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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.
51

Seasonal and Sex Differences in the Effects of Melatonin on Brain Arginine Vasotocin in Green Treefrogs (Hyla cinerea): Relationship to Melatonin Receptor 1a

Howard, Christina Marie 30 May 2014 (has links)
Critical life history events such as breeding, migration and hibernation must take place in the correct environmental context to minimize deleterious consequences on survival and reproductive fitness. Neuroendocrine mechanisms synchronizing internal physiological states with extrinsic environmental cues are vital to timing life history events appropriately. Secretion of the pineal hormone melatonin is sensitive to light and temperature cues, which provides a physiological indicator of time of day and time of year for organisms. Melatonin influences seasonal reproduction in a variety of vertebrates, likely by altering the synthesis and/or release of reproductive neuropeptides in the brain. The neuropeptides arginine vasotocin and its mammalian homologue, arginine vasopressin, are well-known modulators of reproductive and sociosexual behavior across vertebrate taxa, and are likely targets of melatonin in the context of seasonal reproduction. There is extensive evidence that vasotocin/vasopressin innervation in the brain is subject to seasonal variation, and that this variation is frequently sexually dimorphic. However, evidence that melatonin directly modulates this important neuropeptide system is lacking. Melatonin receptor 1a (MT1 in mammals) may be responsible for mediating melatonin's influence on brain vasotocin, as it is known to regulate seasonal reproduction in a variety of vertebrates. In the present study, I asked whether melatonin influences brain vasotocin in male green treefrogs (Hyla cinerea), and compared the distribution of melatonin receptor 1a in the brain of green treefrogs between sexes and seasons. Adult male and female green treefrogs were collected from field sites in Louisiana during the summer breeding season. Summer animals were acclimated to lab conditions for 3 weeks, then euthanized and their brains collected. Winter animals were maintained in the lab for four months under incrementally changing photo-, thermo-, and hygroperiod regimes that mimicked the transition to winter in their natural habitat, followed by euthanasia and brain collection. A subset of winter males (Experiment 1) were implanted with melatonin-filled or blank silastic capsules for a period of one month prior to euthanasia and brain collection. Brains of these males were processed for vasotocin immunohistochemistry. I quantified AVT-ir cell number in Experiment 1 males in the nucleus accumbens (NAcc), amygdala and caudal striatum (AMG), preoptic area (POA), suprachaismatic nucleus (SCN), and ventral hypothalamus (VH). Melatonin did not influence brain vasotocin-ir cell number in any brain region. Brains from untreated summer and winter males and females were collected and processed for MT1 immunohistochemistry. MT1-ir cells were quantified in the NAcc, striatum (STR), AMG, POA, SCN, and VH. In all regions quantified, reproductively active males had significantly more MT1-ir cells than nonreproductive males. Within the summer breeding season, males had significantly more MT1-ir cells in the NAcc than did reproductively active females. In all other regions there was no significant difference in MT1-ir cell number between reproductively active males and females. Collectively, these data suggest that melatonin modulates vasotocin via MT1. These findings assist in elucidating the neuroendocrine mechanisms by which vertebrates integrate seasonal cues with physiology to correctly time critical life history events.
52

An Empirical Study on the Jump-diffusion Two-beta Asset Pricing Model

Chen, Hongqing 01 January 1996 (has links)
This dissertation focuses on testing and exploring the usage of the jump-diffusion two-beta asset pricing model. Daily and monthly security returns from both NYSE and AMEX are employed to form various samples for the empirical study. The maximum likelihood estimation is employed to estimate parameters of the jump-diffusion processes. A thorough study on the existence of jump-diffusion processes is carried out with the likelihood ratio test. The probability of existence of the jump process is introduced as an indicator of "switching" between the diffusion process and the jump process. This new empirical method marks a contribution to future studies on the jump-diffusion process. It also makes the jump-diffusion two-beta asset pricing model operational for financial analyses. Hypothesis tests focus on the specifications of the new model as well as the distinction between it and the conventional capital asset pricing model. Both parametric and non-parametric tests are carried out in this study. Comparing with previous models on the risk-return relationship, such as the capital asset pricing model, the arbitrage pricing theory and various multi-factor models, the jump-diffusion two-beta asset pricing model is simple and intuitive. It possesses more explanatory power when the jump process is dominant. This characteristic makes it a better model in explaining the January effect. Extra effort is put in the study of the January Effect due to the importance of the phenomenon. Empirical findings from this study agree with the model in that the systematic risk of an asset is the weighted average of both jump and diffusion betas. It is also found that the systematic risk of the conventional CAPM does not equal the weighted average of jump and diffusion betas.
53

