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@PHDTHESIS{Dartsch:474356,
      author       = {Dartsch, Michael},
      othercontributors = {Gruebel, Gerhard and Pearson, Arwen},
      title        = {{H}igher-{O}rder {C}orrelations in {C}omplex {L}iquids},
      school       = {Universität Hamburg},
      type         = {Dissertation},
      address      = {Hamburg},
      publisher    = {Verlag Deutsches Elektronen-Synchrotron DESY},
      reportid     = {PUBDB-2022-00714, DESY-THESIS-2022-003},
      series       = {DESY-THESIS},
      pages        = {113},
      year         = {2022},
      note         = {Dissertation, Universität Hamburg, 2022},
      abstract     = {Colloidal dispersions show a peculiar rheological behavior
                      known as shear-thinning,that is the viscosity of a sample
                      decreases with increasing shear rate. In thiswork the
                      underlying structural changes that lead to this effect are
                      studied byusing samples consisting of polyacrylate-coated
                      silica nanoparticles dispersed inpolyethylene glycol-200.
                      The silica particles are synthesized using a modifiedStöber
                      method and samples with volume fractions between $\phi$ =
                      0.22 and $\phi$ = 0.53are prepared.The experiments performed
                      in this thesis utilize a setup combining a
                      cone-platerheometer with a small-angle x-ray scattering
                      (SAXS) setup. In this way rheological and structural
                      properties of the samples can be measured
                      simultaneously.Data collected from the SAXS measurements are
                      evaluated further using x-raycross-correlation analysis
                      (XCCA) in order to study higher-order correlations andlocal
                      symmetries.It is shown that under shear the highly
                      concentrated nanoparticle dispersionsform structures with
                      hexagonal symmetry which can be interpreted as layersof
                      hexagonal close-packed spheres. From XCCA the sixth Fourier
                      coefficient ofthe cross-correlation function can be used as
                      an order parameter to quantify thedegree of local hexagonal
                      order. In the regime of intermediate shear rates thedegree
                      of hexagonal order is correlated with the magnitude of the
                      shear rate. Anincrease of the shear rate corresponds to an
                      increase of local hexagonal order.Since the viscosity is
                      decreasing with increasing shear rate it can be
                      concludedthat a higher degree of local order minimizes
                      internal friction of the sample, andtherefore lowers its
                      viscosity.},
      cin          = {FS-CXS},
      cid          = {I:(DE-H253)FS-CXS-20130727},
      pnm          = {633 - Life Sciences – Building Blocks of Life: Structure
                      and Function (POF4-633) / 6G3 - PETRA III (DESY) (POF4-6G3)},
      pid          = {G:(DE-HGF)POF4-633 / G:(DE-HGF)POF4-6G3},
      experiment   = {EXP:(DE-H253)P-P10-20150101},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      doi          = {10.3204/PUBDB-2022-00714},
      url          = {https://bib-pubdb1.desy.de/record/474356},
}