Ensemble forecast of solar radiation using TIGGE weather forecasts and HelioClim database

International audienceMedium-range forecasts (one day to two weeks) of solar radiation are commonly assessed with a single forecast at a given location. In this paper, we forecast maps of surface solar irradiance, using ensembles of forecasts from the THORPEX Interactive Grand Global Ensemble (TIGGE) with a 6-h timestep. We compare our forecasts with observations derived from MeteoSat Second Generation (MSG) and provided by the HelioClim-3 database as gridded observations over metropolitan France. First, we study the ensembles from six meteorological centers. Second, we use sequential aggregation to linearly combine all the forecasts with weights that vary in space and time. Sequential aggregation updates the weights before any forecast, using available observations. We use the global numerical weather prediction from the European Center for Medium-range Weather Forecasts (ECMWF) as a reference forecast. The issue of spatial resolution is discussed because the low resolution forecasts from TIGGE are compared to high resolution irradiance estimated from MSG data. We found that the TIGGE ensembles are under-dispersed but rather different from one to another. Aggregation decreases the forecast error by 20%, and produces a more realistic spatial pattern of predicted irradiance

Combining short-range dispersion simulations with fine-scale meteorological ensembles: probabilistic indicators and evaluation during a 85Kr field campaign

Numerical atmospheric dispersion models (ADMs) are used for predicting the health and environmental consequences of nuclear accidents in order to anticipate countermeasures necessary to protect the populations. However, these simulations suffer from significant uncertainties, arising in particular from input data: weather conditions and source term. Meteorological ensembles are already used operationally to characterize uncertainties in weather predictions. Combined with dispersion models, these ensembles produce different scenarios of radionuclide dispersion, called “members”, representative of the variety of possible forecasts. In this study, the fine-scale operational weather ensemble AROME-EPS (Applications of Research to Operations at Mesoscale-Ensemble Prediction System) from Météo-France is coupled with the Gaussian puff model pX developed by the IRSN (French Institute for Radiation Protection and Nuclear Safety). The source term data are provided at 10 min resolution by the Orano La Hague reprocessing plant (RP) that regularly discharges 85Kr during the spent nuclear fuel reprocessing process. In addition, a continuous measurement campaign of 85Kr air concentration was recently conducted by the Laboratory of Radioecology in Cherbourg (LRC) of the IRSN, within 20 km of the RP in the North-Cotentin peninsula, and is used for model evaluation. This paper presents a probabilistic approach to study the meteorological uncertainties in dispersion simulations at local and medium distances (2–20 km). First, the quality of AROME-EPS forecasts is confirmed by comparison with observations from both Météo-France and the IRSN. Then, the probabilistic performance of the atmospheric dispersion simulations was evaluated by comparison to the 85Kr measurements carried out during a period of 2 months, using two probabilistic scores: relative operating characteristic (ROC) curves and Peirce skill score (PSS). The sensitivity of dispersion results to the method used for the calculation of atmospheric stability and associated Gaussian dispersion standard deviations is also discussed. A desirable feature for a model used in emergency response is the ability to correctly predict exceedance of a given value (for instance, a dose guide level). When using an ensemble of simulations, the “decision threshold” is the number of members predicting an event above which this event should be considered probable. In the case of the 16-member dispersion ensemble used here, the optimal decision threshold was found to be 3 members, above which the ensemble better predicts the observed peaks than the deterministic simulation. These results highlight the added value of ensemble forecasts compared to a single deterministic one and their potential interest in the decision process during crisis situations.</p

Combining short-range dispersion simulations with fine-scale meteorological ensembles: probabilistic indicators and evaluation during a 85Kr field campaign

Numerical atmospheric dispersion models (ADMs) are used for predicting the health and environmental consequences of nuclear accidents in order to anticipate countermeasures necessary to protect the populations. However, these simulations suffer from significant uncertainties, arising in particular from input data: weather conditions and source term. Meteorological ensembles are already used operationally to characterize uncertainties in weather predictions. Combined with dispersion models, these ensembles produce different scenarios of radionuclide dispersion, called “members”, representative of the variety of possible forecasts. In this study, the fine-scale operational weather ensemble AROME-EPS (Applications of Research to Operations at Mesoscale-Ensemble Prediction System) from Météo-France is coupled with the Gaussian puff model pX developed by the IRSN (French Institute for Radiation Protection and Nuclear Safety). The source term data are provided at 10 min resolution by the Orano La Hague reprocessing plant (RP) that regularly discharges 85Kr during the spent nuclear fuel reprocessing process. In addition, a continuous measurement campaign of 85Kr air concentration was recently conducted by the Laboratory of Radioecology in Cherbourg (LRC) of the IRSN, within 20 km of the RP in the North-Cotentin peninsula, and is used for model evaluation. This paper presents a probabilistic approach to study the meteorological uncertainties in dispersion simulations at local and medium distances (2–20 km). First, the quality of AROME-EPS forecasts is confirmed by comparison with observations from both Météo-France and the IRSN. Then, the probabilistic performance of the atmospheric dispersion simulations was evaluated by comparison to the 85Kr measurements carried out during a period of 2 months, using two probabilistic scores: relative operating characteristic (ROC) curves and Peirce skill score (PSS). The sensitivity of dispersion results to the method used for the calculation of atmospheric stability and associated Gaussian dispersion standard deviations is also discussed. A desirable feature for a model used in emergency response is the ability to correctly predict exceedance of a given value (for instance, a dose guide level). When using an ensemble of simulations, the “decision threshold” is the number of members predicting an event above which this event should be considered probable. In the case of the 16-member dispersion ensemble used here, the optimal decision threshold was found to be 3 members, above which the ensemble better predicts the observed peaks than the deterministic simulation. These results highlight the added value of ensemble forecasts compared to a single deterministic one and their potential interest in the decision process during crisis situations.</p

