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排序方式: 共有193条查询结果,搜索用时 15 毫秒
51.
V. Ney S. Ye T. Kammermeier K. Ollefs A. Ney T.C. Kaspar S.A. Chambers F. Wilhelm A. Rogalev 《Journal of magnetism and magnetic materials》2010,322(9-12):1232-1234
We compare the magnetic properties of two types of Co-doped ZnO films grown on sapphire with distinct structural quality. SQUID magnetometry as well as element-specific synchrotron studies reveal pure paramagnetic behavior for the samples with the highest structural quality, whereas samples with reduced structural quality exhibit superparamagnetic blocking behavior. In this sample signatures of phase separation are detected by X-ray diffraction and X-ray linear dichroism which accounts for the superparamagnetic blocking. 相似文献
52.
53.
Michele Ghisletta Kaspar Hegetschweiler Hans-Peter Jalett Tobias Gerfin Volker Gramlich 《Helvetica chimica acta》1992,75(7):2233-2242
A new, convenient, and safe route to 1,3,5-triamino-1,3,5-trideoxy-cis-inositol (taci) was investigated by hydrogenation of azo-coupled derivatives of phloroglucinol. In the presence of acetic anhydride, the reduction of trisphenylazophloroglucinol (H2/Pd(5%) on C) resulted in the formation of tri-, hexa-, and nona-acetylated derivatives of triaminophloroglucinol. All three compounds are air-stable, colorless solids. However, the succeeding hydrogenation to the cyclohexane derivative failed. Trisodiumtris(p-sulfonatophenylazo)phloroglucinol could be hydrogenated in a one-pot reaction to the desired taci· 1.5H2SO4 using a Pt/Rh oxide as catalyst. taci provides two distinct chair conformations with either three amino or three hydroxy groups for metal binding. The unique metal-binding properties are discussed in terms of minimal conformational changes required for coordination. Conformational analysis, based on X-ray structural data of [BiCl6][H3(taci)] ·2 H2O (Pnma, a = 24.314 (5) Å, b = 10.215 (2) Å, c = 7.422 (8) Å, R = 5.8%) and [Co(taci)2(NO3)3]·2H2O (C2/c, a = 22.912 (8) Å, b = 8.942 (2) Å, c = 14.731 (3) Å, β = 128.66 (2)°, R = 4.9%) and the previously investigated [Cr(taci)2]3+ revealed an almost ideal chair conformation in all three molecules. 相似文献
54.
Morgenstern B Steinhauser S Hegetschweiler K Garribba E Micera G Sanna D Nagy L 《Inorganic chemistry》2004,43(10):3116-3126
The complex formation of vanadium(IV) with 1,3,5-triamino-1,3,5-trideoxy-cis-inositol (taci) and 1,3,5-trideoxy-1,3,5-tris(dimethylamino)-cis-inositol (tdci) was studied in aqueous solution and in the solid state. The formation constants of [V(IV)O(taci)](2+), [V(IV)O(tdci)](2+), and [V(IV)(tdci)(2)](4+) and of the deprotonation product [V(IV)(tdci)(2)H(-)(1)](3+) were determined (25 degrees C, 0.1 M KNO(3)). Cyclic voltammetry measurements established a reversible one-electron transfer for the [V(IV)(tdci)(2)H(-)(m)]((4)(-)(m))/[V(III)(tdci)(2)H(-)(n)]((3)(-)(n)) couple (0 相似文献
55.
56.
I. Peter W. von Oertzen S. Thummerer H.G. Bohlen B. Gebauer J. Gerl M. Kaspar I. Kozhoukharov T. Kröll M. Rejmund H.J. Wollersheim I.J. Thompson 《The European Physical Journal A - Hadrons and Nuclei》2003,16(4):509-525
At energies below the Coulomb barrier, neutron transfer and Coulomb excitation have been measured in a very heavy asymmetric
nuclear system, in 206Pb + 118Sn. These are semi-magic nuclei showing super-fluid properties. Particle-γ coincidence techniques using 5 Euroball Cluster
detectors (EB), combined in a set-up with the Heidelberg-Darmstadt NaI Crystal Ball (CB), have been used. Position-sensitive
detectors allowed the observation of scattering processes covering angles from 110 up to 150 degrees. The fragments are identified
via the known γ-decays of the lowest excited states using the high resolution of EB. Using the unique feature of the set-up
with the CB, transfer to well-defined final channels with known quantum numbers is selected using the high-efficiency multiplicity
filter of the CB with no second γ-ray, i.e. without feeding. The data are analysed using the semi-classical approach and transfer probabilities are obtained. Coulomb
excitation has been analysed using known transition probabilities. The enhancement is deduced for the two-neutron transfer
populating the low-lying super-fluid 2+ states in 120Sn and 116Sn, while the 2n transition remains in the ground state for the 20NPb nuclei. Large enhancements up to EF ≃ 103 are observed. This is the first observation of neutron pair transfer enhancement for a heavy nuclear binary system with super-fluid
properties with experimentally separated levels. The calculations with microscopic 2-neutron wave functions, with configuration
mixing over six shell model configurations and using the coupled reaction channels approach, reproduce well the observed probabilities
and the enhancement.
Received: 27 August 2002 / Accepted: 9 December 2002 / Published online: 25 March 2003
RID="a"
ID="a"e-mail: oertzen@hmi.de
Communicated by D. Schwalm 相似文献
57.
Kaspar TC Heald SM Wang CM Bryan JD Droubay T Shutthanandan V Thevuthasan S McCready DE Kellock AJ Gamelin DR Chambers SA 《Physical review letters》2005,95(21):217203
We reexamine the mechanism of ferromagnetism in doped TiO(2) anatase, using epitaxial Cr:TiO(2) with excellent structural quality as a model system. In contrast to highly oriented but defective Cr:TiO(2) (approximately 0.5 micro(b)/Cr), these structurally superior single crystal films exhibit negligible ferromagnetism. Similar results were obtained for Co:TiO(2). We show for the first time that charge-compensating oxygen vacancies alone, as predicted by F-center mediated exchange, are not sufficient to activate ferromagnetism. Instead, the onset of ferromagnetism correlates with the presence of structural defects. 相似文献
58.
59.
Appel R Atoyan GS Bassalleck B Bergman DR Brown DN Cheung N Dhawan S Do H Egger J Eilerts S Felder C Fischer H Gach M Herold W Issakov VV Kaspar H Kraus DE Lazarus DM Leipuner L Lichard P Lowe J Lozano J Ma H Majid W Menzel W Pislak S 《Physical review letters》2000,85(12):2450-2453
We report results of a search for the lepton-family number violating decay K+-->pi(+)&mgr;(+)e(-) from data collected by experiment E865 in 1996 at the Alternating Gradient Synchroton of Brookhaven National Laboratory. We place an upper limit on the branching ratio at 3.9x10(-11) ( 90% C.L.). Together with results based on data collected in 1995 and an earlier experiment, E777, this result establishes a combined 90% confidence level upper limit on the branching ratio at 2.8x10(-11). We also report a new upper limit on the branching ratio for pi(0)-->&mgr;(+)e(-) of 3.8x10(-10) ( 90% C. L.). 相似文献
60.
R. Spogliarich A. Tencich J. Kaspar M. Graziani 《Journal of organometallic chemistry》1982,240(4):453-459
The reduction of ketones and olefins by hydrogen transfer from isopropanol is catalyzed by tertiary phosphine complexes of rhodium and iridium. The influence of the nature of the ligands and of the reaction conditions on the catalytic activity has been investigated. The reduction of the carbonyl group in the presence of olefins is also reported. 相似文献