Now showing items 7261-7280 of 20719

    • Extension Service Teaches

      Pickrell, Chas. U. (College of Agriculture, University of Arizona (Tucson, AZ), 1949)
    • Extension Takes Research to the Farmers

      Pou, J. W.; Agricultural Extension Service (College of Agriculture, University of Arizona (Tucson, AZ), 1960)
    • Extension Veteran: Emil Rovey

      College of Agriculture, University of Arizona (Tucson, AZ), 1989
    • Extension Veteran: Jean Stewart

      College of Agriculture, University of Arizona (Tucson, AZ), 1989
    • Extension Veteran: John Burnham

      College of Agriculture, University of Arizona (Tucson, AZ), 1989
    • Extension Veteran: K.K. Henness

      McCoy, Jan (College of Agriculture, University of Arizona (Tucson, AZ), 1989)
    • Extension Veteran: Robert Moody

      College of Agriculture, University of Arizona (Tucson, AZ), 1989
    • Extension Veteran: Thomas Rigden

      College of Agriculture, University of Arizona (Tucson, AZ), 1989
    • "Extension" Reaches Farms

      College of Agriculture, University of Arizona (Tucson, AZ), 1953
    • Extent of chondrule melting: Evaluation of experimental textures, nominal grain size, and convolution index

      Nettles, Jeffrey W.; Lofgren, Gary E.; Carlson, William D.; McSween, Harry Y. (The Meteoritical Society, 2006-01-01)
      Dynamic crystallization experiments on the ordinary chondrite Queen Alexandra Range (QUE) 97008 document textural features that occur in partially melted chondrules with changes in the degree of partial melting and cooling rate. We carried out a matrix of experiments, at peak temperatures of 1250, 1350, 1370, and 1450 degrees C, and cooling rates of 1000, 100, and 10 degrees C/h, and quenched. All experimentally produced textures closely resemble textures of porphyritic chondrules. Because peak temperatures were well below the liquidi for typical chondrule compositions, the textural similarities support an incomplete melting origin for most porphyritic chondrules. Our experiments can be used to determine the extent of melting of natural chondrules by comparing textural relationships among the experimental results with those of natural chondrules. We used our experiments along with X-ray computerized tomography scans of a Semarkona chondrule to evaluate two other methods that have been used previously to quantify the degree of melting: nominal grain size and convolution index. Proper applications of these methods can result in valid assessments of a chondrule's degree of melting, but only if accompanied by careful interpretation, as chondrule textures are controlled by more than just the extent of melting. Such measurements of single aspects of chondrule textures might be coupled with qualitative analysis of other textural aspects to accurately determine degree of melting.
    • Extent of Coterminous US Rangelands: Quantifying Implications of Differing Agency Perspectives

