Large sample statistical estimation of streamflow sensitivity to climate and land cover change

Some of the perennial questions in hydrology relate to how land cover change and precipitation affect streamflow change. These questions have been addressed in many ways over the years, but some common assumptions remain insufficiently challenged or addressed. The work presented in this thesis seeks to address some of these gaps using a large sample of observed hydrological, climatological, and land surface data. The increased availability of large-sample hydrological data in recent years and growing interest in the use of statistical models for causal inference with observed data have made it possible to conduct research which sheds light on patterns and drivers of hydrological non-stationarity, a topic that is a matter of increasing importance for the community. I take advantage of large-sample hydrological methods and data availability to produce novel insights into hydrologic sensitivity and elasticity, defined throughout as the expected change in streamflow associated with a one percent change in another variable. I address the following interrelated questions: 1. What is the effect of tree cover change and urbanisation on streamflow in the United States? 2. How robust are single-site regression models relative to causally interpretable panel regression models in this space? 3. How does streamflow elasticity to precipitation vary spatially and across the streamflow distribution? and 4. How do climate and hydrological behaviour co-evolve in the context of streamflow elasticity? In this thesis, I find small but statistically significant effects of urbanisation on median and high streamflow across the U.S. The effects of tree cover change on flow and urbanisation on low flows are not statistically significant. I interrogate the relationship between streamflow and precipitation across many segments of the flow distribution, and create a new approach for investigating these relationships. Termed “elasticity curves”, this concept visually represents the elasticity of streamflow to average annual and seasonal precipitation across the entirety of the flow distribution. I cluster the curve according to their normalized shape and the resulting groups correspond, to some extent, with hydrologic signatures and catchment characteristics, including the baseflow index, slope of the flow duration curve, and the aridity index, among others. I posit that the shape of the curve corresponds to water storage capacity within a catchment. Thus, the normalized and clustered curve shapes might be used as a tool for understanding hydrologic behaviour relative to catchment storage. This work represents one of very few studies to investigate elasticity across different segments of the flow distribution simultaneously and offers new insights into hydrologic response to climate. Finally, I investigate temporal variation in elasticity to precipitation for low, median, and high streamflow at a regional scale. This work shows high interannual and spatial variability with mean absolute year-to-year differences as high as 0.5 in some regions, relative to long-term averages typically ranging from about 1-2.5. Long term trends in regional-scale interannual elasticity were uncommon but present in some regions. Total absolute changes in elasticity based on Mann-Kendall trend test results in regions with significant trends range from 0.28 to 0.60 over the study period. The time period used to estimate elasticity may have an effect on the resultant value, because large year-to-year variability exists in some regions. The results of this work have implications for hydrologic management and fundamental process understanding of hydrologic behaviour

Fabrication of silicon nanowires with controlled nano-scale shapes using wet anisotropic etching

Silicon nanowires can enable important applications in energy and healthcare such as biochemical sensors, thermoelectric devices, and ultra-capacitors. In the energy sector, for example, as the need for more efficient energy storage continues to grow for enabling applications such as electric vehicles, high energy storage density capacitors are being explored as a potential replacement to traditional batteries that lack fast charge/discharge rates as well as have shorter life cycles. Silicon nanowire based ultra-capacitors offer increased energy storage density by increasing the surface area per unit projected area of the electrode, thereby allowing more surface “charge” to reside. The motivation behind this dissertation is the study of low-cost techniques for fabrication of high aspect ratio silicon nanowires with controlled geometry with an exemplar application in ultra-capacitors. Controlled transfer of high aspect ratio, nano-scale features into functional device layers requires anisotropic etch techniques. Dry reactive ion etch techniques are commonly used since most solution-based wet etch processes lack anisotropic pattern transfer capability. However, in silicon, anisotropic wet etch processes are available for the fabrication of nano-scale features, but have some constraints in the range of geometry of patterns that they can address. While this lack of geometric and material versatility precludes the use of these processes in applications like integrated circuits, they can be potentially realized for fabricating nanoscale pillars. This dissertation explores the geometric limitations of such inexpensive wet anisotropic etching processes and develops additional methods and geometries for fabrication of controlled nano-scale, high aspect ratio features. Jet and Flash Imprint Lithography (J-FIL™) has been used as the preferred pre-etch patterning process as it enables patterning of sub-50 nm high density features with versatile geometries over large areas. Exemplary anisotropic wet etch processes studied include Crystalline Orientation Dependent Etch (CODE) using potassium hydroxide (KOH) etching of silicon and Metal Assisted Chemical Etching (MACE) using gold as a catalyst to etch silicon. Experiments with CODE indicate that the geometric limitations of the etch process prevent the fabrication of high aspect ratio nanowires without adding a prohibitive number of steps to protect the pillar geometry. On the other hand, MACE offers a relatively simple process for fabricating high aspect ratio pillars with unique cross sections, and has thus been pursued to fabricate fully functional electrostatic capacitors featuring both circular and diamond-shaped nano-pillar electrodes. The capacitance of the diamond-shaped nano-pillar capacitor has been shown to be ~77.9% larger than that of the circular cross section due to the increase in surface area per unit projected area. This increase in capacitance approximately matches the increase calculated using analytical models. Thus, this dissertation provides a framework for the ability to create unique sharp cornered nanowires that can be explored further for a wider variety of cross sections.Mechanical Engineerin

