The physical habitat that controls ecosystem functioning is determined by local hydraulics and channel morphology. Hydraulic field studies were conducted in a boreal stream 1) to test the hypothesis that the local hydraulic conditions are determined by cross-sectional geometry and flow resistance in boreal conditions by analysing the relationship between flow velocities, cross-sectional geometr...

The flow-resistive characteristics of a variety of commercially available expiratory positive-pressure valve systems used to provide continuous positive airway pressure (CPAP) and positive end-expiratory pressure were evaluated. One flow-resistor and seven threshold-resistor expiratory pressure valve systems were set at 5, 10, 15, 20, and 25 cm H2O of expiratory pressure, and sinusoidal exhaled...

Alterations of pressure, flow, and resistance to flow in peripheral vascular beds occur frequently and are often grave (5). Because of technical difficulties, however, pressure and flow are infrequently measured and resistance is rarely calculated. As a result, certain facets of the alterations continue to provoke controversy. The exact site of the increase in peripheral resistance in essential...

The unicellular conifer tracheid should have greater flow resistance per length (resistivity) than the multicellular angiosperm vessel, because its high-resistance end-walls are closer together. However, tracheids and vessels had comparable resistivities for the same diameter, despite tracheids being over 10 times shorter. End-wall pits of tracheids averaged 59 times lower flow resistance on an...

In this paper the rapidly varied unsteady flow caused by the failure of a dam in a rectangular dry bed horizontal channel has been studied both theoretically and experimentally. Experiments with dam-break flows in smooth and rough channel have been carried out. Comparisons have been made between measured depth hydrographs at different stations along the channel and analytical solution of Ritter...

Accurate assessment of gestational age, fetal growth, and the detection of fetal and placental abnormalities are major benefits of sonography. Color Doppler can be used to assist in the identification of vascular architecture, detection of vascular pathology and visualization of blood flow changes associated with physiologic processes and disease states. The clinical applications of obstetrical...

To test the hypothesis that, in response to an increase in placental vascular resistance and progressive fetal asphyxia, the changes in external carotid blood flow waveforms are directly related to changes in external carotid vascular resistance, we embolized the fetal side of the placenta in pregnant sheep and measured cerebral and external carotid artery circulatory changes in relation to cha...

The purpose of the present study was to determine the effect of a spinal cord injury (SCI) on resting vascular resistance in paralyzed legs in humans. To accomplish this goal, we measured blood pressure and resting flow above and below the lesion (by using venous occlusion plethysmography) in 11 patients with SCI and in 10 healthy controls (C). Relative vascular resistance was calculated as mea...