Showing papers by "Tokyo University of Science published in 2004"

Photocatalytic Activities of Noble Metal Ion Doped SrTiO3 under Visible Light Irradiation

Abstract: Mn-, Ru-, Rh-, and Ir-doped SrTiO3 possessed intense absorption bands in the visible light region due to excitation from the discontinuous levels formed by the dopants to the conduction band of the SrTiO3 host. Mn- and Ru-doped SrTiO3 showed photocatalytic activities for O2 evolution from an aqueous silver nitrate solution while Ru-, Rh-, and Ir-doped SrTiO3 loaded with Pt cocatalysts produced H2 from an aqueous methanol solution under visible light irradiation (λ > 440 nm). The Rh(1%)-doped SrTiO3 photocatalyst loaded with a Pt cocatalyst (0.1 wt %) gave 5.2% of the quantum yield at 420 nm for the H2 evolution reaction.

Preparation of PAMAM− and PPI−Metal (Silver, Platinum, and Palladium) Nanocomposites and Their Catalytic Activities for Reduction of 4-Nitrophenol

Abstract: Dendrimer-metal (silver, platinum, and palladium) nanocomposites are prepared in aqueous solutions containing poly(amidoamine) (PAMAM) dendrimers with surface amino groups (generations 3, 4, and 5) or poly(propyleneimine) (PPI) dendrimers with surface amino groups (generations 2, 3, and 4) The particle sizes of the metal nanoparticles obtained are almost independent of the generation as well as the concentration of the dendrimer for both the PAMAM and the PPI dendrimers; the average sizes of silver, platinum, and palladium nanoparticles are 56-75, 12-16, and 16-20 nm, respectively It is suggested that the dendrimer-metal nanocomposites are formed by adsorbing the dendrimers on the metal nanoparticles Studies of the reduction reaction of 4-nitrophenol by these nanocomposites show that the rate constants are very similar between PAMAM and PPI dendrimer-silver nanocomposites, whereas the rate constants for the PPI dendrimer-platinum and -palladium nanocomposites are greater than those for the corresponding PAMAM dendrimer nanocomposites In addition, it is found that the rate constants for the reduction of 4-nitrophenol involving all the dendrimer-metal nanocomposites decrease with an increase in the dendrimer concentrations, and the catalytic activity of dendrimer-palladium nanocomposites is highest

Copolymerization of carbon dioxide and epoxide

Abstract: Alternating copolymerization of CO2 and epoxide to give aliphatic polycarbonate with high molecular weight proceeds under mild conditions by organometallic catalyst systems. The reaction product of diethylzinc with a polyhydric compound, such as water or polyhydric phenol, exhibits high catalytic activity. Elementary reactions for the copolymerization of CO2 and epoxide with an organozinc catalyst system is considered to be the reaction of a zinc alkoxide with CO2 to form a zinc alkyl carbonate, and the reaction of the zinc alkyl carbonate with epoxide to regenerate zinc alkoxide. The system of aluminum porphyrin such as (tetraphenylporphinato)aluminum chloride, coupled with a quaternary ammominum or phosphonium salt, such as ethyltriphenylphosphonium bromide, is a good catalyst for this copolymerization. Of much interest is the very narrow molecular weight distribution of the copolymer obtained by this system. Aluminum porphyrin and the quaternary salt forms a hexa-coordinate complex, and the copolymerization reaction is considered to proceed on both sides of the porphyrin ring. Some properties of the copolymer for possible application are described.

Strategies for the Development of Visible-light-driven Photocatalysts for Water Splitting

Abstract: Photocatalysts for water splitting developed by the present authors are reviewed. A NiO (0.2 wt %)/NaTaO3:La (2%) photocatalyst with a 4.1-eV band gap showed high activity for water splitting into ...

Construction of Z-scheme Type Heterogeneous Photocatalysis Systems for Water Splitting into H2 and O2 under Visible Light Irradiation

Abstract: The water splitting under visible light irradiation has been achieved by the Z-scheme system constituted of an Fe3+/Fe2+ redox couple as an electron relay and two powdered heterogeneous photocataly...

