Superconducting Plate in Transverse Magnetic Field: New State

A model to describe Cooper pairs near the transition point (on temperature and magnetic field), when the distance between them is big compared to their sizes, is proposed. A superconducting plate whose thickness is less than the pair size in the transverse magnetic field near the critical value $H_{c2}$ is considered as an application of the model. A new state that is energetically more favourable than that of Abrikosov vortex state within an interval near the transition point was obtained. The system's wave function in this state looks like that of Laughlin's having been used in fractional quantum Hall effect (naturally, in our case - for Cooper pairs as Bose-particles) and it corresponds to homogeneous incompressible liquid. The state energy is proportional to the first power of value $(1 - H/H_{c2})$, unlike the vortex state energy having this value squared. The interval of the new state existence is greater for dirty specimens.Comment: 7 page

Mesoscale simulations of surfactant dissolution and mesophase formation

The evolution of the contact zone between pure surfactant and solvent has been studied by mesoscale simulation. It is found that mesophase formation becomes diffusion controlled and follows the equilibrium phase diagram adiabatically almost as soon as individual mesophases can be identified, corresponding to times in real systems of order 10 microseconds.Comment: 4 pages, 2 figures, ReVTeX

Detection and measurement of planetary systems with GAIA

We use detailed numerical simulations and the $\upsilon$ Andromedae, planetary system as a template to evaluate the capability of the ESA Cornerstone Mission GAIA in detecting and measuring multiple planets around solar-type stars in the neighborhood of the Solar System. For the outer two planets of the $\upsilon$ Andromedae, system, GAIA high-precision global astrometric measurements would provide estimates of the full set of orbital elements and masses accurate to better than 1--10%, and would be capable of addressing the coplanarity issue by determining the true geometry of the system with uncertainties of order of a few degrees. Finally, we discuss the generalization to a variety of configurations of potential planetary systems in the solar neighborhood for which GAIA could provide accurate measurements of unique value for the science of extra-solar planets.Comment: 4 pages, 2 pictures, accepted for publication in A&A Letter

Electrons in the Earth's Outer Radiation Zone

Electrons in the earths outer radiation bel

First Results from the Transit Ephemeris Refinement and Monitoring Survey (TERMS)

Transiting planet discoveries have yielded a plethora of information towards understanding the structure and atmospheres of extra-solar planets. These discoveries have been restricted to the short-period or low-periastron distance regimes due to the bias inherent in the geometric transit probability. Through the refinement of planetary orbital parmaters, and hence reducing the size of transit windows, long-period planets become feasible targets for photometric follow-up. Here we describe the TERMS project which is monitoring these host stars at predicted transit times

Kinetic Approach to Fractional Exclusion Statistics

We show that the kinetic approach to statistical mechanics permits an elegant and efficient treatment of fractional exclusion statistics. By using the exclusion-inclusion principle recently proposed [Phys. Rev. E49, 5103 (1994)] as a generalization of the Pauli exclusion principle, which is based on a proper definition of the transition probability between two states, we derive a variety of different statistical distributions interpolating between bosons and fermions. The Haldane exclusion principle and the Haldane-Wu fractional exclusion statistics are obtained in a natural way as particular cases. The thermodynamic properties of the statistical systems obeying the generalized exclusion-inclusion principle are discussed.Comment: 6 pages, REVTE

Pairing via Index theorem

This work is motivated by a specific point of view: at short distances and high energies the undoped and underdoped cuprates resemble the $\pi$-flux phase of the t-J model. The purpose of this paper is to present a mechanism by which pairing grows out of the doped $\pi$-flux phase. According to this mechanism pairing symmetry is determined by a parameter controlling the quantum tunneling of gauge flux quanta. For zero tunneling the symmetry is $d_{x^2-y^2}+id_{xy}$, while for large tunneling it is $d_{x^2-y^2}$. A zero-temperature critical point separates these two limits

Topological Quantum Phase Transitions in Topological Superconductors

In this paper we show that BF topological superconductors (insulators) exibit phase transitions between different topologically ordered phases characterized by different ground state degeneracy on manifold with non-trivial topology. These phase transitions are induced by the condensation (or lack of) of topological defects. We concentrate on the (2+1)-dimensional case where the BF model reduce to a mixed Chern-Simons term and we show that the superconducting phase has a ground state degeneracy $k$ and not $k^2$. When the symmetry is $U(1) \times U(1)$, namely when both gauge fields are compact, this model is not equivalent to the sum of two Chern-Simons term with opposite chirality, even if naively diagonalizable. This is due to the fact that U(1) symmetry requires an ultraviolet regularization that make the diagonalization impossible. This can be clearly seen using a lattice regularization, where the gauge fields become angular variables. Moreover we will show that the phase in which both gauge fields are compact is not allowed dynamically.Comment: 5 pages, no figure

Estrogen blocks the protective action of melatonin in a behavioral model of ethanol-induced hangover in mice

Melatonin has antioxidant and neuroprotective properties in human beings and experimental models, as well as 'anti-estrogenic' effects. Ethanol (EtOH) affects various behavioral parameters during a period known as ethanol-induced hangover. Our study evaluated the neuroprotective effect of melatonin on motor performance during ethanol hangover in male and female Swiss mice. The females were subjected to specific hormonal states: ovariectomized (OVX) and OVX estrogenized (OVX-E2). Mice received melatonin (25μg/ml) or vehicle in their drinking water for seven days and were given intraperitoneal (i.p.) injections of EtOH (3.8g/kg) or saline on the morning of the eighth day. Motor performance was evaluated by the tightrope test 6h after EtOH exposure (hangover onset). During ethanol hangover, males exhibited lower motor performance than controls (p<0.01) but pretreatment with melatonin significantly improved performance during hangover (p<0.05). In females, melatonin treatment before ethanol-induced hangover led to a better motor performance in OVX compared with intact females (p<0.01) and a lower performance in OVX-E2 compared with not-estrogenized OVX (p<0.05). Consequently, estrogen reversed the motor performance enhancement afforded by melatonin. We conclude that estrogen interferes with the protective action of melatonin on motor performance during ethanol hangover.Fil: Karadayian, A. G.. Universidad de Buenos Aires. Facultad de Medicina; ArgentinaFil: Mc Laughlin, M. A.. Universidad de Buenos Aires. Facultad de Medicina; ArgentinaFil: Cutrera, Rodolfo Angel. Universidad de Buenos Aires. Facultad de Medicina; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentin

Finite Density of States in a Mixed State of d_x^2-y^2+id_xy Superconductor

We have calculated the density of states of quasiparticles in a d_x^2-y^2+id_xy superconductor, and show that in the mixed state the quasiparticle spectrum remains gapless because of the Doppler shift by superflow. It was found that if the d_{xy} order gap $\Delta_1\propto \sqrt{H}$ as suggested by experiments, then thermal conductivity $\kappa \propto \sqrt{H}$ in accord with experimental data at lowest temperatures. This is an appended version of the paper published in Phys. Rev. {\bf B 59}, 6024, (1999). We now also discuss the disorder effects and analyze the H log H crossover at small fields. We argue that H log H regime is present and disorder effect is dominant as the field-induced seconary gap is small at small fields.Comment: This is an appended version of the paper published in Phys. Rev. {\bf B 59}, 6024, (1999). We now also discuss the disorder effects and analyze the H log H crossover at small fields. 3 pages, Latex file with 2 eps figure file