Now showing items 1903-1922 of 3332

• #### Nanotribological Characterization Of Dynamic Surfaces

This dissertation research includes three fundamental areas: utilizing an atomic force microscope (AFM) to study the nanomechanical and tribological properties, to understand friction and wear at nanometer length, and to study wear mechanisms of boride coatings for biological applications. This was the first time that an AFM was used to study the nanomechanical and tribological properties and the performance of the materials. The AFM enables detailed investigation of the wear modes at multi-length scales as well as the surface mechanical properties. Surface analysis using an AFM included the surface texture, profile of indents, wear tracks, and wear scars. The friction force microscope (FFM) revealed the relationship between surface texture and frictional properties, thus contributing to the fundamental understanding of nanotribology. A new wear model was proposed. Also, hardening was discovered under the indents. The multi-scale wear study was focused on fundamental wear mechanisms. New wear modes, different than the traditional ones, were proposed. In this research, nanocracks and other damage (hardening and plastic flow) were found at different scales. Boride coatings on refractory metals were investigated for biological applications. Tribological performance of these coatings was studied in dry and wet (biofluid) conditions. It was found that boron plays an important role in forming amorphous and crystalline wear debris.
• #### Natural abundance of nitrogen(15) in a subarctic lake and biogeochemical implications to nitrogen cycling

Stable isotope ratios of nitrogen ($\delta\sp{15}$N) were employed to track the origin and fate of nitrogen in a subarctic lake, Alaska. The annual planktonic nitrogen cycle was dominated by N$\sb2$ fixation in spring and NH$\sb4\sp+$ assimilation in summer. In winter, microbial nitrification was the major sink for NH$\sb4\sp+$ and denitrification was accounted for most of the loss of NO$\sb3\sp-.$ The small isotope fractionation in nitrification is proposed as a result of substrate (NH$\sb4\sp+)$ limitation. The temporal and spatial homogeneity of the $\delta\sp{15}$N of dissolved organic nitrogen may be related to its large pool size and refractory nature. A stable isotope mass balance suggests that the winter phytoplankton was only composed of 10 to 20% of the suspended organic matter in water column due to low primary productivity during the ice cover period. A close correlation between $\delta\sp{15}$N of phytoplankton and $\delta\sp{15}$N of dissolved pools indicates that NH$\sb4\sp+$ was the predominant nitrogen source for non-N$\sb2$-fixing algae. The similarity of $\delta\sp{15}$N between a spring blue-green bloom and N$\sb2$ suggests an atmospheric origin for nitrogen. A mixing model estimated that the blue-green algal bloom derived approximately 70% of its nitrogen from molecular nitrogen. This fixed nitrogen was further transferred to higher trophic levels via the food chain and to other primary producers following mineralization. The $\delta\sp{15}$N of aquatic macrophytes indicates that non-rooted species obtained their nitrogen from the water column while rooted species obtained their nitrogen largely from the sediment. Evidence from dual isotope tracers ($\delta\sp{15}$N and $\delta\sp{13}$C) suggests that the zooplankton were supported by phytoplankton throughout the growing season despite an apparent abundance of detritus in the water column. Benthic fauna relied on either phytoplankton detritus or other organic matter in the sediment. The $\delta\sp{15}$N data exhibit only two to three trophic levels in both planktonic and the benthic communities in Smith Lake.
• #### Natural Attenuation Of Chlorinated Solvents In Subarctic Ground Water

