139 research outputs found
Reflection-driven turbulence in the super-Alfv\'enic solar wind
In magnetized, stratified astrophysical environments such as the Sun's corona
and solar wind, Alfv\'enic fluctuations ''reflect'' from background gradients,
enabling nonlinear interactions and thus dissipation of their energy into heat.
This process, termed ''reflection-driven turbulence,'' is thought to play a
crucial role in coronal heating and solar-wind acceleration, explaining a range
of observational correlations and constraints. Building on previous works
focused on the inner heliosphere, here we study the basic physics of
reflection-driven turbulence using reduced magnetohydrodynamics in an expanding
box -- the simplest model that can capture the local turbulent plasma dynamics
in the super-Alfv\'enic solar wind. Although idealized, our high-resolution
simulations and simple theory reveal a rich phenomenology that is consistent
with a diverse range of observations. Outwards-propagating fluctuations, which
initially have high imbalance, decay nonlinearly to heat the plasma, becoming
more balanced and magnetically dominated. Despite the high imbalance, the
turbulence is strong because Els\"asser collisions are suppressed by
reflection, leading to ''anomalous coherence'' between the two Els\"asser
fields. This coherence, together with linear effects, causes the turbulence to
anomalously grow the ''anastrophy'' (squared magnetic potential) as it decays,
forcing the energy to rush to larger scales and forming a ''-range''
energy spectrum as it does so. At late times, the expansion overcomes the
nonlinear and Alfv\'enic physics, forming isolated, magnetically dominated
''Alfv\'en vortex'' structures that minimize their nonlinear dissipation. These
results can plausibly explain the observed radial and wind-speed dependence of
turbulence imbalance, residual energy, plasma heating, and fluctuation spectra,
as well as making testable predictions for future observations
CACDA: A knowledge graph for a context-aware cognitive design assistant
The design of complex engineered systems highly relies on a laborious zigzagging between computer-aided design (CAD) software and design rules prescribed by design manuals. Despite the emergence ofknowledge management techniques (ontology, expert system, text mining, etc.), companies continue tostore design rules in large and unstructured documents. To facilitate the integration of design rules andCAD software, we propose a knowledge graph that structures a large set of design rules in a computableformat. The knowledge graph organises entities of design rules (nodes), relationships among design rules(edges), as well as contextual information. The categorisation of entities and relationships in four sub-contexts: semantic, social, engineering, and IT â facilitates the development of the data model, especiallythe definition of the âdesign contextâ concept. The knowledge graph paves the way to a context-awarecognitive design assistant. Indeed, connected to or embedded in a CAD software, a context-aware cog-nitive design assistant will capture the design context in near real time and run reasoning operationson the knowledge graph to extend traditional CAD capabilities, such as the recommendation of designrules, the verification of design solutions, or the automation of design routines. Our validation experi-ment shows that the current version of the context-aware cognitive design assistant is more efficientthan the traditional document-based design. On average, participants using an unstructured design rulesdocument have a precision of 0.36 whereas participants using our demonstrator obtain a 0.61 precisionscore. Finally, designers supported by the design assistant spend more time designing than searching forapplicable design rules compared to the traditional design approach.Capgemini DEM
Melanin is an essential component for the integrity of the cell wall of Aspergillus fumigatus conidia
BACKGROUND: Aspergillus fumigatus is the most common agent of invasive aspergillosis, a feared complication in severely immunocompromised patients. Despite the recent commercialisation of new antifungal drugs, the prognosis for this infection remains uncertain. Thus, there is a real need to discover new targets for therapy. Particular attention has been paid to the biochemical composition and organisation of the fungal cell wall, because it mediates the host-fungus interplay. Conidia, which are responsible for infections, have melanin as one of the cell wall components. Melanin has been established as an important virulence factor, protecting the fungus against the host\u27s immune defences. We suggested that it might also have an indirect role in virulence, because it is required for correct assembly of the cell wall layers of the conidia.
