Equations, inequations and inequalities characterizing the configurations of two real projective conics

Couples of proper, non-empty real projective conics can be classified modulo rigid isotopy and ambient isotopy. We characterize the classes by equations, inequations and inequalities in the coefficients of the quadratic forms defining the conics. The results are well--adapted to the study of the relative position of two conics defined by equations depending on parameters.Comment: 31 pages. See also http://emmanuel.jean.briand.free.fr/publications/twoconics/ Added references to important prior work on the subject. The title changed accordingly. Some typos and imprecisions corrected. To be published in Applicable Algebra in Engineering, Communication and Computin

TO INFORM THEIR DISCRETION: POLICY EDUCATION AND DEMOCRATIC POLITICS

Political Economy,

Marginal Cost Versus Average Cost Pricing with Climatic Shocks in Senegal: A Dynamic Computable General Equilibrium Model Applied to Water

The model simulates on a 20-year horizon, a first phase of increase in the water resource availability taking into account the supply policies by the Senegalese government and a second phase with hydrologic deficits due to demand evolution (demographic growth). The results show that marginal cost water pricing (with a subsidy ensuring the survival of the water production sector) makes it possible in the long term to absorb the shock of the resource shortage, GDP, investment and welfare increase. Unemployment drops and the sectors of rain rice, market gardening and drinking water distribution grow. In contrast, the current policy of average cost pricing of water leads the long-term economy in a recession with an agricultural production decrease, a strong degradation of welfare and a rise of unemployment. This result questions the basic tariff (average cost) on which block water pricing is based in Senegal.Computable General Equilibrium Model, Dynamic, Imperfect Competition, Water, Pricing, Sub Saharan Africa

Crystallization of self-propelled hard-discs : a new scenario

We experimentally study the crystallization of a monolayer of vibrated discs with a built-in polar asymmetry, a model system of active liquids, and contrast it with that of vibrated isotropic discs. Increasing the packing fraction $\phi$, the quasi-continuous crystallization reported for isotropic discs is replaced by a transition, or a crossover towards a "self-melting" crystal. Increasing the packing fraction from the liquid phase, clusters of dense hexagonally-ordered packed discs spontaneously form, melt, split and merge leading to a highly intermittent and heterogeneous dynamics. The resulting steady state cluster size distribution decreases monotonically. For packing fraction larger than $\phi^*$, a few large clusters span the system size and the cluster size distribution becomes non monotonic, the transition being signed by a power-law. The system is however never dynamically arrested. The clusters permanently melt from place to place forming droplets of active liquid which rapidly propagate across the system. This state of affair remains up to the highest possible packing fraction questioning the stability of the crystal for active discs, unless at ordered close packing.Comment: 4 pages, 4 figures, 1 Supp Mat

Quadratic BSDEs with convex generators and unbounded terminal conditions

In a previous work, we proved an existence result for BSDEs with quadratic generators with respect to the variable z and with unbounded terminal conditions. However, no uniqueness result was stated in that work. The main goal of this paper is to fill this gap. In order to obtain a comparison theorem for this kind of BSDEs, we assume that the generator is convex with respect to the variable z. Under this assumption of convexity, we are also able to prove a stability result in the spirit of the a priori estimates stated in the article of N. El Karoui, S. Peng and M.-C. Quenez. With these tools in hands, we can derive the nonlinear Feynman--Kac formula in this context

Combinatorial proof for a stability property of plethysm coefficients

Plethysm coefficients are important structural constants in the representation the- ory of the symmetric groups and general linear groups. Remarkably, some sequences of plethysm coefficients stabilize (they are ultimately constants). In this paper we give a new proof of such a stability property, proved by Brion with geometric representation theory techniques. Our new proof is purely combinatorial: we decompose plethysm coefficients as a alternating sum of terms counting integer points in poly- topes, and exhibit bijections between these sets of integer points.Ministerio de Ciencia e Innovación MTM2010–19336Junta de Andalucía FQM–333Junta de Andalucía P12–FQM–269

'You get the quickest and the cheapest stuff you can': Food security issues among low-income earners living with diabetes

