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Recent Submissions

  • Alaska Earthquake Center Quarterly Technical Report January-March 2022

    Ruppert, Natalia (2022-05)
    This series of technical quarterly reports from the Alaska Earthquake Center (AEC) includes detailed summaries and updates on Alaska seismicity, the AEC seismic network and stations, field work, our social media presence, and lists publications and presentations by AEC staff. Multiple AEC staff members contribute to this report. It is issued in the following month after the completion of each quarter Q1: January-March, Q2: April-June, Q3: July-September, and Q4: October-December. First report was published for January-March, 2021.
  • Current exposure of Yukon Flats tribal villages' residents to PM₂.₅ from natural and anthropogenic sources: establishing baselines for climate change adaptation and resilience

    Edwin, Stanley G.; Mölders, Nicole; Collins, Richard L.; Fochesatto, Javier; Stuefer, Martin (2020-08)
    How healthy is the air in the villages during the summer fire seasons? Why does Fort Yukon always seem to be colder than the surrounding villages in winter and spring? How healthy is the air we breathe in our homes and workplaces? These are but a few of the questions asked by Alaska's Eastern Interior residential village's Indigenous Tribal Governments. A tribal-owned network of aerosol monitors and meteorological stations was installed at Ts'aahudaaneekk'onh Denh, Gwichyaa Zheh, Jałgiitsik, and Danzhit Khànlaj̜j̜ in the Yukon Flats, Alaska. To assess the exposure of residents in rural communities in the Yukon Flats to particulate matter of 2.5 [micro]m or less in diameter (PM2.5), both indoor and outdoor concentration observations were carried out from spring 2017 through to August 2019. Surface-based-temperature inversions occurred under calm wind conditions due to surface radiative cooling. In May, local emissions governed air quality with worst conditions related to road and river dust. As the warm season progressed, worst air quality was due to transport of pollutants from upwind wildfires. Absorption of solar radiation in the smoke layer and upward scattering enhanced stability and fostered the persistence of the surface-based-temperature inversions. Under weak large-scale forcing mountain-valley circulations develop that are driven by the differences in insolation. During the long dark nights, surface radiative cooling occurs in the near-surface layer of the mountain slopes of the Brooks, Ogilvie and White Mountains Ranges and at the bottom of the valley. Here surface-based-temperature inversion - known as roof-top inversions - form, while the cold air drains from the slopes. A frontal wedge forms when the cold air slides over the relatively colder air in the valley. Drainage of cold air from the Brooks Range governed the circulation and cold air pooling in the valley. At the site, which is closest to the mountains, concentrations marginally changed in the presence of temperature inversions. Indoor concentrations were measured at 0.61 m in homes and at 1.52 m heights both in homes and office/commercial buildings. Air quality was better at both heights in cabins than frame homes both during times with and without surface-based-temperature inversions. During summer indoor concentrations reached unhealthy for sensitive groups to hazardous conditions for extended times that even exceeded the high outdoor concentrations. Indoor and outdoor concentrations were strongest related for office/commercial buildings, followed by frame houses and cabins. These are but a few of the answers found in this research of meteorology effects, unhealthy locations for breathing PM2.5 air outdoors and in homes.
  • Anchoring the sky

    Kaynor, Carol; Crouse, David; Soos, Frank; Box, Mark (2010-05)
    'Anchoring the Sky' chronicles the narrator's experiences over a period of more than twenty years after her younger sister is diagnosed with cancer, rallies for a short time, and then dies. The narration, which follows a roughly chronological structure with some flashbacks, is divided into three sections. The first section describes the narrator's initial experiences of caregiving in a chaotic household, ending on a note of hope. The second section describes the loss of hope, the sister's death, and the narrator's experiences of intense grief immediately afterward. In the third section, the narrator describes selected moments in a 20-year quest for some sense of resolution over her sister's death. Throughout the story, the narrator vacillates between emotive and objective expression as she struggles to come to terms with both the loss of her sister and with the loss of long-term memories caused by the narrator's own chronic illness. Though she never finds the magical resolution she seeks, she finally finds support and assistance both for her loss of precious memories and her unresolved grief by reconnecting with her family's experiences during her sister's illness and death
  • Buddy reading for reading comprehension growth and reading engagement

