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21.
A new hydrophilic copolymer having three kinds of hydroxyl groups, i.e. primary OH on -hydroxy allyl alcohol component, secondary OH on cyclic hemiacetal component and tertiary OH on -hydroxy acrylate component, was prepared by reducing a ‘polylactone’, poly(1-oxa-2-oxobutane-1,4:3,3-tetrayl), with NaBH4 in mixed solvents containing an alcohol. The structural analyses were performed by the solution 1H NMR and the solid state 13C NMR spectroscopies of the reduced samples. The composition of the three components turned out to be variable to the alcohol species used for the mixed solvent. 相似文献
22.
采用PM 3半经验方法对肾上腺素和二甲亚砜与肾上腺素形成的 1∶1复合物的结构进行了几何优化 .在此基础上用密度泛函理论 (DFT)的B3LYP方法 ,分别在 6 31G、6 31G 、6 31+G 基组水平上进行了精确计算 ,并通过单点能计算考察了它们之间在形成各种复合物前后的能量和分子结构参数变化特点 .在各基组水平上所有物种的能量均进行零点振动能 (ZPVE)校正 .计算结果表明 ,二甲亚砜与肾上腺素能形成 6种稳定的复合物 ,在这些复合物中都具有较强的氢键作用 .计算结果能够解释有关实验现象 相似文献
23.
Wenping Deng Gang Xu Lei Wan Anwen Liu Bo Gao Junhe Du Shuiming Hu Yang Chen 《Acta Physico》2008,24(8):1329-1334
Apparatus integrating a Fourier transform-infrared (FT-IR) spectrometer and a mid-infrared difference frequency generation (DFG) laser spectrometer was built for the study of the matrix isolation spectrum in solid molecular hydrogen. A 3-cm-long molecular hydrogen crystal was grown in a liquid-helium Dewar, and its infrared absorption spectrum in the 1-5 μm region was recorded to test the system. The W0(0) (ν=0←0, J=6←0) line around 2410 cm−1 of solid hydrogen was investigated with the DFG laser spectroscopy. High-resolution matrix isolation spectrum of CO2 co-deposited with hydrogen on a BaF2 cold plate at liquid-helium temperature was studied. 相似文献
24.
《Tetrahedron letters》2004,45(21):4081-4084
β-d-Gluco and mannopyranosyl selenoureas have been prepared by coupling of the corresponding glycosylamines with phenyl isoselenocyanate in aqueous pyridine. Alkyl and aryl isoselenocyanates, and 1,4-phenylene diisoselenocyanate have been obtained from the corresponding formamides with an excess of triphosgene, black selenium and triethylamine. Treatment of the O-unprotected β-d-glucopyranosyl selenourea with aqueous oxygen peroxide afforded a 1,2-trans-fused bicyclic isourea. 相似文献
25.
Periodic, self-consistent, density functional theory (GGA-PW91) calculations are performed for both surface and subsurface atomic hydrogen on and in Ni(1 1 1). At a low coverage (θ=0.25 ML), the binding energies (BEs) of a hydrogen atom in surface fcc, subsurface octahedral (first layer), and subsurface octahedral (second layer) sites are −2.89, −2.18, and −2.11 eV, respectively. The activation energy barriers for hydrogen diffusion from the surface to the first subsurface layer and from the first to the second subsurface layer are estimated to be 0.88 and 0.52 eV, respectively. In the entire coverage range studied, hydrogen occupies surface fcc and hcp sites and subsurface octahedral sites. In addition, the magnitude of the BE per hydrogen atom and the magnetization of the nickel slabs both decrease as hydrogen coverage increases. Vibrational frequencies of hydrogen at various surface and subsurface sites are calculated and are in reasonable agreement with experimental data. A phase stability calculation with a 2 × 2 surface unit cell shows that a p(2 × 2)-2H overlayer structure (θ=0.5 ML) and a p(1 × 1)-1H structure (θ=1.0 ML) are stable at low hydrogen pressures, in agreement with numerous experimental results. A very large increase in pressure is required to populate subsurface sites. After such an increase occurs, the first subsurface layer is filled completely. 相似文献
26.
Summary Six commercial hydrogen standards containing helium, oxygen, nitrogen, methane and carbon dioxide at trace levels were analyzed
by gas chromatography, for periods up to 105 days. The concentrations, in the range of 0–120 μmol mol−1, were stable (with the exception of oxygen) but often significantly different from the certified values provided by the suppliers,
especially for helium, oxygen and nitrogen. Concurrently, some experiments were carried out to verify the stability of gas
mixtures based on hydrogen stored in cylinders submitted to different chemical and physical treatments. The causes that led
to the deviations observed, as well as the decreases in oxygen, are discussed.
Presented at the 21st ISC held in Stuttgart, Germany, 15th–20th September, 1996. 相似文献
27.
C. Scheidenberger K. Beckert P. Beller F. Bosch C. Brandau D. Boutin L. Chen B. Franzke H. Geissel R. Knöbel C. Kozhuharov J. Kurcewicz S. A. Litvinov Yu. A. Litvinov M. Mazzocco G. Münzenberg F. Nolden W. R. Plaß M. Steck B. Sun H. Weick M. Winkler 《Hyperfine Interactions》2006,173(1-3):61-66
One important goal of the ILIMA project at FAIR is the study of masses and decay properties of relativistic isomeric beams
stored and cooled in the planned storage-ring complex. A new scheme is described, where a storage-cooler ring is used for
high-resolution mass separation. Experimental results on the separation of the isobaric pair 140Pr-140Ce are presented.
P. Beller, deceased. 相似文献
28.
Wolfgang H. Binder Laura Petraru Robert Sachenshofer Ronald Zirbs 《Monatshefte für Chemie / Chemical Monthly》2006,137(7):835-841
Summary. The surface modification of nanoparticles via azide/alkine-1,3-dipolar cycloaddition-reactions is described. Ligand exchange onto various nanoparticles was monitored by
1H NMR spectroscopy and formed the basis for the attachment of ligands onto the nanoparticles and their subsequent modification
by dipolar cycloaddition reactions. Nanoparticle-surfaces were monitored by binding onto self-assembled monolayers derivatized
with matching supramolecular interactions after derivatization. 相似文献
29.
Hynd Remita Prem Felix Siril Israel-Martyr Mbomekalle Bineta Keita Louis Nadjo 《Journal of Solid State Electrochemistry》2006,10(7):506-511
Three Pt-based catalysts prepared in different radiolytic conditions and supported on graphite powder were packed into a carbon paste electrode configuration. They were compared to each other, to the commercial (Pt) deposited on activated carbon powder (Johnson Matthey) and to pure Vulcan XC-72 for their respective abilities toward the hydrogen evolution reaction (HER). The Tafel parameters were determined for all these electrodes. From the I–V curves and their quantitative treatment, the following order of activity emerged unambiguously and reads: (PtCO)2 (fcc structure) > (PtCO)1 (Chini cluster) > (Pt)neat > (Pt)JM (Johnson Matthey) ≫ (Vulcan XC-72). As expected, all the Pt-loaded electrodes were more efficient than Vulcan XC-72. The classification appears to be linked with the mean nanoparticle size, and for comparable sizes, with the surface morphology of the materials. The results and the stability of the electrodes suggest that the small particle sizes and the good dispersity on the carbon support were maintained during the HER. 相似文献
30.