Search results for "Velocity"

A velocity–diffusion method for a Lotka–Volterra system with nonlinear cross and self-diffusion

2009

The aim of this paper is to introduce a deterministic particle method for the solution of two strongly coupled reaction-diffusion equations. In these equations the diffusion is nonlinear because we consider the cross and self-diffusion effects. The reaction terms on which we focus are of the Lotka-Volterra type. Our treatment of the diffusion terms is a generalization of the idea, introduced in [P. Degond, F.-J. Mustieles, A deterministic approximation of diffusion equations using particles, SIAM J. Sci. Stat. Comput. 11 (1990) 293-310] for the linear diffusion, of interpreting Fick's law in a deterministic way as a prescription on the particle velocity. Time discretization is based on the …

Gamma Vel cluster membership and IMF

2016

Understanding the properties of young open clusters, such as the Initial Mass Function (IMF), star formation history and dynamic evolution, is crucial to obtain reliable theoretical predictions of the mechanisms involved in the star formation process. We want to obtain a list, as complete as possible, of confirmed members of the young open cluster Gamma Velorum, with the aim of deriving general cluster properties such as the IMF. We used all available spectroscopic membership indicators within the Gaia-ESO public archive together with literature photometry and X-ray data and, for each method, we derived the most complete list of candidate cluster members. Then, we considered photometry, gra…

Experimental investigation on the “horizontal” turbulence and the bed deformation: preliminary results

2005

The application of the photoacoustic transmittance oscillations for determining elastic constants in gallium and indium selenides

1996

Transmittance periodic oscillations are observed in GaSe and InSe on excitation with optical pulses. Such oscillations are explained in terms of photoacoustic generation of dilatational waves, which become resonant within the crystal. Spectral analysis of those oscillations in samples of different thickness has led to an accurate determination of the longitudinal acoustic‐wave velocity along the crystallographic axis c. Julio.Pellicer@uv.es ; Chantal.Ferrer@uv.es ; Vicente.Munoz@uv.es

Oxygen diffusion in tissues supplied by capillaries.

1968

(1968). Oxygen Diffusion in Tissues Supplied by Capillaries. Scandinavian Journal of Clinical and Laboratory Investigation: Vol. 21, No. sup102, pp. II-B-II-B.

Automated Measurement of Microcirculatory Blood Flow Velocity in Pulmonary Metastases of Rats

2014

Because the lung is a major target organ of metastatic disease, animal models to study the physiology of pulmonary metastases are of great importance. However, very few methods exist to date to investigate lung metastases in a dynamic fashion at the microcirculatory level, due to the difficulty to access the lung with a microscope. Here, an intravital microscopy method is presented to functionally image and quantify the microcirculation of superficial pulmonary metastases in rats, using a closed-chest pulmonary window and automated analysis of blood flow velocity and direction. The utility of this method is demonstrated to measure increases in blood flow velocity in response to pharmacologi…

Assessment of the fundamental flexural guided wave in cortical bone by an ultrasonic axial-transmission array transducer

2013

Abstract The fundamental flexural guided wave (FFGW), as modeled, for example, by the A0 Lamb mode, is a clinically useful indicator of cortical bone thickness. In the work described in this article, we tested so-called multiridge-based analysis, based on the crazy climber algorithm and short-time Fourier transform, for assessment of the FFGW component recorded by a clinical array transducer featuring a limited number of elements. Methods included numerical finite-element simulations and experiments in bone phantoms and human radius specimens ( n  = 41). The proposed approach enabled extraction of the FFGW component and determination of its group velocity. This group velocity was in good ag…

Immune-inflammatory markers and arterial stiffness indexes in subjects with acute ischemic stroke with and without metabolic syndrome.

2014

Objective: The aim of our study was to evaluate the associations between arterial stiffness indexes and immune-inflammatory markers in subjects with acute ischemic stroke with and without metabolic syndrome. Materials/Methods: We enrolled 130 patients with acute ischemic stroke and metabolic syndrome, 127 patients with acute ischemic stroke without metabolic syndrome and 120 control subjects without acute stroke. Applanation tonometry was used to record the augmentation index (Aix) and pulse wave velocity (PWV). We also evaluated plasma levels of C-reactive protein (CRP), Interleukin-1beta (IL-1β), tumor necrosis factor-alpha (TNF-α), Interleukin-6 (IL-6) and Interleukin-10 (IL-10), E-selec…

The Effect of Tomography Imaging Artefacts on Structural Analysis and Numerical Permeability Simulations

2011

Fluid flow phenomena in porous materials can be found in many important processes in nature and in society. In particular, fluid flow through a porous medium contribute to several technological problems, e.g. extraction of oil or gas from porous rocks, spreading of contaminants in fluid-saturated soils and certain separation processes, such as filtration (Torquato, 2001). In paper and wood industry single and multi phase fluid flow properties in porous media play important roles related to manufacturing process and product development. The general laws describing creeping fluid flows are well known. However, a detailed study of fluid flow in porous heterogeneous media is complicated. This i…

Untersuchungen �ber eine akute Wirkung von Trijodthyronin auf Refrakt�rzeit und Leitungsgeschwindigkeit des Meerschweinchenvorhofs

1962

Es wird uber die Untersuchung einer akuten Wirkung von T3 in vitro auf die Refraktarperiode und die Leitungsgeschwindigkeit des Meerschweinchenvorhofs berichtet. T3 verkurzte die Refraktarzeit geringfugig (5,2%). Bei vermindertem K-Gehalt der Badlosung oder nach Vorgabe von ACh oder DNP trat die Verkurzung der Refraktarzeit unter T3 wesentlich deutlicher in Erscheinung, und es konnte Flimmern ausgelost werden, obwohl die Substanzen vor der Gabe von T3 vollstandig ausgespult waren. Adrenalin hatte keinen Einflus auf den T3-Effekt. Die Leitungsgeschwindigkeit wurde durch T3 nicht verandert.