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101.
The adsorption of water on perfect TiO(2)(110) surface is studied by quantum molecular dynamics simulation adopting a periodic model formed by five water molecules on a (5 x 1) surface unit cell of a five layer slab of TiO(2). The total simulation time is 3.2 ps. At about 1.3 ps, one water molecule dissociates with the help of other adsorbed waters and surface bridging oxygens. During the remaining 1.9 ps, the waters and OH groups vibrate, but no more dissociation or recombination is observed. By comparing recent experimental O1s photoemission (x-ray photoelectron spectroscopy) spectra of H(2)O/TiO(2)(110) to the computed spectrum of the adsorbate in the configurations supplied by the molecular dynamics simulation, the observed peaks can be attributed to different oxygen species. The proposed assignment of the main spectral features supports the occurrence of partial water dissociation (approximately 20%) also on a perfect TiO(2) surface. 相似文献
102.
Studies focusing on different groups of students show that the prevalence of vocal symptoms and voice disorder vary depending on the study populations. A previous study of vocal symptoms and voice disorders among teacher students has shown that 20% of the students studying to become teachers in comprehensive schools and upper secondary schools reported frequently occurring vocal symptoms, ie, two symptoms or more occurring weekly or more often during the past year, and that most of these students had an organic voice disorder. This raised the question of whether other university students would also report similar, frequently occurring vocal symptoms. A questionnaire was distributed to 220 students of several faculties at the University of Turku, Finland. The results were compared with the results of a study of vocal symptoms reported by 175 students studying to become teachers. This comparison showed that students in general reported frequently occurring vocal symptoms, whereas the students studying to become teachers reported a greater number of frequently occurring symptoms than did other students at the university. 相似文献
103.
104.
Molecular dynamics simulations are carried out to study the adsorption of three lipids, namely, DOPC, DOPS, and DMTAP, on TiO2(110) rutile surfaces and the influence of the interface on their conformational properties. Three types of rutile (110) surfaces, characterized by a different degree of hydroxylation (the neutral nonhydroxylated and hydroxylated surfaces and a partially hydroxylated surface with charge density corresponding to physiological pH) are investigated using force fields derived from ab initio calculations and experimental data. It is found that the stability of the adsorbate and the strength of the attachment are strictly connected with the nature of both the lipid and the surface. Direct coordination of the phosphate or carbonyl oxygens of the lipids with available titanium sites, observed in the case of partially or nonhydroxylated layers, determines stronger adsorption and, as a consequence, reduced dynamics. For a given hydration state of the surface, the adsorption strengths are in the order DOPS > DOPC > DMTAP, in agreement with experimental data according to which the presence of DOPS units inside lipid bilayers favors stronger adsorption and lower mobility. The adsorption geometry, the hydration state of the lipid headgroups, and the dynamical processes (detachment, diffusion, etc.) occurring at the lipid/oxide interface are analyzed in detail, putting on a roughly quantitative basis time scales and energy barriers of the latter processes. 相似文献
105.
106.
Veronica Felli Elsa M. Marchini Susanna Terracini 《Journal of Functional Analysis》2007,250(2):265-316
Positivity, essential self-adjointness, and spectral properties of a class of Schrödinger operators with multipolar inverse-square potentials are discussed. In particular a necessary and sufficient condition on the masses of singularities for the existence of at least a configuration of poles ensuring the positivity of the associated quadratic form is established. 相似文献
107.
Evaluation of volatile chlorinated hydrocarbons distribution along depth profiles in the Ross Sea, Antarctica 总被引:1,自引:0,他引:1
The presence and the distribution along depth profiles of volatile chlorinated hydrocarbons (VCHCs) were evaluated in seawater samples collected in the Ross Sea (Southern Ocean, Antarctica) during the 2002-2003 Italian expedition. Sampling areas were located where the Circumpolar Deep Water interacts with the shelf waters that supply the Ross Sea.The VCHCs investigated were: 1,1,1-trichloroethane (C2H3Cl3), tetrachloromethane (CCl4), trichloroethylene (C2HCl3), tetrachloroethylene (C2Cl4). The analytical procedure consisted of a liquid-liquid extraction carried out with n-hexane directly in Antarctica, followed by gas chromatographic analysis with electron capture detection carried out in Italy.Concentration levels for the VCHCs analysed ranged from digits to hundreds of ng/L according to the station, depth and substance considered. Important differences in concentration levels between the three stations near the Ross Ice Shelf and the two stations located in the Cape Adare area were observed. In particular the stations situated in the Cape Adare zone, at certain depths, showed a thermal inversion due to the mixing of the Circumpolar Deep Water with the waters generated inside the Ross Sea Basin. The lowest concentration levels were recorded at this temperature increase. 相似文献
108.
J. John H. Filipská K. Černochová P. Beneš M. Semelová J. Bočan G. Geipel V. Kubeček 《Czechoslovak Journal of Physics》2006,56(1):D565-D568
Early in 2006, construction and equipment of a new TRLFS (Time-Resolved Laser-induced Fluorescence Spectroscopy) laboratory
was accomplished at the Czech Technical University in Prague, Czech Republic. In this contribution, the system is described
in detail, the results of the first measurements obtained in the new laboratory for a standard UO
2
2+
- SO
4
2−
system are presented, and the future research plans are outlined. 相似文献
109.
110.