Résurgence des systèmes différentiels linéaires et calcul des matrices de Stokes

Le but de cette thèse est la construction d'une méthode de calcul effectif des multiplicateurs de Stokes avec évaluation de l'erreur. Cette méthode s'applique à tous les systèmes de niveau unique et au premier niveau des systèmes de niveaux multiples. Dans une partie théorique, nous commençons par établir la résurgence des solutions formelles en suivant la méthode d'Ecalle par perturbation régulière et séries majorantes. Nous déduisons de celle-ci une description précise des singularités dans le plan de Borel en déterminant les coefficients de résurgence et les multiplicateurs de Stokes. Dans la partie numérique, nous supposons que les systèmes sont à coefficients rationnels et nous choisissons de travailler dans le plan de Borel en calculant les coefficients de résurgence par prolongements analytiques successifs. En particulier, nous construisons des algorithmes permettant d'évaluer l'erreur. Nous illustrons également cette méthode de calcul par plusieurs exemples numériques.The aim of this thesis is the construction of a method of effective calculation of Stokes multipliers with error estimation. This method applies itself to all systems with single level and the first level of systems with multiple levels. In a theoretical part, we begin by stating the resurgence of formal solutions following Ecalle's method by regular perturbation and majorant series. We deduce from it a precise description of singularities in the Borel plane determining the resurgence coefficients. We make then explicit formulae between these resurgence coefficients and the Stokes multipliers. In the numerical part, we suppose that the entries of the systems are rational and we choose to work in the Borel plane where we calculate the resurgence coefficients by successive analytic continuations. In particular, we build algorithms in order to estimate the error. We give too several numerical examples.ANGERS-BU Lettres et Sciences (490072106) / SudocSudocFranceF

Cycloplegic refractive errors in children: comparison of a standard and a hand-held refractor.

The present study compares the refraction of normal children and young adults measured with a standard refractor and a hand-held refractor. Refractive errors were estimated for each refractor under cycloplegia: sphere, cylinder and cylinder axis were compared. No significant difference was found between the two methods. We performed this study before starting a screening campaign in preschool children to evaluate if the pediatrician and paramedical staff may rely on the hand-held refractors.JOURNAL ARTICLEinfo:eu-repo/semantics/publishe

Straightforward Access to alpha-Methylamines through Cross-Metathesis

International audienceA two-step procedure involving cross-metathesis and reductive amination enables easy access to alpha-methylamines and alpha,alpha'-dimethyldiamines from a wide variety of terminal olefins

Biomolecules capturing live bacteria from clinical samples.

Rapid phenotypic antimicrobial susceptibility testing (AST) requires the enrichment of live bacteria from patient samples, which is particularly challenging in the context of life-threatening bloodstream infections (BSIs) due to low bacterial titers. Over two decades, an extensive array of pathogen-specific biomolecules has been identified to capture live bacteria. The prevailing biomolecules are immune proteins of the complement system, antibodies, aptamers, phage proteins, and antimicrobial peptides. These biomolecules differ by their binder generation technologies and exhibit highly variable specificities, ranging from bacterial strains to most pathogenic bacteria. Here, we summarize how these diverse biomolecules were identified, list examples of successfully reported capture assays, and provide an outlook on the use of nanobodies raised against conserved surface-accessible proteins as promising biomolecules for pathogen capture

Biomolecules capturing live bacteria from clinical samples

Rapid phenotypic antimicrobial susceptibility testing (AST) requires the enrichment of live bacteria from patient samples, which is particularly challenging in the context of life-threatening bloodstream infections (BSIs) due to low bacterial titers. Over two decades, an extensive array of pathogen-specific biomolecules has been identified to capture live bacteria. The prevailing biomolecules are immune proteins of the complement system, antibodies, aptamers, phage proteins, and antimicrobial peptides. These biomolecules differ by their binder generation technologies and exhibit highly variable specificities, ranging from bacterial strains to most pathogenic bacteria. Here, we summarize how these diverse biomolecules were identified, list examples of successfully reported capture assays, and provide an outlook on the use of nanobodies raised against conserved surface-accessible proteins as promising biomolecules for pathogen capture

