Discrete event front tracking simulator of a physical fire spread model

International audienceSimulation of moving interfaces, like a fire front usually requires the resolution of a large scale and detailed domain. Such computing involves the use of supercomputers to process the large amount of data and calculations. This limitation is mainly due to the fact that large scale of space and time is usually split into nodes, cells or matrices, and the solving methods often require small time steps. This paper presents a novel method that enables the simulation of large scale/high resolution systems by focusing on the interface. Unlike the conventional explicit and implicit integration schemes, it is based on the discrete-event approach, which describes time advance in terms of increments of physical quantities rather than discrete time stepping. Space as well is not split into discrete nodes or cells, but we use polygons with real coordinates. The system is described by the behaviour of its interface, and evolves by computing collision events of this interface in the simulation. As this simulation technique is suited for a class of models that can explicitly provide rate of spread for a given configuration, we developed a specific radiation based propagation model of physical wildland fire. Simulations of a real large scale fire performed with an implementation of our method provide very interesting results in less than 30 seconds with a 3 metres resolution with current personal computers

Relations entre qualité du substrat, flux de matières et activités humaines. Connaissance pour la gestion des ressources en eau de la Région Aquitaine

Les résultats de ce travail de recherche, confirment une fois de plus l'absence de déterminisme apparent entre qualité du substrat et occupation des sols. Ils montrent qu'il n'y a pas de variables prépondérantes ou explicatives de facteurs sociaux ou physiques qui soient responsables des variations affectant les milieux étudiés. Cependant, les analyses régressives des rapports entre homme et milieu montrent les liens étroits entre habitat et types de sol. L'action humaine a des effets sur la couverture végétale, sur les sols et sur l'hydraulique qui avec le climat et la topographie constituent les principaux facteurs d'érosion

Protective Efficacy against Respiratory Syncytial Virus following Murine Neonatal Immunization with BBG2Na Vaccine: Influence of Adjuvants and Maternal Antibodies

Alum-adsorbed BBG2Na, a recombinant vaccine derived in part from the respiratory syncytial virus (RSV) subgroup A G protein, induced moderate antibody titers after 1 immunization in 1-week-old mice but conferred complete lung protection upon RSV challenge. The anti-BBG2Na IgG1-IgG2a neonatal isotype profile was suggestive of dominant Th2 responses compared with those in adults. Formulation of BBG2Na with a Th1-driving adjuvant efficiently shifted neonatal responses toward a more balanced and adultlike IgG1-IgG2a profile without compromising its protective efficacy. BBG2Na-induced protective immunity was maintained even after early life immunization in the presence of high titers of maternal antibodies. Under these conditions, the protective efficacy (86%-100%) reflected the high capacity of the nonglycosylated G2Na immunogen to escape inhibition by RSV-A—induced maternal antibodies. Thus, immunization with BBG2Na protected against viral challenge despite neonatal immunologic immaturity and the presence of maternal antibodies, two major obstacles to neonatal RSV vaccine developmen

Using Inuit traditional ecological knowledge for detecting and monitoring avian cholera among common eiders in the eastern Canadian Arctic

In recent decades, traditional ecological knowledge (TEK) has played an increasing role in wildlife management and biodiversity conservation in Canada and elsewhere. This study examined the potential contribution that Inuit TEK (which is one aspect of Inuit Qaujimajatuqangit or Inuit traditional knowledge) could offer to detect and monitor avian cholera and other disease-related mortality among Northern Common Eiders (Somateria mollissima borealis) breeding in the eastern Canadian Arctic. Avian cholera is an infectious disease (Pasteurella multocida) that has been a major conservation issue because of its potential to cause high rates of disease and mortality in several bird species in repeating epizootics; it has spread geographically in North America since the 1940s. In 2004, Inuit hunters from Ivujivik, Nunavik, Québec, were the first to detect avian disease outbreaks among Northern Common Eiders nesting in northeastern Hudson Bay and western Hudson Strait. Laboratory analysis of bird tissues confirmed avian cholera in that region. From 2007 to 2009, we collected Inuit TEK about mortality among Common Eiders and other bird species north and west of where the outbreaks were first detected. During interviews in the communities of Kimmirut, Cape Dorset, Coral Harbour, and Igloolik, Nunavut, Canada (n = 40), Inuit participants reported seeing a total of 8 Common Eiders and 41 specimens of other bird species either sick or dead in northern Hudson Strait, Hudson Bay, and Foxe Basin. Most of the observed disease and mortality events were at sea, on sea ice, or on small nesting islands. Such events probably would have gone undetected by biologists, who were mainly monitoring avian cholera outbreaks on large nesting islands in that region. Inuit participants readily recalled details about the timing, location, and numbers of sick and dead birds that they observed. Some reported signs of disease that were consistent with avian cholera. Inuit also revealed knowledge of two past bird mass mortality events that took place about 60 years and a century ago. Those interviewed indicated that that bird mass mortality events potentially caused by avian cholera had not occurred in the study area prior to 2004, supporting the hypothesis that avian cholera emerged only recently in th

