1925 research outputs found
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Evaluation of mobile lidar scanning and associated workflows for estimating structural attributes in mixed-conifer forests
No full textRemote sensing techniques, such as light detection and ranging (lidar), have commonly been applied to forestry projects where traditional measurements of forest structure are too time consuming or costly to implement. Advances in lidar technology have led to increased interest in assessing the suitability of terrestrial mobile lidar scanning (MLS) for quickly assessing forest structure, but this type of scanner has not been tested in complex forest structural conditions in the southwestern United States. The highly variable and often complex forest structure that characterizes the dry mixed-conifer forests on the Mogollon Rim in Arizona make it an ideal forest type to test the potential advantages and limitations of using MLS to assess forest structure in complex systems. These forests have seen shifts in forest structure generally attributed to the increase of Euro-American settlers in the mid- to late-1800s, that have increased the need for ecological restoration to improve their resilience to severe disturbances. If MLS could produce accurate estimates of forest structure in dry mixed-conifer forests, it could decrease the resources needed to effectively monitor forest change and inform the adaptive management cycle employed by land managers to monitor the effectiveness of ecological restoration treatments. In this study, I tested the ability of a commercial MLS unit to accurately assess structure in dry mixed-conifer forests by answering the following research questions: 1) How does mobile lidar compare with traditional forest inventory techniques in estimating forest structural metrics in dry mixed-conifer forests using a range of accessible processing tools? 2) Which elements of dry mixed-conifer forest structure affect mobile lidar accuracy in characterizing forest structure? 3) Does the application of an eigenvalue point cloud filter in the processing workflow increase the accuracy of mobile lidar-derived measurements of forest structure?
I used six processing workflows utilizing three processing tree identification tools and a point cloud filter to derive forest inventory metrics from MLS point clouds. MLS-derived trees were also matched to field-observed trees using a published tree matching algorithm. I then calculated error between MLS estimates and field-observed inventories and investigated the potential role of some structural conditions and species composition as sources of increased MLS error. All six workflows generally underestimated trees density (trees per hectare), and overestimated basal area and quadratic mean diameter. On average, the number of trees less than 15 cm in diameter at breast height (DBH) were underestimated by at least 400 trees per hectare or 16 trees per 0.04-hectare plot by all MLS workflows. Trees 15 – 45 cm DBH were overestimated by the workflows using the spanner R package while the LiDAR360 commercial software and custom processing workflow using clustering tools in the dbscan R package overestimated the number of trees greater than 60 cm DBH. Landscape-level omission and commission percent error rates ranged from 40.7 to 84.6%. The three workflows in which a verticality filter was applied to the point clouds produced more accurate trees density estimates but increased basal area error. The ability to classify the species and live or dead status of identified trees was not evaluated due to the lack of readily available processing tools for MLS point-clouds. Plot composition and structural attributes, such as the presence of New Mexico locust (Robinia neomexicana) and bigtooth maple (Acer grandidentatum), higher overall tree density, and higher density of small trees (<15 cm DBH) appeared to increase MLS estimation errors. The number of trees with canopy base heights at or below 1.4 m also increased errors. My work expands existing MLS literature to fill the knowledge gap of MLS performance in complex forest systems. MLS is emerging as a new tool for forestry applications, so a thorough understanding of how these tools can be applied and what further refinements are needed to make them viable are essential to the future application of MLS and related technologies. To increase the capability of MLS as a tool for assessing forest structure in dry mixed-conifer forests, additional work is necessary to develop tree-segmentation workflows that can better identify stems in structurally complex forests and that can identify tree species and live or dead status
Movement and ceramic variability in northern Arizona