    Triplett, Kimberly L.; Rickey, Melissa; Austin, Terri; Waltenbaugh, Eric; Waltenbaugh, Jennifer (2008-12)
    "Teachers wonder how to motivate students to become better readers. Teachers of older remedial readers are challenged to provide reading material at students' reading levels relevant enough for them to want to read. Students are less likely to learn strategies to help them comprehend text if they are not engaged with the material. This project provided seventh grade remedial reading students a purpose for reading books at their level by reading children's picture books to first grade students. Prior to the buddy reading sessions, seventh grade students practiced reading with expression and fluency. In addition, their teacher taught cognitive strategies to assist comprehension. Concurrently, their first grade partners were exposed to the same strategies during classroom instruction. The seventh grade readers assisted their first grade 'buddies' in applying the taught strategies during the sessions. This research examined the interaction and engagement of students during buddy reading experiences. In addition, attention was paid to how students used the taught comprehension strategies during buddy reading. Conclusions were drawn from field observations, transcribed recordings, student work, and interviews indicating buddy reading had a positive impact on reading engagement and students' awareness of comprehension strategies to be used during reading"--Leaf iii
  • Determination of minimum miscibility pressure using vanishing interfacial tension in support of Alaska North Slope heavy oil development

    Tathed, Vinit Santosh; Dandekar, Abhijit Y.; Patil, Shirish L.; Khataniar, Santanu (2008-12)
    "Developing Alaskan heavy oils resources has become necessary as, the production from light oil fields in Alaska's North Slope (ANS) is on the decline. Due to the extremely viscous nature of these heavy oils, they are hard to produce by natural pressure. Miscible gas injection Enhanced Oil Recovery (EOR) can be one of the methods for production of these heavy oils. Minimum miscibility pressure (MMP) is an important optimization parameter for EOR processes involving CO₂ or hydrocarbon gas injection. The MMP for a gas-oil system is directly related to the interfacial tension between the injected gas and the reservoir crude oil. In this study, a new technique called Vanishing Interfacial Tension (VIT) was used to measure MMP at reservoir conditions. Experiments were conducted using various gas-oil systems to determine the MMP. The experimental results were modeled using the Peng-Robinson Equation-of-State (EOS) with a commercial simulator (CMG). The Peng-Robinson EOS was tuned with experimental data to predict the MMP accurately. This study has demonstrated the accuracy of the VIT technique in predicting MMP by pendant drop method experiments and simulations using CMG software."--Leaf iii
  • The distribution of nitric oxide at 150 km

    Stern, Timothy E. (2008-12)
    "The objectives of this thesis are to determine the morphology of nitric oxide at the altitude of 150 km and to determine what drives the observed variability. Those objectives are accomplished by characterizing satellite observations of nitric oxide at that altitude and comparing them with those at 106 km, the altitude of peak density. The global distribution of nitric oxide and its response to geomagnetic activity vary between the two altitudes. At 150 km, nitric oxide is most abundant at high latitudes in the sunlit summer hemisphere, in contrast to nitric oxide at 106 km, which is most abundant at high latitudes in the winter hemisphere. The high-latitude component of nitric oxide at both altitudes is associated with geomagnetic activity, although the primary production mechanisms differ between the two altitudes. At 106 km, high-latitude nitric oxide density enhancements are driven by particle precipitation. At 150 km, nitric oxide at high latitudes is enhanced by increased temperatures arising from Joule heating. Enhancements at 150 km occur more rapidly than those at 106 km. At both altitudes, the response of nitric oxide to geomagnetic activity exhibits a seasonal variation that is attributed to seasonal variations in the production mechanisms"--Leaf iii
  • Remote sensing aspen leaf miner (Phyllocnistis populiella chamb) infestations near Ester Dome in Fairbanks, Alaska

