Now showing items 13979-13998 of 20719

    • Quantifying Vegetation Change by Point Sampling Landscape Photography Time Series

      Hardegree, Stuart P.; Clark, Patrick E. (Society for Range Management, 2005-11-01)
      Quantitative assessment of vegetation change is often conducted by digitally analyzing time series of aerial or vertical photography. Change analysis conducted using repeated oblique or landscape photography, however, has been limited to qualitative assessments. The purpose of this study was to develop sampling and analysis techniques for using a time series of digitized landscape photography to quantify vegetation change on rangeland landscapes. Digital images were created from black-and-white landscape photographs acquired in 1917, 1962, and 2000 near Whiskey Mountain in the Reynolds Creek Experimental Watershed of southwestern Idaho. Images were spatially registered to each other using control points and a polynomial transformation algorithm. Thirty random pixels along each of 30 random image lines were selected as point samples (n = 900) from within each image. The landscape feature represented in each selected pixel was classified into 1 of 15 cover types. Cover-type classification accuracy for the 2000 image was estimated to be 92.2% based on ground-truth data collected in the field. Classification accuracy was increased to 98.9% by combining rare or poorly separable cover-type classes. Image cover of vegetation cover types was quantified for each photography acquisition date. Changes in image cover of each cover type and direction of cover-type conversions were determined for each intervening time period. Analysis of image cover using repeated landscape photography is constrained by limitations imposed by oblique view angles and variable image quality. Repeat landscape photography, however, can be used to quantitatively assess long-term dynamics of vegetation cover on rangeland landscapes with visually distinct vegetation types. 
    • Quantitative Assessment of Grazing Behaviour of Sheep in Arid Areas

      Dudzinski, M. L.; Pahl, P. J.; Arnold, G. W. (Society for Range Management, 1969-07-01)
      Five indices are suggested to quantify components of spatial distribution of grazing sheep which were observed by aerial photography. Indices based on sheep numbers were more sensitive to environmental changes than those based on distances between sheep. It is suggested that the adjustment takes place by a change in the numbers within independently grazing flocks, while social contact between sheep, as reflected by various nearest-neighbour distances, remains unaltered.
    • Quantitative Determination by 14C Analysis of the Biological Component in Fuels

      Dijs, Ivo J.; van der Windt, Eric; Kaihola, Lauri; van der Borg, Klaas (Department of Geosciences, The University of Arizona, 2006-01-01)
      Radiocarbon analysis was performed by liquid scintillation counting (LSC) and accelerator mass spectrometry (AMS) to assess whether the content of biological components in hydrocarbon fuels could be derived. Different fuel mixtures were prepared containing bioethanol, fossil ethanol, and fossil gasoline. The specific 14C activity of these mixtures was obtained from LSC measurements and directly related to the concentration of carbon originating from the bioethanol (biocarbon). The results were checked via standardized carbon dating procedures and AMS. A good linear correlation exists between the fuel mixtures specific 14C activity and the concentration of biocarbon. Also, the biocarbon fraction of the fuel mixture (the ratio biocarbon : total carbon) and the normalized fraction of biocarbon (%M) showed good linear correlation. Therefore, both relations provide a possibility to quantitatively determine a fuels biocarbon content by 14C analysis. When the sample composition is known (e.g. Resolved by gas chromatography-mass spectroscopy [GC-MS] and nuclear magnetic resonance [NMR]), the amount of particular biological components in a fuel sample can be derived subsequently. For mixtures of bioethanol, fossil ethanol, and gasoline with bioethanol contents in the range of 0.52% m/m, it was found that errors in the normalized fraction of biocarbon (%M) were in the range of 2510%, respectively. For samples with a higher bioethanol content (up to pure bioethanol), the errors in %M were 10%. Errors might be larger if substantial changes in the concentration of atmospheric 14C took place during the growth period of the biofuel feedstock. By taking into account the variation in specific 14C activity of carbon over the last decades, and by modeling simple tree-growth, it could be illustrated that this effect becomes significant only if the biofuel feedstock stopped growing more than 1 decade ago, e.g. With wood from constructions.
    • Quantitative Effects of Clipping Treatments on Five Range Grasses

