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Description
The oceans play an essential role in global biogeochemical cycles and in regulating climate. The biological carbon pump, the photosynthetic fixation of carbon dioxide by phytoplankton and subsequent sequestration of organic carbon into deep water, combined with the physical carbon pump, make the oceans the only long-term net sink for anthropogenic carbon dioxide. A full understanding of the workings of the biological carbon pump requires a knowledge of the role of different taxonomic groups of phytoplankton (protists and cyanobacteria) to organic carbon export. However, this has been difficult due to the degraded nature of particles sinking into particle traps, the main tools employed by oceanographers to collect sinking particulate matter in the ocean. In this study DNA-based molecular methods, including denaturing gradient gel electrophoresis, cloning and sequencing, and taxon-specific quantitative PCR, allowed for the first time for the identification of which protists and cyanobacteria contributed to the material collected by the traps in relation to their presence in the euphotic zone. I conducted this study at two time-series stations in the subtropical North Atlantic Ocean, one north of the Canary Islands, and one located south of Bermuda. The Bermuda study allowed me to investigate seasonal and interannual changes in the contribution of the plankton community to particle flux. I could also show that small unarmored taxa, including representatives of prasinophytes and cyanobacteria, constituted a significant fraction of sequences recovered from sediment trap material. Prasinophyte sequences alone could account for up to 13% of the clone library sequences of trap material during bloom periods. These observations contradict a long-standing paradigm in biological oceanography that only large taxa with mineral shells are capable of sinking while smaller, unarmored cells are recycled in the euphotic zone through the microbial loop. Climate change and a subsequent warming of the surface ocean may lead to a shift in the protist community toward smaller cell size in the future, but in light of these findings these changes may not necessarily lead to a reduction in the strength of the biological carbon pump.
ContributorsAmacher, Jessica (Author) / Neuer, Susanne (Thesis advisor) / Garcia-Pichel, Ferran (Committee member) / Lomas, Michael (Committee member) / Wojciechowski, Martin (Committee member) / Stout, Valerie (Committee member) / Arizona State University (Publisher)
Created2011
Description
This dissertation explores the lives of women who are on the Severely Mentally Ill (SMI) caseload at Maricopa County Adult Probation in Arizona (The Phoenix metro region). The project focuses on three primary issues: (1) what are the pathways to the criminal justice and mental health systems for women on the SMI caseload (2) how does discretion and expansive formal social control (both benevolent and coercive) impact the lives of these women on the SMI caseload and (3) what are the gendered aspects to successful completion of SMI probation. To answer these questions a mixed-methods research design was employed. First, in-depth semi-structured interviews were completed with 65 women on the SMI caseload. Second, these interviews were supplemented with a case file review of each participant, and field observations (encompassing roughly 100 hours) were conducted at the Maricopa County Mental Health Court. Third, analysis also included 5.5 years of quantitative intake data from the SMI caseload, exploring demographic information and risk and assessment needs scores. The biographies of the women on the SMI caseload revealed similar histories of victimization, substance abuse, and relationship difficulty that previous pathways research has noted. Additionally, mental health problems directly impacted the path to the criminal justice system for some women on the SMI caseload. Results also showed many aspects of expanded social control for women on the SMI caseload. This expanded control appeared to be gendered at times and often created double binds for women. Finally, quantitative analysis showed that some predictive factors of SMI probation completion were gendered. Policy implications and summaries of findings are discussed.
ContributorsMulvey, Philip (Author) / Decker, Scott H. (Thesis advisor) / Spohn, Cassia (Committee member) / Holtfreter, Kristy (Committee member) / Arizona State University (Publisher)
Created2013
Description
Microbial electrochemical cells (MXCs) are promising platforms for bioenergy production from renewable resources. In these systems, specialized anode-respiring bacteria (ARB) deliver electrons from oxidation of organic substrates to the anode of an MXC. While much progress has been made in understanding the microbiology, physiology, and electrochemistry of well-studied model ARB such as Geobacter and Shewanella, tremendous potential exists for MXCs as microbiological platforms for exploring novel ARB. This dissertation introduces approaches for selective enrichment and characterization of phototrophic, halophilic, and alkaliphilic ARB. An enrichment scheme based on manipulation of poised anode potential, light, and nutrient availability led to current generation that responded negatively to light. Analysis of phototrophically enriched communities suggested essential roles for green sulfur bacteria and halophilic ARB in electricity generation. Reconstruction of light-responsive current generation could be successfully achieved using cocultures of anode-respiring Geobacter and phototrophic Chlorobium isolated from the MXC enrichments. Experiments lacking exogenously supplied organic electron donors indicated that Geobacter could produce a measurable current from stored photosynthate in the dark. Community analysis of phototrophic enrichments also identified members of the novel genus Geoalkalibacter as potential ARB. Electrochemical characterization of two haloalkaliphilic, non-phototrophic Geoalkalibacter spp. showed that these bacteria were in fact capable of producing high current densities (4-8 A/m2) and using higher organic substrates under saline or alkaline conditions. The success of these selective enrichment approaches and community analyses in identifying and understanding novel ARB capabilities invites further use of MXCs as robust platforms for fundamental microbiological investigations.
