Now showing items 13263-13282 of 19159

    • N Volatilization from Arizona Irrigated Waters

      Norton, E. R.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      A laboratory study was initiated to investigate the potential loss of fertilizer nitrogen (N) through volatilization at four different temperatures (25, 30, 35, and 40°C) out of irrigation waters collected from a number of Arizona locations. Complete water analysis was conducted on each of the water samples. A 300 ml volume of each water was placed in 450 ml beakers open to the atmosphere in a constant temperature water bath with 10 mg of analytical grade (NH₄)₂SO₄ added to each sample. Small aliquots were drawn at specific time intervals over a 24 hour period and then analyzed for NH₄⁺-N concentrations. Results showed potential losses from volatilization to be highly temperature dependent. Total losses (after 24 hours) ranged from 30-48% at 25°C to over 90% at 40°C. In this study where (NH₄)₂SO₄ was used as the N source, the initial concentration of SO₄⁻-S in the solution had a repressive effect on volatilization due to the decreased availability of free NH₄⁺ in waters with high initial SO₄⁻-S concentrations due to the formation of complex ion pairs (NH₄SO₄⁻). It was also observed that at lower temperatures complexation and ion pair formation affected volatilization of NH₃ by reducing the NH₄⁺ activity in solution and thereby reducing NH₃ volatilization. Potential volatilization loss of fertilizer N from these irrigation waters was found to be significant and should be considered when making decisions regarding fertilizer N applications for crop production in Arizona.
    • N2O emissions from wheat agro-ecosystems under elevated atmospheric CO2

      Weber, Marie Aimee.; Matthias, A.; Leavitt, Steven W.; Riley, James J. (The University of Arizona., 1997)
      Fertilizer-derived nitrous oxide, N20, may cause an increase of tropospheric N20, which could contribute to the destruction of the ozone layer and enhance the "greenhouse effect". The impact of fertilizer on tropospheric N20 may be enhanced by increased carbon dioxide, CO2, which may alter soil N dynamics. The goal of this research was to measure N20 emissions from soil within a field of wheat grown under two levels of atmospheric CO2 (ambient and ambient plus 200 ppm), two irrigation levels (15 and 30% depletion of available water in the root zone), and two levels N-fertilizer (15 and 350 kg N/ha). Spring wheat (Triticum aestivum L. cv. Yecora Rojo) was planted at the University of Arizona Agricultural Center, Maricopa, Arizona, December 1996 and harvested May 1997 in conjunction with a Free Air CO2 Enrichment (FACE) experiment. Chamber measurements of N20 emissions were made five days during the season. The results showed that emissions were not different for the two different irrigation levels. There was, however, a positive correlation between emissions and air temperature. The elevated CO2 had no statistically significant effect on the N20 emissions.
    • NAFTA and the flow of illegal immigration

      Cepak, Natalie Ann (The University of Arizona., 2009-05)
    • NAGPRA Consultation and the National Park Service

      Evans, Michael J.; Dobyns, Henry F.; Stoffle, Richard W.; Austin, Diane; Krause, Elizabeth L.; Bureau of Applied Research in Anthropology, University of Arizona (Bureau of Applied Research in Anthropology, University of Arizona, 1994-06-10)
    • Nahookos constellation

      Flandrau Science Center & Planetarium, University of Arizona (1993)
    • Naloxone Utilization in a Tertiary Care Medical Center

      Shah, Ruby; The University of Arizona College of Medicine - Phoenix; Rosenfeld, David (The University of Arizona., 2013-03)
      The purpose of this research project was to review the use of naloxone for oversedation events from 2008-2011 at the Mayo Clinic Hospital in Phoenix, Arizona. Opiates are generally an accepted form of acute and chronic pain management. Opiate analgesic use has increased in past decades due to several factors including cultural and healthcare ideas on the importance of pain management, as well as the availability, cost, and marketing of the drugs. Concomitant with the increased use of opiates has been a rise in addiction, diversion, and abuse. In addition, opiate overdose is a potentially lethal consequence. Balancing the use of opiates for effective pain control and the possible risks of opiates is a constant effort for healthcare professionals. Monitoring the use of naloxone has arisen as an effective metric to examine the safety and outcomes of opiate utilization in a hospital setting. Reviewing every dose of naloxone delivered over the years 2008-2011 has allowed us to recognize trends that have led to improvements in patient safety. 154 cases of naloxone use for sedation events were reviewed in a retrospective case controlled unmatched chart review. We were able to determine that patient risk for oversedation is greatest within our surgical practices, especially general and orthopedic, and that the overall risk is greatest within the first 24 hours in all surgical patients. In addition, we were able to determine statistically significant increase in risk with elevated creatinine level, American Society of Anesthesiology (ASA) Class, and patient controlled analgesia (PCA) use compared to our unmatched control group. The significance of these findings is that it identifies certain risk groups and factors that carry increased risk for sedation events, and therefore can lead to improvements in quality and education across the institution.
    • Name Networks: A Content-Based Method for Automated Discovery of Social Networks to Study Collaborative Learning

