Showing papers by "Tokyo University of Science published in 1996"
TL;DR: In this paper, the authors investigated the emission mechanisms of InGaN single quantum well blue and green light emitting diodes and multiquantum well structures by means of modulation spectroscopy and assigned the static electroluminescence peak to recombination of excitons localized at certain potential minima in the quantum well.
Abstract: Emission mechanisms of InGaN single quantum well blue and green light emitting diodes and multiquantum well structures were investigated by means of modulation spectroscopy. Their static electroluminescence (EL) peak was assigned to the recombination of excitons localized at certain potential minima in the quantum well. The blueshift of the EL peak caused by the increase of the driving current was explained by combined effects of the quantum‐confinement Stark effect and band filling of the localized states by excitons.
1,089 citations
307 citations
161 citations
TL;DR: In this paper, excitonic photoluminescence (PL) peaks from hexagonal GaN epilayers were investigated making a connection with the analysis of the photoreflectance spectra.
Abstract: Excitonic photoluminescence (PL) peaks from hexagonal GaN epilayers were investigated making a connection with the analysis of the photoreflectance spectra. Free exciton emissions associated with transitions from the conduction (Γ7c) band to the A (Γ9v) and B (Γ7uv) valence bands are dominant above 100 K. Values of the full widths at half maximum of them were smaller than the thermal energy kBT up to room temperature, which suggests the dominance of excitons in the PL spectra.
150 citations
TL;DR: In this paper, the stability of the α-helix structure of poly(l-lysine) segment in poly(ethylene glycol)−poly(llysine)-block copolymer was demonstrated in aqueous medium through circular dichroism (CD), 1H-NMR, and static light scattering (SLS) measurements.
Abstract: Stabilization of the α-helix structure of the poly(l-lysine) segment in a poly(ethylene glycol)−poly(l-lysine) block copolymer was evidenced in aqueous medium through circular dichroism (CD), 1H-NMR, and static light scattering (SLS) measurements. It was revealed that poly(l-lysine) oligomers (Mw = 2450), which themselves cannot form an α-helix structure due to substantially lower molecular weight, form an α-helix structure under high-pH condition when they are conjugated with poly(ethylene glycol). Moreover, it has been suggested by static light scattering that the block copolymer under high-pH condition exists as a dimer with α-helical poly(l-lysine) segments. The α-helix content in the block copolymer gradually decreased in a linear manner with the addition of urea, which is in sharp contrast to the high molecular weight poly(l-lysine) (Mw = 170 000), showing a steep transition from an α-helix structure to a random coil at a critical urea concentration (1.0 M). To completely shift the conformation of t...
115 citations
TL;DR: In this paper, numerical and experimental studies of the transient shock wave phenomena in a liquid containing non-condensable gas bubbles are presented, where individual bubbles are tracked to estimate the effect of volume oscillations on the wave phenomena.
Abstract: Numerical and experimental studies of the transient shock wave phenomena in a liquid containing non‐condensable gas bubbles are presented. In the numerical analysis, individual bubbles are tracked to estimate the effect of volume oscillations on the wave phenomena. Thermal processes inside each bubble, which have significant influence on the volume oscillation, are calculated directly using full equations for mass, momentum and energy conservation, and those results are combined with the averaged conservation equations of the bubbly mixture to simulate the propagation of the shock wave. A silicone oil/nitrogen bubble mixture, in which the initial bubble radius is about 0.6 mm and the gas volume fraction is 0.15% – 0.4%, is used in the shock tube experiments. The inner diameter of the shock tube is chosen to be 18 mm and 52 mm in order to investigate the multidimensional effects on the wave phenomena. In a fairly uniform bubbly mixture, the experimental results agree well with the numerical ones computed using a uniform spatial distribution of bubbles. On the other hand, in all the other experiments, the bubbles in the shock tubes are not distributed uniformly, being relatively concentrated along the axis of the tube. This non‐uniformity substantially alters the profile of the shock waves. The numerical predictions where such a distribution is taken into account agree well with those experimental data.
112 citations
TL;DR: In this article, the Luttinger-Kohn type Hamiltonian was used for the valence bands under the inplain biaxial stress, and the shear deformation potential constants and energy gap in unstrained crystal.
