Status Review and Conservation Initiatives for American Bison: A Continental Perspective

Five hundred years ago, there were tens of millions of American bison (Bison bison) roaming free on the plains of North America from Alaska to northern Mexico. The decimation of the American bison in the late 1800s inspired the first recovery of bison and an entire conservation movement that protected wildlife and wild places across North America. As of 2008, there were ~ 400,000 bison in commercial herds in North America, some 93 percent of the continental population. There were 61 plains bison conservation herds containing ~ 20,500 animals, and 11 conservation herds of wood bison, containing nearly 11,000 animals. Little progress has been made in recent decades to increase the number of animals in conservation herds. Many factors affect survival of bison populations, including limited habitat and severe winters. Yet, the greatest challenge is to overcome the common perception that the bison, which has had a profound influence on the human history of North America, socially, culturally and ecologically, no longer belongs on the landscape. The key to recovery of this species is recognition that the American bison is a wildlife species and needs to be conserved as wildlife. Recently a new conservation strategy was developed by the IUCN bison specialist group and a new vision for the ecological restoration of bison was described by the Wildlife Conservation Society under our American Bison Society initiative. A new Continental vision for the American bison is inspiring a second recovery and helping to restore functional grassland ecosystems

Gyroscopic polynomials

Gyroscopic alignment of a fluid occurs when flow structures align with the rotation axis. This often gives rise to highly spatially anisotropic columnar structures that in combination with complex domain boundaries pose challenges for efficient numerical discretizations and computations. We define gyroscopic polynomials to be three-dimensional polynomials expressed in a coordinate system that conforms to rotational alignment. We remap the original domain with radius-dependent boundaries onto a right cylindrical or annular domain to create the computational domain in this coordinate system. We find the volume element expressed in gyroscopic coordinates leads naturally to a hierarchy of orthonormal bases. We build the bases out of Jacobi polynomials in the vertical and generalized Jacobi polynomials in the radial. Because these coordinates explicitly conform to flow structures found in rapidly rotating systems the bases represent fields with a relatively small number of modes. We develop the operator structure for one-dimensional semi-classical orthogonal polynomials as a building block for differential operators in the full three-dimensional cylindrical and annular domains. The differential operators of generalized Jacobi polynomials generate a sparse linear system for discretization of differential operators acting on the gyroscopic bases. This enables efficient simulation of systems with strong gyroscopic alignment

Teacher opinions as to their relations to the guidance functions of a school

Call number: LD2668 .R4 1965 E4

Analysis Of Hot Section Failures On Gas Turbines In Process Plant Service.

LecturePg. 9-20In-service failures of process plant gas turbines can have major economic consequences in terms of repairs and downtime. Following such an incident, steps need to be taken to avoid a recurrence. This is best accomplished through a formal analysis of failure, and this paper discusses the key aspects of the procedure. Several case histories pertaining to hot section failures on mechanical drive and generator drive gas turbines in a variety of process plant applications are also presented. These provide a representative cross-section of the different failure mechanisms and range of causes that can be encountered as well as demonstrating the multidisciplinary approaches used to investigate the incidents. Lessons learned are highlighted

Quantifying the impact of an extreme climate event on species diversity in fragmented temperate forests: the effect of the October 1987 storm on British broadleaved woodlands

1. We report the impact of an extreme weather event, the October 1987 severe storm, on fragmented woodlands in southern Britain. We analysed ecological changes between 1971 and 2002 in 143 200-m2 plots in 10 woodland sites exposed to the storm with an ecologically equivalent sample of 150 plots in 16 non-exposed sites. In both years, understorey species-richness, species composition, soil pH and woody basal area of the tree and shrub canopy were measured. 2. We tested the hypothesis that the storm had deflected sites from the wider national trajectory of an increase in woody basal area and reduced understorey species-richness associated with ageing canopies and declining woodland management. We also expected storm disturbance to amplify the background trend of increasing soil pH, a UK-wide response to reduced atmospheric sulphur deposition. Path analysis was used to quantify indirect effects of storm exposure on understorey species richness via changes in woody basal area and soil pH. 3. By 2002, storm exposure was estimated to have increased mean species richness per 200 m2 by 32%. Woody basal area changes were highly variable and did not significantly differ with storm exposure. 4. Increasing soil pH was associated with a 7% increase in richness. There was no evidence that soil pH increased more as a function of storm exposure. Changes in species richness and basal area were negatively correlated: a 3.4% decrease in richness occurred for every 0.1-m2 increase in woody basal area per plot. 5. Despite all sites substantially exceeding the empirical critical load for nitrogen deposition, there was no evidence that in the 15 years since the storm, disturbance had triggered a eutrophication effect associated with dominance of gaps by nitrophilous species. 6. Synthesis: Although the impacts of the 1987 storm were spatially variable in terms of impacts on woody basal area, the storm had a positive effect on understorey species richness. There was no evidence that disturbance had increased dominance of gaps by invasive species. This could change if recovery from acidification results in a soil pH regime associated with greater macronutrient availability