INTRODUCTION Some types of antenatal maternal psychological distress may be associated with reduced fetal growth and birthweight. A stress-mediated reduction in placental blood flow has been suggested as a mechanism. Previous studies have examined this using ultrasound-derived arterial resistance measures in the uterine (UtA) and umbilical (UA) arteries, with mixed conclusions. However, a reduc...

Vegetation growing in the water along rivers has been the subject of several studies since it was recognized that it could have a significant impact on the water flow. It may increases resistance to flow and causes higher water levels. Also, it has affects on the turbulent structure such as the mean velocity profiles. For flow of water through emergent vegetation, previous investigations show d...

Flow resistance was measured as bovine and primate aqueous humor was passed through Nuclepore polycarbonate filters having flow dimensions similar to those found within the juxtacanalicular meshwork of the aqueous outflow network. The results indicate that aqueous humor has a greater flow resistance than isotonic saline; this greater resistance is attributable to proteins or glycoproteins in aq...

The possibility that norepinephrine (NE) influences lymphoid cell outflow independently of its vasoconstrictor action was investigated in the perfused rat spleen. Using agents that affect the vasoconstrictor tonus of the spleen, we observed an inverse correlation between flow resistance and splenic cell output. The curve obtained served as a reference for evaluating effects of different treatme...

BACKGROUND Few studies have examined the time-course of localized exercise training on regional blood flow in humans. The study examined the influence of handgrip exercise training on forearm reactive hyperemic blood flow and vascular resistance in apparently healthy men. METHODS Forearm blood flow and vascular resistance were evaluated, in 17 individuals [Age: 22.6 +/- 3.5], in both arms, at...

TVFUMEROUS studies have been published •*• ^ on the effect of heart rate and various drugs on coronary flow. It has not been possible to estimate the relative importance of changes in intravaseular and extravascular resistance in determining the observed alterations in coronary flow. Recently, Sabiston and Gregg suggested that in a heart in which coronary arteries were perfused at constant pres...

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...

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 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...

Dry powder inhalers (DPIs) are widely and increasingly used in clinical practice because they represent a substantial advancement in inhalation technology. The effectiveness of a powdered drug to inhale depends on the inspiratory flow rate generated by the patient and on the turbulence produced by the intrinsic resistance of the DPI. While the inspiratory flow is variable with the patient's abi...