Initial analysis of k-factor in the Gulf region

AbouAlmal, A., Usman, Muhammad, Abd-Alhameed, Raed, Al-Ahmad, Hussain, Jones, Steven M.R., Excell, Peter S. January 2013 (has links)
No / This paper investigates the seasonal variations of effective earth radius factor, k, in the Arabian Gulf region where non-standard propagation phenomena are commonly experienced. The k-factor is derived from the vertical profile of refractivity in the area under study. The vertical refractivity gradient, δN, in the first kilometre of the atmosphere above the ground surface is analysed using long term meteorological data. Long-term radiosonde data gathered in the United Arab Emirates (UAE), are used to calculate the variations of refractivity gradient and k-factor parameter.
54

Uptake of Mercury and Relationship to Food Habits of Selected Fish Species in the Shenandoah River Basin, Virginia

Murphy, Gregory W. 17 August 2004 (has links)
Mercury poses significant challenges to human health and fisheries management. Historical industrial practices in Waynesboro, Virginia left portions of the Shenandoah River basin contaminated with mercury and stringent health advisories for fish consumption. I investigated processes affecting the bioaccumulation of mercury in Catostomus commersoni, Ictalurus punctatus, Lepomis auritus, and Micropterus dolomieu by studying food habits, total mercury and methylmercury in common prey items, and bioaccumulation dynamics of methylmercury in the mercury contaminated South River and South Fork of the Shenandoah River and uncontaminated North River. Additionally, I evaluated sexual and seasonal variations of total mercury in M. dolomieu in the South Fork of the Shenandoah River. Algae, aquatic insects, crayfish, detritus, and fish accounted for 75-97% of the diet. Total mercury in aquatic invertebrates and forage fish in contaminated rivers ranged from 66.7-398.3 and 198.0-594.9 ng/g wet weight, while total mercury in aquatic invertebrates and forage fish in the reference river were 4.4 and 29.3 ng/g. Model simulations indicated that dietary pathways accounted for 87% of methylmercury uptake by fish in contaminated rivers, but only 57% in the reference river. Total mercury in M. dolomieu was 19-20% higher in females than males and 14-21% higher during spring than summer and fall. Results of this study indicate that bioenergetics-based bioaccumulation models are valuable tools for evaluating field data, identifying processes critical to contaminant accumulation, and comparing outcomes of alternative management options associated with pollution control, ecosystem management, and/or restoration activities for management guidance prior to costly expenditures. / Master of Science
55

Seasonal variations in the chemical composition of selected Hong Kong seaweeds.

