Now showing items 448-467 of 3321

• #### Characterization of Alaska North Slope oils for wax deposition

Wax deposition during crude oil production is a major problem that has plagued the oil industry for decades especially in cold environments such as Alaska North Slope (ANS) fields, with adverse consequences in huge mitigation cost and lost production. It is therefore imperative to adequately and accurately identify the conditions for wax precipitation and deposition in order to optimize operation of the production systems of ANS. In order to assess ANS crude's potential for wax precipitation, Viscometry and Cross Polarization Microscopy (CPM) are used to determine the temperature at which paraffins begin to precipitate from ANS dead oils. Wax dissolution temperatures (WDT) are also determined by CPM. Results show that wax precipitation is possible at temperatures as high as 41°C (106°F) while it takes up to 50°C (122°F) to get all waxes back into solution. The CPM technique was more sensitive while Viscometry results did not provide a high level of certainty in some samples and therefore appear over-estimated relative to CPM results. Previous thermal history was observed to influence test results. Pour point, viscosity, density and specific gravity have also been measured. Pour point results indicate that oil could form gel in the temperature range 12°C (53.6°C) to less than -31°C ( -23.8°F).
• #### Characterization of host-pathogen interactions in two model pathogens: Francisella tularensis and simian virus SV40

We sought to elucidate the molecular mechanisms of host-pathogen interaction. The bacterium Francisella tularensis and simian virus SV40 represent two ideal model systems. Francisella tularensis is a facultative intracellular bacterium known to dampen the host immune response to infection. The Francisella pathogenicity island (FPI) encodes a cluster of 19 genes essential for full virulence and the observed change in immune response. We investigated the role of two FPI encoded proteins, PdpC and PdpD, on immune response. While both proteins affect a change, the effect of PdpD is more pronounced, and appears to play a role in modulation of host immune responses. SV40 is a DNA polyoma virus that targets GM1 receptors for entry into cells. The GM I receptor is localized to cholesterol-rich membrane microdomains, termed lipid rafts. Disruption of lipid rafts using the cholesterol chelator methyl-P-cyclodextrin prevents SV40 entry into cells. We investigated whether natural product alternatives would similarly disrupt lipid raft integrity and prevent viral entry. The triterpenoid ursolic acid, present in many plants, has been shown to possess antimicrobial properties and was used to treat cells prior to infection with SV40. We found ursolic acid to have no effect on the viral infectivity of SV40.
• #### Characterization of metal-organic complexes in aspen and birch forest soils in interior Alaska

Complexation of iron, copper, and manganese by organic substances contained in aqueous soil extracts obtained from the mineral B horizon of contiguous aspen (Populus tremuloides) and birch (Betula papyrifera) forests was characterized by gel-permeation chromatography (GPC), thin-layer chromatography (TLC), ion-exchange chromatography, atomic absorption spectrometry, and infrared spectroscopy. Fractionation of these extracts on Sephadex G-25 (medium) yielded 6 fractions for birch extracts and 5 fractions for aspen extracts. This result indicated that the chemical composition of the birch extracts differed from the chemical composition of the aspen extracts. The largest quantity of metals was found in fractions that represented substances with apparent molecular weights less than 5000 daltons. Metal distribution patterns indicated different metal-organic associations within fractions of a forest-type extract as well as between fractions of the two forest-type extracts. Fractionation of each GPC fraction on thin-layer plates yielded a total of 27 TLC bands for the birch GPC fractions and 19 TLC bands for the aspen GPC fractions. This result indicated that fewer components were separated in the aspen GPC fractions than in the birch GPC fractions. Solutions derived from the TLC bands, when passed through a Chelex 100 column, provided qualitative information regarding the strength of copper, iron, and manganese complexation by organic substances in those solutions. Manganese was not strongly bound by organic substances derived from birch soil or aspen soil. Copper and iron were usually strongly complexed by organic materials regardless of the source. Significant differences in copper and iron complexation were observed within a forest-type soil extract and between forest-type soil extracts. TLC bands that exhibited little evidence of undissociated carboxylic acid character, as revealed by infrared spectroscopy, contained most of the iron and suggested that carboxylate anion was the principal complexing moiety for iron. Copper generally appeared to be concentrated in TLC bands that fluoresced which was in contrast to those containing iron. This result suggested separations of copper complexes from iron complexes.
• #### Characterization of muskox habitat in northeastern Alaska

