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S R Bussolari

Publications and source records attributed to S R Bussolari.

8 recordsLinked to original sources
PubMed1992

The distribution of fluid forces on model arterial endothelium using computational fluid dynamics.

Numerical calculations are used in conjunction with linear perturbation theory to analyze the problem of laminar flow of an incompressible fluid over a wavy surface which approximates a monolayer of vascular endothelial cells. These calculations model flow conditions in an artery very near the vessel wall at any instant in time, providing a description of the velocity field with detail that would be difficult to identify experimentally. The surface pressure and shear stress distributions are qualitatively similar for linear theory and numerical computations. However, the results diverge as the amplitude of surface undulation is increased. The shear stress gradient along the cell model surface is reduced for geometries which correspond to aligned endothelial cells (versus nonaligned geometries).

Arteries↗
PubMed1990

Dual-task performance on an interactive human/computer space shuttle flight experiment.

INTRODUCTION: This paper details ground-based results of the Mental Workload and Performance Experiment (MWPE) which examines human performance for cognitive decision-making and eye-hand-coordinated motor tasks. MWPE is manifest on the International Microgravity Laboratory (IML-1) Space Shuttle Mission and is scheduled to fly in December of 1990. The MWPE protocol combines a Sternberg memory search with a Fitts' target acquisition resulting in a "Fittsberg" dual-task paradigm. The purpose of this study was to evaluate the serial execution theory underlying the Fittsberg dual-task paradigm. METHODS: A total of nineteen subjects performed two experimental test batteries. Unusual body dynamics were imposed on subjects in order to assess altered environment performance. In the first test battery, subjects performed experiments in either the upright postural orientation or the supine (recumbent) postural orientation. During the second test battery, an altered environment was electronically created by introducing a first-order lag characteristic between the graphic input device and the computer. Performance and workload were evaluated by reaction time, movement time, and subjective rating measurements for the dual-task paradigm. RESULTS: The major contributors to reaction and movement times are as predicted by Sternberg and Fitts, however, there are many other influences not accounted for by the classical models. For MWPE, interdependence among the memory set size and index of difficulty experimental variables is in conflict with the serial execution assumption of the Fittsberg dual-task paradigm. CONCLUSIONS: When interaction among variables exists, the dual-task paradigm can not simply be modeled as a Sternberg memory task plus a Fitts target acquisition, rather, new performance metrics for the memory search and target acquisition tasks require that all the significant variables in the MWPE protocol be modeled. The interdependence among variables hints that the operator incorporates some degree of parallel processing rather than exclusively performing in a serial manner.

Humans↗
PubMed1989

Flight simulator platform motion and air transport pilot training.

The influence of flight simulator platform motion on pilot training and performance was examined in two studies utilizing a B-727-200 aircraft simulator. The simulator, located at Ames Research Center, is certified by the FAA for upgrade and transition training in air carrier operations. Subjective ratings and objective performance of experienced B-727 pilots did not reveal any reliable effects of wide variations in platform motion design. Motion platform variations did, however, affect the acquisition of control skill by pilots with no prior heavy aircraft flying experience. The effect was limited to pitch attitude control inputs during the early phase of landing training. Implications for the definition of platform motion requirements in air transport pilot training are discussed.

Adult↗
PubMed1984

Influence of hemodynamic forces on vascular endothelial function. In vitro studies of shear stress and pinocytosis in bovine aortic cells.

The relationships between fluid shear stress, a physiologically relevant mechanical force in the circulatory system, and pinocytosis (fluid-phase endocytosis) were investigated in cultured bovine aortic endothelial cells using a specially designed apparatus. Continuous exposure to steady shear stresses (1-15 dyn/cm2) in laminar flow stimulated time- and amplitude-dependent increases in pinocytotic rate which returned to control levels after several hours. After 48 h continuous exposure to steady shear stress, removal to static conditions also resulted in a transient increase in pinocytotic rate, suggesting that temporal fluctuations in shear stress may influence endothelial cell function. Endothelial pinocytotic rates remained constant during exposure to rapidly oscillating shear stress at near physiological frequency (1 Hz) in laminar flow. In contrast, however, a sustained elevation of pinocytotic rate occurred when cells were subjected to fluctuations in shear stress amplitude (3-13 dyn/cm2) of longer cycle time (15 min), suggesting that changes in blood flow of slower periodicity may influence pinocytotic vesicle formation. As determined by [3H]thymidine autoradiography, neither steady nor oscillating shear stress stimulated the proliferation of confluent endothelial cells. These observations indicate that: (a) alterations in fluid shear stress can significantly influence the rate of formation of pinocytotic vesicles in vascular endothelial cells, (b) this process is force- and time-dependent and shows accommodation, (c) certain patterns of fluctuation in shear stress result in sustained elevation of pinocytotic rate, and (d) shear stresses can modulate endothelial pinocytosis independent of growth stimulation. These findings are relevant to (i) transendothelial transport and the metabolism of macromolecules in normal endothelium and (ii) the role of hemodynamic factors in the localization of atherosclerotic lesions in vivo.

Animals↗
PubMed1981

The dynamic response of vascular endothelial cells to fluid shear stress.

We have developed an in-vitro system for studying the dynamic response of vascular endothelial cells to controlled levels of fluid shear stress. Cultured monolayers of bovine aortic endothelial cells are placed in a cone-plate apparatus that produces a uniform fluid shear stress on replicate samples. Subconfluent endothelial cultures continuously exposed to 1-5 dynes/cm2 shear proliferate at a rate comparable to that of static cultures and reach the same saturation density (congruent to 1.0-1.5 X 10(5) cells/cm2). When exposed to a laminar shear stress of 5-10 dynes/cm2, confluent monolayers undergo a time-dependent change in cell shape from polygonal to ellipsoidal and become uniformly oriented with flow. Regeneration of linear "wounds" in confluent monolayer appears to be influenced by the direction of the applied force. Preliminary studies indicate that certain endothelial cell functions, including fluid endocytosis, cytoskeletal assembly and nonthrombogenic surface properties, also are sensitive to shear stress. These observations suggest that fluid mechanical forces can directly influence endothelial cell structure and function. Modulation of endothelial behavior by fluid shear stresses may be relevant to normal vessel wall physiology, as well as the pathogenesis of vascular diseases, such as atherosclerosis.

Animals↗