La post-évaluation des investissements, un dispositif d'apprentissage et de gouvernance.

apprentissage; gouvernance; post-évaluation; investissement;

ICAR, a tool for Blind Source Separation using Fourth Order Statistics only

International audienceThe problem of blind separation of overdetermined mixtures of sources, that is, with fewer sources than (or as many sources as) sensors, is addressed in this paper. A new method, named ICAR (Independent Component Analysis using Redundancies in the quadricovariance), is proposed in order to process complex data. This method, without any whitening operation, only exploits some redundancies of a particular quadricovariance matrix of the data. Computer simulations demonstrate that ICAR offers in general good results and even outperforms classical methods in several situations: ICAR ~(i) succeeds in separating sources with low signal to noise ratios, ~(ii) does not require sources with different SO or/and FO spectral densities, ~(iii) is asymptotically not affected by the presence of a Gaussian noise with unknown spatial correlation, (iv) is not sensitive to an over estimation of the number of sources

Serological evidence for Japanese encephalitis and West Nile virus infections in domestic birds in Cambodia

Mosquito-borne flaviviruses with an enzootic transmission cycle like Japanese encephalitis virus (JEV) and West Nile virus (WNV) are a major public health concern. The circulation of JEV in Southeast Asia is well-documented, and the important role of pigs as amplification hosts for the virus is long known. The influence of other domestic animals especially poultry that lives in high abundance and close proximity to humans is not intensively analyzed. Another understudied field in Asia is the presence of the closely related WNV. Such analyses are difficult to perform due to the intense antigenic cross-reactivity between these viruses and the lack of suitable standardized serological assays. The main objective of this study was to assess the prevalence of JEV and WNV flaviviruses in domestic birds, detailed in chickens and ducks, in three different Cambodian provinces. We determined the flavivirus seroprevalence using an hemagglutination inhibition assay (HIA). Additionally, we investigated in positive samples the presence of JEV and WNV neutralizing antibodies (nAb) using foci reduction neutralization test (FRNT). We found 29% (180/620) of the investigated birds positive for flavivirus antibodies with an age-depended increase of the seroprevalence (OR = 1.04) and a higher prevalence in ducks compared to chicken (OR = 3.01). Within the flavivirus-positive birds, we found 43% (28/65) with nAb against JEV. We also observed the expected cross-reactivity between JEV and WNV, by identifying 18.5% double-positive birds that had higher titers of nAb than single-positive birds. Additionally, seven domestic birds (10.7%) showed only nAb against WNV and no nAb against JEV. Our study provides evidence for an intense JEV circulation in domestic birds in Cambodia, and the first serological evidence for WNV presence in Southeast Asia since decades. These findings mark the need for a re-definition of areas at risk for JEV and WNV transmission, and the need for further and intensified surveillance of mosquito-transmitted diseases in domestic animals

Asymmetrical stripline based method for retrieving the electromagnetic properties of metamaterials

International audienceAn experimental characterization technique for determining the electromagnetic properties of metamaterials in the microwave frequency band is presented. The method consists in measuring the S-parameters of an asymmetrical stripline partially filled with the sample to be characterized. For retrieving the characteristic parameters, two different approaches based on quasi-static approximations are compared. This measurement cell allows an "in situ" characterization because it reproduces the electromagnetic environment frequently found in planar technologies for microwave applications of metamaterials. The whole sample is uniformly excited in magnitude and direction by the interacting electromagnetic field which guarantees representativeness of extracted permittivity and permeability and avoids possible inconsistencies due to anisotropy and heterogeneity of metamaterials

Aligned carbon nanotube based ultrasonic microtransducers for durability monitoring in civil engineering

International audienceStructural health monitoring of porous materials such as concrete is becoming a major component in our resource-limited economy, as it conditions durable exploitation of existing facilities. Durability in porous materials depends on nanoscale features which need to be monitored in situ with nanometric resolution. To address this problem, we put forward an approach based on the development of a new nanosensor, namely a capacitive micrometric ultrasonic transducer whose vibrating membrane is made of aligned single-walled carbon nanotubes (SWNT). Such sensors are meant to be embedded in large numbers within a porous material in order to provide information on its durability by monitoring in situ neighboring individual micropores. In the present paper, we report on the feasibility of the key building block of the proposed sensor: we have fabricated well-aligned, ultra-thin, dense SWNT membranes that show above-nanometer amplitudes of vibration over a large range of frequencies spanning from 100 kHz to 5 MHz

Influence de ferrites de Ni-Zn dans la miniaturisation d'antennes pour applications DVB-H.

