Late Pleistocene climate and proboscidean paleoecology in North America: Insights from stable isotope compositions of skeletal remains

This thesis uses the carbon, nitrogen, and oxygen isotope compositions of mammoth (Mammuthus) and mastodon (Mammut) skeletal remains to reconstruct paleoclimate and paleoecology in Late Pleistocene North America. Analytical methods, sampling strategies, environmental adaptations and seasonal behaviors of proboscideans were investigated. Reliable and reproducible results are crucial for a study of this nature. A persistent methodological problem in the isotope analysis of structural carbonate in bioapatite was solved by reacting bioapatite under “sealed vessel” conditions. Growth rate determinations are critical for designing sampling strategies and interpreting results. Histological and isotopic measurements demonstrated variations in enamel growth rates within and among teeth. Sequentially sampling through the enamel thickness can resolve shorter-term (weekly) isotopic variations, and sampling along the tooth height (especially on the inner enamel surface) can resolve longer-term (monthly or yearly) variations. Proboscideans adapted to the conditions of their local environments. Clovis-age mammoths in Arizona sought out C4 grasslands that “greened up” as a result of summer rainfall. In C3-dominated environments (Great Lakes and Western Canada), seasonal variations were larger in mastodons than mammoths, possibly because the latter exploited a greater number of microhabitats, averaging plant and drinking water isotopic compositions. Mammoths and mastodons occupied different environmental niches, but both consumed a wide range of resources and regional differences were evident. Woolly mammoths in Old Crow delayed the initiation of weaning relative to modern elephants, perhaps as a defensive adaptation to the increased predation risk and decreased food quality/quantity during long hours of winter darkness at this high latitude location. Potential consequences of delayed weaning, such as longer inter-birth intervals and greater maternal energy investments, may have increased the population’s vulnerability to climatic stress or human hunting. Isotope results for Clovis mammoths in the San Pedro Valley are consistent with a relatively warm and dry climate, but do not indicate severe drought. Regional differences in δ13C values of proboscideans from C3-dominated environments were minimal, but variations in δ15N may be related to spruce abundances and/or aridity. Latitudinal variations in proboscidean δ18O values correlate well with modern meteoric water isotope compositions, which indicates their potential for reconstructing past paleoclimatic conditions

Thin Film Charged Particle Trackers

Silicon tracking detectors have grown to cover larger surface areas up to hundreds of square meters, and are even taking over other sub-detectors, such as calorimeters. However, further improvements in tracking detector performance are more likely to arise from the ability to make a low mass detector comprised of a high ratio of active sensor to dead materials, where dead materials include electrical services, cooling, mechanical supports, etc. In addition, the cost and time to build these detectors is currently large. Therefore, advancements in the fundamental technology of tracking detectors may need to look at a more transformative approach that enables extremely large area coverage with minimal dead material and is easier and faster to build. The advancement of thin film fabrication techniques has the potential to revolutionize the next-to-next generation of particle detector experiments. Some thin film deposition techniques have already been developed and widely used in the industry to make LED screens for TV's and monitors. If large area thin film detectors on the order of several square meters can be fabricated with similar performance as current silicon technologies, they could be used in future particle physics experiments. This paper aims to review the key fundamental performance criteria of existing silicon detectors and past research to use thin films and other semi-conductor materials as particle detectors in order to explore the important considerations and challenges to pursue thin film detectors.Comment: 32 pages, 15 figure

Collaborative stewardship in multifunctional landscapes: Toward relational, pluralistic approaches

