Matching Items (21)
Description
In my dissertation, I develop a theoretical model that explains how leaders' daily work demands and recovery affect their leadership behaviors. In a departure from the trait approach of leadership which suggests that leaders tend to behave in certain ways that are determined by their heritable characteristics such as personality and intelligence (e.g., Bono & Judge, 2002), and from the contingency approach that suggests leaders behave in ways that are most suitable to the situation based on the needs of followers and the demands of their tasks (e.g., House, 1971), this dissertation draws from the transactional theory of stress (Lazarus & Folkman, 1984) and positions the stressful demands that leaders experience at work as important determinants of their leadership behaviors. Specifically, I propose that leaders' daily challenge demands (e.g., workload, time pressure, responsibilities) are positively related to job engagement whereas their daily hindrance demands (e.g., role ambiguity, office politics, and hassles) are negatively related to engagement. Engagement, in turn, is positively related to transformational and transactional leadership and negatively related to laissez-faire leadership and abusive supervision. Meanwhile, both challenge and hindrance demands are positively related to strain, which is negatively related to transformational and transactional leadership, and is positively related to laissez-faire leadership and abusive supervision. In addition, leaders' daily after-work recovery experience influences the mediating roles of engagement and strain in the relationships between work demands and leadership behaviors. Specifically, daily recovery moderates both the first stage (i.e., the linkages between work demands and engagement and strain) and the second stage (i.e., the linkages between engagement and strain and leadership behaviors) of the mediation. I test this two-level dual-stage moderated mediation model using a two-week experience sampling design. The sample consists of 26 supervisors and 73 employees who directly report to these supervisors from the flood control district of a metropolitan county in the Southwest United States. Results suggest that leaders' daily challenge demands have a positive influence on transformational leadership attributable to engagement, a negative influence on abusive supervision attributable to engagement, and a positive influence on abusive supervision attributable to strain. Leaders' daily hindrance demands, in contrast, have a positive influence on abusive supervision attributable to strain. In addition, leaders' daily recovery moderates the relationship between strain and laissez-faire leadership so that hindrance demands have a positive influence on laissez-faire leadership when the individual is poorly recovered. Leaders' daily recovery also moderates the relationship between strain and abusive supervision so that hindrance demands have a stronger positive influence on abusive supervision through strain when the individual is poorly recovered.
ContributorsZhang, Yiwen (Author) / Lepine, Jeffery (Thesis advisor) / Judge, Timothy (Committee member) / Ashforth, Blake (Committee member) / Arizona State University (Publisher)
Created2013
Description
Chronic restraint stress impairs hippocampal-mediated spatial learning and memory, which improves following a post-stress recovery period. Here, we investigated whether brain derived neurotrophic factor (BDNF), a protein important for hippocampal function, would alter the recovery from chronic stress-induced spatial memory deficits. Adult male Sprague-Dawley rats were infused into the hippocampus with adeno- associated viral vectors containing the coding sequence for short interfering (si)RNA directed against BDNF or a scrambled sequence (Scr), with both containing the coding information for green fluorescent protein to aid in anatomical localization. Rats were then chronically restrained (wire mesh, 6h/d/21d) and assessed for spatial learning and memory using a radial arm water maze (RAWM) either immediately after stressor cessation (Str-Imm) or following a 21-day post-stress recovery period (Str-Rec). All groups learned the RAWM task similarly, but differed on the memory retention trial. Rats in the Str-Imm group, regardless of viral vector contents, committed more errors in the spatial reference memory domain than did non-stressed controls. Importantly, the typical improvement in spatial memory following recovery from chronic stress was blocked with the siRNA against BDNF, as Str-Rec-siRNA performed worse on the RAWM compared to the non-stressed controls or Str-Rec-Scr. These effects were specific for the reference memory domain as repeated entry errors that reflect spatial working memory were unaffected by stress condition or viral vector contents. These results demonstrate that hippocampal BDNF is necessary for the recovery from stress-induced hippocampal dependent spatial memory deficits in the reference memory domain.
