481 research outputs found
Elaboration de surfaces nano/micro-structurĂ©es pour limiter lâadhĂ©sion de micro-organismes
Avec plus dâun million de dispositifs posĂ©s par an dans le monde, lâutilisation des chambres implantables sâest maintenant gĂ©nĂ©ralisĂ©e pour le traitement de certains cancers. ConstituĂ©es dâun rĂ©servoir de quelques dixiĂšmes de microlitres, le plus souvent en titane, reliĂ© Ă un cathĂ©ter dont lâextrĂ©mitĂ© est placĂ©e dans une veine Ă fort dĂ©bit, ils permettent de dĂ©livrer un traitement de chimiothĂ©rapie avec un confort augmentĂ© pour le patient. Ces dispositifs permettent aussi le cas Ă©chĂ©ant dâapporter une nutrition parentĂ©rale. Cette derniĂšre utilisation provoque de nombreuses infections, qui conduisent dans la plupart des cas au retrait du dispositif.
Afin de rĂ©duire le risque de contamination, il est donc nĂ©cessaire de mieux comprendre les facteurs favorisant lâadhĂ©rence des micro-organismes (bactĂ©ries et levures) dans ces dispositifs mĂ©dicaux invasifs et leur colonisation ultĂ©rieure.
Dans le cadre du projet régional MAT-INNO, nos travaux de recherche visent à mieux
comprendre lâimpact des propriĂ©tĂ©s de surface (en termes de topographie, hydrophobicitĂ© et fonctionnalisation) sur lâadhĂ©sion de bactĂ©ries et de levures. En agissant sur les propriĂ©tĂ©s physiques et/ou chimiques de surface, nous espĂ©rons rĂ©duire les capacitĂ©s d\u27adhĂ©rence des micro-organismes et ainsi limiter le risque d\u27infection. Les Ă©tudes actuelles sont rĂ©alisĂ©es sur des substrats de silicium sur lesquels est dĂ©posĂ©e une couche mince nanomĂ©trique dâoxyde de titane.
Nos efforts portent, dans un premier temps, sur la maĂźtrise de la topographie de surface Ă lâĂ©chelle nanomĂ©trique et micromĂ©trique, notamment par la mise au point de procĂ©dĂ©s de fabrication reproductibles. Lâutilisation de la pulvĂ©risation cathodique sur les supports de silicium ultra-lisses permet dâobtenir des surfaces dâoxyde de titane ayant des rugositĂ©s infĂ©rieures au nanomĂštre. De plus, lâattaque du silicium par lâhydroxyde de potassium permet de modifier la topographie des surfaces avant le dĂ©pĂŽt de films minces dâoxyde de titane. Nous prĂ©sentons sur le poster les rĂ©sultats obtenus rĂ©cemment par microscopie Ă force atomique et par microscopie Ă©lectronique Ă balayage sur les diffĂ©rents types de surface. Lâanalyse des courbes de rĂ©flectivitĂ© des rayons X nous a permis de dĂ©terminer prĂ©cisĂ©ment lâĂ©paisseur des films dĂ©posĂ©s et de suivre les modifications de la composition chimique suivant les paramĂštres appliquĂ©s
Le point sur certains ravageurs du cĂšdre de l'Atlas en Afrique du nord, en France et en Europe.
Cette synthÚse fait le point sur les connaissances acquises depuis une vingtaine d'années sur certains ravageurs du cÚdre de l'Atlas dans son aire naturelle en Afrique du nord (Algérie, Maroc) et dans son aire d'extension en France et en Europe
The CAT Imaging Telescope for Very-High-Energy Gamma-Ray Astronomy
The CAT (Cherenkov Array at Themis) imaging telescope, equipped with a
very-high-definition camera (546 fast phototubes with 0.12 degrees spacing
surrounded by 54 larger tubes in two guard rings) started operation in Autumn
1996 on the site of the former solar plant Themis (France). Using the
atmospheric Cherenkov technique, it detects and identifies very high energy
gamma-rays in the range 250 GeV to a few tens of TeV. The instrument, which has
detected three sources (Crab nebula, Mrk 421 and Mrk 501), is described in
detail.Comment: 24 pages, 15 figures. submitted to Elsevier Preprin
Dielectric response of charge induced correlated state in the quasi-one-dimensional conductor (TMTTF)2PF6
Conductivity and permittivity of the quasi-one-dimensionsional organic
transfer salt (TMTTF)2PF6 have been measured at low frequencies (10^3-10^7 Hz)
between room temperature down to below the temperature of transition into the
spin-Peierls state. We interpret the huge real part of the dielectric
permittivity (up to 10^6) in the localized state as the realization in this
compound of a charge ordered state of Wigner crystal type due to long range
Coulomb interaction.Comment: 11 pages, 3 .eps figure
A new analysis method for very high definition Imaging Atmospheric Cherenkov Telescopes as applied to the CAT telescope
A new method of shower-image analysis is presented which appears very
powerful as applied to those Cherenkov Imaging Telescopes with very high
definition imaging capability. It provides hadron rejection on the basis of a
single cut on the image shape, and simultaneously determines the energy of the
electromagnetic shower and the position of the shower axis with respect to the
detector. The source location is also reconstructed for each individual
gamma-ray shower, even with one single telescope, so for a point source the
hadron rejection can be further improved. As an example, this new method is
