Compressions of a polycarbonate honeycomb

International audienceThe in-plane compressive response of a polycarbonate honeycomb with circular close-packed cells is considered first experimentally then analytically. Under quasi-static uniaxial compression, we observed behaviors strongly depending on the orientation: for one of the two main orientations the compression is homogeneous, while for the other the deformation localizes in a very narrow band of cells. More surprisingly, for not crushing but extreme compression, when the load is released, the deformation is reversed, the localization disappears and the polycarbonate returns to its original shape. In order to explain this strange phenomena, we develop a geometric model of this honeycomb together with an expression of the bending energy. We focus on a basic mechanical element made of an elastica triangle. We also compare our description with previous experimental studies and simulations made with similar material. Finally , to illustrate mathematically this type of behavior, we present a simple model for buckling deformations with two degrees of freedom

Zinc adaptation and resistance to cadmium toxicity in mammalian cells. Molecular insight by proteomic analysis

To identify proteins involved in cellular adaptive responses to zinc, a comparative proteome analysis between a previously developed high zinc- and cadmium- resistant human epithelial cell line (HZR) and the parental HeLa cells has been carried out. Differentially produced proteins included co-chaperones, proteins associated with oxido-reductase activities, and ubiquitin. Biochemical pathways to which these proteins belong were probed for their involvement in the resistance of both cell lines against cadmium toxicity. Among endoplasmic reticulum stressors, thapsigargin sensitized HZR cells, but not HeLa cells, to cadmium toxicity more acutely than tunicamycin, implying that these cells heavily relied on proper intracellular calcium distribution. The similar sensitivity of both HeLa and HZR cells to inhibitors of the proteasome, such as MG-132 or lactacystin, excluded improved proteasome activity as a mechanism associated with zinc adaptation of HZR cells. The enzyme 4-hydroxyphenylpyruvate dioxygenase was overproduced in HZR cells as compared to HeLa cells. It transforms 4-hydroxyphenylpyruvate to homogentisate in the second step of tyrosine catabolism. Inhibition of 4-hydroxyphenylpyruvate dioxygenase decreased the resistance of HZR cells against cadmium, but not that of HeLa cells, suggesting that adaptation to zinc overload and increased 4-hydroxyphenylpyruvate removal are linked in HZR cellsComment: in press in Proteomic

Influence du contexte paysager sur les attaques de processionnaire du pin en ville. Quelles perspectives de méthodes de lutte alternatives ?

We conducted an inventory of all the potential host trees of this species and of its winter tents over an urban area of about 6500 ha. Here we present the preliminary results of a spatial ecology approach and of a neighbourhood analysis exploring relationships between the level of infestation on a given tree and the features of the other host trees occurring around it. The ultimate goal of this work is to help defining urban green infrastructures unfavourable to the spread of this pest.La processionnaire du pin est un insecte défoliateur et urticant inféodé à des résineux forestiers. Elle se propage dans les milieux non forestiers en utilisant les plantations ornementales de ses arbres-hôtes. Dans les zones urbanisées, sa présence pose des problèmes de santé publique auxquels les collectivités territoriales doivent faire face. Nous avons réalisé un inventaire de tous les pins, cèdres et Douglas, et des nids d’hiver qu’ils hébergent, sur le territoire de cinq communes de l’agglomération orléanaise. Nous avons commencé à conduire sur ce jeu de données des analyses d’écologie spatiale et des analyses de voisinage prenant en compte l’influence sur le niveau d’infestation d’un arbre des caractéristiques des autres arbres-hôtes présents dans son environnement. Nous présentons ici les résultats préliminaires de cette approche paysagère en milieu urbain. A terme, l’objectif de ce travail est d’explorer les possibilités de concevoir des infrastructures vertes qui, au lieu de fournir des corridors d’expansion à cette espèce, pourraient en réduire le niveau de nuisance

Contes de Nadal i malsons

Abstract not availabl

Utilisation des données Google Street View pour cartographier la distribution géographique des espèces. Une étude préliminaire de la processionnaire du pin (Thaumetopoea pityocampa)

