Spanwise structure of wall pressure on a cylinder in axial flow

The spanwise structure of wall pressure fluctuations was measured in an axtisymmetric turbulent boundary layer on a cylinder parallel to the mean flow at a momentum thickness Reynolds number of 2530 and a boundary layer thickness to cylinder radius ratio of 4.81. The measurements were made using miniature hearing aid type condenser microphones with spanwise separations of 0?, 10?, 20?, 30?, 60?, and 90?. An improved wall pressure power spectrum was obtained at low frequencies by utilizing a two-point subtraction method to remove low frequency acoustic background noise of the wind tunnel. The spanwise correlations indicate that the spanwise coherent length of the wall pressure is 30? (78v/u? or 0.11?). The spanwise coherence is weak and concentrated in a frequency band that is substantially lower than the most energetic frequency band of the wall pressure spectrum. A mode number-frequency decomposition of the wall pressure spectrum indicates that the greatest quantity of energy is in the circumferential modes nearest zero. Modes -4 to 4 contain most of the wall pressure energy. Conditional sampling by pressure peak and VITA detection schemes (where VITA was applied to wall pressure to detect strong pressure gradient events) indicate that the spanwise extent of the high pressure peaks and high wall pressure gradients is 60? (156v/u? or 0.22?

Decreased activation along the dorsal visual pathway after a 3-month treatment with Galantamine in mild Alzheimer\u27s disease

Visual perception has been shown to be altered in Alzheimer?s disease (AD) patients and it is associated with decreased cognitive function. Galantamine is an active cholinergic agent, which has been shown to lead to improved cognition in mild to moderate AD patients. This study examined brain activation in a group of mild AD patients after a 3 month open-label treatment with galantamine. The objective was to examine the changes in brain activation due to treatment. There were two tasks to visual perception. The first task was a face matching task to test the activation along the ventral visual pathway and the second task was a location matching task, to test neuronal function along the dorsal pathway. Brain activation was measured using functional magnetic resonance imaging. There were 5 mild AD patients in the study. There were no differences in task performance and in the cognitive scores of the CERAD battery before and after treatment. In the location matching task, we found a statistically significant decrease in activation along the dorsal visual pathway after galantamine treatment. A previous study found that AD patients had higher activation in the location matching task compared to healthy controls. There were no differences in activation for the face matching task after treatment. Our data indicate that treatment with galantamine leads to more efficient visual processing of stimuli or changes the compensatory mechanism in the AD patients. A visual perception task recruiting the dorsal visual system may be useful as a biomarker of treatment effects