442 research outputs found

    "They Would Not Take Me There" People, Places, and Stories from Champlain's Travels in Canada 1603-1616

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    This is the publisher's version, also available electronically from http://www.cartographicperspectives.org/index.php/journal/article/view/96.No abstract is available for this item

    Performance of an R-410A Room Air Conditioner Modified for Use with R-1234ze

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    This paper presents the results of a senior design project that challenged a team of undergraduate students to reduce the environmental impact of a room air conditioner (RAC) by reducing its energy consumption and/or use of high-GWP refrigerants. Over the course of an academic year, the team was able to investigate, design, model, evaluate, and build a prototype improved RAC. The team began by reviewing literature on approaches that have been proposed to meet or exceed existing energy efficiency and refrigerant selection regulations. Based on these findings and the specified needs of the project sponsor, the team evaluated the appropriateness of different concepts for improving the existing R-410A RAC design and decided to pursue modifications to adapt the unit for R-1234yf. The first step in the redesign process was to develop a thermodynamic model of the existing system. Because very little information was known about the performance of the individual components in the existing RAC, some rough performance estimates were obtained through measurements. The model of the existing system was then modified to provide the same cooling capacity as the original unit but using R-1234yf, and a replacement compressor was selected based on the model results. After the replacement compressor and resized capillary tubes were installed in the RAC, the team was asked to test the prototype unit using R-1234ze instead of R-1234yf. Therefore, the model was modified to predict the cooling capacity of the unit using R-1234ze as the working fluid. The unit was tested using an environmental chamber to simulate the outdoor air conditions and a large room as the indoor environment. Although this setup could not ensure steady-state operation, air temperature measurements indicated that the room temperature did not vary more than 1.5°F over 12 minutes of RAC operation. The cooling capacity calculated based on experimental measurements agreed within 3% of the model predictions. While the team was able to modify the RAC to operate with R-1234ze and was able to predict the unit’s performance with reasonable accuracy, the modifications required a significantly larger compressor and capillary tubes. Therefore, the project clearly illustrated that fitting within the space and weight constraints of window units presents a significant challenge to implementing R-1234ze in RACs

    Between seas and continents: aspects of the scientific career of Hermann Von Ihering, 1850-1930

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    This paper covers some periods in Hermann von Ihering’s scientific trajectory: his training in zoology in Germany and Naples, his international activities based in Brazil, and his return to Germany. It deals with aspects of the formulation of his theories on land bridges. It focuses on the network of contacts he maintained with German émigrés like himself, and primarily with Florentino Ameghino, which allowed him to interact in international scientific circles. It mentions excerpts of his letters and his publications in the periods when he began corresponding with Ameghino (1890), when he travelled to Europe in search of support for his theories (1907), and when he published his book on the history of the Atlantic Ocean (1927).Facultad de Ciencias Naturales y Muse

    Identification of tungiasis infection hotspots with a low-cost, high-throughput method for extracting Tunga penetrans (Siphonaptera) off-host stages from soil samples–An observational study

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    Background: The sand flea, Tunga penetrans, is the cause of a severely neglected parasitic skin disease (tungiasis) in the tropics and has received little attention from entomologists to understand its transmission ecology. Like all fleas, T. penetrans has environmental off-host stages presenting a constant source of reinfection. We adapted the Berlese-Tullgren funnel method using heat from light bulbs to extract off-host stages from soil samples to identify the major development sites within rural households in Kenya and Uganda. Methods and findings: Simple, low-cost units of multiple funnels were designed to allow the extraction of >60 soil samples in parallel. We calibrated the method by investigating the impact of different bulb wattage and extraction time on resulting abundance and quality of off-host stages. A cross-sectional field survey was conducted in 49 tungiasis affected households. A total of 238 soil samples from indoor and outdoor living spaces were collected and extracted. Associations between environmental factors, household member infection status and the presence and abundance of off-host stages in the soil samples were explored using generalized models. The impact of heat (bulb wattage) and time (hours) on the efficiency of extraction was demonstrated and, through a stepwise approach, standard operating conditions defined that consistently resulted in the recovery of 75% (95% CI 63–85%) of all present off-host stages from any given soil sample. To extract off-host stages alive, potentially for consecutive laboratory bioassays, a low wattage (15–25 W) and short extraction time (4 h) will be required. The odds of finding off-host stages in indoor samples were 3.7-fold higher than in outdoor samples (95% CI 1.8–7.7). For every one larva outdoors, four (95% CI 1.3–12.7) larvae were found indoors. We collected 67% of all off-host specimen from indoor sleeping locations and the presence of off-host stages in these locations was strongly associated with an infected person sleeping in the room (OR 10.5 95% CI 3.6–28.4). Conclusion: The indoor sleeping areas are the transmission hotspots for tungiasis in rural homes in Kenya and Uganda and can be targeted for disease control and prevention measures. The soil extraction methods can be used as a simple tool for monitoring direct impact of such interventions

    The Use of the Cancellation Technique to Quantify the Hermann Grid Illusion

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    When observers view a grid of mid-gray lines superimposed on a black background, they report seeing illusory dark gray smudges at the grid intersections, an effect known as the Hermann grid illusion. The strength of the illusion is often measured using the cancellation technique: A white disk is placed over one of these intersections and the luminance of the disk is reduced until the disk disappears. Its luminance at this point, i.e., the disk's detection threshold, is taken to be a measure of the strength of the illusion. Our experiments showed that some distortions of the Hermann grid, which were sufficient to completely disrupt the illusion, did not reduce the disk's detection threshold. This showed that the cancellation technique is not a valid method for measuring the strength of the Hermann grid illusion. Those studies that attempted to use this technique inadvertently studied a different effect known as the blanking phenomenon. We conclude by presenting an explanation for the latter effect

    Grassmannian flows and applications to nonlinear partial differential equations

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    We show how solutions to a large class of partial differential equations with nonlocal Riccati-type nonlinearities can be generated from the corresponding linearized equations, from arbitrary initial data. It is well known that evolutionary matrix Riccati equations can be generated by projecting linear evolutionary flows on a Stiefel manifold onto a coordinate chart of the underlying Grassmann manifold. Our method relies on extending this idea to the infinite dimensional case. The key is an integral equation analogous to the Marchenko equation in integrable systems, that represents the coodinate chart map. We show explicitly how to generate such solutions to scalar partial differential equations of arbitrary order with nonlocal quadratic nonlinearities using our approach. We provide numerical simulations that demonstrate the generation of solutions to Fisher--Kolmogorov--Petrovskii--Piskunov equations with nonlocal nonlinearities. We also indicate how the method might extend to more general classes of nonlinear partial differential systems.Comment: 26 pages, 2 figure
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