National audienceCette étude se situe dans la problématique de la miniaturisation d'antennes dans le domaine de fréquences 470-862MHz, correspondant à la norme DVB-H. Dans cet objectif les propriétés magnétostrictives de ferrites de Ni-Zn sont mises à profit pour étendre jusqu'à 1 GHz leur potentialité d'application comme substrats d'antennes. Les matériaux réalisés présentent des tangentes de pertes magnétiques qui restent inférieures à 5.10-2 dans la gamme de fréquence 100MHZ-1GHz, avec une perméabilité constante et un indice optique proche de 3 pour le matériau présenté Cette valeur pourra être aisément augmentée jusqu'à 4,5 environ. Ces propriétés prédisposent ces matériaux aux applications dans le domaine UHF

Alpha interferon restricts human T-lymphotropic virus type 1 and 2 De Novo infection through PKR activation

International audienceType I interferon (IFN-I) inhibits the replication of different viruses. However, the effect of IFN-I on the human T-lymphotropic virus type 1 (HTLV-1) viral cycle is controversial. Here, we investigated the consequences of IFN-α addition for different steps of HTLV-1 and HTLV-2 infection. We first show that alpha interferon (IFN-α) efficiently impairs HTLV-1 and HTLV-2 de novo infection in a T cell line and in primary lymphocytes. Using pseudotyped viruses expressing HTLV-1 envelope, we then show that cell-free infection is insensitive to IFN-α, demonstrating that the cytokine does not affect the early stages of the viral cycle. In contrast, intracellular levels of Gag, Env, or Tax protein are affected by IFN-α treatment in T cells, primary lymphocytes, or 293T cells transfected with HTLV-1 or HTLV-2 molecular clones, demonstrating that IFN-α acts during the late stages of infection. We show that IFN-α does not affect Tax-mediated transcription and acts at a posttranscriptional level. Using either small interfering RNA (siRNA) directed against PKR or a PKR inhibitor, we demonstrate that PKR, whose expression is induced by interferon, plays a major role in IFN-α-induced HTLV-1/2 inhibition. These results indicate that IFN-α has a strong repressive effect on the HTLV-1 and HTLV-2 viral cycle during de novo infection of cells that are natural targets of the viruses

Pressure Dependence of the Frequency Permeability Spectra of Soft Ferrite Composite Materials: A Method of Measuring the Natural Ferromagnetic Resonance Frequency

International audienceExperimental studies on the complex susceptibility of soft magnetic composite materials (magnetostrictive Ni-Zn and Ni-Zn-Co spinels) in their region of ferrimagnetic resonance (FMR) show that the FMR is an increasing function of the applied pressure. It is shown that powders could advantageously replace their sintered materials counterpart to measure without any ambiguity the natural ferrimagnetic resonance (NFMR) frequencies of bulk materials. It is also shown that such soft ferrite composites can be realized in order to shift FMR to higher values, and to obtain low magnetic losses up to 900 MHz. High frequencies applications can be envisaged

Gem-Induced Cytoskeleton Remodeling Increases Cellular Migration of HTLV-1-Infected Cells, Formation of Infected-to-Target T-Cell Conjugates and Viral Transmission

International audienceEfficient HTLV-1 viral transmission occurs through cell-to-cell contacts. The Tax viral transcriptional activator protein facilitates this process. Using a comparative transcriptomic analysis, we recently identified a series of genes up-regulated in HTLV-1 Tax expressing T-lymphocytes. We focused our attention towards genes that are important for cytoskeleton dynamic and thus may possibly modulate cell-to-cell contacts. We first demonstrate that Gem, a member of the small GTP-binding proteins within the Ras superfamily, is expressed both at the RNA and protein levels in Tax-expressing cells and in HTLV-1-infected cell lines. Using a series of ChIP assays, we show that Tax recruits CREB and CREB Binding Protein (CBP) onto a cAMP Responsive Element (CRE) present in the gem promoter. This CRE sequence is required to drive Tax-activated gem transcription. Since Gem is involved in cytoskeleton remodeling, we investigated its role in infected cells motility. We show that Gem co-localizes with F-actin and is involved both in T-cell spontaneous cell migration as well as chemotaxis in the presence of SDF-1/CXCL12. Importantly, gem knock-down in HTLV-1-infected cells decreases cell migration and conjugate formation. Finally, we demonstrate that Gem plays an important role in cell-to-cell viral transmission