Showing papers by "Tokyo University of Science published in 1999"
TL;DR: In this paper, highly crystalline monoclinic and tetragonal BiVO4 photocatalysts were obtained by the reaction of layered potassium vanadate powder (KV3O8 and K3V5O14) with Bi(NO3)3 for 3 days in aqueous media at room temperature.
Abstract: BiVO4 photocatalysts for O2 evolution, which work under visible light irradiation, were prepared by an aqueous process. The BiVO4 photocatalysts were obtained by the reaction of layered potassium vanadate powder (KV3O8 and K3V5O14) with Bi(NO3)3 for 3 days in aqueous media at room temperature. Highly crystalline monoclinic and tetragonal BiVO4 were selectively synthesized by changing the ratio of vanadium to bismuth in the starting materials. X-ray diffraction and scanning electron microscopy measurements showed that the monoclinic BiVO4 was formed via a tetragonal BiVO4 intermediate. Tetragonal BiVO4 with a 2.9 eV band gap mainly possessed an ultraviolet absorption band while monoclinic BiVO4 with a 2.4 eV band gap had a characteristic visible light absorption band in addition to the UV band. The UV bands observed in the tetragonal and monoclinic BiVO4 were assigned to the band transition from O2p to V3d whereas the visible light absorption was due to the transition from a valence band formed by Bi6s or ...
1,761 citations
TL;DR: Bi2W2O9, Bi2WO6, and Bi3TiNbO9 consisting of layered structure with perovskite slabs interleaved with Bi2O2 layers showed photocatalytic activities for H2 evolution from an aqueous methanol solution and O 2 evolution from aqueously silver nitrate solution.
Abstract: Bi2W2O9, Bi2WO6, and Bi3TiNbO9 consisting of layered structure with perovskite slabs interleaved with Bi2O2 layers showed photocatalytic activities for H2 evolution from an aqueous methanol solution and O2 evolution from an aqueous silver nitrate solution. Bi2WO6 with the Aurivillius structure and a 2.8 eV band gap was active for the O2 evolution reaction under visible light irradiation (λ > 420 nm).
442 citations
269 citations
TL;DR: Amphiphilic block copolymers with an aldehyde group at one end and a methacryloyl group at the other chain end were synthesized by anionic polymerization.
Abstract: Amphiphilic poly(ethylene glycol)-b-polylactide (PEG/PLA) copolymers with an aldehyde group at one end and a methacryloyl group at the other chain end were synthesized by anionic polymerization. The efficiencies of the functionalization at both ends were almost quantitative. The amphiphilic block copolymers formed micelles in aqueous media. Acetal groups on the micelle surface were quantitatively converted to aldehyde groups by an acid treatment. The end methacryloyl group located in the core of the micelle was polymerized effectively to form core−shell-type nanoparticles having reactive aldehyde groups on the surface. The size of the reactive nanoparticle was 20−30 nm which was constant with temperatures up to 60 °C. The stability of the micelle was also confirmed by a sodium dodecyl sulfate (SDS) treatment. When SDS was added to the nanosphere solution to 20 mg/mL, the particle was not collapsed. The particle was stable enough even in organic solvents. This functionalized micelle having high stability i...
252 citations
TL;DR: A T cell-specific H-Ras-dominant-negative transgenic mouse is used to show that TCR-mediated activation of the Ras/mitogen-activated protein kinase pathway alters IL-4R function and is required for Th2 cell differentiation.
Abstract: The central role of type-2 helper T (Th2) cells in the development of allergic responses and immune responses against helminthic parasites is well documented. The differentiation of Th2 cells from naive T cells requires both the recognition of antigen by T cell antigen receptors (TCR) and the activation of downstream signal-transduction molecules of the interleukin 4 receptor (IL-4R) pathway, including Jak1, Jak3, and STAT6. Little is known, however, about how these two distinct pathways cooperate with each other to induce Th2 cells. Here, we use a T cell-specific H-Ras-dominant-negative transgenic mouse to show that TCR-mediated activation of the Ras/mitogen-activated protein kinase pathway alters IL-4R function and is required for Th2 cell differentiation. The enhancement of IL-4R signaling seems to be a consequence of both direct “crosstalk” with the TCR signaling pathway and increased protein expression of downstream signaling molecules of the IL-4R pathway. Therefore, successful Th2 differentiation depends on the effectiveness of the TCR-mediated activation of the Ras/mitogen-activated protein kinase pathway in modifying the IL-4R-mediated signaling pathway.