In northeastern Alaska, muskoxen have been most often found in riparian habitats and proximate uplands. Vegetation was studied in nine adjacent river drainages; six of the drainages are regularly used by muskoxen. Twenty-two vegetation/land cover types were described using aerial photographs, point-intercept sampling, and ocular cover estimates. The proportion of each cover type was estimated for each drainage and compared among drainages by MANOVA. There was no significant difference among non-muskox drainages in the average proportion of cover types. A marginally significant difference was found among muskox drainages. There were no significant differences in the proportions of each vegetation type in non-muskox drainages versus muskox drainages. Five vegetation types associated with high forage quality and availability and low snow accumulation were often used by muskoxen. Four of these five vegetation types typically had <7% cover in the nine drainages and are critical habitat components in northeastern Alaska.
• #### Characterization Of Permafrost Development By Isotopic And Chemical Analysis Of Soil Cores Taken From The Copper River Basin And An Upland Loess Deposit In Interior Alaska

Chemical and isotopic analyses of pore water from permafrost cores taken from the dry lake bed of ancient Lake Atna in the Copper River Basin and from an upland loess deposit northeast of Fairbanks, Alaska reveal information about the local past environments not available by other means. Thawed core samples from both sites were analyzed for delta18O and deltaD values using an isotope ratio mass spectrometer. Water content was determined as well, and subsamples of the cores were analyzed for nitrogen and carbon content. Water extracts of the core samples were analyzed for cations (Ca, Mg, K and Fe), as well as pH, electrical conductivity, and bicarbonate. Magnetic susceptibility was determined on samples from the Fairbanks site. Data from samples taken from the Lake Atna site revealed a sequence of events that occurred in the basin after the lake drained about 10,000 years ago. At one location, oxygen isotopes show that permafrost formed continuously down through the lakebed. At the other location, 400 m distant, oxygen isotopes show that after permafrost formed, a thaw lake was produced on top of the permafrost. After the thaw lake had drained at least one wildfire passed through the area, large enough to thaw the surface permafrost to a depth of over 2 m at both core sites. The surface permafrost refroze, and currently the permafrost at the research site extends from 1 m depth to between 45 and 55 m depth. At the Fairbanks site chemical analyses showed indications of pedogenesis at several depths in the loess profile of the permafrost core. Water isotope data from a site where the permafrost table is at less than 1 m depth show repeated episodes of thawing and refreezing. Charcoal and ash in several layers of soil in the area and from the sample core suggest that fire may be the cause for the thawing events. The primary core water isotope analyses also show several thawing and refreezing events, but the depths of the signatures in the core indicate that these episodes happened thousands of years ago when the ground surface was much lower than it is today.
• #### Characterization of the adenosine A1 receptor in summer and winter Arctic ground squirrels

Hibernation is an adaptation that allows the Arctic ground squirrel (Urocitellus parryii) to survive the harsh arctic winter. Recently the activation of the Adenosine A1 receptor (A₁AR) has been shown to be necessary for entrance into hibernation during the winter but not summer season. In the current study we characterize the A₁AR in the forebrain, hippocampus and hypothalamus of summer and winter AGS. We also tested the hypothesis that increased A₁AR agonist efficacy is responsible for increased sensitization of the A₁AR during the winter season. The resulting ³⁵S-GTPγS binding data indicated an increase in agonist potency during the winter season in all three brain regions. A plausible explanation of our results is that increased potency in the forebrain during the winter season is due to an increase in efficacy as indicated by a greater number of receptors in the high affinity state. In addition ³⁵S-GTPγS binding, [³H] DPCPX saturation and competition assays establish for the first time pharmacological characteristics such as EC⁵⁰, Kd, Kilo and Kihi in AGS brain.
• #### Characterization Of The Dat Zone, Eastern Alaska Range, Alaska: A Calcic Iron (Copper-Gold) Skarn Prospect

