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Garden climate effects on endophyte abundance and morphology of Populus fremontii (Fremont cottonwoods) populations from across their temperature range
Get PDFPremise of the study: Fungal endophytes are symbionts that reside asymptomatically in plant tissues and have relationships that can range from mutualistic to parasitic. These fungi can have profound impacts on plant fitness, evolution, and communities as well as on the structure of the broader phytosphere community. It is known that biotic and abiotic factors affect the endophyte community and abundance; however, few studies have looked at the effect of source population and site simultaneously. We investigated three main questions: (1) Is endophyte abundance in Populus fremontii (Fremont cottonwood) affected by population source climate, garden climate, and their interaction? (2) Are quantitative tree traits linked to endophyte abundance? (3) Do population source climate, garden climate, and their interaction have an effect on quantitative tree traits in P. fremontii? We also present preliminary data on endophyte community composition across the three gardens.Methods: Endophytes were isolated from twigs of replicated P. fremontii populations in three common gardens across an elevational and temperature gradient and characterized with DNA sequencing. Twig length and diameter and leaf mass were also quantified.
Key results:1) Fungal endophyte abundance varied by garden climate and population source climate, but there was no significant population by garden interaction. Garden climate had the greatest effect with cottonwoods from all source populations showing dramatically reduced endophyte abundance in the coldest garden. Interestingly, cottonwoods from the coldest
populations had the highest endophyte abundance in all three gardens. 2) Shoot length and dried leaf mass were associated with endophyte abundance in Fremont cottonwoods while twig diameter was not. 3) Twig diameter was only affected by population source climate; however, shoot length and dried leaf mass were significantly affected by population source climate, garden climate, and their interaction. 4) The Warm and Hot gardens were dominated by endophytes of the genus Alternaria, while the Cold garden was dominated by members of the genus Valsa. Conclusions: These results suggest that even a modest change in temperature can greatly influence fungal endophyte abundance and host plant morphology; however, endophyte abundance and the plant traits we measured were not tightly linked and in the opposite direction of our prediction. Given that climate change is affecting temperatures across the globe, the relationship between host plant and endophyte abundance and community may be crucial to conservation efforts for foundation species, but difficult to predict from plant traits.
Key words: Endophyte, class III endophyte, Fremont cottonwood, abundance, climate, plant response
Weaving the way: developmental education in three Southwestern tribally controlled colleges
No full textAccording to American Indian Higher Education Consortium (AIHEC) data, 13.8% of American Indians 25 years and older have a bachelor’s degree. The single most important barrier to student success remains preparation (Adelman, 2006). Underprepared students are disproportionately students of color, students of low socioeconomic status, and students who would be the first in their family to attend college (Sparks and Malkus, 2013). Unfortunately, students who matriculate with limited educational, social, and economic resources disproportionately leave college without earning a degree or credential, limiting their abilities to achieve their goals for school and work (Adelman, Daniel and Berkovits, 2003). In the National Education Longitudinal Study (NELS) 2018 sample, less than one-quarter of community college students who enroll in remedial education complete a degree or certificate in eight years. Tribal Colleges and Universities (TCUs) play a dual role in their communities: education and perpetuation of tribal customs and culture. The growing number of Indigenous students testing into and taking remediation courses at TCUs has an enormous effect on their future opportunities in education, employment, politics, and society. The purpose of my study is to take an in-depth look at developmental education within three Tribal College and University settings in the southwestern United States – Tohono O’odham Community College (TOCC), Diné College (DC), and Navajo Technical University (NTU). While much research exists on developmental education in college, very little is known about developmental education specifically at TCUs—a gap in the literature that I address with this dissertation
Gene flow of common side-blotched lizards across the Colorado River in Arizona and Utah
No full textThe 1963 completion of the Glen Canyon Dam in Arizona profoundly changed the Colorado River and altered habitat for many species. It created a relatively constant flow rate, much colder temperatures, and eliminated slow moving, warm periods that had historically characterized this system and gave wildlife opportunities to cross the river at certain times of year. The common side-blotched lizard (Uta stansburiana) provides an excellent opportunity to examine the effects of linear water barriers created by impoundments such as Glen Canyon Dam on migration and gene flow in wildlife. To assess the impact of these changes on an ectothermic reptile, we collected tissue samples from 241 common side-blotched lizards at three cross-river study areas in Arizona and Utah and used eight microsatellite loci to estimate gene flow as a function of genetic diversity