Dynamic analysis of evolutive conservative systems. Discussion of eigenmode crossings

After an analysis of the close connection between the symmetries of a dynamical system and the multiplicity of its vibrational natural frequencies, it is proved by variational arguments that for a system of invariable symmetry the eigenfrequencies associated with the eigenmodes of a given symmetry type do not cross, in general, during the evolution of this system. The theory is implemented by some numerical calculations applied to the analysis of the evolution of the axisymmetric hydroelastic modes of the Ariane launch vehicle during burning of the first stage

Connections and dynamical trajectories in generalised Newton-Cartan gravity I. An intrinsic view

The "metric" structure of nonrelativistic spacetimes consists of a one-form (the absolute clock) whose kernel is endowed with a positive-definite metric. Contrarily to the relativistic case, the metric structure and the torsion do not determine a unique Galilean (i.e. compatible) connection. This subtlety is intimately related to the fact that the timelike part of the torsion is proportional to the exterior derivative of the absolute clock. When the latter is not closed, torsionfreeness and metric-compatibility are thus mutually exclusive. We will explore generalisations of Galilean connections along the two corresponding alternative roads in a series of papers. In the present one, we focus on compatible connections and investigate the equivalence problem (i.e. the search for the necessary data allowing to uniquely determine connections) in the torsionfree and torsional cases. More precisely, we characterise the affine structure of the spaces of such connections and display the associated model vector spaces. In contrast with the relativistic case, the metric structure does not single out a privileged origin for the space of metric-compatible connections. In our construction, the role of the Levi-Civita connection is played by a whole class of privileged origins, the so-called torsional Newton-Cartan (TNC) geometries recently investigated in the literature. Finally, we discuss a generalisation of Newtonian connections to the torsional case.Comment: 79 pages, 7 figures; v2: added material on affine structure of connection space, former Section 4 postponed to 3rd paper of the serie

Small-scale distribution of macroplankton and micronekton in the Ligurian Sea (Mediterranean Sea) as observed from the manned submersible Cyana

International audienc

A Quantitative Prioritisation of Human and Domestic Animal Pathogens in Europe

Disease or pathogen risk prioritisations aid understanding of infectious agent impact within surveillance or mitigation and biosecurity work, but take significant development. Previous work has shown the H-(Hirsch-)index as an alternative proxy. We present a weighted risk analysis describing infectious pathogen impact for human health (human pathogens) and well-being (domestic animal pathogens) using an objective, evidence-based, repeatable approach; the H-index. This study established the highest H-index European pathogens. Commonalities amongst pathogens not included in previous surveillance or risk analyses were examined. Differences between host types (humans/animals/zoonotic) in pathogen H-indices were explored as a One Health impact indicator. Finally, the acceptability of the H-index proxy for animal pathogen impact was examined by comparison with other measures. 57 pathogens appeared solely in the top 100 highest H-indices (1) human or (2) animal pathogens list, and 43 occurred in both. Of human pathogens, 66 were zoonotic and 67 were emerging, compared to 67 and 57 for animals. There were statistically significant differences between H-indices for host types (humans, animal, zoonotic), and there was limited evidence that H-indices are a reasonable proxy for animal pathogen impact. This work addresses measures outlined by the European Commission to strengthen climate change resilience and biosecurity for infectious diseases. The results include a quantitative evaluation of infectious pathogen impact, and suggest greater impacts of human-only compared to zoonotic pathogens or scientific under-representation of zoonoses. The outputs separate high and low impact pathogens, and should be combined with other risk assessment methods relying on expert opinion or qualitative data for priority setting, or could be used to prioritise diseases for which formal risk assessments are not possible because of data gaps

Participatory diagnosis and adaptive management of small-scale fisheries in the Niger River Basin

In a broad sense, analysis of ‘resilience’ is about the capacity of systems to adapt to shocks, recognizing that disturbance and change are integral component of complex systems. More formally, resilience analysis proposes to focus on mechanisms and processes that help systems absorbing perturbations and shocks, and coping with uncertainty and risks. Defined in such a way, the concept of resilience thus appears particularly useful for the management of small-scale fisheries. However, while the resilience concept is appealing, particularly in the face of the failure of current management approaches, the danger is that it remains largely academic and theoretical, and not of a great help in effectively improving the way natural resources are managed on the ground. The challenge, therefore, lies in a pragmatic approach to operationalizing the concept of resilience and making its implementation on the ground practical and meaningful. In this project we propose a framework aimed at this objective and we test it in the specific context of small-scale fisheries in the Niger River Basin

Méthodologie d’analyse et d’évaluation technico- économique des systèmes de production ovine et caprine

