve method constructed with an aqueous standard solution of potassium bromate(V). The detection limit (3σ) was estimated to be 0.77 pg of bromine, which corresponds to a concentration of 0.31 ng g^?1 of bromine in plastic samples when a sample amount taken of 2.5 mg is studied. The relative standard deviation was calculated to be 2.2%. Analytical results of some plastic samples, which contained both inorganic bromide salts and also organic bromine species, are given. Copyright © 2010 John Wiley & Sons, Ltd.     

An integral representation of the Mordell-Tornheim double zeta function and its values at non-positive integers

A surface integral representation of the Mordell-Tornheim double zeta function is given, which is a direct analogue of a well-known integral representation of the Riemann zeta function of Hankel’s type. As an application, we investigate its values and residues at integers, where generalizations of a generating function of Bernoulli numbers naturally appear.