Archipelagos

Honors (Bachelor's)Individual Concentration ProgramUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/91879/1/pawhalen.pd

THE OLIGOCENE WEST ELK BRECCIA: EVIDENCE FOR MASSIVE VOLCANIC DEBRIS AVALANCHES IN THE EASTERN GUNNISON RIVER VALLEY, WEST-CENTRAL COLORADO, U.S.A.

The West Elk Breccia has been studied since the late 1800’s with many interpretations regarding its origin. One unrecognized possibility is that parts of it are debris-avalanche deposits. This study has recognized evidence for this interpretation at three scales: volcano scale, outcrop scale, and intra-outcrop scale. At the volcano scale, a scarp in the old volcano reveals underlying Mesozoic bedrock, suggesting sector collapse. At the outcrop scale, megablocks of the original edifice, up to hundreds of meters in length, have atypical orientations and are surrounded by a gravel matrix. At the intra-outcrop scale, jigsaw-fit fracturing and rip-up clasts are common in distal deposits, which are documented in analogous debris-avalanche deposits. Similar to the debris-avalanche deposit at Mt. Shasta, medial-to-distal-matrix volcaniclast content decreases by 23%; Paleozoic and Mesozoic clasts increase by 5%; and the size of megablocks decreases. The geochemical and petrographic signatures reveal breccia blocks composed of pyroxene-andesite, a more silicic matrix facies, and the andesitic-to-dacitic East Elk Creek Tuff, all compositions that corroborate previous work on this northern extension of the San Juan volcanic field. Measured sections in the 100-km² study area allow for an estimation of total formation volume of approximately 8.5 km3

Carrier field shock formation of long wavelength femtosecond pulses in dispersive media

We numerically demonstrate the formation of carrier field shocks in various dispersive media for a wide variety of input conditions using two different electric field propagation models. In addition, an investigation of the impact of numerous physical effects on carrier wave shock is performed. It is shown that in many cases a field shock is essentially unavoidable and therefore extremely important in the propagation of intense long wavelength pulses in weakly dispersive nonlinear media such as noble gases, air, and single-crystal diamond. The results presented here are expected to have a significant impact in the field of ultrashort nonlinear optics, attosecond pulse generation, and wavepacket synthesis where the use of mid-IR wavelengths is becoming increasingly more important.Comment: 14 pages, 17 figure

The Collapse of Atomically-Cooled Primordial Haloes. I. High Lyman-Werner Backgrounds

Pristine, atomically-cooled haloes are leading contenders for the sites of primordial quasar formation because atomic cooling triggers rapid baryon collapse that can create 10$^4$ - 10$^5$ M$_{\odot}$ black hole seeds. However, until now no numerical simulations with a wide range of halo spins and assembly histories have followed the collapse for the times required to form a black hole. We have now performed cosmological simulations of baryon collapse in atomically-cooled haloes for times that are sufficient for supermassive stars to form and die as direct-collapse black holes (DCBHs). Our simulations reveal that fragmentation of the accretion disk at the center of the halo after $\sim$ 500 kyr is nearly ubiquitous and in most cases leads to the formation of binary or multiple supermassive stellar systems. They also confirm that rapid baryon collapse proceeds for the times required for these stars to form DCBHs. Our discovery raises the exciting possibility of detecting gravitational waves from DCBH mergers with LISA and tidal disruption events in the near infrared with the James Webb Space Telescope and ground-based telescopes in the coming decade.Comment: 13 pages, 10 figures, submitted to MNRA

Radio Power from Direct-Collapse Black Holes

Direct-collapse black holes (DCBHs) forming at $z \sim$ 20 are currently the leading candidates for the seeds of the first quasars, over 200 of which have now been found at $z >$ 6. Recent studies suggest that DCBHs could be detected in the near infrared by the James Webb Space Telescope, Euclid, and the Roman Space Telescope. However, new radio telescopes with unprecedented sensitivities such as the Square Kilometer Array (SKA) and the Next-Generation Very Large Array (ngVLA) may open another window on the properties of DCBHs in the coming decade. Here we estimate the radio flux from DCBHs at birth at $z =$ 8 - 20 with several fundamental planes of black hole accretion. We find that they could be detected at $z \sim$ 8 by the SKA-FIN all-sky survey. Furthermore, SKA and ngVLA could discover 10$^6$ - 10$^7$ $M_{\odot}$ BHs out to $z \sim$ 20, probing the formation pathways of the first quasars in the Universe.Comment: 6 pages. 4 figures, accepted by ApJ

Indoor Inertial Waypoint Navigation for the Blind

Indoor navigation technology is needed to support seamless mobility for the visually impaired. This paper describes the construction and evaluation of an inertial dead reckoning navigation system that provides real-time auditory guidance along mapped routes. Inertial dead reckoning is a navigation technique coupling step counting together with heading estimation to compute changes in position at each step. The research described here outlines the development and evaluation of a novel navigation system that utilizes information from the mapped route to limit the problematic error accumulation inherent in traditional dead reckoning approaches. The prototype system consists of a wireless inertial sensor unit, placed at the users’ hip, which streams readings to a smartphone processing a navigation algorithm. Pilot human trials were conducted assessing system efficacy by studying route-following performance with blind and sighted subjects using the navigation system with real-time guidance, versus offline verbal directions

2007-2008 Mostly Music: Mozart

Hosted by Marshall Turkin and Staging by Jan McArt Presented in cooperation with the Lewis Jewish Community Center Date & Time: Saturday, February 9, 2008 at 7:30 pm and Sunday, February 10, 2008 at 4:00 pmhttps://spiral.lynn.edu/conservatory_mostlymusic/1001/thumbnail.jp