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Item Tidal Freshwater Potomac River Eutrophication: Patterns and Relations to Climate Change, Nutrient Management and In Situ Factors(2000-05-15) Sklarew, Daniel M.; Sklarew, Daniel M.; Jones, R. ChristianEutrophication, the transition of an aquatic ecosystem from nutrient-scarce to nutrient enriched conditions, is a water quality concern for rivers and coastal zones globally. The tidal freshwater (TFW) Potomac River, in particular, was strongly impacted by anthropogenic eutrophication throughout the twentieth century. Hydrometeorological and in situ biogeochemical factors may contribute to the persistence of eutrophic conditions in the TFW Potomac River, despite advancing nutrient management initiatives. This study investigated the patterns of TFW Potomac River eutrophication and examined water quality relations to nutrient inputs, climate change, and in situ factors over the 1985-1997 period. Eutrophication indicators included total phosphorus (TP), total nitrogen (TN), and algal biomass as Chlorophyll a (Chl a). Nutrient inputs from the non- tidal river and nearby wastewater treatment plants (WWTPs) were examined separately and in aggregate. Climatic factors, such as solar energy, air temperature, wind, precipitation, and freshwater inflow, were also considered. In situ factors comprised both abiotic (e.g., pH) and biotic (e.g., the Asiatic clam, Corbicula fluminea) variables. Statistical parametric, non-parametric and graphical methods were used to analyze historical data from various federal, state, and local monitoring agencies, both before and after a basin-wide ban on phosphate in laundry detergents. A field study over summer 1997 further clarified effects of partial effluent denitrification at Blue Plains, the region’s largest WWTP. Data analysis examined patterns and relations longitudinally, across various temporal scales (multi-day, seasonal, annual, and inter-annual). Ambient nutrient concentrations were generally an attenuated function of upstream source nutrient concentrations. TP was longitudinally stable, while TN crested near the outfall pipes from the largest WWTPs. Below this area, Chl a increased substantially. Chl a varied directly with 14-day solar energy, 4-day temperature and, in upper segments, wind speed; and inversely to freshwater inflow and, in lower segments, 4-day wind speed. Chl a also increased with TP during warm, dry weather, consistent with pH-related sediment TP release. No clear relation was established between Corbicula and algal biomass, however. Both the phosphate detergent ban and Blue Plains denitrification were found to have limited impact on TFW Potomac eutrophication. Season-specific and year-to-year patterns and relations are also discussed.Item New Unit Root Tests to Decrease Spurious Results with Applications in Finance and Temperature Anomalies(2006) Herranz, Edward; Herranz, Edward; Gentle, Dr. JamesSimulation studies show that when testing for cointegration with pairs of independent explosive($\gls{phi1} >1$) AR(1) time series almost invariably lead to spurious cointegrating relationships. A new unit root test, the lagged-series test, is proposed with similar power to the ADF test for non-explosive AR(1) series but higher power in the explosive case. The lagged-series unit root test can be combined with other unit root tests such as the Elliot-Rothenberg-Stock tests and the Zivot-Andrews test, as well as the ADF test to improve the statistical power in the explosive case. A new unit root test, the Hybrid Bai-Perron Zivot-Andrews test, is proposed which allows for structural breaks in intercept and linear trend under the null hypothesis and compares favorably in some cases to the Lee-Stratizich unit root test. A new testing procedure to check for stationary to nonstationary shifts in a time series, referred to as the Hybrid Bai-Perron ADF procedure, is proposed and tested. It is shown that different unit root test related statistics can be combined using deep learning neural networks and results in techniques that outperform individual unit root tests in various simulation studies. Simulation based studies of the ADF, ERS-Ptest, ERS-DFGLS, the Zivot-Andrews, and the new lagged-series unit root tests, under various model configurations were made and compared.Item An Analysis of the Potential Direct or Indirect Influence Exerted by an Al Qaeda Social Network Actor on Future Biological Weapon Mission Planning(2007-11-21T16:57:02Z) Baken, Denise; Baken, DeniseThe current conflict known as the “War on Terror” pits several sovereign states (United States and its Allies) against a non-state entity. This entity, al Qaeda, is a global social network with religious doctrine adherence as its declared locus. Terror experts agree that the economic and psychological damage al Qaeda inflicted on 9/11 is miniscule compared to the potential damage by a biological weapon. This dissertation is an analysis of the potential direct or indirect ability of al Qaeda members to select and use a biological weapon.Item Low Ionization Nuclear Emission Line Regions: The "Missing Link" in the Active Galactic Nucleus Population(2007-11-21T17:05:30Z) Dudik, Rachel; Dudik, RachelThe horizon of the universe, once thought to extend only to the disk of the Milky Way, is now known to embrace a host of diverse galaxies, from active galaxies such as quasars and Seyfert galaxies to normal galaxies such as our own. The recent discovery that virtually all local galaxies harbor massive nuclear black holes, has provided convincing evidence that active galactic nuclei (AGNs) and normal galaxies are indeed connected. The nature of this connection and the evolutionary history connecting them, however, continues to be elusive. Low Ionization Nuclear Emission-line Regions (LINERs) are the dominant population of 'active' galaxies in our local universe and may indeed be the missing piece to the evolutionary puzzle. LINERs are defined by optical line ratios uncharacteristic of photoionization by normal main sequence stars. While classical AGNs represent at most a few percent of the galaxy population, LINERs constitute as much as 50% of the total local extragalactic population. However, despite several decades of intense research, the ionization mechanism responsible for the unusual LINER spectrum remains a mystery. What is the ionization mechanism responsible for the empirical line ratios characteristic of LINER galaxies? How do LINERs fit into the overall evolution of galaxies as we know it? Are LINERs a subclass of AGN? What is the evolutionary connection, if any, between galaxies with heavy starburst activity and AGNs? The majority of LINERs are dust enshrouded and therefore very luminous in the far-infrared. The far-infrared (far-IR) luminosity to the luminosity in the optical Bband (center = 4400A), the so-called IR-brightness ratio, can be used as a gauge of the amount of dust in host galaxy. LINERs span a wide range of LFIR/LB ratios, tending predominantly toward the IR-bright end. However, the majority of research to-date has been based on optically selected samples which are partial toward IR-faint LINERs. This bias toward IR-faint galaxies could have important consequences on statistical analyses which examine the fraction of LINERs hosting AGNs. In order for an accurate picture of LINERs to emerge, IR-bright as well as IR-faint galaxies must be studied. What fraction of IR-bright LINERs are AGNs? In light of the open questions regarding these remarkable objects, the central goal of this dissertation is to carry out a systematic multi-wavelength X-ray imaging and Infrared spectroscopic survey of nearby LINERs spanning a wide range of IRbrightness ratios in order to 1) characterize the dominant energy source responsible for their optical line ratios, 2) compare the AGN detection rate in our infrared selected sample with the optically selected samples, 3) determine the luminosities, spectral characteristics and accretion properties of the AGN-LINERs and compare them with the standard active galaxies, and finally, 4) relate the host galaxies properties to the properties of the central source in an attempt to constrain the role of LINERs in galaxy evolution and formation models.Item Multi-Objective Optimization of Blast Simulation Using Surrogate Model(2007-12-12T16:14:50Z) Tsuga, Toshihiro; Tsuga, ToshihiroA multi objective optimization approach using a Kriging model coupled with a Multi Objective Genetic Algorithm (MOGA) is applied to a blast damage maximization problem composed of two objectives, namely number of casualties and damage to buildings. The predicted Pareto front is located using a MOGA on the Kriging model. The location with maximum uncertainty along the Pareto front is added to the list of sample points. After each sampling, the Kriging model is reconstructed and this process is repeated until the maximum uncertainty is reduced. The cases run show that the Pareto front is not always intuitively discernable. `Best locations’ can vary significantly depending on the weight given to each optimization objective. The results also indicate that the effect of the additional cost incurred by the procedure to construct the `model of the model’ totally compensates the computational expense.Item Comparative Profiling of Circulatory Levels of Adipokines and Cytokines in Patients With Various Types of Non Alcoholic Fatty Liver Disease(2007-12-14T16:03:57Z) Jarrar, Mohammed; Jarrar, MohammedNon-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of metabolic syndrome and the most common cause of liver disease. The NAFLD spectrum ranges from simple benign steatosis to NASH to fibrosis and cirrhosis. Omental adipose tissue is a biologically active organ that plays a role in pathogenesis of NAFLD. Expansion of adipose tissue mass accompanied by alteration in adipocytokines could be a prominent mechanism in the pathogenesis and progression of NAFLD. Adipocytokines play a role in insulin resistance, oxidative stress and hepatocyte apoptosis and may be there is imbalance in their serum levels in NAFLD spectrum and the degree of insulin resistance. Accordingly, we explored the differences in the level of transcription of genes in adipose tissue and liver as well as adipocytokines serum levels in different types of NAFLD. This would help to identify non-invasive diagnostic marker profiles for early distinction between NASH and steatosis. In this study of gene expression analyses, we show that there is a prominent adipose-specific deregulation of the inflammation and immune system related genes in NASH. In addition, there are increases in the hepatic detoxification enzymes in obese patients. A number of liver and adipose-specific functional networks centered by TNFalpha, JUN/JUNB and IFNgamma were highlighted in relation to the NASH pathogenesis. Our results also show that serum levels of TNF-α and IL-8 were significantly higher in NAFLD patients compared to both obese and non-obese controls. Univariate analyses involving all patients revealed a significant correlation between serum concentrations of TNF-α and IL-8, as well as between IL-6 and IL-8. Insulin resistance measured by homeostasis