Evaluation de l'efficacité d'un schéma de sélection basé sur la résistance naturelle aux strongles gastro-intestinaux dans la race ovine laitière Manech Tête Rousse

Les strongles gastro-intestinaux (SGI) sont l'une des contraintes majeures en élevage ovin à cause des pertes économiques engendrées et de leur gestion coûteuse. La lutte contre ces parasites repose essentiellement sur l utilisation de traitements chimiques dont l'arsenal est limité. Depuis plusieurs années, des cas de multi-résistance parasitaire aux grandes familles d'anthelminthiques, y compris vis-à-vis des molécules les plus récemment développées, ont été rapportés à travers le monde, rendant indispensable la limitation de l'utilisation massive de ces produits. Des stratégies de contrôle alternatives sont actuellement à l'étude, dont la sélection d'animaux pour leur résistance naturelle aux SGI. Ce travail de recherche montre que les brebis issues de pères résistants excrètent significativement moins d'oeufs de SGI que les filles de béliers sensibles. Ainsi, la sélection de béliers de centre d'insémination artificielle à l'aide d'un phénotypage lors d'infestations expérimentales est un moyen efficace et peu contraignant pour l'éleveur d'augmenter la résistance de son cheptel aux SGI

Delivery and use of individualised feedback in large class medical teaching

Background: Formative feedback that encourages self-directed learning in large class medical teaching is difficult to deliver. This study describes a new method, blueprinted feedback, and explores learner’s responses to assess its appropriate use within medical science teaching. Methods: Mapping summative assessment items to their relevant learning objectives creates a blueprint which can be used on completion of the assessment to automatically create a list of objectives ranked by the attainment of the individual student. Two surveys targeted medical students in years 1, 2 and 3. The behaviour-based survey was released online several times, with 215 and 22 responses from year 2, and 187, 180 and 21 responses from year 3. The attitude-based survey was interviewer-administered and released once, with 22 responses from year 2 and 3, and 20 responses from year 1. Results: 88-96% of learners viewed the blueprinted feedback report, whilst 39% used the learning objectives to guide further learning. Females were significantly more likely to revisit learning objectives than males (p = 0.012). The most common reason for not continuing learning was a ‘hurdle mentality’ of focusing learning elsewhere once a module had been assessed. Conclusions: Blueprinted feedback contains the key characteristics required for effective feedback so that with further education and support concerning its use, it could become a highly useful tool for the individual and teacher

The quantum canonical ensemble in phase space

The density operator for a quantum system in thermal equilibrium with its environment depends on Planck's constant, as well as the temperature. At high temperatures, the Weyl representation, that is, the thermal Wigner function, becomes indistinguishable from the corresponding classical distribution in phase space, whereas the low temperature limit singles out the quantum ground state of the system's Hamiltonian. In all regimes, thermal averages of arbitrary observables are evaluated by integrals, as if the thermal Wigner function were a classical distribution. The extension of the semiclassical approximation for quantum propagators to an imaginary thermal time, bridges the complex intervening region between the high and the low temperature limit. This leads to a simple quantum correction to the classical high temperature regime, irrespective of whether the motion is regular or chaotic. A variant of the full semiclassical approximation with a real thermal time, though in a doubled phase space, avoids any search for particular trajectories in the evaluation of thermal averages. The double Hamiltonian substitutes the stable minimum of the original system's Hamiltonian by a saddle, which eliminates local periodic orbits from the stationary phase evaluation of the integrals for the partition function and thermal averages.Comment: 24 pages, 2 figure

Exact Markovian evolution of multicomponent quantum systems: phase space representations

The exact solution of the Lindblad equation with a quadratic Hamiltonian and linear coupling operators was derived within the chord representation, that is, for the Fourier transform of the Wigner function. It is here generalized for multiple components, so as to provide an explicit expression for the reduced density operator of any component, as well as moments expressed as derivatives of this evolving chord function. The Wigner function is then the convolution of its straightforward classical evolution with a widening multidimensional gaussian window, eventually ensuring its positivity. Futher on, positivity also holds for the Glauber-Sundarshan P-function, which guarantees separability of the components. In the multicomponent context, a full dissipation matrix is defined, whereas its trace, equal to twice the previously derived dissipation coefficient, governs the rate at which the phase space volume of the argument of the Wigner function contracts, while those of the chord function expands. Examples of markovian evolution of a triatomic molecule and of an array of harmonic oscillators are discussed.Comment: 29 pages, 5 figure

Periodic orbit analysis of an elastodynamic resonator using shape deformation

We report the first definitive experimental observation of periodic orbits (POs) in the spectral properties of an elastodynamic system. The Fourier transform of the density of flexural modes show peaks that correspond to stable and unstable POs of a clover shaped quartz plate. We change the shape of the plate and find that the peaks corresponding to the POs that hit only the unperturbed sides are unchanged proving the correspondence. However, an exact match to the length of the main POs could be made only after a small rescaling of the experimental results. Statistical analysis of the level dynamics also shows the effect of the stable POs.Comment: submitted to Europhysics Letter