• Language Switching On English Compositions Of Latino Students In Alaska And Puerto Rico

      Jimenez-Lugo, Edna; Burleson, Derick (2007)
      The main objective of the research described in this dissertation was to explore how English second language (ESL) writers used their first language (L1) when composing in their second language (L2). This task was undertaken by identifying participants according to their L2 (English) proficiency level, Latino ethnic subgroup, and generational status. Another objective of this study was to better understand the writer's perspective regarding first language use in L2 writing, referred to as language-switching (L-S) in this study. Eight high school Latinos were recruited in Fairbanks, Alaska, and a group of twenty-three college-level participants in Mayaguez, Puerto Rico. Participants were asked to complete a self-report questionnaire, provide a writing sample, and participate in a guided focus group discussion. Findings indicated that participants with low L2 proficiency were more likely to switch languages at the lexical level than participants at an intermediate or advanced level of English proficiency. Switching languages from English to Spanish at the lexical level was of no benefit for text coherence. Lack of L2 linguistic competence was a contributing factor for switching to the L1 as participants compensated for L2 difficulties with their L1 knowledge at the morphological, syntactical, and semantic level. A qualitative analysis of the focus group data suggests that thinking in the L1 is a common strategy for ESL learners, which they perceive to be an advantage for generating ideas faster and to decide what to write. However, participants' perceived writing text in the L1 for later content translation to be counterproductive. An important factor that cannot be discounted and that may have contributed to the language switching frequency among the participants in this study is the learning contexts: learning English in the U.S. versus learning English in Puerto Rico. Additional research is needed to explore the relationship between language switching and learning context. I conclude this dissertation by suggesting pedagogical implications regarding L2 writing instruction and for placement of L2 learners in ESL programs.
    • Latching mechanism between UAV and UGV team for mine rescue

      Hoffman, Sarah; Peterson, Rorik; Hatfield, Michael; Lin, Chuen-Sen (2017-08)
      Safety is a concern in the mining industry when a tunnel collapse could result in the casualties and deaths of workers and rescuers due to the hazards posed to them. The Alaska Center for Unmanned Aircraft Systems Integration (ACUASI) is working on a project to increase mine safety by sending an Unmanned Ground Vehicle (UGV) fit with LiDAR sensors and an Unmanned Aircraft Vehicle (UAV) to map the tunnels and to find a collapsed tunnel in an effort to determine the location and condition of trapped workers. The UGV will drive to the collapsed tunnel, at which point the U AV will launch to find any gap in the tunnel that it could fly through to assess the damage. This overall project requires a releasing and latching system to secure the UAV, allow it to launch at the appropriate location, and dock the UAV when its mission is complete or its battery needs recharging. A simple pin-through design was adopted to latch and release the UAV by implementing a Scotch yoke and servo as the actuator. All necessary components were analyzed for stress using two forces, 16 N (maximum takeoff weight of the potential UAV) and 150 N (im pact force of the maximum w eight of the potential UAV from 0.15 m or just under 6 inches). Three sets of properties for PLA were applied in the stress analyses to thoroughly investigate the feasibility of creating the parts out of PLA, a commonly used plastic for 3D printing. These three property sets were found in literature and consisted of bulk values of PLA, empirically determined values of 3D printed PLA, and values calculated using porosity equations. It was found that most components would function satisfactorily without risking fracture except in extreme conditions. The stress analyses for the landing gear illustrated its weaknesses, revealing a potential need for a different material or redesign. The landing gear as it is could be utilized under nominal operation, but it could not withstand any significant impact such as one that might occur in the event of a hard landing. The latching mechanism itself succeeded in securing the UAV. Future work includes redesigning the landing gear, another design concept for a latching mechanism that may prove more reliable, and adjusting the landing pad in the event a different UAV is selected.
    • Late Cenozoic unroofing sequence and foreland basin development of the central Alaska Range: implications from the Nenana Gravel