      Branson, F. A. (Society for Range Management, 1956-03-01)
    • Quantitative Effects of Twenty-three Years of Controlled Use on Mountain Range

      Branson, F. A.; Lommasson, T. (Society for Range Management, 1958-03-01)
    • Quantitative Extraction of Dissolved Inorganic Carbon (as CO2) and Water by Vacuum Distillation from Sediments of the Unsaturated Zone for Carbon Isotope Analysis (13C and 14C)

      Carmi, I.; Kronfeld, J.; Yechieli, Y.; Yakir, D.; Stiller, M.; Boaretto, M. (Department of Geosciences, The University of Arizona, 2007-01-01)
      Vacuum distillation is shown to be useful for the quantitative extraction of dissolved inorganic carbon (as CO2) and water from sediments of the unsaturated zone in the Coastal Aquifer of Israel. Several tests of vacuum extractions from tap water and sediments are presented, including standard addition, which show that the distillation procedure is quantitative, with minimal or no carbon isotope fractionation. The optimal temperature of the sediment during the extraction was also defined. Examples of vacuum extractions of sediments are shown.
    • Quantitative organic and light-element analysis of comet 81P/Wild 2 particles using C-, N-, and O-μ-XANES

      Cody, G. D.; Ade, H.; Alexander, C. M. O'D.; Araki, T.; Butterworth, A.; Fleckenstein, H.; Flynn, G.; Gilles, M. K.; Jacobsen, C.; Kilcoyne, A. L. D.; et al. (The Meteoritical Society, 2008-01-01)
      Synchrotron-based soft X-ray micro-analysis was performed on particles extracted from the Stardust aerogel collector in order to obtain detailed organic functional group information on any organic solids captured as part of the Principal Examination suite of analyses for samples from comet 81P/Wild 2. It is observed that cometary organic carbon captured in aerogel is present in a number of different manifestations and often intimately associated with silicates. Carbon X-ray absorption near edge structure (XANES) spectra reveal considerable chemical complexity in all of the organic particles studied so far. Universally, the comet 81P/Wild 2 organic particles contain low concentrations of aromatic and/or olefinic carbon relative to aliphatic and heteroatom-containing functional groups, e.g., amide, carboxyl, and alcohol/ethers. N-XANES confirms the presence and assignments of these functional groups. In general, the XANES data record considerable chemical complexity across the range of organic samples currently analyzed. The atomic ratios, N/C and O/C, derived from XANES data reveal a wide range in heteroatom content; in all cases these elemental ratios are higher than that of primitive meteoritic organic matter. The wide range in chemistry, both in elemental abundances and specific organic functional groups, suggests that the comet 81P/Wild 2 organic solids may have multiple origins.
    • Quantity (in)sensitivity and underlying glottal-stop deletion in Capanahua

      Elias-Ulloa, Jose; Rutgers University (University of Arizona Linguistics Circle (Tucson, Arizona), 2004)
      This article accounts for two superficially contradicting phenomena found in Capanahua. In this language, underlying glottal stops are deleted in the coda of even syllables. The account of the distribution of glottal-stop deletion depends on quantity-insensitive footing. Glottal stops cannot occur at the right edge of metrical feet. However, contrary to expectations, Capanahua has a quantity-sensitive stress. Closed syllables attract stress. The account presented solves the puzzle in a straightforward and unified way. While both phenomena rely on disyllabic feet, the quantity of closed syllables contextually varies within disyllabic feet: closed syllables surface as heavy if they are stressed and if they do not form part of an (HL) foot; otherwise, they surface as light.
    • Quantity and Germinability of Oryzopsis hymenoides Seed in Lahontan Sands

