Matching Items (469)
Filtering by
- All Subjects: psychology
- All Subjects: Materials Science
- Genre: Masters Thesis
- Genre: Diaries--Authorship.
Description
Microwave dielectrics are widely used to make resonators and filters in telecommunication systems. The production of thin films with high dielectric constant and low loss could potentially enable a marked reduction in the size of devices and systems. However, studies of these materials in thin film form are very sparse. In this research, experiments were carried out on practical high-performance dielectrics including ZrTiO4-ZnNb2O6 (ZTZN) and Ba(Co,Zn)1/3Nb2/3O3 (BCZN) with high dielectric constant and low loss tangent. Thin films were deposited by laser ablation on various substrates, with a systematical study of growth conditions like substrate temperature, oxygen pressure and annealing to optimize the film quality, and the compositional, microstructural, optical and electric properties were characterized. The deposited ZTZN films were randomly oriented polycrystalline on Si substrate and textured on MgO substrate with a tetragonal lattice change at elevated temperature. The BCZN films deposited on MgO substrate showed superior film quality relative to that on other substrates, which grow epitaxially with an orientation of (001) // MgO (001) and (100) // MgO (100) when substrate temperature was above 500 oC. In-situ annealing at growth temperature in 200 mTorr oxygen pressure was found to enhance the quality of the films, reducing the peak width of the X-ray Diffraction (XRD) rocking curve to 0.53o and the χmin of channeling Rutherford Backscattering Spectrometry (RBS) to 8.8% when grown at 800oC. Atomic Force Microscopy (AFM) was used to study the topography and found a monotonic decrease in the surface roughness when the growth temperature increased. Optical absorption and transmission measurements were used to determine the energy bandgap and the refractive index respectively. A low-frequency dielectric constant of 34 was measured using a planar interdigital measurement structure. The resistivity of the film is ~3×1010 ohm·cm at room temperature and has an activation energy of thermal activated current of 0.66 eV.
ContributorsLi, You (Author) / Newman, Nathan (Thesis advisor) / Alford, Terry (Committee member) / Singh, Rakesh (Committee member) / Arizona State University (Publisher)
Created2013
Description
The development of self-regulation is believed to play a crucial role in predicting later psychopathology and is believed to begin in early childhood. The early postpartum period is particularly important in laying the groundwork for later self-regulation as infants' dispositional traits interact with caregivers' co-regulatory behaviors to produce the earliest forms of self-regulation. Moreover, although emerging literature suggests that infants' exposure to maternal stress even before birth may be integral in determining children's self-regulatory capacities, the complex pathways that characterize these developmental processes remain unclear. The current study considers the complex, transactional processes in a high-risk, Mexican American sample. Data were collected from 305 Mexican American infants and their mothers during prenatal, 6- and 12-week home interviews. Mother self-reports of stress were obtained prenatally between 34-37 weeks gestation. Mother reports of infant temperamental negativity and surgency were obtained at 6-weeks as were observed global ratings of maternal sensitivity during a structured peek-a-boo task. Microcoded ratings of infants' engagement orienting and self-comforting behaviors were obtained during the 12-week peek-a-boo task. Study findings suggest that self-comforting and orienting behaviors help to modulate infants' experiences of distress, and also that prenatal stress influences infants' engagement in each of those regulatory behaviors, both directly by influence tendencies to engage in orienting behaviors and indirectly by programming higher levels of infant negativity and surgency, both of which may confer risk for later regulatory disadvantage. Advancing our understandings about the nature of these developmental pathways could have significant implications for targets of early intervention in this high-risk population.
