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Ijiri Y Schulthess TC Borchers JA van der Zaag PJ Erwin RW 《Physical review letters》2007,99(14):147201
In studying well-characterized, exchange-biased Fe(3)O(4)/CoO superlattices, we demonstrate a causal link between the exchange bias effect and the perpendicular coupling of the ferrimagnetic and antiferromagnetic spins. Neutron diffraction studies reveal that for thin CoO layers the onset temperature for exchange biasing T(B) matches the onset of locked-in, preferential perpendicular coupling of the spins, rather than the antiferromagnetic ordering temperature T(N). The results are explained by considering the role of anisotropic exchange first proposed by Dzyaloshinsky and Moriya and developing a model based purely on information on structural defects and exchange for these oxides. The devised mechanism provides a general explanation of biasing in systems with perpendicular coupling. 相似文献
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The cluster size dependence of superconductivity in the conventional two-dimensional Hubbard model, commonly believed to describe high-temperature superconductors, is systematically studied using the dynamical cluster approximation and quantum Monte Carlo simulations as a cluster solver. Because of the nonlocality of the d-wave superconducting order parameter, the results on small clusters show large size and geometry effects. In large enough clusters, the results are independent of the cluster size and display a finite temperature instability to d-wave superconductivity. 相似文献
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René Stepánek Bernhard Kräutler Peter Schulthess Bernhard Lindemann Daniel Ammann Wilhelm Simon 《Analytica chimica acta》1986
The synthesis of aquocyanocobalt(III)-hepta(2-phenylethyl)-cobyrinate is described. It is a more lipophilic substitute for a previously reported nitrite-carrier. Membranes based on this more readily accessible cobyrinate exhibit selectivity coefficients for nitrite (Kpot) over nitrate and chloride of 10?4.2 and 10–4.6, respectively. Near-theoretical slopes were found for 10?4.5?10?1.0 M nitrite. After contact of the sensor with flowing tap water for 35 days, no deterioration of the electrode characteristics was observed. 相似文献
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From a Base Catalyzed Ring Opening of 2H-Azirines to an α-Alkylation Method of Primary Amines It is shown that fluorene-9′-spiro-2-(3-phenyl-2H-azirine) ( 1 ) on treatment with various alcohols in the presence of the corresponding alkoxide ions yields N-(9′-fluorenyl)benzimidates 2a-d (Scheme 1). 2,2,3-Triphenyl-2H-azirine ( 3 ) reacts with methanol in a similar manner (Scheme 2). Benzimidates 2a (Scheme 3), 8 (Scheme 4) and and 10 (Scheme 5) can easily be deprotonated by butyllithium (BuLi) or lithium diisopropylamide (LDA) in tetrahydrofuran (THF) to 1-methoxy-2-aza-allylanions, that can be alkylated, at C(3), exclusively, by various electrophiles (e.g. R-X(X = I, Br), RCHO or methyl acrylate (see also Scheme 6)). As the acidic hydrolyses (1N HCl) of benzimidates 9 and 11 leads to the corresponding α-alkylated free amines 15 and 18 (Scheme 7 and 8), benzoyl derivatives 16 and 19 are obtained from the hydrolysis under basic conditions. On the other hand, it is observed that a catalyzed Chapman rearrangement of 9 and 11 results in the formation of N-benzoyl-N-methyl derivatives 17 and 20 (Scheme 7 and 8). The described reactions offer a simple method for the α-alkylation of activated primary amines. 相似文献
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An electrically neutral hydrogen ion-selective carrier, tri-n-dodecylamine, is used as the active component for liquid-membrane electrodes. The observed ion selectivities are superior to those of previously described pH-sensitive liquid-membrane electrodes. The electrode characteristics permit the study of intracellular as well as extracellular hydrogen ion activities. 相似文献
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Daniel Ammann Marin Huser Bernhard Krutler Bruno Rusterholz Peter Schulthess Bernhard Lindemann Ernst Halder Wilhelm Simon 《Helvetica chimica acta》1986,69(4):849-854
Lipophilic Co(III) and Mn(III) complexes of 5,10,15,20-tetrakis[4-(hexyloxycarbonyl)phenyl]porphyrin act as positively charged carriers for anions and induce anion selectivities in membranes clearly deviating from the sequence of classical anion exchangers. Different anion selectivities are observed for the Co(III) and Mn(III) porphyrins. 相似文献
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