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 Department: Department of Biology
 Decade: 2000-2009
 Collection: UNT Theses and Dissertations
A geospatial tool for assessing potential wildland fire risk in central Texas.

A geospatial tool for assessing potential wildland fire risk in central Texas.

Date: August 2005
Creator: Hunter, Bruce Allan
Description: Wildland fires in the United States are not always confined to wilderness areas. The growth of population centers and housing developments in wilderness areas has blurred the boundaries between rural and urban. This merger of human development and natural landscape is known in the wildland fire community as the wildland urban interface or WUI, and it is within this interface that many wildland fires increasingly occur. As wildland fire intrusions in the WUI increase so too does the need for tools to assess potential impact to valuable assets contained within the interface. This study presents a methodology that combines real-time weather data, a wildland fire behavior model, satellite remote sensing and geospatial data in a geographic information system to assess potential risk to human developments and natural resources within the Austin metropolitan area and surrounding ten counties of central, Texas. The methodology uses readily available digital databases and satellite images within Texas, in combination with an industry standard fire behavior model to assist emergency and natural resource managers assess potential impacts from wildland fire. Results of the study will promote prevention of WUI fire disasters, facilitate watershed and habitat protection, and help direct efforts in post wildland fire mitigation and ...
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Construction of a  Pseudomonas aeruginosa Dihydroorotase Mutant and the Discovery of a Novel Link between Pyrimidine Biosynthetic Intermediates and the Ability to Produce Virulence Factors

Construction of a Pseudomonas aeruginosa Dihydroorotase Mutant and the Discovery of a Novel Link between Pyrimidine Biosynthetic Intermediates and the Ability to Produce Virulence Factors

Date: August 2003
Creator: Brichta, Dayna Michelle
Description: The ability to synthesize pyrimidine nucleotides is essential for most organisms. Pyrimidines are required for RNA and DNA synthesis, as well as cell wall synthesis and the metabolism of certain carbohydrates. Recent findings, however, indicate that the pyrimidine biosynthetic pathway and its intermediates maybe more important for bacterial metabolism than originally thought. Maksimova et al., 1994, reported that a P. putida M, pyrimidine auxotroph in the third step of the pathway, dihydroorotase (DHOase), failed to produce the siderophore pyoverdin. We created a PAO1 DHOase pyrimidine auxotroph to determine if this was also true for P. aeruginosa. Creation of this mutant was a two-step process, as P. aeruginosa has two pyrC genes (pyrC and pyrC2), both of which encode active DHOase enzymes. The pyrC gene was inactivated by gene replacement with a truncated form of the gene. Next, the pyrC2 gene was insertionally inactivated with the aacC1 gentamicin resistance gene, isolated from pCGMW. The resulting pyrimidine auxotroph produced significantly less pyoverdin than did the wild type. In addition, the mutant produced 40% less of the phenazine antibiotic, pyocyanin, than did the wild type. As both of these compounds have been reported to be vital to the virulence response of P. aeruginosa, ...
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Integrating Concepts in Modern Molecular Biology into a High School Biology Curriculum

Integrating Concepts in Modern Molecular Biology into a High School Biology Curriculum

Access: Use of this item is restricted to the UNT Community.
Date: August 2003
Creator: Parker, Timothy P.
Description: More so than any other science in the past several decades, Biology has seen an explosion of new information and monumental discoveries that have had a profound impact on much more than the science itself. Much of this has occurred at the molecular level. Many of these modern concepts, ideas, and technologies, as well as their historical context, can be easily understood and appreciated at the high school level. Moreover, it is argued here that the integration of this is critical for making biology relevant as a modern science. A contemporary high school biology curriculum should adequately reflect this newly acquired knowledge and how it has already has already begun to revolutionize medicine, agriculture, and the study of biology itself. This curriculum provides teachers with a detailed framework for integrating molecular biology into a high school biology curriculum. It is not intended to represent the curriculum for an entire academic year, but should be considered a significant component. In addition to examining key concepts and discoveries, it examines modern molecular techniques, their applications, and their relevance to science and beyond. It also provides several recommended labs and helpful protocols.
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Laboratory and field studies of cadmium effects on  Hyalella azteca in effluent dominated systems.

Laboratory and field studies of cadmium effects on Hyalella azteca in effluent dominated systems.