RESULTS: We used three A. fumigatus isolates which grew as white or brown powdery colonies, to demonstrate the role of melanin. Firstly, sequencing the genes responsible for biosynthesis of melanin (ALB1, AYG1, ARP1, ARP2, ABR1 and ABR2) showed point mutations (missense mutation, deletion or insertion) in the ALB1 gene for pigmentless isolates or in ARP2 for the brownish isolate. The isolates were then shown by scanning electron microscopy to produce numerous, typical conidial heads, except that the conidia were smooth-walled, as previously observed for laboratory mutants with mutations in the PKSP/ALB1 gene. Flow cytometry showed an increase in the fibronectin binding capacity of conidia from mutant isolates, together with a marked decrease in the binding of laminin to the conidial surface. A marked decrease in the electronegative charge of the conidia and cell surface hydrophobicity was also seen by microelectrophoresis and two-phase partitioning, respectively. Ultrastructural studies of mutant isolates detected considerable changes in the organisation of the conidial wall, with the loss of the outermost electron dense layer responsible for the ornamentations seen on the conidial surface in wild-type strains. Finally, analysis of the conidial surface of mutant isolates by atomic force microscopy demonstrated the absence of the outer cell wall rodlet layer which is composed of hydrophobins.
CONCLUSION: These results suggest that, in addition to a protective role against the host\u27s immune defences, melanin is also a structural component of the conidial wall that is required for correct assembly of the cell wall layers and the expression at the conidial surface of adhesins and other virulence factors
Molecular Characterization of a Streptococcus gallolyticus Genomic Island Encoding a Pilus Involved in Endocarditis
Background.âStreptococcus gallolyticus is a causative agent of infective endocarditis associated with colon cancer. Genome sequence of strain UCN34 revealed the existence of 3 pilus loci (pil1, pil2, and pil3). Pili are long filamentous structures playing a key role as adhesive organelles in many pathogens. The pil1 locus encodes 2 LPXTG proteins (Gallo2178 and Gallo2179) and 1 sortase C (Gallo2177). Gallo2179 displaying a functional collagen-binding domain was referred to as the adhesin, whereas Gallo2178 was designated as the major pilin. Methods.âS. gallolyticus UCN34, Pil1+ and Pil1â, expressing various levels of pil1, and recombinant Lactococcus lactis strains, constitutively expressing pil1, were studied. Polyclonal antibodies raised against the putative pilin subunits Gallo2178 and Gallo2179 were used in immunoblotting and immunogold electron microscopy. The role of pil1 was tested in a rat model of endocarditis. Results.âWe showed that the pil1 locus (gallo2179-78-77) forms an operon differentially expressed among S. gallolyticus strains. Short pilus appendages were identified both on the surface of S. gallolyticus UCN34 and recombinant L. lactis-expressing pil1. We demonstrated that Pil1 pilus is involved in binding to collagen, biofilm formation, and virulence in experimental endocarditis. Conclusions.âThis study identifies Pil1 as the first virulence factor characterized in S. gallolyticu
The In Situ Signature of Cyclotron Resonant Heating
The dissipation of magnetized turbulence is an important paradigm for
describing heating and energy transfer in astrophysical environments such as
the solar corona and wind; however, the specific collisionless processes behind
dissipation and heating remain relatively unconstrained by measurements. Remote
sensing observations have suggested the presence of strong temperature
anisotropy in the solar corona consistent with cyclotron resonant heating. In
the solar wind, in situ magnetic field measurements reveal the presence of
cyclotron waves, while measured ion velocity distribution functions have hinted
at the active presence of cyclotron resonance. Here, we present Parker Solar
Probe observations that connect the presence of ion-cyclotron waves directly to
signatures of resonant damping in observed proton-velocity distributions. We
show that the observed cyclotron wave population coincides with both flattening
in the phase space distribution predicted by resonant quasilinear diffusion and
steepening in the turbulent spectra at the ion-cyclotron resonant scale. In
measured velocity distribution functions where cyclotron resonant flattening is
weaker, the distributions are nearly uniformly subject to ion-cyclotron wave
damping rather than emission, indicating that the distributions can damp the
observed wave population. These results are consistent with active cyclotron
heating in the solar wind
MASCIPO â Centre dâĂ©tudes nord-amĂ©ricaines (CENA)
Nicolas Barreyre, maĂźtre de confĂ©rences Ă lâUniversitĂ© Paris-Ouest/Nanterre La DĂ©fenseRomain Huret, maĂźtre de confĂ©rences Ă lâUniversitĂ© Lyon-II/LumiĂšreAlexandre Rios-Bordes, ATER LâĂtat amĂ©ricain Ă la pĂ©riode contemporaine (XIXe-XXe siĂšcles). Perspectives historiographiques, analyse comparĂ©e, modalitĂ©s dâĂ©criture Ce sĂ©minaire avait pour premier objectif de reprendre Ă nouveaux frais la question de lâĂtat aux Ătats-Unis, Ă la fois surinvestie par la mythologie nationale et relativement margin..
