Noeuds mous d'un graphe

L'exposé reprendra en partie des résultats de l'article suivant : http://iopscience.iop.org/1751-8121/46/3/035101 Oscillations of networks: the role of soft nodes Jean-Guy Caputo et al 2013 J. Phys. A: Math. Theor. 46 035101International audienceNous nous plaçons dans le contexte de phénomènes physiques d'oscillation dans des réseaux (typiquement des réseaux électriques ou des systèmes mécaniques). Ces phénomènes sont modélisés par des systèmes d'équations différentielles associées à un graphe, et le comportement du système est lié à la matrice de Laplacien du graphe L=D-A (où D est une matrice diagonale des degrés et A est une matrice d'adjacence). Dans le cas de systèmes linéaires, on se ramène à étudier les valeurs propres et vecteurs propres de L. Lorsque les phénomènes étudiés ne sont pas linéaires, une approche consiste à projeter sur une base de vecteurs propres.En fonction du graphe, il peut arriver qu'une composante d'un vecteur propre soit nulle : nous appelons noeud mou le sommet du graphe correspondant, car agir sur ce noeud n'a aucune influence sur le réseau pour le mode correspondant à la valeur propre en régime linéaire. Nous nous intéressons à la détection de tels noeuds. Calculer une valeur propre ne peut pas se faire de façon exacte dans tous les cas, et les résultats généraux existants sur les valeurs propres de graphes donnent généralement des bornes peu précises. Nous montrons qu'on peut déterminer certaines configurations précises de sous-graphes qui entraînent automatiquement la présence de noeuds mous pour des valeurs propres qui dépendent uniquement de ces sous-graphes.  </p

Chapter 2. “We Were Defending the State”: Nationalism, Myth, and Memory in Twentieth-Century Croatia

Since the collapse of Communism in 1989, Central and Southeast Europeans have experienced a “revival of memory” and been involved in a painstaking revision of their national pasts. This is both understandable and necessary, given the Communist domination of historical “truth” since the 1940s. New historical interpretations, often of a markedly nationalist hue, have formed a new orthodoxy. The transition from ideological, party-sponsored history to a more dispassionate and professional history..

Techno-economic and environmental analysis of a hybrid PV/T solar system based on vegetable and synthetic oils coupled with TiO2 in Cameroon

To assess the production potential, economic profitability and ecobalance of the photovoltaic/thermal (PV/T) system in Cameroon, different configurations of HTF based on water, vegetable and synthetic oils, coupled with different forms of titanium dioxide (TiO2) are used. A numerical code is written in Matlab. The PV/T model connected in direct contact PV-absorber is validated and a multi-objective optimization of the system is performed. The hourly evolution of PV cell temperature for the six HTF configurations revealed a value below 36 °C with Coton/TiO2. The platelets-and spherical-shaped nanoparticles increase the convection transfer coefficient between the fluids and the tubes. TiO2 showed a higher thermal influence in vegetable and synthetic oils than in water at a volume concentration of 4 %. The cotton/TiO2 configuration showed a 12.08 % improvement in electrical efficiency over conventional PV systems with low exergy efficiency compared to water. Configurations with therminolVP-1/TiO2 are better, with the proposed energy cost reduced to 33 % of the price of electricity in Cameroon. The PV/T-Palm/TiO2 system showed an energy cost of $0.03 with a net present value of$568.45, an emission rate of 7.78 kg, a reversibility index of 1.95, an annual cost of $7.07 and a payback time of 5.97yr. This shows that PV/T systems based on vegetable oils are economical

Chirurgie cardiaque au Cameroun. Résultats à un an de la phase pilote.

In the framework of implementation of his national program for control and prevention of cardiovascular diseases, Cameroonian government has set up a cardiac surgery project. We report in this manuscript results of one year follow up of the patients operated during the pilot phase. From September 22 till 26, 2008, 11 patients have been operated in Cameroun. Surgical procedures were 5 mitral mechanic valve replacement, 2 aortic mechanic valve replacement, 1 atrial septal defect closure, 2 pace maker implantation. No intrahospital death was observed. One patient died at 11th month after the operation due to mitral valve thrombosis and attributed to lack of compliance. One patient presented low cardiac output, pneumonia and a pleural effusion. 2 patients presented 2 minor complications consisting of pericarditis and superficial wound infection. The results of the pilot phase of cardiac surgery in Cameroon are effective. However, the sustainability of the program require human, material capacity building, and funding mechanism as well.English AbstractJournal Articleinfo:eu-repo/semantics/publishe

Frequency and management of maternal infection in health facilities in 52 countries (GLOSS): a 1-week inception cohort study

Background Maternal infections are an important cause of maternal mortality and severe maternal morbidity. We report the main findings of the WHO Global Maternal Sepsis Study, which aimed to assess the frequency of maternal infections in health facilities, according to maternal characteristics and outcomes, and coverage of core practices for early identification and management. Methods We did a facility-based, prospective, 1-week inception cohort study in 713 health facilities providing obstetric, midwifery, or abortion care, or where women could be admitted because of complications of pregnancy, childbirth, post-partum, or post-abortion, in 52 low-income and middle-income countries (LMICs) and high-income countries (HICs). We obtained data from hospital records for all pregnant or recently pregnant women hospitalised with suspected or confirmed infection. We calculated ratios of infection and infection-related severe maternal outcomes (ie, death or near-miss) per 1000 livebirths and the proportion of intrahospital fatalities across country income groups, as well as the distribution of demographic, obstetric, clinical characteristics and outcomes, and coverage of a set of core practices for identification and management across infection severity groups. Findings Between Nov 28, 2017, and Dec 4, 2017, of 2965 women assessed for eligibility, 2850 pregnant or recently pregnant women with suspected or confirmed infection were included. 70·4 (95% CI 67·7–73·1) hospitalised women per 1000 livebirths had a maternal infection, and 10·9 (9·8–12·0) women per 1000 livebirths presented with infection-related (underlying or contributing cause) severe maternal outcomes. Highest ratios were observed in LMICs and the lowest in HICs. The proportion of intrahospital fatalities was 6·8% among women with severe maternal outcomes, with the highest proportion in low-income countries. Infection-related maternal deaths represented more than half of the intrahospital deaths. Around two-thirds (63·9%, n=1821) of the women had a complete set of vital signs recorded, or received antimicrobials the day of suspicion or diagnosis of the infection (70·2%, n=1875), without marked differences across severity groups. Interpretation The frequency of maternal infections requiring management in health facilities is high. Our results suggest that contribution of direct (obstetric) and indirect (non-obstetric) infections to overall maternal deaths is greater than previously thought. Improvement of early identification is urgently needed, as well as prompt management of women with infections in health facilities by implementing effective evidence-based practices