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22.
Grimmer Arnd-Rüdiger von Lampe Fred Mägi Mart Lippmaa Endel 《Monatshefte für Chemie / Chemical Monthly》1983,114(10):1053-1057
Monatshefte für Chemie - Chemical Monthly - High-resolution solid-state29Si NMR spectra of polycrystalline rare earth disilicatesLn 2Si2O7 (Ln=Sc, Y, In, La, Yb and Sm) have been investigated.... 相似文献
23.
We show that the minimum number of orientations of the edges of the n-vertex complete graph having the property that every triangle is made cyclic in at least one of them is \(\lceil \log _2(n-1)\rceil \). More generally, we also determine the minimum number of orientations of \(K_n\) such that at least one of them orients some specific k-cycles cyclically on every k-element subset of the vertex set. Though only formally related, the questions answered by these results were motivated by an analogous problem of Vera T. Sós concerning triangles and 3-edge-colorings. Some variants of the problem are also considered. 相似文献
24.
Thomas Bjørn Egede Grønbech Kasper Tolborg Helle Svendsen Jacob Overgaard Yu-Sheng Chen Bo Brummerstedt Iversen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(39):8651-8662
FeSb2 exhibits a colossal Seebeck coefficient ( ) and a record-breaking high thermoelectric power factor. It also has an atypical shift from diamagnetism to paramagnetism with increasing temperature, and the fine details of its electron correlation effects have been widely discussed. The extraordinary physical properties must be rooted in the nature of the chemical bonding, and indeed, the chemical bonding in this archetypical marcasite structure has been heavily debated on a theoretical basis since the 1960s. The two prevalent models for describing the bonding interactions in FeSb2 are based on either ligand-field stabilization of Fe or a network structure of Sb hosting Fe ions. However, neither model can account for the observed properties of FeSb2. Herein, an experimental electron density study is reported, which is based on analysis of synchrotron X-ray diffraction data measured at 15 K on a minute single crystal to limit systematic errors. The analysis is supplemented with density functional theory calculations in the experimental geometry. The experimental data are at variance with both the additional single-electron Sb−Sb bond implied by the covalent model, and the large formal charge and expected d-orbital splitting advocated by the ionic model. The structure is best described as an extended covalent network in agreement with expectations based on electronegativity differences. 相似文献
25.
Toshiyuki Taniuchi Hiroshi Kumigashira Masato Kubota Takanori Wakita Takanori Yokoya Kanta Ono Masaharu Oshima Mikk Lippmaa Hideomi Koinuma 《Surface science》2007,601(20):4690-4693
We have used photoelectron emission microscopy (PEEM) and X-ray magnetic circular dichroism (XMCD) to study the effect of thin film thickness on the magnetic domain formation in La0.6Sr0.4MnO3 samples that were epitaxially grown on stepped SrTiO3 (0 0 1) substrates. The magnetic image exhibited a stripe structure elongated along the step direction, irrespective of film thickness, suggesting that uniaxial magnetic anisotropy induced by step-and-terrace structures plays an important role in the magnetic domain formation. Additional domains evolved gradually with increasing film thickness. In these domains, the direction of magnetization differed from the step direction due to biaxial magneto-crystalline anisotropy. The evolution of additional magnetic domains with increasing film thickness implies that a competition exists between the two anisotropies in LSMO films. 相似文献
26.
Arnd-Rüdiger Grimmer Fred von Lampe Mart Mägi Endel Lippmaa 《Monatshefte für Chemie / Chemical Monthly》1984,115(5):561-564
Starting from high-resolution solid-state29Si NMR spectra of two modifications of Y2Si2O7 with different Si-O-Si bond angles it was verified that increasing bond angles cause high-field isotropic29Si chemical shifts. 相似文献
27.
Dependence of linewidth in porton-decoupled 13C NMR spectra of diamagnetic polycrystalline samples on external magnetic field strength is studied. Spectral resolution is limited by magnetic heterogencity of powder samples. It is suggested that in magic-angle rotation spectra, the linewidth is determined by the amsotropy of the magnetic susceptibility Δxυ rather than xυ of the crystallites. 相似文献
28.
29.
T. Harada I. Ohkubo M. Lippmaa Y. Matsumoto M. Sumiya H. Koinuma M. Oshima 《固体物理学:研究快报》2011,5(1):34-36
Ferromagnetic insulator Pr0.8Ca0.2Mn1–yCoy O3 (0 ≤ y ≤ 0.7) thin films were epitaxially grown by pulsed laser deposition on substrates of (LaAlO3)0.3(SrAl0.5Ta0.5O3)0.7 (100). To probe the ferromagnetic insulator state, the Co content dependences of the structural, magnetic, and transport properties were studied. Variation of lattice constant by the Co substitution is well reproduced considering that divalent and trivalent Co ions substitute for Mn ions at the perovskite B‐sites. For 0 ≤ y ≤ 0.3, the Curie temperature, saturation magnetization, and magnetoresistance increase with increasing Co content, retaining the insulating properties. Detailed analyses of transport and magnetic properties indicate the contribution of both double exchange and superexchange interactions to the appearance of the ferromagnetic insulating phase. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
30.
Ann Louise Worsøe Jørgensen Helle Risdahl Juul‐Madsen Jan Stagsted 《Journal of mass spectrometry : JMS》2009,44(3):338-345
A simple and sensitive ligand affinity capture method (LAC) was developed to detect biotinylated biomolecules bound to a biotin–avidin base by matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI ToF MS). Glass slides covered with a metal film for MALDI MS applications were treated with amino‐silane and derivatized with biotin followed by binding of avidin. Washing buffers with high ionic strength increased the specificity of the subsequent binding of biotinylated biomolecules to the avidin layer. A combined thin layer‐dried droplet method using α‐cyano‐4‐hydroxycinnamic acid (CHCA) in acetone or ethyl acetate resulted in the most intense ions of biotinylated polymyxin B, whereas the matrix conditions did not influence the detection of angiotensin II. Addition of biotinylated biomolecules in the low femtomole to low picomole range resulted in sufficient ion intensity for detection by the LAC method. The LAC concept was extended by binding of biotinylated lipopolysaccharide to the biotin–avidin base followed by preferential capture and specific detection of the binding antagonist polymyxin B. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献