On the Structure of Minimizers of Causal Variational Principles in the Non-Compact and Equivariant Settings

We derive the Euler-Lagrange equations for minimizers of causal variational principles in the non-compact setting with constraints, possibly prescribing symmetries. Considering first variations, we show that the minimizing measure is supported on the intersection of a hyperplane with a level set of a function which is homogeneous of degree two. Moreover, we perform second variations to obtain that the compact operator representing the quadratic part of the action is positive semi-definite. The key ingredient for the proof is a subtle adaptation of the Lagrange multiplier method to variational principles on convex sets.Comment: 24 pages, LaTeX, 2 figures, minor improvements (published version

Services policies in transition economies : on the European Union and the World Trade Organization as commitment mechanisms

The authors analyze the extent to which the EU-15 and 16 transition economies used the WTO General Agreement on Trade in Services (GATS) to commit to service sector policy reforms. They compare GATS commitments with the evolution of actual policy stances over time. While there is substantial variance across transition economies on both actual policies and GATS commitments, the authors find an inverse relationship between the depth of GATS commitments and the"quality"of actual services policies as assessed by the private sector. In part this can be explained by the fact that the prospect of EU accession makes GATS less relevant as a commitment device for a subset of transition economies. But for many of the non-EU accession candidates, the WTO seems to be a weak commitment device. One explanation is that the small size of the markets concerned generates weak external enforcement incentives. The authors'findings suggest greater collective investment by WTO members in monitoring and the need for transparency to increase the benefits of WTO membership to small countries.Trade and Services,Trade Law,World Trade Organization,Trade and Regional Integration,Free Trade

Services policy reform and economic growth in transition economies, 1990-2004

Major changes have occurred in the structure of former centrally planned economies, including a sharp rise in the share of services in GDP, employment, and international transactions. However, large differences exist across transition economies with respect to services intensity and services policy reforms. The authors find that reforms in policies toward financial and infrastructure services, including telecommunications, power, and transport, are highly correlated with inward foreign direct investment. Controlling for regressors commonly used in the growth literature, they find that measures of services policy reform are statistically significant explanatory variables for the post-1990 economic performance of transition economies. These findings suggest services policies should be considered more generally in empirical analyses of economic growth

Tackling post-harvest cereal losses in sub-Saharan Africa

Post-harvest loss reduction raises food availability without increasing the use of land, water and agricultural inputs. This article refers to the case of grain to show the hurdles that farmers have to clear in taking measures to reduce losses and suggests ways that post-harvest practitioners can target mitigating actions in sub-Saharan Africa

Die Epidemiologie der Risikofaktoren für kardiovaskuläre Krankheiten in der Schweiz = Epidémiologie des facteurs de risque des maladies cardio-vasculaires en Suisse

[Contient] Introduction = Einführung - Programme national suisse de recherche sur la prévention des maladies cardio-vasculaires: l'examen de santé initial / B. Junod, F. Gutzwiller - Rauchgewohnheiten in vier Schweizer Städten / C. Schucan, T. Abelin - Distribution du chlolestérol plasmatique dans quatre villes suisses / H. Micheli - Ernährungsverhalten, Verzehrsgewohnheiten und Massenindex in vier Schweizer Städten / G. Ritzel - Epidemiologie des Blutdrucks in vier Schweizer Städten / F. Gutzwiller - Körperliche Aktivität und Leistungsfähigkeit in vier Schweizer Städten / H. Howald - Prévalence de l'exposition aux facteurs de risque des maladies cardio-vasculaires dans quatre villes suisses (Nyon, Vevey, Aarau, Soleure) / J. Alexander, B. Junod

APHLIS - Postharvest cereal losses in Sub-Saharan Africa, their estimation, assessment and reduction

APHLIS provides estimates of the postharvest weight losses (PHLs) of cereal grains for Sub-Saharan Africa. These loss estimates support agricultural policy formulation, identification of opportunities to improve value chains, improvement in food security (by improving the accuracy of cereal supply estimates), andmonitoring of loss reduction activities. APHLIS is based on a network of local experts (see Annex 1). Each country supplies and quality controls its own data that are stored in an exclusive area of a shared database. The APHLIS website displays the loss estimates as maps and tables. The APHLIS Network members also have the opportunity to post a ‘Country Narrative’ that gives a commentary on these postharvest losses in the context of the postharvest systems and projects of their countries. The loss estimates are generated by an algorithm (the PHL Calculator) that works on two data sets, the postharvest loss (PHL) profiles and the seasonal data. Each PHL profile is itself a set of figures, one for each link in the postharvest chain. These figures are derived from a very detailed search of the scientific literature followed by screening for suitability. They remain more or less constant between years. The seasonal data are contributed by the APHLIS Network and address several factors that are taken into account in the loss calculation. They may vary significantly from season to season and year to year. APHLIS estimates are not intended to be ‘statistics’ although they are computed using the best available evidence; they give an understanding of the scale of postharvest losses using a ‘transparent’ method of calculation. The estimates are assigned by primary administative unit (province) and may be aggregated to country or to region. Provinces are usually large geographical units and may include several agro-climatic zones, consequently the loss figures are generalisations, i.e. may be at variance from those experienced in particular situations. APHLIS recognises this limitation and offers a downloadable PHL Calculator that enables practitioners to change the default values to those that are specific to the situation of interest and to obtain loss estimates at a chosen geographical scale. The PHL Calculator can also be used with hypothetical data inorder to model ‘what if’ scenarios. APHLIS offers a robust system for the estimation of PHLs, is transparent in operation and can capture improvements in loss estimation over time by the accumulation of new and more accurate data. It encourages the collection of new data and offers advice on modern approaches to loss asssessment. For the future, APHLIS is envisaged as a much broader communcition hub that informs, motivates and coordinates efforts to optimise postharvest mangement

Multivalued robust tracking control of fully actuated Lagrange systems: Continuous and discrete–time algorithms

International audienceIn this paper the robust trajectory tracking problem of a class of nonlinear systems described by the Euler–Lagrange equations of motion is studied. We start considering a plant under the effects of an unknown external perturbation and also with uncertainties on its parameters. After that a class of passivity-based multivalued control laws is proposed and the well–posedness together with the stability of the closed–loop are established in the continuous–time setting. The discrete–time version of the plant and the controller are studied and well–posedness together with stability results are obtained, using the so-called implicit discretization approach introduced in [1, 2]. Numerical simulations are presented and demonstrate the effectiveness of the proposed discrete-time controller

Set-valued sliding-mode control of uncertain linear systems: continuous and discrete-time analysis

International audienceIn this paper we study the closed-loop dynamics of linear time-invariant systems with feedback control laws that are described by set-valued maximal monotone maps. The class of systems considered in this work is subject to both, unknown exogenous disturbances and parameter uncertainty. It is shown how the design of conventional sliding mode controllers can be achieved using maximal monotone operators (which include the set-valued signum function). Two cases are analyzed: continuous-time and discrete-time controllers. In both cases well-posedness together with stability results are presented. In discrete time we show how the implicit scheme proposed for the selection of control actions makes sense resulting in the chattering effect being almost suppressed even with uncertainty in the system