      Gruzd, Anatoliy (2009)
      As a way to gain greater insight into the operation of Library and Information Science (LIS) e-learning communities, the presented work applies automated text mining techniques to text-based communication to identify, describe and evaluate underlying social networks within such communities. The main thrust of the study is to find a way to use computers to automatically discover social ties that form between students just from their threaded discussions. Currently, one of the most common but time consuming methods for discovering social ties between people is to ask questions about their perceived social ties via a survey. However, such a survey is difficult to collect due to the high cost associated with data collection and the sensitive nature of the types of questions that must be asked. To overcome these limitations, the paper presents a new, content-based method for automated discovery of social networks from threaded discussions dubbed name networks. When fully developed, name networks can be used as a real time diagnostic tool for educators to evaluate and improve teaching models and to identify students who might need additional help or students who may provide such help to others.
    • Naming and Reclaiming Indigenous Knowledges in Public Institutions: Intersections of Landscapes and Experience

      Doyle, Ann M.; Budin, Gerhard; Swertz, Christian; Mitgutsch, Konstantin (Ergon Verlag, 2006)
      Abstract: This paper tells a story of a practitionerâ s experience in a First Nations library and how it shaped a doctoral research project on knowledge organization. It connects the landscape on the edge of a pacific forest to considerations of the impacts of the erasures of Indigenous knowledges by dominant knowledge organization systems and practices. The LIS literature on cultural bias in knowledge organization is reviewed and some ameliorative initiatives described. A theoretical lens conjoins the new sociology of education with analyses by Indigenous governance organizations. The potential of LIS research to contribute to the naming and reclaiming of Indigenous knowledges is highlighted and a proposed research plan to contribute to methodologies for Indigenous knowledge organization is outlined.
    • Naneeskadi

      Tapahonso, Luci (University of Arizona Press (Tucson, AZ), 2008)
    • NanoPort: A Web Portal for Nanoscale Science and Technology

      Chau, Michael; Chen, Hsinchun; Qin, Jailun; Zhou, Yilu; Sung, Wai-Ki; Chen, Mark; Qin, Yi; McDonald, Daniel M.; Lally, Ann M. (ACM/IEEE-CS, 2002)
      Areas related to nanotechnology, or nanoscale science and engineering (NSSE), have experienced tremendous growth over the past few years. While there are a large variety of useful resources available on the Web, such information are usually distributed and difficult to locate, resulting in the problem of information overload. To address the problem, we developed the NanoPort system, an integrated Web portal aiming to provide a one-stop shopping service to satisfy the information needs of researchers and practitioners in the field of NSSE [1]. We believe that the approaches taken also can be applied to other domains.
    • Nanosecond Pulse Dielectric Barrier Discharge Plasma Actuation in Supersonic Flow

      Davis, Amanda Kathryn (The University of Arizona., 2012-05)
      Boundary layer control is a topic of constant concern in the area of aerodynamics. This study addresses a possible new method of affecting boundary layers and shock structure in supersonic flow. Nanosecond pulse dielectric barrier discharge plasma actuators are tested on a flat plate in a supersonic wind tunnel. Effects were observed using schlieren imaging to analyze changes in density gradients in the flow. While no noticeable results were found, the flow Mach numbers and electrical characteristics tested were very limited in variety due to complications with discharge formation and plate design. Much was learned to suggest improvements for further testing and this will facilitate later tests of similar technologies in this area of interest.
    • Nanostructured Si Thin Films for Supercapacitor Applications

      Potter, B. G.; Tang, Christopher Robert (The University of Arizona., 2017)
      Nanostructured silicon thin films are of interest as an electrode material for supercapacitor and Li-ion battery applications. In this work silicon thin films with varied nanostructure were created using RF magnetron sputter deposition. The sputter deposition was performed at 0.27W/cm2, 0.49 W/cm2, and 1.23 W/cm2 to observe the effect of sputtering power on the resulting film nanostructure. In preparation for electrical measurements, all films were deposited onto thermally evaporated copper films on glass substrates. Atomic force microscopy (AFM), coupled with computer-automated image analysis was used to quantify average grain size and size distribution in the sputtered films. A 24% decrease in average grain size was found as the deposition rate increased from 0.7 Å/s to 0.9 Å/s over the range of sputtering powers examined. Preliminary cyclic voltammetry was pursued using a symmetric electrode capacitor arrangement and an organic electrolyte to examine the charge storage behavior of the Si films. These results will be described in the context of the thin film nanostructures observed.
    • Naphthalene biodegradation in a cadmium cocontaminated system: Effects of rhamnolipid, pH, and divalent cations

