Now showing items 8032-8051 of 20709

    • G. S. C. Tree-Ring Scanning Densitometer and Data Acquisition System

      Jones, F. W.; Parker, M. L. (Tree-Ring Society, 1970-11)
      A tree-ring scanning densitometer and data acquisition system has been built by the Geological Survey of Canada to extract tree-ring density and tree-ring width data from dendrochronological specimens and X-ray negatives of specimens. The system produces tree-ring density plots, ring density and ring-width bar graphs, and printed and punch tape digital data. This prototype was built primarily from commercial pre-constructed electronic components, but a modified densitometer and other original-design units also were used in the construction.
    • GAFTA Arbitration as the Most Appropriate Forum for Disputes Resolution in Grain Trade [Article]

      Polovets, Iryna; Smith, Matthew; Terry, Bradley (The University of Arizona James E. Rogers College of Law (Tucson, AZ), 2013)
    • Gain and loss of uranium by meteorites and rocks, and implications for the redistribution of uranium on Mars

      Dreibus, G.; Haubold, R.; Huisl, W.; Spettel, B. (The Meteoritical Society, 2007-01-01)
      Terrestrial alteration of meteorites results in the redistribution, gain, or loss of uranium and other elements. We have measured the maximum U adsorption capacity of a meteorite and two geochemical reference materials under conditions resembling terrestrial ones (pH 5.8). The basaltic eucrite Sioux County adsorbs 7 ppm of U. The result for the terrestrial granite AC-E is similar (5 ppm), while the basalt BE-N adsorbs 34 ppm of U. We have also investigated U adsorption in the presence of phosphate (0.01 M or less) in imitation of conditions that probably occurred in the earlier history of Mars. Such a process would have alterated Martian surface material and would be noticeable in Martian meteorites from the affected surface. The experiments demonstrated the counteracting effects of phosphate, which increases U adsorption, but decreases the quantity of dissolved U that is available for adsorption. U adsorption by AC-E increases to 7 ppm. The lowered value for BE-N of 8 ppm results from the low quantity of dissolved U in the volume of solution used. The results from the adsorption experiments and from leaching the Martian meteorite Zagami and a terrestrial basalt imply that the aqueous redistribution of U on Mars was moderate. Acidic liquids mobilized uranium and other metals, but present phosphate impeded the dissolution of U compounds. Some mobilized U may have reached the global sinks, while most of it probably was transported in the form of suspended particles over a limited distance and then settled.
    • Gain-Test Bulls Go At Excellent Prices

      College of Agriculture, University of Arizona (Tucson, AZ), 1967
    • Gains of Steers and Calves Grazing Crested Wheatgrass

      Hart, R. H.; Balla, E. F.; Waggoner, J. W. (Society for Range Management, 1983-07-01)
      Efficient utilization of pasture requires proper class of livestock, stocking rate, and season of use. Crested wheatgrass was grazed with steers in spring for 3 years at two stocking rates and with calves in fall for 2 years at 2 stocking rates to evaluate alternate uses. Differences in forage production and lengths of grazing season over years produced grazing pressures of 47-79 steer days or 53-73 calf days per metric tonne of forage produced. Steer gains of 0.85-1.20 kg/day were unaffected by grazing pressure, but lighter steers gained faster. Implantation of 36 mg of Ralgro per steer increased daily gains by 13%. Calf gains were 0.15-0.24 kg/day, and decreased with increasing grazing pressure according to the function ADG=0.45-0.0041 (calf days/tonne forage); r2=0.95. Such grazing pressure-gain response functions facilitate comparisons between seasons of use and class of livestock, as well as those between stocking rates, and help range managers make management decisions. Maximum steer gains in spring per hectare and tonne of forage were over 3 and 6 times, respectively, the gains of calves in fall.
    • Gakushuin Natural Radiocarbon Measurements I

      Kigoshi, Kunihiko; Tomikura, Y.; Endo, Kunihiko (American Journal of Science, 1962-01-01)
    • Gakushuin Natural Radiocarbon Measurements II

      Kigoshi, Kunihiko; Endo, Kunihiko (American Journal of Science, 1963-01-01)
    • Gakushuin Natural Radiocarbon Measurements III

      Kigoshi, Kunihiko; Lin, Der-Hwang; Endo, Kunihiko (American Journal of Science, 1964-01-01)
    • Gakushuin Natural Radiocarbon Measurements IV

      Kigoshi, Kunihiko; Kobayashi, Hiromi (American Journal of Science, 1965-01-01)
    • Gakushuin Natural Radiocarbon Measurements V

