2000-2019

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https://hdl.handle.net/10217/100538

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Open Access
Loss and plenty: a banquet of age and spirit
(Colorado State University. Libraries, 2000) Sternlieb, Susan Joy, author; Voss, Gary Wayne, advisor; Lundberg, Thomas R., committee member; Fahey, Patrick G., committee member; Kneller, Jane E., committee member
This exhibition presents a still life tableau on a wooden banquet table, eighteen feet by three and one half feet. The objects on the table are platters, bowls, shards and potatoes of fired clay and urethane rubber. All of the objects are metaphors for spiritually enriched aging human beings, and relate to each other and the viewer in an attraction/repulsion play. Three decades of feminist artwork have coalesced into the analysis and exposure of many discriminating myths which have defined women. In addition, we have seen the creation of an enormous body of women-defined, substantive and empowering images. These gifts from women artists who have come before me have made it possible for me to make self defining work about age and spirit.
Open Access
Cattle use of prairie dog towns on the Shortgrass Steppe of Colorado
(Colorado State University. Libraries, 2000) Guenther, Debra A., author; Detling, James K., advisor; Rittenhouse, L. R. (Larry Ronald), 1940-, committee member; Steingraeber, David Allen, 1953-, committee member
Studies on the mixed-grass prairie have found that native large herbivores preferentially graze on prairie dog towns. I investigated the use of prairie dog towns by cattle (Bos taurus) in northeast Colorado by conducting surveys of cattle and vegetation on the Shortgrass Steppe Long Term Ecological Research Site from June-August, 1999. Twelve pastures containing 15 black-tailed prairie dog (Cynomys ludovicianus) towns were surveyed three times a week, and the number of cattle on the towns and their behavior were recorded. A subset of three pastures was intensively surveyed twice weekly wherein the habitat and activity of a randomly chosen focal animal was recorded every six minutes for 3.5 hours. Bite and step counts of other individuals were recorded for five-minute intervals. Vegetation height and cover data were collected monthly on each of the six habitat types. Resource selection functions for driving survey data indicated no significant difference between prairie dog town use and availability. Regression analysis showed no correlation between rain events and prairie dog town use by cattle. The intensively surveyed pastures yielded similar results: i.e., cattle did not significantly prefer or avoid the prairie dog towns. Cattle spent 60% of their time grazing, 13% resting, and 15% traveling when present on prairie dog towns. These percentages were not significantly different from most other habitat types. There were no significant differences in the number of bites per step taken by cattle on towns compared to off town swales, Atriplex canescens terraces, and crested wheatgrass (Agropyron cristatum) strips. Five plant species palatable to cattle occurred in relatively high frequencies (36-65%) on prairie dog towns. In general, bare ground, litter, and vegetation cover on prairie dog towns did not significantly differ from most other habitat types. Vegetation on prairie dog towns was however significantly shorter on (mean= 6.7cm) than that off (mean= 11.9cm) prairie dog towns. This research indicates that cattle on the shortgrass steppe use prairie dog towns randomly and do not avoid them despite the shorter vegetation on prairie dog towns. However, cattle do not prefer to graze on prairie dog towns as bison (Bison bison) do on the mixed-grass prairie.
Open Access
The total synthesis of (-)-paraherquamide A
(Colorado State University. Libraries, 2000) Cao, Jianhua, author; Williams, Robert M., advisor
The first stereocontrolled total synthesis of (-)-paraherquamide A is described in 48 chemical steps. The synthesis is a convergent one, starting from ethyl glycinate, ethyl acrylate and vanillin. The longest linear route is 35 steps. Vanillin was acetylated and nitrated to provide nitrovanillins (94 and 95). These were converted to the azalactones, hydrolyzed to the α-ketocarboxylic acids, oxidatively decarboxylated to acids 99 and 108. Compound 99 was reductively cyclized to oxindoles 100, which was then demethylated to give pure oxindole 101. The oxindole was regioselectively prenylated, epoxidized, and subjected to a key seven-membered ring forming procedure to provide the unique dioxepin 104. Compound 104 was reduced to indole 105 and indoline 106 which was converted to 105 by reaction with DDQ. Indole 105 was protected and subjected to a Mannich reaction to afford the gramine derivative 60. The Michael adduct 150 from ethyl glycinate and ethyl acrylate was protected, intramolecularly condensed and reduced with Baker's yeast to give cis-β-hydroxy proline ester 129. Stereoselective α-alkylation of 129, protection, deprotection, bromoacetyl amide formation, aminolysis, cyclization and dimethoxycarbonylation provided diketopiperazine (DKP) 91. DKP 91 was alkylated with compound 60 to provide indoles 303 and 304, which were then individually decarbomethoxylated to afford four separable diastereomers anti-305 (305E/Z) and syn-306 (306E/Z). These four diastereomers were individually converted to the corresponding SN2' substrates through lactim ether formation, protection of the indole nitrogen, deprotection, allylic chloride formation and TBS ether formation. SN2' cyclization of these four SN2' substrates individually provided the same product 327. Cyclization of lactim ether 327, ring opening of the lactim ether moiety and ring closure afforded DKP 338. Selective amide group reduction of 338, N-methylation, MOM ether deprotection, oxidation, bis-deprotection by TFA provided indole-ketone 344. Oxidative spirooxidation of 344 followed by dehydration gave ketone-olefin 43. Stereoselective methyl addition to 43 afforded (-)-paraherquamide A.
