403 Matching Results

Search Results

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 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 + 18.6 mg/kg respectively. The largest forms of P retained by the expanded shale pilot cells were Fe+Al- bound P (108 mg/kg), followed by labile-P (46.7 mg/kg) and humic-P (39.8). Increases in the P forms of masonry sand were greatest in labile-P (7.5 mg/kg). The cost of an expanded shale wetland is within the range of costs conventional technologies for P removal. Accurate cost comparisons are dependent upon expansion capacity of the system under consideration. Materials with a high P sorption capacity also have potential for enhancing P removal in other constructed wetland applications such as stormwater wetlands and wetlands ...
Access: This item is restricted to UNT Community Members. Login required if off-campus.
Date: August 2002
Creator: Forbes, Margaret G.
Partner: UNT Libraries

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 in an average of 47% control (Abbott's formula) in summer trials and 19-88% control in the fall trials, compared with 39% and 47% control, respectively with amidinohydrazone. Active mounds treated with nematodes or amidinohydrazone had significantly fewer individuals than control mounds in summer trials.
Date: August 1989
Creator: Morris, John R. (John Robert), 1949-
Partner: UNT Libraries

Effects of Long-Term Moderate Ethanol Intake on the Stress Response in Rats

Description: The effect of ethanol on the stress response in rats was examined. Experimental animals were given 0.25 ml of 28 percent ethanol or 0.25 ml of water orally once a day, five days a week, for a period of twelve months and were then subjected to fifteen minute cold stress. Corticosterone levels in ethanol-treated males following stress were significantly lower (22 percent) than in the sham group. Adrenal weights in sham-treated females were significantly higher (15 percent) than in the ethanol group at the end of twelve months. Mortality in sham-treated males was significantly higher (60 percent) than in ethanol-treated males. The effects observed may be due to the sedative action of ethanol on cortical centers controlling the hypothalmus.
Date: December 1984
Creator: Williams, Judy L. (Judy Lee)
Partner: UNT Libraries

The Reproductive Consequences of Carriers of Methylenebisacrylamide-Induced Balanced Reciprocal Translocations in Mus Musculus

Description: N,N'-methylenebisacrylamide (MBA) was studied because of its effectiveness in inducing heritable translocations in germ cells of male mice. The health impact of translocations was studied through anatomical analysis of the progeny of semisterile translocation carriers. As expected, the semisterility of translocation carriers resulted primarily from embryonic death during periimplantation stages due to unbalanced chromosome sperm segregants. Among conceptuses that survived to mid- and late-gestation stages, there was an increased incidence of developmental anomalies including fetal death and phenotypic defects. These abnormalities are associated with unbalanced chromosome complements that allow survival to the later stages of development.
Date: May 1989
Creator: Kile, Joanna L. (Joanna Le)
Partner: UNT Libraries

Changes in Heterozygosity Through Time in American Standardbred and American Saddlebred Horses (1960-1990)

Description: Observed and expected heterozygosity (H) levels for ten electrophoretic blood marker loci and expected H for seven red blood cell (RBC) anitgen/antibody loci were examined for 20 years in American Standardbred and 30 years in American Saddlebred horses. Standardbreds were classed by gait, Trotter and Pacer, and evaluated separately in most analyses. 4,404 Trotters and 12,271 Pacers were found to have statistically highly significant losses of mean total observed H through time for the ten electrophoretic loci (P<0.005), although in Trotters the loss was more extreme (P<<0.001). Loss of H in 5984 Saddlebreds was not significant (P=0.259). Correlations of RBC expected H through time showed decreases in all three groups.
Date: May 1992
Creator: King, Judith A. (Judith Ann), 1955-
Partner: UNT Libraries

Characterization of the OCT Plasmid-Encoded Mercury Resistance Genetic Locus in Pseudomonas putida

Description: A 17.1 Kb genetic element encoding for mercury resistance (OCT-Hg^r) was shown to translocate from its original location on the OCT plasmid to the resistance plasmid, RPl, in Pseudomonas putida. Analysis of RPl-Hg^r recombinant plasmids revealed that insertion of mercury resistance genes into RPl could occur at a variety of sites, with all recombinants having common EcoRI restriction fragments of 9.4, 3.8, 2.3, and 1.6 Kb, derived from the insertion. Hybridization analysis suggested the existence of extensive homology between this insertion and the prototypic mercury resistance transposon, Tn501, as well as the location of a similar merA sequence. Although the overall size was shown to be quite different from Tn501, striking physical similarities are shared between these two elements.
Date: May 1989
Creator: Armbruster, Steven C. (Steven Christopher)
Partner: UNT Libraries