ContributorsBadalamenti, Jonathan P (Author) / Krajmalnik-Brown, Rosa (Thesis advisor) / Garcia-Pichel, Ferran (Committee member) / Rittmann, Bruce E. (Committee member) / Torres, César I (Committee member) / Vermaas, Willem (Committee member) / Arizona State University (Publisher)
Created2013
Description
The study of non-U.S. citizens in criminal justice system outcomes has often been neglected in the sentencing literature. When citizenship is considered, there are generally no distinctions made within this group. The research fails to consider differences according to legal status, race/ethnicity, nationality and other distinctive markers that might play a role in sentencing outcomes. Using federal sentencing data collected by the United States Sentencing Commission for fiscal year 2006 through fiscal year 2008, this study examines the effect of offender citizenship status, legal status, and national origin on the likelihood of imprisonment and length of imprisonment for offenders convicted of drug offenses. The current study considers differences among foreign-born and Latino immigrant subgroups (e.g., Colombian, Cuban, Dominican, and Mexican nationals). The key findings in this dissertation include: (1) non-U.S. citizens have greater odds of imprisonment than U.S. citizens. However, non-U.S. citizen offenders receive significantly shorter prison terms relative to U.S. citizen offenders; (2) undocumented immigrants are more likely to be incarcerated compared to similarly situated authorized immigrants and U.S. citizens. However, legal status does not have an effect on sentence length; and (3) with respect to national origin, Mexican nationals are significantly more likely than Colombians to be incarcerated and are given significantly longer prison sentences than Dominican nationals. The implications of these findings and future research are addressed in the concluding chapter.
ContributorsValadez, Mercedes (Author) / Spohn, Cassia (Thesis advisor) / Wang, Xia (Committee member) / Wright, Kevin (Committee member) / Arizona State University (Publisher)
Created2013
Description
Human activity has increased loading of reactive nitrogen (N) in the environment, with important and often deleterious impacts on biodiversity, climate, and human health. Since the fate of N in the ecosystem is mainly controlled by microorganisms, understanding the factors that shape microbial communities becomes relevant and urgent. In arid land soils, these microbial communities and factors are not well understood. I aimed to study the role of N cycling microbes, such as the ammonia-oxidizing bacteria (AOB), the recently discovered ammonia-oxidizing archaea (AOA), and various fungal groups, in soils of arid lands. I also tested if niche differentiation among microbial populations is a driver of differential biogeochemical outcomes. I found that N cycling microbial communities in arid lands are structured by environmental factors to a stronger degree than what is generally observed in mesic systems. For example, in biological soil crusts, temperature selected for AOA in warmer deserts and for AOB in colder deserts. Land-use change also affects niche differentiation, with fungi being the major agents of N2O production in natural arid lands, whereas emissions could be attributed to bacteria in mesic urban lawns. By contrast, NO3- production in the native desert and managed soils was mainly controlled by autotrophic microbes (i.e., AOB and AOA) rather than by heterotrophic fungi. I could also determine that AOA surprisingly responded positively to inorganic N availability in both short (one month) and long-term (seven years) experimental manipulations in an arid land soil, while environmental N enrichment in other ecosystem types is known to favor AOB over AOA. This work improves our predictions of ecosystem response to anthropogenic N increase and shows that paradigms derived from mesic systems are not always applicable to arid lands. My dissertation also highlights the unique ecology of ammonia oxidizers and draws attention to the importance of N cycling in desert soils.
ContributorsMarusenko, Yevgeniy (Author) / Hall, Sharon J (Thesis advisor) / Garcia-Pichel, Ferran (Thesis advisor) / Mclain, Jean E (Committee member) / Schwartz, Egbert (Committee member) / Arizona State University (Publisher)
Created2013
Description
Criminologists have directed significant theoretical and empirical attention toward the institution of marriage over the past two decades. Importantly, the momentum guiding this line of research has increased despite the fact that people are getting married far less often and much later in the life course than in any point in American history. The aim of this dissertation is to address this disconnect by focusing attention to nonmarital romantic relationships and their instability during emerging adulthood. To do so, it uses data from the Pathways to Desistance Study, a longitudinal study of 1,354 at-risk males and females who were adjudicated from the juvenile and adult systems in Phoenix and Philadelphia between 2000 and 2003. The project focuses attention to the following issues: (1) the effect of romantic dissolution on aggressive and income-based offenses; (2) the extent to which strain
egative emotionality and peer influence/exposure account for the effect of romantic dissolution on crime; and (3) the extent to which certain relationship and individual circumstances moderate the effect of romantic dissolution. The models reveal a few key findings. First, romantic dissolution is strongly related to an increase in both aggressive and income-based crime, but is more strongly related to income-based crime. Second, the effect of romantic dissolution is reduced when measures of strain
egative emotionality and peer influence/exposure measures are added to models, but the peer influence/exposure measures account for the strongest reduction. Finally, romantic dissolution does not serve as a positive life event among these at-risk youth, but its effect is exacerbated under a number of contexts (e.g. when an individual is unemployed). This study closes with a summary of these findings as well as its key limitations, and offers insight into potential policy implications and avenues of future research.