Landscape stewardship offers a means to put social-ecological approaches to stewardship into practice. The growing interest in landscape stewardship has led to a focus on multistakeholder collaboration. Although there is a significant body of literature on collaborative management and governance of natural resources, the particular challenges posed by multifunctional landscapes, in which there are often contested interests, require closer attention. We present a case study from South Africa to investigate how collaborative stewardship can be fostered in contested multifunctional landscapes. We conducted this research through an engaged transdisciplinary research partnership in which we integrated social-ecological practitioner and academic knowledge to gain an in-depth understanding of the challenges of fostering collaboration. We identified five overarching factors that influence collaboration: contextual, institutional, social-relational, individual, and political-historical. Collaborative stewardship approaches focused on the development of formal governance institutions appear to be most successful if enabling individual and social-relational conditions are in place. Our case study, characterized by high social diversity, inequity, and contestation, suggests that consensus-driven approaches to collaboration are unlikely to result in equitable and sustainable landscape stewardship in such contexts. We therefore suggest an approach that focuses on enhancing individual and social-relational enablers. Moreover, we propose a bottom-up patchwork approach to collaborative stewardship premised on the notion of pluralism. This would focus on building new interpersonal relationships and collaborative capacity through small collective actions. Taking a relational, pluralistic approach to fostering collaborative stewardship is particularly important in contested, socially heterogeneous landscapes. Drawing on our study and the literature, we propose guiding principles for implementing relational, pluralistic approaches to collaborative stewardship and suggest future research directions for supporting such approaches

Taxonomy, location of origin, and health status of proboscideans from Western Canada investigated using stable isotope analysis

We investigated the application of stable isotope analysis of proboscidean remains (collagen in bone/dentin/cementum and structural carbonate in enamel bioapatite) for genus-level identification of isolated specimens, assessment of geographic origins, and testing for nutritional stress. Mammoths (Mammuthus sp.) tended to have higher δ15Ncol and lower δ13Ccol than mastodons (Mammut americanum), but differences were not significant in every location. Determining the genus of isolated specimens may be possible for locations and time periods with good isotopic baselines, but environmental changes can confound interpretations. For example, an Alberta proboscidean with a δ15Ncol of +1.4‰ (characteristic of mastodons) ultimately proved to be a mammoth. Its surprisingly low nitrogen isotope composition is attributable to the recently deglaciated environment it inhabited. We provided a baseline for isotopic assessment of geographic origins of isolated proboscideans in Western Canada. Bioapatite δ13Csc and δ18Osc can be used to distinguish specimens from Alberta, Klondike, Old Crow, Herschel Island, and further south (e.g., Arizona, Great Lakes). Finally, we found that an Alberta mammoth with morphological evidence of nutritional stress experienced a change in diet, environment, or physiology prior to death, but its isotopic compositions did not suggest a link to hypothesized starvation (catabolism of proteins or reliance on lipids)

AstroPix: Investigating the Potential of Silicon Pixel Sensors in the Future of Gamma-ray Astrophysics

This paper details preliminary photon measurements with the monolithic silicon detector ATLASPix, a pixel detector built and optimized for the CERN experiment ATLAS. The goal of this paper is to determine the promise of pixelated silicon in future space-based gamma-ray experiments. With this goal in mind, radioactive photon sources were used to determine the energy resolution and detector response of ATLASPix; these are novel measurements for ATLASPix, a detector built for a ground-based particle accelerator. As part of this project a new iteration of monolithic Si pixels, named AstroPix, have been created based on ATLASPix, and the eventual goal is to further optimize AstroPix for gamma-ray detection by constructing a prototype Compton telescope.The energy resolution of both the digital and analog output of ATLASPix is the focus of this paper, as it is a critical metric for Compton telescopes. It was found that with the analog output of the detector, the energyresolution of a single pixel was 7.69 +/- 0.13% at 5.89 keV and 7.27 +/- 1.18% at 30.1 keV, which exceeds the conservative baseline requirements of 10% resolution at 60 keV and is an encouraging start to an optimistic goal of<2% resolution at 60 keV. The digital output of the entire detector consistently yielded energy resolutions that exceeded 100% for different sources. The analog output of the monolithic silicon pixels indicates that thisis a promising technology for future gamma-ray missions, while the analysis of the digital output points to the need for a redesign of future photon-sensitive monolithic silicon pixel detectors.Comment: 12 pages, proceedings, International Society for Optics and Photonics (SPIE) Astronomical Telescopes and Instrumentation Digital Forum, Dec. 14-18 202

