Now showing items 19992-20011 of 20306


      Zube, Ervin H.; DENNIS, STEPHEN RICHARD.; King, David A.; Shaw, William W.; Clarke, Jeanne Neanaber; Gregg, R. Frank (The University of Arizona., 1987)
      Social researchers have independently investigated behaviors in voluntary association membership and participation in outdoor recreation activities. A small amount of scholarly work has theorized a link between activity in voluntary associations and recreation behavior. These studies have concentrated on the associational affiliations of outdoor recreationists, and their concern for the environment. The purpose of this study was to determine if differences exist between outdoor recreationists who are members of environmental/outdoor recreation voluntary associations, and those who are nonmembers. Organizational membership was designated as the dependent variable. Independent variables were designed to assess (1) incentives for voluntary association membership, (2) motivations for participation in outdoor recreation activities, (3) environmental concern, and (4) social class. A random sample of outdoor recreationists was drawn from the California membership of a large recreational equipment cooperative (R.E.I. Co-op). Data were collected by mail survey. Of the 1500 questionnaires sent, thirty-four were undeliverable, and 1085 were returned for a response rate of 74.0 percent. The sample reflected a substantially higher organizational membership level than the general population with a forty percent membership rate. Members were differentiated from nonmembers by significantly higher ratings on (1) instrumental incentives (public goods) for membership in voluntary associations, (2) intellectual motivations for participation in outdoor recreation, (3) environmental concern, and (4) age and education level. A discriminant function analysis identified instrumental incentives as the most powerful predictor of organizational membership. Results indicated public goods are a primary incentive for outdoor recreationists to join voluntary associations. This suggests a need to re-define instrumental benefits in light of the personal values associated with them. A common thread of intellectual pursuit distinguished members from nonmembers. Intellectual motivations for outdoor recreation, education level, age and environmental concern provided evidence that members are somewhat more oriented toward intellectual development, suggesting that environmental and outdoor recreation-related voluntary associations might benefit from focusing on the educational benefits of membership, and directing promotional communications through channels used by outdoor recreationists. Given the findings of a strong relationship between outdoor recreation and voluntary association membership, further scholarly work should concentrate on the instrumental and intellectual benefits of both behaviors to promote understanding of their synergy.
    • Voluntary Regulation of the Environment: Understanding Institutional Factors that Shape Voluntary Environmental Programs

      Bakkensen, Laura; Li, Qianhui; Schlager, Edella; Baldwin, Elizabeth (The University of Arizona., 2021)
      This dissertation focuses on the role of institutions in shaping the establishment, dissemination, and efficacy of voluntary environmental governance regimes. In particular, the institutional lens was introduced to understand the motivations and the mechanisms that govern the behavior of individuals in the context of voluntary environmental programs (VEPs). By drawing upon research relating to policy design, regulatory innovation, and the policy feedback theory, I explore and analyze how regulatory, individual, and institutional based factors complementarily influence the adoption and efficacy of the VEPs. Given the growing need for reducing environmental impact, such insights can help policymakers better understand the appropriateness and efficacy of different policy instruments in managing the environment. To fulfill my research agenda, I conduct three empirical tests to not only show whether the voluntary instruments are effective in addressing environmental problems but also how and under what conditions such instruments can help and produce a broader effect on society as a whole. First, I provide a meta-analytical test of the effects of VEPs on improving environmental performance, finding that the institutional design elements of the programs can explain why VEP studies over the past twenty years have drawn different conclusions about VEP efficacy. I also examine one specific voluntary program: the green building standard, LEED. I look at different factors leading to LEED adoptions. A cross-country study of LEED adoptions explains why VEPs develop in some countries but not the others. Different from existing literature that focuses more on individual level corporate practices, I explore whether country-level factors such as income level and regulatory stringency can explain the dissemination dynamics of VEPs. To extend on this adoption dynamics, I also examine “public adopters”. I investigate the scenario when public regulation integrates a private regime, such as LEED, in laws and even make the voluntary commitments mandatory. I analyze how interest groups respond to such a policy change and how this will impact the future trajectories of sustainability transitions. The overall findings of this dissertation indicate a prominent role of institutional design in developing VEPs, provide implications for policy practitioners that VEPs might be helpful in addressing green investment deficits, and add to the growing understanding of local governments as innovators in aspects of environmental governance.

