A Walleye Pollock (Theragra Chalcogramma) Depletion Estimator For The Eastern Bering Sea

Thesis (Ph.D.) University of Alaska Fairbanks, 2005The decline of the Steller Sea lion in the eastern Bering Sea over the last 25 years has resulted in increased management of the pollock fishery due to requirements of the Endangered Species Act, as food competition was hypothesized to contribute to the decline. Our research focused on determining if the pollock fishery was causing significant depletion in the eastern Bering Sea, particularly in Steller sea lion critical habitat. DeLury depletion models were fitted to catch and effort data from 1995 to 1999, from the observer program, which required considerable processing to obtain a database at a temporal and spatial scale that is much finer than that used for stock assessment in the eastern Bering Sea. The catch per unit effort (CPUE) data were standardized in a unique way in that the data were stratified in space and time and standardized using separate general linear models for each stratum. A significant amount of depletion was detected in the pollock fishery from 1995--1999. Depletion estimates of fishery mortality tended to be an order of magnitude smaller than those found in traditional stock assessments. Post hoc analyses indicated that depletion is detected more easily in areas of low abundance due to the hyperstable relationship between CPUE and biomass, possibly exacerbated by a lack of search time in the model. Evidence further suggested that dispersing exploitation pressure decreases local depletion, and pollock may repopulate a depleted area within weeks. Finally, a hierarchical spatial Bayesian analysis with a conditional autoregressive model was constructed to unify the analysis. Because the data were relatively clean of outliers and not over dispersed, significant changes in the results between the frequentist and Bayesian based analyses were not found as was little evidence of spatial autocorrelation in the estimates of catchability

Fire Regimes of Lower-elevation Forests in Great Smoky Mountains National Park, Tennessee, U.S.A.

Disturbance is a natural part of any forest ecosystem. When disturbance regimes are altered, the forest stands will reflect those changes. Southern Appalachian xeric pine-oak woodlands are one forest type that has experienced such change, primarily in the form of fire suppression. The western side of Great Smoky Mountains National Park contains stands of large trees that escaped earlier intensive logging, show evidence of past fire, and provide an ideal setting for reconstructing stand histories. For three lower-elevation (ca. 500 m ASL) study sites, I used crossdated yellow pine tree-ring chronologies and records from cross-sections taken from living and dead pines to reveal historical patterns and relationships of wildfire, climate, and human activity. Cores and vegetation data collected at three 20 x 50 m plots per site provided age structure, stand structure, and stand composition. All three chronologies displayed a high degree of sensitivity to yearly environmental fluctuations and extended back through the 1700s. Yellow pine growth was strongly and positively correlated with winter temperatures, which were primarily influenced by the North Atlantic Oscillation. The tested climate variables displayed relationships that appeared to shift over time, or across an ambiguous boundary on which the park resides. Climate oscillations in both the Atlantic Ocean and Pacific Ocean modulated wildfire frequency and events. Wildfire events occurred frequently prior to park establishment in 1934 and were primarily anthropogenic in origin. Most fires burned during dormancy or early in the growing season, but widespread and more recent fires tended to occur later. Fire frequency peaked in the 1800s with an average return interval of two years. Absence of wildfire during suppression was associated with establishment of fire-sensitive species, such as red maple and eastern white pine. Yellow pine regeneration was weak and dominated by Virginia pine. Results from this study can be used by park personnel to plan and manage fires to restore ecosystem processes to a pre-suppression state. The chronologies provided three centuries of data that can be used to reconstruct climate variables and to enhance our understanding of climate dynamics

Measurements and simulations of grain-scale deformation in tantalum multicrystals

Most engineering materials have complex microstructures that can affect their properties in various ways. Metals are usually polycrystalline, and their inherently heterogeneous crystallographic nature can produce strong variations in deformation behavior at the grain (i.e., micron) scale. In small components, or when deformations are localized by defects or intentional geometry (e.g., holes or fillets), the details of grain-scale deformation can dictate the material’s performance. In this study, we used micron-scale digital image correlation (µDIC), electron backscatter diffraction (EBSD), and finite element analysis to measure and predict, respectively, the evolution of surface strains and crystallographic orientations during the tensile deformation of tantalum multicrystals containing only a few columnar grains in the gauge section. These measurements are compared to crystal plasticity finite element simulations of the subgrain surface strain fields, and the predictions provide an accurate estimate of the location of failure initiation. We will outline the µDIC, EBSD, and crystal plasticity finite element methods; describe the procedure by which large-grained tantalum multicrystals were fabricated; discuss the validation of the simulations’ predictions against the experimental data; and provide examples of the application of the simulations to real engineering components

