Cosmic-Ray Positrons: Are There Primary Sources?

Cosmic rays at the Earth include a secondary component originating in collisions of primary particles with the diffuse interstellar gas. The secondary cosmic rays are relatively rare but carry important information on the Galactic propagation of the primary particles. The secondary component includes a small fraction of antimatter particles, positrons and antiprotons. In addition, positrons and antiprotons may also come from unusual sources and possibly provide insight into new physics. For instance, the annihilation of heavy supersymmetric dark matter particles within the Galactic halo could lead to positrons or antiprotons with distinctive energy signatures. With the High-Energy Antimatter Telescope (HEAT) balloon-borne instrument, we have measured the abundances of positrons and electrons at energies between 1 and 50 GeV. The data suggest that indeed a small additional antimatter component may be present that cannot be explained by a purely secondary production mechanism. Here we describe the signature of the effect and discuss its possible origin.Comment: 15 pages, Latex, epsfig and aasms4 macros required, to appear in Astroparticle Physics (1999

It's getting hot in here – Microcontextual study of a potential pit hearth at the Middle Paleolithic site of El Salt, Spain

By studying combustion structures, which conceal information about anthropogenic activity, we might learn about their makers. This is especially important for remote time periods like the Middle Paleolithic, whose archaeological record comprises numerous combustion structures. The majority of these are simple, flat, open hearths, although a small number of features situated in pit-like depressions have been recorded. Given that hearths built on a flat surface can result in pit-like color alteration of the underlying sediment, accurate identification of pit hearths is a crucial step prior to behavioral interpretation. Here we present a comprehensive study of a possible pit hearth from the Middle Paleolithic site of El Salt, Spain, using a microcontextual approach combining micromorphology, lipid biomarker analysis, archaeomagnetism and zooarchaeology. This pit hearth involves a true depression containing a thick plant ash deposit. It reached very high temperatures, possibly multiple burning events and long combustion times. Morphologically distinct combustion structures in a single archaeological context may indicate different functions and thus a diverse fire technology, pointing to Neanderthal behavioral variability.ERC Consolidator Grant project PALEOCHAR – 648871 https://erc.europa.eu/funding/consolidator-grants, I + D Project HAR2008-06117/HIST, HAR2015-68321-P (MINECO-FEDER/UE), and the Cultural Heritage Department of the Valencia Government and the Archaeological Museum Camil Visedo of Alcoy, under the direction of Professor Bertila Galván of Universidad de La Laguna, Junta de Castilla y León (project BU235P18), the European Fund for Economic and Regional Development (EFRD) and the project PID2019-105796 GB-I00 of the Agencia Estatal de Investigación (AEI/10.13039/501100011033

Influence of handaxe size and shape on cutting efficiency: a large-scale experiment and morphometric analysis

Handaxes represent one of the most temporally enduring and geographically widespread of Palaeolithic artifacts and thus comprised a key technological strategy of many hominin populations. Archaeologically observable variation in the size (i.e., mass) and shape properties of handaxes has been frequently noted. It is logical to ask whether some of this variability may have had functional implications. Here, we report the results of a large-scale (n = 500 handaxes) experiment designed to examine the influence of variation in handaxe size and shape on cutting efficiency rates during a laboratory task. We used a comprehensive dataset of morphometric (size-adjusted) shape variables and statistical methods (including multivariate methods) to address this issue. Our first set of analyses focused on handaxe mass/size variability. This analysis demonstrated that, at a broad-scale level of variation, handaxe mass may have been free to vary independently of functional (cutting) efficiency. Our analysis also, however, identified that there will be a task-specific threshold in terms of functional effectiveness at the lower end of handaxe mass variation. This implies that hominins may have targeted design forms to meet minimal (task-specific) thresholds, and may also have managed handaxe reduction and discard in respect to such factors. Our second set of analyses focused on handaxe shape variability. This analysis also indicated that considerable variation in handaxe shape may occur independently of any strong effect on cutting efficiency. We discuss how these results have several implications for considerations of handaxe variation in the archaeological record. At a general level, our results demonstrate that variability within and between handaxe assemblages in terms of their size and shape properties will not necessarily have had immediate or strong impact on their effectiveness when used for cutting, and that such variability may have been related to factors other than functional issues

Use-alteration of pottery: An ethnoarchaeological and experimental study.

Archaeologists rely heavily on pottery data to make inferences about the past. Although a critical component of such inferences is knowing how the pots were used, archaeologists at present cannot reconstruct accurately pottery function. This research provides the means whereby actual pottery use can be determined from traces that remain on pots. The study focuses on an analysis of nearly 200 vessels collected in the Kalinga village of Guina-ang. Traces, in the form of organic residues, attrition, and carbon deposits, are linked to pottery use activities observed in Kalinga households. The analysis of organic residue focuses on fatty acids absorbed into the vessel wall; samples are taken from Kalinga cooking pots and several types of food. It is found that rice cooking pots can be discriminated from vegetable/meat cooking pots, though individual plant species cannot be distinguished in the latter. In several cases, however, there is conclusive evidence for meat cooking. An analysis of Kalinga "archaeological" sherds was also performed to look at fatty acid preservation. A pottery attrition analysis, similar to the study of lithic use-wear, is also performed on Kalinga pottery. The objective is to understand the general principles in the formation of an attritional trace. Nine areas on Kalinga cooking vessels are found to have attritional patches. The two forms of Kalinga cooking vessels could be discriminated based on attrition. Carbon deposits reflect what was cooked, how it was heated, and some general activities of cooking. Interior carbon deposits result from the charring of food and is governed by the source of heat, intensity of heat, and the presence of moisture. The processes that govern the different types of exterior soot are difficult to identify and several experiments are performed. It is found that soot deposition is controlled by wood type, temperature of the ceramic surface, and the presence of moisture. This research demonstrates that archaeologists can begin looking at organic residues, attrition and carbon deposits to infer how their vessels were used in the past

Book Review: Learning from Things: Method and Theory of Material Culture Studies, W. David Kingery (Ed.)

Book Review: Learning from Things: Method and Theory of Material Culture Studies, W. David Kingery (Ed.). Washington, D. C., Smithsonian Institution Press (1996).This material was digitized as part of a cooperative project between Radiocarbon and the University of Arizona Libraries.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Acorn Processing and Pottery Use in the Upper Great Lakes: An Experimental Comparison of Stone Boiling and Ceramic Technology

The adoption of pottery in the Upper Great Lakes region occurs quite late compared to the greater Eastern Woodlands. Recent organic residue analyses suggest that the earliest pottery in the Upper Great Lakes region was likely used to process acorns. Through experimental means using temperature as a proxy, this paper evaluates the efficacy of leaching tannins from acorns by comparing two regionally available cooking technologies: stone boiling versus simmering in a ceramic vessel. Our results indicate that tannins can be more effectively leached at simmering temperatures like those provided by ceramic vessels. At boiling temperatures, tannins are irreversibly bound to the acorn starches, rendering the nutmeat inedible in further processing. While there are a number of reasons to adopt and use pottery, it appears that processing acorns may be another important addition to this growing list.Social and Behavioral Sciences Research Institute at the University of Arizona (SBSRI Pre-Doctoral Research Grant) [16PDF0610]18 month embargo; published online: 27 July 2019This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]