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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)
Partner: UNT Libraries
open access

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
Partner: UNT Libraries
open access

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
Partner: UNT Libraries
open access

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
Partner: UNT Libraries
open access

Investigations of neuronal network responses to electrical stimulation in murine spinal cultures.

Description: Spontaneous activity in neuronal networks in vitro is common and has been well documented. However, alteration of spontaneous activity in such networks via conditioning electrical stimulation has received much less experimental attention. Two different patterns of electrical stimulation were used to enhance or depress the level of spontaneous activity in spinal cord cultures. High-frequency stimulation (HFS), a method routinely shown to increase the efficacy of synaptic transmission, was employ… more
Date: December 2001
Creator: Sparks, Christopher A.
Partner: UNT Libraries

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

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 sub… more
Access: Restricted to UNT Community Members. Login required if off-campus.
Date: August 2002
Creator: Forbes, Margaret G.
Partner: UNT Libraries
open access

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-
Partner: UNT Libraries
open access

Ecotoxicological Investigations in Effluent-Dominated Stream Mesocosms

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 str… more
Date: December 2002
Creator: Brooks, Bryan W.
Partner: UNT Libraries
open access

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

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 Arthr… more
Date: May 2003
Creator: Meixner, Jeffery Andrew
Partner: UNT Libraries
open access

Remote Sensing of Landscape-Level Ecological Attributes at Ray Roberts Lake in North Texas

Description: Biological diversity is a key component in assessing ecosystem health. Alteration, degradation and loss of habitat due to human influence is currently the primary stressor resulting in decreases in diversity. Reliable assessment of large areas in terms of biological integrity are needed for conservation and preservation efforts. Remotely sensed data provide an integrated view of reflected electromagnetic energy over large areas of the earth. These energy patterns provide unique spectral signatu… more
Date: December 1997
Creator: Smith, David P. (David Paul), 1956-
Partner: UNT Libraries
open access

The Isolation and Characterization of a Hitherto Undescribed Gram-Negative Bacterium

Description: A unique undosciribed gramnegative rod is extensively characterized in this study. The cells of this unusual water isolate measure 1.2 X 6.5 microns, The most distinguishing characteristic of the bacterium is a polar tuft of 35-40 flagella that aggregate to function as a single organelle which is visible under phase contrast. Aging cells deposit poly- -hydroxybutyric acid granules which are bound by an inclusion membrane made up of four distinct layers. It also possesses an unusual exterior mem… more
Date: August 1972
Creator: Lassiter, Carroll Benson
Partner: UNT Libraries
open access

A Vegetative Analysis of and Distribution of the Grasses of North Central Texas

Description: Accurate identification is fundamental in any study of grasses by farmers, ranchers, range specialists, ecologists, or students interested in the changes taking place in the grass habitat. Frequently it is convenient, and sometimes it is necessary, to identify the grasses by their vegetative characters. Some are readily recognized at a glance by their habitat and certain characters well known to the experienced observer. In other cases, identification is more difficult; and, perhaps with a few,… more
Date: August 1970
Creator: Smith, David Lawrence, 1932-
Partner: UNT Libraries
open access

Cardiovascular Fetal Programming in Quail (Colinus virginianus), An Avian Comparative Model

Description: The consequences of early embryonic insults and how they affect subsequent life reflects the emerging concept of "fetal programming". The aim of this project is to study the effects of embryonic insults as they subsequently manifest themselves in adults, with emphasis on the heart and vasculature. My experiments establish that fetal programming operates on the bobwhite quail inducing similar changes as those observed in mammalians and other birds. The quail's fast development provides reliable … more
Date: December 2016
Creator: Flores Santin, Josele R.
Partner: UNT Libraries
open access

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
Partner: UNT Libraries
open access

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)
Partner: UNT Libraries
open access

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)
Partner: UNT Libraries
open access

A Floristic Study of the Woody Vegetation of the North American Cross Timbers

Description: This research represents the first systematic collection of the woody plants throughout the Cross Timbers. It provides the first keys to these plants in their vegetative condition, plant descriptions, distribution maps, and some quantitative measurements used for descriptive purposes. Descriptions of the woody plants were constructed as an aid in verification after a specimen has been identified by use of the keys. The measurements given pertain only to the woody plants as they occur in the Cro… more
Date: December 1974
Creator: Harrison, Thieron Pike
Partner: UNT Libraries

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

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 explorat… more
Access: Restricted to the UNT Community Members at a UNT Libraries Location.
Date: May 2003
Creator: Dohanich, Francis Albert
Partner: UNT Libraries
open access

Spatially Explicit Modeling of West Nile Virus Risk Using Environmental Data

Description: West Nile virus (WNV) is an emerging infectious disease that has widespread implications for public health practitioners across the world. Within a few years of its arrival in the United States the virus had spread across the North American continent. This research focuses on the development of a spatially explicit GIS-based predictive epidemiological model based on suitable environmental factors. We examined eleven commonly mapped environmental factors using both ordinary least squares regress… more
Date: December 2015
Creator: Kala, Abhishek K.
Partner: UNT Libraries
open access

Impact of a Genetically Engineered Probiotic Therapy and IGF-1 Genomics in the PAHenu2 Mouse Model of PKU

Description: Absence of functional phenylalanine hydroxylase results in phenylketonuria (PKU). Viable treatments remain few, expensive and secondary conditions such as osteopenia occur in most PKU patients. Objective 1: Given the recently described roles of gut microbes to aid host digestion, an orally administered genetically engineered probiotic as the delivery vehicle for enzyme replacement therapy was created. The engineered probiotic, pHENOMMenal, produced phenylalanine ammonia lyase with significant… more
Date: December 2015
Creator: Durrer, Katherine Elaine
Partner: UNT Libraries
open access

Immunofluorescence as a Method for the Rapid Identification of Streptococcus Faecalis in Water

Description: The development and refinement of FA has been adequately investigated with major emphasis on pathogenic microorganisms. The development of this technique has reduced both the time and number of biochemical tests necessary to identify a diversity of organisms. The organisms included are the protozoans, as described by Goldman (1953 and 1957) and by Ingram (1961), viruses, as reported by Liu (1955a) and Burgdorfer and Lackman (1960a), pathogenic bacteria which have been investigated by Moody, Gol… more
Date: August 1970
Creator: Abshire, Robert Louis
Partner: UNT Libraries
open access

Toxicological Evaluation for the Ocular Administration of Tolrestat: An Aldose Reductase Inhibitor for the Treatment of Diabetes

Description: Aldose reductase inhibitors (ARI's) have been shown to attenuate or prevent several complications of diabetes in animals. Tolrestat is a potent and unique ARI from Ayerst Laboratories, New York, NY. The efficacy and toxicology of tolrestat via topical ocular administration was examined. Tolrestat effectively enhanced corneal reepithelialization and was efficacious in the prevention of cataracts in the streptozotocin-diabetic rat. Ocular tissues were examined by slit lamp biomicroscopy, scanning… more
Date: December 1987
Creator: Carney, Gerald R.
Partner: UNT Libraries
open access

Eutrophic Levels of Different Areas of a Reservoir: A Comparative Study

Description: It was the purpose of this investigation to attempt to demonstrate if differences in eutrophic levels existed among selected areas of Garza-Little Elm, and to demonstrate the role that sediments play in affecting eutrophication.
Date: August 1970
Creator: Hendricks, Albert C.
Partner: UNT Libraries
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