On The Fluid Dynamics of Virtual Impaction and The Design of a Slit Aerosol Sampler

It has been long established that Reynolds number effects can lead to flow instabilities and/or transition from laminar to turbulent flow regimes. The nature of free shear jets is well understood and heavily covered in the fluid mechanics literature. On the other hand, the study of confined nozzles presents some challenges and is still a developing area of research. In this work, we focus on quasi-impinging jets, such as the ones feeding into a virtual impactor. Virtual impactors are popular, inexpensive aerosol collection devices capable of separating airborne solid particles. Recently they found increased application in areas that require concentration of dilute aerosols, such as biological-laden flows. In essence, this research is motivated by the need to fundamentally understand the fluid-particle interaction mechanisms entailed during virtual impaction. To this end, we rely on theoretical insight gained by numerical analysis of the classical equations within a one-way coupled Lagrangian framework. In the first part of this investigation we perform a direct transient simulation of the two-dimensional incompressible Navier-Stokes equations for air as the carrier phase. The momentum and continuity equations are solved by FLUENT. The solutions of three separate computations with jet Reynolds numbers equal to 350, 2100, and 3500 are analyzed. The 2-D time-mean results established the nature of the jet potential core and clarifications about the role of the Reynolds number were proposed. Transient analysis deciphered the characteristics of the mirrored Kelvin-Helmholtz instability, along with particle-eddy interaction mechanisms. In the second part we perform a large eddy simulation (LES) on a domain of a real-life sampler. The Lagrangian dynamic residual stress model is implemented and validated for two canonical turbulent flows. The newly contrived code is then applied to the study of a prototype device. A three-dimensional growth mechanism is proposed for the jet mixing layers. The Lagrangian dynamic model LES exhibited significant regions of high subgrid turbulent viscosity, compared to the dynamic Lilly-model simulation, and we were able to identify the origin, and learn the dynamics of five key coherent structures dominant during transition. Comparison with preliminary experimental data for the aerosol separation efficiency showed fairly good agreement

FLUID AND PARTICLE DYNAMICS IN AN AEROSOL VIRTUAL IMPACTOR

The collection and characterization of chemical and biological aerosols is essential to many areas of particle research such as toxicological studies, pollutant sampling, and biohazard assessment. This work presents the simulation of a low cutpoint, high volume aerosol sampling device known as the "virtual impactor". A steady state, three dimensional RANS type calculation is done using the FLUENT(TM) computational fluid dynamics code to predict the turbulent flow field inside the device. Particle collection efficiency and wall losses are then obtained by solving the particle equation of motion governed by drag for mono-dispersed samples of spherical particles in the 0.1-0.4 micro-meter diameter range. Predictions of the mean fluid velocity field with the incompressible Reynolds stress model and the compressible k-epsilon turbulence model are relied upon for conducting particle tracking calculations. FORTRAN 90 computer code is developed to solve the particle equation of motion using an implicit second order accurate time integration scheme. In addition, a multi-variate, scattered point interpolation method is implemented to obtain the fluid velocity at a position away from an Eulerian mesh point. It is found that "adaptive" drag law models are necessary to correctly account for slip and compressibility. The results indicate the trends observed in the experiments, and a 50% cutpoint diameter between 0.250 and 0.275 micro-meter. Recommendations for improved modeling in future work are made

Characterization by ab initio calculations on the physical properties of Yttrium based compounds for thermoelectric applications

La physique des solides joue un rôle important dans la technologie actuelle. Parmi ces matériaux , les semi-conducteurs IIIB-N (ScN, YN, LaN) et leurs mélanges IIIB-IIIB-NA et IIIB-N-VA qui sont basés sur d'Yttrium, ces matériaux ont une efficacité très importante lorsqu'ils sont utilisés dans le développement de nouvelles technologies. De nos jours, les méthodes de types ab initio se révèlent de plus en plus comme étant un outil de choix pour interpréter à l’échelle microscopique les observations . Les propriétés physiques des composés IIIB-N (ScN, YN, LaN) et leurs mélanges IIIB-IIIB-NA et IIIB-N-VA sont calculées par la théorie de la fonctionnelle de la densité (DFT) et la méthode des pseudo potentiels couplés avec les ondes planes (PP-PW) à l'aide du programme CASTEP. Nous avons calculé les propriétés structurales et élastiques (constantes élastiques Cij et Sij, et module d'élasticité : module de compression B, module de cisaillement G, module d'Young E, module de Poisson ν, ainsi que module d'Young, module de Poisson et vitesses de propagation des élastiques longitudinales et transversales ondes selon différentes directions cristallographiques, Calcul de la température de Debye pour Y1-xMxN (Sc = M, La) et YN1-xBx (Sb, As, P = B ), propriétés électroniques (bandes d'énergie, densité d'états total DOS et états partiels TDOS), propriétés optiques (coefficient diélectrique réel ε� et imaginaire ε, indice de réfraction n, coefficient d'extinction k, coefficient d'absorption, réflectivité) et phonon (la courbe de dissipation des phonons et la densité d'états des phonons). Les résultats obtenus sont en bon accord avec les résultats expérimentaux disponibles et les calculs théoriques et d'autre part ce sont des prédictions fiables comme référence