Genetic Variation in a Population of the Plains Woodrat Neotoma micropus

Description: Neotoma micropus from Jack County, Texas, were studied over a 9-month period. Loci from blood and saliva were used to determine genetic variation within the population. Deviations from Hardy-Weinberg equilibrium were found at one locus. The average temporal F over all seven loci was 0.040. Genetic structuring was subtle, fluctuated on a seasonal basis, and was due to differential migration or predation on genotypes. Heterozygotes tended to move more than homozygotes, and a greater proportion of heterozygotes were lost from the population during each season. Genetic variation was maintained in the population by immigrant individuals. This differential in dispersal of genotypes fits current models of reorganization within the genome of populations.
Date: August 1988
Creator: Stewart, John E. B. (John Edward Bakos)
Partner: UNT Libraries

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, it is impossible to be certain of the species from vegetative characters. However, this may also be true when the characters of the floral parts alone are considered. The inflorescence, used in most keys and descriptions, is often available only for a short period of time. Identification by the characters of the vegetation can be used throughout the growing season, even if grazing or mowing has removed or prevented the development of the floral parts. There have been other studies of grass identification related to vegetative characters, but they have been local and have not covered North Central Texas. This paper provides a means of identifying grasses by their vegetative characters. It can be used by the scientist, the technician, and the layman interested in the grasses of North Central Texas. A key using technical terminology is provided for use by the ecologist, range specialist, plant taxonomist, and student in these areas of study. For the ranchman, farmer, greens keeper, gardener, or nurseryman, a key with symbols is given that can be used without a technical knowledge of taxonomic botany. The distribution maps and diagnoses will aid any user of the keys. They will also make available additional information that may be useful in the establishment of a numerical classification and identification of plants--grasses in particular.
Date: August 1970
Creator: Smith, David Lawrence, 1932-
Partner: UNT Libraries

Adenylate Energy Charge Determinations of Soil Bacteria Grown in Soil Extract Medium

Description: The adenylate energy charge values of twenty bacteria isolated from soil and cultured in a medium consisting of soil and distilled water were determined by the luciferin-luciferase bioluminescense method. The purpose of this study was to examine the growth and energy charge values of these organisms in soil extract medium, and to determine what effect the addition of glucose has on their energy charge values. Three of the organisms employed in this study showed energy charge values similar to those reported for bacteria grown in enriched media. The remainder of the isolates demonstrated low energy charge values, and scant growth in the soil medium.
Date: August 1988
Creator: Rodriguez, Luis A. (Luis Antonio)
Partner: UNT Libraries

Mutagenic Potential of Tetramethylthiuram Disulfide (42-S Thiram) on the Germ Cell Stages of Drosophila melanogaster

Description: Tetramethylthiuram disulfide (42-S Thiram), a carbamate fungicide was studied for its mutagenic potential on the germ cell stages of wild-type male Drosophila melanogaster. The mutagenicity was tested using the sex-linked recessive lethal assay (SLRL). Any lethals induced in the F2 generation were evidenced by the absence of wild-type males. Although there was an increase in mutation rates in the 42-S Thiram treated wild-type males over the control wild-type males, it was not significantly higher. According to the laboratory conditions in this preliminary study, tetramethylthiuram disulfide failed to produce mutagenic effect.
Date: December 1990
Creator: Lowe-Chatham, Janice E. (Janice Elaine)
Partner: UNT Libraries