A kinetic Monte Carlo method for the atomic-scale simulation of chemical vapor deposition: Application to diamond

We present a method for simulating the chemical vapor deposition (CVD) of thin films. The model is based upon a three-dimensional representation of film growth on the atomic scale that incorporates the effects of surface atomic structure and morphology. Film growth is simulated on lattice. The temporal evolution of the film during growth is examined on the atomic scale by a Monte Carlo technique parameterized by the rates of the important surface chemical reactions. The approach is similar to the N-fold way in that one reaction occurs at each simulation step, and the time increment between reaction events is variable. As an example of the application of the simulation technique, the growth of {111}-oriented diamond films was simulated for fifteen substrate temperatures ranging from 800 to 1500 K. Film growth rates and incorporated vacancy and H atom concentrations were computed at each temperature. Under typical CVD conditions, the simulated growth rates vary from about 0.1 to 0.8 μm/hr between 800 and 1500 K and the activation energy for growth on the {111}: H surface between 800 and 1100 K is 11.3 kcal/mol. The simulations predict that the concentrations of incorporated point defects are low at substrate temperatures below 1300 K, but become significant above this temperature. If the ratio between growth rate and point defect concentration is used as a measure of growth efficiency, ideal substrate temperatures for the growth of {111}-oriented diamond films are in the vicinity of 1100 to 1200 K. © 1997 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70750/2/JAPIAU-82-12-6293-1.pd

Modeling the interaction of light between diffuse surfaces

Mary Wollstonecraft and her daughter Mary Shelley are arguably the most important female writers of the eighteenth and nineteenth century, while Wollstonecraft is one of the most significant contributors to the women’s rights movement, with some of her ideas expressed in A Vindication of the Rights of Woman being referenced in the modern-day laws about the rights of women. This paper will analyze the life and work of Mary Wollstonecraft and Mary Shelley, focusing mostly on their most famous and most significant works, A Vindication of the Rights of Woman and Frankenstein; or The Modern Prometheus, respectively. Furthermore, it will analyze the position of women through the biographies of both writers and the autobiographical elements in their works, as well as through the analysis of the female characters in Frankenstein; or, The Modern Prometheus as a representation of more or less typical women of the time. Finally, it will search for and analyze the influence of Mary Shelley’s mother’s works and ideas on her writing in Frankenstein; or, The Modern Prometheus and her work in general. The aim of this BA paper is to analyze the position of women in society and literature through the above mentioned aspects of the life and work of Mary Wollstonecraft and Mary Shelley and to prove the importance of both of these authors, but especially Wollstonecraft, in the female struggle for obtaining the most basic human rights and the still persisting fight for gender equality

Tracking marine mammals in 3D using electronic tag data

1. Information about at-depth behaviour of marine mammals is fundamental yet very hard to obtain from direct visual observation. Animal-borne multisensor electronic tags provide a unique window of observation into such behaviours. 2. Electronic tag sensors allow the estimation of the animal's 3-dimensional (3D) orientation, depth and speed. Using tag flow noise level to provide an estimate of animal speed, we extend existing approaches of 3D track reconstruction by allowing the direction of movement to differ from that of the animal's longitudinal axis. 3. Data are processed by a hierarchical Bayesian model that allows processing of multisource data, accounting for measurement errors and testing hypotheses about animal movement by comparing models. 4. We illustrate the approach by reconstructing the 3D track of a 52-min deep dive of a Blainville's beaked whale Mesoplodon densirostris adult male fit with a digital tag (DTAG) in the Bahamas. At depth, the whale alternated regular movements at large speed (>1·5 m s-1) and more complex movements at lower speed (<1·5 m s-1) with differences between movement and longitudinal axis directions of up to 28°. The reconstructed 3D track agrees closely with independent acoustic-based localizations. 5. The approach is potentially applicable to study the underwater behaviour (e.g. response to anthropogenic disturbances) of a wide variety of species of marine mammals fitted with triaxial magnetometer and accelerometer tags.PostprintPeer reviewe