      Roinestad, Frank Andrew, 1940- (The University of Arizona., 1973)
    • Vortex filaments in three dimensional excitable media.

      Henze, Christopher Ernest.; Walsh, J. Bruce; Schaffer, Bill; Strauss, Richard (The University of Arizona., 1993)
      An "excitable medium", such as nerve fiber or heart tissue, can be locally provoked by a relatively small stimulus to execute a relatively large transient response, followed by recovery to the original rest state. In one-, two-, or three-dimensional excitable media, such episodes of excitation can propagate as nondecrementing pulses, until they are extinguished at the domain boundaries. In two- or three-dimensional excitable media, these travelling wavefronts of excitation can become arranged in self-perpetuating spirals (in 2D) or "scrolls" (in 3D), which rotate indefinitely, organizing the entire medium with periodic wavetrains. In three dimensions, the pivot of the scroll, around which the sheetlike wavefront unfurls, is a one-dimensional space curve, a "vortex filament", which may end only on domain boundaries, or close into rings, and which may be knotted or linked. Vortex filaments and their associated scroll waves are of interest as periodic solutions to the underlying reaction-diffusion equations, and they may also play a role in understanding the behavior of certain natural systems, perhaps most prominently the disintegration of normal coordinated activity in large mammalian hearts known as ventricular fibrillation. Analytic or experimental approaches to investigating vortex filaments have met with limited success, and in any case stand in need of testing. This thesis presents the results of four largescale numerical investigations of vortex filaments, using supercomputers. Starting with various carefully contrived initial conditions, three-dimensional volumes of excitable media are simulated by numerical integration of partial differential equation models. During the run, the form and behavior of the simulated vortex filaments are monitored by means of a "differential geometry toolkit". Emphasis is given to two fronts. First, I tried to establish the existence and properties of stable filament configurations. This resulted in the discovery of half a dozen stable organizing centers, more than doubling the number of previously known periodic solutions. Second, I attempted to discern the factors and rules which govern filament dynamics. This effort is largely guided by and aims to test the so-called "local geometry hypothesis", which supposes that local filament dynamics are determined by local filament geometry.
    • Vortex Formation by Merging and Interference of Multiple Trapped Bose-Einstein Condensates

      Anderson, Brian P.; Scherer, David Rene; Anderson, Brian P.; Cronin, Alexander; Jessen, Poul S. (The University of Arizona., 2007)
      An apparatus for producing atomic-gas Bose-Einstein condensates (BECs) of 87-Rb atoms is described. The apparatus produces 87-Rb BECs in a dual-chamber vacuumsystem that incorporates magnetic transport of trapped atoms from the magneto-optical trapping cell to the BEC production cell via the operation of a series of overlapping magnet coils. The design, construction, and operation of the apparatus are described in detail.The apparatus is used to study the creation of quantized vortices in BECs by the merging and interference of multiple trapped condensates. In this experiment, a single harmonic potential well is partitioned into three sections by an optical barrier,enabling the simultaneous formation of three independent, uncorrelated BECs. The BECs may either merge together during their growth, or, for high-energy barriers, the BECs can be merged together by barrier removal after their formation. Either process may instigate vortex formation in the resulting BEC, depending on the initially indeterminate relative phases of the condensates and the merging rate.
    • Vortex Retarders

