303 research outputs found
Droit comme ressources des minorités nationales : un modèle de mobilisation politique du droit
[Ă€ l'origine dans / Was originally part of : CRDP - Droit et nouveaux rapports sociaux
Higgs amplitude mode in ballistic superconducting hybrid junctions
In superconductors (SC), the Higgs amplitude mode is a coherent oscillation
of the order parameter typically generated by THz laser irradiation. In this
paper we propose to probe the Higgs mode using electronic transport in
ballistic superconducting hybrid devices. We first confirm the existence of a
non-zero amplitude mode in the clean case using the Keldysh-Eilenberger
formalism. We then investigate two different geometries, respectively a
normal-insulating-superconductor (NIS) tunnel junction and a NSN junction with
transparent interfaces, the superconductor being irradiated in both situations.
In the NIS case, the Higgs manifests itself in the second-order AC current
response which is resonant at the Higgs frequency. In the NSN case, the DC
differential conductance allows to probe the gaps generated by the Higgs mode
in the Floquet spectrum.Comment: 13 pages, 8 figure
Vers un jeu sérieux pour enseigner la programmation
International audienceLes jeux vidéo font partie intégrante de la culture au même titre que la télévision, les films et les livres. Nous pensons que ces applications de réalité virtuelle, grandement utilisées, peuvent servir à la formation des étudiants. Ce type d’outil est appelé : jeux sérieux. Les jeux sérieux sont présents, aujourd’hui, dans de nombreux secteurs d’activité comme l’éducation, la santé, la défense, l’industrie, la sécurité civile et les sciences. Ce document présente une étude pour déterminer le type de jeu le plus adapté à l’enseignement de la programmation. Les jeux de stratégie temps réel semblent êtreparticulièrement intéressants dans ce cadre
The battle for chitin recognition in plant-microbe interactions
Fungal cell walls play dynamic functions in interaction of fungi with their surroundings. In pathogenic fungi, the cell wall is the first structure to make physical contact with host cells. An important structural component of fungal cell walls is chitin, a well-known elicitor of immune responses in plants. Research into chitin perception has sparked since the chitin receptor from rice was cloned nearly a decade ago. Considering the widespread nature of chitin perception in plants, pathogens evidently evolved strategies to overcome detection, including alterations in the composition of cell walls, modification of their carbohydrate chains and secretion of effectors to provide cell wall protection or target host immune responses. Also non-pathogenic fungi contain chitin in their cell walls and are recipients of immune responses. Intriguingly, various mutualists employ chitin-derived signaling molecules to prepare their hosts for the mutualistic relationship. Research on the various types of interactions has revealed different molecular components that play crucial roles and, moreover, that various chitin-binding proteins contain dissimilar chitin-binding domains across species that differ in affinity and specificity. Considering the various strategies from microbes and hosts focused on chitin recognition, it is evident that this carbohydrate plays a central role in plant-fungus interaction
Arabidopsiscell wall composition determines disease resistance specificity and fitness
[EN] Plant cell walls are complex structures subject to dynamic remodeling
in response to developmental and environmental cues and
play essential functions in disease resistance responses. We tested
the specific contribution of plant cell walls to immunity by
determining the susceptibility of a set of Arabidopsis cell wall mutants
(cwm) to pathogens with different parasitic styles: a vascular
bacterium, a necrotrophic fungus, and a biotrophic oomycete. Remarkably,
most cwm mutants tested (29/34; 85.3%) showed alterations
in their resistance responses to at least one of these
pathogens in comparison to wild-type plants, illustrating the relevance
of wall composition in determining disease-resistance phenotypes.
