Strontium (Sr) is an element naturally present in the human skeleton and is acquired through dietary means. Exposure to strontium has been linked to both harmful and beneficial effects on skeletal health. Recently, the administration of strontium has been shown to induce a therapeutic effect of increasing bone strength and bone mineral density in women suffering from post-menopausal osteoporosis. The advent of this new therapy has warranted the continued development of an energy dispersive x-ray fluorescence (EDXRF) system that may be used as a diagnostic tool for non-invasive measuring and monitoring of in vivo bone strontium levels. This device is currently housed at McMaster University and has been previously optimized to measure bone strontium in vivo. One shortcoming with this system is the inability to quantify absolute amounts of bone strontium in vivo due to Sr x-ray absorption by soft-tissue overlying bone. This work describes an attempt to examine several imaging modalities to determine which modality may provide overlying tissue thickness readings with an acceptable range of accuracy to correct for Sr x-ray absorption. A performance comparison between magnetic resonance imaging, x-ray computed tomography, 8, 25 and 55 MHz ultrasound, in estimating the tissue thickness of seven cadaver fingers, illustrated that 55 MHz ultrasound provided a superior range of accuracy at 3.2%. It further indicated that the currently used 8 MHz ultrasound may be used to accurately estimate tissue thickness, though with a diminished accuracy of 6.6%. EDXRF measurements were performed on cadaver fingers ex vivo. Analysis of results indicated that quantification might be achieved if signals are normalizated to the 35 keV coherent scatter peak and correction of both soft-tissue absorption of Sr x-rays and differences in 125I excitation source activity are carried out. Four EDXRF measurements were performed on a strontium citrate supplemented individual starting six months after Sr medicating had begun. Analysis of strontium levels revealed that bone strontium was already at a plateau by the first measurement and that these levels did not change in the 6 months following. / Thesis / Master of Science (MSc)

Approximately 80% of Virginians with private drinking water (PDW) sources are unaware of the quality of their drinking water. Strontium is a water quality contaminant gaining recognition at the federal level. At concentrations >1.5 mg/L, strontium substitutes calcium in the bones leading to bone density disorders (e.g. rickets). This is particularly problematic for children and individuals with low calcium and low protein diets. Because most Virginians do not know the quality of their PDW and since strontium poses a public health risk, this study investigates the sources of strontium in PDW in Virginia and identifies the areas and populations most vulnerable. Physical factors such as rock type, rock age, and fertilizer use have been linked to elevated strontium concentrations in drinking water. Meanwhile, social factors such as poverty, poor diet, and adolescence also increase social vulnerability to health impacts of strontium. Thus, this study identifies both physically and socially vulnerable regions in Virginia using water quality data from the Virginia Household Water Quality Program and statistical and spatial analyses conducted in RStudio 1.0.153 and ArcMap 10.5.1. Physical vulnerabilities were highest in the Ridge and Valley province where geologic formations with high strontium concentrations (e.g., limestone, dolomite, sandstone, and shale) are the dominant the aquifer rocks. The complex relationship between agricultural land use and strontium concentrations made it difficult to determine the impact of fertilizer use on strontium concentrations in PDW in Virginia. In general, the spatial distribution of social vulnerability factors was distinct from physical factors with the exception of food deserts. This study provides information and analysis to help residents of Virginia understand their risk of strontium exposure in PDW. / Master of Science / There are 1.7 million residents in Virginia that rely on private drinking water supplies in their homes. Those individuals are responsible for knowing how often to test their water, what to test their water for, and how to treat their water, if needed, to achieve safe drinking standards. Unfortunately, approximately 80% of Virginians with private drinking water sources (e.g., wells, cisterns, and springs) do not know if their water is safe to drink. Strontium, an element closely related to calcium, is a contaminant that the federal government recognizes as dangerous because in high quantities (>1.5 mg/L of water) it can replace calcium in bones making them brittle (e.g. rickets). These health impacts are more extreme in children and individuals with low calcium and low protein diets. Since strontium poses a public health risk, this study identified areas and populations in Virginia that have higher chances of being exposed to strontium and higher chances of their health being impacted by high levels of strontium. Physical factors such as rock type, rock age, and fertilizer use have been linked to elevated strontium concentrations in drinking water, indicating various physical vulnerabilities. Meanwhile, social factors such as poverty, poor diet, and adolescence also increase social vulnerability to the health impacts of strontium. This paper investigates regions in Virginia that are likely to contain high strontium levels and thus potential health impacts from strontium. Statistical and spatial analyses of water quality data from Virginia Cooperative Extension’s Virginia Household Water Quality Program combined with risk factor data identified vulnerable areas in Virginia. The highest chance of exposure was in counties near the western border of the state (e.g., Augusta, Fredrick, Highland, Montgomery, Shenandoah, and Wythe) due to the presence of limestone, dolomite, sandstone, and shale, all of which naturally contain high amounts of strontium. The land use data indicated that there were no strong patterns of strontium occurrence relative to fertilizer use. In general, the spatial distribution of social vulnerability factors was distinct from physical factors with the exception of food deserts occurring at high rates in the same areas as the samples with high strontium levels (e.g., Augusta, Fredrick, Highland, Montgomery, Shenandoah, and Wythe). The presence of food deserts prevents individuals from obtaining a high calcium and high protein diet, which makes them more vulnerable to the impacts of strontium. Overall, this study can help people in Virginia who are not on public water systems understand their risk of from being exposed to strontium.