Open Access
Overexpression of mannitol-1-phosphate dehydrogenase increases mannitol production and confers salt and chilling tolerance in transgenic petunia cv. Mitchell
(Colorado State University. Libraries, 2000) Jiang, Yu-Jen, author; Stushnoff, Cecil, advisor; Hughes, Harrison G., committee member; Ishimaru, Carol, committee member; Wallner, Stephen J., committee member
Diploid petunia plants (Petunia hybrid, cv. Mitchell) transformed with a bacterial gene (mt/ D) encoding mannitol-1-phosphate dehydrogenase enzyme (MTL D), resulting in high mannitol expression, were developed and studied in this research. Transgenic lines and wild type control plants were exposed to salinity and chilling stress with the express goal of delineating the impact of manniol on these abiotic stresses. Phenotypically, there was no difference in growth between in vivo wild type and transgenic lines under non-stress conditions. However, transgenic lines expressing high mannitol levels were found to exhibit a greater capacity to tolerate salinity and chilling stresses compared to wild type and transgenic lines expressing low mannitol levels. Enhanced salinity tolerance was observed in seed germination (T2 generation), and in vegetative growth and floral development of transgenic lines expressing high mannitol levels. Also, based upon foliage symptoms and membrane leakage, transgenic lines expressing high mannitol levels were more tolerant of chilling stress compared to with wild type and transgenic lines expressing low mannitol levels. Carbohydrate analysis of wild type and transgenic plants showed that mannitol was the single carbohydrate most affected by plant lines. Two transgenic lines (M3 and M8) always had higher mannitol expression levels when compared to wild type and the other two transgenic lines (M2 and M9) under non-stress and stress conditions. Therefore, the function of high mannitol expression should be considered in developing improved tolerance of petunia plants to salinity and chilling stresses. However, assuming 90 % water content in leaf tissue, leaf osmotic potential of high mannitol expressing lines contributed by mannitol accounted for only 0.006 %-0.01 % of increased osmoregulation caused by salinity stress, and 0.04 %-0.06 % of the increase in osmotic potential caused by chilling stress, respectively. Quantitatively, mannitol appears not to play a role as an osmoregulator in osmotic adjustment in response to both salinity and chilling stresses. Rather, the data from this research suggest that mannitol may function as an important osmoprotectant in enhancing salt and chilling tolerance of those transgenic petunia lines expressing high mannitol levels.
Open Access
Nitrogen availability effects on exotic, invasive plant species
(Colorado State University. Libraries, 2000) Lowe, Petra N., author; Lauenroth, William K., advisor; Burke, Ingrid C., committee member; Milchunas, Daniel G., committee member
The invasion of ecosystems by exotic plant species is a serious concern for land managers and conservationists. One of the most universally recognized exacerbating factors of exotic species invasions is disturbance. Human alterations to the global nitrogen cycle have increased atmospheric nitrogen deposition to terrestrial ecosystems worldwide, a disturbance that may encourage the growth of exotic invasive species that are uniquely capable of growing quickly when excess nitrogen is available. I undertook three experiments, one field and two greenhouse, to test the hypothesis that exotic invasive species are specifically adapted to take advantage of high nitrogen conditions, and outcompete natives as nitrogen availability increases, and that native species are better adapted to low nitrogen conditions and outcompete exotics when this nutrient is low. The field experiment examined the response of a disturbed short grass steppe community dominated by exotics to the addition of humus precursors and a labile carbon source intended to reduce plant available nitrogen. I was hypothesized that decreasing nitrogen availability would disadvantage the dominant exotic species and provide and advantage for the native species, returning the community to a vegetative structure more characteristic of undisturbed sites. Results of the experiment showed that decreasing nitrogen availability had no effect on native or exotic species density, richness, or basal cover. A greenhouse study investigated the response of above and belowground biomass, plant height, and nitrogen tissue concentrations of two species, the native Bouteloua gracilis, and the exotic Bromus tectorum, to a gradient in nitrogen availability and competition. The two species were grown under five levels of nitrogen availability and five levels of competition. I hypothesized that the native species would compete better at the low nitrogen levels, but competitive advantage would shift to the exotic as nitrogen availability increased, as some research has shown native species grow better than exotics at low nitrogen levels whereas exotics are only able to support their rapid growth rates when high amounts of resources are available. The exotic species was the better competitor at all nitrogen levels. A second greenhouse study investigated the above and belowground, height, and nitrogen tissue response of two native species, Bouteloua gracilis and Agropyron smithii, and four exotic species, Bromus