Monte Carlo ab initio simulation of the absorption spectrum of Na4

International audienceThe influence of the classical vibration of the nuclei on the visible absorption spectrum of the Na, cluster is investigated. The classical motion on the ground state potential enemy surface at a given temperature is obtained from a Metropolis Monte Carlo simulation. This dynamical process makes possible a theoretical determination of the widths of the structures in the absorption spectra. The absorption spectrum is integrated from ab initio CI calculations of excited states and oscillator streqth along the random tr&xory. A fuat simulation was achieved at T= 150 K using an ab initio CI determination of the ground and the excited states. The efficiency of the Metropolis process is improved with the use of an approximate representation for the ground state. Simulations are performed for several temperatures T= SO, 150, and 500 K. The simulated spectra are discussed in relationship with the experimental speetnm of KappeJ et al

Cartes de photons et visibilité

Les méthodes de simulation d'éclairage par tracé de photons sont souvent utilisées pour leur simplicité et leur versatilité. Les deux étapes classiques de ces approches sont : (i) les calculs d'inter-réflexions lumineuses, indépendantes du point de vue, correspondant à des suivis de chemins lumineux dont les impacts sur les surfaces de la scène sont stockés sous forme de cartes de photons ; (ii) l'exploitation des cartes de photons pour produire une ou plusieurs images de l'environnement virtuel. La première phase repose exclusivement sur des méthodes de Monte-Carlo ; la seconde requiert au moins une estimation de densité pour le calcul d'éclairement. Malheureusement, le tracé de photons est également connu pour les différents biais produits lors de l'estimation de densité des photons pour le calcul de l'éclairement en un point. Ce rapport montre pourquoi la visibilité est un élément fondamental lors de l'estimation de densité ; nous proposons de la prendre en compte de manière précise pour réduire ou supprimer certains biais. Nos résultats mettent en évidence l'importance de la visibilité dans la qualité des images produites

Competition of Lactobacillus paracasei with Salmonella enterica for Adhesion to Caco-2 Cells

Competition of commensal and probiotic bacteria with pathogens for adhesion and colonization is one of the important protective mechanisms of gastrointestinal tract. In this study, we examined the ability of Lactobacillus paracasei to inhibit the adhesion of pathogenic Salmonella enterica to human colon adenocarcinoma Caco-2 cells. Caco-2 cells were grown for 6 or 21 days to obtain nondifferentiated or well-differentiated cells, respectively. In adhesion experiments, bacteria were added to the cells for 2 or 4 hours. The number of attached bacteria was expressed as colony-forming units (CFUs), Caco-2 cells were counted in hematocytometer. Both bacterial strains used adhered better to well-differentiated than to nondifferentiated Caco-2 cells, however, the amount of Salmonella adhered to Caco-2 after 2 hours of contact was 12-fold higher in comparison to L. paracasei and almost 27-fold higher after 4 hours of contact. Two types of experiments were done: coincubation (both bacteria were added to Caco-2 cells simultaneously), and preincubation (L. paracasei was incubated with Caco-2 cells first, and then S. enterica was added). In coincubation experiment, the presence of L. paracasei decreased S. enterica adhesion by 4-fold and in preincubation experiment even 7-fold. Generally, Lactobacillus spent culture supernatants (SCSs) acted weaker as inhibitors of Salmonella adhesion in comparison to the whole L. paracasei culture in coincubation experiment. In conclusion, the displacement of pathogens by lactic acid bacteria and its secretions showed here depends on the time of bacteria-epithelial cell contact, and also on the stage of Caco-2 differentiation

Lobes de cosinus et visibilité pour la simulation d'éclairage

La simulation des réflexions lumineuses multiples à l'intérieur d'un environnement nécessite de résoudre une intégrale de premier ordre, récursive infinie, pour laquelle il n'existe pas de solution analytique dans le cas général. Certaines méthodes permettent de donner une solution théorique exacte, mais avec des temps de calcul trop important pour espérer produire plusieurs images par seconde dans un avenir proche. De nombreuses méthodes permettent de réaliser ces calculs de manière plus rapide, mais elles reposent sur des approximations dont les effets sont souvent visibles sur les images produites. Notre objectif est de proposer des solutions permettant de réduire les erreurs de calculs en exploitant deux approches complémentaires : (i) une homogénéisation des termes de l'équation de manière à la résoudre seulement à l'aide de quelques opérateurs simples ; (ii) la prise en compte précise des informations de visibilité pour réduire le biais des méthodes reposant sur une estimation de densité. A terme, notre objectif est de diminuer le coût des requêtes de visibilité de nos deux contributions. Pour cela nous envisageons notamment d'introduire des calculs hiérarchiques de visibilité de façon à amortir le coût global des requêtes.Simulating light transfer within a virtual environment requires to solve a first order, infinite recursive integral, that unfortunately doesn't have any solution in general cases. Though theoretically exact solutions exist, their computing time is not adapted to real-time rendering in a near future. Many methods have been proposed for accelerating these computations, but they rely on approximations that often produce visible artifacts on the resulting images. Our goal is to propose some new solutions that can reduce biases with two complementary approaches : (i) a new homogeneous representation of each term of the equation can be used to resolve it using only simple operators ; (ii) considering precise visibility information in order to reduce bias of methods that rely on density estimation. On the long range, we aim at reducing visibility requests costs of each contribution. For that purpose, we particularly plan to introduce hierarchical visibility computations so as to amortize queries cost.POITIERS-SCD-Bib. électronique (861949901) / SudocSudocFranceF

