Now showing items 20600-20619 of 20709

    • "Y" Defends Cyclicity

      Denham, Kristin (University of Arizona Linguistics Circle (Tucson, Arizona), 1992)
      In this paper, I show that there are necessarily cyclic strata in English, using data from a Southeastern United States dialect (hereafter SUS) in which there are special rules of yinsertion and y-deletion. Cole (1990) argues that cyclic rules are unnecessary, and offers alternative proposals for others' cyclic analyses of a variety of problems in several languages. The analysis presented here, however, requires cyclic rule application, thus refuting Cole's claim that cyclicity may be eliminated.
    • Yaere—Seasonally Inundated Rangeland, West Africa

      Stark, Malcolm (Society for Range Management, 1986-04-01)
    • Yaks

      Miller, Daniel J. (Society for Range Management, 1986-06-01)
    • Yale Natural Radiocarbon Measurements IV

      Deevey, Edward S.; Gralenski, L. J.; Hoffrén, Väinö (American Journal of Science, 1959-01-01)
    • Yale Natural Radiocarbon Measurements IX

      Stuiver, Minze (American Journal of Science, 1969-01-01)
    • Yale Natural Radiocarbon Measurements V

      Stuiver, Minze; Deevey, Edward; Gralenski, L. J. (American Journal of Science, 1960-01-01)
    • Yale Natural Radiocarbon Measurements VI

      Stuiver, Minze; Deevey, Edward S. (American Journal of Science, 1961-01-01)
    • Yale Natural Radiocarbon Measurements VII

      Stuiver, Minze; Deevey, Edward S. (American Journal of Science, 1962-01-01)
    • Yale Natural Radiocarbon Measurements VIII

      Stuiver, Minze; Deevey, Edward R.; Rouse, Irving (American Journal of Science, 1963-01-01)
    • Yale University Geology and Geophysics Radiocarbon Dates I

      Nozaki, Y.; Turekian, K. K. (American Journal of Science, 1977-01-01)
    • Yamato 792947,793408 and 82038: The most primitive H chondrites, with abundant refractory inclusions

      Kimura, M.; Hiyagon, H.; Palme, H.; Spettel, B.; Wolf, D.; Clayton, R. N.; Mayeda, T. K.; Sato, T.; Suzuki, A.; Kojima, H. (The Meteoritical Society, 2002-01-01)
      In this paper we report petrological and chemical data of the unusual chondritic meteorites Yamato (Y)-792947, Y-93408 and Y-82038. The three meteorites are very similar in texture and chemical composition, suggesting that they are pieces of a single fall. The whole-rock oxygen isotopes and the chemical compositions are indicative ofH chondrites. In addition, the mineralogy, and the abundances of chondrule types, opaque minerals and matrices suggest that these meteorites are H3 chondrites. They were hardly affected by thermal and shock metamorphism. The degree of weathering is very low. We conclude that these are the most primitive H chondrites, H3.2-3.4 (SI), known to date. On the other hand, these chondrites contain extraordinarily high amounts of refractory inclusions, intermediate between those of ordinary and carbonaceous chondrites. The distribution of the inclusions may have been highly heterogeneous in the primitive solar nebula. The mineralogy, chemistry and oxygen isotopic compositions of inclusions studied here are similar to those in CO and E chondrites.
    • Yamato 86029: Aqueously altered and thermally metamorphosed CI-like chondrite with unusual textures

      Tonui, E. K.; Zolensky, M. E.; Lipschutz, M. E.; Wang, M.-S.; Nakamura, T. (The Meteoritical Society, 2003-01-01)
      We describe the petrologic and trace element characteristics of the Yamato 86029 (Y-86029) meteorite. Y-86029 is a breccia consisting of a variety of clasts, and abundant secondary minerals including coarse- and fine-grained phyllosilicates, Fe-Ni sulfides, carbonates, and magnetite. There are no chondrules, but a few anhydrous olivine-rich grains are present within a very fine-grained phyllosilicate-rich matrix. Analyses of 14 thermally mobile trace elements suggest that Y-86029 experienced moderate, open-system thermal metamorphism. Comparison with data for other heated carbonaceous chondrites suggests metamorphic temperatures of 500-600 degrees C for Y-86029. This is apparent petrographically, in partial dehydration of phyllosilicates to incompletely re-crystallized olivine. This transformation appears to proceed through `intermediate' highly-disordered `poorly crystalline' phases consisting of newly formed olivine and residual desiccated phyllosilicate and their mixtures. Periclase is also present as a possible heating product of Mg-rich carbonate precursors. Y-86029 shows unusual textures rarely encountered in carbonaceous chondrites. The periclase occurs as unusually large Fe-rich clasts (300-500 micrometers). Fine-grained carbonates with uniform texture are also present as small (10-15 micrometers in diameter), rounded to sub-rounded `shells' of ankerite/siderite enclosing magnetite. These carbonates appear to have formed by low temperature aqueous alteration at specific thermal decomposition temperatures consistent with thermodynamic models of carbonate formation. The fine and uniform texture suggests crystallization from a fluid circulating in interconnected spaces throughout entire growth. One isolated aggregate in Y-86029 also consists of a mosaic of polycrystalline olivine aggregates and sulfide blebs typical of shock-induced melt re- crystallization. Except for these unusual textures, the isotopic, petrologic and chemical characteristics of Y- 86029 are quite similar to those of Y-82162, the only other heated CI-like chondrite known. They were probably derived from similar asteroids rather than one asteroid, and hence may not necessarily be paired.
    • Yaupon and Associated Vegetation Response to Seasonal Tebuthiuron Applications

