1925 research outputs found
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Circular dichroism in semiconducting-plasmomic hybrid chiral nanostructures
Get PDFChiral metamaterials have become an active area of research due to the rich possibilities of discovering new fundamental light-matter interactions as well as a multitude of potential applications, including greatly enhanced molecular sensing among many others. The ability to improve, control and fine tune the chiro-optical activity is critical to expanding these areas of cutting-edge research. However, the ability to control and “tune” the chiro-optical activity remains a serious practical challenge. In this dissertation, four different methods for achieving such control are developed and described in detail. By choosing a large bandgap semiconducting material (TiO2) for a periodic array of chiral nanostructures, “giant” chiro-optical activity was achieved at ultraviolet wavelengths for the first time. This is important because the signature frequencies of biomolecules often lie in this region. By only slightly varying the morphology of the semiconducting chiral nanostructures, a high level of tunability over the chiro-optical activity was established. Most impactful, a broadband and tunable CD across UV and visible wavelengths was achieved with heterogeneous nanohelices made from a combination of semiconducting and plasmonic materials. Critically, the optical activity of these hybrid nanostructures was found not to be a simple algebraic sum of the CD of the underlying materials, but a strong synergistic enhancement arising from the hybrid nature of the metamaterial was instead observed. We ascribe this effect to the strongly modified electronic band structure induced by the interface between the disparate materials. The highly enhanced optical activity, i.e., CD, opens the door to targeted engineering of chiral metamaterials for a multitude of novel applications
Fungi-assisted uranium uptake by plants: considerations of soil biogeochemistry and its mechanistic implications
No full textHundreds of abandoned uranium mines pepper the landscape of the Navajo Nation, which exposes residents to radiogenic and chemotoxic hazards.1,2 Uranium soil contamination also impacts regions of China, Canada, and Europe. Typical uranium remediation techniques (e.g., soil removal, plant uptake) are undesirable because they increase erosion, release uranium-containing dust, or potentially lead to the unintentional consumption of uranium by livestock such as mutton and local fauna.3, 4 A method that could reduce this exposure is phytostabilization, which has the primary goal of quelling contaminant transport by using plants to take up uranium but keeps uranium predominantly in the plant roots where livestock would be less likely to consume the plant. New discoveries associated with this method prompt new questions about underlying mechanisms. One discovery is that root symbiotic arbuscular mycorrhizal fungi (AMF) can increase the uptake and isolation of uranium in the roots of sunflowers.5 Studies have demonstrated this phenomenon, but researchers have yet to pinpoint the underlying mechanism or mechanisms.3, 6, 7, 8, 9 A missing element of study may be the mineralogy of the plant growing medium, which can influence the bioavailability of uranium and other metals.10 We hypothesize that AMF are able to increase the uptake of uranium in the roots of plants because they can access a phase of uranium that is chemically held to clay minerals that plants cannot acquire alone. To test this hypothesis, we conducted sunflower growth experiments using kaolinite and native soils, continuously exposing the plants to uranium of varying concentration for eight weeks. The plants were processed and analyzed via ICP-MS to determine the concentrations of uranium in the roots and shoots. Statistical analysis using ANOVA was performed where appropriate to determine the significance of the treatments. In the kaolinite growth experiment, the only groups with statistically significant differences in uranium concentrations were the roots of the +AMF +Clay 10 ppb uranium treatment, which had a higher uranium concentration, and the +AMF -Clay 10 ppb uranium treatment, which had a lower uranium concentration. In the soil growth experiment, there were no statistically significant differences in mean uranium concentrations between any groups. These results indicate that soil uranium host phase likely impacts the ways in which uranium is taken up by sunflowers
Zeolitization and feldspathization processes of the Campanian Ignimbrite, southern Italy
