Learning Process and Contract Adaptation with Quality Uncertainty: Some Paradoxes in Retailer-Producer Relationships

The optimal level of formalisation of contracts and their dynamic is at stake in the economic literature on the optimum design of ex post renegotiation with third party enforcement. Another theoretical interpretation is that contract adaptations may also reflect mutual learning process between contractors. Why transactors write explicit contract that they know cannot be court enforced? The central idea is that explicit contract terms makes it clearer to the transactors what has been agreed upon, thus are decreasing the cost of private enforcement sanctions (Klein, 1996). Empirical evidences are provided by the diachronic analysis of the full set of tri-partite contracts between one of the top-ten french large retailer and its beef suppliers before and after the BSE crisis (period 1993-1999). The analysis emphasizes also the role of this increased codification of supply contracts with a progressive change in the internal retailer's organization, i.e. increased centralization of decision and supervision mechanisms. Contract design and organizational choices are then strongly interrelated.Contract design, Hold-up problems, beef sector, Self-Enforcement, Agribusiness,

HAWC Upgrade for Multi-TeV {\gamma}-ray Detection

The High Altitude Water Cherenkov (HAWC) high-energy {\gamma}-ray observatory was completed in march 2015 in central Mexico. The detector, consisting of 300 water tanks, is currently being upgraded to improve its performance at Multi-TeV energies, with a sparse array of small water Cherenkov tanks. It will extend the instrumental area by a factor of 4, and enhance the sensitivity at the highest energies. In this contribution, the current status of the observatory is presented, as well as the coming upgrade. The electronics and the readout system for the new sparse array of small water tanks are also desrcibed, and results from simulations performed to optimize the performance of the array are discussed.Comment: Proceeding paper of a contribution at the 6th International Symposium on High-Energy Gamma-Ray Astronomy (Gamma2016) in Heidelberg, German

Why observers should train clinical scoring

Epidemiological studies often involve clinical scoring of animals by several observers due to the high number of farms to be visited. Detailed written procedures and intensive observer training minimize variation between observers. This, however, is still not common in international cooperation. We present data on clinical assessment of sows from an EU project on organic pig health (COREPIG) to illustrate the consequences. The clinical scoring system was based on procedures from the Welfare Quality ® project and included measures regarding body condition (5-level scale), injuries (number of lesions >3cm on shoulder, side and hindquarters), lameness (3-level scale), dirtiness (3-level scale) and skin problems (3-level scale). Nine observers from 6 EU countries trained clinical scoring during two days in two herds. Of the 9 observers, 4 had no or little, 2 had intermediate and 3 had extensive experience in working with pigs. Four observers each had little or intermediate experience in clinical scoring of sows and only 1 had extensive experience. Training comprised parameter discussions and joint scoring of animals. After training, each observer scored up to 30 pregnant sows per farm in 3 to 20 herds in six European countries as part of a larger epidemiological protocol. After completion of farm visits, observers scored up to 50 sows independently but at the same day and farm in order to assess inter-observer agreement. Parameters were collapsed into binary variables. We calculated Kendall's Coefficient of Concordance (W) across all observers and Prevalence Adjusted Bias Adjusted Kappas (PABAK) for observer pairs as measures of agreement. Agreement across observers was not acceptable for skin problems and lameness (W 0.60 (N = 26 sows for skin problems, and 31 to 34 sows for other parameters). Pairwise agreement was not acceptable for skin problems and dirtiness (mean PABAK <0.41) and acceptable for injuries shoulder and side (mean PABAK between 0.41 and 0.60). Agreement was good for hindquarter injuries and animal too thin (PABAK = 0.66 and 0.65, respectively), while obesity and lameness had mean PABAK of 0.84 and 0.95. Observer pairs scored 40 to 50 sows per parameter except for skin problems (36 to 49 sows). Results for lameness and obesity should be interpreted with care, as average prevalence across observers were only 3 and 8 %, respectively. Determination of whether a sow was too thin was the parameter with best agreement. The poor agreement for skin problems and dirtiness can be explained by misunderstandings regarding the parameter definition (e.g. inclusion of mud soiling). Extensive practical experience with pigs was of highest benefit for inter-observer agreement. Average PABAK was 0.70 (STD = 0.19, N = 24 scorings; 3 observer pairs, 8 parameters) for experienced observers but ranged between 0.49 and 0.56 (STD range 0.32 to 0.40) for all other combinations of experience level. The level of experience with clinical scoring of pigs did not have obvious positive effects. Average PABAK for all experience combinations ranged from 0.51 to 0.61 (STD range 0.32 to 0.40). By way of explanation, general experience with pigs helps to score an animal because observers will know a wider range of possible scenarios. By contrast, scores of observers who have already learned a scoring system will tend to be biased by their experience. As a conclusion, our data emphasize the importance of intensive observer training before data collection and the need for inter-observer agreement tests before and after data collection

