Now showing items 1-20 of 41787

• #### Quantifying X-ray Diffraction Reconstruction Fidelity

With increasing transport security awareness and the demand for threat detection, X-ray diffraction (XRD) technology is developing continuously [1]. X-ray diffraction imaging refers to the method of using X-rays, namely beams with photon energy between 1keV to 150keV , to detect the scattered light from the interaction between objects with different materials and X-ray photons, to infer the type of material by measuring momentum transfer of photons. Unlike computed tomography (CT), X-ray diffraction not only provides the spatial distribution of objects, but also the molecular material composition. As such X-ray diffraction requires complex computations and a challenging measurement. A variety of XRD reconstruction algorithm have been developed, such as state-of-the-art Group Total Variation. The goal of this work is to quantify XRD reconstruction algorithm performance with respect to signal-to-noise ratio (SNR), material categories and collimation/coding schemes.
• #### The Phase-Space Distribution of Galaxy Clusters

We provide the modeling framework to enable a proposed new measurement of the Hubble constant, using the radial extent of galaxy clusters as a standard ruler. Observationally, we plan to measure the angular extent of the cluster and the velocity of galaxies around the cluster. More massive clusters have galaxies that orbit faster, so we can use the velocity of galaxies within clusters to estimate an effective cluster mass. To enable this, we have calibrated the relation between line-of-sight galaxy velocity and cluster mass using cosmological simulations. With an estimate of halo mass now in hand, we can infer the radius of the dark matter halo containing it. To enable this, we have also calibrated the relationship between halo mass and radius with simulations. We find that a halo whose mass is $1\times10^{14}$ $M_\odot/h$ has a physical radius of $596\pm3$ kPc/h, better than $1\%$ precision. Comparing the halo radius inferred from galaxies' velocities to their angular extent allows us to estimate the distance to the cluster, which in turn can be used to assemble a Hubble diagram for galaxy clusters. The high level of precision in the halo radius needed to establish this measurement is founded on a recent insight in halo modeling: galaxies in halos can be split into two populations: those orbiting their host dark matter halo, and those falling into the host for the first time. Here, we present an algorithm that uses the galaxies' accretion history to distinguish between them. We use our split catalog to generate fits for the orbiting and infalling galaxy phase space densities. Importantly, each can be described as depending on a single fundamental scale, the halo radius $r_h$. Both the orbiting and density profiles can be described with 5$\%$ accuracy using $r_h$ as the length scale. In velocity space, we show that the infalling velocity distribution has a bimodal appearance due to the impact of the Hubble flow on galaxy velocities. Our model of the distribution of galaxy line-of-sight velocities is also 5\% accurate. Finally, to prepare the calibration for application to galaxy clusters, we characterize the impact of cluster selection effects the phase space distribution of galaxies. To do so, we select clusters based on the galaxy counts in cylinders of height $\pm$20 h$^{-1}$~Mpc and $\pm$60 h$^{-1}$~Mpc along the line of sight. The distributions of line-of-sight velocities for both orbiting and infalling galaxies are robust to cluster selection; so is the projected orbiting surface density. The projected surface density of the infalling population, however, exhibits a strong scale-dependent bias, where the scale is set by the aperture used in the process of cluster selection. Finally, we suggest the next steps needed to characterize the dependence of the halo radius on the assumed cosmology, as well as the possible influence of baryonic processes on it. As a coda, we also include work on the broadband emission of galaxy clusters, and examine the possible detection of extra-solar neutrinos (via the ICECUBE and Auger experiments) from the Coma cluster of galaxies, as well as for $\gamma$-ray-bright clusters.
• #### Ultrafast Carrier Dynamics in Two-Dimensional Materials