ContributorsOrtiz, J. Bryce (Author) / Conrad, Cheryl D. (Thesis advisor) / Olive, M. Foster (Committee member) / Taylor, Sara (Committee member) / Bimonte-Nelson, Heather A. (Committee member) / Arizona State University (Publisher)
Created2013
Description
Due to depletion of oil resources, increasing fuel prices and environmental issues associated with burning of fossil fuels, extensive research has been performed in biofuel production and dramatic progress has been made. But still problems exist in economically production of biofuels. One major problem is recovery of biofuels from fermentation broth with the relatively low product titer achieved. A lot of in situ product recovery techniques including liquid-liquid extraction, membrane extraction, pervaporation, gas stripping and adsorption have been developed and adsorption is shown to be the most promising one compared to other methods. Yet adsorption is not perfect due to defect in adsorbents and operation method used. So laurate adsorption using polymer resins was first investigated by doing adsorption isotherm, kinetic, breakthrough curve experiment and column adsorption of laurate from culture. The results indicate that polymer resins have good capacity for laurate with the highest capacity of 430 g/kg achieved by IRA-402 and can successfully recover laurate from culture without causing problem to Synechocystis sp.. Another research of this paper focused on a novel adsorbent: magnetic particles by doing adsorption equilibrium, kinetic and toxicity experiment. Preliminary results showed excellent performance on both adsorption capacity and kinetics. But further experiment revealed that magnetic particles were toxicity and inhibited growth of all kinds of cell tested severely, toxicity probably comes from Co (III) in magnetic particles. This problem might be solved by either using biocompatible coatings or immobilization of cells, which needs more investigation.
ContributorsWang, Yuchen (Author) / Nielsen, David Ross (Thesis advisor) / Andino, Jean (Committee member) / Torres, Cesar (Committee member) / Arizona State University (Publisher)
Created2012
Description
The southwestern willow flycatcher (Empidonax traillii extimus) is listed as an endangered species throughout its range in the southwestern United States. Little is known about its sub-population spatial structure and how this impacts its population viability. In conjunction with being listed as endangered, a recovery plan was produced by the US Fish and Wildlife Service, with recovery units (sub-populations) roughly based on major river drainages. In the interest of examining this configuration of sub-populations and their impact on the measured population viability, I applied a multivariate auto-regressive state-space model to a spatially extensive time series of abundance data for the southwestern willow flycatcher over the period spanning 1995-2010 estimating critical growth parameters, correlation in environmental stochasticity or "synchronicity" between sub-populations (recovery units) and extinction risk of the sub-populations and the whole. The model estimates two parameters, the mean and variance of annual growth rate. Of the models I tested, I found the strongest support for a population model in which three of the recovery units were grouped (the Lower Colorado, Gila Basin, and Rio Grande recovery units) while keeping all others separate. This configuration has 6.6 times more support for the observed data than a configuration assigning each recovery unit to a separate sub-population, which is how they are circumscribed in the recovery plan. Given the best model, the mean growth rate is -0.0234 (CI95 -0.0939, 0.0412) with a variance of 0.0597 (CI95 0.0115, 0.1134). This growth rate is not significantly different from zero and this is reflected in the low potential for quasi-extinction. The cumulative probability of the population experiencing at least an 80% decline from current levels within 15 years for some sub-populations were much higher (range: 0.129-0.396 for an 80% decline). These results suggest that the rangewide population has a low risk of extinction in the next 15 years and that the formal recovery units specified by the original recovery plan do not correspond to proper sub-population units as defined by population synchrony.