model assessment (HOMA) scores negatively correlated with serum Adiponectin levels in NAFLD patients. Serum Visfatin was significantly higher in steatosis and obese controls than the non-obese controls. Visfatin and IL-6 serum levels in NASH patients were lower in comparison to patients with steatosis implicating their possible co-regulated protective role from progression of steatosis to NASH. Multivariate analyses revealed that TNF-α serum level levels influenced mainly by serum glucose, HOMA, BMI and IL-8 in NAFLD, while IL-6 levels influenced mainly by HOMA scores and IL-8. A multivariate analysis indicated that TNF-α was the only independent predictor of histologic fibrosis in patients with NASH. Apoptosis per se, measured by levels of Ck-18 cleaved at Asp396-neoepitope and secreated to the circulation is significantly increased in the serum of NASH patients in comparison to patients with steatosis and BMI matched morbidly obese patients. In NAFLD and obese controls, both apoptosis and total cell death measured by serum levels of intact CK18, closely correlated with TNF-α levels and IL-8, but in NAFLD apoptosis and total cell death only correlated with TNF-α. Of special importance, NASH could be reliably predicted by a combination of apoptosis, necrosis, serum Adiponectin and serum Resistin, with sensitivity of 95.45%, specificity of 70.21%, and AUC of 0.908. HCV infection is clearly characterized by alterations in cytokine serum levels. There are significant differences in serum levels of major pro-inflammatory cytokines (IL-6, IL-8 and TNF-α) between patients groups with HCV infection regardless of genotype or association with steatosis when compared to group of patients with steatosis only. In addition, IL-8 and TNF-α were significantly increased in HCV3 infections compared to HCV1. Some of these cytokines play more prominent roles in development of steatosis accompanied by HCV infection. Our data shows that there is strong connection between the HCV genotype 3, steatosis and increases in IL-8 serum levels. Multiple correlation analyses showed that steatosis in HCV is mostly dependent on IL-6 and IL-8; in HCV1 on IL-6, TNF-α and IL-1B while in HCV3 is mostly dependent on IL-8. Actually HCV3 associated steatosis can be predicted by serum levels of IL-8 with 87.5% specificity, 100% sensitivity and AUC of 0.931.Item Genetic Structure and Phylogeography of the Fox Squirrel, Sciurus niger, as Inferred From a Mitochondrial Gene(2007-12-14T16:51:45Z) Bryant, Katherine; Bryant, KatherineSciurus niger (Rodentia: Sciuridae) is a large tree squirrel which inhabits the southeastern portion of North America. Currently there are ten recognized subspecies which are distinguished based on differences in morphology and ecology. While molecular work has been undertaken for a few subspecies of S. niger, the patterns of genetic differentiation of the entire species have yet to be examined. This study attempts to characterize the genetic structure of S. niger in order to help determine the validity of current subspecies designations and offer insight into the post-glacial colonization patterns of the species. A 296 base pair fragment of the mitochondrial control region (dloop) was sequenced from 55 specimens of S. n. vulpinus, 13 samples of S. n. niger, and 13 samples of S. n. rufiventer. Fifteen previously reported haplotypes (Lance et al. 2003) representing S. n. cinereus, S. n. rufiventer, and S. n. vulpinus were incorporated into the analysis. Additionally, a data set of 89 sequences generated at the Van Den Bussche Laboratory of Molecular Systematics and Conservation Genetics were added to this data set. These sequences included representatives of the following 8 subspecies: S. n. bachmani, S. n. cinereus, S. n. limitis, S. n. ludovicianus, S. n. niger, S. n. rufiventer, S. n. subauratus, and S. n. vulpinus. The compiled data set of 258 individuals belonging to 8 subspecies yielded 125 unique haplotypes, indicating extremely high levels of diversity in the control region. Several tree-based methods recovered two distinct shallow clades which do not correspond to geographic regions or subspecies. A parsimony-based minimum spanning network revealed two haplotype clusters which correspond to the two clades found in the tree-based methods. The haplotypes are closely linked in a starshaped phylogenetic network; several of the most frequent haplotypes were internal, while the majority were unique to single populations and presented distal positions in the network. Overall there was a lack of genetic structure amongst populations with most of the variance explained by within population genetic diversity. Despite poor branch support, the congruent recovery of the two S. niger clades via both clustering-based and optimality criterion-based methods supports the separation of haplotypes into two major haplogroups. These results indicate that the currently recognized subspecies based on alpha taxonomic characters are not concordant with the mitochondrial history of S. niger. Instead, my findings suggest that the control region haplotype distribution in fox squirrels may be the result of repeated and rapid habitat expansions/retractions during glacial events in the Pleistocene. The shallow divergence between haplotypes across wide geographic distances suggest that the patterns of morphological and ecological differentiation the we observe within S. niger may have occurred much more recently than previously thought.Item Manganese Enhanced Functional Magnetic Resonance Imaging of Endogenous Pancreas and Isolated Human