ContributorsLin, Betty (Author) / Crnic, Keith A (Thesis advisor) / Lemery-Chalfant, Kathryn S (Committee member) / Mackinnon, David P (Committee member) / Arizona State University (Publisher)
Created2013
Description
The purpose of the current study was to use structural equation modeling-based quantitative genetic models to characterize latent genetic and environmental influences on proneness to three discrete negative emotions in middle childhood, according to mother-report, father-report and in-home observation. One primary aim was to test the extent to which covariance among the three emotions could be accounted for by a single, common genetically- and environmentally-influenced negative emotionality factor. A second aim was to examine the extent to which different reporters appeared to be tapping into the same genetically- and environmentally-influenced aspects of each emotion. According to mother- and father-report, moderate to high genetic influences were evident for all emotions, with mother- and father-report of fear and father-report of anger showing the highest heritability. Significant common environmental influences were also found for mother-report of anger and sadness in both univariate and multivariate models. For observed emotion, anger was moderately heritable with no evidence for common environmental variance, but sadness, object fear and social fear all showed modest to moderate common environmental influences and no significant genetic variance. In addition, cholesky decompositions examining genetic and environmental influences across reporter suggested that despite considerable overlap between mother-report and father-report, there was also reporter-specific variance on anger, sadness, and fear. Specifically, there were significant common environmental influences on mother-report of anger- and sadness that were not shared with father-report, and genetic influences on father-report of sadness and fear that were not shared with mother-report. In-home observations were not highly correlated enough with parent-report to support multivariate analysis for any emotion. Finally, according to both mother- and father-report, a single set of genetic and environmental influences was sufficient to account for covariance among all three negative emotions. However, fear was primarily explained by genetic influences not shared with other emotions, and anger also showed considerable emotion-specific genetic variance. In both cases, findings support the value of a more emotion-specific approach to temperament, and highlight the need to consider distinctions as well as commonalities across emotions, reporters and situations.
ContributorsClifford, Sierra (Author) / Lemery, Kathryn (Thesis advisor) / Shiota, Michelle (Committee member) / Eisenberg, Nancy (Committee member) / Arizona State University (Publisher)
Created2013
Description
After natural menopause in women, androstenedione becomes the primary hormone secreted by the residual follicle deplete ovaries. Two independent studies, in rodents that had undergone ovarian follicular depletion, found that higher serum androstenedione levels correlated with increased working memory errors. This led to the hypothesis that androstenedione impairs memory. The current study directly tested this hypothesis, examining the cognitive effects of androstenedione administration in a rodent model. Middle-aged ovariectomized rats received vehicle or one of two doses of androstenedione (4 or 8 mg/kg daily). Rats were tested on a spatial working and reference memory maze battery including the water radial arm maze, Morris maze, and delay-match-to-sample task. Results showed that androstenedione at the highest dose impaired reference memory and working memory, including ability to maintain performance as memory demand was elevated. The latter was true for both high temporal demand memory retention of one item of spatial information, as well as the ability to handle multiple items of spatial working memory information. Glutamic acid decarboxylase (GAD) levels were measured in multiple brain regions to determine whether the gamma-aminobutyric acid (GABA) system mediates androstenedione's cognitive impairments. Results showed that higher entorhinal cortex GAD levels were correlated with poorer Morris maze performance, regardless of androstenedione treatment. These findings suggest that androstenedione, the main hormone produced by the follicle deplete ovary, is detrimental to spatial learning, reference memory, and working memory, and that spatial reference memory performance might be related to the GABAergic system.
ContributorsCamp, Bryan Walter (Author) / Bimonte-Nelson, Heather A. (Thesis advisor) / Olive, Michael F (Committee member) / Conrad, Cheryl D. (Committee member) / Arizona State University (Publisher)
Created2012
Description
Levels of heavy episodic drinking peak during emerging adulthood and contribute to the experience of negative consequences. Previous research has identified a number of trait-like personality characteristics that are associated with drinking. Studies of the Acquired Preparedness Model have supported positive expectancies, and to a lesser extent negative expectancies, as mediators of the relation between trait-like characteristics and alcohol outcomes. However, expectancies measured via self-report may reflect differences in learned expectancies in spite of similar alcohol-related responses, or they may reflect true individual differences in subjective responses to alcohol. The current study addressed this gap in the literature by assessing the relative roles of expectancies and subjective response as mediators within the APM in a sample of 236 emerging adults (74.7% male) participating in a placebo-controlled alcohol challenge study. The study tested four mediation models collapsed across beverage condition as well as eight separate mediation models with four models (2 beverage by 2 expectancy/subjective response) for each outcome (alcohol use and alcohol-related problems). Consistent with previous studies, SS was positively associated with alcohol outcomes in models collapsed across beverage condition. SS was also associated with positive subjective response in collapsed models and in the alcohol models. The hypothesized negative relation between SS and sedation was not significant. In contrast to previous studies, neither stimulation nor sedation predicted either weekly drinking or alcohol-related problems. While stimulation and alcohol use appeared to have a positive and significant association, this relation did not hold when controlling for SS, suggesting that SS and stimulation account for shared variability in drinking behavior. Failure to find this association in the placebo group suggests that, while explicit positive expectancies are related to alcohol use after controlling for levels of sensation seeking, implicit expectancies (at least as assessed by a placebo manipulation) are not. That the relation between SS and stimulation held only in the alcohol condition in analyses separate by beverage condition indicates that sensation seeking is a significant predictor of positive subjective response to alcohol (stimulation), potentially above and beyond expectancies.
