Elaboration de composites polymère ferroélectrique-fils submicroniques ferromagnétiques : analyse des propriétés magnétoélectriques

Ce travail de thèse a pour objectif l'élaboration de composites magnétoélectriques à matrice polymère. L'utilisation de fils submicroniques magnétiques de différentes natures chimiques préparés par électrodéposition est originale. Les composites ont été mis en œuvre en dispersant ces particules magnétiques dans une matrice polymère ferroélectrique de P(VDF-TrFE). L'étude des propriétés électriques des composites chargés en fils de cobalt met en évidence un mécanisme de percolation avec un seuil de 1,15 %vol. Cette faible valeur montre une dispersion homogène des charges. Cette homogénéité est confirmée par les performances mécaniques. Pour les propriétés magnétoélectriques, les composites sont chargés à 0,3 %vol i.e. au-dessous du seuil de percolation : des particules de différentes compositions chimiques et facteurs de forme ont été utilisées. Après polarisation des composites, la piézoélectricité de la matrice polymère persiste. Lorsque les échantillons sont soumis à un champ magnétique, les propriétés ferromagnétiques se manifestent par un cycle d'hystérésis. Un coefficient magnétoélectrique comparable à celui des céramiques a été obtenu pour ces composites qui conservent la faible densité et la ductilité des polymères.The purpose of this work is to elaborate magnetoelectric polymer matrix composites. An electrodeposition process was used to prepare original magnetic submicron wires with different chemical compositions. Magnetic particles were dispersed in a P(VDF-TrFE) ferroelectric polymer matrix. The study of electrical properties of composites filled with cobalt wires shows a percolation mechanism with a threshold at 1.15 vol%. This low value demonstrates a homogenous dispersion. This homogeneity is confirmed by mechanical strength. For magnetoelectric properties, composites are filled with 0.3 vol% i.e. below the percolation threshold: particles with different chemical compositions and aspect ratio have been used. After poling, composites keep the polymeric matrix piezoelectricity. Upon magnetic field, ferromagnetic properties are exhibited by a hysteresis loop. A magnetoelectric coefficient of the same magnitude order than the one of ceramics has been measured on these composites remarkable for their low density and ductility

High conductive Ag nanowire–polyimide composites: Charge transport mechanism in thermoplastic thermostable materials

High conductive composites were elaborated by incorporating high aspect ratio (250) silver nanowires in polyimide matrix via solvent mixing way. Silver nanowires were synthesized in solution by polyol synthesis. The composite conductivity reaches the value of 102 S·m−1 above a very lowpercolation threshold (0.48 vol.% of silver nanowires). SEM-FEG images showed that metallic nanowires are well dispersed in PI matrix. They do not influence the physical structure of the polymer. Below the percolation threshold, γ, β and α relaxation modes were detected. γ relaxation mode was fitted to determinate the activation energy value (32.7 kJ·mol−1) and the relaxation time (1.5 × 10−16 s). The mobility associated with the γ relaxation is considered to be localized and non-cooperative. According to the Mott theory, studies on composites below the percolation threshold showed that the conduction mechanism is ruled by tunneling at low temperatures. The transport mechanism led by hopping is activated at −50 °C

Leucine Zipper-Bearing Kinase Is a Critical Regulator of Astrocyte Reactivity in the Adult Mammalian CNS.

Reactive astrocytes influence post-injury recovery, repair, and pathogenesis of the mammalian CNS. Much of the regulation of astrocyte reactivity, however, remains to be understood. Using genetic loss and gain-of-function analyses in vivo, we show that the conserved MAP3K13 (also known as leucine zipper-bearing kinase [LZK]) promotes astrocyte reactivity and glial scar formation after CNS injury. Inducible LZK gene deletion in astrocytes of adult mice reduced astrogliosis and impaired glial scar formation, resulting in increased lesion size after spinal cord injury. Conversely, LZK overexpression in astrocytes enhanced astrogliosis and reduced lesion size. Remarkably, in the absence of injury, LZK overexpression alone induced widespread astrogliosis in the CNS and upregulated astrogliosis activators pSTAT3 and SOX9. The identification of LZK as a critical cell-intrinsic regulator of astrocyte reactivity expands our understanding of the multicellular response to CNS injury and disease, with broad translational implications for neural repair

