Search

This paper deals with the depolarization and decoherence effects of an incident pure state of polarization and of arbitrary state of coherence by a linear scattering medium which changes randomly with position. Using symmetry arguments and a maximum entropy principle we deduce the general form of the Mueller matrix describing the scattering medium which is consistent with the explicit computation done in the context of the Bethe-Salpeter equation handled in the diffusion approximation. The main result expresses the output degree of polarization and degree of spatial coherence as a function of the number of scattering events. From these results, two main conclusions can be drawn. The first is that the entropy production per scattering due to the irreversible process of depolarization is an exponentially decreasing function of the number of scattering events. The second result obtained is that full depolarization of linearly polarized light by Rayleigh scatterers requires more scattering events (typically a factor-of-2) than are required for a circularly polarized lightwave.

The paper examines the prevalence of equine infectious anemia (EIA) in horse populations in the northern part (comprising 89 cities) of Minas Gerais State, Brazil, from January 2002 to December 2004. Data on 8,981 agar gel immunodiffusion test results from the region were used as input for a statistical and autoregressive analysis model to construct a city-level map of the distribution of EIA prevalence. The following EIA prevalence (P) levels were found: 49 cities with 0 < P ≤ 0.5%, 26 with 0.5% < P ≤ 1.5%, 10 with 1.5% < P ≤ 5%, and 4 with 5% < P ≤ 25%.

Modelling of contagious disease usually employs compartmental SEIR-like models where the waiting times in respective compartments are exponentially distributed. In this paper, we are interested in investigating how the distributions of sojourn times in infective compartments affect the dynamics and persistence of the contagious bovine pleuropneumonia, a chronic respiratory disease of cattle. Two kinds of extreme distributions of the sojourn times are considered: a Dirac delta-function and truncated Gaussian function leading to a model with (non-constant) delay and the classical exponential distribution that stands for a model without delay. Expressions of the basic reproductive numbers are derived and dynamical behaviours are discussed for the three models. It is found that the spreading of disease exhibits wave-like oscillations for the time-delay dynamics. In contrast, the disease appears to last longer when the spreading is described by the classical dynamics without delay. Subsequently, the time-delay dynamics turns out to be more appropriate for the description of an experimental epidemic of CBPP.

1. Introduction 328 2. Basic concepts of neutron scattering 329 2.1 Introduction 329 2.2 Neutron-scattering functions 331 2.3 Coherent and incoherent neutron scattering. The particular role of hydrogen in incoherent scattering 332 2.4 Total elastic scattering, EISF and mean square displacement (MSD) 333 2.5 Quasielastic scattering and relaxation function 334 2.6 Inelastic scattering and density of states 335 3. Experimental aspects and instruments 335 3.1 Energy and space resolution 335 3.2 General sample aspects 335 3.3 Potential effects of D2O on dynamics 336 3.4 Experimental 2H (deuterium) labelling 336 4. Physics of protein dynamics 336 4.1 Models 336 4.2 The dynamical transition 338 4.3 Effective force constants 339 5. Dynamics of hydrated protein powders 339 5.1 First experiments on myoglobin 340 5.2 Dynamical transitions in other proteins 340 5.3 The role of hydration water 341 5.4 Influence of the solvent 344 5.5 Diffusional motions within proteins by QENS 346 5.6 Inelastic neutron scattering and vibrational spectra 347 5.7 Conclusions 351 6. Membranes 352 6.1 Lipid bilayers 353 6.2 BR and the purple membrane (PM) 353 6.2.1 The dynamical transition in the PM 353 6.2.2 QENS from oriented PM 354 6.2.3 Hydration dependence of PM motions 355 6.2.4 Local dynamics in PM studied by isotope labelling 356 6.2.5 Dynamics of different BR conformations 357 7. Protein solutions 358 7.1 From powders to solutions 358 7.2 Water dynamics and solvent dependence of the dynamical transition in proteins 359 8. Comparing neutron scattering with other techniques 359 9. Biological relevance 360 9.1 Dynamics–activity relations 360 9.2 Dynamics–stability relations (adaptation to extreme environments) 360 9.3 Protein folding 361 10. Acknowledgements 364 11. References 364 This review of protein dynamics studied by neutron scattering focuses on data collected in the last 10 years. After an introduction to thermal neutron scattering and instrumental aspects, theoretical models that have been used to interpret the data are presented and discussed. Experiments are described according to sample type, protein powders, solutions and membranes. Neutron-scattering results are compared to those obtained from other techniques. The biological relevance of the experimental results is discussed. The major conclusion of the last decade concerns the strong dependence of internal dynamics on the macromolecular environment.

