UNT Theses and Dissertations - 418 Matching Results

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Biological Control of the Red Imported Fire Ant by the Entomopathogenic Nematode, Steinernema Carpocapsae (Weiser)

Description: Field trials were conducted in 1988 to evaluate the effectiveness of Steinernema (=Neoaplectana) carpocapsae (Weiser) in controlling the fire ant. Infective juveniles (IJ) of the nematode were applied as drench on 235 and 422 mounds, respectively for 2-month summer and 6-week fall evaluation periods. In comparative trials, amidinohydrazone (Amdro) was applied to 249 (summer) and 65 (fall) active mounds, with 245 (summer) and 78 (fall) untreated active as controls. Nematode treatments resulted i… more
Date: August 1989
Creator: Morris, John R. (John Robert), 1949-
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Partner: UNT Libraries
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Phototoxic Effects of Titanium Dioxide Nanoparticles on Daphnia Magna

Description: Titanium dioxide nanoparticles (TiO2-NP) are one of the most abundantly utilized nanomaterials in the world. Studies have demonstrated the mechanism of acute toxicity in TiO2-NP to be the production of reactive oxygen species (ROS) leading to oxidative stress and mortality in exposed organisms. It has also been demonstrated that the anatase crystalline conformation is capable of catalyzing the cleavage of water molecules to further increase the concentration of ROS in the presence of ultraviole… more
Date: December 2013
Creator: Mansfield, Charles M.
Item Type: Refine your search to only Thesis or Dissertation
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The Evolution, Applications, and Statistical Interpretations of DNA Typing in Forensic Science

Description: This thesis examines the evolution, applications, and statistical interpretations of DNA typing as a tool in the field of forensic science as well as in our criminal justice system. The most controversial aspect of DNA typing involves the determination of how likely it is that two people share the same DNA profile. This involves the use of population genetics and databases of allelic frequencies as well as some assumptions about population structuring.
Date: August 1997
Creator: Schober, Cassandra C. (Cassandra Carolyn)
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Assessment of Changes in Aquatic Macrophyte Occurrence Following Introduction of Triploid Grass Carp in a North Texas Reservoir

Description: The objectives of this project were to measure changes in frequency of occurrence of submerged macrophytes over the first two growing seasons following stocking with triploid grass carp at two fish per acre and to measure differences in macrophyte biomass between areas excluded from herbivory and adjacent control sites after 16 months following establishment of exclosures. The project also seeks to measure concentrations of fluridone following the herbicide treatment, and to compare two methods… more
Date: August 1997
Creator: Bickel, Ken (Kenneth E.)
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Partner: UNT Libraries
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L-asparaginase II Production by Escherichia coli

Description: Growth of Escherichia coli A-l under aerobic conditions in an enriched medium with a total amount of 0.2 per cent glucose was biphasic and asparaginase II activity was detected after depletion of ammonia from the growth medium in the second phase of growth. Glucose was exhausted two hours before ammonia and three hours before asparaginase II activity was detected. The concentration of 3',5'-cyclic adenosine monophosphate was found to fluctuate when the dissolved oxygen in the medium reached a l… more
Date: May 1985
Creator: Johnson, Terrance L. (Terrance Lewyne), 1950-
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Evaluation of a Constructed Wetland to Reduce Toxicity from Diazinon at the Pecan Creek Wastewater Treatment Plant, Denton, TX

Description: The City of Denton Pecan Creek Wastewater Treatment Facility has periodically failed effluent toxicity testing. A Toxicity Identification Evaluation has determined that Diazinon in the effluent is contributing to the observed toxicity. Chlorpyrifos is also implicated as a factor. The City of Denton constructed a half acre experimental wetland to remove Diazinon related toxicity. Results from spiking and microcosm experiments indicate that the wetland can reduce the Diazinon.
Date: May 1996
Creator: Baerenklau, Amy L. (Amy Lyn)
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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A Comparison of Predicted and Actual Trophic Status of Lake Ray Roberts, Texas Based on Chlorophyll A

Description: Two years before impoundment, the trophic status of Lake Ray Roberts was predicted by applying the total phosphorus input into the Organization for Economic Cooperation and Development (OECD) eutrophication model. Predicted mean summer epilimnetic (MSE) chlorophyll a of Elm Fork arm, Isle duBois arm and Main Body were in the eutrophic category of the OECD model. Observed MSE chlorophyll a two years after impoundment of Elm Fork arm, Isle duBois and Main Body had not reached their predicted mean… more
Date: May 1999
Creator: Lytle, Lili Lisa
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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A Laboratory Study of the Asiatic Clam (Corbicula fluminea Müller) as Influenced by Substrate, Food Source and Water Type

