Now showing items 7281-7300 of 20709

    • F.O.B. Auctions

      O'Connell, Chas. (College of Agriculture, University of Arizona (Tucson, AZ), 1924-11)
    • Fabric analysis of Allende matrix using EBSD

      Watt, Lauren E.; Bland, Phil A.; Prior, Dave J.; Russell, Sara S. (The Meteoritical Society, 2006-01-01)
      Fabric analysis of the interstitial matrix material in primitive meteorites offers a novel window on asteroid formation and evolution. Electron backscatter diffraction (EBSD) has allowed fabrics in these fine-grained materials to be visualized in detail for the first time. Our data reveal that Allende, a CV3 chondrite, possesses a uniform, planar, short-axis alignment fabric that is pervasive on a broad scale and is probably the result of deformational shortening related to impact or gravitational compaction. Interference between this matrix fabric and the larger, more rigid components, such as dark inclusions (DIs) and calcium-aluminium-rich inclusions (CAIs), has lead to the development of locally oriented and intensified matrix fabrics. In addition, DIs possess fabrics that are conformable with the broader matrix fabric. These results suggest that DIs were in situ prior to the deformational shortening event responsible for these fabrics, thus providing an argument against dark inclusions being fragments from another lithified part of the asteroid (Kojima and Tomeoka 1996; Fruland et al. 1978). Moreover, both DIs and Allende matrix are highly porous (~25%) (Corrigan et al. 1997). Mobilizing a highly porous DI during impact-induced brecciation without imposing a fabric and incorporating it into a highly porous matrix without significantly compacting these materials is improbable. We favor a model that involves Allende DIs, CAIs, and matrix accreting together and experiencing the same deformation events.
    • Fabric Scope for 1973-1974

      Cook, Barbara; Vaughn, Janet L.; School of Home Economics; School of Home Economics (College of Agriculture, University of Arizona (Tucson, AZ), 1973)
    • Facies distribution of post-impact sediments in the Ordovician Lockne and Tvaren impact craters: Indications for unique impact-generated environments

      Frisk, Å. M.; Ormö, J. (The Meteoritical Society, 2007-01-01)
      The Lockne and Tvären craters formed in the Late Ordovician Baltoscandian epicontinental sea. Both craters demonstrate similarities concerning near-synchronous age, target seabed, and succeeding resurge deposits; however, the water depths at the impact sites and the sizes of the craters were not alike. The post-impact sedimentary succession of carbonates, i.e., the Dalby Limestone, deposited on top of the resurge sediments in the two craters, is nevertheless similar. At least three main facies of the Dalby Limestone were established in the Lockne crater, depending on sea-floor topography, location with respect to the crater, and local water currents. The dominating nodular argillaceous facies, showing low values of inorganic carbon (IC), was distributed foremost in the deeper and quiet areas of the crater floor and depressions. At the crater rim, consisting of crushed crystalline basement ejecta, a rim facies with a reef-like fauna was established, most certainly due to topographical highs and substrate-derived nutrients. Between these facies are occurrences of a relatively thick-bedded calcilutite rich in cephalopods (cephalopod facies). In Tvären, the lower part of the succession consists of an analogous argillaceous facies, also showing similar low IC values as in Lockne, followed by calcareous mudstones with an increase of IC. Occasionally biocalcarenites with a distinctive fauna occur in the Tvären succession, probably originating as detritus from a facies developed on the rim. They are evident as peaks in IC and lows in organic carbon (Corg). The fauna in these biocalcarenites corresponds very well with those of erratic boulders derived from Tvären; moreover, they correspond to the rim facies of Lockne except for the inclusion of photosynthesizing algae, indicating shallower water at Tvären than Lockne. Consequently, we suggest equivalent distribution patterns for the carbonates of the Dalby Limestone in Lockne and Tvären.
    • Facilities Excellent, People Friendly and Cooperative

      Humphrey, Robert R.; College of Agriculture (College of Agriculture, University of Arizona (Tucson, AZ), 1964)
    • Facilities for Complete Dairy Ration

      Stott, G. H.; Welchert, W. T.; Department of Dairy Science; Cooperative Extension Service (College of Agriculture, University of Arizona (Tucson, AZ), 1969)
    • A Factor Analysis of Correspondences to Ring Widths

