Numerical Study of a One-Dimensional Poisson-Nernst–Planck Ion Channel Model By Finite Element Backward and Forward Euler Methods

This thesis presents a numerical study of a one-dimensional Poisson-Nernst-Planck (PNP) ion channel model,which describes the transport of charged species in an electrolyte under the influence of an electric field. We develop a new numerical scheme for solving the PNP model by combining the method of lines with the finite element and Euler\u27s forward and backward methods. We then implement the scheme based on the finite element library from the FEniCS project. To validate the accuracy of our numerical scheme, we construct an analytical solution of the PNP model with source terms. We find in numerical tests that the backward Euler method is more accurate and stable than the forward Euler method, especially for larger time steps. Furthermore, we use our numerical scheme to investigate the properties of the PNP model for an electrolyte with two ionic species. Our numerical results show that our numerical scheme can accurately capture the solution behavior of the PNP model

The flow structure behind vortex generators embedded in a decelerating turbulent boundary layer

The objective of the present work is to analyse the behaviour of a turbulent decelerating boundary layer under the effect of both passive and active jets vortex generators (VGs). The stereo PIV database of Godard and Stanislas [1, 2] obtained in an adverse pressure gradient boundary layer is used for this study. After presenting the effect on the mean velocity field and the turbulent kinetic energy, the line of analysis is extended with two points spatial correlations and vortex detection in instantaneous velocity fields. It is shown that the actuators concentrate the boundary layer turbulence in the region of upward motion of the flow, and segregate the near-wall streamwise vortices of the boundary layer based on their vorticity sign

Technique of Papineau in the Management of Chronic Osteomyelitis in a Low Setting Area. A 12 Years’ Experience

Introduction: Chronic osteomyelitis, a bone infectious pathology is difficult to treat. The authors report their experience in a series of patients treated in a low-income country.Methods: We report a prospective study of 53 patients suffering of chronic osteomyelitis for a long time, covering our experience between January 1998 to December 2010 at the Kinshasa University Hospital in central Africa. We used the technique described by Papineau with success, until the consolidation of the bones and the drying up of the wounds.The following elements were analyzed and taken into account: age and sex of the patients, sites involved, germs, surgical technique, length of stay in the hospital and estimated cost of the treatment.Result: The majority of patients were between 26 and 35 years old with extremes between 15 and 80 years old, with 34 males and 19 females with a sex ratio of 1.7/1. Upper limb was involved with 7 humerus, 6 radius, 6 cubitus and the lower limb with 14 femurs and 20 tibias. Staphylococcus aureus was the germ most found in cultures from dead bone from intraoperative technique. Stay in hospital on average was 17 weeks for upper limb and 28 weeks for the management of lower limb injuries. The average cost for the treatment was estimated for 700 to 800 dollars. Conclusion: Chronic osteomyelitis is a tenacious condition for long-term evolution, but it is nevertheless encouraging to dry up foci, which were the toughest challenges for orthopedics and plastic surgeons. In a low setting region, the management of the disease remains a condition with a high economic cost and it is absolutely useless to begin a Papineau treatment if the patients do not have enough money

Active control of a separated turbulent boundary layer in adverse pressure gradient