tectorum, Euphorbia esula, Cirsium arvense, and Centaurea repens, to a gradient in nitrogen availability. I grew the six species individually under five levels of nitrogen availability. I hypothesized that the native plant species would gain more mass than the exotics at the low nitrogen levels, but the exotics would gain more mass at the high nitrogen levels. The native species failed to perform better than the exotics at the lowest nitrogen levels, but only two exotics performed better than the natives at the highest nitrogen levels. My results support the hypothesis that exotic species respond more readily to increasing nitrogen availability than native species, but do not support the hypothesis that all exotic species have a competitive advantage under high nitrogen conditions. Furthermore, my results do not support the hypothesis that native species have a competitive advantage over all exotic invasive weeds at low nitrogen conditions, as one of the exotics, Bromus tectorum, competed and grew comparatively better than the native species even at low nitrogen levels. The success of all exotic invasive weeds cannot be completely attributed to a rapid growth response to nutrient availability; it is likely that different species utilize a combination of strategies to outcompete native plant species.
Open Access
Role of data analysis methods selection and documentation in producing comparable information to support water quality management
(Colorado State University. Libraries, 2000) Martin, Lindsay Melissa, author; Ward, Robert C., advisor; Loftis, Jim C., committee member
Water quality monitoring is being used in local, regional, and national scales to measure how water quality variables behave in the natural environment. A common problem, which arises from monitoring, is how to relate information contained in data to the information needed by water resource management for decision-making. This is accomplished through analysis of the monitoring data. However, how the selection of methods with which to analyze the data impacts the quality and comparability of information produced is not well understood. To help understand the connectivity between data analysis methods selection and the information produced to support management, the following tasks were performed: (1) examined the data analysis methods that are currently being used to analyze water quality monitoring data, as well as the criticisms of using those types of methods; (2) explored how the selection of methods to analyze water quality data can impact the comparability of information used for water quality management purposes, and; (3) developed options by which data analysis methods employed in water quality management can be made more transparent and auditable. These tasks were accomplished through a literature review of texts, guidance and journals related to water quality. Then, the common analysis methods found were applied to the New Zealand Water Quality River Network data set. The purpose of this was to establish how information changes as analysis methods change, and to determine if the information produced from different analysis methods is comparable. The results of the literature review and data analysis were then discussed and recommendations made addressing problems with current data analysis procedures, and options through which to begin solving these problems and produce better information for water quality management. It was found that significance testing is the most popular method through which to produce information, yet assumptions and hypotheses are loosely explained and alternatives rarely explored to determine the validity and comparability of the results. Other data analysis methods that might be more appropriate for producing more comparable information were discussed, along with recommendations for further research and cooperative efforts to establish water quality data analysis protocols for producing information for management.
Open Access
Synthetic and biosynthetic studies of the brevianamides
(Colorado State University. Libraries, 2000) Halligan, Kathleen Marie, author; Williams, Robert M., advisor
The preparation of a pinacol-type rearrangement precursor towards the total synthesis of target indoxyl 8 is presented. The route contains three key steps. These include a photooxidation reaction that installs a hydroxy group in the required stereospecific position, a pinacol-type rearrangement to provide the indoxyl core structure and a Strecker reaction to extend the carbon chain to the aminonitrile derivative. Though several other routes to hydroxyindolenines were pursued, this particular pathway shows the most promise for the completion of indoxyl 8 since the crucial pinacol rearrangement was successful. This route is also amenable to 13C-labeled synthesis of indoxyl 8 and azadiene 29. The biomimetic synthesis of brevianamide B is described. Brevianamide B and epibrevianamide A were synthesized from deoxybrevianamide E in six steps. A Diels-Alder precursor was formed via oxidation of the diketopiperazine moiety and praline ring followed by rearrangement to the azadiene. A [4 + 2] cycloaddition reaction took place to provide two hexacyclic adducts. Oxidation at the 3-position of the indole supplied the hydroxyindolenines. A pinacol-type rearrangement of the respective hydroxy derivatives furnished brevianamide B and epibrevianamide A.
