Now showing items 20595-20614 of 20709

    • X-ray Densitometry of Norway Spruce Subfossil Wood from the Austrian Alps

      Klusek, M.; Grabner, M. (Tree Ring Society, 2016-01)
      The processing of subfossil wood poses some difficulties in densitometric research. Problems arise because of the physiochemical changes of wood occurring in the sedimentation environment. Subfossil wood modification can result from the uptake of mineral and organic substances into the wood tissue. It can also occur as the effect of microbiological degradation of wood. The goal of this study was to identify the appropriate method of subfossil wood preparation for the densitometric research. For this purpose the wood of Norway spruce from Lake Schwarzensee was subjected to extraction in deionized water, acetone and diluted acetic acid. The application of acetic acid did not significantly influence the density of the wood and acetone seemed to be too aggressive. The best result was obtained by rinsing the samples in cold de-ionized water. This extraction procedure allowed removal of unwanted water-soluble, organic and inorganic compounds from wood and simultaneously did not lead to the degradation of subfossil samples. © 2016 by The Tree-Ring Society.
    • The X-Ray Technique as Applied to Dendroclimatology

      Schweingruber, F. H.; Fritts, H. C.; Bräker, O. U.; Drew, L. G.; Schär, E.; Eidgenössische Anstalt, für das forstliche Versuchswesen, Birmensdorf, Switzerland; Laboratory of Tree-Ring Research, The University of Arizona (Tree-Ring Society, 1978)
    • Xeric big sagebrush, a new subspecies in the Artemisia tridentata complex

      Rosentreter, R.; Kelsey, R. G. (Society for Range Management, 1991-07-01)
      In 1970 a xeric form of mountain big sagebrush (Artemisia tridentata ssp. vaseyana (Rydb.) Beetle) was reported in west central Idaho. Observations of morphology, habitat, and ecology, and analyses of foliage chemical components, clearly indicate these plants represent a new subspecies (xericensis) in the big sagebrush complex. It grows at lower elevations, 762-1,524 m (2,500-5,000 ft) and drier environments, 305-560 mm (12-22 in) precipitation, than most mountain big sagebrush, and is found on basaitic foothill soils often in association with bluebunch wheatgrass (Agropyron spicatum (Pursh) Scribn. & Smith). In addition to soil type, the radiate growth form and a more branched paniculate inflorescence are 2 morphological characteristics useful in separating ssp. xericensis from ssp. vaseyana. It contains higher concentrations of crude protein (10.4%), phosphorus (0.3%), and total volatiles, and lower concentrations of tannins and total phenols than mountain big sagebrush. Distinct chromatograms were obtained for both subspecies when extracts were analyzed by gas and high performance liquid chromatography. Leaf morphology and fluorescence of leaf water extracts are useful characters for separating ssp. xericensis from ssp. tridentata. The chemical data, in combination with morphology and ecology, suggest this new subspecies was initially derived by hybridization of ssp. tridentata and ssp. vaseyana.
    • Xeriscaping: A Common Sense Solution

      Woywood, Brett G.; New Mexico State University (University of Arizona (Tucson, AZ), 1999-06)
    • Xylem Tracheid Development in Pinus Resinosa Seedlings in Controlled Environments

      Danzer, Shelley R.; Leavitt, Steven W.; Panyushkina, Irina P.; Mergner, Andreas; Garcia, Evelyn; Best-Svob, Valeria; Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ (Tree-Ring Society, 2001)
      Progressive tree-ring xylem cell size changes may reveal the influence of changing environment during the growing season. This study examines xylem tracheid cell growth in red pine (Pious resinosa Ait.) seedlings grown in cabinets under controlled environment, where single parameters (temperature, light, soil moisture and CO2) were varied step-wise in each chamber at ca. 30-day increments for ca. 6 months. Control and temperature treatments were replicated. Cross-sections (20 μm thick) sliced with a sliding microtome from each of four seedling stems from each cabinet were mounted on glass slides. Lumen diameters and cell-wall thickness were measured on 4 orthogonal tracheid radial files on 4 radii of each stem. Mean cell sizes were 11-17 μm among treatments and growth periods, whereas numbers of cells formed averaged 0.2-1.3 cells per day. Cell size increased throughout the experiment in most of the treatments, including one of the control treatments and those with the greatest potential to limit growth (decreasing temperature, light and soil moisture). Soil moisture was the only environmental parameter that tended to cause late declining growth, and CO, up to 500 (μmol mol⁻¹ did not appear to influence cell development. Despite a substantial range of environmental shifts in the chambers (100 μmol mol⁻¹ CO₂; 125 μEinsteins m⁻² s⁻¹ light; 8 °C temperature; 35% relative humidity; watering every day to every 5th day), the continued stem elongation and cell-size increases indicate that conditions never became significantly limiting to growth in most treatments. Although the range of environmental variability is undoubtedly much greater in most natural red pine systems, these results indicate that fairly large variations in environment during development of juvenile wood in seedlings may not leave an imprint retrievable from cell-size measurements made on the earliest rings of mature trees.
    • "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)