Little is known about natural attenuation of chlorinated solvents in subarctic ground water. This study aimed to better understand the biogeochemistry and microbiology associated with naturally occurring processes of contaminant removal at two hydrologically diverse sites near Fairbanks, Alaska. Six Mile Village, located several km north of the Tanana River, is hydrologically stable, experiencing minor fluctuations in ground-water levels. Fort Wainwright is located adjacent to the Chena River and is hydrologically dynamic, experiencing seasonal flow reversals and substantial fluctuations in water-table elevations. By comparing data collected seasonally and with data collected at the two sites, I determined how ground-water/surface-water interactions affected in situ redox conditions and, hence, natural attenuation processes. A portion of the aquifer at Fort Wainwright was undergoing active treatment so I was also able to compare differences in chlorinated solvent transformations in treated and untreated ground water. Although ground water at Fort Wainwright was generally more oxidized than ground water at Six Mile Village, hydrogen concentrations at both sites were almost uniformly within ranges suggestive of iron or manganese reduction. However, aquifer sediments in the Tanana/Chena Alluvium are composed of mafic (containing reduced iron and manganese) minerals; suspended ferric iron appeared to result from oxidation of ferrous iron as ground water rose through the unsaturated zone. Sulfate concentrations were substantial and dissolved sulfide in most samples suggested that sulfate reduction might have been an important process. Calculated in situ Gibbs free energies for iron and sulfate reduction were energetically favorable at both sites; given other geochemical data, it seems likely these two processes co-occurred. Although methane was present in most samples, methanogenesis from H2 /CO2 was generally not energetically feasible at either site. Methane likely diffused from underlying permafrost or peat. The presence of less chlorinated intermediates of solvent degradation suggested that biological reductive dechlorination occurred, providing further support that sulfate-reducing conditions existed. However, low rates of microbial activity, incomplete degradation and persistence of contaminants imply that biologically mediated mechanisms did not likely represent an important contribution to natural attenuation of contaminants at either site where dilution appeared to be a major attenuation mechanism.
• #### Natural compounds isolated from wild Alaska bog blueberries intervene with molecular targets of neuroinflammation

NADPH Oxidase (NOX) has emerged as a key mediator of inflammatory processes that are prevalent in acute and chronic pathologies of the nervous system, cardiovascular system, and the immune system. Activation of NOX results in the formation of superoxide, a specific type of reactive oxygen species (ROS). Excessive accumulation of superoxide causes severe oxidative stress and ultimately, progressive cellular damage and degeneration. Despite the implications of NOX in a multitude of pathologies, pharmaceutical interventions against this molecular target remain non-existent. A diet rich in fruits and vegetables has immense health benefits beyond the high content of antioxidant compounds. Dietary intake of blueberries improves age related cognitive deficits and alleviates inflammatory damage as shown through human trials and animal studies. These findings imply that blueberries harbor specific inhibitors against molecular targets implicated in neuronal inflammation. Our investigations unveil natural compounds present in wild Alaska bog blueberries that potently inhibit NOX activity, reduce oxidative stress, and protect neuronal health in a cellular model of neuroinflammation. These studies illuminate nutrition-guided strategies as potential therapies for the prevention and intervention of neurodegeneration and cognitive decline associated with aging and with disease.
• #### Natural disturbance at the site and landscape levels in temperate rainforests of southeast Alaska

Wind disturbance in forests of southeast Alaska is poorly understood. Dynamics of canopy gaps, formed primarily by wind, were investigated in the western hemlock (Tsuga heterophylla)/blueberry (Vaccinium spp.)/shield fern (Dryopteris austriaca) plant association in northern southeast Alaska; twenty gaps were sampled at each of 3 sites. Gaps comprised about 9% of the forest area. The majority of gaps were $<$50 m$\sp2$ in area, had a diameter-to-height (D/H) $<$0.50, were created from the death of 1 or 2 gapmakers, and had experienced gap expansion. Emulating the small-scale natural disturbance regime would be best achieved if single tree selection and small group selection cuts were administered within a stand. Diffuse light levels were greatest and most variable at both the shrub and herb layers in canopy gaps, and lowest and least variable under closed canopy forest. Shrub layer light levels were positively associated with mean and median canopy gap areas. Herb layer light levels, however, were determined by the amount of light interception at the shrub layer and not by canopy gap size. Most species were robust in terms of their light requirements compared to the range of light conditions present in the understory. Sorenson Index values indicated that gaps and closed canopy forest generally were very similar in species composition. Seedling heights suggest that western hemlock and Sitka spruce seedlings benefit from the presence of canopy gaps. However, the ability of Sitka spruce to maintain itself through gap-phase replacement is limited. Techniques are needed that allow forest managers to interpret wind patterns in remote locations, at both site- and landscape-levels, and across complex topography. I demonstrated the use of circular data analysis of treefall directions as a technique to investigate wind flows at the site-level. I also demonstrated the feasibility of mapping wind flows across a large landscape of complex terrain in southeast Alaska using flagged trees, treefall directions of large-scale natural blowdowns, and treefall directions of blowdowns associated with clearcuts.
• #### Natural fracture character and distribution adjacent to the Nenana basin, central Alaska

