Sökning: "Impact structure"

Visar resultat 1 - 5 av 1289 avhandlingar innehållade orden Impact structure.

  1. 1. Geochronology of impact structures - constraining syn- and post-impact processes using the 40Ar/39Ar and U-Pb techniques

    Författare :Maria Herrmann; Berggrundsgeologi; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Impact structure; Dating impact events; 40Ar 39Ar dating; U-Pb dating; Siljan impact structure; Mien impact structure; Hummeln impact structure; Puchezh-Katunki impact structure;

    Sammanfattning : The discovery, at the beginning of the 20th century, that elements can transform into other elements, due to the spontaneous decay of an instable to a stable atomic nuclei, gave rise to a powerful source for age information in many fields of earth science. For impact structures, it is crucial to establish well-defined and precise ages in order to understand how impact events affect the Earth’s geo and biosphere and also with regard to possible future events that can have devastating effects on our civilization. LÄS MER

  2. 2. Terrestrial consequences of hypervelocity impact – shock metamorphism, shock barometry, and newly discovered impact structures

    Författare :Sanna Alwmark; Berggrundsgeologi; []
    Nyckelord :Impact cratering; Impact structure; Shock metamorphism; Shock barometry; Quartz; Planar deformation features; Siljan; Målingen; Hummeln;

    Sammanfattning : Impact cratering was once considered a rare geological process of no, or little, importance to the evolution of the Solar System and planet Earth. After more than 50 years of space exploration and the discovery of numerous (~190 as of October 2016) impact structures on Earth, this view has changed, and it is now clear that impact craters are in fact one of the most common morphological features on solid bodies in the Solar System. LÄS MER

  3. 3. Leave no trace: A non-destructive correlative approach providing new insights into impactites and meteorites

    Författare :Josefin Martell; Berggrundsgeologi; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; impact cratering; Mars; Mien impact structure; X-ray tomography; Neutron tomography; Shock metamorphism; Impact structure;

    Sammanfattning : Impact cratering is today recognized as a fundamental geological process on all rocky bodies in the solar system. On Earth, however, processes such as plate tectonics and erosion have eradicated most craters from the geological record, or they may be buried under sediments, oceans, and vegetation. LÄS MER

  4. 4. Species interactions and community structure

    Författare :Peter Frodin; Technology and Social Change (WTS) Centre for Work; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Ecology; Ekologi; spatial structure; local stability; enrichment; species interactions; Community structure; population dynamics;

    Sammanfattning : In this theses I have focused on how the mechanisms of species interactions affect community structure. It is well known that certain species may have a particularly strong influence on the structure of a community. What is not fully understood is how to characterize these species that have such a strong impact on community structure. LÄS MER

  5. 5. Structure determination of beam sensitive crystals by rotation electron diffraction : the impact of sample cooling

    Författare :Fei Peng; Junliang Sun; Xiaodong Zou; Dag Nores; Ute Kolb; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; electron crystallography; rotation electron diffraction; structure determination; cooling; Inorganic Chemistry; oorganisk kemi;

    Sammanfattning : Electron crystallography is complementary to X-ray crystallography. Single crystal X-ray diffraction requires the size of a crystal to be larger than about 5 × 5 × 5 μm3 while a TEM allows a million times smaller crystals being studied. This advantage of electron crystallography has been used to solve new structures of small crystals. LÄS MER