      Reeves, Matthew Clark; Mitchell, John E. (Society for Range Management, 2011-11-01)
      Rangeland extent is an important factor for evaluating critical indicators of rangeland sustainability. Rangeland areal extent was determined for the coterminous United States in a geospatial framework by evaluating spatially explicit data from the Landscape Fire and Resource Management Planning Tools (LANDFIRE) project describing historic and current vegetative composition, average height, and average cover through the viewpoints of the Natural Resources Inventory (NRI) administered by the Natural Resources Conservation Service and the Forest Inventory and Analysis (FIA) program administered by the US Forest Service. Three types of rangelands were differentiated using the NRI definition encompassing rangelands, afforested rangelands, and transitory rangelands. Limitations in the FIA definition permitted characterization of only two rangeland types: rangeland and rangeland vegetation with a small patch size. These classes were similar to those from the NRI definition but differed in tree canopy cover threshold requirements. Estimated rangeland area resulting from the NRI- and FIA-LANDFIRE models were 268 and 207 Mha, respectively. In addition, the NRI-LANDFIRE model identified 19 Mha of afforested rangelands due principally to encroachment and increased density by species classified as trees belonging to the genera Quercus, Prosopis, and Juniperus. The biggest discrepancies between acreage estimates derived from NRI- and FIA-LANDFIRE models occurred in oak, pinyon-juniper, and mesquite woodlands. The differences in area estimates between the NRI and FIA perspectives demonstrate the need for development of unified, objective methods for determining rangeland extent that can be applied consistently to all rangelands regardless of ownership or jurisdiction. While the models and geospatial information developed here are useful for national-scale estimates of rangeland extent, they are subject to the limitations of the LANDFIRE data products./La extensión de los pastizales es un importante factor para evaluar indicadores críticos de la sustentabilidad de estas aéreas. La extensión aérea de los pastizales se determinó por los colindantes de Estados Unidos (US) en un marco geoespacial para evaluar espacialmente los datos explícitos del proyecto LANDFIRE describiendo su composición botánica histórica y actual, altura promedio, y cobertura promedio mediante el uso los criterios desarrollados por el Natural Resources Inventory (NRI) administrado por el Natural Resources Conservation Service y el Forest Inventory and Analysis Program (FIA) administrado por el US Forest Service. Tres tipos de pastizales se evaluaron usando la definición del NRI abarcando: pastizales, pastizales forestados y pastizales transitorios. Limitaciones en la definición de la FIA solo permiten la caracterización de dos tipos de pastizales: pastizales y vegetación con pequeñas areas de pastizal. Estas clases fueron similares a aquellas de la definición de NRI pero difirieron en los requerimientos de la cubierta aérea de los árboles. Las areas de pastizal estimadas usando los modelos NRI y FIA-LANDFIRE fueron 268 y 207 Mha, respectivamente. Además, el modelo NRI-LANDFIRE identificó 19 Mha de pastizales forestados principalmente debido a la invasión y el incremento de la densidad de especies clasificadas como arboles pertenecientes al género Quercus, Prosopis, y Juniperus. Las mayores discrepancias entre la estimación de superficie generadas por los modelos NRI y FIA-LANDFIRE se identificaron en bosques de encino, piñón-junípero y mezquite. Las diferencias entre las estimaciones de perspectivas aéreas generadas entre los modelos NRI y FIA demostraron la necesidad de desarrollar un modelo unificado; los métodos objetivos para determinar la condición de los pastizales pueden aplicarse consistentemente a todos los pastizales sin importar propiedad y jurisdicción. Mientras que los modelos e información geoespacial desarrollados aquí son útiles para la estimación a escala nacional de la condición de los pastizales, aunque están sujetas a la limitación de los productos de datos generados por LANDFIRE.
    • Extent of Stem Dieback in Trembling Aspen (Populus tremuloides) as an Indicator of Time-Since Simulated Browsing

      Carson, Allan W.; Rea, Roy V.; Fredeen, Arthur L. (Society for Range Management, 2007-09-01)
      Simulated browsing treatments were imposed on an important browse species of the North American moose (Alces alces L.) to see if the development and extent of subsequent stem dieback in trembling aspen (Populus tremuloides Michx.) could be used to determine the time of browsing during the growing season. Two hundred naturally growing aspen saplings of similar size and form were randomly selected in a 20-ha area near the endowment lands of the University of Northern British Columbia, Prince George, British Columbia, Canada. Plants were randomly assigned to treatment categories so that the apical meristems of 50 plants each were assigned to a control or were clipped on one of the following dates 6 weeks apart: 1 June, 16 July, and 30 August 2005. The leader of each aspen was clipped and dieback was left to progress until the onset of winter dormancy. Our results showed that the earlier the simulated browsing occurs in the growing season, the greater the length of stem dieback, up to the maximum of the subapical axillary node below the point of clipping. The average rate at which dieback progressed varied between treatments and decreased throughout the growing season. Our results suggest that the ratio of the actual length of stem dieback to the overall length of stem between the clip point and the subapical axillary node serves as a good indicator for estimating the time at which aspen meristems have been browsed during the growing season. 
    • Extent of thermal ablation suffered by model organic microparticles during aerogel capture at hypervelocities