      Thoms, E. E. (2000-05)
      Facies architecture analysis, lithostratigraphy, and ⁴⁰AR/³⁹AR analyses of syn-orogenic sediments from the Nenana Gravel consistently demonstrate that deformation and erosion of the Late Cenozoic Alaska Range progressed in a foreland propagating sequence. Alluvial braidplain sediments, the oldest sourced from south of the present range divide, were shed into depozones exhibiting characteristics that indicate the growth of an underlying orogenic wedge primarily controlled deposition. Those characteristics include very immature and locally derived sediments, erosional unconformities, evidence for the competing influences of uplift and subsidence, lithology transitions that are correlated with facies transitions, and evidence for drainages that were defeated by surface uplift. Deposition of the Nenana Gravel took place between roughly 7 and 3 Ma. The Nenana Gravel depositional system changed when deformation within the proximal reaches of the basin brought resistant basement rocks to the surface forcing antecedent drainages to incise and abandon the alluvial braidplain they once fed.
    • Late quaternary and future biome simulations for Alaska and eastern Russia

      Hendricks, Amy S.; Walsh, John; Saito, Kazuyuki; Bigelow, Nancy; Bhatt, Uma (2016-05)
      Arctic biomes across a region including Alaska and Eastern Russia were investigated using the BIOME4 biogeochemical and biogeography vegetation model. This study investigated past (the last 21,000 years), present, and future vegetation distributions in the study area, using climate forcing from five CMIP5 models (CCSM4, GISS-E2-R, MIROC-ESM, MPI-ESM, and MRI-CGCM3). The present-day BIOME4 simulations were generally consistent with current vegetation observations in the study region characterized by evergreen and deciduous taiga and shrub tundras. Paleoclimatological simulations were compared with pollen data samples collected in the study region. Pre-industrial biome simulations are generally similar to the modern reconstruction but differ by having more shrub tundra in both Russia and Alaska to the north, as well as less deciduous taiga in Alaska. Pre-industrial simulations were in good agreement with the pollen data. Mid-Holocene simulations place shrub tundras along the Arctic coast, and in some cases along the eastern coast of Russia. Simulations for the Mid-Holocene are in good agreement with pollen-based distributions of biomes. Simulations for the Last Glacial Maximum (LGM) show that the Bering Land Bridge was covered almost entirely by cushion forb, lichen and moss tundra, shrub tundra, and graminoid tundra. Three out of the five models’ climate data produce evergreen and deciduous taiga in what is now southwestern Alaska, however the pollen data does not support this. The distributions of cushion forb, lichen, and moss tundra and graminoid tundra differ noticeably between models, while shrub tundra distributions are generally similar. Future simulations of BIOME4 based on the RCP8.5 climate scenario indicate a northward shift of the treeline and a significant areal decrease of shrub tundra and graminoid tundra regions in the 21st century. Intrusions of cool mixed, deciduous, and conifer forests above 60°N, especially in southwest Alaska, were notable. Across eastern Russia, deciduous taiga begins to overtake evergreen taiga, except along the coastal regions where evergreen taiga remains the favored biome.
    • Late Quaternary vegetation and lake level changes in central Alaska

      Bigelow, Nancy Horner; Edwards, Mary E.; Powers, W. Roger (1997)
      The threat of significant high-latitude global warming over the next 50 years requires that we assess the response of vegetation to climate change. One approach is to see how plants have reacted to past climate change. In this study high-resolution reconstructions of past vegetation and climate, based on pollen and lake level changes, provide useful insights into vegetation and climate change in central Alaska since 14,000 years ago. Climate changed substantially at about 12,000 years ago, between 11,000 and 10,000 years ago, and about 8,000 years ago. At 12,000 years ago, a significant transition is reflected by the appearance of shrub birch into a region that had been dominated by grass, sage, and sedge. The vegetation became denser; shrubs occupied the moister sites, and herbaceous taxa grew on well-drained, exposed ridges and slopes. Lake levels increased at this time, suggesting the climate became warmer and wetter than it had been previously. Between 11,000 and 10,000 years ago, the vegetation at some sites reverted to a grass and sage-rich flora, suggesting a return to drier and/or cooler conditions. This period of climate change has not been recognized before from pollen records in central Alaska. The timing of this vegetation shift suggests it is related to the Younger Dryas event, a world-wide episode of climatic deterioration. About 8,500 to 8,000 years ago, spruce appeared in the region, coincident with a significant lake level rise, suggesting that the spruce expansion was aided by wetter conditions, as well as warmer temperatures. In central Alaska, periods of past vegetation change are marked by shifts in moisture. Today, central Alaska receives very little rain, and in some areas the vegetation is moisture-limited, suggesting that during the past, changes in moisture could have had a strong effect on the vegetation. In terms of future global change, this study suggests that any shifts in moisture associated with the predicted temperature changes, especially towards drier conditions, will strongly affect the current vegetation distribution.
    • Later that night: three studies in horror