January 1997 (has links)
by Chan Ching Ching Jenny. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (leaves 118-127). / Acknowledgments --- p.i / Abstract --- p.ii / List of figures --- p.iv / List of tables --- p.vii / List of abbreviations --- p.viii / Chapter Chapter 1. --- Introduction / Chapter 1.1 --- Consumption and classification of seaweeds --- p.1 / Chapter 1.2 --- Present uses of seaweeds --- p.4 / Chapter 1.2.1 --- The chemical composition of seaweeds --- p.4 / Chapter 1.2.2 --- Industrial uses - phycocolloids / Chapter 1.2.2.1 --- Alginate --- p.7 / Chapter 1.2.2.2 --- Carrageenan --- p.9 / Chapter 1.2.2.3 --- Agar --- p.12 / Chapter 1.3 --- Seasonal variations studies --- p.14 / Chapter 1.4 --- Seaweeds in Hong Kong --- p.16 / Chapter 1.5 --- Seaweeds selected for study / Chapter 1.5.1 --- Sargassum species / Chapter 1.5.1.1 --- Uses of Sargassum --- p.16 / Chapter 1.5.1.2 --- Seasonal variations of Sargassum --- p.17 / Chapter 1.5.2 --- Hypnea species --- p.19 / Chapter 1.6 --- Drying methods used in seaweed studies and industrial processing --- p.20 / Chapter 1.7 --- Significance of the present study --- p.22 / Chapter Chapter 2. --- Materials and methods / Chapter 2.1 --- "Location, seaweed collection, and environmental parameters" --- p.24 / Chapter 2.2 --- Sample preparation --- p.24 / Chapter 2.3 --- Chemical composition analysis / Chapter 2.3.1 --- Protein --- p.26 / Chapter 2.3.2 --- Amino acids --- p.28 / Chapter 2.3.3 --- Dietary fiber --- p.29 / Chapter 2.3.4 --- Sugar --- p.30 / Chapter 2.3.5 --- Ash --- p.31 / Chapter 2.3.6 --- Mineral elements --- p.32 / Chapter 2.3.7 --- Vitamin C --- p.32 / Chapter 2.3.8 --- Moisture --- p.33 / Chapter 2.4 --- Characterization of alginate from brown seaweed Sargassum hemiphyllum / Chapter 2.4.1 --- Alginate extraction --- p.33 / Chapter 2.4.2 --- Uronic acid block composition determination --- p.34 / Chapter 2.4.2.1 --- M/G ratio determination --- p.35 / Chapter 2.4.2.2 --- Phenol-sulfuric acid method for determination of sugar --- p.35 / Chapter 2.5 --- Characterization of carrageenan from red seaweed Hypnea charoides / Chapter 2.5.1 --- Carrageenan extraction --- p.35 / Chapter 2.5.2 --- Chemical analysis of carrageenan - sulfate content --- p.36 / Chapter 2.5.3 --- Physical analysis of carrageenan / Chapter 2.5.3.1 --- Gelling temperature --- p.37 / Chapter 2.5.3.2 --- Gelling concentration --- p.37 / Chapter 2.6 --- Data Analysis --- p.38 / Chapter Chapter 3. --- "Comparative studies on the effect of sun-drying, oven-drying, and freeze- drying methods on the chemical composition of brown seaweed Sargassum hemiphyllum" / Chapter 3.1 --- Results and discussion / Chapter 3.1.1 --- Color and appearance --- p.39 / Chapter 3.1.2 --- Chemical composition / Chapter 3.1.2.1 --- "Protein, dietary fiber, ash, and moisture" --- p.39 / Chapter 3.1.2.2 --- Amino acids --- p.42 / Chapter 3.1.2.3 --- Mineral elements --- p.44 / Chapter 3.1.2.4 --- Vitamin C --- p.46 / Chapter 3.1.3 --- Characterization of alginate / Chapter 3.1.3.1 --- Extraction of alginate --- p.46 / Chapter 3.1.3.2 --- Uronic acid block composition and M/G ratio --- p.48 / Chapter 3.2 --- Summary --- p.50 / Chapter Chapter 4. --- Seasonal variations in the chemical composition of brown seaweed Sargassum hemiphyllum / Chapter 4.1 --- Results and discussion / Chapter 4.1.1 --- Environmental parameters --- p.53 / Chapter 4.1.2 --- Morphology --- p.58 / Chapter 4.1.3 --- Chemical composition / Chapter 4.1.3.1 --- Protein and amino acids --- p.60 / Chapter 4.1.3.2 --- Dietary fiber and polysaccharide sugars --- p.64 / Chapter 4.1.3.3 --- Ash and mineral elements --- p.69 / Chapter 4.1.3.4 --- Vitamin C --- p.76 / Chapter 4.1.3.5 --- Water and moisture --- p.78 / Chapter 4.1.4 --- Characterization of phycocolloid - alginate / Chapter 4.1.4.1 --- Alginate extraction --- p.78 / Chapter 4.1.4.2 --- Uronic acid block composition and M/G ratio --- p.79 / Chapter Chapter 5. --- Seasonal variations in the chemical composition of red seaweed Hypnea charoides / Chapter 5.1 --- Results and discussion / Chapter 5.1.1 --- Environmental parameters --- p.82 / Chapter 5.1.2 --- Color and appearance --- p.86 / Chapter 5.1.3 --- Chemical composition / Chapter 5.1.3.1 --- Protein and amino acids --- p.88 / Chapter 5.1.3.2 --- Dietary fiber and polysaccharide sugars --- p.93 / Chapter 5.1.3.3 --- Ash and mineral elements --- p.97 / Chapter 5.1.3.4 --- Vitamin C --- p.104 / Chapter 5.1.3.5 --- Water and moisture --- p.104 / Chapter 5.1.4 --- Characterization of phycocolloid - carrageenan / Chapter 5.1.4.1 --- Carrageenan extraction --- p.106 / Chapter 5.1.4.2 --- Chemical characteristic of carrageenan - sulfate content --- p.109 / Chapter 5.1.4.3 --- Physical characteristics of carrageenan / Chapter 5.1.4.3.1 --- Gelling temperature --- p.110 / Chapter 5.1.4.3.2 --- Gelling concentration --- p.110 / Chapter Chapter 6. --- Conclusion --- p.113 / Chapter 6.1 --- Development perspectives of seaweeds --- p.116 / Chapter Chapter 7. --- References --- p.118 / Chapter Chapter 8. --- Appendixes --- p.128
56