      Burchell, M. J.; Foster, N. J.; Ormond-Prout, J.; Dupin, D.; Armes, S. P. (The Meteoritical Society, 2009-01-01)
      New model organic microparticles are used to assess the thermal ablation that occurs during aerogel capture at speeds from 1 to 6 km s^(-1). Commercial polystyrene particles (20 m diameter) were coated with an ultrathin 20 nm overlayer of an organic conducting polymer, polypyrrole. This overlayer comprises only 0.8% by mass of the projectile but has a very strong Raman signature, hence its survival or destruction is a sensitive measure of the extent of chemical degradation suffered. After aerogel capture, microparticles were located via optical microscopy and their composition was analyzed in situ using Raman microscopy. The ultrathin polypyrrole overlayer survived essentially intact for impacts at ~1 km s^(-1), but significant surface carbonization was found at 2 km s^(-1), and major particle mass loss at greater than or equal to 3 km s^(-1). Particles impacting at ~6.1 km s^(-1) (the speed at which cometary dust was collected in the NASA Stardust mission) were reduced to approximately half their original diameter during aerogel capture (i.e., a mass loss of 84%). Thus significant thermal ablation occurs at speeds above a few km s^(-1). This suggests that during the Stardust mission the thermal history of the terminal dust grains during capture in aerogel may be sufficient to cause significant processing or loss of organic materials. Further, while Raman D and G bands of carbon can be obtained from captured grains, they may well reflect the thermal processing during capture rather than the pre-impact particles thermal history.
    • External Argument Focus and the Syntax of Reflexivity

      Ahn, Byron; University of California, Los Angeles (University of Arizona Linguistics Circle (Tucson, Arizona), 2012)
      It is unexpected under previous accounts that, in a subclass of sentences that contain reflexive anaphors, focus on a reflexive anaphor can be felicitously interpreted as a response to a subject-question (e.g. "Johnny burned HIMSELF" as a response to "Who burned Johnny?"). This focus phenomenon can only be accounted for under existing theories of focus and syntax-prosody mapping if the syntactic representation of reflexivity is amended, as is pursued in this paper. A revised model of reflexivity such as the one presented in this paper is not only able to account for this focus data, but is generally more empirically robust: able to better account for the distribution of phrasal stress in clauses with reflexive anaphors, as well as the realization of reflexivity of other languages.
    • External Competences of the European Union and the Treaty-Making Power of Its Member States [Comment]

      Geiger, Rudolf (The University of Arizona James E. Rogers College of Law (Tucson, AZ), 1997)
    • External Radon Disturbance of 14C Measurements in Gas-Proportional Counters

      Hedberg, Magnus; Theodórsson, Páll (Department of Geosciences, The University of Arizona, 1995-01-01)
      Low-level detector systems for 14C dating are frequently located in underground or basement laboratories to reduce the influence of cosmic radiation. However, if careful precautions are not taken, the presence of radioactive radon as may severely disturb the analytical results. Measurements of the influence of radon on a proportional counter system, show that a radon level of 100 Bq m-3, a level not uncommon in basement rooms, is sufficient to produce an unacceptable uncertainty in the 14C results. Radon levels of up to 1500 Bq m-3 can be demonstrably reduced to about 30 Bq m-3, using a separate ventilation system that generates a slight overpressure in the laboratory.
    • 'Extinct' Wire-Lettuce, Stephanomeria schottii (Compositae), Rediscovered in Arizona after More Than One Hundred Years

      Lehto, Elicnor; Herbarium, University of Arizona (University of Arizona (Tucson, AZ), 1979-08)
    • Extra 'Hands' for the Rancher

      Phillips, Pat (Society for Range Management, 1979-12-01)
    • Extra Training for School Food Workers Tried as Way to Improve Lunch Program

      Webster, Guy (College of Agriculture, University of Arizona (Tucson, AZ), 1979)
    • Extracting Plant Root Samples with the Kelly Core Sampler

      Kinsinger, F. (Society for Range Management, 1955-09-01)