Molecular orientation and dynamics of flexible polymers in strongly deforming flow fields

A method of spatially resolved magnetic resonance spectroscopy has been developed to allow studies of order and dynamics in complex fluids having transverse relaxation times on the order of tens of milliseconds, studies which were otherwise not possible using existing techniques. The model of Doi and Edwards is a microscopic description for stress transmission in concentrated polymer solutions and melts under deformation. Central to the Doi-Edwards model is the dependence of the stress on bond orientational order of the chain segments. Different elements of the segmental alignment tensor for a polymer melt under strong shearing flow are measured here using localized deuterium NMR spectroscopy on a 61 OK molecular weight poly (dimethyl siloxane) melt in a concentric cylinder Couette rheometric cell. This approach provides a new means of testing the Doi-Edwards model and its refinements, in the important regime far from equilibrium where the entangled polymers exhibit nonlinear viscoelastic behaviour. -- The same rheo-NMR methodology is also used to test predictions of the model of Leslie and Ericksen which describes director dynamics in semi-flexible rod-like polymers subjected to viscous stresses. Director dynamics are studied in a lyotropic liquid crystal polymer PBLG (300K) in a highly ordered, nematic phase in a planar extensional flow around a stagnation point. In addition, bulk 2H NMR studies are carried out on PBLG under shear, in concentric cylinder Couette and cone and plate rheometric cells. Magnetic alignment (equivalent to the dynamic Freedericksz transition) is investigated in all three cells following deformation. Values are obtained for the Leslie viscosity coefficients a2 and a3, scaled by the diamagnetic susceptibility. Possible development of mesoscale structure under shear is discussed

Understanding, Quantifying, and Reducing Bias in Fisheries-independent Visual Surveys

Understanding spatiotemporal changes in populations is vital for conservation managers to assess current recovery efforts, determine future conservation priorities, and forms the basis to explore complex ecological questions. In fisheries, these data have traditionally been collected using fisheries-independent surveys that rely on extractive sampling practices (e.g., longlines, gillnets, trawls). However, with the growing availability of low-cost, high-definition cameras, researchers are increasingly using visual surveys as a non-invasive alternative. Camera surveys have a number of advantages including their archivable data, and offer insights into species habitat use and behavior. However, the use of cameras has a number of inherent biases. Understanding, quantifying, and mitigating against these biases is critical if camera systems are to be used to inform management and policy. In this dissertation, potential biases were explored for two commonly used visual survey methods; baited remote underwater videos (BRUV), and unmanned aerial vehicles (UAV). Specifically, our objectives were to answer: (1) Are metrics of relative abundance derived from BRUVs linearly related to true changes in abundance for elasmobranchs, (2) Are these same metrics sensitive to changes in density-independent factors, and (3) Can UAVs be used to replace or supplement traditional diver transects for marine invertebrate species? Using a combination of standard and full-spherical camera BRUV deployments, Chapter One found that tradition BRUVs likely undercount sharks in high density environments, while also having lower probability of detection than full-spherical cameras. Using a spatially-explicit, individual-based-model, Chapter Two revealed that metrics of relative abundance derived BRUVs are also highly sensitive to factors unrelated to changes in abundance (e.g., swimming speed, current strength, and movement patterns). Lastly, using paired snorkeler-UAV transect sampling Chapter Three found counts derived from UAV transects did not significantly differ from divers, and offered a number of advantages over this traditional technique (increased percision, larger surveyed area, and automation). Furthermore, we found that UAVs could be used to improve sampling design used to quantify invertebrates, by estimating their distribution within a study region prior to initiating transect sampling. Collectively, these works improve our understanding and interpretation of video survey results that are used for management across the globe

Modulation of cardiac Kv currents by Kvbeta2 and pyridine nucleotides.

Myocardial voltage-gated potassium (Kv) channels regulate the resting membrane potential and the repolarization phase of the action potential. Members of the Kv1 and Kv4 family associate with ancillary subunits, such as the Kvβ proteins, that modify channel kinetics, gating and trafficking. Previous investigation into the function of cardiac β subunits demonstrated that Kvβ1 regulates Ito and IK,slow currents in the heart, but the role of Kvβ2 in the myocardium remains unknown. In heterologous expression systems, Kvβ2 increases surface expression of Kv1 channels, shifts the activation potential of Kv1 channels to more polarized voltages, and increases the inactivation of Kv1 channels. Accordingly, the electrophysiological phenotype in Kvβ2-/- mice was examined to uncover its role. To investigate the effects of the loss of Kvβ2 on cardiac repolarization, we performed whole-cell electrophysiology on primary cardiac myocytes. We found Kv current density was reduced and action potential duration prolonged in myocytes lacking Kvβ2. To isolate the molecular interactions by which Kvβ2 was affecting Kv currents, we show that Kvβ2 co-immunoprecipitates with Kv1.4 and Kv1.5 in heart lysates. To measure if surface expression of these Kv channels was reduced with the loss of Kvβ2, we performed immunofluorescent confocal microscopy of isolated cardiac myocytes. We found that the surface expression of Kv1.5 was reduced in Kvβ2-/- myocytes. We also performed a membrane fractionation technique to demonstrate that the proportion of total cellular Kv1.5 at the membrane was reduced in Kvβ2-/-. Together, these findings support our hypothesis that Kvβ2 plays a role in the generation of functional Kv currents in the myocardium by interacting with members of the Kv family. The pyridine nucleotides, NAD[P](H), are ubiquitous cofactors utilized as electron donors and acceptors by over 250 cellular oxidoreductases. Work out of our laboratory has shown that the Kvβ proteins are functional enzymes of the aldo-keto reductase family, that utilize NAD[P]H to catalyze the reduction of substrates. Furthermore, follow up work has shown that the redox status of bound pyridine nucleotide (PN) modifies the gating of Kvα-Kvβ channel complexes in heterologous expression systems. To examine a physiological role for PN in cardiac repolarization, whole-cell and single channel cardiac myocyte currents were recorded under the exposure to various PN redox states. We found that the inactivation rates and open probabilities of Kv currents in isolated myocytes are sensitive to the redox status of PN, and that surface action potentials in an isolated heart model are prolonged by treatment with factors that increase intracellular NADH concentration

The language politics of doctoral studies in rhetoric and composition : toward a translingual revision of graduate education in the field.