Description: Growth of Corbicula fluminea was monitored in the laboratory. Three experiments were conducted. Experiment I utilized three substrates and one food type. Experiment II utilized three substrates and two food types. Experiments I and II were conducted to determine if substrate type or food type effected growth. Experiment III used no substrates, one food type and was conducted to determine growth response to different types of water. Clams were maintained in three substrates: sand, gravel and cla… more
Date: May 1995
Creator: Halbrook, Courtney (Courtney Ann)
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Development and Application of an Assessment Protocol for Watershed Based Biomonitoring

Description: With numerous bioassessment methodologies available, a regional protocol needs to be developed to ensure that results are comparable. A regional assessment protocol was developed that includes collecting five benthic macroinvertebrate samples, identifying organisms to genus, and calculating the following metrics: Number of Taxa, Total Number of Individuals, Simpson's Diversity Index, Shannon's Diversity Index, Percent Contribution of Dominant Taxa, Hilsenhoffs Biotic Index, and Percent Contribu… more
Date: May 1998
Creator: Schwartz, Joseph Howard
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Impacts of the Pyrethroid Insecticide Cyfluthrin on Aquatic Invertibrate Populations in Outdoor Experimental Tanks

Description: The chemical fate and biological impacts of cyfluthrin in aquatic ecosystems were investigated using microcosms (1.9 m^3 concrete tanks) during 1989. Results were compared to a concurrent pesticide registration study using mesocosms (634.7 m^3 earthen ponds). Ten spray drift and five soil runoff simulations were conducted. Pesticide loadings were scaled by system volume, with the same experimental design in ponds and microcosms. Aqueous cyfluthrin concentrations and sediment residue values were… more
Date: May 1992
Creator: Johnson, Philip C. (Philip Charles)
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Forest Landscape Dynamics: a Semi-Markov Modeling Approach

Description: A transition model (MOSAIC) is used to describe forest dynamics at the landscape scale. The model uses a semi-Markov framework by considering transition probabilities and Erlang distributed holding times in each transition. Parameters for the transition model are derived from a gap model (ZELIG). This procedure ensures conceptual consistency of the landscape model with the fine scale ecological detail represented by the forest gap model. Spatial heterogeneity in the transition model is driven b… more
Date: August 1997
Creator: Ablan, Magdiel
Item Type: Refine your search to only Thesis or Dissertation
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Light Spectra Distributions in Temperate Conifer-Forest Canopy Gaps, Oregon and in Tropical Cloud-Forest Canopy, Venezuela

Description: Light spectra distributions were measured in two different montane forests: temperate and tropical. Spectral light measurements were made in different sized canopy gaps in the conifer forest at H. J. Andrews Experimental Forest in Oregon, USA. Researchers at Oregon State University created these gaps of 20 m, 30 m, and 50 m in diameter. In the tropical cloud forest, spectral light measurements were made in two plots that were permanently established at La Mucuy Parque Nacional in Venezuela, in … more
Date: December 1997
Creator: Monteleone, Susan Elaine
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Biological and Toxicological Responses Resulting from Dechlorination of a Major Municipal Wastewater Treatment Plant Discharge to the Trinity River

Description: Federal regulations such as the Clean Water Act (P.L. 92-500), and its amendments, direct the Environment Protection Agency (EPA) to implement programs to control the releases of conventional pollutants and toxics into the waterways of the United States. The EPA began requiring treatment plants to conduct toxicity tests (biomonitoring) of their effluent discharges. To control toxicity caused by chlorination of wastewater discharges, the EPA also began requiring some treatment facilities to dech… more
Date: August 1995
Creator: Guinn, Richard J. (Richard Joe)
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Short Term Effects of External Electric Fields on Electrical Activity of the Pineal Gland in Rats

