abstract: Growth of the Phoenix metropolitan area led to exposures of the internal bedrock structure of surrounding semi-arid mountain ranges as housing platforms or road cuts. Such exposures in the Sonoran and Mojave deserts reveal the presence of sedimentary calcium carbonate infilling the pre-existing fracture matrix of the bedrock. Field surveys of bedrock fractures filled with carbonate (BFFC) reveal an average of 0.079 +/- 0.024 mT C/m2 stored in the upper 2 m of analyzed bedrock exposures. Back-scattered electron microscopy images indicate the presence of carbonate at the micron scale, not included in this estimation. Analysis of the spatial extent of bedrock landforms in arid and semi-arid regions worldwide suggests that ~1485 GtC could potentially be stored in the upper 2 m horizon of BFFCs. Radiocarbon dating obtained at one of the sites indicates it is likely that some of the carbonate was flushed into the bedrock system during glacial wet pulses, and is stored on Pleistocene timescales or longer. Strontium isotope analysis at the same site suggest the potential for a substantial cation contribution from weathering of the local bedrock, indicating the potential exists for sequestration of atmospheric carbon in BFFCs. Rates of carbon release from BFFCs are tied to rates of erosion of bedrock ranges in desert climates. / Dissertation/Thesis / M.A. Geography 2013

The Newmarket Till is a regional aquitard in southern Ontario that overlies the Illinoian to Middle Wisconsinan Lower Sediments and is overlain by the Oak Ridges Moraine (ORM). Geological investigations have mapped the distribution of the till and it is understood that erosional channels, subsequently infilled with fluvial material, breach the till and may create enhanced hydraulic connection between overlying and underlying aquifers. However, little is known about the protective capability of the Newmarket Till where it is intact. This study used natural tracers to assess the extent of transport in the aquitard-aquifer system. Stable isotopes of water (δ18O and δ2H) showed a depletion trend versus depth. In the Newmarket Till most of the samples had isotope ratios similar to meteoric water data from the nearest location (Egbert, ON). The depleted values of δ18O in the Thorncliffe Formation suggest a remnant signature of early-Holocene precipitation (-16‰ at the depth of 60 m). Elevated levels of NO3- and Cl- were detected near the surface and because of the low permeability aquitard (Newmarket Till), they could not migrate to depth. Total extractable ammonium concentrations are ranging from 4.09 ppm from near the surface to 60 ppm in the lowest part of the Newmarket and then gradually increase to 514 ppm in the bottom of the Thorncliffe Formation. The combination of high NH4+ values and organic carbon content in the Thorncliffe Formation suggests a natural source from mineralization of organic N. The fractionation which happened between δ15Nsediment and δ15N-NH4 may have three explanations: (1) lighter isotopes diffuse faster than heavier ones, so the higher rate of diffusion can cause fractionation; (2) heavier isotopes partition to exchange sites, causing fractionation along the transport pathway; (3) dissociation of NH4+ to NH3 under anaerobic condition. Positive values for δ13C in groundwater in the Thorncliffe Formation are likely due to i) a contribution of carbonate mineral dissolution, and ii) methanogenesis - the Archea favor the lighter isotope of C (12C). Methanogenesis, therefore, enriches the δ13C-DIC was enriched; however, the δ13C in dissolved organic carbon (DOC) is depleted. These geochemical characteristics demonstrate a long residence time for the porewater in the system and indicate that the Newmarket till inhibits recharge of recent precipitation, thereby providing protection to the underlying aquifers from surface-derived contaminants.

