Observations of OB-stars at the former Leiden Southern Station

Wetensch. publicati

The Palomar-Leiden survey of faint minor planets - Conclusion

Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe

The second Palomar-Leiden Trojan survey

Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe

Five-colour photometry of OB-stars in the Southern Hemisphere

Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe

Negative 4-Probe Conductances of Mesoscopic Superconducting Wires

We analyze the longitudinal 4-probe conductance of mesoscopic normal and superconducting wires and predict that in the superconducting case, large negative values can arise for both the weakly disordered and localized regimes. This contrasts sharply with the behaviour of the longitudinal 4-probe conductance of normal wires, which in the localized limit is always exponentially small and positive.Comment: Latex, 3 figures available on request to [email protected] (Simon Robinson

Size-effects in the Density of States in NS and SNS junctions

The quasiparticle local density of states (LDOS) is studied in clean NS and SNS junctions with increasing transverse size, from quasi-one-dimensional to three-dimensional. It is shown that finite transverse dimensions are related to pronounced effects in the LDOS, such as fast oscillations superimposed on the quasiparticle interference oscillations (for NS) and additional peaks in the bound state spectrum in the subgap region (for SNS). Also, the validity of the Andreev approximation is discussed. It turns out to be an acceptable approximation in all situations tested.Comment: 9 pages, RevTex, 5 figures, accepted in Phys. Rev.

A tomographic study of the classical nova RR Pic

We present the results of spectrophotometric observations of the old nova RR Pic performed in two spectral ranges, one centered in the Ha line and other covering Hb and Hg spectral lines. From the Hb radial velocity study we found a primary radial semi-amplitude of K1 = 37(1) km/s and a systemic velocity of g = 1.8(2) km/s. With this new values a mass diagram is constructed, constraining the possible mass intervals for the system. The possible orbital inclination range was restricted using the fact that RR Pic presents shallow eclipses. A secondary mass range below the limit of a main sequence star filling its Roche lobe indicate an evolved companion. We also calculated the Ha, Hb, Hg, HeI 6678 and HeII 4686 Doppler tomograms. The most conspicuous differences are found between the HeI and HeII tomograms, the former has a ring shape, while the second is filled at low velocities, suggesting that the low velocity emission is not coming from the accretion disk. Radial emissivity profiles for these lines were also derived.Comment: 8 pages, 8 figures, accepted to appear in PAS

Nonequilibrium Josephson effect in mesoscopic ballistic multiterminal SNS junctions

We present a detailed study of nonequilibrium Josephson currents and conductance in ballistic multiterminal SNS-devices. Nonequilibrium is created by means of quasiparticle injection from a normal reservoir connected to the normal part of the junction. By applying a voltage at the normal reservoir the Josephson current can be suppressed or the direction of the current can be reversed. For a junction longer than the thermal length, $L\gg\xi_T$, the nonequilibrium current increases linearly with applied voltage, saturating at a value equal to the equilibrium current of a short junction. The conductance exhibits a finite bias anomaly around $eV \sim \hbar v_F/L$. For symmetric injection, the conductance oscillates $2\pi$-periodically with the phase difference $\phi$ between the superconductors, with position of the minimum ($\phi=0$ or $\pi$) dependent on applied voltage and temperature. For asymmetric injection, both the nonequilibrium Josephson current and the conductance becomes $\pi$-periodic in phase difference. Inclusion of barriers at the NS-interfaces gives rise to a resonant behavior of the total Josephson current with respect to junction length with a period $\sim \lambda_F$. Both three and four terminal junctions are studied.Comment: 21 pages, 19 figures, submitted to Phys. Rev.

Simvastatin treatment reduces the cholesterol content of membrane/lipid rafts, implicating the N -methyl-D-aspartate receptor in anxiety: a literature review

ABSTRACT Membrane/lipid rafts (MLRs) are plasmalemmal microdomains that are essential for neuronal signaling and synaptic development/stabilization. Inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme-A reductase (statins) can disable the N-methyl-D-aspartate (NMDA) receptor through disruption of MLRs and, in turn, decrease NMDA-mediated anxiety. This hypothesis will contribute to understanding the critical roles of simvastatin in treating anxiety via the NMDA receptor