208 citations
TL;DR: In this article, the NiO(0.05 wt%)/NaTaOO3 photocatalyst was used for water splitting at 270 nm and the quantum yield was 28% for the water splitting without co-catalysts.
Abstract: NaTaO3 with 4.0 eV band gap showed a high activity for the decomposition of pure water into H2 and O2 without co-catalysts when it was prepared in the presence of excess Na in order to prevent the formation of defects by the volatilization of Na. When NiO was supported on the NaTaO3 powder, the activity was drastically increased. The quantum yield of the NiO(0.05 wt%)/NaTaO3 photocatalyst was 28% for the water splitting at 270 nm.
183 citations
TL;DR: In this article, a poly(ethylene glycol)−poly(d,l-lactide) block copolymer (PEG−PLA) having a site specifically protected-sugar group at the PEG chain end was synthesized through a successive ring-opening polymerization of ethylene oxide and d, lactide using a metalated protected sugar as an initiator.
Abstract: A poly(ethylene glycol)−poly(d,l-lactide) block copolymer (PEG−PLA) having a site specifically protected-sugar group at the PEG chain end was synthesized through a successive ring-opening polymerization of ethylene oxide and d,l-lactide using a metalated protected sugar as an initiator. Removal of protective groups from the sugar residue in the block copolymer was quantitatively carried out using 80% trifluoroacetic acid at room temperature, yielding a block copolymer having a glucose or galactose residue at the chain end in a regioselective manner. Polymer micelles having sugar residues on the surface were then prepared by dialyzing an N,N-dimethylacetamide solution of the sugar-bearing PEG−PLA block copolymer against water. Dynamic light-scattering measurement of the polymer micelle solution revealed that the scaled characteristics line width had essentially no angular dependence, consistent with the spherical geometry of the polymer micelle. The diameter and polydispersity index of the polymer micelle,...
172 citations
TL;DR: In this article, the atmospheric boundary layer with a polarization lidar, a Sun photometer, and a high volume sampler at a coastal area of Tokyo Bay was intensively observed.
Abstract: We intensively observed the atmospheric boundary layer with a polarization lidar, a Sun photometer, and a high-volume sampler at a coastal area of Tokyo Bay. The purpose of the observation is to investigate a phenomenon discovered in the past summer: relatively high depolarization ratio events (≃ 10% at peak) in the lower atmosphere associated with sea breeze. From the chemical analyses of the simultaneously sampled aerosols, we found that the depolarization ratio might be related to crystallized sea salt and dust particles. A boundary structure was clearly revealed by the depolarization ratio in the lower atmosphere, which might correspond to the mixed layer (the internal boundary layer) or the sea breeze in which crystallized sea salt and/or dust particles were diffused. We also presented the first numerical calculation on the depolarization ratio of the cubic particles to apply crystallized sea-salt (NaCI) particles by the dipole discrete approximation (DDA) method: the calculation yields 8-22% of depolarization ratio for the effective size larger than 0.8 μm at the investigated wavelength (532 nm).
167 citations
TL;DR: In this article, the authors compared the optical properties of bulk GaN and InGaN quantum wells by comparing their optical properties as a function of threading dislocation (TD) density, which was controlled by lateral epitaxial overgrowth.
