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Natural variations in 238U/235U of marine carbonates might provide a useful way of constraining redox conditions of ancient environments. In order to evaluate the reliability of this proxy, we conducted aragonite and calcite coprecipitation experiments at pH ~7.5 and ~ 8.5 to study possible U isotope fractionation during incorporation into these minerals.
Small but significant U isotope fractionation was observed in aragonite experiments at pH ~ 8.5, with heavier U in the solid phase. 238U/235U of dissolved U in these experiments can be fit by Rayleigh fractionation curves with fractionation factors of 1.00007+0.00002/-0.00003, 1.00005 ± 0.00001, and 1.00003 ± 0.00001. In contrast, no resolvable U isotope fractionation was observed in an aragonite experiment at pH ~7.5 or in calcite experiments at either pH. Equilibrium isotope fractionation among different aqueous U species is the most likely explanation for these findings. Certain charged U species are preferentially incorporated into calcium carbonate relative to the uncharged U species Ca2UO2(CO3)3(aq), which we hypothesize has a lighter equilibrium U isotope composition than most of the charged species. According to this hypothesis, the magnitude of U isotope fractionation should scale with the fraction of dissolved U that is present as Ca2UO2(CO3)3 (aq). This expectation is confirmed by equilibrium speciation modeling of our experiments. Theoretical calculation of the U isotope fractionation factors between different U species could further test this hypothesis and our proposed fractionation mechanism.
These findings suggest that U isotope variations in ancient carbonates could be controlled by changes in the aqueous speciation of seawater U, particularly changes in seawater pH, PCO2, [Ca], or [Mg] concentrations. In general, these effects are likely to be small (<0.13 ‰), but are nevertheless potentially significant because of the small natural range of variation of 238U/235U.
Small but significant U isotope fractionation was observed in aragonite experiments at pH ~ 8.5, with heavier U in the solid phase. 238U/235U of dissolved U in these experiments can be fit by Rayleigh fractionation curves with fractionation factors of 1.00007+0.00002/-0.00003, 1.00005 ± 0.00001, and 1.00003 ± 0.00001. In contrast, no resolvable U isotope fractionation was observed in an aragonite experiment at pH ~7.5 or in calcite experiments at either pH. Equilibrium isotope fractionation among different aqueous U species is the most likely explanation for these findings. Certain charged U species are preferentially incorporated into calcium carbonate relative to the uncharged U species Ca2UO2(CO3)3(aq), which we hypothesize has a lighter equilibrium U isotope composition than most of the charged species. According to this hypothesis, the magnitude of U isotope fractionation should scale with the fraction of dissolved U that is present as Ca2UO2(CO3)3 (aq). This expectation is confirmed by equilibrium speciation modeling of our experiments. Theoretical calculation of the U isotope fractionation factors between different U species could further test this hypothesis and our proposed fractionation mechanism.
These findings suggest that U isotope variations in ancient carbonates could be controlled by changes in the aqueous speciation of seawater U, particularly changes in seawater pH, PCO2, [Ca], or [Mg] concentrations. In general, these effects are likely to be small (<0.13 ‰), but are nevertheless potentially significant because of the small natural range of variation of 238U/235U.
ContributorsChen, Xinming (Author) / Anbar, Ariel (Thesis advisor) / Herckes, Pierre (Committee member) / Shock, Everett (Committee member) / Arizona State University (Publisher)
Created2015
ContributorsJavidahmadabadi, Mahdi (Author) / Kitchen, Jennifer (Thesis advisor) / Bakkaloglu, Bertan (Committee member) / Aberle, James T., 1961- (Committee member) / Arizona State University (Publisher)
Created2015
Description
Node-link diagrams are widely used to visualize the relational structure of real world datasets. As identical data can be visualized in infinite ways by simply changing the spatial arrangement of the nodes, one of the important research topics of the graph drawing community is to visualize the data in the way that can facilitate people's comprehension. The last three decades have witnessed the growth of algorithms for automatic visualization. However, despite the popularity of node-link diagrams and the enthusiasm in improving computational efficiency, little is known about how people read these graphs and what factors (layout, size, density, etc.) have impact on their effectiveness (the usability aspect of the graph, e.g., are they easy to understand?). This thesis is comprehensive research to investigate the factors that affect people's understanding of node-link diagrams using eye-tracking methods. Three experiments were conducted, including 1) a pilot study with 22 participants to explore the layout and size effect; 2) an eye tracking experiment with 43 participants to investigate the layout, size and density effect on people's graph comprehension using abstract node-link diagram and generic tasks; and 3) an eye tracking experiment with the same participants to investigate the same effects using a real visualization analytic application. Results showed that participants' spatial reasoning ability had significant impact on people's graph reading performance. Layout, size, and density were all found to be significant effects under different task circumstances. The applicability of the eye tracking methods on visualization evaluation has been confirmed by providing detailed evidence that demonstrates the cognitive process of participants' graph reading behavior.
