3,478 research outputs found

    Notes on the frugivorous fruit fly (Diptera: Tephritidae) fauna of western Africa, with description of a new Dacus species

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    The species richness of the frugivorous fruit fly fauna of western African (in particular of Ivory Coast, Ghana, Togo, Benin and Nigeria) is discussed. The diversity is compared at a national level and between the ecoregions within the national boundaries of the study area. A new species, Dacus goergeni sp. nov. is described and additional taxonomic notes are presented

    The Politically Engaged Society, the State, Policy, Comparison

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    Summaries Gordon White's contributions to the study of China fall under at least four major rubrics. Most important was his analysis of political engagement by a breathtaking range of social classes and groups in both the Maoist and Dengist periods. Second, he appreciated the role of the state analytically in shaping society's political engagement, and normatively because he thought it had essential social and economic responsibilities. Third, he hoped to influence policy indirectly, by providing cautionaries for policy?makers and by writing for and collaborating with social scientists in other countries, especially China. Fourth, he placed China squarely in comparative contexts, first of revolutionary socialist states, and then of East Asian developmental states

    Multi-epoch Sub-arcsecond [Fe II] Spectroimaging of the DG Tau Outflows with NIFS. II. On the Nature of the Bipolar Outflow Asymmetry

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    The origin of bipolar outflow asymmetry in young stellar objects (YSOs) remains poorly understood. It may be due to an intrinsically asymmetric outflow launch mechanism, or it may be caused by the effects of the ambient medium surrounding the YSO. Answering this question is an important step in understanding outflow launching. We have investigated the bipolar outflows driven by the T Tauri star DG Tauri on scales of hundreds of AU, using the Near-infrared Integral Field Spectrograph (NIFS) on Gemini North. The approaching outflow consists of a well-collimated jet, nested within a lower-velocity disc wind. The receding outflow is composed of a single-component bubble-like structure. We analyse the kinemat- ics of the receding outflow using kinetic models, and determine that it is a quasi-stationary bubble with an expanding internal velocity field. We propose that this bubble forms because the receding counterjet from DG Tau is obstructed by a clumpy ambient medium above the circumstellar disc surface, based on similarities between this structure and those found in the modeling of active galactic nuclei outflows. We find evidence of interaction between the obscured counterjet and clumpy ambient material, which we attribute to the large molecular envelope around the DG Tau system. An analytical model of a momentum-driven bubble is shown to be consistent with our interpretation. We conclude that the bipolar outflow from DG Tau is intrinsically symmetric, and the observed asymmetries are due to environmental effects. This mechanism can potentially be used to explain the observed bipolar asymmetries in other YSO outflows.Comment: 16 pages, 10 figures, accepted for publication in MNRA

    Particle Astrophysics and Cosmology: Cosmic Laboratories for New Physics (Summary of the Snowmass 2001 P4 Working Group)

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    The past few years have seen dramatic breakthroughs and spectacular and puzzling discoveries in astrophysics and cosmology. In many cases, the new observations can only be explained with the introduction of new fundamental physics. Here we summarize some of these recent advances. We then describe several problem in astrophysics and cosmology, ripe for major advances, whose resolution will likely require new physics.Comment: 27 pages, 14 figure

    Illinois River Phosphorus Sampling Results and Mass Balance Computation

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    Phosphorus levels in the Illinois River are of great interest to the people of the States of Arkansas and Oklahoma. A great deal of effort has been expended to ascertain and modify the phosphorus impacts on the river. An automatic water sampling station was installed on the Illinois River just upstream from the State line in 1996 to accurately quantify the phosphorus in the Arkansas portion of the watershed. This paper summarizes five years worth of phosphorus sampling results at that site. In addition, a simple mass balance for phosphorus in the Illinois River Watershed above the sampling station was developed. The mass balance consisted of determining phosphorus inputs in the drainage area and comparing these to phosphorus outputs, during the same five-year period, allowing for an estimation of phosphorus accumulation. Sampling results showed that phosphorus levels were rapidly increasing in the Illinois River at the State line. Input information showed that over 7 million pounds of phosphorus were discharged into the 575 square mile basin annually. Mass balance calculations indicated that the point source discharges were responsible for up to 43% of the phosphorus in the river. The calculations indicate that only 4% of the phosphorus applied in the watershed reached the river annually. The remaining 96% accumulated in the watershed at an average rate of 8 kg per pasture acre per year. The effect of point source reductions was investigated and resulting mean concentrations were compared to a 0.037 mg/l in-stream phosphorus limit recently adopted by the State of Oklahoma
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