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921.
Yasuji Nakahama Norio Kanetsuki Takeshi Funaki Masaru Kadono Yasuhisa Sano Kazuya Yamamura Katsuyoshi Endo Yuzo Mori 《Surface and interface analysis : SIA》2008,40(12):1566-1570
A high‐quality bulk gallium nitride (GaN) substrate, which is suitable for high‐quality homoepitaxial growth, is indispensable for realizing high‐performance GaN devices. With improvement in the quality of the bulk GaN substrate, the removal of subsurface damage induced during surface polishing has become increasingly necessary. To remove the subsurface damage from the bulk GaN substrate, a chemical finishing method that does not produce further damage is required. We applied plasma chemical vaporization machining (CVM) to remove the subsurface damage from the bulk GaN substrate. In this study, we investigated the etching characteristics of GaN by plasma CVM applying atmospheric pressure Cl2/He plasma. The maximum removal rate in the depth direction by plasma CVM was 9100 nm/min, which is seven times greater than that of reactive ion etching (RIE). The activation energy in plasma CVM was estimated to be 2.1 kcal/mol, which is 1.75 times greater than that in RIE. It is supposed that some of the energy required for the removal reaction in RIE is supplied by ion bombardment, but plasma CVM depends on only a chemical reaction without high‐energy ion collision. This result suggests that plasma CVM is a finishing method that causes less subsurface damage than RIE. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
922.
The concentrations of dissolved silica species in electrolyte solutions were derived from the relative intensities of silica
species, obtained from FAB-MS measurements (fast atom bombardment mass spectrometry), and the total concentration of dissolved
silica. Generally, silica species in aqueous solutions form various complexes with cations such as sodium (Na+) or calcium (Ca2+), and it has been difficult to determine the concentration of each species. From the observed results from FAB-MS, the chemical
species of silica dissolved in lithium chloride (LiCl) and magnesium chloride (MgCl2) solutions do not include complexes with these cations, and thus Li+ and Mg2+ do not replace protons of the silanol groups in silica. Therefore, in LiCl and MgCl2 solutions, all of the simple structures of silicate species can be identified. The concentration of each silica species was
estimated on the basis of its mass spectra peak intensities and the total concentration of silica as determined by colorimetry.
This study yields the concentration of each silica species within small errors, whereas conventional methods (such as 29Si-NMR) have not yielded the concentrations of individual silica species. From these results, dimers and cyclic tetramers
are concluded to be the main species in silica solutions with concentrations of at most 0.1 to 0.2 μmol⋅dm−3. This tendency should also occur in NaCl and CaCl2 solutions, which are major electrolytes in natural waters. 相似文献
923.
Yusaku Takita Susumu Hikazudani Kazuya Soda Katsutoshi Nagaoka 《Journal of molecular catalysis. A, Chemical》2008,280(1-2):164-172
The catalytic activity of MV2O6 and M2V2O7 type oxides prepared by the molten method (MM) for anaerobic oxidation of isobutane was studied in order to construct a system for the selective oxidation of isobutene using a thin layer reactor. Isobutene, CO and CO2 were formed by every catalyst tested. The activities for isobutene formation were CuV2O6 > ZnV2O6, NiV2O6, CoV2O6 > MgV2O6 > MnV2O6 CaV2O6. Isobutene was a major product over M2V2O7 (MM). Co2V2O7 showed the highest activity and high isobutene selectivity exceeded 90%, demonstrating that Co2V2O7 is a suitable oxide for a thin layer reactor for anaerobic oxidation of isobutane. Partial substitution of Mg by Cu in Mg2V2O7 (MM) improved the activity. It is shown by the oxidation at low O2 concentration as 2–3% that two types of oxidations occurred simultaneously: isobutene formation by the lattice oxygen ions diffused from the bulk, and CO and CO2 formation by the oxygen species derived from molecular oxygen in the gas phase. 相似文献
924.
A new algorithm of two-electron repulsion integral (ERI) calculations has been developed. In this algorithm, Cartesian axes
are rotated to make several coordinate components zero or constant using the Pople–Hehre algorithm, and ERIs are evaluated
at the rotated coordinate by the McMurchie–Davidson algorithm. The new algorithm applicable to (ss|ss) to (dd|dd) ERIs is implemented in the quantum chemistry program GAMESS. Test calculations show that the new algorithm reduces the computational
times by 10–40%, as compared with the Pople–Hehre and the Rys quadrature algorithms. 相似文献
925.
926.
Horike S Kishida K Watanabe Y Inubushi Y Umeyama D Sugimoto M Fukushima T Inukai M Kitagawa S 《Journal of the American Chemical Society》2012,134(24):9852-9855
We elucidated the specific adsorption property of CO(2) for a densely interpenetrated coordination polymer which was a nonporous structure and observed gas separation properties of CO(2) over CH(4), C(2)H(4), and C(2)H(6), studied under both equilibrium and kinetic conditions of gases at ambient temperature and pressure. 相似文献
927.
The production of giant lipid vesicles with controlled size and structure will be an important technology in the design of quantitative biological assays in cell-mimetic microcompartments. For establishing size control of giant vesicles, we investigated the vesicle formation process, in which inverted emulsion droplets are transformed into giant unilamellar vesicles (GUVs) when they pass through an oil/water interface. The relationship between the size of the template emulsion and the converted GUVs was studied using inverted emulsion droplets with a narrow size distribution, which were prepared by microfluidics. We successfully found an appropriate centrifugal acceleration condition to obtain GUVs that had a desired size and narrow-enough size distribution with an improved yield so that emulsion droplets can become the template for GUVs. 相似文献
928.
In the presence of amorphous MnO(2), various methylarenes (even with two or more methyl groups) could be selectively converted into the corresponding primary monoamides in moderate to high yields. The observed catalysis was truly heterogeneous, and the retrieved amorphous MnO(2) catalyst could be reused without an appreciable loss of its catalytic performance. 相似文献
929.
Song Z Ge D Ishii K Yamada H Toriumi K Watanabe H Nabeshima T Fukushima T 《Biomedical chromatography : BMC》2012,26(2):147-151
The concentration of brain N-acetylaspartic acid (NAA) in mice was determined by high-performance liquid chromatography (HPLC) using fluorescence detection after pre-column derivatization with 4-N,N-dimethylaminosulfonyl-7-N-(2-aminoethyl)amino-2,1,3-benzoxadiazole (DBD-ED). Six different brain parts, namely, the prefrontal cortex, olfactory bulb, nucleus accumbens, striatum, cerebellum and hippocampus, of male C57BL6/J mice, were investigated. The NAA concentration (nmol/mg protein) was highest in the olfactory bulb (58.2 ± 4.0, n = 8) and lowest in the hippocampus (42.8 ± 1.6, n = 8). The proposed HPLC method with fluorescence detection was successfully used to determine the NAA concentration in each investigated brain area. 相似文献
930.
Terai T Kikuchi K Urano Y Kojima H Nagano T 《Chemical communications (Cambridge, England)》2012,48(16):2234-2236
Arylamine N-acetyltransferase (NAT) is an important phase II metabolizing enzyme that influences drug efficacy and adverse effects. Here, we report a long-lived luminescent lanthanide complex as a probe for NAT, employing an intraligand photoinduced electron transfer strategy. The probe shows approximately 100-fold increase of luminescence upon N-acetylation catalyzed by NAT, with relatively high specificity for NAT2 over NAT1. It is the first NAT probe that is suitable for sensitive, homogeneous, and rapid detection of NAT activity of recombinant enzyme or cell lysate, and is expected to be useful for drug discovery and clinical diagnosis. 相似文献