I studied a Cu-Fe-Au prospect in the eastern Alaska Range, Alaska, informally known as 'the DAT Zone'. Previous workers disagreed about the prospect's genesis; my work conclusively shows it to be a calcic iron skarn deposit with late quartz-pyrite-gold mineralization, broadly coeval with the host Pennsylvanian island arc-related volcanic and associated sedimentary rocks. A sericite-quartz-pyrite altered shear yields a $\sp{40}$Ar/$\sp{39}$Ar age similar to that of a nearby quartz monzodiorite pluton (300 Ma $\pm$ 1 Ma). The skarn consists of andradite extensively retrograded to ferrotremolite, quartz, magnetite, hematite, calcite, and chalcopyrite. Based on alteration pseudomorphs, the prograde assemblage was clinopyroxene with 20-40 %Hd, wollastonite, and andradite. The main-stage fluids were approximately 600$\sp\circ$C, moderately oxidized, and extremely saline ($>$60% NaCl equivalent). This fluid was clearly different from those of volcanogenic massive sulfide, metamorphic, or epithermal deposits. The lack of explosive textures is inconsistent with the DAT Zone as a porphyry copper deposit. <p>

• #### Characterizing glucocorticoid levels in five species of sea ducks occurring in Alaska

Stress hormone analysis, used in conjunction with other physiological parameters, may help identify factors affecting sea duck populations in their natural environment. Corticosterone, the primary 'stress hormone' in birds, is secreted in response to a stressor and enhances an individual's chance of survival by inducing physiological and behavioral changes. Establishing a valid method for evaluating stress hormone levels in sea ducks and gaining basic information on baseline concentrations and stress response in these birds are important first steps to identify factors that may negatively affect sea duck populations. This study validated a radioimmunoassay (RIA) procedure to measure corticosterone concentrations in harlequin duck serum and feces and in Steller's, spectacled, common, and king eider serum. Other objectives included characterization of baseline corticosterone concentrations, investigation of stress response, and the relationship between corticosterone and other variables in captive and wild sea ducks. The results indicate that fecal samples can be used to non-invasively measure corticosterone in harlequin ducks. Captive birds exhibited overall lower baseline levels of corticosterone than wild birds. The stress response observed in harlequin ducks was similar to other avian species. Rapid post-capture blood sampling is critical for evaluation of baseline corticosterone levels.
• #### Characterizing the Afghanistan aerosol environment using size- and time- resolved aerosol chemical composition measurements

The exposure to aerosols is one danger U.S. soldiers face in Afghanistan that may go unseen. Using the Davis Rotating-drum Universal-size-cut Monitoring (DRUM) cascade impactor, size- and time- resolved aerosol chemical concentrations from Bagram, Afghanistan were collected. These aerosol concentrations were combined with a meteorological analysis and Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model meteorological backward trajectories to establish source sectors. These sectors, along with time of year, were then used as a predictive tool for the chemical composition and relative concentration of aerosols in Afghanistan. Principal components analysis (PCA) was used to determined potential source types. PM₁₀ and PM₂.₅ were compared to military exposure guidelines and U.S. national ambient air quality standards. Results reveal aerosol concentrations in Afghanistan were at levels for which adverse health effects could be anticipated.

