Low Loss Metamaterials Based on Classical Electromagnetically Induced Transparency

We demonstrate theoretically that electromagnetically induced transparency can be achieved in metamaterials, in which electromagnetic radiation is interacting resonantly with mesoscopic oscillators rather than with atoms. We describe novel metamaterial designs that can support full dark resonant state upon interaction with an electromagnetic beam and we present results of its frequency-dependent effective permeability and permittivity. These results, showing a transparency window with extremely low absorption and strong dispersion, are confirmed by accurate simulations of the electromagnetic field propagation in the metamaterial

Planar designs for electromagnetically induced transparency in metamaterials

We present a planar design of a metamaterial exhibiting electromagnetically induced transparency that is amenable to experimental verification in the microwave frequency band. The design is based on the coupling of a split-ring resonator with a cut-wire in the same plane. We investigate the sensitivity of the parameters of the transmission window on the coupling strength and on the circuit elements of the individual resonators, and we interpret the results in terms of two linearly coupled Lorentzian resonators. Our metamaterial designs combine low losses with the extremely small group velocity associated with the resonant response in the transmission window, rendering them suitable for slow light applications at room temperature.Comment: 11 pages, 8 figure

Ondes internes du lac du Bourget: analyse des observations par des modèles linéaires

Deux campagnes de mesures effectuées sur le lac du Bourget en période de faible stratification (avril et décembre 1994) ont mis en évidence des oscillations de la thermocline de période comprise entre deux et trois jours. Ces oscillations atteignent 40 m d'amplitude pour une profondeur maximale de 145 m. Elles ont probablement un impact sur les processus biologiques et physico-chimiques qui gouvernent l'évolution de la qualité des eaux du lac.L'analyse des données brutes des températures révèle une corrélation étroite entre la génération des ondes internes et les événements de vents importants. Il apparaît en particulier que seuls les vents violents (< 8 m/s) affectent la stratification thermique de manière significative.Deux approches sont utilisées pour caractériser ces ondes :- une approche par traitement du signal qui donne accès aux périodes d'oscillations prédominantes ainsi qu'à la répartition de l'énergie dans la colonne d'eau en fonction de la fréquence.- une approche par modélisation mathématique au cours de laquelle les résultats obtenus par tjjois techniques distinctes utilisant plusieurs degrés de représentation de la bathymétrie du lac sont comparés. Ces modèles permettent de calculer les périodes d'oscillations ainsi que les déplacements de l'interface de densité et les vitesses dans chaque couche. A partir des valeurs des amplitudes d'oscillation obtenues expérimentalement, des vitesses maximales de l'ordre de 7 cm/s dans l'épîlîmnion et 3 cm/s dans l'hypolimnion ont pu être estimées pour les deux épisodes considérés.On montre que les modèles mathématiques et l'analyse spectrale corroborent les observations.There is a great concern about the understanding of water mass movements in lakes as they play a crucial role in the way nutrients and pollutants are trans-ported. This work brings new insights to the study of internal waves as it compares field data to various mathematical approaches. During the months of April and December 1994, a thermistor chain was deployed in Lake Bourget, France (length 18 km, width 3 km, maximum depth 145 m) to record temperature every 10 min, over nine unevenly spaced depths, from 10 to 51m. The time series of measurements provide a detailed picture of the characteristics and dynamics of internal waves. Records are discussed in view of the wind data observed at a meteorological station located at the south-end of the lake. According to the intensity of the wind forcing, the thermal structure is altered in different ways. When the winds are weak, the thermo-cline tilts and sets up a hydrostatic pressure gradient which balances the wind stress (TURNER, 1973). When the wind stops, the density interface oscillates until buoyancy is strong enough to balance the baroclinic pressure field. Strong winds, however, enhance large amplitude nonlinear waves which may break (Kelvin-Helmoltz instabilities), and therefore give rise to vertical mixing in the hypolimnion. During the recording periods wind stress in general is low, but occasional bursts of energy generate internal waves (fig. 2 and 3). In this paper, we focus on linear internal waves as records display a dominant response of the first longitudinal mode. The internal seiche continues to oscillate with decreasing amplitude after the wind has ceased. Two approaches have been implemented in order to characterize the internal waves. One consiste of signal treatment through spectral analysis and the second one involves mathematical modeling.Spectral analysis discloses responses of the first mode with periods of about 80h and 40h, respectively, for the April and December fleld survey (fig. 4 and 5). Further analysis of the April spectra shows that winds generate highly non-linear waves with high energy levels in a large band located in the first 30m. This band results from the mergence of two peaks of high energy at 80 and 40h respectively which probably correspond to the fundamental and second harmonie of a nonlinear wave. Then, as the wind stops, internal seiche of the first mode develops in the layer located between 30 and 50m indicating a deepening of the thermocline.Those fluctuations and their energy spectra are compared with the prédictions of three methods which are based on linear théories and consequently are not valid when the magnitude of oscillations is too high. The full phenomenon of wind-forced motion in a lake is not treated here. However, the analysis of postforcing phase is undertaken to charaterize free internai waves. One method is the Merian formula, which considers the lake as a two-layer system of constant properties and assumes the lake as a rectangular box. Another is a modified version of the Defant procédure (MORTIMER, 1979) which again assumes two layers but solves the momentum and mass équations with a varying cross section. The third method is the two layered variable depth model (TVDM) deve-loped by Schwab (HORN et aL, 1986), fitted to the basin topography and inclu-ding the free surface displacement It is expressed here through a one dimensional version directed along the main axis of the lake (i.e. the lateral variations of depth are not considered).The models display pattems of thermocline displacements (illustrated in fig. 7 and 8) which, in periodicity, are closely similar to those observed. Moreover, they give estimates of the maximum velocity induced by the seiche. Values of the order of 7 cm/s and 3 cm/s are found in the epilimnion and hypolimnion respectively. Finally, the influence exerted by the morphometry on the wave shape and associated field velocity is emphasized. In particular, the difference in the maximum speed calculated in the hypolimnion probably stems from the lateral contraction of the lake (and thus increasing speed) near Aix-les-Bains which is not taken into account in the TVD Model. The validity of the models implemented here is thrown back into question when the magnitude of the oscillations is sufficiently high to steepen the thermocline and in this particular case, a nonlinear theory (Korteweg-de Vries Equation) would be appropriate.The importance of a better knowledge of internal seiches goes beyond the field of physics. Through their influence on mixing and dispersal, those motions profoundly affect the chemical and biological economies of many lakes. Internal waves are responsible for periodic vertical displacement of the resuspended biomass, and consequently for variation in the light intensity to which algal cells are exposed. Furthermore, associated bottom currents can enhance dissolution and remobilization of nutrients by transporting the products of bacterial decomposition away from the sediment-water interface into the water column

