6,014 research outputs found

    Functional requirements document for the Earth Observing System Data and Information System (EOSDIS) Scientific Computing Facilities (SCF) of the NASA/MSFC Earth Science and Applications Division, 1992

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    Five scientists at MSFC/ESAD have EOS SCF investigator status. Each SCF has unique tasks which require the establishment of a computing facility dedicated to accomplishing those tasks. A SCF Working Group was established at ESAD with the charter of defining the computing requirements of the individual SCFs and recommending options for meeting these requirements. The primary goal of the working group was to determine which computing needs can be satisfied using either shared resources or separate but compatible resources, and which needs require unique individual resources. The requirements investigated included CPU-intensive vector and scalar processing, visualization, data storage, connectivity, and I/O peripherals. A review of computer industry directions and a market survey of computing hardware provided information regarding important industry standards and candidate computing platforms. It was determined that the total SCF computing requirements might be most effectively met using a hierarchy consisting of shared and individual resources. This hierarchy is composed of five major system types: (1) a supercomputer class vector processor; (2) a high-end scalar multiprocessor workstation; (3) a file server; (4) a few medium- to high-end visualization workstations; and (5) several low- to medium-range personal graphics workstations. Specific recommendations for meeting the needs of each of these types are presented

    The big-fish-little-pond effect and overclaiming

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    Using the OECD's Programme for International Student Assessment (PISA) study, we investigate whether students’ relative ability in mathematics (in comparison to their school peers) is linked to their tendency to overclaim. Although the estimated effect size is modest (around 0.1 standard deviations) we find empirical support that being a big fish in a small pond is linked to overclaiming, with this robust to different analytic approaches and model specifications. Thus, being one of the highest academic achievers within a school may push young people's beliefs in their own abilities too far, straying into overconfidence and making claims about their knowledge and skills that they cannot justify

    What effect did the global financial crisis have upon youth wellbeing? Evidence from four Australian cohorts

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    Recent research has suggested significant negative effects of the Global Financial Crisis (GFC) on mental health and wellbeing. In this article, the authors suggest that the developmental period of late adolescence may be at particular risk of economic downturns. Harmonizing 4 longitudinal cohorts of Australian youth (N = 38,017), we estimate the impact of the GFC on 1 general and 11 domain specific measures of wellbeing at age 19 and 22. Significant differences in wellbeing in most life domains were found, suggesting that wellbeing is susceptible to economic shocks. Given that the GFC in Australia was relatively mild, the finding of clear negative effects across 2 ages is of international concern

    Overclaiming. An international investigation using PISA data

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    This paper investigates the phenomena of overclaiming – the propensity for individuals to claim more knowledge about an issue or topic than they really (or could possibly) do. Using Programme for International Student Assessment (PISA) data from nine Anglophone countries and over 40,000 young people, we examine teenagers’ propensity to claim knowledge of three mathematics constructs that do not really exist. We find substantial differences in young people’s tendency to overclaim across countries, genders, and socio-economic groups. Those who are most likely to overclaim are also found to exhibit high levels of overconfidence and believe they work hard, persevere at tasks, and are popular amongst their peers. Together this provides important new insight into overclaiming, how this differs across groups, and how it relates to other psychological constructs

    Novel Weapons Testing: Are Invasive Plants More Chemically Defended than Native Plants?

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    Background: Exotic species have been hypothesized to successfully invade new habitats by virtue of possessing novel biochemistry that repels native enemies. Despite the pivotal long-term consequences of invasion for native food-webs, to date there are no experimental studies examining directly whether exotic plants are any more or less biochemically deterrent than native plants to native herbivores. Methodology/Principal Findings: In a direct test of this hypothesis using herbivore feeding assays with chemical extracts from 19 invasive plants and 21 co-occurring native plants, we show that invasive plant biochemistry is no more deterrent (on average) to a native generalist herbivore than extracts from native plants. There was no relationship between extract deterrence and length of time since introduction, suggesting that time has not mitigated putative biochemical novelty. Moreover, the least deterrent plant extracts were from the most abundant species in the field, a pattern that held for both native and exotic plants. Analysis of chemical deterrence in context with morphological defenses and growth-related traits showed that native and exotic plants had similar trade-offs among traits. Conclusions/Significance: Overall, our results suggest that particular invasive species may possess deterrent secondary chemistry, but it does not appear to be a general pattern resulting from evolutionary mismatches between exotic plants and native herbivores. Thus, fundamentally similar processes may promote the ecological success of both native and exotic species