ContributorsLiu, Qing (Author) / McKenna, Anna (Thesis advisor) / Jennifer, Jennifer (Committee member) / Cooke, Nancy J. (Committee member) / Arizona State University (Publisher)
Created2015
Description
Sexual and social signals have long been thought to play an important role in speciation and diversity; hence, investigations of intraspecific communication may lead to important insights regarding key processes of evolution. Though we have learned much about the control, function, and evolution of animal communication by studying several very common signal types, investigating rare classes of signals may provide new information about how and why animals communicate. My dissertation research focused on rapid physiological color change, a rare signal-type used by relatively few taxa. To answer longstanding questions about this rare class of signals, I employed novel methods to measure rapid color change signals of male veiled chameleons Chamaeleo calyptratus in real-time as seen by the intended conspecific receivers, as well as the associated behaviors of signalers and receivers. In the context of agonistic male-male interactions, I found that the brightness achieved by individual males and the speed of color change were the best predictors of aggression and fighting ability. Conversely, I found that rapid skin darkening serves as a signal of submission for male chameleons, reducing aggression from winners when displayed by losers. Additionally, my research revealed that the timing of maximum skin brightness and speed of brightening were the best predictors of maximum bite force and circulating testosterone levels, respectively. Together, these results indicated that different aspects of color change can communicate information about contest strategy, physiology, and performance ability. Lastly, when I experimentally manipulated the external appearance of chameleons, I found that "dishonestly" signaling individuals (i.e. those whose behavior did not match their manipulated color) received higher aggression from unpainted opponents. The increased aggression received by dishonest signalers suggests that social costs play an important role in maintaining the honesty of rapid color change signals in veiled chameleons. Though the color change abilities of chameleons have interested humans since the time of Aristotle, little was previously known about the signal content of such changes. Documenting the behavioral contexts and information content of these signals has provided an important first step in understanding the current function, underlying control mechanisms, and evolutionary origins of this rare signal type.
ContributorsLigon, Russell (Author) / McGraw, Kevin J. (Committee member) / DeNardo, Dale F (Committee member) / Karsten, Kristopher B (Committee member) / Rutowski, Ronald L (Committee member) / Deviche, Pierre (Committee member) / Arizona State University (Publisher)
Created2015
Description
ABSTRACT
This dissertation examines contemporary U.S. women writing about war, with primarily women subjects and protagonists, from 1991-2013, in fiction, memoir, and media. The writers situate women at the center of war texts and privilege their voices as authoritative speakers in war, whether as civilians and soldiers trying to survive or indigenous women preparing for the possibility of war. I argue that these authors are rewriting scripts of war to reflect gendered experiences and opening new ways of thinking about war. Women Rewriting Scripts of War argues that Leslie Marmon Silko’s novel Almanac of the Dead juxtaposes an indigenous Story concept against a white industrialized national “Truth,” and indigenous women characters will resort to war if needed to oppose it. Silko’s and the other texts here challenge readers to unseat assumptions about the sovereignty of the U.S. and other countries, about the fixedness of gender, of capitalism, and of how humans relate to each other‒and how we should. I argue in Essay 3 that the script of “the body” or “the soldier” in military service can be expanded by moving toward language and concepts from feminist and queer theory and spectrums of gender and sexuality. This can contribute to positive change for all military members. In each of the texts, there are some similarities in connections with others. Connections enable solidarity for change, possibilities for healing, and survival; indeed, without connections with others to work together, survival is not possible. Changes to established economic structures become necessary for women in Barbara Kingsolver’s novel The Poisonwood Bible; I argue that women engaging in alternative modes of economy subvert the dominant economic constraints, gender hierarchies, and social isolation during and after war in the Congo. In Essay 5, I explore two fictional texts about the U.S. wars in Iraq and Afghanistan, Helen Benedict's novel Sand Queen and Katey Schultz’s short story collection Flashes of War. The connections in these women’s texts about war are not idealized, and they function as the antithesis to the fragmentation and isolation of postmodern texts.