      Maier, Raina M.; Sandrin, Todd Ryan (The University of Arizona., 2000)
      Forty percent of hazardous waste sites on the U.S. Environmental Protection Agency's National Priority List (NPL) are cocontaminated with organic and metal pollutants. Conventional approaches to remediating these sites are costly and often ineffective. Bioremediation is a promising, cost-effective alternative but metal toxicity at cocontaminated sites may limit its efficacy. The research described in this dissertation provides two new possible approaches to enhance the bioremediation of cocontaminated environments and sheds light on the relationship between metal concentration and inhibition of organic pollutant biodegradation. In Objective 1, a rhamnolipid biosurfactant was employed to increase naphthalene biodegradation in the presence of cadmium. The biosurfactant reduced bioavailable cadmium concentrations and increased naphthalene bioavailability. Neither of these phenomena, however, fully accounted for the ability of rhamnolipid to reduce cadmium toxicity. The ability of rhamnolipid to alter the cell surface appeared critical to its ability to mitigate toxicity. In Objective 2, pH was lowered to increase naphthalene biodegradation in the presence of cadmium. Reductions in pH had previously been reported to mitigate metal toxicity, but the mechanism of such reductions warranted elucidation. Previous studies implicated the formation of monovalent hydroxylated metal in the mechanism by which pH mediates toxicity. Results of this study, however, suggest that the importance of such species in determining toxicity may be much less than that of the increased competition between hydrogen and metal ions for binding sites on the cell surface at reduced pH. An indirect relationship between metal concentration and inhibition of organic biodegradation was revealed in Objective 3. Naphthalene biodegradation was more sensitive to cadmium concentrations of 10 and 37.5 mg/L than 100 mg/L. For this reason, we investigated whether naphthalene biodegradation could be increased in the presence of a toxic concentration of cadmium by raising the total metal concentration to a higher, but relatively less toxic concentration. Only elevated concentrations of zinc reduced cadmium toxicity. High but less toxic levels of metal may more rapidly induce the transcription of a gene(s) important in metal efflux than lower more toxic concentrations.
    • NAPL remediation by vacuum-enhanced recovery: Laboratory and model evaluations

      Wierenga, Peter J.; Dayal, Prabhu, 1947- (The University of Arizona., 1996)
      This dissertation presents an innovative methodology in the form of two papers for the feasibility assessment and optimization of Vacuum Enhanced Recovery (VER) to remediate non aqueous phase liquids (NAPLs) in the vadose zone. The first paper demonstrates the use of a pilot-scale two-dimensional laboratory soil cell and an automated dual-energy gamma ray attenuation system for the feasibility assessment of VER to remediate free-product NAPL spills. The investigations were conducted in a 1.5 x 1 x 0.08 meter cell filled with heterogeneous soils for the simultaneous and continuous measurement of NAPL and water saturations at 96 programmed locations. The dynamic laboratory method determines the spatial distributions of three-phase fluid saturations of an oil spill simulation from the surface as it migrates through the vadose zone during the sequential stages of infiltration, redistribution and VER. Contour plots of observed NAPL and water saturations identify the distribution of NAPL as entrapped liquid in heterogeneous soils unavailable for free-product recovery by VER. The accuracy of the methodology used for the measurement of NAPL retention in soil was illustrated by a NAPL retention measurement precision analysis. A mean difference of 0.97% was achieved by comparing gamma system measured NAPL retention volumes in the soil with that derived by the VER system. The second paper utilizes the pilot-scale laboratory results for a comparative analysis with model simulations to calibrate a three-phase model and optimize the design of VER systems for free-product NAPL remediation in heterogeneous soils.
    • Narrative-Based Linguistic Predictors of Well-Being

      Mehl, Matthias R.; Herringer, Gregory Thomas Miller (The University of Arizona., 2014)
    • Narrow Row Cotton Evaluation, Marana Agricultural Center

      Thacker, Gary W. (College of Agriculture, University of Arizona (Tucson, AZ), 1987-03)
      In a preliminary, unreplicated test, cotton was planted in 40 inch and 27 inch rows on April 10 and again on May 1. Narrow rows outyielded 40 inch rows at both planting dates. The yield difference between the row spacing treatments was greatest in the May 1 planting. Both row spacings had higher yields when planted on the later date, as did both the DPL 90 and ST506 varieties used in the test.
    • Narrow Row Cotton Production in Vicksberg

      Knowles, Tim C.; Cramer, Roc; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      Deltapine 458B/RR, Deltapine 5415RR, Deltapine 20B, and Deltapine 20 cotton varieties were planted on June 5 into narrow 15 inch wide rows. Populations ranged from 80,000 to 100,000 plants per acre. Seed cotton was stripper harvested on December 17. Although lint yields were somewhat low (1- 2 bale/acre) for this late planted cotton, we learned several important practices for effective narrow row cotton production systems, based on our first years experience in western Arizona.
    • Narrow Row Cotton Trial

      Hazlitt, J. R.; Stedman, Sam; Farr, C. R. (College of Agriculture, University of Arizona (Tucson, AZ), 1971-02)
    • Narrow-Row Harvesting

      Cannon, M. D. (College of Agriculture, University of Arizona (Tucson, AZ), 1976-02)
    • Narrow-Row Irrigation and Variety Trial

      Turner, Fred (College of Agriculture, University of Arizona (Tucson, AZ), 1972-02)