Marooned plants : vernacular naming practices in the Mascarene Islands

This article explores possible histories of plant exchanges and plant naming tied to the slave trade between East Africa, Madagascar and the Mascarene Islands. The subsequent 'marronnage' of slaves on these islands - their escape from captivity, sometimes to live in mountain hideouts - continues to inspire cultural references. Inspired by the use of the adjective 'marron/marronne' for a number of plants on Reunion Island, we compile evidence of plant exchanges and plant naming from ecological records, historical accounts and the use of descriptive, emotive or symbolic vernacular names as clues for deepening our knowledge of historical societies and environments. The evidence from the Mascarenes opens a window into the role of the African diaspora in plant introduction, diffusion, domestication and cultivation. We document that maroons relied on a variety of wild, escaped and cultivated plants for their subsistence. We also highlight the role of marronnage in the popular and literary imaginary, with the result that many plants are named 'marron/marrone' in a metaphorical sense. Finally, we identify a few plants that may have been transported, cultivated, or encouraged in one way or another by maroons. Along the way, we reflect on the pitfalls and opportunities of such interdisciplinary work

Tunable hybrid surface waves supported by a graphene layer

We study surface waves localized near a surface of a semi-infinite dielectric medium covered by a layer of graphene in the presence of a strong external magnetic field. We demonstrate that both TE-TM hybrid surface plasmons can propagate along the graphene surface. We analyze the effect of the Hall conductivity on the disper- sion of hybrid surface waves and suggest a possibility to tune the plasmon dispersion by the magnetic field.Comment: 3 pages, 3 figure

Past Achievements and Future Challenges in 3D Photonic Metamaterials

Photonic metamaterials are man-made structures composed of tailored micro- or nanostructured metallo-dielectric sub-wavelength building blocks that are densely packed into an effective material. This deceptively simple, yet powerful, truly revolutionary concept allows for achieving novel, unusual, and sometimes even unheard-of optical properties, such as magnetism at optical frequencies, negative refractive indices, large positive refractive indices, zero reflection via impedance matching, perfect absorption, giant circular dichroism, or enhanced nonlinear optical properties. Possible applications of metamaterials comprise ultrahigh-resolution imaging systems, compact polarization optics, and cloaking devices. This review describes the experimental progress recently made fabricating three-dimensional metamaterial structures and discusses some remaining future challenges

Do stormwater source control policies deliver the right hydrologic outcomes?

