In: Optics Express, 2010, vol. 18, no. 14, p. 14519-14534
We study the noise of the intensity variance and of the intensity correlation and structure functions measured in light scattering from a random medium in the case when these quantities are obtained by averaging over a finite number N of pixels of a digital camera. We show that the noise scales as 1/N in all cases and that it is sensitive to correlations of signals corresponding to adjacent...
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In: Physical Review Letters, 2010, vol. 104, no. 12, p. 128304
Using a simplified microstructural picture we show that interactions between thermosensitive microgel particles can be described by a polymer brushlike corona decorating the dense core. The softness of the potential is set by the relative thickness L0 of the compliant corona with respect to the overall size of the swollen particle R. The elastic modulus in quenched solid phases derived from the...
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In: Soft Matter, 2010, vol. 6, p. 2174-2177
We describe the synthesis of thermoresponsive, magnetic, optically anisotropic and orientable colloidal particles based on poly(N-isopropylacrylamide) hybrid microgels (PNIPAMs) with an embedded ellipsoidal hematite (α-Fe₂O₃) core. Our ability to orient the particles with a magnetic field is demonstrated by small angle X-ray scattering and by optical polarization microscopy.
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In: Langmuir, 2009, vol. 25, no. 2, p. 716–723
The frequency-dependent shear modulus of aqueous wormlike micellar solutions of cetylpyridinium chloride (CPyCl) and sodium salicylate (NaSal) has been measured over a broad frequency range from 10⁻² to 10⁶ rad/s using diffusing wave spectroscopy (DWS) based tracer microrheology as well as mechanical techniques including rotational rheometry and oscillatory squeeze flow. Good agreement...
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In: Applied Physics Letters, 2007, vol. 91, no. 17, p. 171904
Amorphous photonic materials based on dense assemblies of high refractive index spherical particles are presented. Light transmission through these photonic glasses shows a nontrivial wavelength dependence. The transmission spectra can be quantitatively reproduced by modeling the optical properties starting from their building blocks. Our results emphasize the relevance of including short range...
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In: Current Opinion in Colloid & Interface Science, 2007, vol. 12, no. 1, p. 50-57
In this article we review some of the most important new developments in light scattering that have emerged over the past 10 years. Some of the new methods substantially extend the range of accessible time and length scales. Different cross-correlation methods are now available to suppress multiple scattering over a large concentration range. Novel low coherent light sources on the other hand...
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In: Optics Communications, 2008, vol. 281, no. 1, p. 18-22
We discuss the impact of the scattering anisotropy parameter on the path length distribution of multiply scattered light. A quantitative treatment based on the radiative transfer equation is compared to an extended photon diffusion formalism. We compare both models with diffusing-wave spectroscopy measurements using randomly polarized light.
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In: Physical Review Letters, 2007, vol. 99, no. 6, p. 068302
We characterize the linear viscoelastic shear properties of an aqueous wormlike micellar solution using diffusing wave spectroscopy (DWS) based tracer microrheology as well as various mechanical techniques such as rotational rheometry, oscillatory squeeze flow, and torsional resonance oscillation covering the frequency range from 10⁻¹ to 10⁶ rad/s. Since DWS as well as mechanical oscillatory...
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In: Physical Review Letters, 2006, vol. 97, p. 103901
We report the first observation of the impact of mesoscopic fluctuations on the photocount statistics of coherent light scattered in a random medium. A Poisson photocount distribution of the incident light widens and gains additional asymmetry upon transmission through a suspension of small dielectric spheres. The effect is only appreciable when the average number of photocounts becomes...
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In: European Journal of Neuroscience, 2004, vol. 20, p. 2664-2670
Oxidative metabolism and cerebral blood flow (CBF) are two of the most important measures in neuroimaging. However, results from concurrent imaging of the two with high spatial and temporal resolution have never been published. We used flavoprotein autofluorescence (AF) and laser speckle imaging (LSI) in the anaesthetized rat to map oxidative metabolism and CBF in response to single vibrissa...
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