This dissertation examines contemporary U.S. women writing about war, with primarily women subjects and protagonists, from 1991-2013, in fiction, memoir, and media. The writers situate women at the center of war texts and privilege their voices as authoritative speakers in war, whether as civilians and soldiers trying to survive or indigenous women preparing for the possibility of war. I argue that these authors are rewriting scripts of war to reflect gendered experiences and opening new ways of thinking about war. Women Rewriting Scripts of War argues that Leslie Marmon Silko’s novel Almanac of the Dead juxtaposes an indigenous Story concept against a white industrialized national “Truth,” and indigenous women characters will resort to war if needed to oppose it. Silko’s and the other texts here challenge readers to unseat assumptions about the sovereignty of the U.S. and other countries, about the fixedness of gender, of capitalism, and of how humans relate to each other‒and how we should. I argue in Essay 3 that the script of “the body” or “the soldier” in military service can be expanded by moving toward language and concepts from feminist and queer theory and spectrums of gender and sexuality. This can contribute to positive change for all military members. In each of the texts, there are some similarities in connections with others. Connections enable solidarity for change, possibilities for healing, and survival; indeed, without connections with others to work together, survival is not possible. Changes to established economic structures become necessary for women in Barbara Kingsolver’s novel The Poisonwood Bible; I argue that women engaging in alternative modes of economy subvert the dominant economic constraints, gender hierarchies, and social isolation during and after war in the Congo. In Essay 5, I explore two fictional texts about the U.S. wars in Iraq and Afghanistan, Helen Benedict's novel Sand Queen and Katey Schultz’s short story collection Flashes of War. The connections in these women’s texts about war are not idealized, and they function as the antithesis to the fragmentation and isolation of postmodern texts.
ContributorsStamper, Cambria A (Author) / Clarke, Deborah (Thesis advisor) / Hogue, Cynthia (Committee member) / Fonow, Mary Margaret (Committee member) / Arizona State University (Publisher)
Created2015
Description
Background: Heart failure is the leading cause of hospitalization in older adults and has the highest 30-day readmission rate of all diagnoses. An estimated 30 to 60 percent of older adults lose some degree of physical function in the course of an acute hospital stay. Few studies have addressed the role of posture and mobility in contributing to, or improving, physical function in older hospitalized adults. No study to date that we are aware of has addressed this in the older heart failure population.
Purpose: To investigate the predictive value of mobility during a hospital stay and patterns of mobility during the month following discharge on hospital readmission and 30-day changes in functional status in older heart failure patients.
Methods: This was a prospective observational study of 21 older (ages 60+) patients admitted with a primary diagnosis of heart failure. Patients wore two inclinometric accelerometers (rib area and thigh) to record posture and an accelerometer placed at the ankle to record ambulatory activity. Patients wore all sensors continuously during hospitalization and the ankle accelerometer for 30 days after hospital discharge. Function was assessed in all patients the day after hospital discharge and again at 30 days post-discharge.
Results: Five patients (23.8%) were readmitted within the 30 day post-discharge period. None of the hospital or post-discharge mobility measures were associated with readmission after adjustment for covariates. Higher percent lying time in the hospital was associated with slower Timed Up and Go (TUG) time (b = .08, p = .01) and poorer hand grip strength (b = -13.94, p = .02) at 30 days post-discharge. Higher daily stepping activity during the 30 day post-discharge period was marginally associated with improvements in SPPB scores at 30 days (b = <.001, p = .06).
