Peristaltic Transport of a Rheological Fluid: Model for Movement of Food Bolus Through Esophagus

Fluid mechanical peristaltic transport through esophagus has been of concern in the paper. A mathematical model has been developed with an aim to study the peristaltic transport of a rheological fluid for arbitrary wave shapes and tube lengths. The Ostwald-de Waele power law of viscous fluid is considered here to depict the non-Newtonian behaviour of the fluid. The model is formulated and analyzed with the specific aim of exploring some important information concerning the movement of food bolus through the esophagus. The analysis has been carried out by using lubrication theory. The study is particularly suitable for cases where the Reynolds number is small. The esophagus is treated as a circular tube through which the transport of food bolus takes places by periodic contraction of the esophageal wall. Variation of different variables concerned with the transport phenomena such as pressure, flow velocity, particle trajectory and reflux are investigated for a single wave as well as for a train of periodic peristaltic waves. Locally variable pressure is seen to be highly sensitive to the flow index `n'. The study clearly shows that continuous fluid transport for Newtonian/rheological fluids by wave train propagation is much more effective than widely spaced single wave propagation in the case of peristaltic movement of food bolus in the esophagus.Comment: Accepted for publication in Applied Mathematics and Mechanics (AMM), Springe

De la crise économique à la critique de la science économique

C’est l’une des singularités de l’« économie » – et pas la moindre de ses complications – que de désigner tout à la fois la science et son objet : l’économie n’est rien d’autre en effet que la science de… l’économie. La définition classique de la discipline économique, entendue comme science de l’allocation optimale des ressources rares, ne change d’ailleurs rien au fait qu’il ne saurait y avoir dans la réalité, non plus que dans la nature, de référent répondant spontanément au nom d’« alloca..

Rick ANDERSON, Scholarly communication. What everyone needs to know®

Rick Anderson est un personnage bien connu des professionnels de l’information et de la communication scientifiques. Lui-même doyen associé (associate dean) à la Willard Marriott Library (Université de Utah), il a occupé durant toute sa carrière différents postes dans le secteur des bibliothèques universitaires, en charge de l’acquisition des ressources et de la gestion des collections, tout en assurant des activités de conseil auprès de grands éditeurs scientifiques. Il doit sa notoriété pub..

De la crise économique à la critique de la science économique

C’est l’une des singularités de l’« économie » – et pas la moindre de ses complications – que de désigner tout à la fois la science et son objet : l’économie n’est rien d’autre en effet que la science de… l’économie. La définition classique de la discipline économique, entendue comme science de l’allocation optimale des ressources rares, ne change d’ailleurs rien au fait qu’il ne saurait y avoir dans la réalité, non plus que dans la nature, de référent répondant spontanément au nom d’« alloca..

Peristaltic Pumping of Blood Through Small Vessels of Varying Cross-section

The paper is devoted to a study of the peristaltic motion of blood in the micro-circulatory system. The vessel is considered to be of varying cross-section. The progressive peristaltic waves are taken to be of sinusoidal nature. Blood is considered to be a Herschel-Bulkley fluid. Of particular concern here is to investigate the effects of amplitude ratio, mean pressure gradient, yield stress and the power law index on the velocity distribution, streamline pattern and wall shear stress. On the basis of the derived analytical expression, extensive numerical calculations have been made. The study reveals that velocity of blood and wall shear stress are appreciably affected due to the non-uniform geometry of blood vessels. They are also highly sensitive to the magnitude of the amplitude ratio and the value of the fluid index.Comment: Accepted for publication in ASME journal of Applied Mechanics. arXiv admin note: text overlap with arXiv:1108.1285v

The Structure of Radiative Shock Waves. IV. Effects of Electron Thermal Conduction

We considered the structure of steady-state radiative shock waves propagating in the partially ionized hydrogen gas with density rho1 = 1e-10 gm/cm^3 and temperature 3000K <= T1 <= 8000K. The radiative shock wave models with electron thermal conduction in the vicinity of the viscous jump are compared with pure radiative models. The threshold shock wave velocity above of which effects of electron thermal conduction become perceptible is of U1=70 km/s and corresponds to the upstream Mach numbers from M1= 6 at T1=8000K to M1=11 at T1=3000K. In shocks with efficient electron heat conduction more than a half of hydrogen atoms are ionized in the radiative precursor, whereas behind the viscous jump the hydrogen gas undergoes the full ionization. The existence of the electron conductive precursor leads to the enhancement of the Lyman continuum flux trapped in the surroundings of the discontinuous jump. For upstream velocities ranged within 70 km/s <= U1 <= 85 km/s the partially ionized hydrogen gas of the radiative precursor undergoes the additional ionization (<= 5%), whereas the total radiave flux emerging from the shock wave increases by 10% <= delta(FRad) <= 25% .Comment: 6 pages, 5 figures, LaTeX, accepted for publication in A

Geometric Mixing, Peristalsis, and the Geometric Phase of the Stomach

Mixing fluid in a container at low Reynolds number - in an inertialess environment - is not a trivial task. Reciprocating motions merely lead to cycles of mixing and unmixing, so continuous rotation, as used in many technological applications, would appear to be necessary. However, there is another solution: movement of the walls in a cyclical fashion to introduce a geometric phase. We show using journal-bearing flow as a model that such geometric mixing is a general tool for using deformable boundaries that return to the same position to mix fluid at low Reynolds number. We then simulate a biological example: we show that mixing in the stomach functions because of the "belly phase": peristaltic movement of the walls in a cyclical fashion introduces a geometric phase that avoids unmixing.Comment: Revised, published versio

A comparison of azimuthal and axial oscillation microfiltration using surface and matrix types of microfilters with a cake-slurry shear plane exhibiting non-Newtonian behaviour

The mode of application of oscillation, axial or azimuthal, did not influence filtration performance, when filtering a calcite mineral with a d32 value of 2.7 µm. The equilibrium flux and deposit thickness correlated with shear stress, regardless of: filter type (metal slotted surface filter or homogeneous sintered filter); and mode of oscillation. Shear stress values up to 240 Pa were used and the particle compact believed to be at, or near, the deposited solids showed non-Newtonian flow behaviour described by the Herschel-Bulkley equation. The shear was computed using Comsol® to model the shear at, and near, the oscillating surface. The peak shear (maximum value) was used in the correlation for flux, which appeared to fit the data well and provide a realistic prediction for sustainable flux using a force balance model. The existence of a yield stress in the compact appeared to limit the internal fouling of the matrix (homogeneous) type of filter, which had a membrane thickness of 8 mm, but did not demonstrate significant internal fouling over time, nor between filtrations. Thus, the results were similar to those obtained for the surface filters, and the resistance to filtration was dominated by the deposit formed