This dissertation critiques graduate education in rhetoric and composition in relationship to recent calls for a “translingual” approach to the teaching of writing and a transnational, cross-cultural approach to writing research (Horner, Lu, Royster, Trimbur; Canagarajah; Donahue). Building on this scholarship, I attend to the (re)production of disciplinary dispositions toward language difference in rhetoric and composition doctoral studies. Through textual analysis of the Rhetoric Review surveys of doctoral programs in the field (1987, 1995, 2000, 2007, and the current wiki), archival materials from various programs (including three focal schools), and a survey of doctoral students currently enrolled in the University of Louisville’s Rhetoric and Composition Ph.D. program, I investigate tensions between official discourses of rhetoric and composition doctoral studies and the lived experiences of graduate teaching and learning in the field. Within these tensions, I identify dominant and emergent language ideologies in rhetoric and composition and describe the ways in which these are exercised and transmitted through its doctoral training. Though, I argue, rhetoric and composition doctoral curricula have evolved to reflect a dominant monolinguist ideology in U.S. higher education and society at large, this ideology has been relocalized and resisted in the practices of students and teachers negotiating the material conditions of composition teaching and learning in the late 20th and early 21st centuries. At the level of local practice, rhetoric and composition graduate education suggests the emergence of a translingual ideology in the discipline that recognizes and responds to more complex social identities and cross-language practices in a globalizing world. In Chapter One, I discuss the globalization of higher education, the changing institutional conditions it brings about, and recent arguments for translingual and crosscultural approaches to composition teaching and research meant to address these conditions. I then provide a description of my methodology in examining Ph.D. programs in rhetoric and composition to identify their language politics and, ultimately, suggest possibilities for change. In Chapters Two and Three, I analyze curricular policies surrounding the practices of rhetoric and composition doctoral studies to argue that graduate education in the field has been structured, currently and historically, in relationship to an ideal of English monolingualism. In Chapter Four, I explore the dissonance between policy and procedure—curriculum and education—to reveal the translingual work already taking place in rhetoric and composition doctoral studies in the context of teaching and learning. In Chapter Five, I discuss language education policy initiatives in Europe. I use lessons learned from these initiatives to frame suggestions for how composition studies can serve as a vehicle for institutional change when it comes to matters of language and language relations in U.S. universities. I argue that change can best be achieved not through top-down policy initiatives, but through making local changes to specific rhetoric and composition graduate program practices

CALF HEMODYNAMICS DURING VENOUS OCCLUSION AND HEAD-UP TILT

The potential role of lower limb blood pooling in reducing venous return to the heart during orthostasis and elevated venous pressure is investigated. This study compares lower limb capacitance, microvascular filtration, and peripheral resistance between a group of highly trained endurance athletes and a group of their sedentary peers. Seven endurance trained males were selected between the ages of 23-33 [(29.1 4.1 yr), mean SD]. The subjects weekly cycling mileage ranged from 80 to 150 miles per week with an average of 125 8.5 miles/week. Nine healthy, age-matched sedentary subjects (25.8 4.8 yr.) were selected for the control group, based upon their reporting they had not participated in repeated lower-body or cardiovascular exercise in the months prior to their study. Results show that both subject groups had similar calf venous capacitances, rates of capillary fluid filtration, and local flow shunting (vascular resistance change) in response to venous thigh occlusion and 70 head-up tilt (HUT). The only significant difference found between groups was the cyclist groups smaller rise in heart rate in response to HUT. The findings of this study suggest that cyclists are not predisposed to orthostatic intolerance due to any changes in lower limb function

Mindfulness: An Educational Module to Address Stigmatic and Negative Thoughts Through Mindfulness

Mental health stigma complicates the ability of psychiatric mental health (PMH) nurses to establish an emotional balance stemming from generalized negative perspectives. This educational module aimed to increase PMH nurses’ knowledge of stigmatic negative thoughts contributing to psychological distress in an inpatient setting. PMH nurses’ inability to cope results in absenteeism, high staff turnover, psychotropic medications, and sleep aids. The conceptual framework, ADDIE (Analysis, Design, Development, Implementation, and Evaluation) model, and cognitive theory (CT) change automatic negative thoughts with positive ones. A pre-and post-test was conducted with a 10-question, 5-point Likert scale test on mindfulness meditation for mental health nursing. A paired t-test was used to compare the pre-and-post responses during data analysis. The t-test revealed that the pre-test mean (M= 23.75) was significantly different from the post-test (M=12.94), t (4.934) = 10.813, and p \u3c .001 scores that answered the guiding question that mindfulness meditation decreases automatic negative thoughts. Data analysis was conducted using a Likert scale that measured the knowledge of PMH nurses related to mental health and stigma. The findings and implications revealed that PMH nurses lacked knowledge of mental health stigma and mindfulness. The recommendations would be to offer mindfulness training annually, clinical ladder specific to mental health, and recruit and retain a master’s level nurse educator. The positive social change could enhance job satisfaction and retention, improve nurses’ mental well-being, and create an environment of empowerment