A posteriori error analysis of Euler-Galerkin approximations to coupled elliptic-parabolic problems

21 pagesWe analyze Euler-Galerkin approximations (conforming finite elements in space and implicit Euler in time) to coupled PDE systems in which one dependent variable, say u, is governed by an elliptic equation and the other, say p, by a parabolic-like equation. The targeted application is the poroelasticity system within the quasi-static assumption. An abstract setting is proposed to identify a natural energy norm for the PDE system. Two a posteriori error analyzes are performed, both yielding reliable upper error bounds in the sense that all the constants are specified. The first analysis hinges directly on the stability of the continuous problem and can be used to estimate the dominant term associated with the p-component in the energy norm. The second analysis is an extension of the elliptic reconstruction technique introduced by Makridakis and Nochetto for linear parabolic problems. It is used here to derive an a posteriori error estimate for the u-component in the energy norm that exhibits an optimal convergence rate with respect to mesh size. Numerical results are presented to illustrate the performance of the various estimators

A posteriori error analysis of Euler-Galerkin approximations to coupled elliptic-parabolic problems

21 pagesWe analyze Euler-Galerkin approximations (conforming finite elements in space and implicit Euler in time) to coupled PDE systems in which one dependent variable, say u, is governed by an elliptic equation and the other, say p, by a parabolic-like equation. The targeted application is the poroelasticity system within the quasi-static assumption. An abstract setting is proposed to identify a natural energy norm for the PDE system. Two a posteriori error analyzes are performed, both yielding reliable upper error bounds in the sense that all the constants are specified. The first analysis hinges directly on the stability of the continuous problem and can be used to estimate the dominant term associated with the p-component in the energy norm. The second analysis is an extension of the elliptic reconstruction technique introduced by Makridakis and Nochetto for linear parabolic problems. It is used here to derive an a posteriori error estimate for the u-component in the energy norm that exhibits an optimal convergence rate with respect to mesh size. Numerical results are presented to illustrate the performance of the various estimators

Assessing the reliability of an automated method for measuring dominance hierarchy in non-human primates

Among animal societies, dominance is an important social factor that influences inter-individual relationships. However, assessing dominance hierarchy can be a time-consuming activity which is potentially impeded by environmental factors, difficulties in the recognition of animals, or disturbance of animals during data collection. Here we took advantage of novel devices, machines for automated learning and testing (MALT), designed primarily to study non-human primate cognition, to additionally measure the dominance hierarchy of a semi-free-ranging primate group. When working on a MALT, an animal can be replaced by another, which could reflect an asymmetric dominance relationship. To assess the reliability of our method, we analysed a sample of the automated conflicts with video scoring and found that 74% of these replacements included genuine forms of social displacements. In 10% of the cases, we did not identify social interactions and in the remaining 16% we observed affiliative contacts between the monkeys. We analysed months of daily use of MALT by up to 26 semi-free-ranging Tonkean macaques (Macaca tonkeana) and found that dominance relationships inferred from these interactions strongly correlated with the ones derived from observations of spontaneous agonistic interactions collected during the same time period. An optional filtering procedure designed to exclude chance-driven displacements or affiliative contacts suggests that the presence of 26% of these interactions in data sets did not impair the reliability of this new method. We demonstrate that this method can be used to assess the dynamics of both individual social status, and group-wide hierarchical stability longitudinally with minimal research labour. Further, it facilitates a continuous assessment of dominance hierarchies in captive groups, even during unpredictable environmental or challenging social events, which underlines the usefulness of this method for group management purposes. Altogether, this study supports the use of MALT as a reliable tool to automatically and dynamically assess dominance hierarchy within captive groups of non-human primates, including juveniles, under conditions in which such technology can be used

Functional imaging and radiotherapy

peer reviewedLes progrès technologiques réalisés par l’image- rie médicale l’ont placée au centre de la prise en charge des patients oncologiques, tant au niveau du diagnostic, du pro - nostic et du suivi que dans la prise en charge thérapeutique. En effet, l’imagerie représente, à l’heure actuelle, la pierre angulaire des traitements de radiothérapie. Les objectifs du radiothérapeute sont d’irradier le plus précisément possible la tumeur à dose curative, tout en évitant les organes sains. Pour y arriver, le radiothérapeute utilise de façon routinière l’imagerie anatomique (Scanner et IRM). Depuis quelques années, le développement des différentes imageries métabo - liques et fonctionnelles, comme l’imagerie par émission de positons (PET-CT) et la résonnance magnétique fonctionnelle, ouvrent de nouvelles possibilités thérapeutiques grâce aux informations qu’elles apportent sur la biologie des tumeurs. Cet article décrit, de manière non exhaustive, les différentes imageries anatomiques et métaboliques à la disposition du radiothérapeute

Population affinities in pre‐colonial West Africa: The case of the burial cave Iroungou (Gabon, 14th–15th century CE )