Scaling laws and vortex profiles in 2D decaying turbulence

We use high resolution numerical simulations over several hundred of turnover times to study the influence of small scale dissipation onto vortex statistics in 2D decaying turbulence. A self-similar scaling regime is detected when the scaling laws are expressed in units of mean vorticity and integral scale, as predicted by Carnevale et al., and it is observed that viscous effects spoil this scaling regime. This scaling regime shows some trends toward that of the Kirchhoff model, for which a recent theory predicts a decay exponent $\xi=1$. In terms of scaled variables, the vortices have a similar profile close to a Fermi-Dirac distribution.Comment: 4 Latex pages and 4 figures. Submitted to Phys. Rev. Let

Validation of TROPOMI Surface UV Radiation Product

The TROPOspheric Monitoring Instrument (TROPOMI) onboard the Sentinel-5 Precursor (S5P) satellite was launched on 13 October 2017 to provide the atmospheric composition for atmosphere and climate research. The S5P is a sun-synchronous polar-orbiting satellite providing global daily coverage. The TROPOMI swath is 2600 km wide, and the ground resolution for most data products is 7.2x3.5 km2 (5.6x3.5 km2 since 6 August 2019) at nadir. The Finnish Meteorological Institute (FMI) is responsible for the development and processing of the TROPOMI Surface Ultraviolet (UV) Radiation Product which includes 36 UV parameters in total. Ground-based data from 25 sites located in arctic, subarctic, temperate, equatorial and antarctic areas were used for validation of TROPOMI overpass irradiance at 305, 310, 324 and 380 nm, overpass erythemally weighted dose rate / UV index and erythemally weighted daily dose for the period from 1 January 2018 to 31 August 2019. The validation results showed that for most sites 60–80% of TROPOMI data was within ±20% from ground-based data for snow free surface conditions. The median relative differences to ground-based measurements of TROPOMI snow free surface daily doses were within ±10% and ±5% at two thirds and at half of the sites, respectively. At several sites more than 90% of clear sky TROPOMI data were within ±20% from ground-based measurements. Generally median relative differences between TROPOMI data and ground-based measurements were a little biased towards negative values, but at high latitudes where nonhomogeneous topography and albedo/snow conditions occurred, the negative bias was exceptionally high, from -30% to -65%. Positive biases of 10–15% were also found for mountainous sites due to challenging topography. The TROPOMI Surface UV Radiation Product includes quality flags to detect increased uncertainties in the data due to heterogeneous surface albedo and rough terrain which can be used to filter the data retrieved under challenging conditions

Periodontal treatment to improve glycaemic control in diabetic patients: study protocol of the randomized, controlled DIAPERIO trial

<p>Abstract</p> <p>Background</p> <p>Periodontitis is a common, chronic inflammatory disease caused by gram-negative bacteria leading to destruction of tissues supporting the teeth. Epidemiological studies have consistently shown increased frequency, extent and severity of periodontitis among diabetic adults. More recently, some controlled clinical trials have also suggested that periodontal treatment could improve glycaemic control in diabetic patients. However current evidence does not provide sufficient information on which to confidently base any clinical recommendations. The main objective of this clinical trial is to assess whether periodontal treatment could lead to a decrease in glycated haemoglobin levels in metabolically unbalanced diabetic patients suffering from chronic periodontitis.</p> <p>Methods</p> <p>The DIAPERIO trial is an open-label, 13-week follow-up, randomized, controlled trial. The total target sample size is planned at 150 participants, with a balanced (1:1) treatment allocation (immediate treatment vs delayed treatment). Periodontal treatment will include full mouth non-surgical scaling and root planing, systemic antibiotherapy, local antiseptics (chlorhexidine 0.12%) and oral health instructions. The primary outcome will be the difference in change of HbA1c between the two groups after the 13-weeks' follow-up. Secondary outcomes will be the difference in change of fructosamine levels and quality of life between the two groups.</p> <p>Discussion</p> <p>The DIAPERIO trial will provide insight into the question of whether periodontal treatment could lead to an improvement in glycaemic control in metabolically unbalanced diabetic patients suffering from periodontitis. The results of this trial will help to provide evidence-based recommendations for clinicians and a draft framework for designing national health policies.</p> <p>Trial registration</p> <p>Current Controlled Trials ISRCTN15334496</p