Viscous resuspension of non-Brownian particles: determination of the concentration profiles and particle normal stresses

We perform local measurements of both the shear rate and the particle fraction to study viscous resuspension in non-Brownian suspensions. A suspension of PMMA spherical particles dispersed in a lighter Newtonian fluid (Triton X100) is sheared in a vertical Couette cell. The vertical profiles of the particle volume fraction are measured for Shields numbers ranging from 10 −3 to 1, and the variation in the particle normal stress in the vorticity direction of the particle fraction is deduced

Caractérisation des vents dans la moyenne atmosphère et basse thermosphère à partir d'observations d'ondes infrasonores

Le Système de Surveillance International (SSI), destiné à vérifier l'application du Traité d'Interdiction Complète des Essais Nucléaire (TICE), est constitué de quatre réseaux de stations : sismologiques, hydroacoustiques, radionucléides et microbarométriques. Ces dernières enregistrent en continu les ondes infrasonores dans la bande de fréquence 0.02-4 Hz. Ces ondes se propagent dans l'atmosphère sur de longues distances à travers les guides résultant de la stratification naturelle des propriétés atmosphériques (température, densité, vents, ...) et représentent une source d'information pour comprendre la dynamique atmosphérique jusque dans la basse thermosphère. L'objectif de cette thèse est d'analyser dans quelle mesure les observations infrasonores peuvent être assimilées dans les modèles atmosphériques.Nous commençons par décrire l'atmosphère et ses mécanismes de circulation ainsi que les différentes techniques d'observations utilisées pour le développement des modèles atmosphériques. L'analyse descriptive de l'interaction des ondes infrasonores avec l'atmosphère permet de mettre en évidence l'intérêt des mesures infrasonores par rapport aux méthodes de mesures conventionnelles. Afin de rendre compte de ce potentiel nous développons un algorithme d'inversion afin d'estimer des paramètres atmosphériques dont le problème direct est traité par une méthode de tracé de rayons. Le développement des formes perturbatives des équations des rayons pour des perturbations du milieu de propagation, et plus particulièrement des paramètres de vents, est décrit en détail. Nous formulons et analysons le problème inverse au travers de différents cas d'études synthétiques visant à mettre en évidence les conditions d'applications de l'algorithme.Les résultats obtenus témoignent de la pertinence de notre approche et montre que l'apport des observations infrasonores peut-être significatif au niveau des altitudes de réfraction de l'énergie acoustique, c'est-à-dire à environ 50 km et entre 100 et 120 km d'altitude.The International Monitoring System (IMS) designed to monitor compliance with the Comprehensive Nuclear Test-Ban Treaty (CTBT) uses four complementary verification methods : seismic, hydroacoustic, radionucleide and microbarometric stations spanning the entire globe. Microbarometric stations record continuously infrasonic waves in the frequency band 0.02-4 Hz. These waves propagate at long-ranges through atmospheric ducts resulting from the natural stratification of atmospheric properties (temperature, density, winds, ...) and represent a valuable information to understand atmospheric dynamic until the lower thermosphere. In this thesis, we seek to determine the possible contribution of infrasound observations for improving current atmospheric specifications.We describe the atmospheric media and its circulation mechanisms as well as the conventional observations used in the development of atmospheric models. A description of the interaction between infrasonic waves and the atmosphere help to understand the interest of microbarometric measurement compared with conventional observations. To highlight this potential we develop an inverse algorithm in order to estimate atmospheric parameters from infrasonic observations. The forward problem is handled by a ray-tracing algorithm. First-order perturbation equation resulting from perturbation of atmospheric properties, and especially wind parameters, are developped and numerically validated. We then analyse the inverse problem through several numerical experiments in order to show the capabilities and limitations of our algorithm.Results show the suitability of our approach and indicate that infrasonic observations can significantly improve current atmospheric specification at the altitudes of acoustic energy refraction, i.e. around 50 km and between 100 and 120 km.LYON-Ecole Centrale (690812301) / SudocSudocFranceF

Rheology of non-Brownian suspensions of rough frictional particles under shear reversal: A numerical study