The discovery of graphene led to an eruption of research into the expansive collection of two-dimensional materials. The ability to fabricate stacked heterostructures with van der Waals materials layer-by-layer has allowed the production of unique devices and has rapidly advanced research in electronics and optics. Understanding the dynamics of carrier and phonon interactions within these systems is crucial for the development of optoelectronic devices. This thesis explores the dynamics of photo-excited carriers in two-dimensional systems: the effects of substrate choice on carrier relaxation in graphene and phonon induced bandgap renormalization in monolayer tungsten disulfide at high carrier densities. Graphene-hBN (hexagonal boron nitride) heterostructures show promising use in electronics applications due to high carrier mobility. We first explore the effect of the hBN substrate on the relaxation rates of photo-excited carriers in these heterostructures using femtosecond pump-probe spectroscopy. Time dynamics of photo-excited carriers in graphene-hBN heterostructures show a cooling rate approximately four times faster on hBN substrates compared to silicon oxide substrates. We next study the effect of variation in isotopic concentration in hBN substrates on the relaxation rates of photo-excited carriers. We measure and compare the time dynamics of photo-excited carriers in graphene-hBN heterostructures using naturally occurring hBN (containing 20% 10B and 80% 11B) and isotopically pure hBN (containing 100% 10B or 100% 11B). We observed a carrier relaxation rate ~1.7 times faster for isotopically pure hBN substrate. Isotopically pure hBN substrates samples allow more efficient decay of optical phonons from graphene into acoustic phonons in the substrate, while the isotopic disorder in naturally occurring hBN causes isotope-phonon scattering. Monolayer transition metal dichalcogenides are another van der Waals material which have garnered a lot of interest due to their direct optical band gap and strongly bound excitonic states in the visible light range. We utilize non-degenerate femtosecond pump-probe spectroscopy to measure the differential reflectivity in monolayer WS2 to investigate the interactions between carriers, defects, and phonons in the high carrier density regime. We find photo-excited carriers are trapped by defect states, which act as non-radiative recombination sites and emit phonons, which cause a phonon-induced band gap renormalization up to 23 meV.
• #### Conifer Resilience Following Wildfire and Drought in Southeastern Arizona Sky Islands

Wildfire size, severity, and frequency have been increasing in the Southwestern US since the mid-1980s as a direct result of anthropogenic climate change and land management practices. Significantly, high severity burn area in Arizona and New Mexico has been increasing at a rate of about 1,000 ha per year since 1985. This increase in more frequent, higher severity wildfire, combined with two decades of drought, threatens the persistence, regeneration, and resilience of conifer trees in the dry pine forests of Southern Arizona’s sky islands. Failure of conifers to recover may result in ecosystem conversion, where forested areas are replaced by oak or shrub woodlands. Here we report on radial tree growth, conifer regeneration, and community composition in the Santa Catalina Mountains (SCM) following wildfires in 2002, 2003 and 2020. For our tree growth analysis, we found a striking resilience to both drought and wildfire in three dominant conifers. Pines that burned at high and low severity in particular showed non-significant positive growth trajectories following wildfire exposure in 2003. Douglas-fir growth was more climate-dependent and less fire-dependent than Pinus growth. For areas that burned only in the earlier fires, conifer regeneration over the 17–18-year interval was found in the majority of burned plots, although density varied greatly. Community composition analysis in these areas found some loss of conifer overstory dominance in areas burned at high severity; in general, these were replaced mainly by Aspen (Populus tremuloides) in higher elevation stands, not deciduous or evergreen oaks. Community composition analysis for areas that burned in the most recent fire showed wide variability and may be seen as a starting point for future trajectories of change in Southwestern forests under the influence of changing climate and fire regimes.
• #### Mortality Thresholds of Juvenile Trees to Drought and Heatwaves: Implications for Forest Regeneration Across a Landscape Gradient

Tree loss is increasing rapidly due to drought- and heat- related mortality and intensifying fire activity. Consequently, the fate of many forests depends on the ability of juvenile trees to establish following exposure to heightened climate anomalies. Climate extremes, such as droughts and heatwaves, are increasing in frequency and severity, and tree survival in mountainous regions must contend with these landscape-level climate episodes. Recent research focuses on how mortality of individual tree species may be driven by drought and heatwaves, but how mortality from protracted drought and associated warming would vary among multiple species spanning an elevational gradient given concurrent variation in climate, ecohydrology, and physiology remains unclear. We address this question by implementing a growth chamber study, imposing extreme drought with and without a compounding heatwave, for five species that span elevations across a semiarid elevational gradient in the southwestern United States. Overall, the length of a progressive drought required to trigger mortality differed by up to 20 weeks among species, whereas inclusion of a heatwave hastened mortality by about one week. Lower elevation species that grow in warmer ambient conditions died earlier (Pinus ponderosa in 10 weeks, Pinus edulis in 14 weeks) than did higher elevation species from cooler ambient conditions (Picea engelmannii and Pseudotsuga menziesii in 19 weeks, and Pinus flexilis in 30 weeks). When exposed to a heatwave atop drought, mortality advanced significantly only for species from cooler ambient conditions (Pinus flexilis: 2.7 weeks earlier; Pseudotsuga menziesii: 2.0 weeks earlier). Cooler ambient temperatures and associated differences in ecohydrology-related soil evaporation may have provided a buffer against moisture loss during drought, potentially overriding expected differences in drought tolerance due to tree physiology. Our study suggests that droughts will play a leading role in juvenile tree mortality and will most directly impact species at warmer climate thresholds, with heatwaves atop drought potentially exacerbating mortality especially of high elevation species. These responses are relevant for assessing the potential success of both natural and managed reforestation, as differential juvenile survival following episodic extreme events will determine future landscape-scale vegetation trajectories under changing climate.
• #### Phenology of Lesser Long-Nosed Bats and their Food Plants

