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The Numerical Design Of A Parallel Plate Flow Chamber For Investigation Of Endothelial Cell Response To Shear Stress, Bong Jae Chung, A. M. Robertson, D. G. Peters May 2003

The Numerical Design Of A Parallel Plate Flow Chamber For Investigation Of Endothelial Cell Response To Shear Stress, Bong Jae Chung, A. M. Robertson, D. G. Peters

Department of Applied Mathematics and Statistics Faculty Scholarship and Creative Works

Parallel plate chambers are frequently used to examine the response of biological cells to a constant wall shear stress. However, the stress can vary more than 80% across the chamber due to end effects. Earlier estimates of the magnitude of this inhomogeneity used boundary layer theory and experiments. Here, the full equations for steady, three-dimensional flow in a novel parallel plate device were solved numerically and used to identify an active test region where the shear stress is within 5% of a constant value. Endothelial cells can be confined to this region to assure a nearly uniform shear stress exposure.


Noise-Induced Unstable Dimension Variability And Transition To Chaos In Random Dynamical Systems, Ying-Cheng Lai, Zonghua Liu, Lora Billings, Ira B. Schwartz Feb 2003

Noise-Induced Unstable Dimension Variability And Transition To Chaos In Random Dynamical Systems, Ying-Cheng Lai, Zonghua Liu, Lora Billings, Ira B. Schwartz

Department of Mathematics Facuty Scholarship and Creative Works

Results are reported concerning the transition to chaos in random dynamical systems. In particular, situations are considered where a periodic attractor coexists with a nonattracting chaotic saddle, which can be expected in any periodic window of a nonlinear dynamical system. Under noise, the asymptotic attractor of the system can become chaotic, as characterized by the appearance of a positive Lyapunov exponent. Generic features of the transition include the following: (1) the noisy chaotic attractor is necessarily nonhyperbolic as there are periodic orbits embedded in it with distinct numbers of unstable directions (unstable dimension variability), and this nonhyperbolicity develops as soon …


Cross-Modal Enhancement Of Perceived Brightness: Sensory Interaction Versus Response Bias, Yoav Arieh, Lawrence E. Marks, Eric C. Odgaard Jan 2003

Cross-Modal Enhancement Of Perceived Brightness: Sensory Interaction Versus Response Bias, Yoav Arieh, Lawrence E. Marks, Eric C. Odgaard

Department of Psychology Faculty Scholarship and Creative Works

Stein, London, Wilkinson, and Price (1996) reported the presence of cross-modal enhancement of perceived visual intensity: Participants tended to rate weak lights as brighter when accompanied by a concurrent pulse of white noise than when presented alone. In the present study, two methods were used to determine whether the enhancement reflects an early-stage sensory process or a later-stage decisional process, such as a response bias. First, the enhancement was eliminated when the noise accompanied the light on only 25% versus 50% of the trials. Second, the enhancement was absent when tested with a paired-comparison method. These findings are consistent with …