Open Access
Determination of optimum storage conditions for orthodox seeds
(Colorado State University. Libraries, 2000) Fang, Jian, author; Moore, Frank D., III, advisor; Roos, Eric E., advisor
To view the abstract, please see the full text of the document.
Open Access
Gloss: an incomplete glossary
(Colorado State University. Libraries, 2000) Lindsten, Scott, author; Gravdahl, John, advisor; Lundberg, Thomas R., committee member; Reid, Louann, committee member; Kwiatkowski, Ronald W., committee member
Artmaking at the end of the twentieth century became engulfed by theory. In the wake of such movements as poststructuralism, deconstructionism, and postmodernism, came a reexamination of aesthetics which incorporated an ever-broadening intellectual discourse. Many of these theories have their conception in the realm of linguistics, and language itself begins to exert its ascendency on other fields of study-indeed, on reality itself. This written accompaniment to my thesis art exhibit examines the complex, sometimes oppressive, sometimes sublime, nature of words and language and their effects on my approach to art.
Open Access
A synthesis of reinforcement learning and robust control theory
(Colorado State University. Libraries, 2000) Kretchmar, R. Matthew, author; Anderson, Charles, advisor; Howe, Adele E., committee member; Whitley, L. Darrell, committee member; Young, Peter M., committee member; Hittle, Douglas C., committee member
The pursuit of control algorithms with improved performance drives the entire control research community as well as large parts of the mathematics, engineering, and artificial intelligence research communities. A fundamental limitation on achieving control performance is the conflicting requirement of maintaining system stability. In general, the more aggressive is the controller, the better the control performance but also the closer to system instability. Robust control is a collection of theories, techniques, the tools that form one of the leading edge approaches to control. Most controllers are designed not on the physical plant to be controlled, but on a mathematical model of the plant; hence, these controllers often do not perform well on the physical plant and are sometimes unstable. Robust control overcomes this problem by adding uncertainty to the mathematical model. The result is a more general, less aggressive controller which performs well on the both the model and the physical plant. However, the robust control method also sacrifices some control performance in order to achieve its guarantees of stability. Reinforcement learning based neural networks offer some distinct advantages for improving control performance. Their nonlinearity enables the neural network to implement a wider range of control functions, and their adaptability permits them to improve control performance via on-line, trial-and-error learning. However, neuro-control is typically plagued by a lack of stability guarantees. Even momentary instability cannot be tolerated in most physical plants, and thus, the threat of instability prohibits the application of neuro-control in many situations. In this dissertation, we develop a stable neuro-control scheme by synthesizing the two fields of reinforcement learning and robust control theory. We provide a learning system with many of the advantages of neuro-control. Using functional uncertainty to represent the nonlinear and time-varying components of the neuro networks, we apply the robust control techniques to guarantee the stability of our neuro-controller. Our scheme provides stable control not only for a specific fixed-weight, neural network, but also for a neuro-controller in which the weights are changing during learning. Furthermore, we apply our stable neuro-controller to several control tasks to demonstrate that the theoretical stability guarantee is readily applicable to real-life control situations. We also discuss several problems we encounter and identify potential avenues of future research.
Open Access
The role of organic matter and other soil properties in Zn2+ activity and AB-DTPA-extractable Zn in soils
(Colorado State University. Libraries, 2000) Catlett, Kathryn M., author; Lindsay, Willard Lyman, 1926-, advisor; Heil, Dean, advisor; Sutton, Sally J., committee member; Barbarick, K. A., committee member; Ebinger, Michael, committee member; Soltanpour, P. N. (Parviz Neil), 1937-, committee member
Zinc is a plant micronutrient as well as a potential heavy metal contaminant in soils. In soil solution, the free Zn activity determines the availability of Zn as a micronutrient and its characteristics as a heavy metal contaminant. A better understanding of the mechanism that controls free Zn activity could improve soil treatments of Zn deficiency or toxicity. In this study, Zn2+ activity (measured by chelation) was related to soil properties for 18 alkaline soils from three farms in eastern Colorado. Organic carbon and pH were statistically significant parameters in a regression with log Zn2+ activity. Principal component analysis and path analysis were studied and applied to these soils. Results of principal component analysis showed that the first principal component, summing clay and total soil Zn and subtracting soil carbon, accounted for 52% of the variability in the soils. Soil pH and inorganic carbon dominated the second principal component, which accounted for 32% of the variability. Results of path analysis showed that direct effects of pH, total soil Zn, and organic carbon are important in predicting free Zn activity in these soils. Indirect effects of clay through organic carbon, of inorganic carbon through pH, and between pH and organic carbon were also important. Results from statistical analyses indicate that adsorption of Zn on organic matter may control Zn solubility in soils. To further explore this potential mechanism, Zn adsorption to organic matter was modeled using the chemical equilibrium model, MINTEQA2, and model results were compared to experimental data from the three Colorado farms. Experimental and model results were in close agreement. Adsorption onto organic matter may control Zn solubility in acidic to neutral soils, while precipitation may control Zn in alkaline soils. The AB-DTPA soil test can also be used as a measure of the availability of micronutrients to plants. AB-DTPA-extractable Zn was measured and correlated to soil chemical properties for soil samples described above. Soil organic carbon and total soil Zn were statistically significant parameters in a linear regression with AB-DTPA extractable Zn. Organic matter and clay contents were positively correlated with AB-DTPA-extractable Zn.