Islets(2007-12-17T19:50:30Z) Haque, Muhammad; Haque, MuhammadIt is well established that diabetes is of critical importance in the world as the number of people affected increases globally. Although a great deal is known about the pancreas and its function, there are still unanswered basic questions about normal pancreatic physiology/function. Presently, pancreatic endocrine function is assessed using biochemical tests of insulin release or serum glucose. Knowing the functional efficiency of the pancreas would certainly be beneficial in the development of novel therapies aimed at maintaining or increasing endocrine function particularly during progressive pathologies. Here we present an application of functional MRI to the rodent pancreas using manganese (Mn) enhanced imaging (MEMRI) in response to glucose stimulation. To image rodent pancreas is extremely difficult for many reasons including organ size, tissue density, location, and motion. To overcome these constraints, a novel application xi i of Magnetization Prepared RApid Gradient Echo (MP-RAGE) was applied to achieve significant T1 weighted contrast in response to glucose stimulation. A pre- and post glucose activation in rodent pancreas indicated a signal increment or decrement depending on the dynamic of the stimulant. A simultaneous injection of stimulant with Mn has shown an overall increase of 20% to 26%, signal enhancement. Uptake of Mn was confirmed via atomic absorption and insulin release via ELISA. In addition, the research also focused to aid islet transplantation by developing a method to make pre-transplant functional assessments of isolated human islets as they were subjected to both physiological and mechanical stress during isolation. As proposed, the islets labeled with a contrast agent (manganese) would alter their molecular magnetic properties such as longitudinal (T1) and transverse (T2) relaxation time, and there as a result there would be a change in their signal intensity. This change in signal intensity has been exploited to distinguish between adjacent soft tissues, to delineate pathologic tissues, and, in principle, to characterize tissue viability. μMRI of isolated islets revealed a significant change in T1 and diffusion coefficient between the controls versus stimulated islet where no changes was observed in transverse relaxation.Item Comparisons of Gene Expression Patterns in Progressive Breast Carcinoma and the Adjacent Stromal Microenvironment(2007-12-19T14:35:33Z) King, John; King, JohnHuman breast ductal carcinoma in situ (DCIS) is categorized as Stage 0 because it is noninvasive and limited to the duct lining. However, women diagnosed with DCIS have a 30-40% chance of developing invasive breast cancer (IBC) if it is left untreated. The breast tissue microenvironment of the surrounding stroma plays an important role in the malignant invasion and migration of tumor cells across the basement membrane, which separates the epithelial cells from the stroma in the normal breast. Far from being passive, the stroma plays an active role in invasiveness and perhaps throughout the entire progression of malignancy. Complex signaling networks, both intracellular and extracellular, are activated along with dramatic extracellular matrix (ECM) remodeling and growth factor release, which in turn leads to significant changes in cellular gene expression profiles. This study examines those gene expression profiles across the full range of breast cancer progression from normal to hyperplasia through DCIS and IBC, looking specifically at changes in gene expression between the cancerous epithelial tissue and the surrounding stroma, using the recent advancement of laser capture microdissection to obtain highly purified, cell type specific samples.Item The Geography of Significant Colorants: Antiquity to the Twentieth Century(2007-12-19T15:51:12Z) Zagorski, Melissa; Zagorski, MelissaThis thesis attempts to answer the question: Where does color come from? In order to answer this question, a rigorous analysis of art-related, chemical, scientific, and geographical literature was required in order to create a comprehensive inventory of colorants in the form of a geodatabase of Colorants (included as a CD with this thesis). The geodatabase of Colorants is compatible with ESRI’s ArcMap 9.x geographic information system (GIS) and can be used to explore the geography of significant colorants (antiquity to the twentieth century). This thesis provides a summary of colorants per continent and provides maps to illustrate where different hues and types of colorants come from. In order to understand the distribution of colorants per continent, statistical analyses were performed to reveal potentially significant correlations between number of ecoregions per continent and various colorant-related variables per continent. Linear bivariate regression analysis indicates that terrestrial ecoregions account for approximately 59.4% of the unexplained variation in number of types of colorants per continent. Results from the statistical analyses of colorant-related variables indicate some interesting possibilities about human interaction with color and the search for color in general. Pearson’s and Spearman’s bivariate correlation analyses and multiple linear regression analyses indicate that diversity in nature yields more types of colorants, a good reason to maintain ecosystem integrity. A chapter on the commonly used colorants in maps, specifically antique hand-colored maps, is also provided that explores the importance of colorants from a curatorial perspective. Knowledge of the geography of colorants