    Smart, Douglas D. (2008-12)
    "Mapping trembling aspen stands (Populous tremuloides Michx.) versus Alaskan birch (Betula neoalaskana Sarg.) in interior Alaska is possible as a byproduct of remote sensing aspen leaf miner (Phyllocnistis populiella Chamb.) damage. P. populiella is a defoliator of trembling aspen that has been observed in epidemic proportions in Alaska since 2001. Where it is observed it is ubiquitous. Unlike most remote sensing studies of insect damage, I found no significant change in the near-infrared related to leaf miner damage. The feeding morphology of P. populiella is different from most other leaf defoliating insects. P. populiella feeds only in the epidermal tissue of aspen leaves whereas most other leaf mining insect pests consume mesophyll tissue. This means that P. populiella causes no significant change in near-infrared reflectance whereas most other defoliators do. This lack of change in near-infrared range coupled with the timing of leaf miner foraging can be used to discriminate P. populiella damage from that of other leaf defoliators. The ability to remotely sense damage in aspen stands provides an opportunity to identify P. tremuloides in locations where damage is epidemic. If new image acquisition and historic image purchases are timed to correspond with P. populiella outbreak conditions, it will be possible to identify areas that are P. tremuloides stands and not other species"--Leaf iii
  • An engineering study to investigate the methane hydrate resource potential associated with the Barrow gas fields in Alaska

    Singh, Praveen Kumar; Dandekar, Abhijit Y.; Patil, Shirish L.; Panda, Manmath N.; Stokes, Peter J.; Khataniar, Santanu; Walsh, Thomas P. (2008-12)
    "Previous studies on the Barrow Gas Fields (BGF) in Alaska have suggested that accumulations of natural gas hydrates could exist within these reservoirs. In consideration of future energy challenges, and the potential of gas hydrates in meeting them, a comprehensive engineering study was undertaken to investigate the BGF for hydrates, and to recommend an optimal plan for future field development. The methane hydrate resource potential of the BGF, viz. the East Barrow (EB), South Barrow (SB), and Walakpa (WAL) gas pools, was analyzed by developing gas hydrate stability models. Material balance studies were performed on the EB gas field to understand the reservoir drive mechanisms. Gas-water relative permeability experiments were conducted on a hydrate-saturated consolidated core sample, by maintaining the EB reservoir conditions, to model two-phase fluid flow behavior. Finally, field-scale dynamic reservoir simulation models were developed for the EB and WAL gas fields. Production history data were matched, reservoir drive mechanisms were confirmed, free gas and hydrate resources were quantified, hydrate dissociation patterns were examined, optimum locations for drilling infill wells were identified, and future production scenarios were simulated. Findings from this work indicate that BGF are associated with hydrates that are constantly recharging the gas reservoir by dissociation"--Leaf iii
  • Classroom culture and indigenous classrooms

    Sikorski, Hishinlai' Kathy R.; Siekmann, Sabine; Marlow, Patrick; Leonard, Beth (2008-12)
    "Indigenous languages have been traditionally learned by doing activities on the land, with the family or around a village. Sometimes, because this is not feasible, Indigenous languages can be learned in a classroom. This is a qualitative research on the author's own Indigenous language classroom with the theoretical foundations of second language acquisition and group formation processes. Data collected were videotapes, audiotapes, student journals, and an exit interview, which were triangulated and verified by an interrater. Results were that the instructor had to possess a philosophy of second language teaching and learning; set high expectations, and create a positive classroom culture. Learners had to be extremely motivated; participate, and pull their own weight. The overall recommendations are that (a) learners need to learn their ancestral language as a second language, (b) Native language teachers need training on theories of second language acquisition, (c) Native language teachers need to have a strong philosophy of second language learning and teaching, and (d) learners need to have a mindset that they will learn to speak their ancestral languages by practicing. These recommendations have worked in the researcher's classroom, and can be extended to any second language teaching or learning arena"--Leaf iii
  • Balancing the conservation of wildlife habitat with road access for subsistence hunting in Yakutat, Alaska