Description: The effects of short term exposure (5 minutes) to EEFs at relatively high dosages (10, 25, 39, kV/m) on the electrical activity in rat pineal glands was studied. Daytime and nighttime recordings were taken from an implanted microelectrode in the gland. The data show that (1) both the activity and frequency were enhanced when the animals were exposed to EEFs at 39 kV/m continuously and discontinuously; (2) the later condition yielded a sustained increase (36%) whereas the former a brief (10 sec)… more
Date: May 1996
Creator: Vu, Hung Quoc
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Primary Productivity and Nutrient Relationships in Garza-Little Elm Reservoir

Description: A large, multi-basin, reservoir (Garza-Little Elm Reservoir) in north central Texas was studied to determine the relative effects of various parameters on primary productivity. The basins were impounded several years apart,thus allowing the influence of age on water chemistry and biota to be considered. Another principal influence on water quality was secondary sewage effluent that entered one basin from a nearby source.
Date: May 1973
Creator: Smith, Jerry Allen
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Landscape Ecological Characteristics of Habitat of the Red-cockaded Woodpecker

Description: Geographic information systems (GIS) technology was used to analyze factors influencing habitat use by an endangered species, the red-cockaded woodpecker. The study area was the western part of the Raven Ranger District of the Sam Houston National Forest, Texas. The factors considered included both structural characteristics and spatial relationships among stands of trees in the habitat.
Date: December 1993
Creator: Thomlinson, John Richard
Item Type: Refine your search to only Thesis or Dissertation
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The Response of Aquatic Insect Communities and Caged In situ Asiatic Clams (Corbicula fluminea) to Dechlorinated Municipal Effluent in the Trinity River in North Texas

Description: Dischargers to the Trinity River in North Texas were required to dechlorinate their effluents in 1990-91. Field surveys were conducted above and below an outfall to determine the response of resident immature insects and caged in situ juvenile Asiatic clams to chlorinated and dechlorinated effluent. Within six months after dechlorination began, insect community composition and C. fluminea survival significantly improved at stations below the outfall. Significantly lower clam growth within one m… more
Date: December 1994
Creator: Spon, Sandra T. (Sandra Teresa)
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Genetics Lecture and Laboratory Syllabus for a Junior-Level Course

Description: The following is a complete syllabus for a college level genetics course. The syllabus contains lecture outlines and notes for each chapter, along with a list of transparencies needed. The quizzes and exams are prepared and placed at the beginning of the syllabus. The beginning of the course will consist of a lecture to introduce the students to the basics of genetics, followed by many applications of genetics. The process of cell division will be mastered by the students, as well as Mendelian … more
Date: August 1999
Creator: Harper, Kasey
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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The Use of Similarity Indicies to Assess the Spatial Differences of the Phytoplankton Communities in Lake Ray Roberts, Texas

Description: A study of the phytoplankton communities of Lake Ray Roberts was conducted at three sampling sites on two sampling dates during the summer of 1995, assessing both community structure and chlorophyll a concentrations. Eight similarity indices were then used to characterize and compare the communities of these sites. Both community similarity and chlorophyll a concentrations were evaluated using a minimum detectable difference equation to determine the amount of change that must occur in these pa… more
Date: August 1996
Creator: Banks, Kenneth E. (Kenneth Edward)
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The Effects of Organic Surface Amendments on Soil Nutrients and Initial Tree Establishment

Description: This study examined the effects of replicating woodland soil surface horizonation on the nutrient status of underlying soils and the initial establishment and growth of trees. A total of 283 container grown trees were planted in a bufferzone around a future landfill site. Control amendments consisted of an 8 cm layer (0.5 m3) of wood chips applied in a circular area of 4.6 m2 around the trees' planting pit. For the treatment, a 2.5 cm layer of composted biosolids (0.15 m3 or 80 Mg/ha) was appli… more
Date: May 1999
Creator: Thuesen, Kevin (Kevin Andrew)
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Changes in Gene Expression Levels of the Ecf Sigma Factor Bov1605 Under Ph Shift and Oxidative Stress in the Sheep Pathogen Brucella Ovis

Description: Brucella ovis is a sexually transmitted, facultatively anaerobic, intracellular bacterial pathogen of sheep (Ovis aries) and red deer (Cervus elaphus). Brucella spp. infect primarily by penetrating the mucosa and are phagocytized by host macrophages, where survival and replication occurs. At least in some species, it has been shown that entry into stationary phase is necessary for successful infection. Brucella, like other alphaproteobacteria, lack the canonical stationary phase sigma factor ?s… more
Date: December 2012
Creator: Kiehler, Brittany Elaine
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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