Article publié suite à l'événement : MEDINSECT 3 ; Hammamet-Tunis (Tunisie) - (2012-05-08 - 2012-05-11).Mapping species distribution is an important and useful task to monitor invasive species spread or native species expansion under climate change. Unfortunately it requires a lot of occurrence data that are not easily available from literature and that are very time-consuming to collect in the field. For that reason, we designed a survey with the aim to explore to which extent large-scale databases such as Google Street View could be used to derive valid occurrence data. We worked with an insect species, the Pine Processionary Moth (PPM) Thaumetopoea pityocampa because the larvae of that moth build silk nests on its host tree that are easily visible. The presence of the species at one location can therefore be inferred from visual records derived from the panoramic views available from Google Street View. We designed a standardized procedure allowing the evaluation of the presence of the PPM on a large sampling grid (covering 46 848 km2) located in France. Field sampling has been conducted in parallel, which allowed a straightforward comparison between field and Google-derived datasets. Data derived from Google Street View were highly similar to field data as we found an accuracy (percentage of field values correctly predicted using Google Street View) of 92.9%. We conclude that Google database might provide useful occurrence data for mapping the distribution of species which presence can be visually evaluated such as the PPM. More data are needed, however, to assess the range of spatial scales at which Google Street View actually provides reliable occurrence data.La cartographie de la distribution géographique des espèces est importante pour suivre l’évolution des aires de distribution d’espèces invasives ou d’espèces natives en expansion géographique. Malheureusement, les données nécessaires sont parfois difficilement accessibles à partir de la littérature et sont coûteuses à collecter sur le terrain. Pour cette raison, nous avons conçu une étude dans le but d'explorer dans quelle mesure il est possible d’utiliser les bases de données telles que Google Street View (GSV) pour obtenir des données d’occurrence valides. Nous avons choisi de travailler avec une espèce d’insecte, la chenille processionnaire du pin (PP) Thaumetopoea pityocampa car les larves de cette espèce se développent dans le feuillage des arbres hôtes et tissent un nid blanc aisément visible. La présence de l'espèce dans un site donné peut donc être facilement renseignée en examinant les vues panoramiques disponibles pour de nombreuses localités dans la base de données de Google Street View. Nous avons conçu une procédure standardisée permettant d'évaluer la présence de la PP à partir des données GSV et nous l’avons mise en oeuvre sur une aire d’étude couvrant 46 848 km2dans la région Centre en France. La distribution de l’espèce a également été décrite à l’aide d’échantillonnages réalisés sur le terrain. Les données issues de l’examen des images Google Street View ont été comparées aux données de terrain et se sont révélées de bons estimateurs de la présence de la processionnaire du pin avec une précision (proportion de valeurs correctement estimées) de 92.9% sur notre zone d’étude pour un maillage de 16 km x 16 km. Ces résultats suggèrent que l’exploitation des bases de données de GSV pourrait permettre de produire des données écologiques intéressantes pour les espèces dont la présence peut être estimée visuellement à partir de photographies. Des études complémentaires sont cependant nécessaires pour mieux cerner la gamme d’échelles spatiales auxquelles GSV fournit des données d’occurrence fiables

VSI: a milli-arcsec spectro-imager for the VLTI

VLTi Spectro-Imager (VSI) is a proposition for a second generation VLTI instrument which is aimed at providing the ESO community with the capability of performing image synthesis at milli-arcsecond angular resolution. VSI provides the VLTI with an instrument able to combine 4 telescopes in a baseline version and optionally up to 6 telescopes in the near-infrared spectral domain with moderate to high spectral resolution. The instrument contains its own fringe tracker in order to relax the constraints onto the VLTI infrastructure. VSI will do imaging at the milli-arcsecond scale with spectral resolution of: a) the close environments of young stars probing the initial conditions for planet formation; b) the surfaces of stars; c) the environment of evolved stars, stellar remnants and stellar winds, and d) the central region of active galactic nuclei and supermassive black holes. The science cases allowed us to specify the astrophysical requirements of the instrument and to define the necessary studies of the science group for phase A.Comment: 12 page

The planar optics phase sensor: a study for the VLTI 2nd generation fringe tracker

In a few years, the second generation instruments of the Very Large Telescope Interferometer (VLTI) will routinely provide observations with 4 to 6 telescopes simultaneously. To reach their ultimate performance, they will need a fringe sensor capable to measure in real time the randomly varying optical paths differences. A collaboration between LAOG (PI institute), IAGL, OCA and GIPSA-Lab has proposed the Planar Optics Phase Sensor concept to ESO for the 2[SUP]nd[/SUP] Generation Fringe Tracker. This concept is based on the integrated optics technologies, enabling the conception of extremely compact interferometric instruments naturally providing single-mode spatial filtering. It allows operations with 4 and 6 telescopes by measuring the fringes position thanks to a spectrally dispersed ABCD method. We present here the main analysis which led to the current concept as well as the expected on-sky performance and the proposed design

