Now showing items 14643-14662 of 15343

    • U-Pb and Hf Isotopic Analysis of Detrital Zircons from Paleozoic and Cretaceous Strata of Southern Vancouver Island, British Columbia

      Gehrels, George E.; Alberts, Daniel G.; Kapp, Paul; Nelson, JoAnne (The University of Arizona., 2019)
      Wrangellia, an exotic arc terrane to North America, is interpreted to have been constructed near the margin of the Paleo-Arctic and Paleo-Pacific during middle-late Paleozoic time, before finally accreting to the western margin of North America during Late Jurassic to Early Cretaceous time. Utilizing the detrital zircon record of Paleozoic sedimentary rocks and Cretaceous basin fill we can provide further insight into the magmatic and depositional evolution of southern Wrangellia. 1422 U-Pb LA-ICPMS analyses from five samples of the Fourth Lake Formation in the Carboniferous Buttle Lake Group were performed. 1055 U-Pb LA-ICPMS analyses from four samples of the Comox formation within the Cretaceous Nanaimo Group were acquired in order to provide a broader sampling of the Lower Mesozoic-Paleozoic rocks of Vancouver Island. U-Pb analyses within the Fourth Lake Formation reveal prominent Carboniferous age peaks (344, 339, 336, 331, and 317 Ma), with minor pre-400 Ma grains from adjacent terranes of Paleo-Arctic origin. Paleozoic detrital zircons exhibit juvenile, with ƐHf(t) values between +15 and +5. U-Pb analyses of Nanaimo Group sedimentary rocks reveal dominant peak ages at 341, 195, 167, and 86 Ma. All major populations yield juvenile epsilon ƐHf(t) values in the range of +15 to +6. The detrital zircon U-Pb geochronologic and Hf isotope data in this study suggest that sediment from the Fourth Lake Formation was derived mainly from bimodal magmatism within the Paleozoic southern Wrangellia arc system as well as minor contributions of recycled detritus from the adjacent Alexander Terrane. Hf isotope data from the Comox Formation indicate that Triassic and Jurassic igneous rocks of the Bonanza Arc, and Late Jurassic-Early Cretaceous sources from the central Coast Mountains Batholith (CMB), are highly juvenile. This new geochronologic and geochemical data set contributes to a new tectonic model for the Paleozoic Southern Wrangellia Arc system from Late Devonian to Early Permian time and reveals, during Cretaceous time, very locally derived detritus was deposited in sedimentary basins along the inboard margin of Wrangellia.
    • U-Th-Pb LA-ICP-MS Detrital Zircon Analysis of the Triassic Chinle and Moenkopi Formations and Permian Coconino Sandstone of Chinde Point, Petrified Forest National Park, Arizona

      Gehrels, George E.; Giesler, Dominique; Carrapa, Barbara; Reiners, Peter W. (The University of Arizona., 2019)
      The Petrified Forest National Park (PEFO) of Arizona preserves outstanding exposures of the Triassic Chinle and Moenkopi Formations that are underlain by upper Paleozoic strata of the Coconino Sandstone. In 2013, drill core was collected from these strata in an effort to establish links with the astrochronological time scale developed in the Newark basin. Other workers involved in this project are using this core to refine and improve an absolute time scale employing Milankovitch cycles. To improve constraints on provenance and depositional ages of the Coconino, Moenkopi, and Chinle formations, we acquired 7,511 individual U-Pb detrital zircon dates from 29 samples from the core. Comparison of U-Pb ages with ages of rocks in various potential source terranes suggests that our samples were shed from rocks of the Archean (2.7-2.5 Ga) Wyoming Province and Paleoproterozoic terranes (2.1-2.0 Ga) of the Canadian Shield, the Yavapai and Mazatzal Provinces (1.8-1.6 Ga), Ancestral Rocky Mountains (1.8-1.4 Ga), midcontinent basement and overlying platformal strata (1.5-1.3 Ga), Grenvillian orogen (1.3-0.95 Ga), Yucatán-Campeche block (720-420 Ma) and Amarillo-Wichita uplift (600-500 Ma), Appalachian orogen (450-350 Ma), eastern Mexico magmatic arc (310-232 Ma), and Triassic magmatic arc of western North America (230-210 Ma). The youngest peak age of the Permian Coconino sandstone is 260 Ma, whereas the youngest peak age for the Early-Middle Triassic Moenkopi Formation is 250 Ma. All samples from the Late Triassic Chinle Formation have youngest peak ages from 224-214 Ma. These maximum depositional ages compare well with CA-TIMS and ID-TIMS dates from strata of the Moenkopi and Chinle Formations, as well as the Adamanian-Revueltian land vertebrate faunachron (LVF) from Lucas (1998) and Parker and Martz (2011). U-Pb detrital zircon ages document a depositional hiatus/erosional period of ~250-225 Ma between the Moenkopi and Chinle Formations.
    • U.S. smelter acid sales and revenues: The implications of adopting European acid trade and marketing practices

