Spin-wave instabilities in spin-transfer-driven magnetization dynamics

We study the stability of magnetization precessions induced in spin-transfer devices by the injection of spin-polarized electric currents. Instability conditions are derived by introducing a generalized, far-from-equilibrium interpretation of spin-waves. It is shown that instabilities are generated by distinct groups of magnetostatically coupled spin-waves. Stability diagrams are constructed as a function of external magnetic field and injected spin-polarized current. These diagrams show that applying larger fields and currents has a stabilizing effect on magnetization precessions. Analytical results are compared with numerical simulations of spin-transfer-driven magnetization dynamics.Comment: 4 pages, 2 figure

A lattice of double wells for manipulating pairs of cold atoms

We describe the design and implementation of a 2D optical lattice of double wells suitable for isolating and manipulating an array of individual pairs of atoms in an optical lattice. Atoms in the square lattice can be placed in a double well with any of their four nearest neighbors. The properties of the double well (the barrier height and relative energy offset of the paired sites) can be dynamically controlled. The topology of the lattice is phase stable against phase noise imparted by vibrational noise on mirrors. We demonstrate the dynamic control of the lattice by showing the coherent splitting of atoms from single wells into double wells and observing the resulting double-slit atom diffraction pattern. This lattice can be used to test controlled neutral atom motion among lattice sites and should allow for testing controlled two-qubit gates.Comment: 9 pages, 11 figures Accepted for publication in Physical Review

RAO-II: an AUV for underwater inspection

AIRSUB is a research project funded by the Spanish Ministry of Science and Technology whose aim is to explore the industrial applications of underwater robots. The Systems, Robotics and Vision Group (SRV) from the University of the Balearic Islands (UIB) is responsible for the subproject of cable/pipeline inspection [1]. To this purpose, an Autonomous Underwater Vehicle (AUV) is under development as a platform to test the vision algorithms, control strategies and software architectures devised in the last years. This paper describes the main characteristics of the new platform, which is based on a commercial Remotely Operated Vehicle (ROV). The original vehicle has been deeply modifi ed in structure as well as in its electric, electronic and sensorial facets to obtain fully autonomous operation

Tumour heterogeneity: principles and practical consequences

Two major reasons compel us to study tumour heterogeneity: firstly, it represents the basis of acquired therapy resistance, and secondly it may be one of the major sources of the low level of reproducibility in clinical cancer research. The present review focuses on the heterogeneity of neoplastic disease, both within the primary tumour, and between primary tumour and metastases. We discuss different levels of heterogeneity and the current understanding of the phenomenon, as well as imminent developments relevant for clinical research and diagnostic pathology. It is necessary to develop new tools to study heterogeneity and new biomarkers for heterogeneity. Established and new in situ methods will be very useful. In future studies, not only clonal heterogeneity needs to be addressed, but also non-clonal phenotypic heterogeneity which might be important for therapy resistance. We also review heterogeneity established in major tumour types, in order to explore potential similarities that might help to define new strategies for targeted therapy

Les forêts à Alnus cordata en Italie méridionale - Comparaison avec les groupements de Corse

Le but de cet article est d’apporter des informations sur les groupements forestiers à Alnus cordata Desf. des massifs montagneux de la partie occidentale de l’Italie méridionale. Cette essence centro-méditerranéenne est présente en Corse et sur certains versants sud italiens. Dans cette région, elle constitue de véritables groupements forestiers, peu étendus certes, mais bien individualisés. C’est pourquoi ces groupements sont rattachés aux grandes unités de végétation présentes dans cette région. Leurs affinités sont discutées et leur position dans l’étagement de la végétation bien précisée. Quelques considérations sur la composition floristique de ces formations permettent de mieux appréhender les affinités biogéographiques de ces aulnaies

Trente ans d'apport de la recherche sur les forêts méditerranéennes

Cet article présente un bilan des apports de la recherche écologique dans le cadre général des forêts méditerranéennes durant des trois dernières décennies. Il convient de préciser qu'il s'agit essentiellement de recherche écologique, car il existe des champs de recherche qui n'y sont pas abordés

Synthèse des acquis du colloque "Changements climatiques et forêt méditerranéenne" de 2007 -

En novembre 2007, l'Association Forêt Méditerranéenne organisait un colloque original associant effets du changement climatique et forêts méditerranéennes. Cette manifestation connut un grand succès, attirant plus de 400 participants de toutes catégories professionnelles et d'origines géographiques variées, justifiant ainsi la décision de recommencer l'expérience en 2010, pour faire un point sur l'évolution des connaissances théoriques et pratiques. L'auteur rappelle ici brièvement les principales idées développées en 2007

Quelques aspects des forêts d'Afrique du nord.

L'article a pour objet d'évoquer l'éventail des entités forestières d'Afrique du nord. Leur hétérogénéité ainsi que leur vulnérabilité constituent leur caractéristique moyenne

Atom interferometry measurement of the electric polarizability of lithium

Using an atom interferometer, we have measured the static electric polarizability of $^7$Li $\alpha =(24.33 \pm 0.16)\times10^{-30}$ m$^3$ $= 164.19\pm 1.08$ atomic units with a 0.66% uncertainty. Our experiment, which is similar to an experiment done on sodium in 1995 by D. Pritchard and co-workers, consists in applying an electric field on one of the two interfering beams and measuring the resulting phase-shift. With respect to D. Pritchard's experiment, we have made several improvements which are described in detail in this paper: the capacitor design is such that the electric field can be calculated analytically; the phase sensitivity of our interferometer is substantially better, near 16 mrad/$\sqrt{Hz}$; finally our interferometer is species selective it so that impurities present in our atomic beam (other alkali atoms or lithium dimers) do not perturb our measurement. The extreme sensitivity of atom interferometry is well illustrated by our experiment: our measurement amounts to measuring a slight increase $\Delta v$ of the atom velocity $v$ when it enters the electric field region and our present sensitivity is sufficient to detect a variation $\Delta v/v \approx 6 \times 10^{-13}$.Comment: 14 page