      Michael, Kathryn; Kamerling, Leonard; Farmer, Daryl; Carr, Richard (2015-05)
      To write a successful screenplay is to form a blueprint, a set of dramatic instructions; a structural plan to be executed at a later date by film artists and technicians. It is vital not to become attached to the details; components such as character names and place settings will often change as a project undergoes different stages of development. Above all else, what must remain on the page is the story's dramatic structure, its intention. If this is accomplished, the integrity of the screenplay is intact, and the writer is in control. Later that Night: Three Studies in Horror is a compilation of three short screenplays, each showcasing a popular horror subgenre. The screenplays follow Anna and Gabriel, a pair of con-artists, as they try to maneuver their way through the back roads of Nebraska on one fateful summer night. In In Sight, the pair is wrapping up a con job when an unexpected guest turns up on the front porch in need of help, with surprising consequences. In Pit Stop, a routine fill-up at a local gas station takes a bloody turn for the worse when two men attempt a hold-up. Finally, in Overnight Guest, Anna's freedom from Gabriel is cut short when his spirit refuses to grant her peace. These three screenplays are written as stand-alone pieces that can be viewed in chronological order to form a continuous storyline. The purpose of this structure is to highlight specific subgenres of horror in each of the three scripts and to create an understanding of how each functions as a storytelling genre. In Sight is a psychological thriller, focusing on feelings of unease and impending action. Pit Stop is a "gore script", highlighting gratuitous amounts of blood and death. Overnight Guest is a story of the supernatural, with the protagonist's life being directly affected by an angry spirit.
    • Lateral magma transport during the 1912 eruption of Novarupta: insights from magnetic imaging

      Hill, Graham J.; Eichelberger, John; Freymueller, Jeff; Faust-Larsen, Jessica (2003-08)
      The Valley of Ten Thousand Smokes (VTTS), on the Alaska Peninsula, was formed by the cataclysmic eruption of Novarupta (Katmai) in 1912. During the eruption, three magma types were tapped (7-8 km³ of rhyolite, 4.5 km³ of dacite, and 1 km³ of andesite). Contemporaneous collapse of Mount Katmai while Katmai-like andesite and dacite magma joined the eruption at Novarupta provides incontrovertible evidence for magma transport from beneath Mount Katmai caldera to the vent 10 km west at Novarupta (Hildreth and Fierstein, 2000). Shallow storage of the andesite and dacite magmas beneath Mt. Katmai prior to the eruption of 1912 is consistent with the volume of collapse at Katmai, equivalent to the combined volume of andesite and dacite erupted. A ground-based magnetic survey of the area was conducted to characterize the intriguing connection between Mt. Katmai and Novarupta. The magnetic field strength and gradient survey results suggest a linear anomaly that is best modelled by the presence of a shallowly (200-300 m) emplaced dike on the order of 5-10 m wide, which resembles the known physical properties of the 7 m-wide rhyolitic dike discovered during the drilling of Inyo Domes.
    • Latitudinal gradients in leaf litter decomposition in streams: Effects of leaf chemistry and temperature