egative emotionality and peer influence/exposure account for the effect of romantic dissolution on crime; and (3) the extent to which certain relationship and individual circumstances moderate the effect of romantic dissolution. The models reveal a few key findings. First, romantic dissolution is strongly related to an increase in both aggressive and income-based crime, but is more strongly related to income-based crime. Second, the effect of romantic dissolution is reduced when measures of strain
egative emotionality and peer influence/exposure measures are added to models, but the peer influence/exposure measures account for the strongest reduction. Finally, romantic dissolution does not serve as a positive life event among these at-risk youth, but its effect is exacerbated under a number of contexts (e.g. when an individual is unemployed). This study closes with a summary of these findings as well as its key limitations, and offers insight into potential policy implications and avenues of future research.
ContributorsLarson, Matthew Joseph (Author) / Sweeten, Gary (Thesis advisor) / Piquero, Alex (Committee member) / Spohn, Cassia (Committee member) / Wallace, Danielle (Committee member) / Arizona State University (Publisher)
Created2013
Description
Biological soil crusts (BSCs), topsoil microbial assemblages typical of arid land ecosystems, provide essential ecosystem services such as soil fertilization and stabilization against erosion. Cyanobacteria and lichens, sometimes mosses, drive BSC as primary producers, but metabolic activity is restricted to periods of hydration associated with precipitation. Climate models for the SW United States predict changes in precipitation frequency as a major outcome of global warming, even if models differ on the sign and magnitude of the change. BSC organisms are clearly well adapted to withstand desiccation and prolonged drought, but it is unknown if and how an alteration of the precipitation frequency may impact community composition, diversity, and ecosystem functions. To test this, we set up a BSC microcosm experiment with variable precipitation frequency treatments using a local, cyanobacteria-dominated, early-succession BSC maintained under controlled conditions in a greenhouse. Precipitation pulse size was kept constant but 11 different drought intervals were imposed, ranging between 416 to 3 days, during a period of 416 days. At the end of the experiments, bacterial community composition was analyzed by pyrosequencing of the 16s rRNA genes in the community, and a battery of functional assays were used to evaluate carbon and nitrogen cycling potentials. While changes in community composition were neither marked nor consistent at the Phylum level, there was a significant trend of decreased diversity with increasing precipitation frequency, and we detected particular bacterial phylotypes that responded to the frequency of precipitation in a consistent manner (either positively or negatively). A significant trend of increased respiration with increasingly long drought period was detected, but BSC could recover quickly from this effect. Gross photosynthesis, nitrification and denitrification remained essentially impervious to treatment. These results are consistent with the notion that BSC community structure adjustments sufficed to provide significant functional resilience, and allow us to predict that future alterations in precipitation frequency are unlikely to result in severe impacts to BSC biology or ecological relevance.
ContributorsMyers, Natalie Kristine (Author) / Garcia-Pichel, Ferran (Thesis advisor) / Hall, Sharon (Committee member) / Turner, Benjamin (Committee member) / Krajmalnik-Brown, Rosa (Committee member) / Arizona State University (Publisher)
Created2013
Description
The purpose of this project is to better understand the factors associated with, and effects of, prison visitation for children during maternal and paternal incarceration. As gatekeepers, caregivers play a pivotal role in the facilitation of parent-child prison visitation. Yet, some caregivers may be more likely to take children to visit than others. Additionally, among those children who do visit, visitation may be positive in some ways and negative in others. To advance prior work, this study (1) assesses the relationship between caregiver type and parent-child prison visitation and (2) investigates the emotional and behavioral responses of children who visit. The current research uses mixed-methods and is carried out in two phases. For Phase 1, quantitative data on 984 children collected from structured interviews with incarcerated parents (N=279 mothers; N=143 fathers) in the Arizona Department of Corrections are used to examine the relationship between caregiver type and the likelihood of parent-child prison visitation. Descriptive statistics and logistic regression analyses are conducted separately for maternal and paternal incarceration. Phase 2 draws on caregivers' accounts of 40 children who visit their parent in prison to assess children's emotional and behavioral reactions to visitation. Data are coded to identify positive and negative responses, "visitation paradox" indicators, prior life circumstances and child age. Thematic content analyses are conducted to capture major themes. Analyses from Phase 1 confirm a significant relationship between caregiver type and mother-child and father-child visitation. Other factors that affected the likelihood of parental visitation included child situational factors, parent stressors, institutional barriers and child demographics, although these effects differed depending upon which parent was in prison. Results from Phase 2 revealed overwhelmingly negative responses among children to parental prison visitation. Key themes that accounted for child reactions included institutional context and parental attachment. This research adds to the collateral consequences of incarceration literature by providing greater insight into the imprisonment experience for vulnerable families. Further, these results have direct implications for correctional policy and practice pertaining to the manner and regulation of prison visits and also inform reentry efforts through a family-centric approach.