and structure. One study area (Cataract Canyon) has annual periods of warm temperatures and low flows that most resembled pre-dam conditions, whereas the other two study areas (Badger/Jackass and Tanner/Basalt) have cold water temperature year-round and no low-flow episodes. We found genetic differentiation between pairs of sampling sites on opposite sides of the river in two out of three study areas. Surprisingly the greatest cross-river gene flow was in one of the two below-dam study areas characterized by cold temperatures and no periods of low flow. We speculate that the lack of a significant rapid in this study area, or the presence of two pedestrian bridges ~27 km away, might facilitate cross-river movement in that study area. These results suggest that this small ectotherm can move across the post-dam Colorado River often enough to facilitate gene flow in under certain conditions, but the river presents a barrier to movement in most cases. Our study provides new genetic data for 241 common side-blotched lizards, a previously understudied species with minimal genetic information. These results provide a foundation for future studies on the effects of dams to animal movement and shed light on the genetic diversity and structure of the common side-blotched lizard in Arizona and Utah
Twisted and coiled polymer actuators: design, mechanics, and biomimetics
Get PDFIn the past few decades, interest in novel soft actuators that can mimic the compliant nature of biological muscles has grown fast. Such actuation technologies have the potential to improve current human-machine interactions in applications such as smart exoskeletons and prosthetics, wearables, intelligent surgical tools, and even humanoids. To this end, it was recently shown that inexpensive drawn polymer monofilaments, such as nylon fishing lines, can be used to create thermally driven linear or torsional soft actuators. These actuators are called twisted polymer actuators (TPAs), and their actuation mechanism relies on the anisotropic microstructure of the virgin material used for fabrication, specifically, the axial thermal contraction and radial thermal expansion. In the past few years, researchers have attempted to model the actuation response of TPAs; however, it has been shown that such actuation is moisture-content- and time-dependent (viscoelastic), which have limited the accuracy of actuation models for TPAs. Furthermore, the thermal activation of TPAs is generally an inefficient and time-consuming (particularly during cooling) driver.
This Ph.D. work first presents a literature review on soft actuators and a comparison to biological muscles, focusing on those properties that make biological muscles highly adaptable systems. This study helps better understand the current accomplishments of each soft actuation technology, the remaining challenges, and future directions that are required for soft actuation technologies to be used as successful muscle substitutes.
Next, a study on the hygroscopic behavior and moisture content effects of TPAs actuation performance is presented. This study found that TPAs made from drawn monofilaments of nylon 66 are hygroscopic and moisture-content-dependent. Moreover, the hygroscopic properties of TPAs are strongly affected by temperature changes, and temperature changes are required for actuation, which makes TPAs challenging to model and therefore control in environments with different relative humidity levels. As a result of the previously mentioned shortcomings of thermally activated twisted polymer actuators, therest of this Ph.D. work focuses on the conception, characterization, modeling, and initial optimization of a new soft actuation technology inspired by TPAs named cavatappi artificial muscles. Cavatappi artificial muscles use an actuation mechanism that relies upon specific processing of inexpensive polymer tubes to develop microstructural anisotropy, which mimics the anisotropic mechanical properties of the precursor monofilaments used to fabricate TPAs. These tubes can be configured as torsional actuators when twisted or linear actuators when helically coiled, similar to TPAs. After drawing and twisting, hydraulic or pneumatic pressure applied inside the tube results in localized untwisting of the helical microstructure. This untwisting manifests as a contraction of the helical pitch for the coiled configuration. Given the hydraulic or pneumatic activation source and the constant material temperature, these new devices have been shown to outperform TPAs with regard to actuation bandwidth, efficiency, modeling, and practical implementation. Since cavatappi can generate high forces and power, this technology could be used in bioengineering and robotics applications. Cavatappi show contractions greater than 50% of their initial length, mechanical contractile efficiencies of about 45%, and specific work and power metrics ten and five times higher than human skeletal muscles, respectively. Finally, this dissertation also presents an actuation model that uses the material properties of the precursor structure to predict the actuation response of cavatappi artificial muscles and validation using experimental actuation dat
Ethical behavior in the outdoors: the impact of COVID-19 on outdoor recreation
