The predictability of advection-dominated flux-transport solar dynamo models

Space weather is a matter of practical importance in our modern society. Predictions of forecoming solar cycles mean amplitude and duration are currently being made based on flux-transport numerical models of the solar dynamo. Interested in the forecast horizon of such studies, we quantify the predictability window of a representative, advection-dominated, flux-transport dynamo model by investigating its sensitivity to initial conditions and control parameters through a perturbation analysis. We measure the rate associated with the exponential growth of an initial perturbation of the model trajectory, which yields a characteristic time scale known as the e-folding time $\tau_e$. The e-folding time is shown to decrease with the strength of the $\alpha$-effect, and to increase with the magnitude of the imposed meridional circulation. Comparing the e-folding time with the solar cycle periodicity, we obtain an average estimate for $\tau_e$ equal to 2.76 solar cycle durations. From a practical point of view, the perturbations analysed in this work can be interpreted as uncertainties affecting either the observations or the physical model itself. After reviewing these, we discuss their implications for solar cycle prediction.Comment: 33 pages, 12 figure

A pure jump Markov process with a random singularity spectrum

We construct a non-decreasing pure jump Markov process, whose jump measure heavily depends on the values taken by the process. We determine the singularity spectrum of this process, which turns out to be random and to depend locally on the values taken by the process. The result relies on fine properties of the distribution of Poisson point processes and on ubiquity theorems.Comment: 20 pages, 4 figure

A mean-field Babcock-Leighton solar dynamo model with long-term variability

Dynamo models relying on the Babcock-Leighton mechanism are successful in reproducing most of the solar magnetic field dynamical characteristics. However, considering that such models operate only above a lower magnetic field threshold, they do not provide an appropriate magnetic field regeneration process characterizing a self-sustainable dynamo. In this work we consider the existence of an additional \alpha-effect to the Babcock-Leighton scenario in a mean-field axisymmetric kinematic numerical model. Both poloidal field regeneration mechanisms are treated with two different strength-limiting factors. Apart from the solar anti-symmetric parity behavior, the main solar features are reproduced: cyclic polarity reversals, mid-latitudinal equatorward migration of strong toroidal field, poleward migration of polar surface radial fields, and the quadrature phase shift between both. Long-term variability of the solutions exhibits lengthy periods of minimum activity followed by posterior recovery, akin to the observed Maunder Minimum. Based on the analysis of the residual activity during periods of minimum activity, we suggest that these are caused by a predominance of the \alpha-effect over the Babcock-Leighton mechanism in regenerating the poloidal field.Comment: 21 pages, 6 figure

L'indépendance de la Couronne canadienne : une question de droit et de conventions

Ce mémoire explore les règles distinguant, tant dans sa dévolution que dans l’exercice de ses pouvoirs, la Couronne du Canada de la Couronne britannique. Le droit canadien constitue et encadre tous les organes de l’État, et, au premier chef, la Couronne, par des règles de droit et des conventions constitutionnelles que ce mémoire se fixe comme objectif d’identifier. Il s’agit donc de mettre en lumière comment la Couronne, pourtant indivisible à l’échelle de l’Empire à l’époque impériale, est devenue divisible lors de l’accession du Canada à l’indépendance. Pour ce faire, ce mémoire procède à l’étude du droit relatif à la Couronne partagé par le Royaume-Uni et ses anciens Dominions ainsi que celle de l’évolution des organes habilités à régir, et à faire agir, la Couronne au Canada.This memory explores the rules that distinguish the Crown of Canada from the British Crown, both in its demise and in the exercise of its powers. Canadian law establishes and manages all State organs, and primarily the Crown, by rules of law and constitutional conventions that this memory intends to identify. The intent is, therefore, to highlight how the Crown, though indivisible through the Empire at its heyday, has became divisible at Canadian independence. It is done by the study of law related to the Crown shared by the United Kingdom and its late Dominions and the evolution of the organs that can legislate on, and make act, the Crown in Canada

Aux confins des faits et du droit : quel droit de la preuve pour les litiges constitutionnels?

