Fabrication of p-CuGaS2/n-ZnO:Al heterojunction light-emitting diode grown by metalorganic vapor phase epitaxy and helicon-wave-excited-plasma sputtering methods

Greenish-white electroluminescence (EL) was observed from the heterojunction light-emitting diodes (LEDs) composed of p-type (001) CuGaS₂ chalcopyrite semiconductor epilayers and preferentially (0001)-oriented polycrystalline n-type ZnO thin films. The CuGaS₂ layers were grown on a (001) GaP substrate by metalorganic vapor phase epitaxy and the ZnO films were deposited by the surface-damage-free helicon-wave-excited-plasma sputtering method. The n-ZnO/p-CuGaS₂ LED structure was designed to enable an electron injection from the n-type wider band gap material forming a TYPE-I heterojunction. The EL spectra exhibited emission peaks and bands between 1.6 and 2.5 eV, although their higher energy portions were absorbed by the GaP substrate. Since the spectral lineshape resembled that of the photoluminescence from identical CuGaS₂ epilayers, the EL was assigned to originate from p-CuGaS₂.     

Twisted endoscopy and the generic packet conjecture

We prove a twisted analogue of the result of Rodier and Moeglin-Waldspurger on the dimension of the space of degenerate Whittaker vectors. This allows us to prove that certain twisted endoscopy forGL(n) implies the (local) generic packet conjecture for many classical groups. Partially supported by the Grants-in-Aid for Scientific Research No. 12740018, the Ministry of Education, Science, Sports and Culture, Japan.     

Ammonium hydrogen tartronate at 240 and 20 K

The low-temperature structure determination of the title compound, alternatively called ammonium hydrogen hydroxy­propane­dioate, NH₄⁺·C₃H₃O₅⁻, has revealed that the H atom involved in a very short asymmetric O—H⋯O hydrogen bond [O⋯O = 2.448 (2) Å at 240 K and 2.4393 (10) Å at 20 K] is disordered.     

Selective surface modification technique for improvement of chromatographic separation selectivity for sugar derivatives.

Highly cross-linked macroporous polymers were prepared utilizing ethylene dimethacrylate as a cross-linking agent, in the presence or absence of methyl-alpha-D-glucoside as a kind of template molecule with methacrylic acid as a functional monomer. After the preparation of the polymers, we applied a high temperature to the cross-linked polymers to study the changes of adsorption properties of the polymers for sugar derivatives including the template molecule utilized. Interestingly, the heat treatment up to 250 degrees C afforded improvement of relative adsorption affinity for several sugar derivatives including the template molecule, while heat treatment up to 150 degrees C did not afford those improvements. The detailed studies including polymers prepared using acrylic acid as a functional monomer instead of methacrylic acid prove that temperatures higher than the Tg temperature of the polymer derived from a functional monomer such as methacrylic acid and higher than the melting point (mp) of the sugar template are necessary to afford the observed improvement of relative affinity based on the surface modification effects through the heat treatment to cross-linked polymers.     

Studies on isoindoline derivatives and related compounds. I Synthesis and reduction of 1,3-dicarboethoxymethyleneisoindoline

The reaction of iminoether III with benzyl cyanoacetate gave ethyl 1-(α-cyanocarbobenzyl-oxymethylene)isoindoline-3-acetate (V) in a 26% yield. Decarboxylation of ethyl 1-(α-cyanocarboxymethylene)isoindoline-3-acetate (VI), obtained by hydrogenolysis of V, gave a mixture of 1-carboethoxymethyleneisoindoline-3-acetonitrile (VII) as major component and 1-carboethoxymethylene-3-cyanomethyleneisoindoline (VIII) as minor component, which were reconvertible into each other. On the other hand, decarboxylation of VI was successfully carried out to give VII as a single product under a nitrogen atmosphere. Ethanolysis and autoxidation of VII gave crystalline diethyl 1,3-dicarboethoxymethyleneisoindoline (XIII). Catalytic hydrogenation of of XIII over platinum oxide gave diethyl isoindoline-cis-1,3-diacetate (XIV) in a yield of 92%. The uv spectra of these 1,3-disubstituted isoindoline derivatives are summarized in Table I.     

Synthesis and Crystallochromy of 1,4,7,10‐Tetraalkyltetracenes: Tuning of Solid‐State Optical Properties of Tetracenes by Alkyl Side‐Chain Length

We synthesized a series of 1,4,7,10‐tetraalkyltetracenes using a new 2,6‐naphthodiyne precursor and 2,5‐dialkylfurans as starting materials (alkyl=methyl to hexyl). Surprisingly, the solid‐state color of the tetracenes ranges through yellow, orange, and red. Both yellow and red solids are obtained for the butyl derivative. Optical properties in solution show no marked differences; however, those in the solid state show characteristics that vary with alkyl side‐chain length: methyl, propyl, and pentyl derivatives are orange; ethyl and butyl derivatives are yellow; and another butyl and hexyl derivative are red. X‐ray analyses reveal that the molecular structures are planar, semi‐chair, or chair forms; the chair form takes a herringbone‐like arrangement and the other forms take slipped parallel arrangements. The mechanism of crystallochromy is discussed in terms of molecular structure, crystal packing, and calculations that take account of exciton coupling.     

Diversity of the Structures in a Distannene Complex and its Reduction to Generate a Six‐Membered Ti2Sn4 Ring Complex

In contrast to olefin complexes, their congeners of heavier elements display various coordination modes, and their complexes may be present as bis(metallylene) complexes, with side‐on coordination, as metallacyclopropanes, or as π complexes. In the course of our studies on the reactivity of dilithiostannoles towards transition‐metal reagents, three‐membered TiSn₂ and six‐membered Ti₂Sn₄ ring complexes were obtained. According to its geometric parameters, NMR analysis, and theoretical calculations, the TiSn₂ complex cannot be categorized into any of these previously described bonding modes. Therefore, a novel resonance structure has been proposed for a complex that has a delocalized σ‐orbital over the TiSn₂ ring to understand its electronic structure. The mechanism for the formation of the Ti₂Sn₄ ring complex and its EPR spectrum are also discussed.     

Study of electro-optical properties of liquid crystal/reactive mesogen-coated liquid crystal display fabricated by slit coater

We have recently proposed a slit coater method for printable liquid crystal (LC) devices. In this method, the LC/reactive mesogen (RM) mixture was directly coated uniaxially onto the substrate surface by shear flow between the slit nozzle and the substrate, and the liquid crystalline molecules were anchored by in situ photopolymerisation of RM monomers. In this study, the dependence of electro-optical properties and device parameters of LC sample cells fabricated by the slit coater on ultraviolet (UV) exposure dosage was investigated. Moreover, effects of UV exposure dosage and thermal annealing on the azimuthal anchoring energy of LC sample cells fabricated by the slit coater are presented.     

An IMT-type quadrature formula with the same asymptotic performance as the DE formula

We propose an IMT-type quadrature formula which achieves the same asymptotic error estimate as the DE formula. The point of the idea is to optimize the parameters of the IMT-type transformation depending on the number of sampling points. We also show the performance of our IMT-type quadrature formula by numerical examples.