International audienceWe perform particle scale simulations of suspensions submitted to shear reversal. The simulations are based on the Force Coupling Method, adapted to account for short range lubrication interactions together with direct contact forces between particles, including surface roughness, contact elasticity and solid friction. After shear reversal, three consecutive steps are identified in the viscosity transient: an instantaneous variation, followed by a rapid contact force relaxation, and finally a long time evolution. The separated contributions of hydrodynamics and contact forces to the viscosity are investigated during the transient, allowing a qualitative understanding of each step. In addition, the influence of the contact law parameters (surface roughness height and friction coefficient) on the transient are evaluated. Concerning the long time transient, the difference between the steady viscosity and minimum viscosity is shown to be proportional to the contact contribution to the steady viscosity, allowing in principle easy determination of the latter in experiments. The short time evolution is studied as well. After the shear reversal, the contact forces vanish over a strain that is very short compared to the typical strain of the long time transient, allowing to define an apparent step between the viscosity before shear reversal and after contact force relaxation. This step is shown to be an increasing function of the friction coefficient between particles. Two regimes are identified as a function of the volume fraction. At low volume fraction, the step is small compared to the steady contact viscosity, in agreement with a particle pair model. As the volume fraction increases, the value of the viscosity step increases faster than the steady contact viscosity, and, depending on the friction coefficient, may approach it

Mesures locales de la viscosité dans les suspensions non-browniennes concentrées

Nous nous intéressons au comportement transitoire d'une suspension concentrée de particules non-browniennes lors d'une inversion de cisaillement. Nous étudions la réponse visqueuse de la suspension grâce à des mesures couplées de PIV et de rhéométrie. Lorsque le cisaillement est inversé, la viscosité chute abruptement, passe par un minimum pour croître à nouveau vers une valeur plateau. Nous montrons en particulier que la viscosité au minimum et sur le plateau n'obéissent pas à la même loi de variation avec la fraction volumique

Human Papillomavirus, Chlamydia trachomatis and Herpes Simplex Virus

Introduction: Some sexually transmitted infections (STIs) are possible risk factors for oral cancer although their role as etiological agents of head and neck cancer is controversial and should be further studied. Among STI that can infect the oral mucosa stand out Human Papillomavirus (HPV), Herpes Simplex Virus (HSV) and Chlamydia trachomatis (C. trachomatis), an obligate intracellular bacterium that causes inflammation and dysplasia in the cervix. Objectives: To evaluate the presence of HPV, C. trachomatis and HSV in benign, potentially malignant and cancerous oral cavity lesions, in Córdoba, Argentina. Methods: We studied oral cytobrush of lesion from 318 patients (149 men and 169 female). Samples consisted of 137 benign lesions (BL), 96 potentially malignant lesions (PML) and 85 oral squamous cell carcinomas (OSCC). These were analyzed by Polymerase Chain Reaction method and Restriction Fragment Length Polymorphism (RFLP) was used to detect HPV genotype. Results: The prevalence of HPV was 34% (n=109). The HPV detection rate was increasing as the severity of the lesion increased (28% BL, 35% PML and 42% OSCC). The most frequent HPV genotypes were 6 and 16. There was no statistical significance between HPV, lesions, genotypes and gender. However, greater detection of high-risk HPV could be observed in OSCC and low risk HPV in BL. The prevalence of C. trachomatis was 16% (n=54) and HSV was 3% (n=10). We detected 4% (n=13) co infections HPV- C. trachomatis, mostly in BL and 0.3% (n=1) co infection HPV-HSV in BL too. Conclusions. Due the association of HPV and cervical cancer and morphological similarity of genital and oropharyngeal epithelia, these preliminary results allow us to infer that the evolution of the oral lesions could be influenced not only by the conventional risk factors, also the HPV genotype detected. These results show the importance of detecting these pathogens as well as HPV genotype in all kind of oral lesions. Such data are important to improve our knowledge of the epidemiology of oral HPV and co-infections. Indeed, C. trachomatis infection can alter the normal structure of epithelial cell junctions, increasing susceptibility to HPV or HSV infection, both in genital and oral mucosa.Fil: Mosmann, Jessica Paola. Universidad Nacional de Córdoba. Facultad de Ciencias Médicas; Argentina.Fil: Mosmann, Jessica Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Virología Dr. José María Vanella; ArgentinaFil: Talavera, Angel Daniel. Universidad Nacional de Córdoba. Facultad de Odontología. Cátedra de Estomatología A; Argentina.Fil: Criscuolo, María Inés. Universidad Nacional de Córdoba. Facultad de Odontología. Cátedra de Estomatología B; Argentina.Fil: Venezuela, Raul Fernando. Universidad Nacional de Córdoba. Facultad de Ciencias Médicas; Argentina.Fil: Kiguen, Ana Ximena. Universidad Nacional de Córdoba. Facultad de Ciencias Médicas; Argentina.Fil: Ferreyra de Prato, Ruth. Universidad Nacional de Córdoba. Facultad de Odontología. Cátedra de Anatomía Patológica A; Argentina.Fil: López de Blanc, Silvia. Universidad Nacional de Córdoba. Facultad de Odontología. Cátedra de Estomatología B; Argentina.Fil: Ré, Viviana Elisabeth. Universidad Nacional de Córdoba. Facultad de Ciencias Médicas; Argentina.Fil: Ré, Viviana Elisabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Virología Dr. José María Vanella; ArgentinaFil: Cuffini, Cecilia Gabriela . Universidad Nacional de Córdoba. Facultad de Ciencias Médicas; Argentina.Fil: Cuffini, Cecilia Gabriela . Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Virología Dr. José María Vanella; Argentina.Otras Ciencias de la Salu