      Irons, John Gillam, Iii (1993)
      Autumnal leaf litter that falls into streams of forested regions forms a major source of energy for stream food webs. The processing of this litter has been studied for many years, and two generalizations have come from this research: (1) nitrogen concentration is positively correlated with breakdown rate, and (2) temperature is negatively correlated with breakdown rate. Along with investigators in Michigan and Costa Rica, I examined these generalizations by estimating breakdown rates of litter of ten tree species with widely varying nutritional quality along the latitudinal gradient of Costa Rica to Michigan to Alaska. At each site, litter processing experiments were done using leaves of the same ten tree species and the same methods in streams with similar character. We found that (1) condensed tannin, a plant defense against herbivory, was more highly correlated (negatively) with breakdown rates than was nitrogen (positively correlated with breakdown), and (2) breakdown rate showed a complex response to water temperature (i.e., latitude). I propose a model of leaf litter breakdown in which the microbial contribution to litter breakdown is negatively correlated with latitude (i.e., temperature) and the invertebrate contribution to litter breakdown is positively correlated with latitude. In addition, I suggest that secondary compounds of low solubility, especially condensed tannin, should be considered along with nitrogen when evaluating a tree species for leaf litter quality.
    • Latitudinal patterns of amino acid cycling and plant N uptake among North American forest ecosystems

      McFarland, Jack W.; Ruess, Roger; Boone, Richard; Chapin, Stuart F. III; Kielland, Knut; Hendrick, Ronald L. (2008-12)
      Interest in the role of organic nitrogen (N) to the N economy of forest ecosystems is gaining momentum as ecologists revise the traditional paradigm in N cycling to emphasize the importance of depolymerization of soil organic matter (SOM) in controlling the bioavailability of N in forest soils. Still, there has yet to be a coordinated effort aimed at developing general patterns for soil organic N cycling across ecosystems that vary in climate, SOM quality, plant taxa, or dominant mycorrhizal association: ectomycorrhizae (EM) vs. arbuscular mycorrhizae (AM). In this study, experimental additions of 13C15N-glycine and 15NH4+ were traced in situ through fine root and soil N pools for six North American forest ecosystems in an effort to define patterns of plant and microbial N utilization among divergent forest types. Recovery of 15N in extractable soil pools varied by N form, forest type, and sampling period. At all sites, immobilization by the soil microbial biomass represented the largest short-term (<24 h) biotic sink for NH4+ and amino acid-N, but differences in microbial turnover of the two N forms were linked to cross-ecosystem differences in SOM quality, particularly the availability of labile carbon (C). At the conclusion of the experiment, microbial N turnover had transferred the majority of immobilized 15N to non-extractable soil N pools. By comparison, fine root uptake of NH4+ and glycine-N was low (<10% total tracer recovery), but 15N enrichment of this pool was still increasing at the final sampling period. Since there was no significant loss of 15N tracer within the bulk soil after 14 days for any forest type except sugar maple, it suggests plants have the capacity to capitalize on multiple N turnover events and thus represent an important long-term sink for ecosystem N. Plants in all stands had some capacity to absorb glycine intact, but plant N preference again varied by forest type. Relative uptake of amino acid-N versus inorganic N was lowest in tulip poplar and highest in red pine and balsam poplar, while white oak, sugar maple, and white spruce stands were statistically near unity with respect to the two N forms. However, N uptake ratios were threefold higher in EM-dominated stands than in AM-dominated stands indicating mycorrhizal association in part mediated plant N preference. Thus, amino acids represent an important component of the N economies of a broad spectrum of forest ecosystems, but their relevance to plant nutrition likely varies as a function of microbial demand for C as well as N.
    • Launch environment data logger design and implementation for CubeSats

      Johnson, Morgan; Thorsen, Denise; Hawkins, Joe; Raskovic, Dejan (2016-12)
      Designing to the CubeSat standard has allowed many universities the ability to launch satellites missions to space. These small satellites are secondary, or even tertiary, payloads on launch vehicles. In fact, these ride-share payloads are frequently used as ballast for weight and balance of the launch vehicle and are often mounted near the engines. The environment experienced by these CubeSats is not well known. The Launch Environment Data Logger was designed to measure temperature and vibrations of the launch vehicle to better understand what kind of environment these small satellites must survive on their ride to space. Through this thesis the requirements of the Launch Environment Data Logger system are established and the initial design developed.
    • Layout and fabrication process from generic to high speed printed circuit boards (PCBS)