and the conclusive identification of colorants is important to proper authentication, preservation, and restoration of antique maps. The Vinland Map reprint is given as an example.Item Day to Day Longitudinal Variability of the Nighttime Low Latitude Terrestrial Ionosphere(2007-12-19T21:30:08Z) McDonald, Sarah; McDonald, SarahThe Earth’s ionosphere is the region of upper atmosphere that is a partially ionized gas. It extends from the mesosphere and through the thermosphere to altitudes ~1000 km where it ultimately merges with the magnetosphere. The strong coupling of the ionosphere to the dense regions below and the solar-driven magnetosphere above make it the most variable component of the atmosphere. Sources of ionospheric variability or “weather” originate from solar and geomagnetic activity and meteorological influences. One motivation for studying the ionosphere is to improve techniques to predict ionospheric weather that affects space-borne and ground-based technological systems used for communication, navigation, surveillance and basic research. Geomagnetic storms can be particularly disruptive leading to significant satellite systems failures. Even quiet-time disturbances, such as scintillation and spread-F events, can impact high frequency radio communications, especially in the equatorial and high-latitude regions. To improve prediction capabilities, a better understanding of the drivers of the variability is needed. In this study we used recent ionospheric measurements, particularly remote ultraviolet (UV) sensing of the airglow, along with recently developed analysis techniques to better characterize the day to day and longitudinal variability of the nighttime low-latitude ionosphere and to advance the understanding of the origins of such variations. We performed a case study of the longitudinal variability in the occurrence of equatorial scintillation on 22-23 March 2002 and found evidence of longitudinal differences in the daytime and evening vertical plasma drifts that may affect the conditions for the occurrence of scintillation. This work prompted an investigation the day to day variability of the nighttime ionosphere using UV remote sensing data from the Low Resolution Airglow and Aurora Spectrograph (LORAAS). UV limb scans from March 2001 and March 2002 were used to determine the density and morphology of the post-midnight (~0230 LT) Equatorial Anomaly (EA), a prominent feature of the nighttime ionosphere. The most variable feature was the latitude and separation of the EA crests (46-67% variation about the mean). The least variable was the height of the peak densities in the EA crests (< 10% variation about the mean). The monthly mean values of the EA features are in agreement with the International Reference Ionosphere (IRI-90), a climatology model. We used the LORAAS data along with a physics-based model of the ionosphere (SAMI2) to investigate a wavelike pattern in the longitudinal variation of ionospheric densities in the EA region. We discovered a pronounced hemispheric asymmetry in the longitudinal variations of the EA crests and showed that this is due to both longitudinally varying thermospheric winds and effects associated with the offset of the geographic and geomagnetic equators.Item Who’s Afraid of the Big, Bad Coyote? A Survey of Messaging and Existing Attitudes in the National Capital Region(2008-01-30T18:49:34Z) Draheim, Megan; Draheim, MeganCoyotes are relatively recent arrivals to the Washington, D.C. metropolitan area. In an effort to understand and obtain baseline data about existing attitudes, a survey was conducted in 2006. Most respondents had neutral attitudes towards coyotes, which might be in part due to low levels of awareness about their presence in the area. Of particular interest, pet owners seemed to have more extreme attitudes, either positively or negatively, towards coyotes, and women tended to have more negative attitudes towards coyotes. Wildlife managers and others interested in preventing and reducing human-coyote conflict should capitalize on the current situation and develop outreach programs that will teach people how to live near coyotes as well as engender positive attitudes towards them. The survey also looked at the effect that small pieces of information in various categories (coyote behavior and ecology, human-coyote interactions, and images of coyotes) had on attitudes. Statements about coyote behavior, especially those that emphasized the social aspects of their lives, proved to be the most effective in increasing positive attitudes. Amongst other findings, statements about attempts to eradicate coyotes were viewed negatively and some traditional images associated with coyotes (especially a coyote howling) were also viewed negatively. This information will be useful to wildlife managers and others interested in designing outreach materials.Item Computational Mutagenesis Models for Protein Activity and Stability Analysis(2008-01-30T19:11:57Z) Zhan, Bill; Zhan, BillMissense mutations may cause structural alterations of a protein and lead to a loss/gain of activity and stability. Studies of missense mutations in proteins are important for understanding protein structure-function relationships, analyzing the function of gene variations, and designing new proteins. In this dissertation, we have developed computational mutagenesis models to predict the changes of stability and activity of protein mutants using the four-body statistical potential derived from Delaunay tessellations of protein structures. First, our results show that a strong correlation exists between