No full textDefining ethical behavior in the outdoors has been a growing point of discussion among people with an interest in outdoor recreation. With increased popularity of outdoor recreation over the past twenty years, those who regularly take part in recreational activities in the outdoors are questioning how people should behave when engaged in outdoor pursuits. The Outdoor community, includes a broad and diverse group of individuals who enjoy outdoor recreation, is engaged in attempts to construct a shared image of appropriate behavior to guide the larger community. In attempting to create a version of what “appropriate behavior” consists of in the outdoors, community members employ a variety of mechanisms to portray their form of outdoor recreation as encompassing ethical behavior. In this thesis, I use Mary Douglas’ framework of boundary creation and maintenance to consider three key areas of negotiating appropriate behavior in the outdoors. The first area is how community insiders work to separate insiders from outsiders by upholding an image of what an outdoor enthusiast looks like and defining the “other” who does not belong. Second, insiders engage in what Douglas refers to as a purification process, maintaining standards of wildness and purity as central to outdoor recreation and approaching the natural environment. Outdoor enthusiasts point to certain behaviors as unacceptable, even framing them as forms of defilement. Third, I explore how outdoor enthusiasts capitalized on the COVID-19 pandemic, using social media and news outlines, to demarcate ethical behavior in the outdoors and further define who belongs and who does not. COVID-19 In this research I explored how the COVID-19 Pandemic allowed for a clear example of how outdoor enthusiasts use different interpretations of behavior to create a set of rules and demonstrate what it means to be an outdoor person
Performance evaluation of cryptographic algorithms in software and with hardware implementation of specialized instructions for the RISC-V instruction set architecture
Get PDFThe ever-increasing need for securing computing systems using cryptographic algorithms is spurring interest in efficient implementation of common algorithms. While the algorithms can be implemented in software using the base instruction set of processors, there is considerable potential to reduce memory cost and improve speed using specialized instructions and associated hardware. However, there is a need to assess the relative benefits and costs of software implementations and new instructions that implement key cryptographic algorithms in fewer cycles. The primary aim of this thesis is to improve understanding of the cost of implementing cryptographic algorithms for the RISC-V instruction set architecture (ISA) for both implementations of the algorithms in software using the base RV32I instruction set and with implementation of instructions as hardware in additional functional units. RISC-V was designed a decade ago. Since then, the ISA has been improved and extended with new instruction sets, where the RISC-V cryptography instruction set extension is one of the upcoming instruction set extensions. This thesis provides hand-optimized RISC-V assembly language implementations of eleven cryptographic algorithms with and without the cryptography extension. For a cost-benefit analysis, a RISC-V processor with the cryptography extension is designed in hardware. Also, a new instruction is proposed to increase the implementation efficiency of the cryptography algorithms. The results show that software implementation requirements can change significantly according to algorithm and implementation method. Compared to implementations with only the base RV32I instruction set, implementations with the cryptography set extension provide 1.5X to 8.6X faster execution speed and 1.2X to 5.8X less program memory for five of the eleven algorithms
Arizona Chief Fire Officers' Opinions Regarding Firefighter Behavioral Health Problems: Causes and Help Approaches
No full textThis research study evaluated the opinions of Arizona chief fire officers regarding the causes and help approaches of firefighters’ behavioral health problems caused by post-traumatic stress secondary to the duties of being a first responder. These behavioral health problems include post-traumatic stress, anxiety, depression, substance abuse, and suicide. This research study utilized a modified research instrument called the Opinions Regarding Firefighter Behavioral Health Problems Questionnaire and online survey research to collect data. The researcher conducted a Spearman ρ test to determine if relationships exist between the questionnaire subscale scores and chief fire officers’ career factors which are based on their knowledge, motivational factors, and organizational factors including their fire department budget size, college degree earned, total years of fire department employment, and fire department firefighter roster size. Three significant relationships resulted from this study. First, there was a positive relationship between chief fire officers’ organic subscale scores and the career factor of their total years of fire department employment. The results indicated that as chief fire officers’ years of employment increases, the chief fire officers’ opinion of firefighter behavioral health problems intensifies into the organic psychological subscale. Second, there is a positive relationship between chief fire officers’ cognitive subscale scores and the career factor of their department roster size. The results indicated that as the chief fire officers’ fire department roster size increases, the chief fire officers’ opinion of firefighter behavioral health problems intensifies into the cognitive psychological subscale. Finally, there was a negative relationship between chief fire officers’ social/economic subscale scores and the career factor of their college degree. The results indicated as the chief fire officers’ level of college degree completion increases, the chief fire officers’ opinion of firefighter behavioral health problems decreases in the social/economic psychological subscale.