Open Access
Culturally specific information in water and river corridor management: the Wind River Indian Reservation, Wyoming
(Colorado State University. Libraries, 2000) Flanagan, Cathleen M., author; Laituri, Melinda Jean, advisor; Smith, Freeman M. (Freeman Minson), 1939-, committee member; Galvin, Kathleen A., 1949-, committee member
Knowledge is based on a set of assumptions about reality and the world that is dictated by environment, tradition and religion (Sterling, 1990). Indigenous people and their culturally specific knowledge associated with local ecosystems are being credited with bio-diversity protection around the world. As a result, environmental managers are acknowledging the long-range environmental benefits of indigenous approaches for managing natural resources. This recognition has catalyzed the inclusion of indigenous people in the development of sustainable resource management solutions, affording them a voice in nature conservation and resource management agendas in areas around the world. However, in the United States, Native Americans' cultural and ecological knowledge of local ecosystems has been overlooked in making resource management decisions. Although current research has explored the value and protection of indigenous knowledge, little effort has been focused on developing ways to integrate indigenous ecological knowledge with Euro-American scientific knowledge to obtain sustainable solutions to resource dilemmas. This thesis concentrated on developing a conceptual model of Shoshone and Arapaho indigenous ecological knowledge associated with water and the riparian corridor. The research has shown that elements of the Shoshone and Arapaho indigenous knowledge systems that were incorporated in Tribal water law are not reflected in Wyoming water laws. The methodology applied in this thesis was developed into a procedural outline to determine whether indigenous ecological and cultural knowledge has been equitably integrated into Euro-American water management schemes. This procedure may provide a concrete outline for applying these techniques to varying resource management questions within different indigenous cultures. The research shows that indigenous ecological knowledge and management practice associated with river corridor areas are related to the culturally significant perceptions and uses of biological and natural resources of the localized ecosystem.
Open Access
Pressure flow effects on scour at bridges
(Colorado State University. Libraries, 2000) Robeson, Michael D., author; Thornton, Christopher I., advisor; Abt, Steven R., committee member; Arneson, Larry A., committee member; Doe, William W., committee member
Scour caused by the occurrence of pressure flow requires a comprehensive understanding. Pressure flow can be defined as flow in which the low chord of a bridge becomes inundated and the flow through the bridge opening transitions from free surface flow to a pressurized condition, leading to a submerged or partially submerged bridge deck condition. A pressure flow condition often occurs at a bridge during a flood, potentially leading to bridge failure. Scour of bridge foundations (piers and abutments) represents the largest single cause of bridge failure in the United States (ASCE, 1999). Methodical scour research began in 1949 with the research of E.M. Laursen. Unfortunately, the application of scour research to the design of bridges did not occur until several bridges failed due to local scour. Over the years, bridge scour research has focused on the study of free surface flow. During the past decade, research related to pressure flow scour has become increasingly important. A testing program was developed and performed at the Hydraulics Laboratory of Colorado State University to examine pressure flow effects on scour at and around bridges. Flume experiments were conducted incorporating a physical model of a generic bridge with supporting abutments constructed at an approximate scale of 8:1. In an effort to simulate varying magnitudes of a pressure flow condition, the model was constructed in a manner that permitted the bridge deck to be lowered into the flow. By lowering the bridge deck and holding the level of the approach flow constant, multiple levels of deck submergence could be examined. Six vertical bridge positions, three discharges, two abutment widths and two sediment sizes were incorporated into a matrix comprising 69 tests. Data collected included hydraulic parameters and topographic surveys. Analysis of data collected during the study resulted in the formulation of a set of multivariate linear regression equations enabling the user to estimate abutment, local and deck scour depths during a pressure flow condition. Results of a dimensional analysis indicate that the dominant variables in predicting scour depths for a pressure flow condition include; the critical velocity of a given sediment size, the average velocity under the bridge deck, the height of the bridge deck above the initial and final bed surface, the depth of flow upstream of the bridge and the Froude number of the approach flow. Coefficients of determination for the developed equations ranged from 0.82 to 0.95.