applied to data from the CAT (Cherenkov Array at Themis) imaging telescope,
which has been operational since Autumn, 1996.Comment: 22 pages. submitted to Elsevier Preprin
Prototype Tests for the CELESTE Solar Array Gamma--Ray Telescope
The CELESTE experiment will be an Atmospheric Cherenkov detector designed to
bridge the gap in energy sensitivity between current satellite and ground-based
gamma-ray telescopes, 20 to 300 GeV. We present test results made at the former
solar power plant, Themis, in the French Pyrenees. The tests confirm the
viability of using a central tower heliostat array for Cherenkov wavefront
sampling.Comment: LaTeX2e,30 pages including 14 figures, accepted for publication by
Nuclear Instruments & Methods Section
Regulation of 5-HT Receptors and the Hypothalamic-Pituitary-Adrenal Axis
Disturbances in the serotonin (5-HT) system is the neurobiological abnormality most consistently associated with suicide. Hyperactivity of the hypothalmic-pituitary-adrenal (HPA) axis is also described in suicide victims. The HPA axis is the classical neuroendocrine system that responds to stress and whose final product, corticosteroids, targets components of the limbic system, particularly the hippocampus. We will review resulsts from animal studies that point to the possibility that many of the 5-HT receptor changes observed in suicide brains may be a result of, or may be worsened by, the HPA overactivity that may be present in some suicide victims. The results of these studies can be summarized as follows: (1) chronic unpredictable stress produces high corticosteroid levels in rats; (2) chronic stress also results in changes in specific 5-HT receptors (increases in cortical 5-HT2A and decreases in hipocampal 5-HT1A and 5-HT1B); (3) chronic antidepressant administration prevents many of the 5-HT receptor changes observed after stress; and (4) chronic antidepressant administration reverses the overactivity of the HPA axis. If indeed 5-HT receptors have a partial role in controlling affective states, then their modulation by corticosteroids provides a potential mechanism by which these hormones may regulate mood. These data may also provide a biological understanding of how stressful events may increase the risk for suicide in vulnerable individuals and may help us elucidate the neurobiological underpinnings of treatment resistance.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73437/1/j.1749-6632.1997.tb52357.x.pd
Measurement of the W+W-gamma Cross Section and Direct Limits on Anomalous Quartic Gauge Boson Couplings at LEP
The process e+e- -> W+W-gamma is analysed using the data collected with the
L3 detector at LEP at a centre-of-mass energy of 188.6GeV, corresponding to an
integrated luminosity of 176.8pb^-1. Based on a sample of 42 selected W+W-
candidates containing an isolated hard photon, the W+W-gamma cross section,
defined within phase-space cuts, is measured to be: sigma_WWgamma = 290 +/- 80
+/- 16 fb, consistent with the Standard Model expectation. Including the
process e+e- -> nu nu gamma gamma, limits are derived on anomalous
contributions to the Standard Model quartic vertices W+W- gamma gamma and W+W-Z
gamma at 95% CL: -0.043 GeV^-2 < a_0/Lambda^2 < 0.043 GeV^-2 0.08 GeV^-2 <
a_c/Lambda^2 < 0.13 GeV^-2 0.41 GeV^-2 < a_n/Lambda^2 < 0.37 GeV^-2
Production of Single W Bosons at \sqrt{s}=189 GeV and Measurement of WWgamma Gauge Couplings
Single W boson production in electron-positron collisions is studied with the
L3 detector at LEP. The data sample collected at a centre-of-mass energy of
\sqrt{s} = 188.7GeV corresponds to an integrated luminosity of 176.4pb^-1.
Events with a single energetic lepton or two acoplanar hadronic jets are
selected. Within phase-space cuts, the total cross-section is measured to be
0.53 +/- 0.12 +/- 0.03 pb, consistent with the Standard Model expectation.
Including our single W boson results obtained at lower \sqrt{s}, the WWgamma
gauge couplings kappa_gamma and lambda_gamma are determined to be kappa_gamma =
0.93 +/- 0.16 +/- 0.09 and lambda_gamma = -0.31 +0.68 -0.19 +/- 0.13
Search for Neutral Higgs Bosons of the Minimal Supersymmetric Standard Model in e+e- Interactions at \sqrt{s} = 189 GeV
A search for the lightest neutral scalar and neutral pseudoscalar Higgs
bosons in the Minimal Supersymmetric Standard Model is performed using 176.4
pb^-1 of integrated luminosity collected by L3 at a center-of-mass energy of
189 GeV. No signal is observed, and the data are consistent with the expected
Standard Model background. Lower limits on the masses of the lightest neutral
scalar and pseudoscalar Higgs bosons are given as a function of tan(beta).
Lower mass limits for tan(beta)>1 are set at the 95% confidence level to be m_h
> 77.1 GeV and m_A > 77.1 GeV
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