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- Creators: Arizona State University
- Creators: Anbar, Ariel
- Status: Published
Description
Phosphorus (P), an essential element for life, is becoming increasingly scarce, and its global management presents a serious challenge. As urban environments dominate the landscape, we need to elucidate how P cycles in urban ecosystems to better understand how cities contribute to — and provide opportunities to solve — problems of P management. The goal of my research was to increase our understanding of urban P cycling in the context of urban resource management through analysis of existing ecological and socio-economic data supplemented with expert interviews in order to facilitate a transition to sustainable P management. Study objectives were to: I) Quantify and map P stocks and flows in the Phoenix metropolitan area and analyze the drivers of spatial distribution and dynamics of P flows; II) examine changes in P-flow dynamics at the urban agricultural interface (UAI), and the drivers of those changes, between 1978 and 2008; III) compare the UAI's average annual P budget to the global agricultural P budget; and IV) explore opportunities for more sustainable P management in Phoenix. Results showed that Phoenix is a sink for P, and that agriculture played a primary role in the dynamics of P cycling. Internal P dynamics at the UAI shifted over the 30-year study period, with alfalfa replacing cotton as the main locus of agricultural P cycling. Results also suggest that the extent of P recycling in Phoenix is proportionally larger than comparable estimates available at the global scale due to the biophysical characteristics of the region and the proximity of various land uses. Uncertainty remains about the effectiveness of current recycling strategies and about best management strategies for the future because we do not have sufficient data to use as basis for evaluation and decision-making. By working in collaboration with practitioners, researchers can overcome some of these data limitations to develop a deeper understanding of the complexities of P dynamics and the range of options available to sustainably manage P. There is also a need to better connect P management with that of other resources, notably water and other nutrients, in order to sustainably manage cities.
ContributorsMetson, Genevieve (Author) / Childers, Daniel (Thesis advisor) / Aggarwal, Rimjhim (Thesis advisor) / Redman, Charles (Committee member) / Arizona State University (Publisher)
Created2011
Description
The under-representation of women in science, technology, engineering and mathematics (STEM) fields indicates the presence of gender related barriers that impacted the persistence of women in science and engineering doctoral studies. The purpose of this study was to investigate the barriers of women doctoral students in STEM fields which identified supporting factors for them as well. This study also tried to determine if there was any difference in perceiving barriers among three disciplines - engineering, life sciences and natural sciences. An online questionnaire (19 Likert-type questions and one open-ended question) was sent to women STEM doctoral students studying at the Arizona State University (ASU). Questions were based on some factors which might act as obstacles or supports during their doctoral studies. Both quantitative and qualitative analyses were conducted. Factors such as work-life balance, time-management, low self-confidence, lack of female role model, fewer numbers of women in science and engineering classes, and male dominated environment revealed as significant barriers according to both the analyses but factors such as difficulty with the curriculum, gender discrimination, and two-career problem were chosen as barriers only in the free response question. Positive treatment from advisor, family support, availability of funding, and absence of sexual harassment assisted these women continuing their PhD programs at ASU. However, no significant difference was observed with respect to perceiving barriers among the three groups mentioned above. Recommendations for change in science and engineering curricula and active recruitment of female faculty are discussed to reduce or at best to remove the barriers and how to facilitate participation and retention of more women in STEM fields especially at the doctoral level.