Abstract: The emission mechanisms of bulk GaN and InGaN quantum wells (QWs) were studied by comparing their optical properties as a function of threading dislocation (TD) density, which was controlled by lateral epitaxial overgrowth Slightly improved excitonic photoluminescence (PL) intensity was recognized by reducing TD density from 1010 cm−2 to less than 106 cm−2 However, the major PL decay time was independent of the TD density, but was rather sensitive to the interface quality or material purity These results suggest that TDs simply reduce the net volume of light-emitting area This effect is less pronounced in InGaN QWs where carriers are effectively localized at certain quantum disk size potential minima to form quantized excitons before being trapped in nonradiative pathways, resulting in a slow decay time The absence of any change in the optical properties due to reduction of TD density suggested that the effective band gap fluctuation in InGaN QWs is not related to TDs
159 citations
TL;DR: Reactive micelle was prepared from an end-derivatized block copolymer, acetal− poly(ethylene glycol)−poly(dl-lactic acid)−methacrylate (PEG-PLA), and the coating was characterized by ζ-potential profile, dynamic contact angle, and atomic force microscopy.
Abstract: Reactive micelle was prepared from an end-derivatized block copolymer, acetal−poly(ethylene glycol)−poly(dl-lactic acid)−methacrylate (PEG-PLA). The block copolymer of PEG-PLA formed a micelle with a diameter of approximately 30 nm determined from dynamic light scattering. The glass and Si wafer surfaces coated with 3-aminopropyltriethoxysilane and poly(dimethylsiloxane) (PDMS) treated with N2 + H2 plasma were coated with the micelle, and the coating was characterized by ζ-potential profile, dynamic contact angle, and atomic force microscopy. The micelle with polymerized core maintained its structure on the surface while the nonpolymerized micelle was disrupted upon attachment. Compared with PEG coatings, micelle coating has higher advancing angle, and larger hysteresis, resulting from the conformational difference of PEG between the homopolymer and the micelle, and the micelle-induced surface topography. The ζ-potential of glass surface coated with the micelle is similar to that with PEG despite the larg...
101 citations
TL;DR: In this paper, Orthorhombic (orth.) SrTa2O6 powder which was hardly obtained by a solid state reaction was easily synthesized by using a strontium borate flux.
Abstract: Orthorhombic (orth.) SrTa2O6 powder which was hardly obtained by a solid state reaction was easily synthesized by using a strontium borate flux. The native SrTa2O6 powder showed photoluminescence and a photocatalytic activity for decomposition of pure water into H2 and O2. The photocatalytic activity was drastically increased by loading a NiO co-catalyst even without pretreatment. The optimum amount of NiO loaded was 0.10 wt%. The quantum yield of the NiO(0.10 wt%)/SrTa2O6 photocatalyst was 7% at least.
TL;DR: In this article, structural and vibrational properties of pure GaN substrate grown using a lateral epitaxial overgrowth (LEO) technique were studied using x-ray diffraction, Brillouin, Raman, and infrared spectroscopy.
Abstract: Structural and vibrational properties of device quality pure GaN substrate grown using a lateral epitaxial overgrowth (LEO) technique were studied using x-ray diffraction, Brillouin, Raman, and infrared spectroscopy. Lattice constants were found to be a=3.1896±0.0002 A and c=5.1855±0.0002 A. Comparing the results with those on GaN epilayer directly grown on sapphire substrate, it is shown that the GaN substrate is indeed of high quality, i.e., the lattice is relaxed. However the GaN substrate has a small enough but finite residual strain arising from the pileup of the lateral growth front on SiO2 masks in the course of LEO. It was also found that the elastic stiffness constants C13 and C44, are more sensitive to the residual strain than the optical phonon frequencies. The high frequency and static dielectric constants were found to be 5.14 and 9.04. The Born and Callen effective charges were found to be 2.56 and 0.50.
Boston University1, Budker Institute of Nuclear Physics2, Brookhaven National Laboratory3, Cornell University4, Fairfield University5, Heidelberg University6, University of Illinois at Urbana–Champaign7, Max Planck Society8, Lawrence Berkeley National Laboratory9, University of Minnesota10, Tokyo University of Science11, Tokyo Institute of Technology12, Yale University13
TL;DR: In this article, the anomalous magnetic moment was measured in a new experiment at Brookhaven, where polarized muons were stored in a superferric ring, and the angular frequency difference between the spin precession and orbital frequencies was determined by measuring the time distribution of high-energy decay positrons.