No full textThe concept of movement is prevalent in discussions of Four Corners archaeology, and analyses of ceramic export is one method often used to identify trade networks and exchange between cultural groups. My research examines social interaction in the northern Arizona Kayenta region during the Pueblo I, II, and III periods, using ceramics as a proxy for exchange on sites occupied between the years of 850-1300 CE. To do this, I will use archival data from past CRM projects to compare 102 sites from the Black Mesa core area to 31 sites from the Glen Canyon periphery region, specifically examining local and non-local ceramics found on these sites. I have also created social network maps, showing sites with similar ceramic assemblages, and allowing for the comparison of four basic network centrality metrics over time between the core and periphery regions. The results show significant amounts of non-local San Juan Red Ware on Black Mesa, far more nonlocal ceramics than in the San Juan region, where sites contained smaller amounts of Virgin Tradition and Mesa Verde (Northern San Juan Tradition) pottery. Quantitative analysis of network centrality shows, at least based on this small sample, that periods of migration and exchange are correlated with higher mean centrality scores. Possible explanations for these findings are discussed, including migration and cultural diffusion. Future research on these topics will focus on Puebloan identity, migration, movement, and exchange
Heterogeneity of social skills trajectories: associations with problem behavior in adolescents born to unmarried parents
No full textAmple empirical evidence documents risk factors associated with adjustment problems in children born to unmarried parents. These risk factors include lower socioeconomic status, poor parental mental health, and reduced father involvement. However, comparatively less is known about protective factors that buffer adolescents born to unmarried parents from problem behaviors. Prosocial or adaptive social skills—defined as the effectiveness in which one can meet social and cultural expectations for interacting with others—are a promising target for scholarly investigation, as social skills are both malleable and have the ability to generate greater resources for the child. This study used a subsample of children born to unmarried mothers (n = 2,555) from the Fragile Families and Child Wellbeing Study database, resilience theory, and growth mixture modeling (GMM) with regression to examine whether particular variations in patterns of social skills development over twelve years’ time is associated with lower levels of adolescent problem behavior at age 15, while accounting for risk factors for male and female children. Findings from GMM suggest that two groups of trajectories generally characterized social skills development over time for both male and female children. Two latent classes emerged for both males and females: a high declining and a low improving. Regression analysis revealed for both males and females that these social skill trajectory subgroups could not predict child problem behavior at age 15 as measured by the Child Behavior Checklist
Geochemical investigations of Miocene-initiated volcanism of the Erciyes Corridor, Central Anatolia, Turkey
Get PDFThe Erciyes Corridor lavas erupted from a suite of Miocene stratovolcanoes at the northeastern extent of the Central Anatolian Volcanic Province in central Turkey. Previous workers have hypothesized that volcanism in the Central Anatolian Volcanic Province was initiated by rollback of the Cyprus slab following flat-slab subduction. Recent geochemical investigations have focused predominantly on Quaternary CAVP volcanism, whereas Erciyes Corridor lavas may have accompanied the beginning of slab rollback. New geochemical data are presented here for the Erciyes Corridor lavas, including major and trace elements, Pb and Hf isotopes, and petrographic thin section observations. These data have been used to characterize the Erciyes Corridor volcanoes, to determine potential mantle source components for these centers, and to evaluate how mantle source contributions may have evolved with slab rollback.
Erciyes Corridor lavas range from basalt to dacite (~48 to 67 wt. % SiO2), with most lavas being evolved (≥ 52 wt. % SiO2). These lavas are predominantly calc-alkaline, enriched in LREE with respect to HREE, and depleted in HFSE with respect to mantle values. REE patterns of basalts and evolved lavas cross, as represented by lower La/Yb values in basalts as compared to evolved lavas (La/YbN ~ 3 to 5 in basalts, ~ 5 to 14 in evolved lavas) at comparable values of Dy/Yb (Dy/YbN ~ 1.2 to 1.3 in basalts, ~ 1.0 to 1.3 in the evolved lavas). This, combined with isotopic differences e.g., higher 206Pb/204Pb, lower Δ7/4, Δ8/4 in some basalts), suggest the Erciyes Corridor basalts were sourced differently from the evolved lavas.