The NE-trending Nenana basin is a Cenozoic-aged basin located in central Alaska between the Denali and Tintina fault systems. The narrow, deep basin is a current exploration target for oil and gas resources in Interior Alaska. Natural fractures were analyzed to further understand larger structural features such as faults and folds related to the structural evolution of the Nenana basin and surrounding areas. Fracture sets were measured and described on the margin of the basin at four field locations: the Fairbanks area, along the Parks Highway between Fairbanks and Nenana, and in outcrop around the Nenana and Healy areas. In addition to measuring fracture sets in outcrop and collecting oriented samples, statistical and thin section analyses were used to further analyze fracture characteristics. Calcite twin thermometry and apatite fission track analysis were used to constrain the timing and thermal evolution of the field area. Based on the orientations of observed map-scale faults, folds, and fracture sets, I divided the four field locations into two structural domains. Domain I is characterized by NE-striking faults and associated active seismicity while Domain II is dominated by E-W striking folds and faults related to the late Cenozoic development of the Northern Foothills fold-and-thrust belt. I interpret that fracture sets in Domain I are related to the evolution of high angle faulting between the Nenana basin and the Fairbanks area during Cenozoic time. In Domain II, I interpret fracture sets are related to the evolution of the fold-and-thrust belt north of the Alaska Range. By combining fracture characteristics and apatite fission track analyses I provide constraints for the timing and shear sense of larger structural features related to the opening history of the Nenana basin. Furthermore, I propose that the evolution of the Nenana basin took place in three distinct tectonic phases during the Cenozoic. The three phases represent the transition from a pure extensional setting in the Late Paleocene to oblique-extensional faulting from the Late Miocene to present day.
• #### Natural fracturing in carbonate rocks as a function of lithology and structural position in a detachment fold: examples from the northeastern Brooks Range, Alaska

Fractures in detachment folded Mississippian-Pennsylvania Lisburne Group carbonates provide insight into the distribution and character of natural fractures as a function of folding and lithology. Data from five detachment folds suggest that hinges show a higher fracture density than limbs. This study also suggests that the amount of shortening does not play a significant role in determining fracture density or uniformity of fracture orientation. A mechanical classification based on lithologic homogeneity reflects natural fracture distribution as a function of lithology more accurately than conventional lithologic classifications. Two main fracture sets were observed, a N-S set, perpendicular to fold axes, and an E-W set, parallel to fold axes. Statistical analyses suggest that E-W fracturing occurred before and during folding and that N-S fracturing occurred both before and after folding.
• #### Natural histories of Yup'ik memoirs