Conclusion: For older heart failure patients, increased time lying while hospitalized is associated with slower walking time and poor hand grip strength 30 days after discharge. Higher daily stepping after discharge may be associated with improvements in physical function at 30 days.
Purpose: To investigate the predictive value of mobility during a hospital stay and patterns of mobility during the month following discharge on hospital readmission and 30-day changes in functional status in older heart failure patients.
Methods: This was a prospective observational study of 21 older (ages 60+) patients admitted with a primary diagnosis of heart failure. Patients wore two inclinometric accelerometers (rib area and thigh) to record posture and an accelerometer placed at the ankle to record ambulatory activity. Patients wore all sensors continuously during hospitalization and the ankle accelerometer for 30 days after hospital discharge. Function was assessed in all patients the day after hospital discharge and again at 30 days post-discharge.
Results: Five patients (23.8%) were readmitted within the 30 day post-discharge period. None of the hospital or post-discharge mobility measures were associated with readmission after adjustment for covariates. Higher percent lying time in the hospital was associated with slower Timed Up and Go (TUG) time (b = .08, p = .01) and poorer hand grip strength (b = -13.94, p = .02) at 30 days post-discharge. Higher daily stepping activity during the 30 day post-discharge period was marginally associated with improvements in SPPB scores at 30 days (b = <.001, p = .06).
Conclusion: For older heart failure patients, increased time lying while hospitalized is associated with slower walking time and poor hand grip strength 30 days after discharge. Higher daily stepping after discharge may be associated with improvements in physical function at 30 days.
ContributorsFloegel, Theresa A (Author) / Buman, Matthew P (Thesis advisor) / Hooker, Steven (Committee member) / Dickinson, Jared (Committee member) / DerAnanian, Cheryl (Committee member) / McCarthy, Marianne (Committee member) / Arizona State University (Publisher)
Created2015
Description
This dissertation examines a planned missing data design in the context of mediational analysis. The study considered a scenario in which the high cost of an expensive mediator limited sample size, but in which less expensive mediators could be gathered on a larger sample size. Simulated multivariate normal data were generated from a latent variable mediation model with three observed indicator variables, M1, M2, and M3. Planned missingness was implemented on M1 under the missing completely at random mechanism. Five analysis methods were employed: latent variable mediation model with all three mediators as indicators of a latent construct (Method 1), auxiliary variable model with M1 as the mediator and M2 and M3 as auxiliary variables (Method 2), auxiliary variable model with M1 as the mediator and M2 as a single auxiliary variable (Method 3), maximum likelihood estimation including all available data but incorporating only mediator M1 (Method 4), and listwise deletion (Method 5).
The main outcome of interest was empirical power to detect the mediated effect. The main effects of mediation effect size, sample size, and missing data rate performed as expected with power increasing for increasing mediation effect sizes, increasing sample sizes, and decreasing missing data rates. Consistent with expectations, power was the greatest for analysis methods that included all three mediators, and power decreased with analysis methods that included less information. Across all design cells relative to the complete data condition, Method 1 with 20% missingness on M1 produced only 2.06% loss in power for the mediated effect; with 50% missingness, 6.02% loss; and 80% missingess, only 11.86% loss. Method 2 exhibited 20.72% power loss at 80% missingness, even though the total amount of data utilized was the same as Method 1. Methods 3 – 5 exhibited greater power loss. Compared to an average power loss of 11.55% across all levels of missingness for Method 1, average power losses for Methods 3, 4, and 5 were 23.87%, 29.35%, and 32.40%, respectively. In conclusion, planned missingness in a multiple mediator design may permit higher quality characterization of the mediator construct at feasible cost.
