Fluctuations of the local density of states probe localized surface plasmons on disordered metal films

We measure the statistical distribution of the local density of optical states (LDOS) on disordered semi-continuous metal films. We show that LDOS fluctuations exhibit a maximum in a regime where fractal clusters dominate the film surface. These large fluctuations are a signature of surface-plasmon localization on the nanometer scale

A Requirement of TolC and MDR Efflux Pumps for Acid Adaptation and GadAB Induction in Escherichia coli

BACKGROUND: The TolC outer membrane channel is a key component of several multidrug resistance (MDR) efflux pumps driven by H(+) transport in Escherichia coli. While tolC expression is under the regulation of the EvgA-Gad acid resistance regulon, the role of TolC in growth at low pH and extreme-acid survival is unknown. METHODS AND PRINCIPAL FINDINGS: TolC was required for extreme-acid survival (pH 2) of strain W3110 grown aerobically to stationary phase. A tolC deletion decreased extreme-acid survival (acid resistance) of aerated pH 7.0-grown cells by 10(5)-fold and of pH 5.5-grown cells by 10-fold. The requirement was specific for acid resistance since a tolC defect had no effect on aerobic survival in extreme base (pH 10). TolC was required for expression of glutamate decarboxylase (GadA, GadB), a key component of glutamate-dependent acid resistance (Gad). TolC was also required for maximal exponential growth of E. coli K-12 W3110, in LBK medium buffered at pH 4.5-6.0, but not at pH 6.5-8.5. The TolC growth requirement in moderate acid was independent of Gad. TolC-associated pump components EmrB and MdtB contributed to survival in extreme acid (pH 2), but were not required for growth at pH 5. A mutant lacking the known TolC-associated efflux pumps (acrB, acrD, emrB, emrY, macB, mdtC, mdtF, acrEF) showed no growth defect at acidic pH and a relatively small decrease in extreme-acid survival when pre-grown at pH 5.5. CONCLUSIONS: TolC and proton-driven MDR efflux pump components EmrB and MdtB contribute to E. coli survival in extreme acid and TolC is required for maximal growth rates below pH 6.5. The TolC enhancement of extreme-acid survival includes Gad induction, but TolC-dependent growth rates below pH 6.5 do not involve Gad. That MDR resistance can enhance growth and survival in acid is an important consideration for enteric organisms passing through the acidic stomach

Explicit simulation and high-performance computing, application to a bolt tensile test

International audienceThe European project Maaximus (More Affordable Aircraft Structure Lifecycle through eXtended, Integrated & Mature nUmerical Sizing) aims at demonstrating the fast development and right-first-time validation of a highly optimized composite airframe. In this context, fasteners models are crucial to ensure correct structure modelling at a higher level. The present study focuses on a bolt tensile test. After a review of the state-of-the-art in this domain, the first part of the study is dedicated to explicit simulation and its specificities: resolution algorithm, mass and time scaling, comparison of energies. We also discuss about High-Performance Computing (HPC), and the need of consistency between model and computation structure. These simulation techniques are then applied to the modelling of the fastener tensile test. Experiments have been led with various fasteners diameters. We observe successful correlation between simulation and experiments both qualitatively and quantitatively

Explicit simulation and high-performance computing, application to a bolt tensile test

International audienceThe European project Maaximus (More Affordable Aircraft Structure Lifecycle through eXtended, Integrated & Mature nUmerical Sizing) aims at demonstrating the fast development and right-first-time validation of a highly optimized composite airframe. In this context, fasteners models are crucial to ensure correct structure modelling at a higher level. The present study focuses on a bolt tensile test. After a review of the state-of-the-art in this domain, the first part of the study is dedicated to explicit simulation and its specificities: resolution algorithm, mass and time scaling, comparison of energies. We also discuss about High-Performance Computing (HPC), and the need of consistency between model and computation structure. These simulation techniques are then applied to the modelling of the fastener tensile test. Experiments have been led with various fasteners diameters. We observe successful correlation between simulation and experiments both qualitatively and quantitatively

Absorption by an Optical Dipole Antenna in a Structured Environment

We compute generalized absorption and extinction cross-sections of an optical dipole nanoantenna in a structured environment. The expressions explicitly show the influence of radiation reaction and the local density of states on the intrinsic absorption properties of the antenna. Engineering the environment could allow to modify the overall absorption as well as the frequency and the linewidth of a resonant antenna. Conversely, a dipole antenna can be used to probe the photonic environment, in a similar way as a quantum emitter

Experimental and numerical analysis of pull-through of fasteners in laminates

International audienceno abstrac

Experimental and numerical analysis of pull-through of fasteners in laminates

International audienceno abstrac