Absolute Electron Scattering Cross Sections for the CF2 Radical

Using a crossed electron-molecular beam experiment, featuring a skimmed nozzle beam with pyrolytic radical production, absolute elastic cross sections for electron scattering from the CF2 molecule have been measured. A new technique for placing measured cross sections on an absolute scale is used for molecular beams produced as skimmed supersonic jets. Absolute differential cross sections for CF2 are reported for incident electron energies of 30–50 eV and over an angular range of 20–135 deg. Integral cross sections are subsequently derived from those data. The present data are compared to new theoretical predictions for the differential and integral scattering cross sections, as calculated with the Schwinger multichannel variational method using the static-exchange and static-exchange plus polarization approximations

Retention of hunter-gatherer economies among maritime foragers from Caleta Vitor, northern Chile, during the late Holocene: evidence from stable carbon and nitrogen isotopic analysis of skeletal remains

On the basis of stable carbon and nitrogen isotope analysis of human remains, this paper provides evidence for the retention of hunter-gatherer economies among coastal inhabitants in northern Chile during the late Holocene - at the same time that inland populations were adopting agricultural economies. Coastal diets from the Caleta Vitor region of the Atacama Desert were dominated by marine-based foods, predominantly from upper trophic levels. The focus on reliable marine food resources is interpreted as a risk minimisation strategy in this marginal arid environment. Although these coastal hunter-gatherers adopted other goods and traditions from agricultural populations, their participation in this larger interregional exchange network did not affect their basic subsistence economies. Associated new radiocarbon dates from the site are also discussed. Skeletal remains and artefacts associated with the Caleta Vitor shell middens generally originate from sites with dates ranging from c. 9000-476 BP. However, the human remains that are the subject of this research cover the time period c. 4000-476 BP

Retention of hunter-gatherer economies among maritime foragers from Caleta Vitor, northern Chile, during the late Holocene: evidence from stable carbon and nitrogen isotopic analysis of skeletal remains

On the basis of stable carbon and nitrogen isotope analysis of human remains, this paper provides evidence for the retention of hunter-gatherer economies among coastal inhabitants in northern Chile during the late Holocene - at the same time that inland populations were adopting agricultural economies. Coastal diets from the Caleta Vitor region of the Atacama Desert were dominated by marine-based foods, predominantly from upper trophic levels. The focus on reliable marine food resources is interpreted as a risk minimisation strategy in this marginal arid environment. Although these coastal hunter-gatherers adopted other goods and traditions from agricultural populations, their participation in this larger interregional exchange network did not affect their basic subsistence economies.Associated new radiocarbon dates from the site are also discussed. Skeletal remains and artefacts associated with the Caleta Vitor shell middens generally originate from sites with dates ranging from c. 9000-476 BP. However, the human remains that are the subject of this research cover the time period c. 4000-476 BP

Low energy lepton scattering: Recent results for electron and positron interactions

This report will review several new experimental developments for low energy (1-50 eV) scattering of both electrons and positrons from atoms and molecules. Experiments include an apparatus for studies of scattering from unstable molecular radicals, a position- and time-sensitive time-of-flight spectrometer for studies of near threshold electronic excitation of atoms and molecules and a trap-based positron scattering experiment for measurements of low energy positron scattering from rare gas atoms. Where possible, comparisons are also made with other experimental determinations and with contemporary scattering theory