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61.
Wang JG Li WX Borg M Gustafson J Mikkelsen A Pedersen TM Lundgren E Weissenrieder J Klikovits J Schmid M Hammer B Andersen JN 《Physical review letters》2005,95(25):256102
Using core-level spectroscopy and density functional theory we show that a one-dimensional (1D) oxide structure forms at the steps of the Pt(332) surface after exposure. The 1D oxide is found to be stable in an oxygen pressure range, where bulk oxides are only metastable, and is therefore argued to be a precursor to the Pt oxidation. As an example of the consequences of such a precursor exclusively present at the steps, we investigate the reaction of CO with oxygen covered Pt(332). Albeit more strongly bound, the oxidic oxygen is found to react more easily with CO than oxygen chemisorbed on the Pt terraces. 相似文献
62.
Se vapor pressures were measured by the dew point method for the binary system Ga1·xSex, 0.60 < x < 1.00 (Ga2Se3-Se), between 700 and 1050°C. The Se vapor pressure was found to decrease rapidly near x = 60 atomic% Se. The T-X and P-X liquidus curves are thermodymanically modelled by a regular associated solution model for the liquid phase, with the associate, Ga2Se3. The best fit to the data was obtained with 4000 cal/mole of Ga2Se3 for the regular solution interaction parameter and 0.10 for the degree of dissociation in the stoichiometric liquid (x = 0.60). 相似文献
63.
From measurements on single crystals of Li2Ti3O7, the conductivity is determined to be predominately ionic with an anisotropy of and . This anisotropy is significant but is not sufficient to classify this channel-structured ramsdellite material as a one-dimensional conductor. A conduction path through the ramsdellite crystal structure consistent with the determined anisotropy is presented. 相似文献
64.
65.
Weissenrieder J Mikkelsen A Andersen JN Feibelman PJ Held G 《Physical review letters》2004,93(19):196102
Core-level photoelectron spectra, in excellent agreement with ab initio calculations, confirm that the stable wetting layer of water on Ru[0001] contains O-H and H2O in roughly 3:5 proportion, for OHx coverages between 0.25 and 0.7 ML, and T<170 K. Proton disorder explains why the wetting structure looks to low energy electron diffraction (LEED) to be an ordered p(square root of 3 x square root of 3)R30 degrees adlayer, even though approximately 3/8 of its molecules are dissociated. Complete dissociation to atomic oxygen starts near 190 K. Low photon flux in the synchrotron experiments ensured that the diagnosis of the nature of the wetting structure quantified by LEED is free of beam-induced damage. 相似文献
66.
I. V. Naumov V. V. Rahmanov V. L. Okulov C. M. Velte K. E. Meyer R. F. Mikkelsen 《Thermophysics and Aeromechanics》2012,19(2):171-181
This paper presents results of a study of vortex wake structures and measurements of instantaneous 3D velocity fields downstream of a triblade turbine model. Two operation modes of flow around the rotor with different tip speed ratios were tested. Initially the wake structures were visualized and subsequently quantitative data were recorded through velocity field restoration from particle tracks using a stereo PIV system. The study supplied flow diagnostics and recovered the instantaneous 3D velocity fields in the longitudinal cross section behind a tribladed rotor at different values of tip speed ratio. This set of data provided a basis for testing and validating assumptions and hypothesis regarding classical theories of rotors. 相似文献
67.
Viktor Bliksted Roug Pedersen Jeppe Granhøj Andreas Erbs Hillers-Bendtsen Prof. Dr. Anders Kadziola Prof. Dr. Kurt V. Mikkelsen Prof. Dr. Mogens Brøndsted Nielsen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(32):8315-8324
Polycyclic aromatic hydrocarbons (PAHs) have found strong interest for their electronic properties and as model systems for graphene. While PAHs have been studied intensively as single units, here PAHs were constructed in ladder-type arrangements using cross-conjugated fulvalene and dithiafulvalene motifs as connecting units and moving forward a convenient synthetic approach for dimerizing (thio)ketones into olefins by the action of Lawesson's reagent. Some of the PAHs can also be regarded as “super-extended” tetrathiafulvalenes (TTFs) with some of the largest cores ever explored, being multi-redox systems that exhibit both reversible oxidations and reductions. Concomitant absorption redshifts were observed when expanding the ladder-type structures from one to two to three indenofluorene units, and optical and electrochemical HOMO-LUMO gaps were found to correlate linearly. Various conformations (and solid-state packing arrangements) were studied by X-ray crystallography and computations. 相似文献
68.
Alvis Mengots Andreas Erbs Hillers-Bendtsen Dr. Sandra Doria Frederik Ørsted Kjeldal Nicolai Machholdt Høyer Dr. Anne Ugleholdt Petersen Prof. Dr. Kurt V. Mikkelsen Dr. Mariangela Di Donato Prof. Dr. Martina Cacciarini Prof. Dr. Mogens Brøndsted Nielsen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(48):12437-12446
Photoswitch triads comprising two dihydroazulene (DHA) units in conjugation with a central trans-azobenzene (AZB) unit were prepared in stepwise protocols starting from meta- and para-disubstituted azobenzenes. The para-connected triad had significantly altered optical properties and lacked the photoactivity of the separate photochromes. In contrast, for the meta-connected triad, all three photochromes could be photoisomerized to generate an isomer with two vinylheptafulvene (VHF) units and a cis-azobenzene unit. Ultrafast spectroscopy of the photoisomerizations revealed a fast DHA-to-VHF photoisomerization and a slower trans-to-cis AZB photoisomerization. This meta triad underwent thermal VHF-to-DHA back-conversion with a similar rate of all VHFs, independent of the identity of the neighboring units, and in parallel thermal cis-to-trans AZB conversion. The experimental observations were supported by computation (excitation spectra and orbital analysis of the transitions). 相似文献
69.
M L Sandvold A Mikkelsen A Elgsaeter 《Acta chemica Scandinavica (Copenhagen, Denmark : 1989)》1989,43(8):783-786
The frequency dependence (119-7860 Hz) of the storage and loss shear moduli, G' and G', of human erythrocyte spectrin dimer crude solutions at 22.5 degrees C has been measured using a Birnboim-Schrag multiple lumped resonator viscoelastometer. The measurements were carried out on solutions of ionic strength 1 mM containing 1.1-3.7 mg ml-1 spectrin. This corresponds to the terminal zone for G' and G'. Analysis of the data using the standard theory of hybrid relaxation spectra yields a relaxation time of 22.5 +/- 1 microseconds. The pure spectrin dimer relaxation time is estimated to be 16 +/- 3 microseconds. This result suggests that at an ionic strength of 1 mM, the spectrin dimers are extended and that the main relaxation process is simple end-over-end rotation. 相似文献
70.
We consider methods for determining properties of molecules between electrodes. We utilize a heterogeneous and structured solvation model for describing the physical situation of a molecule located between electrodes. This method includes directly the polarization terms of the surrounding environment in the quantum mechanical equations.Contribution to the Jacopo Tomasi Honorary Issue 相似文献