Matching Items (45,029)
Description
In this work, a novel method is developed for making nano- and micro- fibrous hydrogels capable of preventing the rejection of implanted materials. This is achieved by either (1) mimicking the native cellular environment, to exert fine control over the cellular response or (2) acting as a protective barrier, to camouflage the foreign nature of a material and evade recognition by the immune system. Comprehensive characterization and in vitro studies described here provide a foundation for developing substrates for use in clinical applications. Hydrogel dextran and poly(acrylic acid) (PAA) fibers are formed via electrospinning, in sizes ranging from nanometers to microns in diameter. While "as-electrospun" fibers are continuous in length, sonication is used to fragment fibers into short fiber "bristles" and generate nano- and micro- fibrous surface coatings over a wide range of topographies. Dex-PAA fibrous surfaces are chemically modified, and then optimized and characterized for non-fouling and ECM-mimetic properties. The non-fouling nature of fibers is verified, and cell culture studies show differential responses dependent upon chemical, topographical and mechanical properties. Dex-PAA fibers are advantageously unique in that (1) a fine degree of control is possible over three significant parameters critical for modifying cellular response: topography, chemistry and mechanical properties, over a range emulating that of native cellular environments, (2) the innate nature of the material is non-fouling, providing an inert background for adding back specific bioactive functionality, and (3) the fibers can be applied as a surface coating or comprise the scaffold itself. This is the first reported work of dex-PAA hydrogel fibers formed via electrospinning and thermal cross-linking, and unique to this method, no toxic solvents or cross-linking agents are needed to create hydrogels or for surface attachment. This is also the first reported work of using sonication to fragment electrospun hydrogel fibers, and in which surface coatings were made via simple electrostatic interaction and dehydration. These versatile features enable fibrous surface coatings to be applied to virtually any material. Results of this research broadly impact the design of biomaterials which contact cells in the body by directing the consequent cell-material interaction.
ContributorsLouie, Katherine BoYook (Author) / Massia, Stephen P (Thesis advisor) / Bennett, Kevin (Committee member) / Garcia, Antonio (Committee member) / Pauken, Christine (Committee member) / Vernon, Brent (Committee member) / Arizona State University (Publisher)
Created2011
Description
This study utilized symbolic interaction as a framework to examine the impact of mobility on four veteran elementary general music teachers' identities, roles, and perceptions of role support. Previous research has focused on teacher identity formation among preservice and novice teachers; veteran teachers are less frequently represented in the literature. Teacher mobility research has focused on student achievement, teachers' reasons for moving, and teacher attrition. The impact of mobility on veteran teachers' identities, roles, and perceptions of role support has yet to be considered. A multiple case design was employed for this study. The criteria for purposeful selection of the participants were elementary general music teachers who had taught for at least ten years, who had changed teaching contracts and taught in at least two different schools, and who were viewed as effective music educators by fine arts coordinators. Data were collected over a period of eight months through semi-structured interviews, email correspondence, observations, review of videotapes of the participants' teaching in previous schools, and collection of artifacts. Data were analyzed within and across cases. The cross-case analysis revealed themes within the categories of identity, role, and role support for the participants. The findings suggest that the participants perceived their music teacher roles as multi-dimensional. They claimed their core identities remained stable over time; however, shifts in teacher identity occurred throughout their years as teachers. The participants asserted that mobility at the start of their careers had a positive impact because they each were challenged to solidify their own teacher identities and music teacher roles in varied school contexts. Mobility negatively impacted role and teacher practices during times when the participants adjusted to new school climates and role expectations. Role support varied depending upon school context, and the participants discovered active involvement in the school community was an effective means of seeking and acquiring role support. Reflection experiences in music teacher preparation programs, as well as mentoring and professional development geared toward teacher identity formation and role maturation, may assist teachers in matching their desired school context with their teacher identities and perceptions of the music teacher role.
ContributorsGray, Lori F (Author) / Stauffer, Sandra (Committee member) / Schmidt, Margaret (Committee member) / Sullivan, Jill (Committee member) / Bush, Jeffrey (Committee member) / Tobias, Evan (Committee member) / Arizona State University (Publisher)
Created2011
Description
In this study, I examined how African American students in a church youth group constructed ethnic and spiritual identities as they engaged with community literacy practices. Arizona's small, scattered population of African Americans is reflected within participants' multi-ethnic schools where they describe feelings of being almost invisible to school agents and peers. Listening to students, I came to deeply understand how they struggled with cultural isolation and racial discrimination. The growing tensions with state immigration reform only magnified those feelings as participants perceived the ban on ethnic studies to be another attempt to exclude them from school curriculums. By using utilizing four identity types, I gained greater insights into participants' negotiation of ethnicity and spirituality. Drawing from critical race theory, I utilized counter-storytelling to not only recapture participants' experiences with social injustice, but also to illustrate how the youth group empowers the students to become activists. Resisting the paralyzing effects of racial stereotypes, participants emerged as essayists, artists, orators, and spoken word poets.