Date: August 2003
Creator: Stanley, Jacob K.
Description: Laboratory single-species toxicity tests are used to assess the effects of contaminants on aquatic biota. Questions remain as to how accurately these controlled toxicity tests predict sitespecific bioavailability and effects of metals. Concurrent 42-day Hyalella azteca exposures were performed with cadmium and final treated municipal effluent in the laboratory and at the University of North Texas Stream Research Facility. Further laboratory testing in reconstituted hard water was also conducted. Endpoints evaluated include survival, growth, reproduction, and Cd body burden. My results demonstrate that laboratory toxicity tests may overestimate toxicity responses to cadmium when compared to effluent dominated stream exposures. Discrepancies between endpoints in the three tests likely resulted from increased food sources and decreased cadmium bioavailability in stream mesocosms
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Investigation of Pyrimidine Salvage Pathways to Categorize Indigenous Soil Bacteria of Agricultural and Medical Importance and Analysis of the Pyrimidine Biosynthetic Pathway's Enzyme Properties for Correlating Cell Morphology to Function in All Phases of Growth

Investigation of Pyrimidine Salvage Pathways to Categorize Indigenous Soil Bacteria of Agricultural and Medical Importance and Analysis of the Pyrimidine Biosynthetic Pathway's Enzyme Properties for Correlating Cell Morphology to Function in All Phases of Growth

Date: May 2003
Creator: Meixner, Jeffery Andrew
Description: This dissertation comprises three parts and is presented in two chapters. Chapter 1 concerns Arthrobacter, a bacterium with an intriguing growth cycle. Whereas most bacteria exist as either a rod or coccus, this bacterium shares the rod/coccus lifestyle. It therefore seemed important to examine the growth regulatory pathways from the rod and coccus. The committed step, that catalyzed by aspartate transcarbamoylase (ATCase), in the pyrimidine biosynthetic pathway was chosen. The ATCase in Arthrobacter is like the well known Pseudomonas enzyme except that it has an active dihydroorotase (DHOase) associated. Included in Chapter 1 is the description of a microorganism, Burkholderia cepacia, whose ATCase has characteristics that are at once reminiscent of bacteria, mammals, and fungi. It differs in size or aggregation based on environmental conditions. In addition, it has an active DHOase associated with the ATCase, like Arthrobacter. B. cepacia is important both medically and for bioremediation. Since B. cepacia is resistant to most antibiotics, its unique ATCase is a prime target for inhibition. Whereas the first chapter deals with the de novo pathway to making pyrimidines, which is found mainly in the lag and log phase, Chapter 2 addresses the salvage pathway, which comes more into play during the ...
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On-Road Remote Sensing of Motor Vehicle Emissions: Associations between Exhaust Pollutant Levels and Vehicle Parameters for Arizona, California, Colorado, Illinois, Texas, and Utah

On-Road Remote Sensing of Motor Vehicle Emissions: Associations between Exhaust Pollutant Levels and Vehicle Parameters for Arizona, California, Colorado, Illinois, Texas, and Utah

Access: Use of this item is restricted to the UNT Community.
Date: May 2003
Creator: Dohanich, Francis Albert
Description: On-road remote sensing has the ability to operate in real-time, and under real world conditions, making it an ideal candidate for detecting gross polluters on major freeways and thoroughfares. In this study, remote sensing was employed to detect carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxide (NO). On-road remote sensing data taken from measurements performed in six states, (Arizona, California, Colorado, Illinois, Texas, and Utah) were cleaned and analyzed. Data mining and exploration were first undertaken in order to search for relationships among variables such as make, year, engine type, vehicle weight, and location. Descriptive statistics were obtained for the three pollutants of interest. The data were found to have non-normal distributions. Applied transformations were ineffective, and nonparametric tests were applied. Due to the extremely large sample size of the dataset (508,617 records), nonparametric tests resulted in "p" values that demonstrated "significance." The general linear model was selected due to its ability to handle data with non-normal distributions. The general linear model was run on each pollutant with output producing descriptive statistics, profile plots, between-subjects effects, and estimated marginal means. Due to insufficient data within certain cells, results were not obtained for gross vehicle weight and engine type. The "year" ...
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Ecotoxicological Investigations in Effluent-Dominated Stream Mesocosms