Introduction: Our knowledge of the populations of sub‐Saharan Africa in the periods before European colonization is limited. Few archeological sites containing human remains have been identified, and written sources for these periods are rare. The discovery in 2018 of the Iroungou sepulchral cave (Gabon), whose use predates the arrival of the Portuguese (14th–15th centuries CE), is an exceptional source of information: at least 28 individuals associated with numerous metal artifacts were found there. The anthropobiological remains were left in situ, but the eight best preserved crania were digitized. Objectives: This study focuses on the population affinities of these crania, whose morphology was described using 237 landmarks. Materials and Methods: Geometric morphometric analyses were used to compare the eight Iroungou specimens with 154 individuals representing 12 well‐defined African populations. After alignment (Generalized Procrustes Analysis), morphological affinity was assessed using Euclidean and Mahalanobis distances, and posterior probabilities of population membership (discriminant analysis). Results: Results indicate that the eight Iroungou crania have, on average, more affinity with Bayaka Pygmy, followed by Central African Bantu. Nevertheless, individually, the Iroungou specimens show an important morphological variation and the eight crania can be separated into different affinity groups: Bayaka and Central African Bantu, KhoeSan, and East‐African Bantu. Finally, one individual presents strong affinity with Somalis. Conclusion: This phenetic mapping of the Iroungou sample raises questions about the profile of the individuals deposited in the cave in a geographical area known for the Loango pre‐colonial kingdom, which ruling class seemed to have had privileged relationships with the Pygmy populations

Classification of the fibronectin variants with curvelets

International audienceThe role of the extracellular matrix (ECM) in the evolution of certain diseases (e.g. fibrosis, cancer) is generally accepted but yet to be completely understood. A numerical model that captures the physical properties of the ECM, could convey certain connections between the topology of its constituents and their associated biological features. This study addresses the analysis and modeling of fibrillar networks containing Fibronectin (FN) networks, a major ECM molecule, from 2D confocal microscopy images. We leveraged the advantages of the fast discrete curvelet transform (FDCT), in order to obtain a multiscale and multidirectional representation of the FN fibrillar networks. This step was validated by performing a classification among the different variants of FN upregulated in disease states with a multi-class classification algorithm, DAG-SVM. Subsequently, we designed a method to ensure the invariance to rotation of the curvelet features. Our results indicate that the curvelets offer an appropriate discriminative model for the FN networks, that is able to characterize the local fiber geometry

Coupled study by TEM/EELS and STM/STS of electronic properties of C- and CNx-nanotubes

Carbon nanotubes are the focus of considerable research efforts due to their fascinating physical properties. They provide an excellent model system for the study of one dimensional materials and molecular electronics. The chirality of nanotubes can lead to very different electronic behaviours, either metallic or semiconducting. Their electronic spectrum consists of a series of Van Hove singularities defining a bandgap for semiconducting tubes and molecular orbitals at the corresponding energies. A promising way to tune the nanotubes electronic properties for future applications is to use doping by heteroatoms. Here we report on experimental investigation of the role of many-body interactions in nanotube bandgaps, the visualization in direct space of the molecular orbitals of nanotubes and the properties of nitrogen doped nanotubes using scanning tunneling microscopy and transmission electron microscopy as well as electron energy loss spectroscopy

Body mass index influences the response to infliximab in ankylosing spondylitis

INTRODUCTION: The excess of adipose tissue in obese individuals may have immunomodulating properties and pharmacokinetic consequences. The aim of this study was to determine whether body mass index (BMI) affects response to infliximab (IFX) in ankylosing spondylitis (AS) patients. METHODS: In 155 patients retrospectively included with active AS, the BMI was calculated before initiation of IFX treatment (5 mg/kg intravenously). After 6 months of treatment, changes from baseline in BASDAI, Visual Analogue Scale (VAS) pain, C-reactive protein (CRP) level, and total dose of nonsteroidal antiinflammatory drug (NSAID) were dichotomized with a threshold corresponding to a decrease of 50% of initial level of the measure, into binary variables assessing response to IFX (BASDAI50, VAS50, CRP50, NSAID50). Whether the BMI was predictive of the response to IFX therapy according to these definitions was assessed with logistic regression. RESULTS: Multivariate analysis found that a higher BMI was associated with a lower response for BASDAI50 (P = 0.0003; OR, 0.87; 95% CI (0.81 to 0.94)), VAS50 (P < 0.0001; OR, 0.87; 95% CI (0.80 to 0.93)); CRP50 (P = 0.0279; OR, 0.93; 95% CI (0.88 to 0.99)), and NSAID50 (P = 0.0077; OR, 0.91; 95% CI (0.85 to 0.97)), criteria. According to the three WHO BMI categories, similar results were found for BASDAI50 (77.6%, 48.9%, and 26.5%; P < 0.0001), VAS50 (72.6%, 40.4%, and 16.7%; P < 0.0001); CRP50 (87.5%, 65.7%, and 38.5%; P = 0.0001), and NSAID50 (63.2%, 51.5%, and 34.6%; P = 0.06). CONCLUSIONS: This study provides the first evidence that a high BMI negatively influences the response to IFX in AS. Further prospective studies, including assessment of the fat mass, pharmacokinetics, and adipokines dosages are mandatory to elucidate the role of obesity in AS IFX response