This thesis explores how cultural knowledge is committed to textual form and circulated within and outside of linguistically marginalized communities. Working within a Central Yup'ik context, I have focused my research on collections of Yup'ik elders' memoirs housed within the Alaska Native Language Archive. Published Yup'ik elders' memoirs offer rich descriptions of Yup'ik cultural histories, epistemologies and statements about language, the expression and inclusion of which varies based on the interactional contexts, participant frameworks and funding institutions through which they were produced. This study incorporates both Indigenous and non-Indigenous theoretical frameworks related to the process of entextualization, or text creation, and the transmission of cultural knowledge. Drawing from archival materials and interviews with participants involved in their production and circulation, I identify the relevant linguistic ideologies and participant frameworks involved in the creation of these publications or "text artifacts" and frame my analysis with respect to the following research questions: How have published memoirs of Yup'ik elders emerged as a culturally salient genre of text? Who are the primary participants in the production, publication and circulation of Yup'ik memoirs? How do issues of identity, agency, authenticity and essentialism shape the form, thematic content and circulation of Yup'ik memoirs in Alaska? This thesis seeks to identify the primary participants and ideologies contributing to the publication of Yup'ik elders' memoirs, as well as the visibility or erasure of these actors within the published text of the memoirs. I further explore the specific ways in which individual voices, tribal, political and academic institutions and their ideological goals presuppose and contribute to broader cultural processes and shape the linguistic structure and content of textual artifacts produced. Although the documentation, description and analysis of Yup'ik language and culture has received sustained attention both within and outside the academy, this project is the first to investigate the processes and participant frameworks through which traditional Yup'ik cultural knowledge is entextualized and circulated as contemporary published text. This research offers significant insights into the collaborative efforts of Native and non-Native participants in the production of Yup'ik textual materials, while also contributing to a broader understanding of ideological goals and obstacles relative to processes of entextualization within communities facing marginalization or language endangerment within, and outside of, the circumpolar north. An analysis of the participants and ideologies shaping the production and circulation of Yup'ik memoirs provides and empirical framework for understanding the relationship between text artifacts and ongoing cultural processes, and contributes to an increasingly reflexive approach to anthropological and sociolinguistic research concerning identity, authenticity and the entextualization of traditional knowledge.

• #### Navigating the predator gauntlet: consumption of hatchery- and wild-born juvenile chum salmon (Oncorhynchus keta) by common nearshore marine fishes in Southeast Alaska

Juvenile chum salmon (Oncorhynchus keta) undergo extensive mortality at marine entry, a period which is believed to be a potential population bottleneck. Although this early mortality has been consistently observed, our understanding of the mechanisms responsible is limited. Furthermore, the implications of large-scale salmon hatchery releases for the ecology of juvenile chum salmon and their consumers is another important knowledge gap. To better understand the predation responses of abundant consumers to hatchery- and wild-born juvenile chum salmon, we examined the diets of Pacific staghorn sculpin (Leptocottus armatus) and Dolly Varden (Salvelinus malma) near Juneau, Alaska, in 2016 and 2017. Chum salmon composed 4.5% and 19.6% of the diets of staghorn sculpin and Dolly Varden by weight, respectively, and 88% of chum salmon individuals consumed were of hatchery origin. Chum salmon prey were shorter than average when compared to chum salmon concurrently collected by beach seine and hatchery releases of chum salmon. Regression analyses indicated that occurrence of juvenile chum salmon in diets varied primarily by date and site. Predation generally occurred more frequently at sites closer to hatchery release areas. The quantity of chum salmon in staghorn sculpin stomachs was related to predator length, chum salmon catch-per-unit-effort (CPUE), and the proportion of hatchery fish present; however, date was the only important predictor explaining quantity of chum salmon in Dolly Varden stomachs. To translate diet data into consumption rate, we experimentally determined gastric evacuation rate for staghorn sculpin and implemented a field-based consumption model. Average daily consumption of chum salmon was low relative to all other prey groups. Estimates of average seasonal consumption of juvenile chum salmon by staghorn sculpins suggest that predator populations would have to be implausibly large to consume even 1% of local hatchery chum salmon production. Together, these results yield new insights into the interactions between the predators of wild-born and hatchery-born salmon during the critical stage of marine entry.
• #### NCPA propagation code users manual

This manual was written for University of Alaska Fairbanks infrasound group to assist researchers in using the National Center for Physical Acoustics (NCPA) code suite to further investigate observed infrasonic phenomena. The NCPA code suite is designed to simulate various aspects of infrasound propagation through a model atmosphere. This suite was developed and tested by the University of Mississippi National Center for Physical Acoustics infrasound group. Included are raytrace routines to initially establish signal paths, both single frequency and broadband modal routines to calculate pressure fields and transmission losses, and a parabolic method to calculate pressure fields and transmission losses in model atmospheres.

