Now showing items 1-20 of 726

• #### A Comparative Analysis Of Mhc Genetic Diversity At The Class Ii Loci In Some Arctic Mammalian Species

The genetic diversity at the Major Histocompatibility Complex (MHC) class II loci in some arctic mammalian species, musk ox, moose, caribou, and bears, have been characterized. The general objective of this study was to broaden the knowledge of the MHC polymorphism, selection, evolution and function in natural populations of arctic mammals. Allelic variation was assessed by analysis of MHC class II DR and DQ loci at exon 2 region. Sequences were amplified via the polymerase chain reaction (PCR), followed by either DNA sequencing after cloning of the PCR products or single-stranded conformation polymorphism (SSCP) analysis and sequencing. Monomorphism was observed at DRA, DRB, and DQA loci in both musk ox and moose, but relatively high polymorphism was observed at DQB locus. For the first time, four DQB alleles and one DQA allele were found identical in these two distantly related species which split approximately 23 million years ago, indicating stringent trans-species polymorphism. Both DRB and DQB seem to be functional by analyzing their cDNA expression. An intermediate level of MHC polymorphism at DRB locus was found in caribou and reindeer. Phylogenetic analysis of cervid DRB alleles indicated that all reindeer and caribou DRB alleles were from a monophyletic lineage, implying an ancient bottleneck in R. tarandus. High polymorphism at the DRB locus in polar bear was also observed. Four DRB alleles were found to be shared by polar bear and dog. The trans-species polymorphism of the shared alleles may have been persistent for 10 to 15 million years. Nine DQB alleles rather than two DRB alleles were also found in a pure domestic dog lineage of Doberman pinschers. These data imply that selection pressure may vary among MHC loci. In summary, the general level of MHC polymorphism at the class II loci is lower in herbivores (musk ox, moose, and caribou) than carnivores (polar bear). Biased selection may be applied on DQB locus. Stringent trans-species polymorphism between two distantly related species may be the result of persistent selection by shared parasites in the same environment.
• #### A Comparison Of The Effects Of Analysis Techniques And Computer Systems In Remote Sensing Technology And A Reference Data Collection Technique

A technique for collecting and recording reference data which considers the spectral and spatial characteristics of Landsat data, the computer system being used, and the gradient nature of wildland vegetation was developed and described. Different analysis techniques for four critical factors affecting the accuracy of computer-aided analysis products were evaluated. Comparisons were made on the basis of accuracy evaluations of two methods of data/analyst interface, three methods of deriving training statistics, three methods of spectral class descriptions, and two levels of map category detail. The primary data set used was digital Landsat multispectral data for a study area around Fairbanks, Alaska. Reference data were developed from field work and photo-interpretation. The training methods compared were supervised, unsupervised, and modified clustering. The three spectral class description methods were: (1) labels derived from the training data; (2) the color display screen; and (3) from ground plot data. Community level cover types were compared with generalized map categories. The effect of post-classification stratification was evaluated. The reference data technique provides geographically located stands and cover types identifications with a flexible coding system that can be aggregated to correspond to the spectral data categories. No difference in classification accuracy was found for an experienced analyst using a printout oriented system such as EDITOR or a screen oriented system such as IDIMS. The modified cluster method of developing training statistics was more effective and efficient than supervised or unsupervised training methods. The use of ground plot data and subsequent stratification improved the descriptions of spectral classes. Generalized mapping categories were more accurate than detailed mapping categories. Knowledge of the ecologic, floristic, and spectral characteristics of the cover types in the study area is necessary to develop spectral class descriptions and stratification criteria.
• #### A Computer Simulation Of Auroral Arc Formation