ContributorsNicholson, Cynthia Salley (Author) / Paris, Django (Thesis advisor) / Nilsen, Alleen (Committee member) / Stanfield, John H. (Committee member) / Arizona State University (Publisher)
Created2011
Description
Infectious diseases are a leading cause of death worldwide. With the development of drugs, vaccines and antibiotics, it was believed that for the first time in human history diseases would no longer be a major cause of mortality. Newly emerging diseases, re-emerging diseases and the emergence of microorganisms resistant to existing treatment have forced us to re-evaluate our optimistic perspective. In this study, a simple mathematical framework for super-infection is considered in order to explore the transmission dynamics of drug-resistance. Through its theoretical analysis, we identify the conditions necessary for the coexistence between sensitive strains and drug-resistant strains. Farther, in order to investigate the effectiveness of control measures, the model is extended so as to include vaccination and treatment. The impact that these preventive and control measures may have on its disease dynamics is evaluated. Theoretical results being confirmed via numerical simulations. Our theoretical results on two-strain drug-resistance models are applied in the context of Malaria, antimalarial drugs, and the administration of a possible partially effective vaccine. The objective is to develop a monitoring epidemiological framework that help evaluate the impact of antimalarial drugs and partially-effective vaccine in reducing the disease burden at the population level. Optimal control theory is applied in the context of this framework in order to assess the impact of time dependent cost-effective treatment efforts. It is shown that cost-effective combinations of treatment efforts depend on the population size, cost of implementing treatment controls, and the parameters of the model. We use these results to identify optimal control strategies for several scenarios.
ContributorsUrdapilleta, Alicia (Author) / Castillo-Chavez, Carlos (Thesis advisor) / Wang, Xiaohong (Thesis advisor) / Wirkus, Stephen (Committee member) / Camacho, Erika (Committee member) / Arizona State University (Publisher)
Created2011
Description
Intuitive decision making refers to decision making based on situational pattern recognition, which happens without deliberation. It is a fast and effortless process that occurs without complete awareness. Moreover, it is believed that implicit learning is one means by which a foundation for intuitive decision making is developed. Accordingly, the present study investigated several factors that affect implicit learning and the development of intuitive decision making in a simulated real-world environment: (1) simple versus complex situational patterns; (2) the diversity of the patterns to which an individual is exposed; (3) the underlying mechanisms. The results showed that simple patterns led to higher levels of implicit learning and intuitive decision-making accuracy than complex patterns; increased diversity enhanced implicit learning and intuitive decision-making accuracy; and an embodied mechanism, labeling, contributes to the development of intuitive decision making in a simulated real-world environment. The results suggest that simulated real-world environments can provide the basis for training intuitive decision making, that diversity is influential in the process of training intuitive decision making, and that labeling contributes to the development of intuitive decision making. These results are interpreted in the context of applied situations such as military applications involving remotely piloted aircraft.
ContributorsCovas-Smith, Christine Marie (Author) / Cooke, Nancy J. (Thesis advisor) / Patterson, Robert (Committee member) / Glenberg, Arthur (Committee member) / Homa, Donald (Committee member) / Arizona State University (Publisher)
Created2011
Description
Due to the growing concerns on the depletion of petroleum based energy resources and climate change; fuel cell technologies have received much attention in recent years. Proton exchange membrane fuel cell (PEMFCs) features high energy conversion efficiency and nearly zero greenhouse gas emissions, because of its combination of the hydrogen oxidation reaction (HOR) at anode side and oxygen reduction reaction (ORR) at cathode side. Synthesis of Pt nanoparticles supported on multi walled carbon nanotubes (MWCNTs) possess a highly durable electrochemical surface area (ESA) and show good power output on proton exchange membrane (PEM) fuel cell performance. Platinum on multi-walled carbon nanotubes (MWCNTs) support were synthesized by two different processes to transfer PtCl62- from aqueous to organic phase. While the first method of Pt/MWCNTs synthesis involved dodecane thiol (DDT) and octadecane thiol (ODT) as anchoring agent, the second method used ammonium lauryl sulfate (ALS) as the dispersion/anchoring agent. The particle size and distribution of platinum were examined by high-resolution transmission electron microscope (HRTEM). The TEM images showed homogenous distribution and uniform particle size of platinum deposited on the surface of MWCNTs. The single cell fuel cell performance of the Pt/MWCNTs synthesized thiols and ALS based electrode containing 0.2 (anode) and 0.4 mg (cathode) Pt.cm-2 were evaluated using Nafion-212 electrolyte with H2 and O2 gases at 80 oC and ambient pressure. The catalyst synthesis with ALS is relatively simple compared to that with thiols and also showed higher performance (power density reaches about 1070 mW.cm-2). The Electrodes with Pt/MWCNTs nanocatalysts synthesized using ALS were characterized by cyclic voltammetry (CV) for durability evaluation using humidified H2 and N2 gases at room temperature (21 oC) along with commercial Pt/C for comparison. The ESA measured by cyclic voltammetry between 0.15 and 1.2 V showed significant less degradation after 1000 cycles for ALS based Pt/MWCNTs.
