112 research outputs found
A Fluorescent Material Model for Non-Spectral Editing & Rendering
No full textInternational audienceFluorescent materials are characterized by a spectral reradiation toward longer wavelengths. Recent work [Fichet et al. 2024] has shown that the rendering of fluorescence in a non-spectral engine is possible through the use of appropriate reduced reradiation matrices. But the approach has limited expressivity, as it requires the storage of one reduced matrix per fluorescent material, and only works with measured fluorescent assets.In this work, we introduce an analytical approach to the editing and rendering of fluorescence in a non-spectral engine. It is based on a decomposition of the reduced reradiation matrix, and an analytically-integrable Gaussian-based model of the fluorescent component. The model reproduces the appearance of fluorescent materials accurately, especially with the addition of a UV basis. Most importantly, it grants variations of fluorescent material parameters in real-time, either for the editing of fluorescent materials, or for the dynamic spatial variation of fluorescence properties across object surfaces. A simplified one-Gaussian fluorescence model even allows for the artist-friendly creation of plausible fluorescent materials from scratch, requiring only a few reflectance colors as input
Risk maps of Lassa fever in West Africa
No full textBackground: Lassa fever is caused by a viral haemorrhagic arenavirus that affects two to three million people in West Africa, causing a mortality of between 5,000 and 10,000 each year. The natural reservoir of Lassa virus is the multi-mammate rat Mastomys natalensis, which lives in houses and surrounding fields. With the aim of gaining more information to control this
disease, we here carry out a spatial analysis of Lassa fever data from human cases and infected rodent hosts covering the period 1965–2007. Information on contemporary environmental conditions (temperature, rainfall, vegetation) was derived from NASA Terra MODIS satellite sensor data and other sources and for elevation from the GTOPO30 surface for the region from Senegal to the Congo. All multi-temporal data were analysed using temporal Fourier techniques to generate images of means, amplitudes and phases which were used as the predictor variables in the models. In addition, meteorological rainfall data collected between 1951 and 1989 were used to generate a synoptic rainfall surface for the same region.
Methodology/Principal Findings: Three different analyses (models) are presented, one superimposing Lassa fever outbreaks on the mean rainfall surface (Model 1) and the other two using non-linear discriminant analytical techniques. Model 2 selected variables in a step-wise inclusive fashion, and Model 3 used an information-theoretic approach in which many different random combinations of 10 variables were fitted to the Lassa fever data. Three combinations of absence:presence clusters were used in each of Models 2 and 3, the 2 absence:1 presence cluster combination giving what appeared to be the best result. Model 1 showed that the recorded outbreaks of Lassa fever in human populations occurred in zones receiving between 1,500 and 3,000 mm rainfall annually. Rainfall, and to a much lesser extent temperature
variables, were most strongly selected in both Models 2 and 3, and neither vegetation nor altitude seemed particularly important. Both Models 2 and 3 produced mean kappa values in excess of 0.91 (Model 2) or 0.86 (Model 3), making them ‘Excellent’.
Conclusion/Significance: The Lassa fever areas predicted by the models cover approximately 80% of each of Sierra Leone and Liberia, 50% of Guinea, 40% of Nigeria, 30% of each of Coˆ te d’Ivoire, Togo and Benin, and 10% of Ghana.Citation: Fichet-Calvet, E. & Rogers, D. J. (2009). 'Risk maps of Lassa fever in West Africa', PLoS Neglected Tropical Diseases, 3(3), e388. [Available at http://www.plosntds.org]. © E. Fichet-Calvet & D. J. Rogers. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Perlite for permanent confinement of cesium
Get PDFWe present the potential use of expanded perlite, a metastable amorphous hydrated aluminium silicate, as a permanent medium for the long-term confinement of cesium. The method requires simply a loading by mixing an aqueous cesium nitrate solution and expanded perlite at 300 K followed by densification by sintering. The formation of pollucite, CsAlSi2O6, a naturally occurring mineral phase, upon careful heat treatment is demonstrated by X-ray diffraction. Leaching tests on the resulting glass-ceramics reveal a very low Cs departure of 0.5 mg m−2 d−1
Taming systematic uncertainties at the LHC with the central limit theorem
No full textAbstractWe study the simplifications occurring in any likelihood function in the presence of a large number of small systematic uncertainties. We find that the marginalisation of these uncertainties can be done analytically by means of second-order error propagation, error combination, the Lyapunov central limit theorem, and under mild approximations which are typically satisfied for LHC likelihoods. The outcomes of this analysis are i) a very light treatment of systematic uncertainties ii) a convenient way of reporting the main effects of systematic uncertainties, such as the detector effects occurring in LHC measurements