The Erciyes Corridor basalts are similar overall to other basalts from the Central Anatolian Volcanic Province with respect to alkalinity and mantle-normalized trace element patterns. Subtle trace element differences, such lower Th/Yb, Nb/Yb, Ce/Y, and higher Zr/Nb, distinguish the Erciyes Corridor basalts from other Central Anatolian Volcanic Province basalts. Values for these ratios show that the Erciyes Corridor basalts likely were sourced predominantly from a depleted, MORB-like upper mantle under Central Anatolia with lesser contribution from a sediment-modified mantle component.
Evolved Erciyes Corridor lavas can be subdivided into two groups based on their isotopic characteristics. Group 1 lavas have lower Δ7/4 and Δ8/4 values and a narrow range in ?Hf values, which could reflect differentiation via closed type-system crystal fractionation with negligible crustal contamination. Modeling shows that Group 1 dacitic compositions could potentially be derived from Group 1 basaltic andesites via crystal fractionation of a mineral assemblage containing plagioclase, orthopyroxene, clinopyroxene, and hornblende ± small amounts of apatite or titanite. Alternatively, Group 1 evolved lavas may have been derived from basaltic melts similar to those in other Central Anatolian eruptive centers. Group 2 lavas may have been generated by fractionation of the same mineral assemblage, accompanied by crustal assimilation.
If, as proposed, the evolved Group 1 lavas differentiated in a nearly closed system, these same trace element ratios show that their mantle source was dominated by a sediment-modified upper mantle component. Significantly, the Erciyes Corridor basalts do not require incorporation of a deeper, OIB-like intraplate-like mantle component, in contrast to some Quaternary basalts from the Central Anatolian Volcanic Province. The predominance of the ambient upper mantle component and lack of the deeper component in the Miocene-aged Erciyes Corridor lavas could reflect early stages of flat slab rollback in Central Anatolia; incorporation of the deeper component in younger lavas could then represent the progression of rollback-driven convection over time
Avian malaria on Kaua'i : prevalence and survival as a function of sex, age, and species
No full textThe Hawaiian Islands are the most remote archipelago on Earth, some 3,700 kilometers from the nearest landmass. The introduction of a growing number of non-native species has permanently altered much of the islands’ habitat and displaced native species at an alarming rate. This rapid habitat degradation and loss of native species has led to Hawai'i earning the label of “extinction capital of the world.” One of the most devastating species to arrive on the islands has been Culex quinquefasciatus, the southern house mosquito, a vector for diseases including avian malaria (Plasmodium relictum). Both species are now ecologically established and have caused range reductions, population declines, and extinctions for most populations of native songbirds. The thermal requirements of P. relictum and Cx. quinquefasciatus have in the past provided high-elevation refuges for vulnerable native species. On Kaua'i, this refuge has been the Alaka'i Plateau. However, recent surveys indicate that mosquitoes have encroached on this last pocket of safe habitat, posing a significant and immediate threat to Kaua'i’s remaining passerine species. Malarial prevalence has been studied for a handful of these species, but recent research indicates that it is rapidly increasing on Kaua'i and elsewhere in the Hawaiian Islands. Survival rates with malaria have been poorly studied, and largely for captive birds. We used blood testing and resights taken over a ten-year period to examine prevalence of and survival from P. relictum infection in four species of native songbirds on Kaua'i. We discovered lower prevalence and lower apparent survival rates in honeycreepers than in the two native birds from other taxonomic groups. Our results confirm that honeycreepers are extremely vulnerable to the disease, and will likely require sweeping mosquito prevention efforts if they are to survive into the next century
Understanding e-mentoring: a quantitative study of online undergraduate students