      Reddy, Indrani (2005-12)
      Printed circuit boards (PCBs) are exceeding the limits of the classic board design. The goal of this thesis is to inform the reader about the layout and fabrication of PCBs from generic to high speed designs. In chapter 2, Basic Design and Layout, I provide the generic PCB design that will give a basic understanding of board layout and fabrication using Cadence® software tools, which will simplify understanding of the high speed PCB design. Cadence® provides a path to designing PCBs, but to rapidly prototype the design we need to implement simulations. We accomplished the simulations using the Advanced Design System (ADS) tool which is used for designing high frequency PCBs. In this thesis the reader will see examples developed to illustrate high speed issues in digital designs using ADS and correlated simulated and measured values.
    • Leading and following at a 21st century university: identifying desired outcomes for a student leadership program

      Trabant, Tonya Denise (2004-05)
      Leadership has been discussed, debated, practiced, and researched for millennia. In the 20th century alone, no less than ten types of leadership were defined and empirically studied. In the higher education context, student leadership development is addressed from a wide variety of theoretical and programmatic approaches and co-curricular leadership programs have been one of the fastest growing areas in higher education in the past decade. The University of Alaska Fairbanks (UAF) Leadership Program was initially structured as adaptations of other models. Critical to the future success of the program is the reformation of elements to fit UAF's unique context and an adequate outcomes assessment plan to determine that elements are functioning as intended. In order to develop an understanding of leading and following at UAF, program stakeholders participated in focus group interviews, individual interviews, and a written assessment. Participant observation was also used to gather rich data about the institutional culture of leadership at UAF. Data was thematically analyzed as well as categorized using national standards. One final result is a model of desired student leadership competencies for the UAF Leadership Program.
    • Leadlight

      Dyer, Daniel; Burleson, Derick; Hirsch, Alexander; Coffman, Chris; Carr, Richard (2016-05)
      This collection of poems explores the spiritual experience of trauma and the diverse stimuli, such as violence, sexual abuse, loss, witness, and epiphany that may instigate fragmentation and repressions in the subconscious. The many allusions throughout the collection, from Homeric and Shakespearean characters to eastern religious figures, serve to imbue the work with a sense of variegation while also gentrifying and consecrating trauma. The poems take much inspiration from Jacques Lacan’s work on trauma, language, and the gaze, the writings of existentialists Sartre and Kierkegaard, and, of course, the poet’s own biography, and are arranged so as to suggest a coherent, albeit fragmented, narrative profluence. The collection as a whole attempts to emphasize the similarities between religious and traumatic experience and the ways in which language may or may not serve to reorient the traumatize mind.
    • Learning from the local scale: identifying and addressing local blind spots in Arctic environmental governance

      Curry, Tracie; Meek, Chanda; Trainor, Sarah; Berman, Matthew; Lopez, Ellen; Streever, Bill (2019-08)
      Environmental governance in the context of climate change adaptation brings together diverse actors and stakeholders to develop and enact policies across a broad range of scales. However, local needs and priorities are often mismatched with those pursued by entities at different levels of decision-making. This mismatch is perpetuated, in part, by the dominating influence of the Western worldview in knowledge processes involving the creation, sharing, and use of environmental knowledge. Persistent biases that favor Western science and technical information while marginalizing other important sources like local and Indigenous knowledge create blind spots that may adversely affect adaptation outcomes. In this research, a case study of the Native Village of Wainwright, Alaska is used to explore the topic of information blind spots in environmental governance resulting from 1) low resolution tools employed within broad scale adaptation initiatives; 2) preferences for easily quantifiable information; and 3) the challenge of communicating context-rich details to outside decision makers, given disciplinary biases and organizational conventions. This dissertation comprises manuscripts based on three studies undertaken to address the above blind spots in specific areas of adaptation planning. The first manuscript furthers conventional methods of adaptation classification through a place-based approach that uses directed content analysis to identify aspects of local adaptation not readily captured by low resolution frameworks. The second manuscript employs contextual analysis and extends Ostrom's Institutional Analysis and Development framework to characterize the role of local informal institutions in adaptation and provide insights into how difficult-to-quantify social and cultural norms might be leveraged in planned adaptation initiatives. The third manuscript reports on a formative endeavor that looked practically at conventions for communicating environmental change to public sector decision-makers, and tested a survey that explored the potential for context-rich visuals and other reporting strategies to effectively convey information about local observations and experiences of change.
    • Learning To Teach Where You Are: Preparation For Context-Responsive Teaching In Alaska's Teacher Certification Programs

