Sökning: "naturvetenskap sm"

Visar resultat 1 - 5 av 75 avhandlingar innehållade orden naturvetenskap sm.

  1. 1. Spectral Analysis of Neutron Capture Elements in the Laboratory and Stars

    Författare :Martin Lundqvist; Astronomi - Genomgår omorganisation; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; cosmic chemistry; Astronomy; space research; Atom- och molekylärfysik; Atomic and molecular physics; Astronomi; Sm; Hf; Os; Ir; Neutron capture processes; rymdvetenskap; kosmisk kemi; cool stars; Spectroscopy; atomic data;

    Sammanfattning : The pedigree of the elements heavier than iron is a vital question in the history and evolution of our galaxy. The elements up to and including those of the iron group are produced mainly through fusion processes within stars, giving the stars their energy. LÄS MER

  3. 2. Quasicrystal Approximants in the RE-Au-SM systems (RE = Gd, Tb, Ho, Yb; SM = Si, Ge) : Syntheses, structures and properties

    Författare :Girma Hailu Gebresenbut; Cesar Pay Gómez; Martin Sahlberg; Torbjörn Gustafsson; Alan I. Goldman; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Quasicrystal approximant; structure; physical property; Chemistry with specialization in Inorganic Chemistry; Kemi med inriktning mot oorganisk kemi; Physics with spec. in Atomic; Molecular and Condensed Matter Physics; Fysik med inriktning mot atom- molekyl- och kondenserande materiens fysik;

    Sammanfattning : In this study, new Tsai-type 1/1 quasicrystal approximants (ACs) in the RE-Au-SM systems (RE = Gd, Tb, Ho, Yb; SM = Si, Ge) were synthesized using high temperature synthesis techniques such as self-flux, arc-melting-annealing and novel arc-melting-self-flux methods. The syntheses not only provided appropriate samples for the intended structural and physical property measurements but could also be adapted to other systems, especially where crystal growth is a challenge. LÄS MER

  4. 3. Syntheses, structure determination, magnetic and thermoelectric properties of quasicrystal approximants in RE-Au-SM systems (RE = Gd, Tb and Yb and SM = Si, Ge)

    Författare :Girma Hailu Gebresenbut; Cesar Gomez; Martin Sahlberg; Torbjörn Gustafsson; Lars Eriksson; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Quasicrystals; quasicrystal approximants; thermoelectric properties; magnetic properties; Materialvetenskap; Materials Science;

    Sammanfattning : In this study, new compositions of Tsai-type 1/1 quasicrystal approximants Gd(14)Au(70)Si(16), Gd(14)Au(67)Ge(19), Tb(14)Au(70)Si(16) and Yb(16)Au(65)Ge(19)are synthesized using both self-flux and arc-melting-annealing techniques. Both syntheses routes resulted single phase samples. LÄS MER

  5. 4. A study of mixed valence in Sm by XPS and LEED when it is deposited onto Pd(001)

    Författare :Dan K. Kristensson; Chalmers tekniska högskola; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; rare earth metals; XPS; x-ray photoemission; ESCA; intermediate valence; Low energy electron diffraction; mixed valence; Samarium; LEED;

    Sammanfattning : .... LÄS MER

  7. 5. Mesoproterozoic crustal evolution in Southern Africa

    Författare :Åsa Pettersson; Göteborgs universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Namaqua-Natal province; Mezoproterozoic; geochronology; U-Pb zirkon dating; Sm-Nd model ages; Ar-Ar dating; Southern Africa;

    Sammanfattning : The objects of this thesis were to use geochronology to investigate crustal evolution of part of Southern Africa that formed during a global event, resulting in the ~1 Ga supercontinent Rodinia. The timing of assembly by continent-continent collisions and the position of the individual continental blocks of this ancient landmass is still largely unknown. LÄS MER