Abstract: Exciton resonance energies of hexagonal (h‐) GaN(0001) epilayers were determined by a combination of high‐resolution modulated photoreflectance methods. The results were analyzed thoretically using the Luttinger‐Kohn type Hamiltonian for the valence bands under the in‐plain biaxial stress, and we obtained the shear deformation potential constants and energy gap in unstrained crystal. Occurrence of the anticrossing of B and C valence bands in tensile biaxially strained h‐GaN was suggested.
101 citations
TL;DR: The PB1 subunit is involved in the catalytic activities of nucleotide elongation, and the PA subunit may act as an allosteric modulator and cause a conformational change from a cRNA-to a vRNA-synthesizing form of the PB1Subunit.
Abstract: We indicated that the PB1 and PA subunits of RNA polymerase and nucleoprotein (NP) can support replication of the influenza virus genome as well as transcription to yield uncapped poly(A)(+)-RNA (Y. Nakagawa, N. Kimura, T. Toyoda, K. Mizumoto, A. Ishihama, K. Oda, and S. Nakada, J. Virol. 69:728-733, 1995). To analyze the functions of the PB1 and PA subunits in replication and transcription, YP1N clones in which the PB1 and NP genes can be expressed in response to dexamethasone were established. cRNA was transcribed from model viral RNA (vRNA), but vRNA synthesis from model cRNA was not detected in YP1N clones. Furthermore, poly(A)(+)-RNA directed from model vRNA was synthesized in YP1N clones. These results indicated that PB1 and NP can support the syntheses of cRNA and poly(A)(+)-RNA and that the PA subunit, in addition to that of PB1 and to NP, is required for vRNA synthesis. In summary, the PB1 subunit is involved in the catalytic activities of nucleotide elongation, and the PA subunit may act as an allosteric modulator and cause a conformational change from a cRNA-to a vRNA-synthesizing form of the PB1 subunit.
79 citations
TL;DR: In this paper, the Hartree-Fock (HF) level was used to calculate the equilibrium structures of Li 2 CO 3 and K 2 CO3 using ab initio molecular orbital calculations.
76 citations
TL;DR: The enantiomeric excess of a chiral 3-quinolylalkanol increases from 8.9 to 88.1% by a series of asymmetric autocatalytic alkylations of quinoline-3-carbaldehyde using diisopropylzinc as mentioned in this paper.
57 citations
TL;DR: In this article, a photoluminescence spectrum dominated by sharp free exciton emissions has been observed for the first time from CuInSe2 films indicative of significant improvement in crystalline quality and substantial reduction in the point defect density.
Abstract: CuInSe2 films have been grown by molecular beam epitaxy on pseudo‐lattice‐matched substrates that consist of a 1‐μm‐thick In0.29Ga0.71As layer grown on a linearly composition‐graded InxGa1−xAs buffer (0≤x≤0.29) grown in turn on GaAs (001). The properties of these films have been compared with those of the films grown directly on GaAs (001). High resolution x‐ray diffraction analysis on CuInSe2 grown on pseudo‐lattice‐matched substrates indicated substantial reduction on residual strain in the CuInSe2 films. A photoluminescence spectrum dominated by sharp free exciton emissions has been observed for the first time from CuInSe2 films indicative of significant improvement in crystalline quality and substantial reduction in the point defect density.
TL;DR: The results indicated that Irgasan DP300 inhibits MC- and PB-inducible P450-dependent monoxygenase in vitro competitively or noncompetitively, and that the P450 enzymes of the CYP1A or CYP2B subfamily may contribute to Irgasans DP300 toxicity.
TL;DR: Results confirm that the interaction of neighboring amines (unprotonated) to PBA strengthens the binding with glucose, especially at pH 7.4 and above.
Abstract: A new 'intelligent' polymer system was developed utilizing the binding and exchange of phenylboronic acid (PBA) with polyols and/or glucose. In this improved system, an amine component was incorporated into the polymer chain along with PBA, to enhance binding between PBA and glucose under physiological conditions. The PBA-based polymer was formed by free-radical copolymerization of 3-methacrylamidophenylboronic acid (MAPB) with comonomers, N,N-dimethylaminopropylacrylamide (DMAPAA) and acrylamide (AAm) in the presence of N,N'-methylenebis(acrylamide) (Bis-AAm) as a cross-linker. The proportion of the amount of PBA groups complexed with glucose vs total amount of PBA groups was determined by the batch method. Compared to PBA copolymers synthesized without amine component, the proportion increased as a function of the amine content as well as the pH of the buffer. These results confirm that the interaction of neighboring amines (unprotonated) to PBA strengthens the binding with glucose, especially at pH 7.4...
