This paper is concerned with the simultaneous flow of liquid water and gaseous reactants in mini-channels of a proton exchange membrane PEM) fuel cell. Envisaging the mini-channels as structured and ordered porous media, we develop a continuum model of two-phase channel ow based on two-phase Darcy’s law and the M2 formalism, which allow estimate of the parameters key to fuel cell operation such...

BACKGROUND Receptor occupancy, or saturation, assays are often utilized in preclinical and clinical development programs to evaluate the binding of a biologic to a cellular target. These assays provide critical information regarding the dose of drug required to "saturate" the target as well as important pharmacodymamic (PD) data. A flow cytometric method was developed to measure the degree of S...

An important feature of tumor hypoxia is its temporal instability, or "cycling hypoxia." The primary consequence of cycling hypoxia is increased tumor aggressiveness and treatment resistance beyond that of chronic hypoxia. Longitudinal imaging of tumor metabolic demand, hemoglobin oxygen saturation, and blood flow would provide valuable insight into the mechanisms and distribution of cycling hy...

mean values for Po2 of 58, 60, and 72 mm Hg, respectively, were found for the three groups. When the same patients breathed oxygen via a nasal cannula or face mask at flow rates of 8 to 12 L/min, values were 106, 128, and 160 mm Hg, respectively. In all instances hemoglobin saturation values in excess of 95% were obtained when the patient breathed oxygen. In 15 patients measurements of the oxyg...

A novel noninvasive magnetic resonance imaging (MRI) method was developed to determine in vivo blood oxygen saturation and its changes during motor cortex activation in small cerebral veins. Specifically, based on susceptibility measurements in the resting states, pial veins were found to have a mean oxygen saturation of Yrest=0.544+/-0.029 averaged over 14 vessels in 5 volunteers. During activ...

The Flow through saturated-unsaturated porous media is extremely important in various natural and industrial based applications. While the Darcy's law with various modifications are used to model the flow through a porous media, the flow through unsaturated porous media is largely based on conservation of mass and modified Darcy's law where non-linear relationship exists between the p...

The aim of this study was to determine whether it is possible using ear-oximetry to prescribe the correct oxygen flow rates during exercise in chronic obstructive pulmonary disease (COPD) patients on long-term oxygen therapy (LTOT). Twenty COPD patients on LTOT, with exercise desaturation breathing oxygen at resting flow rates, performed a series of 6-min treadmill walking tests, with a progres...

RATIONALE Impaired endothelium-dependent vasodilation has been documented in patients with sleep apnea. This impairment may result in blood flow dysregulation during apnea-induced fluctuations in arterial blood gases. OBJECTIVES To test the hypothesis that hypoxic and hypercapnic vasodilation in the forearm and cerebral circulation are impaired in patients with sleep apnea. METHODS We expos...

Abstract A finite element method with mass-lumping and flux upwinding is formulated for solving the immiscible two-phase flow problem in porous media. The approximates directly wetting phase pressure saturation, which are primary unknowns. discrete saturation satisfies a maximum principle. Stability of scheme existence solution established.

The purpose of this study was to determine whether chronic fatigue syndrome (CFS) is associated with reduced blood flow and muscle oxidative metabolism. Patients with CFS according to Centers for Disease Control criteria (n = 19) were compared with normal sedentary subjects (n = 11). Muscle blood flow was measured in the femoral artery with Doppler ultrasound after exercise. Muscle metabolism w...