3,918 research outputs found

    Diurnal and Seasonal Activity Patterns of Drosophilid Species (Diptera: Drosophilidae) Present in Blackberry Agroecosystems With a Focus on Spotted-Wing Drosophila

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    Drosophilid species with different life histories have been shown to exhibit similar behavioral patterns related to locating and utilizing resources such as hosts, mates, and food sources. Drosophila suzukii (Matsumura) is an invasive species that differs from other frugivorous drosophilids in that females lay eggs in ripe and ripening fruits instead of overripe or rotten fruits. We hypothesized that there may be diurnal and/or seasonal patterns associated with the movement of drosophilid species into and out of crop fields and their attraction to fermentation-odor-based monitoring traps, and that D. suzukii would conform to similar patterns. To test these hypotheses, we deployed passive, 2-headed Malaise traps between crop fields and wooded edges to simultaneously catch flies moving into and out of crop fields. We also deployed monitoring traps with a fermentation-based bait between crop fields and wooded edges and within crop rows. Traps were deployed weekly in June–August in 2014 and 2015 at two commercial blackberry farm in Cleveland County, NC, and were checked hourly for 24 h, except during darkness. Both D. suzukii and other drosophilid species moved between crop fields and wooded edges and were attracted to monitoring traps primarily during the morning and evening hours. Whereas other drosophilids were captured in traps throughout the season, few D. suzukii were caught in traps until early to mid-July in both years and increased as the season progressed. Understanding D. suzukii movement and activity patterns is essential for the development of effective management strategies

    PUBLIC AND PRIVATE FOOD ASSISTANCE CHOICES OF FOOD NEEDY FAMILIES

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    A bivariate probit model was used to determine public and private food assistance participation among the population below 125 percent poverty level, using the Current Population Survey data. Food stamp use and food pantry use were complements. Household income, food insecurity status, household structure, and rural residence affected participation decisions.Food Security and Poverty,

    THE NEW ECONOMICS OF DISTANCE: LONG-TERM TRENDS IN INDEXES OF SPATIAL FRICTION

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    Distance-related costs have changed at different rates across categories of resource flows and across modes and media between 1960 and 1998. The cost of moving knowledge/information has dropped much faster than the costs of moving people or materials. The costs of processing and moving information have dropped by 98% and 92% respectively, in real terms since 1960. In addition, there are big differences in the rates of change within the real costs of moving people using different travel modes--just as big differences exist within the real costs of moving materials using different modes. For example, the real costs of moving materials by domestic rail and inland waterway have decreased by 58% and 42% in real terms, respectively, while inter-city trucking costs have not changed significantly in real terms since 1960. Thus, this paper suggests that the 'new economics of distance' is not about the disappearance of distance nor the demise of borders as factors in economics. Rather, 'the new economics of distance' is about the increasing role played by logistics management and the adjustment processes that are occurring as firms creatively seek to substitute between types of resources and between the modes and media for moving those resources.Industrial Organization,

    Large and realistic models of Amorphous Silicon

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    Amorphous silicon (a-Si) models are analyzed for structural, electronic and vibrational characteristics. Several models of various sizes have been computationally fabricated for this analysis. It is shown that a recently developed structural modeling algorithm known as force-enhanced atomic refinement (FEAR) provides results in agreement with experimental neutron and x-ray diffraction data while producing a total energy below conventional schemes. We also show that a large model (500 atoms) and a complete basis is necessary to properly describe vibrational and thermal properties. We compute the density for a-Si, and compare with experimental results

    Realistic inversion of diffraction data for an amorphous solid: the case of amorphous silicon

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    We apply a new method "force enhanced atomic refinement" (FEAR) to create a computer model of amorphous silicon (a-Si), based upon the highly precise X-ray diffraction experiments of Laaziri et al. The logic underlying our calculation is to estimate the structure of a real sample a-Si using experimental data and chemical information included in a non-biased way, starting from random coordinates. The model is in close agreement with experiment and also sits at a suitable minimum energy according to density functional calculations. In agreement with experiments, we find a small concentration of coordination defects that we discuss, including their electronic consequences. The gap states in the FEAR model are delocalized compared to a continuous random network model. The method is more efficient and accurate, in the sense of fitting the diffraction data than conventional melt quench methods. We compute the vibrational density of states and the specific heat, and find that both compare favorably to experiments.Comment: 7 pages and 10 figure

    Studying resist stochastics with the multivariate poisson propagation model

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    Progress in the ultimate performance of extreme ultraviolet resist has arguably decelerated in recent years suggesting an approach to stochastic limits both in photon counts and material parameters. Here we report on the performance of a variety of leading extreme ultraviolet resist both with and without chemical amplification. The measured performance is compared to stochastic modeling results using the Multivariate Poisson Propagation Model. The results show that the best materials are indeed nearing modeled performance limits

    Regional Differences in Use of Food Stamps and Food Pantries by Low Income Households in the United States

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    The purpose of this paper is to examine the use of food stamps and private food assistance in different regions of the country during 1999, a year when food stamp use dropped to its lowest point in the recent past. Our results show that impoverished families in the South are less likely than those in other regions to obtain private food assistance, although they are more likely than those in the West or Midwest to use food stamps. Low-income families in the Northeast are also more likely than those in the West or Midwest to use food stamps.food insecurity, food stamps, food pantries, Food Security and Poverty,

    Data Note: Persons Served in Community Mental Health Programs and Employment

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    State Mental Health Agencies provide a wide range of supports to consumers including rehabilitation services, vocational and pre vocational training, and supported and competitive employment supports. This Data Note explores how states vary in number of individuals served in Community Mental Health Programs, i.e., all services not provided in an inpatient setting, who are employed as well as the percentage of individuals served in Community Mental Health Programs who are employed
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