A New LC Column for the Separation and the Quantitation of Nucleotides

Description: A new column, Dionex AS4A, (polystyrenedivinylbenzene matrix) used for the separation of ribonucleotides and deoxyribonucleotides for the first time, and previously used for ion analysis was found superior to conventional silica columns because it separates ribonucleotides and deoxyribonucleotides. Resolution of dGTP was not possible with the Dionex column and CTP and GDP often co-eluted. Using conventional silica columns, monophosphates separated from diphosphates and diphosphates from triphosphates. Using the new Dionex column resolves all three simultaneously. The Dionex column resolved nucleotides with sharper peaks than silica columns, and the longer its retention time the better was the resolution. This Dionex column is stable, with 80 runs possible without cleaning while resolving ribonucleotides and deoxyribonucleotides to the picomole level.
Date: December 1987
Creator: Brock, Patricia C. (Patricia Charlene)
Partner: UNT Libraries

Predicting the Site-Specific Bioavailability of Zinc Using the Indicator Species Procedure: A Case Study

Description: National Water Quality Criteria intended to protect aquatic life and their uses from the adverse effects of pollutants may not be appropriate due to site-specific factors that alter chemical bioavailability. The Indicator Species Procedure may be used to derive site-specific criteria in order to account for differences in site-specific bioavailability. This procedure was implemented using zinc for three chemically different site (river) waters. The purpose of this study was to quantify the bioavailability of zinc in each site water and correlate results to water quality parameters and/or zinc speciation. Results demonstrated that national criteria for zinc accurately predicted the experimentally derived site-specific values within a factor of two when adjusted for water hardness. Particulate forms of zinc were shown to be biologically unavailable under conditions tested.
Date: May 1987
Creator: Parkerton, Thomas F.
Partner: UNT Libraries

Development and Validation of a Ramping Treadmill Protocol for the On-Line Measurement of Four Aerobic Parameters

Description: Previously, Whipp et. al. (J. Appl. Physiol.: Respirat. Environ. Exerc. Physiol. 50(1):217-221, 1981) demonstrated the feasibility of determining four parameters of aerobic function, identified as maximum oxygen uptake (μVO_2), VO_2 at anaerobic threshold (θan), the time constant for oxygen uptake kinetics (rVO_2) and work efficiency (η), using a short duration ramped bicycle ergometer exercise test. Because of the importance of being able to measure these parameters on a variety of measurement instruments a short duration ramping treadmill protocol has been developed. The ability of this protocol to determine the four aerobic parameters has been validated against conventional methods. The results of this investigation indicate that μVO_2, θan, rVO_2 and, η may be obtained from a single, short-duration ramping treadmill test.
Date: May 1990
Creator: Cowell, Lynda L. (Lynda Lea)
Partner: UNT Libraries

Development of an In Vitro Protoplast Culture System for Albizia Lebek (L.) Benth., an Economically Important Leguminous Tree

Description: An in vitro system of generating protoplasts from their callus cultures was established. The friable callus was more productive in terms of producing protoplasts than the green compact callus. The concentration of the various cell wall degrading enzymes had an effect on the viability of the protoplasts in the medium. The protoplast system developed from the experiments was stable and could be used for the transformation experiments of Albizia lebek and for other plant improvement practices.
Date: August 1998
Creator: Sinha, Debleena
Partner: UNT Libraries

Comparative Toxicity Responses in Earthworms Lumbricus Terrestris and Eisenia Foetida to Cadmium Nitrate and Chlordane Using Artificial Soil and Filter Paper Exposures

Description: This research compares LC50 and LD50 of earthworms, Lumbricus terrestris and Eisenia foetida exposed to cadmium nitrate and chlordane using 48-h contact filter paper (FP) and 14-d artificial soil (AS) protocols. Both LC50 and LD50 showed that chlordane was more toxic than cadmium in both species regardless of the exposure. The reference toxicant 2-chloroacetamide using the standardized 48-h FP exposure was used to assess the general response of the earthworm prior to toxicity experiments. A glucose test was developed as an internal standard to assess homogeneity of mixtures among both replicates and dilutions. Accuracy of dilutions is assessed by the slope of a regression line relating nominal dilution to observed internal standard concentration. Precision of replicate preparation is assessed by among replicate variance.
Date: August 1992
Creator: Muratti Ortiz, Joseph F.
Partner: UNT Libraries

Estimated Extent and Fate of Chlorinated Solvent Contamination in the Soil of the Naval Air Station, Dallas, Texas