      Chipman, Russell A.; McEldowney, Scott; Chipman, Russell A.; Mansuripur, Masud; Dereniak, Eustace (The University of Arizona., 2008)
      This dissertation addresses the creation of polarization vortex beams. Vortex retarders are components with uniform retardance but a fast axis which rotates around its center with can create polarization vortices. The goal was to develop a simple method for producing vortex retarders for visible wavelengths, with a continuous fast axis, and for multiple vortex modes.The approach was to use photo-aligned liquid crystal polymers (LCP). The target was a halfwave retardance for wavelengths in the range of 540~550nm. A photo-alignment layer was spin-coated onto a substrate, baked, and alignment was set through exposure to linear polarized UV (LPUV) light. The alignment layer was exposed through a narrow wedge shaped aperture located between the substrate and polarizer. Both the polarizer and substrate were continuously rotated during exposure process in order to create a continuous variation in photo-alignment orientation with respect to azimuthal locations on the substrate. The mode of the vortex retarder was determined by the relative rotation speeds. The LCP precursor was spin-coated and subsequently polymerized using a UV curing processes. Elements produced were analyzed by measuring the space variant Mueller Matrix of each component. Our measurements demonstrated that the vortex retarders were half wave plates with a continuous fast axis orientation. Measurement of the center region of the vortex retarders identifies a 100-200um region of disorientation. At 0.5mm resolution, a high depolarization index in the center of the vortex retarders was observed. The DOP was low in the center for a horizontal linear polarized input field but remained high for circular polarized input.The viability of these components was assessed by determining the point spread matrix (PSM) and the optical transfer matrix (OTM) and comparing these to theoretical calculations. The agreement between the measured and predicted PSM was excellent. The major difference was the non-zero response in the m03 and m30 elements indicating circular diattenuation. The OTM comparison between measured and predicted demonstrated an excellent quantitative match at lower spatial frequencies and a good qualitative match at higher spatial frequencies. Measured results confirm that vortex retarders produced using photo-aligned LCP produce near theoretical performance in an optical system.

      Paolino, Michael Anthony, 1939- (The University of Arizona., 1972)

      Santi, Lawrence Lee (The University of Arizona., 1981)
      This dissertation is concerned with recent changes in levels of voter turnout for presidential elections. Turnout decreased at each election from 1960 to 1976 despite a variety of changes taking place in American society which might have been expected to lead to increased turnout. The present research attempts to shed light on this paradox by means of a longitudinal analysis of a variety of surveys of the American electorate. Data collected by the Bureau of the Census were used in an investigation of changes in turnout across various demographically defined subgroups between 1964 and 1976. The Census surveys provide information about approximately 100,000 persons. Data collected by the University of Michigan's Survey Research Center (SRC) were used in an analysis of the attitudinal correlates of the turnout decline. The SRC samples ranged in size from 1500 to 2000 respondents. A comparison of the Census and SRC surveys revealed that although turnout levels were generally higher in the SRC series than in the Census series, the two series provided similar estimates of the relationships of turnout to such demographic characteristics as region, color, and sex. The traditional sex differential in turnout was found to have narrowed steadily from 1964 to 1976 so that by 1976, female turnout equalled that of males among non-Southern whites and Southern blacks and exceeded that of males among non-Southern blacks. Reversals of the traditional sex differential were particularly pronounced within younger, more educated segments of the population. Further analysis revealed that the sex differential in turnout was related to sex differences in patterns of labor force participation. Differential change by color and region between 1964 and 1968 was also observed; the turnout of non-Southern blacks decreased sharply over this four year period while that of Southern blacks increased markedly. No further change in the color differential was observed in either region from 1968 to 1976, although this finding was later discovered to be the result of increases in the color differential among younger, more educated persons and counterbalancing decreases in this differential among older, less educated persons. Also observed over this 12 year period was a decrease in the traditional regional turnout differential. From 1964 to 1968 and again from 1972 to 1976, Southern and non-Southern turnout rates converged. Approximately 27% of the turnout decline observed between 1968 and 1972 could be attributed to the lowering of the voting age. Among whites, the greatest decreases in turnout over the entire 12 year interval were observed among persons between the ages of 45 and 54. Among blacks, the greatest decreases were observed among the 25 to 34 year old age group while actual increases were observed at the oldest end of the age continuum. Patterns of change by education paralleled to a certain extent the age-related patterns, with the greatest turnout decreases from 1964 to 1976 being observed among whites with between 9 and 11 years of education and among black high school graduates. The attitudinal correlates of turnout examined in this research included measures of party identification, political interest, political efficacy, and political trust. It was found that the aggregate turnout decline from 1964 to 1972 could be statistically "explained" by decreasing party identification and increasing political cynicism. Further analysis revealed that increased cynicism accounted for the sharp decrease in turnout observed among non-Southern blacks between 1964 and 1968 and suppressed the increase in turnout observed among Southern blacks over this same period. The other attitudinal items, although cross-sectionally related to turnout in theoretically predicted ways, failed to explain away the turnout decline.
    • Voyager and Galileo SSI views of volcanic resurfacing on Io and the search for geologic activity on Europa

