6,780 research outputs found

    Effect of Bridges on Low Order Stream Fish Assemblages, South Georgia, USA

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    Anthropogenic impacts such as bridge sites can greatly alter established streambed morphology, associated ecology and flora and fauna. At bridge sites, streams are often channelized approaching the site and deep pools are created at the bridge site causing ecological alterations of faunal assemblages. However, restoring channels and reducing negative construction practices allows the return of natural habitats that are likely to include more sensitive species. Recent conservation studies have suggested that anthropogenic sites may serve as potential habitats for reestablishment of populations following a drought event. This study examined the impact of bridges on fish assemblages at first through fourth order streams in the Suwannee River Basin of South Georgia. Collections were made at bridge, upstream and downstream sites via seining and setting of gill nets. Assemblage structure at bridge sites was compared to bridge structure, biological and physiochemical factors at fourteen bridge sites. Fish assemblages were least diverse upstream of bridge sites, most diverse at bridge sites, and intermediate in diversity downstream of bridge sites. The results suggest that bridge sites, if properly engineered, can serve as valuable refuges for reestablishing fish assemblages up and down stream after events such as the severe drought that impacted South Georgia in 2011

    Electric Motor & Power Source Selection for Small Aircraft Propulsion

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    The research conducted in this project is on electrical propulsion in aviation. A Cessna 172K aircraft with a Lycoming O-320-E2D piston engine serves as a baseline measurement. Investigation of the components required for electrical flight is performed, and components are selected based on market availability and operational performance criteria. This research focuses on electrical propulsion in the aviation industry, and is tailored to aircraft within the General Aviation sector leading to the following research question: Can current electric motor and battery technologies conceptually support flight operations for a Cessna 172K in terms of aircraft performance criteria? The results explore the potential for a fully-electric aircraft powered by means of batteries. A demonstrated flight is examined and the center of gravity is calculated

    HIV Transmission Rates in the United States, 2006-2008

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    National HIV incidence for a given year x [I(x)] equals prevalence [P(x)] times the transmission rate [T(x)]. Or, simply rearranging the terms, T(x) = [I(x)/P(x)]*100 (where T(x) is the number of HIV transmissions per 100 persons living with HIV in a given year). The transmission rate is an underutilized measure of the speed at which the epidemic is spreading. Here, we utilize recently updated information about HIV incidence and prevalence in the U.S. to estimate the national HIV transmission rate for 2006 through 2008, and present a novel method to express the level of uncertainty in these estimates. Transmission rate estimates for 2006 through 2008 are as follows (respectively): 4.39 (4.01 to 4.73); 4.90 (4.49 to 5.28); and 4.06 (3.70 to 4.38). Although there are methodological challenges inherent in making these estimates, they do give some indications that the U.S. HIV transmission rate is at a historically low level

    The Shortcomings of Globalised Internet Technology in Southern Africa

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    Network protocols and applications have mostly been devel- oped in and for a Western context and usually have an embedded set of assumptions about network performance and availability. As a result web-browsing, cloud-based services, live voice and video over IP, desktop applications and software updates often fail or perform poorly in (rural) areas of Southern Africa. This paper uncovers some of the reasons for this poor performance such as Windows TCP failing to reach capacity in high-delay networks, long DNS delays or time-outs and applications such as Office365 assuming constant connectivity to function, and de- scribes them, set in the Southern African contexts. We address the issue of colonisation in ICT context and show the extend of such in the area of networking. These observations provide strong motivation for Africa- based engineering research to ensure that future network protocols and applications are context-sensitive, adaptive and truly global

    Book Reviews

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    P6: Predictors of compliance with COVID-19 related non- pharmaceutical interventions amongst university students

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    College campuses have been an area where the novel coronavirus has spread rapidly, thus this study is focused on compliance with COVID-19 related non-pharmaceutical interventions among college students.We surveyed over 600 college students from across the United States and modeled predictors of compliance with non-pharmaceutical interventions. To determine how applicable nationwide modeling might be to individual local campuses we also administered this same survey to nearly 600 students at two large universities in Utah County (Brigham Young University and Utah Valley University). We then ran structural equation modeling (SEM) to determine what factors are related to student compliance with non-pharmaceutical interventions
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