      Serre, Françoise; Laboratoire de Botanique Historique et Palynologie, Université d'Aix-Marseille III, Faculté des Sciences et Techniques de Marseille St-Jérôme (Tree-Ring Society, 1977)
      The factor analysis of correspondences has been applied to variations as a function of time of the ring widths of the Aleppo pine (Pinus halepensis Mill.) in the French Mediterranean region. This study, involving rings corresponding to 36 years of growth, demonstrates that a general climatic factor (factor 1) intervenes, as well as the constraint of external factors vis-a-vis individual reactions (factor 2). Numerous factors govern ring width. The factor analysis of correspondences enables the demonstration that an important factor is the rain which falls during the vegetation period preceding the summer drought. The importance of the rainfall factor is conditioned by the date at which the average minimum daily temperature exceeds + 4°C, as well as by the distribution of rain during the period in question and by the multiplying effect of the climate of the preceding year. The important effect of unusually low
    • Factorial Design Techniques Applied to Optimization of AMS Graphite Target Preparation

      Verkouteren, R. M.; Klouda, G. A. (Department of Geosciences, The University of Arizona, 1992-01-01)
      Many factors influence the preparation and quality of graphite targets for 14C accelerator mass spectrometry (AMS). We identified four factors (sample size, HZ pressure, catalyst temperature and pretreatment time) as potentially critical, and investigated their effects on two particular characteristics; the integrated rates of CO2 reduction (to graphite) and methane production. We used a 2-level fractional factorial experimental design and determined chemical reduction yield rates through manometry and partial pressure monitoring of residual gases by mass spectrometry. Chemical reduction yield rates ranged from 0.2% to 6.2% per hour. With respect to their influence on percent yield rate, the factors we studied were ordered as; sample size > level of hydrogen > pretreatment of the catalyst. The temperature of the catalyst, and the sample size x hydrogen (2-factor) interaction, were only marginally influential. Other interactions did not appear to be significantly important. We estimated uncertainty in the order of influence and magnitudes of the effects by the Monte Carlo method of error propagation. We observed significant methane production in only one experiment, which suggests that methane originates from indigenous carbon in untreated iron catalyst only in the presence of hydrogen and only at thermodynamically favorable temperatures. This exploratory investigation indicates that factorial design techniques are a useful means to investigate multivariate effects on the preparation and quality of AMS graphite targets.
    • Factors Affecting Bollworm Control

      Wene, George P.; Sheets, L. W.; Department of Entomology; USDA Agricultural Research Service (College of Agriculture, University of Arizona (Tucson, AZ), 1965)
    • Factors Affecting Bromus tectorum Seed Bank Carryover in Western Utah

      Smith, Duane C.; Meyer, Susan E.; Anderson, V. J. (Society for Range Management, 2008-07-01)
      Cheatgrass (Bromus tectorum L.) is a winter annual weed that presents a serious obstacle to rangeland restoration in the Intermountain West. The objective of this study was to evaluate factors regulating the size and persistence of cheatgrass carryover seed banks on semiarid sites in western Utah. We prevented current-year seed production in each of four habitats, then tallied emerging seedlings over the next 4 yr. Two iterations of the study were conducted during consecutive years. One year before initiation of each iteration, we estimated seed rain at each site. Above-average precipitation in 1998-1999 resulted in relatively high seed rain (13 942 seeds m-2) for the first iteration, whereas seed rain for the second iteration averaged only 3 567 m-2 because of drought conditions in 1999-2000. Mean total number of seedlings emerging from carryover seeds for the first and second iterations were 1 304 and 270 seedlings m-2. Seedling emergence from carryover seed was positively correlated with production-year seed rain (R2 = 0.69). The fraction of seed rain that carried over tended to be lower when precipitation the year following production favored fall emergence of the transient seed bank. First-year emergence of carryover seeds averaged 96% of total emergence, whereas third-year emergence averaged , 1% and was zero for six of eight cases. Carryover seeds persisted somewhat longer at the xeric black greasewood site than at more upland sites. Our study shows that cheatgrass seeds rarely persist beyond the second carryover year even on semiarid sites. Emergence from the carryover seed bank can be predicted from site attributes and precipitation patterns in previous years. 
    • Factors Affecting Budbreak in Honey Mesquite in West Texas

      Goen, J. P.; Dahl, B. E. (Society for Range Management, 1982-07-01)
      Budbreak in honey mesquite in west Texas rarely occurs prior to the last spring frost. We monitored many trees from 1970 to 1980 attempting to better correlate mesquite mortality from herbicides to growth stage. In doing so, we found clues to the probable conditions triggering budbreak. Budbreak was closely correlated to daily minimum winter temperatures but totally unrelated to winter maximum, mean, or soil temperatures. Our data showed that the higher the number of consecutive days with minimums below -1°C during January 15 to February 14, the earlier spring budbreak would occur. Once chilling requirements were met, date of budburst then became a function of relatively warmer daily minimum temperatures from February 15 to March 15. Being able to predict budbreak (from equations developed herein) as early as February 15 and/or March 15 should give ranchers and herbicide applicators 4 to 6 weeks lead time in planning mesquite control programs.
    • Factors affecting dietary preferences for genotypes of a hybrid wheatgrass