ContributorsChaudhuri, Dola (Author) / Baker, Dale (Thesis advisor) / Sandlin, Jennifer (Committee member) / Edwards, Vicki (Committee member) / Arizona State University (Publisher)
Created2011
Description
Molybdenum (Mo) is a key trace nutrient for biological assimilation of nitrogen, either as nitrogen gas (N2) or nitrate (NO3-). Although Mo is the most abundant metal in seawater (105 nM), its concentration is low (<5 nM) in most freshwaters today, and it was scarce in the ocean before 600 million years ago. The use of Mo for nitrogen assimilation can be understood in terms of the changing Mo availability through time; for instance, the higher Mo content of eukaryotic vs. prokaryotic nitrate reductase may have stalled proliferation of eukaryotes in low-Mo Proterozoic oceans. Field and laboratory experiments were performed to study Mo requirements for NO3- assimilation and N2 fixation, respectively. Molybdenum-nitrate addition experiments at Castle Lake, California revealed interannual and depth variability in plankton community response, perhaps resulting from differences in species composition and/or ammonium availability. Furthermore, lake sediments were elevated in Mo compared to soils and bedrock in the watershed. Box modeling suggested that the largest source of Mo to the lake was particulate matter from the watershed. Month-long laboratory experiments with heterocystous cyanobacteria (HC) showed that <1 nM Mo led to low N2 fixation rates, while 10 nM Mo was sufficient for optimal rates. At 1500 nM Mo, freshwater HC hyperaccumulated Mo intercellularly, whereas coastal HC did not. These differences in storage capacity were likely due to the presence in freshwater HC of the small molybdate-binding protein, Mop, and its absence in coastal and marine cyanobacterial species. Expression of the mop gene was regulated by Mo availability in the freshwater HC species Nostoc sp. PCC 7120. Under low Mo (<1 nM) conditions, mop gene expression was up-regulated compared to higher Mo (150 and 3000 nM) treatments, but the subunit composition of the Mop protein changed, suggesting that Mop does not bind Mo in the same manner at <1 nM Mo that it can at higher Mo concentrations. These findings support a role for Mop as a Mo storage protein in HC and suggest that freshwater HC control Mo cellular homeostasis at the post-translational level. Mop's widespread distribution in prokaryotes lends support to the theory that it may be an ancient protein inherited from low-Mo Precambrian oceans.
ContributorsGlass, Jennifer (Author) / Anbar, Ariel D (Thesis advisor) / Shock, Everett L (Committee member) / Jones, Anne K (Committee member) / Hartnett, Hilairy E (Committee member) / Elser, James J (Committee member) / Fromme, Petra (Committee member) / Arizona State University (Publisher)
Created2011
Description
The nature of science (NOS) is included in the National Science Education Standards and is described as a critical component in the development of scientifically literate students. Despite the significance of NOS in science education reform, research shows that many students continue to possess naïve views of NOS. Explicit and reflective discussion as an instructional approach is relatively new in the field of research in NOS. When compared to other approaches, explicit instruction has been identified as more effective in promoting informed views of NOS, but gaps in student understanding still exist. The purpose of this study was to deepen the understanding of student learning of NOS through the investigation of two variations of explicit instruction. The subjects of the study were two seventh grade classes taught by the same classroom teacher. One class received explicit instruction of NOS within a plate tectonics unit and the second class received explicit instruction of NOS within a plate tectonics unit plus supporting activities focused on specific aspects of NOS. The instruction time for both classes was equalized and took place over a three week time period. The intention of this study was to see if the additional NOS activities helped students build a deeper understanding of NOS, or if a deep understanding could be formed solely through explicit and reflective discussion within content instruction. The results of the study showed that both classes progressed in their understanding of NOS. When the results of the two groups were compared, the group with the additional activities showed statistically significant gains on two of the four aspects of NOS assessed. These results suggest that the activities may have been valuable in promoting informed views, but more research is needed in this area.
ContributorsMelville, Melissa (Author) / Luft, Julie (Thesis advisor) / Baker, Dale (Committee member) / Brem, Sarah (Committee member) / Arizona State University (Publisher)
Created2011
Description
ABSTRACT Early career science teachers are often assigned to classrooms with high numbers of English language learners (ELL students). As these teachers learn to become effective practitioners, the circumstances surrounding them merit a thorough examination. This study examines the longitudinal changes in Pedagogical Content Knowledge (PCK) and practices of six early career science teachers who taught in urban schools. The teachers participated in the Alternative Support for Induction Science Teachers (ASIST) program during their initial two years of teaching. Our research team followed the participants over a five-year period. This study focuses on data from Years 1, 3, and 5. The data collected included classroom observations and interviews. In addition, classroom artifacts were collected periodically for the purpose of triangulation. The analysis of the data revealed that with the support of the ASIST program, the teachers implemented inquiry lessons and utilized instructional materials that promoted academic language skills and science competencies among their ELL students. Conversely, standardized testing, teaching assignment, and school culture played a role in constraining the implementation of inquiry-based practices. The results of this study call for collaborative efforts among university science educators and school administrators to provide professional development opportunities and support for the implementation of inquiry and language practices among early career science teachers of ELL students.