A Geoarchaeological Analysis of Ground Stone Tools and Architectural Materials from Mitrou, East Lokris, Greece

Important but seldom asked questions in the study of practice in Bronze Age Aegean society (ca. 3100-1100 B.C.) pertain to the acquisition and usage of stone material in architecture and ground stone tools. My main research questions are, “How did people’s choice of stone material change over time?” and “Why did stone usage change over time?” During the 2013 and 2014 study seasons at Mitrou, I studied the stone inclusions in clayey architectural materials, as well as stone types used in the site’s architecture, and stone types used for ground stone tools at the site. My geological identifications allowed me to first determine whether stone materials used at the site were obtained locally or were imported; then to understand how practices of Mitrou’s inhabitants changed over time with respect to stone materials; and lastly how these practices varied within the settlement of Mitrou. My research indicates that during times of socio-political change at Mitrou (Van de Moortel and Zahou 2012), the availability of various stone resources changed, as did practices with regard to these artifact classes. Even though the production of architectural materials and ground stone tools is not well understood in the context of Bronze Age society in the Aegean, my work shows that they cannot be assumed to be completely local activities nor completely standardized activities. At Mitrou, people’s use of architectural materials changed drastically at the beginning of the Prepalatial period, and the use of ground stone tools also changed at several points during Mitrou’s 1500-year-long occupation, especially at the beginning of the Prepalatial period and during the Postpalatial period. These changes occurred in conjunction with the changing socio-political dynamics of the settlement

Using a Student Success Course and Transferred Credit Hours to Predict Student\u27s Likelihood to Retain in Online Higher Education

As online education permeates a larger percentage of postsecondary student attendance, higher education institutions place a greater focus on online student retention. Online learners are entering college with varied backgrounds, demographics, and prior experience, yet most institutions are not differentiating the first-year programs for their incoming students with previous college-level experience. The following research used a binomial logistic regression analysis to explore existing, archival data to determine whether college transfer credit and a student success course can predict short- or long-term online student retention. This correlational study evaluated a randomized sample of 3,000 students who took a student success course and transferred in fewer than 60 credit hours and evaluated whether the success course could predict their retention at the university for the subsequent term (short-term) or through current enrollment (long-term). Results from the quantitative study showed that both predictor variables were statistically significant as predictors of student retention, both in the short- and long-term