• #### Characterizing the diet and population structure of lampreys Lethenteron spp. using molecular techniques

Lampreys contribute to the health of aquatic ecosystems and are targeted in both subsistence and commercial fisheries. Despite their ecological and commercial importance, the management and conservation of native lampreys have been largely overlooked. The goal of this study was to close current knowledge gaps of lamprey biology through the examination of Lethenteron spp. in Alaska. This study applied two molecular techniques, DNA metabarcoding and microsatellite genotyping, to (1) characterize the diet of marine-phase Arctic lamprey Lethenteron camtschaticum (N = 250) in the eastern Bering Sea and (2) investigate the population structure of larval lampreys Lethenteron spp. (N = 120) within and among three Yukon River tributaries. A combination of visual observations and DNA metabarcoding revealed the presence of diagnostic structures/tissues (i.e., eggs, fin[s], internal organs, otoliths, and vertebrae) and detected DNA sequences of ten ray-finned fishes in the diets of L. camtschaticum. The most frequent prey taxa were Pacific sand lance Ammodytes hexapterus, Pacific herring Clupea pallasii, gadids, and capelin Mallotus villosus. Five of the ten taxa identified in this study were reported for the first time as prey for L. camtschaticum. To investigate the genetic diversity of larval lampreys, a recognized knowledge gap for populations in Alaska, a total of 81 larval lampreys were successfully genotyped at all loci. Global FST of larvae was 0.074 (95% CI: 0.042 - 0.110), while pairwise FST values among the three localities examined ranged from 0.066 - 0.081. Hierarchical model-based Bayesian clustering analyses detected three genetic clusters (K = 3) among all larval lampreys and two genetic clusters (K = 2) among Chena River larvae; no further genetic clustering was identified within the remaining two tributaries. Estimates of contemporary gene flow indicated reciprocal migration among sites. The diet analyses indicated anadromous L. camtschaticum function as flesh-feeding predators that prey upon pelagic fishes in the eastern Bering Sea, while genetic analyses suggested that larval lamprey aggregations within three Yukon River tributaries exhibited higher levels of genetic diversity than are typically found among broad-ranging populations of anadromous lamprey species. Ultimately, this study highlighted the value of molecular techniques to improve our understanding of the biology of a poorly studied fish species in Alaska.

• #### Chemical and mass spectral studies of 2,2-dialkylglycine decarboxylase

2,2-Dialkylglycine Decarboxylase, DGD, is a decarboxylating transaminase that is dependent on a vitamin B6 cofactor, pyridoxal 5'-phosphate (PLP). DGD catalyzes the decomposition of 2-methylalanine in two steps. DGD was purified by ammonium sulfate precipitation and ion-exchange chromatography. The enzyme was reduced to form a covalent bond between the enzyme and the PLP. Also, [alpha]-(Trifluoromethyl) Alanine, a suicide mechanism based inhibitor was reacted with DGD until the enzyme was completely inactivated. The nonmodified DGD and these two modified forms of the enzyme were subjected to enzymatic digestion by trypsin. Finally, all three peptide mixtures were analyzed by LC/MS/MS. The mass spectra confirmed the amino acid sequence as predicted by the nucleotides of the gene, and the covalent attachment of the cofactor to lysine 272.
• #### Chemical and microbial characterization of North Slope viscous oils for MEOR application

Viscous oil reservoirs tend to be low-energy, low-gas/oil-ratio systems with high viscosities and are difficult to produce, transport and refine by conventional methods. Some of the commonly considered viscous oil recovery methods include processes such as steam flooding, in-situ combustion and miscible gas injection. The large viscous oil deposits in the ANS cannot be produced entirely by conventional methods like pressure displacement or waterflooding. Other methods such as miscible (gas injection and water alternating gas (WAG) also have limited success. Microbial enhanced oil recovery (MEOR) is one of the techniques for improving the oil recovery for viscous deposits. This method has not yet been applied to the ANS fields. This study includes experimental work to analyze the application of MEOR to the ANS oil fields. A microbial formulation was developed in order to simulate the MEOR. Coreflooding experiments were performed to simulate the improved recovery oil recovery and quantify the incremental oil recovery. Properties like viscosity, density and chemical composition of oil were monitored to propose a mechanism of oil recovery. Terminal restriction fragment length polymorphism (T-RFLP) was performed on the oil samples to qualitatively study the effect of the microbial formulation on a molecular scale.
• #### Chemical Composition Of Ice Surfaces: Implications For Springtime Bromine Chemistry