HUILE D’ARGAN UNE PRODUCTION DEVENUE ADULTE

L’huile d’argan est obtenue à partir des amandes écrasées du fruit de l’arganier, un arbre uniquement endémique au Maroc. L’huile d’argan est utilisée en cosmétologie ou comme huile alimentaire. Longtemps préparée de façon artisanale et dans des conditions d’hygiène incertaines, l’huile d’argan est dorénavant préparée selon des normes de qualité sanitaire et réglementaire strictes au sein de coopératives de femmes et d’industriels implantées au milieu de l’arganeraie. Cette huile est maintenant commercialisée dans tous les pays industrialisés où son goût de noisette, spécifique de l’huile d’argan, et sa capacité à prévenir les maladies cardiovasculaires sont particulièrement appréciés

The relationship between the strength of pain and the oral expressions among a sample of nerves patients in Lattakia.

 This study aimed to investigating the relationship between the strength of pain and expressions of pain among a sample of patients with inflammation of the nerves in Lattakia, and to find out the relationship between the strength of pain and sensory expressions of pain, and to find out the relationship between the strength of pain and Emotional expressions of pain. Participants were (40) patient from inflammation of the nerves, The measures of pain were EVA to strength of pain and Saint –Antoine scale to assess pain, and anxiety test as (state and trait), The results showed that there is correlation between the strength of pain and expressions of pain among the members of the sample as a whole, and there are correlation between the strength ofpain and sensory and emotional expressions of pain

Arganier, une énigme en voie d'être résolue : portrait d'une chercheure, Zoubida Charrouf

Version anglaise disponible dans la Bibliothèque numérique du CRDI: Solving pieces of the argan puzzle : researcher profile, Zoubida Charrou

Helping Moroccan women preserve the argan tree at the gateway to the Sahara

French version available in IDRC Digital Library: Femmes assurent la préservation de l'arganeraie aux portes du Sahar

Solving pieces of the Argan puzzle : researcher profile, Zoubida Charrouf

French version available in IDRC Digital Library: Arganier, une énigme en voie d'être résolue : profil d'une chercheuse, Zoubida Charrou

Femmes assurent la préservation de l'arganeraie aux portes du Sahara

Version anglaise disponible dans la Bibliothèque numérique du CRDI : Helping Moroccan women preserve the argan tree at the gateway to the Sahar

Insulin-sensitizing and Anti-proliferative Effects of Argania spinosa Seed Extracts

Argania spinosa is an evergreen tree endemic of southwestern Morocco. Many preparations have been used in traditional Moroccan medicine for centuries to treat several illnesses including diabetes. However, scientific evidence supporting these actions is lacking. Therefore, we prepared various extracts of the argan fruit, namely keel, cake and argan oil extracts, which we tested in the HTC hepatoma cell line for their potential to affect cellular insulin responses. Cell viability was measured by Trypan Blue exclusion and the response to insulin evaluated by the activation of the extracellular regulated kinase (ERK1/2), ERK kinase (MEK1/2) and protein kinase B (PKB/Akt) signaling components. None of the extracts demonstrated significant cytotoxic activity. Certain extracts demonstrated a bi-phasic effect on ERK1/2 activation; low doses of the extract slightly increased ERK1/2 activation in response to insulin, whereas higher doses completely abolished the response. In contrast, none of the extracts had any significant effect on MEK whereas only a cake saponin subfraction enhanced insulin-induced PKB/Akt activation. The specific action of argan oil extracts on ERK1/2 activation made us consider an anti-proliferative action. We have thus tested other transformed cell lines (HT-1080 and MSV-MDCK-INV cells) and found similar results. Inhibition of ERK1/2 activation was also associated with decreased DNA synthesis as evidenced by [(3)H]thymidine incorporation experiments. These results suggest that the products of Argania spinosa may provide a new therapeutic avenue against proliferative diseases