ContributorsDockens, Patrick E. T. (Author) / Sabo, John (Thesis advisor) / Stromberg, Juliet (Committee member) / Fenichel, Eli (Committee member) / Arizona State University (Publisher)
Created2012
Description
Chronic stress results in functional and structural changes to the hippocampus. Decades of research has led to insights into the mechanisms underlying the chronic stress-induced deficits in hippocampal-mediated cognition and reduction of dendritic complexity of hippocampal neurons. Recently, a considerable focus of chronic stress research has investigated the mechanisms behind the improvements in hippocampal mediated cognition when chronic stress ends and a post-stress rest period is given. Consequently, the goal of this dissertation is to uncover the mechanisms that allow for spatial ability to improve in the aftermath of chronic stress. In chapter 2, the protein brain derived neurotrophic factor (BDNF) was investigated as a mechanism that allows for spatial ability to show improvements following the end of chronic stress. It was found that decreasing the expression of BDNF in the hippocampus prevented spatial memory improvements following a post-stress rest period. Chapter 3 was performed to determine whether hippocampal CA3 apical dendritic complexity requires BDNF to show improvements following a post-stress rest period, and whether a receptor for BDNF, TrkB, mediates the improvements of spatial ability and dendritic complexity in a temporal manner, i.e. during the rest period only. These experiments showed that decreased hippocampal BDNF expression prevented improvements in dendritic complexity, and administration of a TrkB antagonist during the rest period also prevented the improvements in spatial ability and dendritic complexity. In chapter 4, the role of the GABAergic system on spatial ability following chronic stress and a post-stress rest period was investigated. Following chronic stress, it was found that male rats showed impairments on the acquisition phase of the RAWM and this correlated with limbic glutamic acid decarboxylase, a marker for GABA. In chapter 5, a transgenic mouse that expresses a permanent marker on all GABAergic interneurons was used to assess the effects of chronic stress and a post-stress rest period on hippocampal GABAergic neurons. While no changes were found on the total number of GABAergic interneurons, specific subtypes of GABAergic interneurons were affected by stressor manipulations. Collectively, these studies reveal some mechanisms behind the plasticity seen in the hippocampus in response to a post-stress rest period.
ContributorsOrtiz, J. Bryce (Author) / Conrad, Cheryl D. (Thesis advisor) / Newbern, Jason M. (Committee member) / Orchinik, Miles (Committee member) / Sanabria, Federico (Committee member) / Arizona State University (Publisher)
Created2018
Description
In developed countries, municipalities deliver drinking water to constituents through water distribution systems. These transport water from a treatment plant to homes, restaurants, and any other site of end use. Proper water distribution system infrastructure functionality is a critical concern to city planners and managers because component failures within these systems restrict or prevent the ability to deliver water. The reduced capacity to deliver water forces the health and well being of all citizens into jeopardy. The breakdown of a component can even spark the failure of several more components, causing a sequence of cascading failures with catastrophic consequences. To make matters worse, some forms of component failures are unpredictable and it is impossible to foresee every possible failure that could occur. In order to prevent cataclysmic losses that are experienced during system failures, the development of resilient water distribution infrastructure is vital. A resilient water distribution system possesses an adaptive capacity to mitigate the loss of service resulting from component failures. Traditionally, infrastructure resilience research has been retrospective in nature, analyzing the infrastructure system after it suffered a failure event. However, this research project takes water distribution resilience research in a new direction. The research identifies the Sensing Anticipating, Adaptation, and Learning processes that are inherent in the current operations of each component in the water distribution system (pumps, pipes, valves, tanks, nodes). Additional SAAL processes have been recommended for the components that lack adaptive management in current practice. This workis unique in that it applies resilience theory to water distribution systems in an anticipatory manner. This anticipatory application of resilience will provide operators with actionable process for them to implement during failure situations. In this setting, resilience is applied to existing systems for noticeable improvements in operation during failure situations.
ContributorsRodriguez, Jordan Robert (Author) / Seager, Thomas (Thesis director) / Eisenberg, Daniel (Committee member) / Bondank, Emily (Committee member) / Civil, Environmental and Sustainable Engineering Programs (Contributor) / School of Sustainability (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
The stress response facilitates our ability to deal effectively with threatening situations, but exposure to severe or chronic stressors can lead to undesirable neural, physiological, and behavioral outcomes. Chronic stress is associated with structural changes in the rat hippocampus, with corresponding deficits in learning and memory. Recent studies have uncovered an inherent neuroplasticity that allows the hippocampus to recover from these stress-induced neural changes. Underlying mechanisms likely involve several different cellular and molecular pathways. In order to gain a more comprehensive understanding of these pathways, we investigated differences in protein expression throughout the timeline of chronic stress and recovery. Male Sprague-Dawley rats were randomly assigned to chronic restraint stress for 6hr/d/10d or 6hr/d/21d, stress for 6hr/d/21d followed by a recovery period of no stress for 10 or 21 days, or a control group. The proteome from the hippocampus of these rats was sequenced using liquid chromatography tandem mass spectrometry (LC-MS/MS) and analyzed. We hypothesized that chronic stress alters interneuronal signaling in the hippocampus by enhancing or attenuating the expression of proteins responsible for synaptic plasticity (functional) and neuronal structure (morphology). So far we have found that structural proteins, such as alpha-internexin, homer protein homolog 3, neurofilament light, and vimentin were significantly altered by chronic stress and recovery. In contrast, proteins necessary for or associated with myelination such as 2',3'-cyclic-nucleotide 3'-phosphodiesterase, myelin-associated glycoprotein, myelin basic protein S, and myelin proteolipid protein were significantly downregulated by chronic stress. Collectively, these results will provide a resource for further investigations into the mechanisms of the brain's recovery from chronic stress.