      Young, J. A.; Evans, R. A.; Roundy, B. A. (Society for Range Management, 1983-01-01)
      The location, quantity, and germinability of seed (caryopses) reserves of Oryzopsis hymenoides (R. & S.) Ricker in the soil were investigated at 4 locations in the Carson Desert of western Nevada. Numerous germinable seeds were recovered from the surface 15 cm of Lahontan sands. There was no clear relation between the number of seeds and depth of burial. On sites with pronounced dunes more seeds were found in the dune sands than in the interspaces. Seeds were recovered with and without evidence of sand abrasion of the indurate lemma and paleas. Seeds without wear marks were much more highly germinable (80%) than the more numerous seeds with wear marks (6%). The germinable seed reserve consisted of seeds that germinated without pretreatment when incubated at 20 degrees C; a much larger portion that required dissection to remove the indurate lemma and palea; and a fraction with embryo dormancy that had to be overcome with gibberellin enrichment of the germination substrate. Large numbers of opened, empty lemma and palea were found in the sands. Rodent enhancement of the germination of Oryzopsis hymenoides seeds appears to be a more valid hypothesis than mechanical abrasion from saltation.
    • Quantity is not Always Economical!

      Teuteberg, Judy Chernin; School of Home Economics (College of Agriculture, University of Arizona (Tucson, AZ), 1974)
    • The Quarter Horse Enterprise in Arizona

      Angus, Robert C.; Hanekamp, William J.; Department of Agricultural Economics; Department of Agricultural Economics (College of Agriculture, University of Arizona (Tucson, AZ), 1973)
    • Quaternary Community Loses Glenn Goodfriend

      Brigham-Grette, Julie (Department of Geosciences, The University of Arizona, 2002-01-01)
    • Que Hacer Sobre La Anticuada Ley De Garantia Prendaria Mexicana [Article]

      Kozolchyk, Boris (The University of Arizona James E. Rogers College of Law (Tucson, AZ), 1995)
    • Quebec Independence and United States Security: A Question of Continuing Rights and Duties [Article]

      Dycus, Stephen (The University of Arizona James E. Rogers College of Law (Tucson, AZ), 1998)
    • Quebec Radiocarbon Measurements I

      Samson, Claude; Barrette, Louis; LaSalle, P.; Fortier, J. (American Journal of Science, 1977-01-01)
    • Quebec Radiocarbon Measurements II

      Barrette, L.; Lasalle, P.; Samson, C. (American Journal of Science, 1977-01-01)
    • Quebec Radiocarbon Measurements III

      Barrette, Louis; La Salle, Pierre; Samson, Claude (American Journal of Science, 1981-01-01)
    • Queen Alexandra Range 93148: A new type of pyroxene pallasite?

      Floss, Christine (The Meteoritical Society, 2002-01-01)
      Trace elements, including the rare earth elements, were measured in olivine and orthopyroxene from Queen Alexandra Range (QUE) 93148, and in olivine from two main group pallasites, Springwater and Mount Vernon. Although QUE 93148 was originally classified as a lodranite, a variety of data including oxygen isotopic compositions (Goodrich and Righter, 2000), preclude a genetic relationship with the acapulcoites/lodranites. Incompatible trace element (e.g., Ti, Zr) distributions in orthopyroxene do indicate large amounts of melting and are consistent with the ultramafic assemblage observed in this meteorite. Trace element abundances in olivine are consistent with suggestions that QUE 93148 may be related to the main group pallasites (Goodrich and Righter, 2000), although there are some inconsistencies. Its trace element distributions are most like those of the pyroxene pallasites, suggesting that it may have formed in a similar manner. QUE 93148 may represent a new type of pyroxene pallasite with links to the main group pallasites.
    • Queens College Radiocarbon Measurements I

      Pardi, Richard (American Journal of Science, 1976-01-01)
    • Queens College Radiocarbon Measurements II

      Pardi, R. (American Journal of Science, 1977-01-01)