Now showing items 21-40 of 50

    • 22nd Annual Student Showcase Program (2014)

      Graduate & Professional Student Council (GPSC) (The University of Arizona (Tucson, AZ), 2014-11)
    • Non-parents recover faster than parents following divorce

      Rojo-Wissar, Darlynn M.; Dawson, Spencer C.; Davidson, Ryan D.; Sbarra, David A.; Beck, Connie J.A.; Mehl, Matthias R.; Bootzin, Richard R.; Department of Psychology, University of Arizona (2013-11-08)
    • Knowledge is Empowering Utilizing 21st Century Library Services to Build Annotated Bibliographic Databases that Connect Native American Communities with Environmental Health Information

      Ruddle, David (2013-11-08)
      Is it possible for a student to create an information resource that helps someone in need? In a two month span, the student author conducted research into the availability of environmental articles and collected over 250 academic papers and grey literature. Library tools and services provided by The University of Arizona Libraries on Southwestern Environmental and Health Issues specifically targeting Native American communities were used to near exclusivity. Locating articles for the database was done quicker than expected by a Library Science student (the author) who had some previous familiarity with academic databases such as PubMED™ and Web of Science™. The database itself was designed in Drupal as a Deep Web (not public) Internet project and completed before schedule. Over the course of this research it was discovered that by properly utilizing library resources its possible for motivated students at the collegiate level to create a database of articles that could aid underserved groups with their understanding of desired specialized issues.
    • Passivation of III-V Semiconductor Surfaces

      Contreras, Yissel; Muscat, Anthony; Department of Chemical and Environmental Engineering, University of Arizona; Department of Chemical and Environmental Engineering, University of Arizona (2013-11-08)
      Computer processor chips of the last generation are based on silicon, modified to achieve maximum charge mobility to enable fast switching speeds at low power. III-V semiconductors have charge mobilities that are much higher than that of silicon making them suitable candidates for boosting the performance of new electronic devices. However, III-V semiconductors oxidize rapidly in air after oxide etching and the poor quality of the resulting oxide limits device performance. Our goal is to design a liquid-phase process flow to etch the oxide and passivate the surface of III-V semiconductors and to understand the mechanism of layer formation.Self-assembled monolayers of 1-eicosanethiol (ET) dissolved in ethanol, IPA, chloroform, and toluene were deposited on clean InSb(100) surfaces. The InSb passivated surfaces were characterized after 0 to 60 min of exposure to air. Ellipsometry measurements showed a starting overlayer thickness (due to ET, oxides, or both) of about 20 Å in chloroform and from 32 to 35 Å in alcohols and toluene. Surface composition analysis of InSb with X-ray photoelectron spectroscopy after passivation with 0.1 mM ET in ethanol confirmed the presence of ET and showed that oxygen in the Auger region is below detection limits up to 3 min after the passivation. Our results show that a thiol layer on top of a non-oxidized or low-oxide semiconductor surface slows oxygen diffusion in comparison to a surface with no thiol present, making this a promising passivation method of III-V semiconductors.
    • 21st Annual Student Showcase Program (2013)

      Graduate & Professional Student Council (GPSC) (The University of Arizona (Tucson, AZ), 2013-11)
    • Noninvasive Genetics - A Powerful Tool for Wildlife Management

      Naidu, Ashwin; Smythe, Lindsay; Thompson, Ron; Culver, Melanie; School of Natural Resources and the Environment, University of Arizona; U.S. Fish and Wildlife Service - Kofa National Wildlife Refuge, Yuma, Arizona; Borderlands Research Institute, Sul Ross State University, Alpine, Texas; U.S. Geological Survey - Arizona Co-operative Fish and Wildlife Research Unit, Tucson, Arizona (2012-11-09)
    • 20th Annual Student Showcase Program (2012)

      Graduate & Professional Student Council (GPSC); University of Arizona (The University of Arizona, 2012-11)
    • Epigenetic loss of SLIT2 leads to an autocrine-to-paracrine switch of the SLIT2/ROBO1 signaling axis in pancreatic cancer