      Kigoshi, Kunihiko; Kobayashi, Hiromi (American Journal of Science, 1966-01-01)
    • Gakushuin Natural Radiocarbon Measurements VI

      Kigoshi, Kunihiko (American Journal of Science, 1967-01-01)
    • Gakushuin Natural Radiocarbon Measurements VII

      Kigoshi, Kunihiko; Aizawa, Hiroko; Suzuki, Nobuko (American Journal of Science, 1969-01-01)
    • Gakushuin Natural Radiocarbon Measurements VIII

      Kigoshi, Kunihiko; Suzuki, Nobuko; Fukatsu, Hiroko (American Journal of Science, 1973-01-01)
    • Galactic cosmic ray-produced 129Xe and 131Xe excesses in troilites of the Cape York iron meteorite

      Mathew, K. J.; Marti, K. (The Meteoritical Society, 2009-01-01)
      The flux of galactic cosmic rays (GCR) in the solar system appears to change with time. Based on the abundances in iron meteorites of cosmogenic nuclides of different half lives, Lavielle et al. (1999) found that the GCR flux increased in recent times (<100 Ma) by about 38% compared to average flux in the past 150 Ma to 700 Ma ago. A promising technique for calibrating the GCR flux during the past ~50 Ma, based on the 129I and 129Xe pair of nuclides, was discussed earlier (Marti 1986; Murty and Marti 1987). The 129I-129Xen chronometer provides a shielding-independent system as long as the exposure geometry remained fixed. It is especially suitable for large iron meteorites (Te-rich troilite) because of the effects by the GCR secondary neutron component. Although GCR-produced Xe components were identified in troilites, several issues require clarifications and improvements; some are reported here. We developed a procedure for achieving small Xe extraction blanks which are required to measure indigenous Xe in troilites. The 129Xe and 131Xe excesses (129Xen, 131Xen) due to neutron reactions in Te are correlated in a stepwise release run during the troilite decomposition. Our data show that indigenous Xe in troilite of Cape York has isotopic abundances consistent with ordinary chondritic Xe (OC-Xe), in contrast to a terrestrial signature which was reported earlier. Two methods are discussed which assess and correct for an interfering radiogenic 129Xer component from extinct 129I. The corrected 129Xen concentration in troilite D4 of Cape York yields a cosmic ray exposure (CRE) age of 82 +/- 7 Ma consistent, within uncertainties, with reported data (Murty and Marti 1987; Marti et al. 2004).
    • Gambel Oak Control Studies in Southwestern Colorado

      Marquiss, R. W. (Society for Range Management, 1973-01-01)
      Gambel oak (Quercus gambelii) was treated with several brush-killing herbicides in southwestern Colorado. Tordon, alone or in a mixture, as a foliar spray increased the percentage of dead stems and reduced the occurrence of root sprouts when compared to other herbicides tested. One-half pound of Tordon 22K mixed with 2,4,5-TP at the 1 1/2 and 2-pound rates (ae/acre) and Tordon 22K at the 2-pound rate have resulted in the best herbicide treatments for controlling Gambel oak in southwestern Colorado.
    • Gambel oak root carbohydrate response to spring, summer, and fall prescribed burning

      Harrington, Michael G. (Society for Range Management, 1989-11-01)
      Control of Gambel oak (Quercus gambelii Nutt.) for increased forage production and conifer regeneration is difficult because of its vigorous sprouting ability. Nonstructural root carbohydrate concentrations, generally a good indicator of sprouting potential, were measured in understory Gambel oak in a dense ponderosa pine (Pinus ponderosa Laws.) stand following prescribed fire. Carbohydrates in roots of 1- to 2-year-old sprouts after a single fire treatment were similar to those in unburned, mature oaks. Two prescribed burns, 2 years apart during the summer carbohydrate depression, caused these root reserves to remain low into fall dormancy and probably contributed to an observed oak reduction. This summer carbohydrate depression, also observed in open-grown Gambel oak, can be recognized by rapid stem growth and new leaf production.
    • Game Animals: A Substitute for Cattle?

      Lambrecht, Frank L. (Society for Range Management, 1983-02-01)
    • Game Habitat and the Multiple Use of Southern Forest Ranges

      Burke, H. D. (Society for Range Management, 1956-07-01)
    • Game Ranching in Western Canada

      Renecker, Lyle A.; Kozak, Henry M. (Society for Range Management, 1987-10-01)
    • Games People Play: Human Behavior and Invasive Weed Management

      McCoy, Nicole Haynes; Amatya, Pradyumna (Society for Range Management, 2005-12-01)