No full textThe Campanian Ignimbrite formed the Campi Flegrei caldera, located to the west of Naples, Italy, at about 39 ka. The dilute pyroclastic density current, which had an emplacement temperature above 580 ºC, surmounted high topography (over 1400 m) and traveled over water, depositing a trachytic to phonolitic tuff. What would have supplied the additional gas needed for this dilute current, however, is still unknown. Today, there is a hydrothermal system at Campi Flegrei and if one were present 39 ka, this could add the additional gas required to sustain such a diluted ignimbrite. Campi Flegrei’s proximity to the coastline makes seawater (or a mixture of seawater with another source) a reasonable source for a hydrothermal system. The alteration mineral assemblage of two distal deposits, the Welded Gray Ignimbrite and the Lithified Yellow Tuff, contain alteration minerals whose chemistry reflect that of the fluid. This study analyzed chemical compositions of chabazite, analcime, phillipsite, and feldspars to see if there was an enrichment of Na, K, Mg, Sr, etc. that may be found in specific water sources (i.e. seawater, meteoric, or magmatic). XRPD, SEM/EDS, WDS, and thermodynamic modeling methods were used to analyze the Campanian Ignimbrite. These methods revealed an abundance of Na-rich and K-rich minerals. Basal units contain more Na-rich minerals and calcite, likely precipitated from dissolution of carbonaceous clasts that could have then neutralized the fluids in conjunction with the dissolution of trachytic glass, allowing minor zeolitization to later occur. The Lithified Yellow Tuff contains mostly K-rich zeolites and evidence for vapor-phase alteration in fast-growth, spherulite crystals and the potential presence of marialite. These findings indicate a hydrothermal system existed within Campi Flegrei at the time of the Campanian Ignimbrite, but I propose that this system did not become incorporated into the deposits. Rather, devitrification processes and interstitial pore fluid would have been sufficient to generate the mineral assemblage observed in the Welded Gray Ignimbrite and part of the Lithified Yellow Tuff. Further zeolitization occurred in the Lithified Yellow Tuff by meteoric water, once the deposit cooled enough and became favorable for zeolitization. Na-rich zeolites found in this uppermost unit are likely detrital material. They would have come from the Campi Flegrei hydrothermal system, forming prior to eruption in marine-like fluids, and later becoming incorporated into the Breccia Museo and some of the distal deposit
Juvenile justice system in different cultural contexts: a comparison of juvenile justice administration in Malawi and the United States of America
No full textJuvenile crime has become a pressing issue in many societies in today’s world. The juvenile crime rate varies from one country to another, with some having relatively low rates and others experiencing higher rates. As such, each country has a unique system in response to juvenile crime. The juvenile justice systems are shaped by the different perceptions and beliefs concerning age, maturity, and adolescent development. Thus, juvenile justice systems are rooted in the way adolescence is perceived. This study compared two juvenile justice systems of two culturally different countries—Malawi and the United States of America. The comparison analysis answered the question; How are the historical and modern juvenile justice systems in Malawi and the United States of America similar and distinct in terms of (i). their views of adolescent development? (ii) their response to areas of race and class? (iii) their attempts to social control of the youth population? (iv) their success in preventing juvenile crime? The study analyzed how each country’s juvenile justice system is rooted in the unique way that the country perceived adolescence and childhood. This comparative analysis revealed that the two juvenile justice systems have their origins influenced by the western legal philosophies and ideas of adolescent development. Although the two countries have established juvenile justice systems based on the perception that adolescents are different from adults, there is evidence that the two countries still treat young offenders as adult offenders. In addition, the study has established that the two countries use the juvenile justice system as a measure for social control of the youth population. In the effort to prevent juvenile crime, the study established that the two juvenile justice systems have not been successful as recidivism among young offenders has become a growing problem despite the different rehabilitative programs that were developed. The study recommends that the Malawi juvenile justice system should develop coherent rehabilitative programs which will include community leaders, parents, or guardians; the country should prioritize early intervention measures instead of focusing on rehabilitation always, the country should train officers dealing with young offenders, and the country should introduce restorative justice system.