The main outcome of interest was empirical power to detect the mediated effect. The main effects of mediation effect size, sample size, and missing data rate performed as expected with power increasing for increasing mediation effect sizes, increasing sample sizes, and decreasing missing data rates. Consistent with expectations, power was the greatest for analysis methods that included all three mediators, and power decreased with analysis methods that included less information. Across all design cells relative to the complete data condition, Method 1 with 20% missingness on M1 produced only 2.06% loss in power for the mediated effect; with 50% missingness, 6.02% loss; and 80% missingess, only 11.86% loss. Method 2 exhibited 20.72% power loss at 80% missingness, even though the total amount of data utilized was the same as Method 1. Methods 3 – 5 exhibited greater power loss. Compared to an average power loss of 11.55% across all levels of missingness for Method 1, average power losses for Methods 3, 4, and 5 were 23.87%, 29.35%, and 32.40%, respectively. In conclusion, planned missingness in a multiple mediator design may permit higher quality characterization of the mediator construct at feasible cost.
ContributorsBaraldi, Amanda N (Author) / Enders, Craig K. (Thesis advisor) / Mackinnon, David P (Thesis advisor) / Aiken, Leona S. (Committee member) / Tein, Jenn-Yun (Committee member) / Arizona State University (Publisher)
Created2015
Description
There is a strong medical need and important therapeutic applications for improved wireless bioelectric interfaces to the nervous system. Multichannel devices are desired for neural control of robotic prosthetics that interface to remaining nerves in limb stumps of amputees and as alternatives to traditional wired arrays used in for some types of brain stimulation. This present work investigates a new approach to ultrasound-powering of implantable microelectronic devices within the tissue that may better support such applications. These devices are of ultra-miniature size that is enabled by a wireless technique. This study investigates two types of ultrasound-powered neural interfaces for multichannel sensory feedback in neurostimulation. The piezoceramics lead zirconate titanate (PZT) ceramic and polyvinylidene fluoride (PVDF) polymer were the primary materials used to build the devices. They convert ultrasound to electricity that when rectified by a diode produce a current output that is neuro stimulatory to peripheral nerve or the neurons in the brain. Multichannel devices employ a form of spatial multiplexing that directs focused ultrasound towards localized and segmented regions of PVDF or PZT that allows independent channels of nerve actuation. Different frequencies of ultrasound were evaluated for best results. Firstly, a 2.25 MHz frequency signal that is reasonably penetrating through body tissue to an implant several centimeters deep and also a 5 MHz frequency more suited to application for actuation of devices within a less than a centimeter of nerve. Results show multichannel device performance to have a complex inter-relationship with frequency, size and thickness, angular incidence, channel separations, and number of folds (layers connected in series and parallel). The output electrical port impedances of PVDF devices were examined in relationship to that of stimulating electrodes and tissue interfaces. Miniature multichannel devices were constructed using an unreported method of employing state of the art laser cutting systems. The results show that PVDF based devices have advantages over PZT, because of better acoustic coupling with tissue, known better biocompatibility, and better separation between multiple channels. However, the PZT devices proved to be better overall in terms of compactness and higher outputs for a given ultrasound power level.
ContributorsNanda Kumar, Yashwanth (Author) / Towe, Bruce (Thesis advisor) / Muthuswamy, Jitendran (Committee member) / Nikkhah, Mehdi (Committee member) / Arizona State University (Publisher)
Created2015
Description
Excessive gestational weight gain (GWG) during pregnancy is a major public health concern. Studies have reported more than 70% of pregnant women gain excessive weight which may pose increased maternal and fetal risks. Little is known about the relationships of GWG to behavioral factors (i.e., physical activity, sleep, social support) and maternal mental health (i.e., stress, anxiety, depression) during pregnancy. This descriptive, cross-sectional study explored the relationships of GWG to behavioral factors and maternal mental health during pregnancy. Secondarily, this study described the preferences, uses of, and interests in alternative approaches as well as the mental health differences between users and non-users of alternative approaches during pregnancy. A national survey was administered to women ≥8 weeks pregnant, ≥18 years old, and residing in the United States (N=968). Bivariate correlations were used to determine relationships between GWG and variables of interest. Independent t-tests were used to observe mental health differences between users and non-users of alternative approaches. Data were analyzed throughout pregnancy and by trimester. Throughout pregnancy, significant relationships were found in GWG to stressful events (r=-.112, p<.01), depression (r=.066, p<.05), mindfulness (r=-.067, p<.05), and sleep (r=.089, p<.01). When GWG was assessed by trimester, stressful events were significant in the second (r=-.216, p<.01) and third trimesters (r=-.085, p<.05). Depression remained positively related to GWG in the first (r=.409, p<.01) and second trimesters (r=.162, p<.01). A positive relationship emerged between GWG and anxiety in the first trimester (r=.340, p<.01) and physical activity became significant in the second (r=-.136; p<.05) and third trimesters (r=-.100; p<.05). Mindfulness was the only variable significantly related to GWG throughout all time points. Mean anxiety (d=.236; p=.001) and depression (d=.265; p<.001) scores were significantly lower in users compared to non-users of alternative approaches throughout pregnancy and when assessed by trimester anxiety (d=.424; p=.001) and depression (d=.526; p<.001) were significant in the second trimester. This study provides a framework for future analyses in GWG and maternal mental health. The information presented here may inform future interventions to test the effectiveness of alternative approaches to simultaneously manage maternal mental health and GWG due to the integrative nature of alternative approaches.