Abstract: The muon anomalous magnetic moment has been measured in a new experiment at Brookhaven. Polarized muons were stored in a superferric ring, and the angular frequency difference, {omega}{sub a} , between the spin precession and orbital frequencies was determined by measuring the time distribution of high-energy decay positrons. The ratio R of {omega}{sub a} to the Larmor precession frequency of free protons, {omega}{sub p} , in the storage-ring magnetic field was measured. We find R=3.707thinsp220(48){times}10{sup {minus}3} . With {mu}{sub {mu}}/{mu}{sub p}=3.183thinsp 345thinsp47(47) this gives a{sub {mu}{sup +}}=1thinsp165thinsp 925(15){times}10{sup {minus}9} ({plus_minus}13 ppm ), in good agreement with the previous CERN measurements for {mu}{sup +} and {mu}{sup {minus}} and of approximately the same precision. {copyright} {ital 1999} {ital The American Physical Society}
TL;DR: A comprehensive review of the physico-chemical properties of room-temperature molten salts composed of binary solutions of metal halides with either alkylpyridinium halides or di-alkylimidazolium halide is given in this paper.
TL;DR: In this article, high-resolution reflectance and emission spectra for high-quality free-standing GaN nearly free from residual strains and impurities are analyzed based on a model exciton-polariton picture in which free A, B, and C excitons couple simultaneously to an electromagnetic wave, where the effective-mass anisotropy and the optical anisotropic are taken into account.
Abstract: High-resolution reflectance and emission spectra have been measured for high-quality free-standing GaN nearly free from residual strains and impurities. They have been analyzed based on a model exciton-polariton picture in which free A, B, and C excitons couple simultaneously to an electromagnetic wave, where the effective-mass anisotropy and the optical anisotropy are taken into account. Taking account of the free-exciton damping, we have calculated not only the dispersion relations but also the energy dependence of the imaginary part of the wave vectors for the excitonic polaritons. Furthermore, the lifetime of each polariton branch has been calculated combining the imaginary part of the polariton wave vectors and the group velocity obtained from the polariton dispersion relations. It is demonstrated that information on the polariton lifetime is indispensable for interpreting the emission spectra. A brief discussion will be given on obtained values for some physical parameters, including hole parameters.
TL;DR: A stable cyclic dialkylgermylene (1) was synthesized by reductive dechlorination of the corresponding dichlorogermane (6) with sodium as discussed by the authors.
Abstract: A stable cyclic dialkylgermylene (1) was synthesized by reductive dechlorination of the corresponding dichlorogermane (6) with sodium. Germylene 1 is monomeric both in solution and in the solid state, as observed by UV-vis spectroscopy and X-ray crystallography.
TL;DR: In rats given AFB1 as an initiator, treatment with MC-LR resulted in a synergistic increase in the development of GST-P-positive foci, a biomarker for preneoplastic liver lesion, which suggests that the hepatocarcinogenicities of MC- LR and AFB1 can be predicted in experimental animals with a medium-term bioassay.