Open Access
An integrated method for improving testing effectiveness and efficiency
(Colorado State University. Libraries, 2000) Stringfellow, Catherine V., author; Von Mayrhauser, Anneliese, advisor; Bieman, James M., committee member; Zimmerman, Donald E., committee member; France, Robert B., committee member
The aim of testing is to find errors and to find them as early as possible. Specifically, system testing should uncover more errors before release to reduce the number of errors found in post-release. System testing should also prevent the release of the products that would result in discovery of many post-release errors. Studies indicate that post-release errors cost more to fix than errors found earlier in the life cycle. The effectiveness and efficiency of system testing depends on many factors, not only the expertise and quality of the tester and the techniques they employ. This dissertation develops and integrated method using various techniques that will improve testing effectiveness and efficiency. Some of these techniques already exist, but are applied in a new or different way. The integrated method enables root cause analysis of post-release problems by tracing these problems to one or more factors that influence system testing efficiency. Development defect data help to identify which parts of the software should be tested more intensely and earlier because they were fault-prone in development. Based on assessment results, testers can develop testing guidelines to make system test more effective. A case study applies this evaluation instrument to existing project data from large software product (medical record system). Successive releases of the software product validate the method. During system testing, testers may need to determine quantitatively whether to continue testing or to stop, recommending release. Early stopping could decrease the cost of testing, but has the disadvantage of possibly missing problems that would have been detected, had system testing continued. Testers need to evaluate the efficiency of currently used methods and to improve the efficiency of future testing efforts. This dissertation develops empirical techniques to determine stopping points during testing. It proposed a new selection method for software reliability growth model(s) that can be used to make release decision. The case study compares and evaluates these techniques on actual test result data from industry. Quality assessment of multiple releases of the same product forms the basis of longitudinal decisions, such as re-engineering. Techniques using data from prior releases help to identify parts of the system that are consistently problematic. This information aids in developing additional testing guidelines for future releases of the product. This dissertation adds to a study that adapted a reverse architecting technique to identify fault relationships among system components based on whether they are involved in the same defect fix. The case study applies this technique to identify those parts of the software that need to be tested more. Results of the case study demonstrate that the integrated method can improve the effectiveness and efficiency of system test. The method identified problematic software components using data from prior releases and development. Results of prioritizing show that fault-prone components tested earlier reveal more defects earlier. Development should, therefore, have more time to fix these defects before release. The method was also able to estimate remaining defect content. The estimates were used to make release decisions. Based on data from post-release and interviews with the test manager, the method recommended the right release decisions.
Open Access
The assimilation and elimination of cesium by freshwater invertebrates
(Colorado State University. Libraries, 2000) Tostowaryk, Tracy M., author; Whicker, F. Ward, advisor; Rowan, David, advisor; Clements, W. H. (William H.), committee member; Hinton, Tom, committee member
Freshwater invertebrates are important vectors of radioactive cesium 134Cs and 137CS) in aquatic food webs, yet little is known about their cesium uptake and loss kinetics. This study provides a detailed investigation of cesium assimilation and elimination by freshwater invertebrates. Using five common freshwater invertebrates (Gammarus lacustris, Anisoptera sp. nymphs, Claassenia sabulosa and Megarcys signata nymphs, and Orconetes sp.), a variety of food types (oligochaete worms, mayfly nymphs and algae) and six temperature treatments (3.5 to 30°C), the following hypotheses were tested: 1) cesium elimination rates are a positive function of water temperature; 2) cesium elimination rates increase with decreasing body size; 3) assimilation efficiencies range between 0.6 and 0.8 for diet items low in clay. Cesium loss exhibited first order, non-linear kinetics, best described by a two component exponential model. Cesium assimilation efficiencies were higher for invertebrates fed oligochaetes (0.77) and algae (0.80) than those fed mayfly nymphs (0.20). Cesium elimination rate constants ranged from 0.002 to 0.125 d-1 across taxa and temperatures. Within each taxon, linear regressions of the natural logarithm of cesium elimination rate constants on temperature yielded positive, significant relationships. As temperature coefficients were not significantly different across taxa, the data were combined into a general model of cesium elimination by freshwater invertebrates as a function of temperature, body size and a categorical variable for thermal optima (warmwater and cool-water adapted taxa). Cesium elimination rate constants were found to increase with temperature, decrease with body size, and be much lower for warmwater adapted invertebrates than cool-water adapted invertebrates. Both the cesium assimilation efficiencies and general model of cesium elimination rate constants for freshwater invertebrates are in excellent agreement with those for fish. Quantification of cesium assimilation efficiencies and elimination rate constants for freshwater invertebrates allows, for the first time, development of dynamic aquatic food web models for .risk assessments, and it enables the in situ quantification of invertebrate feeding rates and other bioenergetic parameters.