Depuis l'avènement de la Charte canadienne des droits et libertés, le contrôle de constitutionnalité, qu'il soit effectué en vertu de la Charte ou d'autres règles constitutionnelles, repose, comme jamais auparavant, sur les faits. Pour prouver ces faits, un courant doctrinal et jurisprudentiel a promu un régime de preuve de plus en plus souple, sui generis et presque libéré des règles du droit commun. Cette thèse poursuit l'objectif d'expliquer les problèmes affectant le droit de la preuve causés par la libéralisation des faits pertinents en matière constitutionnelle. Notre hypothèse est que, bien qu'elles aient existé à une époque antérieure, la « souplesse » et l'instabilité du droit de la preuve en matière constitutionnelle tendent à se résorber. Bien que le degré de souplesse dans la réception des faits ait pu varier dans le temps, il n'existe plus un régime de preuve libre ou sui generis en matière constitutionnelle au Canada. Les faits doivent être prouvés suivant les moyens habituels, en première instance. Pour démontrer cette hypothèse, il y a lieu d'analyser l'application, en matière constitutionnelle, des règles régissant la pertinence, le degré de l'obligation de convaincre, la connaissance d'office et le témoignage. Pour ce faire, de nombreuses comparaisons sont faites avec le droit de la preuve qui s'applique dans les matières civiles, pénales et criminelles.Since the advent of the Canadian Charter of Rights and Freedoms, constitutional review, whether based on the Charter or other constitutional rules, has become grounded in the facts as never before. To prove these facts, a major doctrinal and case law trend has promoted a sui generis model regime close to the free evidence model. This thesis pursues the objective of explaining the problems affecting the law of evidence caused by the liberalization of the relevant facts in constitutional matters. Our hypothesis is that, although it existed at an earlier time, the "flexibility" and the instability of the law of evidence in constitutional cases tend to diminish. The point is to show that the degree of flexibility in the reception of the facts may have varied over time, but that there is no longer a free or sui generis regime of evidence in constitutional cases in Canada. The facts must be proven, at trial, by the traditional means of proof. To demonstrate this hypothesis, it is necessary to analyze the application, in constitutional law, of the rules governing relevance, the standard of proof, judicial notice and testimony. To do this analysis, many comparisons are made with the law of evidence that applies in civil and criminal law

OpenAlea 2.0: Architecture of an integrated modeling environment on the web

International audiencePlant modeling is based on the use of a diverse set of design paradigms (L-systems, visual programming, imperative languages or sketch-based interfaces). In this poster, the architecture of a new multi-paradigm and integrated modeling environment is presented. This desktop application will become a distributed web application, allowing to run simulations on a cloud computing system and share virtual experiments on the web. The modeling environment will run on a web browser using HTML5 and WebGL technologies

Tension wood and opposite wood in 21 tropical rain forest species. 2. Comparison of some anatomical and ultrastructural criteria

International audienceThe anatomy of tension wood and opposite wood was compared in 21 tropical rain forest trees from 21 species belonging to 18 families from French Guyana. Wood secimens were taken from the upper and lower sides of naturally titled trees. Measurement of the growth stress level ensured that the two samples were taken from wood tissues in a different mechanical state: highly tensile-stressed wood on the upper side, called tension wood and normally tensile-stressed wood on the lower side, called opposite wood. Quantitative parameters relating to fibres and vessels were measured on transverse sections of both tension and opposite wood to check if certain criteria can easily discriminate the two kinds of wood. We observed a decrease in the frequency of vessels in the tension wood in all the trees studied. Other criteria concerning shape and surface area of the vessels, fibre diameter or cell wall thickness did not reveal any general trend.At the ultrastructural level, we observed that the microfibril angle in the tension wood sample was lower than in opposite wood in all the trees except one (Licania membranacea)

Absence of antibodies to Rickettsia spp., Bartonella spp., Ehrlichia spp. and Coxiella burnetii in Tahiti, French Polynesia

International audienceAbtractBackgroundIn the Pacific islands countries and territories, very little is known about the incidence of infectious diseases due to zoonotic pathogens. To our knowledge, human infections due to Rickettsia spp., Coxiella burnetii, Ehrlichia spp. and Bartonella spp. have never been reported in French Polynesia; and infections due to C. burnetti have been reported worldwide except in New Zealand. To evaluate the prevalence of this disease, we conducted a serosurvey among French Polynesian blood donors.MethodsThe presence of immunoglobulin G antibodies against R. felis, R. typhi, R. conorii, C. burnetii, B. henselae, B. quintana, and E. chaffeensis was evaluated by indirect immunofluorescence assay in sera from 472 French Polynesian blood donors collected from 2011 to 2013. In addition, 178 ticks and 36 cat fleas collected in French Polynesia were also collected and tested by polymerase chain reaction to detect Rickettsia spp., B. henselae and Ehrlichia spp.ResultsNone of the blood donors had antibodies at a significant level against Rickettsia spp., Coxiella burnetii, Ehrlichia spp. and Bartonella spp. All tested ticks and cat fleas were PCR-negative for Rickettsia spp., B. henselae, and Ehrlichia spp.ConclusionWe cannot conclude that these pathogens are absent in French Polynesia but, if present, their prevalence is probably very low. C. burnetii has been reported worldwide except in New Zealand. It may also be absent from French Polynesia