Abstract: The objective of this study was to elucidate whether microcystin-LR (MC-LR), a hepatotoxic blue-green algal toxin in drinking water, is carcinogenic or possesses the ability to modulate aflatoxin B1 (AFB1)-induced hepatocarcinogenicity. In a medium-term liver bioassay, male Fischer 344 rats were given a single i.p. injection of diethylnitrosamine (DEN, 200 mg/kg) followed by an i.p. injection of MC-LR for 6 weeks after 2 weeks of DEN treatment. To study the synergism between AFB1 and MC-LR, DEN-treated rats were given an i.p. injection of AFB1 (0.5 mg/kg) dissolved in dimethyl sulfoxide (DMSO) followed by MC-LR at 2 weeks after the treatment. In a separate experiment, the rats were first given AFB1 (0.5 mg/kg) and 2 weeks later an i.p. injection of 1 or 10 microg/kg of MC-LR twice a week for 6 weeks. Most rats were subjected to a two-thirds partial hepatectomy (PH) at week 3 and were killed under anesthesia at week 8. Liver sections were analyzed for glutathione S-transferase placental form (GST-P) expression, and subjected to histopathological examination for phenotypic alteration of hepatocellular foci. In rats that did not receive DEN, MC-LR did not cause a significant increase in the numbers of GST-P-positive foci, whereas AFB1 induced a slight increase in GST-P-positive foci development. In rats given DEN, MC-LR enhanced the expression of GST-P-positive foci, as did AFB1 but no synergism was observed. Histopathological analysis revealed that the area of eosinophilic foci, a biomarker for preneoplastic liver lesion, markedly increased because of MC-LR. In rats given AFB1 as an initiator, treatment with MC-LR resulted in a synergistic increase in the development of GST-P-positive foci. These results suggest that the hepatocarcinogenicities of MC-LR and AFB1 can be predicted in experimental animals with a medium-term bioassay. Furthermore, tumor promoting activity of MC-LR was demonstrated in rats treated with AFB1.
01 Jan 1999
TL;DR: NiO-loaded ZnNb2O6 photocatalysts showed an activity for decomposition of pure water into H2 and O2 under band gap irradiation (hν > 4.0 eV) as discussed by the authors.
Abstract: NiO-loaded ZnNb2O6 photocatalysts showed an activity for decomposition of pure water into H2 and O2 under band gap irradiation (hν > 4.0 eV). This oxide photocatalyst is a new type of a photocataly...
TL;DR: Weyl as discussed by the authors gave a Weyl estimate of unipotent contributions for the holonomy of groups and showed that it is possible to compute the multiplicities of discrete series.
Abstract: Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1. Basic structure on symmetric spaces and Eisenstein series . . . . . . . . . . . . . . . . . 7 2. Harmonic analysis on groups and the Selberg trace formula . . . . . . . . . . . . . . . 11 3. Multiplicities of discrete series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 4. Estimate of unipotent contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 5. Values of infinitesimal characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 6. Trace formulas attached to the representations of holonomy group . . . . . . . . . 35 7. The Chebotarev-type density theorem for the conjugacy of holonomy . . . . . . 44 Appendix: A Weyl estimate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
TL;DR: A dynamical entropy for not only shift but also completely positive (CP) map is defined by generalizing the AOW entropy1 defined through quantum Markov chain and AF entropy defined by a finite operational partition.
Abstract: A dynamical entropy for not only shift but also completely positive (CP) map is defined by generalizing the AOW entropy1 defined through quantum Markov chain and AF entropy defined by a finite operational partition. Our dynamical entropy is numerically computed for several models.
TL;DR: In this paper, the aldol-type reaction of the epoxylactone and aldehydes was accomplished by a two-step procedure via the trimethylsilyl epoxide.
TL;DR: The alternating one-dimensional Heisenberg chain compound with spin gap was studied by the high-field magnetization and NMR measurements in this article, which revealed the coexistence of two magnetic systems with independent spin gaps.
Abstract: The alternating one-dimensional Heisenberg $S\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1/2$ chain compound with spin gap, $(\mathrm{VO}{)}_{2}{\mathrm{P}}_{2}{\mathrm{O}}_{7}$, has been studied by the high-field magnetization and ${}^{31}\mathrm{P}$ NMR measurements. Two critical phenomena at $25\ifmmode\pm\else\textpm\fi{}1$ and $46\ifmmode\pm\else\textpm\fi{}2\mathrm{T}$ are observed in the magnetization curve, which are considered to be a crossover between the ground state and the excited state in two kinds of gap systems. ${}^{31}\mathrm{P}$ NMR also revealed the coexistence of two magnetic systems with independent spin gaps. Results obtained from the present and previous studies are well explained by the model in which two kinds of magnetic chains along the $b$ axis behave as alternating spin chains with independent gap energies.