      Truscott, D. R.; Currie, P. O. (Society for Range Management, 1987-11-01)
      Interspecific hybridization of grasses represents a valuable plant breeding procedure for developing new species with superior grazing value for livestock. Evaluations were made of the hybrid cross between quackgrass (Elytrigia repens [L.] Beauv.) × bluebunch wheatgrass (Pseudoroegneria spicata [Pursh.] Scribn and Smith) to determine how animal preferences for these hybrids were influenced by grazing season and year. Significant differences in the preference shown by steers as measured by bite counts in 1981 and percent utilization (P<0.01) in 1982 existed among the 46 clonal lines for each of the 2 successive years. Preference rankings for lines selected the first year were not identical to those selected a second year although lines with high preference rankings the first year were generally preferred the second year. A clonal line, designated line 30, was most preferred in 7 of 8 subtrials in 1981 and ranked in the top 3 preferred plants in all trials in 1982. There was a 4-week period in early summer when preference differences were minimal. It was attributed to the abundant regrowth on all lines at this time and was found to have a significant (P<0.01) effect on steers' dietary choices.
    • Factors Affecting Fill and Consequently Overnight Shrinkage in Range Cattle

      Wagnon, K. A.; Rollins, W. C. (Society for Range Management, 1962-05-01)
    • Factors Affecting Forage Consumption by Cattle in Arizona Ponderosa Pine Forests

      Clary, W. P.; Ffolliott, P. F.; Larson, F. R. (Society for Range Management, 1978-01-01)
      Forage consumption was significantly correlated with forage production and tree density, but not with steepness of slope, rockiness of soil, or distance from water. This suggests that good range management practices can effectively distribute livestock use.
    • Factors Affecting Forage Intake by Range Ruminants: A Review

      Allison, C. D. (Society for Range Management, 1985-07-01)
      Variation in voluntary forage intake is undoubtedly the major dietary factor determining level and efficiency of ruminant production. This variation is largest and least predictable for grazing ruminants. Range ruminant productivity and efficiency is relatively low due, in part, to intake limitations; therefore, productivity could probably be increased most by increasing intake. Most available literature points to digestibility and rate of ingesta passage and reticulo-rumen fill as primary mechanisms of intake regulation in range ruminants. Body size and physiological status of ruminants appear to have the largest effect of animal-related factors in governing level of voluntary intake. Kind and amount of supplementation, forage availability, and grazing intensity are major management-controlled variables affecting intake by domestic range ruminants.
    • Factors Affecting Germination, Emergence and Establishment of Sand Bluestem

      Stubbendieck, J.; McCully, W. G. (Society for Range Management, 1972-09-01)
      Response of sand bluestem seed units (florets) to three rates of cotton-bur mulch and treatment with an organic mercury pathogenicide was measured by germination, emergence and establishment. All rates of cotton-bur mulch improved soil moisture conditions, but heavier rates formed a physical barrier to the emergence of grass seedlings. More than three times as many plants became established from florets treated with a pathogenicide than from untreated florets.
    • Factors Affecting Mesquite Control with Tordon 225 Mixture

      Sosebee, R. E.; Dahl, B. E.; Goen, J. P. (Society for Range Management, 1973-09-01)
      The influence of various site characteristics was studied for Tordon 225 Mixture effectiveness in honey mesquite control in the Rolling Plains of Texas. Tordon 225 Mixture was commercially applied in 1970 at 0.5 lb a.e./acre under an experimental label for Texas. Generally, soil temperature (18-inch depth) above 75 degrees F, relatively low soil water content (0 to 6-inch depth), and tree height (less than 8 ft) were most influential in the root mortalities obtained in this study.
    • Factors affecting private rangeland lease rates

      Vantassell, L. W.; McNeley, S. M. (Society for Range Management, 1997-03-01)
      Private rangeland lease rates have been used historically as an indication of the price of public grazing lease rates. The ability of these prices to adequately reflect short-term fluctuations in the rancher's ability to pay for forage has been questioned by policy makers and researchers. Multiple regression techniques were used in this study to evaluate how responsive private rangeland lease rates have been to short-term (yearly) fluctuations in market conditions. Independent variables included yearling prices, cattle numbers, hay prices, production cost index, land prices, forage condition index, and the previous year's lease rate. Yearling prices lagged 1 year, hay prices, production cost index lagged 1 year, and lease rates lagged 1 year statistically (P < 0.10) explained lease rates. The previous year's lease rate was the most influential explanatory variable, with more than half of the previous year's lease price reflected in the current year's rate. Statistically significant (P < 0.10) differences in lease rates were also found between western regions.
    • Factors Affecting Resistance to Heavy Grazing In Needle-and-Thread Grass

      Peterson, R. A. (Society for Range Management, 1962-07-01)