Détermination et variation du profil physique du footballeur de très haut niveau : référence spéciale aux performances athlétiques selon les différents postes de jeu orientant sur la validation d’un test d’agilité / Athletic profile variation on elite soccer players : special reference to athletic performance according to playing positions to direct on a specific soccer agility test

Vigne, Grégory 13 December 2011 (has links)
Cette thèse s’adresse aussi bien aux scientifiques, aux entraîneurs, aux préparateurs physiques et aux sportifs souhaitant approfondir leurs connaissances de l’activité football. Les aspects scientifiques abordés ainsi que leur transposition en outils de terrain pourront être utilisés comme moyen d’évaluation et d’orientation des séances d’entraînement. Ainsi, au travers de ce travail, nous avons abordé le ratio entre le temps de travail et le temps de récupération réalisés en matches de très haut niveau dans le Championnat de Première Division Italienne au cours de la saison 2004/2005. Ce ratio moyen de compétition est de 1/8, à savoir 2.2 secondes d’effort et 18 secondes de récupération. La deuxième partie de ce travail consistait à analyser l’évolution du profil d’effort et la possession de balle collective de footballeurs de très haut niveau au cours de trois saisons consécutives avec un effectif et un staff technique stables. L’étude a permis de mettre en avant une diminution de la quantité d’effort produite par les joueurs de l’ordre de 5% sans altération de la performance ainsi que l’augmentation de la possession de balle collective. La troisième et dernière partie a été de créer et d’analyser un test d’agilité spécifique à l’activité football. Après, une analyse complète des différents éléments liés à la reproductibilité et à la validité du test, il s’avère que ce test semble rendre compte de l’activité motrice du footballeur. De plus, les mesures réalisées dans le cadre de ce travail ont permis de fournir les premières normes de performance qui peuvent être attendues en fonction de l’âge du joueur et de son niveau de jeu. Au terme de notre travail, nous pouvons conclure que cette thèse a apporté des résultats spécifiques pour orienter l’entraînement athlétique du footballeur moderne et à proposer un nouvel outil de détection des jeunes footballeurs. / This work is dedicated to scientists, coaches and physical trainers as well as athletes involved in elite soccer activity. The scientific results and their practical applications could be used as a basis for the work of scientists as well as football professionals. The first part of this thesis showed that playing positions significantly influence activity profile. Moreover, this study demonstrated that the work/rest ratio observed in elite soccer Italian Serie A championship attained 1/8 and represented a mean work time of 2.2 seconds for an averaged recovery time of 18 seconds. The second part of this thesis, explored the evolution of activity profile and total ball possession during 3 consecutive seasons in the same elite team. This study has showed how for three consecutive seasons the players of successful Serie-A team reduced their distances performed at submaximal speeds, and increased ball possession while maintaining the distances covered at high/maximal speeds. It is suggested that this is due to a better understanding of tactical roles and team organization. The third part of the thesis tended to develop and to valid a specific agility soccer test composed with fundamental soccer tasks which has to be performed as quickly as possible. The validity and repeatability of the test has been demonstrated and it has been applied on a large population of different ages, positions and levels. As a conclusion, this thesis provided new specific results and perspectives that would influence professional soccer athletic conditioning and that provided a new specific test to detect young soccer players.
57