Private Ordering, Collective Action, and the Self-Enforcing Range of Contracts. The Case of French Livestock Industry

Contract enforcement is acknowledged as a major issue in Law and in Economics. Contrasting substitution and complementary perspectives with respect to the role of private versus public enforcement institutions, this article analyses how contract law can support private institutions, and enhance economic efficiency. With multilateral agreements at stake, self-regulation and reputation mechanisms at the core of private ordering have limitations that collective organizations backed by the Law help to overcome. The analysis is substantiated by empirical data from the cattle industry. Our results suggest the need for a broader approach to contract regulation by legal scholars and antitrust-authorities.Contract Law, Private Enforcement, Transaction Costs, Self-Regulation, Coalitions, Cartels, Collective Organization

On the Influence of the Data Sampling Interval on Computer-Derived K-Indices

The K index was devised by Bartels et al. (1939) to provide an objective monitoring of irregular geomagnetic activity. The K index was then routinely used to monitor the magnetic activity at permanent magnetic observatories as well as at temporary stations. The increasing number of digital and sometimes unmanned observatories and the creation of INTERMAGNET put the question of computer production of K at the centre of the debate. Four algorithms were selected during the Vienna meeting (1991) and endorsed by IAGA for the computer production of K indices. We used one of them (FMI algorithm) to investigate the impact of the geomagnetic data sampling interval on computer produced K values through the comparison of the computer derived K values for the period 2009, January 1st to 2010, May 31st at the Port-aux-Francais magnetic observatory using magnetic data series with different sampling rates (the smaller: 1 second; the larger: 1 minute). The impact is investigated on both 3-hour range values and K indices data series, as a function of the activity level for low and moderate geomagnetic activity

Viscoroute 2.0: a tool for the simulation of moving load effects on asphalt pavement

As shown by strains measured on full scale experimental aircraft structures, traffic of slow-moving multiple loads leads to asymmetric transverse strains that can be higher than longitudinal strains at the bottom of asphalt pavement layers. To analyze this effect, a model and a software called ViscoRoute have been developed. In these tools, the structure is represented by a multilayered half-space, the thermo-viscoelastic behaviour of asphalt layers is accounted by the Huet-Sayegh rheological law and loads are assumed to move at constant speed. First, the paper presents a comparison of results obtained with ViscoRoute to results stemming from the specialized literature. For thick asphalt pavement and several configurations of moving loads, other ViscoRoute simulations confirm that it is necessary to incorporate viscoelastic effects in the modelling to well predict the pavement behaviour and to anticipate possible damages in the structure.Comment: 27 pages

PAKing up to the endothelium

Angiogenesis recapitulates the growth of blood vessels that progressively expand and remodel into a highly organized and stereotyped vascular network. During adulthood, endothelial cells that formed the vascular wall retain their plasticity and can be engaged in neo-vascularization in response to physiological stimuli, such as hypoxia, wound healing and tissue repair, ovarian cycle and pregnancy. In addition, numerous human diseases and pathological conditions are characterized by an excessive, uncontrolled and aberrant angiogenesis. The signalling pathways involving the small Rho GTPase, Rac and its downstream effector the p21-activated serine/threonine kinase (PAK) had recently emerged as pleiotropic modulators in these processes. Indeed, Rac and PAK were found to modulate endothelial cell biology, such as sprouting, migration, polarity, proliferation, lumen formation, and maturation. Elucidating the Rac/PAK molecular circuitry will provide essential information for the development of new therapeutic agents designed to normalize the blood vasculature in human diseases.Comment: Cell Signal (2009) epub ahead of prin

Statistics of extremes under random censoring

We investigate the estimation of the extreme value index when the data are subject to random censorship. We prove, in a unified way, detailed asymptotic normality results for various estimators of the extreme value index and use these estimators as the main building block for estimators of extreme quantiles. We illustrate the quality of these methods by a small simulation study and apply the estimators to medical data.Comment: Published in at http://dx.doi.org/10.3150/07-BEJ104 the Bernoulli (http://isi.cbs.nl/bernoulli/) by the International Statistical Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm