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61.
V. Jedináková L. Kuča M. Vojtíšková 《Journal of Radioanalytical and Nuclear Chemistry》1980,59(1):125-132
We have investigated the effect of coextraction of lanthanides and yttrium on the distribution coefficients DAm in the extraction of americium by benzyldimethyldodecylammonium nitrate (BDMLNNO3) from nitrate solutions. In the coextraction of lanthanides, the extraction of Am(NO3)3 is suppressed, which is markedly manifested in the extraction of light lanthanides (La, Ce, Pr); of the series of lanthanides their extraction is the highest. The effect of nitric acid and the possibility of separation of lanthanides and americium by the application of three-stage multiple extraction is discussed. 相似文献
62.
Electrosorption of hydrogen into palladium-gold alloys 总被引:1,自引:0,他引:1
M. Łukaszewski K. Kuśmierczyk J. Kotowski H. Siwek A. Czerwiński 《Journal of Solid State Electrochemistry》2003,7(2):69-76
Hydrogen electrosorption into Pd-Au alloys has been studied in acidic solutions (1 M H2SO4) using cyclic voltammetry. Pd-Au electrodes with limited volume were prepared by electrochemical co-deposition. It was found
that the maximum H/(Pd+Au) ratios decrease monotonically with increasing gold content and reach zero at ca. 70 at% Au. Similarly
to the case of Pd limited volume electrodes, two peaks in the hydrogen region, corresponding to two types of sorbed hydrogen,
are observed on voltammograms for Pd-rich alloys. The hydrogen capacity, H/(Pd+Au), measured electrochemically, depends on
the sweep rate in the cyclic voltammetry experiments, which suggests that two different mechanisms for hydrogen desorption
from the Pd-Au alloy are possible. After a strong decrease of Pd concentration at the electrode surface, caused by long cyclic
polarization to sufficiently anodic potentials, the amount of absorbed hydrogen is still significant for alloys initially
rich in Pd. The results obtained from CO adsorption experiments suggest that only Pd atoms are active in the hydrogen absorption/desorption
process.
Electronic Publication 相似文献
63.
Summary A comparison of three binary mobile phases in LC separation of C60 and C70 fullerences on chemically bonded 2,4-dinitroanilinopropyl (DNAP) stationary phase was carried out, n-Hexane-benzene has been found to be the best mobile phase for efficient separation of the all-carbon molecules permitting high loads in preparative LC. 相似文献
64.
We characterized valence anionic states of 1-methylcytosine using various electronic structure methods. We found that the most stable valence anion is related to neither the canonical amino-oxo nor a rare imino-oxo tautomer, in which a proton is transferred from the N4 to N3 atom. Instead, it is related to an imino-oxo tautomer, in which the C5 atom is protonated. This anion is characterized by an electron vertical detachment energy (VDE) of 2.12 eV and it is more stable than the anion based on the canonical tautomer by 1.0 kcal/mol. The latter is characterized by a VDE of 0.31 eV. Another unusual low-lying imino-oxo tautomer with a VDE of 3.60 eV has the C6 atom protonated and is 3.6 kcal/mol less stable than the anion of the canonical tautomer. All these anionic states are adiabatically unbound with respect to the canonical amino-oxo neutral, with the instability of 5.8 kcal/mol for the most stable valence anion. The mechanism of formation of anionic tautomers with carbon atoms protonated may involve intermolecular proton transfer or dissociative electron attachment to the canonical neutral tautomer followed by a barrier-free attachment of a hydrogen atom to the C5 or C6 atom. The six-member ring structure of anionic tautomers with carbon atoms protonated is unstable upon an excess electron detachment. Indeed the neutral systems collapse without a barrier to a linear or a bicyclo structure, which might be viewed as lesions to DNA or RNA. Within the PCM hydration model, the anions become adiabatically bound with respect to the corresponding neutrals, and the two most stable tautomers have a carbon atom protonated. 相似文献
65.
The structure of bis(dimethylammonium) pentachloroantimonate(III), [(CH3)2NH2]2[SbCl5], BDP, was studied at 15 K and ambient pressure by single-crystal X-ray diffraction as well as at ambient temperature and high pressures up to 4.87(5) GPa by Raman spectroscopy. BDP crystallizes in the orthorhombic Pnma space group with a=8.4069(4), b=11.7973(7), c=14.8496(7) Å, and Z=4; R1=0.0381, wR2=0.0764. The structure consists of distorted [SbCl6]3− octahedra forming zig-zag [{SbCl5}n]2n− chains that are cross-linked by dimethylammonium [(CH3)2NH2]+ cations. The organic and inorganic substructures are bound together by the N-H…Cl hydrogen bonds. The distortions of [SbCl6]3− units increase, partly due to the influence of the hydrogen bonds which became stronger, with decreasing temperature. The preliminary room temperature, high-pressure X-ray diffraction experiments suggest that BDP undergoes a first-order phase transition below ca. 0.44(5) GPa that destroys single-crystal samples. The transition is accompanied by changes in the intensities and positions of the Raman lines below 400 cm−1. 相似文献
66.
Maciej Bujak Jacek Zaleski Victor Prezhdo Boris Uspenskiy 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(2):o76-o77
The title molecule, C11H12O3, is almost planar, with an average deviation of the C and O atoms from the least‐squares plane of 0.146 (4) Å. The geometry about the C=C bond is trans. The phenyl ring and –COOCH3 group are twisted with respect to the double bond by 9.3 (3) and 5.6 (5)°, respectively. The endocyclic angle at the junction of the propenoate group and the phenyl ring is decreased from 120° by 2.6 (2)°, whereas two neighbouring angles around the ring are increased by 2.3 (2) and 0.9 (2)°. This is probably associated with the charge‐transfer interaction of the phenyl ring and –COOCH3 group through the C=C double bond. The molecules are joined together through C—H?O hydrogen bonds between the methoxy and ester groups to form characteristic zigzag chains extended along the c axis. 相似文献
67.
Dabkowska I Rak J Gutowski M Nilles JM Stokes ST Bowen KH 《The Journal of chemical physics》2004,120(13):6064-6071
The photoelectron spectrum of the uracil-alanine anionic complex (UA)(-) has been recorded with 2.540 eV photons. This spectrum reveals a broad feature with a maximum between 1.6 and 2.1 eV. The vertical electron detachment energy is too large to be attributed to an (UA)(-) anionic complex in which an intact uracil anion is solvated by alanine, or vice versa. The neutral and anionic complexes of uracil and alanine were studied at the B3LYP and second-order M?ller-Plesset level of theory with 6-31++G(*) (*) basis sets. The neutral complexes form cyclic hydrogen bonds and the three most stable neutral complexes are bound by 0.72, 0.61, and 0.57 eV. The electron hole in complexes of uracil with alanine is localized on uracil, but the formation of a complex with alanine strongly modulates the vertical ionization energy of uracil. The theoretical results indicate that the excess electron in (UA)(-) occupies a pi(*) orbital localized on uracil. The excess electron attachment to the complex can induce a barrier-free proton transfer (BFPT) from the carboxylic group of alanine to the O8 atom of uracil. As a result, the four most stable structures of the uracil-alanine anionic complex can be characterized as a neutral radical of hydrogenated uracil solvated by a deprotonated alanine. Our current results for the anionic complex of uracil with alanine are similar to our previous results for the anion of uracil with glycine, and together they indicate that the BFPT process is not very sensitive to the nature of the amino acid's hydrophobic residual group. The BFPT to the O8 atom of uracil may be relevant to the damage suffered by nucleic acid bases due to exposure to low energy electrons. 相似文献
68.
69.
Jakub Čížek Ivan Procházka Radomír Kužel Rinat K. Islamgaliev 《Monatshefte für Chemie / Chemical Monthly》2002,133(6):873-887
Summary. Ultra-fine grained (UFG) Cu (grain size 80 nm) containing 0.5 wt.% Al2O3 nanoparticles (size 20 nm) was prepared by high pressure torsion (HPT). Positron lifetime spectroscopy was employed to characterize
the microstructure of this material, especially with respect to types and concentration of lattice defects. The evolution
of microstructure with increasing temperature was studied by positron lifetime spectroscopy and X-ray diffraction measurements.
The thermal stability of the Cu + 0.5 wt.% Al2O3 nanocomposite was compared with that of pure UFG Cu prepared by the same technique. The processes taking place during thermal
recovery of the initial nanoscale structure in both studied materials are described.
Received October 5, 2001. Accepted (revised) December 20, 2001 相似文献
70.
Kuśtrowski P Chmielarz L Dziembaj R Cool P Vansant EF 《The journal of physical chemistry. A》2005,109(2):330-336
The novel mesoporous templated silicas (MCM-48, SBA-15, MCF, and MSU) were used as supports for transition metal (Cu, Cr, or Fe) oxides. The catalysts were synthesized using the incipient wetness impregnation, and characterized by low-temperature N2 sorption, DRIFT, photoacoustic IR spectroscopy, UV-vis diffuse reflectance spectroscopy, and temperature-programmed desorption of ammonia. It was shown that the preparation method used results in different distributions and dimensions of the transition metal oxide clusters on the inert support surface. The prepared catalysts were tested in the reaction of oxidative dehydrogenation of ethylbenzene in the presence of nitrous oxide. The iron-containing catalysts showed the highest catalytic activity. The presence of isolated Fe3+ was found to be the most important factor influencing the ethylbenzene conversion. The undesirable effect of the increase in selectivity toward CO2 was observed for the samples with the highest concentrations of acidic surface sites. 相似文献