Now showing items 1398-1417 of 3446

• #### Heat And Freshwater Controlling Processes On The Northern Gulf Of Alaska Shelf

We examined conditions and processes that control the distribution of heat and freshwater on the northern Gulf of Alaska (GOA) shelf. Cross-shelf heat gradients are weak throughout the year, while salinity gradients are substantial due to the impact of coastal freshwater runoff. Outer shelf water properties are influenced by large anticyclonic eddies, while the inner and middle shelves may be regulated by wind and freshwater runoff dynamics around the Alaska Coastal Current (ACC). On the outer shelf, anticyclonic eddies propagate from the eastern GOA southwestward along the continental slope, where they favor on-shelf (off-shelf) transport of saline and nutrient-rich (fresh and iron-rich) waters Certain along-shelf locations are identified where low-salinity coastal waters are found near the shelfbreak within reach of eddies and may be regions of enhanced cross-shelf freshwater transport. The eddies have lifetimes of ~5 years and increase in size and sea level anomaly west of the Seward Line, which implies more vigorous eddy cross-shelf exchange in the northwestern GOA. By comparison, on the inner shelf the heat and freshwater distribution is dominated by large coastal river runoff, which forces the ACC and controls the vertical distribution of temperatures through stratification. In May 2007, the coastal GOA revealed some of the lowest ocean temperatures since the early 1970s, initiated by strong atmospheric cooling and reduced coastal runoff in November 2006. Stepwise regression shows that 81% of the variability of deep temperatures is explained by salinity stratification and air-sea heat fluxes. Weak baroclinic flow in May 2007 likely aided the cooling through reduced along-shore heat transport. A more detailed examination of heat transport indicated that along-shore heat flux convergence in the ACC may re-supply 10-35% of the heat removed by air-sea fluxes throughout the coastal GOA cooling season, while the annual mean cross-shore heat flux convergence is insignificant. Spatial gradients show increasing heat fluxes from off- to on-shore and from east to west. The cross-shore gradients result from wind speed gradients due to ageostrophic near-shore wind jets near coastal mountains, while the along-shore gradients result from larger-scale pressure systems. While the ACC advects coastal freshwater around the GOA shelf its waters are subjected to disproportional heat loss west of the Seward Line.
• #### Heat Increment And Methane Production By Muskoxen Fed Browse

Many browse species contain anti-herbivory compounds that deter consumers by their toxicity or digestive inhibitory effects. Animals that consume browse are assumed to pay a detoxification energy cost, which increases the heat increment of feeding (HIF). Ruminants also lose potentially metabolizable energy as methane (CH4); but browse may lower CH4 production. I hypothesized that increases in energy loss to HIF by animals eating browse could be offset by a reduction in energy lost via CH4 production. Muskoxen eat both graminoids and browse and are considered to be energetically conservative due to their existence in a sparse arctic environment. These traits make them ideal for energetic studies. Muskoxen were fasted for 24 h and then fed a test meal composed of hay mixed with graded percentages of one of three browse species (Willow: S. alaxensis, S. pulchra, birch: Betula nana). Browse consisted of twigs in winter and leaves in the summer. Heat increment of feeding and CH4 production were estimated with an indirect calorimeter. Muskoxen had a 33% lower metabolic rate in winter in comparison to summer. The main increase in EE from winter to summer occurred between April and May, and the summer to winter decrease between August and September. Addition of woody twigs or leaves of birch to hay diets tended to depress HIF following the test meal. Woody twigs and leaves of willow added to hay diets tended to increase HIF. Woody browse tended to lower CH4 production when fed at >20% of the meal. Leafy browse had variable effects on CH4 production; S. alaxensis was stimulatory, S. pulchra was inhibitory, while B. nana showed not consistent pattern. Generally, CH 4 production by muskoxen was low at 2.0--3.2% of GE intake when compared with estimates for sheep and cattle (2--12% of GE intake). Although diets high in fermentable carbohydrates stimulated methane production, secondary compounds apparently had a suppressing effect as deduced from the relation of in vitro digestibility to methane production. Given the low overall CH4 production in muskoxen, and the inconsistency of the relationship of CH4 to HIF, it is unlikely that significant gains in energy retention are made by reductions in CH4 production through browse consumption.
• #### Heavy metal tissue distributions in southwestern Alaskan waterfowl: total mercury assays from muscle, brain, and bone