Increasing the imaging capabilities of the VLTI using integrated optics

Several scientific topics linked to the observation of extended structures around astrophysical sources (dust torus around AGN, disks around young stars, envelopes around AGBs) require imaging capability with milli-arcsecond spatial resolution. The current VLTI instruments, AMBER and MIDI, will provide in the coming months the required high angular resolution, yet without actual imaging. As a rule of thumb, the image quality accessible with an optical interferometer is directly related to the number of telescopes used simultaneously: the more the apertures, the better and the faster the reconstruction of the image. We propose an instrument concept to achieve interferometric combination of N telescopes (4 ≤ N ≤ 8) thanks to planar optics technology: 4 x 8-m telescopes in the short term and/or 8 x 1.8-m telescopes in the long term. The foreseen image reconstruction quality in the visible and/or in the near infrared will be equivalent to the one achieved with millimeter radio interferometers. Achievable spatial resolution will be better than the one foreseen with ALMA. This instrument would be able to acquire routinely 1 mas resolution images. A 13 to 20 magnitude sensitivity in spectral ranges from 0.6 to 2.5 μm is expected depending on the choice of the phase referencing guide source. High dynamic range, even on faint objects, is achievable thanks to the high accuracy provided by integrated optics for visibility amplitude and phase measurements. Based on recent validations of integrated optics presented here an imaging instrument concept can be proposed. The results obtained using the VLTI facilities give a demonstration of the potential of the proposed technique

Comparison of accuracy of fibrosis degree classifications by liver biopsy and non-invasive tests in chronic hepatitis C

<p>Abstract</p> <p>Background</p> <p>Non-invasive tests have been constructed and evaluated mainly for binary diagnoses such as significant fibrosis. Recently, detailed fibrosis classifications for several non-invasive tests have been developed, but their accuracy has not been thoroughly evaluated in comparison to liver biopsy, especially in clinical practice and for Fibroscan. Therefore, the main aim of the present study was to evaluate the accuracy of detailed fibrosis classifications available for non-invasive tests and liver biopsy. The secondary aim was to validate these accuracies in independent populations.</p> <p>Methods</p> <p>Four HCV populations provided 2,068 patients with liver biopsy, four different pathologist skill-levels and non-invasive tests. Results were expressed as percentages of correctly classified patients.</p> <p>Results</p> <p>In population #1 including 205 patients and comparing liver biopsy (reference: consensus reading by two experts) and blood tests, Metavir fibrosis (F_M) stage accuracy was 64.4% in local pathologists vs. 82.2% (p < 10^-3) in single expert pathologist. Significant discrepancy (≥ 2F_Mvs reference histological result) rates were: Fibrotest: 17.2%, FibroMeter^2G: 5.6%, local pathologists: 4.9%, FibroMeter^3G: 0.5%, expert pathologist: 0% (p < 10^-3). In population #2 including 1,056 patients and comparing blood tests, the discrepancy scores, taking into account the error magnitude, of detailed fibrosis classification were significantly different between FibroMeter^2G(0.30 ± 0.55) and FibroMeter^3G(0.14 ± 0.37, p < 10^-3) or Fibrotest (0.84 ± 0.80, p < 10^-3). In population #3 (and #4) including 458 (359) patients and comparing blood tests and Fibroscan, accuracies of detailed fibrosis classification were, respectively: Fibrotest: 42.5% (33.5%), Fibroscan: 64.9% (50.7%), FibroMeter^2G: 68.7% (68.2%), FibroMeter^3G: 77.1% (83.4%), p < 10^-3(p < 10^-3). Significant discrepancy (≥ 2 F_M) rates were, respectively: Fibrotest: 21.3% (22.2%), Fibroscan: 12.9% (12.3%), FibroMeter^2G: 5.7% (6.0%), FibroMeter^3G: 0.9% (0.9%), p < 10^-3(p < 10^-3).</p> <p>Conclusions</p> <p>The accuracy in detailed fibrosis classification of the best-performing blood test outperforms liver biopsy read by a local pathologist, i.e., in clinical practice; however, the classification precision is apparently lesser. This detailed classification accuracy is much lower than that of significant fibrosis with Fibroscan and even Fibrotest but higher with FibroMeter^3G. FibroMeter classification accuracy was significantly higher than those of other non-invasive tests. Finally, for hepatitis C evaluation in clinical practice, fibrosis degree can be evaluated using an accurate blood test.</p

Electrophysiological evidence for an early processing of human voices

<p>Abstract</p> <p>Background</p> <p>Previous electrophysiological studies have identified a "voice specific response" (VSR) peaking around 320 ms after stimulus onset, a latency markedly longer than the 70 ms needed to discriminate living from non-living sound sources and the 150 ms to 200 ms needed for the processing of voice paralinguistic qualities. In the present study, we investigated whether an early electrophysiological difference between voice and non-voice stimuli could be observed.</p> <p>Results</p> <p>ERPs were recorded from 32 healthy volunteers who listened to 200 ms long stimuli from three sound categories - voices, bird songs and environmental sounds - whilst performing a pure-tone detection task. ERP analyses revealed voice/non-voice amplitude differences emerging as early as 164 ms post stimulus onset and peaking around 200 ms on fronto-temporal (positivity) and occipital (negativity) electrodes.</p> <p>Conclusion</p> <p>Our electrophysiological results suggest a rapid brain discrimination of sounds of voice, termed the "fronto-temporal positivity to voices" (FTPV), at latencies comparable to the well-known face-preferential N170.</p