    Shanley, Colin S.; Pyare, Sanjay; Kofinas, Gary; Hundertmark, Kris (2008-12)
    "This thesis was an interdisciplinary investigation with the goal of balancing the conservation of wildlife habitat with road access for subsistence hunting in Yakutat, Alaska. The problem posed by land managers and subsistence moose hunters revolved around the use of off-highway vehicles (OHVs; e.g. 'four-wheelers') for subsistence moose hunting and the potential disturbance OHVs have on moose. This complex social-ecological problem is becoming an increasingly common management dilemma faced by rural mixed cash-subsistence communities across the Circumpolar North. I addressed this problem in two chapters with a combination of methods from wildlife ecology, landscape modeling, subsistence land-use, and scenario planning. The data used for analysis in Chapter 1 was derived from a three-year moose GPS-collar dataset, remote sensing imagery, and mapped routes. I modeled moose distribution with multi-scale, seasonal and sex-specific resource selection functions in a GIS. The best-fit models suggested female moose were displaced by OHV routes. Male moose were displaced by routes or areas where routes were in close proximity to primary forage. A combined pattern of route avoidance was quantified beyond approximately 1 km of total vehicle travel/km²/day. Chapter 2 describes the application of distribution models from Chapter 1 to a social-ecological assessment of route closures. Meetings with land managers and moose hunters were conducted to identify their respective values and management goals. Then I evaluated the effect of four road closure scenarios on moose habitat and hunting access. A measure of hunting access was evaluated with interviews about hunter land-use patterns, as well as the mapping of harvest areas in a GIS. The results of the scenario evaluation showed the spatial arrangement of routes influenced the total amount of high probability moose habitat and access to preferred harvest areas. A balance in the conservation of wildlife habitat and the maintenance of hunting access may be found in the closure of routes through valuable moose habitat and the spatial arrangement of future routes around valuable moose habitat, within reach of important harvest areas. The results of the analysis and interdisciplinary approach may prove useful to land managers who must evaluate the trade-offs between wildlife habitat conservation and the increasing use of motorized access for contemporary subsistence hunting practices"--Leaf iii
  • Shallow surface thermogenic hydrocarbon migration over western Prudhoe Bay Region, Alaska

    Sarkar, Sudipta (2008-12)
    "Hydrocarbons leak from petroleum reservoirs to the surface. In continuous permafrost regions like the Alaska North Slope, surface migration of thermogenic hydrocarbons may be hindered by the presence of ground ice. However, suitable permeable migration pathways in the permafrost can exist. Unfrozen sediments at the bottom of the lakes, or open faults can facilitate thermogenic hydrocarbon migration. I studied the nature and distribution of gaseous alkanes (C1 to C6) and helium in the shallow permafrost cores (2 m depth); depth profiles of alkanes (C1 to C7) in the two wells (1500 m deep); and stable isotopes of CH₄ trapped in lake gas bubbles, to trace the presence of thermogenic hydrocarbons and their migration pathways. Geostatistical analysis of the alkane and helium distributions shows that most anomalies occur along northwest-southeast oriented lineaments, roughly corresponding to the trend of the Eileen fault mapped at 2675 m depth, high fault density zones of the Kuparuk Formation, and northwest-southeast trending Sagavanirktok faults mapped at 457 m depth. The anomalies above the Eileen fault can be explained by a fluid-flow model in a dilational jog along a wrench fault. This model agrees with the movements along the Eileen fault"--Leaf iii
  • Measurement of rheological and thermal properties and the freeze-thaw characteristics of nanofluids

