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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
291

Establishing Buffalograss in Fine Fescue Turfgrass on the Central Coast of California

Axtell, Brittani Jean 01 May 2010 (has links) (PDF)
Buffalograss [Buchloe dactyloides (Nutt.) Engelm.] is a warm season, perennial grass native to the Great Plains from southern Canada to Mexico (Beetle, 1950). This newly developed, low input, turf-type grass is recommended for use on low maintenance sites (Falkenberg-Borland and Butler, 1982; Pozarnsky, 1983; Wu and Harivandi, 1989; Shearman et al., 2005). Recently, the use of buffalograss as a turfgrass has increased due to its drought tolerance, low nutrient requirements, and low growing height (Harivandi and Wu, 1995; Frank et al., 2004). It is an excellent choice in California where water use is limited. Unsightly winter dormancy of buffalograss can be overcome by growing mixtures of buffalograss and fine fescue (Festuca spp.). Overtime species composition can be overtaken by the fine fescue, unintentionally converting the mixed turfgrass stand to a fine fescue monostand (Severmutlu, et al., 2005). Research on buffalograss establishment in fine leaved fescues from seed or by vegetative methods was completed from 2007 to 2009 at the California Polytechnic State University Horticulture Unit in San Luis Obispo, California. Comparisons were made between mixtures of eight cultivars of buffalograss (Prairie, Prestige, UC Verde, 609, Bowie, Cody, Texoka, and Bison) and three fine leaved fescue species [hard fescue (Festuca trachyphylla Thuill.), sheep fescue (Festuca ovina L), and red fescue (Festuca rubra L.)] to determine which combination and establishment strategy provides the highest quality turf for the California central coast region. Evaluations made on buffalograss establishment and competitive ability when grown in pre-existing fine fescue turfgrasses showed seeded cultivars (Bowie, Cody, Texoka, and Bison) were unsuccessfully established (zero percent coverage in two growing seasons), and vegetative cultivar (Prairie, Prestige, 609 and UC Verde) establishment was greatly dependent on the type of cultivar planted. After two growing seasons, buffalograss cultivar UC Verde had the highest establishment rate (38.6 percent living ground cover) and Prestige had the lowest (11.4 percent living ground cover). Results from this study do not recommend establishing seeded buffalograss cultivars into pre-existing fine leaved fescue turfgrass stands. Vegetative buffalograss cultivars can be established into pre-existing fine leaved fescue turfgrass stands; however, this process is too slow for most turfgrass practitioners and is quite unsightly in winter dormancy during the establishment process.
292

International Water Quality: Global Patterns of Water Pollutants and Pathogens

Lange, Leslie 17 June 2022 (has links) (PDF)
Water quality is an essential component of vibrant societies and ecosystems. For decades, researchers, managers, and policymakers around the world have struggled to accelerate societal progress while preserving and enhancing water quality and human health. This thesis consists of two studies that I hope will contribute to better understanding, policy, and management. In the first study, I evaluated spatial and temporal patterns in global water quality and their relationship to gross domestic product (GDP) per capita, as a metric of socioeconomic development status. Using global water quality datasets containing over 2.7 million observations, I tested the Environmental Kuznet Curve (EKC) hypothesis, which predicts that environmental degradation is highest at intermediate levels of socioeconomic development. I found that 46% of pollutants persisted at elevated concentrations despite GDP per capita. Because of this, high income countries experience a false sense of water security as water regulation violations are common on a global scale. In the second study, I measured waterborne pathogens in Guayaquil, the largest city in Ecuador. With a population of over 3 million and distinct hydrology from monsoonal rains and estuarine flooding, the Guayaquil metropolitan area faces drinking water and sanitation challenges similar to much of the developing world. I found that 100% of the samples we collected had unsafe total coliform counts. Water pollution is widespread and is a result of careless action. Moving forward, chronic pollution can be prevented with proper legislation that holds governments, companies, and individuals accountable.
293

The Roles of Natural and Semi-Natural Habitat in the Provisioning of Biodiversity and Ecosystem Services of Beneficial Insects in Agricultural Landscapes

