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81.
Yasuhiro Isobe Hiromichi Ikki Tatsuyuki Sakakibara Motoaki Iwaya Tetsuya Takeuchi Satoshi Kamiyama Isamu Akasaki Takayuki Sugiyama Hiroshi Amano Mamoru Imade Yusuke Mori 《Journal of Crystal Growth》2012,351(1):126-130
We investigated unintentionally doped nonpolar a- and m-plane GaN layers grown by metalorganic vapor phase epitaxy under several sets of conditions on freestanding a- and m-plane GaN substrates. Oxygen contamination in a-plane GaN is greatly reduced by increasing the V/III ratio during growth. As a result, a high-resistivity GaN buffer layer for an AlGaN/GaN heterostructure field-effect transistor was realized. 相似文献
82.
Yumiko Nakano Yuezhen Bin Mami Bando Teruo Nakashima Tsumuko Okuno Hiromichi Kurosu Masaru Matsuo 《Macromolecular Symposia》2007,258(1):63-81
Summary: The origins of the thermal and mechanical properties of chitosan and poly(vinyl alcohol) (PVA) with inter- and intra-hydrogen bonds were investigated systematically by using X-ray, DSC, positron annihilation and viscoelastic measurements. Based on their individual properties, the characteristics of the blend films were estimated in relation to their morphology and mechanical properties as a function of chitosan content. The characteristics of the blend films were also analyzed in terms of the deviation from a simple additive rule of chitosan and PVA content. These results suggested that the miscibility of chitosan and PVA could be ensured by entanglement of the amorphous chain segments of chitosan and PVA. Further detailed analysis revealed that the chitosan content on the film surface is higher than that of the admixture content of chitosan after elongation, although the chitosan and PVA chains were crystallized independently. The elongation could be achieved for the blend films whose PVA content was higher than 50% and the drawn blend films were transparent. Thus, it may be expected that sufficiently entangled meshes formed between chitosan and PVA amorphous chains within the film, the PVA content being higher than 50%, were maintained under the elongation process. 相似文献
83.
84.
V. Bharathi M. Sivakumar R. Udayabhaskar Hiromichi Takebe B. Karthikeyan 《Applied Physics A: Materials Science & Processing》2014,116(1):395-401
We studied structural, optical and vibrational properties of K-doped ZnO nanostructures. X-ray diffraction studies reveal that the prepared particles are hexagonal wurtzite in structure. Increase in lattice parameters and unit cell volume is observed after K doping. Dopant influences on stress, strain of the system are studied using W–H plots. Band gap variation by doping of K is identified from optical absorption studies. Photoluminescence studies have given insight into the enhancement in blue emission observed by K doping along with the near band emission of nano ZnO. From Fourier transform infrared spectral measurements, K-related local vibration mode is observed along with the information related to influence of doping on characteristic vibrational modes of ZnO. 相似文献
85.
Hiromichi Nakazato 《Foundations of Physics》1997,27(12):1709-1723
A one-dimensional scattering problem off a δ-shaped potential is solved analytically and the time development of a wave packet is derived from the time-dependent Schrödinger equation. The exact and explicit expression of the scattered wave packet supplies us with interesting information about the “time delay” by potential scattering in the asymptotic region. It is demonstrated that a wave packet scattered by a spin-flipping potential can give us quite a different value for the delay times from that obtained without spin-degrees of freedom. 相似文献
86.
Suzuki TM Llosa Tanco MA Pacheco Tanaka DA Hayashi H Takahashi Y 《The Analyst》2005,130(11):1537-1542
A Pb(2+) selective membrane filter was fabricated from the fibrous CeO(H(2)PO(4))(2).2H(2)O (CeP) crystals by blending with cellulose fiber. Enrichment of ppb level of Pb(2+) was achieved simply by filtration of aqueous sample solution through the membrane filter. Pb(2+) was strongly retained on the membrane filter by accommodation into the interlayer gallery of a CeP crystal. Visual detection of the enriched Pb(2+) was achieved by subsequent color signaling as PbS deposit upon treatment of the membrane filter with 3% Na(2)S solution. The analytical procedure and sample treatment conditions were optimized with respect to pH of the sample solution, filtration rate and masking of interfering ions. Detection of 20 ppb of Pb(2+) was not interfered by the presence of 1000-fold of Ca(2+), Mg(2+), and up to 100-fold of Fe(3+)and Cu(2+) by masking with 1 x 10(-3) mol dm(-3) of iminodiacetic acid (IDA). Most anions including phosphate (20 000 times) did not interfere with the determination of Pb(2+). The present simple method was applied to the determination of Pb(2+) in real samples like mine valley water. 相似文献
87.
Hiromichi Egami 《Tetrahedron letters》2005,46(36):6049-6052
The mechanism of aerobic oxidation of alcohols using (ON)Ru(salen) complex as catalyst under photo-irradiation was examined through studies of kinetics of the oxidation, kinetic isotope effect in the oxidation, and effect of the ligand structure on the chemoselectivity of the oxidation of primary and secondary alcohols. It was demonstrated that the aerobic oxidation includes an intramolecular hydrogen atom transfer process that is attributed to realization of efficient differentiation of primary and secondary alcohols in the oxidation. 相似文献
88.
[reaction: see text]. CAN is a good reagent for the transformation of 2-hydroxyethyl ether units to alcohols. Significantly, many functional groups can tolerate the reaction conditions, although they do not survive under many previously reported removal conditions. The reaction mechanism is clarified. 相似文献
89.
The iron mixed-valence complex (n-C(3)H(7))(4)N[Fe(II)Fe(III)(dto)(3)] exhibits a novel type of phase transition called charge-transfer phase transition (CTPT), where the thermally induced electron transfer between Fe(II) and Fe(III) occurs reversibly at ~120 K, in addition to the ferromagnetic phase transition at T(C) = 7 K. To investigate the mechanism of the CTPT, we have synthesized a series of magnetically diluted complexes (n-C(3)H(7))(4)N[Fe(II)(1-x)Zn(II)(x)Fe(III)(dto)(3)] (dto = C(2)O(2)S(2); x = 0-1), and carried out magnetic susceptibility and dielectric constant measurements and (57)Fe M?ssbauer spectroscopy. With increasing Zn(II) concentration (x), the CTPT is gradually suppressed and disappears at x ≈ 0.13. On the other hand, the ferromagnetic transition temperature (T(C)) is initially enhanced from 7 K to 12 K between x = 0.00 and 0.05, despite the nonmagnetic nature of Zn(II) ions, and then it decreases monotonically from 12 K to 3 K with increasing Zn(II) concentration. This anomalous dependence of T(C) on Zn(II) concentration is related to a change in the spin configuration of the ferromagnetic state caused by the partial suppression of the CTPT. 相似文献
90.
Koui Horiai Hiromichi Uehara 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,63(5):1009
A vibrational–rotational spectrum of the ν = 2 transitions of a high-temperature molecule AlF was observed between 1490 and 1586 cm−1 with a diode laser spectrometer. Measurements were made on the ν = 3–1, 4–2, 5–3 and 8–6 bands at a temperature of 900 °C. Measured spectral lines were fitted to effective band constants ν0, Bν and Dν for each band. Present measurements were made with only one Pb-salt laser diode. Physical significance of the effective band constants is discussed. 相似文献