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101.
102.
Ernó Kuzmann Sándor Nagy Zoltán Homonnay Attila Vértes István Halász Miklós Gál Béla Csákvári Kornél Torkos József Bánkúti István Kirschner Yen Wei Amar Nath 《Structural chemistry》1991,2(3-4):(59)267-(67)275
151Eu,119Sn,57Fe, and57Co Mössbauer spectroscopy was used to study YBa2Cu3O7– high-Tc superconductors in which sites were replaced by various Mössbauer nuclides in order to get information about site preference and structural changes. By decomposition of the Mössbauer spectra, the Y site substituted by Eu and the Cu sites occupied by Sn, Fe, and Co substituents were identified. It was found that Fe and Co prefer the Cu(1) site while Sn prefers the Cu(2) site in the orthorhombic perovskite lattice of these superconductors. The site preference is enhanced in the presence of additional substituents. A sequence of thermal heat treatments permits reversible cycling of57Co between the two copper sites in the YBa2[Cu(57Co)]3O7– perovskite. In all cases Eu(III) and Sn(IV) states are determined, but the valence state of Fe and Co can be both three and four. BelowT
c, low-temperature phase transformation and phonon softening were shown from the anomalous temperature dependence of isomer shifts and the area fractions of151Eu and119Sn Mössbauer spectra of EuBa2(Cu1-xSnx)3O7- cuprates. 相似文献
103.
K. Yuan R. J. Kahan C. Si A. Williams S. Kirschner M. Uzelac E. Zysman-Colman M. J. Ingleson 《Chemical science》2020,11(12):3258
The synthesis of a range of brominated-Bn-containing (n = 1, 2) polycyclic aromatic hydrocarbons (PAHs) is achieved simply by reacting BBr3 with appropriately substituted alkynes via a bromoboration/electrophilic C–H borylation sequence. The brominated-Bn-PAHs were isolated as either the borinic acids or B-mesityl-protected derivatives, with the latter having extremely deep LUMOs for the B2-doped PAHs (with one example having a reduction potential of E1/2 = −0.96 V versus Fc+/Fc, Fc = ferrocene). Mechanistic studies revealed the reaction sequence proceeds by initial alkyne 1,1-bromoboration. 1,1-Bromoboration also was applied to access a number of unprecedented 1-bromo-2,2-diaryl substituted vinylboronate esters directly from internal alkynes. Bromoboration/C–H borylation installs useful C–Br units onto the Bn-PAHs, which were utilised in Negishi coupling reactions, including for the installation of two triarylamine donor (D) groups onto a B2-PAH. The resultant D–A–D molecule has a low optical gap with an absorption onset at 750 nm and emission centered at 810 nm in the solid state.The synthesis of a range of brominated-Bn-containing (n = 1, 2) polycyclic aromatic hydrocarbons (PAHs) is achieved simply by reacting BBr3 with appropriately substituted alkynes via a bromoboration/electrophilic C–H borylation sequence. 相似文献
104.
Montero Gerardo A. Kirschner Todd F. Tanner Robert D. 《Applied biochemistry and biotechnology》1993,39(1):467-475
Applied Biochemistry and Biotechnology - Experiments were conducted to determine the effect of pH and sparging-gas composition on the bubble and foam separation of an aqueous protein solution.... 相似文献
105.
Carbonyl sulfide is the most abundant sulfur gas in the atmosphere. We have used MP2 and CCSD(T) theory to study the structures and thermochemistries of carbonyl sulfide interacting with one to four water molecules. We have completed an extensive search for clusters of OCS(H2O)n , where n = 1-4. We located three dimers, two trimers, five tetramers, and four pentamers with the MP2/aug-cc-pVDZ method. In each of the complexes with two or more waters, OCS preferentially interacts with low-energy water clusters. Our results match current theoretical and experimental literature, showing correlation with available geometries and frequencies for the OCS(H2O) species. The CCSD(T)/aug-cc-pVTZ thermochemical values combined with the average amount of OCS and the saturated concentration of H2O in the troposphere, lead to the prediction of 10(6) OCS(H2O) clusters x cm(-3) and 10(2) OCS(H2O)2 clusters x cm(-3) at 298 K. We predict the structures of OCS(H2O)n , n = 1-4 that should predominate in a low-temperature molecular beam and identify specific infrared vibrations that can be used to identify these different clusters. 相似文献
106.
F.?DorfbauerEmail author T.?Schrefl D.?Suess M.?Kirschner G.?Hrkac J.?Fidler 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,45(2):267-271
Micromagnetic simulations of a pulsed inductive microwave magnetometer (PIMM) experiment are performed using a well established model for exchange bias. The model (Interacting Grain Model) consists of ferromagnetic grains and antiferromagnetic grains with randomly distributed easy axes. A perfectly compensated interface between the ferromagnet and the antiferromagnet is assumed which leads to spin flop coupling. The antiferromagnetic layer is modelled as two totally antiparallel sublattices with a small intergrain exchange between each antiferromagnetic sublattice. Simulations of an experimental PIMM setup provide a shift of the minimum of the resonance frequency which is also observered experimentally. 相似文献
107.
Finken KH Abdullaev SS de Bock MF von Hellermann M Jakubowski M Jaspers R Koslowski HR Krämer-Flecken A Lehnen M Liang Y Nicolai A Wolf RC Zimmermann O de Baar M Bertschinger G Biel W Brezinsek S Busch C Donné AJ Esser HG Farshi E Gerhauser H Giesen B Harting D Hoekzema JA Hogeweij GM Hüttemann PW Jachmich S Jakubowska K Kalupin D Kelly F Kikuchi Y Kirschner A Koch R Korten M Kreter A Krom J Kruezi U Lazaros A Litnovsky A Loozen X Lopes Cardozo NJ Lyssoivan A Marchuk O Matsunaga G Mertens P 《Physical review letters》2005,94(1):015003
The first results of the Dynamic Ergodic Divertor in TEXTOR, when operating in the m/n=3/1 mode configuration, are presented. The deeply penetrating external magnetic field perturbation of this configuration increases the toroidal plasma rotation. Staying below the excitation threshold for the m/n=2/1 tearing mode, this toroidal rotation is always in the direction of the plasma current, even if the toroidal projection of the rotating magnetic field perturbation is in the opposite direction. The observed toroidal rotation direction is consistent with a radial electric field, generated by an enhanced electron transport in the ergodic layers near the resonances of the perturbation. This is an effect different from theoretical predictions, which assume a direct coupling between rotating perturbation and plasma to be the dominant effect of momentum transfer. 相似文献
108.
A spin-dependent three-step photoemission formalism for non-magnetic crystals is outlined, in which unpolarized Bloch electrons are diffracted at the surface. Assuming no spin dependence of the excitation process in the bulk, appreciable spin polarization features are obtained for W(001) at off-normal emission, in fairly good agreement with the first angle- and energy-resolved measurements of photo-electron spin polarization (using unpolarized light). 相似文献
109.
110.