Contribution à l'étude de plaques perforées en régime élastoplastique

Il est avantageux de procéder au dimensionnement mécanique des plaques tubulaires des échangeurs de chaleur dans le domaine plastique. En effet, ces plaques ont tout intérêt à être d'épaisseur la plus faible possible, d'une part afin de réduire les gradients internes de température et les risques liés à la fatigue thermique et, d'autre part afin de réduire les coûts de réalisation liés au matériau et au perçage. Dans la pratique, les plaques sont forées selon un réseau de perforation périodique suivant un pas carré ou triangulaire équilatéral. Ces réseaux sont caractérisés géométriquement par le facteur de ligament dépendant du diamètre de perforation et du pas de la maille. L'objectif de l'article est de proposer une méthode de dimensionnement des plaques tubulaires basée sur l'emploi de plaques pleines équivalentes. Dans un premier temps, les résultats de l'analyse élastoplastique de plaques perforées par voie numérique sont commentés. Une plaque pleine équivalente à la plaque perforée peut servir au dimensionnement à l'état limite de la plaque tubulaire. Dans ce cas, une loi d'écoulement plastique est reformulée pour tenir compte des perforations

Développement d'un élément fini semi-rigide pour l'étude des structures planes en bois

Bien souvent, les calculs de dimensionnement des structures en bois suppose que les nœuds d'assemblages se comportent comme des rotules parfaites ou comme des encastrements parfaits. A l'exception de certains assemblages collés, les assemblages utilisés dans la pratique présentent un comportement semi-rigide bien marqué. Pour de tels assemblages, des déformations relatives apparaissent entre les membrures connectées. Le travail entrepris a pour finalité de développer un élément fini semi-rigide (EFSR) connectant les degrés de liberté en translation et en rotation des nœuds assemblés et dédicacé à la modélisation des assemblages par gousset en bois. La matrice de raideur locale de cet élément est alors définie à partir de résultats expérimentaux caractérisant les rigidités parallèle et perpendiculaire aux fibres. Un des intérêts de cette approche est la prise en compte au niveau même de la matrice de raideur le l'EFSR du comportement orthotrope et éventuellement plastique du bois

Study of mechanical compatibility at the mortar-block interface in a heritage building

ce travail a pour objectif de modéliser l'ensemble mortier/bloc et d'analyser la résistance mécanique à l'interface. l'étude prend comme support d'étude une batisse historique au Maroc. Nous choisissons un mur de la construction et nous procédons à une simulation numérique. Nous étudierons la répartition des contraintes dans le mur. Deux cas seront considérés : un mur sollicité non restauré et un mur sollicité non restauré. Le but de ces simulations étant de comparer les répartitions des contraintes dans chacun des deux cas afin de justifier ou non l’intérêt de l’utilisation d’un mortier de restauration de faible résistance. Les caractéristiques mécaniques obtenues lors des essais non-conventionnels, en l’occurrence le module d’élasticité statique et le coefficient de Poisson seront utilisés dans cette analyse. le comportement du système est considéré comme élastoplastique

EXPERIENCIA EDUCATIVA : TALLER DE RECURSOS NATURALES II

El Taller de Recursos Naturales II (TRN II) se desarrolla durante el 2do cuatrimestre del segundo año de Agronomía. La información obtenida por los alumnos es utilizada en el Taller de Producción Vegetal en el 4to Año. De acuerdo a la estructura y lineamientos del Plan de Estudios, el TRN II integra actividades de las asignaturas dictadas en ese cuatrimestre como: Propiedades Edáficas y Fertilidad, Fisiología Vegetal, Genética Básica y Aplicada y Agrometeorología, además de Ecología y Zoología Agrícola, asignaturas de tercero y cuarto año respectivamente. Tiene como objetivo conducir al alumno hacia una compresión global de los factores que afectan el crecimiento de las plantas con el fin de mantener o aumentar la producción, dentro del marco de una agricultura sustentable. Finaliza con una puesta en común donde se interpretan los resultados en términos ecofisiológicos y de interacción genotipo-ambiente, utilizando información obtenida de las demás asignaturas. Así, otorga a los futuros profesionales la capacidad de analizar los conocimientos adquiridos a campo y en el laboratorio, a la luz de los factores investigados durante el desarrollo del Taller