Keywords: juvenile justice system, adolescence development, young offender, rehabilitation, juvenile crime, juvenile justice administrations, recidivism
Determining magmatic volatile contributions to the Campanian Ignimbrite, Italy
No full textThe trachytic Campanian Ignimbrite was emplaced at 39.8 ka near Naples, Italy, in the largest European eruption of the past 200 ka. Many factors, including the far-reaching extent of deposits, with co-ignimbrite fallout found as far away as Russia, indicate emplacement via a dilute (gas-rich and solids-poor) pyroclastic density current. Elevated concentrations of magmatic volatiles (i.e., H2O, Cl, and S) may represent a mechanism for dilution of the pyroclastic density current. Trace- and major-element and volatile concentrations of clinopyroxene-hosted melt inclusions were analyzed via Secondary Ion Mass Spectrometry and Electron Microprobe analysis in both the proximal and distal deposits of the Campanian Ignimbrite to quantify the magmatic volatile contributions.Trace elements and volatiles are similarly enriched in melt as they are both excluded from growing crystalline phases. Unlike trace elements, volatiles will reach a point in which exsolution via second boiling occurs. Very incompatible trace elements will continue to enrich in the melt until a mineral phase that accepts them begins to form, while volatiles create a separate vapor phase rather than concentrate in the melt (i.e., saturation). Melt inclusions in the Campanian Ignimbrite show increasing incompatible trace elements (e.g., zirconium), while water concentrations stay consistent at ~2 wt%. The uniformity of measured water concentrations with highly variable incompatible trace elements suggests that these melt inclusions were volatile saturated prior to eruption. It is unlikely that the melt inclusions were all trapped at the same time and record a similarly undersaturated ~2 wt% H2O magma, especially because the melt inclusions have trace element concentrations that vary over a factor of ~6 implying different degrees of evolution. It is proposed that magmas feeding the Campanian Ignimbrite eruption underwent shallow storage (~1.5 km), with H2O contents re-equilibrating to their saturation limit at this storage depth prior to eruption. Higher water concentrations (~3.4 wt%) and lower trace element concentrations found in some inclusions likely correspond to eruption of magmas from deeper portions of the magma system. This can be envisaged as discrete sills at differing depths that supplied magmas for different portions of the Campanian Ignimbrite eruption. Preliminary hydrogen diffusion modeling suggests that re-equilibration at shallow depths could occur within ~2 hours to 2 weeks prior to eruption. Therefore, melt inclusions do not record the full magmatic volatile history of the Campanian Ignimbrite, but, rather, melt inclusions record magmatic volatile conditions during a short-lived, shallow storage event during which re-equilibration allowed H+ to escape from the melt inclusions while water exsolved from the magma. This re-equilibration may have provided a large amount of free gas phase just at the time of the eruption, with little time before the eruption for it to escape the system
From community to transcriptome: Responses of Syntrichia caninervis and biocrusts to climate change
No full textThe increasing temperatures and severity of droughts are modifying dryland ecosystems worldwide and reducing the provision of ecosystem services in the home of about 3 billion people. Biological soil crusts (biocrusts) - assemblages of cyanobacteria, lichen, fungi, bryophytes and other organisms - are major contributors to the functionality of surface landscape features in the Southwestern USA. Here, we investigated how biocrust communities and one common biocrust moss species, Syntrichia caninervis, will respond to climate disturbances, to better understand and predict global change impacts on drylands biodiversity. This dissertation explores the climate disturbance impacts across organizational scales in biocrusts, examining the responses of the community, moss population morphological traits and transcriptomic profiles. To better understand the effects of long-term induced drought on the composition and maturity development of biocrusts, we conducted a community structure survey on sites with 8 years of rainfall reduction across an aridity gradient in the Colorado Plateau region in the Southwestern USA. We tested the hypothesis that higher diversity promotes stability using the compositional resistance as a measure for ecosystem stability. We found biocrust communities to have lower later successional moss cover and an increased early successional cyanobacterial cover, despite an overall similar species composition with the control plots. In addition, we found richer communities to be more susceptible to greater change in their composition, not less, refuting our hypothesis.
To understand how populations of dryland moss respond to altered climatic conditions, we explored the changes in Syntrichia caninervis morphological traits and transcriptomic expression in altered environments. Phenotypic plasticity is often thought of as a rapid-response mechanism by which one genotype can express varying phenotypes when exposed to different environmental conditions. Phenotypic plasticity is observed throughout the life of an organism and could allow it to survive in novel environments. For plant species, plastic phenotypic changes of morphological and physiological traits are mostly controlled by gene expression. We used two reciprocal transplant experiments at the community and species level in a natural elevational gradient, and the previously mentioned 8 year community multi-site rainfall reduction experiment on the Colorado Plateau to test the hypotheses of morphological variability and phenotypic plasticity in response to novel climates. We found climate-driven phenotypes that present rapid morphological plasticity to climate disturbance, supportive of our hypothesis. Despite the influence of population provenance in the levels of plasticity, most of the changes that occurred after one-year in the novel environments appear non-adaptive and may or may not be advantageous to the persistence of the species.