MASCIPO â Centre dâĂ©tudes nord-amĂ©ricaines (CENA)
Nicolas Barreyre, maĂźtre de confĂ©rences Ă lâUniversitĂ© Paris-Ouest/Nanterre La DĂ©fenseRomain Huret, maĂźtre de confĂ©rences Ă lâUniversitĂ© Lyon-II/LumiĂšreAlexandre Rios-Bordes, ATER LâĂtat amĂ©ricain Ă la pĂ©riode contemporaine (XIXe-XXe siĂšcles). Perspectives historiographiques, analyse comparĂ©e, modalitĂ©s dâĂ©criture Ce sĂ©minaire avait pour premier objectif de reprendre Ă nouveaux frais la question de lâĂtat aux Ătats-Unis, Ă la fois surinvestie par la mythologie nationale et relativement margin..
Poverty and inequality in real-world schizophrenia: a national study
BackgroundSchizophrenia has high socioeconomic impact among severe psychiatric disorders.AimsTo explore clinician-reported and patient-reported inequities between patients under the poverty threshold vs. the others.Method916 patients consecutively recruited in 10 national centers received a comprehensive standardized evaluation of illness severity, addictions and patient-reported outcomes.Results739 (80.7%) of the patients were classified in the poverty group. This group had poorer objective illness outcomes (lower positive, negative, cognitive, excitement/aggressive and self-neglect symptoms and lifetime history of planned suicide) in multivariate analyses. While they had similar access to treatments and psychotherapy, they had lower access to socially useful activities, coupleâs life, housing and parenthood. They had also more disturbed metabolic parameters. On the contrary, the poverty group reported better self-esteem. No significant difference for depression, risky health behavior including addictions and sedentary behavior was found.InterpretationThe equity in access to care is attributed to the French social system. However, mental and physical health remain poorer in these patients, and they still experience poor access to social roles independently of illness severity and despite healthcare interventions. These patients may have paradoxically better self-esteem due to decreased contact with society and therefore lower stigma exposure (especially at work). Schizophrenia presents itself as a distinct impoverished population concerning health-related outcomes and social integration, warranting focus in public health initiatives and improved treatment, including tailored interventions, collaborative care models, accessible mental health services, housing support, vocational training and employment support, community integration, education and awareness, research and data collection, culturally competent approaches, and long-term support
Sequential induction of auxin efflux and influx carriers regulates lateral root emergence
Peer reviewe
A striking correspondence between the dynamics generated by the vector fields and by the scalar parabolic equations
The purpose of this paper is to enhance a correspondence between the dynamics
of the differential equations on and those
of the parabolic equations on a bounded
domain . We give details on the similarities of these dynamics in the
cases , and and in the corresponding cases ,
and dim() respectively. In addition to
the beauty of such a correspondence, this could serve as a guideline for future
research on the dynamics of parabolic equations
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