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排序方式: 共有156条查询结果,搜索用时 31 毫秒
1.
Yasuo Kameda Motoya Sasaki Masahiro Yaegashi Kosuke Tsuji Shingo Oomori Shuji Hino Takeshi Usuki 《Journal of solution chemistry》2004,33(6-7):733-745
Time-of-Flight (TOF) neutron diffraction measurements have been carried out on aqueous 8 mol% sodium acetate solutions in D2O. Scattering cross sections that were observed for sample solutions involving 12C/13C and H/D isotopically substituted acetate ions were used to derive the first-order difference functions, ΔH(Q) and ΔC(Q), and corresponding distribution functions, G H(r;r) and G C(r;r), which describe the environmental structure around the methyl and the carboxyl groups within the acetate ion, respectively. Structural parameters concerning the first hydration shell of the carboxyl group within the acetate ion were obtained through the least squares fit to the observed intermolecular difference function, ΔC inter(Q). The nearest neighbor C O...D W1 (CO: carboxyl carbon atom, DW1: water deuterium atom) distance, r(C O...D W1 ), and the angle, ∠ C O ...D W1 -O W (O W : water oxygen atom), were determined to be 2.63(1) Å and 120(1)°, respectively. The coordination number, n(C O ...D W1 ), was obtained to be 4.0(1). These results are consistent with the hydration structure in which water molecules in the first hydration shell of the carboxyl group are hydrogen-bonded with oxygen atoms of the carboxyl group. 相似文献
2.
The change in the conformation of the flexible O-CH2-CH2-CH2-O segment of poly(trimethylene terephthalate) (PTT) monofilament caused by drawing was investigated by means of the gamma-gauche effect on the 13C solid-state NMR chemical shift of the internal methylene carbon, combined with the NMR relaxations. The conformation around the O-CH2 and CH2-O bonds for as-spun fiber was trans/trans. On drawing, followed by heat treatment, the conformation changed to gauche/gauche. The ratio of gauche/gauche to trans/trans for the drawn PTT fiber was determined quantitatively. 相似文献
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The microwave-assisted acid-digestion for the determination of metals in coal by ICP-AES was investigated, especially focusing on the necessity of adding HF. By testing five certified reference materials, BCR-180, BCR-040, NIST-1632b, NIST-1632c, and SARM-20, it was found that the two-stage digestion without HF (HNO3 + H2O2 was used) was very effective for the pretreatment of ICP-AES measurement. Both major metals (Al, Ca, Fe, and Mg) and minor or trace metals (Co, Cr, Cu, Mn, Ni, Pb, and Zn) in coal gave good recoveries for their certified or reference values. The possibility of ‘HF-memory effect’ was cancelled by the use of a set of vessels which had been never contacted with HF. Twenty-four Japanese standard coals (SS coals) were analyzed by the present method, and the concentrations of major metals measured by the present method provided very high accordance with those from the authentic JIS (Japanese Industrial Standard) method. 相似文献
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Yamamoto Y Terui N Tachiiri N Minakawa K Matsuo H Kameda T Hasegawa J Sambongi Y Uchiyama S Kobayashi Y Igarashi Y 《Journal of the American Chemical Society》2002,124(39):11574-11575
Paramagnetic NMR and optical studies of the oxidized forms of mesophile Pseudomonas aeruginosa cytochrome c(551) and its quintuple mutant (F7A/V13M/F34Y/E43Y/V78I), and thermophile Hydrogenobacter thermophilus cytochrome c(552) demonstrated that the amino acid side chain packings in the protein interior influence the coordination bond between the heme iron and the axial methionine in the proteins. The strength of heme axial coordinations was found to correlate with the overall protein thermostability. 相似文献
6.
H2 generation during mechanochemical treatment of kaolinite by dry grinding was examined by X-ray diffraction analysis, Fourier transform infrared spectroscopy, and BET surface area measurement. The H2 concentration in the mill pot, measured by gas chromatography, increased with grinding time up to a maximum concentration of 156 ppm (0.35 micromol) after 600 min. This H2 generation is considered to occur as a result of three processes: (1) structural destruction characterized by the delamination and loss of hydroxyl groups as a result of dry grinding, (2) transformation of liberated hydroxyls into water molecules by mechanochemical effects such as prototropy, and (3) H2 generation through reaction between surface water molecules and mechanoradicals created by the rupture of Si-O or Al-O-Si bonds. Although the surface area plateaued after 240 min grinding, the H2 concentration continued to increase, indicating that surface mechanoradicals are created during this later grinding stage. Thus, H2 generation can be used as an indicator of mechanoradical formation during mechanochemical treatment. 相似文献
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Yasuo Kameda Takuya Miyazaki Toshiya Otomo Yuko Amo Takeshi Usuki 《Journal of solution chemistry》2014,43(9-10):1588-1600
Neutron diffraction measurements were carried out at 25 °C for aqueous LiNO3 heavy water solutions, (*LiNO3) x (D2O)1?x where x = 0.1, 0.05 and 0.01, in which the 6Li/7Li isotopic ratios were varied. Structural information on intermolecular nearest neighbor Li+···D2O interactions in the extensive concentration range was derived from the first-order difference function, ?Li(Q), obtained from the difference in scattering cross sections between 6Li- and 7Li-enriched sample solutions. The nearest neighbor Li+···O distance and coordination number for sample solution with x = 0.1 were determined to be r LiO = 1.969 (8) Å and n LiO = 4.12 (6), respectively, corresponding to the four-coordinated Li+ ion in the solution. On the other hand, those obtained for the solution with x = 0.01 are r LiO = 2.00 (2) Å and n LiO = 6.0 (2), respectively, indicating that hexaaqua Li+ is dominant in the dilute solution. These results clearly indicate that a concentration dependence of the hydration number of Li+ occurs in the aqueous solutions. 相似文献
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