Recent satellite measurements have revealed two intriguing features associated with the formation of auroral arcs. The first is that an auroral arc is produced by a sheet of electrons accelerated along a geomagnetic field-aligned potential drop, and the second is that these electrons carry a field-aligned, upward directed electric current. In order to explain these measurements, a self-consistent, time dependent, computer simulation of auroral arc formation has been developed. The simulation demonstrates for the first time that a stable V-shaped potential structure, called an auroral double layer, develops spontaneously as a result of an ion shielded electron current sheet interacting with a conducting ionosphere. The double layer accelerates current-carrying electrons into the upper atmosphere at auroral energies. The double layer potential depends critically on the drift speed of the current-carrying electrons and on the temperature of the ambient shielding ions. Localized double layers occur near the ionosphere when the geomagnetic field is assumed to be uniform, but when a converging magnetic field is introduced, the double layer becomes extended due to the presence of an additional population of electrons trapped between the magnetic mirror and the double layer potential. The simulated auroral current sheet is subject to auroral curl and fold type deformations due to unstable Kelvin-Helmholtz waves. The previous incompletely understood auroral fold producing mechanism is described.
• #### A Descriptive Analysis Of Yakutat Tlingit Musical Style.

Ninety-nine songs from Yakutat, Alaska were analyzed in an effort to determine a musical style of the Gulf Coast Tlingit. Songs were grouped into seven categories from which general trends of style were deduced. Analysis, which was based on the transcriptions of David P. McAllester, included interval distribution, range, tone systems, weighted scales, melodic contour, tempo, duration and rest values, drumming patterns, formal structure, and song length. The transcriptions and data for drumming patterns, formal structure and song length were provided by McAllester in "Under Mount Saint Elias: The History and Culture of the Yakutat Tlingit," by Frederica de Laguna, 1972, Smithsonian Contributions to Anthropology, Volume 7, Washington, D.C: Smithsonian Institution Press. Stylistic differences in the areas of interval distribution, range, tone systems, weighted scales, melodic contour, and tempo were discovered between the two largest categories, the traditional Sib Potlatch songs and the songs of more recent composition called Haida Mouth songs. <p>
• #### A Detailed Structural Analysis Across A Regional Unconformity, Forks Of The Canning River, Franklin Mountains, Northeastern Brooks Range, Alaska

Structural analysis on the northern flank of the 'Franklin Mountains anticlinorium,' northeastern Brooks Range, Alaska, addressed the geometry and sequence of structures, and the deformational mechanics of the Franklinian and Ellesmerian sequences, which are separated by a sub-Mississippian unconformity. The anticlinorium is comprised of two horses of Franklinian sequence rocks in a Cenozoic north-vergent duplex thrust system. South-dipping pre-Mississippian slaty cleavage may have been a plane of preferred failure during ramp formation. Above the unconformity, the Kekiktuk Conglomerate remained attached to pre-Mississippian rocks, deforming with them beneath a roof thrust in the Mississippian Kayak Shale. Increased shear stress and overburden pressure beneath overthrust Franklinian sequence rocks may have led to local detachment near the unconformity surface. Above the Kayak Shale, progressive detachment folding and thrust faulting occurred in the Lisburne and Sadlerochit Groups as a result of emplacement of the two underlying horses. <p>
• #### A fully two-dimensional flux-corrected transport algorithm for hyperbolic partial differential equations

Numerical solutions of the hyperbolic partial differential equation, $\partial p\over\partial t$ + $\vec\nabla \cdot (p\vec u)$ = 0, will generally encounter the difficulties of large diffusion and oscillations near steep gradients or discontinuities. The method of Flux-Corrected Transport (FCT) developed by Boris and Book has conquered these difficulties for the one-dimensional case. Motivated by this one-dimensional FCT algorithm, a fully two-dimensional FCT algorithm is developed in this present work. This fully two-dimensional FCT algorithm is a two-step procedure: (1) the transport scheme, and (2) the antidiffusion scheme. The second step of the procedure could also be replaced by an application of the one-dimensional antidiffusion algorithm in the x direction and the y direction separately. The stability, phase shift errors and positivity for the fully two-dimensional transport scheme are analyzed. Test results are presented. The possibility of the extension of the FCT method to three dimensions are discussed.
• #### A Maritime Sense Of Place: Southeast Alaska Fishermen And Mainstream Nature Ideologies