Functional Characterization of pH-Sensitive Organic Anion Transporting Polypeptide OATP-B in Human

Abstract: The pH-sensitive activity of human organic anion transporting polypeptide OATP-B, which is expressed at the apical membrane of human small intestinal epithelial cells, was functionally characterized. When initial uptake of estrone-3-sulfate, a typical substrate of OATP, was studied kinetically, we observed an increase in V(max) with decrease of pH from 7.4 to 5.0, whereas the change in K(m) was negligible. OATP-B-mediated uptake of estrone-3-sulfate was independent of sodium, chloride, bicarbonate, or glutathione, whereas the proton ionophore carbonylcyanide p-trifluoromethoxyphenylhydrazone exhibited a pH-dependent inhibitory effect, suggesting that a proton gradient is a driving force for OATP-B. When OATP-B was expressed in human embryonic kidney 293 cells, uptake activities for anionic compounds showed various kinds of pH sensitivity. Dehydroepiandrosterone-sulfate, estrone-3-sulfate, and fexofenadine were transported by OATP-B at both neutral and acidic pH, whereas estradiol-17beta-glucuronide, acetic acid, and lactic acid were not transported at all. Transport of taurocholic acid and pravastatin by OATP-B was observed only at acidic pH, demonstrating a pH-sensitive substrate specificity of OATP-B. Because the physiological pH close to the surface of intestinal epithelial cells is acidic, the roles of OATP-B in the small intestine might be different from those in other tissues, such as liver basolateral membrane. Although the driving force for OATP-B has not been fully established, the clarification of factors, such as pH, that affect the OATP-B-activity is essential for an understanding of the physiological and pharmacological relevance of the transporter in the small intestine.

An effective use of benzoic anhydride and its derivatives for the synthesis of carboxylic esters and lactones: A powerful and convenient mixed anhydride method promoted by basic catalysts

Abstract: Various carboxylic esters are obtained at room temperature in excellent yields with high chemoselectivities from nearly equimolar amounts of carboxylic acids and alcohols using 2-methyl-6-nitrobenzoic anhydride with triethylamine by the promotion of a basic catalyst such as 4-(dimethylamino)pyridine. A variety of lactones are also prepared in high yields at room temperature from the corresponding ω-hydroxycarboxylic acids with use of 2-methyl-6-nitrobenzoic anhydride in the presence of 4-(dimethylamino)pyridine. A similar reaction occurs with triethylamine when using a catalytic amount of 4-(dimethylamino)pyridine 1-oxide as an effective promoter for the intramolecular condensation reaction. These methods are successfully applied to the synthesis of erythro-aleuritic acid lactone and an eight-membered-ring lactone moiety of octalactins A and B. The efficiency of the cyclizations is compared to those of other reported lactonizations.

H2 evolution from an aqueous methanol solution on SrTiO3 photocatalysts codoped with chromium and tantalum ions under visible light irradiation

Abstract: SrTiO 3 photocatalysts doped with chromium ions showed photocatalytic activities for H 2 evolution from an aqueous methanol solution under visible light irradiation However, it had a long induction period Codoping of niobium or tantalum ions with chromium ions shortened the induction period, and increased the photocatalytic activities in respect of the H 2 evolution The photocatalytic activities of chromium- and chromium/tantalum-doped SrTiO 3 were improved when they were pretreated at 773 K in the hydrogen reduction atmosphere Codoping of tantalum ions suppressed the formation of Cr 6+ ions and oxygen defects which would work as nonradiative recombination centers between photogenerated electrons and holes, resulting in the shortening of induction periods and the improvement of photocatalytic activities

Mutations of ARX are associated with striking pleiotropy and consistent genotype–phenotype correlation

Abstract: We recently identified mutations of ARX in nine genotypic males with X-linked lissencephaly with abnormal genitalia (XLAG), and in several female relatives with isolated agenesis of the corpus callosum (ACC). We now report 13 novel and two recurrent mutations of ARX, and one nucleotide change of uncertain significance in 20 genotypic males from 16 families. Most had XLAG, but two had hydranencephaly and abnormal genitalia, and three males from one family had Proud syndrome or ACC with abnormal genitalia. We obtained detailed clinical information on all 29 affected males, including the nine previously reported subjects. Premature termination mutations consisting of large deletions, frameshifts, nonsense mutations, and splice site mutations in exons 1 to 4 caused XLAG or hydranencephaly with abnormal genitalia. Nonconservative missense mutations within the homeobox caused less severe XLAG, while conservative substitution in the homeodomain caused Proud syndrome. A nonconservative missense mutation near the C-terminal aristaless domain caused unusually severe XLAG with microcephaly and mild cerebellar hypoplasia. In addition, several less severe phenotypes without malformations have been reported, including mental retardation with cryptogenic infantile spasms (West syndrome), other seizure types, dystonia or autism, and nonsyndromic mental retardation. The ARX mutations associated with these phenotypes have included polyalanine expansions or duplications, missense mutations, and one deletion of exon 5. Together, the group of phenotypes associated with ARX mutations demonstrates remarkable pleiotropy, but also comprises a nearly continuous series of developmental disorders that begins with hydranencephaly, lissencephaly, and agenesis of the corpus callosum, and ends with a series of overlapping syndromes with apparently normal brain structure.