No full textE-mentoring is commonly practiced in the workplace yet understudied and under-practiced in higher education. The COVID-19 pandemic pushed universities to pivot to online teaching and learning, which created a monumental opportunity for e-mentoring to develop and thrive. Considering that over 30% of the U.S. college student population is engaged in some form of online education, and despite its benefits, only one in four students report having access to mentoring while in college. This study sought to understand what individual characteristics might influence online undergraduate students’ perceptions of and engagement with e-mentoring. The findings, based on a survey administered to 414 online students via Prolific, indicate that digital competence and goal orientation were the most significant predictors of online students’ perceptions of and engagement with e-mentoring, whereas social self-efficacy and gender influenced students’ perceptions of role modeling and psychological and emotional support, respectively. Furthermore, digital competence, social self-efficacy, and goal orientationinfluenced students’ likelihood of engaging in future e-mentoring opportunities. Age and the type of e-mentoring, formal or informal, did not influence or mediate students’ perceptions of e- mentoring or their likelihood of engaging in future e-mentoring opportunities. These findings contribute to the e-mentoring literature and can help practitioners design and deploy responsive e-mentoring opportunities for their online students
Aftertaste: an examination of perpetuation and change of food service during COVID-19
Get PDFFood is perhaps the most ubiquitous cultural signifier for all peoples across the globe. What people eat and why they eat it denotes heritage, geography, movement, ritual, stratification, and technology. It is through the combination of these elements that food is, first and foremost, political. In communities, how food is produced, procured, exchanged, and laborers compensated are all emblematic of how the dominant power structure is enacted. This has been true since sedentary agriculture and animal husbandry became dominant modes of caloric sustainability and only became more apparent as the world turned increasingly globalized through empire giving way into capitalism. Throughout the COVID-19 pandemic, what foodstuffs were available, how people got food, then how and where people ate, all became questions of state authority and efficiency as well as calling into question personal agency and social responsibility. These were not new issues then, and have not been for millennia, however COVID-19 offers a lens through which to examine what a food system says about the society in which it exists. Values are exposed by food all the way from the fields to the bank accounts of fast-food employees. COVID-19 was a showcase for the tenuous nature of a for profit system being coupled with survival. To explore the political nature of the food industry during COVID-19, I conducted a media analysis of world and United States news articles and commercials pertaining to the food industry during the pandemic, as a retrospective of the pandemic and how the pandemic changed or maintained, the infrastructure of food service, such as the supply chain and production of foodstuffs. The shift in marketing of food that was necessitated by lockdowns and the somber nature of the current reality. Worker safety and elevated position of turning front line workers into heroes became the norm as frame of reference for the occupation. How workers were or were not compensated for keeping such a large sector of the economy running at great personal risk, and how adversarial that conversation became as the rejection of wage slavery grew in prominence, and, how food establishments and corporations engaged in political theater during the ideological battles taking place on the political spectrum.
I found confirmation of the adage that, “the more things change, the more they stay the same,” insofar as that, many issues which arose during COVID-19 were only new because the virus was, but the systemic nature that had brought them to exist was not new
College-in-prison access, financial aid, and importance: what do Arizonans think?
No full textThe United States, with just 5% of the world’s population, imprisons almost 25% of the world’s incarcerated people. Furthermore, the vast majority of people released from prison will recidivate. Research has shown that earning a college degree while incarcerated significantly reduces recidivism rates. This study considered the opinions of adults living in Arizona regarding college-in-prison access, financial aid, and importance. The study was designed to determine what demographic factors influenced opinions and if a particular intervention, exposure to incarceration and recidivism facts and narrative regarding the value and benefits of college in prison programs, also influenced people’s opinions. The study was accomplished in two phases: a quantitative research phase that employed surveys and interventions and a qualitative phase that used interviews to better understand the quantitative results.