      McEwen, Alfred S.; Phillips, Cynthia Baya (The University of Arizona., 2000)
      Observational evidence and theoretical arguments suggest that Jupiter's satellite Europa could be geologically active and possess an "ocean" of liquid water beneath its surface at the present time. We have searched for evidence of current geologic activity on Europa in the form of active plumes venting material above the surface and by comparison of Voyager and Galileo images to look for any changes on the surface. So far, we have observed no plumes and have detected no definitive changes. The lack of observed activity allows us to estimate a maximum steady state surface alteration rate of 1 km² y⁻¹ in the regions analyzed, assuming alterations will cover contiguous areas of at least 4 km² over a period of 20 years. Assuming this as a constant, globally uniform resurfacing rate leads to a minimum average surface age of 30 million years. Lava flows and plumes are the two main types of volcanic activity that resurface Io. We have used the Galileo Io dataset to observe the detailed sequences of interconnected plume activity, hotspot activity, and new surface deposits at a number of volcanic centers on Io. Red material has faded on a timescale of less than a year, and a green coating has formed on a caldera over a time period of about 3 months. Change detection maps can illustrate the percentage of the surface newly covered by plume deposits and lava flows, and constrain volume and mass resurfacing rates. Areal resurfacing is dominated by plume deposits, but volume resurfacing is dominated by lava flows. Estimates of resurfacing from these change maps range from 0.4 to 12.9 cm/year, assuming a flow thickness of 1 to 10 meters. The minimum resurfacing rate required for the lack of impact craters on Io's surface is about 0.02 cm/year. If high-magnesium (komatiitic) lavas dominate the observed Io heat flux, the maximum resurfacing rate is about 0.69 cm/year. Basaltic lavas could produce a rate of 1.3 cm/year. The komatiitic rate produces an average flow thickness of about half a meter. Thus, we suggest that the average resurfacing rate of lo is between 0.1 and 1 cm/year.
    • Voyages of the Vikings: Human haploid variation in northern Europe

      Hammer, Michael F.; Tillquist, Christopher (The University of Arizona., 2002)
      Europe is a region characterized by a long history of both settlement and resettlement. This study uses information from the haploid systems of the human genome in order to investigate the presence of population structure in Europe and discuss the mitigating effects of shared population history and the impact of evolutionary forces. By means of two kinds of data from the Y chromosome, the study first establishes patterns of diversity across the entirety of Europe. More in-depth analyses investigate the evolutionary effects of settlement and colonization on overall genetic diversity of populations. Finally, considering data from the entire control region sequence, an effort is made to estimate patterns of mitochondrial diversity and compare their import to that of the Y chromosome.
    • Vulgar Grandeur: Literature and the American Monument during the Long Nineteenth Century

      Raval, Suresh; Winet, Ryan; Raval, Suresh; Nathanson, Tenney; Melillo, John (The University of Arizona., 2017)
      My dissertation focuses on nineteenth-century American literature texts that engage with ruins and monuments. Traditionally, this interaction has been treated as a formal curiosity for literary critics, but this project argues interarts literature carries important implications for public sphere theory, especially in cases when an author writes about nationalist architecture and iconography.