ContributorsKachemov, Marketta Marilyn (Author) / Orchinik, Miles (Thesis director) / Pirrotte, Patrick (Committee member) / Conrad, Cheryl (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
The purpose of this thesis was to identity various sports psychology techniques utilized during the injury recovery process of an NCAA athlete. Using a qualitative approach, past research was analyzed to uncover different features of an athletic injury as well as possible intervention methods. Findings suggested that effective intervention techniques structured around the Self Determination Theory (SDT), more specifically the concept of strengthening the satisfaction of an individual's three basic psychological needs: competence, autonomy and relatedness. Following the collection of past research, a series of interviews were conducted with four practicing sports psychologists. Interview questions focused on determining possible distinctions between acute, chronic and career-ending injuries as well as intervention techniques employed. Utilizing data collected from past research as well as the interviews, an applied brochure was developed for the potential benefit of an injured athlete. The established techniques, if utilized properly, should strengthen the satisfaction of an athlete's psychological needs according to the SDT, which may ultimately foster a positive and successful return-to-sport experience.
ContributorsLieb, Juliann Rose (Author) / Heywood, William (Thesis director) / Hoffner, Kristin (Committee member) / Barrett, The Honors College (Contributor) / Department of Psychology (Contributor)
Created2014-05
Description
The purpose of this thesis was to identity various sports psychology techniques utilized during the injury recovery process of an NCAA athlete. Using a qualitative approach, past research was analyzed to uncover different features of an athletic injury as well as possible intervention methods. Findings suggested that effective intervention techniques structured around the Self Determination Theory (SDT), more specifically the concept of strengthening the satisfaction of an individual's three basic psychological needs: competence, autonomy and relatedness. Following the collection of past research, a series of interviews were conducted with four practicing sports psychologists. Interview questions focused on determining possible distinctions between acute, chronic and career-ending injuries as well as intervention techniques employed. Utilizing data collected from past research as well as the interviews, an applied brochure was developed for the potential benefit of an injured athlete. The established techniques, if utilized properly, should strengthen the satisfaction of an athlete's psychological needs according to the SDT, which may ultimately foster a positive and successful return-to-sport experience.
ContributorsLieb, Juliann Rose (Author) / Heywood, William (Thesis director) / Hoffner, Kristin (Committee member) / Barrett, The Honors College (Contributor) / Department of Psychology (Contributor)
Created2014-05
Description
This study was designed with the goal of measuring the effects of sleep deprivation on muscle function. Participants in this study consisted of 19 individuals, 11 of which were in the restricted group (age 251) and 8 were in the control group (age 231). Measurements of muscle function included isometric strength, isokinetic velocity, and muscle soreness. Isometric strength and isokinetic velocity were taken for knee extension using a dynamometer. Muscle soreness was measured via a 100mm likert visual analogue scale for the step-up and step-down movements with the effected leg. Measurements were taken at baseline, and 48 hours after the damaging bout of eccentric exercise following either 8 hours of sleep per night or 3 hours of sleep per night. Results show that there were no statistical differences between groups for either measurements of isometric strength, isokinetic velocity, or muscle soreness. Due to possible confounding factors, future research needs to be conducted in order to get a better understanding of the effects of sleep deprivation on muscle function.
ContributorsSalmeron-Been, Aaron James (Author) / Dickinson, Jared (Thesis director) / Youngstedt, Shawn (Committee member) / School of Nutrition and Health Promotion (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12