• #### Negotiating the languages of landscape: place naming and language shift in an Inupiaq community

This thesis examines the correlations between language shift, language death, and cultural change through the use of place names in White Mountain, Alaska. Traditionally Inupiaq place names have served as descriptive tools for navigating the landscape and as memory markers for oral histories, taboos, and places of harvest. Local Inupiaq place names have been inscribed in social memory for generations and, according to Inupiaq elders in White Mountain, none are without significance. As English replaces the Inupiaq language, these traditional place names fall out of use, as well as the local histories and other information associated with them. English place names used today continue to inscribe information into the land, but of a different sort. This thesis finds that cultural change and cultural resiliency can be clearly observed through and are related to language shift in White Mountain. Included in this thesis are listings and maps of traditional Inupiaq place names from White Mountain, Alaska.
• #### Neotectonic framework of the north-central Alaska Range foothills

The northern foothills of the Alaska Range form a northward-convex salient at the apex of this orogen and the Denali fault. Despite the proximity of the northern foothills to the Denali fault and several historic large-magnitude earthquakes, the tectonic framework of this region has not been well-studied. A distinct pattern of east-trending folds and faults exists in both the bedrock and the geomorphic features. To assess the active structures of the region, I interpreted previous geologic mapping, developed cross-sections across the foothills belt, analyzed topographic and stream profiles, mapped the sequence of Quaternary fluvial terraces, and performed GPS transects across several terrace treads. A northward topographic slope across the northern foothills corresponding with the pattern of faulting and folding suggests the presence of an orogenic wedge overlying a south-dipping basal detachment. Mapping and GPS transects show evidence for progressive deformation of the terraces. Geomorphic analyses suggest deformation and differential uplift over the entire foothills belt. These results indicate that the northern foothills are an active fold-and-thrust belt and are prograding northward into the Tanana Basin. Tectonic activity of these structures suggests that this region represents a potential seismic hazard for nearby military facilities and important transportation corridors.
• #### The neotectonics, uplift, and accommodation of deformation of the Talkeetna mountains, south-central Alaska

South-central Alaska is home to many tectonic structures and mountain ranges that have experienced active uplift and deformation within the past 5 to 10 Ma. The Talkeetna Mountains are located above the area of flat-slab subduction of the Yakutat microplate. I hypothesize that the Talkeetna Mountains have been uplifted as a result of this underlying flat-slab subduction and that areas of the Talkeetna Mountains are neotectonically active. The Talkeetna Mountains are deforming heterogeneously across four different structural domains defined by differences in geomorphic patterns, seismicity, dominant fault types, and the orientation of horizontal maximum stress (SHmax). A strain partitioning structure divides the northern and southern domains, and is observed by a change in SHmax orientation from E-W in southern domains to NW-SE in the northern domain. The strain partition is accommodated by a crustal break along the Talkeetna thrust fault, which is expressed at the surface as a wide zone of deformation. Apatite fission-track analysis suggests two distinct periods of uplift: one dated from 45 to 30 Ma and another from approximately 10 Ma to present, with uplift rates of 0.14 mm/yr and 0.24 mm/yr, respectively. The first phase of uplift coincides with a time of significant plate reorganization in the north Pacific which resulted in translation of terranes northwestward. The second phase of uplift correlates with Neogene accretion of the Yakutat microplate. I propose that the majority of Neogene deformation and uplift in the Talkeetna Mountains is due to farfield deformation in the upper plate above the subducting slab. Variations in both composition of the crust and depth to the downgoing slab resulted in strain partitioning and northwest-directed compression in the northern Talkeetna Mountains and northwest compression and warping in the southern Talkeetna Mountains.
• #### Nest -Building Behavior In House Mice (Mus Musculus), A Potential Model Of Obsessive -Compulsive Disorder In Humans

