The relationships between organic farming and agroecology.

While acknowledging an extension of agroecology in the organic sector and a growing influence of agroecology in the academic world, we explore their relationships. These relationships cannot be reduced to an opposition between a scientific field and a practical domain. A Brazilian case study based on the analysis of researchers and social actors trajectories exemplifies the diversity of existing relations, whether inclusive or exclusive. With a literature review, this allows characterising the specific attributes of both organic agriculture and agroecology. We discuss them in the light of current challenges for organic farming research and development

Testing gravity law in the solar system

The predictions of General relativity (GR) are in good agreement with observations in the solar system. Nevertheless, unexpected anomalies appeared during the last decades, along with the increasing precision of measurements. Those anomalies are present in spacecraft tracking data (Pioneer and flyby anomalies) as well as ephemerides. In addition, the whole theory is challenged at galactic and cosmic scales with the dark matter and dark energy issues. Finally, the unification in the framework of quantum field theories remains an open question, whose solution will certainly lead to modifications of the theory, even at large distances. As long as those "dark sides" of the universe have no universally accepted interpretation nor are they observed through other means than the gravitational anomalies they have been designed to cure, these anomalies may as well be interpreted as deviations from GR. In this context, there is a strong motivation for improved and more systematic tests of GR inside the solar system, with the aim to bridge the gap between gravity experiments in the solar system and observations at much larger scales. We review a family of metric extensions of GR which preserve the equivalence principle but modify the coupling between energy and curvature and provide a phenomenological framework which generalizes the PPN framework and "fifth force" extensions of GR. We briefly discuss some possible observational consequences in connection with highly accurate ephemerides.Comment: Proceedings of Journ\'ees 2010 "Syst\`emes de r\'ef\'erence spatio-temporels", New challenges for reference systems and numerical standards in astronom

Large scale EPR correlations and cosmic gravitational waves

We study how quantum correlations survive at large scales in spite of their exposition to stochastic backgrounds of gravitational waves. We consider Einstein-Podolski-Rosen (EPR) correlations built up on the polarizations of photon pairs and evaluate how they are affected by the cosmic gravitational wave background (CGWB). We evaluate the quantum decoherence of the EPR correlations in terms of a reduction of the violation of the Bell inequality as written by Clauser, Horne, Shimony and Holt (CHSH). We show that this decoherence remains small and that EPR correlations can in principle survive up to the largest cosmic scales.Comment: 5 figure

Agroecology: Polysemy, Pluralism And Controversies

In recent years, a growing number of actors and institutions, in different countries, have begun using the notion of Agroecology, which has led to an expansion of its polysemy and its controversies. Taking this into account, this paper analyzes, based on the Brazilian and French experiences, the peculiarities of Agroecology in four different fields: science, social movements, government policies, and education. It also discusses three other issues: the analytical, programmatic and normative discourses; the different definitions, in the fields of science and education, of the object of study of Agroecology; and the different formulations regarding its fundamental principles. It is argued that, in this new context, recognition of this pluralism and the controversies acquires a central role in the construction of knowledge in the various fields linked to Agroecology.19312

Testing Gravitation in the Solar System with Radio Science experiments

The laws of gravitation have been tested for a long time with steadily improving precision, leading at some moment of time to paradigmatic evolutions. Pursuing this continual effort is of great importance for science. In this communication, we focus on Solar System tests of gravity and more precisely on possible tests that can be performed with radio science observations (Range and Doppler). After briefly reviewing the current tests of gravitation at Solar System scales, we give motivations to continue such experiments. In order to obtain signature and estimate the amplitude of anomalous signals that could show up in radio science observables because of modified gravitational laws, we developed a new software that simulates Range/Doppler signals. We present this new tool that simulates radio science observables directly from the space-time metric. We apply this tool to the Cassini mission during its cruise from Jupiter to Saturn and derive constraints on the parameters entering alternative theories of gravity beyond the standard Parametrized Post Newtonian theory.Comment: proceedings of SF2A 2011 - minor changes (typos corrected - references updated

New physicochemical interpretations for Adsorption of Trichloroethylene on Activated Carbon: Steric and Energetic Interpretation using Statistical Physics Approach

Experimental adsorption isotherms of trichloroethylene (TCE) on activated carbon at four temperatures were analyzed theoretically by a double layer with one energy established through statistical physics approach. This model contains three parameters affecting the adsorption process i.e. the number of molecules per site n, the monolayer adsorbed quantity Q0 and the concentration at half- saturation c1/2. In this work, we propose a steric and energetic interpretation for the different adsorption isotherms of TCE on activated carbon. We calculate also the thermodynamic functions to characterize the adsorption process such as, entropy, free energy, and internal energy as function concentration. The different parameters and the thermodynamic functions were discussed with temperature

Analysis of transition forms towards more ecologically-oriented farming: the case of organic farming and integrated crop protection

Interdisciplinary approaches developed concerning the conversion to organic farming show that the types of conversion trajectories can be differentiated on the basis of the progression of crop protection changes within a larger framework where relationships to other “objects” are transformed – the soil, products, rotations, work organisation, marketing, social networks and knowledge acquisition. In the case of integrated plant production, the extent of changes depends on the degree of recomposition of agronomic practices. This transition implies major knowledge acquisition that relies on the support and contribution of advisors and on the group dynamics that develop within a group of farmers. Transitions towards integrated crop protection are, by their nature, more reversible and therefore more fragile than the conversion to organic farming. This is due to the fact that they are not stabilised by a certification or by the market, and analysis shows that their sustainability is linked in part to their integration within a group dynamics