ContributorsOrtega, Irasema (Author) / Luft, Julie A (Thesis advisor) / Artiles, Alfredo (Committee member) / Baker, Dale R. (Committee member) / Arizona State University (Publisher)
Created2011
Description
ABSTRACT For more than thirty years the gender gap in science and related careers has been a key concern of researchers, teachers, professional organizations, and policy makers. Despite indicators of progress for women and girls on some measures of achievement, course enrollment patterns, and employment, fewer women than men pursue college degrees and careers in science, technology, engineering, and mathematics. According to the results of national assessments, the gender gap in science achievement begins to be evident in the middle school years. Gender and school science achievement involve a complex set of factors associated with schools and child/family systems that may include school leadership, institutional practices, curriculum content, teacher training programs, teacher expectations, student interests, parental involvement, and cultural values. This ethnographic case study was designed to explore the context for science education reform and the participation of middle school girls. The study analyzed and compared teaching strategies and female student engagement in sixth, seventh, and eighth grade science classrooms. The setting was a middle school situated in a district that was well-known for its achievement in reading, math, and technology. Findings from the study indicated that while classroom instruction was predominantly organized around traditional school science, the girls were more disciplined and outperformed the boys. The size of the classrooms, time to prepare for hands-on activities, and obtaining resources were identified as barriers to teaching science in ways that aligned with recent national science reform initiatives. Parents who participated in the study were very supportive of their daughters' academic progress and career goals. A few of the parents suggested that the school's science program include more hands-on activities; instruction designed for the advanced learner; and information related to future careers. Overall the teachers and students perceived their science program to be gender fair. Eighth grade participants who had career goals related to science and engineering, indicated that their science instruction did not provide the rigor they needed to improve their critical skills for advanced placement in high school. Recommendations include the need for professional development on inquiry-based science, equitable student achievement, and diverse perspectives in science education.
ContributorsSmiley, Bettie (Author) / Powers, Jeanne M. (Thesis advisor) / Appleton, Nicholas (Committee member) / Macey, Donna (Committee member) / Arizona State University (Publisher)
Created2011
Description
Conceptual change has been a large part of science education research for several decades due to the fact that it allows teachers to think about what students' preconceptions are and how to change these to the correct scientific conceptions. To have students change their preconceptions teachers need to allow students to confront what they think they know in the presence of the phenomena. Students then collect and analyze evidence pertaining to the phenomena. The goal in the end is for students to reorganize their concepts and change or correct their preconceptions, so that they hold more accurate scientific conceptions. The purpose of this study was to investigate how students' conceptions of the Earth's surface, specifically weathering and erosion, change using the conceptual change framework to guide the instructional decisions. The subjects of the study were a class of 25 seventh grade students. This class received a three-week unit on weathering and erosion that was structured using the conceptual change framework set by Posner, Strike, Hewson, and Gertzog (1982). This framework starts by looking at students' misconceptions, then uses scientific data that students collect to confront their misconceptions. The changes in students' conceptions were measured by a pre concept sketch and post concept sketch. The results of this study showed that the conceptual change framework can modify students' preconceptions of weathering and erosion to correct scientific conceptions. There was statistical significant difference between students' pre concept sketches and post concept sketches scores. After examining the concept sketches, differences were found in how students' concepts had changed from pre to post concept sketch. Further research needs to be done with conceptual change and the geosciences to see if conceptual change is an effective method to use to teach students about the geosciences.
ContributorsTillman, Ashley (Author) / Luft, Julie (Thesis advisor) / Middleton, James (Committee member) / Semken, Steven (Committee member) / Arizona State University (Publisher)
Created2011
Description
Fibromyalgia (FM) is a chronic musculoskeletal disorder characterized by widespread pain, fatigue, and a variety of other comorbid physiological and psychological characteristics, including a deficit of positive affect. Recently, the focus of research on the pathophysiology of FM has considered the role of a number of genomic variants. In the current manuscript, case-control analyses did not support the hypothesis that FM patients would differ from other chronic pain groups in catechol-O-methyltransferase (COMT) and mu-opioid receptor (OPRM1) genotype. However, evidence is provided in support of the hypothesis that functional single nucleotide polymorphisms on the COMT and OPRM1 genes would be associated with risk and resilience, respectively, in a dual processing model of pain-related positive affective regulation in FM. Forty-six female patients with a physician-confirmed diagnosis of FM completed an electronic diary that included once-daily assessments of positive affect and soft tissue pain. Multilevel modeling yielded a significant gene X environment interaction, such that individuals with met/met genotype on COMT experienced a greater decline in positive affect as daily pain increased than did either val/met or val/val individuals. A gene X environment interaction for OPRM1 also emerged, indicating that individuals with at least one asp allele were more resilient to elevations in daily pain than those homozygous for the asn allele. In sum, the findings offer researchers ample reason to further investigate the contribution of the catecholamine and opioid systems, and their associated genomic variants, to the still poorly understood experience of FM.
