Theoretical limits on magnetic field strengths in low-mass stars

Observations have suggested that some low-mass stars have larger radii than predicted by 1-D structure models. Some theoretical models have invoked very strong interior magnetic fields (of order 1 MG or more) as a possible cause of such large radii. Whether fields of that strength could in principle by generated by dynamo action in these objects is unclear, and we do not address the matter directly. Instead, we examine whether such fields could remain in the interior of a low mass object for a significant time, and whether they would have any other obvious signatures. First, we estimate timescales for the loss of strong fields by magnetic buoyancy instabilities. We consider a range of field strengths and simple morphologies, including both idealized flux tubes and smooth layers of field. We confirm some of our analytical estimates using thin flux tube magnetohydrodynamic (MHD) simulations of the rise of buoyant fields in a fully-convective M-dwarf. Separately, we consider the Ohmic dissipation of such fields. We find that dissipation provides a complementary constraint to buoyancy: while small-scale, fibril fields might be regenerated faster than they rise, the dissipative heating associated with such fields would in some cases greatly exceed the luminosity of the star. We show how these constraints combine to yield limits on the internal field strength and morphology in low-mass stars. In particular, we find that for stars of 0.3 solar masses, no fields in flux tubes stronger than about 800 kG are simultaneously consistent with both constraints.Comment: 19 pages, 10 figures, accepted to Ap

Enhancing the selection of a model-based clustering with external qualitative variables

In cluster analysis, it can be useful to interpret the partition built from the data in the light of external categorical variables which were not directly involved to cluster the data. An approach is proposed in the model-based clustering context to select a model and a number of clusters which both fit the data well and take advantage of the potential illustrative ability of the external variables. This approach makes use of the integrated joint likelihood of the data and the partitions at hand, namely the model-based partition and the partitions associated to the external variables. It is noteworthy that each mixture model is fitted by the maximum likelihood methodology to the data, excluding the external variables which are used to select a relevant mixture model only. Numerical experiments illustrate the promising behaviour of the derived criterion

De l’usage politique du peuple ‘Padano’ : la construction d’identité dans le cas de la Ligue du Nord

International audienceDans le champ politique, l’appel au « peuple » se focalise sur les principes d’unité, de faire-valoir de légitimité et de pouvoir. Le cas de la Lega Nord (Ligue du Nord) italienne illustre un processus de construction symbolique d’un peuple et de catégories « d’autres » polysémiques, variables dans le temps. Le peuple de la Ligue s’est adossé originellement au façonnage d’une identité « padane ». En dépit de l’absence de tout substrat culturel ou géographique, la pérennité du référent « padano » témoigne de l’instrumentalisation d’un système de croyances et de représentations qui a longtemps été essentiel au maintien de l’unité du parti et à sa capacité de mobilisation électorale. Au fil du temps, toutefois, de nouvelles frontières sociales et symboliques ont été élaborées à partir d’aspects identitaires, socio-économiques, politiques et ethniques, complétés plus récemment par un repositionnement au cœur de l’espace des droites radicales populistes en Europe. Cette complexité tient en partie à la nature opportuniste et caméléonienne du régional-populisme léguiste, au gré des reconfigurations et enjeux politiques. Elle témoigne en outre du statut hybride du mouvement, entre force de coalition gouvernementale et parti d’opposition. Elle illustre enfin la variabilité des structures d’opportunités politiques qui existent au nord et au sud de l’Italie.In ambito politico, l’appello al popolo si focalizza sul principio di unità, di legittimità e potere sovrano. In Italia, il caso della Lega Nord mostra un processo di costruzione di un popolo “simbolico” accompagnato da molteplici categorie “dell’altro” in grado di variare nel tempo. Il “popolo” leghista si è fatto dapprima portatore di un’identità “padana”, totalmente priva di un substrato culturale oltre che geografico. Il costante riferimento alla Padania testimonia dunque una strumentalizzazione all’interno di un sistema di credenze che per molto tempo è stato in grado di mantenere unito il partito e di funzionare come strumento di mobilitazione elettorale. Tuttavia, nel corso del tempo, la Lega è stata in grado di creare nuove barriere sociali e simboliche partendo da aspetti identitari, socio-economici, politici ed etnici. Questo processo di cambiamento si è completato più recentemente attraverso un riposizionamento del partito nell’area della destra radicale europea. Questi aspetti eterogenei hanno, in parte, a che fare con la natura strategica e camaleontica del regional-populismo leghista. Le stesse caratteristiche mostrano inoltre una natura ibrida del partito, che oscilla tra forza politica all’interno di una coalizione di governo e partito d’opposizione. Emerge, infine, una capacità di variare le proprie strutture e le proprie strategie nelle diverse aree del Paese (Nord/Sud)