      Vinlove, Amy Louise; Richey, Jean; Hornig, Joan; Hirshberg, Diane; Rickard, Anthony; Roehl, Roy (2012)
      Context-responsive teaching is defined in this project as teaching that responds to individual student needs and interests, linguistic backgrounds and family characteristics, the local community and the local natural environment. Context-responsive teaching, as defined in Chapter 1 of this dissertation, consolidates into one concept the pedagogical knowledge, skills and dispositions associated with culturally responsive teaching, place-based teaching, differentiated instruction, and purposeful collaboration with parents, families and communities. The research completed for this project examines current practices relative to preparing context-responsive teachers in Alaska's elementary and secondary teacher certification programs. A survey examining context-responsive teacher preparation experiences was developed and distributed to practicing teachers in Alaska who received their initial teaching certification from the University of Alaska Anchorage (UAA), the University of Alaska Fairbanks (UAF), or the University of Alaska Southeast (UAS), and who graduated in 2006, 2007 or 2008. The experiences of the graduates were juxtaposed with information on the three programs gathered through interviews with teacher educators currently working at UAA, UAF and UAS. Current practices at the three institutions are examined in relation to a literature-based framework of "best practices" in context-responsive teacher preparation. Following a presentation of the data gathered in this mixed-method investigation, nine research-based recommendations are offered for strengthening context-responsive teacher preparation in the state of Alaska.
    • Learning to work and think for life

      Sprankle, Elizabeth; Daku, Mike; Duke, J. Robert; Boldt, Frank (2019-08)
      This paper explores literature related to the use of restorative discipline and restorative practices in school communities. It draws heavily on the ideas presented in Ron and Roxanne Claassens’ book, Discipline that Restores, in order to illustrate why students, staff, administrators, families and the community connected to a traditional public high school, such as West Valley High School, in Fairbanks, Alaska, would benefit from shifting to a restorative approach to discipline. The paper also examines numerous sources to demonstrate why embedding lessons related to social justice and restorative practices into content areas is logical and beneficial and attainable and that both these embedded courses and this approach to discipline support and foster content related to a Career Technical Education pathway focused on Education, Public & Human Services.
    • Leaving Centralia and other stories

      Small, Sarah; Brightwell, Geri; Kamerling, Leonard; Harney, Eileen (2018-05)
      In the eight short stories within this collection, we encounter characters against a variety of backdrops, from the mundane--middle school shop class, and a short road trip--to the more bizarre--a town with an underground fire predicted to burn for two hundred years, and a forbidden island potter's field. Many of the protagonists are adolescents, positioned between their childhood, when they played a more passive role in their own lives, and adulthood, when they more deliberately make decisions about their own actions and lives. However, in all of these settings and regardless of age, the characters find that it is not under exceptional circumstances but through the course of the ordinary moments in their daily lives that they encounter testing points for their maturity and integrity.
    • Leaving King Island: The Closure Of A Bureau Of Indian Affairs School And Its Consequences

