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Search: WFRF:(Helm Richard) > (2018)

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  • Shipton, Ceri, et al. (author)
  • 78,000-year-old record of Middle and Later stone age innovation in an East African tropical forest
  • 2018
  • In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9:1
  • Journal article (peer-reviewed)abstract
    • The Middle to Later Stone Age transition in Africa has been debated as a significant shift in human technological, cultural, and cognitive evolution. However, the majority of research on this transition is currently focused on southern Africa due to a lack of long-term, stratified sites across much of the African continent. Here, we report a 78,000-year-long archeological record from Panga ya Saidi, a cave in the humid coastal forest of Kenya. Following a shift in toolkits ~67,000 years ago, novel symbolic and technological behaviors assemble in a non-unilinear manner. Against a backdrop of a persistent tropical forest-grassland ecotone, localized innovations better characterize the Late Pleistocene of this part of East Africa than alternative emphases on dramatic revolutions or migrations.
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3.
  • Lehtipalo, Katrianne, et al. (author)
  • Multicomponent new particle formation from sulfuric acid, ammonia, and biogenic vapors
  • 2018
  • In: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 4:12
  • Journal article (peer-reviewed)abstract
    • A major fraction of atmospheric aerosol particles, which affect both air quality and climate, form from gaseous precursors in the atmosphere. Highly oxygenated organic molecules (HOMs), formed by oxidation of biogenic volatile organic compounds, are known to participate in particle formation and growth. However, it is not well understood how they interact with atmospheric pollutants, such as nitrogen oxides (NOx) and sulfur oxides (SOx) from fossil fuel combustion, as well as ammonia (NH3) from livestock and fertilizers. Here, we show how NOx suppresses particle formation, while HOMs, sulfuric acid, and NH3 have a synergistic enhancing effect on particle formation. We postulate a novel mechanism, involving HOMs, sulfuric acid, and ammonia, which is able to closely reproduce observations of particle formation and growth in daytime boreal forest and similar environments. The findings elucidate the complex interactions between biogenic and anthropogenic vapors in the atmospheric aerosol system.
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