“Culture Is So Interspersed”: Child-Minders’ and Health Workers’ Perceptions of Childhood Obesity in South Africa

Introduction. Forty-one million children globally are overweight or obese, with most rapid rate increases among low- and middle-income nations. Child-minders and health workers play a crucial role in obesity prevention efforts, but their perceptions of childhood obesity in low- and middle-income countries are poorly understood. This study aims to (1) explore child-minders and health workers’ perceptions of the causes, consequences, potential strategies, and barriers for childhood obesity prevention and intervention in Cape Town, South Africa and (2) to provisionally test the fit of a socioecological framework to explain these perceptions. Methods. Twenty-one interviews were recorded, transcribed, and analyzed through analytic induction. Results. Participants identified multilevel factors and contexts, as well as potential consequences and priorities of interest in addressing childhood obesity. An adapted childhood obesity perceptions model was generated, which introduces an overarching cultural dimension embedded across levels of the socioecological framework. Conclusions. Culture plays a pivotal role in explaining obesogenic outcomes, and the results of this study demonstrate the need for further research investigating how obesity perceptions are shaped by cultural frames (e.g., social, political, and historical). Understanding the causes, consequences, and potential interventions to address obesity through a cultural lens is critical for promoting health in low- and middle-income nations

Identifying gene network patterns and associated cellular immune responses in children with or without nut allergy

Background: Although evidence suggests that the immune system plays a key role in the pathophysiology of nut allergy, the precise immunological mechanisms of nut allergy have not been systematically investigated. The aim of the present study was to identify gene network patterns and associated cellular immune responses in children with or without nut allergy. Methods: Transcriptome profiling of whole blood cells was compared between children with and without nut allergy. Three genes were selected to be validated on a larger cohort of samples (n = 86) by reverse transcription-polymerase chain reactions (RT-qPCR). The composition of immune cells was inferred from the transcriptomic data using the CIBERSORTx algorithm. A co-expression network was constructed employing weighted gene co-expression network analysis (WGCNA) on the top 5000 most variable transcripts. The modules were interrogated with pathway analysis tools (InnateDB) and correlated with clinical phenotypes and cellular immune responses. Results: Proportions of neutrophils were positively correlated and CD4+ T-cells and regulatory T-cells (Tregs) were negatively correlated with modules of nut allergy. We also identified 2 upregulated genes, namely Interferon Induced With Helicase C Domain 1 (IFIH1), DNA damage-regulated autophagy modulator 1 (DRAM1) and a downregulated gene Zinc Finger Protein 512B (ZNF512B) as hub genes for nut allergy. Further pathway analysis showed enrichment of type 1 interferon signalling in nut allergy. Conclusions: Our findings suggest that upregulation of type 1 interferon signalling and neutrophil responses and downregulation of CD4+ T-cells and Tregs are features of the pathogenesis of nut allergy

AstroPix: novel monolithic active pixel silicon sensors for future gamma-ray telescopes

Space-based gamma-ray telescopes such as the Fermi Large Area Telescope have used single sided silicon strip detectors to track secondary charged particles produced by primary gamma-rays with high resolution. At the lower energies targeted by keV-MeV telescopes, two dimensional position information within a single detector is required for event reconstruction - especially in the Compton regime. This work describes the development of monolithic CMOS active pixel silicon sensors - AstroPix - as a novel technology for use in future gamma-ray telescopes. Based upon sensors (ATLASPix) designed for use in the ATLAS detector at the Large Hadron Collider, AstroPix has the potential to maintain high performance while reducing noise with low power consumption. This is achieved with the dual detection and readout capabilities in each CMOS pixel. The status of AstroPix development and testing, as well as outlook for future testing and application, will be presented