Finally, we ask if novel climates induce change in the transcriptomic profile in S. caninervis populations across an elevational gradient, we compared whole-genome transcriptome profiles of S. caninervis from the two reciprocal transplants. We found a clear pattern of differential transcript abundance driven by the environment, that could be linked to the (1) time of acclimation, (2) directionality of the climate change and/or (3) influenced by biotic interactions. These results confirmed the knowledge of Syntrichia caninervis phenotypic plasticity and its potential for adaptation; however, the lack of detectable transcriptomic plasticity after one year in response to climate stresses could potentially be a disadvantage in the persistence of the species in scenarios of rapid and/or erratic climate changes
Latina/o/x community college students pursuing stem degrees: an analysis of early momentum metrics at a southwestern community college
No full textThe Fourth Industrial Revolution is changing the job labor market and accelerating the need for science, technology, engineering, and mathematics (STEM) jobs. To meet the needs of the job labor market, the Latino population will be a critical component as it is growing in the United States overall and in the southwest. Community colleges are a stepping-stone and gateway to a bachelor’s degree with its inherent open-access and affordable mission. Community colleges serve a vast number of Latino students who intend to transfer to a university and earn a STEM degree. As community colleges embark in Guided Pathways, an institutional-wide reform, there is a strong emphasis on associate degree attainment and community college to university transfer as measurable outcomes. Associate degree attainment and community college to university transfer could take years to measure the effectiveness of guided pathways. Early momentum metrics are an avenue to measure first-year academic momentum that sets the trajectory for associate degree attainment and transfer. This study considered if there was a relationship between early momentum metrics for Latino transfer-oriented students pursuing a STEM Associate of Science degree attainment and community college to university transfer at Western Community College, a large, multi-campus Hispanic-serving institution in the southwest
The Impact Social Networks Have On Parent School-Choice Decision Making
No full textParents have been afforded the right and the responsibility to choose the school that they feel best fits the academic and social emotional needs of their children, and they are expected to choose a school within a reasonable choice set of school-choice options. This phenomenological study aimed to understand how parents of kindergarten through third grade students gather information to make this decision, and to know if their social networks influence their school-choice decisions. Finally, this study sought to describe how parents experience choosing a traditional public school. The researcher found that parents use internet searches, take tours, and speak with their friends, family, and colleagues to make a school-choice decision. Participants of this study decided to enroll their child at their chosen tradition public school when they were, simultaneously, making a home-choice decision. They made their decisions when their children were pre-school aged. They sought to join a community, and they were aware of their responsibility and empowered to choose the right school for their child.
Because these participants were confident in their ability and their knowledge of their child, they were not influenced by the feedback their social networks provided. They used their social networks to gain information on schools they may place in their choice set, or to confirm what they believed the school reputation to be or their decision to enroll.
The participants of this study shared a common experience in getting married, having a child, and finding the right community to raise their family
Concussion: Quantitative Electroencephalogram and the Comparison with Established Measures
No full textThe present study aimed to investigate whether the EEG Concussion Index (CI) is a stronger predictor over established measures of concussion in relationship to a physician diagnosis. A cohort of 9 concussed participants and 15 age- and gender-matched non-concussed control participants from Northern Arizona University were exposed to five concussion assessment tools in a cross-sectional design. The assessment tools range from cognitive to neurological measures: Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT), Vestibular Oculomotor Screening (VOMS), King-Devick (KD), Post-Concussion Symptom Scale (PCSS), and Quantitative Electroencephalogram (QEEG) CI. The data obtained from these assessment tools were examined in a series of logistic regression analyses to determine which measure is the single best predictor of medically diagnosed concussion, and which pair of predictors most accurately predict concussion when compared to other pairs. Due to the obtained sample size, the data for analysis were bootstrapped for 1000 samples. It was hypothesized that 1) QEEG will serve as a stronger predictor for medically diagnosed concussion compared to each established measure individually and that 2) QEEG partnered with the KD will be superior to the other grouped measures of VOMS and KD, VOMS and PCSS, QEEG and PCSS, and ImPACT and QEEG. Both hypotheses were rejected, as the QEEG CI was not a significant predictor of concussion. Results showed that the PCSS was the strongest single predictor of medically diagnosed concussion, B = 7.40, p = .010, 95% CI [2.38, 9.01]. When assessing pairs of predictors, only two pairs yielded -2 log likelihood values that were not equal to .000: the KD and QEEG, explaining between 21% (Cox and Snell R2) and 28% (Nagelkerke R2) of the variance in concussion, and the ImPACT and QEEG which explained between 13% (Cox and Snell R2) and 17% (Nagelkerke R2) of the variance in concussion. However, when these pairs were entered into a test of the full model against a constant-only model, they were not able to distinguish concussed and non-concussed participants, resulting in a non-significant model. With these observed outcomes, no conclusion can be made about which are the best pair. It is important to note that because this was an underpowered and preliminary analysis, these outcomes should be interpreted with caution. It is likely that results may be different in a larger or more severe TBI sample and/or with a different neurological measure