This paper deals with the depolarization and decoherence effects of an incident pure state of polarization and of arbitrary state of coherence by a linear scattering medium which changes randomly with position. Using symmetry arguments and a maximum entropy principle we deduce the general form of the Mueller matrix describing the scattering medium which is consistent with the explicit computation done in the context of the Bethe-Salpeter equation handled in the diffusion approximation. The main result expresses the output degree of polarization and degree of spatial coherence as a function of the number of scattering events. From these results, two main conclusions can be drawn. The first is that the entropy production per scattering due to the irreversible process of depolarization is an exponentially decreasing function of the number of scattering events. The second result obtained is that full depolarization of linearly polarized light by Rayleigh scatterers requires more scattering events (typically a factor-of-2) than are required for a circularly polarized lightwave. Dans cette ?tude, on consid?re les ph?nom?nes de d?polarisation et de d?coh?rence d'un faisceau d'ondes planes incident, d'?tat pur de polarisation et d'?tat arbitraire de coh?rence, par int?raction avec un milieu diffusant d?sordonn?. Par des arguments de sym?trie et un principe d'entropie maximum, nous d?duisons la forme de la matrice de Mueller caract?risant le milieu diffusant qui est en accord avec le calcul explicite bas? sur l'?quation de Bethe-Salpeter trait?e dans l'approximation de la diffusion. Le r?sultat principal exprime les degr?s de polarisation et de coh?rence spatiale en fonction du nombre de diffusions. Deux faits saillants sont ? noter. Le premier exprime la d?croissance exponentielle de la production d'entropie due ? l'irr?versibilit? du processus de d?polarisation, en fonction du nombre de diffusions. Le second indique que la d?polarisation compl?te d'un faisceau incident polaris? lin?airement par des diffuseurs de type Rayleigh n?cessite davantage de diffusions (facteur 2) que pour une polarisation circulaire.

Les hémopathies lymphoïdes regroupent diverses entités dont les lymphomes, les myélomes et la leucémie lymphoïde chronique. La littérature permet de retenir une association certaine entre les lymphomes et l’exposition à certains pesticides ou au butadiène, ce qui a conduit à la création récente de deux tableaux de maladies professionnelles. Une relation entre ces maladies et d’autres nuisances ou certaines professions est suggérée par certaines études, avec un niveau de preuve plus limité, notamment les rayonnements ionisants, le benzène, le formaldéhyde et certains solvants.

ABSTRACTTularemia is a zoonosis caused by the bacterium Francisella tularensis. Its specific diagnosis remains based on serological methods, while F. tularensisis rarely detected in clinical samples by culture or PCR. The aim of the present study was to evaluate the performance of the Serion enzyme-linked immunosorbent assay (ELISA) classic Francisella tularensisIgG and IgM tests (Virion/Serion GmbH Institute, Würzburg, Germany) and the VIRapid tularemia immunochromatographic test (ICT) (Vircell, Granada, Spain) compared to that of the in-house microagglutination test (MAT) and indirect immunofluorescence assay (IFA) currently used at the French National Reference Center for Francisella. We evaluated 256 consecutive sera from 208 patients, including 51 confirmed and 23 probable tularemia cases, and 134 control patients not infected with F. tularensis. The IFA tests displayed 72.5% sensitivity for IgM (cutoff titer =80) and 74.5% for IgG (cutoff titer =160), and 99.3% specificity for both IgM and IgG. Using cutoffs advocated by the manufacturer, the Serion ELISAs displayed 88.2% sensitivity for IgM and 86.3% for IgG antibodies; specificity was 94.8% for IgM and 95.5% for IgG. Compared to MAT and IFA tests, the Serion ELISAs allowed earlier detection of specific antibodies (1 to 2 weeks versus 2 to 3 weeks after the onset of symptoms). The ICT sensitivity and specificity were 90% and 83.6%, respectively, when considering the cutoff advocated by the manufacturer. In conclusion, the Serion ELISAs are useful as screening tests for tularemia diagnosis, but additional confirmatory tests (such as MAT and IFA) are needed, especially in areas of low endemicity.

Host-feeding patterns play a key role in the transmission of vector-borne diseases such as West Nile fever, which involves two kinds of vertebrates, birds and mammals. In this study, we propose a theoretical formulation for mosquito host-feeding patterns using three quantities, as follows: the apparent attractiveness/contact probabilities, the conditional host(-feeding) preferences, and the enzootic versus bridge probabilities. Using results from host-baited trap collections, the quantities defined above were assessed for the most abundant mosquito species in the main West Nile virus focus of southern France. We found that host availability is important in determining the efficiency of bridge vectors, and that even ornithophilic mosquitoes like Culex species, classically classified as enzootic vectors, may turn out to be efficient bridge vectors in certain contexts of host abundance. Our developed theoretical framework can easily be adapted and applied to other experimental data and other vector-borne diseases.