Ecotoxicological Investigations in Effluent-Dominated Stream Mesocosms

Date: December 2002
Creator: Brooks, Bryan W.
Description: The University of North Texas Stream Research Facility (UNTSRF) was designed to examine contaminant impacts on effluent-dominated stream ecosystems. Stream mesocosms, fed municipal effluent from the City of Denton, TX, Pecan Creek Water Reclamation Plant (PCWRP), were treated with 0, 15 or 140 µg/L cadmium for a 10-day study in August 2000. Laboratory toxicity test and stream macroinvertebrate responses indicated that cadmium bioavailability was reduced by constituents of effluent-dominated streams. The Biotic Ligand Model (BLM) for Cd was used to predict a 48 hour Cd EC50 for Ceriodaphnia dubia of 280 µg/L in these effluent-dominated streams. This value is higher that an EC50 of 38.3 µg/L Cd and a 7-day reproduction effect level of 3.3 µg/L Cd generated for C. dubia in reconstituted laboratory hard water. These results support use of a cadmium BLM for establishing site-specific acute water quality criteria in effluent-dominated streams. Although not affected by 15 µg/L treatments, organisms accumulated Cd in 15 µg/L treated streams. Hence, over longer exposure periods, Cd accumulation may increase and a no effect level may be lower than the observed 10-day no effect level of 15 µg/L. A toxicity identification evaluation procedure was utilized with in vitro and in vivo bioassays ...
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A Physiological Age-Grading System for Female Hydrellia pakistanae  Deonier (Diptera: Ephydridae)

A Physiological Age-Grading System for Female Hydrellia pakistanae Deonier (Diptera: Ephydridae)

Access: Use of this item is restricted to the UNT Community.
Date: December 2002
Creator: Lenz, Jennifer Marie
Description: Conflicting opinions about the effectiveness of H. pakistanae as a biological control agent for hydrilla prompt researchers to find a method for assessing the fly's success. Developing a physiological age-grading system for the fly using ovarian morphology to detect changes in reproductive activity is useful for evaluating reproductive status of the fly in field populations. Changes in the appearance of follicular relics in ovaries with oviposition provide a reliable method to estimate fecundity. Characteristics of follicular relics were used to develop a system with eight physiological age classes, three nulliparous and five parous. Changes that occur in the fat body were used to assist in classification of nulliparous females or those with low egg counts.
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Managing Cattail (Typha latifolia) Growth in Wetland Systems

Managing Cattail (Typha latifolia) Growth in Wetland Systems

Date: August 2002
Creator: Sharp, Jessica Little
Description: Nutrient availability, water depth, competition, and soil management effects on cattail (Typha latifolia) growth in wetland systems were examined. Soluble reactive phosphorous (SRP), nitrate-nitrogen (NO3-N), and ammonia-nitrogen (NH3-N) removals were tested at a constructed wetland receiving municipal wastewater effluent. Over all, no significant differences in nutrients occurred between diverse planted and cattail areas. T. latifolia seeds, under the canopy of Eleochoris macrostachya, had low seed germination. Established stands of emergent vegetation can prevent cattail colonization and spread. Germination of T. latifolia at various water depths was tested, and depth impacts on cattail seedling growth and survival were ascertained using various moist soil management techniques in three ponds. Water levels at 0cm and >40cm can adversely impact cattail establishment.
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Phosphorus Retention and Fractionation in Masonry Sand and Light Weight Expanded Shale Used as Substrate in a Subsurface Flow Wetland

Phosphorus Retention and Fractionation in Masonry Sand and Light Weight Expanded Shale Used as Substrate in a Subsurface Flow Wetland

Access: Use of this item is restricted to the UNT Community.
Date: August 2002
Creator: Forbes, Margaret G.
Description: Constructed wetlands are considered an inefficient technology for long-term phosphorus (P) removal. The P retention effectiveness of subsurface wetlands can be improved by using appropriate substrates. The objectives of this study were to: (i) use sorption isotherms to estimate the P sorption capacity of the two materials, masonry sand and light weight expanded shale; (ii) describe dissolved P removal in small (2.7 m3) subsurface flow wetlands; (iii) quantify the forms of P retained by the substrates in the pilot cells; and (iv) use resulting data to assess the technical and economic feasibility of the most promising system to remove P. The P sorption capacity of masonry sand and expanded shale, as determined with Langmuir isotherms, was 60 mg/kg and 971 mg/kg respectively. In the pilot cells receiving secondarily treated wastewater, cells containing expanded shale retained a greater proportion of the incoming P (50.8 percent) than cells containing masonry sand (14.5 percent). After a year of operation, samples were analyzed for total P (TP) and total inorganic P (TIP). Subsamples were fractionated into labile-P, Fe+Al-bound P, humic-P, Ca+Mg-bound P, and residual-P. Means and standard deviations of TP retained by the expanded shale and masonry sand were 349 + 169 and 11.9 ...
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