OCD (obsessive-compulsive disorder) is a chronic and debilitating psychiatric condition characterized by intrusive and persistent thoughts (obsessions) and repetitive behaviors (compulsions) that become ritualistic in an attempt to escape the obsessions. Currently there is a paucity of animal models with robust and spontaneous (non-drug or non-behaviorally induced) compulsive-like behaviors. This study is aimed at validating a novel robust and spontaneous genetic mouse model of OCD. The compulsive-like nest-building behavior in mice selected for high levels of nest-building behavior (BIG) has good face validity, with a behavioral phenotype that resembles hoarding behavior characteristic of OCD. In addition, male and female BIG mice displayed compulsivelike digging behavior relative to mice selected for low levels of nest-building behavior (SMALL), as assessed by the marble-burying test. Both chronic oral fluoxetine and clomipramine treatment reduced compulsive-like nest-building behavior in male BIG mice. Furthermore, chronic oral fluoxetine administration decreased nest-building behavior of BIG mice in a dose-dependent manner, while desipramine, an antidepressant not effective for treating OCD, did not significantly alter this behavior. The administration of fluoxetine did not cause a decrease in general locomotor behavior. These findings suggest that the nest-building phenotype has predictive validity. In addition, chronic oral fluoxetine treatment reduced compulsive-like digging behavior in male and female BIG mice as compared to SMALL mice. Gender effects were also found in treatment response. Clomipramine did not reduce nest-building in female BIG mice in a dose-dependent manner, which is consistent with previous studies. These data are in contrast to previous studies using BIG male mice which had a significant decrease in nest-building behavior with oral clomipramine. These results are consistent with studies on humans, which have found gender differences in the treatment effects of antidepressants. Additional construct validity is implicated by the results of targeted serotonergic lesions of the raphe nuclei in male BIG mice, which reduced repetitive nest-building behavior. More research is necessary to confirm the appropriateness of this model for human OCD; however, this model is promising based on the data that support good face, predictive and construct validity.
• #### Nest and duckling survival of scaup at Minto Flats, Alaska

To address the hypothesis that declines in recruitment were related to recent declines in abundance of lesser and greater scaup, I estimated variation in nest and duckling survival of these species at Minto Flats, Alaska (64°50'N, 148°50'W) during 2002-2003. I included nest survival data from two previous studies conducted during 1989-1993 in my analysis. Daily Survival Rate (DSR) of nests was variable within and among years and among habitats. Estimated nest survival of scaup ranged from 0.02 (95% CI: 0.00 to 0.06) in 1992 to 0.61 (95% CI: 0.50 to 0.74) in 1993. Predation was the primary apparent cause of nest failure, and flooding of nests was an important secondary influence. DSR of ducklings varied between years and increased with age of the ducklings and body condition of the brood female. Duckling survival to 30 days was: 0.24 (95% CI: 0.16 to 0.36) in 2002 and 0.03 (95% CI: 0.00 to 0.19) in 2003. I conclude that high temporal variability in production of scaup at Minto Flats was likely related to annual variation in the risks of predation and flooding and indicated that intermittent years of high production could be particularly influential to this population.
• #### Nesting biology of the spectacled eider Somatera fischeri (Brandt) on the Yukon-Kuskokwim Delta, Alaska

Nesting biology of the Spectacled Eider Somateria fischeri (Brandt) on the Yukon-Kuskokwim Delta, Alaska, was studied in 1972 and 1973. These data are compared with data from 1969, 1970, and 1971 (Eisenhauer et al. 1971, Eisenhauer and Frazer 1972, and Mickelson 1973). Paired, the birds arrived mostly from the north within a 3-4 day period in mid-May. Before 7 June, 80 percent of the nests were initiated. Located on islands, shorelines and peninsulas, most nests were within 7 feet of water. Rate of egg laying was 1/day (mean clutch size 4.5 eggs). Incubation lasted 24 days. Hatching took place from 20 June to 10 July (nesting success range 35 percent to 83 percent). Timing of nest site availability appears to dictate clutch size and reproductive success. Ducklings are raised on shallow freshwater ponds within 1.5 miles of their nest site.