Radiochemical method development for strontium-90 caracterization in radioactive waste
No full textLa caractérisation radiologique des déchets et des effluents radioactifs nécessite la mesure de nombreux radionucléides dont le 90Sr. Les méthodes usuelles d’analyse du 90Sr sont performantes mais elles sont relativement longues et nécessitent l’utilisation de produits toxiques tels que l’acide nitrique fumant et les liquides scintillants. Ce travail de thèse a consisté à développer de nouvelles procédures d’analyse du 90Sr, en particulier de nouvelles méthodes de séparation. Une première méthode basée sur des précipitations sélectives successives a été optimisée à partir de la méthodologie des plans d’expériences et de la modélisation de la spéciation. A l’issue de ces travaux, l’acide nitrique fumant a été remplacé par de l’acide nitrique concentré à 69 % tout en préservant la sélectivité de la séparation entre le Sr et le Ca et une compréhension des mécanismes mis en jeu lors de cette précipitation a été apportée. Une seconde méthode utilisant la résine d’extraction chromatographique Sr® a été développée en intégrant un nouveau prétraitement basé sur la résine TRU®, permettant d’éliminer les interférents problématiques pour la mesure par scintillation liquide, comme le 241Pu. Enfin, une dernière méthode a été mise au point avec la résine dite scintillante appelée résine PS-Sr qui permet d’isoler le Sr, d’effectuer une mesure nucléaire par scintillation plastique et ainsi d’être conforme à la directive REACH. Les performances des méthodes ont été validées par la participation à des comparaisons inter-laboratoires.The radiological characterization of radioactive waste and effluents requires the measurement of many radionuclides, including 90Sr. The usual methods for 90Sr analysis are efficient but they are relatively long and require the use of toxic products such as fuming nitric acid and scintillation cocktails. This thesis work consisted in developing new analytical procedures for 90Sr analysis, in particular new separation methods. A first method based on successive selective precipitations was optimized using design of experiments methodology and speciation modelling. Fuming nitric acid was replaced by concentrated nitric acid at 69 % while preserving the separation selectivity between Sr and Ca, and an understanding of the mechanisms involved in this precipitation was provided. A second method using the Sr® chromatographic extraction resin was developed by including a new pre-treatment based on the TRU® resin, allowing the elimination of problematic interferents for liquid scintillation measurements, such as 241Pu. Finally, a method was developed with a scintillating resin called PS-Sr resin, which enables to isolate Sr, to perform a nuclear measurement by plastic scintillation and thus to be compatible with REACH regulation. The performances of the methods were validated by participation in inter-laboratory comparisons
Marquage collectif de rongeurs sauvages au moyen de fluoromarqueurs vitaux des tissus calcifies
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Probing the scale of New Physics at the LHC: The example of Higgs data
No full textAbstractWe present a technique to determine the scale of New Physics (NP) compatible with any set of data, relying on well-defined credibility intervals. Our approach relies on the statistical view of the effective field theory capturing New Physics at low energy. We introduce formally the notion of testable NP and show that it ensures integrability of the posterior distribution. We apply our method to the Standard Model Higgs sector in light of recent LHC data, considering two generic scenarios. In the scenario of democratic higher-dimensional operators generated at one-loop, we find the testable NP scale to lie within [10,260] TeV at 95% Bayesian credibility level. In the scenario of loop-suppressed field strength-Higgs operators, the testable NP scale is within [28,1200] TeV at 95% Bayesian credibility level. More specific UV models are necessary to allow lower values of the NP scale
Non-Orthogonal Reduction for Rendering Fluorescent Materials in Non-Spectral Engines
No full textWe propose a method to accurately handle fluorescence in a non-spectral (e.g., tristimulus) rendering engine, showcasing color-shifting and increased luminance effects. Core to our method is a principled reduction technique that encodes the reradiation into a low-dimensional matrix working in the space of the renderer's Color Matching Functions (CMFs). Our process is independent of a specific CMF set and allows for the addition of a non-visible ultraviolet band during light transport. Our representation visually matches full spectral light transport for measured fluorescent materials even for challenging illuminants.Computer Graphics ForumAppearance43
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