This thesis portrays Southeast Alaska fishermen's 'senses of place' on the sea, elicited through interviews. The distinctiveness of a fishing culture, and the demands and opportunities of the occupation and environment, result in a relationship to place different from the majority society. Themes discussed include being at home on the sea, the environment as a basis for occupational choice, territorial flexibility, preference for wild nature, and wild nature produces exploitatable surpluses. The variability of the environment affects patterns of learning, models of nature, and values in inter-personal interactions. Relationship to 'place' is found to be central to the culture, but as the area becomes identified by outsiders as "wilderness," national environmental organizations and others regard fishermen as 'out of place'. Differences from modern Western society in relationship to 'place' and 'nature', highlighted by the Glacier Bay National Park case, are proposed to explain negative perceptions of these fisheries. <p>
• #### A nested watershed study in the Kuparuk River basin, arctic Alaska: Streamflow, scaling, and drainage basin structure

The central hypothesis of this dissertation is that permafrost influences the form, function, and scaling of hydrologic and geomorphologic characteristics in the Kuparuk River basin in Northern Alaska. This problem was addressed using three approaches: field hydrologic studies, statistical scaling studies, and geomorphology studies using digital elevation models. Permafrost and snow exert significant controls on hydrologic processes in the Kuparuk River basin. Storm hydrographs show fast responses, long time lags, extended recessions, and high runoff/precipitation ratios. These features arise from the diminished storage capacity caused by permafrost. Summer storm flow compositions in the are dominated by old water, as is commonly observed in basins without permafrost. However, the thawing active layer imposes seasonal trends on storm flow composition and other streamflow characteristics. These seasonal trends are often masked by precipitation patterns. Significant differences exist in the spatial variability and scaling of streamflow between arctic and temperate basins. Streamflow in arctic basins is subject to simple scaling, whereas streamflow in temperate regions is subject to multiscaling. Since the variability of streamflow downstream results from the timing of storm hydrographs upstream, regional scaling differences may result from the differences in runoff generation mechanisms in basins with and without permafrost. Fractal analysis of channel networks, and the scaling of mass distribution suggest that channel networks in the Kuparuk River basin are underdeveloped. Hillslope water tracks convey water off slopes, but the organization of water tracks lacks universal characteristics of mass and energy distribution common to other rivers, and hence cannot be considered fluvial channels. However, the heads of water tracks are located where some theoretical models of channel initiation predict that channels should occur. A likely scenario is that a rudimentary channel network was formed soon after deglaciation, but was never allowed to develop into a mature network due to the limits that permafrost imposes on erosion. An encompassing conclusion is that the Kuparuk River basin is adjusted to arctic conditions in both form and function. Consequently, thermal changes to the existing permafrost condition may impose significant changes in the erosional development of channel networks and in the subsequent hydrologic response.
• #### A Search For Thermospheric Composition Perturbations Due To Vertical Winds