Description: This thesis estimates the spatial extent of chlorinated solvent contamination of the soil at the Naval Air Station, Dallas, then estimates the fate and transport of these contaminants, over time, using the Soil Transport and Fate database and the Vadose-Zone Interactive Processes (VIP) modeling software. Geostatistical analysis identifies two areas with serious chlorinated solvent contamination. Fate and transport modeling estimates that this contamination will degrade and disperse from the soil phase to below regulatory limits within one year, although there is a risk of groundwater contamination. Contaminants are estimated to persist in the water and air phases of the soil. Further sampling is recommended to confirm the results of this study.
Date: August 1998
Creator: Trescott, Jill V. (Jill Virginia)
Partner: UNT Libraries

The Effect of Long-Term Moderate Amounts of Ethanol on Paraventricular Nuclei Activity on Cold Stressed Adult Rats

Description: The effects of moderate, long-term intake of ethanol on the hypothalamic response to cold stress were examined. The long-term experimental animals were given .25 ml of 28% ethanol or .25 ml of water orally once a day, five days a week for fourteen months. A stainless steel electrode was then surgically implanted into the paraventricular nucleus, after which the animal was subjected to cold stress (-150 C, 10 min.). Recordings were taken in the forms of frequency and activity. The data clearly indicate that: (1) alcohol fed rats exhibited a suppressed response to cold stress compared to sham-fed rats; (2) this suppression of activity occurred at the level of the hypothalamus, and (3) mortality was significantly lower in alcohol-fed males than it was in sham fed males. This study clearly points out the need for further work in the area of the beneficial effects of moderate doses of alcohol.
Date: December 1990
Creator: McKinnon, Mark S. (Mark Steven)
Partner: UNT Libraries

An Evaluation of the Short-Term Embryo-Larval and Seven-Day Larval Test Methods for Estimating Chronic Toxicity of Zinc to the Fathead Minnow (Pimephales promelas)

Description: Chronic toxicity of zinc to Pimephales promelas was estimated by conducting replicate static and static-renewal short-term embryo-larval tests and static-renewal seven-day larval tests. The two test methods were highly reproducible. Daily renewal of test solutions had little effect on the toxicity of zinc, however, the stage of development at which exposure was initiated affected the sensitivity of the toxic endpoints measured. The most sensitive and reproducible endpoint in the embryo-larval tests was survival of viable (non-deformed) larvae and in the seven-day larval test was growth of the larvae, which was slightly more sensitive than the embryo-larval test endpoint. The estimated MATC of 0.18 and 0.15 mg/L mean total and mean soluble zinc, respectively, compared well with published results. Because of its advantages and similar sensitivity, the short-term embryo-larval test was recommended for estimating chronic toxicity.
Date: May 1987
Creator: Stewart, Susan Michels
Partner: UNT Libraries

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 signatures which can be correlated to land cover and habitat. This research sought relationships between traditional ecological measures and information gathered from satellite digital imagery. Reliable interpretation of earth surface characteristics relies largely on accurate rectification to a map projection and subsequent thematic classification. Use of the Global Positioning System (GPS) for rectification was superior than digitizing topographical maps. Differentially corrected GPS locations provided optimum rectification with SPOT satellite imagery while marginally better rectifications were obtained for Landsat MSS imagery using uncorrected GPS positions. SPOT imagery provided more accurate land cover classifications than did MSS. Detection of temporal land cover change using MSS imagery was hampered by confusion among intermediate successional classes. Confusion between upland and bottomland forest classes occurred with both SPOT and MSS. Landscape analyses using thematic maps produced from the previously discussed endeavors suggested that terrestrial habitat in the Ray Roberts Lake area became more fragmented and complex in shape. Habitat patches became smaller but more numerous. Forested areas were most effected and conservation efforts should focus on management strategies that promote vegetation succession and forest maturation. Remotely sensed SPOT data were successfully used to predict tree basal area. There were no significant relationships found with other in situ measures or between MSS data and any vegetation measures. Remote sensing provided information suitable for large scale projects concerning landscape-level ecological issues. Rectification and classification accuracies were the ...
Date: December 1997
Creator: Smith, David P. (David Paul), 1956-
Partner: UNT Libraries

The Effects of 3-Deazaguanine on Chick Embryo Fibroblasts and Rat Kidney Cells Infected with Temperature-Sensitive Mutant and Wild-Type Rous Sarcoma Viruses