Le contrôle d écoulement permet d éliminer le phénomène de décollement de couches limites, très néfaste pour les performances des machines interagissant avec un fluide (avions, voitures, turbomachines ...). Ces travaux s intéressent plus particulièrement au contrôle actif d écoulement au moyen de jets continus. Une maquette permettant de manipuler l équilibre de la couche limite a été conçue et installée dans la soufflerie du Laboratoire de Mécanique de Lille. La première partie du travail a consisté en la caractérisation de l écoulement autour du modèle à l aide de visualisations par fils de laine et par enduit gras, de mesures de répartition de pression, de mesures par anémométrie à fils chauds et par PIV. Ceci a permis de définir la configuration du modèle la plus appropriée pour les études de contrôle mais aussi de connaître précisément les caractéristiques de l écoulement sélectionné. La configuration retenue correspond à un écoulement en gradient de pression adverse suivi d une séparation sur le volet, un peu comme sur l extrados d une aile d avion. L utilisation de sondes de frottement associées à des visualisations aux fils de laine ont permis d étudier et d optimiser des actionneurs passifs, puis des actionneurs à jets continus. Certaines des configurations actives optimales ont ensuite été caractérisées plus en détail par une mesure par PIV englobant toute la zone de séparation. Il apparaît que les jets continus ne suppriment pas complètement les mécanismes de la séparation mais réduisent leur intensité et les concentrent plus ou moins près de la paroiFlow control allows to suppress boundary layers separation, which largely deteriorates the performances of machineries which interact with fluid (aircraft, cars, turbomachineries, etc.). This study concentrates more particularly on active flow control with continuous jets. A ramp model which allows to manipulate the boundary layer equilibrium was realized and set in Laboratoire de Mécanique de Lille wind tunnel. The first part of the work was to characterize the flow over the model with wool-tufts and oil-film visualisations, pressure distribution, hot-wire anemometry and PIV measurements. The aim was to define a ramp configuration for the flow control study and to know precisely the characteristics of the retained flow. The selected configuration corresponds to an adverse pressure gradient flow followed by a separation on the flap, which mimics the flow on the suction side of a wing. With friction probes coupled with wool-tufts visualisations, passive actuators and active continuous jets were studied and optimised. Finally, some of the optimum active configurations found were characterized in more details with PIV measurements over the entire separated region. It appears that continuous jets do not suppress the separation mechanisms, but only reduce their intensity and squeeze them more or less against the wallVILLENEUVE D'ASCQ-ECLI (590092307) / SudocSudocFranceF

The impact of early and late literacy on the functional connectivity of vision and

Introduction: Learning to read leads to functional and structural changes in the cortical regions related to vision and language. The visual word-form area (VWFA) is though to play a key role in the interaction between these two systems (Dehaene et al. 2015). For instance, the VWFA is activated not only from bottom-up during reading but also in a top-down manner during speech listening without visual stimulation (Dehaene et al. 2010). The objective of this study was twofolded: how literacy acquisition affects four intrinsic functional connectivity networks related to vision and language (a dorsal language [DLN], a bilateral auditory [AN], a low-level [LLVN] and a high-level visual [HLVN] networks); and to explore the role of the VWFA as an interface between high-level vision and language functions. Methods: Independent component analysis (ICA) was applied to functional magnetic resonance imaging data from 40 adult participants with variable levels of literacy (illiterate, late literate and early literate). The four functional connectivity networks were compared across groups using dual-regression (Filippini et al. 2009). In addition, we directly explored the functional connectivity between the VWFA and each of the studied networks. Finally, the strengh of connectivity between the VWFA and each network was compared across groups and correlated with individual reading fluency scores. Results: ICA produced 40 networks, and spatial crosscorrelation was used to identify the four networks of interest. Literacy was positively correlated with increased connectivity within the four networks. A major difference separating early literate from illiterate and late literate subjects was found. The connectivity between the VWFA and the DLN increased with literacy. Conversely, the strength of connectivity between the VWFA and the HLVN correlated negatively with literacy. Finally, , the HLVN-VWFA connectivity was negatively correlated with reading scores while the connectivity between the DLN-VWFA was positively correlated with reading scores. Discussion:Literacy has a strong influence on the visual and language functional networks. Literacy modifies the VWFA connectivity, by making it functionally closer to the language system, and more distinct from other associative visual areas that do not contribute to the reading process. The current results suggest that early acquisition of literacy plays a critical role for the tuning of the functional brain architecture. References: -Dehaene S et al. Nat Rev Neurosci.(2015)16:234 244 -Dehaene S et al. Science.(2010)330:1359–1364 -Filippini N et al. PNAS.(2009)106, 7209–7214Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Detection of complete and partial chromosome gains and losses by comparative genomic in situ hybridization

