Family Hierarchy and Large Neutrino Mixings

The recent neutrino data seem to favor two large and one small mixing angles and a hierarchy of their squared mass differences. We discuss these within the context of hierarchical neutrino masses. We show that this scheme suggests a specific neutrino mass matrix with mild fine-tuning. We then present a Froggatt-Nielsen model that reproduces this matrix

A Peptidoglycan Fragment Triggers β-lactam Resistance in Bacillus licheniformis

To resist to β-lactam antibiotics Eubacteria either constitutively synthesize a β-lactamase or a low affinity penicillin-binding protein target, or induce its synthesis in response to the presence of antibiotic outside the cell. In Bacillus licheniformis and Staphylococcus aureus, a membrane-bound penicillin receptor (BlaR/MecR) detects the presence of β-lactam and launches a cytoplasmic signal leading to the inactivation of BlaI/MecI repressor, and the synthesis of a β-lactamase or a low affinity target. We identified a dipeptide, resulting from the peptidoglycan turnover and present in bacterial cytoplasm, which is able to directly bind to the BlaI/MecI repressor and to destabilize the BlaI/MecI-DNA complex. We propose a general model, in which the acylation of BlaR/MecR receptor and the cellular stress induced by the antibiotic, are both necessary to generate a cell wall-derived coactivator responsible for the expression of an inducible β-lactam-resistance factor. The new model proposed confirms and emphasizes the role of peptidoglycan degradation fragments in bacterial cell regulation

Gauge Problems in Dynamically Broken Pure Yang-Mills Theory

Print-76-0147info:eu-repo/semantics/publishe

Burkina Faso: The Fall of Blaise Compaoré

This paper first discusses the actual sequence of events that led to the fall of the Président Blaise Compaoré in Burkina Faso in October 2014. We then identify some deeper trends that weakened the regime, including the dilemma of succession in a semi-authoritarian regime, the rise of youth and cultural elites as opposition actors who placed themselves beyond the reach of regime co-optation, and the use of Sankara imagery as a tool of mobilization. We then jointly analyse two features of the transition and the current regime of Lt-Col Isaac Yacouba Zida who, despite being only prime minister, appears to be the country’s new strongman. The first is the relative institutional uncertainty that accompanied the fall of the Compaoré regime and which continues to hamper the transition. The second is the enduring role of the military in Burkinabè politics. We conclude by singling out some implications of the transition and the challenges ahead.info:eu-repo/semantics/publishe

Gauge-invariant content of the effective potential

info:eu-repo/semantics/publishe

Marie-Victorin à Cuba

Marie-Victorin (1885-1944) est le scientifique le plus connu du Québec. Sa renommée repose avant tout sur le Jardin botanique de Montréal, qu'il fonda en 1931, et sur sa célèbre Flore laurentienne (1935). À partir de 1938, il fit sept voyages à Cuba, des séjours qui lui permirent de prendre contact avec un certain frère Léon, Français émigré à Cuba et auteur de la Flora de Cuba, avec qui il publia les Itinéraires botaniques dans l'île de Cuba en trois volumes. Ces ouvrages dominèrent pendant des décennies l'histoire botanique de la Perle des Antilles. Marie-Victorin et le frère Léon ont entretenu de 1907 à 1944 une correspondance soutenue qui nous permet de comprendre leur cheminement respectif. Cette correspondance, souvent émaillée d'humour, nous fait découvrir de nombreuses facettes de cette période cubaine d'un Marie-Victorin maladif, détestant l'hiver canadien, se réfugiant dans un hôtel de La Havane et désirant vivre autrement deux ou trois mois par année, loin de son Jardin botanique et des exigences de sa communauté. On y sent toute la ferveur des deux botanistes et leur connivence de scientifiques ayant pris les ordres

First evidences of the flexoelectric responses of PEDOT-PSS polymers

National audienceThe project concerns the field of electroactive polymer films intended to ensure a mechanical to electrical energy conversion. The transduction mechanism considered is the flexoelectric effect, which corresponds to the appearance of an electric polarization induced by a deformation gradient (equal to the curvature) This effect that is different from piezoelectricity is present in all the dielectric (insulator) solids [1]. However, a recent study [2] about flexoelectric effect in oxide thin films revealed a three orders of magnitude enhancement of the effective flexoelectric coefficient accompanied by a large increase in the dielectric constant, after the insulating oxide has been reduced to a semi-conducting sample. Thus, the main objective of the present study is to explore the flexoelectric responses of organic (semi)-conductor films. As a first step films of poly (3, 4-ethylenedioxythiophene- poly (styrene sulfonate) (PEDOT-PSS) have been studied. PEDOT-PSS is a classical conducting polymer used in the elaboration of optoelectronic devices [3].In this way, various commercially available PEDOT-PSS polymer solutions have been deposited by drop casting on stainless steel substrates with different volumes leading to varied polymer thicknesses (µm range). Polymer films were covered with aluminum top electrodes up to 100 nm in thickness using a metal evaporator) and the complex permittivity and conductivity were measured to possibly establish a correlation with the flexoelectric coefficient. This latter has been obtained by current output and deflections measurements of bending cantilever-shaped samples using the lab setup showed in fig.1.1.Merupo, V.I., et al., Flexoelectric response in soft polyurethane films and their use for large curvature sensing. Journal of Applied Physics, 2017. 122(14): p. 144101.2. J. Narvaez, F. Vasquez-Sancho, and G. Catalan, Enhanced flexoelectric-like response in oxide semiconductors. Nature, Sep. 2016. 538: p. 219.3.Kirchmeyer, S. and K. Reuter, Scientific importance, properties and growing applications of poly(3,4-ethylenedioxythiophene). Journal of Materials Chemistry, 2005. 15(21): p. 2077-2088