An assessment of temperature variability over South Africa

Lakhraj-Govender, Rakhee January 2017 (has links)
A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. November 2017, Johannesburg. / The main aim of this PhD research is to use accurate, relatively long-temperature data sets (spanning 1851-2016) available in South Africa, to establish a more precise understanding of temporal temperature variability over this region. This is achieved through the use of robust methodology (i.e. data quality control and homogenization procedures, using a reference series) to produce high quality data sets for temperature trend analysis. Data quality and homogenization of data sets are conducted using RClimDex, ProClim and AnClim software. Long-term temperature trends are determined using a nonparametric statistic (i.e., Mann Kendall test). The core objectives are to provide a homogeneous dataset for the Western Cape region in South Africa and establish long-term (97 years) annual and seasonal instrumental temperature trends for this region. The second objective is to extend past work by examining temperature trends for KwaZulu-Natal (KZN) over a considerably longer period, with a specific focus on contrasting coastal and adjacent higher lying interior regions. The last objective is to assess the extent and timing of El Niño/La Niña impacts on maximum temperature (Tmax) and minimum temperature (Tmin) over selected South African stations for the period 1884-2016, and to establish any possible direct change in such temperature responses to ENSO over time. Long-term temperature trends for the Western Cape Province indicate statistically significant increasing annual temperature trends for adjusted (homogenized) Tmax and Tmin data over the period 1916-2013, with the exception of an insignificant decreasing Tmax trend at Cape St Blaize. For the common period (1937-2001), a statistically significant increasing trend (0.13°C/decade) is recorded for all stations in Western Cape Province, with a 0.04°C/decade stronger warming signal than before homogenization was applied. The seasonal trends also support significant increasing trends, with the exception of Tmax trends for summer (-0.03°C/decade) and autumn (0°C/decade) at Kirstenbosch. For KZN, cooler conditions are noted for the second half of the 19th century (i.e. 1851, 1858, 1860-1864) compared to more recent times. For the period 1930-2015, annual Tmin records significant warming at all stations, with the rates of warming (°C/decade) over the interior being double that for the coast. Tmin warming trends are 1.31 (summer), 2.75 (autumn), 3.33 (winter) and 1.25 (spring) times faster over the interior compared to the coast. Thus, higher lying interior regions are warming considerably faster than adjacent coastal areas mainly due to Tmin warming trends. The impact of El Niño and La Niña events on Tmax and Tmin over South Africa is investigated using composite and Fourier series analysis (1884-2016). For 17 stations spread across South Africa, it is concluded that strong coherent relationships exist between El Niño/La Niña events and Tmax/Tmin. Contingency tables were constructed for each station during the austral summer season (December, January and February) and analysed using the Chi-squared statistic. The most notable finding is that El Niño events have had a stronger warming effect over many regions in South Africa after the late 1970s, the most prominent regions being the northern interior and southeast coast, where associated Tmax record an average of 0.41°C and 0.45°C higher values over the period 1979-2016 compared to the earlier period (1940-1978) respectively. The Chi-squared statistic results indicate that ENSO phases exert a stronger influence over the interior of South Africa compared to that over the coast. Keywords: homogeneity, temperature, trend analysis, Mann Kendall, historical climate, Western Cape, KwaZulu-Natal, South Africa, ENSO. / LG2018
58