Nelson, Jason M. 13 August 2012 (has links)
No description available.
294

Reduced Chemical Weed Control Options in Virginia for Corn and Turfgrass and Characterization of Sorghum halepense Expressing Multiple Resistance to Nicosulfuron and Glyphosate

Smith, Adam N. 24 April 2014 (has links)
Sustainable weed control in managed agricultural systems requires the judicious use of multiple weed control tactics and prevents over-reliance on any one tactic. In this context, sustainable weed management plays a critical role in the mitigation of one of agriculture's most pressing problems- herbicide resistance. Research conducted in Virginia sought to explore the effects of integrating multiple weed management tactics in corn and cool-season turfgrass. Additionally, research was conducted to confirm nicosulfuron and glyphosate herbicide resistance in Virginia johnsongrass and elucidate the molecular mechanisms conferring those resistances. Rye and hairy vetch cover crop residues, combined with reduced rates of preemergence herbicide and postemergence glyphosate applications, were shown to provide sufficient weed control and corn yield. Cover crop type or residue level did not augment weed control in corn production systems, but the use of glyphosate was essential for late-season weed control. Rye and vetch biculture as a cover crop increased corn yield compared to rye cover crop alone. In cool-season turfgrass, the addition of reduced preemergence herbicide rates to corn gluten meal, an organic herbicide product, reduced crabgrass 25%. Moreover, control was dependent on herbicide choice. Herbicides applied at half of recommended labeled rates or less did not control crabgrass at a commercially-acceptable level, regardless of corn gluten meal addition. In field experiments, Virginia johnsongrass expressed resistance to nicosulfuron and glyphosate. Glyphosate at 0.88 kg ae ha-1 controlled johnsongrass 65%. Nicosulfuron at 0.14 kg ai ha-1 controlled the same population 10%. Greenhouse experiments confirmed differential sensitivity of putative herbicide-resistant johnsongrass seedlings to nicosulfuron and glyphosate when compared to a susceptible population. Herbicide resistance was not conferred via target-site mutation. Five ALS-gene site mutations were confirmed absent in Virginia johnsongrass, while three others were located in coding regions that could not be elucidated in johnsongrass. Further investigations showed glyphosate resistance was not conferred via reduction in herbicide absorption or translocation. The susceptible johnsongrass caused an increase in a polar metabolite at Rf = 0.17 with concomitant reduction in glyphosate over time. Although the mechanism is not clear, these data suggests that glyphosate resistance in johnsongrass may be associated with differential metabolism. / Ph. D.
295

Influence of Several Herbicides on Visual Injury, Leaf Area Index, and Yield of Glyphosate-Tolerant Soybean <I>(Glycine max)</I>

Johnson, Bryan Fisher 09 May 2001 (has links)
The occasional failure of glyphosate to control all weeds throughout the entire growing season has prompted growers to sometimes use herbicides other than glyphosate on glyphosate-tolerant soybean. Field studies were conducted in 1999 and 2000 to investigate potential crop injury from several herbicides on glyphosate-tolerant soybean, and to determine the relationship between soybean maturity, planting date, and herbicide treatment on soybean injury, leaf area index (LAI), and yield. Three glyphosate-tolerant soybean cultivars representing maturity groups III, IV and V were planted at dates representing the full-season and double-crop soybean production systems used in Virginia. Within each cultivar and planting date, 15 herbicide treatments, in addition to a control receiving only metolachlor preemergence, were applied to cause multiple levels of crop injury. Results of this study indicate that glyphosate-tolerant soybean generally recovered from early-season herbicide injury and LAI reductions; however, reduced yield occurred with some treatments. Yield reductions were more common in double-crop soybean than in full-season soybean. In full-season soybean, most yield reductions occurred only in the early maturing RT-386 cultivar. These yield reductions may be attributed to the reduced developmental periods associated with early maturing cultivars and double-crop soybean that often lead to reduced vegetative growth and limited LAI. Additional reductions of LAI by some herbicide treatments on these soybean may have coincided with yield reductions; however, reduced LAI did not occur with all yield reducing treatments. Therefore, soybean LAI response to herbicide treatments does not always accurately indicate the potential detrimental effects of herbicides on soybean yield. Further, yield reductions associated with herbicide applications occurred, although soybean sometimes produced leaf area exceeding the critical LAI level of 3.5 to 4.0 which is the minimum LAI needed for soybean to achieve maximum yield. / Master of Science
296

