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101.
Atsushi Hayashida Takuya Sato Shinjiro Hara Junichi Motohisa Kenji Hiruma Takashi Fukui 《Journal of Crystal Growth》2010,312(24):3592-3598
We developed a growth method for forming a GaAs quantum well contained in an AlGaAs/GaAs heterostructure nanowire using selective-area metal organic vapor phase epitaxy. To find the optimum growth condition of AlGaAs nanowires, we changed the growth temperature between 800 and 850 °C and found that best uniformity of the shape and the size was obtained near 800 °C but lateral growth of AlGaAs became larger, which resulted in a wide GaAs quantum well grown on the top (1 1 1)B facet of the AlGaAs nanowire. To form the GaAs quantum well with a reduced lateral size atop the AlGaAs nanowire, a GaAs core nanowire about 100 nm in diameter was grown before the AlGaAs growth, which reduced the lateral size of AlGaAs to roughly half compared with that without the GaAs core. Photoluminescence measurement at 4.2 K indicated spectral peaks of the GaAs quantum wells about 60 meV higher than the acceptor-related recombination emission peak of GaAs near 1.5 eV. The photoluminescence peak energy showed a blue shift of about 15 meV, from 1.546 to 1.560 eV, as the growth time of the GaAs quantum well was decreased from 8 to 3 s. Transmission electron microscopy and energy dispersive X-ray analysis of an AlGaAs/GaAs heterostructure nanowire indicated a GaAs quantum well with a thickness of 5−20 nm buried along the 〈1 1 1〉 direction between the AlGaAs shells, showing a successful fabrication of the GaAs quantum well. 相似文献
102.
Mesoporous SiO2–TiO2 was synthesized by the sol–gel method using Si(OC2H5)4, Ti(OC2H5)4, and stearyltrimethylammonium chloride. By using acetylacetone as the capping agent of Ti(OC2H5)4, homogeneous SiO2–TiO2 composite was obtained. Spherical mesoporous SiO2–TiO2 was also synthesized by the sol–gel method using W/O emulsion under microwave irradiation. The specific surface area of these
mesoporous SiO2–TiO2 materials decreased when the Ti/Si molar ratio was higher than 0.1, which indicated that Ti was homogeneously distributed
in mesoporous SiO2 matrix at Ti/Si ≦ 0.1. The photocatalytic activity of mesoporous SiO2–TiO2 materials was investigated by the degradation of methylene-blue in water under UV light irradiation. Mesoporous SiO2–TiO2 was effective for the adsorption–decomposition of methylene-blue. 相似文献
103.
Junichi Noma Hiroya Abe Takehito Kikuchi Makio Naito 《Journal of magnetism and magnetic materials》2010,322(13):1868-1871
Spherical crystalline Fe nanoparticles, ∼100 nm in diameter, were synthesized under Ar-50% H2 arc-plasma. These nanoparticles were dispersed in silicone oil after silane treatment on as-grown thin oxide layer (∼2 nm) to make their surfaces hydrophobic. The resulting Fe nanoparticles exhibited a high saturation magnetization of ∼190 emu/g at room temperature. The static magnetorheological behavior was measured for the colloidal dispersion (solid concentration: 15 vol%) at room temperature under magnetic flux densities of 0-0.3 T, using a parallel-plate-type commercial rheometer. The yield stress continuously increased with magnetic flux density, demonstrating the Bingham plastic behavior. Moreover, subjecting the sample to a magnetic flux density of 0.3 T increased the yield stress by ∼102. Additionally, the colloidal dispersion exhibited good stability against sedimentation. 相似文献
104.
Kakiyama G Hosoda A Iida T Fujimoto Y Goto T Mano N Goto J Nambara T 《Journal of chromatography. A》2006,1125(1):112-116
A direct method for the separation and quantification of a series of bile acid acyl glycosides using high-performance liquid chromatography coupled to an evaporative light scattering detector (HPLC-ELSD) is described. Complete separation of each of 15 bile acid acyl 24-alpha-glucosides and their 24-beta-anomers and 24-beta-galactosides was achieved by the stepwise gradient elution mode on a C18 column using a mixture of acetonitrile-methanol (8:2, v/v) and 1% aqueous acetic acid as the mobile phase. 24-beta-Galactosides were always eluted faster than the corresponding 24-beta-glucosides, which eluted after the corresponding 24-alpha-anomers. Calibration curves of different 24-beta-galactosides were linear over a range of 0.2-40 nmol of injected amount and the detection limits (S/N > 3) were from 0.08 to 0.1 nmol. The present HPLC-ELSD method may provide an insight into the separation and quantification of the biologically interesting neutral bile acids. 相似文献
105.
