A study of estimation method for conduction band offset in semiconductor heterostructure by using triple-barrier resonant tunneling diodes

A method for evaluating a band offset of a heterojunction is proposed by measuring temperature dependence of current–voltage (I–V) characteristics in triple-barrier resonant tunneling diodes (TBRTDs). The method was applied for investigating a conduction band offset by using GaAs_0.25P_0.75/GaAs TBRTDs with thin strain heterobarriers grown by MOCVD and ΔE_c was estimated as 200–240 meV. In the strain-barrier TBRTDs, negative differential resistance was observed below 100 K.     

HRTEM image contrast of short range order in Ni4Mo

The high resolution transmission electron microscope (HRTEM) imaging of short range order (SRO) in Ni4Mo was investigated by means of multi-slice image simulations. The HRTEM images of Ni4Mo exhibit locally bright dot patterns corresponding to the [001] projections of the N2M2-type (chalcopyrite-like) structure. The multi-slice simulations revealed that the N2M2 patterns are rationalized as the projection patterns of the SRO structure which consists of subunit cell clusters of D1a, D022 and Pt2Mo structures. The N2M2-type image contrast appears when both the fundamental fcc lattice reflections and the 1 1/2 0 diffuse scattering of SRO contribute enough to imaging. This suggests that a good coincidence in intensity distribution between the Fourier power spectra of HRTEM images and the electron diffraction patterns is one of the conditions for the image contrast of SRO to be interpreted in terms of the projection contrast.     

Proton conduction in CsHSO4–mesoporous silica composite electrolytes

Novel proton-conducting composites were prepared by incorporating molten CsHSO₄ (CHS) into two types of mesoporous silica, MCM-41 with a one-dimensional (1-D) hexagonal structure and MCM-48 with a three-dimensional (3-D) cubic structure. Their proton conductivities (σ) were measured to examine effects of the incorporation and the dimensionality of the mesopores on their conductivity. Incorporation of proper amounts of MCMs maintained high proton conductivities as high as ~ 10^? 3 S cm^? 1 at temperatures above the superprotonic phase-transition temperature (T_s: 414 K) of CHS and improved the conductivity by 2 to 3 orders of magnitude at temperatures below T_s. In the case of MCM-41, more than 40 mol% mixing, however, caused steep drops in σ in both temperature ranges. On the other hand, the CHS/MCM-48 composite showed a linear increase in σ below T_s and a gradual decrease in σ above T_s with an increase in the MCM-48 content at least up to 60 mol%. X-ray diffraction (XRD) analysis revealed that CHS filled in the MCM mesopores became X-ray crystallographically amorphous and the amount of the amorphous phase increased with an increase in the MCM contents. In the case of the CHS/MCM-48 composites, the activation energy (E_a) for proton conduction below T_s drastically came close to that above T_s by mixing with MCM-48 up to 30 mol%. This indicates that the proton can transport similarly to the conduction mechanism in the superprotonic phase even below T_s. These results suggest that CHS adopts a highly proton-conducting amorphous phase in the mesopores at temperatures below T_s, and that MCM-48 with the 3-D cubic structure is more suitable for formation of high proton-conducting percolation paths.     

Liquid Pressure Varifocus Lens

A liquid pressure varifocus lens that consists of a thin polymer film and liquid is described. The lens can be continuously changed from a concave to a convex shape by driving the liquid pressure in the lens. The dynamic range of the focal length of the convex lens is from 50 to 250 mm. A beam spot verifies the variable focal function on a photographic film exposed by a He-Ne laser. In addition, the application of the laser for processing is demonstrated to manufacture Fe compressed powder sheets by normal pulse YAG laser. Its melting marks along a focus change are formed with a minimum width of 0.1 mm.     