Reactive bromine chemistry is responsible for events of almost total tropospheric O3 destruction and the deposition of mercury during the Arctic spring. The source of the majority of the atmospheric bromine loading is salts from seawater, but many questions remain on the mechanism by which salts are transported and chemically activated to reactive species. Specifically, the role of snow and ice surfaces in exchanging bromine with the atmosphere needed investigation. Therefore, we undertook a detailed study of the ionic composition of selected ice surfaces near Barrow, Alaska and tracked modifications with respect to Cl- and Na+ (sea-salt tracers) in approximately 1,400 samples. We developed data analysis tools to observe modifications and related these methods to the traditional enrichment factor and the non-sea-salt abundance methods. Surface snow was highly modified in Br- composition by atmospheric exchanges that both add and remove bromine, providing evidence for snow's involvement in reactive bromine chemistry. Calcium was enriched by dust input. Sulfate in surface snow was fractionated at the source by mirabilite (Na2SO 4 &bull; 6H2O) precipitation and enriched by Arctic haze inputs. Frost flowers are vapor-grown ice crystals that wick brine and may be involved in sea-salt aerosol production and production of reactive halogen species. Detailed examination of frost flower growth and chemical composition shows that they are sites of mirabilite precipitation and separation, which can lead to sulfate-depleted aerosol particles, but show no sign of direct reactive bromine production. By simultaneously studying snow, ice, aerosol particles, and gas-phase bromine species, we made a mass balance of bromine in various reservoirs. This mass balance points away from frost flowers and towards snow as the dominant source of reactive bromine. This work develops a mechanistic picture of how reactive bromine chemistry depends upon snow and sea ice that is needed to make meaningful predictions of how the recent changes to the Arctic sea ice cover will affect air pollution chemistry.
• #### Chemical Defense Of Boreal Woody Plants Against Vertebrate Herbivores (Snowshoe Hare, Defense, Secondary Metabolite)

Snowshoe hares avoid feeding upon winter-dormant woody plant species, growth stages and parts that contain high concentrations of deterrent secondary plant metabolites. Winter browse that is highly palatable to showshoe hares is also high quality food for these hares: snowshoe hares maintain weight in winter when fed highly palatable browse, but do not maintain weight when fed unpalatable browse. A theory is presented that accounts for the allocation of resources to secondary plant metabolites on both evolutionary and physiological time scales. This theory predicts that: (1) Slowly growing woody plants adapted to growth on nutrient-deficient soils or in deep shade will have more effective constitutive antiherbivore defenses than more rapidly growing woody plants adapted to growth in early stages of succession on fertile soils. (2) Juvenile woody plants will be more strongly selected for antiherbivore defenses than adult woody plants. (3) Ontogenetic variation in the effectiveness of antiherbivore defenses will usually be greater in rapidly growing than slowly growing woody plants. (4) A widespread juvenile reversion of rapidly growing woody plants caused by severe winter hare browsing in the peak phase of the hare cycle is a partial cause of the cycle. Evidence for this theory is presented.
• #### Chemical variations in the waters draining the Hi-Yu Mine

