C2 interpolation of spatial data subject to arc-length constraints using Pythagorean-hodograph quintic splines

International audienceIn order to reconstruct spatial curves from discrete electronic sensor data, two alternative C2 Pythagorean-hodograph (PH) quintic spline formulations are proposed, interpolating given spatial data subject to prescribed constraints on the arc length of each spline segment. The first approach is concerned with the interpolation of a sequence of points, while the second addresses the interpolation of derivatives only (without spatial localization). The special structure of PH curves allows the arc-length conditions to be expressed as algebraic constraints on the curve coefficients. The C2 PH quintic splines are thus defined through minimization of a quadratic function subject to quadratic constraints, and a close starting approximation to the desired solution is identified in order to facilitate efficient construction by iterative methods. The C2 PH spline constructions are illustrated by several computed examples

Asymptomatic carriers of COVID-19 in a confined adult community population in Quebec: a cross-sectional study

Several countries have undertaken social distancing measures to stop SARS-CoV-2 spread. Asymptomatic carriers’ prevalence is unknown and would provide essential information on hidden viral circulation. In our cross-sectional study, 1.82% of 330 asymptomatic confined individuals living in the community carried SARS-CoV-2 despite no contact with declared cases, raising concerns about unnoticed transmission

Adipose Gene Expression Prior to Weight Loss Can Differentiate and Weakly Predict Dietary Responders

BACKGROUND: The ability to identify obese individuals who will successfully lose weight in response to dietary intervention will revolutionize disease management. Therefore, we asked whether it is possible to identify subjects who will lose weight during dietary intervention using only a single gene expression snapshot. METHODOLOGY/PRINCIPAL FINDINGS: The present study involved 54 female subjects from the Nutrient-Gene Interactions in Human Obesity-Implications for Dietary Guidelines (NUGENOB) trial to determine whether subcutaneous adipose tissue gene expression could be used to predict weight loss prior to the 10-week consumption of a low-fat hypocaloric diet. Using several statistical tests revealed that the gene expression profiles of responders (8-12 kgs weight loss) could always be differentiated from non-responders (<4 kgs weight loss). We also assessed whether this differentiation was sufficient for prediction. Using a bottom-up (i.e. black-box) approach, standard class prediction algorithms were able to predict dietary responders with up to 61.1%+/-8.1% accuracy. Using a top-down approach (i.e. using differentially expressed genes to build a classifier) improved prediction accuracy to 80.9%+/-2.2%. CONCLUSION: Adipose gene expression profiling prior to the consumption of a low-fat diet is able to differentiate responders from non-responders as well as serve as a weak predictor of subjects destined to lose weight. While the degree of prediction accuracy currently achieved with a gene expression snapshot is perhaps insufficient for clinical use, this work reveals that the comprehensive molecular signature of adipose tissue paves the way for the future of personalized nutrition

PH quintic splines subject to arc-length constraints and applications to curve reconstruction

International audienc

PH quintic splines subject to arc-length constraints and applications to curve reconstruction

International audienc

Reconstruction of quasi developable surfaces from ribbon curves

International audienceThis paper deals with the acquisition and reconstruction of physical surfaces by mean of a ribbon device equipped with micro-sensors, providing geodesic curves running on the surface. The whole process involves the reconstruction of these 3D ribbon curves together with their global treatment so as to produce a consistent network for the geodesic surface interpolation by filling methods based on triangular Coons-like approaches. However, the ribbon curves follow their own way, subdividing thus the surface into arbitrary n-sided patches. We present here a method for the reconstruction of quasi developable surfaces from such n-sided curvilinear boundary curves acquired with the ribbon device

Reconstruction de Surfaces Développables à Partir de Courbes Géodésiques

National audienceNous considérons le problème de la reconstruction de surfaces développables équipées de rubans de micro-capteurs. Les capteurs permettent l'acquisition d'un réseau de courbes géodésiques sur la surface. En exploitant les données géodésiques obtenues et les propriétés particulières des surfaces développables, on développe une méthode de reconstruction pour l'ensemble de ces surfaces

Interpolation géodésique d'un polygone curviligne

National audienceNous considérons le problème général de l'acquisition et de la reconstruction de surfaces physiques 3D à l'aide de rubans équipés de microaccéléromètres et micromagnétomètres suivant des géodésiques sur la surface. La méthode générale consiste dans un premier temps, à reconstruire les courbes 3D représentant ces géodésiques sur la surface, puis à les caler dans l'espace afin d'obtenir un réseau consistant pour reconstruction surfacique basée sur des méthodes d'interpolation géodésique. Nous présentons ici une méthode de remplissage géodésique par subdivision d'un contour à n bords permettant de se ramener au cas triangulaire curviligne

Interpolation géodésique d'un polygone curviligne

National audienceNous considérons le problème général de l'acquisition et de la reconstruction de surfaces physiques 3D à l'aide de rubans équipés de microaccéléromètres et micromagnétomètres suivant des géodésiques sur la surface. La méthode générale consiste dans un premier temps, à reconstruire les courbes 3D représentant ces géodésiques sur la surface, puis à les caler dans l'espace afin d'obtenir un réseau consistant pour reconstruction surfacique basée sur des méthodes d'interpolation géodésique. Nous présentons ici une méthode de remplissage géodésique par subdivision d'un contour à n bords permettant de se ramener au cas triangulaire curviligne

Serret Frenet frame interpolation under length constraints for surface reconstruction

National audienc