Induction of Apoptosis in Leukemic Cells by Homovanillic Acid Derivative, Capsaicin, through Oxidative Stress: Implication of Phosphorylation of p53 at Ser-15 Residue by Reactive Oxygen Species

Abstract: Capsaicin (N-vanillyl-8-methyl-1-nonenamide) is a homovanillic acid derivative found in pungent fruits. Several investigators have reported the ability of capsaicin to inhibit events associated with the promotion of cancer. However, the effects of capsaicin on human leukemic cells have never been investigated. We investigated the effects of capsaicin on leukemic cells in vitro and in vivo and further examined the molecular mechanisms of capsaicin-induced apoptosis in myeloid leukemic cells. Capsaicin suppressed the growth of leukemic cells, but not normal bone marrow mononuclear cells, via induction of G(0)-G(1) phase cell cycle arrest and apoptosis. Capsaicin-induced apoptosis was in association with the elevation of intracellular reactive oxygen species production. Interestingly, capsaicin-sensitive leukemic cells were possessed of wild-type p53, resulting in the phosphorylation of p53 at the Ser-15 residue by the treatment of capsaicin. Abrogation of p53 expression by the antisense oligonucleotides significantly attenuated capsaicin-induced cell cycle arrest and apoptosis. Pretreatment with the antioxidant N-acetyl-L-cystein and catalase, but not superoxide dismutase, completely inhibited capsaicin-induced apoptosis by inhibiting phosphorylation of Ser-15 residue of p53. Moreover, capsaicin effectively inhibited tumor growth and induced apoptosis in vivo using NOD/SCID mice with no toxic effects. We conclude that capsaicin has potential as a novel therapeutic agent for the treatment of leukemia.

Control of Viscoelasticity Using Redox Reaction

Abstract: The viscoelasticity of a fluid was tuned with the Faradaic reaction of (11-ferrocenylundecyl)trimethylammonium bromide (FTMA), a "redox-switchable" surfactant. An aqueous solution of the reduced form of FTMA exhibited a remarkable viscoelasticity in the presence of sodium salicylate (NaSal) because of the formation of three-dimensional entanglement of wormlike micelles. Electrolytic oxidation of FTMA caused the viscosity of the system to dramatically decrease and the elasticity to disappear. This drastic decrease in viscoelasticity arose from the disruption of wormlike micelles. This novel electrorheological phenomenon is expected to be applicable to ink for inkjet printers, the electrochemically controlled release of substances entrapped in wormlike micelles of FTMA, and fluid flow rate control using electric signals.

Spiral Structure in the Circumstellar Disk around AB Aurigae

Abstract: We present a near-infrared image of the Herbig Ae star AB Aur obtained with the Coronagraphic Imager with Adaptive Optics mounted on the Subaru Telescope. The image shows a circumstellar emission extending out to a radius of r = 580 AU, with a double spiral structure detected at r = 200-450 AU. The surface brightness decreases as r-3.0±0.1, steeper than the radial profile of the optical emission possibly affected by the scattered light from the envelope surrounding AB Aur. This result, together with the size of the infrared emission similar to that of the 13CO (J = 1-0) disk, suggests that the spiral structure is indeed associated with the circumstellar disk but is not part of the extended envelope. We identified four major spiral arms, which are trailing if the brighter southeastern part of the disk is the near side. The weak gravitational instability, maintained for millions of years by continuous mass supply from the envelope, might explain the presence of the spiral structure at the relatively late phase of the pre-main-sequence period.

An Indispensable Role for STAT1 in IL-27-Induced T-bet Expression but Not Proliferation of Naive CD4 + T Cells

