2,896 research outputs found
Radiocarbon and stable isotope evidence of dietary change from the Mesolithic to the Middle Ages in the iron gates: New results from Lepenski Vir
A previous radiocarbon dating and stable isotope study of directly associated ungulate and human bone samples from Late Mesolithic burials at Schela Cladovei in Romania established that there is a freshwater reservoir effect of approximately 500 yr in the Iron Gates reach of the Danube River valley in southeast Europe. Using the delta(15)N values as an indicator of the percentage of freshwater protein in the human diet, the C-14 data for 24 skeletons from the site of Lepenski Vir were corrected for this reservoir effect. The results of the paired C-14 and stable isotope measurements provide evidence of substantial dietary change over the period from about 9000 BP to about 300 BR The data from the Early Mesolithic to the Chalcolithic are consistent with a 2-component dietary system, where the linear plot of isotopic values reflects mixing between the 2 end-members to differing degrees. Typically, the individuals of Mesolithic age have much heavier delta(15)N signals and slightly heavier delta(13)C, while individuals of Early Neolithic and Chalcolithic age have lighter delta(15)N and delta(13)C values. Contrary to our earlier suggestion, there is no evidence of a substantial population that had a transitional diet midway between those that were characteristic of the Mesolithic and Neolithic. However, several individuals with "Final Mesolithic" C-14 ages show delta(15)N and delta(13)C values that are similar to the Neolithic dietary pattern. Provisionally, these are interpreted either as incomers who originated in early farming communities outside the Iron Gates region or as indigenous individuals representing the earliest Neolithic of the Iron Gates. The results from Roman and Medieval age burials show a deviation from the linear function, suggesting the presence of a new major dietary component containing isotopically heavier carbon. This is interpreted as a consequence of the introduction of millet into the human food chain
Charge-Focusing Readout of Time Projection Chambers
Time projection chambers (TPCs) have found a wide range of applications in
particle physics, nuclear physics, and homeland security. For TPCs with
high-resolution readout, the readout electronics often dominate the price of
the final detector. We have developed a novel method which could be used to
build large-scale detectors while limiting the necessary readout area. By
focusing the drift charge with static electric fields, we would allow a small
area of electronics to be sensitive to particle detection for a much larger
detector volume. The resulting cost reduction could be important in areas of
research which demand large-scale detectors, including dark matter searches and
detection of special nuclear material. We present simulations made using the
software package Garfield of a focusing structure to be used with a prototype
TPC with pixel readout. This design should enable significant focusing while
retaining directional sensitivity to incoming particles. We also present first
experimental results and compare them with simulation.Comment: 5 pages, 17 figures, Presented at IEEE Nuclear Science Symposium 201
Redfield ratios revisited: Removing the biasing effect of anthropogenic CO2
Redfield ratios of remineralization are calculated based on chemical data analysis on isopycnal surfaces. The concentrations of dissolved inorganic carbon used in this study were corrected for the anthropogenic CO2 content as estimated with a back-calculation technique. The corrections increased the apparent carbon remineralization by 25-30%, thus proving important for the reliable estimation of Redfield carbon ratios in the presence of anthropogenic CO2. Best estimates from this study largely confirm the more recently published Redfield ratios of remineralization. The following results were obtained for the latitude range 3-41°N along 20-29°W in the Northeast Atlantic Ocean: Corg: P ratio = 123 ± 10; Corg : N ratio = 7.2 ± 0.8; -O2 :Corg ratio = 1.34 ± 0.06; -O2 : P ratio = 165 ± 15; N: P ratio = 17.5 ± 2.0. These ratios are in close agreement with the average composition of phytoplankton and represent respiration of organic matter consisting on average of 52% protein, 36% polysaccharide, and 12% lipid
Contexts of diffusion: Adoption of research synthesis in Social Work and Women's Studies
Texts reveal the subjects of interest in research fields, and the values,
beliefs, and practices of researchers. In this study, texts are examined
through bibliometric mapping and topic modeling to provide a birds eye view of
the social dynamics associated with the diffusion of research synthesis methods
in the contexts of Social Work and Women's Studies. Research synthesis texts
are especially revealing because the methods, which include meta-analysis and
systematic review, are reliant on the availability of past research and data,
sometimes idealized as objective, egalitarian approaches to research
evaluation, fundamentally tied to past research practices, and performed with
the goal informing future research and practice. This study highlights the
co-influence of past and subsequent research within research fields;
illustrates dynamics of the diffusion process; and provides insight into the
cultural contexts of research in Social Work and Women's Studies. This study
suggests the potential to further develop bibliometric mapping and topic
modeling techniques to inform research problem selection and resource
allocation.Comment: To appear in proceedings of the 2014 International Conference on
Social Computing, Behavioral-Cultural Modeling, and Prediction (SBP2014
Effects of poisons and preservatives on the composition of organic matter in a sediment trap experiment
Fluxes and molecular compositions of a group of major biochemical classes (lipids, lignin, pigments, amino acids, and carbohydrates) were compared among sediment traps treated with different poisons and preservatives and deployed for 1–2 months in a coastal marine environment. Fluxes and compositions of biochemicals were significantly more variable than bulk particle fluxes and elemental compositions. This observation was attributed to a greater influence of dead zooplankton “swimmers” in treated traps rather than differences in microbial decomposition due to the various treatments. Molecular compositions, especially of lipids, confirm the influence of zooplankton swimmers on the biochemical composition of the particulate material in treated traps compared to untreated controls even when large swimmers had been removed. An inventory of the major biochemicals we measured accounted for 25–45% of the organic carbon in our samples, with amino acids and sugars making up the bulk (80–90%) of the identified carbon
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