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1.
2.
An efficient method was developed for the synthesis of the ketoamino acid 2, a key intermediate in the synthesis of the novel sweet compound, monatin 1. Preparation of 2 entails coupling of a suitably protected indole acetate anion to an aspartic acid derivative. 相似文献
3.
An efficient synthesis of dicarbonyl(η5—cyclopentadienyl)iron—(II)—complexes of 2,3—dihydrofuran and 3,4—dihydro—2H—pyran from 3—bromo—2—methoxytetrahydrofuran and—pyran, respectively, is described. 相似文献
4.
Rate equations for the density of excited atoms in a He-Ne discharge are solved for the steady state. The atomistic parameters in the theoretical treatment are replaced by experimental values. Hence inversion density and single pass gain can be calculated as a function of gas mixture, pressure, discharge current and the geometry of the discharge tube. Conditions for maximum inversion density and single pass gain were calculated and compared with experimentally determined values. Good agreement was found for the maximum single pass gain and the related values of discharge current, gas mixture and pressure. 相似文献
5.
This paper reports the observation of an isostructural electronic phase transition in CeAl2 near 77 Kbar pressure at ambient temperature. The present volume compression data obtained under truly hydrostatic pressure
conditions gives a clear indication of the first order nature of this phase transformation. 相似文献
6.
7.
E. Arushanov S. Levcenko G. Fuchs B. Holzapfel S.-L. Drechsler L. Schultz 《Physica C: Superconductivity and its Applications》2011,471(7-8):237-241
We show that the zero-field normal-state resistivity of temperature-dependent resistivity ρ(T) of SrFe2?xNixAs2 can be reproduced by the expression ρ(T) = ρ0 + c T exp(?2Δ/T). ρ(T) can be scaled using both this expression where the energy scale Δ, c and the residual resistivity ρ0 are scaling parameters and a recently proposed model-independent scaling method (H.G. Luo, Y.H. Su, T. Xiang, Phys. Rev. B 77 (2008) 014529). The scaling parameters have been calculated and the compositional variation of 2Δ(x) has been determined. This dependence show almost a linear decreasing in the underdoped regime similar to that reported for cuprates. The existence of a universal metallic ρ(T) curve in a wide temperature range which, however, is restricted for the underdoped compounds to temperatures above a structural and anitiferromagnetic transition is interpreted as an indication of a single mechanism which dominates the scattering of the charge carriers in SrFe2?xNixAs2 (x = 0–0.3). 相似文献
8.
F. Fan Y.M. Lu L.L. Ying Z.Y. Liu C.B. Cai R. Hühne B. Holzapfel 《Physica C: Superconductivity and its Applications》2011,471(15-16):471-475
Biaxially textured Ce2Y2O7 (CYO) films were deposited on Ni–5at.%W (Ni–5W) tapes by a DC reactive sputtering technique in a reel-to-reel system. Subsequent YBa2Cu3O7?δ (YBCO) films were prepared using pulsed laser deposition leading to a simplified coated conductor architecture of YBCO/CYO/Ni–5W. X-ray diffraction measurements revealed an epitaxial growth of the CYO buffer layer with a texture spread down to 2.2° and 4.7° for the out-of-plane and in-plane alignment, respectively. Microstructural investigations showed a dense, smooth and crack-free surface morphology for CYO film up to a thickness of 350 nm, implying an effective suppression of cracks due to the incorporation of Y in CeO2. The superconducting transition temperature Tc of about 90 K with a narrow transition of 0.8 K and the inductively measured critical current density Jc of about 0.7 MA/cm2 indicate the potential of the single CYO buffer layer. 相似文献
9.
E. G. Maksimov A. E. Karakozov A. A. Voronkov B. P. Gorshunov S. S. Zhukov E. S. Zhukova V. S. Nozdrin S. Haindl B. Holzapfel L. Schultz D. Wu M. Dressel K. Iida P. Kallina F. Kurth 《JETP Letters》2011,93(12):736-742
Terahertz and infrared spectra of the conductivity, σ(ν), and dielectric constant, ?(ν), of a Ba(Fe0.9Co0.1)2As2 film (T c = 20 K) have been analyzed together with previous specific-heat and angular resolved photoelectron spectroscopy data. It has been shown that the spectra σ(ν) and ?(ν) of Ba(Fe0.9Co0.1)2As2 in the superconducting phase at T = 5 K, as well as the magnetic field penetration depth, can be described well using the standard Bardeen-Cooper-Schrieffer (BCS) model with an additive contribution of electron and hole bands. It has been found that the measured temperature dependence of the magnetic field penetration depth in a wide temperature range 5 K < T < T c can be described only with the introduction of interband pairing interaction. The coupling constant of electron and hole bands, λ1, 2 = 0.1, as well as the temperature dependences of superconducting gaps in the electron and hole subsystems, has been determined using the model of two-band superconductivity developed earlier for MgB2. 相似文献
10.
Pressure-volume (p – v) isotherms were studied on Si-Ge alloys at room temperature under pressures up to 42GPa by energy dispersive X-ray diffraction. These data are compared with the behaviour of the pure elements and show some characteristic nonlinearities in the variations of the respective elastic parameters with respect to the alloy concentration.Dedicated to H.-J. Queisser on the occasion of this 60th birthday 相似文献