Influence of the Environment Fluctuations on Incoherent Neutron Scattering Functions

In extending the conventional dynamic models, we consider a simple model to account for the environment fluctuations of particle atoms in a protein system and derive the elastic incoherent structure factor (EISF) and the incoherent scattering correlation function C(Q,t) for both the jump dynamics between sites with fluctuating site interspacing and for the diffusion inside a fluctuating sphere. We find that the EISF of the system (or the normalized elastic intensity) is equal to that in the absence of fluctuations averaged over the distribution of site interspacing or sphere radius a. The scattering correlation function is $C(Q,t)=\sum_{n} \psi(t)$, where the average is taken over the Q-dependent effective distribution of relaxation rates \lambda_n(a) and \psi(t) is the correlation function of the length a. When \psi(t)=1, the relaxation of C(Q,t) is exponential for the jump dynamics between sites (since \lambda_n(a) is independent of a) while it is nonexponential for diffusion inside a sphere.Comment: 7 pages, 7 eps figure

Harmonically confined, semiflexible polymer in a channel: response to a stretching force and spatial distribution of the endpoints

We consider an inextensible, semiflexible polymer or worm-like chain which is confined in the transverse direction by a parabolic potential and subject to a longitudinal force at the ends, so that the polymer is stretched out and backfolding is negligible. Simple analytic expressions for the partition function, valid in this regime, are obtained for chains of arbitrary length with a variety of boundary conditions at the ends. The spatial distribution of the end points or radial distribution function is also analyzed.Comment: 14 pages including figure

Temporal fluctuations of waves in weakly nonlinear disordered media

We consider the multiple scattering of a scalar wave in a disordered medium with a weak nonlinearity of Kerr type. The perturbation theory, developed to calculate the temporal autocorrelation function of scattered wave, fails at short correlation times. A self-consistent calculation shows that for nonlinearities exceeding a certain threshold value, the multiple-scattering speckle pattern becomes unstable and exhibits spontaneous fluctuations even in the absence of scatterer motion. The instability is due to a distributed feedback in the system "coherent wave + nonlinear disordered medium". The feedback is provided by the multiple scattering. The development of instability is independent of the sign of nonlinearity.Comment: RevTeX, 15 pages (including 5 figures), accepted for publication in Phys. Rev.

Diffusion incohérente des neutrons : modèles analytiques pour la dynamique interne des protéines

La dynamique interne des protéines joue un rôle central dans la stabilité, la fonction et l'activité biologique de ces biomolécules. Il est maintenant établi que les fluctuations d'états conformationnels des protéines influencent fortement la plupart des réactions biochimiques et s'accompagnent d'une augmentation brutale des déplacements carrés moyens des atomes au dessus de la température de la transition dynamique. Dans cette contribution, nous présentons une revue critique de quelques modèles théoriques couramment utilisés dans la littérature pour l'analyse des mouvements internes des protéines et la description de la transition dynamique

Effect of the climate change on the meteorological driven risk of Dengue occurrence

International audienc

Modelling population dynamics and response to management options in the poultry red mite Dermanyssus gallinae (Acari: Dermanyssidae)

International audienceThe poultry red mite Dermanyssus gallinae is a major pest and widespread ectoparasite of laying hens and other domestic and wild birds. Under optimal conditions, D. gallinae can complete its lifecycle in less than 10 days, leading to rapid proliferation of populations in poultry systems. This paper focuses on developing a theoretical model framework to describe the population dynamics of D. gallinae. This model is then used to test the efficacy and residual effect of different control options for managing D. gallinae. As well as allowing comparison between treatment options, the model also allows comparison of treatment efficacies to different D. gallinae life stages. Three different means for controlling D. gallinae populations were subjected to the model using computer simulations: mechanical cleaning (killing once at a given time all accessible population stages), sanitary clearance (starving the mite population for a given duration, e.g. between flocks) and acaricide treatment (killing a proportion of nymphs and adults during the persistence of the treatment). Simulations showed that mechanical cleaning and sanitary clearance alone could not eradicate the model D. gallinae population, although these methods did delay population establishment. In contrast, the complete eradication of the model D. gallinae population was achieved by several successive acaricide treatments in close succession, even when a relatively low treatment level was used

Risk quantification of arthropod-borne disease in link with meteorological data

National audienc

Interactions entre l'avifaune sauvage et les élevages de volailles : quel risque épidémiologique vis à vis de l'Influenza aviaire ?