Evaluation de la précision des algorithmes de projection affine en virgule fixe

Le but de ce papier est de déterminer de manière analytique la puissance du bruit généré par une implémentation virgule fixe des Algorithmes de Projection Affine (APA). Ces algorithmes ont été développés dans les années 80 mais aucune étude de ce type n'a encore été menée. Dans cet article, nous définissons une expression analytique de la puissance du bruit puis celle-ci est appliquée à l'algorithme NLMS-OCF, un type d'Algorithme de Projection Affine. La validité du modèle est ensuite vérifiée par des simulations

CoViD-19, capital humain et crise économique en Afrique subsaharienne : une analyse prospective

Depuis quelques mois, le monde fait face à une grave crise sanitaire liée à la pandémie de la CoViD-19. Cette crise menace de faire trébucher l’Afrique subsaharienne en inversant les progrès économiques qu’elle a réalisés ces dernières années. L’objectif de cet article est de mener une étude prospective des effets économiques de la pandémie de la CoViD-19 en Afrique subsaharienne, sur la base d’une analyse de la théorie de la croissance endogène (capital humain), des résultats des travaux empiriques sur le lien santé-croissance et des prévisions axées sur les scénarios projetés par les organismes internationaux (le FMI, notamment) et les études antérieures. Selon le FMI (2020), cette pandémie entrainera une contraction du taux de croissance de 1,6% en Afrique subsaharienne en 2020. Pour faire face à cette crise sanitaire et économique, la priorité selon le FMI (2020) est d’accroître les capacités et les dépenses de santé pour sauver des vies et contenir la pandémie. Par ailleurs, pour répondre aux importants besoins de financement engendrés, tous les partenaires du développement devraient apporter leur soutien, en plus d’alléger la dette des pays les plus vulnérables de cette sous-région. Les politiques budgétaires, monétaires et financières doivent être orientées vers la protection des groupes vulnérables en atténuant les pertes économiques et en soutenant la reprise. For the past few months, the world has been facing a serious health crisis linked to the CoViD-19 pandemic. This crisis threatens to trip subSaharan Africa by reversing the economic progress it has made in recent years. The objective of this article is to conduct a prospective study of the economic effects of the CoViD-19 pandemic in sub-Saharan Africa, based on an analysis of the endogenous growth theory (human capital), of the results of empirical works on the link between health and growth and forecasts focusing on the scenarios projected by international organizations (the IMF, in particular) and previous studies. According to the IMF (2020), this pandemic will lead to a contraction of the growth rate of 1.6% in sub-Saharan Africa in 2020. To deal with this health and economic crisis, the priority according to the IMF (2020) is to increase health capacities and spending to save lives and contain the pandemic. In addition, to meet the significant financing needs generated, all development partners should provide support, in addition to reducing the debt of the most vulnerable countries in this sub-region. Fiscal, monetary and financial policies must be geared towards protecting vulnerable groups, by mitigating economic losses and supporting the recovery

New public management and professionals in the public sector:What new patterns beyond opposition?

The proliferation of reforms in public administration based on the principles and instruments of the " New Public Management" (NPM) have triggered protest from and collective action by many professional groups in various sectors (healthcare, education, justice, social work, research...) and raised questions about the future of professionals working in the public service, particularly as concerns their autonomy. However, after analyzing the situation, it seems that the opposition between NPM and certain professional groups is not the last word in the debate. Should changes be seen as the decline of professional groups and of their autonomy or as a transformation of professional models, an overhaul of professionalism, etc.? Such questions, which current events in France and Europe have brought to the fore, are food for ongoing sociological thought. They are broached here empirically, from the field, applying varied levels of analysis and research. The contributors to this dossier explore the different forms of tension existing between professional groups and NPM. © 2012 Elsevier Masso

Suicidality Presented to a Child and Adolescent Psychiatry Emergency Service: Increasing Rate and Changing Characteristics

Background: Children and adolescents who present to child and adolescent psychiatric emergency departments show a variety of reasons for their presentations. Suicidality, in particular suicidal thoughts and suicide attempts, as well as non-suicidal self-injury (NSSI) play a large and important role. In this context, inpatient admissions frequently serve as crisis intervention. Methods: In this study, face-to-face emergency presentations to the emergency department at our Clinic of Child and Adolescent Psychiatry (CAP) were analyzed over the years 2014-2018, the 4th quarter (October-December) of each year. Data from 902 emergency presentations were evaluated, primarily with regard to suicidal thoughts, suicide attempts, and NSSI as reasons for presentation. Results: Data demonstrated that the number of emergency presentations increased in general and especially for suicidal thoughts and NSSI as reasons for presentation. In addition, suicidal thoughts, suicide attempts, and NSSI as reasons for emergency presentation were more likely to result in crisis-related inpatient admissions. Furthermore, reporting suicide attempts at emergency presentation was associated with longer inpatient stays. Finally, cases with multiple diagnoses increased independent of the general increase in emergency presentations. Conclusion: The increase of utilization of clinics with CAP outpatient emergency patients and following admissions to the inpatient units for crisis intervention poses a major challenge for the future. It is important to prepare for the assessment and treatment of suicidality, which is of extraordinary importance in the care of emergency patients