We found that the enhanced resistance of cwm plants to
the necrotrophic and vascular pathogens negatively impacted
cwm fitness traits, such as biomass and seed yield. Enhanced resistance
of cwm plants is not only mediated by canonical immune
pathways, like those modulated by phytohormones or microbeassociated
molecular patterns, which are not deregulated in the
cwm tested. Pectin-enriched wall fractions isolated from cwm
plants triggered immune responses in wild-type plants, suggesting
that wall-mediated defensive pathways might contribute to cwm
resistance. Cell walls of cwm plants show a high diversity of composition
alterations as revealed by glycome profiling that detect
specific wall carbohydrate moieties. Mathematical analysis of glycome
profiling data identified correlations between the amounts of
specific wall carbohydrate moieties and disease resistance phenotypes
of cwm plants. These data support the relevant and specific
function of plant wall composition in plant immune response modulation
and in balancing disease resistance/development trade-offs.SIThis work has been also financially supported by the Severo Ochoa Program for Centers of Excellence in R&D from the Agencia Estatal de InvestigaciĂłn of Spain (Grant SEV-2016-0672 (2017-2021) to the Centro de BiotecnologĂa y GenĂłmica de Plantas). In the frame of this program, H.M. was a postdoctoral fellow. H.M. was also supported by an Individual Fellowship grant (SignWALLINg-624721) from the European Union. E.M. was a Juan de la Cierva Postdoctoral Fellow from MINECO, and L.B. was a Formacion Personal Investigador fellow of MICIU. The generation of the CCRC-series of plant cell glycan-directed monoclonal antibodies used in this work was supported by the US NSF (DBI-0421683 and IOS 0923992) to M.G.H
Intracranial fluids dynamics alterations and cortical thickness
Objectives: The issue of cortical atrophy is important in normal aging and disease since it is associated with cognitive and physical impairments. Cortical atrophy is potentially a relevant biomarker for the early diagnosis of Alzheimer’s disease (AD). The vascular component is also an integral part of AD and other late-life neurodegenerative diseases. Abnormalities in blood flow appear before accumulation of abnormal proteins in AD. The occlusion of capillaries by neutrophils are significantly higher in AD animal models than control and reduction of those occlusions with an antibody increases both blood flow and cognitive capacities. Vascular alterations lead to hypoperfusion, oxidative stress and inflammation, which in turn lead to damage of neurons, glia and myelin, predominantly in the white mater. Implication of vascular pathologies for gray matter remains unclear. A recent study showed that altered cerebral hemodyamics in asymptomatic carotid artery stenosis is associated with cortical thinning. However there is no proven link between vascular pathologies and cortical thinning. We propose to explore brain aging with a combined biomechanical and imaging approach in order to assess both fluid dynamics alterations and brain structural modifications. We hypothesize that there is a link between altered cerebral hemodynamics and loss of cortical thickness during brain aging.
Methods: 80 patients suspected of hydrocephalus were prospectively involved. All patients complain of gait alteration, urinary difficulties, mild apathy and ventriculomegaly on brain imaging. They all underwent brain MRI with T1 weighted images to quantify cortical thickness and phase contrast images to measure arterial, venous and CSF velocities. Lumbar infusion test was also performed to gauge lumbar pressure, a surrogate marker of intracranial pressure (ICP), and CSF dynamics. The cortical volumetric segmentation was done by an automatic post-processing analysis with FREESURFER and local thicknesses were assessed with CorThiZon. Venous, arterial and CSF velocities were measured from PCMRI with BIOFLOWIMAGE software. ICP and CSF dynamics were extracted form infusion tests. Pearson correlations were calculated between cortical thickness and arterial, venous and CSF velocities, but also ICP and derived indices.