the mean residual scores of mutants and the change of mutant stability in 18 proteins extracted from ProTherm database. Second, we developed robust and accurate machine-learning models based on the residual score profiles of protein mutants to predict the sign of mutant stability change. Third, we have demonstrated a correlation between changes of four-body statistical potential and activity alternation in human p53 and rabbit sarcoendo plasmic reticulum calcium-ATPases (SERCA1) mutants. The supervised machine-learning models based on the residual score profiles of protein mutants were also developed to predict the activity changes in p53 and SERCA1 mutants. Fourth, a highly significant correlation between changes in four-body statistical potential with conservation of amino-acid substitutions was observed. Finally, a novel statistical matrix based on the mean residual scores of all 380 types of mutations in 700 proteins was developed and a statistically significant correlation is revealed between the novel matrix and PAM/BLOSUM matrices. Overall, these conclusions support our hypothesis that computational mutagenesis models using four-body statistical potential present a powerful approach for predicting the changes of activity and stability in protein mutants.Item Remote Sensing Techniques for Soil Moisture and Agricultural Drought Monitoring(2008-02-28T20:19:38Z) Wang, Lingli; Wang, LingliDrought is the most complex and least understood of all natural hazards, affecting more people than any other hazard. Soil moisture is a primary indicator for agricultural drought. This dissertation is aimed at evaluating and investigating soil moisture and drought monitoring using remote sensing techniques. Recent technological advances in remote sensing have shown that soil moisture can be measured by a variety of remote sensing techniques, each with its own strengths and weaknesses. This research is designed to combine the strengths of optical/infrared as well as microwave remote sensing approaches for soil moisture estimation. A soil moisture estimation algorithm at moderate resolution was developed based on the well known ‘Universal Triangle’ relation by using MODIS land parameters as well as ground measured soil moisture. Though lower in spatial resolution, AMSR-E microwave measurements provides daily global soil moisture of the top soil layer, which are typically less affected by clouds, making them complementary to MODIS measurements over regions of clouds. Considering that the ‘Universal Triangle’ approach for soil moisture estimation is based on empirical relations which lack solid physical basis, a new physics based drought index, the Normalized Multi-band Drought Index (NMDI) was proposed for monitoring soil and vegetation moisture from space by using one near-infrared (NIR) and two shortwave infrared (SWIR) channels. Typical soil reflectance spectra and satellite acquired canopy reflectances are used to validate the usefulness of NMDI. Its ability for active fire detection has also been investigated using forest fires burning in southern Georgia, USA and southern Greece in 2007. Combining information from multiple NIR and SWIR channels makes NMDI a most promising indicator for drought monitoring and active fire detecting. Given the current technology, satellite remote sensing can only provide soil moisture measurements for the top soil profile, and these near-surface soil moisture must be related to the complete soil moisture profile in the unsaturated zone in order to be useful for hydrologic, climatic and agricultural studies. A new numerical method was presented to solve the governing equation for water transport in unsaturated soil by matching physical and numerical diffusion. By applying a new numerical scheme with which to discrete the kinematic wave equation on the space-time plane, this method shows the capability to simulate the physical diffusion of the diffusive wave with the numerical diffusion generated in the difference solution under certain conditions. Compared with other numerical methods with the first-order finite differences scheme, this method has enhanced the solution precision to the second order. An example application shows a good agreement with the observed data and suggests this new approach can be appropriate for soil moisture profile estimation. By combining the proposed soil moisture and drought estimation techniques, the daily soil moisture profile at high resolution can be gained, and is thus expected to be helpful not only in drought monitoring and active fire detecting, but also in agricultural applications and climate studies.Item Development of a Gas-phase Chemiluminescence Detection System for the Measurement of Arsenic in Environmental and Biological Samples(2008-05-07T17:28:25Z) Assegid, Kirubel; Assegid, KirubelArsenic in groundwater used for drinking is now regarded as one of the most serious health hazards of this decade. Long term exposure to low concentrations of arsenic has been reported to cause cancer of the skin, bladder and other internal organs. Also, various ionic forms of arsenic are known to be very toxic to most microorganisms. Measurement of trace arsenic at parts per billion (ppb) levels in environmental and biological samples is a key component for the mitigation and understanding of this crisis. This M.S. Thesis Project deals with the development of an analytical technique for the measurement of arsenic based on a gas-phase chemiluminescence reaction between ozone (O3) and arsine (AsH3) as the detection principle. The approach is capable of analyzing arsenic