      Rieber, Michael; Virdis, Maria Rosa, 1953- (The University of Arizona., 1989)
      Sulphuric acid obtained as a byproduct of non-ferrous metal ore smelting is often the mandatory result of stringent environmental policies adopted in the industrialized countries to limit sulphur dioxide emissions. For the primary copper industry in the southwestern U.S., improvement of sulphuric acid marketing and distribution economies is a critical factor. In this thesis, through a comparison of the European and U.S. sulphuric acid market structure and organization, both the opportunity and the implications of adopting European acid marketing practices are discussed. A more centralized system of acid distribution, as in the European model, if applied to the U.S. smelter acid market, proves to be potentially beneficial for net revenue enhancement. A rationalization of the logistic aspects could substantially reduce acid transportation costs, allow repayment of at least average variable costs of production and improve southwestern smelter acid competitiveness in the domestic markets.
    • Ultimate flexural strength of flat slabs: with particular attention to membrane action

      Sakolosky, John Joseph, 1941- (The University of Arizona., 1966)
    • Ultimate performance limitations of phase-locked loops

      Paul, William Vincent, 1928- (The University of Arizona., 1961)
    • Ultimate shear strength of footings and flat plates

      Lawrence, Patrick Edward, 1940- (The University of Arizona., 1965)
    • Ultimate strength design of R/C columns by numerical integration method

      Yeung, David Ho-Fung, 1946- (The University of Arizona., 1975)
    • Ultra-compact Integrated Silicon Photonics Balanced Coherent Photodetectors

      Fallahi, Mahmoud; Meyer, Jason T.; Norwood, Robert A.; Pau, Stanley (The University of Arizona., 2016)
      The design, simulation, and initial fabrication of a novel ultra-compact 2x2 silicon multimode-interference device evanescently coupled to a dual germanium metal-semiconductor-metal (MSM) photodetector is presented. For operation at the standard telecom wavelength of 1.5 µm, the simulations demonstrate high-speed operation at 30 GHz, low dark current in the nanoamp range, and external quantum efficiency of 80%. Error analysis was performed for possible tilt error introduced by hybrid integration of the MSM layer on top of the MMI waveguides by use of surface mount technology (SMT) and direct wafer bonding.
    • Ultra-precise measurement of thermal expansion coefficients

      Bradford, James N., 1926- (The University of Arizona., 1969)
    • Ultra-violet light and titanium dioxide catalyzed oxidation of red dye-79

      Sierka, Raymond A.; Adharapurapu, Krishna, 1965- (The University of Arizona., 1991)
      This research focused on the color destruction of red dye-79 in aqueous solution. Red dye-79 is a typical pollutant in the textile industrial wastewater streams. A 50 parts per million (ppm) aqueous solution of this dye was used for all experiments. Although, there are many conventional techniques for the treatment, the research investigated a new methodology, which uses the synthetic ultraviolet radiation (254 nanometers) in combination with an undoped semi-conductor powder titanium dioxide (TiO₂) anatase for the photo-catalytic destruction of inorganics and organic moieties responsible for color in aqueous solution of red dye-79. Also, investigated were the effects of the oxidant hydrogen peroxide (H₂O₂) added externally to enhance the reaction kinetics for color destruction. Ultraviolet absorbance readings at 512 nanometers were employed to quantify the color destruction. The effects of reaction parameters catalyst (TiO₂), oxidant (H₂O₂), alkalinity and, dye concentrations as well as pH, on dye destruction kinetics were also quantified.
    • Ultrafine Bubble-Enhanced Ozonation For Water Treatment