Results: Mean cortical thickness is positively correlated with mean ICP (r=0.48, p=0.001), ICP pulse amplitude (r=0.43, p=0.001), arterial flow (r=0.44, p=0.001), aqueductal CSF flow(r=046, p=0.001), but negatively correlates with venous flow (r=-0.44, p=0.001). Conclusions: We demonstrate that cortical thickness is correlated with arterial and CSF pulsatility. The causality is more complex since it involves local microcirculation that could not be directly measured. However the association between intracranial pulsatility and gray matter thickness suggests that there is a relationship between vascular alterations at the macroscale level and the pathobiology of cortical atrophy
Approche archéologique et environnementale des premiers peuplements alpins autour du col du Petit-Saint-Bernard (Savoie, vallée d’Aoste) : un bilan d’étape
De 2003 à 2007, une étude archéologique et sédimentaire a été réalisée sur les versants du col du Petit-Saint-Bernard (2188 m, Alpes occidentales), par de grandes séries de sondages manuels effectués dans des contextes sélectionnés. Les avantages et les inconvénients de cette méthode sont exposés et discutés. Ce travail a permis d’identifier, interstratifiés dans les remplissages holocènes, des sols bruns fersiallitiques sur les versants et des sols hydromorphes en altitude. Les répartitions chronologique et altitudinale des découvertes archéologiques sont analysées, puis comparées à une compilation des connaissances préexistantes dans les vallées alpines du Beaufortin, de la Maurienne et de la Tarentaise. Les analyses paléo-environnementales et archéologiques en cours sont présentées.An archaeological and sedimentary study was realized on the hillsides of the Petit-Saint-Bernard pass (2188 m, western Alps), from 2003 to 2007. It consisted of great series of manual boreholes in selected contexts. The efficiency of this method is discussed. This work allowed identifying brown fersiallitics soils in hillsides and hyrdromorphic soils in the heights, interstratified in the Holocene fillings. The chronological and altitudinal distributions of the findings are analysed and compared to previous data from Beaufortin, Maurienne and Tarentaise. An additional project of palaeo-environmental and archaeological analyses is presented
An integrative approach to decipher the chemical antagonism between the competing endophytes paraconiothyrium variabile and Bacillus subtilis
An integrative approach combining traditional natural products chemistry, molecular networking, and mass spectrometry imaging has been undertaken to decipher the molecular dialogue between the fungus Paraconiothyrium variabile and the bacterium Bacillus subtilis, which were isolated as endophytes from the conifer Cephalotaxus harringtonia and are characterized by a strong and mutual antibiosis. From this study, we highlight that bacterial surfactins and a fungal tetronic acid are involved in such competition and that the fungus is able to hydrolyze surfactins to fight against the bacterial partner
Disruption of abscisic acid signaling constitutively activates Arabidopsis resistance to the necrotrophic fungus Plectosphaerella cucumerina.
Plant resistance to necrotrophic fungi is regulated by a complex set of signaling pathways that includes those mediated by the hormones salicylic acid (SA), ethylene (ET), jasmonic acid (JA), and abscisic acid (ABA). The role of ABA in plant resistance remains controversial, as positive and negative regulatory functions have been described depending on the plant-pathogen interaction analyzed. Here, we show that ABA signaling negatively regulates Arabidopsis (Arabidopsis thaliana) resistance to the necrotrophic fungus Plectosphaerella cucumerina. Arabidopsis plants impaired in ABA biosynthesis, such as the aba1-6 mutant, or in ABA signaling, like the quadruple pyr/pyl mutant (pyr1pyl1pyl2pyl4), were more resistant to P. cucumerina than wild-type plants. In contrast, the hab1-1abi1-2abi2-2 mutant impaired in three phosphatases that negatively regulate ABA signaling displayed an enhanced susceptibility phenotype to this fungus. Comparative transcriptomic analyses of aba1-6 and wild-type plants revealed that the ABA pathway negatively regulates defense genes, many of which are controlled by the SA, JA, or ET pathway. In line with these data, we found that aba1-6 resistance to P. cucumerina was partially compromised when the SA, JA, or ET pathway was disrupted in this mutant. Additionally, in the aba1-6 plants, some genes encoding cell wall-related proteins were misregulated. Fourier transform infrared spectroscopy and biochemical analyses of cell walls from aba1-6 and wild-type plants revealed significant differences in their Fourier transform infrared spectratypes and uronic acid and cellulose contents. All these data suggest that ABA signaling has a complex function in Arabidopsis basal resistance, negatively regulating SA/JA/ET-mediated resistance to necrotrophic fungi
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