Willard Libby's development of carbon-14 dating at the University of Chicago immediately following World War II provided an unprecedented opportunity for the collaboration of archaeologists with a physical chemist. Libby's need for archaeological samples to test the dating process (1947-1951) meant that he relied upon the Committee on Radioactive Carbon 14, formed by the American Anthropological Association, for datable materials, as well as for assistance in all other archaeologically related aspects of the testing phase. The committee, under the leadership of archaeologist Frederick Johnson, served the mandated function of providing assistance to Libby, but simultaneously endeavored to utilize the new dating method to promote the development of the authority of anthropological professional organizations and further establish Americanist archaeology in a national and global context. Johnson's and the committee's approach to collaboration was informed by an understanding of opportunities provided by the postwar restructuring of the sciences. The purpose of the present study is to provide a history of the Committee on Radioactive Carbon 14 (1948-1952) as well as a to provide the context necessary to describe the bureaucratic and scientific goals of the committee. Frederick Johnson's career, and the manner in which it reflected general trends in twentieth century American anthropology, is discussed in detail, and utilized to present an explanation of his actions as committee chair. Willard Libby's development of carbon-14 dating is also discussed in detail, particularly in regard to his request for assistance from the archaeological community and subsequent collaborative work. The undeniable influence of carbon-14 dating on archaeological practice worldwide, and Libby's acceptance of the Nobel Prize in Chemistry (1960) for his development of the dating method, has provided reason enough for a plethora of articles and book length studies regarding carbon-14 dating. Yet, little has been written about the Committee on Radioactive Carbon 14 and its place in an analysis of the bureaucratic and collaborative science of the American mid-century. It is for this reason that the present study was undertaken.

No description available.

Thesis (S.M.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 49-50). / The focus of this thesis is the design and development of a system for rapid extraction of dissolved inorganic carbon from seawater and groundwater samples for radiocarbon dating. The Rapid Extraction of Dissolved Inorganic Carbon System (REDICS) consists of two subsystems - one for sample introduction, acidification, and carbon dioxide extraction, and one for carbon dioxide quantification and storing. The first subsystem efficiently extracts the dissolved inorganic carbon from the water sample in the form of carbon dioxide by utilizing a gas-permeable polymer membrane contractor. The second subsystem traps, quantifies and stores the extracted gas using cryogenics. The extracted carbon dioxide is further processed for stable and radiocarbon isotope analysis at the National Ocean Sciences Accelerator Mass Spectrometer Facility at the Woods Hole Oceanographic Institution. The REDICS system was tested using seawater standards collected at 470m and 4000m depth in the Atlantic Ocean and analyzing the extracted CO₂. The results were compared to the results for the same standards processed on the current NOSAMS water stripping line. The results demonstrate that the system successfully extracts more than 99% of the dissolved inorganic carbon in less than 20 minutes. Stable isotope and radiocarbon isotope analyses demonstrated system precision of 0.02%c and 3.5% respectively. / by Kalina Doneva Gospodinova. / S.M.

The sequence of timber circle - henge monument - stone circle is widely accepted. This is in spite of the reality that the datable evidence and contextual data upon which this series is based has seldom been subjected to any real form of critical evaluation. The aim of this research was to determine whether this order could still be deemed tenable in light of contemporary research and the continued advances that have been achieved relating to the application of radiocarbon dating. The findings of this study demonstrated that sufficient contextual data exists to enable phases of construction to be identified. However rarely did these data appear to support the currently accepted chronologies. Indeed more commonly they alluded to an alternative series, one that demonstrated how some individual site sequences may have been previously misinterpreted. This study has also proven how methodological and interpretative weaknesses, relating to the use of radiocarbon dating, have created a quantifiable degree of accuracy between individual radiocarbon determinations and their ability to be reliably associated with the event or act that they have been used to date. These findings have not only cast sufficient doubt upon the reliability of the currently accepted chronologies for these three monumental forms but have also alluded to the existence of a far more appropriate sequence that conforms to the overall conclusions of this review far more convincingly. Accordingly a new series of timber circle(s) - stone circle - henge monument is proposed by this study.