Lesser long-nosed bats (Leptonycteris yerbabuenae) are important pollinators and seasonal residents along the U.S-Mexico border. Because they feed on flowering and fruiting plants, they are vulnerable to phenological shifts in those species. To evaluate synchrony between bats and their key food plants, we characterized seasonal abundance of bats and flowering and fruiting phenology of food plants at roosts in 2010, 2011, and 2021. Although phenology of bats and their food plants was generally consistent across years, we observed modest changes in aspects of flowering and fruiting of saguaro (Carnegiea gigantea) and organ pipe cacti (Stenocereus thurberi). At maternity roosts, bat abundance was synchronized more tightly with flowering phenology of saguaros in 2021 than in 2010-11. At post-maternity transient roosts, bat abundance was synchronized less tightly with flowering phenology of agaves (Agave palmeri) in 2021 than in 2010-11. We complemented these analyses by improving methods for non-invasive genetic sampling of this species. Specifically, we developed a two-step amplification approach to analyze microsatellite loci and identify individual bats via DNA extracted from fecal samples. As a proof of concept, five highly polymorphic microsatellite loci distinguished 434 individuals reliably. The probability of two closely related individuals having the same genotype at all five loci was 0.003, and the overall probability of identity was 7.5E-09. Addition of a multiplex step added minimal cost, improved amplification success, and conserved DNA extracts. Repeated analyses showed genotyping error was <2%. We explore the benefits and limits of our approaches for population studies of lesser long-nosed bats and other species that provide key ecosystem services and are commonly of conservation concern.
• #### The “Bel Canto” Viola: The Role of Alessandro Rolla in the Viola Catalog

The music of Italian composer Alessandro Rolla (1757–1841) serves a vital role in the catalog of important viola repertoire. Nonetheless, his vast contributions are woefully neglected by the majority of modern viola players. Familiarity with Rolla’s music can help dispel the misconception that only a small pool of viola repertoire existed prior to the 20th century. As a violist and composer, Rolla championed the viola as a viable solo instrument on equal footing with the violin. Even more significant is the critical role he played as a musical leader in Milan during the pinnacle of the Bel Canto period. It is evident that his close connection to the world of Italian opera shaped his compositional style. It is because of this that Rolla’s music holds a special position in the viola catalog.Rolla’s mature style is best understood in the context with the Italian operatic idiom known as Bel Canto. Bel Canto translates simply to “beautiful singing,” but its true definition is more elusive and remains a topic of contention. The term Bel Canto has become heavily associated with vocal technique; however, it can be understood to have much broader implications as it relates to composition, performance practice, and overall aesthetics. When examining the origins and meaning of Bel Canto, it is crucial to recognize how the development of vocal and instrumental technique evolved simultaneously. The study of Rolla’s life and work grants an invaluable opportunity to illuminate this nebulous subject. The core of this research document will focus on several of Rolla’s compositions that incorporate versions of opera arias. Also, several of his original compositions will be analyzed through the lens of the Bel Canto tradition. Comparisons will be made between Rolla’s compositional elements and those of Rossini, Donizetti, and Bellini.
• #### The Preservation and Development of Black American Folk Music and of the Exodus Emblem in R. Nathaniel Dett’s the Ordering of Moses

Black American composer R. Nathaniel Dett (1882–1943) is a pioneering figure of American classical music composed by Black musicians. During his career—as a composer, performer, and educator—Dett advocated for the preservation of Black American folk music and its development via its use in “serious” classical music. While initially not interested in doing so, after hearing the masterful use of Black American folk music in Dvořák’s American Quartet during his student years at Oberlin College, Dett’s perspective changed; Dvořák’s composition provided a conceptual foundation for this fusion. In light of this, Dett’s career is defined by his mission to preserve and develop Black American folk music, of which his oratorio, The Ordering of Moses (1937), represents this fulfillment. This dissertation asserts that R. Nathaniel Dett’s The Ordering of Moses embodies his distinct views on preserving and developing Black American folk music, as demonstrated through his utilization of Negro Spirituals as thematic material within this work. Similarly, this dissertation holds that Dett’s symphonic work preserves and develops broader Black American idioms on account of its use of the Exodus emblem as its narrative focus, consistent with its use in the cultural expressions of Black arts, letters, and religion (Christianity).
• #### An Investigation of Acid Mist Formation and Suppression Mechanisms in Copper EW Plants