    Sahoo, Bhaskar C. (2008-12)
    "This research investigates the rheological and thermal properties and the freeze-thaw characteristics of nanofluids. Nanofluids are dispersions of nano-scale particles (<100 nm) in a base fluid such as water, ethylene glycol, propylene glycol or a mixture of more than one fluid. In cold regions, a mixture of 60% ethylene glycol in water by mass (60:40 EG/W) is normally used as the heat transfer fluid due to its low freezing point. Rheological properties of aluminum oxide nanofluid in the 60:40 EG/W base fluid were investigated and new correlations, expressing viscosity as a function of temperature and particle concentration, were developed. Results from the specific heat experiments on zinc oxide nanofluid in the 60:40 EG/W were compared with available correlations and a new model was developed. The thermal conductivity of silicon dioxide nanofluid in a 60:40 EG/W was measured and compared with existing models, considering the Brownian motion of nanoparticles. A new correlation, expressing thermal conductivity as a function of particle concentration, size, base fluid properties and temperature, was proposed by improving an existing model. Freeze-thaw characteristics of copper oxide nanoparticle dispersions in water were studied for a single freeze-thaw cycle. The freezing rate, agglomeration of nanoparticles and the effect on the freezing point of nanofluid were examined"--Leaf iii
  • Sensitivity of boreal forest carbon dynamics to long-term (1989-2005) throughfall exclusion in Interior Alaska)

    Runck, Sarah A.; Valentine, David; Chapin, Terry; Yarie, John (2008-12)
    "The objective of this study was to assess the effect of throughfall exclusion (1989-2005) on forest vegetation and soil in upland and floodplain landscape positions. In uplands, imposed drought reduced soil moisture at 5, 10, and 20 cm depths and increased soil C storage by slowing decomposer activity at the surface. In the drought plots, aboveground tree growth was reduced and root biomass in mineral soil was increased. In floodplains, imposed drought did not reduce soil moisture as strongly as it did in uplands, though near-surface soil C storage was still increased as a result of reduced decomposer activity. Floodplain vegetation response to imposed drought differed from that of uplands; imposed drought did not reduce aboveground tree growth but instead reduced root biomass in mineral soil. At both landscape positions, imposed drought accelerated the loss of understory vegetation. Overall, the results of the throughfall exclusion indicated that chronic soil drying is likely to increase forest C storage only in floodplains. In uplands, where soil moisture is more limited, forest C storage is not as likely to change because an increase in soil C may be offset by reduced tree growth"--Leaf iii
  • Habitat analysis of major fishing grounds on the continental shelf off Kodiak, Alaska

    Rooney, Sean Charles; Reynolds, Jennifer; Norcross, Brenda; Heifetz, Jonathan; Kruse, Gordon (2008-12)
    "The continental shelf and upper slope of the Gulf of Alaska support diverse and commercially important communities of demersal fishes. Twenty-eight video-strip transects conducted from a research submersible, together with habitat maps based on interpreted multibeam sonar data, were used to classify distribution and abundance patterns of fishes relative to seafloor substrate type and water depth on Albatross and Portlock Banks on the Kodiak Shelf in the Gulf of Alaska. These associations were examined across spatial scales: ranging from tens of kilometer centimeters in size. A total of 5,778 fishes were recorded from 33 taxa. Fish community distribution patterns were largely correlated with depth and to a lesser extent with substrate type. Individual fish species habitat associations were also influenced by depth and substrate type; however, the spatial scale at which these factors were relevant varied by fish species. There was strong regional concordance among observed fish species habitat associations and those previously documented in studies from central California to the northern Gulf of Alaska. Although integrating substrates classified at different scales was challenging, the resulting information of scale specific habitat associations provides a more comprehensive understanding of how demersal fishes utilize benthic habitats"--Leaf iii
  • Non-volcanic tremor in the Alaska/Aleutian subduction zone and its relationship to slow-slip events