    Plant-herbivore interactions : consequences for the structure of freshwater communities and exotic plant invasions

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    Invasive exotic species threaten native biodiversity, alter ecosystem structure and function, and annually cost over $100 billion in the US alone. Determining the ecological traits and interactions that affect invasion success are thus critical for predicting, preventing, and mitigating the negative effects of biological invasions. Native herbivores are widely assumed to facilitate exotic plant invasions by preferentially consuming native plants and avoiding exotic plants. Here, I use freshwater plant communities scattered broadly across the Southeastern U.S. to show that herbivory is an important force driving the ecology and evolution of freshwater systems. However, native consumers often preferentially consume rather than avoid exotic over native plants. Analyses of 3 terrestrial datasets showed similar patterns, with native herbivores generally preferring exotic plants. Thus, exotic plants appear defensively nave against these evolutionarily novel consumers, and exotic plants may escape their coevolved, specialist herbivores only to be preferentially consumed by the native generalist herbivores in their new ranges. In further support of this hypothesis, a meta-analysis of 71 manipulative field studies including over 100 exotic plant species and 400 native plant species from terrestrial, aquatic, and marine systems revealed that native herbivores strongly suppressed exotic plants, while exotic herbivores enhanced the abundance and species richness of exotic plants by suppressing native plants. Both outcomes are consistent with the hypothesis that prey are susceptible to evolutionarily novel consumers. Thus, native herbivores provide biotic resistance to plant invasions, but the widespread replacement of native with exotic herbivores eliminates this ecosystem service, facilitates plant invasions, and triggers an invasional meltdown. Consequently, rather than thriving because they escape their co-evolved specialist herbivores, exotic plants may thrive because their co-evolved generalist herbivores have stronger negative effects on evolutionarily nave, native plants.Ph.D.Mark E. Hay, Committee Chair ; Julia Kubanek, Committee Member ; Joseph Montoya, Committee Member ; J. Todd Streelman, Committee Member ; David M. Lodge, Committee Membe

    Shippers usage of the internet including e-marketplaces in the trucking industry

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    The research reported in this manuscript provides insights regarding trucking related e-marketplaces and web-based offerings by truckers. Over 2,000 shippers were surveyed with 420 total responses. Overall, only 7% of shippers were currently utilizing e-marketplaces; however, those that are appear to be satisfied. Shippers ranked tracking, freight posting, and pricing, in that order of importance for trucking web sites

    New Horizons: Long-Range Kuiper Belt Targets Observed by the Hubble Space Telescope

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    We report on Hubble Space Telescope (HST) observations of three Kuiper Belt Objects (KBOs), discovered in our dedicated ground-based search campaign, that are candidates for long-range observations from the New Horizons spacecraft: 2011 JY31, 2011 HZ102, and 2013 LU35. Astrometry with HST enables both current and future critical accuracy improvements for orbit precision, required for possible New Horizons observations, beyond what can be obtained from the ground. Photometric colors of all three objects are red, typical of the Cold Classical dynamical population within which they reside; they are also the faintest KBOs to have had their colors measured. None are observed to be binary with HST above separations of ~0.02 arcsec (~700 km at 44 AU) and {\Delta}m less than or equal to 0.5.Comment: Pages: 11, Figures: 2, Tables: 3, Icarus, available online May 2014 (http://dx.doi.org/10.1016/j.icarus.2014.04.014
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