UDP-glycosyltransferase family in Haemonchus contortus: Phylogenetic analysis, constitutive expression, sex-differences and resistance-related differences

UDP-glycosyltransferases (UGT), catalysing conjugation of UDP-activated sugar donors to small lipophilic chemicals, are widespread in living organisms from bacteria to fungi, plant, or animals. The progress of genome sequencing has enabled an assessment of the UGT multigene family in Haemonchus contortus (family Trichostrongylidae, Nematoda), a hematophagous gastrointestinal parasite of small ruminants. Here we report 32 putative UGT genes divided into 15 UGT families. Phylogenetic analysis in comparison with UGTs from Caenorhabditis elegans, a free-living model nematode, revealed several single member homologues, a lack of the dramatic gene expansion seen in C. elegans, but also several families (UGT365, UGT366, UGT368) expanded in H. contortus only. The assessment of constitutive UGT mRNA expression in H. contortus adults identified significant differences between females and males. In addition, we compared the expression of selected UGTs in the drug-sensitive ISE strain to two benzimidazole-resistant strains, IRE and WR, with different genetic backgrounds. Constitutive expression of UGT368B2 was significantly higher in both resistant strains than in the sensitive strain. As resistant strains were able to deactivate benzimidazole anthelmintics via glycosylation more effectively then the sensitive strain, UGT368B2 enhanced constitutive expression might contribute to drug resistance in H. contortus

Connaissance, perception et définition du concept « Patient Partenaire de Soins » : Qu’en pensent les acteurs impliqués en éducation thérapeutique ? Résultats d’une enquête nationale

peer reviewe

Reducing harm from HIV/AIDS misconceptions among female sex workers in Tijuana and Ciudad Juarez, Mexico: A cross sectional analysis

Abstract Background HIV prevalence is increasing among female sex workers (FSWs) in Mexico’s Northern border region, who experience multiple occupational risks. Improving vulnerable populations’ education, empowerment, and access to preventive services are important components of harm reduction strategies. Given the increasing interest in adapting harm reduction principles from drug use to sex work and other public health responses to the HIV epidemic, we used a sex work harm reduction framework to guide our investigation of FSWs’ HIV knowledge. Methods From 2004–2006, FSWs aged ≥18 years in Tijuana and Ciudad Juarez participated in a behavioral intervention study and completed structured interviews. Measures included HIV knowledge assessment and factors within each domain of our theoretical framework for sex work harms: (1) socio-demographic factors that may lead to sex work, (2) sex work characteristics and behaviors that may lead to harm, and (3) mutually reinforcing harms that lead to sex work and result from it (e.g., drug abuse). Negative binomial regression identified factors independently associated with suboptimal HIV knowledge (i.e., incorrect responses during the HIV knowledge assessment). Results Among 924 FSWs, the median proportion of incorrect responses was nearly one third (28% incorrect). Examination of item responses revealed misconceptions regarding specific transmission and prevention mechanisms, including prevention of mother to child transmission. Suboptimal HIV knowledge was independently associated with older age, lower education, living in Tijuana (vs. Ciudad Juarez), inconsistent condom use for vaginal sex with male clients, and lacking prior HIV testing. Conclusions Our application of a sex work harm reduction framework to the study of FSWs’ HIV knowledge is an important first step in enhancing HIV prevention efforts in Northern Mexican border cities. Our findings imply that interventions should identify and discredit local HIV misconceptions to improve knowledge of specific HIV transmission routes and self-protective strategies (e.g., condom negotiation). Interventions will require materials appropriate for women from diverse socio-economic backgrounds and may benefit from innovative harm reduction approaches such as peer education and outreach

