Les stratégies de contrôle de la qualité sanitaire dans les Organisations de Producteurs de tomates

Our paper deals with free-riding issues in product safety control at the collective marketing level. It focuses on the empirical findings of the exhaustive face to face survey that has been conducted in 2007 by the authors with the quality managers of the tomato growers'unions of France. Our survey was supported by the National Tomato Charter, a regrouping of most of the French tomato growers'unions. Its aim was to identify the differences in monitoring and enforcement practices at the collective marketing level and to search for any group size effect on such practices. A main finding of our paper is that, beyond public regulation and collective rules imposed by the National Tomato Charter, POs implement voluntary control rules for a better control of free riding behavior within the group. Such additional rules differ both in monitoring intensity (measured by the number of pesticide residue analysis performed voluntarily by the group) and in sanction level (applied in case of deviation to the collective rule). Differences in safety control are not only triggered by customers specific requirements but also by group size (measured by the number of growers within the group). Eventually, our paper draws some perspectives for a more in-depth analysis of free riding issues. First, it calls for paying more attention to factors such as intra-group heterogeneity and differences in customers requirements. Second, it underlines the need for a more extensive analysis which includes safety control practices at the production level and wonders whether such practices are a complement or a substitute of control practices at the marketing level. ...French Abstract : Ce texte aborde les problèmes d'action collective dans le contrôle de la qualité sanitaire des produits avant leur mise en marché par les Organisations de Producteurs. Il est une synthèse des résultats de l'enquête menée auprès des responsables qualité de l'ensemble des OP adhérant à la Charte Nationale Tomate sur leurs pratiques de contrôle de la qualité sanitaire des tomates. L'enquête a eu le soutien des responsables de la Charte Nationale Tomate, qui regroupe la quasi-totalité de la production organisée en France. Elle avait pour objectif d'identifier la diversité des pratiques de contrôle au sein des OP et de mesurer l'effet de la "taille de l'OP" sur les modalités de contrôle mises en place. L'enquête montre qu'au-delà des règles communes imposées par la réglementation et la Charte Nationale Tomate, les OP mettent en place des démarches de contrôle diversifiées qui se différencient à la fois par l'importance de la surveillance (mesurée en nombre d'analyses de résidus de pesticides) et par le niveau des sanctions appliquées en cas de dérogation à la règle adoptée. Elle explique enfin la diversité de ces démarches, non seulement par les exigences de la clientèle mais aussi par la taille du groupe (mesurée par le nombre de producteurs). Notre rapport se termine par une discussion sur les améliorations à apporter à ce premier travail. Des précisions sont à apporter tout d'abord sur l'hétérogénéité intra et inter groupes et sur les niveaux d'exigences de la clientèle. Un complément d'analyse est ensuite nécessaire pour mieux caractériser l'effort de contrôle en amont du produit, au niveau de la production et pour étudier la complémentarité ou la substituabilité des deux types de contrôle: contrôle sur les pratiques en production, contrôle sur le produit.PRODUCERS' UNIOS; FREE-RIDING; MONITORING; ENFORCEMENT; CONTROL; PESTICIDE RESIDUES; TOMATO; FRANCE; ORGANISATIONS DE PRODUCTEURS; PASSAGER CLANDESTIN; SANCTION; CONTROLE; RESIDUS DE PESTICIDES; TOMATE

Opportunities for polymer-based nanowires in optoelectronics and nanophotonics

International audienceSee document joine

Opportunities for polymer-based nanowires in optoelectronics and nanophotonics

International audienceSee document joine

Search for the glueball candidates f0(1500) and fJ(1710) in gamma gamma collisions

Data taken with the ALEPH detector at LEP1 have been used to search for gamma gamma production of the glueball candidates f0(1500) and fJ(1710) via their decay to pi+pi-. No signal is observed and upper limits to the product of gamma gamma width and pi+pi- branching ratio of the f0(1500) and the fJ(1710) have been measured to be Gamma_(gamma gamma -> f0(1500)). BR(f0(1500)->pi+pi-) < 0.31 keV and Gamma_(gamma gamma -> fJ(1710)). BR(fJ(1710)->pi+pi-) < 0.55 keV at 95% confidence level.Comment: 10 pages, 3 figure

Anisotropy studies around the galactic centre at EeV energies with the Auger Observatory

Data from the Pierre Auger Observatory are analyzed to search for anisotropies near the direction of the Galactic Centre at EeV energies. The exposure of the surface array in this part of the sky is already significantly larger than that of the fore-runner experiments. Our results do not support previous findings of localized excesses in the AGASA and SUGAR data. We set an upper bound on a point-like flux of cosmic rays arriving from the Galactic Centre which excludes several scenarios predicting sources of EeV neutrons from Sagittarius $A$. Also the events detected simultaneously by the surface and fluorescence detectors (the `hybrid' data set), which have better pointing accuracy but are less numerous than those of the surface array alone, do not show any significant localized excess from this direction.Comment: Matches published versio

Limit on Bs0B^0_s oscillation using a jet charge method

A lower limit is set on the B_{s}^{0} meson oscillation parameter \Delta m_{s} using data collected from 1991 to 1994 by the ALEPH detector. Events with a high transverse momentum lepton and a reconstructed secondary vertex are used. The high transverse momentum leptons are produced mainly by b hadron decays, and the sign of the lepton indicates the particle/antiparticle final state in decays of neutral B mesons. The initial state is determined by a jet charge technique using both sides of the event. A maximum likelihood method is used to set a lower limit of \, \Delta m_{s}. The 95\% confidence level lower limit on \Delta m_s ranges between 5.2 and 6.5(\hbar/c^{2})~ps^{-1} when the fraction of b quarks from Z^0 decays that form B_{s}^{0} mesons is varied from 8\% to 16\%. Assuming that the B_{s}^{0} fraction is 12\%, the lower limit would be \Delta m_{s} 6.1(\hbar/c^{2})~ps^{-1} at 95\% confidence level. For x_s = \Delta m_s \, \tau_{B_s}, this limit also gives x_s 8.8 using the B_{s}^{0} lifetime of \tau_{B_s} = 1.55 \pm 0.11~ps and shifting the central value of \tau_{B_s} down by 1\sigma

Measurement of the Bs0^0_s lifetime and production rate with Ds−l+^-_s l^+ combinations in Z decays

The lifetime of the \bs meson is measured in approximately 3 million hadronic Z decays accumulated using the ALEPH detector at LEP from 1991 to 1994. Seven different \ds decay modes were reconstructed and combined with an opposite sign lepton as evidence of semileptonic \bs decays. Two hundred and eight \dsl candidates satisfy selection criteria designed to ensure precise proper time reconstruction and yield a measured \bs lifetime of \mbox{\result .} Using a larger, less constrained sample of events, the product branching ratio is measured to be \mbox{\pbrresult