    Peterson, Chloe L. (2008-12)
    "We document non-volcanic tremor (NVT) in Southcentral Alaska and the Aleutian Arc in terms of durations and locations. In Southcentral Alaska, we tabulate NVT events occurring during the summer months of each year between 1999 and 2001 to test for a relationship with a slow-slip event that occurred during this time frame. We tabulate NVT events in the Aleutians starting in the summer of 2005 through the summer of 2008. The observed NVT events in both Southcentral Alaska and the Aleutian arc are sequences of emergent pulses with frequencies of 1-10 Hz. The majority of the events have durations ranging from 5-15 minutes. In Southcentral Alaska, the majority of the NVT events locate in the region of the slow-slip event and the quantity of events decreases significantly by the summer of 2001, coinciding with the end of the slow-slip event. Locating NVT events in the Aleutians is problematic due to the linearity and sparse distribution of seismic stations. General locations are established simply by the distribution of volcano seismic networks on which the signal is observed and the strength of that signal. These general locations appear to coincide with regions where the plate interface is locked or is transitioning from creeping to locked. Furthermore, several episodes of NVT in the Aleutians occurring during times of heightened volcanic and seismic activity in the arc, suggesting large regional stress changes possibly caused by undetected slow-slip events"--Leaf iii
  • Comparative and sensitivity study of the effects of flow parameters on pressure drop in vertical tubing

    Elekwachi, George Kaetochi; Chukwu, Godwin; Patil, Shirish; Khataniar, Santanu; Dandekar, Abhijit (2008-12)
    "Two-phase gas-liquid flow occurs in vertical pipes during the production of reservoir fluids. The two most common flow patterns that are observed during oil production are the Bubble and Slug flows. Determination of pressure drop in two-phase flow is more complicated than single-phase flow because two fluids with different densities flow in the tubing at different velocities. Using two multiphase correlations (Hagedorn and Brown, and Duns and Ros), the effect of fluid properties variation at different flow conditions on pressure drop were studied. Fluid data developed with correlations and West Sak fluid data were used for the analysis. Plots showing the relationship between pressure drop and different fluid properties were made. From the analysis, it was concluded that oil density, oil viscosity and oil flow rate are the three factors that influence pressure drop in vertical pipes the most. The Hagedorn and Brown correlation was shown to be able to compute pressure drop for high-viscosity oil"--Leaf iii
  • Improving Safety for RITI Communities in Idaho: Documenting Crash Rates and Possible Intervention Measures

    Lowry, Michael; Swoboda-Colberg, Skye; Prescott, Logan; Abdel-Rahim, Ahmed (2022-03-23)
    This report describes a new set of Geographic Information System (GIS) tools that we created to conduct safety analyses. These new GIS tools can be used by state DOTs and transportation agencies to document crash rates and prioritize safety improvement projects. The tools perform Network Segment Screening, the first step in the Roadway Safety Management Process (RSMP) outlined in the Highway Safety Manual (HSM). After developing these new tools, we conducted two case studies to demonstrate how they can be used. The first case study was for screening intersections. Our analysis included all intersections on the Idaho State Highway System. In practice, the analysis would likely be done only for a subset of intersections, such as only for signalized intersections on urban arterials. We chose all intersections for illustration purposes. The result was a ranking of intersections that would most likely benefit from safety improvement efforts. We applied three performance measures to rank the intersections: Crash Frequency, Crash Rate, and Equivalent Cost. The second case study was for screening roadway segments. Again, the entire Idaho State Highway System was included for illustration. The HSM describes two key methods for screening roadway segments: Simple Ranking and Sliding Window. Both methods are available in the new tools. This case study demonstrates the advantage of the Sliding Window, which would be impractical to accomplish on a large scale without the assistance of our new GIS tools. The final part of the work presented in this report is a synthesis to identify and document possible measures to reduce crashes for RITI communities in Idaho and throughout the northwest region.
  • Evaluation of Delivery Service in Rural Areas with CAV