concentration in a 1.0 mL sample in one minute. The determination of As(III) and As(V) was achieved based on the different pH dependence and the reducibility of these species to arsine gas by sodium borohydride (NaBH4). The intense chemiluminescence formed in a reflective glass reaction cell from the reaction of AsH3 – O3 is detected by a sensitive photomultiplier tube (PMT). The signal is further amplified, digitalized and recorded with a complete data acquisition computer controlled system. The limit of detection (LOD) is 0.146 μg/L (ppb or 146 ppt) for total arsenic concentration in 10 determinations. To validate the performance of the gas-phase chemiluminescence based arsenic analyzer, results were compared with Hydride Generation Atomic Absorption Spectroscopy (HG-AAS) and Atomic Fluorescence Spectroscopy (AFS) techniques. The chemiluminescence detection system was also coupled with a flow injection system to enhance its efficiency. Sequential procedures including direct chemical and data analysis methods and step by step development of the analyzer are described in depth. The system has been effectively tested using standard and unique field water samples from several regions of Ethiopia.Item Assessment of Potential Relationships Between Microclimate Variables Measured Within a Forest Patch and the Presence of Interior Forest Birds(2008-05-16T18:42:37Z) Farabaugh, Christopher Scott; Farabaugh, Christopher ScottResearch was conducted over three field seasons in isolated eastern deciduous forest patches of three different sizes (~10, ~90, and ~300 hectares) in Loudoun and Prince William Counties in Virginia, to determine if there was a relationship between microclimate variables, temperature and photosynthetically active radiation (PAR), the presence of interior forest birds, and forest patch size. The results of this study indicate that microclimate variables, temperature, and photosynthetically active radiation (PAR), generally decreased from the edge to the interior of the forest patch. The number of birds observed held fairly constant from the edge to the interior of the forest patch, while the number of species observed increased from the edge to the interior of the forest patch. The number of birds observed was significantly related to PAR in the ~10 hectare forest patch and to distance from the edge in the ~90 hectare forest patch. The number of birds observed was not significantly related to any of the variables measured in the ~300 hectare forest patch. When data from all three patches were combined, the Wood Thrush, which was the most frequently observed species, was statistically linked to distance from the forest edge with the number of Wood Thrush observed decreasing with distance from the forest edge. Overall, the number of birds seen per day per location, the number of species of birds seen per day per location, and the number of forest-interior species increased with increasing forest patch size. Policy makers should be aware of these results when determining minimum remnant patch size when allowing forest fragmentation.Item A Dynamic Graph Model for Representing Streaming Text Documents(2008-06-05T19:30:28Z) Hohman, Elizabeth Leeds; Hohman, Elizabeth LeedsThis work presents new techniques for representing an evolving stream of text documents. Text processing is traditionally performed on a fixed corpus of documents by representing the documents as vectors in a high-dimensional space with each dimension corresponding to a different word in the lexicon. The lexicon is formed by the set of unique words in the corpus. The vector entries are equal to the counts of the word in the document and often weighted by the inverse of the probability of the corresponding word occurring in a document. The probability of word occurrence, also called the document frequency, is needed in order to create document vectors which emphasize the informative words in each document. In order to apply statistical text processing techniques to a changing corpus of documents, a generalization of the vector space model is introduced. The generalization relies on managing a changing lexicon of words and approximating the probability of word occurrence over documents in the document stream. The methods presented here can be used to represent any new document as a vector, including documents that contain words that have not been seen previously in the document stream. Additionally, this work presents a graph model for representing a dynamic corpus of text documents. The graph model differs from other methods for text clustering which act on a fixed corpus of documents. The vertices in the graph represent topics and evolve as the document stream changes. The vertices contain statistics on documents of a similar topic. Each vertex has an associated lexicon and document frequency which can be used to provide information about the document stream. The graph model is demonstrated on a dataset of news articles collected over several years.Item A Numerical Study of Topographical Effects on Flow Regimes in the Lower Atmosphere(2008-06-05T19:57:39Z) Lindeman, John David; Lindeman, John DavidOrographically generated gravity waves, or mountain waves, have been the focus of much research for decades because of their importance on the general mean atmospheric circulation. These waves affect the flow on scales which are too small to be resolved by global weather and climate models, and so their impact on the larger scale flow must be parameterized. Linear theory has proven useful for obtaining a quantitative understanding of wave processes and their effects