Remote sensing of the spatio-temporal distribution of invasive water hyacinth (Eichhornia crassipes) in the Greater Letaba River System in Tzaneen, South Africa

Thamaga, Kgabo Humphrey January 2018 (has links)
Thesis (MSc. (Geography)) --University of Limpopo, 2018 / Water hyacinth (Eichhornia crassipes) is recognised as the most notorious invasive species the world-over. Although its threats and effects are fully documented, its distribution is not yet understood, especially in complex environments, such as river systems. This has been associated with the lack of accurate (high spatial resolution) and robust techniques, together with the reliable data sources necessary for its quantification and monitoring. The advent of new generation sensors i.e. Landsat 8 Operational Land Imager (OLI) and Sentinel-2 MultiSpectral Instrument (MSI) data, with unique sensor design and improved sensing characteristics is therefore perceived to provide new opportunities for mapping the distribution of invasive water hyacinth in small waterbodies. This study aimed at mapping and understanding the spatio-temporal distribution of invasive water hyacinth in the Greater Letaba river system in Tzaneen, Limpopo Province of South Africa using Landsat 8 OLI and Sentinel-2 MSI data. Specifically, the study sought to identify multispectral remote sensing variables that can optimally detect and map invasive water hyacinth. Landsat 8 OLI and Sentinel-2 MSI were tested based on the spectral bands, vegetation indices, as well as the combined spectral bands plus vegetation indices, using discriminant analysis algorithm. From the findings, Sentinel-2 MSI outperformed Landsat 8 OLI in mapping water hyacinth, with an overall classification (OA) accuracy of 77.56% and 68.44%, respectively. This observation was further confirmed by a t-test statistical analysis which showed that there were significant differences (t=6.313, p<0.04) between the performance of the two sensors. Secondly, the study sought to map the spatial distribution of invasive water hyacinth in the river system over time (Seasonal). Multi-date 10 m Sentinel-2 MSI images were used to detect and monitor the seasonal distribution and variations of water hyacinth in the Greater Letaba River system. The study demonstrated that, about 63.82% of the river system was infested with water hyacinth during the wet season and 28.34% during the dry season. Sentinel-2 MSI managed to depict species spatio-temporal distribution with an OA of 80.79% during wet season and 79.04% in dry season, using integrated spectral bands and vegetation indices. New generation sensors provide new opportunities and potential for seasonal or long-term monitoring of aquatic invasive species like water hyacinth- a previously challenging task with broadband multispectral sensors. / Risk and Vulnerability Science Centre (RSVC)
59

Seasonal relationships between dissolved nitrogen and landuse/landcover and soil drainage at multiple spatial scales in the Calapooia Watershed, Oregon

