Matching Items (70)
Description
It is well known that deficiencies in key chemical elements (such as phosphorus, P) can reduce animal growth; however, recent empirical data have shown that high levels of dietary nutrients can also reduce animal growth. In ecological stoichiometry, this phenomenon is known as the "stoichiometric knife edge," but its underlying mechanisms are not well-known. Previous work has suggested that the crustacean zooplankter Daphnia reduces its feeding rates on phosphorus-rich food, causing low growth due to insufficient C (energy) intake. To test for this mechanism, feeding rates of Daphnia magna on algae (Scenedesmus acutus) differing in C:P ratio (P content) were determined. Overall, there was a significant difference among all treatments for feeding rate (p < 0.05) with generally higher feeding rates on P-rich algae. These data indicate that both high and low food C:P ratio do affect Daphnia feeding rate but are in contradiction with previous work that showed that P-rich food led to strong reductions in feeding rate. Additional experiments are needed to gain further insights.
ContributorsSchimpp, Sarah Ann (Author) / Elser, James (Thesis director) / Neuer, Susanne (Committee member) / Peace, Angela (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor) / School of Sustainability (Contributor)
Created2014-05
Description
Large quantities of sodic and alkaline bauxite residue are produced globally as a by-product from alumina refineries. Ecological stoichiometry of key elements [nitrogen (N) and phosphorus (P)] plays a critical role in establishing vegetation cover in bauxite residue sand (BRS). Here we examined how changes in soil chemical properties over time in rehabilitated sodic and alkaline BRS affected leaf N to P stoichiometry of native species used for rehabilitation. Both Ca and soil pH influenced the shifts in leaf N:P ratios of the study species as supported by consistently significant positive relationships (P < 0.001) between these soil indices and leaf N:P ratios. Shifts from N to P limitation were evident for N-fixing species, while N limitation was consistently experienced by non-N-fixing plant species. In older rehabilitated BRS embankments, soil and plant indices (Ca, Na, pH, EC, ESP and leaf N:P ratios) tended to align with those of the natural ecosystem, suggesting improved rehabilitation performance. These findings highlight that leaf N:P stoichiometry can effectively provide a meaningful assessment on understanding nutrient limitation and productivity of native species used for vegetating highly sodic and alkaline BRS, and is a crucial indicator for assessing ecological rehabilitation performance.
ContributorsGoloran, Johnvie B. (Author) / Chen, Chengrong (Author) / Phillips, Ian R. (Author) / Elser, James (Author) / College of Liberal Arts and Sciences (Contributor) / School of Life Sciences (Contributor)
Created2015-10-07
Description
Suicide is one of the leading causes of death worldwide and statistical analysis of suicide by profession reveals that physicians and veterinarians experience abnormally high suicide rates. This paper seeks to provide a comprehensive literature review over what some general theories of suicide are, why these professions exhibit high suicide rates, what assistance is currently being provided, and where do these assistance efforts succeed or fail. Moreover, this paper addresses what advancements may be made within these fields to further combat suicide in physicians and veterinarians. To achieve this, general theories behind suicide, risk factors unique to or heavily prevalent in these professions, and current assistance efforts are read, organized, and summarized.<br/><br/>A summary of these risk factors includes stress and mental health disorders accumulated through school and work, personal and professional isolation, access to lethal substances, suicide contagion, exposure to euthanasia, and the role of perfectionism. There are several assistance efforts in place with the most successful ones being highly personalized, but many are still underutilized. Moreover, the stigma of suicide pervades these professions and is addressed by several researchers as something to combat or prevent. Going forward, it is hopeful that not only will more assistance efforts will be created and provided for physicians and veterinarians suffering from suicidal tendencies, but efforts to reduce the stigma of suicide be implemented and utilized as soon as possible.
ContributorsSinclair, Andrew (Author) / DeNardo, Dale (Thesis director) / Sterner, Beckett (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
Color changes are observed across a wide range of taxa and can provide a variety of functions, such as communication, thermoregulation, and camouflage. One type of color change observed in various species is pattern change, occurring notably during development as ontogenetic pattern change. Ontogenetic pattern change may continue throughout maturation to align with changing morphology and behavior as the organism ages. We studied the ontogenetic pattern change in Gila monsters, because they are easily maintained in captivity, and undergo ontogenetic change. For this thesis, we examined (1) the relative change in the presence and distribution of the two contrasting skin colors over time, as well as (2) the importance of growth vs. age in the timing of pattern change in Gila monsters. Using FIJI and R Studio software to analyze the data/pictures, the data suggested that neonate Gila monsters start with a high standard deviation in their light spots, and experience pattern breakup (increasing their light/dark spot count), whilst maintaining similar proportions of dark/light areas as they develop. We also found that age is the main driver of ontogenetic change in Gila monsters across 60 weeks, not growth.