There are two sources of contamination from the Hi-Yu mine: the 'mill seep' and the mine tailings. The mill seep has an acid pH (4.8) containing 20 parts per billion (ppb) Cd and 2400 ppb Zn. Water draining the mine tailings contains 300 ppb As and 30 ppb Sb. These concentrations are above the EPA and State of Alaska Maximum Contaminant Levels (MCL). Once the mill seep mixes with Moose Creek, the pH increases, leading to the precipitation of iron and manganese hydroxides with associated As, Cd, Sb, and Zn. Samples of the iron precipitate contain> 10,000 parts per million (ppm) As, 20 ppm Cd, 240 ppm Sb, and 2600 ppm Zn. Precipitation of metals, along with interaction of organic material and dilution, lowers metal contaminant levels below MCL levels within 0.8 km of the mixing point. Although technically a point source of pollution, the seep and tailings cause no significant increase in the metal content of Fairbanks Creek, 1.2 km downstream of the Hi- Yu mine. The mixing and dilution of waters, adsorption of metals onto Fe and Mn oxy-hydroxide phases, and the settling of particles make the discharge relatively benign, despite the unsightly iron hydroxide precipitate locally present.
• #### Chemo-ecological and evolutionary aspects of the pollinator reward system in Clusia grandiflora (Clusiaceae)

The dioecious, neotropical plant species Clusia grandiflora produces two major pools of secondary metabolites, latex and floral resin. Latex serves as a defense against herbivory and floral resin as a pollinator reward. This reward is gathered by bees who use it as a nest construction material. Nuclear magnetic resonance and mass spectral studies show that C. grandiflora latex and resin share two classes of compounds, poly-isoprenylated benzophenones and tocotrienoic acids as major or minor components. The close chemical correspondence between latex and resin indicate that they are evolutionarily related. Though the tocotrienes were not found to have biological activity, benzophenones with potent bactericidal activity were isolated from both latex and resin. Bioassays show that these compounds are especially toxic to the honeybee pathogens Paenibacillus larvae and P. alvei. In pollinator reward resin, bioactive benzophenones are major components, whereas in latex they are minor components. Since latex is ancestral to resin in Clusia, it appears that the pollinator reward system may have arisen from the defensive system through modification of latex-producing tissues in the flower. Subsequent selective pressure from bee pollinators, who benefited from bactericidal activity in the reward, caused resin chemistry to diverge from its latex-like ancestral form. This selection has resulted in the high levels of activity observed in modern resin. In populations of C. grandifora growing in southeastern Venezuela, male and female resins exhibit a pronounced dimorphism in chemical makeup. Female resin possesses a single benophenone and male resin numerous benzophenones. Female resin is more bioactive and hardens quickly; male resin remains pliable for weeks. Female resin composition more closely resembles modern latex than does male resin. Assuming that latex has not evolved substantially since the point at which resin and latex diverged, it appears that male resin has undergone more extensive evolutionary modification than female, a result of selection for progressively earlier flowering times and of necessity a lower viscosity resin reward. The research presented here provides the first detailed chemical evidence of a functional switch in secondary metabolite pathway from the production of defensive compounds to the production of a pollinator reward.
• #### Chemosensory responses and foraging behavior of Pycnopodia helianthoides: predator or scavenger?

Chemical cues released by damaged or dead organisms can affect how and where benthic scavengers feed, whether damage or mortality is natural or fishery-related. These cues may also cause predators to act as facultative scavengers. Experiments were performed to determine the role that the seastar Pycnopodia helianthoides plays in the presence of scavengable prey. The results of these experiments suggest that P. helianthoides preferentially scavenge in lieu of its normal predatory role. When given a choice, P. helianthoides choose damaged or decaying food over live prey even when live prey is encountered en route to the damaged animal. The densities and activities of P. helianthoides were compared between areas where food was continually introduced and areas where food was not introduced. Adding scavengable food to areas with P. helianthoides caused a spatial redistribution of the seastar population, a change in the foraging dynamics of the seastars, and in some cases, a change in the densities of the prey that P. helianthoides normally consume. The effects of introducing food appeared to result in a change in the role that P. helianthoides plays in the benthic community. This change in modes could have significant effects on the equilibrium of the benthic community.