Textes issus des travaux du programme Casdar "Innovation et Partenariat" de 2007 et présentés lors d'un colloque le 4 décembre 2012, sous l'égide du GIS Relance AgronomiqueNational audienceThe outbreak of highly pathogenic avian Influenza that has spread to the territories of Western Europe in 2006 generated questions about the risks of contact between wild birds and poultry that have access to an outdoor trail. Within this framework, the birds likely to attend the courses of poultry as well as their surroundings were characterized on the territories of the Dombes, Bresse, the Pays de la Loire and the Landes with standard observation protocols. Specific monitoring of the movements of Mallard, species the AI tank, has been implemented. At the end of this study, certain factors increasing or decreasing the risk of exposure of poultry to the virus have been highlighted. Furthermore, the mallard duck does not appear to come into contact with poultry. The question arose on the role of birds frequenting both ponds and farms, which can be an intermediary between mallard ducks and poultry.L’épizootie d’Influenza aviaire hautement pathogène qui s’est propagée aux territoires d’Europe occidentale en 2006 a engendré des questionnements quant aux risques de contacts entre l’avifaune sauvage et les volailles qui ont accès à un parcours extérieur. Dans ce cadre, l’avifaune susceptible de fréquenter les parcours de volailles ainsi que leurs abords a été caractérisée sur les territoires de la Dombes, de la Bresse, des Pays de Loire et des Landes à partir de protocoles d’observation standards. Un suivi spécifique des mouvements du canard colvert, espèce réservoir des Influenzas, a été mis en place. A l’issue de cette étude, certains facteurs d’augmentation ou de diminution du risque d’exposition des volailles au virus ont été mis en évidence. Par ailleurs, le canard colvert ne semble pas entrer en contact avec les volailles. La question se pose alors du rôle des oiseaux fréquentant à la fois les étangs et les élevages, pouvant être un intermédiaire entre le canard colvert et les volailles

Interactions entre l'avifaune sauvage et les élevages de volailles : quel risque épidémiologique vis à vis de l'Influenza aviaire ?

L’épizootie d’Influenza aviaire hautement pathogène qui s’est propagée aux territoires d’Europe occidentale en 2006 a engendré des questionnements quant aux risques de contacts entre l’avifaune sauvage et les volailles qui ont accès à un parcours extérieur. Dans ce cadre, l’avifaune susceptible de fréquenter les parcours de volailles ainsi que leurs abords a été caractérisée sur les territoires de la Dombes, de la Bresse, des Pays de Loire et des Landes à partir de protocoles d’observation standards. Un suivi spécifique des mouvements du canard colvert, espèce réservoir des Influenzas, a été mis en place. A l’issue de cette étude, certains facteurs d’augmentation ou de diminution du risque d’exposition des volailles au virus ont été mis en évidence. Par ailleurs, le canard colvert ne semble pas entrer en contact avec les volailles. La question se pose alors du rôle des oiseaux fréquentant à la fois les étangs et les élevages, pouvant être un intermédiaire entre le canard colvert et les volailles.The outbreak of highly pathogenic avian Influenza that has spread to the territories of Western Europe in 2006 generated questions about the risks of contact between wild birds and poultry that have access to an outdoor trail. Within this framework, the birds likely to attend the courses of poultry as well as their surroundings were characterized on the territories of the Dombes, Bresse, the Pays de la Loire and the Landes with standard observation protocols. Specific monitoring of the movements of Mallard, species the AI tank, has been implemented. At the end of this study, certain factors increasing or decreasing the risk of exposure of poultry to the virus have been highlighted. Furthermore, the mallard duck does not appear to come into contact with poultry. The question arose on the role of birds frequenting both ponds and farms, which can be an intermediary between mallard ducks and poultry