ContributorsTasca, Melinda (Author) / Rodriguez, Nancy (Thesis advisor) / Spohn, Cassia (Committee member) / Zatz, Marjorie S (Committee member) / Arizona State University (Publisher)
Created2014
Improving cyanobacterial hydrogen production through bioprospecting of natural microbial communities
Description
Some cyanobacteria can generate hydrogen (H2) under certain physiological conditions and are considered potential agents for biohydrogen production. However, they also present low amounts of H2 production, a reaction reversal towards H2 consumption, and O2 sensitivity. Most attempts to improve H2 production have involved genetic or metabolic engineering approaches. I used a bio-prospecting approach instead to find novel strains that are naturally more apt for biohydrogen production. A set of 36, phylogenetically diverse strains isolated from terrestrial, freshwater and marine environments were probed for their potential to produce H2 from excess reductant. Two distinct patterns in H2 production were detected. Strains displaying Pattern 1, as previously known from Synechocystis sp. PCC 6803, produced H2 only temporarily, reverting to H2 consumption within a short time and after reaching only moderately high H2 concentrations. By contrast, Pattern 2 cyanobacteria, in the genera Lyngbya and Microcoleus, displayed high production rates, did not reverse the direction of the reaction and reached much higher steady-state H2 concentrations. L. aestuarii BL J, an isolate from marine intertidal mats, had the fastest production rates and reached the highest steady-state concentrations, 15-fold higher than that observed in Synechocystis sp. PCC 6803. Because all Pattern 2 strains originated in intertidal microbial mats that become anoxic in dark, it was hypothesized that their strong hydrogenogenic capacity may have evolved to aid in fermentation of the photosynthate. When forced to ferment, these cyanobacteria display similarly desirable characteristics of physiological H2 production. Again, L. aestuarii BL J had the fastest specific rates and attained the highest H2 concentrations during fermentation, which proceeded via a mixed-acid pathway to yield acetate, ethanol, lactate, H2, CO2 and pyruvate. The genome of L. aestuarii BL J was sequenced and bioinformatically compared to other cyanobacterial genomes to ascertain any potential genetic or structural basis for powerful H2 production. The association hcp exclusively in Pattern 2 strains suggests its possible role in increased H2 production. This study demonstrates the value of bioprospecting approaches to biotechnology, pointing to the strain L. aestuarii BL J as a source of useful genetic information or as a potential platform for biohydrogen production.
ContributorsKothari, Ankita (Author) / Garcia-Pichel, Ferran (Thesis advisor) / Vermaas, Willem F J (Committee member) / Rittmann, Bruce (Committee member) / Torres, Cesar (Committee member) / Arizona State University (Publisher)
Created2013
Description
The purpose of this preliminary study is to determine if sentencing disparities exist between male and female teachers who have been convicted of sexual misconduct with a student in Maricopa County, Arizona over a ten-year period. The hypothesis is that male teachers convicted of sexual misconduct with a student will receive harsher punishment than their female counterparts. In addition, this research will analyze the sentencing decisions of Arizona judges and prosecutors through plea-bargaining when compared with the presumptive sentence set by the Arizona Legislature. Issues that will be addressed include: a brief review of gender disparities in sentencing, sex offender sentencing, Arizona's rules of criminal procedure, and a review of the Arizona Revised Statutes pertaining to sexual crimes as well as the Arizona Supreme Court sentencing guidelines. The data set consists of fifteen different Maricopa County teachers who committed a sexual offense against a student and were convicted of that offense from February 2000 through September 2009. According to the results of this study, male teachers do receive harsher penalties than their female counterparts within Maricopa County.
ContributorsSimmon, Christopher (Author) / Holtfreter, Kristy (Thesis advisor) / Wright, Kevin (Committee member) / Spohn, Cassia (Committee member) / Arizona State University (Publisher)
Created2012