The detection of dairying is essential to understand prehistoric economies, particularly in northwest Europe, where a high degree of lactose tolerance implies that fresh milk has long been a significant dietary component. Domestic cattle (Bos taurus) are biologically able to breed year-round, potentially enabling farmers to select a calving strategy to suit their economic focus. Published literature and interviews with farmers suggests that spring calving would have been favoured by economies focussed on meat or storable dairy products, whereas the year-round provision of fresh milk would have required two calving seasons, in spring and autumn, or an extended period through spring, summer and autumn. This thesis uses intra-tooth isotope ratio analysis of cattle tooth enamel to predict birth seasonality as an indicator of dairying. Analysis was performed on first, second and third cattle molars from the archaeological sites of Mine Howe, Pool and Earl’s Bu (Iron Age and Viking period Orkney), Old Scatness (Iron Age Shetland) and Grimes Graves (Bronze Age Norfolk). Modern molars from Chillingham Wild White cattle were also analysed. A new method to determine cattle birth seasonality has been proposed utilising the isotopic patterning (δ13C, δ18O) recorded within first and second molar enamel. Results suggest that birth seasonality estimates are of sufficient accuracy to discriminate between single-and multiple-season calving. Although Pool and Grimes Graves have been interpreted as dairying sites from their age-at-death slaughter patterns, birth seasonality predictions imply an economy focussed on year-round fresh milk at Pool but an emphasis on storable dairy products at Grimes Graves. In addition, it has been demonstrated that intra-tooth enamel data can provide information regarding sub-annual variation in diet and environment. A new method to investigate weaning strategy has also been proposed.

No / The adventus Saxonum is a crucial event in English protohistory. Scholars from a range of disciplines dispute the scale and demographic profile of the purported colonizing population. The 5th-7th century burial ground at West Heslerton, North Yorkshire, is one of the few Anglian cemeteries where an associated settlement site has been identified and subjected to extensive multidisciplinary postexcavation study. Skeletal and grave good evidence has been used to indicate the presence of Scandinavian settlers. A small, preliminary study using lead and strontium isotope analysis of tooth enamel, mineralized in early childhood, from Neolithic/Early Bronze Age (n = 8), Iron Age (n = 2), and Early Anglo-Saxon (n = 32) skeletons, was carried out to directly investigate this hypothesis. Results suggest that lead provides dissimilar types of information in different time periods. In post-Roman England, it appears to reflect the level of exposure to circulated anthropogenic rather than natural geological lead, thus being a cultural rather than geographical marker. Consequently, only strontium provides mobility evidence among the Anglian population, whereas both isotope systems do so in pre-Roman periods. Strontium data imply the presence of two groups: one of local and one of nonlocal origin, but more work is required to define the limits of local variation and identify immigrants with confidence. Correlations with traditional archaeological evidence are inconclusive. While the majority of juveniles and prehistoric individuals fall within the local group, both groups contain juveniles, and adults of both sexes. There is thus no clear support for the exclusively male, military-elite invasion model at this site.

Yes / The Early Bronze Age round barrows at Irthlingborough, Northamptonshire and Gayhurst, Buckinghamshire contained remarkably large quantities of cattle (Bos taurus) remains. At Irthlingborough, at least 185 skulls with smaller numbers of mandibles, shoulder blades and pelves were found together with a small number of skeletal elements from aurochs (Bos primigenius). In contrast, the remains from Gayhurst are dominated by the limb bones from more than 300 animals. This study employed strontium isotope ratio analysis of cattle tooth enamel from 15 cattle and one aurochs to investigate the diversity of the animals’ origins at both sites and provide insights into Early Bronze Age funerary practices. Although strontium results show that most of the cattle and the aurochs included in this study were consistent with local origins, one animal from each barrow was born remotely, most likely in western Britain. In addition, a second Gayhurst animal was consistent with origins in a region of chalk rather than the local Jurassic sediments.

