Jacobi fields along harmonic 2-spheres in S3S^3 and S4S^4 are not all integrable

In a previous paper, we showed that any Jacobi field along a harmonic map from the 2-sphere to the complex projective plane is integrable (i.e., is tangent to a smooth variation through harmonic maps). In this paper, in contrast, we show that there are (non-full) harmonic maps from the 2-sphere to the 3-sphere and 4-sphere which have non-integrable Jacobi fields. This is particularly surprising in the case of the 3-sphere where the space of harmonic maps of any degree is a smooth manifold, each map having image in a totally geodesic 2-sphere.Comment: 43 pages. Some typos corrected; introduction expande

On the existence of harmonic maps

We study different properties of harmonic maps between two compact Riemannian manifolds M and M' and in particular the following existence question: do there exist harmonic elements in the different homotopy classes of maps from M to M'? Our first result is an affirmative answer to that question when M is a surface and the second homotopy group of M' is zero. This result is then extended to certain products of manifolds and to ψ-harmonic maps. When M and M' are orientable surfaces, this solves the existence question as long as M' is not a sphere. When M is a surface of genus p and M' a sphere, the question was answered by J. Eells and J. Wood for all classes of maps of degree greater or equal to p. For all remaining cases (degree ≤ p - 1), we obtain existence results for particular metrics on M and M'. We also study the question of existence for non-orientable surfaces, and obtain complete results for maps between spheres and projective planes. A second type of results is a finiteness theorem for harmonic maps: we show that if the sectional curvature of M' is negative, there is only a finite number of non-constant harmonic maps from M to M' of dilatation bounded by a fixed constant. This implies a similar result on the number of almost complex maps between almost Kaehlerian manifolds. Other results include an example of a continuous family of harmonic maps, a remark on the derivatives of the harmonicity equations and an answer to a question of H. Eliasson concerning a higher order energy

SLDLT: une technique de mise à jour de la décomposition LDLT pour l'accélération des simulations de Monte Carlo dans le cas de champs stochastiques non uniformes

National audienceSee http://hal.archives-ouvertes.fr/docs/00/59/29/54/ANNEX/r_79AK56I8.pd

Fusion d'Experts pour une Biométrie Faciale 3D Robuste aux Déformations

Session "Posters"National audienceNous étudions dans cet article l'apport de la géométrie tridimensionnelle du visage dans la reconnaissance des individus. La principale contribution est d'associer plusieurs experts (matcheurs) de biométrie faciale 3D afin d'achever de meilleures performances comparées aux performances individuelles de chacun, notamment en présence d'expressions. Les experts utilisés sont : (E1) Courbes radiales élastiques, (E2) MS-eLBP, une version étendue multi-échelle de l'opérateur LBP, (E3) l'algorithme de recalage non-rigide TPS, en plus d'un expert de référence (Eref) l'algorithme de recalage rigide connu ICP. Profitant de la complémentarité de chacun des experts, la présente approche affiche un taux d'identification qui dépasse les 99% en présence d'expressions faciales sur la base FRGCv2. Une étude comparative avec l'état de l'art confirme le choix et l'intérêt de combiner plusieurs experts afin d'achever de meilleurs performance

Effect of Maternal Obesity and Preconceptional Weight Loss on Male and Female Offspring Metabolism and Olfactory Performance in Mice

According to the “developmental origins of health and disease” (DOHaD) concept, maternal obesity predisposes the offspring to non-communicable diseases in adulthood. While a preconceptional weight loss (WL) is recommended for obese women, its benefits on the offspring have been poorly addressed. We evaluated whether preconceptional WL was able to reverse the adverse effects of maternal obesity in a mouse model, exhibiting a modification of foetal growth and of the expression of genes encoding epigenetic modifiers in liver and placenta. We tracked metabolic and olfactory behavioural trajectories of offspring born to control, obese or WL mothers. After weaning, the offspring were either put on a control diet (CD) or a high-fat (HFD). After only few weeks of HFD, the offspring developed obesity, metabolic alterations and olfactory impairments, independently of maternal context. However, male offspring born to obese mother gained even more weight under HFD than their counterparts born to lean mothers. Preconceptional WL normalized the offspring metabolic phenotypes but had unexpected effects on olfactory performance: a reduction in olfactory sensitivity, along with a lack of fasting-induced, olfactory-based motivation. Our results confirm the benefits of maternal preconceptional WL for male offspring metabolic health but highlight some possible adverse outcomes on olfactory-based behaviours

Prevalence and Clinical Associations of Antiphospholipid Antibodies in Systemic Sclerosis: New Data From a French Cross-Sectional Study, Systematic Review, and Meta-Analysis

Objectives: Antiphospholipid antibodies (aPL) can be present in the sera of systemic sclerosis (SSc) patients. This study aimed to determine the prevalence of aPL in a cross-sectional study of SSc patients, to assess their clinical associations, to perform a systematic review of published reports and a meta-analysis to estimate the worldwide prevalence of aPL in SSc.Methods: Two-hundred and forty-nine SSc patients were consecutively tested once for lupus anticoagulant (LA), anticardiolipin (aCL), and anti-β2glycoprotein I (anti-β2GpI) antibodies. Clinical associations with aPL positivity were studied using a logistic regression model. A systematic review of the literature was carried out in PubMed and Embase. Meta-analysis was performed using number of aPL positive (at least one of the three antibodies positive) and negative patients. Meta-regression was used to study potential factors explaining the heterogeneity between studies.Results: In our cross-sectional study, aPL positivity was found in 16 patients (prevalence 6.4%; 95%CI [3.8–10.4]). In multivariate analysis, there was a significant association between aPL positivity and venous thrombosis (VT) (OR 6.25 [1.18–33.00]; p = 0.028) and miscarriage (OR 5.43; 95%CI [1.31–22.13]; p = 0.017). Twenty-four studies were included in the meta-analysis, representing a total population of 3036 SSc patients. The overall pooled prevalence of aPL in SSc was 14% (9–20) with a high degree of heterogeneity among studies.Conclusion: This study found a prevalence of aPL positivity in our SSc population of 6.4% (3.8–10.4) and an overall worldwide pooled prevalence of 14% (9–20). In our SSc population, aPL positivity was associated with VT and miscarriage. These data provide additional insights into the role of aPL in the vasculopathy observed in SSc