Androgen receptors are only present in mesenchyme-derived dermal papilla cells of red deer (Cervus elaphus) neck follicles when raised androgens induce a mane in the breeding season

Randall, Valerie A., Hibberts, Nigel A., Street, T., Thornton, M. Julie January 2001 (has links)
No / Red deer stags produce an androgen-dependent mane of long hairs only in the breeding season; in the non-breeding season, when circulating androgen levels are low, the neck hair resembles the rest of the coat. This study was designed to determine whether androgen receptors are present in deer follicles throughout the year or only in the mane (neck) follicles when circulating testosterone levels are high in the breeding season. Although androgens regulate much human hair growth the mechanisms are not well understood; they are believed to act on the hair follicle epithelium via the mesenchyme-derived dermal papilla. The location of androgen receptors in the follicle was investigated by immunohistochemistry and androgen binding was measured biochemically in cultured dermal papilla cells derived from mane and flank follicles during the breeding season and from neck follicles during the non-breeding season. Immunohistochemistry of frozen skin sections using a polyclonal antibody to the androgen receptor localised nuclear staining only in the dermal papilla cells of mane follicles. Saturation analysis assays of 14 primary dermal papilla cell lines using [(3)H]-mibolerone demonstrated high-affinity, low-capacity androgen receptors were present only in mane (breeding season neck) cells; competition studies with other steroids confirmed the specificity of the receptors. Androgen receptors were not detectable in cells from either the breeding season flank nor the non-breeding season neck follicles. The unusual biological model offered by red deer of androgen-dependent hair being produced on the neck in the breeding, but not the non-breeding season, has allowed confirmation that androgen receptors are required in follicle dermal papilla cells for an androgen response; this concurs with previous human studies. In addition, the absence of receptors in the non-breeding season follicles demonstrates that receptors are not expressed unless the follicle is responding to androgens. Androgen receptors may be induced in mane follicles by seasonal changes in circulating hormone(s).
297

The influence of habitat features and co-occurring species on puma (Puma concolor) occupancy across eight sites in Belize, Central America

Rowe, Christopher Brian 05 February 2018 (has links)
Large carnivores play many vital biological, economic, and conservation roles, however, their biological traits (low population densities, cryptic behavior) make them difficult to monitor. Pumas have been particularly difficult to study because the lack of distinctive markings on their coats prevents individual identification, precluding mark-recapture and other similar analyses. Further, compared to temperate areas, research on the interspecific interactions of Central American felids is particularly lacking. I used single- and multi-season, single-species occupancy models and two-species co-occurrence models to analyze camera trapping and habitat data collected at eight study sites across Belize. Puma occupancy was positively influenced by jaguar trap success, understory density, canopy cover, and human trap success, and negatively influenced by stream density. Jaguar trap success was the best predictor of where pumas occurred, while prey species were not found to influence puma occupancy. Mean occupancy was 0.740 (0.013) and ranged from 0.587 (0.042) to 0.924 (0.030). Over time, puma occupancy rates were generally high (> 0.90) and stable. Puma occupancy was higher in logged areas, suggesting that current levels of natural resource extraction at those sites were not detrimental to the species. Co-occurrence modeling showed little evidence for interactions between the carnivores, suggesting that jaguars may be acting as an umbrella species and that conservation efforts directed at jaguars are likely to benefit the other carnivores, including pumas. Overall, these findings are positive for puma conservation, but human-induced land use change is expanding and further monitoring will give us insight into how pumas respond to human encroachment. / Master of Science / Large carnivores play many vital biological, economic, and conservation roles, however, their biological traits (low population densities, cryptic behavior) make them difficult to monitor. Pumas have been particularly difficult to study because they lack distinctive markings on their coats, making it difficult to identify individuals. Further, compared to temperate areas, there is little research on how cat species in Central American interact. To learn more about the habitat that pumas prefer and how they interact with other carnivores, I used single- and multi-season, single-species occupancy models and two-species co-occurrence models to analyze camera trapping and habitat data collected at eight study sites over multiple years across Belize. Puma distribution across the landscape was positively influenced by jaguar activity levels, understory density, canopy cover, and human activity levels, and negatively influenced by how wet sites were. Jaguar activity level was the best predictor of where pumas occurred, while prey species did not influence puma occupancy. Over time, these puma occupancy rates were generally high and stable. Puma occurrence was higher in logged areas, suggesting that current levels of natural resource extraction at those sites were not detrimental to the species. There was little evidence of interactions between the carnivores, suggesting that jaguars could act as an umbrella species and that conservation efforts directed at jaguars are also likely to benefit pumas. Overall, these findings are good news for puma conservation, but human-induced land use change is expanding and further monitoring will give us insight into how pumas respond to human encroachment.
298