Floyd, William C. 20 June 2005 (has links)
The Calapooia River, a major tributary of the Willamette River in western Oregon, is a watershed typical of many found in the Willamette Basin. Public and private forested lands occur in the steep Upper Zone of the watershed, mixed forest and agriculture lands are found in the Middle Zone, and the Lower Zone of the watershed is comprised primarily of grass seed agriculture on relatively flat topography with poorly drained soils. High levels of dissolved nitrogen (DN) have been identified as a water-quality concern within the Calapooia River. To gain a better understanding of the relationship between landuse/landcover (LULC), soil drainage, and DN dynamics within the watershed on a seasonal basis, we selected 44 sub-basins ranging in size between 3 and 33 km² for monthly synoptic surface water-quality sampling from October 2003 through September 2004. We selected an additional 31 sample locations along the length of the Calapooia River to determine relative influence of the 44 sub-basins on DN concentrations in the river. T-tests were used to analyze differences between zones (Upper, Middle and Lower) and regression analysis was used to determine relationships between DN and LULC or soil drainage class. The agriculture-dominated sub-basins had significantly higher (< 0.05) DN concentrations than the predominantly forested sub-basins. Winter concentrations of nitrate-N were 43 times higher in agriculturally dominated sub-basins than in forested sub-basins, whereas in the spring, the difference was only 7-fold. High DN concentrations associated with the predominantly agriculture sub-basins were substantially reduced once they mixed with water in the Calapooia River, highlighting the likelihood that water draining the relatively nutrient-poor, forested sub-basins from the Upper Zone of the watershed, was diluting DN-rich water from the agriculture sub-basins. Relationships between DN and agriculture, woody vegetation or poorly drained soils were moderate to strong (0.50 < R² > 0.85) during the winter, spring and summer seasons. Results indicated an exponential increase in DN concentration when proportion agriculture or poorly drained soils increased, whereas an increase in woody vegetation was related to an exponential decrease in DN concentration. The high variability in DN concentration in the agriculture-dominated sub-basins suggests factors in addition to LULC and poorly drained soils influence DN in surface water. Seasonal relationships were developed between DN and proportion of poorly drained soils, agriculture, and woody vegetation at differing scales (10 m, 20 m, 30 m, 60 m, 90 m, 150 m, 300 m, and entire sub-basin), which we defined as Influence Zones (IZs), surrounding the stream network. Correlations between DN and proportion LULC or poorly drained soil at each IZ were analyzed for significant differences (p-value < 0.05) using the Hotelling-Williams test. Our results show strong seasonal correlations (r > 0.80) between DN and proportion of woody vegetation or agriculture, and moderate-to-strong seasonal correlations (r > 0.60) between DN and proportion of sub-basins with poorly drained soils. Altering scale of analysis significantly changed correlations between LULC and DN, with IZs < 150 m generally having higher correlations than the sub-basin level. In contrast, DN correlations with poorly drained soil were generally higher at the sub-basin scale than the 60- through 10-m IZs during winter and spring. These results indicate that scale of analysis is an important factor when determining relationships between DN concentration and proportion LULC or poorly drained soils. Furthermore, seasonal shifts in significant differences among IZs for correlations between LULC and DN suggest land management proximity and its influence on DN concentration changes temporally. DN relationships with poorly drained soil suggest that during winter and spring, when rainfall is highest, sub-basin scale soil drainage properties have a greater influence on DN than soil properties within IZs in close proximity to the stream network. / Graduation date: 2006
60

The Seasonal Predicability of Snowpack Behavior During Spring / The Seasonal Predictability of Snowpack Behavior During Spring

Jelinek, Mark Thomas 10 July 2007 (has links)
While significant research has been performed in predicting winter snowpack behavior, maximums and extent, no efforts focused on predicting large-scale spring snowpack behavior have produced successful results. Increasing sensitivity to snowpack changes in the areas of water supply, energy production, agriculture, transportation, tourism and safety are making seasonal prediction of snowpack particularly important. The known breakdown of the wintertime relationship between tropospheric dynamics and snow characteristics indicates the need to explore new approaches to seasonal snowpack forecasts for the spring melt season. To examine possible new methods, Northern Hemisphere snow water equivalent and snow cover data from 1980-2004 are used in correlation analysis with traditional climate indices as well as newly defined sea surface temperature and sea ice regions. Additionally, large scale continental and latitude divisions are applied to the snow variables and the impact of ENSO is incorporated into the analysis. Results suggest the following: 1) Both sea ice and sea surface temperatures show promise as seasonal predictors for snowpack; 2) ENSO plays a critical role even though it is represented through indirect relationships; 3) Predicting spring snowpack behavior is feasible.

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