5 resultados para Usa
em DigitalCommons@University of Nebraska - Lincoln
Resumo:
A new species of a philometrid nematode, Margolisianum bulbosum, is described from the subcutaneous tissue in the mouth (larvigerous females), head (males, ovigerous, and larvigerous females), and eye (preovigerous females) of the southern flounder, Paralichthys lethostigma, from Mississippi Sound. It is placed in a new genus diagnosed by the combination of 8 large, paired but separate cephalic papillae; no inner cephalic papillae; an esophagus with a separate, muscular anterior bulb; a prominent mononuclear esophageal gland; and variable, irregularly distributed cuticular bosses in the females, as well as a vestigial rectum, particularly in larvigerous females. Some female specimens exhibit rows of lateral grooves and longitudinal ridges near the posterior end. Males have two small slightly subequal spicules, a barbed gubernaculum, 4 pairs of small cephalic papillae, and a bipartite hypodermal extension within a membranous cuticle on the posterior end. Males, ovigerous females, and larvigerous females appear to be present year round in this sporadic infection in Mississippi.
Resumo:
The availability of water shapes life in the western United States, and much of the water in the region originates in the Rocky Mountains. Few studies, however, have explicitly examined the history of water levels in the Rocky Mountains during the Holocene. Here, we examine the past levels of three lakes near the Continental Divide in Montana and Colorado to reconstruct Holocene moisture trends. Using transects of sediment cores and sub-surface geophysical profiles from each lake, we find that mid-Holocene shorelines in the small lakes (4–110 ha) were as much as ~10 m below the modern lake surfaces. Our results are consistent with existing evidence from other lakes and show that a wide range of settings in the region were much drier than today before 3000–2000 years ago. We also discuss evidence for millennial-scale moisture variation, including an abruptly-initiated and -terminated wet period in Colorado from 4400 to 3700 cal yr BP, and find only limited evidence for low-lake stands during the past millennium. The extent of low-water levels during the mid-Holocene, which were most severe and widespread ca. 7000–4500 cal yr BP, is consistent with the extent of insolation-induced aridity in previously published regional climate model simulations. Like the simulations, the lake data provide no evidence for enhanced zonal flow during the mid-Holocene, which has been invoked to explain enhanced mid-continent aridity at the time. The data, including widespread evidence for large changes on orbital time scales and for more limited changes during the last millennium, confirm the ability of large boundary-condition changes to push western water supplies beyond the range of recent natural variability.
Resumo:
The changes in diatom species composition in a sediment core from Crevice Lake, Yellowstone National Park, spanning the past 2550 yr, were used to reconstruct long-term limnological and ecological conditions that may be related to late Holocene climate variability. Planktic forms dominate the fossil diatom assemblages throughout this record, but changes in species dominance indicate varying nutrient levels over time, particularly phosphorus. The changes in the nutrient concentrations in the lake were probably driven by changes in temperature and wind strength that affected the duration of watercolumn mixing and thus the extent of nutrient recycling from deep waters. Prior to 2100 cal before present (BP), Stephanodiscus minutulus and Synedra tenera dominated, suggesting long cool springs with extensive regeneration of phosphorus from the hypolimnion that resulted from isothermal mixing. From 2100 to 800 cal BP, these species were replaced by Cyclotella michiganiana and Cyclotella bodanica. These species are characteristic of lower nutrient concentrations and are interpreted here to reflect warm summers with long periods of thermal stratification. From 800 to 50 cal BP, S. minutulus dominated the diatom assemblage, suggesting a return to lengthy mixing during spring. The most dramatic late Holocene changes in the fossil diatom assemblages occurred during the transition from the Medieval Period to the Little Ice Age, approximately 800 cal BP.
Resumo:
Responding to a U.S. Federal court order to improve discharged wastewater quality, Augusta, Georgia initiated development of artificial wetlands in 1997 to treat effluents. Because of the proximity to Augusta Regional Airport at Bush Field, the U.S. Federal Aviation Administration expressed concern for potential increased hazard to aircraft posed by birds attracted to these wetlands. We commenced weekly low-level aerial surveys of habitats in the area beginning January, 1998. Over a one-year period, 49 surveys identified approximately 42,000 birds representing 52 species, including protected Wood Storks and Bald Eagles, using wetlands within 8 km of the airport. More birds were observed during the mid-winter and fall/spring migratory seasons (1,048 birds/survey; October - April) than during the breeding/post-breeding seasons (394 birds/survey; May - September). In winter, waterfowl dominated the avian assemblage (65% of all birds). During summer, wading birds were most abundant (56% of all birds). Habitat changes within the artificial wetlands produced fish kills and exposed mudflats, resulting in increased use by wading birds and shorebirds. No aquatic birds were implicated in 1998 bird strikes, and most birds involved could safely be placed within songbird categories. Airport incident reports further implicated songbirds. These findings suggested that efforts to decrease numbers of songbirds on the airport property must be included in the development of a wildlife hazard management plan. Seasonal differences in site use among species groups should also be considered in any such plan. Other wetlands within 8 km of the airport supported as many or more birds than the artificial wetlands. With proper management of the artificial wetlands, it should be possible to successfully displace waterfowl and wading birds to other wetlands further from the airport.
Resumo:
Lessons from around the world; What does it matter about early childhood education? Why the controversy about public support for early childhood education? What process or system should be used to determine what works in early education? Can the same process be used to improve services? What is the role of government? Alternatives: 1. Consumers should determine… (What happens when private choices drive the market for early childhood services?) Observed quality of care in four Midwestern states; Parent data: “All things considered, how would you grade the quality of the care your child is receiving from his/her current caregiver?” Role of government What is a Quality Rating System? Ten states have implemented statewide systems (e.g. Colorado, Kentucky, Oklahoma, North Carolina) Findings 2. Objective science should determine… Firm findings from empirical research 3. Something else is needed: Some differences between Italian and American models. Teacher action research (and documentation) from a Reggio-inspired preschool in South Korea by Misuk Kim. Teacher Action Research at the Ruth Staples CDL. Can we now answer our opening questions? What process or system should be used to determine what is best for young children? Can the same process be used to improve the quality of services? Conclusions: The free market does not work well to determine quality in early education and care; Licensing, accreditation, and quality rating systems can help improve the market; Empirical research is useful for measuring what works; Teacher action research (reflective practice) is necessary for fostering continuous quality improvement. The tower of quality.