Food containing mercury has been identified as a possible health risk. Total mercury (THg), which is inorganic (Hg²), and methylmercury (MeHg) species, has been found in the arctic food web. In Alaska, birds are an important seasonal component of the diet, but have not been studied extensively and characterized for the presence of mercury. Birds are good subjects for examination because they feed at different trophic levels, can be long-lived, and are both abundant and widely distributed. Not only can birds monitor local Alaskan food webs, but, if they are migratory, can be used to compare exposure in different regions. Mercury levels in muscle, brain, and bone tissue of 140 birds taken by subsistence hunters across southwestern Alaska were determined. I tested the null hypothesis of no interspecific differences in total mercury levels in the 18 species of Alaska birds surveyed. There were interspecific differences with the Lesser Scaup (Aythyra marila mariloides), and the Black Scoter (Melanita nigra Americana), having the highest levels of mercury. In general, mercury levels were higher in muscle than in brain or bone. The mean values for mercury in the species studied were lower than the levels known to cause adverse reproductive or behavioral effects.
• #### Heavy metals in the sediments of an arctic lagoon, northern Alaska

The total abundances of V, Cr, Mn, Fe, Co, Ni, Cu, and Zn in oxic, nearshore sediments of north arctic Alaska, are similar to those of corresponding pristine or pre-industrial-age sediments of many tropical-temperate regions, and thus do not reflect the unique weathering and depositional processes of the Arctic. Laboratory experiments on metal partitioning suggest that about 50% of the metal contents (<20% for V, Cr), which are bound predominantly in Fe oxides, may be mobilized into solution following the onset of reducing conditions at the sediment surface. A three-part extraction design would be effective in discriminating the three major associations of heavy metals in the sediments: easily leachable, Fe hydroxides, and refractory particles, and is recommended for use in monitoring the nearshore Beaufort Sea for future contamination by heavy metals.
• #### Helping veterans through outreach

The present Master's project seeks to develop a better understanding of Veterans and what they are going through. Research methods include extensive data on the high suicide rates of Veterans. Veteran and service members are in need of a service to them that will address the issue of suicide and what can be done to help and eliminate this problem. The programs that need to be designed to help needs should be in locations that have Veteran populations so as to serve them with their needs. Ultimately, Veterans Affairs (VA) officials have boosted their mental health personnel and suicide hotline staff in recent years, but at this time their data does not reflect it helping Veterans getting the help that they so desperately need.
• #### Hemocyte and tissue changes by crude oil in the blue mussel Mytilus edulis

This study examines the effects of Prudhoe Bay crude oil on the number and types of circulating hemocytes, on the phagocytic response, on spawning progression, and on internal structural changes. The number of hemocytes was reduced with 4-5 week exposure to 1000 nL/L of oil; a significant number of individuals showed a higher than average cell count with longer exposure. An increase in agranulocytes in the 8-9 week control population does not occur in populations exposed to 1000 nL/L and 500 nL/L of oil for 8-9 weeks, but, the phagocytic response was significantly depressed. The Chi-square test showed that oil interferes significantly with progression of spawning. Analysis of internal tissue structure indicates that oil can affect adipogranular storage cells, vesicular tissue, and digestive tubule cells. The changes occurring in circulating hemocytes are not necessarily consistent with changes in internal morphology.
• #### Hepatitis B in Arctic ground squirrels (Spermophylus parryi): epidemiology and population biology