The Public\u27s Perception of Medical Ultrasound

Ultrasound (sonography) is a primary imaging modality predominantly used in the Diagnostic Radiology department to aid in the findings of internal pathological conditions. Sonography has been used for medical diagnosis since the early 1970’s; however, in comparison to other imaging modalities, it is relatively young and evolving. Since Ian Donald’s discovery in obstetrical ultrasound, there has been a significant growth in Maternal and Fetal Medicine as well as an explosion in the use of non-medical obstetrical imaging, better known as keepsake or entertainment ultrasound. Unlike all other imaging examinations, in obstetrics, family members accompany the patient for viewing where the sonographer can provide narrative on the fetal anatomic structures but not give a diagnosis. The sonographer does not interpret or make the diagnosis of the case, therefore they can not share any results with the patient. Ultrasound’s historical and progressive development of use, slow development of formal education, lack of requirement of national certification, and minimal research to support any bioeffects when used for medical purposes, stereotypes of what the role of ultrasound is and the role of the sonographer stereotypes are in existence. Derived from these stereotypes, a survey was designed to assess the public’s understanding and perception of diagnostic medical ultrasound and the role of the sonographer. The responses from the survey contradicted the researchers’ hypothesis; however, results indicate the opportunity to improve the public’s knowledge.https://digitalcommons.misericordia.edu/research_posters2021/1006/thumbnail.jp

Brush control on sandy rangelands in central Alberta

Balsam poplar, aspen, and willows that had invaded subirrigated sandy rangeland were treated with (1) prescribed spring burning, (2) the herbicide 2,4-D ester, and (3) prescribed burning followed by 2,4-D ester. After 5 years, burning and spraying had reduced brush the most. Brush reinvasion was occurring rapidly on all treated areas. Stand openings of about one quarter hectare in an 8 meter high poplar forest resulting from these treatments did persist for at least 5 years. Treatments were effective enough to lower the forest cover and in some cases increase forage production. Repeated burning and spraying substantially reduced the density of reinvading woody suckers.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202

Risks of requiring a dedicated molecular specimen for HIV diagnosis and a potential strategy for mitigation

BACKGROUND: HIV screening (i.e. antigen/antibody) tests are followed by a supplemental (i.e. antibody-only) if the screen is positive. Discrepant results can result from two scenarios: a false-positive screening test or acute HIV infection. These scenarios can be distinguished by a molecular HIV test, but due to contamination concerns, our laboratory recently implemented a policy requiring a second specimen dedicated for molecular HIV testing. Our objective was to (1) characterize the effect of this policy on the time-to-diagnosis for patients with discrepant screening and supplemental test results, and (2) explore strength of positivity as an interim predictor of screening test accuracy while awaiting confirmatory test results. METHODS: Data from our laboratory information system, electronic health record, and instrument logs were used to collate data for all HIV testing performed at Barnes-Jewish Hospital (BJH) between January 1, 2014 and October 18, 2017. RESULTS: Requiring a dedicated specimen for molecular testing significantly increased the time-to-diagnosis for patients with discrepant screening and supplemental HIV tests (p = 0.0084). This policy also contributed to loss-to-followup, with 0/35 discrepant cases lost-to-followup prior to policy implementation compared to 2/10 after implementation. However, by optimizing the signal-to-cutoff (S/CO) ratio of the screening test, we were able to more accurately distinguish false-positives from acute-HIV prior to molecular testing (sensitivity of 100%, specificity of 89%). CONCLUSIONS: We propose utilizing quantitative fourth-generation assay results (S/CO) ratios as a predictor of infection true positivity in situations where the screening assay is reactive but the supplemental test is negative and confirmatory molecular results are not immediately available

Promoting independent learning skills using video on digital language laboratories

This is the author's PDF version of an article published in Computer assisted language learning ©2006. The definitive version is available at http://www.informaworld.com/The article discusses the potential for developing independent learning skills using the digital language laboratory with particular reference to exploiting the increasingly available resource of digital video. It investigates the potential for recording and editing video clips from online sources and digitalising clips from analogue recordings and reflects on the current status quo regarding the complex copyright regulations in this area. It describes two pilot self-access programmes based on video clips which were undertaken with University College Chester undergraduates and reflects on the value of the experience for students in developing a wide range of language skills as well as independent learning skills using their feedback on the experience

Solution of an infection model near threshold

We study the Susceptible-Infected-Recovered model of epidemics in the vicinity of the threshold infectivity. We derive the distribution of total outbreak size in the limit of large population size $N$. This is accomplished by mapping the problem to the first passage time of a random walker subject to a drift that increases linearly with time. We recover the scaling results of Ben-Naim and Krapivsky that the effective maximal size of the outbreak scales as $N^{2/3}$, with the average scaling as $N^{1/3}$, with an explicit form for the scaling function