TL;DR: In this article, a catalytic amount of a chiral zinc alkoxide of 2-methyl-1-(3-quinolyl)propan-1-ol catalyses the enantioselective alkylation of quinoline-3-carbaldehyde by diisopropylzinc.
TL;DR: In this paper, the authors examined models and measures of efficiency dominance as treated by Free Disposal Hull and Russell Measure approaches to efficiency evaluation as they relate to additive models and MED (Measures of Efficiency Dominance) in DEA.
Abstract: Models and measures of efficiency dominance as treated by Free Disposal Hull and Russell Measure approaches to efficiency evaluation are examined as they relate to additive models and MED (Measures of Efficiency Dominance) in DEA.
Journal Article•
TL;DR: The expression of B7-1a mRNA like CD80 mRNA was considerably augmented in spleen cells treated with either LPS in vitro or OVA/CFA conjugate in vivo, and the IgV-like region of CD80 contains a critical region for functional interaction with its ligands and can transduce a costimulatory signal for T cell proliferation.
Abstract: B7 molecules (CD80 (B7-1) and CD86 (B7-2/B70)) on APCs provide costimulatory signals for T cell proliferation We previously described the presence of an alternatively spliced form of murine CD80 (previously termed MB7-2 and renamed as B7-1a) that completely lacks the second Ig-like domain coded by exon 3 in activated murine B cells in this study, we first examined whether B7-1a mRNA can be detected in vivo by RNase protection assay The expression of B7-1a mRNA was only detected in lymphoid organs although the level of expression was lesser than that of CD80 mRNA However, we demonstrated that the expression of B7-1a mRNA like CD80 mRNA was considerably augmented in spleen cells treated with either LPS in vitro or OVA/CFA conjugate in vivo We next determined the functional activity of B7-1a using Chinese hamster ovary (CHO) cells transfected by B7 genes When resting T cells were cocultured with CHO cells expressing B7-1a molecules in the presence of PMA/ionomycin, T cell proliferation was not detected, while CHO cells either expressing CD80 or CD86 could promote the proliferation of resting T cells in contrast to resting T cells, CHO cells expressing B7-1a could support the proliferation of activated T cells Thus, costimulatory activity of B7-1a molecules was dependent upon the activation stage of T cells Therefore the IgV-like region of CD80 contains a critical region for functional interaction with its ligands and can transduce a costimulatory signal for T cell proliferation
TL;DR: In this article, photoreflectance (PR) spectroscopy has been developed as a powerful technique for the characterization of the heteroepitaxial layer of the Cu-III-VI2 semiconductors having chalcopyrite structure.
Abstract: Photoreflectance (PR) spectroscopy has been developed as a powerful technique for the characterization of the heteroepitaxial layer of the Cu–III–VI2 semiconductors having the chalcopyrite structure. PR measurements have been carried out in the energy region near the fundamental absorption edge at 77 K for the heteroepitaxial layers of CuAlSe2, CuGaSe2, CuGaS2, and CuAlS2 grown on GaAs and GaP substrates by means of the low‐pressure metalorganic chemical vapor deposition. Crystal quality, stress, and the crystallographic orientation have been well characterized, based on the analysis of the PR spectra in terms of transition energy, intensity, and broadening parameter.
TL;DR: In this article, the dissociation energy of free excitons and their localization energy to a center were found to be 16.2 and 3.3 meV, respectively, and the band gap energy was estimated to be 1.7310 eV at low temperature.
Abstract: Slightly Cu‐rich CuGaSe2 films were grown on [001] oriented GaAs substrates by molecular beam epitaxy. Photoluminescence of the films showed a remarkable emission peaked at 1.71 eV at low temperature, which is attributed to recombination of free excitons and bound excitons. The dissociation energy of free excitons and their localization energy to a center are found to be 16.2 and 3.3 meV, respectively. The band‐gap energy Eg is estimated to be 1.7310 eV at low temperature. It is suggested that the temperature variation of Eg is dominated by interaction with phonons of 26 meV which corresponds to the mean energy of the optical phonons in CuGaSe2.