The researcher created the Lay Social Cognitive Attribution Theory Model to evaluate the process of opinion formation. Through the results of this research study, the fire service now has additional information to refer to regarding the influencing career factors and the Arizona chief fire officers’ opinions related to firefighter behavioral health problems
Adaptive control strategies for lower-limb exoskeletons to assist gait
Get PDFWalking is a critical mode of transportation during everyday life. As a result, gait impairments can greatly affect the quality of life and personal independence of those who are affected. About 15% of people in the world have some type of physical disability, and that population is increasing rapidly. One type of disability that refers to a group of conditions that affect movement control is Cerebral Palsy (CP). Exoskeletons may help patients with CP extend their lower limb joints during walking by providing assistance and helping them walk more efficiently. Alternatively, the strategy of this assistance may vary depending on the type and severity of crouch gait. In this dissertation, we worked on four different adaptive control strategies for lower-limb exoskeletons capable of providing assistance during walking on different terrains for unimpaired individuals and individuals with CP. In the first chapter of this doctoral dissertation, we describe an adaptive control strategy development of a light-weight ankle exoskeleton based on the biomechanics of walking and how the ankle plantarflexion assistance provided based on this strategy improved the walking performance of unimpaired individuals and individuals with CP. The second chapter describes the development of a user-adaptive control strategy of a light-weight hip exoskeleton. Then the assistance provided by this control strategy is evaluated on unimpaired individuals during level and incline treadmill, as well as one individual with CP walking during level treadmill walking. In chapter three, we describe the development of a synergic ankle-knee control strategy of a lightweight unilateral ankle-knee exoskeleton based on the biomechanics of walking and validation of this control strategy on an unimpaired individual. The fourth chapter describes a bioinspired ankle joint torque simulation method based on the Winding Filament Muscle model with the potential to control the ankle joint of commercialized exoskeletons. A conclusion of these four control strategies is provided in the final chapter of this doctoral dissertation
Fungal Endophyte Communities are Similar in Composition but have Different Effects on a Native and an Invasive Plant Species
Get PDFRoot associated fungi are highly diverse and have important ecological functions, yet most studies focus on mycorrhizal or pathogenic fungi. The more poorly understood root endophytes and a sub class of these fungi, the dark septate endophytes (DSE) are widespread, abundant and appear equally likely to colonize the roots of native and non-native host plants. While DSE can improve plant soil resource uptake, provide defense against pests, and produce plant growth regulators, it is unclear if these fungi differentially affect native and invasive plants. We surveyed the root endophyte community of both a foundation native riparian tree species, Populus fremontii (Fremont Cottonwood), and its invasive competitor, Tamarix sp.. (tamarisk) and assessed how three common DSE influenced Populus fremontii and Tamarix sp.. growth and functional traits using greenhouse experiments. We found Populus fremontii hosted twice as many DSE isolates than found on tamarisk, but both plant species had similar but diverse DSE communities. We isolated a total of 27 different fungal root endophyte genera from the trees, with 19 genera found on cottonwood roots and 17 genera on tamarisk roots. The DSE communities of these plants were also similar with 8 genera on Populus fremontii and 12 on Tamarix sp.., 5 of these genera were shared by the plant species. Interestingly, the 5 fungal genera shared by the two plant species were also the most common and the DSE community composition did not differ significantly between the species. Inoculation with the DSE Phialophora sp., Phomopsis sp. and Pleosporales sp. affected the growth and biomass allocation of both cottonwoods and Tamarix sp. . relative to sterile-inoculated controls. In both plant species, inoculation with DSE decreased root biomass. However, DSE increased specific root length and decreased root to leaf surface area in tamarisk, while having a stronger effect on the roots of Populus fremontii and decreasing the root to leaf surface area for all DSE treatments. For aboveground traits, only Phialophora sp. increased leaf dry mass in Tamarix sp. . while all DSE species increased leaf mass in P. fremontii. These results demonstrate that taxa of DSE colonize the roots of native and invasive riparian plants similarly. However, the fungi differed in how they affected the functional traits of the two plant species, which could have implications for their growth, survival, and competitive dynamics
Tissue structure and mechanical properties associated with various skin decellularization methods
No full textBurn wounds contribute to an increase in morbidity around the world and have a financial burden on the healthcare system. Third-degree burns lead to destruction of the epidermis, dermis, and hypodermis, limiting wound healing and increasing the risk of environmental or nosocomial infections. To treat these burns, acellular skin grafts are used to cover wounds and assist with wound healing. One common type of graft is an allogeneic skin graft, recovered from cadaveric tissue. However, cadaveric tissue containing cells with intact major histocompatibility (MHC) antigens has the potential for host immune rejection. While allogeneic skin grafts can be decellularized to mitigate this, decellularization has also been shown to disrupt the architecture of the tissue. Establishing a method that retains the skin biochemical, structural, and mechanical properties will be a beneficial treatment for wound healing. Three chemical-based decellularization reagents were compared to understand the impacts each method had on the skin’s properties. The success of cellular removal, architecture of the extracellular matrix, and mechanical properties were evaluated and compared to native tissue. These data demonstrated that the SDS-treatment method resulted in the most successful removal of cellular material on skin samples but negatively altered the structure and mechanics of the tissue. Tonicity treated skin appeared to fully remove cellular material as determined visually through hematoxylin and eosin staining, but the use of PicoGreen indicated that DNA was still present in the skin samples. Triton X-100-treatment did not remove the cellular or nuclear material on skin samples and caused damage to the skin’s structure that was visible through scanning electron microscopy. Evaluation of the tissue’s mechanical properties demonstrated that SDS-treatment negatively impacted the tissue’s strength and elasticity, whereas Tonicity-treatment was comparable to the native tissue. This study determined the effects each chemical reagent had on the skin’s properties and provides an initial assessment for the future possibility of in vitro recellularization