Kurosaki Y Abe H Morioka H Hirayama J Ikebuchi K Kamo N Nikaido O Azuma H Ikeda H 《Photochemistry and photobiology》2003,78(4):349-354
The mechanism by which UV-C irradiation inactivates M13 bacteriophage was studied by analyzing the M13 genome using agarose gel electrophoresis and South-Western blotting for pyrimidine dimers. The involvement of singlet oxygen (1O2) was also investigated using azide and deuterium oxide and under deoxygenated conditions. With a decrease in M13 infectivity on irradiation, single-stranded circular genomic DNA (sc-DNA) was converted to Form I and Form II, which had an electrophoretic mobility between that of sc-DNA and linear-form DNA. However, the amount of sc-DNA remaining was not correlated with the survival of M13. The formation of cyclobutane pyrimidine dimers (CPD) and pyrimidine (6-4) pyrimidone photoproducts ((6-4)PP) increased as a function of irradiation dose. The decrease in M13 infectivity was highly correlated with the increase in CPD and (6-4)PP, whereas no change was seen in M13 coat protein on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. 8-Oxo-7,8-dihydro-2'-deoxyguanosine did not form in the M13 genome after UV-C irradiation. Inactivation of M13 was neither enhanced by deuterium oxide nor inhibited by azide. Deoxygenation of the M13 suspension did not affect the inactivation, indicating that 1O2 did not participate in the inactivation of M13 by UV-C irradiation under these conditions. These results indicated that UV-C irradiation induced not only CPD and (6-4)PP formation but also additional tertiary structural change in DNA inside the M13 virions, resulting in primary damage and a loss of infectivity. The indirect effect of UV-C irradiation such as 1O2 production followed by oxidative damage to nucleic acids and proteins might have contributed less, if at all, to the inactivation of M13 than the direct effect of UV-C. 相似文献
106.
Single crystals of the Ba-containing silicon clathrate superconductor Ba(7.76)Si(46) were prepared using a high-pressure and high-temperature condition (3 GPa, 1300 degrees C). It crystallized in the cubic space group Pm-3n with a = 10.3141(7) A and Z = 1. There are two crystallographically different types of Ba sites, at the centers of Si dodecahederal (Ba@Si(20)) and Si tetrakaidecahedral (Ba@Si(24)) cages. On evacuation at 527 degrees C, a part of Ba atoms were removed from the Ba@Si(20) sites. The superconducting transition temperature (T(c)) decreased from 9.0 to 6.0 K with the decrease of the Ba content from 7.76 to 6.63 Ba/Si(46). The Ba deficient sites and the deficiency were determined by the structural refinement in the single-crystal X-ray analyses. 相似文献
107.
Chyongjin Pac Junichi Kubo Tetsuro Majima Hiroshi Sakurai 《Photochemistry and photobiology》1982,36(3):273-282
Abstract Redox photosensitization using the phenanthrene-p-dicyanobenzene pair in acetonitrile has been applied to the respective four isomeric dimers of N.N′-dimethylthymine (DMT) and N,N′-dimethyluracil (DMU) as well as to several related cyclobutane compounds. The head-to-head (syn) dimers of both DMT and DMU can undergo photosensitized splitting in the following order of efficiency: cis, syn dimer of DMT > cis, syn dimer of DMU > trans, syn dimer of DMT. On the other hand, the head-to-tail (anti) dimers are totally unreactive and have higher oxidation potentials than the corresponding syn dimers. It is suggested that the key mechanistic pathway is the formation of π complexes between the dimers and the photo-generated cation radical of phenanthrene by way of which splitting of the cyclobutane ring catalytically occurs without the formation of the discrete cation radical of the dimers. Structure-reactivity relationships are interpreted in terms of through-bond interactions between the n orbitals of N(l) and N(l′) involving the C(6)-C(6′) bond, as well as in terms of steric repulsion. It was found that aeration of solution greatly enhances the quantum yields of photosensitized splitting; the limiting quantum yield for splitting of the cis, syn dimer of DMT is 100. 相似文献
108.
[chemical reaction: see text]. Diorganophosphide anions, which usually function as nontransferable ligands on mixed cuprates, undergo smooth 1,2-migration on ate-type copper carbenoids. Phosphinodisilylmethylcoppers prepared by this protocol are converted into the corresponding phosphines, which can be used as bulky, highly basic and air-stable ligands. 相似文献
109.
Water-soluble constituents of anise: new glucosides of anethole glycol and its related compounds 总被引:1,自引:0,他引:1
From the water-soluble portion of the methanolic extract of the fruit of anise (Pimpinella anisum L.), which has been used as a spice and medicine since antiquity, twelve new and five known glucosides of phenylpropanoids, including four stereoisomers of anethole glycol 2'-O-beta-D-glucopyranoside and four stereoisomers of 1'-(4-hydroxyphenyl)propane-1',2'-diol 2'-O-beta-D-glucopyranoside were isolated together with anethole glycols and guaiacyl glycerol. The structures of the new compounds were clarified by spectral investigation. 相似文献
110.
Kakiyama G Iida T Goto T Mano N Goto J Nambara T 《Chemical & pharmaceutical bulletin》2004,52(3):371-374
A method for the synthesis of 3alpha,7alpha,14alpha-trihydroxy-5beta-cholan-24-oic acid which is a possible candidate of bile acid metabolite in vertebrates was developed. The principal reactions involved were 1). stereoselective remote-hydroxylation of methyl ursodeoxycholate diacetate with dimethyldioxirane, 2). site-selective protection at C-3 by tert-butyldimethylsilylation of the resulting 3alpha,7alpha,14alpha-trihydroxy ester, 3). oxidation of the diol with pyridinium dichromate adsorbed on activated alumina, 4). stereoselective reduction of the 7-ketone with zinc borohydride, and 5). cleavage of the protecting group at C-3 with p-toluenesulfonic acid. A facile elimination of the 14alpha-hydroxy group under an acidic or neutral condition is also described. The synthetic reference compound is now available for comparison with unidentified biliary bile acids detected in vertebrate bile. 相似文献