Systems-Level Immunomonitoring from Acute to Recovery Phase of Severe COVID-19

Peer reviewe

Using multiple lines of evidence to assess the risk of ecosystem collapse

Effective ecosystem risk assessment relies on a conceptual understanding of ecosystem dynamics and the synthesis of multiple lines of evidence. Risk assessment protocols and ecosystem models integrate limited observational data with threat scenarios, making them valuable tools for monitoring ecosystem status and diagnosing key mechanisms of decline to be addressed by management. We applied the IUCN Red List of Ecosystems criteria to quantify the risk of collapse of the Meso-American Reef, a unique ecosystem containing the second longest barrier reef in the world. We collated a wide array of empirical data (field and remotely sensed), and used a stochastic ecosystem model to backcast past ecosystem dynamics, as well as forecast future ecosystem dynamics under 11 scenarios of threat. The ecosystem is at high risk from mass bleaching in the coming decades, with compounding effects of ocean acidification, hurricanes, pollution and fishing. The overall status of the ecosystem is Critically Endangered (plausibly Vulnerable to Critically Endangered), with notable differences among Red List criteria and data types in detecting the most severe symptoms of risk. Our case study provides a template for assessing risks to coral reefs and for further application of ecosystem models in risk assessment.This work was supported by the Australian Research Council LP 130100435 and a Veski Inspiring Women Fellowship to E.N

Survival of metastatic melanoma patients after dendritic cell vaccination correlates with expression of leukocyte phosphatidylethanolamine-binding protein 1 / Raf Kinase inhibitory protein

Item does not contain fulltextImmunotherapy for metastatic melanoma offers great promise but, to date, only a subset of patients have responded. There is an urgent need to identify ways of allocating patients to the most beneficial therapy, to increase survival and decrease therapy-associated morbidity and costs. Blood-based biomarkers are of particular interest because of their straightforward implementation in routine clinical care. We sought to identify markers for dendritic cell (DC) vaccine-based immunotherapy against metastatic melanoma through gene expression analysis of peripheral blood mononuclear cells. A large-scale microarray analysis of 74 samples from two treatment centers, taken directly after the first round of DC vaccination, was performed. We found that phosphatidylethanolamine binding protein 1 (PEBP1)/Raf Kinase inhibitory protein (RKIP) expression can be used to identify a significant proportion of patients who performed poorly after DC vaccination. This result was validated by q-PCR analysis on blood samples from a second cohort of 95 patients treated with DC vaccination in four different centers. We conclude that low PEBP1 expression correlates with poor overall survival after DC vaccination. Intriguingly, this was only the case for expression of PEBP1 after, but not prior to, DC vaccination. Moreover, the change in PEBP1 expression upon vaccination correlated well with survival. Further analyses revealed that PEBP1 expression positively correlated with genes involved in T cell responses but inversely correlated with genes associated with myeloid cells and aberrant inflammation including STAT3, NOTCH1, and MAPK1. Concordantly, PEBP1 inversely correlated with the myeloid/lymphoid-ratio and was suppressed in patients suffering from chronic inflammatory disease

Using multiple lines of evidence to assess the risk of ecosystem collapse

Effective ecosystem risk assessment relies on a conceptual understanding of ecosystem dynamics and the synthesis of multiple lines of evidence. Risk assessment protocols and ecosystem models integrate limited observational data with threat scenarios, making them valuable tools for monitoring ecosystem status and diagnosing key mechanisms of decline to be addressed by management. We applied the IUCN Red List of Ecosystems criteria to quantify the risk of collapse of the Meso-American Reef, a unique ecosystem containing the second longest barrier reef in the world. We collated a wide array of empirical data (field and remotely sensed), and used a stochastic ecosystem model to backcast past ecosystem dynamics, as well as forecast future ecosystem dynamics under 11 scenarios of threat. The ecosystem is at high risk from mass bleaching in the coming decades, with compounding effects of ocean acidification, hurricanes, pollution and fishing. The overall status of the ecosystem is Critically Endangered (plausibly Vulnerable to Critically Endangered), with notable differences among Red List criteria and data types in detecting the most severe symptoms of risk. Our case study provides a template for assessing risks to coral reefs and for further application of ecosystem models in risk assessment