Control of hypertension in renal transplantation : the EPARA study

Blood pressure (BP) is a cardiovascular but also kidney disease risk factor, especially in high risk populations such as kidney transplantated one (KT). Therefore it must be accurately measured. The aim of the current study was to evaluate the quality of BP control in such a population followed at the CHU Liège

Control of hypertension in a kidney transplanted population : the EPARA study

The prevalence of hypertension in this specific KT population remains high in spite of different antiHTA drugs use and the well known deleterious effect of HTA on kidney function and cardiovascular risk. Home BP (and/or ABPM) should thus be recommended to identify this situation and secondary to adapt the treatment

A molecular analysis of the patterns of genetic diversity in local chickens from western Algeria in comparison with commercial lines and wild jungle fowls

The objectives of this study were to characterize the genetic variability of village chickens from three agro-ecological regions of western Algeria: coastal (CT), inland plains (IP) and highlands (HL), to reveal any underlying population structure, and to evaluate potential genetic introgression from commercial lines into local populations. A set of 233 chickens was genotyped with a panel of 23 microsatellite markers. Geographical coordinates were individually recorded. Eight reference populations were included in the study to investigate potential gene flow: four highly selected commercial pure lines and four lines of French slow-growing chickens. Two populations of wild red jungle fowls were also genotyped to compare the range of diversity between domestic and wild fowls. A genetic diversity analysis was conducted both within and between populations. Multivariate redundancy analyses were performed to assess the relative influence of geographical location among Algerian ecotypes. The results showed a high genetic variability within the Algerian population, with 184 alleles and a mean number of 8.09 alleles per locus. The values of heterozygosity (He and Ho) ranged from 0.55 to 0.62 in Algerian ecotypes and were smaller than values found in Jungle fowl populations and higher than values found in commercial populations. Although the structuring analysis of genotypes did not reveal clear subpopulations within Algerian ecotypes, the supervised approach using geographical data showed a significant (p < 0.01) differentiation between the three ecotypes which was mainly due to altitude. Thus, the genetic diversity of Algerian ecotypes may be under the influence of two factors with contradictory effects: the geographical location and climatic conditions may induce some differentiation, whereas the high level of exchanges and gene flow may suppress it. Evidence of gene flow between commercial and Algerian local populations was observed, which may be due to unrecorded crossing with commercial chickens. Chicken ecotypes from western Algeria are characterized by a high genetic diversity and must be safeguarded as an important reservoir of genetic diversity

Regulatory B Cells with a Partial Defect in CD40 Signaling and Overexpressing Granzyme B Transfer Allograft Tolerance in Rodents

International audienceEmerging knowledge regarding B cells in organ transplantation has demonstrated that these cells can no longer be taken as mere generators of deleterious Abs but can also act as beneficial players. We previously demonstrated in a rat model of cardiac allograft tolerance induced by short-term immunosuppression an accumulation in the blood of B cells overexpressing inhibitory molecules, a phenotype also observed in the blood of patients that spontaneously develop graft tolerance. In this study, we demonstrated the presence in the spleen of regulatory B cells enriched in the CD24intCD38+CD27+IgD2IgM+/low subpopulation, which are able to transfer donor-specific tolerance via IL-10 and TGF-b1–dependent mechanisms and to suppress in vitro TNF-a secretion. Following anti-CD40 stimulation, IgD2IgM+/low B cells were blocked in their plasma cell differentiation pathway, maintained high expression of the inhibitory molecules CD23 and Bank1, and upregulated Granzyme B and Irf4, two molecules described as highly expressed by regulatory B cells. Interestingly, these B cells recognized specifically a dominant donor Ag, suggesting restricted specificity that could lead to a particular B cell response. Regulatory B cells were not required for induction of tolerance and appeared following Foxp3+CD4+CD25+ regulatory T cells, suggesting cooperation with regulatory T cells for their expansion. Nevertheless, following transfer to new recipients, these B cells migrated to the allograft, kept their regulatory profile, and promoted local accumulation of Foxp3+CD4+CD25+ regulatory T cells. Mechanisms of regulatory B cells and their cell therapy potential are important to decipher in experimental models to pave the way for future developments in the clinic