ContributorsScott, Caitlin (Author) / Corbin, William (Thesis advisor) / Shiota, Michelle (Committee member) / Chassin, Laurie (Committee member) / Arizona State University (Publisher)
Created2012
Description
III-Nitride nanostructures have been an active area of research recently due to their ability to tune their optoelectronic properties. Thus far work has been done on InGaN quantum dots, nanowires, nanopillars, amongst other structures, but this research reports the creation of a new type of InGaN nanostructure, nanorings. Hexagonal InGaN nanorings were formed using Metal Organic Chemical Vapor Deposition through droplet epitaxy. The nanorings were thoroughly analyzed using x-ray diffraction, photoluminescence, electron microscopy, electron diffraction, and atomic force microscopy. Nanorings with high indium incorporation were achieved with indium content up to 50% that was then controlled using the growth time, temperature, In/Ga ratio and III/N ratio. The analysis showed that the nanoring shape is able to incorporate more indium than other nanostructures, due to the relaxing mechanism involved in the formation of the nanoring. The ideal conditions were determined to be growth of 30 second droplets with a growth time of 1 minute 30 seconds at 770 C to achieve the most well developed rings with the highest indium concentration.
ContributorsZaidi, Zohair (Author) / Mahajan, Subhash (Thesis advisor) / O'Connell, Michael J (Committee member) / Krause, Stephen (Committee member) / Arizona State University (Publisher)
Created2012
Description
The work presented in this thesis covers the synthesis and characterization of an ionomer that is applicable to zinc-air batteries. Polysulfone polymer is first chloromethylated and then quaternized to create an ion-conducting polymer. Nuclear magnetic resonance (NMR) spectra indicates that the degree of chloromethylation was 114%. The chemical and physical properties that were investigated include: the ionic conductivity, ion exchange capacity, water retention capacity, diameter and thickness swelling ratios, porosity, glass transition temperature, ionic conductivity enhanced by free salt addition, and the concentration and diffusivity of oxygen within the ionomer. It was found that the fully hydrated hydroxide form of the ionomer had a room temperature ionic conductivity of 39.92mS/cm while the chloride form had a room temperature ionic conductivity of 11.80mS/cm. The ion exchange capacity of the ionomer was found to be 1.022mmol/g. The water retention capacity (WRC) of the hydroxide form was found to be 172.6% while the chloride form had a WRC of 67.9%. The hydroxide form of the ionomer had a diameter swelling ratio of 34% and a thickness swelling ratio of 55%. The chloride form had a diameter swelling ratio of 32% and a thickness swelling ratio of 28%. The largest pore size in the ionomer was found to be 32.6nm in diameter. The glass transition temperature of the ionomer is speculated to be 344°C. A definite measurement could not be made. The room temperature ionic conductivity at 50% relative humidity was improved to 12.90mS/cm with the addition of 80% free salt. The concentration and diffusivity of oxygen in the ionomer was found to be 1.3 ±0.2mMol and (0.49 ±0.15)x10-5 cm2/s respectively. The ionomer synthesized in this research had material properties and performance that is comparable to other ionomers reported in the literature. This is an indication that this ionomer is suitable for further study and integration into a zinc-air battery. This thesis is concluded with suggestions for future research that is focused on improving the performance of the ionomer as well as improving the methodology.