Evolution and Population Dynamics of Clonal Complex 152 Community-Associated Methicillin-Resistant Staphylococcus aureus

Since the late 1990s, changes in the epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) were recognized with the emergence of community-associated MRSA (CA-MRSA). CA-MRSA belonging to clonal complex 152 (CC152), carrying the small staphylococcal cassette chromosome mec (SCCmec) type V and encoding the Panton-Valentine leukocidin (PVL), has been observed in Europe. The aim of this study was to investigate its origin, evolution, and dissemination. Whole-genome sequencing was performed on a global collection of 149 CC152 isolates spanning 20 years (93 methicillin-susceptible S. aureus [MSSA] and 56 MRSA isolates). Core genome phylogeny, Bayesian inference, in silico resistance analyses, and genomic characterization were applied. Phylogenetic analysis revealed two major distinct clades, one dominated by MSSA and the other populated only by MRSA. The MSSA isolates were predominately from sub-Saharan Africa, whereas MRSA was almost exclusively from Europe. The European MRSA isolates all harbored an SCCmec type V (5C2&5) element, whereas other SCCmec elements were sporadically detected in MRSA from the otherwise MSSA-dominated clade, including SCCmec types IV (2B), V (5C2), and XIII (9A). In total, 93% of the studied CC152 isolates were PVL positive. Bayesian coalescent inference suggests an emergence of the European CC152-MRSA in the 1990s, while the CC152 lineage dates back to the 1970s. The CA-MRSA CC152 clone mimics the European CC80 CA-MRSA lineage by its emergence from a PVL-positive MSSA ancestor from North Africa or Europe. The CC152 lineage has acquired SCCmec several times, but acquisition of SCCmec type V (5C2&5) seems associated with expansion of MRSA CC152 in Europe. IMPORTANCE Understanding the evolution of CA-MRSA is important in light of the increasing importance of this reservoir in the dissemination of MRSA. Here, we highlight the story of the CA-MRSA CC152 lineage using whole-genome sequencing on an international collection of CC152. We show that the evolution of this lineage is novel and that antibiotic usage may have the potential to select for the phage-encoded Panton-Valentine leukocidin. The diversity of the strains correlated highly to geography, with higher level of resistance observed among the European MRSA isolates. The mobility of the SCCmec element is mandatory for the emergence of novel MRSA lineages, and we show here distinct acquisitions, one of which is linked to the successful clone found throughout Europe today