During the copper electrowinning (EW) process, oxygen gas is produced on the anode and forms bubbles which rise to the surface bursting at the air/solution interface. Acid mist is released and negatively impacts workers’ health while also corroding equipment and tank house surroundings. Although there are several ways of reducing acid mist, adding anti-mist agents is the most economical method currently in use to suppress acid mist. However, the search for an environmentally friendly mist suppressant is greatly hindered by the fact that the acid mist formation as well as suppression mechanism is not fully understood. In the present research, the physical-chemical properties of the electrolyte (density, surface tension, viscosity) are characterized, particularly the effects of changing temperature and surfactant concentration. A High-Speed Video Camera (HSVC) is utilized to study the bubbles’ burst/rupture process at the solution/air interface at varying bubble diameters. The findings not only hope to clarify the mechanisms of acid mist formation and suppression but additionally help with the search for and application of an environmentally friendly anti-mist agent for copper electrowinning.

• #### Coahuilteco Language Reclamation Program

The Coahuilteco language had been dormant for approximately 200 years. It was documented by two Franciscan priests, Gabriel De Vegara (1730) Cuadernillo de los Indios Pajalates and Bartholomé Garcia (1760). Manual para administrator los santos sacraments de penitencia, eucharistia, extrema-uncion, y matimonio: dar gracias despues de comulgar y ayudar a bien morir. These documents represent the limited corpus of the language. These documents were analyzed and described by two American linguists John Reed Swanton (1940) and Rudolph C. Troike (1959-2015). Their analyses and descriptions of the language posed many problems (reading and interpreting linguistic jargon) for the community of lineal descendants attempting to awaken and reclaim the language. Troike (p.c.2016) provided the community with valuable insights and decoding keys to help the community interpret the linguistic jargon; thus, helping the community answer the question of ‘‘How do we facilitate the teaching and learning of the scholarly research of the heritage language to the community?” Further knowledge of teaching the scholarly material has been provided by Wilson De Lima Silva (p.c.2022).
• #### Clínica Integral Almas: Tackling the Social Determinants of Health while Cultivating a Community of Care in Rural Guarijío-Makurawe Communities of Sonora, México

The Mexican health system is fragmented into sub-systems and levels of care, including private and public services, which create inequalities in access and quality of services and treatment in rural and Indigenous communities. In addition, the COVID-19 pandemic has exacerbated the lack of medical and healthcare services (Gomez, 2011 and Doubova et al., 2022). This project aimed to explore how Clínica Integral Almas (CIA), a rural Sonoran non-profit clinic run by a team of Mexican healthcare providers, has addressed the social determinants of health, and has provided services to Guarijío-Makurawe communities of thirteen villages and surrounding municipalities in Álamos. Over the course of two months, eighteen semi-structured interviews and multiple field observations were conducted with Mexican physicians (n=4), patients (n=5), Clínica Integral Almas staff (n=2), community health workers (n=4), and U.S and Mexican healthcare workers (n=3). Patients and community health workers included Guarijío-Makurawe individuals, an Indigenous group from north-central México. Patients, doctors, and staff included Álamos non-Guarijío-Makurawe participants. Lastly, healthcare workers included participants from México and the US. With non-governmental medical healthcare resources and expertise, the cultivation of care, accompaniment, and the use of traditional medicine, Clínica Integral Almas (CIA) physicians and community health workers have been able to address, many of the social determinants of health that can lead to negative health outcomes in rural communities of Álamos, Sonora, México.
• #### The Mexico City Metro: Appropriation and Assimilation of Foreign Technology To Stay on Track With Other Modern Capital Cities and To Produce a Technological and Cultural Marvel

This paper provides a review of the construction of the metro in Mexico City and evaluates themetro as a production of culture. The incorporation and Mexicanization of foreign technology allowed Mexico to build and service a metro while making it uniquely Mexican. The naming of the stations and the use of icons to identify them project Mexican culture and power. The art within the stations and the activities travelers see and participate in are also examples of how Mexico’s metro is unique to its culture. The use of newspaper articles from major cities from around the world demonstrated that the metro was accepted as a successful technological marvel. Newspaper articles, songs, and local art show that Mexicans accepted the metro as their own. We conclude that the metro was a cultural production that propelled Mexico City to the same level as other modern capital cities.

