Incorporating Forcing Terms in Cascaded Lattice-Boltzmann Approach by Method of Central Moments

Cascaded lattice-Boltzmann method (Cascaded-LBM) employs a new class of collision operators aiming to improve numerical stability. It achieves this and distinguishes from other collision operators, such as in the standard single or multiple relaxation time approaches, by performing relaxation process due to collisions in terms of moments shifted by the local hydrodynamic fluid velocity, i.e. central moments, in an ascending order-by-order at different relaxation rates. In this paper, we propose and derive source terms in the Cascaded-LBM to represent the effect of external or internal forces on the dynamics of fluid motion. This is essentially achieved by matching the continuous form of the central moments of the source or forcing terms with its discrete version. Different forms of continuous central moments of sources, including one that is obtained from a local Maxwellian, are considered in this regard. As a result, the forcing terms obtained in this new formulation are Galilean invariant by construction. The method of central moments along with the associated orthogonal properties of the moment basis completely determines the expressions for the source terms as a function of the force and macroscopic velocity fields. In contrast to the existing forcing schemes, it is found that they involve higher order terms in velocity space. It is shown that the proposed approach implies "generalization" of both local equilibrium and source terms in the usual lattice frame of reference, which depend on the ratio of the relaxation times of moments of different orders. An analysis by means of the Chapman-Enskog multiscale expansion shows that the Cascaded-LBM with forcing terms is consistent with the Navier-Stokes equations. Computational experiments with canonical problems involving different types of forces demonstrate its accuracy.Comment: 55 pages, 4 figure

Knudsen Effect in a Nonequilibrium Gas

From the molecular dynamics simulation of a system of hard-core disks in which an equilibrium cell is connected with a nonequilibrium cell, it is confirmed that the pressure difference between two cells depends on the direction of the heat flux. From the boundary layer analysis, the velocity distribution function in the boundary layer is obtained. The agreement between the theoretical result and the numerical result is fairly good.Comment: 4pages, 4figure

Profil epidemiologique et anatomo-clinique des malade du centre d'oncologie de Doula:Une analyse sur neuf ans

Les auteurs présentent une étude rétrospective et analytique, sur neuf ans et sept mois (19 juin 1999 au 1er février 2008) réalisée sur les malades reçus en consultation au Centre d’Oncologie de Douala pendant cette période. L’objectif est d’étudier le profil épidémiologique de ces malades, en particulier le sexe, l’âge, et les localisations tumorales observées pour chaque patient. 4775 patients ont été reçus en consultation durant la période d’étude, comprenant 3065 femmes (64%) et 1710 hommes (36%). Les âges varient de un à 90 ans, avec une moyenne de 41,3 ans. La distribution des fréquences selon la localisation montre une très nette prédominance des localisations gynécologiques et mammaires (2151 cas, soit 45,05%), suivies des lymphomes (845 cas, soit 17,7%) puis des sarcomes de Kaposi (720 cas représentant 15% de l’effectif total). Ainsi, sur 840 tumeurs malignes du sein répertoriées, 90 patientes (11%) sont d’emblée métastatiques, et cent patientes (12%) présentent des mastites carcinomateuses très souvent ulcérées. Quatre cents cancers du col utérin sont dénombrés, dont seulement 50 (12,50%) étaient encore à un stade clinique inférieur ou égal au stade II de la FIGO. L’on relève également que sur 720 cas de sarcomes de Kaposi reçus, seulement 10 patients (1 ,40%) étaient indemnes de l’infection à VIH. Des tentatives d’explications sont amorcées, dans la recherche de perspectives porteuses pour l’avenir.MOTS CLES: Epidémiologie-Localisations-Oncologie–Douala–Cameroun

Volumetric formulation of lattice Boltzmann models with energy conservation

We analyze a volumetric formulation of lattice Boltzmann for compressible thermal fluid flows. The velocity set is chosen with the desired accuracy, based on the Gauss-Hermite quadrature procedure, and tested against controlled problems in bounded and unbounded fluids. The method allows the simulation of thermohydrodyamical problems without the need to preserve the exact space-filling nature of the velocity set, but still ensuring the exact conservation laws for density, momentum and energy. Issues related to boundary condition problems and improvements based on grid refinement are also investigated.Comment: 8 figure

Ku70 alleviates neurodegeneration in drosophila models of Huntington's disease

DNA damage accumulates in genome DNA during the long life of neurons, thus DNA damage repair is indispensable to keep normal functions of neurons. We previously reported that Ku70, a critical molecule for DNA double strand break (DSB) repair, is involved in the pathology of Huntington's disease (HD). Mutant huntingtin (Htt) impaired Ku70 function via direct interaction, and Ku70 supplementation recovered phenotypes of a mouse HD model. In this study, we generate multiple Drosophila HD models that express mutant huntingtin (Htt) in eye or motor neuron by different drivers and show various phenotypes. In such fly models, Ku70 co-expression recovers lifespan, locomotive activity and eye degeneration. In contrast, Ku70 reduction by heterozygous null mutation or siRNA-mediated knock down accelerates lifespan shortening and locomotion disability. These results collectively support that Ku70 is a critical mediator of the HD pathology and a candidate therapeutic target in HD