Abstract: IL-27 is a novel IL-12 family member that plays a role in the early regulation of Th1 initiation, induces proliferation of naive CD4 + T cells, and synergizes with IL-12 in IFN-γ production. It has been recently reported that IL-27 induces T-bet and IL-12Rβ2 expression through JAK1/STAT1 activation. In the present study, we further investigated the JAK/STAT signaling molecules activated by IL-27 and also the role of STAT1 in IL-27-mediated responses using STAT1-deficient mice. In addition to JAK1 and STAT1, IL-27-activated JAK2, tyrosine kinase-2, and STAT2, -3, and -5 in naive CD4 + T cells. The activation of STAT2 and STAT5, but not of STAT3, was greatly diminished in STAT1-deficient naive CD4 + T cells. Comparable proliferative response to IL-27 was observed between STAT1-deficient and wild-type naive CD4 + T cells. In contrast, IL-27 hardly induced T-bet and subsequent IL-12Rβ2 expression, and synergistic IFN-γ production by IL-27 and IL-12 was impaired in STAT1-deficient naive CD4 + T cells. Moreover, IL-27 augmented the expression of MHC class I on naive CD4 + T cells in a STAT1-dependent manner. These results suggest that IL-27 activates JAK1 and -2, tyrosine kinase-2, STAT1, -2, -3, and -5 in naive CD4 + T cells and that STAT1 plays an indispensable role in IL-27-induced T-bet and subsequent IL-12Rβ2 expression and MHC class I expression as well but not proliferation, while STAT3 presumably plays an important role in IL-27-induced proliferation.

Drosophila deltex mediates suppressor of Hairless-independent and late-endosomal activation of Notch signaling.

Abstract: Notch (N) signaling is an evolutionarily conserved mechanism that regulates many cell-fate decisions. deltex (dx) encodes an E3-ubiquitin ligase that binds to the intracellular domain of N and positively regulates N signaling. However, the precise mechanism of Dx action is unknown. Here, we found that Dx was required and sufficient to activate the expression of gene targets of the canonical Su(H)-dependent N signaling pathway. Although Dx required N and a cis-acting element that overlaps with the Su(H)-binding site, Dx activated a target enhancer of N signaling, the dorsoventral compartment boundary enhancer of vestigial (vgBE), in a manner that was independent of the Delta (Dl)/Serrate (Ser) ligands- or Su(H). Dx caused N to be moved from the apical cell surface into the late-endosome, where it accumulated stably and co-localized with Dx. Consistent with this, the dx gene was required for the presence of N in the endocytic vesicles. Finally, blocking the N transportation from the plasma membrane to the late-endosome by a dominant-negative form of Rab5 inhibited the Dx-mediated activation of N signaling, suggesting that the accumulation of N in the late-endosome was required for the Dx-mediated Su(H)-independent N signaling.

Very Large-Scale Structures and Their Effects on the Wall Shear-Stress Fluctuations in a Turbulent Channel Flow up to Reτ=640

Abstract: Direct numerical simulation of a fully developed turbulent channel flow has been carried out at three Reynolds numbers, 180, 395, and 640, based on the friction velocity and the channel half width, in order to investigate very large-scale structures and their effects on the wall shear-stress fluctuations

Preparation of functionally PEGylated gold nanoparticles with narrow distribution through autoreduction of auric cation by α-Biotinyl-PEG-block-[poly(2-(N,N-dimethylamino)ethyl methacrylate)]

Abstract: PEGylated gold nanoparticles with biotin moieties installed at the distal end of the PEG tethered chains were prepared by the autoreduction of HAuCl4 catalyzed by alpha-biotinyl-PEG-block-poly[2-(N,N-dimethylamino)ethyl methacrylate] (biotinyl-PEG/PAMA) in aqueous medium at room temperature. The size of the gold nanoparticles was controllable in a range of 6-13 nm by changing the initial Au3+/polymer ratio, while retaining their narrow size distribution. The dispersion stability of the nanoparticles in aqueous medium was extremely high even under the condition of salt concentration as high as I = 2.0. Biotinyl-PEG/PAMA-anchored gold nanoparticles underwent specific aggregation in the presence of streptavidin, revealing their promising utility as colloidal sensing systems applicable under biological condition.

Metal chelation-controlled twisted intramolecular charge transfer and its application to fluorescent sensing of metal ions and anions.

Abstract: Two fluorescent ligands, N-(2-(5-cyanopyridyl))cyclen (L5) and N-(2-pyridyl)cyclen (L6) (cyclen = 1,4,7,10-tetraazacyclododecane), were designed and synthesized to control twisted intramolecular charge transfer (TICT) by metal chelation in aqueous solution. By complexation with Zn2+, L6 exhibited TICT emissions at 430 nm (excitation at 270 nm) in 10 mM HEPES (pH 7.0) with I = 0.1 (NaNO3) at 25 °C due to the perpendicular conformation of a pyridine ring with respect to a dialkylamino group, which was fixed by Zn2+−N(pyridine) coordination, as proven by potentiometric pH, UV, and fluorescence titrations and X-ray crystal structure analysis. We further describe that the 1:1 complexation of ZnL6 with guests such as succinimide, phosphates, thiolates, and dicarboxylates, which compete with a nitrogen in the pyridine ring for Zn2+ in ZnL6, induces considerable emission shift from TICT emissions (at 430 nm) to locally excited emissions (at ca. 350 nm) in neutral aqueous solution at 25 °C.