      Ram, Sudha; Liu, Jun; Goes, Paulo; Durcikova, Alexandra (The University of Arizona., 2011)
      Data provenance refers to the lineage or pedigree of data, including information such as its origin and key events that affect it over the course of its lifecycle. In recent years, provenance has become increasingly important as more and more people are using data that they themselves did not generate. Tracking data provenance helps ensure that data provided by many different providers and sources can be trusted and used appropriately. Data provenance also has several other critical uses, including data quality assessment, generating data replication recipes, data security management, etc.One of the major objectives of our research is to investigate the semantics or meaning of data provenance. We describe a generic ontology of data provenance called the W7 model that represents the semantics of data provenance. Formalized in the conceptual graph formalism, the W7 model represents provenance as a combination of seven interconnected elements including "what," "when," "where," "how," "who," "which" and "why." The W7 model is designed to be general and comprehensive enough to cover a broad range of provenance-related vocabularies. However, the W7 model alone, no matter how comprehensive it is, is insufficient for capturing all domain-specific provenance requirements. We hence present a novel approach to developing domain ontologies of provenance. This approach relies on various conceptual graph mechanisms, including schema definitions and canonical formation rules, and enables us to easily adapt and extend the W7 model to develop domain ontologies of provenance. The W7 model for data provenance has been widely adopted and adapted for use within Raytheon Missile Systems and the iPlant Collaborative, as well as the US Army's ATRAP IV (Asymmetric Threat Response and Analysis Program) system.We also developed a domain ontology of provenance for Wikipedia based on the W7 model. This domain ontology enables us to extract provenance for each Wikipedia article. We present a study in which we use their provenance to assess the quality of Wikipedia articles. Assessing and guaranteeing data quality has become a critical concern that, to a large extent, determines the future success and survival of Wikipedia since the quality of Wikipedia has been continuously called into question due to various incidents of vandalism and misinformation since its launch in 2001. Our study shows that the quality of Wikipedia articles depends not only on the different types of contributors but also on how they collaborate. We identify a number of contributor roles based on the provenance. Based on the roles and provenance, our research identifies several collaboration patterns that are preferable or detrimental for data quality, thus providing insights for designing tools and mechanisms to improve Wikipedia article quality.
    • Waimiri Atroari grammar: Some phonological, morphological, and syntactic aspects

      Hill, Jane; Langendoen, Terry; Bruno, Ana Carla (The University of Arizona., 2003)
      The Waimiri Atroari people, who call themselves kinja 'people' and whose language belongs to the Carib family, live today in an area in the northern part of the State of Amazonas and in the southern part of the State of Roraima. Like many other languages of the Carib family, Waimiri Atroari is a chronically underdescribed language. There are few linguistics studies about Waimiri Atroari, most of them being phonological sketches (Hill and Hill 1985; and Lacerda 1991, 1996). Taking this situation into consideration, this dissertation intends to describe some phonological, morphological, and syntactic aspects of the Waimiri Atroari grammar. First, in the introductory chapter I provide some information about their language and culture, and I discuss their experience with formal education. Second, I describe the segmental phonology and analyze the syllable structure and reduplication process under Optimality Theory. Next, I present the word classes and a description of their morphology. Then, I investigate the system of case marking. Finally, in syntax I analyze the phrase structure and the word order under the framework of X-bar theory. The appendices contain a set of verbal paradigms and a collection of texts.

      Lotz, Sherry; Yan, Ruoh-Nan; Lotz, Sherry; Shim, Soyeon; Janakiraman, Narayan (The University of Arizona., 2005)
      Management of consumer waiting experiences is critical for practitioners in that unpleasant waiting experiences may result in negative service evaluations. This study focused on consumers' queue waits during the pre-process phase of waiting experiences, i.e., before services are received, and investigated the extent to which relevant variables during this process may impact consumers' subsequent service experience evaluations. The investigation purported to expand and refine the expectation-affect-service evaluation relationship. Specifically, the framework examined the influence of predicted value of service on wait expectations (conceptualized as "consumer zone of wait tolerance" derived from the service literatures), the effects of consumers' comparisons between wait expectations and perceptions (i.e., wait disconfirmation) and perceived wait duration on affective responses to waiting, and the impact of affective responses to waiting on service experience evaluations. In addition, this study predicted the moderating role of actions of the service provider from a social justice perspective in the relationship between affective response to waiting and service experience evaluation.Data were collected at two points in time (i.e., during waiting and at completion of service) via surveys completed by 393 adult consumers intercepted at three restaurants located in a southwestern city in the U.S. Hypotheses were tested through structural equation modeling, MANCOVA statistical techniques, and additional post hoc analyses. Findings suggest that both wait disconfirmation and perceived wait duration influence service experience evaluation through affective response to waiting. Results also revealed a positive relationship between predicted conditional value and zone of wait tolerance. The study provides support for social exchange theory and better understanding of the role of actions of the service provider in the relationship between affective response to waiting and service experience evaluation. Lastly, post hoc analyses lend credence to the concept that consumers' affective responses to waiting and service experience evaluations vary across the wait disconfirmation groups. Both theoretical and managerial implications are discussed and directions for future research are also provided.
    • Walking the Margin: Gender and Urban Spatial Production in La Paz, Mexico

