Nitride‐based hetero‐field‐effect‐transistor‐type photosensors with extremely high photosensitivity

AlGaN/GaN hetero‐field‐effect‐transistor‐type (HFET‐type) photosensors are fabricated with a p‐GaInN optical gate for the detection of visible light. These photosensors employ a two‐dimensional electron gas at the heterointerface between AlGaN and GaN as a highly conductive channel with a high electron mobility. By changing the InN molar fraction in the p‐GaInN optical gate, the wavelength range of the photosensitivity of the HFET‐type photosensors can be controlled. The photosensitivity of the AlGaN/GaN HFET‐type photosensors with a p‐GaInN optical gate greatly surpassed those of commercially available Si pin and Si avalanche photodiodes, and was comparable to those of photomultiplier tubes. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

From Nosé–Hoover chain to Nosé–Hoover network: design of non-Hamiltonian equations of motion for molecular-dynamics with multiple thermostats

A systematic algorithm to design multiple thermostat systems in the framework of the Nosé–Hoover type non-Hamiltonian formulation is presented. Using ‘non uniform’ time transformations in a generalised Hamiltonian equation, we develop the non-Hamiltonian equations of motion for multiple thermostat systems having an arbitrary number of thermostats and arbitrary connections between a physical system and thermostats (‘Nosé–Hoover network’). We then present the algorithm to construct the Nosé–Hoover network equations based on a simple diagram only. On the basis of this algorithm, recursively attached Nosé–Hoover thermostats are introduced as an example of the Nosé–Hoover network and its high efficiency in sampling the canonical distribution for an one-dimensional double-well system is illustrated by numerical calculations.     

The M/G/1 FIFO Queue with Several Customer Classes

In this note we present short derivations of the joint queue length distribution in the M/G/1 queue with several classes of customers and FIFO service discipline.     

Reaction of olefins using cerium(IV) sulfate tetrahydrate in carbonyl compounds–H2O

The reaction of olefins with cerium(IV) sulfate tetrahydrate [Ce(SO₄)₂·4H₂O, CS] in acetone–H₂O under reflux for 5 h gave 2‐oxo‐ and 2‐oxo‐5‐hydroxy derivatives. In this reaction, the yields of 2‐oxo‐5‐hydroxy derivatives were dependent on the quantity of H₂O. Moreover, the reaction of α, β‐unsaturated ketones with CS in acetone–H₂O yielded 2,7‐dioxo‐3‐hydroxy or 3,8‐dioxo‐4‐hydroxy derivatives. The reaction mechanism is also discussed. Copyright © 2005 John Wiley & Sons, Ltd.     

The first enantioselective synthesis of imino-deoxydigitoxose and protected imino-digitoxose by using l-threonine aldolase-catalyzed aldol condensation

The first enantioselective synthesis of protected imino-digitoxose (?)-16 was attained starting with a synthetic intermediate of polyoxin C prepared by the l-threonine aldolase-catalyzed aldol condensation of (2S,3S)-2,3-O-isopropyriden-4-penten-1-al 8 and glycine. The strategy took advantage of an intramolecular nucleophilic attack by a Cbz-protected amino group on the hemiacetal carbon, a side reaction in the synthesis of natural products, for the formation of the piperidine ring of the imino-sugar. Imino-deoxydigitoxose (+)-18 was also synthesized from (?)-16 by reduction and acid hydrolysis.     

Direct observation of rectified motion of vortices by Lorentz microscopy

We have investigated the vortex dynamics for the ‘ratchet’ operation in a niobium superconductor via a direct imaging of Lorentz microscopy. We directly observe one-directional selective motion of field-gradient-driven vortices along fabricated channels. This results from the rectification of vortices in a spatially asymmetric potential under the oscillating magnetic field in a temporally symmetric manner. Based on the observation of the individual motion of vortices, we clarify the elementary process involved in this rectification.     

Self-repelling walk on the Sierpiński gasket

 We construct a one-parameter family of self-repelling processes on the Sierpiński gasket, by taking continuum limits of self-repelling walks on the pre-Sierpiński gaskets. We prove that our model interpolates between the Brownian motion and the self-avoiding process on the Sierpiński gasket. Namely, we prove that the process is continuous in the parameter in the sense of convergence in law, and that the order of H?lder continuity of the sample paths is also continuous in the parameter. We also establish a law of the iterated logarithm for the self-repelling process. Finally we show that this approach yields a new class of one-dimensional self-repelling processes. Received: 8 March 2001 / Revised version: 30 May 2001 / Published online: 22 August 2002     

Demonstration of Optical Isolator with CeY2Fe5O12 Guiding Layer Employing Nonreciprocal Phase Shift

A waveguide optical isolator with a CeY2Fe5O12 guiding layer employing a nonreciprocal phase shift was studied.The isolation ratio of more than 12.2 dB was achieved at a wavelength of 1.55 μm.     

Reduction of Fringe Noise in Wavelength Modulation Spectroscopy Using a One-Dimensional Focal Plane Array

In wavelength modulation spectroscopy using diode lasers, detection limit of molecular absorption is often imposed by spurious fringe noises that arise from slight reflections among optical components. In an attempt to reduce this fringe effect, we propose and demonstrate the use of a one-dimensional focal plane array. With the help of a multiplexer, a single lock-in amplifier is employed to obtain multiple-channel signals from wavelength-modulated output of an array detector. It is found that the intensity change of the molecular absorption signal is nearly proportional to the transversal beam intensity distribution, whereas that of fringe noise is much less conspicuous. These features, as well as the phase difference among the channels, contribute to separate the signal and fringe noise components from the multiplexed spectra, leading to the overall improvement in the signal-to-noise ratio.     

Hydrosilylation of olefins and dehydrogenative double silylation of conjugated dienes catalyzed by lanthanide–imine complexes

Divalent lanthanide–imine complexes and a related species catalyzed the hydrosilylation of olefins with phenyl- and diphenylsilane. On the other hand, conjugated dienes were converted to 1,4-bissilyl-2-butenes and 3-silacyclopentenes, accompanied with hydrogen evolution, under similar conditions.