Dynamical Casimir-Polder atom-surface interaction

We have calculated dynamical Casimir-Polder interaction force between a moving ground state atom and a flat polarizable surface. The velocity of an atom can be close to the velocity of light. The material properties are taken into account using a single oscillator model of the atomic dynamic polarizability and the Drude dielectric function of a metal substrate. The limit cases of nonrelativistic velocities and an ideal metal substrate are also considered. We have found specific dependence of the calculated forces on the velocity (energy), distance and material properties.Comment: 21 pages,11 figures, 1 table; improved version of previous paper; submitted to Surface Scienc

Effective Electromagnetic Lagrangian at Finite Temperature and Density in the Electroweak Model

Using the exact propagators in a constant magnetic field, the effective electromagnetic Lagrangian at finite temperature and density is calculated to all orders in the field strength B within the framework of the complete electroweak model, in the weak coupling limit. The partition function and free energy are obtained explicitly and the finite temperature effective coupling is derived in closed form. Some implications of this result, potentially interesting to astrophysics and cosmology, are discussed.Comment: 14 pages, Revtex

Delta9-tetrahydrocannabinol decreases somatic and motivational manifestations of nicotine withdrawal in mice

The possible interactions between Delta9-tetrahydrocannabinol (THC) and nicotine remain unclear in spite of the current association of cannabis and tobacco in humans. The aim of the present study was to explore the interactions between these two drugs of abuse by evaluating the consequences of THC administration on the somatic manifestations and the aversive motivational state associated to nicotine withdrawal in mice. Acute THC administration significantly decreased the incidence of several nicotine withdrawal signs precipitated by mecamylamine or naloxone, such as wet-dog-shakes, paw tremor and scratches. In both experimental conditions, the global withdrawal score was also significantly attenuated by acute THC administration. THC also reversed conditioned place aversion associated to naloxone precipitated nicotine withdrawal. We have then evaluated whether this effect of THC was due to possible adaptive changes induced by chronic nicotine on CB1 cannabinoid receptors. The stimulation of GTPS-binding proteins by the cannabinoid agonist WIN 55,212-2 and the density of CB1 cannabinoid receptor binding labelled with [3H] CP-55,940 were not modified by chronic nicotine treatment in the different brain structures investigated. Finally, we evaluated the consequences of THC administration on c-Fos expression in several brain structures after chronic nicotine administration and withdrawal. c-Fos was decreased in the caudate putamen and the dentate gyrus after mecamylamine precipitated nicotine withdrawal. However, acute THC administration did not modify c-Fos expression under these experimental conditions. Taken together, these results indicate that THC administration attenuated somatic signs of nicotine withdrawal and this effect was not associated to compensatory changes on CB1 cannabinoid receptors during chronic nicotine administration. In addition, THC also ameliorated the aversive motivational consequences of nicotine withdrawal.This work has been supported by grants from Human Frontier Science Program Organization (RG0077/2000-B), Plan Nacional sobre Drogas, Generalitat de Catalunya (Research Distinction), 2002 SGR00193 and the European Comission “Quality of Life and Management of Living Resources QLRT-2001-01691. Graciela Balerio is a postdoctoral fellow supported by “Fundación Carolina”. Fernando Berrendero is a researcher supported by “Ramón y Cajal” research program of the Ministery of Science and Technology