Chalcogenide perovskites with a distorted ABX3 structure (A: Ca, Ba, Sr; B: Zr, Hf; X: S, Se) are a prominent focus in optoelectronic materials. One of these is BaZrS3 which has garnered significant attention in perovskite materials due to its distinctive distorted perovskite structure and valuable optical properties that are viable for a single-junction solar cell and present a compelling option for tandem solar cell configurations. Another promising material is SrZrS3 which exists in two phases: needle-like non-perovskite α-SrZrS3 and distorted perovskite β-SrZrS3. The distorted perovskite phase shows promising luminescence properties in bulk, making it potentially viable for LED applications. In this work, we show that the non-perovskite α-SrZrS3 was accessed through colloidal synthesis at 330 °C and 365 °C by increasing concentrations of precursors. In order to favor the perovskite phase, we conducted alloying experiments incorporating varying percentages of doped Sr2+ into BaZrS3 to first synthesize a distorted perovskite Ba(1-x)SrxZrS3. Through varying percentages and varying reaction conditions such as temperature, time of reaction, and doping concentrations, we aim to optimize the synthesis of colloidal Ba(1-x)SrxZrS3 nanocrystals.

<div>Understanding grain growth in dielectric ceramics is essential to controlling the electrical and mechanical properties necessary to produce ceramic capacitors and sensors. The effect of alloying barium titanate with strontium titanate on the equilibrium crystal shape was investigated in order to determine possible impacts on grain growth. The equilibrium crystal shape was studied through three experimental methods to identify possible changes in grain boundary energy or anisotropy with changing composition.</div><div>The first method was by imaging intergranular pores to observe faceting behavior and relative interfacial energies. Intergranular pores were reconstructed to determine the relative surface energies of the identified facets. The second method was to perform atomic force microscopy on surface facets to collect topography data. The topography data was combined with orientation data obtained by EBSD analysis from the same region, and used to calculate the normal vector of the surface facets. These datasets were plotted in a stereographic projection to study the faceting anisotropy. The third method involved collecting EBSD orientation data and images of surface faceting behavior. The surface faceting behavior of each grain was categorized by type of facet and plotted on a stereographic projection at the corresponding orientation. This allowed for the analysis of faceting transitions and the differentiation of faceted and continuous regions of the equilibrium crystal shape. The analysis of faceting behavior across compositions has implications on grain growth of the barium titanate/strontium titanate system.</div>

Le Strontium 90 (90Sr) est un radionucléide d’origine anthropogénique, relâché en grandes quantités dans l’environnement à la suite d’essais nucléaires aériens ou d’accidents d’installations nucléaires. Le 90Sr persiste à long terme dans l’environnement, ce qui conduit à la contamination chronique par ingestion de populations des territoires contaminés. L’induction de tumeurs osseuses liées à la fixation du 90Sr a été largement décrite. Par contre, l’occurrence d’effets non cancéreux est beaucoup moins connue. Nous avons utilisé un modèle murin avec une contamination chronique par ingestion d’eau contenant 20 kBq/l de 90Sr. Une étude de biocinétique a confirmé l’accumulation de 90Sr dans les os, avec un taux d’accumulation plus rapide durant la croissance osseuse. Cette accumulation est plus élevée dans les os des femelles que chez les males. Les doses absorbées au corps entier varient de 0.33 ± 0.06 mGy (naissance) à 10.6 ± 0.1 mGy (20 semaines). La dose au squelette peut aller jusqu’à 55 mGy. L’ingestion de 90Sr induit une modification de l’expression des gènes impliqués induisant à un déséquilibre favorisant la résorption osseuse, mais sans répercussion sur la morphologie de l’os. Aucun effet majeur n’a été observé pour le système hématopoïétique. Par contre, des modifications mineures du système immunitaire ont été observées. Afin d’évaluer la fonctionnalité du système immunitaire, un test de vaccination avec les antigènes TT et KLH a été utilisé. Les résultats montrent chez les animaux contaminés une diminution significative de la production d’immunoglobulines spécifiques, une modification de la balance Th1/Th2 dans la rate et une différenciation lymphoïde B perturbée. Ces résultats permettent de mieux comprendre certaines des conséquences non cancéreuses de l’exposition chronique à faible dose à des radionucléides à demi-vie longue pouvant être rejetés accidentellement. / Strontium 90 (90Sr) is a radionuclide of anthropogenic origin released in large quantities in the environment as a result of nuclear atmospheric tests or accidents at nuclear facilities. 90Sr persists on a long-term basis in the environment, leading to chronic contamination by ingestion of populations living on contaminated territories. The induction of bone tumours associated with the fixation of 90Sr has been widely described. However, the occurrence of non-cancer effects is much less known. We used a mouse model with chronic contamination by ingestion of water containing 20 kBq/l of 90Sr. A biokinetic study confirmed the accumulation of 90Sr in the bones, with an increased rate of accumulation during bone growth. This accumulation was higher in the bones of females than in males. The whole-body absorbed doses ranged from 0.33 ± 0.06 mGy (birth) to 10.6 ± 0.1 mGy (20 weeks). The absorbed dose for the skeleton was up to 55 mGy. Ingestion of 90Sr induced a change in the expression of genes inducing an imbalance in favour of bone resorption, but without effect on bone morphology. No significant effect was observed for the hematopoietic system. On the other hand, minor modifications were observed for the immune system. To evaluate the functionality of the immune system, a vaccination test with TT and KLH antigens was used. Results showed in contaminated animals a significant decrease in the production of specific immunoglobulins, changes in the Th1/Th2 balance in the spleen and a disrupted B lymphocyte differentiation. These results improve the understanding of some of the non-cancerous consequences of chronic exposure at low dose of radionuclides with a long half-life, which can be accidentally released.