TL;DR: In this paper, a catalytic enantioselective borohydride reduction of aromatic ketones in presence of 0.1-1 mol% of optically active aldiminato cobalt(II) complex catalysts at 0 °C was successfully achieved using precisely pre-modified borhydride with one equivalent each of tetrahydrofurfuryl alcohol, ethanol and NaBH4.
Abstract: A catalytic enantioselective borohydride reduction of aromatic ketones in presence of 0.1-1 mol% of optically active aldiminato cobalt(II) complex catalysts at 0 °C was successfully achieved using precisely pre-modified borohydride with one equivalent each of tetrahydrofurfuryl alcohol, ethanol and NaBH4. The corresponding secondary alcohols were produced in less than 45 min with high enantiomeric excesses (up to 98% ee). The above method was successfully applied to kinetic and dynamic kinetic resolutions of aromatic ketones.
TL;DR: In this article, the formation of MoSe2 at the Mo/CuInSe2 interface was confirmed by measuring the depth profile of spatially-resolved Raman spectra taken from the cross section of the cell.
Abstract: A CuInSe2‐based thin film solar cell fabricated by the selenization method was investigated by micro‐Raman‐spectroscopy. By measuring the depth‐profile of spatially‐resolved Raman spectra taken from the cross section of the cell, the formation of MoSe2 at the Mo/CuInSe2 interface was confirmed.
TL;DR: In this paper, the effects of oxygen content in the precurosor have been investigated on the synthesis of HgBa2Ca4Cu5O12+δ (Hg-1245) under high pressure.
Abstract: Effects of oxygen content in the precurosor have been investigated on the synthesis of HgBa2Ca4Cu5O12+δ (Hg-1245) under high pressure. The superconducting phases continuously changed from Hg-1234 to Hg-1245 with reducing the oxygen content in the precursor of Ba2Ca4Cu5O11+δ Samples of Hg-1245 have been synthesized by optimizing the oxygen content of the precursor with the stoichiometrical composition.
TL;DR: In this paper, the enantioselective borohydride reduction of ketones catalyzed by optically active (β-oxoaldiminato) cobalt(II) complexes was remarkably improved by using the borhydride which was modified with furfuryl alcohol dervatives and ethanol.
Abstract: The enantioselective borohydride reduction of ketones catalyzed by optically active (β-oxoaldiminato) cobalt(II) complexes was remarkably improved by using the borohydride which was modified with furfuryl alcohol dervatives and ethanol. In the presence of 1 mol% of the above complex catalysts, asymmetric reduction of aromatic ketones proceeded smoothly to give the corresponding optically active alcohols in quantitative yields within 6–12 h with high enantiomeric excesses (90–97% ee).
TL;DR: Novel zirconium-iron dinuclear complexes have been proposed in this article, where the authors proposed a new structure called FcSiMeMe2Cp{ZrCl2(Me5Cp)}] for dinuclear complex.
Abstract: Novel zirconium–iron dinuclear complexes, [FcSiMe2(R1R2Cp)ZrCl2Cp] (Fc; Ferrocenyl, R1 = R2 = H; 2a, R1 = Me, R2 = H; 2b, R1 = R2 = Me; 2c, R1 = Ph, R2 = H; 2d), [FcSiMe2Cp{ZrCl2(Me5Cp)}] (3a), haf...
TL;DR: In this paper, the conformation of the poly(β-benzyl l-aspartate) segment in the PEO/PBLA block copolymer was investigated by 1H NMR, by specific optical rotation measurements, and by 2D 1H,1H NOESY NMR in chloroform, dimethyl sulfoxide (DMSO), and mixtures of chloromethane/DMSo.
Abstract: The conformation of the poly(β-benzyl l-aspartate) segment in the poly(ethylene oxide-co-β-benzyl l-aspartate) (PEO/PBLA) block copolymers (Mw of PEO = 5000 and 20 units of β-benzyl l-aspartate) was investigated by 1H NMR, by specific optical rotation measurements, and by 2D 1H,1H NOESY NMR in chloroform, dimethyl sulfoxide (DMSO), and mixtures of chloroform/DMSO. The comparison between the 1H NMR spectra of the block copolymer in CDCl3 and the one in DMSO-d6 showed that the PBLA blocks adopt a different conformation depending upon the solvents. The specific rotation of the block copolymer at 546 nm demonstrated that the PBLA segments adopt a left-handed α-helix conformation in chloroform. PBLA homopolymer with the same molecular weight as the PBLA segment in the block copolymer showed no evidence of α-helix formation in the same conditions, indicating that the PEO segment in the block copolymer is essential to allow PBLA to take the α-helix structure. On the other hand, the specific rotation of the PEO/P...
