Characterization of quantum well structures using a photocathode electron microscope

Present day integrated circuits pose a challenge to conventional electronic and mechanical test methods. Feature sizes in the submicron and nanometric regime require radical approaches in order to facilitate electrical contact to circuits and devices being tested. In addition, microwave operating frequencies require careful attention to distributed effects when considering the electrical signal paths within and external to the device under test. An alternative testing approach which combines the best of electrical and optical time domain testing is presented, namely photocathode electron microscope quantitative voltage contrast (PEMQVC)

Design Considerations for a Water Treatment System Utilizing Ultra-Violet Light Emitting Diodes

UV LED technology is in its infancy and research as it applies to UV water treatment is required to advance knowledge for practical application. This thesis focused on two subjects. First, the design, fabrication, and operation of a water treatment reaction system utilizing Ultra-Violet (UV) Light Emitting Diodes (LEDs). Second, the measurement of UV LED output angle in water which is necessary to support future reactor designs. Several characteristics of the LED-water interface were revealed which impacted the effectiveness of the vessel including; UV dose requirements, LED wavelength, photon dispersion geometry, LED placement, optical efficiency, vessel material, and electronic control system. The reactor vessel design balanced optimal characteristics with experiment design flexibility, fabrication speed, and procurement considerations. Expeditious construction was required to permit laboratory exploration performed by other researchers studying bacterial spore disinfection, an advanced oxidation process, and UV LED output wavelength and intensity observations. Two reactor vessels and three electronic boards were completed and modified as the research matured. Next, the UV LED output angle in air and water was measured. The conclusions of the literature review, practical application, and output angle calculations led to future design considerations for a UV LED, water reaction vessel, and electronic control system

VALUING WATER QUALITY MONITORING: A CONTINGENT VALUATION EXPERIMENT INVOLVING HYPOTHETICAL AND REAL PAYMENTS

This paper studies the preferences and willingness-to-pay for individuals for volunteer water quality monitoring programs. The study involves supporting water quality monitoring at two ponds in the state of Rhode Island. The paper uses both a hypothetical and a real-payment contingent valuation survey to directly measure individual preferences and willingness-to-pay (WTP) for volunteer water quality monitoring at the two ponds. The overall results of the study suggest that hypothetical WTP is not statistically greater than real WTP, and that the average survey respondent is willing to support water quality monitoring on one of the two ponds. The study also finds that the specified purpose of water quality monitoring and certain socioeconomic characteristics of a respondent significantly affect the respondent's decision to support volunteer water quality monitoring.Environmental Economics and Policy,

The flask security architecture: system support for diverse security policies

technical reportOperating systems must be flexible in their support for security policies, i.e., the operating system must provide sufficient mechanisms for supporting the wide variety of real-world security policies. Systems claiming to provide this support have failed to do so in two ways: they either fail to provide sufficient control over the propagation of access rights, or they fail to provide enforcement mechanisms to support fine-grained control and dynamic security policies. In this paper we present an operating systems security architecture that solves both of these problems. The first problem is solved by ensuring that the security policy (through a consistent replica) is consulted for every security decision. The second problem is solved through mechanisms that are directly integrated into the service-providing components of the system. The architecture is described through its prototype implementation in the Flask microkernel-based OS, and the policy flexibility of the prototype is evaluated. We present initial evidence that the architecture's performance impact is modest. Moreover, our architecture is applicable to many other types of operating systems and environments

