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991.
R.V. Chopdekar M. Liberati L.F. Kourkoutis B.B. Nelson-Cheeseman A. Doran D.A. Muller 《Journal of magnetism and magnetic materials》2010,322(19):2915-2921
Magnetic order and coupling at the interfaces of highly spin polarized Fe3O4 heterostructures have been determined by surface sensitive and element specific soft X-ray spectroscopy and spectro-microscopy techniques. At ambient temperature, the interface between paramagnetic CoCr2O4 or MnCr2O4 and ferrimagnetic Fe3O4 isostructural bilayers exhibits long range magnetic order of Co, Mn and Cr cations which cannot be explained in terms of the formation of interfacial MnFe2O4 or CoFe2O4. Instead, the ferrimagnetism is induced by the adjacent Fe3O4 layer and is the result of the stabilization of a spinel phase not achievable in bulk form. Magnetism at the interface region is observable up to 500 K, far beyond the chromite bulk Curie temperature of 50-95 K. 相似文献
992.
While it is known that shared quantum entanglement can offer improved solutions to a number of purely cooperative tasks for groups of remote agents, controversy remains regarding the legitimacy of quantum games in a competitive setting. We construct a competitive game between four players based on the minority game where the maximal Nash-equilibrium payoff when played with the appropriate quantum resource is greater than that obtainable by classical means, assuming a local hidden variable model. 相似文献
993.
Labroille G Pillai RS Solinas X Boudoux C Olivier N Beaurepaire E Joffre M 《Optics letters》2010,35(20):3444-3446
We demonstrate selective two-photon excited fluorescence microscopy with shaped pulses produced with a simple yet efficient scheme based on dispersive optical components. The pulse train from a broadband oscillator is split into two subtrains that are sent through different amounts of glass. Beam recombination results in pulse-shape switching at a rate of 150MHz. Time-resolved photon counting detection then provides two simultaneous images resulting from selective two-photon excitation, as demonstrated in a live embryo. Although less versatile than programmable pulse-shaping devices, this novel arrangement significantly improves the performance of selective microscopy using broadband shaped pulses while simplifying the experimental setup. 相似文献
994.
We investigate the effect of the anisotropy of a harmonic trap on the behaviour of a fast rotating Bose-Einstein condensate. This is done in the framework of the 2D Gross-Pitaevskii equation and requires a symplectic reduction of the quadratic form defining the energy. This reduction allows us to simplify the energy on a Bargmann space and study the asymptotics of large rotational velocity. We characterize two regimes of velocity and anisotropy; in the first one where the behaviour is similar to the isotropic case, we construct an upper bound: a hexagonal Abrikosov lattice of vortices, with an inverted parabola profile. The second regime deals with very large velocities, a case in which we prove that the ground state does not display vortices in the bulk, with a 1D limiting problem. In that case, we show that the coarse grained atomic density behaves like an inverted parabola with large radius in the deconfined direction but keeps a fixed profile given by a Gaussian in the other direction. The features of this second regime appear as new phenomena. 相似文献
995.
Nicolas Chevrot 《Journal of Mathematical Analysis and Applications》2009,355(1):110-125
We obtain criteria for the Riesz basis property for families of reproducing kernels in vector-valued de Branges-Rovnyak spaces H(b). In particular, it is shown that in several situations the property implies a special form for the function b. We also study the completeness of a related family. 相似文献
996.
Nicolas Nisse 《Discrete Applied Mathematics》2009,157(12):2603-2610
997.
We construct superefficient estimators of Stein type for the intensity parameter λ > 0 of a Poisson process, using integration
by parts and superharmonic functionals on the Poisson space.
相似文献
998.