ContributorsLiu, Xuan (Author) / Madakannan, Arunachalanadar (Thesis advisor) / Munukutla, Lakshmi (Committee member) / Tamizhmani, Govindasamy (Committee member) / Arizona State University (Publisher)
Created2011
Description
Previous research suggests that the relation between sport participation and alcohol use is positive, but small in size. Few explanations for this positive relation have been empirically tested. Theories denote that the relation between sport participation and alcohol use is explained by peers and that the relation varies based on the models adolescents are exposed to. This study tested mediators (popularity and friends' alcohol use) and moderators (sport-focus, teammates' alcohol use, gender, popularity, and friends' alcohol use) for the relation between sport participation and alcohol use. Analyses were conducted through path models in Mplus v5.1. The sample included 48,390 adolescents (mean age=15.8 years; 51% female) from the National Longitudinal Study of Adolescent Health. In the self-administered in-school questionnaire, adolescents reported on their activity participation, alcohol use, friendship nominations, and demographic characteristics. Friend indicators were based on friends' self-reported alcohol use. Results suggested that popularity mediated, but did not moderate the relation between sport participation and alcohol use. In contrast, friends' alcohol use moderated, but did not mediate this relation. The relation was positive and strongest for sport-focused adolescents, and for adolescents whose teammates and sport friends used high levels of alcohol. The findings of this study suggest athletes are at an elevated risk for alcohol use, but not all athletes drink. Peers are important predictors, such that, sport participation may be related to alcohol use, partially, because it promotes adolescents' social status. The sport context is also important, such that, athletes are more likely to use alcohol if they are highly involved in sports, and they have sport friends and teammates who drink. Specific types of athletes, such as popular athletes, should be targeted for alcohol use interventions. Intervention programs should also be designed to capture specific aspects of the sport context, such as teams without no tolerance substance use policies, and highly competitive or stressful sports.
ContributorsVest, Andrea Elaine (Author) / Simpkins, Sandra D. (Thesis advisor) / Updegraff, Kimberly A. (Committee member) / Schaefer, David R. (Committee member) / Arizona State University (Publisher)
Created2011
Description
This thesis describes several approaches to next generation DNA sequencing via tunneling current method based on a Scanning Tunneling Microscope system. In chapters 5 and 6, preliminary results have shown that DNA bases could be identified by their characteristic tunneling signals. Measurements taken in aqueous buffered solution showed that single base resolution could be achieved with economic setups. In chapter 7, it is illustrated that some ongoing measurements are indicating the sequence readout by making linear scan on a piece of short DNA oligomer. However, to overcome the difficulties of controlling DNA especially ssDNA movement, it is much better to have the tunneling measurement incorporated onto a robust nanopore device to realize sequential reading of the DNA sequence while it is being translocated.
ContributorsHuang, Shuo (Author) / Lindsay, Stuart (Thesis advisor) / Sankey, Otto (Committee member) / Tao, Nongjian (Committee member) / Drucker, Jeff (Committee member) / Ros, Robert (Committee member) / Arizona State University (Publisher)
Created2011
Description
The purpose of this study was to explore the relationship between childhood maltreatment and juvenile homicide offending. Specifically, this study compared a sample of maltreated male juvenile homicide offenders (N = 51) with non-maltreated male juvenile homicide offenders (N = 364) among the following areas: familial dysfunction and disorganization, mental health issues, academic functioning, prior delinquency, substance abuse and homicide-related crime characteristics. Data was obtained from the following aggregate sources: Supervision Risk Classification Instrument (SRCI), the State Attorney's Recommendation form (SAR), the Predisposition Report (PR), and the Massachusetts Juveniles Screening Instrument 2 (MAYSI-2). Chi square and t-tests were then utilized to compare the two groups and preform analyses. Maltreated male juvenile homicide offenders significantly differed from non-maltreated male juvenile homicide offenders in terms of familial dysfunction and disorganization, academic functioning, prior delinquency and homicide-related crime characteristics. As a result of these significant differences, tailored prevention and treatment efforts were discussed.
ContributorsJohnson, Whitney Randoll (Author) / Roe-Sepowitz, Dominique (Thesis advisor) / Krysik, Judy (Committee member) / Ashford, Jose (Committee member) / Arizona State University (Publisher)
Created2011
Description
This study examines the differences in demographic and life characteristics between transgender and female prostitutes in a prostitution diversion program and identifies specialized treatment and exiting strategies for transgender prostitutes. The purpose of this study was to develop a better understanding of the transgender experience in prostitution and to contribute to the descriptive literature. Participants were 465 individuals who were arrested for prostitution and attended a prostitution-focused diversion program. Differences found to be significant between transgender and female prostitutes included demographic characteristics, history of childhood sexual abuse, and experience of violence in prostitution. Implications for treatment, exiting strategies and future research are discussed.
ContributorsSchepel, Elizabeth (Author) / Roe-Sepowitz, Dominique (Thesis advisor) / Krysik, Judy (Committee member) / Androff, David (Committee member) / Arizona State University (Publisher)
Created2011