Comparative genomic in situ hybridization (CGH) provides a new possibility for searching genomes for imbalanced genetic material. Labeled genomic test DNA, prepared from clinical or tumor specimens, is mixed with differently labeled control DNA prepared from cells with normal chromosome complements. The mixed probe is used for chromosomal in situ suppression (CISS) hybridization to normal metaphase spreads (CGH-metaphase spreads). Hybridized test and control DNA sequences are detected via different fluorochromes, e.g., fluorescein isothiocyanate (FITC) and tetraethylrhodamine isothiocyanate (TRITC). The ratios of FITC/TRITC fluorescence intensities for each chromosome or chromosome segment should then reflect its relative copy number in the test genome compared with the control genome, e.g., 0.5 for monosomies, 1 for disomies, 1.5 for trisomies, etc. Initially, model experiments were designed to test the accuracy of fluorescence ratio measurements on single chromosomes. DNAs from up to five human chromosome-specific plasmid libraries were labeled with biotin and digoxigenin in different hapten proportions. Probe mixtures were used for CISS hybridization to normal human metaphase spreads and detected with FITC and TRITC. An epifluorescence microscope equipped with a cooled charge coupled device (CCD) camera was used for image acquisition. Procedures for fluorescence ratio measurements were developed on the basis of commercial image analysis software. For hapten ratios 4/1, 1/1 and 1/4, fluorescence ratio values measured for individual chromosomes could be used as a single reliable parameter for chromosome identification. Our findings indicate (1) a tight correlation of fluorescence ratio values with hapten ratios, and (2) the potential of fluorescence ratio measurements for multiple color chromosome painting. Subsequently, genomic test DNAs, prepared from a patient with Down syndrome, from blood of a patient with Tcell prolymphocytic leukemia, and from cultured cells of a renal papillary carcinoma cell line, were applied in CGH experiments. As expected, significant differences in the fluorescence ratios could be measured for chromosome types present in different copy numbers in these test genomes, including a trisomy of chromosome 21, the smallest autosome of the human complement. In addition, chromosome material involved in partial gains and losses of the different tumors could be mapped to their normal chromosome counterparts in CGH-metaphase spreads. An alternative and simpler evaluation procedure based on visual inspection of CCD images of CGH-metaphase spreads also yielded consistent results from several independent observers. Pitfalls, methodological improvements, and potential applications of CGH analyses are discussed

Development of a Darcy- Brinkman model to simulate water flow and tracer transport in a heterogeneous karstic aquifer (Val d'Orléans, France)

International audienceModelling karstic aquifers is problematic because the equation of references (i.e. Darcy) is adapted to describe hydrodynamics of flow in a rock where porosity is low. The modelling of the karstic drains requires to use a macroscopic equation representative of the physics of flows occurring in rock where pores are important in size. To answer this question, our study presents an example of the hydrodynamic model adapted to the karstic aquifer of the Val d'Orléans starting from two equations characterizing the dynamics of the fluids: i) the Darcy law used to describe the hydraulic behaviour of massive limestone, and ii) the equation of Brinkman models the flows in vacuums of big sizes within the karstic drain. In the second objective, the flow equations are coupled with the transport equation to predict the karst properties. The results are tested by using six tracer tests carried out in the Val d'Orléans. The simulations show that the draining permeability ranges from 5 10-6 to 5.5 10-5 m2, the limestone permeability ranges from 8 10-11 to 6 10-10 m2. The dispersivity coefficients in the drains range from 23 to 43 m and in the fractured zone from 1 to 5 m

Experimental observation of the straining field responsible for vortex ring instability

The aim of this work is to show experimentally the straining field responsible for the vortex ring instability. To do so, the velocity field in the neighbourhood of the core is measured with Particle Image Velocimetry. This field is compared with the one coming from theoretical work on a thin vortex ring in an ideal fluid. Theoretical and experimental data fit well. This indicates that the linear phase of the instability is weakly influenced by viscosit