Kyoto University1, Osaka University2, Université Paris-Saclay3, University of New Mexico4, Korea University5, Los Alamos National Laboratory6, University of Tokyo7, Gifu University8, Tokyo University of Science9, Tohoku University10, Sejong University11, Joint Institute for Nuclear Research12, Korea Research Institute of Standards and Science13, Yonsei University14, Fukui University of Technology15, Kyoto Sangyo University16, Academy of Sciences of the Czech Republic17, Osaka City University18
TL;DR: In this article, the authors have performed a hyperon-proton scattering experiment with a scintillating fiber active target and obtained the differential cross sections of the Σ − p elastic scattering in the momentum region from 400 to 700 MeV /c.
TL;DR: In this article, a set of equations for the motion of a spherical bubble cloud is formulated and the behavior of bubble clouds are simulated numerically when the surrounding pressure is decreased from 50 kPa to a 10 kPa and then increased to 50kPa.
Abstract: It is well known that a cloud cavitation is one of the most destructive forms of cavitation. The set of equations for the motion of a spherical bubble cloud is formulated. Behavior of bubble clouds are simulated numerically when the surrounding pressure is decreased from 50 kPa to a 10 kPa and then increased to 50 kPa. To study the collapse of cloud cavitation more strictly, the internal phenomena of bubble and the compressibility of liquid are considered in the governing equations. An inward propagating shock wave is formed during the collapse of bubble cloud and the shock wave is focused in the center region of the cloud. This makes a violent bubble collapse, which causes a high emitted pressure from the bubbles, which is several hundreds times larger than the single bubble collapse. Moreover, relationship between the cloud collapse and cavitation erosion is studied.
Journal Article•
TL;DR: This study demonstrated that low-dose irradiation with 50 cGy of X-ray induces in vivo production of superoxide dismutase (SOD)-like substances and accelerates antioxidant activity and suggested thatLow- dose irradiation induced synthesis and production of S OD itself, leading to elevation of SOD-specific activity.
Abstract: We demonstrated that low-dose irradiation with 50 cGy of X-ray induces in vivo production of superoxide dismutase (SOD)-like substances and accelerates antioxidant activity. To elucidate the defense mechanism against X-ray radiation, we examined which components among these SOD-like substances, such as SOD, vitamin C and celuroplasmin, are produced by low-dose irradiation. Our study revealed that SOD-like specific activity hardly involved SOD-like substances other than SOD. Moreover, it is suggested that low-dose irradiation induced synthesis and production of SOD itself, leading to elevation of SOD-specific activity.
TL;DR: The transcutaneous energy transmission and the charging control characteristics of the ECTETS, while simultaneously supplying energy to the TITAH and the RIBB, were evaluated in an in vitro experiment and it may, reasonably, reasonably be concluded that theECTETS with the R IBB is sufficient to drive theTITAH.
Abstract: We have been developing an externally coupled transcutaneous energy transmission system (ECTETS) for a totally implantable total artificial heart (TITAH). When the ECTETS is unable to supply the energy to drive the TITAH from outside the body, a rechargeable internal back-up battery (RIBB) implanted inside the body is used as a back-up to supply the required energy. This paper reports on the performance characteristics of our ECTETS with an RIBB. In this study, a lithium-ion (Li+) secondary battery was used as the RIBB. The transcutaneous energy transmission and the charging control characteristics of the ECTETS, while simultaneously supplying energy to the TITAH and the RIBB, were evaluated in an in vitro experiment. The output power and transmission efficiency of the ECTETS operating in this mode were found to vary from 20 W to 34 W and from 84% to 71%, respectively. It was also found that a sufficient power of more than 20 W could be supplied to the TITAH. The time needed to fully charge the RIBB was 117 minutes, and a fully charged RIBB could drive the TITAH, consuming 20 W for 62 minutes. It may, therefore, reasonably be concluded that the ECTETS with the RIBB is sufficient to drive the TITAH.