L-Malate-sensing electrode based on malate dehydrogenase and NADH oxidase

An L-malate-sensing electrode was constructed from an oxygen electrode and a layer containing immobilized malate dehydrogenase (MDH) and NADH oxidase. MDH catalyses the dehydrogenation of L-malate by NAD⁺ and NADH oxidase catalyses the regeneration of NAD⁺ with the use of oxygen. The regeneration enables the L-malate oxidation to proceed efficiently even in a medium of neutral pH. At pH 8.0, L-malate in the concentration range 5 μM–1.5 mM can be measured. The relative standard deviation for the measurement is 1.2% (L-malate concentration, 0.2 mM; n=10). The present L-malate-sensing electrode is stable for 8 weeks. A two-electrode sensor system consisting of the L-malate-sensing electrode and an L-lactate-sensing electrode based on lactate oxidase was prepared and applied to the simultaneous determination of the two components in wines.     

Effective one-dimensional dipole moment function for the OH stretching overtone spectra of simple acids and alcohols

To gain insight on the absorption intensities, as well as the direction of the transition moment for the OH stretching vibration in alcohols and acids, we performed detailed analyses for nitric acid, acetic acid, methanol, tert-butyl alcohol, water, and OH radical. We obtained both the potential energy surface and the dipole moment function (DMF) by the B3LYP method and performed quantum mechanical vibrational calculation using the grid variational method based on the local mode model. In this work, we employed the sum rule of the absorption intensities for the one-dimensional (1-D) vibrational Hamiltonian to construct an effective 1-D DMF, which is responsible for the total sum of the overtone intensities. The direction of this effective DMF was found to be tilted away from the OH bond by about 30 degrees for the polyatomic molecules. The nonlinearity of the DMFs in the directions parallel and perpendicular to the OH bond is discussed to rationalize the tilting. Furthermore, we analyzed the effective 1-D DMFs with the vibrational wave function expansion method and derived the effective portion of the 1-D DMF that is responsible for the overtone transition moment.     

Suzuki-Miyaura cross-coupling of benzylic carbonates with arylboronic acids

The cross-coupling of benzylic carbonates with arylboronic acids gave the corresponding diarylmethanes in high yields by use of the palladium catalyst generated in situ from [Pd(eta(3)-C(3)H(5))Cl](2) and 1,5-bis(diphenylphosphino)pentane (DPPPent). The Suzuki-Miyaura reaction using DPPPent-palladium catalyst is applicable to syntheses of a broad range of functionalized diarylmethanes. [reaction: see text]     

Generation of functionalized azomethine ylides and their application to stereoselective heterocycle synthesis: an equivalent process of C-unsubstituted nitrile ylide cycloaddition reaction

The synthetic process equivalent to C-unsubstituted (CH) nitrile ylides cycloaddition reaction is achieved via cycloaddition of NH-azomethine ylide and the following fission reaction of the cycloadducts under acidic conditions. Cycloaddition of NH-azomethine ylide generated by a thermal 1,2-prototropy in 4-oxo-4H-pyrido[1,2-a]pyrimidine-3-carbaldehyde system with maleimides provides proline derivatives under extremely mild conditions. Heating their adducts in AcOH at 85 °C causes a cleavage of C-C bond between the proline and heterocyclic moiety to give the parent heterocyclic system and dehydroproline derivatives, which is regarded as a cycloadduct of C-unsubstituted (CH) nitrile ylide. This cycloaddition-fission reaction sequences can be applied to one-pot three-component reaction.     

Asymmetric allylation of unsymmetrical 1,3-diketones using a BINAP-palladium catalyst

[reaction: see text] The chiral palladium complex generated in situ from [Pd(eta(3)-allyl)Cl](2) and (R)-BINAP is a good catalyst for the catalytic asymmetric allylation of 1,3-diketones. The reaction provided chiral 2,2-dialkyl-1,3-diketones with 64-89% ee in high yields (13 examples). Enantiomeric excesses are strongly affected by the gamma-substituent of the allylic substrates. A variety of unsymmetrical 1,3-diketones were alkylated with cinnamyl acetate in good enantioselectivities via use of the BINAP-palladium catalyst (77-89% ee).