TL;DR: In this paper, a scanning electron microscope (SEM) combined with an oxygen gas introduction system was used for electron beam assisted chemical etching (EBACE) with oxygen gas is applicable to direct patterning of single crystal diamond substrates.
Abstract: Electron beam assisted chemical etching (EBACE) with oxygen gas is applicable to direct fine patterning of single crystal diamond substrates. A scanning electron microscope (SEM) combined with an oxygen gas introduction system was used for EBACE of diamond. In order to prevent surface charge-up during etching and SEM observation, a hydrocarbon contamination layer, which has conductivity and can be deposited during electron beam irradiation using oil vapor in a vacuum system, was used. Etching characteristics of single crystal diamond substrates by EBACE with oxgen gas were mainly investigated. It was found by in-situ SEM observation that hole, line and rectangular patterns with several μm 2 area and sub-μm depth into the diamond substrates were successfully fabricated by EBACE utilizing spot, line and raster scanning modes of the SEM. The depths of holes and rectangular patterns were proportional to electron beam exposure times. Etched areas of line and rectangular patterns were larger than scanned area. An etching yield of 1.99 x 10 -2 carbon atoms of diamond per electron has been observed for EBACE using oxygen gas.
TL;DR: In this article, a quadratic dependence of exciton energies on x was confirmed, and the magnitudes of crystal field splittings were larger than that of bulk crystals, and this was explained by residual tensile biaxial strain in the epilayers.
Abstract: CuAlxGa1−xSe2 alloy layers were successfully grown on GaAs(001) by low‐pressure metalorganic vapor phase epitaxy. The distribution coefficient of Al was unity. All alloy layers had their c‐axis normal to the substrate plane. Exciton resonance energies were determined as a function of x by means of photoreflectance measurements. A quadratic dependence of exciton energies on x was confirmed. The spin‐orbit splittings of the epilayers were approximately the same as that of bulk crystals. The magnitudes of crystal‐field splittings were larger than that of bulk crystals, and this was explained in terms of residual tensile biaxial strain in the epilayers. The color of the low‐temperature photoluminescence (PL) changed from red to crimson, orange, yellow, green, and bluish‐purple with increasing x. A peak due to a free‐to‐acceptor transition was dominant in the PL spectra of the alloy layers. The acceptor ionization energy increased with increasing x, and the result may reflect an increase of the hole effective ...
TL;DR: In this article, a single-phase Bi4Ti3O12 thin film consisting of plate-like crystals with predominantly c-axis orientation was obtained by sintering at 800°C.
Abstract: Crystallization of precursor micropatterns of ferroelectric Bi4Ti3O12 fabricated by electron beam scanning was investigated in comparison with that of thin films. Precursor solutions were prepared by mixing bismuth and titanium octylates with various Bi : Ti molar ratios. Single-phase Bi4Ti3O12 thin films were formed by spin-coating a solution containing Bi and Ti atoms at a molar ratio of 5.2 : 3.0 and successive heat treatment. It was possible to control orientation of the Bi4Ti3O12 thin films by changing the sintering temperature. Bi4Ti3O12 thin films consisting of platelike crystals with predominantly c-axis orientation were obtained by sintering at 800°C. Precursor micropatterns were fabricated by scanning an electron beam on metal octylate films and development with toluene. They were crystallized into single-phase Bi4Ti3O12 by sintering at 800°C. However, the Bi4Ti3O12 micropatterns consisted of small grains, unlike the large platelike crystals in thin films. There was a clear difference in crystallization between the thin films and the micropatterns.
TL;DR: In this paper, the smoothing effects of solutions to the Benjamin-Ono equation were studied and it was shown that if φ ∈ H2 and (x∂x)4φ then the solution u of(BO) belongs to, where H is the Hilbcrt transform defined by
Abstract: In this paper we study smoothing effects of solutions to the Benjamin–Ono equationwhere H is the Hilbcrt transform defined byWe prove that if φ ∈ H2 and (x∂x)4φ then the solution u of(BO) belongs to, where