on the background flow, though one must assume that the low level flow in mountainous regions is approximately linear. Numerical simulations and field experiments indicate that this is often not the case, however, as nonlinear effects can dominate the flow near the orography. These nonlinear effects, which include processes such as flow splitting around a mountain or upstream blocking of the flow, affect gravity wave generation and decrease the accuracy of predictions based on linear theory. The purpose of this dissertation is to investigate the extent that linear theory-based mountain wave predictions can be improved by using an alternative initialization scheme. Linear orographic gravity wave models traditionally have been initialized at the lower boundary assuming the orography is equivalent to the surface vertical displacement field. While this method works when wave-induced perturbations are small compared to the mean flow, this has been shown to fail in weak flow regimes and tall mountains. We introduce an initialization technique where the linear model is initialized on a horizontal plane with results from a corresponding simulation from a nonlinear numerical model. The height level of initialization must be in a region in which the flow can be approximated by linear theory, and in practice this occurs above the low level nonlinear processes in the vicinity of the mountain. We show that this method leads to greater accuracy in the solutions of the wavefield above the orography. This new method is tested for flow regimes of uniform background wind and stability, and for simple bell shaped hills and more complex and realistic orography. Parameters derived from linear theory which are useful for global weather models are shown to be significantly affected by the new initialization scheme. These results have the potential to quantitatively improve global weather model mountain wave parameterization schemes in the relatively common instance of orographically-induced nonlinear flows , as well as to provide quick and accurate forecasts of wave activity for the aviation community.Item Trace Gas Detection in Hyperspectral Imagery Using the Wavelet Packet Subspace(2008-06-06T18:52:43Z) Salvador, Mark A. Z.; Salvador, Mark A. Z.This dissertation describes research into a new remote sensing method to detect trace gases in hyperspectral and ultra-spectral data. This new method is based on the wavelet packet transform. It attempts to improve both the computational tractability and the detection of trace gases in airborne and spaceborne spectral imagery. Atmospheric trace gas research supports various Earth science disciplines to include climatology, vulcanology, pollution monitoring, natural disasters, and intelligence and military applications. Hyperspectral and ultra-spectral data significantly increases the data glut of existing Earth science data sets. Spaceborne spectral data in particular significantly increases spectral resolution while performing daily global collections of the earth. Application of the wavelet packet transform to the spectral space of hyperspectral and ultra-spectral imagery data potentially improves remote sensing detection algorithms. It also facilities the parallelization of these methods for high performance computing. This research seeks two science goals, 1) developing a new spectral imagery detection algorithm, and 2) facilitating the parallelization of trace gas detection in spectral imagery data.Item The Association of Tall Eyewall Convection with Tropical Cyclone Intensification(2008-06-11T22:07:15Z) Kelley, Owen A.; Kelley, Owen A.Despite decades of research, operational weather agencies still find it difficult to predict change in the intensity of a tropical cyclone's surface wind. This dissertation examines whether precipitation cells in a tropical cyclone eyewall provide information about change in wind intensity. Nine years of tropical cyclone overflights are studied with the first radar in space capable of resolving the detailed three-dimensional structure of precipitation. This radar is the Precipitation Radar on the Tropical Rainfall Measuring Mission (TRMM) satellite. With a single satellite overflight, the presence or absence of a tall eyewall cell correctly identifies whether or not intensification is occurring 62% of the time (166 out of 269 overflights). The empirical association of tall eyewall cells and wind intensification is also examined in a decade of tropical cyclones near landfall observed with the WSR-88D ground radars along the U.S. coast. With at least a 3 hour period of continuous ground radar observation, the frequent occurrence of tall eyewall cells (at least 1 in 3 volume scans) correctly identifies whether or not wind intensification is occurring 83% of the time (24 out of 29 observation periods). These results suggest that the near-continuous nature of ground radar data compensates for the ground radar's coarser vertical resolution compared with the TRMM satellite radar. Physical mechanisms for the observed association are discussed. Based on an upper bound calculation, the energy released during a 9 hour long burst of tall eyewall cells could warm a tropical cyclone's eye by at most 4 K if the eye's radius were small (20 km). If the eye's radius were large (40 km), the same cells could warm the eye by at most 1 K. These upper bounds are based on the amount of latent heat released by the burst of tall cells. From the upper bound to the eye warming, an upper bound can be estimated for the maximum wind intensification that might be caused by the tall eyewall cells.