. Cet article rapporte le travail effectué depuis 1994 par le groupe d’experts du sous-réseau FAO-CIHEAM sur les systèmes de production ovine et caprine, concernant la méthodologie d’évaluation de ces systèmes. L’objectif de ce travail était de mettre au point une méthodologie pour analyser, évaluer et comparer les systèmes de production ovine et caprine, et ainsi pour répondre aux besoins des éleveurs et des agents de développement dans les domaines du diagnostic, du conseil et de l’aide à la décision. La méthode repose sur l’estimation d’un ensemble d’indicateurs directement mesurés, ou d’indicateurs calculés à partir d’autres indicateurs concernant l’exploitation agricole dans son ensemble ou l’atelier ovin ou caprin exclusivement. Les indicateurs sont choisis après validation du groupe d’experts. L’article décrit comment dans certains cas, les difficultés sur le choix d’un ou plusieurs indicateurs ont été résolues. Au total, 196 indicateurs sont décrits dans les tableaux de 1 à 8 avec des conseils sur les conditions de calcul, la signification et l’interprétation de chaque indicateur. Cette méthode repose sur le travail d’enquête des agents de développement qui peuvent être aidés par les éleveurs au niveau de l’enregistrement des données. Les différentes approches pour interpréter les résultats en fonction des objectifs de l’étude sont passées en revue, en particulier l’interprétation par des "blocs diagnostics" et l’identification des points forts ou faibles de chaque système. La restitution des résultats aux éleveurs est considérée comme une phase essentielle de la méthode. La méthode a été appliquée dans des conditions différentes en Andalousie, en Roumanie, au Portugal et au Nord du Maroc pour validation ; ce qui a permis d’améliorer certains points de la méthode afin qu’elle puisse être appliquée de façon plus large.This paper presents the work undertaken since 1994 by a working group of experts from sub-network FAO-CIHEAM on systems of sheep and goat production, on evaluation’s methodology of such systems. The objective of this study was to set up a methodology for analysing and comparing the various systems of sheep and goat production, an so as to meet farmers and extension officers’ requirements in terms of diagnosis, advise and help to decision. This methodology may be applied only if the characteristics of sheep and goat units can be measurable and measured. The method is based on the assessment of a set of directly measured indicators, as well as indicators calculated by other indicators concerning the whole farm or sheep or goat units exclusively. The indicators are selected after validation decided by a working group of experts. The present paper reports on how in some cases, the difficulties on the choice of one or several indicators were solved. On overall, 196 indicators were described in tables from 1 to 8 with advises on conditions of calculation, the significance and interpretation of each indicator. This method is based on the work of survey of development agents likely to be helped by farmers at recording of data. The different approaches for interpreting results in accordance with the objectives of the study are presented in the present paper, particularly the interpretation by "indicators sets for diagnostic" and identification of major or weak points of each system. The diffusion of results to farmers is an essential phase of the method. This method was applied in different conditions in Andalusia, in Romania, in Portugal and Northern Morocco for validation purpose; this enabled the improvement of some points of the method so as to enlarge its field of applicatio

The Effects of the Atmospheric Pressure Changes on Seismic Signals or How to Improve the Quality of a Station

Seismic investigations are mainly limited by seismic noise. Two microbarometers have been installed in the seismic vault of two different GEOSCOPE stations, one at SSB and the other at TAM. All vertical components and most of the horizontal components show a significant correlation with pressure. In order to correct the seismic signals from the atmospheric pressure noise, a transfer function between the pressure data and the seismic data is inverted. Results show that, after correction, the noise levels reached on the horizontal components are similar between the two stations, and the vertical components display noise levels below the low-noise model as defined by Peterson (1993). This technique reduces part of the noise and allows detection of small earthquakes and a better extraction of normal modes. The analysis of the lowest normal modes of the Earth excited by the M_S = 8.2 Macquarie Island earthquake is given to illustrate the perspectives of the method

A Quantitative Prioritisation of Human and Domestic Animal Pathogens in Europe

Abstract Disease or pathogen risk prioritisations aid understanding of infectious agent impact within surveillance or mitigation and biosecurity work, but take significant development. Previous work has shown the H-(Hirsch-)index as an alternative proxy. We present a weighted risk analysis describing infectious pathogen impact for human health (human pathogens) and wellbeing (domestic animal pathogens) using an objective, evidence-based, repeatable approach; the H-index. This study established the highest H-index European pathogens. Commonalities amongst pathogens not included in previous surveillance or risk analyses were examined. Differences between host types (humans/animals/zoonotic) in pathogen Hindices were explored as a One Health impact indicator. Finally, the acceptability of the H-index proxy for animal pathogen impact was examined by comparison with other measures. 57 pathogens appeared solely in the top 100 highest H-indices (1) human or (2) animal pathogens list, and 43 occurred in both. Of human pathogens, 66 were zoonotic and 67 were emerging, compared to 67 and 57 for animals. There were statistically significant differences between H-indices for host types (humans, animal, zoonotic), and there was limited evidence that H-indices are a reasonable proxy for animal pathogen impact. This work addresses measures outlined by the European Commission to strengthen climate change resilience and biosecurity for infectious diseases. The results include a quantitative evaluation of infectious pathogen impact, and suggest greater impacts of human-only compared to zoonotic pathogens or scientific under-representation of zoonoses. The outputs separate high and low impact pathogens, and should be combined with other risk assessment methods relying on expert opinion or qualitative data for priority setting, or could be used to prioritise diseases for which formal risk assessments are not possible because of data gaps