Glandut N Monson CF Majda M 《Langmuir : the ACS journal of surfaces and colloids》2006,22(25):10697-10704
A new method is described to simultaneously determine the kinetics of surface partitioning and the lateral diffusion constant of redox active amphiphiles. It concerns water-soluble amphiphiles for which the surface adsorption equilibrium constant and the solution diffusion constant are measured independently. The method involves cyclic voltammetric experiments carried out at the air/water interface with microband electrodes aligned with the plane of the water surface. Typically, 100 nm wide, 1.0 cm long microband electrodes are fabricated by the vacuum vapor deposition of gold films on glass. The front face of the electrode substrates are coated with impermeable, dimensionally stable, polymer barrier films with thickness L in the range of approximately 0.1-1.0 microm. Fracturing such gold-coated glass substrates exposes gold microbands. The recorded voltammetric current sensitively depends on the barrier film thickness, the surfactant surface diffusion constant, Dsurf, and its rate constant of desorption, kdes. For a given surfactant, such as the nitroxyl piperidine free radical TEMPO featured in this report, large currents are observed with microband electrodes that do not carry a barrier film (L = 0). This is because the surfactant surface population diffusing along the air/water interface can be directly electro-oxidized at the edge of the microband. Smaller currents are measured in the presence of a barrier film, since, in those instances, the surface population may contribute to the voltammetric current only via a mechanism involving surfactant desorption from the water surface into bulk, where it contributes to the three-dimensional solution diffusion processes. The quantitative interpretation of the voltammetric experiments was made possible with finite element simulations with FEMLAB. These produce a set of calibration curves, Dsurf versus log kdes, for each value of the barrier film thickness. The intersection of the calibration curves determines the unique values of Dsurf and kdes. For TEMPO, Dsurf = 4.4 +/- 1.2 x 10(-5) cm2/s and kdes >/= 2 x 10(4) s(-1). Surfactant desorption rate constants of this magnitude have not been previously experimentally accessible. Since, in our earlier report (Wu, D. G.; Malec, A. D.; Head-Gordon, M.; Majda, M. J. Am. Chem. Soc. 2005, 27, 4490-4496), we showed that TEMPO is not immersed in water and that it diffuses along the interface hydrogen-bonded to just one or two water molecules, its Dsurf value approximates the water diffusion constant in the aqueous liquid-vapor interfacial region. 相似文献
999.
Novel zwitterionic reverse micelles for encapsulation of proteins in low-viscosity media 总被引:4,自引:0,他引:4
Doussin S Birlirakis N Georgin D Taran F Berthault P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(15):4170-4175
Large proteins remain inaccessible to structural NMR studies because of their unfavorable relaxation properties. Their solubilization in the aqueous core of reverse micelles, in a low-viscosity medium, represents a promising approach, provided that their native tertiary structure is maintained. However, the use of classical ionic surfactants may lead to protein unfolding, due to strong electrostatic interactions between the polar head groups and the protein charges. To design reverse micelles in which these interactions are weakened, a new zwitterionic surfactant molecule was synthesized and studied by high-resolution NMR spectroscopy, for which cytochrome C and 15N-labeled ubiquitin were used as guest candidates. At different ionization states, both proteins are encapsulated in the absence of salts or other additives, in a folded conformation similar to the native one. 相似文献
1000.
Pichon N Harrison-Marchand A Toupet L Maddaluno J 《The Journal of organic chemistry》2006,71(5):1892-1901
A new stereocontrolled synthetic pathway to 1,2,4-trioxygenated 1,3-dienes from pyruvic aldehyde dimethyl acetal (14a) is described. Reacting the cyclohexylamine-derived imine of this starting material with chloroalkyl ethers under basic conditions affords ketoacetals 18-20, which were then transformed into eight different enoxysilanes 12. A delta-elimination triggered by tert-butyllithium yields 1,2,4-trioxygenated dienes 13. Increasing the bulkiness of the silyloxy group or that of the acetal moiety leads stereoselectively to the (1E,3E) or (1Z,3E) isomers of 13, respectively. Hyperbaric [4 + 2] cycloadditions between 13 (13c, 13d, 13g) and N-methylmaleimide or methyl- and phenylacrylates give access to the expected cycloadducts with fine stereo- and regiocontrol. 相似文献