ContributorsPadilla, Manuel (Author) / Friesen, Cody A (Thesis advisor) / Buttry, Daniel (Committee member) / Sieradzki, Karl (Committee member) / Arizona State University (Publisher)
Created2012
Description
Ethnic identity has consistently been associated with Latino youths' psychosocial well-being; however, an area that has received much less attention is how parents' characteristics inform their ethnic socialization efforts and, in turn, youths' ethnic identity. In addition, we know little about how this process unfolds in specific at-risk samples of youth, such as adolescent mothers. Thus, the current prospective study examined how mothers' cultural characteristics informed adolescents' and mothers' reports of ethnic socialization, and how this, in turn, informed adolescents' ethnic identity exploration and resolution among a sample of 193 adolescent mothers and their mothers. In addition, the current study tested whether mothers' ethnic identity affirmation was directly related to adolescents' ethnic identity affirmation over time. Results indicated that mothers' familism was associated with increases in mothers' reports of maternal ethnic socialization, and, in turn, with increases in ethnic identity exploration for foreign-born adolescents, and decreases in ethnic identity exploration for U.S.-born adolescents. In addition, adolescents' reports of familial ethnic socialization were associated with increases in their ethnic identity exploration and resolution. Finally, mothers' ethnic identity affirmation was associated with increases in adolescents' ethnic identity affirmation. Findings are discussed with special attention to the importance of mothers' cultural values in how they socialize their adolescents, and this impact on adolescents' ethnic identity, as well as the implications this study has for interventions focused on bolstering positive outcomes for adolescent mothers.
ContributorsDerlan, Chelsea L (Author) / Umaña-Taylor, Adriana J. (Thesis advisor) / Knight, George P. (Committee member) / Updegraff, Kimberly A. (Committee member) / Arizona State University (Publisher)
Created2012
Description
Recommendations made by expert groups are pervasive throughout various life domains. Yet not all recommendations--or expert groups--are equally persuasive. This research aims to identify factors that influence the persuasiveness of recommendations. More specifically, this study examined the effects of decisional cohesion (the amount of agreement among the experts in support of the recommendation), framing (whether the message is framed as a loss or gain), and the domain of the recommendation (health vs. financial) on the persuasiveness of the recommendation. The participants consisted of 1,981 undergraduates from Arizona State University. The participants read a vignette including information about the expert group making a recommendation--which varied the amount of expert agreement for the recommendation--and the recommendation, which was framed as either a gain or loss. Participants then responded to questions about the persuasiveness of the recommendation. In this study, there was a linear main effect of decisional cohesion such that the greater the decisional cohesion of the expert group the more persuasive their recommendation. In addition, there was a main effect of domain such that the health recommendation was more persuasive than the financial recommendation. Contrary to predictions, there was no observed interaction between the amount of decisional cohesion and the framing of the recommendation nor was there a main effect of framing. Further analyses show support for a mediation effect indicating that high levels of decisional cohesion increased the perceived entitativity of the expert group--the degree to which the group was perceived as a unified, cohesive group¬--which increased the recommendation's persuasiveness. An implication of this research is that policy makers could increase the persuasiveness of their recommendations by promoting recommendations that are unanimously supported by their experts or at least show higher levels of decisional cohesion.
ContributorsVotruba, Ashley M (Author) / Kwan, Virginia S.Y. (Thesis advisor) / Saks, Michael J. (Committee member) / Demaine, Linda (Committee member) / Arizona State University (Publisher)
Created2013
Description
Although aggression is sometimes thought to be maladaptive, evolutionary theories of resource control and dominance posit that aggression may be used to gain and maintain high social prominence within the peer group. The success of using aggression to increase social prominence may depend on the form of aggression used (relational versus physical), the gender of the aggressor, and the prominence of the victim. Thus, the current study examined the associations between aggression and victimization and social prominence. In addition, the current study extended previous research by examining multiple forms of aggression and victimization and conceptualizing and measuring social prominence using social network analysis. Participants were 339 6th grade students from ethnically diverse backgrounds (50.4% girls). Participants completed a peer nomination measure assessing relational and physical aggression and victimization. They also nominated friends within their grade, which were used to calculate three indices of social prominence, using social network analysis. As expected, results indicated that relational aggression was associated with higher social prominence, particularly for girls, whereas physical aggression was less robustly associated with social prominence. Results for victimization were less clear, but suggested that, for girls, those at mid-levels of social prominence were most highly victimized. For boys, results indicated that those both high and low in prominence were most highly relationally victimized, and those at mid-levels of prominence were most highly physically victimized. These findings help inform intervention work focused on decreasing overall levels of aggressive behavior.
ContributorsAndrews, Naomi C. Z (Author) / Hanish, Laura D. (Thesis advisor) / Martin, Carol Lynn (Committee member) / Updegraff, Kimberly A (Committee member) / Arizona State University (Publisher)
Created2013