    Prevedouros, Panos; Alghamdi, Abdulrahman (2022-03-15)
    Urban areas have been experiencing automated delivery technology for several servings of food or a few bags of groceries, with automated (robotic) mini vehicles. The benefits of such automated delivery may be much more significant for rural areas with long distances due to the large potential savings in travel time, travel cost, and crash risk. Compared to urban areas, rural areas have older and more disabled residents, longer distances, higher traffic fatality rates, and high ownership of less fuel-efficient vehicles such as pickup trucks. An evaluation of connected autonomous vehicle (CAV) delivery service in rural areas was conducted. A detailed methodology was developed and applied to two case studies: One for deliveries between Hilo and Volcano Village in Hawaii as a case of deliveries over a moderate distance (~50-mile roundtrip) in a high-energy-cost environment, and another for deliveries between Spokane and Sprague in Washington State as a case of deliveries over a longer distance (~80-mile roundtrip) in a low-energy-cost environment. The delivery vehicles were based on the same compact van: A person-driven gasoline-powered van, a person-driven electric-powered van, and a CAV electric-powered van. The case study results suggest that the CAV van can be a viable option for implementing a delivery business for rural areas based on the evaluation results that accounted for a large number of location-specific costs and benefits and the number of orders served per trip.
  • Determination of the diffusion coefficient for trimethylaluminum in the thermosphere at altitudes 120 to 180 km

    Bhattacharya, Tapas (2009-05)
    "The object of this work is to determine the diffusion coefficient (D) of trimethylaluminum (TMA) in the lower thermosphere as a function of altitude (h). This is done by measuring the dispersion of chemiluminescent TMA that is released in discrete quantities, or puffs, from sounding rockets at altitudes 120 to 180 km. Diffusing TMA, which glows in contact with atmospheric oxygen, is observed with stereoscopic ground-based imaging. Brightness profiles across a puff are found to be Gaussian in shape, with width parameter [sigma](t, h) that increases with age (t) of the puff leading to D = [sigma]² (t, h)/2t, independent of time, which is in good agreement with some past results. For example D = (2.5 ± 0.2) x 10³m²s⁻¹ at an altitude of 128 km for the state of the thermosphere at that time. A constant A links three altitude-dependent terms, the diffusion coefficient, temperature and density, at a particular location of the atmosphere, via D(h) = ATS (h)/n(h). It is determined from this study to be A=(4.42±0.05)x10¹⁸(m·s)⁻¹ for s = 0.75. Using these values for A and s, and temperatures and the densities determined from the MSIS-90 thermospheric model, diffusion coefficients for TMA can be determined at other locations and under different geomagnetic conditions"--Leaf iii
  • Characterization of reproductive cyclicity of sex steroids by fecal analysis in Steller sea lions (Eumetopias jubatus)

    Litz, Beate (2008-08)
    "Steller sea lions (Eumetopias jubatus) have experienced a drastic population decline in the past several decades. Among hypotheses for the decline and failure of the population to recover is decreased reproductive success. Harsh environmental conditions within the species range and the large body size of the animals can limit sampling efforts to investigate these hypotheses. Three captive Steller sea lions were used as models to validate the use of fecal steroid analysis for this species. Their annual endocrine fluctuations were monitored over four years to gain a better understanding of their reproductive endocrinology and overcome sampling challenges typically associated with hormonal studies of large mammals. Radioimmunoassays (RIA) and enzyme immunoassays (EIA) reliably measured testosterone, total estrogens, and progesterone extracted from Steller sea lion feces. Lack of refrigeration for five days and freezing ( -20°C) for 8 weeks did not alter concentrations of fecal testosterone and total estrogens measured. The stability of fecal progesterone in the absence of cold storage was compromised by 4.5 days; however, it remained stable while frozen ( -20°C) for 8 weeks. Thus, for field research, there are two primary implications. Firstly, samples of freshly voided scat collected from rookeries and haulouts can reliably reflect hormone concentrations for <̲ 4.5 days and secondly, these samples can be stored for later analysis for at least 8 weeks. Long-term serial sampling demonstrated fecal progesterone may be more useful in providing information on reproductive function than fecal estrogens. Annual endocrine profiles suggest the females are seasonally monoestrus, supporting the general assumption for the species, and the male has a strong seasonal cycle in testosterone with maximum concentrations measured just prior to the natural breeding season. These data also suggest fecal testosterone reflects changes in testicular activity despite breeding status and proximity to females. Collectively, these data suggest this non-invasive endocrine monitoring technique has potential to provide a useful alternative method of sample collection"--Leaf iii

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