ContributorsNarisawa, Ryosuke (Author) / DeNardo, Dale (Thesis director) / Dollion, Alexis (Committee member) / Barrett, The Honors College (Contributor) / College of Health Solutions (Contributor)
Created2023-05
Description
It is the intent of this research to determine the feasibility of utilizing industrial byproducts in cementitious systems in lieu of Portland Cement to reduce global CO2 emissions. Class C and Class F Fly Ash (CFA and FFA, respectively) derived from industrial coal combustion were selected as the replacement materials for this study. Sodium sulfate and calcium oxide were used as activators. In Part 1 of this study, focus was placed on high volume replacement of OPC using sodium sulfate as the activator. Despite improvements in heat generation for both CFA and FFA systems in the presence of sulfate, sodium sulfate was found to have adverse effects on the compressive strength of CFA mortars. In the CFA mixes, strength improved significantly with sulfate addition, but began to decrease in strength around 14 days due to expansive ettringite formation. Conversely, the addition of sulfate led to improved strength for FFA mixes such that the 28 day strength was comparable to that of the CFA mixes with no observable strength loss. Maximum compressive strengths achieved for the high volume replacement mixes was around 40 MPa, which is considerably lower than the baseline OPC mix used for comparison. In Part 2 of the study, temperature dependency and calcium oxide addition were studied for sodium sulfate activated systems composed of 100% Class F fly ash. In the presence of sulfate, added calcium increased reactivity and compressive strength at early ages, particularly at elevated temperatures. It is believed that sulfate and calcium react with alumina from fly ash to form ettringite, while heat overcomes the activation energy barrier of fly ash. The greatest strengths were obtained for mixes containing the maximum allowed quantity of calcium oxide (5%) and sodium sulfate (3%), and were around 12 MPa. This is a very low compressive strength relative to OPC and would therefore be an inadequate substitute for OPC needs.
ContributorsTweedley, Shannon Elizabeth (Author) / Neithalath, Narayanan (Thesis director) / Mamlouk, Michael (Committee member) / Civil, Environmental and Sustainable Engineering Programs (Contributor) / Barrett, The Honors College (Contributor) / School of Sustainable Engineering and the Built Environment (Contributor)
Created2014-05
Description
Attitudes toward animal welfare have been evolving in our society as we have developed from early agricultural roots to an increasingly urban and technologically advanced community. However, despite the growing societal appreciation and care for animals in our homes and backyards, veterinarians are still faced with cases of abuse and neglect. Although it may seem obvious for veterinarians, as animal welfare advocates, to confront this dilemma each time they are faced with it, that is not always the case. In order to assess the responsibilities of veterinarians in regard to neglect and abuse, an extensive literature review and analysis was performed and practicing veterinarians were interviewed to determine their attitudes regarding the responsibility to report suspected cases of animal neglect and abuse. Specifically, these interviews focused on such topics as the educational background of the practitioners, how empathy impacts their perception of animal welfare, their relationship with law enforcement agencies, and related questions. The study demonstrated that the most prominent factor in a veterinarian's understanding of violations of animal welfare stems from their educational background. Therefore, it is recommended that veterinary medicine programs alter their curricula to emphasize animal welfare training and the obligation of veterinarians to report suspected cases of neglect and abuse.
ContributorsMichael, Allison Therese (Author) / Minteer, Ben (Thesis director) / Ellison, Karin (Committee member) / DeNardo, Dale (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor)
Created2013-12
Description
Many studies have shown that as the calcium carbonate precipitates, it sequesters phosphate. Although the geochemical interactions between phosphate and calcium carbonate are known, only a few studies have considered calcium carbonate deposition's effect on stream ecology. Further, those studies considering decomposition have produced conflicting results. In this study, nutrient-diffusing cups with organic substrata were used to determine the nutrient limitation of decomposers in the travertine streams in the Huachuca Mountains. After processing a subset of the experiments, only one site (in Huachuca Canyon) from the four study streams was significantly nutrient-limited (NP co-limitation).
ContributorsNevarez, Nicole Michelle (Author) / Elser, James (Thesis director) / Sabo, John (Committee member) / Corman, Jessica (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor)
Created2013-05
Description
There are numerous strategies for determining an organism's metabolic rate, one of which is the heart rate method. The heart rate method is based on a relationship between an organism's heart rate and its oxygen consumption (V(O2)). Although validations of the heart rate method have focused on adult animals, researchers could benefit from applying this method to embryonic animals. In this study, the heart rate's reliability as an indicator of oxygen consumption in early stage embryos of reptiles (or more specifically, lizards) is evaluated. The focus is primarily on the earliest stages of cardiovascular detection. The results suggest that while it may be possible to use a reliable heart rate method to find an accurate value for oxygen consumption of a group of early embryos in lizards if the oxygen pulse can be accurately identified, it is more likely that in the earliest stages of cardiovascular development, the heart rate cannot serve as a reliable indicator of V(O2) because it may not be the primary manner in which oxygen is distributed in Sceloporus undulatus.