      Babcock, Barbara A; Tang, Donna Taxco; Babcock, Barbara A; Doxtater, Dennis; Marston, Sallie A.; Alvarez, Maribel (The University of Arizona., 2005)
      This comparison of two urban public spaces in the city of La Paz, Baja California Sur, examines the production of gendered space within an ethnohistorical context of material and discursive practices related to socio-spatial order, cultural and biological reproduction, and the construction of urban scale. The focus of the study of these two “commons” is on the liminal spatiality of the central plaza and the seaside promenade, the role of everyday life and consumption in the production of these spaces, and the role of women in these successive spatial transformations. In order to understand the relations and practices that produce these commons, the various spatial transformations that have affected the southern Baja California Peninsula are described and discussed. It is a place that has been constituted and reconstituted within successive globalizing forces since at least the beginning of the sixteenth century, up to and including contemporary international tourism. The city of La Paz, its people, and its sense of itself as expressed in its public spaces have emerged from these historical and cross-cultural processes. By examining and comparing the Parque Velasco and the Malecón as the products of both past and emerging patterns of spatial discourse in the negotiation, rehearsal and affirmation of gender identities, the following specific questions are addressed: What is the role women play in the cultural production and reproduction of these public spaces in a borderland? How do the spaces differ--materially, discursively, and in usage? What or whose purposes do they serve? How do they position peripheral agents within a hegemonic globalizing process? Finally, the study considers the question of what future can be envisioned for La Paz and its commons as border spaces.
    • Walking Two Worlds: Integrating Lumbee Indian Values and Practices in Education

      Arenas, Alberto; Lucas, Sandy; Arenas, Alberto; Taylor, John; Fox, Mary Jo (The University of Arizona., 2006)
      This study investigates how Lumbee values and practices are integrated in a formal schooling system. A qualitative study was conducted to determine how Lumbee school administrators experience their work, and how Lumbee values and practices are integrated in formal education, and what they thought these values and practices were. The main instruments used to collect data were in-depth interviews and a survey designed by the researcher. The data was collected in Pembroke, North Carolina at the School District's Indian Education Office during 2004 and 2005.The four participants in the study are all Lumbee education administrators, employed with a school district in southeastern North Carolina. Ironically, all four administrators received their undergraduate degrees from the tribe's university, the University of North Carolina at Pembroke, UNCP. The research study focused on the Lumbee tribe, the largest tribe east of the Mississippi river, which has organized the largest Indian education program of any public school district in the United States, with approximately 11,500 Indian students.This is the researcher's personal synthesis of stories and "shared metaphors" that Lumbee Indians hold in common with regard to Tribal education and Indigenous education. This research examines the creative possibilities inherent in the introduction of an Indigenous frame of reference toward the development of a contemporary philosophy of American Indian education. Also, this study explores a "culturally-informed alternative" in education that advocates the development of a contemporary community-based education process, which is founded upon traditional Tribal values, orientations, and principles, but simultaneously utilizes the most appropriate concepts and technologies of modern education. This study offers a creative option for thinking about the evolving expressions of American Indian values and the education of Native American students as they attempt to walk in two worlds, their own and the Non Native.

      Coxon, Moran, 1930- (The University of Arizona., 1971)
    • Wallace Stegner's "Angle of Repose": One reader's response.