Based on the data collected, a Pearson Chi-square analysis was conducted and themes and sub-themes were developed and coded. The results showed that the people who identified as liberal had favorable views of college-in-prison programs, those who identified as moderate had moderate views, and those who identified as conservative had a more unfavorable view. Exposure to relevant information in the form of a fact sheet and peer-reviewed positional article did influence participants opinions in general. However, for several participants this was tempered by a self-identified position of skepticism towards college-in-prison programs
Structural properties of braid graphs in simply-laced triangle-free Coxeter systems
No full textAny two reduced expressions for the same Coxeter group element are related by a sequence of commutation and braid moves. We say that two reduced expressions are braid equivalent if they are related via a sequence of braid moves, and the corresponding equivalence classes are called braid classes. Each braid class can be encoded in terms of a braid graph in a natural way. In a recent paper, Awik et al. proved that every reduced expression in a simply-laced Coxeter group has a unique factorization as a product of so-called links, which in turn induces a decomposition of the braid graph into a box product of the braid graphs for each link factor. Moreover, the authors proved that when the Coxeter system is triangle free (i.e., the corresponding Coxeter graph has no three-cycles), the braid graph for a reduced expression is a partial cube (i.e., isometric to a sub- graph of a hypercube). In this thesis, we study the structural properties of braid classes in simply-laced triangle-free Coxeter systems. In particular, we provide precise information about the local structure of reduced expressions in the braid class for a link and produce an alternate proof of the fact that every braid graph in simply-laced triangle-free Coxeter systems is a partial cube. Moreover, we outline the obstructions to proving the conjectures that every braid graph in a simply-laced triangle-free Coxeter system is median and corresponds to the Hasse diagram for a distributive lattice
The Mirrorball
Get PDFThe Mirrorball is a multimedia collection of short stories, personal essays, images, and original music. The collection reflects me, one that reveals my fears, joy, and all the intricacies of life in between. It was important to me that I gave myself entirely to this collection, so that it may reflect me the best way that it possibly could. Alongside my essays, each of the fictional women within the short stories is presented as their own mirrorball in some way, shape, or form. The collection intends to represent experiences that come with being the The Mirrorball through the lens of a woman, and specifically as a black woman. The collection emphasizes this ongoing need to hide, strategize and play the part so that I may have some sort of seat at the table. Each piece in the collection invites a different outlook on being the ideal— or better yet, what it means to be the The Mirrorball. Most of the collection was written in a season of depression, a season unbeknownst to me until I was at the very end of it. It is joyous and sad and raw, all feelings I experienced when these stories were written. It intends to follow women from all walks of life who come to face demons, whether they belong to them or others. I divided The Mirrorball into three parts in hopes that the intention of each part would represent the most meaningful themes during my hard season. Each part finishes with an original song to encapsulate a progression of the healing that I endured while writing the collection. The songs share the same sounds and are ultimately imperfect; there are street noises, piano-key thumping, missed notes, and awkward slip-ups. These are all things that I honestly struggled to include in the collection. But the music is intended to showcase a vulnerable side to The Mirrorball; it's what makes the collection come to life for me.
Then there are the three parts themselves. In Part One, the focus concerns itself with some level of invisibility, whether purposeful or not; the women are ignored, hidden, or silent in some way; they are not truly seen. Part One represents a time in my life when I was existing; I was visible but never truly seen. In Part Two, the women progress from being hidden to being exposed. Black women are often mistreated and are the least protected in regards to emotional and physical dangers. The women in Part Two are raw and call for protection in ways that they aren’t afforded repeatedly; the hope and desire are that black women may be understood and seen as women who deserve protection. They represent the pain I’ve carried and the hope that black women will be cared for and loved on, just as we deserve. Finally, Part Three represents the idea that black women can be free to be exactly who they are; the women are no longer bound to the invisibility or the unforeseen consequences of not being protected. They are free to embrace whomever they may or may not be. In this way, it represents a healing version of myself, one that is unafraid of the goodness that is meant for me.
Overall, I hope the collection engages its readers visually and audibly so that they may experience new perspectives and ways of understanding. The Mirrorball serves as a letter to society to consider the black woman’s struggle against the harmful limitations and expectations they have to work through before they can just be. It is a reminder of the season that taught me, shaped me, and forced me to address challenging spaces so that I might heal. And more importantly, it is a reminder that I can be more than The Mirrorball; that I can explore the pieces of myself that go beyond the ideals and expectations that were placed on me before I had a chance to choose differently