ContributorsHambsch, Zakary Jordan (Author) / Angilletta, Michael (Thesis director) / DeNardo, Dale (Committee member) / Condon, Catriona (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor)
Created2013-05
Description
Objective: To explore the dimensions of the human animal bond and provide a community needs assessment to inform the community stake holders such as the Arizona Humane Society and Nina Mason Pulliam Charitable Trust Foundation how many animals are in need of veterinary services within the homeless population of Phoenix, Arizona. In addition to this, pets of the homeless individuals will be able to gain access to veterinary services for eight consecutive weeks. Background: Pets have an important impact on human mental, physical, social, and emotional health. It has been reported that about one third of the homeless population in Arizona has pets that are not able to gain access to veterinary care (Wang, 2015). Most homeless shelters will not allow people to access services with pets. As a consequence people will sleep out in the streets. Animals as Lifechangers and Lifesavers: Pets in the Redemption Narratives of Homeless People (Irvine, 2013) contains interviews of homeless people based on their life stories. A common theme among interviewees was that they felt they had a responsibility to their pets that served as a motivating purpose for giving up horrible personal habits because they had a sense of responsibility. Methods/Materials: Wandering Paws was launched in February 2015, but did not officially start as an eight-week study until March 2016. This pilot program serves the homeless populations' dogs and cats with veterinary care. The Arizona Humane Society was approached to acquire their services for this project including a veterinarian, a technician, and usage of their seventy-one foot mobile unit. Homeless individuals who wanted veterinary services were recruited and asked to fill out a twenty-three-question survey. Secondary data was procured from the Arizona Humane Society about the animal and services rendered for that pet. Results: Over the course of the first four weeks 22 surveys have been completed. 86% of the surveys completed indicate a strong bond between the owner and animal. The remaining 14% of the surveys completed indicate a weaker bond between the animal and owner. Conclusion/Implications: The research indicates a strong connection between most people and their animals. The veterinary services provided for the homeless population should be continued on a monthly basis as a wellness clinic in the future, as these services are in great demand.
ContributorsHowarth, Amber (Author) / DeNardo, Dale (Thesis director) / Thatcher, Craig (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Land management practices such as domestic animal grazing can alter plant communities via changes in soil structure and chemistry, species composition, and plant nutrient content. These changes can affect the abundance and quality of plants consumed by insect herbivores with consequent changes in population dynamics. These population changes can translate to massive crop damage and pest control costs. My dissertation focused on Oedaleus asiaticus, a dominant Asian locust, and had three main objectives. First, I identified morphological, physiological, and behavioral characteristics of the migratory ("brown") and non-migratory ("green") phenotypes. I found that brown morphs had longer wings, larger thoraxes and higher metabolic rates compared to green morphs, suggesting that developmental plasticity allows greater migratory capacity in the brown morph of this locust. Second, I tested the hypothesis of a causal link between livestock overgrazing and an increase in migratory swarms of O. asiaticus. Current paradigms generally assume that increased plant nitrogen (N) should enhance herbivore performance by relieving protein-limitation, increasing herbivorous insect populations. I showed, in contrast to this scenario, that host plant N-enrichment and high protein artificial diets decreased the size and viability of O. asiaticus. Plant N content was lowest and locust abundance highest in heavily livestock-grazed fields where soils were N-depleted, likely due to enhanced erosion and leaching. These results suggest that heavy livestock grazing promotes outbreaks of this locust by reducing plant protein content. Third, I tested for the influence of dietary imbalance, in conjunction with high population density, on migratory plasticity. While high population density has clearly been shown to induce the migratory morph in several locusts, the effect of diet has been unclear. I found that locusts reared at high population density and fed unfertilized plants (i.e. high quality plants for O. asiaticus) had the greatest migratory capacity, and maintained a high percent of brown locusts. These results did not support the hypothesis that poor-quality resources increased expression of migratory phenotypes. This highlights a need to develop new theoretical frameworks for predicting how environmental factors will regulate migratory plasticity in locusts and perhaps other insects.
ContributorsCease, Arianne (Author) / Harrison, Jon (Thesis advisor) / Elser, James (Thesis advisor) / DeNardo, Dale (Committee member) / Quinlan, Michael (Committee member) / Sabo, John (Committee member) / Arizona State University (Publisher)
Created2012