Open Access
The development of the Fort Collins Mormon community during the twentieth century
(Colorado State University. Libraries, 2000) McGehee, Linda C., author; Leyendecker, Liston E., advisor; Hansen, James E., 1938-, committee member; Boyd, James W. (James Waldemar), 1934-, committee member; Fiege, Mark T., committee member
Separated by the formidable Rocky Mountains from Brigham Young's Utah stronghold, the northern Colorado town of Fort Collins was not numbered among the western settlements founded by members of the Church of Jesus Christ of Latter-day Saints. Nevertheless, followers of this sect would be drawn to Fort Collins in ever-increasing numbers. Early Mormons in the town lacked the well-established religious traditions of their Utah counterparts and struggled to define their group identity. Later, the growth of the L.D.S. congregation paralleled the increase in Fort Collins population, as the rapid expansion of Colorado State University attracted large numbers of Latter-day Saint students and faculty after the second world war. The Fort Collins Mormons gathered often for religious and social activities. They gradually formed a community that fit the definition given by Thomas Bender, who describes "community" as a deeply meaningful social network, bound together by close emotional ties, solidarity and communion with other members of the group. Fort Collins Latter-day Saints found a sense of connection through three major influences: shared religious beliefs, development of strong emotional ties, and organizational structure provided by the church headquarters in Salt Lake City. Utilizing primary source material from church records, local newspapers and personal interviews, this thesis traces the history of the Latter-day Saints in Fort Collins, examining ways in which church members created a close-knit, identifiable Mormon community in this northern Colorado city.
Open Access
Exploring my art
(Colorado State University. Libraries, 2001) Jendlin, D. Sean, author; Sullivan, Patrice M., advisor; Coronel, Patricia D., committee member; Williams, Ron G., committee member; Yust, Dave, 1939-, committee member
This thesis is an interpretation of a Tarot spread used as a tool to investigate my relationship to my art. My thesis paintings interface only with the ideas found in a specific number of Tarot cards. My thesis Paper concentrates on the functionality and depth present in Tarot as both a source for my work and the results of a divination about my work. Through this experience I have learned a process of painting which investigates and explores the human experience.
Open Access
Development, characterization and application of a high average power capillary discharge soft x-ray laser
(Colorado State University. Libraries, 2001) Benware, Brady Robert, author; Rocca, Jorge, advisor
A compact high repetition rate, high average power capillary discharge laser operating at a wavelength of 46.9 nm that is of the size of many widely utilized visible and UV lasers has been developed and characterized. Two significant differences from previously developed capillary discharge soft x-rays lasers, the use of ceramic capillaries rather than poly-acetal and significantly longer plasma columns of up to 36 cm, allowed for the generation of greatly increased output pulse energies and average power. Lasing at a repetition rate of 4 Hz and an average laser pulse energy of 0.88 mJ has been obtained, which amounts to an average power of 3.5 mW. Lasing at repetition rates as high as 10 Hz was also achieved, but with lower output pulse energy. In this work the beam energy and divergence were measured as a function of capillary length, and the temporal evolution of the laser pulse was also studied. The combined high pulse energy and high repetition rate of this laser make it unique in the field of soft x-ray lasers to date. This laser has been used to perform angular dependent reflectivity measurements to determine optical constants of materials at 46.9 nm, which are in good agreement with those previously measured, or in some cases represent the first recorded values at this wavelength. This experiment constitutes the first application of a table-top soft x-ray laser to the field of material characterization. In a separate experiment, the output beam was polarized using two multi-layer coated mirrors that were configured for optimum reflectivity at 45 degrees. The resulting 96% polarized beam was then used to characterize the efficiency of a diffraction grating. Finally, in a third experiment, the beam was focused using a spherical multi-layer coated mirror to a spot size where the majority of the energy was confined to a 2 μm diameter. The peak intensity was estimated to be 1x1011 W/cm2. Through ray tracing computations, the focused spot size was determined to be dominated by spherical aberration. This focused beam reached intensities that were sufficient to induce ablation on brass and stainless steel targets realizing the first demonstration of material ablation with a coherent soft x-ray beam.
