Mantle flow and melting beneath young oceanic lithosphere: Seismic studies of the Galápagos Archipelago and the Juan de Fuca Plate

In this dissertation, I use seismic imaging techniques to constrain the physical state of the upper mantle beneath regions of young oceanic lithosphere. Mantle convection is investigated beneath the Galápagos Archipelago and then beneath the Juan de Fuca (JdF) plate, with a focus on the JdF and Gorda Ridges before turning to the off-axis asthenosphere. In the Galápagos Archipelago, S-to-p receiver functions reveal a discontinuity in seismic velocity that is attributed to the dehydration of the upper mantle. The depth at which dehydration occurs is shown to be consistent with prior constraints on mantle temperature. A comparison between results from receiver functions, seismic tomography and petrology shows that mantle upwelling and melt generation occur shallower than the depth of the discontinuity, despite the expectation of high viscosities in the dehydrated layer. Beneath the JdF and Gorda Ridge, low Vs anomalies are too large to be explained by the cooling of the lithosphere and are attributed to partial melt. The asymmetry, large Vs gradients, and sinuosity of the anomalies beneath the JdF Ridge are consistent with models of buoyancy-driven upwelling. However, deformation zone processes appear to dominate mantle flow over seafloor spreading beneath the Explorer and Gorda diffuse plate boundaries. Finally, S-to-p receiver functions reveal a seismic discontinuity beneath the JdF plate that can only be attributed to seismic anisotropy. Synthesis of the receiver function results with prior SKS splitting results requires heterogeneous anisotropy between the crust and the discontinuity. Models of anisotropy feature increasing anisotropy before the decrease at the discontinuity, but well below the base of the lithosphere, and a clockwise rotation of the fast direction with increasing depth. In these results and even in the SKS splitting results, additional driving mechanisms for mantle flow such as density or pressure anomalies are required

Whole-Body Dynamic Telelocomotion: A Step-to-Step Dynamics Approach to Human Walking Reference Generation

Teleoperated humanoid robots hold significant potential as physical avatars for humans in hazardous and inaccessible environments, with the goal of channeling human intelligence and sensorimotor skills through these robotic counterparts. Precise coordination between humans and robots is crucial for accomplishing whole-body behaviors involving locomotion and manipulation. To progress successfully, dynamic synchronization between humans and humanoid robots must be achieved. This work enhances advancements in whole-body dynamic telelocomotion, addressing challenges in robustness. By embedding the hybrid and underactuated nature of bipedal walking into a virtual human walking interface, we achieve dynamically consistent walking gait generation. Additionally, we integrate a reactive robot controller into a whole-body dynamic telelocomotion framework. Thus, allowing the realization of telelocomotion behaviors on the full-body dynamics of a bipedal robot. Real-time telelocomotion simulation experiments validate the effectiveness of our methods, demonstrating that a trained human pilot can dynamically synchronize with a simulated bipedal robot, achieving sustained locomotion, controlling walking speeds within the range of 0.0 m/s to 0.3 m/s, and enabling backward walking for distances of up to 2.0 m. This research contributes to advancing teleoperated humanoid robots and paves the way for future developments in synchronized locomotion between humans and bipedal robots.Comment: 8 pages, 8 figure

CMB Constraints on Primordial non-Gaussianity from the Bispectrum (f_{NL}) and Trispectrum (g_{NL} and \tau_{NL}) and a New Consistency Test of Single-Field Inflation

We outline the expected constraints on non-Gaussianity from the cosmic microwave background (CMB) with current and future experiments, focusing on both the third (f_{NL}) and fourth-order (g_{NL} and \tau_{NL}) amplitudes of the local configuration or non-Gaussianity. The experimental focus is the skewness (two-to-one) and kurtosis (two-to-two and three-to-one) power spectra from weighted maps. In adition to a measurement of \tau_{NL} and g_{NL} with WMAP 5-year data, our study provides the first forecasts for future constraints on g_{NL}. We describe how these statistics can be corrected for the mask and cut-sky through a window function, bypassing the need to compute linear terms that were introduced for the previous-generation non-Gaussianity statistics, such as the skewness estimator. We discus the ratio A_{NL} = \tau_{NL}/(6f_{NL}/5)^2 as an additional test of single-field inflationary models and discuss the physical significance of each statistic. Using these estimators with WMAP 5-Year V+W-band data out to l_{max}=600 we constrain the cubic order non-Gaussianity parameters \tau_{NL}, and g_{NL} and find -7.4 < g_{NL}/10^5 < 8.2 and -0.6 < \tau_{NL}/10^4 < 3.3 improving the previous COBE-based limit on \tau_{NL} < 10^8 nearly four orders of magnitude with WMAP.Comment: 15 pages. 14 figure

Seismic Architecture of the Lithosphere-Asthenosphere System in the Western United States from a Joint Inversion of Body- and Surface-wave Observations: Distribution of Partial Melt in the Upper Mantle

Quantitative evaluation of the physical state of the upper mantle, including mapping temperature variations and the possible distribution of partial melt, requires accurately characterizing absolute seismic velocities near seismic discontinuities. We present a joint inversion for absolute but discontinuous models of shear-wave velocity (Vs) using 4 types of data: Rayleigh wave phases velocities, P-to-s receiver functions, S-to-p receiver functions, and Pn velocities. Application to the western United States clarifies where upper mantle discontinuities are lithosphere-asthenosphere boundaries (LAB) or mid-lithospheric discontinuities (MLD). Values of Vs below 4 km/s are observed below the LAB over much of the Basin and Range and below the edges of the Colorado Plateau; the current generation of experimentally based models for shear-wave velocity in the mantle cannot explain such low Vs without invoking the presence of melt. Large gradients of Vs below the LAB also require a gradient in melt-fraction. Nearly all volcanism of Pleistocene or younger age occurred where we infer the presence of melt below the LAB. Only the ultrapotassic Leucite Hills in the Wyoming Craton lie above an MLD. Here, the seismic constraints allow for the melting of phlogopite below the MLD

Comparison of Goal Achievement When Transitioning from In-Person Therapy to Teletherapy in the Westchester County Early Intervention Program Due to the COVID-19 Pandemic

The sudden transition to virtual therapeutic services during the COVID-19 pandemic provided a unique opportunity to explore telehealth as a platform for delivering early intervention (EI) services. Through retrospective chart review of 93 children, we collected the following data: demographics, diagnosed conditions, therapy type, service format, and provider-reported participant goal achievement (1=no progress, 2=little progress, 3=moderate progress, 4=great deal of progress, 5=outcome achieved) over a six-month period before and after transitioning to telehealth. Pre- and post-transition progress scores were compared using the Wilcoxon signed-rank test. Results demonstrated maintained progress among children who transitioned from in-person to virtual services for similar therapy types. Children receiving speech therapy in-person and virtually demonstrated increased achievement (3.00 vs 3.33; p=0.032). Participants receiving a particular therapy post-transition but not in-person attained similar achievement as those who received the same therapy only in-person. Our research suggests that teletherapy may be a viable option for delivering EI services. &nbsp

Epidemiology and Evolution of Fungal Pathogens in Plants and Animals

International audienc