Late Precambrian glaciation of central East Greenland

The Vendian succession of the central East Greenland fjord region is among the best preserved and most extensively exposed in the world and is represented approximately by the Tillite Group, comprising five formations, which from bottom to top are: the Ulvesø Formation (formerly Lower Tillite, dominantly diamictite), the Arena Formation (formerly Inter-Tillite beds, dominantly sandstone and shale), the Storeelv Formation (formerly Upper Tillite, dominantly diamictite, sandstone and conglomerate), the Canyon Formation (dominantly shale and dolostone) and the Spiral Creek Formation (dominantly sandstone, shale and dolostone). The group is underlain by Bed group 20 (limestone) and Bed group 19 (dominantly carbonate, shale and breccia) in different places and in the peripheral areas by older Bed groups of the Eleonore Bay Group. Above, the transgressive Cambrian sandstones of the Kløftelv Formation cap the Vendian sequence, though the exact level of the Precarmbrian-Cambrian boundary may be slightly lower. This paper reviews previous work on the succession and presents numerous new stratigraphic sections and an assessment of the sedimentary structures. The stratigraphic and palaeoenvironmental significance of the succession can therefore be assessed. Both main diamictite horizons contain other facies, which together with sedimentary structural and fabric data indicate that the following sediments have been produced: lodgement tillites, waterlain tillites, proximal and distal glaciomarine sediments (with ice-rafted dropstones), glaciolacustrine sediments, fluvioglacial deposits,  subaqueous and sub-aerial mass-flows and periglacial phenomena. The other sediments of the Tillite Group were deposited in a dominantly shallow marine or lacustrine environment. Deeper water turbidites are recorded in part of the Arena Formation, whilst the upper part of the group indicates periodic emergence. Stromatolites, desiccation cracks and halite pseudomorphs are particularly distinctive in this part of the succession. A hiatus preceded deposition of the Kløftelv Formation, a transgressive unit of tidally-influenced sandstones. Stratigraphic thicknesses vary considerably, and whereas individual formations can be recognised throughout most of the fjord region, intraformational horizons cannot normally be traced for more than several kilometres. The nature of the bottom contact of the Tillite Group remains enigmatic, and transitional sedimentary, unconformable and thrust contacts are all present. It is possible that Bed Group 20 may be the lateral equivalent of the Ulves0 Formation, or of Bed Group 19. Although local palaeogeography was complex during deposition of the diamictites, these rocks indicate that a low-level ice sheet prevailed at the time. Together with Svalbard and western Scotland they represent the periphery of an ice-sheet which stretched across much of northern Europe to the Urals. However, much of Vendian time was not characterised by glacial conditions, and warm climates prevailed when the upper part of the Tillite Group was deposited

Potential impacts of statewide relaxation of COVID-19 policies, the B.1.1.7 variant, and vaccination in Austin - March 2021

To support public health decision-making and healthcare planning, we developed a model for the five-county Austin-Round Rock Metropolitan Statistical Area (henceforth Austin​) that can provide real-time estimates of the prevalence and transmission rate of COVID-19 and project healthcare needs into the future. The model incorporates key epidemiological characteristics of the disease, demographic information for Austin, and local mobility data from anonymized cell phone traces. It uses daily COVID-19 hospitalization data to estimate the changing transmission rate and prevalence of disease. The framework can be readily applied to provide pandemic situational awareness and short-term healthcare projections in other cities around the US. In this report, we use COVID-19 hospitalization data for Austin from March 13, 2020 to March 5, 2021 to estimate the state of the pandemic in early March and project hospitalizations up to June of 2021.Integrative Biolog

Potential Impact of Holiday Gatherings on COVID-19 Hospitalizations in Austin

To support public health decision-making and healthcare planning, we developed a model for the five-county Austin-Round Rock Metropolitan Statistical Area (henceforth Austin)that can provide real-time estimates of the prevalence and transmission rate of COVID-19 and project healthcare needs into the future. The model incorporates key epidemiological characteristics of the disease, demographic information for Austin, and local mobility data from anonymized cell phone traces. It uses daily COVID-19 hospitalization data to estimate the changing transmission rate and prevalence of disease. The framework can be readily applied to provide pandemic situational awareness and short-term healthcare projections in other cities around the US. In this report, we use COVID-19 hospitalization data for Austin from March 13 to December 19, 2020 to estimate the state of the pandemic in late December and project hospitalizations through mid January of 2021, under three hypothetical scenarios for the impact of winter holiday gatherings on the transmission of COVID-19 in Austin. The projections are based on multiple assumptions about the age-specific severity of COVID-19 and the role of asymptomatic infections in the transmission of the virus. These graphs below do not present the full range of uncertainty for the city of Austin, but are intended to provide basic insight into the changing risks of COVID-19 transmission and potential healthcare surges in Austin. Our estimates suggest that if transmission is elevated to levels measured just after the Thanksgiving holiday for one week starting on December 24, 2020, then there is a 36% chance that the COVID-19 ICU census will reach the estimated capacity of 200 by January 7, with a median date of hitting 200 of January 14 (95% prediction interval: December 30-undetermined ). If the higher levels of transmission are sustained for two weeks, then there is a 39% chance that the COVID-19 ICU census will reach the estimated capacity of 200 by January 7, with a median date of hitting 200 of January 11 (95% prediction interval: December 30-undetermined). We are posting these results prior to peer review to provide intuition for both policy makers and the public regarding both the immediate threat of COVID-19 and the importance of heightened social distancing and transmission reducing-precautions as we enter the holiday period, including abstaining from indoor social gatherings, keeping physical distance, wearing cloth face coverings and staying isolated when symptomatic. As new hospitalization data become available, we will provide updated estimates and projections on the UT COVID-19 Modeling Consortium's Austin COVID-19 Dashboard.Integrative Biolog