      Rheinheimer, Brenna; Vrba, Lukas; Futscher, Bernard; Heimark, Ronald; Cancer Biology Graduate Interdisciplinary Program; Arizona Cancer Center; Department of Pharmacology and Toxicology and Arizona Cancer Center; Department of Surgery and Arizona Cancer Center (2012-11-09)
      Guidance molecules from the Netrin, Slit, Ephrin, and Semaphorin gene families were originally described as cues for the directional guidance of axons in the developing nervous system. More recently, members of these families have been found to have critical roles in epithelial development, angiogenesis and cancer. The SLIT2/ROBO1 signaling axis has properties of a potential tumor suppressor pathway via the inhibition of epithelial cell growth, directional migration, ductal morphogenesis, and is epigenetically silenced in lung, colon and breast cancers. We proposed that changes in SLIT2 and ROBO1 expression in pancreatic ductal adenocarcinoma may mediate ductal expansion following the conversion of PanIN precursor lesions to invasive carcinoma. The SLIT2 receptor, ROBO1, is a member of the immunoglobulin (Ig) superfamily and is required for lung and mammary development in mammals. ROBO1 has an alternative splice variant, DUTT1, and these two variants have different initial exons and initiating codons which may suggest the two proteins have distinct functions. In our studies, we found that all pancreatic cancer cell lines and primary pancreatic cancer specimens express only the DUTT1 isoform. We also determined that as pancreatic cancer cell lines become KRAS-independent, ROBO1 expression increases. Furthermore, using immunohistochemistry (IHC), we found that ROBO1 protein expression in primary pancreatic cancer tissue specimens is localized to the ductal compartment with no stromal staining seen. In normal pancreas, ROBO1 expression is weak while its ligand SLIT2 is strongly expressed in both the acinar and ductal compartments in vitro and in vivo. Mammals encode three SLIT genes (SLIT1-3). The secreted SLIT2 protein is not diffusible, but has a cleavage site within its EGF-like repeats creating two fragments which allow it to act either as a short or long range guidance cue with each fragment appearing to have its own cell-association characteristics. The 5’ promoter of SLIT2 has been shown to be methylated resulting in gene silencing in early stages of several epithelial cancers suggesting a possible tumor suppressor role. miR-218-1 is an intronic microRNA found between exons 15 and 16 of the SLIT2 gene and targets a complimentary sequence in the ROBO1 3’ untranslated region (UTR) indicative of a potential regulation of receptor availability in the presence of ligand. In our studies, we determined that the KRAS-dependent pancreatic cancer cell lines express SLIT2 and ROBO1 in a cell autonomous manner. The KRAS-independent cell lines, however, have silenced SLIT2 and miR-218-1 expression. Using IHC we found that high levels of SLIT2 are seen in normal pancreas localized to the acinar and ductal compartments. Reduced SLIT2 expression is seen in primary pancreatic cancer tissue specimens. We confirmed that loss of SLIT2 mRNA in KRAS-independent lines was due to DNA hypermethylation shown by methylation specific PCR and Sequenom analysis. Chromatin immunoprecipitation analysis shows that silencing histone marks are found in the 5’ promoter of the SLIT2 gene in KRAS-independent lines. Treatment with demethylating agents reactivate SLIT2 and miR-218-1 expression suggesting that epigenetic mechanisms controlling the SLIT2 promoter also regulate miR-218-1 expression. Overall, our data establishes that the SLIT2/ROBO1 signaling axis is a dynamic pathway in pancreatic cancer that can act in the tumor expansion and progression along intrapancreatic neurons that express the SLIT2 ligand.
    • Assessment of the Unemployment Season in the Yuma County Seasonal Farm Worker Community

      Pecotte de Gonzalez, Brenda C.; College of Public Health, Center for Latin American Studies (2012-11-09)
    • Biopolymer Stabilization for Mine Tailings Dust Control