ContributorsFinan, Patrick Hamilton (Author) / Zautra, Alex (Thesis advisor) / Davis, Mary (Committee member) / Lemery-Chalfant, Kathryn (Committee member) / Presson, Clark (Committee member) / Arizona State University (Publisher)
Created2011
Description
The purpose of this study was to analyze the impact of a context-based teaching approach (STS) versus a more traditional textbook approach on the attitudes and achievement of community college chemistry students. In studying attitudes toward chemistry within this study, I used a 30-item Likert scale in order to study the importance of chemistry in students' lives, the importance of chemistry, the difficulty of chemistry, interest in chemistry, and the usefulness of chemistry for their future career. Though the STS approach students had higher attitude post scores, there was no significant difference between the STS and textbook students' attitude post scores. It was noted that females had higher postattitude scores in the STS group, while males had higher postattitude scores in the textbook group. With regard to postachievement, I noted that males had higher scores in both groups. A correlation existed between postattitude and postachievement in the STS classroom. In summary, while an association between attitude and achievement was found in the STS classroom, teaching approach or sex was not found to influence attitudes, while sex was also not found to influence achievement. These results, overall, suggest that attitudes are not expected to change on the basis of either teaching approach or gender, and that techniques other than changing the teaching approach would need to be used in order to improve the attitudes of students. Qualitative analysis of an online discussion activity on Energy revealed that STS students were able to apply aspects of chemistry in decision making related to socioscientific issues. Additional analysis of interview and written responses provided insight regarding attitudes toward chemistry, with respect to topics of applicability of chemistry to life, difficulties with chemistry, teaching approach for chemistry, and the intent for enrolling in additional chemistry courses. In addition, the surveys of female students brought out subcategories with regard to emotional and professional characteristics of a good teacher, under the category of characteristics of teaching approach. With respect to the category of course experience, subcategories of useful knowledge to solve real-life problems and knowledge for future career were revealed. The differences between the control group females and STS group females with respect to these characteristics was striking and threw insight into how teacher behavior and teaching approach shape student attitudes to chemistry in case of female students.
ContributorsPerkins, Gita (Author) / Baker, Dale R. (Thesis advisor) / Sloane, Finbarr (Committee member) / Marsh, Josephine P (Committee member) / Arizona State University (Publisher)
Created2011
Description
An understanding of the Nature of Science (NOS) remains a fundamental goal of science education in the Unites States. A developed understanding of NOS provides a framework in which to situate science knowledge. Secondary science teachers play a critical role in providing students with an introduction to understanding NOS. Unfortunately, due to the high turnover rates of secondary science teachers in the United States, this critical role is often filled by relatively novice teachers. These beginning secondary science teachers make instructional decisions regarding science that are drawn from their emerging knowledge base, including a tentative understanding of NOS. This tentative knowledge can be affected by environment and culture of the classroom, school, and district in which beginning teachers find themselves. When examining NOS among preservice and beginning teachers the background and demographics of the teachers are often ignored. These teachers are treated as a homogenous block in terms of their initial understanding of NOS. This oversight potentially ignores interactions that may happen over time as teachers cross the border from college students, preservice teachers, and scientists into the classroom environment. Through Symbolic Interactionism we can explain how teachers change in order to adapt to their new surroundings and how this adaptation may be detrimental to their understanding of NOS and ultimately to their practice. 63 teachers drawn from a larger National Science Foundation (NSF) funded study were interviewed about their understanding of NOS over three years. Several demographic factors including college major, preservice program, number of History and Philosophy of Science classes, and highest academic degree achieve were shown to have an affect on the understanding of NOS over time. In addition, over time, the teachers tended to 'converge' in their understanding of NOS regardless of preservice experiences or induction support. Both the affect of different demographics amongst teachers and the 'converging' aspect of their understanding of NOS provide much needed insight for teacher trainers, mentors, and researchers.
ContributorsFirestone, Jonah B (Author) / Luft, Julie A (Thesis advisor) / Baker, Dale (Committee member) / Perry, Ronald (Committee member) / Arizona State University (Publisher)
Created2011