T cell immunity is crucial for human survival, coordinating responses to new pathogens and establishing immune memory in early life, and, in later life, maintaining immune homeostasis through immune and tumor surveillance. A lifetime of exposure to diverse antigens through infections and vaccination generate memory T cells that can persist for decades in the absence of antigenic re-exposure and comprise the predominant T cell subset throughout adult life. These memory T cells are susceptible to repeated stimulation over time due to chronic infections, and with age, T cells undergo dynamic alterations that are associated with immunodeficiency. Studies of memory T cell persistence and aging mostly sample peripheral blood while the majority of T cells, particularly tissue-resident memory T cells (TRM), are maintained in diverse tissues, including lymphoid and mucosal sites, where they mediate frontline protection. The longevity, maintenance, and age-associated changes of T cells across these key sites remain unknown and are important for developing age-targeted strategies for immune modulation. Utilizing our human tissue resource through a collaboration with LiveOnNY, a local organ procurement organization, we presented a comprehensive analysis of human T cell subset dynamics and aging in blood and tissue samples obtained from 88 organ donors over 10 decades of life. We revealed that T cell tissue localization and subset are factors that influence the phenotypic, functional, and epigenetic changes observed over age. Using retrospective radiocarbon (14C) birth dating and assessment of cellular turnover, we showed that T cells across blood and tissues are maintained through continuous turnover. However, within tissues, histological and flow cytometric analyses demonstrated age-associated structural changes, regression, and senescence in lymphoid but not in mucosal organs. We observed differential expression of proliferation marker Ki67 and senescence markers between T cell subsets, with CD8+ TRM having the lowest expression of these markers compared to circulating TEM and TEMRA, suggesting that TRM may undergo less turnover for their maintenance. Epigenetic analysis revealed comparable age-associated loss in global DNA methylation for CD8+ TEM and TRM cells but increased epigenetic regulation of gene expression over age for TRM cells. Paired with transcriptomic analysis, we observed inverse correlation between promoter DNA methylation and gene expression at genes related to T cell differentiation, homing, survival, regulation, and effector function, predominantly in TRM. Our results provide compelling evidence for continuous turnover for T cells across the body but different aging phenotypes depending on tissue localization and/or T cell subset, with tissue residency potentially protecting T cells from senescent changes over age, and these findings may have implications in the design of effective age-targeted treatment and prevention strategies.

No / A log-coffin excavated in the early nineteenth century proved to be well enough preserved in the early twenty-first century for the full armoury of modern scientific investigation to give its occupants and contents new identity, new origins and a new date. In many ways the interpretation is much the same as before: a local big man buried looking out to sea. Modern analytical techniques can create a person more real, more human and more securely anchored in history. This research team shows how.

Yes / Precise chronologies underpin all aspects of archaeological interpretation and, in addition to improvements in scientific dating methods themselves, one of the most exciting recent developments has been the use of Bayesian statistical analysis to reinterpret existing information. Such approaches allow the integration of scientific dates, stratigraphy and typological data to provide chronologies with improved precision. Settlement period sites in Iceland offer excellent opportunities to explore this approach, as many benefit from dated tephra layers and AMS radiocarbon dates. Whilst tephrochronology is widely used and can provide excellent chronological control, this method has limitations; the time span between tephra layers can be large and they are not always present. In order to investigate the improved precision available by integrating the scientific dates with the associated archaeological stratigraphy within a Bayesian framework, this research reanalyses the dating evidence from three recent large scale excavations of key Viking Age and medieval sites in Iceland; Aðalstræti, Hofstaðir and Sveigakot. The approach provides improved chronological precision for the dating of significant events within these sites, allowing a more nuanced understanding of occupation and abandonment. It also demonstrates the potential of incorporating dated typologies into chronological models and the use of models to propose sequences of activities where stratigraphic relationships are missing. Such outcomes have considerable potential in interpreting the archaeology of Iceland and can be applied more widely to sites with similar chronological constraints. / British Academy (MD120020) awarded to C. Batt. Rannís PhD funding for M.Schmid. / The full text was made available at the end of the publisher's embargo.

Yes / In the present paper, the author offers new absolute and contextual dating evidence for Scottish archaeological pitchstone. Much archaeological pitchstone from the Scottish mainland is recovered from unsealed contexts of multi-period or palimpsest sites, and pitchstone artefacts from radiocarbon-dated pits therefore provide important dating evidence for this material group and its associated exchange network. In Scotland, all archaeological pitchstone derives from outcrops on the Isle of Arran, in the Firth of Clyde, and on the source island pitchstone-bearing assemblages include diagnostic types from the Mesolithic, Neolithic and Early Bronze Age period. Off Arran, pitchstone-bearing assemblages never include Mesolithic types, such as microliths, suggesting a post Mesolithic date. This suggestion is supported by worked pitchstone from radiocarbon-dated pits, where all presently available dates indicate that, on the Scottish mainland, Arran pitchstone was traded and used after the Mesolithic period, and in particular during the Early Neolithic period.