Using a mark-recapture design, an epidemiological investigation of Hepatitis B was performed on four colonies of Spermophylus parryi. Animals were trapped, marked and bled. Serum samples were screened for Hepatitis B markers. Program MARK was used to estimate survival rates. Prevalence rates ranged over 55% and 1999 rates were 10% higher than 1998. Vertical transmission of the virus was not observed and juveniles were unaffected by the mother's hepatitis status. Immigrants had lower prevalence rates than residents and incidence rates accelerated throughout the study. Survival was highest during the over-winter period and adult rates were lower in 1999. Recovered animals had different survival rates than other animals and survival rates of recovered animals were lower in 1999. Evidence suggests that delayed development of disease and/or environmental conditions lowered survival rates of recovered adults in 1999. Techniques that integrated epidemiology and population biology proved fruitful and worthy of further development.
• #### Herbivore-mediated effects on ecosystem processes in a near-Arctic salt marsh

Herbivores influence, and often regulate energy flow. I investigated interactions between herbivory and the foods on which geese rely while nesting and rearing their broods on the Yukon-Kuskokwim Delta in southwestern Alaska. In a captive Cackling Canada gosling (Branta Canadensis minima) experiment I decoupled the effects of seasonal declines in forage quality and availability on gosling development. An 11% decline in forage quality translated to goslings that were structurally smaller and 100 g lighter at 31 days of age. Forage availability had similar effects on gosling size, and the combined magnitude of these effects are similar to those observed in wild populations. I manipulated within-season grazing history of 'Carex subspathacea' swards within brood-rearing areas used by Black Brant geese (Branta bernicla nigricans). Spatial variation in forage quality and availability exceeded seasonal variation. Brant consumed over 95% of the annual aboveground production of these swards without any short- or apparent long-term effects on aboveground growth. Adding grazing pressure to 'C. ramenskii, ' or removing grazing pressure from 'C. subspathacea, ' resulted in a bi-directional shift in the morphology and nutritional characteristics of these sedges. The areal extent of 'C. subspathacea' increased 2 to 8% of the Tutakoke landscape with a concomitant decrease in 'C. ramenskii' meadows between 1991-1998. Brant have been increasing the carrying capacity of the Tutakoke River colony following a population decline in the early 1980's. The population has increased beginning in 1988, yet remains below historic numbers. Density-dependent effects on gosling growth accompanied the population increase initially. However, gosling mass has increased over the past decade due to herbivore-mediated increases in the areal extent of grazing lawns.
• #### Heterogeneity and bias in abundance estimates of outmigrating chinook salmon in the Chena River, Alaska

The objective was to examine bias due to heterogeneity in capture probability (p) in an abundance estimate for chinook salmon (Oncorhynchus tschawytscha) outmigrants in the Chena River, Alaska. A higher proportion of day-marked fish (21 / 636 = 0.0330) compared to night-marked fish (17 / 1724 = 0.0098; p<0.0001, α=0.05) was recaptured at the lower site in a Cormack-Jolly-Seber experiment with upper, middle and lower sites. Heterogeneity was also likely at the middle site between upper site-marked and unmarked fish. Simulations with heterogeneity confined to the middle and lower sites (i.e., due to inadequate mixing) caused small bias (<2.5%) in the upper site abundance estimate. With heterogeneity at all three sites (a subpopulation effect), the upper site estimate had 22.9% to 29.3% negative bias. Because heterogeneity observed in the Chena was probably due to inadequate mixing (related to daytime trap evasion), bias in the upper site estimate was probably small.
• #### Heterogeneity And Bias In Abundance Estimates Of Outmigrating Chinook Salmon In The Chena River, Alaska

The objective was to examine bias due to heterogeneity in capture probability (p) in an abundance estimate for chinook salmon (Oncorhynchus tschawytscha) outmigrants in the Chena River, Alaska. A higher proportion of day-marked fish (21/636 = 0.0330) compared to night-marked fish (17/1724 = 0.0098; p $<$ 0.0001, $\alpha$ = 0.05) was recaptured at the lower site in a Cormack-Jolly-Seber experiment with upper, middle and lower sites. Heterogeneity was also likely at the middle site between upper site-marked and unmarked fish. Simulations with heterogeneity confined to the middle and lower sites (i.e., due to inadequate mixing) caused small bias ($<$2.5%) in the upper site abundance estimate. With heterogeneity at all three sites (a subpopulation effect), the upper site estimate had 22.9% to 29.3% negative bias. Because heterogeneity observed in the Chena was probably due to inadequate mixing (related to daytime trap evasion), bias in the upper site estimate was probably small. <p>

