12 research outputs found

    Design and Performance of a Spectrometer for Deployment on MISSE 7

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    A spectrometer for reflectance and transmission measurements of samples exposed to the space environment has been developed for deployment on the Materials on the International Space Station Experiment (MISSE) 7. The instrument incorporates a miniature commercial fiber optic coupled spectrometer with a computer control system for detector operation, sample motion and illumination. A set of three spectrometers were recently integrated on the MISSE7 platform with launch and deployment on the International Space Station scheduled for summer of this year. The instrument is one of many active experiments on the platform. The performance of the instrument prior to launch will be discussed. Data from samples measured in the laboratory will be compared to those from the instrument prior to launch. These comparisons will illustrate the capabilities of the current design. The space environment challenges many materials. When in operation on the MISSE 7 platform, the new spectrometer will provide real time data on the how the space environment affects the optical properties of thermal control paints and optical coatings. Data obtained from comparison of pre and post flight measurements on hundreds of samples exposed on previous MISSE platforms have been reported at these meetings. With the new spectrometer and the ability to correlate measured changes with time on orbit and the occurrence of both natural events and human activities, a better understanding of the processes responsible for degradation of materials in space will be possible

    Robust processor allocation for independent tasks when dollar cost for processors is a constraint

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    Includes bibliographical references (pages 9-10).In a distributed heterogeneous computing system, the resources have different capabilities and tasks have different requirements. Different classes of machines used in such systems typically vary in dollar cost based on their computing efficiencies. Makespan (defined as the completion time for an entire set of tasks) is often the performance feature that is optimized. Resource allocation is often done based on estimates of the computation time of each task on each class of machines. Hence, it is important that makespan be robust against errors in computation time estimates. The dollar cost to purchase the machines for use can be a constraint such that only a subset of the machines available can be purchased. The goal of this study is to: (1) select a subset of all the machines available so that the cost constraint for the machines is satisfied, and (2) find a static mapping of tasks so that the robustness of the desired system feature, makespan, is maximized against the errors in task execution time estimates. Six heuristic techniques to this problem are presented and evaluated

    The role of cultural norms in shaping attitudes towards amphibians in Cape Town, South Africa.

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    Urban ecosystems are increasingly viewed as an important component within strategies for wildlife conservation but are shaped as much by natural systems as they are by social and political processes. At the garden scale, attitudes and preferences govern design and maintenance choices including the decision to encourage or discourage specific faunal presence. At the global scale, charismatic taxa that are well-liked attract more conservation funding and volunteer stewardship. Amphibians are a class of animals that are both loved and loathed making them a suitable subject for comparing and unpacking the drivers of preference and attitudes towards animals. We conducted a mixed methods survey of 192 participants in three adjacent neighbourhoods in Cape Town, South Africa. The survey included both quantitative and qualitative questions which were analysed thematically and used to explain the quantitative results. The results revealed that attitudes formed during childhood tended to be retained into adulthood, were shaped by cultural norms, childhood experiences and the attitudes of primary care-givers. The findings are significant for environmental education programmes aimed at building connectedness to nature and biophilic values

    Robust static allocation of resources for independent tasks under makespan and dollar cost constraints

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    Includes bibliographical references (pages 413-414).Heterogeneous computing (HC) systems composed of interconnected machines with varied computational capabilities often operate in environments where there may be inaccuracies in the estimation of task execution times. Makespan (defined as the completion time for an entire set of tasks) is often the performance feature that needs to be optimized in such systems. Resource allocation is typically performed based on estimates of the computation time of each task on each class of machines. Hence, it is important that makespan be robust against errors in computation time estimates. In this research, the problem of finding a static mapping of tasks to maximize the robustness of makespan against the errors in task execution time estimates given an overall makespan constraint is studied. Two variations of this basic problem are considered: (1) where there is a given, fixed set of machines, (2) where an HC system is to be constructed from a set of machines within a dollar cost constraint. Six heuristic techniques for each of these variations of the problem are presented and evaluated

    Processor allocation for tasks that is robust against errors in computation time estimates

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    Heterogeneous computing systems composed of interconnected machines with varied computational capabilities often operate in environments where there may be sudden machine failures, higher than expected load, or inaccuracies in estimation of system parameters. Makespan (defined as the completion time for an entire set of tasks) is often the performance feature that is optimized in such systems. It is important that the makespan of a resource allocation (mapping) be robust against errors in task computation time estimates. The problem of optimally mapping tasks onto machines of a heterogeneous computing environment has been shown, in general, to be NP-complete. Therefore, heuristic techniques to find near optimal solutions to this mapping problem are required. The goal of this research is to find a static mapping of tasks so that the robustness of the desired system feature, makespan, is maximized against the errors in task execution time estimates. Seven heuristics to derive near-optimal solutions and an upper bound to this problem are presented and evaluated

    BTBR Ob/Ob Mutant Mice Model Progressive Diabetic Nephropathy

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    There remains a need for robust mouse models of diabetic nephropathy (DN) that mimic key features of advanced human DN. The recently developed mouse strain BTBR with the ob/ob leptin-deficiency mutation develops severe type 2 diabetes, hypercholesterolemia, elevated triglycerides, and insulin resistance, but the renal phenotype has not been characterized. Here, we show that these obese, diabetic mice rapidly develop morphologic renal lesions characteristic of both early and advanced human DN. BTBR ob/ob mice developed progressive proteinuria beginning at 4 weeks. Glomerular hypertrophy and accumulation of mesangial matrix, characteristic of early DN, were present by 8 weeks, and glomerular lesions similar to those of advanced human DN were present by 20 weeks. By 22 weeks, we observed an approximately 20% increase in basement membrane thickness and a >50% increase in mesangial matrix. Diffuse mesangial sclerosis (focally approaching nodular glomerulosclerosis), focal arteriolar hyalinosis, mesangiolysis, and focal mild interstitial fibrosis were present. Loss of podocytes was present early and persisted. In summary, BTBR ob/ob mice develop a constellation of abnormalities that closely resemble advanced human DN more rapidly than most other murine models, making this strain particularly attractive for testing therapeutic interventions

    'Exploding the limits of law': judgment and freedom in Arendt and Adorno

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    In Eichmann in Jerusalem, Hannah Arendt struggled to defend the possibility of judgment against the obvious problems encountered in attempts to offer legally valid and morally meaningful judgments of those who had committed crimes in morally bankrupt communities. Following Norrie, this article argues that Arendt’s conclusions in Eichmann are equivocal and incoherent. Exploring her perspectival theory of judgment, the article suggests that Arendt remains trapped within certain Kantian assumptions in her philosophy of history, and as such sees the question of freedom in a binary way. The article argues that Adorno’s philosophy of freedom provides the resources to diagnose and overcome Arendt’s shortcomings. Adorno’s position provides a way of embracing the antinomical character of judgment, by emphasising the need for elements of reason and nature in the phenomenon of freedom. In Adorno’s lights, judgment becomes an attempt to express a ‘spirit of solidarity’ with the tragic status of the potentially free but actually unfree subject of modernity
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