      Dryden, Edgar; Hepworth, James Ralph.; Evers, Lawrence; Momaday N. Scott (The University of Arizona., 1989)
      This dissertation reads Wallace Stegner's Angle of Repose by combining objective and subjective critical approaches in an attempt to bridge the gap between storytelling understood formalistically and story in its moving immediacy. The study combines a close textual analysis of the novel with a detailed and extensive account of the critic's personal and emotional responses to it, and these two interpretive perspectives are supplemented by a series of three interviews conducted with the novelist over a period of ten years as well as by an exchange of letters between Stegner and Bernard DeVoto just prior to the publication of Stegner's Beyond the Hundredth Meridian (1951-1953). The study opens with a survey of Stegner's career and argues that his critics have misperceived him as a "regionalist" and undervalued him as a world-class American writer whose work transcends the limitations of place. The ensuing chapters focus on the relationship between the journal form of Angle of Repose and the westering tradition in American letters and on the way the novel situates itself in relation to native American aesthetics and the oral tradition. The burden of these early chapters is to demonstrate that the form of Stegner's novel is symbolic, not only in the formal sense of standing for something other than itself but also in the more subjective sense of figuring the emotional rhythms that it generates in the reader. Later chapters examine in detail the relations between the personal and emotional life of the critic and such technical and thematic issues as unreliable narrator, the Doppelganger motif, and the problems of origins and originality in American fiction. Taken together, the individual chapters are designed to show that Stegner is a postmodern storyteller with postmodern concerns, that he has, in fact, created Angle of Repose as a "counter-subversive novel" by employing the techniques of the so-called "chaos drunk writers" of the 1970's against themselves to produce a work of art that is at once highly original and self-consciously traditional.
    • Wandering Behavior in Manduca Sexta: Investigating Steroid Hormone Effects on Neural Circuits For Locomotor Behavior

      Levine, Richard B.; Miller, Julie Elizabeth; Levine, Richard B.; Tolbert, Leslie P.; Rance, Naomi E.; Yool, Andrea J.; Gruener, Raphael P.; Fregosi, Ralph F. (The University of Arizona., 2005)
      Steroid hormones alter the excitability of neural circuits for motor behavior in vertebrates and invertebrates. The insect Manduca sexta, with its well-characterized developmental and endocrinological history, is a useful model system to study these effects. The wandering behavior is a stage-specific locomotor behavior triggered by the steroid hormone 20-hydroxyecdysone (20E) and consists of crawling and burrowing movements as the animal searches for a pupation site.The results of this dissertation show that 20E acts on the isolated larval nervous system to induce wandering activity. The mechanisms underlying the generation of this activity share features similar to other invertebrate systems, including the presence of segmental central pattern generating circuits. The time course for the nervous system response to 20E is long, suggestive of a genomic mechanism of action, and there are no earlier rapid effects of 20E on the intrinsic membrane properties of the abdominal motoneurons. The site of 20E action in inducing wandering locomotion is unlikely to be the abdominal motoneurons, but interneurons presynaptic to these motoneurons. One possible site of 20E action is the brain, which shows stage-dependent expression of ecdysteroid receptors in certain populations of neurons.Descending regulation by the brain and subesophageal ganglion (SEG) is exerted over the segmental motor circuits for crawling and burrowing and reflects stage-dependent differences. Prior to wandering, the brain exerts inhibition over the segmental motor circuits for crawling, but this inhibition is not present during wandering. Removal of the brain, SEG, and thoracic ganglia during on-going fictive locomotion alters the phase relationships between abdominal segments. Further alterations of fictive crawling motor output are observed in more reduced preparations, indicating the importance of intact connections between abdominal ganglia in the production of a reliable motor program. The SEG drives the fictive burrowing motor program. The burrowing motor program is more robustly expressed in nerve cords from wandering larvae, suggesting a stage-dependent difference due to 20E exposure. Subsequent future experiments will use electrophysiological methods and genetic manipulations in Manduca sexta and Drosophila melanogaster, respectively, to explore target sites for hormone action in the brain and the characterization of brain neurons that drive wandering behavior.