Wheels & Chicken Legs
Get PDF“Wheels & Chicken Legs” is a nonfiction essay collection that asks readers to consider how we endure our own human stories as members of the greater ecological community. The collection begins by examining the ways in which human identity is shaped by family history, gender and trauma. Throughout the collection, I suggest that by immersing ourselves in relationship with the landscapes and nonhuman beings that surround us, we will be able to heal, grow and move beyond the limitations of our human constructs. As the cover painting on page 8 attempts to visually express: we are part of our trees, our rivers and our mountains, one life form interwoven with the next. Ultimately, I hope my work will disrupt anthropocentric hierarchies of being by critically addressing issues of gender, trauma and identity, while simultaneously celebrating the human and nonhuman relationships that shape us. The ten essays range from more lyrical and descriptive styles to playful and even jocular recollections, while consistently centering both place and identity. A rather whimsical tone is apparent in all the pieces. The title essay “Wheels & Chicken Legs” serves as the thematic and stylistic umbrella for all of the essays included, tying together family history, gender and folklore to shape personal identity and a deeply held ecocritical philosophy. The subsequent essays trace the formation of this identity through family relationships, violent trauma, the challenges of survival and interactions with the ecological community. The second essay “What We Learned from the Badger” explores the narrator’s familial, often ceremonial reverence for wild spaces, specifically as taught by her late uncle in the Adirondacks of New York. “Funeral for a Caterpillar” dives deeper into childhood memories in the Adirondacks to more specifically articulate this understanding of the human- nonhuman relationship through ceremony; by placing these pieces in this order, readers are encouraged to consider a more horizontal ontology of being.
“At the Edge of the Arc” continues to trace the development of the narrator’s identity by recounting a distressing childhood experience, which forces her to accept the ways that gender has and will continue to shape her reality. “To Be Clean” expands on this theme, recounting traumatic sexual violence that occurs in her young adult years in a sparse and disturbing lyric retelling. This fifth essay is intentionally placed at the heart of this ten-piece collection, as a commentary on the way we carry such trauma tucked deeply within the very center of ourselves.
The narrator’s relationship with water in “To Be Clean” is reimagined in “When Thunder Sings Alone” which uses a similarly lyrical style to comment on water shortages due to climate change in the Southwest, with the narrator’s personal struggles with plumbing at the tiny house as a metaphor for society’s inability to adequately address these issues. Again, we are asked: how will we endure? Meanwhile, an intimate relationship with her partner suggests the path towards healing from former trauma. “Languages We Understand” continues to explore life at the tiny house, as the narrator engages with the beings around her. Here, we see the compassion in these relationships, particularly between the narrator and her dog, her partner and the beings that share the area.
“Invasion of the Hissing Beetles & How to Live through the Night” expands on the tension of sharing space with nonhuman beings, using the prolific hissing beetles as a metaphor for the barrage of emotional baggage that comes with participating in human society— in particular, a materialistic capitalist society. We are both victim and perpetrators, just as the hissing beetles are. “A Lesson from Catan” is perhaps the most theoretically grounded of all pieces, providing a critique of settler-colonialism by through a game of Catan as the narrator considers the way the rules of this game reflect our own relationship with landscape and property ownership.
The tenth essay “The Broken Teeth of Winter Beasts” takes us back to the tiny house as the narrator grapples with the complexity of her relationship with the life that she has built during a moment of seasonal transition, as she and her dog heal from injuries and find liberation and solace in the forest that surrounds them. In this final essay, this grounded yet lyric piece is meant to remind us of the central theme of this collection: in order to endure the shape of our human form, we must engage with and embrace the untamed spaces that sustain us.
“Wheels & Chicken Legs” contains some of the most polished and meaningful works that I have completed here in the M.F.A. programs, but that certainly does not mean it is complete. I plan to continue expanding this collection, particularly with the intention of including more stories from family history and more character descriptions to expand on the complexity of human-human relationships. Additionally, I hope to produce more essays that apply a variety of theoretical lenses to explore and critique human society and relationship with nature. Finding the balance between the lyrical and the rhetorical is challenging for me, and I feel that I have finally begun to understand how to accomplish this throughout the past few years here.
I am so grateful to my time in this program, and although I’m sad to leave, I know I will be taking these skills and a wealth of knowledge with me. Most importantly, the relationships I have built here are beyond invaluable, and I have no doubt that these connections will continue to guide and support me for years to come. Rather than this thesis being an ending, I see this moment as the beginning of my writing career. After all of these hours of discussion, deliberation, perfectionism, procrastination and ongoing existential crisis throughout these past years, I think I finally understand how to be a writer: by writing, one letter alongside another, one word at a time