Open Access
Salinity tolerance and associated salinity tolerance mechanisms of four turfgrasses
(Colorado State University. Libraries, 2001) Alshammary, Saad Farhan, author; Qian, Yaling, advisor; Wallner, Stephen J., advisor; Brick, Mark A., committee member; Stushnoff, Cecil, committee member
The need for salinity tolerant turfgrasses is increasing because of the increased use of effluent or other low quality water for turfgrass irrigation. Greenhouse container and hydroponic experiments were conducted to determine the relative salinity tolerance, growth characteristics, and physiological responses (especially water and ion relations) of 'Challenger' Kentucky bluegrass (Poa pratensis L.) (KBG), 'Arid' tall fescue (Festuca arundinacea Schreb) (TF), 'Fults' alkaligrass (Puccinellia distans (L.) Parl.) (AG), and saltgrass (Distichlis spicata (Torr.) Beetle) (SG). Salinity treatments were applied for 8 weeks using 1NaCl:1CaCl2 solution at 2.0, 4.7, 9.4, 14.1, 18.8, and 23.5 dS/m. Based on data on shoot dry mass, KBG, TF, AG, and SG experienced a 50% shoot growth reduction at 5.5, 14.2, 23.0, and 34.5 dS/m, respectively, suggesting the ranking of salinity tolerance was SG > AG > TF > KBG. Leaf firing of KBG, TF, and AG increased as salinity increased, but no injury was noticeable in SG. Salinity caused root cortex cells to collapse in KBG at 14.1 dS/m and in TF at 23 .5 dS/m. Alkaligrass and SG only had a few cell collapses even at 23.5 dS/m. Osmotic adjustment (OA) occurred in all species under salinity stress. However, in KBG and TF, the contribution of Na+ and Cl- to OA increased and became the major contributors at high levels of salinity, whereas Na+ and Cl- contributions to OA in SG were maintained at stable levels as salinity increased from 4.7 to 23 .5 dS/m. As salinity increased, the contribution of unidentified osmolytes to OA increased in SG and decreased in KBG and TF. The proportion of K+ to OA in AG and TF was lower than SG but higher than KBG. The ability to maintain a K+/Na+ ratio close to or above 1 appeared to be important for these grasses to tolerate high salinity. Saltgrass, AG, TF, and KBG could maintain a shoot K+/Na+ ratio of 1 when salinity levels were less than 22.3, 13.6, 7.4, and 3.7 dS/m, respectively. Salt glands present in SG, root growth stimulation of SG and AG, maintenance of high root to shoot ratio in TF, synthesis of compatible solutes, regulation of ion concentrations, and maintenance of high K+/Na+ ratio in shoots are important salinity tolerance mechanisms among these grasses.
Open Access
Chromosome races and polypoid cytoforms in Distichlis spicata
(Colorado State University. Libraries, 2001) Reid, Scott D., author; Hughes, Harrison G., advisor; Koski, Anthony, advisor
Saltgrass (Distichlis spicata [L.] Greene) is a salt-tolerant C4 grass native to the Americas that is currently being evaluated for use as a turfgrass species. Saltgrass has a highly variable morphology in different regional occurrences, and this has led some botanists to consider it as two species or as comprising several botanical varieties over its wide distribution in the U.S. west of the Mississippi River and along coastal regions. Chromosome numbers of 160 saltgrass accessions, primarily from nine western states, were determined. A 38-chromosome saltgrass race with distributions separate from the previously known 40-chromosome type has been identified. Both races are fertile and hybridize readily. The distribution pattern and the cytological behavior of hybrids between the races suggest they are adaptively different. No aneuploidy in the 38-chromosome race has been found, and no deficient aneuploids have been found in the 40-chromosome race. Meiotic irregularities in the 40-chromosome race suggest a pathway for the evolution of the 38-chromosome race, dependant on hypothesized genetic changes that allow fitness in individuals lacking the pair of homologues defining the difference between the races. More research is needed to evaluate broad but varied morphological differences between the races. The consequences of intermating the two cytoraces in breeding efforts are unknown, but karyotypic instability may result in some cases. An octaploid saltgrass cytotype, previously considered rare, has been found to occur more commonly, distributed among both of the cytoraces. One accession, believed to be a 6x cytotype, represents a ploidy level previously undescribed in saltgrass. Screening to identify individuals of different ploidy levels among collections made for the turfgrass breeding program is advisable. Aneuploidy and multivalent associations in meiosis suggest the higher-order polyploid cytoforms may reproduce with less efficiency sexually, but this has not been adequately studied. Two ca. 74-chromosome accessions showed high estimated pollen viability. B chromosomes are reported for the first time in saltgrass, occurring in some individuals of all three cytotypes.