Correlation of histological localization of tumor-associated macrophages with clinicopathological features in endometrial cancer.

Abstract: Background: To clarify the pathophysiological role of tumor-associated macrophages (TAMs), we performed clinicopathological analysis of CD68+ cells in 70 cases of human endometrial cancer. Materials and Methods: Using immunohistochemistry for CD68, we classified CD68+ cells into four groups: (a) those infiltrated into cancer cell nests or in close contact with cancer cells (nest TAM); (b) those in necrosis in the tumor center (hot-spot TAM); (c) those infiltrated into cancer stroma (stroma TAM); and (d) those distributed along the invasive margin of a tumor (Margin TAM). Results: The aggregation of nest TAM related to high relapse-free survival rate after surgery. On the contrary increased hot-spot TAM was a hazard to relapse-free survival and was proportionately-associated with clinical stage, myometrial invasion and histological differentiation. The extent of stroma TAM was associated with the presence of lymph node metastasis. Conclusion: Our findings demonstrate that the histological location of infiltrated TAMs may be taken into account in the clinical evaluation of endometrial cancer.

Human-following mobile robot in a distributed intelligent sensor network

Abstract: The robots that will be needed in the near future are human-friendly robots that are able to coexist with humans and support humans effectively. To realize this, humans and robots need to be in close proximity to each other as much as possible. Moreover, it is necessary for their interactions to occur naturally. It is desirable for a robot to carry out human following, as one of the human-affinitive movements. The human-following robot requires several techniques: the recognition of the target human, the recognition of the environment around the robot, and the control strategy for following a human stably. In this research, an intelligent environment is used in order to achieve these goals. An intelligent environment is a space in which many sensors and intelligent devices are distributed. Mobile robots exist in this space as physical agents providing humans with services. A mobile robot is controlled to follow a walking human using distributed intelligent sensors as stably and precisely as possible. The control law based on the virtual spring model is proposed to mitigate the difference of movement between the human and the mobile robot. The proposed control law is applied to the intelligent environment and its performance is verified by the computer simulation and the experiment.

ydk1-D, an auxin-responsive GH3 mutant that is involved in hypocotyl and root elongation

Abstract: To study the GH3 gene family of Arabidopsis, we investigated a flanking sequence database of Arabidopsis activation-tagged lines. We found a dwarf mutant, named yadokari 1-D (ydk1-D), that had a T-DNA insertion proximal to a GH3 gene. ydk1-D is dominant and has a short hypocotyl not only in light but also in darkness. Moreover, ydk1-D has a short primary root, a reduced lateral root number, and reduced apical dominance. A GH3 gene, named YDK1, was upregulated in ydk1-D, and YDK1 transgenic plants showed the ydk1-D phenotype. YDK1 gene expression was induced by exogenously applied auxin and regulated by auxin-response factor (ARF)7. In addition, YDK1 gene expression was downregulated by blue and far-red (FR) lights. Strong promoter activity of YDK1 was observed in roots and flowers. These results suggest that YDK1 may function as a negative component in auxin signaling by regulating auxin activity.

Universal features of quantized thermal conductance of carbon nanotubes.

Abstract: The universal features of quantized thermal conductance of carbon nanotubes (CNTs) are revealed through a theoretical analysis based on the Landauer theory of heat transport. The phonon-derived thermal conductance of semiconducting CNTs exhibits a universal quantization in the low-temperature limit, independent of the radius or atomic geometry. The temperature dependence follows a single curve given in terms of temperature scaled by the phonon energy gap. The thermal conductance of metallic CNTs has an additional contribution from electronic states, which also exhibits quantized behavior up to room temperature.

Thin-Film Silicon-Growth Process and Solar Cell Application-

Abstract: Growth processes of hydrogenated amorphous silicon (a-Si:H) and microcrystalline silicon (µc-Si:H) from SiH4 and H2/SiH4-glow discharge plasmas are reviewed. Differences and similarities between µc-Si:H and a-Si:H growth reactions in the plasma and on the film-growing surface are discussed, and the nucleus-formation process followed by the epitaxial-like crystal growth process is explained as being processes unique to µc-Si:H. The governing reaction of dangling-bond-defect density in the resulting a-Si:H and µc-Si:H films is also discussed in order to obtain a clue to improve the optoelectronic properties of these materials to enable device applications, particularly to thin-film silicon-based solar cells. Material issues concerning the realization of low-cost high-efficiency solar cells are described, and finally, recent progress in those issues is presented.