• #### The Association Between Oral Glucose-Control Agents and Incident Dementia in Type 2 Diabetes Within the Veteran’s Affairs Healthcare Enrollees

INTRODUCTION: Dementia is a major contributor to disability and death. A risk factor of dementia is type 2 diabetes (T2D). Current evidence suggests shared causes of the two diseases and a potential to repurpose specific glucose-control agents (GCAs) for dementia prevention or treatment. However, clinical trials and population studies focusing on this topic are insufficient to conclude GCAs anti-dementia effects and compare effectiveness of different GCAs. This dissertation intended to compare the effects of monotherapy and concomitant use of GCAs on dementia. The results should be able to provide suggestions on GCAs selection in T2D, in terms of dementia risk management. METHODS: In this dissertation, study 1 and study 2 used medical records from the Veteran’s Affairs Healthcare (VAH) database. Glucose-control treatment histories were extracted from prescription records and were aggregated at drug class level. Disease conditions were extracted from outpatient diagnosis records, coded by ICD-9 or ICD-10. Four antidiabetic drug classes were assessed based on a literature review and VAH data richness. Among T2D, study 1 compared the associations of first-generation antidiabetic drug classes (metformin [MET], sulfonylureas [SU], and thiazolidinedione [TZD]) with the risk of dementia. And study 2 compared the associations of adding dipeptidyl peptidase-4 inhibitors (DPP-4is) to MET and/or SU (MET/SU) treatment with risks of dementia and other vascular events. To capture the trends of clinical evidence in relevant fields, study 3 reviewed phase II, III, and IV clinical trials repurposing GCAs for Alzheimer's disease (AD). RESULTS: In T2D without prior dementia, study 1 found that after at least one year of treatment, compared with MET monotherapy users, the risk of all-cause dementia was 22% lower in TZD monotherapy users (HR: 0.78, 95% CI 0·75-0·81), and 11% lower in MET and TZD dual therapy users (HR 0.89, 95% CI 0·86-0·93), whereas the risk was 12% higher in sulfonylurea monotherapy users (HR 1.12 95% CI 1·09-1·15). In study 2, compared with participants staying on MET/SU treatment, participants who added DPP-4is to MET/SU regiments had lower risks for the cerebrovascular outcome (HR, 0.68, 95% CI, 0.62-0.74), and the microvascular outcome (HR, 0.91; 95% CI, 0.88-0.94), but not associated with the risk for the renal outcome (HR, 1.03, 95% CI, 0.97-1.10). In study 3, 26 clinical trials were reviewed and summarized in a narrative way. Elders with mild cognitive impairment, AD, and other types of dementia were the main trial participants. Among studied GCAs, insulin, MET, and pioglitazone showed protective effects on subsets of cognitive function but findings on global cognition and AD biomarkers were neutral. But evidence of other GCAs was either insufficient to make conclusions or unavailable. CONCLUSION: These studies suggest that different GCAs had varied effects on dementia risk within elder T2D, although GCAs may be unable to modify AD progression after AD onset. Without disturbing diabetes management, clinicians may consider lowering patients’ dementia risk through GCAs selection. Additional research is warranted to exam whether our findings apply to younger populations and minority groups.
• #### "I Don't Get Drunk. I Get Awesome!" Employing a Vulnerability-Stress-Adaptation Framework to Examine Alcohol Use in Emerging Adulthood

Building on emerging adulthood theory and the Vulnerability-Stress-Adaptation (VSA) framework, this dissertation research examined emerging-adult newlywed couples’ alcohol drinking behaviors. Four-annual-wave, dyadic data from 963 couples were analyzed with an Actor-Partner Interdependence Model (APIM) to investigate 1) personality traits and stressful life events (SLEs) as predictors of emerging adults’ alcohol use, and 2) personality traits and alcohol use as predictors of emerging adults’ experiences with SLEs. Results revealed great predictive power of personality traits, especially for emerging-adult men; trait kindness and trait sociability were influential in alcohol involvement while trait anxiety and trait depression were closely associated with SLEs. Emerging-adult women’s perceived stressfulness of SLEs displayed both actor and partner effects, positively predicting alcohol involvement for themselves as well as for their emerging-adult husbands. The potential vicious circle of SLEs and alcohol drinking behaviors suggested by the VSA model was not supported. The findings inspire researchers to further explore whether men are more affected by internal characteristics whereas women are more susceptible to the external circumstances, which may enlighten couple therapy on coping strategies.