The Influence of Large Prestrains on Dynamic Properties of Sand

The development of the UMR Resonant Column/Torsional simple Shear device has provided the means to evaluate high and low amplitude shear moduli on a single sand specimen. Results of cyclic torsional simple shear tests showed that progressive strain increases w1th the cyclic strain amplitude and the number of cycles and decreases with density of the sand. Large accumulated prestrains were found to decrease the maximum dynamic shear modulus by 30 to 35%

Encoded and updated spatial working memories share a common representational format in alpha activity

Working memory (WM) flexibly updates information to adapt to the dynamic environment. Here, we used alpha-band activity in the EEG to reconstruct the content of dynamic WM updates and compared this representational format to static WM content. An inverted encoding model using alpha activity precisely tracked both the initially encoded position and the updated position following an auditory cue signaling mental updating. The timing of the update, as tracked in the EEG, correlated with reaction times and saccade latency. Finally, cross-training analyses revealed a robust generalization of alpha-band reconstruction of WM contents before and after updating. These findings demonstrate that alpha activity tracks the dynamic updates to spatial WM and that the format of this activity is preserved across the encoded and updated representations. Thus, our results highlight a new approach for measuring updates to WM and show common representational formats during dynamic mental updating and static storage

Seismic Evaluation of the US41 Southbound Bridge over the Ohio River at Henderson, KY

This report presents the seismic evaluation of the US41 Southbound bridge over the Ohio River connecting Evansville, Indiana and Henderson, Kentucky. The main bridge is a four-span cantilever through-truss type. The approach bridge has 9 spans on the Evansville, IN side and 20 spans on the Henderson, side. Although this bridge has not yet been subjected to a moderate or major earthquake, it is situated within the influence of the New Madrid and Wabash Valley Seismic Zones. The seismic evaluation program consisted of field testing and seismic response analysis. The modal properties of the main bridge were determined through field testing, and were used to calibrate a three dimensional finite element model. The finite element model was then subjected to the acceleration time histories of the 50-year earthquake event. Stresses and displacements due to projected earthquakes are found to be very low. Analytical results indicate that the main bridge superstructure will survive the projected 50-year earthquake without any damage and no loss-of-span. However, all the supports on the piers of the main bridge require additional anchor bolts or seismic isolation bearings. The Kentucky and Indiana approach spans are analyzed using the response spectrum method with simplified single-degree-of-freedom models. Ten out of twelve supports having fixed bearings on both the approach spans require additional anchor bolts or seismic isolation bearings. At three out of twenty-five supports having expansion bearings, the existing rocker bearings need to be replaced with elastomeric bearings or cable restrainers need to be provided to avoid loss-of-span

Seismic Evaluation of the US41 Northbound Bridge over the Ohio River at Henderson, KY

This report presents the seismic evaluation of the US41 Northbound bridge over the Ohio River connecting Evansville, Indiana and Henderson, Kentucky. The main bridge is a four-span cantilever through-truss type. The approach bridge has 8 spans on the Evansville, IN side and 35 spans on the Henderson, KY side. Although this bridge has not yet been subjected to a moderate or major earthquake, it is situated within the influence of the New Madrid and Wabash Valley Seismic Zones. The seismic evaluation program consisted of field testing and seismic response analysis. The modal properties of the main bridge were determined through field testing, and were used to calibrate a three dimensional finite element model. The finite element model was then subjected to time histories of the 50-year earthquake event. Stresses and displacements obtained were found to be within the acceptable limits. Analytical results indicate that the superstructure of the main bridge will survive the projected 50-year earthquake without any damage and no loss-of-span. However, all supports on the piers of the main bridge require additional anchor bolts or seismic isolation bearings. The approach spans were analyzed using response spectrum method with simplified single-degree-of-freedom models. Thirteen out of forty-two supports having fixed bearings on both the Kentucky and Indiana approach spans require additional anchor bolts at the fixed bearings or seismic isolation bearings

Mapping effective connectivity in the human brain with concurrent intracranial electrical stimulation and BOLD-fMRI

Background: Understanding brain function requires knowledge of how one brain region causally influences another. This information is difficult to obtain directly in the human brain, and is instead typically inferred from resting-state fMRI. New method: Here, we demonstrate the safety and scientific promise of a novel and complementary approach: concurrent electrical stimulation and fMRI (es-fMRI) at 3 T in awake neurosurgical patients with implanted depth electrodes. Results: We document the results of safety testing, actual experimental setup, and stimulation parameters, that safely and reliably evoke activation in distal structures through stimulation of amygdala, cingulate, or prefrontal cortex. We compare connectivity inferred from the evoked patterns of activation with that estimated from standard resting-state fMRI in the same patients: while connectivity patterns obtained with each approach are correlated, each method produces unique results. Response patterns were stable over the course of 11 min of es-fMRI runs. Comparison with existing method: es-fMRI in awake humans yields unique information about effective connectivity, complementing resting-state fMRI. Although our stimulations were below the level of inducing any apparent behavioral or perceptual effects, a next step would be to use es-fMRI to modulate task performances. This would reveal the acute network-level changes induced by the stimulation that mediate the behavioral and cognitive effects seen with brain stimulation. Conclusions: es-fMRI provides a novel and safe approach for mapping effective connectivity in the human brain in a clinical setting, and will inform treatments for psychiatric and neurodegenerative disorders that use deep brain stimulation

Mapping effective connectivity in the human brain with concurrent intracranial electrical stimulation and BOLD-fMRI

Background: Understanding brain function requires knowledge of how one brain region causally influences another. This information is difficult to obtain directly in the human brain, and is instead typically inferred from resting-state fMRI. New method: Here, we demonstrate the safety and scientific promise of a novel and complementary approach: concurrent electrical stimulation and fMRI (es-fMRI) at 3 T in awake neurosurgical patients with implanted depth electrodes. Results: We document the results of safety testing, actual experimental setup, and stimulation parameters, that safely and reliably evoke activation in distal structures through stimulation of amygdala, cingulate, or prefrontal cortex. We compare connectivity inferred from the evoked patterns of activation with that estimated from standard resting-state fMRI in the same patients: while connectivity patterns obtained with each approach are correlated, each method produces unique results. Response patterns were stable over the course of 11 min of es-fMRI runs. Comparison with existing method: es-fMRI in awake humans yields unique information about effective connectivity, complementing resting-state fMRI. Although our stimulations were below the level of inducing any apparent behavioral or perceptual effects, a next step would be to use es-fMRI to modulate task performances. This would reveal the acute network-level changes induced by the stimulation that mediate the behavioral and cognitive effects seen with brain stimulation. Conclusions: es-fMRI provides a novel and safe approach for mapping effective connectivity in the human brain in a clinical setting, and will inform treatments for psychiatric and neurodegenerative disorders that use deep brain stimulation