Description: Chick embryo fibroblasts and rat kidney cells infected in vitro with Rous Sarcoma viruses were treated with 3-deazaguanine (3-DG). The findings revealed that 3-DG inhibited virus-induced cellular transformation. Degree of inhibition is dependent on concentration and frequency of media change. 3-DG at the concentrations tested will not reverse transformed cells to the untransformed state and does not have marked effect on replication of viruses. Upon removal of 3-DG, its effect was shown to be reversible. Cell growth was generally retarded in medium containing 3-DG. When xanthosine and inosine were added to the medium, cell growth was unaffected, but it increased in guanosine.
Date: December 1979
Creator: Fadare, Samuel O.
Partner: UNT Libraries

Aquatic Vegetation Nutrient Budgets and Sedimentation in a Southwestern Reservoir

Description: During four growing seasons, aquatic vascular plant production and distribution were studied in Pat Mayse Lake, Texas, a 2425 hectare oligo-mesotrophic reservoir. The dominant macrophyte population was Myriophyllum spicatum L. Growth rates and regrowth rates of mechanically harvested Myriophyllum beds were found to be dissimilar. Based on estimates of watermilfoil nutrient content, there were insufficient nutrients in the entire population to alter the trophic status of this reservoir should all of the nutrients be instantaneously released. Sediments were the primary nutrient (nitrogen and phosphorus) sink. Bank erosion and solids transport from the watershed appear to contribute most of the sediments and a lake-wide mean sedimentation rate of 2.5 cm/year was estimated from sediment trap and core sample data.
Date: May 1986
Creator: Clifford, Philip A. (Philip Alan)
Partner: UNT Libraries

Isolation and Partial Characterization of Pigment Mutants of Corynebacterium poinsettie ATCC 9682

Description: Carotenoid pigments were extracted from Corynebacteriuma poinsettiae (wild type) ATCC 9682, and from 108 mutants obtained by exposure of a streptomycin resistant strain of C. poinsettiae to ultra-violet light irradiation and N-methyl- N'-nitro-N-nitrosoguanidine. The pigments were characterized by their absorption maxima, Rf-values, and partition ratios in petroleum ether and methanol. Thin layer chromatography was used to compare pigments of the wild type with those of the mutants. Possible biosynthetic pathways in carotenoid synthesis of the wild type were postulated on the basis of the observed genetic blocks. Mutants were found which suggested the existence of a linear pathway in carotenoid synthesis from the aliphatic C4 0 molecule to the bi-cyclic C50-diol. Other mutants suggested possible alternative pathways in the biosynthesis of these pigments or the presence of intermediates not detectable by thin layer chromatography.
Date: August 1980
Creator: Wariso, Benjamin A.
Partner: UNT Libraries

Molecular Cloning and Functional Analysis of Transposable Mercury Resistance Genes Encoded by the OCT Plasmid

Description: Translocation of a 17.1 kilobase region of the OCT plasmid encoding mercury resistance (mer) in Pseudomonas putida was shown to occur in a recombination-deficient host with plasmid PP1 serving as a recipient replicon. The frequency of transposition in Pseudomonas was estimated at 10^3 -10 -^2, but undetectable in Escherichia soli. ' DNA comprising all of mr as well as subregions there of were cloned and subjected to DNA sequence analysis. Like other transposons, mer was found to contain inverted repeat sequences at its termini. These were similar to, but not identical to the inverted repeat structures found in the prototypical mercury resistance transposon Tn501 from E. aeruginosa.
Date: August 1991
Creator: Wang, Chien-Sao
Partner: UNT Libraries

Nutritional Requirements of Corynebacterium poinsettiae

Description: In a minimal medium supplemented with glucose and yeast extract, the optimum pH for the growth of C. poinsettias was found to be 7.5. The organism requires thiamine, biotin, and pantothenic acid for growth. No absolute requirement was found for any amino acid, purine or pyrimidine although an amino acid mixture was stimulatory. Casamino acids could be substituted for the synthetic amino acid mixture. Yeast extract provided an additional factor(s) necessary for maximal growth. The results suggest that the unknown factor found in yeast extract might be purified by a combination of solvent extraction, and adsorption and elution from charcoal.
Date: December 1983
Creator: Hooshdaran, Farideh
Partner: UNT Libraries