      Chen, Rui; Gregory, Mark; Zhang, Lianyang; Department of Civil Engineering and Engineering Mechanics (2012-11-09)
    • Modeling Advanced Oxidation Processes for Water Treatment

      Anhalt, Ashley; Sáez, A. Eduardo; Arnold, Robert; Rojas, Mario; Department of Chemical and Environmental Engineering (2012-11-09)
      Civilization is dependent on wastewater treatment plants. However, many conventional wastewater treatment processes only partially remove trace organics that result from human use, such as pharmaceuticals and endocrine disrupters. Advanced oxidation process (AOP) can be used to remove chemicals that may remain in the treated wastewater. AOP is an enhanced alternative to the traditional water treatment processes because it turns water contaminants into carbon dioxide (CO2), as opposed to simply transporting the contaminants across the different treatment phases. In order to model this process, one proposed idea uses ultraviolet light and hydrogen peroxide to oxidize the unwanted organic compounds. Previous mathematical models have been developed to simulate the UV/H2O2 process, however, the model employed in this work has advanced beyond previous efforts. Our UV/H2O2 model aims to characterize the mechanism and kinetics behind the decomposition of nonylphenol (NP) and p-cresol (PC), two chemicals in wastewater that serve as surrogates for endocrine disrupters. The model demonstrates agreement between experimental results and AOP simulations accounting for light intensity, pH, hydrogen peroxide levels, and concentrations of other radical scavengers. Our goal is to improve an already robust UV/H2O2 AOP model by taking into account spatial variations of radical concentrations. Our results take into account time and space, and show significant improvement in the accuracy of the model. This broadens the applications of this model and consequently, the degradation of organic contaminants is predictable over a wide range of conditions. The potential for polishing conventionally treated wastewater is evident.
    • Modeling of nucleation rate of supersaturated calcium sulfate solutions

      Jonathas, David; Department of Chemical and Environmental Engineering (2012-11-09)
    • 19th Annual Student Showcase Program (2011)

      Graduate & Professional Student Council (GPSC); University of Arizona (The University of Arizona, 2011-11)
    • Queer-Ability: History, Culture, and the Future of the Intersection of LGBTQ and Disability Studies

      Przybylowicz, Stephan Elizander; School of Information Resources & Library Science; Sonoran UCEDD Interdisciplinary Training Program (2011-11-04)
    • Stage of invasion: How do sensitive seedlings respond to buffelgrass?

      Sommers, Pacifica; Ecology and Evolutionary Biology (2011-11-04)
    • Characterization of a Gene that Responds to Mitochondrial Retrograde Regulation in Arabidopsis thaliana

      Sepulveda, Jennifer; Rhoads, David M.; School of Plant Sciences (2011-11-04)
      The Rhoads Lab found an Arabidopsis gene (At5g40690) that encodes for a protein similar to yeast ATPase Assembly Proteins (AAPs), which is strongly increased in expression by MRR and during plant stresses such as pathogen attack. Characterization of At5g40690 will be performed by the analysis of knock out (KO) lines, constitutive expressor (CE) lines in comparison to wild-type using northern blots. If this gene is an AAP, then this will be the first AAP in plants to be extensively studied in relation to MRR and stress responses, and will provide researchers with a better understanding of MRR and define a new category of proteins involved in stress response. Findings will give a better understanding of heat stress in crops such as Zea mays.
    • Database Forensics in the Service of Information Accountability