      Livingston, Peter; Slack, Donald; Hung, Isaac; Yitayew, Muluneh (The University of Arizona., 2016)
      Ultrafine bubbles, often referred to as nanobubbles, have been used in various applications from environmental remediation to medicine. Even though the technology to generate ultrafine bubbles has been around for many years, the full potential of its applications has not been completely studied. This project seeks to study the use of ultrafine bubble technology for water treatment in combination with ozone gas. A factorial design experiment was chosen to test the effects of ultrafine bubbles on the concentration of an indicator organism, E. coli, in water as well as their effects on ozone gas being injected into water. Ozone gas or nitrogen gas was injected into water contaminated with E. coli as either ultrafine bubbles or fine bubbles as treatments for up to 60 minutes. Ultrafine bubbles were found to not have any significant effect on the concentration of E. coli in water. However, ultrafine bubbles did provide benefits when used in conjunction with ozone gas that regular, fine bubbles did not provide. The benefits included allowing the concentration of dissolved ozone in the water to decrease at a slower rate as well as allowing more ozone to dissolve into water at a higher rate than conventional methods of bubbling in ozone. While in this particular set of experiments the concentration of dissolved ozone in water didn't surpass 2 mg/L, which didn't allow for rapid disinfection and treatment of water, it is believed that with a more powerful ozone generator better results can be achieved. This project demonstrates the benefits and potential of injecting ozone gas as ultrafine bubbles into water as a way to effectively and efficiently disinfect and treat water.

      McIntosh, Michael Philip. (The University of Arizona., 1982)
    • Ultrasonic transducer modeling in homogeneous and nonhomogeneous media

      Kundu, Tribikram; Lee, Joon Pyo (The University of Arizona., 2001)
      Ultrasonic transducer modeling is important and fundamental research for nondestructive testing of materials. Traditionally, in most nondestructive evaluation applications, the ultrasonic transducers are modeled as point sources generating spherical wave fronts, line sources generating cylindrical wave fronts, or planar surfaces generating plane wave fronts. In reality, the transducer front face has finite dimensions; it is neither point source nor planar source. This study shows how the ultrasonic field in the neighborhood of a transducer with finite dimension varies in homogeneous and nonhomogeneous media. In this thesis, the pressure variation in front of a transducer face is computed for the following three situations: (1) the transducer is immersed in a homogeneous fluid; (2) the transducer is near a fluid-fluid interface; and (3) the transducer is near a fluid-solid interface using Distributed Point Source Method For the nonhomogeneous fluid medium, both normal incidence and oblique incidence cases have been studied.
    • An ultrasound phased array system for intracavitary hyperthermia

      Mylrea, Kenneth C.; Buchanan, Mark Thomas, 1967- (The University of Arizona., 1992)
      Intracavitary ultrasound hyperthermia applicators have the potential to better heat certain tumor sites, especially in the pelvic region, than external techniques. To allow deep, controlled heating, an intracavitary phased array has been developed. The hardware required to drive the array was also developed; including amplifiers, phase shifters, power meters and matching circuits. The entire system is computer controlled and capable of driving up to 64 individual ultrasound transducers. This system was used to conduct acoustic field measurements and in vivo perfused kidney experiments with the phased arrays. These results show that these arrays focus as predicted, and are capable of controlling the heating field by electrically controlling the position of the focus.

      Takessian, Alex. (The University of Arizona., 1983)
    • Ultrastructure changes induced by Scutellonema brachyurum in roots of potato

      Schuerger, Andrew Conrad (The University of Arizona., 1981)