Not enough there, too many here: understanding geographical imbalances in the distribution of the health workforce

Access to good-quality health services is crucial for the improvement of many health outcomes, such as those targeted by the Millennium Development Goals (MDGs) adopted by the international community in 2000. The health-related MDGs cannot be achieved if vulnerable populations do not have access to skilled personnel and to other necessary inputs. This paper focuses on the geographical dimension of access and on one of its critical determinants: the availability of qualified personnel. The objective of this paper is to offer a better understanding of the determinants of geographical imbalances in the distribution of health personnel, and to identify and assess the strategies developed to correct them. It reviews the recent literature on determinants, barriers and the effects of strategies that attempted to correct geographical imbalances, with a focus on empirical studies from developing and developed countries. An analysis of determinants of success and failures of strategies implemented, and a summary of lessons learnt, is included

The aetiology of infectious intestinal disease in the community in Malta

Routine sources of data provide limited information on aetiological agents causing infectious intestinal disease (IID) in the community. A retrospective, age-stratified, cross-sectional, telephone study at community level was performed whereby identified cases were asked to submit stools for analysis. Of a total of 3504 persons who participated, 99 respondents were suffering from IID. Of these, 37.4% (n=37) cases submitted stools for analysis. These samples were analysed for bacteria (Salmonella, Campylobacter, Escherichia coli, Shigella), protozoa and viruses (rotavirus, norovirus). Salmonella goldcoast was identified in 2.7% (n=1 of 37 tested) of cases, rotavirus in 10% (n=3 of 30 tested) of cases and norovirus in 20% (n=6 of 30 tested) of cases. This study describes norovirus being the commonest aetiological cause of IID in the community of Malta, which along with the data from the national surveillance system is of value in planning policies for the control of infectious intestinal disease.peer-reviewe

Structure and magnetism of orthorhombic epitaxial FeMnAs

The molecular beam epitaxy growth of Fe on MnAs/GaAs(001) leads to the formation of an epitaxial FeMnAs phase at the Fe/MnAs interface. The investigation of the structure by high angle annular dark field imaging in a scanning transmission electron microscope reveals an unusual orthorhombic structure, with vacancy ordering. Ab initio calculations show an antiferromagnetic ground state for this orthorhombic FeMnAs.Fil: Demaille, Dominique. Laboratorio Internacional Franco-Argentino en Nanociencias; Francia. Universite Pierre et Marie Curie. Institut des Nanosciences de Paris; FranciaFil: Patriarche, Gilles. Centre National de la Recherche Scientifique; FranciaFil: Helman, Christian. Comisión Nacional de Energía Atómica; Argentina. Laboratorio Internacional Franco-Argentino en Nanociencias; FranciaFil: Eddrief, Mahmoud. Laboratorio Internacional Franco-Argentino en Nanociencias; Francia. Universite Pierre et Marie Curie. Institut des Nanosciences de Paris; FranciaFil: Etgens, Hugo. Laboratorio Internacional Franco-Argentino en Nanociencias; Francia. Universite Pierre et Marie Curie. Institut des Nanosciences de Paris; FranciaFil: Sacchi, Maurizio. Laboratorio Internacional Franco-Argentino en Nanociencias; Francia. Universite Pierre et Marie Curie. Institut des Nanosciences de Paris; Francia. L’Orme des merisiers Saint-Aubin. Synchrotron SOLEIL; FranciaFil: Llois, Ana Maria. Comisión Nacional de Energía Atómica; Argentina. Laboratorio Internacional Franco-Argentino en Nanociencias; Francia. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Marangolo, Massimiliano. Laboratorio Internacional Franco-Argentino en Nanociencias; Francia. Universite Pierre et Marie Curie. Institut des Nanosciences de Paris; Franci

Quasistatic evolution in non-associative plasticity - The cap model

International audienceNon-associative elasto-plasticity is the working model of plasticity for soil and rocks mechanics. Yet, it is usually viewed as non-variational. In this work, we prove a contrario the existence of a variational evolution for such a model under a natural capping assumption on the hydrostatic stresses and a less natural mollification of the stress admissibility constraint. The obtained elasto-plastic evolution is expressed for times that are conveniently rescaled