Perinatal acquisition of drug-resistant HIV-1 infection: mechanisms and long-term outcome

<p>Abstract</p> <p>Background</p> <p>Primary-HIV-1-infection in newborns that occurs under antiretroviral prophylaxis that is a high risk of drug-resistance acquisition. We examine the frequency and the mechanisms of resistance acquisition at the time of infection in newborns.</p> <p>Patients and Methods</p> <p>We studied HIV-1-infected infants born between 01 January 1997 and 31 December 2004 and enrolled in the ANRS-EPF cohort. HIV-1-RNA and HIV-1-DNA samples obtained perinatally from the newborn and mother were subjected to population-based and clonal analyses of drug resistance. If positive, serial samples were obtained from the child for resistance testing.</p> <p>Results</p> <p>Ninety-two HIV-1-infected infants were born during the study period. Samples were obtained from 32 mother-child pairs and from another 28 newborns. Drug resistance was detected in 12 newborns (20%): drug resistance to nucleoside reverse transcriptase inhibitors was seen in 10 cases, non-nucleoside reverse transcriptase inhibitors in two cases, and protease inhibitors in one case. For 9 children, the detection of the same resistance mutations in mothers' samples (6 among 10 available) and in newborn lymphocytes (6/8) suggests that the newborn was initially infected by a drug-resistant strain. Resistance variants were either transmitted from mother-to-child or selected during subsequent temporal exposure under suboptimal perinatal prophylaxis. Follow-up studies of the infants showed that the resistance pattern remained stable over time, regardless of antiretroviral therapy, suggesting the early cellular archiving of resistant viruses. The absence of resistance in the mother of the other three children (3/10) and neonatal lymphocytes (2/8) suggests that the newborns were infected by a wild-type strain without long-term persistence of resistance when suboptimal prophylaxis was stopped.</p> <p>Conclusion</p> <p>This study confirms the importance of early resistance genotyping of HIV-1-infected newborns. In most cases (75%), drug resistance was archived in the cellular reservoir and persisted during infancy, with or without antiretroviral treatment. This finding stresses the need for effective antiretroviral treatment of pregnant women.</p

Risk factors for virological failure and subtherapeutic antiretroviral drug concentrations in HIV-positive adults treated in rural northwestern Uganda

ABSTRACT: BACKGROUND: Little is known about immunovirological treatment outcomes and adherence in HIV/AIDS patients on antiretroviral therapy (ART) treated using a simplified management approach in rural areas of developing countries, or about the main factors influencing those outcomes in clinical practice. METHODS: Cross-sectional immunovirological, pharmacological, and adherence outcomes were evaluated in all patients alive and on fixed-dose ART combinations for 24 months, and in a random sample of those treated for 12 months. Risk factors for virological failure (>1,000 copies/mL) and subtherapeutic antiretroviral (ARV) concentrations were investigated with multiple logistic regression. RESULTS: At 12 and 24 months of ART, 72% (n=701) and 70% (n=369) of patients, respectively, were alive and in care. About 8% and 38% of patients, respectively, were diagnosed with immunological failure; and 75% and 72% of patients, respectively, had undetectable HIV RNA (<400 copies/mL). Risk factors for virological failure (>1,000 copies/mL) were poor adherence, tuberculosis diagnosed after ART initiation, subtherapeutic NNRTI concentrations, general clinical symptoms, and lower weight than at baseline. About 14% of patients had low ARV plasma concentrations. Digestive symptoms and poor adherence to ART were risk factors for low ARV plasma concentrations. CONCLUSIONS: Efforts to improve both access to care and patient management to achieve better immunological and virological outcomes on ART are necessary to maximize the duration of first-line therapy

Recent HIV-1 Infection Contributes to the Viral Diffusion over the French Territory with a Recent Increasing Frequency

To analyse the contribution of primary human immunodeficiency virus type 1 (HIV-1) infection (PHI) to the French viral epidemic. sequences included 987 PHI from the French ANRS PRIMO cohort between 1999 and 2010 and were analysed using a population-based phylogenetic approach. Clinical features, risk factors, sexual behaviour and drug resistance for clustered and nonclustered transmission events were ascertained.Viruses from 125 (12.7%) of PHI cosegregated into 56 transmission chains, with increasing frequency during the last years (10.2% before 2006 versus 15.2% of clusters in 2006–2010, p = 0.02). The mean number of patients per cluster was 2.44. Compared to unique PHI, clusters involved more often men, infected through homosexual intercourse, of young age, with a high number of casual sexual partnerships and frequent previous HIV serological tests. Resistant strains were found in 16.0% and 11.1% of clusters and unique PHI, respectively (p = 0.11). Overall, 34% (n = 19) clusters included patients followed in French regions far apart, involving 13 clusters with at least one Parisian patient.PHIs are a significant source of onward transmission, especially in the MSM population. Recently infected people contribute to the spread of the viral epidemic throughout the French territory. Survey of transmitted drug resistance and behavioural characteristics of patients involved into clustered PHI may help to guide prevention and treatment interventions