International audienceThe number of stormwater source control (SC) regulations adopted by local authorities is rapidly growing in many countries. We can expect that, in the near future, the hydrologic behavior of many urban and periurban catchments will reflect this diffusion. This paper discusses SC regulations through two complementary approaches: starting on three French case-studies, it analyzes how regulations are developed today and identifies a set of shortcuts in policy-making practices. Then, the hydrologic model of a periurban catchment in the Paris region is used to test the impacts that these regulations can produce if widely applied. The main finding is that inertia in policy-making, driving a singular focus on flow-rate based regulations, can produce negative impacts in the long-term. Further efforts on volume-based regulations are advocated, both in terms of research and policy-making. © 2012 Elsevier B.V. All rights reserved

Analysis of Xq27-28 linkage in the international consortium for prostate cancer genetics (ICPCG) families.

BACKGROUND: Genetic variants are likely to contribute to a portion of prostate cancer risk. Full elucidation of the genetic etiology of prostate cancer is difficult because of incomplete penetrance and genetic and phenotypic heterogeneity. Current evidence suggests that genetic linkage to prostate cancer has been found on several chromosomes including the X; however, identification of causative genes has been elusive. METHODS: Parametric and non-parametric linkage analyses were performed using 26 microsatellite markers in each of 11 groups of multiple-case prostate cancer families from the International Consortium for Prostate Cancer Genetics (ICPCG). Meta-analyses of the resultant family-specific linkage statistics across the entire 1,323 families and in several predefined subsets were then performed. RESULTS: Meta-analyses of linkage statistics resulted in a maximum parametric heterogeneity lod score (HLOD) of 1.28, and an allele-sharing lod score (LOD) of 2.0 in favor of linkage to Xq27-q28 at 138 cM. In subset analyses, families with average age at onset less than 65 years exhibited a maximum HLOD of 1.8 (at 138 cM) versus a maximum regional HLOD of only 0.32 in families with average age at onset of 65 years or older. Surprisingly, the subset of families with only 2-3 affected men and some evidence of male-to-male transmission of prostate cancer gave the strongest evidence of linkage to the region (HLOD = 3.24, 134 cM). For this subset, the HLOD was slightly increased (HLOD = 3.47 at 134 cM) when families used in the original published report of linkage to Xq27-28 were excluded. CONCLUSIONS: Although there was not strong support for linkage to the Xq27-28 region in the complete set of families, the subset of families with earlier age at onset exhibited more evidence of linkage than families with later onset of disease. A subset of families with 2-3 affected individuals and with some evidence of male to male disease transmission showed stronger linkage signals. Our results suggest that the genetic basis for prostate cancer in our families is much more complex than a single susceptibility locus on the X chromosome, and that future explorations of the Xq27-28 region should focus on the subset of families identified here with the strongest evidence of linkage to this region.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

A multi-stage genome-wide association study of bladder cancer identifies multiple susceptibility loci.

We conducted a multi-stage, genome-wide association study of bladder cancer with a primary scan of 591,637 SNPs in 3,532 affected individuals (cases) and 5,120 controls of European descent from five studies followed by a replication strategy, which included 8,382 cases and 48,275 controls from 16 studies. In a combined analysis, we identified three new regions associated with bladder cancer on chromosomes 22q13.1, 19q12 and 2q37.1: rs1014971, (P = 8 × 10⁻¹²) maps to a non-genic region of chromosome 22q13.1, rs8102137 (P = 2 × 10⁻¹¹) on 19q12 maps to CCNE1 and rs11892031 (P = 1 × 10⁻⁷) maps to the UGT1A cluster on 2q37.1. We confirmed four previously identified genome-wide associations on chromosomes 3q28, 4p16.3, 8q24.21 and 8q24.3, validated previous candidate associations for the GSTM1 deletion (P = 4 × 10⁻¹¹) and a tag SNP for NAT2 acetylation status (P = 4 × 10⁻¹¹), and found interactions with smoking in both regions. Our findings on common variants associated with bladder cancer risk should provide new insights into the mechanisms of carcinogenesis