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41.
S. Piano J. W.A. Robinson G. Burnell M. G. Blamire 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(2):123-126
The physics of the π phase shift in ferromagnetic
Josephson junctions may enable a range of applications for
spin-electronic devices and quantum computing. We investigate
transitions from “0” to “π” states in Nb/Fe/Nb Josephson
junctions by varying the Fe barrier thickness from 0.5 nm to 5.5 nm. From magnetic measurements we estimate for Fe a magnetic
dead
layer of about 1.1 nm. By fitting the characteristic voltage
oscillations with existing theoretical models we extrapolate an
exchange energy of 256 meV, a Fermi velocity of 1.98 ×105
m/s and an electron mean free path of 6.2 nm, in agreement with
other reported values. From the temperature dependence of the
ICRN product we show that its decay rate exhibits a nonmonotonic
oscillatory behavior with the Fe barrier thickness. 相似文献
42.
43.
Dallas K. Bates R. Thomas Winters Burnell A. Sell 《Journal of heterocyclic chemistry》1986,23(3):695-699
Treatment of 1-(2-alkylsulfinylphenyl)pyrroles with trifluoroacetic acid in refluxing toluene gives 4-substituted pyrrolo[2,1-c][1,4]benzothiazines in good yield when the alkyl group bears an electron withdrawing substituent on the α-carbon. In the absence of such a group, starting material is recovered. The sulfoxides are prepared by oxidation (mCBPA) of the corresponding sulfide. The sulfides are prepared from 2-aminobenzenethiol either by S-alkylation followed by conversion to the pyrrole using 1,4-dimethoxytetrahydrofuran in glacial acetic acid or by S-alkylation of 1-(2-phenylmercapto)pyrrole followed by oxidation to the sulfoxide. 相似文献
44.
An overview is presented of modern NMR techniques and a variety of experimental and theoretical tools employed in the study of solutes dissolved in liquid crystals. The NMR techniques involve multiple quantum and spectral subtraction methods. In addition, various experimental and theoretical tools are discussed, including: the theoretical background of observed order parameters; the use of ‘magic mixtures’ to separate orientational contributions; the reorientation–vibration interaction; the use of model calculations based on size and shape of the various solutes; and the use of computer simulations. Applications to the benchmark probe molecules hydrogen, methane, ethane, and butane and their isotopomers are treated. 相似文献
45.
Recent tunneling studies of tantalum using a proximity technique reveal stronger coupling to the longitudinal modes relative to the transverse modes than observed previously for any transition metal. This result has implications for modeling the electron-phonon coupling mechanism and for future tunneling investigations. We obtain parameter values for Ta of ,in agreement with optimized conventional results. 相似文献
46.
New experimental NMR work on 13CH3F dissolved in various nematic phases is reported. These as well as previous results cannot be interpreted solely as the effect of J anisotropy, molecular vibrations or solvent dependence of J. The results demonstrate that CH3F is rapidly exchanging between at least two sites which have slightly different geometries and orientation parameters of opposite sign. 相似文献
47.
The order parameters of a number of different solutes dissolved in a number of different nematic liquid-crystal solvents are measured and compared. It is shown that the order parameters can all be rationalized with the ansatz that there exist two independent ordering mechanisms operating in the liquid crystals employed. With this ansatz it is possible to fit the experimental order parameters to better than 5%. This opens the possibility of the accurate prediction of order parameters in ordered liquids. 相似文献
48.
Similarity profiles of pressure and saturation are analysed which result from one-dimensional planar withdrawal of fluid from a porous region initially containing a two phase mixture of steam and water. Approximate expressions are derived for the evolution of pressure and saturation profiles, and boundary-layer changes in saturation are identified. The existence of a similarity variable implies that the saturation conditions for the reservoir tend with time either to having both phases flowing; or to a single phase vapour. In particular, the nonlinear nature of the governing equations implies that infinitesimal changes in pressure can produce finite changes in saturation. The two mechanisms responsible for saturation changing with time involve local changes in energy storage in rock and fluid; together with spatial variations in flowing enthalpy. The latter mechanism occurred relatively slowly in the examples treated, and was responsible for boundary-layer formation when one phase was initially immobile. Dimensional analysis reveals that when a boundary layer develops, the underlying equations involve essentially only one dimensionless parameter which is typically small, being associated with the ratio of the energy density of the mobile phase relative to the total energy density. 相似文献
49.
Capitani D Yethiraj A Burnell EE 《Langmuir : the ACS journal of surfaces and colloids》2007,23(6):3036-3048
We report a detailed analysis of deuteron NMR spectra of micellar, lamellar, cubic, and hexagonal mesophases in the aqueous non-ionic surfactant system C(12)E(6)/water. Samples are prepared with and without shear. Particular attention is paid to an interesting temperature-driven phase sequence that includes all of the above phases that are studied before and after shear parallel or perpendicular to the magnetic field direction. Surprising memory effects are found across mesophase transitions. These memory effects provide clues to the structure of the various phases. 相似文献
50.
The Diels-Alder reactions of maleimide with the acetonide derivative (6a) of cis-3,5-cyclohexadiene-1,2-diol (1a) in various solvents showed facial selectivities ranging from 1 : 1 to 1 : 9. The same derivative 6a reacted in benzene with ethylenic dienophiles with generally modest facial selectivity, but acetylenic dienophiles added exclusively anti to the oxygen functions of 6a. Dimerization of cyclic acetals 6a and 7 was mainly, but for 6a not exclusively, by anti addition with respect to both the diene and the dienophile partners. Reactions of azo dienophiles with derivatives of 1a were predominantly by anti addition, but the diol itself (1a) gave the syn adduct as the major product. 相似文献