• #### High latitude ionospheric effects on error rates over a geostationary satellite-to-earth transmission path at 136 mhz

Error rate data obtained for a high latitude transionospheric earth-space VHF communications channel are presented. Interpretation of these data with respect to certain ionospheric indicators has resulted in qualitative as well as quantitative correlation between the observed error rate data and F-region irregularities. Amplitude scintillation has been found to be of the most critical importance to data channel efficiency and reliability. Indications of extra-terrestriaI (i.e., solar) control have also been documented. Transionospheric propagation phenomena have been shown to give rise to adverse channel carrier/noise ratios, while waveform distortion and timing instability remain essentially unaffected. Information on channel reliability during extreme geomagnetic storms has shown that fading margins in excess of 20 dB are necessary in order to maintain channel error rates of 10⁻⁵ or better at VHF over a transionospheric channel at high latitudes.
• #### A high performance neural network javascript library

This report covers Intellect.js, a new high-performance Artificial Neural Network (ANN) library written in JavaScript and intended for use within a web browser. The library is designed to be easy to use, whilst remaining highly customizable and flexible. A brief history of JavaScript and ANNs is presented, along with decisions made while developing Intellectjs. Lastly, performance benchmarks are provided, including comparisons with existing ANN libraries written in JavaScript. Appendices include a code listing, usage examples, and complete performance data. Intellect.js is available on GitHub under the MIT License. https://github.com/sutekidayo/intellect.js
• #### High resolution sequence stratigraphy and geochemistry of middle and upper Triassic sedimentary rocks, northeast and central Brooks Range, Alaska

Triassic age rocks constitute an important sedimentary interval on the North Slope of Alaska, because they include organic-rich source rocks that generated much of the oil that accumulated in the Prudhoe Bay field. Three detailed measured sections in the northeast and north-central Brooks Range are characterized using sequence stratigraphy, chemostratigraphy, biostratigraphy and ichnofabric, allowing interpretations about the evolution of the depositional environment and general paleogeographic setting through the Middle and Upper Triassic. High resolution correlation provides insight into the timing and pattern of source rock accumulation in the Shublik and Otuk Formations. Sequence and chemo-stratigraphic analyses suggest that deposition took place on a broad, low-angle shelf under fluctuating paleoceanographic conditions. Recorded are three third order sequences, each containing a sea level rise and highstand. Glauconitic, phosphatic, and organic-rich rocks of the Shublik and Otuk Formations indicate deposition in an environment characterized by oceanic upwelling. Organic and inorganic geochemical data support interpretations concerning paleoxygenation gradients. The cerium anomaly, manganese, phosphorus, vanadium, total organic carbon, and calcium-manganese ratio indicate dominantly oxic bottom waters during the Middle Triassic, dominantly low oxygen or anoxic conditions during much of the Upper Triassic, and a return to more oxic conditions in the late Upper Triassic.
• #### High tunnel production of lettuce (Lactuca sativa) and snap beans (Phaseolus vulgaris l.) in a High Latitude location

Fairbanks, Alaska (lat. 64°49’N) has a short, variable growing season which necessitates alternative growing techniques for reliable vegetable production. Air and soil temperatures, relative humidity, light penetration, and management requirements were evaluated for a double bay high tunnel [15.8 m wide × 3.7 m high × 14.6 m long]. Mean air temperature was 0.5 °C and soil 1.2 °C higher in the high tunnel than the adjacent field, but differences varied with ventilation and heating practices. Yield and growth characteristics of lettuce (Lactuca sativa: ‘Paris Island cos’ and ‘Two Star’) and snap beans (Phaseolus vulgaris L.: ‘Concesa’ and ‘Provider’) were evaluated. Lettuce was frost hardy in the open field, prone to bolting in the high tunnel, and in general did not benefit from the high tunnel environment, except in quality due to cleanliness. ‘Concesa’ produced significantly more in the high tunnel compared with the field (P < 0.005). ‘Provider’, produced more in the high tunnel in 2006 compared to the field, but differences were not statistically significant over two seasons. The perceived benefits of high tunnel production included protection from frost, wind, pest, and rain, improved yields depending on crop and cultivar, and decreased weed emergence and moisture accumulation.
• #### High-latitude over-the-horizon radar applications

