Browsing by Author "Luo, CW"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Atmospheric iron deposition: global distribution, variability, and human perturbations
    (Annual Reviews, 2009-01) Mahowald, NM; Engelstaedter, S; Luo, CW; Sealy, A; Artaxo, P; Benitez-Nelson, C; Bonnet, S; Chen, YS; Chuang, PY; Cohen, DD; Dulac, F; Herut, B; Johansen, AM; Kubilay, N; Losno, R; Maenhaut, W; Paytan, A; Prospero, JM; Shank, LM; Siefert, RL
    Atmospheric inputs of iron to the open ocean are hypothesized to modulate ocean biogeochemistry. This review presents an integration of available observations of atmospheric iron and iron deposition, and also covers bioavailable iron distributions. Methods for estimating temporal variability in ocean deposition over the recent past are reviewed. Desert dust iron is estimated to represent 95% of the global atmospheric iron cycle, and combustion sources of iron are responsible for the remaining 5%. Humans may be significantly perturbing desert dust (up to 50%). The sources of bioavailable iron ire less well understood than those of iron, partly because we do not know what speciation of the iron is bioavailable. Bioavailable iron can derive from atmospheric processing of relatively insoluble desert dust iron or from direct emissions of soluble iron from combustion sources. These results imply that humans could be substantially impacting it-on and bioavailable iron deposition to ocean regions, but there are large uncertainties in our understanding. © 2009, Annual Reviews
  • No Thumbnail Available
    Item
    Magnetic ordering anisotropy in epitaxial orthorhombic multiferroic YMnO3 films
    (American Institute of Physics, 2008-11-15) Hsieh, CC; Lin, TH; Shih, HC; Hsu, CH; Luo, CW; Lin, JY; Wu, KH; Uen, TM; Juang, JY
    Orthorhombic YMnO3 thin films with (200), (020), and (001) orientations were, respectively, obtained by pulsed laser deposition on SrTiO3(110), LaAlO3(110), and SrTiO3(001) substrates. The results demonstrate that the strain between film and substrate can serve as an alternative in transforming the thermodynamically stable hexagonal YMnO3 into the orthorhombic phase, which previously could be obtained with high-pressure high temperature syntheses and epitaxy-stabilized thin film processes. More importantly, these films allow us, for the first time, to unambiguously disclose the intrinsic magnetic property along different crystallographic orientations. Our results show that, although the antiferromagnetic (AFM) ordering remains the same, there is an additional spin reordering transition which is very much dependent on the crystallographic orientation along which the measuring field was applied and on the in-plane crystallographic alignment of the films. Detailed analyses indicate that the origin of the observed second reordering may be due to some strain-induced canted AFM state instead of the incommensurate lock-in transitions conceived previously. © 2008, American Institute of Physics