期中財務報表預測盈餘功能之研究

王富中, WANG, FU-ZHONG Unknown Date (has links)
1.主題說明 財務報導的目在協助使用者擬定明智的決策。隨著社會、經濟環境的變遷,使用者對 資訊的需冬日切,鑑於資的時效性,期中財務報導的地位愈形重要。本論文的研究目 的,即針對期中財務報表的預測功能及其相關問題,作一探詩。 2.研究方法 本研究於實證方面,採郵寄問卷的方式,受試者有證券投資分析人員、財務經理,及 銀行經理等。由受試者分析問卷所列的公司財務報表資料後,預測其稅前純益。實證 目的在驗證:(1)提供期中財務報表(分別為一季、二季、三季)與僅提供年報, 在預測當年度稅前純益的準確度上,有無顯著差異;(2)提供期中財務報表與僅提 供年報,在預測次年度同季稅前純益的準確度上,有無顯著差異。 3.結果 實證分析結果顯示:不論在預測當年度稅前純益或次年度同季稅前純益時提供期中財 務報表與提供年報,在預測的準確度上,皆有顯著差異。
299

Změny ukazatelů kondice v přípravném období vybraných fotbalových klubů žákovské kategorie U15 / Changes of the fitness indicators during pre-season period of selected football clubs of U15 category

Švomová, Veronika January 2017 (has links)
Title: Changes of the fitness indicators during pre - season period of selected football clubs of U15 category Objectives: The aim of this work was a diagnostic subseqent comparasion of two selected indicators of fitness clubs youth category U15 in the summer pre - season period. Methods: The research was performed by motor testing. To determine the status fitness indicators and its changes in the pre - season of the two clubs we have chosen five selected motor tests battery by the Football Association of the Czech Republic - tests of strength skills, speed skills, endurance and agility. Results: Significant change of fitness indicators during pre - season period occurred in one club in two motor tests and in the second one in three motor tests. Although partial changes occurred the assumption of improvement in overall fitness indicators has not been confirmed. The observation period (5 and 8 weeks) to achieve substantial changes is probably insufficient. Keywords: Managing training, control of fitness, condition, ability to move, motor Tests, pre - season period
300

Změny délek odobí s charakteristickými teplotami vzduchu / Changes of length of periods with characteristic temperatures

Černochová, Eva January 2006 (has links)
Title: Changes of lengths of periods with characteristic air temperatures Author: Eva Černochová Department: Department of Meteorology and Environment Protection Supervisor: doc. RNDr. Jaroslava Kalvová, CSc. Supervisor's e-mail address: jaroslava.kalvova@mff.cuni.cz Abstract: Lengths of periods with characteristic air temperatures were derived using two different methods (linear interpolation, robust locally weighted regression) for 10 stations in the Czech Republic and for output data of regional climate models HIRHAM and RCAO in 4 grid points. Averages for a forty-year period (1961-2000) and for a thirty-year period (1961-1990) were computed as well as averages for every decade. Considerable attention was also paid to the analysis of methods used in the research. Most stations showed lengthening of growing season and summer during the twentieth century. Decennary average length of growing season and summer shortened in the years 1971-1980. The comparison of output data of regional climate models HIRHAM and RCAO and measured station data showed that the thirty-year average lengths of growing season and summer estimated by the two models were reasonably accurate approximately half of all cases. The models' estimates were not accurate at all concerning decennary averages. Keywords: robust locally...

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