Over-the-horizon radar (OTHR) systems that operate at high-latitudes often must contend with multipath and pronounced diffusive scattering effects produced by the anisotropic, birefringent, and heterogeneous nature of the ionosphere. In this thesis, radar performance at high-latitudes is quantified and several applications for either mitigating the deleterious effects of multipath and diffusive scattering or deriving information about the state of the ionosphere are proposed. The first application is inspired by adaptive optics techniques in other fields and involves the coherent summation of the received plane wave spectrum in order to improve angular resolution and array gain. The second application involves deriving ionospheric E x B drift from applying spatial correlation analysis to ground clutter echoes. The third application is the development of a new spatial adaptive processing technique designed specifically to preserve the Doppler spectrum of angle-Doppler coupled clutter like that observed at high-latitudes.
• #### High-Resolution Paleoceanography Of The Gulf Of Alaska, Subarctic Northeast Pacific Ocean, Since The Last Glacial Maximum: Insights Into A Dynamic Atmosphere-Ocean-Ecosystem Linkage At Decadal To Millennial Timescales

Environmental conditions in the Subarctic Northeast Pacific Ocean are an important component of North American climate patterns, as well as a potential driver of Northern Hemisphere climate variability. The North Pacific Ocean is also the terminus of modern global thermohaline circulation, suggesting that paleoceanographic records from this region have the potential to preserve evidence of both climate forcing and response on regional and global scales. A suite of high-resolution marine sediment cores collected from the Gulf of Alaska margin in 2004 provide new paleoceanographic records at decadal and centennial timescales from fjord and continental slope environments. Key findings include: (i) decadal oscillations in marine productivity correlate with previously identified terrestrial records, indicative of forcing by the Aleutian Low pressure cell; (ii) the standard binary model of the modern Pacific Decadal Oscillation (PDO) as the major pattern of ocean-atmosphere variability is insufficient to describe the full range of Holocene paleoenvironmental fluctuations observed in Gulf of Alaska records of marine productivity, freshwater discharge, and bottom-water anoxia; (iii) the North Pacific ecosystem is a sensitive recorder of abrupt climate events observed in global records; and (iv) the fjords of Southeast Alaska contain a detailed record of volcanic activity and fallout events useful for developing composite chronological models of sedimentation that correlate with other regionally important stratigraphic records. Collectively, the results presented here will potentially redefine current theoretical models of atmosphere-ocean-ecosystem variability in the North Pacific Ocean, as well as contribute to a growing body of high-resolution paleoenvironmental time-series datasets from the high latitudes.
• #### Highland Hunters: Prehistoric Resource Use In The Yukon-Tanana Uplands

The purpose of this study was to conduct a first approximation of explorations and excavations throughout the White Mountain and Steese Conservation areas during the summer field seasons of 2010 and 2011 in the Yukon Tanana Uplands. An analysis of the lithic artifacts from five site excavations (the Big Bend, Bachelor Creek, Bear Creek, US Creek and Cripple Creek) was then undertaken. These assemblages were then examined and modeled using risk-assessments, optimal resource use, and behavior processes in order to explore the interdependence of environment, ecology, and material culture that drove prehistoric subsistence cycles in this area. This archaeological research will supplement ethnographies to indicate patterns of change in landscape value, trade networks, and local economic strategies.
• #### Highlighting School of Education successes to build community

The project is a WordPress site to showcase faculty and students. This site is a companion piece to the redesigned University of Alaska Fairbanks School of Education website. It is intended to provide a visual resource to be used by faculty and staff to promote the uniqueness of current and recent developments in the School o f Education. The site should serve as a space where staff and faculty may promote opportunities for current and recent graduates. It will also include graduate students’ experiences via research, projects, career stories and testimonials provided by students. These materials will be linked in from the School of Education website under the proposed title of Showcase.