Background: Diabetes prevalence is increasing in Australia and worldwide. More than 800,000 Australians live with diabetes, and there are stark inequities in prevalence and clinical outcomes among Indigenous people and low socio-economic groups.The ability to maintain a healthy diet – an essential component of diabetes self-management – is compromised by food availability, accessibility and affordability issues. This paper focuses on food security issues experienced by low-income earners living with type 2 diabetes in Perth, Western Australia. The results presented here are part of a broader qualitative study exploring the impact of socio-economic disadvantage on the experience of diabetes. MethodData were collected through focus groups and semi-structured interviews conducted from October 2008 to November 2009. The sample, comprising 38 participants (Indigenous and non-Indigenous), was recruited from areas with high indices of socio-economic disadvantage in the Perth metropolitan area. Deductive data analysis identified categories from an existing conceptual framework for the relationship between socio-economic position and diabetes health outcomes, while an inductive approach was adopted to identify new themes.ResultsDiet was perceived as the main component of diabetes self-management, and there was a common understanding of the dietary requirements for a person with diabetes. However, access to healthy food was not always realised, as many participants depended on others for food provision and meal preparation and had little control over their diets., and Furthermore, the majority struggled to accommodate the price of healthy food within a limited budget.ConclusionIn this study, low-income earners living with diabetes faced food security issues which limited their ability to implement and sustain recommended dietary changes. Participants reported cost barriers, but also physical barriers relating to functional limitations and lack of transport. This study highlights that the socio-economic circumstances in which the experience of disease of vulnerable populations are embedded need to be understood and addressed in order to reduce the inequities surrounding diabetes outcomes

CONTRIBUTION À LA RÉORGANISATION DES SAVOIRS PRÉ-NUMÉRIQUES ET NUMÉRIQUES: ÉTUDE ET RÉALISATION D'UNE SITUATION D'ENSEIGNEMENT DE L'ÉNUMÉRATION DANS LE DOMAINE PRÉ-NUMÉRIQUE

International audienceSeveral research works, since more than fifty years, have been dedicated to the construction by children of the concept of number, in particular whole numbers. Many aspects regarding the manipulation of collections and operations on these collections have been studied. Yet, paradoxically, enumeration has hardly ever been considered as a fundamental component of counting up activity or measurement of discrete quantities, for the construction of first numbers, as well as for arithmetical operations or combinatorics. This paper is based on the part of our research in relation with pre-numerical activities and construction of first numbers. The first part shows the reasons why enumeration remained absent in pre-numerical knowledge and the consequences of this absence on children' s numerical intellectual attainments. In the second part we present a teaching design adapted for the learning of enumeration by 4-5 year old children. In this part, we raise micro-didactical questions concerning the organization of the experimental apparatus, the necessary vigilance of the teacher and language difficulties.De très nombreux travaux ont été consacrés, depuis plus de cinquante ans, à la construction de la notion de nombre chez l'enfant et, tout particulièrement, à la notion de nombre entier. Au cours de ces études, un très grand nombre d'aspects associés aux manipulations des collections et aux opérations sur ces collections ont fait l'objet de recherches importantes. Paradoxalement, l'énumération n'a pratiquement jamais été considérée comme une composante fondamentale de l'activité de dénombrement et de mesure des quantités discrètes, que ce soit d'ailleurs pour la construction des premiers nombres, pour la construction des opérations arithmétiques ou pour l'analyse combinatoire. L'article qui suit se fonde sur la partie de ma recherche relative aux domaines du pré-numérique et des premiers nombres. La première partie montre les raisons pour lesquelles l'énumération est restée absente des savoirs pré-numériques et les conséquences de cette absence sur les acquisitions numériques des enfants. La deuxième partie propose une ingénierie adaptée à des élèves de 4-5 ans en vue de l'apprentissage de l'énumération. Au cours de cette deuxième partie, sont abordées des questions de micro-didactique touchant à l'organisation du dispositif, la nécessaire vigilance de l'enseignant, ainsi que les difficultés langagières rencontrées

Manuel d'utilisation de COSI 0.1

COSI (Caiman Object Solver Interface) est à la fois un environnement de programmation C++/fortran et une interface graphique d'utilisation, conçu pour fournir aux concepteurs de solveurs une aide et un standard de programmation