ContributorsMatthews, Jennifer L. (Author) / Huberty, Jennifer L (Thesis advisor) / Leiferman, Jenn (Committee member) / Larkey, Linda (Committee member) / McClain, Darya (Committee member) / Arizona State University (Publisher)
Created2015
Description
Vitamin D deficiency has been previously associated with a higher Alzheimer’s disease (AD) risk, a condition marked by dependent living and severe cognitive impairment. AD is histologically defined by the presence of brain amyloid beta (Aβ) plaques and neurofibrillary tangles. Ways to enhance Aβ clearance have been examined in order to sustain cognition and delay AD onset. In vitro and in vivo studies suggest that vitamin D might enhance brain Aβ transportation to the periphery by up-regulating P-glycoprotein production. The purpose of this study was to examine the effect of vitamin D supplementation on plasma Aβ in an older population.
This study was a parallel-arm, double-blinded, randomized control trial. Participants consumed either a vitamin D supplement or placebo once a week for eight weeks (n=23). Only vitamin D insufficient (serum total 25-OH, D < 30 ng/mL) people were included in the study, and all participants were considered to be cognitively normal (MMSE scores > 27). Serum total 25-OH, D and plasma Aβ1-40 measurements were recorded before and after the eight-week trial. The plasma Aβ1-40 change was compared between the vitamin D group and control group.
The vitamin D group experienced a 45% greater change in plasma Aβ1-40 than the control group. The effect size was 0.228 when controlling for baseline plasma Aβ1-40 (p=0.045), 0.197 when controlling for baseline plasma Aβ1-40 and baseline physical activity (p=0.085), and 0.179 when controlling for baseline plasma Aβ1-40, baseline physical activity, and age (p=0.116). In conclusion, vitamin D supplementation might increase brain Aβ clearance in humans, but physical activity and age also appear to modulate Aβ metabolism.
This study was a parallel-arm, double-blinded, randomized control trial. Participants consumed either a vitamin D supplement or placebo once a week for eight weeks (n=23). Only vitamin D insufficient (serum total 25-OH, D < 30 ng/mL) people were included in the study, and all participants were considered to be cognitively normal (MMSE scores > 27). Serum total 25-OH, D and plasma Aβ1-40 measurements were recorded before and after the eight-week trial. The plasma Aβ1-40 change was compared between the vitamin D group and control group.
The vitamin D group experienced a 45% greater change in plasma Aβ1-40 than the control group. The effect size was 0.228 when controlling for baseline plasma Aβ1-40 (p=0.045), 0.197 when controlling for baseline plasma Aβ1-40 and baseline physical activity (p=0.085), and 0.179 when controlling for baseline plasma Aβ1-40, baseline physical activity, and age (p=0.116). In conclusion, vitamin D supplementation might increase brain Aβ clearance in humans, but physical activity and age also appear to modulate Aβ metabolism.
ContributorsMiller, Brendan Joseph (Author) / Johnston, Carol (Thesis advisor) / Whisner, Corrie (Committee member) / Tasevska, Natasha (Committee member) / Arizona State University (Publisher)
Created2015