      Duncan, K. W.; Scifres, C. J. (Society for Range Management, 1983-09-01)
      Broadcast applications of tebuthiuron pellets (20% active ingredient [a.i.]) at 2 kg/ha (a.i.) in spring more effectively controlled yaupon than applications in summer, fall or winter on the Post Oak Savannah. Tebuthiuron applications in spring reduced the live canopy of yaupon by 80%. Tebuthiuron at 1 kg/ha did not effectively control yaupon, regardless of season of treatment. Herbaceous response to tebuthiuron was relatively slow because of lack of a seed source in the heavy yaupon covers. However, by December 1980 after applications of tebuthiuron at 2 or 4 kg/ha in spring or summer 1978, grass standing crops were significantly increased. Forb standing crops were highly variable, but there was no apparent forb reduction in 1980 of 1981 where herbicide was applied in 1978-1979.
    • Yavapai County, Mister, Is Great Cattle Country!

      Allen, Alvin (College of Agriculture, University of Arizona (Tucson, AZ), 1964)
    • Yavapai Tour Still Popular

      Kingdon, Lorraine (College of Agriculture, University of Arizona (Tucson, AZ), 1984-06)
    • Yearlong Grazing of Slash Pine Ranges: Effects on Herbage and Browse

      Pearson, H. A.; Whitaker, L. B. (Society for Range Management, 1974-05-01)
      Total herbage yields under immature slash pine were not appreciably changed by yearlong cattle grazing which removed 30 to 60% of the annual growth. However, moderate (45%) and heavy (60%) grazing reduced pinehill bluestem frequency and increased carpetgrass. Individual browse species were not affected by grazing intensity, but total cover was reduced with moderate grazing. As tree density increased, the total herbage yields decreased.
    • Yearly Variation in Germination in Three Subspecies of Big Sagebrush

      Harniss, R. O.; McDonough, W. T. (Society for Range Management, 1976-03-01)
      Yearly variation in germination between individual plants of three subspecies of big sagebrush (Artemisia tridentata) was examined. The subspecies vaseyana germinated less than tridentata or wyomingensis. Only tridentata showed a significant difference in year-to-year variation. In all years, germination rates of the three subspecies were high enough to exclude seed germination as a limiting factor in sagebrush reinvasion.
    • Yellow Clover Aphid

      Tuttle, D. M.; Hopkins, L.; Butler, G. D.; Department of Entomology; Department of Entomology; Department of Entomology (College of Agriculture, University of Arizona (Tucson, AZ), 1955)
    • Yellow impact glass from the K/T boundary at Beloc (Haiti): XANES determination of the Fe oxidation state and implications for formation conditions

      Giuli, Gabriele; Eeckhout, Sigrid Griet; Koeberl, Christian; Pratesi, Giovanni; Paris, Eleonora (The Meteoritical Society, 2008-01-01)
      We determined the iron oxidation state and coordination number in five samples of yellow impact glass from the Cretaceous-Tertiary (K/T) boundary section at Beloc, Haiti, which formed as the result of impact melting during the Chicxulub impact event. The samples were analyzed by Fe K-edge XANES spectroscopy and the results were compared with published data on eight black impact glasses and one high Si-K impact spherule from the same impact layer. The pre-edge peak of our high-resolution XANES spectra displays evident variations indicative of significant changes in the Fe oxidation state, spanning a wide range from about 75 to 100 mole% Fe3+. Yellow K/T glasses have significantly higher Fe3+/(Fe2+ + Fe3+) ratios compared to black K/T impact glasses (from 20 to 75 mole% Fe3+) and high Si-K glass (20 mole% Fe3+). In particular, all the pre-edge peak data on these three types of impact glasses plot between two mixing lines joining a point calculated as the mean of a group of tektites studied so far (consisting of [4]Fe2+ and [5]Fe2+) to [4]Fe3+ and [5]Fe3+, respectively. Thus, the XANES spectra of the yellow K/T glasses can be interpreted as a mixture of [4]Fe2+, [5]Fe2+, [4]Fe3+, and [5]Fe3+. Our observations can be explained by a very large range of oxygen fugacity conditions during melt formation. Furthermore, there is a clear positive relationship between the Fe3+/(Fe2+ + Fe3+) ratio and the Ca content of these glasses, suggesting that the Fe oxidation state was influenced by the relative contribution of Ca-sulfate-and Ca-carbonate-bearing sedimentary rocks at the impact site.
    • Yellow-Blossomed Alfalfa on Rangeland in South Dakota

      Smith, Norman G. (Society for Range Management, 1997-08-01)