The thermosphere is generally in hydrostatic equilibrium, with winds blowing horizontally along stratified constant-pressure surfaces, driven by the dayside-to-nightside pressure gradient. A marked change in this paradigm resulted after Spencer et al. [1976] reported vertical wind measurements of 80 m&middot;s-1 from analyses of AE-C satellite data. It is now established that the thermosphere routinely supports large-magnitude (~30-150 m&middot;s-1) vertical winds at auroral latitudes. These vertical winds represent significant departure from hydrostatic and diffusive equilibrium, altering locally---and potentially globally---the thermosphere's and ionosphere's composition, chemistry, thermodynamics and energy budget. Because of their localized nature, large-magnitude vertical wind effects are not entirely known. This thesis presents ground-based Fabry-Perot Spectrometer OI(630.0)-nm observations of upper-thermospheric vertical winds obtained at Inuvik, NT, Canada and Poker Flat, AK. The wind measurements are compared with vertical displacement estimates at ~104 km2 horizontal spatial scales determined from a new modification to the electron transport code of Lummerzheim and Lilensten [1994] as applied to FUV-wavelength observations by POLAR spacecraft's Ultraviolet Imager [Torr et al. , 1995]. The modification, referred to as the column shift, simulates vertical wind effects such as neutral transport and disruption of diffusive equilibrium by vertically displacing the Hedin [1991] MSIS-90 [O2]/[N2] and [O]/([N2]+[O2]) mixing ratios and subsequently redistributing the O, O2, and N 2 densities used in the transport code. Column shift estimates are inferred from comparisons of UVI OI(135.6)-nm auroral observations to their corresponding modeled emission. The modeled OI(135.6)-nm brightness is determined from the modeled thermospheric response to electron precipitation and estimations of the energy flux and characteristic energy of the precipitation, which are inferred from UVI-observed Lyman-Birge-Hopfield N2 emissions in two wavelength ranges. Two-dimensional column shift maps identify the spatial morphology of thermospheric composition perturbations associated with auroral forms relative to the model thermosphere. Case-study examples and statistical analyses of the column shift data sets indicate that column shifts can be attributed to vertical winds. Unanticipated limitations associated with modeling of the OI(135.6)-nm auroral emission make absolute column shift estimates indeterminate. Insufficient knowledge of thermospheric air-parcel time histories hinders interpretations of point-to-point time series comparisons between column shifts and vertical winds.
• #### A statewide training model for supported employment using master trainers

Alaska's vast land mass and diversified urban, rural, and remote communities require innovative training curricula to meet training needs in supported employment. A competency-based training program using an independent learning format and master trainers was developed to meet these extreme needs. These training methods were evaluated with survey instruments at the time of training and at 3 months, 6 months, and 1 year follow up. The data demonstrate that the training materials as well as the independent study format and master trainer model were effective training methods. We conclude that the training methods developed are effective in meeting the diverse training needs of urban, rural, and remote sites.
• #### A study of one-dimensional nonlinear hydromagnetic waves and collisionless shocks

A variety of nonlinear hydromagnetic waves have been observed in the collisionless solar wind plasma. A comprehensive theoretical study of nonlinear hydromagnetic waves, including rotational discontinuities and collisionless shocks, is carried out in this thesis by means of both analytical solutions and numerical simulations. Nonlinear hydromagnetic waves are governed by the interplay of the dispersion process, the collisionless dissipation process and the nonlinear steepening process. The purpose of this thesis is to understand the nonlinear behavior of hydromagnetic waves in terms of these fundamental processes. It is shown that the rotational discontinuity structures observed in the solar wind and at the magnetopause are nonlinear Alfven wave solutions of the collisionless two-fluid plasma equations. In these nonlinear wave solutions, nonlinear steepening is self-consistently balanced by dispersion. Collisionless viscous dissipation is the dominant dissipation in high Mach number shocks, which converts the flow energy into thermal energy. Hybrid simulations show that the collisionless viscous dissipation can result from the reflection and pitch-angle scattering of incoming ions flowing through the magnetic structures in the shock transition region. Collisionless dissipations in hydromagnetic shocks is governed by the magnetic structures in the shock transition region. The dissipation in turn can modify the wave structures and balance the nonlinear steepening. However, such delicate balance of the dispersion, dissipation, and nonlinear steepening has been observed to break down momentarily in high Mach number quasi-parallel shocks. This leads to the so-called cyclic shock front reformation seen in the hybrid simulations. The shock front reformation can be explained in terms of momentary off-balance between the dispersion-dissipation on the one hand and the nonlinear steepening on the other hand. The off-balance occurs after a significant fraction of incoming ions are reflected. Each off-balance lasts a few ion gyro periods, which governs the shock front reformation time scale.