      Snodgrass, Richard; Pavlou, Kyriacos; Department of Computer Science (2011-11-04)
      Regulations and societal expectations have recently expressed the need to mediate access to valuable databases, even by insiders. At one end of the spectrum is the approach of restricting access to information and on the other that of information accountability. The focus of the proposed work is effecting information accountability of data stored in databases. One way to ensure appropriate use and thus end-to-end accountability of such information is tamper detection in databases via a continuous assurance technology based on cryptographic hashing. In our current research we are working to show how to develop the necessary approaches and ideas to support accountability in high performance databases. This will include the design of a reference architecture for information accountability and several of its variants, the development of forensic analysis algorithms and their cost model, and a systematic formulation of forensic analysis for determining when the tampering occurred and what data were tampered with. Finally, for privacy, we would like to create mechanisms for allowing as well as (temporarily) preventing the physical deletion of records in a monitored database. In order to evaluate our ideas we will design and implement an integrated tamper detection and forensic analysis system. This work will show that information accountability is a viable alternative to information restriction for ensuring the correct storage, use, and maintenance of databases.
    • Deposition of CuInS₂ Absorber Layer for a Prototype Solar Cell

      Fang, Yizhou; Jiang, Feng; Muscat, Anthony J.; Chemical and Environmental Engineering (2011-11-04)
      A copper indium disulfide (CuInS₂ or CIS) film could potentially be used as the absorber layer in a solar cell that converts solar energy into electricity. CuInS₂ was chosen to lower the cost and environmental impact of manufacturing as an alternate to Si solar cells. The objective of this project is to deposit a uniform CuInS₂ film with a thickness of 2-3 μm. Both spin-coating and painting methods were compared. The substrate, oxidation method, and sulfurization temperature were varied and characterized.
    • Conserve to Enhance: An Innovative Mechanism for Environmental Benefits

      Choate, Brittany Lynn; Nadeau, Joanna; Rupprecht, Candice; Lien, Aaron; Megdal, Sharon B.; Water Resources Research Center (2011-11-04)
      Arizona’s riparian ecosystems have been susceptible to degradation because state water laws do not consider environmental water needs. This lack of legal authority has led to water being diverted away from desert waterways through surface water and groundwater withdrawals (Megdal et al. 2011). To help bring the environment to the table as a water using sector, the University of Arizona Water Resources Research Center (WRRC) has developed the Conserve to Enhance (C2E) program. C2E is an innovative water conservation mechanism that addresses ecological water needs by raising funds through individual donations for river and riparian enhancement projects. The C2E Program invites community members to implement water conservation methods, track their monthly water savings through a Water Conservation Calculator, and then donate those savings to a C2E fund. Tucson is home to the first C2E Pilot Program, which began January 2011 with 60 participants. The goal is to determine if a program like C2E would be successful at a larger, city-wide scale and if such a program is applicable for other water-scarce communities in the Southwest.
    • Ashes to Ashes, Dust to Dust: Decomposition in the Desert

      Aguillon, Stepfanie; School of Natural Resources and the Environment (2011-11-04)
      Decomposition, the process of breaking down organic material into its increasingly finer physical and chemical constituents, is an important component in the cycling of carbon and nutrients through an ecosystem. While ultraviolet (UV) radiation is known to be detrimental to human health, might it also play an important role in decomposition, and consequently soil fertility and land cover, in the arid southwestern US? To address this question, a 4-week field experiment was designed to quantify decomposition under contrasting radiant energy regimes at the Santa Rita Experimental Range near Tucson from July-August 2011. Velvet mesquite (Prosopis velutina) leaves were placed in litterbags constructed with fiberglass mesh and plastic that was either UV transparent or UV-B absorbing. The litterbags were deployed in open areas receiving full sun or in the shaded area beneath a shrub canopy. Leaf mass loss (an indicator of decomposition rates), soil-surface temperature, levels of photosynthetically active radiation, soil moisture, and precipitation were quantified over the 4-week period. UV (present vs. absent) and radiant energy environments (open areas vs. shaded) were compared using a mixed-effect model controlling for temporal autocorrelation. Soil-surface temperatures and decomposition rates in open areas were significantly higher (F1, 64 = 89.4, p < 0.0001; F1, 97 = 4.83, p = 0.0303, respectively) than those in shaded areas, but did not differ between UV treatments (F1, 97 = 0.064, p = 0.8012). These results suggest that over a short time period, radiant energy levels influence decomposition, but via temperature effects rather than via levels of UV.