Cette thèse se décompose en deux parties.Dans la première, nous nous intéressons au premier champ critique, Hc1, du titanate de strontium, que nous mesurons à l’aide d’un réseau de microsondes de Hall taillées dans un gaz bidimensionnel. La valeur du premier champ critique nous permet alors d’évaluer la densité superfluide à six différents dopages couvrant l’ensemble du dôme supraconducteur. À bas dopage, nous trouvons que celle-ci correspond à la densité de porteurs dans l’état normal tandis qu’au-delà du dopage optimal, celle-ci chute drastiquement. En plaçant nos résultats dans le contexte de la loi de Homes, nous voyons que cette chute s’explique par l’entrée dans la limite sale. Un fit multibande de Hc1(T), dans ce contexte semble également indiquer que la supraconductivité émerge de la bande la plus basse et est seulement induite dans les deux autres bandes.Dans la seconde partie, nous regardons l’évolution de la densité de porteurs, n, du cuprate Nd-LSCO. Nous mesurons ainsi six échantillons de dopages proches du point critique pseudogap, p*, via trois sondes de transport : effet Hall, résistivité et effet Seebeck. Nous trouvons que n chute de 1+p à p à l’entrée dans la phase pseudogap. En comparant les différentes sondes, nous montrons que cette chute est due à une reconstruction de la surface de Fermi et qu’il existe sûrement des poches d’électrons et de trous juste en dessous de p*. Ceci est en accord, entre autres, avec un scénario antiferromagnétique. Finalement, nous trouvons que la mobilité est inchangée à l’entrée dans la phase pseudogap et que les mesures de transports semblent insensibles à la divergence de la masse effective vue par chaleur spécifique. / This thesis consists of two parts.The first one is about the lower critical field of strontium titanate, measured thanks to an array of Hall micro-probes tailored in a 2D electron gas. The value of the lower critical field allows us to quantify superfluid density at six different dopings spreading all along the superconducting dome. At low doping, we find that it follows the normal state carrier density while it dramatically falls above optimal doping. Analyzing our results in the context of the Homes law, we understand that this drop is due to the entering into the dirty limit. A multiband fit Hc1(T) in this context seems to indicate that superconductivity is born in the lowest band and only induced in the two others.In the second part, we focus on the carrier density, n, of the cuprate Nd-LSCO. We measure six samples with doping close to the pseudogap critical point p*, thanks to three different transport probes : Hall effect, resistivity and Seebeck effect. We find that entering the pseudogap phase induces a drop in n from 1+p to p. The comparison of the different probes shows that this drop is due to a Fermi surface reconstruction and that both holes and electrons pockets may exist just under p*. This observation is consistent with an antiferromagnetic scenario. Finally, we find that mobility is not affected by the pseudogap and that transport measurements seems insensitive to the diverging effective mass as observed by specific heat.

Thesis (M.S.)--University of Alabama at Birmingham, 2008. / Description based on contents viewed May 30, 2008; title from title screen. Includes bibliographical references (p. 50-51).