      Braem, Nicole M.; Schneider, William (2004)
      By 1966, the King Island Inupiat had moved from their island village and lived at Nome. Little has been written about the de facto relocation of the King Islanders---and how and why it happened. What follows is an ethnohistory of the relocation based on the anthropology and history of the Bering Strait region, archival records of the Bureau of Indian Affairs and interviews with King Islanders in Nome. The heart of the matter was the village's school. Based on the evidence, the BIA closed the school because of the expense and inconvenience of operating at King Island. This accomplished what the BIA had been unable for decades to do by persuasion---to move the village to the mainland. The immediate result of the closure, the resettlement of the villagers in Nome, fits within the established pattern of BIA policy over time, one that had assimilation as its ultimate goal.
    • The legacy of shamans? Structural and cognitive perspectives of prehistoric symbolism in the Bering Strait region

      Qu, Feng; 曲, 枫; Potter, Ben; Schweitzer, Peter; Plattet, Patrick; Koester, David (2013-08)
      This research explores the meanings of prehistoric artistic artifacts discovered in the Bering Strait region. The research focuses on the prehistoric period between AD 100 and 1700, including Okvik culture, Old Bering Sea culture, Punuk Culture, Birnirk Culture, Thule culture, and Ipiutak Culture. My archaeological data in this research were collected from the archaeological collections of the Okvik site on Punuk Islands, the Kukulik site on St. Lawrence Island, and the Nukleet site at Cape Denbigh at the University of Alaska Museum of the North. Based on abundant ethnographic records from the Bering Strait region, this research relies on ethnographic analysis as methodology to approach prehistoric symbolism. Applying ethnographic analysis results in diverse interpretations of the archaeological artifacts, which bear potential spiritual or secular meanings. Theoretically, the research provides an assessment of contemporary archaeological theories such as cognitive archaeology, structural archaeology, and shamanism theory (general shamanism theory and the neuropsychological model) in order to examine the reliability of these theories in the study of prehistoric art. Due to the problems of cognitive, structural, and shamanism theories, the conclusion of this research builds on practice theory and animist ontology to interpret the variants of art productivity, cosmological structures, and relationship between humans and materials.
    • Length-based models and population analyses for northern shrimp Pandalus borealis Krøyer

      Fu, Caihong (2000-08)
      The lack of basic knowledge on stock dynamics o f northern shrimp Pandalus borealis, a protandric hermaphrodite, has caused difficulty in regulating fishing effort on a scientific basis and in understanding potential causes behind population fluctuations and collapses. Previous length-based population models (LBMs), developed for other species, are undesirable primarily for two reasons: (1) individual cohort dynamics are masked; (2) variations in annual natural mortality (M) are ignored. This research was primarily aimed at developing a more advanced LBM that provides estimates of parameters such as recruitment (R), fishing mortality (F) and especially annual M. Simulation-estimation experiments were conducted to evaluate model performance. Despite model complexity, annual M can be well estimated provided measurement errors in survey biomass estimates are low. The common assumption of constant M created biased parameter estimates. Estimated M of P. borealis in Kachemak Bay, Alaska increased steadily in the 1980s. Retrospective projections showed that the increasing trend in M in the 1980s resulted in the population collapse. The ultimate goal o f stock assessment is to develop sound harvest strategies. With the widely observed abundance fluctuations in shrimp populations, it is impossible to manage solely based on conventional methods, such as maximum sustainable yield (MSY). Thus, harvest strategies were compared under various situations o f M and R. With M increasing over time, it is important to execute threshold management, i.e., closing the fishery at population levels below a threshold value. Simulations indicated that overfishing caused by underestimated M or overestimated R can be greatly alleviated if the population is sampled once every year. Life history aspects of sex change, growth, M, and their seasonal variations were also incorporated into the LBM. Populations with protandrous animals are likely to be subject to recruitment overfishing; merely protecting older females while allowing high exploitation on younger males can lead to population collapse. Fishing after spring egg hatching is superior to fishing after mating and egg extrusion in fall when F is high. In summary, the length-based model developed here provided a convenient framework for understanding population processes and harvest strategies and should be useful for a variety of hard-to-age species.